Download - Welding Inspection CSWIP

5/16/2018 Welding Inspection CSWIP - slidepdf.com

http://slidepdf.com/reader/full/welding-inspection-cswip-55a752434d409 1/682

4/23/20074/23/2007 11 of 691of 691

Duties and ResponsibilitiesDuties and ResponsibilitiesSection 1Section 1

Welding Inspector Welding Inspector



4/23/20074/23/2007 22 of 691of 691

Code complianceCode compliance

Workmanship controlWorkmanship control

Documentation controlDocumentation control

Main ResponsibilitiesMain Responsibilities 1.11.1



4/23/20074/23/2007 33 of 691of 691

Personal AttributesPersonal Attributes 1.11.1

Important qualities that good Inspectors are expectedImportant qualities that good Inspectors are expectedto have are:to have are:

HonestyHonesty

IntegrityIntegrity

KnowledgeKnowledge

Good communicator Good communicator

Physical fitnessPhysical fitness

Good eyesightGood eyesight



4/23/20074/23/2007 44 of 691of 691

Standard for Visual InspectionStandard for Visual Inspection 1.11.1

Basic RequirementsBasic RequirementsBS EN 970BS EN 970 -- NonNon--destructive examination of fusiondestructive examination of fusion

weldswelds -- Visual examinationVisual examination

Welding Inspection Personnel should:Welding Inspection Personnel should:

be familiar with relevant standards, rules and specificationsbe familiar with relevant standards, rules and specifications

applicable to the fabrication work to be undertakenapplicable to the fabrication work to be undertaken

be informed about the welding procedures to be usedbe informed about the welding procedures to be used

have good visionhave good vision (whic h should be c hecked every 12 (whic h should be c hecked every 12

mont hs)mont hs)



4/23/20074/23/2007 55 of 691of 691

Welding InspectionWelding Inspection 1.21.2

Conditions for Visual Inspection (to BS EN 970)Conditions for Visual Inspection (to BS EN 970)Illumination:Illumination:

350 lux minimum required350 lux minimum required

(recommends 500 lux(recommends 500 lux -- normal shop or office lighting)normal shop or office lighting)

Vision Access:Vision Access: eye should be within 600mm of the surfaceeye should be within 600mm of the surface

viewing angle (line from eye to surface) to be not less thanviewing angle (line from eye to surface) to be not less than

3030°°

3030°°

600mm600mm



4/23/20074/23/2007 66 of 691of 691


Aids to Visual Inspection (to BS EN 970) Aids to Visual Inspection (to BS EN 970)

When access is restricted may use:When access is restricted may use:

a mirrored boroscopea mirrored boroscope

a fibre optic viewing systema fibre optic viewing system

Other aids:Other aids:

welding gaugeswelding gauges (f or c hecking bevel angles, w eld (f or c hecking bevel angles, w eld

prof ile, f illet sizing, undercut dept h ) prof ile, f illet sizing, undercut dept h )

dedicated welddedicated weld--gap gauges and linear misalignmentgap gauges and linear misalignment(high(high--low) gaugeslow) gauges

straight edges and measuring tapesstraight edges and measuring tapes

magnifying lensmagnifying lens ( i f magni f ication lens used it ( i f magni f ication lens used it

should have magni f ication bet w een X2 to X5)should have magni f ication bet w een X2 to X5)

usually byusually by

agreementagreement}}



4/23/20074/23/2007 77 of 691of 691

Welding Inspectors EquipmentWelding Inspectors Equipment 1.31.3

Measuring devices:Measuring devices:

flexible tape, steel ruleflexible tape, steel rule

Temperature indicating crayonsTemperature indicating crayons

Welding gaugesWelding gauges

Voltmeter Voltmeter

Ammeter Ammeter

Magnifying glassMagnifying glass

Torch / flash lightTorch / flash light

Gas flowGas flow--meter meter



4/23/20074/23/2007 88 of 691of 691

TWI MultiTWI Multi--purpose Welding Gaugepurpose Welding Gauge Misalignment GaugesMisalignment Gauges

HiHi--Lo GaugeLo Gauge

Fillet Weld GaugesFillet Weld Gauges

G.A.L.

S.T.D.

10mm

16mm

L

G.A.L.

S.T.D.

10mm

16mm

Welding Inspectors GaugesWelding Inspectors Gauges 1.31.3

01/4 1/2 3/4

IN

H

I - L O

S i n g l e P u r p o s e W e l d i n g G

a u g e

1

2

3

4

5

6



4/23/20074/23/2007 99 of 691of 691

Tong Tester Tong Tester

Ammeter Ammeter Voltmeter Voltmeter

Welding Inspectors EquipmentWelding Inspectors Equipment 1.31.3



4/23/20074/23/2007 1010 of 691of 691


Stages of Visual Inspection (to BS EN 970)Stages of Visual Inspection (to BS EN 970)

Extent of examination and when required should be defined inExtent of examination and when required should be defined in

the application standard or by agreement between thethe application standard or by agreement between the

contracting partiescontracting parties

For high integrity fabrications inspection required throughoutFor high integrity fabrications inspection required throughout

the fabrication process:the fabrication process:

Before weldingBefore welding

(Before assemble & After assembly)(Before assemble & After assembly)

During weldingDuring welding

After weldingAfter welding



4/23/20074/23/2007 1111 of 691of 691

Typical Duties of a Welding Inspector Typical Duties of a Welding Inspector 1.51.5

Before WeldingBefore Welding

Preparation:Preparation:

Familiarisation with relevant µdocuments¶«Familiarisation with relevant µdocuments¶«

Application Standard/CodeApplication Standard/Code -- for visual acceptancefor visual acceptance

requirementsrequirements

DrawingsDrawings -- item details and positions/tolerances etcitem details and positions/tolerances etc

Quality Control ProceduresQuality Control Procedures -- for activities such as materialfor activities such as material

handling, documentation control, storage & issue of handling, documentation control, storage & issue of

welding consumableswelding consumables

Quality Plan/Inspection & Test Plan/Inspection ChecklistQuality Plan/Inspection & Test Plan/Inspection Checklist --

details of inspection requirements, inspection proceduresdetails of inspection requirements, inspection procedures

& records required& records required



4/23/20074/23/2007 1212 of 691of 691



Welding Procedures:Welding Procedures:

are applicable to joints to be welded & approvedare applicable to joints to be welded & approved

are available to welders & inspectorsare available to welders & inspectors

Welder Qualifications:Welder Qualifications:

list of available qualified welders related to WPS¶slist of available qualified welders related to WPS¶s

certi f icates are valid and µincerti f icates are valid and µin- -date¶ date¶



4/23/20074/23/2007 1313 of 691of 691



Equipment:Equipment:

all inspection equipment is in good condition &all inspection equipment is in good condition &

calibrated as necessarycalibrated as necessary

all safety requirements are understood & necessaryall safety requirements are understood & necessaryequipment availableequipment available

Materials:Materials:

can be identified & related to test certificates,can be identified & related to test certificates,traceability !traceability !

are of correct dimensionsare of correct dimensions

are in suitable condition (no damage/contamination)are in suitable condition (no damage/contamination)



4/23/20074/23/2007 1414 of 691of 691



Consumables:Consumables:

in accordance with WPS¶sin accordance with WPS¶s

are being controlled in accordance with Procedureare being controlled in accordance with Procedure

Weld Preparations:Weld Preparations:

comply with WPS/drawingcomply with WPS/drawing

free from defects & contaminationfree from defects & contamination

Welding Equipment:Welding Equipment:

in good order & calibrated as required by Procedurein good order & calibrated as required by Procedure



4/23/20074/23/2007 1515 of 691of 691


Before WeldingBefore WeldingFitFit--upup

complies with WPScomplies with WPS

Number / size of tack welds to Code / goodNumber / size of tack welds to Code / goodworkmanshipworkmanship

PrePre--heatheat

if specifiedif specifiedminimum temperature complies with WPSminimum temperature complies with WPS



4/23/20074/23/2007 1616 of 691of 691


During WeldingDuring Welding

Weather conditionsWeather conditions

suitable if site / field weldingsuitable if site / field welding

Welding Process(es)Welding Process(es)

in accordance with WPSin accordance with WPS

Welder Welder

is approved to weld the jointis approved to weld the joint

PrePre--heat (if required)heat (if required) minimum temperature as specified by WPSminimum temperature as specified by WPS

maximum interpass temperature as WPSmaximum interpass temperature as WPS



4/23/20074/23/2007 1717 of 691of 691


During WeldingDuring WeldingWelding consumablesWelding consumables

in accordance with WPSin accordance with WPS

in suitable conditionin suitable conditioncontrolled issue and handlingcontrolled issue and handling

Welding ParametersWelding Parameters

current, voltage & travel speedcurrent, voltage & travel speed ± ± as WPSas WPSRoot runsRoot runs

if possible, visually inspect root before singleif possible, visually inspect root before single--sidedsidedwelds are filled upwelds are filled up



4/23/20074/23/2007 1818 of 691of 691


During WeldingDuring Welding

Inter Inter--run cleaningrun cleaning

in accordance with an approved method (& backin accordance with an approved method (& backgouging) to good workmanship standardgouging) to good workmanship standard

Distortion controlDistortion control

welding is balanced & over welding is balanced & over--welding is avoidedwelding is avoided



4/23/20074/23/2007 1919 of 691of 691


After WeldingAfter Welding

Weld IdentificationWeld Identification

identified/numbered as requiredidentified/numbered as required

is marked with welder¶s identityis marked with welder¶s identity

Visual InspectionVisual Inspection

ensure weld is suitable for ensure weld is suitable for allall NDTNDT

visually inspect & µsentence¶ toCode requirementsvisually inspect & µsentence¶ toCode requirements

Dimensional SurveyDimensional Survey

ensure dimensions comply withCode/drawingensure dimensions comply withCode/drawing

Other NDTOther NDT

ensure all NDT is completed & reports availableensure all NDT is completed & reports available



4/23/20074/23/2007 2020 of 691of 691


After Welding After Welding

RepairsRepairs

monitor repairs to ensure compliance with Procedure,monitor repairs to ensure compliance with Procedure,ensure NDT after repairs is completedensure NDT after repairs is completed

PWHTPWHT

monitor for compliance with Proceduremonitor for compliance with Procedure

check chart records confirm Procedure compliancecheck chart records confirm Procedure compliance

Pressure / Load TestPressure / Load Test

ensure test equipment is suitably calibratedensure test equipment is suitably calibrated

monitor to ensure compliance with Proceduremonitor to ensure compliance with Procedure

ensure all records are availableensure all records are available



4/23/20074/23/2007 2121 of 691of 691


After Welding After Welding

DocumentationDocumentation

ensure any modifications are on µasensure any modifications are on µas--built¶ drawingsbuilt¶ drawings

ensure all required documents are availableensure all required documents are available

Collate / file documents for manufacturing recordsCollate / file documents for manufacturing records

Sign all documentation and forward it to QCSign all documentation and forward it to QC

department.department.



4/23/20074/23/2007 2222 of 691of 691

Summary of DutiesSummary of Duties

A Welding Inspector must: A Welding Inspector must:

ObserveObserveTo observe all relevant actions related to weld qualityTo observe all relevant actions related to weld quality

throughout production.throughout production.

RecordRecordTo record, or log all production inspection points relevant toTo record, or log all production inspection points relevant to

quality, including a final report showing all identifiedquality, including a final report showing all identified

imperfectionsimperfections

CompareCompare

To compare all recorded information with the acceptanceTo compare all recorded information with the acceptancecriteria and any other relevant clauses in the appliedcriteria and any other relevant clauses in the applied

application standardapplication standard

It is the duty of a Welding Inspector to ensure all the welding andIt is the duty of a Welding Inspector to ensure all the welding and

associated actions are carried out in accordance with theassociated actions are carried out in accordance with thespecification and any applicable procedures.specification and any applicable procedures.



4/23/20074/23/2007 2323 of 691of 691


Terms & DefinitionsTerms & Definitions

Section 2Section 2



4/23/20074/23/2007 2424 of 691of 691

Welding Terminology & DefinitionsWelding Terminology & Definitions 2.12.1

What is a Weld?What is a Weld?

A localised coalescence of metals or nonA localised coalescence of metals or non--metals producedmetals produced

either by heating the materials to the welding temperature,either by heating the materials to the welding temperature,

with or without the application of pressure, or by thewith or without the application of pressure, or by the

application of pressure alone (AWS)application of pressure alone (AWS)

A permanent union between materials caused by heat, andA permanent union between materials caused by heat, and

or pressure (BS499)or pressure (BS499)

An Autogenous weld:An Autogenous weld:

A weld made with out the use of a filler material and canA weld made with out the use of a filler material and canonly be made by TIG or Oxyonly be made by TIG or Oxy--Gas WeldingGas Welding



4/23/20074/23/2007 2525 of 691of 691

Welding Terminology & DefinitionsWelding Terminology & Definitions 2.12.1

What is a Joint?What is a Joint?

The junction of members or the edges of membersThe junction of members or the edges of members

that are to be joined or have been joined (AWS)that are to be joined or have been joined (AWS)

A configuration of members (BS499) A configuration of members (BS499)



4/23/20074/23/2007 2626 of 691of 691

Joint TerminologyJoint Terminology 2.22.2

EdgeEdge Open & Closed Corner Open & Closed Corner LapLap

TeeTee ButtButtCruciformCruciform



4/23/20074/23/2007 2727 of 691of 691

Welded Butt JointsWelded Butt Joints 2.22.2

A_________A_________Welded butt jointWelded butt jointButtButt

A_________A_________Welded butt jointWelded butt jointFilletFillet

A____________A____________Welded butt jointWelded butt jointCompoundCompound



4/23/20074/23/2007 2828 of 691of 691

A_________A_________WeldedT jointWelded T jointFilletFillet

A_________A_________WeldedT jointWelded T jointButtButt

A____________A____________WeldedT jointWelded T jointCompoundCompound

Welded Tee JointsWelded Tee Joints 2.22.2



4/23/20074/23/2007 2929 of 691of 691

Weld TerminologyWeld Terminology 2.32.3

Compound weldCompound weld

Fillet weldFillet weldButt weldButt weld

Edge weldEdge weld

Spot weldSpot weld

Plug weldPlug weld



4/23/20074/23/2007 3030 of 691of 691

Butt PreparationsButt Preparations ± ± SizesSizes 2.42.4

Full Penetration Butt Weld

Partial Penetration Butt Weld

Design Throat

Thickness

Design Throat

Thickness

Actual Throat

Thickness

Actual Throat

Thickness



4/23/20074/23/2007 3131 of 691of 691

WeldWeldBoundaryBoundary

C

A B

D

HeatHeatAffectedAffectedZoneZone

RootRoot

WeldWeld

metalmetal

A, B, C & D = Weld ToesA, B, C & D = Weld Toes

FaceFace

Weld Zone TerminologyWeld Zone Terminology 2.52.5



4/23/20074/23/2007 3232 of 691of 691

Excess RootExcess RootPenetrationPenetration

ExcessExcessCap heightCap height

or Weldor WeldReinforcementReinforcement

Weld Zone TerminologyWeld Zone Terminology 2.52.5

Weld cap widthWeld cap width

Design

Throat

Thickness

Actual Throat

Thickness



4/23/20074/23/2007 3333 of 691of 691

Heat Affected Zone (HAZ)Heat Affected Zone (HAZ) 2.52.5

tempered zonetempered zone

grain growth zonegrain growth zone

recrystallised zonerecrystallised zone

partially transformed zonepartially transformed zone

MaximumMaximum

TemperatureTemperature

solidsolid--liquid Boundaryliquid Boundarysolidsolid

weldweld

metalmetal

unaffected baseunaffected base

materialmaterial



4/23/20074/23/2007 3434 of 691of 691

Joint Preparation TerminologyJoint Preparation Terminology 2.72.7

Included angleIncluded angle

Root GapRoot GapRoot FaceRoot Face

Angle of Angle of

bevelbevel

Root FaceRoot FaceRoot GapRoot Gap

Included angleIncluded angle

RootRootRadiusRadius

SingleSingle--V ButtV Butt SingleSingle--U ButtU Butt



4/23/20074/23/2007 3535 of 691of 691

Joint Preparation TerminologyJoint Preparation Terminology 2.8 & 2.92.8 & 2.9

Root GapRoot Gap

Root FaceRoot Face Root FaceRoot FaceRoot GapRoot Gap

RootRoot

RadiusRadius

Single Bevel ButtSingle Bevel Butt SingleSingle--J ButtJ Butt

Angle of bevelAngle of bevel Angle of bevel

LandLand



4/23/20074/23/2007 3636 of 691of 691

Single Sided Butt PreparationsSingle Sided Butt Preparations 2.102.10

Single BevelSingle Bevel Single VeeSingle Vee

SingleSingle--JJ SingleSingle--UU

Single sided preparations are normally made on thinner materials, or Single sided preparations are normally made on thinner materials, or

when access form both sides is restrictedwhen access form both sides is restricted



4/23/20074/23/2007 3737 of 691of 691

Double Sided Butt PreparationsDouble Sided Butt Preparations 2.112.11

Double sided preparations are normally made on thicker materials, or Double sided preparations are normally made on thicker materials, or

when access form both sides is unrestrictedwhen access form both sides is unrestricted

--VeeVeeDoubleDouble--BevelBevelDoubleDouble

-- JJDoubleDouble -- UUDoubleDouble



4/23/20074/23/2007 3838 of 691of 691

Weld PreparationWeld Preparation

Terminology &

Typical Dimensions:

Terminology &

Typical Dimensions: VV--JointsJoints

bevel anglebevel angle

root faceroot face

root gaproot gap

included angleincluded angle

Typical DimensionsTypical Dimensions

bevel anglebevel angle 30 to 3530 to 35°°

root faceroot face ~1.5 to ~2.5mm~1.5 to ~2.5mm

root gaproot gap ~2 to ~4mm~2 to ~4mm



4/23/20074/23/2007 3939 of 691of 691

6 mm6 mm

8080°°

Poor WeldToe Blend AnglePoor Weld

Toe Blend Angle

Improved Weld Toe BlendImproved Weld Toe Blend

AngleAngle

2020°°

3 mm3 mm

Most codes quote the weldMost codes quote the weld

toestoes shall blend smoothlyshall blend smoothly

This statement is notThis statement is not

quantitative and thereforequantitative and therefore

openopen to individualto individual

interpretationinterpretation

The higher the toe blendThe higher the toe blend

angleangle the greater thethe greater the

amountamount of of stressstress

concentrationconcentration

The toe blend angle ideallyThe toe blend angle ideally

shouldshould bebe between 20between 20oo--3030oo

Butt WeldButt Weld -- Toe BlendToe Blend



4/23/20074/23/2007 4040 of 691of 691

Fillet Weld FeaturesFillet Weld Features 2.132.13

DesignDesign

ThroatThroat

VerticalVertical

LegLeg

LengthLength

Horizontal legHorizontal leg

LengthLength

ExcessExcess

WeldWeld

MetalMetal



4/23/20074/23/2007 4141 of 691of 691

Fillet Weld Throat ThicknessFillet Weld Throat Thickness 2.132.13

bb

aa

b = Actual Throat Thicknessb = Actual Throat Thickness

a = Design Throat Thicknessa = Design Throat Thickness



4/23/20074/23/2007 4242 of 691of 691

bb

aa

b = Actual Throat Thicknessb = Actual Throat Thickness

a = Design Throat Thicknessa = Design Throat Thickness

Deep Penetration Fillet Weld FeaturesDeep Penetration Fillet Weld Features 2.132.13



4/23/20074/23/2007 4343 of 691of 691

Fillet Weld SizesFillet Weld Sizes 2.142.14

CalculatingCalculating ThroatThroat ThicknessThickness fromfrom aa knownknown LegLegLengthLength::

Design Throat Thickness = Leg Length x 0.7Design Throat Thickness = Leg Length x 0.7

Question:Question: The Leg length is 14mm.The Leg length is 14mm.

What is the Design Throat?What is the Design Throat?

Answer: Answer: 14mm x 0.7 =14mm x 0.7 = 10mm10mm Throat ThicknessThroat Thickness



4/23/20074/23/2007 4444 of 691of 691


CalculatingCalculating LegLeg LengthLength fromfrom aa knownknown DesignDesignThroatThroat ThicknessThickness::

Leg Length = Design Throat Thickness x 1.4Leg Length = Design Throat Thickness x 1.4

Question:Question: The Design Throat is 10mm.The Design Throat is 10mm.

What is the Leg length?What is the Leg length?

Answer: Answer: 10mm x 1.4 =10mm x 1.4 = 14mm14mm Leg LengthLeg Length



4/23/20074/23/2007 4545 of 691of 691

Features to Consider 2Features to Consider 2 2.142.14

Approximately the same weld volume in both Fillet Approximately the same weld volume in both Fillet

Welds, but theWelds, but the effective throat thickness has beeneffective throat thickness has been

altered, reducing considerably the strength of weld Baltered, reducing considerably the strength of weld B

Importance of Fillet Weld Leg Length SizeImportance of Fillet Weld Leg Length Size

2mm2mm

(b)(b)

4mm4mm

8mm8mm

(a)(a)

4mm4mm



4/23/20074/23/2007 4646 of 691of 691


Area Area == 4 x 44 x 4 ==8mm8mm22

22

Area Area == 6 x 66 x 6 ==18mm18mm22

22

The c.s.a. of The c.s.a. of (b)(b) is over is over doubledouble the area of the area of (a)(a) without the extrawithout the extra

excess weld metal being addedexcess weld metal being added

4mm 6mm

(a) (b)

Importance of Fillet weld leg length SizeImportance of Fillet weld leg length Size

4mm 6mm

(a) (b)

Excess

Excess



4/23/20074/23/2007 4747 of 691of 691

Mitre FilletMitre Fillet Convex FilletConvex Fillet

Concave FilletConcave Fillet

A concave profileA concave profileis preferred for is preferred for

joints subjected to joints subjected to

fatigue loadingfatigue loading

Fillet Weld ProfilesFillet Weld Profiles 2.152.15

F illet w eldsF illet w elds - - S hapeS hape



4/23/20074/23/2007 4848 of 691of 691

EFFECTIVE THROAT THICKNESS EFFECTIVE THROAT THICKNESS ³s´ = Effective throat thickness

sa

³a´ = Nominal throat thickness

Deep penetration fillet welds from high heat

input welding process MAG, FCAW & SAW etc

Fillet Features to Consider 2.15



4/23/20074/23/2007 4949 of 691of 691

Welding PositionsWelding Positions 2.172.17

PAPA 1G / 1F1G / 1F Flat / DownhandFlat / Downhand

PBPB 2F2F HorizontalHorizontal--VerticalVertical

PCPC 2G2G HorizontalHorizontal

PDPD 4F4F HorizontalHorizontal--Vertical (Overhead)Vertical (Overhead)

PEPE 4G4G OverheadOverhead

PFPF 3G / 5G3G / 5G VerticalVertical--UpUp

PGPG 3G / 5G3G / 5G VerticalVertical--DownDown

HH--L045L045 6G6G Inclined Pipe (Upwards)Inclined Pipe (Upwards)

JJ--L045L045 6G6G Inclined Pipe (Downwards)Inclined Pipe (Downwards)



4/23/20074/23/2007 5050 of 691of 691

Welding PositionsWelding Positions 2.172.17

ISO



4/23/20074/23/2007 5151 of 691of 691

Welding position designationWelding position designation 2.172.17

Butt welds in plate (see ISO 6947)Butt welds in plate (see ISO 6947)

Flat - PA Overhead - PE

Vertical

up - PF

Vertical

down - PG

Horizontal - PC



4/23/20074/23/2007 5252 of 691of 691


Butt welds in pipe (see ISO 6947)Butt welds in pipe (see ISO 6947)

Flat - PA

axis: horizontal

pipe: rotated

H-L045

axis: inclined at 45°

pipe: fixed

Horizontal - PC

axis: vertical

pipe: fixed

Vertical up - PF

axis: horizontalpipe: fixed

Vertical down - PG

axis: horizontalpipe: fixed

J-L045

axis: inclined at 45°

pipe: fixed

W ldi i i d i iW ldi i i d i i



4/23/20074/23/2007 5353 of 691of 691


Fillet welds on plate (see ISO 6947)Fillet welds on plate (see ISO 6947)

Flat - PA Overhead - PD

Vertical up - PF Vertical down - PG

Horizontal - PB

W ldi iti d i tiW ldi iti d i ti



4/23/20074/23/2007 5454 of 691of 691


Fillet welds on pipe (see ISO 6947)Fillet welds on pipe (see ISO 6947)

Flat - PAaxis: inclined at 45°

pipe: rotated

Overhead - PDaxis: vertical

pipe: fixed

Vertical up - PFaxis: horizontal

pipe: fixed

Vertical down - PGaxis: horizontal

pipe: fixed

Horizontal - PBaxis: vertical

pipe: fixed

Horizontal - PBaxis: horizontal

pipe: rotated



4/23/20074/23/2007 5555 of 691of 691

PA / 1GPA / 1GPA / 1FPA / 1F

PC / 2GPC / 2GPB / 2FPB / 2F

PD / 4FPD / 4FPE / 4GPE / 4G PG / 3GPG / 3G

PF / 3GPF / 3G

Plate/Fillet Weld PositionsPlate/Fillet Weld Positions 2.172.17

Pi W ldi P itiPi W ldi P iti



4/23/20074/23/2007 5656 of 691of 691

Pipe Welding PositionsPipe Welding Positions 2.172.17

Weld: FlatWeld: Flat

Pipe: rotatedPipe: rotated

Axis: HorizontalAxis: Horizontal

PA / 1GPA / 1G

Weld: Vertical DownwardsWeld: Vertical Downwards

Pipe: FixedPipe: Fixed


PG / 5GPG / 5G

Weld: Vertical upwardsWeld: Vertical upwards



PF / 5GPF / 5G

Weld: UpwardsWeld: Upwards


Axis: InclinedAxis: Inclined

Weld: HorizontalWeld: Horizontal


Axis: VerticalAxis: Vertical

PC / 2GPC / 2G

4545oo

Weld: DownwardsWeld: Downwards


Axis: InclinedAxis: Inclined

JJ--LO 45 / 6GLO 45 / 6G

4545oo

HH--LO 45 / 6GLO 45 / 6G

T l S d MT l S d M



4/23/20074/23/2007 5757 of 691of 691

Travel Speed MeasurementTravel Speed Measurement 2.182.18

Definition:Definition: the rate of weld progressionthe rate of weld progressionmeasured in case of mechanised and automaticmeasured in case of mechanised and automatic

welding processeswelding processes

in case of MMA can be determined using ROL and arcin case of MMA can be determined using ROL and arc

timetime



4/23/20074/23/2007 5858 of 691of 691


Welding ImperfectionsWelding Imperfections

Section 3Section 3



4/23/20074/23/2007 5959 of 691of 691

Welding ImperfectionsWelding Imperfections 3.13.1

All welds have imperfectionsAll welds have imperfections

Imperfections are classed asImperfections are classed as defectsdefects when they are of awhen they are of a

type, or size, not allowed by the Acceptance Standardtype, or size, not allowed by the Acceptance Standard

A defect is an unacceptable imperfectionA defect is an unacceptable imperfection

A weld imperfection may be allowed by one AcceptanceA weld imperfection may be allowed by one Acceptance

Standard but be classed as a defect by another StandardStandard but be classed as a defect by another Standard

and require removal/rectificationand require removal/rectification



4/23/20074/23/2007 6060 of 691of 691


Standards for Welding ImperfectionsStandards for Welding Imperfections

BSBS EN ISO 6520EN ISO 6520--11( 1998)( 1998) Welding and allied processesWelding and allied processes ± ±

Classification of geometricClassification of geometric

imperfections in metallic materialsimperfections in metallic materials --

Part 1: Fusion weldingPart 1: Fusion welding

Imperfections are classified into 6 groups, namely:Imperfections are classified into 6 groups, namely:

1 Cracks1 Cracks

2 Cavities2 Cavities

3 Solid inclusions3 Solid inclusions

4 Lack of fusion and penetration4 Lack of fusion and penetration5 Imperfect shape and dimensions5 Imperfect shape and dimensions

6 Miscellaneous imperfections6 Miscellaneous imperfections



4/23/20074/23/2007 6161 of 691of 691


Standards for Welding ImperfectionsStandards for Welding Imperfections

EN ISO 5817EN ISO 5817 ( 2003)( 2003) WeldingWelding -- FusionFusion--welded joints in steel,welded joints in steel,

nickel, titanium and their alloys (beamnickel, titanium and their alloys (beam

welding excluded)welding excluded) -- Quality levels for Quality levels for

imperfectionsimperfections

This main imperfections given in EN ISO 6520This main imperfections given in EN ISO 6520--1 are listed in1 are listed inEN ISO 5817 with acceptance criteria at 3 levels, namelyEN ISO 5817 with acceptance criteria at 3 levels, namely

Level B (highest)Level B (highest)

Level C (intermediate)Level C (intermediate)

Level D (general)Level D (general)

This Standard is µdirectly applicable toThis Standard is µdirectly applicable to visualvisual testing of welds¶testing of welds¶

......(w eld sur f aces & macro examination)(w eld sur f aces & macro examination)



4/23/20074/23/2007 6262 of 691of 691

Welding imperfectionsWelding imperfections 3.13.1

classificationclassification

CracksCracks

CracksCracks



4/23/20074/23/2007 6363 of 691of 691

CracksCracks 3.13.1

Cracks that may occur in welded materialsCracks that may occur in welded materialsare caused generally by many factors andare caused generally by many factors andmay be classified by shape and position.may be classified by shape and position.

Note:Note: Cracks are classed as Planar Cracks are classed as Planar Defects.Defects.

Classified by ShapeClassified by Shape

LongitudinalLongitudinal

TransverseTransverse

ChevronChevron

Lamellar Tear Lamellar Tear

Classified by PositionClassified by Position

HAZHAZ

CenterlineCenterline

Crater Crater

Fusion zoneFusion zone

Parent metalParent metal

C kC k



4/23/20074/23/2007 6464 of 691of 691

Longitudinal parent metalLongitudinal parent metal

Longitudinal weld metalLongitudinal weld metal

Lamellar tearingLamellar tearing

Transverse weld metalTransverse weld metal

CracksCracks 3.13.1



4/23/20074/23/2007 6565 of 691of 691

Transverse crackTransverse crack Longitudinal crackLongitudinal crack

CracksCracks 3.13.1



4/23/20074/23/2007 6666 of 691of 691

Main Crack TypesMain Crack Types

Solidification CracksSolidification CracksHydrogen Induced CracksHydrogen Induced Cracks

Lamellar TearingLamellar Tearing

Reheat cracksReheat cracks

CracksCracks 3.23.2



4/23/20074/23/2007 6767 of 691of 691

Solidification CrackingSolidification CrackingOccurs during weld solidification processOccurs during weld solidification process

Steels with high sulphur impurities content (lowSteels with high sulphur impurities content (low

ductility at elevated temperature)ductility at elevated temperature)

Requires high tensile stressRequires high tensile stress

Occur longitudinally down centre of weldOccur longitudinally down centre of weld

CracksCracks 3.23.2

CracksCracks



4/23/20074/23/2007 6868 of 691of 691

CracksCracks 3.33.3

Hydrogen Induced Cold CrackingHydrogen Induced Cold CrackingRequires susceptible hard grain structure, stress, lowRequires susceptible hard grain structure, stress, low

temperature and hydrogentemperature and hydrogen

Hydrogen enters weld via welding arc mainly asHydrogen enters weld via welding arc mainly as

result of contaminated electrode or preparationresult of contaminated electrode or preparation

Hydrogen diffuses out into parent metal on coolingHydrogen diffuses out into parent metal on cooling

Cracking developing most likely in HAZCracking developing most likely in HAZ




4/23/20074/23/2007 6969 of 691of 691

Lamellar TearingLamellar Tearing 3.53.5

Location:Location: Parent metalParent metal

Steel Type:Steel Type: Any steel type possible Any steel type possible

Susceptible Microstructure:Susceptible Microstructure: Poor through thicknessPoor through thicknessductilityductility

Lamellar tearing has a step like appearance due to theLamellar tearing has a step like appearance due to the

solid inclusions in the parent material (e.g. sulphidessolid inclusions in the parent material (e.g. sulphidesand silicates) linking up under the influence of weldingand silicates) linking up under the influence of weldingstressesstresses

Low ductile materials in the short transverse directionLow ductile materials in the short transverse direction

containing high levels of impurities are very susceptiblecontaining high levels of impurities are very susceptibleto lamellar tearingto lamellar tearing

It forms when the welding stresses act in the shortIt forms when the welding stresses act in the shorttransverse direction of the material (through thicknesstransverse direction of the material (through thicknessdirection)direction)



4/23/20074/23/2007 7070 of 691of 691

Gas CavitiesGas Cavities 3.63.6

Root pipingRoot piping

Cluster porosityCluster porosityGas poreGas pore

Blow holeBlow holeHerringbone porosityHerringbone porosity

Gas pore <1.5mmGas pore <1.5mm

Blow hole.>1.6mmBlow hole.>1.6mm

Causes:Causes:

Loss of gas shieldLoss of gas shield

Damp electrodesDamp electrodes

ContaminationContamination

Arc length too largeArc length too large

Damaged electrode fluxDamaged electrode flux

Moisture on parent materialMoisture on parent material

Welding current too lowWelding current too low



4/23/20074/23/2007 7171 of 691of 691

Root piping Root piping

Porosity Porosity


Gas CavitiesGas Cavities



4/23/20074/23/2007 7272 of 691of 691

Cluster porosityCluster porosity Herringbone porosityHerringbone porosity




4/23/20074/23/2007 7373 of 691of 691

Crater pipeCrater pipe

Weld crater Weld crater

Crater PipeCrater Pipe 3.93.9



4/23/20074/23/2007 7474 of 691of 691

Crater pipe is a shrinkage defect and not a gas defect, it hasCrater pipe is a shrinkage defect and not a gas defect, it has

the appearance of a gas pore in the weld crater the appearance of a gas pore in the weld crater

Causes:Causes:

Too fast a coolingToo fast a cooling

raterate

DeoxidizationDeoxidization

reactions andreactions and

liquid to solidliquid to solid

volume changevolume change


Crater cracksCrater cracks

(Star cracks)(Star cracks)

Crater pipeCrater pipe

Crater PipeCrater Pipe 3.93.9

S lid I l iS lid I l i



4/23/20074/23/2007 7575 of 691of 691

Solid InclusionsSolid Inclusions 3.103.10

Slag inclusions are defined as a nonSlag inclusions are defined as a non--metallic inclusionmetallic inclusion

caused by some welding processcaused by some welding processCauses:Causes:

Slag originates fromSlag originates from

welding fluxwelding flux

MAG andT

IG weldingMAG andT

IG weldingprocess produce silicaprocess produce silica

inclusionsinclusions

Slag is caused bySlag is caused by

inadequate cleaninginadequate cleaning

Other inclusions includeOther inclusions includetungsten and copper tungsten and copper

inclusions from the TIGinclusions from the TIG

and MAG welding processand MAG welding process

Slag inclusionsSlag inclusions

Parallel slag linesParallel slag lines

Lack of sidewallLack of sidewallfusion withfusion withassociated slagassociated slag

Lack of interunLack of interun

fusion + slagfusion + slag



4/23/20074/23/2007 7676 of 691of 691

Elongated slag linesElongated slag linesInterpass slag inclusionsInterpass slag inclusions

Solid InclusionsSolid Inclusions 3.113.11

Welding ImperfectionsWelding Imperfections



4/23/20074/23/2007 7777 of 691of 691


Typical Causes of Lack of Fusion:Typical Causes of Lack of Fusion:

welding current too low

bevel angle too steep

root face too large (single-sided weld)

root gap too small (single-sided weld)

incorrect electrode angle

linear misalignment

welding speed too high

welding process related ± particularly dip-transfer GMAW

flooding the joint with too much weld metal (blocking Out)

L k f F iL k f F i



4/23/20074/23/2007 7878 of 691of 691

Lack of FusionLack of Fusion 3.133.13

Incomplete filled groove +Incomplete filled groove +

Lack of sidewall fusionLack of sidewall fusion

11

22

1.1. Lack of sidewall fusionLack of sidewall fusion

2.2. Lack of inter Lack of inter--run fusionrun fusion

Causes:Causes:

Poor welder skillPoor welder skill

Incorrect electrodeIncorrect electrode

manipulationmanipulation

Arc blowArc blow

Incorrect weldingIncorrect welding

current/voltagecurrent/voltage

Incorrect travel speedIncorrect travel speed

Incorrect inter Incorrect inter--run cleaningrun cleaning

k f F ik f F i



4/23/20074/23/2007 7979 of 691of 691

Lack of sidewall fusion + incomplete filled grooveLack of sidewall fusion + incomplete filled groove

Lack of FusionLack of Fusion 3.133.13

Weld Root ImperfectionsWeld Root Imperfections



4/23/20074/23/2007 8080 of 691of 691

Weld Root ImperfectionsWeld Root Imperfections 3.153.15

Lack of Root FusionLack of Root FusionLack of Root PenetrationLack of Root Penetration

C U d tC U d t



4/23/20074/23/2007 8181 of 691of 691

Cap UndercutCap Undercut 3.183.18

Intermittent Cap UndercutIntermittent Cap Undercut

U d tU d t



4/23/20074/23/2007 8282 of 691of 691

Cap undercutCap undercutRoot undercutRoot undercut

UndercutUndercut 3.183.18

S f d P filS f d P fil



4/23/20074/23/2007 8383 of 691of 691

Surface and ProfileSurface and Profile 3.193.19

Incomplete filled grooveIncomplete filled groove Poor cap profilePoor cap profile

Excessive cap heightExcessive cap height

Poor cap profiles andPoor cap profiles and

excessive cap reinforcementsexcessive cap reinforcements

may lead to stressmay lead to stress

concentration points at theconcentration points at the

weld toes and will alsoweld toes and will also

contribute to overall poor toecontribute to overall poor toe

blendblend

Surface and ProfileSurface and Profile



4/23/20074/23/2007 8484 of 691of 691

Incomplete filled grooveIncomplete filled grooveExcess cap reinforcementExcess cap reinforcement

Surface and ProfileSurface and Profile 3.193.19

W ld R t I f tiW ld R t I f ti



4/23/20074/23/2007 8585 of 691of 691

Excessive rootExcessive root

penetrationpenetration


OverlapOverlap



4/23/20074/23/2007 8686 of 691of 691

OverlapOverlap 3.213.21

An imperfection at the toe or root of a weld caused by metalAn imperfection at the toe or root of a weld caused by metal

flowing on to the surface of the parent metal without fusing to itflowing on to the surface of the parent metal without fusing to it

Causes:Causes:


Slow travel speedSlow travel speed

Incorrect weldingIncorrect welding

techniquetechnique

Current too lowCurrent too low

OverlapOverlap



4/23/20074/23/2007 8787 of 691of 691

OverlapOverlap 3.213.21

Toe OverlapToe Overlap

Toe OverlapToe Overlap

SetSet Up IrregularitiesUp Irregularities



4/23/20074/23/2007 8888 of 691of 691

SetSet--Up IrregularitiesUp Irregularities 3.223.22

Plate/pipe Linear MisalignmentPlate/pipe Linear Misalignment

(Hi(Hi--Lo)Lo)

Angular MisalignmentAngular Misalignment

Linear misalignmentLinear misalignment isismeasured from the lowestmeasured from the lowest

plate to the highest point.plate to the highest point.

Angular misalignmentAngular misalignment isis

measured in degreesmeasured in degrees




4/23/20074/23/2007 8989 of 691of 691


Linear MisalignmentLinear Misalignment




4/23/20074/23/2007 9090 of 691of 691

Linear MisalignmentLinear Misalignment


Incomplete GrooveIncomplete Groove



4/23/20074/23/2007 9191 of 691of 691

Lack of sidewall fusion + incomplete filled grooveLack of sidewall fusion + incomplete filled groove

Incomplete GrooveIncomplete Groove 3.233.23




4/23/20074/23/2007 9292 of 691of 691

Concave RootConcave Root

Causes:Causes:

Excessive back purgeExcessive back purge

pressure during TIG weldingpressure during TIG welding

Excessive root bead grindingExcessive root bead grinding

before the application of thebefore the application of the

second passsecond pass

welding current too high for welding current too high for

2nd pass2nd pass overhead weldingoverhead welding

root gap too largeroot gap too large -- excessiveexcessive

µweaving¶µweaving¶

A shallow groove, which may occur in the root of a butt weldA shallow groove, which may occur in the root of a butt weld





4/23/20074/23/2007 9393 of 691of 691

Concave RootConcave Root


Weld Root ImperfectionsWeld Root Imperfections 3 243 24



4/23/20074/23/2007 9494 of 691of 691

Concave rootConcave root Excess root penetrationExcess root penetration





4/23/20074/23/2007 9595 of 691of 691

Causes:Causes:

High Amps/voltsHigh Amps/volts Small Root faceSmall Root face

Large Root GapLarge Root Gap

Slow TravelSlow TravelSpeedSpeedBurn throughBurn through

A localized collapse of the weld pool due to excessiveA localized collapse of the weld pool due to excessive

penetration resulting in a hole in the root runpenetration resulting in a hole in the root run


Weld Root ImperfectionsWeld Root Imperfections 3 253 25



4/23/20074/23/2007 9696 of 691of 691

Burn ThroughBurn Through


Oxidized Root (Root Coking)Oxidized Root (Root Coking)



4/23/20074/23/2007 9797 of 691of 691

Causes:Causes:

Loss or insufficientLoss or insufficient

back purging gas (TIG)back purging gas (TIG)

Most commonly occursMost commonly occurswhen welding stainlesswhen welding stainless

steelssteels

Purging gases includePurging gases includeargon, helium andargon, helium and

occasionally nitrogenoccasionally nitrogen

Oxidized Root (Root Coking)Oxidized Root (Root Coking)

Miscellaneous ImperfectionsMiscellaneous Imperfections



4/23/20074/23/2007 9898 of 691of 691

Miscellaneous ImperfectionsMiscellaneous Imperfections 3.263.26

Arc strikeArc strike

Causes:Causes:

Accidental striking of theAccidental striking of the

arc onto the parentarc onto the parent

materialmaterial

Faulty electrode holder Faulty electrode holder

Poor cable insulationPoor cable insulation

Poor return leadPoor return lead

clampingclamping

Miscellaneous ImperfectionsMiscellaneous Imperfections



4/23/20074/23/2007 9999 of 691of 691

Miscellaneous ImperfectionsMiscellaneous Imperfections 3.273.27

Causes:Causes:

Excessive currentExcessive current

Damp electrodesDamp electrodes


Incorrect wire feedIncorrect wire feed

speed when weldingspeed when welding

with the MAG weldingwith the MAG welding

processprocess

Arc blow Arc blowSpatter Spatter

Mechanical DamageMechanical Damage 3 283 28



4/23/20074/23/2007 100100 of 691of 691

Mechanical DamageMechanical Damage 3.283.28

Mechanical damage can be defined as any surfaceMechanical damage can be defined as any surface

materialmaterial

damage cause during the manufacturing process.damage cause during the manufacturing process.

GrindingGrinding

HammeringHammering

ChisellingChiselling

ChippingChipping

Breaking off welded attachmentsBreaking off welded attachments

(torn surfaces)(torn surfaces)

Using needle guns to compressUsing needle guns to compress

weld capping runsweld capping runs

Mechanical DamageMechanical Damage 3 283 28



4/23/20074/23/2007 101101 of 691of 691

Mechanical DamageMechanical Damage 3.283.28

Mechanical Damage/Grinding MarkMechanical Damage/Grinding Mark

Chipping MarksChipping Marks



4/23/20074/23/2007 102102 of 691of 691


Destructive TestingDestructive Testing

Section 4Section 4

Quantitative and Qualitative TestsQuantitative and Qualitative Tests 4.14.1



4/23/20074/23/2007 103103 of 691of 691

Qua t tat e a d Qua tat e estsQua t tat e a d Qua tat e ests 4.14.1

Quantitative Tests:Quantitative Tests:

For measuring a µquantity¶For measuring a µquantity¶ ( a mec hanical property )( a mec hanical property )

Mechanical testsMechanical tests -- tensile testtensile test

-- hardness testhardness test

-- Charpy VCharpy V--notch test (& CTOD)notch test (& CTOD)

Qualitative Tests:Qualitative Tests:

For assessing joint µquality¶For assessing joint µquality¶ ( good f usion & f ree f rom def ects)( good f usion & f ree f rom def ects)

Qualitative testsQualitative tests -- bend testsbend tests

-- macro examinationmacro examination

-- fillet fracture & nickfillet fracture & nick--break testsbreak tests

Qualitative and Quantitative TestsQualitative and Quantitative Tests 4.14.1



4/23/20074/23/2007 104104 of 691of 691

Q QQ Q

The following mechanical tests have units and are termedThe following mechanical tests have units and are termed

quantitativequantitative tests totests to measure Mechanical Propertiesmeasure Mechanical Properties

Tensile tests (Transverse Welded Joint, All Weld Metal)Tensile tests (Transverse Welded Joint, All Weld Metal)

Toughness testing (Charpy, Izod, CTOD)Toughness testing (Charpy, Izod, CTOD)

Hardness tests (Brinell, Rockwell, Vickers)Hardness tests (Brinell, Rockwell, Vickers)

The following mechanical tests have no units and are termedThe following mechanical tests have no units and are termed

qualitativequalitative tests for tests for assessing joint qualityassessing joint quality

Macro testingMacro testing

Bend testingBend testing

Fillet weld fracture testingFillet weld fracture testing

Butt weld nickButt weld nick--break testingbreak testing

Mechanical Test SamplesMechanical Test Samples 4.14.1



4/23/20074/23/2007 105105 of 691of 691

Tensile SpecimensTensile Specimens

Fracture FilletFracture Fillet

SpecimenSpecimen

CTOD SpecimenCTOD Specimen

Charpy SpecimenCharpy Specimen

Bend TestBend Test

SpecimenSpecimen

Mechanical Test SamplesMechanical Test Samples 4.14.1

Destructive TestingDestructive Testing 4.14.1



4/23/20074/23/2007 106106 of 691of 691

Typical Positions for TestTypical Positions for Test

PiecesPieces

Specimen Type PositionSpecimen Type Position

Macro + HardnessMacro + Hardness 55

Transverse TensileTransverse Tensile 2, 42, 4

Bend TestsBend Tests 2, 42, 4

Charpy Impact TestsCharpy Impact Tests 33

Additional TestsAdditional Tests 33

WELDING PROCEDURE QUALIFICATION TESTINGWELDING PROCEDURE QUALIFICATION TESTING

22

33

44

55

top of fixed pipetop of fixed pipe

DefinitionsDefinitions



4/23/20074/23/2007 107107 of 691of 691

MalleabilityMalleability

DuctilityDuctility ToughnessToughness

HardnessHardness

Tensile StrengthTensile Strength

Ability of a material to Ability of a material to

withstand deformationwithstand deformationunder static compressiveunder static compressive

loading without ruptureloading without rupture

DefinitionsDefinitionsMechanical Properties of metalsMechanical Properties of metals are related to the amount of are related to the amount of

deformation which metals can withstand under differentdeformation which metals can withstand under differentcircumstances of force application.circumstances of force application.




4/23/20074/23/2007 108108 of 691of 691



HardnessHardness


Ability of a material Ability of a material

undergo plasticundergo plasticdeformation under staticdeformation under static

tensile loading withouttensile loading without

rupture. Measurablerupture. Measurable

elongation and reductionelongation and reduction

in cross section areain cross section area






4/23/20074/23/2007 109109 of 691of 691



HardnessHardness


Ability of a material to Ability of a material to

withstand bending or thewithstand bending or theapplication of shear application of shear

stresses by impact loadingstresses by impact loading

without fracture.without fracture.






4/23/20074/23/2007 110110 of 691of 691



HardnessHardness


Measurement of aMeasurement of a

materials surfacematerials surface

resistance to indentationresistance to indentation

from another material byfrom another material by

static loadstatic load

Mechanical Properties of metalsMechanical Properties of metals are related to the amount of are related to the amount of





4/23/20074/23/2007 111111 of 691of 691



HardnessHardness


MeasurementMeasurement of theof the

maximum force required tomaximum force required to

fracture a materials bar of fracture a materials bar of

unit crossunit cross--sectional area insectional area in

tensiontension



Transverse Joint Tensile TestTransverse Joint Tensile Test 4.24.2



4/23/20074/23/2007 112112 of 691of 691

Weld on plateWeld on plate

Multiple cross jointMultiple cross joint

specimensspecimensWeld on pipeWeld on pipe

Tensile TestTensile Test 4 34 3



4/23/20074/23/2007 113113 of 691of 691

AllAll--Weld Metal TensileWeld Metal Tensile

SpecimenSpecimen

Transverse TensileTransverse Tensile

SpecimenSpecimen

Tensile TestTensile Test 4.34.3

STRA (Short Transverse Reduction Area)STRA (Short Transverse Reduction Area)



4/23/20074/23/2007 114114 of 691of 691

STRA (Short Transverse Reduction Area)STRA (Short Transverse Reduction Area)For materials that may be subject to Lamellar TearingFor materials that may be subject to Lamellar Tearing

UTS Tensile testUTS Tensile test 4.44.4



4/23/20074/23/2007 115115 of 691of 691

U S e s e testU S e s e test 4.44.4

Charpy VCharpy V--Notch Impact TestNotch Impact Test 4.54.5



4/23/20074/23/2007 116116 of 691of 691

yy

Objectives:Objectives:

measuring impact strength in different weld joint areasmeasuring impact strength in different weld joint areas

assessing resistance toward brittle fractureassessing resistance toward brittle fracture

Information to be supplied on the test report:Information to be supplied on the test report:

Material typeMaterial type

Notch typeNotch type

Specimen sizeSpecimen size

Test temperatureTest temperature Notch locationNotch location

Impact Strength ValueImpact Strength Value

Ductile / Brittle Transition CurveDuctile / Brittle Transition Curve 4.64.6



4/23/20074/23/2007 117117 of 691of 691

-- 5050 00-- 2020 -- 1010-- 4040 -- 3030

Ductile fractureDuctile fracture

Ductile/BrittleDuctile/Brittletransitiontransitionpointpoint

47 Joules47 Joules

28 Joules28 Joules

Testing temperatureTesting temperature - Degrees CentigradeDegrees Centigrade

Temperature rangeTemperature range

Transition rangeTransition range

Brittle fractureBrittle fracture

Three specimens are normally tested at each temperatureThree specimens are normally tested at each temperature

Energy absorbedEnergy absorbed

Comparison Charpy Impact Test ResultsComparison Charpy Impact Test Results 4.64.6



4/23/20074/23/2007 118118 of 691of 691

Impact Energy JoulesImpact Energy JoulesRoom TemperatureRoom Temperature --2020ooC TemperatureC Temperature

1.1. 197 Joules197 Joules

2.2. 191191 JoulesJoules





Average =Average = 191191 JoulesJoules Average =Average = 5151 JoulesJoules

The test results show the specimens carried out at roomThe test results show the specimens carried out at room

temperature absorb more energy than the specimens carriedtemperature absorb more energy than the specimens carried

out atout at --2020ooCC

Charpy VCharpy V--notch impact test specimennotch impact test specimen 4.74.7



4/23/20074/23/2007 119119 of 691of 691

Specimen dimensions according ASTM E23Specimen dimensions according ASTM E23

ASTM: American Society of Testing MaterialsASTM: American Society of Testing Materials

Charpy VCharpy V--Notch Impact TestNotch Impact Test 4.84.8



4/23/20074/23/2007 120120 of 691of 691

SpecimeSpecimenn

PenduluPendulumm

(striker)(striker)

Anvil (support) Anvil (support)

Charpy Impact TestCharpy Impact Test 4.94.9



4/23/20074/23/2007 121121 of 691of 691

10 mm10 mm

8 m m

8 m m

2 m m

2 m m

22.522.5oo

MachinedMachined

notchnotch

100% Ductile100% DuctileMachinedMachined

notchnotch

Large reductionLarge reduction

in area, shear in area, shear

lipslips

Fracture surfaceFracture surface

100% bright100% bright

crystalline brittlecrystalline brittle

fracturefracture

Randomly torn,Randomly torn,

dull gray fracturedull gray fracture

surfacesurface

py ppy p

100% Brittle100% Brittle

Hardness TestingHardness Testing 4.104.10



4/23/20074/23/2007 122122 of 691of 691

gg

DefinitionDefinition

Measurement of resistance of a material againstMeasurement of resistance of a material against

penetration of an indenter under a constant loadpenetration of an indenter under a constant load

There is a direct correlation between UTS andThere is a direct correlation between UTS and

hardnesshardness

Hardness tests:Hardness tests:

BrinellBrinell

VickersVickers

RockwellRockwell




4/23/20074/23/2007 123123 of 691of 691

Objectives:Objectives:

measuring hardness in different areas of a welded jointmeasuring hardness in different areas of a welded joint

assessing resistance toward brittle fracture, cold crackingassessing resistance toward brittle fracture, cold cracking

and corrosion sensitivity within a Hand corrosion sensitivity within a H22S (Hydrogen Sulphide)S (Hydrogen Sulphide)

environment.environment.

Information to be supplied on the test report:Information to be supplied on the test report:

material typematerial type

location of indentationlocation of indentation

type of hardness test and load applied on the indenter type of hardness test and load applied on the indenter

hardness valuehardness value

Vickers Hardness TestVickers Hardness Test 4.114.11



4/23/20074/23/2007 124124 of 691of 691

Vickers hardness tests:Vickers hardness tests:

indentation body is a square based diamond pyramidindentation body is a square based diamond pyramid(136º included angle)(136º included angle)

the average diagonal (d) of the impression isthe average diagonal (d) of the impression is

converted to a hardness number from a tableconverted to a hardness number from a table

it is measured in HV5, HV10 or HV025it is measured in HV5, HV10 or HV025AdjustableAdjustableshuttersshuttersIndentationIndentationDiamondDiamond

indentor indentor

Vickers Hardness Test MachineVickers Hardness Test Machine 4.114.11



4/23/20074/23/2007 125125 of 691of 691

Brinell Hardness TestBrinell Hardness Test 4.114.11



4/23/20074/23/2007 126126 of 691of 691

Hardened steel ball of given diameter is subjected for Hardened steel ball of given diameter is subjected for

a given time to a given loada given time to a given load

Load divided by area of indentation gives BrinellLoad divided by area of indentation gives Brinell

hardness in kg/mmhardness in kg/mm22

More suitable for on site hardness testingMore suitable for on site hardness testing

30KN30KN

Ø=10mm

steel ball

Rockwell Hardness TestRockwell Hardness Test



4/23/20074/23/2007 127127 of 691of 691

Rockwell Hardness TestRockwell Hardness Test

1KN1KN

Ø=1.6mm

steel ball

Rockwell BRockwell B Rockwell CRockwell C

1.5KN1.5KN

120°Diamond

Cone




4/23/20074/23/2007 128128 of 691of 691

Hardness Test Methods Typical DesignationsHardness Test Methods Typical Designations

VickersVickers 240 HV10240 HV10

RockwellRockwell Rc 22Rc 22

BrinellBrinell 200 BHN200 BHN--WW

usually the hardest regionusually the hardest region

1.5 to 3mm1.5 to 3mm

HAZHAZ

fusion linefusion line

or or

fusionfusion

boundaryboundary

Hardness specimens can also be used for CTOD samples

Crack Tip Opening Displacement testingCrack Tip Opening Displacement testing 4 124 12



4/23/20074/23/2007 129129 of 691of 691

Crack Tip Opening Displacement testingCrack Tip Opening Displacement testing 4.124.12

Test is for fracture toughnessTest is for fracture toughness

Square bar machined with a notch placedSquare bar machined with a notch placedin the centre.in the centre.

Tested below ambient temperature at aTested below ambient temperature at aspecified temperature.specified temperature.

Load is applied at either end of the testLoad is applied at either end of the testspecimen in an attempt to open a crack atspecimen in an attempt to open a crack atthe bottom of the notchthe bottom of the notch

Normally 3 samplesNormally 3 samples

Fatigue FractureFatigue Fracture 4.134.13



4/23/20074/23/2007 130130 of 691of 691

Location:Location: Any stress concentration areaAny stress concentration area

Steel Type:Steel Type: All steel typesAll steel types

Susceptible Microstructure:Susceptible Microstructure: All grain structuresAll grain structures

Test for Fracture Toughness is CTODTest for Fracture Toughness is CTOD

(Crack Tip Opening Displacement)(Crack Tip Opening Displacement)

Fatigue FractureFatigue Fracture 4.134.13



4/23/20074/23/2007 131131 of 691of 691

Fatigue cracks occur under cyclic stress conditionsFatigue cracks occur under cyclic stress conditions

Fracture normally occurs at a change in section, notchFracture normally occurs at a change in section, notch

and weld defects i.e stress concentration areaand weld defects i.e stress concentration area

All materials are susceptible to fatigue cracking All materials are susceptible to fatigue cracking

Fatigue cracking starts at a specific point referred to asFatigue cracking starts at a specific point referred to asa initiation pointa initiation point

The fracture surface is smooth in appearanceThe fracture surface is smooth in appearance

sometimes displaying beach markingssometimes displaying beach markings

The final mode of failure may be brittle or ductile or aThe final mode of failure may be brittle or ductile or a

combination of bothcombination of both

Fatigue FractureFatigue Fracture



4/23/20074/23/2007 132132 of 691of 691

Toe grinding, profile grinding.

The elimination of poor profiles

The elimination of partial penetration welds and weld

defects

Operating conditions under the materials endurance limits

The elimination of notch effects e.g. mechanical damage

cap/root undercut

The selection of the correct material for the service

conditions of the component

Precautions against Fatigue Cracks




4/23/20074/23/2007 133133 of 691of 691

Fatigue fracture occurs in structures subject to repeatedFatigue fracture occurs in structures subject to repeated

application of tensile stress.application of tensile stress.

Crack growth is slow (in same cases, crack may growCrack growth is slow (in same cases, crack may grow

into an area of low stress and stop without failure).into an area of low stress and stop without failure).




4/23/20074/23/2007 134134 of 691of 691

Initiation points / weld defectsInitiation points / weld defects

Fatigue fracture surfaceFatigue fracture surface

smooth in appearancesmooth in appearance

Secondary mode of failureSecondary mode of failure

ductile fracture rough fibrousductile fracture rough fibrousappearanceappearance




4/23/20074/23/2007 135135 of 691of 691

Crack growth is slowCrack growth is slow

It initiate from stress concentration pointsIt initiate from stress concentration points

load is considerably below the design or yield stress levelload is considerably below the design or yield stress level

The surface is smoothThe surface is smooth

The surface is bounded by a curveThe surface is bounded by a curve

Bands may sometimes be seen on the smooth surfaceBands may sometimes be seen on the smooth surface ± ±´beachmarks´. They show the progress of the crack front from the´beachmarks´. They show the progress of the crack front from thepoint of originpoint of origin

The surface is 90The surface is 90°° to the loadto the load

Final fracture will usually take the form of gross yielding (as theFinal fracture will usually take the form of gross yielding (as themaximum stress in the remaining ligament increase!)maximum stress in the remaining ligament increase!)

Fatigue crack need initiation + propagation periodsFatigue crack need initiation + propagation periods

Fatigue fracture distinguish features:Fatigue fracture distinguish features:

Object of test:Object of test:

Bend TestsBend Tests 4.154.15



4/23/20074/23/2007 136136 of 691of 691


To determine the soundness of the weld zone. BendTo determine the soundness of the weld zone. Bend

testing can also be used to give an assessment of testing can also be used to give an assessment of

weld zone ductility.weld zone ductility.

There are three ways to perform a bend test:There are three ways to perform a bend test:

Root bendRoot bend

Face bendFace bend

Side bendSide bend

Side bend tests are normally carried out on welds over 12mm in thicknessSide bend tests are normally carried out on welds over 12mm in thickness

Bending testBending test 4.164.16



4/23/20074/23/2007 137137 of 691of 691

Types of bend test for welds (acc. BS EN 910):Types of bend test for welds (acc. BS EN 910):

Thickness of materialThickness of material -- ³t´³t´

³t´ up to 12 mm³t´ up to 12 mm

³t´ over 12 mm³t´ over 12 mm

Root / faceRoot / face

bendbend

Side bendSide bend

Fillet Weld Fracture TestsFillet Weld Fracture Tests 4.174.17



4/23/20074/23/2007 138138 of 691of 691


To break open the joint through the weld to permitTo break open the joint through the weld to permitexamination of the fracture surfacesexamination of the fracture surfaces

Specimens are cut to the required lengthSpecimens are cut to the required length

A saw cut approximately 2mm in depth is applied A saw cut approximately 2mm in depth is appliedalong the fillet welds lengthalong the fillet welds length

Fracture is usually made by striking the specimenFracture is usually made by striking the specimenwith a single hammer blowwith a single hammer blow

Visual inspection for defectsVisual inspection for defects




4/23/20074/23/2007 139139 of 691of 691

Fracture should break weld saw cut to rootFracture should break weld saw cut to root

2mm2mm

NotchNotch

Hammer Hammer




4/23/20074/23/2007 140140 of 691of 691

This fracture indicatesThis fracture indicates

lack of fusionlack of fusionThis fracture hasThis fracture has

occurred saw cut to rootoccurred saw cut to root

Lack of PenetrationLack of Penetration

NickNick--Break TestBreak Test 4.184.18



4/23/20074/23/2007 141141 of 691of 691


To permit evaluation of any weld defects acrossTo permit evaluation of any weld defects across

the fracture surface of a butt weld.the fracture surface of a butt weld.

Specimens are cut transverse to the weldSpecimens are cut transverse to the weld

A saw cut approximately 2mm in depth is applied A saw cut approximately 2mm in depth is applied

along the welds root and capalong the welds root and cap

Fracture is usually made by striking the specimen withFracture is usually made by striking the specimen with

a single hammer blowa single hammer blow

Visual inspection for defectsVisual inspection for defects

NickNick--Break TestBreak Test 4.184.18



4/23/20074/23/2007 142142 of 691of 691

Approximately 230 mmApproximately 230 mm

19 mm19 mm

2 mm2 mm

2 mm2 mm

Notch cut by hacksawNotch cut by hacksaw

Weld reinforcementWeld reinforcement

may or may not bemay or may not be

removedremoved

Nick Break TestNick Break Test 4.184.18



4/23/20074/23/2007 143143 of 691of 691

Inclusions on fractureInclusions on fracture

linelineLack of root penetrationLack of root penetration

or fusionor fusion

Alternative nickAlternative nick--break testbreak test

specimen, notch applied allspecimen, notch applied all

way around the specimenway around the specimen

Summary of Mechanical TestingSummary of Mechanical Testing 4.194.19



4/23/20074/23/2007 144144 of 691of 691

We test welds to establish minimum levels of mechanical

properties, and soundness of the welded joint

We divide tests into Qualitative & Quantitative methods:

Qualitative: (Have no units/numbers)

For assessing joint quality

Macro tests

Bend tests

Fillet weld fracture tests

Butt Nick break tests

Quantitative: (Have units/numbers)

To measure mechanical properties

Hardness (VPN & BHN)

Toughness (Joules & ft.lbs)

Strength (N/mm2 & PSI, MPa)

Ductility / Elongation (E%)

Welding InspectorWelding Inspector



4/23/20074/23/2007 145145 of 691of 691

e d g spectoe d g specto

WPSWPS ± ± Welder QualificationsWelder Qualifications

Section 5Section 5

Welding Procedure QualificationWelding Procedure Qualification 5.15.1



4/23/20074/23/2007 146146 of 691of 691

Question:Question:

What is the main reason for carrying out a Welding ProcedureWhat is the main reason for carrying out a Welding ProcedureQualification Test ?Qualification Test ?

(What is t he test trying to show ?)(What is t he test trying to show ?)

Answer:Answer:

To show that the welded joint has theTo show that the welded joint has the propertiesproperties** that satisfythat satisfythe design requirements (fit for purpose)the design requirements (fit for purpose)

* p* propertiesroperties

mechanical properties are the main interestmechanical properties are the main interest -- always strengthalways strength butbuttoughness & hardness may be important for some applicationstoughness & hardness may be important for some applications

test also demonstrates that the weld can be made without defectstest also demonstrates that the weld can be made without defects

Welding ProceduresWelding Procedures 5.15.1



4/23/20074/23/2007 147147 of 691of 691

Producing a welding procedure involves:Producing a welding procedure involves:

Planning the tasksPlanning the tasks

Collecting the dataCollecting the data

Writing a procedure for use of for trialWriting a procedure for use of for trial

Making a test weldsMaking a test welds

Evaluating the resultsEvaluating the results

Approving the procedure Approving the procedure

Preparing the documentationPreparing the documentation

In most codes reference is made to how the procedure are toIn most codes reference is made to how the procedure are to




4/23/20074/23/2007 148148 of 691of 691

In most codes reference is made to how the procedure are toIn most codes reference is made to how the procedure are to

be devised and whether approval of these procedures isbe devised and whether approval of these procedures is

required.required.The approach used for procedure approval depends on theThe approach used for procedure approval depends on the

code:code:

Example codes:Example codes:

AWS D.1.1: Structural Steel Welding CodeAWS D.1.1: Structural Steel Welding Code

BS 2633: Class 1 welding of Steel Pipe WorkBS 2633: Class 1 welding of Steel Pipe Work

API 1104: Welding of PipelinesAPI 1104: Welding of Pipelines

BS 4515: Welding of Pipelines over 7 Bar BS 4515: Welding of Pipelines over 7 Bar

Other codes may not specifically deal with the requirement of Other codes may not specifically deal with the requirement of

a procedure but may contain information that may be used ina procedure but may contain information that may be used in

writing a weld procedurewriting a weld procedure

EN 1011Process of Arc Welding SteelsEN 1011Process of Arc Welding Steels




4/23/20074/23/2007 149149 of 691of 691

The welding engineer writesThe welding engineer writes qualified Welding ProcedureWelding Procedure

Specifications (WPS) for production weldingSpecifications (WPS) for production welding

ProductionProduction welding conditions must remain within themust remain within the range of

qualification allowed by the WPQR

( according to EN ISO 15614)( according to EN ISO 15614)




4/23/20074/23/2007 150150 of 691of 691

( according to EN Standards)( according to EN Standards)

welding conditionswelding conditions are calledare called welding variableswelding variables

welding variables are classified by the EN ISO Standard as:welding variables are classified by the EN ISO Standard as:

Essential variablesEssential variables

NonNon--essential variablesessential variablesAdditional variablesAdditional variables

Note:Note: additional variables = ASME supplementary essential additional variables = ASME supplementary essential

TheThe range of qualificationrange of qualification for production welding is based onfor production welding is based on

the limits that the EN ISO Standard specifies for the limits that the EN ISO Standard specifies for essentialessentialvariables*variables*

( ( ** and when applicableand when applicable - - t he additional variables)t he additional variables)




4/23/20074/23/2007 151151 of 691of 691


WELDING ESSENTIALWELDING ESSENTIAL VARIABLESVARIABLES

Question:Question:

Why are some welding variables classified asWhy are some welding variables classified as essential essential ??

Answer:Answer:

A variable, that if changed beyond certain limits (specified byA variable, that if changed beyond certain limits (specified by

the Welding Standard) may havethe Welding Standard) may have a significant effecta significant effect on theon the

propertiesproperties* of the joint* of the joint

* particularly joint strengt h and ductility * particularly joint strengt h and ductility




4/23/20074/23/2007 152152 of 691of 691


SOME TYPICALSOME TYPICAL ESSENTIALESSENTIAL VARIABLESVARIABLES

Welding ProcessWelding Process

Post Weld Heat Treatment (PWHT)Post Weld Heat Treatment (PWHT)

Material TypeMaterial Type

Electrode Type, Filler Wire Type (Classification)Electrode Type, Filler Wire Type (Classification) Material ThicknessMaterial Thickness

Polarity (AC, DC+ve / DCPolarity (AC, DC+ve / DC--ve)ve)

PrePre--Heat TemperatureHeat Temperature

Heat InputHeat Input Welding PositionWelding Position




4/23/20074/23/2007 153153 of 691of 691

Components of a welding procedureComponents of a welding procedure

Parent materialParent materialType (Grouping)Type (Grouping)

ThicknessThickness

Diameter (Pipes)Diameter (Pipes)

Surface condition)Surface condition)

Welding processWelding processType of process (MMA, MAG, TIG, SAW etc)Type of process (MMA, MAG, TIG, SAW etc)

Equipment parametersEquipment parameters

Amps, Volts, Travel speedAmps, Volts, Travel speed

Welding ConsumablesWelding ConsumablesType of consumable/diameter of consumableType of consumable/diameter of consumable

Brand/classificationBrand/classification

Heat treatments/ storageHeat treatments/ storage




4/23/20074/23/2007 154154 of 691of 691

Components of a welding procedureComponents of a welding procedure

Joint designJoint designEdge preparationEdge preparation

Root gap, root faceRoot gap, root face

Jigging and tackingJigging and tacking

Type of baking

Type of baking

Welding PositionWelding Position

Location, shop or siteLocation, shop or site

Welding position e.g. 1G, 2G, 3G etcWelding position e.g. 1G, 2G, 3G etc

Any weather precautionAny weather precaution

Thermal heat treatmentsThermal heat treatments

Preheat, tempsPreheat, temps

Post weld heat treatments e.g. stress relievingPost weld heat treatments e.g. stress relieving




4/23/20074/23/2007 155155 of 691of 691

Object of a welding procedure testObject of a welding procedure test

To give maximum confidence that the welds mechanicalTo give maximum confidence that the welds mechanicaland metallurgical properties meet the requirements of theand metallurgical properties meet the requirements of the

applicable code/specification.applicable code/specification.

Each welding procedure will show a range to which theEach welding procedure will show a range to which the

procedure is approved (extent of approval)procedure is approved (extent of approval)

If a customer queries the approval evidence can beIf a customer queries the approval evidence can be

supplied to prove its validitysupplied to prove its validity

Welding ProceduresWelding Procedures



4/23/20074/23/2007 156156 of 691of 691

Summary of designations:Summary of designations:

pWPS:pWPS: Preliminary Welding Procedure SpecificationPreliminary Welding Procedure Specification

(Before procedure approval)(Before procedure approval)

WPAR (WPQR):WPAR (WPQR): Welding Procedure Approval RecordWelding Procedure Approval Record

(Welding procedure Qualification record)(Welding procedure Qualification record)

WPS:WPS: Welding Procedure SpecificationWelding Procedure Specification

(After procedure approval)(After procedure approval)



4/23/20074/23/2007 157157 of 691of 691

Example:Example:

W elding W elding

ProcedureProcedure

Speci f icationSpeci f ication

(W PS)(W PS)

Welder QualificationWelder Qualification 5.45.4



4/23/20074/23/2007 158158 of 691of 691

Numerous codes and standards deal with welder qualification,Numerous codes and standards deal with welder qualification,

e.g. BS EN 287.e.g. BS EN 287.

Once the content of the procedure is approved the nextOnce the content of the procedure is approved the next

stage is to approve the welders to the approved procedure.stage is to approve the welders to the approved procedure.

A welders test know as aA welders test know as a W elders Quali f ication Test (W QT).W elders Quali f ication Test (W QT).

Object of a welding qualification test:Object of a welding qualification test:

To give maximum confidence that the welder meets theTo give maximum confidence that the welder meets the

quality requirements of the approved procedure (WPS).quality requirements of the approved procedure (WPS).

The test weld should be carried out on the same material andThe test weld should be carried out on the same material and

same conditions as for the production welds.same conditions as for the production welds.

Welder QualificationWelder Qualification 5.4 & 5.55.4 & 5.5



4/23/20074/23/2007 159159 of 691of 691


Question:Question:

What is the main reason for qualifying a welder ?What is the main reason for qualifying a welder ?

Answer:Answer:

To show that he has the skill to be able to make productionTo show that he has the skill to be able to make production

welds that are free from defectswelds that are free from defects

Note:Note: when w elding in accordancew it h a Quali f ied W PS when w elding in accordancew it h a Quali f ied W PS


( according to EN 287 )( according to EN 287 )



4/23/20074/23/2007 160160 of 691of 691

The welder is allowed to make production welds within theThe welder is allowed to make production welds within the

range of qualification shown on theCertificaterange of qualification shown on theCertificateTheThe range of qualification allowed for production welding isrange of qualification allowed for production welding is

based on the limits that the EN Standard specifies for thebased on the limits that the EN Standard specifies for the

welder qualification essential variables

A Certificate may be withdrawn by the Employer if there isA Certificate may be withdrawn by the Employer if there is

reason to doubt the ability of the welder, for examplereason to doubt the ability of the welder, for example a high repair ratea high repair rate

not working in accordance with a qualified WPSnot working in accordance with a qualified WPS

The qualification shall remain valid for 2 years provided there is certifiedThe qualification shall remain valid for 2 years provided there is certifiedconfirmation of welding to the WPS in that time.confirmation of welding to the WPS in that time.

A Welder¶s Qualification Certificate automatically expires if the welder has notA Welder¶s Qualification Certificate automatically expires if the welder has not

used the welding process for 6 months or longer.used the welding process for 6 months or longer.

W ldi E i itW ldi E i it li i W ldi P dW ldi P d





4/23/20074/23/2007 161161 of 691of 691

Welding Engineer writes aWelding Engineer writes a preliminary Welding ProcedureWelding Procedure

Specification (Specification (ppWPS) for each test weld to be madeWPS) for each test weld to be made

A welder makes a test weld in accordance with theA welder makes a test weld in accordance with the ppWPSWPS

A welding inspector records all the welding conditions usedA welding inspector records all the welding conditions used

for the test weld (referred to as the µasfor the test weld (referred to as the µas--run¶ conditions)run¶ conditions)

An Independent Examiner/ Examining Body/ T hird Party An Independent Examiner/ Examining Body/ T hird Party

inspector inspector may may bebe requested to monitor t he quali f icationrequested to monitor t he quali f ication

process process

The finished test weld is subjected to NDT in accordance withThe finished test weld is subjected to NDT in accordance withthe methods specified by the EN ISO Standardthe methods specified by the EN ISO Standard -- Visual, MT or Visual, MT or

PT & RT or UTPT & RT or UT





4/23/20074/23/2007 162162 of 691of 691

Test weld is subjected to destructive testing (tensile, bend,Test weld is subjected to destructive testing (tensile, bend,

macro)macro)

The Application Standard, or Client, may require additionalThe Application Standard, or Client, may require additional

tests such as impact tests, hardness tests (and for sometests such as impact tests, hardness tests (and for some

materialsmaterials -- corrosion tests)corrosion tests)

AA Welding Procedure Qualification Record (WPQR) is preparedis preparedgiving details of:giving details of: --

The welding conditions used for the test weldThe welding conditions used for the test weld

Results of the NDTResults of the NDT

Results of the destructive testsResults of the destructive tests

T

he welding conditions that the test weld allows for T

he welding conditions that the test weld allows for production weldingproduction welding

TheThe Third Party may be requested to sign the WPQR as a truemay be requested to sign the WPQR as a true

recordrecord





4/23/20074/23/2007 163163 of 691of 691

An approved WPS should be available covering the range of An approved WPS should be available covering the range of qualification required for the welder approval.qualification required for the welder approval.

The welder qualifies in accordance with an approved WPSThe welder qualifies in accordance with an approved WPS

A welding inspector monitors the welding to make sure that theA welding inspector monitors the welding to make sure that thewelder uses the conditions specified by the WPSwelder uses the conditions specified by the WPS

EN W elding Standard states t hat an Independent Examiner,EN W elding Standard states t hat an Independent Examiner,

Examining Body or T hird Party Inspector Examining Body or T hird Party Inspector may may bebe required torequired to

monitor t he quali f ication processmonitor t he quali f ication process


( di t EN 287 )( di t EN 287 )



4/23/20074/23/2007 164164 of 691of 691

The finished test weld is subjected to NDT by the methodsThe finished test weld is subjected to NDT by the methods

specified by the EN Standardspecified by the EN Standard -- Visual, MT or PT & RT or UTVisual, MT or PT & RT or UT

The test weld may need to be destructively tested - for certain

materials and/or welding processes specified by the EN

Standard or the Client Specification


A Welder¶s Qualification Certificate is prepared showing theA Welder¶s Qualification Certificate is prepared showing the

conditions used for the test weld and the range of qualificationconditions used for the test weld and the range of qualification

allowed by the EN Standard for production weldingallowed by the EN Standard for production welding

The Qualification Certificate is usually endorsed by a ThirdThe Qualification Certificate is usually endorsed by a Third

Party Inspector as a true record of the testParty Inspector as a true record of the test

I f ti th t h ld b i l d d ld t t tifi tI f ti th t h ld b i l d d ld t t tifi t




4/23/20074/23/2007 165165 of 691of 691

Information that should be included on a welders test certificate are,Information that should be included on a welders test certificate are,

which the welder should have or have access to a copy of !which the welder should have or have access to a copy of !

Welders name and identification number

Date of test and expiry date of certificate

Standard/code e.g. BS EN 287

Test piece details

Welding process. Welding parameters, amps, volts

Consumables, flux type and filler classification details

Sketch of run sequence

Welding positions

Joint configuration details

Material type qualified, pipe diameter etc

Test results, remarks

Test location and witnessed by

Extent (range) of approval

Tests methods required for welder qualification (BS EN 287)Tests methods required for welder qualification (BS EN 287)

Welder QualificationWelder Qualification



4/23/20074/23/2007 166166 of 691of 691

Tests methods required for welder qualification (BS EN 287)Tests methods required for welder qualification (BS EN 287)




4/23/20074/23/2007 167167 of 691of 691

Materials InspectionMaterials Inspection

Section 6Section 6

Material InspectionMaterial InspectionOne of the most important items to consider is TraceabilityOne of the most important items to consider is Traceability..



4/23/20074/23/2007 168168 of 691of 691

One of the most important items to consider is TraceabilityOne of the most important items to consider is Traceability..

The materials are of little use if we can not, by use of anThe materials are of little use if we can not, by use of aneffective QA system trace them from specification andeffective QA system trace them from specification andpurchase order to final documentation package handed over topurchase order to final documentation package handed over tothe Client.the Client.

All materials arriving on site should be inspected for: All materials arriving on site should be inspected for:

Size / dimensionsSize / dimensions

ConditionCondition

Type / specificationType / specification

In addition other elements may need to be consideredIn addition other elements may need to be considereddepending on the materials form or shapedepending on the materials form or shape

We inspect the condition

Pipe InspectionPipe Inspection



4/23/20074/23/2007 169169 of 691of 691


(C

orrosion, Damage, Wall thickness Ovality, Laminations & Seam)

Specification

Weldedseam

Size

LP5

Other checks may need to be made such as: distortion tolerance,number of plates and storage.

Plate InspectionPlate InspectionPlate InspectionPlate Inspection



4/23/20074/23/2007 170170 of 691of 691

Size


(Corrosion, Mechanical damage, Laps, Bands &Laminations)

5L

Specification

Other checks may need to be made such as: distortiontolerance, number of plates and storage.

Parent Material ImperfectionsParent Material Imperfections

Mechanical damageMechanical damage LapLap



4/23/20074/23/2007 171171 of 691of 691

LaminationLamination

Mechanical damageMechanical damage LapLap

Segregation lineSegregation lineLaminationsLaminations are caused in the parent plate by the steel makingare caused in the parent plate by the steel making

process, originating from ingot casting defects.process, originating from ingot casting defects.

Segregation bandsSegregation bands occur in the centre of the plate and are lowoccur in the centre of the plate and are low

melting point impurities such as sulphur and phosphorous.melting point impurities such as sulphur and phosphorous.

LapsLaps are caused during rolling when overlapping metal does notare caused during rolling when overlapping metal does not

fuse to the base material.fuse to the base material.

LappingLappingLappingLapping



4/23/20074/23/2007 172172 of 691of 691

LaminationLaminationLaminationLamination



4/23/20074/23/2007 173173 of 691of 691

LaminationsLaminations



4/23/20074/23/2007 174174 of 691of 691

Plate LaminationPlate Lamination




4/23/20074/23/2007 175175 of 691of 691

Codes & StandardsCodes & Standards

Section 7Section 7

Codes & StandardsCodes & Standards

T 3 f



4/23/20074/23/2007 176176 of 691of 691

The 3 agencies generally identified in a code or standard:

The customer, or client

The manufacturer, or contractor

The 3rd party inspection, or clients representative

Codes often do not contain all relevant data, but may

refer to other standards

Standard/Codes/SpecificationsStandard/Codes/Specifications



4/23/20074/23/2007 177177 of 691of 691

STANDARDSSTANDARDS

SPECIFICATIONSSPECIFICATIONS CODESCODES

ExamplesExamples

plate, pipeplate, pipe

forgings, castingsforgings, castings

valvesvalves

electrodeselectrodes

ExamplesExamples

pressure vesselspressure vessels

bridgesbridges

pipelinespipelines

tankstanks




4/23/20074/23/2007 178178 of 691of 691

Welding SymbolsWelding Symbols

Section 8Section 8

Advantages of symbolic representation:Advantages of symbolic representation:

Weld symbols on drawingsWeld symbols on drawings



4/23/20074/23/2007 179179 of 691of 691

Advantages of symbolic representation: Advantages of symbolic representation:

simple and quick plotting on the drawingsimple and quick plotting on the drawing

does not over does not over--burden the drawingburden the drawing

no need for additional viewno need for additional view

gives all necessary indications regarding the specificgives all necessary indications regarding the specific joint to be obtained joint to be obtained

Disadvantages of symbolic representation:Disadvantages of symbolic representation:

used only for usual jointsused only for usual joints

requires training for properly understanding of symbolsrequires training for properly understanding of symbols




4/23/20074/23/2007 180180 of 691of 691

The symbolic representation includes:The symbolic representation includes:an arrow linean arrow line

a reference linea reference line

an elementary symbolan elementary symbol

The elementary symbol may be completed by:The elementary symbol may be completed by:

a supplementary symbola supplementary symbol

a means of showing dimensionsa means of showing dimensions

some complementary indicationssome complementary indications

DimensionsDimensions

Convention of dimensionsConvention of dimensions



4/23/20074/23/2007 181181 of 691of 691

In most standards the cross sectional dimensions are given toIn most standards the cross sectional dimensions are given tothe left side of the symbol, and all linear dimensions are give onthe left side of the symbol, and all linear dimensions are give on

the right sidethe right side

Convention of dimensionsConvention of dimensions

a = Design throat thickness

s = Depth of Penetration, Throat thicknessz = Leg length (min material thickness)

BS EN ISO 22553BS EN ISO 22553

AWS A2.4AWS A2.4

In a fillet weld, the size of the weld is the leg lengthIn a butt weld, the size of the weld is based on the depth of the

joint preparation

A method of transferring information from theA method of transferring information from the




4/23/20074/23/2007 182182 of 691of 691

A method of transferring information from theA method of transferring information from the

design office to the workshop is:design office to the workshop is:

The above information does not tell us much about the wishesThe above information does not tell us much about the wishes

of the designer. We obviously need some sort of code whichof the designer. We obviously need some sort of code which

would be understood by everyone.would be understood by everyone.

Most countries have their own standards for symbols.Most countries have their own standards for symbols.

Some of them are AWS A2.4 & BS EN 22553 (ISO 2553)Some of them are AWS A2.4 & BS EN 22553 (ISO 2553)

Please weldPlease weld

herehere

Weld symbols on drawings



4/23/20074/23/2007 183183 of 691of 691

Joints in drawings may be indicated:Joints in drawings may be indicated:

by detailed sketches, showing every dimensionby detailed sketches, showing every dimension

by symbolic representationby symbolic representation

Elementary Welding SymbolsElementary Welding Symbols(BS EN ISO 22553 & AWS A2.4)(BS EN ISO 22553 & AWS A2.4)



4/23/20074/23/2007 184184 of 691of 691

Convention of the elementary symbols:Convention of the elementary symbols:

Various categories of joints are characterised by an elementarysymbol.

The vertical line in the symbols for a fillet weld, single/double bevelbutts and a J-butt welds must always be on the left side.

Square edgeSquare edge

butt weldbutt weld

Weld typeWeld type SketchSketch SymbolSymbol

SingleSingle--vv

butt weldbutt weld

Elementary Welding SymbolsElementary Welding Symbols




4/23/20074/23/2007 185185 of 691of 691

SingleSingle--V buttV butt

weld with broadweld with broad

root faceroot face


SingleSinglebevel buttbevel butt

weldweldSingle bevelSingle bevel

butt weld withbutt weld with

broad rootbroad rootfaceface

Backing runBacking run

Elementary Welding SymbolsElementary Welding Symbols




4/23/20074/23/2007 186186 of 691of 691

SingleSingle--UU

butt weldbutt weld


SingleSingle--JJ

butt weldbutt weld

Fillet weldFillet weld

SurfacingSurfacing

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553



4/23/20074/23/2007 187187 of 691of 691

Plug weld

Resistance spot weld

Resistance seam weld

Square Butt weld

Steep flanked

Single-V Butt

Surfacing

Arrow LineArrow Line

(BS EN ISO 22553 & AWS A2.4):(BS EN ISO 22553 & AWS A2.4):



4/23/20074/23/2007 188188 of 691of 691

(BS EN ISO 22553 & AWS A2.4):(BS EN ISO 22553 & AWS A2.4):

Convention of the arrow line:Convention of the arrow line:

ShallShall touch the joint intersectiontouch the joint intersection

ShallShall not be parallel to the drawingnot be parallel to the drawing

ShallShall point towards a single plate preparation (when onlypoint towards a single plate preparation (when onlyone plate has preparation)one plate has preparation)

(AWS A2.4)(AWS A2.4)

Reference LineReference Line



4/23/20074/23/2007 189189 of 691of 691

( S )( S )

Convention of the reference line:Convention of the reference line:

ShallShall touch the arrow linetouch the arrow line

ShallShall be parallel to the bottom of the drawingbe parallel to the bottom of the drawing

Reference LineReference Line

(BS EN ISO 22553)(BS EN ISO 22553)



4/23/20074/23/2007 190190 of 691of 691

or or

( )( )

Convention of the reference line:Convention of the reference line:

ShallShall touch the arrow linetouch the arrow line

ShallShall be parallel to the bottom of the drawingbe parallel to the bottom of the drawing

There shallThere shall be a further broken identification line above or be a further broken identification line above or beneath the reference line (Not necessary where the weldbeneath the reference line (Not necessary where the weld

is symmetrical!)is symmetrical!)

(BS EN ISO 22553 & AWS A2.4)(BS EN ISO 22553 & AWS A2.4)

Double side weld symbolsDouble side weld symbols



4/23/20074/23/2007 191191 of 691of 691

( )( )

Convention of the double side weld symbols:Convention of the double side weld symbols:

Representation of welds done fromRepresentation of welds done from bot h sidesbot h sides of the jointof the joint

intersection, touched by the arrow headintersection, touched by the arrow head

Fillet weldFillet weld

Double VDouble V

Double bevelDouble bevel

Double UDouble U

Double JDouble J

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553



4/23/20074/23/2007 192192 of 691of 691

Arrow lineArrow line

Reference linesReference lines

Arrow sideArrow side

Other sideOther side Arrow sideArrow side

Other sideOther side

M RM R

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553



4/23/20074/23/2007 193193 of 691of 691

SingleSingle--V Butt flush capV Butt flush cap SingleSingle--U Butt with sealing runU Butt with sealing run

SingleSingle--V Butt withV Butt withpermanent backing strippermanent backing strip

MM

SingleSingle--U Butt withU Butt withremovable backing stripremovable backing strip

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553



4/23/20074/23/2007 194194 of 691of 691

SingleSingle--bevel buttbevel butt DoubleDouble--bevel buttbevel butt

SingleSingle--bevel buttbevel butt SingleSingle--J buttJ butt

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553



4/23/20074/23/2007 195195 of 691of 691

Partial penetration singlePartial penetration single--V buttV butt

µS¶ indicates the depth of penetrationµS¶ indicates the depth of penetration

ss1010

10101515

aa = Design throat thickness= Design throat thickness

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553



4/23/20074/23/2007 196196 of 691of 691

ss = Depth of Penetration,T

hroat= Depth of Penetration,T

hroatthicknessthickness

zz = Leg length(min material thickness)= Leg length(min material thickness)

aa = (= (00..77 x z)x z)

a 4a 4

4mm Design throat4mm Design throat

z 6z 6

6mm leg6mm leg

az s

s 6s 66mm Actual throat6mm Actual throat

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553



4/23/20074/23/2007 197197 of of 691691



ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

s6



4/23/20074/23/2007 198198 of 691of 691



s6

6mm fillet weld

nn = number of weld elements= number of weld elements

ISOISO 25532553 / BS EN/ BS EN 2255322553



4/23/20074/23/2007 199199 of 691of 691

u be o e d e e e tsu be o e d e e e ts

l l = length of each weld element= length of each weld element((ee)) = distance between each weld element= distance between each weld element

nn xx l l ((ee))

Welds to beWelds to bestaggeredstaggered

ProcessProcess

2 x 402 x 40 (50)(50)

3 x 403 x 40 (50)(50)111111

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

All di i iAll di i i



4/23/20074/23/2007 200200 of 691of 691

80 80 80

909090

6

6

5

5

z5z5

z6z6

3 x 80 (90)3 x 80 (90)

33 xx 8080 ((9090))

All dimensions in mmAll dimensions in mm

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553

All di i iAll di i i



4/23/20074/23/2007 201201 of 691of 691

All dimensions in mmAll dimensions in mm

8

8

6

6 80 80 80

909090

z8z8

z6z6

3 x 80 (90)3 x 80 (90)

33 xx 8080 ((9090))

Supplementary symbolsSupplementary symbols(BS EN ISO(BS EN ISO 2255322553 & AWS A& AWS A22..44))

Convention of supplementary symbolsConvention of supplementary symbols



4/23/20074/23/2007 202202 of 691of 691

Concave or ConvexConcave or Convex

Toes to be ground smoothlyToes to be ground smoothly

(BS EN only)(BS EN only)

Site WeldSite Weld

Weld all roundWeld all round


Supplementary informationSupplementary information such as welding process, weldprofile, NDT and any special instructions

Supplementary symbolsSupplementary symbols

(BS EN ISO 22553 & AWS A2.4)(BS EN ISO 22553 & AWS A2.4)



4/23/20074/23/2007 203203 of 691of 691

Further supplementary information, such as WPS number, or Further supplementary information, such as WPS number, or

NDT may be placed in the fish tailNDT may be placed in the fish tail

Ground flushGround flush

111111

Welding processWelding process

numerical BS ENnumerical BS EN

MRMR

RemovableRemovable

backing stripbacking strip

PermanentPermanent

backing stripbacking strip

MM


Supplementary informationSupplementary information such as welding process, weld profile,

NDT and any special instructions

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553



4/23/20074/23/2007 204204 of 691of 691

bbaa

ddcc

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553



44//2323//20072007 205205 of 691of 691

ConvexConvexMitreMitre

ToesToesshall beshall be

blendedblended

ConcaveConcave

aa = Design throat thickness= Design throat thickness

TT

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553



4/23/20074/23/2007 206206 of 691of 691

ss = Depth of Penetration,T

hroat= Depth of Penetration,T

hroatthicknessthickness

zz = Leg length(min material thickness)= Leg length(min material thickness)

aa = (0.7 x z)= (0.7 x z)

a 4a 4

4mm Design throat4mm Design throat

z 6z 6

66mm legmm leg

az s

s 6s 6

6mm Actual throat6mm Actual throat

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553Complimentary SymbolsComplimentary Symbols



44//2323//20072007 207207 of 691of 691

Field weld (site weld)Field weld (site weld)

The component requiresThe component requiresNDT inspectionNDT inspection

WPSWPS

Additional information,Additional information,the reference documentthe reference document

is included in the boxis included in the box

Welding to be carried outWelding to be carried out

all round componentall round component

(peripheral weld)(peripheral weld)

NDTNDT

Numerical Values for Welding Processes:Numerical Values for Welding Processes:

ISO 2553 / BS EN 22553ISO 2553 / BS EN 22553



44//2323//20072007 208208 of 691of 691

111:111: MMA welding with covered electrodeMMA welding with covered electrode

121:121: SubSub--arc welding with wire electrodearc welding with wire electrode

131:131: MIG welding with inert gas shieldMIG welding with inert gas shield

135:135: MAG welding with nonMAG welding with non--inert gas shieldinert gas shield

136:136: Flux core arc weldingFlux core arc welding

141:141: TIG weldingTIG welding

311:311: OxyOxy--acetylene weldingacetylene welding

72:72: ElectroElectro--slag weldingslag welding

15:15: Plasma arc weldingPlasma arc welding



4/23/20074/23/2007 209209 of 691of 691

AWS A2.4 Welding Symbols AWS A2.4 Welding Symbols

AWS Welding Symbols AWS Welding Symbols



4/23/20074/23/2007 210210 of 691of 691

11(1(1--1/8)1/8)6060oo

1/81/8

Depth of Depth of

BevelBevel

EffectiveEffective

ThroatThroat

Root OpeningRoot Opening

Groove AngleGroove Angle




4/23/20074/23/2007 211211 of 691of 691

11(1(1--1/8)1/8)6060oo

1/81/8

GSFCAWGSFCAW

Welding ProcessWelding Process

GMAWGMAW

GTAWGTAW

SAWSAW

Welds to beWelds to be




4/23/20074/23/2007 212212 of 691of 691

33 ± ± 1010

33 ± ± 1010

staggeredstaggered

SMAWSMAW

ProcessProcess

1010

33 33




4/23/20074/23/2007 213213 of 691of 691

1(1-1/8)

60o

1/8

FCAW

Sequence of Operations

1st Operation

2nd Operation

3rd Operation




44//2323//20072007 214214 of 691of 691

1(1-1/8)

60o

1/8

FCAW

Sequence of Operations

RT

MT

MT

Dimensions- Leg Length




4/23/20074/23/2007 215215 of 691of 691

6/8

6 leg on member A

8

6Member A

Member B

Welds ³Welds ³on arrow side´on arrow side´ of joint goof joint go underneathunderneath thethe

³³

AWS A 2.4 rules



4/23/20074/23/2007 216216 of 691of 691

reference line whilereference line while weldswelds the other side´the other side´ of the joint, goof the joint, goon topon top of the reference lineof the reference line

Symbols with aSymbols with a vertical linevertical line component must be drawncomponent must be drawn

with the vertical line to thewith the vertical line to the left sideleft side of the symbolof the symbol

AllAll CSACSA dimensions are shown to thedimensions are shown to the leftleft of the symbolof the symbol

AllAll linear linear dimensions are shown on thedimensions are shown on the rightright of theof the

symbol i.e. number of welds, length of welds, length of symbol i.e. number of welds, length of welds, length of

any spacesany spaces

Included angle and root opening are shown onIncluded angle and root opening are shown on toptop of theof the

symbolsymbol

AWS A 2.4 rules-example



4/23/20074/23/2007 217217 of 691of 691

1010 3 x 50 (70)3 x 50 (70)

1010

5050

7070

Fillet weld dimensions according AWS A 2.4Fillet weld dimensions according AWS A 2.4

Fillet weldsFillet welds



4/23/20074/23/2007 218218 of 691of 691

8888

55

5 x 85 x 8

88

5 leg on5 leg on

verticalvertical

member member

Intermittent fillet weldsIntermittent fillet welds

Chain intermittent fillet weldChain intermittent fillet weld



4/23/20074/23/2007 219219 of 691of 691

length (l)length (l)pitch (e)pitch (e)zz

zz

ll -- eezz

ll -- ee

Symbol to AWS A2.4Symbol to AWS A2.4

Intermittent fillet weldsIntermittent fillet welds

Staggered intermittent fillet weldStaggered intermittent fillet weld



4/23/20074/23/2007 220220 of 691of 691

length (l)length (l)pitch (e)pitch (e)

zz

zz ll -- ee

zz ll -- eeSymbol to AWS ASymbol to AWS A22..44

e/2e/2




4/23/20074/23/2007 221221 of 691of 691

Intro To Welding ProcessesIntro To Welding Processes

Section 9Section 9

Welding is regarded as a joining process in which the workWelding is regarded as a joining process in which the work

pieces are in atomic contactpieces are in atomic contact

Welding ProcessesWelding Processes



4/23/20074/23/2007 222222 of 691of 691

Pressure weldingPressure welding

Forge weldingForge welding

Friction weldingFriction welding

Resistance WeldingResistance Welding

Fusion weldingFusion welding

OxyOxy--acetyleneacetylene

MMA (SMAW)MMA (SMAW)

MIG/MAG (GMAW)MIG/MAG (GMAW) TIG (GTAW)TIG (GTAW)

SubSub--arc (SAW)arc (SAW)

ElectroElectro--slag (ESW)slag (ESW)

Laser Beam (LBW)Laser Beam (LBW)

ElectronElectron--Beam (EBW)Beam (EBW)

The four essential factors for fusion welding:The four essential factors for fusion welding:

Welding ProcessesWelding Processes



4/23/20074/23/2007 223223 of 691of 691

1.1. Fusion is achieved by melting using a high intensity heatFusion is achieved by melting using a high intensity heatsourcesource

2.2. The welding process must be capable of removing anyThe welding process must be capable of removing any

oxide and contamination from the jointoxide and contamination from the joint

3.3. Atmosphere contamination must be avoidedAtmosphere contamination must be avoided

4.4. The welded joint must possess the mechanical propertiesThe welded joint must possess the mechanical properties

required by the specification being adaptedrequired by the specification being adapted

Process Electrical characteristic Electrode current type

Welding Process ComparisonWelding Process Comparison



44//2323//20072007 224224 of 691of 691

MMA Drooping / constant current DC+ve, DC-ve, AC

TIG Drooping / constant current DC-ve, AC

MIG/MAG Flat / constant voltage DC+ve,

MAG FCAW Flat / constant voltage DC+ve, DC-ve,

Sub-arc DC+ve, DC-ve, AC

Electro-slag Flat / constant voltage DC+ve,

Drooping / constant current >1000amp

Flat / constant voltage <1000amp

100100

Constant Current Pow er SourceConstant Current Pow er Source( Drooping C haracteristic)( Drooping C haracteristic)



4/23/20074/23/2007 225225 of 691of 691

2020 80804040 6060 130130 140140120120100100 180180160160 200200

1010

6060

5050

4040

3030

2020

8080

7070

9090

Normal OperatingNormal Operating

Voltage RangeVoltage Range

Large voltage variation, e.g.Large voltage variation, e.g. ++

1010v (due to changes in arcv (due to changes in arc

length)length)

Small amperage changeSmall amperage changeresulting in virtually constantresulting in virtually constant

current e.g.current e.g. ++ 5A.5A.

V o l t a g e

V o l t a g e

Amperage Amperage

Required for: MMA, TIG, PlasmaRequired for: MMA, TIG, Plasma

arc and SAW > 1000 AMPSarc and SAW > 1000 AMPS

O.C.V. Striking voltage (typical) for O.C.V. Striking voltage (typical) for arc initiationarc initiation

ARC CHARACTERISTICS ARC CHARACTERISTICSConstant Voltage Characteristic



44//2323//20072007 226226 of of 691691

Volts

Amps

OCV Small change in voltage =

large change in amperage

The self

adjusting arc.

Large arc gap

Small arc gap

Large & momentary change in

current due to arc gap

Monitoring Heat InputMonitoring Heat Input

Heat Input:Heat Input:



44//2323//20072007 227227 of of 691691

The amount of heat generated in theThe amount of heat generated in the

welding arc per unit length of weld.welding arc per unit length of weld.

Expressed in kilo Joules per millimetreExpressed in kilo Joules per millimetre

length of weld (kJ/mm).length of weld (kJ/mm).

Heat Input (kJ/mm)=Heat Input (kJ/mm)= Volts x AmpsVolts x Amps

Travel speed(mm/s) x 1000Travel speed(mm/s) x 1000




4/23/20074/23/2007 228228 of 691of 691

Weld and weld pool temperatures




4/23/20074/23/2007 229229 of 691of 691


Monitoring Heat Input As Required byMonitoring Heat Input As Required by



4/23/20074/23/2007 230230 of 691of 691

BS EN ISOBS EN ISO 1561415614--11::20042004

In accordance with ENIn accordance with EN 10111011--11::19981998When impact requirements and/or hardness requirements

are specified, impact test shall be taken from the weld inthe highest heat input position and hardness tests shall be

taken from the weld in the lowest heat input position in

order to qualify for all positions




4/23/20074/23/2007 231231 of 691of 691

MMA WeldingMMA WeldingSection 10Section 10

Manual Metal Arc IntroductionManual Metal Arc Introduction



4/23/20074/23/2007 232232 of of 691691

The MMA welding Process was first developed in the lateThe MMA welding Process was first developed in the late 1919thth

century using bare wire consumables.century using bare wire consumables.

MMA is a simple process in terms of equipmentMMA is a simple process in terms of equipment

The process can by used in AC, DC+ or DCThe process can by used in AC, DC+ or DC--

The process is a manual process and demands aThe process is a manual process and demands a highhighskill from the welder.skill from the welder.

The process is widely used throughout the weldingThe process is widely used throughout the welding

industry both for shop and site working conditionsindustry both for shop and site working conditions

MMAMMA -- Principle of operationPrinciple of operation



4/23/20074/23/2007 233233 of 691of 691

MMA weldingMMA welding



4/23/20074/23/2007 234234 of of 691691

Main features:Main features:Shielding provided by decomposition of flux coveringShielding provided by decomposition of flux covering

Electrode consumableElectrode consumable

Manual processManual process

Welder controls:Welder controls:

Arc length Arc length

Angle of electrode Angle of electrode

Speed of travelSpeed of travel

Amperage settings Amperage settings

Manual Metal Arc Basic EquipmentManual Metal Arc Basic Equipment



4/23/20074/23/2007 235235 of 691of 691

Power sourcePower source

Holding ovenHolding oven

Inverter power Inverter power

sourcesource

Electrode holder Electrode holder

Power cablesPower cablesWelding visor Welding visor filter glassfilter glass

Return leadReturn lead

ElectrodesElectrodes

ElectrodeElectrode

ovenoven

Control panelControl panel

(amps, volts)(amps, volts)

Transformer:Transformer:

MMA Welding PlantMMA Welding Plant



4/23/20074/23/2007 236236 of 691of 691

Changes mains supply voltage to a voltage suitable for welding.Changes mains supply voltage to a voltage suitable for welding.Has no moving parts and is often termed static plant.Has no moving parts and is often termed static plant.

Rectifier:Rectifier:

Changes a.c. to d.c., can be mechanically or statically achieved.Changes a.c. to d.c., can be mechanically or statically achieved.

Generator:Generator:

Produces welding current. The generator consists of an armatureProduces welding current. The generator consists of an armaturerotating in a magnetic field, the armature must be rotated at arotating in a magnetic field, the armature must be rotated at a

constant speed either by a motor unit or, in the absence of constant speed either by a motor unit or, in the absence of electrical power, by an internal combustion engine.electrical power, by an internal combustion engine.

Inverter:Inverter:

An inverter changes d.c. to a.c. at a higher frequency. An inverter changes d.c. to a.c. at a higher frequency.

VoltageVoltage

The arc voltage in the MMA process is measured as close toThe arc voltage in the MMA process is measured as close to

th ibl It i i bl ith h i l thth ibl It i i bl ith h i l th

MMA Welding VariablesMMA Welding Variables



4/23/20074/23/2007 237237 of 691of 691

the arc as possible. It is variable with a change in arc lengththe arc as possible. It is variable with a change in arc length

O.C.V.O.C.V.

The open circuit voltage is the voltage required to initiate, or The open circuit voltage is the voltage required to initiate, or

rere--ignite the electrical arc and will change with the type of ignite the electrical arc and will change with the type of

electrode being used e.g 70electrode being used e.g 70--90 volts90 volts

CurrentCurrent

The current used will be determined by the choice of The current used will be determined by the choice of

electrode, electrode diameter and material type andelectrode, electrode diameter and material type and

thickness. Current has the most effect on penetration.thickness. Current has the most effect on penetration.

PolarityPolarity Polarity is generally determined by operation and electrodePolarity is generally determined by operation and electrode

type e.g DC +ve, DC type e.g DC +ve, DC ± ±ve or ACve or AC

OCV open circuit voltsOCV open circuit volts

A check should be made to ensure that the equipment canA check should be made to ensure that the equipment can

d th OCV i d b th bl d th td th OCV i d b th bl d th t

MMA Welding ChecksMMA Welding Checks



4/23/20074/23/2007 238238 of 691of 691

produce the OCV required by the consumable and that anyproduce the OCV required by the consumable and that anyvoltage selector has been moved to the correct positionvoltage selector has been moved to the correct position

Current & polarityCurrent & polarity

A check should be made to ensure the current type and rangeA check should be made to ensure the current type and range

is as detailed on the WPSis as detailed on the WPS

Other variablesOther variables

Checks should be made for correct electrode angle, arc gapChecks should be made for correct electrode angle, arc gap

and travel speedand travel speed

SafetySafety

Check should be made on the current carrying capacity, or Check should be made on the current carrying capacity, or

duty cycle of the equipment and all electrical insulation isduty cycle of the equipment and all electrical insulation is

sound and in place.Correct extraction systems should be insound and in place.Correct extraction systems should be in

use to avoid exposure to toxic fume.use to avoid exposure to toxic fume.

100100

O C V St iki lt (t i l) fO C V St iki lt (t i l) f

Constant Current Power SourceConstant Current Power Source(Drooping Characteristic)(Drooping Characteristic)



4/23/20074/23/2007 239239 of 691of 691

2020 80804040 6060 130130 140140120120100100 180180160160 200200

1010

6060

5050

4040

3030

2020

8080

7070

9090

Normal OperatingNormal Operating

Voltage RangeVoltage Range

Large voltage variation, e.g.Large voltage variation, e.g. ++

10v (due to changes in arc10v (due to changes in arc

length)length)

Small amperage changeSmall amperage change

resulting in virtually constantresulting in virtually constant

current e.g.current e.g. ++ 5A.5A.

V o l t a g

e

V o l t a g

e

Amperage Amperage

O.C.V. Striking voltage (typical) for arcO.C.V. Striking voltage (typical) for arcinitiationinitiation

MMA welding parametersMMA welding parameters

Travel speedTravel speed



4/23/20074/23/2007 240240 of 691of 691

TravelTravel

speedspeed Too highToo highToo lowToo low

wide weld bead contour wide weld bead contour

lack of penetrationlack of penetration

burnburn--throughthrough

lack of root fusionlack of root fusion

incomplete rootincomplete root


undercutundercut

poor bead profile,poor bead profile,

difficult slag removaldifficult slag removal


Type of current:Type of current:

lt d i ldi bl i l ith AClt d i ldi bl i l ith AC



4/23/20074/23/2007 241241 of 691of 691

voltage drop in welding cables is lower with ACvoltage drop in welding cables is lower with ACinductive looses can appear with AC if cables are coiledinductive looses can appear with AC if cables are coiled

cheaper power source for ACcheaper power source for AC

no problems with arc blow with ACno problems with arc blow with AC

DC provides a more stable and easy to strike arc,DC provides a more stable and easy to strike arc,especially with low current,especially with low current, better positional weld, thinbetter positional weld, thin

sheet applicationssheet applications

welding with a short arc length (low arc voltage) is easier welding with a short arc length (low arc voltage) is easier

with DC,with DC, better mechanical propertiesbetter mechanical properties

DC provides a smoother metal transfer, less spatter DC provides a smoother metal transfer, less spatter


Welding currentWelding current

35 A/ f di t35 A/ f di t



44//2323//20072007 242242 of of 691691

± ± approx. 35 A/mm of diameter approx. 35 A/mm of diameter ± ± governed by thickness, type of joint and weldinggoverned by thickness, type of joint and welding

positionposition

WeldingWelding

currentcurrentToo highToo highToo lowToo low

poor startingpoor starting

slag inclusionsslag inclusions

weld bead contour tooweld bead contour too

highhighlack of lack of

fusion/penetrationfusion/penetration

spatter spatter

excessexcess


undercutundercutburnburn--throughthrough


Arc length = arc voltage Arc length = arc voltage

ArcArc



44//2323//20072007 243243 of of 691691

ArcArcvoltagevoltage Too highToo highToo lowToo low

arc can be extinguishedarc can be extinguished

³stubbing´³stubbing´

spatter spatter

porosityporosity

excessexcesspenetrationpenetration

undercutundercut

burnburn--throughthrough

Polarity: DCEP generally gives deeper penetrationPolarity: DCEP generally gives deeper penetration

MMAMMA -- TroubleshootingTroubleshooting



44//2323//20072007 244244 of of 691691

MMA quality (left to right)MMA quality (left to right)current, arc length and travel speed normal;current, arc length and travel speed normal;

current too low;current too low;

current too high;current too high;arc length too short;arc length too short;

arc length too long;arc length too long;

travel speed too slow;travel speed too slow;

travel speed too hightravel speed too high

MMA electrode holder MMA electrode holder



4/23/20074/23/2007 245245 of 691of 691

Collet or twist typeCollet or twist type³Tongs´ type with³Tongs´ type with

springspring--loaded jawsloaded jaws

MMA Welding ConsumablesMMA Welding Consumables

MMA C d El t dMMA C d El t d



4/23/20074/23/2007 246246 of 691of 691

The three main electrode covering types used in MMA weldingThe three main electrode covering types used in MMA welding

CellulosicCellulosic -- deep penetration/fusiondeep penetration/fusion

RutileRutile -- general purposegeneral purpose

BasicBasic -- low hydrogenlow hydrogen

(Covered in more detail in Section(Covered in more detail in Section 1414))

MMA Covered ElectrodesMMA Covered Electrodes

Most welding defects in MMA are caused by a lack of welder Most welding defects in MMA are caused by a lack of welder

skill (not an easily controlled process), the incorrect settingsskill (not an easily controlled process), the incorrect settings

of the equipment or the incorrect use and treatment ofof the equipment or the incorrect use and treatment of

MMA welding typical defectsMMA welding typical defects



4/23/20074/23/2007 247247 of 691of 691

of the equipment, or the incorrect use, and treatment of of the equipment, or the incorrect use, and treatment of electrodeselectrodes

Typical Welding Defects:Typical Welding Defects:

Slag inclusionsSlag inclusions

Arc strikesArc strikes

PorosityPorosity

UndercutUndercut

Shape defects (overlap, excessive root penetration, etc.)Shape defects (overlap, excessive root penetration, etc.)

Advantages:Advantages:

Field or shop useField or shop use

Range of consumablesRange of consumables

Manual Metal Arc Welding (MMA)Manual Metal Arc Welding (MMA)



4/23/20074/23/2007 248248 of of 691691

Range of consumablesRange of consumables

All positionsAll positions

PortablePortable

Simple equipmentSimple equipment

Disadvantages:Disadvantages: High welder skill requiredHigh welder skill required

High levels of fumeHigh levels of fume

Hydrogen control (flux)Hydrogen control (flux)

Stop/start problemsStop/start problems

Comparatively uneconomic when compared withComparatively uneconomic when compared with somesomeother processes i.e MAG, SAW and FCAWother processes i.e MAG, SAW and FCAW


TIG W ldiTIG W ldi



4/23/20074/23/2007 249249 of 691of 691

TIG WeldingTIG WeldingSection 11Section 11

The TIG welding process was first developed in the USAThe TIG welding process was first developed in the USA

during theduring the 22ndnd world war for the welding of aluminum alloysworld war for the welding of aluminum alloys

Tungsten Inert Gas WeldingTungsten Inert Gas Welding



4/23/20074/23/2007 250250 of of 691691

The process uses a nonThe process uses a non--consumable tungsten electrodeconsumable tungsten electrode

The process requires a high level of welder skillThe process requires a high level of welder skill

The process produces very high quality welds.The process produces very high quality welds.

The TIG process is considered as a slow process comparedThe TIG process is considered as a slow process comparedto other arc welding processesto other arc welding processes

The arc may be initiated by a high frequency toThe arc may be initiated by a high frequency to avoid scratchavoid scratch

starting, which could causestarting, which could cause contamination of contamination of the tungstenthe tungsten

and weldand weld

TIGTIG -- Principle of operationPrinciple of operation



4/23/20074/23/2007 251251 of 691of 691

USA: GTAWUSA: GTAW




4/23/20074/23/2007 252252 of of 691691

Gas ShieldGas Shield

ArcArc

Weld PoolWeld Pool

CeramicCeramicNozzleNozzle

TungstenTungstenElectrodeElectrode

Filler WireFiller Wire

Contact TubeContact Tube

Welding TorchWelding Torch Current Conductor Current Conductor

Shielding gasShielding gas

Gas type and flow rateGas type and flow rate

Generally two types of gases are used in TIG welding, argonGenerally two types of gases are used in TIG welding, argon

and helium though nitrogen may be considered for weldingand helium though nitrogen may be considered for welding

TIG Welding VariablesTIG Welding Variables



4/23/20074/23/2007 253253 of 691of 691

and helium, though nitrogen may be considered for weldingand helium, though nitrogen may be considered for welding

copper and hydrogen may be added for the welding of copper and hydrogen may be added for the welding of

austenitic stainless steels.austenitic stainless steels.

The gas flow rate is also important.The gas flow rate is also important.

Argon (Ar) InertArgon (Ar) Inert Suitable for welding carbonSuitable for welding carbon

steel,stainless steel,steel,stainless steel,

aluminiumaluminium and magnesiumand magnesium

Lower cost, lower flow ratesLower cost, lower flow rates

More suitable for thinner More suitable for thinner

materials andmaterials and positionalpositional

weldingwelding

Helium Argon mixesHelium Argon mixes Suitable for weldingSuitable for welding

carboncarbon steel, stainlesssteel, stainless

steel,steel, copper, aluminiumcopper, aluminium

and magnesiumand magnesium

High cost, high flow ratesHigh cost, high flow rates

More suitable for thicker More suitable for thicker

materials andmaterials and materials of materials of

high thermal conductivity.high thermal conductivity.

VoltageVoltage

The voltage of the TIG welding process is variable only by theThe voltage of the TIG welding process is variable only by the




4/23/20074/23/2007 254254 of 691of 691

The voltage of the TIG welding process is variable only by theThe voltage of the TIG welding process is variable only by thetype of gas being used, and changes in the arc lengthtype of gas being used, and changes in the arc length

CurrentCurrent

The current is adjusted proportionally to the tungstenThe current is adjusted proportionally to the tungsten

electrodes diameter being used. The higher the current theelectrodes diameter being used. The higher the current thedeeper the penetration and fusiondeeper the penetration and fusion

PolarityPolarity

The polarity used for steels is always DC The polarity used for steels is always DC ± ±ve as most of theve as most of the

heat is concentrated at the +ve pole, this is required to keepheat is concentrated at the +ve pole, this is required to keepthe tungsten electrode at the cool end of the arc. Whenthe tungsten electrode at the cool end of the arc. When

welding aluminium and its alloys AC current is usedwelding aluminium and its alloys AC current is used

Transformers for AC ± aluminium alloys

Rectifiers for DC - steels

POWER SOURCE

440v 50Hz 3 phase or

TIG power sourceTIG power source



4/23/20074/23/2007 255255 of 691of 691

Sizes/types vary depending on current/applicationTORCH

To deliver correct gas flow (velocity) depending on weldingposition and joint configuration.

FLOWMETER(graduated in ltr/min)

Correct type for application.(ar, he, ar/he mixture)

Argon/hydrogen for austenitic stainless steel

INERT GAS SUPPLY

(Cylinder & regulator)

Note that current actually flows from this leadRETURN LEAD

Flexible ± may carry current, gas, cooling water.TORCH HOSE

Rectifiers for DC steelsTransformer/rectifier for AC/DC

Inverters for AC/DC ± more portable - expensive

440v 50Hz 3 phase or 240v single phase input

Types of currentTypes of current

can be DCEN or DCEPcan be DCEN or DCEP

DCEN gives deep penetrationDCEN gives deep penetrationDCDC



4/23/20074/23/2007 256256 of 691of 691

requires special power sourcerequires special power source

low frequencylow frequency -- up toup to 2020pulses/sec (thermal pulsing)pulses/sec (thermal pulsing)

better weld pool controlbetter weld pool control

weld pool partially solidifiesweld pool partially solidifiesbetween pulsesbetween pulses

Type of Type of

weldingwelding

currentcurrent

can be sine or square wavecan be sine or square wave

requires a HF current (continuosrequires a HF current (continuos

or periodical)or periodical)

provide cleaning actionprovide cleaning action

ACAC

PulsedPulsed

currentcurrent

Choosing the proper electrodeChoosing the proper electrodeCurrent type influenceCurrent type influence



4/23/20074/23/2007 257257 of 691of 691

++++

++

++++

++

++++

++

----

--

----

--

----

--

Electrode capacityElectrode capacity

Current type & polarity

Heat balanceHeat balance

Oxide cleaning actionOxide cleaning action

PenetrationPenetration

DCENDCEN DCEPDCEPAC (balanced)AC (balanced)

70% at work

30% at electrode30% at electrode

50% at work

5050% at electrode% at electrode

35% at work

6565% at electrode% at electrode

Deep, narrowDeep, narrow MediumMedium Shallow, wideShallow, wide

NoNo Yes Yes -- every half cycleevery half cycle Yes Yes

ExcellentExcellent

(e.g. 3,2 mm/400A)(e.g. 3,2 mm/400A)

GoodGood

(e.g. 3,2 mm/225A)(e.g. 3,2 mm/225A)

Poor Poor

(e.g. 6,4 mm/120A)(e.g. 6,4 mm/120A)

ARC CHARACTERISTICS ARC CHARACTERISTICSConstant Current/Amperage CharacteristicConstant Current/Amperage Characteristic

Large change in voltage =Large change in voltage =



4/23/20074/23/2007 258258 of 691of 691

VoltsVolts

AmpsAmps

OCVOCV

Large change in voltage =Large change in voltage =

Smaller change in amperageSmaller change in amperage

Welding VoltageWelding Voltage

Large arc gapLarge arc gap

Small arcSmall arc

gapgap

TIGTIG -- arc initiation methodsarc initiation methods

Arc initiationArc initiation

methodmethod



4/23/20074/23/2007 259259 of 691of 691

simple methodsimple method

tungsten electrode is in contacttungsten electrode is in contactwith the workpiece!with the workpiece!

high initial arc current due tohigh initial arc current due tothe short circuitthe short circuitimpractical to set arc length inimpractical to set arc length inadvanceadvance

electrode should tap theelectrode should tap theworkpieceworkpiece -- no scratch!no scratch!

ineffective in case of ACineffective in case of ACused when a high quality is notused when a high quality is notessentialessential

methodmethodLift arcLift arc HF startHF start

need a HF generator (sparkneed a HF generator (spark--

gap oscillator) that generates agap oscillator) that generates ahigh voltage AC output (radiohigh voltage AC output (radio

frequency)frequency) costlycostly

reliable methodreliable method required onrequired on

both DC (for start) and AC (toboth DC (for start) and AC (torere--ignite the arc)ignite the arc)

can be used remotelycan be used remotely

HF produce interferenceHF produce interference

requires superior insulationrequires superior insulation

Pulsed currentPulsed current

usually peak current is 2usually peak current is 2--1010

times background currenttimes background current

useful on metals sensitive touseful on metals sensitive ton

t (

A )

Pulse

time

Cycle

time

Peak

current

Background

current



4/23/20074/23/2007 260260 of 691of 691

useful on metals sensitive touseful on metals sensitive tohigh heat inputhigh heat input

reduced distortionsreduced distortions

in case of dissimilar thicknessesin case of dissimilar thicknesses

equal penetration can beequal penetration can be

achievedachieved

Time

C u r r e n

Average current

one set of variables can be used in all positionsone set of variables can be used in all positionsused for bridging gaps in open root jointsused for bridging gaps in open root joints

require special power sourcerequire special power source

Choosing the proper electrodeChoosing the proper electrode

Polarity InfluencePolarity Influence ± ± cathodic cleaning effectcathodic cleaning effect



44//2323//20072007 261261 of 691of 691

Old types: (Slightly Radioactive)Old types: (Slightly Radioactive)

Thoriated: DC electrodeThoriated: DC electrode --veve -- steels and most metalssteels and most metals

Tungsten ElectrodesTungsten Electrodes



4/23/20074/23/2007 262262 of 691of 691

11% thoriated + tungsten for higher current values% thoriated + tungsten for higher current values

22% thoriated for lower current values% thoriated for lower current values

Zirconiated: AC Zirconiated: AC -- aluminum alloys and magnesiumaluminum alloys and magnesium

New types: (Not Radioactive)New types: (Not Radioactive)

Cerium: DC electrodeCerium: DC electrode --veve -- steels and most metalssteels and most metals

Lanthanum: AC Lanthanum: AC -- Aluminum alloys and magnesiumAluminum alloys and magnesium

TIG torch setTIG torch set--upup

Electrode extensionElectrode extension



4/23/20074/23/2007 263263 of 691of 691

ElectrodeElectrode

extensionextension

StickoutStickout22--3 times3 timeselectrodeelectrode

diameter diameter

ElectrodeElectrode

extensionextension

Low electronLow electron

emissionemission

Unstable arcUnstable arc

TooToo

smallsmall

OverheatingOverheating

TungstenTungsten


TooToo

largelarge

Choosing the correct electrodeChoosing the correct electrode

Polarity InfluencePolarity Influence ± ± cathodic cleaning effectcathodic cleaning effect



4/23/20074/23/2007 264264 of of 691691

Old types: (Slightly Radioactive)Old types: (Slightly Radioactive)

Thoriated: DC electrodeThoriated: DC electrode --veve -- steels and most metalssteels and most metals

Tungsten ElectrodesTungsten Electrodes



4/23/20074/23/2007 265265 of 691of 691

1% thoriated + tungsten for higher current values1% thoriated + tungsten for higher current values

2% thoriated for lower current values2% thoriated for lower current values

Zirconiated: AC Zirconiated: AC -- aluminum alloys and magnesiumaluminum alloys and magnesium

New types: (Not Radioactive)New types: (Not Radioactive)

Cerium: DC electrodeCerium: DC electrode --veve -- steels and most metalssteels and most metals

Lanthanum: AC Lanthanum: AC -- Aluminum alloys and magnesiumAluminum alloys and magnesium

Tungsten electrode typesTungsten electrode typesPure tungsten electrodes:Pure tungsten electrodes:

colour codecolour code -- greengreen



4/23/20074/23/2007 266266 of 691of 691

no alloy additionsno alloy additions

low current carrying capacitylow current carrying capacity

maintains a clean balled endmaintains a clean balled endcan be used for AC welding of Al and Mg alloyscan be used for AC welding of Al and Mg alloys

poor arc initiation and arc stability with AC comparedpoor arc initiation and arc stability with AC compared

with other electrode typeswith other electrode types

used on less critical applicationsused on less critical applications

low costlow cost

Tungsten electrode typesTungsten electrode types

Thoriated tungsten electrodes:Thoriated tungsten electrodes:

colour codecolour code -- yellowyellow//redred//violetviolet



44//2323//20072007 267267 of 691of 691

co ou codeco ou code ye oye o // eded// o eo e

20% higher current carrying capacity compared to20% higher current carrying capacity compared to

pure tungsten electrodespure tungsten electrodes

longer lifelonger life -- greater resistance to contaminationgreater resistance to contamination

thermionicthermionic -- easy arc initiation, more stable arceasy arc initiation, more stable arc

maintain a sharpened tipmaintain a sharpened tip

recommended for DCEN, seldom used on ACrecommended for DCEN, seldom used on AC(difficult to maintain a balled tip)(difficult to maintain a balled tip)

This slightly radioactiveThis slightly radioactive


Ceriated tungsten electrodes:Ceriated tungsten electrodes:

colour codecolour code -- grey (orange acc. AWS Agrey (orange acc. AWS A--5.12)5.12)



4/23/20074/23/2007 268268 of 691of 691

g y ( gg y ( g ))

operate successfully with AC or DCoperate successfully with AC or DC

Ce not radioactiveCe not radioactive -- replacement for thoriated typesreplacement for thoriated types

Lanthaniated tungsten electrodes:Lanthaniated tungsten electrodes:

colour codecolour code -- black//goldgold//blueblue

operating characteristics similar with ceriatedoperating characteristics similar with ceriated

electrodeelectrode


Zirconiated tungsten electrodes:Zirconiated tungsten electrodes:

colour codecolour code -- brownbrown//white



4/23/20074/23/2007 269269 of 691of 691

operating characteristics fall between those of pureoperating characteristics fall between those of pure

and thoriated electrodesand thoriated electrodes

retains a balled end during weldingretains a balled end during welding -- good for ACgood for ACweldingwelding

high resistance to contaminationhigh resistance to contamination

preferred for radiographic quality weldspreferred for radiographic quality welds

Electrode tip for DCENElectrode tip for DCEN


increaseincrease

e re r



4/23/20074/23/2007 270270 of 691of 691

Electrode tip prepared for lowElectrode tip prepared for low

current weldingcurrent welding

Electrode tip prepared for highElectrode tip prepared for high

current weldingcurrent welding

VertexVertex

angleangle

IncreaseIncrease

Bead widthBead width

increaseincrease

DecreaseDecrease

2 2 - - 2 2 , , 5 5 t i m e s

t i m e s

e l e c

t r o d e d i a m e t

e l e c

t r o d e d i a m e t

Electrode tip for ACElectrode tip for AC

DC -ve AC



4/23/20074/23/2007 271271 of 691of 691

Electrode tip groundElectrode tip groundElectrode tip ground andElectrode tip ground and

then conditionedthen conditioned

Tungsten electrodesTungsten electrodes

The electrode diameter, type and vertex angle are all criticalThe electrode diameter, type and vertex angle are all critical

factors considered as essential variables. The vertex angle isfactors considered as essential variables. The vertex angle is




4/23/20074/23/2007 272272 of 691of 691

gg

as shownas shown

Vetex angleVetex angle

Note:Note: when weldingwhen welding

aluminium with AC

aluminium with AC

current, the tungsten endcurrent, the tungsten end

is chamfered and forms ais chamfered and forms a

ball end when weldingball end when welding

DC DC --veve

Note:Note: too fine an angle willtoo fine an angle will

promote melting of thepromote melting of the

electrodes tipelectrodes tip

ACAC

Choosing the proper electrodeChoosing the proper electrode

Factors to be considered:Factors to be considered:



4/23/20074/23/2007 273273 of 691of 691

UnstableUnstable

arcarc

TungstenTungsten


WeldingWelding

currentcurrent

Electrode tipElectrode tip

not properlynot properly

heatedheated

ExcessiveExcessive

melting or melting or

volatilisationvolatilisation

TooToo

lowlow

TooToo

highhigh


Gas type and flow rateGas type and flow rate

Generally two types of gases are used in TIG welding, argonGenerally two types of gases are used in TIG welding, argon

and helium, though nitrogen may be considered for weldingand helium, though nitrogen may be considered for welding

TIG Welding GasesTIG Welding Gases



4/23/20074/23/2007 274274 of of 691691

copper and hydrogen may be added for the welding of copper and hydrogen may be added for the welding of

austenitic stainless steels.austenitic stainless steels.

The gas flow rate is also important.The gas flow rate is also important.

Argon (Ar) InertArgon (Ar) Inert Suitable for welding carbonSuitable for welding carbon

steel,stainless steel,steel,stainless steel,

aluminiumaluminium and magnesiumand magnesium

Lower cost, lower flow ratesLower cost, lower flow rates

More suitable for thinner More suitable for thinner materials andmaterials and positionalpositional

weldingwelding

Helium Argon mixesHelium Argon mixes Suitable for weldingSuitable for welding

carboncarbon steel, stainlesssteel, stainless

steel,steel, copper, aluminiumcopper, aluminium

andand magnesiummagnesium

High cost, high flow ratesHigh cost, high flow rates More suitable for thicker More suitable for thicker

materials andmaterials and materials of materials of

high thermal conductivity.high thermal conductivity.

Shielding gas requirementsShielding gas requirements

Preflow andPreflow and

postflowpostflow

Shielding gas flowShielding gas flow

Welding currentWelding current



4/23/20074/23/2007 275275 of 691of 691

postflowpostflow

PreflowPreflow PostflowPostflow

Flow rateFlow rate

too lowtoo low

Flow rateFlow rate

too hightoo high

Special shielding methodsSpecial shielding methods

Pipe root run shieldingPipe root run shielding ± ± Back Purging to preventBack Purging to prevent

excessive oxidation during welding, normally argon.excessive oxidation during welding, normally argon.



4/23/20074/23/2007 276276 of 691of 691

TIG torch setTIG torch set--upupElectrode extensionElectrode extension



4/23/20074/23/2007 277277 of 691of 691

ElectrodeElectrode

extensionextension

StickoutStickout 22--3 times3 times

electrodeelectrode

diameter diameter

ElectrodeElectrode

extensionextension

Low electronLow electron

emissionemission

Unstable arcUnstable arc

TooToo

smallsmall

OverheatingOverheating

TungstenTungsten


TooToo

largelarge

TIG Welding ConsumablesTIG Welding Consumables

Welding consumables for TIG:Welding consumables for TIG:

Filler wires, Shielding gases, tungsten electrodes (nonFiller wires, Shielding gases, tungsten electrodes (non--consumable)consumable)



4/23/20074/23/2007 278278 of 691of 691

consumable).consumable).

Filler wires of different materials composition andFiller wires of different materials composition and

variable diameters available in standard lengths, withvariable diameters available in standard lengths, with

applicable code stamped for identificationapplicable code stamped for identification

Steel Filler wires of very high quality, with copper Steel Filler wires of very high quality, with copper

coating to resist corrosion.coating to resist corrosion.

shielding gases mainly Argon and Helium, usually of shielding gases mainly Argon and Helium, usually of

highest purity (99.9%).highest purity (99.9%).

Tungsten InclusionTungsten Inclusion

May be caused by Thermal Shock of heating to fast and small fragments



4/23/20074/23/2007 279279 of 691of 691

A Tungsten Inclusion always shows up asA Tungsten Inclusion always shows up as

bright white on a radiographbright white on a radiograph

break off and enter the weld pool, so a³slope up´ device is normally fitted to

prevent this could be caused by touch

down also.

Most TIG sets these days have slope-up devices that brings the current to

the set level over a short period of time so the tungsten is heated more

slowly and gently

Most welding defects with TIG are caused by a lack of welder Most welding defects with TIG are caused by a lack of welder

skill, or incorrect setting of the equipment. i.e. current, torchskill, or incorrect setting of the equipment. i.e. current, torch

manipulation, welding speed, gas flow rate, etc.manipulation, welding speed, gas flow rate, etc.

( )( )

TIG typical defectsTIG typical defects



4/23/20074/23/2007 280280 of 691of 691

Tungsten inclusions (low skill or wrong vertex angle)Tungsten inclusions (low skill or wrong vertex angle)

Surface porosity (loss of gas shield mainly on site)Surface porosity (loss of gas shield mainly on site)

Crater pipes (bad weld finish technique i.e. slope out)Crater pipes (bad weld finish technique i.e. slope out)

Oxidation of S/S weld bead, or root by poor gas cover Oxidation of S/S weld bead, or root by poor gas cover

Root concavity (excess purge pressure in pipe)Root concavity (excess purge pressure in pipe)

Lack of penetration/fusion (widely on root runs)Lack of penetration/fusion (widely on root runs)


Advantages Advantages

High qualityHigh quality

DisadvantagesDisadvantages

High skill factor requiredHigh skill factor required



4/23/20074/23/2007 281281 of 691of 691

Good controlGood control

All positions All positions

Lowest HLowest H22 processprocess

Minimal cleaningMinimal cleaning

Autogenous welding Autogenous welding

(No filler material)(No filler material)

Can be automatedCan be automated

Low deposition rateLow deposition rate

Small consumableSmall consumable

rangerangeHigh protection requiredHigh protection required

Complex equipmentComplex equipment

Low productivityLow productivity

High ozone levels +HFHigh ozone levels +HF


MIG/MAG WeldingMIG/MAG Welding



4/23/20074/23/2007 282282 of 691of 691

MIG/MAG WeldingMIG/MAG WeldingSection 12Section 12

The MIG/MAG welding process was initially developed in theThe MIG/MAG welding process was initially developed in the

USA in the late 1940s for the welding of aluminum alloys.USA in the late 1940s for the welding of aluminum alloys.

The latest EN Welding Standards now refer the process by theThe latest EN Welding Standards now refer the process by the

A i t GMAW (G M t l A W ldiA i t GMAW (G M t l A W ldi ))

Gas Metal Arc WeldingGas Metal Arc Welding



4/23/20074/23/2007 283283 of 691of 691

American term GMAW (Gas Metal Arc WeldingAmerican term GMAW (Gas Metal Arc Welding))

The process uses a continuously fed wire electrodeThe process uses a continuously fed wire electrode

The weld pool is protected by a separately suppliedThe weld pool is protected by a separately supplied

shielding gasshielding gas

The process is classified as a semiThe process is classified as a semi--automatic weldingautomatic welding

process but may be fully automatedprocess but may be fully automated

The wire electrode can be either bare/solid wire or fluxThe wire electrode can be either bare/solid wire or flux

cored hollow wirecored hollow wire

MIG/MAGMIG/MAG -- Principle of operationPrinciple of operation



4/23/20074/23/2007 284284 of 691of 691

AdvantagesAdvantages DisadvantagesDisadvantages

High productivityHigh productivity Easily automatedEasily automated

Lack of fusion (dip)Lack of fusion (dip) Small range ofSmall range of consumablesconsumables




4/23/20074/23/2007 285285 of 691of 691

Easily automatedEasily automated

All positional (dip & pulse)All positional (dip & pulse)

Material thicknessMaterial thickness

rangerange

Continuous electrodeContinuous electrode

Wide range of applicationWide range of application

Small range of Small range of consumablesconsumables

Protection on siteProtection on site

Complex equipmentComplex equipment

Not so portableNot so portable

MIG/MAG process variablesMIG/MAG process variables

Welding current



4/23/20074/23/2007 286286 of 691of 691

Polarity

Increasing welding current

Increase in depth and width

Increase in deposition rate

MIG/MAG process variablesMIG/MAG process variables

Arc voltage



4/23/20074/23/2007 287287 of 691of 691

Travel speedIncreasing travel speed

Reduced penetration and width, undercut

Increasing arc voltage

Reduced penetration, increased widthExcessive voltage can cause porosity,

spatter and undercut

Shielding Gases:Shielding Gases:

The gasses used in MIG/MAG welding can be either 100%

CO

The gasses used in MIG/MAG welding can be either 100%

CO22

or Argon + COor Argon + CO22 mixes.mixes.

MAG Welding Variable ParametersMAG Welding Variable Parameters



4/23/20074/23/2007 288288 of 691of 691

100% CO100% CO22: Can not sustain true spray transfer, but gives: Can not sustain true spray transfer, but gives

very good penetration.The arc is unstable which producesvery good penetration.The arc is unstable which produces

a lot of spatter and a coarse weld profile.a lot of spatter and a coarse weld profile.

Argon + COArgon + CO22 mixesmixes: Argon can sustain spray transfer : Argon can sustain spray transfer aboveabove24 volts, and gives a very stable arc with a reduction24 volts, and gives a very stable arc with a reduction inin

spatter. Argon being a cooler gas produces lessspatter. Argon being a cooler gas produces less penetrationpenetration

than COthan CO22. Argon in normally mixed with CO. Argon in normally mixed with CO22 atat a mixture of a mixture of

between 5between 5--25%25%

Gas Metal Arc WeldingGas Metal Arc WeldingTypes of Shielding GasTypes of Shielding Gas

MIG (Metal Inert Gas)MIG (Metal Inert Gas)I t G i i d fI t G i i d f llll f llf ll (Al C Ni)(Al C Ni)



4/23/20074/23/2007 289289 of 691of 691

Inert Gas is required for Inert Gas is required for all nonall non--ferrous alloysferrous alloys (Al, Cu, Ni)(Al, Cu, Ni)

Most common inert gas is ArgonMost common inert gas is Argon

Argon + Helium used to give a µhotter¶ arcArgon + Helium used to give a µhotter¶ arc -- better for thicker better for thicker

joints and alloys with higher thermal conductivity joints and alloys with higher thermal conductivity

MIG/MAGMIG/MAG ± ± shielding gasesshielding gases

Type of materialType of material Shielding gasShielding gas



4/23/20074/23/2007 290290 of 691of 691

Carbon steelCarbon steel

Stainless steelStainless steel

AluminiumAluminium

COCO22 , Ar+(5, Ar+(5--20)%CO20)%CO22

Ar+2%OAr+2%O22

Ar Ar

MIG/MAG shielding gasesMIG/MAG shielding gases

Argon (Ar):Argon (Ar):

Ar Ar-He He CO2



4/23/20074/23/2007 291291 of 691of 691

Argon (Ar): Argon (Ar):

higher density than air; low thermal conductivityhigher density than air; low thermal conductivity thethearc has a high energy inner cone; good wetting at thearc has a high energy inner cone; good wetting at thetoes; low ionisation potentialtoes; low ionisation potential

Helium (He):Helium (He):

lower density than air; high thermal conductivitylower density than air; high thermal conductivity uniformly distributed arc energy; parabolic profile; highuniformly distributed arc energy; parabolic profile; highionisation potentialionisation potential

Carbon Dioxide (COCarbon Dioxide (CO22):):

cheap; deep penetration profile; cannot support spraycheap; deep penetration profile; cannot support spraytransfer; poor wetting; high spatter transfer; poor wetting; high spatter

MIG/MAG shielding gasesMIG/MAG shielding gasesGases for dip transfer Gases for dip transfer ::

COCO22:: carbon steels onlycarbon steels only: deep penetration; fast welding: deep penetration; fast weldingspeed; high spatter levelsspeed; high spatter levels



44//2323//20072007 292292 of 691of 691

Ar + up to 25% CO Ar + up to 25% CO22:: carbon and low alloy steelscarbon and low alloy steels::

minimum spatter; good wetting and bead contour minimum spatter; good wetting and bead contour

90% He + 7.5% Ar + 2.5% CO90% He + 7.5% Ar + 2.5% CO22::stainless steelsstainless steels::minimises undercut; small HAZminimises undercut; small HAZ

Ar: Ar: Al, Mg, Cu, Ni and their alloys on thin sections Al, Mg, Cu, Ni and their alloys on thin sections

Ar + He mixtures: Ar + He mixtures: Al, Mg, Cu, Ni and their alloys on Al, Mg, Cu, Ni and their alloys onthicker sections (over 3 mm)thicker sections (over 3 mm)

MIG/MAG shielding gasesMIG/MAG shielding gasesGases for spray transfer Gases for spray transfer

Ar + (5 Ar + (5--18)% CO18)% CO22:: carbon steelscarbon steels: minimum spatter;: minimum spatter;

good wetting and bead contour good wetting and bead contour



4/23/20074/23/2007 293293 of 691of 691

Ar + 2% O Ar + 2% O22:: low alloy steels:low alloy steels: minimise undercut;minimise undercut;provides good toughnessprovides good toughness

Ar + 2% O Ar + 2% O22

or COor CO22

:: stainless steelsstainless steels: improved arc: improved arcstability; provides good fusionstability; provides good fusion

Ar: Ar: Al, Mg, Cu, Ni, Ti and their alloys Al, Mg, Cu, Ni, Ti and their alloys

Ar + He mixtures: Ar + He mixtures: Al, Cu, Ni and their alloys Al, Cu, Ni and their alloys: hotter arc: hotter arc

than pure Ar to offset heat dissipationthan pure Ar to offset heat dissipation Ar + (25 Ar + (25--30)% N30)% N22:: Cu alloysCu alloys: greater heat input: greater heat input

Gas Metal Arc WeldingGas Metal Arc WeldingTypes of Shielding GasTypes of Shielding Gas

MAG (Metal Active Gas)MAG (Metal Active Gas)O CO C



4/23/20074/23/2007 294294 of 691of 691

Active gases used are Oxygen and Carbon Dioxide Active gases used are Oxygen and Carbon Dioxide

Argon with a small % of active gas is required for all Argon with a small % of active gas is required for all

steels (including stainless steels) to ensure a stablesteels (including stainless steels) to ensure a stable

arc & good droplet wetting into the weld poolarc & good droplet wetting into the weld pool

Typical active gases areTypical active gases are

Ar + Ar + 2020% CO% CO22 for Cfor C--Mn & low alloy steelsMn & low alloy steels

Ar + Ar + 22% O% O22 for stainless steelsfor stainless steels

100100% CO% CO22 can be used for Ccan be used for C -- steelssteels

MIG/MAG Gas Metal Arc WeldingMIG/MAG Gas Metal Arc Welding

ElectrodeElectrodeorientationorientation



4/23/20074/23/2007 295295 of 691of 691

Penetration Deep Moderate ShallowPenetration Deep Moderate Shallow

Excess weld metal Maximum Moderate MinimumExcess weld metal Maximum Moderate Minimum

Undercut Severe Moderate MinimumUndercut Severe Moderate Minimum

Electrode extensionElectrode extension

Increased extensionIncreased extension

MIG / MAGMIG / MAG -- self self--regulatingregulatingarcarc

Stable conditionStable condition Sudden change in gun positionSudden change in gun position

Arc length L = 6,4 mmArc length L = 6,4 mm

Arc voltage = 24VArc voltage = 24V

Welding current = 250AWelding current = 250AWFS = 6,4 m/minWFS = 6,4 m/min

Arc length L¶ = 12,7 mmArc length L¶ = 12,7 mm

Arc voltage = 29VArc voltage = 29V

Welding current = 220AWelding current = 220AWFS = 6,4 m/minWFS = 6,4 m/min



4/23/20074/23/2007 296296 of 691of 691

LL19 mm19 mm

25 mm25 mmL¶L¶

Melt off rate = 6,4 m/minMelt off rate = 6,4 m/min Melt off rate = 5,6Melt off rate = 5,6

m/minm/min

Current (A)Current (A)

V o l t a g e ( V )

V o l t a g e ( V )

MIG/MAGMIG/MAG -- self self--regulating arcregulating arcSudden change in gun positionSudden change in gun position

Arc length L¶ =Arc length L¶ = 1212,,77 mmmm

Arc voltage =Arc voltage = 2929VV

Welding current =Welding current = 220220AAWFS =WFS = 66,,44 m/minm/min

Melt off rate =Melt off rate = 55 66 m/minm/min

ReRe--established stable conditionestablished stable condition

Arc length L =Arc length L = 66,,44 mmmm

Arc voltage =Arc voltage = 2424VV

Welding current =Welding current = 250250AAWFS =WFS = 66,,44 m/minm/min

Melt off rate =Melt off rate = 66 44 m/minm/min



4/23/20074/23/2007 297297 of of 691691

25 mm25 mmL¶L¶

Melt off rate Melt off rate 55,,66 m/minm/min

Current (A)Current (A)

V o l t a g e ( V )

V o l t a g e ( V )

25 mm25 mmLL

Melt off rate Melt off rate 66,,44 m/minm/min

Terminating the arcTerminating the arc

Burnback timeBurnback time

± ± delayed current cutdelayed current cut--off to prevent wire freezeoff to prevent wire freezein the weld end craterin the weld end crater

Crater fillCrater fill



4/23/20074/23/2007 298298 of 691of 691

in the weld end crater in the weld end crater

± ± depends on WFS (set as short as possible!)depends on WFS (set as short as possible!)

Contact tipContact tip

WorkpiecWorkpiec

ee

Burnback timeBurnback time 0.05 sec0.05 sec 0.10 sec0.10 sec 00..1515 secsec

14 mm14 mm88 mmmm

3 mm3 mm

CurrentCurrent -- 250A250A

VoltageVoltage -- 27V27V

WFSWFS -- 7,8 m/min7,8 m/min

Wire diam.Wire diam. -- 1,2 mm1,2 mm

Shielding gasShielding gas --

Ar+18%COAr+18%CO22

InsulatinInsulatin

g slagg slag

MIG/MAGMIG/MAG -- metal transfer modesmetal transfer modes



4/23/20074/23/2007 299299 of of 691691

SetSet--up for dip transfer up for dip transfer SetSet--up for spray transfer up for spray transfer

ElectrodeElectrode

extensionextension

1919--25 mm25 mm


recessedrecessed

(3(3--5 mm)5 mm)


extensionextension((00--33,,22 mm)mm)

ElectrodeElectrode

extensionextension

66--13 mm13 mm

Gas Metal Arc WeldingGas Metal Arc WeldingMODES OF METAL TRANSFERMODES OF METAL TRANSFER

The current and voltage settings determine the way moltenThe current and voltage settings determine the way molten

droplets of weld metal transfer from the tip of the wire to thedroplets of weld metal transfer from the tip of the wire to theweld poolweld pool



44//2323//20072007 300300 of 691of 691

weld poolweld pool

There are 3 principle modes of droplet transfer, namelyThere are 3 principle modes of droplet transfer, namely

dip transfer (shortdip transfer (short--circuiting)circuiting)

spray transfer spray transfer

pulsed transfer pulsed transfer

MIG/MAGMIG/MAG -- metal transfer modesmetal transfer modes

VoltageVoltageElectrode diameter = 1,2 mmElectrode diameter = 1,2 mm

WFS = 8,3 m/minWFS = 8,3 m/min

Current = 295 ACurrent = 295 A

Voltage = 28VVoltage = 28V



4/23/20074/23/2007 301301 of 691of 691Current/voltage conditionsCurrent/voltage conditions

CurrentCurrent

Dip transfer Dip transfer

SpraySpray

transfer transfer

Globular Globular

transfer transfer

Electrode diameter = 1,2 mmElectrode diameter = 1,2 mm

WFS = 3,2 m/minWFS = 3,2 m/min

Current = 145 ACurrent = 145 A

Voltage = 18Voltage = 18--20V20V

Voltage 28VVoltage 28V


Dip Transfer Dip Transfer

Dip transfer occurs when current & voltage settings are lowDip transfer occurs when current & voltage settings are low

(typically < ~ 200amps & ~ 22volts)(typically < ~ 200amps & ~ 22volts)

There is just enough energy to give an arc and cause fusionThere is just enough energy to give an arc and cause fusion



44//2323//20072007 302302 of 691of 691

There is just enough energy to give an arc and cause fusionThere is just enough energy to give an arc and cause fusionat the tip of the wireat the tip of the wire

A droplet grows to a size larger than the wire diameter andA droplet grows to a size larger than the wire diameter andeventually extinguishes the arceventually extinguishes the arc -- causing a shortcausing a short--circuitcircuit

The short circuit causes the current rises very quickly givingThe short circuit causes the current rises very quickly givingenergy to violently µpinchenergy to violently µpinch--off¶ the dropletoff¶ the droplet

This is akin to µblowing a fuse¶ and causes spatter This is akin to µblowing a fuse¶ and causes spatter

When the droplet detaches, the arc is reWhen the droplet detaches, the arc is re--established and theestablished and thecurrent fallscurrent falls

This cycle occurs at up to ~ 200 times per secondThis cycle occurs at up to ~ 200 times per second

MIG/MAGMIG/MAG--methods of metal transfer methods of metal transfer Dip transfer Dip transfer

Transfer occur due to short circuitsTransfer occur due to short circuits

between wire and weld pool,between wire and weld pool, highhigh

level of spatter, need inductancelevel of spatter, need inductancecontrol to limit current raisecontrol to limit current raise



4/23/20074/23/2007 303303 of 691of 691

control to limit current raisecontrol to limit current raise

Can use pure COCan use pure CO22 or Ar or Ar-- COCO22

mixtures as shielding gasmixtures as shielding gas

Metal transfer occur when arc isMetal transfer occur when arc isextinguishedextinguished

Requires low welding current/arcRequires low welding current/arc

voltage, avoltage, a low heat input process.low heat input process.

Resulting in low residual stressResulting in low residual stress

and distortionand distortion

Used for thin materials and allUsed for thin materials and all

position weldsposition welds

Gas Metal Arc WeldingGas Metal Arc WeldingDip Transfer Dip Transfer

Transfer Transfer--mode advantagesmode advantages

The low energy conditions allow welding in all positionsThe low energy conditions allow welding in all positions

It b d f tti i th t i lIt b d f tti i th t i l id did d



4/23/20074/23/2007 304304 of of 691691

It can be used for putting in the root run on singleIt can be used for putting in the root run on single--sidedsided

weldswelds

It can be used for welding thin materialsIt can be used for welding thin materials

Transfer Transfer--mode disadvantagesmode disadvantages

It frequently gives lack of fusion and may not be allowed inIt frequently gives lack of fusion and may not be allowed in

semisemi--automatic mode for highautomatic mode for high--integrity applicationsintegrity applications

It tends to give spatter It tends to give spatter

( t his can be reduced/controlled by having an µinductance¶ ( t his can be reduced/controlled by having an µinductance¶ control on t he pow er source)control on t he pow er source)


Spray Transfer Spray Transfer

When current & voltage are raised together higher energy isWhen current & voltage are raised together higher energy is

available for fusion (typically > ~ 25 volts & ~ 250 amps)available for fusion (typically > ~ 25 volts & ~ 250 amps)

This causes a fine droplets of weld metal to be µsprayed¶ fromThis causes a fine droplets of weld metal to be µsprayed¶ from



4/23/20074/23/2007 305305 of 691of 691

This causes a fine droplets of weld metal to be sprayed fromThis causes a fine droplets of weld metal to be sprayed fromthe tip of the wire into the weld poolthe tip of the wire into the weld pool


High energy gives good fusionHigh energy gives good fusion High rates of weld metal deposition are givenHigh rates of weld metal deposition are given

These characteristics make it suitable for welding thicker These characteristics make it suitable for welding thicker joints joints

Transfer Transfer--mode disadvantagesmode disadvantages

It cannot be used for positional weldingIt cannot be used for positional welding

MIG/MAGMIG/MAG--methods of metal transfer methods of metal transfer Spray transfer Spray transfer

Transfer occur due to pinchTransfer occur due to pinch

effecteffect NO contact between wireNO contact between wireand weld pool!and weld pool!



44//2323//20072007 306306 of 691of 691

Requires argonRequires argon--rich shieldingrich shieldinggasgas

Metal transfer occur in smallMetal transfer occur in small

droplets, adroplets, a large volume weldlarge volume weldpoolpool

Requires high weldingRequires high weldingcurrent/arc voltage, acurrent/arc voltage, a high heathigh heatinput process. Resulting in highinput process. Resulting in highresidual stress and distortionresidual stress and distortion

Used for thick materials andUsed for thick materials andflat/horizontal position weldsflat/horizontal position welds

MIG/MAGMIG/MAG--methods of metal transfer methods of metal transfer Pulsed transfer Pulsed transfer

Controlled metal transfer,Controlled metal transfer, one droplet per pulse,one droplet per pulse,

No transfer between droplet and weld pool!No transfer between droplet and weld pool!



4/23/20074/23/2007 307307 of 691of 691

Requires special power sourcesRequires special power sources

Metal transfer occur in small droplets (diameter equalMetal transfer occur in small droplets (diameter equal

to that of electrode)to that of electrode)

Requires moderate welding current/arc voltage, aRequires moderate welding current/arc voltage, a

reduced heat input . Resulting in smaller residualreduced heat input . Resulting in smaller residual

stress and distortion compared to spray transfer stress and distortion compared to spray transfer

Pulse frequency controls the volume of weld pool,Pulse frequency controls the volume of weld pool,

used for root runs and out of position weldsused for root runs and out of position welds

MIG/MAGMIG/MAG -- metal transfer modesmetal transfer modesPulsed transfer Pulsed transfer

Controlled metal transfer.Controlled metal transfer. one dropletone dropletper pulse. NO transfer duringper pulse. NO transfer during



4/23/20074/23/2007 308308 of of 691691

background current!background current!

Requires special power sourcesRequires special power sources

Metal transfer occur in small dropletsMetal transfer occur in small droplets(diameter equal to that of electrode)(diameter equal to that of electrode)

Requires moderate welding current/arc voltage,Requires moderate welding current/arc voltage, reducedreduced

heat input¶ smaller residual stress and distortionsheat input¶ smaller residual stress and distortions

compared to spray transfer compared to spray transfer

Pulse frequency controls the volume of weld pool, usedPulse frequency controls the volume of weld pool, used

for root runs and out of position weldsfor root runs and out of position welds

Gas Metal Arc WeldingGas Metal Arc WeldingPulsed Transfer Pulsed Transfer


Good fusionGood fusion



4/23/20074/23/2007 309309 of 691of 691

Small weld pool allows allSmall weld pool allows all--position weldingposition welding

Transfer

Transfer--mode disadvantagesmode disadvantages

More complex & expensive power sourceMore complex & expensive power source

Difficult to set parametersDifficult to set parameters -- requires power sourcerequires power source

manufacturer to provide pulse programmes to suit wire type,manufacturer to provide pulse programmes to suit wire type,

dia. and type of gasdia. and type of gas

MIG/MAGMIG/MAG--methods of metal transfer methods of metal transfer

Globular transfer Globular transfer

Transfer occur due to gravityTransfer occur due to gravity or or

short circuits between drops andshort circuits between drops andweld poolweld pool



4/23/20074/23/2007 310310 of 691of 691

Requires CORequires CO22 shielding gasshielding gas

Metal transfer occur in large dropsMetal transfer occur in large drops(diameter larger than that of (diameter larger than that of

electrode) henceelectrode) hence severe spatter severe spatter Requires high welding current/arcRequires high welding current/arc

voltage, avoltage, a high heat input process.high heat input process.Resulting in high residual stressResulting in high residual stress

and distortionand distortion

Non desired mode of transfer!Non desired mode of transfer!

Dip Transfer:Dip Transfer: (Voltage < 22) / (Amperage < 200)(Voltage < 22) / (Amperage < 200)

Thin materials positional weldingThin materials positional welding

Globular Transfer:Globular Transfer: Between Dip & Spray Transfer Between Dip & Spray Transfer




4/23/20074/23/2007 311311 of 691of 691

Limited commercial, Used only in some mechanized MAGLimited commercial, Used only in some mechanized MAGprocess using COprocess using CO22 shielding gasshielding gas

Spray Transfer:Spray Transfer: (Voltage > 27) / (Amperage > 220)(Voltage > 27) / (Amperage > 220) Thicker materials, limited to flat welding positions, highThicker materials, limited to flat welding positions, high

depositiondeposition

Pulse Transfer:Pulse Transfer: Both spray and dip transfer inBoth spray and dip transfer in

one mode of operation, frequency range 50one mode of operation, frequency range 50--300300pulses/secondpulses/second

Positional welding and root runsPositional welding and root runs

Inductance:Inductance:

Applicable to MIG/MAG process in dip transfer mode. Applicable to MIG/MAG process in dip transfer mode. The electrode is fed slowly through the arc until itThe electrode is fed slowly through the arc until it




4/23/20074/23/2007 312312 of of 691691

The electrode is fed slowly through the arc until itThe electrode is fed slowly through the arc until it

touches the weld pool, at this point the output fromtouches the weld pool, at this point the output from

the power supply is short circuited and a very highthe power supply is short circuited and a very high

current flows through the electrode. If this wascurrent flows through the electrode. If this wasallowed to continue, the wire would melt and ejectallowed to continue, the wire would melt and eject

excessive amounts of spatter.excessive amounts of spatter.

The inclusion or the choke in the welding circuitThe inclusion or the choke in the welding circuit

controls the rate at which the current rises so that thecontrols the rate at which the current rises so that theelectrode tip is melted uniformly without excessiveelectrode tip is melted uniformly without excessive

spatter spatter

The effect of inductanceThe effect of inductanceMaximum inductanceMaximum inductance Minimum inductanceMinimum inductanceHotter arc,Hotter arc, moremore

penetrationpenetrationreduced spatter reduced spatter

More fluid weld poolMore fluid weld pool flatterflatter

Colder arc,Colder arc, used only for arcused only for arc

stability when welding widestability when welding widegapsgaps

ConvexConvex weld, more spatter weld, more spatter



4/23/20074/23/2007 313313 of 691of 691

More fluid weld pool,More fluid weld pool, flatter flatter and smoother weldand smoother weld

Recommended on thicker Recommended on thicker materials and stainlessmaterials and stainless

steelssteels

pp

Improved weld pool controlImproved weld pool control

Recommended on thinRecommended on thinmaterialsmaterials

ARC CHARACTERISTICS ARC CHARACTERISTICS

OCV

Constant Voltage Characteristic

Small change in voltage =large change in amperage



4/23/20074/23/2007 314314 of 691of 691

Volts

Amps

The self adjusting arc.

Large arc gap

Small arc gap

O.C.V. Arc VoltageO.C.V. Arc Voltage

Virtually no ChangeVirtually no Change

Flat or Constant Voltage Characteristic Used WithFlat or Constant Voltage Characteristic Used With

MIG/MAG, ESW & SAW < 1000 ampsMIG/MAG, ESW & SAW < 1000 amps

Flat or Constant Voltage CharacteristicFlat or Constant Voltage Characteristic



4/23/20074/23/2007 315315 of 691of 691

Virtually no Change.Virtually no Change.

V oltageV oltage

100100 200200 300300

3333

3232

3131

Large Current ChangeLarge Current Change

Small VoltageSmall VoltageChange.Change.

Amperage Amperage

MIG/MAG welding gun assemblyMIG/MAG welding gun assembly

ContactContact

tiptip

GasGas

diffuser diffuser

The PushThe Push--Pull gunPull gun



4/23/20074/23/2007 316316 of 691of 691

HandleHandle

GasGas

nozzlenozzle

Trigger Trigger WFS remoteWFS remote

controlcontrol

potentiometer potentiometer

Union nutUnion nut

Wire feed speed:Wire feed speed:

Increasing the wire feed speed automatically increases theIncreasing the wire feed speed automatically increases the

current in the wirecurrent in the wire

V ltV lt




4/23/20074/23/2007 317317 of 691of 691

Voltage:Voltage:

The voltage is the most important setting in the spray transfer The voltage is the most important setting in the spray transfer

mode, as it controls the arc length. In dip transfer it controlsmode, as it controls the arc length. In dip transfer it controls

the rise in currentthe rise in current

Current:Current:

The current is automatically increased as the wire feed isThe current is automatically increased as the wire feed is

increased. Current mainly affects penetrationincreased. Current mainly affects penetration

Gas Metal Arc WeldingGas Metal Arc WeldingPROCESS CHARACTERISTICSPROCESS CHARACTERISTICS

Requires a constant voltage power source, gas supply, wireRequires a constant voltage power source, gas supply, wire

feeder, welding torch/gun and µhose package¶feeder, welding torch/gun and µhose package¶

Wire is fed continuously through the conduit and is burntWire is fed continuously through the conduit and is burnt--offoff



4/23/20074/23/2007 318318 of 691of 691

Wire is fed continuously through the conduit and is burntWire is fed continuously through the conduit and is burnt off off

at a rate that maintains a constant arc length/arc voltageat a rate that maintains a constant arc length/arc voltage

Wire feed speed is directly related to burnWire feed speed is directly related to burn--off rateoff rate

Wire burnWire burn--off rate is directly related to currentoff rate is directly related to current

When the welder holds the welding gun the process is saidWhen the welder holds the welding gun the process is said

to be a semito be a semi--automatic processautomatic process

The process can be mechanised and also automatedThe process can be mechanised and also automated

In Europe the process is usually called MIG or MAGIn Europe the process is usually called MIG or MAG

Gas Metal Arc WeldingGas Metal Arc WeldingTypes of Filler WireTypes of Filler Wire

Filler wires have similar composition to the base materialFiller wires have similar composition to the base material

Wires can be solid, flux cored or metal coredWires can be solid, flux cored or metal cored Flux cored wires are designed to run in spray mode and thereforeFlux cored wires are designed to run in spray mode and therefore

they give good fusionthey give good fusion



4/23/20074/23/2007 319319 of 691of 691

they give good fusionthey give good fusion

Flux cored wires cannot be used for root runs on unbacked jointsFlux cored wires cannot be used for root runs on unbacked joints

The slag formed from flux cored wire enables welding to be done inThe slag formed from flux cored wire enables welding to be done in

allall--positionspositions Most flux cored wires have a folded seam that can allow moisture toMost flux cored wires have a folded seam that can allow moisture to

get into the fluxget into the flux

Controlled storage & handling is required for µseamed¶ wiresControlled storage & handling is required for µseamed¶ wires

Metal cored wires have the same general characteristics as solidMetal cored wires have the same general characteristics as solid

wireswires -- they can be operated in dip or spray modethey can be operated in dip or spray mode

Some flux cored wires do not require a gas shield (Innershield)Some flux cored wires do not require a gas shield (Innershield)

The welding equipmentThe welding equipment

A visual check should be made on the equipment toA visual check should be made on the equipment to

ensure it is in good working order ensure it is in good working order

Checks when MAG WeldingChecks when MAG Welding



4/23/20074/23/2007 320320 of of 691691

The electrodesThe electrodes

The diameter, specification and the quality of the wireThe diameter, specification and the quality of the wire

are essential for inspection. The level of deoxidisation inare essential for inspection. The level of deoxidisation in

the wire, single, double or triple dethe wire, single, double or triple de--oxidised. The qualityoxidised. The quality

of the wire winding and the copper coating should alsoof the wire winding and the copper coating should also

be inspected to minimize wire feed problems.be inspected to minimize wire feed problems.

Wire liner Wire liner

Check that the liner is the correct type and size for the wireCheck that the liner is the correct type and size for the wire

being used. Steel liners for steel and Teflon liners for being used. Steel liners for steel and Teflon liners for

aluminium.aluminium.

Contact tipsContact tips

Checks when MAG WeldingChecks when MAG Welding



4/23/20074/23/2007 321321 of 691of 691

Contact tipsContact tips

Check the tip is the correct size for the wire being used andCheck the tip is the correct size for the wire being used and

check the amount of wear. Excessive wear will affect wirecheck the amount of wear. Excessive wear will affect wire

speed and electrical current pickspeed and electrical current pick--upupGas and gas flowGas and gas flow--ratesrates

Type of gas and the flow rate need to be checked to ensureType of gas and the flow rate need to be checked to ensure

they comply with the WPSthey comply with the WPS

Other welding variablesOther welding variablesCheck WFS, amps, volts and travel speedCheck WFS, amps, volts and travel speed

Most welding imperfections in MIG/MAG are caused by lack of Most welding imperfections in MIG/MAG are caused by lack of

welder skill, or incorrect settings of the equipmentwelder skill, or incorrect settings of the equipment

Worn contact tips will cause poor power pick up, or transfer Worn contact tips will cause poor power pick up, or transfer

Bad power connections will cause a loss of voltage in the arcBad power connections will cause a loss of voltage in the arc

MIG/MAG typical defectsMIG/MAG typical defects



4/23/20074/23/2007 322322 of 691of 691

p gp g

Silica inclusions (in Fe steels) due to poor inter Silica inclusions (in Fe steels) due to poor inter--run cleaningrun cleaning

Lack of fusion (primarily with dip transfer)Lack of fusion (primarily with dip transfer)

Porosity (from loss of gas shield on site etc)Porosity (from loss of gas shield on site etc)

Solidification problems (cracking, centerline pipes, crater Solidification problems (cracking, centerline pipes, crater

pipes) especially on deep narrow weldspipes) especially on deep narrow welds

Flux Core Arc WeldingFlux Core Arc Welding

WELDING PROCESSWELDING PROCESS



4/23/20074/23/2007 323323 of 691of 691

gg

(Not In The Training Manual)(Not In The Training Manual)

Flux cored arc weldingFlux cored arc welding

FCAWFCAW

methodsmethods



4/23/20074/23/2007 324324 of of 691691

With gasWith gas

shieldingshielding --

³Outershield´³Outershield´

Without gasWithout gas


³Innershield´³Innershield´

With metalWith metal

powder powder --

³Metal core´³Metal core´

³³Outershield´Outershield´ -- principle of operationprinciple of operation



4/23/20074/23/2007 325325 of 691of 691

³Innershield´³Innershield´ -- principle of operationprinciple of operation



4/23/20074/23/2007 326326 of 691of 691


OCVOCV

Constant Voltage CharacteristicConstant Voltage Characteristic

Small change in voltage =Small change in voltage =large change in amperagelarge change in amperage




4/23/20074/23/2007 327327 of 691of 691

VoltsVolts

AmpsAmps

The self The self adjusting arc.adjusting arc.


Small arc gapSmall arc gap

Insulated extension nozzleInsulated extension nozzle

Current carrying guild tubeCurrent carrying guild tube

Flux cored hollow wireFlux cored hollow wire

Flux coreFlux core

Wire jointWire joint

Flux Core Arc Welding (FCAW)Flux Core Arc Welding (FCAW)



4/23/20074/23/2007 328328 of 691of 691

Flux powder Flux powder

Arc shield composed of Arc shield composed of vaporized and slag formingvaporized and slag formingcompoundscompounds

Metal droplets coveredMetal droplets covered

with thin slag coatingwith thin slag coating

MoltenMoltenweldweldpoolpool

Solidified weldSolidified weldmetal and slagmetal and slag

Flux coreFlux corewireswires

Flux cored arc weldingFlux cored arc weldingFCAWFCAW

methodsmethods

WithWith With tWith t With t lWith t l



4/23/20074/23/2007 329329 of 691of 691

With gasWith gas


³Outershield´³Outershield´

Without gasWithout gas


³Innershield´³Innershield´

(114)(114)

With metalWith metal

powder powder --

³Metal core´³Metal core´

With activeWith activegas shieldinggas shielding

(136)(136)

With inert gasWith inert gasshielding (shielding (137137))

FCAWFCAW -- differences from MIG/MAGdifferences from MIG/MAGusually operates in DCEPusually operates in DCEPbut some ³Innershield´but some ³Innershield´wires operates in DCENwires operates in DCEN

power sources need topower sources need tobe more powerful due tobe more powerful due to



4/23/20074/23/2007 330330 of 691of 691

ppthe higher currentsthe higher currents

doesn't work in deepdoesn't work in deep

transfer modetransfer moderequire knurled feed rollsrequire knurled feed rolls

³Innershield´ wires use³Innershield´ wires use

a different type of a different type of welding gunwelding gun

Backhand (³drag´) techniqueBackhand (³drag´) technique

Advantages Advantagespreferred method for flat or horizontal positionpreferred method for flat or horizontal position

slower progression of the weldslower progression of the weld

d t tid t ti



44//2323//20072007 331331 of 691of 691

deeper penetrationdeeper penetration

weld stays hot longer,weld stays hot longer, easy to remove dissolvedeasy to remove dissolved

gassesgassesDisadvantagesDisadvantages

produce a higher weld profileproduce a higher weld profile

difficult to follow the weld jointdifficult to follow the weld jointcan lead to burncan lead to burn--through on thin sheet platesthrough on thin sheet plates

Forehand (³push´) techniqueForehand (³push´) technique

Advantages Advantagespreferred method for vertical up or overheadpreferred method for vertical up or overhead

positionpositionarc is directed towards the unwelded jointarc is directed towards the unwelded joint , preheat, preheat

effecteffect



4/23/20074/23/2007 332332 of 691of 691

effecteffect

easy to follow the weld joint and control theeasy to follow the weld joint and control the

penetrationpenetrationDisadvantagesDisadvantages

produce a low weld profile, with coarser ripplesproduce a low weld profile, with coarser ripples

fast weld progression, shallower depth of penetrationfast weld progression, shallower depth of penetration

the amount of spatter can increasethe amount of spatter can increase

FCAW advantagesFCAW advantages

less sensitive to lack of fusionless sensitive to lack of fusion

requires smaller included angle compared to MMArequires smaller included angle compared to MMA

high productivityhigh productivity

all positionalall positional



4/23/20074/23/2007 333333 of 691of 691

all positionalall positional

smooth bead surface, less danger of undercutsmooth bead surface, less danger of undercut

basic types produce excellent toughness propertiesbasic types produce excellent toughness propertiesgood control of the weld pool in positional weldinggood control of the weld pool in positional welding

especially with rutile wiresespecially with rutile wires

seamless wires have no torsional strain, twist freeseamless wires have no torsional strain, twist free

ease of varying the alloying constituentsease of varying the alloying constituentsno need for shielding gasno need for shielding gas

FCAW disadvantagesFCAW disadvantageslimited to steels and Nilimited to steels and Ni--base alloysbase alloys

slag covering must be removedslag covering must be removed

FCAW wire is more expensive on a weight basisFCAW wire is more expensive on a weight basisthan solid wires (exception: some high alloy steels)than solid wires (exception: some high alloy steels)

for gas shielded process the gaseous shield may befor gas shielded process the gaseous shield may be



4/23/20074/23/2007 334334 of 691of 691

for gas shielded process, the gaseous shield may befor gas shielded process, the gaseous shield may beaffected by winds and draftsaffected by winds and drafts

more smoke and fumes are generated comparedmore smoke and fumes are generated comparedwith MIG/MAGwith MIG/MAG

in case of Innershield wires, it might be necessary toin case of Innershield wires, it might be necessary tobreak the wire for restart (due to the high amount of break the wire for restart (due to the high amount of insulating slag formed at the tip of the wire)insulating slag formed at the tip of the wire)

Advantages:Advantages:

1) Field or shop use1) Field or shop use

2) High productivity2) High productivity

Disadvantages:Disadvantages:

11) High skill factor ) High skill factor

2) Slag inclusions2) Slag inclusions

FCAW advantages/disadvantagesFCAW advantages/disadvantages



4/23/20074/23/2007 335335 of 691of 691

2) High productivity2) High productivity

3) All positional3) All positional

4) Slag supports and4) Slag supports and

shapes the weld Beadshapes the weld Bead

5) No need for shielding5) No need for shielding

gasgas

) g) g

3) Cored wire is3) Cored wire is

ExpensiveExpensive

4) High level of fume4) High level of fume

(Inner (Inner--shield)shield)

55) Limited to steels and) Limited to steels and

nickel alloysnickel alloys


Submerged Arc WeldingSubmerged Arc WeldingSection 13Section 13



4/23/20074/23/2007 336336 of 691of 691

Section 13Section 13

Submerged arc welding was developed in the Soviet Unionduring the 2nd world war for the welding of thick section steel.

The process is normally mechanized.

The process uses amps in the range of 100 to over 2000, which

i hi h t d it i th i d i d

Submerged Arc Welding IntroductionSubmerged Arc Welding Introduction



4/23/20074/23/2007 337337 of of 691691

gives a very high current density in the wire producing deeppenetration and high dilution welds.

A flux is supplied separately via a flux hopper in the form of either fused or agglomerated.

The arc is not visible as it is submerged beneath the flux layer

and no eye protection is required.

SAW Principle of operationSAW Principle of operation



4/23/20074/23/2007 338338 of 691of 691

Principles of operationPrinciples of operationFactors that determine whether to use SAWFactors that determine whether to use SAW chemicalchemical

composition and mechanical properties required for the weldcomposition and mechanical properties required for the weld

depositdeposit

thickness of base metal to be weldedthickness of base metal to be welded

joint accessibilityjoint accessibility



4/23/20074/23/2007 339339 of 691of 691

joint accessibility joint accessibility

position in which the weld is to be madeposition in which the weld is to be made

frequency or volume of welding to be performedfrequency or volume of welding to be performed

SAW methodsSAW methods

SemiautomaticSemiautomatic MechanisedMechanised AutomaticAutomatic

Submerged Arc WeldingSubmerged Arc Welding

Power Power

supplysupply

Filler wire spoolFiller wire spool

Flux hopper Flux hopper



4/23/20074/23/2007 340340 of 691of 691

-- ++

Wire electrodeWire electrode

FluxFlux

Slide railSlide rail

SAW process variablesSAW process variables welding currentwelding current

current type and polaritycurrent type and polarity

welding voltagewelding voltage

travel speedtravel speed



4/23/20074/23/2007 341341 of 691of 691

electrode sizeelectrode size

electrode extensionelectrode extension

width and depth of the layer of fluxwidth and depth of the layer of flux

SAW process variablesSAW process variablesWelding currentWelding current

controls depth of penetration and the amount of controls depth of penetration and the amount of

base metal meltedbase metal melted && dilutiondilution



44//2323//20072007 342342 of 691of 691

SAW operating variablesSAW operating variablesCurrent type and polarityCurrent type and polarity

Usually DC

EP, deepUsually DC

EP, deeppenetration, better penetration, better

resistance toresistance to



4/23/20074/23/2007 343343 of 691of 691

porosityporosity

DC

EN increaseDC

EN increasedeposition rate butdeposition rate but

reduce penetrationreduce penetration

(surfacing)(surfacing)

AC used to avoidAC used to avoid

arc blow; can givearc blow; can give

unstable arcunstable arc

SAW ConsumablesSAW Consumables(Covered in detail in Section 14)(Covered in detail in Section 14)

Fused fluxes advantages:Fused fluxes advantages:

good chemical homogeneitygood chemical homogeneity

easy removal of fines without affecting fluxeasy removal of fines without affecting fluxcompositioncomposition

normally not hygroscopicnormally not hygroscopic & easy storage and handling& easy storage and handling



4/23/20074/23/2007 344344 of of 691691

normally not hygroscopicnormally not hygroscopic & easy storage and handling& easy storage and handling

readily recycled without significant change in particlereadily recycled without significant change in particle

size or compositionsize or composition

Fused fluxes disadvantages:Fused fluxes disadvantages:difficult to add deoxidizers and ferrodifficult to add deoxidizers and ferro--alloys (due toalloys (due to

segregation or extremely high loss)segregation or extremely high loss)

high temperatures needed to melt ingredients limit thehigh temperatures needed to melt ingredients limit therange of flux compositionsrange of flux compositions

SAW ConsumablesSAW ConsumablesAgglomerated fluxes advantages:Agglomerated fluxes advantages:

easy addition of deoxidizers and alloying elementseasy addition of deoxidizers and alloying elements

usable with thicker layer of flux when weldingusable with thicker layer of flux when welding

colour identificationcolour identification



4/23/20074/23/2007 345345 of 691of 691

Agglomerated fluxes disadvantages:Agglomerated fluxes disadvantages:

tendency to absorb moisturetendency to absorb moisture

possible gas evolution from the molten slag leading topossible gas evolution from the molten slag leading to

porosityporosity

possible change in flux composition due to segregation or possible change in flux composition due to segregation or removal of fine mesh particlesremoval of fine mesh particles

SAW equipmentSAW equipmentPower sources can be:Power sources can be:

transformers for ACtransformers for AC

transformer transformer--rectifiers for DCrectifiers for DC

Static characteristic can be:Static characteristic can be:



4/23/20074/23/2007 346346 of 691of 691

Constant Voltage (flat)Constant Voltage (flat) -- most of the power sourcesmost of the power sources

Constant Current (drooping)Constant Current (drooping)

SAW equipmentSAW equipmentConstant Voltage (Flat Characteristic) power sources:Constant Voltage (Flat Characteristic) power sources:

most commonly used supplies for SAWmost commonly used supplies for SAW

can be used for both semiautomatic and automatic weldingcan be used for both semiautomatic and automatic welding

self self--regulating arcregulating arc



4/23/20074/23/2007 347347 of 691of 691

simple wire feed speed controlsimple wire feed speed control

wire feed speed controls the current and power supplywire feed speed controls the current and power supplycontrols the voltagecontrols the voltage

applications for DC are limited to 1000A due to severe arcapplications for DC are limited to 1000A due to severe arc

blow (also thin wires!)blow (also thin wires!)


OCV

Constant Voltage Characteristic

Small change in voltage =large change in amperage

Large arc gap



4/23/20074/23/2007 348348 of of 691691

Volts

Amps

The self adjusting arc.

Small arc gap

SAW equipmentSAW equipmentConstant Current (DroopingCharacteristic) power sources:Constant Current (DroopingCharacteristic) power sources:

Over Over 10001000AA -- very fast speed requiredvery fast speed required -- control of burn off control of burn off

rate and stick out lengthrate and stick out length

can be used for both semiautomatic and automatic weldingcan be used for both semiautomatic and automatic welding

not selfnot self regulating arcregulating arc



4/23/20074/23/2007 349349 of 691of 691

not self not self--regulating arcregulating arc

must be used with a voltagemust be used with a voltage--sensing variable wire feedsensing variable wire feed

speed controlspeed control

more expensive due to more complex wire feed speedmore expensive due to more complex wire feed speed

controlcontrol

arc voltage depends upon wire feed speed whilst the power arc voltage depends upon wire feed speed whilst the power

source controls the currentsource controls the current

cannot be used for highcannot be used for high--speed welding of thin steelspeed welding of thin steel

SAW equipmentSAW equipmentWelding heads can be mounted on a:Welding heads can be mounted on a:

Tractor type carriageTractor type carriage

provides travel along straight or provides travel along straight or

gently curved jointsgently curved joints

can ride on tracks set up along thecan ride on tracks set up along the



4/23/20074/23/2007 350350 of 691of 691

can ride on tracks set up along thecan ride on tracks set up along the

joint (with grooved wheels) or on joint (with grooved wheels) or on

the workpiece itself the workpiece itself

can use guide wheels as trackingcan use guide wheels as tracking

devicedevice

due to their portability, are used indue to their portability, are used in

field welding or where the piecefield welding or where the piece

cannot be movedcannot be moved

Courtesy of ESAB ABCourtesy of ESAB AB


SAW operating variablesSAW operating variablesWelding currentWelding current

too high current: excessive excess weld metaltoo high current: excessive excess weld metal

(waste of electrode), increase weld shrinkage and(waste of electrode), increase weld shrinkage and

causes greater distortionscauses greater distortions

excessively high current:excessively high current: digging arc, undercut,digging arc, undercut,



44//2323//20072007 351351 of 691of 691

excessively high current:excessively high current: digging arc, undercut,digging arc, undercut,

burn through; also a high and narrow bead &burn through; also a high and narrow bead &

solidification crackingsolidification cracking

too low current:too low current: incompleteincomplete

fusion or inadequate penetrationfusion or inadequate penetration

excessively low current:excessively low current:

unstable arcunstable arc

SAW operating variablesSAW operating variablesWelding voltageWelding voltage

welding voltage controls arcwelding voltage controls arc

lengthlengthincrease in voltage produce aincrease in voltage produce a

flatter and wider beadflatter and wider bead



4/23/20074/23/2007 352352 of 691of 691

an increased voltage can increase pickan increased voltage can increase pick--up of alloying elementsup of alloying elements

from an alloy fluxfrom an alloy flux

increase in voltage increaseincrease in voltage increase

flux consumptionflux consumption

increase in voltage tend toincrease in voltage tend to

reduce porosityreduce porosity

an increased voltage mayan increased voltage may

help bridging an excessivehelp bridging an excessive

root gaproot gap


low voltage produce alow voltage produce a

³stiffer´ arc & improves³stiffer´ arc & improves

penetration in a deeppenetration in a deep



4/23/20074/23/2007 353353 of 691of 691

penetration in a deeppenetration in a deep

weld groove and resistsweld groove and resists

arc blowarc blowexcessive low voltageexcessive low voltage

produce a high narrowproduce a high narrow

bead & difficult slagbead & difficult slag

removalremoval


excessively high voltageexcessively high voltageproduce a ³hatproduce a ³hat--shaped´ beadshaped´ bead

& tendency to crack& tendency to crack



4/23/20074/23/2007 354354 of 691of 691

excessively high voltageexcessively high voltage

increase undercut & make slagincrease undercut & make slagremoval difficult in grooveremoval difficult in groove

weldswelds

excessively high voltageexcessively high voltageproduce a concave fillet weldproduce a concave fillet weld

that is subject to crackingthat is subject to cracking

SAW operating variablesSAW operating variablesTravel speedTravel speed

increase in travel speed: decrease heat inputincrease in travel speed: decrease heat input & less& less

filler metal applied per unit of length, less excessfiller metal applied per unit of length, less excessweld metalweld metal && weld bead becomes smaller weld bead becomes smaller



4/23/20074/23/2007 355355 of 691of 691

SAW operating variablesSAW operating variablesTravel speedTravel speed

excessively high speedexcessively high speed

lead to undercut, arclead to undercut, arc

blow and porosityblow and porosity



4/23/20074/23/2007 356356 of 691of 691

excessively low speedexcessively low speedproduce ³hatproduce ³hat--shaped´ beadsshaped´ beads

danger of crackingdanger of cracking

excessively low speed produce rough beads andexcessively low speed produce rough beads and

lead to slag inclusionslead to slag inclusions

SAW operating variablesSAW operating variablesElectrode sizeElectrode size

at the same current, small electrodes have higher at the same current, small electrodes have higher

current densitycurrent density & higher deposition rates& higher deposition rates



4/23/20074/23/2007 357357 of 691of 691

SAW operating variablesSAW operating variablesElectrode extensionElectrode extension

increased electrode extension adds resistance in theincreased electrode extension adds resistance in the

welding circuitwelding circuit I increase in deposition rate, decrease inI increase in deposition rate, decrease in

penetration and bead widthpenetration and bead width



4/23/20074/23/2007 358358 of 691of 691

to keep a proper weld shape, when electrode extension isto keep a proper weld shape, when electrode extension is

increased, voltage must also be increasedincreased, voltage must also be increased

when burnwhen burn--through is a problem (e.g. thin gauge), increasethrough is a problem (e.g. thin gauge), increase

electrode extensionelectrode extension

excessive electrode extension: it is more difficult toexcessive electrode extension: it is more difficult to

maintain the electrode tip in the correct positionmaintain the electrode tip in the correct position

SAW operating variablesSAW operating variablesDepth of fluxDepth of flux

depth of flux layer influence the appearance of welddepth of flux layer influence the appearance of weld

usually, depth of flux is 25usually, depth of flux is 25--30 mm30 mm

if flux layer is to deepif flux layer is to deep the arc is too confined result isthe arc is too confined result is



4/23/20074/23/2007 359359 of 691of 691

if flux layer is to deepif flux layer is to deep the arc is too confined, result isthe arc is too confined, result is

a rough ropelike appearing welda rough ropelike appearing weld

if flux layer is to deep the gases cannot escape & theif flux layer is to deep the gases cannot escape & thesurface of molten weld metal becomes irregularlysurface of molten weld metal becomes irregularly

distorteddistorted

if flux layer is too shallow, flashing and spattering willif flux layer is too shallow, flashing and spattering will

occur, give a poor appearance and porous weldoccur, give a poor appearance and porous weld

SAWSAW



4/23/20074/23/2007 360360 of 691of 691

SAWSAW



4/23/20074/23/2007 361361 of 691of 691

SAWSAW



44//2323//20072007 362362 of 691of 691

SAW technological variablesSAW technological variablesTravel angle effectTravel angle effect -- Butt weld on platesButt weld on plates



4/23/20074/23/2007 363363 of 691of 691

Penetration Deep Moderate ShallowPenetration Deep Moderate Shallow

Excess weld metal Maximum Moderate MinimumExcess weld metal Maximum Moderate Minimum

Tendency to undercut Severe Moderate MinimumTendency to undercut Severe Moderate Minimum

SAW technological variablesSAW technological variablesEarth positionEarth position ++

--

Direction of Direction of traveltravel



4/23/20074/23/2007 364364 of 691of 691

--

welding towards earth produces backward arc blowwelding towards earth produces backward arc blow

deep penetrationdeep penetration

convex weld profileconvex weld profile

SAW technological variablesSAW technological variablesEarth positionEarth position

++

Direction of Direction of traveltravel



4/23/20074/23/2007 365365 of 691of 691

--

welding away earth produces forward arc blowwelding away earth produces forward arc blow

normal penetration depthnormal penetration depth

smooth, even weld profilesmooth, even weld profile

Weld backingWeld backing

Backing stripBacking strip



4/23/20074/23/2007 366366 of 691of 691

Backing weldBacking weld

Copper backingCopper backing

Starting/finishing the weldStarting/finishing the weld



44//2323//20072007 367367 of of 691691

SAW variantsSAW variantsTwin wire SAW weldingTwin wire SAW welding two electrodes are feedtwo electrodes are feed

into the same weld poolinto the same weld pool

wire diameter usually 1,6 towire diameter usually 1,6 to3,2 mm3,2 mm

electrodes are connectedelectrodes are connected



4/23/20074/23/2007 368368 of 691of 691

electrodes are connectedelectrodes are connected

to a single power sourceto a single power source & a& a

single arc is establishedsingle arc is established

normally operate withnormally operate with

DCEPDCEP

offers increased depositionoffers increased deposition

rate by up to 80% comparedrate by up to 80% compared

to single wire SAWto single wire SAW

SAW variantsSAW variants

Wi b i t dWi b i t d



4/23/20074/23/2007 369369 of of 691691

Wires can be orientedWires can be oriented

for maximum or for maximum or

minimum penetrationminimum penetration

SAW variantsSAW variantsTandem arc SAW processTandem arc SAW process usually DCEP on leadusually DCEP on lead

and AC on trail toand AC on trail to reducereduce

arc blowarc blow

requires two separaterequires two separate

power sourcespower sources



4/23/20074/23/2007 370370 of 691of 691

pp

the electrodes are activethe electrodes are active

in the same puddle BUT in the same puddle BUT there are 2 separate arcsthere are 2 separate arcs

increased depositionincreased deposition

rate by up to 100%rate by up to 100%

compared with singlecompared with singlewire SAWwire SAW

SAW variantsSAW variantsSAW tandem arcSAW tandem arc

with two wireswith two wires



4/23/20074/23/2007 371371 of of 691691


SAW variantsSAW variants



4/23/20074/23/2007 372372 of 691of 691

Single poolSingle pool -- highest deposition ratehighest deposition rate

Twin poolTwin pool -- travel speed limited by undercut;travel speed limited by undercut;

very resistant to porosity and cracksvery resistant to porosity and cracks

SAW variantsSAW variantsTandem arc SAW processTandem arc SAW process -- multiple wiresmultiple wires

only for welding thickonly for welding thicksections (>30 mm)sections (>30 mm)

not suitable for use innot suitable for use in



4/23/20074/23/2007 373373 of 691of 691

narrow weldnarrow weld

preparations (rootpreparations (root

passes)passes)

one 4 mm wire at 600 A,one 4 mm wire at 600 A,

6.8 kg/hr 6.8 kg/hr

tandem two 4 mm wirestandem two 4 mm wiresat 600 A, 13.6 kg/hr at 600 A, 13.6 kg/hr Courtesy of ESAB ABCourtesy of ESAB AB

SAW variantsSAW variantsStrip cladding needs aStrip cladding needs a

special welding headspecial welding head



4/23/20074/23/2007 374374 of 691of 691

SAW variantsSAW variantsNarrow gap weldingNarrow gap welding

for welding thickfor welding thick

materialsmaterials

less filler metal requiredless filler metal required

requires special grooverequires special groove



4/23/20074/23/2007 375375 of 691of 691

q p gq p g

preparation and specialpreparation and special

welding headwelding headrequires special fluxes,requires special fluxes,

otherwise problems withotherwise problems with

slag removalslag removal

defect removal is verydefect removal is verydifficultdifficult

SAW variantsSAW variantsCold wire weldingCold wire welding

the cold wire is not connected to power sourcethe cold wire is not connected to power source

increase deposition rates up to 75%increase deposition rates up to 75%

high deposition rate at fixed heat input results inhigh deposition rate at fixed heat input results in

lower penetration!lower penetration!



4/23/20074/23/2007 376376 of 691of 691

lower penetration!lower penetration!

SAW variantsSAW variantsHot wire weldingHot wire welding

the hot wire is connected to power sourcethe hot wire is connected to power source & much& much

more efficient than cold wire (current is used entirelymore efficient than cold wire (current is used entirelyto heat the wire!)to heat the wire!)

increase deposition ratesincrease deposition rates



4/23/20074/23/2007 377377 of of 691691

up to 100%up to 100%

requires additionalrequires additionalwelding equipment,welding equipment,

additional control of additional control of

variables, considerablevariables, considerable

setset--up time and closer up time and closer operator attentionoperator attention

SAW variantsSAW variantsSAW with metal powder additionSAW with metal powder addition

increased deposition rates up toincreased deposition rates up to

70%; increased welding speed70%; increased welding speedgives smooth fusion, improvedgives smooth fusion, improvedbead appearance, reducedbead appearance, reducedpenetration and dilution from parentpenetration and dilution from parent

t lt l & hi h i t t th& hi h i t t th



4/23/20074/23/2007 378378 of 691of 691

metalmetal & higher impact strength& higher impact strength

metal powders can modifymetal powders can modifychemical composition of final weldchemical composition of final welddepositdeposit

does not increase risk of crackingdoes not increase risk of cracking

do not require additional arc energydo not require additional arc energy

metal powder can be added aheadmetal powder can be added aheador directly into the weld poolor directly into the weld pool

SAW variantsSAW variantsSAW with metal powder additionSAW with metal powder addition

magnetic attachment of powder magnetic attachment of powder



4/23/20074/23/2007 379379 of 691of 691

SAW with metal cored wiresSAW with metal cored wires

SAW variantsSAW variantsStorage tankStorage tank

SAW of circular SAW of circular

weldswelds



4/23/20074/23/2007 380380 of 691of 691


15%

Submerged arc welds are difficult to predict as the weld isSubmerged arc welds are difficult to predict as the weld is

made up of three elements. The dilution may be as much asmade up of three elements. The dilution may be as much as

60% resulting in a high susceptibility to solidification cracking60% resulting in a high susceptibility to solidification cracking

Submerged Arc Welding Process (SAW)Submerged Arc Welding Process (SAW)



4/23/20074/23/2007 381381 of 691of 691

25%60%

Flux elements Electrode Dilution

Advantages of SAW Advantages of SAW high current density,high current density, high deposition rates (up to 10 timeshigh deposition rates (up to 10 times

those for MMA), high productivitythose for MMA), high productivity

deep penetration allowing the use of small welding groovesdeep penetration allowing the use of small welding grooves

fast travel speed, less distortionfast travel speed, less distortion

deslagging is easier deslagging is easier

uniform bead appearance with good surface finish and gooduniform bead appearance with good surface finish and good



44//2323//20072007 382382 of of 691691

uniform bead appearance with good surface finish and gooduniform bead appearance with good surface finish and good

fatigue propertiesfatigue properties

can be easily performed mechanised, giving a higher dutycan be easily performed mechanised, giving a higher dutycycle and low skill level requiredcycle and low skill level required

provide consistent quality when performed automatic or provide consistent quality when performed automatic or

mechanisedmechanised

Virtually assured radiographically sound weldsVirtually assured radiographically sound welds

arc is not visiblearc is not visible

little smoke/fumes are developedlittle smoke/fumes are developed

Disadvantages of SAWDisadvantages of SAW limited mainly between flat and horizontal positionslimited mainly between flat and horizontal positions

limited to carbon, low alloy, creep resisting, stainless steelslimited to carbon, low alloy, creep resisting, stainless steelsand nickel alloysand nickel alloys

due to the high heat input, impact strength of welddue to the high heat input, impact strength of weldmetal/HAZ may be low; also high dilutionmetal/HAZ may be low; also high dilution

slag must be cleared away after welding due to theslag must be cleared away after welding due to the dangerdanger



4/23/20074/23/2007 383383 of 691of 691

slag must be cleared away after welding due to theslag must be cleared away after welding due to the danger danger of slag inclusionsof slag inclusions

need flux storage, handling and recirculation controlneed flux storage, handling and recirculation control

difficult to apply ondifficult to apply on--site due to complicated equipmentsite due to complicated equipment

high capital costshigh capital costs

weld line must be regular (straight or circumferential seamsweld line must be regular (straight or circumferential seams

only) with accurate fitonly) with accurate fit--upup

AdvantagesAdvantages

Low weldLow weld--metal costmetal cost

Easily automatedEasily automated

L l l fL l l f


Restricted weldingRestricted weldingpositionspositions

Arc blow on DC Arc blow on DC

Submerged Arc WeldingSubmerged Arc Welding



4/23/20074/23/2007 384384 of 691of 691

Low levels of ozoneLow levels of ozone

High productivityHigh productivity

No visible arc lightNo visible arc light

Minimum cleaningMinimum cleaning

currentcurrent

Shrinkage defectsShrinkage defects

Difficult penetrationDifficult penetration

controlcontrol

Limited jointsLimited joints


Welding ConsumablesWelding ConsumablesSection 14Section 14



4/23/20074/23/2007 385385 of 691of 691

BS EN 499 MMA Covered ElectrodesBS EN 499 MMA Covered Electrodes

Covered Electrode

Covered Electrode

ToughnessToughness

Yield Strength N/mm Yield Strength N/mm22

EE 5050 33 2Ni2Ni BB 77 22 H10H10



4/23/20074/23/2007 386386 of of 691691

Chemical compositionChemical composition

Flux CoveringFlux Covering

Weld Metal RecoveryWeld Metal Recovery

and Current Typeand Current Type


Hydrogen ContentHydrogen Content

Welding consumables are any products that are used up inWelding consumables are any products that are used up in

the production of a weldthe production of a weld

Welding consumables may be:Welding consumables may be: Covered electrodes, filler wires and electrode wires.Covered electrodes, filler wires and electrode wires.

Shielding or oxyShielding or oxy--fuel gases.fuel gases.

Welding consumablesWelding consumables



4/23/20074/23/2007 387387 of 691of 691

g yg y gg

Separately supplied fluxes.Separately supplied fluxes.

Fusible inserts.Fusible inserts.

Welding Consumable StandardsWelding Consumable Standards

MMA (SMAW)MMA (SMAW)

BS EN 499: Steel electrodesBS EN 499: Steel electrodes

AWS A5.1 Non AWS A5.1 Non--alloyed steelalloyed steel


MIG/MAG (GMAW) TIGMIG/MAG (GMAW) TIG

(GTAW)(GTAW)

BS 2901: Filler wiresBS 2901: Filler wires

BS EN 440: Wire electrodesBS EN 440: Wire electrodes



4/23/20074/23/2007 388388 of of 691691


AWS A5.4 Chromium AWS A5.4 Chromiumelectrodeselectrodes

AWS A5.5 Alloyed steel AWS A5.5 Alloyed steel


AWS A5.9: Filler wires AWS A5.9: Filler wires

BS EN 439: Shielding gasesBS EN 439: Shielding gases

SAWSAW

BS 4165: Wire and fluxesBS 4165: Wire and fluxes

BS EN 756: Wire electrodesBS EN 756: Wire electrodes

BS EN 760: FluxesBS EN 760: Fluxes

AWS A5.17: Wires and fluxes AWS A5.17: Wires and fluxes

Welding Consumable GasesWelding Consumable Gaseswelding gaseswelding gases

GMAW, FCAW, TIG, OxyGMAW, FCAW, TIG, Oxy-- FuelFuel

Supplied in cylinders or Supplied in cylinders or storagestoragetanks for large quantitiestanks for large quantities

Colour coded cylinders to minimiseColour coded cylinders to minimisewrong usewrong use

Subject to regulations concernedSubject to regulations concerned



4/23/20074/23/2007 389389 of 691of 691

Subject to regulations concernedSubject to regulations concernedhandling, quantities and positioninghandling, quantities and positioning

of storage areasof storage areas Moisture content is limited to avoidMoisture content is limited to avoid

cold crackingcold cracking

Dew point (the temperature at whichDew point (the temperature at whichthe vapour begins to condense)the vapour begins to condense)must be checkedmust be checked

Welding ConsumablesWelding ConsumablesEach consumable is critical in respect to:Each consumable is critical in respect to:

Size, (diameter and length)Size, (diameter and length)

Classification / Supplier Classification / Supplier

ConditionCondition



4/23/20074/23/2007 390390 of 691of 691

Treatments e.g. baking / dryingTreatments e.g. baking / drying

Handling and storage is critical for consumableHandling and storage is critical for consumable

controlcontrol

Handling and storage of gases is critical for safetyHandling and storage of gases is critical for safety

Quality AssuranceQuality AssuranceWelding Consumables:Welding Consumables:

filler material must be stored in an area with controlledfiller material must be stored in an area with controlled

temperature and humiditytemperature and humidity poor handling and incorrect stacking may damage coatings,poor handling and incorrect stacking may damage coatings,

rendering the electrodes unusablerendering the electrodes unusable

there should be an issue and return policy for weldingthere should be an issue and return policy for welding



4/23/20074/23/2007 391391 of 691of 691

there should be an issue and return policy for weldingthere should be an issue and return policy for welding

consumables (system procedure)consumables (system procedure)

control systems for electrode treatment must be checked andcontrol systems for electrode treatment must be checked and

calibrated; those operations must be recordedcalibrated; those operations must be recorded

filler material suppliers must be approved before purchasingfiller material suppliers must be approved before purchasing

any materialany material



MMA Covered ElectrodesMMA Covered Electrodes



44//2323//20072007 392392 of of 691691


CellulosicCellulosic -- deep penetration/fusiondeep penetration/fusion

RutileRutile -- general purposegeneral purpose

BasicBasic -- low hydrogenlow hydrogen


Welding consumables for MMA:Welding consumables for MMA:

Consist of a core wire typically between 350Consist of a core wire typically between 350--450mm in450mm inlength and from 2.5mmlength and from 2.5mm -- 6mm in diameter 6mm in diameter

The wire is covered with an extruded flux coatingThe wire is covered with an extruded flux coating



4/23/20074/23/2007 393393 of 691of 691

The core wire is generally of a low quality rimming steelThe core wire is generally of a low quality rimming steel

The weld quality is refined by the addition of alloyingThe weld quality is refined by the addition of alloying

and refining agents in the flux coatingand refining agents in the flux coating

The flux coating contains many elements andThe flux coating contains many elements and

compounds that all have a variety of functions duringcompounds that all have a variety of functions duringweldingwelding

MMA Welding ConsumablesMMA Welding ConsumablesFunction of the Electrode Covering:Function of the Electrode Covering:

To facilitate arc ignition and give arc stabilityTo facilitate arc ignition and give arc stability

To generate gas for shielding the arc & molten metal from air To generate gas for shielding the arc & molten metal from air contaminationcontamination

To deTo de--oxidise the weld metal and flux impurities into the slagoxidise the weld metal and flux impurities into the slag

T f t ti l bl k t th lidif i dT f t ti l bl k t th lidif i d



4/23/20074/23/2007 394394 of 691of 691

To form a protective slag blanket over the solidifying andTo form a protective slag blanket over the solidifying andcooling weld metalcooling weld metal

To provide alloying elements to give the required weld metalTo provide alloying elements to give the required weld metalpropertiesproperties

To aid positional welding (slag design to have suitableTo aid positional welding (slag design to have suitablefreezing temperature to support the molten weld metal)freezing temperature to support the molten weld metal)

To control hydrogen contents in the weld (basic type)To control hydrogen contents in the weld (basic type)

1: Electrode size (diameter and length)1: Electrode size (diameter and length)

2: Covering condition: adherence, cracks, chips and concentricity2: Covering condition: adherence, cracks, chips and concentricity

Covered electrode inspectionCovered electrode inspection



4/23/20074/23/2007 395395 of 691of 691

3: Electrode designation3: Electrode designation

EN 499-E 51 3 B

Arc ignition enhancing materials (optional!)Arc ignition enhancing materials (optional!)

See BS EN ISO 544 for further informationSee BS EN ISO 544 for further information

MMA Welding ConsumablesMMA Welding ConsumablesPlastic foil sealed cardboard boxPlastic foil sealed cardboard boxrutile electrodesrutile electrodes

general purpose basic electrodesgeneral purpose basic electrodes

Courtesy of Lincoln ElectricCourtesy of Lincoln Electric

c t r i c

c t r i c



4/23/20074/23/2007 396396 of of 691691

Tin canTin can

cellulosic electrodescellulosic electrodes

Vacuum sealed packVacuum sealed packextra low hydrogen electrodesextra low hydrogen electrodes

C o u r t e s y o f L i n c o l n E l e c

C o u r t e s y o f L i n c o l n E l e c

MMA Welding ConsumablesMMA Welding ConsumablesCellulosic electrodes:Cellulosic electrodes:

covering contains cellulose (organic material).covering contains cellulose (organic material).

produce a gas shield high in hydrogenproduce a gas shield high in hydrogen raising the arcraising the arcvoltage.voltage.

Deep penetration / fusion characteristicsDeep penetration / fusion characteristics enablesenables



4/23/20074/23/2007 397397 of 691of 691

welding at high speed without risk of lack of fusion.welding at high speed without risk of lack of fusion.

generates high level of fumes and Hgenerates high level of fumes and H22 cold cracking.cold cracking.

Forms a thin slag layer with coarse weld profile.Forms a thin slag layer with coarse weld profile.

not require baking or drying (excessive heat willnot require baking or drying (excessive heat will

damage electrode covering!).damage electrode covering!).

Mainly used for stove pipe weldingMainly used for stove pipe welding

hydrogen content ishydrogen content is 8080--9090 ml/ml/100100 g of weld metal.g of weld metal.

MMA Welding ConsumablesMMA Welding ConsumablesCellulosic ElectrodesCellulosic Electrodes


weld beads have high hydrogenweld beads have high hydrogen

risk of crackingrisk of cracking ( need to k eep j oint hot during w elding to allow ( need to k eep j oint hot during w elding to allow

H to escape)H to escape)



4/23/20074/23/2007 398398 of 691of 691

not suitable for higher strength steelsnot suitable for higher strength steels -- cracking risk toocracking risk too

highhigh (may not be allow ed f or Grades stronger t han X70 )(may not be allow ed f or Grades stronger t han X70 )

not suitable for very thick sectionsnot suitable for very thick sections (may not be used on (may not be used on

t hic k nesses > ~ 35 mm )t hic k nesses > ~ 35 mm )

not suitable when low temperature toughness is requirednot suitable when low temperature toughness is required

( i m pact toug hness satisf actory dow n to ~( i m pact toug hness satisf actory dow n to ~ --20 20°°C )C )


Advantages: Advantages:

Deep penetration/fusionDeep penetration/fusion

S it bl f ldi i llS it bl f ldi i ll

DisadvantagesDisadvantages::

High in hydrogenHigh in hydrogen

High crack tendencHigh crack tendenc

Cellulosic ElectrodesCellulosic Electrodes



44//2323//20072007 399399 of 691of 691

Suitable for welding in allSuitable for welding in all

positionspositions

Fast travel speedsFast travel speeds

Large volumes of shieldingLarge volumes of shielding

gasgas

Low controlLow control

High crack tendencyHigh crack tendency

Rough weldRough weldappearanceappearance

High spatter contentsHigh spatter contents

Low deposition ratesLow deposition rates

MMA Welding ConsumablesMMA Welding ConsumablesRutile electrodes:Rutile electrodes:

covering contains TiOcovering contains TiO22 slag former and arc stabiliser.slag former and arc stabiliser.

easy to strike arc, less spatter, excellent for positionaleasy to strike arc, less spatter, excellent for positionalwelding.welding.

stable, easystable, easy--toto--use arcuse arc can operate in both DC and AC.can operate in both DC and AC.

slag easy to detach, smooth profile.slag easy to detach, smooth profile.



4/23/20074/23/2007 400400 of 691of 691

Reasonably good strength weld metal.Reasonably good strength weld metal.

Used mainly on general purpose work.Used mainly on general purpose work.

Low pressure pipework, support brackets.Low pressure pipework, support brackets.

electrodes can be dried to lower H2 content but cannot beelectrodes can be dried to lower H2 content but cannot be

bakedbaked as it willwill destroy the coating.

hydrogen content is 25hydrogen content is 25--30 ml/100 g of weld metal.30 ml/100 g of weld metal.

MMA Welding ConsumablesMMA Welding ConsumablesRutile electrodesRutile electrodes


they cannot be made with a low hydrogen contentthey cannot be made with a low hydrogen content

cannot be used on high strength steels or thick jointscannot be used on high strength steels or thick joints --

cracking risk too highcracking risk too high



4/23/20074/23/2007 401401 of 691of 691

they do not give good toughness at low temperaturesthey do not give good toughness at low temperatures

these limitations mean that they are only suitable for generalthese limitations mean that they are only suitable for general

engineeringengineering -- low strength, thin steellow strength, thin steel



Easy to useEasy to use

Low cost / controlLow cost / control


High in hydrogenHigh in hydrogen

High crack tendencyHigh crack tendency

Rutile ElectrodesRutile Electrodes



4/23/20074/23/2007 402402 of 691of 691

Smooth weld profilesSmooth weld profiles

Slag easily detachableSlag easily detachable

High depositionHigh deposition

possible with thepossible with the

addition of iron powder addition of iron powder

Low strengthLow strength

Low toughness valuesLow toughness values

MMA Welding ConsumablesMMA Welding ConsumablesRutile VariantsRutile Variants

High Recovery Rutile ElectrodesHigh Recovery Rutile Electrodes

Characteristics:Characteristics:

coating is µbulked out¶ with iron powder coating is µbulked out¶ with iron powder

iron powder gives the electrode µhigh recovery¶iron powder gives the electrode µhigh recovery¶

extra weld metal from the iron powder can mean that weldextra weld metal from the iron powder can mean that weld



4/23/20074/23/2007 403403 of 691of 691

deposit from a single electrode can be as high as 180% of deposit from a single electrode can be as high as 180% of

the core wire weightthe core wire weight

give good productivitygive good productivity

large weld beads with smooth profile can look very similar tolarge weld beads with smooth profile can look very similar to

SAW weldsSAW welds

MMA Welding ConsumablesMMA Welding ConsumablesHigh Recovery Rutile ElectrodesHigh Recovery Rutile Electrodes


Same as standard rutile electrodes with respect to hydrogenSame as standard rutile electrodes with respect to hydrogen

controlcontrol

large weld beads produced cannot be used for alllarge weld beads produced cannot be used for all--positionalpositional



4/23/20074/23/2007 404404 of of 691691

weldingwelding

the very high recovery types usually limited to PA & PBthe very high recovery types usually limited to PA & PB

positionspositions

more moderate recovery may allow PC usemore moderate recovery may allow PC use

MMA Welding ConsumablesMMA Welding ConsumablesBasic covering:Basic covering:

Produce convex weld profile and difficult to detach slag.Produce convex weld profile and difficult to detach slag.

Very suitable for Very suitable for for for high pressure work,high pressure work, thick section steelthick section steeland for high strength steels.and for high strength steels.

Prior to usePrior to use electrodeselectrodes should be baked, typically 350should be baked, typically 350°°C for 2C for 2hour plushour plus to reduce moisture to very low levels and achieveto reduce moisture to very low levels and achievelow hydrogen potential statuslow hydrogen potential status



4/23/20074/23/2007 405405 of 691of 691

low hydrogen potential status.low hydrogen potential status.

Contain calcium fluoride and calcium carbonate compounds.Contain calcium fluoride and calcium carbonate compounds.

cannot be recannot be re--baked indefinitely!baked indefinitely!

low hydrogen potential giveslow hydrogen potential gives weld metal very goodweld metal very goodtoughness and YS.toughness and YS.

have the lowest level of hydrogen (less than 5 ml/100 g of have the lowest level of hydrogen (less than 5 ml/100 g of weld metal).weld metal).

MMA Welding ConsumablesMMA Welding ConsumablesBasic ElectrodesBasic Electrodes


Careful control of baking and/or issuing of electrodes isCareful control of baking and/or issuing of electrodes isessential to maintain low hydrogen status and avoid risk of essential to maintain low hydrogen status and avoid risk of crackingcracking

Typical baking temperature 350Typical baking temperature 350°°C for 1 to 2hours.C for 1 to 2hours.



4/23/20074/23/2007 406406 of 691of 691

yp g pyp g p

Holding temperature 120 to 150Holding temperature 120 to 150°°C

.C

. Issue in heated quivers typically 70Issue in heated quivers typically 70°°C.C.

Welders need to take more care / require greater skill.Welders need to take more care / require greater skill.

Weld profile usually more convex.Weld profile usually more convex.

Deslagging requires more effort than for other types.Deslagging requires more effort than for other types.

Basic E lectrodesBasic E lectrodes


High toughness valuesHigh toughness values

Low hydrogen contentsLow hydrogen contents


High costHigh cost

High controlHigh control




4/23/20074/23/2007 407407 of 691of 691

Low crack tendencyLow crack tendency High welder skillHigh welder skill

requiredrequired

Convex weld profilesConvex weld profiles

Poor stop / startPoor stop / start

propertiesproperties

BS EN 499 MMA Covered ElectrodesBS EN 499 MMA Covered Electrodes

Covered ElectrodeCovered Electrode

ToughnessToughness

Yield Strength N/mm Yield Strength N/mm22


EE 5050 33 2Ni2Ni BB 77 22 H10H10



4/23/20074/23/2007 408408 of of 691691


Flux CoveringFlux CoveringWeld Metal RecoveryWeld Metal Recovery

and Current Typeand Current Type


Hydrogen ContentHydrogen Content

BS EN 499 MMA Covered ElectrodesBS EN 499 MMA Covered ElectrodesElectrodes classified as follows:Electrodes classified as follows:

EE 3535 -- Minimum yield strengthMinimum yield strength 350350 N/mmN/mm22

Tensile strengthTensile strength 440440 -- 570570 N/mmN/mm22





4/23/20074/23/2007 409409 of 691of 691







BS ENBS EN 499499 electrode designationelectrode designationRecovery and type of Recovery and type of

current designationcurrent designation

SymbolSymbol Weld metalWeld metalrecovery (%)recovery (%)

Type of Type of currentcurrent

11

22

ee105105

ee105105

AC /DCAC /DC

DCDC

Welding positionWelding position

designationdesignation

SymbolSymbol Welding positionWelding position

11

22

All positionsAll positions

All positions exceptAll positions except

vertical downvertical down



4/23/20074/23/2007 410410 of 691of 691

33

44

55

66

77

88

>105>105 ee125125

>105>105 ee125125

>125>125 ee160160

>125>125 ee160160

>1>16060

>>116060

AC /DCAC /DC

DCDC

AC /DCAC /DC

DCDC

AC /DCAC /DC

DCDC

33

44

55

Flat butt/fillet,Flat butt/fillet,

horizontal fillethorizontal fillet

Flat butt/filletFlat butt/fillet

Flat butt/fillet,Flat butt/fillet,

horizontal fillet,horizontal fillet,

vertical downvertical down

AWS A5.1 Alloyed Electrodes AWS A5.1 Alloyed Electrodes


Tensile Strength (p.s.i)Tensile Strength (p.s.i)


EE 6060 11 33



4/23/20074/23/2007 411411 of 691of 691


Flux CoveringFlux Covering

AWS A5.5 Alloyed Electrodes AWS A5.5 Alloyed Electrodes


Tensile Strength (p.s.i)Tensile Strength (p.s.i)


EE 7070 11 88 MM GG



4/23/20074/23/2007 412412 of 691of 691


Flux CoveringFlux CoveringMoisture ControlMoisture Control

Alloy ContentAlloy Content

MMA Welding ConsumablesMMA Welding ConsumablesTYPES OF ELECTRODESTYPES OF ELECTRODES

(for C, C(for C, C--Mn Steels)Mn Steels)

BS EN 499BS EN 499 AWS A5.1AWS A5.1

CellulosicCellulosic E XX XE XX X CC EXX1EXX100

EXX1EXX111



4/23/20074/23/2007 413413 of 691of 691

RutileRutileE XX XE XX X RR EXX1EXX122

EXX1EXX133

Rutile Heavy CoatedRutile Heavy Coated E XX XE XX X RRRR EXX2EXX244

BasicBasic E XX XE XX X BB EXX1EXX155

EXX1EXX166EXX1EXX188

Electrode efficiencyElectrode efficiencyup to 180% for iron powder electrodesup to 180% for iron powder electrodes

Mass of weld metal depositedMass of weld metal deposited

Electrode Eficiency =Electrode Eficiency =

Mass of core wire meltedMass of core wire melted



4/23/20074/23/2007 414414 of 691of 691

7575--90% for usual electrodes90% for usual electrodes

Mass of core wire meltedMass of core wire melted

Covered electrode treatmentCovered electrode treatment

CellulosicCellulosic


RutileRutile

Use straight from theUse straight from the

boxbox -- No baking/drying!No baking/drying!

If necessary, dry up toIf necessary, dry up to

120120°°CC-- No baking!No baking!



4/23/20074/23/2007 415415 of 691of 691

electrodeselectrodesgg

VacuumVacuum

packed basicpacked basic


Use straight from the packUse straight from the pack

within 4 hourswithin 4 hours -- NoNo

rebaking!rebaking!

Covered electrode treatmentCovered electrode treatment

After baking, maintain inAfter baking, maintain in

oven at 150oven at 150°°CC

Basic electrodesBasic electrodesBaking in oven 2 hoursBaking in oven 2 hours

at 350at 350°°C!C!

Limited number of Limited number of

rebakes!rebakes!



4/23/20074/23/2007 416416 of 691of 691

oven at 150oven at 150 CC

Use from quivers atUse from quivers at

7575°°CC

If not used within 4If not used within 4

hours, return to ovenhours, return to oven

and rebake!and rebake!

WeldWeld

rebakes!rebakes!

TIG ConsumablesTIG Consumables

W elding ConsumablesW elding Consumables



44//2323//20072007 417417 of 691of 691

TIG Welding ConsumablesTIG Welding ConsumablesWelding consumables for TIG:Welding consumables for TIG:

Filler wires, Shielding gases, tungsten electrodes (nonFiller wires, Shielding gases, tungsten electrodes (non--

consumable).consumable).

Filler wires of different materials composition andFiller wires of different materials composition and

variable diameters available in standard lengths, withvariable diameters available in standard lengths, with




4/23/20074/23/2007 418418 of 691of 691


Steel Filler wires of very high quality, with copper Steel Filler wires of very high quality, with copper

coating to resist corrosion.coating to resist corrosion.

shielding gases mainly Argon and Helium, usually of shielding gases mainly Argon and Helium, usually of

highest purity (99.9%).highest purity (99.9%).

TIG Welding ConsumablesTIG Welding ConsumablesWelding rods:Welding rods:

supplied in cardboard/plastic tubessupplied in cardboard/plastic tubes



4/23/20074/23/2007 419419 of 691of 691

must be kept clean and free from oil and dustmust be kept clean and free from oil and dust

might require degreasingmight require degreasing

Courtesy of Lincoln ElectricCourtesy of Lincoln Electric

Fusible InsertsFusible Inserts


PrePre--placed filler materialplaced filler material

After WeldingAfter Welding



4/23/20074/23/2007 420420 of 691of 691

Other terms used include:Other terms used include:

EB inserts (Electric Boat Company)EB inserts (Electric Boat Company)

Consumable socket rings (CSR)Consumable socket rings (CSR)

Fusible InsertsFusible InsertsConsumable inserts:Consumable inserts:

used for root runs on pipesused for root runs on pipes

used in conjunction with TIG weldingused in conjunction with TIG welding

available for carbon steel, Cr available for carbon steel, Cr--Mo steel, austenitic stainlessMo steel, austenitic stainless

steel, nickel and copper steel, nickel and copper--nickel alloysnickel alloys

different shapes to suit applicationdifferent shapes to suit application



4/23/20074/23/2007 421421 of 691of 691

RadiusRadius

Fusible InsertsFusible InsertsApplication of consumable insertsApplication of consumable inserts



4/23/20074/23/2007 422422 of 691of 691

Shielding gases for TIG weldingShielding gases for TIG welding Argon Argon

low cost and greater availabilitylow cost and greater availability

heavier than air heavier than air -- lower flow rates than Heliumlower flow rates than Helium

low thermal conductivitylow thermal conductivity -- wide top bead profilewide top bead profile

low ionisation potentiallow ionisation potential -- easier arc starting better arceasier arc starting better arc



4/23/20074/23/2007 423423 of 691of 691

low ionisation potentiallow ionisation potential easier arc starting, better arceasier arc starting, better arc

stability with AC, cleaning effectstability with AC, cleaning effectfor the same arc current produce less heat thanfor the same arc current produce less heat thanheliumhelium -- reduced penetration, wider HAZreduced penetration, wider HAZ

to obtain the same arc arc power, argon requires ato obtain the same arc arc power, argon requires a

higher currenthigher current -- increased undercutincreased undercut

Shielding gases for TIG weldingShielding gases for TIG weldingHeliumHelium

costly and lower availability than Argoncostly and lower availability than Argon

lighter than air lighter than air -- requires a higher flow rate comparedrequires a higher flow rate compared

with argon (2with argon (2--3 times)3 times)

higher ionisation potentialhigher ionisation potential -- poor arc stability with AC,poor arc stability with AC,



4/23/20074/23/2007 424424 of 691of 691

g pg p p y ,p y ,

less forgiving for manual weldingless forgiving for manual welding

for the same arc current produce more heat thanfor the same arc current produce more heat than

argonargon -- increased penetration, welding of metals withincreased penetration, welding of metals with

high melting point or thermal conductivityhigh melting point or thermal conductivity

to obtain the same arc arc power, helium requires ato obtain the same arc arc power, helium requires a

lower currentlower current -- no undercutno undercut

Shielding gases for TIG weldingShielding gases for TIG weldingHydrogenHydrogen

not an inert gasnot an inert gas -- not used as a primary shielding gasnot used as a primary shielding gas

increase the heat inputincrease the heat input -- faster travel speed andfaster travel speed andincreased penetrationincreased penetration

better wetting actionbetter wetting action -- improved bead profileimproved bead profile



4/23/20074/23/2007 425425 of 691of 691

produce a cleaner weld bead surfaceproduce a cleaner weld bead surfaceadded to argon (up to 5%)added to argon (up to 5%) -- only for austeniticonly for austeniticstainless steels and nickel alloysstainless steels and nickel alloys

flammable and explosiveflammable and explosive

Shielding gases for TIG weldingShielding gases for TIG welding

NitrogenNitrogen

not an inert gasnot an inert gas

high availabilityhigh availability -- cheapcheap

added to argon (up to 5%)added to argon (up to 5%) -- only for back purge foronly for back purge for



4/23/20074/23/2007 426426 of 691of 691

added to argon (up to 5%)added to argon (up to 5%) only for back purge for only for back purge for

duplex stainless, austenitic stainless steels and copper duplex stainless, austenitic stainless steels and copper alloysalloys

not used for mild steels (age embritlement)not used for mild steels (age embritlement)

strictly prohibited in case of Ni and Ni alloys (porosity)strictly prohibited in case of Ni and Ni alloys (porosity)

MIG / MAG ConsumablesMIG / MAG Consumables(Gases Covered previously)(Gases Covered previously)




4/23/20074/23/2007 427427 of 691of 691

MIG/MAG Welding ConsumablesMIG/MAG Welding ConsumablesWelding consumables for MIG/MAGWelding consumables for MIG/MAG

Spools of Continuous electrode wires and shieldingSpools of Continuous electrode wires and shielding

gasesgases variable spool size (1variable spool size (1--15Kg) and Wire diameter (0.615Kg) and Wire diameter (0.6--

1.6mm) supplied in random or orderly layers1.6mm) supplied in random or orderly layers

Basic Selection of different materials and their alloysBasic Selection of different materials and their alloys



4/23/20074/23/2007 428428 of 691of 691

Basic Selection of different materials and their alloysBasic Selection of different materials and their alloys

as electrode wires.as electrode wires.

Some Steel Electrode wires copper coating purposeSome Steel Electrode wires copper coating purpose

is corrosion resistance and electrical pickis corrosion resistance and electrical pick--upup

Gases can be pure COGases can be pure CO22, CO, CO22+Argon mixes and+Argon mixes and Argon+2%O Argon+2%O22 mixes (stainless steels).mixes (stainless steels).

MIG/MAG Welding ConsumablesMIG/MAG Welding ConsumablesWelding wires:Welding wires:

carbon and low alloy wires may be copper coatedcarbon and low alloy wires may be copper coated

stainless steel wires are not coatedstainless steel wires are not coated



4/23/20074/23/2007 429429 of 691of 691

wires must be kept clean and free from oil and dustwires must be kept clean and free from oil and dustflux cored wires does not require baking or dryingflux cored wires does not require baking or drying

Courtesy of Lincoln ElectricCourtesy of Lincoln Electric Courtesy of ESAB ABCourtesy of ESAB AB

MIG/MAG Welding ConsumablesMIG/MAG Welding ConsumablesWire designation acc. BS EN 440:

EN 440 - G 46 3 M G3Si1

Standard number

Tensile properties

Type of shielding gas



4/23/20074/23/2007 430430 of 691of 691

Weld deposit produced bygas shielded metal arc

welding

Impact properties

Type of wire electrode

MIG/MAG Welding ConsumablesMIG/MAG Welding Consumables

Wire designation acc. AWS A-5.18:

Minimum UTS of weld metal (ksi)

Chemical composition of the solid wire or

of the weld metal in case of composite

electrodes

Standard number



4/23/20074/23/2007 431431 of of 691691

AWS A-5.18 ER 70 S-6

Designate an electrode/rod (ER) or

only an electrode (E)

Solid (S) or composite (C) wire

MIG/MAG shielding gasesMIG/MAG shielding gasesGas shielded metalGas shielded metal

arc weldingarc welding

MIG process (131)MIG process (131) MAG process (135)MAG process (135)

BS EN 439BS EN 439



44//2323//20072007 432432 of 691of 691

BS EN 439BS EN 439

Group ³I´Group ³I´ -- Ar, HeAr, He

and Ar and Ar--HeHe

mixturesmixtures

Group ³R´Group ³R´ --

Ar + HAr + H22

(<35%)(<35%)

Group ³M´Group ³M´ -- Ar +Ar +

COCO22 /O /O22

(<50/15%)(<50/15%)

Group ³C´Group ³C´ --

COCO22, CO, CO22 + O+ O22

(<30%)(<30%)

Flux Core Wire ConsumablesFlux Core Wire Consumables(Not in training manual)(Not in training manual)




4/23/20074/23/2007 433433 of 691of 691

Flux Core Wire ConsumablesFlux Core Wire Consumables

Functions of metallic sheath: Function of the filling powder:



4/23/20074/23/2007 434434 of 691of 691

provide form stabilityto the wire

serves as currenttransfer duringwelding

stabilise the arcadd alloy elements

produce gaseousshield

produce slag

add iron powder

Types of cored wireTypes of cored wire

t iti t i tt iti t i t

SeamlessSeamless

cored wirecored wire

Butt jointButt joint


OverlappingOverlapping




4/23/20074/23/2007 435435 of 691of 691

not sensitive to moisturenot sensitive to moisturepickpick--upup

can be copper coated,can be copper coated,better current transfer better current transfer

thick sheath, good formthick sheath, good formstability,stability, 22 roll driveroll drive

feeding possiblefeeding possibledifficult to manufacturedifficult to manufacture

good resistance togood resistance tomoisture pickmoisture pick--upup

can be copper can be copper coatedcoated

thick sheaththick sheath

difficult to seal thedifficult to seal thesheathsheath

sensitive tosensitive tomoisture pickmoisture pick--upup

cannot becannot be

copper coatedcopper coated

thin sheaththin sheath

easy toeasy to

manufacturemanufacture

Core elements and their functionCore elements and their function

Aluminium Aluminium -- deoxidize & denitrifydeoxidize & denitrify

CalciumCalcium -- provide shielding & form slagprovide shielding & form slag

CarbonCarbon -- increase hardness & strengthincrease hardness & strengthManganeseManganese -- deoxidize & increase strength and toughnessdeoxidize & increase strength and toughness

MolybdenumMolybdenum -- increase hardness & strengthincrease hardness & strength

NickelNickel improve hardness strength toughness & corrosionimprove hardness strength toughness & corrosion



4/23/20074/23/2007 436436 of 691of 691

NickelNickel -- improve hardness, strength, toughness & corrosionimprove hardness, strength, toughness & corrosion

resistanceresistance

PotassiumPotassium -- stabilize the arc & form slagstabilize the arc & form slag

SiliconSilicon -- deoxidize & form slagdeoxidize & form slag

SodiumSodium -- stabilize arc & form slagstabilize arc & form slag

TitaniumTitanium -- deoxidize, denitrify & form slagdeoxidize, denitrify & form slag

SAW ConsumablesSAW Consumables




4/23/20074/23/2007 437437 of 691of 691

SAW ConsumablesSAW ConsumablesWelding fluxes:Welding fluxes:

are granular mineral compounds mixed according to variousare granular mineral compounds mixed according to various

formulationsformulations

shield the molten weld pool from the atmosphereshield the molten weld pool from the atmosphere

clean the molten weld poolclean the molten weld pool

can modify the chemical composition of the weld metalcan modify the chemical composition of the weld metal



44//2323//20072007 438438 of 691of 691

prevents rapid escape of heat from welding zoneprevents rapid escape of heat from welding zone

influence the shape of the weld bead (wetting action)influence the shape of the weld bead (wetting action)

can be fused, agglomerated or mixedcan be fused, agglomerated or mixed

must be kept warm and dry to avoid porositymust be kept warm and dry to avoid porosity

SAW ConsumablesSAW ConsumablesWelding flux:Welding flux:

might be fused or agglomeratedmight be fused or agglomerated

supplied in bagssupplied in bags

must be kept warm and drymust be kept warm and dry

handling and stacking requires carehandling and stacking requires careCourtesy of Lincoln ElectricCourtesy of Lincoln Electric



4/23/20074/23/2007 439439 of 691of 691

Fused fluxes are normally not hygroscopic but particles canFused fluxes are normally not hygroscopic but particles canhold surface moisturehold surface moisture so only dryingso only drying

Agglomerated fluxes contain chemically bonded water. SAgglomerated fluxes contain chemically bonded water. Similar imilar

treatment as basic electrodestreatment as basic electrodes

If flux is too fine it will pack and not feed properly. It cannot beIf flux is too fine it will pack and not feed properly. It cannot be

recycled indefinitelyrecycled indefinitely

SAW ConsumablesSAW ConsumablesWelding flux:Welding flux:supplied in bags/pails (approx. 25 kg) or bulk bagssupplied in bags/pails (approx. 25 kg) or bulk bags(approx. 1200 kg)(approx. 1200 kg)

might be fused, agglomerated or mixedmight be fused, agglomerated or mixed



4/23/20074/23/2007 440440 of 691of 691

Courtesy of Lincoln ElectricCourtesy of Lincoln Electric Courtesy of Lincoln ElectricCourtesy of Lincoln Electric Courtesy of Lincoln ElectricCourtesy of Lincoln Electric

SAW ConsumablesSAW ConsumablesFused FluxFused Flux

Flaky appearanceFlaky appearance

Lower weld qualityLower weld quality

Low moisture intakeLow moisture intake

Low dust tendencyLow dust tendency

Good reGood re--cyclingcycling



4/23/20074/23/2007 441441 of 691of 691

Fused Flux:Fused Flux:

Baked at high temperature, glossy, hard and black in colour,

cannot add ferro-manganese, non moisture absorbent andtends to be of the acidic type

Very smooth weldVery smooth weld

profileprofile

SAW ConsumablesSAW ConsumablesTYPES OF FLUXTYPES OF FLUX

FUSED (ACID TYPE)FUSED (ACID TYPE)

name indicates method of manufacturename indicates method of manufacture

minerals are fused (melted) and granules produced byminerals are fused (melted) and granules produced byallowing to cool to a solid mass and then crushing or byallowing to cool to a solid mass and then crushing or by

spraying the molten flux into water spraying the molten flux into water

flux tends to be µglassflux tends to be µglass--like¶ (high in Silica)like¶ (high in Silica)

granules are hard and may appear shinygranules are hard and may appear shiny



4/23/20074/23/2007 442442 of 691of 691

g y pp yg y pp y

granules do not absorb moisturegranules do not absorb moisture

granules do not tend break down into powder when beinggranules do not tend break down into powder when being

rere--circulatedcirculated

are effectively a low hydrogen fluxare effectively a low hydrogen flux

welds do not tend to give good toughness at lowwelds do not tend to give good toughness at lowtemperaturestemperatures

SAW ConsumablesSAW ConsumablesFused fluxes advantages:Fused fluxes advantages:

good chemical homogeneitygood chemical homogeneity

easy removal of fines without affecting fluxeasy removal of fines without affecting flux

compositioncompositionnormally not hygroscopicnormally not hygroscopic easy storage andeasy storage and

handlinghandling

readily recycled without significant change inreadily recycled without significant change in



44//2323//20072007 443443 of 691of 691

particle size or compositionparticle size or compositionFused fluxes disadvantages:Fused fluxes disadvantages:

difficult to add deoxidizers and ferrodifficult to add deoxidizers and ferro--alloys (due toalloys (due to

segregation or extremely high loss)segregation or extremely high loss)

high temperatures needed to melt ingredients limithigh temperatures needed to melt ingredients limitthe range of flux compositionsthe range of flux compositions

SAW ConsumablesSAW ConsumablesAgglomerated FluxAgglomerated Flux

Granulated appearanceGranulated appearance

High weld qualityHigh weld quality

Addition of alloysAddition of alloys

Lower consumptionLower consumption

Easy slag removalEasy slag removal



4/23/20074/23/2007 444444 of 691of 691

Agglomerated Flux:

Baked at a lower temperature, dull, irregularly shaped, friable,

(easily crushed) can easily add alloying elements, moisture

absorbent and tend to be of the basic type

Easy slag removalEasy slag removal

Smooth weld profileSmooth weld profile

SAW ConsumablesSAW ConsumablesAgglomerated fluxes advantages:Agglomerated fluxes advantages:

easy addition of deoxidizers and alloying elementseasy addition of deoxidizers and alloying elements

usable with thicker layer of flux when weldingusable with thicker layer of flux when welding

colour identificationcolour identification

Agglomerated fluxes disadvantages:Agglomerated fluxes disadvantages:



4/23/20074/23/2007 445445 of 691of 691

gg ggg g

tendency to absorb moisturetendency to absorb moisture

possible gas evolution from the molten slag leading topossible gas evolution from the molten slag leading to

porosityporosity

possible change in flux composition due to segregation or possible change in flux composition due to segregation or

removal of fine mesh particlesremoval of fine mesh particles

SAW ConsumablesSAW ConsumablesTYPES OF FLUXTYPES OF FLUX

AGGLOMERATED (BASIC TYPE)AGGLOMERATED (BASIC TYPE)

name indicates method of manufacturename indicates method of manufacture

basic minerals are used in powder form and are mixed with abasic minerals are used in powder form and are mixed with abinder to form individual granulesbinder to form individual granules

granules are soft and easily crushed to powder granules are soft and easily crushed to powder

granules will absorb moisture and it is necessary to protectgranules will absorb moisture and it is necessary to protect



4/23/20074/23/2007 446446 of 691of 691

the flux from moisture pickthe flux from moisture pick--upup -- usually by holding in ausually by holding in aheated siloheated silo

granules tend to break down into powder when being regranules tend to break down into powder when being re--circulatedcirculated

are a low hydrogen fluxare a low hydrogen flux -- if correctly controlledif correctly controlled

welds give good toughness at low temperatureswelds give good toughness at low temperatures

SAW ConsumablesSAW Consumables

Mixed fluxes advantages:Mixed fluxes advantages:several commercial fluxes may be mixed for highlyseveral commercial fluxes may be mixed for highly

critical or proprietary welding operationscritical or proprietary welding operations

Mixed fluxes disadvantages:Mixed fluxes disadvantages:

Mixed fluxesMixed fluxes -- two or more fused or bonded fluxes aretwo or more fused or bonded fluxes are

mixed in any ratio necessary to yield the desiredmixed in any ratio necessary to yield the desired

resultsresults



4/23/20074/23/2007 447447 of 691of 691

segregation of the combined fluxes duringsegregation of the combined fluxes duringshipment, storage and handlingshipment, storage and handling

segregation occurring in the feeding and recoverysegregation occurring in the feeding and recovery

systems during weldingsystems during welding

inconsistency in the combined flux from mix to mixinconsistency in the combined flux from mix to mix

SAW filler materialSAW filler material

Welding wires can be used to weld:Welding wires can be used to weld:

carbon steelscarbon steels

low alloy steelslow alloy steels

creep resisting steelscreep resisting steels

stainless steelsstainless steels



4/23/20074/23/2007 448448 of of 691691

nickelnickel--base alloysbase alloysspecial alloys for surfacing applicationsspecial alloys for surfacing applications

Welding wires can be:Welding wires can be:

solid wiressolid wires

metalmetal--cored wirescored wires

SAW filler materialSAW filler material

Welding wires:Welding wires:

carbon and low alloy wires are copper coatedcarbon and low alloy wires are copper coated

stainless steel wires are not coatedstainless steel wires are not coated



4/23/20074/23/2007 449449 of 691of 691

wires must be kept clean and free from oil and dustwires must be kept clean and free from oil and dust

Courtesy of Lincoln ElectricCourtesy of Lincoln Electric Courtesy of Lincoln ElectricCourtesy of Lincoln Electric

SAW filler materialSAW filler materialCopper coating functions:Copper coating functions:

to assure a good electric contact between wireto assure a good electric contact between wireand contact tipand contact tip

to assure a smooth feed of the wire through theto assure a smooth feed of the wire through the

guide tube, feed rolls and contact tip (decreaseguide tube, feed rolls and contact tip (decrease



4/23/20074/23/2007 450450 of 691of 691

contact tube wear)contact tube wear)to provide protection against corrosionto provide protection against corrosion

Ceramic BackingCeramic Backing

Ceramic backing:Ceramic backing:

used to support theused to support the

weld pool on rootweld pool on rootrunsruns

usually fitted on anusually fitted on an

aluminium self aluminium self

adhesive tapeadhesive tape



4/23/20074/23/2007 451451 of 691of 691

allow increased welding current without danger of burnallow increased welding current without danger of burn--through,through,

increased productivity, consistent qualityincreased productivity, consistent quality

different profiles to suit different applicationsdifferent profiles to suit different applications

no backing/drying requiredno backing/drying required


Non Destructive TestingNon Destructive Testing




4/23/20074/23/2007 452452 of 691of 691

NonNon--Destructive TestingDestructive Testing A welding inspector should have a working knowledge of A welding inspector should have a working knowledge of

NDT methods and their applications, advantages andNDT methods and their applications, advantages and

disadvantages.disadvantages.

Four basic NDT methodsFour basic NDT methods

Radiographic inspection (RT)Radiographic inspection (RT)



4/23/20074/23/2007 453453 of of 691691

Ultrasonic inspection (UT)Ultrasonic inspection (UT)

Magnetic particle inspection (MT)Magnetic particle inspection (MT)

Dye penetrant inspection (PT)Dye penetrant inspection (PT)

NonNon--Destructive TestingDestructive TestingSurface Crack DetectionSurface Crack Detection

Liquid Penetrant (PT or DyeLiquid Penetrant (PT or Dye--Penetrant)Penetrant)

Magnetic Particle Inspection (MT or MPI)Magnetic Particle Inspection (MT or MPI)

Volumetric & Planar InspectionVolumetric & Planar Inspection

Ultrasonics (UT)Ultrasonics (UT)

Radiography (RT)Radiography (RT)



4/23/20074/23/2007 454454 of 691of 691

Each technique has advantages & disadvantages with respectEach technique has advantages & disadvantages with respect

to:to:

Technical Capability and CostTechnical Capability and Cost

Note:Note: The choice of NDT techniques is based on considerationThe choice of NDT techniques is based on consideration

of these advantages and disadvantagesof these advantages and disadvantages

Radiographic Testing (RT)Radiographic Testing (RT)



4/23/20074/23/2007 455455 of 691of 691

The principles of radiographyThe principles of radiography

X or Gamma radiation is imposed upon a test objectX or Gamma radiation is imposed upon a test object

Radiation is transmitted to varying degreesRadiation is transmitted to varying degrees

dependant upon the density of the material throughdependant upon the density of the material through

which it is travellingwhich it is travelling

Radiographic TestingRadiographic Testing



4/23/20074/23/2007 456456 of 691of 691

Thinner areas and materials of a less density show asThinner areas and materials of a less density show asdarker areas on the radiographdarker areas on the radiograph

Thicker areas and materials of a greater density showThicker areas and materials of a greater density show

as lighter areas on a radiographas lighter areas on a radiograph

Applicable to metals,non Applicable to metals,non--metals and compositesmetals and composites




44//2323//20072007 457457 of 691of 691

X X ± ± R aysR ays

Electrically generatedElectrically generated

Gamma R aysGamma R ays

Generated by the decayGenerated by the decay

of unstable atomsof unstable atoms

SourceSource

Radiation beamRadiation beam Image quality indicator Image quality indicator




4/23/20074/23/2007 458458 of 691of 691

Radiographic film with latent image after exposureRadiographic film with latent image after exposure

Test specimenTest specimen

Radiographic TestingRadiographic TestingDensityDensity -- relates to the degree of darknessrelates to the degree of darkness



4/23/20074/23/2007 459459 of 691of 691

ContrastContrast -- relates to the degree of differencerelates to the degree of difference

DefinitionDefinition -- relates to the degree of sharpnessrelates to the degree of sharpness

SensitivitySensitivity -- relates to the overall quality of the radiographrelates to the overall quality of the radiograph

Densitometer

Radiographic SensitivityRadiographic Sensitivity



4/23/20074/23/2007 460460 of of 691691

7FE127FE12

Step / Hole type IQIStep / Hole type IQI Wire type IQIWire type IQI

Step/Hole Type IQIStep/Hole Type IQI

Radiographic SensitivityRadiographic Sensitivity



4/23/20074/23/2007 461461 of 691of 691

Wire Type IQIWire Type IQI

p ypp yp

Single Wall Single Image (SWSI)Single Wall Single Image (SWSI)

film inside, source outsidefilm inside, source outside

Single Wall Single Image (SWSI)Single Wall Single Image (SWSI) panoramicpanoramic

film outside, source inside (internal exposure)film outside, source inside (internal exposure)

Double Wall Single Image (DWSI)Double Wall Single Image (DWSI)

Radiographic TechniquesRadiographic Techniques



4/23/20074/23/2007 462462 of 691of 691

film outside, source outside (external exposure)film outside, source outside (external exposure)

Double Wall Double Image (DWDI)Double Wall Double Image (DWDI)

film outside, source outside (elliptical exposure)film outside, source outside (elliptical exposure)

FilmFilm

S ingle W all S ingle I mage ( SWSI )S ingle W all S ingle I mage ( SWSI )



4/23/20074/23/2007 463463 of 691of 691

IQI¶s should be placed source sideIQI¶s should be placed source side

FilmFilm

Single Wall Single Image PanoramicSingle Wall Single Image Panoramic



4/23/20074/23/2007 464464 of 691of 691

IQI¶s are placed on the film sideIQI¶s are placed on the film side

Source inside film outside (single exposure)Source inside film outside (single exposure)

FilmFilm




4/23/20074/23/2007 465465 of 691of 691

IQI¶s are placed on the film sideIQI¶s are placed on the film side

Source outside film outside (multiple exposure)Source outside film outside (multiple exposure)

This technique is intended for pipe diametersThis technique is intended for pipe diametersover 100mmover 100mm

FilmFilm

IdentificationIdentification

Unique identificationUnique identificationEN W10EN W10

IQI placingIQI placing




4/23/20074/23/2007 466466 of 691of 691

RadiographRadiograph

IDID MR11MR11

AA BB Pitch marks indicatingPitch marks indicatingreadable film lengthreadable film length




4/23/20074/23/2007 467467 of of 691691

RadiographRadiograph




4/23/20074/23/2007 468468 of 691of 691

FilmFilm

IQI¶s are placed on the source or film sideIQI¶s are placed on the source or film side

Source outside film outside (multiple exposure)Source outside film outside (multiple exposure)

A minimum of two exposuresA minimum of two exposures

This technique is intended for pipe diameters less than 100mmThis technique is intended for pipe diameters less than 100mm

IdentificationIdentification

Unique identificationUnique identification EN W10

IQI placingIQI placing

4 3




44//2323//20072007 469469 of 691of 691

Shot A RadiographShot A Radiograph

ID MR12

1 2 Pitch marks indicatingPitch marks indicating

readable film lengthreadable film length

44 33




4/23/20074/23/2007 470470 of 691of 691

Elliptical RadiographElliptical Radiograph

11 22

Radiography Radiography PENETRATING POWERPENETRATING POWER

Question:Question:

What determines the penetrating power of an XWhat determines the penetrating power of an X--ray ?ray ?

the kilothe kilo--voltage appliedvoltage applied ( bet w een anode & cat hode)( bet w een anode & cat hode)

Question:Question:

Wh t d t i th t ti fWh t d t i th t ti f ??



4/23/20074/23/2007 471471 of 691of 691

What determines the penetrating power of What determines the penetrating power of a gamma ray ?a gamma ray ?

the type of isotopethe type of isotope ( t he w avelengt h of t he gamma rays)( t he w avelengt h of t he gamma rays)

Radiography Radiography GAMMA SOURCESGAMMA SOURCES

IsotopeIsotope Typical Thickness RangeTypical Thickness Range

Iridium 192Iridium 192 10 to 50 mm10 to 50 mm (mostly used)(mostly used)

Cobalt 60Cobalt 60 > 50 mm> 50 mm

Ytterbium Ytterbium < 10 mm< 10 mm



44//2323//20072007 472472 of 691of 691

ThuliumThulium < 10 mm< 10 mm

CesiumCesium < 10 mm< 10 mm


Permanent recordPermanent record

Little surface preparationLittle surface preparation Defect identificationDefect identification

No material type limitationNo material type limitation

Not so reliant upon operator Not so reliant upon operator

killkill


Expensive consumablesExpensive consumables

Bulky equipmentBulky equipment

Harmful radiationHarmful radiation

Defect require significantDefect require significant

depth in relation to thedepth in relation to the

radiation beam (not goodradiation beam (not good

f l d f t )f l d f t )




4/23/20074/23/2007 473473 of 691of 691

skillskill

Thin materialsThin materials

for planar defects)for planar defects)

Slow resultsSlow results

Very little indication of Very little indication of

depthsdepths

Access to both sidesAccess to both sidesrequiredrequired

Radiographic Testing Radiographic Testing Comparison with Ultrasonic ExaminationComparison with Ultrasonic Examination

ADVANTAGESADVANTAGES

good for nongood for non--planar defectsplanar defectsgood for thin sectionsgood for thin sections

gives permanent recordgives permanent record

easier for easier for 22nd party interpretationnd party interpretation



4/23/20074/23/2007 474474 of 691of 691

can use on all material typescan use on all material types

high productivityhigh productivity

direct image of imperfectionsdirect image of imperfections

Radiographic TestingRadiographic TestingComparison with Ultrasonic ExaminationComparison with Ultrasonic Examination

DISADVANTAGESDISADVANTAGES

health & safety hazardhealth & safety hazard

not good for thick sectionsnot good for thick sections

high capital and relatively high running costshigh capital and relatively high running costs

t d f l d f tt d f l d f t



44//2323//20072007 475475 of 691of 691

not good for planar defectsnot good for planar defects

XX--ray sets not very portableray sets not very portable

requires access to both sides of weldrequires access to both sides of weld

frequent replacement of gammafrequent replacement of gamma source needed (half life)source needed (half life)

Ultrasonic Testing (UT)Ultrasonic Testing (UT)



44//2323//20072007 476476 of 691of 691

Main Features:Main Features:

Surface and subSurface and sub--surface detectionsurface detection

This detection method uses high frequency sound waves,This detection method uses high frequency sound waves,

typically abovetypically above 22MHz to pass through a materialMHz to pass through a material

A probe is used which contains a piezo electric crystal toA probe is used which contains a piezo electric crystal to

transmit and receive ultrasonic pulses and display thetransmit and receive ultrasonic pulses and display the

signals on a cathode ray tube or digital displaysignals on a cathode ray tube or digital display

The actual display relates to the time taken for the

The actual display relates to the time taken for the

Ultrasonic TestingUltrasonic Testing



4/23/20074/23/2007 477477 of 691of 691

he actual display relates to the time taken for thehe actual display relates to the time taken for theultrasonic pulses to travel the distance to the interface andultrasonic pulses to travel the distance to the interface and

backback

An interface could be the back of a plate material or a defectAn interface could be the back of a plate material or a defect

For ultrasound to enter a material a couplant must beFor ultrasound to enter a material a couplant must be

introduced between the probe and specimenintroduced between the probe and specimen

DigitalDigital

UT Set,UT Set,

Pulse echoPulse echo

signalssignals

A scanA scan

DisplayDisplay




4/23/20074/23/2007 478478 of 691of 691

Compression probeCompression probe checking the materialchecking the material ThicknessThickness

d fd f

defectdefect

echoecho

Back wallBack wall

echoecho

Material ThkMaterial Thk

initial pulseinitial pulse




4/23/20074/23/2007 479479 of of 691691

defectdefect

00 1010 2020 3030 4040 5050

CRT DisplayCRT DisplayCompression ProbeCompression Probe

UT SetUT SetA ScanA Scan

DisplayDisplay




4/23/20074/23/2007 480480 of 691of 691

Angle ProbeAngle Probe

initial pulse

defect echo

defect

defect

0 10 20 30 40 50

CRT Display½ Skip




4/23/20074/23/2007 481481 of 691of 691

defect 0 10 20 30 40 50

initial pulse

defect echo

CRT DisplayFull Skip


Rapid resultsRapid results

Both surface andBoth surface andsubsub--surface detectionsurface detection

SafeSafe

Capable of measuring theCapable of measuring the

depth of defectsdepth of defects


Trained and skilled operator Trained and skilled operator

requiredrequired

Requires high operator skillRequires high operator skill

Good surface finish requiredGood surface finish required

Defect identificationDefect identification

Couplant may contaminateCouplant may contaminate




4/23/20074/23/2007 482482 of 691of 691

depth of defectsdepth of defects

May be battery poweredMay be battery powered

PortablePortable

No permanent recordNo permanent record

Calibration RequiredCalibration Required

Ferritic Material (Mostly)Ferritic Material (Mostly)

UltrasonicTestingUltrasonicTesting

Comparison with RadiographyComparison with Radiography


good for planar defectsgood for planar defects

good for thick sectionsgood for thick sections

instant resultsinstant results

can use on complex jointscan use on complex joints

can automatecan automate



44//2323//20072007 483483 of 691of 691

can automatecan automate

very portablevery portable

no safety problemsno safety problems ( µparallel¶ w orking is possible)( µparallel¶ w orking is possible)

low capital & running costslow capital & running costs

Ultrasonic TestingUltrasonic TestingComparison with RadiographyComparison with Radiography


no permanent recordno permanent record ( w it h standard equipment)( w it h standard equipment)

not suitable for very thin joints <8mmnot suitable for very thin joints <8mm

reliant on operator interpretationreliant on operator interpretation

t d f i i P itt d f i i P it



4/23/20074/23/2007 484484 of 691of 691

not good for sizing Porositynot good for sizing Porosity

good/smooth surface profile neededgood/smooth surface profile needed

not suitable for coarse grain materials (e.g., castings)not suitable for coarse grain materials (e.g., castings)

Ferritic MaterialsFerritic Materials ( w it h standard equipment)( w it h standard equipment)

Magnetic Particle testing (MT)Magnetic Particle testing (MT)



4/23/20074/23/2007 485485 of 691of 691

Magnetic Particle TestingMagnetic Particle TestingMain features:Main features:

Surface and slight subSurface and slight sub--surface detectionsurface detection

Relies on magnetization of component being testedRelies on magnetization of component being tested

Only FerroOnly Ferro--magnetic materials can be testedmagnetic materials can be tested

A magnetic field is introduced into a specimen being A magnetic field is introduced into a specimen beingtestedtested

Methods of applying a magnetic field, yoke, permanentMethods of applying a magnetic field, yoke, permanent

magnet prods and flexible cablesmagnet prods and flexible cables



4/23/20074/23/2007 486486 of 691of 691

magnet, prods and flexible cables.magnet, prods and flexible cables.Fine particles of iron powder are applied to the test areaFine particles of iron powder are applied to the test area

Any defect which interrupts the magnetic field, will create Any defect which interrupts the magnetic field, will createa leakage field, which attracts the particlesa leakage field, which attracts the particles

Any defect will show up as either a dark indication or in Any defect will show up as either a dark indication or in

the case of fluorescent particles under UVthe case of fluorescent particles under UV--A light a A light agreen/yellow indicationgreen/yellow indication

Electro-magnet (yoke) DC or AC

Collection of inkCollection of ink

particles due toparticles due to

leakage fieldleakage field

Magnetic Particle TestingMagnetic Particle Testing



44//2323//20072007 487487 of 691of 691

Prods DC or AC

A crack likeA crack like

indicationindication




4/23/20074/23/2007 488488 of of 691691




4/23/20074/23/2007 489489 of 691of 691

Alternatively to contrast inks, fluorescent inks may be usedAlternatively to contrast inks, fluorescent inks may be used

for greater sensitivity. These inks require a UVfor greater sensitivity. These inks require a UV--A light sourceA light source

and a darkened viewing area to inspect the componentand a darkened viewing area to inspect the component

Typical sequence of operations to inspect a weldTypical sequence of operations to inspect a weld

Clean area to be testedClean area to be tested

Apply contrast paintApply contrast paint

Apply magnetisism to the componentApply magnetisism to the component

Apply ferroApply ferro--magnetic ink to the component duringmagnetic ink to the component during

magnatisingmagnatising

Iterpret the test areaIterpret the test area




4/23/20074/23/2007 490490 of 691of 691

Iterpret the test areaIterpret the test area

Post clean and dePost clean and de--magnatise if requiredmagnatise if required


Simple to useSimple to use

InexpensiveInexpensive Rapid resultsRapid results

Little surface preparationLittle surface preparation

requiredrequired

Possible to inspect throughPossible to inspect through


Surface or slight subSurface or slight sub--surfacesurface

detection onlydetection only

Magnetic materials onlyMagnetic materials only

No indication of defectsNo indication of defects

depthsdepths

Only suitable for linear Only suitable for linear

defectsdefects




4/23/20074/23/2007 491491 of 691of 691

Possible to inspect throughPossible to inspect throughthin coatingsthin coatings

defectsdefects

Detection is required in twoDetection is required in two

directionsdirections

Magnetic ParticleTestingMagnetic ParticleTesting

Comparison with Penetrant TestingComparison with Penetrant Testing


much quicker than PTmuch quicker than PT

instant resultsinstant results

can detect near can detect near--surface imperfectionssurface imperfections ( by current f low ( by current f low

tec hnique)tec hnique)

less surface preparation neededless surface preparation needed




44//2323//20072007 492492 of of 691691


only suitable for ferromagnetic materialsonly suitable for ferromagnetic materials

electrical power for most techniqueselectrical power for most techniques

may need to demay need to de--magnetise (machine components)magnetise (machine components)

Penetrant Testing (PT)Penetrant Testing (PT)



4/23/20074/23/2007 493493 of 691of 691

Penetrant TestingPenetrant TestingMain features:Main features:

Detection of surface breaking defects only.Detection of surface breaking defects only.

This test method uses the forces of capillary actionThis test method uses the forces of capillary action

Applicable on any material type, as long they are non Applicable on any material type, as long they are nonporous.porous.

Penetrants are available in many different types:Penetrants are available in many different types:

Water washable contrastWater washable contrast



4/23/20074/23/2007 494494 of 691of 691

Water washable contrastWater washable contrast

Solvent removable contrastSolvent removable contrast

Water washable fluorescentWater washable fluorescent

Solvent removable fluorescentSolvent removable fluorescent PostPost--emulsifiable fluorescentemulsifiable fluorescent

Step 1. PreStep 1. Pre--CleaningCleaning

Ensure surface is very Clean normally with the use of a solventEnsure surface is very Clean normally with the use of a solvent

Penetrant TestingPenetrant Testing



4/23/20074/23/2007 495495 of 691of 691

Step 2. Apply penetrantStep 2. Apply penetrant

After the application, the penetrant is normally left on theAfter the application, the penetrant is normally left on the

components surface for approximately 15components surface for approximately 15--20 minutes (dwell20 minutes (dwell

time).time).

The penetrant enters any defects that may be present byThe penetrant enters any defects that may be present bycapillary action.capillary action.




44//2323//20072007 496496 of of 691691

Step 3. Clean off penetrantStep 3. Clean off penetrant

the penetrant is removedthe penetrant is removed after sufficient penetration time (dwellafter sufficient penetration time (dwell

time).time).

Care must be taken not to wash any penetrant out off anyCare must be taken not to wash any penetrant out off any

defects presentdefects present




44//2323//20072007 497497 of of 691691

Step 3. Apply developer Step 3. Apply developer

After the penetrant has be cleaned sufficiently, a thin layer of After the penetrant has be cleaned sufficiently, a thin layer of

developer is applied.developer is applied.

The developer acts as a contrast against the penetrant andThe developer acts as a contrast against the penetrant and

allows for reverse capillary action to take place.allows for reverse capillary action to take place.




4/23/20074/23/2007 498498 of of 691691

Step 4. Inspection / development timeStep 4. Inspection / development time

Inspection should take place immediately after the developer Inspection should take place immediately after the developer

has been applied.has been applied.

any defects present will show as a bleed out duringany defects present will show as a bleed out during

development time.development time.After full inspection has been carried out post cleaning isAfter full inspection has been carried out post cleaning is

generally required.generally required.




44//2323//20072007 499499 of of 691691

Fluorescent PenetrantFluorescent Penetrant Bleed out viewedBleed out viewedunder a UVunder a UV--A lightA lightsourcesource




4/23/20074/23/2007 500500 of 691of 691

Colour contrast PenetrantColour contrast Penetrant

Bleed out viewedBleed out viewed

under white lightunder white light



Simple to useSimple to use

InexpensiveInexpensive

Quick resultsQuick results

Can be used on any nonCan be used on any non--

porous materialporous material

PortabilityPortability


Surface breaking defectSurface breaking defect

onlyonlylittle indication of depthslittle indication of depths

Penetrant mayPenetrant maycontaminate componentcontaminate component

Surface preparation criticalSurface preparation critical

Post cleaning requiredPost cleaning required



4/23/20074/23/2007 501501 of 691of 691

yy

Low operator skill requiredLow operator skill required

g qg q

Potentially hazardousPotentially hazardouschemicalschemicals

Can not test unlimitedCan not test unlimitedtimestimes

Temperature dependantTemperature dependant

PenetrantTestingPenetrantTesting

Comparison with Magnetic Particle InspectionComparison with Magnetic Particle Inspection


easy to interpret resultseasy to interpret results

no power requirementsno power requirements

relatively little training requiredrelatively little training required

can use on all materialscan use on all materials




44//2323//20072007 502502 of 691of 691

good surface finish neededgood surface finish needed

relatively slowrelatively slow

chemicalschemicals -- health & safety issuehealth & safety issue


Weld RepairsWeld Repairs




4/23/20074/23/2007 503503 of 691of 691

Weld RepairsWeld RepairsWeld repairs can be divided intoWeld repairs can be divided into 22 specificspecificareas:areas:

ProductionProduction repairsrepairs

InIn serviceservice repairsrepairs



4/23/20074/23/2007 504504 of 691of 691

A weld repair can be a relatively straight forward A weld repair can be a relatively straight forward

activity, but in many instances it is quite complex, andactivity, but in many instances it is quite complex, and

various engineering disciplines may need to be involvedvarious engineering disciplines may need to be involved

to ensure a successful outcome.to ensure a successful outcome.

Analysis of the defect types may be carried out by Analysis of the defect types may be carried out by

the Q/C department to discover the likely reason for the Q/C department to discover the likely reason for

their occurrence, (Material/Process or Skill related).their occurrence, (Material/Process or Skill related).




4/23/20074/23/2007 505505 of 691of 691

In general terms, a welding repair involvesIn general terms, a welding repair involves What!What!

Weld RepairsWeld Repairs A weld repair may be used to improve weld profiles or A weld repair may be used to improve weld profiles or

extensive metal removal:extensive metal removal:

Repairs to fabrication defects are generally easier Repairs to fabrication defects are generally easier than repairs to service failures because the repair than repairs to service failures because the repair

procedure may be followedprocedure may be followed

The main problem with repairing a weld is theThe main problem with repairing a weld is the

maintenance of mechanical propertiesmaintenance of mechanical properties



44//2323//20072007 506506 of 691of 691

p pp p During the inspection of the removed area prior toDuring the inspection of the removed area prior to

welding the inspector must ensure that the defectswelding the inspector must ensure that the defects

have been totally removed and the original jointhave been totally removed and the original joint

profile has been maintained as close as possibleprofile has been maintained as close as possible

Weld RepairsWeld RepairsIn the event of repair, it is required:In the event of repair, it is required:

Authorization and procedure for repair Authorization and procedure for repair

Removal of material and preparation for repair Removal of material and preparation for repair

Monitoring of repair WeldMonitoring of repair Weld

Testing of repair Testing of repair -- visual and NDTvisual and NDT



4/23/20074/23/2007 507507 of 691of 691

g pg p

There are a number of key factors that need to beThere are a number of key factors that need to be

considered before undertaking any repair:considered before undertaking any repair:

The most importantThe most important -- is it financially worthwhile?is it financially worthwhile?

Can structural integrity be achieved if the item is repaired?Can structural integrity be achieved if the item is repaired?

Are there any alternatives to welding? Are there any alternatives to welding?

What caused the defect and is it likely to happen again?What caused the defect and is it likely to happen again?

How is the defect to be removed and what welding processHow is the defect to be removed and what welding process




4/23/20074/23/2007 508508 of 691of 691

How is the defect to be removed and what welding processHow is the defect to be removed and what welding process

is to be used?is to be used?

What NDE is required to ensure complete removal of theWhat NDE is required to ensure complete removal of the

defect?defect?

Will the welding procedures require approval/reWill the welding procedures require approval/re--approval?approval?

Weld RepairsWeld RepairsCleaning the repair area, (removal of paint, grease, etc)Cleaning the repair area, (removal of paint, grease, etc)

A detailed assessment to find out the extremity of the A detailed assessment to find out the extremity of thedefect. This may involve the use of a surface or sub surfacedefect. This may involve the use of a surface or sub surface

NDE method.NDE method.Once established the excavation site must be clearlyOnce established the excavation site must be clearlyidentified and marked out.identified and marked out.

An excavation procedure may be required (method used An excavation procedure may be required (method usedi.e. grinding, arci.e. grinding, arc--air gouging, preheat requirements etc).air gouging, preheat requirements etc).

NDE should be used to locate the defect and confirm itsNDE should be used to locate the defect and confirm its



4/23/20074/23/2007 509509 of 691of 691

NDE should be used to locate the defect and confirm itsNDE should be used to locate the defect and confirm itsremoval.removal.

A welding repair procedure/method statement with the A welding repair procedure/method statement with theappropriate welding process, consumable, technique,appropriate welding process, consumable, technique,

controlled heat input and interpass temperatures etc willcontrolled heat input and interpass temperatures etc willneed to be approved.need to be approved.

Use of approved welders.Use of approved welders.

Dressing the weld and final visual.Dressing the weld and final visual.

A NDT procedure/technique prepared and carried out to A NDT procedure/technique prepared and carried out toensure that the defect has been successfully removed andensure that the defect has been successfully removed and

repaired.repaired.

Any post repair heat treatment requirements. Any post repair heat treatment requirements.

Final NDT procedure/technique prepared and carried outFinal NDT procedure/technique prepared and carried outafter heat treatment requirementsafter heat treatment requirements




44//2323//20072007 510510 of 691of 691

after heat treatment requirements.after heat treatment requirements.

Applying protective treatments (painting etc as required). Applying protective treatments (painting etc as required).

(*Appropriate¶ means suitable for the alloys being repaired(*Appropriate¶ means suitable for the alloys being repaired

and may not apply in specific situations)and may not apply in specific situations)

What will be the effect of welding distortion andWhat will be the effect of welding distortion and

residual stress?residual stress?

Will heat treatment be required?Will heat treatment be required?

What NDE is required and how can acceptability of theWhat NDE is required and how can acceptability of the

repair be demonstrated?repair be demonstrated?

Will approval of the repair be requiredWill approval of the repair be required ± ± if yes, howif yes, how

and by whom?and by whom?




4/23/20074/23/2007 511511 of 691of 691

Production Weld RepairsProduction Weld RepairsBefore the repair can commence, a number of elements needBefore the repair can commence, a number of elements need

to be fulfilled:to be fulfilled:

If the defect is surface breaking and has occurred at the fusionIf the defect is surface breaking and has occurred at the fusion

face the problem could be cracking or lack of sidewall fusion.face the problem could be cracking or lack of sidewall fusion.If the defect is found to be cracking the cause may beIf the defect is found to be cracking the cause may be

associated with the material or the welding procedureassociated with the material or the welding procedure

If the defect is lack of sidewall fusion this can be apportionedIf the defect is lack of sidewall fusion this can be apportioned

to the lack of skill of the welder.to the lack of skill of the welder.

In this particular case as the defect is open to the surface, MPIIn this particular case as the defect is open to the surface, MPI



4/23/20074/23/2007 512512 of 691of 691

p p ,p p ,

or D YEor D YE--PEN may be used to gauge the length of the defect andPEN may be used to gauge the length of the defect and

U/T inspection used to gauge the depth.U/T inspection used to gauge the depth.

Weld RepairsWeld RepairsThe specification or procedure will govern how theThe specification or procedure will govern how the

defective areas are to be removed. The method of defective areas are to be removed. The method of

removal may be:removal may be:

GrindingGrinding

ChippingChipping

MachiningMachining

FilingFiling



4/23/20074/23/2007 513513 of 691of 691

FilingFiling

OxyOxy--Gas gougingGas gouging

Arc air gouging Arc air gouging

Defect ExcavationDefect Excavation

Arc Arc- -air gouging air gouging



44//2323//20072007 514514 of 691of 691

Arc Arc--air gouging featuresair gouging features Operate ONL Y on DCEPOperate ONL Y on DCEP

Special gougingSpecial gouging copper copper

coated carbon electrodecoated carbon electrode

Can be used on carbonCan be used on carbon

and low alloy steels,and low alloy steels,

austenitic stainless steelsaustenitic stainless steels

and nonand non--ferrous materialsferrous materials

Requires CLEAN/DR Y Requires CLEAN/DR Y

compressed air supplycompressed air supply



4/23/20074/23/2007 515515 of 691of 691

Provides fast rate of metal removalProvides fast rate of metal removal

Can remove complex shape defectsCan remove complex shape defects

After gouging, grinding of carbured layer is mandatoryAfter gouging, grinding of carbured layer is mandatory

Gouging doesn¶t require a qualified welder!Gouging doesn¶t require a qualified welder!

Production RepairsProduction Repairs

are usually identified during productionare usually identified during production

inspectioninspectionevaluation of the reports is usually carried outevaluation of the reports is usually carried outby the Welding Inspector, or NDT operator by the Welding Inspector, or NDT operator

Production Weld RepairsProduction Weld Repairs



4/23/20074/23/2007 516516 of 691of 691

Production Weld RepairsProduction Weld Repairs

Plan View of defect



4/23/20074/23/2007 517517 of 691of 691

Production Weld RepairsProduction Weld RepairsSide View of defect excavation

D

W

Side View of repair welding



4/23/20074/23/2007 518518 of 691of 691

In Service Weld RepairsIn Service Weld RepairsIn service repairsIn service repairs

Can be of a very complex nature, as the component isCan be of a very complex nature, as the component is

very likely to be in a different welding position andvery likely to be in a different welding position and

condition than it was during productioncondition than it was during production

It may also have been in contact with toxic, or It may also have been in contact with toxic, or

combustible fluids hence a permit to work will need tocombustible fluids hence a permit to work will need to

be sought prior to any work being carried outbe sought prior to any work being carried out

The repair welding procedure may look very differentThe repair welding procedure may look very different



4/23/20074/23/2007 519519 of 691of 691

The repair welding procedure may look very differentThe repair welding procedure may look very different

to the original production procedure due to changes into the original production procedure due to changes in

these elements.these elements.

In Service Weld RepairsIn Service Weld RepairsOther Other factorsfactors toto bebe takentaken intointo considerationconsideration::

EffectEffect of of heatheat onon anyany surroundingsurrounding areasareas of of thethe

componentcomponent ii..ee.. electricalelectrical components,components, or or materialsmaterials thatthat

maymay becomebecome damageddamaged byby thethe repair repair procedureprocedure..

ThisThis maymay alsoalso includeinclude difficultydifficulty inin carryingcarrying outout anyany

requiredrequired prepre or or postpost weldingwelding heatheat treatmentstreatments andand aa

possiblepossible restrictionrestriction of of accessaccess toto thethe areaarea toto bebe

repairedrepaired..



4/23/20074/23/2007 520520 of 691of 691

For For largelarge fabricationsfabrications itit isis likelylikely thatthat thethe repair repair mustmust

alsoalso taketake placeplace onon sitesite andand withoutwithout aa shutshut downdown of of

operations,operations, whichwhich maymay bringbring other other elementselements thatthat needneed

toto bebe consideredconsidered..

Is welding the best method of repair?Is welding the best method of repair?

Is the repair really like earlier repairs?Is the repair really like earlier repairs?

What is the composition and weldability of the base metal?What is the composition and weldability of the base metal?What strength is required from the repair?What strength is required from the repair?

Can preheat be tolerated?Can preheat be tolerated?

Can softening or hardening of the HAZ be tolerated?Can softening or hardening of the HAZ be tolerated?

Is PWHT necessary and practicable?Is PWHT necessary and practicable?




44//2323//20072007 521521 of of 691691

Is PWHT necessary and practicable?Is PWHT necessary and practicable?

Will the fatigue resistance of the repair be adequate?Will the fatigue resistance of the repair be adequate?

Will the repair resist its environment?Will the repair resist its environment?

Can the repair be inspected and tested?Can the repair be inspected and tested?

Weld repair related problemsWeld repair related problemsheat from welding may affect dimensional stabilityheat from welding may affect dimensional stability

and/or mechanical properties of repaired assemblyand/or mechanical properties of repaired assembly

due to heat from welding, YS goes down,due to heat from welding, YS goes down, danger of danger of

collapsecollapse

filler materials used on dissimilar welds may lead tofiller materials used on dissimilar welds may lead to

galvanic corrosiongalvanic corrosion

local preheat may induce residual stresseslocal preheat may induce residual stresses



4/23/20074/23/2007 522522 of of 691691

cost of weld metal deposited during a weld jointcost of weld metal deposited during a weld joint

repair can reach up to 10 times the original weldrepair can reach up to 10 times the original weld

metal cost!metal cost!


Residual Stress & DistortionResidual Stress & Distortion

SectionSection 1717



4/23/20074/23/2007 523523 of 691of 691

Residual stressResidual stressResidual stresses are undesirable because:Residual stresses are undesirable because:

they lead to distortionthey lead to distortion

they affect dimensional stability of thethey affect dimensional stability of the

welded assemblywelded assembly

they enhance the risk of brittle fracturethey enhance the risk of brittle fracture



4/23/20074/23/2007 524524 of 691of 691

they can facilitate certain types of they can facilitate certain types of

corrosioncorrosion

The heating and subsequent cooling from welding producesThe heating and subsequent cooling from welding producesexpansion and contractions which affect the weld metal andexpansion and contractions which affect the weld metal andadjacent material.adjacent material.

If this contraction is prevented or inhibited residual stress willIf this contraction is prevented or inhibited residual stress will

develop.develop.

The tendency to develop residual stresses increases when theThe tendency to develop residual stresses increases when theheating and cooling is localised.heating and cooling is localised.

Residual stresses are very difficult to measure with any realResidual stresses are very difficult to measure with any realaccuracy.accuracy.

Residual stresses are self balancing internal forces and notResidual stresses are self balancing internal forces and not

Residual StressesResidual Stresses



44//2323//20072007 525525 of of 691691

ggstresses induced whilst applying external loadstresses induced whilst applying external load

Stresses are more concentrated at the surface of theStresses are more concentrated at the surface of thecomponent.component.

The removal of residual stresses is termed stress relieving.The removal of residual stresses is termed stress relieving.

Normal StressNormal Stress

Stress arising from a force perpendicular toStress arising from a force perpendicular to thethe

crosscross sectional areasectional area

CompressionCompression

StressesStresses



4/23/20074/23/2007 526526 of 691of 691

TensionTension

Shear StressShear Stress

Stress arising from forces which are parallel to, andStress arising from forces which are parallel to, and

lielie inin the plane of the cross sectionalthe plane of the cross sectional area.area.

StressesStresses



4/23/20074/23/2007 527527 of 691of 691

Shear StressShear Stress

Hoop StressHoop Stress

Internal stress acting on the wall a pipe or cylinder Internal stress acting on the wall a pipe or cylinder

due to internal pressure.due to internal pressure.

StressesStresses



4/23/20074/23/2007 528528 of 691of 691

Hoop StressHoop Stress

LongitudinalLongitudinal

Along the weldAlong the weld ± ± longitudinal residual stresseslongitudinal residual stresses

Across the weldAcross the weld ± ± transverse residual stressestransverse residual stresses

Through the weldThrough the weld ± ± short transverse residual stressesshort transverse residual stresses

Residual stresses occur in welds in the following directionsResidual stresses occur in welds in the following directionsResidual StressesResidual Stresses



44//2323//20072007 529529 of 691of 691

TransverseTransverse

Short TransverseShort Transverse

Residual stressResidual stress

Heating andHeating and

cooling causescooling causesexpansion andexpansion and

contractioncontraction



4/23/20074/23/2007 530530 of of 691691

Residual stressResidual stress

In case of a heatedIn case of a heated

bar, the resistancebar, the resistanceof the surroundingof the surrounding

material to thematerial to the

expansion andexpansion andcontraction leadscontraction leads



4/23/20074/23/2007 531531 of 691of 691

co t act o eadsco t act o eads

to formation of to formation of

residual stressresidual stress

1.1. Residual stresses are locked in elastic strain, which isResidual stresses are locked in elastic strain, which is

caused by local expansion and contraction in the weldcaused by local expansion and contraction in the weld

area.area.

2.2. Residual stresses should be removed from structuresResidual stresses should be removed from structuresafter welding.after welding.

3.3. The amount of contraction is controlled by, the volume of The amount of contraction is controlled by, the volume of

weld metal in the joint, the thickness, heat input, jointweld metal in the joint, the thickness, heat input, joint

design and the materials propertiesdesign and the materials properties

4.4. Offsetting may be used to finalise the position of the joint.Offsetting may be used to finalise the position of the joint.

SummarySummary



44//2323//20072007 532532 of 691of 691

5.5. If plates or pipes are prevented from moving by tacking,If plates or pipes are prevented from moving by tacking,

clamping or jigging etc (restraint), then the amount of clamping or jigging etc (restraint), then the amount of

residual stresses that remain will be higher.residual stresses that remain will be higher.

6.6. The movement caused by welding related stresses isThe movement caused by welding related stresses is

called distortion.called distortion.

7.7. The directions of contractional stresses and distortion isThe directions of contractional stresses and distortion is

very complex, as is the amount and type of final distortion,very complex, as is the amount and type of final distortion,however we can say that there are three directions:however we can say that there are three directions:

a.a. Longitudinal Longitudinal b.b. TransverseTransverse c.c. S hort transverseS hort transverse

8.8. A high percentage of residual stresses can be removed byA high percentage of residual stresses can be removed by

heat treatments.heat treatments.

9.9. The peening of weld faces will only redistribute theThe peening of weld faces will only redistribute the

SummarySummary



4/23/20074/23/2007 533533 of 691of 691

residual stress, and place the weld face in compression.residual stress, and place the weld face in compression.

Types of distortionTypes of distortion Angular distortion Angular distortion



4/23/20074/23/2007 534534 of of 691691

Angular DistortionAngular DistortionTransverse DistortionTransverse Distortion

DistortionDistortion



4/23/20074/23/2007 535535 of 691of 691

Bowing DistortionBowing Distortion Longitudinal DistortionLongitudinal Distortion

Factors which affect distortionFactors which affect distortion

Material properties and conditionMaterial properties and condition

Heat inputHeat input

The amount of restrainThe amount of restrain

The amount of weld metal depositedThe amount of weld metal deposited


Control of distortion my be achieved in the following way:Control of distortion my be achieved in the following way:

The used of a different joint designThe used of a different joint design



4/23/20074/23/2007 536536 of 691of 691

Presetting the joints to be weldedPresetting the joints to be welded ± ± so that theso that the metal distortsmetal distorts

into the required position.into the required position.

The use of a balanced welding techniqueThe use of a balanced welding technique

The use of clamps, jigs and fixtures.The use of clamps, jigs and fixtures.

Distortion will occur in all welded joints if the materialDistortion will occur in all welded joints if the material areare

free to move i.e. not restrainedfree to move i.e. not restrained

Restrained materials result in low distortion but highRestrained materials result in low distortion but high

residual stressresidual stress More than one type of distortion may occur at one timeMore than one type of distortion may occur at one time

Highly restrained joints also have a higher crackHighly restrained joints also have a higher crack tendencytendency

than joints of a low restraintthan joints of a low restraint

The action of residual stress in welded joints is to causeThe action of residual stress in welded joints is to causedistortiondistortion




44//2323//20072007 537537 of of 691691

DistortionDistortionFactors affecting distortion:Factors affecting distortion:

parent material propertiesparent material properties

amount of restrainamount of restrain

joint design joint design

fitfit--upup



44//2323//20072007 538538 of 691of 691

pp

welding sequencewelding sequence

Factors affecting distortionFactors affecting distortionParent material properties:Parent material properties:

thermal expansion coefficientthermal expansion coefficient -- the greater the value, thethe greater the value, thegreater the residual stressgreater the residual stress

yield strengthyield strength -- the greater the value, the greater thethe greater the value, the greater theresidual stressresidual stress

Young¶s modulusYoung¶s modulus -- the greater the value (increase inthe greater the value (increase instiffness), the greater the residual stressstiffness), the greater the residual stress

thermal conductivitythermal conductivity -- the higher the value, the lower thethe higher the value, the lower theresidual stressresidual stress

transformation temperaturetransformation temperature during phaseduring phase



4/23/20074/23/2007 539539 of 691of 691

transformation temperaturetransformation temperature -- during phaseduring phasetransformation, expansion/contraction takes place. Thetransformation, expansion/contraction takes place. Thelower the transformation temperature, the lower thelower the transformation temperature, the lower the

residual stressresidual stress

Factors affecting distortionFactors affecting distortionJoint design:Joint design:

weld metal volumeweld metal volume

type of jointtype of joint -- butt vs. fillet, single vs. double sidebutt vs. fillet, single vs. double side

Amount of restrain: Amount of restrain:thicknessthickness -- as thickness increase, so do the stressesas thickness increase, so do the stresses

high level of restrain lead to high stresseshigh level of restrain lead to high stresses

preheat may increase the level of stresses (pipepreheat may increase the level of stresses (pipewelding!)welding!)



4/23/20074/23/2007 540540 of 691of 691

FitFit--up:up:misalignment may reduce stresses in some casesmisalignment may reduce stresses in some cases

root gaproot gap -- increase in root gap increases shrinkageincrease in root gap increases shrinkage

Factors affecting distortionFactors affecting distortionWelding sequence:Welding sequence:

number of passesnumber of passes -- every pass adds to the totalevery pass adds to the totalcontractioncontraction

heat inputheat input -- the higher the heat input, the greater the higher the heat input, the greater the shrinkagethe shrinkage

travel speedtravel speed -- the faster the welding speed, thethe faster the welding speed, the

less the stressless the stressbuildbuild--up sequenceup sequence



4/23/20074/23/2007 541541 of 691of 691

buildbuild up sequenceup sequence

Distortion preventionDistortion preventionDistortion prevention by preDistortion prevention by pre--settingsetting

a) prea) pre--setting of fillet joint tosetting of fillet joint to

prevent angular distortionprevent angular distortion

b) preb) pre--setting of butt joint tosetting of butt joint to

prevent angular distortionprevent angular distortionc) tapered gap to preventc) tapered gap to prevent



44//2323//20072007 542542 of of 691691

) p g p p) p g p p

closureclosure

PrePre--set or Offsetting:set or Offsetting:

The amount of offsetting required is generally a function of The amount of offsetting required is generally a function of

trial and error.trial and error.




4/23/20074/23/2007 543543 of of 691691

Distortion preventionDistortion prevention

Distortion prevention by preDistortion prevention by pre--bendingbending

using strongbacks and wedgesusing strongbacks and wedges



4/23/20074/23/2007 544544 of of 691691

Clamping and jigging:Clamping and jigging:

The materials to be welded are prevented from moving by theThe materials to be welded are prevented from moving by theclamp or jig the main advantage of using a jig is that theclamp or jig the main advantage of using a jig is that theelements in a fabrication can be precisely located in theelements in a fabrication can be precisely located in theposition to be welded. Main disadvantage of jigging is highposition to be welded. Main disadvantage of jigging is highrestraint and high levels of residual stresses.restraint and high levels of residual stresses.




4/23/20074/23/2007 545545 of 691of 691

Distortion preventionDistortion preventionDistortion prevention by restraint techniquesDistortion prevention by restraint techniques

a) use of welding jigsa) use of welding jigs



4/23/20074/23/2007 546546 of 691of 691

b) use of flexibleb) use of flexible

clampsclamps

Distortion preventionDistortion preventionDistortion prevention by restraint techniquesDistortion prevention by restraint techniques

c) use of strongbacksc) use of strongbacks

with wedgeswith wedges

d) use of fully weldedd) use of fully welded



4/23/20074/23/2007 547547 of 691of 691

d) use of fully weldedd) use of fully welded

strongbacksstrongbacks

Distortion preventionDistortion preventionDistortion prevention by designDistortion prevention by design

Consider eliminating the welding!!Consider eliminating the welding!!



44//2323//20072007 548548 of 691of 691

a) by forming the platea) by forming the plate

b) by use of rolled or extruded sectionsb) by use of rolled or extruded sections


consider weld placementconsider weld placement

reduce weld metal volumereduce weld metal volume



4/23/20074/23/2007 549549 of 691of 691

and/or number of runsand/or number of runs

The volume of weld metal in a joint will affect the amount of The volume of weld metal in a joint will affect the amount of local expansion and contraction, hence the more weldlocal expansion and contraction, hence the more welddeposited the higher amount of distortiondeposited the higher amount of distortion

Preparation anglePreparation angle 6060oo

Preparation angle 40Preparation angle 40oo




4/23/20074/23/2007 550550 of 691of 691

Preparation angle 0Preparation angle 0oo


use of balanced weldinguse of balanced welding



4/23/20074/23/2007 551551 of 691of 691


-- Transverse ShrinkageTransverse Shrinkage

Fillet WeldsFillet Welds 00..88mm per weld where the leg lengthmm per weld where the leg length

does not exceeddoes not exceed 33/ /44 plate thicknessplate thickness

Butt weldButt weld 11..55 toto 33mm per weld for mm per weld for 6060°° V joint,V joint,depending on number of runsdepending on number of runs

Allowances to cover shrinkage Allowances to cover shrinkage

Distortions prevention by designDistortions prevention by design



4/23/20074/23/2007 552552 of 691of 691

-- Longitudinal ShrinkageLongitudinal Shrinkage

Fillet WeldsFillet Welds 00..88mm per mm per 33m of weldm of weld

Butt WeldsButt Welds 33mm per mm per 33m of weldm of weld


Distortion prevention by fabrication techniquesDistortion prevention by fabrication techniques

tack weldingtack weldinga) tack weld straight througha) tack weld straight through

to end of jointto end of joint

b) tack weld one end, then useb) tack weld one end, then use

backback--step technique for step technique for

tacking the rest of the jointtacking the rest of the jointc) tack weld the centre, thenc) tack weld the centre, then



4/23/20074/23/2007 553553 of 691of 691

complete the tack weldingcomplete the tack welding

by the backby the back--step techniquestep technique



back to back assemblyback to back assembly

a)a) assemblies tacked together assemblies tacked together

before weldingbefore welding

b) use of wedges for b) use of wedges for components that distort oncomponents that distort on

separation after weldingseparation after welding



4/23/20074/23/2007 554554 of 691of 691

separation after weldingseparation after welding



use of stiffenersuse of stiffeners

control welding process by:control welding process by:



4/23/20074/23/2007 555555 of 691of 691

g p yg p y

-- deposit the weld metal as quickly as possibledeposit the weld metal as quickly as possible

-- use the least number of runs to fill the jointuse the least number of runs to fill the joint


Distortion prevention by welding procedureDistortion prevention by welding procedure

reduce the number of reduce the number of

runs required to make aruns required to make a

weld (e.g. angular weld (e.g. angular

distortion as a functiondistortion as a functionof number of runs for aof number of runs for a



4/23/20074/23/2007 556556 of 691of 691

o u be o u s o ao u be o u s o a

10 mm leg length weld)10 mm leg length weld)



control welding techniques by usecontrol welding techniques by use

balanced welding about the neutral axisbalanced welding about the neutral axis

control welding techniques by keepingcontrol welding techniques by keepingthe time between runs to a minimumthe time between runs to a minimum



4/23/20074/23/2007 557557 of 691of 691





4/23/20074/23/2007 558558 of of 691691

control welding techniques bycontrol welding techniques by

a) Backa) Back--step weldingstep welding

b) Skip weldingb) Skip welding

BackBack--skip welding techniqueskip welding technique

BackBack--step welding techniquestep welding technique

1.1. 2.2. 33.. 4.4. 55.. 6.6.

1.1. 2.2. 33.. 6.6.4.4. 5.5.




4/23/20074/23/2007 559559 of 691of 691

Distortion preventionDistortion preventionDistortionDistortion -- Best practice for fabrication corrective techniquesBest practice for fabrication corrective techniques

using tack welds to set up and maintain the joint gapusing tack welds to set up and maintain the joint gap

identical components welded back to back so welding can beidentical components welded back to back so welding can be

balanced about the neutral axisbalanced about the neutral axis

attachment of longitudinal stiffeners to prevent longitudinalattachment of longitudinal stiffeners to prevent longitudinal

bowing in butt welds of thin plate structuresbowing in butt welds of thin plate structures

where there is choice of welding procedure, process andwhere there is choice of welding procedure, process andtechnique should aim to deposit the weld metal as quickly astechnique should aim to deposit the weld metal as quickly as

ibl MIG i f t MMA ldi dibl MIG i f t MMA ldi d



4/23/20074/23/2007 560560 of of 691691

possible; MIG in preference to MMA or gas welding andpossible; MIG in preference to MMA or gas welding and

mechanised rather than manual weldingmechanised rather than manual welding

in long runs, the whole weld should not be completed in onein long runs, the whole weld should not be completed in onedirection; backdirection; back--step or skip welding techniques should be usedstep or skip welding techniques should be used

Distortion corrective techniquesDistortion corrective techniques

DistortionDistortion -- mechanical corrective techniquesmechanical corrective techniques



4/23/20074/23/2007 561561 of 691of 691

Use of press to correct bowing in T butt jointUse of press to correct bowing in T butt joint

Distortion corrective techniquesDistortion corrective techniquesDistortionDistortion -- Best practice for mechanical corrective techniquesBest practice for mechanical corrective techniques

Use packing pieces which will over correct the distortion soUse packing pieces which will over correct the distortion so

that springthat spring--back will return the component to the correct shapeback will return the component to the correct shapeCheck that the component is adequately supported duringCheck that the component is adequately supported during

pressing to prevent bucklingpressing to prevent buckling

Use a former (or rolling) to achieve a straight component or Use a former (or rolling) to achieve a straight component or

produce a curvatureproduce a curvature

As unsecured packing pieces may fly out from the press, the As unsecured packing pieces may fly out from the press, the

following safe practice must be adopted:following safe practice must be adopted:



4/23/20074/23/2007 562562 of of 691691

g p pg p p

-- bolt the packing pieces to the platenbolt the packing pieces to the platen

-- place a metal plate of adequate thickness to intercept theplace a metal plate of adequate thickness to intercept the

'missile''missile'

-- clear personnel from the hazard areaclear personnel from the hazard area


DistortionDistortion -- thermal corrective techniquesthermal corrective techniques

Localised heating toLocalised heating to

correct distortioncorrect distortion

Spot heating forSpot heating for



44//2323//20072007 563563 of 691of 691

Spot heating for Spot heating for

correcting bucklingcorrecting buckling



Line heating to correct angular Line heating to correct angular distortion in a fillet welddistortion in a fillet weld

Use of wedge shaped heatingUse of wedge shaped heating



4/23/20074/23/2007 564564 of of 691691

Use of wedge shaped heatingUse of wedge shaped heating

to straighten plateto straighten plate



Wedge shaped heating to correct distortionWedge shaped heating to correct distortion

a)a) standard rolledstandard rolledsteel sectionsteel section

b)b) buckled edge of buckled edge of plateplate

c)c) box fabricationbox fabrication



4/23/20074/23/2007 565565 of 691of 691

General guidelines:

Length of wedge = two-thirds of the plate width

Width of wedge (base) = one sixth of its length (base to apex)



use spot heating to remove buckling in thin sheet structures

other than in spot heating of thin panels, use a wedge-shapedheating technique

use line heating to correct angular distortion in plate

restrict the area of heating to avoid over-shrinking the component

limit the temperature to 60° to 650°C (dull red heat) in steels to

prevent metallurgical damage

in wedge heating, heat from the base to the apex of the wedge,



4/23/20074/23/2007 566566 of 691of 691

g g, p g ,

penetrate evenly through the plate thickness and maintain an even

temperature


Heat TreatmentHeat Treatment

SectionSection 1818



44//2323//20072007 567567 of of 691691


Why?Why?

Improve mechanical propertiesImprove mechanical properties

Change microstructureChange microstructure

Reduce residual stress levelReduce residual stress level

Change chemical compositionChange chemical composition

How?How?

Flame ovenFlame ovenElectric oven/electric heating blanketsElectric oven/electric heating blankets

induction/HF heating elementsinduction/HF heating elements



4/23/20074/23/2007 568568 of 691of 691

induction/HF heating elementsinduction/HF heating elements

Where?Where? LocalLocalGlobalGlobal

Heat TreatmentsHeat TreatmentsMany metals must be given heat treatment before andMany metals must be given heat treatment before andafter welding.after welding.

The inspector¶s function is to ensure that the treatmentThe inspector¶s function is to ensure that the treatmentis given correctly in accordance with the specification or is given correctly in accordance with the specification or

as per the details supplied.as per the details supplied.

Types of heat treatment available:Types of heat treatment available:

PreheatPreheat

Annealing AnnealingNormalisingNormalising



44//2323//20072007 569569 of 691of 691

Quench HardeningQuench Hardening

Temper Temper

Stress Relief Stress Relief

Heat TreatmentsHeat TreatmentsPrePre--heat treatmentsheat treatments

are used to increase weldability, by reducing suddenare used to increase weldability, by reducing sudden

reduction of temperature, and control expansion andreduction of temperature, and control expansion and

contraction forces during weldingcontraction forces during welding

Post weld heat treatmentsPost weld heat treatments

are used to change the properties of the weld metal,are used to change the properties of the weld metal,

controlling the formation of crystalline structurescontrolling the formation of crystalline structures



4/23/20074/23/2007 570570 of of 691691

controlling the formation of crystalline structurescontrolling the formation of crystalline structures

Post WeldPost Weld --Heat TreatmentsHeat Treatments

Post Hydrogen ReleasePost Hydrogen Release (according to BS EN(according to BS EN10111011--22))

Temperature:Temperature: Approximately Approximately 250250°°C hold up toC hold up to 33 hourshours

Cooling:Cooling: Slow cool in air Slow cool in air

Result:Result: Relieves residual hydrogenRelieves residual hydrogen

Procedure:Procedure: Maintaining preMaintaining pre--heat / interpass temperatureheat / interpass temperature

after completion of welding for after completion of welding for 22 toto 33 hours.hours.



4/23/20074/23/2007 571571 of 691of 691

Post Weld Heat TreatmentsPost Weld Heat Treatments

(A) Normalised

(B) Fully Annealed

(C) Water-quenched

(D) Water-quenched & tempered

A B

C D



4/23/20074/23/2007 572572 of of 691691

Post Weld Heat TreatmentsPost Weld Heat Treatments

The inspector, in general, should ensure that:The inspector, in general, should ensure that:

Equipment is as specifiedEquipment is as specified

Temperature control equipment is in good conditionTemperature control equipment is in good condition

Procedures as specified, is being used e.g.Procedures as specified, is being used e.g.

oo Method of applicationMethod of application

oo Rate of heating and coolingRate of heating and coolingoo Maximum temperatureMaximum temperature



44//2323//20072007 573573 of 691of 691

oo Soak timeSoak time

oo Temperature measurement (and calibration)Temperature measurement (and calibration)

DOCUMENTATION AND RECORDSDOCUMENTATION AND RECORDS

Post Weld Heat TreatmentPost Weld Heat Treatment

PWHT ProceduresPWHT Procedures -- Basic RequirementsBasic Requirements

Maximum Heating RateMaximum Heating Rate

Usually from 300 or 400Usually from 300 or 400°°C C -- need to avoid large temperatureneed to avoid large temperature

gradients that may cause distortion/crackinggradients that may cause distortion/cracking

Maximum rate depends on thickness but typically up to ~ 200Maximum rate depends on thickness but typically up to ~ 200°°C /hC /h

µSoak¶ TemperatureµSoak¶ Temperature depends on steel typedepends on steel type -- usually specified by Codeusually specified by Code

(~550 to ~750(~550 to ~750 °°C )C )

Minimum µSoak¶ TimeMinimum µSoak¶ Time

need to make sure and whole item/full thickness reaches specifiedneed to make sure and whole item/full thickness reaches specified

temp.temp.Codes typically specify 1h per 25mm related to max. joint thicknessCodes typically specify 1h per 25mm related to max. joint thickness

Maximum Cooling RateMaximum Cooling Rate



4/23/20074/23/2007 574574 of 691of 691

Maximum Cooling RateMaximum Cooling Rate

usually down to 400 or 300usually down to 400 or 300°°C C -- for same reasons as controlled heatingfor same reasons as controlled heating

raterate

Post Weld Heat Treatment CyclePost Weld Heat Treatment Cycle

TimeTime

TemperatureTemperatureSoakingSoakingTemperatureTemperature

and time at theand time at theattained temperatureattained temperature

heating rateheating rate Cooling rateCooling rate

Variables for heat treatment process must be carefully controlledVariables for heat treatment process must be carefully controlled



44//2323//20072007 575575 of 691of 691

HeatingHeating SoakingSoaking CoolingCooling

Post Weld Heat TreatmentPost Weld Heat TreatmentRemoval of Residual StressRemoval of Residual Stress

100100 200200 300300 400400 500500 600600 700700

Yield Yield

StrengthStrength

(N/mm(N/mm22

))

100100

200200

300300

400400

500500Cr Cr--Mo steelMo steel -- typicaltypical

CC--Mn steelMn steel -- typicaltypical

At PWHT temp. the yieldAt PWHT temp. the yield

strength of steel reducedstrength of steel reduced

so that it it is not strongso that it it is not strong

enough to give restraint.enough to give restraint.

Residual stress reducedResidual stress reduced

to very low level byto very low level by

strainingstraining ( typically < ~( typically < ~

0 0..5 5% strain)% strain)



44//2323//20072007 576576 of 691of 691

Temperature (Temperature (°°C)C)

100100 200200 300300 400400 500500 600600 700700


RecommendationsRecommendations

Provide adequate support (low YS at high temperature!)Provide adequate support (low YS at high temperature!)

Control heating rate to avoid uneven thermal expansionsControl heating rate to avoid uneven thermal expansions

Control soak time to equalise temperaturesControl soak time to equalise temperatures

Control temperature gradientsControl temperature gradients -- NO direct flameNO direct flame

impingement!impingement!

Control furnace atmosphere to reduce scalingControl furnace atmosphere to reduce scaling

Control cooling rate to avoid brittle structure formationControl cooling rate to avoid brittle structure formation



4/23/20074/23/2007 577577 of of 691691

Control cooling rate to avoid brittle structure formationControl cooling rate to avoid brittle structure formation

Post Weld Heat Treatment MethodsPost Weld Heat Treatment Methods


Easy to set upEasy to set up

Good portabilityGood portability

repeatability andrepeatability and

temperature uniformitytemperature uniformity




44//2323//20072007 578578 of of 691691

Gas furnace heat treatmentGas furnace heat treatment

gg

Limited to size of partsLimited to size of parts

Post Weld Heat Treatment MethodsPost Weld Heat Treatment Methods Advantages: Advantages:

High heating ratesHigh heating rates

Ability to heat a Ability to heat anarrow bandnarrow band


High equipmentHigh equipmentcostcost

L i tL i t



4/23/20074/23/2007 579579 of 691of 691

HF (Induction) local heat treatmentHF (Induction) local heat treatment

Large equipment,Large equipment,

less portableless portable

Post Weld Heat Treatment MethodsPost Weld Heat Treatment Methods


Ability to vary Ability to vary

heatheat Ability to Ability to

continuouslycontinuously

maintain heatmaintain heat


Elements mayElements may



44//2323//20072007 580580 of 691of 691

Local heat treatment usingLocal heat treatment usingelectric heating blanketselectric heating blankets

Elements mayElements may

burn out or arcingburn out or arcing

during heatingduring heating


Cutting ProcessesCutting Processes




4/23/20074/23/2007 581581 of 691of 691

Use of gas flameUse of gas flame

WeldingWelding GougingGougingBrazingBrazing CuttingCutting



44//2323//20072007 582582 of of 691691

HeatingHeating StraighteningStraightening BlastingBlasting SprayingSpraying

Oxygen regulatorOxygen regulator Fuel gas regulatorFuel gas regulator

RegulatorsRegulators

RegulatorRegulatortypetype

Single stageSingle stage used when slight rise in deliveryused when slight rise in deliverypressure from full to empty cylinder pressure from full to empty cylinder

condition can be toleratedcondition can be tolerated



44//2323//20072007 583583 of 691of 691

typetype

Two stageTwo stage used when a constant deliveryused when a constant delivery

pressure from full to emptypressure from full to emptycylinder condition is requiredcylinder condition is required

Flashback arrestorsFlashback arrestors

FlashbackFlashback -- recession of the flame into or back of the mixing chamber recession of the flame into or back of the mixing chamber

Flashback

flame

quenched

at the

flashback

barrier

Flame

barrier

Built-

in

check

valve

Normal

flow

Reverse

flow

Flashback

Built-in

check

valve

stops

reverseflow

SAFETY SAFETY SAFETY



44//2323//20072007 584584 of 691of 691

A jet of pure oxygen reacts with iron, that has been A jet of pure oxygen reacts with iron, that has beenpreheated to its ignition point, to produce thepreheated to its ignition point, to produce theoxide Feoxide Fe33OO44 by exothermic reaction.This oxide isby exothermic reaction.This oxide isthen blown through the material by the velocity ofthen blown through the material by the velocity of

the oxygen streamthe oxygen streamDifferent types of fuel gases may be used for theDifferent types of fuel gases may be used for theprepre--heating flame in oxy fuel gas cutting: i.e.heating flame in oxy fuel gas cutting: i.e.acetylene, hydrogen, propane. etcacetylene, hydrogen, propane. etc

By adding iron powder to the flame we are ableBy adding iron powder to the flame we are able

to cut most metalsto cut most metals -- Iron Powder Injection Iron Powder InjectionThe high intensity of heat and rapid cooling willThe high intensity of heat and rapid cooling willcause hardening in low alloy and medium/high Ccause hardening in low alloy and medium/high C

Oxyfuel gas cutting processOxyfuel gas cutting processOxyfuel gas cutting processOxyfuel gas cutting process



4/23/20074/23/2007 585585 of 691of 691

cause hardening in low alloy and medium/high C cause hardening in low alloy and medium/high C steelssteels they are thus prethey are thus pre--heated to avoid theheated to avoid thehardening effecthardening effect

Oxyfuel gas cutting equipmentOxyfuel gas cutting equipmentOxyfuel gas cutting equipmentOxyfuel gas cutting equipment

The cutting torchThe cutting torch

Neutral cutting flameNeutral cutting flame



4/23/20074/23/2007 586586 of 691of 691

Neutral cutting flame withNeutral cutting flame with

oxygen cutting streamoxygen cutting stream

Oxyfuel gas cutting related termsOxyfuel gas cutting related terms



44//2323//20072007 587587 of 691of 691

Oxyfuel gas cutting qualityOxyfuel gas cutting quality

Good cutGood cut -- sharp top edge, fine and even drag lines,sharp top edge, fine and even drag lines,little oxide and a sharp bottom edgelittle oxide and a sharp bottom edge

Cut too fastCut too fastCut too slowCut too slow -- top edge istop edge is



4/23/20074/23/2007 588588 of 691of 691

Cut too fastCut too fast --pronounced break inpronounced break inthe drag line,the drag line,irregular cut edgeirregular cut edge

Cut too slowCut too slow -- top edge istop edge ismelted, deep groves in themelted, deep groves in thelower portion, heavy scaling,lower portion, heavy scaling,

rough bottom edgerough bottom edge



P h t fl t hi hP h t fl t hi hP h t fl t lP h t fl t l



4/23/20074/23/2007 589589 of 691of 691

Preheat flame too highPreheat flame too high --

top edge is melted,top edge is melted,

irregular cut, excess of irregular cut, excess of adherent drossadherent dross

Preheat flame too lowPreheat flame too low --

deep groves in the lower deep groves in the lower

part of the cutpart of the cut faceface



I l t l dI l t l dNozzle is too high aboveNozzle is too high aboveh kh k ii



4/23/20074/23/2007 590590 of 691of 691

Irregular travel speedIrregular travel speed -- unevenuneven

space between drag lines,space between drag lines,

irregular bottom with adherentirregular bottom with adherentoxideoxide

the worksthe works -- excessiveexcessivemelting of the top edge,melting of the top edge,

much oxidemuch oxide

Mechanised oxyfuel cuttingMechanised oxyfuel cutting

can use portable carriages or gantry type machinescan use portable carriages or gantry type machines

and obtainand obtain high productivityhigh productivity

accurate cutting for complicate shapesaccurate cutting for complicate shapes



44//2323//20072007 591591 of 691of 691

OFW/C advantages/disadvantagesOFW/C advantages/disadvantagesOFW/C advantages/disadvantagesOFW/C advantages/disadvantages


1) High skill factor1) High skill factor

2) Wide H AZ2) Wide H AZ

44) Slow process) Slow process

5) Limited range of5) Limited range ofconsumablesconsumables

3) Safety issues3) Safety issues


1) No need for power1) No need for powersupply,supply, portableportable

3) Low equipment cost3) Low equipment cost

44) Can cut carbon and low) Can cut carbon and lowalloy steelsalloy steels

2) Versatile: preheat,2) Versatile: preheat,brazing, surfacing, repair,brazing, surfacing, repair,straighteningstraightening

66) i bl f i) i bl f i



44//2323//20072007 592592 of 691of 691

alloy steelsalloy steels

5) Good on thin materials5) Good on thin materials

66) Not suitable for reactive) Not suitable for reactive& refractory metals& refractory metals

Special oxyfuel operationsSpecial oxyfuel operations

GougingGouging Rivet cuttingRivet cutting



44//2323//20072007 593593 of 691of 691

Special oxyfuel operationsSpecial oxyfuel operations

Thin sheet cuttingThin sheet cutting Rivet washingRivet washing



44//2323//20072007 594594 of 691of 691

Cutting ProcessesCutting ProcessesPlasma arc cuttingPlasma arc cutting

Uses high velocity jet of ionised gasUses high velocity jet of ionised gasthrough a constricted nozzle to remove thethrough a constricted nozzle to remove the

molten metalmolten metal

Uses a tungsten electrode and water Uses a tungsten electrode and water

cooled nozzlecooled nozzle

High quality cuttingHigh quality cutting



44//2323//20072007 595595 of 691of 691

g q y gg q y g

High intensity and UV radiationHigh intensity and UV radiation ± ± EYES !EYES !

Cutting ProcessesCutting Processes

Air Air--arc for cutting or gougingarc for cutting or gouging



4/23/20074/23/2007 596596 of 691of 691

Air Air--arc gouging featuresarc gouging features Operate ONL Y on DCEPOperate ONL Y on DCEP

Special gougingSpecial gouging copper copper

coated carbon electrodecoated carbon electrode

Can be used on carbonCan be used on carbonand low alloy steels,and low alloy steels,

austenitic stainless steelsaustenitic stainless steels

and nonand non--ferrous materialsferrous materials

Requires CLEAN/DR Y Requires CLEAN/DR Y

compressed air supplycompressed air supply Provides fast rate of metal removalProvides fast rate of metal removal

Can remove complex shape defectsCan remove complex shape defects



44//2323//20072007 597597 of 691of 691

After gouging, grinding of carbured layer is mandatoryAfter gouging, grinding of carbured layer is mandatory

Gouging doesn¶t require a qualified welder!Gouging doesn¶t require a qualified welder!


Arc Welding Safety Arc Welding Safety

Please discussPlease discussSectionSection 2020



4/23/20074/23/2007 598598 of 691of 691

SafetySafety

Electrical safetyElectrical safety

Heat & LightHeat & Light ± ± Visible lightVisible light

± ± UV radiationUV radiation -- effects oneffects onskin and eyesskin and eyes

Fumes & ExplosiveFumes & ExplosiveGassesGasses

Noise levelsNoise levels

Fire HazardsFire HazardsScaffolding & StagingScaffolding & Staging

Slips, trips and fallsSlips, trips and falls



4/23/20074/23/2007 599599 of of 691691

Protection of others fromProtection of others fromexposureexposure


Weldability Of SteelsWeldability Of Steels




44//2323//20072007 600600 of 691of 691

Weldability of SteelsWeldability of SteelsDefinitionDefinition

It relates to the ability of the metal (or alloy) to be welded withIt relates to the ability of the metal (or alloy) to be welded with

mechanical soundness by most of the common weldingmechanical soundness by most of the common welding

processes, and the resulting welded joint retain theprocesses, and the resulting welded joint retain theproperties for which it has been designed.properties for which it has been designed.

is a function of many inter is a function of many inter--related factors but these may berelated factors but these may be

summarised as:summarised as:

Composition of parent materialComposition of parent material

Joint design and sizeJoint design and size

Process and techniqueProcess and technique



4/23/20074/23/2007 601601 of 691of 691

Process and techniqueProcess and technique

Access Access

Weldability of SteelsWeldability of SteelsThe weldability of steel is mainly dependant on carbon & other alloyingThe weldability of steel is mainly dependant on carbon & other alloyingelements content.elements content.

If a material has limited weldability, we need to take special measuresIf a material has limited weldability, we need to take special measuresto ensure the maintenance of the properties requiredto ensure the maintenance of the properties required

Poor weldability normally results in the occurrence of crackingPoor weldability normally results in the occurrence of cracking

A steel is considered to have poor weldability when: A steel is considered to have poor weldability when:

an acceptable joint can only be made by using very narrow rangean acceptable joint can only be made by using very narrow rangeof welding conditionsof welding conditions

great precautions to avoid cracking are essentialgreat precautions to avoid cracking are essential ( e.g., hig h pre( e.g., hig h pre--



4/23/20074/23/2007 602602 of 691of 691

g p gg p g ( g , g p( g , g pheat etc)heat etc)

The Effect of Alloying on SteelsThe Effect of Alloying on SteelsElements may be added to steels to produce theElements may be added to steels to produce theproperties required to make it useful for an application.properties required to make it useful for an application.

Most elements can have many effects on the propertiesMost elements can have many effects on the properties

of steels.of steels.Other factors which affect material properties are:Other factors which affect material properties are:

The temperature reached before and during weldingThe temperature reached before and during welding

Heat inputHeat input

The cooling rate after welding and or PWHTThe cooling rate after welding and or PWHT



4/23/20074/23/2007 603603 of of 691691

Iron (Fe):Iron (Fe): Main steel constituent. On its own, is relatively soft, ductile, with lowMain steel constituent. On its own, is relatively soft, ductile, with low

strength.strength.

Carbon (C):Carbon (C): Major alloying element in steels,Major alloying element in steels, a strengthening element witha strengthening element with

major influence on HAZ hardnessmajor influence on HAZ hardness. Decreases weldability.. Decreases weldability.

typically < ~ 0.25%typically < ~ 0.25%

Manganese (Mn):Manganese (Mn): Secondary only to carbon for strength, toughness andSecondary only to carbon for strength, toughness andductility, secondary deductility, secondary de--oxidiser and also reacts with sulphur to formoxidiser and also reacts with sulphur to form

manganese sulphide.manganese sulphide.

< ~0.8% is residual from steel de< ~0.8% is residual from steel de--oxidationoxidation

up to ~1.6% (in Cup to ~1.6% (in C--Mn steels) improves strength & toughnessMn steels) improves strength & toughness

Steel Alloying ElementsSteel Alloying Elements



44//2323//20072007 604604 of 691of 691

Silicon (Si):Silicon (Si): Residual element from steel deResidual element from steel de--oxidation.oxidation.

typically to ~0.35%typically to ~0.35%


Phosphorus (P):Phosphorus (P): Residual element from steelResidual element from steel--making minerals.making minerals. difficult todifficult toreduce below < ~ 0.015% brittlenessreduce below < ~ 0.015% brittleness

Sulphur (S):Sulphur (S): Residual element from steelResidual element from steel--making mineralsmaking minerals

< ~ 0.015% in modern steels< ~ 0.015% in modern steels

< ~ 0.003% in very clean steels< ~ 0.003% in very clean steels

Aluminium (Al): Aluminium (Al): DeDe--oxidant and grain size controloxidant and grain size control

typically ~ 0.02 to ~ 0.05%typically ~ 0.02 to ~ 0.05%

Chromium (Cr):Chromium (Cr): FFor creep resistance & oxidation (scaling) resistance for or creep resistance & oxidation (scaling) resistance for

elevated temperature service.elevated temperature service. Widely used in stainless steels for Widely used in stainless steels for

corrosion resistance, increases hardness and strength but reducescorrosion resistance, increases hardness and strength but reduces



4/23/20074/23/2007 605605 of 691of 691

ductility.ductility.

typically ~ 1 to 9% in low alloy steelstypically ~ 1 to 9% in low alloy steels


Nickel (Ni)Nickel (Ni):: Used in stainless steels, high resistance to corrosion fromUsed in stainless steels, high resistance to corrosion fromacids, increases strength and toughnessacids, increases strength and toughness

Molybdenum (Mo)Molybdenum (Mo):: Affects hardenability. Steels containing Affects hardenability. Steels containing

molybdenum are less susceptible to temper brittleness thanmolybdenum are less susceptible to temper brittleness thanother alloy steels.other alloy steels. Increases the high temperature tensile andIncreases the high temperature tensile andcreep strengths of steel. typically ~creep strengths of steel. typically ~ 00..55 toto 11..00%%

Niobium (Nb)Niobium (Nb):: a grain refiner, typically~a grain refiner, typically~ 00..0505%%

Vanadium (V)Vanadium (V):: a grain refiner, typically ~a grain refiner, typically ~ 00..0505%%

Titanium (Ti)Titanium (Ti):: a grain refiner, typically ~a grain refiner, typically ~ 00..0505%%

Copper (Cu)Copper (Cu):: present as a residual (typically < ~present as a residual (typically < ~ 00 3030%)%)



4/23/20074/23/2007 606606 of 691of 691

Copper (Cu)Copper (Cu):: present as a residual, (typically < ~present as a residual, (typically < ~ 00..3030%)%)added to µweathering steels¶ (~added to µweathering steels¶ (~ 00..66%) to give better resistance%) to give better resistance

to atmospheric corrosionto atmospheric corrosion

Classification of SteelsClassification of Steels

Mild steel (CE < 0.4)Mild steel (CE < 0.4)Readily weldable, preheat generally not required if low hydrogenReadily weldable, preheat generally not required if low hydrogenprocesses or electrodes are usedprocesses or electrodes are used

Preheat may be required when welding thick section material,Preheat may be required when welding thick section material,

high restraint and with higher levels of hydrogen beinghigh restraint and with higher levels of hydrogen beinggeneratedgenerated

CC--Mn, medium carbon, low alloy steels (CE 0.4 to 0.5)Mn, medium carbon, low alloy steels (CE 0.4 to 0.5)

Thin sections can be welded without preheat but thicker sectionsThin sections can be welded without preheat but thicker sections

will require low preheat levels and low hydrogen processes or will require low preheat levels and low hydrogen processes or electrodes should be usedelectrodes should be used

Higher carbon and alloyed steels (CE > 0.5)Higher carbon and alloyed steels (CE > 0.5)



4/23/20074/23/2007 607607 of of 691691

Preheat, low hydrogen processes or electrodes, post weldPreheat, low hydrogen processes or electrodes, post weldheating and slow cooling may be requiredheating and slow cooling may be required

Process CracksProcess Cracks

Hydrogen InducedHydrogen Induced HAZHAZ CrackingCracking (C/Mn steels)(C/Mn steels)

Hydrogen InducedHydrogen Induced Weld MetalWeld Metal CrackingCracking (HSLA steels).(HSLA steels).

Solidification or Hot CrackingSolidification or Hot Cracking (All steels)(All steels)

Lamellar TearingLamellar Tearing (All steels)(All steels)

ReRe--heat Crackingheat Cracking (All steels, very susceptible Cr/Mo/V(All steels, very susceptible Cr/Mo/Vsteels)steels)

InterInter--Crystalline Corrosion or Weld DecayCrystalline Corrosion or Weld Decay (stainless(stainless



44//2323//20072007 608608 of 691of 691

Inter Inter Crystalline Corrosion or Weld DecayCrystalline Corrosion or Weld Decay (stainless(stainless

steels)steels)

CrackingCrackingWhen considering any type of cracking mechanism, threeWhen considering any type of cracking mechanism, threeelements must always be present:elements must always be present:

StressStress

Residual stress is always present in a weldment,Residual stress is always present in a weldment,

through unbalanced local expansion andthrough unbalanced local expansion andcontractioncontraction

RestraintRestraint

Restraint may be a local restriction, or throughRestraint may be a local restriction, or through

plates being welded to each other plates being welded to each other

Susceptible microstructureSusceptible microstructure



4/23/20074/23/2007 609609 of 691of 691

pp

The microstructure may be made susceptible toThe microstructure may be made susceptible to

cracking by the process of weldingcracking by the process of welding

CracksCracks

Hydrogen Induced Cold CrackingHydrogen Induced Cold Cracking



4/23/20074/23/2007 610610 of 691of 691


May occur:May occur:

up to 48 hrs after completionup to 48 hrs after completion

In weld metal, HAZ, parentIn weld metal, HAZ, parentmetal.metal.

At weld toes At weld toes

Under weld beadsUnder weld beads

At stress raisers. At stress raisers.

Also know as:

Cold Cracking, happens when

the welds cool down.

HAZ cracking, normally occurs

in the HAZ.

Delayed cracking, as it takes

time for the hydrogen to

migrate. 48 Hours normally but

up to 72,

Under bead cracking normally



4/23/20074/23/2007 611611 of of 691691

Under-bead cracking, normally

happens in the HAZ under a

weld bead

There is a risk of hydrogen cracking when all of the 4There is a risk of hydrogen cracking when all of the 4

factors occur together:factors occur together:

HydrogenHydrogen More than 15ml/100g of weld metalMore than 15ml/100g of weld metalStressStress More than ½ the yield stressMore than ½ the yield stress

TemperatureTemperature Below 300Below 300ooCC

HardnessHardness Greater than 400HV VickersGreater than 400HV Vickers

Susceptible MicrostructureSusceptible Microstructure (Martensite)(Martensite)




44//2323//20072007 612612 of 691of 691

Susceptible MicrostructureSusceptible Microstructure (Martensite)(Martensite)




44//2323//20072007 613613 of 691of 691


Precautions for controlling hydrogen crackingPrecautions for controlling hydrogen cracking

Pre heat, removes moisture from the joint preparations,Pre heat, removes moisture from the joint preparations,and slows down the cooling rateand slows down the cooling rate

Ensure joint preparations are clean and free fromEnsure joint preparations are clean and free fromcontaminationcontamination

The use of a low hydrogen welding process and correctThe use of a low hydrogen welding process and correctarc lengtharc length

Ensure all welding is carried out is carried out under Ensure all welding is carried out is carried out under controlled environmental conditionscontrolled environmental conditions

Ensure good fitEnsure good fit--up as to reduced stressup as to reduced stress



4/23/20074/23/2007 614614 of 691of 691

The use of a PWHTThe use of a PWHT

Avoid poor weld profiles Avoid poor weld profiles

Hydrogen is the smallest atom knownHydrogen is the smallest atom known

Hydrogen enters the weld via the arcHydrogen enters the weld via the arc

Source of hydrogen mainly from moisture pickSource of hydrogen mainly from moisture pick--up onup onthe electrodes coating, welding fluxes or from thethe electrodes coating, welding fluxes or from the

consumable gasconsumable gas

HH

HH22

HH22

Moisture onMoisture onthe electrodethe electrodeor grease onor grease onthe wirethe wire

Water vapour Water vapour in the air or in the air or in thein theshielding gasshielding gas




4/23/20074/23/2007 615615 of 691of 691

HH22HH22HH22

Oxide or grease onOxide or grease onthe platethe plate

Hydrogen absorbed

in a long, or

unstable arc

Hydrogen introduced in

weld from consumable,

oils, or paint on plate

Cellulosic electrodes

produce hydrogen as a

shielding gas

HydrogenHydrogen

crackcrack

H2H2

H ydrogen Induced Cold Cracking H ydrogen Induced Cold Cracking



4/23/20074/23/2007 616616 of 691of 691

Martensite forms from H2 diffuses to in HAZ


Susceptible Microstructure:Susceptible Microstructure:

Hard brittle structureHard brittle structure ± ± MARTENSITE Promoted by:MARTENSITE Promoted by:

A) A) High Carbon Content, Carbon Equivalent (CE)High Carbon Content, Carbon Equivalent (CE)

CEV = %C +CEV = %C + MnMn ++ Cr+Mo+VCr+Mo+V ++ Ni+CuNi+Cu

6 5 156 5 15B)B) high alloy contenthigh alloy content

C)C) fast cooling rate:fast cooling rate: Inadequate PreInadequate Pre--HeatingHeating

Cold MaterialCold MaterialThick MaterialThick Material

Low Heat Input.Low Heat Input.



44//2323//20072007 617617 of 691of 691

Heat input (Kj/mm)Heat input (Kj/mm) = Amps x Volts x arc time= Amps x Volts x arc time

Run out length x 10Run out length x 1033 (1000)(1000)




44//2323//20072007 618618 of of 691691

Typical locations for Cold CrackingTypical locations for Cold Cracking

HSLA or MicroHSLA or Micro--Alloyed Steels are high strength steelsAlloyed Steels are high strength steels

(800MPa/N/mm2) that derive their high strength from small(800MPa/N/mm2) that derive their high strength from small

percentage alloying (over percentage alloying (over--alloyed Weld metal to match thealloyed Weld metal to match the

strength of parent metal)strength of parent metal)

Typically the level of alloying is in the elements such asTypically the level of alloying is in the elements such asvanadium molybdenum and titanium,vanadium molybdenum and titanium, nickel and chromiumnickel and chromium

StrengthStrength. are used. It would be impossible to match this micro. are used. It would be impossible to match this micro

alloying in the electrode due to the effect of losses across analloying in the electrode due to the effect of losses across an

electric arc (Ti burn in the arc)electric arc (Ti burn in the arc)

It is however important to match the strength of the weld toIt is however important to match the strength of the weld to

the strength of the plate, Mn 1.6Cr Ni Mothe strength of the plate, Mn 1.6Cr Ni Mo

H ICC in H S L A steelsH ICC in H S L A steels



4/23/20074/23/2007 619619 of 691of 691

Transverse WeldCracks in HSLA

Steels*

L it di l t ti l

Low ductility weld metal

H2 HAZ Cracks

in Alloy steels*



4/23/20074/23/2007 620620 of of 691691

Longitudinal contractional

strain

Hydrogen ScalesHydrogen Scales

List of hydrogen scales from BS EN 1011:part 2.List of hydrogen scales from BS EN 1011:part 2.

Hydrogen content related to 100 grams of weldHydrogen content related to 100 grams of weld

metal deposited.metal deposited.

ScaleScale A A High:High: >>15 ml15 ml

ScaleScale BB Medium:Medium: 10 ml10 ml -- 15 ml15 ml

ScaleScale CC Low:Low: 5 ml5 ml -- 10 ml10 ml

ScaleScale DD Very low:Very low: 3 ml3 ml -- 5 ml5 ml



4/23/20074/23/2007 621621 of 691of 691

ScaleScale EE UltraUltra--low:low: << 3 ml3 ml

Potential Hydrogen Level ProcessesPotential Hydrogen Level Processes

list of welding processes in order of potential lowestlist of welding processes in order of potential lowest

hydrogen content with regards to 100g of deposited weldhydrogen content with regards to 100g of deposited weld

metal.metal.

TIGTIG < 3 ml< 3 ml

MIGMIG < 5 ml< 5 ml

ESWESW < 5 ml< 5 ml

MMA (Basic Electrodes)MMA (Basic Electrodes) < 5 ml< 5 ml

SAWSAW < 10ml< 10ml



4/23/20074/23/2007 622622 of 691of 691

FCAWFCAW < 15 ml< 15 ml

WeldabilityWeldabilitySolidification CrackingSolidification Cracking



4/23/20074/23/2007 623623 of 691of 691

Solidification CrackingSolidification Cracking



4/23/20074/23/2007 624624 of 691of 691

Usually Occurs in Weld CenterlineUsually Occurs in Weld Centerline

Solidification CrackingSolidification Cracking Also referred as Also referred as

H ot C rac k ing:H ot C rac k ing: Occurring at hig h tem peratures while t he w eld is hot Occurring at hig h tem peratures while t he w eld is hot

C enterline crac k ing:C enterline crac k ing: crac k s appear dow n t he centre line of t he bead.crac k s appear dow n t he centre line of t he bead.

C rater crac k ing:C rater crac k ing: S mall crac k s in w eld centers are solidi f ication crac k sS mall crac k s in w eld centers are solidi f ication crac k s

Crack type:Crack type: Solidification crackingSolidification cracking

Location:Location: Weld centreline (longitudinal)Weld centreline (longitudinal)

Steel types:Steel types: High sulphur & phosphor concentration in steels.High sulphur & phosphor concentration in steels.

SusceptibleSusceptible Microstructure:Microstructure: Columnar grains In directionColumnar grains In direction

of solidificationof solidification



4/23/20074/23/2007 625625 of 691of 691

of solidificationof solidification

Factors for solidification crackingFactors for solidification cracking

Columnar grain growth with impurities in weld metal (sulphur,Columnar grain growth with impurities in weld metal (sulphur,phosphor and carbon)phosphor and carbon)

The amount of stress/restraintThe amount of stress/restraint

Joint design high depth to width ratiosJoint design high depth to width ratios

Liquid iron sulphides are formed around solidifying grains.Liquid iron sulphides are formed around solidifying grains.

High contractional strains are presentHigh contractional strains are present

High dilution processes are being used.High dilution processes are being used.

There is a high carbon content in the weld metalThere is a high carbon content in the weld metal

M t l i i bM t l i i b ld d j i tld d j i t




4/23/20074/23/2007 626626 of 691of 691

Most commonly occurring in subMost commonly occurring in sub--arc welded jointsarc welded joints


Sulphur in the parent material may dilute in the weldSulphur in the parent material may dilute in the weld

metal to form iron sulphides (low strength, lowmetal to form iron sulphides (low strength, low

melting point compounds)melting point compounds)

During weld metal solidification, columnar crystalsDuring weld metal solidification, columnar crystalspush still liquid iron sulphides in front to the last placepush still liquid iron sulphides in front to the last place

of solidification, weld centerline.of solidification, weld centerline.

The bonding between the grains which areThe bonding between the grains which are

themselves under great stress and may now be verythemselves under great stress and may now be verypoor to maintain cohesion and a crack will result,poor to maintain cohesion and a crack will result,

weld centerline.weld centerline.



4/23/20074/23/2007 627627 of 691of 691

Deep, narrower weld beadDeep, narrower weld bead

On solidification theOn solidification thebonding between the grainsbonding between the grains

may now be very poor tomay now be very poor to

maintain cohesion and amaintain cohesion and a

crack may resultcrack may result

Shallow, wider weld beadShallow, wider weld bead

On solidification theOn solidification thebonding between thebonding between the

grains may be adequate tograins may be adequate to

maintain cohesion and amaintain cohesion and a

crack is unlikely to occurcrack is unlikely to occur


Avoidance AvoidanceHAZHAZ HAZHAZ

Intergranular liquid filmIntergranular liquid filmColumnar Columnar grainsgrains Columnar Columnar

grainsgrains



4/23/20074/23/2007 628628 of 691of 691

crack may resultcrack may resultcrack is unlikely to occur crack is unlikely to occur

Precautions for controlling solidification crackingPrecautions for controlling solidification cracking

The first steps in eliminating this problem would be to choose a lowThe first steps in eliminating this problem would be to choose a lowdilution process, and change the joint designdilution process, and change the joint design

Grind and seal in any lamination and avoid further dilution????Grind and seal in any lamination and avoid further dilution????

Add Manganese to the electrode to form spherical Mn/S which form Add Manganese to the electrode to form spherical Mn/S which form

between the grain and maintain grain cohesionbetween the grain and maintain grain cohesion

As carbon increases the Mn/S ratio required increases As carbon increases the Mn/S ratio required increases

exponentially and is a major factor. Carbon content % should be aexponentially and is a major factor. Carbon content % should be aminimised by careful control in electrode and dilutionminimised by careful control in electrode and dilution

Limit the heat input, hence low contraction, & minimise restraintLimit the heat input, hence low contraction, & minimise restraint




4/23/20074/23/2007 629629 of 691of 691


Precautions for controlling solidification crackingPrecautions for controlling solidification cracking

The use of high manganese and low carbon contentThe use of high manganese and low carbon content

fillersfillers

Minimise the amount of stress / restraint acting on theMinimise the amount of stress / restraint acting on the

joint during welding joint during welding

The use of high quality parent materials, low levels of The use of high quality parent materials, low levels of

impurities (Phosphor & sulphur)impurities (Phosphor & sulphur)

Clean joint preparations contaminants (oil, grease, paintsClean joint preparations contaminants (oil, grease, paints

and any other sulphur containing product)and any other sulphur containing product)



4/23/20074/23/2007 630630 of 691of 691

Joint design selection depth to width ratiosJoint design selection depth to width ratios


Solidification cracking in Austenitic Stainless SteelSolidification cracking in Austenitic Stainless Steel

particularly prone to solidification crackingparticularly prone to solidification cracking

large grain size gives rise to a reduction in grain boundary arealarge grain size gives rise to a reduction in grain boundary areawith high concentration of impuritieswith high concentration of impurities

Austenitic structure very intolerant to contaminants (sulphur, Austenitic structure very intolerant to contaminants (sulphur,phosphorous and other impurities).phosphorous and other impurities).

High coefficient of thermal expansion /Low coefficient of thermalHigh coefficient of thermal expansion /Low coefficient of thermalconductivity, with high resultant residual stressconductivity, with high resultant residual stress

same precautions against cracking as for plain carbon steelssame precautions against cracking as for plain carbon steelsith t h i th h l i d hi h dil tiith t h i th h l i d hi h dil ti



4/23/20074/23/2007 631631 of 691of 691

with extra emphasis on thorough cleaning and high dilutionwith extra emphasis on thorough cleaning and high dilution

controls.controls.

CracksCracks




44//2323//20072007 632632 of 691of 691


Factors for lamellar tearing to occur Factors for lamellar tearing to occur

Cracks only occur in the rolled plate !Cracks only occur in the rolled plate !

Close to or just outside the HAZ !Close to or just outside the HAZ !

Cracks lay parallel to the plate surface and the fusionCracks lay parallel to the plate surface and the fusionboundary of the weld and has a stepped aspect.boundary of the weld and has a stepped aspect.

Low quality parent materials, high levels of impuritiesLow quality parent materials, high levels of impurities

Joint design, direction of stressJoint design, direction of stress

The amount of stress acting across the joint duringThe amount of stress acting across the joint duringweldingwelding



4/23/20074/23/2007 633633 of 691of 691

Note: very susceptible joints may form lamellar tearingNote: very susceptible joints may form lamellar tearingunder very low levels of stressunder very low levels of stress

Susceptible joint types combined with susceptible rolled plateSusceptible joint types combined with susceptible rolled plate

used to make a joint.used to make a joint.

High stresses act in the through thickness direction of the plateHigh stresses act in the through thickness direction of the plate

(know as the short transverse direction).(know as the short transverse direction).

T, K & Y joints normally end up with a tensile residual stressT, K & Y joints normally end up with a tensile residual stress

component in the through thickness direction.component in the through thickness direction.




4/23/20074/23/2007 634634 of 691of 691

Tee fillet weldTee fillet weld Tee butt weldTee butt weld(double(double--bevel)bevel)

Corner butt weldCorner butt weld(single(single--bevel)bevel)

Critical areaCritical area

CriticalCritical

areaarea

Critical areaCritical area




4/23/20074/23/2007 635635 of 691of 691

Modifying a corner joint to avoid lamellar tearingModifying a corner joint to avoid lamellar tearing

SusceptibleSusceptible NonNon--SusceptibleSusceptible

Prior welding bothPrior welding bothplates may be groovedplates may be groovedto avoid lamellar tearingto avoid lamellar tearing

An open corner jointAn open corner jointmay be selected tomay be selected toavoid lamellar tearingavoid lamellar tearing




4/23/20074/23/2007 636636 of of 691691

gg

Precautions for controlling lamellar tearingPrecautions for controlling lamellar tearing

The use of high quality parent materials, low levels of The use of high quality parent materials, low levels of

impuritiesimpurities

The use of buttering runsThe use of buttering runs

A gap can be left between the horizontal and vertical A gap can be left between the horizontal and vertical

members enabling the contraction movement to takemembers enabling the contraction movement to take

placeplace

Joint design selectionJoint design selection

Minimise the amount of stress / restraint acting onMinimise the amount of stress / restraint acting on thethe

joint joint during weldingduring welding




4/23/20074/23/2007 637637 of 691of 691

Hydrogen precautionsHydrogen precautions


Crack type:Crack type: Lamellar tearingLamellar tearingLocation:Location: Below weld HAZBelow weld HAZ

Steel types:Steel types: High sulphur & phosphorous steelsHigh sulphur & phosphorous steels

Microstructure:Microstructure: Lamination & SegregationLamination & Segregation

Occurs when:Occurs when:

High contractional strains are through the shortHigh contractional strains are through the short

transverse direction. There is a high sulfur content intransverse direction. There is a high sulfur content in

the base metal.the base metal.

There is low through thickness ductility in the baseThere is low through thickness ductility in the base

metal.metal.



4/23/20074/23/2007 638638 of of 691691

metal.metal.

There is high restraint on the workThere is high restraint on the work

The short tensile test or through thickness test is aThe short tensile test or through thickness test is a

test to determine a materials susceptibility totest to determine a materials susceptibility to

lamellar tearinglamellar tearing

Friction Welded CapsFriction Welded Caps

Short Tensile SpecimenShort Tensile Specimen

Through

ThroughThicknessThickness

DuctilityDuctility

Sample of Parent MaterialSample of Parent Material

The results are given as aThe results are given as a STRASTRA valuevalue

Short Tensile (Through Thickness) TestShort Tensile (Through Thickness) Test



44//2323//20072007 639639 of of 691691

The results are given as aThe results are given as a STRASTRA valuevalue

ShortT

ransverse Reduction in AreaShortT

ransverse Reduction in Area

High contractionalLamellar tear

Restraint

Lamellar Tearing Lamellar Tearing



44//2323//20072007 640640 of of 691691

strains

Welding Inspector Welding Inspector Practical Visual InspectionPractical Visual Inspection

SectionSection 2222



4/23/20074/23/2007 641641 of 691of 691

Leg Length GaugeLeg Length Gauge

G.A.L.

S.T.D.

10mm

16mm

L

G.A.L.

S.T.D.

10mm

16mm

F illet W eld GaugesF illet W eld Gauges



4/23/20074/23/2007 642642 of 691of 691

Throat Thickness GaugeThroat Thickness Gauge

H I - L O

S i n g l e P u r p

o s e W e l d i n g G a u g e

1

2

3

4

5

6

Root gapRoot gapdimensiondimension

InternalInternal

alignmentalignment

HI HI--LO W elding GaugeLO W elding Gauge



4/23/20074/23/2007 643643 of of 691691

Plate / Pipe InspectionPlate / Pipe Inspection



44//2323//20072007 644644 of of 691691

Remember in the CSWIPRemember in the CSWIP 33..11 Welding InspectorsWelding Inspectors

examination your are required to conduct a practicalexamination your are required to conduct a practical

examination of a plate test weld, complete a thumbexamination of a plate test weld, complete a thumb

print sketch and a final report on your findingsprint sketch and a final report on your findings

Time allowed 1 hour and 15 minutesTime allowed 1 hour and 15 minutes

The code is providedThe code is provided

Plate Inspection ExaminationPlate Inspection Examination



4/23/20074/23/2007 645645 of 691of 691

1)1) Use a pencil for the arrow lines, but make allUse a pencil for the arrow lines, but make all

written comments and measurements inwritten comments and measurements in inkink

onlyonly

3)3) Do not forget toDo not forget to compare and sentencecompare and sentence your your

reportreport

2) Report2) Report everythingeverything that you can observethat you can observe

4) Do not forget to4) Do not forget to date & signdate & sign your reportyour report

5)5) Make any observations, such asMake any observations, such as

recommendations for further investigation for recommendations for further investigation for

Plate Inspection PointsPlate Inspection Points



4/23/20074/23/2007 646646 of of 691691

gg

crackcrack--like imperfections.like imperfections.

After you have observed an imperfection andAfter you have observed an imperfection and

determined its type, you must be able to takedetermined its type, you must be able to take

measurements and complete the thumb print reportmeasurements and complete the thumb print report

sketchsketchThe first thumb print report sketch should be in theThe first thumb print report sketch should be in the

form of a repair map of the weld. (i.e.form of a repair map of the weld. (i.e. AllAll

observations are Identified Sized and Located)observations are Identified Sized and Located)

The thumb print report sketch used in CSWIP examThe thumb print report sketch used in CSWIP exam

will look like the following example.will look like the following example.

Plate Thumb Print ReportPlate Thumb Print Report



44//2323//20072007 647647 of 691of 691

After you have completed your thumb print reportAfter you have completed your thumb print report

sketch of your test plate the next step is to completesketch of your test plate the next step is to complete

your final report again the report must beyour final report again the report must be completed incompleted in

ink (no pencil).ink (no pencil).The report must be completed to your thumb printThe report must be completed to your thumb print

sketch, do not leave any boxes empty,sketch, do not leave any boxes empty, every box mustevery box must

be completed or dashed outbe completed or dashed out. You must also make any. You must also make any

comments you feel are necessary regarding anycomments you feel are necessary regarding anydefects observed.defects observed.

The report form used in CSWIP will look like theThe report form used in CSWIP will look like the

Plate Inspection Final ReportPlate Inspection Final Report



44//2323//20072007 648648 of 691of 691

following example.following example.

Remember in the CSWIPRemember in the CSWIP 33..11 Welding InspectorsWelding Inspectors

examination your are required to conduct aexamination your are required to conduct a

practical examination of a pipe test weld, completepractical examination of a pipe test weld, complete

a thumb print sketch and a final report on your a thumb print sketch and a final report on your

findingsfindings

Time allowed 1 hour and 45 minutesTime allowed 1 hour and 45 minutes

The code is nominated e.g API 1104The code is nominated e.g API 1104

Pipe InspectionPipe Inspection



4/23/20074/23/2007 649649 of of 691691


Application & Control of Pre heat Application & Control of Pre heat




4/23/20074/23/2007 650650 of of 691691

Welding TemperaturesWelding Temperatures

DefinitionsDefinitionsPreheat temperaturePreheat temperature

is the temperature of the workpiece in the weld zone immediatelyis the temperature of the workpiece in the weld zone immediatelybeforebefore anyany welding operation (including tack welding!)welding operation (including tack welding!)

normally expressed as a minimumnormally expressed as a minimum Interpass temperatureInterpass temperature

± ± is the temperature in a multiis the temperature in a multi--run weld and adjacent parent metalrun weld and adjacent parent metal

immediately prior to the application of the next runimmediately prior to the application of the next run

± ± normally expressed as a maximumnormally expressed as a maximum

Minimum interpass temperature = Preheat temperatureMinimum interpass temperature = Preheat temperature

Pre heat maintenance temperature = the minimum temperature in theweld zone which shall be maintained if welding is interrupted and shall be

monitored during the interruption



44//2323//20072007 651651 of 691of 691

monitored during the interruption.

PrePre--heat Applicationheat Application

FurnaceFurnace -- Heating entire componentHeating entire component -- bestbest

Electrical elementsElectrical elements --Controllable; Portable; Site use; Clean;Controllable; Portable; Site use; Clean;

Component cannot be moved.Component cannot be moved.

Gas burnersGas burners -- direct flame impingement; Possible localdirect flame impingement; Possible local

overheating; Less controllable;Portable; Manual operationoverheating; Less controllable;Portable; Manual operation

possible; Component can be moved.possible; Component can be moved.

Radiant gas heatersRadiant gas heaters -- capable of automatic control; No flamecapable of automatic control; No flame

impingement; No contact with component; Portable.impingement; No contact with component; Portable.

Induction heatingInduction heating -- controllable; Rapid heating (mins not hours);controllable; Rapid heating (mins not hours);

Large power supply; Expensive equipmentLarge power supply; Expensive equipment



4/23/20074/23/2007 652652 of 691of 691

Measuring pre heat in WeldingMeasuring pre heat in Welding

Parameters to be measured:Parameters to be measured:

welding currentwelding current

arc voltagearc voltage

travel speedtravel speed

The purposesThe purposes

of measuringof measuring

Demonstration of Demonstration of

conformance toconformance tospecified requirementsspecified requirements

preheat/interpasspreheat/interpasstemperaturetemperature

force/pressureforce/pressure

WeldingWelding

processprocesscontrolcontrol



4/23/20074/23/2007 653653 of of 691691

shielding gas flow rateshielding gas flow rate

pp

humidityhumidity

PrePre--heat Applicationheat Application

Application Of Preheat Application Of Preheat

Heat either side of jointHeat either side of joint

Measure tempMeasure temp 22 mins after heat removalmins after heat removal

Always best to heat complete component rather than Always best to heat complete component rather than

local if possible to avoid distortionlocal if possible to avoid distortion

Preheat always higher for fillet than butt welds due toPreheat always higher for fillet than butt welds due todifferent combined thicknesses and chill effect factors.different combined thicknesses and chill effect factors.



4/23/20074/23/2007 654654 of 691of 691

Manual Gas OperationManual Gas Operation

PrePre--Heat ApplicationHeat Application

Electrical HeatedElectrical HeatedElementsElements



44//2323//20072007 655655 of 691of 691

Welding TemperaturesWelding TemperaturesPoint of MeasurementPoint of Measurement


tt < 50 mm< 50 mm

A = 4 x t but max. 50 mm A = 4 x t but max. 50 mm

the temperature shall bethe temperature shall be

measured on the surfacemeasured on the surfaceof the workpiece facing theof the workpiece facing the

welder welder



44//2323//20072007 656656 of of 691691

Welding TemperaturesWelding Temperatures

Point of MeasurementPoint of Measurement


t > 50mmt > 50mm

A = 75mm minimum A = 75mm minimum

the temperature shall bethe temperature shall be

measured on the facemeasured on the face

opposite to that beingopposite to that being

heatedheated

allow 2 min per every 25allow 2 min per every 25

mm of parent metalmm of parent metal



44//2323//20072007 657657 of 691of 691

thickness for temperaturethickness for temperature

equalisationequalisation

Combined ThicknessCombined Thickness

The Chilling Effect of the JointThe Chilling Effect of the Joint



4/23/20074/23/2007 658658 of 691of 691

Combined ThicknessCombined ThicknessThe Chilling Effect of the JointThe Chilling Effect of the Joint



44//2323//20072007 659659 of 691of 691

Combined ThicknessCombined ThicknessCombined chilling effect of joint type andCombined chilling effect of joint type and

thickness.thickness.



44//2323//20072007 660660 of 691of 691

The Chill Effect of the MaterialThe Chill Effect of the Material



4/23/20074/23/2007 661661 of 691of 691

Heating Temperature ControlHeating Temperature ControlTEMPILSTICKSTEMPILSTICKS -- crayons, melt at set temps. Will notcrayons, melt at set temps. Will not

measure max temp.measure max temp.

PyrometersPyrometers -- contact or remote, measure actual temp.contact or remote, measure actual temp.

ThermocouplesThermocouples -- contact or attached, very accurate,contact or attached, very accurate,

measure actual temp.measure actual temp.



4/23/20074/23/2007 662662 of 691of 691

Temperature Test EquipmentTemperature Test EquipmentTemperature sensitiveTemperature sensitive

materials:materials:

crayons, paints andcrayons, paints and

pillspillscheapcheap

convenient, easy toconvenient, easy to

useuse

doesn¶t measure thedoesn¶t measure the

actual temperature!actual temperature!



4/23/20074/23/2007 663663 of 691of 691

Temperature Test EquipmentTemperature Test EquipmentContact thermometer Contact thermometer

AccurateAccurate

Easy to useEasy to use

Gives the actual temperatureGives the actual temperature

Requires calibrationRequires calibration

suitable for moderatesuitable for moderatetemperaturestemperatures



44//2323//20072007 664664 of 691of 691

Temperature Test EquipmentTemperature Test EquipmentThermocoupleThermocouple

based on measuring the thermoelectric potential differencebased on measuring the thermoelectric potential difference

between a hot junction (on weld) and a cold junctionbetween a hot junction (on weld) and a cold junction

accurate methodaccurate method

measures over a wide range of temperaturesmeasures over a wide range of temperatures

gives the actual temperaturegives the actual temperature

need calibrationneed calibration



44//2323//20072007 665665 of 691of 691

Temperature Test EquipmentTemperature Test Equipment

ThermistorsThermistors

temperaturetemperature--sensitive resistorssensitive resistors

whose resistance varies inverselywhose resistance varies inversely

with temperaturewith temperature

used when high sensitivity isused when high sensitivity is

requiredrequired

gives the actual temperaturegives the actual temperature

need calibrationneed calibration

can be used up tocan be used up to 999999°°CC



4/23/20074/23/2007 666666 of 691of 691

Temperature test equipmentTemperature test equipmentDevices for contactless measurementDevices for contactless measurement

IR radiation and opticalIR radiation and optical

pyrometer pyrometer

measure the radiant energymeasure the radiant energyemitted by the hot bodyemitted by the hot body

contactless method,contactless method, can becan be

used for remote measurementsused for remote measurements

very complexvery complex

for measuring highfor measuring high

temperaturestemperatures



4/23/20074/23/2007 667667 of 691of 691

Welding Inspector Welding Inspector CalibrationCalibration




44//2323//20072007 668668 of 691of 691

Calibration, validation and monitoringCalibration, validation and monitoring

Definitions:Definitions:MeasurementMeasurement = set of operations for determining a value of a= set of operations for determining a value of a

quantityquantity

RepeatabilityRepeatability = closeness between successive measuring= closeness between successive measuring

results of the same instrument carried out under the sameresults of the same instrument carried out under the same

conditionsconditions

Accuracy class Accuracy class = class of measuring instruments that are= class of measuring instruments that are

intended to keep the errors within specified limitsintended to keep the errors within specified limits

CalibrationCalibration = checking the errors in a meter or measuring= checking the errors in a meter or measuring

devicedeviceValidationValidation = checking the control knobs and switches provide= checking the control knobs and switches provide

the same level of accuracy when returned to a prethe same level of accuracy when returned to a pre--determineddetermined

pointpoint

M it iM it i h ki th ldi t ( d thh ki th ldi t ( d th



44//2323//20072007 669669 of of 691691

MonitoringMonitoring = checking the welding parameters (and other = checking the welding parameters (and other

items) are in accordance with the procedure or specificationitems) are in accordance with the procedure or specification

Calibration and validationCalibration and validation

FrequencyFrequency -- When it is required?When it is required?

once a year unless otherwise specifiedonce a year unless otherwise specified

whenever there are indications that thewhenever there are indications that theinstrument does not register properlyinstrument does not register properly

whenever the equipment has beenwhenever the equipment has beendamaged, misused or subject to severedamaged, misused or subject to severe

stressstress

whenever the equipment has been rebuildwhenever the equipment has been rebuildor repairedor repaired



4/23/20074/23/2007 670670 of 691of 691See BS EN ISOSee BS EN ISO 1766217662 for details!for details!

Welding parameter calibration/validationWelding parameter calibration/validation

Which parameters need calibration/validation?Which parameters need calibration/validation?

depends on the welding processdepends on the welding process

see BS EN ISO 17662 and BS 7570 for detailssee BS EN ISO 17662 and BS 7570 for details

How accurate?How accurate?

depends on the applicationdepends on the application

welding currentwelding current -- 2,5%2,5%arc voltagearc voltage -- 5%5%

wire feed speedwire feed speed -- 2,5%2,5%

gas flow rategas flow rate -- 20% (20% ( 25% for backing gas flow rate)25% for backing gas flow rate)

temperature (thermocouple)temperature (thermocouple) -- 5%5%



4/23/20074/23/2007 671671 of 691of 691

PAMS (Portable Arc Monitor System)PAMS (Portable Arc Monitor System)

What does a PAMS measure?What does a PAMS measure?

WeldingWelding

current (Hallcurrent (Hall

effecteffectdevice)device)

Arc voltageArc voltage

(connection(connection

leads)leads)TemperatureTemperature

(thermocouple)(thermocouple)

Wire feedWire feed

speedspeed

(tachometer)(tachometer)

Gas flowGas flow

raterate

(heating(heating

elementelementsensor)sensor)



44//2323//20072007 672672 of of 691691

PAMS (Portable Arc Monitor System)PAMS (Portable Arc Monitor System)

The purposes of The purposes of

a PAMSa PAMS

For calibratingFor calibratingand validatingand validating

the weldingthe welding

equipmentequipment

For measuringFor measuringand recordingand recording

the weldingthe welding

parametersparameters



4/23/20074/23/2007 673673 of of 691691

Use of PAMSUse of PAMS

Wire feed speedWire feed speed

monitoringmonitoring

Incorporated pair of Incorporated pair of

rolls connected to arolls connected to a

tachogenerator tachogenerator



44//2323//20072007 674674 of 691of 691

Use of PAMSUse of PAMS

Shielding gas flowShielding gas flow

rate monitoringrate monitoring

Heating elementHeating element

sensor sensor



44//2323//20072007 675675 of 691of 691

SummarySummarya welding power source can only be calibrated if ita welding power source can only be calibrated if ithas meters fittedhas meters fitted

the inspector should check for calibration stickers,the inspector should check for calibration stickers,dates etc.dates etc.

a welding power source without meters can only bea welding power source without meters can only bevalidated that the control knobs provide repeatabilityvalidated that the control knobs provide repeatability

the main role is to carryout ³in process monitoring´ tothe main role is to carryout ³in process monitoring´ toensure that the welding requirements are met duringensure that the welding requirements are met duringproductionproduction



44//2323//20072007 676676 of 691of 691

Welding Inspector Welding Inspector Macro/Micro ExaminationMacro/Micro Examination




4/23/20074/23/2007 677677 of of 691691

Macro PreparationMacro Preparation

PurposePurpose

To examine the weld crossTo examine the weld cross--section to give assurance that:section to give assurance that: --

The weld has been made in accordance with the WPSThe weld has been made in accordance with the WPS

The weld is free from defectsThe weld is free from defects

Specimen PreparationSpecimen Preparation

Full thickness slice taken from the weldFull thickness slice taken from the weld ( typically ~( typically ~10 10mm t hick)mm t hick)

Width of slice sufficient to show all the weld and HAZ on both sidesWidth of slice sufficient to show all the weld and HAZ on both sides

plus some unaffected base materialplus some unaffected base material

One face ground to a progressively fine finishOne face ground to a progressively fine finish ( grit sizes( grit sizes 120 120 to ~to ~ 400 400) )

Prepared face heavily etched to show all weld runs & all HAZPrepared face heavily etched to show all weld runs & all HAZ

Prepared face examined at up to xPrepared face examined at up to x1010 (& usually photographed for records)(& usually photographed for records)

Prepared face may also be used for a hardness surveyPrepared face may also be used for a hardness survey



4/23/20074/23/2007 678678 of of 691691

Micro PreparationMicro Preparation

PurposePurpose

To examine a particular region of the weld or HAZ in order to:To examine a particular region of the weld or HAZ in order to:--

To examine the microstructureTo examine the microstructure

Identify the nature of a crack or other imperfectionIdentify the nature of a crack or other imperfection

Specimen PreparationSpecimen Preparation

A small piece is cut from the region of interestA small piece is cut from the region of interest

( typically up to ~ 20mm x 20mm)( typically up to ~ 20mm x 20mm)

The piece is mounted in plastic mould and the surface of interestThe piece is mounted in plastic mould and the surface of interest

prepared by progressive grinding (to grit size 600 or 800)prepared by progressive grinding (to grit size 600 or 800)

Surface polished on diamond impregnated cloths to a mirror finishSurface polished on diamond impregnated cloths to a mirror finish

Prepared face may be examined in asPrepared face may be examined in as--polished condition & then lightlypolished condition & then lightly

etchedetched

Prepared face examined under the microscope at up to ~ x 600Prepared face examined under the microscope at up to ~ x 600



4/23/20074/23/2007 679679 of 691of 691

Macro / Micro ExaminationMacro / Micro ExaminationObject:Object:

Macro / microscopic examinations are used to give aMacro / microscopic examinations are used to give a

visual evaluation of a crossvisual evaluation of a cross--section of a welded jointsection of a welded joint

Carried out on full thickness specimensCarried out on full thickness specimens

The width of the specimen should include HAZ, weldThe width of the specimen should include HAZ, weld

and parent plateand parent plate

They maybe cut from a stop/start area on a weldersThey maybe cut from a stop/start area on a weldersapproval testapproval test



44//2323//20072007 680680 of 691of 691

Macro / Micro ExaminationMacro / Micro ExaminationWillWill Reveal:Reveal:

Weld soundnessWeld soundness

Distribution of inclusionsDistribution of inclusions

Number of weld passesNumber of weld passes

Metallurgical structure of weld, fusion zone and HAZMetallurgical structure of weld, fusion zone and HAZ

Location and depth of penetration of weldLocation and depth of penetration of weld

Fillet weld leg and throat dimensionsFillet weld leg and throat dimensions



4/23/20074/23/2007 681681 of of 691691

Visual examination for Visual examination for

defectsdefects

Cut transverse from theCut transverse from the

weldweld

Ground & polished P400Ground & polished P400

grit paper grit paper

Acid etch using 5Acid etch using 5--10%10%

nitric acid solutionnitric acid solution

Wash and dryWash and dry

Visual evaluation under 5xVisual evaluation under 5x

magnificationmagnification

Report on resultsReport on results

Visual examination for Visual examination for

defects & grain structuredefects & grain structure

Cut transverse from aCut transverse from a

weldweld

Ground & polished PGround & polished P12001200

grit paper,grit paper, 11 m pastem paste

Acid etch usingAcid etch using 11--55%%

nitric acid solutionnitric acid solution

Wash and dryWash and dry

Visual evaluation under Visual evaluation under

100100--10001000x magnificationx magnification

Report on resultsReport on results

MacroMacro MicroMicro



4/23/20074/23/2007 682682 of of 691691

Metallographic ExaminationMetallographic Examination

Download - Welding Inspection CSWIP

Top Related