5. weld defect & repair
TRANSCRIPT
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Welding InspectionDefects/Repairs
Course Reference WIS 5
Section Ref 3, 6 & 16
Shaffie Saad
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Defects which may be detected by visual inspection can be grouped under the following headings
Cracks
Solid inclusions
Surface and profiles
Misalignment (set-up
irregularities)
Gas pores and porosity
Weld DefectsWeld Defects
Lack of fusion
Mechanical damage
Parent material damage
Miscellaneous
Section Ref 3 Shaffie Saad
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CracksCracks
Section Ref 3 Shaffie Saad
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Classified by Shape
Longitudinal
Transverse
Branched
Chevron
Classified by Position
HAZ
Centreline
Crater
Fusion zone
Parent metal
CracksCracksCracks that may occur in welded materials are caused
generally by many factors and may be classified by shape and position, cracks are classed as planar.
Section Ref 3 Shaffie Saad
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Process CracksProcess Cracks
Hydrogen induced cold cracking (HICC)
Solidification cracking (Hot Tearing)
Lamellar tearing
Re heat cracking
Section Ref 3 Shaffie Saad
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CracksCracks
Longitudinal parent metal crack
Longitudinal weld metal crack Lamellar tearing
Section Ref 3
Transverse weld metal crack
Shaffie Saad
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Transverse crack Longitudinal crackSection Ref 3 Shaffie Saad
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InclusionsInclusions
Section Ref 3 Shaffie Saad
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Gas CavitiesGas Cavities
Root piping
Cluster porosityGas pore
Blow hole
Herringbone porosity
Loss of gas shield
Damp electrodes
Contamination
Arc length too large
Damaged electrode flux
Moisture on parent material
Welding current too low
Gas pore <1.5mm Blow hole.>1.5mm
Section Ref 3 Shaffie Saad
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Root pipingRoot piping
PorosityPorosity
Section Ref 3
Gas CavitiesGas Cavities
Shaffie Saad
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Cluster porosity Herring bone porositySection Ref 3 Shaffie Saad
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Solid InclusionsSolid Inclusions
Slag originates from welding flux
MAG and TIG welding process produce silica inclusions
Slag is caused by inadequate cleaning
Other inclusions include tungsten and copper inclusions from the TIG and MAG welding process
Slag inclusions are defined as a non-metallic inclusion caused by some welding process
Slag inclusions
Parallel slag lines Lack of interun fusion + slag
Lack of sidewall fusion with
associated slag
Section Ref 3 Shaffie Saad
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Elongated slag linesInterpass slag inclusionsSection Ref 3 Shaffie Saad
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Lack of FusionLack of Fusion
Section Ref 3 Shaffie Saad
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Surface and profile DefectsSurface and profile Defects
Incomplete filled groove + Lack of sidewall fusion
12
1. Lack of sidewall fusion2. Lack of inter-run fusion
Poor welder skill
Incorrect electrode
manipulation
Arc blow
Incorrect welding
current/voltage
Incorrect travel speed
Incorrect inter-run cleaning
Section Ref 3Shaffie Saad
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OverlapOverlapAn imperfection at the toe or root of a weld caused by
metal flowing on to the surface of the parent metal without fusing to it
Contamination
Slow travel speed
Incorrect welding technique
Current too low
Section Ref 3Shaffie Saad
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Section Ref 3
Toe OverlapToe OverlapFillet weldFillet weld
Toe OverlapToe OverlapButt weldButt weld
OverlapOverlap
Shaffie Saad
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Root DefectsRoot Defects
Incomplete root fusion
Incomplete root penetration
Low Amps/volts
Large Root face
Small Root Gap
Fast Travel Speed
Incorrect Electrode Angle
Contamination
Arc blow
Section Ref 3 Shaffie Saad
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Lack of root fusion Lack of root Penetration
Section Ref 3
Root DefectsRoot Defects
Shaffie Saad
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Lack of root penetration Lack of root fusionSection Ref 3 Shaffie Saad
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Surface and ProfileSurface and Profile
Section Ref 3 Shaffie Saad
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Incomplete filled groove Poor cap profile
Excessive cap height
Profile DefectsProfile Defects
Poor cap profiles and excessive cap reinforcements may lead to stress concentration points at the weld toes and will also contribute to overall poor toe blend
Section Ref 3 Shaffie Saad
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Incomplete filled grooveExcess cap reinforcementSection Ref 3 Shaffie Saad
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Profile DefectsProfile Defects
Poor stop/starts
Section Ref 3 Shaffie Saad
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Spatter
Excessive current
Damp electrodes
Contamination
Incorrect wire feed speed
when welding with the MAG
welding process
Arc blow
Miscellaneous DefectsMiscellaneous Defects
Section Ref 3 Shaffie Saad
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Miscellaneous DefectsMiscellaneous Defects
Accidental striking of the arc
onto the parent material
Faulty electrode holder
Poor cable insulation
Poor return lead clamping
Arc strike
Section Ref 3 Shaffie Saad
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UndercutUndercutAn irregular groove at the toe of a weld run in the
parent metal
Excessive amps/volts
Excessive travel speed
Incorrect electrode angle
Excessive weaving
Incorrect welding technique
Electrode too large
Section Ref 3 Shaffie Saad
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Cap UndercutCap Undercut
Measured in both Length & DepthMeasured in both Length & Depth
Section Ref 3 Shaffie Saad
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Cap undercutRoot undercutSection Ref 3 Shaffie Saad
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Shrinkage groove
Shrinkage GrooveShrinkage Groove
Insufficient weld metal deposited in the root pass
Too fast a cooling rate during the application of the root bead pass
Poor welding technique
A shallow groove caused by contraction in the weld metal along each side of the penetration bead
Section Ref 3 Shaffie Saad
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Concave root
Concave RootConcave Root
Root faces too large
Root gap too large
Excessive back purge pressure during TIG welding
Excessive root bead grinding before the application of the second pass
A shallow groove, which may occur in the root of a butt weld
Section Ref 3 Shaffie Saad
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Concave RootConcave Root
Section Ref 3 Shaffie Saad
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Excessive root penetration
Excessive Root PenetrationExcessive Root Penetration
Root faces too small
Root gap too large
Excessive amps/volts
Slow travel speed
Root penetration bead in excess in accordance with the relevant specification being used
Section Ref 3 Shaffie Saad
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Excessive Root PenetrationExcessive Root Penetration
Section Ref 3 Shaffie Saad
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Concave root Excessive root penetrationSection Ref 3 Shaffie Saad
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Burn ThroughBurn Through
High Amps/volts
Small Root face
Large Root Gap
Slow Travel SpeedBurn through
A localized collapse of the weld pool due to excessive penetration resulting in a hole in the root run
Section Ref 3 Shaffie Saad
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Burn through
Burn Through
Section Ref 3
Burn ThroughBurn Through
Shaffie Saad
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Root Coking/Oxidized RootRoot Coking/Oxidized Root
Loss or insufficient back
purging gas
Most commonly occurs
when welding stainless
steels
Purging gases include
argon, helium and
occasionally nitrogen
Section Ref 3 Shaffie Saad
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Crater pipeCrater pipe
Weld craterWeld crater
Section Ref 3
Crater PipeCrater Pipe
Shaffie Saad
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Crater PipeCrater PipeCrater pipe is a shrinkage defect and not a gas defect, it
has the appearance of a gas pore in the weld crater
Too fast a cooling rate
Deoxidization
reactions and liquid to
solid volume change
Contamination
Section Ref 3
Crater cracksCrater cracks(Star cracks)(Star cracks)
Crater pipeCrater pipe
Shaffie Saad
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Mechanical DamageMechanical Damage
Section Ref 3 Shaffie Saad
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Mechanical DamageMechanical DamageMechanical damage can be defined as any surface material damage cause during the manufacturing process.This can included damage caused by:
Grinding
Hammering
Chiselling
Chipping
Breaking off welded attachments (torn surfaces)
Using needle guns to compress weld capping runs
Section Ref 3 Shaffie Saad
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Set-up IrregularitiesSet-up Irregularities
Section Ref 3 Shaffie Saad
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A variation of leg lengths on a fillet weld
Note: Unequal leg lengths on a fillet weld may be specified as part of the design, in which case it will not be considered as a defect.
Unequal Leg LengthsUnequal Leg Lengths
Shaffie Saad
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Set-up IrregularitiesSet-up Irregularities
Plate/pipe Linear Misalignment (Hi-Lo)
Angular Misalignment
Linear misalignment is measured from the lowest plate to the highest point of the cap
Angular misalignment is measured in degrees
Section Ref 3 Shaffie Saad
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Linear MisalignmentLinear Misalignment
mm
Section Ref 3 Shaffie Saad
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Any QuestionsAny Questions
Section Ref 3 Shaffie Saad
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QuestionsQuestionsQU 1. Give two main causes for the occurrence of a burn through
QU 2. Give two main causes for the occurrence of excessive root penetration on a single-V butt weld
QU 3. Give five defects, which may occur when welding carbon steel using the MMA welding process with the current setting to low
QU 4. Give three possible causes for the occurrence of lack of side wall fusion
QU 5. Sketch the following defects
a. Lack of root wall fusion b. Lack of root penetration
c. Incomplete filled groove d. Concave root
Section Ref 3 Shaffie Saad
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Materials InspectionMaterials Inspection
Section Ref 6 Shaffie Saad
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All materials arriving on site should be inspected for:
Size / dimensions
Condition
Type / specification
Material Inspection
In addition other elements may need to be considered depending on the materials form or shape
Section Ref 6 Shaffie Saad
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Parent Material DefectsParent Material DefectsParent material defects include:
Lamination
Mechanical damage Lap
Segregation line
Laminations are caused in the parent plate by the steel making process, originating from ingot casting defects.Segregation bands occur in the centre of the plate and are low melting point impurities such as sulphur and phosphorous.Laps are caused during rolling when overlapping metal does not fuse to the base material.
Section Ref 6 Shaffie Saad
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Plate LaminationPlate Lamination
Section Ref 6 Shaffie Saad
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Weld RepairsWeld Repairs
Section Ref 16 Shaffie Saad
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Welding RepairsWelding Repairs
Authorization for repair
Removal and preparation for repair
Testing of repair - visual and NDT
In the event of repair
Section Ref 16 Shaffie Saad
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A weld repair may be used to improve weld profiles or
extensive metal removal
Repairs to fabrication defects are generally easier than
repairs to service failures because the repair procedure
may be followed
The main problem with repairing a weld is the
maintenance of mechanical properties
During the inspection of the removed area prior to welding
the inspector must ensure that the defects have been
totally removed and the original joint profile has been
maintained as close as possible
Weld RepairsWeld Repairs
Section Ref 16 Shaffie Saad
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The specification or procedure will govern how the defective areas are to be removed. The method of removal may be
Grinding
Chipping
Machining
Filing
Oxy-Gas gouging
Arc air gouging
Section Ref 16
Weld RepairsWeld Repairs
Shaffie Saad
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Any QuestionsAny Questions
Section Ref 16 Shaffie Saad
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QuestionsQuestionsQU 1. State six points of importance of repair welding.
QU 2. State two NDT methods that may be applied to a repair in a weld
QU 3. State three documents, which the inspector should refer to when carrying out repairs.
QU 4. In some cases why might a specification not allow a crack to be repaired, regardless of size and orientation?
Section Ref 16 Shaffie Saad