lesson plan date trade:- welder -...

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LESSON PLAN

Date______________ Trade:- Welder

Name____________ Week No. one

Subject:- General discipline in the institute. Elementary first aid. Importance of welding in

industry. Safety precaution in shielded metal arc welding, oxy-acetylene welding and cutting.

PREPARATION

1) Teaching Aids:-Chalk ,Charts,

INTRODUCTION:- An Industrial training Institute are centre of skill development

in a new trainee for industry. So we must obey general discipline and rules.

PRESENTATION:-

Topic Information Point Spot Hint

General

discipline

Timing:- DGET rule for training is 9:00 AM to 5:00 PM and lunch break

1:00 PM to 1:20 PM with five days week.

Dress code:- A dress code applied to all trainees.

Leave: - Trainees can take 12 leave in a year and 15 medical leave in a

year.

Attendance:- 80% attendance compulsory for participate in final exam.

Elementary

first AID

The treatment done before the doctor , is called first aid. In industrial

training trainees has use many types of tools and equipments, small

mistake causes accident and need first aid.

Injury Burning 2. Cuts 3. Electric shock 4. Fume 5. Radiation

Process of

first Aid

• Avoid unnecessary disturbances

• Ensure open airway

• Control Bleeding

• Check for Injury

• Immobilize injured parts before moving Transport

First Aid

Box

This box contain dressing materials, Potassium permanganate, Barnol,

siprit, some pain killer tablet and clean cloth.

Importance

of welding in

Industry

An industry without welding is not possible. Aerospace, railways,

automobile, fabrication projects, bridges, building construction, heavy

industry, small scale industry all are not complete without welding.

Safety Do not forget “a safe welder is always skill welder”

by [email protected] Sharma Welder Instructor DIT HaryanaParhlad Sharma Welder Inst. DIT Haryana

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Types of

safety

1. Safety of workshop.

2. Safety of equipments.

Safety of personal.

Some safety

instructions

for welding

Types of

Fire:-

Oil fire,

electric fire,

carbonatious

fire, gas fire

1. Always use all type safety device as like apron, goggles, welding

helmet and hand gloves etc.

2. Use #12 for ferrous metal and #11 lenses for non-ferrous metals

3. Make jobs in welding booth so other people keep safe.

4. Always use exhaust fan.

5. Tidy-up the workshop.

6. Arrange always water and fire extinguisher in workshop.

7. Keep workshop floor neat and clean.

8. Check gas leakage before gas welding and cutting.

9. Do not apply welding on inflammable material.

10. Use safety sign in workshop.

11. Do not start any machinery without knowledge.

12. Inform immediately to senior when something goes to wrong.

13. Earthing of electric machine compulsory.

14. Tight all loose electric connections before start the machine.

15. Check moving parts time to time.

16. Safety guard is important.

17. Do not use mobile and other devices while working.

Questions:-

1. Wright three general discipline of ITI.

2. What is elementary first aid?

3. Write five safety points in workshop.

Assignment:-

Discipline in the institute. Elementary first aid. Importance of welding in industry.

Safety precaution in shielded metal arc welding, oxy-acetylene welding and cutting.

Next lesson:- Introduction and definition of welding. Arc and gas welding equipments , tools

and accessories. Various welding process and its application. Arc and gas welding terms and

definitions.

Checked By_______________ Instructor___________


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LESSON PLAN


Name____________ Week No:- Two

Subject:- Introduction and definition of welding. Arc and gas welding equipments , tools and

accessories. Various welding process and its application. Arc and gas welding terms and

definitions.

Motivations:- in previous week we learned about general discipline ,safety , first aid and

importance of welding in industry.

PREPARATION:- Teaching Aids:-Chalk ,Charts,

INTRODUCTION:- Welding is used for making permanent joints. It is used in the

manufacture of automobile bodies, aircraft frames, railway wagons, machine frames, structural

works, tanks, furniture, boilers, general repair work and ship building.

PRESENTATION:-


Welding Welding is a materials joining process which produces

coalescence of materials by heating them to suitable

temperatures with or without the application of pressure or by

the application of pressure alone, and with or without the use of

filler material.

Types Plastic Welding or Pressure Welding

The piece of metal to be joined are heated to a plastic state and

forced together by external pressure (Ex) Resistance welding

Fusion Welding or Non-Pressure Welding

The material at the joint is heated to a molten state and allowed

to solidify (Ex) Gas welding, Arc welding

Classification of

welding processes:

Arc welding 1. Carbon arc

2. Metal arc

3. Metal inert gas

4. Tungsten inert gas

5. Plasma arc

6. Submerged arc

7. Electro-slag

Gas Welding:- 1. Oxy-acetylene

2. Air-acetylene 3. Oxy-hydrogen

(iii). Resistance Welding

1. Butt

2. Spot

3. Seam

4. Projection

5. Percussion

(iv) Thermit Welding

(v) Solid State Welding


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1. Friction

2. Ultrasonic

3. Diffusion

4. Explosive

(vi) Newer Welding

1. Electron-beam

2. Laser

(vii) Related Process

1. Oxy-acetylene cutting

2. Arc cutting

3. Hard facing

4. Brazing

5. Soldering

Arc and gas welding

tools ,equipments and

accessories

1. Marking tools

2. Measuring Tools.

3. Cutting Tools

Tool name Types of tool Specifications

and parts

Materials Size

Snip 1. Straight

2. Bent

Cutting edge

87 degree

High

carbon

steel

200-300-

400 mm

Shear

machine

1. Stock shear

2. Block shear

3. Bench

shear

4. Power

shear

Cutting edge

87 degree

Handle, fixed

blade,

movable

blade

High

carbon

steel

According

to cutting

capacity

Hacksaw solid and

adjustable

Frame and

blade

High

carbon

steel

200-250-

300 mm

Chisel Flat, cross cut,

diamond point,

round nose,

side cut, cow

mouth

Cutting edge

35-70 degree

High

carbon

steel

150-200-

250 and as

per need

File According to

shape- Flat file,

hand file,

square file,

pillar file,

triangular file,

round file, half

round file,

knife edge file

According to

length- 100

mm to 400

mm

According

to grade-

rough file,

bastard

file, second

cut file,

smooth

file, dead

smooth file

According

to cut-

single cut,

Double cut,

curved cut,

rasp cut

Steel rule Made by spring steel and measured in mm and inches both, least

count 0.5 mm. available in size 150mm, 300mm and 600mm

Caliper Use for internal and external diameter/size . Three types – Inside,

outside and odd leg. Available in 4’’, 6’’,8’’,12’’ sizes. Divider Use for make an arc or divide . Types- simple joint, firm joint, needle

point, spring type. Available in 4’’, 6’’,8’’,12’’ sizes. Scriber Use for scrub in marking. Types-ordinary, improved, adjustable,

pocket, knob. Available in 6’’ and 8’’ sizes.


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Try

square

Use for right angle checking. Parts blade and stock. Sizes 100-150-

200 mm

Punch Use for punching the marking line, edge prepare 60 degree. Type dot

punch. Prick punch etc.

Hammer Types –ball pein , cross pein, straight pein. Available by weight.

Steel tape Use for measure length. Available in meter and foot.

Tong Use for pick hot job/part in weld shop. Types-Flat open mouth, flat

close mouth, pickup , hollow bit, side, angle iron.

Vice Use for all purpose to pick and tight the job. size measured from

jaw.parts name- fixed jaw, movable jaw, jaw plates, spindle, handle,

box nut/guide nut and spring.

Rest of above screw driver, spanner set, clamp, zig and fixture, chipping hammer,

wire brush, electrode holder, earth clamp, hand screen, helmet, leg guard, hand

sleeve, Apron and safety shoes.


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Questions:-

1. Wright three general discipline of ITI.

2. What is elementary first aid?

3. Write five safety points in workshop.

Assignment:-

Discipline in the institute. Elementary first aid. Importance of welding in industry.

Safety precaution in shielded metal arc welding, oxy-acetylene welding and cutting.

Next lesson:- Introduction and definition of welding. Arc and gas welding equipments , tools

and accessories. Various welding process and its application. Arc and gas welding terms and

definitions.

Checked By_______________ Instructor___________


1

LESSON PLAN


Name____________ Week No:- Three

Subject :- Different process of metal joining, bolting, riveting, soldering, brazing and seaming.

Types of welding joint and its applications, edge preparation and fit up for different thickness.

Surface cleaning.

Motivations:- in previous week we learned about :- Introduction and definition of welding. Arc

and gas welding equipments , tools and accessories. Various welding process and its

application. Arc and gas welding terms and definitions.


INTRODUCTION:- Joining process done by three types, temporary, semi-temporary

and permanent. A welder weld the joint/ make the joint with these process.

PRESENTATION:-


Joining

process

Metal joint done by three types.

Temporary

Joint

This joint join in temporary stage if needed reopen and rejoin. Example-

Nut bolt, stud, carter key and screw.

Semi

temporary

joint

In this process when joint reopen only joining materials damage, job have

no defects.

Example- Riveting and soldering.

Permanent

Joint

In this process joint made permanent and if reopen then job and joining

materials both damaged. Example- Welding and brazing.

Types of

joint

Joint are five types.

1. Butt joint

2. Lap joint

3. Tee Joint

4. Corner Joint

5. Edge joint


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Brazing It is a low temperature joining process. It is performed at temperatures

above 840º F and it generally affords strengths comparable to those of the

metal which it joins. It is low temperature in that it is done below the

melting point of the base metal. It is achieved by diffusion without fusion

(melting) of the base.

Brazing can be classified as

1. Torch brazing

2. Dip brazing

3. Furnace brazing

4. Induction brazing

Advantages

• Dissimilar metals which canot be welded can be joined by brazing

• Very thin metals can be joined

• Metals with different thickness can be joined easily

• In brazing thermal stresses are not produced in the work piece.

Hence there is no distortion

• Using this process, carbides tips are brazed on the steel tool holders

Disadvantages

• Brazed joints have lesser strength compared to welding

• Joint preparation cost is more

• Can be used for thin sheet metal sections

Soldering • It is a low temperature joining process. It is performed at

temperatures below 840ºF for joining.

• Soldering is used for,

Sealing, as in automotive radiators or tin cans

• Electrical Connections

• Joining thermally sensitive components

• Joining dissimilar metals

Bolting Bolting joint completed by nut bolt. In this process drill the job and tight

the nut bolt in hole.

Limitation- joint only lap.

Riveting Riveting is like as bolting with some difference. I riveting process first drill

the job on desired place and choose rivet and complete process.

Rivet joint are semi temporary joint and rivet not in use after reopen joint.

Seaming This joint is very popular in sheet metal work. In this process bend the

both sheet and fix with each other then use pressure to complete.


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Edge

preparation

for different

weld joint

Edge preparation of weld joint is soul of joints. It depends on following

points. 1. Size of job.

2. Use of job

3. Types of joint


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Question:-

1. What is joining process and how many type it?

2. What is permanent joint?

3. What is Single V butt joint?

Next Week:-

Basic electricity to applicable in Arc welding and related electric terms and definitions. Heat

and temperature and its term related to welding. Principle of arc welding and characteristics of

arc.

Assignments:- Different process of metal joining, bolting, riveting, soldering, brazing and

seaming. Types of welding joint and its applications, edge preparation and fit up for different

thickness. Surface cleaning.

Checked By…………………… Instructor………………….


1

LESSON PLAN


Name____________ Week No:- Four

Subject :- Basic electricity to applicable in Arc welding and related electric terms and

definitions. Heat and temperature and its term related to welding. Principle of arc welding and

characteristics of arc.

Motivations:-

in previous week we learned about Different process of metal joining, bolting, riveting,

soldering, brazing and seaming. Types of welding joint and its applications, edge preparation

and fit up for different thickness. Surface cleaning.


INTRODUCTION:- Electricity have a very important role in arc welding. In arc

welding electric energy convert into heat energy. Here some basic electric terms define

below.

PRESENTATION:-


Electricit

y

Electricity is generated from the motion of tiny charged atomic particles called

electrons and protons!

Protons = + Electrons = -

Effects of

electricity

1. Magnetic effects

2. Heating effects.

3. Chemical effects.

4. Emission of electrons.

5. Contraction of muscles.

Types of

electricity

1. Static electricity.

2. Current electricity.

Current Flow of electrons

EMF Electro motive force. Generate current and measured in volts.

Conductor Metals or non metals which have circuit to flow electrons, called conductor.

electron

neutron

proton


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Insulator To avoid flow of electrons.

DC Direct current

AC Alternating current

Frequency AC currents continue change direction positive to negative many times in a

second. The rate of cycles called frequency.

Voltmeter To measure volt

Ammeter To measure ampere.

Generator To convert mechanical energy into electric energy.

Motor To convert electric energy to mechanical energy.

Electric

circuit

1. Series circuit.

2. Parallel circuit.

Switch Use for connect/disconnect electric circuit.

Types:- Ordinary switch, iron clad switch, oil break switch and remote control

switch.

Principle

of Arc

welding

Heat and

temp.

related to

welding


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Characteristics of Arc


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Questions:-

1. What is electricity and how many types of electricity?

2. What is ammeter and voltmeter?

3. What is heat expansion and how many type this?

Next week:- common gases use for welding and cutting. Flame temperature and uses.

Chemistry of oxy-acetylene flame. Types of oxy-acetylene flame and uses.

oxy-acetylene cutting equipments, parameters and applications.

Assignments:-

Basic electricity to applicable in Arc welding and related electric terms and definitions.

Heat and temperature and its term related to welding. Principle of arc welding and

characteristics of arc.

Checked by…………………… Instructor……………………


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LESSON PLAN


Name____________ Week No:- Five

Subject :- Common gases use for welding and cutting. Flame temperature and uses. Chemistry

of oxy-acetylene flame. Types of oxy-acetylene flame and uses. oxy-acetylene cutting

equipments, parameters and applications.

Motivations:-

in previous week we learned about Basic electricity to applicable in Arc welding and related

electric terms and definitions. Heat and temperature and its term related to welding. Principle

of arc welding and characteristics of arc.


INTRODUCTION:- In gas welding and cutting there are two types gases used, first

combustibles and second support of combustibles.

PRESENTATION:-


Commo

n gases

Gases are three types. 1. Combustible. 2. Support of

combustible. 3. Inert

Uses of

gases in

welding

and

cutting

Coal gas-flame temperature 1800-22000C

Use- under water steel cutting and silver soldering of steel

Hydrogen Gas- flame temperature 2400-27000C

Use-underwater cutting, steel brazing and soldering.

Butane gas- Flame temperature 2700-28000C.

Use- steel gas cutting.

Propane gas- flame temperature 2450-27750C.

Mostly in gas welding and cutting oxy-acetylene gas used.


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oxy-

acetylen

e Flame

This flame is highest temperature flame in gas welding/cutting.

Chemistry of Flame :-

Complete combustion

2C2H2 + 5 O2 -> 4CO2 + 2H2O DH<0

Primary combustion:

C2H2 + O2 -> 2CO + H2 + DH

Secondary combustion:

4CO + 2H2 + 3 O2(from air) ->

4CO2 + 2H2O + DH

Types of Flame:-


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oxy-acetylene cutting equipments:- The oxygen and acetylene hose pipes

Gases used

Gas pressure Regulators

Flashback arrestor

Welding torch/Welding nozzle

The oxygen and acetylene hose pipes Reinforced rubber hoses.

Acetylene hose has left hand thread couplings and colour coded red.

Oxygen hose has right handed thread couplings and colour coded blue.

Gas Pressure Regulators :- One gauge indicates the pressure of the cylinder and the other

indicates the pressure in the supply pipe to the torch.

Welding torch :- Oxygen and acetylene are delivered to the torch by separate hoses. Each gas

is controlled by a valve on the torch. The two gases mix in the torch and after they are ignited

burn at the nozzle.

Flashback Arrestors :- These are positioned on both the fuel gas and oxygen supply

between the hose and the regulator. Their purpose is to prevent the return of a flame

through the hose into the regulator.


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Cutting parameters:-


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Questions:-

1. Define the types of gases?

2. Define the types of Flame?

3. Write three gas cutting equipments with detail.

Next week:-

Arc welding power source- Transformer, rectifier, motor generator set and inverter type

welding machine. Care and maintenance . advantages nad disadvantages of AC and DC

welding machine.

Assignments:-

Common gases use for welding and cutting. Flame temperature and uses. Chemistry of

oxy-acetylene flame. Types of oxy-acetylene flame and uses. oxy-acetylene cutting

equipments, parameters and applications.

Checked by………………….. Instructor………………….


1

LESSON PLAN


Name____________ Week No:- six

Subject :- Arc welding power source- Transformer, rectifier, motor generator set and inverter

type welding machine. Care and maintenance. Advantages and disadvantages of AC and DC

welding machine.

Motivations:- in previous week we learned about Common gases use for welding and cutting.

Flame temperature and uses. Chemistry of oxy-acetylene flame. Types of oxy-acetylene flame

and uses. oxy-acetylene cutting equipments, parameters and applications.

PREPARATION: - Teaching Aids:-Chalk, Charts,

INTRODUCTION: - arc welding power source are main source to convert electrical

energy to heat energy. There is much type of machines available in industry but mainly

three types of arc welding power source. AC Transformer, DC motor/engine generator

set and rectifier set.

PRESENTATION:-


AC

Transformer

AC transformer have input AC 220 volt/440 volt and given output 200

to 800 amp. These transformers available in capacity of welding

current in amp. With phases and cooling system.

Capacity 200 amp to 800 and more as per requirement.

Types Air cool and oil cool and single phase ,two phase and three phase.

Principle of

working

There are two binding inbuilt these transformers. Primary binding

and secondary binding. Ac input (high voltage and low amp)

connected with primary binding and create Electro motive force and

secondary binding output low voltage and high amp. So these

transformers also called step down transformer. A regulator fitted on

secondary binding to control current.

Care and

maintenance

1. Lubricate moving parts time to time.

2. Do not overload machines and use always tight electrical

connections.

3. Do not up and down current during welding.

DC Motor

generator/engine

generator set

These set are have a generator set for output dc welding current which

are driven by electric motor or engine set.

Types Motor generator set and engine generator set. Motor generator set

run by electrical energy and engine generator set run by engine.


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Rectifier set This set use ac transformer and through a diode it converts dc from

ac. A silicon coated plates use for diode covering.


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Questions:-

1. Describe the AC transformer set .

2. Describe the DC generator set.

3. Describe the rectifier set.

Next week:-

Welding position as per EN and ASME :flat, horizontal, vertical and over head. Weld

slop and rotations. Welding symbols as per BIS, AWS and BS.

Assignment:-

Arc welding power source- Transformer, rectifier, motor generator set and inverter type

welding machine. Care and maintenance. Advantages and disadvantages of AC and DC

welding machine.

Checked by……………… Instructor…………………..


1

LESSON PLAN


Name____________ Week No:- seven

Subject :-

Welding position as per EN and ASME :flat, horizontal, vertical and over head. Weld

slop and rotations. Welding symbols as per BIS, AWS and BS.

Motivations:- in previous week we learned about Arc welding power source- Transformer,

rectifier, motor generator set and inverter type welding machine. Care and maintenance.

Advantages and disadvantages of AC and DC welding machine.


INTRODUCTION: - in every job a welder use at least one position. Welding position

mean direction of electrode to the job.

PRESENTATION:-


Weld slop and rotations


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Weld symbols


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Questions:-

1. Describe welding positions in detail.

2. What is weld slop and rotations?

3. Describe weld symbols in details.

Next week:- Arc length-types-effects. Polarity –types and applications.

Assignments: Welding position as per EN and ASME :flat, horizontal, vertical and over head.

Weld slop and rotations. Welding symbols as per BIS, AWS and BS.

Checked by…………………… Instructor…………………..


1

LESSON PLAN


Name____________ Week No:- Eight

Subject :- Arc length-types-effects. Polarity –types and applications.

Motivations:- in previous week we learned about Welding position as per EN and ASME

:flat, horizontal, vertical and over head. Weld slop and rotations. Welding symbols as per BIS,

AWS and BS.


INTRODUCTION: - Arc length have play a main role in welding. Wrong arc length

effected the job and output a weak weld joint.

PRESENTATION:-


Arc Length Distance between electrode tip and job surface called arc length.

Types Arc length are three types.

1. Short arc length –under 2 mm

2. Medium arc length 1.8-2.8 mm

3. Long arc length above 3.5 mm

Detail The choice of arc length depend on job and welding position, for

example in overhead position we choose short arc length. Arc

length should not be more then electrode diameter , if more called

long arc and if less called short arc.


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Polarity In DC welding two polls working negative and positive. Use of

these poll called polarity.

Questions:-

1. What is arc length?

2. What is use of short arc?

3. What is polarity?

Next week:-

Calcium carbide-property and uses. Acetylene gas properties and generating methods.

Acetylene gas purifier, hydraulic back pressure valve and flash back arrestor.

Assignment:- Arc length-types-effects. Polarity –types and applications.

Checked by…………….. Instructor…………………


1

LESSON PLAN


Name____________ Week No:- Nine

Subject :- Calcium carbide-property and uses. Acetylene gas properties and generating

methods. Acetylene gas purifier, hydraulic back pressure valve and flash back arrestor.

Motivations:- in previous week we learned about Arc length-types-effects. Polarity –types

and applications.


INTRODUCTION: - Calcium carbide is a chemical compound and its react with water

and produce acetylene gas. It is made by lime and cock.

PRESENTATION:-


Calcium Carbide This is a mixture of lime and cock which mixed in furnace.

It produces acetylene by react with water.

Properties and production of calcium carbide Chemical formulaCaC2Molar mass64.099 g/mol.

Appearance White powder to grey/black crystalsDensity2.22 g/cm3Melting point2,160 °C

(3,920 °F; 2,430 K) Boiling point2,300 °C (4,170 °F; 2,570 K) Solubility in water decomposes

Structure Crystal structure Tetragonal[1]Space groupD174h, I4/mmm,tI6Coordination

geometry6Thermochemistry

Std Molar entropy (So298)70 J·mol−1·K−1Std enthalpy of formation (ΔfHo298)−63 kJ· mol.

Calcium carbide are grey or brown and consist of about 80–85% of CaC2(the rest is CaO

(calcium oxide), Ca3P2(calcium phosphide), CaS (calcium sulfide), Ca3N2(calcium nitride),

SiC (silicon carbide), etc.).

In the presence of trace moisture, technical-grade calcium carbide emits an unpleasant odor

reminiscent of garlic.

Applications of calcium carbide include manufacture of acetylene gas, and for generation of

acetylene in carbide lamps; manufacture of chemicals for fertilizer; and in steel making.

Production Calcium carbide is produced industrially in an electric arc furnace from a mixture

of lime and coke at approximately 2200 °C.

This method has not changed since its invention in 1892:CaO + 3 C → CaC2+ CO The high temperature required for this reaction is not practically achievable by traditional combustion,

so the reaction is performed in an electric arc furnace with graphite electrodes.

The carbide product produced generally contains around 80% calcium carbide by weight.

The carbide is crushed to produce small lumps that can range from a few mm up to 50 mm.

The impurities are concentrated in the finer fractions.

The CaC2content of the product is assayed by measuring the amount of acetylene produced on

hydrolysis.


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ACETYLENE INTRODUCTION Acetylene (C2H2) is colorless gas used as a fuel and a chemical building block. As an

alkyne, acetylene is unsaturated because its two carbon atoms are bonded together

in a triple bond having CCH bond angles of 1800. It is unstable in pure form and thus is

usually handled as a solution. Pure acetylene is odorless, but commercial grades

usually have a marked odor due to impurities.

In 1836 acetylene identified as a "new carburet of hydrogen" by Edmund Davy. The

name "acetylene" was given by Marcellin Berthelot in 1860. He prepared acetylene

by passing vapours of organic compounds (methanol, ethanol, etc.) through a red-

hot tube and collecting the effluent. He also found acetylene was formed by sparking

electricity through mixed cyanogen and hydrogen gases. Berthelot later obtained

acetylene directly by passing hydrogen between the poles of a carbon arc.

MANUFACTURE Acetylene manufacture by following processes

1. From calcium carbide

2. From paraffin hydrocarbons by pyrolysis (Wulff process)

3. From natural gas by partial oxidation (Sachasse process)

Nowadays acetylene is mainly manufactured by the partial oxidation of natural gas

(methane) or side product in ethylene stream from cracking of hydrocarbons.

Acetylene, ethylene mixture is explosive and poison Zigler Natta catalyst. There so

acetylene is selectively hydrogenated into ethylene, usually using Pd-Ag catalysts.

Acetylene was the main source of organic chemicals in the chemical industry until

1950. It was first prepared by the hydrolysis of calcium carbide, a reaction discovered

by Friedrich Wöhler in 1862.

CaC2 + 2H2O Ca(OH)2 + C2H2

Calcium carbide production requires extremely high temperatures, ~20000C,

necessitating the use of an electric arc furnace.

Also hydrocarbon cracking is carried out in an electric arc furnace. In which electric


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arc provides energy at very high flux density so that reaction time can be kept at a

minimum. There so the design of the electro-thermal furnace is one of the important

factors.

In one design (Huels process) gaseous feedstock enters the furnace tangentially

through a turbulence chamber, then passes with a rotary motion through pipe in

which the arc is passed between a bell shaped cathode and anode pipe. The rotary

motion of the gas causes the arc to rotate and thus reducing fouling. The arc is

operated at 8000kw D.C. at 7000volts and 1150amp cathodes are said to last

800hours while anodes only 150hours.

In other design, fresh hydrocarbon and recycle gas are fed to the arc. The effluent

reaction gases are quenched and purified. 35%w purified acetylene along with 17%w

ethylene and 10%w carbon black, H2 and other products in minor amount is obtained

in one pass through furnace.

The difference is that the arc is rotated by means of an external magnetic coil, and

quenching is carried by propane and water in 1st and 2nd step respectively. Some

propane cracking improves the yield of acetylene. The propane quench cools the

arc gases to 10950C in 0.0001 to 0.0004 sec while the water quench cools the mixture

to 3000C in 0.001 to 0.003 sec. Power consumption is 12.36kwhr/kg of pure acetylene.

21-22%v acetylene is obtained in the product gases.

1. From calcium carbide

Raw materials

Basis: 1000 cu ft. acetylene

Calcium carbide (85%) = 100kg

Water = 815kg

Sources of raw material

Calcium carbide is manufactured from lime and coke in 60:40 ratio in electric furnace

at 2000-21000C temperature.

Reaction

CaC2 + 2H2O Ca(OH)2 + C2H2 ΔH = - 32.5kcals

Manufacture calcium carbide is added to large quantity of water releasing

acetylene gas and calcium hydrate as residue. Later is discharged in the form of lime

slurry containing approximately 90% water.

In the dry process, in order to eliminate the waste of calcium hydrate equal amount

of water is added to CaC2 (1:1 ratio) in a generator. The heat of reaction (166 Btu/ft3

of acetylene) is used to vaporize the excess water over the chemical equivalent,

leaving a substantially dry calcium hydrate which is suitable for reuse as a lime source.

The temperature must be carefully controlled below 1500C at 15psi pressure

throughout the process because the acetylene polymerizes to form benzene at 6000C

and decomposes at 7800C. Further with air-acetylene mixture explodes at 4800C.

The crude acetylene gas containing traces of H2S, NH3 and phosphine (PH3) form

generator is either scrubbed with water and caustic soda solution or sent to purifier

where the impurities are absorbed by the use of iron oxide or active chlorine

compounds. The dry gas is fed to cylinders or sent to manufacturing units.

Safety and handling:- Acetylene is not especially toxic but when generated from

calcium carbide it can contain toxic impurities such as traces of phosphine and

arsine. It is also highly flammable. Concentrated or pure acetylene can easily react in

an addition-type reaction to form number of products like benzene, vinyl acetylene

etc. These reactions are exothermic and unlike other common flammables do not

require oxygen to proceed. Consequently, acetylene can explode with extreme

violence if the absolute pressure of the gas exceeds about 200kPa (29 psi). The safe

limit for acetylene is 101kPag or 15 psig. That so it is shipped and stored by dissolving in

acetone or dimethylformamide (DMF), contained in a metal cylinder with a porous

filling.


4

Acetylene Purifier:-


5


6

Questions:-

1. What is Calcium carbide and how its made?

2. Write properties of Acetylene gas.

3. What is flash back arrester?

Next Week:- Oxygen gas and its properties. Production of oxygen by air liquefaction.

Charging process of oxygen and acetylene gases. Oxygen and DA cylinder , color coding

for different cylinders. Gas regulator types and uses.

Assignments:-

Calcium carbide-property and uses. Acetylene gas properties and generating methods.

Acetylene gas purifier, hydraulic back pressure valve and flash back arrestor.

Checked By……………….. Instructor……………………….


1

LESSON PLAN


Name____________ Week No:- Ten

Subject :-

Oxygen gas and its properties. Production of oxygen by air liquefaction. Charging

process of oxygen and acetylene gases. Oxygen and DA cylinder , color coding for different

cylinders. Gas regulator types and uses.

Motivations:- in previous week we learned about Calcium carbide-property and uses.

Acetylene gas properties and generating methods. Acetylene gas purifier, hydraulic back

pressure valve and flash back arrestor.


INTRODUCTION: -Oxygen gas are very important gas in world for human being and

industry. Each burning process could not done without oxygen.

PRESENTATION:-


Oxygen There are three types of gases.

1. Combustible.

2. Support of combustible (only oxygen)

3. Inret


2

Production of Oxygen


3


4

Questions:-

1. Write oxygen gas properties.

2. What is color coding ?

3. What is Air liquefaction ?

Next week:-Oxy-acetylene gas welding system (low pressure and high pressure)

Difference between gas welding blow pipe(LP and HP) and cutting blow pipe.

Gas welding technique (right ward and left ward.

Assignments :-

Oxygen gas and its properties. Production of oxygen by air liquefaction. Charging

process of oxygen and acetylene gases. Oxygen and DA cylinder , color coding for different

cylinders. Gas regulator types and uses.

Checked By…………………… Instructor………………………..


1

LESSON PLAN


Name____________ Week No:- Eleven

Subject :- Oxy-acetylene gas welding system (low pressure and high pressure)


Gas welding technique (right ward and left ward..

Motivations:- in previous week we learned Oxygen gas and its properties. Production of

oxygen by air liquefaction. Charging process of oxygen and acetylene gases. Oxygen and DA

cylinder , color coding for different cylinders. Gas regulator types and uses.


INTRODUCTION: -Oxy-acetylene gas welding system have two types. Low pressure

and high pressure. In both system we use different setup as like Blow pipe and regulator

etc.

PRESENTATION:-


Oxy-acetylene gas

welding system

In gas welding, oxy-acetylene combination is most popular due

to heat output and cost. This system has two types.

Types 1. Low pressure system.

2. High pressure system

Low Pressure system In this system oxygen used from a cylinder but acetylene

generated on the spot by acetylene generators. There are two

types of generators used in low pressures system.

1. Water to carbide.

2. Carbide to water

Water to carbide type

acetylene generator

This is a portable generator. It used carbide and water to

generate acetylene gas with the pressure of 0.1 kg/cm2 and

medium type generator 0.1 to 1.5 kg/cm2.We used all type

carbide in this generator.

Carbide to water type

generator

This is a portable generator. It used carbide and water to

generate acetylene gas with the pressure more than 1.5 kg/cm2.

Chemical reaction Cac2+2H2O—Ca(OH)2+c2h2

Classification of

generators

1. According to water intake capacity.

2. According to carbide intake capacity.

3. According to gas production (cubic meter per hour)

4. According to operating type (manual, semi automatic)


2

Tools and set up for

Low pressure system

We use different blow pipe (injector type) , hydraulic back

pressure safety valve for Low pressure system.

High pressure system In high pressure system we use both cylinder.

Gas Cutting blow pipe Use injector type blow pipe in low pressure system while non

injector type blow pipe in high pressure system.


3

Gas welding technique Gas welding technique have two types.

1. Rightward

2. Leftward.


4

Questions:-

1. How many types of gas welding plant?

2. What is low pressure system ?

3. What is the difference between rightward and leftward technique ?

Next week:-Arc blow –causes and methods to controlling. Distortion in arc and gas welding

and methods employed to minimized distortion, Arc welding defects –causes, and remedies.

Assignments :-

Oxy-acetylene gas welding system (low pressure and high pressure)


Gas welding technique (right ward and left ward.

Checked By…………………… Instructor………………………..


1

LESSON PLAN


Name____________ Week No:- Twelve

Subject :- Arc blow –causes and methods to controlling. Distortion in arc and gas welding and

methods employed to minimized distortion, Arc welding defects –causes, and remedies.

Motivations:- in previous week we learned Oxy-acetylene gas welding system (low pressure

and high pressure) Difference between gas welding blow pipe(LP and HP) and cutting blow

pipe. Gas welding technique (right ward and left ward..


INTRODUCTION: -Arc blow is defects which falls in DC welding . In dc welding due to

dc current , arc cannot run straight. Distortion means job get changes in length width

and thickness due to heat produce during welding.

PRESENTATION:-



2


3


4


5


6


7


8

Questions:-

1. What is arc blow and how it occurs?

2. What is distortion and how we control it?

3. Write five weld defects?

Next Week:- specifications of pipes, various types of pipe joints, pipe welding position and

procedure. Difference between pipe and plate welding.

Assignments:- Arc blow –causes and methods to controlling. Distortion in arc and gas welding

and methods employed to minimized distortion, Arc welding defects –causes, and remedies.

Instructor…………………….. G.I……………


1

LESSON PLAN


Name____________ Week No:- Thirteen and fourteen

Subject :- specifications of pipes, various types of pipe joints, pipe welding position and

procedure. Difference between pipe and plate welding.

Motivations:- in previous week we learned about Arc blow –causes and methods to

controlling. Distortion in arc and gas welding and methods employed to minimized distortion,

Arc welding defects –causes, and remedies.


INTRODUCTION: -pipe welding is very important in welding procedure. In industry,

fabrication mostly pipe joints used for make a job. We must well skilled and read about

pipe welding in details.

PRESENTATION:-



2


3

Classification of Pipe 1. Standard Pipe

2. Thin wall pipe

3. Structural pipe

4. Mechanical pipe

5. Pressure pipe

6. Line pipe

For ms pipe we use painting, electroplating,

galvanizing for shielding from rust and moisture

Pipe Joints 1. Square butt joint (gap or without gap)

2. Tee joint (root gap or without root gap)

3. Branch pipe joint

4. Bell and spigot joint

5. Elbow joint

6. Flange joint

Difference between pipe and

Plate welding

Pipe Welding

1. Maximum positional welding

required

2. Maximum job no see clearly

3. Sealing run not weld easily

4. Low distortion

5. Leak proof welding required

Plate Welding

1. Used

normally

one position

2. Weld bead

see clearly

3. Sealing run

weld easily

4. High

distortion

5. In rare jobs

leak proof

required

Pipe Development


4


5

Manifold System


6

Questions:-

1. What is pipe and how many types of pipe?

2. What is manifold system?

3. Draw a 45 degree pipe development.

Next Week:- Gas Welding Filler rods, specification and sizes. Gas welding flux-types and

functions. Gas brazing and soldering, principles, types fluxes & uses. Gas welding defects

causes and remedies.

Assignments:- specifications of pipes, various types of pipe joints, pipe welding position and

procedure. Difference between pipe and plate welding. Pipe development for elbow joint, Y

joint and branch joint, manifold system.

Checked by……………………. Instructor…………………


1

LESSON PLAN


Name____________ Week No:- Fifteen

Subject :- Gas Welding Filler rods, specification and sizes. Gas welding flux-types and



Motivations:- in previous week we learned about specifications of pipes, various types of

pipe joints, pipe welding position and procedure. Difference between pipe and plate welding.

Pipe development for elbow joint, Y joint and branch joint, manifold system.


INTRODUCTION: -Filler rod is a materials which are used for fill the joint. A welding

joint’s strength mostly depend on filler rod. Quality of filler rod and base metal must be

match.

PRESENTATION:-


Filler metal To fill the joint as per requirement called filler

metal.

Types Alloy and non-alloy

Specifications For a strong weld joint we use alloy filler rod for

different purpose.

Composition and properties

Organic fluxes typically consist of four major components

Activators - chemicals disrupting/dissolving the metal oxides. Their role is to expose

unoxidized, easily wettable metal surface and aid soldering by other means, e.g. by exchange

reactions with the base metals.

Highly active fluxes contain chemicals that are corrosive at room temperature. The compounds

used include metal halides (most often zinc chloride or ammonium chloride), hydrochloric

acid, phosphoric acid, and hydrobromic acid. Salts of mineral acids with amines are also used

as aggressive activators. Aggressive fluxes typically facilitate corrosion, require careful

removal, and are unsuitable for finer work. Activators for fluxes for soldering and brazing

aluminium often contain fluorides.

Milder activators begin to react with oxides only at elevated temperature. Typical compounds

used are carboxylic acids (e.g. fatty acids (most often oleic acid and stearic acid), dicarboxylic

acids) and sometimes amino acids. Some milder fluxes also contain halides or organohalides.

Vehicles - high-temperature tolerant chemicals in the form of non-volatile liquids or solids

with suitable melting point; they are generally liquid at soldering temperatures. Their role is to

act as an oxygen barrier to protect the hot metal surface against oxidation, to dissolve the

reaction products of activators and oxides and carry them away from the metal surface, and to

facilitate heat transfer. Solid vehicles tend to be based on natural or modified rosin (mostly


2

abietic acid, pimaric acid, and other resin acids) or natural or synthetic resins. Water-soluble

organic fluxes tend to contain vehicles based on high-boiling polyols - glycols, diethylene

glycol and higher polyglycols, polyglycol-based surfactants and glycerol.

Solvents - added to facilitate processing and deposition to the joint. Solvents are typically dried

out during preheating before the soldering operation; incomplete solvent removal may lead to

boiling off and spattering of solder paste particles or molten solder.

Additives - numerous other chemicals modifying the flux properties. Additives can be

surfactants (especially nonionic), corrosion inhibitors, stabilizers and antioxidants, tackifiers,

thickeners and other rheological modifiers (especially for solder pastes), plasticizers (especially

for flux-cored solders), and dyes.

Inorganic fluxes contain components playing the same role as in organic fluxes. They are more

often used in brazing and other high-temperature applications, where organic fluxes have

insufficient thermal stability. The chemicals used often simultaneously act as both vehicles and

activators; typical examples are borax, borates, fluoroborates, fluorides and chlorides.

Halogenides are active at lower temperatures than borates, and are therefore used for brazing of

aluminium and magnesium alloys; they are however highly corrosive.

Fluxes have several important properties: Activity - the ability to dissolve existing oxides on the metal surface and promote wetting with

solder. Highly active fluxes are often of acidic and/or corrosive nature.

Corrosivity - the promotion of corrosion by the flux and its residues. Most active fluxes tend

to be corrosive at room temperatures and require careful removal. As activity and corrosivity

are linked, the preparation of surfaces to be joined should allow use of milder fluxes. Some

water-soluble flux residues are hygroscopic, which causes problems with electrical resistance

and contributes to corrosion. Fluxes containing halides and mineral acids are highly corrosive

and require thorough removal. Some fluxes, especially borax-based brazing ones, form very

hard glass-like coatings that are difficult to remove.

Cleanability - the difficulty of removal of flux and its residues after the soldering operation.

Fluxes with higher content of solids tend to leave larger amount of residues; thermal

decomposition of some vehicles also leads to formation of difficult-to-clean, polymerized and

possibly even charred deposits (a problem especially for hand soldering). Some flux residues

are soluble in organic solvents, others in water, some in both. Some fluxes are no-clean, as they

are sufficiently volatile or undergoing thermal decomposition to volatile products that they do

not require the cleaning step. Other fluxes leave non-corrosive residues that can be left in

place. However, flux residues can interfere with subsequent operations; they can impair

adhesion of conformal coatings, or act as undesired insulation on connectors and contact pads

for test equipment.

Residue tack - the stickiness of the surface of the flux residue. When not removed, the flux

residue should have smooth, hard surface. Tacky surfaces tend to accumulate dust and

particulates, which causes issues with electrical resistance; the particles themselves can be

conductive or they can be hygroscopic or corrosive.

Volatility - this property has to be balanced to facilitate easy removal of solvents during the

preheating phase but to not require too frequent replenishing of solvent in the process

equipment.

Viscosity - especially important for solder pastes, which have to be easy to apply but also thick

enough to stay in place without spreading to undesired locations. Solder pastes may also

function as a temporary adhesive for keeping electronic parts in place before and during

soldering. Fluxes applied by e.g. foam require low viscosity.

Flammability - relevant especially for glycol-based vehicles and for organic solvents. Flux

vapors tend to have low autoignition temperature and present a risk of a flash fire when the

flux comes in contact with a hot surface.

Solids - the percentage of solid material in the flux. Fluxes with low solids, sometimes as little

as 1-2%, are called low solids flux, low-residue flux, or no clean flux. They are often

composed of weak organic acids, with addition of small amount of rosin or other resins.


3

Conductivity - some fluxes remain conductive after soldering if not cleaned properly, leading

to random malfunctions on circuits with high impedances. Different types of fluxes are

differently prone to cause these issues.

The surface of the tin-based solder is coated predominantly with tin oxides; even in alloys the

surface layer tends to become relatively enriched by tin. Fluxes for indium and zinc based

solders have different compositions than fluxes for ordinary tin-lead and tin-based solders, due

to different soldering temperatures and different chemistry of the oxides involved.

The composition of fluxes is tailored for the required properties - the base metals and their

surface preparation (which determine the composition and thickness of surface oxides), the

solder (which determines the wetting properties and the soldering temperature), the corrosion

resistance and ease of removal, and others.

Organic fluxes are unsuitable for flame soldering and flame brazing, as they tend to char and

impair solder flow.

Some metals are classified as "unsolderable" in air, and have to be either coated with another

metal before soldering or special fluxes and/or protective atmospheres have to be used. Such

metals are beryllium, chromium, magnesium, titanium, and some aluminium alloys.


4


5

Questions:-

1. What is gas welding flux and its function?

2. What is the need of filler rods?

3. What is porocity?

Next Lesson :- Electrodes, types, function of flux, coating factor, sizes of electrode. Coding of

electrodes as per BIS, AWS. Moisture pick up of electrode. Storage and baking of electrodes.

Special purpose electrode and their application.

Assignment:- Gas Welding Filler rods, specification and sizes. Gas welding flux-types and



Checked by………………………… Instructor………………..


1

LESSON PLAN


Name____________ Week No:- sixteen

Subject :- Electrodes, types, function of flux, coating factor, sizes of electrode. Coding of



Motivations:- in previous week we learned about Gas Welding Filler rods, specification and

sizes. Gas welding flux-types and functions. Gas brazing and soldering, principles, types fluxes

& uses. Gas welding defects causes and remedies.


INTRODUCTION: -Electrode is used in electric welding for supply current and fill the

joint. The composition of electrode effects the joint so we must have knowledge about

electrode before welding.

PRESENTATION:-


An electrode is a metal wire that is coated. It is made out of materials with a similar

composition to the metal being welded. There are a variety of factors that go into choosing the

right electrode for each project. SMAW or stick electrodes are consumable, meaning they

become part of the weld, while TIG electrodes are non-consumable as they do not melt and

become part of the weld, requiring the use of a welding rod.The MIG welding electrode is a

continuously fed wire referred to as wire.Electrode selection is critical to ease of cleanup, weld

strength, bead quality and for minimizing any spatter. Electrodes need to be stored in a

moisture free environment and carefully removed from any package (follow the directions to

avoid damage).

Covered Welding Electrodes When molten metal is exposed to air, it absorbs oxygen and nitrogen, and becomes brittle or is

otherwise adversely affected.

A slag cover is needed to protect molten or solidifying weld metal from the atmosphere. This

cover can be obtained from the electrode coating.

The composition of the welding electrode coating determines its usability, as well as the

composition of the deposited weld metal and the electrode specification.

The formulation of Welding electrode coatings is based on well-established principles of

metallurgy, chemistry, and physics. The coating protects the metal from damage, stabilizes the

arc, and improves the weld in other ways, which include:

1. Smooth weld metal surface with even edges.

2. Minimum spatter adjacent to the weld.


2

3. A stable welding arc.

4. Penetration control.

5. A strong, tough coating.

6. Easier slag removal.

7. Improved deposition rate.

The metal-arc electrodes may be grouped and classified as bare or thinly coated electrodes, and

shielded arc or heavy coated electrodes. The covered electrode is the most popular type of filler

metal used in arc welding. The composition of the electrode covering determines the usability

of the electrode, the composition of the deposited weld metal, and the specification of the

electrode. The type of electrode used depends on the specific properties required in the weld

deposited. These include corrosion resistance, ductility, high tensile strength, the type of base

metal to be welded, the position of the weld (flat, horizontal, vertical, or overhead); and the

type of current and polarity required.

Popular Welding Electrode (E6010) used for general purpose fabrication, construction,

pipe welding, and shipbuilding

Classification The American Welding Society’s classification number series for welding electrodes has been

adopted by the welding industry. The electrode identification system for steel arc welding is set

up as follows:

1. E indicates electrode for arc welding.

2. The first two (or three) digits indicate tensile strength (the resistance of the material to

forces trying to pull it apart) in thousands of pounds per square inch of the deposited

metal.

3. The third (or fourth) digit indicates the position of the weld. 0 indicates the

classification is not used; 1 is for all positions; 2 is for flat and horizontal positions

only; 3 is for flat position only.

4. The fourth (or fifth) digit indicates the type of electrode coating and the type of power

supply used; alternating or direct current, straight or reverse polarity.

5. The types of coating, welding current, and polarity position designated by the fourth (or

fifth) identifying digit of the electrode classification are as listed in table 5-4.

6. 6) The number E6010 indicates an arc welding electrode with a minimum stress

relieved tensile strength of 60,000 psi; is used in all positions; and reverse polarity

direct current is required.

Coating, Current and Polarity Types Designated By the Fourth Digit in the Electrode

Classification Number

Digit Coating Weld Current

0 * *

1 Cellulose Potassium ac, dcrp, dcsp

2 Titania sodium ac, dcsp

3 Titania potassium ac, dcsp, dcrp

4 Iron Powder Titania ac, dcsp, dcrp

5 Low hydrogen sodium dcrp

6 Low hydrogen potassium ac, dcrp

7 Iron powder iron oxide ac, dcsp

8 Iron powder low hydrogen ac, dcrp, dcsp

When the fourth (or last) digit is 0, the type of coating and current to be used are

determined by the third digit.


http://www.aws.org/w/a/

3

The welding electrode identification system for stainless steel arc welding is set up as follows:

1. E indicates electrode for arc welding.

2. The first three digits indicated the American Iron and Steel type of stainless steel.

3. The last two digits indicate the current and position used.

4. The number E-308-16 by this system indicates stainless steel Institute type 308; used in

all positions; with alternating or reverse polarity direct current.

Classification System for Submerged Arc Electrodes The system for identifying solid bare carbon steel for submerged arc is as follows:

1. The prefix letter E is used to indicate an electrode. This is followed by a letter which

indicates the level of manganese, i.e., L for low, M for medium, and H for high

manganese. This is followed by a number which is the average amount of carbon in

points or hundredths of a percent. The composition of some of these wires is almost

identical with some of the wires in the gas metal arc welding specification.

2. The electrode wires used for submerged arc welding are given in American Welding

Society specification, "Bare Mild Steel Electrodes and Fluxes for Submerged Arc

Welding." This specification provides both the wire composition and the weld deposit

chemistry based on the flux used. The specification does give composition of the

electrode wires. When these electrodes are used with specific submerged arc fluxes and

welded with proper procedures, the deposited weld metal will meet mechanical

properties required by the specification.

3. In the case of the filler reds used for oxyfuel gas welding, the prefix letter is R,

followed by a G indicating that the rod is used expressly for gas welding. These letters

are followed by two digits which will be 45, 60, or 65. These designate the approximate

tensile strength in 1000 psi (6895 kPa).

4. In the case of nonferrous filler metals, the prefix E, R, or RB is used, followed by the

chemical symbol of the principal metals in the wire. The initials for one or two

elements will follow. If there is more than one alloy containing the same elements, a

suffix letter or number may be added.

5. The American Welding Society's specifications are most widely used for specifying

bare welding rod and electrode wires. There are also military specifications such as the

MIL-E or -R types and federal specifications, normally the QQ-R type and AMS

specifications. The particular specification involved should be used for specifying filler

metals.

The most important aspect of solid welding electrode wires and rods in their composition,

which is given by the specification. The specifications provide the limits of composition for the

different wires and mechanical property requirements.

Occasionally, on copper-plated solid wires, the copper may flake off in the feed roll

mechanism and create problems. It may plug liners, or contact tips. A light copper coating is

desirable. The electrode wire surface should be reasonably free of dirt and drawing

compounds. This can be checked by using a white cleaning tissue and pulling a length of wire

through it. Too much dirt will clog the liners, reduce current pickup in the tip, and may create

erratic welding operation.

Temper or strength of the wire can be checked in a testing machine. Wire of a higher strength

will feed through guns and cables better. The minimum tensile strength recommended by the

specification is 140,000 psi (965,300 kPa).

The continuous electrode wire is available in many different packages. They range from

extremely small spools that are used on spool guns, through medium-size spools for fine-wire

gas metal arc welding. Coils of electrode wire are available which can be placed on reels that

are a part of the welding equipment. There are also extremely large reels weighing many

hundreds of pounds. The electrode wire is also available in drums or payoff packs where the

wire is laid in the round container and pulled from the container by an automatic wire feeder.



4

Coatings The coatings of welding electrodes for welding mild and low alloy steels may have from 6 to

12 ingredients, which includes:

cellulose to provide a gaseous shield with a reducing agent in which the gas shield

surrounding the arc is produced by the disintegration of cellulose

metal carbonates to adjust the basicity of the slag and to provide a reducing atmosphere

titanium dioxide to help form a highly fluid, but quick-freezing slag and to provide

ionization for the arc

ferromanganese and ferrosilicon to help deoxidize the molten weld metal and to

supplement the manganese content and silicon content of the deposited weld metal

clays and gums to provide elasticity for extruding the plastic coating material and to

help provide strength to the coating

calcium fluoride to provide shielding gas to protect the arc, adjust the basicity of the

slag, and provide fluidity and solubility of the metal oxides

mineral silicates to provide slag and give strength to the electrode covering

alloying metals including nickel, molybdenum, and chromium to provide alloy content

to the deposited weld metal

iron or manganese oxide to adjust the fluidity and properties of the slag and to help

stabilize the arc

iron powder to increase the productivity by providing extra metal to be deposited in the

weld.

The principal types of welding electrode coatings for mild steel and are described below.

1. Cellulose-sodium (EXX10): Electrodes of this type cellulosic material in the form of

wood flour or reprocessed low alloy electrodes have up to 30 percent paper. The gas

shield contains carbon dioxide and hydrogen, which are reducing agents. These gases

tend to produce a digging arc that provides deep penetration. The weld deposit is

somewhat rough, and the spatter is at a higher level than other electrodes. It does

provide extremely good mechanical properties, particularly after aging. This is one of

the earliest types of electrodes developed, and is widely used for cross country pipe

lines using the downhill welding technique. It is normally used with direct current with

the electrode positive (reverse polarity).

2. Cellulose-potassium (EXX11): This electrode is very similar to the cellulose-sodium

electrode, except more potassium is used than sodium. This provides ionization of the

arc and makes the electrode suitable for welding with alternating current. The arc

action, the penetration, and the weld results are very similar. In both E6010 and E6011

electrodes, small amounts of iron powder may be added. This assists in arc stabilization

and will slightly increase the deposition rate.

3. Rutile-sodium (EXX12): When rutile or titanium dioxide content is relatively high

with respect to the other components, the electrode will be especially appealing to the

welder. Electrodes with this coating have a quiet arc, an easily controlled slag, and a

low level of spatter. The weld deposit will have a smooth surface and the penetration

will be less than with the cellulose electrode. The weld metal properties will be slightly

lower than the cellulosic types. This type of electrode provides a fairly high rate of

deposition. It has a relatively low arc voltage, and can be used with alternating current

or with direct current with electrode negative (straight polarity).

4. Rutile-potassium (EXX13): This electrode coating is very similar to the rutile-sodium

type, except that potassium is used to provide for arc ionization. This makes it more

suitable for welding with alternating current. It can also be used with direct current with

either polarity. It produces a very quiet, smooth running arc.

5. Rutile-iron powder (EXXX4): This coating is very similar to the rutile coatings

mentioned above, except that iron powder is added. If iron content is 25 to 40 percent,

the electrode is EXX14. If iron content is 50 percent or more, the electrode is EXX24.


5

With the lower percentage of iron powder, the electrode can be used in all positions.

With the higher percentage of iron paler, it can only be used in the flat position or for

making horizontal fillet welds. In both cases, the deposition rate is increased, based on

the amount of iron powder in the coating.

6. Low hydrogen-sodium (EXXX5): Coatings that contain a high proportion of calcium

carbonate or calcium fluoride are called low hydrogen, lime ferritic, or basic type

electrodes. In this class of coating, cellulose, clays, asbestos, and other minerals that

contain combined water are not used. This is to ensure the lowest possible hydrogen

content in the arc atmosphere. These electrode coatings are baked at a higher

temperature. The low hydrogen electrode family has superior weld metal properties.

They provide the highest ductility of any of the deposits. These electrodes have a

medium arc with medium or moderate penetration. They have a medium speed of

deposition, but require special welding techniques for best results. Low hydrogen

electrodes must be stored under controlled conditions. This type is normally used with

direct current with electrode positive (reverse polarity).

7. Low hydrogen-potassium (EXXX6): This type of coating is similar to the low

hydrogen-sodium, except for the substitution of potassium for sodium to provide arc

ionization. This electrode is used with alternating current and can be used with direct

current, electrode positive (reverse polarity). The arc action is smother, but the

penetration of the two electrodes is similar.

8. Low hydrogen-potassium (EXXX6): The coatings in this class of electrodes are

similar to the low-hydrogen type mentioned above. However, iron powder is added to

the electrode, and if the content is higher than 35 to 40 percent, the electrode is

classified as an EXX18.

9. Low hydrogen-iron powder (EXX28): This electrode is similar to the EXX18, but has

50 percent or more iron powder in the coating. It is usable only when welding in the flat

position or for making horizontal fillet welds. The deposition rate is higher than

EXX18. Low hydrogen coatings are used for all of the higher-alloy electrodes. By

additions of specific metals in the coatings, these electrodes become the alloy types

where suffix letters are used to indicate weld metal compositions. Electrodes for

welding stainless steel are also the low-hydrogen type.

10. Iron oxide-sodium (EXX20): Coatings with high iron oxide content produce a weld

deposit with a large amount of slag. This can be difficult to control. This coating type

produces high-speed deposition, and provides medium penetration with low spatter

level. The resulting weld has a very smooth finish. The electrode is usable only with

flat position welding and for making horizontal fillet welds. The electrode can be used

with alternating current or direct current with either polarity.

11. Iron-oxide-iron power (EXX27): This type of electrode is very similar to the iron

oxide-sodium type, except it contains 50 percent or more iron power. The increased

amount of iron power greatly increases the deposition rate. It may be used with

alternating direct current of either polarity.

There are many types of coatings other than those mentioned here, most of which are usually

combinations of these types but for special applications such as hard surfacing, cast iron

welding, and for nonferrous metals.

Storage Electrodes must be kept dry. Moisture destroys the desirable characteristics of the

coating and may cause excessive spattering and lead to porosity and cracks in the the formation

of the welded area. Electrodes exposed to damp air for more than two or three hours should be

dried by heating in a suitable oven (fig 5-32) for two hours at 500°F (260°C).

After they have dried, they should be stored in a moisture proof container. Bending the

electrode can cause the coating to break loose from the core wire. Electrodes should not be

used if the core wire is exposed.

Electrodes that have an "R" suffix in the AWS classification have a higher resistance to

moisture.


6

The Types of Electrodes Bare Electrodes

Bare welding electrodes are made of wire compositions required for specific applications.

These electrodes have no coatings other than those required in wire drawing. These wire

drawing coatings have some slight stabilizing effect on the arc but are otherwise of no

consequence. Bare electrodes are used for welding manganese steel and other purposes where a

coated electrode is not required or is undesirable.

Light Coated Electrodes Light coated welding electrodes have a definite composition. A light coating has been applied

on the surface by washing, dipping, brushing, spraying, tumbling, or wiping. The coatings

improve the characteristics of the arc stream. They are listed under the E45 series in the

electrode identification system.

The coating generally serves the functions described below:

1. It dissolves or reduces impurities such as oxides, sulfur, and phosphorus.

2. It changes the surface tension of the molten metal so that the globules of metal leaving

the end of the electrode are smaller and more frequent. This helps make flow of molten

metal more uniform.

3. It increases the arc stability by introducing materials readily ionized (i.e., changed into

small particles with an electric charge) into the arc stream.

4. Some of the light coatings may produce a slag. The slag is quite thin and does not act in

the same manner as the shielded arc electrode type slag.

Light Coated Electrode

Shielded Arc or Heavy Coated Electrodes Shielded arc or heavy coated welding electrodes have a definite composition on which a

coating has been applied by dipping or extrusion. The electrodes are manufactured in three

general types: those with cellulose coatings; those with mineral coatings; and those whose

coatings are combinations of mineral and cellulose. The cellulose coatings are composed of

soluble cotton or other forms of cellulose with small amounts of potassium, sodium, or

titanium, and in some cases added minerals. The mineral coatings consist of sodium silicate,

metallic oxides clay, and other inorganic substances or combinations thereof. Cellulose coated

electrodes protect the molten metal with a gaseous zone around the arc as well as the weld

zone. The mineral coated electrode forms a slag deposit. The shielded arc or heavy coated

electrodes are used for welding steels, cast iron, and hard surfacing. See figure 5-31 below.

Shielded Arc Electrode


7

Functions of Shielded Arc or Heavy Coated Electrodes These welding electrodes produce a reducing gas shield around the arc. This prevents

atmospheric oxygen or nitrogen from contaminating the weld metal. The oxygen readily

combines with the molten metal, removing alloying elements and causing porosity. Nitrogen

causes brittleness, low ductility, and in Some cases low strength and poor resistance to

corrosion.

They reduce impurities such as oxides, sulfur, and phosphorus so that these impurities will not

impair the weld deposit.

They provide substances to the arc which increase its stability. This eliminates wide

fluctuations in the voltage so that the arc can be maintained without excessive spattering.

By reducing the attractive force between the molten metal and the end of the electrodes, or by

reducing the surface tension of the molten metal, the vaporized and melted coating causes the

molten metal at the end of the electrode to break up into fine, small particles.

The coatings contain silicates which will form a slag over the molten weld and base metal.

Since the slag solidifies at a relatively slow rate, it holds the heat and allows the underlying

metal to cool and solidify slowly. This slow solidification of the metal eliminates the

entrapment of gases within the weld and permits solid impurities to float to the surface. Slow

cooling also has an annealing effect on the weld deposit.

The physical characteristics of the weld deposit are modified by incorporating alloying

materials in the electrode coating. The fluxing action of the slag will also produce weld metal

of better quality and permit welding at higher speeds.

Tungsten Electrodes Non consumable welding electrodes for gas tungsten-arc (TIG) welding are of three types: pure

tungsten, tungsten containing 1 or 2 percent thorium, and tungsten containing 0.3 to 0.5 percent

zirconium. Tungsten electrodes can be identified as to type by painted end marks as follows.

1. Green -- pure tungsten.

2. Yellow -- 1 percent thorium.

3. Red -- 2 percent thorium.

4. Brown -- 0.3 to 0.5 percent zirconium.

Pure tungsten (99. 5 percent tungsten) electrodes are generally used on less critical welding

operations than the tungstens which are alloyed. This type of electrode has a relatively low

current-carrying capacity and a low resistance to contamination.

Thoriated tungsten electrodes (1 or 2 percent thorium) are superior to pure tungsten electrodes

because of their higher electron output, better arc-starting and arc stability, high current-

carrying capacity, longer life, and greater resistance to contamination.

Tungsten welding electrodes containing 0.3 to 0.5 percent zirconium generally fall between

pure tungsten electrodes and thoriated tungsten electrodes in terms of performance. There is,

however, some indication of better performance in certain types of welding using ac power.

Finer arc control can be obtained if the tungsten alloyed electrode is ground to a point (see

figure 5-33). When electrodes are not grounded, they must be operated at maximum current

density to obtain reasonable arc stability. Tungsten electrode points are difficult to maintain if

standard direct current equipment is used as a power source and touch-starting of the arc is

standard practice. Maintenance of electrode shape and the reduction of tungsten inclusions in

the weld can best be accomplished by superimposing a high-frequency current on the regular

welding current. Tungsten electrodes alloyed with thorium and zirconium retain their shape

longer when touch-starting is used.

The welding electrode extension beyond the gas cup is determined by the type of joint being

welded. For example, an extension beyond the gas cup of 1/8 in. (3.2 mm) might be used for

butt joints in light gage material, while an extension of approximately 1/4 to 1/2 in. (6.4 to 12.7

mm) might be necessary on some fillet welds. The tungsten electrode of torch should be

inclined slightly and the filler metal added carefully to avoid contact with the tungsten. This

will prevent contamination of the electrode. If contamination does occur, the electrode must be

removed, reground, and replaced in the torch.


http://www.weldguru.com/tig-welding.html

8

Direct Current Arc Welding Electrodes The manufacturer’s recommendations should be followed when a specific type of welding

electrode is being used. In general, direct current shielded arc electrodes are designed either for

reverse polarity (electrode positive) or for straight polarity (electrode negative), or both. Many,

but not all, of the direct current electrodes can be used with alternating current. Direct current

is preferred for many types of covered, nonferrous, bare and alloy steel electrodes.

Recommendations from the manufacturer also include the type of base metal for which given

electrodes are suited, corrections for poor fit-ups, and other specific conditions.

In most cases, straight polarity electrodes will provide less penetration than reverse polarity

electrodes, and for this reason will permit greater welding speed. Good penetration can be

obtained from either type with proper welding conditions and arc manipulation.

Alternating Current Arc Welding Electrodes Coated electrodes which can be used with either direct or alternating current are available.

Alternating current is more desirable while welding in restricted areas or when using the high

currents required for thick sections because it reduces arc blow. Arc blow causes blowholes,

slag inclusions, and lack of fusion in the weld.

Alternating current is used in atomic hydrogen welding and in those carbon arc processes that

require the use of two carbon electrodes. It permits a uniform rate of welding and electrode

consumption. In carbon-arc processes where one carbon electrode is used, direct current

straight polarity is recommended, because the electrode will be consumed at a lower rate.

Electrode Defects and Their Effects If certain elements or oxides are present in electrode coatings, the arc stability will be affected.

In bare electrodes, the composition and uniformity of the wire is an important factor in the

control of arc stability. Thin or heavy coatings on the electrodes will riot completely remove

the effects of defective wire.

Aluminum or aluminum oxide (even when present in 0.01 percent), silicon, silicon dioxide,

and iron sulphate unstable. Iron oxide, manganese oxide, calcium oxide, and stabilize the arc.

When phosphorus or sulfur are present in the electrode in excess of 0.04 percent, they will

impair the weld metal because they are transferred from the electrode to the molten metal with

very little loss. Phosphorus causes grain growth, brittleness, and "cold shortness" (i. e., brittle

when below red heat) in the weld. These defects increase in magnitude as the carbon content of

the steel increases. Sulfur acts as a slag, breaks up the soundness of the weld metal, and causes

"hot shortness" (i. e., brittle when above red heat). Sulfur is particularly harmful to bare, low-

carbon steel electrodes with a low manganese content. Manganese promotes the formation of

sound welds.

If the heat treatment, given the wire core of an electrode, is not uniform, the electrode will

produce welds inferior to those produced with an electrode of the same composition that has

been properly heat treated.

Deposition Rates The different types of electrodes have different deposition rates due to the composition of the

coating. The electrodes containing iron power in the coating have the highest deposition rates.

In the United States, the percentage of iron power in a coating is in the 10 to 50 percent range.

This is based on the amount of iron power in the coating versus the coating weight. This is

shown in the formula:

These percentages are related to the requirements of the American Welding Society (AWS)

specifications. The European method of specifying iron power is based on the weight of

deposited weld metal versus the weight of the bare core wire consumed. This is shown as

follows:


9

Thus, if the weight of the deposit were double the weight of the core wire, it would indicate a

200 percent deposition efficiency, even though the amount of the iron power in the coating

represented only half of the total deposit. The 30 percent iron power formula used in the United

States would produce a 100 to 110 percent deposition efficiency using the European formula.

The 50 percent iron power electrode figured on United States standards would produce an

efficiency of approximately 150 percent using the European formula.

Non-consumable Electrodes Types There are two types of nonconsumable welding electrodes.

1. The carbon electrode is a non-filler metal electrode used in arc welding or cutting,

consisting of a carbon graphite rod which may or may not be coated with copper or

other coatings.

2. The tungsten electrode is defined as a non-filler metal electrode used in arc welding or

cutting, made principally of tungsten.

Carbon Electrodes The American Welding Society does not provide specification for carbon welding electrodes

but there is a military specification, no. MIL-E-17777C, entitled, "Electrodes Cutting and

Welding Carbon-Graphite Uncoated and Copper Coated".

This specification provides a classification system based on three grades: plain, uncoated, and

copper coated. It provides diameter information, length information, and requirements for size

tolerances, quality assurance, sampling, and various tests. Applications include carbon arc

welding, twin carbon arc welding, carbon cutting, and air carbon arc cutting and gouging.

Stick Electrodes Stick welding electrodes vary by:

size: common sizes are 1⁄16, 5⁄64, 3⁄32 (most common), 1⁄8, 3⁄16, 7⁄32, 1⁄4, and 5⁄16 inch. Core wire used with electrodes needs to be narrower than the materials that are

welded.

material: stick welding electrodes come in cast iron, high carbon steel, mild steel,

iron-free (nonferrous) and special alloys.)

strength: referred to as tensile strength. Each weld needs to be stronger than the metal

being welded. This means that the materials in the electrode need to be stronger as well.

welding position (horizontal, flat etc): different electrodes are used for each welding

position.

iron powder mix (up to 60% in flux): iron powder in the flux increases the amount of

molten metal available for the weld (heat turns powder into steel).

soft arc designation: for thinner metals or for metals that don't have a perfect fit or

gap. As described above there are many kinds of electrodes. Here are the most popular

stick welding (SMAW) electrodes:

E6013 and E6012: For thin metals and joints that do not easily fit together.

E6011: Good for working on surfaces that are oily, rusted or has dirt. Versatile in that it

works with DC or AC polarity. Creates little slag, another big plus. Note that this

electrode should not be placed into an electrode oven.

E6010: Similar to the E6011 but only works with direct current (DC). Note that this

electrode should not be placed into an electrode oven.

E76018 and E7016: Manufactured with iron powder in the flux. Creates strong welds,

but has a puddle that might present some control issues for beginners.



https://rdl.train.army.mil/catalog-ws/view/100.ATSC/9F320990-3E63-4D5E-A278-85756E134BCC-1274444848162/9-237/Appa.htm#mil_E_17777c

10

Electrodes for Shielded Metal Arc Welding (SMAW) or stick electrodes must be properly

stored in order to deposit quality welds. When stick electrodes absorb moisture from the

atmosphere, they must be dried in order to restore their ability to deposit quality welds.

Electrodes with too much moisture may lead to cracking or porosity. Operational

characteristics may be affected as well. If you've experienced unexplained weld cracking

problems, or if the stick electrode arc performance has deteriorated, it may be due to your

storage methods or re-drying procedures.

Follow these simple storage, exposure and redrying techniques to ensure the highest quality

welds, as well as the best operational characteristics from your stick electrodes.

Storing Low Hydrogen Stick Electrodes

Low hydrogen stick electrodes must be dry to perform properly. Unopened Lincoln

hermetically sealed containers provide excellent protection in good storage conditions. Opened

cans should be stored in a cabinet at 250 to 300°F (120 to 150°C) Low hydrogen stick

electrode coatings that have picked up moisture may result in hydrogen induced cracking,

particularly in steels with a yield strength of 80,000 psi (550 MPa) and higher.

Moisture resistant electrodes with an "R" suffix in their AWS classification have a high

resistance to moisture pickup coating and, if properly stored, will be less susceptible to this

problem, regardless of the yield strength of the steel being welded. Specific code requirements

may indicate exposure limits different from these guidelines.

All low hydrogen stick electrodes should be stored properly, even those with an "R" suffix.

Standard EXX18 electrodes should be supplied to welders twice per shift. Moisture resistant

types may be exposed for up to 9 hours.

When containers are punctured or opened, low hydrogen electrodes may pick up moisture.

Depending upon the amount of moisture, it will damage weld quality in the following ways:

1. A greater amount of moisture in low hydrogen electrodes may cause porosity. Detection of

this condition requires x-ray inspection or destructive testing. If the base metal or weld metal

exceeds 80,000 psi (550 MPa) yield strength, this moisture may contribute to under-bead or

weld cracking.

2. A relatively high amount of moisture in low hydrogen electrodes causes visible external

porosity in addition to internal porosity. It also may cause excessive slag fluidity, a rough weld

surface, difficult slag removal, and cracking.

3. Severe moisture pickup can cause weld cracks in addition to under-bead cracking, severe

porosity, poor appearance and slag problems.

Redrying Low Hydrogen Stick Electrodes

Redrying, when done correctly, restores the electrodes' ability to deposit quality welds. Proper

redrying temperature depends upon the electrode type and its condition.

One hour at the listed final temperature is satisfactory. DO NOT dry electrodes at higher

temperatures. Several hours at lower temperatures is not equivalent to using the specified

requirements.

Electrodes of the E8018 and higher strength classifications should be given no more than three

one-hour re-dries in the 700 to 800°F (370 to 430°C) range. This minimizes the possibility of

oxidation of alloys in the coating resulting in lower than normal tensile or impact properties.

Any low hydrogen electrode should be discarded if excessive redrying causes the coating to

become fragile and flake or break off while welding, or if there is a noticeable difference in

handling or arc characteristics, such as insufficient arc force.

Electrodes to be redried should be removed from the can and spread out in the oven because

each electrode must reach the drying temperature.


11

Final Redrying Temperature

Condition

Pre-drying

Temperature(1)

E7018,

E7028

E8018, E9018,

E10018,

E11018

Electrodes exposed to air for less than

one week; no direct contact with water. N/A

650 to 750°F

(340 to

400°C)

700 to 800°F

(370 to 430°C)

Electrodes which have come in direct

contact with water or which have been

exposed to high humidity.

180 to 220°F (80 to

105°C)

650 to 750°F

(340 to

400°C)

700 to 800°F

(370 to 430°C)

(1) Pre-dry for 1 to 2 hours. This will minimize the tendency for coating cracks or oxidation of

the alloys in the coating.

Storing and Redrying Non-Low Hydrogen Electrodes

Electrodes in unopened Lincoln cans or cartons retain the proper moisture content indefinitely

when stored in good condition.

If exposed to humid air for long periods of time, stick electrodes from opened containers may

pick up enough moisture to affect operating characteristics or weld quality. If moisture appears

to be a problem, store electrodes from the opened containers in heated cabinets at 100 to 120°F

(40 to 50°C). DO NOT use higher temperatures, particularly for electrodes from the "Fast

Freeze" group.Some electrodes from wet containers or long exposure to high humidity can be

re-dried. Adhere to the procedures in the following table for each type.


12

Redrying Conditions - Non-Low Hydrogen Stick Electrodes

Stick

Electrode Electrode Group

Final Redrying

Temperature Time

E6010:

Fleetweld

5P, 5P+

E6011:

Fleetweld 35,

35LS, 180

E7010-A1:

SA-85(1)

E7010-G:

SA-HYP+(1)

E8010-G:

SA-70+(1),

SA-80(1)

E9010-G:

SA-90(1)

Fast Freeze - excessive moisture is indicated by a

noisy arc and high spatter, rusty core wire at the

holder end or objectionable coating blisters while

welding.

Re-baking of this group of stick electrodes is

not recommended.

Not

Recommended N/A


13

E7024:

Jetweld 1, 3

E6027:

Jetweld 2

Fast Fill - excessive moisture is indicated by a

noisy or "digging" arc, high spatter, tight slag, or

undercut. Pre-dry unusually damp electrodes for

30 - 45 minutes at 200°F to 230°F (90 - 110°C)

before final drying to minimize cracking of the

coating.

400 to 500°F

(200to 260°C)

30 - 45

minutes

E6012:

Fleetweld 7

E6013:

Fleetweld 37

E7014:

Fleetweld 47

E6022:

Fleetweld 22

Fill Freeze - Excessive moisture is indicated by a

noisy or "digging" arc, high spatter, tight slag or

undercut. Pre-dry unusually damp electrodes for

30 - 45 minutes at 200° - 230°F (90° - 110°C)

before final drying to minimize cracking of the

coating

300 to 350°F

(150 to 180°C)

20 - 30

minutes

(1) Pre-dry for 1 to 2 hours. This will minimize the tendency for coating cracks or oxidation of

the alloys in the coating.

Using longer drying times or higher temperatures can easily damage the electrodes. For drying,

remove the electrodes from the container and spread them out in the furnace because each stick

electrode must reach the drying temperature.

Standard

Number Title

AWS A2.4 Standard symbols for welding, brazing, and non-destructive examination

AWS A3.0 Standard welding terms and definitions

AWS A5.1 Specification for carbon steel electrodes for shielded metal arc welding

AWS A5.18 Specification for carbon steel electrodes and rods for gas shielded arc

welding

AWS B2.1 Specification for Welding Procedure and Performance Qualification

AWS B1.10 Guide for the nondestructive examination of welds

AWS D1.1 Structural welding (steel)

AWS D1.2 Structural welding (aluminum)

AWS D1.3 Structural welding (sheet steel)

AWS D1.4 Structural welding (reinforcing steel)

AWS D1.5 Bridge welding

AWS D1.6 Structural welding (stainless steel)

AWS D1.7 Structural welding (strengthening and repair)

AWS D1.8 Structural welding seismic supplement

AWS D1.9 Structural welding (titanium)

AWS D8.1 Automotive spot welding

AWS D8.14 Automotive arc welding (aluminum)


14

AWS D8.6 Automotive spot welding electrodes supplement

AWS D8.7 Automotive spot welding recommendations supplement

AWS D8.8 Automotive arc welding (steel)

AWS D8.9 Automotive spot weld testing

AWS D9.1 Sheet metal welding

AWS D10.10 Heating practices for pipe and tube

AWS D10.11 Root pass welding for pipe

AWS D10.12 Pipe welding (mild steel)

AWS D10.13 Tube brazing (copper)

AWS D10.18 Pipe welding (stainless steel)

AWS D11.2 Welding (cast iron)

AWS D14.1 Industrial mill crane welding

AWS D14.3 Earthmoving & agricultural equipment welding

AWS D14.4 Machinery joint welding

AWS D14.5 Press welding

AWS D14.6 Industrial mill roll surfacing

AWS D15.1 Railroad welding

AWS D15.2 Railroad welding practice supplement

AWS D16.1 Robotic arc welding safety

AWS D16.2 Robotic arc welding system installation

AWS D16.3 Robotic arc welding risk assessment

AWS D16.4 Robotic arc welder operator qualification

AWS D17.1 Aerospace fusion welding

AWS D17.2 Aerospace resistance welding

AWS D18.1 Hygienic tube welding (stainless steel)

AWS D18.2 Stainless steel tube discoloration guide

AWS D18.3 Hygienic equipment welding

Standard

Number Description

BS 499-1 Welding terms and symbols. Glossary for welding, brazing and thermal

cutting

BS 499-2C Welding terms and symbols. European arc welding symbols in chart form

BS 2633 Specification for Class I arc welding of ferritic steel pipework for carrying

fluids

BS 2971 Specification for class II arc welding of carbon steel pipework for carrying

fluids

BS 4515-1 Specification for welding of steel pipelines on land and offshore - Part 1:

Carbon and carbon manganese steel pipelines

BS 4515-2 Specification for welding of steel pipelines on land and offshore. Duplex

stainless steel pipelines

PD 6705-2 Structural use of steel and aluminium. Recommendations for the execution of

steel bridges to BS EN 1090-2

PD 6705-3 Structural use of steel and aluminium. Recommendations for the execution of

aluminium structures to BS EN 1090-3


15

Questions:-

1. What is the role of electrode in welding?

2. Right the AWS code of any types of electrode.

3. What is PD6705-3?

Next Lesson: - weld ability of metals, importance of pre-heating, post –heating and

maintenance of inter pass temperature.

Assignment:- Electrodes, types, function of flux, coating factor, sizes of electrode. Coding of





1

LESSON PLAN


Name____________ Week No:- seventeen

Subject :- weld ability of metals, importance of pre-heating, post –heating and maintenance of

inter pass temperature.

Motivations:- in previous week we learned about Electrodes, types, function of flux, coating

factor, sizes of electrode. Coding of electrodes as per BIS, AWS. Moisture pick up of

electrode. Storage and baking of electrodes. Special purpose electrode and their application.


INTRODUCTION: -weld ability is the structure of metal. In this point we assure that the

job is ready to weld or not. Pre-heating and post heating balance the metal’s structure.

PRESENTATION:-

Weldability The weldability, also known as joinability,

[1] of a material refers to its ability to be welded. Many metals and

thermoplastics can be welded, but some are easier to weld than others (see Rheological Weldability). A material's

weldability is used to determine the welding process and to compare the final weld quality to other materials.

Weldability is often hard to define quantitatively, so most standards define it qualitatively. For instance the

International Organization for Standardization (ISO) defines weldability in ISO standard 581-1980 as: "Metallic

material is considered to be susceptible to welding to an established extent with given processes and for given

purposes when welding provides metal integrity by a corresponding technological process for welded parts to

meet technical requirements as to their own qualities as well as to their influence on a structure they form." Other

welding organizations define it similarly.

Preheating can be defined as the application of heat to the base metal or substrate before welding. Gas torches,

electric heaters, or infra-red radiant pane heaters can all be used to apply preheat, which decreases the weld

cooling speed and thereby prevents cold cracking in welds. Figure 1 shows how an increase of preheating

temperature affects the cooling rate of welds. For example, where heat input is constant (e.g., 20 kJ/cm), a 50-

degree-C preheat results in an approximate cooling rate of 17°C/sec, while a preheat of 250°C decreases the

cooling rate to approximately 3°C/sec. Decreasing the cooling rates prevents the formation of brittle weld

structures, and removes diffusible hydrogen, which in turn prevents the occurrence of cold cracking in welds.

Postheating can be defined as the application of heat to an assembly after welding. Postheating includes postweld

heat treatment (PWHT), immediate postweld heating (IPWH), normalizing, quenching, and tempering (aging).

The main purposes of these operations in welding fabrication are as follows:

■ PWHT: relieves residual stresses ■ IPWH: relieves diffusible hydrogen ■ Normalizing: refines microstructures deformed by hot forming (e.g., applied on the end plate of vessels)

■ Quenching: hardens welds by rapid cooling, using water, air, or mist (e.g., applied on surfaced shafts) ■ Tempering (Aging): stabilizes microstructures after quenching or welding

Among these heating or heat treatments, PWHT and IPWH are the most common procedures used in welding.

The others are used for limited applications in some welding fabrication fields. The purposes and procedures of

PWHT are detailed in Kobelco Welding Today, Vol. 4, No. 2, April 2001. IPWH is usually carried out with gas

torches, on welds right after welding is finished, while the weld still maintains the preheat temperature, by using

comparatively lower temperatures and shorter heating times (250-350°C x 0.5-1h), prior to PWHT. IPWH

decreases diffusible hydrogen to an adequate level (though higher than with PWHT as shown in Fig. 3) to prevent

cold cracking.


https://en.wikipedia.org/wiki/Weldability#cite_note-degarmo-1

https://en.wikipedia.org/wiki/Welding

https://en.wikipedia.org/wiki/Metal

https://en.wikipedia.org/wiki/Thermoplastic

https://en.wikipedia.org/wiki/Rheological_Weldability

https://en.wikipedia.org/wiki/International_Organization_for_Standardization

2

Material Arc

welding

Oxy-

acetylene

welding

Electron

beam

welding

Resistance

welding Brazing Soldering

Adhesive

bonding

Cast iron C R N S D N C

Carbon steel and

low-alloy steel R R C R R D C

Stainless steel R C C R R C C

Aluminum and

magnesium C C C C C S R

Copper and

copper alloys C C C C R R C

Nickel and

nickel alloys R C C R R C C

Titanium C N C C D S C

Lead and zinc C C N D N R R

Thermoplastic† N N N N N N C

Thermosets N N N N N N C

Elastomers N N N N N N R

Ceramics N S C N N N R

Dissimilar

metals D D C D D/C R R

†Heated tool = R; Hot gas = R; Induction = C

Key: C = Commonly performed; R = Recommended; D = Difficult; S = Seldom; N = Not

used

Interpass temperature is a range of temperature between passes on a multiple pass weld.

It can be measured using a temperature stick. You can also use a infrared temperature gun.

Going above the temperature can cause the microstructure of a material to change and loose

characteristics of the material for example a hardened steel like QT plate will loose its hardness

or stainless steel can loose its corrosion resistance.Welding below the temperature can cause

lack of penetration or cracking from the shock of stress caused by the sudden increase in heat

which is usually a problem on thicker materials. Same reason for a pre heat.

With mild steel interpass temperature usually isn't a big deal because Heat wont cause a

dramatic change in the materials characteristic. It becomes very critical with hardened

materials, stainless steel, High carbon content material, materials with high alloy content, ect...

If the material you are welding has a specified interpass temperature stay within it, it is critical

to maintain that temperature so the weld metal will have proper fusion to the sound material

and maintains its material characteristics (Strength, hardness, corrosion resistance, flexibility)

“Interpass temperature” refers to the temperature of the material in the weld area immediately before the second and each subsequent pass of a multiple pass weld. In practice, the minimum specified interpass temperature is often equal to the minimum specified preheat temperature, but this is not required according to the definition.


http://www.caltechindia.com/TempSticks.htm

3

Questions:-

1. What is weldability and its role in welding?

2. What is pre heating?

3. What is post heating and interpass temprature?

Next Lesson: - Classification of steel.welding of low, medium, high carbon and alloy steel.

Assignment:- weld ability of metals, importance of pre-heating, post –heating and maintenance

of inter pass temperature.



4


1

LESSON PLAN


Name____________ Week No:-eighteen & nineteen

Subject :- Classification of steel. welding of low, medium, high carbon and alloy steel. Effects

of alloying elements on steel. Stainless steel- types. weld decay and weld ability.

Motivations:- in previous week we learned about weld ability of metals, importance of pre-

heating, post –heating and maintenance of inter pass temperature.


INTRODUCTION: -steel is a very important metal for general industry. More than 80

industry establish for steel work. So it is also important for welding.

PRESENTATION:-


Plain Carbon Steels

These steels usually are iron with less than 1 percent carbon, plus small amounts of manganese,

phosphorus, sulfur, and silicon. The weldability and other characteristics of these steels are primarily a

product of carbon content, although the alloying and residual elements do have a minor influence.

Plain carbon steels are further subdivided into four groups:

1. Low

2. Medium

3. High

4. Very high

Low. Often called mild steels, low-carbon steels have less than 0.30 percent carbon and are the most

commonly used grades. They machine and weld nicely and are more ductile than higher-carbon steels.

Medium. Medium-carbon steels have from 0.30 to 0.45 percent carbon. Increased carbon means increased

hardness and tensile strength, decreased ductility, and more difficult machining.

High. With 0.45 to 0.75 percent carbon, these steels can be challenging to weld. Preheating, postheating (to

control cooling rate), and sometimes even heating during welding become necessary to produce acceptable

welds and to control the mechanical properties of the steel after welding.

Very High. With up to 1.50 percent carbon content, very high-carbon steels are used for hard steel

products such as metal cutting tools and truck springs. Like high-carbon steels, they require heat treating

before, during, and after welding to maintain their mechanical properties.

Low-alloy Steels

When these steels are designed for welded applications, their carbon content is usually below 0.25 percent

and often below 0.15 percent. Typical alloys include nickel, chromium, molybdenum, manganese, and

silicon, which add strength at room temperatures and increase low-temperature notch toughness.

These alloys can, in the right combination, improve corrosion resistance and influence the steel's response

to heat treatment. But the alloys added can also negatively influence crack susceptibility, so it's a good idea

to use low-hydrogen welding processes with them. Preheating might also prove necessary. This can be

determined by using the carbon equivalent formula, which we'll cover in a later issue.


2

High-alloy Steels

For the most part, we're talking about stainless steel here, the most important commercial high-alloy steel.

Stainless steels are at least 12 percent chromium and many have high nickel contents. The three basic types

of stainless are:

1. Austenitic

2. Ferritic

3. Martensitic

Martensitic stainless steels make up the cutlery grades. They have the least amount of chromium, offer

high hardenability, and require both pre- and postheating when welding to prevent cracking in the heat-

affected zone (HAZ).

Ferritic stainless steels have 12 to 27 percent chromium with small amounts of austenite-forming alloys.

Austenitic stainless steels offer excellent weldability, but austenite isn't stable at room temperature.

Consequently, specific alloys must be added to stabilize austenite. The most important austenite stabilizer

is nickel, and others include carbon, manganese, and nitrogen.

Special properties, including corrosion resistance, oxidation resistance, and strength at high temperatures,

can be incorporated into austenitic stainless steels by adding certain alloys like chromium, nickel,

molybdenum, nitrogen, titanium, and columbium. And while carbon can add strength at high temperatures,

it can also reduce corrosion resistance by forming a compound with chromium. It's important to note that

austenitic alloys can't be hardened by heat treatment. That means they don't harden in the welding HAZ.


3

* Stainless steels always have a high chromium content, often considerable amounts of nickel,

and sometimes contain molybdenum and other elements. Stainless steels are identified by a

three-digit number beginning with 2, 3, 4, or 5.

Steel Classification Systems Before we look at a couple of common steel classification systems, let's consider one more high-

carbon metal, cast iron. The carbon content of cast iron is 2.1 percent or more. There are four

basic types of cast iron:

1. Gray cast iron , which is relatively soft. It's easily machined and welded, and you'll find it

used for engine cylinder blocks, pipe, and machine tool structures.

2. White cast iron, which is hard, brittle, and not weldable. It has a compressive strength of

more than 200,000 pounds per square inch (PSI), and when it's annealed, it becomes

malleable cast iron.

3. Malleable cast iron, which is annealed white cast iron. It can be welded, machined, is

ductile, and offers good strength and shock resistance.

4. Ductile cast iron, which is sometimes called nodular or spheroidal graphite cast iron. It

gets this name because its carbon is in the shape of small spheres, not flakes. This makes it

both ductile and malleable. It's also weldable.

Now let's take a look at a typical steel classification system. Both the Society of Automotive

Engineers (SAE) and the American Iron and Steel Institute (AISI) use virtually identical systems.

Both are based on a four-digit system with the first number usually indicating the basic type of

steel and the first two numbers together indicating the series within the basic alloy group.

Keep in mind there may be a number of series within a basic alloy group, depending on the

amount of the principal alloying elements. The last two or three numbers refer to the approximate

permissible range of carbon content in points (hundredths of a percent).

These classification systems can become fairly complex, and Figure 1 is just a basic

representation. Be sure to reference the most recent AISI and SAE publications for the latest

revisions.

That's a look at some basics concerning the iron-carbon-steel relationship and its influences on

welding and metal alloys. Next time we'll look at hardening and ways to make metals stronger.

We'll also consider the influences of some key alloying elements and the effects of welding on

metallurgy.


4


5


6

Questions:-

1. What is steel ?

2. What is high carbon steel ?

3. What is alloy steel ?

4. What is weld decay?

Next Lesson: - Brass –types-properties and welding methods. Copper–types-properties and

welding methods.

Assignment:- Classification of steel. welding of low, medium, high carbon and alloy steel.

Effects of alloying elements on steel. Stainless steel- types. weld decay and weld ability.



1

LESSON PLAN


Name____________ Week No:- Twenty

Subject :- Brass-types-properties and welding methods. Copper-types-properties and welding

methods.

Motivations:- in previous week we learned about Classification of steel. welding of low,

medium, high carbon and alloy steel. Effects of alloying elements on steel. Stainless steel-

types. weld decay and weld ability.


INTRODUCTION: - Brass is a binary alloy composed of copper and zinc that has been

produced for millennia and is valued for its workability, hardness, corrosion resistance and

attractive appearance.

PRESENTATION:-


Brass Properties: Alloy Type: Binary

Content: Copper & Zinc

Density: 8.3-8.7 g/cm3

Melting Point: 1652-1724 °F (900-940 °C)

Moh's Hardness: 3-4

Characteristics: The exact properties of different brasses depend on the composition of the brass alloy, particularly

the copper-zinc ratio.

In general, however, all brasses are valued for their machinability, or the ease with which the

metal can be formed into desired shapes and forms while retaining high strength.

While there are differences between brasses with high and low zinc contents, all brasses are

considered malleable and ductile (low zinc brasses more so). Due to its low melting point, brass

can also be cast relatively easily. However, for casting applications, a high zinc content is usually

preferred.

Brasses with a lower zinc content can be easily cold worked, welded and brazed. A high copper

content also allows the metal to form a protective oxide layer (patina) on its surface that guards

against further corrosion, a valuable property in applications that expose the metal to moisture and

weathering.

The metal has both good heat and electrical conductivity (it's electrical conductivity can from 23%

to 44% that of pure copper), and it is wear and spark resistant.

Like copper, its bacteriostatic properties have resulted in its use in bathroom fixtures and

healthcare facilities.

Brass is considered a low friction and non-magnetic alloy, while its acoustic properties have


https://www.thebalance.com/metal-alloys-2340254

https://www.thebalance.com/metal-profile-copper-2340132

https://www.thebalance.com/metal-profile-zinc-2340195

https://www.thebalance.com/what-is-corrosion-2339700

https://www.thebalance.com/composition-of-common-brass-alloys-2340109

https://www.thebalance.com/malleability-2340002

https://www.thebalance.com/ductility-metallurgy-4019295

https://www.thebalance.com/what-is-cold-working-2340011

https://www.thebalance.com/electrical-conductivity-in-metals-2340117

2

resulted in its use in many 'brass band' musical instruments.

Artists and architects value the metal's aesthetic properties, as it can be produced in a range of

colors, from deep red to golden yellow.

Types: 'Brass' is a generic term that refers to a wide range of copper-zinc alloys. In fact, there are over 60

different types of brass specified by EN (European Norm) Standards. These alloys can have a

wide range of different compositions depending upon the properties required for a particular

application.

Production: Brass is most often produced from copper scrap and zinc ingots. Scrap copper is selected based on

its impurities, as certain additional elements are desired in order to produce the exact grade of

brass required.

Because zinc begins to boil and vaporize at 1665°F (907°C), below copper's melting point 1981°

F (1083°C), the copper must first be melted. Once melted, zinc is added at a ratio appropriate for

the grade of brass being produced. While some allowance is still made for zinc loss to

vaporization.

At this point, any other additional metals, such as lead, aluminum, silicon or arsenic, are added to

the mixture to create the desired alloy.

Once the molten alloy is ready, it is poured into molds where it solidifies into large slabs or billets

Billets - most often of alpha-beta brass - can directly be processed into wires, pipes and tubes via

hot extrusion, which involves pushing the heated metal through a die, or hot forging.

If not extruded or forged, the billets are then reheated and fed through steel rollers (a process

known as hot rolling). The result is slabs with a thickness of less than half an inch (<13mm).

After cooling, the brass is then fed through a milling machine, or scalper, that cuts a thin layer

from the metal in order to remove surface casting defects and oxide.

Under a gas atmosphere to prevent oxidization, the alloy is heated and rolled again, a process

known as annealing, before it is rolled again at cooler temperatures (cold rolling) to sheets of

about 0.1" (2.5mm) thick.

The cold rolling process deforms the internal grain structure of the brass, resulting in a much

stronger and harder metal. This step can be repeated until the desired thickness or hardness is

achieved.

Finally, the sheets are sawed and sheared to produce the width and length required.

All sheets, cast, forged and extruded brass materials are given a chemical bath, usually used

hydrochloric and sulfuric acid to remove black copper oxide scale and tarnish.

Applications: Brass's valuable properties and relative ease of production has made it one of the mostly widely

used alloys. Compiling a complete list of all of brass's applications would be a colossal task, but to

get an idea of industries and the types of products in which brass is found we can categorize and

summarize some end-uses based on the grade of brass used:

Free cutting brass (e.g. C38500 or 60/40 brass):

Nuts, bolts, threaded parts

Terminals

Jets

Taps

Injectors


https://www.thebalance.com/metal-profile-lead-2340140

https://www.thebalance.com/annealing-explained-2340013

3

Brass types

Class Copper

(%)

Zinc

(%) Notes

Alpha

brasses > 65 < 35

Alpha brasses are malleable, can be worked cold, and are used in

pressing, forging, or similar applications. They contain only one

phase, with face-centered cubic crystal structure. With their high

proportion of copper, these brasses have a more golden hue than

others

Alpha-beta

brasses 55–65

35–45

Also called duplex brasses, these are suited for hot working. They

contain both α and β' phases; the β'-phase is body-centered cubic

and is harder and stronger than α. Alpha-beta brasses are usually

worked hot. The higher proportion of zinc means these brasses are

brighter than alpha brasses.

Beta

brasses[citation

needed]

50–55 45–50

Beta brasses can only be worked hot, and are harder, stronger, and

suitable for casting. The high zinc-low copper content means these

are some of the brightest and least-golden of the common brasses.

Gamma

brasses 61–67

33–39

There are also Ag-Zn and Au-Zn gamma brasses, Ag 30–50%, Au

41%.[26]

White brass < 50 > 50

These are too brittle for general use. The term may also refer to

certain types of nickel silver alloys as well as Cu-Zn-Sn alloys

with high proportions (typically 40%+) of tin and/or zinc, as well

as predominantly zinc casting alloys with copper additives. These

have virtually no yellow coloring at all, and instead have a much

more silvery appearance.

Brass alloys

Alloy name Copper

(%)

Zinc

(%)

Tin

(%)

Lea

d

(%)

Other Notes

Abyssinian gold 90 10

Admiralty brass 69 30 1

Tin inhibits loss of zinc in many

environments.

Aich's alloy 60.66 36.5

8 1.02

1.74

iron

Designed for use in marine service owing

to its corrosion resistance, hardness and

toughness. A characteristic application is to

the protection of ships' bottoms, but more

modern methods of cathodic protection

have rendered its use less common. Its

appearance resembles that of gold.[27]

Aluminum

brass 77.5 20.5

2%

alumin

um

Aluminum improves corrosion resistance.

It is used for heat exchanger and condenser

tubes.[28]

Arsenical brass

arseni

c,

freque

ntly

alumin

um

Used for boiler fireboxes.


https://en.wikipedia.org/wiki/Face-centered_cubic

https://en.wikipedia.org/wiki/Crystal_structure

https://en.wikipedia.org/wiki/Body-centered_cubic

https://en.wikipedia.org/wiki/Wikipedia:Citation_needed


https://en.wikipedia.org/wiki/Brass#cite_note-26

https://en.wikipedia.org/wiki/Nickel_silver

https://en.wikipedia.org/wiki/Dezincification_resistant_brass


https://en.wikipedia.org/wiki/Brass#cite_note-Davis2001-28

https://en.wikipedia.org/wiki/Arsenic

https://en.wikipedia.org/wiki/Arsenic

https://en.wikipedia.org/wiki/Aluminum

https://en.wikipedia.org/wiki/Aluminum

https://en.wikipedia.org/wiki/Firebox_%28steam_engine%29

4

Cartridge brass

(C260) 70 30 —

≤ 0.07 [29]

Good cold working properties. Used for

ammunition cases, plumbing, and

hardware.

Common brass 63 37

Also called rivet brass. Cheap and

standard for cold working.

DZR brass

arseni

c

Dezincification resistant brass with a small

percentage of arsenic.

Delta metal 55 41-

43

1-3%

iron

with

the

balanc

e

consist

ing of

variou

s other

metals

.

The proportions used make the material

harder and suitable for valves and bearings.

Free machining

brass (C360) 61.5 35.5

3

0.35%

iron

Also called 360 or C360 brass. High

machinability. Lead content 2.5%–3.7% [29]

Gilding metal 95 5

Softest type of brass commonly available.

Gilding metal is typically used for

ammunition bullet "jackets", e.g., full metal

jacket bullets. Almost red in color.

High brass 65 35

Has a high tensile strength and is used for

springs, screws, and rivets.

Leaded brass

>0

An alpha-beta brass with an addition of

lead for improved machinability.

Lead-free brass

< 0.2

5

Defined by California Assembly Bill AB

1953 contains "not more than 0.25 percent

lead content".[15]

Prior upper limit was 4%.

Low brass 80 20

Light golden color, very ductile; used for

flexible metal hoses and metal bellows.

Manganese

brass 70 29

1.3%

manga

nese

Most notably used in making golden dollar

coins in the United States.[30]

Muntz metal 60 40

traces

of iron Used as a lining on boats.

Naval brass 59 40 1

Similar to admiralty brass.

Nickel brass 70 24.5

5.5%

nickel

Used to make pound coins in the pound

sterling currency. Also the main constituent

of the bi-metallic One Euro coin and the

centre part of the Two Euro coin.

Nordic gold 89 5 1

5%

alumin

ium

Used in 10, 20, and 50 cents euro coins.


https://en.wikipedia.org/wiki/Brass#cite_note-alcobrametals.com-29

https://en.wikipedia.org/wiki/Cold_work


https://en.wikipedia.org/wiki/Gilding_metal

https://en.wikipedia.org/wiki/Full_metal_jacket_bullet

https://en.wikipedia.org/wiki/Full_metal_jacket_bullet

https://en.wikipedia.org/wiki/Tensile_strength

https://en.wikipedia.org/wiki/Spring_%28device%29

https://en.wikipedia.org/wiki/Screw

https://en.wikipedia.org/wiki/Rivet

https://en.wikipedia.org/wiki/Lead

https://en.wikipedia.org/wiki/Brass#cite_note-info.sen.ca.gov-15

https://en.wikipedia.org/wiki/Bellows

https://en.wikipedia.org/wiki/Manganese


https://en.wikipedia.org/wiki/Dollar_coin_%28United_States%29


https://en.wikipedia.org/wiki/Muntz_metal

https://en.wikipedia.org/wiki/Nickel_brass

https://en.wikipedia.org/wiki/Pound_sterling

https://en.wikipedia.org/wiki/Pound_sterling

https://en.wikipedia.org/wiki/Euro_coins#Specification

https://en.wikipedia.org/wiki/Nordic_gold

https://en.wikipedia.org/wiki/Euro_coins#Small-denomination_coins

5

Prince's metal 75 25

A type of alpha brass. Due to its yellow

color, it is used as an imitation of gold.[31]

Also called Prince Rupert's metal, the

alloy was named after Prince Rupert of the

Rhine.

Red brass, Rose

brass (C230) 85 5 5 5

Both an American term for the copper-

zinc-tin alloy known as gunmetal, and an

alloy which is considered both a brass and

a bronze.[32][33]

Red brass is also an

alternative name for copper alloy C23000,

which is composed of 14–16% zinc, a

minimum 0.05% iron and minimum 0.07%

lead content,[29]

and the remainder

copper.[34]

It may also refer to ounce metal,

another copper-zinc-tin alloy.

Rich low brass,

Tombac 5–20

Often used in jewelry applications.

Silicon tombac 80 16

4%

silicon

Used as an alternative for investment

casted steel parts.

Tonval brass

>0

Also called CW617N or CZ122 or OT58. It

is not recommended for seawater use, being

susceptible to dezincification.[35][36]

Yellow brass 67 33

An American term for 33% zinc brass.

Weldingmethod of brass and copper:- due to composition of zink difficulties is

vaporize zink during welding so we must use oxidizing flame .Copper is high sensitive metal

and heat flow rate very high so we must use backing plate and intermittent welding

methods.

Page 1

Copper is a metal with some very important properties, the main ones being its high electrical

conductivity, its high thermal conductivity, its excellent resistance to corrosion, and its ease of

fabrication, either hot or cold. Copper is also ductile and malleable and has a relatively low

melting point at just over 1080°C. The three basic commercial grades of copper that are available

are: Tough pitch copper, containing up to 0.1% oxygen Phosphorous deoxidised (PDO) copper,

containing up to 0.04% phosphorus Oxygen-free copper, containing no deoxidants The

phosphorus deoxidised grade was originally developed to overcome problems encountered when

flame welding tough pitch copper. It is now the standard commercial weldable grade used for

pressure vessels and radiators. Oxygen-free grades have significantly higher electrical

conductivity than oxygen-containing grades and are therefore used widely as electrical

conductors. Types Copper and copper alloys are generally grouped by compositional type and

identified in standards by number or letter/number designations. However, it has been, and still is,

common practice to refer to copper and copper alloys by their traditional names, such as brass and

bronze, rather than by letters and number designations. Copper and copper alloys may be divided

into groups by general composition, and each group contains a range of specific alloys. The main

groups considered here are: Unalloyed copper Beryllium copper Brasses Bronzes Silicon bronzes

Aluminium bronzes Cupro-nickels. Welding As has been stated earlier, copper has a very high

thermal conductivity and a high coefficient of expansion. These provide the main problems

encountered during welding of unalloyed copper. High levels of preheat and heat inputs are

required for fusion welding. These in turn can cause distortion problems. Copper is also

susceptible to hot cracking so heavy restraint needs to be avoided. The thermal conductivity of



https://en.wikipedia.org/wiki/Prince_Rupert_of_the_Rhine

https://en.wikipedia.org/wiki/Prince_Rupert_of_the_Rhine

https://en.wikipedia.org/wiki/Gunmetal





https://en.wikipedia.org/wiki/Ounce_metal

https://en.wikipedia.org/wiki/Tombac

https://en.wikipedia.org/wiki/Silicon_tombac



6

many copper alloys is relatively low and welding without preheat may be possible. However,

many alloys will crack readily when welded if too much heat is put into the weld area or if

welding is carried out under restraint. Any copper alloys containing lead should not be welded.

Welding Processes Copper and its alloys can be welded, most frequently using inert gas shielded

processes, such as MIG and TIG. MMA is used occasionally for welding some copper alloys and

gas welding and brazing are also used for some applications.

Questions:-

1. What is brass?

2. Right brass welding process.

3. Write three copper alloys.

Next Lesson:- Aluminum and its alloy, properties and weld ability, welding methods. Arc

cutting and gauging.

Assignment:- Brass-types-properties and welding methods. Copper-types-properties and

welding methods.

Checked by………………………….. Instructor……………..


1

LESSON PLAN


Name____________ Week No:- Twenty one

Subject :- Aluminum and its alloy, properties and weld ability, welding methods. Arc cutting

and gauging.

Motivations:- in previous week we learned about Brass-types-properties and welding

methods. Copper-types-properties and welding methods.


INTRODUCTION: - Aluminium or aluminum (in North American English) is a chemical element in the boron group with symbol Al and atomic number 13. It is a silvery-white, soft, nonmagnetic, ductile metal. Aluminium is the third most abundant element in the Earth's crust (after oxygen and silicon) and its most abundant metal. Aluminium makes up about 8% of the crust by mass, though it is less common in the mantle below.

PRESENTATION:-


Aluminium metal is so chemically reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is found combined in over 270 different minerals.[7] The chief ore of aluminium is bauxite.

Aluminium is remarkable for the metal's low density and its ability to resist corrosion through the phenomenon of passivation. Aluminium and its alloys are vital to the aerospace industry and important in transportation and structures, such as building facades and window framesThe oxides and sulfates are the most useful compounds of aluminium.

The weldability of aluminium alloys varies significantly, depending on the chemical composition of the alloy used. Aluminium alloys are susceptible to hot cracking, and to combat the problem, welders increase the welding speed to lower the heat input. Preheating reduces the temperature gradient across the weld zone and thus helps reduce hot cracking, but it can reduce the mechanical properties of the base material and should not be used when the base material is restrained. The design of the joint can be changed as well, and a more compatible filler alloy can be selected to decrease the likelihood of hot cracking. Aluminium alloys should also be cleaned prior to welding, with the goal of removing all oxides, oils, and loose particles from the surface to be welded. This is especially important because of an aluminium weld's susceptibility to porosity due to hydrogen and dross due to oxygen.

Aluminium alloys (or aluminum alloys; see spelling differences) are alloys in which aluminium (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon, tin and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories heat-treatable and non-heat-treatable. About 85% of aluminium is used for wrought products, for example rolled plate, foils and extrusions. Cast aluminium alloys yield cost-effective products due to the low melting point, although they generally have lower tensile strengths than wrought alloys. The most important cast aluminium alloy system is Al–Si, where the high levels of silicon (4.0–13%) contribute to give good casting characteristics. Aluminium alloys are widely used in engineering structures and components where light weight or corrosion resistance is required.[1]

Alloys composed mostly of aluminium have been very important in aerospace manufacturing since the introduction of metal-skinned aircraft. Aluminium-magnesium alloys are both lighter than other aluminium alloys and much less flammable than alloys that contain a very high percentage of


https://en.wikipedia.org/wiki/North_American_English

https://en.wikipedia.org/wiki/Chemical_element

https://en.wikipedia.org/wiki/Chemical_element

https://en.wikipedia.org/wiki/Boron_group

https://en.wikipedia.org/wiki/Atomic_number

https://en.wikipedia.org/wiki/Ductility


https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust

https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust

https://en.wikipedia.org/wiki/Oxygen

https://en.wikipedia.org/wiki/Silicon

https://en.wikipedia.org/wiki/Native_metal

https://en.wikipedia.org/wiki/Redox

https://en.wikipedia.org/wiki/Mineral

https://en.wikipedia.org/wiki/Aluminium#cite_note-7

https://en.wikipedia.org/wiki/Ore

https://en.wikipedia.org/wiki/Bauxite

https://en.wikipedia.org/wiki/Density

https://en.wikipedia.org/wiki/Corrosion

https://en.wikipedia.org/wiki/Passivation_(chemistry)

https://en.wikipedia.org/wiki/Aluminium_alloy

https://en.wikipedia.org/wiki/Aerospace

https://en.wikipedia.org/wiki/Transport

https://en.wikipedia.org/wiki/Oxides

https://en.wikipedia.org/wiki/Sulfates

https://en.wikipedia.org/wiki/Aluminium

https://en.wikipedia.org/wiki/Oxide

https://en.wikipedia.org/wiki/Oil

https://en.wikipedia.org/wiki/Dross

https://en.wikipedia.org/wiki/American_and_British_English_spelling_differences

https://en.wikipedia.org/wiki/Alloys

https://en.wikipedia.org/wiki/Aluminium

https://en.wikipedia.org/wiki/Copper

https://en.wikipedia.org/wiki/Magnesium



https://en.wikipedia.org/wiki/Tin

https://en.wikipedia.org/wiki/Zinc

https://en.wikipedia.org/wiki/Casting

https://en.wikipedia.org/wiki/Heat_treatment

https://en.wikipedia.org/wiki/Extruding


https://en.wikipedia.org/wiki/Silumin

https://en.wikipedia.org/wiki/Aluminium_alloy#cite_note-ReferenceA-1

https://en.wikipedia.org/wiki/Aerospace_manufacturing

2

magnesium.[2]

Aluminium alloy surfaces will develop a white, protective layer of aluminium oxide if left unprotected by anodizing and/or correct painting procedures. In a wet environment, galvanic corrosion can occur when an aluminium alloy is placed in electrical contact with other metals with more positive corrosion potentials than aluminium, and an electrolyte is present that allows ion exchange. Referred to as dissimilar-metal corrosion, this process can occur as exfoliation or as intergranular corrosion. Aluminium alloys can be improperly heat treated. This causes internal element separation, and the metal then corrodes from the inside out.[citation needed]

Aluminium alloy compositions are registered with The Aluminum Association. Many organizations publish more specific standards for the manufacture of aluminium alloy, including the Society of Automotive Engineers standards organization, specifically its aerospace standards subgroups,

Aluminium alloys with a wide range of properties are used in engineering structures. Alloy systems are classified by a number system (ANSI) or by names indicating their main alloying constituents (DIN and ISO). Selecting the right alloy for a given application entails considerations of its tensile strength, density, ductility, formability, workability, weldability, and corrosion resistance, to name a few. A brief historical overview of alloys and manufacturing technologies is given in Ref.[4]Aluminium alloys are used extensively in aircraft due to their high strength-to-weight ratio. On the other hand, pure aluminium metal is much too soft for such uses, and it does not have the high tensile strength that is needed for airplanes and helicopters.

Often, the metal's sensitivity to heat must also be considered. Even a relatively routine workshop procedure involving heating is complicated by the fact that aluminium, unlike steel, will melt without first glowing red. Forming operations where a blow torch is used can reverse or remove heat treating, therefore is not advised whatsoever. No visual signs reveal how the material is internally damaged. Much like welding heat treated, high strength link chain, all strength is now lost by heat of the torch. The chain is dangerous and must be discarded.

Aluminium is subject to internal stresses and strains. Sometimes years later, as is the tendency of improperly welded aluminium bicycle frames to gradually twist out of alignment from the stresses of the welding process. Thus, the aerospace industry avoids heat altogether by joining parts with rivets of like metal composition, other fasteners, or adhesives.

Stresses in overheated aluminium can be relieved by heat-treating the parts in an oven and gradually cooling it—in effect annealing the stresses. Yet these parts may still become distorted, so that heat-treating of welded bicycle frames, for instance, can result in a significant fraction becoming misaligned. If the misalignment is not too severe, the cooled parts may be bent into alignment. Of course, if the frame is properly designed for rigidity (see above), that bending will require enormous force.

Aluminium's intolerance to high temperatures has not precluded its use in rocketry; even for use in constructing combustion chambers where gases can reach 3500 K. The Agena upper stage engine used a regeneratively cooled aluminium design for some parts of the nozzle, including the thermally critical throat region; in fact the extremely high thermal conductivity of aluminium prevented the throat from reaching the melting point even under massive heat flux, resulting in a reliable, lightweight component.

The Aluminum Association (AA) has adopted a nomenclature similar to that of wrought alloys. British Standard and DIN have different designations. In the AA system, the second two digits reveal the minimum percentage of aluminium, e.g. 150.x correspond to a minimum of 99.50% aluminium. The digit after the decimal point takes a value of 0 or 1, denoting casting and ingot respectively.[1] The main alloying elements in the AA system are as follows

1xx.x series are minimum 99% aluminium

2xx.x series copper

3xx.x series silicon, copper and/or magnesium

4xx.x series silicon

5xx.x series magnesium

7xx.x series zinc

8xx.x series tin

9xx.x other elements


https://en.wikipedia.org/wiki/Aluminium_alloy#cite_note-2

https://en.wikipedia.org/wiki/Aluminium_oxide

https://en.wikipedia.org/wiki/Galvanic_corrosion


https://en.wikipedia.org/wiki/The_Aluminum_Association

https://en.wikipedia.org/wiki/Society_of_Automotive_Engineers

https://en.wikipedia.org/wiki/Society_of_Automotive_Engineers

https://en.wikipedia.org/wiki/American_National_Standards_Institute

https://en.wikipedia.org/wiki/Deutsches_Institut_f%C3%BCr_Normung

https://en.wikipedia.org/wiki/International_Organization_of_Standardization



https://en.wikipedia.org/wiki/Density

https://en.wikipedia.org/wiki/Ductility

https://en.wikipedia.org/wiki/Weldability

https://en.wikipedia.org/wiki/Corrosion

https://en.wikipedia.org/wiki/Aluminium_alloy#cite_note-sanders-4

https://en.wikipedia.org/wiki/Helicopter

https://en.wikipedia.org/wiki/Annealing_(metallurgy)

https://en.wikipedia.org/wiki/RM-81_Agena

https://en.wikipedia.org/wiki/The_Aluminum_Association

https://en.wikipedia.org/wiki/British_Standard

https://en.wikipedia.org/wiki/British_Standard

https://en.wikipedia.org/wiki/Aluminium_alloy#cite_note-ReferenceA-1

3

Wrought aluminium alloy composition limits (% weight)

Alloy Si Fe Cu Mn Mg Cr Zn V Ti Bi Ga Pb Zr

Limits††

Al

Each

Total

1050[9

]0.25 0.40 0.05 0.05 0.05

0.05

0.03

99.5 min

1060 0.25 0.35 0.05 0.03 0.03 0.03 0.05 0.05 0.03 0.03 0.03 0.03 0.03 0.03

99.6 min

1100 0.95 Si+Fe 0.05–

0.05

0.10

0.05 0.15 99.0 min

1199[9

]0.006

0.006

0.006

0.002

0.006

0.006

0.005

0.002

0.005

0.002

99.99 min

2014 0.50–1.2

0.7 3.9–5.0

0.40–1.2

0.20–0.8

0.10 0.25

0.15

0.05 0.15 remainder

2024 0.50 0.50 3.8–4.9

0.30–0.9

1.2–1.8

0.10 0.25

0.15

0.05 0.15 remainder

2219 0.2 0.30 5.8–6.8

0.20–

0.02

0.10 0.05–

0.02–

0.10–

0.05 0.15 remainder

3003 0.6 0.7 0.05–

1.0–1.5

0.10

0.05 0.15 remainder

3004 0.30 0.7 0.25 1.0–1.5

0.8–1.3

0.25

0.05 0.15 remainder

3102 0.40 0.7 0.10 0.05–

0.30

0.10

0.05 0.15 remainder

4041 4.5–6.0

0.80 0.30 0.05 0.05

0.10

0.20

0.05 0.15 remainder

5005 0.3 0.7 0.2 0.2 0.5-1.1

0.1 0.25

0.05 0.15 remainder

5052 0.25 0.40 0.10 0.10 2.2–2.8

0.15–

0.10

0.05 0.15 remainder

5083 0.40 0.40 0.10 0.40–1.0

4.0–4.9

0.05–

0.25

0.15

0.05 0.15 remainder

5086 0.40 0.50 0.10 0.20–0.7

3.5–4.5

0.05–

0.25

0.15

0.05 0.15 remainder

5154 0.25 0.40 0.10 0.10 3.10–

0.15–

0.20

0.20

0.05 0.15 remainder

5356 0.25 0.40 0.10 0.10 4.50–

0.05–

0.10

0.06–

0.05 0.15 remainder

5454 0.25 0.40 0.10 0.50–1.0

2.4–3.0

0.05–

0.25

0.20

0.05 0.15 remainder

5456 0.25 0.40 0.10 0.50–1.0

4.7–5.5

0.05–

0.25

0.20

0.05 0.15 remainder

5754 0.40 0.40 0.10 0.50 2.6–3.6

0.30 0.20

0.15

0.05 0.15 remainder

6005 0.6–0.9

0.35 0.10 0.10 0.40–0.6

0.10 0.10

0.10

0.05 0.15 remainder

6005A†

0.50–0.9

0.35 0.30 0.50 0.40–0.7

0.30 0.20

0.10

0.05 0.15 remainder

6060 0.30–0.6

0.10–

0.10 0.10 0.35–0.6

0.05 0.15

0.10

0.05 0.15 remainder



https://en.wikipedia.org/wiki/Iron




https://en.wikipedia.org/wiki/Chromium

https://en.wikipedia.org/wiki/Zinc

https://en.wikipedia.org/wiki/Vanadium

https://en.wikipedia.org/wiki/Titanium

https://en.wikipedia.org/wiki/Bismuth

https://en.wikipedia.org/wiki/Gallium

https://en.wikipedia.org/wiki/Lead

https://en.wikipedia.org/wiki/Zirconium

https://en.wikipedia.org/wiki/1050_aluminium_alloy


https://en.wikipedia.org/wiki/Aluminium_alloy#cite_note-asm-v2-9





https://en.wikipedia.org/wiki/Aluminium_alloy#cite_note-asm-v2-9







https://en.wikipedia.org/w/index.php?title=4043_aluminium_alloy&action=edit&redlink=1











https://en.wikipedia.org/wiki/6005A_aluminium_alloy

https://en.wikipedia.org/wiki/6005A_aluminium_alloy


4

6061 0.40–0.8

0.7 0.15–

0.15 0.8–1.2

0.04–

0.25 0.15 0.05 0.15 remainder

6063 0.20–0.6

0.35 0.10 0.10 0.45–0.9

0.10 0.10

0.10

0.05 0.15 remainder

6066 0.9–1.8

0.50 0.7–1.2

0.6–1.1

0.8–1.4

0.40 0.25

0.20

0.05 0.15 remainder

6070 1.0–1.7

0.50 0.15–

0.40–1.0

0.50–1.2

0.10 0.25

0.15

0.05 0.15 remainder

6082 0.7–1.3

0.50 0.10 0.40–1.0

0.60–1.2

0.25 0.20

0.10

0.05 0.15 remainder

6105 0.6–1.0

0.35 0.10 0.10 0.45–0.8

0.10 0.10

0.10

0.05 0.15 remainder

6162 0.40–0.8

0.50 0.20 0.10 0.7–1.1

0.10 0.25

0.10

0.05 0.15 remainder

6262 0.40–0.8

0.7 0.15–

0.15 0.8–1.2

0.04–

0.25

0.15 0.40–0.7

0.40–0.7

0.05 0.15 remainder

6351 0.7–1.3

0.50 0.10 0.40–0.8

0.40–0.8

0.20

0.20

0.05 0.15 remainder

6463 0.20–0.6

0.15 0.20 0.05 0.45–0.9

0.05

0.05 0.15 remainder

7005 0.35 0.40 0.10 0.20–

1.0–1.8

0.06–

4.0–5.0

0.01–

0.08–

0.05 0.15 remainder

7022 0.50 0.50 0.50–

0.10–

2.60–

0.10–

4.30–

0.20

0.05 0.15 remainder

7068 0.12 0.15 1.60–

0.10 2.20–

0.05 7.30–

0.01

0.05–

0.05 0.15 remainder

7072 0.7 Si+Fe 0.10 0.10 0.10

0.8–1.3

0.05 0.15 remainder

7075 0.40 0.50 1.2–2.0

0.30 2.1–2.9

0.18–

5.1–6.1

0.20

0.05 0.15 remainder

7079 0.3 0.40 0.40–

0.10–

2.9–3.7

0.10–

3.8–4.8

0.10

0.05 0.15 remainder

7116 0.15 0.30 0.50–1.1

0.05 0.8–1.4

4.2–5.2

0.05 0.05

0.03

0.05 0.15 remainder

7129 0.15 0.30 0.50–0.9

0.10 1.3–2.0

0.10 4.2–5.2

0.05 0.05

0.03

0.05 0.15 remainder

7178 0.40 0.50 1.6–2.4

0.30 2.4–3.1

0.18–

6.3–7.3

0.20

0.05 0.15 remainder





















5

Arc Gouging The main advantage of manual metal arc (MMA) gouging is that the same power source can be used for

welding, gouging, or cutting, simply by changing the type of electrode.

As in conventional MMA welding, the arc is formed between the tip of the electrode and the workpiece.

MMA gouging differs because it requires special purpose electrodes with thick flux coatings to generate

a strong arc force and gas stream. Unlike MMA welding where a stable weld pool must be maintained,

this process forces the molten metal away from the arc zone to leave a clean cut surface.

The gouging process is characterised by the large amount of gas which is generated to eject the molten

metal. However, because the arc/gas stream is not as powerful as a gas or a separate air jet, the

surface of the gouge is not as smooth as an oxyfuel gouge or air carbon arc gouge.

MMA gouging is used for localised gouging operations, removal of defects for example, and where it is

more convenient to switch from a welding electrode to a gouging electrode rather than use specialised

equipment. Compared with alternative gouging processes, metal removal rates are low and the quality

of the gouged surface is inferior.

When correctly applied, MMA gouging can produce relatively clean gouged surfaces. For general

applications, welding can be carried out without the need to dress by grinding. However, when gouging

stainless steel, a thin layer of higher carbon content material will be produced; this should be removed

by grinding.

According to the size of gouge specified, there is a wide range of electrode diameters available. These

grooving electrodes are also not just restricted to steels, the same electrode composition may be used

for gouging stainless steel and non-ferrous alloys.

TWI can provide you with technical support, including:

Welding Engineering Helpdesk: call our qualified welding engineers or metallurgists free of charge

Consultancy on fabrication problems

Technology audit: TWI can review your welding procedures impartially; can assess your workshop

layout and quality management system and can improve your quality and reduce your costs

Visit TWI to take advantage of the latest technical developments and discuss your business needs

Re-appraise your products and be offered recommendations on alternative designs, materials and

innovative joining processes

TWI is noted for its experience on Health and Safety about fume (and hazards) emanating from cutting

processes.

TWI can help your company developing, supervising/implementing and providing guidance on specialist

cutting procedures for a wide range of applications across all industry sectors.


6

Air carbon arc cutting previously known as air arc cutting,[1] is an arc cutting process where metal is cut and melted by the heat of a carbon arc. Molten metal is then removed by a blast of air. It employs a consumable carbon or graphite electrode to melt the material, which is then blown away by an air jet. This process is useful for cutting a variety of materials, but it is most often used for cutting, and gouging aluminum, copper, iron, magnesium, and carbon and stainless steels. Because the metal is blown away by the air jet, it does not need to be oxidized. This process differs from plasma cutting operations because in air carbon cutting, an open, or un-constricted, arc is used, and the arc operates separately from the air jet.[2] Air pressures for the jet usually vary from 60 to 100 psig. The carbon electrode can be worn away by oxidation from heat buildup. This can be reduced by coating the carbon electrodes with copper. The sharpened carbon electrode is drawn along the metal, an arc forms and melts the metal. The air jet is then used to blow away molten material. This can be dangerous as the molten material can be blown substantial distances.[3] The process is also very noisy.

Questions:-

1. What is aluminum?

2. Right aluminum welding process.

3. Write three aluminum alloys.

Next Lesson:- Cast iron –its properties and types.welding methods of cast iron.

Assignment:- Aluminum and its alloy, properties and weld ability, welding methods. Arc

cutting and gauging.



https://en.wikipedia.org/wiki/Air_carbon_arc_cutting#cite_note-1

https://en.wikipedia.org/wiki/Cutting


https://en.wikipedia.org/wiki/Cutting

https://en.wikipedia.org/wiki/Melted

https://en.wikipedia.org/wiki/Heat

https://en.wikipedia.org/wiki/Air

https://en.wikipedia.org/wiki/Plasma_cutting

https://en.wikipedia.org/wiki/Plasma_cutting



1

LESSON PLAN


Name____________ Week No:- Twenty Two

Subject :- Cast iron –its properties and types.welding methods of cast iron.

Motivations:- in previous week we learned about Aluminum and its alloy, properties and weld

ability, welding methods. Arc cutting and gauging.


INTRODUCTION: - Cast iron is a group of iron-carbon alloys with a carbon content greater than 2%.[1] Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its colour when fractured: white cast iron has carbideimpurities which allow cracks to pass straight through; grey cast iron has graphite flakes which deflect a passing crack and initiate countless new cracks as the material breaks; ductile cast iron which stops the crack from further progressing due to their spherical graphite "nodules". PRESENTATION:-


Carbon (C) ranging from 1.8–4 wt%, and silicon (Si) 1–3 wt% are the main alloying elements of cast iron. Iron alloys with less carbon content are known as steel. While this technically makes the Fe–C–Si system ternary, the principle of cast iron solidification can be understood from the simpler binary iron–carbon phase diagram. Since the compositions of most cast irons are around the eutectic point (lowest liquid point) of the iron–carbon system, the melting temperatures usually range from 1,150 to 1,200 °C (2,100 to 2,190 °F), which is about 300 °C (540 °F) lower than the melting point of pure iron.

Cast iron tends to be brittle, except for malleable cast irons. With its relatively low melting point, good fluidity, castability, excellent machinability, resistance to deformation and wear resistance, cast irons have become an engineering material with a wide range of applications and are used in pipes, machines and automotive industry parts, such as cylinder heads (declining usage), cylinder blocks and gearbox cases (declining usage). It is resistant to destruction and weakening by oxidation (rust).

Production:-

Cast iron is made by re-melting pig iron, often along with substantial quantities of iron, steel, limestone, carbon (coke) and taking various steps to remove undesirable contaminants. Phosphorus and sulfur may be burnt out of the molten iron, but this also burns out the carbon, which must be replaced. Depending on the application, carbon and silicon content are adjusted to the desired levels, which may be anywhere from 2–3.5% and 1–3%, respectively. Other elements are then added to the melt before the final form is produced by casting.[citation needed]

Cast iron is sometimes melted in a special type of blast furnace known as a cupola, but in modern applications, it is more often melted in electric induction furnacesor electric arc furnaces.[4] After melting is complete, the molten cast iron is poured into a holding furnace or ladle.

Alloying elements

Cast iron's properties are changed by adding various alloying elements, or alloyants. Next to carbon, silicon is the most important alloyant because it forces carbon out of solution. A low percentage of silicon allows carbon to remain in solution forming iron carbide and the production of


https://en.wikipedia.org/wiki/Iron

https://en.wikipedia.org/wiki/Carbon

https://en.wikipedia.org/wiki/Alloys

https://en.wikipedia.org/wiki/Cast_iron#cite_note-1

https://en.wikipedia.org/wiki/Carbide

https://en.wikipedia.org/wiki/Grey_iron

https://en.wikipedia.org/wiki/Ductile_iron


https://en.wikipedia.org/wiki/Steel

https://en.wikipedia.org/wiki/Binary_compound

https://en.wikipedia.org/wiki/Eutectic_point

https://en.wikipedia.org/wiki/Brittle

https://en.wikipedia.org/wiki/Malleable_iron

https://en.wikipedia.org/wiki/Castability

https://en.wikipedia.org/wiki/Machinability

https://en.wikipedia.org/wiki/Wear_resistance

https://en.wikipedia.org/wiki/Engineering_material

https://en.wikipedia.org/wiki/Cast_iron_pipe

https://en.wikipedia.org/wiki/Automotive_industry

https://en.wikipedia.org/wiki/Cylinder_head

https://en.wikipedia.org/wiki/Cylinder_block

https://en.wikipedia.org/wiki/Cylinder_block

https://en.wikipedia.org/wiki/Gearbox

https://en.wikipedia.org/wiki/Oxidation

https://en.wikipedia.org/wiki/Rust

https://en.wikipedia.org/wiki/Pig_iron

https://en.wikipedia.org/wiki/Phosphorus

https://en.wikipedia.org/wiki/Sulfur

https://en.wikipedia.org/wiki/Casting_(metalworking)


https://en.wikipedia.org/wiki/Blast_furnace

https://en.wikipedia.org/wiki/Cupola_furnace

https://en.wikipedia.org/wiki/Induction_furnace


https://en.wikipedia.org/wiki/Alloyant

https://en.wikipedia.org/wiki/Carbon


2

white cast iron. A high percentage of silicon forces carbon out of solution forming graphite and the production of grey cast iron. Other alloying agents, manganese, chromium, molybdenum, titanium and vanadium counteracts silicon, promotes the retention of carbon, and the formation of those carbides. Nickel and copper increase strength, and machinability, but do not change the amount of graphite formed. The carbon in the form of graphiteresults in a softer iron, reduces shrinkage, lowers strength, and decreases density. Sulfur, largely a contaminant when present, forms iron sulfide, which prevents the formation of graphite and increases hardness. The problem with sulfur is that it makes molten cast iron viscous, which causes defects. To counter the effects of sulfur, manganese is added because the two form into manganese sulfide instead of iron sulfide. The manganese sulfide is lighter than the melt so it tends to float out of the melt and into the slag. The amount of manganese required to neutralize sulfur is 1.7 × sulfur content + 0.3%. If more than this amount of manganese is added, then manganese carbide forms, which increases hardness and chilling, except in grey iron, where up to 1% of manganese increases strength and density.[5]

Nickel is one of the most common alloying elements because it refines the pearlite and graphite structure, improves toughness, and evens out hardness differences between section thicknesses. Chromium is added in small amounts to reduce free graphite, produce chill, and because it is a powerful carbide stabilizer; nickel is often added in conjunction. A small amount of tin can be added as a substitute for 0.5% chromium. Copper is added in the ladle or in the furnace, on the order of 0.5–2.5%, to decrease chill, refine graphite, and increase fluidity. Molybdenum is added on the order of 0.3–1% to increase chill and refine the graphite and pearlite structure; it is often added in conjunction with nickel, copper, and chromium to form high strength irons. Titanium is added as a degasser and deoxidizer, but it also increases fluidity. 0.15–0.5% vanadium is added to cast iron to stabilize cementite, increase hardness, and increase resistance to wear and heat. 0.1–0.3% zirconium helps to form graphite, deoxidize, and increase fluidity.[5]

In malleable iron melts, bismuth is added, on the scale of 0.002–0.01%, to increase how much silicon can be added. In white iron, boron is added to aid in the production of malleable iron; it also reduces the coarsening effect of bismuth.[5]

Grey cast iron[edit] Main article: Grey iron

Grey cast iron is characterised by its graphitic microstructure, which causes fractures of the material to have a grey appearance. It is the most commonly used cast iron and the most widely used cast material based on weight. Most cast irons have a chemical composition of 2.5–4.0% carbon, 1–3% silicon, and the remainder iron. Grey cast iron has less tensile strength and shock resistance than steel, but its compressive strength is comparable to low- and medium-carbon steel. These mechanical properties are controlled by the size and shape of the graphite flakes present in the microstructure and can be characterised according to the guidelines given by the ASTM.[6]

White cast iron[edit]

White cast iron displays white fractured surfaces due to the presence of an iron carbide precipitate called cementite. With a lower silicon content (graphitizing agent) and faster cooling rate, the carbon in white cast iron precipitates out of the melt as the metastable phase cementite, Fe3C, rather than graphite. The cementite which precipitates from the melt forms as relatively large particles. As the iron carbide precipitates out, it withdraws carbon from the original melt, moving the mixture toward one that is closer to eutectic, and the remaining phase is the lower iron-carbon austenite (which on cooling might transform to martensite). These eutectic carbides are much too large to provide the benefit of what is called precipitation hardening (as in some steels, where much smaller cementite precipitates might inhibit plastic deformation by impeding the movement of dislocations through the pure iron ferrite matrix). Rather, they increase the bulk hardness of the cast iron simply by virtue of their own very high hardness and their substantial volume fraction, such that the bulk hardness can be approximated by a rule of mixtures. In any case, they offer hardness at the expense of toughness. Since carbide makes up a large fraction of the material, white cast iron could reasonably be classified as a cermet. White iron is too brittle for use in many structural components, but with good hardness and abrasion resistance and relatively low cost, it finds use in such applications as the wear surfaces (impeller and volute) of slurry pumps, shell liners and lifter bars in ball mills and autogenous grinding mills, balls and rings in coal pulverisers, and the teeth of a backhoe's digging bucket (although cast medium-carbon martensitic steel is more common for this application).

It is difficult to cool thick castings fast enough to solidify the melt as white cast iron all the way


https://en.wikipedia.org/wiki/Graphite

https://en.wikipedia.org/wiki/Sulfur

https://en.wikipedia.org/wiki/Iron(II)_sulfide

https://en.wikipedia.org/wiki/Hardness


https://en.wikipedia.org/wiki/Manganese_sulfide

https://en.wikipedia.org/wiki/Slag

https://en.wikipedia.org/w/index.php?title=Manganese_carbide&action=edit&redlink=1

https://en.wikipedia.org/wiki/Chill_(foundry)

https://en.wikipedia.org/wiki/Cast_iron#cite_note-gillespie-5

https://en.wikipedia.org/wiki/Nickel

https://en.wikipedia.org/wiki/Pearlite

https://en.wikipedia.org/wiki/Chromium

https://en.wikipedia.org/wiki/Carbide

https://en.wikipedia.org/wiki/Tin


https://en.wikipedia.org/wiki/Molybdenum

https://en.wikipedia.org/wiki/Titanium

https://en.wikipedia.org/wiki/Vanadium

https://en.wikipedia.org/wiki/Wear

https://en.wikipedia.org/wiki/Zirconium


https://en.wikipedia.org/wiki/Bismuth

https://en.wikipedia.org/wiki/Boron


https://en.wikipedia.org/w/index.php?title=Cast_iron&action=edit&section=4

https://en.wikipedia.org/wiki/Grey_iron


https://en.wikipedia.org/wiki/Shock_resistance

https://en.wikipedia.org/wiki/Compressive_strength

https://en.wikipedia.org/wiki/ASTM_International



https://en.wikipedia.org/wiki/Metastable

https://en.wikipedia.org/wiki/Cementite

https://en.wikipedia.org/wiki/Austenite

https://en.wikipedia.org/wiki/Martensite

https://en.wikipedia.org/wiki/Plastic_deformation

https://en.wikipedia.org/wiki/Dislocation

https://en.wikipedia.org/wiki/Hardness

https://en.wikipedia.org/wiki/Toughness

https://en.wikipedia.org/wiki/Cermet

https://en.wikipedia.org/wiki/Impeller

https://en.wikipedia.org/wiki/Volute_(pump)

https://en.wikipedia.org/wiki/Slurry_pump

https://en.wikipedia.org/w/index.php?title=Lifter_bar&action=edit&redlink=1

https://en.wikipedia.org/wiki/Ball_mill

https://en.wikipedia.org/wiki/Autogenous_grinding_mill

https://en.wikipedia.org/wiki/Autogenous_grinding_mill

https://en.wikipedia.org/w/index.php?title=Coal_pulveriser&action=edit&redlink=1

https://en.wikipedia.org/wiki/Backhoe

3

through. However, rapid cooling can be used to solidify a shell of white cast iron, after which the remainder cools more slowly to form a core of grey cast iron. The resulting casting, called a chilled casting, has the benefits of a hard surface with a somewhat tougher interior.

High-chromium white iron alloys allow massive castings (for example, a 10-tonne impeller) to be sand cast, as the chromium reduces cooling rate required to produce carbides through the greater thicknesses of material. Chromium also produces carbides with impressive abrasion resistance.[citation

needed] These high-chromium alloys attribute their superior hardness to the presence of chromium carbides. The main form of these carbides are the eutectic or primary M7C3carbides, where "M" represents iron or chromium and can vary depending on the alloy's composition. The eutectic carbides form as bundles of hollow hexagonal rods and grow perpendicular to the hexagonal basal plane. The hardness of these carbides are within the range of 1500-1800HV[7]

Malleable cast iron[edit] Main article: Malleable iron

Malleable iron starts as a white iron casting that is then heat treated for a day or two at about 950 °C (1,740 °F) and then cooled over a day or two. As a result, the carbon in iron carbide transforms into graphite and ferrite plus carbon (austenite). The slow process allows the surface tension to form the graphite into spheroidal particles rather than flakes. Due to their lower aspect ratio, the spheroids are relatively short and far from one another, and have a lower cross section vis-a-vis a propagating crack or phonon. They also have blunt boundaries, as opposed to flakes, which alleviates the stress concentration problems found in grey cast iron. In general, the properties of malleable cast iron are more like those of mild steel. There is a limit to how large a part can be cast in malleable iron, as it is made from white cast iron.

Ductile cast iron[edit] Main article: Ductile cast iron

Developed in 1948, nodular or ductile cast iron has its graphite in the form of very tiny nodules with the graphite in the form of concentric layers forming the nodules. As a result, the properties of ductile cast iron are that of a spongy steel without the stress concentration effects that flakes of graphite would produce. Tiny amounts of 0.02 to 0.1% magnesium, and only 0.02 to 0.04% cerium added to these alloys slow the growth of graphite precipitates by bonding to the edges of the graphite planes. Along with careful control of other elements and timing, this allows the carbon to separate as spheroidal particles as the material solidifies. The properties are similar to malleable iron, but parts can be cast with larger sections.

Comparative qualities of cast irons[8]

Name Nominal composition

Form and condition

Yield strength

Tensile strength

Elongation [% (in

Hardness [Brinell

Uses

Grey cast iron

C 3.4, Si 1.8, Mn 0.5

Cast — 50 0.5 260 Engine cylinder blocks, flywheels, gearbox

White cast iron

C 3.4, Si 0.7, Mn 0.6

Cast (as cast)

— 25 0 450 Bearing surfaces

Malleable iron (ASTM

C 2.5, Si 1.0, Mn 0.55

Cast (annealed)

33 52 12 130 Axle bearings, track wheels, automotive crankshafts

Ductile or nodular iron

C 3.4, P 0.1, Mn 0.4, Ni 1.0,

Cast 53 70 18 170 Gears, camshafts, crankshafts

Ductile or nodular iron

— cast (quench

108 135 5 310 —

Ni-hard type 2

C 2.7, Si 0.6, Mn 0.5, Ni 4.5,

Sand-cast — 55 — 550 High strength applications

Ni-resist type 2

C 3.0, Si 2.0, Mn 1.0,

Cast — 27 2 140 Resistance to heat and corrosion






https://en.wikipedia.org/wiki/Malleable_iron

https://en.wikipedia.org/wiki/Heat_treatment

https://en.wikipedia.org/wiki/Surface_tension

https://en.wikipedia.org/wiki/Aspect_ratio

https://en.wikipedia.org/wiki/Cross_section_(geometry)

https://en.wikipedia.org/wiki/Phonon

https://en.wikipedia.org/wiki/Mild_steel


https://en.wikipedia.org/wiki/Ductile_cast_iron


https://en.wikipedia.org/wiki/Cerium


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https://en.wikipedia.org/wiki/Brinell_scale

https://en.wikipedia.org/wiki/ASTM_International


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https://en.wikipedia.org/wiki/Flywheel

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https://en.wikipedia.org/w/index.php?title=Gearbox_case&action=edit&redlink=1

https://en.wikipedia.org/wiki/Bearing_(mechanical)

https://en.wikipedia.org/wiki/Axle

https://en.wikipedia.org/wiki/Crankshaft

https://en.wikipedia.org/wiki/Nickel

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A cast iron is an alloy of iron, carbon, and silicon, in which the amount of carbon is usually more

than 1.7 percent and less than 4.5 percent. The overall weldability of cast iron is low and depends

on the material type, complexity, thickness, casting complexity and need for machinability. Ductile

and malleable irons have good weldability while grey cast iron and white cast iron are only weldable

for small attachments.

The most widely used type of cast iron is known as gray iron. Gray iron has a variety of

compositions, but is usually such that it is primarily perlite with many graphite flakes dispersed

throughout.

There are also alloy cast irons which contain small amounts of chromium, nickel, molybdenum,

copper, or other elements added to provide specific properties.

Another alloy iron is austenitic cast iron, which is modified by additions of nickel and other elements

to reduce the transformation temperature so that the structure is austenitic at room or normal

temperatures. Austenitic cast irons have a high degree of corrosion resistance.

In white cast iron, almost all the carbon is in the combined form. This provides a cast iron with

higher hardness, which is used for abrasion resistance.

Malleable cast iron is made by giving white cast iron a special annealing heat treatment to change

the structure of the carbon in the iron. The structure is changed to perlitic or ferritic, which increases

its ductility.

Nodular iron and ductile cast iron are made by the addition of magnesium or aluminum which will

either tie up the carbon in a combined state or will give the free carbon a spherical or nodular

shape, rather than the normal flake shape in gray cast iron. This structure provides a greater degree

of ductility or malleability of the casting.

A major factor contributing to the difficulty of welding cast iron

is its lack of ductility. If cast irons are loaded beyond their yield

points, they break rather than deform to any significant extent. Weld

filler metal and part configuration should therefore be selected to

minimize welding stresses.

MMA, flux cored arc, MIG, TIG and gas welding processes are

normally used with nickel-based welding consumables to produce

high-quality welds, but cast iron and steel electrodes can also

produce satisfactory welds in certain alloys.

Weldability by Metal Type

Table Credit:TWI


5

Applications These types of metal are widely used in:

agricultural equipment on machine tools as bases, brackets, and covers

for pipe fittings cast iron pipe

automobile engine blocks, heads, manifolds water preps

repair defects in order to upgrade or salvage a casting before service It is rarely used in structural work except for compression members. It is

widely used in construction machinery for counterweights and in other applications for which weight is required.

Characteristics

Grey (Gray) or flake graphite

Where the graphite exists as branched interconnected flakes; this

type of iron is relatively cheap and has poor mechanical properties. Grey irons are usually weldable with MMA(SMA), MIG (GMA)

or FCAW as long as special consumables and procedures are used. Gray cast iron has low ductility and therefore will not expand or

stretch to any considerable extent before breaking or cracking. Because of this characteristic, preheating is necessary when cast iron

is welded by the oxyacetylene welding process. It can, however, be welded with the metal-arc process without preheating if the welding

heat is carefully controlled. This can be accomplished by welding only

short lengths of the joint at a time and allowing these sections to cool. By this procedure, the heat of welding is confined to a small

area, and the danger of cracking the casting is eliminated. Large castings with complicated sections, such as motor blocks, can be

welded without dismantling or preheating. Special electrodes

designed for this purpose are usually desirable. Ductile cast irons,

such as malleable iron, ductile iron, and nodular iron, can be successfully welded. For best results, these types of cast irons should

be welded in the annealed condition. Nodular or spheroidal graphite (ductile iron)

Where the graphite exists as graphite in a spheroidal form and the mechanical properties approach those of steel. Nodular irons are

generally easier to weld than grey irons, but still require special consumables and procedures.

Malleable CI

Where the graphite exists as nodules or rosettes produced by heat treatment. Malleable irons have two main forms: blackheart

malleable, which has similar weldability to nodular cast iron, and


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whiteheart malleable, which is readily weldable with ferritic consumables provided care is taken to limit penetration.

White A hard, brittle iron containing no free graphite. White irons are

generally considered unweldable. Austenitic

Where the graphite may exist in either flake or nodular form, resulting in good corrosion and heat resistance. Many grades of

austenitic irons can be welded with special consumables and procedures.

CI with High Silicon and Aluminum Content Where the graphite exists mainly as flakes and the material has good

corrosion resistance. This alloy can be welded with special consumables and procedures.

Tips for Repairing a Crack in Cast Iron Most problems have to do with the high carbon content. This results in

cracking problems and thermal control issues. Cast irons have

approximately 2 to 4% carbon. Stick welding can be used to repair castings with several types of welds

that are machine friendly: nickel 55 soft weld

nickel 99 soft weld HTS-528 Brazing Rod (strongest brazing rod made for joining cast

iron, with the convenience of a built in flux) Nickel is a non-ferrous alloy that does not absorb any carbon making it a

good choice for repair. Pre-heat any casting to avoid cracking. Control the pre-heating with

a temple stick. When it melts it means that you can weld into the casting. Preheating a casting before weld repair can be very useful in

controlling the cooling rate after welding. This is particularly important when repairing complex shapes since different thicknesses

of material respond differently to the heat from the weld pool, which

can result in damaging thermal stresses and distortion. Clean any joints that will be repaired or welded including grease and

dirt. Use grinding or cleaning solvents. If after the repair porosity is a problem, grind the area back to the

sound metal For repairs where there are casting imperfections, such as blow holes

or cracks, all defective areas should be removed by cold chiseling, gouging or grinding. If gouging with a covered electrode or air-

carbon arc, a heat affected zone will form around the gouged area. The casting should be preheated to 300°C before gouging to reduce

the risk of cracking in this region. The groove should also be lightly ground to remove hardened material before depositing the repair,

since graphite in this region may dissolve during gouging, increasing its sensitivity to cracking during subsequent welding. When removing

cracks or linear defects, the ends of the crack should be blunted by

drilling before gouging, to prevent further propagation during the preparation for repair. The true ends of the crack, which may be very


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fine, should be located by dye penetrant or magnetic particle methods before drilling.

In video DC positive is used. Use the appropriate safety gear and eliminate fume exposure.

Cast Iron Welding Repair Preheating Is Recommended Benefits

Benefits as a welding metal: More fluid than steel (better castability)

Lower melting point than steel Low cost material

Can be shaped with sand casting Desirable Properties such as:

- Damping capacity - Thermal conductivity

- Ductility - Hardness

- Strength

Design Recommendations Poor vs Improved Cast Iron Weld Design


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Modifications to Joint Design that Reduce Risk of Cracking When Welding Cast Iron

Welding Processes Welding is used to salvage new iron castings, to repair castings that have

failed in service, and to join castings to each other or to steel parts in manufacturing operations.

Table 7-19 shows the welding processes that can be used for welding cast, malleable, and nodular irons. The selection of the welding process and the

welding filler metals depends on the type of weld properties desired and the service life that is expected. For example, when using the shielded

metal arc welding process, different types of filler metal can be used. The filler metal will have an effect on the color match of the weld compared to

the base material. The color match can be a determining factor, specifically in the salvage or repair of castings, where a difference of color would not

be acceptable No matter which of the welding processes is selected, certain preparatory

steps should be made. It is important to determine the exact type of cast

iron to be welded, whether it is gray cast iron or a malleable or ductile type. If exact information is not known, it is best to assume that it is gray

cast iron with little or no ductility. In general, it is not recommended to weld repair gray iron castings that are subject to heating and cooling in

normal service, especially when heating and cooling vary over a range of temperatures exceeding 400°F (204°C). Unless cast iron is used as the

filler material, the weld metal and base metal may have different coefficients of expansion and contraction. This will contribute to internal

stresses which cannot be withstood by gray cast iron. Repair of these types of castings can be made, but the reliability and service life on such repairs

cannot be predicted with accuracy. Welding Processes and Filler Metals for Cast Iron - Figure 7-19


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Welding Preparation In preparing the casting for welding, it is necessary to remove all surface

materials to completely clean the casting in the area of the weld. This means removing paint, grease, oil, and other foreign material from the

weld zone. It is desirable to heat the weld area for a short time to remove entrapped gas from the weld zone of the base metal. The skin or high

silicon surface should also be removed adjacent to the weld area on both the face and root side. The edges of a joint should be chipped out or

ground to form a 60° angle or bevel. Where grooves are involved, a V groove from a 60-90° included angle should be used. The V should extend

approximately 1/8 in. (3.2 mm) from the bottom of the crack. A small hole should be drilled at each end of the crack to keep it from spreading.

Complete penetration welds should always be used, since a crack or defect not completely removed may quickly reappear under service conditions.

Preheating is desirable for welding cast irons with any of the welding processes. It can be reduced when using extremely ductile filler metal.

Preheating will reduce the thermal gradient between the weld and the

remainder of the cast iron. Preheat temperatures should be related to the welding process, the filler metal type, the mass, and the complexity of the

casting. Preheating can be done by any of the normal methods. Torch heating is normally used for relatively small castings weighing 30.0 lb

(13.6 kg) or less. Larger parts may be furnace preheated, and in some cases, temporary furnaces are built around the part rather than taking the

part to a furnace. In this way, the parts can be maintained at a high interpass temperature in the temporary furnace during welding. Preheating

should be general, since it helps to improve the ductility of the material and will spread shrinkage stresses over a large area to avoid critical

stresses at any one point. Preheating tends to help soften the area adjacent to the weld; it assists in degassing the casting, and this in turn

reduces the possibility of porosity of the deposited weld metal; and it increases welding speed.

Slow cooling or post heating improves the machinability of the heat-

affected zone in the cast iron adjacent to the weld. The post cooling should be as slow as possible. This can be done by covering the casting with

insulating materials to keep the air or breezes from it. Electrodes

Cast iron can be welded with a coated steel electrode, but this method should be used as an emergency measure only. When using a steel

electrode, the contraction of the steel weld metal, the carbon picked up from the cast iron by the weld metal, and the hardness of the weld metal

caused by rapid cooling must be considered. Steel shrinks more than cast iron when ceded from a molten to a solid state. When a steel electrode is

used, this uneven shrinkage will cause strains at the joint after welding. When a large quantity of filler metal is applied to the joint, the cast iron

may crack just back of the line of fusion unless preventive steps are taken. To overcome these difficulties, the prepared joint should be welded by

depositing the weld metal in short string beads, 0.75 to 1.0 in. long (19.0

to 25.4 mm). These are made intermittently and, in some cases, by the backstep and skip procedure. To avoid hard spots, the arc should be struck

in the V, and not on the surface of the base metal. Each short length of


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weld metal applied to the joint should be lightly peened while hot with a small ball peen hammer, and allowed to cool before additional weld metal

is applied. The peening action forges the metal and relieves the cooling strains.

The electrodes used should be 1/8 in. (3.2 mm) in diameter to prevent excessive welding heat. Welding should be done with reverse polarity.

Weaving of the electrode should be held to a minimum. Each weld metal deposit should be thoroughly cleaned before additional metal is added.

Cast iron electrodes must be used where subsequent machining of the welded joint is required. Stainless steel electrodes are used when

machining of the weld is not required. The procedure for making welds with these electrodes is the same as that outlined for welding with mild steel

electrodes. Stainless steel electrodes provide excellent fusion between the filler and base metals. Great care must be taken to avoid cracking in the

weld, contracts approximately 50 percent more than because stainless steel expands and mild steel in equal changes of temperature.

Arc Welding

The shielded metal arc welding process can be utilized for welding cast iron. There are four types of filler metals that may be used: cast iron

covered electrodes; covered copper base alloy electrodes; covered nickel base alloy electrodes; and mild steel covered electrodes. There are reasons

for using each of the different specific types of electrodes, which include the machinability of the deposit, the color match of the deposit, the

strength of the deposit, and the ductility of the final weld. When arc welding with the cast iron electrodes (ECI), preheat to between

250 and 800°F (121 and 425°C), depending on the size and complexity of the casting and the need to machine the deposit and adjacent areas. The

higher degree of heating, the easier it will be to machine the weld deposit. In general, it is best to use small-size electrodes and a relatively 1ow

current setting. A medium arc length should be used, and, if at all possible, welding should be done in the flat position. Wandering or skip welding

procedure should be used, and peening will help reduce stresses and will

minimize distortion. Slow cooling after welding is recommended. These electrodes provide an excellent color match cm gray iron. The strength of

the weld will equal the strength of the base metal. There are two types of copper-base electrodes: the copper tin alloy and the copper aluminum

types. The copper zinc alloys cannot be used for arc welding electrodes because of the low boiling temperature of zinc. Zinc will volatilize in the arc

and will cause weld metal porosity. When the copper base electrodes are used, a preheat of 250 to 400°F (121

to 204°C) is recommended. Small electrodes and low current should be used. The arc should be directed against the deposited metal or puddle to

avoid penetration and mixing the base metal with the weld metal. Slow cooling is recommended after welding. The copper-base electrodes do not

provide a good color match. There are three types of nickel electrodes used for welding cast iron. These

electrodes can be used without preheat; however, heating to 100°F (38°C)

is recommended. These electrodes can be used in all positions; however, the flat position is recommended. The welding slag should be removed

between passes. The nickel and nickel iron deposits are extremely ductile


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and will not become brittle with the carbon pickup. The hardness of the heat-affected zone can be minimized by reducing penetration into the cast

iron base metal. The technique mentioned above, playing the arc on the puddle rather than on the base metal, will help minimize dilution. Slow

cooling and, if necessary, post heating will improve machinability of the heat-affected zone. The nickel-base electrodes do not provide a close color

match. Copper nickel type electrodes cane in two grades. Either of these

electrodes can be used in the same manner as the nickel or nickel iron electrode with about the same technique and results. The deposits of these

electrodes do not provide a color match. Mild steel electrodes are not recommended for welding cast iron if the

deposit is to be machined. The mild steel deposit will pick up sufficient carbon to make a high-carbon deposit, which is impossible to machine.

Additionally, the mild steel deposit will have a reduced level of ductility as a result of increased carbon content. This type of electrode should be used

only for small repairs and should not be used when machining is required.

Minimum preheat is possible for small repair jobs. Small electrodes at low current are recommended to minimize dilution and to avoid the

concentration of shrinkage stresses. Short welds using a wandering sequence should be used, and the weld should be peened as quickly as

possible after welding. The mild steel electrode deposit provides a fair color match.

Carbon-arc Welding of Cast Iron Iron castings may be welded with a carbon arc, a cast iron rod, and a cast

iron welding flux. The joint should be preheated by moving the carbon electrodes along the surface. This prevents too-rapid cooling after welding.

The molten puddle of metal can be worked with the carbon electrode so as to move any slag or oxides that are formed to the surface. Welds made

with the carbon arc cool more slowly and are not as hard as those made with the metal arc and a cast iron electrode. The welds are machinable.

Oxyfuel Gas Welding

The oxyfuel gas process is often used for welding cast iron. Most of the fuel gases can be used. The flame should be neutral to slightly reducing. Flux

should be used. Two types of filler metals are available: the cast iron rods and the copper zinc rods. Welds made with the proper cast iron electrode

will be as strong as the base metal. Good color match is provided by all of these welding reds. The optimum welding procedure should be used with

regard to joint preparation, preheat, and post heat. The copper zinc rods produce braze welds. There are two classifications: a manganese bronze

and a low-fuming bronze. The deposited bronze has relatively high ductility but will not provide a color match.

Brazing and Braze Welding Brazing is used for joining cast iron to cast iron and steels. In these cases,

the joint design must be selected for brazing so that capillary attraction causes the filler metal to flow between closely fitting parts. The torch

method is normally used. In addition, the carbon arc, the twin carbon arc,

the gas tungsten arc, and the plasma arc can all be used as sources of heat. Two brazing filler metal alloys are normally used; both are copper

zinc alloys. Braze welding can also be used to join cast iron. In braze


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welding, the filler metal is not drawn into the joint by capillary attraction. This is sometimes called bronze welding. The filler material having a

liquidous above 850°F (454°C) should be used. Braze welding will not provide a color match.

Braze welding can also be accomplished by the shielded metal arc and the gas metal arc welding processes. High temperature preheating is not

usually required for braze welding unless the part is extremely heavy or complex in geometry. The bronze weld metal deposit has extremely high

ductility, which compensates for the lack of ductility of the cast iron. The heat of the arc is sufficient to bring the surface of the cast iron up to a

temperature at which the copper base filler metal alloy will make a bond to the cast iron. Since there is little or no intermixing of the materials, the

zone adjacent to the weld in the base metal is not appreciably hardened. The weld and adjacent area are machinable after the weld is completed. In

general, a 200°F (93°C) preheat is sufficient for most application. The cooling rate is not extremely critical and a stress relief heat treatment is

not usually required. This type of welding is commonly used for repair

welding of automotive parts, agricultural implement parts, and even automotive engine blocks and heads. It can only be used when the absence

of color match is not objectionable. Gas Metal Arc Welding

The gas metal arc welding process can be used for making welds between malleable iron and carbon steels. Several types of electrode wires can be

used, including: Mild steel using 75% argon + 25% CO2 for shielding.

Nickel copper using 100% argon for shielding. Silicon bronze using 50% argon + 50% helium for shielding.

In all cases, small diameter electrode wire should be used at low current. With the mild steel electrode wire, the Argon-CO2 shielding gas mixture

issued to minimize penetration. In the case of the nickel base filler metal and the Copper base filler metal, the deposited filler metal is extremely

ductile. The mild steel provides a fair color match. A higher preheat is

usually required to reduce residual stresses and cracking tendencies. Flux-cored Arc Welding

This process has recently been used for welding cast irons. The more successful application has been using a nickel base flux-cored wire. This

electrode wire is normally operated with CO2 shielding gas, but when lower mechanical properties are not objectionable, it can be operated without

external shielding gas. The minimum preheat temperatures can be used. The technique should minimize penetration into the cast iron base metal.

Post heating is normally not required. A color match is not obtained. Other Processes

Other welding processes can be used for cast iron. Thermit welding has been used for repairing certain types of cast iron machine tool parts.

Soldering can be used for joining cast iron, and is sometimes used for repairing small defects in small castings. Flash welding can also be used for

welding cast iron.

Welding Techniques Studding

Studding Method for Cast Iron Repair


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Cracks in large castings are sometimes repaired by studding (figure 7-10).

In this process, the fracture is removed by grinding a V groove. Holes are drilled and tapped at an angle on each side of the groove, and studs are

screwed into these holes for a distance equal to the diameter of the studs, with the upper ends projecting approximately 1/4 in. (6.4 mm) above the

cast iron surface. The studs should be seal welded in place by one or two beads around each stud, and then tied together by weld metal beads.

Welds should be made in short lengths, and each length peened while hot to prevent high stresses or cracking upon cooling. Each bead should be

allowed to cool and be thoroughly cleaned before additional metal is deposited. If the studding method cannot be applied, the edges of the joint

should be chipped out or machined with a round-nosed tool to form a U groove into which the weld metal should be deposited.

Joint Design Modification It is preferred that a full penetration weld is used over one where there is

partial penetration. Welds that have varying thickness can result in uneven

contraction stresses and uneven expansion during the welding cycle. Changing welding designs to locate welds in an area where there is

constant thickness can be beneficial. Another tip is to use a backing fillet weld to support stressed areas.

Groove Face Grooving Cast Iron Groove Face Grooving

Gouging or grinding grooves into the surface area of a prepared weld

groove, followed by using a weld bead to fill the grooves, before filling the

whole joint is sometimes a preferred method (see illustration below). This approach lowers cracking risks by deflecting the crack path. Beads that are

in contact with the casting are deposited first, when the stress heat affected zone and fusion line are at a low.

Peening (Hammering) Peening or hammering using a 13-19mm ball-peen hammer applied to a

deformable weld bead, putting it into a state of compressive stress, the tensile stresses caused be thermal contraction can be opposed, thus

reducing the risk of cracking in and around the weld. When the hammer is applied manually, it strikes a moderate blow

perpendicular to the weld surface. The process requires a ductile weld metal. Nickel fillers are used,

particularly when working with gray cast iron. Peening is performed at higher temperatures while the metal is soft.


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Questions:-

1. What is Cast Iron?

2. Right Cast iron welding process.

3. Write all types of cast iron.

Assignment:- Cast iron –its properties and types.welding methods of cast iron.



lesson plan date trade:- welder -...

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