Welding process

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by: C B Singh

SCIENCE & TECHNOLOGY OF WELDING

It is needless to emphasize that the welding has become, now, the most efficient, economical & popular means of joining materials; Because:• It enables act as one . • It improves strength. •Reduces the over-all weight.•Reduces labor time & the cost.

WELDING

Definition :A localized coalescence of material with or without the use of filler and also with or without the application of pressure.

or

Bringing two perfectly smooth & clean material surfaces to an intimate contact, which is an atomic distance, indeed, between the two, is known as welding.

WELDING

Fusion

Diffusion

PressureNon-

pressure

* Soldering < 427 0C * Brazing > 427 0C * Braze-welding

&

* Resistance welding* Explosive welding

* Forge welding

* Friction/Inertia welding*Ultrasonic welding

* Cold welding* Thermit welding * Pressure gas

welding

* Oxy-Fuel gas welding* Electric Arc welding* Plasma Arc welding* Electron Beam welding* Laser Beam welding* Electro Slag / Gas

welding

Ag100%

Cu100%

500

700

900

1100

0C

72%Ag + 28%Cu

Liquidus Solid +

Liquid

Solid

(Eutectic composition)

Silver–Copper Equilibrium Diagram

Molten liquid

BRAZING & SOLDERING

Brazing & Soldering:

Low temp. Brazing 450-850 0C Medium temp. Brazing 850-950 0C High temp. Brazing > 950 0C

There is no bead formation, but only with capillary attraction.& diffusion.

Low temp. Soldering 427 0C Max.

SteelSteel

Bronze

CopperCopperSteel

SteelCopper

Steel

Pb-Sn EutecticSteelCopper

Brazing & SolderingBrazing & Soldering

Some Typical Brazing Applications:

Ring

Foil

BRAZE WELDING

Braze welding: There is a bead formation, but without the fusion & capillary attraction.

An age-old joining technique

OPERATION– Manual/ mechanized/ auto. 

ADVANTAGE – Usually no distortion & heat damages; easy adaptability for the mass production of several intricate component parts. TYPICAL APPLICATIONS –Repair & maintenance, tool-tips, heat-exchangers, electrical switches, electric motor parts, gas turbine parts, bicycle frames, utensils & kitchen-wares etc.

BRAZE WELDING, BRAZING & SOLDERING

An age-old metal joining techniques:

BRAZING & SOLDERING

THERMIT WELDING (TW)

Thermit Powder

Molten Crucible

RAILS

Mould

Igniter

Molten metal flows down

developed in 1893

Flame heating gate

Thermit powder: Fe2O3 + 2Al = 2Fe + Al2O3

THERMIT WELDING (TW)

THERMIT WELDING (TW)

OPERATION – Manual skill .

TYPICAL APPLICATIONS – Confined to the railway tracks only, but can also be used for reinforced concrete bars & copper conductors & easy to use on site.

LIMITATIONS – Limited range of joints and materials., difficult to ensure consistency in it’s weld quality, slow & expansive, require a group of five people to work in tandem.

Oxy-Acetylene Gas

Filler Rod

Gas

Flame

Weld Bead

OXY- FUEL GAS WELDING (OFW)

developed in 1904

OPERATION – Manual skill.

ADVANTAGE –No power supply needed, low investment, highly - portable, excellent performance on Cast-iron, Cast-steel, depositing Tungsten-carbide & Stellite for hard surfacing.

TYPICAL APPLICATIONS – Repair & reclamation welding of motor vehicle parts, sheet metal & light fabrication welding.

OXY- FUEL GAS WELDING

OXY-FUEL GAS CUTTING

CARBON ARC WELDING (CAW)

Carbon electrode

AirFiller Rod Weld

Bead

Developed in 1884

1. Power source2. Holder cable3. Earth cable4. Work5. Carbon electrode & 6.Filler rod

CARBON ARC GOUGING(C. A.

G.)

CARBON/AIR ARC GOUGING (CAG)

1. Power source2. Holder cable3. Earth cable4. Work5. Carbon electrode & 6. Compressed Air.

SHIELDED METAL ARC WELDING (SMAW)

_+_

1. Power source2. Holder cable3. Earth cable4. Work &5. Electrode

developed in 1907

MANUAL METAL ARC WELDING (MMAW)

OPERATION – Manual skill. ADVANTAGE – Low capital investment, wide variety of application even in restricted areas.

TYPICAL APPLICATIONS – Ship building, Structural steel work, High-rise Buildings, Locomotive, Rail-road, Armament, Automotive, Transmission Pipeline, Mining, Repair & Construction of plant and machinery of all types. It is used for joining, rebuilding & hard-surfacing.

SHIELDED METAL ARC WELDING (SMAW)MANUAL METAL ARC WELDING (MMAW)

An arch-bridge on river Chenab in Kashmir by Konkan Rly, Usage 26,000 Tons of steel,

1.3K.M. long & 359 M high > Affil tower (324M)

This will be the tallest bridge made within 30Months

Ref: www.bbchindi.com – dated 17th, Apr, 2006

Mechanized wire feed

Mechanized arc tracking

SUBMERGED ARC WELDER (SAW)

Granulated SAW flux

developed in 1936

SUBARC WELDER

SUBARC WELDER

WELDING POSITIONERS

REBUILDING BY SAW

SUBMERGED ARC WELDER (SAW)

OPERATION – Usually mechanized or automatic. ADVANTAGE – High deposition rate, high quality radiographic sound weld, invisible arc underneath the flux granules causes least fatigue to the operator.

TYPICAL APPLICATIONS – High quality pressure vessel, chemical plant, ship building, structural engineering component parts, and also for rebuilding & surfacing.

Mechanized wire feed

FCAW - with or without external gas shield

Flux Cored Electrode

FLUX CORED ARC WELDING (FCAW)

developed in 1955

OPERATION – Usually semi-automatic but also mechanized or automated, if the need arises. ADVANTAGE –High deposition rate, high quality weld for shop & site welding, it causes lesser fatigue than GMAW to the welder.

TYPICAL APPLICATIONS– Pressure vessel, chemical plant, pipe work, structural work, ship building, and also popular for rebuilding & surfacing on shop and site.

FLUX CORED ARC WELDING (FCAW)

GAS-SHIELDED METAL ARC WELDING (GMAW)

GMAW , SIGMA, MIG/MAG or CO2/MIG Welding

Mechanized wire

feeding

Consumable

ElectrodeInert/active gas

feed

MIG developed in 1950 & MAG welding during 1953

GAS-SHIELDED METAL ARC WELDING (GMAW)

OPERATION–Usually semi-automatic but also mechanized or robotic. ADVANTAGE – Continuous process with reduced finishing operation, high quality weld including in vertical down with extra low hydrogen.

TYPICAL APPLICATIONS – Light, medium & heavy fabrication such as ship-containers, light and heavy vehicle, earth movers, heavy machinery fabrication etc.

GAS-SHIELDED METAL ARC WELDING (GMAW)

Filler Rod

H2 gas

Tungsten Electrodes

~~

ATOMIC HYDROGEN WELDING (AHW)

developed in around 1940, but it was made to disappeare soon

OPERATION – Usually manual but also mechanized.

ADVANTAGE – Similar to those of GTAW process.

TYPICAL APPLICATIONS – Welds in thin materials particularly stainless steel; mechanized thin sheet welding.

GTAW / TIG Welding

Inert gas feed

Filler rod

Non-consumable Tungsten Electrode

GAS-SHIELDED TUNGSTEN ARC WELDING (GTAW)

developed in 1942

GAS-SHIELDED TUNGSTEN ARC WELDING

OPERATION – Usually manual but also scarcely mechanized for tube to tube sheet & orbital welding. ADVANTAGE – Wide range of metals, produces high quality standard weld with extra low hydrogen.

TYPICAL APPLICATIONS– High quality weld in stainless steel for nuclear reactors, chemical & fertilizer plants, industrial piping, nickel alloys for aircraft engines, aluminum alloys for food industry.

GAS-SHIELDED TUNGSTEN ARC WELDING (GTAW)

PAWFiller rod

Plasma gas

Shielding Gas

PLASMA ARC WELDING (PAW)

+

developed in 1959

TRANSFER & NON-TRANSFER PLASMA ARC

PLASMA ARC WELDING (PAW)

OPERATION – Usually mechanized. ADVANTAGE – Wide range of metals, produces high quality deep penetration weld with extra low hydrogen.

TYPICAL APPLICATIONS– High quality weld in stainless steel sheet foil butt welds, electronics cans, thermo couples, bellows, capsuls, filters by MPW and high speed tube manufacturing, high speed unprepared butt joint making in chemical plant.

E.B.W. Gun

Beam alignment coil

Optics

Vacuum Chamber

Deflection Coil

Focus Coil

Work

ELECTRON BEAM WELDER (EBW)

developed in 1960

OPERATION –Fully mechanized. ADVANTAGE – Excellent penetration; Low distortion; Non-contaminated weld; High speed welding; Ability to weld several non-weld-able materials. Any metal may be welded compatible with the vacuum while in molten state.

TYPICAL APPLICATIONS –Gear clusters/shafts joint; Turbine blade root joint; Fully mechanized.

ELECTRON BEAM WELDER (EBW)

LASER BEAM WELDER (LBW)

Capacitor Bank

Flash tube

Focusing lens

Work

Laser beam

developed in 1967

OPERATION:Fully mechanized. ADVANTAGE: Wide range of materials.

TYPICAL APPLICATIONS:Continuous laser for the develop-mental activities; Pulsed laser for reputed application to some small assemblies such as electronic component parts.

ELECTRO SLAG WELDER (ESW)

Electrode wire

Copper shoe

Weld metal

Work

Developed in 1956

OPERATION–Mechanized only. ADVANTAGE –Fast completion of thick joint in singular run.

TYPICAL APPLICATIONS – Thick wall pressure vessels; Thick civil engineering & structural fabric-ation work and Ship-building.

CONSUMABLE GUIDE ESW

COLD WELDING (CW)

Split die

Split die

ADVANTAGE – Large area of weld made in high conducting materials such as copper and aluminum; Low cost welding.

TYPICAL APPLICATIONS:Welding of copper overhead conductors for electric traction; Aluminum - copper joints for electric cables.

FORGE WELDING (FOW)

Force

An age-old welding technique

FORGE WELDING (FOW)

TECHNIQUE –Pressure welding .

OPERATION –Manual or mechanized. APPLICATION – Black-smith’s artistic iron ware only; dimensions not easily controlled and difficult to assure quality. Limited low carbon & some alloy steels only.

~

~

ELECTRIC RESISTANCE SPOT WELDER (ERW)Developed in

1887

RESISTANCE SPOT WELDER (ERW)

OPERATION – Mechanized or robotized.ADVANTAGE – Consumable & skill is not required thus consistent weld quality with high productivity. Commonly used ferrous & non-ferrous metals but difficult to weld copper.

TYPICAL APPLICATIONS – Light fabrication from pressed sheet parts such as motor vehicle bodies, domestic washing machines, and cabinets for refrigerators etc.

ELECTRIC RESISTANCE SPOT WELDER (ERW)

PROJECTION SPOT WELDER (RPW) ~

~Step-1

Step-2

Ideal for making multiple spots, where the spacing may be the designers constraint.

RESISTANCE SEAM WELDER (RSEW)

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~

RESISTANCE FLASH-BUTT WELDER (FW)

~ ~

Developed in 1927

RESISTANCE UPSET- BUTT WELDER (UW)

Upsetting

~ ~

H.F. RESISTANCE BUTT WELDER (HFRW)

~ ~

INDUCTION BUTT WELDER (IW)

~ ~

CD STUD - WELDER

Step-1Step-2

~~

ARC STUD – WELDER (SW)

Stud

Weld metal

Ceramic ferrule

Step-1

Step-2~ ~

FRICTION WELDER (FRW)Developed in

1955

OPERATION – Mechanized. ADVANTAGE – Produces consistently high quality welds; Fast joining of large area; Suitable for wide range of materials; Mechanized & works on simple principle; & Consumable is not required.

TYPICAL APPLICATIONS –Internal combustion engin valves; Head to stem joint of dissimilar metals; Stud welding; Rear axle casings; Transmission and steering components for vehicles and Electrical part connections .

EXPLOSIVE WELDING (EXW)

Flyer plate

Explo-siveBuffe

r

APPLICATIONS – Manufacture of steel to aluminum or copper transition pieces for fabrication; Cladding steel parent plate; Tube - to -tube sheet joints. The wide range of metals studied to date give good results The process is particularly suited to dissimilar metals.

ADVANTAGE –Cladding large plates without preheat; Suitable for wide range of dissimilar metals; Fast as a large area is joined in single shot.

PROCESSES & THEIR LETTER DESIGNATIONS

LETTER DESIGNATION

WELDING PROCESS

GROUPArc welding

Carbon Arc Flux Cored ArcGas Metal ArcGas Tungsten ArcPlasma Arc Shielded Metal ArcStud ArcSubmerged Arc

CAW FCAWGMAW GTAWPAW SMAWSWSAW

Brazing

Diffusion Brazing Dip Brazing Furnace BrazingInduction Brazing Infrared BrazingResistance BrazingTorch Brazing

DFBDBFB IB IRBRB TB

Continued …

Oxyfuel Gas Welding

Oxyacetylene WeldingOxyhydrogen Welding Pressure Gas Welding

OAWOHW PGW

Resistance Welding Flash Welding High Frequency Resistance Percussion WeldingProjection Welding Resistance-Seam WeldingResistance-Spot Welding Upset Welding

FWHFRW PEWRPW RSEWRSW UW

Solid State Welding

Cold WeldingDiffusion Welding Explosion WeldingForge WeldingFriction WeldingHot Pressure WeldingRoll Welding Ultrasonic Welding

CW DFW EXW FOWFRW HPWROW USW

PROCESSES & THEIR LETTER DESIGNATIONS

Soldering

Other Welding Processes

Dip SolderingFurnace SolderingInduction SolderingInfrared SolderingIron Soldering Resistance SolderingTorch Soldering Wave Soldering

DSFS IS IRSINSRSTS WS

Electron Beam Welding Electro Slag Welding Induction Welding Laser Beam WeldingThermit Welding

EBW ESWIWLBW TW

PROCESSES & THEIR LETTER DESIGNATIONS

Ref: AWS