Submitted to: By Sri. M.P.Gururajan Srihari prasad Gorti

2008AMD2919

• What is fusion welding.

•Fusion welding is a secondary manufacturing process.

•Repair works also possible.

Gas welding Arc welding High energy beam welding

Oxy-acetylene welding Shielding metal arc welding(SMAW) Electron beam welding(EBW) (OAW) Gas-tungsten arc welding(GTAW)

Plasma arc welding (PAW) Laser beam welding(LBW) Gas-metal arc welding(GMAW)

Flux-cored arc welding(FAW) Submerged arc welding(SAW) Electroslag welding (ESW)

•Solidification of crystalline materials

formation of a liquid pool interface between liquid and solidSolidification

•Micro-structure casting in a mould,

•Heat is generated in the gas welding by chemical reactions

•Stage 1C2H2+O2 2 CO+H2+448 KJ/Mol (18.75 MJ/m3of acetylene)

•Stage 2:•4CO+2H2+3O2 CO2+2H2O+812 KJ/mol (35.77 MJ/ m3)

Equal amounts of oxygenDoes not alter the composition, best for most

metals. Temperature is approximately 3232°C.

 Burning an excess of acetylene,

Three distinct colors.

 Burning an excess of oxygen.Appearance is similar to the neutral flame, but the inner

cone is shorter, slightly pointed, and has a purplish tinge. This flame burns with a hissing sound.For ferrous metals Numerous sparks

Foam that forms on the surface.

Principle of arc welding

Arc is generated between two conductors of electricity.

Heat is liberated by

Electrons Charged ions The positively charged ions,

65 to 75 % of heat at the anode

Metals are reactive at high temperatures

Formation oxides and nitrides are formed.

Protective shield of gas, vapor, or slag (arc shielding)

Arc functions in weldingTo melt the metalTo transport the molten metal from the tip of

the electrode to the work. Surface Tension Transfer Metal Spray Arc Globular transfer

Arc welding may be done with Direct current (DC) Alternating current (AC).  

In Direct current there will be two types depending upon the direction of flow of current.Direct current electrode negative (DCEN): •Electrode is cathode.•2/3rd of heat is at anode. •Non-consumable electrode welding processes.

Direct current electrode positive (DCEP):

•Electrode is anode.•consumable electrode welding processes.

Material Thicknessb SMAW SAW GMAW FCAW GTAW PAW ESW OFW EBW LBWCarbon steel alloys

SIMT

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XX X

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Low-alloy steels

SIMT

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XX X

X XXXX

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Stainless steels

SIMT

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XX

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XX X

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Cast iron IMT

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XX

XX

XX

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Nickel and alloys

SIMT

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XX X

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Aluminium and alloys

SIMT

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X X XXXX

XX

S:sheet up to 3 mm; I: intermediate, 3-6 mm; M: medium, 6-19 mm; T: thick, 19 mm and up;X: recommended

Cost Cleanness of the weld

HAZ width Level of automation Thickness of plate Comments and typical applications

Metal arc welding Low Poor-ok 5-6 mm Not Any multipass Only use for relatively short runs, repair

works on bridges, oil rigs etc.

Submerged arc welding

Medium Poor 7-10 mm Very high Any multipass Only use horizontally, used for high

production runs like pipelines

Metal inert gas welding (MIG)

Low-medium OK 3-4 mm Medium Any multipass Use for production runs on thinner

sections than SAW

Tungsten inert gas (TIG)

Low-Medium Good 2-3 mm Medium Any- multipass Used for similar applications as MIG

but for longer production runs

Laser Very high Very good 12 mm Very high Up to 30 mm

Low distortion, no filler materials

Electron beam welding

Very high Very good 0.5-12 mm for thick plate

Low Up to 250 mm

Very expensive, used in aerospace industry,

can be used for welding Al, Ti, Cu

and relatively reactive materials

Advantages DisadvantagesGas welding i) Equipment is simple, portable and inexpensive.

ii) Suitable for repair worksi) Large heat affected zones, sever distortionii) Not suitable for reactive materials such as titanium and zirconium

SMAW i) Compared to other welding process equipment is simple, inexpensive

i) Shielding gas is not suited for reactive metals.ii) Deposition rate is low.Production rate is low.

SAW i) Clean welds.ii) Spatter and heat losses are eliminated.iii) Increase deposition rate

i) Weld quality is lowii) Increase in distortion

GTAW i) Suitable for thin sections.ii) Ease of control over size of weld.iii) Clean weldment can be obtained.iv) Used for reactive metals also

i) Deposition rate is low.ii) Chance for formation of brittle tungsten inclusions.

GMAW i) Higher deposition rateii) Clean weldment is possible

i) Guns are heavy and bulky.ii) Difficult to reach small areas and corners.

PAW i) Less sensitive in arc length variation.ii) Higher welding speeds

i) Paw torch is more complicated.ii) Equipment cost is higher.

ESW i) High deposition rate.ii) No angular distortion

i) Weld quality is poor.

EBW i) Single pass welding at high speeds.ii) Total heat input is much lower.iii) Used for reactive metals also.

i) Equipment cost is very high.

LAW i) Deep and narrow welds at high welding speedsii) Little distortion

i) Equipment cost is very high.ii) Precise joint fit-up and alignment is needed.

Nitrogen Oxygen HydrogenSteels Increases strength but

reduces toughnessReduces toughness Induces hydrogen cracking

Austenitic steels Reduces ferrite and promotes solidification cracking

Aluminium Forms oxide films that can be trapped as inclusions

Forms gas porosity and reduces both strength and ductility

Titanium Increases strength but reduces ductility

•The weldability of steels is inversely proportional to a property known as the hardenability of the steel. As the hardness of the steel is high there may be possibility of hot cracking.

•For the aluminum alloys proper shielding has to be provided otherwise the metal gets oxidized.

•Excessive heat supply leads to distortion of welded parts.

Advantages of welding:Strong and tight joiningCost effectivenessSimplicity of welded structures designWelding processes may be automated.

Disadvantages of welding: Internal stresses, distortions and changes of micro-structure in

the weld region Harmful effects: light, ultra violate radiation, fumes, high

temperature.

Applications of welding: Buildings and bridges structures Automotive, ship and aircraft constructions Pipe lines Tanks and vessels Railroads Machinery elements.

Thank you