What Is Welding Process

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What is Welding Process?

The welding process is a joining process used for various materials.
The large varieties of materials that can be welded are metals and their alloys, although the term welding is also applied to the joining of other materials such as thermoplastics.
Welding joins various metals with the help of a number of processes in which heat is supplied either electrically or by using a gas torch.
For joining two or more pieces of metal together by one of the welding processes, the most essential requirement is heating.
Pressure is also required, but not in all the processes.

A large number of metals or alloys, both similar and dissimilar can be joined by welding.
Welding can be mechanized.
A good weld is as strong as the base metal.
Welding can join workpieces through spots, end to end, and in a number of other configurations.
General welding equipment is not very costly.
Portable welding equipment is also available.

Welding gives out harmful radiations, fumes and spatter.
Welding results in residual stresses and distortion of the work pieces.
To hold and position the parts to be welded, generally jigs and fixtures are required.
To produce a good welding job, a skilled welder is required.
Heat generated due to welding produces metallurgical changes hence, the structure of welded joint is different than that of parent metal.
Before welding, generally edge preparation of the work pieces is required.

Some of the important applications of welding process are as follows:

Aircraft construction (Welding of engine parts, turbine frame, ducts, etc.)
Rail-road equipment’s (Air receiver, engine, front and rear hoods, etc.)
Piping’s and pipelines (Open pipe joints, oil and gas pipelines, etc.).
Pressure vessels (boilers) and tanks (joining of nozzles, ends, tanks, etc.). Buildings and bridges (Columns base plates, erection of structures, etc.).
Automobile parts (Trucks, buses, cars, cranes, bikes parts, etc.).
Machine parts (Frames, beds, toots, dies, etc.).

There are different ways of classifying welding and allied processes.
Modern methods of welding may be classified under two broad categories i.e. Mastic welding and fusion welding.
In plastic (pressure) welding, the metal pieces to be joined are heated to a plastic state and then forced together by external pressure. In this method filler metal is not required. For example, forge welding, electric resistance welding, etc.
In fusion (non-pressure) welding, the material at the joint is heated to molten state and allowed to solidify. In this method, filler material is required during the process. For example, arc welding, gas welding, etc.
In general, welding and allied processes are classified as follows:

1. Arc welding

a) Gas tungsten arc welding (TIG)

b) Gas metal arc welding (MIG)

c) Electro-slag welding

d) Stud arc welding

e) Shielded metal arc welding

f) Submerged arc welding

g) Plasma arc welding

2. Gas welding

a) Oxy-acetylene welding

b) 0xy-hydrocarbon welding

c) Air acetylene welding

d) Pressure gas welding

3. Resistance welding

a) Spot welding

b) Seam welding

c) Projection welding

d) Percussion welding

e) Resistance butt welding