In the following paragraphs distinguishing features, attributes, limitations and comparisons where applicable will be discussed for the commonly used welding processes. This introduction to the welding processes will help the modern welding engineers to consider alternative proc­esses available for the situation. This aspect may otherwise be overlooked. A major problem, frequently arises when several processes can be used for a particular application. Selection could be based upon fitness for service and cost. These two factors, sometimes, may not be compatible. Process selection is also affected by such factors as:

(a) production quantity, (6) acceptability of installation costs, (c) joint location, (d) joint service requirements, (e) adaptability of the process to the location of the operation, (f) avail­ability of skill/experience of operators.

In this review of conventional welding processes we shall be discussing Gas Welding, Arc Welding, Shielded Metal Arc, Submerged Arc, Tungsten Inert Gas, Metal Inert Gas, Metal Active Gas Welding, Resistance Welding, Electroslag Welding, Spot, Seam and Projection Welding, Flash Butt and Upset Butt Welding, and high Frequency Welding.

Advanced welding processes such as Electron Beam welding, Laser Beam Welding, Plasma Arc Welding, Explosive Welding, Friction Welding, Ultrasonic Welding and Underwater Welding are discussed in chapter 4. Now let us start to review the conventional welding processes, starting with gas welding.