Welding is a fabrication process that joins material, usually metals or thermoplastics, by causing coalescence. This is often done by melting the wont pieces and adding a filler material to form a pool of molten material (the meld puddle) that cools to become a strong joint but sometimes pressure is used in conjunction with heat or by itself, to produce the weld. This is in contrast with soldering and brazing, which involve melting a lower-melting-point material between the work pieces to form a bond between them without merting the work pieces. Many different energy sources can be used for welding including a gas name, an electric arc, a laser, an electron beam, friction, and ultrasound.
Today welding is used in diverse areas of industry ranging from aircraft and rocket engines to small pipes.
The AWS definition for a welding process is "a material 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 atone and with or without the use of filler material". AWS has grouped the processes together according to the "mode of energy transfer" as the primary consideration. A secondary factor is the Influence of capillary attraction in effecting distribution of filler metal" in the joint. Capillary attraction distinguishes the welding processes grouped under "Brazing" and "Soldering" from "Arc Welding", "Gas Welding", "Resistance Welding", "Solid State Welding",and "Other Processes."