Welding

Abstract

Welding is a technique used for joining metal parts usually through the application of heat. Since classical antiquity, smiths have used forge welding and this technique is known from the earliest uses of iron. Nowadays, there are several types of welding techniques but only a few of them are currently in use to a greater extent. In metal welding, heat could be generated by gas or electricity. Heating is done to a suitable temperature and welding could be done with or without the application of pressure and with or without filler material. In gas welding, heat is supplied mostly by burning acetylene in oxygen. Gas welding is nowadays mostly used for small repairs and by, for example, artists. In resistance welding, the required heat for joining is generated by the interface, by the electrical resistance of the joint. Spot, seam, and projection welding are resistance welding and they are used in car industries and when making household appliances. Arc welding is a group of welding processes which produces coalescence of metals by heating them with an arc, with or without application of pressure or filler material. Shielded metal arc welding is the most used welding process today. In gas shielded arc welding, the arc is shielded from the air mostly by an inert gas such as helium or argon. Tungsten could be used as the electrode and it is used when welding with, for example, stainless steel. Welding fluxes are used to prevent, dissolve, or facilitate removal of oxides and other undesirable surface substances. Welding rod is a form of filler metal used, which does not conduct the electrical current. Welding alloys may be aluminum powder with iron oxide, nickel, manganese, or steel.