Welding is a fabrication process that joins two parts by causing fusion, which is different from low temperature metal-joining techniques such as brazing and soldering, which do not melt the base metal. In addition to melting the base metal, a filler material is typically added to the joint to form a pool of molten material that cools to form a joint that is typically stronger than the base material. Welding also requires a form of shield to protect the filler metals or melted metals from being contaminated or oxidized. This shield is typically a gas that is emitted by the welding gun, such as Argon.
In metals manufacturing, welding is a common process to join two parts where bolting the pieces together is either not strong enough, not functionally possible, or not cost effective.
Some of the best known welding methods include:
Oxy Fuel Welding – also known as oxyacetylene welding or oxy welding, uses fuel gases and oxygen to weld and cut metals.
Shielded metal arc welding (SMAW) – also known as "stick welding" or "electric welding", uses an electrode that is coated in flux to protect the weld puddle. The electrode holder holds the electrode as it slowly melts away. Slag protects the weld puddle from atmospheric contamination.
Gas Tungsten Arc Welding (GTAW) – also known as TIG (tungsten, inert gas), uses a non-consumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by an inert shielding gas such as argon or helium.
Gas Metal Arc Welding (GMAW) – commonly termed MIG (metal, inert gas), uses a wire feeding gun that feeds wire at an adjustable speed and flows an argon-based shielding gas or a mix of argon and carbon dioxide (CO2) over the weld puddle to protect it from atmospheric contamination.
Flux-Cored Arc welding (FCAW) – almost identical to MIG welding except it uses a special tubular wire filled with flux; it can be used with or without shielding gas, depending on the filler.
Many different energy sources can be used for welding, including a gas flame, an electric arc, a laser, an electron beam, friction, and ultrasound. While often an industrial process, welding may be performed in many different environments, including in open air, under water, and in outer space. Welding is a hazardous undertaking and precautions are required to avoid burns, electric shock, vision damage, inhalation of poisonous gases and fumes, and exposure to intense ultraviolet radiation.