Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG) and metal active gas (MAG) is a welding process in which an electric arc forms between a consumable MIG wire electrode and the workpiece metal(s), which heats the workpiece metal(s), causing them to fuse (melt and join). Along with the wire electrode, a shielding gas feeds through the welding gun, which shields the process from atmospheric contamination.
The process can be semi-automatic or automatic. A constant voltage, direct
current power source is most commonly used with GMAW, but constant current
systems, as well as alternating current, can be used. There are four primary
methods of metal transfer in GMAW, called globular, short-circuiting, spray, and
pulsed-spray, each of which has distinct properties and corresponding advantages
and limitations.
Originally developed in the 1940s for welding aluminium and other non-ferrous
materials, GMAW was soon applied to steels because it provided faster welding
time compared to other welding processes. The cost of inert gas limited its use
in steels until several years later, when the use of semi-inert gases such as
carbon dioxide became common. Further developments during the 1950s and 1960s
gave the process more versatility and as a result, it became a highly used
industrial process.
