GAS METAL ARC WELDING

Gas metal arc welding (GMAW), sometimes referred to by its
subtypes metal inert gas (MIG) welding or metal active
gas (MAG) welding, is a semi-automatic or automatic arc
welding process in which a continuous and consumable wire
electrode and a shielding gas are fed through a welding gun. 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 for welding aluminum and other non-ferrous
materials in the 1940s, GMAW was soon applied to steels because
it allowed for lower 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. Today, GMAW
is the most common industrial welding process, preferred for its
versatility, speed and the relative ease of adapting the process to
robotic automation. The automobile industry in particular uses
GMAW welding almost exclusively. Unlike welding processes that
do not employ a shielding gas, such as shielded metal arc
welding, it is rarely used outdoors or in other areas of air volatility.
A related process, flux cored arc welding, often does not utilize a
shielding gas, instead employing a hollow electrode wire that is
filled with flux on the inside.