OPERATION
§4.1.11 MIG Welding
Definition of MIG Welding
MIG (metal inert gas) welding also known as GMAW (gas metal arc welding) or MAG (metal active
gas 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 MIG welding. There are four primary
methods of metal transfer in MIG welding, called short circuit (also known as dip transfer) globular
transfer, spray transfer and pulsed-spray, each of which has distinct properties and corresponding
advantages and limitations. To perform MIG welding, the basic necessary equipment is a welding
gun, a wire feed unit, a welding power supply, an electrode wire, and a shielding gas supply. Short
circuit transfer is the most common used method whereby the wire electrode is fed continuously down
the welding torch through to and exiting the contact tip. The wire touches the work piece and causes
a short circuit the wire heats up and begins to form a molten bead, the bead separates from the end of
the wire and forms a droplet that is transferred into the weld pool. This process is repeated about 100
times per second, making the arc appear constant to the human eye.
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