The GMAW process was developed and made commercially available in 1948, although the basic concept was actually introduced in the 1920’s. In its early commercial applications, the process was used to weld aluminum with an inert shielding gas, giving rise to the term “MIG” (metal inert gas) which is still commonly used when referring to the process. Variations have been added to the process, among which was the use of active shielding gases, particularly CO2, for welding certain ferrous metals. This eventually led to the formally accepted AWS term of gas metal arc welding (GMAW) for the process. Further developments included the short circuiting mode of metal transfer (GMAW-S), a lower heat energy variation of the process that permits welding out-of-position and also on materials of sheet metal thicknesses; and a method of controlled pulsating current (GMAW-P) to provide a uniform spray droplet metal transfer from the electrode at a lower average current levels.
The GMAW process uses either semiautomatic or automatic equipment and is principally applied in high duction welding. Most metals can be welded with this process and may be welded in all positions with the lower energy variations of the process. GMAW is an economical process that requires little or no cleaning of the weld deposit. Warpage is reduced and metal finishing is minimal compared to stick welding.
FUNDAMENTALS
Principles of Operation. GMAW is an arc welding process which incorporates the automatic feeding of a continuous, consumable electrode that is shielded by an externally supplied gas. Since the equipment provides for automatic selfregulation of the electrical characteristics of the arc and deposition rate, the only manual controls required by the welder for semiautomatic operation are gun positioning, guidance, and travel speed. The arc length and the current level are automatically maintained. Process control and function are achieved through these three basic elements of equipment :
1. Gun and cable assembly
2. Wire feed unit
3. Power source
MIG Weld How TO - EQUIPMENT
The MIG process can be used either semiautomatically or automatically. The basic equipment for any MIG installation consist of the following:
1. A welding gun
2. A wire feed motor and associated gears or drive rolls
3. A welding control
4. A welding power source
5. A regulated supply of shielding gas
6. A supply of electrode
7. Interconnecting cables and hoses
