GMAW is also known as MIG or CO2 welding process. It was introduced in 1948. in the beginning it was used to weld aluminum (Al) using Argon (Ar) gas for shielding as a result the process was known as MIG which stands for Metal Inert Gas welding^TM. The later introduction of CO2 to shielding gas resulted in re-naming as CO2. MIG/CO2 machine is available to perform most of the wire-feed process semi-automatically. Much of the increase in the use of MIG/CO2 welding process is due to

It is extremely fast and economical. 

The machine under this process is easily used for welding on thin gauge metal to heavy plates. 

High welding rate.

Negligible post-weld clean-up. 

Welding cost is very economical. 

MIG/CO2 welding machines have a 100% duty cycle. This allows the machine to be run continuously without damage.Flat or constant-voltage type power sources Fig.2-b are conventionally used orsemi automatic and fully automatic processes involving a continuous electrode fed at a constant rate, such as MIG/CO2 welding, flux-cored arc welding and submerged-arc welding. The flat type power source together with a continuous electrode fed at a constant wire-feed speed form essentially a self-regulating arc. The arc length and weld current are interrelated in such a way as to corrent sudden changes.