Gas Metal Arc Welding (GMAW) is a type of welding that uses a gas flowing through a hand held gun to shield the weld. Often referred to as MIG welding (which stands for metal inert gas), this process is the quickest and most common form of welding. The system lends itself for automatic or semi-automatic processes because of the ease of using continue wire feed setup. There are four main modes of transfer when welding with GMAW: Globular, Short-Circuiting, Spray and Pulse Spray. Each have a different advantages when it comes to economics, quality, speed and heat input into the metal being welded. These include:
· Globular: high heat, low efficiency but economic because of cheaper shielding gas possibilities
· Short-circuit: low current and there for low heat. Often used to weld thin walled non-structural pieces.
· Spray: high heat, high deposition rate but also good penetration and good for structural welds.
· Pulsed-Spray: a type of spray transfer that uses a pulsed current to control the arc characteristics. Allows for more control of heat input and is more suited to welding in positions other than flat. Special equipment is required for this mode of transfer.