Training on GMAW Fundamentals

Posted by Florida Gas Welding

welding11History Of Gmaw

Gas Metal Arc Welding (GMAW) is an arc welding process which joins metals. It does this by heating the metals to their melting point with an electric arc. The arc is between a continuous, consumable electrode wire and the metal being welded. The arc is shielded from contaminants in the atmosphere by a shielding gas.

GMAW had its beginning in the late 1940’s. It was developed as a means to speed up welding being done by the Gas Tungsten Arc Welding (GTAW) process. GTAW is also an arc welding process shielded by a shield-ing gas, but GTAW uses a nonconsumable tungsten electrode. The filler rod for GTAW is generally added manually at a much slower rate. GMAW was therefore developed to make welding a faster, more profitable process.

GMAW developed when GTAW proved to be too slow a process to weld thick sections of aluminum, where-as GTAW worked very well on thin gauge material thicknesses. GMAW became much more efficient and profitable for welding thicker materials.

During its early days, GMAW was generally accomplished with small diameter electrode wires, high amperage and shielding gases that were inert (non-reactive). Because an inert gas was used, the term Metal Inert Gas, or MIG welding was used to refer to this process. This term is still a very common reference for the welding process, even though technically incorrect. The development and use of reactive shielding gases gave rise to the term Gas Metal Arc Welding, or GMAW.

Since its development there have been many advances in the GMAW process. These have included advances in power source and wire feeder technology along with new developments in electrode filler wire and shielding gases. In the 1960’s it was found that there was a new way to weld with spray transfer GMAW, and not be limited to the flat and horizontal fillet weld joint positions.

It was found that this variation of GMAW-spray transfer would provide all position welding capability. Developments in pulsed spray transfer and the various power sources and controls, have increased the flexibility and use of this spray transfer variations.

Gmaw Fundamentals

Types Of Gmaw

GMAW can be done in basically three different ways. Semiautomatic welding means that the equipment controls only the electrode wire feeding. The movement of the welding gun is controlled by hand. This is sometimes called hand held welding.

Machine welding uses a gun that is connected to a manipulator of some kind (not hand held). An operator has to constantly set and adjust controls that move the manipulator. Automatic welding uses equipment which welds without the constant adjusting of controls by a welder or operator. On some equipment, automatic sensing devices control the correct gun alignment in a weld joint.

Gmaw Equipment Setup

A GMAW semiautomatic set-up may include a constant voltage welding power source with a constant speed wire feeder or a voltage sensing wire feeder, or a constant current welding power source may be used with a voltage sensing wire feeder. The choice of what type of welding power source and feeder to use will be determined by the mode of GMAW transfer desired.

The welding machine provides welding electrical power, the wire feeder controls the supply of wire to the welding gun. The welding gun directs the electrode wire into the joint. The shielding gas provides arc area protection and helps determine weld arc characteristics.

welding gmawBasic GMAW Equipment

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