GAS METAL ARC WELDING (GMAW)

GAS METAL ARC WELDING (GMAW)

Gas Metal Arc Welding (GMAW) is a welding process which joins metals 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 can be done in three different ways:

_ Semiautomatic Welding - equipment controls only the electrode wire feeding. Movement of welding gun is controlled

by hand. This may be 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.

Basic equipment for a typical GMAW semiautomatic setup:

_ Welding Power Source - provides welding power.

_ Wire Feeders (Constant Speed And Voltage-Sensing) - controls supply of wire to welding gun.

Constant Speed Feeder - Used only with a constant voltage (CV) power source. This type of feeder has a control

cable that will connect to the power source. The control cable supplies power to the feeder and allows the capability

of remote voltage control with certain power source/feeder combinations. The wire feed speed (WFS) is set on the

feeder and will always be constant for a given preset value.

Voltage-Sensing Feeder - Can be used with either a constant voltage (CV) or constant current (CC) - direct current

(DC) power source. This type of feeder is powered off of the arc voltage and does not have a control cord. When

set to (CV), the feeder is similar to a constant speed feeder. When set to (CC), the wire feed speed depends on

the voltage present. The feeder changes the wire feed speed as the voltage changes. A voltage sensing feeder

does not have the capability of remote voltage control.

_ Supply of Electrode Wire.

_ Welding Gun - delivers electrode wire and shielding gas to the weld puddle.

_ Shielding Gas Cylinder - provides a supply of shielding gas to the arc.

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