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Fastening
& Joining Methods
Gas-metal
Arc Welding (GMAW) or (MIG)
In Gas Metal Arc Welding (GMAW), more commonly
known as Metal Inert Gas (MIG) welding,
an electric arc is established between the
workpiece and a consumable bare wire electrode.
The arc continuously melts the wire as it
is fed to the weld puddle. The weld metal
is shielded from the atmosphere by a flow
of an inert gas, or gas mixture.
The mig welding process operates on D.C.
(direct current) usually with the wire electrode
positive. This is known as ”reverse”
polarity. ”Straight” polarity,
is seldom used because of poor transfer
of molten metal from the wire electrode
to the workpiece. Welding currents of from
50 amperes up to more than 600 amperes are
commonly used at welding voltages of 15V
to 32V. A stable, self correcting arc is
obtained by using the constant potential
(voltage) power system and a constant wire
feed speed.
Continuing developments have made the mig
process applicable to the welding of all
commercially important metals such as steel,
aluminum, stainless steel, copper and several
others. Materials above .030 in. (.76 mm)
thick can be welded in all positions, including
flat, vertical and overhead. It is simple
to choose the equipment, wire electrode,
shielding gas, and welding conditions capable
of producing high-quality welds at a low
cost.
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