Figure 8-23.GMA welding process.
Figure 8-24.Diagram of GMA welding equipment.
position as possible. The electrode is advanced along the
line of weld, using the forehand technique.
Always be sure there is good ventilation
when welding. The fumes from some of these
metals are highly toxic; therefore, a good ven-
tilating system is essential.
GAS METAL-ARC WELDING-GMAW
The gas metal-arc welding process (GMAW), often
called MIG, has revolutionized arc welding. In this
process, a consumable electrode (in the form of wire) is
fed from a spool through the torch (welding gun) at a
preset controlled speed. As the wire passes through the
contact tube of the gun, it picks up the welding current.
The consumable wire electrode serves two functions: it
maintains the arc and provides filler metal to the joint.
The method of delivery of the filler metal allows
GMAW welding to be basically a one-handed operation
which does not require the same degree of skill as
GTAW. Figure 8-23 shows the basic principle of gas
An important factor in the GMA welding process is
the high rate at which metal can be deposited. This high
rate of metal deposition and high speed of welding
results in minimum distortion and a narrow heat-af-
fected zone. When you are deciding whether to use GTA
or GMA welding, the thickness of the material should