MIG stands for Metal Inert Gas welding, many times called Wire-feed.. Also
referred as GMAW (Gas Metal Arc Welding).
The "Metal" refers to the wire which is what is used to start the arc. It is
shielded by inert gas and the feeding wire also acts as the filler rod. A
semi-automatic process, it is fairly easy to learn and use.
MIG torch nozzle cutaway image: (1) Torch handle, (2)
Molded phenolic dielectric (shown in white) and threaded metal nut insert
(yellow), (3) Shielding gas nozzle, (4) Contact tip, (5) Nozzle output face
MIG is required by law and by insurance
companies in many localities for structural repair of automotive frames. MIG
is also much easier to learn and faster to weld. For doing other types of
welding, like sheet metal, it can be a matter of personal preference. For
an auto body repair shop or a novice welder, a MIG is a good, practical
all-around welder.
The electrode is fed automatically through
the torch. In gas tungsten arc welding, the welder must handle a welding
torch in one hand and a separate filler wire in the other, and in
shielded metal arc welding, the operator must frequently chip off slag
and change welding electrodes. GMAW, on the other hand, requires only
that the operator guide the welding gun with proper position and
orientation along the area being welded. Keeping a consistent contact
tip-to-work distance (the stick out distance) is important, because a
long stick out distance can cause the electrode to overheat and will also
waste shielding gas. The orientation of the gun is also important—it
should be held so as to bisect the angle between the work pieces; that
is, at 45 degrees for a fillet weld and 90 degrees for welding a flat
surface. The travel angle or lead angle is the angle of the torch with
respect to the direction of travel, and it should generally remain
approximately vertical. However, the desirable angle changes somewhat
depending on the type of shielding gas used—with pure inert gases, the
bottom of the torch is out often slightly in front of the upper section,
while the opposite is true when the welding atmosphere is carbon
dioxide.
Course Duration: 1,2,3,or 4 months
depending on the candidate's previous experience in welding.
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