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Gas Metal Arc Welding (GMAW)
This process, also known as MIG welding, CO2
welding, Micro Wire Welding, short arc welding,
dip transfer welding, wire welding etc., is an electric
arc welding process which fuses together the parts
to be welded by heating them with an arc between
a solid continuous, consumable electrode and the
work.
Shielding is obtained from an externally supplied
welding grade shielding gas. The process is
normally applied semi automatically; however the
process may be operated automatically and can
be machine operated. The process can be used
to weld thin and fairly thick steels, and some non-
ferrous metals in all positions.
GMAW Process
(Fig 1-1)
Weld Metal
Molten Weld Metal
Flux Cored Arc Welding (FCAW)
This is an electric arc welding process which
fuses together the parts to be welded by heating
them with an arc between a continuous flux filled
electrode wire and the work. Shielding is obtained
through decomposition of the flux within the
tubular wire. Additional shielding may or may
not be obtained from an externally supplied gas
or gas mixture. The process is normally applied
semi automatically; however the process may be
applied automatically or by machine.
It is commonly used to weld large diameter
electrodes in the flat and horizontal position and
small electrode diameters in all positions. The
process is used to a lesser degree for welding
stainless steel and for overlay work.
FCAW Process
(Fig 1-2)
Shielding Gas
(Optional)
Molten Metal
Molten
Slag
Slag
Weld Metal
12
Shielding Gas
Nozzle
Electrode Arc
Base Metal
Nozzle
(Optional)
Flux Cored
Electrode
Arc
Base
Metal
Position of MIG Torch
(Fig 1-3)
Push
The angle of MIG torch to the weld has an effect on
the width of the weld.
The welding gun should be held at an angle to the
weld joint. (See Secondary Adjustment Variables
below).
Hold the gun so that the welding seam is viewed at
all times. Always wear the welding helmet with
proper filter lenses and use the proper safety
equipment.
CAUTION!!
Do not pull the welding gun back when the arc is
established. This will create excessive wire
extension (stick-out) and make a very poor
weld.
The electrode wire is not energized until the gun
trigger switch is depressed. The wire may therefore
be placed on the seam or joint prior to lowering
the helmet.
5
(Fig 1-4)
Longitudinal Angle
90
o
Transverse
Angle
(Fig 1-5)
o
o
5
to 15
Longitudinal Angle
Vertical
Drag Pull
o
to 15
o
Direction of Travel
o
o
30
to 60
Transverse
Angle
Direction
of Travel
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