MIG WELDING GUIDE
MIG BASIC WELDING TECHNIQUES
Two different welding processes are covered in this section (GMAW and FCAW),
with the intention of providing the very basic concepts in MIG welding, where
a welding gun is hand held, and the electrode (welding wire) is fed into a weld
puddle, and the arc is shielded by a gas (GMAW) or flux cored wire (FCAW).
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)
Shielding Gas
Molten Weld Metal
Nozzle
Electrode Arc
Base Metal
Solidified 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
Nozzle
(Optional)
Arc
Flux Cored
Electrode
Base
Metal
Solidified
Weld Metal
Position of MIG Torch (Fig 1-3)
The angle of MIG torch to the weld has an effect on the width of the weld.
Push
Vertical
Drag Pull
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.
(Fig 1-4)
5
o
to 15
o
Longitudinal Angle
90
o
Transverse
Angle
Direction of Travel
(Fig 1-5)
5
o
to 15
o
Longitudinal Angle
30
o
to 60
o
Transverse
Angle
Direction of Travel
Vertical Fillet Welds (Fig 1-6)
10
o
Longitudinal Angle
10
o
to 20
o
Longitudinal Angle
30
o
to 60
o
Transverse
Angle
30
o
to 60
o
Transverse
Angle
Direction of Travel
(Fig 1-7)
5
o
to 15
o
Longitudinal
Angle
30
o
to 60
o
Transverse Angle
Direction of Travel
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