Tweco VAF4HD Transmig - Manual (Page 64)

TRANSMIG VAF4HD
SERVICE 4-4 Manual 0-5269
4.06 MIG (GMAW/FCAW) Basic Welding Technique
Two different welding processes are covered in this section (GMAW and FCAW), with the intention of providing
the very basic concepts in using the Mig mode of welding, where a MIG Torch is hand held, and the electrode
(welding wire) is fed into a weld puddle, and the arc is
shielded by an inert welding grade shielding gas or inert
welding grade shielding gas mixture.
GAS METAL ARC WELDING (GMAW): This process,
also known as MIG welding, CO
2
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 or weld-
ing grade shielding gas mixture. 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.
Art # A-8991_AB
Shielding Gas
Molten Weld Metal
Solidified
Weld Metal
Nozzle
Electrode
Arc
Base Metal
GMAW Process
Figure 4-1 GMAW Process
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 continu-
ous 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.
Art # A-08992_AB
Molten
Slag
Nozzle
(Optional)
FCAW Process
Flux Cored
Electrode
Arc
Shielding Gas
(Optional)
Slag
Molten Metal
Base Metal
Solidified
Weld Metal
Figure 4-2 FCAW Process
Position of MIG Torch
The angle of MIG Torch to the weld has an effect on the
width of the weld.
Push Vertical Drag/Pull
Art # A-07185_AB
Figure 4-3 Position of MIG Torch
The MIG Torch should be held at an angle to the weld
joint. (See Secondary Adjustment Variables below)
Hold the MIG Torch 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 MIG Torch 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 MIG Torch
trigger switch is depressed. The wire may therefore be
placed on the seam or joint prior to lowering the helmet.
Butt & Horizontal Welds
Direction of
Travel
5° to 15°
Longitudinal
Angle
90°
Transverse
Angle
Art # A-08993
Figure 4-4 Butt & Horizontal Welds