Tweco 250i Transmig Inverter - Manual (Page 57)

BASIC WELDING TRANSMIG 250I
Manual 0-5187 4-1 BASIC WELDING
SECTION 4:
BASIC WELDING GUIDE
4.01 MIG (GMAW/FCAW) Basic Welding
Technique
Two different welding processes are covered in this sec-
tion (GMAW and FCAW), with the intention of providing
the very basic concepts in using the Mig mode of weld-
ing, 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 welding grade shielding gas mix-
ture. 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
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 ob-
tained 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
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
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.