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Possible Causes
Excessive heat input.
8. Basic welding guide – gas metal arc welding (MIG / GMAW)
Gas Metal Arc Welding (GMAW) is a welding process where an electrode wire is continuously fed
from an automatic wire feeder and welding gun to the base metal, where a weld pool is created,
and the arc is shielded by an inert (Argon) or active gas (CO2).
A - Input power cable
B - Gas line from cylinder to machine
C - MIG gun
D - Mass clamp
E - Workpiece
Advantages of GMAW:
- GMAW is the only consumable process that can weld most commercial alloys.
- GMAW, with its continuous wire electrode, overcomes the start-and-stop cycle of SMAW and
leads to fewer discontinuities and higher deposition rates.
- Since there is no need to stop welding to change consumed electrodes, long continuous welds
can be done manually.
- GMAW can easily be adapted to fully automatic welding processes.
- All welding positions can be used using the short-circuit transfer mode.
- Significantly higher utilization of filler metal than SMAW: There is no end loss as with the upper,
unconsumed end of an SMAW electrode.
- With spray transfer, deeper penetration with higher deposition than SMA and may permit
smaller fillets of the same strength.
- Metals as thin as 0.5842 mm may be welded.
- Easier to learn than most other welding processes.
8.1.
GMAW Process: Setting power source.
- Power source and wirefeeder setting requires some practice by the operator, as the welding
plant has two control settings that have to balance. There are the wire speed control and the
welding voltage control.
EN
Corrective Actions
Use restraint (clamp) to hold base metal in position.
Weld in small segments and allow cooling between welds.
Make tack welds along joint before starting welding
operation.
Select lower voltage range and/or reduce wire feed speed.
Increase travel speed.
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