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11.7 MIG Welding (GMAW) Variables
Most of the welding done by all processes is on carbon steel. The items below describe the welding
variables in short-arc welding of 0.6mm to 6mm mild sheet or plate. The applied techniques and end results
in the MIG process are controlled by these variables.
11.7.1 Preselected Variables
Preselected variables depend upon the type of material being welded, the thickness of the material, the
welding position, the deposition rate and the mechanical properties.
These variables are:
1. Type of welding wire
2. Size of welding wire
3. Type of shielding gas
4. Gas flow rate
11.7.2 Primary Adjustable Variables
These control the process after preselected variables have been found. They control the penetration,
bead width, bead height, arc stability, deposition rate and weld soundness.
These variables are:
1. Arc Voltage
2. Welding current (wire feed speed)
3. Travel speed
11.7.3 Secondary Adjustable Variables
These variables cause changes in primary adjustable variables which in turn cause the desired change
in the bead formation. They are:
1. Stick-Out: This is the distance between the end of the contact tube (tip) and the end of the
welding wire). Maintain at about 10mm stick-out for solid wire and 15-20mm for gasless wire.
Figure 41
2. Wire Feed Speed: Increase in wire feed speed increases weld current/amperage. Decrease in
wire feed speed decreases weld current.
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