Mig Welding (Gmaw) Variables - Firepower FP 125 Operating Manual & Installation Manual

FIREPOWER FP 125,135,165

4.08 MIG Welding (GMAW) Variables

Most of the welding done by all processes is on carbon steel. The following items describe the welding variables in short-arc weld-
ing of 24 gauge (0.024", 0.6mm) to ¼" (6.4mm) mild sheet or plate. The applied techniques and end results in the GMAW process are
controlled by these variables.
Pre-selected Variables
Pre-selected variables depend upon the type of material being welded, the thickness of the material, the welding position, the deposi-
tion rate and the mechanical properties. These variables are:
1. Type of electrode wire
2. Size of electrode wire
3. Type of gas (not applicable to self-shielding wires FCAW)
4. Gas flow rate (not applicable to self-shielding wires FCAW)
Primary Adjustable Variables
These control the process after Pre-selected Variables have been found. They control the penetration, bead width, bead height, arc
stability, deposition rate and weld soundness. They are:
1. Arc Voltage
2. Welding Current (wire feed speed)
3. Travel Speed
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. Stickout—distance between the end of the contact tube (tip) and the end of the electrode wire. Keep this at about 3/8" (10mm)
stickout (as shown in Figure 4-8).
2. Wire Feed Speed. Increase in wire feed speed increases weld current. Decrease in wire feed speed decreases weld current.
3. Nozzle Angle. (Figures 4-9 and 4-10) This refers to the position of the welding gun in relation to the joint. The transverse angle
is usually one half the included angle between plates forming the joint. The longitudinal angle is the angle between the center
line of the welding gun and a line perpendicular to the axis of the weld. The longitudinal angle is generally called the Nozzle
Angle and can be either trailing (pulling) or leading (pushing). Whether the operator is left-handed or right-handed has to be
considered to realize the effects of each angle in relation to the direction of travel.
OPERATION
Gas Nozzle
Tip to Work
Distance
Average Arc Length
Figure 4-9: Electrode Stick-Out
Longitudinal
Angle
Axis of Weld
Figure 4-10: Transverse and Longitudinal Nozzle Axes
4-6
Contact Tip (Tube)
Electrode Wire
Actual Stickout
Art: A-05109
Transverse
Angle
Art: A-05110
Manual 0-5123