4.2 Arc Welding Parameters

In manual metal arc welding (MMAW / SMAW), an electric arc between a coated electrode and the job melts both, and they fuse to form the weld. The quality of the weld depends on the correct welding parameters.

1. Welding current

• Chosen according to electrode diameter and job thickness.
• Rough rule: about 40 A per mm of electrode core diameter (e.g. 3.15 mm electrode ≈ 100–130 A).
• Too low current → poor fusion, arc sticks. Too high → excessive spatter, undercut, burn-through.

2. Arc length

• Distance between the electrode tip and the job.
• Correct (normal) arc length ≈ diameter of the electrode core wire.
• Long arc → spatter, poor penetration, porosity. Short arc → electrode sticks.

3. Travel speed

Too fast → narrow, weak bead. Too slow → wide, heavy bead and overheating.

4. Electrode angle

For a flat butt weld: about 70°–80° to the line of travel, 90° to the job on either side.

5. Polarity (with DC)

• DCEN (straight polarity) – electrode negative: more heat on the job, deeper penetration.
• DCEP (reverse polarity) – electrode positive: more heat on electrode; used for thin sheets and many coated electrodes.
• AC has no polarity.