Development of high-speed MIG welding process. First report: Arc phenomena and formation mechanisms of surface defects

Summary

High-speed MIG welding is an effective process for reducing welding distortion and increasing the weld strength of aluminium alloys. The effects of welding conditions and the pulse duration of the pulsed current on the occurrence of pit-like surface defects in weld beads are examined to improve weld bead stability and to suppress the occurrence of surface defects during high-speed MIG welding. The formation mechanisms of surface defects are studied by observations of arc phenomena and weld bead appearances. The occurrence of surface defects during short arc and long arc welding respectively corresponds to changes in the welding current and arc voltage. Surface defects are considered to be formed by explosive scattering of the welding wire during short arc welding and solidification shrinkage during long arc welding. Surface defects can be suppressed through optimisation of the welding conditions. Reduction of the pulse duration of the pulsed current is effective for improving the appearance of weld beads, because the molten droplets increase with a decreasing pulse duration.