Abstract
Suppression of weld slag formation has been studied to improve corrosion resistance of ultra-high strength steel sheet for automotive chassis parts. Although Metal Inert Gas welding can prevent slag formation, its unstable arc phenomena on carbon steel induces weld bead shape defects. This study aims to develop a highly stable MIG welding process for hot-rolled UHSS which forms sound bead shape with decreasing slag. Detailed observation of metal transfer behavior revealed that the combination of higher pulse peak current and lower pulse base current than conventional MIG welding realize cyclic short-circuit transfer and it can lead to proper bead shape. Low base current leads to a stable growth of metal droplet and the metal droplet are pushed down by accelerated plasma flow in peak period. The MIG welding utilizing high current pulse offered sound weld bead shape and slag-less simultaneously. Through these findings, the combination of intensive pulse current and extremely low base current is proposed as a new pulsed current pattern for hot-rolled UHSS.
