Penetration characteristics in YAG laser and TIG arc hybrid welding, and arc and plasma /plume behaviour during welding. Welding phenomena in hybrid welding using YAG laser and TIG arc (First Report)

Abstract

Hybrid welding was carried out on Type 304 stainless steel plate under various conditions using a YAG laser combined with a TIG arc, and the effects of various welding conditions on the penetration and porosity formation were investigated for respective arrangements of a YAG laser beam or TIG torch ahead in hybrid welding, and the welding results were compared with the ones obtained with a TIG arc only or a YAG laser alone. In most cases the hybrid weld beads were deeper and wider in comparison with the YAG laser ones; however, this fact did not always take place. It was consequently found that a laser beam should be shot inside the molten pool made readily with a TIG arc alone to produce deeper weld beads effectively. It was also confirmed that, under the focused condition, the hybrid weld beads at the arc current of 200 A had a smaller amount of porosity than the YAG laser ones. The behavior of arc plasma and laser-induced plume as well as the relationship between a laser-shot spot and the molten pool made with TIG arc only was observed through a CCD camera and a high-speed camera during arc and hybrid welding to understand the hybrid welding phenomena and factors affecting penetration.