Penetration characteristics and plume behavior in laser-arc hybrid welding

Hybrid welding using a YAG laser combined with a TIG arc was carried out on Type 304 stainless steel plate with various distances from the laser beam axis to the electrode for the establishment of high-efficient high-quality welding. It was consequently found that the optimum distance between the laser axis and the electrode for the production of deeper penetration was different between the backward welding and the forward welding. To establish the reason and the hybrid welding phenomena, arc plasma, laser-induced plume, evaporation spots and molten pool behavior during welding were observed using a CCD camera. Plasma plume behavior was found not to be different. The deepest weld bead could be produced when the YAG laser beam of high power density was targeted on the molten pool made stably with the TIG arc.