Relationship between the weldability and the process parameters for laser-TIG hybrid welding of galvanized steel sheets

Abstract

In the lap welding of zinc-coated steel, porosity formation is one of most significant weld defects. It is caused by zinc vapor generated between the steel sheets. Various solutions have been proposed in the past but development of more effective method remains a valuable subject to be investigated. In this study, laser-TIG hybrid welding was applied to the lap welding of zinc-coated steel without a gap. The weld defects could be eliminated by laser-TIG hybrid welding, as the leading TIG arc partially melted the upper sheet, and the coated zinc on the lapped surfaces were vaporized or oxidized before the trailing laser irradiated on the specimen. Optimization of the process parameters for laser-arc hybrid welding process is intrinsically sophisticated because the process has three types of parameters-arc, laser and hybrid welding parameters. In this paper, the relationship between weldability and the process parameters of the laser beam-arc distance, welding current and welding speed were investigated using a full factorial experimental design. Weld quality was evaluated using the weight of the spatter, as porosity formation is a major weld defect in the lap welding of zinc-coated steel sheets. It was found that the weld quality was increased as the laser beam-arc distance and welding current increased, and that this decreased as welding speed increased. © 2008 The Japan Institute of Metals.