Laser beam welding has been very successfully applied to butt joining of zinc-coated steel sheet and does not harm the property of corrosion resistance of the steel sheet. However, when this technology is applied to lap joint of these sheets, good quality welds are not easily obtained. Special techniques must be employed to vent the zinc vapor generated at the interface of the sheets; otherwise the vapor will expel the liquid metal out of the melt pool leaving porosity. Many efforts have been attempted with some success and most of the processes need additional procedure, which add cost to entire welding process. A new welding technique has been developed in ATC for lap joint of zinc coated steel sheets without maintaining a gap. This technology uses a high-quality tilted CO_2 laser beam. Experimental results are presented and a possible explanation of zinc vapor venting mechanism for this welding technique is discussed in this paper.
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