Optimization of butt welding of zinc-coated thin sheets with oscillating fiber laser beams: weld formation, microstructure, and mechanical properties

In this study, a series of butt welding tests with oscillating fiber laser beams were performed on zinc-coated thin sheets of 0.8 and 1.2 mm thicknesses. The optimized welding parameters were used to produce robust welds with no perforations or pores. The weld formation process, microstructure, and mechanical properties of welded joints with the butt surfaces processed via laser and shear cutting techniques were systematically investigated. Besides, the corrosion resistance of the laser oscillating welded joint was analyzed in detail. The welded joint with the butt surface processed by laser cutting shows less undercutting degree with a more favorable weld appearance. The two welded joints had similar microstructures containing different forms of ferrites. The heat-affected zone was almost identical to the base metal in microstructure but had larger grains. Widmanstatten ferrites’ content in the large-grained weld metal of welded joints with surface processed via laser cutting exceeded that of shear cutting-processed ones. The former had lower tensile strength than the latter, but their overall mechanical performance was better than base metal. After salt spray corrosion and electrochemical corrosion tests, the laser oscillating welded joint was only slightly corroded and exhibited no obvious deterioration in corrosion resistance.