Laser weldability of zinc-coated steels

Abstract

A study was performed with the objectives of understanding porosity formation mechanism and producing sound weld beads in Zn-coated steels with a CO2 laser or a Nd:YAG laser. The formation conditions of porosity and underfilled weld beads were established for cw YAG laser lap welding. The effects of Zn-coated layer thickness and gap between sheets on porosity formation and bead appearances were confirmed. In the case of no gap, good weld beads were not obtained in cw laser welding, while relatively sound ones were formed under properly pulse-modulated laser conditions. From the observation of welding phenomena by ultra-high speed video and microfocused X-ray transmission imaging system, the formation mechanisms of porosity and spattering was interpreted. The welding of butt-joints or lap edge joints with and without Zn-coated layers between sheets was recommended for easier production of porosity-reduced weld beads.A study was performed with the objectives of understanding porosity formation mechanism and producing sound weld beads in Zn-coated steels with a CO2 laser or a Nd:YAG laser. The formation conditions of porosity and underfilled weld beads were established for cw YAG laser lap welding. The effects of Zn-coated layer thickness and gap between sheets on porosity formation and bead appearances were confirmed. In the case of no gap, good weld beads were not obtained in cw laser welding, while relatively sound ones were formed under properly pulse-modulated laser conditions. From the observation of welding phenomena by ultra-high speed video and microfocused X-ray transmission imaging system, the formation mechanisms of porosity and spattering was interpreted. The welding of butt-joints or lap edge joints with and without Zn-coated layers between sheets was recommended for easier production of porosity-reduced weld beads.