In-Situ Surface Ablation to Mitigate Liquid Metal Embrittlement Cracking In Resistance Welding of Galvanized Steels

摘要

It is known that when zinc coated steel components (e.g., galvanized or galvannealed) are welded, liquid zinc which melts at approximately 400°C interacts with the steel, which together with the strains and stresses from heat-up and cool-down of the workpieces occurring during resistance welding can cause liquid metal embrittlement (LME) cracking. Thus, it is essential that a method to mitigate LME cracking in welding (e.g., resistance, laser, arc...etc.) of galvanized steel components be developed. A method of surface ablation (e.g., laser, plasma...etc.) to remove Zn completely or partially at the regions where LME cracking is formed while leaving enough Zn to retain sound corrosion performance prior to welding is proposed. The removal of Zn element on the surfaces of the workpieces reduces the propensity of molten Zn penetrating into the grain boundaries of austenite, and consequently LME cracking is mitigated in welding of galvanized steel. This method would enable the automotive industry to implement galvanized high strength steels for vehicle lightweighting.