Effect of Welding Current on Liquid Metal Embrittlement of the Resistance Spot Welded Galvanized QP980 Advanced High-Strength Steel

QP980 advanced high-strength steel used in automobile is usually protected from corrosion by Zn-based coating. However, liquid metal embrittlement (LME) is tended to occur in galvanized QP980 steel during the resistance spot welding process and therefore leads to the reduction of load-carrying property of the involved welded joint. In this paper, the effect of welding current on LME of the resistance spot welded galvanized QP980 steel was comparatively studied. The results showed that more and longer LME cracks inside and around the spot weld indentation could be observed in the specimens with increasing the welding current, reflecting that the increased welding current with the added heat input could result in the LME cracks under the same electrode force. Therefore, appropriate welding current was required to control the heat input and thus suppress the LME of the QP980 welded joint.