Effect of the Welding Current on the Liquid Metal Embrittlement in the Resistance Spot Welded Galvanized DP1180 Advanced High Strength Steel

DP1180 advanced high strength steel (AHSS) used in automobiles is usually protected from corrosion by the Zn-based coating. However, liquid metal embrittlement (LME) tends to occur in galvanized DP1180 steel during the resistance spot welding (RSW) process. This kind of crack is potentially harmful to the load-carrying performance of the involved welded joints. In this paper, the effect of the welding current on the LME in the resistance spot welded galvanized DP1180 steel was comparatively investigated. With the welding current of 10.5 kA, no obvious LME cracks could be observed on the surface of the welding spot. When the current increased to 11.5 kA, the LME cracks were produced, and the longest one was about 56.3 μm. Compared with the first two states, more and longer LME cracks inside or around the spot weld indentation could be observed, and the longest one was 118.2 μm in the specimen with the current of 13.5 kA. Moreover, the results reflected that the increased welding current with the added heat input could produce more and longer LME cracks under the same electrode force. Therefore, appropriate welding current was required to be controlled to suppress the LME in the DP1180 welded joint.