Study on influence factors of liquid metal embrittlement cracks in resistance spot welded joints of galvanized Q & P980 steel

The new generation ultrahigh strength Q & P (Quenching and Partitioning) steel owns both high strength and fine ductility, it has wide application prospect in automobile industry. However, after carrying out resistance spot welding experiment on the galvanized high strength Q & P980 steel plates, cracks were detected on the surface of joint, former researches showed that the cracks were caused by liquid metal embrittlement (LME), that was the steel plates were intergranular fractured under the effect of liquid zinc and stress. Experiment results indicated that process parameters (including welding current, welding time and electrode force) and process conditions (including electrode morphology, pressure mode and electrode alignment) were found to have influence on the LME cracks of joints. Thus, there is a possibility to reduce the crack sensibility by adjusting the process parameters and conditions.