Effects of Welding Factors on Liquid Metal Embrittlement Cracking during Resistance Spot Welding of Zinc-coated High-strength Steel

During resistance spot welding of zinc-coated advanced high-strength steels (AHSS), cracks which are promoted by liquid metal embrittlement (LME) may occur. According to previous researches, welding current, welding time, electrode tip diameter and electrode misalignment angle are significant factors on LME cracking. In this study, the effects of these four factors on LME cracking were compared with an orthogonal design experiment. After welding, numbers and lengths of cracks were measured, and Crack Index (CI) of each experiment group was calculated for comparison. As the result, two types of LME cracks, i.e., Type A cracks located at the indentation of electrode tip and Type B cracks located at the indentation of electrode shoulder were observed. The order of influence degree on CI of Type A crack from high to low was welding current > electrode tip diameter > electrode misalignment angle > welding time. The order of influence degree on CI of Type B crack was electrode tip diameter > electrode misalignment angle > welding time > welding current. The result reveals that modifying welding current is the most effective way to reduce Type A cracks and optimizing the electrode tip diameter is significant for preventing Type B cracks.