Liquid metal embrittlement susceptibility of galvanized advanced high strength steel with high manganese content

Abstract The galvanized advanced high strength steel (AHSS) with high manganese content tends to suffer the liquid metal embrittlement (LME) during the resistance spot welding (RSW) process. In this study, the LME susceptibility of one kind of galvanized AHSS with high manganese content was systematically evaluated based on the criterion of Auto/Steel Partnership (A/SP). The galvanized AHSS with high manganese content was welded at 16 groups of different welding currents from 7.0 kA to 14.5 kA with intervals of 0.5 kA. No evident LME cracks could be observed in the cross sections of those specimens below expulsion. However, numerous severe LME cracks could be clearly observed for the joints at or above expulsion. It was considered that the increase of the welding current aggravated the LME severity of this kind of steel. Additionally, the nugget size could be measured after the chemical etching. The nugget size gradually increased with increasing the welding current. Based on the A/SP criterion, the results revealed that this kind of galvanized AHSS with high manganese content exhibited high LME susceptibility, thus not meeting the requirements. Except for the large welding current, it was deemed that the high Mn content was the crucial factor to lead to high LME susceptibility of this steel.