Reduction in liquid metal embrittlement cracking using weld current ramping

Advanced high-strength steels (AHSS) used in automotive structural components are commonly protected from corrosion using zinc coatings. However, the steel/zinc system creates the potential for liquid metal embrittlement (LME) during welding. Although adjustments to the welding process have been studied, the present literature has not examined the use of variable input currents for LME reduction. In this work, a ramp down welding current showed LME severity decreased by 60% compared to a standard constant current. Reductions in both crack size and number of cracks were observed for high currents (Imax + 20%). A numerical model of the resistance spot welding process was constructed, which showed when welding with a ramp down welding current, the electrode-to-sheet interface spends less time at an LME-sensitive temperature compared to the standard welding current. Furthermore, it avoids a large jump in tensile stress when the electrodes are removed.