Reduction in liquid metal embrittlement cracking using weld current ramping

• Published in: Welding in the world Vol. 63; no. 6; pp. 1583 - 1591
• Main Authors: DiGiovanni, Christopher, Bag, S., Mehling, C., Choi, K. W., Macwan, A., Biro, E., Zhou, N. Y.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-11-2019; Springer Nature B.V
• Subjects: Automobile industry; Automotive parts; Chemistry and Materials Science; Cracks; Electrodes; High strength steels; Liquid metal embrittlement; Materials Science; Metallic Materials; Numerical models; Protective coatings; Reduction; Reduction (metal working); Research Paper; Resistance spot welding; Solid Mechanics; Structural steels; Tensile stress; Theoretical and Applied Mechanics; Welding current; Zinc coatings; Advanced high-strength steel; Finite element analysis; Variable input current; Liquid metal embrittlement; Resistance spot welding; Thermal modelling
• ISSN: 0043-2288; 1878-6669
• DOI: 10.1007/s40194-019-00790-5

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 (
I
max
 + 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.