Development of a constant load test to determine the liquid metal embrittlement susceptibility of advanced high-strength steels

Abstract Liquid metal embrittlement (LME) poses a challenge in resistance spot welding (RSW) of high-strength steels. The diffusion of zinc along the steel’s grain boundaries leads to a loss of ductility and premature material fractures. To test steel grades for LME susceptibility, RSW tests and hot tensile tests (HTT) have been developed. However, these methods sometimes fail to differentiate accurately. This study introduces a constant load test (CLT) and evaluates its feasibility as alternative test method for assessing LME susceptibility. The current work is conducted using a thermomechanical simulator, with specific settings developed for testing. Three steel grades are examined within a balanced preload range. The test speed being a dynamic parameter is measured at up to 180 mm/s during fracture. Temperature and elongation are correlated dependent on the preload, allowing better differentiation of steels compared to the standard HTT. Additionally, key values are derived to estimate LME susceptibility as relation of uncoated and Zn-coated samples.