Analysis of Weld Process Dependence on LME Crack Severity

Susceptibility to Liquid Metal Embrittlement (LME) during welding, particularly resistance spot welding (RSW), has been observed in select zinc-coated Advanced High Strength Steel (AHSS) grades, with significant variability reported as a function of alloy design, coating type, and manufacturing source. The industry is seeking a cost-effective production relevant LME susceptibility test. Many test methodologies have been explored, with most techniques based on common welding processes to ensure applicability of the results with production experience. These techniques characterize crack severity using different criteria, such as RSW welding, which uses the Crack Index, and gas metal arc welding (GMAW) and gas metal arc brazing (GMAB), which measure surface cracking on the faying surface. This work examines the relationships between different weld processes and crack analysis method pairs to determine if they show consistent crack sensitivity across materials, or if they exhibit a dependency on the weld process. RSW samples were collected based on standardized weld procedures targeting LME cracks around a consistent 6√t weld nugget diameter and expulsion current, whereas GMA samples were collected based on consistent heat inputs for an 8 mm circular fillet weld while varying Wife Feed Speed. To further characterize this relationship, a Bonferroni correction was used to indicate which weld process/crack analysis method pairs provide comparable results. The culmination of this study provides a comparison benchmark that allows for multiple process characterizations with the fewest number of tests, resulting in overall cost and labour reductions, in line with industry objectives.