The Identification of a New Liquid Metal Embrittlement (LME) Type in Resistance Spot Welding of Advanced High-Strength Steels on Reduced Flange Widths

Liquid metal embrittlement (LME) cracking is a phenomenon observed during resistance spot welding (RSW) of zinc-coated advanced high-strength steels (AHSS) in automotive manufacturing. In this study, severe cracks are observed at the edge of the sheet under reduced flange widths. These cracks, traversing the AHSS sheet, culminate at the edge with a width of approximately 1.2 mm. Through combined numerical and experimental investigations, and material testing, these cracks are identified and validated as a new type of LME crack. The mechanism behind this crack formation is attributed to unique geometric conditions that, when compared to center welding, amplify radial material flow by ninefold to 0.87 mm. The resultant tangential tensile stresses approximate 760 MPa, which exceed the yield strength of the examined advanced high-strength steel (AHSS) under heightened temperature conditions, and when combined with liquid zinc, promote the formation of this new type of LME crack.

Automated summary

In resistance spot welding of zinc-coated AHSS in automotive manufacturing, severe cracks are observed at the sheet edge under reduced flange widths. Through combined numerical and experimental investigations, these cracks are identified as a new type of LME crack caused by unique geometric conditions that amplify radial material flow and result in tangential tensile stresses exceeding the yield strength under heightened temperature conditions, combined with liquid zinc.