Shear band formation at the fusion boundary and failure behaviour of resistance spot welds in ultra-high-strength hot-stamped steel

Abstract

The failure of resistance spot welds in ultra-high-strength press-hardened steels often occurs due to martensite tempering in the heat-affected zone. In the present work, however, it is shown that the failure occurs by local shear band formation at the fusion boundary (FB) in spot welds in press-hardened 22MnB5 (Al–Si coated). The failure behaviour of spot welds was investigated to understand failure mechanisms with respect to microstructural features. The results showed that a 104 μm wide shear band is located in a local area of softening adjacent to the FB. A fine-meshed model was developed using hardness-based local properties to simulate the softened zone which was able to capture the observed failure at the FB interface.