This study consisted of a comparative evaluation of the mechanical properties and failure behavior of QP980 steel with those of DP980 steel spot welds. Moreover, this paper contributes to the existing knowledge of the resistance spot welding behavior of QP steels by analyzing their microstructure, hardness profile, tensile shear strength, cross tension strength, and failure behavior. It was found that the cross tension and tensile shear test samples all failed in a partial or full button pull-out mode, with an acceptable ductility ratio and cross tension strength as per AWS. Fractography of the testing samples showed that the crack propagated along the fusion boundary, an occurrence previously reported in the literature for QP980, but with no comprehensive explanation regarding the mechanism behind the behavior. This work discusses the similarities between this behavior and welds exhibiting a possible softened region at the fusion boundary, a phenomenon known as the halo ring. The role of this softened region on the failure behavior of the welds is described.

该研究包括对 QP980 钢与 DP980 钢点焊的机械性能和失效行为的比较评估。此外，本文通过分析 QP 钢的显微组织、硬度分布、拉伸剪切强度、横向拉伸强度和破坏行为，有助于了解 QP 钢的电阻点焊行为。发现横向张力和拉伸剪切试验样品都在部分或完全按钮拉出模式下失败，具有可接受的延展性比和横向拉伸强度，符合 AWS。测试样品的断口分析表明裂纹沿熔合边界扩展，这是先前在 QP980 文献中报道的一种情况，但没有对行为背后的机制进行全面解释。这项工作讨论了这种行为与在熔合边界处可能出现软化区域的焊缝之间的相似性，这种现象称为晕环。描述了该软化区域对焊缝失效行为的作用。