【摘要】 使用显微硬度仪、电子拉伸剪切试验机、SEM和IBIS等手段表征SUS301L不锈钢电阻点焊接头不同区域的微观组织、微区性能、断口形貌并研究其力学性能。结果表明，接头的熔核形貌呈椭圆形，分为母材区、热影响区和熔核区。接头熔核的边缘至核心区域的组织分布依次为柱状枝晶和等轴枝晶，接头的主要缺陷有熔核边缘的飞溅、熔核心部的缩孔和微裂纹，飞溅与缩孔的发生密切相关。熔核的直径是影响接头力学性能的关键因素，其力学性能与熔核直径呈正相关。随着双层板厚度的增加，单位熔核直径的增量产生的最大拉剪力增量随之显著增大。热影响区的硬度和强度均低于母材区和熔核区，导致在塑性环形成了一个软化区。这种软化区的强度较低，能承载的拉剪力较小，因此成为拉剪开裂的起始区域。拉剪断裂形式分为穿核断裂和沿核断裂，熔核的直径影响接头的断裂形式。更多还原

【Abstract】 The microstructure, micro zone properties, fracture morphology, and mechanical properties of different areas for the resistance spot welding joint of SUS301L stainless steel are systematically characterized via microhardness tester, electronic tensile shear testing machine, SEM, and IBIS. The results indicate that the morphology of the fusion zone in the joint is elliptical and which can be differentiated into the base metal zone, heat affected zone, and nugget zone. The microstructure distribution from the edge of the fusion core to the core center is columnar structure and equiaxed structure in sequence.The main defects of the joint include sputters on the edge of the fusion core, shrinkage porosity in the fusion core, and micro cracks, and the sputtering phenomenon is closely related to the occurrence of shrinkage porosity. The size of the nugget diameter is a key indicator that affects the mechanical properties, and there is a positive correlation between the two. As the thickness of the double-layer plate increases, the maximum tensile and shear force increment caused by the increment of the unit nugget diameter also significantly increases. The hardness and strength of the heat affected zone are lower than those of the base metal zone and the fusion zone, which leads to the formation of a softening zone at the corona bond. Due to the lower strength of this zone, the tensile shear force it can bear is relatively small,making it the starting area for tensile shear cracking. The forms of tensile shear fracture may be differentiated into passing through-core fracture and along-core fracture, the nugget diameter will affect the fracture mode of the joint.更多还原