DP600和HC180Y异种钢点焊接头组织和性能研究

Study on Microstructure and Mechanical Properties of DP600 Steel and HC180Y Steel Spot Welded Joints

研究了1.4 mm厚度的DP600和HC180Y异种钢电阻点焊接头的断口形貌、微观组织和力学性能。通过扫描电镜观察了接头的断口形貌及显微组织特征,采用显微硬度计测试了接头各区域的显微硬度。结果表明,DP600/HC180Y电阻点焊接头的破坏方式有三种,即界面分离、部分界面分离和熔核拔出,熔核拔出断裂形式的试样力学性能最佳,在该断裂模式下,裂纹始于HC180Y侧并向HC180Y侧扩展。DP600/HC180Y异种钢熔核区的组织并没有因为钢种不同而有差异,热影响区的组织因发生相变而具有明显的差异性。点焊接头显微组织决定了其硬度分布的特点,熔核区的硬度均高于母材区的。

The fracture morphology, microstructure, and mechanical properties of resistance spot welded joints of DP600 and HC180 Y dissimilar steels with 1.4 mm thickness were studied. The fracture and microstructure of the joints were observed by scanning electron microscopy(SEM), and the microhardness of the joints was measured by microhardness tester. The results show that there are three failure modes of DP600/HC180 Y resistance spot welding joint, i.e. interface separation,partial interface separation and nugget pull-out. The mechanical properties of samples with nugget pull-out fracture mode are the best, under the fracture mode, crack begins at HC180 Y side and propagate at HC180 Y side.The structure of nucleation zone of DP600/HC180 Y dissimilar steel does not differ because of different steel types. The structure of heat affected zone has obvious difference because of phase transformation.The hardness distribution of spot welded joint is determined by its microstructure. The hardness of nugget zone is higher than that of base metal zone.