热冲压成形钢与双相钢点焊接头组织及显微硬度分析

Microstructure andmicrohardness analysis of spot welded joint of hot stamping forming steel and dual phase steel

本文以厚度为1.8 mm热成形钢T1500HS与厚度为1.3 mm的DP600钢板电阻焊点为研究对象,对其微观组织和显微硬度进行了测试分析。试验结果表明,从母材、热影响区到焊核区域,T1500HS侧的微观组织依次为:马氏体/回火马氏体/铁素体+马氏体/细晶马氏体/板条状马氏体;DP600侧微观组织依次为:铁素体+少量马氏体/铁素体+马氏体/细小铁素体+马氏体/马氏体+少量铁素体/板条状马氏体。由于各区域微观组织的变化,在显微硬度测试中可观察到DP600侧自母材、热影响区到焊核中心硬度呈增加趋势而在T1500HS一侧,硬度自母材、热影响区到焊核中心则呈现先减小后增加再降低的特点,其在热影响区位置出现了明显的软化现象。

Resistance spot welding of 1.8 mm Press-hardened steel T1500HS and 1.3 mm dual phase steel DP600 was undertaken.The microstructure and vickers hardness of weld joint were investigated.The results indicate that in sequence from the base metal to weld nugget,the microstructure of T1500HS side shows M/tempered M/F+M/fine M/lath M,while the DP600 side expresses F+M/F+M/fine F+M/M+F/lathM.Due to the difference of microstructure in each region,a obvious softened area appears in the heat affected zone of T1500HS side,and thevickers hardnessgradually increases along the direction from base metal to weld nugget in the heat affected zone of DP600 side.