304&Q235异种钢TIG焊接接头组织及力学性能研究

Study on Microstructure and Mechanical Properties of TIG Welded Joint of Dissimilar Steel 304&Q235

为了充分发挥材料各自的优势,异种钢材料的组合应用应运而生。本文采用TIG焊对Q235普通碳钢和304奥氏体不锈钢进行异种钢焊接试验,并采用控制变量的方法优化焊接工艺,获取符合工程实践要求的焊接接头。结合金相显微镜以及扫描电镜对焊接接头各区域微观组织演变过程进行观察,采用X射线衍射仪对焊缝进行物相分析,利用万能拉伸试验机和显微硬度计分别对焊接试样进行了拉伸性能测试及显微硬度测试。结果表明,焊缝区域微观组织由板条马氏体组成;在Q235碳钢界面明显发生了碳迁移现象;在焊接接头完全熔透的条件下,拉伸断裂位置发生在母材Q235碳钢一侧,说明焊接接头强度高于母材,断口呈现韧性断裂特征;焊接接头各区域显微硬度分布规律为:焊缝>304侧热影响区>304母材>Q235侧热影响区>Q235母材。

In order to give full play to their respective advantages,the combined application of dissimilar steel materials came into being,in this study,the dissimilar steel welding experiments of Q235 carbon steel and 304 austenitic stainless steel were carried out by TIG welding,and the welding process was optimized by controlling variables to obtain the qualified welding joints.The microstructure evolution of the welded joint was observed by metallographic microscope and scanning electron microscope and the analysis of phases in the weld seam were tested by X-ray diffractometer.The tensile properties and microhardness of the welded specimens were tested by universal tensile testing machine and microhardness tester respectively.The results show that the weld zone is composed of lath martensite;Carbon migration occurs obviously at Q235 interface,decarburization layer appears on one side of Q235 and carburization layer appears on one side of weld;The microstructure of 304 side fusion zone is fine and discontinuous vermicular ferrite distributed in austenite matrix.When the welded joint is fully penetrated,the tensile fracture occurs on the side of Q235 steel,which indicates that the strength of the welded joint is higher than that of the base metal,and presenting ductile fracture;The distribution rule of microhardness in each area of welded joint is as follows:weld zone>304 heat affected zone>304 base metal>Q235 heat affected zone>Q235 base metal.