高碳马氏体不锈钢M390与奥氏体不锈钢304闪光对焊的微观组织及力学性能

Microstructure and mechanical properties of flash butt welding high carbon martensitic stainless steel M390 and austenitic stainless steel 304

通过闪光对焊方法连接M390高碳马氏体不锈钢与304奥氏体不锈钢.通过室温拉伸试验、显微硬度测试表征了焊接接头的力学性能.采用扫描电镜(SEM)、能谱分析(EDS)和X射线衍射(XRD)分析了焊接接头的微观组织形貌、元素扩散及各区域相组成.结果表明,利用合适的焊接工艺参数,M390与304之间可以形成焊缝形貌美观、抗拉强度最大值为480.62 MPa、断后伸长率为6.2%的闪光对焊焊接接头.焊缝组织由马氏体、奥氏体、M_(23)C_(6)和M_(7)C_(3)组成.M390侧及焊缝中碳化物类型为(Cr,V)碳化物.M390热影响区不同位置受到的热影响不同,导致在不同位置碳化物的聚集长大程度不同.M390粗晶区中碳化物聚集长大的同时有新的碳化物不断析出,碳化物以长条状和颗粒状两类形貌存在,而细晶区中碳化物尺寸小,以颗粒状存在.焊接接头为脆性断裂,断裂位置在焊缝,这与焊缝组织及焊接接头元素扩散相关.

The weldability of M390 high carbon martensitic stainless steel and 304 austenitic stainless steel has been investigated by flash butt welding method. Firstly, the mechanical properties of the welded joint were measured by the room temperature tensile experiment, the microhardness test was characterized. At the same time, scanning electron microscope(SEM), Energy Dispersive Spectroscopy(EDS) and X-ray diffraction(XRD) were used to analyze the microstructure morphology, element diffusion and phase composition of each region of the welded joint. The experimental results show that by appropriate welding parameters, M390 and 304 can form a macroscopically beautiful weld, the maximum tensile strength reaches is 480.62 MPa, and the elongation can reach 6.2%.The weld metal is composed of martensite, austenite, M_(23)C_(6) and M_(7)C_(3). The type of carbide on M390 side and in weld metal is(Cr, V) carbide. Different positions of M390 heat-affected zone are affected by different heat input, resulting in different aggregation and growth of carbides in different positions of M390 heat-affected zone. The carbides in the coarsegrained heat-affected zone of M390 aggregate and grow, and new carbides are continuously precipitated, the carbides exist in two types of morphologies: elongated and granular. The carbides in the fine-grained region are small in size and granular in morphology. Brittle fracture dominates the fracture surface of the welded joint. The fracture position is located in the weld metal, which is related to the weld metal microstructure and the diffusion of elements in the welded joint.