M390高碳马氏体不锈钢与304奥氏体不锈钢TIG焊连接机理

TIG Welding Mechanism of M390 Martensitic Stainless Steel and 304 Austenitic Stainless Steel

针对M390高碳马氏体不锈钢与304奥氏体不锈钢的连接问题,使用TIG焊接方法,并对M390/304焊接接头进行拉伸、维氏显微硬度测试、SEM及EDS表征焊接接头力学性能及微观组织,X射线衍射分析各区域中相组成,统计焊缝及M390一侧不同区域的晶粒尺寸,揭示焊接接头的断裂机理。研究结果表明,采用TIG焊可以实现M390高碳马氏体不锈钢与304奥氏体不锈钢异种金属连接,得到焊缝形貌美观、无孔洞、无夹杂等缺陷的焊接接头。最佳焊接工艺参数为:焊接电流120 A,电弧电压16 V,焊接速度3.3 mm/s;对应的抗拉强度为266 MPa。焊缝由马氏体、M23C6及M7C3组成,焊缝中晶粒尺寸最大,平均晶粒尺寸为17.96μm。由于焊缝基体组织为马氏体且晶粒尺寸最大,焊接接头断裂在焊缝,断裂类型为解理断裂。M390侧和焊缝中碳化物主要为(Cr、V)碳化物,从M390母材到粗晶区,碳化物形貌逐渐由颗粒状向长条状演变,热的作用导致碳化物长大聚集。

M390 high carbon martensitic stainless steel and 304 austenitic stainless steel are joined by Tungsten Inert Gas arc welding(TIG)experiments in the manufacturing of high-end cutting tools.The mechanical properties and microstructure of the welded joint were characterized by tensile experiment,vickers microhardness test,Scanning Electron Microscope(SEM)and Energy Dispersive Spectrometer(EDS).Analysis of phase composition in each location using X-ray diffraction.The grain sizes in different areas on M390 side are measured and joining mechanism of the welded joint was revealed.The results show that:M390 high carbon martensitic stainless steel and 304 austenitic stainless steel TIG welding joints with beautiful weld appearance,no holes,no inclusions and other defects can be achieved.The best welding process parameters are welding current of 120 A,welding voltage of 16 V,welding speed of 3.3 mm/s,the corresponding tensile strength can reach 266 MPa.The weld metal is composed of martensitic、M23C6 and M7C3.The grain size in weld metal is the largest,which can reach an average grain size of 17.96μm.Because the weld metal matrix is martensitic,with the highest grain size,cleavage fracture occurs in the weld metal.The carbides in M390 side and weld metal are mainly(Cr,V)carbides.The car‐bide morphology gradually evolves from block shape to long strip shape from M390 base metal to the coarse-grained region.