热处理工艺对M390/304 CMT焊接接头微观组织及力学性能的影响

基于改善M390高碳马氏体不锈钢与304奥氏体不锈钢焊接接头的力学性能特别是提高焊接接头硬度，以达到高端刀具生产的要求，对冷金属过渡焊接M390高碳马氏体不锈钢与304奥氏体不锈钢获得的焊接接头进行不同工艺的热处理研究.采用拉伸、维氏显微硬度测试及扫描电镜(SEM)表征不同热处理工艺的焊接接头力学性能及微观组织演变，统计了不同热处理工艺下焊接接头中M390母材、M390细晶区和M390粗晶区等区域的碳化物分布，研究了不同热处理工艺下焊接接头的断裂机理.研究结果表明，在1 150℃水淬热处理工艺下焊接接头既满足刀具钢硬度的要求，又具有良好的力学性能，可以作为M390/304焊接接头的最佳热处理工艺，对应焊接接头的抗拉强度和断后伸长率为502 MPa和20.8%，抗拉强度和断后伸长率分别是焊态的98%和95%. 1 150℃水淬热处理工艺的M390母材、细晶区和粗晶区中碳化物平均尺寸最小，碳化物形貌以细小的块状均匀分布.淬火温度升高，抗拉强度和断后伸长率均呈现出先下降后升高的趋势，随着冷却速度的减小，抗拉强度和断后伸长率均呈现出下降的趋势.不同热处理工艺下焊接接头的断裂位置在M390粗晶区...

Effect of heat treatment process on microstructure and mechanical properties of M390/304 CMT welded joints

In order to improve the mechanical properties of M390 high carbon martensitic stainless steel and 304 austenitic stainless steel welded joints, especially the hardness of welded joints to meet the requirements of advanced knives production, different heat treatment processes of welded joints were performed for M390 high carbon martensitic stainless steel and 304 austenitic stainless steel joints obtained by cold metal transfer welding. Tensile, Vickers microhardness tests and scanning electron microscopy (SEM) were used to characterize the mechanical properties and microstructure evolution of welded joints with different heat treatment processes, the carbide distributions of M390 base metal, M390 fine-grained region and M390 coarse-grained region in welded joints under different heat treatment processes were calculated, the fracture mechanism of welder joints under different heat treatment processes was studied. The research results show that the water quenching at 1 150 ℃ heat treatment process not only meets the hardness requirements of advanced knives, but also has good mechanical properties, and can be used as the best heat treatment process for M390/304 welded joints, the tensile strength and elongation of the corresponding welded joints reach 502 MPa and 20.8%, the tensile strength and elongation of the corresponding welded joints reach 98% and 95% of as-welded joint. The average size of carbides in M390 base metal, fine-grained region and coarse-grained region of water quenching at 1 150 ℃ heat treatment process is the smallest, and the carbide morphology is uniformly distributed in small blocks. With the increase of quenching temperature, both the tensile strength and elongation showed a trend of first decreasing and then increasing. With the decrease of cooling rate, both the tensile strength and elongation showed a decreasing trend. The welded joints under different heat treatment processes are fractured at the interface between M390 coarse-grained region and weld metal, where the hardness varies greatly, and there is a phenomenon of uneven stress distribution.