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采用显微组织观察、XRD分析和硬度测试,研究了热处理后18Ni无钴马氏体钢薄壁管径向收缩0.20%～0.38%的现象。结果表明,材料经旋压后组织呈现明显的织构形貌,晶粒被拉长,沿环向排列,相应硬度值升高。固溶处理后,晶粒细化并回复正常形貌,大部分残余应力消除;时效过程中,形成一定量的逆转变奥氏体,同时基体中析出弥散分布的沉淀强化相。分析表明,形变引起的内应力消除是薄壁管径缩的主要原因,时效过程产生逆转变奥氏体以及沉淀析出等相关的微观结构变化对径缩现象有明显的贡献。
The microstructure observation, XRD analysis and hardness test were used to study the phenomenon of radial shrinkage of thin-walled tubes of 18Ni cobalt-free martensitic steel by 0.20% ~ 0.38% after heat treatment. The results show that the microstructure of the material is obvious after spinning, and the grains are elongated and arranged in the circumferential direction, and the corresponding hardness increases. After solution treatment, the grain refinement and normal morphology, most of the residual stress elimination; aging process, the formation of a certain amount of reverse austenite, while precipitated matrix precipitated precipitation enhanced phase. The analysis shows that the elimination of internal stress caused by deformation is the main reason for shrinkage of thin-walled tubes. The microstructure changes associated with austenite during aging and precipitation and precipitation have obvious contribution to the shrinkage phenomenon.