18Ni无钴马氏体钢薄壁管径缩机理研究

Radial-shrinkage mechanism of 18Ni Co-free maraging steel thin-wall pipes

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 0.20%-0.38% radial-shrinkage of the thin-wall pipes made of 18Ni Co-free maraging steel after heat treatment was studied with hardness test,micrographs observation,and X-ray diffraction analysis.The results show that the microstructure of the material after hardness spinning presents texture patterns,the grains are stretched and arranged in certain orientation,and corresponding hardness values are increased.After solution treatment,grains are refined and resume to normal state,most of the residual stresses are eliminated.During the aging process,certain amounts of reversed austenite are formed.At the same time,dispersed strengthening phase is precipitated.The analysis indicates that the main reasons for the radial shrinkage are caused by elimination of the residual stress resulted from deformation and the reversed-austenite and other microstructure changes accompanying with precipitation are significantly contributing to the radial shrinkage.