9Ni钢临界区热处理

Intercritical Heat Treatment of 9Ni Steel

采用热力学软件Thermo-Calc计算了9Ni钢相图、相变温度以及合金元素Ni在奥氏体和铁素体中的含量。计算结果表明:Ni扩大了奥氏体区,并且当温度低于700℃时在奥氏体中形成偏聚。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)等对经淬火+临界区淬火+回火处理的9Ni钢进行了观察。结果表明:9Ni钢显微组织为回火马氏体组织和逆变奥氏体,逆变奥氏体约占7%,9Ni钢的冲击断口含有大量韧窝,强韧性满足性能要求。

Phase diagram,phase transformation temperature and the mass fraction of Ni in austenite and ferriteof 9 Ni steelwere calculated by Thermo-Calc. The calculation results indicated that Ni enlarge the austenite phase region and Ni enrichment in austenite. The present9 Ni steel that was processed by the heat treatment of normal quenching and intercritical quenching,followed tempering was studied by X-ray diffraction（ XRD）,scanning electron microscope. The experimental results indicate that the microstructure contained tempered martensite and 7 % austenite. Amount of dimples was found in the morphology of impact fracture surface. The micro-morphologies of the fracture exhibited as micro-dimples. The strength and toughness of the studied 9 Ni steel meet the technical requirement.