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采用“控制轧制、轧后超快冷、亚温淬火+回火(UFC-LT)”工艺制备了5%Ni钢,系统研究了这一工艺条件下5%Ni钢的微观组织与力学性能,并与常规调质工艺(QT)和离线淬火、亚温淬火加回火工艺(QLT)进行了对比。结果表明,经UFC-LT工艺处理后,5%Ni钢的显微组织由回火马氏体、临界铁素体和5.83%的逆转奥氏体组成,并可以获得优于QT和QLT工艺的强韧性匹配(抗拉强度为608 MPa,屈服强度为491 MPa,-196℃时Charpy冲击功为185 J),韧脆转变温度由QT工艺的-152℃下降到-196℃以下。与QT工艺相比,UFC-LT工艺改善韧性的因素主要有渗碳体的溶解、高密度的大角度晶界及5.83%的逆转奥氏体。
The 5% Ni steel was prepared by “controlled rolling, ultra-rapid cooling after rolling and UFC-LT” process. The microstructure of 5% Ni steel under this condition Mechanical properties, and compared with the conventional quenching and tempering (QT) and off-line quenching, sub-temperature quenching and tempering process (QLT) were compared. The results show that the microstructure of 5% Ni steel is composed of tempered martensite, critical ferrite and 5.83% reversed austenite after UFC-LT treatment, and can be obtained better than QT and QLT process Toughness match (tensile strength of 608 MPa, yield strength of 491 MPa, Charpy impact energy of 185 J at -196 ° C), and the ductile-brittle transition temperature decreases from -152 ° C to -196 ° C in the QT process. Compared with the QT process, UFC-LT process to improve the toughness of the main factors are the dissolution of cementite, high-density high-angle grain boundaries and 5.83% of the reverse austenite.