一种超细晶粒超高强韧性的高速车轴钢,所述车轴钢包括均匀的细晶奥氏体晶粒及Nb微合金纳米第二相增强的马氏体组织,所述奥氏体晶粒的平均晶粒尺寸在10μm以下；所述车轴钢的化学成分以重量百分比计包含Nb：0.00～0.06％和V：0.16～0.30％。同时本发明还提供所述钢的热处理方法。本发明充分发挥各元素在车轴钢中的作用,并采用两次淬火+高温回火热处理,最终使高速车轴具有良好的抗冲击、抗疲劳等服役性能、优异的强韧性匹配和良好的淬透性。本发明所车轴钢的组织中奥氏体晶粒的平均晶粒尺寸在10μm以下,屈服强度Rp0.2≥900MPa,抗拉强度Rm≥1000MPa,延伸率A≥15％,5mm缺口室温纵向冲击吸收功KU2≥100J,韧脆转变温度低于-80℃。

An ultra-fine grain ultra-high strength and toughness of high-speed axle steel, the axle steel includes uniform fine austenite grain and Nb micro alloy nano second phase enhanced martensite structure, the average grain size of the austenite grain is less than 10μm; The chemical composition of the axle steel by weight percentage includes Nb: 0.00 ~ 0.06% and V: 0.16 ~ 0.30%. The invention also provides a heat treatment method for the steel. The invention gives full play to the role of each element in axle steel, and adopts double quenching + high temperature tempering heat treatment to finally make high-speed axle have good impact resistance, fatigue resistance and other service performance, excellent matching of strength and toughness and good hardenability. The average austenite grain size in the structure of the axle steel of the invention is below 10μm, yield strength Rp0.2≥900MPa, tensile strength Rm≥1000MPa, elongation A≥ 15%,5mm notch longitudinal impact absorption work KU2≥100J at room temperature, and toughness and brittle-transition temperature below -80℃.