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引言结构钢的机械性能在很大程度上取决于晶粒的尺寸。在常温下,钢的屈服强度、断裂强度和疲劳强度都随晶粒的细化而增加,并显示良好的强韧效应。工业上为获得细晶粒钢,常常采用添加微量元素的方法,如用Al、Ti、V、Zr和稀土抑制晶粒长大,但通过常规热处理后,其强度性能,尤其是综合性能并无显著增加。研究表明,一旦晶粒细化到超细范畴时,材料强化效应将显著增加。六十年代,R.A.Grange等人提出反复多次快速加热到奥氏体化温度和冷却进行超细化处理,引起了人们的注意。以后,为改善钢的强韧性能,发展为在两相区(γ+α)加热淬火(一次淬火+回火),但晶粒未细化,强度水平也不高。如果在两相区的温区A~(c1)～A~(c3)内反复循环加热淬火(亦称亚温循
Introduction The mechanical properties of structural steels depend to a large extent on the grain size. At room temperature, the yield strength, breaking strength and fatigue strength of steel increase with the grain refinement and show a good toughness effect. In order to obtain fine grain steel industrially, the method of adding trace elements such as Al, Ti, V, Zr and rare earth is often used to suppress grain growth. However, after conventional heat treatment, the strength properties, especially the comprehensive properties, are not A significant increase. Research shows that once the grain refinement to the ultra-fine areas, the material strengthening effect will be significantly increased. In the sixties, R.A. Grange et al. Proposed that people should pay more attention to the rapid and repeated heating to austenitizing temperature and cooling for superfine treatment. Later, in order to improve the toughness of steel, it was developed to be heated and quenched (once quenched and tempered) in the two-phase zone (γ + α), but the grain was not refined and the strength level was not high. If in the two-phase zone temperature A ~ (c1) ~ A ~ (c3) within the cycle of repeated heating quenching (also known as sub-temperature cycle