用液氮作为冷却介质对45钢进行了深冷处理,测试并比较了深冷处理和未深冷处理试样的洛氏硬度,用光学显微镜观察了两组试样的显微组织。结果表明:45钢深冷处理后的组织变得更加均匀,珠光体片层间距也变小,且大量残余奥氏体转化为力学性能更好的马氏体;深冷处理是一种提高45钢硬度的有效方法。 45 steel was cryogenic treated with liquid nitrogen as the cooling medium. The Rockwell hardness of cryogenic and non-cryogenic treated specimens was tested and compared. The microstructures of the two specimens were observed with light microscope. The results show that the microstructure of 45 steel is more uniform after cryogenic treatment, the spacing of pearlite sheets becomes smaller, and a large amount of retained austenite is transformed into martensite with better mechanical properties. Cryogenic treatment is a kind of method to improve the hardness of 45 steel Effective method.