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采用光学显微镜、扫描电镜和洛氏硬度计试验研究了20Mn2钢在两种不同热处理方式下的组织特征,通过多功能拉力试验机检测钢材的力学性能。分析表明,20Mn2钢常规热处理的最优参数为淬火890℃保温20 min、回火450℃保温30 min;中频热处理的最优参数为淬火温度950℃、回火温度550℃。试验结果显示,中频热处理后20Mn2钢材的组织和力学性能均优于常规热处理,其主要原因是中频热处理的加热模式使得20Mn2钢材的组织晶粒更加细化。在中频热处理之前20Mn2钢再进行一次正火处理来细化晶粒,还可以进一步提高钢的力学性能。
The microstructures of 20Mn2 steel under two different heat treatments were studied by optical microscope, scanning electron microscopy and Rockwell hardness tester. The mechanical properties of the steel were tested by multi-purpose tensile testing machine. The analysis shows that the optimum parameters of conventional heat treatment for 20Mn2 steel are quenching 890 ℃ holding 20 min, tempering 450 ℃ holding 30 min; the optimum parameters of medium frequency heat treatment are quenching temperature 950 ℃, tempering temperature 550 ℃. The experimental results show that the microstructure and mechanical properties of 20Mn2 steel after medium frequency heat treatment are better than those of conventional heat treatment. The main reason is that the heating mode of medium frequency heat treatment makes the grain of 20Mn2 steel more refined. 20Mn2 steel in the intermediate frequency heat treatment before normalizing to refine the grain, but also further improve the mechanical properties of steel.