在本研究中，先在预磨机上进行预磨，然后在150、320、600和1000号砂纸上依次水磨后，在抛光机上进行机械抛光，抛光后的试样置于4 ml 硝酸（HNO3） + 96 ml 无水乙醇（CH3CH2OH）混合溶液浸蚀10~20 s，在Olympus GX53光学显微镜中观察其金相组织，粒状贝氏体组织发生分解。

In this study, pre-grinding was carried out on a pre-grinding machine, followed by water grinding on 150,320,600 and 1000 sandpapers, and then mechanical polishing was carried out on a polishing machine. The polished samples were immersed in 4 ml nitric acid ( HNO3 ) + 96 ml anhydrous ethanol ( CH3CH2OH ) mixed solution for 10-20 s. The metallographic structure was observed by Olympus GX53 optical microscope, and the granular bainite structure was decomposed.