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，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300℃ 15min的金相组织，微观组织没有明显变化，为粒状贝氏体。

In this study, pre-grinding was carried out on a pre-grinding machine, and then water grinding was carried out on sand paper 150, 320, 600 and 1000 in turn, and mechanical polishing was carried out on a polishing machine. After polishing, the sample was immersed in a mixed solution of 4 mL nitric acid (HNO3) + 96 mL anhydrous ethanol (CH3CH2OH) for 10~20 s. The metallographic structure was observed in Olympus GX53 optical microscope at 300℃ for 15min, and the microstructure showed no obvious change, indicating granular bainite.