残留奥氏体量较多(4级以上)时,由于背景亮,分布在其上的白色碳化物块形状模糊,难以区分残留奥氏体和碳化物而造成碳化物评级的困难。常规办法是将该试样在230~250℃的温度下,重新回火30~45 min,以减少或消除残留奥氏体,然后用硝酸酒精侵蚀,进行碳化物评级,该方法比较麻烦。新方法:将渗碳试样抛光后,先用4%(质量分数)的硝酸酒精溶液侵蚀,在放大400倍下观察,如果遇到残留奥氏体级别 When the amount of retained austenite is large (Grade 4 or above), the difficulty of grading the carbide due to the ambiguous shape of the white carbide blocks distributed on the background and the difficulty in distinguishing between the retained austenite and the carbide. The conventional method is to re-temper the sample at 230-250 ° C for 30-45 min to reduce or eliminate retained austenite and then attack the sample with nitric alcohol to grade the carbide. This method is troublesome. New method: The carburized sample after polishing, first with 4% (mass fraction) of nitric acid solution erosion, observed at 400 magnifications, if you encounter the residual austenite level