某厂生产35CrMo零件，车削表面裂纹废品率高达35%，为分析裂纹形成原因，采用低倍、金相显微镜，扫描电镜等分析手段对样品裂纹进行了检验和分析。结果表明:裂纹系由钢中夹渣和夹杂引起。这些夹渣和夹杂在车削过程中剥落，暴露于表面，形似宏观裂纹的变形痕迹。夹渣和夹杂是由炼钢浇铸过程中裹入的锆铬质引流砂及伴生物所形成的。

The rejection rate caused by the turning surface cracks of parts made of 35CrMo steel is as high as 35% in a certain plant. Macro-etching method, metallurgraphic microscope and scanning electron microscope(SEM)were applied to analyze the formation of cracks. The results show that the cracks are caused by the slag inclusions and nonmetallic inclusions. Scaling off during the turning process, these inclusions are exposed to the part surface, which display as the deformation marks of macro-cracks on the surface. The slag inclusions and nonmetallic inclusions are formed by the wrapped stuffing sand containing Cr and Zr and its accompanied matter during the pouring process.