为找到轧钢机齿轮在生产中磨削后齿面出现裂纹缺陷的原因，对轧钢机渗碳淬火齿轮进行了宏观分析、化学成分分析、硬度测试及金相检验等。结果表明：磨齿工艺不当导致齿轮最表层形成未经回火的二次淬火隐晶马氏体，硬度高且脆性大，渗碳层最终形成高-低-高的典型磨削淬火烧伤硬度分布特征，当齿轮磨削表面产生的热应力、拉应力和组织应力大于齿轮表面的断裂强度时将在此处产生裂纹。可通过控制渗碳淬火后的马氏体为隐晶状或细针状，控制残余奥氏体含量面积分数在20%以内、表面碳含量质量分数为0.7%~0.9%，以及选择合理的回火温度、回火时间和磨齿工艺等措施来防止磨齿裂纹的产生。

In order to find out the causes of cracks on the gear surface of rolling mill after grinding in production, macro analysis, chemical composition analysis, hardness test and metallographic examination were carried out on the carburized and quenched gear of rolling mill. The results show that the improper grinding process led to the formation of secondary quenched cryptocrystalline martensite without tempering on the surface layer of gear, with high hardness and brittleness, and the carburized layer finally formed high-low-high typical hardness distribution characteristics of grinding quenching burn. When the thermal stress, tensile stress and microstructural stress on the ground surface are greater than the fracture strength of the gear surface, cracks will appear here. The generation of grinding crack can be prevented by controlling the martensite after carburizing and quenching to be cryptocrystalline or fine acicular, controlling the area fraction of retained austenite content to be less than 20%, the surface carbon content to be 0.7%~0.9%, and selecting reasonable tempering temperature, tempering time and grinding process.