针对某公司生产的45钢齿轮轴零件加工批量开裂现象，采用光学显微镜、扫描电镜和ICP光谱仪等对开裂试样进行观察和分析。结果表明: 该45钢齿轮轴零件加工开裂的主要原因是由于淬火加热温度较高造成过热以及冷却时间过长造成冷却速率太快，使得工件热应力和组织应力增大超过其抗拉强度，齿轮轴台部薄弱处发生淬火开裂。同时，45钢齿轮零件的台部厚度正好处在淬火易裂范围5～14 mm，这也是导致其淬火开裂因素之一。

For the phenomenon of batch quenching cracking of 45 steel gear shafts, instruments and devices such as optical microscope, scanning electron microscope and ICP spectrometer were used to analyze the cracking samples. The results show that the cracking of the 45 steel gear shafts were mainly due to the overheating caused by the high quenching heating temperature and fast cooling because of too long cooling time, which increased the thermal stress and structural stress. And when the stress exceeded the tensile strength of the material, quenching cracking would happen at the weak step positions. At the same time, the step position thickness of 45 steel gear shafts was in the easy quenching cracking range of 5 - 14 mm, which was another reason for the cracking.