采用化学成分分析、金相检验、硬度测试以及拉伸试验等方法, 对某40Cr钢二级合闸支撑轴的弯曲失效原因进行了分析。结果表明: 由于该支撑轴设计图纸标注的硬度范围太宽, 使加工者无法明确确定的热处理工艺, 导致所制造支撑轴的硬度和抗拉强度偏低, 从而在磨合试验过程中发生弯曲失效。通过适当降低支撑轴回火温度, 提高其硬度和抗拉强度, 较好地解决了支撑轴磨合试验过程中弯曲失效问题。

By means of chemical compositions analysis, metallographic examination, hardness test and tensile test, the bending failure reasons of a 40Cr steel level 2 switching support shaft were analyzed. The results show that because the hardness range illustrated in the design paper was too wide and the manufacturer could not determine the heat treatment process, the hardness and strength of the support shaft was lower than the wanted values, and bending failure happened during running-in test. By appropriately reducing the tempering temperature and raising the hardness and strength of the support shaft, the bending failure problem could be well resolved.