40Cr钢螺母断裂失效分析

Failure Analysis About 40Cr Steel Nut

某公司生产的汽车半轴锁紧螺母在装配时被拧裂,用宏观断口、金相观察、电子探针及硬度测量等方法对其断裂原因进行分析。结果表明,淬火裂纹是造成螺母断裂的主要原因,而回火温度较低,导致其硬度值偏高又增加了材料的脆性。因此,要优化热处理工艺,严格质量检验。

The automobile axle locking nut was split in the assembly. The fatigue cause was analyzed through macroscopic fracture, microstructure, electron probe and hardness surveys. The results show that the quenching crack is the main reason for fracture, and the tempering temperature is lower, which leads to its high hardness and the increase of material brittleness. Therefore, it is necessary to optimize heat treatment process and strict qualification test.