20Cr2Ni4A钢制框架轴开裂原因分析

某20Cr2Ni4A钢制框架轴在装配过程中发现,框架侧板外侧通油孔与销轴孔交界处开裂。对其进行理化分析,发现有疑似渗碳层和硬度偏高现象;对其进行仿真分析,通油孔处和销轴孔处在渗碳和非渗碳状态下的应力数值差异很大,渗碳状态明显高于非渗碳状态;进行淬火试验,发现在800 ℃×60 min保温并附加较高碳势时,20Cr2Ni4A钢表面会产生不同程度的渗碳。综合上述分析及生产验证情况可知,裂纹是由于销轴孔壁和通油孔壁存在渗碳层,淬火时应力达到临界开裂状态,导致部分框架轴产生裂纹。

Crack cause analysis of 20 Cr2 Ni4 A steel gimbal axis

During the assembly process of 20Cr2Ni4A steel gimbal shaft, it was found that cracks were located at the oil hole and pin hole on the outer side of the frame. The physical and chemical analysis results show that there are suspected carburized layers and high hardness phenomenon. The simulation analysis shows that the stress values of the oil through-hole and the pin hole in the carburized and non-carburized states are different, and that of the carburized state is significantly higher than that of the non-carburized state. By quenching test, it is found that when the temperature is kept at 800 ℃ for 60 min and a higher carbon potential is applied, the surface of the 20Cr2Ni4A steel have different degrees of carburization. Based on the above analysis and production verification, it can be concluded that the cause of crack formation is the existence of carburized layer on the wall of pin hole and oil hole, and the stress reaches the cracking critical state during quenching, which leads to cracks in part of the gimbal axis.