Failure cause analysis of 40Cr bolt used in hanger of train brake lever

doi:10.13251/j.issn.0254-6051.2024.01.045

Abstract

Abstract: 40Cr bolt used in hanger of train brake lever was broken after running about two years. The reasons for failure of the 40Cr bolt were analyzed through fracture analysis, chemical composition analysis, metallography detection, hardness test and impact test. The results show that the microstructure of the failed bolt is banded structure consisting of tempered sorbite, upper bainite, low bainite, retained austenite and non-metallic inclusion, while the hardness and impact property of the bolt do not meet the standard requirements. During the running of train, the fastening nut become loose, and the long-term vibration and impact make the root of the thread at junction with the screw crack first, which leads to the subsequent intergranular brittle fracture of the bolt.

Key words: 40Cr bolt, banded structure, brittle rupture, upper bainite

CLC Number:

TG115

Liu Yanfeng, Liu Xiaomin, Wang Fayun, Zhao Yuqing, Li Xiaozeng, Pan Yonghong. Failure cause analysis of 40Cr bolt used in hanger of train brake lever[J]. Heat Treatment of Metals, 2024, 49(1): 279-283.

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