Cracking analysis of 42CrMo steel hexagon head bolt by hot dip galvanizing

doi:10.13251/j.issn.0254-6051.2023.01.045

Abstract

Abstract: Cracks were found at the round corners of the 42CrMo steel hexagon head bolts after hot dip galvanizing through magnetic particle inspection. Fracture, microstructure and composition analysis of the cracked bolt were carried out by means of optical microscope, SEM and EDS. The results show that the fracture of the cracked bolts conforms to the characteristics of hydrogen embrittlement, and the mass fraction of hydrogen near the fracture is as high as 4×10^-6.The crack characteristics are consistent with the hydrogen embrittlement crack characteristics. The microstructure on both sides of the crack is normal quenched and tempered structure and zinc residue is found in the crack, which can exclude that the crack is caused by abnormal tissue or quenching. Therefore, it can be reasonably inferred that the crack of 42CrMo steel hexagonal bolt is hydrogen-induced cracking, which occurs in the process of hot dip galvanizing.

Key words: 42CrMo steel, hexagon bolts, hot dip galvanizing, hydrogen induced cracking

CLC Number:

TG142.15

Zhao Quanyu, Liang Jiajun, Chen Xupeng, Tong Bo, Xia Guohua, Yan Qin, Ding Zhimin. Cracking analysis of 42CrMo steel hexagon head bolt by hot dip galvanizing[J]. Heat Treatment of Metals, 2023, 48(1): 257-260.

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