Failure analysis of fatigue fracture of engine cylinder head bolts

doi:10.13251/j.issn.0254-6051.2023.02.048

Abstract

Abstract: Failure analysis of fatigue fracture of SCM435 steel engine cylinder head bolts was carried out by means of fracture (macroscopic) analysis, microstructure analysis, chemical composition detection and hardness test. The results show that the chemical composition and microstructure of the failed SCM435 steel cylinder head bolts are qualified, and the hardness meets the technical requirement. The brittle fracture of the failed specimen 1 is caused by surface decarburization, the width of surface decarburization layer at the fractured part of the bolt is 120 μm. The fracture of the failed specimen 2 is mainly fatigue fracture caused by nonmetallic inclusions, and the near spherical CaS-CaO-Al₂O₃-MgO composite metallurgical inclusions cause intergranular crack. Suggestions for improving the indicators such as plasticity and toughness, surface decarburization and nonmetallic inclusions of the material are put forward.

Key words: engine, cylinder head bolt, fatigue fracture, fracture analysis, microstructure

CLC Number:

TG142.41

Chen Jilin, Zhang Yuming, Meng Yi, Yan Cong, Lin Peng. Failure analysis of fatigue fracture of engine cylinder head bolts[J]. Heat Treatment of Metals, 2023, 48(2): 308-313.

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