Fracture failure analysis of 20Cr1Mo1VTiB steel bolt

doi:10.13251/j.issn.0254-6051.2024.12.049

Abstract

Abstract: A high-temperature fastening bolt (20Cr1Mo1VTiB steel) for the high-stress main steam valve of a steam turbine unit cracked after serving for 1.29×10⁵ h. The cracking failure cause of the high-temperature fastening bolt was analyzed by means of chemical composition examination, SEM and TEM microstructure observation, XRD detection, and mechanical property testing. The results show that the fracture of the bolt is primarily due to creep damage from long-term high-temperature and high-stress conditions of serving. Additionally, the accumulation of creep damage is mainly due to two types of creep voids forming in microcrack zones near coarse inclusions sharp corners and along the interface of Laves phase. With the increase of running time, the number of creep voids in the 20Cr1Mo1VTiB steel bolt matrix continuously rises and aggregates, eventually forming crack sources that lead to fatigue rupture.

Key words: 20Cr1Mo1VTiB steel bolt, creep, fracture faliure, inclusions, Laves phase

CLC Number:

TG146

Liu Fei, Zhang Xuechao, Sun Changming, Dong Yunhe, Liu Yang, Zheng Jianjun. Fracture failure analysis of 20Cr1Mo1VTiB steel bolt[J]. Heat Treatment of Metals, 2024, 49(12): 306-311.

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