40Cr浮头螺栓断裂原因分析

浮头式换热器40Cr紧固螺栓使用时间不到2 a即发生断裂。通过宏观观察、化学成分分析、硬度测试、金相检验和断口分析，确定螺栓的断裂原因。结果表明:由于调质处理不当，螺栓显微组织为保持马氏体位向的回火索氏体，铁素体沿原奥氏体晶界网状析出，硬度值偏高，导致材料抵抗硫化物应力腐蚀能力不足。长期在湿硫化氢环境中服役，在拉应力作用下，发生湿硫化氢应力腐蚀和氢致开裂，导致螺栓断裂。

Fracture Cause Analysis of 40Cr Floating Head Bolt

The 40Cr bolt of a floating head heat exchanger broke after service for less than 2 a. The failure cause of the bolt was analyzed by macroscopic observation, chemical component analysis, hardness testing, metallographic examination and fracture analysis. The results show that due to improper quenching and tempering treatment, the microstructure of the bolt was tempered sorbite with the martensite orientation. Ferrite precipitated along the network of the original austenite grain boundaries, leading to higher hardness and insufficient resistance to sulfide stress corrosion. After long-term service in the wet hydrogen sulfide environment and under tensile stress, wet hydrogen sulfide stress corrosion and hydrogen induced cracking took place, resulting in the fracture of the bolt.