某电厂汽轮机高压外缸结合面双头20Cr1Mo1VTiB钢螺栓在安装时发生断裂,通过断口分析、化学成分分析、金相检验以及力学性能测试等方法对螺栓的断裂原因进行了分析。结果表明:该螺栓钢存在严重的显微组织缺陷,力学性能指标不符合技术条件要求,减弱了螺栓的承载能力,螺纹处的应力集中效应会加剧螺栓的缺口敏感性,导致螺栓在安装时于螺纹处发生脆性断裂。

Two stud bolts used for high pressure outer casing faying face of turbine in a power plant fractured when installing. Its material was 20Cr1Mo1VTiB steel. The fracture reason of the bolts was analyzed by means of fracture analysis, chemical composition analysis, metallographic examination and mechanical properties testing. The results showed that there were serious microstructure defects in the bolt material, and its mechanical property index didn′t conform to technical requirements. So bearing capacity of the bolt was weakened. Stress concentration effect at the thread position aggravated notch sensitivity of bolt, then it led to brittle fracture happened at the thread position.