某石化厂管道连接法兰用40Cr钢紧固螺栓在使用不到1 a(年)后发生径向断裂。通过宏观分析、化学成分分析、光学显微镜和扫描电镜观察、硬度测试等方法对螺栓断裂原因进行了分析。结果表明: 螺栓在较高应力水平下服役, 在应力和氢的共同作用下发生了氢脆断裂; 导致其氢脆断裂的主要原因是螺栓在酸洗磷皂化和磷化过程中引入了较多的氢。

The 40Cr steel fastening bolts used for connecting pipe flanges of a petrochemical plant, fractured transversally after less than a year of use. And the fracture reasons were analyzed by means of macroscopic analysis, chemical composition analysis, optical microscopy and scanning electron microscopy observation, and hardness test. The results show that the bolts serviced under high stress level, so hydrogen embrittlement fracture occurred under the combined action of stress and hydrogen. More hydrogen introduced during acid pickling phosphorus and phosphating process were main cause for the hydrogen embrittlement fracture of the fastening bolts.