某铁路桥梁用20MnTiB钢高强螺栓断裂原因

Fracture cause of 20MnTiB steel high strength bolt for a railway bridge

某铁路主桥钢桁梁杆间20MnTiB钢高强螺栓发生断裂。采用复检试验、化学成分分析、金相检验、硬度测试、力学性能测试和断口分析等方法,分析了螺栓断裂的原因。结果表明:螺栓的断裂形式为氢致断裂,断裂原因是螺栓中锰元素含量偏高,导致耐腐蚀性下降,长期在潮湿环境下服役,致使螺栓发生氢致断裂。

The 20MnTiB steel high strength bolt between the steel truss rods of a railway main bridge broke. The causes of bolt fracture were analyzed by means of recheck test, chemical composition analysis, metallographic examination, hardness test, mechanical property test and fracture analysis. The results show that the fracture mode of the bolt was hydrogen induced fracture. The fracture cause was that the content of manganese element in the bolt was too high, which led to the decline of corrosion resistance. The bolt had been in service for a long time in a humid environment, resulting in hydrogen induced fracture.