核电土建设备产品见证件弯曲试验钢筋断裂原因分析

Cause Analysis on Fracture of Steel Bar in Nuclear Power Civil Construction Product Witness Samples during Bend Testing

某核电土建设备产品见证件在弯曲试验时发生钢筋纵向断裂现象,采用化学成分分析、硬度检测、金相检验和冲击试验等方法对钢筋的断裂原因进行了分析。结果表明:由于产品焊接时的热量将钢筋加热到了产生第二类回火脆性的温度,加之焊后冷却速度过慢,使杂质元素在晶界处偏聚,造成晶界弱化而产生脆性,从而导致产品见证件在弯曲试验时于钢筋处纵向断裂。

Steel bar longitudinal fracture occured during bend testing for nuclear power civil construction product witness samples.Fracture reason of the steel bar was analyzed by chemical compositions analysis,hardness testing,metallographic examination and impact test.The results show that the heat produced by welding heated the steel bar to the temperature producing second category tempering brittleness,and the cooling rate was too slow,so impurity elements segregated at the grain boundary,and resulted in weakening of the brittle grain boundary.So the product witness sample fractured at the steel bar along the longitudind direction during bend testing.