铁路辙叉用贝氏体钢的氢脆

he hydrogen embrittlement behavior of the average composition region (ACR) and maximum positive segregation region (MPSR) in an actual bainitic casting steel ingot for railway crossing was investigated. The conventional mechanical properties such as hardness, tensile properties and impact toughness were tested. The critical hydrogen concentration and the characteristics of hydrogen embrittlement of the two regions were investigated by means of cathodic electrolytic hydrogen charging and slow-strain-rate test. The microstructure, phase content and fracture morphology were characterized by metallography, XRD and SEM, respectively. The results showed that there was an obvious inhomogeneous distribution of chemical compositions in bainitic casting steel ingot for railway crossing. The contents of carbon and alloying elements in the MPSR increased by 5~15%, and phosphor and sulfur contents increased by twice, as compared with those in the ACR. The embrittlement index of MPSR was much higher than that of ACR. The critical hydrogen concentration in the MPSR decreased significantly when compared with that in the ACR. It indicates that the hydrogen embrittlement is much enhanced due to the positive segregation of chemical compositions.