Research on hydrogen-induced cracking behavior of normalized pipeline steel

Hydrogen sulfide corrosion test was used to test the hydrogen-induced cracking sensitivity of the normalized BNS pipeline steel. The microstructure and morphology of hydrogen induced crack(HIC) of the normalized BNS pipeline steel after hydrogen sulfide corrosion test were observed with optical microscopy(OM), scanning electron microscopy(SEM). Combined with electron probe microanalyzer(EPMA) and hardness test, the hydrogen-induced cracking behavior of BNS pipeline steel was studied from the aspects of microstructure, crack morphology, center segregation and harness. The results showed that the pearlite band with high hardness caused by center segregation of C and Mn was the main crack initiation and propagation path for the long-size and linear shape hydrogen induced crack at the center of plate thickness, and the type of crack propagation was transgranular. Some tiny hydrogen induced crack nucleated from the small calcium-aluminate inclusion and the tiny hydrogen induced crack would not propagate to form long-size cracks with no suitable propagation path existing around the inclusion