Comparison of hydrogen-induced cracking susceptibility of pipeline steel under different finishing cooling temperatures

Abstract

Pipeline steels are usually applied to oil and gas transportation over long ranges. Because of its served environment with wet H₂S, cracks caused by hydrogen are most likely to be huge potential invalidity threats during the served life. The cooling techniques can significantly affect the micro structure, the mechanical properties, and the ability to hinder cracks in the pipeline steel. Therefore, it was necessary to research the influence of finishing cooling temperature on cracks caused by hydrogen of pipeline steel. So, in the study, concerning microstructure, the scattering condition of high angle grain boundaries and dislocation, as well as the effect of finishing cooling temperature on cracks caused by hydrogen of pipeline steel, were studied. The discoveries showed that among the three finishing cooling temperatures, such as 650 °C (Specimen 1), 550 °C (Specimen 2), and 450 °C (Specimen 3), Specimen 2 had the highest proportion of HAGB, with 48.0%. HAGB can effectively promote crack deflection during crack propagation and hinder the crack’s extension. Also, its lower dislocation density can produce excellent hydrogen-induced cracking performance for pipeline steel. Overall, when the finishing cooling temperature is 550°C (Specimen 2), steel can have the best hydrogen-induced cracking resistance performance.