Hydrogen-induced cracking of longitudinally submerged arc welded HSLA API 5L X65 carbon steel pipeline

This study investigates the hydrogen-induced cracking (HIC) of a thermomechanical controlled processed (TMCP) API 5L X65 steel pipe fabricated using the JCOE forming process. Despite passing HIC testing as a plate, the final pipe exhibited unexpected failure, highlighting the critical influence of pipe fabrication on material performance. In this study, failed pipes were subjected to heat treatment, and HIC testing following NACE TM 0284 standard, SEM, and EDX examinations. The effect of heat treatment on the grain size, residual stress and susceptibility to HIC was investigated. The findings revealed that welding played a detrimental role, as all the HIC failures occurred at the welded area (0° orientation) due to welding-induced stresses and potential microstructural changes. It is believed that the welding process imposed reversible hydrogen traps in the HIC resistance plate ultimately reducing the HIC resistance. The heat treatment proved an effective method for relieving the applied micro-residual stresses that resulted in enhanced HIC resistance of the material.