Fracture toughness of X80 pipeline girth welding joints under H2S corrosive environment with harsh heat input

This study investigates the fracture toughness of X80 pipeline girth welding joint under both 2.5kJ/cm and 30kJ/cm in H₂S acidic solution. The resistance curve based on crack tip opening displacement (CTOD) was obtained by static immersion and slow strain rate three-point bending tests of the single edge notch bending (SENB) specimens in the improved NACE B solution Results shows that under combining of H₂S environment and slow strain loading, the stress concentration at pre-fatigued crack tips significantly promotes dynamic hydrogen permeation and accumulation, leading to marked decreases in CTOD characteristic values for weld metal (WM), heat-affected zone (HAZ), and base metal (BM), with the joint exhibiting brittle fracture characteristics. In comparison, hydrogen diffusion during static immersion alone showed weaker effects on toughness. This study reveals that dynamic hydrogen induced embrittlement is the dominant mechanism for fracture toughness degradation, providing a basis for weld quality assessment and safety control of pipelines in acidic media.