Fracture Toughness of X70 Steel Pipeline Girth Weld under Low Constraint Condition Joint

The single-edge-notched-tensile (SENT) test was carried out on strain-based design of X70 steel pipeline to measure crack tip opening displacement of girth weld metal and heat affected zone. The fracture resistance curves during crack ductile extension process were obtained and tested results of heat affected zone sample were validated. The results show that the distance from crack tip of heat affected zone sample to fusion line was within 0.5 mm. Fracture resistance curves of weld metal and heat affected zone samples as followed: δ=1.395 78(Δa)0.783 35, δ=1.553 38(Δa)0.821 75. Fracture toughness of pipeline girth weld under low constraint condition can be accurately measured by SENT test. The tested results can provide evidence for strain-based design pipeline and engineering critical assessment.