STUDY ON FRACTURE TOUGHNESS AND DEFECT TOLERANCE OF X80 PIPELINE STEEL IN SIMULATED NATURAL GAS ENVIRONMENT CONTAINING 2%H₂

Hydrogen will degrade the mechanical properties and lead to the hydrogen embrittlement of pipeline steel, which has an important impact on its safe transportation. Therefore, the fracture toughness experiment of X80 pipeline steel in hydrogen-containing environment was carried out in this paper, and the influence of hydrogen on fracture toughness of X80 pipeline steel was evaluated. The scanning electron microscopy (SEM) was used to observe and analyze the fracture surface to determine its fracture mode under different conditions. The results show that the fracture toughness of X80 pipeline steel in H₂ environment is lower than that in nitrogen environment. The fracture toughness CTOD value of X80 pipeline steel in nitrogen is 0.42 mm, and the fracture toughness CTOD value in 2% hydrogen is 0.33 mm. H₂ reduces the fracture toughness of X80 pipeline steel by 21.42%. From the fracture morphology, hydrogen does not change the fracture mode of the material. X80 pipeline steel still shows obvious characteristics of ductile fracture, but there are a few local micro-cracks.