STUDY OF A METHOD FOR DETERMINING THE FRACTURE TOUGHNESS OF PIPE STEEL BASED ON INSTRUMENTED CHARPY IMPACT TESTING

With the development of oil and gas transmission pipelines towards large diameter, and high strength, high steel grade pipeline steel materials represented by X80 have become the primary choice for oil and gas transmission pipelines. In order to achieve a low-cost and rapid acquisition of fracture toughness of pipeline steel in engineering, the feasibility of Charpy impact testing is investigated. In this paper, the test method of pipe fracture toughness based on instrumented Charpy impact test is investigated in detail, taking X80 pipeline steel as an example, and its fracture mode and expansion law are studied in combination with fracture morphology analysis. The dynamic J-integral of the material was obtained by the rate of change curve method of flexibility, and then the equation for solving the quasi-static J-integral based on the dynamic test method of CVN specimens was established. An innovative empirical equation for solving the J-integral based on the load-displacement curve was established based on the method of dimensional analysis. The results show that the method is suitable for rapid engineering solutions with good results, offering new possibilities for the assessment and study of weld fracture toughness.