Pressure reduction strategy based on a new CTOD model considering room temperature creep for X80 pipeline steel.

• Experimental analysis of the effect of room temperature creep on the fracture toughness of X80 pipeline steel. • The test data were fitted to a power-law equation which showed that after 36 h of creep at room temperature, the incremental crack tip opening displacement was approximately 0.0098 mm. • A time-dependent CTOD model was proposed regarding room temperature creep. And a pressure reduction strategy is proposed based on this criterion. The growing demand for energy consumption has led to the rapid development of high strength and high toughness pipeline steel technology, with fracture toughness being a crucial factor in evaluating the mechanical properties of pipeline steel. Despite experimental studies demonstrating that metallic materials, including pipeline steel, undergo creep at room temperature, the effects of room temperature creep (RTC) on pipeline steel fracture properties are still relatively unexplained. This study analyzes the impact of RTC on the fracture toughness of X80pipeline steel, using the X80pipeline steel base material as the research object. Firstly, the time-dependent change in crack notch opening displacement is added to the calculation formula for fracture toughness of three-point bending specimens, considering the effect of RTC. The test data is fitted to a power-law equation of the form, where k = 0.01423 and m = - 0.89651 , with the improved formula indicating an incremental CTOD of approximately 0.0098 mm after 36 h of RTC for X80 pipeline steel. Secondly, a time-dependent CTOD model is proposed based on the ductile defect growth model, with the plastic part derived from the D-B model and the creep part obtained by fitting the test data. The study proposes a CTOD criterion for RTC and a pressure reduction strategy based on this criterion, providing a reference for quantitatively assessing the fracture toughness of pipeline steel under RTC conditions. [ABSTRACT FROM AUTHOR]