Thermal Deformation Behavior and Strain Compensation Constitutive Model of X80M Pipeline Steel

Single-pass thermal compression tests of X80M pipeline steel were carried out by Gleeble-3800 thermal simulator. The thermal deformation behavior under conditions of deformation temperature ranging from 900 ℃ to 1 100 ℃ and strain rate ranging from 0.1 s⁻¹ to 7 s⁻¹ was studied. According to the true stress-strain curves obtained by tests, the strain compensation Arrhenius constitutive model of X80M pipeline steel was constructed considering the effect of the true strain on the flow stress, and the model was verified. The results show that with the increase of deformation temperature or the decrease of strain rate, the flow stress of X80M pipeline steel decreased; the X80M pipeline steel had negative temperature sensitivity and positive strain rate sensitivity. Under high deformation temperatures (1 050–1 100 ℃) and low strain rates (0.1–1 s⁻¹), X80M pipeline steel exhibited dynamic recrystallization characteristics. Under low deformation temperatures (900–1 000 ℃) and high strain rates (4–7 s⁻¹), it showed dynamic recovery characteristics. The true stress calculated by the constructed strain compensation constitutive model was consistent with the test results. The linear correlation coefficient was 0.997 and the average relative error was 1.791%, indicating that this model had a high prediction accuracy and could accurately predict the high-temperature rheological behavior of X80M pipeline steel.