Coupling effect of manufacturing and creep on remaining strength of 2.25Cr-1Mo-0.25 V steel ring shells

Abstract

Manufacturing and creep inevitably cause material degradation and a subsequent decline in the performance of 2.25Cr-1Mo-0.25 V steel ring shells. However, their combined effect remains inadequately understood, leading to a paucity of reliable assessment methods. The present study introduced an innovative approach to investigate the coupling effect of manufacturing and creep on the remaining strength of 2.25Cr-1Mo-0.25 V steel ring shells. Firstly, a series of experiments—including pre-strain tests, heat treatments, interrupted creep tests, and tensile tests—were carefully conducted. Results indicated that the high-temperature strength of 2.25Cr-1Mo-0.25 V steel initially increases with extended creep duration, followed by a subsequent decrease. In contrast, a consistent reduction in strength is observed as warm deformation increases. Secondly, a novel approach was developed for predicting remaining strength, incorporating the coupling effect of manufacturing and creep. This approach integrates a data-driven model for strength prediction, finite element simulation of forming, and a direct technique for limit load analysis. Finally, the strength distribution and evolution of 2.25Cr-1Mo-0.25 V steel ring shells, along with their load-bearing capacity, were calculated and analyzed. Numerical analyses revealed that manufacturing induces material strength inhomogeneity in 2.25Cr-1Mo-0.25 V steel ring shells. Additionally, during prolonged creep aging, the central regions of the ring shells consistently demonstrate superior performance compared to the surface regions. As for load-bearing capacity, manufacturing is associated with a reduction of 20 % to 30 %, whereas creep initially results in an increase of up to 10 %, followed by a subsequent decrease of 25 %. Furthermore, a diminished diameter-to-thickness ratio is correlated with an increased likelihood of premature failure. This work contributes to the safety assessments of high-temperature hydrogen-bearing pressure vessels.