Determination of creep behavior of vessel steel Q345R at elevated temperatures

Vessel steel Q345R is widely used in pressure applications in China due to its martensitic structure, often operating in high-temperature, high-stress environments. This study investigates its susceptibility to creep strain, which can lead to significant deformation and structural damage, compromising safety. Thermal creep tests for Q345R steel were conducted within the temperature range of 400 °C–600 °C under various stress ratios. Results indicate that, below 500 °C, stages I and II predominate creep curves, with stage II evolving slowly. However, as temperature rises, stage II becomes predominant, with stage III emerging earlier, especially under high stress, leading to accelerated creep and potential fracture. Temperature significantly influences creep rates, with even minor stress increments at elevated temperatures inducing substantial creep effects. Through fitting by creep strain curves, parameters for three different time hardening creep models were determined. Subsequently, material CREEP subroutines based on these models were developed and integrated into ABAQUS to simulate the entire creep test process. The simulation results validate the ability of calibrated creep models to accurately characterize Q345R steel's creep properties, facilitating the evaluation of safety in high-temperature service structures.