Mathematical Modeling for Microstructural Evolution in Multi-pass Hot Compression of Q345E Alloy Steel

The deformation process and inter-pass time of hot working are always accompanied by complicated microstructural evolution. As a kind of low alloy steels with good malleability, Q345E steel is widely used. The specimens of Q345E steel were heated to 1123, 1223, 1323, 1423, and 1523 K and held for 0, 120, 240, 360, and 480 s, respectively, on Gleeble-3500 thermo-mechanical simulator to develop the austenite grain growth equation of Q345E steel. In addition, the ‘single-pass hot compression tests,’ ‘double-pass hot compression tests,’ and ‘single-pass hot compression and thermal insulation tests’ at temperature from 1123 to 1423 K with the strain rate from 0.01 to 10 s −1 were carried out on Gleeble-3500 thermo-mechanical simulator to investigate the behavior of dynamic recrystallization (DRX), meta-dynamic recrystallization (MDRX), and static recrystallization (SRX), and to establish the mathematical equations of DRX, MDRX, and SRX, which can predict the volume fraction of recrystallization and grain size after recrystallization. The result of error analysis and a 2D finite element simulation model during hot upsetting verifies that the experimental data agree well with the predicted values calculated by these mathematical equations, which indicates that the established mathematical equations can be applied to accurately predict the microstructural evolution of Q345E steel during hot deformation.