Analysis and Simulation Research on Static Softening Mechanism Following Multistage Hot Deformation of 1.3 GPa Grade Bulb Flat Steel

In this study, the flow stress behavior of 1.3 GPa grade bulb flat steel (BFS) is studied under different deformation temperature and strain rate using the Gleeble‐3800 thermomechanical simulator, and the Arrhenius‐type constitutive equation is established. A static recrystallization kinetics model of 1.3 GPa grade BFS is established based on double‐pass hot compression tests. The established constitutive equation and static recrystallization kinetics model are embedded into the finite‐element model of the hot‐rolling process, and the static recrystallization and residual stress distribution between each pass are analyzed. In the results, it is indicated that static softening happens rapidly after the end of the pass, and then the speed gradually slows down. Reasonably controlling the interval time between each pass helps to fully utilize the effect of static softening relaxation residual stress. After the K12–K8 and K7–K2 passes, the rolled pieces can undergo fully static recrystallization after being heated for 5 and 8–11 s, respectively, eliminating residual stresses during hot rolling and reducing the impact on plate shape. The results give data support for the optimization of the hot‐rolling process of 1.3 GPa grade BFS. It provides a new way to control the shape accuracy of hot‐rolling‐section steel.