Microstructure Simulation and Experiment Investigation of Dynamic Recrystallization for Ultra High Strength Steel During Hot Forging

Abstract

The hot working process has a great influence on the properties of steel because it affects the microstructure evolution of steel. In this paper, the flow behavior and evolution of microstructure during the hot forging process are predicted using numerical simulation, providing a reference for optimizing the process. The flow stress-strain curve of 30Cr2Ni3MoV steel was obtained by conducting hot compression experiments using Gleeble-3500 thermal simulator. The constitutive and dynamic recrystallization Cellular Automaton(CA) models were established by analyzing the thermal deformation behavior, considering work hardening and dynamic recrystallization softening. This model was optimized by combining the dislocation density difference drive mechanism, increasing the total number of grain orientations, and then implementing Hash mapping to obtain the actual grain orientation. The simulation results of strain and strain rate in the process of thermal deformation were obtained through the constitutive model. Compared with the results of the hot compression experiment and the metallographic experiment, the accuracy of the simulation results of the dynamic recrystallization CA model was verified. Finally, the real-time updating module of deformation parameters is established, and the real-time process parameters of deformation calculation are updated to the CA model. The simulation results are consistent with the experimental results through metallographic experiments. Thus, it was demonstrated that the dynamic recrystallization model can be useful for predicting microstructure evolution, optimizing the hot forging process, and reducing the number of trial-and-error experiments.

Keywords: Ultra-high strength steel, Microstructure, Cellular Automata, dynamic recrystallization, numerical simulation