Original Article

Numerical investigation of dynamic recrystallization and following softening behaviors of steels

¹ Research & Development, Nipponsteel Corporation, 20-1 Shintomi, Futtsu, Chiba 293-8511, Japan
² Faculty of Mechanical Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan

^* e-mail: yamashita.9xm.yui@jp.nipponsteel.com

Received: 19 September 2024
Accepted: 7 March 2025

Abstract

This study investigated the post-deformation mechanical and microstructural phenomena of hot strip steels, considering the importance of multipass hot-rolling load prediction in the steel industry. A numerical model was developed consisting of a mechanical simulation model using a fast Fourier transform and a microstructural simulation model using a multi-phase field. Two different plane strain cases are simulated: below the dynamic recrystallization threshold strain and above the threshold. The former case exhibited complete softening with two distinct softening behaviors: (1) static recrystallization (SRX) nucleation with modest softening at the beginning of the static process, and (2) grain growth of the SRX nuclei and static recovery (SRV), leading to complete softening. The latter case revealed incomplete softening with three distinct softening behaviors: (1) abrupt growth of dynamic recrystallization grains with low dislocation density and small deviation (meta-dynamic recrystallization); (2) decrease in the dislocation density of dynamic recrystallization grains with high dislocation deviation (meta-dynamic recovery) and the simultaneous occurrence of static recovery and recrystallization in a high-dislocation-density area, and (3) static recovery occurred in conjunction with static recrystallization grain growth. The simulated microstructural evolution, as well as the softening curves both with and without dynamic recrystallization, appear to be in good agreement with the experimental results observed in the reference.