Modeling of the Dynamic Recrystallization Kinetics of a Continuous Casting Slab Under Heavy Reduction

Heavy reduction (HR) is used to implement a large reduction amount to improve the internal quality and refine the microstructure of continuous casting billets with large section sizes. In this paper, microstructural evolution and dynamic recrystallization (DRX) kinetic models for continuous casting slabs under HR were investigated for an experimental temperature range from [1173 K to 1573 K (900 °C) to (1300 °C)] and strain rates of 0.001 to 0.1 s−1. Based on the experimental data, various DRX kinetics models for a continuous casting slab as functions of the strain rate, strain, initial austenite grain size, and temperature were established to predict DRX-induced softening behaviors. A comparison of the new modified model, with Laasraoui and Jonas’s model, the modified Yoda’s model, and Liu’s model, revealed that the new modified model is the most suitable model for a continuous casting slab under HR. Based on this research, constitutive models with the characteristics of DRX and dynamic recovery (DRV) were established to predict the flow stress curve with the parameters of the strain rate (ε˙\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{\varepsilon } $$\end{document}), deformation temperature (T), and the initial austenite grain size (d0). Moreover, the microstructural evolution of a tested slab after hot compression tests was investigated by optical microscopy and a DRX grain size model under different deformation conditions was established.