Conventional and Multiscale Modeling of Microstructure Evolution During Laminar Cooling of DP Steel Strips

Abstract

Physical and numerical simulations of the hot rolling and laminar cooling of DP steel strips are presented in the paper. The objectives of the paper were twofold. Physical simulations of hot plastic deformation were used to identify and validate numerical models. Validated models were applied to simulate the manufacturing of DP steel strips. Conventional flow stress model and microstructure evolution model were used in the hot deformation part. The approach to the complex systems analysis based on global thermodynamic characterization and detailed microstructure characterization was applied to determine equilibrium state at various temperatures. Finally, two numerical models were used to simulate kinetics of austenite decomposition at varying temperatures: the first, conventional model based on the Avrami equation, and the second, the discrete Cellular Automata approach. Plastometric tests and stress relaxation tests were used for identification of the hot rolling model for the DP steel. Dilatometric tests were performed to identify the phase transformation models. Verification confirmed good accuracy of all models. Validated models were applied to simulate the manufacturing of DP steel strips. Influence of technological parameters (e.g., strip thickness and velocity, active sections in the laminar cooling, and water flux in the sections) on the DP microstructure was analyzed. The cooling schedules, which give required microstructures were proposed. The numerical tool, which simulates manufacturing chain for DP steel strips is the main output of the paper.

Simulations and Optimization of Manufacturing of Automotive Parts

“…The original crash box with stains transformed from the stamping, as well as the crash box after the test, are shown in this figure. All results presented in this section of the paper, as well as in publications (Kuziak and Pietrzyk, 2011) for hot rolling, (Pietrzyk et al, 2014b) for laminar cooling and (Ambrozinski et al, 2015) for stamping and crash tests, confirmed capabilities of the models to simulate the whole manufacturing chain for automotive parts.…”

“…For each process in Figure 3 models of various complexities were developed by the Authors. The models ranged from simple closed form equations describing selected parameters to advanced multiscale approaches combining FE code in macro scale with the Cellular Automata method in micro scale, see for example (Pietrzyk et al, 2014b). Selection of the best model of each process in the cycle for the purpose of the optimization of the manufacturing technology is described in (Rauch et al, 2014a).…”

“…Since the final product properties are obtained either during laminar cooling or during continuous annealing, validation of the phase transformation model during these processes is essential. The former process was thoroughly investigated by Pietrzyk et al (2014b), therefore, in the present paper the focus was on the continuous annealing. Physical simulations of thermal cycles characteristic for the continuous annealing were performed on the dilatometer according to the general scheme shown in Figure 4.…”

Computer-Integrated Platform for Automatic, Flexible, and Optimal Multivariable Design of a Hot Strip Rolling Technology Using Advanced Multiphase Steels

“…Typical hot strip rolling mill composed of the furnace, reverse rouging stand, six stand continuous finishing train, laminar cooling and coiler was considered. The laminar flow cooling system is composed of two sections with 40 boxes in each section, see [25] for details. The length of each box is 1 m. The sections are divided into eight zones of three types: intensive, normal, and trimming zone.…”

Fast model for phase transformations during cooling of pre-annealed multiphase steels

“…Finite element model of the laminar cooling and coiling processes is described in (Pietrzyk et al, 2014). Phase transformation models described in the present paper were implemented into the FE code and current, local changes of the temperature were used in the calculations of the kinetics of transformation.…”