MODELING OF MICROSTRUCTURAL EVOLUTION AND MECHANICAL-PROPERTIES OF STEEL PLATES PRODUCED BY THERMOMECHANICAL CONTROL PROCESS

For manufacturing the steel plates with good mechanical properties by Thermo-Mechanical Control Process (TMCP), the manufacturing conditions are necessary to be controlled in an integrated manner through the reheating step to the accelerated cooling step. The present mathematical model for the prediction of the microstructural evolution and the mechanical properties of the steel plates produced by TMCP enables this integrated control. The present report describes the flow and the each equation of the model and the comparison between the calculated results with this model and the data obtained by the rolling experiments. The model consists of four modules such as Reheating, Rolling, Cooling and Mechanical Properties in which the metallurgical phenomena occurring at each step are calculated. The characteristic of the model is shown as follows: (1) The effect of work hardening of austenite by rolling in non recrystallization temperature region is represented as the effect of average dislocation density (rho) accumulated in austenite grains. The nucleation rate of intragranular ferrite and that of grain boundary ferrite are distinctively formulated as functions of rho. (2) The effects of microalloying elements are considered in the formulation of metallurgical phenomena and mechanical properties such as pinning and solute drag effects on the grain growth of austenite at the reheating step, the restraining effect on recovery and recrystallization of work-hardened austenite at the rolling step, the restraining effect of solute elements on the progress of transformation at the cooling step, and the solution hardening and the precipitation hardening for the mechanical properties of the plates.