Verification of New Model for Calculation of Critical Strain for the Initialization of Dynamic Recrystallization Using Laboratory Rolling

Development of computer technology offers ever more elaborated and some novel mathematical modeling methods for description of materials response to rolling. Research in this field has been undertaken by a number of experts who proposed numerous particular models 1-7 . Using these models can provide detailed information on changes in thermomechanical variables during rolling and enable the prediction of microstructure formation and mechanical properties. One of the fundamental purposes of hot rolling is to obtain a final product with small and uniform ferrite grain size and resulting favourable properties. The ferrite grain size depends primarily on the austenite grain size at the end of the rolling process, on the amount of strain, the temperature schedule and other parameters 8 . It is possible to obtain required microstructure parameters with controlled forming combining suitable temperatures, reductions and delays between passes in relation to strain rate. At present, a number of semi-empirical models were describing the kinetics of restoration processes in material 8-14 . However, these models still use simplified and do not fully utilize results obtained with mathematical modelling. The following section contains an introduction to a new model describing dynamic recrystallization in steel constructed directly for the use in FEM-based programs.