MODELING THE THERMOMECHANICAL AND MICROSTRUCTURAL EVOLUTION DURING ROLLING OF A NB HSLA STEEL

A simple approach to calculate rolling loads based on Sims' model was compared to a finite element model (FEM) using the same constitutive l aw and recrystallization equations. The comparison was done with a Nb microalloyed steel using a laboratory rolling simulation of plate and strip mill rolling schedules. The FEM model accurately predicted the t emperature, the change in rolling loads, and the evolution of microstr ucture before and after transformation. These results clarified the ac curacy of various microstructure models, particularly the model for re crystallization. The FEM model gave an improved prediction of the roll ing loads slightly compared with the slab method. For on-line modellin g of the rolling loads a simpler approach based on Sims model gave acc eptable prediction when using an accurate temperature model to predict the average temperature throughout the rolling process. The combinati on of the constitutive law and recrystallization kinetics in both case s enabled the prediction of the increase in rolling loads over the ent ire temperature range. The results also suggest that solute drag, rath er than strain induced precipitation, has the primary effect on retard ing recrystallization under the conditions examined.