Mathematical modelling of hot rolling steel strip

Abstract

Thermal and microstructural evolution during hot rolling of low carbon steel in a continuous six stand mill is simulated with a two-dimensional explicit finite difference model in which the cross-sectional area of the strip is divided into small elements of equal volume. The heat transfer coefficients at the surface of the strip are allowed to change as it is assumed that the strip is in air or is being descaled or deformed. Results of the microstructural modelling indicate that austenite is able to undergo dynamic recrystallisation when the conditions within the roll gap are propitious. This model also allows for the occurrence of metadynamic and static recrystallisation once the material leaves the gap and for grain growth after their completion. From this, it is concluded that the most important controlling mechanism is grain growth. The thermal portion of the model was validated with measurements made on a six stand continuous mill. It was not possible to obtain a direct validation of the microstructural algorithms, but they are considered to be correct, since it was possible to achieve a good correlation between the separation forces predicted by the model and those recorded experimentally during actual production once the kinetics of the different mechanisms were incorporated into the model.