MATHEMATICAL-MODELING OF HOT-ROLLING STEEL STRIP

Thermal and microstructural evolution during hot rolling of low carbon steel in a continuous six stand mill is simulated with a two-dimensio nal 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 chan ge as it is assumed that the strip is in air or is being descaled or d eformed. Results of the microstructural modelling indicate that austen ite is able to undergo dynamic recrystallisation when the conditions w ithin the roll gap are propitious. This model also allows for the occu rrence of metadynamic and static recrystallisation once the material l eaves the gap and for grain growth after their completion. Front this, it is concluded that the most important controlling mechanism is grai n growth. The thermal portion of the model was validated with measurem ents made on a six stand continuous mill. It,ras not possible to obtai n a direct validation of the microstructural algorithms, but they are considered to be correct, since it was possible to achieve a good corr elation 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. (C) 1998 T he Institute of Materials.