Speaker
Description
Mold fluxes are critical in continuous casting (CC), because they control both lubrication and heat transfer in the CC mould. Heat transfer is primarily influenced by the crystallization behaviour of the mould flux, while lubrication depends on the viscosity of the slag pool formed by molten flux. Primarily, these two factors depend on the type and composition of mould fluxes used for casting a particular grade. Therefore, the same composition (of mould flux) cannot be used for casting all the different grades which are typically cast in an integrated steel plant.
In this work, we will discuss about the methodology for grade-specific selection of mould fluxes for some industrially relevant grades. To design a composition for a mould flux, determination of crystallisation kinetics, using a DSC/SHTT/CLSM is important. Also, estimation of thermophysical properties, especially viscosity, using existing models or laboratory experiments is necessary. The crystallisation kinetics along with the thermophysical properties data are then fed into a numerical model for evaluating the performance of a mould flux. In this work, we develop a heat transfer model for calculating the horizontal heat flux as a function of distance in the continuous casting mould by incorporating the thermophysical properties and crystallization behaviour of the mould fluxes. The model is validated using values of horizontal heat flux and shell thickness at mould exit, whatever available in the literature. Finally, the model is applied to two industrial steel grades with widely varying chemistries. Elucidating the effects of slag film characteristics on the performance of mould fluxes, the model provides useful insights for designing a mould flux for a particular steel grade, with the purpose of attaining the right balance between lubrication and heat transfer.
Keywords: Mould Fluxes, Crystallisation, Viscosity, Heat Flux, Continuous Casting.