Theoretical and experimental investigation of thermal behavior of a mold powder used in the continuous casting process.

摘要

Mold powders are added to the mold of a continuous caster to provide a source of the liquid flux that acts as a lubricant for the casting process. Varying the nature of this powder controls the formation of the liquid flux; however, little is understood about the mechanism of heating and fluid formation during casting. The purposes of this study are to develop a better understanding of the phenomena encountered during the heating of mold powders and to develop a model to describe this behavior and to predict the melting rate of mold powders.; In the theoretical study, a mathematical model was developed to explain the heating, sintering and combustion of a casting powder. Transient state heat transfer, kinetics of the carbon combustion reaction, shrinkage of the casting powder, diffusion of all gaseous species through the casting powder were taken into account in the formulation of the mathematical model. The simulation results yielded both a quantitative and a qualitative understanding of the relationship between the temperature, concentration of each gas and the concentration of carbon developed within the powder layer during heating.; In the experimental study, a one-directional heating apparatus was constructed that simulated the heating pattern in the continuous casting mold and allowed an investigation of the heating, sintering and combustion of the casting powder, to be performed. After the experiment, a variation of the carbon content along the powder column was measured and the presence of the carbon-enriched layer was documented.; Finally, the simulation results were compared with the experimental results to validate the mathematical model. The match between them was found to be satisfactory. The validated model was then modified to take into account the addition and the consumption of the mold powder and the kinetics of the slag pool formation. The model was then used to predict the heating and melting behavior in an actual casting mold. The simulation results explained the relationship between the thermal and chemical profiles in the powder layer during casting and revealed the existence and the details of the formation of the carbon enriched-layer.