Modeling for characterization of continuous casting simulator using CFD

Abstract: In order to improve the continuous casting process of steel, it’s important to have an understanding of the fuid mechanics of the casting process. As experiments on a real caster are usually impractical, both physical and numerical modeling are important for creating this understanding. This report concerns itself with the creation of a numerical model of a physical model of a slab caster, which uses eutectic bismuth-tin alloy to simulate steel, and is built and operated by Swerim in Luleå, Sweden. The geometry of the model was constructed in Siemens NX, and meshing was done using Ansys Meshing. The CFD model itself was made in Ansys Fluent, and data from previous experiments on the physical model was used to verify it. The numerical model does not model any discrete phases in the liquid metal, including slag, argon fow, solid particles or any form of phase transition or heat transfer. The model uses a pump to continuously recirculate the liquid metal into the tundish, from where it fows down into the mold. Qualitatively, the model shows the expected double-roll fow pattern in the mold, and also pressure gradients in the SEN entry region which are consistent with experimental data. Verifcation was done using experimentally determined pump curves, for which the model shows reasonable behavior for mass fows above roughly 20 kg/s, but deviates somewhat below this value. Verifcation was also done using data for mass fows out of the tundish, which is regulated by the stopper position. Here, a large discrepancy between experimental and simulated data is present. Several explanations for this discrepancy were investigated, including the possibility of improper calibration of the stopper positional tracking and incorrect data for dynamic viscosity of the alloy, but the most likely explanation is that cavitation occurs in the SEN entry region due to a large pressure drop which occurs in this region. Cavitation is not implemented in the model, which leads to incorrect mass fow out of the tundish. If this fow is to be accurately captured, it is likely necessary to implement cavitation modeling in future versions of the numerical model.