Thomas, Brian G.Liang, Mingyi2022-11-142022-11-142022https://hdl.handle.net/11124/15480Includes bibliographical references.2022 Summer.Over 96% of steel is produced by continuous casting process. During this process, fluid flow in the nozzle and strand can capture detrimental particles such as: inclusions from upstream ladle refining and tundish, entrainment of mold slag, and argon bubbles which are often injected into the nozzle in order to lessen nozzle clogging. In this study, with the aid of existing models, computational fluid dynamics knowledge, and commercial software ANSYS FLUENT, a model system is developed to predict the effect of nozzle design, superheat, and mold-electromagnetic stirrer on multiphase flow in the tundish, nozzle and strand. This model system includes a heat transfer / solidification model, a two-stage bubble-formation model, a Eulerian-Eulerian model of fluid flow, heat transfer in the liquid, a discrete phase model of particle transport, a slag-layer energy-balance model, a Primary Dendrite Arm Spacing model, and particle capture models of hook, entrapment, and engulfment mechanisms. The results match plant nail-board dipping tests of top-surface velocity and ultra-sonic maps of particle capture, both qualitatively and quantitatively. Results suggest that higher superheat lessens the penetration depth of large particles, which leads to less and shallower capture. In the tundish, similar models are developed to investigate the effect of ladle exchange with temperature changes and nozzle misalignment on tundish flow and inclusion exit fraction. Results show that a ladle exchange with lower temperature causes detrimental flow pattern, as the colder and heavier steel tends to flow along the bottom of the hotter steel already in the tundish. This creates a short-cut path for inclusions to exit the tundish rather than being removed into the top slag layer. This makes the steel quality worse, until the tundish liquid eventually cools and the flow pattern returns to its previous state. Nozzle misalignment leads to asymmetrical flow in the tundish, with more large inclusions exiting the far outlet, leading to worse steel quality on that side. This study has practical value, as it provides, for the first time, quantitative insight into the benefits of high superheat / temperature on inclusion-related defects in steel production.born digitaldoctoral dissertationsengCopyright of the original work is retained by the author.argon bubblesCFDcontinuous castingmeniscus hooksmultiphase flowsuperheatText2022-11-05