Speaker
Description
In ingot casting, powder bags are placed inside the mold to release a complex mixture of oxides during filling. Their melting and spreading over the liquid metal form a protective layer that serves as an insulating barrier, prevents re-oxidation, and ensures mold lubrication. Effectiveness depends on the powder melting rate, governed by the free carbon content through a complex interplay of heat transfer, combustion kinetics and gas transport phenomena (Mills and Däcker, 2017). No model fully captures this complexity. Purely thermal models neglect chemical effects, kinetic models reduce reactions to temperature dependence, and the most complex approaches remain restricted to 850 °C, far below the 1500 °C of industrial conditions (Supradist et al., 2004).
A novel one-dimensional multiphysics front-tracking model is being developed to investigate powder evolution during bottom-pouring ingot casting and describe the melting stage. The powder bed is represented as three successive domains: liquid slag, a mushy zone and loose casting powder, bounded by liquid steel below and open air above. Coupled energy and mass conservation equations are solved within a transient moving-grid framework and integrated with CALPHAD-based thermodynamic calculations, describing phase transformations and interface positions. Each interface evolves according to a local mass balance equation. Phase change, carbon combustion, powder densification and multi-component gas transport are treated simultaneously within a unified formulation.
The model predicts the spatial and temporal evolution of temperature, carbon concentration, gas species composition and liquid slag thickness. Carbon concentration is tracked because residual carbon threatens steel quality through carburization (Supradist et al., 2004), while O₂, CO and CO₂ profiles help identify whether oxidation governs carbon removal. Simulations are expected to reveal the dominance of the Boudouard reaction above 1000 °C and that exothermic carbon combustion paradoxically slows melting, as energy is transported away by product gases rather than transferred to the powder.
| Speaker Company/University | MinesParis - PSL - CEMEF |
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