3-D prediction of alloy solidification in the presence of turbulent fow in a vertical direct chill caster with a porous filter near the top

摘要

An industrial size vertical Direct Chill (DC) caster fitted with a porous filter above the mold is simulated by developing control volume finite difference based computational fluid dynamics code. Specifically, the 3-D laminar/turbulent melt flow in the sump and mushy zone solidification characteristics in the DC caster are modeled for aluminium alloy AA-1050. To account for the turbulence in the sump a popular version of the low Reynolds number κ-ε model is employed. A single domain enthalpy-porosity approach is used to account for the solidification heat transfer of the above short solidification range alloy. The melt flows through the stainless steel porous filter placed near the top of the caster is modeled using the Brinkman-Forchheimer extended Darcy equation and by invoking the local thermal equilibrium condition between the melt and the porous structure. The verified code is used to study the effects of casting speed and heat transfer coefficient in the metal-mold contact region on various aspects of this casting problem. Sensitivity analysis is also carried out by varying the latent heat of solidification of the said alloy. The predicted results are presented and discussed for the solid-shell thickness, the sump depth, the mushy layer thickness as well as for the temperature and velocity fields.