Thermo-fluid modeling of direct chill casting of metal alloys using an inverse finite element method

Abstract

Direct chill (DC) casting is used extensively in the production of wrought nonferrous metals and alloys, particularly in the aluminum industry. For alloys, a semi-solid region known as the “mushy zone” and defined by the liquidus and solidus temperatures, marks the solidification front. The liquidus and solidus isotherms represent respectively the onset and completion of solidification. Pure metals exhibit no mushy zone while alloys with increasing freezing ranges exhibit larger mushy zones. In this work, a two-dimensional Eulerian steady-state finite element model is used to analyze the melt flow as well as the mushy region during continuous casting. The simultaneous solution to the melt flow problem and the non-uniform release of latent heat in the mushy region is achieved using an inverse approach. This is a novel method in the numerical modelling of DC casting which offers distinct advantages over other methods of solution. In this analysis we are including the effects of the mushy region in an idealized continuous casting problem of an Al-.7% Mg alloy. Specifically, we are investigating the effects of the temperature field, melt flow, and the casting and cooling rates on the position and shape of the solidification front.