Analysis of the upward direct chill casting of magnesium alloys

The upward direct chill casting, where the continuous casting is operated vertically against gravity, is a novel technology which has been applied to the production of high quality magnesium alloys circumventing the main disadvantages of using conventional continuous casting processes, since the risks of burning and explosion are practically eliminated. This represents a key aspect to increase the industrial application of magnesium wrought products. In order to help on the understanding of the process, a mathematical model for the simulation of the upward continuous casting of round billets of magnesium alloys has been developed. The equations for the flow field with heat transfer are numerically solved by a finite volume method and the solidification is accounted via an enthalpy-porosity formulation where the mushy region is modeled as a pseudo porous medium. The obtained temperature distribution is then used as input for a thermo-mechanical analysis to determine the deformation and stress field developed in the billet during the casting process. Several configurations have been simulated and comparison of computed results with available experimental data is provided.