The Development of Alsim – a Modelling Tool for Direct Chill Casting, Twin Roll Casting, Wheel and Belt Casting and Chain Conveyor Casting

Abstract

A coupled heat and fluid flow, stresses and deformation modelling tool including macrosegregation and inter-dendritic flows have been developed for various semi-continuous or batch casting processes in use by the light metal industries. Results from the mechanical calculation are back-coupled to the thermal boundary conditions regarding size of contact zones and air-gaps and thereby enabling automatic calculation of gap dependent heat transfer coefficients, which is very useful for the industrial use of the tool. Examples from the application of the model on direct chill castings are made, as well as on twin roll, wheel and belt and chain conveyor casting. Comparison with measurements and other process data are done. The finite element method is used for the modelling tool including dynamic treatment of elements in moving parts of the calculation domains. In continuous casting there are frequently interfaces where the metal slides against the equipment, and although the grid across such surfaces does not match they are still coupled implicitly in Alsim. This adds an ability to model complex processes involving stresses and deformations in mechanical coupled moving parts and it alleviates the time consuming process of producing the initial finite element grids for the geometries. In order to handle solidification phenomena like hot-tearing, macrosegregation and exudation local adaptive grid refinement is necessary, as well as parallelization of the code, to achieve acceptable accuracies. How these numerical challenges are handled in the model is described.