On the prediction of macrosegregation in vacuum arc remelted ingots

The chemical homogeneity and metallurgical structure of vacuum arc remelted (VAR) zirconium ingots are directly responsible for product quality. It is therefore important to understand the relationship between these properties and the operating conditions. An in-depth analysis of the modelling of solidification phenomena during the VAR was carried out. Such model, solves a coupled set of transient equations for heat, momentum, solute transport and turbulence in an axisymmetric geometry. The remelting and cooling of a cylindrical ingot are calculated for time-dependent operating parameters. The solidification mechanisms implemented in the model can be applied to multi-component industrial alloys such as Zircaloy-4, which provides information on the macrosegregation phenomena studied in this paper. The model results were validated, based on the remelting of a specially designed chemically homogeneous Zircaloy-4 electrode. The results illustrate the importance of thermal and solute convection, the importance of the permeability of the partially solid material and the weak influence of nuclei density and solute diffusion in the solid phase on the prediction of macrosegregation in Zircaloy-4 ingots