Numerical investigation of the macrosegregation during thin strip casting of carbon steel

The influence of forced convection, shrinkage-induced interdendritic fluid flow, and solute diffusion in the liquid phase on macrosegregation during thin ship casting is investigated numerically. It is shown that solute diffusion in the liquid phase causes a thin layer, namely, the diffusion boundary layer, to form near the casting table. This diffusion boundary layer is characterized by an essentially decreased concentration of the solute. It is also shown that, depending on the permeability of the mushy zone, three regimes of macrosegregation are possible. For small permeability of the mushy rone the solute transport in the strip is mainly governed by the interdendritic fluid flow, which compensates for shrinkage. For large permeability of the mushy zone the solute transport is mainly governed by forced convection. Between these two regimes there is an intermediate regime when these two phenomena balance each other. This regime corresponds to the minimum macrosegregation level in the strip.