Liquid steel flow, heat transfer and solidification in mold of continuous casters during grade transition

A computational study of the unsteady axisymmetric turbulent liquid steel flow, heat transfer and solidification in continuous casting molds during the grade transition operation is presented. The computations are based on an iterative, finite-volume numerical procedure using primitive dependent variables, whereby the governing time-dependent continuity, momentum and energy equations in combination with a low-Reynolds number turbulence model are solved. A single-domain enthalpy formulation is used for simulation of the phase change phenomenon. Darcyʹs Law-type porous media treatment is used to account for the effect of phase change on convection. In spite of the transient nature of the incoming liquid steel velocity, increase in size of the liquid pool is not significant, whereas the increase of the volume of the mushy zone is marked and is as much as 48% relative to its initial size. Distinct temperature rise signatures on the surface of the casting were detected. The heat removal rate from the mold increases almost linearly similar to the ramping of the casting speed. Thinning of the solidified shell during tundish change is significant and must be taken into account in practice to prevent breakout.