FLOW AND THERMAL-BEHAVIOR OF THE TOP SURFACE FLUX POWDER LAYERS IN CONTINUOUS-CASTING MOLDS/

Steady-state finite-element models have been formulated to investigate the coupled fluid flow and thermal behavior of the top-surface flux l ayers in continuous casting of steel slabs. The three-dimensional (3-D ) FIDAP model includes the shear stresses imposed on the flux/steel in terface by flow velocities calculated in the molten steel pool. It als o includes different temperature-dependent powder properties for solid ification and melting. Good agreement between the 3-D model and experi mental measurements was obtained. The shear forces, imposed by the ste el surface motion toward the submerged entry nozzle (SEN), create a la rge recirculation zone in the liquid flux pool. Its depth increases wi th increasing casting speed, increasing liquid flux conductivity, and decreasing flux viscosity. For typical conditions, this zone contains almost 4 kg of flux, which contributes to an average residence time of about 2 minutes. Additionally, because the shear forces produced by t he narrowface consumption and the steel flow oppose each other, the fl ow in the liquid flux layer separates at a location centered 200 mm fr om the narrowface wall. This flow separation depletes the liquid flux pool at this location acid may contribute to generically poor feeding of the mold-strand gap there. As a further consequence, a relatively c old spot develops at the wideface mold wall near the separation point. This nonuniformity in the temperature distribution may result in nonu niform heat removal, and possibly nonuniform initial shell growth in t he meniscus region along the wideface off-corner region. In this way, potential steel quality problems may be linked to flow in the liquid f lux pool.