EFFECT OF VARYING LADLE STREAM TEMPERATURE ON THE MELT FLOW AND HEAT-TRANSFER IN CONTINUOUS-CASTING TUNDISHES

The effect of varying ladle stream temperature on the fluid flow and heat transfer phenomena in a typical twin strand slab caster tundish has been mathematically modeled in the present study. The model involves solution of the transient, three dimensional form of the turbulent Navier-Stokes' equation, along with the equations of turbulence energy, energy dissipation rate of turbulence energy and thermal energy conservation. The incoming melt stream temperature has been assumed to decline at a constant rate of 0.5-degrees-C/min over a casting period of 50 min. Under the conditions examined in the present mathematical model, the temperature of the incoming melt stream becomes lower than the bulk temperature of the melt in the tundish by about 1-2-degrees-C, after 25 min from the start of teeming of a heat. Due to buoyancy effects, the cooler incoming melt starts to flow along the bottom of the tundish instead of the normal top free surface directed flow. The calculations show that the inverse flow pattern develops over the remainder of the teeming period and persists for about 1 min into the teeming of the next heat. Thus, the inclusion flotation and removal of the non-metallic inclusions during the later half of the casting period are expected to be worse compared to the first half.