Numerical simulation and industrial investigation on the melt stratification phenomena in ladles holding molten steel

摘要

The melt stratification phenomenon, which results from the natural convection in ladles holding molten steel, is of fundamental importance for the temperature control in the continuous casting process. The progressively increasing stress on the quality of continuously cast products necessitates much tighter tundish temperature control, which in turn will require a more precise definition of the extent of melt temperature stratification in ladles. For this reason, ladle melt stratification phenomena were studied both by numerical simulations, using the PHOENICS package, and by plant measurements at SSAB Tunnplat AB's steelworks in Lulea. The parameters studied in the numerical simulations were the fluid flow velocity field, the temperature distribution field, ladle initial heat content and height to diameter ratio of ladles. One of the important boundary conditions that was used in these numerical simulations was the time and geometry-dependent heat loss rate through the ladle walls, which is the major cause of the natural convection. This transient boundary condition was obtained from the temperature simulation model TempSim. Steel temperatures measured at different positions along the ladle height are compared in the paper with results from the numerical calculations. The possibility of expressing the stratification with a simple formula was discussed. However, to propose this mode for industrial use, experimental verification with prolonged holding time is needed.