Abstract: In order to improve the steel cleanliness during ladle change, the steel-slag-air flow behavior in the tundish was investigated using numerical simulation and physical modeling. The effect of the refilling time on the multiphase flow behavior in the tundish during ladle change was also studied. The results showed that for the refilling time of 97 s the reoxidation was always occurred in the tundish during ladle change. A massive amount of gas phase was sucked into the impact zone at the start of pouring from the new ladle and the exposed area fraction of slag phase at the top surface was rapidly increased. After 5 s, the amount of sucked gas and the exposed area fraction of slag phase remained relatively stable. Reasons for the slag exposure mainly included: 1) the slag layer near the ladle shroud was directly impinged by the liquid steel at the start of pouring from the new ladle; 2) the thickness of the slag layer became thinner due to the shear effect of liquid steel flow. Increasing the refilling time during ladle change decreased not only the kinetic energy of liquid steel acting on the slag phase near the ladle shroud, but the shear effect at the slag-steel interface. Therefore, the amount of sucked gas and the slag exposure in the impact zone were significantly decreased. To improve the steel cleanliness during ladle change, the refilling time in the tundish should be larger than 184 s.

Key words: tundish, ladle change, reoxidation, refilling time, numerical simulation