Discussion on Inclusions Movement Behavior in Tundish on Non-Isothermal Condition

摘要

According to the industrial measurement data, the average liquid temperature in ladle is usually 30-40°C higher than that in tundish. The liquid with higher temperature tends to flow upward, while the liquid with lower temperature tend to flow downward. So when jets with different temperature mix together, it forms "natural convection" flow pattern, which has a big difference from the case of isothermal mixing. During the continuous casting process, the higher temperature liquid from ladle flows into the tundish, with a extra heat loss in the tundish, it forms the natural convection flow pattern tin the tundish during the entire period of casting process, and the flow pattern in the tundish is changing all the time. And the "natural convection " makes flow pattern change in the tundish, which is different from isothermal flow pattern as many researchers do. And inclusions removal rate in the tundish depends strongly on the tundish flow pattern.In this paper, ladle and tundish is considered to be a combined system, and then movement regular of inclusions in tundish is discussed on this non-isothermal condition. The emphasis in this paper is very different from others'. This paper reveals that:(i) for isothermal case, the plug flow region, dead region and backmix region's volume fraction in tundish is 67.5%, 1.6%, 30.9% respectively, while for the non-isothermal case, the different regions' volume fraction is 75.7%, 6.1%, 18.2%,which is quite different from the isothermal case; (ii) the incoming flow from ladle tend to flow along the tundish bottom at the middle-later period of casting process, and inclusions tend to flow with the incoming flow, which is very bad for inclusions-removing, and it might cause quality of slab declined.