Inclusion Float-out Behavior in Continuous Casting Tundish Bath

The Floating behavior of inclusions in the tundish bath was studied in connection with the fluid flow state of molten steel. A mathematical model which predicts the inclusion removal efficiency has been developed. It was postulated in the model that the tundish bath consists of three regions : a mixing flow region, a plug flow region and a stagnant region. In the mixing flow region, predominated by inertia force or turbulent viscous force, inclusions are transferred by various sized vortices. In the plug flow region, predominated by viscous force, inclusions are transferred approximately according to Stokes's law. The stagnant region is not involved in inclusion transfer owing to long-stagnation. The validity of the model was comfirmed by the results of cold model experiments and actual operations. It was found by the above model that the use of a longer and deeper tundish bath was effective for promoting the floating removal of inclusions owing to the increased plug flow region. In addition, placing dams in the tundish retarded the removal efficiency, since the dam increased the mixing flow region.