Fluid flow and inclusion removal in continuous casting tundish

Abstract

Three-dimensional fluid flow in continuous casting tundishes with and without flow control devices is first studied. The results indicate that flow control devices are effective to control the strong stirring energy within the inlet zone, and other zones are with much uniform streamline. By dividing tundish into two zones with different inclusion removal mechanisms the inclusion removal is calculated. Three modes of inclusion removal from molten steel in the tundish, i.e., flotation to the free surface, collision and coalescence of inclusions to form larger ones, and adhesion to the lining solid surfaces, are taken into account. The Brownian collision, Stokes collision, and turbulent collision are examined and discussed. The suitable coagulation coefficient is discussed, and a value of 0.18 is derived. Calculation results indicate that, besides flotation, collision of inclusion and adhesion to the lining solid surfaces are also important ways for inclusion removal from molten steel in tundish especially for the smaller inclusions. The flotation removal holds 49.5 pct, and the adhesion removal holds 29.5 pct for the tundish with flow control devices; the collision effect is reflected in improving flotation and adhesion. Finally, industrial experiment data are used to verify the inclusion removal model.