CFD Investigation of Effect of Multi-hole Ceramic Filter on Inclusion Removal in a Two-Strand Tundish

Abstract

Multi-hole ceramic filter is regarded as an effective and cheap method of additional flow control device in tundish. In order to evaluate the performance of the ceramic filter, a transient three-dimensional (3D) comprehensive numerical model has been developed to study the flow pattern, temperature distribution and residence time of the molten steel, as well as the elimination of inclusion in a full size two-strand tundish. One-way coupled Euler–Lagrange approach with random walk model was adopted to track the inclusion motion trajectory. The gravity, buoyancy, drag, virtual mass, lift, pressure gradient, and rebound forces were included. The inclusion Reynolds number was utilized for the judgment of the inclusion separation at the slag-steel interface and the internal surface of the filter hole. Besides, the residence time distribution curve has been analyzed for figuring out the macroscopic mixing of the molten steel. The results indicate that the ceramic filter increases the flow resistance of the molten steel in the tundish, resulting in a longer residence time and a higher temperature drop. Except removed by the covering molten slag, the inclusion could also be trapped by the filter hole when the molten steel travels through the ceramic filter. The elimination of the smaller inclusion is significantly improved. The removal ratio of the 1 μm inclusion in the tundish without ceramic filter is only 59.3 pct, while the value is improved to 65.3 pct if we apply the ceramic filter with slenderness ratio of 3 to the tundish. And with the slenderness ratio changing from 3 to 5, the removal ratio of the 1 μm inclusion increases from 65.3 to 72.0 pct. Additionally, the ceramic filter could counteract certain side effects of the increasing inclusion density on the removal, especially for the smaller inclusion. With the inclusion density increasing from 3990 to 5000 kg/m3, the removal ratio of the 1 μm inclusion decreases by 14.5 pct in the tundish without ceramic filter, and after using the ceramic filter, the removal ratio decreases by 13.0, 7.4, and 5.0 pct with the slenderness ratio varies from 3 to 5.