A microporous MgO-MgAl2O4 functional refractory for small inclusions removal of tundish: Preparation and parameters optimization

Abstract

A microporous MgO–MgAl2O4 gas-permeable brick was fabricated for use in tundish to remove small inclusions in liquid steel using argon bubbles, based on the optimization of particle gradation. The effect of activated alumina addition on the properties and pore size distribution of microporous MgO–MgAl2O4 bricks was investigated. The flow rate parameters of argon for inclusion removal were optimized. The results showed that the microporous MgO–MgAl2O4 permeable brick, prepared by adding 5 wt% activated alumina, had a minimum average pore diameter of 10.9 μm and greater air permeability compared to no introduction of activated alumina. The thermal stability was significantly improved due to the long cone-shaped magnesium-rich spinels generated by the solid-state reaction between magnesium oxide and activated alumina distributed in the pores; this further remodeled the structure of the pores. The addition of more activated alumina caused a sharp drop in the volume density and strength and formed more spinels, with the morphology of spinels changing from long cone to octahedron with larger average pore size; these are not beneficial to the production and application of gas-permeable brick. When the flow rate was 60 L/min, the total oxygen content (T.[O]) in the billet was reduced by 7 ppm, the content of pores and cracks in the billet decreased dramatically, and the removal rates of inclusion size distributions of 20–50 μm, 50–100 μm, and >100 μm in the billets increased by 15%, 20%, and 61%, respectively.