| To study reoxidation of molten steel in contact with Al₂O₃-MgO castables in the teeming ladle, the crucibles made of castables were reacted with Al, Si-Al and Al-Ti killed steels in an inert gas for 30, 60, 90 and 120 minutes at 1600±10℃. The samples from crucibles were cut into thin and polished sections to be observed under optical microscope. Steels were chemically analyzed. The main results could be summarized as follows: (1) As Al₂O₃ and MgO would form a very stable spinel (MgAl₂O₄), they do not react with any component in the molten steel. Al₂O₃-MgO castables are confirmed to be excellent as refractories in contact with molten steel in the teeming ladle. (2) SiO₂, added as the mineralizes in the castables plays a role as the source of oxygen to the molten steel, oxidizing [Al], [Ti], [C] and [Mn] and thus forming oxide inclusions. Therefore, it exerts a harmful influence upon steel cleanliness. (3) The manganese in the melt reacted with SiO₂ in the refractory to form manganese oxide, which resulted in excessive wear of refractory by complexing Al₂O₃ and SiO₂ in the refractories. (4) The deepest altered zone is observed in the case of using Al-Ti killed steel probably due to the formation of a relatively low-melting compound of TiO₂and Al₂O₃. |
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