COMPARISON OF PROPERTIES AMONG SPINEL-CONTAINING CASTABLES FOR STEEL LADLE

Recently, the material of castables used for wall and bottom of steel ladle has been changed from alumina-spinel to alumina-magnesia because the corrosion and penetration resistance of the alumina-magnesia castables are improved more than the alumina-spinel castables due to the in-situ spinel formation. Regarding the properties of spinel-containing castables, we have carried out laboratory experiments on three types of spinel-containing castables (alumina-spinel, alumina-spinel-magnesia and alumina-magnesia), and the results have been applied to steel ladle. According to the laboratory experiments the magnesia-containing castable showed dramatic linear expansion at the over 1200 degrees C due to the in-situ spinel formation, and the alumina-magnesia castables showed the highest corrosion resistance among three types of castables. However, the field test showed different result. The alumina-spinel castable could maintain stability without spalling. On the other hand, the alumina-spinel-magnesia could not satisfy the expected life time due to spalling. We can assume that it is due to the difference in spinel generation speed, which is caused by the reaction between alumina and magnesia on the movable and unmovable surface. One of effective methods to control the expansion is addition of microsilica. Nonetheless, it is important to control the optimal speed and microsilica content in castables according to the operational condition.