Application of Alumina-magnesia Precast Blocks for LF Refining Ladle

摘要

The alumina-magnesia precast blocks developed in author's company have been successfully used in 90-ton LF refining with an average service life 80-85 heats to meet the smelting demand of low carbon steel and ultra low carbon steel. The observation of the residual blocks revealed that the section of the used blocks was divided into four layers from inside to the surface, i.e., slag layer, reaction layer, penetration layer and the original block. It has been found that there was a certain degree of structure spalling of the used blocks. The main factor of blocks' damage may be due to the penetration and erosion of molten slag. The results of SEM microstructure analysis indicated that the calcium oxide(CaO) of high basicity slag easily penetrated into the blocks and formed CA_6 phase, and then transformed into CA_2 or C_(12)A_7 phases gradually with the decreasing content of alumina (Al_2O_3). It has been found that an annular distribution structure, and the silicon dioxide (SiO_2) was easily lost together with slag and formed SiO_2-rich part in the penetration layer due to the formation of low viscosity and low melting point phase of C_2AS. A large number of -5um spinel particles (MgAl_2O_4) were synthesized at 1600- 1700℃, which could absorb FeO, MnO and other impurities in slag to form composite spinel phase. It is believed that the high melting point phases intertwined to form a dense area which was beneficial to improve the bricks' slag resistances to penetration and corrosion.