The paper describes the effect of additives Al, Si,SiC and B4 C on the expansion of MgO-ZrO2-C material after being coked . The results indicate that Al and Si can not increase its hot and cold strength. Al and Si were oxidized to form Al2 O3 and SiO2 respectively, and then reacted with CaZrO3 or stabilizer in c-ZrO2 to form calcium aluminate , spinel ( MA ), dicalcium silicate ( C2 S ) and forsterite (M2S). Meanwhile, α-C2S was transformed to γ-C2S and c-ZrO2 to m-ZrO2 when temperature changed.All the above reactions resulted in the decrease of the amount of Al4 C3 and SiC and the increase in bulk volume ,which caused the structure of MgO-ZrO2-C material destroyed. Hence, contrary to the MgO-C material, when adding Al. and Si, the MgO-ZrO2-C material would be structurally deteriorated after heat-treatment and its strength and corrosion resistance decreased.
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