| Properties and microstructures of Al2O3-C materials with suitable amount of additives such as Si powder, Al powder, B4C, Si+B4C and Al+B4C were examined. Slag resistance test was carried out in tundish at plant site. And the effects of additives on slag resistance of the materials were studied.The results show that the addition of 3wt% additive such as Si powder, Al powder or 840 is effective to increase CMOR and to improve oxidation resistance of Al2O3-C materials. And the 840 additive has shown the best effect, not only in increasing the CMOR of the materials, but in improving remarkably the oxidation resistance and thermal shock resistance. The addition of composite additive in Al2O3-C material can decrease the apparent porosity and increase the CMOR respectively. The material with the additive of Si+EUC is more resistant to oxidation than that with Al+B4C.It is found that all the used additives can improve the slag resistance of Al2O3-C materials to some extent, in which the addition of Si powder has shown better effect and the composite additive of Si+B4C the best. And it is also found that ZrB2 was formed through the reaction of B4C and ZrO2 derived from the decomposition of zirconia-mullite in the materials with B4C.It can be concluded that the addition of the composite additives is more efficient in the improvement of the properties of Al2O3-C material than that of the single additives. And considering the factors such MOR, oxidation resistance, thermal shock resistance, slag resistance, and the materials cost and so on, the most suitable additive in Al2O3-C material is 2 wt% Si+1 wt% B4C.
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