The effects of aluminum and aluminum borate addition on the properties of MgO-C refractories

Aluminum and aluminum borate powders were used as antioxidants to increase oxidation resistance of magnesia-graphite refractories. Bulk density and cold crushing strength of bodies without additives and also containing 4 and 6 wt.% aluminum and aluminum borate were investigated. XRD results of the samples containing aluminum borate and aluminum after firing in coke bed and also oxidized atmosphere (in air) at 1200 and 1400 °C showed that spinel (MgAl2O4) was formed. In addition to the high refractoriness, this phase can improve strength and fill the porosities of refractories. A liquid phase was formed in the bodies containing aluminum borate which developed a coating on the graphite surfaces, and can stimulate the formation of spinel. The results of oxidation resistance tests, which were measured according to weight percent of the samples, showed that the oxidation resistance of the bodies containing aluminum borate was better than that of the bodies containing aluminum.