Papers by Keyword: Magnesia-Carbon Refractory

Abstract: Carbon-containing refractories are widely used in metallurgical industry due to their excellent thermal property and resistance to corrosion by molten iron. In the present work, slip casting colloidal process, which is used to fabricate high performance structural ceramics, has been introduced into the preparation for magnesia-carbon refractory with selection of suitable dispersant. The results indicated that the curve of zeta-potential of magnesia was similar with that of carbon just containing dispersant and the homogenized mixtures were attained under a controlling of low pH value. Three kinds of preparing routes for green bodies were designed, and all of the final densities and the resultant hardness of sintered bodies using colloidal process were superior to these of the specimen using conventional dry pressing, whereas its high green density can be plausibly observed in dry pressing body because of high compaction pressure used.

Abstract: The corrosion test for magnesia-carbon refractory, MgO-C, with dense layer has been carried out by a rotating cylinder method at 1673 K. The specimen, which was a cylinder of 25 mm diameter and 25mm height, was rotated in molten slag at 50 rpm. The chemical composition of slag was CaO-SiO2-FeO-MgO-CaF2. The corrosion rate was determined by the variation of radius of the cylindrical specimen against corrosion time. The decrease of radius was obtained by a calculation of dissolved MgO into the slag. In addition, the diameter of the specimen was measured with a slide calipers after the corrosion test. The cylindrical specimen was heated to form a dense layer before the corrosion test. The corrosion rate of the MgO-C refractory with dense layer was slower than that of the MgO-C refractory without dense layer. The oxidized layer, where the dense layer formed, dissolved at much the same rate as the MgO brick. The dense layer probably obstructed contact between slag and carbon in the matrix, and then oxidation of C by slag did not take place. Formation of the dense layer was effective to inhibit corrosion of MgO-C refractory by molten slag.

Abstract: An effect of addition of 2 mass % aluminum powder on the oxidation rate of magnesia-carbon refractory, MgO-C, containing 5 mass % carbon has been investigated by measuring weight change with a thermobalance for the cubic specimens in the temperature range from 1073 to 1823 K in air. The oxidation rate of carbon was measured by analyzing the residual carbon in the specimens at some oxidation time. The variations of the weight with oxidation time at temperatures from 1273 to 1673 K showed the similar tendency. The oxidation rate of carbon in the MgO-C refractory with 2 mass % of aluminum additive was a little smaller than that of the MgO-C refractory with no additives. When the oxidation temperature increased to 1823 K, the weight change became very small. It was suggested that the gaps between MgO grains in the thin oxidation layer were bridged by MgO·Al2O3, which was identified by a X-ray diffraction method.