As we all know, in the production process of aluminum-magnesium-carbon bricks and magnesium-carbon bricks, the raw materials used in the wholesale of magnesium-carbon bricks are mainly premium bauxite clinker, high-purity magnesia, fused magnesia, graphite, etc., so what do these raw materials play in the products? What kind of effect?

       1. Super bauxite clinker

       The main mineral composition of China's high bauxite raw materials is gibbsite and kaolinite. The change of its Al2O3 / SiO2 ratio corresponds to the relative increase and decrease of the content ratio of the two minerals, gibbsite and kaolinite. Bauxite clinker is the product after high temperature calcination. The Al2O3 content of super bauxite clinker is above 88.2% and can reach 91.3%. Although Al2O3 has strong erosion resistance, pure Al2O3 has a large expansion coefficient and is not resistant to spalling. When pure Al2O3 is used as the matrix, the matrix part is easily penetrated and melted by the slag, and the aggregate is exposed, resulting in structural spalling.

       2.High purity magnesia

       Magnesite, brucite, seawater magnesia and other raw materials are fully sintered at 1600 ~ 1900 ° C to obtain magnesia. Magnesia is divided into sintered magnesia and seawater magnesia. Sintered magnesia is fired from natural ore. Seawater magnesium Sand is fired from seawater gasified magnesium. The main component of magnesia is magnesia, and it also contains a small amount of SiO2, CaO, Fe2O3, B2O3, etc. The color ranges from yellow to brown, the main crystal phase is periclase, the grain size is 0.02 ~ 0.05mm, and the density is 3.50 ~ 3.65g. / cm3. Has good resistance to alkaline slag erosion.

       The main indicators of high-purity magnesia are MgO content, CaO / SiO2 ratio, microstructure and particle bulk density. The main crystal phase of magnesia with high MgO content is periclase, with few impurities and cements. The obtained refractory has Very high resistance to erosion; CaO / SiO2 ratio determines the phase composition of the matrix in magnesia, which directly affects the combination of periclase and the high temperature performance of refractory materials. Generally, magnesia with a C / S of 3-8 High temperature resistance performance, beyond this range, it will bring side effects; microstructure is an important means to characterize the grain size and bonding state of periclase. Generally, the grain size is required to be 80 ~ 150μm, and the bulk density is a characterization of magnesium. An important indicator of sand sintering degree and compactness, magnesia with a high bulk density can resist the intrusion of slag and improve the corrosion resistance of refractory products.

       3. Fused magnesia

       Fused magnesite or sintered magnesia is fused in an electric arc furnace at a high temperature of 2500 ° C. After cooling, the fused magnesia is also called fused magnesia. The fused magnesia is determined by the purity of the raw materials. Purity, the main crystal phase of which is periclase. The periclase crystals crystallized from the melt are coarse, dense in structure, and the degree of direct contact with the crystals is high. The water resistance and slag resistance in the atmosphere are very good. It has good chemical stability and can maintain stability in an oxidizing atmosphere at 2300 ° C. Various performance indicators of magnesium carbon bricks are directly related to the performance indicators of magnesia. In order to improve the performance of magnesium carbon bricks, it is necessary to increase the MgO content and make magnesium The direct binding degree of periclase in the sand is enhanced. Controlling C / S can reduce the amount of silicate and reduce the degree of division of periclase by the silicate phase. Therefore, the magnesium content and the calcium-silicon ratio are important indicators for measuring magnesia.

       4.Graphite

       Graphite has excellent thermal conductivity and fire resistance. The melting point is as high as 3500 ° C. Graphite has a low thermal expansion rate (1.4 × 10-6 at 1000 ° C), high thermal conductivity, good resistance to rapid cooling and rapid heating, and its strength increases with temperature. And one of the few materials that grows. The wetting angle of graphite on slag is also quite large. It has no eutectic relationship with Al2O3, SiC, and SiO2. It can prevent the slag from penetrating into the product. Because carbon can reduce the iron oxide in the slag to metallic iron, the viscosity of the slag is increased and reduced. The migration of slag components into the brick is achieved to reduce the effect of erosion.

       The main role of graphite in carbon-containing products is to effectively prevent slag from intruding into the brick structure. By increasing the wetting angle between the working surface of the brick and the slag and reacting with MgO in the brick, the metal magnesium is reduced. At the same time, CO gas is generated. The pressure of the gas can prevent the slag from permeating, and the magnesium diffuses and volatilizes and oxidizes on the working surface of the brick, forming a dense and impervious MgO layer, which makes the brick in a strong reduced state, which can reduce iron oxide in the slag It can also increase the viscosity of the slag and prevent the slag from penetrating into the brick. The stronger the resistance to erosion and slagging, the higher the carbon content of graphite and the larger the scale.