Four kinds of magnesia-carbon bricks are commonly used as refractory materials. What are their main roles?

1, super grade bauxite clinker

The main mineral composition of high bauxite raw materials in China is bauxite and kaolinite. The change of Al2O3/SiO2 ratio corresponds to the absolute offset of the content ratio of two minerals, bauxite and kaolinite. Bauxite clinker is the product of calcination at high temperature. The content of Al2O3 in super grade bauxite clinker is more than 88.2%, up to 91.3%. Although Al2O3 has strong corrosion resistance, simple Al2O3 has a large expansion coefficient and is not resistant to spalling. When pure Al2O3 is used as the matrix, the matrix part is easy to be permeated by molten slag, so that the aggregate is revealed, leading to structural spalling.

2, high purity magnesia

Magnesite, brucite, sea water magnesium oxide and other raw materials at 1600~1900℃ fully sintered lost magnesia, magnesia is divided into sintered magnesia and sea water magnesia, sintered magnesia is fired by natural ore, sea water magnesia is fired by sea water magnesium gasification. The main component of magnesia is magnesium oxide, but also contains a large number of SiO2, CaO, Fe2O3, B2O3, color from yellow to brown, the main crystal phase is magnesite, grain size of 0.02~0.05mm, density 3.50~3.65g/cm3. It has good function of resisting alkaline slag corrosion.

3, electric melting magnesia

Magnesite or sintered magnesia in electric arc furnace, after 2500 ℃ high temperature melting, cooling after the crushing of call fused magnesia and fused magnesia, in accordance with the purity of raw materials to determine the purity of fused magnesia and its main crystal phase is periclase crystallization from the melt of periclase crystal bulky, compact structure, crystal direct contact with the degree of high, in the atmosphere are good water resistance and slag resistance, high temperature and chemical is firmly on the volume, can keep firmly in the oxidizing atmosphere of 2300 ℃, the various functions of magnesia carbon brick is directly related to the purpose and the function of magnesia purpose, in order to improve the function of magnesia carbon brick, In order to increase the content of MgO and enhance the direct bonding degree of magnesite in magnesia, the amount of silicate can be added by controlling C/S and the contact degree of magnesite by silicate can be reduced. Therefore, the content of magnesium and the ratio of calcium to silicon are the important purposes of weighing magnesia.

4, graphite

Graphite has excellent thermal conductivity and fire resistance function, melting point as high as 3500℃, low thermal expansion rate of graphite (1.4×10-6 at 1000℃), high thermal conductivity, good quenching and heat resistance, is one of the few materials whose strength increases with temperature decrease. Graphite on slag infiltration Angle is also quite large, and Al2O3, SiC, SiO2 no eutectic relationship, can prevent slag to products in the penetration, because carbon can be molten slag in the iron oxide recovery into metal iron, make slag viscosity increased, add slag composition to the migration of brick, arrived to add the effect of corrosion.

With the increase of SiO2 content, the corrosion index increases from time to time, and the corrosion resistance decreases from time to time. When the SiO2 content in graphite is more than 3%, the corrosion index of magnesia-carbon brick decreases sharply, and the corrosion resistance decreases sharply. With the addition of the flake size of magnesia-carbon brick graphite. The antioxidant ability is enhanced, when the size of flake graphite across 0.125mm, the antioxidant growth is slow, the appropriate graphite particle size is 0.125mm. Because graphite is easy to oxidize to produce CO, oxidized graphite will lose these excellent functions, so that the corrosion resistance of refractory materials is reduced, which is the fatal weakness of graphite, but also an important reason for the damage of carbon-containing materials.