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The raw materials used in the production of magnesia-chrome bricks are: natural raw materials, magnesia-carbon brick synthetic raw materials for ladle, and magnesia-carbon brick manufacturers such as industrial chromium oxide and industrial alumina. Natural raw materials: Magnesia carbon bricks for converters such as various grades of sintered magnesia, ordinary chrome ore and chromium concentrates with low impurity content. Synthetic raw material: a co-sintered magnesia-chrome material obtained by finely grinding, mixing, compacting and then calcining magnesia and chrome concentrate; and electroforming from magnesite and chrome ore. Magnesium chrome; also fused magnesia. The synthetic material should generally be a raw material with a low impurity content.
The above materials are used differently. The combination and formula can be made into a variety of magnesia chrome bricks, and the factory is not willing to explain its formula. Therefore, the variety and name of magnesia chrome bricks are messy and confusing. According to the existing names of magnesia chrome bricks at home and abroad, the following can be standardized.
(1) Ordinary magnesia-chrome bricks (ie, silicate-bonded magnesia-chrome bricks) made of chrome ore and magnesia with more impurities (SiO2 and CaO). The firing temperature is not high at around 1550 °C. The microstructure of the brick is characterized by the combination of silicates between the refractory grains.
The fine powder of the refractory brick produced by the method is a magnesium chrome material which is ground, mixed, compacted, calcined by ordinary chrome ore and magnesia, and is still combined with silicate. However, the performance is improved compared with ordinary magnesia bricks.
(2) Directly combining magnesia bricks, which are made of chrome concentrate with low impurity content and relatively pure magnesia. The firing temperature is above 1700 °C. The structural feature of the refractory brick is that there is much direct contact between the refractory grains. Therefore, its high temperature performance, erosion resistance and erosion resistance are better than ordinary magnesia chrome bricks.
(3) Recombined with magnesia-chrome bricks, magnesia-chrome bricks made from synthetic raw materials co-sintered magnesia-chromium or fused magnesia-chrome (or partially fused magnesia) are often referred to as re-combined magnesium-chromium. brick. In China, only the magnesia chrome bricks made of fused magnesia chrome are called recombined magnesia chrome bricks. In order to be more consistent with the international, it is advisable to use co-sintered magnesia chrome bricks and electrofusion materials in combination with magnesia chrome bricks or fused granules and then combined with magnesia chrome bricks.
In combination with magnesia-chrome bricks, since the brick making materials are relatively pure, they need to be fired at a high temperature of 1750 ° C or higher. Its microstructure is characterized by uniform distribution of components such as spinel and direct contact between refractory grains. It is better than the first two kinds of magnesia chrome bricks in terms of erosion resistance and erosion resistance.
The high-quality magnesia chrome bricks we developed for the nickel-smelting converter tuyères are also classified as refractory bricks because the raw materials used are all synthetic materials.
(4) Semi-recombined magnesia-chrome bricks, according to the above meaning of combining magnesia-chrome bricks, as long as synthetic raw materials are used as granules, magnesia-chrome bricks made of chrome concentrate and magnesia as fine powder should be called semi-re- Combine magnesium chrome bricks. In the domestic, the fused magnesia-chromium material is used as the granule, and the magnesia-chrome brick prepared by using the eutectic material as the fine powder or the chrome concentrate powder and the magnesia powder as the mixed fine powder is called a semi-recombined magnesia chrome brick. In order to distinguish, the magnesia chrome brick made of electro-melt granules and co-sintered magnesia chrome as fine powder can be called fused-co-sintered magnesia chrome brick.
Such refractory bricks are also fired at a high temperature above 1700 ° C, and the refractory grains in the bricks are also directly combined. The advantage is that the thermal shock resistance is good, and the erosion resistance and erosion resistance are also good.
(5) Casting magnesia-chrome bricks, adding a certain amount of admixtures with magnesia and chrome ore, mixing, compacting and burning, breaking into blocks, melting into an electric arc furnace, injecting into the mold, annealing, and producing into a mother brick. The mother brick is cut and milled to produce the required refractory brick model.
The structural characteristics of the fused cast magnesia chrome bricks are uniform distribution of components, direct contact between the refractory grains, and silicates in the form of islands. Such refractory bricks are particularly resistant to melt ablation, penetration and erosion. It is a product specially developed for non-ferrous smelting. It is most suitable for laying in a continuous production equipment melting furnace such as the lower part of the flash furnace reaction tower and the sedimentation tank slag line area.
(6) Chemically combining non-calcined magnesia-chrome bricks, generally using magnesia and chrome ore as brick raw materials, magnesium chrome bricks pressed with sodium polyphosphate or sodium hexametaphosphate or water glass as a binder. It does not need to be fired at a high temperature and is only baked at a temperature of about 200 °C. Since the refractory brick is not fired at a high temperature, the magnesia in the brick is hydrated, so the refractory brick cannot be stored for a long period of time.
Since chrome ore has a small shrinkage when used at high temperatures, it can be used as a raw material for non-burning bricks.