The use of Mgo-C bricks in the wall area of ​​the ladle, although capable of satisfying severe operating conditions, is costly and may increase the carbon content of the molten steel during the smelting of low carbon steels, which limits its use. In addition, higher thermal conductivity lowers the temperature of molten steel in the ladle, causing problems during continuous casting. The use of Mgo-C refractories at the slag line has other characteristics. Especially on the pouring side of the slag line, due to continuous injection of hydrogen, MgO-c bricks are eroded; due to the long residence time of the molten steel in the ladle, and the high smelting temperature, the brick seams crack; the carbon in the Mgo-C bricks Oxidation occurs at high smelting temperatures (>1700°C).
Due to chemical attack, although slag and molten steel penetrate into bricks, A12O3-C bricks have very good thermal properties, chemical properties and mechanical properties, but they also have residual line rate change (PLC) negative values ​​and oxidation. problem. A new trend in the development of refractories is the production of Mgo-A12O, a C brick (magnesium aluminum carbon) and A12o with a high fire resistance and volume stability. This enables them to be successfully used in the metallurgical industry, especially in the field of steelmaking, ie the slag line and the bottom impact area of ​​the ladle 1, because the in-situ formation of spinel can produce a large residual expansion; Better resistance to structural spalling and thermal peeling. There is no crack between the brick and the brick and between the layer and the layer, thereby preventing penetration of the molten steel and the slag; the thermal conductivity is low, and thus heat loss is less. Strong impact resistance.
The experimental process crushes bauxite and dead burned magnesia to a particle size of about 90 m. The flake graphite had a particle size of 20 m and the chemical composition of these raw materials was determined (see Table 1). Two series of compositions were prepared, each containing 6 formulations (see Table 2).
The graphite content in both series is fixed at 10%. After drying at 180[deg.] C. for 24 h, the sample was placed on alumina embedded carbon and calcined at 1580[deg.] C. for 4 h.
After mixing these ingredients evenly, X-ray diffraction pictures of the four-phase composition AO along the axial direction using a semi-dry method (Fig. 1, abbreviated) show that there are strong graphite and a-A1203 (corundum) peak lines, There is also a weaker iron ore and Mgo-A120, the peak of the spinel. The X-ray diffraction pattern of the formulation AZ shows an ore phase similar to that of the formula AO, but the peak line of the M Sha-1120 phase of the spinel is stronger. The increase in bulk density and mechanical strength of the sample is due to the high content of impurities from the bauxite. These impurities form some glass phases during sintering and fill in the pores, resulting in increased sintering parameters and mechanical strength.
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