The sintered corundum refractories with high purity of Al2O3 and its content can reach 99.5%~99.6%, with fewer impurities, especially fewer Na2O.
2, Organizational structure
The structure of sintered corundum is a dense polycrystalline sintered body without glass phase, while the fused corundum is a parallel single crystal. Sintered corundum is irregular and polygonal crystals with a crystal size of 5-80um, while fused corundum is composed of flake-like and virgulate 100um large crystals.
3, Sintering Performance
The sintering performance of sintered corundum is better than that of fused corundum because it is calcined at a temperature above 1800°C, and the crystal size changes from 10 microns to more than 100 microns forming dense sintering between crystals. The most obvious difference in the structure of sintered corundum and fused corundum is the crystal size and the state of pores. The fused corundum has more large pores, but the shape is not stable, and there is more open porosity. The total porosity of sintered corundum is not much different from that of fused corundum, but most of the closed porosity is distributed in the particles in the form of spheres, and some are concentrated in the grain boundaries. The more developed the crystallization, the larger the pore diameter. During sintering, the shrinkage of sintered corundum is larger than that of fused corundum, precisely because the sintered size shrinks, so that the refractory bricks have a small shrinkage during firing, which can ensure to get refractory products with accurate dimensions, and the products have the characteristics of being able to be sintered at a lower temperature; the products of fused corundum have no change after firing, and it is difficult to sinter, And it is difficult to produce the strength after being shaped.
4，High mechanical strength
Sintered corundum has higher mechanical strength than the point. Because the surface of the crystal particles has tiny protrusions and depressions, it is easy to combine with the binder. Since the crystal does not grow too large, it retains proper activity, so it is easy to combine with various types. The fused corundum is densely combined with high strength; the crystals of fused corundum grow from hundreds of micrometers to thousands of micrometers, and the surface of the particles is smooth and lacks activity. It is difficult to combine with the binder to form a strong combination. The mechanical strength of sintered corundum is in addition to It is related to the size of crystals and also to the size of porosity. Because sintered corundum has a high density and few pores, its strength is high.
Sintered corundum has high chemical stability, high melting and softening temperature, high thermal conductivity, excellent resistance to rapid cooling and heating, corrosion resistance to molten metal and slag, and excellent high temperature and low-temperature electrical insulation, It is stable under oxidizing and reducing atmosphere, and it is very hard, has high wear resistance, and is most suitable for refractory material.
And sintered alumina corundum refractory bricks that our company developed have very excellent chemical and physical properties like high purity, excellent compactness, and excellent resistance to molten glass, it is the ideal refractory products for molten glass furnace, cement kiln, heaters, molten steel ladles, metallurgical furnace for nonferrous metals, chemical kilns.