The types of special refractory include high melting point oxides, high melting point non-oxides and the resulting composite compounds, metal ceramics, high-temperature coating, high-temperature fiber and its reinforcing materials. The high melting point non-oxides are usually called refractory compounds, which include carbide, nitrogen, boride, silicified and sulfide, and the application of special oxide refractory materials will be introduced today.
Alumina products have good high-temperature performance and low price ratio, so they are widely used in modern industry. Corundum bricks with high purity, high density, and high performance are widely used in large blast furnaces and the ladle of steel mills, and good results have been achieved. Corundum bricks with high thermal stability are the first choice of lining materials for various ultra-high temperature furnaces such as special materials and products firing furnaces, molybdenum wire furnaces, tungsten bar furnaces, diffusion furnaces, ceramic metallization furnaces, silicified molybdenum electric furnaces.
Alumina hollow ball products and alumina fiber products are high-temperature energy-saving products. Due to its small volume density and low thermal conductivity, it is an ideal lining material for energy saving and consumption reduction. Alumina precision ceramics can be made into crucible and gasket for smelting or purifying colored, rare and precious metals, high temperature furnace tube, thermocouple protective tube and insulating porcelain tube, laser tube, rectifier tube, transparent sodium lamp tube, radar antenna cover, microwave device, sodium sulfur battery case, gas purifier and spark plug, etc. Alumina ceramics can also be made into reactor insulating sheets in the peaceful use of atomic energy, and artificial joints, teeth and so on can be made in biological engineering.
Magnesia (magnesite) is a basic refractory with high refractoriness under load and low creep. While it’s melting point can reach 2800 ℃, it is easy to volatilize in reducing atmosphere, so it’s highest use temperature is only 2000 ℃. Magnesia is a good structural material of ultra-high temperature kiln, and also a good lining material for industrial frequency furnace, intermediate frequency furnace, and high-frequency heating furnace. The high purity magnesia brick can be used as the channel lining material of magneto-fluid power generation. Magnesia ceramic products can be made into non-ferrous, rare metals and precious metals smelting, purification of magnesia crucible, high-temperature furnace tube, ultra-high temperature w-re thermocouple protective tube, insulating porcelain beads.
Zirconia is the acid refractory material with the melting point of 2650 ℃. Since it has excellent high-temperature chemical stability and the highest temperature can reach 2400 ℃, it can be used as a lining material in the vacuum furnace, molybdenum wire furnace, gas furnace, high-frequency electric furnace, such as single crystal furnace, etc. Besides that, the crucible for smelting non-ferrous, rare metals and precious metals, high-temperature furnace tube and thermocouple protective tube can be made from zirconia high-temperature ceramics. What’s more, zirconia can also be made into solid electrolyte for oxygen determination and temperature measurement of high-temperature liquid such as flue and molten steel, ceramic adiabatic engine and its parts, magnetohydroelectricity generation insulation sheet, insulating and ablative materials of jet aircraft, missile, burners of rocket, spacecraft front cone and nose cone, etc.
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