Silicon carbide kiln furniture have good alkali corrosion resistance, molten cryolite wettability, oxidation resistance, wear resistance, high thermal conductivity, thermal shock resistance and extremely low electrical conductivity. Silicon nitride combined with silicon carbide bricks are mainly used as the lining of the lower furnace body of the blast furnace, which is more than twice as long as the use of traditional refractory materials. In addition, it can be used as the lining of aluminum reduction electrolyzers and ceramic kiln furniture, which can save energy, increase life It can also be used as a blast furnace tuyere water-cooled pipe sleeve brick because of its advantages such as environmental pollution.
Silicon carbide kiln furniture have high thermal conductivity, good wear resistance, thermal shock resistance, and corrosion resistance. Therefore, silicon carbide bricks are widely used in industry. It can be used for metallurgical steel cylinder lining, nozzle, plug, blast furnace bottom and hearth, heating furnace without water-cooled slide rail; non-ferrous metal smelting distiller, distillation tower tray, electrolytic tank side wall, smelting metal crucible; silica acid Sheds and muffle materials for kilns in the salt industry; oil and gas generators and organic waste combustion furnaces in the chemical industry; kiln furniture for high-tech ceramics; aluminum electrolytic cell linings, molten aluminum pipes and kiln furniture for ceramic kilns, large and medium-sized blast furnaces Lower body, furnace waist and belly, aluminum refining furnace lining, zinc distillation tank lining, etc.
Silicon carbide kiln furniture production: The formula of coarse, medium and fine SiC should be 5:1:4. The raw material for making silicon carbide bricks is generally black SiC. Its chemical composition is as follows: SiC 98.0%, free C 0.5%, Fe 0.2%, and free SiO2 0.6%. Due to the different combination methods, there are differences in the process. The brief process of different combinations is: (1) Silicon nitride bonded silicon carbide brick: a green body formed with coarse, medium and fine silicon carbide particles and fine silicon powder, in pure N2 gas, at 1370 ℃, produces a kind of %26α-SiC as the skeleton and %26α and %26β-Si3N4. The substrate is silicon nitride bonded with silicon carbide bricks. There are still a small amount of residual silicon and SiO2N2 in the matrix in the product, and the relative content of these components varies with manufacturing plants.
(2) Combining silicon carbide bricks: SiC, silicon powder, and carbon powder are mixed and shaped according to a certain ratio, and then fired in a reducing atmosphere at 1400°C. In most cases, buried charcoal firing is used. During the firing process, a %26β-Si3N4 bonded SiC brick with %26α-SiC as the framework and fine grain %26β-SiC as the matrix is produced. %26β-SiC is produced by the reaction of fine silicon powder and fine carbon powder during the firing process. This product also contains a small amount of residual silicon and carbon.
(3) Silicon oxynitride combined with silicon carbide brick: When this kind of brick is compounded, the proportion of fine silicon powder is less than that of silicon carbide.
