The biggest advantage of silicon carbide refractory castable is that it has high heat conduction, low thermal expansion, and no reaction with slag. Silicon carbide castable with good wear resistance. The reason why silicon carbide castables are wear-resistant is that their matrix is SiC, silicon carbide is wear-resistant, and silicon carbide has high hardness. Rongsheng monolithic refractory manufacturers can provide high-quality silicon carbide refractory castables. In terms of the physical and chemical properties of silicon carbide castables, learn about the wear resistance of silicon carbide.
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Mineral properties
The molecular formula of silicon carbide is SiC, which contains trace elements such as Al, Ca, Mg, Fe, and so on. Silicon carbide has two crystal forms, α and β. β-silicon carbide is low-temperature silicon carbide; α-silicon carbide is high-temperature silicon carbide. β-is an equiaxed crystal mineral, with a refractive index of 2.63, a density of 3.215g/㎝3, and a hardness of 9.5. α-silicon carbide is a hexagonal mineral, α-silicon carbide is divided into 4H, 6H, 8H, 15R, and other crystal forms, and its refractive index [n. ]=2.647-2.649, n=2.689-2.693. [n. ]-n=0.042~0.043, density 17g, ㎝3, hardness 9.5. Commercially available silicon carbide is divided into black and green. Black silicon carbide is named for its black color. Its SiC content is about 98%, which is composed of 90% 6H and 10% 15R crystals. Green silicon carbide is named for its green color and low impurity content. Its SiC content is about 99%, composed of 75% 6H, 10% 15R and 15% 4H type crystals.
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Physical properties
Silicon carbide is widely used in abrasives, heating elements, structural ceramics, and refractory materials due to its high hardness, electrical conductivity, high-temperature resistance, and high strength. The Mohs hardness of silicon carbide is 9.5, and the grinding ability of silicon carbide is 0.25~0.28, which is much higher than that of corundum (about 0.01). Among them, the Vickers hardness of black silicon carbide is Hv=30380~32340MPa, brittle and sharp, and is used for grinding materials with low tensile strength. Such as gray cast iron, non-ferrous metals, non-metals, and silicate materials such as stone, ceramics, and glass. Green silicon carbide has higher hardness, HV=31360~33320MPa, strong cutting force, and good self-sharpness, but is more brittle. It is used for grinding materials with high hardness and high brittleness, such as cemented carbide, optical glass, etc. Silicon carbide has strong conductivity and is a semiconductor. When the temperature reaches 2000°C, the conductivity of silicon carbide is equivalent to that of graphite. Silicon carbide is often used to manufacture heating elements such as silicon carbon rods and silicon carbon tubes. Silicon carbide has good high-temperature resistance. At atmospheric pressure, the inconsistent melting temperature of silicon carbide is 2760 °C. Up to 625MPa. Silicon carbide has good thermal shock resistance due to its moderately low coefficient of thermal expansion and high thermal conductivity. Therefore, silicon carbide is widely used in the manufacture of various ceramics and refractory materials.
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Chemical properties
The important chemical properties of silicon carbide are oxidation resistance, corrosion resistance, primary grinding, and reaction just now. When heated to 1000°C, the surface of SiC is oxidized and a layer of SiC2 film is formed. This layer of film hinders the diffusion of oxygen, delays the oxidation rate, protects the silicon carbide covered by the film, and improves the service life of the silicon carbide material. At 1300°C, cristobalite begins to precipitate in the film, and the crystal transformation of cristobalite causes the cracking of the film and accelerates the oxidation rate. At 1500~1600°C, the oxidation rate is accelerated, but the resulting SiC2 layer is also thick, and silicon carbide can still work for a long time. When the temperature rises to 1627°C, SiC2 and SiC react to form SiO gas, the SiO layer is destroyed, and the unprotected silicon carbide will burn quickly. The chemical properties of silicon carbide are relatively stable, and the acid resistance is very good. Silicon carbide does not react with boiling hydrochloric acid, sulfuric acid, and nitric acid, and does not corrode with H2, N2, and COR2O at ≤1300°C, and is corroded by RO above 1000°C. At high temperatures, silicon carbide is eroded by Cl2, F2, and H2, and can also react with H2O. Silicon carbide and Cr2O3 react to form metal silicide when the temperature is ≥1370°C. Silicon carbide is not suitable for cutting steel. When the temperature rises, SiC will react with Fe to form ferrosilicon alloy and iron carbide. But silicon carbide can be used to grind cast iron. This is due to the high content of carbon and silicon in cast iron, which is not sensitive to the reaction of silicon carbide.
Silicon carbide in silicon carbide castables is especially beneficial at high temperatures (1100°C). Especially when the silicon carbide powder is 150 mesh, it is impossible to be completely oxidized, and some gaps are formed around the SiC particles, which improves the thermal shock resistance stability and strength of the castable. Unoxidized SiC also acts as a particle reinforcement. The more silicon carbide content, the better the anti-skinning performance of the material. The higher the SiC content, the better the alkali resistance.
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