sic 探究 research
SiC, commonly known as diamond sand, is generally made of silica after mixing and coke.Silicon carbide is a covalent bond compound with a glass luster at a density of 3.17~3.47g/m3. Mo hardness is 9.2,2600℃ in reducing atmosphere; tensile strength 71.5MPa, is 1029MPa.The interatomic binding force is strong, has a high melting point, high hardness, high strength and low expansion, high heat conductivity, high conductivity, strong chemical stability, and therefore is a good refractory raw material.However, in an oxidative atmosphere, SiC is prone to oxidation, only when the SiO2 protective membrane is formed.
SiC has properties not found in many usual oxide raw materials such as high heat conduction, low thermal expansion and difficulty to react with slag.To this end, it was used as a primary raw material from early on for refractory to severe slag reaction and high temperature peeling sites.The same is true in indefinite refractory, and the importance of SiC remains unchanged from the era of tamping and plastic to the present era of low cement pouring.The SiC antioxidant atmosphere is weak, accompanied by oxidation of solid phase SiO2 and carbon as well as gas phase CO and COs gases.At temperatures above 1823K, the SiC is unstable and converted to SiO2. Turn the ASC line into the Al2O3-SiO2-C line.However, if the system is not a closed system, the ASC mass working lining in contact with the outside world, the CO partial pressure may be less than 0.1Mpa,, SiC is the most stable.
Carbon has the characteristics of incompatible slag iron reaction and low thermal expansion rate, so carbon material has the characteristics of strong slag corrosion resistance and easy adhesion, and under certain temperature conditions, Si in the substrate reacts with C to generate very small (about 0.1~0.5 μm diameter) fibrous SiC, to form the tonic effect of SiC.Therefore, in developing ASC quality refractory materials, less volatile and relatively more fixed carbon-containing materials should be selected, and antioxidants and dispersants should be added according to a certain proportion.Graphite materials have very high thermal stability, with a sublimation temperature of 3,800℃, which can easily reach saturation in iron water, so graphite has the advantage of resisting ferrowater erosion.Commonused graphite materials have qualitative, artificial, spherical and squamous graphite.Graphite materials contain some volatiles, which are easy to be oxidized, so it is not easy to add graphite materials in the pursuit of material compaction.However, the large thermal conductivity of graphite can make the uniform distribution of heat inside the pouring material, and reduce the thermal stress accordingly, and improve the thermal shock stability and peeling resistance of the cast material.In pouring materials, both graphite and asphalt can be introduced as carbon additives.In the pouring mixture, the graphite is difficult to stabilize, and when water is added to the pouring, most of the graphite reaches the surface and easily disappears during construction due to its structure.Due to its poor weidability, dispersability and the hydration trend of aluminum antioxidants, there are many new problems that have hindered the development and application of carbon pouring materials.To include graphite in the poured mixture, the graphite was treated with a certain modifier to improve its adhesion.
Bitumen as a C source can avoid the above disadvantages. Aspumen is a residue of coal tar or oil. It is a mixture of aromatic and aliphatic structure and is brown-black and insoluble in water. Its composition and performance vary with raw material source, distillation method and processing treatment method.