When selecting and purchasing refractory materials, we are always easy to be confused because of its various performance indicators, service temperature and application range. But in fact, if you know the raw materials of various refractories, you can quickly select the appropriate refractories.
Therefore, today I’d like to introduce to you the 8 types of commonly used refractory materials in high-temperature kiln industry, so as to help you have a deeper understanding of refractory materials, and be reasonable and reasonable when understanding, distinguishing and selecting refractory materials!
In fact, the main raw materials in modern high-efficiency refractory products have widely used high-purity raw materials, homogeneous raw materials, electrofusion raw materials and synthetic raw materials, so as to greatly improve the performance of refractory products. So, what are the main common raw materials used for refractories in the cement industry?
1. Mullite
Mullite is a refractory material with 3Al2O3 · 2SiO2 as the main crystalline phase. There are very few natural mullites, which are usually synthesized by sintering or electrofusion.
Features: uniform expansion, good thermal shock stability, high load softening point, small high temperature creep value, high hardness, good chemical corrosion resistance, etc.
2. Magnesia alumina spinel
Magnesia alumina spinel is synthesized by high temperature sintering or electrofusion with industrial alumina and light burned magnesia as raw materials. The chemical formula of magnesia alumina spinel is MgO Al2O3, in which the content of MgO is 28.2% and the content of Al2O3 is 71.8%.
Features: high temperature resistance, wear resistance, corrosion resistance, high melting point, small thermal expansion, low thermal stress, good thermal shock stability, strong resistance to alkaline slag erosion and good electrical insulation performance.
3. Sillimanite, Andalusite, Kyanite
It is also often called three stones. The chemical formula is Al2O3 – SiO2, and the theoretical composition is 63.1% Al2O3 and 36.9% SiO2.
Features: irreversibly transformed into mullite and cristobalite after heating, with good slag corrosion resistance, good thermal shock stability and high load softening point.
Kyanite mineral products are high-quality raw materials for amorphous refractories. Sillimanite and andalusite can be directly used as bricks or refractory aggregates because of their small volume change during heating.
4. High Alumina Bauxite
The high alumina bauxite clinker calcined at high temperature is mainly used for high alumina refractories, and can also be used to make fused brown corundum and sub white corundum.
Features: low absorption rate and stable performance.
5. Magnesite
Magnesite is a natural alkaline mineral raw material with magnesium carbonate (MgCO3) as the main component. Magnesite is mainly used to produce sintered magnesia, fused magnesia and alkaline refractories.
6. Sintered Magnesia
Sintered magnesia is the product of fully sintering magnesite at 1600 ~ 1900 ℃, and the main mineral is periclase. Sintered magnesia is one of the main raw materials for the production of alkaline refractories.
Features: the MgO content of high-quality magnesia is generally more than 95%, and the particle bulk density is not less than 3.30g/cm3. It has excellent resistance to alkaline slag erosion.
7. Fused magnesia
Fused magnesia is made by melting selected magnesite or sintered magnesia at a high temperature above 2500 ℃ in an electric arc furnace.
Features: compared with sintered magnesia, the main crystalline phase periclase has coarse grains and direct contact, high purity, dense structure, strong alkali slag resistance and good thermal shock stability.
8. Silicon Carbide
Silicon carbide is usually made from a mixture of coke and silica sand by electric furnace high temperature melting. It is formed at a temperature of 1400-1800 ℃ β- SiC (cubic crystal), formed when the temperature is higher than 18001 α- SiC (hexagonal crystal).
Features: high hardness, high thermal conductivity, low thermal expansion and excellent resistance to neutral and acid slag.