Mullite refractory brick is a lightweight mullite product synthesized by artificial synthetic mullite, adding organic composite filler according to the specific gravity of the product, vacuum extrusion molding, and high temperature sintering. With its light weight and excellent thermal insulation properties, mullite lightweight refractory bricks are widely used in hot surface refractory linings or thermal insulation layers of various thermal equipment, creating conditions for improving the utilization rate of equipment.
Mullite light refractory brick is a high alumina refractory material with mullite main crystal phase, generally the alumina content is between 65% and 75%. The refractory temperature of mullite light refractory bricks can reach above 1790°C. The starting temperature of softening under load is 1600-1700°. Good thermal shock resistance.
What are mullite refractory bricks?
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Mullite Lightweight Brick
According to the grades, it is divided into JM23, JM26, JM28, JM30, and according to different operating temperatures, it is mainly divided into: 1350 light weight mullite brick, 1450 mullite insulation brick, 1550 mullite light weight brick and so on.
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Features of mullite light refractory bricks:
1. Low thermal conductivity, with good thermal insulation effect.
2. Low heat capacity, due to low thermal conductivity, mullite series light insulation bricks accumulate little heat energy, and the energy saving effect is obvious in intermittent operation;
3. Low impurity content has a very low content of oxides such as alkali metals in iron boxes, therefore, high refractoriness; high aluminum content enables it to maintain good performance in a reducing atmosphere;
4. High thermal compressive strength;
5. Appearance size, speed up the masonry, reduce the use of refractory mud, ensure the strength and stability of the masonry, thereby prolonging the life of the lining;
6. Can be processed into special shapes. To reduce the number of bricks and joints.
Product Usage:
Mullite lightweight insulation bricks can be used as hot surface refractory lining or backing insulation layer of other refractory materials, used in ethylene cracking furnaces, tubular heating furnaces, synthetic ammonia reformers, gas generators, high temperature shuttles in petroleum and chemical industries Type kiln, tunnel kiln, ceramic roller kiln, push plate kiln and other industrial furnace refractory furnace insulation materials, etc.
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Zirconium Mullite Brick
By adding ZrO2 into the A12O3-SiO2 series brick to improve the structure of mullite, it can improve the chemical corrosion resistance, thermal shock resistance and reduce the expansion coefficient of mullite. This ZrO2-containing mullite brick, Commonly known as zirconium mullite brick, it is generally made by electrofusion method, and it is also produced by sintering method.
Sintered mullite brick is a special refractory made by using industrial alumina and zircon concentrate as raw materials, and adding zirconia into mullite matrix through reaction sintering process. The add of zirconia into mullite bricks can greatly improve the high temperature mechanical properties of mullite materials by using the phase transformation toughening of zirconia. Zirconia can promote the sintering of mullite materials. The addition of ZrO2 can accelerate the densification and sintering process of ZTM materials due to the generation of low melting point compounds and the formation of vacancies. When the mass fraction of ZrO2 is 30%, the relative theoretical density of the green body fired at 1530°C reaches 98%, the strength reaches 378MPa, and the toughness reaches 4.3MPa•m1/2.
Using industrial alumina and zircon as raw materials, the zirconium mullite bricks made by reaction sintering are difficult to control because the reaction and sintering are carried out at the same time. Usually, during firing, the temperature is kept at 1450°C to make it densified, and then the temperature is raised to 1600°C for reaction. ZrSiO4 is decomposed into ZrO2 and SiO2 at greater than 1535°C, wherein SiO2 and AI2O3 react to form mullite. When ZrSiO4 decomposes, a part of the liquid phase appears, and the decomposition of ZrSiO4 can refine the particles and increase the specific surface area, thereby promoting sintering. The research shows that when the addition of zircon is less than 54.7%, with the increase of the addition of zircon, the microstructure of the sintered sample gradually transitions from the network composed of columnar corundum to the network structure composed of columnar mullite. . The high-temperature flexural strength (1400°C) of the sample also increases with the increase of zirconia content, and a larger value appears when the content of zirconia is 23.7%, and then the strength decreases. The addition of zircon contributes to the improvement of thermal shock resistance.
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Sintered mullite brick
Sintered mullite brick is a synthetic mullite made of aluminum and silicon oxides or other compounds and aluminosilicate minerals as raw materials. Refractory bricks sintered at high temperature.
In the synthetic mullite of good quality, the content of mullite should reach 95%, which controls the requirement on the chemical purity of the raw material. When the sintering conditions are constant, the higher the purity of the raw material, the more difficult the crystal growth will be, and the smaller the mullite crystal size will be; when it contains 5%~10% glass phase, the mullite can develop into columnar euhedral crystals , the length can reach about 10μm.
Synthetic mullite containing about 90% mullite has glass phase and pores between mullite crystals; when the content of glass phase increases (for example, it accounts for 20%), mullite crystals develop well, and mullite is surrounded by glass phase. cemented.
Fused mullite brick
Mullite bricks prepared by melting-solidification crystallization process are called fused mullite bricks. The columnar mullite crystals in the bricks can reach the millimeter level. By changing the process system, the mullite crystals can be controlled to be smaller in size.
The analysis shows that although the design Al2O3/SiO2 is 3:2, the Al2O3/SiO2 ratio in the fused mullite composition is often close to 2:1, which is because the fused crystalline brick contains 10%~15% Glass phase, if the ingredient composition is higher than 3: 2, or close to 2: 1, the intercrystalline glass phase will be reduced to less than 5%. Therefore, the fused mullite brick made of a mixture containing about 72% Al2O3 is always a lot of glass phase in it, and the composition of the phase is also related to the melting system and atmosphere.
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Corundum mullite brick
Corundum mullite bricks are high-alumina refractory bricks composed of main crystal phases of corundum and mullite. Corundum mullite bricks refer to refractory bricks made of high-purity or relatively pure raw materials. The presence of low melting point oxide impurities will reduce its high temperature performance. Corundum mullite bricks are much more expensive than ordinary high alumina bricks. Performance: It has good high temperature strength, high temperature creep resistance, thermal shock resistance and erosion resistance. The physical and chemical properties of a typical corundum mullite brick are: Al2O3≥85%, Fe2O3 0.45%, apparent porosity 19%, compressive strength at room temperature greater than 55MPa, softening temperature under load greater than 1700°C, heating line change (1600°C , 3h) -0.1%, thermal shock resistance (1100°C water cooling) is greater than 30 times.
Zhengzhou Shennan Refractory Co.,Ltd are specializes in producing all kinds of mullite bricks, any demands, please contact with us .Thank you.
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