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Fused Mullite Refractory Bricks/Blocks for Glass Kilns
Re-sintered fused mullite bricks for glass kilns. Re-sintered fused mullite bricks are mainly made of fused mullite and alumina and other raw materials mixed in a certain proportion, using special refractory molding technology and high-temperature sintering synthesis. It can improve and enhance the high-temperature performance of the product. Compared with sintered mullite, it has the advantages of high density, high purity, high-temperature structural strength, low high-temperature creep rate, low thermal expansion rate, strong resistance to chemical erosion, and good thermal shock resistance. Therefore, re-sintered fused mullite bricks are mainly used in the upper structure of thermal kilns and parts with high thermal stress, such as E-glass, borosilicate glass melting furnace breast wall, crown top, and crown foot bricks. RS Refractory Brick Manufacturer can provide refractory bricks for glass kilns, including various fused refractory bricks. Contact Rongsheng for free samples and quotations.
Fused Refractory Bricks for Glass Kilns
Fused refractory brick materials are made by melting a precisely prepared mixture in an electric arc furnace, then casting it in a sand mold, and then machining the ingot after heat treatment. The smelting process can obtain complete and coarse crystals and a dense structure. Compared with sintered refractory materials, it has the characteristics of dense structure, very low porosity, high volume density, high mechanical strength and high-temperature structural strength, and strong resistance to glass liquid erosion. The main varieties currently produced are: fused mullite bricks, fused zirconium corundum bricks, fused chromium zirconium corundum bricks, fused quartz bricks, fused corundum bricks, etc.
Fused mullite bricks use high-alumina alumina as raw material, and different aluminas are mixed into the composition of mullite (3AL2O3·2SiO2 mass fraction is: AL2O3 72%, SiO2 28%). It melts at around 2300℃, is poured into a sand mold at 1850℃, and then annealed to eliminate stress. The main crystal phases are mullite and corundum, and the glass phase is filled between the crystal phases. Its resistance to glass liquid erosion is stronger than that of sintered refractory materials. Adding a small amount (7%-8.5%) of tungsten dioxide can make the mullite crystals smaller and the brick structure dense, and the amount of mullite increases to 60%-70%, which relatively reduces the content of the glass phase and reduces the cracks of the product. Fused mullite bricks have a low thermal expansion coefficient, good thermal vibration resistance, and strong resistance to glass liquid erosion.
Mullite bricks should not be in contact with alkaline substances above 1450℃, otherwise the mullite will decompose. In a reducing atmosphere above 1370℃, mullite will also decompose, and part of SiO2 will become gaseous SiO2 and leave the brick body. When the temperature is higher than 1650℃, even if it is not a reducing atmosphere but under a lower oxygen partial pressure, mullite will decompose.
Rongsheng Fused Zirconia Corundum Brick for Glass Kiln
Fused zirconium corundum bricks belong to the Al2O3-ZrO2-SiO2 system (AZS bricks for short). According to the content of ZrO2, they are divided into three grades, and the corresponding grades are: AZS-33 (containing 33% ZrO2), AZS~36 (containing 36% ZrO2), AZS-41 (containing 41% ZrO2). Fused zirconium corundum bricks are made of zircon and industrial alumina as the main raw materials, and a small amount of zircon-rich sand (in order to increase the content of ZrO2), soda ash and borax are added.
Fused zirconium corundum bricks, according to the different atmospheres during melting, have two methods: reduction melting method and oxidation melting method. At present, the oxidation method is mainly used. The oxidation melting method can remove the pollution caused by graphite electrodes in the molten liquid, and the carbon content is low (0.005%0.02%), which can reduce the bubble content in the glass and improve the quality of the glass liquid.
There are several things to note when using fused zirconium corundum bricks.
① Irregular changes in thermal expansion
Fused zirconium corundum bricks are characterized by stable and dense structures and strong resistance to glass liquid erosion. The thermal expansion curve of bricks containing 31%~33% ZrO2 has abnormal expansion between 900~1200℃.
② Electrical insulation
Fused zirconium corundum bricks have good electrical insulation and decrease with increasing temperature. According to their electrical insulation, fused zirconium corundum bricks can be used as electrode bricks in the production of soda-lime glass melting furnaces.
③ Thermal conductivity
The thermal conductivity of fused zirconium corundum bricks is more than twice that of clay bricks. Therefore, when used as pool wall bricks, the cooling air volume required near the liquid surface should be 1 times larger than when clay bricks are used as pool walls.
Fused corundum bricks are made of high-purity alumina as raw materials, and a small amount of soda ash is introduced, and melted at 2000~2200℃. The production process is similar to that of high-alumina products. There are fused α-corundum bricks, fused α, β-corundum bricks, fused β-corundum bricks, etc.
Fused α-corundum bricks are mainly suitable for melting borosilicate glass, opal glass and melts containing sulfates. The composition of fused α, β-corundum bricks contains only a small amount of glass phase, which will not seep out during use and has little pollution to the glass liquid. Direct contact with the glass liquid will not color the glass liquid, and it has good corrosion resistance. It is an ideal material for the pool wall, kiln bottom and float glass melting furnace flow channel of the cooling part of the glass melting furnace. Fused corundum bricks are suitable for the upper structure of the working pool of the melting furnace and the burner at the rear of the melting zone and the breast wall and small furnace flat near it.
Fused chrome zirconium corundum bricks
10%~30% Cr2O3 is introduced into AZS-33 bricks, and fused chrome zirconium corundum bricks (abbreviated as AZCS bricks) are produced by non-shrinkage cavity casting method. The surface and interior of the bricks are dark green. The bricks contain 4.5% shrinkage pores and no connected pores. Due to the formation of aluminum-chromium spinel solid solution, the viscosity of the glass phase is increased, and the resistance to glass liquid corrosion is greatly improved. It is 3.4 times that of fused AZS-33 bricks and 2.6 times that of fused AZS-41 bricks.
The production process of fused quartz bricks is the same as that of quartz glass. High-purity quartz sand (SiO2 content above 99.5%) is used as raw material, a small amount of Na2O is added as a mineralizer, and melted in a graphite resistance furnace (1750~1800℃). After melting, the entire molten material is quickly taken out, rolled into bricks, and then mechanically processed after cooling in the air. The thermal expansion coefficient is extremely small and the thermal shock resistance is good. It has strong resistance to the erosion of boron glass liquid, but not to the erosion of sodium-lime-silicon glass liquid.
Zircon bricks
The main components of zircon products are ZrO2·SiO2. Zircon decomposes into ZrO2 and SiO2 in large quantities when heated at 1680℃. Zircon products have good corrosion resistance in liquid glass. Aluminum-zirconium-silicon (AZS) cast bricks and fired bricks have good resistance to erosion by molten glass and can be used for the pool wall and upper structure of glass melting furnaces.
Zircon bricks are refractory products fired with zircon as the main raw material. Zircon is the only compound in the ZrO2-SiO2 system, and its chemical formula is ZrSiO4. The theoretical chemical composition of zircon is: ZrO2 67.2%, SiO2 32.8%. Zircon bricks have excellent properties such as high temperature resistance, good thermal vibration resistance and resistance to erosion by molten glass.
