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Introduction of fused refractory fused mullite bricks

2022-07-26 15:56:30

Introduction of fused refractory fused mullite bricks


The fused refractory is made by melting the precisely prepared mixture in an electric arc furnace, then pouring it in a sand mold, and the ingot is heat-treated before machining. The smelting process can obtain complete coarse crystals and dense structures. Compared with sintered refractories, it has the characteristics of compact structure, low porosity, high bulk 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

Mullite bricks are a silicon-alumina system refractory product with mullite as the main phase. The refractoriness is about 1850 ℃, the load softening temperature is high, the high temperature creep rate is low, the thermal vibration resistance is good, and the acid corrosion resistance is good.


The fused mullite bricks are made of high-alumina geosite as raw material, and different bauxites are mixed into the composition of mullite (the mass fraction of 3AL203·2SiO2 is: AL2O3 72%, Si02 28%). It is melted at around 2300°C, poured into a sand mold at 1850°C, and then annealed to relieve stress. The main crystal phases are mullite and corundum, and the glass phase is filled between the crystal phases. Its resistance to glass erosion is stronger than that of sintered refractories, but not as good as other fused refractories. Adding a small amount (7%-8.5%) of gallium dioxide can make the mullite crystal smaller and the brick structure denser, and the mullite content increases to 60%-70%, which relatively reduces the content of glass phase and reduces the cracks in the product. Fused mullite bricks have low thermal expansion coefficient, good thermal shock resistance and strong corrosion resistance to glass liquid.


Mullite bricks should not be in contact with alkaline substances above 1450 ℃, otherwise mullite will decompose. In the reducing atmosphere above 1370℃, mullite will also decompose, and part of SiO2 will become gaseous SiO and leave the brick body. When the temperature is higher than 1650 ℃, even if it is not a reducing atmosphere but at a lower oxygen partial pressure, mullite will decompose.