The so-called "electric melting" refers to a manufacturing process of refractory bricks. The batch materials are heated and melted in an electric arc furnace, and poured into a mold when they are in a liquid state, and then solidified to achieve ceramic bonding. Compared with sintered bricks, it has the characteristics of compact structure, low porosity, high volume density, high mechanical strength and high temperature structure strength, and strong resistance to molten glass. As a Refractory Solution Supplier, share it with you.
Silica Bricks
The main varieties in the current market are: fused mullite bricks, fused zirconia corundum bricks, fused chromium zirconium corundum bricks, fused quartz bricks, fused corundum bricks, etc. Which of these types of fused refractory materials is more suitable for use in glass melting furnaces?
Fused mullite bricks use high alumina bauxite as raw material, and mix different bauxite into mullite composition (3Al2O3·2SiO2, mass fractions are: Al2O372%, SiO228%). It melts at around 2300℃, is poured into a sand mould at 1850℃, 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 molten glass is stronger than that of sintered refractories, but not as good as other fused refractories. Adding a small amount (7%8.5%) of zirconium dioxide can make the mullite crystal smaller and the brick structure dense. The amount of mullite can be increased to 60% 70%, which relatively reduces the content of the glass phase and reduces the amount of the product. crack. Fused mullite bricks are gradually replaced by fused zirconium bricks.
fused zirconia corundum bricks are made of zircon and industrial alumina as the main raw materials, and a small amount of zirconium-rich sand (in order to increase the content of ZrO2), soda ash and borax are added. According to the different atmosphere during melting, there are two kinds of reduction melting method and oxidative melting method. At present, the oxidation method is the main method. The oxidation melting method can remove the pollution caused by the graphite electrode in the molten liquid, and the carbon content is low (0.005% 0.02%), can reduce the bubble content in the glass, and improve the quality of the glass liquid.
fused corundum bricks are made of high-purity alumina as raw material, and a small amount of soda ash is introduced, and it is melted at 20002200℃. The production process is similar to that of high-aluminum products. There are fused α-corundum bricks, fused α, β-corundum bricks, and fused β-corundum bricks. Fused α-corundum bricks are mainly suitable for melting borosilicate glass, opal glass and sulfate-containing melts. The composition of the fused α, β-corundum bricks contains only a small amount of glass phase, which will not ooze out during use, and has little pollution to the glass liquid. Direct contact with the glass liquid will not cause the glass liquid to be colored. It has good corrosion resistance and is glass melting. Ideal material for kiln cooling part wall, kiln bottom and float glass melting furnace launder. Fused corundum bricks are suitable for the upper structure of the working pool of the melting furnace and the combustion port at the rear of the melting zone and the breast wall and small furnace flat screed near it.
The production process of fused quartz brick is the same as that of quartz glass. Using high-purity quartz sand (with SiO2 content above 99.5%) as raw material, adding a small amount of Na20 as a mineralizer, and melting it in a graphite resistance furnace (17501800°C). After melting, the whole piece of molten material is quickly taken out, rolled into bricks, and then machined after cooling in the air. The coefficient of thermal expansion is extremely small, and the thermal shock resistance is good. It has strong corrosion resistance to boron glass liquid, but it is not resistant to the erosion of soda lime silica glass liquid.
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