For magnesium bricks, some use conditions are to take advantage of the product's high porosity and high air permeability. At present, argon-breathing corundum bricks used in ladle bottoms are widely used in steel plants. Gases are used to blow metals, that is, corundum bricks for liquids. The same particle size is used, and the filler and binder are used to tightly bond the particles during the sintering process, so that the product becomes a solid block, and the same size of the particle material determines the shape and size of the pores. If it is necessary to increase the air permeability of the product, the particle size of the scum additive should also be added, and its shape should be the same as that of the filler.
The porous and breathable magnesia bricks used for smelting metals have some advantages with corundum magnesia. For industrial applications, 80% of fused alumina bricks can be used as granules, and a mixture of industrial alumina (65%) and refractory clay (35%) can be used as a binder. The binder must be 20%. It is finely ground together, and the content greater than 60 μm cannot exceed 1% to 1.5%. The mud is kneaded on a wet mill. It is required to knead for 10 minutes, the mud moisture is 4.3% to 5%, and then sieved on a sieve with a mesh size of 5mm. The bricks are formed on a hydraulic press with a pressure of 35 MPa, and the density of the bricks reaches 2.60 g / cm3. The product is fired in a tunnel kiln or an inverted flame kiln. The firing temperature is 1570 ° C, the heat preservation is 22 ± 2h, and the total firing time cannot be less than 150h.
There are many methods for manufacturing breathable corundum bricks. The 20% binder is made by grinding together corundum waste (60%) and clay (40%). The moisture content of the mud is 4% ~ 5%. It is 2.60 g / cm3: it is fired in a tunnel kiln for 86h, the firing temperature is 1560 ° C, and the temperature is maintained for (5 ± 1) h.
Others use magnesium bricks as aggregates, pure calcium aluminate cement and SiO2 superfine powder as binders, phosphates as dispersants, and ultra-low cement castables.
