Brief introduction of neutral refractory high aluminum products and carbon products

 
The main crystal phases in high-aluminum products are mullite and corundum. The content of corundum increases with the increase of the alumina content. Corundum products containing more than 95% of alumina are a wide range of high-quality refractories. Chrome brick is mainly made of chrome ore, and the main crystal phase is chromite. Its corrosion resistance to steel slag is good, but its thermal shock resistance is poor, and the high temperature load deformation temperature is low. Chromium-magnesium bricks made of chrome ore and magnesia in different proportions have good thermal shock resistance, and are mainly used as alkaline open-hearth roof bricks. Carbonaceous products are another type of neutral refractory materials. According to the composition of the carbon-containing raw materials and the mineral composition of the products, they are divided into three types: carbon bricks, graphite products and silicon carbide products. Carbon bricks are made from high-grade petroleum coke, tar and asphalt are used as the binder, and fired under the condition of 1300 ℃ isolated from air. Graphite products (except natural graphite) are made by using carbonaceous materials in an electric furnace through graphitization at 2500-2800 ° C. Silicon carbide products use silicon carbide as the raw material, and add clay, silicon oxide and other binders to sinter at 1350 ~ 1400 ° C. It is also possible to produce silicon nitride-silicon carbide products by adding silicon carbide and silicon powder in a nitrogen atmosphere in an electric furnace.
 
Carbon products have low thermal expansion coefficient, high thermal conductivity, good thermal shock resistance, and high temperature strength. It does not soften under long-term use at high temperatures, is not affected by any acid and alkali, has good salt resistance, and is not affected by the wetting of metals and slag. It is lightweight and is a high-quality high-temperature resistant material. The disadvantage is that it is easy to oxidize at high temperature, and it is not suitable to use in an oxidizing atmosphere. Carbon products are widely used in high-temperature furnace linings (hearth, hearth, bottom of furnace body, etc.) and linings for melting non-ferrous metal furnaces. Graphite products can be used as liners for reaction tanks and petrochemical autoclaves. Silicon carbide and graphite products can also be made into crucibles for smelting copper, gold and light alloys.