Refractories are structurally neutral

The main crystalline phase of high aluminum products is mullite and corundum. The content of corundum increases with the increase of alumina content. Corundum products containing over 95% of alumina are a kind of high quality refractory material with wide application. Chromium brick is mainly made of chrome ore as raw material, the main crystal phase is chromite. It is good corrosion resistance of steel slag, but poor thermal shock resistance, high temperature load deformation temperature is low. Chrome chrome ore and magnesia made by different proportions of chrome magnesia good thermal shock resistance, mainly used as alkaline flat roof brick.

Carbonaceous products are another type of neutral refractory materials, which are divided into three categories, namely carbon brick, graphite products and silicon carbide products, according to the composition of the raw materials containing carbon and the mineral composition of the products. Carbon brick is a high-grade petroleum coke as raw material, add tar, asphalt as a binder, at 1300 ℃ isolated under the conditions of air firing. Graphite products (except natural graphite) with carbonaceous materials in the furnace by 2500 ~ 2800 ℃ graphitization obtained. Silicon carbide products are based on silicon carbide as raw materials, plus clay, silica and other binders at 1350 ~ 1400 ℃ firing. Silicon carbide plus silicon powder can also be made into silicon nitride-silicon carbide products in an electric furnace in a nitrogen atmosphere.

Low coefficient of thermal expansion of carbonaceous products, high thermal conductivity, thermal shock resistance, high temperature strength. Long-term use at high temperatures is not softened, without any acid and alkali erosion, good salt resistance, and not by the metal and slag wetting, light weight, high-quality high-temperature materials. The disadvantage is easily oxidized at high temperatures, should not be used in an oxidizing atmosphere. Carbonaceous products are widely used in high temperature furnace lining (hearth, hearth, the lower part of the body, etc.), smelting non-ferrous metal furnace lining. Graphite products can be used as reaction tank and petrochemical autoclave lining. Silicon carbide and graphite products can also be made of smelting copper with gold and light alloy crucible.

Alkaline

Magnesia products represented. It contains magnesium oxide 80% ~ 85%, with periclase as the main crystalline phase. The main raw material for the production of magnesia magnesia, sea magnesia from seawater extracted magnesium hydroxide by high temperature calcination) and so on. Alkaline slag and iron slag have good resistance. Pure magnesium oxide melting point up to 2800 ℃, therefore, the refractory magnesia than clay brick and silica brick are high. Since the mid-1950s, the production of basic refractories has been gradually increasing due to the adoption of BOF steelmaking and the use of an alkaline hearth top, while the production of clay bricks and silica bricks has been declining. Alkaline refractories are mainly used in open hearth, oxygen blowing furnace, electric furnace, non-ferrous metal smelting and some high temperature thermal equipment.

Composites

Oxide material

Such as alumina, lanthanum oxide, beryllium oxide, calcium oxide, zirconium oxide, uranium oxide, magnesium oxide, cerium oxide and thorium oxide melting point of 2050 ~ 3050 ℃.

Refractory compound material

Such as carbides (silicon carbide, titanium carbide, tantalum carbide and the like), nitrides (boron nitride, silicon nitride and the like), borides (zirconium boride, titanium boride, hafnium boride and the like), silicides Molybdenum, etc.) and sulfides (thorium sulfide, cerium sulfide, etc.). Their melting point is 2000 ~ 3887 ℃, of which the most refractory to carbide.

High temperature composite materials

Such as cermets, high temperature inorganic coatings and fiber-reinforced ceramics.