Acid refractories are mainly composed of silica, and commonly used are silica bricks and clay bricks. Silica brick is a siliceous product containing more than 94% silicon oxide. The raw materials used include silica, waste silica brick, etc. It has strong resistance to acid slag corrosion, high load softening temperature, and its volume does not shrink after repeated calcination, even slightly expands; However, it is easy to be eroded by alkaline slag and has poor thermal shock resistance. Silicon bricks are mainly used in coke ovens, glass furnaces, acid steelmaking furnaces and other thermal equipment. The clay brick is made of refractory clay as the main raw material, containing 30%~46% aluminum oxide. It is a weak acid refractory material with thermal shock resistance

The refractory material is good and has corrosion resistance to acid slag. It is widely used.

Neutral refractories are mainly composed of aluminum oxide, chromium oxide or carbon. The corundum product containing more than 95% alumina is a kind of high-quality refractory with wide use. The chrome brick with chromium oxide as the main component has good corrosion resistance to steel slag, but poor thermal shock resistance and low deformation temperature under high temperature load. Carbon refractories include carbon bricks, graphite products and silicon carbide products. They have low thermal expansion coefficient, high thermal conductivity, good thermal shock resistance, high high temperature strength, and resistance to acid, alkali and salt corrosion, especially weak acid and alkali. They are not wetted by metal and slag and are light in weight. It is widely used as high temperature furnace lining material, as well as high-pressure kettle lining in petroleum and chemical industry.

Basic refractories are mainly composed of magnesia and calcium oxide, and magnesia bricks are commonly used. The magnesia brick containing 80%~85% magnesia has good resistance to alkaline slag and iron slag, and its refractoriness is higher than that of clay brick and silica brick. It is mainly used in open hearth furnace, oxygen blowing converter, electric furnace, non-ferrous metal smelting equipment and some high-temperature equipment.

Refractories used in special occasions include high-temperature oxide materials, such as aluminum oxide, lanthanum oxide, beryllium oxide, calcium oxide, zirconia, etc., refractory compound materials, such as carbide, nitride, boride, silicide, sulfide, etc; High temperature composite materials mainly include metal ceramics, high temperature inorganic coatings and fiber reinforced ceramics.

Refractories commonly used include AZS bricks, corundum bricks, direct bonded magnesia chrome bricks, silicon carbide bricks, silicon nitride bonded silicon carbide bricks, and non oxide refractories such as nitride, silicide, sulfide, boride and carbide; Calcium oxide, chromium oxide, aluminum oxide, magnesium oxide, beryllium oxide and other refractories.

Thermal insulation refractory materials often used include diatomite products, asbestos products, thermal insulation boards, etc.

Unshaped refractory materials often used include furnace mending materials, ramming materials, castables, plastic materials, refractory mud, refractory gunning materials, refractory projectiles, refractory coatings, light refractory castables, blasting mud, etc.

Bulk refractories (unshaped refractories): unshaped refractories are refractories that are composed of reasonably graded granular and powdered materials and binders and are directly used without forming and firing. Generally, the granular materials constituting this material are called aggregates, the powder materials are called admixtures, and the binders are called cements. This kind of material has no fixed shape, and can be made into slurry, mud paste and loose, so it is also known as bulk refractory. This kind of refractory can be used to form an integral structure without joints, so it is also called integral refractory.

The basic composition of amorphous refractory is granular and powdery refractory. According to its use requirements, it can be made of various materials. In order to combine these refractory materials as a whole, except for a few special cases, proper types and quantities of binders are generally added. In order to improve its plasticity or reduce water consumption, a small amount of appropriate plasticizer and water reducer can be added. In order to meet other special requirements, a small amount of appropriate other admixtures can also be added. Generality

Common varieties of ordinary and special refractory materials are as follows:

acidic

Silica bricks and clay bricks are used in large quantities. Silicon bricks are siliceous products containing more than 93% SiO2, and the raw materials used include silica, waste silica bricks, etc. Silica brick has strong resistance to acid slag erosion, but is vulnerable to alkali slag erosion. Its load softening temperature is very high, close to its fire resistance. After repeated calcination, the volume does not shrink, or even slightly expand, but it is resistant to

Refractory abrasives have poor thermal shock. Silicon bricks are mainly used in coke ovens, glass furnaces, acid steelmaking furnaces and other thermal equipment. Clay brick contains 30%~46% alumina. It uses refractory clay as the main raw material, with a refractoriness of 1580~1770 ℃ and good thermal shock resistance. It belongs to weak acid refractory, and has corrosion resistance to acid slag. It has a wide range of uses. It is the largest class of refractory produced.

neutral

The main crystal phases in high alumina products are mullite and corundum. The content of corundum increases with the increase of alumina content. Corundum products containing more than 95% alumina are a kind of high-quality refractory with wide use. The chrome brick is mainly made of chrome ore, and the main crystal phase is chromite. It has good corrosion resistance to steel slag, but poor thermal shock resistance and low deformation temperature under high temperature load. The chrome magnesia bricks made of chrome ore and magnesia in different proportions have good thermal shock resistance and are mainly used as the top bricks of alkaline open hearth furnace.

Carbon products are another kind of neutral refractory materials. According to the composition of carbon containing raw materials and the mineral composition of products, they are divided into three categories: carbon bricks, graphite products and silicon carbide products. Carbon bricks are made of high-grade petroleum coke as raw materials, tar and asphalt as adhesives, and fired at 1300 ℃ under the condition of air isolation. Graphite products (except natural graphite) are made of carbon materials by graphitizing at 2500~2800 ℃ in an electric furnace. Silicon carbide products are fired at 1350-1400 ℃ with silicon carbide as raw material, clay, silicon oxide and other binders. Silicon nitride silicon carbide products can also be made by adding silicon carbide and silicon powder in an electric furnace under nitrogen atmosphere.

Refractory abrasives Carbon products have low thermal expansion coefficient, high thermal conductivity, good thermal shock resistance and high high temperature strength. It will not be softened after long-term use under high temperature, will not be corroded by any acid or alkali, has good salt resistance, and will not be wetted by metal and slag. It is light in weight, and is a high-quality high temperature resistant material. The disadvantage is that it is easy to be oxidized at high temperature and is not suitable for use in oxidation atmosphere. Carbon products are widely used for lining of high temperature furnace (furnace bottom, hearth, lower part of furnace stack, etc.) and lining of smelting nonferrous metal furnace. Graphite products can be used as the lining of reaction tank and petrochemical autoclave. Silicon carbide and graphite products can also be made into crucibles for smelting copper, gold and light alloys.

alkalinity

Take magnesium products as representative. It contains more than 80%~85% magnesium oxide, with periclase as the main crystal phase. The main raw materials for producing magnesite bricks are magnesite and seawater magnesite, which are calcined from magnesium hydroxide extracted from seawater at high temperature. It has good resistance to alkaline slag and iron slag. The melting point of pure magnesia is as high as 2800 ℃, so the refractoriness of magnesia brick is higher than that of clay brick and silica brick. Since the mid 1950s, due to the adoption of oxygen blowing converter for steelmaking and the adoption of basic open hearth furnace roof, the production of basic refractories has gradually increased, while the production of clay bricks and silica bricks has decreased. Alkaline refractory materials are mainly used in open hearth furnace, oxygen blowing converter, electric furnace, nonferrous metal smelting and some high-temperature thermal equipment. compound material

Oxide material

For example, the melting point of alumina, lanthanum oxide, beryllium oxide, calcium oxide, zirconia, uranium oxide, magnesium oxide, cerium oxide and thorium oxide is 2050~3050 ℃.

Refractory compound material

Such as carbide (silicon carbide, titanium carbide, tantalum carbide, etc.), nitride (boron nitride, silicon nitride, etc.), boride (zirconium borate, titanium borate, hafnium borate, etc.), silicide (molybdenum disilicide, etc.) and sulfide (thorium sulfide, cerium sulfide, etc.). Their melting points range from 2000 ℃ to 3887 ℃, among which carbide is the most difficult to melt.

High temperature composite

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