Among the common and specialty refractories, the following varieties are commonly used:

Acid refractories

The larger amount of silicon bricks and clay bricks. Silica brick is a siliceous product containing more than 93% SiO2, using raw materials such as silica, waste silica bricks. Silica brick acid slag corrosion resistance is strong, but vulnerable to alkaline slag corrosion, its load softening temperature is very high, close to its refractoriness, repeated calcination volume does not shrink, and even a slight expansion, but resistance to

Refractory material abrasive

Poor thermal shock. Silica bricks are mainly used in coke ovens, glass kilns, acid steel furnaces and other thermal equipment. Clay brick containing 30% to 46% alumina, it is refractory clay as the main raw material, refractoriness 1580 ~ 1770 ℃, good thermal shock resistance, belongs to the weakly acidic refractories, acidic slag corrosion resistance, wide range of uses, is currently the largest output of a class of refractories.

Neutral refractories

The main crystalline phase of high alumina products is mullite and corundum, the content of corundum increases with the increase of alumina content, corundum products containing more than 95% of alumina are a kind of high-quality refractories with wide range of uses. 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 high temperature load deflection temperature. Chrome ore and magnesium sand with different ratios of chromium and magnesium bricks made of good thermal shock resistance, mainly used as alkaline flat furnace roof brick.

Carbon products is another type of neutral refractories, according to the composition of carbon raw materials and products of the mineral composition, divided into carbon bricks, graphite products and silicon carbide products of three categories. Carbon bricks are made of high-grade petroleum coke, plus tar, asphalt as a binder, fired at 1300 ℃ under the premise of air isolation. Graphite products (in addition to natural graphite) with carbon materials in the electric furnace by 2500 ~ 2800 ℃ graphitization process. Silicon carbide products are based on silicon carbide as raw material, plus clay, silicon oxide and other binders in 1350 ~ 1400 ℃ firing. Silicon carbide can also be added to silicon powder in an electric furnace under nitrogen atmosphere made of silicon nitride - silicon carbide products.

Refractory abrasives

Carbon products have very low coefficient of thermal expansion, high thermal conductivity, good heat shock resistance and high temperature strength. Long-term use at high temperatures does not soften, not subject to corrosion of any acid or alkali, good salt function, not subject to metal and slag wetting, lightweight, is a high-quality high-temperature resistant materials. The disadvantage is that it is easy to oxidize at high temperature and should not be used in oxidizing atmosphere. Carbon products are widely used in high-temperature furnace lining (furnace bottom, furnace cylinder, lower part of the furnace body, etc.), the lining of the furnace for melting non-ferrous metals. Graphite products can be used as reaction tanks and petrochemical autoclave linings. Silicon carbide and graphite products can also be made of melting copper with gold and light alloys with the crucible.

Alkaline refractories

Represented by magnesium products. It contains magnesium oxide 80% ~ 85% or more, with magnesite as the main crystal phase. The main raw materials for magnesium brick production are magnesite, seawater magnesia extracted from seawater magnesium hydroxide calcined at high temperature) and so on. It has good resistance to alkaline slag and iron slag. The melting point of pure magnesium oxide is as high as 2800 ℃, therefore, the refractoriness of magnesium bricks is higher than that of clay bricks and silica bricks.Since the middle of the 1950s, because of the adoption of oxygen blowing converter steelmaking and the use of alkaline flat furnace roof, the production of alkaline refractories gradually increased, and the production of clay bricks and silica bricks is decreasing. Alkaline refractories are mainly used in flat furnaces, oxygen blowing converters, electric furnaces, non-ferrous metal smelting and some high-temperature thermal equipment.

Oxide materials

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

Refractory compound materials

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

High-temperature composite materials

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