High temperature refractory use
(1580 ~ 1770 ℃), high-grade refractory materials (1770 ~ 2000 ℃) and special refractory materials (above 2000 ℃); according to the chemical characteristics of acid refractory material is divided into high-grade refractory materials, Neutral refractory materials and alkaline refractories. In addition, there are refractory materials for special occasions.
Now for the definition of refractories, has not only depends on whether the refractoriness is above 1580 ℃. Refractory materials are currently used in metallurgy, petrochemical, cement, ceramics and other production equipment lining inorganic non-metallic materials.
Acid refractory material to silicon oxide (SiO2) as the main component, commonly used silica brick and clay brick. Silica brick is containing more than 93% SiO2 siliceous products, the use of raw materials are silica, waste silicon brick. Silica brick anti-acid slag erosion ability, but susceptible to alkaline slag erosion, and its load softening temperature is very high, close to its refractoriness, repeated calcination volume does not shrink, or even slightly inflated, but the thermal shock stability is poor. Silica brick is mainly used for coke oven, glass melting furnace, acid steelmaking furnace and other thermal equipment, silica brick in accordance with the SiO2 content and physical and chemical indicators can be divided into several grades, the main sub-glass kiln and coke oven with silicon Brick two categories. Clay brick with refractory clay or coke gem clinker as the main raw material, containing 30% to 46% of alumina, refractoriness 1580 ~ 1770 ℃, is a weak acid refractory, good thermal shock resistance, corrosion resistance to acid slag , Widely used in clay bricks to refractory clay as the main raw material produced by ordinary clay brick, coke gem clinker as the main raw material, the porosity of 17% or less clay brick called low porosity clay brick. The two kinds of clay tiles are divided into several grades according to their physical and chemical indexes. The price difference between ordinary clay brick and low porosity clay brick is different.
Neutral refractories are mainly composed of alumina, chromium oxide, silicon carbide or carbon. Neutral refractory main products are: corundum brick, high alumina brick, silicon brick, mullite brick, aluminum chrome brick, aluminum carbon brick, graphite or carbon brick. High-alumina products in the main crystal phase is mullite and corundum, corundum content with the increase in alumina content increased, more than 95% alumina corundum products is a wide range of high-quality refractory alumina More than 95% of the corundum products is a wide range of high-quality refractory materials. Chromium chrome as the main component of the steel brick on the steel slag resistance to corrosion, but the thermal shock resistance is poor, the load softening degree is low. High alumina brick of the indicators are relatively good, with a good price, so widely used, but because of the high alumina brick alkali resistance is poor, it can not be used in the key conditions of the use of complex parts, silicon brick is used Bauxite and silicon carbide two materials as the main raw material, mainly used for cement rotary kiln transition zone.
Carbon refractories are carbon brick, graphite products and silicon carbide products. Carbon products are another kind of neutral refractory material, according to the composition of carbonaceous raw materials and products of mineral composition, divided into carbon brick, graphite products and silicon carbide products three categories. Carbon brick is a high grade petroleum coke as raw material, plus tar, asphalt as a binder, at 1300 ℃ under the conditions of air burning. Graphite products (except for natural graphite) with carbonaceous materials in the furnace by 2500 ~ 2800 ℃ graphite processing in the system. Silicon carbide products are silicon carbide as raw materials, plus clay, silicon oxide and other adhesives in the 1350 ~ 1400 ℃ firing. Silicon carbide-silicon carbide products can also be made of silicon carbide and silica fume in an electric furnace under a nitrogen atmosphere. Carbon products have a low coefficient of thermal expansion, high thermal conductivity, good thermal shock resistance, high temperature strength. Long-term use at high temperatures do not soften, from any acid-base erosion, good salt resistance, but also from the metal and slag wetting, light, high-quality high-temperature materials. The disadvantage is easy oxidation at high temperatures, not in the use of oxidizing atmosphere. Carbon products are widely used in high temperature furnace lining (bottom, hearth, furnace body, etc.), smelting non-ferrous metal furnace lining. Graphite products can be used as reaction tank and petrochemical kettle lining. Silicon carbide and graphite products can also be made into smelting copper alloy and light alloy crucible. Carbon brick and graphite products, the main component of carbon (C), its thermal expansion coefficient is very low, high thermal conductivity, good thermal shock resistance, high temperature strength, acid and alkali erosion, especially weak acid Of the resistance, not from the metal and slag wetting, light weight, generally used in iron and steel smelting industry, but also for the oil, chemical industry, autoclave lining. Silicon carbide is an excellent refractory, good corrosion resistance, but at high temperatures (above 1400 degrees) easy to oxidation, is not suitable for use in an oxidizing atmosphere.
The main products are magnesia brick, magnesia chrome brick, magnesium zirconium brick, magnesium aluminum brick, magnesium aluminum spinel brick, magnesia bricks, dolomite brick and the latest development of the main products are magnesium oxide, calcium oxide as the main component Mafic spinel bricks and so on. Magnesium oxide (MgO) more than 80% of the refractory brick is called magnesium bricks, according to the indicators can be divided into many grades, magnesia on the basic slag and iron slag has a good resistance, refractoriness than clay brick and silicate brick The Mainly used for flat furnace, oxygen converter, electric furnace, nonferrous metal smelting equipment and glass industry and some high temperature equipment. Magnesium chrome brick is more resistant to alkaline slag, and the thermal shock resistance is much higher than that of magnesia brick, so the application is more extensive, magnesia chrome brick in the iron and steel smelting and nonferrous metal smelting industry has almost replaced the magnesium brick , Because it contains chromium oxide (Cr2O3) can continue to spread, so that magnesia-chrome brick can be easy to stick hanging kiln skin, so in the last 30 years, has been the cement kiln firing with the preferred refractory materials, magnesium chrome brick Cr2O3 will occur after the reaction of water, trivalent chromium can become carcinogenic hexavalent chromium, will cause pollution to water, is facing gradually withdraw from the cement industry market trends. Magnesium and aluminum brick with magnesia and alumina as raw material, compared with magnesium, its thermal shock stability and high temperature creep performance is better, the use of parts and magnesium bricks almost the same. Dolomite brick and magnesium calcium brick performance is almost the same, dolomite brick to dolomite as raw material, magnesium calcium brick to synthetic magnesium calcium sand as raw material, calcium oxide content is generally 15-30%, the rest of the main components of magnesium oxide, With the role of purification of molten steel, generally only for the special steel smelting, magnesium calcium brick production process is more complex, water and steam easy to hydration decomposition, easy to save transport, the use of the process must be preventive work. Magnesium iron spinel brick is a new product, mainly used for cement rotary kiln firing zone and transition zone, will be the cement industry to replace the main products of magnesia chrome brick.
Refractory materials for special applications include high temperature oxide materials such as alumina, lanthanum oxide, beryllium oxide, calcium oxide, zirconia and the like, refractory compound materials such as carbides, nitrides, borides, silicides and sulfides Refractory materials such as carbides (silicon carbide, titanium carbide, tantalum carbide, etc.), nitrides (boron nitride, silicon nitride, etc.), borides (boron, boron nitride, etc.), and other refractory materials having a melting point of 2050 to 3050 ° C, Zirconium boride, hafnium boride, etc.), silicides (molybdenum disilicide, etc.) and sulfides (thorium sulfide, cerium sulfide, etc.). They have a melting point of 2000 to 3887 ° C, the most refractory of which is carbide. High temperature composites such as cermets, high temperature inorganic coatings and fiber reinforced ceramics.
Commonly used special materials are AZS brick (ie zirconium corundum brick), corundum brick, directly combined with magnesia-chrome brick, silicon carbide brick, silicon nitride combined with silicon carbide brick, nitride, silicide, sulfide, boride, carbonization Non-oxide refractories; calcium oxide, chromium oxide, alumina, magnesium oxide, beryllium oxide and other refractories. Frequently used insulation refractories are diatomite products, asbestos products, thermal panels and so on. Often use the refractory refractory refractory castable, refractory mud, refractory ramming material, refractory plastic, fill charge, refractory spray feed, refractory material, refractory paint, light refractory castable, gun mud and so on.