Refractory properties, scope of application and service life

refractory materials

(1580-1770 ℃), high-grade refractory materials (1770-2000 ℃) and special refractory materials (above 2000 ℃); according to the chemical characteristics of acid refractory materials, according to the chemical characteristics of refractory materials, Neutral refractory suppliers materials and alkaline refractories. In addition, there are refractory materials for special occasions.
Now for the definition of refractories, has not only depends on the refractoriness is above 1580 ℃. Refractory materials are currently used in metallurgy, petrochemical, cement, ceramics and other production equipment lining the inorganic non-metallic materials.

First, the acid refractory material

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% of silicon silicate products, the use of raw materials are silica, waste silicon brick.
Silica brick anti-acid slag erosion ability, but vulnerable to alkaline slag erosion, and its load softening temperature is very high, close to its refractoriness, repeated exercise after the volume does not shrink, or even slightly inflated, poor thermal shock stability. Silica brick is mainly used for coke oven, glass melting furnace acidic steel-making furnace and other thermal equipment, silica brick in accordance with the SiO2 content and physical and chemical indicators can be divided into several levels, mainly divided into glass kiln with silicon brick and coke oven Two categories.
Clay brick with refractory clay or gemstone clinker as the main raw material, containing 30% -46% of alumina, refractoriness 1580-1770 ℃, is a weak acid refractory, thermal shock resistance, acid corrosion resistance , Widely used in clay bricks to refractory clay as the main raw material produced by the ordinary clay brick, coke gem clinker as the main raw material, the porosity of 17% below the clay brick called low porosity clay brick.
→ two kinds of clay brick and according to which the physical and chemical indicators are divided into several levels, ordinary clay brick and low porosity clay brick between the price difference.

Second, neutral refractories

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, alumina 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 materials. Chromium chrome as the main component of the chromium brick on the steel slag of good corrosion resistance, but the thermal shock resistance is poor, the load softening degree of alkali erosion resistance is poor, it can not be applied to the use of complex conditions, the key parts, Using bauxite and silicon carbide two materials as the main raw material, mainly used for cement rotary kiln transition zone.

Third, carbon refractories

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 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 electric furnace in the nitrogen atmosphere made of silicon nitride - silicon carbide products. Carbon products, thermal expansion coefficient is very low, high thermal conductivity, 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 refractory materials. Disadvantages are easy to oxidize at high temperatures, and should not be used in an 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 salt erosion, especially weak acid Of the resistance, not from the metal and slag melting wet, light, generally used in iron and steel smelting industry, but also for the oil, chemical industry, autoclave lining. Silicon carbide is an excellent refractory material, good corrosion resistance, but at high temperature (higher than 1400 degrees) easy to oxidation, is not suitable for use in the oxidizing atmosphere.

Fourth, alkaline refractories

The main products are magnesia brick, magnesia chrome brick, magnesium zirconium brick, magnesia aluminum brick, magnesia aluminum spinel brick, magnesia bricks, dolomite brick and the latest development of alkaline refractory materials to magnesium oxide, calcium oxide as the main component Of the mafic spinel bricks. Magnesite (Mgo) more than 80% of the refractory brick is called magnesia 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 silica brick The Mainly used for the furnace, oxygen converter, electric furnace, non-ferrous metal smelting equipment and glass industry and some high-temperature equipment. Magnesia 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 magnesite brick The

Magnesia 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.

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Continuous use of functional refractories

tundish nozzle

With the development of continuous casting, the proportion of high-clean steel production increased, sliding water mouth with skateboard, long nozzle, the sink, the outlet, immersion nozzle and other flow control and blowing function of the need for a sharp increase in refractory materials. In contrast to the earlier use of imported refractory bricks and other imported bricks of different circumstances, continuous casting refractory materials are still dominated by domestic production of products.

Sliding with a skateboard, the main use of aluminum carbon, and later, due to improved material, the use of improved conditions, greatly improved the number of durable. Material, due to the addition of zirconia, peeling resistance greatly improved. According to the experimental and stress calculation, the shape of the skateboard is improved, which inhibits the generation and expansion of the crack. Due to the miniaturization of the skateboard and the re-use of the rear skateboard, the consumption of the refractory suppliers material is reduced, so that the iron making is propelled. On the other hand, the development of high-corrosive steel slabs such as Ca-treated steel and high-carbon steels has been developed. For example, an aluminum-magnesium carbon alkaline skateboard having both corrosion resistance and peeling resistance has been developed.

Long water tundish nozzle is the most recent 10 years to improve the maximum refractory material, recently, long water mouth life can reach 30 furnace or 40 furnace is not surprising. Preheating, insulation and residue cleaning and other aspects of the use of improvements, for the extension of life has a significant effect. Material, to take to strengthen the strength of the bowl material, inhibit the inner tube steel wear, to prevent external oxidation and to prevent peeling and other measures.

Immersion nozzle, its characteristics and the flow pattern within the mold and the relationship between the quality of slab larger, it is generally from the material and shape of the two aspects of development and improvement. Material development is representative of the nozzle inside the alumina difficult to adhere to the development of materials. Generally use ZrO2-CaO-C material, the recent widespread use of carbon-free lining. Shape of the development, there are ladder-type immersion nozzle, this nozzle can effectively prevent the bias current, reduce the nozzle inside the alumina adhesion. In addition, a scheme for the use of a swirling flow nozzle and a vortex flow nozzle with spherical protrusions is proposed, and a furnace test is underway.

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Classification and main properties of high aluminum refractory products

High Alumina Brick

(1) cement kiln with high alumina brick

Cement kiln combined with high alumina brick is a high bauxite clinker as aggregate and fine powder, phosphoric acid or aluminum phosphate as a binder, semi-dry press molding, in the 400 ℃ ~ 600 ℃ temperature heat treatment , Made of cement for the cement kiln with high alumina refractory products.
Products are divided into two varieties according to the binder. High-alumina brick (referred to as phosphate brick), the binder for the concentration of 42.5% to 50.0% of the phosphate solution, code-named P, lock brick code for the PC.
Phosphate directly combined with high alumina bricks, the high temperature of the higher strength, hanging kiln skin medium, high thermal conductivity, thermal shock stability is better. In the commissioning stage, open kiln and kiln kiln more times, showing a better properties.
(2) mullite and mullite refractory products
Mullite is the only stable binary mineral phase in the Al2O3-SiO2 binary system. The chemical composition of 3 Al2O3 · 2 SiO2 (abbreviated as A3S2), the theoretical aluminum oxide and silicon oxide mass ratio of 71.88: 28.12. Mullite has a high melting point, high strength, small thermal expansion coefficient, and strong resistance to chemical corrosion. The use of pure mullite made of refractory bricks for the rotary kiln transition zone, showing a high load softening temperature, high high temperature strength, small expansion coefficient, thermal shock stability, good resistance to chemical corrosion Series of good use of properties. Due to its poor properties of hanging kiln skin, for the burning with the effect is not ideal. Industrial mullite are synthetic. According to the thermal processing method is divided into less combined into mullite and fused synthetic mullite.
(3) corundum refractory products
Corundum refers to the presence of Al2O3 crystals in the alpha crystal form. Theoretical composition of 100% pure Al2O3, crystal for the three crystal system. Corundum as the main raw material made of refractory suppliers, the Al2O3 content of not less than 90%. Corundum refractories high refractoriness, high temperature strength, good wear resistance, strong resistance to chemical corrosion, but the thermal expansion rate is higher, thermal conductivity is also high. According to the impurity content is divided into white corundum (almost 100% Al2O3) and brown corundum. White corundum is almost rarely used.
(4) anti-peeling high alumina brick
Is a special high bauxite clinker and zirconia synthesis of raw materials as raw materials, according to a certain ratio of high-pressure molding through the firing products. Products with high temperature impact resistance, high thermal strength, anti-peeling ability, alkali and sulfur, chlorine erosion and other characteristics, a large number of large-scale dry cement kiln for the transition zone and decomposition zone.


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