English Name: Definition of Refractory: Non-metallic material with fire resistance not lower than 1580℃, with good thermal shock resistance and chemical corrosion resistance, low thermal conductivity and low expansion coefficient. Applied discipline: electric power (first-class discipline); The above contents of thermal power generation (two disciplines) are examined and published by the National Committee for the Examination and Approval of Scientific and Technical Terminology.
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Inorganic nonmetallic materials with fire resistance not lower than 1580℃. Refractory refers to the celsius temperature at which a conical refractory sample can withstand high temperature without softening and melting under no load. Refractory materials are widely used in metallurgy, chemical industry, petroleum, machinery manufacturing, silicate, electric power and other industrial fields, among which the consumption of metallurgical industry is the largest, accounting for 50% ~ 60% of the total output.
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Main varieties of acid refractories
neutral refractory
basic refractory
Oxide material
Refractory composite material
High temperature composite material
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Ordinary refractory material
Bulk refractory
Introduction to refractory specialty
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Main varieties of acid refractories
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Oxide material
Refractory composite material
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Production technology, operability, ordinary refractories, bulk refractories, refractories, professional introduction, editing, this paragraph introduces.
Refractory and high temperature technology appeared together, which originated in the middle of the Bronze Age. During the Eastern Han Dynasty in China, clay refractories were used as kiln materials and saggers for firing porcelain. At the beginning of the 20th century, refractories developed towards high purity, high density and ultra-high temperature products, and refractories appeared at the same time.
Unformed refractory materials and refractory fibers do not need to be fired at all, and the energy consumption is low. Nowadays, with the development of atomic energy technology, aerospace technology and new energy technology, refractories with comprehensive excellent properties such as high temperature resistance, corrosion resistance, thermal shock resistance and erosion resistance have been applied.
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China used clay with less impurities to make pottery more than 4,000 years ago, and has been able to cast bronzes. During the Eastern Han Dynasty (AD 25-220), clay refractories were used as kiln materials and saggers for firing porcelain. At the beginning of the 20th century, refractories developed towards high purity, high density and ultra-high temperature products. At the same time, amorphous refractories and high refractory fibers (used in industrial furnaces above 1600℃) have been developed, which do not need to be fired and have low energy consumption. The former, such as alumina refractory concrete, is often used in the inner wall of the secondary reformer in the synthetic ammonia plant of large chemical plants, and the effect is good. Since 1950s, the rapid development of atomic energy technology, space technology and new energy development technology requires the use of special refractories with excellent comprehensive properties such as high temperature resistance, corrosion resistance, thermal shock resistance and erosion resistance, such as oxides, refractory compounds and high-temperature composite refractories with melting point higher than 2000℃.
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Refractories in ancient times, Middle Ages and Renaissance, refractories for blast furnaces, coke ovens and hot stoves before and after the industrial revolution, new refractories and their manufacturing technology in late modern times, manufacturing technology and major technological progress of modern refractories, development prospects of future refractories, refractories and high-temperature technology appeared together, which generally originated in the middle of the Bronze Age. During the Eastern Han Dynasty in China, clay refractories were used as kiln materials and saggers for firing porcelain. At the beginning of the 20th century, refractories developed towards high purity, high density and ultra-high temperature products. At the same time, unshaped refractories and low-energy refractories have appeared without burning at all. Modern, with the development of atomic energy technology, aerospace technology and new energy technology, it has the properties of high temperature resistance, corrosion resistance, thermal shock resistance and fire resistance.
Refractory materials with comprehensive excellent properties such as scouring have been applied. There are many factories producing refractory products in China. China is rich in resources, and it is precisely for this reason that major foreign investors come to China to show their talents and make their marks. In the northeast of China, there are abundant suppliers of refractories, which leads other foreign investors to question the low export price. Therefore, in 2003, the EU put forward anti-dumping measures against China's new refractories, which restricted the export of products to the EU. In 2006, in order to protect a large number of lost raw material resources, China reduced the product tax rebate for some industries, which greatly restricted the export of products. However, this does not restrict the sales of some foreign brands to a great extent, because they have decades or even hundreds of years of sales and production experience, and have greatly occupied the market, and also created their brand effects on various continents.
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There are many kinds of refractories, which are usually divided into ordinary refractories (1580 ~ 1770℃), advanced refractories (1770 ~ 2000℃) and super refractories (above 2000℃). According to chemical characteristics, it can be divided into acid refractories, neutral refractories and basic refractory. In addition, there are refractories for special occasions. Now the definition of refractories depends not only on whether the refractoriness is above 1580℃. At present, refractories generally refer to inorganic non-metallic materials used for lining production equipment such as metallurgy, petrochemical, cement and ceramics.
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Acid refractories are mainly composed of silicon oxide, and commonly used are silicon bricks and clay bricks. Silicon brick is a kind of siliceous product with more than 94% silicon content. The raw materials used are silica, waste silica bricks, etc. Strong corrosion resistance of acid slag, high softening temperature under load, and no shrinkage or even slight expansion after repeated calcination. But it is easy to be corroded by alkaline slag and has poor thermal shock resistance. Silicon bricks are mainly used in coke ovens, glass melting furnaces, acid steelmaking furnaces and other thermal equipment. Clay brick takes refractory clay as the main raw material and contains 30% ~ 46% alumina, which belongs to weak acid refractory and thermal shock resistant refractory.
Good, corrosion-resistant to acid residue, and widely used. Neutral refractories are mainly composed of alumina, chromium oxide or carbon. Corundum products with alumina content greater than 95% are a kind of high-quality refractory with wide applications. Chromium bricks with chromium oxide as the main component have good steel slag corrosion resistance, but poor thermal shock resistance and low deformation temperature under high temperature load. There are carbon bricks, graphite products and silicon carbide products in carbon refractories, which have low thermal expansion coefficient, high thermal conductivity, good thermal shock resistance, high high-temperature strength, acid and alkali resistance and salt corrosion, especially weak acid and alkali resistance, and are not wetted by metals and slag, so they are light in weight. It is widely used as lining material for high-temperature furnaces and autoclave lining in petroleum and chemical industries. In basic refractory, the main components are magnesium oxide and calcium oxide, and magnesium bricks are commonly used. Magnesium bricks with more than 80% ~ 85% magnesium oxide have good resistance to alkali slag and iron slag, and their fire resistance is higher than that of clay bricks and silica bricks. Mainly used in open hearth furnace, oxygen blowing converter, electric furnace, nonferrous metal smelting equipment and some high temperature equipment. Refractory materials used in special occasions include high-temperature oxide materials, such as alumina, lanthanum oxide, beryllium oxide, calcium oxide, zirconia and so on. And refractory compound materials such as carbides, nitrides, borides, silicides and sulfides. High temperature composite materials mainly include cermets, high temperature inorganic coatings and fiber reinforced ceramics.
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Among ordinary and special refractories, the commonly used varieties mainly include the following:
acid refractory
Silicon bricks and clay bricks are widely used. Silica bricks are siliceous products containing more than 93% silica, and the raw materials used are silica, waste silica bricks and so on. Silicon brick has strong resistance to acid slag erosion, but it is easy to be eroded by alkaline slag. Its load softening temperature is very high, close to its fire resistance. After repeated calcination, its volume does not shrink, even slightly expands, but it is resistant to refractory abrasives.
Thermal shock difference. Silicon bricks are mainly used in coke ovens, glass melting furnaces, acid steelmaking furnaces and other thermal equipment. Clay brick contains 30% ~ 46% alumina. It takes refractory clay as the main raw material, with a fire resistance limit of 1580 ~ 1770℃ and good thermal shock resistance. It belongs to weakly acidic refractory material, has corrosion resistance to acidic slag and is widely used. It is a kind of refractory with the largest output at present.
neutral refractory
The main crystal phases of high alumina products are mullite and corundum, and the content of corundum increases with the increase of alumina content. Corundum products with alumina content greater than 95% are a kind of high-quality refractory with wide applications. Chrome bricks are mainly made of chromite, 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. Chrome-magnesia bricks made of chrome ore and magnesia in different proportions have good thermal shock resistance and are mainly used as alkaline flat-topped bricks. Carbonaceous products are another kind of neutral refractories. According to the composition of carbon-containing raw materials and the mineral composition of products, it can be divided into three categories: carbon brick, graphite products and silicon carbide products. Carbon brick is made of high-quality petroleum coke as raw material, tar and asphalt as binder, and fired at 1300℃ under the condition of air isolation. Graphite products (except natural graphite) is formed by graphitizing carbonaceous materials in an electric furnace at 2500 ~ 2800℃. Silicon carbide products are made of silicon carbide as raw material, with binders such as clay and silicon oxide, and sintered at 1350 ~ 1400℃. Silicon carbide and silicon powder can also be made into silicon nitride-silicon carbide products in nitrogen atmosphere of electric furnace. Refractory abrasive tool
Carbon products have low thermal expansion coefficient, high thermal conductivity, good thermal shock resistance and high high temperature strength. It does not soften after long-term use at high temperature, is not corroded by any acid and alkali, has good salt resistance, is not wetted by metal and slag, and is light in weight, so it is a high-quality high-temperature resistant material. 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 lining of high temperature furnaces (bottom, hearth, lower part of furnace shaft, etc.). ) and furnaces for smelting non-ferrous metals. Graphite products can be used as the lining of petrochemical reaction tanks and autoclaves. Silicon carbide and graphite products can also be made into crucibles for smelting copper, gold and light alloys.
basic refractory
Represented by magnesium products. It contains more than 80% ~ 85% magnesium oxide, and the main crystal phase is periclase. The main raw materials for producing magnesia bricks are magnesite, seawater magnesium oxide and magnesium hydroxide extracted from seawater and calcined at high temperature. Good resistance to alkaline slag and iron slag. The melting point of pure magnesium oxide is as high as 2800℃, so the fire resistance of magnesium brick is higher than that of clay brick and silicon brick. Since the mid-1950s, the output of basic refractory has gradually increased, while the output of clay bricks and silica bricks has decreased due to the use of oxygen-blown converter steelmaking and alkaline open hearth furnace top. Basic refractory is mainly used in open hearth furnace, oxygen-blown converter, electric furnace, nonferrous metal smelting and some high-temperature thermal equipment.
Oxide material
Such as alumina, lanthanum oxide, beryllium oxide, calcium oxide, zirconia, uranium oxide, magnesium oxide, cerium oxide and thorium oxide, with a melting point of 2050-3050 DEG C..
Refractory composite material
Such as carbide (silicon carbide, titanium carbide, tantalum carbide, etc.). ), nitride (boron nitride, silicon nitride, etc. ), borides (zirconium boride, titanium boride, hafnium boride, etc. ), silicide (molybdenum disilicide, etc. ) and sulfide (thorium sulfide, cerium sulfide, etc. Their melting point is 2000 ~ 3887℃, and the most refractory is carbide.
High temperature composite material
Such as cermets, high-temperature inorganic coatings and fiber-reinforced ceramics.
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Commonly used special materials include AZS brick, corundum brick, direct bonded magnesia-chrome brick, silicon carbide brick, silicon nitride bonded silicon carbide brick, nitride, silicide, sulfide, boride, carbide and other non-oxide refractory materials; Refractory materials such as calcium oxide, chromium oxide, aluminum oxide, magnesium oxide and beryllium oxide. Commonly used heat-insulating refractory abrasives
Refractory materials include diatomite products, asbestos products, heat insulation boards, etc. Commonly used unshaped refractory materials include filler, refractory ramming material, refractory castable, refractory plastic refractory, refractory slurry, refractory gunning material, refractory projectile, refractory coating, lightweight refractory castable and stemming.
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The physical properties of refractories include structural properties, thermal properties, mechanical properties, service properties and working properties. The structural properties of refractories include porosity, bulk density, water absorption, air permeability and pore size distribution. The thermal properties of refractories include thermal conductivity, thermal expansion coefficient, specific heat, heat capacity, thermal conductivity, thermal emissivity and so on. The mechanical properties of refractories include compressive strength, tensile strength, flexural strength, torsional strength, shear strength, impact strength, wear resistance, creep, bonding strength and elastic modulus. The properties of refractories include refractoriness, load softening temperature, reheat line change, thermal shock resistance, slag resistance, acid resistance, alkali resistance, hydration resistance, CO corrosion resistance, electrical conductivity and oxidation resistance.
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According to the different density and shape of products, there are sintering method, casting method and melt blowing method. Sintering method is that some raw materials are pre-sintered, crushed and screened, and then mixed with raw materials in a certain proportion, and then molded, dried and sintered. The purpose of raw material pre-burning is to burn off water, organic impurities and gas decomposed by sulfate, so as to reduce the sintering shrinkage of products and ensure the accuracy of product appearance and size. After the raw materials are crushed and ground, they need to be screened, because the blanks are graded from powders with different particle sizes, which can ensure the closest accumulation and obtain dense blanks. In order to make the components and particles of various raw materials and clinker uniform, it is necessary to mix and add binders at the same time to enhance the bonding strength of the green body. For example, aluminum silicate blank is added with bonded clay, magnesium blank is added with sulfite slurry waste liquid, and silica blank is added with lime milk. According to the water content of the green body, semi-dry molding (about 5% water content), plastic molding (about 0/5% water content/kloc) and grouting molding (about 40% water content) can be adopted. And then dried and fired. Melting and casting method is to melt raw materials at high temperature through batching and fine grinding, directly cast, cooled, crystallized and annealed to form products. Such as mullite brick, corundum brick and magnesia brick. Their green bodies are compact, their mechanical strength is high, their structural strength is high at high temperature, their slag resistance is good, and their application scope is constantly expanding. Melt-blowing method is a method of melting ingredients and blowing them with high-pressure air or superheated steam to disperse them into fibers or hollow spheres. This product is mainly used as lightweight refractory and heat insulation material. In addition, it can also be made into powder or granular amorphous refractories, which can be bonded with binders such as tar, asphalt, cement, phosphate, sulfate or chloride salt, and can be used directly without molding and sintering.
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The machinability of refractories includes consistency, slump, fluidity, plasticity, cohesiveness, elasticity, coagulability and hardenability.
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Commonly used refractory materials include AZS brick, corundum brick, direct bonded magnesia-chrome brick, silicon carbide brick, silicon nitride bonded silicon carbide brick, nitride, silicide, sulfide, boride, carbide and other non-oxide refractory materials; Refractory materials such as calcium oxide, chromium oxide, aluminum oxide, magnesium oxide and beryllium oxide. Commonly used thermal insulation refractory materials include diatomite products, asbestos products, thermal insulation boards, etc. Commonly used unshaped refractory materials include filler, refractory ramming material, refractory castable, refractory plastic refractory, refractory slurry, refractory gunning material, refractory projectile, refractory coating, lightweight refractory castable and stemming.
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Block refractories (unshaped refractories): unshaped refractories are refractories composed of reasonably graded granular and powdery materials and binders, which can be used directly without molding and firing. Generally, the granular material that constitutes this material is called aggregate, the powdery material is called admixture and the binder is called cementing agent. This kind of material has no fixed shape and can be made into slurry, mud paste and loose shape, so it is also called block refractory. This kind of refractory can form a seamless integral structure, so it is also called integral refractory. The basic components of unshaped refractories are granular and powdery refractories. It can be made of various materials according to its use requirements. In order to combine these refractories into a whole, except for a few special cases, it is generally necessary to add suitable varieties and quantities of binders. In order to improve its plasticity or reduce water consumption, a small amount of appropriate plasticizing water reducer or other additives can be added to meet other special requirements.
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Training objectives: This major trains senior engineering and technical personnel with knowledge of refractory science and engineering, who can engage in scientific research, technology development, process and equipment design, production and management in the fields of refractory structure research and analysis, material preparation, material molding, processing and engineering construction. Training requirements: Students in this major mainly study the basic theory, composition, structure, performance of refractory materials and their relationship with production conditions, and have the ability of material testing, production process design, material modification, new products, new technologies, equipment research and development and technical management. Skills: Graduates should acquire the following knowledge and abilities: 1. Master the professional basic knowledge of production technology, equipment and production technology in refractory industry; 2. Master the principle and technological basis of refractory preparation, the structure and properties of the material; 3. Master the basic knowledge and skills of mechanical, electronic, engineering and computer applications necessary for this major; 4. Have the preliminary ability of industrial production, quality control and technical management of products; 5. Ability to correctly select materials and equipment and carry out process design; 6. Have the preliminary ability to study and improve the properties of materials and develop new materials, new products and new processes. Courses offered: Main courses: Material Science and Engineering, Thermodynamic Basis, Solution Thermodynamics, Electrochemical Thermodynamics, Surface and Interface Phenomena Thermodynamics, Refractory Oxide Thermodynamics, carbon refractory Thermodynamics, Refractory Non-oxide Thermodynamics and Its Composite Refractory Materials Thermodynamics. Main courses: physical chemistry, properties of inorganic materials, testing and research methods, powder engineering, material preparation principle, thermal process and equipment, and inorganic material technology. Main practical teaching: including professional experiment, engineering practice, production practice, curriculum design, computer application and computer practice, graduation design. [