Classification of refractory materials
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2024-04-03
The definition of refractory materials: Inorganic non-metallic materials with a fire resistance greater than 1580 degrees Celsius are refractory materials. Refractory materials are a part of the materials industry, named after their use in thermal kilns. Refractory materials are divided into conventional refractory materials and special refractory materials. Conventional refractory materials refer to materials used for lining thermal kilns such as metallurgical furnaces, cement kilns, and glass kilns, mostly processed from natural raw materials. Special refractory materials have high purity and are mostly oxide synthetic materials used in special smelting equipment or special parts of kilns. There are a wide variety of refractory materials, and there are four commonly used classifications:
01
Classified by high or low refractory temperature
Refractory materials are composed of multiple minerals, each of which has its own melting point. At high temperatures, they either coexist or form third-party minerals, resulting in a low co melting temperature. Refractory materials have a temperature in a low eutectic state, but higher than the low eutectic temperature. The higher the refractory material index. Indicating better resistance to high temperatures, refractory materials are classified into three levels: "ordinary", "advanced", and "special" based on their indicators.
1. Normal: The fire resistance is 1580-1770 degrees Celsius, which is equivalent to 15% -45% of Al2O3 refractory products in the SiO2-Al2O3 binary system. The main mineral used as the raw material is kaolin.
2. Advanced refractory materials: with a fire resistance of 1770-2000 degrees Celsius, high alumina bricks, mullite bricks, ordinary magnesium products, magnesium aluminum bricks, ordinary magnesium chromium bricks, and olivine bricks belong to this category.
3. Special grade refractory materials: with a fire resistance greater than 2000 degrees Celsius, pure oxide products, cast products, high-purity directly bonded magnesia chromium bricks, spinel bricks, non oxide products, etc. belong to this category.
At present, this classification method is rarely used in the refractory material industry. It simply describes the refractory material technology. Some products (using synthetic materials) may not have a high refractory degree, but their technical content is very high, making them truly high-grade refractory materials.
02
Classified by whether it is standardized or not
According to the shape of products delivered before leaving the factory, they are divided into standardized products and unshaped products. Any product referred to as a brick is a standardized product. Various pouring materials, furnace repair materials, ramming materials, fire clay, etc. are all amorphous products. Fixed products are divided into dense and insulation types. Refractory bricks belong to dense products, while concrete is a fixed delivery product, but it belongs to unshaped products.
03
Classified by the acidic and alkaline properties of the main crystal phase
1. Acidic material products: In this type of product, quartz (SiO2) is the first phase, which belongs to acidic oxides and is named after it. Silicon bricks are representative products of acidic materials; The SiO2 content in semi silica bricks, alkali resistant bricks, and acid resistant bricks ranges from 60% to 80%, making them semi acidic materials.
2. Alkaline material products: with MgO and CaO as the main crystal phases, they are called alkaline refractory materials because they are alkaline earth oxides. They have a high melting point and strong resistance to alkaline slag (C/S>2) erosion. They belong to advanced refractory materials, but they are easy to hydrate. Products such as magnesium chromium bricks, dolomite bricks, and olivine bricks mainly contain MgO and CaO, which are also alkaline materials.
3. Neutral material products: Al2O3 and ZrO2 are the main crystalline phases, and their chemical behavior is variable. When encountering alkaline oxides, they exhibit acidic characteristics, such as the formation of MgO, Al2O3, Al2O3, ZrO2; When encountering strongly acidic oxides, it exhibits alkaline characteristics. Representative products of neutral materials include clay bricks, high alumina bricks, and alumina bricks. Zircon products are also neutral products.
04
Classification based on the main components of refractory materials
The so-called main components refer to the first and second phase components, which account for about 90% of the total chemical composition. The development of modern refractory material technology involves more and more material ingredients, resulting in the emergence of second phase and third phase components. Adjusting the composition of the second phase and third phase can generate new technologies, which go beyond the limitations of the first phase classification in terms of chemical composition and are the most commonly used classification method.
1. Silicon aluminum series products: In the silicon aluminum series materials, the main components are SiO2 and Al2O3, which include clay bricks, high alumina bricks, sillimanite, kyanite, andalusite, mullite bricks and other products.
2. Magnesium chromium series products: The main components of the magnesium chromium series are MgO and Cr2O3, with periclase as the first phase and magnesium chromium spinel as the second phase. Products belonging to this series include magnesium chromium bricks and chromium magnesium bricks.
3. Magnesium aluminum series products: The main components are MgO and Al2O3, which generate MgO Al2O3 and magnesium chromium series products contain magnesium based materials.
4. Magnesium calcium series products: The main components are MgO and CaO. They all have extremely high melting points and are important magnesium materials.
5. Magnesium silicon series products: The main component of the magnesium sand series is SiO2. When C/S<5, SiO2 and MgO form MgO Al2O3 (magnesium olivine), from the perspective of microscopic mineral composition, the main products of the pure aluminum series include magnesium aluminum bricks, periclase spinel bricks, and corundum spinel bricks. Aluminum spinel castables in amorphous materials also belong to the magnesium aluminum series products.
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