Classification of refractories
Definition: Inorganic non-metallic materials with a refractoriness greater than 1580 degrees Celsius are refractory materials. It is a part of the material industry and is derived from its use in thermal kilns. It is divided into conventional and special refractory materials. The conventional ones refer to the materials used for the lining of thermal kilns such as metallurgical furnaces, cement kilns, glass kilns, etc., and most of them are processed from natural raw materials. Special materials are of high purity, mostly oxide synthetic materials, used for special smelting equipment, or special parts of kilns. There are many varieties, and there are four commonly used classifications:
01
Classified by refractory temperature
It is composed of a variety of minerals, each of which has its own melting point. At high temperature, they either coexist or form a third party mineral, showing a low eutectic melting temperature. The refractory material is at the temperature of the eutectic melting state, but it is higher than the eutectic melting temperature. The higher the index, the better the ability to resist high temperature. The index is divided into three grades of “ordinary”, “advanced” and “special grade”.
1. Ordinary: Refractoriness 1580-1770 degrees Celsius, refractoriness 1580-1770 degrees Celsius is equivalent to Al2O3 15%-45% refractory products in SiO2-Al2O3 binary system, and the main mineral constituting the raw material is kaolinite.
2. High-grade: refractoriness 1770-2000 degrees Celsius, high-alumina bricks, mullite bricks, ordinary magnesia products, magnesia-alumina bricks, ordinary magnesia-chrome bricks, and olivine bricks belong to this grade.
3. Special grade: The refractoriness is greater than 2000 degrees Celsius. Pure oxide products, cast products, high-purity direct bonded magnesia-chrome bricks, spinel bricks, and non-oxide products belong to this grade.
At present, this classification method is rarely used in the refractory industry. It expresses the technology too simply. Although some products (using synthetic materials) have not high refractoriness, their technical content is very high, and they are truly special grades.
02
Classified by stereotype
According to the delivery shape of the product before leaving the factory, it is divided into stereotyped products and unshaped products. Those who are called bricks are stereotyped products. All kinds of castables, furnace repair materials, ramming materials, fire clay, etc. are unshaped products. Shaped products are divided into dense type and heat insulation type. Refractory bricks are dense type products. Although concrete is a shaped product, it is an unshaped product.
03
Classified according to the main crystal phase acid and alkali properties
1. Acidic material products: Quartz (SiO2) is the first phase in this type of product, and SiO2 is an acidic oxide, so it is named after it. Silica bricks are representative products of acidic materials; semi-silicic bricks, alkali-resistant bricks, and acid-resistant bricks contain 60% to 80% SiO2, which is a semi-acidic material.
2. Alkaline material products: MgO and CaO are the main crystal phases. Because MgO and CaO are alkaline earth oxides, they are called alkaline refractory materials. They have a high melting point and strong corrosion resistance to alkaline slag (C/S>2). They are high-grade refractory materials, but they are easy to hydrate. Magnesia-chrome bricks, dolomite bricks, olivine bricks and other products, the main chemical composition is also MgO, CaO is also an alkaline material.
3. Neutral material products: Al2O3 and ZrO2 are the main crystal phases, and their chemical behavior is variable. When they encounter alkaline oxides, they show acidic characteristics, such as generating MgO, Al2O3, Al2O3, and ZrO2; when encountering strong When it is an acidic oxide, it also exhibits basic characteristics. For example, clay bricks, high-alumina bricks, and stone bricks are representative products of neutral materials. Zircon products are also neutral products.
04
Classified by main ingredient
The so-called main components refer to the first phase and second phase components, and the content accounts for about 90% of the total chemical components. The development of modern refractory technology is more and more multi-material ingredients, so the second phase and the third phase composition appear, and the new technology can be produced by adjusting the second phase and the third phase composition, which exceeds the first phase classification in terms of chemical composition Limitation is the most commonly used classification method.
1. Silicon-aluminum series products
3. Magnesium-aluminum series products
4. Magnesium calcium series products
5. Magnesium silicon series products