News

Classification of refractory

1. Classification by chemical properties

Refractories with chemical properties can be divided into acid refractories, alkaline refractories and neutral refractories.

1, acid refractory. Usually refers to silica as the main component of the refractory. At high temperature, it is easy to react with alkaline refractory materials, alkaline slag, high-aluminum refractory materials or alkali-containing compounds.

2, alkaline refractory material. Refractory materials that react easily with acid refractory materials, acid slag, acid flux or alumina at high temperatures. Such refractories usually use magnesium oxide, calcium oxide or both as their main components.

3, neutral refractory material. Refractories that do not react chemically with acidic refractories, alkaline refractories, acidic or alkaline slags or fluxes at high temperatures. Such as corundum and silicon carbide products. It should be noted that no obvious chemical reaction is not the same as no reaction at all. Under certain conditions, the reaction can proceed.

Second, according to the type of refractory supply

According to the supply form, refractories can be divided into shaped refractories and amorphous refractories.

1, shaped refractory material. Refers to refractory products and thermal insulation products with a fixed shape. It is divided into two categories: compact shaped products and heat preservation shaped products. The former refers to products with a total porosity of less than 45%, while the latter refers to products with a total porosity of more than 45%. According to the complexity of the shape, shaped refractory products can be divided into standard bricks and special-shaped bricks. The former refers to refractory products with relatively simple shapes, such as straight bricks (brick shape is parallelepiped) and wedge-shaped bricks, etc., while the latter refers to refractory products with more complex shapes. The complexity of special-shaped brick is not specified in the existing standard in our country.

2, amorphous refractories. A mixture consisting of aggregates (particles), fine powders and binders and additives, used directly in bulk for delivery, or used after adding one or more suitable liquids that do not affect the performance of refractory materials. A small amount of metal, organic or inorganic fiber materials can also be added to some amorphous refractories. There are many kinds of amorphous refractory materials, mainly castable, plastic, ramming material, dry material, jet material, joint material, extrusion material, paint, mud, mud and so on.

It should be noted that the so-called shaped and amorphous refractories are also relative. The prefabricated block obtained by casting or molding the amorphous refractory into a certain shape and after pretreatment is supplied in the form of a shaped product, but its entire production process is the same as that of the amorphous refractory. Therefore, it can also be classified into amorphous refractories.

3. Classification by combination form

According to the combination form between the components (particles, fine powder) in the refractory, the refractory can be divided into ceramic bonding, chemical bonding, hydration bonding, organic bonding and resin bonding.

1, ceramic combination. At a certain temperature, the bond produced by sintering or liquid phase formation is called ceramic bond. This kind of combination exists in fired products, fired bricks are mostly ceramic bonded refractory materials.

In ceramic bonded refractories, the so-called direct bonded refractories should also be mentioned. There is no definition of refractories directly combined in China and ISO standards. However, it is still stipulated in the American standard ASTM and the Japanese standard JIS. The former defines direct-bonded bricks as fired refractories connected primarily by solid phase diffusion mechanism (ASTM C71). The JIS standard defines direct-bonded refractories as refractories with a high refractory particle direct-bonded structure (JIS R2001). The term direct bonding first appeared in magnesia-chromium refractories. It is considered that the cubic magnesite or spinel of a high purity magnesia-chrome brick is directly connected, and there is no mesophase. However, with the development of modern microscopy technology and materials science, it is found that the particles are not really directly combined, and the binding part often exists in the area of impurity concentration or lattice distortion. However, the term direct combination also often appears in refractory materials, mainly alkaline refractory literature, here is a brief introduction.

2. Chemical bonding. A bond formed by hardening at room temperature or higher through a chemical reaction (not a hydration reaction), including inorganic or inorganic-organic complex bonds. This combination is common in all kinds of non-fired products.

3, hydration combination. A bond formed at room temperature by a chemical reaction of a fine powder with water to coagulate and harden. This combination is common in castables. Such as cement binding castable.

4. Organic combination. A bond formed by the hardening of organic substances at room temperature or slightly higher. This combination is commonly seen in unburned products.

5. Resin bonding. Refractories containing resins are heated at lower temperatures, resulting in bonding due to resin curing and carbonization. It is mainly found in carbon-containing refractories.

6. Asphalt/tar combination. A bond produced by asphalt/tar in pressed non-fired refractories.

The categories mentioned above are not absolute. In fact, in several forms such as hydration bonding, organic bonding, resin bonding and asphalt/tar bonding, some chemical reaction occurs to a certain extent during the combination formation process. Resin bonding with asphalt/tar can also be incorporated into organic bonding. This classification method is only artificial division according to various commonly used binders.

In refractories, various combinations can exist alone or simultaneously. Usually people in a certain combination of the main refractories into a certain combination refractory.