Types and physical properties of common refractory materials

1、 What is refractory material?

Refractory materials generally refer to inorganic non-metallic materials with a fire resistance of over 1580. It includes natural ores and various products made through certain processes according to certain purpose requirements. Having certain high-temperature mechanical properties and good volume stability, it is a necessary material for various high-temperature equipment. It has a wide range of uses.

2、 Types of refractory materials

1. Acid refractory materials usually refer to refractory materials with a SiO2 content greater than 93%. Its main characteristic is that it can resist the erosion of acidic slag at high temperatures, but is easy to react with alkaline slag. Acid refractory materials commonly used include silica bricks and clay bricks. Silicon bricks are siliceous products containing over 93% silicon oxide, using raw materials such as silica and waste silicon bricks. They have strong resistance to acid slag erosion, high load softening temperature, and do not shrink in volume after repeated calcination, even slightly expanding; But it is susceptible to erosion by alkaline slag and has poor thermal vibration resistance. Silicon bricks are mainly used in thermal equipment such as coke ovens, glass furnaces, and acid steelmaking furnaces. Clay bricks are mainly made of refractory clay and contain 30% to 46% alumina. They are weakly acidic refractory materials with good thermal vibration resistance and corrosion resistance to acidic slag, and are widely used.

2. Alkaline refractories generally refer to refractories with magnesium oxide or magnesium oxide and Calcium oxide as the main components. This type of refractory material has a high fire resistance and strong resistance to alkaline slag. For example, magnesia brick, magnesia chrome brick, chrome magnesia brick, magnesia alumina brick, dolomite brick, Forsterite brick, etc. Mainly used for alkaline steelmaking furnaces, non-ferrous metal smelting furnaces, and cement kilns.

3. Aluminosilicate refractories refer to refractories with SiO2-Al2O3 as the main component. According to the content of Al2O3, they can be divided into semi siliceous (Al2O3 15~30%), clayey (Al2O3 30~48%) and high alumina (Al2O3 more than 48%).

4. Molten refractory material refers to a refractory product with a certain shape that is poured from a mixture melted at high temperature using a certain method.

5. Neutral refractory materials refer to refractory materials that are not easily reactive with acidic or alkaline slag at high temperatures, such as carbon refractory materials and chromium refractory materials. Some also classify high alumina refractory materials as such.

6. Special refractory materials are a new type of inorganic non-metallic materials developed on the basis of traditional ceramics and general refractory materials.

7. Unshaped refractory materials are mixtures composed of refractory aggregates and powders, binders, or other admixtures in a certain proportion, which can be directly used or mixed with appropriate liquids before use. Unshaped refractory material is a new type of refractory material without calcination, with a fire resistance of not less than 1580.


3、 What are the commonly used refractory materials?

Commonly used ordinary refractory materials include silica bricks, semi silica bricks, clay bricks, high alumina bricks, magnesium bricks, etc.

Special materials often used 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; Calcium oxide, chromium oxide, aluminum oxide, magnesium oxide, Beryllium oxide and other refractories.

The commonly used insulation refractory materials include diatomaceous earth products, asbestos products, insulation boards, etc.

The commonly used amorphous refractory materials include furnace repair materials, refractory ramming materials, refractory casting materials, refractory plastic, refractory mud, refractory gunning materials, refractory projection materials, refractory coatings, lightweight refractory casting materials, gun mud, ceramic valves, etc.


4、 What are the physical properties of refractory materials?

The physical properties of refractory materials include structural performance, thermal performance, mechanical performance, service performance, and operational performance.

The structural properties of refractory materials include porosity, bulk density, water absorption, permeability, and pore size distribution.

The thermal properties of refractories include thermal conductivity, coefficient of thermal expansion, specific heat, heat capacity, thermal conductivity, Thermionic emission, etc.

The mechanical properties of refractories include compressive strength, tensile strength, flexural strength, torsional strength, Shear strength, impact strength, abrasion resistance, creep, bonding strength, elastic modulus, etc.

The performance of refractory materials includes fire resistance, load softening temperature, change in firing line, thermal shock resistance, slag resistance, acid resistance, alkali resistance, hydration resistance, CO corrosion resistance, conductivity, oxidation resistance, etc.

The workability of refractory materials includes consistency, slump, flowability, plasticity, adhesion, rebound, setting, hardening, etc.


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