There are many kinds of refractories, which can be classified according to their different characteristics such as shape, composition and use. The following are the main classification methods and specific types of refractories:
I. Classification by morphology
(1) Shaped refractory materials
Shaped refractory refers to a product with a fixed shape, which is usually used for lining or structural parts of high-temperature equipment. Common shaped refractories include:
firebrick
Clay brick: clay is the main raw material, and its fire resistance is about 1580℃. It has good thermal shock resistance and slag resistance and is suitable for lining of general industrial furnaces.
High alumina brick: It contains a high proportion of alumina (Al₂O₃), usually more than 48%, and its fire resistance can reach more than 1750℃. It has high strength and corrosion resistance, and is widely used in iron and steel smelting furnaces and glass melting furnaces.
Silicon brick: The main component is silicon dioxide (SiO₂), with fire resistance above 1690℃ and good acid corrosion resistance. It is often used in glass melting furnaces and ceramic kilns.
Magnesia brick: The main component is magnesium oxide (MgO), and its fire resistance is above 2000℃. It has good alkaline corrosion resistance and is suitable for alkaline environment, such as lining of steelmaking furnace.
Silicon carbide brick: The main component is silicon carbide (SiC), which has extremely high hardness and good thermal shock resistance and is suitable for the bottom and wall of high temperature furnace.
insulating brick
Lightweight clay brick: made by adding porous materials, it has low thermal conductivity and is used for heat insulation.
Foam brick: it contains a lot of air holes, which has good heat insulation performance, light weight and convenient construction.
Micro-porous insulating brick: It is made by a special process and contains tiny pores, which has excellent thermal insulation performance and is often used as the thermal insulation layer of high-temperature furnaces.
(2) unshaped refractories
The unshaped refractory has no fixed shape, so it is usually shaped according to the needs in site construction. Common unshaped refractories include:
Refractory castable
Clay castable: clay is the main raw material, which has good construction performance and corrosion resistance, and is suitable for lining of general industrial furnaces.
High alumina castable: contains a high proportion of alumina, has high fire resistance and high strength, and is suitable for high temperature environment.
Steel fiber reinforced castable: steel fiber is added to castable to improve the thermal shock resistance and impact resistance of the material, which is often used in furnace wall and bottom.
plastic refractory
Clay plastic refractory: It has good plasticity and convenient construction, and is suitable for repair and local protection.
High alumina plastic refractory: It has high fire resistance and good corrosion resistance, and is suitable for high temperature environment.
refractory mortar
Clay refractory mud: it is used to build the joints of refractory bricks, with good cohesiveness and corrosion resistance.
High alumina refractory mud: high refractoriness, suitable for high temperature environment.
II. Classification by chemical composition
(1) Acid refractories
Acid refractories mainly contain silicon dioxide (SiO₂), which has good acid corrosion resistance. Common acid refractories include:
Silicon brick: the main component is silicon dioxide, and the fire resistance is above 1690℃, which is suitable for glass melting furnaces and ceramic furnaces.
Quartz brick: The main component is Shi Ying, which has high fire resistance and excellent acid corrosion resistance.
(2) basic refractory
Basic refractory mainly contains magnesium oxide (MgO) or calcium oxide (CaO), which has good alkaline corrosion resistance. Common basic refractory include:
Magnesium brick: the main component is magnesium oxide, and its fire resistance is above 2000℃, which is suitable for lining of steelmaking furnace.
Dolomite brick: the main component is dolomite, which has high fire resistance and good alkaline corrosion resistance.
(3) Neutral refractories
Neutral refractories have certain resistance to both acidic and alkaline corrosion. Common neutral refractories include:
High-alumina brick: the main component is alumina, and its fire resistance is above 1750℃, which is suitable for various high-temperature environments.
Silicon carbide brick: the main component is silicon carbide, which has good thermal shock resistance and corrosion resistance, and is suitable for the bottom and wall of high temperature furnace.
Corundum brick: the main component is alumina, which has high fire resistance and high strength and is suitable for high temperature environment.
III. Classification by purpose
(1) Refractory materials for industrial furnaces
Refractory materials for iron and steel smelting furnaces: such as high alumina bricks, magnesia bricks, silicon carbide bricks, etc., are used in iron-making blast furnaces, steel-making converters, electric furnaces, etc.
Refractory materials for glass melting furnace: such as silicon brick and zirconium brick, etc., which are used for the furnace body and tank wall of glass melting furnace.
Refractory materials for ceramic kilns: such as clay bricks, high alumina bricks, etc., are used for the body and kiln furniture of ceramic firing kilns.
(2) Refractory materials for heat insulation
Insulating brick: such as light clay brick, foam brick, microporous insulating brick, etc., used as heat insulation layer of high temperature furnace.
Thermal insulation fiber products: such as ceramic fiber blanket, ceramic fiber board, etc., have good thermal insulation performance and low thermal conductivity.
(3) Special purpose refractories
Corrosion-resistant refractory materials: such as acid-resistant bricks and alkali-resistant bricks, which are used in the corrosion-resistant environment in the chemical industry.
High-temperature wear-resistant refractory materials: such as silicon carbide bricks and corundum bricks, which are used for wear-resistant parts in high-temperature environment.
IV. Classification by production process
(1) Fired refractory materials
Fired refractories are made by high temperature sintering process, which has high strength and refractoriness. Common fired refractories include:
Burnt brick: such as clay brick, high alumina brick, silicon brick, etc.
Fired products: such as fired ceramic fiber modules.
(2) Non-fired refractory materials
Non-fired refractories are made by chemical bonding agents or physical methods, and do not need high temperature firing. Common unfired refractories include:
Refractory castable: It is solidified by chemical binder (such as aluminate cement).
Plastic refractory: Forming by physical methods (such as compaction).
Refractory mud: solidified by chemical bonding agent.
V. Classification by microstructure
(1) Dense refractory materials
Dense refractories have high density and strength and are suitable for high temperature environment. Common dense refractories include:
High alumina brick: It has high density, high strength and high fire resistance.
Corundum brick: It has extremely high density and strength and high fire resistance.
(2) Porous refractory materials
Porous refractory contains a large number of pores and has good thermal insulation performance. Common porous refractories include:
Insulating brick: such as lightweight clay bricks and foam bricks.
Ceramic fiber products: such as ceramic fiber carpet, ceramic fiber board, etc.
VI. Classification by Special Performance
(1) Thermal shock-resistant refractories
Thermal shock-resistant refractories can maintain structural integrity when the temperature changes sharply. Common thermal shock-resistant refractories include:
Silicon carbide brick: it has good thermal shock resistance and is suitable for the bottom and wall of high temperature furnace.
Nano-composite refractories: improving thermal shock resistance through nano-technology.
(2) Oxidation-resistant refractory materials
Oxidation-resistant refractories can remain stable in high-temperature oxidation environment. Common antioxidant refractories include:
Silicon carbide brick: It has good oxidation resistance.
Corundum brick: It has good oxidation resistance.
(3) High-temperature wear-resistant refractory materials
High-temperature wear-resistant refractories can resist wear in high-temperature environment. Common high-temperature wear-resistant refractories include:
Silicon carbide brick: It has high hardness and good wear resistance.
Corundum brick: It has high hardness and good wear resistance.
VII. Summary
There are many kinds of refractories, which can be classified according to their morphology, chemical composition, use, production technology, microstructure and special properties. Each type of refractory has its unique properties and application fields, which can meet the needs of different high-temperature environments. In practical application, the selection of suitable refractories needs to comprehensively consider its performance, cost and use environment to ensure the safe operation and efficient production of equipment.
