Recently, as a new refractory material, zircon refractory material has been developed. In the refractory industry, natural zircon minerals and artificial extracted or synthetic zircon oxides and composite oxides have been widely developed.
Zircon materials have been more widely used in the glass industry, metallurgical industry, cement industry, ceramics industry and refractory industry, due to high melting temperature, good chemical stability, good thermal shock, and good resistance to molten metals, slags or glass liquid.
Zircon materials are mainly used in the melting zone, superstructure, sidewall and throat. Zircon refractory materials mainly include dense zircon brick, fused cast AZS block, fused cast zircon mullite brick and rebounded AZS brick.
Zircon materials have a wide application in the metallurgical industry. According to the material, zircon materials can be divided into zircon brick, zirconite bricks, alumina zircon carbon products, zircon carbon products, zirconic acid calcium products, zirconium diboride products and zirconium oxide modified refractories.
Zirconite products have good high temperature resistance, good resistance to acid slags, low thermal expansion coefficient and good thermal shock resistance. It can be used in the ladle lining and critical parts such as the slag line and the outlet. It can also be used in the ladle nozzle, tundish nozzle and pocket block.
Wednesday, January 20, 2016
Thursday, January 14, 2016
Features of Semi-Silica Bricks
Semi-silica brick is an aluminosilicate refractory product containing 15-30% Al2O3. It is usually made of fire clay containing quartz, pyrophyllite (Al2O3 · 4SiO2 · H2O), refractory clay or tailings of kaolin.
According to the manufacturing method, semi-silica brick can be divided into fired brick and unfired brick. Unfired bricks are made with water glass as the binding agent. The manufacturing process of fired bricks is similar to that of fire clay brick.
Whether to add clinkers is up to the properties of raw materials and refractory bricks. Siliceous clay has small firing shrinkage and the clinker is not required. In order to improve the thermal shock resistance of semi-silica bricks, 10%-20% clinker is added.
If the raw materials contain a few fusible materials and coarse quartz grains, semi-silica bricks have low density and poor strength but good thermal shock resistance and high softening temperature under load. On the contrary, the refractory bricks have bad refractory performance and poor thermal shock resistance. Besides, according to the working conditions, fine or coarse quartz or silica clinker is added.
Under 1250℃, semi-silica brick has small volume shrinkage. At high temperature, with the increase of the liquid phase, the brick has large volume shrinkage. So, its firing temperature is higher than that of the fire clay brick, generally within 1350℃-1410℃ to obtain high density refractory bricks.
When pyrophyllite is used as the raw material of semi-silica brick, the manufacturing method is up to the chemical composition of pyrophyllite. The main chemical composition of pyrophyllite has small weight loss after dehydrated and can maintain its lattice structure. It can be directly used to manufacture bricks. In order to avoid firing expansion, it can also be calcined into clinker and added when batching.
Semi-silica brick has good volume stability at high temperature and can help to improve the integrity of the masonry and reduce the slag erosion to the masonry. When contacting hot slag, it can from a layer of glaze-like substances on the surface which can block pores, prevent the penetration of slags into the brick.
Semi-silica brick is mainly used in the ladle lining and the refractory layer of the lower steel casting system. In addition, it is also used in the roof of heating furnaces, regenerator checker bricks, the lining of Cupola furnaces, the hearth and flues of furnaces.
According to the manufacturing method, semi-silica brick can be divided into fired brick and unfired brick. Unfired bricks are made with water glass as the binding agent. The manufacturing process of fired bricks is similar to that of fire clay brick.
Whether to add clinkers is up to the properties of raw materials and refractory bricks. Siliceous clay has small firing shrinkage and the clinker is not required. In order to improve the thermal shock resistance of semi-silica bricks, 10%-20% clinker is added.
If the raw materials contain a few fusible materials and coarse quartz grains, semi-silica bricks have low density and poor strength but good thermal shock resistance and high softening temperature under load. On the contrary, the refractory bricks have bad refractory performance and poor thermal shock resistance. Besides, according to the working conditions, fine or coarse quartz or silica clinker is added.
Under 1250℃, semi-silica brick has small volume shrinkage. At high temperature, with the increase of the liquid phase, the brick has large volume shrinkage. So, its firing temperature is higher than that of the fire clay brick, generally within 1350℃-1410℃ to obtain high density refractory bricks.
When pyrophyllite is used as the raw material of semi-silica brick, the manufacturing method is up to the chemical composition of pyrophyllite. The main chemical composition of pyrophyllite has small weight loss after dehydrated and can maintain its lattice structure. It can be directly used to manufacture bricks. In order to avoid firing expansion, it can also be calcined into clinker and added when batching.
Semi-silica brick has good volume stability at high temperature and can help to improve the integrity of the masonry and reduce the slag erosion to the masonry. When contacting hot slag, it can from a layer of glaze-like substances on the surface which can block pores, prevent the penetration of slags into the brick.
Semi-silica brick is mainly used in the ladle lining and the refractory layer of the lower steel casting system. In addition, it is also used in the roof of heating furnaces, regenerator checker bricks, the lining of Cupola furnaces, the hearth and flues of furnaces.
Tuesday, January 12, 2016
The Application of Insulation Materials in Heating Furnaces
Insulation materials are always used as the insulation layer and lining of heating furnaces. It can reduce heat loss and save energy. There are a variety of insulation materials, including lightweight refractory products, insulation monolithic materials and refractory fiber products.
The roofs of the heating zone and soaking zone are constructed with high alumina hanging brick, with a layer of insulation board laid over it. The wall is successively constructed with high alumina brick, fire clay brick, fire clay insulation brick and insulation board. The bottom of heating zone is constructed with magnesia chrome brick, magnesia brick, fire clay brick, fire clay insulation brick and insulation board. The lining of the preheating zone is constructed with fire clay brick. Recently, more and more refractory castables are used in the heating furnace. High alumina cement, refractory castables, clay bonding refractory castables and lightweight casting materials is used in the lining.
Lightweight refractory products mainly include silica insulation brick, fire clay insulation brick, high alumina insulating brick and alumina bubble brick. The bulk density of lightweight refractory products is generally 0.6-1.2g/cm3. Its service temperature is 900-1350℃. alumina bubble brick can be used below 1800℃ for a long time.
Refractory fiber is a type of new efficient fibrous refractory insulation material. The main manufacturing methods include Melting-blowing method, high-speed centrifugation method and colloidal method.
Refractory fiber products mainly include ceramic fiber, zirconia ceramic fiber, high-purity high alumina ceramic fiber, polycrystalline mullite fiber, alumina fiber and zirconia fiber. Besides, materials for low temperature insulation include slag wool and glass fiber.
Refractory fiber products have low bulk density, low thermal conductivity, good thermal stability and mechanical shock resistance. It is soft and easy to cut and construct. Using refractory fiber as the lining can effectively reduce heat loss, save energy and rise the temperature.
The roofs of the heating zone and soaking zone are constructed with high alumina hanging brick, with a layer of insulation board laid over it. The wall is successively constructed with high alumina brick, fire clay brick, fire clay insulation brick and insulation board. The bottom of heating zone is constructed with magnesia chrome brick, magnesia brick, fire clay brick, fire clay insulation brick and insulation board. The lining of the preheating zone is constructed with fire clay brick. Recently, more and more refractory castables are used in the heating furnace. High alumina cement, refractory castables, clay bonding refractory castables and lightweight casting materials is used in the lining.
Lightweight refractory products mainly include silica insulation brick, fire clay insulation brick, high alumina insulating brick and alumina bubble brick. The bulk density of lightweight refractory products is generally 0.6-1.2g/cm3. Its service temperature is 900-1350℃. alumina bubble brick can be used below 1800℃ for a long time.
Refractory fiber is a type of new efficient fibrous refractory insulation material. The main manufacturing methods include Melting-blowing method, high-speed centrifugation method and colloidal method.
Refractory fiber products mainly include ceramic fiber, zirconia ceramic fiber, high-purity high alumina ceramic fiber, polycrystalline mullite fiber, alumina fiber and zirconia fiber. Besides, materials for low temperature insulation include slag wool and glass fiber.
Refractory fiber products have low bulk density, low thermal conductivity, good thermal stability and mechanical shock resistance. It is soft and easy to cut and construct. Using refractory fiber as the lining can effectively reduce heat loss, save energy and rise the temperature.
Wednesday, January 6, 2016
Rebonded fused cast AZS block
Rebonded fused cast AZS block is made of AZS frit or waste fused cast AZS block by adding a small amount of kaolin or alumina as binder. Rebonded fused cast AZS block is composed of A12O3 (50-60%), ZrO2 (20-30%) and SiO2 (14-20%).
When heated to a certain temperature, glass phase exuded by fused cast AZS forms mullite with binding agents. Bricks should be fired at 1600-1700℃. The frits should have homogeneous chemical composition and a low content of glass phase. Waste bricks have non-homogeneous composition and a high content of glass phase (15%-25%).
When Fused cast AZS is heated, glass phase is melted and exuded. The exuded glass phase has peritectic reaction with the main crystal phase and forms mullite. In this case, mullite and ZrO2 coexists with each other by wrapping and being wrapped. It makes the fused cast AZS scraps fired into a solid brick. The finer the fused cast AZS scraps are, the bigger the specific surface of glass phase is.
After sintered, rebonded fused cast AZS block has a significant change in microstructure.
1) Glass phase in the fine fused cast AZS reacts with Al2O3 and forms mullite.
2) Glass phase in the coarse granular materials is exuded to the surface and forms a mullite layer by reacting with Al2O3. The layer encloses the liquid exuding channel and ensures the peritectic reaction happens within the particles.
3) After glass phase in the coarse granular materials is all exuded, voids and cracks are left.
Compared to fused cast AZS block, rebonded fused cast AZS block has a higher exudation temperature of glass phase. It has good thermal shock resistance, high temperature mechanical properties, creep resistance and corrosion resistance to glass.
When heated to a certain temperature, glass phase exuded by fused cast AZS forms mullite with binding agents. Bricks should be fired at 1600-1700℃. The frits should have homogeneous chemical composition and a low content of glass phase. Waste bricks have non-homogeneous composition and a high content of glass phase (15%-25%).
When Fused cast AZS is heated, glass phase is melted and exuded. The exuded glass phase has peritectic reaction with the main crystal phase and forms mullite. In this case, mullite and ZrO2 coexists with each other by wrapping and being wrapped. It makes the fused cast AZS scraps fired into a solid brick. The finer the fused cast AZS scraps are, the bigger the specific surface of glass phase is.
After sintered, rebonded fused cast AZS block has a significant change in microstructure.
1) Glass phase in the fine fused cast AZS reacts with Al2O3 and forms mullite.
2) Glass phase in the coarse granular materials is exuded to the surface and forms a mullite layer by reacting with Al2O3. The layer encloses the liquid exuding channel and ensures the peritectic reaction happens within the particles.
3) After glass phase in the coarse granular materials is all exuded, voids and cracks are left.
Compared to fused cast AZS block, rebonded fused cast AZS block has a higher exudation temperature of glass phase. It has good thermal shock resistance, high temperature mechanical properties, creep resistance and corrosion resistance to glass.
Sunday, January 3, 2016
The Classification of Alpha-Beta Fused Cast Alumina Block
As we all know, alpha-beta fused cast alumina block is widely used in industrial furnaces. It is composed of alpha alumina and beta alumina crystals in a most ideal proportion which is approximately 50% and 50% respectively, where intertwined crystals of both materials result in a very dense structure.
Alpha-beta fused cast alumina block is made of high quality fused alumina as the raw material.
1) White fused alumina
White fused alumina is made of industrial alumina powder as the raw material. It is melted in an arc electric furnace and crystalized by cooling. White fused alumina is white and abbreviated as WFA.
2) Dense fused alumina
Dense fused alumina is made of industrial alumina powder as the raw material with the addition of additives. It is melted in an arc electric furnace and crystalized by cooling. It is gray or hoary and abbreviated as OFA.
3) Sub-white fused alumina
Sub-white fused alumina is also called high alumina corundum. It is made of bauxite as the main raw material with addition of additives. It is melted in an arc electric furnace and crystalized by cooling. It is brown grey or gray and abbreviated as SFA.
4) Gray fused alumina
Gray fused alumina is made of bauxite as the main raw material with addition of additives. It is melted in an arc electric furnace and crystalized by cooling. It is chocolate brown and abbreviated as BFA.
Below 1350 degree, alpha-beta fused cast alumina block has excellent corrosion resistance to glass liquid. It is widely used in the working tank of glass furnaces.
Alpha-beta fused cast alumina block is made of high quality fused alumina as the raw material.
1) White fused alumina
White fused alumina is made of industrial alumina powder as the raw material. It is melted in an arc electric furnace and crystalized by cooling. White fused alumina is white and abbreviated as WFA.
2) Dense fused alumina
Dense fused alumina is made of industrial alumina powder as the raw material with the addition of additives. It is melted in an arc electric furnace and crystalized by cooling. It is gray or hoary and abbreviated as OFA.
3) Sub-white fused alumina
Sub-white fused alumina is also called high alumina corundum. It is made of bauxite as the main raw material with addition of additives. It is melted in an arc electric furnace and crystalized by cooling. It is brown grey or gray and abbreviated as SFA.
4) Gray fused alumina
Gray fused alumina is made of bauxite as the main raw material with addition of additives. It is melted in an arc electric furnace and crystalized by cooling. It is chocolate brown and abbreviated as BFA.
Below 1350 degree, alpha-beta fused cast alumina block has excellent corrosion resistance to glass liquid. It is widely used in the working tank of glass furnaces.
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