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Персональный блог REFRACTORY — Это просто Вьюи блог
Персональный блог REFRACTORY — Это просто Вьюи блог
The mostly applied type of refractory in the glass industry, in direct contact with the glass melt, is fused cast AZS block.
Zirconia is a very insoluble oxide in most glass melts and therefore has great corrosion resistance. However, in addition to being very expensive, zirconia has a tendency to crack during manufacture and use, and is very difficult to make in large shapes. Zirconia is therefore combined with oxides, usually alumina and silica, to descrease the solubility of the composite refractory.
The fused cast AZS block is produced by melting the raw materials in an electric arc furnace at about 2200-2400 ℃. The melt is treated with oxygen to oxidize zirconium oxy-carbo-nitride or other reduced constituents, produced by the reaction with the graphite electrodes during melting. The molten material is then cast into molds to, or very near to, the final shape of the block desired. The mold with the fused cast ceramic is cooled down very slowly in order to anneal (free of thermal stresses) the fused cast product.
The fused cast AZS block is available in a number of grades, principally distinguished by zircon content: 33#, 36# and 41#. Among the three, 33# and 41# are most widely used. For the most severe applications, the 41# is recommeded. For less severe applications, 33# is used.
The AZS fused cast 33# block contains 33% ZrO2. It is unlikely to cause defections of stones, blisters and cords. Therefore, it is most suitable for superstructures of melters, side walls of refiners, paving blocks, and forehearth channel blocks.
The AZS fused cast 36# block contains 36% ZrO2. It is corrosion resistant and shows minimal contamination against molten glass. It is most suitable for glass contact parts of melters, and has shown considerable results in side walls and paving blocks.
The AZS fused cast 41# block contains 41% ZrO2. It is highly corrosion resistant against molten glass, and by strengthening matrix glass, it shows minimal contamination to molten glass. It is most suitable for glass melting furnaces; on throats of parts that demand high corrosion resistance, dog house corner blocks, electrode blocks, bubbler blocks and electric furnaces.
The AZS fused cast block from Sunrise Refractory has passed the ISO international certified. High purity raw material, scientific formula, advanced technology and professional guide all contribute to our qualified azs blocks production.
Alpha alumina is one of the most important ceramic materials with properties and applications having been thoroughly explored. Fused Cast Alpha Alumina block comprises about 99% alumina (90% alpha alumina and 4% beta Al2O3), 0.4% SiO2 and 0.9% Na2O.
Alumina (Al2O3) is an aluminium compound with many crystalline forms or polymorphs. Alumina exists in many forms, α, χ, η, δ, κ, θ, γ, ρ. Alpha alumina or corundum is the only thermodynamically stable form amongst the different polymorphs. Alpha alumina stable at very high temperature and this property is also used as refractory and thermal barrier.
Alumina is characterized with high compression strength, high hardness, good resistance to abrasion, high resistance to chemical attack, high thermal conductivity, good resistance to thermal shock, and high degree of refractoriness.
Its applications are widespread, and include spark plugs, tap washers, pump seals, electronic substrates, grinding media, abrasion resistant tiles, cutting tools, bioceramics, (hip-joints), body armour, laboratory ware and wear parts for the textile and paper industries. It is also used in the manufacture of monolithic and brick refractories. It is also used mixed with other materials such as flake graphite for even more severe applications.
Fused Cast Alpha Alumina block is relatively resistant to molten glass corrosive action, though not at the level of Baddeleyite. Most importantly, it does not develop a passivation layer like fused cast AZS refractory. It dissolves slowly in the glass through a concentration gradient at the contact surface. Temperature and glass velocity tangential to the surface determine the corrosion speed.
Fused cast alpha alumina block is an ideal product for the lower temperature zones of the glass melting furnaces due to its high density, superior corrosion resistance and low blister potential. It is also an ideal material for Metallurgical Titanium Furnace because the superior thermal stability.
Refractoriness points to temperature at which the material softens. Refractoriness under load (RUL) is a measure of the deformation behavior of refractory ceramic products subjected to a constant load and increasing temperature.
RUL is a critical property for refractory bricks, which basically reflects the service temperature of the bricks, raw materials, etc. The RUL is of great importance to check the suitability of refractory products for high-temperature applications. It gives an indication of the temperature at which the bricks will collapse, in service conditions with similar load. The refractoriness is indicated by PCE (Pyrometric cone equivalent). It should be higher than the application temperatures.
Refractoriness decreases when refractory is under load. Refractoriness under load is an important consideration because usually a refractory fails at a lower temperature when subjectured to load. Therefore more important is refractoriness under load (RUL) rather than refractoriness.
The refractoriness under load test (RUL test) gives an indication of the temperature at which the bricks will collapse, in service conditions with similar load. However, under actual service where the bricks are heated only on one face, most of the load is carried by the relatively cooler rigid portion of the bricks. Hence the RUL, test gives only an index of the refractory quality, rather than a figure which can be used in a refractory design. Under service conditions, where the refractory used is heating from all sides such as checkers, partition walls, etc. the RUL test data is quite significant.
It is generally measured as the softening temperature. It is necessary that a refractory material should have a softening temperature higher than the operating temperature of the furnace in which it is to be used. Most of the commercial refractories do not exhibit sharp melting points and they soften gradually over a range of temperatures. The temperature range in which the softening of refractory products occurs is not identical with the melting range of the pure raw material; therefore it must be reliably determined.
RUL values(T0.6 @0.2MPa) for fireclay-based refractory bricks are usually below 1500 °C, medium duty fireclay bricks only at about 1300 °C, high duty fireclay bricks at 1350 to 1420 °C, and superduty fireclay bricks between 1420 to 1500 °C (sometimes even higher than 1500 °C). Such properties could vary depending different industrial standards, different companies in different areas.
Sunrise Refractory is a refractory supplier from China, specializing in manufacturign various types of refractories for glass industry including fused cast AZS 33#,36#,41#, glass furnace fireclay bottom block, mullite brick, zircon brick, alumina bubble brick, sillimanite brick, corundum brick, low porosity fireclay brick, high alumina brick, all kinds of glass furnace ramming masses, sealing materials, building fireclay, etc.
The cold crushing strength is the resistance of the refractory to crushing, which mostly happens during transport. It has an useful indicator to refractory performance and to the adequacy of firing and abrasion resistance in consonance with other properties such as bulk density and porosity.
The Cold Crushing Strength tells us how much load that refractory can bear in cold conditions. Generally, the higher the Cold Crushing Strength of a material is the greater should be the resistance to abrasion. But too high Cold Crushing Strength normally cause an increased brittleness, which may lead to premature spalling under sever operating conditions.
Also refractories with high Cold Crushing Strength are expected to have higher resistance to slag attack. Cold Crushing Strength is also highly important in case of insulating refractory bricks where bricks have to be porous as well as strong.
The Cold Crushing Strength can be determined by following the steps given in any of the Standard Methods for Refractory Testing like - ASTM, Indian Standards (IS), Ghost, DIN etc. CCS is not a measure of performance at elevated temperature. It measures the mechanical strength at room temperature. It is not indicative of mechanical strength at operating temperature.
The variation in cold crushing strength is as a result of variation in their chemical composition. For Alumina refractories, as the alumina content increases, the cold crushing strength also increases. The absence of oxide impurities (i.e. Fe2O3 and CaO) and the addition of Cr2O3 can double the cold crushing strength.
Sunrise Refractory is a refractory material supplier from China, offering high quality refractory materials with great Cold Crushing Strength.
Refractories are used at elevated temperatures for structural purposes and they are used in many cases to contain a high temperature corrosive environment. In any process environment, refractories are potentially continuously under attack from a number of corrosive processes.
The corrosion envirenment usually contains materials and byproducts of the process in chemical reactions with the refractory at elevated temperatures resulting in refractory consumption or wear, potentially causing glassing or softening of the refractories. It is usually not immediately obvious, but the oxidation and reduction state of the environment can participate in and influence the chemical reactions that take place. Along with chemical reaction during corrosion, physical changes occur that may be accelerated by the corrosion process.
Erosion is another prevalent refractory wear mechanism. Refractories can be worn away over time from the washing action of moving liquids, such as molten metals or slags. Erosion further exposes refractory to destruction by corrosive or abrasive elements.
Abrasive media, including fuel, ash, and other particles, can wear away refractories over time, much like sandblasting. Refractory resistance against abrasion is a key issue for many industrial furnace applications.
Moving parts and equipment within a process can wear against the refractory lining, jeopardizing the structural integrity of the refractory lining.
As refractories undergo the heating and cooling cycles of a process, the refractories expands and contracts, eventually weakening and wearing down the lining. If refractories experiences a rapid change in temperature, a.k.a Thermal Shock, the refractories can experience immediate damage.
As a result of the high temperature corrosive environment, refractories will wear down over time, requiring periodic maintenance and eventual replacement. Refractory wear can be mitigated or minimized by selecting the right refractories to withstand the corrosive environments.
Sunrise Refractory offers a wide range of refractories with good wear resistance for high temperature corrosive environments in glass industry.
Silica brick is a kind of acid refractory containing at least 93% SiO2. It is mainly made from tridymite, cristobalite and a small amount of residual quartz as well as glass phase. Various grades of silica bricks have been used in different industries such as the iron and steel industry, glass and ceramic industry, and metallurgy industry.
The raw material is natural silica sand of which SiO2 content should be more than 96%. The higher SiO2 content in silica sand, the higher temperature silica bricks resist.
Silica bricks feature high purity, long service life, good thermal conductivity, high refractoriness under load, and good creep resistance. In addition, it has accurate size tolerance, pure color and luster appearance.
One of the outstanding characteristics of silica bricks is that silica brick does not begin to soften under high loads until its fusion point is approached. This behavior contrasts with that of many other refractories, for example alumina silicate materials, which begin to fuse and creep at temperatures considerably lower than their fusion points.
Another of the outstanding characteristics of silica bricks is their resistance to corrosion by acid slag and iron oxide, but they are easily attacked by basic slag.
The drawback of silica bricks is bad thermal shock resistance because large volume changes take place at elevated temperatures during conversion from one modification to another. Therefore it is mainly used in the continuous operating furnace.
The silica brick can be widely used in coke oven, hot blast furnace, glass furnace and carbon furnace as well as for hot repairs. In glass industry, it is mainly employed to build the roof and superstructure, doghouse crown, suspended wall of channel, top crown and inlet sealing. In metallurgy industry, it is adopted as the steel making open hearth regenerator, slag pocket, soaking pit and nozzle brick. In ceramic kilns, it is used in arch crown and other weight bearing areas, hot blast furnace and acid open hearth. It is also used to build the partition walls in coke oven carbonization and burning chamber.
Adopting high quality raw materials and advanced technology, Sunrise Refractory offers various grades of silica bricks of high quality and excellent performance for different applications.
Magnesium alumina spinel brick is a kind of advanced alkaline refractory material with perriclase as main phase magnesia alumina spinel clinker as basic material. Superior strength at ambient and elevated temperatures, better corrosion, erosion and abrasion resistance and thermal shock resistance makes it an excellent refractory material.
Magnesium alumina spinel is a member of a group of oxides that have the same crystal structure, which is named the spinel structure. Magnesium aluminate spinel is synthesized and then added to magnesia refractory brick compositions in the range of 0–30 weight percentages. The final magnesium alumina spinel brick is featured with high refractoriness, superior thermal shock resistance, good temperature vibration, good corrosion resistance at high temperature.
Magnesia Chrome refractory has the similar features to magnesium alumina spinel brick, but the later is more eco-friendly. So magnesium alumina spinel brick can overcome health concerns against chromium containing refractories in various regions worldwide. It also imparts the improved thermal shock resistance normally compared to Magnesia Chrome refractory, but without the potential problem of hazardous waste disposal.
Magnesium alumina spinel brick has low thermal expansion coefficient, so it has excellent thermal shock resistance. The reversible thermal expansion of the spinel is approximately half that of the magnesia.
Magnesium alumina spinel brick has very high strength at both elevated and normal temperature and has no phase transition up to the melting temperature.
The drawback of magnesium alumina spinel brick is that they are more expensive than the conventional magnesite-chrome brick as the raw materials used to make the brick are expensive and some processing costs are high.
Magnesia alumina spinel brick is widely used in transition zone of cement rotary kilns, glass tank regenerators and lime kilns.
Aluminium Oxide (Al2O3) or alumina is one of the most versatile of refractory ceramic oxides and finds use in a wide range of applications. High alumina refractories are alumina refractories containing more than 45% alumina.
High alumina bricks is made of high-quality bauxite chamotte as raw materials by shaping at high pressure and sintering at high temperature. Alumina is one of the most chemically stable oxides known, which offers excellent hardness, strength and spalling resistance, which imparts high alumina refractories great features.
The alumina content ranges from 45 to 100%. The refractoriness of high alumina refractories increases with increase of alumina content. So high alumina refractories have high refractoriness and excellent high temperature performance.
High alumina refractories are a kind of acid refractories. Therefore, they have good resistance to acid slags. High alumina refractories are also featured with high cold crushing strength. As the alumina content increases, the cold crushing strength also increases. This makes them to bear more load during use. The high hardness of alumina imparts high wear and abrasion resistance.
Manufacturing cost and price of these brick increase more rapidly with % alumina content, so it is essential to determine experimentally or by test installations the most economical alumina content for each service. In some areas such as the regenerators, fire clay bricks can be used as a replacement for high alumina refractories.
Due to severe service conditions prevailing in modern reheating furnaces, there is an increasing tendency to use more and more of high alumina bricks in place of conventional fireclay bricks. The applications of high alumina refractories includes the hearth and shaft of blast furnaces, ceramic kilns, cement kilns, glass tanks and crucibles for melting a wide range of metals.
Sunrise Refractory is refractory supplier from China, providing high quality high alumina refractories in various shapes at competitive prices.
Fused cast Alumina block is made by fusing a mass of Alumina raw material of the desired composition to the molten condition, casting the fused material while molten into suitable molds, and cooling the cast material under controlled conditions to form a monolithic article of desired size and shape. Fused Cast Alumina are perfect complements to the AZS range for sensitive applications.
Fused cast Alumina blocks are available in 3 types: Alpha-Beta Fused cast Alumina Block, Alpha fused cast alumina block and Beta fused cast alumina block.
Alpha-Beta Fused cast Alumina Block is formed by the compact structure of approximately 50% alpha alumina and 50% beta alumina crystals respectively in a most ideal proportion, where intertwined crystals of both materials result in a very dense structure. It has excellent corrosion resistance against molten glass and great performance against contamination to molten glass, thus it is very suitable for paving blocks and fore-hearth channel blocks.
When in contact with molten glass, it barely produces any blistering or stones. So, Alpha-Beta alumina blocks may be widely used in working tank, feeder channels, superstructures and lipstone, etc. In general, in soda-lime container furnaces Alpha-Beta alumina fused-cast is installed in the Alcove and channel areas, as alternative to AZS fused-cast for Alcoves and as alternative to AZS fused-cast, sintered alumina and other sintered refractories for channels.
Alpha fused cast alumina block is an ideal product for the lower temperature zones of the glass melting furnaces due to its high density, superior corrosion resistance and low blister potential. It is also an ideal material for Metallurgical Titanium Furnace because the superior thermal stability.
Beta fused cast alumina block comprises of a majority of Beta alumina crystals and a slight portion of Alpha alumina crystals in compact structure. Moreover, the intersected texture of large Beta alumina ensures great dimensional stability and great resistance against spalling. Its property of base saturation enables a higher resistance to alkali vapor, thus it has excellent thermal shock resistance and does not form molten droplets. It is the best material for molter crown, port crown, feeder channel, ect.
Fused cast Alumina blocks are the typical glass contact materials for the end zones of furnaces when glass quality is the priority: TV Glass, high quality container glass, float glass. Its neutrality against alkali vapors makes it the best choice for the downstream part of superstructures in demanding applications.
Magnesia Carbon brick is a resin-bonded basic refractory brick made from dead-burned (sintered) or fused magnesia and graphite and bonded with high carbon containing pitch and resin, with some metallic powder as anti-oxidants to protect the carbon. Magnesia-Carbon bricks have many advantages over the conventional alumina brick lining.
Between 1975 and 1980 magnesia-carbon refractories were developed and started to be used in Japan first for electric arc furnace hot spots and shortly thereafter for BOFs.
The magnesia carbon brick is produced by adding a carbon-bonding formative agent to dead-burned (sintered) or fused magnesia and graphite, which are then pressed by the usual method and then subjected to heat treatment. It replaces pitch with resin and allows for a dramatic increase in the carbon level as a result of graphite additions. Subsequently, antioxidants are added to the magnesia-carbon brick to protect the carbon from oxidation and improve high temperature strength by the formation of carbides.
Carbon is added to refractories because it is not wetted by slags.The carbon can form a film blocking the slag penetration thereby minimizing the damage it causes to the brick. However, the weakness of carbide is easily oxidized in high temperature environment. In addition, as magnesia-carbon Brick is belong to one of resin-bond bricks, the resistant oxidation is low when they are operated in middle temperature.
The magnesia carbon bricks have high refractoriness as no low melting phase occurs between MgO and C. Because of the non-wetting of carbon, the magnesia carbon bricks prevent the penetration of slag and molten steel. As The magnesia carbon brick is made by high pressure, it shows excellent resistance to thermal shock and slag corrosion at elevated temperatures.
Graphite, the carbon source, has very low thermal expansion and very high thermal conductivity. So magnesia carbon bricks have low thermal expansion and high thermal conductivity, which make magnesia carbon bricks have excellent thermal shock resistance.
It is widely used in converters, BOF, EAF, ladles and refining furnaces as they possess superior slag penetration resistance and excellent thermal shock resistance at elevated temperature because of the non- wetting properties of carbon (graphite) with slag, high thermal conductivity, low thermal expansion and high toughness, etc.
Zhengzhou Sunrise Refractory Co., Ltd. is a refractory supplier from china, offering high quality Magnesia Carbon brick made from high quality dead-burned or fused magnesia and graphite.
The refractory lining plays a critical role for the total performance and reliable operation of the furnace. It can be the controlling factor in the success or failure of a furnace. The service life of the furnace depends mainly on the operating life of the refractory lining.
The following practices can be adopted while carrying out the refractory lining, in order to ensure longer operating life of the refractory lining.
The quality of the refractories used in pot furnace floor needs to be consistent and assured. Blocks are to be procured from reputed manufacturers, as the quality of such blocks can be expected to be uniform.
Using larger refractory blocks
The use of larger blocks reduces the number of joints while constructing a furnace lining. However, this does not always result in improvement of performance. The manufacturing of large blocks requires a high-capacity press for developing uniform property characteristics. Hence, it is necessary to consider the dimensions of the block and its properties to ensure its suitability for a particular application. Further, random samples from the procured lots should be analyzed to verify the manufacturer’s claim with the results obtained from sample analyses.
Use of anti-corrosive coating
The floor of the furnace is likely to be damaged due to the spillage of charge materials containing alkalis or due to contact with molten glass in case of pot failure. Sparking and corrosion are the main causes of wear and tear of refractories in industrial processes. The glass industry is no exception. Bricks with resistance to sparking and corrosion are preferable for using on the floor of the glass melting furnaces. Anti-corrosion coating materials particularly suitable for alkali attack could be considered. The coating should be uniform, and may be 5 mm thick.
The qualities of mortar used in the furnace lining should be similar to the refractory qualities and properties. Low shrinkage (less than 1%) high-alumina mortar should be used for joining the high-alumina blocks.
Anchors are used for almost all types of refractory applications. These are mostly metallic type. Lining failures due to inadequacies in the anchoring system are very common. Selecting the proper metallurgy, anchor dimensions, configurations, and spacing are very important to achieve the maximum service life of the lining. Where metal liners are used over the lining, the mechanical design should be sound and allow free movement of the liner on one end from its fixed positions.
blocks used in furnace lining should be accurate in dimensions and warpage-free.
Refractory materials can be categorized into two kinds: refractories bricks (shaped refractories) and monolithic refractories (unshaped refractories). Both have its pros and cons and applications in the refractory lines.
Refractories bricks are shaped refractories which have fixed shapes. The shapes of refractories bricks maybe divided into two types: standard shapes and special shapes. Standard shapes have dimensions that are conformed to by most refractory manufacturers and are generally applicable to kilns and furnaces of the same type. Special shapes are specifically made for particular kilns and furnaces. This may not be applicable to another furnaces or kiln of the same type.
Shaped Refractory bricks are almost always machine-pressed, thus, high uniformity in properties are expected. Special shapes are most often hand-molded and are expected to exhibit slight variations in properties.
Refractory bricks possess high thermal strength at elevated temperatures. Combined with chemical resistance to alkali attack, the performance is improved for areas with mechanical and chemical impact. These performance characteristics are important in where archways and belly band areas are exposed to mechanical wear and chemical attack. One advantage of refractory bricks over monolithic refractories is that the structural properties are defined during the production process.
Unshaped refractories are without definite form and are only given shape upon application. It forms joint less lining and are better known as monolithic refractories. These are categorized as plastic refractories, ramming mixes, castables, gunning mixes, fettling mixes and mortars.
Monolithic refractories exhibits properties that outperform traditional refractory bricks. They have better volume stability and better mechanical resistance to vibration and impact. Another advantage over fired bricks is that shrinkage and expansion of monolithic linings can be matched to the application. In some cases shrinkage can offset the thermal expansion resulting in a significantly different thermo-mechanical behavior compared to refractory bricks.
Use of Monolithic refractories eliminates difficult brick laying tasks and joints which may be accompanied with weakness in construction. Under certain conditions, monolithic linings of the same composition as firebrick provide better insulation, lower permeability and improved resistance to the spalling effects of thermal shock. With little or no preparation, monolithic refractories can be applied to form monolithic or joint free furnace linings in new constructions or to repair existing refractory lining.
Monolithic refractories are widely used in the construction of new kilns and furnaces and in the maintenance of older ones because substantial repairs can be made with a minimum loss of time and, in some cases, even during operations, and in a variety of other applications.
Fused Cast AZS blocks are the most widely used materials both in glass contact and superstructure of glass melting furnaces. Fused cast AZS block is abbreviated as AZS because it contains Al2O3－ZrO2－SiO2. Fused cast AZS blocks are used in glass furnace both in the superstructure and in glass contact due to the very high glass and vapour resistance.
Fused cast AZS blocks began to be used in glass furnace applications for the glass contact and superstructure in the middle of the last century. They are intrinsically superior to the silico-alumina sintered materials, and extend the furnace campaign life.
Fused cast AZS blocks are made from pure alumina powder and Zircon sand (composed of 65% zirconia and 34% SiO2) through special casting process. The term Fused Cast refers to a manufacturing process in which the ceramic bonding is obtained by the solidification of a mixture which has been melted in an electric furnace and cast in liquid state into molds. After Alumina powder and zircon sand melting in electric furnace, they are cast into various molds and cool themselves down to become white solid.
Fused cast AZS blocks are characterized by high mechanical strength, excellent thermal shock resistance, resistance to corrosion by alkaline compounds, low creep at high temperature and a very low porosity (close to zero).
Based on the zirconia content which basically defines their corrosion resistance, fused cast AZS blocks can be divided into three types:
Fused Cast AZS—33#
Fused Cast AZS—33# contains 33% ZrO2. It has dense micro structure which ensures its great resistance in glass liquid. A variety of formats and shapes of Fused Cast AZS—33# are available for furnace different working areas. It is widely applied to glass furnace for superstructure, working-end side wall, paving tiles, feeder channels, tank bottoms, C-shaped block and doghouse crown, etc.
Fused Cast AZS—36#
Fused Cast AZS—36# contains 36% ZrO2. With its improved corrosion resistance and combined with the "reinforced filling" process, the optimum choice for side walls of flame furnaces with embedded melter bottoms, superstructures, front wall, back wall, top crown, doghouses, throat, bottom budding, Dam blocks, and electric block corners in glass melting furnace.. This type is only available for straight brick.
Fused Cast AZS—41#
Fused Cast AZS—41# contains 41% ZrO2. It is available in a large size straight or approximate bricks and special formats and shapes which are available for special machining processes. With the highest corrosion resistance within the AZS family, this type of material is used for all demanding glass contact applications in the void free configuration: electric block corners, Dam blocks, submerged walls, doghouses, throats, bottom budding, and in some cases melter sidewalls in the specific "reinforced filling" version (RR-EVF).
Zhengzhou Sunrise Refractory Co., Ltd. offers a wide range of refractories of high quality at affordable price for glass industry. The TY-AZS series of Sunrise Fused Cast AZS blocks are made of artificial synthesis high purity raw materials through special casting process, specially designed refractory for glass furnace application. Visit our official site https://www.sunriserefractory.com/ to learn more.
Monolithic refractory, the name generally given to all unshaped refractory products, are materials installed as some form of suspension that ultimately harden to form a solid mass.
Castable refractories, also known as refractory concretes, is a dry, granular material designed to be mixed on site with water and capable of curing to a stable dimensional form through hydraulic or chemical setting. These are the materials that contain cement binder, which imparts hydraulic setting properties when mixed with water. Castable refractories have the advantage of being readily usable at the operating temperature of the equipment after hydraulic or chemical setting and removal of all moisture has taken place.
Castable refractories can be used to create the monolithic linings within all types of furnaces and kilns. Castable refractories are particularly suited to the molding of special shapes and parts at the installation site. The can be applied by pouring, pumping, troweling, funning, and shotcreting.
Plastic refractories are mixtures of refractory aggregates and cohesive clays which is prepared in stiff, unfired and formable plastic condition at the proper consistency for use without further preparation. Plastic refractories has high refractoriness and wide range of compositions, and can easily be rammed into place. They are often highly resistant to destructive spalling. Plastic refractories are used to form refractory monolithic linings in various kinds of furnaces, and are especially adaptable for making quick, economical emergency repairs.
Ramming mixes consist essentially of ground refractory aggregates, with a semi-plastic bonding matrix which can be purchased ready-to-use or prepared by adding water in the mixer at the construction site. Ramming mixes are very similar to plastic refractories, but ramming mixes supply a denser, stronger refractory body than plastic refractories. They need some sort of form to restrain them when rammed. Ramming mixes is characterized by thermal stability, corrosion resistance and wear resistance because it contains less binders, fire clay and moisture compared to plastic refractories.
The ramming mixes are used in constructing the internal refractory lining of the stack for filling the gaps between the refractory elements and the walls or other metal elements forming the blast furnace stack. Ramming mixes are used mostly in cold applications where proper consolidation of the material is a concern.
Gunning mixes are granular refractory materials sprayed on application area using a variety of air placement guns. Gunning mixes consist of graded refractory aggregate and a bonding compound, and may contain plasticizing agent to increase their stickiness when pneumatically placed onto a furnace wall. Dense, homogeneous monolithic linings can be gunned without the use of forms to save time. More than a third of all monolithic refractories are installed by gunning.
These are heat setting and are used for patching and maintenance works for kilns and furnaces. In some industrial furnaces, turnaround time and installation costs are the major factors when choosing a refractory lining. In other cases, repairs need to be made with little or no downtime. In both circumstances, pneumatic convey-ing of material, or gunning, is often the method of choice.
Mortars are generally neither classified under refractory brick nor monolithic refractories. These are finely ground refractory materials, which become plastic when mixed with water. Mortars must have good water retention properties and must not sediment. The composition and characteristics of the mortar materials, grain size and consistency are the important properties of the mortars.
These are used to bond the brickwork into solid unit, to provide cushion between the slightly irregular surfaces of the brick, to fill up spaces created by a deformed shell, and to make a wall gas-tight to prevent penetration of slag into the joints. Refractory mortars can be with ceramic bonding, chemical bonding or hydraulic bonding.
Patching Refractories are similar to plastic refractories though have a very soft plasticity allowing them to be pounded into place. They have been widely used for steel industry, chemical furnaces, boilers, nonferrous furnaces and the other high temperature furnaces.
Refractory coatings designed to protect the bricks, steel, monolithics, castables, refractory and steel shells in furnaces, kilns, boilers and various high temperature vessels usually against chemical attack. Coating refractories are normally intended to cover just the working surface of a lining. They tend to be fairly thin layers.
Fettling mixes are also granular refractory materials, with function similar to gunning mixes, but are applied by shoveling into the furnace needing patching.
Zhengzhou Sunrise Refractory Co., Ltd. is a refractory material supplier from China, offering a wide range of refractory materials of high quality at affordable prices, including fused cast AZS bricks, mullite brick, zircon brick, alumina bubble brick, sillimanite brick, corundum brick, low porosity fireclay brick, high alumina brick, monolithic refractories, sealing materials, building fireclay, etc..
Unshaped refractories, better known as monolithic refractories, are special mixes or blends of dry granular or cohesive plastic materials without definite form.
Monolithic refractories are used to form virtually joint free linings and are only given shape upon application. They are installed as some form of suspension that ultimately harden to form a solid mass. Most monolithic formulations consist of large refractory particulates, fine filler materials and a binder phase. Monolithic refractories can be divided into plastic refractories, patching refractories, ramming mixes, castables, gunning mixes, fettling mixes, mortars, etc..
Monolithic refractories have advantages over refractory bricks in different type of furnaces. Their use promotes quick installation, avoid delays for the manufacture of special brick shapes. Use of monolithic refractories frequently eliminates difficult brick laying tasks and joints, which may be accompanied with weakness in construction.
Monolithic refractories represent a wide range of mineral compositions and vary greatly in their physical and chemical properties. Some are low in refractoriness while others approach high purity brick compositions in their ability to withstand severe environments. Under certain conditions, monolithic linings of the same composition as refractory bricks provide better insulation, lower permeability and improved resistance to the spalling effects of thermal shock. It has better volume stability and improved mechanical resistance to vibration and impact. Another advantage is that shrinkage and expansion can be matched to the application.
With little or no preparation, monolithic refractories can be applied to form monolithic or joint free furnace linings in new constructions or to repair existing refractory lining. Transportation and handling are simple. It offers considerable scope to reduce inventory and eliminate special shapes. It has ability to install in hot standby mode.
Monolithic refractories are of major importance in the maintenance of furnaces because substantial repairs can be made with a minimum loss of time and, in some cases, even during operations. They are replacing the traditional refractories at a much faster rate in many applications.
Zhengzhou Sunrise Refractory Co., Ltd. provides all kinds of refractories used in glass furnaces at affordable prices, including fused cast AZS blocks, fireclay block, mullite brick, zircon brick, sillimanite brick, corundum brick, high alumina brick, monolithic refractories, etc.
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