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Unshaped Refractory Aluminum-Magnesium Spinel Castables Application and Construction

September 24, 2024 by rsrefractorycastable

Rongsheng Unshaped Refractory Materials Manufacturer is a powerful manufacturer and seller of refractory materials. Rongsheng Environmental Protection’s fully automatic unshaped refractory material production line provides a reliable guarantee for the efficient and long-life operation of high-temperature industrial furnace linings. Among them, the application of alumina-magnesium spinel castables is becoming increasingly widespread. Contact us to get free samples and quotes. This article will introduce the practical application of unshaped refractory materials, alumina-magnesium spinel castables.

Application and Construction of Aluminum Magnesium Spinel Castables

Tundish aluminum-magnesium castables and ladle aluminum-magnesium castables are both based on aluminum-magnesium spinel materials. There are also steel fiber aluminum-magnesium castables, which are the main working layer refractory castables often used in steel plants. Because they are more convenient during construction, they are welcomed by steel mills and enterprises. However, sometimes due to changes in the construction conditions of alumina-magnesia spinel castables, some problems may occur, affecting the use effect and life of the furnace lining.

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Problems and Solutions in the Construction of Aluminum-Magnesium Spinel Castables

Solidification time is an important factor affecting the construction of aluminum-magnesium castables. The ambient temperature has a great influence on the solidification time of aluminum-magnesium castables, especially in summer. When the ambient temperature exceeds 35°C, aluminum-magnesium castables tend to solidify quickly, which brings a series of problems to the casting construction:

①Increased the labor intensity of construction workers. When the ambient temperature is high and the solidification time of the castable is shortened, the rheology of the castable itself becomes worse. Especially when the castable is rapidly solidified, the castable released from the mixer has no time to enter the bag, and has solidified on the upper surface of the bag and the launder. This makes feeding castables into the wall more labor-intensive.

②Influence the service life. In hot summer, workers often add more water to increase the fluidity of castables. Due to the increase in water consumption, the porosity of the castables increases and the strength decreases after drying. In addition, when the ambient temperature exceeds 40°C, even if more water is added, the castable will still tend to set quickly, affecting the service life.

③ Difficulty in rebirth. Under normal circumstances, after the ladle is poured, it needs to be left for 24 hours before it comes out. However, in the hot summer, due to the shortened solidification time of the castable, the castable and the tire package are tightly stuck together, making it difficult to remove the tire.

Therefore, whether it is from the perspective of reducing the labor intensity of workers, or creating a good condition for pouring construction, extending the service life of castables, and reducing usage accidents. It is necessary to fundamentally adjust the solidification time of aluminum-magnesium castables to meet the on-site usage requirements. After a period of research, it was found that lignosulfonate can change the setting time of castables, so that the initial setting time of aluminum-magnesium castables can be extended to more than 30 minutes even when the ambient temperature exceeds 35°C. This completely solves the problem of short solidification time of aluminum-magnesium castables in summer. It should be noted that the solidification time of aluminum-magnesium castable is related to the amount of lignosulfonate added. On the premise of meeting construction requirements, the smaller the amount added, the better. In addition, as the seasons change, the amount added must also be adjusted accordingly. Generally, a large amount is added in summer, and less or even no amount is added in winter. If more lignosulfonate is added in winter, the final setting time of the aluminum-magnesium castable will be extended, which will cause material collapse during normal operation, which is harmful.

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Problems and Solutions when Using Aluminum-Magnesium Spinel Castables

(1) Cracks.

Aluminum-magnesium castables crack during use, reducing their service life. When the ladle was used for 5 heats, cracks began to appear on the inner wall of the ladle, covering the entire ladle wall. As the number of uses increased, the cracks became deeper and wider. When more than 20 furnaces were used, they had to be discontinued. To solve the problem of castable cracks, some methods have been tried:

① Replace the bauxite clinker calcined in the vertical kiln with bauxite calcined in the down-flame kiln. In this way, the sinterability and bulk density of alumina are increased. It was thought that the volume shrinkage caused by incomplete calcination of the alumina and re-sintering during use could be reduced, but this was not successful.

② It is believed that the cracks are related to the total amount of fine powder in the castable. Trying to reduce the fine powder in the castable to less than 30% (mass fraction), or as low as 25%, did not solve the problem.

③ Solve the cracks starting from a chemical reaction. Because Al2O3 and MgO can generate alumina-magnesia spinel under the action of high temperature, it is accompanied by large volume expansion. After a series of tests and adjusting the ratio of Al2O3/MgO, satisfactory results were not achieved. Even when the MgO content is too high, peeling occurs instead.

Finally, the following method is basically used to solve this problem:

① Increase the upper limit of aggregate particle size from the original 15mm to 25mm. Among them, the 20-25mm part accounts for 7.2% (mass fraction) of the total. This is due to the presence of oversized particles, which not only act as a skeleton but also change the direction of long cracks, helping to prevent the expansion of internal cracks.
② Add zircon powder to the matrix. This zircon powder is produced in Australia, and its ZrO2 content is about 66%. Since ZrO2 itself has a high melting point, it can absorb CaO in the slag during use, react to generate CaZrO3 with high melting point and high corrosion resistance, and seal pores and cracks. At the same time, due to the presence of zircon, micro-crack structures can also be formed in the castable to improve the high-temperature performance of the castable.
③ Reduce the dosage of activated silicon carbon powder as much as possible. Since the quality of silica fume powder is unstable and a large amount is added, a lot of impurities will be brought in, which is detrimental to use. Controlling the amount of silica fume in the castable below 1.5% (mass fraction) will achieve better results.
④When pouring, it is also critical to strictly control the amount of water added and ensure uniform vibration.

(2) Peeling

Spalling is also one of the common problems in the use of aluminum-magnesium castables. It is the result of uneven stress within the castables. If A12O3 and MgO in the matrix are affected by high-temperature molten steel during use, they will easily react to form MA spinel, accompanied by a large volume expansion. If this reaction is very intense, structural peeling will easily occur under the impact of molten steel. Therefore, to control this spinel reaction in the matrix, it is necessary to control the content of each component, especially the content of MgO, which is critical. If the MgO content is too high, in addition to the spinel reaction, it also has a large linear change rate, resulting in volume expansion, which will also promote spalling. Generally, the content of magnesia is controlled at about 10% (mass fraction), and the effect is better.

Pouring construction also has an impact on the occurrence of spalling. In this regard, the amount of water added must be strictly controlled and uniform vibration must be achieved. If the amount of water added is too large and the green body vibrates unevenly, the porosity will increase, and steel drilling will easily occur during use, causing the wall of the bag to peel off.

(3) The slag line erodes quickly

Due to the complex composition of steel slag, it is easy to react chemically with the castables, causing the castables in the slag line to be prematurely corroded, resulting in the slag line and the wall being unable to be used simultaneously. This is also a problem encountered in actual use. On the premise of significantly increasing costs, some methods are adopted:

① Specially configured slag line material is used for pouring the slag line parts. The raw materials of slag strand materials are improved to a higher level. For example, the bauxite powder uses high-quality high-alumina bauxite clinker with ω (A1203) = 86% and a bulk density of >3.2g/cm3.
② Add some pre-synthesized aluminum-magnesium spinel to the slag strand material and use a high MgO ratio, which can improve the ability to resist alkaline slag.
③ Reduce the dosage of active silica fume and control it to around 1.0% (mass fraction).
④Strictly control the amount of water added and vibrate evenly during pouring. Through these measures, the lifespan of the slag line and the package wall is basically synchronized.

Measures and Methods for Efficient Use of Aluminum-Magnesium Spinel Castables

①Retarding technology is one of the key technologies in the construction of magnesium-aluminum castables. According to changes in seasons and ambient temperature, retarders such as lignosulfonate should be added in a timely manner to make the setting time meet the needs of pouring construction.
② Adding some oversized aggregate and zircon powder to the castable is very beneficial to inhibit the occurrence of cracks.
③ The slag line uses a high MgO ratio and adds some pre-synthesized aluminum-magnesium spinel powder to improve the slag erosion resistance of the slag line.
④ During pouring construction, strictly control the amount of water added and vibrate evenly, which is of great significance to increase the service life of the castables.

To ensure the efficient and long-life operation of the ladle lining, it is not only necessary to purchase high-quality aluminum-magnesium spinel castable products, but also strictly follow the construction instructions and adjust the formula of the aluminum-magnesium spinel castable according to the actual construction conditions. Rongsheng unshaped refractory material manufacturers can customize the formula of refractory castables according to the actual working conditions of customers. To improve the service life of high-temperature furnace linings and save production costs for enterprises.

Application of Micro-Expansion Wear-Resistant Refractory Plastic in Power Plant Boilers

September 17, 2024 by rsrefractorycastable

Micro-expansion refractory plastic is made of water glass as a binder and sodium fluorosilicate as a coagulant. It was originally used in wall-through pipes of pulverized coal furnaces. It has the characteristics of strong plasticity at room temperature, strong adhesion, high fire resistance, good sealing performance, and convenient construction. It has high strength after natural drying, and its volume can expand slightly at high temperatures. It can be widely used in industrial kilns such as CFB boilers and pulverized coal furnaces, such as top wall-penetrating pipes, flame angles in the furnace, complex parts of the furnace wall, etc. It mainly plays a sealing role. Currently, this material can be used in boiler flues, chimneys, and other pipes containing acidic gases.

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Micro-Expansion Refractory Plastic for Power Plant Boilers

With the continuous development of modern industry, the power industry plays an increasingly important role in people’s lives. As an important part of power plant boilers, the performance of the lining material has a great impact on the operating efficiency and life of the boiler. Therefore, the emergence of micro-expansion wear-resistant and refractory plastic has become an important lining material and is favored by power plant boiler manufacturers and maintenance engineers.

Micro-expansion wear-resistant refractory plastic has the characteristics of low thermal conductivity, high-temperature resistance, good thermal shock stability, wear resistance, corrosion resistance, and not susceptible to mechanical vibration. Its obvious feature is that under high-temperature conditions, the formation of an oxide layer can effectively protect the lining material, thereby extending the service life of the boiler. In addition, the micro-expansion properties allow the material to have better crack resistance and wear resistance at high temperatures, further improving the boiler’s operating efficiency and performance.

In the application of power plant boilers, micro-expansion wear-resistant, and refractory plastics are widely used in lining materials, patch materials and supplementary materials. As a lining material, it replaces traditional hard materials and can reduce the noise and vibration of the boiler and extend the life of the boiler. Patch materials are often used for boiler lining repairs and will not peel off the base material or affect thermal conductivity during the repair process. Supplementary materials refer to adding micro-expansion wear-resistant refractory plastic to the lining of the boiler to improve overall performance and life.

In short, the application of micro-expansion wear-resistant and refractory plastics in power plant boilers has become a trend. It is known for its high performance and excellent fire resistance. The range of applications is getting wider and wider. In the future, we believe that this material will play a more important role in the power industry and continue to provide a strong guarantee for the operating efficiency and performance of boilers.

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How to Identify Refractory Plastic and Refractory Clay

Refractory plastics are made of refractory aggregates and powders, raw clay, chemical composite binders, and admixtures, which are mixed and extruded into brick shapes. Refractory materials that still have good plasticity after being packaged and stored for a certain period of time can be constructed using the tamping method. Commonly used bonding methods include chemical bonding, ceramic bonding, polycondensation bonding, etc.

Refractory mud, also known as refractory mud or joint material, is a joint material used for the masonry of refractory products. According to the material, it can be divided into clay, high alumina, silica and magnesia refractory clay. It is composed of refractory powder, binder, and admixture. Almost all refractory raw materials can be made into powders used to prepare refractory mud. Ordinary refractory clay, which is made from refractory clinker powder and an appropriate amount of plastic clay as a binder and plasticizer, has low strength at room temperature. Only when it forms a ceramic bond at high temperatures does it have higher strength. Chemically bonded refractory mud, which uses hydraulic, gas-hardening or thermo-hardening bonding materials as binding agents, hardens through a certain chemical reaction before the temperature drops below the temperature at which ceramic bonding occurs. The particle size of refractory mud varies according to the use requirements. Its limit particle size is generally less than 1mm, and some are less than 0.5mm or finer. When selecting the material of refractory mud, it should be consistent with the material of the refractory products of the masonry. In addition to being used as a joint material, refractory mud can also be used as a protective coating for the lining by applying or spraying.

Refractory mud properties and applications. 1. Good plasticity and convenient construction. 2. High bonding strength and strong corrosion resistance. 3. The refractoriness is relatively high, reaching up to (around 1650℃). 4. Good resistance to slag erosion. 5. Good thermal peelability. Refractory mud is mainly used in coke ovens, glass kilns, blast furnaces, and other industrial kilns.

Rongsheng Unshaped Refractory Material Manufacturer

Rongsheng Refractory Castable Manufacturer is a powerful manufacturer and seller of unshaped refractory materials. Rongsheng’s environmentally friendly, fully automatic unshaped refractory castable production line reliably guarantees the production and supply of refractory castables for high-temperature industrial furnaces. Rongsheng Refractory Castable Manufacturer already has customers in more than 120 countries, such as South Africa, Chile, Egypt, Colombia, Uzbekistan, Italy, Indonesia, Ukraine, Hungary, Spain, Kenya, Syria, Zambia, Oman, Venezuela, India, Peru, the United States, Ethiopia, etc. If you have the need to purchase unshaped refractory castables, or micro-expansion refractory plastics for power plant boiler maintenance, please contact us. Get free samples and quotes.

Silicon Carbide Refractory Castable for Furnace Lining in Reducing Atmosphere

September 5, 2024September 3, 2024 by rsrefractorycastable

Silicon carbide refractory castable has stable properties and excellent corrosion resistance and wear resistance. It is not corroded by boiling hydrochloric acid, sulfuric acid, or hydrofluoric acid. SiC 75-80% castable. Silicon carbide refractory castable for reducing atmosphere furnace lining. It will not oxidize when used in a reducing atmosphere with a temperature of 1600°C, but oxidation will occur in an oxidizing atmosphere.

The Optimal Operating Temperature of Silicon Carbide Castables in Reducing Atmosphere Furnaces

Silicon carbide castable is used at a temperature of 800-1140℃, rather than 1300-1500℃. Because within the range of 800-1140°C, the oxide film formed by oxidation has a loose structure and cannot play the role of silicon carbide. Above 1140°C, especially between 1300-1500°C, the oxide film formed by oxidation covers the surface of the silicon carbide substrate, preventing oxygen from contacting the silicon carbide. Therefore, the antioxidant capacity is the best within the temperature range of 1300-1500°C. However, when the temperature exceeds 1500°C, the oxidation protective layer will be destroyed. At this time, the silicon carbide castable will be strongly oxidized and the matrix will be decomposed and destroyed.

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Application Advantages of Silicon Carbide Castables

Silicon carbide castable is a hard material with high hardness. It has good creep resistance, thermal shock resistance, and wear resistance, but has high thermal conductivity. However, silicon carbide castables also have different qualities, that is, different proportions of silicon carbide are added. However, no matter what type of castable it is, metal silicon powder must be added to adjust it to resist oxidative decomposition. Including refractory bricks, they must also be adjusted to prevent oxidation.

In fact, silicon carbide castable is a composite castable, which is made of alumina aggregate and powder, mixed with a certain proportion of silicon carbide and binder. So they are all composite.

Generally used in furnace linings with severe erosion. If the temperature is below 1300°C for the furnace lining, do not use silicon carbide refractory castables. Furnace linings in oxidizing atmosphere are also not suitable for this castable. Silicon carbide refractory castables are best used in reducing atmosphere furnace linings at 1300-1500°C.

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Silicon Carbide and Its Application in Refractory Materials

Silicon carbide can maintain high strength and high wear resistance at high temperatures. After adding a certain proportion of silicon carbide, refractory castables have good chemical stability and will not be corroded by acid and alkali solutions. Silicon carbide has a larger wetting angle with molten metal and slag. Compared with oxide refractory castables, it has good corrosion resistance to various furnace lining solids, liquids and gases.

Wear-resistant

The hardness of silicon carbide is second only to diamond, and it has strong wear resistance. It is an ideal material for wear-resistant pipes, impellers, pump chambers, cyclones, and linings of ore hoppers. Its wear resistance is 5-20 times that of cast iron and rubber, and it is also one of the ideal materials for aviation runways. Using a special process to coat silicon carbide powder on the inner wall of the turbine impeller or cylinder block can improve its wear resistance and extend its service life by 1 to 2 times.

Thermal shock resistance

Due to the high thermal conductivity and small thermal expansion coefficient of silicon carbide, silicon carbide refractory materials have good thermal shock resistance. The thermal shock resistance of silicon carbide products is also closely related to the type and nature of the bonding base material. In actual application, since silicate-bonded silicon carbide products can be observed to expand, crack, and deform after being subjected to thermal shock, the service life of the material can be easily predicted.

High thermal conductivity

Since silicon carbide itself has good thermal conductivity, refractory materials with high silicon carbide content have higher thermal conductivity. Most of their thermal conductivity exceeds 14.4W/(m·K). Used in heat exchangers, saggers, water-cooled walls of coal gasification furnaces, indirectly heated kiln furniture products, etc. During the use of silicon carbide products, the thermal conductivity of the particle surface will gradually become smaller. The properties of the bonding base material have a certain impact on the thermal conductivity of silicon carbide products. The thermal conductivity of silicon oxynitride bonded and silicon nitride bonded silicon carbide is higher, and the thermal conductivity of silicate bonded silicon carbide is smaller.

Anti-oxidation

Silicon carbide has good oxidation resistance. Oxidation is weak below 1300°C. Significant oxidation does not occur until the temperature is above 1300°C. The oxidation generates a SiO2 glass protective film, which can inhibit the oxidation of silicon carbide.

The oxidation resistance of silicon carbide refractory products also varies significantly with the type of binding base material. The lower oxidation resistance of silicon nitride-bonded silicon carbide products can be explained by their microstructural characteristics. Because the base material of silicon nitride combined with silicon carbide products is in the form of interwoven fibers and has high air permeability, it plays a small protective role on silicon carbide particles. In silicate bonded and silicon oxynitride bonded silicon carbide products, the surface of the silicon carbide particles is wrapped by a continuous base material. Therefore, it has strong antioxidant properties. The antioxidant properties of silicate-bonded silicon carbide and silicon oxynitride-bonded silicon carbide show similar properties in the above tests, but the differences between them can be clearly shown in long-term use.

Resistance to slag

SiC is a compound with strong covalent bonds and maintains high bonding strength at high temperatures. Therefore, SiC has good chemical stability and will not be corroded by most acid and alkali solutions. Silicon carbide has a larger wetting angle with molten metal and slag. Compared with oxide refractory materials, it has good corrosion resistance to various solids, liquids and gases. Such as Al2O3-SiC-C castables and products used in iron-making systems, silicon molybdenum bricks and silicon carbide-containing castables used in cement kilns, various acid-base reaction vessels, etc.

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Application of Carbonaceous Castables Containing Silicon Carbide Raw Materials in Blast Furnace Bottom

Blast furnaces are the basis for stable and smooth ironmaking production, and the most important ones are carbon bricks and water cooling systems. Carbon bricks and molten iron are not easily wetted and have strong corrosion resistance. Water cooling is the key to ensuring the longevity of carbon bricks. During the blast furnace bottom masonry process, after the water-cooling pipes are laid, the existing technology mostly uses carbon ramming material to level and fill the carbon brick joints. In order to ensure the water cooling effect, the carbon ramming material is required to have high thermal conductivity, a certain strength, and good construction performance. Since the performance of ramming materials is closely related to the construction process and quality, and there are many human-influenced factors, the thermal conductivity often fails to meet the expected requirements. In recent years, the results of analyzing carbon castables show that the thermal conductivity of castables mainly made of carbon raw materials is relatively low, and some are less than 10W·(m·K)⁻¹. The thermal conductivity of carbonaceous castables containing silicon carbide raw materials is greater than 15W·(m·K)⁻¹. Its construction is more convenient than ramming material, and its operation is simple. It only needs vibration forming and quick smoothing, which can save a lot of man-hours. Performance of carbonaceous castables containing silicon carbide raw materials in blast furnace bottoms.

(1) Carbonaceous castables using silicon carbide as the main raw material have higher strength. The compressive strength after 24 hours of insulation at 110°C is greater than 17MPa, and the compressive strength after 3 hours of insulation at 1450°C is greater than 70MPa. The thermal conductivity at 700°C measured using the laser method is 7.2W·(m·K)⁻¹. The compressive strength of imported carbon castables using carbon as the main raw material after being kept at 110°C for 24 hours is 18.3MPa. The compressive strength after being kept at 1450°C for 3 hours was significantly reduced. The thermal conductivity at 700℃ measured by laser method is 5.08W·(m·K)⁻¹. Its thermal conductivity is relatively low compared to the technical requirements of blast furnace bottom carbonaceous castables.
(2) After the sol-bonded carbon castable with silicon carbide as the main raw material is soaked in water, the compressive strength and volume density increase, while the shape remains unchanged. After soaking in 2% (w) hydrochloric acid solution, the compressive strength after 30 days decreased. After immersion in 2% (w) sulfuric acid solution, the compressive strength decreased after 30 days, and the decrease was smaller than that in hydrochloric acid solution. After soaking in 2% (w) sodium hydroxide solution, it was completely loosened into powdered materials in 30 days. Carbon castables made of silicon carbide as the main raw material are not resistant to immersion in alkali solutions. In an environment where alkali metal vapor may penetrate into the blast furnace bottom, such carbonaceous castables should be used with caution if there is cooling water leakage.

Rongsheng Refractory Castable Manufacturer is a powerful refractory material manufacturer. Rongsheng Manufacturer has an environmentally friendly, fully automatic unshaped refractory material production line. The refractory lining materials products of Rongsheng manufacturer have been sold to more than 120 countries around the world, such as South Africa, Chile, Egypt, Colombia, Uzbekistan, Italy, Indonesia, Ukraine, Hungary, Spain, Kenya, Syria, Zambia, Oman, Venezuela, India, Peru, the United States, Ethiopia, etc. We can customize refractory lining materials according to the actual working conditions of high-temperature furnace linings. To purchase high-quality silicon carbide refractory materials, please choose Rongsheng Refractory Castable Manufacturer.

Castables Refractory for Regenerative Heating Furnaces

September 3, 2024August 20, 2024 by rsrefractorycastable

Regenerative continuous heating furnaces enable steel companies to efficiently utilize low calorific value fuels. However, compared with ordinary steel rolling heating furnaces, the combustion method, heat exchange method, heat exchange medium and other aspects of the regenerative heating furnace have undergone major changes. The furnace structure has also changed as a result, resulting in a series of problems such as more channels in the furnace wall of the regenerative heating furnace, complex structure, and difficulties in construction and baking. As a result, the airtightness and comprehensive integrity of the working lining are poor, and the refractory materials in the furnace lining and burner area are prone to cracking and damage during use.

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In addition, the high-temperature flue gas and high-temperature preheated combustion medium of the regenerative heating furnace are circulated from the burner body and the working conditions are frequent switching between pairs of burners. It is easy to cause thermal shock cracks, thermal stress fatigue damage and burner nozzle deformation in the refractory materials in the furnace lining and burner area. In response to the above situation, refractory castable manufacturers have taken the following measures:

Improvement Measures for Castables Refractory for Regenerative Heating Furnaces

(1) Select high-quality high-alumina bauxite clinker with an impurity content not exceeding 2% as large aggregate. In order to prevent the raw materials from containing more impurities and producing low melting point substances during the high temperature process, the load softening temperature of the castables will be reduced. It affects the high-temperature performance of the castables, causing the burner to deform during operation and reducing its working performance.

(2) Select sintered mullite as fine aggregate and powder. The advantages of mullite include good structural structure, low creep rate, small thermal expansion, good thermal shock resistance and strong resistance to chemical erosion. Improve the linear change rate, thermal shock stability, erosion resistance and high temperature creep resistance of the castable, and increase the high temperature compressive strength of the castable.

(3) Select andalusite and kyanite as expansion materials, and use the volume expansion effect of andalusite and kyanite during the mulliteization process at high temperatures to improve the linear changes of the castable after high-temperature burning and improve the thermal shock stability of the castable. sex.

(4) Select dense corundum fine powder, α-Al2O3 micro powder, and silica micro powder as micro powder materials. While improving the density of the castable, the high melting point of α-Al2O3 is used to improve the refractoriness of the burner castable. Mullite and secondary mullite are generated by sintering powder and aggregate under high temperature conditions. While improving the line change rate of the castable, it also improves the comprehensive mechanical strength and high temperature performance of the castable.

In addition, the researchers added a small amount of Al-80 cement as a binding agent to improve the medium and low-temperature bonding strength of the castable by taking advantage of its rapid hardening, high strength, and fire resistance. Polycrystalline alumina fiber is added as reinforcing and toughening material, and explosion-proof fiber is added as explosion-proof agent to further improve the bonding strength and thermal shock stability of the castable. Sodium hexametaphosphate and FS20 are used as high-efficiency composite dispersants (water reducing agents) to improve the construction performance of castables.

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Excellent Physical and Chemical Properties of Castables for Regenerative Heating Furnaces

Compared with ordinary high-aluminum castables, the improved castables have better comprehensive indicators. The change of its line after burning shows that it has micro-expansion, which can effectively prevent shrinkage cracks in the furnace lining and burner nozzle. The number of water cooling times at 1100°C reaches 25 times, which indicates that the thermal shock stability of the castable is good and can reduce thermal shock cracking of the refractory material in the burner part. The starting temperature of high-temperature load softening is greater than 1400°C, which is higher than the maximum operating temperature of the heating furnace. It can avoid the problems of furnace lining bulging and burner nozzle deformation, and delay the deterioration of burner performance.

In summary, the improved integral castable of the regenerative heating furnace lining and burner has a reasonable microstructure. It has the advantages of good medium and high-temperature sintering bonding, high mechanical strength, excellent linear change rate and thermal shock stability, and high load softening starting temperature. Moreover, the improved castable has good construction performance and its service life is more than doubled to more than 12 months under maintenance-free conditions. It effectively reduces the workload of furnace lining and burner maintenance, and reduces the consumption and maintenance costs of heating furnace castables, and repair materials.

Improvement of Furnace Body Refractory Castable Structure of Chamber Heating Furnace

Forging heating furnace is a key equipment in the forging industry. It is characterized by intermittent operation and large temperature changes. It often works under conditions such as high temperature and strong vibration, collision of loading and unloading machinery, and chemical erosion of iron oxide scale. It seriously damages the lining bricks of the furnace, shortens the service life of the furnace, and also causes the heat loss of the furnace to increase.

Application of High-Strength Refractory Castables in Reforging Heating Furnaces

High-strength refractory castables are good lining materials for forging heating furnaces, which extend the life of the furnace, reduce energy consumption, and achieve good economic results. In the design, the overall furnace structure of the chamber heating furnace was improved. The improvement steps are carried out according to the reservation of furnace top, furnace wall, furnace bottom and expansion joints.

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(1) Stove top

The furnace top is a composite flat furnace top, and 48 high-aluminum hanging anchor bricks are evenly buried in the furnace top, with the brick length being 460mm. The anchor bricks and refractory castables form a whole, and the thickness of the cast layer is 300mm. The furnace top adopts a metal hanging structure, and the hanging bolts are connected to the metal hanging beams. The force of the hook is adjusted evenly to maintain the overall force and is in a free hanging state. The upper surface of the furnace roof is covered with a layer of 70mm thick refractory fiber to enhance the heat preservation performance of the furnace.

(2) Furnace wall

The furnace wall is a composite type. A δ=8mm steel plate is added around the furnace wall. A 40mm thick refractory fiber is pasted on the inside of the steel plate, and a 114mm lightweight refractory brick is built on the inside of the refractory fiber. The lining is integrally cast with high-strength refractory castables, and the thickness of the casting layer is 300mm. The burner hole is reserved during pouring, and the burnt bricks are embedded after the castable solidifies. The gap between the burner brick and the castable is filled with fine powder, and the furnace wall is poured at one time. Compared with brick furnace walls, it has good impact resistance and thermal insulation effects, reduces heat loss and saves energy.

(3) Furnace bottom

In order to improve the wear resistance of the furnace bottom, steel fiber reinforced castables are used and integrally poured into the pit surface. The working layer at the furnace bottom is 280mm thick, and 210mm thick refractory clay bricks and lightweight refractory clay bricks are laid underneath. Some clay bricks were laid in areas with lower temperatures, up to the ground level. Three flue holes are left in each room to communicate with the main flue, and the flues are all built with refractory sticky bricks.

(4) Connection between furnace top and furnace wall

The furnace wall does not bear the weight of the furnace top, and there is a 20mm gap between the two to allow the furnace wall to expand due to heat. In order to prevent the flame from escaping from the joint between the furnace wall and the furnace top, the two should overlap by at least 150mm, and clay bricks should be built on the side of the furnace top to isolate the flame. At the same time, wet clay bricks are used on top, and the gaps between the furnace top castables, refractory clay bricks and refractory fiber fillers are sealed to prevent fire escape.

(5) Expansion joints left

Leave an expansion joint at the four corners of the furnace wall, at the center of the middle partition wall, and at the joint between the partition wall and the front and rear. The width of the expansion joint is 3~4mm, and flammable corrugated board is used as the filling material. There are no expansion joints in the stove top itself. 20mm refractory fiber is laid around the working layer of the furnace top to replace the expansion joint.

(6)Construction

The construction of high-strength refractory castables is different from ordinary refractory castables. Therefore, careful construction must be carried out in accordance with relevant regulations. Before installing the formwork, install the burner, flue and furnace door membrane. Then set up the furnace wall formwork, and connect the hole membrane to the furnace wall formwork. The furnace top formwork is set up after the furnace bottom castables have a certain strength. After the support is completed, the anchor bricks are hung. The gap between the lower end of the anchor brick and the formwork is 0~5mm. The formwork support must be firm and must not be loose. High-strength refractory castables are finished materials that must be stirred evenly by a forced mixer before pouring. After the materials are put into the mixer and mixed dry for 1 minute, 6.5%~7.2% water is added, and then wet mixed for 3~4 minutes before the material is discharged. The mixture poured out from the mixer must be used within 30 minutes.

To purchase high-quality refractory castable products, please choose Rongsheng Refractory Castable Manufacturer. Our refractory products have been sold to more than 120 countries around the world, such as South Africa, Chile, Egypt, Colombia, Uzbekistan, Italy, Indonesia, Ukraine, Hungary, Spain, Kenya, Syria, Zambia, Oman, Venezuela, India, Peru, the United States, Ethiopia, etc. Moreover, our product quality is reliable and our after-sales service is guaranteed. Contact us for a free sample and quote for your refractory castables.

Applications of Wear-Resistant Castables and Refractory Precast Shapes

August 6, 2024 by rsrefractorycastable

Silicon carbide castables are often used in boiler linings or linings of iron trenches in front of blast furnaces. High-strength wear-resistant castables are used in boiler linings. It is also used in the unloading part of the rotary kiln and the use effect is very good, here, it is called anti-crushing castable in this part.

Conditions for Use of Silicon Carbide Wear-Resistant Castables

Silicon carbide castables can be used under high temperatures and harsh conditions. Silicon carbide castables have particularly good wear resistance. As long as it is used in the right location, its service life will be increased by more than 50% compared with ordinary low-cement castables.

Wear-Resistant Corundum Silicon Carbide Castable — Wear-resistant Corundum Silicon Carbide Castable in Rongsheng Factory

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What is the Suitable Working Temperature for Silicon Carbide Castables?

Silicon carbide castables are suitable for use in furnace linings under reducing atmospheres, and are more effective when used at temperatures above 1500°C.

Silicon carbide castable is a composite refractory castable. A certain proportion of silicon carbide, alumina powder, corundum or high-content bauxite raw materials is added to the inner matrix. The bonding agent is composed of pure calcium aluminate cement and some other chemical ingredients.

The use temperature of silicon carbide in reducing atmosphere is as high as 2454°C. If used in an oxidizing atmosphere, oxidation reactions may easily occur. If used in an oxidizing atmosphere, silicon carbide cannot produce a protective film on the surface. If the oxidation pressure is high, the surface layer will crack or peel due to temperature changes and mechanical impact.

If the oxygen partial pressure is low, the protective layer cannot be formed and will diffuse in the pores, resulting in a reduction in the quality of silicon carbide castables.

Castable manufacturers will add a certain proportion of binder to the composite process ratio to adjust the oxidation reaction. Under normal circumstances, metallic silicon is used to regulate the oxidation reaction. It is also useful to use sodium salt solution or sol to penetrate into the open pores of the material to inhibit oxidation and increase the service life.

Therefore, silicon carbide castables are not suitable for use at low temperatures, especially in oxidizing atmospheres. When used in a reducing atmosphere, the higher the temperature, the better the effect.

Refractory Precast Shapes for Sleeve Kiln Arch Blocks

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Application of Wear-Resistant Castables and Refractory Precast Shapes in Sleeve Kiln Arch Blocks

In the arch bridge part of the sleeve kiln, both wear-resistant castables and refractory Precast Shapes can meet the requirements. Prefabricated parts have a long cycle but good results, and the construction of wear-resistant castables is complicated but has strong adaptability. Enterprises can make reasonable choices based on actual working conditions.

The arch bridge of sleeve lime kiln has always been a difficult problem to overcome. Because this part needs to be load-bearing, wear-resistant, and wind-resistant, the required refractory materials are difficult to determine with just one material.

In this case, many manufacturers use a dual method of laying refractory bricks first and then making refractory castables to increase the service life of the arch bridge. Another reason is that there are many types of refractory bricks used in this part, their weight is small, production is inconvenient, and the production cycle is long. In this case, Refractory Precast Shapes were used to meet the requirements of this part.

According to the current feedback from manufacturers, the service life of refractory prefabricated parts used in arch bridges is quite good, usually more than 3 years, while the use of magnesia bricks is only about one year. Using a mixture of refractory bricks and castables, the service life is probably more than one year.

However, the use of refractory Precast Shapes requires large molds, and the production cycle must be at least 20 days. During construction, a crane can be used to place them at the location of use. As the temperature of the kiln body rises, the refractory Precast Shapes are also baked, which can be said to be the best of both worlds. However, the model is large and the price will be higher than using wear-resistant castables.

If the production cycle of refractory prefabricated parts will be limited in the case of emergency repair, wear-resistant castables should be used. However, due to the large area and thickness of wear-resistant castables, the anchors must be changed into cage shapes according to the specifications of the parts used. Weld the cage-like anchoring material at the arch bridge part and then find high wear-resistant castables, which can also meet the use needs of this part.

In short, prefired Precast Shapes or wear-resistant castables are used for the arch bridge of the sleeve kiln, both of which can meet the usage requirements. Enterprises can decide based on actual construction time and other advantageous conditions.

Ultra-Low Cement Iron Ditch Castable – Long Service Life Refractory Lining

July 30, 2024 by rsrefractorycastable

At this stage, most blast furnaces use alumina-silicon carbide-carbon iron trench castables. With the advancement of smelting technology, the amount of iron passed through at one time has increased from the initial tens of thousands of tons to hundreds of thousands of tons, which has also put forward higher requirements for the performance of iron trench materials. The fastest eroding part of the tap trench is the impact zone. In addition to thermal shock, molten iron erosion, and oxidation, the main damage to the iron trench is the high-temperature erosion of molten iron and iron slag.

During the smelting process of molten iron, more silica will be generated. Calcium oxide (the main source of calcium oxide is cement), silica and alumina will react together to form anorthite and anorthite (liquid phase at the operating temperature). Or low melting phase such as calcium aluminate. These low melting phases greatly reduce the high-temperature performance of the iron trench material. Seriously affects the corrosion resistance of the product, thereby affecting its service life. When the low-melting phase is generated, the alumina powder used as the matrix is also consumed. After the matrix is consumed and eroded, the aggregate particles that serve as the skeleton will loosen and peel off, causing the product structure to be destroyed.

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Ultra-Low Cement Bonded Al2O3-SiC-C Iron Trench Castable

At present, most blast furnace trenches use alumina-silicon carbide-carbon castables with high-purity calcium aluminate cement as the binding agent. Calcium oxide is inevitably introduced, thus forming a low-melting phase during high-temperature use. If cement is not used and only ultrafine powders such as alumina powder and silica powder are used, the demoulding strength at room temperature will be low and cannot meet the Stinging requirements. Although there are reports using P-Al2O3 combination (hydraulic alumina) and sol-gel (silicon and aluminum) combination to make iron trench castables. However, there are problems such as fast solidification and difficult control during on-site construction, so it has not been widely used. Cement is still the main binding agent for iron trench materials at this stage. Develop ultra-low cement-bound Al2O3-SiC-C iron trench castables and combine them with ultra-fine powder to minimize the introduction of calcium oxide while ensuring the demoulding strength at room temperature. It not only ensures that it will not be damaged after casting and demoulding, but also improves the high-temperature strength and performance of the material by reducing the low melt content of the castable at high temperatures. It can well resist the erosion of molten iron and slag, thereby extending the service life of the iron trench.

Through experiments, it was found that if the amount of cement added is too small, the demoulding strength at room temperature cannot be guaranteed, and if the amount added is high, the high-temperature performance will deteriorate. Based on the above properties, the optimal addition amount of cement in Al2O3-SiC-C iron trench castable is 0.6%.

Rongsheng Low Cement Silicon Carbide Castable (Al2O3-48%,SiC-30%)

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Industrial testing and applications. On the basis of laboratory research results, a plan to add 0.6% cement will be carried out industrial testing in a steel company. The blast furnace capacity is 1080m3, the length from the main trench to the small pit is 14.5m, the slag trench is 11m, and the shared material is 73t. Among them, the main ditch uses 49t. From use to the next set-up, it was used for a total of 84 days, and the iron output was about 165,000 tons, which achieved good results.

in conclusion. Reducing the amount of cement added can improve the high-temperature performance of iron ditch castables. The main reason is to reduce the formation of eutectic anorthite and generate staggered network mullite crystals in the castable to improve high-temperature performance. When the cement addition amount is 0.6%, the overall performance of the castable is better. The iron ditch castable produced on this basis has achieved good industrial test results.

The Castables used in Copper Smelting Trenches Must Have the Following Properties:

According to the working environment and conditions of the copper tapping trench, the castables used for the copper tapping trench must have the following properties.

(1) It has good thermal shock stability.
(2) Resistant to corrosion and erosion, and resistant to structural spalling.
(3) It has suitable expansion properties, anti-permeability, and does not stick to copper liquid.
(4) It has lower porosity and higher strength.

Aluminum Silicon Carbide Castables for Sale

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High Alumina-SiC Ultra-Low Cement Castable

In response to usage requirements, refractory material manufacturers have cooperated with enterprises to develop high-aluminum-SiC ultra-low cement castables.

The Adding Amount of Silicon Carbide

Silicon carbide has the advantages of excellent slag resistance, small thermal expansion coefficient, high thermal conductivity, and good wear resistance. Adding an appropriate amount of silicon carbide to high-aluminum ultra-low cement castables can improve its resistance to copper liquid erosion and structural spalling. For the sample with SiC added, as the silicon carbide content in the matrix increases, the compressive strength of the castable first increases and then decreases. The linear change rate after burning increases with the temperature, from shrinkage to expansion, and changes with the SiC content. increases with the increase. This is because as the temperature continues to increase, the oxidation rate of SiC accelerates.

The Adding Amount of Silica Powder

The addition of silica powder can improve the normal temperature strength and post-fired strength at medium and high temperatures of the castable, and reduce the apparent porosity of the material. Microsilica powder can effectively reduce the oxidation rate of SiC at high temperatures. Because silica powder not only forms a siliceous protective film on SiC, but also sinters easily at high temperatures, increasing the thickness of the protective siliceous layer. Therefore, silica powder has a protective effect in inhibiting SiC oxidation when the temperature is above 1000°C. The results show that when the SiC addition amount is optimal and an appropriate amount of silica powder is added, the various properties of the sample are the best and the oxidation rate of SiC is the lowest.

Sintering Agent

The temperature of copper extraction is between 1150 and 1300°C. At this time, the bonding phase of the general castable is at the weak link. That is, a strong ceramic bond is not formed, and erosion often occurs. In order to improve the erosion resistance of the castable and the oxidation resistance of SiC, appropriate sintering agents should be added. To this end, the types and amounts of sintering agents were studied. The results show that when the adding amount of composite sintering agent is 10%, products with excellent performance can be obtained.

Application of High-Aluminum-SiC Ultra-Low Cement Castable in Copper Channel of Copper Converter

Based on the above experimental results, high-aluminum-SiC ultra-low cement castables were used for industrial testing on the copper tapping channel of the blister copper converter. The service life has reached more than three times that of the original magnesia ramming material. The main reason for the damage of high-aluminum-SiC ultra-low cement castables is that the surface layer is oxidized, followed by slag hanging, and peeling off due to thermal shock. The new surface layer oxidizes, slags, and peels off, over and over again, and is finally destroyed. Due to the superior oxidation resistance of this castable, oxidation is limited to the surface layer, so the damage rate is much slower than that of magnesia ramming materials.

Application of Ferrosilicon Nitride in Al2O3-SiC-C Blast Furnace Iron Trench Castables

July 23, 2024 by rsrefractorycastable

The blast furnace iron trench is a channel for guiding high-temperature molten iron and molten slag. Its refractory lining is subject to high temperature, mechanical and chemical erosion by molten iron and slag liquid. The first is the scouring effect on the surface of the refractory material when iron and slag flow. Secondly, due to the frequent alternation of hot and cold during tapping or the long-term action of high temperature, micro-cracks occur in the refractory material. Such microcracks promote the penetration and structural damage of molten iron and slag. Therefore, the iron trench lining material is required to have strong resistance to the erosion of molten iron and slag, good thermal expansion stability, small change in burnt volume, and strong oxidation resistance. It is easy to construct and does not adhere to slag iron, making it easy to repair and dismantle. It has a uniform, highly dense structure and high strength. It does not produce harmful gases and is conducive to environmental protection.

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Service Life of Blast Furnace Tap Trough Refractory Materials

After the blast furnace became larger, the usage conditions of the tap trough also changed, and the erosion and wear of the trough wall by molten iron increased. Increasing the generation gap, reducing costs and reducing the work pressure of workers behind the furnace are the main goals of the work behind the furnace. For the main iron trench and different parts, the erosion conditions are different, and the selection of materials should be different to achieve a comprehensive and balanced economic life. For iron ditches, efforts should be made to improve the anti-penetration properties of the material. As far as the construction technology and maintenance process are concerned, some operating methods are also closely related to the service life of the material.

Damage Mechanism of Blast Furnace Iron Trench Refractory Materials

The damage to refractory materials used in blast furnace iron trenches is mainly due to cracks, chemical erosion, penetration, and erosion caused by thermal shock of high-temperature molten iron and slag.

The first is the effect of high-temperature molten iron. Since the blast furnace has a certain pressure, the molten iron with a temperature of up to 1500°C spurting out from the blast furnace directly impacts the working surface of the iron trench. This results in erosion and damage of trench lining materials, especially within the impact zone. The vortex formed here not only intensifies the thermal impact of molten iron and slag on the trench lining, but also intensifies the erosion and erosion of the iron trench lining. The most severe damage is to the trench lining material. Therefore, the damage here determines the service life of the tap hole.

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Secondly, in the metallurgical industry, the damage caused by molten slag to refractory materials is the most serious. Since the slag contains relatively complex chemical components, it is easy to react with components in refractory materials to form low melting point substances. Causes damage to the structure of the refractory material and reduces the corrosion resistance, erosion resistance and other properties of the refractory material. When the blast furnace taps iron, in addition to high-temperature molten iron, there is also high-temperature slag entering the tap trough. Slag not only aggravates the erosion of the iron trench lining, but also tends to adhere to the trench wall. It is the main factor that damages the trench lining material. In addition, the damage to the iron trench lining material caused by molten slag also varies depending on the structure of the tap trench. For molten iron tap trenches, the main damage caused by molten slag is erosion and erosion. As for the non-molten iron tap trough, in addition to the above functions, more and more slag adheres to the trench wall and is deposited, which hinders the normal use of the tap trough. Therefore, slagging operations must be carried out in front of the furnace. When slag removal is carried out, the refractory material of the trench wall will be removed together with the bonded slag, which is the greatest damage to the non-molten iron tapping trench lining.

Third, although the blast furnace is a high-temperature equipment that operates continuously, tapping is an intermittent operation, causing the trench lining refractory material to withstand rapid changes in temperature. At this point, the molten iron tap trough also has advantages over the non-molten iron tap trough. Therefore, rapid changes in temperature reduce the thermal shock stability of iron trench lining refractory materials.

In addition to the above damage, the penetration of molten iron into the iron trench lining material is also one of the factors that destroys the material structure. It causes the material to erode and peel off, thereby reducing erosion resistance.

Rongsheng Silicon Nitride Combined Silicon Carbide Castable for Iron Trench

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Ferrosilicon Nitride is Used in Al2O3-SiC-C Blast Furnace Iron Trench Castables

In the past, the iron trenches of small and medium-sized blast furnaces were mainly artificial ramming materials mixed with coke, clay clinker and clay, mixed with tar or syrup, and were manufactured by each ironworks. This kind of iron trench lining has a short service life and the iron flow capacity is less than 10,000 tons. In long-term production practice, people have gradually realized that adding silicon carbide and graphite can significantly increase the service life of the tap hole. In terms of refractory aggregates, corundum materials, high-aluminum vanadium clay, magnesia-aluminum spinel materials, etc. have been tested. In terms of binders, various iron trench materials including resin bond, cement bond, and clay bond were tested. After continuous attempts, various types of iron trench materials suitable for large, medium and small blast furnaces have been gradually formed. For high-temperature and high-pressure operations, the tapping volume is large, the flow rate is fast, the temperature is high (1500°C), the tapping times are frequent, the time is long, the amount of slag is large, and the tap trough lining material is used in harsh conditions. To this end, a new generation of iron trench materials based on Al2O3-SiC-C has been developed, which basically meets the production requirements, and the iron throughput ranges from tens of thousands to 100,000 tons. Blast furnace trench castables.

Al2O3-SiC-C castable has good slag erosion resistance and erosion resistance. It has been widely used in the main trench, skimmer and branch trench of blast furnace tap trench. However, due to the development of smelting technology, the continuous improvement of blast furnace utilization coefficient and the requirement of longevity of blast furnace, it is urgent to further improve the service life of Al2O3-SiC-C iron trench castables. However, the current Al2O3-SiC-C iron trench castables are prone to falling off due to periodic chemical erosion of slag and molten iron, thermal shock and erosion of slag and iron. At the same time, the oxidation of silicon carbide and carbonaceous materials in the castables at high temperatures will also cause structural damage to the materials, which will lead to the damage of the castables.

Ferrosilicon Nitride Al2O3-SiC-C Iron Trench Castable

In recent years, research on the use of ferrous silicon nitride in Al2O3-SiC-C iron trench castables has been increasing. Si3N4 in ferrosilicon nitride has the advantage of not being completely wetted with slag and iron, which can improve the corrosion resistance of iron trench castables. The oxidation product of Si3N4 will form a SiO2 protective film on the surface of the sample, hindering further oxidation of the material and enhancing its anti-oxidation performance. The metallic phase Fe has the effect of assisting sintering and can improve the mechanical properties of the castable. It has better antioxidant properties than pure Si3N4. At the same time, the N2 generated by the oxidation of Si3N4 in ferrosilicon nitride at high temperatures and the CO generated by the oxidation of carbon materials will block the internal pores of the material, thus effectively preventing further oxidation.

Long Service Life Silicon Nitride Combined Silicon Carbide Thermal Shock Resistant Castables

July 16, 2024 by rsrefractorycastable

With the development of the cement industry, in order to adapt to the requirements of large-scale, long-lasting, energy-saving and environmentally friendly cement industry, the requirements for refractory materials for the lining of large and medium-sized cement kilns are becoming increasingly stringent. Existing refractory materials can no longer meet production needs in actual use. Especially at the kiln mouth, grate cooler, coal injection pipe, smoke chamber, top of preheater and other parts. Due to high-temperature thermal stress, rapid cooling and rapid hot air flow impact, high-temperature cement clinker wear and high-temperature gas alkali corrosion, it is easy to cause cracking, peeling and wear of the lining, making it difficult to meet the requirement of the kiln age being more than one year. Moreover, the corundum-silicon nitride-silicon carbide composite castable used in the tuyere belt of the ironmaking blast furnace can be poured and constructed quickly. However, its alkali resistance and thermal shock stability cannot meet the requirements for refractory materials for large and medium-sized cement kiln linings.

Silicon Nitride Combined Silicon Carbide Castable

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Therefore, it has become a primary task to prepare a refractory material with strong thermal shock stability, high compressive strength, small thermal expansion coefficient, low thermal conductivity, good alkali resistance and long service life. Long-life silicon nitride combined with silicon carbide thermal shock-resistant castables solves the above technical problems for the blast furnace and cement industry.

Silicon Nitride Combined with Silicon Carbide Thermal Shock Resistant Castable

This castable uses silicon nitride and silicon carbide as the main raw materials and is also supplemented with corundum, activated alumina and other materials. Using composite explosion-proof materials and additives, silicon nitride combined with silicon carbide thermal shock-resistant castables are made. Its raw material composition is as follows:

Silicon nitride 150-300 mesh, 5-20%.
Black silicon carbide 100-200 mesh, 10-30%.
Green silicon carbide 150-300 mesh, 5-20%.
Tabular corundum, 20-30%.
White corundum, 15-30%.
Activated alumina 300-600 mesh, 3-12%.
Metal aluminum powder 80-150 mesh, 0. 5-3%.
Heat-resistant steel fiber 5%.
Metal silicon powder 100-200 mesh, 2-8%
Aluminate cement 3-6%.

The silicon nitride combined with silicon carbide castable has excellent high-temperature stability, high thermal shock stability (water cooling, 1100°C ≥ 30 times), and high alkali corrosion resistance (level 2 or above). Excellent normal and high-temperature strength and high-temperature material wear resistance. Suitable as long-life (more than one year) large and medium-sized cement kiln lining materials. It is especially suitable for key parts with harsh working conditions such as the kiln mouth, coal injection pipe, cement kiln smoke chamber, grate cooler, and top of the preheater of large and medium-sized cement kilns.

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Analysis of the Causes of Peeling, Cracking, and Peeling of Castables for Cement Kiln Burner Linings

The burner is an important process equipment of the cement kiln firing system. It has a great relationship with clinker output and quality, the life of refractory materials in the kiln, clinker coal consumption, environmental protection emissions, etc. The main reason that affects the service life of the burner is the damage of the burner lining castable. How to extend the service life of the burner lining castable is particularly important. The four-channel pulverized coal burner of a cement manufacturer uses Al₂O₃-SiC series low-cement refractory castable as a protective lining with a thickness of 100mm. Serious damage occurred to the burner head and bottom 2 months after it was put into use. The main modes of damage are peeling, cracking and peeling.

Burner Lining Castable Damage

The damage to the burner lining castable is shown in Figure 1. Take a piece of lining castable from the burner that is completed from outside to inside as a sample, and observe the overall condition of the sample. Divide the residual lining sample into four layers from outside to inside according to different colors. The division of residual lining layers is shown in Figure 2.

Figure 1 Damage to Burner Lining Castables

Figure 2 Analysis of 4 Levels of Lining Castables

From the appearance of the damaged castable, it can be clearly seen that the first layer is light yellow and has obvious erosion, indicating that a liquid phase has been produced on the surface of the castable. The second layer appears white and has the loosest structure. The castable has completely deteriorated and is basically a crystallized accumulation of alkali salts. Layer 3 appears light black and has a dense structure, and the aggregate particles in the castable components can be seen. Layer 4 appears gray and has a dense structure. No crystalline material is found. The matrix part of the castable and the aggregate particles can be clearly seen.

After combining experiments and analyzing its components, a conclusion is drawn.

(1) The outer surface of the burner lining castable produces low melting point anorthite and potassium feldspar, which produces a liquid phase at high temperatures, reducing the surface strength of the castable and causing corrosion damage to the castable.
(2) The middle brushing of high-temperature secondary air damages the SiO₂ film formed by the oxidation of SiC on the surface of the castable, causing alkali salts to enter the castable to form continuous erosion.
(3) The chemical corrosion damage of the burner mainly comes from K salt, which mainly has two aspects: on the one hand, the K salt that penetrates into the castable reacts with the matrix to generate new compounds, destroying the matrix composition of the castable. On the other hand, due to the density difference of the potassium salt itself, volume expansion occurs after deposition and cooling in the castable matrix. The combined effect of two reasons leads to damage to the castable lining.

Cost-Effective Low-Cement Castable with Excellent Thermal Shock Stability

July 10, 2024July 9, 2024 by rsrefractorycastable

Low cement castable is one of the most widely used castables in thermal kiln linings, with Cost-Effective performance and easy construction. Low-cement castables have the advantages of less water addition, high density, good volume stability, and high strength at high temperatures. However, low-cement castables have poor air permeability and poor thermal shock resistance at high temperatures. When the castable is baked after being demolded, the low-cement castable is prone to bursting, peeling, peeling, etc. In severe cases, it may even damage the entire kiln lining. Therefore, how to improve and enhance the explosion-proof performance of low-cement castables is of great significance to the large-scale application and development of low-cement castables.

Low Cement Castable Directly from Factory

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How to Increase the Explosion-Proof and Thermal Shock Stability of Low-Cement Castables?

Rongsheng castable manufacturer, in order to improve the explosion-proof properties of low-cement castables, uses the method of adding explosion-proof fibers to low-cement castables to increase the permeability of the castables. The addition of explosion-proof fiber significantly improves the explosion-proof performance of low-cement castables. After the explosion-proof fiber is added to the castable, the explosion-proof fiber will shrink and melt when the castable is heated and baked after demoulding. Elongated pores are formed in the castable, increasing the opening vents inside the castable and improving the air permeability of the castable. This accelerates the discharge of water vapor, thereby improving the burst resistance of the castable and improving the explosion-proof performance of the castable.

The overall strength of low cement castables is very high at high temperatures. However, in some thermal kilns that work intermittently, frequent shutdowns and restarts will affect the service life of the low-cement castable working lining. In the case of rapid cooling and heating, it is very easy for the castable lining to peel off and crack, affecting the service life of the low cement castable.

Rongsheng Unshaped Refractory Castable Manufacturer, adding a certain amount of silicon carbide to low-cement castables will significantly improve the thermal shock stability of low-cement castables when facing rapid cooling and rapid heating conditions. However, the amount of silicon carbide incorporated needs to be strictly controlled. Because silicon carbide has a high thermal conductivity, when too much silicon carbide is added, the overall thermal expansion coefficient of low cement castables will increase, which is detrimental to the thermal shock stability of low cement castables. Castable manufacturers strictly control the amount of silicon carbide added to optimize the thermal stress of low-cement castables caused by excessively high thermal conductivity of silicon carbide. Only then will the low-cement castables have the best thermal shock stability when subjected to thermal shock. .

Whether low-cement castables need to improve their explosion protection or thermal shock stability, a comprehensive analysis needs to be made based on the working environment, operating temperature, erosion conditions, etc. of the thermal kiln. Then, make a reasonable formula based on the actual use needs of the enterprise’s kiln. The refractory material industry is an industry with very strong practical applications. There is no perfect refractory material. You can only find the most suitable refractory material based on the actual situation.

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Silicon Carbide Composite Refractory Castable

What happens when silicon carbide is added to low-cement refractory castables? That turns into silicon carbide low cement castable!

The biggest feature of silicon carbide castable is wear resistance, followed by strong corrosion resistance. Its technological feature is that based on the process of refractory castables, a certain proportion of silicon carbide is added to form a composite refractory castable.

Because silicon carbide has strong wear resistance, adding it to refractory castables can improve the wear resistance of the castables. Moreover, the wear resistance coefficient of the castable is reduced, and the service life can be increased by 1 to 2 times. Silicon carbide has high thermal conductivity and small thermal expansion coefficient. Adding an appropriate proportion can increase the thermal shock resistance of the castable, and the thermal shock resistance of the castable is also relatively good. Especially for silicon carbide combined with silicon nitride products, the thermal shock resistance will be increased by 2 times compared to the thermal shock of the castable before adding it. It also prevents slagging or skin formation on the surface of the castable.

However, refractory castables with high silicon carbide content have high thermal conductivity, and the disadvantage of silicon carbide castables is that they are easily oxidized. Manufacturers add metallic silicon powder to the castable to inhibit the oxidation of silicon carbide. Castables combining silicon nitride with silicon carbide have lower oxidation resistance. Because the base material of silicon nitride combined with silicon carbide castable is in the form of interwoven fibers, it has high air permeability and plays a small protective role on silicon carbide particles. In silicate-bonded and silicon oxynitride-bonded silicon carbide products, the surface of the silicon carbide particles is wrapped by a continuous base material. Therefore, it has strong antioxidant properties.

Silicon carbide castables can maintain high strength and wear resistance at high temperatures, and have good chemical stability and will not be eroded by acid and alkali solutions. In addition, the wetting angle of silicon carbide with molten metal and slag is large. It has good corrosion resistance to various furnace lining solids, liquids and gases.

Rongsheng Unshaped Refractory Castable Manufacturer

Rongsheng Unshaped Refractory Castable Materials Manufacturer is a powerful manufacturer of refractory materials production and sales. Our environmentally friendly, fully automatic unshaped refractory material production line ensures the smooth delivery of unshaped refractory materials. Moreover, our professional technical team can customize the refractory castable formula according to the actual working conditions of the kiln lining to ensure the long service life of the refractory lining. Contact us to get free samples and quotes.

Castable Low Cement Lining With Silicon Carbide

July 2, 2024 by rsrefractorycastable

Low cement silicon carbide refractory castable is a special refractory material. Made of low cement ratio, silicon carbide aggregates and powders, ultrafine powder, CA-70 cement and antioxidants. It is suitable for thermal equipment such as power generation boilers, non-ferrous metallurgical furnaces and incinerators. It has low linear expansion coefficient, high thermal conductivity, high strength and good wear resistance. Low-cement silicon carbide refractory castables can improve the fire resistance and thermal efficiency of the equipment under reasonable proportions and use under appropriate conditions, and the application effect is good.

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Low Cement Silicon Carbide Refractory Castable

Low cement silicon carbide refractory castable is a special refractory material suitable for thermal equipment such as power generation boilers, non-ferrous metallurgical furnaces and incinerators. This silicon carbide refractory castable has the following characteristics:

Low coefficient of linear expansion. As the main refractory aggregate and powder, silicon carbide has a low coefficient of linear expansion, which can reduce the possibility of thermal stress.
High thermal conductivity. Silicon carbide has good thermal conductivity and can effectively conduct heat and improve the thermal efficiency of the equipment.
High strength. The use of low cement ratio and reasonable binder can improve the strength of the castable and increase its compression and flexural resistance.
Good wear resistance. Due to the use of silicon carbide with SiC greater than 97% as refractory aggregate, the castable has excellent wear resistance.

Low Cement Silicon Carbide Castable in RS Factory

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Raw Material Composition of Low Cement Silicon Carbide Refractory Castable

The preparation of low cement silicon carbide refractory castable includes the following ingredients:

Refractory aggregates and powders mainly use silicon carbide with SiC greater than 97%, which has excellent refractory properties.
Ultra-fine powder. Adding SiO2 ultrafine powder can improve the density and refractoriness of the castable.
Binder, using CA-70 cement as the binder, can ensure that the castable has a certain strength and durability.
Antioxidants. Metallic silicon antioxidants are used to prevent the oxidation of silicon carbide.

The performance test results of the castable at different temperatures are as follows:

After drying at 110℃, the bulk density is 2.5g/cm³, the compressive strength is 45MPa, and the flexural strength is 9MPa.
After firing at 1000℃, the linear change is -0.2%, the compressive strength is 107MPa, and the flexural strength is 24MPa.
After firing at 1450℃, the linear change is +0.3%, the compressive strength is 130MPa, and the flexural strength is 54MPa.
The thermal conductivity at 400℃ is 12.2W/(m·K).

In summary, low cement silicon carbide refractory castable has a low linear expansion coefficient, high thermal conductivity, high strength and good wear resistance. Through reasonable proportions and the use of appropriate materials, the fire resistance and thermal efficiency of the equipment can be improved. The castable has good application results in thermal equipment such as power generation boilers, non-ferrous metallurgical furnaces, and incinerators.

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Low Cement Mullite Corundum Castable

Low-cement mullite-corundum refractory castables use sintered or electro-fused mullite, brown corundum, alumina-based corundum and white corundum as refractory bone powder. Sometimes special-grade alumina clinker powder is also used, and ultra-fine powder is mixed with α-Al2O3 and silica fume. It is formulated with aluminate cement as binder and additional dispersant. This material is used for steel rolling heating furnace lining, water cooling pipe wrapping and burner bricks. The use effect is good on thermal equipment such as tundish slag weir, medium and small blast furnace tap trough and electric furnace cover.

Does Low Cement Castable Need to Add Steel Fiber when Used in Settling Chamber?

When low-cement castables are used in settling chambers, steel fibers are usually not required. When the design of the settling chamber is unreasonable, the discharge opening of the cone section is too small and the smoke dust needs to be beaten. At this time, steel fibers can be added to the low cement castable to enhance wear resistance and extend the service life. Under special circumstances, the settling chamber can be lined with clay bricks or high-aluminum castables with high-voltage electrical porcelain added.

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If low-cement castables are used in settling chambers, there is generally no need to add steel fibers.

If the lower opening of the cone section of the settling chamber is too small and needs to be beaten during use, just add steel fibers to the low-cement castable used in the cone section to increase traction, wear resistance, and erosion resistance. However, if the discharge port of the settling chamber is reasonable, and the size of the settling chamber and the rotary kiln are also reasonable, there is no need to add steel fiber to the castable.

The temperature of the settling chamber is not high, and it mainly plays the role of dust removal. The dust has fallen to the bottom before the flue gas flows out of the settling chamber, and is collected by the ash hopper at the bottom of the settling chamber. The unsettled dust is brought out with the flue gas. General low-cement castables can be used.

Generally, it is common to use high-aluminum castables and low-cement castables. However, clay bricks are also used as linings for settling chambers. There is also the use of high-aluminum castables with a certain proportion of high-voltage electrical porcelain added to the castables to create a glazed surface to facilitate the fall of smoke and dust.

Adding steel fibers to low-cement castables is rarely used in settling chambers. In recent years, the settling chambers of some white ash rotary kilns and zinc volatilization kilns are often lined with clay bricks. However, the size design of some settling chambers is not reasonable. If the settling chamber is too small, and the cone section discharge opening is also too small, there will be a situation of beating during the production process to make the smoke and dust sink. This will speed up the service life of the cone section lined with clay bricks or low-cement castables.

Therefore, under special circumstances, a reasonable proportion of steel fibers is added to the low-cement castable to increase the wear resistance of the cone section and extend its service life.

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