Rongsheng Refractory Castables is a refractory material manufacturer with rich production and sales experience. Rongsheng, based on years of production and sales experience, can customize refractory lining solutions for high-temperature industrial furnace linings. The determination of the thickness of high-temperature refractory castables mainly depends on the working environment temperature, material properties and usage requirements. Contact Rongsheng for detailed information.
Working environment temperature: The working environment temperature is the most important factor in determining the thickness of refractory castables. The higher the temperature, the greater the castable thickness required to withstand the thermal stress at high temperatures.
Monolithic Refractory Castables for Refractory Linings
Material properties: Refractory castables of different materials have different refractory properties and thermal expansion coefficients, and the differences in these properties will directly affect the choice of thickness. For example, the thickness design ranges of light and heavy materials are 10-200mm and 200-300mm respectively.
Usage requirements: Usage requirements are also an important factor in determining thickness. Some projects may require that the castables not only withstand high temperatures but also have corrosion resistance, which requires a more sophisticated design.
Recommendations on the thickness of refractory castables in different application scenarios
Ladle: The thickness of the working lining is usually 100-150mm, and the thickness of the coating layer is 10-15mm.
General furnace type: The thickness is generally 200-230mm, and there are also designs of 150-200mm thick according to the location conditions.
Special requirements: If the furnace weight needs to be reduced, it can be designed to be 80-100mm thick, but the service life will be shortened accordingly.
As the amount of refractory castables continues to increase, the scope of use is also getting larger and larger. However, the thickness of different refractory castables and the thickness of spray coatings and coatings are different.
The thickness of heavy refractory castables or refractory concrete cannot be less than 100mm. If it is less than 100mm, the service life of heavy castables will be affected. The most suitable thickness is 200mm. When there are certain restrictions on the use of some parts, it is also possible to pour at a thickness of not less than 100mm, and of course 150mm is also possible. If conditions permit, it is best to pour 200mm.
Of course, some user manufacturers require that refractory castables be poured at 220mm? Of course. Generally, 200mm is suitable. If 220-250mm is OK, the service life will be longer. If the user requires the refractory castable to be poured at a thickness of 50mm, be sure to tell the user that 50mm castables are not possible. Not only does it affect the service life, but also because the particles of the refractory castables are large and the thickness is too thin, it will not work at all.
The pouring thickness of lightweight refractory castables cannot be less than 80mm. If there is no specific restriction on the location of use, pouring 100-150mm is most appropriate.
There are also some user manufacturers who cannot distinguish whether to use refractory castables for pouring, coating or spraying. They should first ask the required thickness of pouring or spraying, and give users suggestions on using castables or spray coatings and coatings. The thickness of spray coatings and coatings is 30-50mm, usually 50mm is the most suitable. Too thick spray coatings or coatings will cause delamination, and too thin will affect the service life.
Therefore, as long as the user requires 30-50mm thickness, spray coatings or coatings must be used.
There are also refractory plastics, and the thickness is the same as spray coatings and coatings, 50mm is the most suitable. If 80mm is used for a specific temperature and environment, it can also be used, but the thickness cannot exceed 80mm. Too thick will also cause delamination and affect the service life.
Suggestions for the construction and maintenance of refractory castables
During construction, adjustments need to be made according to the specific parts and conditions to ensure the versatility of the construction parts.
In actual construction, the thickness selection needs to be adjusted and optimized according to the specific situation to ensure the quality and safety of the project.
Plastic is a refractory material that was developed and applied earlier and is mainly used in heating furnaces, electric furnace tops, and other parts. Due to its shortcomings such as short storage time and poor fire resistance, its application range is limited. However, this refractory material has some irreplaceable advantages, such as the high-temperature strength of the furnace body constructed with plastic, excellent thermal shock resistance, low thermal conductivity, and flexible construction methods.
Selection of Refractory Plastic Aggregates
Refractory plastics should have excellent plasticity, moisture retention, and high-temperature performance. To meet these conditions, it is very important to select suitable raw materials. The raw materials should have good volume stability. During the heating process, they can be well-sintered and reacted with binders such as clay. Aggregates should have appropriate particle size and grading. Generally, the critical particle size of refractory plastic aggregates is less than 10 mm, the aggregate content is 55% to 65%, and the powder content is 35% to 45%. Through strength tests and moisture retention tests, it was found that although the plastic produced with grade 3 high aluminum and grade 2 high aluminum as the main raw materials has a higher strength after burning, the moisture retention of the material is poor. Therefore, it is determined to use special grade high aluminum alumina as the main raw material, and it is required to be sintered densely and have a low impurity content. In order to improve the moisture retention performance, the iron oxide content in the material should be strictly controlled.
Effect of Clay and Powder Addition on the Performance of Refractory Plastic
Binding clay is added to plastic, which mainly plays a bonding role and improves its plasticity and sintering performance. The particle size of clay should generally be less than 200 mesh. Its dosage should be minimized while ensuring the plasticity and bonding ability of plastic. If too much is added, the linear shrinkage of plastic will increase after high-temperature firing, the load softening temperature will decrease, and the high-temperature creep will increase. If the amount added is too little, the plasticity of the material cannot be guaranteed. Through experiments, it is determined that the amount of clay added is 5% to 15%. In order to reduce the linear change of plastic after firing, an appropriate amount of kyanite is added. Since kyanite produces volume expansion at high temperatures, it can offset part of the shrinkage of plastic. Its fineness is 150 mesh, and the amount added is controlled at about 5%. In order to improve the plasticity and thermal shock resistance of plastic and further reduce the impurity content in the raw materials, alumina powder, and silicon powder are added. This can not only improve the construction performance of the material but also increase the medium and high-temperature strength of the product. The total amount of the two is generally controlled at 6% to 12%, which is more reasonable.
Through experiments, it is found that when the plastic index is around 14%, the plastic is relatively hard and the construction performance is poor. When the plastic index is around 26%, the plastic feels softer and the construction is easier. In order to facilitate construction and meet the requirements of other performance indicators. Through repeated experiments, it is confirmed that the plastic index of the plastic is about 28%.
Selection of Fire-Resistant Plastic Binder
In order to make plastic have higher strength and excellent moisture retention performance, various binders were tested, such as phosphoric acid, water glass and aluminum sulfate. Through experiments, it can be proved that plastic with phosphoric acid as binder has higher strength index. However, due to the strong acidity of phosphoric acid and the high iron oxide content in the raw material, phosphoric acid can easily react chemically with iron oxide, which makes the moisture retention performance of plastic worse. Using aluminum sulfate as a binder, plastic has a longer moisture retention performance, but the strength index of plastic cannot meet the use requirements. Using water glass as a binder, the moisture retention performance of the material is better in the short term, but after a long storage time, the construction performance of plastic deteriorates. In addition, when the plastic combined with water glass is baked, the hard shell produced on the surface will have an adverse effect on the strength of the plastic construction body. Through repeated experiments, it was determined that the two binders of phosphoric acid and aluminum sulfate were used in combination, so that the moisture retention performance and strength index of the plastic can meet the use requirements.
Through continuous moisture retention experiments, it was found that the moisture retention performance of plastics with high-aluminum from special downdraft kilns as aggregates is significantly better than that of plastics with other low-grade aggregates. This is due to the dense sintering of special-grade aggregates and the low water absorption rate of particles.
Influence of binder types
Binders have the greatest impact on the moisture retention performance of plastics and also play a key role in other properties. If improperly selected, plastics will not meet the requirements of use.
Through experimental research on the moisture retention performance and compressive strength performance of the test blocks, as well as comprehensive considerations such as raw material costs, phosphoric acid, and aluminum sulfate were finally selected as composite binders. This can not only meet the moisture retention performance requirements of plastics but also meet the requirements of medium and high-temperature strength.
Effect of admixture types
Experiments show that adding organic acids (such as oxalic acid) and dextrin and other admixtures can prevent or delay the reaction between the binder and the refractory material, and play a role in extending the moisture retention of plastic. Some admixtures are oily and can effectively reduce the agglomeration of plastic, which mainly extends the moisture retention of the material from a physical aspect. Oily moisturizers and main binders such as phosphoric acid are not miscible but can reduce the chance of chemical reactions between phosphoric acid and raw materials, making the moisturizing effect better.
When used in furnaces such as heating furnaces and annealing furnaces, plastic has certain advantages over castables. It does not require on-site mixing equipment and can be directly constructed. It has a large viscosity and does not flow. It is easier to combine with the old lining during repair, and local repairs can be performed without templates. Because it has a low water content, the requirements for baking conditions are not very strict.
Conclusion
(1) Using high-grade downdraft kiln high-alumina bauxite as the main raw material can significantly improve the moisture retention performance of plastics.
(2) Using phosphoric acid and sulfuric acid in a composite form, and adding an appropriate amount of additives, plastics with relatively good moisture retention and strength indicators can be produced. The effect of using a single combination is not ideal.
(3) Select high-grade high-alumina bauxite with dense sintering and low impurity content to minimize the iron oxide content in the material. In addition, adding an appropriate amount of moisturizing agent can significantly extend the moisture retention period of plastics.
Rongsheng amorphous refractory castable manufacturer can provide high-quality amorphous refractory lining materials for high-temperature industrial furnaces. If you need to purchase refractory plastics to extend the service life of refractory furnace lining materials. Please contact Rongsheng for free solutions for high-temperature industrial furnace linings.
Ladle is an essential container in the steelmaking process. With the continuous development of smelting technology, especially the processing of out-of-furnace refining LF and RH, its role has evolved from the simplest receiving molten steel to a furnace that undertakes certain smelting functions. If the molten steel stays in the ladle for a long time, it will inevitably cause the temperature of the molten steel to dissipate, and the ladle lining with high thermal conductivity will cause the heat dissipation loss of the molten steel to increase. The deformation of the ladle shell becomes more serious, and the temperature drop rate of the molten steel increases, causing serious slag hanging nodulation, and cold steel on the ladle wall. Excessive low temperatures may even force the middle package to cut off the flow and final pouring. It not only affects the quality of the cast slab but also reduces the yield of molten steel and increases the production cost. Therefore, thermal insulation ladles are increasingly becoming a need for steel mills. The structural model of thermal insulation ladle refractory materials is usually lightweight insulation panels or nano panels + permanent layer castables + working layer refractory materials. Rongsheng’s long-life thermal insulation refractory castable for ladle furnace lining. Contact Rongsheng to get a free quote.
Lightweight High-Strength Castable for Steel Ladle
The insulation board itself, which plays the most important role in thermal insulation, needs a layer of refractory material to protect it. The material must first protect the insulation material from too much pressure, and secondly, protect the insulation material from exceeding the operating temperature (if it must be below 1000°C), then the ladle Permanent layer castables are such important materials. The ideal permanent layer refractory material for thermal insulation ladles should have good thermal stability, thermal insulation, corrosion resistance, safe and reliable application, complete structure, and long service life. In order to maintain the good thermal insulation performance of the ladle and reduce the temperature drop of the molten steel, the performance evaluation of the new CA6 castable and the lightweight mullite castable was conducted in this work and applied to the ladle, achieving a relatively good comprehensive thermal insulation effect.
Performance comparison of thermal insulation refractory castables for ladles
At present, the permanent layer materials of ladles are mostly ordinary high-aluminum castables, and the main raw material is bauxite. There are the following shortcomings in the use of this refractory castable. First, the thermal conductivity is high, which causes energy loss during use. Second, the refractoriness is low. If the working layer is used abnormally and the molten steel directly contacts the permanent layer, the probability of steel leakage will be greater and the safety factor is low. Third, the volume density is larger and the empty ladle weighs more. Therefore, the special requirements for ladle insulation are not met, and it is necessary to develop new permanent layer castables with excellent comprehensive properties. Performance comparison of new CA6 castable and lightweight mullite castable.
Among them, the CA6 raw material (CaAl12O19, abbreviated as CA6) is the calcium aluminate phase with the highest Al₂O₃ content in the CaO-Al₂O₃ system. Its melting point is 1875℃, its thermal expansion coefficient is 8.0×10-6℃⁻¹, its particle volume density is 2.70g·cm⁻³, and its apparent porosity is 26.8%. The fire resistance of this material is similar to that of plate corundum, but its thermal conductivity is only 1/3 of corundum. It is a new type of high-quality thermal insulation material that has emerged in recent years. CA6 castable is made of CA6 as aggregate, and the matrix part is made of plate-shaped corundum fine powder, alumina powder, and calcium aluminate cement as binding agents. The volume density of spherical lightweight mullite particles is 1.59g·cm⁻³, and the apparent porosity is 38.9%. The lightweight mullite castable is made of microporous M70 spherical lightweight mullite balls as aggregate, and the matrix part is made of plate-like corundum fine powder, alumina powder, and calcium aluminate cement as binding agents to ensure Better resistance to slag erosion to improve the safety of the permanent layer.
The volume density of lightweight mullite castable is 2.17g·cm ⁻³, and its unit weight is 24% lower than the currently used high-aluminum castable. At the same time, the thermal conductivity is reduced by 16%, which can achieve the purpose of lightweight and low thermal conductivity of the ladle. CA6 castable is also 5.6% lighter than ordinary high-aluminum castable, and its thermal conductivity is reduced by 26%.
Pour the original ladle permanent layer castable B, the new CA6 castable C, and the lightweight mullite castable 3# into crucibles respectively. Add the final converter slag and conduct a slag corrosion resistance test on the crucible under the condition of 1500°C for 3 hours. Observe the resistance to melting loss and penetration of different materials. After completing the test, the crucible was cut open. The erosion status is as follows:
CA6 castable has the best resistance to erosion and penetration, with a large amount of slag remaining in the crucible hole; light mullite castable has the second-best resistance to erosion and penetration. The boundary between ordinary high-aluminum permanent layer casting slag and refractory material is not clear, and the crucible refractory material and slag are melted together. The resistance to penetration is slightly better than the resistance to erosion, indicating that more liquid phases have appeared in the high-aluminum castable at 1500°C. Therefore, the material needs to be improved to improve its high-temperature resistance, which is very important for the safety of the ladle. The micropores of spherical lightweight mullite are beneficial to improve corrosion resistance and permeability, so this lightweight material can also perform better in insulation and corrosion resistance.
Application Comparison
The above three kinds of castables are used for construction and application on 300t steel ladle. The target requirement of the lightweight mullite castable and CA6 castable for the permanent layer of the thermal insulation ladle is to have both good resistance to molten steel erosion and good thermal insulation properties. At the same time, the furnace has good structural integrity and a stable thermal insulation effect during the furnace service process. After three furnace campaigns, the surface conditions of the permanent layer of the steel ladle were different, and cracks of varying degrees appeared in the permanent layer of the steel ladle in the later stages of the furnace campaign. This is related to the thermal shock resistance, strength and damage of the material during the unpacking process. The comprehensive technology of how to reduce the cracking of the permanent layer material of the thermal insulation ladle still needs further in-depth research.
Judging from the average temperatures of each slag line in each furnace, the steel shells of the uninsulated ladle slag lines are all above 320°C, while the average temperatures of the four test slag lines using insulation are below 280°C. Generally, the temperature of the slag line steel shells has dropped. 50～100℃. The temperature drop of the steel shell in the wall part is between 20 and 50°C, which varies slightly depending on the configuration of the insulation material and permanent layer material. The insulation material of the thermal insulation test package remained in good condition during the furnace service period, and the average temperatures of the slag line and wall steel shell were lower than those of ordinary steel ladles, indicating that the permanent layer played a good protective role. In order to ensure safety, the current situation of obvious cracks in the new permanent layer material after two furnace operations still needs to be optimized and improved to ensure that it can be applied to four furnace operations.
In Conclusion
Insulated ladles have become an important technical measure for steel companies to save energy, protect the environment, and improve the quality of steel products. The permanent layer materials of ladles have been given higher requirements. The physical properties such as strength and strength of the developed CA6 castable and lightweight mullite castable meet the application requirements of the permanent layer of the ladle. At the same time, they have better thermal insulation and corrosion resistance than conventional high-aluminum castables and can protect thermal insulation materials. The function ensures that the ladle maintains good heat preservation during the furnace service period. Further in-depth research is needed on the comprehensive technology to reduce the cracking of the permanent layer material of the thermal insulation ladle.
Rongsheng Refractory Castable Manufacturer
Rongsheng refractory castable manufacturer, an environmentally friendly and advanced fully automatic unshaped refractory material production line, provides a reliable guarantee for refractory castable lining materials for high-temperature industrial furnaces. Annual output is 6W tons. Rongsheng Manufacturer can provide high-quality insulation and refractory castable products for ladles, rotary kilns, and non-ferrous smelting furnaces, as well as the design and construction of insulation layer refractory lining materials. The ladle is made of long-life insulation castables and is shipped directly from the manufacturer at a low price. Contact Rongsheng for free details.
The main unshaped refractory materials used in blast furnaces include refractory castables, refractory spray coatings, refractory plastics, and refractory coating materials. The use of amorphous refractory materials in high-temperature industrial furnace linings can effectively extend the service life of blast furnaces and improve the overall application efficiency of the equipment. It can also effectively reduce internal wear problems caused by increased labor intensity.
Monomorphous Refractory Materials for Blast Furnaces
How to use unshaped refractory materials in blast furnaces, and what are the characteristics and uses of unshaped refractory materials? The development and application of amorphous refractory materials can effectively improve the construction efficiency of the furnace lining, shorten the construction period, improve the integrity of the furnace lining, and enhance the overall performance of the lining body. It can effectively help enterprises reduce the number of furnace shutdowns and furnace repairs and improve economic benefits. Rongsheng Unshaped Refractory Castable Materials Manufacturer is a professional manufacturer and seller of refractory furnace lining materials. Furnace lining solutions can be customized according to the actual working conditions of the kiln. Contact us to get free samples and quotes.
Use of Amorphous Refractory Materials in Blast Furnaces
Characteristics of Unshaped Refractory Materials Commonly Used in Blast Furnaces
Compared with shaped refractory materials, the entire combustion process is canceled during the manufacturing process, which also makes the material itself amorphous. This is because the production process of amorphous refractory materials is relatively simple, and the materials are malleable. In the subsequent use process, unshaped refractory materials have the characteristics of convenient shaping. In this regard, during the casting process of the preliminary equipment, this method can be used to carry out the internal transformation of its furnace construction. This not only ensures cost reduction, but the simple manufacturing process can also increase the processing speed. It is worth noting that the service life of amorphous refractory materials is similar to that of refractory bricks, and its fire resistance and chemical stability can also reach the level of refractory bricks of the same type. Therefore, prefabrication can also be carried out before the furnace lining construction, and the unshaped refractory materials can be directly made into larger refractory precast blocks. Then, it is baked at low temperature before use, so as to ensure that it can survive long-term use inside the casting blast furnace. It can effectively extend the service life of the inner wall of the blast furnace and reduce the occurrence of internal damage caused by temperature changes.
The Use of Amorphous Refractory Materials in Blast Furnaces
(1) When manufacturing the internal structure of a blast furnace, the brick joints are the weak links of the blast furnace brick masonry. This also makes the corrosion process mainly destroy the joints during its application. In order to ensure that the overall service life of the blast furnace is extended, the damage and damage caused by furnace lining erosion can also be reduced. When filling the brick joints, it is necessary to use refractory mud to modify them, so as to ensure that the sealing degree of the furnace lining can be improved. Since refractory mud itself is an amorphous refractory material, during the preparation process, in order to ensure the overall adhesion and refractory degree, it is necessary to identify the brick joint material of the furnace lining. And the temperature of its application effect needs to be debugged, and then its gaps must be matched. This can ensure that after the filling is completed, the blast furnace lining can completely form a smooth hole. This ensures that the overall high-temperature resistance of the lining is reduced due to erosion.
(2) During the process of stacking the blast furnace lining, it is necessary to ensure that there is a cooling stave between the lining and the furnace shell. This kind of cooling stave requires the addition of filler so that the insulation or adhesive between the two layers of furnace lining can form its own protective film. And it can also bring out the application effect of internal substances. When a blast furnace is put into production for a period of time, the waist and lower part of the furnace body will be severely eroded due to the erosion of thermal energy. This also causes the composite energy to increase when it is working, causing the cooling equipment to be damaged under high temperatures and high pressure. At this time, bulges or cracks will appear on the surface of the furnace shell. In this regard, it is necessary to press the amorphous refractory material into the extended furnace body through the grouting method, so as to effectively increase the service life of the blast furnace. It can also reduce a series of safety risks caused by equipment damage.
(3) When cracks appear in the blast furnace lining, the surface can be treated by gunning the lining. Under normal circumstances, a layer of unshaped refractory material needs to be sprayed at this time to prevent fission caused by cracks. At the same time, the blast furnace itself is forged with high-quality bauxite and graphite as the main raw materials. Therefore, adding a certain amount of silicide can ensure that it becomes a hard object after high pressure and high temperature. It has the functions of high-temperature resistance and good thermal conductivity. Therefore, when used, it can also effectively improve its service life.
Application Methods of Unshaped Refractory Materials
Application Methods of Unshaped Refractory Materials in Blast Furnaces
New water wall technology
During the stacking process of the blast furnace, it is necessary to ensure that the internal cooling protection wall is formed by injection. The lining of this refractory material can also play the role of internal heat preservation and external heat insulation so that it can effectively reduce the loss of heat energy. Under normal circumstances, after one to two years of use, the internal cooling staves of a blast furnace will break. This also leaves exposed parts on the surface of the cooling stave, which increases heat energy consumption and also leads to safety hazards. Therefore, it can be said that if there is no refractory material, the slag will directly adhere to the cooling stave after combustion and cooling. Due to the large difference in its own expansion coefficient, the slag skin will fall off at any time. In order to effectively solve this problem, cermet lining can be used to transform it. Not only can it effectively protect its cooling stave, but its cermet lining can also be used to improve its fire resistance through the application of its own thermally conductive fibers, and ensure that its own metallic characteristics can be intact. This also makes it have the characteristics of better thermal conductivity and better plastic deformation ability. During application, the material will not become brittle even in high-temperature environments.
Furnace lining injection technology
Carbon monoxide inside the blast furnace will cause the deposition of carbon elements in the refractory material, which will in turn cause the overall structure of the material to be destroyed. The problems displayed on the furnace wall are internal fractures or a reduction in the strength of the material itself, or the material has cracked, resulting in irregular fractures at both ends of the material. Therefore, if it contains iron elements inside, it will catalyze this reaction, thereby increasing its overall collapse efficiency. Because, among all refractory materials, iron oxide must be used, which will react with carbon monoxide and form iron element. These iron elements happen to act as catalysts reflected in carbon deposition. Therefore, under the normal application of the blast furnace, this problem is unavoidable, which also causes the blast furnace to reduce its service life.
After a blast furnace has been used for several years, its taphole will show varying degrees of wear and tear, and its working efficiency will be reduced. Traditionally, when repairing it, mud cannons are used to press in to achieve overall improvement. However, this will not only increase the consumption of mud cannons, but also fail to cure the problem. In this regard, it is necessary to apply some new technologies to realize the transformation of its iron mouth. At the current stage, nano-silica combined with castable casting is one of the main application methods for taphole repair. Since silicon carbide is the main raw material, silica is used as a gelling agent, which not only effectively improves its overall structural strength, but also enables rapid drying without causing explosions. At the same time, after the repair is completed, it can also achieve an effective increase in its own structural strength.
The use of amorphous refractory materials in blast furnaces can effectively increase the service life of the furnace lining and save production costs for enterprises. Rongsheng Unshaped Refractory Materials Manufacturer, an environmentally friendly and fully automatic unshaped refractory material production line, provides a reliable guarantee for the longevity of lining materials for high-temperature industrial furnaces. Moreover, our professional technical team provides customized furnace lining materials and customized furnace lining solutions. Contact us to improve the life of your furnace lining.
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.
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.
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.
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.
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.
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 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.
Rongsheng Silicon Carbide Refractory Castable for Sale
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.
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.
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.
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.
Industrial Kiln Insulation Refractory Castables Construction
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.
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.
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.
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 in Rongsheng Factory
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
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.
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.
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%.
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.
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.
