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

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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
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.

    Rongsheng Silicon Nitride Combined Silicon Carbide Castable
    Rongsheng Silicon Nitride Combined Silicon Carbide Castable

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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 1 Damage to Burner Lining Castables
      Figure 2 Analysis of 4 Levels of 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.

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

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        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
        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.

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

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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.

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              Castable Low Cement Lining With Silicon Carbide

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              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.

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

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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
                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.

                  Low Cement Castable Directly from Factory
                  Low Cement Castable Directly from Factory

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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.

                    Rongsheng Low Cement Castable Materials
                    Rongsheng Low Cement Castable Materials

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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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                        Application Advantages of Refractory Precast Shapes

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                        Application cases of RS refractory prefabricated parts. Refractory prefabricated parts are most commonly used in small high-temperature kiln equipment. The products required at the construction site are produced in advance by the manufacturer to facilitate customer construction. Used for special-shaped or special-shaped refractory products. Refractory prefabricated parts are widely used in various industrial kilns due to their irreplaceable advantages. Its biggest advantage is that it can be pre-baked and directly hoisted, so the construction period is greatly shortened, and the quality is stable and easy to control.

                        Application Solutions for Refractory Precast Shapes

                        Refractory prefabricated parts are an important variety of refractory materials, and their applications account for an increasing proportion. Refractory prefabricated parts are made by dividing the parts of the high-temperature kiln to be constructed into small pieces in advance. And design it into a special shape, and make the mold according to the shape. In the factory, refractory castables and other materials are pre-cast, cured, and baked before being transported to the site for hanging and assembly before use.

                        Ultra Low-Cement Castable Precast Shapes for Iron Trough
                        Ultra Low-Cement Castable Precast Shapes for Iron Trough

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                          Castable precast shape refractories can be preformed into various shapes at will, with good thermal shock stability, high strength, and good spalling resistance. No joints, good air tightness, less heat loss, and energy saving. It can quickly repair the kiln and improve the furnace operation rate. It can realize direct hoisting and mechanized furnace construction, and the construction efficiency is high. It can solve technical problems in furnace construction for users and can be customized according to user requirements and furnace-type conditions. Consider lining body design and multiple construction options for users.

                          There are the following solutions for the shaping of unshaped refractory materials in cement kilns. As a result, the unshaped refractory materials used in special parts of the cement kiln are customized and produced. The product has the following characteristics:

                          • (1) There is no need for on-site pouring construction or formwork pouring, which reduces labor costs and material costs.
                          • (2) Heat-resistant anchors are not required, eliminating the material and construction costs of anchors.
                          • (3) The pouring, curing, drying, and baking steps of prefabricated parts have been completed when delivered, saving a lot of construction time.
                          • (4) It is not restricted by environmental and climatic conditions, which solves the problem that castable materials cannot be constructed on-site under natural conditions during hot summer and severe winter.
                          • (5) It can be made into various special products with different sizes and shapes. Such as grate cooler low wall, tertiary air duct elbow, lifting gate valve, kiln tail smoke chamber, coal injection pipe, kiln mouth, and other refractory materials.
                          • (6) Maintenance is easy to replace, has little waste loss, and saves labor and time. Corundum, fused mullite, special grade bauxite aggregate, and special wear-resistant materials are added to the material, and a certain proportion of special additives are added. Vibration forming. Therefore, the product has high strength, wear resistance, corrosion resistance, good mechanical impact resistance, and excellent thermal shock resistance. It has excellent peeling resistance and cracking resistance, long service life, convenient construction, safety, and reliability, and greatly shortens the construction period.

                          Application Advantages of Refractory Prefabricated Parts

                          Refractory Preforms refer to components with a certain shape and size made of refractory materials according to specific ratios and process conditions. The main raw materials of refractory precast shapes usually include refractory castables, refractory bricks, refractory fibers, and other special refractory materials. Refractory prefabricated parts are prepared under certain process conditions, which usually include mixing, molding, curing, and drying.

                          Rotary Kiln Lining Precast Blocks
                          Rotary Kiln Lining Precast Blocks

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                            Refractory Precast Shapes have the Following Advantages

                            • stable quality. During the production process of prefabricated components in the factory, raw materials, proportions, and process conditions are strictly controlled. Therefore, product quality is stable and reliable.
                            • Save construction time. The use of refractory prefabricated parts can significantly shorten the construction period and improve construction efficiency.
                            • Reduce on-site labor. Prefabricated components are produced in factories, reducing the workload of construction workers and material handling on-site.
                            • Good performance. Because the production process of prefabricated components is strictly controlled, their performance is often better than that of refractory materials constructed on-site.

                            Refractory prefabricated parts are widely used in various industrial furnaces and equipment in petrochemicals, metallurgy, building materials, electric power, and other industries. Such as heating furnaces, smelting furnaces, converters, gas generators, glass kilns, etc. Depending on the actual application environment and needs, refractory prefabricated parts can be customized with different shapes, sizes, and properties. When selecting refractory prefabricated parts, factors such as the working environment, usage conditions, performance of refractory materials, and construction requirements should be considered.

                            When using refractory prefabricated parts, you need to pay attention to the following points.

                            • Storage and transportation. During storage and transportation, prefabricated parts should be protected from moisture, heat, and external force damage. It is recommended to store prefabricated parts in a dry, ventilated, and cool warehouse. And pay attention to reasonable stacking to avoid extrusion and deformation.
                            • Install. When installing refractory prefabricated parts, design requirements, and construction specifications should be strictly followed. For different types of prefabricated parts, corresponding installation methods and connection methods need to be adopted. During the installation process, it should be ensured that the position of the prefabricated parts is accurate and that good connection and sealing properties are maintained.
                            • Seam treatment. Seams between precast parts should be kept clean and tight to prevent heat loss and the penetration of aggressive gases. Depending on the actual working conditions and precast material, appropriate filling materials can be used for joint treatment. Such as refractory mud, refractory fiber, etc.
                            • temperature control. During the initial heating and operation of the furnace, the heating rate and temperature should be strictly controlled. To prevent the refractory prefabricated parts from being damaged due to thermal stress caused by excessive heating. At the same time, regularly check the use of prefabricated parts to detect and deal with potential problems in a timely manner.
                            • Maintenance and overhaul. During use, the refractory prefabricated parts should be inspected and maintained regularly. If damage, cracks, and other problems are found, they should be repaired or replaced in time. For prefabricated parts with a long service life, timely cleaning and maintenance can be carried out to extend their service life.
                            • With proper selection, installation, and maintenance, refractory prefabricated components can provide efficient and stable performance for industrial furnaces. Save construction time and cost at the same time. In the continuously developing industrial field, the application of refractory prefabricated parts will continue to expand to meet the needs of various working conditions and environments.
                            Precast Shapes with Refractory Anchor Bricks for Heating Furnace Top
                            Precast Shapes with Refractory Anchor Bricks for Heating Furnace Top

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                              What Should We Do if These Problems Arise with Refractory Castables and Castable Precast Shapes?

                              Unshaped refractory castables and castable refractory precast shapes have the advantages of convenient and fast construction and low labor intensity. It has been widely used in more and more high-temperature industrial kilns.

                              However, many corporate users have discovered some abnormal phenomena in refractory castables or prefabricated parts during storage or maintenance. For example, some have chalking, some have white hair, etc. In fact, these are caused by the contact between the high alumina cement hydration products in the refractory castable and the acidic gases in the atmosphere. As the water in the castable evaporates, salt substances continue to migrate and precipitate to the surface, and then slowly intensify the damage process of the refractory castable. Powdering occurs during the storage of prefabricated parts made from cement-containing refractory castables. Some of them have “white hair” growing on the surface, commonly known as white alkali, which causes the surface of the castable to become powdery. In severe cases, the strength of the castable will decrease.

                              Solution

                              1. Dry the castables as soon as possible after construction to remove moisture. Eliminate the carrier of sodium salt in the pouring body, so that the alkali stays in the construction body and no longer migrates to the surface.
                              2. When the construction conditions do not allow for timely drying, the castable environment must be sealed and the surface covered with plastic film to prevent moisture from carrying alkali from migrating to the surface.
                              3. Use refractory raw materials with low alkali content in the refractory castable to increase the viscosity and rapid hardening of the refractory castable, which can reduce the migration speed of sodium salt. Strengthen quality management and strictly control the amount of water added during construction.

                              Tips: Leave a message to ask your questions about kiln refractory castables, and we can provide solutions for free.

                              Steel Fiber Refractory Castable Precast Shapes
                              Steel Fiber Refractory Castable Precast Shapes

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                                RS Unshaped Refractory Castable Manufacturer

                                RS unshaped refractory castable manufacturer is a powerful manufacturer of refractory materials production and sales. Our environmentally friendly, fully automatic unshaped refractory material production line customizes unshaped refractory lining materials for high-temperature industrial furnaces. Extend the service life of the kiln lining, save the cost of production energy, and improve economic benefits. Customize refractory precast shapes, wear-resistant refractory castables, insulation castables, refractory plastics, refractory ramming materials, etc. from Rongsheng unshaped refractory material manufacturer. Contact us to get a free customized plan and quote.

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                                  The Difference between Hot Ramming and Cold Ramming of Carbon Ramming Materials

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                                  [Introduction] There are two types of carbon ramming materials, hot ramming and cold ramming. Hot pounding requires crushing and heating, and the wind pressure cannot be less than 0.5MPa. Cold ramming does not require heating, and the maximum thickness of each ramming cannot exceed 100mm. Carbon ramming materials are mainly used for gap filling and leveling of blast furnaces to achieve non-leakage requirements. Cold ramming changes the traditional hot ramming process and improves the performance of the lining. RS, a manufacturer of unshaped refractory castables, can provide high-quality carbon ramming materials and advanced construction technology guidance to help you extend the service life of your kiln lining and save production costs.

                                  Construction Technology of Carbon Ramming Material

                                  Carbon ramming material–Refractory Encyclopedia. RS Refractory Castable Manufacturer. There are two types of carbon ramming materials: hot ramming materials and cold ramming materials. Both hot and cold ramming carbon materials are monolithic refractory materials composed of powdery and granular refractory materials and binders. Under normal circumstances, it is recommended to use cold-rammed carbon materials.

                                  Carbon Ramming Material
                                  Carbon Ramming Material

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                                    Before ramming hot carbon ramming materials, the carbon ramming materials must be crushed and heated. The heating temperature is set evenly according to the mixing temperature of the finished material. There are no hard lumps in the heated carbon material, so it can be laid and pounded. Use a hot hammer when pounding, and the material temperature should not be lower than 70°C. When using hot pounding, the hammer head should be heated to dark red, and the wind pressure should not be less than 0.5MPa. The upper and lower material layers should be staggered at a certain angle, and the pounding should be done continuously to prevent delamination. RS Castable Refractory Manufacturer. When each joint is made, the surface should be “scraped” or adhesive should be brushed, and then the material should be spread and pounded. When pounding, hammer half or one-third of the hammer back and forth 2-3 times in a straight line.

                                    When adopting cold carbon ramming materials, due to the product process upgrade, there is no need to reheat the materials, and there is no need to stir during construction, and the materials can be poured directly into the use site. Subsequently, manual or mechanical methods are used for construction, and the ramming material is also rammed with one hammer and half hammer. RS Castable Refractory Manufacturer. However, it should be noted that the thickness of each pounding should not exceed 100mm until it is dense. The reference compression ratio is 40-45%. If additional thickness is required, a second layer can be laid for pounding. However, before laying, the surface of the upper layer must be roughened to make the upper and lower layers densely bonded. The wind pressure during ramming is the same as that during hot tamping, and cannot be less than 0.5Mpa.

                                    Carbon ramming material is mainly used in the gap between the blast furnace bottom carbon bricks and the furnace bottom sealing plate, or between the hearth carbon bricks and the cooling stave. There is also leveling above the center line of the furnace bottom water-cooling tube and filling of the cooling staves, filling every corner and small gap to meet the requirements of no leakage of molten iron and gas. RS Castable Refractory Manufacturer.

                                    The biggest difference between hot ramming and cold ramming of carbon ramming materials is that cold ramming has changed the old process of traditional hot ramming, the working conditions have been improved, and the performance of the lining has been improved.

                                    RS Castable Refractory Manufacturers

                                    RS Castable Refractory Manufacturer is a powerful manufacturer and seller of unshaped refractory materials. We can provide high-quality refractory lining material products, including various castables, ramming materials, refractory precast shapes, etc. Our products are of reliable quality and our professional construction technical team can customize refractory lining solutions and construction techniques for you. Maximize the service life of high-temperature industrial furnace linings and save production costs for enterprises. Contact us to get a free refractory lining solution and quote.

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                                      24 Kinds of Refractory Raw Materials Commonly Used in Unshaped Refractory Castables (2)

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                                      In recent years, the output of unshaped refractory products has become higher and higher, and their application range has become wider and wider. Refractory castables do not need to be fired at high temperatures and can be used directly after being baked during construction. It is a new refractory material with a simple production process, saving energy and labor, mechanized construction, good integrity, easy repair, and long life.

                                      Refractory castables are a type of refractory material that is mixed with a certain grade of refractory aggregates and powdery materials, binders, and admixtures and is used directly without going through the molding and firing processes.

                                      According to the combination of raw materials, refractory castables can be divided into oxide refractory castables, non-oxide refractory castables, and composite refractory castables. Oxide refractory castables can be subdivided into non-alkaline refractory castables and alkaline refractory castables. Therefore, the performance of refractory castables mainly depends on the raw materials used in the formulation. In order to improve the performance of refractory castables, most manufacturers have used high-purity raw materials, homogeneous materials, electrofusion materials, synthetic materials, transformation materials, and ultra-fine powders as main raw materials. Let’s talk about the 24 raw materials that are often used in the formula of refractory castables.

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                                        The Main Raw Material of Refractory Castables (13-24)

                                        (13) Magnesite.

                                        Magnesite is a natural alkaline mineral raw material with magnesium carbonate (MgCO3) as the main component. Our country is rich in magnesite resources, with high quality and large reserves. Magnesite is mainly distributed in Liaoning Province. Magnesite is mainly used to produce sintered magnesia, fused magnesia, and raw materials for the production of alkaline refractory materials.

                                        (14) Sintered magnesia.

                                        Sintered magnesia is a product obtained by fully sintering magnesite at 1600~1900℃. The main mineral is periclase. The MgO content of high-quality magnesia is generally above 95%, the particle volume density is not less than 3.30g/cm3, and it has excellent resistance to alkaline slag erosion. Sintered magnesia is one of the main raw materials for the production of alkaline refractory materials.

                                        (15) Fused magnesia.

                                        Fused magnesia is made by melting selected magnesite or sintered magnesite at a high temperature of 2500°C in an electric arc furnace. Compared with sintered magnesia, the main crystal phase periclase grains are coarse and in direct contact, with high purity, dense structure, strong resistance to alkaline slag, and good thermal shock stability. It is a good raw material for high-grade carbon-containing unburned bricks and amorphous refractory materials.

                                        (16) Silicon carbide.

                                        Silicon carbide is usually made from a mixture of coke and silica sand as the main raw materials through high-temperature smelting in an electric furnace. β-SiC (cubic crystal) is generated at a temperature of 1400-1800°C, and α-SiC (hexagonal crystal) is generated when the temperature is higher than 1800°C. Silicon carbide has high hardness, high thermal conductivity, low thermal expansion rate and excellent resistance to neutral and acidic slag. The composition range of commercial silicon carbide is 90%~99.5% SiC. Refractory castables, gunning materials, ramming materials and plastics often use silicon carbide with higher purity.

                                        (17) Silica fume.

                                        Silica fume is a by-product of the production of ferrosilicon and silicon products. Appearance: white to dark gray fine powder with round particles. The particle diameter is generally 0.02~0.45μm, the specific surface area is about 15~25m2/g, and the volume density is 0.15~0.25g/cm3. In recent years, some silica fume has become the leading product and is no longer a by-product. It has high purity, white color and stable ingredients. Shows good rheology when used in self-flowing castables.

                                        (18) Graphite.

                                        Graphite is divided into artificial graphite and natural graphite. Artificial graphite is made by sintering petroleum coke (heating to above 2800°C) or using graphite electrodes. Natural graphite crystal is a hexagonal crystal system with rhombohedral symmetry. There are usually three forms: amorphous, flake graphite and pure crystalline. Amorphous graphite (no form) and artificial graphite have better fluidity than flake graphite and crystalline graphite in castable applications.

                                        (19)Asphalt.

                                        Coal tar pitch has a higher residual carbon content than petroleum pitch, and both can effectively provide carbon components to refractory materials. According to the formula design requirements of the material, it can be used in the form of fine powder or granules. The use of bitumen is preferred over other forms of carbon (such as graphite) in amorphous refractory applications. Because asphalt has a low melting temperature, it can coat particles and thus provide a good protective layer against slag erosion.

                                        (20) Calcium aluminate cement.

                                        The main method for producing high alumina cement is the sintering method. Pureer limestone is the calcium oxide raw material from which all calcium aluminate cements are produced. Sintered alumina is used to produce high-grade calcium aluminate cement, while low-iron, low-silica bauxite is used as alumina raw material for mid-grade and low-grade high-alumina cement. Pure calcium aluminate cement or high alumina cement is the most important hydraulic cement used in the binding phase of refractory castables and shotcrete. During the construction of the refractory castable lining, the water temperature, water addition amount, mixing intensity and time, temperature and heating rate must be strictly controlled. Among them, temperature is the most important parameter, which significantly affects the generation of cement binding phase and the discharge of water in the early stage of heating.

                                        (21) Silica sol.

                                        Silica sol is a water-containing colloid with dispersed silica particles. It is a milky white liquid that is slightly sticky to the touch and has a high specific surface area. Silica sol can be cemented by dehydration, changing the pH value, adding salt or water-miscible organic solvents. When drying, silicon-oxygen (Si-0-Si) bonds are formed on the surface of the particles through rapid dehydration, resulting in polymerization and internal bonding. Silica sol is converted from solution into solid, commonly known as cementation. Commonly used in coatings, castables, pumped materials, ramming materials and gunning materials.

                                        (22) Sodium silicate.

                                        Commonly used silicates are sodium silicate (Na₂O·mSiO·nH₂O), potassium silicate and lithium silicate. The dehydrated product of sodium silicate is usually as transparent as glass and soluble in water, so it is also called water glass. The molar ratio of SiO₂/N₂O (called the modulus of water glass) in industrial products is between 0.5 and 4.0, and the molar ratio of sodium silicate for refractory materials is 2.2 and 3.35. The viscosity of sodium silicate aqueous solution is affected by its molar ratio and concentration, and changes significantly with temperature. Sodium silicate hydrates in aqueous solution, and the solution becomes alkaline. The smaller the molar ratio, the more obvious the hydration of sodium silicate is, and the pH value decreases as the molar ratio decreases. Sodium silicate with a high molar ratio reacts slowly. The choice of curing agent for sodium silicate combined refractory materials needs to be determined based on the application of the refractory materials. Commonly used curing agents include sodium fluorosilicate, polyaluminum chloride, phosphoric acid, sodium phosphate, polyaluminum phosphate, polymagnesium phosphate, ammonium pentaborate, glyoxal, citric acid, tartaric acid, ethyl acetate, etc.

                                        (23) Phosphoric acid and phosphate.

                                        Orthophosphoric acid itself has no binding properties. When it comes into contact with refractory materials, the two react quickly to form phosphate, which makes it show good adhesion. Different forms of phosphates can be used as binding agents. The salt most commonly used in refractory materials is aluminum phosphate. As a binding agent, aluminum dihydrogen phosphate is known for its solubility in water, binding strength and stability. Sodium phosphate is mainly used in refractory materials for cohesion, depolymerization and as a binding agent for alkaline gunning materials. Sodium polyphosphate is often used as a water reducing agent in castables. In addition, sodium phosphate can react with alkaline earth metal compounds (such as CaO and MgO), resulting in agglomeration. It is based on this performance of sodium phosphate that it is used in magnesia alkaline gunning materials.

                                        (24)ρ-Al₂O₃

                                        ρ-Al₂O₃ is a kind of activated alumina. It is different from other crystalline Al₂O₃ and is the worst crystallized Al₂O₃ variant. Among the various crystal states of Al₂O₃, only ρ-Al₂O₃ has a spontaneous hydration reaction at room temperature. The gibbsite and boehmite sol generated by hydration can play a cementing and hardening role. ρ-Al₂O₃ is eventually transformed into α-Al₂O₃ (corundum), an excellent refractory material at high temperatures. Therefore, this ρ-Al₂O₃ combined castable can be regarded as a self-bonding castable of refractory materials, which also acts as a binder. It itself is a high-grade refractory oxide with obvious excellent properties.

                                        (THE END)

                                        By selecting different raw materials as the main raw materials of refractory castables, castables with different properties, operating temperatures, and ranges can be made. Of course, only the main raw materials are not enough. Binders, admixtures, and some special additives are also needed. These are all to improve the performance of refractory castables. Rongsheng Unshaped Refractory Castables Manufacturer is a powerful manufacturer and seller of refractory castables. Our environmentally friendly, fully-automatic unshaped refractory material production line provides high-quality customized refractory lining materials for high-temperature industrial furnaces. Contact us to get a free refractory lining solution and quote.

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                                          24 Kinds of Refractory Raw Materials Commonly Used in Unshaped Refractory Castables (1)

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                                          Refractory castables are a type of refractory material that is mixed with a certain grade of refractory aggregates and powdery materials, binders, and admixtures and is used directly without going through the molding and firing processes.

                                          In recent years, the output of unshaped refractory products has become higher and higher, and their application range has become wider and wider. Refractory castables do not need to be fired at high temperatures and can be used directly after being baked during construction. It is a new refractory material with a simple production process, saving energy and labor, mechanized construction, good integrity, easy repair, and long life.

                                          According to the combination of raw materials, refractory castables can be divided into oxide refractory castables, non-oxide refractory castables, and composite refractory castables. Oxide refractory castables can be subdivided into non-alkaline refractory castables and alkaline refractory castables. Therefore, the performance of refractory castables mainly depends on the raw materials used in the formulation. In order to improve the performance of refractory castables, most manufacturers have used high-purity raw materials, homogeneous materials, electrofusion materials, synthetic materials, transformation materials, and ultra-fine powders as main raw materials. Let’s talk about the 24 raw materials that are often used in the formula of refractory castables.

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                                            The Main Raw Material of Refractory Castables (1-12)

                                            (1) Sintered corundum.

                                            Sintered corundum, also known as sintered alumina or semi-fused alumina. It is a refractory clinker made from calcined alumina or industrial alumina as raw material, ground into balls or green bodies, and sintered at a high temperature of 1750~1900℃. Sintered alumina containing more than 99% of aluminum oxide is mostly made of uniform fine-grained corundum directly combined. The gas appearance rate is less than 3.0%, and the volume density reaches 3.60%/m³. The refractoriness is close to the melting point of corundum, and it has good volume stability and chemical stability at high temperatures. It is not corroded by reducing atmosphere, molten glass and molten metal, and has good mechanical strength and wear resistance at room temperature and high temperature.

                                            (2) Fused corundum.

                                            Fused corundum is artificial corundum made by melting pure alumina powder in a high-temperature electric furnace. It has the characteristics of high melting point, high mechanical strength, good thermal shock resistance, strong corrosion resistance and small linear expansion coefficient. Fused corundum is a raw material for manufacturing high-grade special refractory materials. Mainly include fused white corundum, fused brown corundum, sub-white corundum, etc.

                                            (3) Fused white corundum.

                                            Fused white corundum is made from pure alumina powder and smelted at high temperature. It is white in color. The smelting process of white corundum is basically a process of melting and recrystallization of industrial alumina powder, and there is no reduction process. The Al₂O₃ content is not less than 9%, and the impurity content is very small. The hardness is slightly smaller than brown corundum and the toughness is slightly lower. Often used to make abrasive tools, special ceramics and advanced refractory materials.

                                            (4) Fused brown corundum.

                                            Fused brown corundum is made from high-alumina bauxite as the main raw material and mixed with coke (anthracite), and is smelted in a high-temperature electric furnace at temperatures above 2000°C. The main chemical components are Al₂O₃, TiO₂ and contain a small amount of SiO₂ and Fe₂O₃. Fused brown corundum has a dense texture and high hardness and is often used in ceramics, precision castings and advanced refractory materials.

                                            (5) Sub-white corundum.

                                            Subwhite corundum is produced by electromelting special grade or first grade bauxite under reducing atmosphere and controlled conditions. When melting, add reducing agent (carbon), settling agent (iron filings) and decarburizing agent (iron scale). Because its chemical composition and physical properties are close to white corundum, it is called sub-white corundum. Its bulk density is above 3.80g/cm3 and its apparent porosity is less than 4%. It is an ideal material for manufacturing advanced refractory materials and wear-resistant materials.

                                            (6) Mullite.

                                            Mullite is a refractory raw material with 3Al₂O₃·2SiO₂ as the main crystal phase. Natural mullite is very rare and is usually synthesized artificially by sintering or electrofusion. Mullite has the characteristics of uniform expansion, good thermal shock stability, high load softening point, small high-temperature creep value, high hardness, and good chemical corrosion resistance.

                                            (7) Zirconium corundum mullite.

                                            Zirconium corundum mullite is made of industrial alumina, kaolin, and zircon as its main raw materials. It is synthesized by fine grinding, uniform mixing, semi-dry briquetting, and high-temperature calcination at 1600~1700℃. Increasing the zircon content will increase the sintering temperature, reduce the total shrinkage, and increase the closed pores. These reactions give sintered zirconium corundum mullite higher density and strength as well as better thermal shock resistance and slag resistance.

                                            (8) Magnesia-aluminum spinel.

                                            Magnesia-aluminum spinel is synthesized from industrial alumina and light-burned magnesium oxide through high-temperature sintering or electric fusion. The chemical formula of magnesia-aluminum spinel is MgO·Al₂O₃, in which the MgO content is 28.2% and the Al₂O₃ content is 71.8%. It has the advantages of high-temperature resistance, wear resistance, corrosion resistance, high melting point, small thermal expansion, low thermal stress, good thermal shock stability, strong resistance to alkaline slag erosion, and good electrical insulation properties.

                                            (9) Sillimanite, andalusite, and kyanite.

                                            The chemical formula is Al₂O₃·SiO₂, and the theoretical composition is Al₂O₃63.1% and SiO₂36.9%. After heating, they are irreversibly converted into mullite and cristobalite, which have the advantages of good slag corrosion resistance, good thermal shock stability, and high load softening point. Kyanite mineral products are high-quality raw materials for amorphous refractory materials. Because sillimanite and andalusite change little in volume when heated, they can be directly made into bricks or used as refractory aggregates. Kyanite expands greatly when heated and can be used directly as an expansion agent for amorphous refractory materials.

                                            (10) High alumina bauxite.

                                            my country’s high-alumina bauxite resources are mainly distributed in Shanxi, Henan, Guangxi and Guizhou. High-alumina bauxite clinker calcined at high temperature is mainly used for high-aluminum refractory materials, and can also be used to make fused brown corundum and sub-white corundum. In recent years, the homogenized alumina clinker produced in my country has been developed due to its low absorption rate and stable performance. The application in unshaped refractory materials has achieved good results.

                                            (11) Soft clay.

                                            The mineral composition of soft clay is mainly kaolinite or halloysite, mixed with other impurity minerals. The Al₂O₃ content can range from 22% to 38%, and the average refractoriness is around 1600℃. Soft clay is mostly earth-like, with fine particles, easily dispersed in water, and has strong plasticity and cohesiveness. It is widely used in plastics, ramming materials, gunning materials, refractory mud, and medium and low-grade refractory materials.

                                            (12) Clay clinker.

                                            Refractory clay clinker can be divided into two types according to the raw materials used and production methods. One type is obtained by calcining hard clay blocks directly in a kiln. The other type is made of kaolin or hard clay, which is finely ground, homogenized, filtered, dehydrated, dried, and finally burned in a kiln. It is a high-quality clay clinker. The main mineral phase of hard clay clinker is mullite, accounting for 35% to 55%. Followed by glass phase and cristobalite. Clay clinker is the main raw material of ordinary aluminum silicate refractory materials.

                                            (To be continued. Since the article is too long, I will post it in two parts.)

                                            By selecting different raw materials as the main raw materials of refractory castables, castables with different properties, operating temperatures and ranges can be made. Of course, only the main raw materials are not enough. Binders, admixtures and some special additives are also needed. These are all to improve the performance of refractory castables. Rongsheng Unshaped Refractory Castables Manufacturer is a powerful manufacturer and seller of refractory castables. Our environmentally friendly, fully-automatic unshaped refractory material production line provides high-quality customized refractory lining materials for high-temperature industrial furnaces. Contact us to get a free refractory lining solution and quote.

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                                              Coke Oven Refractory Gunning Material Coating – High Temperature Lining Construction

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                                              Refractory gunning material is an unshaped refractory material used to repair the lining of thermal equipment using spraying construction methods. It is composed of refractory aggregates, binders and admixtures proportioned according to particle gradation, including active coagulants, sintering aids mineralizers, etc.). Generally they are thermosetting or air-setting materials. Gunmetal repair is usually a repair method used when a small part of the interior of the furnace lining is prematurely damaged, but most of it is still relatively complete. It can achieve balanced damage to the furnace lining. Its characteristics are that the construction is simple, the construction period is short, and the construction does not require templates and formwork. It can effectively extend the life of the furnace lining and reduce the consumption of refractory materials.

                                              Refractory Spraying Material
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                                                Coke Oven Refractory Gunning Material Coating Materials – high temperature resistant adhesive products

                                                The high-temperature resistant adhesive can be used for hot repair of unevenness, erosion, cracks, melting, and falling bricks in the coke oven carbonization chamber and other parts. This product has high refractoriness, high flexural strength, good adhesion, easy hanging and long hanging time. No bubbles or cracks, strong wear resistance, and good construction performance.

                                                Performance Advantages of Coke Oven Refractory Gunning Materials

                                                1. Good high-temperature performance. When using this product to repair coke ovens, there is no need to cool down, just spray the repair directly and then put it into operation. It greatly shortens the coke oven repair time, reduces production costs, improves work efficiency, and has obvious energy-saving effects.
                                                2. Under the action of a high temperature of 1000℃, this product has high bonding strength with the silica bricks in the coke oven carbonization chamber. It is also wear-resistant, shock-resistant, peel-resistant, strong and durable.
                                                3. On-site construction is convenient and not affected by seasonal temperature.
                                                4. Long service life, its service life is 7-10 times that of similar products currently used in China, and the hanging time is longer.

                                                Coke oven refractory gunning material coating material – high-temperature resistant binder product overcomes the characteristics of large pores, poor wear resistance and short hanging time of similar products on the market. The high-temperature-resistant binder for coke ovens is acidic and should be stirred evenly before use. When repairing the wall of the gunnery furnace, the wall should be cleaned first to make the mud easy to hang. Clean it before spraying. The spraying surface should be flat and smooth and should not be higher than the wall. When the adhesive is relatively viscous, you can add a small amount of water to dilute it before use.

                                                Hot Repair of Coke Oven Lining
                                                Hot Repair of Coke Oven Lining

                                                Refractory Spray Paint Lining Construction

                                                Start by welding metal grabber nails or metal mesh to the furnace shell. Load the refractory spray paint that is dry-mixed or semi-dry-mixed with a forced mixer into the spray machine. Use compressed air (wind pressure is 0.10~0.15MPa) to send the mixture to the nozzle. Add an appropriate amount of water or chemical binding agent to mix with the material, and spray it to the sprayed surface. The nozzle outlet should be perpendicular to the sprayed surface, and the distance should be 1 to 1.5m. The spraying of the lining should be carried out continuously, and the thickness of each spraying layer should be less than 200mm. When the lining is too thick, it should be sprayed in layers, but it must be done after the previous layer has sufficient strength. After the lining is sprayed, level the working surface in time and remove the rebound material. The maintenance and baking of refractory spray paint linings are the same as those of refractory castable linings.

                                                What is flame spraying material? Flame gunned material is a shaped refractory material composed of refractory powder, combustion accelerant, and sintering agent.

                                                Compared with other gunning and spraying, flame gunning has strong gunning ability, short time, and fast drying. Gunmetal has the characteristics of high volume density, relatively low porosity, and long service life.

                                                The main raw materials of flame spraying materials are magnesia, magnesia dolomite, and magnesia chromium sand. The sintering agents used are soft clay, bentonite, and silica fume. The combustion accelerant is coke powder, aluminum powder, etc. The flame gunning layer is used as the refractory slag layer, which is to protect the refractory brick layer with lining and hanging slag.

                                                High Temperature Resistant Adhesive Refractory Products
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                                                  Flame spraying materials are mainly used in the slag line and furnace cap of the converter and are also used in steelmaking electric furnaces and ladles. When gunning on the converter, gunning can be carried out when the lining temperature is around 1500°C, and the gunning time is 4-7 minutes. That is to say, spraying can be carried out directly without stopping the furnace.

                                                  Gun spraying is carried out using a spray gun, and there are two methods of gunning: horizontal and vertical. When gunning in the converter, gunning can be started after tapping and pouring slag. At first, the spray gun jacket needs to be cooled with water, and then the spray gun can be moved up and down, or it can be rotated and inserted into the furnace. After oxygen supply and spraying, the material is sprayed out from the nozzle of the spray gun.

                                                  Because the combustible gas and oxygen mix and burn, the combustion accelerant ignites. The flame-spraying material is melted within a distance of 1.5mm and then sprayed onto the sprayed surface. Then it is sprayed into a gunning layer. After spraying, it can be loaded and used immediately without baking.

                                                  Flame spraying materials for converter linings have been developed and used in my country for more than ten years, and the results have been good. However, the use of other furnace linings has not been significantly developed and used. Because the construction of the spray gun is subject to certain restrictions and it is inconvenient to transport it back and forth, it is only used fixedly on some converters. Other furnace lining developments have not yet used this gunning method.

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                                                    Phosphoric Acid bonded High Aluminum Castable with Good Wear Resistance and Air Tightness

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                                                    What are the advantages of phosphate-bound high-aluminum castables? Phosphoric acid combined with high aluminum castable is one of the castables. Compared with other castables, its advantage is that high-aluminum phosphate castables have the advantages of high medium-temperature strength, good thermal shock resistance, wear resistance, and good air tightness.

                                                    Phosphoric Acid Bonded High Aluminum Castable

                                                    Phosphoric acid-bonded high-aluminum castables are not only resistant to high temperatures and corrosion but also have excellent thermal shock resistance and wear resistance. It is widely used in metallurgical heating furnaces water-cooled tube wrapping, heating furnace top prefabricated blocks, high-temperature flame furnace burner bricks, and kiln car table prefabricated blocks. The overall lining of induction furnaces in the precision casting industry, as well as the abrasive parts of power plant boilers and other thermal kilns.

                                                    High-Strength Aluminum Phosphate Bonded Refractory Plastics
                                                    High-Strength Aluminum Phosphate Bonded Refractory Plastics

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                                                      Phosphoric acid combined with high alumina castables generally uses high alumina cement as a setting accelerator. When the amount of high alumina cement is increased, the castable hardens and sets too quickly, making construction difficult. When the amount of high alumina cement is increased, the castable does not solidify, and there is no way to demould it later, and the castable needs to be baked after demoulding to develop strength.

                                                      Although phosphoric acid combined with high-aluminum castables has many advantages, the amount of high-aluminum cement added is difficult to control and the construction is too difficult, which affects the progress of castable construction. These problems also hinder the widespread application of high-aluminum phosphate castables. In a large number of practical applications by castable manufacturers, continuous exploration and research have found that fused spinel fine powder has an accelerating effect on phosphoric acid. This procoagulant effect is relatively mild and easy to control. At the same time, the phosphoric acid-bound castable can produce high strength without baking after demolding.

                                                      Phosphoric acid combined spinel high alumina castable, after adjusting the formula of the castable manufacturer and adding fused spinel powder. In various industrial kilns and in various temperature ranges, it has higher strength than ordinary phosphate-bonded high-aluminum castables. The high-temperature resistance is more than 200 ℃ higher than that of ordinary phosphoric acid combined with high aluminum castables. At the same time, it can produce strength without baking, overcoming the disadvantages of the difficult construction of ordinary phosphate-bonded high-aluminum castables. The adjusted phosphoric acid combined with high aluminum castable material does not absorb moisture after natural curing and is not afraid of water, which brings great convenience to on-site construction and storage and transportation of prefabricated parts. Its good thermal shock resistance greatly extends the service life of furnace linings or objects working under alternating hot and cold conditions.

                                                      High-Quality High Alumina Castable of Rongsheng
                                                      High-Quality High-Alumina Castable of Rongsheng

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                                                        High Alumina Cement Combined Refractory Castable

                                                        High alumina cement refractory castables are made by using high alumina cement as a cementing agent, mixing refractory aggregates and powders in proportion, adding water, mixing, shaping, and curing. Refractory aggregates and powders are generally made of clay, high alumina, corundum, etc. Commonly known as clay castables, high alumina castables, corundum castables, etc.

                                                        The main mineral of high alumina cement is calcium aluminate (CA), which hydrates quickly and does not precipitate calcium hydroxide. Therefore, refractory castables formulated with high alumina cement have the characteristics of rapid hardening and high strength.

                                                        Factors Affecting the Performance of Aluminate Cement Bonded Castables

                                                        The general ratio of aluminate cement combined with refractory castables is. Refractory aggregate 62%-76%, refractory powder 17%-28%, cement 10%-24%, water 7%-14%, and appropriate amount of admixtures. This is also the general ratio of refractory castables. On the premise of meeting construction and use requirements, the amount of cement and water should be minimized. This type of castable is divided into many categories based on aggregate types, and many factors affect performance.

                                                        1. Cement dosage.

                                                        Cement is one of the important components of refractory castables. It is an important material that determines the strength of the material and also affects other properties. Different types of cement and their dosages have different effects on performance. As the amount of cement increases, the normal temperature compressive strength increases, and later the compressive strength and high-temperature compressive strength decrease, and the linear change after burning changes from expansion to contraction. Therefore, while ensuring that the normal temperature strength meets the requirements, the amount of high-alumina cement should be reduced as much as possible to improve the high-temperature performance of refractory castables. However, while reducing the amount of cement, it is necessary to appropriately increase the refractory powder so that the mixture of powder and cement can fully wrap the refractory aggregate.

                                                        1. Water consumption.

                                                        When configuring aluminate cement combined with refractory castables, the amount of water used is very important. When too much water is used, the water will overflow after heating, resulting in increased pores and loose structure, resulting in a decline in overall performance. Therefore, under the conditions of ensuring construction, the amount of water added should be reduced as much as possible. Without adding a water-reducing agent, the suitable water content of aluminate cement castable is 10%-13%.

                                                        1. Refractory powder dosage.

                                                        The type, fineness, and dosage of refractory powder are important factors affecting the performance of castables. The fineness of the powder directly affects the strength, volume density, and apparent porosity of the castable. The finer the refractory powder, the better the performance of the castable. When the amount of powder is small, the mixture with cement cannot completely wrap the aggregate, resulting in a loose structure. When the amount of powder is too much, there will be a significant surplus of aggregate wrapped in the mixture with cement, resulting in an increase in the amount of water used and a large shrinkage during high-temperature sintering.

                                                        1. Amount of refractory aggregate.

                                                        The variety, grade, and particle matching of aggregates are the main properties that affect the performance of castables. It plays a skeleton role in the castable. The aggregates are divided into coarse aggregates and fine aggregates. It is very important to match the particles of the aggregates. The most ideal particle gradation is that the gaps caused by coarse aggregate are filled by the fine aggregate, and the gaps between the two are filled by powder, with no shortage or surplus.

                                                        In addition, high alumina cement refractory castables can also be added with admixtures (such as water-reducing agents, etc.) to improve construction performance and fire resistance.

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                                                          Iron Ditch Anti-Scouring Silicon Carbide Refractory Castable

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                                                          The blast furnace tap trough system consists of a main tap trough, branch troughs, and slag troughs. It is an important system to realize the separation of molten iron and slag in the blast furnace. With the enlargement of iron-making blast furnaces and the development of high-temperature and high-pressure technology, higher requirements have been placed on the service life and iron flux of the blast furnace tap trough. The trough material is the main factor affecting the performance of the blast furnace tap trough. Its high-temperature resistance, thermal shock resistance, erosion resistance, erosion resistance, and other properties directly affect the iron flux and service life of the blast furnace tap channel. This in turn affects the production cost and labor intensity of the entire production process.

                                                          Aluminum Silicon Carbide Castables
                                                          Aluminum Silicon Carbide Castables

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                                                            Refractory Material Al2O3-SiC-C Castable for Tap Trough

                                                            At present, the refractory materials used in the blast furnace tap trough are mainly Al2O3-Si C-C castables. Although it has the advantages of good high-temperature mechanical strength, good resistance to slag erosion and permeability, good thermal shock resistance, and small changes in reburning. However, in the face of technological advancements such as increased molten iron temperature, increased iron tapping volume, prolonged iron tapping time, and faster-molten iron flow rate caused by modern large-scale blast furnace smelting. The original iron trench materials cannot meet production needs. Therefore, improving Al2O3-SiC-C castables or developing new refractory materials for blast furnace tap troughs are the research directions of many scholars.

                                                            Aluminum silicon carbide carbonaceous castables, which are unshaped refractory materials, are often used in blast furnace tap troughs, so they are also called trough castables. The blast furnace tap trough castable is made of fused corundum (or sintered corundum, special high-aluminum clinker) and silicon carbide. It is a high-performance refractory castable containing 90%-95% fixed carbon (or flake graphite), binder, and various admixtures.

                                                            Aluminum silicon carbide carbonaceous castable. The aggregate part can be made of one or two types of fused or sintered corundum, brown corundum, spinel, and bauxite clinker. Carbonaceous raw materials can be asphalt, coke, graphite, or electrode powder. The binding agent can be bonded clay, oxide micro powder or ultrafine powder, and pure calcium aluminate cement with good dispersion properties.

                                                            Silicon Carbide Refractory Castable
                                                            Silicon Carbide Refractory Castable

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                                                              The blast furnace tap trough is a channel through which high-temperature molten iron or molten slag flows. Its refractory lining should have the following characteristics. These features are complementary to each other and should be compatible with each other.

                                                              • ① Strong resistance to erosion and erosion from molten iron and slag.
                                                              • ② Good thermal shock resistance and small change in volume after reheating.
                                                              • ③ Strong antioxidant capacity.
                                                              • ④ Easy to construct, can be baked quickly without bursting, and is easy to repair and dismantle.
                                                              • ⑤ When used, it does not produce harmful gases, does not stick to slag iron, and has a long service life.

                                                              Iron trench castable is a high-tech refractory castable with exquisite preparation technology and excellent performance, which can significantly increase the service life of the trench lining. The key issue is that the amount of construction water must be strictly controlled, operated carefully, and maintained carefully to achieve the expected purpose.

                                                              At the same time, the specific selection of tap trough castables also depends on the size of the blast furnace. Generally speaking, high-aluminum silicon carbide carbonaceous castables can be used for the main ditch, slag ditch, and slag line of small blast furnaces. Corundum silicon carbide carbonaceous castables can be selected for medium and large blast furnaces.

                                                              Wear-Resistant Corundum Silicon Carbide Castable
                                                              Wear-Resistant Corundum Silicon Carbide Castable

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                                                                Erosion-resistant Molten Iron-Clad Aluminum Silicon Carbide Castable

                                                                Spheroidized ladle castable is an unshaped refractory material with high aluminum and silicon carbide materials as the main raw materials and refractory cement as the binder. It is widely used in molten running ladles, launders, and working linings of kilns. It has high strength and refractory resistance and has good impact resistance, corrosion resistance, wear resistance, and other properties. It has a long service life, convenient construction, and easy maintenance. It is suitable for the overall lining of ladles and is the refractory material of choice for spheroidized ladles.

                                                                Molten iron and slag react with the castable, resulting in chemical slag sticking. According to ASTM C01-91 Al2O3-SiO2 series castables, those with CaO content >2.5 are traditional cement-bound castables. The CaO content between 1.0% and 2.5% is low cement castable. The CaO content <1.0% is cement-castable. The lower the CaO content, the higher the temperature at which the liquid phase appears, and therefore the higher the fire resistance. The CaO content of the existing castable is 3.78%, which is a traditional high cement content castable. Aluminum silicon carbide castables are erosion-resistant, heat-exchange-resistant, refractory castables, and ladle castables.

                                                                The liquid phase of this material appears at a low temperature, about 1300°C. The temperatures of molten iron and slag are generally >1300°C, and the interface is prone to reaction at this time. For example, the components in the refractory material, especially the liquid phase in the matrix, easily react with CaO, SiO2, Fe2O3, etc. in the slag to form Al2O3-SiO2-CaO-Fe2O3 series low-melting materials. The molten iron, molten slag, and refractory materials are melted together to form sticky slag. The sticky residue that occurs in this form is strong and difficult to clean.

                                                                Low Cement Silicon Carbide Castable in RS Factory
                                                                Low Cement Silicon Carbide Castable in RS Factory

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                                                                  Development of Aluminum Silicon Carbide Refractory Castables for Tap Trench

                                                                  Al2O3-SiC-C castable is the most widely used iron trench refractory material in my country. Improving the quality of Al2O3-Si C-C castables is an important factor in reducing the cost of molten iron and achieving efficient production. RS Unshaped Refractory Castable Manufacturer puts forward several suggestions based on the current development situation.

                                                                  (1) Different companies have different compositions of molten iron and slag. The reasons why molten slag and molten iron corrode the iron trench materials should be analyzed based on the actual situation to achieve “prescribing the right medicine”.

                                                                  (2) Using slag or other industrial waste residues as raw materials to prepare Al2O3-Si C-C castables has extremely high added value. At the same time, it can also solve problems such as waste residue accumulation and environmental pollution.

                                                                  (3) Improve the production of Al2O3-Si C-C castables in the direction of green and environmental protection, and remove or replace toxic and harmful components in the raw materials. It not only achieves green production but also protects the health of workers.

                                                                  (4) Many new Al2O3-Si C-C castables have been applied in enterprise blast furnace production, achieving mutual benefit and win-win results between scientific research and enterprises.

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