A tundish coating material

Abstract

This invention discloses an intermediate ladle spray coating, relating to the field of intermediate ladle refractory material technology. The mass percentages of the raw material components in the intermediate ladle spray coating are as follows: 22-25% 3-1mm 91 magnesia, 46-51% 1-0mm 94 magnesia, 16-20% 200-mesh 94 magnesia, 1.5-3% 800-mesh 95 magnesia, 2-3% silica fume, 2-3% quicklime, 0.1-0.15% silica whiskers, 0.4-0.6% 70 cement, 0.6-0.8% sodium metasilicate nonahydrate, and polyethylene. The intermediate ladle spray coating of this invention contains 0.3-0.5% alcohol, 0.01-0.03% composite hydrophobic agent, 0.5-0.7% paper fiber, 0.01% organic fiber, 0.02-0.03% metallic aluminum powder, 0.2-0.3% sodium tripolyphosphate, and 0.1-0.3% citric acid. Compared with traditional processes, the water addition rate of the intermediate ladle spray coating of this invention is significantly reduced, the overall strength of the spray coating is greatly enhanced, the risk of cracking after drying is reduced, the service life of the spray coating is extended, and the construction efficiency, construction performance, and continuity of continuous casting operations are improved.

Description

Technical Field

[0001] This invention belongs to the technical field of tundish refractory materials, and specifically relates to a tundish spray coating. Background Technology

[0002] In modern continuous steel casting processes, the tundish is a crucial link connecting the ladle and the crystallizer. The quality of its refractory material directly affects the quality of the cast billet, production efficiency, and cost control. Tundish magnesia spray coatings are widely used for lining protection of tundishes due to their excellent high-temperature resistance, slag erosion resistance, and good workability. However, the control of water addition during the construction process of traditional magnesia spray coatings has always been one of the key factors affecting their final performance.

[0003] Currently, most magnesium-based spray coatings on the market require a water content between 16% and 22%, and in some cases even as high as 25%, to ensure good application flow and adhesion to the permanent substrate. While this high water content construction method temporarily meets the need for ease of application, it brings serious performance drawbacks. First, excessive water content can lead to significant evaporation stress within the coating layer during the drying process, causing cracking and, in severe cases, peeling, greatly reducing service life and safety. Second, excessive water evaporation can leave pores within the coating layer, and these tiny defects become initiation points for thermal shock cracks, further weakening the overall strength and thermal shock resistance of the coating layer. In addition, residual water may react with certain components in the refractory material to form low-melting-point phases, reducing refractoriness and affecting its stability and service life under high-temperature conditions.

[0004] In view of the aforementioned technical challenges, research institutions and manufacturers in this field have actively engaged in research on improving the application of spray coatings while reducing water requirements. These research efforts primarily focus on the following aspects: First, the innovative development of binders, aiming to reduce water demand while maintaining or even improving the smoothness and high-temperature stability of the spray coating through the introduction of novel binders such as organic resins and phosphates; second, the refined adjustment of particle size distribution, achieving higher bulk density and filling efficiency by optimizing the ratio of refractory aggregates to fine powder, thereby reducing dependence on water without compromising ease of application. Thirdly, the ingenious application of additives, such as specific activators, expanding agents, or fiber materials, enhances the wet and dry strength of the spray coating, effectively reducing cracks caused by moisture evaporation. Fourthly, innovative formulation design, such as the development of new magnesium spray coating formulations like magnesium-calcium composite materials, fundamentally reduces the use of water and significantly improves the overall performance of the material through material modification. Although the above efforts have alleviated the problems caused by high moisture content to some extent, no technology has yet been able to fully solve the high moisture dependence during construction while simultaneously meeting the stringent requirements of industrial production for high-performance refractory materials. Summary of the Invention

[0005] To address the problem of poor workability and insufficient strength of existing intermediate tundish spray coatings caused by the amount of water added during construction, this invention provides an intermediate tundish spray coating that overcomes the shortcomings of traditional intermediate tundish spray coatings in controlling the amount of water added. This significantly improves the workability and strength of the intermediate tundish spray coating and effectively extends its service life.

[0006] The solution adopted by this invention to solve its technical problem is: an intermediate ladle spray coating, wherein the mass percentage of each raw material component in the intermediate ladle spray coating is as follows: 22-25% of 3-1mm 91 magnesia, 46-51% of 1-0mm 94 magnesia, 16-20% of 200-mesh 94 magnesia, 1.5-3% of 800-mesh 95 magnesia, 2-3% of silica fume, 2-3% of quicklime, 0.1-0.15% of silica whiskers, 0.4-0.6% of 70 cement, 0.6-0.8% of sodium metasilicate nonahydrate, 0.3-0.5% of polyvinyl alcohol, 0.01-0.03% of composite hydrophobic agent, 0.5-0.7% of paper fiber, 0.01% of organic fiber, 0.02-0.03% of metallic aluminum powder, 0.2-0.3% of sodium tripolyphosphate, and 0.1-0.3% of citric acid.

[0007] Furthermore, the intermediate liner coating contains 23% 3-1mm 91 magnesia, 49% 1-0mm 94 magnesia, 18% 200-mesh 94 magnesia, 2% 800-mesh 95 magnesia, 2.4% silica fume, 2.7% quicklime, 0.12% silica whiskers, 0.5% 70 cement, 0.7% sodium metasilicate nonahydrate, 0.43% polyvinyl alcohol, 0.02% composite hydrophobic agent, 0.6% paper fiber, 0.01% organic fiber, 0.02% metallic aluminum powder, 0.3% sodium tripolyphosphate, and 0.2% citric acid.

[0008] Furthermore, the total mass percentage of 800-mesh 95 magnesia, silica fume, and quicklime in the intermediate liner spray coating is 6.2% to 8.4%.

[0009] Furthermore, the silica fume contains ≥94% SiO2; the quicklime has a particle size of 600 mesh and a purity of 98%.

[0010] Furthermore, the silica whiskers contain ≥99.9% SiO2, have a fiber length of 2–10 μm, and a bulk density of 0.78 g / cm³. 3 The actual density is 2.2–2.4 g / cm³. 3 It has a refractoriness of 1720℃, a Mohs hardness of 7, and a loss on ignition of ≤0.10%.

[0011] Furthermore, the composite hydrophobic agent has the following raw material components by mass percentage: 75% polydimethylsiloxane and 25% fluorinated modified polyurethane.

[0012] Furthermore, the sodium metasilicate nonahydrate, polyvinyl alcohol, sodium tripolyphosphate, and citric acid in the intermediate package coating are all industrial grade.

[0013] Furthermore, the sum of the mass percentages of sodium metasilicate nonahydrate, polyvinyl alcohol, and sodium tripolyphosphate in the intermediate package spray coating is ≥1.15%.

[0014] Furthermore, the aluminum powder has a particle size of 80 mesh and an Al content of ≥98%.

[0015] This invention utilizes 800-mesh 95 magnesia and 600-mesh quicklime ultrafine powder, primarily to enhance the performance of the spray coating and optimize its steel purification capabilities. The 800-mesh 95 magnesia improves the refractoriness, density, and structural stability of the spray coating, and enhances its thermal conductivity. Having undergone high-temperature smelting, the 95 magnesia exhibits complete crystallization, high purity, and low impurity content, thus significantly improving the refractoriness and corrosion resistance of the spray coating. Especially when subjected to continuous impact from high-temperature molten steel, it effectively prevents thermal shock damage. The 800-mesh fine powder helps the spray coating form a denser working layer, reducing porosity and enhancing the overall stability and impermeability of the coating layer. This is crucial for preventing the penetration and erosion of non-metallic inclusions in molten steel. Furthermore, the high purity of the 95 magnesia improves the spray coating's... The thermal conductivity helps distribute heat more evenly, reducing damage caused by localized overheating. 600-mesh quicklime promotes the sintering and hardening of the spray coating, adjusts the matrix alkalinity, and improves workability. When added to the spray coating, quicklime rapidly releases heat upon contact with water and transforms into hydrated lime. This process, accompanied by volume expansion, aids in the adhesion and rapid curing of the spray coating layers, enhancing the overall strength and anti-stripping properties. As an alkaline substance, quicklime can adjust the alkalinity of the spray coating, effectively inhibiting certain acidic corrosions (such as sulfides in molten steel), thus protecting the tundish spray coating from corrosion. Furthermore, appropriate addition of quicklime can improve the workability of the spray coating, such as increasing its fluidity and adhesion, making it easier to spray and achieve uniform coverage, ensuring the continuity and integrity of the coating layer. These two ultrafine powders, through their unique physical and chemical properties, work together in the magnesium-based spray coating to effectively improve the coating's refractory properties, structural strength, and corrosion resistance, while also optimizing the construction process.

[0016] In this invention, the addition of silica whiskers as a reinforcing phase can further improve the mechanical and thermophysical properties of the spray coating. Firstly, the addition of silica whiskers as a reinforcing phase to the magnesium spray coating can significantly enhance its crack propagation resistance and overall mechanical strength by bridging cracks and dispersing stress concentration points, thereby effectively improving the wear resistance and impact resistance of the coating layer and extending its service life. Secondly, given the low coefficient of thermal expansion of silica whiskers, their incorporation into magnesium materials can effectively regulate the overall thermal expansion behavior of the material, reducing the impact of rapid temperature changes. The internal stress caused by the change enhances the coating's resistance to thermal shock damage, ensuring structural integrity under rapid temperature changes. Secondly, the excellent high-temperature resistance of silica whiskers improves the structural stability of the coating layer, reducing deformation and damage even under prolonged high-temperature conditions, ensuring the coating layer remains in good working order. Finally, the uniform dispersion of silica whiskers in the coating matrix increases the interfacial contact area between the whiskers and the matrix material, strengthening the bond between the whiskers and the matrix through physical adsorption and chemical bonding, thereby improving the overall performance of the coating layer. The introduction of silica whiskers in this invention utilizes the classic theory of composite material reinforcement, namely, using highly oriented or randomly distributed high-strength, high-modulus whiskers to hinder crack propagation, while the good interaction between the whiskers and the matrix enhances the overall integrity of the coating layer. Furthermore, the small size effect and quantum size effect of silica whiskers also have a positive impact on the performance of the coating, such as reducing the coefficient of thermal expansion, all of which contribute to the long-term stable operation of the coating under harsh conditions.

[0017] This invention employs a composite hydrophobic agent, composed of polydimethylsiloxane and fluorinated polyurethane. The mass percentages of the raw materials are: 75% polydimethylsiloxane and 25% fluorinated polyurethane. The composite hydrophobic agent has the following functions: First, by forming a hydrophobic layer on the surface of material particles, it reduces the amount of water added to the spray coating. Polydimethylsiloxane is a highly efficient hydrophobic material because its organosilicon groups effectively repel water. The fluorinated polyurethane further enhances the hydrophobic effect by introducing fluorine, as fluorine atoms have extremely low surface energy, making it difficult for water to spread on its surface. The combined hydrophobic layer significantly reduces the water addition rate of the spray coating. Secondly, the hydrophobic layer effectively isolates oxygen in the air from direct contact with the refractory material, reducing oxidative erosion and slowing down the oxidation rate of the spray coating at high temperatures, thus extending its service life. Finally, by forming a hydrophobic barrier on the surface of the spray coating material, it reduces the chance of chemical reactions between harmful components in the molten steel (such as oxides and sulfides) and the refractory material, improving erosion resistance, protecting the refractory substrate from corrosion, and maintaining its good thermal insulation and erosion resistance properties. The composite hydrophobic agent is uniformly distributed on the surface or within the micropores of the spray coating material through chemical bonding or physical adsorption, forming a dense protective layer. The low surface energy characteristics of polydimethylsiloxane and the special fluorine chain structure of fluorinated modified polyurethane work together to reduce the water addition rate of the spray coating, indirectly enhancing the strength, thermal stability, and durability of the spray coating layer.

[0018] This invention employs a composite binder system composed of sodium metasilicate nonahydrate, polyvinyl alcohol, and sodium tripolyphosphate. Its functions are as follows: First, sodium metasilicate nonahydrate, a water-soluble silicate with strong alkalinity, is used to improve bonding strength and regulate the flowability of the spray coating. It hydrolyzes in water to generate silicic acid, which then reacts with active oxides (such as MgO) in refractory materials to form hydrated silicates, enhancing the bonding force within the spray coating layer and improving its overall strength and durability. An appropriate amount of sodium metasilicate nonahydrate can also adjust the viscosity of the spray coating slurry, giving it good workability and facilitating spraying operations. Simultaneously, it promotes the curing and hardening process of the spray coating during drying or heating. Second, polyvinyl alcohol, a water-soluble polymer, is used to enhance the adhesion and improve water retention of the spray coating. It has good film-forming properties and adhesion. In the spray coating, it can form a continuous polymer network structure, enhancing the adhesion between particles through physical entanglement and hydrogen bonding, thereby improving the crack resistance and toughness of the spray coating layer. Polyvinyl alcohol can absorb and retain a significant amount of moisture, helping the coating material remain moist before hardening, slowing down the drying process, allowing for a more complete bonding reaction, and improving the density and strength of the coating layer. Finally, sodium tripolyphosphate, as a highly efficient dispersant, can improve the leveling and dispersibility of the coating material, enhance the bonding strength at high temperatures, effectively reduce the electrostatic attraction and van der Waals forces between coating particles, prevent particle agglomeration, and make the solid particles in the coating system more uniformly dispersed. This improves the strength, stability, and uniformity of the coating material, and helps to form a smooth and even coating layer surface, improving surface quality and aesthetics, and enhancing corrosion resistance. These three composite binders work together through their respective chemical properties and physical effects to promote the transformation of the spray coating from a rheological state to a solid state. During the transformation process, a strong bonding network is formed, which enhances the structural strength, workability, and final performance of the spray coating layer. Sodium metasilicate nonahydrate provides initial bonding force through chemical reaction, polyvinyl alcohol strengthens the structure through the entanglement of polymer chains, and sodium tripolyphosphate ensures the uniformity and ease of application of the spray coating through dispersion. The synergistic effect of the three significantly improves the overall performance of the magnesium-based spray coating.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. This invention significantly improves the refractoriness, density, structural stability and thermal conductivity of the spray coating by introducing 800-mesh 95 magnesia and 600-mesh quicklime ultrafine powder, effectively resisting high-temperature molten steel erosion and thermal shock damage, and optimizing the construction performance.

[0021] 2. The present invention incorporates silica whiskers as a reinforcing phase, which significantly enhances the mechanical properties, thermophysical properties, and thermal shock resistance of the spray coating, and extends its service life.

[0022] 3. The present invention uses a composite hydrophobic agent composed of polydimethylsiloxane and fluorinated modified polyurethane, which reduces the water addition rate, reduces oxidative erosion, and improves erosion resistance.

[0023] 4. This invention uses a composite binder system composed of sodium metasilicate nonahydrate, polyvinyl alcohol and sodium tripolyphosphate, which enhances the adhesion, flowability, dispersibility and construction performance of the spray coating layer, ensuring the high strength, durability and aesthetics of the spray coating layer.

[0024] In summary, compared with traditional processes, the intermediate ladle spray coating of the present invention significantly reduces the water addition rate during construction, greatly enhances the overall strength of the coating, reduces the risk of cracking after drying, extends the service life of the coating, improves construction efficiency, construction performance and the continuity of continuous casting operations, reduces production costs, and improves product quality. In addition, reducing water usage helps to save energy and reduce emissions, which is in line with the concept of green manufacturing. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] This invention provides a technical solution for intermediate pack spray coating:

[0027] A tundish spray coating, wherein the mass percentage of each raw material component in the tundish spray coating is as follows: 22-25% of 3-1mm 91 magnesia, 46-51% of 1-0mm 94 magnesia, 16-20% of 200-mesh 94 magnesia, 1.5-3% of 800-mesh 95 magnesia, 2-3% of silica fume, 2-3% of quicklime, 0.1-0.15% of silica whiskers, 0.4-0.6% of 70 cement, 0.6-0.8% of sodium metasilicate nonahydrate, 0.3-0.5% of polyvinyl alcohol, 0.01-0.03% of composite hydrophobic agent, 0.5-0.7% of paper fiber, 0.01% of organic fiber, 0.02-0.03% of metallic aluminum powder, 0.2-0.3% of sodium tripolyphosphate, and 0.1-0.3% of citric acid.

[0028] In a preferred embodiment of the present invention, the intermediate ladle spray coating contains 23% 3-1mm 91 magnesia, 49% 1-0mm 94 magnesia, 18% 200-mesh 94 magnesia, 2% 800-mesh 95 magnesia, 2.4% silica fume, 2.7% quicklime, 0.12% silica whiskers, 0.5% 70 cement, 0.7% sodium metasilicate nonahydrate, 0.43% polyvinyl alcohol, 0.02% composite hydrophobic agent, 0.6% paper fiber, 0.01% organic fiber, 0.02% aluminum powder, 0.3% sodium tripolyphosphate, and 0.2% citric acid.

[0029] This invention uses 3-1mm 91 magnesia, which acts as a skeleton in the coating, helping to form a robust structure and improving the overall strength and wear resistance of the coating. It also uses 1-0mm 94 magnesia, whose medium particle size fills the gaps between larger particles, making the coating denser, reducing porosity, and improving impermeability and erosion resistance. The use of 200-mesh fine powder 94 magnesia helps to form a smoother coating surface and fills even smaller gaps, further enhancing the density and uniformity of the coating. Simultaneously, both high-purity 91 and 94 magnesia have high refractoriness and erosion resistance, maintaining the stability and durability of the coating under high temperature and corrosive environments. Finally, this invention uses an appropriate amount of 70 cement as a binder, which firmly bonds magnesia particles of different sizes together to form a robust coating. The appropriate amount of cement added ensures the strength of the coating while avoiding embrittlement caused by excessive cement. The addition of paper fiber and organic fiber improves the toughness and anti-peeling properties of the coating, which helps prevent cracking and peeling under high temperature and mechanical stress. It is also very effective in improving thermal shock resistance.

[0030] In a preferred embodiment of the present invention, the total mass percentage of 800-mesh 95 magnesia, silica fume and quicklime in the intermediate liner spray coating is 6.2-8.4%, the silica fume contains ≥94% SiO2, and the quicklime has a particle size of 600 mesh and a purity of 98%.

[0031] This invention utilizes 800-mesh 95 magnesia and 600-mesh quicklime ultrafine powder to enhance the performance of the spray coating and optimize its steel purification capabilities. The 800-mesh 95 magnesia, smelted at high temperatures, possesses high purity and low impurities, significantly improving the refractoriness and corrosion resistance of the spray coating, particularly effectively preventing thermal shock damage under the impact of high-temperature molten steel. Furthermore, its fine particle size helps form a dense working layer, reducing porosity and enhancing overall stability and impermeability, thereby preventing the erosion of non-metallic inclusions. The 600-mesh quicklime releases heat upon contact with water in the spray coating and transforms into hydrated lime, promoting sintering and hardening, and improving overall strength and resistance to spalling. As an alkaline substance, quicklime can regulate the alkalinity of the spray coating, effectively inhibiting acidic corrosion and protecting the coating layer. Furthermore, the appropriate addition of quicklime can improve workability, enhance fluidity and adhesion, and ensure the continuity and integrity of the sprayed coating. High-purity quicklime can also reduce additional costs and environmental pollution caused by impurity discharge and treatment, while increasing coating utilization and tundish lifespan, thereby reducing overall production costs. Silica fume, with its extremely small particle size and high specific surface area, can fill the tiny pores in the coating, improving its density and strength. Simultaneously, silica fume can chemically react with other components in the coating to generate harder substances, further enhancing the coating's abrasion resistance. SiO2 is one of the main components of silica fume, and its high content helps enhance the overall strength and hardness of the coating. This allows the tundish sprayed coating to maintain better stability when subjected to high temperatures, high pressures, and corrosive media, reducing the risk of coating damage and peeling. By adjusting the ratio of 95% magnesia, silica fume, and quicklime, this invention can, to a certain extent, regulate the thermal conductivity and coefficient of thermal expansion of the coating, making it better suited to the high-temperature working environment of the tundish. This helps reduce problems such as coating cracking or peeling caused by temperature changes.

[0032] In a preferred embodiment of the present invention, the silica whiskers contain ≥99.9% SiO2, have a fiber length of 2–10 μm, and a bulk density of 0.78 g / cm³. 3 The actual density is 2.2–2.4 g / cm³. 3 It has a refractoriness of 1720℃, a Mohs hardness of 7, and a loss on ignition of ≤0.10%.

[0033] This invention utilizes high-refractory silica whiskers. Under extreme high-temperature environments, silica whiskers maintain stable chemical and physical properties, resisting melting or decomposition. Therefore, adding silica whiskers to the tundish coating significantly improves the coating's refractoriness, enabling it to withstand the erosion of molten steel and other high-temperature liquids without failure. Low loss on ignition indicates that silica whiskers possess good stability at high temperatures, resisting volatilization or decomposition to generate gas. This helps reduce mass loss and porosity formation in the coating at high temperatures, thus maintaining the integrity and density of the coating. Silica whiskers with a Mohs hardness of 7 enhance the coating's hardness and abrasion resistance. Under the scouring and erosion of molten steel and other high-temperature liquids, the high-hardness coating better resists wear and scratches, extending the service life of the tundish. The fiber length of 2–10 μm allows the silica whiskers to form an effective fiber network structure in the coating, contributing to enhanced strength and toughness, and improving the coating's crack resistance and spalling resistance. The bulk density is 0.78 g / cm³. 3 The actual density is 2.2–2.4 g / cm³. 3 This indicates that silica whiskers have a large specific surface area and porosity, enabling them to form more micropores and interfaces in spray coatings, which helps enhance the adsorption and reactivity of the coating. Simultaneously, the microporous structure also helps improve the air permeability and thermal stability of the spray coating.

[0034] In a preferred embodiment of the present invention, the composite hydrophobic agent has the following raw material components by mass percentage: 75% polydimethylsiloxane and 25% fluorinated modified polyurethane.

[0035] This invention employs a composite hydrophobic agent composed of 75% polydimethylsiloxane and 25% fluorinated modified polyurethane. The composite hydrophobic agent is uniformly distributed on the surface or within the micropores of the spray coating material through chemical bonding or physical adsorption, forming a dense protective layer. The low surface energy of polydimethylsiloxane and the special fluorine chain structure of the fluorinated modified polyurethane work together to reduce the water addition rate of the spray coating, indirectly enhancing the strength, thermal stability, and durability of the coating layer.

[0036] In a preferred embodiment of the present invention, the sodium metasilicate nonahydrate, polyvinyl alcohol, sodium tripolyphosphate, and citric acid in the intermediate liner coating are all industrial grade.

[0037] This invention selects sodium metasilicate nonahydrate, polyvinyl alcohol, sodium tripolyphosphate, and citric acid as industrial-grade additives, which have multiple advantages in the preparation of intermediate tundish spray coatings. Sodium metasilicate nonahydrate provides initial binding force through chemical reaction, polyvinyl alcohol enhances the structure through the entanglement of polymer chains, sodium tripolyphosphate ensures the uniformity and ease of application of the spray coating through dispersion, and citric acid ensures the stability of the spray coating by adjusting the pH value in the spray coating. The synergistic effect of the four additives can significantly improve the fluidity, pumpability, adhesion, durability, dispersibility, stability, and corrosion resistance of the spray coating, thereby improving the overall performance and quality of the intermediate tundish spray coating.

[0038] In a preferred embodiment of the present invention, the sum of the mass percentages of sodium metasilicate nonahydrate, polyvinyl alcohol and sodium tripolyphosphate in the intermediate liner spray coating is ≥1.15%.

[0039] This invention adjusts the proportions of sodium metasilicate nonahydrate, polyvinyl alcohol, and sodium tripolyphosphate. The synergistic effect of these additives can significantly improve the performance of intermediate tundish spray coatings to a certain extent. They work together to improve the coating's bonding strength, flowability, adhesion, and durability, making the coating more suitable for the intermediate tundish operating environment and improving production efficiency and product quality.

[0040] In a preferred embodiment of the present invention, the aluminum powder has a particle size of 80 mesh and an Al content of ≥98%.

[0041] The high melting point of aluminum powder allows it to remain stable at high temperatures, making it less prone to melting or evaporation. This enhances the fire resistance of the tundish coating. The moderate particle size of the 80-mesh aluminum powder ensures uniform distribution in the coating during spraying, preventing agglomeration and sedimentation. This ensures the uniformity and consistency of the coating, increases the cohesion of the coating, making it more robust and durable, and improves the overall mechanical strength of the tundish.

[0042] Specific implementation examples:

[0043] The following provides a specific embodiment of an intermediate liner spray coating of the present invention.

[0044] Example 1:

[0045] This embodiment provides an intermediate ladle spray coating. The percentages of each component in the intermediate ladle spray coating by mass percentage are as follows: 23% 3-1mm 91 magnesia, 49% 1-0mm 94 magnesia, 18% 200-mesh 94 magnesia, 2% 800-mesh 95 magnesia, 2.4% silica fume, 2.7% quicklime, 0.12% silica whiskers, 0.5% 70 cement, 0.7% sodium metasilicate nonahydrate, 0.43% polyvinyl alcohol, 0.02% composite hydrophobic agent, 0.6% paper fiber, 0.01% organic fiber, 0.02% aluminum powder, 0.3% sodium tripolyphosphate, and 0.2% citric acid.

[0046] Example 2:

[0047] This embodiment provides an intermediate ladle spray coating. The percentages of each component in the intermediate ladle spray coating by mass percentage are as follows: 22% 3-1mm 91 magnesia, 51% 1-0mm 94 magnesia, 16% 200-mesh 94 magnesia, 3% 800-mesh 95 magnesia, 2.3% silica fume, 3% quicklime, 0.14% silica whiskers, 0.54% 70 cement, 0.6% sodium metasilicate nonahydrate, 0.4% polyvinyl alcohol, 0.01% composite hydrophobic agent, 0.63% paper fiber, 0.01% organic fiber, 0.03% aluminum powder, 0.24% sodium tripolyphosphate, and 0.1% citric acid.

[0048] Example 3:

[0049] This embodiment provides an intermediate ladle spray coating. The percentages of each component in the intermediate ladle spray coating by mass percentage are as follows: 24% 3-1mm 91 magnesia, 47.5% 1-0mm 94 magnesia, 19% 200-mesh 94 magnesia, 1.7% 800-mesh 95 magnesia, 2.6% silica fume, 2% quicklime, 0.13% silica whiskers, 0.6% 70 cement, 0.68% sodium metasilicate nonahydrate, 0.5% polyvinyl alcohol, 0.02% composite hydrophobic agent, 0.7% paper fiber, 0.01% organic fiber, 0.02% aluminum powder, 0.3% sodium tripolyphosphate, and 0.24% citric acid.

[0050] Example 4:

[0051] This embodiment provides an intermediate ladle spray coating. The percentages of each component in the intermediate ladle spray coating by mass percentage are as follows: 23% 3-1mm 91 magnesia, 48% 1-0mm 94 magnesia, 18.5% 200-mesh 94 magnesia, 2.2% 800-mesh 95 magnesia, 3% silica fume, 2.7% quicklime, 0.1% silica whiskers, 0.44% 70 cement, 0.64% sodium metasilicate nonahydrate, 0.3% polyvinyl alcohol, 0.02% composite hydrophobic agent, 0.54% paper fiber, 0.01% organic fiber, 0.03% aluminum powder, 0.22% sodium tripolyphosphate, and 0.3% citric acid.

[0052] Example 5:

[0053] This embodiment provides an intermediate ladle spray coating. The percentages of each component in the intermediate ladle spray coating by mass percentage are as follows: 23% 3-1mm 91 magnesia, 50% 1-0mm 94 magnesia, 18% 200-mesh 94 magnesia, 1.5% 800-mesh 95 magnesia, 2.5% silica fume, 2.2% quicklime, 0.15% silica whiskers, 0.51% 70 cement, 0.8% sodium metasilicate nonahydrate, 0.41% polyvinyl alcohol, 0.03% composite hydrophobic agent, 0.5% paper fiber, 0.01% organic fiber, 0.03% aluminum powder, 0.2% sodium tripolyphosphate, and 0.16% citric acid.

[0054] Example 6:

[0055] This embodiment provides an intermediate ladle spray coating. The percentages of each component in the intermediate ladle spray coating by mass percentage are as follows: 25% 3-1mm 91 magnesia, 46% 1-0mm 94 magnesia, 200-mesh 94 magnesia, 1.8% 800-mesh 95 magnesia, 2% silica fume, 2.5% quicklime, 0.11% silica whiskers, 0.4% 70 cement, 0.73% sodium metasilicate nonahydrate, 0.36% polyvinyl alcohol, 0.01% composite hydrophobic agent, 0.58% paper fiber, 0.01% organic fiber, 0.02% aluminum powder, 0.27% sodium tripolyphosphate, and 0.21% citric acid.

[0056] Comparative Example 1:

[0057] This comparative example provides an intermediate ladle spray coating. The percentages of each component in the intermediate ladle spray coating by mass percentage are as follows: 22% 3-1mm 91 magnesia, 51% 1-0mm 94 magnesia, 16% 200-mesh 94 magnesia, 3% 800-mesh 95 magnesia, 2.3% silica fume, 3% quicklime, 0.14% silica whiskers, 0.54% 70 cement, 0.6% sodium metasilicate nonahydrate, 0.4% polyvinyl alcohol, 0.64% paper fiber, 0.01% organic fiber, 0.03% aluminum powder, 0.24% sodium tripolyphosphate, and 0.1% citric acid. This comparative example does not contain a composite hydrophobic agent.

[0058] Comparative Example 2:

[0059] This comparative example provides an intermediate ladle spray coating. The percentages of each component in the intermediate ladle spray coating by mass percentage are as follows: 24.5% 3-1mm 91 magnesia, 47.5% 1-0mm 94 magnesia, 19% 200-mesh 94 magnesia, 1.7% 800-mesh 95 magnesia, 2.6% silica fume, 2% quicklime, 0.13% silica whiskers, 0.6% 70 cement, 0.68% sodium metasilicate nonahydrate, 0.02% composite hydrophobic agent, 0.7% paper fiber, 0.01% organic fiber, 0.02% aluminum powder, 0.3% sodium tripolyphosphate, and 0.24% citric acid. This comparative example does not contain polyvinyl alcohol.

[0060] Comparative Example 3:

[0061] This comparative example provides an intermediate ladle spray coating. The percentages of each component in the intermediate ladle spray coating by mass percentage are as follows: 23.64% 3-1mm 91 magnesia, 48% 1-0mm 94 magnesia, 18.5% 200-mesh 94 magnesia, 2.2% 800-mesh 95 magnesia, 3% silica fume, 2.7% quicklime, 0.1% silica whiskers, 0.44% 70 cement, 0.3% polyvinyl alcohol, 0.02% composite hydrophobic agent, 0.54% paper fiber, 0.01% organic fiber, 0.03% aluminum powder, 0.22% sodium tripolyphosphate, and 0.3% citric acid. This comparative example does not contain sodium metasilicate nonahydrate.

[0062] Comparative Example 4:

[0063] This comparative example provides an intermediate ladle spray coating. The percentages of each component in the intermediate ladle spray coating by mass percentage are as follows: 23.15% 3-1mm 91 magnesia, 50% 1-0mm 94 magnesia, 18% 200-mesh 94 magnesia, 1.5% 800-mesh 95 magnesia, 2.5% silica fume, 2.2% quicklime, 0.51% 70 cement, 0.8% sodium metasilicate nonahydrate, 0.41% polyvinyl alcohol, 0.03% composite hydrophobic agent, 0.5% paper fiber, 0.01% organic fiber, 0.03% metallic aluminum powder, 0.2% sodium tripolyphosphate, and 0.16% citric acid. This comparative example does not contain silica whiskers.

[0064] In this invention, samples of an intermediate ladle spray coating from Examples 1-6 and Comparative Examples 1-4 were prepared according to GB / T4513.5-2017 "Unshaped Refractories - Part 5: Sample Preparation and Pretreatment". The bulk density, linear shrinkage rate, flexural strength, and compressive strength were tested according to the methods in GB / T 4513.6-2017 "Unshaped Refractories - Part 6: Determination of Physical Properties". The acceptable product test index range is as follows: water content ≤15%; fluidity ≥167mm; the sum of the mass percentages of 800-mesh 95 magnesia, silica fume, and quicklime is 6.2-8.4%; the sum of the mass percentages of sodium metasilicate nonahydrate, polyvinyl alcohol, and sodium tripolyphosphate is ≥1.15%; and the linear shrinkage rate (1100℃ / 3h) is -0.8%. ~0%, linear change rate (1550℃ / 3h) is -2.2~0%; flexural strength (110℃) is ≥2.5MPa, flexural strength (1100℃ / 3h) is ≥1.5MPa, flexural strength (1550℃ / 3h) is ≥3.5MPa; compressive strength (110℃) is ≥9MPa, compressive strength (1100℃ / 3h) is ≥3MPa, compressive strength (1550℃ / 3h) is ≥10MPa; workability is good. Test results are shown in Table 1:

[0065] Table 1. Test results of Examples 1-6 and Comparative Examples 1-4

[0066] Comparative Example 1 is based on Example 2, but the introduction of the composite hydrophobic agent is removed and paper fibers are added accordingly. As can be seen from Table 1, compared with Example 2, Comparative Example 1 has significantly increased water addition rate and linear change rate, significantly decreased flowability, flexural strength and compressive strength, poor workability, and unqualified test results. The test results of Comparative Example 1 are significantly lower than those of Example 2.

[0067] Comparative Example 2 is based on Example 3, but the introduction of polyvinyl alcohol is removed and 3-1mm of 91 magnesia is added accordingly. As can be seen from Table 1, compared with Example 3, the sum of the mass percentages of sodium metasilicate nonahydrate, polyvinyl alcohol and sodium tripolyphosphate in Comparative Example 2 is too low, the flexural strength and compressive strength are significantly reduced, the workability is poor, and the test results are unqualified. The test results of Comparative Example 2 are significantly lower than those of Example 3.

[0068] Comparative Example 3 is based on Example 4, but the introduction of sodium metasilicate nonahydrate is omitted, and 3-1mm of 91 magnesia is added accordingly. As can be seen from Table 1, compared with Example 4, the sum of the mass percentages of sodium metasilicate nonahydrate, polyvinyl alcohol and sodium tripolyphosphate in Comparative Example 3 is too low, the flexural strength and compressive strength are significantly reduced, the workability is poor, and the test results are unqualified. The test results of Comparative Example 3 are significantly lower than those of Example 4.

[0069] Comparative Example 4 is based on Example 5, but the introduction of silica whiskers is removed and 3-1mm of 91 magnesia is added accordingly. As can be seen from Table 1, compared with Example 5, the flexural strength and compressive strength of Comparative Example 4 at 110℃ are significantly reduced, the workability is average, and the test results are unqualified. The test results of Comparative Example 4 are significantly lower than those of Example 5.

[0070] In summary, this invention effectively improves the flexural and compressive strength of intermediate tundish spray coatings by adding composite hydrophobic agents, polyvinyl alcohol, sodium metasilicate nonahydrate, and silica whiskers, reducing the risk of cracking after drying and significantly improving workability. The addition of composite hydrophobic agents significantly reduces the water addition rate. By setting a reasonable ratio of sodium metasilicate nonahydrate, polyvinyl alcohol, and sodium tripolyphosphate, their synergistic effect in the spray coating significantly enhances the coating's bonding strength, flowability, adhesion, durability, and erosion resistance, thereby increasing the coating's service life and performance stability, reducing production costs, and improving product quality.

[0071] The above description is only a preferred embodiment of the present invention and does not limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An intermediate pack spray coating, characterized in that: The mass percentage of each raw material component in the intermediate liner spray coating is as follows: 22-25% of 3-1mm 91 magnesia, 46-51% of 1-0mm 94 magnesia, 16-20% of 200-mesh 94 magnesia, 1.5-3% of 800-mesh 95 magnesia, 2-3% of silica fume, 2-3% of quicklime, 0.1-0.15% of silica whiskers, 0.4-0.6% of 70 cement, 0.6-0.8% of sodium metasilicate nonahydrate, 0.3-0.5% of polyvinyl alcohol, 0.01-0.03% of composite hydrophobic agent, 0.5-0.7% of paper fiber, 0.01% of organic fiber, 0.02-0.03% of metallic aluminum powder, 0.2-0.3% of sodium tripolyphosphate, and 0.1-0.3% of citric acid.

2. The intermediate ladle spray coating according to claim 1, characterized in that: The intermediate liner coating contains 23% 3-1mm 91 magnesia, 49% 1-0mm 94 magnesia, 18% 200-mesh 94 magnesia, 2% 800-mesh 95 magnesia, 2.4% silica fume, 2.7% quicklime, 0.12% silica whiskers, 0.5% 70 cement, 0.7% sodium metasilicate nonahydrate, 0.43% polyvinyl alcohol, 0.02% composite hydrophobic agent, 0.6% paper fiber, 0.01% organic fiber, 0.02% aluminum powder, 0.3% sodium tripolyphosphate, and 0.2% citric acid.

3. The intermediate ladle spray coating according to claim 1, characterized in that: The total mass percentage of 800-mesh 95 magnesia, silica fume, and quicklime in the intermediate liner spray coating is 6.2% to 8.4%.

4. The intermediate ladle spray coating according to claim 3, characterized in that: The silica fume contains ≥94% SiO2; the quicklime has a particle size of 600 mesh and a purity of 98%.

5. The intermediate ladle spray coating according to claim 1, characterized in that: The silica whiskers contain ≥99.9% SiO2, have a fiber length of 2–10 μm, and a bulk density of 0.78 g / cm³. 3 The actual density is 2.2–2.4 g / cm³. 3 It has a refractoriness of 1720℃, a Mohs hardness of 7, and a loss on ignition of ≤0.10%.

6. The intermediate ladle spray coating according to claim 1, characterized in that: The composite hydrophobic agent has the following raw material components by mass percentage: 75% polydimethylsiloxane and 25% fluorinated modified polyurethane.

7. The intermediate ladle spray coating according to claim 1, characterized in that: The sodium metasilicate nonahydrate, polyvinyl alcohol, sodium tripolyphosphate, and citric acid in the intermediate package spray coating are all industrial grade.

8. The intermediate ladle spray coating according to claim 7, characterized in that: The sum of the mass percentages of sodium metasilicate nonahydrate, polyvinyl alcohol, and sodium tripolyphosphate in the intermediate package spray coating is ≥1.15%.

9. The intermediate ladle spray coating according to claim 1, characterized in that: The aluminum powder has a particle size of 80 mesh and an Al content of ≥98%.

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