Tundish dry material suitable for ultra-low carbon steel smelting and preparation method thereof

Abstract

The invention relates to a refractory material technology, in particular to a tundish dry material suitable for ultra-low carbon steel smelting and a preparation method thereof, and the tundish dry material comprises the following components: mullite, phenolic resin, magnesium sulfate, sodium silicate, kaolin, calcium oxide, magnesia powder, silicon carbide powder, boron carbide and brucite fiber. Phenolic resin carbon is combined with a magnesium sulfate and sodium silicate inorganic combination system to obtain a composite combination system, then pores of phenolic resin are filled with silica sol sprayed twice, and calcium oxide powder, kaolin and matrix mullite react to form spinel, so that the compactness of the dry material is enhanced; the compact and continuous protective layer can significantly enhance the barrier ability to oxygen and molten steel permeation, effectively avoid the recarburization phenomenon of molten steel, meet the requirement for the high-oxygen-content slag environment of ultra-low carbon steel, better resist the erosion of slag and the like to the dry material, greatly improve the overall strength of the dry material and prolong the service life of the dry material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refractory materials, in particular to a tundish dry mix suitable for smelting ultra-low carbon steel and a preparation method thereof. BACKGROUND

[0002] In the steel continuous casting process system, the initial tundish only plays the role of a buffer between the ladle and the crystallizer. With the optimization of the continuous casting process and the improvement of the quality requirements of the continuous casting billet, the tundish has evolved into a terminal device for molten steel refining, and its main functions are two: one is the refining of molten steel, and the other is the elimination of non-metallic inclusions. In order to achieve new functions, the working lining (one of the inner linings, usually including permanent lining and working lining) of the tundish requires two things: one is "longevity", and the other is "cleanliness". Therefore, in the process of continuously meeting the two requirements, the tundish working lining has roughly gone through four development stages, and four generations of working linings have appeared in turn: no working lining, heat insulation plate, coating and dry vibration material (hereinafter referred to as dry material). They are the historical products of the continuous development of the steel continuous casting process, and each subsequent generation shows its unique advantages, among which the fourth generation of dry material has the greatest superiority. Dry material combines the advantages of heat insulation plate and coating, and has the following advantages over heat insulation plate and coating: since it is a non-aqueous material, it is convenient to use mechanical vibration for construction; it can be put into use immediately after construction, which speeds up the turnover of the tundish; it has a long service life (the service life is 2-4 times that of the coating), which reduces the cost of refractory materials per ton of steel; the residual lining has good disintegration, and is easy to remove; the working lining is gradually sintered during the steel pouring process, and the sintered layer is thin, the permanent lining will not hang steel and slag, which is beneficial to the improvement of the service life of the permanent lining.

[0003] Dry material has superior performance that cannot be compared with the other three generations, and the cost of raw materials used is not expected to increase significantly, and in addition, its service life can be at least 2-4 times that of the coating under the same use conditions, so the application prospect of dry material is very broad.

[0004] The "tundish composite dry material for smelting and casting and a preparation method thereof" (CN201811108633.9) patent technology, the tundish composite dry material for smelting and casting includes the following components by mass fraction: 20-30 parts of forsterite, 5-10 parts of hydroxymethyl cellulose, 4-7 parts of industrial glucose, 3-8 parts of high alumina bauxite, 1-5 parts of chromium oxide powder, and 2-4 parts of sodium hexametaphosphate. The low-carbon organic binders such as hydroxymethyl cellulose and glucose are used to replace the resin, and the inorganic binders such as chromium oxide, aluminum oxide and silicon dioxide are used for compounding. The dry material produced by the method has a low residual carbon rate, meets the production needs of ultra-low carbon steel and clean steel, but the overall strength is low, cannot adapt to high continuous casting furnace number, and the service life is far lower than that of the resin-bonded dry material, so it loses the advantage of long service life of the tundish dry material.

[0005] Therefore, there is an urgent need for a dry tundish feedstock suitable for ultra-low carbon steel smelting to meet the needs of the steel industry in developing low-carbon steel. Summary of the Invention

[0006] (a) Technical problems to be solved To address the shortcomings of existing technologies, the present invention aims to provide a dry tundish material suitable for ultra-low carbon steel smelting and its preparation method. It employs a composite binding system of phenolic resin, magnesium sulfate, and sodium silicate. By improving the density of the dry material and protecting the carbon chain structure of the phenolic resin, residual carbon from the organic binder is prevented from entering the molten steel, ultimately resulting in a dry tundish material suitable for ultra-low carbon steel smelting.

[0007] (II) Technical Solution To achieve the above objectives, the present invention adopts the following technical solution: a dry intermediate ladle material suitable for ultra-low carbon steel smelting and its preparation method, comprising the following components by weight: 20-30 parts mullite, 5-10 parts phenolic resin, 2-6 parts magnesium sulfate, 4-7 parts sodium silicate, 3-8 parts kaolin, and 1-5 parts calcium oxide.

[0008] Furthermore, by weight, the intermediate dry material includes the following components: 26-30 parts mullite, 5-8 parts phenolic resin, 2-5 parts magnesium sulfate, 4-5 parts sodium silicate, 5-8 parts kaolin, and 3-5 parts calcium oxide.

[0009] Furthermore, by weight, the intermediate dry material comprises the following components: 28 parts mullite, 6 parts phenolic resin, 4 parts magnesium sulfate, 5 parts sodium silicate, 5 parts kaolin, and 3 parts calcium oxide.

[0010] Furthermore, by weight, the intermediate dry material also includes 1 to 3 parts of magnesia powder and 0.5 to 1.5 parts of silicon carbide powder.

[0011] Furthermore, by weight, the intermediate dry material also includes: 4-6 parts boron carbide and 1-3 parts magnesia fiber.

[0012] Preferably, the composition is 5 parts boron carbide and 3 parts brucite fiber.

[0013] Another object of the present invention is to provide a method for preparing the tundish dry feedstock suitable for ultra-low carbon steel smelting, comprising the following steps: S1: Mix the above raw materials evenly in a mixer to obtain a mixture; S2: Place the mixture in a mold, pound and vibrate to form a molded blank, and then spray the molded blank with silica sol; S3: Place the mold and the formed blank together in an oven at 200-300℃ and bake for 0.5-1 hour. After cooling, demold to obtain a dry material intermediate. The obtained dry material intermediate is then sprayed with silica sol again. S4: The dry material intermediate is held at 1100-1200℃ for 2-4 hours and at 1500-1600℃ for 1-2 hours in sequence to obtain a dry material for tundish smelting of ultra-low carbon steel.

[0014] Furthermore, in step S1, the stirring speed is 120–200 rpm.

[0015] Furthermore, during step S2 vibration molding, a needle-shaped air hammer is used to pound the blank, and after vibration molding is completed, a block-shaped air hammer is used to pound it.

[0016] This invention provides a dry-mix tundish material suitable for ultra-low carbon steel smelting, using mullite as a matrix, phenolic resin, magnesium sulfate, and sodium silicate as binders, kaolin and calcium oxide powder as modifiers, and boron carbide as an antioxidant. The billet is formed by spraying a modified silica sol, which penetrates into the pores and interparticle spaces of the billet, binding the particles together with its excellent adhesion properties and enhancing the overall strength of the billet.

[0017] The main difference between high, medium, low carbon steel, and ultra-low carbon steel slag lies in the oxygen content. As the carbon content of the steel decreases, the oxygen content in the slag increases. Higher oxygen content in the slag makes the carbon-bonded dry charge more porous, causing the charge layer to peel off and rapidly reducing its lifespan. High and medium carbon steels have a relatively high number of consecutive castings, requiring good erosion resistance. Magnesium sulfate and sodium silicate are non-carbon-bonded systems, which are severely corroded under high blast furnace counts. The main problem is the severe overall sintering of the charge layer; even if there are residual layers, they adhere to the permanent layer, affecting disintegration. Resin-bonded carbon chains, on the other hand, have a more stable structure and are effective against both chemical erosion and scouring. Therefore, this invention employs an inorganic and organic composite system, combining magnesium sulfate and sodium silicate within a phenolic resin carbon-bonded system. This system can adapt to both high oxygen content environments and high consecutive casting counts.

[0018] Magnesium sulfate and sodium silicate, as inorganic binders, react at high temperatures to form magnesium silicate and sodium sulfate. Magnesium silicate fills the pores of phenolic resin, enhancing the material's density. Sodium sulfate, generally solid or molten at high temperatures, also fills the pores, reducing oxygen permeation pathways and thus protecting the carbon chain structure of the phenolic resin. This combination of organic and inorganic binders leverages the advantages of the phenolic resin's carbon chain structure in resisting chemical corrosion while utilizing the inorganic binder to enhance density and protect the carbon chain. This prevents carbon from the phenolic resin from slowly permeating into the molten steel, thus avoiding an increase in the steel's carbon content.

[0019] In order to better improve the density of dry charge, avoid carbonization of molten steel, and further enhance the barrier ability of dry charge to oxygen and molten steel penetration, this invention modifies the silica sol.

[0020] Furthermore, the preparation method of modified silica sol includes the following steps: (1) Preparation of zirconium dioxide suspension: Add nano-zirconia powder to deionized water, then add a dispersant and adjust the pH value to 7.5-8.5. Then, sonicate in an ultrasonic device for 20-40 minutes to obtain a stable nano-zirconia suspension. (2) Preparation of zirconium dioxide-coated silica gel mixture: The nano-zirconia suspension was slowly added to the alkaline silica sol while the stirring equipment was turned on and heated. The mixture was stirred at 300-500 rpm to allow the zirconia particles to be adsorbed onto the surface of the sol particles. The suspension was then heated and stirred to obtain a zirconia-coated silica gel mixture. (3) Preparation of modified silica sol: The mixture was filtered through a filter membrane with a pore size of 0.22–0.45 μm to remove impurities, yielding nano-modified silica sol.

[0021] Further, in step (1), the volume ratio of zirconium dioxide powder to deionized water is 1:2 to 3, the dispersant is polyvinyl alcohol, the amount of polyvinyl alcohol is 0.1 to 0.4 wt% of zirconium dioxide powder, the pH adjuster is a buffer solution composed of sodium carbonate and sodium bicarbonate, the nano-zirconia particle size is 20 to 80 nm, and the ultrasonic oscillation power is 200 to 400 W.

[0022] Further, in step (2), the amount of alkaline silica sol added is 0.5% to 5.0% of the total mass of zirconium dioxide and silica, based on silica. When heating the suspension, first slowly raise the temperature to 50 to 60°C, maintain it for 2 to 4 hours while stirring, and then slowly raise the temperature of the suspension to 90 to 100°C, maintain it for 2 to 4 hours while stirring.

[0023] In the innovative design of dry tundish billets for ultra-low carbon steel smelting, nano-zirconia-modified silica sol plays a crucial role in constructing a multi-layered protection and reinforcement system. The core advantage of this modified silica sol lies in the uniformly embedded 20-80nm zirconia particles, which effectively block the micropores within the silica sol itself and the dry billet, significantly reducing cracks caused by silica sol shrinkage at high temperatures, thus forming an exceptionally dense physical barrier. This barrier greatly reduces the rate of oxygen penetration into the material, providing crucial physical isolation for the carbon chain structure of the core component, phenolic resin, making it less susceptible to oxidation and damage in high-oxygen slag environments, fundamentally cutting off the risk pathway of carbon increase in molten steel.

[0024] During the low-temperature baking stage (200~300℃), the sprayed silica sol penetrates into the pores and interparticle spaces of the billet. Thanks to its excellent bonding properties, it tightly binds the raw material particles, such as mullite, magnesium sulfate, and inorganic binders, significantly enhancing the overall strength of the billet and the inter-component bonding force. Simultaneously, the uniform, smooth, and dense film formed on the billet surface not only greatly reduces demolding difficulty and decreases friction and erosion losses during subsequent slag and molten steel flow, but also provides a relatively closed environment for the phenolic resin carbon chain from the initial stage, initially blocking oxygen penetration. Even after low-temperature treatment, the billet may still contain micropores; therefore, the secondary spraying after demolding is crucial. It effectively seals these pores, forming a denser and continuous final protective layer, minimizing early slag penetration and erosion.

[0025] As the temperature rises to the mid-temperature range (1100~1200℃), the modified silica sol exhibits stronger bonding and structural strengthening capabilities. The polysilicic acid within forms a siloxane network structure and adheres to the surface of the matrix particles, creating a stable hydration layer similar to structural water, significantly improving the material's overall integrity and stability. At this stage, the magnesium silicate generated by the reaction of the silica sol and magnesia powder forms a hard outer shell on the material layer surface, significantly enhancing its resistance to initial erosion by molten steel and mechanical impact, effectively preventing small-piece spalling. Entering the final high-temperature sintering stage (1500~1600℃), the modified silica sol's full potential is realized. Nano-zirconia particles further fill the pores and react with the silica sol to generate zirconium silicate (ZrSiO4), whose thermal expansion coefficient matches that of the mullite matrix, reducing interfacial stress cracking. Simultaneously, the silica sol reacts with alumina in mullite and kaolin to form aluminosilicate gel, acting as a high-temperature binder to strengthen interparticle bonding. The reaction between calcium oxide and mullite, along with the reaction involving kaolin impurities, together generate a dense and uniform spinel layer on the matrix surface, accompanied by volume expansion. This synergistically fills the pores, greatly improving the material's high-temperature strength and resistance to slag penetration.

[0026] Crucially, nano-zirconia endows the modified silica sol with a unique "active oxygen-consuming" chemical protection capability. Its oxygen ion conduction properties enable it to capture free oxygen ions in the slag and consume them through migration via lattice vacancies, thereby reducing the content of reactive oxygen species that attack the carbon chains of phenolic resins in the environment at the source, and providing additional chemical protection for the stability of the carbon chains in high-oxygen environments.

[0027] The entire dry-mix system design demonstrates a high degree of synergy. The introduction of magnesia powder, on the one hand, reacts with the molten slag to form a high-viscosity surface slag layer, physically blocking oxygen permeation, and on the other hand, improves the material's high-temperature stability. The addition of brucite fibers indirectly hinders oxygen diffusion by enhancing overall strength and toughness and reducing crack formation. Boron carbide, as a highly efficient antioxidant, significantly oxidizes and consumes oxygen in the molten slag in the 500–1000℃ range. The optimized vibration molding process (first using needle-shaped air hammers to promote flow and compaction, then using block-shaped air hammers for focused tamping) also aims to maximize initial density and reduce micropores, a potential oxygen permeation channel.

[0028] In summary, nano-zirconia-modified silica sol represents a key technological innovation in resolving the core contradiction in the dry-material tundish of ultra-low carbon steel smelting—namely, the ultimate prevention of carbon gain in molten steel and the achievement of an ultra-long service life. It achieves this by constructing a dense physical barrier, providing active chemical protection, and synergistically enhancing the material's structure and properties at various temperature stages. Combined with a phenolic resin system, other inorganic additives, and optimized processes, it successfully achieves effective protection of the phenolic resin carbon chain, excellent high-temperature erosion and penetration resistance, and a long service life that meets the requirements of high continuous casting cycles.

[0029] The magnesia, binder, modifier, and antioxidant provided by this invention work together to improve the density of the dry material, thereby improving its corrosion resistance, protecting the carbon chain structure of the phenolic resin, preventing residual carbon from the organic binder from entering the molten steel, promoting the service life of the tundish, and resulting in a smooth steel surface free of pores, thus meeting the processing requirements of ultra-low carbon steel.

[0030] (III) Beneficial Effects This invention proposes a dry tundish material suitable for ultra-low carbon steel smelting and its preparation method, comprising the following components: mullite, phenolic resin, magnesium sulfate, sodium silicate, kaolin, calcium oxide, magnesia powder, silicon carbide powder, boron carbide, and brucite fiber. A composite bonding system is obtained by combining the carbon of phenolic resin with the inorganic bonding system of magnesium sulfate and sodium silicate. Then, silica sol is sprayed twice to fill the pores of the phenolic resin. Additionally, calcium oxide powder, kaolin, and the mullite matrix react to form spinel, enhancing the density of the dry tundish material. This dense and continuous protective layer significantly enhances the barrier against oxygen and molten steel penetration, effectively preventing carbonization of the molten steel and meeting the high-oxygen slag environment of ultra-low carbon steel. It also better resists erosion by slag and other contaminants, greatly improving the overall strength and service life of the dry tundish material and extending its service life. Detailed Implementation

[0031] The technical solution of the present invention will be further described below through specific embodiments. Unless otherwise specified, the raw materials and equipment used in the present invention can be purchased from the market or are commonly used in the art. The methods in the embodiments are conventional methods in the art unless otherwise specified.

[0032] Example 1 A dry tundish material suitable for ultra-low carbon steel smelting is prepared from the following raw materials in parts by weight: 20 parts mullite, 5 parts phenolic resin, 2 parts magnesium sulfate, 4 parts sodium silicate, 3 parts kaolin, 1 part calcium oxide, 1 part magnesia powder, 0.5 parts silicon carbide powder, 4 parts boron carbide, and 1 part brucite fiber.

[0033] A dry-type feedstock for tundish smelting of ultra-low carbon steel specifically includes the following steps: S1: Mix the above raw materials evenly in a mixer at 120 rpm to obtain a mixture; S2: Place the mixture in a mold and pound and vibrate it to form a blank. When vibrating and molding, use a needle-shaped air hammer to pound the blank. After the vibration molding is completed, use a block-shaped air hammer to pound it to obtain a shaped blank. Then spray the shaped blank with silica sol. S3: Place the mold and the formed blank together in an oven at 200℃ and bake for 0.5h. After cooling, demold to obtain a dry material intermediate. The obtained dry material intermediate is then sprayed with silica sol again. S4: The dry material intermediate is held at 1100℃ for 2 hours and at 1500℃ for 1 hour in sequence to obtain a dry material suitable for tundish smelting of ultra-low carbon steel.

[0034] In order to better improve the density of dry charge, avoid carbonization of molten steel, and further improve the barrier ability of dry charge to oxygen and molten steel penetration, the present invention modifies the silica sol.

[0035] Furthermore, the preparation method of modified silica sol includes the following steps: (1) Preparation of zirconium dioxide suspension: Nano-zirconia powder was added to deionized water at a volume ratio of 1:2. Then, 0.1 wt% polyvinyl alcohol of the zirconia powder was added, and the pH value was adjusted to 7.5 with a buffer solution composed of sodium carbonate and sodium bicarbonate. The solution was then ultrasonically treated for 20 minutes with an ultrasonic oscillation power of 200W to obtain a stable nano-zirconia suspension. (2) Preparation of zirconium dioxide-coated silica gel mixture: The nano-zirconia suspension was slowly added to the alkaline silica sol. The amount of alkaline silica sol added was 0.5% of the total mass of zirconia and silica, based on silica. At the same time, the stirring device was turned on and heated. The suspension was first slowly heated to 50°C and kept for 2 hours while stirring at 300 rpm. Then the suspension was slowly heated to 90°C and kept for 2 hours while stirring at 300 rpm, so that the zirconia particles were adsorbed on the surface of the sol particles. The suspension was then heated and stirred to obtain a zirconia-coated silica gel mixture. (3) Preparation of modified silica sol: The mixture was filtered through a 0.22 μm pore size filter membrane to remove impurities, yielding nano-modified silica sol.

[0036] Example 2 A dry tundish material suitable for ultra-low carbon steel smelting is made from the following raw materials in parts by weight: 30 parts mullite, 10 parts phenolic resin, 6 parts magnesium sulfate, 7 parts sodium silicate, 8 parts kaolin, 5 parts calcium oxide, 3 parts magnesia powder, 1.5 parts silicon carbide powder, 6 parts boron carbide, and 3 parts brucite fiber.

[0037] A dry-type feedstock for tundish smelting of ultra-low carbon steel specifically includes the following steps: S1: Mix the above raw materials evenly in a mixer at 200 rpm to obtain a mixture; S2: Place the mixture in a mold and pound and vibrate it to form a blank. When vibrating and molding, use a needle-shaped air hammer to pound the blank. After the vibration molding is completed, use a block-shaped air hammer to pound it to obtain a shaped blank. Then spray the shaped blank with silica sol. S3: Place the mold and the formed blank together in an oven at 300℃ and bake for 1 hour. After cooling, demold to obtain a dry material intermediate. The obtained dry material intermediate is then sprayed with silica sol again. S4: The dry material intermediate is held at 1200℃ for 4 hours and at 1600℃ for 2 hours in sequence to obtain a dry material suitable for tundish smelting of ultra-low carbon steel.

[0038] In order to better improve the density of dry charge, avoid carbonization of molten steel, and further improve the barrier ability of dry charge to oxygen and molten steel penetration, the present invention modifies the silica sol.

[0039] Furthermore, the preparation method of modified silica sol includes the following steps: (1) Preparation of zirconium dioxide suspension: Nano-zirconia powder was added to deionized water at a volume ratio of 1:3. Then, 0.4 wt% polyvinyl alcohol of the zirconia powder was added, and the pH value was adjusted to 8.5 with a buffer solution composed of sodium carbonate and sodium bicarbonate. The solution was then ultrasonically treated for 40 minutes with an ultrasonic oscillation power of 400W to obtain a stable nano-zirconia suspension. (2) Preparation of zirconium dioxide-coated silica gel mixture: The nano-zirconia suspension was slowly added to the alkaline silica sol. The amount of alkaline silica sol added was 5.0% of the total mass of zirconia and silica, based on silica. At the same time, the stirring equipment was turned on and heated. The suspension was first slowly heated to 60°C and kept for 4 hours while stirring at 500 rpm. Then the suspension was slowly heated to 100°C and kept for 4 hours while stirring at 500 rpm, so that the zirconia particles were adsorbed on the surface of the sol particles. The suspension was then heated and stirred to obtain a zirconia-coated silica gel mixture. (3) Preparation of modified silica sol: The mixture was filtered through a 0.45 μm pore size filter membrane to remove impurities, yielding nano-modified silica sol.

[0040] Example 3 A dry tundish material suitable for ultra-low carbon steel smelting is prepared from the following raw materials in parts by weight: 25 parts mullite, 7.5 parts phenolic resin, 4 parts magnesium sulfate, 6.5 parts sodium silicate, 5.5 parts kaolin, 3 parts calcium oxide, 2 parts magnesia powder, 1 part silicon carbide powder, 5 parts boron carbide, and 2 parts brucite fiber.

[0041] A dry-type feedstock for tundish smelting of ultra-low carbon steel specifically includes the following steps: S1: Mix the above raw materials evenly in a mixer at 160 rpm to obtain a mixture; S2: Place the mixture in a mold and pound and vibrate it to form a blank. When vibrating and molding, use a needle-shaped air hammer to pound the blank. After the vibration molding is completed, use a block-shaped air hammer to pound it to obtain a shaped blank. Then spray the shaped blank with silica sol. S3: Place the mold and the formed blank together in an oven at 250°C and bake for 0.75 hours. After cooling, demold to obtain a dry material intermediate. The obtained dry material intermediate is then sprayed with silica sol again. S4: The dry material intermediate is held at 1150℃ for 3 hours and at 1550℃ for 1.5 hours in sequence to obtain a dry material suitable for tundish smelting of ultra-low carbon steel.

[0042] In order to better improve the density of dry charge, avoid carbonization of molten steel, and further improve the barrier ability of dry charge to oxygen and molten steel penetration, the present invention modifies the silica sol.

[0043] Furthermore, the preparation method of modified silica sol includes the following steps: (1) Preparation of zirconium dioxide suspension: Nano-zirconia powder was added to deionized water at a volume ratio of 1:2.5. Then, 0.25 wt% polyvinyl alcohol of the zirconia powder was added, and the pH value was adjusted to 8.0 with a buffer solution composed of sodium carbonate and sodium bicarbonate. The solution was then ultrasonically treated for 30 minutes with an ultrasonic oscillation power of 300 W to obtain a stable nano-zirconia suspension. (2) Preparation of zirconium dioxide-coated silica gel mixture: The nano-zirconia suspension was slowly added to the alkaline silica sol. The amount of alkaline silica sol added was 3.0% of the total mass of zirconia and silica, based on silica. At the same time, the stirring equipment was turned on and heated. The suspension was first slowly heated to 55°C and kept for 3 hours while stirring at 400 rpm. Then the suspension was slowly heated to 95°C and kept for 3 hours while stirring at 400 rpm, so that the zirconia particles were adsorbed on the surface of the sol particles. The suspension was then heated and stirred to obtain a zirconia-coated silica gel mixture. (3) Preparation of modified silica sol: The mixture was filtered through a 0.35 μm pore size filter membrane to remove impurities, yielding nano-modified silica sol.

[0044] Comparative Example 1 The difference between Comparative Example 1 and Example 3 is that the silica sol was not modified.

[0045] Comparative Example 2 The difference between Comparative Example 2 and Example 3 is that the silica sol was not sprayed onto the molded blank in step S2.

[0046] Comparative Example 3 The difference between Comparative Example 3 and Example 3 is that the dry material intermediate was not coated with silica sol in step S3.

[0047] Performance testing The following are performance tests conducted on the dry materials used in the casting tundishes in Examples 1-6: The tundish dry materials from Examples 1-3 and Comparative Examples 1-3 were selected, and the sample size was 100mm × 100mm. ×100mm.

[0048] 1. The compressive strength at room temperature of the sample was determined according to the national standard (GB / T 5072-2008) after baking at 220℃ for 6 hours; heat treatment at 1100℃ for 3 hours; and heat treatment at 1550℃ for 3 hours. 2. The linear change rate of the sample after heat treatment at 1550℃ for 3 hours was determined according to the national standard (GB / T 5988-2007).

[0049] 3. Slag erosion tests were conducted according to the national standard (GB / T 8931-2007, using the static crucible method, holding at 1550℃ for 3 hours) to determine the erosion penetration depth. The chemical composition (mass fraction) of the intermediate ladle slag used for the erosion sample was: MgO 18.61, CaO 28.50, SiO 210.51, Fe 2O 36.32, Al 2O 318.93, K 2O 0.65. The test results are as follows: Table 1. Performance test results of dry feedstock in tundish This invention is not limited to the optional embodiments described above, and anyone can derive other various forms of products based on the inspiration of this invention. The specific embodiments described above should not be construed as limiting the scope of protection of this invention; the scope of protection of this invention should be determined by the claims, and the specification can be used to interpret the claims.

Claims

1. A dry charge for a tundish suitable for the smelting of ultra-low carbon steel, characterised in that it comprises: The invention discloses a dry charge material for tundish, which comprises the following components in parts by weight: 20-30 parts of mullite, 5-10 parts of phenolic resin, 2-6 parts of magnesium sulfate, 4-7 parts of sodium silicate, 3-8 parts of kaolin, 1-5 parts of calcium oxide, 4-6 parts of boron carbide, and 1-3 parts of magnesite fiber.

2. A dry material for a tundish suitable for smelting ultra-low carbon steel according to claim 1, characterized in that, The preparation method of the intermediate package dry charge material comprises the following steps: S1: uniformly stirring the raw material in the blender to obtain a mixture; S2: placing the mixture in a mold for vibration molding to obtain a molding blank, and spraying the molding blank with silica sol; S3: placing the mold and the molding blank together in an oven at 200-300 DEG C for 0.5-1 h, demolding after cooling, and obtaining the dry charge intermediate, and spraying the obtained dry charge intermediate with silica sol again; S4: sequentially keeping the dry charge intermediate at 1100-1200 DEG C for 2-4 h and at 1500-1600 DEG C for 1-2 h to obtain the intermediate package dry charge material suitable for smelting ultra-low carbon steel.

3. A dry material for a tundish suitable for the smelting of ultra-low carbon steel according to claim 2, characterized in that, The stirring speed in step S1 is 120-200 rpm.

4. A dry material for a tundish suitable for smelting ultra-low carbon steel according to claim 2, characterized in that, The needle-shaped air hammer is used to compact the molding blank during the vibration molding, and the block-shaped air hammer is used after the vibration molding.

5. A dry material for a tundish suitable for smelting ultra-low carbon steel according to claim 2, characterized in that, The silica sol is modified, and the preparation method of the modified silica sol comprises the following steps: (1) preparing a zirconium dioxide suspension: adding nano zirconium dioxide powder into deionized water, adding a dispersant, adjusting the pH value to 7.5-8.5, and then ultrasonically treating for 20-40 min in an ultrasonic device to obtain a stable nano zirconium dioxide suspension; (2) preparing a zirconium dioxide coated silica gel mixture: slowly adding the nano zirconium dioxide suspension into the alkaline silica sol, simultaneously starting a stirring device and heating, stirring at 300-500 rpm to make the zirconium dioxide particles adsorbed on the surface of the sol particles, and then heating and keeping stirring to obtain the zirconium dioxide coated silica gel mixture; (3) preparing a modified silica sol: filtering the mixture with a filter membrane with a pore size of 0.22-0.45 μm to remove impurities, and obtaining the nano modified silica sol.

6. A dry material for a tundish suitable for the smelting of ultra-low carbon steel according to claim 5, characterized in that, In step (1), the volume ratio of the zirconium dioxide powder to the deionized water is 1:2-3, the dispersant is polyvinyl alcohol, the amount of the polyvinyl alcohol is 0.1-0.4 wt% of the zirconium dioxide powder, the pH regulator is a buffer solution composed of sodium carbonate and sodium bicarbonate, the nano zirconium dioxide particle size is 20-80 nm, and the ultrasonic oscillation power is 200-400 W.

7. A dry material for a tundish suitable for the smelting of ultra-low carbon steel according to claim 5, characterized in that, In step (2), the alkaline silica sol is added in an amount of 0.5%-5.0% of the total mass of the zirconium dioxide and the silica.

8. A dry material for a tundish suitable for smelting ultra-low carbon steel according to claim 5, characterized in that, In step (2), when the suspension is heated, it is first slowly heated to 50-60 DEG C, kept for 2-4 h and kept stirring, and then the suspension is slowly heated to 90-100 DEG C, kept for 2-4 h and kept stirring.

9. The tundish dry charge suitable for the smelting of ultra-low carbon steel according to claim 1, characterized in that, The dry charge material further comprises 1-3 parts of magnesia powder and 0.5-1.5 parts of silicon carbide powder.

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