An Al@AlN coated composite corundum-based refractory material for RH refining furnaces

Abstract

This application relates to the field of refractory material preparation technology, specifically to an Al@AlN coated composite corundum-based refractory material for RH refining furnaces. It uses magnesium aluminum spinel as aggregate and a mixture of functionalized alumina powder, aluminum nitride powder, and aluminum powder as matrix. A modifying binder is added to the aggregate and matrix mixture to obtain a raw material mixture, which is then subjected to gradient calcination under a nitrogen atmosphere. This invention improves the mechanical properties, resistance to slag and iron penetration, and thermal shock stability of the refractory material by adding functionalized alumina powder and a modifying binder. The functionalized alumina powder consists of an innermost layer of alumina, a next outermost layer of magnesium oxide, and an outermost layer of silicon dioxide. The modifying binder is a blend of magnesium aluminate sol and aluminum phosphate. Through their synergistic effect, these properties enhance the refractory material's mechanical properties, resistance to slag and iron penetration, and thermal shock stability.

Description

Technical Field

[0001] This application relates to the field of refractory material preparation technology, and more specifically, it relates to an Al@AlN coated composite corundum-based refractory material for RH refining furnaces. Background Technology

[0002] In modern ironmaking processes, blast furnace ironmaking boasts numerous advantages, including large-scale production, high operating efficiency, low production costs, low fuel consumption, efficient energy utilization, and mature technology. It will continue to dominate the development of the ironmaking industry. Improving production efficiency, reducing production costs, and minimizing energy consumption are core pathways for steel enterprises to achieve sustainable development. Against this backdrop, the scaling up of blast furnaces and the intensification of smelting technologies have become inevitable choices for the industry. These technological innovations, while increasing production capacity, also place revolutionary demands on the refractory lining, which serves as the "protective armor" of the blast furnace.

[0003] Compared to traditional oxide refractories, non-oxide refractories exhibit superior resistance to erosion, thermal shock, and thermochemical stability, without contaminating molten steel. During high-temperature applications, metal-oxide composite refractories undergo a series of thermochemical reactions, generating in-situ non-oxide reinforcing phases, thus optimizing composition and microstructure, transforming into non-oxide-oxide composite refractories, which hold promise for excellent applications in RH refining. Among these, MgAlON, with its superior resistance to slag erosion, resistance to liquid metal dissolution, and good mechanical properties, shows promising application prospects in the fields of refractory materials and high-tech ceramics.

[0004] Pichlbauer et al. used Al2O3, MgO, AlN and MgAl2O4 as main raw materials to prepare MgAlON single-phase materials at 1650℃ and 1800℃ respectively. At the same time, they analyzed the effect of MgO as a magnesium source on the synthesis of MgAlON materials. The study showed that the volume expansion caused by the in-situ generation of MgAl2O4 resulted in higher porosity of the materials synthesized with MgO as the magnesium source, which reduced the mechanical properties and thermal shock stability of the prepared refractory materials. Summary of the Invention

[0005] To address the technical problems mentioned in the background art, this application provides an Al@AlN coated composite corundum-based refractory material for RH refining furnaces.

[0006] An Al@AlN coated composite corundum-based refractory material for RH refining furnaces is prepared using the following technical solution:

[0007] Magnesium aluminum spinel is used as aggregate, and a mixture of functionalized alumina powder, aluminum nitride powder and metallic aluminum powder is used as matrix. A modified binder is added to the mixture of aggregate and matrix to obtain a raw material mixture. The mixture is placed in a high-temperature furnace under nitrogen atmosphere and heated to 550-660℃ for 4-8 hours. Then it is placed at 1560-1680℃ for 3-5 hours and cooled to obtain Al@AlN coated composite corundum-based refractory material for RH refining furnace. The mass ratio of aggregate, matrix and modified binder is 76-82:10-14:2-4.

[0008] Preferably, the magnesium aluminum spinel in the aggregate is one or a mixture of several types of fused magnesium aluminum spinel, sintered magnesium aluminum spinel, or high-purity magnesium aluminum spinel, and the weight fraction of each component of the aggregate is as follows: 15-33% of 5-3mm magnesium aluminum spinel particles, 48-59% of 3-1mm magnesium aluminum spinel particles, and the balance of 1-0mm magnesium aluminum spinel particles.

[0009] Preferably, in the matrix, the functionalized alumina powder has a weight fraction of 52-70%, the aluminum nitride powder has a particle size ≤72µm, the aluminum nitride powder has a weight fraction of 12-25%, and the balance is metallic aluminum powder with a particle size <65µm and an Al content of 99-99.9%.

[0010] Preferably, the modified binder is a mixture of magnesium aluminate sol and aluminum phosphate in a mass ratio of 3:1-2.

[0011] Preferably, the functionalized alumina powder is prepared by the following steps:

[0012] Step A1: Dissolve cationic aluminum salt, sodium aluminate, and polyethylene glycol separately in equal masses of deionized water, and stir magnetically for 0.5-1 h to obtain cationic aluminum salt aqueous solution, sodium aluminate aqueous solution, and polyethylene glycol aqueous solution; then mix the cationic aluminum salt aqueous solution and sodium aluminate aqueous solution, and react in an ultrasonic reactor for 2-3 h, filter and wash to obtain aluminum hydroxide precipitate, then add the aluminum hydroxide precipitate to the polyethylene glycol aqueous solution, disperse in an ultrasonic reactor for 1-2 h, let stand for aging for 5-7 h, filter, wash and dry to obtain aluminum hydroxide precursor, wherein the mass ratio of cationic aluminum salt, sodium aluminate, polyethylene glycol and deionized water is 1-3:4-6:0.4-0.6:60-70;

[0013] In the above reaction process, the present invention utilizes the double hydrolysis of cationic aluminum salt and sodium aluminate to obtain aluminum hydroxide precipitate. To accelerate the double hydrolysis process and make the reaction more thorough, the present invention adds ultrasonic treatment: because the double hydrolysis reaction is an endothermic process, ultrasonic treatment increases the temperature of the reaction solution and promotes the forward progress of the double hydrolysis reaction; in addition, the generated aluminum hydroxide precipitate is prone to agglomeration and affects the subsequent silica encapsulation process, so the present invention utilizes the combined action of ultrasonic treatment and polyethylene glycol to obtain a well-dispersible aluminum hydroxide precursor, and polyethylene glycol also acts as a pore expander;

[0014] Step A2: Dissolve ammonia and aluminum hydroxide precursor in ethanol solution to obtain precursor solution; add magnesium chloride hexahydrate to precursor solution, stir magnetically for 16-20 hours, age, and dry to obtain core-shell aluminum hydroxide precursor-magnesium hydroxide, wherein the weight fraction of ethanol solution is 28-32%, the mass ratio of ammonia, aluminum hydroxide precursor and ethanol solution is 110-120:10-12:260-320; the mass ratio of magnesium chloride hexahydrate to precursor solution is 8-12:210-230;

[0015] Step A3: Dissolve tetraethyl orthosilicate in an ethanol solution. Then, add ammonia and the core-shell aluminum hydroxide precursor—magnesium hydroxide—sequentially to the tetraethyl orthosilicate ethanol solution. Stir magnetically for 16-20 hours, centrifuge, wash, dry, and calcine at 600-800℃ for 1.4-2.0 hours. Grind and sieve to obtain functionalized alumina powder. The mass ratio of tetraethyl orthosilicate, ethanol solution, ammonia, and core-shell aluminum hydroxide precursor—magnesium hydroxide is 2-4:260-340:80-100:10-12. The solution has a weight fraction of 32-36%. During the above reaction, magnesium chloride hexahydrate undergoes a hydrolysis-condensation reaction on the surface of the aluminum hydroxide precursor, resulting in a core-shell aluminum hydroxide precursor-magnesium hydroxide with the aluminum hydroxide precursor as the core and magnesium hydroxide as the shell. The aluminum hydroxide precursor undergoes subsequent high-temperature calcination to dehydrate and form activated alumina, thus coating the surface of the activated alumina with a layer of magnesium oxide. Magnesium oxide can effectively fill the cation vacancies on the surface of the activated alumina γ-Al₂O₃, inhibiting ion diffusion. Simultaneously, because Mg… 2+ and A1 3+ With similar ionic radii, Mg 2+ The Si atoms that can replace the tetrahedral positions of γ-Al2O3 and enter the lattice of γ-Al2O3 inhibit the structural rearrangement of γ-Al2O3, thereby suppressing the nucleation of α-Al2O3 and improving the thermal stability of γ-Al2O3.

[0016] Preferably, in step A1, the cationic aluminum salt is at least one of aluminum nitrate, aluminum chloride, and aluminum sulfate.

[0017] In summary, this application has the following beneficial effects: To improve the mechanical properties and thermal shock stability of the prepared refractory material, this application takes two approaches. First, functionalized alumina powder is added. The functionalized alumina powder consists of a three-layer structure: the core is alumina, the next outermost layer is magnesium oxide, and the outermost layer is silicon dioxide. In the initial stage of calcination, the metallic aluminum powder undergoes low-temperature nitriding treatment (550-660℃) in a nitrogen atmosphere, forming an aluminum nitride or alumina protective shell on the surface of the metallic aluminum powder. During calcination in a high-temperature nitrogen environment, the alumina in the core of the functionalized alumina powder can undergo a solid-phase reaction with the next outermost layer of magnesium oxide to generate MgAlON. The outer silicon dioxide not only penetrates into the microstructure of MgAlON to form a spatial network structure, reducing the pore size and improving the refractory material's resistance to slag and iron penetration erosion and its mechanical strength, but also the SiOH on its surface forms hydrogen bonds with the oxygen generated by the high-temperature decomposition of magnesium oxide, resulting in a lower oxygen partial pressure. At high temperatures, the metallic Al... The first step involves the conversion of Al(g), N2(g), Mg(g), and O2(g) into plate-like MgAlON, which improves the mechanical properties, resistance to slag and iron penetration, and thermal shock stability of the refractory material. Secondly, a modified binder is added, a blend of magnesium aluminate sol and aluminum phosphate. This modified binder, obtained through compounding, not only generates MgAlON under high-temperature calcination but also forms a dense magnesium aluminum phosphate ceramic phase, significantly reducing porosity. Introducing it into composite corundum-based refractory materials allows it to synergistically work with functionalized alumina powder to further enhance the mechanical properties, resistance to slag and iron penetration, and thermal shock stability of the refractory material. Detailed Implementation

[0018] The present application will be further described in detail below with reference to the embodiments.

[0019] Preparation Examples 1-3 and Comparative Preparation Examples 1-3 provide a functionalized alumina powder.

[0020] Preparation Example 1

[0021] This preparation example provides a functionalized alumina powder, which is prepared by the following steps:

[0022] Step A1: Dissolve aluminum chloride hexahydrate, sodium aluminate, and polyethylene glycol with a molecular weight of 1000 in equal masses of deionized water and stir at 600 rpm for 0.5 h to obtain aqueous solutions of aluminum chloride hexahydrate, sodium aluminate, and polyethylene glycol. Mix the aqueous solutions of aluminum chloride hexahydrate and sodium aluminate and react at room temperature for 2 h at an ultrasonic frequency of 35 kHz and an ultrasonic power of 500 W. Filter and wash three times with deionized water to obtain aluminum hydroxide precipitate. Add the aluminum hydroxide precipitate to the polyethylene glycol aqueous solution and ultrasonically disperse at an ultrasonic frequency of 30 kHz and an ultrasonic power of 450 W for 1 h. Let stand for 5 h, filter, wash three times with deionized water, and dry at 90 °C to constant weight to obtain aluminum hydroxide precursor. The mass ratio of aluminum chloride hexahydrate, sodium aluminate, polyethylene glycol, and deionized water is 1:4:0.4:60.

[0023] Step A2: Dissolve ammonia and aluminum hydroxide precursor in ethanol solution to obtain precursor solution; add magnesium chloride hexahydrate to precursor solution, stir at 500 rpm for 16 h, age, and dry at 70℃ to constant weight to obtain core-shell aluminum hydroxide precursor-magnesium hydroxide, wherein the mass ratio of ammonia, aluminum hydroxide precursor and ethanol solution is 110:10:260; the mass ratio of magnesium chloride hexahydrate and precursor solution is 8:210, and the weight fraction of ethanol solution is 28%;

[0024] Step A3: Dissolve tetraethyl orthosilicate in an ethanol solution, then add ammonia and the core-shell aluminum hydroxide precursor - magnesium hydroxide sequentially into the tetraethyl orthosilicate ethanol solution, stir magnetically for 16 hours, centrifuge, wash three times sequentially with anhydrous ethanol and deionized water, dry at 80°C to constant weight, calcine at 600°C for 1.4 hours, grind, and pass through a 100-mesh sieve to obtain functionalized alumina powder. The mass ratio of tetraethyl orthosilicate, ethanol solution, ammonia, and core-shell aluminum hydroxide precursor - magnesium hydroxide is 2:260:80:10, and the weight fraction of the ethanol solution is 32%.

[0025] Preparation Example 2

[0026] This preparation example provides a functionalized alumina powder, which is prepared by the following steps:

[0027] Step A1: Dissolve aluminum nitrate nonahydrate, sodium aluminate, and polyethylene glycol with a molecular weight of 1000 in equal masses of deionized water and stir at 650 rpm for 0.75 h to obtain aqueous solutions of aluminum nitrate nonahydrate, sodium aluminate, and polyethylene glycol. Mix the aqueous solutions of aluminum nitrate nonahydrate and sodium aluminate and react at room temperature for 2.5 h at an ultrasonic frequency of 40 kHz and an ultrasonic power of 550 W. Filter and wash four times with deionized water to obtain aluminum hydroxide precipitate. Add the aluminum hydroxide precipitate to the polyethylene glycol aqueous solution and ultrasonically disperse at an ultrasonic frequency of 35 kHz and an ultrasonic power of 500 W for 1.5 h. Let stand for aging for 6 h, filter, wash four times with deionized water, and dry at 95 °C to constant weight to obtain aluminum hydroxide precursor. The mass ratio of aluminum nitrate nonahydrate, sodium aluminate, polyethylene glycol, and deionized water is 2:5:0.5:65.

[0028] Step A2: Dissolve ammonia and aluminum hydroxide precursor in ethanol solution to obtain precursor solution; add magnesium chloride hexahydrate to precursor solution, stir at 520 rpm for 18 h, age, and dry at 75℃ to constant weight to obtain core-shell aluminum hydroxide precursor-magnesium hydroxide, wherein the mass ratio of ammonia, aluminum hydroxide precursor and ethanol solution is 115:11:290; the mass ratio of magnesium chloride hexahydrate and precursor solution is 10:220, and the weight fraction of ethanol solution is 30%.

[0029] Step A3: Dissolve tetraethyl orthosilicate in an ethanol solution, then add ammonia and the core-shell aluminum hydroxide precursor - magnesium hydroxide sequentially into the tetraethyl orthosilicate ethanol solution, stir magnetically for 18 hours, centrifuge, wash with anhydrous ethanol and deionized water four times sequentially, dry at 85°C to constant weight, calcine at 700°C for 1.7 hours, grind, and pass through a 150-mesh sieve to obtain functionalized alumina powder. The mass ratio of tetraethyl orthosilicate, ethanol solution, ammonia, and core-shell aluminum hydroxide precursor - magnesium hydroxide is 3:300:90:11, and the weight fraction of the ethanol solution is 34%.

[0030] Preparation Example 3

[0031] This preparation example provides a functionalized alumina powder, which is prepared by the following steps:

[0032] Step A1: Dissolve aluminum sulfate octahydrate, sodium aluminate, and polyethylene glycol with a molecular weight of 1000 in equal masses of deionized water and stir at 700 rpm for 1 hour to obtain aqueous solutions of aluminum sulfate octahydrate, sodium aluminate, and polyethylene glycol. Then mix the aqueous solutions of aluminum sulfate octahydrate and sodium aluminate and react at room temperature for 3 hours at an ultrasonic frequency of 45 kHz and an ultrasonic power of 600 W. Filter and wash 5 times with deionized water to obtain aluminum hydroxide precipitate. Add the aluminum hydroxide precipitate to the polyethylene glycol aqueous solution and ultrasonically disperse at an ultrasonic frequency of 45 kHz and an ultrasonic power of 550 W for 2 hours. Let it stand for 7 hours to age, filter, wash 5 times with deionized water, and dry at 100°C to constant weight to obtain aluminum hydroxide precursor. The mass ratio of aluminum sulfate octahydrate, sodium aluminate, polyethylene glycol, and deionized water is 3:6:0.6:70.

[0033] Step A2: Dissolve ammonia and aluminum hydroxide precursor in ethanol solution to obtain precursor solution; add magnesium chloride hexahydrate to precursor solution, stir at 540 rpm for 20 h, age, and dry at 80℃ to constant weight to obtain core-shell aluminum hydroxide precursor-magnesium hydroxide, wherein the mass ratio of ammonia, aluminum hydroxide precursor and ethanol solution is 120:12:320; the mass ratio of magnesium chloride hexahydrate and precursor solution is 12:230, and the weight fraction of ethanol solution is 32%;

[0034] Step A3: Dissolve tetraethyl orthosilicate in an ethanol solution, then add ammonia and the core-shell aluminum hydroxide precursor - magnesium hydroxide sequentially into the tetraethyl orthosilicate ethanol solution, stir magnetically for 20 hours, centrifuge, wash with anhydrous ethanol and deionized water five times sequentially, dry at 90°C to constant weight, calcine at 800°C for 2.0 hours, grind, and pass through a 200-mesh sieve to obtain functionalized alumina powder. The mass ratio of tetraethyl orthosilicate, ethanol solution, ammonia, and core-shell aluminum hydroxide precursor - magnesium hydroxide is 4:340:100:12, and the weight fraction of the ethanol solution is 36%.

[0035] Comparative Preparation Example 1

[0036] Preparation Example 1 is the same as Preparation Example 1, except that polyethylene glycol in step A1 is replaced with deionized water.

[0037] Comparative Preparation Example 2

[0038] Comparative Example 2 is the same as Preparation Example 1, except that magnesium chloride hexahydrate is replaced with aluminum chloride hexahydrate in step A2.

[0039] Comparative preparation example 3

[0040] Comparative Example 3 is the same as Preparation Example 1, except that the tetraethyl orthosilicate ethanol solution in step A3 is replaced with an ethanol solution.

[0041] Examples 1-3 and Comparative Examples 1-5 provide a method for preparing Al@AlN coated composite corundum-based refractory materials for RH refining furnaces.

[0042] Example 1

[0043] This embodiment provides an Al@AlN-coated composite corundum-based refractory material for RH refining furnaces, which is prepared by the following steps:

[0044] Aggregate, matrix, and modified binder were stirred at 300 rpm for 30 minutes until homogeneous, then mixed for another 30 minutes. The mixture was then dry-pressed using a 500t press, and the brick blanks were dried at 90℃ for 16 hours. They were then placed in a high-temperature furnace under a nitrogen atmosphere and held at 550℃ for 8 hours, followed by sintering at 1560℃ for 5 hours. After the furnace temperature cooled to room temperature, Al@AlN coated composite corundum-based refractory material for RH refining furnaces was obtained. The mass ratio of aggregate, matrix, and modified binder was 76:10:2. The weight fractions of the aggregate components are as follows: 15% of 5-3mm magnesium aluminum spinel particles, 48% of 3-1mm magnesium aluminum spinel particles, and the balance of 1-0mm magnesium aluminum spinel particles. The matrix includes 52% functionalized alumina powder by weight, 12% aluminum nitride powder by weight (with a particle size ≤72µm), and the balance of metallic aluminum powder (with a particle size <65µm and an Al content of 99%). The modified binder is a mixture of magnesium aluminate sol and aluminum phosphate at a mass ratio of 3:1.

[0045] Example 2

[0046] This embodiment provides an Al@AlN-coated composite corundum-based refractory material for RH refining furnaces, which is prepared by the following steps:

[0047] Aggregate, matrix, and modified binder were stirred at 400 rpm for 25 minutes until homogeneous, then mixed for another 30 minutes. The mixture was then dry-pressed using a 550t press, and the brick blanks were dried at 95℃ for 14 hours. They were then placed in a high-temperature furnace under a nitrogen atmosphere and held at 605℃ for 4 hours, followed by sintering at 1620℃ for 4 hours. After the furnace temperature cooled to room temperature, the Al@AlN coated composite corundum-based refractory material for RH refining furnaces was obtained. The mass ratio of aggregate, matrix, and modified binder was 79:12:3. The weight fractions of each component are as follows: 24% 5-3mm magnesium aluminum spinel particles, 53.5% 3-1mm magnesium aluminum spinel particles, and the balance 1-0mm magnesium aluminum spinel particles; the matrix includes 61% functionalized alumina powder by weight, 18.5% aluminum nitride powder by weight (particle size ≤72µm), and the balance metallic aluminum powder (particle size <65µm, Al content 99.5%); the modified binder is magnesium aluminate sol and aluminum phosphate in a mass ratio of 3:1.5.

[0048] Example 3

[0049] This embodiment provides an Al@AlN-coated composite corundum-based refractory material for RH refining furnaces, which is prepared by the following steps:

[0050] Aggregate, matrix, and modified binder were stirred at 500 rpm for 25 minutes until homogeneous, then mixed for another 30 minutes. The mixture was then dry-pressed using a 600t press, and the brick blanks were dried at 100℃ for 12 hours. They were then placed in a high-temperature furnace under a nitrogen atmosphere and held at 660℃ for 4 hours, followed by sintering at 1680℃ for 3 hours. After the furnace temperature cooled to room temperature, Al@AlN coated composite corundum-based refractory material for RH refining furnaces was obtained. The mass ratio of aggregate, matrix, and modified binder was 82:14:4. The weight fractions of each component are as follows: 33% of 5-3 mm magnesium aluminum spinel particles, 59% of 3-1 mm magnesium aluminum spinel particles, and the balance of 1-0 mm magnesium aluminum spinel particles; the matrix includes 70% by weight of the functionalized alumina powder prepared in Preparation Example 3, 25% by weight of aluminum nitride powder with a particle size ≤72 μm, and the balance of metallic aluminum powder with a particle size <65 µm and an Al content of 99.9% in the metallic aluminum powder; the modifying binder is composed of magnesium aluminate sol and aluminum phosphate in a mass ratio of 3:2.

[0051] Comparative Example 1

[0052] Comparative Example 1 is the same as Example 1, except that the functionalized alumina powder in Example 1 is replaced with the functionalized alumina powder prepared in Comparative Preparation Example 1.

[0053] Comparative Example 2

[0054] Comparative Example 2 is the same as Example 1, except that the functionalized alumina powder in Example 1 is replaced with the functionalized alumina powder prepared in Comparative Preparation Example 2.

[0055] Comparative Example 3

[0056] Comparative Example 3 is the same as Example 1, except that the functionalized alumina powder in Example 1 is replaced with the functionalized alumina powder prepared in Comparative Preparation Example 3.

[0057] Comparative Example 4

[0058] Comparative Example 4 is the same as Example 1, except that the modified binder in Example 1 is replaced with magnesium aluminate sol.

[0059] Comparative Example 5

[0060] Comparative Example 5 is the same as Example 1, except that the modified binder in Example 1 is replaced with aluminum phosphate.

[0061] Performance testing

[0062] The following performance tests were conducted on the Al@AlN coated composite corundum-based refractory materials for RH refining furnaces prepared in Examples 1-3 and Comparative Examples 1-5:

[0063] Flexural strength at room temperature: tested according to the refractory materials industry standard GB / T3001-2017;

[0064] High-temperature flexural strength: Tested according to the refractory materials industry standard GB / T3002-2017, with specific test conditions of 1400℃ and treatment for 0.5h;

[0065] Slag resistance test: The test was conducted according to GB / T8931-2007, and the erosion depth and erosion resistance were tested respectively. The results were obtained by erosion test with molten high-temperature iron slag.

[0066] Thermal shock resistance: Tested according to GB / T17617-2018.

[0067] Table 1 Performance Indicators of Al@AlN Coated Composite Corundum Refractory Materials for RH Refining Furnace

[0068]

[0069] As can be seen from the test data in Table 1, the comprehensive performance of the Al@AlN coated composite corundum-based refractory material for RH refining furnace provided by the present invention is significantly better than that of the refractory materials prepared in Comparative Examples 1-5.

[0070] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An Al@AlN coated composite corundum-based refractory material for RH refining furnaces, characterized in that, The material is prepared by the following steps: using magnesium aluminum spinel as aggregate, and a mixture of functionalized alumina powder, aluminum nitride powder and metallic aluminum powder as matrix, a modified binder is added to the mixture of aggregate and matrix to obtain a raw material mixture, which is placed in a high-temperature furnace under nitrogen atmosphere, heated to 550-660℃ and held for 4-8 hours, then placed at 1560-1680℃ and held for 3-5 hours, and cooled to obtain Al@AlN coated composite corundum-based refractory material for RH refining furnace; The functionalized alumina powder is first prepared by double hydrolysis of cationic aluminum salt and sodium aluminate to obtain aluminum hydroxide precipitate. The aluminum hydroxide precipitate is then placed in polyethylene glycol and ultrasonically dispersed to obtain an aluminum hydroxide precursor. The aluminum hydroxide precursor is then dissolved in ammonia water and hydrolyzed and condensed with magnesium chloride hexahydrate to obtain a core-shell aluminum hydroxide precursor - magnesium hydroxide. Finally, it is hydrolyzed and condensed with tetraethyl orthosilicate to obtain the final product. The modified binder is composed of magnesium aluminate sol and aluminum phosphate mixed in a mass ratio of 3:1-2.

2. The Al@AlN coated composite corundum-based refractory material for RH refining furnaces according to claim 1, characterized in that, The weight fractions of the aggregate components are as follows: 15-33% of 5-3mm magnesium aluminum spinel particles, 48-59% of 3-1mm magnesium aluminum spinel particles, and the balance of 1-0mm magnesium aluminum spinel particles.

3. The Al@AlN coated composite corundum-based refractory material for RH refining furnaces according to claim 1, characterized in that, The matrix comprises 52-70% by weight of functionalized alumina powder, 12-25% by weight of aluminum nitride powder with a particle size ≤72µm, and the balance of metallic aluminum powder with a particle size <65µm and an Al content of 99-99.9% in the metallic aluminum powder.

4. The Al@AlN coated composite corundum-based refractory material for RH refining furnaces according to claim 1, characterized in that, The functionalized alumina powder is prepared by the following steps: Step A1: Dissolve cationic aluminum salt, sodium aluminate, and polyethylene glycol separately in equal masses of deionized water, and stir magnetically for 0.5-1 h to obtain cationic aluminum salt aqueous solution, sodium aluminate aqueous solution, and polyethylene glycol aqueous solution; then mix the cationic aluminum salt aqueous solution and sodium aluminate aqueous solution, and react in an ultrasonic reactor for 2-3 h, filter and wash to obtain aluminum hydroxide precipitate, then add the aluminum hydroxide precipitate to the polyethylene glycol aqueous solution, disperse in an ultrasonic reactor for 1-2 h, let stand for aging for 5-7 h, filter, wash, and dry to obtain aluminum hydroxide precursor; Step A2: Dissolve ammonia and aluminum hydroxide precursor in ethanol solution to obtain precursor solution; add magnesium chloride hexahydrate to precursor solution, stir magnetically for 16-20 hours, age, and dry to obtain core-shell aluminum hydroxide precursor - magnesium hydroxide. Step A3: Dissolve tetraethyl orthosilicate in an ethanol solution, then add ammonia and the core-shell aluminum hydroxide precursor - magnesium hydroxide sequentially into the tetraethyl orthosilicate ethanol solution, stir magnetically for 16-20 hours, centrifuge, wash, dry, and calcine at 600-800℃ for 1.4-2.0 hours, grind, and sieve to obtain functionalized alumina powder.

5. The Al@AlN coated composite corundum-based refractory material for RH refining furnaces according to claim 4, characterized in that, In step A1, the mass ratio of cationic aluminum salt, sodium aluminate, polyethylene glycol, and deionized water is 1-3:4-6:0.4-0.6:60-70.

6. The Al@AlN coated composite corundum-based refractory material for RH refining furnaces according to claim 4, characterized in that, In step A2, the mass ratio of ammonia, aluminum hydroxide precursor, and ethanol solution is 110-120:10-12:260-320, the mass ratio of magnesium chloride hexahydrate to precursor solution is 8-12:210-230, the weight fraction of ammonia is 24-26%, and the weight fraction of ethanol solution is 28-32%.

7. The Al@AlN coated composite corundum-based refractory material for RH refining furnaces according to claim 4, characterized in that, In step A3, the mass ratio of tetraethyl orthosilicate, ethanol solution, ammonia, and core-shell aluminum hydroxide precursor-magnesium hydroxide is 2-4:260-340:80-100:10-12, and the weight fraction of the ethanol solution is 32-36%.

8. The Al@AlN coated composite corundum-based refractory material for RH refining furnaces according to claim 1, characterized in that, The mass ratio of the aggregate, matrix, and modified binder is 76-82:10-14:2-4.

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