Metal-carbon composite-containing magnesia-carbon refractory and method for producing the same

Abstract

The application relates to the technical field of refractory materials, in particular to a magnesium-carbon refractory material containing metal-carbon complex phases and a preparation method thereof, which comprises fused magnesia particles, silicon-carbon complex phase particles, modified flake graphite, aluminum powder, elemental silicon powder, nano carbon black and boron carbide. The SiC-Si-C complex phase particles are used for slag resistance and residual Si oxidation self-repairing. The graphite is modified by triethyl phosphate and triethyl borate to form a BPO4 coating, which realizes physical blocking at medium and low temperatures and liquid phase sealing at high temperatures, and the graphite is not damaged by the mild modification. The two components build a multi-scale strengthening system, and effectively inhibit carbon oxidation and slag corrosion.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically a magnesium-carbon refractory material containing a metal-carbon complex phase and its preparation method. Background Technology

[0002] Magnesia-carbon refractories are made from fused magnesia or high-purity sintered magnesia as the main raw materials, combined with flake graphite and pressed together. They combine the high melting point and high alkalinity and slag resistance of magnesium oxide with the high thermal conductivity and low thermal expansion of graphite, and are widely used in the lining of key steelmaking equipment such as converters, electric arc furnaces, and ladles.

[0003] However, under converter blowing conditions, the carbon phase faces dual erosion from direct and indirect oxidation, which are coupled in mechanism and progressively worsen in damage. On the one hand, the high-oxygen partial-pressure gas flow directly impacts the furnace lining surface, reacting directly with the graphite carbon phase to form an initial decarburization zone on the material surface. On the other hand, highly reactive FeO in the slag penetrates into the material interior along the initial pores, undergoing redox reactions with the carbon phase. The continuous escape of carbon monoxide gas breaks through the matrix structure, forming a large number of interconnected pores and microcrack networks inside the material, further providing channels for the deep penetration of the slag. As the interconnected porosity increases sharply, the penetrated slag comes into contact with the exposed MgO particles and undergoes a dissolution reaction, generating low-melting-point phases such as calcium magnesium olivine and iron magnesium olivine, leading to a sharp drop in grain boundary strength and structural spalling.

[0004] Existing technologies typically introduce antioxidants such as aluminum powder, silicon powder, and boron carbide, which can generate in-situ phases such as Al2O3 and MgAl2O4 at the matrix level, thus playing a certain role in inhibiting oxidation. However, their effect on strengthening the phase interface inside the aggregate particles and improving the slag wettability of the aggregate surface is limited. Furthermore, the interfacial bonding between flake graphite and the matrix depends on phenolic resin carbon, and its high-temperature stability is not as good as that of the in-situ ceramic bonding phase, posing a risk of preferential interface failure under harsh service conditions. Summary of the Invention

[0005] (1) Technical problems to be solved

[0006] The purpose of this invention is to provide a magnesium-carbon refractory material containing a metal-carbon multiphase and its preparation method, in order to solve the problem that under converter blowing conditions, the carbon phase is continuously consumed by the dual erosion caused by direct oxidation by high oxygen partial pressure gas flow and indirect oxidation by FeO in the slag, which induces the expansion of interconnected pores and drives the deep penetration of slag.

[0007] (2) Technical solution

[0008] To achieve the above objectives, on the one hand, the present invention provides a magnesia-carbon refractory material containing a metal-carbon multiphase, comprising the following components in parts by weight: 60-75 parts of fused magnesia particles, 8-15 parts of silicon-carbon multiphase particles, 8-15 parts of modified flake graphite, 2-4 parts of aluminum powder, 1-3 parts of elemental silicon powder, 1-2 parts of nano carbon black, and 0.3-1.0 parts of boron carbide;

[0009] The silicon-carbon composite particles are SiC-Si-C three-phase composite particles obtained by ball milling and mixing silicon powder and flake graphite, surface activation treatment with tetraethyl orthosilicate, and high-temperature solid-state reaction sintering. The composite particles have SiC as the main bonding phase and contain residual elemental Si and C phases. The modified flake graphite is flake graphite modified by triethyl borate and triethyl phosphate.

[0010] Furthermore, the particle size of the fused magnesia particles includes 5-8 mm, 3-5 mm, 1-3 mm and 0-1 mm, and the mass ratio of the four particle sizes of fused magnesia particles is 3:3:2:2.

[0011] Furthermore, the aluminum powder has a particle size of less than 0.074 mm; the elemental silicon powder has a particle size of less than 0.045 mm; and the nano carbon black has an average particle size of 30–50 nm.

[0012] Furthermore, the method for preparing the silicon-carbon multiphase particles includes the following steps:

[0013] S11. After mixing silicon powder and flake graphite powder, dry the mixture to remove adsorbed water and obtain a mixed powder.

[0014] S12. Place the mixed powder and zirconia balls in a ball mill jar, add anhydrous ethanol, and ball mill to obtain a slurry; after separating the slurry from the milling balls, add a surface-activating solution containing tetraethyl orthosilicate dropwise to the slurry while stirring, and add deionized water and adjust the pH with glacial acetic acid; after the addition is complete, stir to obtain a modified slurry, allowing tetraethyl orthosilicate to fully hydrolyze and condense, forming a Si-OH active layer on the particle surface; dry the modified slurry and grind and sieve to obtain a surface-activated mixed fine powder;

[0015] S13. Add a 5% polyvinyl alcohol aqueous solution to the surface-activated mixed fine powder as a temporary binder, granulate, and then press to form a green body;

[0016] S14. The billet is placed in a high-temperature furnace and sintered in sections under an argon protective atmosphere. After cooling to room temperature with the furnace, sintered particles are obtained. The sintered particles are crushed and sieved to obtain silicon-carbon multiphase particles.

[0017] Further, in step S12, the ratio of zirconium oxide balls to mixed powder is 2:1; the solid-liquid ratio of mixed powder to anhydrous ethanol is 1:3; in the surface activation solution containing tetraethyl orthosilicate, the amount of tetraethyl orthosilicate added is 1.5% of the total mass of the mixed powder; and the molar ratio of tetraethyl orthosilicate to deionized water is 1:4.

[0018] Furthermore, the preparation method of the modified flake graphite includes the following steps:

[0019] S21. Dry the flake graphite powder to remove adsorbed water and obtain the dried flake graphite powder.

[0020] S22. The dried flake graphite powder is added to a mixed solvent containing ethanol and deionized water, and the pH is adjusted with glacial acetic acid. After ultrasonic dispersion, a uniform graphite suspension is obtained.

[0021] S23. Under nitrogen protection, the graphite suspension is heated, and a triethyl phosphate solution is added dropwise while stirring. Under these conditions, triethyl phosphate is mainly adsorbed onto the graphite surface in molecular form. At the same time, limited ester bond alcoholysis occurs in the weakly acidic water and alcohol mixture, forming a phosphorus-containing organic-inorganic precursor adsorption layer. Subsequently, the temperature is lowered, and a triethyl borate solution is added dropwise while stirring, so that the hydrolysis products of triethyl phosphate and triethyl borate are deposited together on the graphite surface, forming a precursor coating containing phosphorus and boron elements, thus obtaining a suspension slurry.

[0022] S24. After the reaction is complete, the suspension slurry is filtered to obtain a filter cake; the filter cake is washed with anhydrous ethanol and then dried to obtain a dry powder.

[0023] S25. The dry powder is heated under a nitrogen atmosphere to react, causing the precursor to decompose and react in situ, forming a composite ceramic coating containing the BPO4 phase on the graphite surface; after cooling, it is ground and sieved to obtain modified flake graphite.

[0024] Further, in step S23, the triethyl phosphate solution is prepared by mixing triethyl phosphate and anhydrous ethanol at a volume ratio of 1:4; the triethyl phosphate is 1-3% of the mass of the flake graphite powder; the triethyl borate solution is prepared by mixing triethyl borate and anhydrous ethanol at a volume ratio of 1:9; the triethyl borate is 2-4% of the mass of the flake graphite powder.

[0025] Furthermore, the method for preparing the magnesium-carbon refractory material containing a metal-carbon multiphase comprises the following steps:

[0026] S1. Add fused magnesia particles, silicon-carbon composite particles, and modified flake graphite to a mixer in sequence and dry mix to obtain uniformly distributed aggregate; mix aluminum powder, elemental silicon powder, nano carbon black, and boron carbide fine powder evenly to obtain composite fine powder; add the composite fine powder to the mixer and continue to dry mix with the aggregate to fully fill the gaps between the aggregate to obtain magnesia-carbon refractory material.

[0027] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0028] 1. In this invention, silicon-carbon composite particles (SiC-Si-C three-phase coexistence) play a role at the aggregate scale: the pre-synthesized SiC phase, with its high melting point and low wettability, blocks the penetration of slag along grain boundaries and delays the dissolution of MgO particles, thereby inhibiting the formation of low-melting-point silicate phases and maintaining grain boundary strength; the residual Si phase oxidizes to generate SiO2 during high-temperature service, which, along with the volume effect, fills the micropores and plays a role in structural repair. The SiO2 generated by the hydrolysis of tetraethyl orthosilicate during the preparation process is distributed at the particle interface, which helps to enhance the structural integrity of the composite particles.

[0029] 2. Modified flake graphite provides multi-temperature protection at the matrix scale: A composite coating containing the BPO4 phase is generated by reacting and depositing triethyl phosphate and triethyl borate on the graphite surface and then heat-treating. During the medium-low temperature range (room temperature to 1300℃), this coating remains solid, preventing direct oxygen contact with the graphite. When the temperature rises above 1300℃, the BPO4 coating undergoes high-temperature decomposition, releasing B2O3 and residual phosphate to form a low-viscosity borophosphorus glass liquid phase on the graphite surface. This liquid phase can flow and fill micro-defects on the surface, achieving dynamic sealing.

[0030] 3. At the structural level, silicon-carbon composite particles enhance the erosion resistance of the aggregate particles themselves, while modified flake graphite protects the carbon phase in the matrix, forming a spatial complementarity. Mechanistically, modified graphite focuses on "barrier" to delay oxidation damage, while the residual Si in the composite particles focuses on "repair" to compensate for structural defects. Together, they reduce the apparent porosity and decarburized layer thickness of the material, improving high-temperature strength and slag erosion resistance. Attached Figure Description

[0031] Figure 1 This is a physical image of the magnesium-carbon refractory material of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1: This example discloses a magnesium-carbon refractory material containing a metal-carbon multiphase, comprising the following components in parts by weight: 68 parts of fused magnesia particles, 12 parts of silicon-carbon multiphase particles, 12 parts of modified flake graphite, 3 parts of aluminum powder, 2 parts of elemental silicon powder, 1.5 parts of nano carbon black, and 0.6 parts of boron carbide.

[0034] The particle size of the fused magnesia particles includes 5-8 mm, 3-5 mm, 1-3 mm and 0-1 mm, and the mass ratio of the four particle sizes of fused magnesia particles is 3:3:2:2.

[0035] The silicon-carbon composite particles are SiC-Si-C three-phase composite particles obtained by ball milling and mixing silicon powder and flake graphite, surface activation treatment with tetraethyl orthosilicate, and high-temperature solid-state reaction sintering. The composite particles have SiC as the main bonding phase and contain residual elemental Si and C phases. The modified flake graphite is flake graphite modified by triethyl borate and triethyl phosphate.

[0036] The aluminum powder has a particle size of less than 0.074 mm; the elemental silicon powder has a particle size of less than 0.045 mm; and the nano carbon black has an average particle size of 30–50 nm.

[0037] The method for preparing the silicon-carbon multiphase particles includes the following steps:

[0038] S11. Mix 120g of silicon powder and 36g of flake graphite powder, dry at 120℃ for 4 hours to remove adsorbed water, and obtain mixed powder.

[0039] S12. Place the mixed powder and 300g of zirconia balls in a ball mill jar, add 300mL of anhydrous ethanol, and ball mill at 300rpm for 8 hours to obtain a slurry; after separating the slurry from the milling balls, add a surface-activating solution containing tetraethyl orthosilicate dropwise to the slurry while stirring, and add deionized water and adjust the pH to 3.5-4.0 with glacial acetic acid; after the dropwise addition is complete, stir in a water bath at 40℃ for 2 hours to obtain a modified slurry, so that tetraethyl orthosilicate is fully hydrolyzed and condensed to form a Si-OH active layer on the particle surface; dry the modified slurry at 80℃ to constant weight, grind it through a 200-mesh sieve to obtain a surface-activated mixed fine powder;

[0040] S13. Add 20 mL of 5% polyvinyl alcohol aqueous solution to the surface-activated mixed fine powder as a temporary binder, and manually granulate to obtain 1-3 mm particles; place the particles in a mold and press them into shape with a pressure of 10 MPa to obtain a green body;

[0041] S14. The billet is placed in a high-temperature furnace and sintered in stages under an argon protective atmosphere: First, the temperature is increased to 600℃ at 2℃ / min and held for 1 hour to fully remove the temporary binder; then, the temperature is increased to 1350-1380℃ at 3-5℃ / min and held for 4 hours. By utilizing the partial solid-phase reaction between silicon powder and graphite, a three-phase coexisting complex structure with silicon carbide as the bonding phase and containing residual silicon and carbon is generated. The upper limit of the temperature in this step is lower than the melting point of elemental silicon (1414℃) and a safety margin is left to avoid the loss of local silicon phase due to uneven furnace temperature, thereby ensuring the stable generation of the complex structure; after the reaction is completed, the temperature is reduced to 800℃ at 5℃ / min and then cooled to room temperature with the furnace to obtain sintered particles; the sintered particles are crushed, sieved, and 1-3mm particle size is collected to obtain silicon-carbon complex particles.

[0042] In step S12, the ratio of zirconia balls to mixed powder is 2:1; the solid-liquid ratio of mixed powder to anhydrous ethanol is 1:3; the surface activation solution containing tetraethyl orthosilicate is a solution of 7.8g tetraethyl orthosilicate dissolved in 50mL anhydrous ethanol; and the molar ratio of tetraethyl orthosilicate to deionized water is 1:4.

[0043] The method for preparing the modified flake graphite includes the following steps:

[0044] S21. Place the flake graphite powder in an oven at 120℃ and dry for 4 hours to remove adsorbed water, and obtain the dried flake graphite powder.

[0045] S22. Weigh 100g of dried flake graphite powder and place it in a 1000mL three-necked flask; add a mixed solvent containing 450mL ethanol and 50mL deionized water, and adjust the pH to 4.5-5.0 with 1.0g of glacial acetic acid. Disperse the mixture by sonication for 30 minutes to obtain a uniform graphite suspension.

[0046] S23. Under nitrogen protection, the graphite suspension is heated to 65-70℃; a triethyl phosphate solution is added dropwise through a constant pressure dropping funnel at a rate of 2-3 drops / second. After the addition is complete, the mixture is stirred at 65-70℃ for 2 hours. Under these conditions, triethyl phosphate is mainly adsorbed onto the graphite surface in molecular form, while a limited degree of ester bond alcoholysis occurs in the weakly acidic water and alcohol mixture, forming a phosphorus-containing organic-inorganic precursor adsorption layer. Subsequently, the temperature is lowered to 40℃, and a triethyl borate solution is added dropwise at a rate of 1-2 drops / second. After the addition is complete, the mixture is stirred at 40℃ for 2 hours, allowing the hydrolysis products of triethyl phosphate and triethyl borate to co-deposit on the graphite surface, forming a precursor coating containing phosphorus and boron elements, thus obtaining a suspension slurry.

[0047] S24. After the reaction is complete, the suspension slurry is filtered while hot (40℃) to obtain a filter cake; the filter cake is washed once with 200mL of anhydrous ethanol; the filter cake is placed in an 80℃ vacuum drying oven (vacuum degree ≤−0.09MPa) and dried to constant weight to obtain dried powder;

[0048] S25. The dried powder is placed in an alumina crucible and placed in a tube furnace. Under a nitrogen atmosphere (flow rate 3L / min), the temperature is increased to 550℃ at 2℃ / min and held for 2 hours to decompose the precursor and react in situ, forming a composite ceramic coating containing BPO4 phase on the graphite surface. The furnace is cooled to room temperature and ground through a 200-mesh sieve to obtain modified flake graphite.

[0049] In step S23, the triethyl phosphate solution is prepared by mixing triethyl phosphate and anhydrous ethanol at a volume ratio of 1:4; the triethyl phosphate is 1-3% of the graphite mass; the triethyl borate solution is prepared by mixing triethyl borate and anhydrous ethanol at a volume ratio of 1:9; the triethyl borate is 2-4% of the graphite mass.

[0050] The method for preparing a magnesium-carbon refractory material containing a metal-carbon multiphase structure includes the following steps:

[0051] S1. Add fused magnesia particles, silicon-carbon composite particles, and modified flake graphite sequentially to a forced mixer and dry mix for 5-8 minutes to obtain uniformly distributed aggregate. Mix aluminum powder, elemental silicon powder, nano-carbon black, and boron carbide fine powder evenly to obtain composite fine powder. Add the composite fine powder to the mixer and continue dry mixing with the aggregate for 10-15 minutes to ensure the fine powder fully fills the gaps between the aggregates, thus obtaining a magnesia-carbon refractory material. Figure 1 This is a physical image of the magnesium-carbon refractory material of the present invention.

[0052] It should be noted that the magnesium-carbon refractory material prepared by this invention is used to make refractory products according to the following steps:

[0053] Magnesia-carbon refractory material is mixed evenly with 3-5% by mass of thermosetting phenolic resin (residual carbon content ≥46%), and pressed into a green body under a pressure of 150 MPa. The green body is then placed in an oven and cured at 200℃ for 4 hours. The cured green body is then placed in a high-temperature kiln and fired in stages under a nitrogen protective atmosphere: first, the temperature is increased to 600℃ at a rate of 1-2℃ / min and held for 2 hours; then, the temperature is increased to 1200℃ at a rate of 3℃ / min and held for 2 hours; then, the temperature is increased to 1350℃ at a rate of 3℃ / min and held for 3 hours; finally, the temperature is increased to 1450℃ at a rate of 2℃ / min and held for 4 hours. After the holding period, the temperature is decreased to 1200℃ at a rate of 3℃ / min and cooled to room temperature with the furnace to obtain the magnesia-carbon refractory product containing a metal-carbon multiphase structure.

[0054] Example 2: This example is based on Example 1, but differs from Example 1 in that it discloses a magnesium-carbon refractory material containing a metal-carbon multiphase, comprising the following components in parts by weight: 60 parts of fused magnesia particles, 8 parts of silicon-carbon multiphase particles, 8 parts of modified flake graphite, 2 parts of aluminum powder, 1 part of elemental silicon powder, 1 part of nano carbon black, and 0.3 parts of boron carbide.

[0055] The other components and preparation methods are the same as in Example 1.

[0056] Example 3: This example is based on Example 1, but differs from Example 1 in that it discloses a magnesium-carbon refractory material containing a metal-carbon multiphase, comprising the following components in parts by weight: 75 parts of fused magnesia particles, 15 parts of silicon-carbon multiphase particles, 15 parts of modified flake graphite, 4 parts of aluminum powder, 3 parts of elemental silicon powder, 2 parts of nano carbon black, and 1.0 part of boron carbide.

[0057] The other components and preparation methods are the same as in Example 1.

[0058] Comparative Example 1: Based on Example 1, the difference from Example 1 is that a powder obtained by simple physical mixing of silicon powder and flake graphite is used instead of silicon-carbon composite particles. This mixed powder is not subjected to ball milling, tetraethyl orthosilicate surface activation treatment, or high-temperature pre-synthesis sintering. Other components and preparation methods are the same as in Example 1.

[0059] Comparative Example 2: Based on Example 1, except that unmodified flake graphite was used instead of modified flake graphite, while the other components and preparation methods were the same as in Example 1.

[0060] Comparative Example 3: Based on Example 1, but differing from Example 1, the modified flake graphite was modified only with triethyl phosphate. In this comparative example, the preparation method of the modified flake graphite was adjusted from that of Example 1 as follows: in step S23, the addition of triethyl borate was not performed. Other components and preparation methods were the same as in Example 1.

[0061] Comparative Example 4: Based on Example 1, but differing from Example 1, the modified flake graphite was modified only with triethyl borate. In this comparative example, the preparation method of the modified flake graphite was adjusted from that of Example 1 as follows: in step S23, the triethyl phosphate dropwise addition treatment was not performed. Other components and preparation methods were the same as in Example 1.

[0062] Comparative Example 5: Based on Example 1, except that silicon-carbon composite particles were not added, while other components and preparation methods were the same as in Example 1.

[0063] Comparative Example 6: Based on Example 1, but unlike Example 1, no modified flake graphite was added, while the other components and preparation methods were the same as in Example 1.

[0064] Comparative Example 7: Based on Example 1, but unlike Example 1, neither silicon-carbon multiphase particles nor modified flake graphite were added. Other components and preparation methods were the same as in Example 1.

[0065] Comparative Example 8: Based on Example 1, the difference from Example 1 is that the fused magnesia particles are not graded into four sizes of 5-8 mm, 3-5 mm, 1-3 mm and 0-1 mm, but only fused magnesia particles of a single size of 1-3 mm are used. The other components and preparation methods are the same as in Example 1.

[0066] Comparative Example 9: Based on Example 1, except that no nano carbon black was added, while the other components and preparation methods were the same as in Example 1.

[0067] Experimental verification:

[0068] Magnesia-carbon refractory materials prepared in Examples 1-3 and Comparative Examples 1-9 were used to prepare magnesia-carbon refractory products according to the method for preparing refractory products described in Example 1 of the specific embodiments, resulting in standard specimens with dimensions of 230mm × 114mm × 65mm. Five parallel specimens were prepared for each group of samples. The following performance tests were performed on the specimens:

[0069] (1) Apparent porosity and bulk density: tested according to GB / T 2997-2015 standard, using Archimedes' water displacement method.

[0070] (2) Pressure resistance at room temperature: tested according to GB / T 5072-2023 standard.

[0071] (3) High-temperature flexural strength: Tested at 1400℃ according to GB / T 3002-2017 standard. The high-temperature flexural strength test specimens were made by cutting standard specimens (230mm×114mm×65mm) with a diamond saw blade, with a specification of 150mm×25mm×25mm. Deionized water was used for cooling during the cutting process, and the cut surfaces were ground flat to ensure that the parallelism of the surfaces was ≤0.1mm and the angle deviation was ≤0.5°. At least 5 parallel specimens were tested in each group.

[0072] (4) Antioxidant performance: The standard sample was cut into a cube of 50mm×50mm×50mm, placed in a muffle furnace, heated to 1400℃ at 5℃ / min in air atmosphere and held for 3 hours. After cooling, it was cut along the center and the thickness of the decarburized layer was measured.

[0073] (5) Slag penetration resistance: The static crucible method was used to process a blind hole of Φ20mm×25mm in the center of the sample and fill it with 10g of converter final slag (45%CaO, 15%SiO2, 5%Al2O3, 8%MgO, 15%FeO, 5%MnO). The sample was heated to 1600℃ at 5℃ / min under argon protection and held for 3 hours. After cooling, the sample was cut along the center and the thickness of the slag penetration layer was measured.

[0074] (6) Resistance to surface carbon oxidation (apparent oxidation propagation rate): Tested using the flame propagation method. A standard sample (230mm × 114mm × 65mm) was placed horizontally, and a propane torch (approximately 1000℃) was used to vertically apply a flame to the upper surface of one end of the sample for 30 seconds. The time t (seconds) required for the flame front to spread from 50mm to 200mm from the ignition end was recorded. If the flame front reached 200mm within 60 seconds, the rate V (mm / s) = 150 / t; if it did not reach 200mm, the propagation distance L (mm) from the 50mm mark to the actual stopping position was recorded, and the rate V (mm / s) = L / 60. The average of five parallel tests was taken. The lower this value, the better the resistance to oxidation propagation of the carbon phase on the material surface.

[0075] Table 1. Test results of refractory material performance:

[0076]

[0077] As shown in Table 1, the magnesium-carbon refractory material prepared in the embodiments of the present invention is superior to the comparative example in terms of apparent porosity, bulk density, mechanical strength, oxidation resistance, slag erosion resistance, and refractory performance. This demonstrates that the silicon-carbon multiphase particles, modified flake graphite, and the reaction-bonded system effectively construct a multi-scale metal-carbon multiphase reinforcing network. The preparation and surface activation of the silicon-carbon multiphase particles are key to improving oxidation resistance. The combined modification of flake graphite with triethyl phosphate and triethyl borate is more effective than single modification, and their combined effect reduces the apparent oxidation propagation rate of the material. This indicates that the present invention effectively inhibits the spread of oxidation reaction of the carbon phase under high-temperature oxidizing atmosphere and enhances the material's resistance to carbon oxidation.

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A magnesium-carbon refractory material containing a metal-carbon multiphase structure, characterized in that, The composition includes the following components in parts by weight: 60-75 parts fused magnesia particles, 8-15 parts silicon-carbon multiphase particles, 8-15 parts modified flake graphite, 2-4 parts aluminum powder, 1-3 parts elemental silicon powder, 1-2 parts nano carbon black, and 0.3-1.0 parts boron carbide. The silicon-carbon composite particles are SiC-Si-C three-phase composite particles obtained by ball milling and mixing silicon powder and flake graphite, surface activation treatment with tetraethyl orthosilicate, and high-temperature solid-state reaction sintering. The composite particles have SiC as the main bonding phase and contain residual elemental Si and C phases. The modified flake graphite is flake graphite modified by triethyl borate and triethyl phosphate. The coating containing BPO4 phase is generated by reacting and depositing triethyl phosphate and triethyl borate on the graphite surface and then heat-treating.

2. The magnesium-carbon refractory material containing a metal-carbon multiphase as described in claim 1, characterized in that, The particle size of the fused magnesia particles includes 5-8 mm, 3-5 mm, 1-3 mm and 0-1 mm, and the mass ratio of the four particle sizes of fused magnesia particles is 3:3:2:

2.

3. The magnesium-carbon refractory material containing a metal-carbon multiphase as described in claim 1, characterized in that, The aluminum powder has a particle size of less than 0.074 mm; the elemental silicon powder has a particle size of less than 0.045 mm; and the nano carbon black has an average particle size of 30–50 nm.

4. The magnesium-carbon refractory material containing a metal-carbon multiphase as described in claim 1, characterized in that, The method for preparing the silicon-carbon multiphase particles includes the following steps: S11. After mixing silicon powder and flake graphite powder, the mixture is dried to obtain a mixed powder. S12. Place the mixed powder and zirconia balls in a ball mill jar, add anhydrous ethanol, and ball mill to obtain a slurry; after separating the slurry from the milling balls, add a surface-activating solution containing tetraethyl orthosilicate dropwise to the slurry while stirring, and add deionized water and adjust the pH with glacial acetic acid; after the addition is complete, stir to obtain a modified slurry; dry the modified slurry and grind and sieve to obtain a surface-activated mixed fine powder; S13. Add a 5% polyvinyl alcohol aqueous solution to the surface-activated mixed fine powder, granulate, and then press to form a green body; S14. The billet is placed in a high-temperature furnace and sintered in sections under an argon protective atmosphere. After cooling to room temperature with the furnace, sintered particles are obtained. The sintered particles are crushed and sieved to obtain silicon-carbon multiphase particles.

5. A magnesium-carbon refractory material containing a metal-carbon multiphase as described in claim 4, characterized in that, In step S12, the ratio of zirconium oxide balls to mixed powder is 2:1; the solid-liquid ratio of mixed powder to anhydrous ethanol is 1:3; in the surface activation solution containing tetraethyl orthosilicate, the amount of tetraethyl orthosilicate added is 1.5% of the total mass of the mixed powder; and the molar ratio of tetraethyl orthosilicate to deionized water is 1:

4.

6. A magnesium-carbon refractory material containing a metal-carbon multiphase as described in claim 1, characterized in that, The method for preparing the modified flake graphite includes the following steps: S21. Dry the flake graphite powder to obtain dried flake graphite powder; S22. The dried flake graphite powder is added to a mixed solvent containing ethanol and deionized water, and the pH is adjusted with glacial acetic acid. After ultrasonic dispersion, a uniform graphite suspension is obtained. S23. Under nitrogen protection, the graphite suspension is heated and then triethyl phosphate solution is added dropwise while stirring; then the suspension is cooled and triethyl borate solution is added dropwise while stirring to obtain a suspension slurry; S24. After the reaction is complete, the suspension slurry is filtered to obtain a filter cake; the filter cake is washed with anhydrous ethanol and then dried to obtain a dry powder. S25. The dry powder is heated and reacted under a nitrogen atmosphere; after cooling, it is ground and sieved to obtain modified flake graphite.

7. A magnesium-carbon refractory material containing a metal-carbon multiphase as described in claim 6, characterized in that, In step S23, the triethyl phosphate solution is prepared by mixing triethyl phosphate and anhydrous ethanol at a volume ratio of 1:4; the triethyl phosphate is 1-3% of the mass of the flake graphite powder; the triethyl borate solution is prepared by mixing triethyl borate and anhydrous ethanol at a volume ratio of 1:9; the triethyl borate is 2-4% of the mass of the flake graphite powder.

8. A method for preparing a magnesia-carbon refractory material containing a metal-carbon multiphase, applied to the preparation of a magnesia-carbon refractory material containing a metal-carbon multiphase as described in any one of claims 1 to 7, characterized in that, The method includes the following steps: S1. Add fused magnesia particles, silicon-carbon composite particles, and modified flake graphite to a mixer in sequence and dry mix to obtain uniformly distributed aggregate; mix aluminum powder, elemental silicon powder, nano carbon black, and boron carbide fine powder evenly to obtain composite fine powder; add the composite fine powder to the mixer and continue to dry mix with the aggregate to obtain magnesia-carbon refractory material.

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