Ultralow-carbon unfired magnesia carbon brick for stainless steel AOD converter and preparation method of ultralow-carbon unfired magnesia carbon brick

Abstract

The invention discloses an ultralow-carbon unfired magnesia carbon brick for a stainless steel AOD converter. The ultralow-carbon unfired magnesia carbon brick comprises the following raw materials in parts by weight: 95-98 parts of dicalcium fused magnesite, 1-3 parts of graphite, 1-3 parts of resin, 1-3 parts of a metal additive, 3-5 parts of an antioxidant, 1-2 parts of titanium, 1-2 parts of chromium and 1-2 parts of zirconium. Wherein the antioxidant is a mixture of modified nano vanadium pentoxide and rare earth oxide. The invention aims to solve the technical problem of poor oxidation resistance of magnesia carbon bricks.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, and particularly relates to an ultra-low carbon non-burning magnesia-carbon brick for stainless steel AOD converter and its preparation method. Background Technology

[0002] As the stainless steel industry rapidly develops towards high quality and low energy consumption, the demand for ultra-low carbon stainless steel continues to rise in fields such as high-end equipment manufacturing, food and pharmaceutical equipment, and nuclear power engineering due to its excellent corrosion resistance, toughness, and weldability. Currently, the smelting of ultra-low carbon stainless steel mainly relies on AOD converters. The main functions of AOD converters in stainless steel smelting include decarburization, alloying, and desulfurization. The operating environment is relatively harsh, characterized by a strong oxidizing atmosphere in the furnace, frequent mechanical impacts from alloys at the feeding point, high kinetic energy of side-blown gas stirring, and significant temperature fluctuations during the smelting process.

[0003] Magnesia-carbon bricks, due to their high thermal conductivity, low coefficient of thermal expansion, and excellent resistance to slag erosion, have become the mainstream refractory material for AOD converter linings. Magnesia-carbon bricks not only ensure the normal operation of high-temperature chemical reactions and continuous production within the furnace, but also significantly extend the service life of the smelting furnace and reduce maintenance costs. However, their poor oxidation resistance may affect the working efficiency of the AOD converter. Summary of the Invention

[0004] This invention provides an ultra-low carbon unburned magnesia-carbon brick for a stainless steel AOD converter and its preparation method, in order to solve the technical problem of poor oxidation resistance of existing magnesia-carbon bricks.

[0005] In view of this, the present invention provides an ultra-low carbon non-burning magnesia-carbon brick for a stainless steel AOD converter, comprising the following raw materials in parts by weight: 95-98 parts of dicalcium fused magnesia, 1-3 parts of graphite, 1-3 parts of resin, 1-3 parts of metal additives, 3-5 parts of antioxidant, 1-2 parts of titanium, 1-2 parts of chromium, and 1-2 parts of zirconium; wherein the antioxidant is a mixture of modified nano-vanadium pentoxide and rare earth oxides.

[0006] Optionally, the antioxidant is prepared by the following method: modified nano vanadium pentoxide and rare earth oxides are placed in water, a silane coupling agent is added, the mixture is stirred and ultrasonically dispersed to obtain a suspension; the suspension is dried to obtain a blocky mixture, which is then ground and sieved to obtain the antioxidant.

[0007] Furthermore, the antioxidant is prepared by the following method: modified nano-vanadium pentoxide and rare earth oxides are placed in water, a silane coupling agent is added, and the mixture is stirred for 1-2 hours. The mixture is then ultrasonically dispersed at a power of 400-500W for 40-60 minutes to obtain a suspension. The suspension is then dried under reduced pressure at a vacuum degree of -0.08-(-0.09) MPa and a temperature of 60-70℃ for 12-16 hours to obtain a blocky mixture. This mixture is then ground and passed through a 300-mesh sieve to obtain the antioxidant. The amount of water added to each 1g of modified nano vanadium pentoxide is 5-8mL, and the weight ratio of modified nano vanadium pentoxide to silane coupling agent is 1:(0.02-0.05).

[0008] Optionally, the weight ratio of the modified nano-vanadium pentoxide and rare earth oxide is 1:(0.2-0.4).

[0009] Optionally, the modified nano-vanadium pentoxide is prepared by the following method: A1: Place ammonium metavanadate in water, heat to a certain temperature, stir to dissolve, cool, adjust pH to obtain precursor solution; A2: The precursor solution was placed in a high-pressure reactor lined with polytetrafluoroethylene and sealed. Then it was placed in an oven for reaction. After the reaction was completed, it was naturally cooled to room temperature. The reactor was opened, the product was collected, washed, and dried to obtain nano-vanadium pentoxide rod-shaped particles. A3: Dissolve aluminum nitrate in water by stirring to obtain an aluminum source solution; A4: Place nano-vanadium pentoxide rod-shaped particles into water and sonicate to obtain a mixed solution; A5: Under magnetic stirring, the aluminum source solution was added dropwise to the mixture, and the pH value was adjusted. After the addition was complete, stirring was continued, followed by centrifugation. The solid was collected, washed, dried, calcined, kept warm, cooled, and ground to obtain modified nano-vanadium pentoxide.

[0010] Furthermore, the modified nano-vanadium pentoxide is prepared using the following method: A1: Place ammonium metavanadate in water, heat to 40-60℃, stir to dissolve, cool to room temperature, and adjust the pH to 2-4 with 30% hydrochloric acid solution to obtain the precursor solution; A2: Place the precursor solution into a high-pressure reactor lined with polytetrafluoroethylene with a filling degree of 70-80%, seal it, and then place it in an oven. React at 180-200℃ for 2-4 hours. After the reaction is completed, allow it to cool naturally to room temperature, open the reactor, collect the product, wash it 3-5 times with water and anhydrous ethanol respectively, and dry it at 60-80℃ for 12-24 hours to obtain nano-vanadium pentoxide rod-shaped particles. A3: Dissolve aluminum nitrate in water by stirring to obtain an aluminum source solution; A4: Place nano-vanadium pentoxide rod-shaped particles into water and sonicate them at a power of 300-500W for 20-40 minutes to obtain a mixed solution; A5: Under magnetic stirring, the aluminum source solution is added dropwise to the mixture at a rate of 1-2 drops / second, and the pH value is adjusted to 7-9 with 40% ammonia water. After the addition is complete, stirring is continued for 1-2 hours, then centrifuged, the solid is collected, washed with water 2-3 times, dried at 60-80℃ for 10-14 hours, placed in a muffle furnace, heated to 400-500℃ at a rate of 2-5℃ / min in air atmosphere, held at the temperature for 2-3 hours, naturally cooled to room temperature, and ground to obtain modified nano vanadium pentoxide. In step A1, the amount of water added per 1g of ammonium metavanadate is 40-60mL; in step A3, the amount of water added per 1g of aluminum nitrate is 50-60mL; and in step A4, the amount of water added per 1g of nano vanadium pentoxide rod-shaped particles is 40-50mL.

[0011] Optionally, the rare earth oxide is a lanthanum-cerium composite oxide.

[0012] Optionally, the weight ratio of lanthanum oxide to cerium oxide in the lanthanum-cerium composite oxide is 1:(0.8-1.2).

[0013] Optionally, the rare earth oxides are pretreated as follows before use: the rare earth oxides are placed in water, a dispersant is added, ultrasonic dispersion is performed, centrifugation is carried out, solid particles are collected, washed, dried, and ground to obtain pretreated rare earth oxides.

[0014] Furthermore, the rare earth oxides are pretreated as follows before use: the rare earth oxides are placed in water, a dispersant is added, and the mixture is intermittently ultrasonically dispersed at a power of 300-500W for 30-40 minutes, with a 3-second working and 2-second pause. The mixture is then centrifuged, the solid particles are collected, washed 2-3 times with anhydrous ethanol, dried at 60-80℃ for 8-12 hours, and ground to obtain the pretreated rare earth oxides. The amount of water added per 1g of rare earth oxide is 30-50mL, and the weight ratio of rare earth oxide to dispersant is 1:(0.01-0.03).

[0015] Optionally, the graphite is a mixture of flake graphite and amorphous graphite, and the weight ratio of the two is 1:1.

[0016] Optionally, the metal additive is a mixture of silicon powder and aluminum powder, with a weight ratio of 1:1.

[0017] A method for preparing ultra-low carbon non-fired magnesia-carbon bricks for stainless steel AOD converters includes the following steps: S1: Premix graphite, metal additives, antioxidants, titanium, chromium, and zirconium to obtain a premixed material; S2: Dry-mix the fused magnesia, add half of the resin and wet-mix, then add the premix and the remaining resin to obtain the mixture; S3: The mixture is placed in a mold, pressed and shaped, and then cured by low-temperature heat treatment to obtain ultra-low carbon non-fired magnesia-carbon bricks.

[0018] Furthermore, a method for preparing ultra-low carbon non-fired magnesia-carbon bricks for stainless steel AOD converters includes the following steps: S1: Premix graphite, metal additives, antioxidants, titanium, chromium, and zirconium for 25-35 minutes to obtain a premix; S2: Dry mix the fused magnesia for 2-3 minutes, add half of the resin and wet mix for 1-2 minutes, then add the premix and mix for 2-4 minutes, then add the remaining resin and mix for 5-7 minutes to obtain the mixture; S3: Place the mixture into a mold, press it under 100-150MPa pressure, and then cure it at 200-250℃ for 10-14h to obtain ultra-low carbon non-fired magnesia-carbon bricks.

[0019] As can be seen from the above technical solutions, the embodiments of the present invention have the following advantages: 1. The ultra-low carbon non-fired magnesia-carbon brick prepared by this invention has the following advantages through the synergistic effect between the raw materials: High temperature resistance: The refractoriness of the main raw materials of magnesia-carbon refractories is higher than that of magnesia-calcium refractories. In addition, the improved non-burning ultra-low carbon magnesia-carbon bricks use high-purity fused magnesia sand, which further improves the high temperature resistance of the refractory bricks and can meet the temperature requirements of 1250-1800℃ for AOD smelting. Erosion resistance: The erosion resistance physicochemical properties of the improved non-fired ultra-low carbon magnesia-carbon bricks are significantly better than those of fired magnesia-calcium bricks. Furthermore, based on the size and age of the conventional steel ladle bricks, the slag erosion resistance of the improved non-fired ultra-low carbon magnesia-carbon bricks is not the limiting factor. Antioxidant performance: Compared with fired magnesia-calcium bricks, the antioxidant performance of unfired ultra-low carbon magnesia-carbon bricks is a weakness. However, the antioxidant performance of the unfired ultra-low carbon magnesia-carbon bricks tested in this preliminary test was significantly improved due to the addition of a newly developed high-grade antioxidant. Erosion and impact resistance: This property mainly determines the ability of refractory bricks to withstand gas agitation in the vent and impact at the feeding point. As can be seen from the slag resistance compressive strength and flexural strength at 1450℃ of the refractory bricks, the improved non-fired ultra-low carbon magnesia-carbon bricks are significantly better than fired magnesia-calcium bricks. Thermal shock stability: The carbon materials in magnesia-carbon bricks have good resistance to high-temperature creep, so their thermal shock stability is superior to that of magnesia-calcium bricks. Mechanism of action without carbon addition: Carbon source control: The ultra-low carbon content results in extremely low release of free carbon from the bricks at high temperatures, avoiding direct contact with molten steel and thus preventing carbon accumulation.

[0020] Antioxidant barrier: Antioxidants preferentially oxidize at high temperatures to form a protective film, inhibiting carbon oxidation reaction (C + O2 → CO2↑), reducing carbon loss and gas phase mass transfer; Impermeability resistance: The dense structure slows down the penetration of slag and molten metal, preventing carbon from diffusing into the molten steel through the liquid phase. Ultra-low carbon magnesia-carbon bricks, through low-carbon design, oxidation-resistant modification, and structural optimization, effectively solve the carbon increase problem in AOD converter smelting of low-carbon steel grades. They combine high corrosion resistance with economic efficiency, making them an ideal refractory material solution for high-quality low-carbon steel production; and they also have good thermal conductivity.

[0021] 2. This invention uses fused magnesia, flake graphite, amorphous graphite, silicon powder, aluminum powder, antioxidants, resin, titanium, chromium, zirconium, and other additives as raw materials to produce unburned magnesia-carbon bricks. To improve oxidation resistance, the antioxidants are optimized, using a mixture of modified nano-vanadium pentoxide and rare earth oxides. The core advantages of this mixture as an antioxidant for magnesia-carbon bricks lie in the temperature complementarity of "low-temperature sealing-high-temperature film formation," the product synergy of "glass phase-rare earth composite phase," and the performance optimization of "dispersion-interface properties." It can form a dense, stable, and uniform antioxidant barrier across the entire temperature range, further improving the oxidation resistance of magnesia-carbon bricks.

[0022] 3. The modified nano-vanadium pentoxide in this invention is prepared by hydrothermal synthesis using ammonium metavanadate as raw material. Nano-vanadium pentoxide rod-shaped particles are synthesized in a reactor, and then a nano-scale "shell" is grown on its surface by in-situ deposition (forming a vanadium pentoxide-alumina core-shell structure). The mechanism of action is as follows: the rod-shaped structure can reduce the agglomeration tendency of vanadium pentoxide and improve its dispersion uniformity in the magnesia-carbon brick matrix; the surface alumina shell not only protects vanadium pentoxide from premature reduction, but also synergistically forms a "dense-high viscosity" composite glass phase with vanadium pentoxide at high temperature. At the same time, the alumina has good compatibility with the fused magnesia of the magnesia-carbon brick, which can enhance the interfacial bonding force between the glass phase and the matrix and prevent the glass phase from falling off. The rare earth oxides are lanthanum-cerium composite oxides. Lanthanum-cerium composite rare earth oxides can significantly improve the oxidation resistance of magnesia-carbon bricks over a wide temperature range through a multi-dimensional effect of "physical barrier (dense oxide film) - chemical regulation (inhibition of graphite oxidation) - structural strengthening (interface optimization) - synergistic effect (in combination with other antioxidants)". At the same time, it takes into account its high-temperature mechanical properties and refractoriness (lanthanum-cerium oxides themselves have a high melting point and good compatibility with fused magnesia, so they will not reduce the refractoriness of the bricks).

[0023] 4. This invention pretreats rare earth oxides, removing surface impurities and exposing active sites. In addition, the high-frequency mechanical force generated by ultrasonic vibration can break the van der Waals forces and hydrogen bonds between rare earth oxide particles, dissociating the aggregates into native nanoparticles. The dispersant can be adsorbed on the surface of rare earth oxide particles, forming a charge repulsion or steric hindrance layer, preventing the dispersed particles from re-aggregating. The pretreated rare earth oxides can be mixed with modified V2O5 in a monodisperse or weakly aggregated state, avoiding the appearance of "rare earth enrichment zones" or "blank zones" in the composite system. Ultimately, a continuous and dense antioxidant barrier is formed in the magnesium-carbon brick, solving the problem of "preferential oxidation caused by local lack of protection". Detailed Implementation

[0024] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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. Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in the present invention can be purchased on the market or prepared by existing methods.

[0025] Dicalcium fused magnesia, magnesium oxide purity ≥98%, density ≥3.5 g / cm³ 3 The resin is phenolic resin; the silane coupling agent is KH-570; the dispersant is polyvinylpyrrolidone with a molecular weight of 40,000.

[0026] Preparation Example Preparation Example 1 A modified nano-vanadium pentoxide is prepared by the following method: A1: Place ammonium metavanadate in water, heat to 50°C, stir to dissolve, cool to room temperature, and adjust the pH to 3 with 30% hydrochloric acid solution to obtain the precursor solution; A2: The precursor solution was placed in a high-pressure reactor lined with 75% polytetrafluoroethylene and sealed. The reactor was then placed in an oven and reacted at 190°C for 3 hours. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The reactor was then opened, the product was collected, and the product was washed five times with water and five times with anhydrous ethanol. The product was then dried at 70°C for 18 hours to obtain nano-vanadium pentoxide rod-shaped particles. A3: Dissolve aluminum nitrate in water by stirring to obtain an aluminum source solution; A4: Place nano-vanadium pentoxide rod-shaped particles into water and sonicate them at 400W for 30 minutes to obtain a mixed solution; A5: Under magnetic stirring, the aluminum source solution was added dropwise to the mixture at a rate of 2 drops / second, and the pH value was adjusted to 8 with 40% ammonia water. After the addition was completed, stirring was continued for 1.5 hours, then centrifuged, the solid was collected, washed three times with water, dried at 70°C for 12 hours, placed in a muffle furnace, heated to 450°C at a rate of 3°C / min in air atmosphere, held at that temperature for 2.5 hours, naturally cooled to room temperature, and ground to obtain modified nano vanadium pentoxide. In step A1, the amount of water added per 1g of ammonium metavanadate is 50mL; in step A3, the amount of water added per 1g of aluminum nitrate is 55mL; and in step A4, the amount of water added per 1g of nano vanadium pentoxide rod-shaped particles is 45mL.

[0027] Preparation Example 2 An antioxidant prepared by the following method: 10g of the modified nano-vanadium pentoxide prepared in Preparation Example 1 and 2g of rare earth oxides were placed in 60mL of water, 0.3g of silane coupling agent was added, and the mixture was stirred for 1.5h. The mixture was then ultrasonically dispersed for 50min at a power of 450W to obtain a suspension. The suspension was then dried under reduced pressure at a vacuum of -0.08MPa and a temperature of 65℃ for 14h to obtain a blocky mixture. The mixture was then ground and passed through a 300-mesh sieve to obtain an antioxidant. The weight ratio of lanthanum oxide to cerium oxide in the rare earth oxide is 1:0.8.

[0028] Preparation Example 3 An antioxidant, which differs from Preparation Example 2 in that the amount of rare earth oxide added is different; in Preparation Example 3, the amount of rare earth oxide added is 3g.

[0029] Preparation Example 4 An antioxidant, which differs from Preparation Example 2 in that the amount of rare earth oxide added is different; in Preparation Example 4, the amount of rare earth oxide added is 4g.

[0030] Preparation Example 5 An antioxidant, which differs from Preparation Example 3 in that the weight ratio of lanthanum oxide and cerium oxide in the rare earth oxide is different; in Preparation Example 5, the weight ratio of lanthanum oxide and cerium oxide is 1:1.

[0031] Preparation Example 6 An antioxidant, which differs from Preparation Example 3 in that the weight ratio of lanthanum oxide and cerium oxide in the rare earth oxide is different; in Preparation Example 6, the weight ratio of lanthanum oxide and cerium oxide is 1:2.

[0032] Example

[0033] Example 1

[0034] A type of ultra-low carbon non-fired magnesia-carbon brick for stainless steel AOD converter, the raw material ratio of which is shown in Table 1.

[0035] A method for preparing ultra-low carbon non-fired magnesia-carbon bricks for stainless steel AOD converters includes the following steps: S1: Graphite, metal additives, antioxidants prepared using Preparation Example 2, titanium, chromium, and zirconium are premixed for 30 minutes to obtain a premix; S2: Dry mix the fused magnesia for 3 minutes, add half of the resin and wet mix for 2 minutes, then add the premix and mix for 3 minutes, then add the remaining resin and mix for 6 minutes to obtain the mixture; S3: Place the mixture into a mold, press it under 130MPa pressure, and then cure it at 220℃ for 12 hours to obtain ultra-low carbon non-fired magnesia-carbon bricks.

[0036] Examples 2-5 An ultra-low carbon non-fired magnesia-carbon brick for a stainless steel AOD converter differs from Example 1 in that the raw material ratio is different, as shown in Table 1.

[0037] Table 1. Weight of each raw material (kg)

[0038] Examples 6-9 An ultra-low carbon non-fired magnesia-carbon brick for a stainless steel AOD converter differs from Example 4 in that the source of the antioxidant is different. The antioxidants in Examples 6-9 were prepared using Preparation Examples 3-6, respectively.

[0039] Example 10

[0040] A stainless steel AOD converter ultra-low carbon non-fired magnesia-carbon brick, which differs from Example 8 in that the rare earth oxides in the antioxidant are pretreated by the following method before use: the rare earth oxides are placed in water, a dispersant is added, and the mixture is intermittently ultrasonically dispersed at 400W for 35 minutes, working for 3 seconds and pausing for 2 seconds. The mixture is then centrifuged, the solid particles are collected, washed three times with anhydrous ethanol, dried at 70°C for 10 hours, and ground to obtain the pretreated rare earth oxides. The amount of water added per 1g of rare earth oxide is 40mL, and the weight ratio of rare earth oxide to dispersant is 1:0.02.

[0041] Comparative Example Comparative Example 1 An ultra-low carbon non-fired magnesia-carbon brick for a stainless steel AOD converter differs from Example 1 in that no antioxidant is added.

[0042] Comparative Example 2 An ultra-low carbon non-fired magnesia-carbon brick for a stainless steel AOD converter differs from Example 1 in that the modified nano vanadium pentoxide in the antioxidant is replaced by an equal amount of nano vanadium pentoxide.

[0043] Comparative Example 3 An ultra-low carbon non-fired magnesia-carbon brick for a stainless steel AOD converter differs from Example 1 in that the modified nano vanadium pentoxide in the antioxidant is replaced in equal amounts with rare earth oxides.

[0044] Comparative Example 4 An ultra-low carbon non-fired magnesia-carbon brick for a stainless steel AOD converter differs from Example 1 in that rare earth oxides in the antioxidant are replaced in equal amounts with modified nano-vanadium pentoxide.

[0045] Comparative Example 5 An ultra-low carbon non-fired magnesia-carbon brick for a stainless steel AOD converter differs from Example 1 in that lanthanum oxide in the rare earth oxide of the antioxidant is replaced by cerium oxide in equal amounts.

[0046] Comparative Example 6 An ultra-low carbon non-fired magnesia-carbon brick for a stainless steel AOD converter differs from Example 1 in that cerium oxide in the rare earth oxide of the antioxidant is replaced by lanthanum oxide in equal amounts.

[0047] Performance testing

[0048] Magnesia-carbon bricks prepared using Examples 1-10 and Comparative Examples 1-6 were laid on the working lining of an AOD converter. The converter underwent a first firing at 500°C for 25 hours, followed by a second firing at 1600°C for 25 hours, resulting in the AOD converter. The working lining of the AOD converter was then subjected to the following performance tests: Slag erosion resistance of rotary kilns: The test results were obtained according to GB / T8931-2007 "Test Method for Slag Resistance of Refractory Materials". The test results are shown in Table 2.

[0049] Slag-resistant compressive strength: The test results were determined according to GB / T5072-2008 "Test Method for Compressive Strength of Refractory Materials at Room Temperature". The test results are shown in Table 2.

[0050] Flexural strength at 1450℃: The test was conducted according to GB / T3002-2004 "Test Method for High Temperature Flexural Strength of Refractory Materials", and the test results are shown in Table 2.

[0051] Thermal shock resistance: The test was conducted according to YB / T376.1-1995 "Test method for thermal shock resistance of refractory products (water quenching method)" and the test results are shown in Table 2.

[0052] Antioxidant properties: The test results were determined according to GB / T17732-2008 "Test Method for Dense Shaped Carbon-Containing Refractory Products" and are shown in Table 2.

[0053] Table 2 Test Results

[0054] As can be seen from Table 2, the ultra-low carbon non-fired magnesia-carbon brick of the present invention, through the synergistic effect between various raw materials, not only maintains good mechanical properties and has better compressive strength and high-temperature flexural strength after slag removal, but also improves thermal shock stability and oxidation resistance.

[0055] Combining Example 1 and Comparative Examples 1-6, and the fired magnesia-carbon bricks, it can be seen that the experimental data in Example 1 are all superior, indicating that adding an antioxidant prepared by a mixture of modified nano-vanadium pentoxide and rare earth oxides to magnesia-carbon bricks is more suitable, and a mixture of lanthanum oxide and cerium oxide is more suitable for rare earth oxides. Through temperature complementarity of "low temperature sealing-high temperature film formation", product synergy of "glass phase-rare earth composite phase", and performance optimization of "dispersion-interface properties", a dense, stable and uniform antioxidant barrier can be formed in the entire temperature range to further improve the antioxidant properties of magnesia-carbon bricks.

[0056] As can be seen from Examples 1-5, the experimental data in Example 4 are better, indicating that the amount of each raw material added in Example 4 is more appropriate, and the amount of antioxidant added is more appropriate. If the amount of antioxidant added is too small, it will not have a better antioxidant effect; if the amount of antioxidant added is too large, it will easily lead to the aggregation of antioxidant particles, which will also affect the antioxidant properties.

[0057] Combining Examples 4 and 6-9, it can be seen that the experimental data in Example 8 are better, indicating that the antioxidant prepared by Example 5 is more suitable. It also indicates that the rare earth oxides and the amount of each component added in Example 5 are more appropriate. If the amount of rare earth oxides added is too small, it cannot effectively play the role of capturing free radicals and inhibiting oxidation chain reaction, resulting in unstable antioxidant efficiency. If the amount added is too large, it may destroy the molecular chain structure, affect the mechanical properties of magnesium-carbon bricks, and may also accelerate the generation of free radicals and aggravate the oxidation of materials due to the high concentration of rare earth elements, which is completely opposite to the expected function.

[0058] Combining Examples 8 and 10, it can be seen that the experimental data in Example 10 are better, indicating that it is more appropriate to pretreat rare earth oxides before use, which can remove surface impurities, expose active sites, reduce agglomeration, and facilitate their function.

[0059] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A stainless steel AOD converter ultra-low carbon non-fired magnesia-carbon brick, characterized in that: The raw materials include the following parts by weight: 95-98 parts of dicalcium fused magnesia, 1-3 parts of graphite, 1-3 parts of resin, 1-3 parts of metal additives, 3-5 parts of antioxidant, 1-2 parts of titanium, 1-2 parts of chromium, and 1-2 parts of zirconium; wherein the antioxidant is a mixture of modified nano vanadium pentoxide and rare earth oxides.

2. The ultra-low carbon non-fired magnesia-carbon brick for stainless steel AOD converter according to claim 1, characterized in that: The antioxidant is prepared by the following method: modified nano vanadium pentoxide and rare earth oxides are placed in water, a silane coupling agent is added, the mixture is stirred and ultrasonically dispersed to obtain a suspension; the suspension is dried to obtain a blocky mixture, which is then ground and sieved to obtain the antioxidant.

3. The ultra-low carbon non-fired magnesia-carbon brick for stainless steel AOD converter according to claim 2, characterized in that: The weight ratio of the modified nano-vanadium pentoxide and rare earth oxide is 1:(0.2-0.4).

4. The ultra-low carbon non-fired magnesia-carbon brick for stainless steel AOD converter according to claim 2, characterized in that: The modified nano-vanadium pentoxide was prepared using the following method: A1: Place ammonium metavanadate in water, heat to a certain temperature, stir to dissolve, cool, adjust pH to obtain precursor solution; A2: The precursor solution was placed in a high-pressure reactor lined with polytetrafluoroethylene and sealed. Then it was placed in an oven for reaction. After the reaction was completed, it was naturally cooled to room temperature. The reactor was opened, the product was collected, washed, and dried to obtain nano-vanadium pentoxide rod-shaped particles. A3: Dissolve aluminum nitrate in water by stirring to obtain an aluminum source solution; A4: Place nano-vanadium pentoxide rod-shaped particles into water and sonicate to obtain a mixed solution; A5: Under magnetic stirring, the aluminum source solution was added dropwise to the mixture, and the pH value was adjusted. After the addition was complete, stirring was continued, followed by centrifugation. The solid was collected, washed, dried, calcined, kept warm, cooled, and ground to obtain modified nano-vanadium pentoxide.

5. The ultra-low carbon non-fired magnesia-carbon brick for stainless steel AOD converter according to claim 2, characterized in that: The rare earth oxide is a lanthanum-cerium composite oxide.

6. The ultra-low carbon non-fired magnesia-carbon brick for stainless steel AOD converter according to claim 5, characterized in that: The weight ratio of lanthanum oxide to cerium oxide in the lanthanum-cerium composite oxide is 1:(0.8-1.2).

7. The ultra-low carbon non-fired magnesia-carbon brick for stainless steel AOD converter according to claim 5, characterized in that: The rare earth oxides are pretreated as follows before use: the rare earth oxides are placed in water, a dispersant is added, ultrasonic dispersion is performed, centrifugation is carried out, solid particles are collected, washed, dried, and ground to obtain the pretreated rare earth oxides.

8. The ultra-low carbon non-fired magnesia-carbon brick for stainless steel AOD converter according to claim 1, characterized in that: The graphite is a mixture of flake graphite and amorphous graphite, and the weight ratio of the two is 1:

1.

9. The ultra-low carbon non-fired magnesia-carbon brick for stainless steel AOD converter according to claim 1, characterized in that: The metal additive is a mixture of silicon powder and aluminum powder, with a weight ratio of 1:

1.

10. A method for preparing ultra-low carbon non-fired magnesia-carbon bricks for stainless steel AOD converters as described in any one of claims 1-9, characterized in that: Includes the following steps: S1: Premix graphite, metal additives, antioxidants, titanium, chromium, and zirconium to obtain a premixed material; S2: Dry-mix the fused magnesia, add half of the resin and wet-mix, then add the premix and the remaining resin to obtain the mixture; S3: The mixture is placed in a mold, pressed and shaped, and then cured by low-temperature heat treatment to obtain ultra-low carbon non-fired magnesia-carbon bricks.

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