A magnesia-carbon brick for converter mouth and its preparation method

Abstract

This invention relates to the field of magnesia-carbon bricks, and discloses a magnesia-carbon brick for converter mouth and its preparation method. The magnesia-carbon brick for converter mouth comprises the following components by weight: 73-80 parts of fused magnesia particles, 15-22 parts of fused magnesia fine powder, 3-5 parts of flake graphite, 4-6 parts of phenolic resin, 1-4 parts of modified carbon fiber, 0.5-3.5 parts of α-Al₂O₃ micro powder, and 2-5 parts of additives. The modified carbon fiber is prepared by impregnating carbon fiber with boron nitride using a boric acid and urea impregnation reaction process, followed by further carbonization and pyrolysis using phenolic resin at high temperature. The additive is prepared by using octamethylcyclotetrasiloxane and boric acid as raw materials to prepare polyborosiloxane, and simultaneously using titanium tetrachloride and isopropyl ether as raw materials and dichloromethane as solvent to prepare titanium dioxide sol using a non-hydrolyzed sol-gel method. The polyborosiloxane and titanium dioxide sol are then mixed to prepare the magnesia-carbon brick. This invention produces magnesia-carbon bricks with high overall strength, good thermal shock resistance, and good oxidation resistance.

Description

Technical Field

[0001] This invention belongs to the field of magnesia-carbon brick technology, specifically relating to a magnesia-carbon brick for converter mouth and its preparation method. Background Technology

[0002] As one of the major downstream industries of refractory materials, every major technological advancement in the steel industry has relied on the support of refractory materials. In the late 19th century, the emergence of siliceous refractories promoted open-hearth steelmaking based on acidic slag, while the emergence of converter steelmaking technology based on basic slag systems also promoted the development of basic refractories such as dolomite and magnesia. With the increase in smelting intensity and the application of some ladle refining processes, traditional refractories could not meet the production requirements. The emergence of magnesia-carbon bricks (pericarpegite-carbon bricks) in the 1970s enabled the realization and promotion of a series of refining technologies.

[0003] With the continuous development of the high-temperature metallurgical industry, the requirements for the performance of magnesia-carbon bricks are becoming increasingly stringent. Magnesia-carbon bricks possess excellent resistance to erosion, permeation, and slag, and their preparation process is relatively simple. However, excessively high carbon content can lead to increased carbon content in molten steel, restricting the smelting of low-carbon and ultra-low-carbon steel. Furthermore, the high thermal conductivity of the material results in rapid temperature drop and significant heat loss in the molten steel. The carbon in the material is also easily oxidized, which not only consumes a large amount of carbon resources and exacerbates the greenhouse effect but also reduces the material's strength. As the carbon content decreases, carbon particles cannot form a continuous phase structure, directly impacting the oxidation resistance, thermal shock stability, and material strength of magnesia-carbon bricks, thus weakening the advantages of low-carbon magnesia-carbon bricks to some extent. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a magnesia-carbon brick for converter mouth and its preparation method, thereby obtaining a magnesia-carbon brick with high overall strength, good thermal shock resistance and oxidation resistance.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A magnesia-carbon brick for converter mouth comprises the following components by weight: 73-80 parts of fused magnesia particles, 15-22 parts of fused magnesia fine powder, 3-5 parts of flake graphite, 4-6 parts of phenolic resin, 1-4 parts of modified carbon fiber, 0.5-3.5 parts of α-Al2O3 micro powder, and 2-5 parts of additives.

[0007] The modified carbon fiber is prepared by impregnating carbon fiber with boron nitride using a boric acid and urea process, followed by further carbonization and pyrolysis using phenolic resin at high temperature. The additive is prepared by using octamethylcyclotetrasiloxane and boric acid as raw materials to prepare polyborosiloxane, and using titanium tetrachloride and isopropyl ether as raw materials and dichloromethane as solvent to prepare titanium dioxide sol using a non-hydrolyzed sol-gel method. The polyborosiloxane and titanium dioxide sol are then mixed to prepare the final product.

[0008] Preferably, the fused magnesia particles are composed of fused magnesia with particle sizes of 5-3 mm, 3-1 mm, and <1 mm in a mass ratio of 5:6:9.25; the fused magnesia fine powder is fused magnesia with a particle size of <0.088 mm; and the flake graphite has a particle size of <0.15 mm.

[0009] Preferably, the method for preparing the modified carbon fiber includes the following steps:

[0010] A. Dissolve boric acid and urea in a mixture of deionized water and ethanol, stir and mix evenly to obtain a precursor solution, then add carbon fiber and polyvinylpyrrolidone, ultrasonically disperse evenly, then magnetically stir for 10-12 hours, filter and dry, place in a tube furnace for heating to prepare boron nitride coated carbon fiber.

[0011] B. Dissolve phenolic resin in ethanol to obtain a precursor solution, add boron nitride-coated carbon fibers and ultrasonically disperse them evenly, then magnetically stir for 10-12 hours, filter and dry, and place in a tube furnace for heating to prepare modified carbon fibers.

[0012] Preferably, the mass ratio of boric acid, urea, carbon fiber, polyvinylpyrrolidone and phenolic resin is 0.3-0.5:1.7-1.9:1:0.05-0.07:1.9-2.1.

[0013] Preferably, in step A, the heating temperature in the tubular furnace is 970–1120°C and the temperature is maintained for 1.5–2 hours.

[0014] Preferably, in step B, the heating temperature in the tubular furnace is 880–920°C and the temperature is maintained for 1.5–2 hours.

[0015] Preferably, the preparation method of the admixture includes the following steps:

[0016] (1) Take octamethylcyclotetrasiloxane, tetraethyl silicate, hydrochloric acid, boric acid and diethylene glycol dimethyl ether in a reactor, stir and react at 55-70°C for 4-6 hours, then raise the temperature to 110-120°C and continue stirring and reacting for 2-3 hours. After the reaction is completed, filter and distill to prepare polyborosiloxane.

[0017] (2) Anhydrous isopropyl ether, titanium tetrachloride and dichloromethane were placed in a reactor, nitrogen gas was introduced into the reaction, and after stirring and mixing, the mixture was transferred to a reaction vessel with a polytetrafluoroethylene liner and placed in an oven at 105-115℃ for 32-38 hours. After the reaction was completed, the mixture was cooled to room temperature, washed, filtered and dried and then dissolved in anhydrous ethanol to prepare titanium dioxide sol.

[0018] (3) The additive is prepared by stirring and mixing polyborosiloxane and titanium dioxide sol.

[0019] Preferably, in step (1), the molar ratio of octamethylcyclotetrasiloxane, tetraethyl silicate, and boric acid is 10:1:5.

[0020] Preferably, in step (2), the volume ratio of anhydrous isopropyl ether, titanium tetrachloride, and dichloromethane is 2.5–2.8:1:3.4–3.7.

[0021] A method for preparing magnesia-carbon bricks for converter mouths as described above includes the following steps: weighing each component by weight, placing fused magnesia particles into a mixer and mixing for 1 minute, then adding phenolic resin and additives and mixing for 3 minutes, then adding modified carbon fiber, α-Al2O3 micro powder and flake graphite and mixing for 5 minutes, then adding fused magnesia fine powder and mixing for 20 minutes before discharging, pressing the material on a press after discharge, and then baking it in a 200°C oven for 12 hours before cooling to room temperature to obtain magnesia-carbon bricks for converter mouths.

[0022] The beneficial effects of this invention are:

[0023] This invention employs a boron acid and urea impregnation process to coat carbon fibers with boron nitride, followed by high-temperature carbonization and pyrolysis with phenolic resin for further carbon coating. This process yields modified carbon fibers coated with boron nitride and pyrolytic carbon. The carbon fibers exhibit excellent mechanical and thermal properties, while boron nitride demonstrates superior thermal shock resistance. When magnesia-carbon brick refractory materials are oxidized in air, boron nitride reacts with oxygen to generate a liquid phase of B2O3, which covers the material surface and prevents oxygen from penetrating the material. Furthermore, B2O3 can react with MgO to form a low-melting-point phase, Mg3B2O6, which blocks the pores in the material and inhibits air exchange. Simultaneously, the generated nitrogen increases the pressure of closed pores within the material, further hindering oxygen diffusion and preventing further oxidation. The pyrolytic carbon interface phase protects the carbon fiber and boron nitride interface phase from silicon erosion during the high-temperature reaction and infiltration process. Additionally, the modified carbon fibers can deflect cracks and bridge cracks, thus improving the mechanical properties of the material.

[0024] This invention uses octamethylcyclotetrasiloxane and boric acid as raw materials to prepare polyborosiloxane containing high-energy BO and Si-O bonds. Simultaneously, titanium dioxide sol is prepared using titanium tetrachloride and isopropyl ether as raw materials and dichloromethane as solvent via a non-hydrolyzed sol-gel method. The polyborosiloxane and titanium dioxide sol are then mixed to prepare an additive. The -Si-O-Si- network in the additive can be adsorbed onto the surface of α-Al2O3 particles, forming a stable spatial network structure that firmly binds the α-Al2O3 particles together and fills the interparticle gaps, improving dispersibility and permeability. Furthermore, the additive covering the surface of solid particles forms a strong silica film, thereby enhancing the material's adhesion, curing, and molding characteristics. Additionally, the introduction of titanium can reduce it to titanium carbide, carbon nitride, and titanium carbonitride at high temperatures, improving the material's oxidation resistance and thermal shock resistance.

[0025] This invention designs the fused magnesia particle ratio according to the close packing principle to make the magnesia-carbon bricks more compact. In addition to coating the surface of the magnesia particles to relieve the expansion stress of the fused magnesia aggregate, some of the flake graphite also exists in the matrix, which weakens the erosion of slag along the periclase grain boundaries and its penetration into the matrix, thus reducing the damage of the magnesia-carbon bricks. α-Al2O3 micro powder reacts with MgO at high temperature to generate MgAl2O4 in situ, which improves the matrix strength of the material. Modified carbon fiber and additives can effectively improve the mechanical properties, oxidation resistance and thermal shock resistance of the material, while avoiding the expansion of cracks between the fused magnesia particles and graphite in the magnesia-carbon bricks, which would cause longitudinal cracks. Thermosetting phenolic resin is used as a binder. Through the cross-linking reaction of its own chain segments during the curing process, a network structure is formed to build the mechanical interlocking force between the raw materials, thereby preparing magnesia-carbon bricks with high overall strength, good thermal shock resistance and oxidation resistance. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] A method for preparing modified carbon fiber includes the following steps:

[0029] A. Dissolve 0.3g boric acid and 1.8g urea in a mixture of 200mL deionized water and 200mL ethanol, stir and mix evenly to obtain a precursor solution, then add 1g carbon fiber (20mm in length and 10μm in diameter) and 0.05g polyvinylpyrrolidone, ultrasonically disperse evenly, then magnetically stir for 12h, filter and dry, place in a tube furnace and heat to 1000℃ for 2h to prepare boron nitride coated carbon fiber;

[0030] B. Dissolve 2g of phenolic resin in 200mL of ethanol to obtain a precursor solution. Add the prepared boron nitride-coated carbon fiber and ultrasonically disperse it evenly. Then, stir magnetically for 12h, filter and dry. Place it in a tube furnace and heat to 900℃ for 2h to prepare modified carbon fiber.

[0031] Example 2

[0032] A method for preparing an admixture includes the following steps:

[0033] (1) Take 14.8g of octamethylcyclotetrasiloxane, 1g of tetraethyl silicate, 1mL of hydrochloric acid, 1.5g of boric acid and 40mL of diethylene glycol dimethyl ether in a reactor, stir and react at 70℃ for 4h, then raise the temperature to 120℃ and continue stirring and reacting for 2h. After the reaction is completed, filter and distill to prepare polyborosiloxane.

[0034] (2) Take 22.4 mL of anhydrous isopropyl ether, 8.8 mL of titanium tetrachloride and 30 mL of dichloromethane into a reactor, pass nitrogen gas through the reaction, stir and mix, then transfer to a reaction vessel with a polytetrafluoroethylene liner, place in an oven at 110 °C and react for 38 h. After the reaction is completed, cool to room temperature, wash, filter and dry, then dissolve in anhydrous ethanol to prepare titanium dioxide sol.

[0035] (3) The prepared polyborosiloxane and the prepared titanium dioxide sol are stirred and mixed to prepare the additive.

[0036] Example 3

[0037] A magnesia-carbon brick for converter mouth comprises the following components by weight: 74 parts fused magnesia granules, 15 parts fused magnesia fine powder, 3 parts flake graphite, 4 parts phenolic resin, 1.5 parts modified carbon fiber prepared in Example 1, 0.7 parts α-Al2O3 micro powder, and 2.3 parts additives prepared in Example 2. The main chemical composition of the fused magnesia, by mass percentage, includes MgO: 97.21%; CaO: 1.36%; SiO2: 0.35%; Fe2O3: 0.47%, and the flake graphite contains 97.6% carbon by mass.

[0038] The above-mentioned method for preparing magnesia-carbon bricks for converter mouths includes the following steps: weigh each component according to the weight parts, put fused magnesia particles into a mixer and mix for 1 minute, then add phenolic resin and additives and mix for 3 minutes, then add modified carbon fiber and flake graphite and mix for 5 minutes, then add fused magnesia fine powder and mix for 20 minutes before discharging, and then press and mold the material on a press with a molding pressure of 200 MPa, and then place it in a 200℃ oven to bake for 12 hours and then cool it to room temperature to obtain magnesia-carbon bricks for converter mouths.

[0039] Example 4

[0040] A magnesia-carbon brick for converter mouth comprises the following components by weight: 77 parts fused magnesia granules, 18 parts fused magnesia fine powder, 4 parts flake graphite, 5 parts phenolic resin, 2 parts modified carbon fiber prepared in Example 1, 1.8 parts α-Al2O3 micro powder, and 3.6 parts additives prepared in Example 2. The main chemical composition of the fused magnesia, by mass percentage, includes MgO: 97.21%; CaO: 1.36%; SiO2: 0.35%; Fe2O3: 0.47%, and the flake graphite contains 97.6% carbon by mass.

[0041] The preparation method of the magnesia-carbon bricks used at the converter mouth is the same as in Example 3.

[0042] Example 5

[0043] A magnesia-carbon brick for converter mouth comprises the following components by weight: 80 parts of fused magnesia granules, 20.5 parts of fused magnesia fine powder, 4.6 parts of flake graphite, 5.7 parts of phenolic resin, 3.4 parts of modified carbon fiber prepared in Example 1, 3.1 parts of α-Al2O3 micro powder, and 4.5 parts of additives prepared in Example 2. The main chemical composition of the fused magnesia, by mass percentage, includes MgO: 97.21%; CaO: 1.36%; SiO2: 0.35%; Fe2O3: 0.47%, and the flake graphite contains 97.6% carbon by mass.

[0044] The preparation method of the magnesia-carbon bricks used at the converter mouth is the same as in Example 3.

[0045] Comparative Example 1

[0046] A method for preparing modified carbon fiber includes the following steps:

[0047] 0.3g of boric acid and 1.8g of urea were dissolved in a mixture of 200mL of deionized water and 200mL of ethanol. The mixture was stirred until homogeneous to obtain a precursor solution. Then, 1g of carbon fiber (20mm in length and 10μm in diameter) and 0.05g of polyvinylpyrrolidone were added. The mixture was ultrasonically dispersed until homogeneous, and then magnetically stirred for 12h. After filtration and drying, the mixture was placed in a tube furnace and heated to 1000℃ for 2h to obtain modified carbon fiber.

[0048] Comparative Example 2

[0049] A method for preparing an admixture includes the following steps:

[0050] 14.8 g of octamethylcyclotetrasiloxane, 1 g of tetraethyl silicate, 1 mL of hydrochloric acid, 1.5 g of boric acid and 40 mL of diethylene glycol dimethyl ether were placed in a reactor and stirred at 70 °C for 4 h. Then the temperature was raised to 120 °C and the stirring was continued for 2 h. After the reaction was completed, the additive was prepared by filtration and distillation.

[0051] Comparative Example 3

[0052] A magnesia-carbon brick for converter mouth comprises the following components by weight: 80 parts of fused magnesia granules, 20.5 parts of fused magnesia fine powder, 4.6 parts of flake graphite, 5.7 parts of phenolic resin, 3.4 parts of modified carbon fiber prepared in Comparative Example 1, 3.1 parts of α-Al2O3 micro powder, and 4.5 parts of additives prepared in Example 2. The main chemical composition of the fused magnesia, by mass percentage, includes MgO: 97.21%; CaO: 1.36%; SiO2: 0.35%; Fe2O3: 0.47%, and the flake graphite contains 97.6% carbon by mass.

[0053] The preparation method of the magnesia-carbon bricks used at the converter mouth is the same as in Example 3.

[0054] Comparative Example 4

[0055] A magnesia-carbon brick for converter mouth comprises the following components by weight: 80 parts of fused magnesia granules, 20.5 parts of fused magnesia fine powder, 4.6 parts of flake graphite, 5.7 parts of phenolic resin, 3.4 parts of carbon fiber (20 mm in length and 10 μm in diameter), 3.1 parts of α-Al₂O₃ micro powder, and 4.5 parts of additives prepared in Example 2. The main chemical composition of the fused magnesia, by mass percentage, includes MgO: 97.21%; CaO: 1.36%; SiO₂: 0.35%; Fe₂O₃: 0.47%, and the flake graphite contains 97.6% carbon by mass.

[0056] The preparation method of the magnesia-carbon bricks used at the converter mouth is the same as in Example 3.

[0057] Comparative Example 5

[0058] A magnesia-carbon brick for converter mouth comprises the following components by weight: 80 parts of fused magnesia granules, 20.5 parts of fused magnesia fine powder, 4.6 parts of flake graphite, 5.7 parts of phenolic resin, 3.4 parts of modified carbon fiber prepared in Example 1, 3.1 parts of α-Al2O3 micro powder, and 4.5 parts of additives prepared in Comparative Example 2. The main chemical composition of the fused magnesia, by mass percentage, includes MgO: 97.21%; CaO: 1.36%; SiO2: 0.35%; Fe2O3: 0.47%, and the flake graphite contains 97.6% carbon by mass.

[0059] The preparation method of the magnesia-carbon bricks used at the converter mouth is the same as in Example 3.

[0060] Comparative Example 6

[0061] A magnesia-carbon brick for converter mouth comprises the following components by weight: 80 parts of fused magnesia granules, 20.5 parts of fused magnesia fine powder, 4.6 parts of flake graphite, 5.7 parts of phenolic resin, 3.4 parts of modified carbon fiber prepared in Example 1, and 3.1 parts of α-Al2O3 micro powder. The main chemical composition of the fused magnesia, by mass percentage, includes MgO: 97.21%; CaO: 1.36%; SiO2: 0.35%; Fe2O3: 0.47%, and the flake graphite contains 97.6% carbon by mass.

[0062] The preparation method of the magnesia-carbon bricks used at the converter mouth is the same as in Example 3.

[0063] Performance testing

[0064] The performance of the magnesia-carbon bricks prepared in Examples 3-5 and Comparative Examples 3-6 was tested:

[0065] The formed brick sample was cut into 40mm×40mm×160mm strips and 230mm×115mm×65mm standard bricks, and the following properties were measured: (1) flexural and compressive strength at room temperature; (2) flexural and compressive strength after firing at 1000℃ for 3h; (3) flexural and compressive strength and oxide layer thickness after firing at 1550℃ for 3h; (4) flexural strength at 1450℃ for 30min after carbon embedding; (5) thermal shock test was carried out according to YB / T376.1-1995 (water quenching method), and the flexural strength at room temperature after the sample was subjected to 4 water quenching thermal shocks at 1100℃ was tested. The strength retention rate was calculated to compare the thermal shock resistance of the sample. The data results are shown in Table 1.

[0066] Table 1 Sample performance test results

[0067]

[0068] As shown in Table 1, the modified carbon fiber component added in Comparative Example 3 was not coated with a pyrolytic carbon layer; the carbon fiber in Comparative Example 4 was not modified by boron nitride-pyrolytic carbon coating; the additive component added in Comparative Example 5 did not contain nano-titanium dioxide sol; and no additive component was added in Comparative Example 6. The magnesia-carbon bricks prepared in Examples 3-5 of the present invention have higher high-temperature flexural strength than those of Comparative Examples 3-6 (1450℃×30min carbon embedding); higher flexural and compressive strength after firing at room temperature, 1000℃×3h, and 1550℃×3h; a smaller oxide layer thickness than Comparative Examples 4-6; and a higher retention rate of flexural strength at room temperature after thermal shock than Comparative Examples 3-6. The magnesia-carbon bricks prepared in Examples 3-5 of the present invention have the advantages of high compressive and flexural strength at both room temperature and high temperature, good oxidation resistance, and good thermal shock resistance.

[0069] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0070] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A magnesia-carbon brick for converter mouth, characterized in that, It comprises the following components by weight: 73-80 parts of fused magnesia granules, 15-22 parts of fused magnesia fine powder, 3-5 parts of flake graphite, 4-6 parts of phenolic resin, 1-4 parts of modified carbon fiber, 0.5-3.5 parts of α-Al2O3 micro powder, and 2-5 parts of additives. The modified carbon fiber is prepared by impregnating carbon fiber with boron nitride using a boric acid and urea process, followed by further carbonization and pyrolysis using phenolic resin at high temperature. The additive is prepared by using octamethylcyclotetrasiloxane and boric acid as raw materials to prepare polyborosiloxane, and using titanium tetrachloride and isopropyl ether as raw materials and dichloromethane as solvent to prepare titanium dioxide sol using a non-hydrolyzed sol-gel method. The polyborosiloxane and titanium dioxide sol are then mixed to prepare the final product.

2. The magnesia-carbon brick for converter opening according to claim 1, characterized in that, The fused magnesia particles are composed of fused magnesia with particle sizes of 5-3 mm, 3-1 mm, and <1 mm in a mass ratio of 5:6:9.25; the fused magnesia fine powder is fused magnesia with a particle size of <0.088 mm; and the flake graphite has a particle size of <0.15 mm.

3. The magnesia-carbon brick for converter opening according to claim 1, characterized in that, The method for preparing the modified carbon fiber includes the following steps: A. Dissolve boric acid and urea in a mixture of deionized water and ethanol, stir and mix evenly to obtain a precursor solution, then add carbon fiber and polyvinylpyrrolidone, ultrasonically disperse evenly, then magnetically stir for 10-12 hours, filter and dry, place in a tube furnace for heating to prepare boron nitride coated carbon fiber. B. Dissolve phenolic resin in ethanol to obtain a precursor solution, add boron nitride-coated carbon fibers and ultrasonically disperse them evenly, then magnetically stir for 10-12 hours, filter and dry, and place in a tube furnace for heating to prepare modified carbon fibers.

4. The magnesia-carbon brick for converter opening according to claim 3, characterized in that, The mass ratio of boric acid, urea, carbon fiber, polyvinylpyrrolidone and phenolic resin is 0.3-0.5:1.7-1.9:1:0.05-0.07:1.9-2.

1.

5. The magnesia-carbon brick for converter opening according to claim 3, characterized in that, In step A, the heating temperature in the tubular furnace is 970–1120°C and the temperature is maintained for 1.5–2 hours.

6. The magnesia-carbon brick for converter opening according to claim 3, characterized in that, In step B, the heating temperature in the tubular furnace is 880–920°C and the temperature is maintained for 1.5–2 hours.

7. The magnesia-carbon brick for converter opening according to claim 1, characterized in that, The preparation method of the admixture includes the following steps: (1) Take octamethylcyclotetrasiloxane, tetraethyl silicate, hydrochloric acid, boric acid and diethylene glycol dimethyl ether in a reactor, stir and react at 55-70°C for 4-6 hours, then raise the temperature to 110-120°C and continue stirring and reacting for 2-3 hours. After the reaction is completed, filter and distill to prepare polyborosiloxane. (2) Anhydrous isopropyl ether, titanium tetrachloride and dichloromethane were placed in a reactor, nitrogen gas was introduced into the reaction, and after stirring and mixing, the mixture was transferred to a reaction vessel with a polytetrafluoroethylene liner and placed in an oven at 105-115℃ for 32-38 hours. After the reaction was completed, the mixture was cooled to room temperature, washed, filtered and dried and then dissolved in anhydrous ethanol to prepare titanium dioxide sol. (3) The additive is prepared by stirring and mixing polyborosiloxane and titanium dioxide sol.

8. The magnesia-carbon brick for converter opening according to claim 7, characterized in that, In step (1), the molar ratio of octamethylcyclotetrasiloxane, tetraethyl silicate, and boric acid is 10:1:

5.

9. The magnesia-carbon brick for converter opening according to claim 7, characterized in that, In step (2), the volume ratio of anhydrous isopropyl ether, titanium tetrachloride, and dichloromethane is 2.5–2.8:1:3.4–3.

7.

10. A method for preparing magnesia-carbon bricks for converter mouths according to any one of claims 1 to 9, characterized in that, Includes the following steps: Weigh each component according to the weight parts, put the fused magnesia particles into the mixer and mix for 1 minute, then add phenolic resin and additives and mix for 3 minutes, then add modified carbon fiber, α-Al2O3 micro powder and flake graphite and mix for 5 minutes, then add fused magnesia fine powder and mix for 20 minutes before discharging. After discharging, press the material on a press and then bake it in a 200℃ oven for 12 hours before cooling to room temperature to prepare magnesia-carbon bricks for converter mouth.

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