A VD furnace cover castable lining and preparation method thereof

Abstract

The present invention provides a VD furnace cover castable lining and a preparation method thereof, which belongs to the technical field of high-temperature refractory materials, comprising the steps of: mixing an emulsion of hydrogenated silicone oil, aminopropyltriethoxysilane, and pearl sand, heating and soaking, and drying to obtain modified pearl sand; mixing graphite, acetic acid, tetrabutyl titanate, and nano silicon powder, dropping an ethanol aqueous solution, adjusting the pH value to acidic, aging, drying, heating at a high temperature under an inert gas environment, and cooling to obtain TiC-Ti3SiC2 composite coating graphite; mixing brown corundum, silicon carbide, α-Al2O3 powder, calcium aluminate cement, TiC-Ti3SiC2 composite coating graphite, and modified pearl sand, drying, adding distilled water, stirring, putting into a mold, casting and molding, standing, taking out, drying, spraying silicon powder on the surface, and performing heat treatment under a nitrogen atmosphere to obtain a VD furnace cover castable lining. The present invention can improve the thermal insulation performance of the VD furnace cover while improving the thermal shock stability of the VD furnace cover castable lining.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature refractory materials, and in particular to a VD furnace cover castable lining and a preparation method thereof. Background Art

[0002] VD refining (vacuum degassing) is a key method in modern steel refining technology, commonly used in the refining of molten steel in electric furnaces and converters. Its basic principle is to place the initially molten steel in the electric furnace or converter in a sealed vacuum tank. Through vacuuming and bottom-blowing argon gas agitation, impurities and gases, particularly dissolved gases such as hydrogen, nitrogen, and oxygen, are removed from the molten steel, thereby improving its purity and quality. The key to VD refining lies in controlling the vacuum environment and ensuring adequate agitation of the molten steel. The furnace cover, as a crucial accessory, plays a key role in this entire process.

[0003] During the VD refining process, the VD furnace cover is crucial. Its functions are primarily two-fold: first, protecting other equipment within the furnace from damage caused by the high-temperature radiation of the molten steel and slag splashing; and second, reducing heat loss and maintaining a stable furnace temperature to prevent excessive temperature drops during the degassing process. To achieve these two goals, the castable lining of the cover must possess excellent resistance to high temperatures, thermal shock, and corrosion. This ensures stable protection of the furnace environment during frequent fluctuations between high and low temperatures.

[0004] Specifically, the castable lining of the furnace cover needs to be able to withstand complex working environments such as high-temperature airflow scouring, high-temperature slag splashing, chemical gas erosion, and mechanical vibration. Furthermore, because the vacuum degassing process of the molten steel in the VD furnace requires frequent temperature fluctuations, the thermal stress changes between high and low temperatures in the furnace cover generally make the castable lining of the furnace cover susceptible to thermal shock damage, thus affecting its long-term stability. Furthermore, if the castable lining of the furnace cover has insufficient thermal insulation performance, it will lead to a large amount of heat energy waste and exacerbate the temperature instability in the furnace. This temperature instability not only increases energy consumption but also has an adverse impact on the refining quality of the molten steel, resulting in uneven molten steel temperature and fluctuating composition, thus affecting the quality of the final steel.

[0005] Therefore, it is necessary to provide a VD furnace cover castable lining and a preparation method thereof to solve the problems existing in the above-mentioned prior art. Summary of the Invention

[0006] In view of this, the present invention provides a VD furnace cover castable lining and a preparation method thereof, which can improve the thermal insulation performance of the VD furnace cover while improving the thermal shock stability of the VD furnace cover castable lining.

[0007] To achieve the above object, the present invention provides a method for preparing a VD furnace roof castable lining, comprising the following steps:

[0008] S1. Mixing an emulsion of hydrogenated silicone oil, aminopropyltriethoxysilane, and pearlescent sand, heating and soaking the mixture, and drying the mixture to obtain modified pearlescent sand;

[0009] S2, mixing flake graphite, acetic acid, tetrabutyl titanate and nano-silicon powder, adding ethanol aqueous solution dropwise, adjusting the pH value to acidic, aging, drying, heating at high temperature under an inert gas environment, and cooling to obtain TiC-Ti3SiC2 composite coating graphite;

[0010] S3. Mix brown corundum, silicon carbide, α-Al2O3 powder, calcium aluminate cement, TiC-Ti3SiC2 composite coated graphite, and modified pearl sand, dry them, add distilled water, stir them, put them into a mold, cast them into shape, let them stand, take them out, dry them, spray silicon powder on the surface, and perform heat treatment under a nitrogen atmosphere to obtain a VD furnace cover castable lining.

[0011] The present invention uses pearlescent sand as the thermal insulation material in the lining layer of the VD furnace cover castable to reduce heat loss in the furnace. Due to the porous structure of the pearlescent sand, the addition of the pearlescent sand can effectively reduce the thermal conductivity of the castable, thereby improving the overall thermal insulation effect. However, due to its porous structure, it will lead to strong water absorption, resulting in the problem of increased thermal conductivity and reduced mechanical strength after water absorption; the surface of the pearlescent sand is modified with hydrogen-containing silicone oil, so that a thick network of silicone molecular film is formed on the outer surface of the modified pearlescent sand, which prevents the capillary pores from absorbing water and gives the pearlescent sand hydrophobic properties; and the silicone molecules have good thermal stability, so that they can maintain the integrity of the hydrophobic film even under high temperature conditions; in addition, the pearlescent sand modified with hydrogen-containing silicone oil has smaller pores and a denser structure, which gives the overall thermal insulation performance while avoiding the risk of greatly reduced compressive strength and flexural strength due to excessive pores.

[0012] The present invention introduces TiC-Ti3SiC2 composite coated graphite as a carbon source to replace spherical asphalt, thereby avoiding the generation of harmful gases at high temperatures while improving the mechanical properties and thermal shock stability of the castable. The TiC-Ti3SiC2 composite coated graphite is prepared by sol-gel combined with carbothermal reduction. By modifying the surface of flaky graphite to generate a carbide coating to improve its wettability and oxidation resistance, the problem of poor water wettability of graphite, which leads to easy floating and agglomeration in the castable, is solved. In addition, the addition of the TiC-Ti3SiC2 composite coated graphite promotes the densification of the sample after high-temperature sintering, thereby improving the degree of interfacial bonding and thus making the bonding between the substrates tighter. The layered structure of the TiC-Ti3SiC2 composite coated graphite gives it anti-flexural properties, which can prevent crack propagation during the fracture process to a certain extent, thereby improving the thermal shock resistance of the overall material. In addition, a multi-layer oxide protective layer is generated on the Ti3SiC2 surface at high temperatures, which can significantly slow down oxidation and thermal erosion, further improving the overall oxidation resistance and corrosion resistance.

[0013] In the process of preparing the VD furnace cover castable lining, the present invention sprays silicon powder on the surface of the dried blank and sintered in a nitrogen atmosphere to form a silicon nitride surface strengthening layer. The silicon nitride surface strengthening layer forms a dense protective film at high temperature to prevent further penetration of oxygen and slag, thereby resisting the erosion of molten metal (such as molten aluminum, molten steel) and slag. At the same time, the high fracture toughness of silicon nitride can absorb thermal stress through crack deflection and bridging mechanisms, thereby improving the stability of the material in rapid cooling and heating environments.

[0014] Optionally, the hydrogenated silicone oil emulsion is prepared by adding hydrogenated silicone oil to a xylene solvent and stirring for 3 to 5 minutes.

[0015] Optionally, in step S1, the emulsion of hydrogen silicone oil and aminopropyltriethoxysilane are mixed and stirred for 5-10 minutes, pearl sand is added and mixed, mechanically stirred for 20-30 minutes, heated to 40-50°C and soaked for 60-80 minutes, naturally dried for 2-4 hours, and placed in a drying oven at 60°C for 3-5 hours to obtain modified pearl sand.

[0016] The present invention adopts a heating and soaking method when preparing the modified pearlescent sand. In the heated state, the components in the emulsion are more active, can better penetrate into the surface of the pearlescent sand particles, and better cover the surface of the pearlescent sand.

[0017] Optionally, the volume concentration of the ethanol aqueous solution is 50%.

[0018] Optionally, the mixing and stirring time in step S2 is 5-10 minutes, the pH value is adjusted to 3-4 with hydrochloric acid, the aging time is 14-16 hours, the drying time is 18 hours, and the temperature is 110° C.; and the inert gas is argon.

[0019] The present invention uses hydrochloric acid to adjust the pH of the solution to 3-4. Within this pH range, the efficiency of converting the solution into a sol-gel state reaches an optimal level.

[0020] Optionally, in step S2, the TiC-Ti3SiC2 composite coating graphite is obtained by heating to 400°C at a rate of 5°C / min under an argon atmosphere and maintaining it for 0.5-1.5 hours, then continuing to heat to 1350-1450°C and maintaining it for 3-5 hours.

[0021] Optionally, hollow corundum microspheres are also added when the TiC-Ti3SiC2 composite coating graphite is added in step S3.

[0022] The present invention also adds hollow corundum microspheres when preparing the VD furnace cover castable lining, which cooperates with the TiC-Ti3SiC2 composite coating graphite to form a closed-pore-open-pore dual-mode structure, further reducing thermal conductivity and improving the thermal insulation effect of the castable lining.

[0023] Optionally, a water reducing agent is also added when adding distilled water in step S3.

[0024] The present invention adds a water reducing agent when preparing the VD furnace cover castable lining to reduce the water consumption of cement slurry and improve the fluidity of the mixture without affecting the final strength, thereby facilitating the pouring and molding process.

[0025] Optionally, in step S3, the drying time before adding distilled water is 3 to 5 minutes; after adding distilled water, stir for 5 to 10 minutes, put into a mold, cast and shape, let stand for 18 to 24 hours, take out, dry at 120 to 150°C for 16 to 20 hours, spray silicon powder on the surface, heat to 1350 to 1450°C in a nitrogen atmosphere, and heat treat for 3 to 5 hours to obtain a VD furnace cover castable lining.

[0026] Optionally, the VD furnace cover castable lining includes the following raw materials in parts by mass: 70-75 parts of brown corundum, 8 parts of silicon carbide, 4-6 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 2 parts of silicon micropowder, 3-5 parts of TiC-Ti3SiC2 composite coated graphite, 2-3 parts of modified pearlescent sand, and 5 parts of distilled water.

[0027] The present invention adopts brown corundum as the base material. The combination of brown corundum and silicon carbide makes the lining have stronger fire resistance and thermal stability at high temperature. The addition of α-Al2O3 powder and TiC-Ti3SiC2 composite coating graphite cooperates with the strong bonding force of calcium aluminate cement to improve the mechanical properties and thermal shock stability of the lining, effectively avoiding the formation of cracks. According to the above-mentioned mass proportion, the comprehensive performance of the VD furnace cover castable lining can be best exerted.

[0028] The above technical solution of the present invention includes at least the following beneficial effects:

[0029] 1. The present invention modifies pearlescent sand by hydrogenated silicone oil to form a hydrophobic siloxane film, which effectively avoids the water absorption problem of the porous structure of pearlescent sand and improves its thermal insulation performance; the modified pearlescent sand has smaller pores and a denser structure, ensuring excellent thermal stability and high mechanical strength, while maintaining good hydrophobicity and stronger stability at high temperatures.

[0030] 2. This invention improves the mechanical properties and thermal shock stability of the castable by introducing a TiC-Ti3SiC2 composite-coated graphite instead of spherical asphalt. The composite-coated graphite is prepared using a sol-gel combined with a carbothermal reduction method, improving its wettability and oxidation resistance, and addressing issues of graphite floating and agglomeration. Furthermore, the composite-coated graphite promotes densification after high-temperature sintering, enhancing bonding between substrates and improving flexural strength through its layered structure, thereby effectively enhancing the thermal shock resistance of the overall material.

[0031] 3. During the preparation of the VD furnace roof castable lining, the present invention sprays silicon powder onto the surface of the dried blank and sintering in a nitrogen atmosphere to produce a silicon nitride surface strengthening layer. This layer forms a dense protective film at high temperatures, effectively preventing the penetration of oxygen and slag, and resisting erosion by molten metal and slag. Furthermore, the high fracture toughness of silicon nitride absorbs thermal stresses through crack deflection and bridging mechanisms, improving the material's stability in rapid cooling and heating environments. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention. All other embodiments obtained by ordinary technicians in this field based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0033] Example 1

[0034] Add 5 parts of hydrogenated silicone oil to 500 parts of xylene solvent and stir for 5 minutes to obtain an emulsion of hydrogenated silicone oil. Then add 1 part of aminopropyltriethoxysilane and mix and stir for 10 minutes. Add 10 parts of pearl sand and mix. Mechanically stir for 30 minutes. Heat to 40°C and soak for 80 minutes. Naturally dry for 2 hours. Put it in a drying oven at 60°C and dry it for 5 hours to obtain modified pearl sand.

[0035] 25 parts of flake graphite, 4 parts of acetic acid, 8 parts of tetrabutyl titanate and 7 parts of nano-silicon powder were mixed and stirred continuously at room temperature for 10 minutes. Then, 7 parts of 50% ethanol aqueous solution were added dropwise under continuous stirring, and the pH value was adjusted to 3 with hydrochloric acid to obtain a sol-gel. The sol-gel was aged at room temperature for 16 hours and then dried at 110°C for 18 hours to obtain a precursor. Finally, the precursor was placed in a crucible and transferred to a vertical furnace. It was heated to 400°C at a rate of 5°C / min under an argon atmosphere and maintained for 1.5 hours. It was then continued to be heated to 1450°C and maintained for 5 hours. After that, it was cooled to room temperature to obtain TiC-Ti3SiC2 composite coated graphite.

[0036] 70 parts of brown corundum, 5 parts of hollow corundum microspheres, 8 parts of silicon carbide, 4 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 5 parts of TiC-Ti3SiC2 composite coated graphite, and 3 parts of modified pearl sand were mixed and dried in a mixer for 5 minutes. Then, 5 parts of distilled water and 0.2 parts of water reducer were added. After stirring the mixture for 10 minutes, it was placed in a mold and cast on a vibration table. The mixture was allowed to stand at room temperature for 24 hours, then taken out from the mold, transferred to an oven at 120°C and dried for 20 hours to obtain a dry green body. Silicon powder was sprayed on the surface of the dry green body, and heated to 1400°C in a nitrogen atmosphere for heat treatment for 5 hours to obtain a VD furnace cover castable lining.

[0037] Example 2

[0038] Add 5 parts of hydrogen-containing silicone oil to 500 parts of xylene solvent and stir for 3 minutes to obtain an emulsion of hydrogen-containing silicone oil. Then add 0.5 parts of aminopropyltriethoxysilane and mix for 5 minutes. Add 10 parts of pearl sand and mix. Mechanically stir for 20 minutes. Heat to 50°C and soak for 60 minutes. Naturally dry for 4 hours. Put it in a drying oven at 60°C and dry it for 3 hours to obtain modified pearl sand.

[0039] 25 parts of flake graphite, 4 parts of acetic acid, 8 parts of tetrabutyl titanate and 7 parts of nano-silicon powder were mixed and stirred continuously at room temperature for 5 minutes. Then, 5 parts of 50% ethanol aqueous solution were added dropwise under continuous stirring, and the pH value was adjusted to 4 with hydrochloric acid to obtain a sol-gel. The sol-gel was aged at room temperature for 14 hours and then dried at 110°C for 18 hours to obtain a precursor. Finally, the precursor was placed in a crucible and transferred to a vertical furnace. It was heated to 400°C at a rate of 5°C / min under an argon atmosphere and maintained for 0.5 hours. It was then continued to be heated to 1350°C and maintained for 3 hours. After that, it was cooled to room temperature to obtain TiC-Ti3SiC2 composite coated graphite.

[0040] 75 parts of brown corundum, 2 parts of hollow corundum microspheres, 8 parts of silicon carbide, 6 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 3 parts of TiC-Ti3SiC2 composite coated graphite, and 2 parts of modified pearl sand were mixed and dried in a mixer for 3 minutes. Then, 5 parts of distilled water and 0.2 parts of water reducer were added. After stirring the mixture for 5 minutes, it was placed in a mold and cast on a vibration table. The mixture was allowed to stand at room temperature for 18 hours, then taken out from the mold, transferred to an oven at 150°C and dried for 16 hours to obtain a dry green body. Silicon powder was sprayed on the surface of the dry green body, and heated to 1350°C in a nitrogen atmosphere for heat treatment for 5 hours to obtain a VD furnace cover castable lining.

[0041] Example 3

[0042] Add 5 parts of hydrogenated silicone oil to 500 parts of xylene solvent and stir for 4 minutes to obtain an emulsion of hydrogenated silicone oil. Then add 0.8 parts of aminopropyltriethoxysilane and mix and stir for 7 minutes. Add 10 parts of pearl sand and mix. Mechanically stir for 25 minutes. Heat to 45°C and soak for 70 minutes. Naturally dry for 3 hours. Place in a drying oven at 60°C and dry for 4 hours to obtain modified pearl sand.

[0043] 25 parts of flake graphite, 4 parts of acetic acid, 8 parts of tetrabutyl titanate and 7 parts of nano-silicon powder were mixed and stirred continuously at room temperature for 6 minutes. Then, 6 parts of 50% ethanol aqueous solution were added dropwise under continuous stirring, and the pH value was adjusted to 3.7 with hydrochloric acid to obtain a sol-gel. The sol-gel was aged at room temperature for 15 hours and then dried at 110°C for 18 hours to obtain a precursor. Finally, the precursor was placed in a crucible and transferred to a vertical furnace. It was heated to 400°C at a rate of 5°C / min under an argon atmosphere and maintained for 1 hour. It was then continued to be heated to 1450°C and maintained for 3 hours. After cooling to room temperature, TiC-Ti3SiC2 composite coated graphite was obtained.

[0044] 72 parts of brown corundum, 4 parts of hollow corundum microspheres, 8 parts of silicon carbide, 5 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 4 parts of TiC-Ti3SiC2 composite coated graphite, and 2.5 parts of modified pearl sand were mixed and dried in a blender for 4 minutes. Then, 5 parts of distilled water and 0.2 parts of water reducer were added. The mixture was stirred for 8 minutes, placed in a mold, cast on a vibration table, and allowed to stand at room temperature for 20 hours. Then, it was taken out of the mold and transferred to an oven at 130°C for drying for 18 hours to obtain a dry green body. Silicon powder was sprayed on the surface of the dry green body, and heated to 1450°C for heat treatment for 3 hours under a nitrogen atmosphere to obtain a VD furnace cover castable lining.

[0045] Example 4

[0046] Add 5 parts of hydrogen-containing silicone oil to 500 parts of xylene solvent and stir for 3 minutes to obtain an emulsion of hydrogen-containing silicone oil. Then add 0.6 parts of aminopropyltriethoxysilane and mix and stir for 8 minutes. Add 10 parts of pearl sand and mix. Mechanically stir for 30 minutes. Heat to 50°C and soak for 65 minutes. Naturally dry for 4 hours. Put it in a drying oven at 60°C and dry it for 4 hours to obtain modified pearl sand.

[0047] 25 parts of flake graphite, 4 parts of acetic acid, 8 parts of tetrabutyl titanate, and 7 parts of nano-silicon powder were mixed and stirred continuously at room temperature for 5 minutes. Seven parts of a 50% ethanol aqueous solution were then added dropwise with continuous stirring. The pH was adjusted to 3 with hydrochloric acid to produce a sol-gel. The sol-gel was aged at room temperature for 15 hours and then dried at 110°C for 18 hours to obtain a precursor. Finally, the precursor was placed in a crucible and transferred to a vertical furnace. Under an argon atmosphere, it was heated to 400°C at a rate of 5°C / min and held for 1.5 hours. It was then heated to 1350°C and held for 4 hours before being cooled to room temperature to obtain a TiC-Ti3SiC2 composite-coated graphite.

[0048] 70 parts of brown corundum, 5 parts of hollow corundum microspheres, 8 parts of silicon carbide, 6 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 3 parts of TiC-Ti3SiC2 composite coated graphite, and 2 parts of modified pearl sand were mixed and dried in a mixer for 3 minutes. Then, 5 parts of distilled water and 0.2 parts of water reducer were added. After stirring the mixture for 6 minutes, it was placed in a mold and cast on a vibration table. The mixture was allowed to stand at room temperature for 24 hours, then taken out from the mold, transferred to an oven at 130°C and dried for 16 hours to obtain a dry green body. Silicon powder was sprayed on the surface of the dry green body, and heated to 1350°C in a nitrogen atmosphere for heat treatment for 4.5 hours to obtain a VD furnace cover castable lining.

[0049] Example 5

[0050] Add 5 parts of hydrogen-containing silicone oil to 500 parts of xylene solvent and stir for 4 minutes to obtain an emulsion of hydrogen-containing silicone oil. Then add 0.9 parts of aminopropyltriethoxysilane and mix and stir for 7 minutes. Add 10 parts of pearl sand and mix. Mechanically stir for 25 minutes. Heat to 50°C and soak for 60 minutes. Naturally dry for 2.5 hours. Put it in a drying oven at 60°C and dry for 3.5 hours to obtain modified pearl sand.

[0051] 25 parts of flake graphite, 4 parts of acetic acid, 8 parts of tetrabutyl titanate and 7 parts of nano-silicon powder were mixed and stirred continuously at room temperature for 5 minutes. Then, 5 parts of 50% ethanol aqueous solution were added dropwise under continuous stirring, and the pH value was adjusted to 3.2 with hydrochloric acid to obtain a sol-gel. The sol-gel was aged at room temperature for 15 hours and then dried at 110°C for 18 hours to obtain a precursor. Finally, the precursor was placed in a crucible and transferred to a vertical furnace. It was heated to 400°C at a rate of 5°C / min under an argon atmosphere and maintained for 1 hour. It was then continued to be heated to 1400°C and maintained for 4 hours. After cooling to room temperature, TiC-Ti3SiC2 composite coated graphite was obtained.

[0052] 71 parts of brown corundum, 4 parts of hollow corundum microspheres, 8 parts of silicon carbide, 5 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 4 parts of TiC-Ti3SiC2 composite coated graphite, and 2 parts of modified pearl sand were mixed and dried in a mixer for 5 minutes. Then, 5 parts of distilled water and 0.2 parts of water reducer were added. After stirring the mixture for 5 minutes, it was placed in a mold and cast on a vibration table. The mixture was allowed to stand at room temperature for 24 hours, then taken out from the mold, transferred to an oven at 120°C and dried for 20 hours to obtain a dry green body. Silicon powder was sprayed on the surface of the dry green body, and heated to 1450°C for heat treatment for 4 hours under a nitrogen atmosphere to obtain a VD furnace cover castable lining.

[0053] Example 6

[0054] Add 5 parts of hydrogen-containing silicone oil to 500 parts of xylene solvent and stir for 3 minutes to obtain an emulsion of hydrogen-containing silicone oil. Then add 0.8 parts of aminopropyltriethoxysilane and mix and stir for 8 minutes. Add 10 parts of pearl sand and mix. Mechanically stir for 25 minutes. Heat to 45°C and soak for 75 minutes. Naturally dry for 3 hours. Place in a drying oven at 60°C and dry for 3 hours to obtain modified pearl sand.

[0055] 25 parts of flake graphite, 4 parts of acetic acid, 8 parts of tetrabutyl titanate and 7 parts of nano-silicon powder were mixed and stirred continuously at room temperature for 8 minutes. Then, 6 parts of 50% ethanol aqueous solution were added dropwise under continuous stirring, and the pH value was adjusted to 3 with hydrochloric acid to obtain a sol-gel. The sol-gel was aged at room temperature for 14 hours and then dried at 110°C for 18 hours to obtain a precursor. Finally, the precursor was placed in a crucible and transferred to a vertical furnace. It was heated to 400°C at a rate of 5°C / min under an argon atmosphere and maintained for 0.5 hours. It was then continued to be heated to 1450°C and maintained for 3 hours. After that, it was cooled to room temperature to obtain TiC-Ti3SiC2 composite coated graphite.

[0056] 73 parts of brown corundum, 2 parts of hollow corundum microspheres, 8 parts of silicon carbide, 6 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 5 parts of TiC-Ti3SiC2 composite coated graphite, and 3 parts of modified pearl sand were mixed and dried in a mixer for 5 minutes. Then, 5 parts of distilled water and 0.2 parts of water reducer were added. The mixture was stirred for 7 minutes, placed in a mold, cast on a vibration table, and allowed to stand at room temperature for 22 hours. Then, it was taken out of the mold and transferred to an oven at 140°C for drying for 17 hours to obtain a dry green body. Silicon powder was sprayed on the surface of the dry green body, and heated to 1350°C for heat treatment for 5 hours under a nitrogen atmosphere to obtain a VD furnace cover castable lining.

[0057] The present invention also carried out comparative examples and related tests.

[0058] Comparative Example 1

[0059] Compared with Example 1, the only difference is that TiC-Ti3SiC2 composite coating graphite is not prepared, and graphite is directly added instead of TiC-Ti3SiC2 composite coating graphite. The other preparation methods and components are exactly the same, and finally a VD furnace cover castable lining is prepared.

[0060] Comparative Example 2

[0061] Compared with Example 1, the only difference is that modified pearl sand is not prepared, and pearl sand is directly added instead of modified pearl sand. Other preparation methods and components are completely consistent, and finally a VD furnace cover castable lining is prepared.

[0062] Comparative Example 3

[0063] Compared with Example 1, the only difference is that, in the process of preparing the VD furnace cover castable lining, silicon powder is not sprayed and nitrogen is not introduced, and heat treatment is directly carried out. The other preparation methods are exactly the same as the components, namely: 70 parts of brown corundum, 5 parts of hollow corundum microspheres, 8 parts of silicon carbide, 4 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 5 parts of TiC-Ti3SiC2 composite coated graphite, and 3 parts of modified pearl sand are mixed and dried in a blender for 5 minutes, and then 5 parts of distilled water and 0.2 parts of water reducer are added. After stirring the mixture for 10 minutes, it is placed in a mold and cast on a vibration table. It is allowed to stand at room temperature for 24 hours, then taken out from the mold, transferred to an oven at 120°C for drying for 20 hours, and heated to 1400°C for heat treatment for 5 hours to finally obtain the VD furnace cover castable lining.

[0064] Performance testing

[0065] The VD furnace roof castable lining samples prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were tested for basic properties of the samples at room temperature according to GB / T2997-2015 Test method for bulk density, apparent porosity and true porosity of dense shaped refractory products, GB / T5990-2021 Test method for thermal conductivity, specific heat capacity and thermal diffusivity of refractory materials (hot wire method), GB / T5072-2023 Test method for compressive strength of refractory materials at room temperature, and GB / T3001-2017 Test method for flexural strength of refractory materials at room temperature. The basic performance test results are shown in Table 1.

[0066] Table 1: Basic performance test results

[0067]

[0068] As can be seen from Table 1, the mechanical strength and thermal insulation properties of the samples prepared in Examples 1 to 6 are better than those in Comparative Examples 1 to 3; among them, compared with Comparative Example 1, the addition of TiC-Ti3SiC2 composite coating graphite in Example 1 significantly reduces the apparent porosity and significantly increases the bulk density, which to a certain extent promotes the densification of the sample after high-temperature sintering, further improves the overall compressive strength and flexural strength, and compared with Comparative Example 2, the addition of modified pearlescent sand in Example 1 significantly reduces the thermal conductivity, further improves the overall thermal insulation performance, and can effectively avoid the loss of a large amount of heat energy in the furnace.

[0069] The procedure for setting up a thermal shock test for the VD furnace cover castable lining samples prepared in Examples 1 to 6 and Comparative Examples 1 to 3 is as follows: the samples heated to 1500°C are placed in a furnace at 1100°C, kept warm for 20 minutes, immediately taken out, immersed in cold water for 3 minutes, and then placed in air for more than 5 minutes to dry naturally; the above process is cycled until the end breaks to measure its thermal shock resistance. Referring to GB / T39146-2020 Test method for refractory material resistance to molten aluminum alloy corrosion, the state of the sample after the test is tested. The test results of thermal shock resistance and corrosion resistance are shown in Table 2.

[0070] Table 2: Thermal shock and corrosion resistance test results

[0071]

[0072] It can be seen from the data in Table 1 that the thermal shock resistance and erosion resistance of the samples prepared in Examples 1 to 6 are significantly better than those in Comparative Examples 1 to 3; among them, the addition of modified pearlescent sand and TiC-Ti3SiC2 composite coating graphite in Example 1 significantly improves the thermal shock resistance, and the TiC-Ti3SiC2 composite coating graphite also effectively reduces slag penetration, further significantly improving the erosion resistance. In addition, compared with Comparative Example 3, the formation of the silicon nitride strengthening layer in Example 1 can resist the erosion of molten metal and slag, significantly improve the erosion resistance, and can also relieve thermal stress, thereby improving the thermal shock resistance to a certain extent.

[0073] The above is a preferred embodiment of the present invention. Those skilled in the art may make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a VD furnace roof castable lining, characterized in that: The steps include: S1. Mixing an emulsion of hydrogenated silicone oil, aminopropyltriethoxysilane, and pearlescent sand, heating and soaking the mixture, and drying the mixture to obtain modified pearlescent sand; S2, mixing flake graphite, acetic acid, tetrabutyl titanate and nano-silicon powder, adding ethanol aqueous solution dropwise, adjusting the pH value to acidic, aging, drying, heating at high temperature under an inert gas environment, and cooling to obtain TiC-Ti3SiC2 composite coating graphite; S3. Mix brown corundum, silicon carbide, α-Al2O3 powder, calcium aluminate cement, TiC-Ti3SiC2 composite coated graphite, and modified pearl sand, dry them, add distilled water, stir them, put them into a mold, cast them into shape, let them stand, take them out, dry them, spray silicon powder on the surface, and perform heat treatment under a nitrogen atmosphere to obtain a VD furnace cover castable lining.

2. The method for preparing a VD furnace roof castable lining according to claim 1, characterized in that: The hydrogenated silicone oil emulsion is prepared by adding the hydrogenated silicone oil into a xylene solvent and stirring for 3 to 5 minutes.

3. The method for preparing a VD furnace roof castable lining according to claim 1, characterized in that: In the step S1, the emulsion of hydrogen silicone oil and aminopropyltriethoxysilane are mixed and stirred for 5-10 minutes, pearl sand is added and mixed, mechanically stirred for 20-30 minutes, heated to 40-50° C. and soaked for 60-80 minutes, naturally dried for 2-4 hours, and placed in a drying oven at 60° C. and dried for 3-5 hours to obtain modified pearl sand.

4. The method for preparing a VD furnace roof castable lining according to claim 1, characterized in that: The volume concentration of the ethanol aqueous solution is 50%.

5. The method for preparing a VD furnace roof castable lining according to claim 1, characterized in that: The mixing and stirring time in step S2 is 5-10 minutes, the pH value is adjusted to 3-4 with hydrochloric acid, the aging time is 14-16 hours, the drying time is 18 hours, and the temperature is 110° C.; the inert gas is argon.

6. The method for preparing a VD furnace roof castable lining according to claim 1, characterized in that: In the step S2, the TiC-Ti3SiC2 composite coating graphite is obtained by heating to 400°C at a rate of 5°C / min under an argon atmosphere and maintaining the temperature for 0.5-1.5 hours, then continuing to heat to 1350-1450°C and maintaining the temperature for 3-5 hours, and then cooling to room temperature.

7. The method for preparing a VD furnace roof castable lining according to claim 1, characterized in that: In step S3, hollow corundum microspheres are also added when the TiC-Ti3SiC2 composite coating graphite is added.

8. The method for preparing a VD furnace roof castable lining according to claim 1, characterized in that: In step S3, a water reducing agent is also added when adding distilled water.

9. The method for preparing a VD furnace roof castable lining according to claim 1, characterized in that: In the step S3, the drying time before adding distilled water is 3 to 5 minutes; after adding distilled water, stirring is carried out for 5 to 10 minutes, the product is placed in a mold, cast and formed, and allowed to stand for 18 to 24 hours. The product is taken out and dried at 120 to 150° C. for 16 to 20 hours. Silicon powder is sprayed on the surface, and the product is heated to 1350 to 1450° C. in a nitrogen atmosphere and heat treated for 3 to 5 hours to obtain a VD furnace cover castable lining.

10. A VD furnace roof castable lining, prepared by the method for preparing a VD furnace roof castable lining according to any one of claims 1 to 9, characterized in that: The method comprises the following raw materials in parts by mass: 70-75 parts of brown corundum, 8 parts of silicon carbide, 4-6 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 2 parts of silicon micropowder, 3-5 parts of TiC-Ti3SiC2 composite coated graphite, 2-3 parts of modified pearlescent sand, and 5 parts of distilled water.

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