VD furnace cover castable lining and preparation method thereof

Abstract

The invention provides a VD furnace cover castable lining and a preparation method thereof, and belongs to the technical field of high-temperature refractory materials, and the preparation method comprises the following steps: mixing and stirring an emulsion containing hydrogen silicone oil, aminopropyltriethoxysilane and pearlife, heating and soaking, and drying to obtain modified pearlife; the preparation method comprises the following steps: mixing and stirring graphite, acetic acid, tetrabutyl titanate and nano silicon powder, dropwise adding an ethanol aqueous solution, adjusting the pH value to be acidic, aging, drying, heating at high temperature in an inert gas environment, and cooling to obtain TiC-Ti3SiC2 composite coating graphite; brown fused alumina, silicon carbide, alpha-Al2O3 powder, calcium aluminate cement, TiC-Ti3SiC2 composite coating graphite and modified pearlife are mixed and dried, distilled water is added, stirring is conducted, the mixture is put into a mold, casting molding, standing, taking out and drying are conducted, silicon powder is sprayed on the surface, heat treatment is conducted in the nitrogen atmosphere, and the VD furnace cover castable lining is obtained. The thermal shock resistance of the VD furnace cover castable lining can be improved while the thermal insulation performance of the VD furnace cover can be improved.

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: S1. Mix and stir an emulsion of hydrogen-containing silicone oil, aminopropyltriethoxysilane, and pearlite sand, heat and soak, and dry to obtain modified pearlite sand; S2. Mix and stir flake graphite, acetic acid, tetrabutyl titanate, and nano-silicon powder, dropwise add an ethanol aqueous solution, adjust the pH value to acidic, age, dry, then under an inert gas environment, heat at high temperature and cool to obtain TiC-Ti3SiC2 composite coating graphite; S3. Mix brown fused alumina, silicon carbide, α-Al2O3 powder, calcium aluminate cement, TiC-Ti3SiC2 composite coating graphite, and modified pearlite sand, dry, add distilled water, stir, put into a mold, cast and form, stand still, take out, dry, spray silicon powder on the surface, and perform heat treatment under a nitrogen atmosphere to obtain a lining layer of a VD furnace cover castable.

[0008] The present invention uses pearlite sand as a 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 pearlite sand, the addition of pearlite sand can effectively reduce the thermal conductivity of the castable and thus improve the overall thermal insulation effect. However, due to its porous structure, it will cause strong water absorption, resulting in problems such as an increase in thermal conductivity and a decrease in mechanical strength after water absorption; the surface of pearlite sand is modified with hydrogen-containing silicone oil, so that a thick network of siloxane molecular films is formed on the outer surface of the modified pearlite sand, avoiding the absorption of moisture by capillary pores and endowing pearlite sand with hydrophobic properties; moreover, the siloxane molecules have good thermal stability, so that the hydrophobic film can be kept intact at high temperatures; in addition, the pearlite sand modified with hydrogen-containing silicone oil has smaller pores and a denser structure, endowing the overall thermal insulation performance while avoiding the risk of greatly reducing the compressive strength and flexural strength due to too large pores.

[0009] The present invention introduces TiC-Ti3SiC2 composite coating graphite as a carbon source to replace spherical pitch, avoiding the generation of harmful gases at high temperatures while improving the mechanical properties and thermal shock stability of the castable. TiC-Ti3SiC2 composite coating graphite is prepared by sol-gel combined with carbothermal reduction. By modifying the surface of flake graphite to generate a carbide coating, its wettability and oxidation resistance are improved, solving the problem that the poor water wettability of graphite leads to easy floating and agglomeration in the castable; in addition, due to the addition of TiC-Ti3SiC2 composite coating graphite, the densification of the sample after high-temperature sintering is promoted, the degree of interfacial bonding is improved, and thus the bonding between the substrates is tighter; the layered structure characteristics of TiC-Ti3SiC2 composite coating graphite endow it with flexural properties, which can, to a certain extent, prevent crack propagation during the fracture process, thereby improving the thermal shock resistance of the overall material; and a multi-layer oxide protective layer will be generated on the surface of Ti3SiC2 at high temperatures, which can significantly slow down oxidation and thermal erosion, further improving the overall oxidation resistance and erosion resistance.

[0010] In the process of preparing the pouring material lining of the VD furnace cover in the present invention, silicon powder is sprayed on the surface of the dried green body and sintered in a nitrogen atmosphere to form a silicon nitride surface strengthening layer, which forms a dense protective film at high temperature to prevent the further penetration of oxygen and molten slag, thereby resisting the erosion of molten metal (such as aluminum liquid, steel liquid) 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 the environment of rapid cooling and heating.

[0011] Optionally, the emulsion of hydrogen-containing silicone oil is prepared by adding hydrogen-containing silicone oil to xylene solvent and stirring for 3 - 5 min.

[0012] Optionally, in step S1, the emulsion of hydrogen-containing silicone oil and aminopropyltriethoxysilane are mixed and stirred for 5 - 10 min, then pearlite sand is added and mechanically stirred for 20 - 30 min, heated to 40 - 50 °C and soaked for 60 - 80 min, then naturally dried for 2 - 4 h, and then placed in a drying oven at 60 °C and dried for 3 - 5 h to obtain modified pearlite sand.

[0013] When preparing the modified pearlite sand in the present invention, the heating and soaking method is adopted. In the heated state, the components in the emulsion are more active, can better penetrate to the surface of the pearlite sand particles, and better cover the surface of the pearlite sand.

[0014] Optionally, the volume concentration of the ethanol aqueous solution is 50%.

[0015] Optionally, in step S2, the mixing and stirring time is 5 - 10 min, the pH value is adjusted to 3 - 4 with hydrochloric acid, the aging time is 14 - 16 h, the drying time is 18 h, and the temperature is 110 °C; the inert gas is argon.

[0016] In the present invention, by using hydrochloric acid to adjust the pH of the solution to 3 - 4, within this pH range, the efficiency of the solution converting into the sol - gel state reaches the best.

[0017] Optionally, in step S2, under an argon atmosphere, it is heated to 400 °C at a rate of 5 °C / min and held for 0.5 - 1.5 h, then continued to be heated to 1350 - 1450 °C and held for 3 - 5 h, and then cooled to room temperature to obtain TiC - Ti3SiC2 composite - coated graphite.

[0018] Optionally, hollow corundum microspheres are also added when adding TiC - Ti3SiC2 composite - coated graphite in step S3.

[0019] When preparing the pouring material lining of the VD furnace cover in the present invention, hollow corundum microspheres are also added, which cooperate with TiC - Ti3SiC2 composite - coated graphite to form a closed - pore - open - pore dual - mode structure, further reducing the thermal conductivity and improving the heat insulation effect of the pouring material lining.

[0020] Optionally, a water reducing agent is also added when adding distilled water in step S3.

[0021] When preparing the pouring material lining of the VD furnace cover, the present invention adds a water reducing agent to reduce the water consumption of the cement slurry, improve the fluidity of the mixture, and will not affect the final strength, which is helpful for the pouring and molding processes.

[0022] Optionally, in step S3, the drying time before adding distilled water is 3 - 5 min; after adding distilled water, stir for 5 - 10 min, put it into a mold, cast and form, let it stand for 18 - 24 h, take it out, dry it at 120 - 150 °C for 16 - 20 h, spray silicon powder on the surface, and heat it to 1350 - 1450 °C under a nitrogen atmosphere for heat treatment for 3 - 5 h to obtain the pouring material lining of the VD furnace cover.

[0023] Optionally, the pouring material lining of the VD furnace cover comprises the following raw materials in parts by mass: 70 - 75 parts of brown fused alumina, 8 parts of silicon carbide, 4 - 6 parts of α - Al2O3 powder, 5 parts of calcium aluminate cement, 2 parts of silica fume, 3 - 5 parts of TiC - Ti3SiC2 composite coating graphite, 2 - 3 parts of modified pearlite sand, and 5 parts of distilled water.

[0024] The present invention uses brown fused alumina as the base material. The combination of brown fused alumina and silicon carbide makes the lining have stronger fire resistance and thermal stability at high temperatures. With the addition of α - Al2O3 powder and TiC - Ti3SiC2 composite coating graphite, and the strong bonding force of calcium aluminate cement, the mechanical properties and thermal shock stability of the lining are improved, effectively avoiding the formation of cracks. And according to the above mass ratio, the comprehensive performance of the pouring material lining of the VD furnace cover can be best exerted.

[0025] The above technical solution of the present invention has at least the following beneficial effects: 1. The present invention modifies pearlite sand with hydrogen - containing silicone oil to form a hydrophobic siloxane film, effectively avoiding the water absorption problem of the porous structure of pearlite sand and improving its heat - preservation performance; the modified pearlite 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.

[0026] 2. The present invention replaces spherical pitch with TiC - Ti3SiC2 composite coating graphite, improving the mechanical properties and thermal shock stability of the pouring material. The composite coating graphite is prepared by the sol - gel combined with carbothermal reduction method to improve its wettability and oxidation resistance, solving the problems of graphite floating and agglomeration. At the same time, the composite coating graphite promotes densification after high - temperature sintering, enhances the bonding between the base materials, and improves the flexural strength through the layered structure, thus effectively improving the thermal shock resistance of the overall material.

[0027] 3. During the preparation of the gunning refractory lining for the VD furnace cover in the present invention, silicon powder is sprayed on the surface of the dried green body and sintered in a nitrogen atmosphere to form 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 the erosion of molten metal and slag. At the same time, the high fracture toughness of silicon nitride absorbs thermal stress through crack deflection and bridging mechanisms, improving the stability of the material in the environment of rapid cooling and heating. Detailed Embodiments

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 some of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention fall within the scope of protection of the present invention.

[0029] Example 1 5 parts of hydrogen-containing silicone oil are added to 500 parts of xylene solvent, and stirred for 5 min to obtain an emulsion of hydrogen-containing silicone oil. Then, 1 part of aminopropyltriethoxysilane is added and stirred for 10 min. After adding 10 parts of pearlite sand and mixing, mechanical stirring is carried out for 30 min. After heating to 40 °C and soaking for 80 min, it is naturally dried for 2 h and then placed in a drying oven at 60 °C and dried for 5 h to obtain modified pearlite sand.

[0030] 25 parts of flake graphite, 4 parts of acetic acid, 8 parts of tetrabutyl titanate, and 7 parts of nano-silicon powder are mixed, and continuously stirred at room temperature for 10 min. Then, 7 parts of an ethanol aqueous solution with a volume concentration of 50% are added dropwise under continuous stirring, and the pH value is adjusted to 3 with hydrochloric acid to obtain a sol-gel. The sol-gel is aged at room temperature for 16 h, and then dried at 110 °C for 18 h to obtain a precursor. Finally, the precursor is placed in a crucible and transferred to a vertical furnace, heated to 400 °C at a rate of 5 °C / min in an argon atmosphere and held for 1.5 h, and then continuously heated to 1450 °C and held for 5 h, and then cooled to room temperature to obtain TiC-Ti3SiC2 composite coating graphite.

[0031] 70 parts of brown fused alumina, 5 parts of hollow fused alumina microspheres, 8 parts of silicon carbide, 4 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 5 parts of TiC-Ti3SiC2 composite coating graphite, and 3 parts of modified pearlite sand are mixed and dried in a mixer for 5 min. Then, 5 parts of distilled water and 0.2 part of water reducer are added, and the mixture is stirred for 10 min and then put into a mold, cast and molded on a vibrating table, left standing at room temperature for 24 h, then taken out of the mold and transferred to an oven at 120 °C and dried for 20 h to obtain a dried green body. Silicon powder is sprayed on the surface of the dried green body, and heat-treated at 1400 °C for 5 h in a nitrogen atmosphere to obtain the gunning refractory lining for the VD furnace cover.

[0032] Example 2 Add 5 parts of hydrogen-containing silicone oil to 500 parts of xylene solvent, stir for 3 min to obtain an emulsion of hydrogen-containing silicone oil, then add 0.5 part of aminopropyltriethoxysilane and mix and stir for 5 min. After adding 10 parts of pearlite sand and mixing, mechanically stir for 20 min, heat to 50 °C and soak for 60 min, then naturally dry for 4 h, and place in a drying oven at 60 °C to dry for 3 h to obtain modified pearlite sand.

[0033] Mix 25 parts of flaky graphite, 4 parts of acetic acid, 8 parts of tetrabutyl titanate and 7 parts of nano-silicon powder, and continuously stir at room temperature for 5 min. Then, while continuously stirring, dropwise add 5 parts of an aqueous ethanol solution with a volume concentration of 50%. Adjust the pH value to 4 with hydrochloric acid to obtain a sol-gel. Age the sol-gel at room temperature for 14 h, and then dry it at 110 °C for 18 h to obtain a precursor. Finally, place the precursor in a crucible and transfer it to a vertical furnace. Heat it to 400 °C at a rate of 5 °C / min under an argon atmosphere and hold for 0.5 h, then continue to heat to 1350 °C and hold for 3 h, and then cool to room temperature to obtain TiC-Ti3SiC2 composite coating graphite.

[0034] Mix 75 parts of brown fused alumina, 2 parts of hollow fused alumina microspheres, 8 parts of silicon carbide, 6 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 3 parts of TiC-Ti3SiC2 composite coating graphite, and 2 parts of modified pearlite sand and dry in a mixer for 3 min. Then add 5 parts of distilled water and 0.2 part of water reducer, stir the mixture for 5 min, put it into a mold, cast and form on a vibrating table, stand still at room temperature for 18 h, then take it out of the mold, transfer it to an oven at 150 °C to dry for 16 h to obtain a dried blank. Spray silicon powder on the surface of the dried blank, and heat-treat it at 1350 °C for 5 h under a nitrogen atmosphere to obtain a lining for the VD furnace cover casting material.

[0035] Example 3 Add 5 parts of hydrogen-containing silicone oil to 500 parts of xylene solvent, stir for 4 min to obtain an emulsion of hydrogen-containing silicone oil, then add 0.8 part of aminopropyltriethoxysilane and mix and stir for 7 min. After adding 10 parts of pearlite sand and mixing, mechanically stir for 25 min, heat to 45 °C and soak for 70 min, then naturally dry for 3 h, and place in a drying oven at 60 °C to dry for 4 h to obtain modified pearlite sand.

[0036] Mix 25 parts of flake graphite, 4 parts of acetic acid, 8 parts of tetrabutyl titanate, and 7 parts of nano silicon powder, continuously stir for 6 min at room temperature, then dropwise add 6 parts of an aqueous ethanol solution with a volume concentration of 50% under continuous stirring, adjust the pH value to 3.7 with hydrochloric acid to obtain a sol-gel. Age the sol-gel at room temperature for 15 h, then dry it at 110 °C for 18 h to obtain a precursor. Finally, place the precursor in a crucible and transfer it to a vertical furnace, heat it to 400 °C at a rate of 5 °C / min under an argon atmosphere and hold for 1 h, then continue heating to 1450 °C and hold for 3 h, and then cool to room temperature to obtain TiC-Ti3SiC2 composite coating graphite.

[0037] Mix 72 parts of brown fused alumina, 4 parts of hollow fused alumina microspheres, 8 parts of silicon carbide, 5 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 4 parts of TiC-Ti3SiC2 composite coating graphite, and 2.5 parts of modified pearlite sand and dry in a mixer for 4 min, then add 5 parts of distilled water and 0.2 part of water reducer, stir the mixture for another 8 min, then put it into a mold, cast and form on a vibrating table, let it stand at room temperature for 20 h, then take it out of the mold, transfer it to an oven at 130 °C and dry for 18 h to obtain a dried green body. Spray silicon powder on the surface of the dried green body, heat it to 1450 °C under a nitrogen atmosphere and heat-treat for 3 h to obtain a lining for the VD furnace cover casting material.

[0038] Example 4 Add 5 parts of hydrogen-containing silicone oil to 500 parts of xylene solvent, stir for 3 min to prepare an emulsion of hydrogen-containing silicone oil, then add 0.6 part of aminopropyltriethoxysilane and mix and stir for 8 min, add 10 parts of pearlite sand and mix, mechanically stir for 30 min, heat to 50 °C and soak for 65 min, then naturally dry for 4 h, and put it into a drying oven at 60 °C and dry for 4 h to obtain modified pearlite sand.

[0039] Mix 25 parts of flake graphite, 4 parts of acetic acid, 8 parts of tetrabutyl titanate, and 7 parts of nano silicon powder, continuously stir for 5 min at room temperature, then dropwise add 7 parts of an aqueous ethanol solution with a volume concentration of 50% under continuous stirring, adjust the pH value to 3 with hydrochloric acid to obtain a sol-gel. Age the sol-gel at room temperature for 15 h, then dry it at 110 °C for 18 h to obtain a precursor. Finally, place the precursor in a crucible and transfer it to a vertical furnace, heat it to 400 °C at a rate of 5 °C / min under an argon atmosphere and hold for 1.5 h, then continue heating to 1350 °C and hold for 4 h, and then cool to room temperature to obtain TiC-Ti3SiC2 composite coating graphite.

[0040] Mix 70 parts of brown fused alumina, 5 parts of hollow fused alumina microspheres, 8 parts of silicon carbide, 6 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 3 parts of TiC-Ti3SiC2 composite coating graphite, and 2 parts of modified pearlite sand, and dry in a mixer for 3 min. Then add 5 parts of distilled water and 0.2 part of water reducing agent, and stir the mixture for 6 min. Then put it into a mold, cast and form on a vibrating table, let it stand at room temperature for 24 h, then take it out of the mold, transfer it to an oven at 130 °C and dry for 16 h to obtain a dried blank. Spray silicon powder on the surface of the dried blank, and heat it to 1350 °C under a nitrogen atmosphere for heat treatment for 4.5 h to obtain a lining layer of VD furnace cover castable material.

[0041] Example 5 Add 5 parts of hydrogen-containing silicone oil to 500 parts of xylene solvent, stir for 4 min to prepare an emulsion of hydrogen-containing silicone oil, then add 0.9 part of aminopropyltriethoxysilane and mix and stir for 7 min. After adding 10 parts of pearlite sand and mixing, stir mechanically for 25 min, heat to 50 °C and soak for 60 min, then dry naturally for 2.5 h, and put it into a drying oven at 60 °C and dry for 3.5 h to obtain modified pearlite sand.

[0042] Mix 25 parts of flaky graphite, 4 parts of acetic acid, 8 parts of tetrabutyl titanate and 7 parts of nano-silicon powder, and continuously stir at room temperature for 5 min. Then, while continuously stirring, dropwise add 5 parts of an aqueous ethanol solution with a volume concentration of 50%, and adjust the pH value to 3.2 with hydrochloric acid to obtain a sol-gel. Age the sol-gel at room temperature for 15 h, then dry at 110 °C for 18 h to obtain a precursor; finally, put the precursor into a crucible and transfer it to a vertical furnace, heat it to 400 °C at a rate of 5 °C / min under an argon atmosphere and hold for 1 h, then continue to heat to 1400 °C and hold for 4 h, and then cool to room temperature to obtain TiC-Ti3SiC2 composite coating graphite.

[0043] Mix 71 parts of brown fused alumina, 4 parts of hollow fused alumina microspheres, 8 parts of silicon carbide, 5 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 4 parts of TiC-Ti3SiC2 composite coating graphite, and 2 parts of modified pearlite sand, and dry in a mixer for 5 min. Then add 5 parts of distilled water and 0.2 part of water reducing agent, and stir the mixture for 5 min. Then put it into a mold, cast and form on a vibrating table, let it stand at room temperature for 24 h, then take it out of the mold, transfer it to an oven at 120 °C and dry for 20 h to obtain a dried blank. Spray silicon powder on the surface of the dried blank, and heat it to 1450 °C under a nitrogen atmosphere for heat treatment for 4 h to obtain a lining layer of VD furnace cover castable material.

[0044] Example 6 Add 5 parts of hydrogen-containing silicone oil to 500 parts of xylene solvent, stir for 3 min to obtain an emulsion of hydrogen-containing silicone oil, then add 0.8 part of aminopropyltriethoxysilane and mix and stir for 8 min. After adding 10 parts of pearlite sand and mixing, mechanically stir for 25 min, heat to 45 °C and soak for 75 min, then dry naturally for 3 h, and place in a drying oven at 60 °C and dry for 3 h to obtain modified pearlite sand.

[0045] Mix 25 parts of flake graphite, 4 parts of acetic acid, 8 parts of tetrabutyl titanate and 7 parts of nano-silicon powder, and continuously stir at room temperature for 8 min. Then, while continuously stirring, add 6 parts of an aqueous ethanol solution with a volume concentration of 50% dropwise, and adjust the pH value to 3 with hydrochloric acid to obtain a sol-gel. Age the sol-gel at room temperature for 14 h, then dry at 110 °C for 18 h to obtain a precursor. Finally, place the precursor in a crucible and transfer it to a vertical furnace. Heat it to 400 °C at a rate of 5 °C / min in an argon atmosphere and hold for 0.5 h, then continue to heat to 1450 °C and hold for 3 h, and then cool to room temperature to obtain TiC-Ti3SiC2 composite coating graphite.

[0046] Mix 73 parts of brown fused alumina, 2 parts of hollow fused alumina microspheres, 8 parts of silicon carbide, 6 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 5 parts of TiC-Ti3SiC2 composite coating graphite, and 3 parts of modified pearlite sand and dry in a mixer for 5 min. Then add 5 parts of distilled water and 0.2 part of water reducing agent, stir the mixture for 7 min, put it into a mold, cast and form on a vibrating table, let it stand at room temperature for 22 h, then take it out of the mold, transfer it to an oven at 140 °C and dry for 17 h to obtain a dry blank. Spray silicon powder on the surface of the dry blank, and heat it to 1350 °C in a nitrogen atmosphere and heat-treat for 5 h to obtain a lining for the VD furnace cover castable.

[0047] The present invention also carried out comparative examples and related tests.

[0048] Comparative Example 1 Compared with Example 1, the difference is only that TiC-Ti3SiC2 composite coating graphite was not prepared, and graphite was directly added instead of TiC-Ti3SiC2 composite coating graphite. Other preparation methods and components are exactly the same, and finally a lining for the VD furnace cover castable was obtained.

[0049] Comparative Example 2 Compared with Example 1, the difference is only that modified pearlite sand was not prepared, and pearlite sand was directly added instead of modified pearlite sand. Other preparation methods and components are exactly the same, and finally a lining for the VD furnace cover castable was obtained.

[0050] Comparative Example 3 Compared with Example 1, the only difference is that during the preparation of the VD furnace cover castable lining, silicon powder was not sprayed and nitrogen was not introduced, and heat treatment was directly carried out. Other preparation methods and components are exactly the same, that is: 70 parts of brown fused alumina, 5 parts of hollow fused alumina microspheres, 8 parts of silicon carbide, 4 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 5 parts of TiC-Ti3SiC2 composite coating graphite, and 3 parts of modified expanded pearlite are mixed and dried in a mixer for 5 min, then 5 parts of distilled water and 0.2 part of water reducer are added. After the mixture is stirred for 10 min, it is put into a mold and cast into shape on a vibrating table, left standing at room temperature for 24 h, then taken out of the mold, transferred to an oven at 120 °C and dried for 20 h, and then heated to 1400 °C for heat treatment for 5 h to finally obtain the VD furnace cover castable lining.

[0051] Performance detection test The VD furnace cover castable lining samples prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were tested for the basic properties of the samples at room temperature according to GB / T 2997-2015 Test methods for bulk density, apparent porosity and true porosity of dense shaped refractory products, GB / T 5990-2021 Test methods for thermal conductivity, specific heat capacity and thermal diffusivity of refractories (hot wire method), GB / T 5072-2023 Test methods for cold crushing strength of refractories, and GB / T 3001-2017 Test methods for cold bending strength of refractories. The test results of the basic properties are shown in Table 1.

[0052] Table 1: Test results of basic properties

[0053] As can be seen from Table 1, the mechanical strength and heat preservation performance of the samples prepared in Examples 1 to 6 are better than those of 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 samples after high-temperature sintering, further improving the overall compressive strength and flexural strength. And compared with Comparative Example 2, Example 1 significantly reduces the thermal conductivity due to the addition of modified expanded pearlite, further improving the overall heat preservation performance and effectively avoiding the loss of a large amount of heat energy in the furnace.

[0054] The procedures for setting up the thermal shock resistance test for the VD furnace cover castable lining samples prepared in Examples 1-6 and Comparative Examples 1-3 are as follows: The samples heated to 1500 °C are respectively placed in a furnace at 1100 °C, kept warm for 20 min, immediately taken out, immersed in cold water for 3 min, and then left in the air for more than 5 min for natural drying; the above process is cycled until the end breaks to measure its thermal shock resistance. Referring to GB / T 39146-2020 Test method for refractory materials - Resistance to molten aluminum alloy erosion, the state of the samples after the test is tested, and the test results of thermal shock and erosion resistance are shown in Table 2.

[0055] Table 2: Test results of thermal shock and erosion resistance

[0056] From the data in Table 1, it can be seen that the thermal shock resistance and erosion resistance of the samples prepared in Examples 1-6 are significantly better than those in Comparative Examples 1-3; among them, the addition of modified expanded pearlite 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 the penetration of molten slag, 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 improving the erosion resistance, and can also relieve thermal stress, thus also improving the thermal shock resistance to a certain extent.

[0057] The above are the preferred embodiments of the present invention. Without departing from the principle of the present invention, those of ordinary skill in the art can also make several improvements and refinements, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a casting material lining for a VD furnace cover, characterized in that, It includes the following steps: S1. Mix and stir the emulsion of hydrogen-containing silicone oil, aminopropyltriethoxysilane, and pearlite sand, heat and soak, and dry to obtain modified pearlite sand; S2. Mix and stir flake graphite, acetic acid, tetrabutyl titanate, and nano-silicon powder, dropwise add an ethanol aqueous solution, adjust the pH value to acidic, age, dry, then heat at a high temperature in an inert gas environment and cool to obtain TiC-Ti3SiC2 composite coating graphite; S3. Mix brown fused alumina, silicon carbide, α-Al2O3 powder, calcium aluminate cement, TiC-Ti3SiC2 composite coating graphite, and modified pearlite sand, dry, add distilled water, stir, put it into a mold, cast and form, let it stand, take it out, dry, spray silicon powder on the surface, and perform heat treatment in a nitrogen atmosphere to obtain the lining of the VD furnace cover casting material.

2. The preparation method of a pouring material lining for a VD furnace lid according to claim 1, characterized in that, The emulsion of hydrogen-containing silicone oil is prepared by adding hydrogen-containing silicone oil to xylene solvent and stirring for 3 - 5 min.

3. The preparation method of a VD furnace cover castable lining according to claim 1, characterized in that, In step S1, the emulsion of hydrogen-containing silicone oil and aminopropyltriethoxysilane are mixed and stirred for 5 - 10 min, then pearlite sand is added and mixed, followed by mechanical stirring for 20 - 30 min, heated to 40 - 50 °C and soaked for 60 - 80 min, then naturally dried for 2 - 4 h, and then dried in a drying oven at 60 °C for 3 - 5 h to obtain modified pearlite sand.

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

5. The preparation method of a pouring material lining for a VD furnace lid according to claim 1, characterized in that, In step S2, the mixing and stirring time is 5 - 10 min, the pH value is adjusted to 3 - 4 with hydrochloric acid, the aging time is 14 - 16 h, the drying time is 18 h and the temperature is 110 °C; the inert gas is argon.

6. The preparation method of a VD furnace lid castable lining according to claim 1, characterized in that, In step S2, heat to 400 °C at a rate of 5 °C / min in an argon atmosphere and hold for 0.5 - 1.5 h, then continue to heat to 1350 - 1450 °C and hold for 3 - 5 h, and then cool to room temperature to obtain TiC-Ti3SiC2 composite coating graphite.

7. The preparation method of a VD furnace cover castable lining according to claim 1, characterized in that, In step S3, hollow fused alumina microspheres are also added when adding TiC-Ti3SiC2 composite coating graphite.

8. The preparation method of a VD furnace cover 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 preparation method of a VD furnace cover castable lining according to claim 1, characterized in that In step S3, the drying time before adding distilled water is 3 - 5 min; after adding distilled water, stir for 5 - 10 min, put it into a mold, cast and form, let it stand for 18 - 24 h, take it out, dry at 120 - 150 °C for 16 - 20 h, then spray silicon powder on the surface, and heat to 1350 - 1450 °C in a nitrogen atmosphere for heat treatment for 3 - 5 h to obtain the lining of the VD furnace cover casting material.

10. A VD furnace cover castable lining, prepared by using the preparation method of a VD furnace cover castable lining according to any one of claims 1 to 9, characterized in that, It includes raw materials in the following mass parts: 70 - 75 parts of brown fused alumina, 8 parts of silicon carbide, 4 - 6 parts of α-Al2O3 powder, 5 parts of calcium aluminate cement, 2 parts of silicon micro-powder, 3 - 5 parts of TiC-Ti3SiC2 composite coating graphite, 2 - 3 parts of modified pearlite sand, and 5 parts of distilled water.

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