Precast silicon carbide-based refractory composite material for electric furnace bottom and its preparation method

Abstract

This invention provides a silicon carbide-based refractory composite preform for electric furnace bottoms and its preparation method, relating to the field of refractory materials for steelmaking. The preform comprises a matrix layer, a sensing layer, and a functional layer connected sequentially. The matrix layer is a silicon carbide-based refractory block, serving as the load-bearing core of the composite material. The sensing layer is embedded between the matrix layer and the functional layer, including sensing wires for collecting temperature and stress data of the preform. The sensing wires are laid in a mesh structure on the surface of the matrix layer and fixed using sol-gel encapsulation. The functional layer is coated on the surface of the sensing layer, providing both slag erosion resistance and signal transmission capabilities. This invention is the first to propose a sandwich composite structure of "matrix layer-sensing layer-functional layer," deeply integrating an intelligent sensing system with refractory protection functions, enabling real-time status monitoring of the material itself. This differs from existing external sensing and single-point monitoring solutions, filling a structural gap in intelligent refractory materials for electric furnace bottoms.

Description

Technical Field

[0001] This invention relates to the field of refractory materials for steelmaking, and in particular to a silicon carbide-based refractory composite preform for electric furnace bottoms and its preparation method. Background Technology

[0002] Electric arc furnace (EAF) steelmaking, as one of the core smelting processes in the steel industry, exposes its furnace bottom to harsh conditions for extended periods, including high temperatures of 1600-1800℃, strong electric arc radiation, static pressure impact from molten steel, slag erosion, and frequent thermal shock. This makes it the most demanding and highest-risk part of the EAF refractory lining. Traditional EAF furnace bottom refractory materials are mainly magnesia-carbon bricks and alumina-magnesia-carbon bricks. While these materials possess some resistance to slag erosion, they suffer from insufficient high-temperature strength, a high coefficient of thermal expansion, and poor thermal shock resistance. These defects make them prone to cracking and spalling due to sudden temperature changes, and can even lead to furnace leaks, severely restricting the production efficiency and safety of EAFs.

[0003] Meanwhile, existing electric arc furnace bottom condition monitoring technologies have significant shortcomings: First, external sensors (such as thermocouples and stress gauges) can only measure the temperature of molten steel or parameters on the furnace shell surface, and cannot reflect the internal temperature and stress changes of the refractory material itself, resulting in serious early warning lag. Second, in the few attempts to integrate sensing refractory materials, the sensing elements mostly use metal wires or ordinary ceramic sensors, which are prone to oxidation, melting, and signal drift at 1800℃, and the technical bottleneck of signal shielding by the refractory matrix has not been solved. Third, existing smart refractory materials are mostly single-point monitoring, lacking the ability to monitor area grids, and cannot accurately identify potential failure hazards such as local overheating and stress concentration. Fourth, there is a lack of standardized prefabrication and on-site construction processes adapted to electric arc furnace bottoms, making it difficult for smart refractory materials to be industrialized.

[0004] Currently, no domestic or international research has achieved a technical solution that integrates high-temperature strength, resistance to molten slag erosion, real-time monitoring, and intelligent early warning and control. Nor has a complete preparation and construction system been established. Therefore, developing a refractory composite material for electric furnace bottoms that combines high performance, intelligent monitoring, and industrialized construction capabilities has become a technical challenge that the industry urgently needs to solve. Summary of the Invention

[0005] To overcome the shortcomings of the above-mentioned technologies, the present invention aims to provide a silicon carbide-based refractory composite preform for electric furnace bottoms and its preparation method, so as to solve the problems of traditional materials being unable to sense internal conditions and having delayed early warning, thereby improving the operational safety and service life of electric furnace bottoms.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A silicon carbide-based refractory composite preform for electric furnace bottom is characterized by comprising a matrix layer, a sensing layer, and a functional layer connected in sequence. The matrix layer is a silicon carbide-based refractory material block, which serves as the load-bearing core of the composite material. The sensing layer is embedded between the substrate layer and the functional layer, and includes sensing wires for collecting temperature and stress data of the preform; the sensing wires are fixedly laid on the surface of the substrate layer in a mesh structure and are fixed by sol-gel encapsulation. The functional layer is coated on the surface of the sensing layer, and has the dual functions of resisting slag erosion and signal transmission.

[0007] As a preferred embodiment, the raw materials for preparing the matrix layer include solid raw materials and an organic solvent comprising 14-18% of the total weight of the solid raw materials; the solid raw materials include the following components by weight: 90-94 parts of fused silicon carbide aggregate, 4.5-8 parts of binder, 0.5-2 parts of sintering aid, and 0.15-0.3 parts of carboxymethyl cellulose.

[0008] Furthermore, the fused silicon carbide aggregate adopts a three-stage particle size distribution, comprising, by mass percentage: 35-39% coarse particles with a particle size of 3 < ≤ 5 mm, 27-31% medium particles with a particle size of 1 < ≤ 3 mm, and 32-36% fine powder with a particle size of ≤ 1 mm; the SiC content of the fused silicon carbide aggregate is ≥ 99.0%; the binder is silicon nitride with a particle size D 50 ≤5μm, α-Si3N4 content ≥92%; the sintering aid is yttrium oxide, particle size D 50 ≤2μm, Y2O3 content ≥99.9%; the organic solvent is anhydrous ethanol. A three-stage gradation is used to form a continuous skeleton and gradient filling to achieve the densest packing, resulting in high matrix density, low porosity, and high strength; at the same time, it takes into account thermal conductivity, thermal shock resistance, and erosion resistance, perfectly adapting to the extreme working conditions of the electric furnace bottom.

[0009] As a preferred embodiment, the surface of the substrate layer is provided with grid positioning grooves for laying the sensing wire.

[0010] As a preferred embodiment, the sensing wire is made of graphene-platinum composite nanomaterials, with a platinum content of 7.5-12 wt%, 3-8 graphene layers, and a wire diameter of 50-100 μm. The platinum content determines high-temperature stability, conductivity, and accuracy, with 7.5-12 wt% being the optimal range. The number of graphene layers determines the skeleton strength, flexibility, and response speed, with 3-8 layers being the optimal range. The synergy of these two factors enables the sensing wire to achieve high accuracy, long lifespan, and high reliability under the extreme conditions of an electric furnace bottom. Smaller wire diameters result in greater sensitivity and finer precision, but also greater fragility; larger diameters offer greater durability and signal stability, but decrease accuracy. Therefore, this invention selects a wire diameter of 50-100 μm, achieving the best overall performance in terms of accuracy, lifespan, installation, and signal strength.

[0011] As a preferred embodiment, the sensing wire is encapsulated and fixed on the surface of the substrate layer using SiO2-Al2O3 composite sol.

[0012] Furthermore, the SiO2-Al2O3 composite sol has a solid content of 28-32%, comprising the following components by mass percentage: 45-55% SiO2 sol, 15-20% γ-Al2O3 micro powder, and the balance being water. This SiO2-Al2O3 composite sol has a moderate solid content, good fluidity, and cures uniformly and densely after coating, effectively encapsulating the sensing wire. It forms a continuous ceramic phase at high temperatures, exhibiting both good high-temperature stability and corrosion resistance, protecting the sensing wire from oxidation and slag corrosion. Simultaneously, its suitable dielectric properties prevent signal shielding, balancing protection and signal transmission, making it suitable for high-temperature electric furnace conditions.

[0013] As a preferred embodiment, the functional layer is made of zirconia composite material; the raw materials for preparing the zirconia composite material include the following components by weight: 82-88 parts of yttrium-stabilized zirconia powder, 6-10 parts of active silica powder, and 4-8 parts of aluminum dihydrogen phosphate solution; deionized water is added during the preparation of the zirconia composite material, and the amount of deionized water is 20-25% of the solid components in the raw materials; wherein, the particle size D of the yttrium-stabilized zirconia powder is... 50 ≤3μm, obtained by stabilization treatment with Y2O3 comprising 6-8% zirconium oxide by molar percentage; the specific surface area of ​​the active silica micropowder is ≥15m². 2 / g, SiO2 content ≥96%; the aluminum dihydrogen phosphate solution is an aqueous solution, wherein the mass concentration of aluminum dihydrogen phosphate is 45-50%, that is, the mass of aluminum dihydrogen phosphate solute is 45-50% of the mass of aluminum dihydrogen phosphate solution. 6-8 mol% Y2O3-stabilized zirconia can maintain a stable tetragonal phase structure at high temperatures without phase transformation cracking, and has excellent thermal shock resistance and high-temperature strength; at the same time, it has extremely strong resistance to slag erosion, can block steel slag penetration, and has good dielectric properties, does not shield sensor signals, and achieves a dual function of protection and transmission; the high specific surface area and high purity of active silica powder can fill the gaps between zirconia particles, significantly improving the density of the functional layer; at high temperatures, it reacts with zirconia and aluminum dihydrogen phosphate to form a high-melting-point silicate phase, enhancing the coating bonding strength and high-temperature stability, and further improving slag resistance and erosion resistance. Aluminum dihydrogen phosphate solution, as a high-temperature inorganic binder, provides good adhesion and coating properties at room temperature, and decomposes into a high-temperature resistant phosphate ceramic phase at high temperature, which firmly sintersects zirconium oxide and silicon micropowder into a whole, ensuring that the functional layer does not peel off or crack at high temperature and maintains structural integrity.

[0014] As a preferred embodiment, the sensing wire is fixedly welded with an output end, which is connected to the data transmission module via a wireless power supply coil to connect the sensing wire to the furnace's early warning response monitoring system. The output end, wireless power supply coil, and data transmission module are all encapsulated in high-temperature ceramic tubes and installed in grooves on the side of the substrate layer. The output end is a conductive component fixed to the end of the sensing wire, providing both an electrical connection path between the sensing wire and the wireless power supply coil, and a signal transmission path between the sensing wire and the data transmission module. The wireless power supply coil provides a stable 3.6-5.0V power supply to the sensing layer. The data transmission module uses Bluetooth / LoRa dual-mode transmission with a transmission distance ≥50m and a transmission frequency of 1-2 / s. The data transmission module incorporates an intelligent early warning algorithm; when a sudden local temperature rise rate ≥100℃ / min or stress >35MPa is detected, it automatically triggers the furnace's early warning response monitoring system to issue an audible and visual warning, and coordinates with the furnace cooling system to adjust the airflow to 500-1000m³ / min. 3 / h.

[0015] This invention also provides a method for preparing the above-mentioned silicon carbide-based refractory composite preform for electric furnace bottom, characterized by comprising the following steps: For the prefabrication of the matrix layer, a mixture of three-stage particle size distribution electrofused silicon carbide aggregate, silicon nitride binder, and yttrium oxide sintering aid is dry-mixed, and then mixed with carboxymethyl cellulose and anhydrous ethanol to obtain a mixture. The mixture is poured into a mold preheated to 40-60℃ and vibrated and tamped to form the shape. After curing at room temperature for 24 hours, the material is demolded and dried in stages at 80℃×4h, 120℃×6h, and 180℃×3h to obtain a billet. The billet is then heated to 1200-1300℃ at a rate of 2.5-3.5℃ / min under a nitrogen atmosphere and a slight positive pressure of 0.08-0.12MPa and held for 2-3 hours, followed by a high-temperature sintering at 1400-1500℃ for 2-3 hours to complete the prefabrication of the matrix layer. The sensing layer is laid out by etching grid positioning grooves on the surface of the substrate layer, embedding the sensing wire into the positioning grooves and straightening and fixing it, spraying SiO2-Al2O3 composite sol for encapsulation, curing at 120-150℃ for 1-2 hours, and polishing the surface to a smooth surface to obtain the sensing layer. Functional layer coating: Yttrium-stabilized zirconia powder, active silica micro powder, aluminum dihydrogen phosphate solution and deionized water are mixed and ball-milled to obtain functional layer slurry. The slurry is then coated onto the surface of the sensing layer in 2-3 layers by spraying. After drying at 110℃ for 2 hours, it is sintered in air at 900-1050℃ for 1.5-2 hours to form the functional layer. The lead-out end of the sensing wire is welded to the end of the sensing wire. The lead-out end is connected to the data transmission module through a wireless power supply coil. Then, the lead-out end, the wireless power supply coil and the data transmission module are encapsulated in a high-temperature ceramic tube. A groove is opened on the side of the substrate layer and the high-temperature ceramic tube is installed in the groove to obtain the silicon carbide-based refractory composite material preform for the furnace bottom of the electric furnace.

[0016] The present invention also provides a construction method for the above-mentioned silicon carbide-based refractory composite material prefabricated component for electric furnace bottom, which is characterized by including the following steps: For furnace bottom treatment, remove residual steel, slag and impurities from the electric furnace bottom, grind to a surface roughness Ra of 3.2-6.3, repair cracks and pits, preheat to 200-300℃ and hold for 1.5-2.5 hours; For precast component laying, the precast components are arranged in a staggered manner according to the furnace bottom design drawings. The joint width between adjacent precast components is 1.0-1.5mm. A SiC-Al2O3 high-temperature bonding layer is applied to the bottom, and the components are gently tapped to ensure tight splicing. For joint sealing, fill the joints with magnesium ultrafine powder tamping material, tamp it down in layers, and scrape the surface to ensure airtightness. The overall baking and activation process employs a segmented heating method: first, the temperature is increased at 7-9℃ / h to 280-320℃ and held for 5-7 hours; then, the temperature is increased at 11-13℃ / h to 580-620℃ and held for 3-5 hours; next, the temperature is increased at 14-16℃ / h to 950-1050℃ and held for 2-4 hours; finally, the temperature is increased at 18-22℃ / h to 1350-1450℃ and held for 2-3 hours, followed by natural cooling in the oven to below 50℃. System debugging involves connecting the data transmission module to the electric furnace's early warning response monitoring system, calibrating temperature and stress reference parameters on the host computer, setting early warning thresholds and linkage logic, testing the linkage function between the early warning response and the cooling system, and then putting it into normal use after debugging.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a silicon carbide-based refractory composite prefabricated component for electric furnace bottoms, featuring real-time temperature and stress sensing capabilities. It integrates high-temperature strength, slag erosion resistance, real-time monitoring of both temperature and stress parameters, and intelligent early warning and control, making it widely applicable to the refractory lining engineering of furnace bottoms in ultra-high-power electric furnaces, refining electric furnaces, and other steelmaking furnaces. By laying a gridded sensor wire, this invention achieves gridded and area-based real-time monitoring of the internal temperature and stress of the electric furnace bottom refractory material, completely solving the pain points of traditional materials' inability to sense internal conditions and delayed early warning.

[0018] This invention is the first to propose a sandwich composite structure of "substrate layer-sensor layer-functional layer", which deeply integrates intelligent sensing system with fire protection function, realizes real-time status monitoring of the material body, and is different from the existing external sensing and single-point monitoring technical solutions, filling the structural gap of intelligent refractory materials for electric furnace bottom.

[0019] This invention employs a matrix system of high-purity silicon carbide + silicon nitride binder + yttrium oxide additive, adapted to the arc radiation conditions at the bottom of an electric furnace. SiC provides the framework, withstanding high temperatures, arc erosion, and molten steel pressure; Si3N4 provides strong bonding, ensuring high-temperature resistance and forming an anti-oxidation and thermal shock network; Y2O3 optimizes sintering and interfaces, making the material denser, with stronger grain boundaries and greater slag resistance. The overall effect achieved is: high strength at 1600℃ without softening; no ablation or oxidation under arc radiation; thermal shock stability without cracking or peeling; resistance to molten slag erosion and long lifespan. The sensing layer uses graphene-platinum composite nanofibers, combining ultra-high sensitivity and high-temperature stability, capable of long-term operation at 1800℃ without the easy melting problem of existing platinum-rhodium wires. The functional layer uses a yttrium-stabilized zirconia composite coating, simultaneously achieving anti-molten slag erosion and signal transmission functions, overcoming the limitation of traditional coatings that only provide single-function protection.

[0020] This invention develops a complete process method of "prefabricated component preparation - precise layout of sensing layer - gradient coating of functional layer - standardized on-site construction", which solves the industry problems of sensing layer embedding, functional layer coating and furnace bottom adaptation construction. The method has clear steps and parameters, and can be directly adapted to existing refractory material production and construction equipment to achieve industrialization.

[0021] This invention is equipped with a wireless electromagnetic induction power supply and dual-mode data transmission system, which eliminates the drawbacks of wired power supply and avoids damage to the refractory material structure caused by the lead wire; it has a built-in intelligent early warning and cooling linkage algorithm and is connected to the early warning response monitoring system of the electric furnace, forming a closed-loop system of "monitoring-transmission-early warning-adjustment", realizing proactive handling of faults and greatly improving the operational safety of the furnace bottom. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the silicon carbide-based refractory composite material for the furnace bottom of the electric furnace of the present invention; In the diagram, 1 is the substrate layer; 2 is the sensing layer; and 3 is the functional layer. Detailed Implementation

[0023] To better explain the present invention, the main contents of the present invention are further illustrated below with reference to specific embodiments, but the contents of the present invention are not limited to the following embodiments.

[0024] like Figure 1As shown, the prefabricated silicon carbide-based refractory composite material for the bottom of an electric furnace of the present invention adopts a sandwich composite structure of "substrate layer 1 - sensing layer 2 - functional layer 3" from the inside out. The substrate layer 1 is located at the bottom and is a silicon carbide-based refractory material block, which serves as the load-bearing core of the composite material. The side of the substrate layer 1 away from the sensing layer 2 is the working surface that contacts the molten steel. The sensing layer 2 is embedded between the substrate layer 1 and the functional layer 3 and includes sensing wires for collecting temperature and stress data of the prefabricated component. The sensing wires are laid on the surface of the substrate layer 1 in a mesh structure and are fixed by sol-gel encapsulation. The functional layer 3 is coated on the surface of the sensing layer 2 for resisting slag erosion and signal transmission.

[0025] The composition and performance parameters of each layer of the silicon carbide-based refractory composite preform are as follows: The matrix layer, as the load-bearing core of the composite material, comprises the following solid raw materials by weight: 90-94 parts of fused silicon carbide aggregate, 4.5-8 parts of silicon nitride binder, 0.5-2 parts of yttrium oxide sintering aid, and 0.15-0.3 parts of carboxymethyl cellulose; plus 14-18% anhydrous ethanol by weight of the total solid raw materials; wherein, the fused silicon carbide aggregate adopts a three-stage particle size distribution, which by mass percentage includes: 35-39% coarse particles with a particle size of 3 < ≤ 5 mm, 27-31% medium particles with a particle size of 1 < ≤ 3 mm, and 32-36% fine powder with a particle size of ≤ 1 mm; the SiC purity of the fused silicon carbide aggregate is ≥ 99.0%; the particle size D of the silicon nitride binder is... 50 ≤5μm, α-Si3N4 content ≥92%; yttrium oxide sintering aid particle size D 50 ≤2μm, Y₂O₃ purity ≥99.9%. A grid positioning groove is set on the surface of the substrate layer for mounting the sensing layer. The substrate layer is sintered in sections under a nitrogen protective atmosphere to form a block with a bulk density ≥2.80g / cm³. 3 It has a room temperature compressive strength ≥80MPa, a high temperature flexural strength ≥25MPa at 1600℃, and a load softening temperature ≥1750℃, which can meet the high temperature bearing and anti-arc radiation requirements of electric furnace bottom.

[0026] The sensing layer is embedded between the substrate layer and the functional layer. The core component is a sensing wire with a diameter of 50-100 μm. The sensing wire uses graphene-platinum composite nanomaterials, with a platinum content of 7.5-12 wt% and 3-8 graphene layers. It can achieve simultaneous acquisition of dual parameters within a temperature range of 1000-1800℃ and a stress range of 0-50 MPa, with a measurement error ≤2%. FS; The sensing wires are evenly arranged in the grid positioning grooves of the substrate layer with a grid spacing of 10×10mm or 8×8mm; The sensing wires are encapsulated with SiO2-Al2O3 composite sol; The SiO2-Al2O3 composite sol includes SiO2 sol and γ-Al2O3 micro powder; The solid content of the SiO2-Al2O3 composite sol is 28-32%, including the following components by mass percentage: SiO2 sol 45-55%, γ-Al2O3 micro powder 15-20%, and the balance is deionized water; The encapsulation process includes preparing the encapsulation sol and coating it onto the sensing wire network structure for curing and encapsulation; After the encapsulation sol cures, an encapsulation layer is formed with a thickness of 0.2-0.5mm, which can effectively isolate the sensing wires from the erosion of molten slag and high-temperature gases, and ensure the long-term stability of the sensing wires.

[0027] The sensing wire has a lead-out end fixedly welded to its end. The lead-out end is connected to the data transmission module via a wireless power supply coil. The data transmission module is connected to the early warning response monitoring system of the electric furnace. The lead-out end, the wireless power supply coil, and the data transmission module are encapsulated in a high-temperature ceramic tube.

[0028] A functional layer, 1.2-2.0 mm thick, is coated on the surface of the sensing layer and is made of zirconia composite material. The raw materials for preparing the zirconia composite material include the following components by weight: 82-88 parts yttrium-stabilized zirconia powder, 6-10 parts activated silica powder, and 4-8 parts aluminum dihydrogen phosphate solution; deionized water is added, with the amount of deionized water being 20-25% of the solid components (yttrium-stabilized zirconia powder, activated silica powder, and aluminum dihydrogen phosphate solid) in the raw materials; wherein, the particle size D of the yttrium-stabilized zirconia powder is... 50 ≤3μm, obtained by stabilization treatment with Y2O3 accounting for 6-8% of zirconium oxide by molar percentage; the specific surface area of ​​the active silica micropowder is ≥15m². 2 / g, SiO2 content ≥96%; aluminum dihydrogen phosphate aqueous solution as binder, wherein the mass concentration of aluminum dihydrogen phosphate is 45-50%. The functional layer has dual functions of resisting slag erosion and signal transmission, with a bulk density ≥5.5g / cm³. 3 With a slag erosion resistance level ≥RA3, it can effectively prevent molten slag from penetrating into the sensing layer, while ensuring stable transmission of sensing signals without signal shielding.

[0029] The silicon carbide-based refractory composite material of this invention is equipped with a wireless power supply and data transmission module. It employs electromagnetic induction coupling technology to provide a stable 3.6-5.0V power supply to the sensing layer. The data transmission module uses Bluetooth / LoRa dual-mode transmission, with a transmission distance ≥50m and a transmission frequency of 1-2 times / s. The data transmission module has a built-in intelligent early warning algorithm and is connected to the early warning response monitoring system of the electric furnace. When the data transmission module detects a local temperature rise rate ≥100℃ / min or stress >35MPa, it automatically triggers an audible and visual warning from the early warning response monitoring system and coordinates with the electric furnace cooling system to adjust the airflow to 500-1000m³ / min. 3 / h enables rapid fault handling.

[0030] The specific steps of the preparation and construction method of the silicon carbide-based refractory composite preform of the present invention are as follows: The preform preparation stage includes: The first step is the prefabrication of the matrix layer. The three-stage particle size distribution of fused silicon carbide aggregate, silicon nitride binder, and yttrium oxide sintering aid are dry-mixed for 3-5 minutes. Carboxymethyl cellulose and anhydrous ethanol are then added and wet-mixed for 8-12 minutes, controlling the moisture content of the mixture to 3.5-5.0%. The mixture is poured into a mold preheated to 40-60℃, added in three layers, and tamped using 50Hz vibration. The molding pressure is 25-30 MPa, held for 10 seconds, and cured at room temperature for 24 hours. After demolding, the material is dried in stages at 80℃ for 4 hours, 120℃ for 6 hours, and 180℃ for 3 hours. Then, under a nitrogen atmosphere (purity ≥99.99%, slightly positive pressure in the furnace 0.08-0.12MPa), the temperature is increased at 3℃ / min to 1200-1300℃ and held for 2-3 hours. Subsequently, the temperature is increased to 1400-1500℃ and held for 2-3 hours (furnace pressure 0.08-0.12MPa) to complete high-temperature sintering and prefabrication of the substrate layer. The second step is to lay out the sensor layer. A laser engraving machine is used to engrave a grid positioning groove with a width of 0.6-0.8mm and a depth of 0.8-1.2mm on the surface of the substrate layer. The sensor wire is embedded into the grid positioning groove and straightened and fixed. The SiO2-Al2O3 composite sol for encapsulation is sprayed and cured at 120-150℃ for 1-2 hours. The surface is then polished until smooth. The third step is the functional layer coating. Yttrium-stabilized zirconia powder, active silica micro powder, aluminum dihydrogen phosphate binder and deionized water are mixed and ball-milled for 2-3 hours to obtain a functional layer slurry. The slurry is then coated onto the surface of the sensing layer in 2-3 coats using a spraying method. Each coat is 0.6-1.0 mm thick. After drying at 110℃ for 2 hours, the sintering is carried out at 900-1050℃ in air for 1.5-2 hours to form the functional layer. The fourth step is module integration. Weld the lead-out ends of the sensing wire, install the wireless power supply coil and data transmission module, and encapsulate the lead-out ends, wireless power supply coil and data transmission module with a high-temperature ceramic tube. A groove is opened on the side of the substrate layer. The groove structure matches the high-temperature ceramic tube. The lead-out ends, wireless power supply coil and data transmission module encapsulated with high-temperature ceramic tube are inserted into or fixed in the side groove with high-temperature adhesive to obtain the intelligent silicon carbide-based refractory composite material preform.

[0031] The on-site construction phase includes: The first step is to treat the furnace bottom base layer, remove residual steel, slag and impurities from the electric furnace bottom, grind it with an angle grinder until the surface roughness Ra is 3.2-6.3, repair cracks and pits ≤3mm with magnesia refractory mortar, preheat to 200-300℃ and keep it at that temperature for 2 hours; The second step is to lay the precast components. The precast components are arranged in a staggered manner according to the furnace bottom design drawings. The preferred size of a single precast component is 400×400×150mm. The width of the splice joint between adjacent precast components is 1.0-1.5mm. A 1.0mm thick SiC-Al2O3 high-temperature adhesive layer is applied to the bottom and gently tapped to ensure tight splicing. The third step is to seal the joints. Fill the joints with magnesium ultrafine powder ramming material with MgO content ≥85%, ram the material in layers (each layer thickness ≤10mm), and scrape the surface to ensure airtightness. The fourth step is overall baking and activation, which is carried out using a segmented heating method. The temperature is increased at 7-9℃ / h to 280-320℃ and held for 5-7 hours. Then, the temperature is increased at 11-13℃ / h to 580-620℃ and held for 3-5 hours. Next, the temperature is increased at 14-16℃ / h to 950-1050℃ and held for 2-4 hours. Finally, the temperature is increased at 18-22℃ / h to 1350-1450℃ and held for 2-3 hours. The oven is then allowed to cool naturally to below 50℃. The fifth step is system debugging. The data transmission module is connected to the early warning response monitoring system of the electric furnace via wireless transmission. The host computer is used to calibrate the temperature and stress reference parameters, set the early warning threshold and linkage logic, and test the linkage function between the early warning response and the cooling system. After debugging, it can be put into normal use.

[0032] The present invention will be further analyzed and explained below through specific embodiments. Embodiments 1-3 all adopt the solution of the present invention, and are specifically described below.

[0033] Example 1 A silicon carbide-based refractory composite preform for electric furnace bottoms, comprising a matrix layer, a sensing layer, and a functional layer connected in sequence, according to the present invention. The matrix layer, by weight, comprises the following solid raw materials: 90 parts of fused silicon carbide aggregate and 8 parts of silicon nitride binder (D...). 50=3μm, α-Si3N4≥93%), yttrium oxide sintering aid 1.7 parts (D 50 =1μm, Y2O3≥99.95%), 0.3 parts of carboxymethyl cellulose (industrial grade, 2% aqueous solution viscosity ≥500mPa•s at 25℃). An additional 16 parts of anhydrous ethanol (industrial grade, purity ≥99.5%) are added during the preparation process. The electrofused silicon carbide aggregate includes 34.0 parts of coarse electrofused silicon carbide particles with a particle size of 3 < ≤ 5mm, 26.0 parts of medium electrofused silicon carbide particles with a particle size of 1 < ≤ 3mm, and 30.0 parts of fine electrofused silicon carbide powder with a particle size of ≤ 1mm (all SiC purity ≥ 99.2%). By mass percentage, these represent 37.8% coarse particles with a particle size of 3 < ≤ 5mm, 28.9% medium particles with a particle size of 1 < ≤ 3mm, and 33.3% fine powder with a particle size of ≤ 1mm.

[0034] The sensing layer uses a 75μm diameter graphene-platinum composite sensing wire. In the graphene-platinum composite material, the platinum content is 9wt%, the number of graphene layers is 5, and the sensing wire is evenly arranged in a 10×10mm grid. In the encapsulation sol, the content is 32% solids, consisting of 50% SiO2 sol, 18% γ-Al2O3 micro powder, and 32% deionized water. The thickness of the encapsulation layer is 0.3mm.

[0035] Functional layers, by weight, contain D 50 86 parts of 8 mol% Y₂O₃ stabilized zirconium oxide powder with a specific surface area of ​​20 m² and a diameter of 2 μm. 2 The coating consists of 8 parts of active silicon micropowder with a SiO2 content ≥ 96% and 6 parts of aluminum dihydrogen phosphate solution with a mass concentration of 48%; 22 parts of deionized water are added, and the weight of deionized water accounts for 22.7% of the total weight of Y2O3 stabilized zirconia powder (86 parts), active silicon micropowder (8 parts), and aluminum dihydrogen phosphate solute (2.88 parts); the total coating thickness is 1.5 mm.

[0036] The preparation method of the above-mentioned silicon carbide-based refractory composite preform is as follows: First, dry mix all solid raw materials of the matrix layer for 5 minutes, then add carboxymethyl cellulose and anhydrous ethanol and wet mix for 10 minutes. In a mold preheated to 50°C, add the materials in layers and vibrate and tamp to form the matrix. Vibrate each layer for 40 seconds, with a forming pressure of 28 MPa and a holding pressure of 10 seconds. After curing at room temperature (0-25°C) for 24 hours, dry in stages at 80°C for 4 hours, 120°C for 6 hours, and 180°C for 3 hours. Then, in a nitrogen atmosphere with a purity of 99.99% (furnace pressure 0.1 MPa), heat to 1200°C at 3°C / min and hold for 2 hours. Then, continue to heat to 1450°C and hold for 3 hours (furnace pressure 0.1 MPa) to complete sintering and obtain the matrix layer. A fiber laser engraving machine was used to engrave a grid positioning groove with a width of 0.7 mm and a depth of 1.0 mm on the surface of the substrate layer, with an engraving accuracy of ±0.05 mm. After embedding the sensing wire, an encapsulating sol was sprayed on and cured at 120℃×1h and 150℃×1h to obtain the sensing layer. The functional layer slurry was ball-milled at 300 r / min for 2 h, and then sprayed in two layers at 0.4 MPa pressure. The first layer was 0.8 mm thick, and the second layer was 0.7 mm thick after drying, for a total thickness of 1.5 mm. The slurry was dried at 110℃ for 2 h and sintered at 1000℃ for 1.5 h to obtain the functional layer. Finally, the sensor wire lead-out end is welded, and a wireless power supply coil with a diameter of 20mm and 50 turns and a LoRa transmission module with a working frequency of 433MHz are installed. The coil is encapsulated in an Al2O3 high-temperature ceramic tube, and a groove is opened on the side of the substrate layer. The groove structure matches the high-temperature ceramic tube. The lead-out end, wireless power supply coil and data transmission module encapsulated in the high-temperature ceramic tube are inserted or placed in the side groove to obtain a smart silicon carbide-based refractory composite material preform.

[0037] The construction method for the above-mentioned silicon carbide-based refractory composite precast blocks is as follows: First, remove the residual steel and slag from the bottom of the electric furnace, grind the surface with an angle grinder until the surface roughness Ra=4.5μm, repair the ≤3mm cracks with magnesia refractory slurry with Al2O3-MgO≥90%, and preheat at 240℃ for 2h. Precast blocks with dimensions of 400×400×150mm are laid out in a staggered pattern with a gap of 1.2mm between blocks, and a 1.0mm thick SiC-Al2O3 high-temperature adhesive layer is applied to the bottom. Joint filler: Magnesium-based ultrafine powder ramming mix with MgO ≥ 85% (D) 50 ≤5μm) and compact in layers; The overall baking process follows a curve: heating at 8℃ / h to 300℃ and holding for 6 hours, heating at 12℃ / h to 600℃ and holding for 4 hours, heating at 15℃ / h to 1000℃ and holding for 3 hours, and heating at 20℃ / h to 1400℃ and holding for 2 hours. After natural cooling to 50℃, the system is started for debugging. The wireless power supply voltage is set to 4.2V. The host computer is used to calibrate the temperature reference to 1600℃ and the stress reference to 35MPa. The warning threshold is set to a temperature rise ≥100℃ / min or stress >35MPa. The airflow of the linkage cooling system is 800m³ / min. 3 During the system debugging phase, the data transmission frequency is 1 time / s, and the calibration accuracy is improved to ±1% FS.

[0038] Performance test results The bulk density of the matrix layer in this embodiment was measured to be 2.84 g / cm³. 3The room temperature compressive strength is 84 MPa, the apparent porosity is 14.2%, the high temperature flexural strength at 1600℃ is 27 MPa, the load softening temperature (0.2 MPa, deformation 0.6%) is 1780℃, the oxidation weight loss rate at 1800℃ is 1.8%, and the thermal shock stability (repeated water cooling at 1100℃) is ≥25 cycles; the functional layer bulk density is 5.52 g / cm³. 3 The coating bonding strength is 3.6 MPa, and the slag penetration depth after holding at 1600℃ for 3 hours is 3.8 mm. The intelligent sensing system has a temperature measurement range of 1000~1800℃ with a temperature measurement error of ±1.2% FS, a stress measurement range of 0~50 MPa with a stress measurement error of ±1.5% FS, an early warning response time of 0.35s, a wireless transmission distance of ≥50m, and can work continuously and stably for 680 heats under actual electric furnace smelting conditions.

[0039] Example 2 This embodiment presents a high-lifetime optimization scheme, adjusting the formula and process parameters based on Example 1, as follows: In the matrix layer raw materials, the proportion of coarse fused silicon carbide particles with a particle size of 3 < ≤ 5 mm increased to 35.0 parts, the proportion of medium fused silicon carbide particles with a particle size of 1 < ≤ 3 mm increased to 28.0 parts, and the proportion of fine fused silicon carbide powder with a particle size of ≤ 1 mm increased to 31.0 parts; the total amount of fused silicon carbide aggregate is 94 parts, the amount of silicon nitride binder is adjusted to 4.8 parts, the amount of yttrium oxide sintering aid is adjusted to 1 part, and the amount of carboxymethyl cellulose is adjusted to 0.2 parts; that is, the fused silicon carbide aggregate by mass percentage includes: 37.2% coarse particles with a particle size of 3 < ≤ 5 mm, 29.8% medium particles with a particle size of 1 < ≤ 3 mm, and 33% fine powder with a particle size of ≤ 1 mm; 17 parts of anhydrous ethanol are added; the sintering temperature of the precast block matrix layer pre-sintering process is increased from 1450℃ to 1500℃ and held for 3 hours, and the furnace pressure is adjusted to 0.12 MPa; The thickness of the sensor layer encapsulation layer was adjusted to 0.4mm; The thickness of the functional layer was increased to 2.0 mm; in the raw materials of the functional layer, the amount of Y2O3 stabilized zirconia powder was adjusted to 82 parts, the amount of active silica powder was adjusted to 10 parts, and the amount of 48% aluminum dihydrogen phosphate solution was adjusted to 8 parts; after adjustment, the amount of deionized water remained at 22 parts, which is 23% of the total mass of the solid components; solid components: 82 parts of Y2O3 stabilized zirconia powder, 10 parts of active silica powder, and 3.84 parts of aluminum dihydrogen phosphate solute.

[0040] During the on-site construction phase, the overall baking and activation process at 1400℃ was extended to 3 hours, and the wireless power supply voltage was increased to 5.0V.

[0041] Performance test results The bulk density of the matrix layer in this embodiment was measured to be 2.86 g / cm³. 3The room temperature compressive strength is 87 MPa, the apparent porosity is 13.5%, the high temperature flexural strength at 1600℃ is 29 MPa, the load softening temperature is 1790℃, the oxidation weight loss rate at 1800℃ is 1.5%, and the thermal shock stability is ≥28 cycles; the functional layer bulk density is 5.58 g / cm³. 3 The coating bonding strength is 3.9 MPa, the slag penetration depth is 3.2 mm; the temperature measurement error of the intelligent sensing system is ±1.3% FS, the stress measurement error is ±1.6% FS, the early warning response time is 0.38 s, the number of furnaces with continuous stable operation is increased to 720, and the other performance indicators are comparable to those of Example 1.

[0042] Example 3 This embodiment presents a high-precision monitoring optimization scheme, which adjusts the formula and process parameters based on Embodiment 1, as follows: In the matrix layer raw materials, the amount of fine fused silicon carbide powder with a particle size ≤1mm is increased to 32 parts, coarse fused silicon carbide particles with a particle size ≤5mm (3 < particle size) are 34.0 parts, and medium fused silicon carbide particles with a particle size ≤3mm (1 < particle size) are 26.0 parts, increasing the total amount of fused silicon carbide to 92 parts. The amount of silicon nitride binder is reduced to 7 parts, yttrium oxide sintering aid is reduced to 0.7 parts, and carboxymethyl cellulose is 0.3 parts. The fused silicon carbide aggregate, by mass percentage, includes: 37% coarse particles with a particle size ≤5mm (3 < particle size), 28.2% medium particles with a particle size ≤3mm (1 < particle size), and 34.8% fine powder with a particle size ≤1mm.

[0043] The sensing layer uses a graphene-platinum composite sensing wire with a diameter of 50μm, a platinum content of 12wt%, 8 graphene layers, and a grid spacing of 8×8mm; the laser grooving parameters are adjusted to a groove width of 0.6mm and a groove depth of 0.8mm, and the grid accuracy is improved to ±0.03mm. The sintering temperature of the functional layer was increased to 1050℃ and held for 1.5 hours; during the system debugging phase, the data transmission frequency was increased to 2 times / s and the calibration accuracy was increased to ±0.8% FS.

[0044] Performance test results The bulk density of the matrix layer in this embodiment was measured to be 2.83 g / cm³. 3 The room temperature compressive strength is 82 MPa, the apparent porosity is 14.5%, the high temperature flexural strength at 1600℃ is 26 MPa, the load softening temperature is 1775℃, the oxidation weight loss rate at 1800℃ is 1.9%, and the thermal shock stability is ≥24 cycles; the functional layer bulk density is 5.55 g / cm³. 3The coating bonding strength is 3.5MPa, the slag penetration depth is 3.9mm; the temperature measurement error of the intelligent sensing system is ±0.9% FS, the stress measurement error is ±1.0% FS, the early warning response time is 0.25s, the spatial monitoring resolution is 8mm×8mm, the continuous stable operation is 650 heats, and the other performance indicators meet the requirements for use in electric furnace bottoms.

[0045] This invention enables real-time, gridded, and area-based monitoring of the internal temperature and stress of the refractory material at the bottom of an electric furnace, completely solving the pain points of traditional materials being unable to sense the internal state and having delayed early warnings.

[0046] This invention optimizes the compatibility between the sensing element and the refractory substrate, solves the problems of oxidation, melting, and signal attenuation of the sensing element at a high temperature of 1800℃, and ensures the long-term stable operation of the intelligent monitoring system.

[0047] This invention breaks through the signal shielding bottleneck, achieves efficient transmission of sensing signals, and avoids interference from the refractory substrate on the monitoring data.

[0048] This invention provides a complete and industrially feasible method for the preparation and on-site construction of prefabricated components, enabling standardized production and precise laying of composite materials, and adapting to the complex structural morphology of electric furnace bottoms.

[0049] This invention constructs an intelligent closed-loop system of "monitoring-transmission-early warning-automatic adjustment" to realize real-time linkage handling of faults such as local overheating and excessive stress, thereby improving the operational safety and service life of the electric furnace bottom.

[0050] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made based on the inventive concept of the present invention and the description and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention. Any other parts not described are considered prior art.

Claims

1. A silicon carbide-based refractory composite prefabricated component for electric furnace bottom, characterized in that, It includes a substrate layer, a sensing layer, and a functional layer connected in sequence; The matrix layer is a silicon carbide-based refractory block, which serves as the load-bearing core of the composite material. The sensing layer is embedded between the substrate layer and the functional layer, and includes a sensing wire for collecting temperature and stress data of the preform. The sensing wire is laid in a mesh structure on the surface of the substrate layer and fixed by sol-gel encapsulation. The functional layer is coated on the surface of the sensing layer to resist slag erosion and facilitate signal transmission.

2. The silicon carbide-based refractory composite preform according to claim 1, characterized in that, The raw materials for preparing the silicon carbide-based refractory blocks include solid raw materials and an organic solvent accounting for 14-18% of the total weight of the solid raw materials; the solid raw materials include the following components by weight: 90-94 parts of fused silicon carbide aggregate, 4.5-8 parts of binder, 0.5-2 parts of sintering aid, and 0.15-0.3 parts of carboxymethyl cellulose.

3. The silicon carbide-based refractory composite preform according to claim 2, characterized in that, The fused silicon carbide aggregate adopts a three-stage particle size distribution, comprising, by mass percentage: 35-39% coarse particles with a particle size of 3 < ≤ 5 mm, 27-31% medium particles with a particle size of 1 < ≤ 3 mm, and 32-36% fine powder with a particle size of ≤ 1 mm; the SiC content of the fused silicon carbide aggregate is ≥ 99.0%; the binder is silicon nitride with a particle size D 50 ≤5μm, α-Si3N4 content ≥92%; the sintering aid is yttrium oxide, particle size D 50 ≤2μm, Y2O3 content ≥99.9%; the organic solvent is anhydrous ethanol.

4. The silicon carbide-based refractory composite preform according to claim 2 or 3, characterized in that, The substrate layer surface is provided with grid positioning grooves for laying the sensing wire.

5. The silicon carbide-based refractory composite preform according to claim 1, characterized in that, The sensing wire is made of graphene-platinum composite nanomaterial; in the graphene-platinum composite nanomaterial, the platinum content is 7.5-12wt% and the number of graphene layers is 3-8.

6. The silicon carbide-based refractory composite preform according to claim 1, characterized in that, The sol is a SiO2-Al2O3 composite sol; the SiO2-Al2O3 composite sol comprises the following components by mass percentage: 45-55% SiO2 sol, 15-20% γ-Al2O3 micro powder, and the balance being water.

7. The silicon carbide-based refractory composite preform according to claim 1, characterized in that, The functional layer is made of zirconia composite material; the raw materials for preparing the zirconia composite material include the following components by weight: 82-88 parts of yttrium-stabilized zirconia powder, 6-10 parts of active silica powder, and 4-8 parts of aluminum dihydrogen phosphate solution; deionized water is added during the preparation of the zirconia composite material, and the amount of deionized water is 20-25% of the solid components in the raw materials; wherein, the particle size D of the yttrium-stabilized zirconia powder is... 50 ≤3μm; specific surface area of ​​active silica powder ≥15m² 2 / g, SiO2 content ≥96%; the aluminum dihydrogen phosphate solution is an aqueous solution, wherein the mass concentration of aluminum dihydrogen phosphate is 45-50%.

8. The silicon carbide-based refractory composite preform according to any one of claims 1-7, characterized in that, The sensing wire has a lead-out end fixedly welded to its end. The lead-out end is used to connect to the data transmission module via a wireless power supply coil to connect the sensing wire to the early warning response monitoring system of the electric furnace. The lead-out end, the wireless power supply coil, and the data transmission module are encapsulated in a high-temperature ceramic tube and installed on the side of the substrate layer.

9. A method for preparing a silicon carbide-based refractory composite preform for an electric furnace bottom as described in any one of claims 1-8, characterized in that, Includes the following steps: The matrix layer is prefabricated by mixing the matrix layer material and pouring it into a mold, vibrating and tamping it into shape, curing it at room temperature, demolding it, and drying it in sections to obtain a blank. The blank is then heated to 1200-1300℃ and held for 2-3 hours under an inert atmosphere and a slight positive pressure of 0.08-0.12MPa, followed by high-temperature sintering at 1400-1500℃ for 2-3 hours to obtain the matrix layer. The sensing layer is laid out by engraving grid positioning grooves on the surface of the substrate layer, embedding the sensing wire into the grid positioning grooves and straightening and fixing it, spraying encapsulation sol, curing, and polishing the surface to a smooth surface to obtain the sensing layer. Functional layer coating involves mixing the functional layer raw materials with water and ball milling to obtain a functional layer slurry. The slurry is then coated onto the surface of the sensing layer. After drying, it is sintered in air at 900-1050℃ for 1.5-2 hours to form the functional layer.

10. A construction method for a silicon carbide-based refractory composite prefabricated component for the furnace bottom of an electric furnace as described in any one of claims 1-8, characterized in that, Includes the following steps: For furnace bottom treatment, after cleaning the electric furnace bottom, grind it to a surface roughness Ra of 3.2-6.3, repair cracks and pits, preheat to 200-300℃ and hold for 1.5-2.5 hours; For the laying of silicon carbide-based refractory composite prefabricated components, the silicon carbide-based refractory composite prefabricated components are arranged in a staggered manner according to the furnace bottom design drawings. The joint width between adjacent prefabricated components is 1.0-1.5mm. A high-temperature adhesive layer is applied to the bottom, and the components are gently tapped and compacted to ensure tight splicing. For joint sealing, fill the joint with tamping material, tamp it down in layers, and scrape the surface to ensure airtightness. The overall baking and activation process employs a segmented heating method. The temperature is increased at 7-9℃ / h to 280-320℃ and held for 5-7 hours. Then, the temperature is increased at 11-13℃ / h to 580-620℃ and held for 3-5 hours. Next, the temperature is increased at 14-16℃ / h to 950-1050℃ and held for 2-4 hours. Finally, the temperature is increased at 18-22℃ / h to 1350-1450℃ and held for 2-3 hours. The oven is then allowed to cool naturally to below 50℃.

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