Preparation method of high-speed rail special >=25KN function ceramic rod-shaped insulator

Abstract

This invention discloses a method for preparing high-speed rail-specific ≥25KN functional ceramic rod insulators, belonging to the technical field of high-speed rail transmission line insulation component preparation. It aims to solve the defects of existing preparation methods, such as insufficient mechanical strength, difficulty in balancing insulation and strength, high energy consumption, weak weather resistance, and poor product consistency, meeting the stringent requirements of high-speed rail operation at speeds of 450km / h and above. The method includes eight steps: core-shell composite raw material preparation, high-pressure vacuum-extrusion composite molding, gradient temperature-controlled drying and microwave pre-dehydration, low-temperature atmosphere sintering and microwave-assisted densification, plasma-assisted surface modification treatment, precision binding and assembly, AI-based full-process detection and screening, and packaging and warehousing. This invention reduces energy consumption by more than 30%, increases product qualification rate to over 98%, reduces production costs by more than 25%, extends service life to over 30 years, has strong process feasibility, is easy to achieve industrial-scale production, and is suitable for core components such as high-speed rail contact networks and traction substations, making it highly valuable for widespread application.

Description

Technical Field

[0001] This invention belongs to the technical field of insulation component preparation for high-speed railway transmission lines, specifically relating to a method for preparing a high-speed railway-specific ≥25KN functional ceramic rod insulator. It is applicable to core components such as the contact network and traction substations of high-speed electrified railways with speeds of 450km / h and above. The prepared insulator can stably withstand ≥25KN electromechanical destructive loads and has excellent insulation performance, impact resistance, pollution resistance, and lightweight characteristics, making it suitable for the stringent requirements of high-speed railways with high vibration, high voltage, complex climate, and long service life. Background Technology

[0002] Functional ceramic rod insulators are core components of the high-speed railway catenary system. They mainly play a dual role in suspending contact wires, isolating current, and transmitting mechanical loads (wire weight, wind load, ice load, and vibration load from high-speed train operation). Their mechanical strength, insulation performance, weather resistance, impact resistance, and manufacturing stability directly determine the safe and reliable operation of the high-speed railway catenary, and are one of the core supporting conditions for ensuring that high-speed railway speeds are increased to 450 km / h and above.

[0003] Currently, the manufacturing technology of ceramic rod insulators for high-speed rail still faces many bottlenecks. Existing products generally suffer from insufficient mechanical strength (bending strength mostly stays at 8-12KN, and it is difficult to break through 16KN), poor toughness, difficulty in achieving both insulation performance and mechanical strength, high energy consumption in the manufacturing process, large quality fluctuations, insufficient pollution and corrosion resistance, and excessive weight. These issues prevent them from meeting the requirements of high-speed rail for mechanical loads of ≥25KN and complex operating environments. Specific defects are as follows: Unreasonable raw material formulation: Existing manufacturing processes mostly use single alumina-based raw materials or simply add toughening components such as zirconium oxide, without forming a targeted composite formulation system. This results in insulators either having insufficient mechanical strength or reduced insulation performance after toughening, making it difficult to balance mechanical loads of ≥25KN with excellent insulation performance. At the same time, poor particle size distribution of raw materials easily leads to microscopic defects such as pores and cracks, further reducing product strength and service life. Moreover, the product density is too high, which does not meet the lightweight requirements of high-speed rail.

[0004] The molding process has shortcomings: existing molding methods mostly use single dry pressing or extrusion molding, and the molding pressure and holding pressure parameters are not reasonably controlled, resulting in uneven internal density and high porosity (usually >3%) of the blank, and defects such as delamination and cracks are prone to occur; some processes use manual or semi-automatic molding, which results in large parameter fluctuations, poor product consistency, and difficulty in meeting the high precision and high stability requirements of high-speed railway insulators. At the same time, the blank is difficult to trim after molding, which easily leads to waste of raw materials.

[0005] The sintering process is energy-intensive and lacks densification: Existing processes mostly use traditional high-temperature air sintering, with sintering temperatures as high as 1400-1500℃, resulting in huge energy consumption. Moreover, the temperature gradient is not well controlled during the sintering process, which can easily lead to grain growth in insulators, internal stress concentration, and problems such as cracking and deformation. Although some processes use atmosphere sintering, they do not combine microwave-assisted densification technology, making it difficult to improve the density of insulators and the mechanical strength cannot be stably reached ≥25KN. In addition, the sintering cycle is long (usually 12-18h), resulting in low production efficiency.

[0006] Poor surface treatment adaptability: High-speed railway insulators need to withstand harsh environments such as rain, dust, and salt spray for a long time. Existing surface treatments mostly adopt a single glazing or sandblasting process. The glaze layer is not firmly bonded to the substrate, and it is easy to fall off and crack. It is not resistant to dirt and corrosion. The sandblasting process does not undergo plasma pretreatment, resulting in poor coating adhesion. It cannot effectively resist the erosion of industrial dust and salt mist along the high-speed railway line, and is prone to flashover and corrosion failure. In addition, the surface smoothness is insufficient, and dirt is easy to accumulate.

[0007] Insufficient gluing and overall process control: The gluing process for insulator ceramic parts and metal accessories is simple, the adhesive formula is unreasonable, and vibration degassing and precise coaxiality control are not carried out during the gluing process, resulting in insufficient gluing strength, gaps at the interface, and easy separation of metal accessories from ceramic parts; at the same time, the automation level of the entire preparation process (from material preparation to testing) is low, AI big data management technology has not been introduced, parameter collection, analysis and adjustment are not timely, quality control is difficult, and the product qualification rate is low (usually <85%).

[0008] Inadequate testing processes: Existing testing mainly focuses on the mechanical strength and insulation performance of finished products, without setting up online non-destructive testing for intermediate stages such as forming, sintering, and surface treatment. This makes it impossible to detect defects in the blank, sintering, and surface coating in a timely manner, resulting in unqualified products flowing into subsequent processes, increasing production costs. Furthermore, the testing indicators are not comprehensive, and fatigue strength testing is not set up for the high vibration requirements of high-speed rail, making it difficult to ensure the long-term stable operation of products.

[0009] To address the shortcomings of existing technologies and considering the stringent requirements for high-speed rail-specific functional ceramic rod insulators with a strength of ≥25KN, it is urgent to develop a novel manufacturing method. This method should involve collaborative innovation in raw material formulation, molding, sintering, surface treatment, gluing, and overall process control to solve problems such as insufficient strength, high energy consumption, poor consistency, weak weather resistance, and insufficient lightweighting in existing processes. The goal is to achieve insulators with a mechanical strength of ≥25KN, a density of ≥98%, and a porosity of <1%, while also ensuring excellent insulation, impact resistance, and pollution resistance. Simultaneously, it should reduce energy consumption, improve production efficiency and product qualification rate, and meet the requirements of high-speed rails operating at speeds of 450km / h and above during trial runs. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of existing methods for preparing ceramic rod insulators for high-speed rail, such as unreasonable raw material formulation, poor molding density, high sintering energy consumption, weak surface treatment adaptability, insufficient adhesive strength, lack of whole-process control, and inability to consistently achieve product strength of ≥25KN. This invention provides a method for preparing high-speed rail-specific ≥25KN functional ceramic rod insulators, solving the aforementioned technical problems and achieving a synergistic improvement in the mechanical strength, insulation performance, impact resistance, weather resistance, and lightweight of the insulators. Simultaneously, it reduces preparation energy consumption, improves production efficiency and product qualification rate, and meets the stringent requirements of high-speed rail's high-vibration, high-voltage, and complex environments.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator includes the following steps: S1: Preparation of core-shell composite raw materials: S11: Raw material selection and proportioning: Weigh the core layer raw materials and shell layer raw materials according to the mass percentage. The core layer raw materials include: 30-35% calcined pure cordierite, 25-30% nano alumina, 5-8% zirconium oxide, 1-3% nano SiC, 13-18% ceramic short fibers, and 3-5% feldspar. The shell layer raw materials include: 90-95% α-alumina, 1-2% magnesium oxide, 1-3% silicon oxide, and 0.5-1% boron oxide. The volume ratio of core layer raw materials to shell layer raw materials is 6:4-7:3 to ensure that the core layer focuses on toughness and strength, while the shell layer focuses on insulation and pollution resistance, taking into account the core performance requirements of high-speed railway insulators.

[0012] S12: Particle size distribution optimization: The core layer raw materials and shell layer raw materials are crushed and sieved separately. The particle size of the core layer raw materials is controlled at 1-5μm, and the particle size of the shell layer raw materials is controlled at 0.5-2μm. Multi-stage particle size distribution is adopted to reduce the porosity of the raw materials and improve the compactness of the subsequent green body. At the same time, 0.2-0.5% of the total raw material amount of dispersant (sodium polycarboxylate) and 1-3% of the total raw material amount of binder (polyvinyl alcohol) are added to improve the mixing uniformity of the raw materials and avoid agglomeration.

[0013] S13: Mixing and Granulation: Add the prepared core layer raw material to a ball mill, add deionized water (solid-liquid ratio 1:1.2-1:1.5), and ball mill for 8-12 hours at a speed of 300-400 r / min. After ball milling, remove iron and sieve (300 mesh) to obtain core layer slurry. Prepare shell layer slurry using the same method. Spray dry and granulate the core layer slurry and shell layer slurry separately, controlling the particle size after granulation to be 20-50 μm and the moisture content to be 8-12%, to obtain core layer particles and shell particles, ensuring that the granulated particles are uniform and suitable for subsequent molding processes.

[0014] S2: High-pressure vacuum extrusion composite molding: S21: Mold pretreatment: Clean and dry the customized rod insulator mold, and apply a layer of release agent (silane coupling agent) to the inner wall of the mold. The thickness of the release agent is 0.05-0.1mm to prevent the blank from sticking to the mold and reduce surface defects of the blank.

[0015] S22: Composite Molding: Core and shell particles are loaded into the hoppers of an AI automated molding equipment. The particle flowability is monitored in real time by AI sensors, and the feeding speed is controlled by an AI computing platform. First, the core particles are fed into the extrusion mechanism, with the extrusion pressure controlled at 15-20 MPa and the extrusion speed at 5-10 mm / s to form a core-shell preform. Then, the shell particles are evenly coated on the surface of the core-shell preform and fed into a high-pressure vacuum forming chamber. The forming pressure is controlled at 25-30 MPa and the vacuum degree at -0.08~-0.09 MPa. The pressure is held for 5-8 minutes to form a core-shell composite preform. The AI ​​system collects parameters such as forming pressure and vacuum degree in real time and automatically adjusts and optimizes them to ensure that the preform is dense and uniform.

[0016] S23: Blank trimming and shaping: After the formed blank is taken out, it is trimmed using an automated blank trimming device to remove burrs and excess material from the blank surface and ensure the dimensional accuracy of the blank (error ≤ ±0.1mm); after trimming, the blank is shaped by placing it on a constant temperature shaping table (temperature 25-30℃, humidity 50-60%) for 2-4 hours to eliminate internal stress and avoid cracks during subsequent drying and sintering.

[0017] S3: Gradient temperature controlled drying and microwave pre-dehydration: S31: Gradient Drying: The shaped billet is sent into a gradient drying oven and a segmented temperature-controlled drying process is adopted. The specific parameters are as follows: First stage (pre-drying): room temperature → 60℃, heating rate 5-8℃ / h, holding temperature for 2-3h, to remove free water on the surface of the billet; Second stage (deep drying): 60℃ → 100℃, heating rate 8-10℃ / h, holding temperature for 3-4h, to remove bound water inside the billet; Third stage (constant temperature drying): 100℃ → 120℃, heating rate 3-5℃ / h, holding temperature for 2-3h, to control the final moisture content of the billet ≤0.5% and avoid cracking caused by excessive drying.

[0018] S32: Microwave pre-dehydration: The gradient-dried green body is fed into a microwave dehydration device, with the microwave frequency controlled at 2.45-2.52GHz, the power at 3-5kW, and the processing time at 10-15min, to further remove residual moisture inside the green body, reduce porosity and cracks in the subsequent sintering process, and at the same time improve the density of the green body.

[0019] S4: Low-temperature atmosphere sintering and microwave-assisted densification: S41: Sintering furnace pretreatment: Place the dried green body into the atmosphere sintering furnace, close the furnace door, and evacuate to -0.09~-0.1MPa to remove air from the furnace and prevent the raw materials from oxidizing during the sintering process, which would affect the product performance.

[0020] S42: Staged sintering: A staged controllable sintering process is adopted, combined with microwave-assisted densification. Specific parameters are as follows: First stage (preheating stage): room temperature → 800℃, heating rate 10-15℃ / min, nitrogen gas is introduced (flow rate 5-8L / min), and the temperature is maintained for 1-2 hours to remove the binder and residual organic matter in the green body and prevent the organic matter from burning and creating pores.

[0021] The second stage (pre-sintering stage): 800℃→1200℃, heating rate 5-8℃ / min, nitrogen-hydrogen mixed atmosphere (volume ratio 9:1) is introduced, flow rate is 3-5L / min, hold for 2-3h to achieve core layer pre-sintering and initially improve the strength of the green body.

[0022] The third stage (densification sintering stage): 1200℃→1250-1350℃, heating rate 3-5℃ / min, turn on the microwave auxiliary device (microwave power 5-10kW, power fluctuation range ±5% to ±15%), continuously introduce nitrogen-hydrogen mixed atmosphere, hold for 4-6h, utilize the thermal and non-thermal effects of microwaves to promote grain refinement, increase insulator density, and reduce sintering temperature and energy consumption.

[0023] Fourth stage (cooling stage): After sintering, turn off the microwave device, keep the nitrogen-hydrogen mixed atmosphere flowing, and cool down to 800℃ at a rate of 2-3℃ / min, hold for 2-3 hours to eliminate internal stress in the insulator; then cool down to room temperature at a rate of 5-8℃ / min to complete sintering and obtain ceramic insulator matrix, ensuring that the matrix density is ≥98%, porosity is <1%, and the mechanical strength initially reaches ≥25KN.

[0024] S5: Plasma-assisted surface modification treatment: S51: Plasma blasting: The sintered insulator substrate is fed into a plasma blasting device, using alumina blasting material (particle size 0.1-0.3mm), controlling the blasting pressure at 0.4-0.6MPa, the blasting time at 5-8min, and the plasma power at 1-2kW. The plasma pretreatment improves the surface roughness and activity of the insulator, enhances the adhesion of subsequent coatings, and removes surface sintering defects.

[0025] S52: Composite Coating Spraying: Using automated spraying equipment, a composite coating is sprayed onto the sandblasted surface of the insulator. The composite coating consists of a base layer (ETV liquid high-temperature silicone rubber) and a top layer (polyvinyl fluoride). First, the base layer is sprayed with a thickness of 0.3-0.5mm, and then dried at 80-100℃ for 30-60 minutes to cure. Then, the top layer is sprayed with a thickness of 0.1-0.2mm, and then dried at 120-150℃ for 1-2 hours to cure, resulting in a surface-modified insulator semi-finished product. The composite coating can significantly improve the insulator's resistance to pollution, corrosion, and water, making it suitable for the complex operating environment of high-speed rail.

[0026] S6: Precision binding and assembly: S61: Pretreatment of metal accessories: Hot-dip galvanize the steel caps and feet of the insulators, spray the surface with an epoxy resin anti-corrosion coating (thickness 0.2-0.3mm), and dry them for later use; evenly coat the inner wall of the steel cap with a layer of asphalt paint to form a buffer layer with a thickness of 0.1-0.2mm to reduce stress impact during the gluing process.

[0027] S62: Adhesive preparation: Weigh quartz sand, cement and deionized water in a mass ratio of 4:3:1-6:3:1, add 0.5-1% modifier (silane coupling agent), stir evenly to make adhesive, and improve the bonding strength and sealing performance.

[0028] S63: Precision gluing: Place the semi-finished insulator upright, place the steel caps at both ends of the insulator, and control the coaxiality of the steel caps and insulators (coaxiality < 0.5) using an AI positioning device. Insert the insulator vertically into the steel caps containing adhesive, and vibrate it at low frequency (vibration frequency 50-100Hz) during the insertion process to remove interface gaps and air bubbles. After gluing, place it in a constant temperature and humidity curing chamber (temperature 25-30℃, humidity 70-80%) and cure for 24-48 hours to complete the gluing and obtain the prototype of the finished insulator.

[0029] S7: AI-powered end-to-end detection and screening: S71: Intermediate process inspection: Online non-destructive testing (ultrasonic testing + infrared testing) is performed on the formed blank, dried blank, and sintered substrate using AI sensors to detect the density of the blank, internal cracks, and surface defects. Defective products are reworked to prevent them from flowing into subsequent processes.

[0030] S72: Finished Product Inspection: A comprehensive inspection of the finished insulators after gluing is conducted. Inspection items include: mechanical strength testing (ensuring electromechanical failure load ≥25KN, bending strength ≥28KN, torque load ≥15KN·m), insulation performance testing (insulation strength ≥35kV / mm, creepage distance ≥1600mm), density testing (≥98%), weathering resistance testing (high and low temperature cycling, salt spray corrosion, rain erosion tests, performance degradation ≤5%), and fatigue strength testing (simulating high-speed rail vibration environment, vibration frequency 10-50Hz, test 10...). 6 The product undergoes a second inspection to ensure it is free of cracks and has accurate dimensions. Qualified products are selected, while unqualified products are disassembled, reworked, or scrapped.

[0031] S8: Packaging and Warehousing: Clean and dry the qualified insulator products, package them with shockproof and moisture-proof packaging materials, label them with information such as product model, production date, test results, and electromechanical load level, and store them in a constant temperature and moisture-proof warehouse (temperature 15-25℃, humidity ≤60%) to complete the entire preparation process.

[0032] Furthermore, in S11, the ceramic short fiber is alumina short fiber with a length of 50-100μm and a diameter of 1-5μm, which can significantly improve the toughness and impact resistance of the insulator, while reducing the product density and achieving lightweighting; the nano-SiC is modified nano-SiC, with the surface modified by a silane coupling agent to improve compatibility with other raw materials, avoid agglomeration, and further improve the uniformity of raw material mixing and the strength of the subsequent product.

[0033] Furthermore, in S22, the AI ​​automated molding equipment includes sensor components, a data collection and storage module, an AI computing platform, an automated robot operating device, and a monitoring and control system. The sensor components collect parameters such as feeding speed, molding pressure, and vacuum degree in real time, and transmit them to the data collection and storage module. After analysis and processing by the AI ​​computing platform, control commands are sent to the automated robot operating device to achieve real-time optimization of molding parameters, improve product consistency, and ensure that the product size error is ≤ ±0.1mm.

[0034] Furthermore, in S42, the purity of the nitrogen-hydrogen mixed atmosphere is ≥99.99% to avoid impurity gases affecting the sintering effect; the microwave frequency of the microwave auxiliary device is 2.45-2.52GHz, and the power is periodically fluctuated to promote uniform grain growth, avoid performance degradation caused by excessively large grains, and shorten the sintering cycle, reducing energy consumption by more than 30%.

[0035] Furthermore, in S52, the ETV liquid high-temperature silicone rubber coating has excellent resistance to high and low temperatures, dirt resistance, and waterproof performance, with an operating temperature range of -40℃ to +180℃, which can adapt to the complex climate environment along the high-speed rail line; the polyvinyl fluoride surface layer has excellent corrosion resistance and wear resistance, which can resist the erosion of industrial dust and salt mist, and extend the service life of the insulator.

[0036] Furthermore, in S72, the mechanical strength test uses an electronic universal testing machine with a loading speed of 1-2 mm / min; the insulation performance test uses a high-voltage testing instrument with a test voltage of 100-200 kV; and the weather resistance test uses a high and low temperature cycling test chamber and a salt spray test chamber, with a high and low temperature cycling range of -40℃ to +80℃, 50 cycles, and a salt spray test time of 1000 hours, to ensure that the product is suitable for the harsh operating environment of high-speed rail.

[0037] The beneficial effects of this invention are as follows: 1. Innovative raw material formulation, balancing strength, insulation, and lightweight: A core-shell composite raw material formulation is adopted, with the core layer focusing on toughness and mechanical strength (addition of zirconium oxide, nano-SiC, and ceramic short fibers), and the shell layer focusing on insulation and pollution resistance (high alumina and magnesium oxide composite system). This solves the pain point of existing technologies where "increasing toughness inevitably reduces insulation." Simultaneously, optimized particle size distribution and the addition of modified nano-reinforcing phases reduce microscopic defects, ensuring that the prepared insulators have a stable mechanical strength ≥25KN, bending strength ≥28KN, density ≥98%, porosity <1%, and a product density reduction of over 30%, achieving lightweight design to meet the load requirements of high-speed rail speed increases.

[0038] 2. Optimized molding process to improve density and consistency: The high-pressure vacuum-extrusion composite molding process, combined with AI automated control, allows for real-time adjustment of molding parameters, solving the problems of uneven density and high porosity associated with single molding processes. The porosity of the blank is reduced to below 1%. At the same time, automated blank trimming and constant temperature shaping eliminate internal stress and reduce surface defects. The product dimensional accuracy error is ≤ ±0.1mm, significantly improving consistency and increasing the product qualification rate to over 98%, while also reducing raw material waste.

[0039] 3. Energy-efficient and highly effective sintering process with excellent densification effect: The innovative "low-temperature atmosphere sintering + microwave-assisted densification" process reduces the sintering temperature from 1400-1500℃ to 1250-1350℃, reducing energy consumption by more than 30%, shortening the sintering cycle to 8-12 hours, and increasing production efficiency by 50%. Through staged temperature control and nitrogen-hydrogen mixed atmosphere protection, combined with microwave periodic power fluctuation control, grain growth and oxidation are avoided, internal stress is eliminated, and the density and mechanical strength of the insulator are further improved, ensuring that the electromechanical load requirement of ≥25KN is stably met.

[0040] 4. Strong surface treatment adaptability and significantly improved weather resistance: The surface modification process of plasma sandblasting + composite coating (ETV silicone rubber + polyvinyl fluoride) is adopted. The plasma pretreatment improves the coating adhesion, and the composite coating works together to resist pollution, water, corrosion and wear, solving the problems of easy peeling and poor pollution resistance of existing surface treatment coatings. After testing, the insulator is undamaged and uncorroded after 1000 hours of salt spray corrosion, and the performance decay is ≤5% after 50 high and low temperature cycles. It can be adapted to the complex and harsh environment of dust, salt spray, rain and snow along the high-speed rail line for a long time, and the risk of flashover is reduced by more than 90%.

[0041] 5. Upgraded Adhesive Bonding and End-to-End Management for Significantly Improved Reliability: Optimized adhesive formula, addition of a buffer layer and vibration venting process, and precise control of coaxiality solve the problems of insufficient adhesive strength and interface gaps. Metal accessories and ceramic parts are firmly bonded with no risk of separation. The introduction of AI end-to-end management technology enables real-time collection, analysis, and control of parameters from ingredient preparation and molding to testing. Combined with online non-destructive testing, defects in intermediate links are detected in a timely manner, reducing the flow of unqualified products into subsequent processes, further improving product quality stability and reliability. Lifetime replacement is guaranteed, while the current product lifespan is approximately 15-20 years.

[0042] 6. Comprehensive testing system to meet the stringent requirements of high-speed rail: A dual testing system of "intermediate testing + finished product full-item testing" has been established, with the addition of fatigue strength testing to simulate the high-vibration environment of high-speed rail, ensuring that the insulators can withstand long-term vibration loads without cracks or failures when running at high speeds of 450km / h and above; the testing items comprehensively cover core indicators such as mechanical strength, insulation performance, weather resistance, and density, ensuring that the products fully meet the stringent usage requirements of high-speed rail-specific ≥25KN functional ceramic rod insulators.

[0043] 7. The preparation process is highly feasible and has high promotional value: The preparation method of this invention has clear steps and well-defined parameters. All processes and equipment are optimized integrations of existing mature equipment, eliminating the need for new specialized high-end equipment and facilitating large-scale industrial production. At the same time, it reduces energy consumption, improves efficiency, and reduces raw material waste, resulting in a production cost reduction of more than 25%. The prepared insulators are suitable for core components such as the overhead contact network and traction substations of high-speed railways with speeds of 450km / h and above. After testing, certification, and trial operation by the China Railway Product Certification Center, it has demonstrated strong practicality, significant effects, and extremely high promotional value. Attached Figure Description

[0044] Figure 1 This is a schematic flowchart of a method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator proposed in this invention; Figure 2 This is a schematic diagram of the core-shell composite raw material preparation process for a method of preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator proposed in this invention. Figure 3 This is a schematic diagram of the high-voltage vacuum-extrusion composite molding process for a method of preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator proposed in this invention. Figure 4 This is a schematic diagram of the gradient temperature-controlled drying and microwave pre-dehydration process of a method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator proposed in this invention. Figure 5 This is a schematic diagram of the low-temperature atmosphere sintering and microwave-assisted densification process for a method of preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator proposed in this invention. Figure 6 This is a schematic diagram of the plasma-assisted surface modification process for a method of preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator proposed in this invention. Figure 7 This is a schematic diagram of the precision gluing and assembly process of a method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator proposed in this invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Example 1: A method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator, such as... Figures 1-7 As shown, it includes the following steps: S1: Preparation of core-shell composite raw materials: S11: Raw material screening and proportioning: Weigh the core layer raw materials and shell layer raw materials according to the mass percentage. The core layer raw materials include: 32% calcined high-alumina bauxite, 28% kaolin, 6% zirconium oxide, 2% nano-SiC, 15% ceramic short fibers, and 3% feldspar. The shell layer raw materials include: 92% α-alumina, 1.5% magnesium oxide, 3% silicon oxide, and 0.5% boron oxide. The volume ratio of core layer raw materials to shell layer raw materials is 7:3. The ceramic short fibers are alumina short fibers with a length of 80μm and a diameter of 3μm. The nano-SiC is silane coupling agent modified nano-SiC.

[0047] S12: Particle size optimization: The core material and shell material are crushed and sieved separately. The particle size of the core material is controlled at 3μm and the particle size of the shell material is controlled at 1μm. 0.3% of the total raw material is added as a dispersant (sodium polycarboxylate) and 2% as a binder (polyvinyl alcohol).

[0048] S13: Mixing and granulation: Add the core layer raw material to a ball mill, add deionized water (solid-liquid ratio 1:1.3), and ball mill for 10 hours at a speed of 350 r / min. After ball milling, remove iron and sieve (300 mesh) to obtain core layer slurry. Prepare shell layer slurry using the same method. Spray dry and granulate the two slurries separately, controlling the particle size to be 30 μm and the water content to be 10% to obtain core layer particles and shell layer particles.

[0049] S2: High-pressure vacuum extrusion composite molding: S21: Mold pretreatment: Clean and dry the rod-shaped insulator mold, and apply silane coupling agent and mold release agent to the inner wall with a thickness of 0.08mm.

[0050] S22: Composite molding: Core and shell particles are loaded into the hopper of AI automated molding equipment. AI sensors monitor particle flowability in real time and adjust the feeding speed. The core particles are extruded at a pressure of 18MPa and a speed of 8mm / s to form a core preform. After being coated with shell particles, they are sent to a high-pressure vacuum forming chamber with a forming pressure of 28MPa, a vacuum degree of -0.085MPa, and a holding pressure of 6min. The AI ​​system adjusts the parameters in real time.

[0051] S23: Blank trimming and shaping: After molding, the blank is trimmed using an automated blank trimming device to ensure dimensional accuracy error ≤ ±0.1mm; after trimming, the blank is placed on a constant temperature shaping table (temperature 28℃, humidity 55%) for 3 hours to eliminate internal stress.

[0052] S3: Gradient temperature controlled drying and microwave pre-dehydration: S31: Gradient drying: The material is fed into a gradient drying oven. First stage: room temperature → 60℃, heating rate 6℃ / h, holding for 2.5h; Second stage: 60℃ → 100℃, heating rate 9℃ / h, holding for 3.5h; Third stage: 100℃ → 120℃, heating rate 4℃ / h, holding for 2.5h, controlling the moisture content of the green body to ≤0.5%.

[0053] S32: Microwave pre-dehydration: The product is fed into a microwave dehydration device with a microwave frequency of 2.48 GHz, a power of 4 kW, and a processing time of 12 min to remove residual moisture.

[0054] S4: Low-temperature atmosphere sintering and microwave-assisted densification: S41: Sintering furnace pretreatment: Place the billet into the atmosphere sintering furnace, evacuate to -0.095MPa, and remove the air from the furnace.

[0055] S42: Staged sintering: First stage: room temperature → 800℃, heating rate 12℃ / min, nitrogen gas introduced (flow rate 6L / min), hold for 1.5h; Second stage: 800℃→1200℃, heating rate 6℃ / min, nitrogen-hydrogen mixed atmosphere (volume ratio 9:1, flow rate 4L / min) is introduced, and the temperature is maintained for 2.5h; Third stage: 1200℃→1300℃, heating rate 4℃ / min, turn on microwave auxiliary device (power 8kW, fluctuation range ±10%), continuously introduce mixed atmosphere, keep warm for 5h; Fourth stage: Cool down to 800℃ at a rate of 2.5℃ / min and hold for 2.5h; then cool down to room temperature at a rate of 6℃ / min to obtain ceramic insulator matrix with a density of 98.5% and a porosity of 0.8%.

[0056] S5: Plasma-assisted surface modification treatment: S51: Plasma blasting: The alumina blasting material is fed into the plasma blasting equipment with a particle size of 0.2mm, a blasting pressure of 0.5MPa, a blasting time of 6min, and a plasma power of 1.5kW.

[0057] S52: Composite coating spraying: First, spray the ETV liquid high-temperature silicone rubber base layer with a thickness of 0.4mm and dry it at 80℃ for 45min; then spray the polyvinyl fluoride surface layer with a thickness of 0.15mm and dry it at 130℃ for 1.5h to obtain the insulator semi-finished product.

[0058] S6: Precision binding and assembly: S61: Pretreatment of metal accessories: hot-dip galvanizing of steel caps and steel feet, spraying with epoxy resin anti-corrosion coating (thickness 0.25mm); asphalt paint buffer layer with a thickness of 0.15mm is applied to the inner wall of the steel cap.

[0059] S62: Adhesive preparation: Weigh quartz sand, cement and deionized water in a mass ratio of 5:3:1, add 0.8% silane coupling agent and stir evenly.

[0060] S63: Precision gluing: The semi-finished insulator is placed upright, and the coaxiality between the steel cap and the insulator is controlled by AI positioning to be <0.5. The adhesive is inserted vertically, and the air is vented by low-frequency vibration (70Hz). It is then placed in a constant temperature and humidity curing chamber (temperature 28℃, humidity 75%) for 36 hours.

[0061] S7: AI-powered end-to-end detection and screening: S71: Intermediate process inspection: AI sensors perform ultrasonic + infrared online inspection on the formed blank, dried blank, and sintered matrix, and defective products are reworked.

[0062] S72: Finished Product Inspection: Mechanical strength is tested using an electronic universal testing machine (electromechanical breaking load 28KN, bending strength 30KN, torque load 16KN·m); insulation strength is tested using a high-voltage testing machine (38kV / mm, creepage distance 1650mm); performance degradation is 3% after high and low temperature cycling (-40℃~+80℃, 50 cycles); no corrosion is observed after salt spray testing (1000h); fatigue strength testing (vibration frequency 30Hz, 10... 6 (Next) No cracks; dimensional accuracy error ±0.08mm, judged as qualified product.

[0063] S8: Packaging and Warehousing: Qualified products are cleaned, dried, packaged with shockproof and moisture-proof materials, labeled with relevant information, and stored in a temperature- and moisture-proof warehouse.

[0064] Example 2: The difference between this example and Example 1 is as follows: S11: Core layer raw material ratio: 30% calcined high-alumina bauxite, 30% kaolin, 5% zirconium oxide, 1% nano-SiC, 18% ceramic short fibers, 6% feldspar; Shell layer raw material ratio: 90% α-alumina, 2% magnesium oxide, 2% silicon oxide, 1% boron oxide; Core layer to shell layer volume ratio: 6:4; Ceramic short fibers: 50μm in length and 1μm in diameter.

[0065] S42: The third stage sintering temperature is 1250℃, and the holding time is 6h; the microwave power is 5kW, with a fluctuation range of ±5%.

[0066] S52: Bottom layer thickness 0.3mm, top layer thickness 0.1mm; bottom layer drying temperature 100℃, time 30min; top layer drying temperature 150℃, time 1h.

[0067] Finished product test results: electromechanical breaking load 25KN, bending strength 28KN, density 98%, porosity 1%, insulation strength 35kV / mm, creepage distance 1600mm, weathering resistance test performance degradation 5%, fatigue strength test no cracks, qualified.

[0068] Example 3: The difference between this example and Example 1 is as follows: S11: Core layer raw material ratio: 35% calcined high-alumina bauxite, 25% kaolin, 8% zirconium oxide, 3% nano-SiC, 13% ceramic short fibers, 4% feldspar; Shell layer raw material ratio: 95% α-alumina, 1% magnesium oxide, 1% silicon oxide, 0.5% boron oxide; Core layer to shell layer volume ratio: 7:3; Ceramic short fibers: 100μm in length and 5μm in diameter.

[0069] S42: The third stage sintering temperature is 1350℃, and the holding time is 4h; the microwave power is 10kW, with a fluctuation range of ±15%.

[0070] S52: Bottom layer thickness 0.5mm, top layer thickness 0.2mm; bottom layer drying temperature 80℃, time 60min; top layer drying temperature 120℃, time 2h.

[0071] Finished product test results: electromechanical breaking load 32KN, bending strength 35KN, density 99%, porosity 0.5%, insulation strength 40kV / mm, creepage distance 1700mm, weathering resistance test performance degradation 2%, fatigue strength test no cracks, qualified.

[0072] Comparative Examples (Existing Conventional Preparation Methods) The process uses existing single alumina raw materials (85% alumina, 10% kaolin, 5% feldspar), single dry pressing (pressure 20MPa, holding pressure for 5min), traditional air sintering (temperature 1450℃, holding for 15h), single sandblasting surface treatment, and conventional glue bonding process, without adopting AI control and online detection.

[0073] Test results: Electromechanical breaking load 15KN, bending strength 18KN, density 95%, porosity 4%, insulation strength 30kV / mm, corrosion appeared in salt spray test (500h), performance degradation 10% in high and low temperature cycling (30 cycles), fatigue strength test (vibration frequency 30Hz, 5×10 5 (The product) cracked, the product qualification rate was 80%, the energy consumption was 35% higher than that of Example 1, and the production cost was 28% higher.

[0074] As can be seen from Examples 1-3 and the comparative examples, the preparation method of the present invention, through synergistic innovation in raw material formulation, molding, sintering, surface treatment, gluing, and whole-process control, produces high-speed rail-specific functional ceramic rod insulators with stable mechanical strength ≥25KN, density ≥98%, and porosity <1%. It also takes into account excellent insulation performance, weather resistance, and lightweight characteristics. The product qualification rate is ≥98%, energy consumption is reduced by more than 30%, production cost is reduced by more than 25%, and service life is extended to more than 30 years. It fully meets the stringent requirements of high-speed rails with speeds of 350km / h and above, and is significantly superior to existing conventional preparation methods.

[0075] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator, characterized in that, Includes the following steps: S1: Preparation of core-shell composite raw materials; S2: High-pressure vacuum extrusion composite molding; S3: Gradient temperature controlled drying and microwave pre-dehydration; S4: Low-temperature atmosphere sintering and microwave-assisted densification; S5: Plasma-assisted surface modification treatment; S6: Precision binding and assembly; S7: AI full-process inspection and screening, conducts comprehensive inspection of intermediate links and finished products, and screens out qualified products with mechanical strength ≥25KN; S8: Packaging and warehousing. Qualified products are packaged and stored in a temperature-controlled and moisture-proof warehouse.

2. The method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator according to claim 1, characterized in that, In step S1, the preparation of the core-shell composite raw material includes the following steps: S11: Raw material screening and proportioning: Weigh the core layer raw materials and shell layer raw materials according to the mass percentage. The core layer raw materials include: calcined high-alumina bauxite 30-35%, kaolin 25-30%, zirconium oxide 5-8%, nano-SiC 1-3%, ceramic short fibers 13-18%, and feldspar 3-5%. The shell layer raw materials include: α-alumina 90-95%, magnesium oxide 1-2%, silicon oxide 1-3%, and boron oxide 0.5-1%. The volume ratio of core layer raw materials to shell layer raw materials is 6:4-7:

3. S12: Particle size optimization: The core material and shell material are crushed and sieved separately. The particle size of the core material is controlled to be 1-5μm and the particle size of the shell material is controlled to be 0.5-2μm. Add 0.2-0.5% of dispersant and 1-3% of binder to the total amount of raw materials. S13: Mixing and granulation: The core layer raw material and the shell layer raw material are ball-milled, iron-removed, and sieved to obtain core layer slurry and shell layer slurry, respectively; spray-dried and granulated, controlling the particle size of the granulated particles to be 20-50μm and the moisture content to be 8-12%.

3. The method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator according to claim 1, characterized in that, In step S2, the high-pressure vacuum-extrusion composite molding includes the following steps: S21: Mold pretreatment: Clean and dry the rod-shaped insulator mold, and apply a release agent to the inner wall with a thickness of 0.05-0.1mm; S22: Composite molding: Core and shell particles are loaded into an AI automated molding equipment, first extruded to form a core preform (extrusion pressure 15-20MPa, extrusion speed 5-10mm / s), then the shell particles are coated and sent into a high-pressure vacuum molding chamber (molding pressure 25-30MPa, vacuum degree -0.08~-0.09MPa, holding pressure for 5-8min), and the AI ​​system controls the molding parameters in real time; S23: Blank trimming and shaping: After automated blank trimming, place it on a constant temperature shaping table (temperature 25-30℃, humidity 50-60%) and leave it for 2-4 hours.

4. The method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator according to claim 1, characterized in that, In step S3, the gradient temperature-controlled drying and microwave pre-dehydration include the following steps: S31: Gradient drying: The material is fed into a gradient drying oven and dried in stages with controlled temperature to ultimately control the moisture content of the green body to ≤0.5%; S32: Microwave pre-dehydration: Feed into microwave dehydration equipment (microwave frequency 2.45-2.52GHz, power 3-5kW), process for 10-15 minutes.

5. The method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator according to claim 1, characterized in that, In step S4, the low-temperature atmosphere sintering and microwave-assisted densification include the following steps: S41: Sintering furnace pretreatment: Place the billet into an atmosphere sintering furnace and evacuate it to -0.09~-0.1MPa; S42: Staged sintering: Staged controllable sintering is adopted, combined with microwave-assisted densification, nitrogen-hydrogen mixed atmosphere is introduced, and finally cooled to room temperature to obtain ceramic insulator matrix.

6. The method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator according to claim 1, characterized in that, In step S5, the plasma-assisted surface modification treatment includes the following steps: S51: Plasma blasting: using alumina blasting material, blasting pressure 0.4-0.6MPa, time 5-8min, plasma power 1-2kW; S52: Composite coating spraying: Spray ETV liquid high-temperature silicone rubber base layer (thickness 0.3-0.5mm) and polyvinyl fluoride surface layer (thickness 0.1-0.2mm) in sequence, and dry and cure them respectively.

7. The method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator according to claim 1, characterized in that, In step S6, precision binding and assembly includes the following steps: S61: Pre-treatment of metal accessories: hot-dip galvanizing and spraying anti-corrosion coating on steel caps and steel feet, and applying a buffer layer to the inner wall of steel caps; S62: Adhesive preparation: Weigh quartz sand, cement and deionized water in a mass ratio of 4:3:1-6:3:1, add modifier and stir evenly; S63: Precision gluing: Control the coaxiality of the steel cap and insulator to <0.5, after vibration and degassing, cure at constant temperature and humidity for 24-48 hours.

8. The method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator according to claim 2, characterized in that, In S11, the ceramic short fiber is alumina short fiber with a length of 50-100 μm and a diameter of 1-5 μm; the nano-SiC is silane coupling agent modified nano-SiC; the dispersant is sodium polycarboxylate; and the binder is polyvinyl alcohol. In S13, the ball milling solid-liquid ratio is 1:1.2-1:1.5, the ball milling speed is 300-400 r / min, the ball milling time is 8-12 h, and the sieve mesh is 300 mesh.

9. The method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator according to claim 3, characterized in that, In step S22, the AI ​​automated molding equipment includes sensor components, a data collection and storage module, an AI computing platform, automated robot operation equipment, and a monitoring and control system, which are used to collect, analyze, and regulate molding parameters in real time. In S31, the specific parameters of the gradient drying are as follows: First stage: room temperature → 60℃, heating rate 5-8℃ / h, holding temperature for 2-3h; Second stage: 60℃ → 100℃, heating rate 8-10℃ / h, holding temperature for 3-4h; Third stage: 100℃ → 120℃, heating rate 3-5℃ / h, holding temperature for 2-3h.

10. A method for preparing a high-speed rail-specific ≥25KN functional ceramic rod insulator according to claim 5, characterized in that, In step S42, the specific parameters for the staged sintering are as follows: First stage: room temperature → 800℃, heating rate 10-15℃ / min, nitrogen gas is introduced (flow rate 5-8L / min), and the temperature is maintained for 1-2 hours; Second stage: 800℃→1200℃, heating rate 5-8℃ / min, nitrogen-hydrogen mixed atmosphere (volume ratio 9:1, flow rate 3-5L / min) is introduced, and the temperature is maintained for 2-3 hours.

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