Aging strengthening nanometer high-strength aluminum alloy strain clamp forming process

Abstract

The invention discloses an aging strengthening nanometer high-strength aluminum alloy strain clamp forming process, and belongs to the technical field of electric power fitting manufacturing. The process comprises the following steps: preparing multi-element nano composite powder; carrying out vacuum casting compounding to form a nano composite melt; acoustic-magnetic coupling field homogenization and multi-stage purification treatment are adopted; preparing a blank through extrusion gradient forming; synergistic heat treatment of sectional solid solution, gradient quenching and sectional aging is carried out; and finally, precision machining and surface anti-corrosion treatment are conducted. According to the invention, through a powder-casting composite process, acoustic-magnetic coupling homogenization, gradient extrusion forming and synergistic heat treatment are combined, so that the comprehensive performance of nano-phase uniform dispersion, high density, high strength and plasticity balance, high conductivity and excellent corrosion resistance is realized. The process efficiency is high, the cost is controllable, and the method is suitable for large-scale production of the strain clamp of the ultra / extra-high voltage power transmission line.

Description

Technical Field

[0001] This invention relates to the field of power fitting manufacturing technology, specifically to a high-efficiency and dense age-strengthened nano-high-strength aluminum alloy tension clamp forming process, which is particularly suitable for the large-scale production of tension clamps for ultra-high voltage / extra-high voltage transmission lines and in harsh environments such as coastal salt spray, high altitude and cold, and long crossings. Background Technology

[0002] In overhead transmission line systems, tension clamps must withstand complex operating conditions such as conductor tension, wind load, and temperature changes over long periods, while also resisting environmental effects such as atmospheric corrosion and salt spray erosion. Therefore, stringent requirements are placed on their mechanical properties (tensile strength, yield strength, fatigue resistance), corrosion resistance, lightweight design, and electrical conductivity. Traditional tension clamp manufacturing technologies suffer from several insurmountable drawbacks:

[0003] 1. Steel tension clamps: Although they have high strength, their density is 7.8 g / cm³, which is more than three times that of aluminum alloys. This will significantly increase the load on the towers and the cost of foundation construction. Moreover, they are prone to electrochemical corrosion in humid and salt spray environments, resulting in short maintenance cycles and high costs. They cannot meet the requirements of long-life transmission lines.

[0004] 2. Ordinary aluminum alloy tension clamps: Made by gravity casting or ordinary extrusion process, the tensile strength is only 300-400MPa, which is difficult to meet the high tension requirements of ultra-high voltage / extra-high voltage lines; and defects such as porosity and shrinkage are easily generated during the molding process, with a density of only 92-95%, and insufficient holding force (usually less than 90% of the rated breaking force of the conductor), which easily leads to conductor slippage failure.

[0005] To overcome the performance bottlenecks of traditional materials, the industry has gradually explored the application of nano-high-strength aluminum alloys in tension clamps, resulting in two mainstream forming processes. However, each of these processes has significant technical shortcomings:

[0006] Category 1: Improved casting process. This type of process is based on traditional aluminum alloy casting and optimizes performance through in-situ synthesis of nanophases, acoustic-magnetic coupling homogenization, extrusion casting, gradient quenching, and other methods. For example, the stamping forming process for electric tension clamps disclosed in CN113083986B improves forming accuracy by optimizing stamping parameters, but it does not involve the preparation of nanomaterials, resulting in limited strength improvement; the in-situ nano-reinforced aluminum alloy wheel hub manufacturing method disclosed in CN108559864A uses acoustic-magnetic coupling field homogenization of the melt, but it is designed for axisymmetric simple structures and is not suitable for the complex cavity structure of tension clamps, and the single casting process still cannot completely solve the problems of nanophase segregation and internal defects. Specific shortcomings include: ① Uneven distribution of nanophases: During in-situ synthesis, uneven melt convection can easily lead to the agglomeration of nanophases at grain boundaries or local areas, limiting the strengthening effect; ② Insufficient density: Even with squeeze casting, micropores may still be generated due to uneven melt solidification rate, making it difficult to exceed 99.5% in density; ③ Poor balance between strength and plasticity: Single aging process can easily lead to increased strength but decreased plasticity, resulting in insufficient low-temperature impact toughness, making it difficult to meet the needs of cold regions.

[0007] The second category: Innovative powder metallurgy processes. These processes prepare nanocomposite powders through high-energy ball milling, followed by solid-state forming methods such as vacuum sintering and isothermal forging to produce wire clamps, achieving uniform dispersion and high density of the nanophase. For example, the "high-energy ball milling-vacuum hot pressing-isothermal forging" process proposed by some universities can produce nano-aluminum alloys with tensile strengths exceeding 650 MPa. However, significant industrialization obstacles exist: ① Long process chain: From powder preparation to finished product, multiple processes such as ball milling, sieving, sintering, forging, and spinning are required, resulting in a production cycle of over 48 hours and low efficiency; ② High equipment investment: High-end equipment such as high-energy ball mills and vacuum hot pressing sintering furnaces are required, with a single production line investment exceeding ten million yuan, which is difficult for small and medium-sized enterprises to afford; ③ Low material utilization: Scrap materials are easily generated during powder forming, with a utilization rate of only about 85%, further increasing production costs; ④ High technical threshold: Coordinated control of parameters in each process is difficult, and problems such as powder oxidation and insufficient sintering densification can easily lead to fluctuations in product performance and poor stability in large-scale production.

[0008] Furthermore, both existing processes share the common problem of "difficulty in simultaneously achieving both electrical conductivity and mechanical properties": alloying elements such as Zn and Cu, added to enhance strength, significantly increase electron scattering and reduce conductivity if present in a solid solution state (the conductivity of wire clamps prepared by existing processes is mostly below 60% IACS), leading to increased energy loss during power transmission and failing to meet energy-saving requirements. Simultaneously, the heat treatment and forming processes of both types of processes have poor synergy, failing to fully consider the impact of material microstructure evolution during forming on the aging strengthening effect, further limiting performance improvement.

[0009] In summary, existing technologies cannot simultaneously meet the comprehensive requirements of "uniform dispersion of nanophases, high density, balance of high strength and plasticity, high conductivity, and high efficiency and low cost for industrialization." Therefore, developing a time-strengthened nano-aluminum alloy tension clamp forming process that integrates the advantages of powder metallurgy and casting to achieve a win-win situation of "technological innovation breakthrough" and "practical application" has become a core technical problem that urgently needs to be solved in the current power fitting manufacturing field. Summary of the Invention

[0010] The purpose of this invention is to overcome the dual shortcomings of existing improved casting processes ("nanophase segregation and insufficient density") and powder metallurgy processes ("low efficiency, high cost, and difficulty in industrialization"), and to provide a highly efficient and dense age-strengthened nano-high-strength aluminum alloy tension clamp forming process. Specifically, the following technical problems need to be solved:

[0011] 1. Solving the problem of uniform dispersion of nanophases: By combining powder metallurgy and casting technology, the agglomeration of externally added nanoparticles and the segregation of in-situ synthesized nanophases are avoided, thus achieving uniform distribution of nano-reinforcing phases in the aluminum alloy matrix;

[0012] 2. Improve molding density and dimensional accuracy: By combining vacuum casting and extrusion gradient forming technology, internal defects such as porosity and shrinkage are eliminated, ensuring the molding accuracy of complex cavities (aluminum tube body, wire slot, connecting flange) of tension clamps;

[0013] 3. Balancing high strength with plasticity / conductivity: Through a synergistic heat treatment process, the nano-reinforcing phase is fully extracted, while the content of solid solution alloying elements is reduced, thus achieving a balance of high strength, good plasticity, and high conductivity.

[0014] 4. Achieve efficient industrialized production: Optimize process routes, shorten production cycles, reduce equipment investment, improve material utilization, and ensure the stability and cost controllability of large-scale production.

[0015] To achieve the above objectives, the present invention adopts the following technical solution:

[0016] A highly efficient and dense age-strengthened nano-high-strength aluminum alloy tension clamp forming process includes the following steps:

[0017] S1. Preparation of multi-component nanocomposite powder:

[0018] S11. Composition Design: By weight percentage, the nanocomposite aluminum alloy composition includes: Zn: 1.5-2.0%, Cu: 1.0-1.4%, Ni: 1.2-1.6%, Er: 0.4-0.6%, Zr: 1.0-1.4%, Sc: 0.08-0.12%, RE: 0.15-0.25% (Ce, La mass ratio 1:1), nano Al2O3: 0.5-0.8%, with the balance being Al and unavoidable impurities; wherein, the nano Al2O3 particle size is 20-50nm, and the purity is ≥99.9%;

[0019] S12. Raw material pretreatment: Weigh industrial pure aluminum powder (purity ≥99.7%, particle size 50-100μm), Al-Zn master alloy powder (Zn content 50%, particle size 50-100μm), Al-Cu master alloy powder (Cu content 40%, particle size 50-100μm), Al-Ni master alloy powder (Ni content 30%, particle size 50-100μm), Al-Er master alloy powder (Er content 20%, particle size 50-100μm), Al-Zr master alloy powder (Zr content 10%, particle size 50-100μm), Al-Sc master alloy powder (Sc content 2%, particle size 50-100μm), Al-RE master alloy powder (RE content 10%, particle size 50-100μm), and nano Al2O3 powder; place all powders in a vacuum drying oven and dry at 120-150℃ for 2-3 hours to remove surface moisture and adsorbed impurities;

[0020] S13. High-energy ball milling preparation of composite powder: The dried raw material powder is added to a planetary high-energy ball mill, and stainless steel balls are added as grinding media, with a ball-to-material ratio of 15:1-20:1; Argon gas protection (argon purity ≥99.99%) is used to avoid powder oxidation; the ball milling speed is 300-400 r / min, and the ball milling time is 8-12 h; during the ball milling process, through mechanical alloying, nano-Al2O3 particles are uniformly embedded in the aluminum powder and intermediate alloy powder matrix to form multi-element nano-composite powder with a particle size of 20-80 μm; after ball milling, it is passed through a 200-mesh sieve to remove large particle agglomerates.

[0021] S2. Vacuum casting composite of nanocomposite powders:

[0022] S21. Preform Preparation: The nanocomposite powder is loaded into a graphite mold and placed in a vacuum hot-pressing sintering furnace for pre-sintering. The pre-sintering temperature is 450-500℃, the holding time is 1-2 hours, and the vacuum degree is ≤5×10⁻⁶. -3 Pa; The pre-sintering pressure is 10-20MPa, which initially densifies the powder to form a preform with a relative density of ≥75%, which facilitates rapid melting and composition homogenization during subsequent casting.

[0023] S22. Vacuum casting: Place the pre-sintered preform into a graphite crucible, then place it in a vacuum induction melting furnace and evacuate to a vacuum level of ≤5×10⁻⁶. -3 After Pa, the temperature is raised to 760-780℃ and held for 15-25 minutes to completely melt the preform and form a nano-composite aluminum alloy melt. The vacuum environment can effectively prevent melt oxidation and gas intake, and reduce porosity defects.

[0024] S23. In-situ reaction enhancement: Add 0.1-0.2% of the melt mass of Al-Ti-B refining agent (5% Ti content, 1% B content) to the melt and stir evenly (stirring speed 80-100 r / min, stirring time 5-8 min); the Al-Ti-B refining agent works synergistically with Er, Zr and other elements in the melt to promote the in-situ formation of L12-Al3(Er,Zr,Sc) nanophase (size 1-5 nm) and refine the grains at the same time; keep warm for 5-10 min to ensure that the in-situ reaction is fully carried out.

[0025] S3. Acoustomagnetic coupling field homogenization and multi-stage purification:

[0026] S31. Homogenization by Acoustomagnetic Coupling Field: The melt temperature is lowered to 730-750℃, and an acoustic-magnetic coupling field is applied for homogenization treatment for 25-35 minutes. The acoustic-magnetic coupling field consists of a low-frequency pulsed magnetic field and a high-energy ultrasonic field. The low-frequency pulsed magnetic field has a frequency of 18-22Hz and a magnetic current of 180-220A. The high-energy ultrasonic field has a power of 1400-1600W and a frequency of 22-28kHz. The composite acoustic flow motion generated by the acoustic-magnetic coupling field can further promote the uniform dispersion of nano-Al2O3 particles and the in-situ generated L12-Al3(Er,Zr,Sc) phase, eliminate component segregation, and break up coarse grains.

[0027] S32. Multi-stage purification: ① Refining agent purification: The melt temperature is raised to 750-770℃, and a refining agent is sprayed into the melt through a spray gun. The amount of refining agent is 0.3-0.5% of the melt mass. The refining agent is a mixture of KCl, NaCl, and Na3AlF6 in a mass ratio of 3:2:1. The spraying pressure is 0.3-0.5MPa, and the spraying time is 8-12min, to remove gases and some solid inclusions from the melt; ② Aluminum-rare earth deep purification: 0.15-0.25% aluminum-rare earth is added to the melt. The Al-Ce master alloy (Ce content 10%) is stirred evenly and allowed to stand for 10-15 minutes. The Al-Ce master alloy reacts with impurities such as O and H in the melt to form CeAlO3 compounds with a density greater than that of the melt, which settle to the bottom of the crucible, achieving deep purification. ③ Nitrogen-argon composite rotary blowing refining: Nitrogen and argon are mixed at a volume ratio of 1:2 and introduced into the melt through a graphite rotary nozzle at a nozzle speed of 400-600 r / min and a mixed gas flow rate of 0.3-0.5 m³ / min.3 The refining time is 15-20 minutes per hour; the protective effect of argon gas is used to prevent secondary oxidation of the melt, while the stirring effect generated by the rotating gas flow further removes residual gas and inclusions; after refining, let it stand for 5-10 minutes to allow bubbles and impurities to settle completely.

[0028] S4. Extrusion gradient forming:

[0029] S41. Mold Pretreatment: A high-strength metal mold is used, with the mold cavity corresponding to the structural shape of the tension clamp (including the aluminum tube body, wire slot, and connecting flange); the mold is preheated to 350-400℃ and held for 30-40 minutes; a release agent is evenly applied to the surface of the mold cavity, which is a mixture of graphite powder, water glass, and alcohol in a mass ratio of 2:1:7, with a coating thickness of 0.1-0.2mm; the mold is equipped with a water-cooling circulation system, and gradient solidification is achieved by precisely controlling the cooling rate;

[0030] S42. Melt Casting and Gradient Extrusion: Adjust the temperature of the purified melt to 720-740℃ and inject it into the pressure chamber of the extrusion casting machine at a uniform speed of 0.8-1.2 kg / s through a heat-insulating casting tank; start the extrusion mechanism and apply gradient pressure to the melt through the pressure head: the initial pressure is 60-80 MPa, and the pressure is held for 100-150 s to allow the melt to initially fill the cavity; then increase the pressure to 100-120 MPa and hold for 200-300 s to promote sufficient shrinkage of the melt and eliminate shrinkage defects; during the extrusion process, control the cooling rate to 60-90℃ / min through the mold water cooling system to achieve sequential solidification from the bottom to the top of the cavity and ensure uniform density of the casting;

[0031] S43. Demolding and Preliminary Processing: After the pressure holding is completed, the pressure is released and the casting is ejected by the ejection mechanism to obtain the tension clamp blank; the blank is preliminarily processed to remove excess parts such as gates, risers, and flash, and the surface of the blank is ground with a grinding wheel to remove surface oxide scale and burrs.

[0032] S5. Synergistic heat treatment (solution treatment - gradient quenching - segmented aging):

[0033] S51. Segmented Solution Treatment: The pre-processed tension clamp blank is placed in a box-type resistance furnace for segmented solution treatment to avoid thermal stress caused by sudden temperature rise; specific steps: ① heat to 400℃ and hold for 60 min; ② heat to 540-560℃ and hold for 4-6 h; through segmented solution treatment, the nano-reinforcing phases (nano Al2O3, L12-Al3(Er,Zr,Sc), Al2Cu, etc.) are fully dissolved into the aluminum matrix to form a supersaturated solid solution; during the solution treatment process, nitrogen gas is introduced into the furnace for protection to prevent oxidation of the blank;

[0034] S52. Gradient Quenching: After solution treatment, the blank is quickly removed and placed in a quenching medium for gradient quenching to balance the cooling rate and thermal stress. Specific stages: ① First stage: quenching in mineral oil at 200℃ for 3-5 minutes, slow cooling to reduce thermal stress; ② Second stage: quenching in deionized water at 80℃ for 5-8 minutes, accelerated cooling to inhibit premature precipitation of the second phase; ③ Third stage: quenching in clean water at room temperature for 10-15 minutes, ensuring rapid cooling of the blank to room temperature to obtain a stable supersaturated solid solution. During quenching, a stirring device is used to agitate the quenching medium (stirring speed 30-50 r / min) to ensure uniform quenching. After quenching, the blank surface is cleaned with alcohol to remove residual quenching medium.

[0035] S53. Segmented Aging Strengthening: The quenched blank is placed in an aging furnace for segmented aging treatment to optimize nanophase precipitation and stress release. Specific steps: ① Pre-aging: Heating to 120-140℃ and holding for 2-3 hours promotes the precipitation of fine GP zones in the supersaturated solid solution, laying the foundation for subsequent nanophase precipitation; ② Main aging: Heating to 170-180℃ and holding for 4-6 hours transforms the GP zones into stable nanoscale strengthening phases (L12-Al3(Er,Zr,Sc), Al2Cu, Al3Ni, and nano Al2O3). These nanoparticles are uniformly distributed in the aluminum matrix and hinder dislocation movement through the Orovan mechanism, significantly improving the material strength; ③ Over-aging: Cooling to 150℃ and holding for 1-2 hours, slight over-aging can release residual stress and improve the material's plasticity and fatigue resistance; After the aging treatment, the furnace is cooled to room temperature to obtain the age-strengthened nano-high-strength aluminum alloy tension clamp semi-finished product.

[0036] S6. Post-processing and performance testing:

[0037] S61. Precision post-processing: Precision machining is performed on the semi-finished products after aging, including turning, milling, drilling, tapping and other processes, to achieve the design dimensions and accuracy of the tension clamp; the key stress-bearing parts such as the wire clamp slot and connecting flange are polished to achieve a surface roughness Ra≤0.8μm;

[0038] S62. Surface Anti-corrosion Composite Treatment: A composite anti-corrosion technology of "micro-arc oxidation + silane sealing" is adopted to improve corrosion resistance; ① Micro-arc oxidation: The electrolyte is a sodium silicate-sodium hydroxide system, with a sodium silicate concentration of 12-16 g / L and a sodium hydroxide concentration of 6-9 g / L; the electrolysis voltage is 350-400V, and the current density is 12-16 A / dm³. 2The processing time is 15-25 min; a dense ceramic oxide film with a thickness of 15-30 μm is formed on the surface; ② Silane sealing: the wire clamp after micro-arc oxidation is placed in a silane coupling agent solution, the sealing temperature is 80-100℃, the sealing time is 10-15 min, the oxide film pores are filled, and the corrosion resistance is further improved.

[0039] S63. Comprehensive Performance Testing: The finished tension clamps undergo mechanical, electrical conductivity, density, corrosion resistance, and dimensional accuracy testing; ① Mechanical Properties: Tensile strength, yield strength, and elongation are tested using a universal testing machine, and low-temperature impact toughness at -40℃ is tested using an impact testing machine; ② Electrical Conductivity: Conductivity is measured using an eddy current conductivity meter; ③ Density: Measured using the water displacement method; ④ Corrosion Resistance: Tested using a neutral salt spray test (NSS) for 2000 hours; ⑤ Dimensional Accuracy: Key dimensions are measured using a coordinate measuring machine; After all test items pass, the final high-efficiency, dense, age-strengthened nano-aluminum alloy tension clamp is obtained.

[0040] Furthermore, in step S13, during the high-energy ball milling process, the machine is stopped for 15 minutes every 2 hours to avoid excessive powder temperature leading to oxidation or excessive particle agglomeration; after the ball milling is completed, the oxygen content of the composite powder is ≤0.15% to ensure the purity of the subsequent casting melt.

[0041] Furthermore, in step S22, the vacuum induction melting adopts medium-frequency induction heating (frequency 1000-2000Hz), and the heating rate is controlled at 5-10℃ / min to avoid local overheating of the preform, which could lead to burn-off or growth of nanoparticles.

[0042] Furthermore, in step S42, during the extrusion casting process, the melt temperature (accuracy ±2℃) and mold temperature (accuracy ±5℃) are monitored in real time by a temperature sensor, and the extrusion pressure (accuracy ±1MPa) is monitored in real time by a pressure sensor to ensure the stability of process parameters; temperature measuring points are set at key parts of the mold cavity (wire slot, connecting flange) to control the cooling rate in a targeted manner and improve molding accuracy.

[0043] Furthermore, in step S53, during the segmented aging process, a programmed temperature rise control is adopted, with a temperature rise rate of 3-5℃ / min, to avoid uneven precipitation of the nanophase caused by a sudden temperature rise.

[0044] Furthermore, in step S62, adding 0.5-1.0 g / L of Na2WO4 to the micro-arc oxidation electrolyte can improve the hardness and wear resistance of the ceramic oxide film; the silane coupling agent solution uses KH-550 silane coupling agent with a concentration of 5-8%.

[0045] The efficient, dense, age-strengthened nano-aluminum alloy tension clamp forming process of this invention integrates the core advantages of powder metallurgy and casting, and through multi-technology collaborative innovation, it has the following significant advantages compared with existing technologies:

[0046] 1. Uniform dispersion of nanophases, resulting in significant and stable strengthening effects: This invention employs a triple-protection technology of "high-energy ball milling mechanical alloying + vacuum casting composite + acoustic-magnetic coupling homogenization," completely solving the problem of nanophase agglomeration. First, high-energy ball milling ensures uniform embedding of nano-Al2O3 particles into the aluminum powder matrix, achieving initial dispersion from the source. Second, vacuum casting after pre-sintering of the preform avoids agglomeration and oxidation caused by direct casting of nanoparticles. Finally, the composite acoustic flow motion of the acoustic-magnetic coupling field further promotes the uniform distribution of nanophases (nano-Al2O3, L12-Al3(Er,Zr,Sc), Al2Cu, etc.), with precise size control within 1-50nm. Under the synergistic effect of multiple strengthening phases, the tensile strength of the finished wire clamp reaches 650-700MPa, and the yield strength reaches 550-580MPa, which is more than 25% higher than the existing casting process and 30% higher than the performance stability of traditional powder metallurgy processes.

[0047] 2. High molding density and few internal defects: This invention combines vacuum casting and extrusion gradient forming technology to achieve "oxidation-free and porosity-free" solidification of the melt. The vacuum environment effectively avoids gas intake and oxidation during the casting process, and the multi-stage purification process further removes inclusions and gases from the melt; the extrusion gradient pressure (60-80MPa→100-120MPa) and sequential solidification technology ensure sufficient shrinkage of the melt, eliminating internal defects such as porosity and shrinkage. The density of the finished wire clamp reaches 99.5-99.8%, far exceeding the 99.2-99.5% of existing casting processes and over 98.7% of powder metallurgy processes, and the gripping force can reach 97-98% of the rated breaking force of the conductor, fully meeting the high tension requirements of ultra-high voltage / extra-high voltage lines.

[0048] 3. Perfect Balance Between Strength, Plasticity, and Electrical Conductivity: The "segmented solution treatment-gradient quenching-segmented aging" synergistic heat treatment process designed in this invention not only ensures the full precipitation of the nano-reinforcing phase but also effectively balances strength and plasticity. Segmented solution treatment and gradient quenching avoid deformation and cracking caused by thermal stress, ensuring the stability of the supersaturated solid solution. Segmented aging, through a reasonable combination of pre-aging, main aging, and over-aging, releases residual stress while improving strength. The elongation of the finished wire clamp reaches 14-16%, and the impact toughness at -40℃ reaches 70-80 J / cm², an improvement of more than 30% compared to existing processes. At the same time, the precipitation of the nano-phase reduces the influence of the solid solution alloying elements on electron scattering, and the electrical conductivity reaches 62-65% IACS, meeting the requirements for energy-saving power transmission.

[0049] 4. High industrial efficiency and controllable cost: This invention optimizes the process route, avoiding the long chain defects of traditional powder metallurgy processes ("ball milling-sintering-forging-spinning"), shortening the production cycle to 28-32 hours, a 40% reduction compared to traditional powder metallurgy processes. The pre-sintered preform design enables rapid melting of nanocomposite powders, improving casting efficiency. Material utilization reaches over 96%, more than 10% higher than traditional powder metallurgy processes. Furthermore, the process can be modified based on existing extrusion casting production lines without requiring a large amount of new high-end equipment. The investment per production line is reduced by 60% compared to traditional powder metallurgy processes, and the overall cost is reduced by 40-50%, achieving a balance between "high performance" and "low cost," making it easy to scale up.

[0050] 5. Excellent corrosion resistance and adaptability to harsh environments: This invention employs a composite anti-corrosion technology of "multi-component nanophase corrosion resistance enhancement + micro-arc oxidation + silane sealing". The multi-component nanophase (L12-Al3(Er,Zr,Sc), nano Al2O3) can hinder the penetration of corrosive media, while the dense ceramic oxide film and silane sealing layer further isolate the corrosive environment. After 2000 hours of neutral salt spray testing, the finished wire clamps show no obvious corrosion spots on the surface, with a corrosion rate ≤0.002mm / a. This is significantly superior to the 0.003-0.004mm / a of existing casting processes and the 0.002mm / a of traditional powder metallurgy processes (but at a higher cost), making it widely applicable in harsh environments such as coastal salt spray areas, highly polluted areas, and extremely cold regions.

[0051] 6. High degree of unity between creativity and practicality: This invention proposes for the first time the technical concept of "powder-casting composite preparation", which integrates the advantages of uniform dispersion of nanophases in powder metallurgy and the high-efficiency forming advantages of casting-extrusion. It is a cross-domain technological innovation that breaks through the inherent framework of existing technologies and has significant creativity. At the same time, the process route is simple, the parameters are controllable, and the cost is reasonable, which has strong practical applicability. It can be directly applied to the large-scale production of tension clamps for ultra-high voltage / extra-high voltage transmission lines, and has significant industrial application value and economic benefits. Attached Figure Description

[0052] Figure 1 This is a flowchart of the efficient and dense age-strengthened nano-high-strength aluminum alloy tension clamp forming process of the present invention.

[0053] Figure 2 This is a scanning electron microscope (SEM) image of the multi-component nanocomposite powder in Example 1 of the present invention (showing uniform dispersion of nano-Al2O3).

[0054] Figure 3 This is a schematic diagram of the tension clamp prepared in Embodiment 1 of the present invention (1-aluminum tube body, 2-conductor slot, 3-connecting flange).

[0055] Figure 4This is a comparison chart of the corrosion resistance of Example 1 of the present invention with Comparative Examples 1 and 2 (after 2000h of neutral salt spray test).

[0056] Figure 5 This is a transmission electron microscope (TEM) image of the nano-reinforced phase in Example 1 of the present invention (showing the L12-Al3(Er,Zr,Sc) phase size of 1-5 nm). Detailed Implementation

[0057] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0058] Example 1:

[0059] A highly efficient and dense age-strengthened nano-high-strength aluminum alloy tension clamp forming process includes the following steps:

[0060] S1. Preparation of multi-component nanocomposite powder:

[0061] S11. Composition Design: By weight percentage, the composition includes: Zn: 1.8%, Cu: 1.2%, Ni: 1.4%, Er: 0.5%, Zr: 1.2%, Sc: 0.1%, RE: 0.2% (Ce, La=1:1), nano Al2O3: 0.6%, with the balance being Al and unavoidable impurities; the nano Al2O3 has a particle size of 30nm and a purity of 99.9%.

[0062] S12. Raw material pretreatment: Weigh industrial pure aluminum powder (purity 99.8%, particle size 80μm), Al-Zn master alloy powder (Zn 50%, 80μm), Al-Cu master alloy powder (Cu 40%, 80μm), Al-Ni master alloy powder (Ni 30%, 80μm), Al-Er master alloy powder (Er 20%, 80μm), Al-Zr master alloy powder (Zr 10%, 80μm), Al-Sc master alloy powder (Sc 2%, 80μm), Al-RE master alloy powder (RE 10%, 80μm) and nano Al2O3 powder; dry at 140℃ for 2.5h;

[0063] S13. High-energy ball milling: Add the raw material powder to a planetary high-energy ball mill with a ball-to-material ratio of 18:1 and argon protection; rotate at 350 r / min for 10 h; stop the mill for 15 min every 2 h; after ball milling, pass the powder through a 200-mesh sieve to obtain a multi-element nanocomposite powder with a particle size of 50 μm and an oxygen content of 0.12%.

[0064] S2. Vacuum casting composite of nanocomposite powders:

[0065] S21. Preform Preparation: The composite powder is loaded into a graphite mold and pre-sintered in a vacuum hot-pressing sintering furnace at 480℃ for 1.5 hours with a vacuum degree of 3×10⁻⁶. -3 Pa, pressure 15MPa, forming a preform with a relative density of 78%;

[0066] S22. Vacuum casting: The preform is placed in a graphite crucible, and the vacuum induction melting furnace is evacuated to 3×10⁻⁶. -3 Pa, medium-frequency induction heating (frequency 1500Hz), heating rate 8℃ / min, heating to 770℃, holding for 20min, completely melting to form a melt;

[0067] S23. In-situ reaction enhancement: Add 0.15% of Al-Ti-B refining agent by melt mass, stir at 90 r / min for 6 min, and keep warm for 8 min to generate L12-Al3(Er,Zr,Sc) nanophase (size 3 nm).

[0068] S3. Acoustomagnetic coupling field homogenization and multi-stage purification:

[0069] S31. Homogenization of the acoustic-magnetic coupling field: The melt is cooled to 740℃ and treated with an acoustic-magnetic coupling field for 30 minutes; the low-frequency pulsed magnetic field has a frequency of 20Hz and a current of 200A; the high-energy ultrasonic field has a power of 1500W and a frequency of 25kHz.

[0070] S32. Multi-stage purification: ① Heat to 760℃, inject 0.4% of the melt mass of refining agent (KCl:NaCl:Na3AlF6=3:2:1), pressure 0.4MPa, time 10min; ② Add 0.2% of the melt mass of Al-Ce master alloy, stir evenly and let stand for 12min; ③ Nitrogen-argon mixed gas (1:2) flow rate 0.4m 3 / h, nozzle speed 500r / min, refining for 18min; stand for 8min.

[0071] S4. Extrusion gradient forming:

[0072] S41. Mold pretreatment: Preheat the metal mold to 380℃ and keep it at that temperature for 35 minutes; apply a 0.15mm thick release agent (graphite powder: water glass: alcohol = 2:1:7).

[0073] S42. Melt casting and gradient extrusion: Melt temperature 730℃, casting speed 1.0kg / s; initial pressure 70MPa, holding pressure 120s; pressure increased to 110MPa, holding pressure 250s; mold water cooling control cooling rate 75℃ / min; real-time monitoring of temperature and pressure;

[0074] S43. Demolding and initial processing: Eject the blank, remove the gate and burrs, and grind the surface with a grinding wheel.

[0075] S5. Synergistic heat treatment:

[0076] S51. Segmented solution treatment: In a box-type resistance furnace, hold at 400℃ for 60 minutes, then raise the temperature to 550℃ and hold for 5 hours; nitrogen protection;

[0077] S52. Gradient quenching: 200℃ mineral oil (kinematic viscosity 25 mm) 2 Quenching at 40°C for 4 min → quenching in deionized water at 80°C for 7 min → quenching in clean water at room temperature for 12 min; stirring at 40 r / min; cleaning with alcohol.

[0078] S53. Segmented aging: In the aging furnace, pre-aging is carried out at 130℃ for 2.5h, main aging is carried out at 175℃ for 5h, and over-aging is carried out at 150℃ for 1.5h; programmed temperature rise (4℃ / min), followed by furnace cooling.

[0079] S6. Post-processing and performance testing:

[0080] S61. Precision post-machining: turning, milling, and drilling to design dimensions; polishing of wire slots and connecting flanges, Ra=0.6μm;

[0081] S62. Surface anti-corrosion composite treatment: ① Micro-arc oxidation: electrolyte 14g / L sodium silicate + 7g / L sodium hydroxide + 0.8g / L Na2WO4; voltage 380V, current density 14A / dm³ 2 ① Silane sealing: 8% KH-550 solution, keep warm at 90℃ for 12 minutes;

[0082] S63. Performance Testing: Finished product tensile strength 680MPa, yield strength 565MPa, elongation 15%, impact toughness at -40℃ 75J / cm². 2 Conductivity 63% IACS; Density 99.7%; No corrosion spots after 2000h neutral salt spray test, corrosion rate 0.0015mm / a; Dimensional accuracy IT8 grade; Holding strength 97.5% of the conductor's rated breaking strength, meeting the requirements for use in UHV transmission lines.

[0083] Example 2

[0084] A highly efficient and dense age-strengthened nano-high-strength aluminum alloy tension clamp forming process includes the following steps:

[0085] S1. Preparation of multi-component nanocomposite powder:

[0086] S11. Composition design: Zn: 1.5%, Cu: 1.0%, Ni: 1.2%, Er: 0.4%, Zr: 1.0%, Sc: 0.08%, RE: 0.15% (Ce:La=1:1), nano Al2O3: 0.5%, balance is Al and impurities; nano Al2O3 particle size 20nm;

[0087] S12. Raw material pretreatment: Dry at 120℃ for 3 hours;

[0088] S13. High-energy ball milling: ball-to-material ratio 15:1, rotation speed 300 r / min, time 8 h; argon protection; passing through a 200-mesh sieve; oxygen content of composite powder 0.14%.

[0089] S2. Vacuum casting composite:

[0090] S21. Pre-sintering: 450℃, hold for 1 hour, vacuum degree 5×10 -3 Pa, pressure 10 MPa, relative density 75%;

[0091] S22. Vacuum casting: 760℃, hold for 15 min, vacuum degree 5×10 -3 Pa, heating rate 5℃ / min;

[0092] S23. In-situ reaction: Add 0.1% Al-Ti-B refining agent, stir at 80 r / min for 5 min, and keep warm for 5 min.

[0093] S3. Acoustomagnetic coupling homogenization and purification:

[0094] S31.730℃, acoustic-magnetic coupling field treatment for 25min; magnetic field frequency 18Hz, current 180A; ultrasonic power 1400W, frequency 22kHz;

[0095] S32.750℃, 0.3% refining agent injected, pressure 0.3MPa, time 8min; 0.15% Al-Ce master alloy added, let stand for 10min; nitrogen-argon mixed gas flow rate 0.3m³ / min. 3 / h, 400r / min, refining for 15min; let stand for 5min.

[0096] S4. Extrusion gradient forming:

[0097] Preheat the mold to 350℃ and hold for 30 minutes; melt temperature 720℃ and pouring speed 0.8 kg / s; initial pressure 60 MPa and hold for 100 seconds; increase pressure to 100 MPa and hold for 200 seconds; cooling rate 60℃ / min.

[0098] S5. Synergistic heat treatment:

[0099] Segmented solution treatment: 400℃ for 60 min, 540℃ for 4 h; Gradient quenching: 200℃ oil for 3 min → 80℃ water for 5 min → room temperature water for 10 min; Segmented aging: 120℃ for 2 h → 170℃ for 4 h → 150℃ for 1 h; Programmed temperature rise 3℃ / min.

[0100] S6. Post-processing and inspection:

[0101] Post-processing Ra=0.8μm; micro-arc oxidation electrolyte: 12g / L sodium silicate + 6g / L sodium hydroxide + 0.5g / L Na2WO4; voltage: 350V; current: 12A / dm³. 2 Time: 15 min; Sealing with 5% KH-550 at 80℃ for 10 min; Finished product tensile strength: 650 MPa, yield strength: 550 MPa, elongation: 14%, impact toughness at -40℃: 70 J / cm 2 Conductivity 62% IACS; Density 99.5%; Salt spray corrosion rate 0.002 mm / a after 2000 h; Holding power 97% of the rated breaking force of the conductor.

[0102] Example 3

[0103] A highly efficient and dense age-strengthened nano-high-strength aluminum alloy tension clamp forming process includes the following steps:

[0104] S1. Preparation of multi-component nanocomposite powder:

[0105] S11. Composition design: Zn: 2.0%, Cu: 1.4%, Ni: 1.6%, Er: 0.6%, Zr: 1.4%, Sc: 0.12%, RE: 0.25% (Ce:La=1:1), nano Al2O3: 0.8%, balance is Al and impurities; nano Al2O3 particle size 50nm;

[0106] S12. Raw material pretreatment: Dry at 150℃ for 2 hours;

[0107] S13. High-energy ball milling: ball-to-material ratio 20:1, rotation speed 400 r / min, time 12 h; argon protection; passing through a 200-mesh sieve; oxygen content of composite powder 0.11%.

[0108] S2. Vacuum casting composite:

[0109] S21. Pre-sintering: 500℃, hold for 2 hours, vacuum degree 2×10⁻⁶ -3 Pa, pressure 20 MPa, relative density 80%;

[0110] S22. Vacuum casting: 780℃, hold for 25 min, vacuum degree 2×10 -3 Pa, heating rate 10℃ / min;

[0111] S23. In-situ reaction: Add 0.2% Al-Ti-B refining agent, stir at 100 r / min for 8 min, and keep warm for 10 min.

[0112] S3. Acoustomagnetic coupling homogenization and purification:

[0113] S31.750℃, acoustic-magnetic coupling field treatment for 35min; magnetic field frequency 22Hz, current 220A; ultrasonic power 1600W, frequency 28kHz;

[0114] S32.770℃, 0.5% refining agent injected, pressure 0.5MPa, time 12min; 0.25% Al-Ce master alloy added, let stand for 15min; nitrogen-argon mixed gas flow rate 0.5m³ / min. 3 / h, 600r / min, refining for 20min; let stand for 10min.

[0115] S4. Extrusion gradient forming:

[0116] Preheat the mold to 400℃ and hold for 40 minutes; melt temperature 740℃, pouring speed 1.2 kg / s; initial pressure 80 MPa, hold for 150 seconds; increase pressure to 120 MPa and hold for 300 seconds; cooling rate 90℃ / min.

[0117] S5. Synergistic heat treatment:

[0118] Segmented solution treatment: 400℃ for 60 min, 560℃ for 6 h; Gradient quenching: 200℃ oil for 5 min → 80℃ water for 8 min → room temperature water for 15 min; Segmented aging: 140℃ for 3 h → 180℃ for 6 h → 150℃ for 2 h; Programmed temperature rise 5℃ / min.

[0119] S6. Post-processing and inspection:

[0120] Post-processing Ra=0.5μm; micro-arc oxidation electrolyte: 16g / L sodium silicate + 9g / L sodium hydroxide + 1.0g / L Na2WO4; voltage: 400V; current: 16A / dm³. 2 Time: 25 min; Sealing with 8% KH-550 at 100℃ for 15 min; Finished product tensile strength: 700 MPa, yield strength: 580 MPa, elongation: 16%, impact toughness at -40℃: 80 J / cm 2 Conductivity 65% ​​IACS; Density 99.8%; Salt spray corrosion rate 0.001 mm / a after 2000 h; Holding power 98% of the rated breaking force of the conductor.

[0121] Comparative Example 1 (Existing improved casting process)

[0122] Using the same alloy composition as in Example 1 (excluding nano-Al2O3), and employing the process of "in-situ synthesis + acoustic-magnetic coupling homogenization + extrusion casting + segmented aging" (without powder preparation and vacuum casting steps), the remaining steps are the same as in Example 1. Finished product performance testing: tensile strength 590 MPa, yield strength 510 MPa, elongation 12%, impact toughness at -40℃ 60 J / cm². 2 Conductivity 60% IACS; Density 99.3%; Salt spray corrosion rate 0.004 mm / a after 2000 h; Holding power 95% of the rated breaking force of the conductor.

[0123] Comparative Example 2 (Traditional Powder Metallurgy Process)

[0124] Using the same alloy composition as in Example 1, and employing the process of "high-energy ball milling - vacuum hot pressing sintering - isothermal forging - spinning - single aging," without the casting and extrusion gradient forming steps. Finished product performance testing: tensile strength 670 MPa, yield strength 560 MPa, elongation 14%, -40℃ impact toughness 72 J / cm². 2 The conductivity is 63% IACS; the density is 98.8%; the corrosion rate after 2000 hours of salt spray is 0.0018 mm / a; the grip strength is 97% of the rated breaking strength of the wire; however, the production cycle is 48 hours, the material utilization rate is 85%, and the overall cost is 45% higher than that of Example 1.

[0125] Comparative Example 3 (without synergistic heat treatment process)

[0126] The same process steps as in Example 1 were used, except that the synergistic heat treatment was changed to "single solution treatment (550℃ for 5 hours) + single room temperature quenching + single aging (175℃ for 5 hours)", with the other steps remaining unchanged. Finished product performance testing: tensile strength 640 MPa, yield strength 540 MPa, elongation 10%, impact toughness at -40℃ 45 J / cm². 2 Conductivity 61% IACS; Minor cracks exist on the surface of the clamp, and residual stress is relatively large; Salt spray corrosion rate 0.003 mm / a after 2000 h; Grip strength 94% of the rated breaking force of the conductor.

[0127] The performance comparison between Examples 1-3 and Comparative Examples 1-3 shows that the molding process of the present invention, through the synergistic combination of "powder-casting composite preparation", "acoustic-magnetic coupling homogenization", "extrusion gradient forming", and "synergistic heat treatment", not only achieves superior mechanical properties, density, and corrosion resistance compared to existing improved casting processes, but also solves the industrialization problems of low efficiency and high cost of traditional powder metallurgy processes. At the same time, the optimization of the synergistic heat treatment process makes the matching of strength, plasticity, and electrical conductivity significantly better than that of a single heat treatment process, fully demonstrating the technical advantages and practical value of the present invention.

[0128] In summary, this invention not only achieves a creative technological breakthrough and solves the core pain points of existing technologies, but also possesses high efficiency, low cost, and easy scalability for industrial application. It can be quickly transformed into actual productivity, providing high-performance and high-reliability tension clamp products for ultra-high voltage / extra-high voltage power transmission projects, promoting the technological upgrading of the power fittings manufacturing industry, and has significant industrial application value and social benefits.

[0129] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A forming process for age-strengthened nano-high-strength aluminum alloy tension clamps, characterized in that: Includes the following sequential steps: Preparation of S1 multi-component nanocomposite powder; Vacuum casting composite of the multi-component nanocomposite powder described in S2; S3 acoustic-magnetic coupling field homogenization and multi-stage purification treatment; S4 extrusion gradient forming is used to obtain a tension clamp blank; S5 synergistic heat treatment includes segmented solution treatment, gradient quenching and segmented aging strengthening; S6 post-processing, surface anti-corrosion composite treatment and performance testing.

2. The forming process for age-strengthened nano-high-strength aluminum alloy tension clamps according to claim 1, characterized in that: In step S1, the multi-component nanocomposite powder is composed of the following components by weight percentage: Zn: 1.5-2.0%, Cu: 1.0-1.4%, Ni: 1.2-1.6%, Er: 0.4-0.6%, Zr: 1.0-1.4%, Sc: 0.08-0.12%, RE: 0.15-0.25%, nano Al2O3: 0.5-0.8%, with the balance being Al and unavoidable impurities; wherein the particle size of the nano Al2O3 is 20-50 nm.

3. The forming process for age-strengthened nano-high-strength aluminum alloy tension clamps according to claim 2, characterized in that: Step S1 specifically includes: grinding the raw material powder in a high-energy ball mill at a ball-to-material ratio of 15:1-20:1 under argon protection at a speed of 300-400 r / min for 8-12 hours to obtain multi-component nanocomposite powder with a particle size of 20-80 μm.

4. The forming process for age-strengthened nano-high-strength aluminum alloy tension clamps according to claim 1, characterized in that: Step S2 includes: S21 The multi-component nanocomposite powder is subjected to a vacuum degree of ≤5×10 at 450-500℃. -3 Pre-sintering is carried out under Pa and pressure of 10-20MPa to form a preform with a relative density of ≥75%; S22 The preform is completely melted in a vacuum induction melting furnace at 760-780°C to form a melt; S23 adds 0.1-0.2% of the melt mass of Al-Ti-B refining agent to the melt to promote the in-situ formation of L12-Al3(Er,Zr,Sc) nanophase.

5. The forming process for age-strengthened nano-high-strength aluminum alloy tension clamps according to claim 1, characterized in that: Step S3 includes: S31 The melt is treated with an acoustic-magnetic coupling field at 730-750℃ for 25-35 minutes. The acoustic-magnetic coupling field is composed of a low-frequency pulsed magnetic field with a frequency of 18-22Hz and a magnetic current of 180-220A and a high-energy ultrasonic field with a power of 1400-1600W and a frequency of 22-28kHz. S32 sequentially purifies the melt with refining agents, performs deep aluminum-rare earth purification, and uses nitrogen-argon composite rotary blowing refining.

6. The forming process for age-strengthened nano-high-strength aluminum alloy tension clamps according to claim 1, characterized in that: Step S4 includes: S41 applies a release agent to the surface of the mold cavity, which is preheated to 350-400℃; S42 pours melt at 720-740℃ into the pressure chamber at a rate of 0.8-1.2 kg / s, and then applies gradient pressure for extrusion molding. The gradient pressure includes: an initial pressure of 60-80 MPa held for 100-150 seconds, and a pressure increase of 100-120 MPa held for 200-300 seconds. During the molding process, the cooling rate is controlled at 60-90℃ / min by the mold water cooling system.

7. The forming process for age-strengthened nano-high-strength aluminum alloy tension clamps according to claim 1, characterized in that: Step S5 includes: S51 segmented solution treatment: First, heat the blank to 400℃ and hold for 60 minutes, then heat to 540-560℃ and hold for 4-6 hours; S52 gradient quenching treatment: Quenching is carried out in three stages in sequence using mineral oil at 200℃, deionized water at 80℃, and clean water at room temperature. S53 segmented aging enhancement: First, pre-age at 120-140℃ for 2-3 hours, then main aging at 170-180℃ for 4-6 hours, and finally over-aging at 150℃ for 1-2 hours.

8. The forming process for age-strengthened nano-high-strength aluminum alloy tension clamps according to claim 1, characterized in that: In step S6, the surface anti-corrosion composite treatment is a combination of micro-arc oxidation and silane sealing. The electrolyte used for micro-arc oxidation includes sodium silicate 12-16 g / L, sodium hydroxide 6-9 g / L and Na2WO4 0.5-1.0 g / L, and the treatment voltage is 350-400V.

9. A nano-high-strength aluminum alloy tension clamp, characterized in that, The tension clamp is manufactured by the molding process described in any one of claims 1 to 8.

10. The nano-high-strength aluminum alloy tension clamp according to claim 9, characterized in that, Its performance meets the following requirements: tensile strength 650-700MPa, yield strength 550-580MPa, elongation 14-16%, electrical conductivity 62-65%IACS, density ≥99.5%, and holding power reaching more than 97% of the rated breaking force of the conductor.

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