Preparation method, material and application of aluminum alloy material for power transmission fittings

Abstract

The invention provides a preparation method, material and application of an aluminum alloy material for power transmission fittings, and the method comprises the following steps: mixing pure aluminum, K2TiF6 powder, KBF4 powder and NaNO3 powder according to a mass ratio of 27: 1: 2: 0.02, and processing to obtain Al-TiB2 intermediate alloy; then, pure aluminum, Al-20% Si, Al-10% Mn, Al-5% Zr and Al-5% Er intermediate alloy are mixed and treated, and a first melt is obtained; adding pure magnesium into the first melt, and treating to obtain a second melt; then adding an Al-TiB2 intermediate alloy into the second melt, and treating to obtain a third melt; then adding an Al-10% Sr intermediate alloy into the third melt, and treating to obtain a fourth melt; and finally, the fourth melt is refined, and the high-toughness heat-treatment-free aluminum alloy melt is obtained. The ultra-high-voltage power transmission fitting can meet the use requirements of light weight and high reliability of the ultra-high-voltage power transmission fitting.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy material technology, specifically relating to a method for preparing aluminum alloy material for power transmission fittings, the material itself, and its application. Background Technology

[0002] In the field of power transmission, overhead transmission lines are an important means of realizing large-scale power transmission. Power fittings, as key equipment in overhead transmission lines, play a crucial role in ensuring the safe and stable operation of the lines. They connect and fix components such as conductors and insulators, making the entire transmission system an organic whole.

[0003] Spacer bars, a type of electrical fitting, are primarily used to separate split conductors, effectively preventing conductor collisions caused by natural factors such as wind vibration or icing, thereby avoiding line faults. With the continuous growth of electricity demand, the construction of ultra-high voltage (UHV) lines has developed rapidly. During actual operation, spacer bar breakage accidents frequently occur in some areas. Analysis shows that the main reasons are casting defects, such as porosity and voids, as well as insufficient toughness of the material itself. To meet the higher requirements of UHV lines for fitting materials, high-strength and high-toughness aluminum alloys have become the preferred material for fittings.

[0004] Traditional cast aluminum alloys used in UHV transmission fittings, such as ZL102 and ZL104, suffer from poor plasticity and are prone to fracture due to casting defects. While ZL104 can have its strength improved through T6 heat treatment, this process is energy-intensive and can cause component deformation. Existing heat-treatment-free alloys from abroad, such as Rheinmetall Castasi® 37 and Alcoa C611EZCast™, have not optimized the vacuum die-casting process for thin-walled structures (wall thickness <3mm) in power fittings and do not incorporate the use of recycled aluminum. Traditional vacuum die-casting processes are ill-suited to the characteristics of thin-walled parts, resulting in poor density and unstable performance. These problems mean that existing materials and processes cannot meet the lightweight and high-reliability requirements of UHV fittings. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing aluminum alloy materials for power transmission fittings, materials and applications, to solve the problems of poor plasticity, high energy consumption for heat treatment, insufficient adaptability to thin walls, and incompatibility with recycled aluminum in existing materials, so as to meet the requirements of lightweight and high reliability of UHV power transmission fittings.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing an aluminum alloy material for power transmission fittings, comprising the following steps:

[0008] S1. Pure aluminum, K2TiF6 powder, KBF4 powder and NaNO3 powder are mixed in a mass ratio of 27:1:2:0.02, melted and stirred at 800℃~820℃, cooled to 750℃ and poured, and solidified to obtain Al-TiB2 intermediate alloy.

[0009] S2. Mix pure aluminum, Al-20%Si master alloy, Al-10%Mn master alloy, Al-5%Zr master alloy, and Al-5%Er master alloy, heat to 720℃~740℃ to melt, and stir until homogeneous to obtain the first melt.

[0010] S3. Add pure magnesium to the first melt, heat to 730℃~740℃ to melt and stir until homogeneous to obtain the second melt;

[0011] S4. Add Al-TiB2 master alloy to the second melt, maintain the temperature at 725℃~735℃ and stir until homogeneous to obtain the third melt;

[0012] S5. Add Al-10%Sr master alloy to the third melt, control the temperature at 720℃~730℃ and stir until homogeneous to obtain the fourth melt.

[0013] S6. Adjust the temperature of the fourth melt to 700℃~720℃ and refine it by rotating and blowing nitrogen to obtain a high-strength and tough aluminum alloy melt that does not require heat treatment.

[0014] Furthermore, in step S1, the stirring time is 10 to 30 minutes, and the TiB2 particle size in the Al-TiB2 master alloy is <100 nm.

[0015] Furthermore, in step S2, the heat preservation time is 15 to 20 minutes.

[0016] Furthermore, in step S3, the stirring time is 5 to 8 minutes; in step S4, the stirring time is 8 to 12 minutes; and in step S5, the stirring time is 5 to 10 minutes.

[0017] Furthermore, in step S6, the nitrogen injection flow rate is 0.5 m³ / s. 3 / h~1.0m 3 / h, the refining time is 10 to 15 minutes, and the degassing stage of the refining process takes 12 minutes.

[0018] In a second aspect, the present invention provides an aluminum alloy material for power transmission fittings, which is prepared by the method for preparing the aluminum alloy material for power transmission fittings described in the first aspect, and comprises the following components by mass percentage:

[0019] Si 4.5%~6.0%, Mn 0.3%~0.6%, Mg 0.15%~0.35%, Zr 0.05%~0.15%, Sr 0.02%~0.04%, Er 0.05%~0.2%, Fe≤0.25%, nano TiB2 0.05%~0.5%, impurities≤0.20%, balance aluminum.

[0020] Furthermore, the impurities include one or more of Zn, Ni, Pb, Sn, Ca and V, and the Zn content is not greater than 0.10%.

[0021] Furthermore, in the as-cast microstructure of aluminum alloy materials, the size of primary α-Al grains ranges from 20 μm to 50 μm.

[0022] Thirdly, this invention provides an application of an aluminum alloy material, wherein the aluminum alloy melt is prepared by the method for preparing aluminum alloy material for power transmission fittings described in the first aspect, and is used to prepare spacer frame with a wall thickness of <2.5mm in ultra-high voltage power transmission fittings. The application process includes the following steps:

[0023] Machining die-casting molds; the cavity of the die-casting mold corresponds to the shape of the spacer frame, and a vacuum valve is installed at the top of the cavity;

[0024] After maintaining the aluminum alloy melt at 660℃~680℃ and letting it stand for 5 minutes~8 minutes, pour it into the pressure chamber of the die casting machine; open the vacuum valve to make the cavity vacuum degree <10kPa and then start the die casting machine to press the aluminum alloy melt into the cavity of the die casting mold at a staged injection speed, while applying and holding the pressure.

[0025] After the melt cools to below 200°C, the mold is opened to obtain the spacer frame.

[0026] Furthermore, the spacer frame is a quadrilateral, hexagonal, or octagonal structure, with the width of the frame cross-section ranging from 3mm to 5mm and the height ranging from 1.5mm to 2.5mm.

[0027] In summary, this invention provides a method for preparing aluminum alloy materials for power transmission fittings, the materials themselves, and their applications. The method first involves mixing pure aluminum, K2TiF6 powder, KBF4 powder, and NaNO3 powder in a mass ratio of 27:1:2:0.02, melting and stirring at 800℃~820℃, cooling to 750℃, and then casting. After solidification, an Al-TiB2 master alloy is obtained. Next, pure aluminum, Al-20%Si master alloy, Al-10%Mn master alloy, Al-5%Zr master alloy, and Al-5%Er master alloy are mixed, heated to 720℃~740℃ for melting, and then stirred. The mixture is stirred until homogeneous to obtain a first melt; then pure magnesium is added to the first melt, the temperature is raised to 730℃~740℃ to melt and stirred until homogeneous to obtain a second melt; then Al-TiB2 master alloy is added to the second melt, the temperature is maintained at 725℃~735℃ and stirred until homogeneous to obtain a third melt; then Al-10%Sr master alloy is added to the third melt, the temperature is controlled at 720℃~730℃ and stirred until homogeneous to obtain a fourth melt; finally, the temperature of the fourth melt is adjusted to 700℃~720℃ and refined by rotary nitrogen blowing to obtain a high-strength and tough aluminum alloy melt that does not require heat treatment. This invention prepares high-strength and high-toughness heat-free aluminum alloys through a synergistic process of Al-TiB2 master alloy grain refinement, Sr modification treatment, and rotary nitrogen refining. It effectively solves the problems of poor plasticity of traditional alloys, high energy consumption and easy deformation during heat treatment, insufficient compatibility of foreign alloys with thin walls and incompatibility with recycled aluminum, and poor density and unstable performance of traditional die-cast thin-walled parts. It meets the requirements of lightweight and high reliability for UHV transmission fittings. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart illustrating a method for preparing aluminum alloy materials for power transmission fittings, as provided in an embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0031] Please see Figure 1 This embodiment provides a method for preparing aluminum alloy materials for power transmission fittings, including the following steps:

[0032] S1. Pure aluminum, K2TiF6 powder, KBF4 powder, and NaNO3 powder are mixed in a mass ratio of 27:1:2:0.02, melted and stirred at 800℃~820℃, cooled to 750℃ and poured. After solidification, Al-TiB2 master alloy is obtained.

[0033] This step uses pure aluminum as the matrix, K2TiF6 powder and KBF4 powder as the sources of Ti and B elements, and NaNO3 powder as the reaction promoter. After mixing them in a mass ratio of 27:1:2:0.02, they are melted and stirred at 800℃~820℃. This temperature range ensures that the fluoride salt reacts fully with the aluminum liquid to generate TiB2 particles, while avoiding excessively vigorous reaction that could lead to particle agglomeration. The stirring operation at 800 rpm can break up the agglomerates of TiB2 particles generated by the reaction, allowing them to be evenly dispersed in the aluminum liquid. Cooling to 750℃ for casting and solidification can control the growth rate of TiB2 particles, ultimately obtaining ultrafine TiB2 particles with a particle size of <100nm.

[0034] In one feasible implementation, the following raw materials can be prepared:

[0035] Basic raw materials: pure aluminum (99.7%), pure magnesium (99.9%), Al-20%Si master alloy, Al-10%Sr master alloy, Al-5%Er master alloy;

[0036] Recycled aluminum raw materials: Waste aluminum (purity ≥95%) is crushed, magnetically separated to remove iron (Fe content reduced to below 0.1%), and alkaline washed with 5% NaOH solution (60℃) to remove oil, to meet the needs of recycling;

[0037] Preparation of nano-refining agent: Al-TiB2 master alloy was prepared by K2TiF6+KBF4+NaNO3 molten salt method (melting at 800~820℃, stirring at 800r / min for 10~30min) to ensure that TiB2 particle size <100nm.

[0038] S2. Mix pure aluminum, Al-20%Si master alloy, Al-10%Mn master alloy, Al-5%Zr master alloy, and Al-5%Er master alloy, heat to 720℃~740℃ for melting, and stir until homogeneous to obtain the first melt.

[0039] This step uses pure aluminum and Al-20%Si, Al-10%Mn, Al-5%Zr, and Al-5%Er master alloys as raw materials. This allows for precise control of the amount of each alloying element added, avoiding burn-off or segregation caused by the direct addition of single elements. The melting temperature of 720℃ to 740℃ ensures that all raw materials are fully melted and reduces the high-temperature volatilization loss of elements such as Si and Mn. The stirring until homogeneous operation can eliminate component segregation in the melt and ensure that elements such as Si (forming a eutectic strengthening phase), Mn (regulating the morphology of the iron phase and improving corrosion resistance), Zr (generating an Al3Zr phase to help refine grains), and Er (refining grains and removing gas and impurities) are evenly distributed in the melt.

[0040] S3. Add pure magnesium to the first melt, heat to 730℃~740℃ to melt and stir until homogeneous to obtain the second melt.

[0041] In this step, pure magnesium is added to the first melt and heated to 730℃~740℃. This temperature range matches the melting characteristics of magnesium and its solubility in molten aluminum, which can promote the rapid and uniform dissolution of magnesium into the α-Al matrix. Stirring until homogeneous can prevent magnesium from agglomerating at the bottom due to density differences, ensuring that magnesium can fully exert its solid solution strengthening effect. At the same time, it creates conditions for the formation of GP zones or nano-precipitates by subsequent natural aging, thereby improving the strength of the alloy without additional heat treatment.

[0042] S4. Add Al-TiB2 master alloy to the second melt, maintain the temperature at 725℃~735℃ and stir until homogeneous to obtain the third melt.

[0043] This step involves adding a self-made Al-TiB2 master alloy. Taking advantage of the fact that the lattice mismatch rate between TiB2 and the α-Al phase is less than 5%, it becomes a highly efficient heterogeneous nucleation core during the solidification of the α-Al phase. Temperature control of 725℃~735℃ ensures that the master alloy is fully dissolved, while avoiding the oxidation or growth of TiB2 particles, ensuring that they are uniformly dispersed in the melt. Ultimately, the size of the primary α-Al grains is stably controlled at 20μm~50μm, achieving a simultaneous improvement in strength and toughness.

[0044] S5. Add Al-10%Sr master alloy to the third melt, control the temperature at 720℃~730℃ and stir until homogeneous to obtain the fourth melt.

[0045] In this step, an Al-10%Sr master alloy is added. Sr can be adsorbed on the growth steps of the eutectic Si phase, changing its growth habit. The temperature range of 720℃ to 730℃ provides a suitable environment for the Sr modification reaction, avoiding excessive temperature that could lead to Sr burn-out or deterioration failure. Stirring until homogeneous ensures that Sr is evenly distributed in the melt, transforming the originally coarse, sharp, plate-like eutectic Si phase into a fine fibrous or coral-like structure, significantly reducing stress concentration and improving the alloy's plasticity.

[0046] S6. Adjust the temperature of the fourth melt to 700℃~720℃ and refine it by rotating and blowing nitrogen to obtain a high-strength and tough aluminum alloy melt that does not require heat treatment.

[0047] This step adjusts the melt temperature to 700℃~720℃. This temperature ensures good melt fluidity and improves the contact efficiency between nitrogen bubbles and the melt. The rotary nitrogen injection method allows nitrogen to be evenly dispersed in the melt in the form of tiny bubbles. The adsorption effect of the bubbles carries away gases such as H and O, as well as oxide impurities in the melt. At the same time, stirring the melt promotes the floating of impurities. The refining process can effectively reduce the gas content and inclusion content of the melt, improve the purity of the melt, and reduce defects such as porosity and shrinkage in the subsequent die casting process from the source, ensuring the density and performance stability of thin-walled fittings.

[0048] This embodiment provides a method for preparing aluminum alloy materials for power transmission fittings. This method, through the independent design of the raw material ratio of the Al-TiB2 master alloy (pure aluminum, K2TiF6 powder, KBF4 powder, and NaNO3 powder in a mass ratio of 27:1:2:0.02) and the preparation process (melting at 800℃~820℃, stirring at 800 rpm, and casting at 750℃), obtains an ultra-fine particle size TiB2 grain refiner. Combined with the synergistic refining effect of Zr and Er elements, a multi-dimensional grain refinement mechanism is formed. Simultaneously, through the directional modification of the eutectic Si phase by Sr, the solid solution strengthening by Mg, and the regulation of the harmful iron phase by Mn, the alloy's strength and toughness are improved. Precise balance; the temperature of each preparation step (e.g., basic melting 720℃~740℃, refining 700℃~720℃), stirring operation and element addition sequence are matched, so that the alloy can achieve high strength and toughness without relying on heat treatment processes such as T6; and the rotary nitrogen refining process can efficiently remove gases and impurities from the melt, which not only improves the purity of the melt to meet the vacuum die casting requirements of thin-walled structures (wall thickness <2.5mm) of ultra-high voltage fittings, but also allows for the use of recycled aluminum raw materials. It solves the technical bottlenecks of poor plasticity of traditional alloys, high heat treatment energy consumption, insufficient compatibility of foreign alloys with thin walls and incompatibility with recycled aluminum, and achieves multiple optimizations in material properties, preparation costs and green manufacturing.

[0049] Regarding step S1, in one embodiment of the present invention, the stirring time is 10 to 30 minutes, and the TiB2 particle size in the Al-TiB2 master alloy is <100 nm.

[0050] It should be noted that pure aluminum, K2TiF6 powder, KBF4 powder, and NaNO3 powder are heated and melted together at a melting temperature of 800℃~820℃, and the melt is mechanically stirred at 800 rpm for 10 to 30 minutes. The melt is then cooled to 750℃ and poured. After solidification, an Al-TiB2 master alloy ingot with TiB2 particle size less than 100 nm is obtained, and the TiB2 content in the master alloy is 11%.

[0051] Regarding step S2, in one embodiment of the present invention, the heat preservation time is 15 to 20 minutes.

[0052] It should be noted that the prepared raw materials are placed in a melting furnace for melting, in a graphite clay crucible or silicon carbide crucible that does not contain Fe.

[0053] Regarding steps S3-S5, in one embodiment of the present invention, in step S3, the stirring time is 5 to 8 minutes; in step S4, the stirring time is 8 to 12 minutes; and in step S5, the stirring time is 5 to 10 minutes.

[0054] Regarding step S6, in one embodiment of the present invention, the nitrogen injection flow rate is 0.5 m³ / s. 3 / h~1.0m 3 / h, the refining time is 10 to 15 minutes, and the degassing stage of the refining process takes 12 minutes.

[0055] In addition, the changes in aluminum liquid quality indicators under different degassing times are shown in Table 1:

[0056] Table 1. Changes in aluminum liquid quality indicators under different degassing times

[0057]

[0058] As shown in Table 1, as the degassing time increased from 5 min to 15 min, the density of the molten aluminum decreased from 2.571 g / cm³. 3 Increased to 2.653 g / cm³ 3 The purity increased from 0.790kg to 1.004kg. The K value did not change significantly during the degassing process of 8-10 minutes. The temperature loss of the aluminum melt also increased over time, from 9℃ to 25℃.

[0059] When the degassing time was increased from 5 min to 15 min, the Al2O3 content decreased from 0.66% to 0.11%, and the MgAl2O4 content decreased from 0.94% to 0.10%, indicating that extending the degassing time can effectively reduce oxide inclusions. However, the degassing time did not significantly change the Fe content or the residual refining dosage. Considering both production efficiency and energy consumption, the optimal degassing time is recommended to be 12 min.

[0060] To ensure the purity, density, and compositional uniformity of the high-strength, high-toughness, heat-free aluminum alloy melt obtained by the above preparation method, and to meet the precision forming requirements of vacuum die casting for thin-walled structures (wall thickness <2.5mm) of UHV transmission fittings, and to verify the effect of process parameters (such as the optimal degassing time of 12min) on the quality improvement of the molten aluminum, the following control process for precision melting of high-strength, high-toughness aluminum alloy was established. Precise control of the molten aluminum quality was achieved through multi-dimensional detection:

[0061] (1) Determination of aluminum liquid density: The density of aluminum liquid was determined by reduced pressure test (RPT): ① Preheat the stainless steel sampling spoon to 600℃ before sampling; ② Pour about 200g of aluminum liquid into a preheated graphite mold (φ50×50mm); ③ Immediately place the mold in a vacuum chamber and solidify it under a pressure of 10kPa; ④ After cooling, measure the sample mass (accuracy 0.01g) and volume (measured by water displacement method); ⑤ Calculate the density according to ρ=m / V, measure the density value 3 times for each group, and take the average value.

[0062] (2) K value determination: ① Preheat the K mold to above 400℃ (stainless steel, 150mL volume), use a dry sampling spoon to quickly take aluminum liquid and inject it into the K mold to reduce the introduction of oxide inclusions. After holding for 30s, take it out and cool it to room temperature in the air; ② Measure the number of inclusions (D) and the number of evaluation sections (H) of each K mold cross section; ③ Calculate the K value according to K=H / D, compare it with the standard K value (e.g., K<0.2 is qualified) to evaluate the purity of aluminum liquid; ④ Measure 5 times for each group, remove the maximum and minimum values ​​and take the average.

[0063] (3) ABB purity evaluation: The purity of aluminum liquid was evaluated by pressure filtration: ① The preheated ceramic filter (pore size 30ppi) was loaded into the filtration device; ② 500g of aluminum liquid was filtered under a pressure of 0.2MPa; ③ The mass of the filter residue after 150s of filtration was recorded; ④ The lighter the mass of the filter residue, the higher the purity of the aluminum liquid; ⑤ The filter residue after filtration was retained for electron microscopy analysis.

[0064] (4) Temperature loss measurement: ① Before degassing, use an immersion thermocouple to measure the center temperature of the aluminum liquid (T1); ② After degassing, immediately measure the temperature at the same location (T2); ③ Temperature loss ΔT = T1 - T2; ④ Ensure that the thermocouple insertion depth is ≥200mm during measurement.

[0065] (5) Slag phase analysis: ① Take 50g of aluminum slag sample, clean it with acetone and dry it; ② After gold sputtering treatment, perform SEM observation (accelerating voltage 20kV); ③ EDS analysis of the chemical composition of inclusions; ④ Use Image-ProPlus software to count the area ratio of inclusions; ⑤ Analyze at least 5 fields of view for each condition (each field of view ≥1mm2).

[0066] (6) Other test items: ① Determination of slag amount: collect all slag after refining and weigh it with an electronic scale (accuracy 0.01kg); ② Determination of aluminum content in aluminum slag: use acid dissolution method (HCl 1:1 dissolution, filter and weigh); ③ Gas consumption: record the gas consumption in the refining process through a mass flow meter.

[0067] This invention also provides an aluminum alloy material for power transmission fittings, which is prepared by the method for preparing an aluminum alloy material for power transmission fittings provided in the foregoing embodiments, and comprises the following components by mass percentage:

[0068] Si 4.5%~6.0%, Mn 0.3%~0.6%, Mg 0.15%~0.35%, Zr 0.05%~0.15%, Sr 0.02%~0.04%, Er 0.05%~0.2%, Fe≤0.25%, nano TiB2 0.05%~0.5%, impurities ≤0.20%, balance aluminum.

[0069] Furthermore, the impurities include one or more of Zn, Ni, Pb, Sn, Ca and V, and the Zn content is not greater than 0.10%.

[0070] Furthermore, in the as-cast microstructure of aluminum alloy materials, the size of primary α-Al grains ranges from 20 μm to 50 μm.

[0071] The aluminum alloy material in this embodiment is an Al-Si-Mn-Er alloy, which achieves heat treatment-free strengthening and toughening through multi-element synergistic regulation. The following describes this material from two aspects: formulation design and alloy composition range (mass percentage).

[0072] 1. Formulation Design

[0073] (1) Matrix structure control: The matrix of the alloy is composed of primary α-Al phase and fine Al-Si eutectic structure. The α-Al phase provides good toughness and plasticity, while the uniformly distributed eutectic Si phase serves as the main strengthening phase, effectively hindering dislocation movement and improving strength.

[0074] (2) Synergistic strengthening of multiple elements: solid solution strengthening and aging potential of Mg and Zn: By precisely controlling the amount of Mg and Zn added, they are dissolved into the α-Al matrix, producing a significant solid solution strengthening effect and greatly improving the matrix strength. At the same time, these elements provide the possibility for the formation of GP zones or nano-precipitates in the alloy during subsequent natural aging or short-term artificial aging, thereby achieving further stabilization and improvement of performance without special heat treatment.

[0075] (3) Corrosion resistance of Mn and iron phase regulation: Adding Mn can improve the corrosion resistance of the alloy; on the other hand, Mn can form Mn-rich complex intermetallic compounds with other elements (such as Fe), changing the morphology of the harmful needle-like β-Fe phase (Al5FeSi) and transforming it into a more rounded or skeletal α-Fe phase (Al5FeSi). 15 (Fe,Mn)3Si2) significantly weakens its cutting effect on the matrix, thereby improving the toughness of the alloy.

[0076] (4) Microalloying and modification of rare earth (RE) elements: The introduction of rare earth elements (such as Ce, La, Er, etc.) is the key to achieving high strength and toughness without heat treatment. The mechanism of action is as follows:

[0077] Grain refinement: Rare earth elements accumulate at the solid-liquid interface, causing compositional supercooling, promoting the nucleation of α-Al dendrites, and significantly refining the grain size. According to the Hall-Petch relation, grain refinement can simultaneously improve the strength and toughness of the material.

[0078] Eutectic Si phase transformation: Rare earth elements can be adsorbed on the growth steps of the Si phase, changing its growth habits and transforming the originally coarse and sharp plate-like eutectic Si into a fine fibrous or coral-like morphology, greatly reducing stress concentration and enabling the alloy to achieve high strength while significantly improving elongation.

[0079] Purifying the melt and inhibiting oxidation: Rare earth elements are highly reactive and can react with gaseous elements such as H and O and low-melting-point impurity elements in the melt to form stable compounds with high melting points. This process removes gas and impurities, purifies the melt, and further improves the density and mechanical properties of the material.

[0080] 2. Alloy composition range (mass percentage)

[0081] The aluminum alloy is an Al-Si-Mn-Er system alloy. Its as-cast microstructure consists of primary Al phase, eutectic Al+Si phase, and a small amount of compound phases. By mass percentage, the alloy comprises the following components: silicon 4.5%–6.0%, manganese 0.3%–0.6%, magnesium 0.15%–0.35%, zirconium 0.05%–0.15%, strontium 0.02%–0.04%, erbium 0.05%–0.2%, iron ≤0.25%, impurities ≤0.20%, and the balance being aluminum.

[0082] Unavoidable impurities include zinc, nickel, lead, tin, calcium, and vanadium. In the microstructure, the Al phase is refined into ultrafine crystals by adding a nano-refining agent containing nano-TiB2. Nano-TiB2 is added as an Al-TiB2 master alloy, with an addition amount of 0.05%–0.5%.

[0083] The aluminum alloy material can be (by mass percentage): silicon: 4.5%, manganese: 0.6%, erbium: 0.20%, magnesium: 0.15%, zirconium: 0.15%, strontium: 0.02%, iron: ≤0.25%, unavoidable impurities ≤0.20%, with the balance being aluminum.

[0084] The aluminum alloy material can be (by mass percentage): silicon: 5.5%, manganese: 0.4%, erbium: 0.10%, magnesium: 0.35%, zirconium: 0.10%, strontium: 0.03%, iron: ≤0.25%, unavoidable impurities ≤0.20%, with the balance being aluminum.

[0085] The aluminum alloy material can be (by mass percentage): silicon: 6.0%, manganese: 0.3%, erbium: 0.05%, magnesium: 0.25%, zirconium: 0.05%, strontium: 0.04%, iron: ≤0.25%, unavoidable impurities ≤0.20%, with the balance being aluminum.

[0086] Table 2. Chemical composition design of materials (w%)

[0087]

[0088] The composition of aluminum alloys significantly affects their mechanical properties. Preliminary studies indicate that the optimal Si content is controlled between 4.5% and 6.0%. When the Si content in aluminum alloys increases, Si forms a fine Si phase—a second phase—in Al-Si alloys. This phase hinders dislocation movement within the aluminum matrix, resulting in a reinforcing effect and increasing the tensile strength and yield strength. However, the Si phase is relatively hard and brittle, leading to a decrease in elongation. Simultaneously, increased Si content lowers the melting point, improving the material's casting properties, such as increased fluidity and reduced hot cracking tendency. When the Si content is below 4.5%, the amount of reinforcing Si phase is insufficient, resulting in lower alloy strength but increased elongation. When the Si content is above 6.0%, the material's strength increases while elongation or toughness decreases, which is detrimental to the high toughness objective of this invention.

[0089] Nano-TiB2 particles in the nano-refining agent can refine the primary α-Al crystals of Al-Si alloys, significantly reducing their grain size. In this study, the Si content is relatively low, lower than the 7%–11% Si content of traditional Al-Si die-casting alloys. This results in a higher number of primary α-Al crystals during solidification, with well-developed dendrites. Therefore, refining the primary α-Al crystals is crucial for achieving high toughness. TiB2 particles have a similar lattice constant to the α-Al phase, with a lattice mismatch rate of less than 5%. Therefore, TiB2 particles can act as heterogeneous nuclei for the α-Al phase during solidification. The addition of nano-TiB2 particles significantly increases the number of heterogeneous nuclei within the same volume, thus greatly refining the α-Al phase. The nano-TiB2 addition amount in this invention is 0.05%–0.5%, achieving a good refining effect. The α-Al grains can be refined to 20–50 micrometers, thereby significantly improving the strength and elongation of the die-casting alloy.

[0090] Adding rare earth element Er to the alloy has a low solubility in the aluminum matrix. During solidification, Er is expelled to the solid front and accumulates, forming compositional supercooling, which can refine the grain size and assist in refining the α-Al phase. Er also has an auxiliary modification effect on the eutectic Si phase, making it finer. Furthermore, Er has a high affinity for oxygen or gaseous elements, which can help remove gas and impurities. However, due to the rapid cooling rate of the molten aluminum during die casting, excessive Er can easily lead to segregation of metallic elements and even the formation of Er-rich intermetallic compounds. Therefore, the content of rare earth Er is controlled between 0.05% and 0.20%.

[0091] Sr is added specifically to modify the eutectic Si phase, transforming the lamellar eutectic Si phase into rod-shaped or seaweed-like structures. The Sr addition amount in this study is the same as that used in conventional Al-Si alloys.

[0092] Adding Zr to the alloy primarily serves to refine the primary α-Al phase. Zr readily reacts with Al to form Al3Zr, and during solidification, the fine Al3Zr phase can also act as heterogeneous nuclei for the α-Al phase, increasing the number of crystal nuclei and thus refining the grain size.

[0093] Fe can reduce the tendency of molten aluminum to stick to the mold during die casting. However, during solidification, Fe reacts with Al and Si in the alloy to form needle-like FeAl3 and Al-Fe-Si intermediate compounds, which disrupt the matrix structure and deteriorate the mechanical properties of the material, especially reducing toughness. Therefore, one of the characteristics of this study is that the Fe content in the aluminum alloy must be strictly controlled below 0.25%. This is achieved by controlling the Fe content in the raw materials and using Fe-free melting crucibles to prevent the addition of Fe to the molten aluminum during the melting process.

[0094] The reduced Fe content led to an increased tendency for mold sticking during die casting. To mitigate the risk of mold sticking corrosion, an appropriate amount of Mn was added in this embodiment. Mn has properties similar to Fe, which can prevent mold sticking without generating harmful compounds. When the Mn content is below 0.3%, its effect on reducing mold sticking is limited, while above 0.6%, the material's toughness and other mechanical properties decrease. Therefore, the key feature of this study is that the appropriate Mn addition amount is 0.3%–0.6%.

[0095] Other impurity elements such as zinc, nickel, lead, tin, calcium, and vanadium are all impurities, and their content should be strictly controlled. Otherwise, they will seriously reduce the mechanical properties of the alloy, especially the elongation. The total content of the above impurity elements should be controlled below 0.20%, and the content of zinc should be controlled below 0.10%.

[0096] This invention also provides an application of aluminum alloy material. The aluminum alloy melt is prepared by the method described in the foregoing embodiments for preparing aluminum alloy material for power transmission fittings, and is used to prepare spacer frame with a wall thickness of <2.5mm in ultra-high voltage power transmission fittings. The application process includes the following steps:

[0097] Step 1: Machining the die-casting mold; the cavity of the die-casting mold corresponds to the shape of the spacer frame, and a vacuum valve is installed at the top of the cavity.

[0098] For example, the die-casting mold for the spacer bar frame is machined from H13 mold steel, and the cavity of the part is formed by a combination of a moving mold and a fixed mold. Whether it is a quadrilateral, hexagonal, or octagonal frame, the die-casting gating system is designed as follows: molten aluminum alloy is injected into the mold cavity from the center (straight runner position) of the spacer bar frame, and enters the frame mold cavity through the ingate; each side of the frame has an ingate connected to the central runner. The ingates of each frame are located in the middle of the frame, with the same inlet direction and forming a reasonable angle with the frame, so that the molten aluminum flows in the same direction after entering the mold cavity; the area of ​​each ingate is 15% to 20% of the maximum cross-sectional area of ​​the frame, and the ingate thickness is ensured to be 0.5mm to 1mm. Overflow grooves are provided on the outside of the frame junctions. A vacuum valve is located above the mold cavity and connected to an external vacuum system.

[0099] Step 2: Keep the aluminum alloy melt at 660℃~680℃ and let it stand for 5 minutes to 8 minutes before pouring it into the pressure chamber of the die casting machine; open the vacuum valve to make the cavity vacuum degree <10kPa and start the die casting machine to press the aluminum alloy melt into the cavity of the die casting mold at a staged injection speed, while applying and holding pressure.

[0100] For example, the alloy molten metal is poured into the pressure chamber of a die-casting machine and immediately vacuum die-cast to obtain the spacer frame part. During die casting, the vacuum degree of the mold cavity is controlled below 10 kPa, and the molten metal pouring temperature is controlled between 660℃ and 680℃. The injection pressure of the die-casting machine is 40 MPa to 60 MPa, and the injection speed is 3.5 m / s to 5.0 m / s.

[0101] Step 3: After the melt cools to below 200°C, open the mold to obtain the spacer frame.

[0102] In one embodiment of the present invention, the spacer frame is a quadrilateral, hexagonal or octagonal structure, and the width of the frame cross-section is a rectangle ranging from 3mm to 5mm and the height is ranging from 1.5mm to 2.5mm.

[0103] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0104] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0105] In the embodiments disclosed in this application, it should be understood that the disclosed devices / terminal equipment and methods can be implemented in other ways. For example, the device / terminal equipment embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling or direct coupling or communication connection may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0106] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an aluminum alloy material for power transmission fittings, characterized in that, Includes the following steps: S1. Pure aluminum, K2TiF6 powder, KBF4 powder and NaNO3 powder are mixed in a mass ratio of 27:1:2:0.02, melted and stirred at 800℃~820℃, cooled to 750℃ and poured, and solidified to obtain Al-TiB2 intermediate alloy. S2. Mix pure aluminum, Al-20%Si master alloy, Al-10%Mn master alloy, Al-5%Zr master alloy, and Al-5%Er master alloy, heat to 720℃~740℃ to melt, and stir until homogeneous to obtain the first melt. S3. Add pure magnesium to the first melt, heat to 730℃~740℃ to melt and stir until homogeneous to obtain the second melt; S4. Add the Al-TiB2 master alloy to the second melt, maintain the temperature at 725℃~735℃ and stir until homogeneous to obtain the third melt; S5. Add Al-10%Sr master alloy to the third melt, control the temperature at 720℃~730℃ and stir until homogeneous to obtain the fourth melt. S6. Adjust the temperature of the fourth melt to 700℃~720℃ and refine it by rotating and blowing nitrogen to obtain a high-strength and tough aluminum alloy melt that does not require heat treatment.

2. The method for preparing an aluminum alloy material for power transmission fittings according to claim 1, characterized in that, In step S1, the stirring time is 10 to 30 minutes, and the TiB2 particle size in the Al-TiB2 master alloy is <100 nm.

3. The method for preparing an aluminum alloy material for power transmission fittings according to claim 1, characterized in that, In step S2, the heat preservation time is 15 to 20 minutes.

4. The method for preparing an aluminum alloy material for power transmission fittings according to claim 1, characterized in that, In step S3, the stirring time is 5 to 8 minutes; in step S4, the stirring time is 8 to 12 minutes; in step S5, the stirring time is 5 to 10 minutes.

5. The method for preparing an aluminum alloy material for power transmission fittings according to claim 1, characterized in that, In step S6, the nitrogen injection flow rate is 0.5 m³ / s. 3 / h~1.0m 3 / h, the refining time is 10 to 15 minutes, and the degassing stage of the refining process takes 12 minutes.

6. An aluminum alloy material for power transmission fittings, characterized in that, The material is prepared by the method of any one of claims 1-5, and comprises the following components by mass percentage: Si 4.5%~6.0%, Mn 0.3%~0.6%, Mg 0.15%~0.35%, Zr 0.05%~0.15%, Sr 0.02%~0.04%, Er 0.05%~0.2%, Fe≤0.25%, nano TiB2 0.05%~0.5%, impurities≤0.20%, balance aluminum.

7. The aluminum alloy material for power transmission fittings according to claim 6, characterized in that, The impurities include one or more of Zn, Ni, Pb, Sn, Ca and V, and the Zn content is not greater than 0.10%.

8. The aluminum alloy material for power transmission fittings according to claim 6, characterized in that, In the as-cast microstructure of aluminum alloys, the size of primary α-Al grains ranges from 20 μm to 50 μm.

9. An application of an aluminum alloy material, characterized in that, The aluminum alloy melt is prepared by the method for preparing aluminum alloy material for power transmission fittings according to any one of claims 1-5, and is used to prepare spacer frame with a wall thickness of <2.5mm in ultra-high voltage power transmission fittings. The application process includes the following steps: Processing die-casting molds; the cavity of the die-casting mold corresponds to the shape of the spacer frame, and a vacuum valve is installed at the top of the cavity; After maintaining the aluminum alloy melt at 660℃~680℃ and letting it stand for 5 minutes~8 minutes, pour it into the pressure chamber of the die casting machine; open the vacuum valve to make the cavity vacuum degree <10kPa and start the die casting machine to press the aluminum alloy melt into the cavity of the die casting mold at a staged injection speed, while applying and holding pressure. After the melt cools to below 200°C, the mold is opened to obtain the spacer frame.

10. The application of the aluminum alloy material according to claim 9, characterized in that, The spacer frame is a rectangular structure with a quadrilateral, hexagonal, or octagonal shape, and the width of the frame cross-section ranges from 3mm to 5mm, and the height ranges from 1.5mm to 2.5mm.

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