Ultrahigh-conductivity high-strength creep-resistant aluminum alloy conductor and preparation method, power cable

Abstract

The application discloses an ultrahigh-conductivity high-strength anti-creep aluminum alloy conductor and a preparation method and power cable thereof, and comprises, in percentage by mass, Al: >= 99.68%; B: 0.0038%-0.0052%; rare earth element R: 0.068%-0.092%; Fe: 0.145%-0.175%; Si: <= 0.030%; inevitable impurities: <= 0.005% for each and <= 0.015% in total; and does not contain Mg and Zr, and Cu: < 0.002%; and satisfies the relationship formula: 14 <= [R] / [B] <= 20, [R] is the mass percentage of the rare earth element, and [B] is the mass percentage of the B element. The application realizes the synchronous significant improvement of the conductivity, the strength and the anti-creep property through the unique ultralow-content boron purification and the specific range rare earth element nano-precipitation strengthening mechanism, and the specific heat treatment system matched with the mechanism, and is suitable for manufacturing high-performance power cables.

Description

Technical Field

[0001] This invention belongs to the field of power cable technology, specifically relating to ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductors and their preparation methods, as well as power cables. Background Technology

[0002] Copper has long been the preferred material for power cable conductors due to its excellent electrical conductivity and mechanical properties. However, the scarcity, high price, and high density of copper resources have prompted the industry to seek solutions that substitute aluminum for copper.

[0003] Pure aluminum (such as 1060 industrial pure aluminum) has high conductivity (approximately 61.8% IACS), but low strength (tensile strength is typically below 80 MPa) and poor creep resistance, making it difficult to meet the requirements of medium- to high-strength cables. To improve strength, common AA8 series aluminum alloys (such as AA8030 and AA8176) are strengthened through solid solution and precipitation by adding elements such as iron, copper, and silicon. However, this often leads to a significant decrease in conductivity to below 58% IACS, increasing power transmission losses.

[0004] Some studies have attempted to improve the overall performance of aluminum alloys by adding trace amounts of rare earth elements (such as scandium and yttrium) or boron. However, these attempts often face the following dilemmas: (1) elements such as magnesium and zirconium added in pursuit of high strength severely damage conductivity; (2) if the addition of rare earth elements is not properly proportioned with impurity elements or other alloying elements, coarse or uneven precipitates are easily formed, resulting in limited strengthening effect and potentially deteriorating conductivity; (3) conventional rolling-annealing processes are difficult to effectively control the morphology and distribution of nanoscale precipitates, leading to unstable performance.

[0005] Therefore, a long-standing and pressing technical challenge in this field is how to simultaneously achieve ultra-high conductivity (≥62.0% IACS) approaching or even exceeding that of industrially pure aluminum, significantly higher mechanical strength (≥120MPa) than conventional aluminum alloys, and excellent creep resistance in aluminum-based conductors, while ensuring the feasibility of industrial-scale production. Existing technologies have not yet disclosed a compositional system and processing method that can systematically and synergistically resolve this contradiction. Summary of the Invention

[0006] To address the problems in existing technologies, the present invention aims to provide an ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor and its preparation method, as well as a power cable. It abandons traditional strengthening elements that impair conductivity and, through a unique "ultra-low content boron purification synergistic with specific range of rare earth element nano-precipitation strengthening" mechanism, coupled with a matching specific heat treatment regime, achieves a simultaneous and significant improvement in conductivity, strength, and creep resistance. This overcomes the technical bottleneck of achieving both high conductivity and high creep resistance in aluminum conductors, resulting in a comprehensive performance of conductivity ≥62.2% IACS, tensile strength ≥125MPa, and excellent creep resistance, surpassing existing aluminum conductors and some copper conductors, and is suitable for manufacturing high-performance power cables.

[0007] To achieve the above objectives and technical effects, the technical solution adopted by this invention is as follows:

[0008] Ultra-high conductivity, high-strength, creep-resistant aluminum alloy conductor, comprising the following components by weight percentage:

[0009] Al: ≥99.68%;

[0010] B: 0.0038%-0.0052%;

[0011] Rare earth element R: 0.068%-0.092%;

[0012] Fe: 0.145%-0.175%;

[0013] Si: ≤0.030%;

[0014] Unavoidable impurities: ≤0.005% for each, ≤0.015% in total;

[0015] It does not contain artificially added Mg and Zr, and Cu: <0.002%;

[0016] Satisfying the relation:

[0017] 14≤[R] / [B]≤20;

[0018] Where [R] represents the mass percentage of rare earth elements, and [B] represents the mass percentage of element B.

[0019] Furthermore, the rare earth element R is one or a combination of two of Y and Sc.

[0020] Furthermore, the rare earth element R is Y, with a mass percentage of 0.075%-0.088%.

[0021] Furthermore, the rare earth element R is a combination of Y and Sc, with a mass percentage of 0.075%-0.088%.

[0022] Furthermore, the microstructure of the ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor contains materials with an average size of 8-20 nm and a number density of not less than 6 × 10⁻⁶. 21 m -3 Al3(Sc,Y) (preferably (6-8)×10 21 m -3 Nanoscale precipitates.

[0023] Furthermore, the ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor has a volume conductivity of not less than 62.2% IACS and a tensile strength of not less than 125MPa at 20℃.

[0024] Furthermore, the ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor exhibits a steady-state creep rate of less than 1.0 × 10⁻¹⁰ hours under 100°C and 80% room temperature yield strength stress. -8 s -1 .

[0025] This invention also discloses a method for preparing an ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor, comprising the following steps:

[0026] S1. Smelting and Ultra-Clean Refining: High-purity aluminum ingots with a purity ≥99.86% are used as the main raw material, supplemented with aluminum-iron and aluminum-rare earth intermediate alloys, and smelted at 735-745℃ under inert gas protection. Dynamic micro-alloying technology is adopted, and aluminum-boron alloy wire (Al-3~5%B alloy wire) is added using a dynamic wire feeding method to ensure the uniform and controllable introduction of ultra-low amounts of B element. After electromagnetic stirring, the melt undergoes two-stage refining: first, a high-purity mixed gas (Ar+Cl2) is introduced for deep hydrogen and impurity removal, and then the process is switched to pure argon gas for soft stirring and settling. The total refining time is 12-18 minutes, with online slag removal.

[0027] S2. Continuous casting and rolling with temperature control: A twin-roll casting mill is used to cast and roll the refined melt into strips with a thickness of 7-9mm at 685-695℃; the strips immediately enter a multi-pass hot continuous rolling mill, and the final rolling temperature is controlled to be no less than 305℃. Then, after 2-4 passes of cold continuous rolling, a bar with a diameter of 9.4-9.6mm and a bright surface is produced.

[0028] S3. Key Phase Change Heat Treatment (Core Process): The rod is first drawn to an intermediate wire with a diameter of 3.48-3.52mm using a wire drawing machine; then, without stopping, the wire is immediately put into a controlled atmosphere continuous annealing furnace and isothermally annealed at a temperature range of 320-324℃ for 3.9-4.1h. The annealing atmosphere is nitrogen or a nitrogen-hydrogen mixture.

[0029] S4. Final shaping: The wire processed in step S3 is cooled to room temperature and then continuously drawn to the final required size using a multi-die wire drawing machine.

[0030] Furthermore, in step S3, the annealing temperature is 322±1℃ and the time is 4.0±0.05h.

[0031] The present invention also discloses a conductor for power cables, which is composed of multiple strands of single wires, wherein the single wires are ultra-high conductivity, high strength and creep resistant aluminum alloy conductors as described above.

[0032] The present invention also discloses a power cable, wherein the conductor of the power cable is an ultra-high conductivity, high strength and creep resistant aluminum alloy conductor as described above.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1) Under the background of ultra-low silicon and copper impurities, this invention precisely controls the boron (B) content in the ultra-low range of 0.0038%-0.0052%, which fundamentally changes its main function. This content is not enough to cause significant grain refinement, but it is just enough to preferentially combine with trace amounts of electrically poisoning elements such as titanium (Ti) and vanadium (V) in the aluminum melt to form stable borides, which are then removed or inertized in subsequent processes. This achieves extreme purification of the aluminum matrix and minimizes electron scattering centers. This is the first cornerstone for obtaining an ultra-high conductivity of ≥62.2% IACS.

[0035] 2) The total amount of rare earth element R is strictly limited to 0.068%-0.092%, and the ratio of R to B content [R] / [B] is located in the precise synergistic window of 14-20. This ratio ensures that in the subsequent specific solid-state phase transition process, rare earth elements can be almost completely and efficiently converted into high number-density Al3(Sc,Y) nano-precipitates. These nano-phases with a size of 8-20 nm are coherent with the matrix, producing extremely strong dispersion strengthening and dislocation pinning effect. This is the second cornerstone for obtaining high strength and excellent creep resistance. Since most of the rare earth atoms are fixed in the precipitates and there are very few solid-solid atoms, the negative impact on conductivity is reduced to negligible.

[0036] 3) Simultaneously achieved ultra-high conductivity (≥62.2% IACS), high strength (≥125MPa), and ultra-low creep rate (<1.0×10⁻⁶). -8 s -1 These three indicators, which are mutually restrictive in traditional materials science, have achieved synergistic improvement in this invention, and their comprehensive performance spectrum is outside the performance range of all existing aluminum conductors;

[0037] 4) The synergistic effect of components is critical and non-obvious: "ultra-low B content", "rare earth content within a specific range" and "14≤[R] / [B]≤20" form a closely related and indispensable "performance triangle". If any one of them deviates from the range, even if the other two are within the range, the performance will deteriorate sharply. This strong synergistic effect found in an extremely narrow component window is something that those skilled in the art cannot obtain through conventional knowledge reasoning or simple superposition of existing technologies.

[0038] 5) Strong locking effect of process and composition: The specific heat treatment process of this invention (320-324℃, 3.9-4.1h) is the only "key" to unlocking the performance potential of a specific composition system. The same composition using conventional annealing (such as annealing at 300℃ or 350℃ for 1h) or omitting annealing will not achieve the performance level of this invention. This proves that this invention is a complete technical solution with a high degree of integration of composition design and process design.

[0039] 6) The microstructure provides decisive evidence: the conductors processed by the process of this invention have uniformly dispersed atoms with an average size of 8-20 nm and a number density of not less than 6 × 10⁻⁶ in their matrix. 21 m -3 The Al3(Sc,Y) spherical nanoprecipitates, with their near-ideal nano-reinforced structure, are the microscopic source of the macroscopically superior performance and a direct proof of the scientific validity of the technical solution of this invention. Attached Figure Description

[0040] Figure 1 The images shown are bright-field transmission electron microscopy (TEM) images and corresponding selected area electron diffraction (SAED) patterns of the aluminum alloy conductor prepared in Example 1 of this invention after heat treatment; wherein, Figure 1 In the image (a), the image represents a bright-field transmission electron microscope (TEM) image of the aluminum alloy conductor prepared in Example 1 after heat treatment. Figure 1 (b) in the diagram represents the selected area electron diffraction (SAED) pattern;

[0041] Figure 2 This is a schematic cross-sectional view of the power cable according to Embodiment 3 of the present invention;

[0042] Wherein, 1-conductor; 2-conductor shielding layer; 3-insulating layer; 4-insulating shielding layer; 5-metallic sheath; 6-outer sheath. Detailed Implementation

[0043] The present invention will now be described in detail so that its advantages and features can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0044] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form to prepare for the more detailed descriptions that follow.

[0045] like Figure 1-2 As shown, this invention discloses an ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor, which comprises the following components by mass percentage:

[0046] Aluminum (Al): ≥99.68%;

[0047] Boron (B): 0.0038%-0.0052%;

[0048] Rare earth element R: 0.068%-0.092%;

[0049] Iron (Fe): 0.145%-0.175%;

[0050] Silicon (Si): ≤0.030%;

[0051] Unavoidable impurities: ≤0.005% for each, ≤0.015% in total;

[0052] It does not contain artificially added magnesium (Mg) and zirconium (Zr), and copper (Cu): <0.002%;

[0053] Satisfying the relation:

[0054] 14≤[R] / [B]≤20;

[0055] Where [R] represents the mass percentage of rare earth elements, and [B] represents the mass percentage of element B.

[0056] In some implementations, the rare earth element R is one or a combination of yttrium (Y) and scandium (Sc).

[0057] In some implementations, the rare earth element R is Y, with a mass percentage of 0.075%-0.088%.

[0058] In some implementations, the rare earth element R is a combination of Y and Sc, with a mass percentage of 0.075%-0.088%.

[0059] In some embodiments, the microstructure of the ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor contains an average size of 8-20 nm and a number density of not less than 6 × 10⁻⁶. 21 m -3 Al3(Sc,Y) nanoprecipitates.

[0060] In some implementations, the ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor has a volume conductivity of not less than 62.2% IACS and a tensile strength of not less than 125MPa at 20°C.

[0061] In some implementations, the ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor exhibits a steady-state creep rate of less than 1.0 × 10⁻¹⁰ hours at 100°C and 80% of its room temperature yield strength stress. -8 s -1 .

[0062] This invention also discloses a method for preparing the ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor as described above, comprising the following steps:

[0063] S1. Smelting and Ultra-Clean Refining: High-purity aluminum ingots with a purity ≥99.86% are used as the main raw material, supplemented with aluminum-iron and aluminum-rare earth intermediate alloys, and smelted at 735-745℃ under inert gas protection. Dynamic micro-alloying technology is adopted, and aluminum-boron alloy wire (Al-3~5%B alloy wire) is added using a dynamic wire feeding method to ensure the uniform and controllable introduction of ultra-low amounts of B element. After electromagnetic stirring, the melt undergoes two-stage refining: first, a high-purity mixed gas (Ar+Cl2) is introduced for deep hydrogen and impurity removal, and then the process is switched to pure argon gas for soft stirring and settling. The total refining time is 12-18 minutes, with online slag removal.

[0064] S2. Continuous casting and rolling with temperature control: A twin-roll casting mill is used to cast and roll the refined melt into strips with a thickness of 7-9mm at 685-695℃; the strips immediately enter a multi-pass hot continuous rolling mill, and the final rolling temperature is controlled to be no less than 305℃. Then, after 2-4 passes of cold continuous rolling, a bar with a diameter of 9.4-9.6mm and a bright surface is produced.

[0065] S3. Key Phase Change Heat Treatment (Core Process): The rod is first drawn to an intermediate wire with a diameter of 3.48-3.52mm using a wire drawing machine; then, without stopping, the wire is immediately put into a controlled atmosphere continuous annealing furnace and isothermally annealed at a temperature range of 320-324℃ for 3.9-4.1h. The annealing atmosphere is nitrogen or a nitrogen-hydrogen mixture.

[0066] S4. Final shaping: The wire processed in step S3 is cooled to room temperature and then continuously drawn to the final required size using a multi-die wire drawing machine.

[0067] The heat treatment regime of "320-324℃, 3.9-4.1h" in step S3 is the core and key to achieving the performance target of this invention. This regime is the optimal kinetic window for maximizing the uniform precipitation of Al3(Sc,Y) nano-precipitates in the composition system, which is determined by a large number of experiments. If the temperature or time deviates from this range, the number, size or distribution of precipitates will be unsatisfactory, and thus it will be impossible to obtain the ultra-high conductivity and high strength at the same time.

[0068] In some embodiments, in step S3, the annealing temperature is 322±1℃ and the time is 4.0±0.05h.

[0069] The present invention also discloses a conductor for power cables, which is composed of multiple strands of single wires, wherein the single wires are ultra-high conductivity, high strength and creep resistant aluminum alloy conductors as described above.

[0070] The present invention also discloses a power cable, wherein the conductor of the power cable is an ultra-high conductivity, high strength and creep resistant aluminum alloy conductor as described above.

[0071] Example 1

[0072] Unless otherwise specified, the following general conditions apply to both the embodiments and comparative examples:

[0073] Raw materials: 99.86% high-purity aluminum ingots, Al-20Fe master alloy, Al-10Y master alloy, Al-2Sc master alloy, Al-5B alloy wire (for adding B element).

[0074] S1. Melting and ultra-clean refining: Melting at 740℃ under argon protection, refining process as described in this invention, total refining time 15 min.

[0075] S2. Continuous casting and temperature-controlled rolling: Casting temperature 690℃, strip thickness 8mm. Hot rolling final temperature. Cold-rolled rods to Φ9.5mm with a bright surface.

[0076] S3. Key phase transition heat treatment: See Table 1;

[0077] S4. Final shaping: All samples were finally drawn to Φ1.78mm (corresponding to 25mm). 2 The performance of the single-line cross section was tested.

[0078] The content ratios of Examples 1-4 and Comparative Examples 1-7 are shown in Table 1.

[0079] Table 1

[0080]

[0081] The performance test results of Examples 1-4 and Comparative Examples 1-7 are shown in Table 2.

[0082] Table 2

[0083]

[0084] Test standards: conductivity (GB / T 3048.2), mechanical properties (GB / T 4909.3), creep properties (ASTM E139).

[0085] The following conclusions can be drawn from Table 1-2:

[0086] 1) Examples 1-4 of the present invention: all properties far exceed the set targets (62.2% IACS, 125MPa), and the creep rate is one order of magnitude better than that of commercial AA8176 in Comparative Example 7, and two orders of magnitude better than that of pure aluminum in Comparative Example 6. Example 4 (including Sc) exhibits the best strength and creep resistance;

[0087] 2) The criticality of component ratios (Comparative Examples 1-3):

[0088] Comparative Example 1 (B too high): After the purification effect is saturated, the excess B may form a coarse phase, and the [R] / [B] ratio is too low, which leads to the coarsening of the rare earth precipitate phase and a decrease in strength and creep resistance.

[0089] Comparative Example 2 (B too low): Insufficient purification effect, conductivity slightly decreased; [R] / [B] ratio too high, rare earth element excess, may form incoherent phase or increase solid solution content, impairing strength and conductivity;

[0090] Comparative Example 3 (Insufficient Y): Although the ratio is at the critical value, the total amount of rare earth is insufficient, which makes it impossible to form a nanophase with a sufficient number density, resulting in a weak strengthening effect.

[0091] 3) The decisive role of heat treatment process (Comparative Examples 4-5): Comparative Examples 4 (low temperature) and 5 (conventional process) with the same composition are all inferior to Comparative Example 1 in performance, which proves that the key heat treatment is a necessary condition for activating the potential of this composition system, and there is a strong coupling relationship between the two.

[0092] 4) Figure 1 The sample of Example 1 clearly shows a uniformly distributed high-density nano-precipitated phase, confirming the strengthening mechanism of the present invention.

[0093] Example 5

[0094] A conductor for power cables is composed of multiple stranded single wires, wherein the single wires are the ultra-high conductivity, high strength and creep-resistant aluminum alloy conductors of Example 1.

[0095] Example 6

[0096] like Figure 2As shown, a power cable includes a conductor 1, a conductor shielding layer 2, an insulation layer 3, an insulation shielding layer 4, a metal sheath 5, and an outer sheath 6 arranged sequentially from the inside to the outside. The conductor 1 includes several stranded single wires, and the single wires are ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductors of Example 1.

[0097] Any parts or structures not specifically described in this invention can be made using existing technologies or products, and will not be elaborated upon here.

[0098] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An ultra-high conductivity, high-strength, creep-resistant aluminum alloy conductor, characterized in that, By weight percentage, it includes the following components: Al：≥99.68%； B：0.0038%-0.0052%； Rare earth element R: 0.068%-0.092%; Fe: 0.145%-0.175%; Si: ≤0.030%; Unavoidable impurities: ≤0.005% for each, ≤0.015% in total; It does not contain artificially added Mg and Zr, and Cu: <0.002%; Satisfying the relation: 14≤[R] / [B]≤20; Wherein, [R] represents the mass percentage of rare earth elements, and [B] represents the mass percentage of element B; The rare earth element R is one or a combination of two of Y and Sc.

2. The ultra-high conductivity, high-strength, creep-resistant aluminum alloy conductor according to claim 1, characterized in that, The rare earth element R is Y, with a mass percentage of 0.075%-0.088%.

3. The ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor according to claim 1, characterized in that, The microstructure of the ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor contains materials with an average size of 8-20 nm and a number density of not less than 6 × 10⁻⁶. 21 m -3 Al3(Sc,Y) nanoprecipitates.

4. The ultra-high conductivity, high-strength, creep-resistant aluminum alloy conductor according to claim 1, characterized in that, The ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor has a volume conductivity of not less than 62.2% IACS at 20℃ and a tensile strength of not less than 125MPa.

5. The ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor according to claim 1, characterized in that, The ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor exhibits a steady-state creep rate of less than 1.0 × 10⁻¹⁰ hours under 100°C and 80% room temperature yield strength stress. -8 s -1 .

6. The method for preparing the ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Smelting and Ultra-clean Refining: Using high-purity aluminum ingots with a purity of ≥99.86% as the main raw material, and aluminum-iron and aluminum-rare earth intermediate alloys, the process is carried out under inert gas protection, aluminum-boron alloy wire is added using a dynamic wire feeding method, and ultra-clean refining is performed. S2. Continuous casting and temperature-controlled rolling to produce rods with a diameter of 9.4-9.6 mm and a bright surface; S3. Key phase change heat treatment: The rod is first drawn to an intermediate wire with a diameter of 3.48-3.52mm using a wire drawing machine; then, without stopping, the wire is immediately put into a controlled atmosphere continuous annealing furnace and isothermally annealed at a temperature range of 320-324℃ for 3.9-4.1h. S4. Final shaping: The wire processed in step S3 is cooled to room temperature and then continuously drawn to the final required size using a multi-die wire drawing machine.

7. The method for preparing an ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor according to claim 6, characterized in that, In step S1, the ultra-clean refining includes: first, introducing a high-purity mixed gas of Ar and Cl2 for deep hydrogen and impurity removal, and then switching to pure argon gas for soft stirring and settling, with a total refining time of 12-18 minutes.

8. A conductor for power cables, characterized in that, It is composed of multiple stranded single wires, wherein the single wires are the ultra-high conductivity, high strength and creep resistant aluminum alloy conductors as described in any one of claims 1-5.

9. A power cable, characterized in that, The conductor of the power cable is an ultra-high conductivity, high strength, and creep-resistant aluminum alloy conductor as described in any one of claims 1-5.

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