Aluminum alloy wire and electric wire

Abstract

This aluminum alloy wire contains 0.20-0.35 mass% of Zr, 0.05-0.30 mass% of Fe, 0.01-0.05 mass% of Si, and 0.002-0.020 mass% of Ti, the remaining portion being Al and unavoidable impurities. The tensile strength of the aluminum alloy wire after being subjected to a heat treatment at 280°C for 10 hours is not less than 94% of the tensile strength of the aluminum alloy wire before being subjected to the heat treatment.

Description

Aluminum alloy wire and electric wire

[0001] This application claims priority to Japanese Patent Application No. 2024-104157, filed on June 27, 2024, and incorporates by reference all of the contents of that application.

[0002] Aluminum alloy wires are used, for example, as conductors for electric wires (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2021-188106

[0004] K. Momma and F. Izumi, J. Appl. Crystallogr. , 44, 1272-1276 (2011)

[0005] According to one aspect of the present disclosure, there is provided an aluminum alloy wire containing 0.20 mass% or more and 0.35 mass% or less of Zr, 0.05 mass% or more and 0.30 mass% or less of Fe, 0.01 mass% or more and 0.05 mass% or less of Si, 0.002 mass% or more and 0.020 mass% or less of Ti, with the balance being Al and inevitable impurities, wherein the aluminum alloy wire has a tensile strength after being heat treated at 280°C for 10 hours that is 94% or more of the tensile strength before the heat treatment.

[0006] FIG. 1 is a diagram comparing crystal structures. FIG. 2 is a diagram showing the radial structure function obtained by X-ray absorption fine structure measurement at the K-edge of Zr in an aluminum alloy wire. FIG. 3 is a schematic cross-sectional view perpendicular to the axial direction of an electric wire according to an embodiment of the present disclosure. FIG. 4 is a flowchart showing a method for manufacturing an electric wire according to an embodiment of the present disclosure. FIG. 5 is a diagram showing temperature changes in the aging step S140. FIG. 6 is Table 2 showing evaluation results of examples. FIG. 7 is a diagram showing the Zr coherence dependency of the tensile strength after heat treatment of an aluminum alloy wire.

[0007] [Problem to be Solved by the Invention] An object of the present disclosure is to improve heat resistance.

[0008] Effect of the Invention According to the present disclosure, heat resistance can be improved.

[0009] [Explanation of Embodiments of the Present Disclosure] <Insights Obtained by the Inventors> First, insights obtained by the inventors will be described.

[0010] As a heat-resistant aluminum (Al) alloy wire, an Al alloy wire containing zirconium (Zr), iron (Fe), silicon (Si) and titanium (Ti) has been developed.

[0011] Conventionally, by adding Si as an alloying element, ３ It has been thought that this promotes the precipitation of Zr and improves heat resistance.

[0012] However, if Si is added in excess, Al-Zr-Si compounds (Al described later) that do not contribute to heat resistance may be formed. ２．７ Si ０．３ Zr stable phase) precipitates, and Al ３ The proportion of Zr precipitates was reduced, resulting in a decrease in the heat resistance of the Al alloy wire.

[0013] Therefore, the inventors have reported that, as described in Patent Document 1, a small amount of Si is added and a two-stage aging process is performed to suppress the precipitation of the Al—Zr—Si compound and to prevent the formation of Al. ３ The proportion of Zr precipitates was increased, resulting in an improvement in the heat resistance of the Al alloy wire compared to conventional Al alloy wires.

[0014] However, in recent years, there has been a demand for higher heat resistance than that described in Patent Document 1. That is, there has been a demand for an Al alloy wire that can withstand high-temperature environments for a longer period of time.

[0015] In order to find a structure of an Al alloy wire with further improved heat resistance in response to such new problems, the inventors evaluated the precipitation state of Zr in the Al alloy wire by X-ray absorption fine structure (XAFS). ３ It was found that the proportion of crystalline phases that do not contribute to heat resistance was high as Zr precipitates.

[0016] Here, the relationship between the crystalline phases that can precipitate in the Al alloy wire containing the above-mentioned alloying elements and the heat resistance of the Al alloy wire will be described with reference to Fig. 1 and Table 1. Fig. 1 was created using the crystal structure drawing software described in Non-Patent Document 1.

[0017]

[0018] As shown in FIG. 1, in the Al alloy wire containing the above-mentioned alloying elements, the Al alloy wire has a high Al content depending on the composition and manufacturing method of the Al alloy wire. ３ Zr metastable phase, Al ３ Zr stable phase, Al ２．７ Si ０．３ There is a possibility that a stable Zr phase may precipitate. ３ Zr stable phase, and Al ２．７ Si ０．３ The Zr stable phase does not contribute to the heat resistance of the Al alloy wire. ３ The Zr metastable phase contributes to the heat resistance of the Al alloy wire.

[0019] In Patent Document 1, as described above, by reducing the amount of Si added, Al ２．７ Si ０．３ As a result, the formation of crystals of the Zr stable phase was suppressed. ３ Zr crystals were formed.

[0020] At this time, as shown in Table 1, Al ３ The lattice constant of the Zr metastable phase is ３ Since the lattice constant is closer to that of pure Al than that of the Zr stable phase, ３ The loss of interfacial energy in the Zr metastable phase is due to Al ３ Therefore, in the first aging step of Patent Document 1, the energy loss of the fine Al phase, which is a crystalline phase that matches pure Al, is smaller than that of the Zr stable phase. ３ Precipitation nuclei of the Zr metastable phase were preferentially formed.

[0021] However, in the first aging step of Patent Document 1, the heat treatment temperature is 300° C. or higher and the heat treatment time is 6 hours or less. ３ ​The number of precipitation nuclei of the Zr metastable phase was small.

[0022] In Patent Document 1, Al ３ Since the number of precipitation nuclei of the Zr metastable phase is small, the Al ３ Therefore, in the second aging step, the Al precipitates tended to grow excessively. ３ As the volume of Zr precipitates increased, the specific surface area of ​​the precipitates decreased, and the loss of interfacial energy decreased. ３ Zr metastable phase is Al ３ The phase transition to the Zr stable phase was likely to occur easily, and the number density of precipitates also tended to be low.

[0023] Thus, in Patent Document 1, Al, which does not contribute to heat resistance, ３ The proportion of the Zr stable phase was high. As a result, it was difficult to further improve the heat resistance of the Al alloy wire by the manufacturing method of Patent Document 1.

[0024] As a result of further intensive investigation, the inventors have found that Al ３ Many precipitation nuclei of the Zr metastable phase are formed, and the Al ３ The inventors have discovered a new manufacturing method that allows precipitation nuclei to grow while maintaining the Zr metastable phase, and have succeeded in obtaining an Al alloy wire with improved heat resistance compared to the Al alloy wire of Patent Document 1.

[0025] The present disclosure below is based on the above-mentioned new problem discovered by the inventors.

[0026] <Embodiments of the Present Disclosure> Next, embodiments of the present disclosure will be listed and described.

[0027] [1] An aluminum alloy wire according to one embodiment of the present disclosure contains: 0.20% by mass or more and 0.35% by mass or less of Zr; 0.05% by mass or more and 0.30% by mass or less of Fe; 0.01% by mass or more and 0.05% by mass or less of Si; and 0.002% by mass or more and 0.020% by mass or less of Ti, with the balance being Al and inevitable impurities, and the tensile strength of the aluminum alloy wire after heat treatment at 280°C for 10 hours is 94% or more of the tensile strength before the heat treatment. This configuration can improve heat resistance.

[0028] [2] The aluminum alloy wire according to the above [1], wherein the aluminum alloy wire satisfies formula (1): IZr1 / IZr0≧1.2 (1), where IZr1 is the height of a peak occurring within a radius range of 0.22 nm or more and 0.30 nm or less in a radial structure function obtained from X-ray absorption fine structure measurement at the K absorption edge of Zr in the aluminum alloy wire, and IZr0 is the height of a peak occurring within a radius range of 0.22 nm or more and 0.30 nm or less in a radial structure function of Zr in a rolled Zr material having a purity of 99.2% and a thickness of 0.02 mm as a standard sample, obtained under the same conditions as those under which the radial structure function of Zr in the aluminum alloy wire was obtained. This configuration can improve heat resistance.

[0029] [3] An aluminum alloy wire according to another aspect of the present disclosure contains: 0.20 mass % or more and 0.35 mass % or less of Zr; 0.05 mass % or more and 0.30 mass % or less of Fe; 0.01 mass % or more and 0.05 mass % or less of Si; and 0.002 mass % or more and 0.020 mass % or less of Ti, with the balance being Al and inevitable impurities, and the aluminum alloy wire satisfies formula (1): IZr1 / IZr0≧1.2 (1), where IZr1 is the height of a peak occurring within a radius range of 0.22 nm or more and 0.30 nm or less in a radial structure function obtained from X-ray absorption fine structure measurement at the K absorption edge of Zr in the aluminum alloy wire, IZr0 is the height of a peak occurring within a radius range of 0.22 nm to 0.30 nm in the radial structure function of Zr in a rolled Zr material having a purity of 99.2% and a thickness of 0.02 mm as a standard sample, which is obtained under the same conditions as those under which the radial structure function of Zr in the aluminum alloy wire was obtained. According to this configuration, it is possible to improve heat resistance.

[0030] [4] The aluminum alloy wire according to any one of [1] to [3], wherein the electrical conductivity of the aluminum alloy wire is 60% IACS or more. This configuration can improve electrical conductivity.

[0031] [5] The aluminum alloy wire according to any one of [1] to [4] above, further containing 0.002 mass % or more and 0.050 mass % or less of Sr. With this configuration, occurrence of defects such as cracks can be suppressed.

[0032] [6] An electric wire according to still another aspect of the present disclosure includes a stranded wire portion formed by stranding together a plurality of the aluminum alloy wires according to any one of [1] to [5] above. This configuration can improve heat resistance.

[0033] [Details of the embodiment of the present disclosure] Next, one embodiment of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0034] <One embodiment of the present disclosure> (1) Aluminum alloy wire The Al alloy wire of this embodiment (hereinafter also referred to as "Al alloy wire 210" in accordance with the contents described later) contains, for example, Zr, Fe, Si, and Ti, with the balance being Al and inevitable impurities.

[0035] Hereinafter, the content of each element in the Al alloy wire 210 is the content when the entire Al alloy wire 210 is taken as 100 mass %.

[0036] (Zr) Zr contributes to the strength and heat resistance of the Al alloy wire 210 depending on the precipitation state in the Al matrix.

[0037] Fine Al in the matrix Al ３ Precipitating a large amount of the Zr metastable phase can suppress the propagation of dislocations in the Al alloy structure and make the Al alloy less susceptible to plastic deformation, thereby improving the strength of the Al alloy wire 210.

[0038] Furthermore, fine Al dispersed in the Al alloy ３ The precipitates of the Zr metastable phase match the lattice of the Al matrix. ３ The precipitates of the Zr metastable phase suppress the movement of dislocations due to heat in a high-temperature environment, that is, they exist as obstacles to dislocations. By suppressing the movement of dislocations in this way, it is possible to suppress the annihilation of dislocations and stabilize the Al alloy structure. As a result, it is possible to improve the heat resistance of the Al alloy wire 210.

[0039] In this embodiment, the content of each alloy element is optimized and a new aging step S140 described later is applied, thereby ３ The precipitation rate of the Zr metastable phase is high. ３ The high precipitation rate of the Zr metastable phase can be confirmed by X-ray absorption fine structure measurement, which will be described in detail later.

[0040] In this embodiment, the Zr content in the Al alloy wire 210 is, for example, 0.20 mass % or more and 0.35 mass % or less.

[0041] If the Zr content is less than 0.20 mass%, Al precipitates in the Al matrix. ３ Therefore, it becomes difficult to improve the strength and heat resistance of the Al alloy wire 210. In contrast, in the present embodiment, by setting the Zr content to 0.20 mass % or more, a sufficient absolute amount of Al is obtained. ３ The Zr metastable phase can be precipitated, which can improve the strength and heat resistance of the Al alloy wire 210.

[0042] On the other hand, if the Zr content exceeds 0.35 mass%, the amount of Zr dissolved in the Al matrix increases. As a result, the electrical conductivity of the Al alloy wire 210 decreases. Furthermore, if the Zr content exceeds 0.35 mass%, the molten metal temperature increases, and defects such as cracks tend to occur more easily. In contrast, in this embodiment, by setting the Zr content to 0.35 mass% or less, the amount of Zr dissolved in the Al matrix can be reduced. This can suppress the decrease in electrical conductivity of the Al alloy wire 210. Furthermore, by setting the Zr content to 0.35 mass% or less, the increase in the molten metal temperature can be suppressed, and defects such as cracks can be suppressed.

[0043] Furthermore, the content of Zr in the Al alloy wire 210 may be, for example, 0.34 mass% or less. By setting the content of Zr to 0.34 mass% or less, it is possible to stably suppress an increase in the molten metal temperature and stably suppress the occurrence of defects such as cracks.

[0044] (Fe) In this embodiment, Fe is mainly precipitated in the Al matrix, which can improve the strength of the Al alloy wire 210.

[0045] In this embodiment, the content of Fe in the Al alloy wire 210 is, for example, 0.05 mass % or more and 0.30 mass % or less.

[0046] If the Fe content is less than 0.05 mass%, the amount of Fe precipitated in the Al matrix is ​​small. Therefore, it is difficult to improve the strength of the Al alloy wire 210. Furthermore, if the Fe content is less than 0.05 mass%, Fe is contained as an inevitable impurity in the Al matrix, so the purity of the Al matrix needs to be increased. This increases refining costs. In contrast, in this embodiment, by setting the Fe content to 0.05 mass% or more, Fe can be sufficiently precipitated in the Al matrix. This can improve the strength of the Al alloy wire 210. Furthermore, by setting the Fe content to 0.05 mass% or more, it is not necessary to excessively increase the purity of the Al matrix, and an increase in refining costs can be suppressed.

[0047] On the other hand, if the Fe content exceeds 0.30 mass%, the amount of Fe precipitated in the Al matrix becomes excessively large. As a result, the electrical conductivity of the Al alloy wire 210 decreases. Also, if the Fe content exceeds 0.30 mass%, excessive dislocations are generated in the Al alloy due to processing before the aging step S140. ３ Interaction with Zr precipitates leads to incoherent Al ３ A Zr stable phase is easily formed. As a result, the heat resistance of the Al alloy wire 210 is reduced. In contrast, in this embodiment, by setting the Fe content to 0.30 mass % or less, it is possible to prevent excessive precipitation of Fe in the Al matrix. This makes it possible to prevent a decrease in the electrical conductivity of the Al alloy wire 210. Furthermore, in this embodiment, by setting the Fe content to 0.30 mass % or less, it is possible to prevent excessive dislocations from being introduced into the Al alloy by processing before the aging step S140. This allows the dislocations and Al ３ Incommensurate Al due to interaction with Zr precipitates ３ The formation of the Zr stable phase can be suppressed, and as a result, the deterioration of the heat resistance of the Al alloy wire 210 can be suppressed.

[0048] (Si) In this embodiment, Si is mainly dissolved in the Al matrix. ３ This can promote the precipitation of Zr.

[0049] In this embodiment, by adding a small amount of Si and applying a new aging step S140 described later, even if the Si content is small, Al ３ On the other hand, by reducing the Si content, the formation of Al-Zr-Si compounds is suppressed, and the precipitation of fine Al ３ The precipitation rate of the Zr metastable phase can be increased. As a result, the heat resistance of the Al alloy wire 210 can be efficiently improved.

[0050] Specifically, in this embodiment, the Si content in the Al alloy wire 210 is, for example, 0.01 mass % or more and 0.05 mass % or less.

[0051] When the Si content is less than 0.01 mass%, Al ３ Therefore, Zr is likely to remain in the form of a solid solution in the Al matrix. As a result, the electrical conductivity of the Al alloy wire 210 decreases. In contrast, by setting the Si content to 0.01 mass % or more and applying a new aging step S140 described later, the Al ３ The precipitation of the Zr metastable phase can be promoted, thereby reducing the amount of Zr dissolved in the Al matrix, and as a result, the decrease in the electrical conductivity of the Al alloy wire 210 can be suppressed.

[0052] On the other hand, if the Si content exceeds 0.05 mass %, the amount of precipitated Al—Zr—Si compounds that do not contribute to heat resistance increases, and fine Al ３ The precipitation rate of the Zr metastable phase decreases. As a result, the heat resistance of the Al alloy wire 210 decreases. In contrast, in this embodiment, the Si content is set to 0.05 mass % or less, and a new aging step S140, which will be described later, is applied, thereby making it possible to suppress the generation of Al—Zr—Si compounds, and to prevent the formation of fine Al ３ The precipitation rate of the Zr metastable phase can be increased, thereby improving the heat resistance of the Al alloy wire 210.

[0053] (Ti) At least a part of Ti precipitates in the Al matrix as a Ti compound, such as a Ti—B compound. This allows the crystal grains of the Al alloy to be refined. As a result, the occurrence of defects such as cracks in the Al alloy wire 210 can be suppressed.

[0054] In this embodiment, the Ti content in the Al alloy wire 210 is, for example, 0.002 mass % or more and 0.020 mass % or less.

[0055] If the Ti content is less than 0.002 mass%, it is difficult to refine the crystal grains of the Al alloy. In contrast, in this embodiment, by setting the Ti content to 0.002 mass% or more, the Al crystal grains can be stably refined. As a result, the occurrence of defects such as cracks in the Al alloy wire 210 can be stably suppressed.

[0056] On the other hand, if the Ti content exceeds 0.020 mass%, the amount of Ti dissolved in the Al matrix increases, which reduces the electrical conductivity of the Al alloy wire 210. In contrast, in this embodiment, the Ti content is set to 0.020 mass% or less, which reduces the amount of Ti dissolved in the Al matrix. This improves the electrical conductivity of the Al alloy wire 210.

[0057] (Inevitable Impurities) In this embodiment, scandium (Sc) is not intentionally added to the Al alloy wire 210. Specifically, the content of Sc as one of the inevitable impurities in the Al alloy wire of this embodiment is, for example, less than 0.005 mass %, which can reduce material costs.

[0058] In this embodiment, the total content of unavoidable impurities in the Al alloy wire 210 may be, for example, less than 0.010 mass %, or less than 0.005 mass %.

[0059] (2) Precipitation State of Zr in Al Alloy Wire Next, with reference to FIG. 2, the precipitation state of Zr in the Al alloy wire 210 will be described.

[0060] In X-ray absorption fine structure (XAFS) measurements, a substance is irradiated with X-rays and the intensity of transmitted X-rays or fluorescent X-rays from the substance is measured to obtain an XAFS spectrum derived from a specific target element in the substance. The low-energy region of the XAFS spectrum reflects the chemical state of the element (e.g., simple substance, compound species, etc.). Furthermore, the radial structure function of the target element can be obtained by Fourier transforming the extended X-ray absorption fine structure (EXAFS) oscillations that occur in the high-energy region of the XAFS spectrum. By analyzing the XAFS spectrum or radial structure function, the local structure around the target element (e.g., interatomic distance, coordination number, valence, coordination structure), etc. can be evaluated.

[0061] The inventors evaluated the precipitation state of Zr in the Al alloy wire 210 by performing XAFS measurement of Zr contained in the Al alloy wire 210 of this embodiment.

[0062] As a result, in this embodiment, the content of each alloy element is optimized, and a new aging step S140 described later is applied to achieve the Al ３ The inventors have found that by increasing the precipitation rate of the Zr metastable phase, the Al alloy wire 210 satisfies the requirements described below regarding the results of XAFS measurement of Zr.

[0063] (Zr Coherency) Figure 2 shows the radial structure functions obtained by X-ray absorption fine structure measurements at the Zr K-edge in the Al alloy wires of this embodiment and the comparative example. In Figure 2, the horizontal axis represents the radial distance (unit: nm), and the vertical axis represents the normalized radial structure function |X(R)| (arbitrary unit) at each radial distance.

[0064] The radial structure function X(R) of Zr can be obtained by carrying out the following steps (a) to (d): (a) Measuring the X-ray absorption fine structure spectrum μ(E) at the K absorption edge of Zr. (b) Based on the X-ray absorption fine structure spectrum μ(E), the extended X-ray absorption fine structure vibration χ(k) is obtained by the formula (A): χ(k)={μ(E)-μs(E)} / μ0 (A) where k is the wave number, E is the energy, μs(E) is a component obtained by approximating the center of the vibration component of μ(E) using a spline function, and μ0 is the absorbance difference before and after the absorption edge in μ(E). (c) Measuring the extended X-ray absorption fine structure vibration χ(k) by the formula (A): χ(k)={μ(E)-μs(E)} / μ0 (A) where k is the wave number, E is the energy, μs(E) is a component obtained by approximating the center of the vibration component of μ(E) using a spline function, and μ0 is the absorbance difference before and after the absorption edge in μ(E). ２ (d) The weighting process is performed by (c). ２ χ(k) is the 30 nm wavelength of wave number k. －１ 90nm or more －１ The region within the following range is Fourier transformed:

[0065] 2 is the height of a peak occurring within a radius range of 0.22 nm or more and 0.30 nm or less in the radial structure function X(R) obtained from XAFS measurement of the K-absorption edge of Zr in the Al alloy wire 210. "IZr0" is the height of a peak occurring within a radius range of 0.22 nm or more and 0.30 nm or less in the radial structure function of Zr in a rolled Zr material with a purity of 99.2% and a thickness of 0.02 mm as a standard sample, obtained under the same conditions as those under which the radial structure function of Zr in the Al alloy wire 210 was obtained.

[0066] The vertical axis in Fig. 2 above indicates the value of the radial structure function X(R) normalized by IZr0. For this reason, in Fig. 2, peaks occurring within a radius range of 0.22 nm to 0.30 nm are denoted as "IZr1 / IZr0".

[0067] The ratio "IZr1 / IZr0" is also referred to as "Zr coherence" below. The Zr coherence IZr1 / IZr0 is the ratio of Al coherent with pure Al. ３ This is an index that reflects the precipitation rate of the Zr metastable phase.

[0068] The radial structure function of the comparative example shown in FIG. 2 is, for example, the radial structure function of Zr in the Al alloy wire of Sample 1B in the example described later. In the comparative example, the Zr matching ratio IZr1 / IZr0 is less than 1.2. In the comparative example showing such a tendency, the Zr matching ratio IZr1 / IZr0 is less than 1.2. ３ The precipitation rate of the Zr metastable phase is low. ３ Since the precipitation rate of the Zr metastable phase is low, it is difficult to improve the heat resistance of the Al alloy wire.

[0069] 2 is, for example, the radial structure function of Zr in the Al alloy wire of Sample 6A in the example described later. The Zr matching ratio IZr1 / IZr0 of this embodiment is higher than the Zr matching ratio IZr1 / IZr0 of the comparative example.

[0070] Specifically, the Al alloy wire 210 of the present embodiment satisfies, for example, the following formula (1): IZr1 / IZr0≧1.2 (1)

[0071] In this embodiment, which shows such a tendency, Al is used as a material that matches pure Al. ３ In this way, in this embodiment, the precipitation rate of the Zr metastable phase is high. ３ By increasing the precipitation rate of the Zr metastable phase, the heat resistance of the Al alloy wire 210 can be improved.

[0072] The upper limit of the Zr matching ratio IZr1 / IZr0 is not particularly limited, but may be IZr1 / IZr0≦2.5.

[0073] (3) Characteristics of Al Alloy Wire The Al alloy wire 210 of this embodiment has the following characteristics.

[0074] (Electrical Conductivity) The electrical conductivity of the Al alloy wire 210 of this embodiment is, for example, 60% IACS or more.

[0075] The unit of conductivity "% IACS" used here is the ratio of conductivity when the conductivity of International Annealed Copper Standard is taken as 100%.

[0076] The upper limit of the electrical conductivity of the Al alloy wire 210 of this embodiment is not limited, but the electrical conductivity of the Al alloy wire 210 of this embodiment may be, for example, 62% IACS or less.

[0077] (Tensile strength) The Al alloy wire 210 of this embodiment has fine Al particles in the Al matrix. ３ By precipitating many precipitation nuclei of the Zr metastable phase, high tensile strength is exhibited.

[0078] Specifically, the tensile strength of the Al alloy wire 210 of this embodiment at 20°C is equal to or greater than the minimum tensile strength of an ultra-heat-resistant aluminum alloy wire having a diameter equal to the diameter of the Al alloy wire 210 of this embodiment, as specified in, for example, JEC-3406:2022.

[0079] The minimum tensile strength of ultra heat-resistant aluminum alloy wire by diameter, as specified in JEC-3406:2022, is as follows: 2.6 mm (tolerance ±0.03 mm): 169 MPa 3.2 mm, 3.8 mm (tolerance ±0.04 mm): 162 MPa 4.0 mm, 4.5 mm (tolerance ±0.04 mm): 159 MPa

[0080] More specifically, the tensile strength of the Al alloy wire 210 of this embodiment at 20° C. may be, for example, 150 MPa or more, or 159 MPa or more.

[0081] The upper limit of the tensile strength of the Al alloy wire 210 of this embodiment is not limited, but the tensile strength of the Al alloy wire 210 of this embodiment at 20° C. may be, for example, 230 MPa or less.

[0082] (Tensile Residual Rate) The Al alloy wire 210 of this embodiment exhibits a high tensile residual rate even after being subjected to a long-term heat treatment.

[0083] The "tensile strength retention rate after heat treatment" referred to here is a ratio (%) calculated by (tensile strength after heat treatment) / (tensile strength before heat treatment) × 100. The temperature when measuring the tensile strength before and after heat treatment is 20°C.

[0084] The tensile strength of the Al alloy wire 210 of this embodiment after heat treatment at 280° C. for 5 hours is, for example, 96% or more of the tensile strength before the heat treatment.

[0085] Here, even with the Al alloy wire of Patent Document 1, the maximum tensile strength remaining rate after heat treatment at 280°C for 5 hours can be 95.4%. ３ Since the precipitation rate of the Zr metastable phase is low, the heat resistance is lower than that of the Al alloy wire 210 of the present embodiment. Therefore, in the Al alloy wire of Patent Document 1, for example, the tensile strength after heat treatment for a time longer than the above-mentioned specification is further lower.

[0086] In contrast, in the Al alloy wire 210 of the present embodiment, as described above, ３ The precipitation rate of the Zr metastable phase is high, and as a result, in this embodiment, a high tensile strength can be obtained even after a long heat treatment.

[0087] Specifically, the tensile strength of the Al alloy wire 210 of this embodiment after heat treatment at 280° C. for 10 hours is, for example, 94% or more of the tensile strength before the heat treatment.

[0088] As described above, the Al alloy wire 210 of this embodiment can obtain high heat resistance that could not be obtained by the Al alloy wire of Patent Document 1. That is, in this embodiment, even when the Al alloy wire 210 is exposed to a high-temperature environment for a long period of time, the Al alloy wire 210 can maintain high strength.

[0089] The upper limit of the tensile strength after the heat treatment of the Al alloy wire 210 of the present embodiment is not limited, and the higher the upper limit, the better. That is, in the Al alloy wire 210 of the present embodiment, the tensile strength after the heat treatment at 280°C for 5 hours and the tensile strength after the heat treatment at 280°C for 10 hours may be close to 100%, for example.

[0090] (Compression Ratio of Cracks) In this embodiment, the Zr content in the Al alloy wire 210 is set to 0.35 mass % or less, thereby suppressing the occurrence of defects such as cracks in the Al alloy wire 210 .

[0091] Specifically, the Al alloy wire 210 of this embodiment is compressed in the longitudinal direction at room temperature (20°C) at a strain rate of 20% / min, and the compression ratio K when the first scratch can be visually confirmed on the outer periphery is, for example, 71% or more.

[0092] (4) Electric Wire Next, the electric wire 10 of this embodiment will be described with reference to FIG.

[0093] The electric wire 10 of this embodiment has, for example, a central portion (steel core portion) 100 and a stranded wire portion 200 .

[0094] The central portion 100 is provided at the center of the electric wire 10. The central portion 100 is configured to function as a tension member that bears the tension of the electric wire 10 when the electric wire 10 is strung.

[0095] The central portion 100 includes, for example, a plurality of core wires 110 twisted together in a spiral shape. The central portion 100 includes, for example, a first core layer 100a and a second core layer 100b, arranged in this order from the central axis of the electric wire 10 toward the outside in the radial direction. The first core layer 100a and the second core layer 100b include, for example, one core wire 110 and six core wires 110, respectively.

[0096] Each core wire 110 has, for example, a wire portion 112 and a covering portion 114 provided to cover the outer periphery of the wire portion 112. Examples of the core wire 110 include aluminum-clad steel wire, galvanized steel wire, aluminum-clad Invar wire, and galvanized Invar wire.

[0097] The twisted wire portion 200 is provided so as to cover the outer periphery of the central portion 100. The twisted wire portion 200 is configured to function as a conductor that mainly carries current during power transmission.

[0098] The stranded wire portion 200 includes a plurality of the Al alloy wires 210 of the present embodiment described above. In the stranded wire portion 200, the plurality of Al alloy wires 210 are twisted together in a spiral shape. The diameter of the Al alloy wire 210 is, for example, 0.1 mm or more and 15 mm or less, and may be 2.6 mm or more and 4.5 mm or less.

[0099] The stranded wire portion 200 has, for example, a first stranded wire layer 200a and a second stranded wire layer 200b in this order from a region close to the central axis of the electric wire 10 toward the radially outer side. The first stranded wire layer 200a and the second stranded wire layer 200b have, for example, 12 Al alloy wires 210 and 18 Al alloy wires 210, respectively.

[0100] In this embodiment, for example, when the core wire 110 is an aluminum-clad Invar wire, the tensile load of the electric wire 10 at 20°C is equal to or greater than the minimum tensile load of an aluminum-clad Invar-core ultra-heat-resistant aluminum alloy stranded wire having a total cross-sectional area of ​​the stranded wire portion equal to the total cross-sectional area of ​​the stranded wire portion 200 of this embodiment, as specified in JEC-3406:2022.

[0101] Here, the term "a total cross-sectional area of ​​the stranded wire portion equal to the total cross-sectional area of ​​the stranded wire portion 200 of this embodiment" refers not only to the case where the total cross-sectional area of ​​the stranded wire portion 200 of this embodiment is completely equal to the total cross-sectional area of ​​the stranded wire portion of the ultra heat-resistant aluminum alloy wire specified in JEC-3406:2022, but also to the case where the difference between the two is within ±5 mm. ２ This also includes cases where the scope of the

[0102] The minimum tensile load per total cross-sectional area of ​​the stranded wire when the core wire is an aluminum-clad Invar wire, as specified in JEC-3406:2022, is as follows: ２ :58.7kN 240mm ２ :84.9kN 330mm ２ :93.4kN 410mm ２ :118.6kN 610mm ２ : 159.3 kN

[0103] In this embodiment, when the core wire 110 is a galvanized Invar wire, the tensile load of the electric wire 10 at 20°C is equal to or greater than the minimum tensile load of a heat-resistant aluminum alloy electric wire having a total cross-sectional area of ​​the stranded wire portions equal to the total cross-sectional area of ​​the stranded wire portion 200 of this embodiment, as specified in, for example, JCS1405:2003.

[0104] Here, the term "a total cross-sectional area of ​​the stranded wire portion equal to the total cross-sectional area of ​​the stranded wire portion 200 of this embodiment" refers not only to the case where the total cross-sectional area of ​​the stranded wire portion 200 of this embodiment is completely equal to the total cross-sectional area of ​​the stranded wire portion specified in JCS1405:2003, but also to the case where the difference between the two is within ±5 mm. ２ This also includes cases where the scope of the

[0105] The minimum tensile load per total cross-sectional area of ​​the stranded wire when the core wire is a galvanized Invar wire as specified in JCS1405:2003 is as follows: ２ :48.0kN 160mm ２ :60.3kN 240mm ２ :89.9kN 330mm ２ :98.1kN 410mm ２ :124.6kN 610mm ２ :166.5kN 810mm ２ :171.3kN 1160mm ２ :256.4kN 1520mm ２ : 335.0 kN

[0106] (5) Method for Manufacturing the Electric Wire A method for manufacturing the electric wire 10 of this embodiment will be described with reference to FIG.

[0107] The method for manufacturing the electric wire 10 of this embodiment includes, for example, an aluminum alloy wire forming step S100, a central portion forming step S200, and a stranded portion forming step S300.

[0108] (S100: Aluminum Alloy Wire Forming Step) The aluminum alloy wire forming step S100 includes a method for manufacturing the Al alloy wire 210 of this embodiment. Specifically, the aluminum alloy wire forming step S100 includes, for example, a molten metal preparing step (melting step) S110, a continuous casting and rolling step S120, a first wiredrawing step S130, an aging step S140, and a second wiredrawing step S150.

[0109] (S110: Molten metal preparation step) First, an Al ingot as a raw material is melted in a melting furnace. After the Al ingot is melted, each alloy element is introduced into the molten metal while stirring the molten metal in an adjusting furnace, thereby preparing a molten metal satisfying the composition of the Al alloy wire 210 of the present embodiment.

[0110] Specifically, a molten metal containing 0.20% by mass or more and 0.35% by mass or less of Zr, 0.05% by mass or more and 0.30% by mass or less of Fe, 0.01% by mass or more and 0.05% by mass or less of Si, 0.002% by mass or more and 0.020% by mass or less of Ti, and the balance being Al and unavoidable impurities, is prepared. At this time, Sc and the like are not intentionally added.

[0111] At this time, the temperature of the molten metal is appropriately adjusted to a temperature at which the entire amount of Zr added can be dissolved in the molten metal and at which heat management is easy.

[0112] (S120: Continuous Casting and Rolling Step) Once the molten metal is prepared, the molten metal is continuously cast and hot rolled using, for example, a Properti continuous casting and rolling mill. In this embodiment, in the solidification step, Zr is supersaturated in the Al alloy. Here, "supersaturated solution" refers to a state in which a predetermined element is dissolved in a solid solution in an amount greater than the amount of solid solution in a chemical equilibrium state at room temperature and at the aging precipitation temperature described below. Through this step, an Al alloy wire is formed.

[0113] (S130: First Wire Drawing Step) After the Al alloy wire rod is obtained, the Al alloy wire rod is subjected to cold wire drawing to reduce the diameter of the Al alloy wire rod to a predetermined diameter, thereby forming an Al alloy wire rod.

[0114] Examples of processing conditions for the first wiredrawing step S130 are as follows: Temperature of aluminum wire during wiredrawing: 10° C. or higher and 200° C. or lower Wiredrawing speed: 20 m / min or higher and 600 m / min or lower Area reduction rate per die: 15% or higher and 30% or lower Die angle: 10 degrees or higher and 26 degrees or lower

[0115] (S140: Aging Step) After the Al alloy drawn wire is obtained, the Al alloy drawn wire is subjected to a heat treatment.

[0116] The aging step S140 of the present embodiment includes, for example, a first aging step S142 and a second aging step S144.

[0117] (S142: First Aging Step) As shown in Fig. 5, in the first aging step S142, the drawn Al alloy wire is subjected to heat treatment at a first temperature T1. In Fig. 5, RT means room temperature (20°C).

[0118] In the first aging step S142, first, Si is uniformly dispersed in the Al matrix. ３ This promotes the precipitation of Zr metastable phase. As a result, even if the Si content is small, fine Al particles are formed in the Al matrix. ３ A large number of precipitation nuclei of the Zr metastable phase can be precipitated.

[0119] At this time, in this embodiment, the first temperature T1 is set to, for example, 250°C or higher and lower than 300°C.

[0120] When the first temperature T1 is less than 250°C, Al ３ In contrast, in this embodiment, by setting the first temperature T1 to 250° C. or higher, fine Al nuclei are easily precipitated. ３ Precipitation nuclei of the Zr metastable phase can be stably precipitated.

[0121] On the other hand, when the first temperature T1 is 300° C. or higher as in Patent Document 1, Al ３ The size of the precipitation nuclei of the Zr metastable phase becomes excessive, and Al ３ Therefore, in the second aging step S144 described later, the number of precipitation nuclei of the Zr metastable phase becomes too small. ３ Each of the Zr precipitates tends to grow excessively, and Al ３ Zr metastable phase is Al ３ As a result, Al, which does not contribute to heat resistance, is easily transformed into a stable Zr phase. ３ In contrast, in this embodiment, by setting the first temperature T1 to less than 300° C., the precipitation rate of the Al stable phase increases. ３ The size of the precipitation nuclei of the Zr metastable phase is prevented from becoming excessively large, and Al ３This can prevent the number of precipitation nuclei of the Zr metastable phase from becoming too small. ３ The precipitation nuclei of the Zr metastable phase are prevented from growing excessively, and the Al ３ Zr metastable phase to Al ３ The phase transition to the Zr stable phase can be suppressed. ３ The precipitation nuclei can be grown while maintaining the Zr metastable phase. As a result, Al, which contributes to heat resistance, can be grown. ３ The precipitation rate of the Zr metastable phase can be increased.

[0122] In this case, the temperature rise rate v1 from room temperature (20° C.) to the first temperature T1 may be slower than the temperature rise rate v2 from the first temperature T1 to the second temperature T2, which will be described later. In this way, by extending the time until the heat treatment temperature reaches the temperature at which Zr starts to precipitate, it is possible to uniformly disperse Si during that time.

[0123] The temperature rise rate v1 is preferably set to, for example, 15°C / hr or more and 40°C / hr or less. If the temperature rise rate v1 is less than 15°C / hr, it takes an unnecessarily long time for the heat treatment temperature to reach the first temperature T1, resulting in a decrease in productivity. In contrast, in this embodiment, productivity can be improved by setting the temperature rise rate v1 to 15°C / hr or more. On the other hand, if the temperature rise rate v1 exceeds 40°C / hr, the heat treatment temperature will reach the temperature at which Zr starts to precipitate before Si is uniformly dispersed, resulting in Al. ３ In contrast, in this embodiment, by setting the temperature rise rate v1 to 40° C. / hr or less, it is possible to uniformly disperse Si before the heat treatment temperature reaches the temperature at which Zr precipitation begins. As a result, even if the Si content is small, it is possible to uniformly disperse Al ３ This makes it possible to sufficiently promote the formation of precipitation nuclei of the Zr metastable phase.

[0124] After the heat treatment temperature reaches the first temperature T1, the heat treatment temperature is maintained at the first temperature T1 for the first heat treatment time t1. Here, "maintaining the heat treatment temperature at the first temperature T1" includes not only maintaining a predetermined heat treatment temperature that satisfies the range of the first temperature T1, but also maintaining the heat treatment temperature within the range of the first temperature T1 and within ±25°C of the predetermined temperature.

[0125] In this embodiment, the first heat treatment time t1 is set to, for example, 15 hours or more. If the first heat treatment time t1 is less than 15 hours, the Si content is low and, under the condition that the first temperature T1 is within the above range, a sufficient number of Al atoms are not formed. ３ In contrast, in this embodiment, by setting the first heat treatment time t1 to 15 hours or more, it is possible to form fine Al nuclei in the Al matrix even under the conditions that the Si content is small and the first temperature T1 is within the above-mentioned range. ３ A large number of precipitation nuclei of the Zr metastable phase can be stably precipitated.

[0126] On the other hand, the upper limit of the first heat treatment time t1 is not limited, but from the viewpoint of productivity of the Al alloy wire 210, the first heat treatment time t1 may be set to, for example, 50 hours or less.

[0127] (S144: Second Aging Step) After the first aging step S142 is completed, as shown in Fig. 5, in the second aging step S144, the Al alloy wire drawn after the first aging step S142 is heat-treated at a second temperature T2 higher than the first temperature T1. This allows the numerous fine precipitation nuclei generated in the first aging step S142 to be converted into Al ３ The precipitation nuclei can be grown while maintaining the Zr metastable phase state.

[0128] At this time, in this embodiment, the first aging step S142 and the second aging step S144 are carried out consecutively without any other steps therebetween.

[0129] Here, if cold working or the like is performed between the first aging step S142 and the second aging step S144, the Al generated in the first aging step S142 may be dissolved. ３ The precipitation nuclei of the Zr metastable phase are broken up.３ There is a possibility that the precipitation nuclei of the Zr metastable phase become thermally unstable and are lost.

[0130] In contrast, in the present embodiment, the first aging step S142 and the second aging step S144 are performed consecutively without any other steps, so that the Al generated in the first aging step S142 can be removed. ３ Al without disrupting the precipitation nuclei of the Zr metastable phase. ３ The precipitation nuclei of the Zr metastable phase can be maintained in a thermally stable state. ３ Precipitation nuclei of the Zr metastable phase can be grown stably.

[0131] In this case, in this embodiment, the second temperature T2 may be set to, for example, 350° C. or higher and 450° C. or lower. If the second temperature T2 is lower than 350° C., Al ３ In contrast, in this embodiment, by setting the second temperature T2 to 350° C. or higher, the growth of precipitation nuclei of the Al metastable phase is slowed down. ３ On the other hand, when the second temperature T2 exceeds 450°C, the precipitation nuclei of the Zr metastable phase can be rapidly grown. ３ Each of the precipitation nuclei of the Zr metastable phase tends to grow excessively, and ３ The Zr metastable phase does not contribute to heat resistance. ３ On the other hand, in this embodiment, by setting the second temperature T2 to 450° C. or less, the Al ３ The precipitation nuclei of the Zr metastable phase are prevented from growing excessively, and the Al ３ Zr metastable phase to Al ３ The phase transition to the Zr stable phase can be suppressed.

[0132] At this time, the heat treatment temperature is increased from the first temperature T1 to the second temperature T2 at a temperature increase rate v2.

[0133] After the heat treatment temperature reaches the second temperature T2, the temperature is maintained at the second temperature T2 for a second heat treatment time t2. Here, "maintaining the temperature at the second temperature T2" ​​has the same meaning as "maintaining the temperature at the first temperature T1" described above, except that the temperature is different.

[0134] In this case, in this embodiment, the second heat treatment time t2 may be set to, for example, 10 hours or more and 60 hours or less. ３ In contrast, in this embodiment, the second heat treatment time t2 is set to 10 hours or more, so that the Al ３ On the other hand, if the second heat treatment time t2 exceeds 60 hours, the Al ３ Each of the precipitation nuclei of the Zr metastable phase tends to grow excessively, and ３ The Zr metastable phase does not contribute to heat resistance. ３ In this embodiment, the second heat treatment time t2 is set to 60 hours or less, so that the Al-Zr-Si phase is easily transformed into the Zr stable phase. ３ The precipitation nuclei of the Zr metastable phase are prevented from growing excessively, and the Al ３ Zr metastable phase to Al ３ This can suppress the phase transition to the stable Zr phase, and also suppress the formation of Al-Zr-Si based precipitates.

[0135] (S150: Second Wire Drawing Step) The Al alloy wire after the second aging step S144 is cold drawn to reduce the diameter of the Al alloy wire to a predetermined diameter, thereby forming the Al alloy wire 210 of this embodiment.

[0136] Examples of processing conditions for the second wire drawing step S150 are as follows: Temperature of aluminum wire during wire drawing: 10° C. or higher and 200° C. or lower Wire drawing speed: 20 m / min or higher and 800 m / min or lower Area reduction rate per die: 15% or higher and 30% or lower Die angle: 10 degrees or higher and 26 degrees or lower

[0137] In this manner, the Al alloy wire 210 of this embodiment is obtained.

[0138] (S200: Core portion forming step) After obtaining the Al alloy wire 210, the core portion 100 is formed including a plurality of core wires 110. Specifically, while one core wire 110 that will become the first core layer 100a is fed out from a feed machine, six core wires 110 are twisted together using a twisting machine so as to cover the outer periphery of the first core layer 100a, thereby forming the second core layer 100b.

[0139] (S300: Stranded Wire Portion Forming Step) After the central portion 100 is formed, the stranded wire portion 200 including the Al alloy wires 210 of this embodiment is formed. Specifically, a wire twisting machine is used to twist 12 Al alloy wires 210 together so as to cover the outer periphery of the central portion 100, thereby forming a first stranded wire layer 200a. Next, the wire twisting machine is used to twist 18 Al alloy wires 210 together so as to cover the outer periphery of the first stranded wire layer 200a, thereby forming a second stranded wire layer 200b.

[0140] In this manner, the electric wire 10 of the present embodiment is manufactured.

[0141] (6) Summary of the Present Embodiment According to the present embodiment, one or more of the following effects can be achieved.

[0142] (a) In this embodiment, the content of each alloy element in the Al alloy wire 210 is optimized, and a new aging process S140 is applied, thereby improving the Al content, which contributes to heat resistance. ３ The precipitation rate of the Zr metastable phase can be increased, thereby improving the heat resistance of the Al alloy wire 210.

[0143] Specifically, the tensile strength of the Al alloy wire 210 of this embodiment after heat treatment at 280° C. for 10 hours can be 94% or more of the tensile strength before the heat treatment.

[0144] In this manner, in this embodiment, it is possible to obtain an Al alloy wire 210 having improved heat resistance compared to the Al alloy wire 210 of Patent Document 1.

[0145] (b) The Al alloy wire 210 of this embodiment satisfies the above-mentioned formula (1): IZr1 / IZr0≧1.2 with respect to the Zr coherence in the radial structure function of Zr in the Al alloy wire 210. In this embodiment showing such a tendency, ３In this way, in this embodiment, the precipitation rate of the Zr metastable phase is high. ３ By increasing the precipitation rate of the Zr metastable phase, the heat resistance of the Al alloy wire 210 can be improved.

[0146] (c) In this embodiment, a small amount of Si is added, and a two-stage aging step S140 is performed.

[0147] In the first aging step S142, heat treatment is performed under conditions where the first temperature T1 is set to 250° C. or higher and lower than 300° C., and the first heat treatment time t1 is set to 15 hours or longer.

[0148] In the first aging step S142, Si is uniformly dispersed in the Al matrix, and the first temperature T1 is set to 250° C. or higher, thereby forming fine Al. ３ On the other hand, by setting the first temperature T1 to less than 300°C, the Al ３ The size of the precipitation nuclei of the Zr metastable phase is prevented from becoming excessively large, and Al ３ This can prevent the number of precipitation nuclei of the Zr metastable phase from becoming too small.

[0149] In the first aging step S142, by setting the first heat treatment time t1 to 15 hours or more, even under the conditions where the Si content is low and the first temperature T1 is within the above-mentioned range, fine Al particles are formed in the Al of the matrix. ３ A large number of precipitation nuclei of the Zr metastable phase can be stably precipitated.

[0150] In the subsequent second aging step S144, the Al alloy wire drawn after the first aging step S142 is heat-treated at a second temperature T2 higher than the first temperature T1. ３ By precipitating a large number of precipitation nuclei of the Zr metastable phase, Al ３ The precipitation nuclei of the Zr metastable phase are prevented from growing excessively, and the Al ３ Zr metastable phase to Al ３ The phase transition to the Zr stable phase can be suppressed. ３As a result, the Al alloy wire 210 can have a high heat resistance. ３ The precipitation rate of the Zr metastable phase can be increased.

[0151] (7) Modification of the Present Embodiment In the above-described embodiment, the Al alloy wire 210 may further contain, for example, strontium (Sr).

[0152] Sr is mainly precipitated in the Al matrix, which allows the crystal grains of the Al alloy to be refined, thereby suppressing the occurrence of defects such as cracks in the Al alloy wire 210.

[0153] In this embodiment, the Sr content in the Al alloy wire 210 is, for example, 0.002 mass% or more and 0.050 mass% or less. By setting the Sr content to 0.002 mass% or more, the crystal grains of the Al alloy can be refined and the occurrence of defects such as cracks can be suppressed. On the other hand, by setting the Sr content to 0.050 mass% or less, the Sr present as an impurity in the Al alloy can be reduced and the electrical conductivity can be improved.

[0154] <Other Embodiments of the Present Disclosure> Although the embodiments of the present disclosure have been specifically described above, the present disclosure is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the present disclosure.

[0155] In the above embodiment, the configuration shown in Fig. 3 has been described as an example of the electric wire 10, but the present disclosure is not limited to this case. For example, the number and arrangement of the core wires 110 in the central portion 100, the number of layers in the central portion 100, the number and arrangement of the Al alloy wires 210 in the stranded wire portion 200, and the number of layers in the stranded wire portion 200 may be changed. Alternatively, the electric wire 10 may have only the stranded wire portion 200 without having the central portion 100.

[0156] Next, examples according to the present disclosure will be described. These examples are examples of the present disclosure, and the present disclosure is not limited to these examples.

[0157] (1) Preparation of Aluminum Alloy Wire Al alloy wires of samples 1B to 18A were prepared under the following conditions.

[0158] First, an Al ingot was melted, and then a molten metal having the composition of an Al alloy wire shown in Table 2 below was prepared in a preparation furnace.

[0159] After the molten metal preparation step, the molten metal was continuously cast and hot rolled using a Properti continuous casting and rolling mill to form an Al alloy wire rod having a diameter of 11.7 mm.

[0160] The above-mentioned Al alloy wire rod was cold drawn to form an Al alloy wire rod having a diameter of 7.2 mm.

[0161] The above-mentioned Al alloy wiredrawing was subjected to a first aging step and a second aging step under the conditions shown in Table 2. In Table 2, for example, "350°C x 2H -> 400°C x 30H" for Sample 1B means that in the first aging step, heat treatment was performed under conditions where the first temperature was 350°C and the first heat treatment time was 2 hours, and in the second aging step, heat treatment was performed under conditions where the second temperature was 400°C and the second heat treatment time was 30 hours.

[0162] As a common condition for all samples, before the first aging step, the temperature was raised from room temperature (20°C) to the first temperature over 15 hours. Between the first aging step and the second aging step, the temperature was raised from the first temperature to the second temperature over 2 hours.

[0163] The aluminum alloy wire after the second aging step was cold drawn to form an aluminum alloy wire having a diameter of 3.3 mm, where the aluminum wire temperature during drawing was 150° C. or less, the drawing speed was 650 m / min, the area reduction rate per die was 0% to 30%, and the die angle was 24°.

[0164] Through the above steps, Al alloy wires of samples 1B to 18A were obtained.

[0165] (2) Evaluation Samples 1B to 18A were evaluated as follows.

[0166] (2-1) XAFS Measurement XAFS measurement was carried out on the Al alloy wire of each sample.

[0167] (Zr compatibility) XAFS measurement of the Zr K-absorption edge in each Al alloy wire was performed under the following conditions. For each sample measurement, a thin piece having a thickness of 0.2 mm to 0.4 mm was formed by mechanical polishing. Measurement was performed using the Saga Prefectural Kyushu Synchrotron Light Research Center BL16. Measurement was performed by the transmission method using X-rays monochromated by a Si (111) double crystal spectrometer. Measurement using the fluorescence method is also possible.

[0168] The XAFS spectrum at the Zr K absorption edge obtained by the above measurement was analyzed using free software Athena. Note that REX2000 manufactured by Rigaku Corporation can also be used.

[0169] In the obtained XAFS spectrum μ(E), two points in the range of 17,847 eV to 17,952 eV from the region before the absorption edge were used as reference points. A curve extrapolated to the region above the absorption edge energy was set as the background, and the background was removed from the XAFS spectrum μ(E). Next, μs(E), which is a component obtained by approximating the center of the vibrational component with a spline function in the range up to 18,543 eV of the XAFS spectrum μ(E), was obtained. Then, μ(E) - μs(E) was divided by the absorbance difference μ0 before and after the absorption edge to obtain the EXAFS vibrational χ(k). Note that the "absorbance difference before and after the absorption edge" here refers to the absorbance at 18,148 eV and 18,974 eV after the absorption edge when the background absorbance is set to 0.

[0170] For the EXAFS vibration χ(k) obtained as described above, the square of the wave number k (k ２ ) and weighting was performed. ２ χ(k) is the wave number k at 30 nm. －１ 90nm or more －１ The radial structure function X(R) was obtained by Fourier transforming the region within the following range:

[0171] In the radial structure function X(R) of Zr in the Al alloy wire obtained as described above, the height IZr1 of the peak occurring within a radius range of 0.22 nm or more and 0.30 nm or less was determined.

[0172] Furthermore, an XAFS measurement of the K-absorption edge of Zr in a rolled Zr material with a purity of 99.2% and a thickness of 0.02 mm was performed as a standard sample under the same conditions as those for the XAFS measurement of Zr in the above-mentioned Al alloy wire. From the XAFS spectrum of the standard sample obtained by the above-mentioned measurement, the radial structure function of Zr in the standard sample was obtained under the same conditions as those for the radial structure function of Zr in the above-mentioned Al alloy wire. In the radial structure function X(R) of Zr in the obtained standard sample, the height IZr0 of the peak occurring within a radius range of 0.22 nm to 0.30 nm was determined.

[0173] Based on the IZr1 and IZr0 determined as above, the ratio IZr1 / IZr0 (arbitrary unit) was determined as the Zr coherency.

[0174] (2-2) Tensile Strength The tensile strength of each Al alloy wire was measured in accordance with JIS C3002: 1992. The temperature during measurement was set to 20°C.

[0175] (2-3) Electrical Conductivity The electrical conductivity of each Al alloy wire was measured in accordance with JIS C3002:1992.

[0176] (2-4) Heat Resistance (Tensile Resistance) The tensile strength after heat treatment was measured under the following two time conditions. As described above, the "tensile strength after heat treatment" is the ratio (%) calculated by (tensile strength after heat treatment) / (tensile strength before heat treatment) × 100. The tensile strength before and after heat treatment was measured in accordance with JIS C3002:1992, and the temperature during measurement was 20°C.

[0177] The "tensile strength remaining rate after heat treatment at 280°C" in Table 2 was calculated as the ratio (%) of the tensile strength of the Al alloy wire after heat treatment at 280°C for a predetermined time to the tensile strength before the heat treatment. In Table 2, "5H" and "10H" mean the cases where the heat treatment time in the heat resistance test was 5 hours and 10 hours, respectively.

[0178] (2-5) Crack Evaluation Each sample Al alloy wire was compressed in the longitudinal direction at room temperature (20°C) at a strain rate of 20% / min, and the compression ratio K at which the first scratch was visually confirmed on the outer periphery was determined as an index for crack evaluation. This method allows minute scratches to spread during compression, making it possible to detect minute scratches that are normally invisible to the naked eye. The larger the compression ratio K of the Al alloy wire, the better the surface quality and the lower the risk of wire breakage.

[0179] (3) Results The results of evaluation of each sample will be explained with reference to Table 2 in FIG.

[0180] In the following description, the following ranges for the content of each alloying element are also referred to as "appropriate ranges": Zr content: 0.20 mass% to 0.35 mass%, Fe content: 0.05 mass% to 0.30 mass%, Si content: 0.01 mass% to 0.05 mass%, Ti content: 0.002 mass% to 0.020 mass%.

[0181] In the following description, the following manufacturing conditions are also referred to as "appropriate conditions." In the first aging step, heat treatment is performed under conditions where the first temperature is equal to or higher than 250°C and lower than 300°C, and the first heat treatment time is 15 hours or longer. In the second aging step, heat treatment is performed at a second temperature higher than the first temperature. The first aging step and the second aging step are performed consecutively without any other steps in between.

[0182] (3-1) Dependence on the first aging step The dependence on the first aging step will be explained with reference to the results of Samples 1B to 4B and Samples 5A to 7A, 9A, 10A, and 12A to 18A. As described above, in Samples 1B to 4B, 5A to 7A, 9A, 10A, and 12A to 18A, the contents of each alloy element were set within the appropriate ranges, and the other manufacturing conditions were set to appropriate conditions, except that the conditions for the first aging step were changed.

[0183] (Sample 1B) In Sample 1B, the first temperature was set to 300°C or higher, and the first heat treatment time was set to 2 hours. Therefore, the Zr coherence was less than 1.2. As a result, the tensile strength after 5 hours at 280°C was less than 96% and the tensile strength after 10 hours at 280°C was less than 94%.

[0184] (Samples 2B to 4B) For Samples 2B to 4B, the first temperature was set to 250°C or higher and lower than 300°C, but the first heat treatment time was set to less than 15 hours. As a result, the Zr coherence was less than 1.2. As a result, the tensile strength after 5 hours at 280°C was less than 96%, and the tensile strength after 10 hours at 280°C was less than 94%.

[0185] (Samples 5A to 7A, 9A, 10A, 12A to 18A) In contrast, for Samples 5A to 7A, 9A, 10A, and 12A to 18A, the first temperature was set to 250°C or higher but lower than 300°C, and the first heat treatment time was set to 15 hours or longer. As a result, the Zr coherence was 1.2 or higher. As a result, the tensile strength after 5 hours at 280°C was 96% or higher, and the tensile strength after 10 hours at 280°C was 94% or higher.

[0186] In Samples 5A to 7A, 9A, 10A, and 12A to 18A, the first aging step was performed under the conditions of a first temperature of 250°C or higher and lower than 300°C, and the first heat treatment time was 15 hours or longer, and then the second aging step was performed, thereby reducing Al, which contributes to heat resistance. ３ The precipitation rate of the Zr metastable phase was increased. As a result, it was confirmed that the heat resistance of the Al alloy wire was improved in Samples 5A to 7A, 9A, 10A, and 12A to 18A.

[0187] (3-2) Zr Content Dependence The Zr content dependency will be explained with reference to the results of Samples 8B and 11B and Samples 5A to 7A, 9A, 10A, and 12A to 18A. As described above, in Samples 8B, 11B, 5A to 7A, 9A, 10A, and 12A to 18A, except for the difference in the Zr content, the contents of the other alloying elements were within the appropriate ranges, and the manufacturing conditions were appropriate.

[0188] (Sample 8B) In Sample 8B, the Zr content was set to less than 0.20 mass %, and therefore the tensile retention rate after 5 hours at 280°C was less than 96% and after 10 hours at 280°C was less than 94%.

[0189] (Sample 11B) In Sample 11B, the Zr content was more than 0.35 mass %. Therefore, the electrical conductivity of the Al alloy wire was less than 60% IACS. Furthermore, the compression ratio K, which is an index for crack evaluation, was less than 71%.

[0190] (Samples 5A to 7A, 9A, 10A, 12A to 18A) In contrast, in Samples 5A to 7A, 9A, 10A, and 12A to 18A, the Zr content was set to 0.20 mass% or more and 0.35 mass% or less. As a result, the tensile survival rate after 5 hours at 280°C was 96% or more, and the tensile survival rate after 10 hours at 280°C was 94% or more. In addition, the electrical conductivity of the Al alloy wire was 60% IACS or more. Furthermore, the compression ratio K, which is an index of crack evaluation, was 71% or more.

[0191] In Samples 5A to 7A, 9A, 10A, and 12A to 18A, the Zr content was set to 0.20 mass% or more, so that a sufficient absolute amount of Al was obtained. ３ It was confirmed that the heat resistance of the Al alloy wires was improved in Samples 5A to 7A, 9A, 10A, and 12A to 18A.

[0192] In Samples 5A to 7A, 9A, 10A, and 12A to 18A, the amount of Zr dissolved in the Al matrix was reduced by setting the Zr content to 0.35 mass% or less. As a result, it was confirmed that the decrease in the electrical conductivity of the Al alloy wire 210 was suppressed in Samples 5A to 7A, 9A, 10A, and 12A to 18A. Furthermore, by setting the Zr content to 0.35 mass% or less, it was confirmed that the increase in the molten metal temperature was suppressed. As a result, it was confirmed that the occurrence of defects such as cracks was suppressed in Samples 5A to 7A, 9A, 10A, and 12A to 18A.

[0193] (3-3) Zr Coherence Dependence Figure 7 is a graph plotting the tensile strength after 10 hours at 280°C against the Zr coherence for several samples with a Zr content of 0.32 mass%. As shown in Figure 7, Al with a high Zr coherence, i.e., Al that is coherent with pure Al, ３The higher the precipitation rate of the Zr metastable phase, the higher the tensile survival rate after 10 hours at 280° C. From Fig. 7, it was confirmed that by setting the Zr coherency to 1.2 or more, the tensile survival rate after 10 hours at 280° C. could be made 94% or more.

[0194] <Supplementary Notes> The following provides supplementary notes on aspects of the present disclosure.

[0195] [7] The radial structure function of Zr can be obtained by: (a) measuring an X-ray absorption fine structure spectrum μ(E) at the K absorption edge of Zr; (b) obtaining an extended X-ray absorption fine structure oscillation χ(k) by formula (A) based on the X-ray absorption fine structure spectrum μ(E), χ(k)={μ(E)-μs(E)} / μ0 (A), where k is the wave number, E is the energy, μs(E) is a component obtained by approximating the center of the oscillation component of μ(E) by a spline function, and μ0 is the absorbance difference before and after the absorption edge in μ(E); and (c) calculating the extended X-ray absorption fine structure oscillation χ(k) by using k ２ (d) performing a weighting process using the k obtained by (c); ２ χ(k) is the 30 nm wavelength of wave number k. －１ 90nm or more －１ The aluminum alloy wire according to [2] or [3], obtained by carrying out a step of Fourier transforming a region within the following range:

[0196] [8] A method for manufacturing an aluminum alloy wire rod, comprising: a melting step of preparing a molten metal containing 0.20% by mass or more and 0.35% by mass or less of Zr, 0.05% by mass or more and 0.30% by mass or less of Fe, 0.01% by mass or more and 0.05% by mass or less of Si, 0.002% by mass or more and 0.020% by mass or less of Ti, with the balance being Al and unavoidable impurities; a continuous casting and rolling step of continuously casting and rolling the molten metal to form an aluminum alloy wirerod; a first wiredrawing step of cold drawing the aluminum alloy wirerod to form an aluminum alloy wiredrawn; an aging step of performing heat treatment on the aluminum alloy wiredrawn; and a second wiredrawing step of cold drawing the aluminum alloy wiredrawn after the aging step to form an aluminum alloy wire, wherein the aging step comprises: a first aging step of performing heat treatment on the aluminum alloy wiredrawn at a first temperature; a second aging step of subjecting the aluminum alloy wiredrawn after the first aging step to heat treatment at a second temperature higher than the first temperature, wherein in the first aging step, the heat treatment is performed under conditions where the first temperature is equal to or higher than 250°C and lower than 300°C and the first heat treatment time is 15 hours or longer, and the first aging step and the second aging step are performed continuously without any intervening step.

[0197] REFERENCE SIGNS LIST 10 Electric wire 100 Center portion 100a First central layer 100b Second central layer 110 Core wire 112 Wire portion 114 Covering portion 200 Stranded wire portion 200a First stranded wire layer 200b Second stranded wire layer 210 Al alloy wire

Claims

1. An aluminum alloy wire containing: 0.20% by mass or more and 0.35% by mass or less of Zr; 0.05% by mass or more and 0.30% by mass or less of Fe; 0.01% by mass or more and 0.05% by mass or less of Si; and 0.002% by mass or more and 0.020% by mass or less of Ti, with the remainder consisting of Al and inevitable impurities, wherein the tensile strength of the aluminum alloy wire after heat treatment at 280°C for 10 hours is 94% or more of the tensile strength before the heat treatment.

2. The aluminum alloy wire according to claim 1, wherein the aluminum alloy wire satisfies formula (1): IZr1 / IZr0≧1.2 (1) where IZr1 is the height of a peak occurring within a radius range of 0.22 nm or more and 0.30 nm or less in a radial structure function obtained from X-ray absorption fine structure measurement at the K absorption edge of Zr in the aluminum alloy wire, and IZr0 is the height of a peak occurring within a radius range of 0.22 nm or more and 0.30 nm or less in a radial structure function of Zr in a rolled Zr material having a purity of 99.2% and a thickness of 0.02 mm as a standard sample, obtained under the same conditions as those under which the radial structure function of Zr in the aluminum alloy wire was obtained.

3. An aluminum alloy wire containing: 0.20 mass% or more and 0.35 mass% or less of Zr; 0.05 mass% or more and 0.30 mass% or less of Fe; 0.01 mass% or more and 0.05 mass% or less of Si; and 0.002 mass% or more and 0.020 mass% or less of Ti, with the balance being Al and inevitable impurities, and the aluminum alloy wire satisfies formula (1): IZr1 / IZr0≧1.2 (1), where IZr1 is the height of a peak occurring within a radius range of 0.22 nm or more and 0.30 nm or less in a radial structure function obtained from X-ray absorption fine structure measurement of the K absorption edge of Zr in the aluminum alloy wire, IZr0 is the height of a peak occurring within a radius range of 0.22 nm or more and 0.30 nm or less in the radial structure function of Zr in a rolled Zr material having a purity of 99.2% and a thickness of 0.02 mm as a standard sample, which is obtained under the same conditions as those under which the radial structure function of Zr in the aluminum alloy wire was obtained.

4. The aluminum alloy wire according to any one of claims 1 to 3, wherein the electrical conductivity of the aluminum alloy wire is 60% IACS or more.

5. An aluminum alloy wire according to any one of claims 1 to 4, further containing 0.002 mass % or more and 0.050 mass % or less of Sr.

6. An electric wire having a stranded wire section formed by twisting together a plurality of aluminum alloy wires according to any one of claims 1 to 5.

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