Aluminum alloy wire and electric wire

Abstract

To improve heat resistance.SOLUTION: The aluminum alloy wire 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 unavoidable impurities, and has a tensile strength after heat treatment at 280°C for 10 hours of 94% or more of the tensile strength before the heat treatment.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to aluminum alloy wires and electric wires. [Background technology]

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

[0003] [Patent Document 1] Patent Publication No. 2021-188106 [Non-patent literature]

[0004] [Non-Patent Document 1] K.Momma and F.Izumi, J.Appl.Crystallogr.,44,1272-1276(2011) Summary of the Invention [Problem to be solved by the invention]

[0005] The objective of the present disclosure is to improve heat resistance. [Means for solving the problem]

[0006] According to one embodiment 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, and the balance consisting of Al and unavoidable 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. [Effects of the Invention]

[0007] According to the present disclosure, heat resistance can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] Figure 1 shows a comparison of the crystal structures. [Figure 2] FIG. 2 is a diagram showing the radial structure function obtained by X-ray absorption fine structure measurement at the K absorption edge of Zr in an aluminum alloy wire. [Figure 3] 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. [Figure 4] FIG. 4 is a flowchart illustrating a method for manufacturing an electric wire according to an embodiment of the present disclosure. [Figure 5] FIG. 5 is a diagram showing the temperature change in the aging step S140. [Figure 6] FIG. 6 is a diagram showing the dependency of the tensile strength of an aluminum alloy wire after heat treatment on the Zr coherency. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] <Insights gained by the inventor> First, the findings of the inventors will be explained.

[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] It has been thought that adding Si as an alloying element promotes the precipitation of Al3Zr and improves heat resistance.

[0012] However, if Si is added in excess, Al-Zr-Si compounds (Al described later) will be formed, which do not contribute to heat resistance. 2.7 Si 0.3The ratio of Al3Zr precipitates decreased, resulting in a decrease in the heat resistance of the aluminum alloy wire.

[0013] Therefore, the inventors have suppressed the precipitation of the Al-Zr-Si compound and increased the proportion of Al3Zr precipitates by adding a small amount of Si and performing a two-stage aging process as described in Patent Document 1. As a result, the heat resistance of the Al alloy wire has been improved 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. In other words, there has been a demand for Al alloy wires that can withstand high-temperature environments for a longer period of time.

[0015] To address these new challenges, the inventors evaluated the precipitation state of Zr in the Al alloy wire by X-ray absorption fine structure (XAFS) measurement in order to find an Al alloy wire configuration with further improved heat resistance. As a result of the evaluation, it was found that the Al alloy wire of Patent Document 1 contains a high proportion of crystalline phases that do not contribute to heat resistance as Al3Zr precipitates.

[0016] Here, the relationship between the crystalline phases that can precipitate in an 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] [Table 1]

[0018] As shown in Figure 1, in an Al alloy wire containing the above alloying elements, depending on the composition and manufacturing method of the Al alloy wire, there are three phases: Al3Zr metastable phase, Al3Zr stable phase, and Al 2.7 Si 0.3 Among these, Al3Zr stable phase and Al 2.7 Si 0.3The stable Zr phase does not contribute to the heat resistance of the Al alloy wire, whereas the metastable Al3Zr 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 The formation of crystals of the Zr stable phase was suppressed, and as a result, fine Al3Zr crystals were formed in the first aging step of Patent Document 1.

[0020] At this time, the lattice constant of the Al3Zr metastable phase is closer to that of pure Al than that of the Al3Zr stable phase, and therefore the interfacial energy loss in the Al3Zr metastable phase is smaller than the energy loss in the Al3Zr stable phase, as shown in Table 1. Therefore, in the first aging step of Patent Document 1, precipitation nuclei of fine Al3Zr metastable phase, which is a crystalline phase that is compatible with pure Al, are 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 shorter, which results in a small number of precipitation nuclei of the AlZr metastable phase formed in the first aging step.

[0022] In Patent Document 1, the number of precipitation nuclei of the Al3Zr metastable phase was small, so that each Al3Zr precipitate tended to grow excessively in the second aging step, which was performed at a higher heat treatment temperature than the first aging step. Therefore, in the second aging step, as the volume of the Al3Zr precipitates increased, the specific surface area of ​​the precipitates decreased, and the loss of interfacial energy decreased. As a result, the Al3Zr metastable phase tended to easily undergo a phase transition to the Al3Zr stable phase. In addition, the number density of the precipitates tended to decrease.

[0023] As described above, the proportion of the AlZr stable phase, which does not contribute to heat resistance, is high in Patent Document 1. As a result, it is difficult to further improve the heat resistance of the Al alloy wire using the manufacturing method of Patent Document 1.

[0024] As a result of further intensive research, the inventors have found a new manufacturing method that can form many precipitation nuclei of the Al3Zr metastable phase and grow the precipitation nuclei while maintaining the Al3Zr metastable phase, thereby succeeding 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 comprises: Zr is 0.20 mass% or more and 0.35 mass% or less, Fe is 0.05 mass% or more and 0.30 mass% or less, Si is 0.01 mass% or more and 0.05 mass% or less, Ti is 0.002 mass% or more and 0.020 mass% or less, Contains the balance being Al and unavoidable impurities, 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] In the aluminum alloy wire according to the above [1], 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 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. This configuration can improve heat resistance.

[0029] [3] An aluminum alloy wire according to another aspect of the present disclosure includes: Zr is 0.20 mass% or more and 0.35 mass% or less, Fe is 0.05 mass% or more and 0.30 mass% or less, Si is 0.01 mass% or more and 0.05 mass% or less, Ti is 0.002 mass% or more and 0.020 mass% or less, Contains the balance being Al and unavoidable impurities, 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 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. This configuration can improve heat resistance.

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

[0031] [5] The aluminum alloy wire according to any one of [1] to [4] above, Furthermore, the alloy contains 0.002 mass % or more and 0.050 mass % or less of Sr. This configuration can suppress the occurrence of defects such as cracks.

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

[0033] [Details of the embodiments 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 remainder being Al and unavoidable 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 state of precipitation in the Al matrix.

[0037] By precipitating a large amount of fine Al3Zr metastable phase in the Al matrix, the propagation of dislocations in the Al alloy structure can be suppressed, making the Al alloy less susceptible to plastic deformation, thereby improving the strength of the Al alloy wire 210.

[0038] Furthermore, the fine Al3Zr metastable phase precipitates dispersed in the Al alloy match the lattice of the Al matrix. As a result, the Al3Zr metastable phase precipitates suppress the movement of dislocations due to heat in a high-temperature environment, i.e., 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 the Al alloy structure can be stabilized. As a result, the heat resistance of the Al alloy wire 210 can be improved.

[0039] In this embodiment, the precipitation rate of the Al3Zr metastable phase is increased by optimizing the content of each alloying element and applying a new aging step S140, which will be described later. In the Al alloy wire 210 of this embodiment, the state in which the precipitation rate of the Al3Zr metastable phase is high can be confirmed by X-ray absorption fine structure measurement. This point 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%, the absolute amount of the Al3Zr metastable phase precipitated in the Al matrix is ​​small. This makes it difficult to improve the strength and heat resistance of the Al alloy wire 210. In contrast, in this embodiment, by setting the Zr content to 0.20 mass% or more, a sufficient absolute amount of the Al3Zr metastable phase can be precipitated. This allows the strength and heat resistance of the Al alloy wire 210 to be improved.

[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 makes it possible to suppress a decrease in the electrical conductivity of the Al alloy wire 210. Furthermore, by setting the Zr content to 0.35 mass% or less, it is possible to suppress an increase in the molten metal temperature and suppress the occurrence of defects such as cracks.

[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 becomes small. This makes it 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. This reduces the electrical conductivity of the Al alloy wire 210. Furthermore, if the Fe content exceeds 0.30 mass%, excessive dislocations are introduced into the Al alloy due to processing before the aging step S140. The interaction between dislocations and Al3Zr precipitates makes it easy for an incoherent Al3Zr stable phase to form. As a result, the heat resistance of the Al alloy wire 210 decreases. In contrast, in this embodiment, by setting the Fe content to 0.30 mass% or less, it is possible to prevent excessive Fe precipitation in the Al matrix. This reduces 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 due to processing before the aging step S140. This reduces the generation of an incoherent Al3Zr stable phase due to the interaction between dislocations and Al3Zr precipitates. As a result, it is possible to prevent the heat resistance of the Al alloy wire 210 from being reduced.

[0048] (Si) In this embodiment, Si is mainly dissolved in the Al matrix phase, which can promote the precipitation of Al3Zr in the aging step S140 described below.

[0049] In this embodiment, by adding a small amount of Si and applying a new aging step S140 described later, it is possible to promote the precipitation of the Al3Zr metastable phase even when the Si content is small. On the other hand, by reducing the Si content, it is possible to suppress the generation of Al-Zr-Si compounds and increase the precipitation rate of the fine Al3Zr metastable phase. As a result, it is possible to efficiently improve the heat resistance of the Al alloy wire 210.

[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] If the Si content is less than 0.01 mass%, it is difficult to promote the precipitation of the Al3Zr metastable phase. Therefore, Zr is likely to remain in 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, it is possible to promote the precipitation of the Al3Zr metastable phase. This makes it possible to reduce the amount of Zr in solid solution in the Al matrix. As a result, it is possible to suppress the decrease in the electrical conductivity of the Al alloy wire 210.

[0052] On the other hand, if the Si content exceeds 0.05 mass%, the amount of precipitation of Al-Zr-Si compounds that do not contribute to heat resistance increases, and the precipitation ratio of fine Al3Zr metastable phases decreases. As a result, the heat resistance of the Al alloy wire 210 decreases. In contrast, in this embodiment, by setting the Si content to 0.05 mass% or less and applying a new aging step S140 described later, it is possible to suppress the generation of Al-Zr-Si compounds and increase the precipitation ratio of fine Al3Zr metastable phases. As a result, it is possible to improve the heat resistance of the Al alloy wire 210.

[0053] (Ti) At least a part of Ti is precipitated as a Ti compound, such as a Ti-B compound, in the Al matrix. 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. On the other hand, in this embodiment, by setting the Ti content to 0.002 mass% or more, it is possible to stably refine the Al crystal grains. As a result, it is possible to stably suppress the occurrence of defects such as cracks in the Al alloy wire 210.

[0056] On the other hand, if the Ti content exceeds 0.020 mass%, the amount of Ti dissolved in the Al matrix increases. As a result, the electrical conductivity of the Al alloy wire 210 decreases. In contrast, in this embodiment, the Ti content is set to 0.020 mass% or less, thereby reducing the amount of Ti dissolved in the Al matrix. As a result, the electrical conductivity of the Al alloy wire 210 can be improved.

[0057] (unavoidable 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 the present 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, the precipitation state of Zr in the Al alloy wire 210 will be described with reference to FIG.

[0060] In X-ray absorption fine structure (XAFS) measurements, a material is irradiated with X-rays and the intensity of the transmitted or fluorescent X-rays from the material is measured to obtain an XAFS spectrum derived from a specific target element in the material. The low-energy region of the XAFS spectrum reflects the chemical state of the element (e.g., elemental or compound species). 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 (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 the present embodiment, the inventors have found that the Al alloy wire 210 satisfies the requirements described later with respect to the XAFS measurement result of Zr by optimizing the content of each alloy element and applying a new aging process S140 described later to increase the precipitation ratio of the AlZr metastable phase.

[0063] (Zr consistency) Figure 2 shows the radial structure functions obtained by X-ray absorption fine structure measurements at the Zr K absorption 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) Measure 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 using equation (A). χ(k)={μ(E)-μs(E)} / μ0 ···(A) where: where k is the wave number, E is the energy, μs(E) is the 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) The extended X-ray absorption fine structure vibration χ(k) is expressed as k 2 The weighting process is performed by: (d) k obtained by (c) 2 χ(k) is the 30 nm wavelength of wave number k. -1 More than 90nm -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, which is 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 Figure 2 above shows the value of the radial structure function X(R) normalized by IZr0. For this reason, in Figure 2, peaks occurring within the radius range of 0.22 nm to 0.30 nm are labeled "IZr1 / IZr0."

[0067] The ratio "IZr1 / IZr0" is hereinafter also referred to as "Zr coherency." The Zr coherency, IZr1 / IZr0, is an index reflecting the precipitation rate of the Al3Zr metastable phase, which is coherent with pure Al.

[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 coherence ratio IZr1 / IZr0 is less than 1.2. In the comparative example showing such a tendency, the precipitation ratio of the Al3Zr metastable phase that is coherent with pure Al is low. In the comparative example, since the precipitation ratio of the Al3Zr metastable phase that contributes to heat resistance is low, it is difficult to improve the heat resistance of the Al alloy wire.

[0069] In contrast, the radial structure function of this embodiment shown in Fig. 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 coherence ratio IZr1 / IZr0 of this embodiment is higher than the Zr coherence ratio IZr1 / IZr0 of the comparative example.

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

[0071] In the present embodiment showing such a tendency, the precipitation ratio of the Al3Zr metastable phase that is compatible with pure Al is high. In this way, in the present embodiment, by increasing the precipitation ratio of the Al3Zr metastable phase that contributes to the heat resistance, 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, provided that IZr1 / IZr0≦ 2.5 may be.

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

[0074] (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 exhibits high tensile strength by precipitating many fine precipitation nuclei of the Al3Zr metastable phase in the Al matrix.

[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: 2.6mm (tolerance ±0.03mm): 169MPa 3.2mm, 3.8mm (tolerance ±0.04mm): 162MPa 4.0mm, 4.5mm (tolerance ±0.04mm): 159MPa

[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 survival rate) The Al alloy wire 210 of this embodiment exhibits a high tensile strength even after being subjected to a long-term heat treatment.

[0083] The "tensile strength retention rate after heat treatment" referred to here is the 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 the Al alloy wire of Patent Document 1 may have a maximum tensile strength of 95.4% after heat treatment at 280°C for 5 hours. However, the Al alloy wire of Patent Document 1 has a low precipitation rate of the AlZr metastable phase, and therefore has lower heat resistance than the Al alloy wire 210 of the present embodiment. Therefore, the Al alloy wire of Patent Document 1 has an even lower tensile strength after heat treatment for a time longer than the above-mentioned specified time.

[0086] In contrast, in the Al alloy wire 210 of the present embodiment, as described above, the precipitation ratio of the AlZr metastable phase is high, so that in the present embodiment, a high tensile retention rate 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 heat treatment of the Al alloy wire 210 of this embodiment is not limited, and the higher the upper limit, the better. That is, in the Al alloy wire 210 of this embodiment, the tensile strength after heat treatment at 280°C for 5 hours and the tensile strength after heat treatment at 280°C for 10 hours may be close to 100%, for example.

[0090] (Crack compression rate) 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 core 100 has, for example, a plurality of core wires 110 twisted together in a spiral shape. The core 100 has, for example, a first core layer 100a and a second core layer 100b 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 have, 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 spirally stranded together. 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 in 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: 160mm 2 :58.7kN 240mm 2 :84.9kN 330mm 2 :93.4kN 410mm 2 :118.6kN 610mm 2 :159.3kN

[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 portions 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 galvanized Invar wire, as specified in JCS1405:2003, is as follows: 120mm 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 :335.0kN

[0106] (5) Wire manufacturing method 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 process) 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 process) 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 in an adjusting furnace while stirring the molten metal, thereby preparing a molten metal satisfying the composition of the Al alloy wire 210 of this embodiment.

[0110] Specifically, a molten metal containing 0.20% by mass to 0.35% by mass of Zr, 0.05% by mass to 0.30% by mass of Fe, 0.01% by mass to 0.05% by mass of Si, 0.002% by mass to 0.020% by mass of Ti, and the remainder 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 added Zr can be dissolved in the molten metal and at which heat management is easy.

[0112] (S120: Continuous casting and rolling process) 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, Zr is supersaturated in the Al alloy during the solidification process. The term "supersaturated solution" as used herein 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 process, an Al alloy wire is formed.

[0113] (S130: 1st wire drawing process) After the Al alloy wire rod is obtained, the Al alloy wire rod is subjected to cold 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 wire drawing step S130 are as follows. Temperature of aluminum wire during wire drawing: 10℃ to 200℃ Wire drawing speed: 20m / min or more and 600m / min or less Area reduction rate per die: 15% to 30% Dice angle: 10 degrees or more and 26 degrees or less

[0115] (S140: Aging process) Once the drawn aluminum alloy wire is obtained, the drawn aluminum alloy wire is subjected to 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 heat treated 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. The uniformly dispersed Si promotes the precipitation of the Al3Zr metastable phase. This allows many fine precipitation nuclei of the Al3Zr metastable phase to precipitate in the Al matrix even with a small Si content.

[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., precipitation nuclei of the Al3Zr metastable phase are difficult to precipitate. In contrast, in this embodiment, the first temperature T1 is set to 250° C. or higher, thereby enabling fine precipitation nuclei of the Al3Zr metastable phase to be stably precipitated.

[0121] On the other hand, if the first temperature T1 is 300°C or higher as in Patent Document 1, the size of the precipitation nuclei of the Al3Zr metastable phase becomes excessively large, and the number of precipitation nuclei of the Al3Zr metastable phase becomes too small. Therefore, in the second aging step S144 described later, each of the Al3Zr precipitates is likely to grow excessively, and the Al3Zr metastable phase is likely to undergo a phase transition to the Al3Zr stable phase. As a result, the precipitation rate of the Al3Zr stable phase, which does not contribute to heat resistance, becomes high. In contrast, in the present embodiment, by setting the first temperature T1 to less than 300°C, it is possible to prevent the size of the precipitation nuclei of the Al3Zr metastable phase from becoming excessively large, and to prevent the number of precipitation nuclei of the Al3Zr metastable phase from becoming too small. As a result, in the second aging step S144 described later, it is possible to prevent each of the precipitation nuclei of the Al3Zr metastable phase from growing excessively large, and to suppress the phase transition from the Al3Zr metastable phase to the Al3Zr stable phase. That is, the precipitation nuclei can be grown while maintaining the Al3Zr metastable phase, which increases the precipitation rate of the Al3Zr metastable phase, which contributes to heat resistance.

[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 heating rate v1 is preferably, for example, 15°C / hr or more and 40°C / hr or less. If the heating 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 reduced productivity. In contrast, in this embodiment, by setting the heating rate v1 to 15°C / hr or more, productivity can be improved. On the other hand, if the heating rate v1 exceeds 40°C / hr, the heat treatment temperature reaches the temperature at which Zr precipitation begins before Si is uniformly dispersed, making it difficult to promote the generation of precipitation nuclei of the Al3Zr metastable phase. In contrast, in this embodiment, by setting the heating rate v1 to 40°C / hr or less, Si can be uniformly dispersed before the heat treatment temperature reaches the temperature at which Zr precipitation begins. As a result, even if the Si content is low, it is possible to sufficiently promote the generation of precipitation nuclei of the Al3Zr 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" refers not only to maintaining a predetermined heat treatment temperature that satisfies the range of the first temperature T1, but also to 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, a sufficient number of precipitation nuclei of the Al3Zr metastable phase cannot be precipitated under the conditions that the Si content is low and the first temperature T1 is within the above-mentioned range. In contrast, in this embodiment, by setting the first heat treatment time t1 to 15 hours or more, it is possible to stably precipitate a large number of fine precipitation nuclei of the Al3Zr metastable phase in the Al matrix, even under the conditions that the Si content is low and the first temperature T1 is within the above-mentioned range.

[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, in the second aging step S144, the drawn Al alloy wire after the first aging step S142 is heat treated at a second temperature T2 higher than the first temperature T1, as shown in Fig. 5. This allows the numerous fine precipitation nuclei generated in the first aging step S142 to grow while maintaining the nuclei in the state of the AlZr metastable phase.

[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] If cold working or the like is performed between the first aging step S142 and the second aging step S144, the precipitation nuclei of the Al3Zr metastable phase formed in the first aging step S142 will be broken up, which may cause the precipitation nuclei of the Al3Zr metastable phase to become thermally unstable and be lost.

[0130] In contrast, in the present embodiment, the first aging step S142 and the second aging step S144 are performed consecutively without any intervening steps, so that the precipitation nuclei of the Al3Zr metastable phase formed in the first aging step S142 are not broken down and the precipitation nuclei of the Al3Zr metastable phase can be maintained in a thermally stable state, thereby enabling the precipitation nuclei of the Al3Zr metastable phase to grow stably in the second aging step S144.

[0131] 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, the growth of precipitation nuclei of the Al3Zr metastable phase is slow. In contrast, in this embodiment, by setting the second temperature T2 to 350°C or higher, the precipitation nuclei of the Al3Zr metastable phase can be rapidly grown. On the other hand, if the second temperature T2 exceeds 450°C, each of the precipitation nuclei of the Al3Zr metastable phase is likely to grow excessively, and the Al3Zr metastable phase is likely to undergo a phase transition to an Al3Zr stable phase that does not contribute to heat resistance. In contrast, in this embodiment, by setting the second temperature T2 to 450°C or lower, the excessive growth of each of the precipitation nuclei of the Al3Zr metastable phase can be suppressed, and the phase transition from the Al3Zr metastable phase to the Al3Zr 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 embodiment, the second heat treatment time t2 may be set to, for example, 10 hours or more and 60 hours or less. If the second heat treatment time t2 is less than 10 hours, the precipitation nuclei of the Al3Zr metastable phase cannot be sufficiently grown. In contrast, in this embodiment, by setting the second heat treatment time t2 to 10 hours or more, the precipitation nuclei of the Al3Zr metastable phase can be sufficiently grown. On the other hand, if the second heat treatment time t2 exceeds 60 hours, the precipitation nuclei of the Al3Zr metastable phase tend to grow excessively, and the Al3Zr metastable phase is likely to undergo a phase transition to an Al3Zr stable phase that does not contribute to heat resistance. In addition, there is a possibility that a large amount of Al-Zr-Si-based precipitates may be generated. In contrast, in this embodiment, by setting the second heat treatment time t2 to 60 hours or less, the precipitation nuclei of the Al3Zr metastable phase can be prevented from growing excessively, and the phase transition from the Al3Zr metastable phase to the Al3Zr stable phase can be suppressed. Furthermore, the formation of Al-Zr-Si based precipitates can be suppressed.

[0135] (S150: 2nd wire drawing process) The drawn Al alloy wire after the second aging step S144 is subjected to cold drawing to reduce the diameter of the drawn 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℃ to 200℃ Wire drawing speed: 20m / min or more and 800m / min or less Area reduction rate per die: 15% to 30% Dice angle: 10 degrees or more and 26 degrees or less

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

[0138] (S200: Center forming process) After obtaining the Al alloy wire 210, the central 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: Twisted wire part forming process) 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 stranding machine is used to strand 12 Al alloy wires 210 so as to cover the outer periphery of the central portion 100, thereby forming the first stranded wire layer 200a. Next, the stranding machine is used to strand 18 Al alloy wires 210 so as to cover the outer periphery of the first stranded wire layer 200a, thereby forming the second stranded wire layer 200b.

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

[0141] (6) Summary of this embodiment According to this embodiment, one or more of the following effects are achieved.

[0142] (a) In this embodiment, the content of each alloy element in the Al alloy wire 210 is optimized and a new aging step S140 is applied, thereby increasing the precipitation rate of the AlZr metastable phase, which contributes to heat resistance. This improves 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 way, 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, the precipitation ratio of the Al3Zr metastable phase coherent with pure Al is high. Thus, in this embodiment, the precipitation ratio of the Al3Zr metastable phase, which contributes to heat resistance, is increased, thereby improving the heat resistance of the Al alloy wire 210.

[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, fine precipitation nuclei of the Al3Zr metastable phase can be stably precipitated by setting the first temperature T1 to 250°C or higher while uniformly dispersing Si in the Al matrix. On the other hand, by setting the first temperature T1 to less than 300°C, the size of the precipitation nuclei of the Al3Zr metastable phase can be prevented from becoming excessively large, and the number of precipitation nuclei of the Al3Zr metastable phase can be prevented 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 conditions where the Si content is low and the first temperature T1 is within the above-mentioned range, it is possible to stably precipitate a large number of fine precipitation nuclei of the Al3Zr metastable phase in the Al matrix.

[0150] In the subsequent second aging step S144, the Al alloy wiredrawn after the first aging step S142 is heat-treated at a second temperature T2 higher than the first temperature T1. By precipitating many minute precipitation nuclei of the Al3Zr metastable phase in the first aging step S142, excessive growth of each precipitation nuclei of the Al3Zr metastable phase can be suppressed in the second aging step S144, thereby suppressing the phase transition from the Al3Zr metastable phase to the Al3Zr stable phase. That is, the precipitation nuclei can be grown while maintaining the Al3Zr metastable phase. As a result, the precipitation ratio of the Al3Zr metastable phase, which contributes to heat resistance, can be increased in the final Al alloy wire 210.

[0151] (7) Modification of this 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% by mass or more and 0.050% by mass or less. By setting the Sr content to 0.002% by 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% by 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-described 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 portion 200, and the number of layers in the stranded portion 200 may be changed. Alternatively, the electric wire 10 may have only the stranded portion 200 without having the central portion 100. [Example]

[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 produced 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 Al alloy wire after the second aging process was cold drawn to form an Al alloy wire having a diameter of 3.3 mm. During the drawing, the aluminum wire temperature 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 measurements were carried out on the Al alloy wires of each sample.

[0167] (Zr consistency) XAFS measurements were carried out at the Zr K-absorption edge in each Al alloy wire under the following conditions. For each sample measurement, a thin section with a thickness of 0.2 mm to 0.4 mm was prepared by mechanical polishing. Measurements were carried out using BL16 at the Kyushu Synchrotron Light Research Center in Saga Prefecture. Measurements were carried out using the transmission method, using X-rays monochromated by a Si(111) double crystal monochromator. Measurements using the fluorescence method are also possible.

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

[0169] The XAFS spectrum μ(E) was then extrapolated to the region above the absorption edge using two reference points between 17,847 eV and 17,952 eV. The background curve was then set as a reference point. The background was then removed from the XAFS spectrum μ(E). Next, μs(E), a component obtained by approximating the center of the vibrational component with a spline function, was calculated for the region up to 18,543 eV of the XAFS spectrum μ(E). The EXAFS vibration χ(k) was then obtained by dividing μ(E) - μs(E) by the absorbance difference μ0 between before and after the absorption edge. The "absorbance difference between before and after the absorption edge" here refers to the absorbance at 18,148 eV and 18,974 eV after the absorption edge, with the background absorbance set to zero.

[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 More than 90nm -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, XAFS measurements were performed at the K-absorption edge of Zr in a 0.02 mm thick rolled Zr material with a purity of 99.2% as a standard sample under the same conditions as those for the XAFS measurements of Zr in the Al alloy wire described above. From the XAFS spectrum of the standard sample obtained by the above 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 Al alloy wire described above. The height IZr0 of the peak occurring within the radius range of 0.22 nm to 0.30 nm in the radial structure function X(R) of Zr in the obtained standard sample was calculated.

[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 at a temperature of 20°C.

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

[0176] (2-4) Heat resistance (tensile strength) The tensile strength after heat treatment was measured under the following two time conditions. As mentioned 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 of 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 for the detection of minute scratches that are normally invisible to the naked eye, as minute scratches spread during compression. The higher 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 the evaluation of each sample are described below with reference to Table 2.

[0180] In the following description, the ranges of the contents of the alloying elements below are also referred to as "appropriate ranges." Zr content: 0.20 mass% or more and 0.35 mass% or less, Fe content: 0.05 mass% or more and 0.30 mass% or less, Si content: 0.01 mass% or more and 0.05 mass% or less, Ti content: 0.002 mass% or more and 0.020 mass% or less.

[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 in which the first temperature is 250°C or higher 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 carried out consecutively without any other steps.

[0182] [Table 2]

[0183] (3-1) Dependence on the first aging process The dependency 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 range, and the other manufacturing conditions were set to appropriate conditions, except that the conditions for the first aging step were changed.

[0184] (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%.

[0185] (Samples 2B to 4B) In 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%.

[0186] (Samples 5A-7A, 9A, 10A, 12A-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.

[0187] In Samples 5A to 7A, 9A, 10A, and 12A to 18A, the first aging step was performed at a first temperature of 250°C or higher and lower than 300°C for a first heat treatment time of 15 hours or longer, and then the second aging step was performed, thereby increasing the precipitation rate of the Al3Zr metastable phase, which contributes to heat resistance. As a result, it was confirmed that the heat resistance of the Al alloy wires of Samples 5A to 7A, 9A, 10A, and 12A to 18A was improved.

[0188] (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.

[0189] (Sample 8B) In Sample 8B, the Zr content was set to less than 0.20 mass %, which resulted in a tensile retention rate of less than 96% after 5 hours at 280°C and less than 94% after 10 hours at 280°C.

[0190] (Sample 11B) In Sample 11B, the Zr content was set to more than 0.35 mass %, and therefore the electrical conductivity of the Al alloy wire was less than 60% IACS. Furthermore, the compressibility K, which is an index for crack evaluation, was less than 71%.

[0191] (Samples 5A-7A, 9A, 10A, 12A-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 modulus K, which is an index for crack evaluation, was 71% or more.

[0192] In Samples 5A to 7A, 9A, 10A, and 12A to 18A, by setting the Zr content to 0.20 mass% or more, a sufficient absolute amount of AlZr metastable phase could be precipitated, and it was confirmed that the heat resistance of the Al alloy wires could be improved in Samples 5A to 7A, 9A, 10A, and 12A to 18A.

[0193] 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, the increase in the molten metal temperature was suppressed by setting the Zr content to 0.35 mass% or less. 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.

[0194] (3-3)Zr integrity dependence Figure 6 is a plot of the tensile survival rate after 10 hours at 280°C versus Zr coherence for several samples containing 0.32 mass% Zr. As shown in Figure 6, the higher the Zr coherence, i.e., the higher the precipitation rate of the AlZr metastable phase that is coherent with pure Al, the higher the tensile survival rate after 10 hours at 280°C. Figure 6 confirms that by increasing the Zr coherence rate to 1.2 or higher, the tensile survival rate after 10 hours at 280°C could be increased to 94% or higher.

[0195] <Additional Notes> The following additionally describes aspects of the present disclosure.

[0196] [7] The radial structure function of Zr is (a) measuring the X-ray absorption fine structure spectrum μ(E) at the K absorption edge of Zr; (b) obtaining the extended X-ray absorption fine structure oscillation χ(k) based on the X-ray absorption fine structure spectrum μ(E) using formula (A); χ(k)={μ(E)-μs(E)} / μ0 ···(A) where: k is the wave number, E is the energy, μs(E) is the 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) dividing the extended X-ray absorption fine structure oscillation χ(k) by k 2 a step of performing weighting processing by (d) k obtained by (c) 2 χ(k) is the 30 nm wavelength of wave number k. -1 More than 90nm -1 Fourier transforming a region within This can be achieved by implementing [2] or [3]. The aluminum alloy wire according to [2] or [3].

[0197] [8] a melting step of preparing a molten metal 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 unavoidable impurities; a continuous casting and rolling step of continuously casting and rolling the molten metal to form an aluminum alloy wire rod; a first wiredrawing step of cold drawing the aluminum alloy wire rod to form an aluminum alloy wire; an aging step in which the aluminum alloy wire is subjected to heat treatment; a second wiredrawing step of cold drawing the aluminum alloy wire after the aging step to form an aluminum alloy wire; and The aging step includes: a first aging step of subjecting the aluminum alloy wiredrawn to heat treatment 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; and In the first aging step, The heat treatment is performed under conditions in which the first temperature is 250°C or higher and lower than 300°C, and the first heat treatment time is 15 hours or longer; The first aging step and the second aging step are carried out consecutively without any other steps. A method for manufacturing aluminum alloy wire. [Explanation of symbols]

[0198] 10 Electric wire 100 center 100a 1st central layer 100b 2nd central layer 110 Core Wire 112 Wire section 114 Covering part 200 twisted wire section 200a 1st strand layer 200b 2nd strand layer 210 Al alloy wire

Claims

1. An aluminum alloy wire, Zr is 0.20 mass% or more and 0.35 mass% or less, Fe is 0.05 mass% or more and 0.30 mass% or less, Si is 0.01 mass% or more and 0.05 mass% or less, Ti is 0.002 mass% or more and 0.020 mass% or less, Contains the balance being Al and unavoidable impurities; 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. Aluminum alloy wire.

2. 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 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, obtained under the same conditions as those under which the radial structure function of Zr in the aluminum alloy wire was obtained. The aluminum alloy wire according to claim 1 .

3. An aluminum alloy wire, Zr is 0.20 mass% or more and 0.35 mass% or less, Fe is 0.05 mass% or more and 0.30 mass% or less, Si is 0.01 mass% or more and 0.05 mass% or less, Ti is 0.002 mass% or more and 0.020 mass% or less, Contains the balance being Al and unavoidable impurities; 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 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, obtained under the same conditions as those under which the radial structure function of Zr in the aluminum alloy wire was obtained. Aluminum alloy wire.

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

5. Further, the alloy contains 0.002 mass % or more and 0.050 mass % or less of Sr. The aluminum alloy wire according to any one of claims 1 to 3.

6. A stranded wire portion formed by stranding a plurality of aluminum alloy wires according to any one of claims 1 to 3. Electric wire.

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