Aluminum alloy wire and electric wire

Abstract

Provided is an aluminum alloy wire containing 0.020-0.200% of Fe, 0.005-0.070% of Si, 0.001-0.020% of Ti, and 0.002-0.100% of B by mass, with the balance made up of Al and inevitable impurities. In the aluminum alloy wire, the electrical conductivity is 62.5% IACS or more and the tensile strength after heat treatment at 140°C for 400 hours is 84% or more of the tensile strength before the heat treatment.

Description

Aluminum alloy wire and electric wire

[0001] This application claims priority to Japanese Patent Application No. 2024-104156, 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] International Publication No. 2019 / 189002

[0004] According to one aspect of the present disclosure, there is provided an aluminum alloy wire containing 0.020% by mass or more and 0.200% by mass or less of Fe, 0.005% by mass or more and 0.070% by mass or less of Si, 0.001% by mass or more and 0.020% by mass or less of Ti, 0.002% by mass or more and 0.100% by mass or less of B, with the balance being Al and inevitable impurities, wherein the aluminum alloy wire has an electrical conductivity of 62.5% IACS or more, and a tensile strength after heat treatment at 140°C for 400 hours is 84% ​​or more of the tensile strength before the heat treatment.

[0005] FIG. 1 is a diagram showing a radial structure function obtained by X-ray absorption fine structure measurement at the K-absorption edge of Fe in an aluminum alloy wire. FIG. 2 is an X-ray absorption fine structure spectrum at the K-absorption edge of Ti 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 Table 1 showing evaluation results of examples. FIG. 6 is Table 2 showing evaluation results of examples. FIG. 7 is a diagram showing the dependency of the tensile survival rate of an aluminum alloy wire after heat treatment on the precipitation index of Fe. FIG. 8 is a diagram showing the dependency of the electrical conductivity of an aluminum alloy wire on the precipitation index of Ti.

[0006] [Problem to be Solved by the Invention] An object of the present disclosure is to achieve both electrical conductivity and heat resistance.

[0007] Effect of the Invention According to the present disclosure, both electrical conductivity and heat resistance can be achieved.

[0008] [Explanation of Embodiments of the Present Disclosure] <Insights Obtained by the Inventors> First, insights obtained by the inventors will be described.

[0009] 2. Description of the Related Art As an aluminum (Al) alloy wire having a predetermined electrical conductivity and heat resistance, an Al alloy wire containing iron (Fe), silicon (Si) and titanium (Ti) has been developed.

[0010] As a result of the inventors' investigation into Al alloy wires containing the above-mentioned alloy elements, it was found that with previously known configurations, the following new problems arise based on the states of Fe and Ti in the Al alloy wires.

[0011] (Conventional aluminum alloy wire: JIS C3108:2016 "Hard aluminum wire for electrical use") In conventional aluminum alloy wires, iron is dissolved in the aluminum matrix. This improves the strength and heat resistance of the aluminum alloy wire. However, the dissolved iron reduces the electrical conductivity of the aluminum alloy wire.

[0012] Furthermore, in the case of conventional Al alloy wires, a Ti-boron (B) compound (e.g., TiB ２ By introducing a wire containing Ti—B into the molten metal, the solidification structure of Al is refined and the occurrence of defects during casting is suppressed. However, the above-mentioned TiB wire contains not only Ti—B compounds but also excess Ti. Therefore, the excess Ti incorporated into the Al alloy is dissolved in the Al matrix. As a result, the electrical conductivity of the Al alloy wire is reduced due to the dissolution of Ti.

[0013] (Al alloy wire of Patent Document 1) In order to improve the electrical conductivity compared to that of the above-mentioned conventional Al alloy wire, in Patent Document 1, not only Ti but also B is actively added to Al. Furthermore, in Patent Document 1, an intermediate heat treatment step is performed at a temperature of 300° C. or higher for 1 hour or more between the rolling step and the wiredrawing step.

[0014] In Patent Document 1, Fe is precipitated by the intermediate heat treatment process, thereby reducing the amount of Fe dissolved in the Al alloy wire, and as a result, improving the electrical conductivity of the Al alloy wire.

[0015] In Patent Document 1, the active addition of B causes the excess Ti in the TiB wire to react with B, resulting in the precipitation of Ti-B compound crystals. This reduces the amount of excess Ti in the Al alloy wire, thereby reducing the amount of Ti dissolved in the Al alloy wire. As a result, the decrease in the electrical conductivity of the Al alloy wire caused by the dissolved Ti is suppressed.

[0016] However, although the technique disclosed in Patent Document 1 was able to improve the electrical conductivity of the Al alloy wire, the amount of Fe dissolved in the Al alloy wire was reduced, resulting in a decrease in the heat resistance of the Al alloy wire.

[0017] As described above, it has been difficult for the conventional Al alloy wire and the Al alloy wire of Patent Document 1 to achieve both electrical conductivity and heat resistance.

[0018] Therefore, the inventors further studied the composition of the Al alloy wire and the manufacturing method of the Al alloy wire, and as a result, succeeded in obtaining an Al alloy wire that has both electrical conductivity and heat resistance.

[0019] The present disclosure below is based on the above-mentioned new problem discovered by the inventors.

[0020] <Embodiments of the Present Disclosure> Next, embodiments of the present disclosure will be listed and described.

[0021] [1] An aluminum alloy wire according to one embodiment of the present disclosure contains: 0.020% by mass or more and 0.200% by mass or less of Fe; 0.005% by mass or more and 0.070% by mass or less of Si; 0.001% by mass or more and 0.020% by mass or less of Ti; and 0.002% by mass or more and 0.100% by mass or less of B, with the balance being Al and inevitable impurities; the aluminum alloy wire has an electrical conductivity of 62.5% IACS or more; and the aluminum alloy wire has a tensile strength after heat treatment at 140°C for 400 hours that is 84% ​​or more of the tensile strength before the heat treatment. This configuration makes it possible to achieve both electrical conductivity and heat resistance.

[0022] [2] The aluminum alloy wire according to the above [1], wherein the aluminum alloy wire satisfies formula (1) and formula (2): IFe1 / IFe0≦0.70 (1) xTi1 / xTi2≧1.03 (2), where IFe1 is the height of a peak occurring within a radius range of 0.15 nm or more and 0.25 nm or less in a radial structure function obtained from X-ray absorption fine structure measurement at the K absorption edge of Fe in the aluminum alloy wire, and IFe0 is the height of a peak occurring within a radius range of 0.15 nm or more and 0.25 nm or less in a radial structure function of Fe in a rolled iron material having a purity of 99.99% and a thickness of 0.005 mm as a standard sample, which is obtained under the same conditions as those under which the radial structure function of Fe in the aluminum alloy wire was obtained, xTi1 and xTi2 are the heights of the first peak occurring within an incident X-ray energy range of 4978 eV to 4984 eV and the second peak occurring within an incident X-ray energy range of 4986 eV to 4994 eV, respectively, in an X-ray absorption fine structure spectrum normalized by the absorbance difference before and after the Ti K-absorption edge in the aluminum alloy wire. This configuration makes it possible to achieve both electrical conductivity and heat resistance.

[0023] [3] An aluminum alloy wire according to another aspect of the present disclosure contains: 0.020 mass % or more and 0.200 mass % or less of Fe; 0.005 mass % or more and 0.070 mass % or less of Si; 0.001 mass % or more and 0.020 mass % or less of Ti; and 0.002 mass % or more and 0.100 mass % or less of B, with the balance being Al and inevitable impurities, and the aluminum alloy wire satisfies formula (1) and formula (2): IFe1 / IFe0≦0.70 ... (1) xTi1 / xTi2≧1.03 ... (2) where IFe1 is the height of a peak occurring within a radius of 0.15 nm or more and 0.25 nm or less in a radial structure function obtained from X-ray absorption fine structure measurement at the K absorption edge of Fe in the aluminum alloy wire; IFe0 is the height of a peak occurring within a radius range of 0.15 nm or more and 0.25 nm or less in the radial structure function of Fe in a rolled iron material having a purity of 99.99% and a thickness of 0.005 mm as a standard sample, obtained under the same conditions as those for obtaining the radial structure function of Fe in the aluminum alloy wire, and xTi1 and xTi2 are the heights of a first peak occurring within an incident X-ray energy range of 4978 eV or more and 4984 eV or less and a second peak occurring within an incident X-ray energy range of 4986 eV or more and 4994 eV or less, respectively, in an X-ray absorption fine structure spectrum normalized by the absorbance difference before and after the Ti K-absorption edge in the aluminum alloy wire. This configuration makes it possible to achieve both electrical conductivity and heat resistance.

[0024] [4] In the aluminum alloy wire according to any one of [1] to [3] above, the ratio of the Ti content to the B content in the aluminum alloy wire is 2.5 or less. This configuration makes it possible to stably suppress a decrease in the electrical conductivity of the Al alloy wire. [5] An electric wire according to still another aspect of the present disclosure has a stranded wire portion formed by stranding together a plurality of the aluminum alloy wires according to any one of [1] to [4] above. This configuration makes it possible to achieve both electrical conductivity and heat resistance.

[0025] [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.

[0026] <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, Fe, Si, Ti, and B, with the balance being Al and inevitable impurities.

[0027] 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 %.

[0028] (Fe) As described above, in an Al alloy wire, Fe dissolved in the Al matrix and Fe precipitated in the Al matrix can exist in predetermined proportions.

[0029] In the case of a conventional Al alloy wire in which a relatively large proportion of Fe is dissolved in the Al matrix, the dissolved Fe can improve the strength (tensile strength) and heat resistance of the Al alloy wire. However, the dissolved Fe tends to reduce the electrical conductivity of the Al alloy wire.

[0030] On the other hand, in the case where Fe is precipitated (including crystallized) in the Al matrix, as in the Al alloy wire of Patent Document 1, the amount of Fe dissolved in the wire is reduced, thereby improving the electrical conductivity of the Al alloy wire. However, the heat resistance of the Al alloy wire tends to decrease due to the precipitation of Fe.

[0031] In contrast to this, in the present embodiment, the content of Fe in the Al alloy wire 210 is optimized, and a manufacturing method described later is applied to increase the solid solution ratio of Fe in the Al alloy wire 210. This makes it possible to improve the heat resistance of the Al alloy wire 210 while suppressing a decrease in the electrical conductivity of the Al alloy wire 210.

[0032] Specifically, the Fe content in the Al alloy wire 210 of this embodiment is, for example, 0.020 mass % or more and 0.200 mass % or less.

[0033] If the Fe content is less than 0.020 mass%, the solid solution ratio of Fe in the Al alloy wire 210 is high, but the absolute amount of Fe dissolved in the Al matrix is ​​small. This may result in a decrease in the heat resistance of the Al alloy wire 210. In contrast, in this embodiment, by setting the Fe content to 0.020 mass% or more, it is possible to increase the solid solution ratio of Fe in the Al alloy wire 210 and dissolve Fe in a sufficient absolute amount in the Al matrix. This allows the heat resistance of the Al alloy wire 210 to be improved.

[0034] On the other hand, if the Fe content exceeds 0.200 mass%, the conductivity of the Al alloy wire 210 decreases due to excessive solid solution of Fe. In contrast, in the present embodiment, the Fe content is set to 0.200 mass% or less, thereby suppressing excessive solid solution of Fe. As a result, the decrease in the conductivity of the Al alloy wire 210 can be suppressed.

[0035] In the Al alloy wire 210 of this embodiment, the state in which the proportion of Fe in solid solution is high can be confirmed by X-ray absorption fine structure measurement, which will be described in detail later.

[0036] (Si) In this embodiment, Si is mainly dissolved in the Al matrix. This allows the Al alloy wire 210 to be solid-solution strengthened by Si. This allows the strength (tensile strength) of the Al alloy wire 210 to be improved. However, the solid solution of Si does not significantly improve the heat resistance.

[0037] The Si content in the Al alloy wire 210 of this embodiment is, for example, 0.005 mass % or more and 0.070 mass % or less.

[0038] If the Si content is less than 0.005 mass%, Si is included as an inevitable impurity in the aluminum alloy, so the purity of the aluminum alloy needs to be increased. This increases the refining cost. In contrast, in this embodiment, by setting the Si content to 0.005 mass% or more, it is not necessary to excessively increase the purity of the aluminum alloy, and the increase in refining cost can be suppressed. Furthermore, by setting the Si content to 0.005 mass% or more, Si can be sufficiently dissolved in the aluminum matrix. This allows the strength (tensile strength) of the aluminum alloy wire 210 to be stably improved.

[0039] On the other hand, if the Si content exceeds 0.070 mass%, the conductivity of the Al alloy wire 210 decreases due to excessive solid solution of Si. In contrast, in the present embodiment, the Si content is set to 0.070 mass% or less, thereby suppressing excessive solid solution of Si. As a result, the decrease in the conductivity of the Al alloy wire 210 can be suppressed.

[0040] (Ti) When Ti dissolves in the Al matrix as in the conventional Al alloy wire described above, the electrical conductivity of the Al alloy is significantly reduced.

[0041] In contrast to this, in the present embodiment, as will be described later, B is actively added to the Al alloy wire 210, and the molten metal holding step S120 is performed for a long time, so that Ti is precipitated as a Ti—B compound in the Al alloy. ２ ) crystals are precipitated in a finely dispersed state in the Al alloy.

[0042] The precipitation of Ti—B compounds can reduce the amount of Ti in solid solution, thereby suppressing a decrease in the electrical conductivity of the Al alloy wire 210.

[0043] By finely dispersing the Ti—B compound crystals in the Al alloy, Al solidifies with the dispersed Ti—B compound crystals as nuclei. This allows the Al crystal grains to be refined. As a result, the workability of the Al alloy wire 210 can be improved.

[0044] The Ti content in the Al alloy wire 210 of this embodiment is, for example, 0.001 mass % or more and 0.020 mass % or less.

[0045] If the Ti content is less than 0.001 mass%, the crystals of the Ti-B compound are not sufficiently precipitated, and it is difficult to refine the Al crystal grains. Therefore, there is a possibility that the workability of the Al alloy wire 210 is reduced. In contrast, in the present embodiment, by setting the Ti content to 0.001 mass% or more, the crystals of the Ti-B compound are sufficiently precipitated, and the Al crystal grains can be refined. As a result, the workability of the Al alloy wire 210 can be improved.

[0046] On the other hand, if the Ti content exceeds 0.020 mass%, there is a possibility that Ti will be excessively dissolved in the Al matrix depending on the B content. This may result in a decrease in the electrical conductivity of the Al alloy wire 210. In contrast, in the present embodiment, by setting the Ti content to 0.020 mass% or less, it is possible to suppress saturation of precipitation of Ti-B compounds and to suppress excessive dissolution of Ti. This makes it possible to suppress a decrease in the electrical conductivity of the Al alloy wire 210.

[0047] In the Al alloy wire 210 of this embodiment, the precipitation state of the Ti—B compound can be confirmed by X-ray absorption fine structure measurement, which will be described in detail later.

[0048] (B) In this embodiment, as described above, B is intentionally added to the Al alloy wire 210 .

[0049] Specifically, the B content in the Al alloy wire 210 of this embodiment is, for example, 0.002 mass % or more and 0.100 mass % or less.

[0050] If the B content is less than 0.002 mass%, Ti cannot be sufficiently precipitated as a B compound in the Al matrix. Therefore, it is difficult to reduce the amount of Ti dissolved in the matrix. As a result, the conductivity of the Al alloy wire 210 may decrease. In contrast, in this embodiment, by setting the B content to 0.002 mass% or more, Ti can be precipitated as a B compound in the Al matrix. This reduces the amount of Ti dissolved in the matrix. As a result, the decrease in the conductivity of the Al alloy wire 210 can be suppressed.

[0051] On the other hand, even if the content of B increases, B is less likely to reduce the electrical conductivity than Ti and Fe. However, adding excessive B has a negative effect on the electrical conductivity. Therefore, in this embodiment, by setting the content of B to 0.100 mass% or less, the high electrical conductivity of the Al alloy wire 210 can be stably maintained.

[0052] Furthermore, in this embodiment, the ratio of the Ti content to the B content in the Al alloy wire 210 (hereinafter also referred to as "Ti / B") may be, for example, 2.5 or less.

[0053] If Ti / B>2.5, that is, if there is an excess of Ti relative to B, the crystals of Ti-B compounds do not precipitate sufficiently, and the amount of Ti in solid solution increases, which may result in a decrease in the electrical conductivity of the Al alloy wire 210.

[0054] On the other hand, in the present embodiment, by setting Ti / B≦2.5, the crystals of Ti—B compound are sufficiently precipitated, and the amount of Ti in solid solution can be stably reduced, and as a result, the decrease in the electrical conductivity of the Al alloy wire 210 can be stably suppressed.

[0055] The lower limit of Ti / B is not particularly limited, but based on the above-mentioned lower limit of the Ti content and the upper limit of the B content, Ti / B may be 0.01 or more.

[0056] (Inevitable Impurities) In this embodiment, zirconium (Zr) is not intentionally added to the Al alloy wire 210. Specifically, the content of Zr, which is one of the inevitable impurities in the Al alloy wire of this embodiment, is, for example, less than 0.010 mass%. In this way, by making the Al alloy wire 210 free of Zr or by reducing the Zr content in the Al alloy wire 210, the electrical conductivity can be easily improved. In addition, there is no need to set the molten metal temperature excessively high. This shortens the time required to heat the molten metal. In addition, it is possible to reduce thermal stress during solidification and reduce the risk of scratches. Furthermore, it is possible to suppress damage to the melting furnace and extend the life of the melting furnace.

[0057] In this embodiment, strontium (Sr) is not intentionally added to the Al alloy wire 210. Specifically, the content of Sr, which is one of the inevitable impurities in the Al alloy wire, is, for example, less than 0.005 mass%. In this way, by making the Al alloy wire 210 free of Sr or reducing the Sr content in the Al alloy wire 210, promotion of Fe precipitation caused by Sr can be suppressed.

[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) State of Fe and Ti in Al Alloy Wire Next, the state of Fe and Ti in the Al alloy wire 210 will be described with reference to FIGS. 1 and 2. FIG.

[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 state of solid solution or precipitation of each element in the Al alloy wire 210 by performing XAFS measurement of each element contained in the Al alloy wire 210 of this embodiment.

[0062] As a result, in this embodiment, the inventors have found that by increasing the solid solution ratio of Fe and precipitating Ti-B compounds using the manufacturing method described below, the Al alloy wire 210 satisfies the requirements described below regarding the XAFS measurement results of Fe and Ti.

[0063] (Fe Precipitation Index) Figure 1 shows the radial structure functions obtained by X-ray absorption fine structure measurements at the Fe K-edge in the Al alloy wires of the present embodiment and the comparative example. In Figure 1, 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 Fe is obtained by carrying out the following steps (a) to (d). (a) The X-ray absorption fine structure spectrum μ(E) at the K absorption edge of Fe is measured. (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) The extended X-ray absorption fine structure vibration χ(k) is calculated by the formula (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 More than 80 nm －１ The region within the following range is Fourier transformed:

[0065] 1 is the height of a peak occurring within a radius range of 0.15 nm or more and 0.25 nm or less in the radial structure function X(R) obtained from XAFS measurement of the K absorption edge of Fe in the Al alloy wire 210. "IFe0" is the height of a peak occurring within a radius range of 0.15 nm or more and 0.25 nm or less in the radial structure function of Fe in a rolled iron material (body-centered cubic lattice (bcc) structure) having a purity of 99.99% and a thickness of 0.005 mm as a standard sample, obtained under the same conditions as those under which the radial structure function of Fe in the Al alloy wire 210 was obtained. The radial position of the IFe1 peak and the radial position of the IFe0 peak may be slightly different within a radius range of 0.15 nm or more and 0.25 nm or less.

[0066] The vertical axis in Fig. 1 shows the value of the radial structure function X(R) normalized by IFe0. For this reason, in Fig. 1, peaks occurring within a radius range of 0.15 nm to 0.25 nm are denoted as "IFe1 / IFe0".

[0067] The ratio “IFe1 / IFe0” is hereinafter also referred to as “Fe precipitation index.” The Fe precipitation index IFe1 / IFe0 is an index that reflects the precipitation ratio of Fe in the Al alloy wire.

[0068] The radial structure function of the comparative example shown in Fig. 1 is, for example, the radial structure function of Fe in the Al alloy wire of Sample 40B in the example described later. In the comparative example, the Fe precipitation index IFe1 / IFe0 is greater than 0.70. This is because the Fe precipitation ratio of the Fe in the Al alloy wire is high in the comparative example. In the comparative example showing such a tendency, the solid solution ratio of Fe is low, and therefore the heat resistance of the Al alloy wire is reduced.

[0069] In contrast, the radial structure function of this embodiment shown in Fig. 1 is, for example, the radial structure function of Fe in the Al alloy wire of Sample 5A in the example described later. In this embodiment, the Fe precipitation index IFe1 / IFe0 is lower than that of the comparative example.

[0070] Specifically, the Al alloy wire 210 of the present embodiment satisfies, for example, the following formula (1): IFe1 / IFe0≦0.70 (1)

[0071] In the present embodiment, the Al alloy wire 210 satisfies the formula (1) regarding the Fe precipitation index, so that the proportion of Fe in the Al alloy wire 210 that is in solid solution is increased. This allows the heat resistance of the Al alloy wire 210 to be improved.

[0072] The lower limit of the Fe precipitation index IFe1 / IFe0 is not particularly limited, but may be IFe1 / IFe0≧0.45.

[0073] (Ti Precipitation Index) Figure 2 shows the XAFS spectrum of the Ti K absorption edge in each of the Al alloy wires of this embodiment and the comparative example, normalized by the absorbance difference before and after the absorption edge. In Figure 2, the horizontal axis represents the energy (unit: eV) of the incident X-rays, and the vertical axis represents the absorbance (arbitrary unit) normalized by the absorbance difference before and after the absorption edge.

[0074] "xTi1" and "xTi2" shown in FIG. 2 are the heights of the first peak occurring within the incident X-ray energy range of 4978 eV or more and 4984 eV or less, and the heights of the second peak occurring within the incident X-ray energy range of 4986 eV or more and 4994 eV or less, respectively, in the XAFS spectrum at the Ti K absorption edge in each Al alloy wire.

[0075] The ratio “xTi1 / xTi2” is hereinafter also referred to as “Ti precipitation index.” The Ti precipitation index xTi1 / xTi2 is an index that reflects the precipitation ratio of Ti—B compounds in the Al alloy wire.

[0076] The XAFS spectrum of the comparative example shown in Figure 2 is, for example, the XAFS spectrum of Ti in the Al alloy wire of Sample 26B in the example described later. In the comparative example, the height xTi1 of the first peak and the height xTi2 of the second peak are close to each other, and the Ti precipitation index xTi1 / xTi2 is less than 1.03. This is because much of the Ti in the Al alloy wire is in solid solution in the comparative example. In the comparative example showing this tendency, the conductivity of the Al alloy wire decreases due to the solid solution of Ti.

[0077] In contrast, the XAFS spectrum of this embodiment shown in Figure 2 is, for example, the XAFS spectrum of Ti in the Al alloy wire of Sample 5A in the Examples described later. In this embodiment, the height xTi1 of the first peak is higher than the height xTi2 of the second peak.

[0078] Specifically, the Al alloy wire 210 of the present embodiment satisfies, for example, the following formula (2): xTi1 / xTi2≧1.03 (2)

[0079] In this embodiment, the Al alloy wire 210 satisfies the formula (2) regarding the Ti precipitation index, so that Ti—B compound crystals are sufficiently precipitated in the Al alloy wire 210. This can reduce the amount of Ti dissolved in the wire. As a result, the decrease in the electrical conductivity of the Al alloy wire 210 can be suppressed.

[0080] The upper limit of the Ti precipitation index xTi1 / xTi2 is not particularly limited, but may be xTi1 / xTi2≦1.12.

[0081] (3) Characteristics of Al Alloy Wire The Al alloy wire 210 of this embodiment has the following characteristics.

[0082] (Electrical Conductivity) The electrical conductivity of the Al alloy wire 210 of this embodiment at 20° C. is, for example, 62.5% IACS or more.

[0083] The unit of conductivity "% IACS" used here is the ratio of conductivity when the conductivity of International Annealed Copper Standard is taken as 100%.

[0084] The upper limit of the electrical conductivity of the Al alloy wire 210 of the present embodiment is not limited. However, since the solid solution ratio of Fe in the Al alloy wire 210 is high, the electrical conductivity of the Al alloy wire 210 of the present embodiment at 20° C. may be, for example, 64% IACS or less (the electrical conductivity of 99.99% Al or less).

[0085] (Tensile Strength) The Al alloy wire 210 of this embodiment exhibits high tensile strength due to solid solution strengthening of Fe and Si.

[0086] 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 electrical hard aluminum wire having a diameter equal to the diameter of the Al alloy wire 210 of this embodiment, as specified in, for example, JIS C3108:2016.

[0087] 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.

[0088] The upper limit of the tensile strength of the Al alloy wire 210 of this embodiment is not limited. However, the tensile strength of the Al alloy wire 210 of this embodiment at 20°C may be, for example, 250 MPa or less. This can prevent elements that increase strength (such as dislocations) from becoming electron scattering sites. As a result, a decrease in electrical conductivity can be suppressed.

[0089] (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.

[0090] 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.

[0091] The tensile strength of the Al alloy wire 210 of this embodiment after heat treatment at 120° C. for 400 hours is, for example, 90% or more of the tensile strength before the heat treatment.

[0092] Here, even the Al alloy wire of Patent Document 1 may obtain the above-mentioned tensile strength after heat treatment at 120° C. for 400 hours. However, since Fe is precipitated in the Al alloy wire of Patent Document 1, the heat resistance is lower than that of the Al alloy wire 210 of the present embodiment. Therefore, the Al alloy wire of Patent Document 1 has a lower tensile strength after heat treatment at a temperature (e.g., 140° C.) higher than the above-mentioned specified temperature.

[0093] In contrast, the Al alloy wire 210 of this embodiment has a high solid solution ratio of Fe as described above, so that in this embodiment, a high tensile strength can be obtained even after heat treatment at 140°C.

[0094] Specifically, the tensile strength of the Al alloy wire 210 of this embodiment after heat treatment at 140° C. for 400 hours is, for example, 84% or more of the tensile strength before the heat treatment.

[0095] As described above, the Al alloy wire 210 of the present embodiment can obtain high heat resistance that cannot be obtained by the Al alloy wire of Patent Document 1. That is, 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.

[0096] 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 120°C for 400 hours and the tensile strength after the heat treatment at 140°C for 400 hours may be close to 100%, for example.

[0097] (4) Electric Wire Next, the electric wire 10 of this embodiment will be described with reference to FIG.

[0098] The electric wire 10 of this embodiment has, for example, a central portion (steel core portion) 100 and a stranded wire portion 200 .

[0099] 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.

[0100] 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.

[0101] Each core wire 110 has 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.

[0102] 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.

[0103] 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 2.3 mm or more and 5.0 mm or less.

[0104] 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.

[0105] (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.

[0106] 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.

[0107] (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 S110, a molten metal holding step S120, a casting step S130, a rolling step S140, and a wire drawing step S150.

[0108] (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.

[0109] Specifically, a molten metal is prepared containing, for example, 0.020% by mass to 0.200% by mass of Fe, 0.005% by mass to 0.070% by mass of Si, 0.001% by mass to 0.020% by mass of Ti, and 0.002% by mass to 0.100% by mass of B, with the balance being Al and inevitable impurities. The temperature of the molten metal is set to be equal to the temperature of the molten metal holding step S120 described below.

[0110] At this time, the entire amount of added Fe is dissolved in the molten metal.

[0111] Furthermore, at this time, B is actively added to the molten metal. Specifically, not only the TiB wire described above but also B in the bulk metal is added to the molten metal. Alternatively, a commercially available Al-B master alloy may be added to the molten metal instead of B in the bulk metal. This allows the B content in the molten metal to be higher than when only TiB wire is introduced. As a result, for example, Ti / B≦2.5 can be stably achieved.

[0112] (S120: Molten Metal Holding Step) After the molten metal is prepared, the molten metal is held at a temperature of 700° C. or higher for 7 hours or more in a preparation furnace while being stirred.

[0113] At this time, by setting the molten metal temperature to 700°C or higher, Ti can be reacted with B to precipitate crystals of a Ti-B compound. Note that by setting the molten metal temperature to 700°C or higher, the entire amount of Fe can be maintained in a dissolved state in the molten metal.

[0114] On the other hand, the upper limit of the molten metal temperature is not limited. However, the higher the temperature of the molten metal, the more energy is consumed to heat the molten metal, and the shorter the life of the furnace insulation material. Therefore, the molten metal temperature may be set to, for example, 800°C or less.

[0115] At this time, by setting the molten metal holding time to 7 hours or more, crystals of the Ti—B compound can be stably precipitated.

[0116] On the other hand, the molten metal holding time may be, for example, 20 hours or less, which can save energy and extend the life of the furnace insulation.

[0117] (S130: Casting Step) After the molten metal holding step S120, the molten metal is solidified and continuously cast. In this embodiment, Fe is supersaturated in the Al alloy during solidification. 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. A cast material is formed through these steps.

[0118] (S140: Rolling Step) After the casting step S130, the cast material is rolled (hot rolling) to form a rolled material (wire rod).

[0119] (S150: Wire Drawing Step) After the rolling step S140, the rolled material is subjected to wire drawing (cold wire drawing), whereby the diameter of the rolled material is reduced to the desired diameter of the Al alloy wire 210.

[0120] In this embodiment, an intermediate heat treatment step of heating the rolled material at a temperature of 300°C or higher is not performed after the rolling step S140 and before the wiredrawing step S150. That is, the rolled material is maintained at a temperature of less than 300°C after the rolling step S140 and before the wiredrawing step S150. This makes it possible to maintain the supersaturated solid solution state of Fe until the Al alloy wire 210 is obtained, that is, to suppress the precipitation of Fe. Meanwhile, the crystals of Ti—B compounds in the Al alloy wire 210 are maintained in a precipitated state.

[0121] In this manner, the Al alloy wire 210 of this embodiment is obtained.

[0122] (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.

[0123] (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.

[0124] In this manner, the electric wire 10 of the present embodiment is manufactured.

[0125] (6) Summary of the Present Embodiment According to the present embodiment, one or more of the following effects can be achieved.

[0126] (a) In the present embodiment, the content of Fe in the Al alloy wire 210 is optimized and the above-described manufacturing method is applied, thereby making it possible to increase the solid solution ratio of Fe in the Al alloy wire 210. This makes it possible to improve the heat resistance of the Al alloy wire 210 while suppressing a decrease in the electrical conductivity of the Al alloy wire 210.

[0127] Furthermore, in this embodiment, B is actively added to the Al alloy wire 210, and the molten metal holding step S120 is performed for a long time, whereby Ti is contained in the Al alloy as a Ti—B compound (for example, TiB ２ ) can be precipitated. This can reduce the amount of Ti dissolved in the Al alloy, which significantly reduces the electrical conductivity of the Al alloy. In other words, Ti can be rendered harmless. As a result, the decrease in the electrical conductivity of the Al alloy wire 210 can be suppressed.

[0128] Specifically, the electrical conductivity of the Al alloy wire 210 of this embodiment can be 62.5% IACS or more. Furthermore, the tensile strength of the Al alloy wire 210 of this embodiment after heat treatment at 140°C for 400 hours can be 84% or more of the tensile strength before the heat treatment.

[0129] In this manner, in this embodiment, it is possible to obtain the Al alloy wire 210 that has both electrical conductivity and heat resistance.

[0130] (b) The Al alloy wire 210 of this embodiment satisfies the above-mentioned formula (1): IFe1 / IFe0≦0.70 with respect to the Fe precipitation index in the radial structure function of Fe in the Al alloy wire 210. When the Al alloy wire 210 satisfies formula (1), the proportion of Fe in the Al alloy wire 210 that is in solid solution is increased. This allows the heat resistance of the Al alloy wire 210 to be improved.

[0131] The Al alloy wire 210 of this embodiment satisfies the formula (2): xTi1 / xTi2≧1.03 with respect to the Ti precipitation index in the XAFS spectrum of Ti in the Al alloy wire 210. When the Al alloy wire 210 satisfies the formula (2), Ti—B compound crystals are sufficiently precipitated in the Al alloy wire 210. This allows the amount of Ti in solid solution to be reduced. As a result, the decrease in the electrical conductivity of the Al alloy wire 210 can be suppressed.

[0132] (c) In this embodiment, in the molten metal holding step S120, the molten metal satisfying the composition of the Al alloy wire 210 is held at a temperature of 700°C or higher for 7 hours or more. This allows the actively added B to be uniformly dispersed in the molten metal, and the B to react sufficiently with Ti. This allows fine Ti-B compound crystals to be precipitated throughout the molten metal. By precipitating the Ti-B compound crystals in this manner, the amount of Ti in solid solution can be reduced. As a result, the decrease in the electrical conductivity of the Al alloy wire 210 can be suppressed.

[0133] (d) In this embodiment, the intermediate heat treatment step of heating the rolled material at a temperature of 300° C. or higher is not performed after the rolling step S140 and before the wire drawing step S150.

[0134] In Patent Document 1, an intermediate heat treatment process is performed after the rolling process and before the wire drawing process, in which the rolled material is heated at a temperature of 300°C or higher for 1 hour or more. Therefore, in the rolled material after the rolling process, Fe transitions from a supersaturated solid solution state to an equilibrium state, and the Fe precipitates. As a result, the heat resistance of the Al alloy wire is reduced due to the precipitation of Fe.

[0135] In contrast, in the present embodiment, the above-mentioned intermediate heat treatment step is not performed, so that the supersaturated solid solution state of Fe can be maintained until the Al alloy wire 210 is obtained. That is, the transition of Fe to an equilibrium state can be suppressed, and the precipitation of Fe can be suppressed. As a result, the heat resistance of the finally obtained Al alloy wire 210 can be improved.

[0136] <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.

[0137] 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.

[0138] 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.

[0139] (1) Preparation of Aluminum Alloy Wire Al alloy wires of samples 1B to 41B were prepared under the following conditions.

[0140] (Samples 1B to 10B) First, after melting an Al ingot, a molten metal having the composition of an Al alloy wire shown in Table 1 below was prepared in an adjustment furnace. At this time, not only the TiB wire but also a commercially available Al-4% B master alloy was added to the molten metal to adjust the B content. Note that Zr and Sr were not added.

[0141] After the molten metal preparation step, the molten metal was held at a temperature of 700° C. for 10 hours in a preparation furnace while being stirred.

[0142] After the molten metal holding step, the molten metal was continuously cast to form a cast material. Next, the cast material was rolled to form a rolled material. Thereafter, the rolled material was wiredrawn to a diameter of 3.2 mm.

[0143] In Samples 1B to 10B, the intermediate heat treatment step of heating the rolled material was not performed after the rolling step and before the wiredrawing step. The rolled material was maintained at a temperature of less than 300°C after the rolling step and before the wiredrawing step.

[0144] Through the above steps, Al alloy wires of samples 1B to 10B were obtained.

[0145] (Samples 11A to 18B) The Al alloy wires of Samples 11A to 18B were produced in the same manner as Sample 5A, except that the Si content was different from that of Sample 5A within the range shown in Table 1.

[0146] (Samples 19B to 24B) The Al alloy wires of Samples 19B to 24B were produced in the same manner as Sample 5A, except that the Ti content was different from that of Sample 5A within the range shown in Table 2.

[0147] (Samples 25B to 32A) The Al alloy wires of Samples 25B to 32A were produced in the same manner as Sample 5A, except that the B content was different from that of Sample 5A within the range shown in Table 1.

[0148] (Samples 33B to 36A) The Al alloy wires of Samples 33B to 36A were produced in the same manner as Sample 5A, except that the molten metal holding time was set within the range shown in Table 1 and was different from that of Sample 5A.

[0149] (Samples 37B to 41B) The Al alloy wires of Samples 37B to 41B were produced in the same manner as Sample 5A, except that intermediate heat treatment was carried out under the conditions shown in Table 2.

[0150] (2) Evaluation Samples 1B to 41B were evaluated as follows.

[0151] (2-1) XAFS Measurement XAFS measurement was carried out on the Al alloy wire of each sample.

[0152] (Fe Precipitation Index) XAFS measurement of the K absorption edge of Fe in each Al alloy wire was carried out under the following conditions. The measurement was carried out using BL16 at the Kyushu Synchrotron Light Research Center in Saga Prefecture. The measurement was carried out by a fluorescence method using X-rays monochromated by a Si (111) double crystal monochromator.

[0153] The XAFS spectrum at the K absorption edge of Fe obtained by the above measurement was analyzed using free software Athena. Note that REX2000 manufactured by Rigaku Corporation can also be used.

[0154] In the obtained XAFS spectrum μ(E), two points in the range of 6979 eV to 7079 eV from the region before the absorption edge were used as references. 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 of 7453 eV after the absorption edge 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" refers to the absorbance at 7250 eV and 7400 eV after the absorption edge when the background absorbance is set to 0.

[0155] 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 30 nm wave number k. －１ More than 80 nm －１ The radial structure function X(R) was obtained by Fourier transforming the region within the following range:

[0156] In the radial structure function X(R) of Fe in the Al alloy wire obtained as described above, the height IFe1 of the peak occurring within a radius range of 0.15 nm or more and 0.25 nm or less was determined.

[0157] Furthermore, XAFS measurements of the K-absorption edge of Fe in a rolled iron material with a purity of 99.99% and a thickness of 0.005 mm were performed as a standard sample under the same conditions as those for the XAFS measurements of Fe in the Al alloy wire. From the XAFS spectrum of the standard sample obtained by the above measurement, the radial structure function of Fe in the standard sample was obtained under the same conditions as those for the radial structure function of Fe in the Al alloy wire. The height IFe0 of the peak occurring within a radius range of 0.15 nm to 0.25 nm in the radial structure function X(R) of Fe in the obtained standard sample was calculated.

[0158] Based on the IFe1 and IFe0 determined as above, the ratio IFe1 / IFe0 (arbitrary unit) was determined as the Fe precipitation index.

[0159] (Ti Precipitation Index) XAFS measurement of the Ti K-absorption edge in each Al alloy wire was performed under the following conditions. Prior to the measurement, the surface of the Al alloy wire was mechanically polished to a depth of 10 μm or more to remove the influence of surface oxidation, thereby preparing a measurement sample. For the measurement, the Saga Prefectural Kyushu Synchrotron Light Research Center BL16 was used. Measurement was performed by a fluorescence method using X-rays monochromated by a Si (111) double crystal spectrometer. The horizontal axis, which represents the energy of the incident X-rays during measurement, was calibrated so that the pre-edge peak of the titanium (Ti) metal foil was 4964.0 eV.

[0160] The XAFS spectrum of the Ti K-absorption edge obtained by the above-mentioned measurement was analyzed using the free software Athena. In the obtained XAFS spectrum, two points in the range of 4870 eV to 4950 eV from the region before the absorption edge were used as reference points, and 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. Furthermore, normalization was performed so that the absorbance at 5030 eV and 5100 eV after the absorption edge became 1 when the background absorbance was set to 0.

[0161] In the normalized XAFS spectrum of the Ti K-absorption edge obtained as described above, the height xTi1 of the first peak occurring within the incident X-ray energy range of 4978 eV to 4984 eV and the height xTi2 of the second peak occurring within the incident X-ray energy range of 4986 eV to 4994 eV were determined. Furthermore, the ratio xTi1 / xTi2 (arbitrary unit) was calculated as the Ti precipitation index.

[0162] (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.

[0163] (2-3) Electrical Conductivity The electrical conductivity of each Al alloy wire was measured in accordance with JIS C3002: 1992. The temperature during measurement was 20°C.

[0164] (2-4) Heat Resistance (Tensile Resistance) The tensile strength after heat treatment under the following two temperature conditions was measured. 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.

[0165] As the "tensile strength remaining rate after 400 hours at 120°C" in Tables 1 and 2, the ratio (%) of the tensile strength after the Al alloy wire was subjected to heat treatment at 120°C for 400 hours to the tensile strength before the heat treatment was calculated.

[0166] Furthermore, as the "tensile strength remaining rate after 400 hours at 140°C" in Tables 1 and 2, the ratio (%) of the tensile strength after the Al alloy wire was subjected to heat treatment at 140°C for 400 hours to the tensile strength before the heat treatment was calculated.

[0167] (3) Results The results of evaluation of each sample will be described with reference to Table 1 in FIG. 5 and Table 2 in FIG.

[0168] In the following description, the following ranges for the content of each alloying element are also referred to as "appropriate ranges": Fe content: 0.020% by mass to 0.200% by mass, Si content: 0.005% by mass to 0.070% by mass, Ti content: 0.001% by mass to 0.020% by mass, B content: 0.002% by mass to 0.100% by mass.

[0169] In the following description, the following manufacturing conditions are also referred to as "appropriate conditions." In the molten metal holding step, the molten metal is held at a temperature of 700°C or higher for 7 hours or longer. Between the rolled material forming step and the wire drawing step, no intermediate heat treatment step is performed in which the rolled material is heated to a temperature of 300°C or higher.

[0170] (3-1) Dependence on Fe Content The dependency on Fe content will be explained with reference to the results of Samples 1B to 10B. As described above, in Samples 1B to 10B, except for the fact that the Fe content was different, the contents of the other alloying elements were within appropriate ranges, and the manufacturing conditions were appropriate.

[0171] (Sample 1B) In Sample 1B, the Fe content was set to less than 0.020 mass %, and therefore the tensile survival rate after 400 hours at 120°C was less than 90%, and the tensile survival rate after 400 hours at 140°C was less than 84%.

[0172] (Sample 10B) In Sample 10B, the Fe content was set to more than 0.200 mass %, so the electrical conductivity of the Al alloy wire was less than 62.5% IACS.

[0173] (Samples 2A to 9A) In contrast, in Samples 2A to 9A, the Fe content was set to 0.020 mass% or more and 0.200 mass% or less. As a result, the tensile survival rate after 400 hours at 120°C was 90% or more, and the tensile survival rate after 400 hours at 140°C was 84% ​​or more. Furthermore, the electrical conductivity of the Al alloy wire was 62.5% IACS or more.

[0174] In Samples 2A to 9A, by setting the Fe content to 0.020 mass % or more, it was possible to dissolve Fe in the Al matrix in a sufficient absolute amount, and it was confirmed that the heat resistance of the Al alloy wires in Samples 2A to 9A could be improved.

[0175] In Samples 2A to 9A, the Fe content was set to 0.200 mass% or less, which allowed for suppressing excessive Fe solid solution. As a result, it was confirmed that Samples 2A to 9A allowed for suppressing the decrease in the electrical conductivity of the Al alloy wire.

[0176] (3-2) Si Content Dependence The Si content dependency will be explained with reference to the results of Samples 11A to 18B. As described above, Samples 11A to 18B were manufactured under appropriate conditions, with the exception of the Si content, which was varied, and the contents of the other alloying elements were within the appropriate ranges.

[0177] (Sample 18B) In Sample 18B, the Si content was set to more than 0.070 mass %, so the electrical conductivity of the Al alloy wire was less than 62.5% IACS.

[0178] (Samples 11A to 17A) In contrast, in Samples 11A to 17A, the Si content was set to 0.005 mass % or more and 0.070 mass % or less, and as a result, the electrical conductivity of the Al alloy wire was 62.5% IACS or more.

[0179] In Samples 11A to 17A, the Si content was set to 0.070 mass% or less, which allowed for the suppression of excessive solid solution of Si. As a result, it was confirmed that the decrease in the electrical conductivity of the Al alloy wires was suppressed in Samples 11A to 17A.

[0180] (3-3) Ti Content Dependence The Ti content dependency will be explained with reference to the results of Samples 19B to 24B. As described above, in Samples 19B to 24B, except for the Ti content being different, the contents of the other alloying elements were within the appropriate ranges, and the manufacturing conditions were appropriate.

[0181] (Sample 19B) In Sample 19B, the Ti content was set to less than 0.001 mass %, so that the Al alloy wire could not be processed in Sample 19B.

[0182] (Sample 24B) In Sample 24B, the Ti content was set to more than 0.020 mass%. In addition, in Sample 24B, the Ti / B ratio was more than 2.5. Therefore, the Ti precipitation index was less than 1.03. As a result, in Sample 24B, the electrical conductivity of the Al alloy wire was less than 62.5% IACS.

[0183] (Samples 20A to 23A) In contrast, in Samples 20A to 23A, the Ti content was set to 0.001 mass% or more and 0.020 mass% or less. As a result, in Samples 20A to 23A, the Al alloy wires could be stably processed. Furthermore, in Samples 20A to 23A, the Ti / B ratio was 2.5 or less. As a result, the Ti precipitation index was 1.03 or more. As a result, in Samples 20A to 23A, the electrical conductivity of the Al alloy wires was 62.5% IACS or more.

[0184] In Samples 20A to 23A, by setting the Ti content to 0.001 mass % or more, it was possible to sufficiently precipitate crystals of Ti—B compounds and refine the Al crystal grains, thereby confirming that Samples 20A to 23A were able to improve the workability of the Al alloy wire.

[0185] In Samples 20A to 23A, the Ti content was set to 0.020 mass% or less and Ti / B was set to 2.5 or less, thereby preventing excessive dissolution of Ti. As a result, it was confirmed that Samples 20A to 23A were able to prevent the decrease in the electrical conductivity of the Al alloy wire.

[0186] (3-4) Dependence on B Content The dependency on B content will be explained with reference to the results of Samples 25B to 32A. As described above, in Samples 25B to 32A, except for the difference in the B content, the contents of the other alloying elements were within the appropriate ranges, and the manufacturing conditions were appropriate.

[0187] (Samples 25B and 26B) In Samples 25B and 26B, the B content was less than 0.002 mass%. In addition, in Samples 25B and 26B, the Ti / B ratio was greater than 2.5. Therefore, the Ti precipitation index was less than 1.03. As a result, in Samples 25B and 26B, the electrical conductivity of the Al alloy wire was less than 62.5% IACS.

[0188] (Samples 27A to 32A) In contrast, in Samples 27A to 32A, the B content was set to 0.002 mass% or more and 0.100 mass% or less. In addition, the Ti / B ratio was 2.5 or less. As a result, the Ti precipitation index was 1.03 or more. As a result, in Samples 27A to 32A, the conductivity of the Al alloy wire was 62.5% IACS or more.

[0189] In Samples 27A to 32A, by setting the B content to 0.002 mass% or more, Ti could be precipitated as a Ti-B compound in the Al matrix. This reduced the amount of Ti dissolved in the matrix. As a result, it was confirmed that Samples 27A to 32A could suppress the decrease in the electrical conductivity of the Al alloy wire.

[0190] (3-5) Dependence on molten metal holding time The dependence on molten metal holding time will be explained with reference to the results of Samples 33B to 36A. As described above, for Samples 33B to 36A, the contents of each alloy element were set within the appropriate range, and the manufacturing conditions were all appropriate except for the fact that the molten metal holding time was different.

[0191] (Samples 33B and 34B) In Samples 33B and 34B, the molten metal holding time was set to less than 7 hours. Therefore, the Ti precipitation index was less than 1.03. As a result, in Samples 33B and 34B, the electrical conductivity of the Al alloy wire was less than 62.5% IACS.

[0192] (Samples 35A and 36A) In contrast, in Samples 35A and 36A, the molten metal holding time was set to 7 hours or more. As a result, the Ti precipitation index was 1.03 or more. As a result, in Samples 35A and 36A, the electrical conductivity of the Al alloy wire was 62.5% IACS or more.

[0193] In Samples 35A and 36A, the molten metal was kept for 7 hours or more, which allowed stable precipitation of Ti-B compound crystals. This reduced the amount of Ti in solid solution. As a result, it was confirmed that Samples 35A and 36A were able to suppress the decrease in the electrical conductivity of the Al alloy wire.

[0194] (3-6) Dependence on intermediate heat treatment The dependency on intermediate heat treatment will be explained with reference to the results of Samples 5A, and 37B to 41B. As described above, in Samples 5A, 37B to 41B, the content of each alloy element was set within the appropriate range, except for the fact that the manufacturing conditions were different.

[0195] (Samples 37B to 41B) Samples 37B to 41B were subjected to an intermediate heat treatment step in which the rolled material was heated at a temperature of 300°C or higher for 0.5 hours or longer. As a result, the Fe precipitation index was greater than 0.70. As a result, for Samples 37B to 41B, the tensile survival rate after 400 hours at 120°C was 90% or higher, but the tensile survival rate after 400 hours at 140°C was less than 84%.

[0196] (Sample 5A) In contrast, Sample 5A did not undergo the intermediate heat treatment step of heating the rolled material at a temperature of 300°C or higher for 0.5 hours or more. As a result, the Fe precipitation index was 0.70 or less. As a result, Sample 5A had a tensile survival rate of 90% or more after 400 hours at 120°C and a tensile survival rate of 84% or more after 400 hours at 140°C.

[0197] In Sample 5A, the above-mentioned intermediate heat treatment step was not performed, and thus the supersaturated solid solution state of Fe could be maintained until the Al alloy wire was obtained. As a result, it was confirmed that the heat resistance of Sample 5A could be improved.

[0198] (3-7) Fe precipitation index dependence Figure 7 is a plot of the tensile survival rate after 400 hours at 140 ° C versus the Fe precipitation index for several samples with an Fe content of 0.8 mass%. As shown in Figure 7, the lower the Fe precipitation index, i.e., the more Fe was dissolved, the higher the tensile survival rate after 400 hours at 140 ° C. It was confirmed from Figure 7 that by setting the Fe precipitation index to 0.70 or less, the tensile survival rate after 400 hours at 140 ° C. could be made 84% or more.

[0199] (3-8) Ti precipitation index dependence Figure 8 is a graph plotting the electrical conductivity of Al alloy wires against the Ti precipitation index for multiple samples with the same Fe, Si, and Ti contents and the same Fe precipitation index. As shown in Figure 8, the higher the Ti precipitation index, that is, the more Ti precipitated as Ti-B compounds, the higher the electrical conductivity of the Al alloy wire. From Figure 8, it was confirmed that the electrical conductivity of the Al alloy wire could be made 62.5% IACS or higher by setting the Ti precipitation index to 1.03 or higher.

[0200] <Supplementary Notes> The following provides supplementary notes on aspects of the present disclosure.

[0201] [6] The radial structure function of Fe is obtained by: (a) measuring an X-ray absorption fine structure spectrum μ(E) at the K absorption edge of Fe; (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 More than 80 nm －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:

[0202] [7] A method for manufacturing an aluminum alloy wire, comprising: a step of preparing a molten metal containing 0.020% by mass or more and 0.200% by mass or less of Fe, 0.005% by mass or more and 0.070% by mass or less of Si, 0.001% by mass or more and 0.020% by mass or less of Ti, 0.002% by mass or more and 0.100% by mass or less of B, with the balance being Al and inevitable impurities; a step of holding the molten metal at a temperature of 700°C or more for 7 hours or more; a step of forming a cast material by continuously casting the molten metal; a step of rolling the cast material to form a rolled material; and a step of wiredrawing the rolled material, wherein an intermediate heat treatment step of heating the rolled material at a temperature of 300°C or more is not performed after the step of forming the rolled material and before the step of wiredrawing the rolled material.

[0203] 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: 0.020% by mass or more and 0.200% by mass or less of Fe; 0.005% by mass or more and 0.070% by mass or less of Si; 0.001% by mass or more and 0.020% by mass or less of Ti; 0.002% by mass or more and 0.100% by mass or less of B; and the balance consisting of Al and inevitable impurities; wherein the electrical conductivity of the aluminum alloy wire is 62.5% IACS or more; and wherein the tensile strength of the aluminum alloy wire after heat treatment at 140°C for 400 hours is 84% ​​or more of the tensile strength before the heat treatment.

2. The aluminum alloy wire satisfies formula (1) and formula (2): IFe1 / IFe0≦0.70 (1) xTi1 / xTi2≧1.03 (2), where IFe1 is the height of a peak occurring within a radius range of 0.15 nm or more and 0.25 nm or less in a radial structure function obtained from X-ray absorption fine structure measurement at the K absorption edge of Fe in the aluminum alloy wire, and IFe0 is the height of a peak occurring within a radius range of 0.15 nm or more and 0.25 nm or less in a radial structure function of Fe in a rolled iron material having a purity of 99.99% and a thickness of 0.005 mm as a standard sample, which is obtained under the same conditions as those for obtaining the radial structure function of Fe in the aluminum alloy wire, 2. The aluminum alloy wire according to claim 1, wherein xTi1 and xTi2 are the height of a first peak occurring within an incident X-ray energy range of 4978 eV or more and 4984 eV or less, and the height of a second peak occurring within an incident X-ray energy range of 4986 eV or more and 4994 eV or less, respectively, in an X-ray absorption fine structure spectrum normalized by an absorbance difference before and after the Ti K-absorption edge in the aluminum alloy wire.

3. An aluminum alloy wire containing: 0.020% by mass or more and 0.200% by mass or less of Fe; 0.005% by mass or more and 0.070% by mass or less of Si; 0.001% by mass or more and 0.020% by mass or less of Ti; and 0.002% by mass or more and 0.100% by mass or less of B, with the remainder being Al and inevitable impurities, and the aluminum alloy wire satisfies formulas (1) and (2): IFe1 / IFe0≦0.70 ... (1) xTi1 / xTi2≧1.03 ... (2) where IFe1 is the height of a peak occurring within a radius of 0.15 nm or more and 0.25 nm or less in a radial structure function obtained from X-ray absorption fine structure measurement of the K absorption edge of Fe in the aluminum alloy wire, IFe0 is the height of a peak occurring within a radius range of 0.15 nm or more and 0.25 nm or less in the radial structure function of Fe in a rolled iron material having a purity of 99.99% and a thickness of 0.005 mm as a standard sample, obtained under the same conditions as those for obtaining the radial structure function of Fe in the aluminum alloy wire; and xTi1 and xTi2 are the heights of a first peak occurring within a range of incident X-ray energy of 4978 eV or more and 4984 eV or less and the height of a second peak occurring within a range of incident X-ray energy of 4986 eV or more and 4994 eV or less, respectively, in an X-ray absorption fine structure spectrum normalized by the absorbance difference before and after the Ti K absorption edge in the aluminum alloy wire.

4. The aluminum alloy wire according to any one of claims 1 to 3, wherein the ratio of the Ti content to the B content in the aluminum alloy wire is 2.5 or less.

5. 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 4.

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