Composite wire and coated wire

Abstract

To provide a thin composite wire that has excellent strength and elongation, and to provide a covered wire.SOLUTION: Provided is a composite wire, which is a composite wire comprising a core wire and a sheath covering the outer periphery of the core wire, and in which the constituent material of the core wire is an aluminum alloy containing Fe by 1.0 mass% or more and 4.0 mass% or less and the balance being Al and inevitable impurities, the constituent material of the sheath is pure copper or copper alloy, and the wire diameter is less than 0.2 mm.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to composite wires and covered wires. [Background technology]

[0002] Patent Document 1 discloses a copper-clad aluminum wire as a conductor wire, which includes a core wire and an outer sheath covering the outer periphery of the core wire. A representative example of a copper-clad aluminum wire is a composite wire made of pure metal, as shown in Sample No. 31 in Table 3 of Patent Document 1. In this composite wire, the core wire is made of pure aluminum such as electrical aluminum. The outer sheath covering the core wire is made of pure copper such as oxygen-free copper. Hereinafter, this composite wire may be referred to as a pure metal composite wire.

[0003] Patent Document 1 also discloses a composite wire having a core wire made of an aluminum alloy containing Fe as an additive element. Hereinafter, this composite wire may be referred to as an alloy composite wire. This alloy composite wire is obtained by subjecting an ingot or hot-rolled material made of the above aluminum alloy to a specific two-stage annealing process. The obtained alloy composite wire has higher tensile strength and higher elongation than a pure metal composite wire. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 53-110082 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a demand for a composite wire that is thinner and has superior strength and elongation compared to the pure metal composite wire described above. Furthermore, there is a demand for a composite wire that is superior in electrical conductivity and ease of manufacture.

[0006] The present inventors have found that when an aluminum alloy containing Fe as an additive element is subjected to the above-mentioned specific two-step annealing, breakage is likely to occur during cold drawing after annealing. Therefore, no composite wire having a core wire made of an aluminum alloy containing Fe as an additive element and a wire diameter of less than 0.5 mmφ has been obtained.

[0007] Therefore, an object of the present disclosure is to provide a thin composite wire that is excellent in strength and elongation. [Means for solving the problem]

[0008] The composite wire of the present disclosure is a composite wire including a core wire and an outer sheath covering the outer circumference of the core wire, the core wire is made of an aluminum alloy containing 1.0 mass% or more and 4.0 mass% or less of Fe, with the balance being Al and unavoidable impurities, the outer sheath is made of pure copper or a copper alloy, and has a wire diameter of less than 0.2 mm.

[0009] The covered wire of the present disclosure is a covered wire including a conductor wire and an insulating covering covering an outer periphery of the conductor wire, and the conductor wire is the composite wire of the present disclosure. Effect of the Invention

[0010] The composite wire and the covered wire of the present disclosure are excellent in strength and elongation, and are also thin. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a composite wire according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing another example of the composite wire according to the embodiment. [Diagram 3] FIG. 3 is a cross-sectional view illustrating an example of a covered wire according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing another example of the covered wire according to the embodiment. [Diagram 5] FIG. 5 is a perspective view showing an outline of a coil made of a covered wire according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. (1) A composite wire according to one embodiment of the present disclosure is a composite wire including a core wire and an outer sheath covering an outer periphery of the core wire, the core wire is made of an aluminum alloy containing 1.0 mass% or more and 4.0 mass% or less of Fe with the remainder being Al and unavoidable impurities, the outer sheath is made of pure copper or a copper alloy, and the wire diameter is less than 0.2 mm.

[0013] The composite wire of the present disclosure has a core wire made of an aluminum alloy containing Fe (iron) as an additive element, and is therefore superior in strength and elongation to the above-mentioned pure metal composite wire. Preferably, the composite wire of the present disclosure has a strength superior to that of the alloy composite wire described in Patent Document 1. In addition, the composite wire of the present disclosure is thinner than the above-mentioned alloy composite wire.

[0014] The reasons for the excellent strength and elongation are as follows. The Fe in the aluminum alloy is mainly present as a compound containing Fe and Al (aluminum). The dispersion strengthening of the compound improves the strength, and the composite wire of the present disclosure has high strength. In addition, the compound has a size that makes it difficult for it to become a crack initiation point, as described later. Since breakage caused by the compound is unlikely to occur, the composite wire of the present disclosure has high elongation.

[0015] Furthermore, since Fe exists as the above-mentioned compound, the amount of Fe dissolved in Al is very small. Preferably, Fe is not substantially dissolved in Al. Such an aluminum alloy can prevent the conductivity from decreasing due to the solid solution of the additive element in Al, as compared with other aluminum alloys, for example, aluminum alloys containing Mg and Si as additive elements. From this point of view, the composite wire of the present disclosure is also excellent in conductivity.

[0016] Furthermore, in the manufacturing process of the composite wire of the present disclosure, breaks originating from the above-mentioned compounds are unlikely to occur. Therefore, thin composite wires having a wire diameter of less than 0.2 mm can be mass-produced. From this point of view, the composite wire of the present disclosure is also excellent in manufacturability.

[0017] When the composite wire of the present disclosure is used, for example, as a conductor wire for a coil wire, it is possible to construct a small coil that is less likely to break even when subjected to vibrations, etc.

[0018] (2) An example of the composite wire of the present disclosure is one in which the core wire has a structure in which a compound containing Fe and Al is dispersed, the particle size of the compound is 30 μm or less, and the ratio of the total number of particles of the compound having a particle size of more than 1 μm and 3 μm or less to the total number of particles having a particle size of 30 μm or less is 5% or more and 20% or less.

[0019] In the above embodiment, the compound present in the core wire is a particle having a particle size of 30 μm or less, not a coarse particle having a particle size exceeding 30 μm. Therefore, the effect of improving strength by dispersion strengthening of the compound is obtained well. In addition, particles having a particle size of 30 μm or less are unlikely to become the starting point of cracks. Furthermore, particles having a particle size of more than 1 μm and 3 μm or less contribute to promoting softening of the core wire during the manufacturing process. The promotion of softening allows the core wire to be softened well. Due to the reduction in breakage and the promotion of softening, the above embodiment has better elongation.

[0020] Furthermore, particles with a particle size of 30 μm or less are unlikely to become the starting point of cracks during the manufacturing process, and therefore wire breakage is unlikely to occur during drawing. Therefore, the above embodiment is excellent in manufacturability even when the wire diameter is 0.15 mm or less, or even thinner, such as 0.10 mm or less.

[0021] (3) An example of the composite wire of (2) above is a form in which the ratio of the total number of particles having a particle size of more than 1 μm and not more than 2 μm to the total number of particles having a particle size of 30 μm or less among the compound is 5% or more and 15% or less.

[0022] Among the above compounds, particles having a particle size of more than 1 μm and not more than 2 μm are more likely to promote the softening of the core wire, and therefore the above form is more likely to further increase the elongation.

[0023] (4) An example of the composite wire according to the present disclosure is one in which, in a cross section taken along a plane perpendicular to an axial direction of the composite wire, the ratio of a cross-sectional area of ​​the outer skin to a cross-sectional area of ​​the composite wire is 10% or more and 80% or less.

[0024] The above-mentioned embodiment, by providing an outer cover appropriately, has excellent electrical conductivity and solder wettability, and is also likely to be lightweight.

[0025] (5) An example of the composite wire of the present disclosure has a breaking elongation of 8% or more.

[0026] The above-mentioned configuration is less likely to break even when subjected to vibration or bending with a small bending radius.

[0027] (6) An example of the composite wire of the present disclosure has a tensile strength of 200 MPa or more.

[0028] The above configuration is less likely to break even when subjected to vibration or the like.

[0029] (7) An example of the composite wire of the present disclosure has electrical conductivity of 58% IACS or more.

[0030] The above embodiment has excellent electrical conductivity and can therefore be suitably used for conductor wires.

[0031] (8) An example of the composite wire according to the present disclosure is one in which the cross-sectional shape of the composite wire taken along a plane perpendicular to the axial direction is non-circular.

[0032] The above embodiment provides a high degree of freedom in the cross-sectional shape.

[0033] (9) A covered wire according to one embodiment of the present disclosure is a covered wire including a conductor wire and an insulating covering covering an outer periphery of the conductor wire, the conductor wire being any one of the composite wires described above in (1) to (8).

[0034] The covered wire of the present disclosure is excellent in strength and elongation, and is thin. In addition, the covered wire of the present disclosure is excellent in electrical conductivity and manufacturability.

[0035] When the coated wire of the present disclosure is used as a coil wire, for example, it is possible to construct a small coil that is not easily broken even when subjected to vibrations, etc. In addition, the coated wire of the present disclosure has excellent elongation and is therefore easy to wind. Therefore, the coated wire of the present disclosure is easy to manufacture into a coil.

[0036] [Details of the embodiment of the present disclosure] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same reference numerals denote the same objects.

[0037] Compound Line A composite wire 1 according to an embodiment will be described with reference to FIGS. 1 and 2 are cross-sectional views of a composite wire 1 according to an embodiment, taken along a plane perpendicular to its axial direction. Hereinafter, this cross section may be referred to as a transverse section. The axial direction corresponds to the longitudinal direction of the composite wire 1.

[0038] (overview) The composite wire 1 of the embodiment includes a core wire 11 and an outer sheath 12. The outer sheath 12 covers the outer circumference of the core wire 11. The composite wire 1 is a copper-clad aluminum alloy wire in which the core wire 11 is made of an aluminum alloy and the outer sheath 12 is made of pure copper or a copper alloy.

[0039] In particular, in the composite wire 1 of the embodiment, the additive element of the aluminum alloy constituting the core wire 11 is Fe (iron). The wire diameter of the composite wire 1 is less than 0.2 mm. The details will be explained below.

[0040] (Core wire) <Constituent Materials> The material of the core wire 11 is an aluminum alloy containing 1.0% to 4.0% by mass of Fe, with the remainder being aluminum (aluminum) and unavoidable impurities. The content (mass%) of the additive elements here is the mass ratio with the aluminum alloy being 100% by mass.

[0041] Since the aluminum alloy constituting the core wire 11 contains Fe as an additive element, the core wire 11 has excellent mechanical properties such as strength and elongation, and also has excellent electrical conductivity, as described below. As a result, the composite wire 1 including such a core wire 11 has excellent strength, elongation, and electrical conductivity.

[0042] The amount of Fe dissolved in Al is very small. Therefore, Fe exists in the aluminum phase, which is the parent phase, as a compound containing mainly Fe and Al. In particular, in the composite wire 1 of the embodiment, the compound exists as small and fine particles, not as coarse particles. The small and fine particles are dispersed and present in the parent phase, which improves the strength of the core wire 11. Thus, the composite wire 1 has excellent strength. In addition, the small and fine particles are unlikely to become the starting point of cracks, so that the core wire 11 is unlikely to break. Thus, the composite wire 1 has excellent elongation. Furthermore, since Fe is not dissolved in Al but exists as the compound, the decrease in electrical conductivity caused by the solid solution of Fe in Al is likely to be suppressed. That is, the core wire 11 is likely to maintain the electrical conductivity of Al itself. In addition, since the compound is small, it is unlikely to obstruct the conductive path in Al. The composite wire 1 including such a core wire 11 has excellent electrical conductivity.

[0043] If the Fe content is 1.0 mass% or more, a compound containing Fe and Al is appropriately present. Therefore, the effect of improving the strength by dispersion strengthening can be obtained well. The higher the Fe content, the higher the strength is likely to be. From the viewpoint of improving the strength, the Fe content may be 1.2 mass% or more, 1.5 mass% or more, or 1.8 mass% or more. If the Fe content is 2.0 mass% or more, the strength is likely to be higher.

[0044] If the Fe content is 4.0% by mass or less, the compound containing Fe and Al is unlikely to become coarse. The total amount of the above compounds is also likely to be prevented from becoming excessive. As a result, the elongation and electrical conductivity are likely to be high. The lower the Fe content, the easier it is to prevent the above compounds from becoming coarse and the above compounds from being excessively contained. From the viewpoint of improving the elongation and electrical conductivity, the Fe content may be 3.8% by mass or less, 3.5% by mass or less, or 3.2% by mass or less. If the Fe content is 3.0% by mass or less, the elongation and electrical conductivity are likely to be higher.

[0045] When the Fe content is 1.2 to 3.8 mass %, or 1.5 to 3.5 mass %, or particularly 1.8 to 2.2 mass %, the composite wire 1 has a good balance of strength, elongation, and electrical conductivity.

[0046] The total content of unavoidable impurities is, for example, 0.1 mass % or less.

[0047] <Organization> The core wire 11 has a structure in which a compound containing Fe and Al is dispersed in a matrix. The particle size of the compound is preferably 30 μm or less. This is because the following effects (a) to (c) can be obtained.

[0048] (a) The above compounds are easily dispersed in the matrix. Therefore, the effect of improving the strength due to the dispersion strengthening of the above compounds is effectively obtained. By having a dispersion strengthened structure due to the above compounds, the composite wire 1 has excellent strength. (b) The compounds are unlikely to become the starting point of cracks. In other words, the compounds having a particle size of 30 μm or less are unlikely to affect wire breakage. Since the compounds are unlikely to break, the composite wire 1 has excellent elongation. Breakage is also unlikely to occur during the manufacturing process. Therefore, continuous wire drawing is possible, and the composite wire 1 has excellent manufacturability. (c) The above compounds are unlikely to block the conductive paths in the Al, so that the composite wire 1 has excellent conductivity.

[0049] When the core wire 11 contains coarse particles of more than 30 μm made of a compound containing Fe and Al, the number of the compounds present in the matrix is ​​likely to be small when the Fe content is constant. Therefore, the compounds are likely to be unevenly distributed in the matrix. The coarse particles are equivalent to more than 15% of the wire diameter of the core wire 11. Such coarse particles are likely to become the starting point of cracks and to obstruct the conductive path in the Al. The wire diameter of the composite wire 1 is the sum of the wire diameter of the core wire 11 and the thickness of the outer sheath 12. Therefore, the wire diameter of the core wire 11 is naturally less than 0.2 mm.

[0050] The total number of particles S of compounds containing Fe and Al with a particle size of 30 μm or less all The total number of particles with a particle size of more than 1 μm and less than 3 μm, S 3 The ratio of is preferably 5% or more and 20% or less. The present inventors have found that particles made of the above compound and having the above-mentioned specific particle size contribute to accelerating the softening of core wire 11 during the manufacturing process. By being well softened during the manufacturing process, core wire 11 has excellent elongation. Composite wire 1 including such core wire 11 has excellent elongation.

[0051] Hereinafter, compounds containing Fe and Al and having a particle size of more than 1 μm and not more than 3 μm may be referred to as small particles. The above compounds having a particle size of more than 1 μm and not more than 2 μm may be referred to as first particles. The above compounds having a particle size of more than 2 μm and not more than 3 μm may be referred to as second particles. The total number of particles having a particle size of 30 μm or less, S all The ratio of the total number of particles having a given particle size to the total number of particles having a given particle size is sometimes called the compound ratio. The compound ratio in small particles is (S 3 / S all ) × 100.

[0052] Here, it is preferable that Fe in the aluminum alloy constituting the core wire 11 exists as a compound containing Fe and Al as much as possible. Furthermore, if all of the compounds in the aluminum alloy are fine, for example, with a particle size of 10 μm or less, or even 5 μm or less, the compounds are easily dispersed in the aluminum alloy. Therefore, an improvement in strength can be expected. However, if the particle size of all of the compounds is 1 μm or less, the core wire 11 is not sufficiently softened during the manufacturing process of the composite wire 1. As a result, the elongation is reduced.

[0053] On the other hand, if the compound ratio in the small particles is 5% or more, the Fe in the aluminum alloy is appropriately present as small particles consisting of a compound containing Fe and Al. Therefore, the softening of the core wire 11 is well performed during the manufacturing process. The higher the compound ratio in the small particles, the easier it is to promote the softening of the core wire 11. Therefore, the elongation is likely to be high. From the viewpoint of improving the elongation, the compound ratio may be 6% or more, 9% or more, or 12% or more.

[0054] If the proportion of the compound in the small particles is 20% or less, the decrease in strength and the decrease in elongation caused by a large amount of small particles are likely to be small. The smaller the proportion of the compound, the smaller the decrease in strength and the decrease in elongation are likely to be. From the viewpoint of suppressing the decrease in strength and the decrease in elongation, the proportion of the compound may be 18% or less, 16% or less, or 14% or less.

[0055] Furthermore, the total number S of particles having a particle size of 30 μm or less among the small particles mentioned above all The total number of particles with a particle size of more than 1 μm and less than 2 μm, S 2 The ratio of the second particles is preferably 5% or more and 15% or less. In other words, the core wire 11 preferably contains first particles made of a compound containing Fe and Al. The total number of the second particles is preferably 1 / 100 the total number of the first particles S 2It is preferable that the content of the first particles is less than that of the second particles. The first particles are easier to lower the softening temperature than the second particles. Therefore, when the core wire 11 contains the first particles, the softening of the core wire 11 is easily promoted during the manufacturing process. In addition, the first particles are smaller than the second particles, and therefore (1) they are easier to disperse, (2) they are less likely to become the starting point of cracks, and (3) they are less likely to obstruct the conductive path in the Al. A composite wire 1 including such a core wire 11 has high elongation, and is excellent in strength and conductivity. The compound ratio in the first particles is (S 2 / S all ) × 100.

[0056] If the compound ratio in the first particles is 5% or more, the effects of promoting softening, strengthening dispersion, reducing cracking, and ensuring conductive paths as described above are easily obtained. Since these effects are well obtained, the compound ratio may be 6% or more, 7% or more, or 8% or more. It is preferable that the compound ratio is 5% or more and that more than half of the small particles are first particles.

[0057] If the compound ratio in the first particle is 15% or less, the number of first particles is relatively small. Such a core wire 11 has better manufacturability than a core wire having a compound ratio of more than 15%. From the viewpoint of manufacturability, the compound ratio may be 14% or less, 13% or less, or 12% or less. The compound ratio may further be 10% or less.

[0058] The total number of small particles with a particle size of 30 μm or less, S, is all In contrast, the ratio of the total number of second particles having a size of more than 2 μm and not more than 3 μm is, for example, 1% or more and 10% or less. The compound ratio in the second particles may be 9% or less, 8% or less, 7% or less, or even 5% or less. Alternatively, the compound ratio may be 0%. In other words, the core wire 11 does not need to include second particles as long as it includes first particles.

[0059] In particular, the composite wire 1 having the core wire 11 which is a compound containing Fe and Al, has a particle size of 30 μm or less, and contains small particles in the above-mentioned range, has a good balance of strength, elongation, and electrical conductivity. Furthermore, when the core wire 11 contains the first particles among the small particles in the above-mentioned range, the strength, elongation, and electrical conductivity are likely to be higher.

[0060] The particle size of the compound containing Fe and Al is measured as follows. A cross section of the composite wire 1 is taken. The core wire 11 in the cross section is observed with a scanning electron microscope (SEM). Multiple fields of view are taken from the SEM observation image. The size of the field of view can be about 20 μm × 20 μm. The observation image of each field of view is subjected to image processing to approximate the compound into an ellipse. The major axis length of the approximated ellipse particle is taken as the particle size of the compound. Details of the measurement method will be explained in the test example described later.

[0061] For a compound containing Fe and Al, the compound ratio in a given particle size is determined as follows. The compounds are divided into predetermined particle size classes according to the particle size of the compounds. The total number of each class S 2 ,S 3 etc. Also, the total number of all classes S all Then, (S 2 / S all ) x 100, etc.

[0062] (outer skin) 1 and 2, the outer sheath 12 is an annular region that continuously covers the outer periphery of the core wire 11 in the circumferential direction of the core wire 11. The material constituting the outer sheath 12 is pure copper or a copper alloy. The composite wire 1 having the outer sheath 12 made of a metal mainly composed of copper has superior electrical conductivity, solder wettability, corrosion resistance, etc., compared to the case where only the core wire 11 is included.

[0063] Here, pure copper includes 99.9% by mass or more of Cu (copper), with the remainder consisting of inevitable impurities. Pure copper is generally softer than copper alloys and has excellent electrical conductivity. Therefore, the composite wire 1 having the sheath 12 made of pure copper is easy to bend and has excellent flexibility, and also has excellent electrical conductivity. Specific examples of pure copper include oxygen-free copper, tough pitch copper, electrolytic copper, and phosphorus-deoxidized copper.

[0064] The copper alloy contains additive elements, with the remainder being Cu and unavoidable impurities, with Cu being the most abundant. The additive elements include, for example, one or more elements selected from the group consisting of Zr (zirconium), P (phosphorus), Sn (tin), Ag (silver), and Fe. The total content of the additive elements is, for example, 0.01% by mass or more and 1% by mass or less. Copper alloys are generally stronger than pure copper. Therefore, the composite wire 1 having the outer sheath 12 made of a copper alloy has excellent strength.

[0065] (Hull ratio) In the cross section of the composite wire 1, the cross-sectional area S of the composite wire 1 1 Cross-sectional area S of the outer shell 12 12 The ratio of can be selected in the range of more than 0% and less than 100%. 1 Cross-sectional area S of the outer shell 12 12 The ratio of the skin is sometimes called the skin ratio. The skin ratio (%) is calculated by the following formula: 12 / S 1 ) × 100.

[0066] The proportion of the outer skin is, for example, 10% or more and 80% or less. When the sheath ratio is 10% or more, the effect of improving the electrical conductivity by providing the sheath 12 can be satisfactorily obtained. The higher the sheath ratio, the more excellent the electrical conductivity of the composite wire 1. From the viewpoint of improving the electrical conductivity, the sheath ratio may be 12% or more, 15% or more, 18% or more, or 20% or more.

[0067] If the skin ratio is 80% or less, the weight increase due to the skin 12 is small. Therefore, the composite wire 1 is likely to be lightweight. The smaller the skin ratio, the lighter the composite wire 1 is. From the viewpoint of weight reduction, the skin ratio may be 70% or less, 60% or less, or 50% or less.

[0068] From the viewpoint of good electrical conductivity and weight reduction, the skin ratio may be 10% or more and 50% or less, 15% or more and 40% or less, or 15% or more and 35% or less.

[0069] 1 and 2, the thickness of the outer sheath 12 is typically uniform along the circumferential direction of the core wire 11. The thickness of the outer sheath 12 is adjusted so that the outer sheath ratio falls within the above range.

[0070] (Interface condition between core wire and outer sheath) In the composite wire 1 of the embodiment, it is preferable that a compound containing Al derived from the core wire 11 and Cu derived from the outer sheath 12 is substantially absent at the interface between the core wire 11 and the outer sheath 12. The compound containing Al and Cu becomes the starting point of cracks, thereby preventing the composite wire 1 from breaking. The compound containing Al and Cu is typically generated by heating a wire having a metal coating made of pure copper or a copper alloy to a temperature of 280°C or higher in the manufacturing process of the composite wire 1. The above temperature may further be 300°C or higher, or 400°C or higher. Since the above compound is generated, it is preferable that heat treatment and hot working at a heating temperature of 280°C or higher is not performed in the manufacturing process of the composite wire 1.

[0071] (Wire diameter) The composite wire 1 has a small wire diameter of less than 0.2 mm. Such composite wire 1 is suitable for conductor wires that are desired to have excellent strength and elongation, excellent conductivity, and furthermore, small size and light weight. Examples of such conductor wires include conductor wires for electric wires used in portable electronic devices and small electronic devices, particularly conductor wires for coil wires. The wire diameter of the composite wire 1 may be 0.15 mm or less, 0.12 mm or less, or even 0.10 mm or less. In particular, if the composite wire 1 having a wire diameter of less than 0.1 mm, or even 0.08 mm or less is used as the conductor wire for coil wires, a smaller coil can be obtained. From the viewpoint of manufacturability, the wire diameter of the composite wire 1 may be, for example, 0.01 mm or more, or even 0.02 mm or more.

[0072] The wire diameter of composite wire 1 here is the diameter of the smallest circle that contains the outline of composite wire 1 in the cross section of composite wire 1. If the cross section of composite wire 1 is circular as shown in Fig. 1, the wire diameter of composite wire 1 corresponds to the outer diameter of outer jacket 12. As will be described later, if the cross section of composite wire 1 is square, the wire diameter of composite wire 1 corresponds to the length of the diagonal of the square. In addition, in the square composite wire 1 with the diagonal length of less than 0.2 mm, the length of one side of the square is, for example, 0.03 mm or more and 0.14 mm or less.

[0073] (Cross-sectional shape) The cross-sectional shape of the composite wire 1 can be appropriately selected. A typical cross-sectional shape is a circle as shown in FIG. 1. The cross-sectional shape of the composite wire 1 may be non-circular. Examples of non-circular cross-sectional shapes include curved shapes such as polygons and ellipses. Examples of polygons include a rectangle as shown in FIG. 2 and other shapes such as a hexagon. Examples of rectangles include a square. The composite wire 1 may be a round wire as shown in FIG. 1, a rectangular wire as shown in FIG. 2, or another irregularly shaped wire. In this way, the composite wire 1 has a high degree of freedom in terms of shape.

[0074] Representatively, the cross-sectional shape of the core wire 11 is similar to that of the composite wire 1, as shown in Figs.

[0075] (characteristic) The composite wire 1 of the embodiment satisfies at least one of the following: tensile strength of 200 MPa or more, breaking elongation of 8% or more, and electrical conductivity of 58% IACS or more. It is preferable that two of the above three items are satisfied, and more preferably that all three items are satisfied.

[0076] Tensile strength If the tensile strength of the composite wire 1 is 200 MPa or more, the composite wire 1 has greater strength than the above-mentioned pure metal composite wire. Preferably, the composite wire 1 has greater strength than the above-mentioned alloy composite wire. The higher the tensile strength, the greater the strength of the composite wire 1, and the less likely it is to break even when subjected to vibration or the like. From the viewpoint of improving strength, the tensile strength may be 205 MPa or more, 210 MPa or more, 215 MPa or more, or 220 MPa or more. The higher the Fe content of the core wire 11 and the higher the sheath ratio, the higher the tensile strength tends to be.

[0077] The higher the tensile strength of the composite wire 1, the more likely the elongation to decrease. From the viewpoint of improving the elongation, the tensile strength may be 320 MPa or less, or 300 MPa or less.

[0078] <stretch> If the breaking elongation of the composite wire 1 is 8% or more, the composite wire 1 has excellent elongation. The higher the breaking elongation, the better the elongation of the composite wire 1, and the less likely it is to break even when subjected to vibration or bending with a small bending radius. Furthermore, the composite wire 1 is easy to bend and has excellent flexibility. From the viewpoint of improving elongation, the breaking elongation may be 9% or more, 10% or more, or 12% or more.

[0079] The higher the breaking elongation of the composite wire 1, the more likely it is that the tensile strength will decrease. From the viewpoint of improving the strength, the breaking elongation may be 35% or less, or 30% or less.

[0080] In particular, if the tensile strength of the composite wire 1 is 200 MPa or more and 320 MPa or less, and the breaking elongation of the composite wire 1 is 8% or more and 35% or less, the composite wire 1 has high strength and high toughness.

[0081] <conductivity> If the electrical conductivity of the composite wire 1 is 58% IACS or more, the composite wire 1 has excellent electrical conductivity and can be used well as a conductor wire. In applications where the conductor wire is used, the higher the electrical conductivity, the more preferable it is, and it may be 60% IACS or more, 61% IACS or more, or 62% IACS or more. The higher the proportion of the outer sheath, the higher the electrical conductivity tends to be. Depending on the proportion of the outer sheath, the electrical conductivity may be 65% IACS or more, 68% IACS or more, or 70% IACS or more.

[0082] The Fe content, the sheath ratio, the manufacturing conditions, etc. may be adjusted so that the tensile strength, the breaking elongation, and the electrical conductivity of the composite wire 1 satisfy the above-mentioned ranges. The manufacturing conditions include the cooling rate in the casting process, the degree of wire drawing, and the softening conditions.

[0083] (Main actions and effects) The composite wire 1 of the embodiment has a core wire 11 made of an aluminum alloy containing Fe as an additive element, and therefore has excellent strength and elongation. The composite wire 1 also has excellent electrical conductivity. Such a composite wire 1 can be suitably used as a conductor wire. Furthermore, although the composite wire 1 has a thin wire diameter of less than 0.2 mm, it also has excellent manufacturability.

[0084] [Coated wire] The coated wire 2 of the embodiment will be described with reference to FIG. 3 and FIG. 3 and 4 are cross-sectional views of the covered wire 2 of the embodiment taken along a plane perpendicular to its axial direction. This cross-section corresponds to a cross-section taken along line III-III in FIG. 5, which will be described later. The axial direction corresponds to the longitudinal direction of the covered wire 2.

[0085] The covered wire 2 of the embodiment includes a conductor wire 20 and an insulating coating 25. The insulating coating 25 covers the outer circumference of the conductor wire 20. The conductor wire 20 is a composite wire 1 of the embodiment. FIG. 3 shows the covered wire 2 having a circular cross-sectional shape. The composite wire 1 included in the covered wire 2 shown in FIG. 3 is a round wire having a circular cross-sectional shape shown in FIG. 1. FIG. 4 shows the covered wire 2 having a rectangular cross-sectional shape. The composite wire 1 included in the covered wire 2 shown in FIG. 4 is a rectangular wire having a rectangular cross-sectional shape shown in FIG. 2.

[0086] Examples of materials constituting the insulating coating 25 include various electrical insulating materials, such as resins, etc. When the coated wire 2 is a coil wire, examples of the resin constituting the insulating coating 25 include polyimide, polyamideimide, polyesterimide, polyurethane, polyester, polyolefin, polyamide, polyethersulfone, polyphenylene sulfide, polyetheretherketone, and polytetrafluoroethylene.

[0087] The insulating coating 25 may be a single layer or a multi-layer structure of two or more layers. The thickness of the insulating coating 25 may be selected depending on the magnitude of the current flowing through the conductor wire 20, etc. The thickness of the insulating coating 25 may be, for example, 5 μm to 50 μm. The thickness of the insulating coating 25 is typically uniform along the circumferential direction of the conductor wire 20, as shown in Figs. 3 and 4. Therefore, the cross-sectional shape of the covered wire 2 is similar to the cross-sectional shape of the conductor wire 20, i.e., the cross-sectional shape of the composite wire 1.

[0088] In addition, the coated wire 2 may have a self-lubricating layer or a self-adhesive layer, etc., not shown, as the outermost layer.

[0089] The conductor wire 20 substantially maintains the composition, structure, characteristics, wire diameter, etc. of the composite wire 1 of the embodiment. Therefore, the covered wire 2 of the embodiment has excellent strength and elongation. The covered wire 2 also has excellent conductivity. Such a covered wire 2 can be suitably used as an electric wire, for example, a wire material for coils. Since the covered wire 2 is thin, a small coil can be constructed. Furthermore, since the composite wire 1 constituting the conductor wire 20 has excellent manufacturability, the covered wire 2 also has excellent manufacturability.

[0090] [coil] With reference to FIG. 5, a coil 3 using a coated wire 2 will be described. The coil 3 includes a winding portion 30 made of the covered wire 2 of the embodiment. The winding portion 30 is formed by winding the covered wire 2 in a spiral shape. Fig. 5 illustrates a coil 3 using the covered wire 2 having a circular cross-sectional shape shown in Fig. 3.

[0091] The number of turns of the winding portion 30, the inner diameter of the coil 3, etc. can be appropriately selected.

[0092] The coil 3 is manufactured by winding the coated wire 2 of the embodiment. The coated wire 2 constituting the coil 3 substantially maintains the composition, structure, characteristics, wire diameter, etc. of the coated wire 2 before winding. Therefore, the coil 3 has excellent strength and elongation. The coil 3 also has excellent conductivity. Furthermore, the coil 3 is small because it is composed of the coated wire 2 having the conductor wire 20 with a wire diameter of less than 0.2 mm.

[0093] As described above, the coil 3 is small and therefore suitable for use as a voice coil, a motor coil, or an earphone coil in portable electronic devices, small electronic devices, etc. In particular, the coil 3 is not easily broken even when subjected to vibrations, and is therefore suitable for use as a voice coil that is easily subjected to vibrations.

[0094] [Manufacturing method of composite wire] The composite wire 1 of the embodiment can be produced, for example, by a composite wire production method including the following steps. (First step) A continuously cast and rolled material is produced from an aluminum alloy containing 1.0 mass % or more and 4.0 mass % or less of Fe, with the balance being Al and unavoidable impurities. The cooling rate in the continuous casting process is 0.5°C / s or more. (Second step) The above-mentioned continuously cast and rolled material, or a processed material having a predetermined wire diameter obtained by cold working the above-mentioned continuously cast and rolled material, is used as a core material, and a metal coating portion is formed to cover the outer periphery of the core material. The metal coating portion is made of pure copper or a copper alloy. (Third step) A composite material including the core material and the metal coating portion is subjected to cold wire drawing to produce a drawn wire material having a wire diameter of less than 0.2 mm. (Fourth step) The drawn wire is subjected to a softening treatment. The heating temperature in the softening treatment is less than 280°C.

[0095] The above-mentioned method for producing a composite wire is based on the following findings. In order to increase the strength of the composite wire having a core wire and a sheath, the material of the core wire is preferably an aluminum alloy rather than pure aluminum. In order to obtain a composite wire having excellent strength and excellent electrical conductivity, the additive element of the aluminum alloy is preferably Fe rather than Mg, Si, etc. Furthermore, in order to obtain a composite wire having excellent elongation, it is preferable that the core wire can be well softened.

[0096] Patent Document 1 discloses that two-stage annealing at a temperature of 400°C or higher increases the size of compounds containing Fe and Al, accelerating the softening of the core wire. It is believed that if hot rolling is performed after this annealing, the compounds are likely to increase in size, that is, the softening of the core wire is likely to be accelerated during the softening treatment. However, since the compounds are large, and contain coarse particles, particularly those with a particle size of more than 30 μm, breaks are likely to occur starting from these coarse particles during wire drawing. Therefore, it is practically impossible to mass-produce thin composite wires with a wire diameter of less than 0.2 mm.

[0097] In order to mass-produce a thin composite wire with a wire diameter of less than 0.2 mm, it is necessary to control the size of the compound containing Fe and Al to a size that is unlikely to become a crack starting point. In addition, it is necessary to control the size of the compound to a size that can promote the softening of the core wire. The present inventors have found that in order to control the size of the compound to such a size, it is preferable to set the cooling rate in the casting process to 0.5°C / sec or more depending on the Fe content. In addition, it has been found that it is preferable not to heat the material to a temperature at which the compound is likely to grow in size in the manufacturing process after continuous casting and rolling. For example, it has been found that it is preferable not to perform annealing, hot working, etc. at 400°C or more. Each step will be explained below.

[0098] (first step) The first step is to manufacture an aluminum alloy material that will be the raw material for the core wire 11 of the composite wire 1. This aluminum alloy material is a continuous cast and rolled material. For the composition of the aluminum alloy material, please refer to the above section on (core wire) <Constituent materials>. A known continuous casting and rolling device can be used to manufacture the continuous cast and rolled material.

[0099] The cooling rate in the continuous casting process is preferably 0.5°C / sec or more. The cooling rate here is the rate at which the temperature of the molten metal reaches 300°C. If the cooling rate is 0.5°C / sec, the particle size of the compound containing Fe and Al becomes 30µm or less. In addition, small particles of the compound having the above-mentioned specific particle size are generated. The generation of small particles can promote the softening of the core wire in the fourth step. If the particle size is 30µm or less, the above-mentioned effects (a) to (c) can be obtained.

[0100] The higher the Fe content, the easier it is to generate a compound containing Fe and Al. Therefore, it is preferable to adjust the cooling rate according to the Fe content. Depending on the Fe content, the cooling rate may be 0.8°C / sec or more, 1.0°C / sec or more, 1.5°C / sec or more, or 2.0°C / sec or more. The higher the cooling rate, the easier it is to make the compound finer. If the cooling rate is, for example, 3.0°C / sec or more, fine particles having a particle size of 5 μm or less are more likely to be produced. As a result, breakage is less likely to occur. Since breakage is less likely to occur, in the composite wire 1 of the embodiment, the upper limit of the Fe content can be made larger than the upper limit of the Fe content in the alloy composite wire of Patent Document 1. If the cooling rate is 15°C / sec or less, 8°C / sec or less, it is considered that the above-mentioned small particles are more reliably generated.

[0101] The wire diameter of the continuously cast and rolled material can be appropriately selected. For example, the wire diameter can be set to a wire diameter that is easy to form a metal coating portion in the next second process. In addition, the continuously cast and rolled material can be subjected to cold working to make the wire diameter thinner. The processing applied to the continuously cast and rolled material is cold working, not hot working. Therefore, the size of the compound containing Fe and Al generated during the continuous casting process does not substantially change before and after cold working. That is, the processed material after cold working substantially maintains the size of the compound in the continuously cast and rolled material before cold working.

[0102] (Second process) The second step is a step of manufacturing a metal coating portion which is a material for the outer sheath 12 of the composite wire 1. A known method for manufacturing a copper coating for a composite wire can be used to manufacture the metal coating portion. For example, the metal coating portion can be formed by using a tape or pipe material made of pure copper or a copper alloy, or by providing a plating layer made of pure copper or a copper alloy. The tape material is, for example, attached vertically or wound around the outer periphery of the core material so as to be arranged in a cylindrical shape. The thickness of the metal coating portion, i.e., the thickness of the tape material and the thickness of the plating layer, can be adjusted according to the above-mentioned outer sheath ratio, the degree of wire drawing, and the like. When the outer sheath ratio is relatively large, for example, when the outer sheath ratio is 20% or more, or even 50% or more, a relatively thick metal coating portion can be easily provided by using a pipe material. For details of pure copper and copper alloy, refer to the above-mentioned (Outer Sheath) <Constituent Materials> section.

[0103] A member in which the above-mentioned tape material, pipe material, etc. is arranged on the outer periphery of the core material may be subjected to a cold tightening process before cold drawing. For the tightening process, for example, a diameter reduction process using a fitting die, a diameter reduction roll, etc. can be used. By performing the above-mentioned tightening process in a cold state instead of a hot state, the size of the compound containing Fe and Al in the core material does not substantially change before and after the second process.

[0104] (Third step) The third step is a step of producing a drawn wire material having a wire diameter of less than 0.2 mm from a composite material having a core material made of the above-mentioned aluminum alloy and a metal coating portion made of pure copper or a copper alloy. The drawn wire material has a core wire made of the above-mentioned aluminum alloy and an outer sheath made of pure copper or a copper alloy. By performing cold wire drawing until the wire diameter becomes less than 0.2 mm, the strength of the drawn wire material is increased by work hardening. A known wire drawing device can be used to produce the drawn wire material.

[0105] Since the wire drawing process applied to the composite material is cold working rather than hot working, the size of the compound containing Fe and Al in the core wire provided in the drawn wire material does not substantially change before and after the third step.

[0106] Intermediate heat treatment can be performed during the wiredrawing. The intermediate heat treatment is intended to reduce processing distortion caused by the wiredrawing process. The heating temperature for the intermediate heat treatment is, for example, 200°C or higher and 250°C or lower. If the heating temperature is 250°C or lower, the processing distortion can be reduced and the compound containing Fe and Al is less likely to become coarse.

[0107] (Fourth step) The fourth step is a step of subjecting the drawn wire produced in the third step to a softening treatment, which is a heat treatment, for the purpose of improving elongation.

[0108] The higher the heating temperature of the softening treatment, the higher the elongation of the wire after the softening treatment. In addition, the processing strain is reduced, and the electrical conductivity of the wire after the softening treatment is also likely to be high. However, the strength of the wire after the softening treatment is likely to be reduced. In addition, the higher the heating temperature, the more likely the compound containing Al and Cu described above is generated at the interface between the core wire 11 and the outer sheath 12. This compound is likely to become the starting point of cracks, and cracks are likely to occur at the interface between the core wire 11 and the outer sheath 12. Therefore, the heating temperature of the softening treatment is preferably a temperature at which the compound containing Al and Cu is not generated. Here, the core wire of the drawn wire material subjected to the softening treatment contains the above-mentioned small particles that are a compound containing Fe and Al. Therefore, even if the heating temperature of the softening treatment is relatively low, the drawn wire material can be well softened. Specifically, the heating temperature of the softening treatment is less than 280°C.

[0109] If the heating temperature in the softening treatment is less than 280° C., the drawn wire material can be well softened, and a composite wire 1 having high elongation, strength, and electrical conductivity can be obtained. The heating temperature is preferably 200° C. or higher and 250° C. or lower. The holding time at the heating temperature is, for example, 1 hour or higher and 24 hours or lower.

[0110] When the softening treatment is a continuous treatment, the treatment conditions, such as the linear speed, the current value, and the atmospheric temperature in the furnace, may be adjusted to correspond to the above-mentioned heating temperatures.

[0111] The softening treatment causes Fe dissolved in the aluminum alloy to precipitate as a compound containing Fe and Al. Alternatively, the softening treatment causes the compound already present in the aluminum alloy to become slightly larger. However, as described above, the heating temperature of the softening treatment is relatively low. Therefore, the particle size of the newly precipitated compound is small. Specifically, the particle size satisfies 30 μm or less. Also, the change in the particle size of the compound already present is small. Therefore, the particle size after the change satisfies 30 μm or less. The distribution of the compound in the continuously cast and rolled material does not change substantially except when a heat treatment is performed at a temperature close to the melting point of the aluminum alloy, that is, a high-temperature heat treatment is performed. Therefore, the distribution of the compound in the composite wire 1 after the softening treatment substantially maintains the distribution of the compound in the continuously cast and rolled material. It is to be noted that the precipitation of Fe can be expected to increase the electrical conductivity and strength.

[0112] [Manufacturing method of coated wire] The covered wire 2 of the embodiment can be produced, for example, by forming an insulating cover 25 on the outer periphery of the composite wire 1 of the embodiment. The insulating cover 25 can be formed by using a known method for producing an electrical insulating layer.

[0113] [Coil manufacturing method] The coil 3 described above can be manufactured, for example, by winding the coated wire 2 of the embodiment. A known coil manufacturing method can be used as a method for winding the coated wire 2. The coated wire 2 of the embodiment is resistant to breakage even when bent with a small bending radius, and is easy to bend. Since the wound portion is easy to form, the coil 3 is also easy to manufacture.

[0114] [Test Example 1] Tables 1 and 2 show the mechanical and electrical properties of a composite wire having a core made of an aluminum alloy containing Fe as an additive element and an outer sheath made of pure copper.

[0115] The aluminum alloys constituting the core wires have five different Fe contents: 1.0 mass%, 1.8 mass%, 2.0 mass%, 2.2 mass%, and 4.0 mass%. All of the aluminum alloys contain the above-mentioned Fe contents, with the remainder being Al and unavoidable impurities. The core wires with an Fe content of 1.0 mass % are labeled No. 1 to No. 4. The core wires with an Fe content of 1.8 mass % are labeled No. 5 to No. 8. The core wires with an Fe content of 2.0 mass % are labeled No. 9 to No. 12. The core wires with an Fe content of 2.2 mass % are labeled No. 13 to No. 16. The core wires with an Fe content of 4.0 mass % are labeled No. 17 to No. 20. The composite wires including the core wires No. 1 to No. 4 have the same Fe content in the core wires, but have different properties such as breaking elongation as described below. This is also true for the composite wires including the core wires No. 5 to No. 20.

[0116] In all samples, the composite wire is a round wire with a circular cross-sectional shape. In addition, in all samples, the wire diameter of the composite wire is 0.05 mm (50 μm). However, in the cross section of the composite wire, the ratio of the cross-sectional area of ​​the outer sheath to the cross-sectional area of ​​the composite wire, i.e., the outer sheath ratio, is different. There are eight types of outer sheath ratios: 5%, 10%, 15%, 30%, 50%, 70%, 80%, and 85%. Each outer sheath is assigned the symbols No. 1 to No. 8 in order of the outer sheath ratio. The larger the outer sheath ratio, i.e., the larger the outer sheath number, the thicker the outer sheath and the smaller the wire diameter of the core wire.

[0117] Hereinafter, the outer sheath number and core wire number will be combined in order and referred to as sample No. 4-14, etc.

[0118] (Samples No. 1-1 to No. 8-20) The composite wire having the core wire made of the above-mentioned aluminum alloy is manufactured as follows.

[0119] Continuously cast and rolled materials made of the above-mentioned aluminum alloys are manufactured. For all samples, the cooling rate during the continuous casting process is 1°C / sec. The continuously cast and rolled materials are in the form of round bars with a wire diameter of 10 mm.

[0120] The above-mentioned continuous cast and rolled material is subjected to cold wire drawing to produce a worked material having a wire diameter of 8 mm. The continuous cast and rolled material is not subjected to any heat treatment at a heating temperature of 280° C. or higher or hot working.

[0121] A metal coating made of pure copper is formed on the processed material to manufacture a composite material. Here, a tape material made of oxygen-free copper or a seamless pipe material made of oxygen-free copper is used to form the metal coating. For samples with a relatively large outer sheath ratio, a seamless pipe material is used to form the metal coating. The thickness of the tape material and the seamless pipe material are adjusted according to the outer sheath ratio, etc.

[0122] The composite material is subjected to cold drawing to produce a drawn wire having a wire diameter of 0.05 mm. The composite material is not subjected to any heat treatment at a heating temperature of 280° C. or higher, nor is it subjected to hot working.

[0123] A composite wire is obtained by subjecting the drawn wire material to a softening treatment. The heating temperature for the softening treatment is selected from the range of 200°C or higher and 250°C or lower. Here, the breaking elongation is used as an index, and the heating temperature is selected from the above temperature range so that the breaking elongation is a value selected from the range of 4% or higher and 15% or lower. The larger the breaking elongation, the higher the heating temperature. The same principle of selecting the heating temperature using the breaking elongation as an index applies to the comparative samples described later. In this test, as shown in Tables 1 and 2, composite wires with breaking elongation of 4% or higher were obtained.

[0124] (Sample No. 4-101 to No. 4-103) As a comparative sample, the mechanical and electrical properties of a pure metal composite wire with a wire diameter of 0.05 mm are shown in Table 1. In the pure metal composite wires of samples No. 4-101 to No. 4-103, the core wire is made of pure aluminum (pure Al), the outer sheath is made of pure copper, and the outer sheath ratio is 30%. Known manufacturing methods can be referred to for the basic manufacturing method of the pure metal composite wire. Specifically, continuous casting and rolling, cold wire drawing, and softening treatment are performed in this order. The heating temperature for the softening treatment is selected from the range of 300°C to 450°C.

[0125] (Samples No. 111 to No. 130) As a comparative sample, the mechanical and electrical properties of a wire with a sheath ratio of 0% are shown in Table 3. This wire does not have a sheath, is made of the above-mentioned aluminum alloy, and is an aluminum alloy wire with a wire diameter of 0.05 mm.

[0126] The aluminum alloy wires of Samples No. 111 to No. 130 were produced as follows. A continuous cast and rolled material is manufactured in the same manner as the manufacturing process of the core wire No. 1 and the like. This continuous cast and rolled material is subjected to cold wire drawing to manufacture a drawn wire material having a wire diameter of 0.05 mm. This drawn wire material is subjected to softening treatment to obtain an aluminum alloy wire. The heating temperature for the softening treatment is selected from the range of 300°C to 450°C.

[0127] (Samples No. 131 to No. 134) As a comparative sample, a wire with a sheath ratio of 100% was used, and its mechanical and electrical properties are shown in Table 3. This wire does not have an aluminum alloy core, but is made of pure copper and has a wire diameter of 0.05 mm.

[0128] The pure copper wires of Samples No. 131 to No. 134 can be manufactured by a known method for manufacturing copper wire, specifically by carrying out continuous casting and rolling, cold wire drawing, and softening treatment in that order.

[0129] (mechanical properties) The mechanical properties referred to here are tensile strength (MPa) and elongation at break (%). The tensile strength and elongation at break are measured using a general-purpose tensile testing machine in accordance with JIS Z 2241:2011 "Metallic material tensile test method."

[0130] (Electrical characteristics) The electrical property here is the conductivity (%IACS), which is measured by the bridge method.

[0131] [Table 1]

[0132] [Table 2]

[0133] [Table 3]

[0134] The composite wires of Samples No. 1-1 to No. 8-20, which have a core wire made of an aluminum alloy containing Fe as an additive element, and the pure metal composite wires of Samples No. 4-101 to No. 4-103, which have the same breaking elongation, are compared. In this comparison, as shown in Tables 1 and 2, the composite wires of Samples No. 1-1 to No. 8-20 have a higher tensile strength than the pure metal composite wires of Samples No. 4-101 to No. 4-103. In addition, the composite wires of Samples No. 1-1 to No. 8-20 have a breaking elongation of 4% or more. Most of the composite wires have a breaking elongation of 8% or more. This shows that a composite wire having a core wire made of an aluminum alloy containing 1.0 mass% to 4.0 mass% Fe and having a wire diameter of less than 0.2 mm, and even a thin composite wire of less than 0.1 mm in this case, can be obtained that is excellent in strength and elongation.

[0135] Hereinafter, attention will be focused on the composite wires of samples No. 1-1 to No. 8-20. As shown in Tables 1 and 2, these composite wires satisfy at least one of the following: tensile strength of 200 MPa or more, breaking elongation of 8% or more, and electrical conductivity of 58% IACS or more. Most composite wires with a sheath ratio of 10% or more satisfy two of the above three items. There are also many composite wires that satisfy all three items. This shows that it is possible to obtain a composite wire having a core wire made of an aluminum alloy containing 1.0% by mass or more and 4.0% by mass or less of Fe, with a wire diameter of less than 0.2 mm, and further less than 0.1 mm in this case, which is excellent in strength and elongation as well as electrical conductivity.

[0136] The composite wires of Samples No. 1-1 to No. 8-20 are compared with the aluminum alloy wires of Samples No. 111 to No. 130 shown in Table 3, which have the same Fe content and breaking elongation. From this comparison, it is found that the composite wires have higher tensile strength and are superior in strength than the aluminum alloy wires. The reason for this is believed to be that the composite wires have an outer sheath made of pure copper.

[0137] In particular, the tensile strength of the composite wire tends to be higher as the sheath ratio increases. If the sheath ratio is 10% or more, the tensile strength is 180 MPa or more. If the sheath ratio is 15% or more, the tensile strength of many composite wires is 200 MPa or more. If the sheath ratio is 15% or more and the Fe content is 1.8 mass% or more, the tensile strength of many composite wires is 220 MPa. Depending on the sheath ratio, the tensile strength is 250 MPa or more.

[0138] The composite wires of Samples No. 1-1 to No. 8-20 are compared with the aluminum alloy wires of Samples No. 111 to No. 130 shown in Table 3, which have the same Fe content. From this comparison, it is found that the composite wires have higher electrical conductivity than the aluminum alloy wires, and are more excellent in electrical conductivity. The reason for this is believed to be that the composite wires have an outer sheath made of pure copper.

[0139] In particular, the higher the sheath ratio, the higher the electrical conductivity of the composite wire. If the sheath ratio is 15% or more, the electrical conductivity is 59% IACS or more. If the sheath ratio is 50% or more, the electrical conductivity is 70% IACS or more, and even 75% IACS or more.

[0140] However, the larger the sheath ratio, the larger the specific gravity, which approaches the specific gravity of the pure copper wires of Samples No. 131 to No. 134 shown in Table 3. Therefore, in order to obtain a lightweight composite wire with a good balance of strength, elongation, and electrical conductivity, the sheath ratio is preferably 10% or more and 80% or less. In particular, a composite wire with a sheath ratio of 30% or less has a specific gravity less than twice the specific gravity of the aluminum alloy wire described above, 2.7, and is therefore lightweight.

[0141] In addition, when comparing the composite wires of samples No. 1-1 to No. 8-20 that have the same sheath ratio and breaking elongation, it is found that the higher the Fe content, the higher the tensile strength. This comparison also shows that the lower the Fe content, the higher the electrical conductivity. Furthermore, it is found that a composite wire that satisfies the above three conditions can be obtained when the Fe content is 1.0 mass% or more and 4.0 mass% or less and the sheath ratio is 10% or more.

[0142] This test also demonstrated that it is possible to manufacture a thin composite wire having a wire diameter of less than 0.2 mm, which is equipped with a core wire made of an aluminum alloy containing 1.0% by mass or more and 4.0% by mass or less of Fe. The manufacturing conditions will be discussed in detail in the following Test Example 2.

[0143] [Test Example 2] The manufacturing conditions of a composite wire having a core wire made of an aluminum alloy containing Fe as an additive element and an outer sheath made of pure copper, the structure of the core wire, and the interface state between the core wire and the outer sheath were investigated.

[0144] In this test, the following composite wires were produced. Except for sample No. 202, the basic manufacturing process was the same as that of sample No. 1-1 in Test Example 1. That is, continuous casting and rolling, cold wire drawing, formation of the metal coating, cold wire drawing, and softening treatment were carried out in that order. Details of the produced composite wires are described below.

[0145] <Common matters> All the sample composite wires were round wires having a circular cross-sectional shape. In all samples, the composite wire diameter is 0.1 mm. In all samples, the skin percentage of the composite wire is 15%.

[0146] <Fe content> In the composite wire of sample No. 21, the core wire had an Fe content of 1.0 mass %. In the composite wires of Samples No. 22, No. 23, and No. 202, the Fe content in the core wire was 2.0 mass %. In the composite wire of sample No. 24, the Fe content in the core wire is 4.0 mass %. In the composite wire of sample No. 201, the Fe content in the core wire is 0.5 mass %. In the composite wire of sample No. 203, the Fe content in the core wire is 5.0 mass %.

[0147] <Manufacturing conditions> <Cooling rate during continuous casting> Except for sample No. 23, the cooling rate during the continuous casting process was 1°C / sec. In sample No. 23, the cooling rate during the continuous casting process was 4°C / sec.

[0148] Anneal For sample No. 202, the continuous cast and rolled material was subjected to two-stage annealing. The first annealing conditions were a heating temperature of 600°C and a holding time of 10 hours. The second annealing conditions were a heating temperature of 400°C and a holding time of 1 hour. Samples other than sample No. 202 were not subjected to the above two-stage annealing.

[0149] <Softening treatment> Except for sample No. 201, the heating temperature for the softening treatment is selected from the range of 200°C to 250°C. As in Test Example 1, the breaking elongation is used as an index, and the heating temperature is selected from the above range so that the breaking elongation is a value selected from the range of 4% to 15%. The larger the breaking elongation, the higher the heating temperature. The heating temperature for the softening treatment of sample No. 201 was 350°C.

[0150] (Manufacturability) The occurrence of wire breakage during cold drawing was investigated. Here, a metal coating made of pure copper is formed, and then the composite material with this metal coating is subjected to cold wire drawing to produce a drawn wire material with a wire diameter of 0.9 mm. 100 kg of drawn wire material with a wire diameter of 0.9 mm is prepared. A drawn wire material with a final diameter of 0.1 mm is produced from the drawn wire material with a wire diameter of 0.9 mm. The number of breaks that occurred from the 100 kg of prepared drawn wire material to the time when the drawn wire material with the final wire diameter is obtained is investigated. The number of breaks is divided by 100 kg to find the number of breaks per 1 kg of drawn wire material. The obtained ratio is called the breakage rate (times / kg). The breakage rate (times / kg) is shown in Table 4.

[0151] (Textural Observation) For each sample composite wire obtained by softening the drawn wire with a final wire diameter of 0.1 mm, the state of compounds present in the aluminum alloy constituting the core wire was examined. Also, the state of the boundary between the core wire and the sheath in each sample composite wire was examined.

[0152] <Compounds in aluminum alloys> The aluminum alloy constituting the core wire of each composite wire sample contains a compound containing Fe and Al. The size of this compound was examined as follows.

[0153] A cross section is taken of the composite wire of each sample. Three fields of view of 19 μm × 24 μm are taken from the core wire part of the cross section of the composite wire. Each field of view is observed by SEM. By performing image processing on the SEM observation image of each field of view, the SEM observation image is binarized and the compound containing Fe and Al is approximated to an ellipse. This image processing can be performed using known software such as ImageJ. If known software such as ImageJ that has an ellipse conversion function is used, the binarized compound can be automatically converted to a best-fitting ellipse. The major axis length of each particle that has been made into an ellipse is determined. The major axis length of each particle is taken as the particle size of each particle made of the compound.

[0154] According to the particle size, each particle made of a compound containing Fe and Al is divided into five classes: 1 μm or less, more than 1 μm and less than 2 μm, more than 2 μm and less than 3 μm, more than 3 μm and less than 30 μm, and more than 30 μm. The total number of particles is calculated for each class. In addition, the total number of particles in the five classes, S all Then, the total number S all The ratio of the total number of each class to the total number of compounds is calculated, that is, the compound ratio. Here, the compound ratio of each class is calculated for each field of view. The compound ratio of each class is then averaged over the three fields of view to determine the compound ratio of each class. The compound ratio of each class is shown in Table 4.

[0155] Here, the above-mentioned compounds with a particle size of 0.4 μm or less were excluded from the calculation of the number of particles, since they were considered to be due to processing errors, etc. In other words, the number of compounds with a particle size of more than 0.4 μm was calculated.

[0156] By performing a component analysis on the above-mentioned compound, it can be confirmed that the compound contains Fe and Al, typically an intermetallic compound of Fe and Al. For the component analysis, for example, an energy dispersive X-ray analyzer (SEM-EDX) attached to a SEM can be used.

[0157] <Interface condition between core wire and outer sheath> A cross section was taken for each sample composite wire. The cross section of the composite wire was observed with an SEM to check whether or not there were inclusions at the boundary between the core wire and the sheath. The results are shown in Table 5. If inclusions were present, the components of the inclusions were analyzed. For example, SEM-EDX or the like can be used for the component analysis.

[0158] In addition, in the case of sample No. 201, which contains 0.5% Fe, a composite wire with a breaking elongation of 8% could not be obtained even when the heating temperature in the softening treatment was adjusted. Therefore, in the case of sample No. 201, the results in the case where the breaking elongation is 4% are shown in Table 5.

[0159] Furthermore, for the composite wires of each sample, the tensile strength (MPa) and electrical conductivity (%IACS) when the breaking elongation is 8% are shown in Table 4. For samples No. 21 and No. 22, the tensile strength (MPa) and electrical conductivity (%IACS) when the breaking elongation is 4%, 8%, 12%, and 15% are shown in Table 5. The measuring methods for the tensile strength, breaking elongation, and electrical conductivity were the same as in Test Example 1.

[0160] [Table 4]

[0161] [Table 5]

[0162] Hereinafter, samples No. 21 to No. 24 are collectively referred to as a specific sample group. As shown in Table 4, in the specific sample group, Fe in the aluminum alloy constituting the core wire exists mainly as a compound containing Fe and Al, and the particle size of the compound is 30 μm or less. That is, in the specific sample group, there are no coarse particles of the compound having a particle size of more than 30 μm. On the other hand, in samples No. 202 and No. 203, there are coarse particles of the compound having a particle size of more than 30 μm.

[0163] One of the reasons why the specific sample group is a compound containing Fe and Al and does not contain the above-mentioned coarse particles is thought to be that the cooling rate in the continuous casting process is 0.5°C / sec or more. In this case, the cooling rate is 1°C / sec or more.

[0164] One of the reasons why sample No. 202 contains the above-mentioned coarse particles is thought to be that the above-mentioned two-stage annealing was performed, in which the heating temperature was 400°C or higher.

[0165] One of the reasons why sample No. 203 contains the above-mentioned coarse particles is thought to be that the Fe content in the above-mentioned aluminum alloy is as high as 5 mass %.

[0166] The specific sample group is a compound containing Fe and Al, and contains many fine particles with a particle size of 1 μm or less, but also contains particles over 1 μm. Specifically, the compound ratio in small particles with a particle size of more than 1 μm and less than 3 μm is 5% to 20%. Among the small particles, the compound ratio in first particles with a particle size of more than 1 μm and less than 2 μm is 5% to 15%. Furthermore, more than half of the small particles are first particles, and first particles are always present. The compound ratio in second particles with a particle size of more than 2 μm and less than 3 μm is 0% to less than 5%. Therefore, it can be said that the specific sample group is the compound, does not contain the above-mentioned coarse particles, contains the above-mentioned small particles to a certain extent, and contains many fine particles.

[0167] Comparing sample No. 22 and sample No. 23, sample No. 23 has fewer small particles and more fine particles than sample No. 22. One of the reasons for this is thought to be that the cooling rate in the continuous casting process of sample No. 23 is faster than that of sample No. 22.

[0168] Samples No. 21, No. 22, No. 24, No. 201, and No. 203 are compared. From this comparison, it can be said that the higher the Fe content in the aluminum alloy constituting the core wire, the more the above-mentioned small particles there are. Conversely, the lower the Fe content, the more the above-mentioned fine particles there are. From this, it can be said that the amount of Fe content affects the particle size of the compound containing Fe and Al.

[0169] As shown in Table 4, the specific sample group has a lower breakage rate than samples No. 202 and No. 203. Specifically, the breakage rate of the specific sample group is 0.1 times / kg or less, and even 0.05 times / kg or less, which is 1 / 20 or less of the breakage rate of sample No. 202. From this, it can be said that the composite wire of the specific sample group is excellent in manufacturability even if the wire diameter is less than 0.2 mm.

[0170] One of the reasons why the breakage rate of the specific sample group is low is that the core wires in the specific sample group are compounds containing Fe and Al and do not contain coarse particles with a particle size of more than 30 μm. It is considered that the coarse particles are likely to become the starting points of cracks when cold drawing is performed until the wire diameter becomes less than 0.2 mm, here 0.1 mm or less.

[0171] Samples No. 21 to No. 24 are compared. The fewer the above-mentioned small particles, particularly the fewer the second particles, of the compound containing Fe and Al, the lower the wire breakage rate. The composite wire of sample No. 23, which contains the first particles but does not contain the second particles, is less likely to break during cold drawing in the manufacturing process, and is therefore more manufacturable. One of the reasons for this is thought to be that sample No. 23 has a high cooling rate in the continuous casting process as described above.

[0172] As shown in Table 4, the specific sample group has composite wires with at least one of a tensile strength of 200 MPa or more and an electrical conductivity of 58% IACS or more while having a breaking elongation of 4% or more, and even 8% or more. The specific sample group also has composite wires with a breaking elongation of 8% or more, a tensile strength of 200 MPa or more, and an electrical conductivity of 58% IACS or more. In contrast, as shown in Table 5, sample No. 201 does not have a composite wire with a breaking elongation of 8% or more.

[0173] One of the reasons why the specific sample group has high elongation is thought to be that the core wire is a compound containing Fe and Al and contains the above-mentioned small particles in the above-mentioned specific range. It is thought that the above-mentioned small particles contribute to promoting the softening of the core wire, so that high elongation can be obtained even if the heating temperature of the softening treatment is a relatively low temperature of 250°C or less. Since the heating temperature of the softening treatment is a relatively low temperature, the decrease in strength is reduced. Therefore, it is thought that the specific sample group is likely to have high strength.

[0174] Sample No. 201 has few small particles. Therefore, even if the heating temperature in the softening treatment is 280°C or higher, and even higher than 300°C in this case, only about 4% of breaking elongation was obtained. The reason for the small amount of small particles in sample No. 201 is thought to be that the Fe content is low at 0.5 mass% or less.

[0175] Furthermore, as shown in the right column of Table 5, in the composite wires of samples No. 21 and No. 22, no inclusions were observed at the interface between the core wire and the sheath. In contrast, in the composite wire of sample No. 201, inclusions were observed. These inclusions are compounds containing Al and Cu. One of the reasons for the presence of inclusions at the interface between the core wire and the sheath in sample No. 201 is thought to be that the heating temperature in the softening treatment was high, 280°C or higher, and even 300°C or higher in this case. It is thought that the high heating temperature in the softening treatment caused Al derived from the core wire and Cu derived from the sheath to form a compound.

[0176] From the above explanation, it has been shown that in a thin composite wire having a core wire made of an aluminum alloy containing Fe as an additive element, excellent in strength and elongation, and having a wire diameter of less than 0.2 mm, it is preferable that the aluminum alloy satisfies the following conditions (a) to (c). In addition, in order to make this composite wire excellent in manufacturability, it is preferable that the manufacturing process of the composite wire satisfies the following conditions (A) and (B).

[0177] (a) The Fe content in the aluminum alloy is more than 0.5 mass % and less than 5 mass %, particularly 1.0 mass % or more and 4.0 mass % or less. (b) The aluminum alloy is a compound containing Fe and Al, does not contain the above-mentioned coarse particles, and the proportion of the compound in the above-mentioned small particles is 5% or more and 20% or less. (c) The above (b) is satisfied, and the proportion of the compound in the first particles is 5% or more and 15% or less.

[0178] (A) The cooling rate in the continuous casting process is 0.5°C / sec or more, and further 1°C / sec or more. (B) After continuous casting and rolling, no heat treatment or hot working is performed at a heating temperature of 280°C or higher, further 300°C or higher, or 400°C or higher.

[0179] The composite wires of Samples No. 1-1 to No. 8-20 of Test Example 1 were manufactured under manufacturing conditions roughly equivalent to those of the specific sample group of Test Example 2, and therefore are considered to satisfy the above conditions (b) and (c).

[0180] The present invention is not limited to these examples, but is intended to include all modifications within the scope of the claims and meaning equivalent thereto. For example, in the composite wires shown in Test Examples 1 and 2, the Fe content, the composition of the sheath, the sheath ratio, the wire diameter of the composite wire, the cross-sectional shape of the composite wire, etc. can be changed. For example, the cross-sectional shape of the composite wire may be non-circular, such as rectangular. Or, for example, the constituent material of the sheath may be a copper alloy. [Explanation of symbols]

[0181] 1 composite wire, 11 core wire, 12 outer sheath 2 coated wire, 20 conductor wire, 25 insulating coating 3 coils, 30 turns

Claims

1. A composite wire comprising a core wire and an outer sheath covering an outer periphery of the core wire, The core wire is made of an aluminum alloy containing 1.0% by mass or more and 4.0% by mass or less of Fe, with the remainder being Al and unavoidable impurities. The material of the outer shell is pure copper or a copper alloy, The core wire has a structure in which a compound containing Fe and Al is dispersed, The particle size of the compound is 30 μm or less, The wire diameter is less than 0.2 mm, The breaking elongation is 8% or more. Composite wire.

2. A composite wire as described in claim 1, in which the ratio of the total number of particles having a particle size of more than 1 μm and not more than 3 μm to the total number of particles having a particle size of 30 μm or less among the compounds is 5% or more and 20% or less.

3. 3. The composite wire according to claim 2, wherein the ratio of the total number of particles having a particle size of more than 1 μm and not more than 2 μm to the total number of particles having a particle size of 30 μm or less among the compounds is 5% or more and 15% or less.

4. 4. The composite wire according to claim 1, wherein in a cross section taken along a plane perpendicular to an axial direction of the composite wire, a ratio of a cross-sectional area of ​​the outer jacket to a cross-sectional area of ​​the composite wire is 10% or more and 80% or less.

5. 5. The composite wire according to claim 1, having a tensile strength of 200 MPa or more.

6. 6. The composite wire according to claim 1, having an electrical conductivity of 58% IACS or more.

7. 7. The composite wire according to claim 1, wherein a cross-sectional shape of the composite wire taken along a plane perpendicular to an axial direction of the composite wire is non-circular.

8. A coated wire comprising a conductor wire and an insulating coating covering an outer periphery of the conductor wire, The conductor wire is a composite wire according to any one of claims 1 to 7. Coated wire.

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