Aluminum alloy wire, electrical wire, and wire harness

Abstract

Provided is an aluminum alloy wire, an electric wire, and a wire harness that have high tensile strength and electric conductivity, excellent elongation characteristics, and thus display an excellent balance between these and have a small variation in the tensile strength and the elongation characteristics along the longitudinal direction. The aluminum alloy wire includes: an alloy composition containing 0.30% by mass or more and 0.70% by mass or less of Mg and 0.30% by mass or more and 1.00% by mass or less of Si, with a balance being Al and inevitable impurities; and an abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less being 85% or less with respect to all of the measurement points, in a crystal orientation analysis by an electron backscatter diffraction method performed in an observation region of a transverse section of the aluminum alloy wire.

Description

TECHNICAL FIELD

[0001] The present invention relates to an aluminum alloy wire, an electric wire, and a wire harness.BACKGROUND ART

[0002] In recent years, electric equipment of automobiles has been increasing, and the amount of wire harnesses used for transmitting electric signals has also increased. Accordingly, there is a problem that the total weight of the wire harness per automobile becomes several ten of kilograms due to an increase in the weight of the electric wires constituting the wire harness.

[0003] Although attempts have been made to reduce the weight of the wire harness, for example by reducing the diameter of the electric wire, such attempts have not been sufficient to reduce the weight of the wire harness. On the other hand, as one of the means for reducing the weight of a wire harness, replacement of a copper electric wire with an aluminum electric wire has progressed especially among large-diameter electric wires. Particularly, in recent years, a movement of replacing a copper electric wire with a high-strength aluminum alloy wire has been widened for also small-diameter electric wires.

[0004] As a material for such a high-strength aluminum alloy wire, a 6000 series aluminum alloy is often selected.

[0005] For example, Patent Document 1 discloses an aluminum alloy wire used for a conductor, the aluminum alloy wire containing Mg in a content of 0.2% by mass or more and 1.5% by mass or less, Si in a content of 0.1% by mass or more and 2.0% by mass or less, Fe in a content of 0.1% by mass or more, and 1.0% by mass or less, or at least one element selected from Cu, Cr, Mn, or Zr and Fe in a total content of 0.1% by mass or more and 1.0% by mass or less, Ti in a content of 0.08% by mass or less, and B in a content of 0.016% by mass or less, with a balance being Al and impurities, and having an electric conductivity of 40% IACS or more, a tensile strength of 150 MPa or more, an elongation of 5% or more, a wire diameter of 0.5 mm or less, and a maximum crystal grain size of 50 µm or less.

[0006] Patent Document 2 discloses an aluminum alloy conductor containing Fe in a content of 0.01 to 0.4% by mass, Mg in a content of 0.01% by mass or more and less than 0.3% by mass, Si in a content of 0.01% by mass or more and less than 0.3% by mass, and Cu in a content of 0.01 to 0.5% by mass, with a balance being Al and inevitable impurities. In the aluminum alloy conductor, an area ratio of crystal grains having a plane inclining by an angle of 25° or more relative to the normal direction from a (111) plane disposed parallel to a cross section of the wire perpendicular to the wire drawing direction is at least 50% in a circle of a radius of (3 / 10)R from the center thereof, where R is the radius of the wire; and an area ratio of crystal grains having a plane inclining by an angle of 0° or more and less than 25° relative to the normal direction from a (111) plane disposed parallel to a cross section of the wire perpendicular to the wire drawing direction is at least 50% in an area of the entire wire excluding an inner circle of a radius of (7 / 10)R from the center thereof.

[0007] Further, Patent Document 3 discloses an aluminum alloy wire having a composition including Mg: 0.1 to 1.0% by mass, Si: 0.1 to 1.0% by mass, Fe: 0.01 to 1.40% by mass, Ti: 0.000 to 0.100% by mass, B: 0.000 to 0.030% by mass, Cu: 0.00 to 1.00% by mass, Ag: 0.00 to 0.50% by mass, Au: 0.00 to 0.50% by mass, Mn: 0.00 to 1.00% by mass, Cr: 0.00 to 1.00% by mass, Zr: 0.00 to 0.50% by mass, Hf: 0.00 to 0.50% by mass, V: 0.00 to 0.50% by mass, Sc: 0.00 to 0.50% by mass, Sn: 0.00 to 0.50% by mass, Co: 0.00 to 0.50% by mass, Ni: 0.01 to 0.50% by mass, Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr, Hf, V, Sc, Sn, Co, and Ni in a total content of 2.00% by mass or less, with a balance being Al and inevitable impurities. In the aluminum alloy wire, an area ratio of a region where an angle between a longitudinal direction of the aluminum alloy wire and a <111> direction of the crystal is within 20° is 20% or more and 65% or less.Citation ListPatent Document

[0008] Patent Document 1: Japanese Patent No. 5155464 Patent Document 2: Japanese Patent No. 5846360 Patent Document 3: Japanese Patent No. 6499190 DISCLOSURE OF THE INVENTIONProblems to be Solved by the Invention

[0009] Patent Document 1 discloses an aluminum electric wire in which Mg, Si, or the like is added to an aluminum alloy and the maximum crystal grain size is controlled. In Patent Documents 2 and 3, crystal planes and crystal orientations of the aluminum alloy wire undergo microstructure control. In addition to high tensile strength, high electric conductivity, and excellent elongation characteristics, the aluminum alloy wires of Patent Documents 2 and 3 have characteristics such as excellent elongation characteristics, superior rupture resistance to repeated motions and high proof stress.

[0010] These alloys have common characteristics in that they have at least high tensile strength and high electric conductivity and also excellent elongation characteristics, but there is room for further improvement in terms of reduction in variations in tensile strength and elongation characteristics along the longitudinal direction.

[0011] An object of the present invention is to provide an aluminum alloy wire, an electric wire, and a wire harness which have high tensile strength, high electric conductivity, and excellent elongation characteristics, whereby the aluminum alloy wire, the electric wire, and the wire harness display an excellent balance between the tensile strength, the electric conductivity, and the elongation characteristics, and have a small variation in the tensile strength and the elongation characteristics along the longitudinal direction.Means for Solving the Problems

[0012] As a result of intensive research and development for the above-described conventional problems, the present inventors have found that it is possible to provide an aluminum alloy wire, an electric wire, and a wire harness in which tensile strength, electric conductivity, and elongation characteristics are improved in a well-balanced manner by setting the composition of the aluminum alloy wire to within a specific range and controlling the temperature and time in the heat treatment step in the production of the aluminum alloy wire, such that a crystal orientation difference between adjacent measurement points of crystal orientation analysis is controlled. The present invention has been completed based on this finding.

[0013] In order to achieve the above object, the outline of the present invention is as follows. (1) An aluminum alloy wire including: an alloy composition including 0.30% by mass or more and 0.70% by mass or less of Mg and 0.30% by mass or more and 1.00% by mass or less of Si, with a balance being Al and inevitable impurities; and an abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less being 85% or less with respect to all of the measurement points, in a crystal orientation analysis by an electron backscatter diffraction (EBSD) method performed in an observation region of a transverse section perpendicular to a longitudinal direction of the aluminum alloy wire. (2) An aluminum alloy wire including: an alloy composition including 0.30% by mass or more and 0.70% by mass or less of Mg and 0.30% by mass or more and 1.00% by mass or less of Si, further including one or more components selected from the group consisting of Mn, Fe, Ni, Ti, Cr and Zr in a range of 0.001% by mass or more and 0.55% by mass or less in total, with a balance being Al and inevitable impurities; and an abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less being 85% or less with respect to all of the measurement points, in a crystal orientation analysis by an electron backscatter diffraction (EBSD) method performed in an observation region of a transverse section perpendicular to a longitudinal direction of the aluminum alloy wire. (3) The aluminum alloy wire as described in (1) or (2), in which, in the crystal orientation analysis performed in the observation region, when crystal orientations within <100> orientation ±5° are defined as a <100> orientation group, crystal orientations within <110> orientation ±5° are defined as a <110> orientation group, and crystal orientations within <111> orientation ±5° are defined as a <111> orientation group, a ratio of the number of the crystal grains having the <111> orientation group to the total number of the crystal grains having the <100> orientation group and the <110> orientation group (<111> orientation group / (<100> orientation group + <110> orientation group)) is in a range of 5 or more and 30 or less. (4) The aluminum alloy wire as described in any one of (1) to (3), in which an average crystal grain size of crystal grains obtained from the crystal orientation analysis performed in the observation region is in a range of 5 µm or more and 9 µm or less. (5) An electric wire including the aluminum alloy wire as described in any one of (1) to (4). (6) A wire harness including the electric wire as described in (5). Effects of the Invention

[0014] According to the present invention, it is possible to provide an aluminum alloy wire, an electric wire, and a wire harness that have excellent elongation characteristics while having high tensile strength and high electric conductivity, and thus display an excellent balance among the tensile strength, the electric conductivity, and the elongation characteristics, and have a small variation in the tensile strength and the elongation characteristics along the longitudinal direction.PREFERRED MODE FOR CARRYING OUT THE INVENTION

[0015] Hereinafter, preferred embodiments of the aluminum alloy wire, the electric wire, and the wire harness of the present invention will be described in detail. In the component composition of the alloy of the present invention, "% by mass" may be simply referred to as "%".

[0016] The aluminum alloy wire of the present invention is an aluminum alloy wire including: an alloy composition containing 0.30% by mass or more and 0.70% by mass or less of Mg and 0.30% by mass or more and 1.00% by mass or less of Si, with a balance being Al and inevitable impurities; and an abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less being 85% or less with respect to all of the measurement points, in a crystal orientation analysis by an electron backscatter diffraction (EBSD) method performed in an observation region of a transverse section perpendicular to a longitudinal direction of the aluminum alloy wire.

[0017] In the aluminum alloy wire according to the present invention, the tensile strength, the electric conductivity, and the elongation characteristics can be improved in a well-balanced manner by adjusting the alloy composition to within a specific range and controlling the temperature and time in the heat treatment step in the production of the aluminum alloy wire such that the crystal orientation difference between adjacent measurement points is controlled. More specifically, when the aluminum alloy wire has an alloy composition containing 0.30% by mass or more of Mg and 0.30% by mass or more of Si, and the abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less is 85% or less with respect to all of the measurement points, the tensile strength of the aluminum alloy wire can be increased. On the other hand, when the aluminum alloy wire has an alloy composition containing 0.70% by mass or less of Mg and 1.00% by mass or less of Si, and the abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less is 85% or less with respect to all of the measurement points, the electric conductivity and the elongation characteristics of the aluminum alloy wire can be increased.

[0018] Therefore, by using the aluminum alloy wire of the present invention, which has high tensile strength, high electric conductivity, and excellent elongation characteristics, it is possible to provide an aluminum alloy wire, an electric wire, and a wire harness that display an excellent balance between the tensile strength, the electric conductivity, and the elongation characteristics, and that have small variations in the tensile strength and the elongation characteristics along the longitudinal direction.[1] Alloy Composition of Aluminum Alloy Wire<Essential Components>

[0019] The alloy composition of the aluminum alloy wire of the present invention contains, as essential components, 0.30% by mass or more and 0.70% by mass or less of Mg and 0.30% by mass or more and 1.00% by mass or less of Si.(Mg: 0.30% by mass or more and 0.70% by mass or less)

[0020] Mg (magnesium) is an element that increases the tensile strength and the electric conductivity of the aluminum alloy by finely precipitating in the aluminum alloy together with other additive elements such as Si. In order to exhibit these effects, Mg is contained in a content of 0.30% by mass or more. In this regard, when the content of Mg is less than 0.30% by mass, most of Mg maintains a solid solution state, and thus Mg does not easily precipitate in the aluminum alloy. On the other hand, when the Mg content exceeds 0.70% by mass, Mg in a content significantly exceeding the solid solubility limit is present as a coarse compound, which not only does not contribute to improvement in the tensile strength and the electric conductivity, but also causes wire drawing breakage, thereby adversely affecting the aluminum alloy such that elongation characteristics deteriorate. Therefore, the content of Mg is 0.70% by mass or less. Given the above, the content of Mg is in the range of 0.30% by mass or more and 0.70% by mass or less.(Si: 0.30% by mass or more and 1.00% by mass or less)

[0021] Si (silicon) is an element that increases the tensile strength and the electric conductivity of the aluminum alloy by finely precipitating in the aluminum alloy together with other additive elements. In order to exhibit these effects, Si is contained in a content of 0.30% by mass or more. In this regard, when the content of Si is less than 0.30% by mass, most of Si maintains a solid solution state, and thus Si does not easily precipitate in the aluminum alloy. On the other hand, when the Si content exceeds 1.00% by mass, Si in a content significantly exceeding the solid solubility limit is present as a coarse compound, which not only does not contribute to improvement in the tensile strength and the electric conductivity, but also causes wire drawing breakage, thereby adversely affecting the aluminum alloy such that elongation characteristics deteriorate. Therefore, the content of Si is 1.00% by mass or less. Given the above, the content of Si is in the range of 0.30% by mass or more and 1.00% by mass or less.<Optional Additive Components>

[0022] The alloy composition of the aluminum alloy wire of the present invention may further contain, as an optional additive component, one or more components selected from the group consisting of Mn, Fe, Ni, Ti, Cr and Zr in a range of 0.001% by mass or more and 0.55% by mass or less in total.(Mn: 0.001% by mass or more and 0.50% by mass or less)

[0023] Mn (manganese) is a component that contributes to further refinement of crystal grains and brings about further increase in the strength of the aluminum alloy wire, and is a component that makes grain growth less likely to occur in a heat treatment process accompanied by recrystallization, thereby achieving an effect of wire break prevention. In order to exhibit this effect, Mn is preferably contained in a content of 0.001% by mass or more. On the other hand, if the Mn content is too large, the effect is saturated and does not change, or precipitation is promoted, so that the precipitation amount of a MgSi-based compound, which is particularly effective in the present invention, is relatively decreased. In addition, since there is a possibility that disadvantages such as a decrease in the electric conductivity and an adverse effect on the productivity occurs, the content of Mn is preferably 0.50% by mass or less.(Fe: 0.001% by mass or more and 0.50% by mass or less)

[0024] Fe (iron) is a component that contributes to further increasing the strength of the aluminum alloy wire. In order to exhibit this effect, Ti is preferably contained in a content of 0.001% by mass or more. On the other hand, if the Fe content is too large, the effect is saturated and does not change, and there is also a possibility that disadvantages such as a decrease in the electric conductivity and an adverse effect on the productivity occurs. As such, the Fe content is preferably 0.50% by mass or less.(Ni: 0.001% by mass or more and 0.50% by mass or less)

[0025] Ni (nickel) is a component having an effect of improving impact resistance of the aluminum alloy wire. In order to exhibit this effect, Ni is preferably contained in a content of 0.001% by mass or more. On the other hand, if the Ni content is too large, the effect is saturated and does not change, and there is also a possibility that disadvantages such as a decrease in the electric conductivity and an adverse effect on the productivity occurs. As such, the Ni content is preferably 0.50% by mass or less.(Ti: 0.001% by mass or more and 0.50% by mass or less)

[0026] Ti (titanium) has an effect of making a solidified structure during casting fine by being added as TiB, and is a component contributing to improvement in the productivity in a rolling step after casting. In order to exhibit this effect, Ti is preferably contained in a content of 0.001% by mass or more. On the other hand, the Ti content is preferably 0.50% by mass or less because there is a possibility that disadvantages such as a decrease in the electric conductivity and an adverse effect on the productivity may occur.(Cr: 0.001% by mass or more and 0.50% by mass or less)

[0027] Similarly to Mn, Cr (chromium) is a component having an effect of refining crystal grains and an effect of making grain growth at a high temperature less likely to occur, so that the wire is less likely to break. In order to exhibit this effect, Cr is preferably contained in a content of 0.001% by mass or more. On the other hand, if the Cr content is too large, the effect is saturated and does not change, or precipitation is promoted, so that there is a possibility that the precipitation amount of a MgSi-based compound may relatively decrease. In addition, since there is a possibility that disadvantages such as a decrease in the electric conductivity and an adverse effect on the productivity occurs, the content of Cr is preferably 0.50% by mass or less.(Zr: 0.001% by mass or more and 0.50% by mass or less)

[0028] Zr (zirconium) is a component capable of improving heat resistance of the aluminum alloy wire. In order to exhibit this effect, it is preferable for the aluminum alloy wire to contain 0.001% by mass or more of Zr. On the other hand, the content of Zr is preferably 0.50% by mass or less because the effect is saturated and is not changed even if the content is too large, and there is a possibility that disadvantages such as a decrease in the electric conductivity and an adverse effect on the productivity occur.(Total amount of optional additive components: 0.001% by mass or more and 0.55% by mass or less)

[0029] The optional additive component composed of one or more components selected from the group consisting of Mn, Fe, Ni, Ti, Cr and Zr is preferably contained in a content of 0.001% by mass or more in total in order to obtain the effect of these optional additive components. These optional additive components can also take a form of solid solution or precipitation in the aluminum alloy wire, and can lead to solid solution strengthening by increasing the content thereof, strengthening by refining the crystal grains of a mother phase, and precipitation strengthening by promoting a reaction using the optional additive components. On the other hand, the contents of these optional additive components are preferably 0.55% by mass or less in total, because even if the contents are too large, the effect is saturated and does not change, and disadvantages such as a decrease in the electric conductivity and an adverse effect on the productivity may occur.<Balance: Al and inevitable impurities>

[0030] In the alloy composition of the aluminum alloy wire of the present invention, the balance other than the above-described elements is composed of Al and inevitable impurities. The term "inevitable impurities" as used herein refers to impurities that are generally present in a raw material of an aluminum alloy wire or are unavoidably mixed in the production process. The inevitable impurities are essentially unnecessary, but are in trace amounts and are acceptable because they do not affect the characteristics of the aluminum alloy wire. Examples of the inevitable impurities include nonmetallic elements such as sulfur (S), carbon (C) and oxygen (O), and metal elements such as V (vanadium), Ga (gallium) and Sb (antimony). The upper limit of the content of these components is preferably small because these components can be a factor for lowering the electric conductivity and the tensile strength. The upper limit can be 0.05% by mass for each of the above components, or 0.05% by mass in a total amount of the above components. More preferably, the amount of the components is 0.01% by mass for each component, or 0.01% by mass in total.[2] Metal Structure of Aluminum Alloy Wire

[0031] Next, the metal structure of the aluminum alloy wire will be described.

[0032] In a crystal orientation analysis of the aluminum alloy wire of the present invention by an electron backscatter diffraction (EBSD) method performed in an observation region of a transverse section perpendicular to the longitudinal direction thereof, an abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less is 85% or less with respect to all of the measurement points. Such a low-angle crystal orientation difference of 5° or less is often formed by dislocation defects. When the abundance proportion exceeds 85%, plastic working strain applied in the production process of the aluminum alloy wire is not considered to have been sufficiently removed. As a cause thereof, insufficient heating in a third heat treatment step (solution heat treatment step) to be described later can be exemplified. In other words, sufficient recrystallization does not proceed due to the insufficient heating, resulting in remaining strain. In addition, due to the insufficient heating in the third heat treatment step (solution heat treatment step), the solid solubility of Mg or Si is not sufficiently increased, and recovery of elongation characteristics and precipitation strengthening by the subsequent aging treatment step are insufficient. That is, by adjusting the abundance proportion of the measurement points having a crystal orientation difference between adjacent measurement points of 5° or less to 85% or less with respect to all of the measurement points in the measurement region, plastic working strain is sufficiently removed, and recovery of the elongation characteristics and the precipitation strengthening are achieved, so that the tensile strength and the elongation characteristics of the aluminum alloy wire can be enhanced. The longitudinal direction of the aluminum alloy wire means the drawing direction of the wire in the production process.

[0033] As used herein, the crystal orientation analysis by the electron backscatter diffraction (EBSD) method can be performed, for example, by continuously measuring crystal orientations using an EBSD detector (OIM 5.0 HIKARI manufactured by TSL Corporation) attached to a high-resolution scanning analytical electron microscope JSM-7001FA (manufactured by JEOL), and calculating (processing) crystal orientation data obtained by the measurement using analysis software (OIM-Analysis manufactured by TSL Solution Corporation) to obtain crystal orientation analysis data. "EBSD" is an abbreviation of Electron BackScatter Diffraction, and is a crystal orientation analysis technique using Kikuchi line generated when an aluminum alloy wire as a measurement sample is irradiated with an electron beam in a scanning electron microscope (SEM). An object to be measured is a transverse section perpendicular to the longitudinal direction of one aluminum alloy wire that has been polished and mirror-finished in advance. In the polishing of the transverse section, any means capable of mirror finishing such as wet polishing, FIB, or microtome can be used in addition to polishing using a cross-section polisher (registered trademark) apparatus, and there is no particular limitation to the specific means. The measurement region may be a range obtained by cutting out one aluminum alloy wire, and may be, for example, 50 µm to 300 µm square. The measurement of the crystal orientation when obtaining the crystal orientation data can be performed at a step size of, for example, 0.5 µm to 2 µm. In particular, by using analysis software for analysis of the crystal orientation data, when a specific angle range is allowed as a crystal orientation difference between adjacent measurement points, it is possible to easily determine, for each measurement point, whether or not the crystal orientation difference between adjacent measurement points is within the allowable range.

[0034] In the crystal orientation analysis by the electron backscatter diffraction (EBSD) method performed in the observation region of the transverse section perpendicular to the longitudinal direction of the aluminum alloy wire of the present invention, when crystal orientations within <100> orientation ±5° are defined as a <100> orientation group, crystal orientations within <110> orientation ±5° are defined as a <110> orientation group, and crystal orientations within <111> orientation ±5° are defined as a <111> orientation group, a ratio of the number of the crystal grains having the <111> orientation group to the total number of the crystal grains having the <100> orientation group and the <110> orientation group (<111> orientation group / (<100> orientation group + <110> orientation group)) is preferably in a range of 5 or more and 30 or less.

[0035] In this regard, the crystal grains having the <111> orientation group contribute to the improvement in the tensile strength of the aluminum alloy wire, but have a property of lowering the elongation characteristics. In addition, the crystal grains having the <111> orientation group may exist as a worked texture when the recrystallization does not sufficiently proceed. In such a case, in addition to decrease in the elongation characteristics, the crystal grains may cause insufficient precipitation strengthening due to insufficiently solubilized Mg or Si. As described above, the crystal grains having the <111> orientation group have a disadvantage of reducing the tensile strength and / or the elongation characteristics of the aluminum alloy wire, and when the ratio thereof is high, the disadvantage tends to be strongly exhibited.

[0036] In addition, the crystal grains having the <100> orientation group and the <110> orientation group do not contribute to the improvement in the tensile strength as much as the crystal grains having the <111> orientation group, but can improve the elongation characteristics. In addition, since the crystal grains having the <100> orientation group and the <110> orientation group accumulate when recrystallization sufficiently proceeds, when the proportion of the crystal grains having these orientation groups is high, the solid solubility of Mg or Si is high, and thus the tensile strength of the aluminum alloy wire can be increased. In particular, since there is an advantage that high tensile strength and elongation characteristics can be stably obtained by increasing both the recrystallization proportion and the solid solubility of the aluminum alloy wire, it is desirable to increase the proportion.

[0037] In particular, when the ratio of (<111> orientation group / (<100> orientation group + <110> orientation group)) is 1 or less, the proportion of the crystal grains having the <111> orientation group decreases, and thus the tensile strength of the aluminum alloy wire decreases. On the other hand, when the ratio of (<111> orientation group / (<100> orientation group + <110> orientation group)) is 100 or more, the ratio of (<100> orientation group + <110> orientation group) is small, and thus the elongation characteristics of the aluminum alloy wire are poor. In particular, when the solid solution or recrystallization of Mg or Si has not sufficiently progressed, it is difficult to stably obtain high tensile strength. Therefore, the ratio (<111> orientation group / (<100> orientation group + <110> orientation group)) is preferably in the range of 5 or more and 30 or less.

[0038] When in the analysis of the crystal orientation data obtained in the transverse section by the EBSD detector described above, a boundary with an orientation difference between adjacent measurement points of 15° or more is an interface (grain boundary) of a crystal grain, and a set of continuous measurement points in a range surrounded by the grain boundary is a crystal grain, the number ratio of the crystal grains having the <100> orientation group, the <110> orientation group, or the <111> orientation group, with respect to a total number of the crystal grains in the measurement region can be obtained.

[0039] In the aluminum alloy wire of the present invention, an average crystal grain size obtained from the crystal orientation analysis by the electron backscatter diffraction (EBSD) method performed in the observation region of the transverse section perpendicular to the longitudinal direction may be, for example, in the range of 5 µm or more and 20 µm or less, but is preferably in the range of 5 µm or more and 9 µm or less. In particular, when the average crystal grain size of the crystals contained in the metal structure of the aluminum alloy wire is adjusted to be included in the range of 5 µm or more and 9 µm or less, the average value or the standard deviation of one or both of the tensile strength and the elongation characteristic of the aluminum alloy wire can be further increased. On the other hand, when the average crystal grain size is less than 5 µm, since the solid solution of Mg or Si does not sufficiently proceed, and the precipitation strengthening is insufficient. In addition, when heating for crystallization is insufficient, plastic working strain applied in the production process of the aluminum alloy wire remains, and the elongation characteristics is also easily deteriorated. On the other hand, when the average crystal grain size is larger than 9 µm, particularly larger than 20 µm, wire breakage is likely to occur when recrystallization is performed by annealing during running.

[0040] Here, the average crystal grain size of the crystal grains of the aluminum alloy wire can be obtained in the following manner: assuming that, in the analysis of the crystal orientation data by the electron backscatter diffraction (EBSD) method described above, a boundary with an orientation difference between adjacent measurement points of 15° or more is an interface (grain boundary) of a crystal grain, and cross-sectional areas of the crystal grains are calculated by using the number of the continuous measurement points in a range surrounded by the grain boundaries and the step size described above, an average diameter of circles corresponding to the crystal grains is used as the average crystal size of the aluminum alloy wire.

[0041] Since the aluminum alloy wire of the present invention has high tensile strength and high elongation characteristics, even when the wire diameter (diameter) is adjusted to a small diameter in the range of 0.1 mm or more and 0.5 mm or less, high toughness can be provided. As used herein, the toughness is a characteristic that becomes high when both the tensile strength and the elongation characteristic are high, and when the aluminum alloy wire has high toughness, it is possible to easily maintain the original shape without breaking even when a force in the tensile direction is applied.

[0042] In addition, the aluminum alloy wire of the present invention can form an aluminum alloy twisted wire by twisting a plurality of wires together, and also in this case, high electric conductivity, tensile strength, and elongation characteristics can be improved. In this regard, the number of the aluminum alloy wire to be twisted and the total cross-sectional area of the twisted wires are not limited, but an aluminum alloy twisted wire having a small diameter with a cross-sectional area in a range of 0.1 mm 2< or more and 3.0 mm 2< or less can be formed by twisting 5 or more and 16 or less aluminum alloy wires having the above-described wire diameter.

[0043] Furthermore, the aluminum alloy wire of the present invention is preferably used for electric wires, and it is preferable to constitute an electric wire having the above-described aluminum alloy wire. More specifically, an electric wire including the aluminum alloy wire or the aluminum alloy twisted wire, and an insulating coating layer that covers the outer periphery of the aluminum alloy wire or the aluminum alloy twisted wire can be configured. Since such an electric wire can improve tensile strength, electric conductivity, and elongation characteristics in a well-balanced manner, the weight of a wire harness can be reduced by reducing the weight of an electric wire having a particularly small diameter. That is, it is also preferable to configure a wire harness having an electric wire with the above-described aluminum alloy wire.[3] One Example of Production Processes of Aluminum Alloy Wire

[0044] The aluminum alloy wire described above can be realized by controlling the alloy composition and the production process in combination, and the production process is not particularly limited. Among them, the following method can be raised as one example of the production processes capable of obtaining the aluminum alloy wire described above.

[0045] As an example of the method for producing the aluminum alloy wire of the present invention, the following method can be raised: an aluminum alloy material having an alloy composition substantially the same as the alloy composition of the above-described aluminum alloy wire is sequentially subjected to at least a continuous casting and rolling step, a first heat treatment step, a first wire drawing step, a second heat treatment step, a second wire drawing step, and a third heat treatment step.[Continuous Casting and Rolling Step]

[0046] In the method for producing the aluminum alloy wire of the present invention, first, an aluminum raw material and additive elements are selected so as to obtain a desired component composition, and a continuous casting and rolling step is performed to obtain an aluminum wire rod. The casting method in the continuous casting and rolling step is not limited, but it is preferable from the viewpoint of production efficiency to use a Properzi type continuous casting and rolling machine, in which a casting ring and a belt are combined and a wire rod can be obtained by continuously pouring an aluminum melt into a ring-shaped groove mold to cast, and continuously rolling.

[0047] In the continuous casting and rolling step, for example, a rolled material having a cross-sectional area corresponding to a wire diameter of 9 mm or more and 10 mm or less can be obtained by rolling with a two-way roll or a three-way roll after casting using a continuous casting and rolling machine.

[0048] Although continuous wire drawing is performed on the rolled material until the wire diameter is in the range of 0.1 mm or more and 0.5 mm or less, since the heat treatment performed during the wire drawing affects the crystal orientation distribution of the aluminum alloy wire, it is important to perform heat treatment under appropriate heat treatment condition. At the same time, if a total processing ratio of the wire drawing process is increased without performing the heat treatment, the deformation resistance increases, so that the aluminum alloy wire easily breaks, and the abrasion damage of a die used in the wire drawing process becomes rapid. Therefore, it is useful, from the viewpoint of enhancing not only the mechanical properties but also the mass productivity, to soften by performing the heat treatment at an appropriate timing. More specifically, two or more heat treatment steps are preferably performed except for the heat treatment (heat treatment in the third heat treatment step) performed after the second wire drawing step described later, and the heat treatment condition at that time are preferably performed in a temperature range of 300°C or more and 400°C or less for 1 hour or more and 8 hours or less, for each heat treatment.

[0049] In the following description, an embodiment in which after the continuous casting and rolling step, the first wire drawing step and the second wire drawing step are performed as wire drawing, and the first heat treatment step and the second heat treatment step are performed before each of these wire drawing steps will be described, but the present invention is not limited to this embodiment. As described above, by sequentially performing the first heat treatment step, the first wire drawing step, the second heat treatment step, and the second wire drawing step after performing the continuous casting and rolling step, it is possible to conduct the heat treatment for the aluminum wire at the timing when cold wire drawing is performed at a processing ratio of a certain level or higher, and it is possible to easily perform the wire drawing step and the heat treatment step when continuous processing equipment is used.[First Heat Treatment Step]

[0050] The first heat treatment step is a step of heat-treating the aluminum wire rod as a rolled material having a cross-sectional area corresponding to a wire diameter of 9 mm or more and 10 mm or less in a temperature range of 300°C or more and 400°C or less for 1 hour or more and 8 hours or less. The first heat treatment step is a step for softening the aluminum wire rod and intentionally precipitating pinning particles that prevent crystals from being coarsened.

[0051] Since the crystal orientation during performing the first heat treatment step also affects the crystal orientation after the later-described third heat treatment step, the first heat treatment step needs to be performed in a temperature range of 300°C or more and 400°C or less for 1 hour or more and 8 hours or less. Here, when the heat treatment temperature is less than 300°C or when the heat treatment time is less than 1 hour, it is difficult to perform the first wire drawing step and the second wire drawing step described later because the aluminum wire rod cannot be sufficiently softened. When the heat treatment temperature exceeds 400°C or when the heat treatment time exceeds 8 hours, coarsening of the metal structure occurs, and thus the crystal orientation distribution of the obtained aluminum alloy wire is easily changed. When the size of the precipitate generated during the heat treatment is increased, the precipitate cannot serve as grain boundary pinning in the third heat treatment step described later, and the crystal grain size of the aluminum alloy wire obtained thereby is coarsened, which causes the aluminum alloy wire to easily break and causes deterioration in the tensile strength and the elongation characteristics.

[0052] The first heat treatment step can be performed using a known method such as a bell furnace.[First Wire Drawing Step]

[0053] The first wire drawing step is a step of performing cold wire drawing on the aluminum wire rod after the first heat treatment step. Thereby, it is preferable to obtain a rolled material having a cross-sectional area corresponding to a wire diameter of 1 mm or more and 3 mm or less.

[0054] The first wire drawing step can be performed by a known method such as wire-drawing processing that uses a die. More specifically, for the die material and dimensions, the wire drawing oil, the pass reduction, and the like, which are wire drawing conditions, general conditions in aluminum wire mass production can be employed. The first wire drawing step may be performed in one pass, or may be performed in a plurality of passes until a target wire diameter is obtained.[Second Heat Treatment Step]

[0055] The second heat treatment step is a step of heat-treating the aluminum wire after the first wire drawing step in a temperature range of 300°C or more and 400°C or less for 1 hour or more and 8 hours or less. Similarly to the first heat treatment step, the second heat treatment step is also a step for softening the aluminum wire and intentionally precipitating pinning particles preventing coarsening of crystals.

[0056] For the same reason as in the first heat treatment step, the heat treatment in the second heat treatment step needs to be performed in a temperature range of 300°C or more and 400°C or less for 1 hour or more and 8 hours or less.

[0057] Similarly to the first heat treatment step, the second heat treatment step can be performed using a known method such as a bell furnace.[Second Wire Drawing Step]

[0058] The second wire drawing step is a step of performing cold wire drawing on the aluminum wire after the first heat treatment step. Thereby, an aluminum wire having a desired cross-sectional area can be obtained. Here, the cross-sectional area of the aluminum wire after the second wire drawing step is not particularly limited, but may be, for example, a cross-sectional area corresponding to a wire diameter of 0.1 mm or more and 0.5 mm or less.

[0059] Similarly to the first wire drawing step, the second wire drawing step can be performed by a known method such as wire-drawing processing using a die. The second wire drawing step may be performed in one pass, or may be performed in a plurality of passes until a target wire diameter is obtained.[Third Heat Treatment Step]

[0060] The third heat treatment step is a solution heat treatment, and is a step of heat-treating the aluminum wire after the second wire drawing step in a temperature range of 500°C or more and 580°C or less for 3 seconds or more and 60 seconds or less. By this step, the element in the precipitated state forms a solid solution, and the crystal orientation precipitated by recrystallization in the aluminum alloy wire is determined. Here, when the heat treatment temperature is less than 500°C or when the heat treatment time is less than 3 seconds, in the crystal orientation analysis by the electron backscatter diffraction (EBSD) method described above, the abundance proportion of the measurement points having a crystal orientation difference between adjacent measurement points of 5° or less with respect to all of the measurement points exceeds 85%. When the heat treatment temperature exceeds 580°C or when the heat treatment time exceeds 60 seconds, grain growth occurs in the metal structure of the obtained aluminum alloy wire, which causes deterioration in the tensile strength and / or the elongation characteristics, and causes the aluminum alloy wire to easily break.

[0061] The heat treatment condition of the third heat treatment step may also affect the ratio of the number of the crystal grains having the <111> orientation group to the total number of the crystal grains having the <100> orientation group and the <110> orientation group. When the heat treatment temperature is low or when the heat treatment time is short, since the number of the crystal grains having the <111> orientation group increases, the ratio (<111> orientation group / (<100> orientation group + <110> orientation group)) also tends to increase. At this time, the solid solution does not sufficiently progress, and the formation of crystal grains having a desired crystal orientation by recrystallization also does not sufficiently progress, which may cause a decrease in the tensile strength and the elongation characteristics of the aluminum alloy wire. When the heat treatment temperature is high or when the heat treatment time is long, the number of the crystal grains having the <100> orientation group and the number of the crystal grains having the <110> orientation group increase, and thus the tensile strength of the aluminum alloy wire tends to decrease. In addition, in these cases, coarsening of the crystal grains causes a decrease in the tensile strength and the elongation characteristics, and the aluminum alloy wire is easier to break.

[0062] The third heat treatment step can be performed using a known method such as an annular furnace, but since the heating time is short, it is preferable to rapidly heat the aluminum wire while confirming achieving temperature of the aluminum wire. The aluminum wire after the third heat treatment step is preferably rapidly cooled by water cooling or the like.

[0063] Here, before or after the third heat treatment step, a twisting step of twisting a plurality of aluminum wire by a twisting machine or a compression step of compressing the twisted wires may be performed. This makes it possible to produce an aluminum alloy twisted wire obtained by twisting a plurality of aluminum alloy wires without substantially affecting the metal structure even by the twisting step or the compression step.[Aging Step]

[0064] The aging treatment step is a step of holding the aluminum wire after the third heat treatment step at a temperature lower than that of the third heat treatment step or performing a heat treatment. By this step, in the metal structure of the aluminum wire, crystal grains can be precipitated in a desired balance of crystal orientation by recrystallization, and therefore, the aluminum alloy wire and the aluminum alloy twisted wire can be obtained, which have high tensile strength and high electric conductivity, also have excellent elongation characteristics, thus, display an excellent balance in these characteristics, and have small variations in the tensile strength and the elongation characteristics along the longitudinal direction.

[0065] In the aging treatment step, at least an artificial aging treatment in which the aluminum wire is heat-treated is performed, but a natural aging treatment in which the aluminum wire is held under a temperature condition close to ambient temperature may be further performed before the artificial aging treatment. Here, the heat treatment in the artificial aging treatment can be performed in a temperature range of 100°C or more and 200°C or less for 2 hours or more and 10 hours or less. In addition, the natural aging treatment can be carried out by holding the aluminum wire for 24 hours or more in a temperature range of 20°C or more and 50°C or less.

[0066] The aluminum alloy wire or the aluminum alloy twisted wire obtained as described above is subjected to an extrusion coating step of extrusion coating along the outer circumference of the aluminum alloy wire or the aluminum alloy twisted wire to conduct insulating coating, whereby an electric wire can be produced.

[0067] Although the embodiments have been described above, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present disclosure, including all aspects included in the concept of the present disclosure and the claims.EXAMPLES

[0068] Next, Examples of the present invention and Comparative Examples will be described, but the present invention is not limited to these Examples.

[0069] Aluminum raw materials and additive elements were selected so as to have the compositions shown in Table 1, and a continuous casting and rolling step was performed using a continuous casting and rolling machine (manufactured by Properzi) to produce an aluminum wire rod as a rolled material having a transverse section perpendicular to the longitudinal direction corresponding to a circular shape having a diameter of 9.5 mm. After the aluminum wire rod was subjected to the first heat treatment step under the condition of the temperature and the time shown in Table 1, the aluminum wire rod was subjected to the first wire drawing step of adjusting the size of the transverse section to a size corresponding to a circular shape having a diameter of 2.6 mm, then subjected to the second heat treatment step under the condition of the temperature and the time shown in Table 1, and then subjected to the second wire drawing step of adjusting the size of the transverse section to a size corresponding to a circular shape having a diameter of 0.3 mm. Here, the first heat treatment step and the second heat treatment step were performed in an inert gas environment of a bell furnace.

[0070] The aluminum wire after the second wire drawing step was subjected to the third heat treatment step, which was a solution heat treatment, under the condition of the temperature and the time shown in Table 1, and then immediately cooled by water cooling. Here, the third heat treatment step was performed while heating the aluminum wire in a protective tube in an annular furnace and confirming the achieving temperature with a thermocouple.

[0071] After the third heat treatment step was performed, as the aging treatment step, a natural aging treatment in which the aluminum wire was held in a temperature range of 25°C or more and 40°C or less for 24 hours or more and an artificial aging treatment in which heat treatment was performed in a temperature range of 120°C or more and 170°C or less for 5 hours were performed in the air to obtain the aluminum alloy wires of the Examples of the present invention and Comparative Examples. In an actual aluminum electric wire production process, a twisting step and a compressing step may be performed after these aging treatments are performed, but since the influence of these steps on the characteristics is extremely small, they are omitted in the Examples of the present invention and the Comparative Examples.[Various Measurements and Evaluation Methods]

[0072] The aluminum alloy wires obtained in the Examples of the present invention and the Comparative Examples were subjected to the following characteristic evaluations. The evaluation conditions of each characteristic are as follows.[1] Measurement of Abundance Proportion of Measurement Points having Crystal Orientation Difference between Adjacent Measurement Points of 5° or less with respect to All of Measurement Points

[0073] The abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less with respect to all of the measurement points was obtained from crystal orientation analysis data calculated using the electron backscatter diffraction (EBSD) method. In this regard, the crystal orientation analysis data calculated using the electron backscatter diffraction (EBSD) method was obtained by continuously measuring crystal orientations using an EBSD detector (OIM 5.0 HIKARI manufactured by TSL Corporation) attached to a high-resolution scanning analytical electron microscope JSM-7001FA (manufactured by JEOL), and calculating (processing) crystal orientation data obtained by the measurement using analysis software (OIM-Analysis manufactured by TSL Solution Corporation) to obtain the abundance proportion with respect to all of the measurement points in the measurement region. An object to be measured was a transverse section perpendicular to the longitudinal direction of one aluminum alloy wire that had been polished and mirror-finished in advance. A cross-section polisher (registered trademark) apparatus was used to polish the transverse section. The measurement region was a range obtained by cutting out one aluminum alloy wire, and more specifically, was a range of an area corresponding to a circle having a diameter of 0.3 mm. When obtaining crystal orientation data, the crystal orientation was measured at a step size of 0.5 µm. At this time, the measurement results of the orientation difference between adjacent measurement points were provided in numerical values in increments of 1°. In addition, also in the determination regarding whether or not the crystal orientation difference between adjacent measurement points was 5° or less, measurement results of the crystal orientation difference were similarly provided in numerical values in increments of 1°. When a measurement result is in the range of 1° or more and 5° or less, the crystal orientation difference between the adjacent measurement points was determined as being 5° or less. The results are shown in Table 2.[2] Measurement of Ratio of Number of Crystal Grains having <111> Orientation Group to Total Number of Crystal Grains having <100> Orientation Group and Crystal Grains having <110> Orientation Group

[0074] Assuming that in the analysis of the crystal orientation data obtained in the transverse section by the EBSD detector described above, a boundary with an orientation difference between adjacent measurement points of 15° or more is an interface (grain boundary) of a crystal grain, and a set of continuous measurement points in a range surrounded by the grain boundary is a crystal grain, the number of the crystal grains having the <100> orientation group which is a crystal orientation within <100> orientation ±5°, the number of the crystal grains having the <110> orientation group which is a crystal orientation within <110> orientation ±5°, and the number of the crystal grains having the <111> orientation group which is a crystal orientation within <111> orientation ±5° were obtained and the ratio (<111> orientation group / (<100> orientation group + <110> orientation group)) was obtained from the numbers of the crystal grains having these orientation groups. The results are shown in Table 2.[3] Measurement of Average Crystal Grain Size of Crystal Grains

[0075] An average crystal grain size of the crystal grains of the aluminum alloy wire was determined in the following manner: assuming that a boundary with an orientation difference between adjacent measurement points of 15° or more in the analysis of the crystal orientation data by the electron backscatter diffraction (EBSD) method is an interface (grain boundary) of the crystal grain, cross-sectional areas of the crystal grains were calculated using the number of the continuous measurement points present in a range surrounded by grain boundaries and the step size described above, and an average diameter of circles corresponding to the crystal grains obtained therefrom was used as the average crystal grain size of the crystal grains. The results are shown in Table 2.[4] Measurement and Evaluation of Tensile Strength

[0076] For the tensile strength of the aluminum alloy wire, test pieces having a length of 200 mm including positions at 0 m, 500 m, 1000 m, 1500 m, and 2000 m from one end of the aluminum alloy wire were cut out from the aluminum alloy wire having a length of 2000 m. The tensile strength Rm of these test pieces was determined based on JIS Z2241, and an average value and a standard deviation of the tensile strength Rm at these five positions were defined as the average value [MPa] and the standard deviation [MPa] of the tensile strength, respectively.

[0077] When the average value of the obtained tensile strength was 250 MPa or more, the aluminum alloy wire was evaluated as "excellent (expressed by a bullseye symbol ⊙)" in that the average value of the tensile strength was sufficiently large and the aluminum alloy wire can be used alone without being mounted on a connector. When the average value of the tensile strength was in the range of 230 MPa or more and less than 250 MPa, the aluminum alloy wire was evaluated as "good (expressed by a circle symbol O)" in that the average value of the tensile strength was large and the aluminum alloy wire can be used in a state of being accommodated in a general connector. On the other hand, when the average value of the tensile strength was less than 230 MPa, the aluminum alloy wire was evaluated as "poor (expressed by a cross symbol (X))" in that the average value of the tensile strength was small and the aluminum alloy wire can be broken even if the aluminum alloy wire is put in a connector. In the Examples of the present invention and Comparative Examples, "⊙" and "O" were evaluated as acceptable levels. The results are shown in Table 2.

[0078] Regarding the standard deviation of the obtained tensile strength, when the standard deviation of the tensile strength was 5.00 MPa or less, the aluminum alloy wire was evaluated as "excellent (expressed by a bullseye symbol ⊙)" in that the standard deviation of the tensile strength was sufficiently small and the tensile strength of the aluminum alloy wire can be obtained particularly stably. When the standard deviation of the tensile strength was in the range of more than 5.00 MPa and 10.00 MPa or less, the aluminum alloy wire was evaluated as "good (expressed by a circle symbol O)" in that the standard deviation of the tensile strength was small and the tensile strength was stably obtained, similarly to the case where the tensile strength of the aluminum alloy wire was evaluated as "⊙". On the other hand, when the standard deviation of the tensile strength exceeded 10.00 MPa, the aluminum alloy wire was evaluated as "poor (expressed by a cross symbol (X))" in that the tensile strength of the aluminum alloy wire was not stably obtained. In the Examples of the present invention and Comparative Examples, "⊙" and "O" were evaluated as acceptable levels. The results are shown in Table 2.[5] Measurement and Evaluation of Elongation Characteristics

[0079] For the elongation characteristics of the aluminum alloy wire, test pieces having a length of 200 mm including positions at 0 m, 500 m, 1000 m, 1500 m, and 2000 m from one end of the aluminum alloy wire were cut out from the aluminum alloy wire having a length of 2000 m. Elongations at break A of these test pieces were determined based on JIS Z2241, and an average value and a standard deviation of the elongations at break A at these five positions were defined as the average value [%] and the standard deviation [%] of the elongation characteristics, respectively.

[0080] When the average value of the obtained elongation characteristics was 14.0% or more, the aluminum alloy wire was evaluated as "excellent (expressed by a bullseye symbol ⊙)" in that the average value of the elongation characteristics was sufficiently large and the aluminum alloy wire can be used alone without being mounted on a connector. When the average value of the elongation characteristics was in the range of 12.0% or more and less than 14.0%, the aluminum alloy wire was evaluated as "good (expressed by a circle symbol O)" in that the average value of the elongation characteristics was large and the aluminum alloy wire could be used in a state of being accommodated in a general connector. On the other hand, when the average value of the elongation characteristics was less than 12.0%, the aluminum alloy wire was evaluated as "poor (expressed by a cross symbol (X))" in that the average value of the elongation characteristics was small and the aluminum alloy wire can be broken even if the aluminum alloy wire is put in a connector. In the Examples of the present invention and Comparative Examples, "⊙" and "O" were evaluated as acceptable levels. The results are shown in Table 2.

[0081] When the standard deviation of the obtained elongation characteristics was 0.30% or less, the aluminum alloy wire was evaluated as "excellent (expressed by a bullseye symbol ⊙)" in that the standard deviation of the elongation characteristics was sufficiently small and the elongation characteristics of the aluminum alloy wire can be obtained particularly stably. When the standard deviation of the elongation characteristics was in the range of more than 0.30% and 0.80% or less, the aluminum alloy wire was evaluated as "good (expressed by a circle symbol O)" in that the standard deviation of the tensile strength was small and the tensile strength was stably obtained, similarly to the case where the tensile strength of the aluminum alloy wire was evaluated as "⊙". On the other hand, when the standard deviation of the elongation characteristics exceeded 0.80%, the aluminum alloy wire was evaluated as "poor (expressed by a cross symbol (X))" in that the elongation characteristics of the aluminum alloy wire was not stably obtained. In the Examples of the present invention and Comparative Examples, "⊙" and "O" were evaluated as acceptable levels. The results are shown in Table 2.[6] Electric Conductivity Measurement and Evaluation

[0082] The electric conductivity of the aluminum alloy wire was measured twice in accordance with JIS H0505 (-1975), and the average value of the electric conductivity obtained by the two measurements was defined as the measured value [% IACS] of the electric conductivity.

[0083] When the measured value of the electric conductivity exceeded 50.0% IACS, the aluminum alloy wire was evaluated as "excellent (expressed by a bullseye symbol ⊙)" in that the aluminum alloy wire had a sufficiently large electric conductivity and was likely to be an electric wire capable of responding to further reduction in diameter in the future. When the measured value of the electric conductivity was in the range of 48.0% IACS or more and 50.0% IACS or less, the aluminum alloy wire was evaluated as "good (expressed by a circle symbol ○)" in that the value of the electric conductivity was large and good for an aluminum alloy wire that constitutes current diameter-reduced electric wires. On the other hand, when the measured value of the electric conductivity was less than 48.0% IACS, the aluminum alloy wire was evaluated as "poor (expressed by a cross symbol X" in that the value of the electric conductivity was small and the aluminum alloy wire was poor as an aluminum alloy wire that constitutes the diameter-reduced electric wires. In the Examples of the present invention and Comparative Examples, "⊙" and "O" were evaluated as acceptable levels. The results are shown in Table 2.

[0084] The above-mentioned "% IACS" is a unit of electric conductivity when the resistivity of 1.7241×10 -8< Ωm of universal standard soft copper (International Annealed Copper Standard) is taken as 100% IACS.[7] Overall Evaluation

[0085] Among these evaluation results, regarding all of the five evaluation results relating to the average value of the tensile strength, the standard deviation of the tensile strength, the average value of the elongation characteristics, the standard deviation of the elongation characteristics, and the electric conductivity, the aluminum alloy wire evaluated as "⊙" for all of the five evaluation items was evaluated as "⊙" on account of being particularly excellent in that the aluminum alloy wire had excellent elongation characteristics while having high tensile strength and high electric conductivity, and had small variations in the tensile strength and the elongation characteristics along the longitudinal direction. Further, regarding these five evaluation items, the aluminum alloy wire evaluated as "⊙" or "○" (excluding the aluminum alloy wire that was evaluated as "⊙" for all of the five evaluation items) for all of the five evaluation items was evaluated as "○" on account of being excellent in that the aluminum alloy wire had excellent elongation characteristics while having high tensile strength and high electric conductivity, and had small variations in the tensile strength and the elongation characteristics along the longitudinal direction. On the other hand, regarding these five evaluation items, the aluminum alloy wire evaluated as "x" in at least one of them was evaluated as "x" as failing in at least one of the tensile strength, the electric conductivity, and the elongation characteristics, or failing in that the variation in the tensile strength or the elongation characteristics along the longitudinal direction was large. The results are shown in Table 2. [Table 1]Aluminum alloy wireProduction condition of aluminum alloy wireAlloy composition (% by mass)First heat treatment stepSecond heat treatment stepThird heat treatment stepEssential additiveOptional additiveTotal of optional additiveAlMgSiMnFeNiTiCrZrTemperature (°C)Time (h)Temperature (°C)Time (h)Temperature (°C)Time (h)Inventive Example 10.350.40------0.00Balance3502400556010Inventive Example 20.500.70------0.00Balance3502400556010Inventive Example 30.500.70------0.00Balance3008300454010Inventive Example 40.500.70------0.00Balance350230025603Inventive Example 50.500.70------0.00Balance3004350452040Inventive Example 60.600.80------0.00Balance3502400556010Inventive Example 70.600.80------0.00Balance3254350354010Inventive Example 80.600.80------0.00Balance3506350255015Inventive Example 90.600.80------0.00Balance3751300254010Inventive Example 100.700.90------0.00Balance3502400556010Inventive Example 110.500.700.100.150.100.01--0.36Balance3002400556015Inventive Example 120.500.700.100.150.100.01--0.36Balance3502325254010Inventive Example 130.500.700.100.150.100.01--0.36Balance3502375254010Inventive Example 140.500.700.100.150.100.01--0.36Balance3255350254010Inventive Example 150.500.700.100.050.20---0.35Balance3502400556010Inventive Example 160.500.70-0.050.10-0.15-0.30Balance3502400556010Inventive Example 170.500.70-0.050.10-0.15-0.30Balance3008375254010Inventive Example 180.500.70-0.050.10-0.15-0.30Balance3502350254010Inventive Example 190.500.70-0.050.10-0.15-0.30Balance4001325254010Inventive Example 200.500.70-0.10-0.03-0.050.18Balance3502400556010Inventive Example 210.500.700.100.100.15-0.20-0.55Balance3502400556010Inventive Example 220.500.70-0.20-0.02-0.100.32Balance3502400556010Comparative Example 10.150.20------0.00Balance3502300254010Comparative Example 20.801.10------0.00Balance3254350255010Comparative Example 30.500.70------0.00Balance250 23502480 1 Comparative Example 40.500.70------0.00Balance3250.5 250 0.5 5205Comparative Example 50.500.70------0.00Balance3002200 0.5 50010Comparative Example 60.500.70------0.00Balance35023502450 25Comparative Example 70.500.700.100.150.100.01--0.36Balance475 2350255015Comparative Example 80.500.700.100.150.100.01--0.36Balance3502500 10 54010Comparative Example 90.500.700.100.150.100.01--0.36Balance35023502450 5Comparative Example 100.500.700.100.150.100.01--0.36Balance3508350256090 Comparative Example 110.500.70-0.050.10-0.15-0.30Balance200 8350254010Comparative Example 120.500.70-0.050.10-0.15-0.30Balance3502200 0.5 590 10Comparative Example 130.500.70-0.050.10-0.15-0.30Balance3502450 10 50010Comparative Example 140.500.70-0.050.10-0.15-0.30Balance35023502480 5Note: underlined bold letters in the Table indicate that the value is outside the preferred range of the present invention. [Table 2] Metal structurePerformance evaluationOverall evaluationAbundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less with respect to all of the measurement points in the measurement regionRatio of the number of the crystal grains having the <111> orientation group to the total number of the crystal grains having the <100> orientation group and the <110> orientation group 〈111〉 / (〈100〉+〈110〉)Average crystal grain size (µm)Tensile strengthElongation characteristicsElectric conductivityAverage valueStandard deviationAverage valueStandard deviationAverage valueResult (MPa)EvaluationResult (MPa)EvaluationResult (%)EvaluationResult (%)EvaluationResult (%IACS)EvaluationInventive Example 1721516239○7.45○14.2⊚0.35○52.3⊚○Inventive Example 2752014238○6.25○13.4○0.33○50.1⊚○Inventive Example 37379255⊚3.56⊚143⊚0.26⊚50.3⊚⊚Inventive Example 481139254⊚4.55⊚14.1⊚0.21⊚50.6⊚⊚Inventive Example 57368252⊚3.25⊚143⊚0.11⊚50.4⊚⊚Inventive Example 6681013254⊚5.65○12.8○0.36○48.8○○Inventive Example 775209255⊚3.20⊚14.2⊚0.25⊚50.3⊚⊚Inventive Example 878206254⊚3.12⊚14.1⊚0.28⊚50.5⊚⊚Inventive Example 98145251⊚3.88⊚14.8⊚0.17⊚50.6⊚⊚Inventive Example 10662512273⊚5.31○12.6○0.35○48.3○○Inventive Example 11682011255⊚5.15○13.3○0.42○48.5○○Inventive Example 12742810260⊚5.21○14.5⊚0.37○48.8○○Inventive Example 1378189261⊚3.85⊚14.5⊚0.19⊚50.3⊚⊚Inventive Example 148299263⊚2.58⊚14.6⊚0.16⊚50.2⊚⊚Inventive Example 15582312245○5.67○13.1○0.35○48.7○○Inventive Example 16722713243○5.25○12.8○0.39○48.6○○Inventive Example 17771510263⊚5.35○14.6⊚0.44○49.0○○Inventive Example 1880237268⊚3.83⊚142⊚0.19⊚50.4⊚⊚Inventive Example 1981259260⊚2.64⊚14.3⊚0.14⊚50.3⊚⊚Inventive Example 20741014243○5.85○12.8○0.45○48.7○○Inventive Example 21782815243○5.19○13.1○0.58○48.7○○Inventive Example 22781512245○5.45○12.8○0.62○49.0○○Comparative Example 1741513179 x5.27○18.1⊚0.66○55.0⊚xComparative Example 2772011292⊚6.15○10.8 ×0.34○43.9 ××Comparative Example 388 15010185 ×20.00 ×11.0 ×2.10 ×51.4⊚×Comparative Example 492 7510214 ×14.63 ×11.0 ×1.13 ×49.7○×Comparative Example 587 806234○16.21 ×11.9 ×1.14 ×49.3○×Comparative Example 689 10010223 ×12.34 ×11.6 ×0.88 ×49.6○×Comparative Example 790 1206218 ×10.30 ×11.0 ×0.89 ×49.2○×Comparative Example 892 209208 ×16.91 ×10.9 ×0.84 ×49.9○×Comparative Example 988 7510194 ×13.56 ×10.2 ×0.87 ×51.6⊚×Comparative Example 1090 25025176 ×11.66 ×8.5 ×1.03 ×47.5 ××Comparative Example 1191 259210 ×13.84 ×10.3 ×1.01 ×49.9○×Comparative Example 1293 9015195 ×11.06 ×10.0 ×1.03 ×47.3 ××Comparative Example 1392 2509202 ×9.27○10.3 ×0.94 ×49.9○×Comparative Example 1491 20011206 ×9.70○10.0 ×1.03 ×50.6⊚× Note: underlined bold letters in the Table indicate that the value is outside the preferred range of the present invention.

[0086] As shown in Tables 1 and 2, in Examples 1 to 22 of the present invention, as a result of producing the aluminum alloy wires having a predetermined alloy composition by performing the first heat treatment step, the second heat treatment step, and the third heat treatment step of the production process under the control of the predetermined conditions, the aluminum alloy wires where an abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less was 85% or less with respect to all the measurement points were obtained, in the crystal orientation analysis of the transverse section of the aluminum alloy wire by the electron backscatter diffraction (EBSD) method. As a result of the evaluation, the aluminum alloy wires of all of Examples 1 to 22 of the present invention were confirmed to have excellent elongation characteristics while having high tensile strength and high electric conductivity, and display an excellent balance and small variations in the tensile strength and the elongation characteristics along the longitudinal direction.

[0087] On the other hand, in Comparative Example 1 in which the contents of both Mg and Si in the alloy composition were outside the appropriate range due to low contents thereof, the average value of the tensile strength did not meet the acceptable level and was poor. In Comparative Example 2 in which the contents of both Mg and Si in the alloy composition were outside the appropriate range due to high contents thereof, the average values of the elongation characteristics and the electric conductivity did not meet the acceptable level and were poor. In Comparative Examples 3 to 14 in which the abundance proportion of the measurement points having a crystal orientation difference between adjacent measurement points of 5° or less with respect to all of the measurement points exceeded 85%, at least the average value of the tensile strength, the average value and the standard deviation of the elongation characteristics did not meet the acceptable level and were poor.

Examples

examples

[0068]Next, Examples of the present invention and Comparative Examples will be described, but the present invention is not limited to these Examples.

[0069]Aluminum raw materials and additive elements were selected so as to have the compositions shown in Table 1, and a continuous casting and rolling step was performed using a continuous casting and rolling machine (manufactured by Properzi) to produce an aluminum wire rod as a rolled material having a transverse section perpendicular to the longitudinal direction corresponding to a circular shape having a diameter of 9.5 mm. After the aluminum wire rod was subjected to the first heat treatment step under the condition of the temperature and the time shown in Table 1, the aluminum wire rod was subjected to the first wire drawing step of adjusting the size of the transverse section to a size corresponding to a circular shape having a diameter of 2.6 mm, then subjected to the second heat treatment step under the condition of the tempera...

TECHNICAL FIELD

[0001] The present invention relates to an aluminum alloy wire, an electric wire, and a wire harness.BACKGROUND ART

[0002] In recent years, electric equipment of automobiles has been increasing, and the amount of wire harnesses used for transmitting electric signals has also increased. Accordingly, there is a problem that the total weight of the wire harness per automobile becomes several ten of kilograms due to an increase in the weight of the electric wires constituting the wire harness.

[0003] Although attempts have been made to reduce the weight of the wire harness, for example by reducing the diameter of the electric wire, such attempts have not been sufficient to reduce the weight of the wire harness. On the other hand, as one of the means for reducing the weight of a wire harness, replacement of a copper electric wire with an aluminum electric wire has progressed especially among large-diameter electric wires. Particularly, in recent years, a movement of replacing a copper electric wire with a high-strength aluminum alloy wire has been widened for also small-diameter electric wires.

[0004] As a material for such a high-strength aluminum alloy wire, a 6000 series aluminum alloy is often selected.

[0005] For example, Patent Document 1 discloses an aluminum alloy wire used for a conductor, the aluminum alloy wire containing Mg in a content of 0.2% by mass or more and 1.5% by mass or less, Si in a content of 0.1% by mass or more and 2.0% by mass or less, Fe in a content of 0.1% by mass or more, and 1.0% by mass or less, or at least one element selected from Cu, Cr, Mn, or Zr and Fe in a total content of 0.1% by mass or more and 1.0% by mass or less, Ti in a content of 0.08% by mass or less, and B in a content of 0.016% by mass or less, with a balance being Al and impurities, and having an electric conductivity of 40% IACS or more, a tensile strength of 150 MPa or more, an elongation of 5% or more, a wire diameter of 0.5 mm or less, and a maximum crystal grain size of 50 µm or less.

[0006] Patent Document 2 discloses an aluminum alloy conductor containing Fe in a content of 0.01 to 0.4% by mass, Mg in a content of 0.01% by mass or more and less than 0.3% by mass, Si in a content of 0.01% by mass or more and less than 0.3% by mass, and Cu in a content of 0.01 to 0.5% by mass, with a balance being Al and inevitable impurities. In the aluminum alloy conductor, an area ratio of crystal grains having a plane inclining by an angle of 25° or more relative to the normal direction from a (111) plane disposed parallel to a cross section of the wire perpendicular to the wire drawing direction is at least 50% in a circle of a radius of (3 / 10)R from the center thereof, where R is the radius of the wire; and an area ratio of crystal grains having a plane inclining by an angle of 0° or more and less than 25° relative to the normal direction from a (111) plane disposed parallel to a cross section of the wire perpendicular to the wire drawing direction is at least 50% in an area of the entire wire excluding an inner circle of a radius of (7 / 10)R from the center thereof.

[0007] Further, Patent Document 3 discloses an aluminum alloy wire having a composition including Mg: 0.1 to 1.0% by mass, Si: 0.1 to 1.0% by mass, Fe: 0.01 to 1.40% by mass, Ti: 0.000 to 0.100% by mass, B: 0.000 to 0.030% by mass, Cu: 0.00 to 1.00% by mass, Ag: 0.00 to 0.50% by mass, Au: 0.00 to 0.50% by mass, Mn: 0.00 to 1.00% by mass, Cr: 0.00 to 1.00% by mass, Zr: 0.00 to 0.50% by mass, Hf: 0.00 to 0.50% by mass, V: 0.00 to 0.50% by mass, Sc: 0.00 to 0.50% by mass, Sn: 0.00 to 0.50% by mass, Co: 0.00 to 0.50% by mass, Ni: 0.01 to 0.50% by mass, Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr, Hf, V, Sc, Sn, Co, and Ni in a total content of 2.00% by mass or less, with a balance being Al and inevitable impurities. In the aluminum alloy wire, an area ratio of a region where an angle between a longitudinal direction of the aluminum alloy wire and a <111> direction of the crystal is within 20° is 20% or more and 65% or less.Citation ListPatent Document

[0008] Patent Document 1: Japanese Patent No. 5155464 Patent Document 2: Japanese Patent No. 5846360 Patent Document 3: Japanese Patent No. 6499190 DISCLOSURE OF THE INVENTIONProblems to be Solved by the Invention

[0009] Patent Document 1 discloses an aluminum electric wire in which Mg, Si, or the like is added to an aluminum alloy and the maximum crystal grain size is controlled. In Patent Documents 2 and 3, crystal planes and crystal orientations of the aluminum alloy wire undergo microstructure control. In addition to high tensile strength, high electric conductivity, and excellent elongation characteristics, the aluminum alloy wires of Patent Documents 2 and 3 have characteristics such as excellent elongation characteristics, superior rupture resistance to repeated motions and high proof stress.

[0010] These alloys have common characteristics in that they have at least high tensile strength and high electric conductivity and also excellent elongation characteristics, but there is room for further improvement in terms of reduction in variations in tensile strength and elongation characteristics along the longitudinal direction.

[0011] An object of the present invention is to provide an aluminum alloy wire, an electric wire, and a wire harness which have high tensile strength, high electric conductivity, and excellent elongation characteristics, whereby the aluminum alloy wire, the electric wire, and the wire harness display an excellent balance between the tensile strength, the electric conductivity, and the elongation characteristics, and have a small variation in the tensile strength and the elongation characteristics along the longitudinal direction.Means for Solving the Problems

[0012] As a result of intensive research and development for the above-described conventional problems, the present inventors have found that it is possible to provide an aluminum alloy wire, an electric wire, and a wire harness in which tensile strength, electric conductivity, and elongation characteristics are improved in a well-balanced manner by setting the composition of the aluminum alloy wire to within a specific range and controlling the temperature and time in the heat treatment step in the production of the aluminum alloy wire, such that a crystal orientation difference between adjacent measurement points of crystal orientation analysis is controlled. The present invention has been completed based on this finding.

[0013] In order to achieve the above object, the outline of the present invention is as follows. (1) An aluminum alloy wire including: an alloy composition including 0.30% by mass or more and 0.70% by mass or less of Mg and 0.30% by mass or more and 1.00% by mass or less of Si, with a balance being Al and inevitable impurities; and an abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less being 85% or less with respect to all of the measurement points, in a crystal orientation analysis by an electron backscatter diffraction (EBSD) method performed in an observation region of a transverse section perpendicular to a longitudinal direction of the aluminum alloy wire. (2) An aluminum alloy wire including: an alloy composition including 0.30% by mass or more and 0.70% by mass or less of Mg and 0.30% by mass or more and 1.00% by mass or less of Si, further including one or more components selected from the group consisting of Mn, Fe, Ni, Ti, Cr and Zr in a range of 0.001% by mass or more and 0.55% by mass or less in total, with a balance being Al and inevitable impurities; and an abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less being 85% or less with respect to all of the measurement points, in a crystal orientation analysis by an electron backscatter diffraction (EBSD) method performed in an observation region of a transverse section perpendicular to a longitudinal direction of the aluminum alloy wire. (3) The aluminum alloy wire as described in (1) or (2), in which, in the crystal orientation analysis performed in the observation region, when crystal orientations within <100> orientation ±5° are defined as a <100> orientation group, crystal orientations within <110> orientation ±5° are defined as a <110> orientation group, and crystal orientations within <111> orientation ±5° are defined as a <111> orientation group, a ratio of the number of the crystal grains having the <111> orientation group to the total number of the crystal grains having the <100> orientation group and the <110> orientation group (<111> orientation group / (<100> orientation group + <110> orientation group)) is in a range of 5 or more and 30 or less. (4) The aluminum alloy wire as described in any one of (1) to (3), in which an average crystal grain size of crystal grains obtained from the crystal orientation analysis performed in the observation region is in a range of 5 µm or more and 9 µm or less. (5) An electric wire including the aluminum alloy wire as described in any one of (1) to (4). (6) A wire harness including the electric wire as described in (5). Effects of the Invention

[0014] According to the present invention, it is possible to provide an aluminum alloy wire, an electric wire, and a wire harness that have excellent elongation characteristics while having high tensile strength and high electric conductivity, and thus display an excellent balance among the tensile strength, the electric conductivity, and the elongation characteristics, and have a small variation in the tensile strength and the elongation characteristics along the longitudinal direction.PREFERRED MODE FOR CARRYING OUT THE INVENTION

[0015] Hereinafter, preferred embodiments of the aluminum alloy wire, the electric wire, and the wire harness of the present invention will be described in detail. In the component composition of the alloy of the present invention, "% by mass" may be simply referred to as "%".

[0016] The aluminum alloy wire of the present invention is an aluminum alloy wire including: an alloy composition containing 0.30% by mass or more and 0.70% by mass or less of Mg and 0.30% by mass or more and 1.00% by mass or less of Si, with a balance being Al and inevitable impurities; and an abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less being 85% or less with respect to all of the measurement points, in a crystal orientation analysis by an electron backscatter diffraction (EBSD) method performed in an observation region of a transverse section perpendicular to a longitudinal direction of the aluminum alloy wire.

[0017] In the aluminum alloy wire according to the present invention, the tensile strength, the electric conductivity, and the elongation characteristics can be improved in a well-balanced manner by adjusting the alloy composition to within a specific range and controlling the temperature and time in the heat treatment step in the production of the aluminum alloy wire such that the crystal orientation difference between adjacent measurement points is controlled. More specifically, when the aluminum alloy wire has an alloy composition containing 0.30% by mass or more of Mg and 0.30% by mass or more of Si, and the abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less is 85% or less with respect to all of the measurement points, the tensile strength of the aluminum alloy wire can be increased. On the other hand, when the aluminum alloy wire has an alloy composition containing 0.70% by mass or less of Mg and 1.00% by mass or less of Si, and the abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less is 85% or less with respect to all of the measurement points, the electric conductivity and the elongation characteristics of the aluminum alloy wire can be increased.

[0018] Therefore, by using the aluminum alloy wire of the present invention, which has high tensile strength, high electric conductivity, and excellent elongation characteristics, it is possible to provide an aluminum alloy wire, an electric wire, and a wire harness that display an excellent balance between the tensile strength, the electric conductivity, and the elongation characteristics, and that have small variations in the tensile strength and the elongation characteristics along the longitudinal direction.[1] Alloy Composition of Aluminum Alloy Wire<Essential Components>

[0019] The alloy composition of the aluminum alloy wire of the present invention contains, as essential components, 0.30% by mass or more and 0.70% by mass or less of Mg and 0.30% by mass or more and 1.00% by mass or less of Si.(Mg: 0.30% by mass or more and 0.70% by mass or less)

[0020] Mg (magnesium) is an element that increases the tensile strength and the electric conductivity of the aluminum alloy by finely precipitating in the aluminum alloy together with other additive elements such as Si. In order to exhibit these effects, Mg is contained in a content of 0.30% by mass or more. In this regard, when the content of Mg is less than 0.30% by mass, most of Mg maintains a solid solution state, and thus Mg does not easily precipitate in the aluminum alloy. On the other hand, when the Mg content exceeds 0.70% by mass, Mg in a content significantly exceeding the solid solubility limit is present as a coarse compound, which not only does not contribute to improvement in the tensile strength and the electric conductivity, but also causes wire drawing breakage, thereby adversely affecting the aluminum alloy such that elongation characteristics deteriorate. Therefore, the content of Mg is 0.70% by mass or less. Given the above, the content of Mg is in the range of 0.30% by mass or more and 0.70% by mass or less.(Si: 0.30% by mass or more and 1.00% by mass or less)

[0021] Si (silicon) is an element that increases the tensile strength and the electric conductivity of the aluminum alloy by finely precipitating in the aluminum alloy together with other additive elements. In order to exhibit these effects, Si is contained in a content of 0.30% by mass or more. In this regard, when the content of Si is less than 0.30% by mass, most of Si maintains a solid solution state, and thus Si does not easily precipitate in the aluminum alloy. On the other hand, when the Si content exceeds 1.00% by mass, Si in a content significantly exceeding the solid solubility limit is present as a coarse compound, which not only does not contribute to improvement in the tensile strength and the electric conductivity, but also causes wire drawing breakage, thereby adversely affecting the aluminum alloy such that elongation characteristics deteriorate. Therefore, the content of Si is 1.00% by mass or less. Given the above, the content of Si is in the range of 0.30% by mass or more and 1.00% by mass or less.<Optional Additive Components>

[0022] The alloy composition of the aluminum alloy wire of the present invention may further contain, as an optional additive component, one or more components selected from the group consisting of Mn, Fe, Ni, Ti, Cr and Zr in a range of 0.001% by mass or more and 0.55% by mass or less in total.(Mn: 0.001% by mass or more and 0.50% by mass or less)

[0023] Mn (manganese) is a component that contributes to further refinement of crystal grains and brings about further increase in the strength of the aluminum alloy wire, and is a component that makes grain growth less likely to occur in a heat treatment process accompanied by recrystallization, thereby achieving an effect of wire break prevention. In order to exhibit this effect, Mn is preferably contained in a content of 0.001% by mass or more. On the other hand, if the Mn content is too large, the effect is saturated and does not change, or precipitation is promoted, so that the precipitation amount of a MgSi-based compound, which is particularly effective in the present invention, is relatively decreased. In addition, since there is a possibility that disadvantages such as a decrease in the electric conductivity and an adverse effect on the productivity occurs, the content of Mn is preferably 0.50% by mass or less.(Fe: 0.001% by mass or more and 0.50% by mass or less)

[0024] Fe (iron) is a component that contributes to further increasing the strength of the aluminum alloy wire. In order to exhibit this effect, Ti is preferably contained in a content of 0.001% by mass or more. On the other hand, if the Fe content is too large, the effect is saturated and does not change, and there is also a possibility that disadvantages such as a decrease in the electric conductivity and an adverse effect on the productivity occurs. As such, the Fe content is preferably 0.50% by mass or less.(Ni: 0.001% by mass or more and 0.50% by mass or less)

[0025] Ni (nickel) is a component having an effect of improving impact resistance of the aluminum alloy wire. In order to exhibit this effect, Ni is preferably contained in a content of 0.001% by mass or more. On the other hand, if the Ni content is too large, the effect is saturated and does not change, and there is also a possibility that disadvantages such as a decrease in the electric conductivity and an adverse effect on the productivity occurs. As such, the Ni content is preferably 0.50% by mass or less.(Ti: 0.001% by mass or more and 0.50% by mass or less)

[0026] Ti (titanium) has an effect of making a solidified structure during casting fine by being added as TiB, and is a component contributing to improvement in the productivity in a rolling step after casting. In order to exhibit this effect, Ti is preferably contained in a content of 0.001% by mass or more. On the other hand, the Ti content is preferably 0.50% by mass or less because there is a possibility that disadvantages such as a decrease in the electric conductivity and an adverse effect on the productivity may occur.(Cr: 0.001% by mass or more and 0.50% by mass or less)

[0027] Similarly to Mn, Cr (chromium) is a component having an effect of refining crystal grains and an effect of making grain growth at a high temperature less likely to occur, so that the wire is less likely to break. In order to exhibit this effect, Cr is preferably contained in a content of 0.001% by mass or more. On the other hand, if the Cr content is too large, the effect is saturated and does not change, or precipitation is promoted, so that there is a possibility that the precipitation amount of a MgSi-based compound may relatively decrease. In addition, since there is a possibility that disadvantages such as a decrease in the electric conductivity and an adverse effect on the productivity occurs, the content of Cr is preferably 0.50% by mass or less.(Zr: 0.001% by mass or more and 0.50% by mass or less)

[0028] Zr (zirconium) is a component capable of improving heat resistance of the aluminum alloy wire. In order to exhibit this effect, it is preferable for the aluminum alloy wire to contain 0.001% by mass or more of Zr. On the other hand, the content of Zr is preferably 0.50% by mass or less because the effect is saturated and is not changed even if the content is too large, and there is a possibility that disadvantages such as a decrease in the electric conductivity and an adverse effect on the productivity occur.(Total amount of optional additive components: 0.001% by mass or more and 0.55% by mass or less)

[0029] The optional additive component composed of one or more components selected from the group consisting of Mn, Fe, Ni, Ti, Cr and Zr is preferably contained in a content of 0.001% by mass or more in total in order to obtain the effect of these optional additive components. These optional additive components can also take a form of solid solution or precipitation in the aluminum alloy wire, and can lead to solid solution strengthening by increasing the content thereof, strengthening by refining the crystal grains of a mother phase, and precipitation strengthening by promoting a reaction using the optional additive components. On the other hand, the contents of these optional additive components are preferably 0.55% by mass or less in total, because even if the contents are too large, the effect is saturated and does not change, and disadvantages such as a decrease in the electric conductivity and an adverse effect on the productivity may occur.<Balance: Al and inevitable impurities>

[0030] In the alloy composition of the aluminum alloy wire of the present invention, the balance other than the above-described elements is composed of Al and inevitable impurities. The term "inevitable impurities" as used herein refers to impurities that are generally present in a raw material of an aluminum alloy wire or are unavoidably mixed in the production process. The inevitable impurities are essentially unnecessary, but are in trace amounts and are acceptable because they do not affect the characteristics of the aluminum alloy wire. Examples of the inevitable impurities include nonmetallic elements such as sulfur (S), carbon (C) and oxygen (O), and metal elements such as V (vanadium), Ga (gallium) and Sb (antimony). The upper limit of the content of these components is preferably small because these components can be a factor for lowering the electric conductivity and the tensile strength. The upper limit can be 0.05% by mass for each of the above components, or 0.05% by mass in a total amount of the above components. More preferably, the amount of the components is 0.01% by mass for each component, or 0.01% by mass in total.[2] Metal Structure of Aluminum Alloy Wire

[0031] Next, the metal structure of the aluminum alloy wire will be described.

[0032] In a crystal orientation analysis of the aluminum alloy wire of the present invention by an electron backscatter diffraction (EBSD) method performed in an observation region of a transverse section perpendicular to the longitudinal direction thereof, an abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less is 85% or less with respect to all of the measurement points. Such a low-angle crystal orientation difference of 5° or less is often formed by dislocation defects. When the abundance proportion exceeds 85%, plastic working strain applied in the production process of the aluminum alloy wire is not considered to have been sufficiently removed. As a cause thereof, insufficient heating in a third heat treatment step (solution heat treatment step) to be described later can be exemplified. In other words, sufficient recrystallization does not proceed due to the insufficient heating, resulting in remaining strain. In addition, due to the insufficient heating in the third heat treatment step (solution heat treatment step), the solid solubility of Mg or Si is not sufficiently increased, and recovery of elongation characteristics and precipitation strengthening by the subsequent aging treatment step are insufficient. That is, by adjusting the abundance proportion of the measurement points having a crystal orientation difference between adjacent measurement points of 5° or less to 85% or less with respect to all of the measurement points in the measurement region, plastic working strain is sufficiently removed, and recovery of the elongation characteristics and the precipitation strengthening are achieved, so that the tensile strength and the elongation characteristics of the aluminum alloy wire can be enhanced. The longitudinal direction of the aluminum alloy wire means the drawing direction of the wire in the production process.

[0033] As used herein, the crystal orientation analysis by the electron backscatter diffraction (EBSD) method can be performed, for example, by continuously measuring crystal orientations using an EBSD detector (OIM 5.0 HIKARI manufactured by TSL Corporation) attached to a high-resolution scanning analytical electron microscope JSM-7001FA (manufactured by JEOL), and calculating (processing) crystal orientation data obtained by the measurement using analysis software (OIM-Analysis manufactured by TSL Solution Corporation) to obtain crystal orientation analysis data. "EBSD" is an abbreviation of Electron BackScatter Diffraction, and is a crystal orientation analysis technique using Kikuchi line generated when an aluminum alloy wire as a measurement sample is irradiated with an electron beam in a scanning electron microscope (SEM). An object to be measured is a transverse section perpendicular to the longitudinal direction of one aluminum alloy wire that has been polished and mirror-finished in advance. In the polishing of the transverse section, any means capable of mirror finishing such as wet polishing, FIB, or microtome can be used in addition to polishing using a cross-section polisher (registered trademark) apparatus, and there is no particular limitation to the specific means. The measurement region may be a range obtained by cutting out one aluminum alloy wire, and may be, for example, 50 µm to 300 µm square. The measurement of the crystal orientation when obtaining the crystal orientation data can be performed at a step size of, for example, 0.5 µm to 2 µm. In particular, by using analysis software for analysis of the crystal orientation data, when a specific angle range is allowed as a crystal orientation difference between adjacent measurement points, it is possible to easily determine, for each measurement point, whether or not the crystal orientation difference between adjacent measurement points is within the allowable range.

[0034] In the crystal orientation analysis by the electron backscatter diffraction (EBSD) method performed in the observation region of the transverse section perpendicular to the longitudinal direction of the aluminum alloy wire of the present invention, when crystal orientations within <100> orientation ±5° are defined as a <100> orientation group, crystal orientations within <110> orientation ±5° are defined as a <110> orientation group, and crystal orientations within <111> orientation ±5° are defined as a <111> orientation group, a ratio of the number of the crystal grains having the <111> orientation group to the total number of the crystal grains having the <100> orientation group and the <110> orientation group (<111> orientation group / (<100> orientation group + <110> orientation group)) is preferably in a range of 5 or more and 30 or less.

[0035] In this regard, the crystal grains having the <111> orientation group contribute to the improvement in the tensile strength of the aluminum alloy wire, but have a property of lowering the elongation characteristics. In addition, the crystal grains having the <111> orientation group may exist as a worked texture when the recrystallization does not sufficiently proceed. In such a case, in addition to decrease in the elongation characteristics, the crystal grains may cause insufficient precipitation strengthening due to insufficiently solubilized Mg or Si. As described above, the crystal grains having the <111> orientation group have a disadvantage of reducing the tensile strength and / or the elongation characteristics of the aluminum alloy wire, and when the ratio thereof is high, the disadvantage tends to be strongly exhibited.

[0036] In addition, the crystal grains having the <100> orientation group and the <110> orientation group do not contribute to the improvement in the tensile strength as much as the crystal grains having the <111> orientation group, but can improve the elongation characteristics. In addition, since the crystal grains having the <100> orientation group and the <110> orientation group accumulate when recrystallization sufficiently proceeds, when the proportion of the crystal grains having these orientation groups is high, the solid solubility of Mg or Si is high, and thus the tensile strength of the aluminum alloy wire can be increased. In particular, since there is an advantage that high tensile strength and elongation characteristics can be stably obtained by increasing both the recrystallization proportion and the solid solubility of the aluminum alloy wire, it is desirable to increase the proportion.

[0037] In particular, when the ratio of (<111> orientation group / (<100> orientation group + <110> orientation group)) is 1 or less, the proportion of the crystal grains having the <111> orientation group decreases, and thus the tensile strength of the aluminum alloy wire decreases. On the other hand, when the ratio of (<111> orientation group / (<100> orientation group + <110> orientation group)) is 100 or more, the ratio of (<100> orientation group + <110> orientation group) is small, and thus the elongation characteristics of the aluminum alloy wire are poor. In particular, when the solid solution or recrystallization of Mg or Si has not sufficiently progressed, it is difficult to stably obtain high tensile strength. Therefore, the ratio (<111> orientation group / (<100> orientation group + <110> orientation group)) is preferably in the range of 5 or more and 30 or less.

[0038] When in the analysis of the crystal orientation data obtained in the transverse section by the EBSD detector described above, a boundary with an orientation difference between adjacent measurement points of 15° or more is an interface (grain boundary) of a crystal grain, and a set of continuous measurement points in a range surrounded by the grain boundary is a crystal grain, the number ratio of the crystal grains having the <100> orientation group, the <110> orientation group, or the <111> orientation group, with respect to a total number of the crystal grains in the measurement region can be obtained.

[0039] In the aluminum alloy wire of the present invention, an average crystal grain size obtained from the crystal orientation analysis by the electron backscatter diffraction (EBSD) method performed in the observation region of the transverse section perpendicular to the longitudinal direction may be, for example, in the range of 5 µm or more and 20 µm or less, but is preferably in the range of 5 µm or more and 9 µm or less. In particular, when the average crystal grain size of the crystals contained in the metal structure of the aluminum alloy wire is adjusted to be included in the range of 5 µm or more and 9 µm or less, the average value or the standard deviation of one or both of the tensile strength and the elongation characteristic of the aluminum alloy wire can be further increased. On the other hand, when the average crystal grain size is less than 5 µm, since the solid solution of Mg or Si does not sufficiently proceed, and the precipitation strengthening is insufficient. In addition, when heating for crystallization is insufficient, plastic working strain applied in the production process of the aluminum alloy wire remains, and the elongation characteristics is also easily deteriorated. On the other hand, when the average crystal grain size is larger than 9 µm, particularly larger than 20 µm, wire breakage is likely to occur when recrystallization is performed by annealing during running.

[0040] Here, the average crystal grain size of the crystal grains of the aluminum alloy wire can be obtained in the following manner: assuming that, in the analysis of the crystal orientation data by the electron backscatter diffraction (EBSD) method described above, a boundary with an orientation difference between adjacent measurement points of 15° or more is an interface (grain boundary) of a crystal grain, and cross-sectional areas of the crystal grains are calculated by using the number of the continuous measurement points in a range surrounded by the grain boundaries and the step size described above, an average diameter of circles corresponding to the crystal grains is used as the average crystal size of the aluminum alloy wire.

[0041] Since the aluminum alloy wire of the present invention has high tensile strength and high elongation characteristics, even when the wire diameter (diameter) is adjusted to a small diameter in the range of 0.1 mm or more and 0.5 mm or less, high toughness can be provided. As used herein, the toughness is a characteristic that becomes high when both the tensile strength and the elongation characteristic are high, and when the aluminum alloy wire has high toughness, it is possible to easily maintain the original shape without breaking even when a force in the tensile direction is applied.

[0042] In addition, the aluminum alloy wire of the present invention can form an aluminum alloy twisted wire by twisting a plurality of wires together, and also in this case, high electric conductivity, tensile strength, and elongation characteristics can be improved. In this regard, the number of the aluminum alloy wire to be twisted and the total cross-sectional area of the twisted wires are not limited, but an aluminum alloy twisted wire having a small diameter with a cross-sectional area in a range of 0.1 mm 2< or more and 3.0 mm 2< or less can be formed by twisting 5 or more and 16 or less aluminum alloy wires having the above-described wire diameter.

[0043] Furthermore, the aluminum alloy wire of the present invention is preferably used for electric wires, and it is preferable to constitute an electric wire having the above-described aluminum alloy wire. More specifically, an electric wire including the aluminum alloy wire or the aluminum alloy twisted wire, and an insulating coating layer that covers the outer periphery of the aluminum alloy wire or the aluminum alloy twisted wire can be configured. Since such an electric wire can improve tensile strength, electric conductivity, and elongation characteristics in a well-balanced manner, the weight of a wire harness can be reduced by reducing the weight of an electric wire having a particularly small diameter. That is, it is also preferable to configure a wire harness having an electric wire with the above-described aluminum alloy wire.[3] One Example of Production Processes of Aluminum Alloy Wire

[0044] The aluminum alloy wire described above can be realized by controlling the alloy composition and the production process in combination, and the production process is not particularly limited. Among them, the following method can be raised as one example of the production processes capable of obtaining the aluminum alloy wire described above.

[0045] As an example of the method for producing the aluminum alloy wire of the present invention, the following method can be raised: an aluminum alloy material having an alloy composition substantially the same as the alloy composition of the above-described aluminum alloy wire is sequentially subjected to at least a continuous casting and rolling step, a first heat treatment step, a first wire drawing step, a second heat treatment step, a second wire drawing step, and a third heat treatment step.[Continuous Casting and Rolling Step]

[0046] In the method for producing the aluminum alloy wire of the present invention, first, an aluminum raw material and additive elements are selected so as to obtain a desired component composition, and a continuous casting and rolling step is performed to obtain an aluminum wire rod. The casting method in the continuous casting and rolling step is not limited, but it is preferable from the viewpoint of production efficiency to use a Properzi type continuous casting and rolling machine, in which a casting ring and a belt are combined and a wire rod can be obtained by continuously pouring an aluminum melt into a ring-shaped groove mold to cast, and continuously rolling.

[0047] In the continuous casting and rolling step, for example, a rolled material having a cross-sectional area corresponding to a wire diameter of 9 mm or more and 10 mm or less can be obtained by rolling with a two-way roll or a three-way roll after casting using a continuous casting and rolling machine.

[0048] Although continuous wire drawing is performed on the rolled material until the wire diameter is in the range of 0.1 mm or more and 0.5 mm or less, since the heat treatment performed during the wire drawing affects the crystal orientation distribution of the aluminum alloy wire, it is important to perform heat treatment under appropriate heat treatment condition. At the same time, if a total processing ratio of the wire drawing process is increased without performing the heat treatment, the deformation resistance increases, so that the aluminum alloy wire easily breaks, and the abrasion damage of a die used in the wire drawing process becomes rapid. Therefore, it is useful, from the viewpoint of enhancing not only the mechanical properties but also the mass productivity, to soften by performing the heat treatment at an appropriate timing. More specifically, two or more heat treatment steps are preferably performed except for the heat treatment (heat treatment in the third heat treatment step) performed after the second wire drawing step described later, and the heat treatment condition at that time are preferably performed in a temperature range of 300°C or more and 400°C or less for 1 hour or more and 8 hours or less, for each heat treatment.

[0049] In the following description, an embodiment in which after the continuous casting and rolling step, the first wire drawing step and the second wire drawing step are performed as wire drawing, and the first heat treatment step and the second heat treatment step are performed before each of these wire drawing steps will be described, but the present invention is not limited to this embodiment. As described above, by sequentially performing the first heat treatment step, the first wire drawing step, the second heat treatment step, and the second wire drawing step after performing the continuous casting and rolling step, it is possible to conduct the heat treatment for the aluminum wire at the timing when cold wire drawing is performed at a processing ratio of a certain level or higher, and it is possible to easily perform the wire drawing step and the heat treatment step when continuous processing equipment is used.[First Heat Treatment Step]

[0050] The first heat treatment step is a step of heat-treating the aluminum wire rod as a rolled material having a cross-sectional area corresponding to a wire diameter of 9 mm or more and 10 mm or less in a temperature range of 300°C or more and 400°C or less for 1 hour or more and 8 hours or less. The first heat treatment step is a step for softening the aluminum wire rod and intentionally precipitating pinning particles that prevent crystals from being coarsened.

[0051] Since the crystal orientation during performing the first heat treatment step also affects the crystal orientation after the later-described third heat treatment step, the first heat treatment step needs to be performed in a temperature range of 300°C or more and 400°C or less for 1 hour or more and 8 hours or less. Here, when the heat treatment temperature is less than 300°C or when the heat treatment time is less than 1 hour, it is difficult to perform the first wire drawing step and the second wire drawing step described later because the aluminum wire rod cannot be sufficiently softened. When the heat treatment temperature exceeds 400°C or when the heat treatment time exceeds 8 hours, coarsening of the metal structure occurs, and thus the crystal orientation distribution of the obtained aluminum alloy wire is easily changed. When the size of the precipitate generated during the heat treatment is increased, the precipitate cannot serve as grain boundary pinning in the third heat treatment step described later, and the crystal grain size of the aluminum alloy wire obtained thereby is coarsened, which causes the aluminum alloy wire to easily break and causes deterioration in the tensile strength and the elongation characteristics.

[0052] The first heat treatment step can be performed using a known method such as a bell furnace.[First Wire Drawing Step]

[0053] The first wire drawing step is a step of performing cold wire drawing on the aluminum wire rod after the first heat treatment step. Thereby, it is preferable to obtain a rolled material having a cross-sectional area corresponding to a wire diameter of 1 mm or more and 3 mm or less.

[0054] The first wire drawing step can be performed by a known method such as wire-drawing processing that uses a die. More specifically, for the die material and dimensions, the wire drawing oil, the pass reduction, and the like, which are wire drawing conditions, general conditions in aluminum wire mass production can be employed. The first wire drawing step may be performed in one pass, or may be performed in a plurality of passes until a target wire diameter is obtained.[Second Heat Treatment Step]

[0055] The second heat treatment step is a step of heat-treating the aluminum wire after the first wire drawing step in a temperature range of 300°C or more and 400°C or less for 1 hour or more and 8 hours or less. Similarly to the first heat treatment step, the second heat treatment step is also a step for softening the aluminum wire and intentionally precipitating pinning particles preventing coarsening of crystals.

[0056] For the same reason as in the first heat treatment step, the heat treatment in the second heat treatment step needs to be performed in a temperature range of 300°C or more and 400°C or less for 1 hour or more and 8 hours or less.

[0057] Similarly to the first heat treatment step, the second heat treatment step can be performed using a known method such as a bell furnace.[Second Wire Drawing Step]

[0058] The second wire drawing step is a step of performing cold wire drawing on the aluminum wire after the first heat treatment step. Thereby, an aluminum wire having a desired cross-sectional area can be obtained. Here, the cross-sectional area of the aluminum wire after the second wire drawing step is not particularly limited, but may be, for example, a cross-sectional area corresponding to a wire diameter of 0.1 mm or more and 0.5 mm or less.

[0059] Similarly to the first wire drawing step, the second wire drawing step can be performed by a known method such as wire-drawing processing using a die. The second wire drawing step may be performed in one pass, or may be performed in a plurality of passes until a target wire diameter is obtained.[Third Heat Treatment Step]

[0060] The third heat treatment step is a solution heat treatment, and is a step of heat-treating the aluminum wire after the second wire drawing step in a temperature range of 500°C or more and 580°C or less for 3 seconds or more and 60 seconds or less. By this step, the element in the precipitated state forms a solid solution, and the crystal orientation precipitated by recrystallization in the aluminum alloy wire is determined. Here, when the heat treatment temperature is less than 500°C or when the heat treatment time is less than 3 seconds, in the crystal orientation analysis by the electron backscatter diffraction (EBSD) method described above, the abundance proportion of the measurement points having a crystal orientation difference between adjacent measurement points of 5° or less with respect to all of the measurement points exceeds 85%. When the heat treatment temperature exceeds 580°C or when the heat treatment time exceeds 60 seconds, grain growth occurs in the metal structure of the obtained aluminum alloy wire, which causes deterioration in the tensile strength and / or the elongation characteristics, and causes the aluminum alloy wire to easily break.

[0061] The heat treatment condition of the third heat treatment step may also affect the ratio of the number of the crystal grains having the <111> orientation group to the total number of the crystal grains having the <100> orientation group and the <110> orientation group. When the heat treatment temperature is low or when the heat treatment time is short, since the number of the crystal grains having the <111> orientation group increases, the ratio (<111> orientation group / (<100> orientation group + <110> orientation group)) also tends to increase. At this time, the solid solution does not sufficiently progress, and the formation of crystal grains having a desired crystal orientation by recrystallization also does not sufficiently progress, which may cause a decrease in the tensile strength and the elongation characteristics of the aluminum alloy wire. When the heat treatment temperature is high or when the heat treatment time is long, the number of the crystal grains having the <100> orientation group and the number of the crystal grains having the <110> orientation group increase, and thus the tensile strength of the aluminum alloy wire tends to decrease. In addition, in these cases, coarsening of the crystal grains causes a decrease in the tensile strength and the elongation characteristics, and the aluminum alloy wire is easier to break.

[0062] The third heat treatment step can be performed using a known method such as an annular furnace, but since the heating time is short, it is preferable to rapidly heat the aluminum wire while confirming achieving temperature of the aluminum wire. The aluminum wire after the third heat treatment step is preferably rapidly cooled by water cooling or the like.

[0063] Here, before or after the third heat treatment step, a twisting step of twisting a plurality of aluminum wire by a twisting machine or a compression step of compressing the twisted wires may be performed. This makes it possible to produce an aluminum alloy twisted wire obtained by twisting a plurality of aluminum alloy wires without substantially affecting the metal structure even by the twisting step or the compression step.[Aging Step]

[0064] The aging treatment step is a step of holding the aluminum wire after the third heat treatment step at a temperature lower than that of the third heat treatment step or performing a heat treatment. By this step, in the metal structure of the aluminum wire, crystal grains can be precipitated in a desired balance of crystal orientation by recrystallization, and therefore, the aluminum alloy wire and the aluminum alloy twisted wire can be obtained, which have high tensile strength and high electric conductivity, also have excellent elongation characteristics, thus, display an excellent balance in these characteristics, and have small variations in the tensile strength and the elongation characteristics along the longitudinal direction.

[0065] In the aging treatment step, at least an artificial aging treatment in which the aluminum wire is heat-treated is performed, but a natural aging treatment in which the aluminum wire is held under a temperature condition close to ambient temperature may be further performed before the artificial aging treatment. Here, the heat treatment in the artificial aging treatment can be performed in a temperature range of 100°C or more and 200°C or less for 2 hours or more and 10 hours or less. In addition, the natural aging treatment can be carried out by holding the aluminum wire for 24 hours or more in a temperature range of 20°C or more and 50°C or less.

[0066] The aluminum alloy wire or the aluminum alloy twisted wire obtained as described above is subjected to an extrusion coating step of extrusion coating along the outer circumference of the aluminum alloy wire or the aluminum alloy twisted wire to conduct insulating coating, whereby an electric wire can be produced.

[0067] Although the embodiments have been described above, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present disclosure, including all aspects included in the concept of the present disclosure and the claims.EXAMPLES

[0068] Next, Examples of the present invention and Comparative Examples will be described, but the present invention is not limited to these Examples.

[0069] Aluminum raw materials and additive elements were selected so as to have the compositions shown in Table 1, and a continuous casting and rolling step was performed using a continuous casting and rolling machine (manufactured by Properzi) to produce an aluminum wire rod as a rolled material having a transverse section perpendicular to the longitudinal direction corresponding to a circular shape having a diameter of 9.5 mm. After the aluminum wire rod was subjected to the first heat treatment step under the condition of the temperature and the time shown in Table 1, the aluminum wire rod was subjected to the first wire drawing step of adjusting the size of the transverse section to a size corresponding to a circular shape having a diameter of 2.6 mm, then subjected to the second heat treatment step under the condition of the temperature and the time shown in Table 1, and then subjected to the second wire drawing step of adjusting the size of the transverse section to a size corresponding to a circular shape having a diameter of 0.3 mm. Here, the first heat treatment step and the second heat treatment step were performed in an inert gas environment of a bell furnace.

[0070] The aluminum wire after the second wire drawing step was subjected to the third heat treatment step, which was a solution heat treatment, under the condition of the temperature and the time shown in Table 1, and then immediately cooled by water cooling. Here, the third heat treatment step was performed while heating the aluminum wire in a protective tube in an annular furnace and confirming the achieving temperature with a thermocouple.

[0071] After the third heat treatment step was performed, as the aging treatment step, a natural aging treatment in which the aluminum wire was held in a temperature range of 25°C or more and 40°C or less for 24 hours or more and an artificial aging treatment in which heat treatment was performed in a temperature range of 120°C or more and 170°C or less for 5 hours were performed in the air to obtain the aluminum alloy wires of the Examples of the present invention and Comparative Examples. In an actual aluminum electric wire production process, a twisting step and a compressing step may be performed after these aging treatments are performed, but since the influence of these steps on the characteristics is extremely small, they are omitted in the Examples of the present invention and the Comparative Examples.[Various Measurements and Evaluation Methods]

[0072] The aluminum alloy wires obtained in the Examples of the present invention and the Comparative Examples were subjected to the following characteristic evaluations. The evaluation conditions of each characteristic are as follows.[1] Measurement of Abundance Proportion of Measurement Points having Crystal Orientation Difference between Adjacent Measurement Points of 5° or less with respect to All of Measurement Points

[0073] The abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less with respect to all of the measurement points was obtained from crystal orientation analysis data calculated using the electron backscatter diffraction (EBSD) method. In this regard, the crystal orientation analysis data calculated using the electron backscatter diffraction (EBSD) method was obtained by continuously measuring crystal orientations using an EBSD detector (OIM 5.0 HIKARI manufactured by TSL Corporation) attached to a high-resolution scanning analytical electron microscope JSM-7001FA (manufactured by JEOL), and calculating (processing) crystal orientation data obtained by the measurement using analysis software (OIM-Analysis manufactured by TSL Solution Corporation) to obtain the abundance proportion with respect to all of the measurement points in the measurement region. An object to be measured was a transverse section perpendicular to the longitudinal direction of one aluminum alloy wire that had been polished and mirror-finished in advance. A cross-section polisher (registered trademark) apparatus was used to polish the transverse section. The measurement region was a range obtained by cutting out one aluminum alloy wire, and more specifically, was a range of an area corresponding to a circle having a diameter of 0.3 mm. When obtaining crystal orientation data, the crystal orientation was measured at a step size of 0.5 µm. At this time, the measurement results of the orientation difference between adjacent measurement points were provided in numerical values in increments of 1°. In addition, also in the determination regarding whether or not the crystal orientation difference between adjacent measurement points was 5° or less, measurement results of the crystal orientation difference were similarly provided in numerical values in increments of 1°. When a measurement result is in the range of 1° or more and 5° or less, the crystal orientation difference between the adjacent measurement points was determined as being 5° or less. The results are shown in Table 2.[2] Measurement of Ratio of Number of Crystal Grains having <111> Orientation Group to Total Number of Crystal Grains having <100> Orientation Group and Crystal Grains having <110> Orientation Group

[0074] Assuming that in the analysis of the crystal orientation data obtained in the transverse section by the EBSD detector described above, a boundary with an orientation difference between adjacent measurement points of 15° or more is an interface (grain boundary) of a crystal grain, and a set of continuous measurement points in a range surrounded by the grain boundary is a crystal grain, the number of the crystal grains having the <100> orientation group which is a crystal orientation within <100> orientation ±5°, the number of the crystal grains having the <110> orientation group which is a crystal orientation within <110> orientation ±5°, and the number of the crystal grains having the <111> orientation group which is a crystal orientation within <111> orientation ±5° were obtained and the ratio (<111> orientation group / (<100> orientation group + <110> orientation group)) was obtained from the numbers of the crystal grains having these orientation groups. The results are shown in Table 2.[3] Measurement of Average Crystal Grain Size of Crystal Grains

[0075] An average crystal grain size of the crystal grains of the aluminum alloy wire was determined in the following manner: assuming that a boundary with an orientation difference between adjacent measurement points of 15° or more in the analysis of the crystal orientation data by the electron backscatter diffraction (EBSD) method is an interface (grain boundary) of the crystal grain, cross-sectional areas of the crystal grains were calculated using the number of the continuous measurement points present in a range surrounded by grain boundaries and the step size described above, and an average diameter of circles corresponding to the crystal grains obtained therefrom was used as the average crystal grain size of the crystal grains. The results are shown in Table 2.[4] Measurement and Evaluation of Tensile Strength

[0076] For the tensile strength of the aluminum alloy wire, test pieces having a length of 200 mm including positions at 0 m, 500 m, 1000 m, 1500 m, and 2000 m from one end of the aluminum alloy wire were cut out from the aluminum alloy wire having a length of 2000 m. The tensile strength Rm of these test pieces was determined based on JIS Z2241, and an average value and a standard deviation of the tensile strength Rm at these five positions were defined as the average value [MPa] and the standard deviation [MPa] of the tensile strength, respectively.

[0077] When the average value of the obtained tensile strength was 250 MPa or more, the aluminum alloy wire was evaluated as "excellent (expressed by a bullseye symbol ⊙)" in that the average value of the tensile strength was sufficiently large and the aluminum alloy wire can be used alone without being mounted on a connector. When the average value of the tensile strength was in the range of 230 MPa or more and less than 250 MPa, the aluminum alloy wire was evaluated as "good (expressed by a circle symbol O)" in that the average value of the tensile strength was large and the aluminum alloy wire can be used in a state of being accommodated in a general connector. On the other hand, when the average value of the tensile strength was less than 230 MPa, the aluminum alloy wire was evaluated as "poor (expressed by a cross symbol (X))" in that the average value of the tensile strength was small and the aluminum alloy wire can be broken even if the aluminum alloy wire is put in a connector. In the Examples of the present invention and Comparative Examples, "⊙" and "O" were evaluated as acceptable levels. The results are shown in Table 2.

[0078] Regarding the standard deviation of the obtained tensile strength, when the standard deviation of the tensile strength was 5.00 MPa or less, the aluminum alloy wire was evaluated as "excellent (expressed by a bullseye symbol ⊙)" in that the standard deviation of the tensile strength was sufficiently small and the tensile strength of the aluminum alloy wire can be obtained particularly stably. When the standard deviation of the tensile strength was in the range of more than 5.00 MPa and 10.00 MPa or less, the aluminum alloy wire was evaluated as "good (expressed by a circle symbol O)" in that the standard deviation of the tensile strength was small and the tensile strength was stably obtained, similarly to the case where the tensile strength of the aluminum alloy wire was evaluated as "⊙". On the other hand, when the standard deviation of the tensile strength exceeded 10.00 MPa, the aluminum alloy wire was evaluated as "poor (expressed by a cross symbol (X))" in that the tensile strength of the aluminum alloy wire was not stably obtained. In the Examples of the present invention and Comparative Examples, "⊙" and "O" were evaluated as acceptable levels. The results are shown in Table 2.[5] Measurement and Evaluation of Elongation Characteristics

[0079] For the elongation characteristics of the aluminum alloy wire, test pieces having a length of 200 mm including positions at 0 m, 500 m, 1000 m, 1500 m, and 2000 m from one end of the aluminum alloy wire were cut out from the aluminum alloy wire having a length of 2000 m. Elongations at break A of these test pieces were determined based on JIS Z2241, and an average value and a standard deviation of the elongations at break A at these five positions were defined as the average value [%] and the standard deviation [%] of the elongation characteristics, respectively.

[0080] When the average value of the obtained elongation characteristics was 14.0% or more, the aluminum alloy wire was evaluated as "excellent (expressed by a bullseye symbol ⊙)" in that the average value of the elongation characteristics was sufficiently large and the aluminum alloy wire can be used alone without being mounted on a connector. When the average value of the elongation characteristics was in the range of 12.0% or more and less than 14.0%, the aluminum alloy wire was evaluated as "good (expressed by a circle symbol O)" in that the average value of the elongation characteristics was large and the aluminum alloy wire could be used in a state of being accommodated in a general connector. On the other hand, when the average value of the elongation characteristics was less than 12.0%, the aluminum alloy wire was evaluated as "poor (expressed by a cross symbol (X))" in that the average value of the elongation characteristics was small and the aluminum alloy wire can be broken even if the aluminum alloy wire is put in a connector. In the Examples of the present invention and Comparative Examples, "⊙" and "O" were evaluated as acceptable levels. The results are shown in Table 2.

[0081] When the standard deviation of the obtained elongation characteristics was 0.30% or less, the aluminum alloy wire was evaluated as "excellent (expressed by a bullseye symbol ⊙)" in that the standard deviation of the elongation characteristics was sufficiently small and the elongation characteristics of the aluminum alloy wire can be obtained particularly stably. When the standard deviation of the elongation characteristics was in the range of more than 0.30% and 0.80% or less, the aluminum alloy wire was evaluated as "good (expressed by a circle symbol O)" in that the standard deviation of the tensile strength was small and the tensile strength was stably obtained, similarly to the case where the tensile strength of the aluminum alloy wire was evaluated as "⊙". On the other hand, when the standard deviation of the elongation characteristics exceeded 0.80%, the aluminum alloy wire was evaluated as "poor (expressed by a cross symbol (X))" in that the elongation characteristics of the aluminum alloy wire was not stably obtained. In the Examples of the present invention and Comparative Examples, "⊙" and "O" were evaluated as acceptable levels. The results are shown in Table 2.[6] Electric Conductivity Measurement and Evaluation

[0082] The electric conductivity of the aluminum alloy wire was measured twice in accordance with JIS H0505 (-1975), and the average value of the electric conductivity obtained by the two measurements was defined as the measured value [% IACS] of the electric conductivity.

[0083] When the measured value of the electric conductivity exceeded 50.0% IACS, the aluminum alloy wire was evaluated as "excellent (expressed by a bullseye symbol ⊙)" in that the aluminum alloy wire had a sufficiently large electric conductivity and was likely to be an electric wire capable of responding to further reduction in diameter in the future. When the measured value of the electric conductivity was in the range of 48.0% IACS or more and 50.0% IACS or less, the aluminum alloy wire was evaluated as "good (expressed by a circle symbol ○)" in that the value of the electric conductivity was large and good for an aluminum alloy wire that constitutes current diameter-reduced electric wires. On the other hand, when the measured value of the electric conductivity was less than 48.0% IACS, the aluminum alloy wire was evaluated as "poor (expressed by a cross symbol X" in that the value of the electric conductivity was small and the aluminum alloy wire was poor as an aluminum alloy wire that constitutes the diameter-reduced electric wires. In the Examples of the present invention and Comparative Examples, "⊙" and "O" were evaluated as acceptable levels. The results are shown in Table 2.

[0084] The above-mentioned "% IACS" is a unit of electric conductivity when the resistivity of 1.7241×10 -8< Ωm of universal standard soft copper (International Annealed Copper Standard) is taken as 100% IACS.[7] Overall Evaluation

[0085] Among these evaluation results, regarding all of the five evaluation results relating to the average value of the tensile strength, the standard deviation of the tensile strength, the average value of the elongation characteristics, the standard deviation of the elongation characteristics, and the electric conductivity, the aluminum alloy wire evaluated as "⊙" for all of the five evaluation items was evaluated as "⊙" on account of being particularly excellent in that the aluminum alloy wire had excellent elongation characteristics while having high tensile strength and high electric conductivity, and had small variations in the tensile strength and the elongation characteristics along the longitudinal direction. Further, regarding these five evaluation items, the aluminum alloy wire evaluated as "⊙" or "○" (excluding the aluminum alloy wire that was evaluated as "⊙" for all of the five evaluation items) for all of the five evaluation items was evaluated as "○" on account of being excellent in that the aluminum alloy wire had excellent elongation characteristics while having high tensile strength and high electric conductivity, and had small variations in the tensile strength and the elongation characteristics along the longitudinal direction. On the other hand, regarding these five evaluation items, the aluminum alloy wire evaluated as "x" in at least one of them was evaluated as "x" as failing in at least one of the tensile strength, the electric conductivity, and the elongation characteristics, or failing in that the variation in the tensile strength or the elongation characteristics along the longitudinal direction was large. The results are shown in Table 2. [Table 1]Aluminum alloy wireProduction condition of aluminum alloy wireAlloy composition (% by mass)First heat treatment stepSecond heat treatment stepThird heat treatment stepEssential additiveOptional additiveTotal of optional additiveAlMgSiMnFeNiTiCrZrTemperature (°C)Time (h)Temperature (°C)Time (h)Temperature (°C)Time (h)Inventive Example 10.350.40------0.00Balance3502400556010Inventive Example 20.500.70------0.00Balance3502400556010Inventive Example 30.500.70------0.00Balance3008300454010Inventive Example 40.500.70------0.00Balance350230025603Inventive Example 50.500.70------0.00Balance3004350452040Inventive Example 60.600.80------0.00Balance3502400556010Inventive Example 70.600.80------0.00Balance3254350354010Inventive Example 80.600.80------0.00Balance3506350255015Inventive Example 90.600.80------0.00Balance3751300254010Inventive Example 100.700.90------0.00Balance3502400556010Inventive Example 110.500.700.100.150.100.01--0.36Balance3002400556015Inventive Example 120.500.700.100.150.100.01--0.36Balance3502325254010Inventive Example 130.500.700.100.150.100.01--0.36Balance3502375254010Inventive Example 140.500.700.100.150.100.01--0.36Balance3255350254010Inventive Example 150.500.700.100.050.20---0.35Balance3502400556010Inventive Example 160.500.70-0.050.10-0.15-0.30Balance3502400556010Inventive Example 170.500.70-0.050.10-0.15-0.30Balance3008375254010Inventive Example 180.500.70-0.050.10-0.15-0.30Balance3502350254010Inventive Example 190.500.70-0.050.10-0.15-0.30Balance4001325254010Inventive Example 200.500.70-0.10-0.03-0.050.18Balance3502400556010Inventive Example 210.500.700.100.100.15-0.20-0.55Balance3502400556010Inventive Example 220.500.70-0.20-0.02-0.100.32Balance3502400556010Comparative Example 10.150.20------0.00Balance3502300254010Comparative Example 20.801.10------0.00Balance3254350255010Comparative Example 30.500.70------0.00Balance250 23502480 1 Comparative Example 40.500.70------0.00Balance3250.5 250 0.5 5205Comparative Example 50.500.70------0.00Balance3002200 0.5 50010Comparative Example 60.500.70------0.00Balance35023502450 25Comparative Example 70.500.700.100.150.100.01--0.36Balance475 2350255015Comparative Example 80.500.700.100.150.100.01--0.36Balance3502500 10 54010Comparative Example 90.500.700.100.150.100.01--0.36Balance35023502450 5Comparative Example 100.500.700.100.150.100.01--0.36Balance3508350256090 Comparative Example 110.500.70-0.050.10-0.15-0.30Balance200 8350254010Comparative Example 120.500.70-0.050.10-0.15-0.30Balance3502200 0.5 590 10Comparative Example 130.500.70-0.050.10-0.15-0.30Balance3502450 10 50010Comparative Example 140.500.70-0.050.10-0.15-0.30Balance35023502480 5Note: underlined bold letters in the Table indicate that the value is outside the preferred range of the present invention. [Table 2] Metal structurePerformance evaluationOverall evaluationAbundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less with respect to all of the measurement points in the measurement regionRatio of the number of the crystal grains having the <111> orientation group to the total number of the crystal grains having the <100> orientation group and the <110> orientation group 〈111〉 / (〈100〉+〈110〉)Average crystal grain size (µm)Tensile strengthElongation characteristicsElectric conductivityAverage valueStandard deviationAverage valueStandard deviationAverage valueResult (MPa)EvaluationResult (MPa)EvaluationResult (%)EvaluationResult (%)EvaluationResult (%IACS)EvaluationInventive Example 1721516239○7.45○14.2⊚0.35○52.3⊚○Inventive Example 2752014238○6.25○13.4○0.33○50.1⊚○Inventive Example 37379255⊚3.56⊚143⊚0.26⊚50.3⊚⊚Inventive Example 481139254⊚4.55⊚14.1⊚0.21⊚50.6⊚⊚Inventive Example 57368252⊚3.25⊚143⊚0.11⊚50.4⊚⊚Inventive Example 6681013254⊚5.65○12.8○0.36○48.8○○Inventive Example 775209255⊚3.20⊚14.2⊚0.25⊚50.3⊚⊚Inventive Example 878206254⊚3.12⊚14.1⊚0.28⊚50.5⊚⊚Inventive Example 98145251⊚3.88⊚14.8⊚0.17⊚50.6⊚⊚Inventive Example 10662512273⊚5.31○12.6○0.35○48.3○○Inventive Example 11682011255⊚5.15○13.3○0.42○48.5○○Inventive Example 12742810260⊚5.21○14.5⊚0.37○48.8○○Inventive Example 1378189261⊚3.85⊚14.5⊚0.19⊚50.3⊚⊚Inventive Example 148299263⊚2.58⊚14.6⊚0.16⊚50.2⊚⊚Inventive Example 15582312245○5.67○13.1○0.35○48.7○○Inventive Example 16722713243○5.25○12.8○0.39○48.6○○Inventive Example 17771510263⊚5.35○14.6⊚0.44○49.0○○Inventive Example 1880237268⊚3.83⊚142⊚0.19⊚50.4⊚⊚Inventive Example 1981259260⊚2.64⊚14.3⊚0.14⊚50.3⊚⊚Inventive Example 20741014243○5.85○12.8○0.45○48.7○○Inventive Example 21782815243○5.19○13.1○0.58○48.7○○Inventive Example 22781512245○5.45○12.8○0.62○49.0○○Comparative Example 1741513179 x5.27○18.1⊚0.66○55.0⊚xComparative Example 2772011292⊚6.15○10.8 ×0.34○43.9 ××Comparative Example 388 15010185 ×20.00 ×11.0 ×2.10 ×51.4⊚×Comparative Example 492 7510214 ×14.63 ×11.0 ×1.13 ×49.7○×Comparative Example 587 806234○16.21 ×11.9 ×1.14 ×49.3○×Comparative Example 689 10010223 ×12.34 ×11.6 ×0.88 ×49.6○×Comparative Example 790 1206218 ×10.30 ×11.0 ×0.89 ×49.2○×Comparative Example 892 209208 ×16.91 ×10.9 ×0.84 ×49.9○×Comparative Example 988 7510194 ×13.56 ×10.2 ×0.87 ×51.6⊚×Comparative Example 1090 25025176 ×11.66 ×8.5 ×1.03 ×47.5 ××Comparative Example 1191 259210 ×13.84 ×10.3 ×1.01 ×49.9○×Comparative Example 1293 9015195 ×11.06 ×10.0 ×1.03 ×47.3 ××Comparative Example 1392 2509202 ×9.27○10.3 ×0.94 ×49.9○×Comparative Example 1491 20011206 ×9.70○10.0 ×1.03 ×50.6⊚× Note: underlined bold letters in the Table indicate that the value is outside the preferred range of the present invention.

[0086] As shown in Tables 1 and 2, in Examples 1 to 22 of the present invention, as a result of producing the aluminum alloy wires having a predetermined alloy composition by performing the first heat treatment step, the second heat treatment step, and the third heat treatment step of the production process under the control of the predetermined conditions, the aluminum alloy wires where an abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less was 85% or less with respect to all the measurement points were obtained, in the crystal orientation analysis of the transverse section of the aluminum alloy wire by the electron backscatter diffraction (EBSD) method. As a result of the evaluation, the aluminum alloy wires of all of Examples 1 to 22 of the present invention were confirmed to have excellent elongation characteristics while having high tensile strength and high electric conductivity, and display an excellent balance and small variations in the tensile strength and the elongation characteristics along the longitudinal direction.

[0087] On the other hand, in Comparative Example 1 in which the contents of both Mg and Si in the alloy composition were outside the appropriate range due to low contents thereof, the average value of the tensile strength did not meet the acceptable level and was poor. In Comparative Example 2 in which the contents of both Mg and Si in the alloy composition were outside the appropriate range due to high contents thereof, the average values of the elongation characteristics and the electric conductivity did not meet the acceptable level and were poor. In Comparative Examples 3 to 14 in which the abundance proportion of the measurement points having a crystal orientation difference between adjacent measurement points of 5° or less with respect to all of the measurement points exceeded 85%, at least the average value of the tensile strength, the average value and the standard deviation of the elongation characteristics did not meet the acceptable level and were poor.

Examples

examples

[0068]Next, Examples of the present invention and Comparative Examples will be described, but the present invention is not limited to these Examples.

[0069]Aluminum raw materials and additive elements were selected so as to have the compositions shown in Table 1, and a continuous casting and rolling step was performed using a continuous casting and rolling machine (manufactured by Properzi) to produce an aluminum wire rod as a rolled material having a transverse section perpendicular to the longitudinal direction corresponding to a circular shape having a diameter of 9.5 mm. After the aluminum wire rod was subjected to the first heat treatment step under the condition of the temperature and the time shown in Table 1, the aluminum wire rod was subjected to the first wire drawing step of adjusting the size of the transverse section to a size corresponding to a circular shape having a diameter of 2.6 mm, then subjected to the second heat treatment step under the condition of the tempera...

Claims

1. An aluminum alloy wire comprising: an alloy composition including 0.30% by mass or more and 0.70% by mass or less of Mg and 0.30% by mass or more and 1.00% by mass or less of Si, with a balance being Al and inevitable impurities; and an abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less being 85% or less with respect to all of the measurement points, in a crystal orientation analysis by an electron backscatter diffraction (EBSD) method performed in an observation region of a transverse section perpendicular to a longitudinal direction of the aluminum alloy wire.

2. An aluminum alloy wire comprising: an alloy composition including 0.30% by mass or more and 0.70% by mass or less of Mg and 0.30% by mass or more and 1.00% by mass or less of Si, further including one or more components selected from the group consisting of Mn, Fe, Ni, Ti, Cr and Zr in a range of 0.001% by mass or more and 0.55% by mass or less in total, with a balance being Al and inevitable impurities; and an abundance proportion of measurement points having a crystal orientation difference between adjacent measurement points of 5° or less being 85% or less with respect to all of the measurement points, in a crystal orientation analysis by an electron backscatter diffraction (EBSD) method performed in an observation region of a transverse section perpendicular to a longitudinal direction of the aluminum alloy wire.

3. The aluminum alloy wire according to claim 1 or 2, wherein, in the crystal orientation analysis performed in the observation region, when crystal orientations within <100> orientation ±5° are defined as a <100> orientation group, crystal orientations within <110> orientation ±5° are defined as a <110> orientation group, and crystal orientations within <111> orientation ±5° are defined as a <111> orientation group, a ratio of the number of the crystal grains having the <111> orientation group to the total number of the crystal grains having the <100> orientation group and the <110> orientation group (<111> orientation group / (<100> orientation group + <110> orientation group)) is in a range of 5 or more and 30 or less.

4. The aluminum alloy wire according to claim 1 or 2, wherein an average crystal grain size of crystal grains obtained from the crystal orientation analysis performed in the observation region is in a range of 5 µm or more and 9 µm or less.

5. An electric wire comprising the aluminum alloy wire according to claim 1 or 2.

6. A wire harness comprising the electric wire according to claim 5.

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