Aluminum wire, aluminum stranded wire, coated wire, coated wire with a crimp terminal, and a CVT cable or a CVT cable with a crimp terminal

Abstract

This aluminum wire rod has a composition which contains 3.00% by mass or less of Fe and 0.20% by mass or less of Si, and additionally contains a total of from 0.010% by mass to 0.500% by mass of one or more elements selected from the group consisting of Cu, Mn, Mg, Zn, Ti, B, V and Ni, with the balance being made up of Al and unavoidable impurities. With respect to this aluminum wire rod, in a 25 μm × 60 μm region in a cross-section that is perpendicular to the longitudinal direction, the total length of the portions where the crystal misorientation with respect to an adjacent crystal grain is more than 1° but not more than 15° is from 0.6 mm to 4.8 mm; and the electrical conductivity is 55% IACS or more.

Description

Technical Field

[0001] The present disclosure relates to an aluminum wire, an aluminum stranded wire, a coated electric wire, a coated electric wire with a crimp terminal, and a CVT cable or a CVT cable with a crimp terminal.

Background Art

[0002] When aluminum is used for a power cable such as an underground distribution cable like a CVT cable, pure aluminum with high conductivity or an aluminum alloy with dilute additive elements is used for the purpose of suppressing Joule heat. On the other hand, the strength of such pure aluminum or aluminum alloy wire is lower than that of a copper wire.

[0003] For example, Patent Document 1 describes an aluminum alloy for a wire containing 2.0% by mass or more and 3.5% by mass or less of Fe, with the balance being Al and unavoidable impurities, and further containing 0.2% by mass or more and 1.0% by mass or less of Si. Further, Patent Document 1 describes an aluminum alloy wire having a structure having aluminum crystal grains and particles of an Al—Fe compound or an Al—Fe—Si compound composed of aluminum and iron, and particles of an Al—Fe compound or an Al—Fe—Si compound having an average size of 1000 nm or less are dispersed inside or at the grain boundaries of the aluminum crystal grains.

[0004] As described above, in Patent Document 1, the tensile strength of the aluminum alloy wire is improved by adding Fe and Si and controlling the second phase. However, in the crimped portion with the crimp terminal in the wire of pure aluminum or aluminum alloy, although a decrease in conductivity, a decrease in crimped portion strength, and a decrease in impact resistance become problems, Patent Document 1 has not sufficiently studied the decrease in these properties.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] An object of the present disclosure is to provide an aluminum wire, an aluminum stranded wire, a coated wire, a coated wire with a crimp terminal, and a CVT cable or a CVT cable with a crimp terminal that can suppress a decrease in conductivity, crimp portion strength, and impact resistance at the crimp portion with the crimp terminal even when crimped with the crimp terminal.

MEANS FOR SOLVING THE PROBLEMS

[0007] [1] An aluminum wire having a composition containing 3.00% by mass or less of Fe, 0.20% by mass or less of Si, further containing a total of 0.010% by mass or more and 0.500% by mass or less of one or more elements selected from the group consisting of Cu, Mn, Mg, Zn, Ti, B, V, and Ni, with the balance being Al and unavoidable impurities, and in a region of 25 μm × 60 μm in a cross section perpendicular to the longitudinal direction, the total length of portions where the crystal orientation difference from adjacent crystal grains exceeds 1° and is 15° or less is 0.6 mm or more and 4.8 mm or less, and the conductivity is 55% IACS or more. [2] The aluminum wire according to [1] above, wherein the composition contains 0.25% by mass or less of Fe. [3] The aluminum wire according to [1] or [2] above, wherein the ratio of the KAM value with a crystal orientation difference exceeding 1° and being 15° or less to the region is 0.50 or more and 0.90 or less. [4] The aluminum wire according to any one of [1] to [3] above, wherein the average crystal grain size in the cross section is 0.10 μm or more and 10.00 μm or less. [5] An aluminum stranded wire formed by twisting 19 or more and 61 or less of the aluminum wires according to any one of [1] to [4] above, wherein the wire diameter of the aluminum wire is 1.4 mm or more and 2.9 mm or less. [6] A coated electric wire, characterized by comprising the aluminum stranded wire described in [5] above, a cylindrical insulator covering the outer periphery of the aluminum stranded wire, and a sheath covering the outer periphery of the insulator. [7] A coated electric wire with a crimp terminal, characterized by having a crimp terminal crimped to the coated electric wire described in [6] above. [8] A CVT cable or a CVT cable with a crimp terminal, characterized by twisting three of the coated electric wires described in [6] above or the coated electric wires with a crimp terminal described in [7] above together.

Advantages of the Invention

[0008] According to the present disclosure, it is possible to provide an aluminum wire, an aluminum stranded wire, a coated electric wire, a coated electric wire with a crimp terminal, and a CVT cable or a CVT cable with a crimp terminal that can suppress a decrease in conductivity, crimp strength, and impact resistance at the crimp portion with the crimp terminal even when crimped with a crimp terminal.

Brief Description of the Drawings

[0009]

Figure 1

Modes for Carrying Out the Invention

[0010] Hereinafter, a detailed description will be given based on an embodiment.

[0011] As a result of intensive research, the inventors of the present invention have found that by paying attention to the small-angle grain boundaries in the crystal structure of the aluminum wire, it is possible to suppress a decrease in conductivity, crimp strength, and impact resistance at the crimp portion with the crimp terminal even when crimped with a crimp terminal, and based on such findings, the present disclosure has been completed.

[0012] The aluminum wire of the embodiment contains Fe of 3.00 mass% or less and Si of 0.20 mass% or less, further contains a total of 0.010 mass% or more and 0.500 mass% or less of one or more elements selected from the group consisting of Cu, Mn, Mg, Zn, Ti, B, V, and Ni, and the balance is composed of Al and unavoidable impurities, and in a region of 25 μm × 60 μm in a cross section perpendicular to the longitudinal direction, the total length of portions where the crystal orientation difference from adjacent crystal grains is more than 1° and 15° or less is 0.6 mm or more and 4.8 mm or less, and the conductivity is 55% IACS or more.

[0013] FIG. 1 is a perspective view showing an example of the main part configuration of a coated electric wire with a crimp terminal having the aluminum wire of the embodiment. As shown in FIG. 1, the coated electric wire 10 with a crimp terminal has an aluminum stranded wire 2 formed by stranding a plurality of aluminum wires 1. A cylindrical insulator 3 is provided on the outer periphery of the aluminum stranded wire 2. A cylindrical sheath 4 is provided on the outer periphery of the insulator 3. The coated electric wire 6 has the aluminum stranded wire 2, the insulator 3, and the sheath 4. A crimp terminal 5 is crimped to a portion where the aluminum stranded wire 2 in the coated electric wire 10 with a crimp terminal is exposed.

[0014] <Composition> First, the composition of the aluminum wire will be described. The composition of the aluminum wire contains Fe of 3.00 mass% or less and Si of 0.20 mass% or less, further contains a total of 0.010 mass% or more and 0.500 mass% or less of one or more elements selected from the group consisting of Cu, Mn, Mg, Zn, Ti, B, V, and Ni, and the balance is composed of Al and unavoidable impurities.

[0015] Regarding the composition of the aluminum wire, when the content of Al is 99.5 mass% or more, the conductivity is improved and the availability is increased. From such a viewpoint, the content of Al is preferably 99.7 mass% or more. The composition of the aluminum wire is preferably the composition of pure aluminum such as A1070.

[0016] Fe (iron) is an element that improves the strength of the aluminum wire. The content of Fe contained in the aluminum wire is preferably 0.05% by mass or more, more preferably 0.10% by mass or more. When the content of Fe is 0.05% by mass or more, the strength of the aluminum wire increases, and a decrease in the crimping strength and impact resistance in the crimped portion crimped by the crimp terminal can be sufficiently suppressed. Also, the content of Fe contained in the aluminum wire is 3.00% by mass or less, and when high conductivity is required, it is better to have a lower content of Fe, so it is preferably 0.25% by mass or less.

[0017] Si (silicon) is an element that improves the strength of the aluminum wire. The content of Si contained in the aluminum wire is preferably 0.01% by mass or more, more preferably 0.05% by mass or more. When the content of Si is 0.01% by mass or more, the strength of the aluminum wire increases, and a decrease in the crimping strength and impact resistance in the crimped portion can be sufficiently suppressed. Also, the content of Si contained in the aluminum wire is 0.20% by mass or less, preferably 0.15% by mass or less. When the content of Si exceeds 0.20% by mass, it becomes a practical problem due to a decrease in conductivity.

[0018] <Sub-components> The composition of the aluminum wire can further contain one or more elements selected from the group consisting of Cu, Mn, Mg, Zn, Ti, B, V, and Ni. Considering the balance between strength and conductivity, these components are contained in a total amount of 0.010% by mass or more and 0.500% by mass or less. Each sub-component will be described below.

[0019] When the Cu (copper) content is 0.010 mass% or more, while maintaining the high electrical conductivity of the aluminum wire, the strength of the aluminum wire can be improved, so that a decrease in the crimping strength and impact resistance in the caulked portion can be suppressed. When the Cu content is 0.100 mass% or less, high electrical conductivity can be maintained. Therefore, the lower limit value of the Cu content is preferably 0.010 mass% or more, more preferably 0.030 mass% or more, and the upper limit value of the Cu content is preferably 0.100 mass% or less, more preferably 0.050 mass% or less.

[0020] When the Mn (manganese) content is 0.010 mass% or more, while maintaining the high electrical conductivity of the aluminum wire, the strength of the aluminum wire can be improved. When the Mn content is 0.100 mass% or less, high electrical conductivity can be maintained. Therefore, the lower limit value of the Mn content is preferably 0.010 mass% or more, more preferably 0.030 mass% or more, and the upper limit value of the Mn content is preferably 0.100 mass% or less, more preferably 0.080 mass% or less.

[0021] When the Mg (magnesium) content is 0.030 mass% or more, while maintaining the high electrical conductivity of the aluminum wire, the strength of the aluminum wire can be improved. When the Mg content is 0.500 mass% or less, high electrical conductivity can be maintained. Therefore, the lower limit value of the Mg content is preferably 0.030 mass% or more, more preferably 0.100 mass% or more, and the upper limit value of the Mg content is preferably 0.500 mass% or less, more preferably 0.200 mass% or less.

[0022] When the Zn (zinc) content is 0.020 mass% or more, while maintaining the high electrical conductivity of the aluminum wire, the strength of the aluminum wire can be improved. When the Zn content is 0.100 mass% or less, high electrical conductivity can be maintained. Therefore, the lower limit value of the Zn content is preferably 0.020 mass% or more, more preferably 0.050 mass% or more, and the upper limit value of the Zn content is preferably 0.100 mass% or less, more preferably 0.080 mass% or less.

[0023] When the Ti (titanium) content is 0.005 mass% or more, the crystals in the aluminum ingot obtained in the casting process are refined, so that cracks and wire breaks are less likely to occur during subsequent cold drawing. When the Ti content is 0.100 mass% or less, high ductility and high conductivity can be maintained. Therefore, the lower limit of the Ti content is preferably 0.005 mass% or more, more preferably 0.010 mass% or more, and the upper limit of the Ti content is preferably 0.100 mass% or less, more preferably 0.050 mass% or less.

[0024] When the B (boron) content is 0.004 mass% or more, the crystals in the aluminum ingot obtained in the casting process are refined, so that cracks and wire breaks are less likely to occur during cold drawing. When the B content is 0.050 mass% or less, high ductility and high conductivity can be maintained. Therefore, the lower limit of the B content is preferably 0.004 mass% or more, more preferably 0.010 mass% or more, and the upper limit of the B content is preferably 0.050 mass% or less, more preferably 0.030 mass% or less.

[0025] When the V (vanadium) content is 0.003 mass% or more, impurities can be easily removed from the molten metal during the casting process. When the V content is 0.050 mass% or less, high ductility and high conductivity can be maintained. Therefore, the lower limit of the V content is preferably 0.003 mass% or more, more preferably 0.005 mass% or more, and the upper limit of the V content is preferably 0.050 mass% or less, more preferably 0.030 mass% or less.

[0026] When the Ni (nickel) content is 0.005 mass% or more, the strength of the aluminum wire can be improved while maintaining the high conductivity of the aluminum wire. When the Ni content is 0.020 mass% or less, high conductivity can be maintained. Therefore, the lower limit of the Ni content is preferably 0.005 mass% or more, more preferably 0.010 mass% or more, and the upper limit of the Ni content is preferably 0.020 mass% or less, more preferably 0.015 mass% or less.

[0027] <Remainder: Al and inevitable impurities> Regarding the composition of the aluminum wire, the remainder other than the above-described components is Al (aluminum) and inevitable impurities. Inevitable impurities may be unavoidably contained during the manufacturing process, and depending on the content, they may also be a factor in reducing the conductivity and strength of the aluminum wire. Therefore, it is preferable that the content of inevitable impurities is low. Examples of inevitable impurities include elements such as Li and Cr. The upper limit of the content of inevitable impurities is preferably 0.05% by mass or less, more preferably 0.01% by mass or less.

[0028] <Conductivity> Next, the conductivity of the aluminum wire will be described. The aluminum wire has high conductivity. The conductivity of the aluminum wire can be calculated from the cross-sectional area of the aluminum wire by measuring the resistance value by the four-terminal method in a thermostatic bath maintained at 20°C (±0.5°C) with a terminal distance of 200 mm. The conductivity of the aluminum wire is 55% IACS or more, preferably 62% IACS or more.

[0029] <Crystal orientation difference> Next, the crystal orientation difference of the aluminum wire will be described. In a region of 25 μm × 60 μm (hereinafter also simply referred to as the region) in a cross-section perpendicular to the longitudinal direction of the aluminum wire (hereinafter also referred to as the cross-section), the total length (hereinafter also simply referred to as the length) of the portions where the crystal orientation difference from adjacent crystal grains exceeds 1° and is 15° or less is 0.6 mm or more and 4.8 mm or less. Thus, in the above-described region in the cross-section of the aluminum wire, the portions where the crystal orientation difference from adjacent crystal grains exceeds 1° and is 15° or less, that is, the small-angle grain boundaries, have a length within the above range.

[0030] When the length within the above-mentioned region is 0.6 mm or more, a predetermined amount of strain due to small-angle grain boundaries remains in the aluminum wire, so that the balance between the strength and ductility of the aluminum wire is good. Further, when a predetermined amount of strain due to small-angle grain boundaries remains in the aluminum wire, the change in physical properties of the caulked portion caulked by the crimp terminal can be reduced, so that the decrease in the caulking portion strength and impact resistance in the caulked portion can be suppressed. Also, when the length within the above-mentioned region is 4.8 mm or less, the decrease in the ductility of the aluminum wire due to the excessive amount of strain due to small-angle grain boundaries can be suppressed, and the decrease in the impact resistance of the caulked portion can be suppressed. From such a viewpoint, the lower limit value of the length within the above-mentioned region is 0.6 mm or more, preferably 1.5 mm or more, and the upper limit value is 4.8 mm or less, preferably 4.0 mm or less.

[0031] The total length of all portions with a crystal orientation difference of more than 1° and 15° or less from adjacent crystal grains can be obtained from the crystal orientation analysis data calculated using analysis software (OIM Analysis manufactured by TSL) from the crystal orientation data continuously measured using an EBSD detector (OIM5.0 HIKARI manufactured by TSL) attached to a high-resolution scanning transmission electron microscope (JSM-7001FA manufactured by JEOL Ltd.). "EBSD" is an abbreviation for Electron BackScatter Diffraction, which is a crystal orientation analysis technique that utilizes the reflection electron Kikuchi line diffraction generated when an electron beam is irradiated onto an aluminum wire, which is a measurement sample, in a scanning electron microscope (SEM). "OIM Analysis" is analysis software for the data measured by EBSD. The measurement target is the surface of a cross-section perpendicular to the longitudinal direction of a single aluminum wire that has been mirror-finished by electrolytic polishing, and the measurement region is 25 μm × 60 μm. The measurement is performed at a step size of 0.1 μm. Using the analysis software, based on the image of Rotation Angle, the total length of all portions with a crystal orientation difference of more than 1° and 15° or less from adjacent crystal grains is calculated. This measurement is performed on n3 (samples of three aluminum wires), and the average value is calculated.

[0032] <kam> In addition, the ratio of the KAM value with a crystal orientation difference of more than 1° and 15° or less with respect to the above region in the cross section perpendicular to the longitudinal direction of the aluminum wire is preferably 0.50 or more and 0.90 or less.

[0033] When the ratio of the KAM value is 0.50 or more, a certain amount of strain including small-angle grain boundaries and crystal grains remains in the aluminum wire, so the balance between the strength and ductility of the aluminum wire is good. Furthermore, when a certain amount of strain including small-angle grain boundaries and crystal grains remains, the physical property change of the caulked portion can be reduced, so the decrease in the crimping portion strength and impact resistance in the caulked portion can be suppressed. Also, when the ratio of the KAM value is 0.90 or less, the decrease in the ductility of the aluminum wire due to the excessive amount of strain including small-angle grain boundaries and crystal grains can be suppressed, and the decrease in the impact resistance of the caulked portion can be suppressed. From such a viewpoint, for the ratio of the KAM value, the lower limit is preferably 0.50 or more, more preferably 0.60 or more, and the upper limit is preferably 0.90 or less, more preferably 0.85 or less.

[0034] The KAM (Kernel Average Misorientation) value represents the average orientation difference between the measurement point and the surrounding measurement points. When the orientation difference is large, the KAM value becomes large. When the KAM value is large, a large amount of strain exists in the aluminum wire.

[0035] The KAM value can be obtained from the crystal orientation analysis data calculated using analysis software (OIM Analysis, manufactured by TSL) from the crystal orientation data continuously measured using an EBSD detector (OIM5.0 HIKARI, manufactured by TSL) attached to a high-resolution scanning analytical electron microscope (JSM-7001FA, manufactured by JEOL Ltd.). The measurement target is the surface of a cross-section perpendicular to the longitudinal direction of a single aluminum wire rod, mirror-finished by electrolytic polishing, and the measurement area is 25 μm × 60 μm. The measurement is performed at a step size of 0.1 μm. Using the analysis software, the ratio of the KAM value with a crystal orientation difference exceeding 1° and not exceeding 15° to the measurement area is calculated in the KAM image. Note that the maximum value of the KAM value is set to 15°. This measurement is performed on n3 (samples of three aluminum wire rods), and the average value is calculated.

[0036] <Crystal grain size> Moreover, the average crystal grain size in the cross-section of the aluminum wire rod is preferably 0.10 μm or more and 10.00 μm or less.

[0037] When the above average crystal grain size is 0.10 μm or more, a decrease in the ductility of the aluminum wire rod can be suppressed. Also, when the above average crystal grain size is 10.00 μm or less, a decrease in the strength of the aluminum wire rod can be suppressed. From such a perspective, regarding the average crystal grain size in the cross-section of the aluminum wire rod, the lower limit value is preferably 0.10 μm or more, more preferably 0.20 μm or more, and the upper limit value is preferably 10.00 μm or less, more preferably 5.00 μm or less.

[0038] The average crystal grain size can be obtained from the crystal orientation analysis data calculated using analysis software (manufactured by TSL, OIM Analysis) from the crystal orientation data continuously measured using an EBSD detector (manufactured by TSL, OIM5.0 HIKARI) attached to a high-resolution scanning analytical electron microscope (manufactured by JEOL Ltd., JSM-7001FA). The measurement object is the surface of a cross-section perpendicular to the longitudinal direction of a single aluminum wire rod, which has been mirror-finished by electrolytic polishing, and the measurement area is 25 μm × 60 μm. The measurement is performed with a step size of 0.1 μm. The average crystal grain size is calculated using the Grain Size (Diameter) chart by the analysis software. This measurement is performed on n3 (samples of three aluminum wire rods), and the average value is calculated.

[0039] <Stranded wire> Also, even in an aluminum stranded wire formed by twisting a plurality of the above aluminum wire rods as base wires, similar to the above aluminum wire rods, even when caulked with a crimp terminal, it is possible to suppress a decrease in conductivity, caulking part strength, and shock resistance at the caulking part with the crimp terminal. In an aluminum stranded wire formed by twisting 19 or more and 61 or less aluminum wire rods having a wire diameter of 1.4 mm or more and 2.9 mm or less, a decrease in conductivity, caulking part strength, and shock resistance at the caulking part is further suppressed. In particular, when the number of aluminum wire rods having a wire diameter within the above range is 19 or more, the flexibility of the aluminum stranded wire increases, so the workability with respect to the aluminum stranded wire can be improved. Also, when the number of aluminum wire rods having a wire diameter within the above range is 61 or less, the occurrence of breakage of the base wires of the aluminum wire rods constituting the aluminum stranded wire can be suppressed. The number of aluminum wire rods constituting the aluminum stranded wire and the wire diameter of the aluminum wire rods are appropriately selected according to the use of the aluminum stranded wire, such as the energizing current value and heat-resistant temperature of the aluminum stranded wire.

[0040] <Use> In addition, a coated electric wire having the above aluminum stranded wire formed by twisting the plurality of aluminum wire rods, a cylindrical insulator covering the outer periphery of the aluminum stranded wire, and a sheath covering the outer periphery of the insulator can suppress a decrease in conductivity, crimping portion strength, and impact resistance at the crimping portion with the crimp terminal, even when crimped with a crimp terminal, similar to the above aluminum wire rods and aluminum stranded wire. Further, since the coated electric wire has an insulator and a sheath, it has good insulation properties and heat resistance. When the insulator is made of polyolefin such as polyethylene or polypropylene, or polyvinyl chloride, etc., the insulation properties of the coated electric wire are even better. Also, when the sheath is made of vinyl chloride resin or flame-retardant polyethylene, the heat resistance of the coated electric wire is even better.

[0041] In addition, a coated electric wire with a crimp terminal having a crimp terminal crimped to the above coated electric wire, specifically, a coated electric wire with a crimp terminal having the above coated electric wire and a crimp terminal crimped to the aluminum stranded wire constituting the above coated electric wire can suppress a decrease in conductivity, crimping portion strength, and impact resistance at the crimping portion with the crimp terminal, even when crimped with a crimp terminal, similar to the above aluminum wire rods and aluminum stranded wire. As shown in FIG. 1, in the coated electric wire 10 with a crimp terminal, the crimp terminal 5 is crimped to a portion of the aluminum stranded wire 2 where a part of the insulator 3 and the sheath 4 has been peeled off, so-called skinned, from the coated electric wire 6 to be exposed. The crimp terminal is made of a copper-based material including pure copper and copper alloys, or an aluminum-based material including pure aluminum and aluminum alloys.

[0042] Also, even in a power cable formed by twisting a plurality of the above coated electric wires, a decrease in conductivity, crimping portion strength, and impact resistance at the crimping portion with the crimp terminal can be suppressed, even when crimped with a crimp terminal, similar to the above. A CVT cable formed by twisting three of the above coated electric wires is suitable for three-phase AC wiring where suppression of the above decrease in conductivity, crimping portion strength, and impact resistance is particularly required.

[0043] In addition, a CVT cable with a crimp terminal having the above-described CVT cable and a crimp terminal crimped to an aluminum stranded wire constituting the CVT cable can also suppress a decrease in conductivity, crimping portion strength, and impact resistance at the crimping portion with the crimp terminal even when crimped with the crimp terminal. In the CVT cable with a crimp terminal, the crimp terminal is crimped to a portion of the aluminum stranded wire where a part of the insulator and the sheath is peeled off and exposed from one or more of the three covered wires constituting the CVT cable.

[0044] <Manufacturing method> Next, the manufacturing method of the above aluminum wire will be described. First, using a molten metal adjusted to a predetermined composition in a melting furnace, a rough-drawn wire with a wire diameter of 5 mm or more and 10 mm or less is obtained by a continuous casting and rolling machine. Then, for the purpose of adjusting the recrystallization driving force, the rough-drawn wire is subjected to primary annealing under the conditions of a heating temperature of 550°C or more and 630°C or less and a heating time of 0.5 hour or more and 3 hours or less. Subsequently, cold drawing is performed at a reduction rate of 50% or more and 99% or less. Subsequently, in order to adjust the strain amount and crystal grain size, contact annealing is performed by bringing the wire into contact with a heating body under the conditions of a heating temperature of 150°C or more and 400°C or less and a heating time of 1 second or more and 20 seconds or less. In this way, an aluminum wire can be obtained. Then, a plurality of aluminum wires are bundled by a stranding machine to form an aluminum stranded wire, and an insulator coating is applied to the aluminum stranded wire by an extruder, and further a sheath is applied to the outer periphery thereof to obtain a covered wire. Furthermore, the insulator and the sheath at the end of the covered wire are peeled off to partially expose the aluminum stranded wire, which is inserted into the tube portion of a terminal as a connecting member, and pressure is applied from the outer periphery of the tube portion to perform crimping, thereby obtaining a covered wire with a crimp terminal. Furthermore, three of the above covered wires are twisted together to obtain a CVT cable.

[0045] Under the above first annealing conditions, if annealing with a heating time of less than 0.5 hours within the above temperature range or annealing within the above time range at a heating temperature of less than 550°C is performed, the resulting aluminum wire rod will have a compositional bias, be prone to wire breakage during wire drawing, and have poor productivity. Also, under the above first annealing conditions, if annealing with a heating time exceeding 3 hours within the above temperature range or annealing within the above time range at a heating temperature exceeding 630°C is performed, the resulting aluminum wire rod will have insufficient material strength against the drawing force during wire drawing and cannot be wire-drawn.

[0046] When cold wire drawing is performed at a reduction rate of less than 50%, in the resulting aluminum wire rod, the total length of the portions with a crystallographic orientation difference between adjacent crystal grains of more than 1° and less than or equal to 15° is likely to be short, and in combination with subsequent contact annealing, it is highly likely to be less than 0.6 mm. Therefore, the crimping strength at the crimping part decreases. Also, when cold wire drawing is performed at a reduction rate of more than 99%, the total length of the portions with a crystallographic orientation difference between adjacent crystal grains of more than 1° and less than or equal to 15° is likely to be long, and in combination with subsequent contact annealing, it is highly likely to be more than 4.8 mm. Therefore, along with the decrease in ductility, the impact resistance at the crimping part decreases.

[0047] When cold wire drawing is performed at a reduction rate of 50% or more, the ratio of the KAM value with a crystallographic orientation difference between adjacent crystal grains of more than 1° and less than or equal to 15° is likely to be 0.50 or more, although it also depends on the combination with subsequent contact annealing. Therefore, the decrease in the crimping strength at the crimping part can be suppressed. Also, when cold wire drawing is performed at a reduction rate of 99% or less, the ratio of the KAM value with a crystallographic orientation difference between adjacent crystal grains of more than 1° and less than or equal to 15° is likely to be 0.90 or less, although it also depends on the combination with subsequent contact annealing. Therefore, the decrease in the impact resistance at the crimping part due to the decrease in ductility can be suppressed.

[0048] Under the conditions of the above-mentioned contact annealing, when annealing with a heating time of less than 1 second within the above temperature range or annealing within the above time range at a heating temperature of less than 150°C, in the obtained aluminum wire, the total length of all portions with a crystal orientation difference of more than 1° and less than or equal to 15° from adjacent crystal grains exceeds 4.8 mm. Therefore, along with the decrease in ductility, the impact resistance at the caulked portion decreases. Further, when annealing with a heating time exceeding 20 seconds within the above temperature range or annealing within the above time range at a heating temperature exceeding 400°C, in the obtained aluminum wire, the total length of all portions with a crystal orientation difference of more than 1° and less than or equal to 15° from adjacent crystal grains is less than 0.6 mm. Therefore, the crimping strength at the crimped portion in the caulked portion decreases.

[0049] According to the embodiments described above, by controlling variously the component composition, continuous casting and rolling conditions, first annealing conditions, wire drawing conditions, and contact annealing conditions during manufacturing, it is possible to control within a predetermined range the total length of all portions with a crystal orientation difference of more than 1° and less than or equal to 15° from adjacent crystal grains and the conductivity. As a result, even when the aluminum wire is caulked with a crimp terminal, it is possible to suppress a decrease in conductivity, crimping strength, and impact resistance at the caulked portion with the crimp terminal. Such an aluminum wire is suitable for an aluminum wire for an aluminum stranded wire with a crimp terminal.

[0050] Although the embodiments have been described above, the present invention is not limited to the above embodiments, includes all aspects included in the concept of the present disclosure and the scope of the claims, and can be variously modified within the scope of the present disclosure.

Examples

[0051] Next, examples and comparative examples will be described, but the present invention is not limited to these examples.

[0052] (Examples 1 to 21) Using the molten metal with the composition shown in Table 1, primary annealing, cold wire drawing, and contact annealing were performed under conditions that satisfied the crystal structure shown in Table 1. Then, aluminum wires with the wire diameters and numbers shown in Table 2 were twisted together, and after passing through the processes of stranding, insulator coating, and sheathing, a coated wire was obtained. The insulators and sheaths at both ends of the coated wire were stripped to partially expose the aluminum stranded wire, and terminals were crimped to the exposed portions to obtain a coated wire with crimped terminals. Note that aluminum terminals were used as the terminals for the connection members, and the inside of the tube portion of the terminals was sealed with a compound, which is an oil containing zinc powder, to ensure electrical contact with the exposed aluminum stranded wire. The crimping was performed with a compression ratio of 94%. The compression ratio is the ratio of the cross-sectional area of the aluminum conductor after crimping to the cross-sectional area of the aluminum conductor before crimping. The cross-section is the central portion of the crimped part cut perpendicular to the longitudinal direction of the terminal, and since it is manufactured so that the compression ratio is determined corresponding to the crimping depth, the compression ratio was determined in advance.

[0053] (Comparative Example 1) After obtaining a rough-drawn wire with a wire diameter of 9.5 mm using a continuous casting and rolling machine containing 3.50% by mass of Fe, annealing was performed at a heating temperature of 550°C for 2 hours. Subsequently, cold wire drawing was performed at a processing rate of 97%, and contact annealing was performed at a heating temperature of 300°C for 10 seconds. The subsequent steps were carried out in the same manner as in Example 1 to obtain a coated wire with crimped terminals.

[0054] (Comparative Example 2) It contained 0.50% by mass of Si, and contained a total of 0.530% by mass of Mn, Mg, Ti, B, and V in the composition shown in Table 1, and the rest was produced in the same manner as in Comparative Example 1.

[0055] (Comparative Example 3) Up to the point where cold wire drawing was performed at a processing rate of 97% with the composition shown in Table 1, it was the same as in Comparative Example 1, and then it was finished without performing contact annealing. The subsequent steps were carried out in the same manner as in Example 1 to obtain a coated wire with crimped terminals.

[0056] (Comparative Example 4) Up to the annealing at a heating temperature of 550°C for 2 hours with the composition shown in Table 1, it was carried out in the same manner as Comparative Example 1. After that, it was drawn to a wire diameter of 1.5 mm. Subsequently, after annealing at a heating temperature of 300°C for 2 hours, it was drawn to a wire diameter of 1.4 mm. Then, contact annealing at 300°C for 10 seconds was carried out. The subsequent steps were carried out in the same manner as in Example 1 to obtain a coated electric wire with a crimp terminal.

[0057] (Comparative Example 5) Up to the cold drawing with a processing rate of 97% with the composition shown in Table 1, it was carried out in the same manner as Comparative Example 1. After that, contact annealing at 550°C for 10 seconds was carried out. The subsequent steps were carried out in the same manner as in Example 1 to obtain a coated electric wire with a crimp terminal.

[0058]

Table 1

[0059]

Table 2

[0060] [Measurement and Evaluation] In order to evaluate the cross-sectional area reduction in the crimped portion of the crimp terminal of the coated electric wire with a crimp terminal obtained in the above Examples and Comparative Examples and the influence of the contact state between the inner side of the crimp terminal tube portion and the aluminum stranded wire, the following measurements and evaluations were carried out using a sample including the crimp portion with the crimp terminal. The results are shown in Table 1 and Table 3.

[0061] [1] In a region of 25 μm × 60 μm in a cross-section perpendicular to the longitudinal direction, the total length of all portions where the crystal orientation difference from adjacent crystal grains exceeds 1° and is 15° or less The above length in the above region was obtained from the crystal orientation analysis data calculated using analysis software (manufactured by TSL, OIM Analysis) from the crystal orientation data continuously measured using an EBSD detector (manufactured by TSL, OIM5.0 HIKARI) attached to a high-resolution scanning type analytical electron microscope (manufactured by JEOL Ltd., JSM-7001FA) for the coated electric wire with a crimp terminal.

[0062] The measurement object was the surface of the cross-section of the aluminum wire rod polished to a mirror finish by electrolytic polishing, and the measurement area was 25 μm × 60 μm. The measurement was performed with a step size of 0.1 μm. Based on the image of the Rotation Angle by the analysis software, the total length of all parts with a crystal orientation difference of more than 1° and less than or equal to 15° from adjacent crystal grains was calculated. This measurement was performed n3 times, and the average value was calculated as the above length.

[0063] [2] Ratio of the KAM value with a crystal orientation difference of more than 1° and less than or equal to 15° for a 25 μm × 60 μm region in the cross-section perpendicular to the longitudinal direction The ratio of the KAM value with a crystal orientation difference of more than 1° and less than or equal to 15° for the above region was obtained from the crystal orientation analysis data calculated using the analysis software (manufactured by TSL, OIM Analysis) from the crystal orientation data continuously measured using the EBSD detector (manufactured by TSL, OIM5.0 HIKARI) attached to the high-resolution scanning analytical electron microscope (manufactured by JEOL Ltd., JSM-7001FA) for the coated electric wire with a crimp terminal.

[0064] The measurement object was the surface of the cross-section of the aluminum wire rod polished to a mirror finish by electrolytic polishing, and the measurement area was 25 μm × 60 μm. The measurement was performed with a step size of 0.1 μm. Using the KAM image by the analysis software, the ratio of the KAM value with a crystal orientation difference of more than 1° and less than or equal to 15° for the measurement region was calculated. The maximum value of the KAM value was set to 15°. This measurement was performed n3 times, and the average value was calculated as the above ratio of the KAM value.

[0065] [3] Average crystal grain size The average crystal grain size was obtained from the crystal orientation analysis data calculated using the analysis software (manufactured by TSL, OIM Analysis) from the crystal orientation data continuously measured using the EBSD detector (manufactured by TSL, OIM5.0 HIKARI) attached to the high-resolution scanning analytical electron microscope (manufactured by JEOL Ltd., JSM-7001FA) for the coated electric wire with a crimp terminal.

[0066] The surface of the cross-section of the aluminum wire was mirror-finished by electrolytic polishing, and the measurement area was set to 25 μm × 60 μm. The measurement was carried out with a step size of 0.1 μm. The average grain size was calculated using analysis software on a Grain Size (Diameter) chart. This measurement was performed n3 times, and the average value was calculated as the average grain size.

[0067] [4] Conductivity Using a coated electric wire with a crimp terminal, the wire length was set to 200 mm, and current was passed through both terminals in a thermostat maintained at 20 °C (±0.5 °C). The resistance value was measured by the four-terminal method, and the conductivity of the aluminum stranded wire was calculated from the cross-sectional area of the aluminum wire. The resistance of the two terminals themselves was excluded. Such conductivity measurements were performed on three coated electric wires with crimp terminals, and the average value of the three measurement values was calculated as the conductivity. Regarding the conductivity, the following ranking was carried out. The higher the conductivity, the better, and the C rank is poor.

[0068] A: Conductivity is 62% IACS or more B: Conductivity is 55% IACS or more and less than 62% IACS C: Conductivity is less than 55% IACS

[0069] [5] Nominal breaking strength As the crimping strength, the nominal breaking strength of the coated electric wire with a crimp terminal was measured. The wire length was set to 200 mm, and both terminals were fixed with chucks, and a tensile test was carried out. The maximum force (N) required until breakage was divided by the cross-sectional area of the aluminum conductor (mm 2 ), and the nominal breaking strength (N / mm 2 ) was obtained, and the following ranking was carried out. Since the nominal breaking strength may be affected by variations in crimping and measurement, etc., considering the measurement accuracy, it was calculated in steps of 5 N / mm 2 (that is, for example, if it is 90 N / mm 2 or more to less than 95 N / mm 2 , it is expressed as 90 N / mm 2 ). The higher the nominal breaking strength, the more the decrease in the crimping strength at the crimping part can be suppressed, and the C rank is poor.

[0070] A: Nominal breaking strength is 110 N / mm 2 or more B: Nominal breaking strength is 90 N / mm 2 or more and less than 110 N / mm 2 less than C: Nominal breaking strength is 90 N / mm 2 less than

[0071] [6] Impact absorption energy As impact resistance, using a coated wire with a crimp terminal, the impact absorption energy was measured. Specifically, first, 1 m of a coated wire with a single-sided crimp terminal was prepared, and the insulation coating and sheath were stripped to form an aluminum stranded wire with a single-sided crimp terminal. A weight was attached to the end of the aluminum stranded wire where the crimp terminal was not connected. Subsequently, the crimp terminal was fixed with a vise so as to be perpendicular to the direction of gravity, the weight was lifted to the height of the crimp terminal, and the aluminum stranded wire was also lifted above the height of the crimp terminal. Then, the weight was released, and a free fall of 1 m corresponding to the length of the aluminum stranded wire was performed. In order to suppress the variation in the load on the crimp terminal, the distance between the weight and the crimp terminal immediately before lifting and releasing the weight was set within 10 times the diameter of the aluminum stranded wire. The above test was performed by replacing the weight variously, and the weight of the largest weight at which none of the strands of the aluminum stranded wire connected to the crimp terminal was broken was recorded. The potential energy at that time was divided by the cross-sectional area of the aluminum stranded wire to calculate the impact absorption energy of the aluminum stranded wire against the free fall of the weight. The weight was selected and tested so that the impact absorption energy value was in increments of 0.05 J / mm 2 The weight was selected and tested so as to be in increments. Regarding the impact absorption energy, the following ranking was performed. The greater the impact absorption energy, the more the decrease in impact resistance at the crimp portion can be suppressed.

[0072] A: Impact absorption energy is 0.50 J / mm 2 or more B: Impact absorption energy is 0.25 J / mm 2 or more and less than 0.50 J / mm 2 less than C: Impact absorption energy is 0.25 J / mm 2 less than

[0073] [7] Comprehensive Evaluation As a comprehensive evaluation, the following ranking was performed.

[0074] ◎: The conductivity is 62% IACS or more, the nominal breaking strength is 110 N / mm 2 or more, and the impact absorption energy is 0.50 J / mm 2 or more ○: The conductivity is 55% IACS or more, the nominal breaking strength is 90 N / mm 2 or more, and the impact absorption energy is 0.25 J / mm 2 or more, and the conductivity is 55% IACS or more and less than 62% IACS, or the nominal breaking strength is 90 N / mm 2 or more and less than 110 N / mm 2 or less, or the impact absorption energy is 0.25 J / mm 2 or more and less than 0.50 J / mm 2 or less ×: The conductivity is less than 55% IACS, or the nominal breaking strength is less than 90 N / mm 2 or less, or the impact absorption energy is less than 0.25 J / mm 2 or less

[0075]

Table 3

[0076] As shown in Tables 1 to 3, in Examples 1 to 21, having a predetermined composition, the total length of all portions where the crystal orientation difference from adjacent crystal grains is more than 1° and 15° or less was 0.6 mm or more and 4.8 mm or less, and the conductivity was 55% IACS or more. Therefore, it was possible to suppress a decrease in conductivity, crimping strength, and impact resistance. In particular, in Example 2, since the total length of all portions where the crystal orientation difference from adjacent crystal grains is more than 1° and 15° or less, the ratio of the KAM value where the crystal orientation difference is more than 1° and 15° or less, and the average crystal grain size were all within suitable ranges, it was possible to further suppress a decrease in conductivity, crimping strength, and impact resistance.

[0077] On the other hand, in Comparative Example 1 and Comparative Example 2, the component composition was outside the scope of the present invention, resulting in a decrease in conductivity. Furthermore, the impact resistance was inferior. In Comparative Example 3, since contact annealing was not performed, embrittlement occurred, and the total length of the portions where the crystal orientation difference exceeded 1° and was 15° or less was more than 4.8 mm, resulting in an extremely low impact resistance. In Comparative Example 4, since the working rate of cold drawing was less than 50%, the total length of the portions where the crystal orientation difference exceeded 1° and was 15° or less was less than 0.6 mm, resulting in a decrease in the strength of the crimped portion and the impact resistance. In Comparative Example 5, since the heating temperature of contact annealing was more than 400°C, due to coarsening of the particle size and removal of strain, the total length of the portions where the crystal orientation difference exceeded 1° and was 15° or less was less than 0.6 mm, resulting in a decrease in the strength of the crimped portion and the impact resistance.

Description of Reference Numerals

[0078] 1 Aluminum wire 2 Aluminum stranded wire 3 Insulator 4 Sheath 5 Crimp terminal 6 Coated wire 10 Coated wire with crimp terminal< / kam>

Claims

1. containing Fe of 3.00 mass% or less and Si of 0.20 mass% or less, further containing in total 0.010 mass% or more and 0.500 mass% or less of one or more elements selected from the group consisting of Cu, Mn, Mg, Zn, Ti, B, V, and Ni, with the balance being composed of Al and unavoidable impurities, in a region of 25 μm × 60 μm in a cross-section perpendicular to the longitudinal direction, the total length of portions where the crystal orientation difference from adjacent crystal grains is more than 1° and 15° or less is 0.6 mm or more and 4.8 mm or less, an aluminum wire characterized by having an electrical conductivity of 55% IACS or more.

2. The aluminum wire according to Claim 1, wherein the composition contains Fe of 0.25 mass% or less.

3. The aluminum wire according to Claim 1 or 2, wherein the ratio of the KAM value with a crystal orientation difference of more than 1° and 15° or less to the region is 0.50 or more and 0.90 or less.

4. The aluminum wire according to any one of Claims 1 to 3, wherein the average crystal grain size in the cross-section is 0.10 μm or more and 10.00 μm or less.

5. An aluminum stranded wire characterized by being formed by stranding 19 or more and 61 or less of the aluminum wires according to any one of Claims 1 to 4, and the wire diameter of the aluminum wire being 1.4 mm or more and 2.9 mm or less.

6. A coated electric wire characterized by having the aluminum stranded wire according to Claim 5, a cylindrical insulator covering the outer periphery of the aluminum stranded wire, and a sheath covering the outer periphery of the insulator.

7. A coated electric wire with a crimp terminal characterized by having a crimp terminal crimped to the coated electric wire according to Claim 6.

8. A CVT cable or a CVT cable with a crimp terminal characterized by being formed by stranding three of the coated electric wire according to Claim 6 or the coated electric wire with a crimp terminal according to Claim 7.

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