Aluminum alloy wire

Abstract

An aluminum alloy, an aluminum alloy wire, an aluminum alloy stranded wire, a covered electric wire, and a wire harness that are of high toughness and high electrical conductivity, and a method of manufacturing an aluminum alloy wire are provided. The aluminum alloy wire contains not less than 0.005% and not more than 2.2% by mass of Fe, and a remainder including Al and an impurity. It may further contain not less than 0.005% and not more than 1.0% by mass in total of at least one additive element selected from Mg, Si, Cu, Zn, Ni, Mn, Ag, Cr, and Zr. The Al alloy wire has an electrical conductivity of not less than 58% IACS and an elongation of not less than 10%. The Al alloy wire is manufactured through the successive steps of casting, rolling, wiredrawing, and softening treatment. The softening treatment can be performed to provide an excellent toughness such as elongation and impact resistance and thereby reduce fracture of the electric wire in the vicinity of a terminal portion when the wire harness is installed.

Claims

1. A covered electric wire for a wire harness, comprising: a conductor formed of aluminum alloy stranded wire formed by stranding together a plurality of aluminum alloy wires, and an insulating cover layer formed on an outer periphery of said conductor, said aluminum alloy wires consisting of not less than 1.05% and not more than 2.20% by mass of Fe, not less than 0.05% and not more than 0.5% by mass of Mg, not less than 0.005% and not more than 0.15% by mass in total of at least one additive element selected from the group consisting of Zn, Ni, Mn, Ag, Cr, and Zr, and a remainder of Al and an impurity, wherein the percentage by mass of Mg is greater than the percentage by mass of each one of the at least one additive element.

2. The covered electric wire for a wire harness according to claim 1, wherein a content of said Mg is not less than 0.2% by mass.

3. The covered electric wire for a wire harness according to claim 1, wherein a content of said Mg is not less than 0.1% and not more than 0.4% by mass.

4. The covered electric wire for a wire harness according to claim 1, wherein said group consists of Ni, Mn, Ag, and Zr.

5. The covered electric wire according to claim 1, wherein each of said aluminum alloy wires includes precipitates having a circle-equivalent diameter of 100 nm or less in a cross section of said aluminum alloy wire.

6. The covered electric wire according to claim 1, wherein each of said aluminum alloy wires has a diameter of not less than 0.2 mm and not more than 1.5 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph showing a relationship of a temperature for softening treatment with an electrical conductivity and a tensile strength, for an AlFeMg(Mn, Ni, Zr, Ag)-based alloy wire.

(2) FIG. 2 is a graph showing a relationship of a temperature for softening treatment with an electrical conductivity and a tensile strength, for an AlFeCu-based alloy wire.

(3) FIG. 3 is a microscope photograph of a cross section of an Al alloy wire, FIG. 3 (1) shows a sample having undergone a batch softening treatment, and FIG. 3 (2) shows a sample having undergone a continuous softening treatment.

(4) FIG. 4 is an illustration for illustrating a test method for an impact resistance test.

(5) FIG. 5 is an illustration for illustrating a test method for a terminal-securing-strength test.

MODES FOR CARRYING OUT THE INVENTION

(6) An Al alloy wire is produced, and this Al alloy wire is used to further produce a covered electric wire. Various characteristics of the Al alloy wire and the covered electric wire have been examined. The covered electric wire is produced through a procedure in the order of casting, rolling, wiredrawing, stranded wire, compression, softening, formation of an insulating cover layer.

(7) [Characteristics of Al Alloy Wire]

(8) First, an Al alloy wire is produced. As a base, pure aluminum (not less than 99.7% by mass of Al) is prepared and melt. To the obtained molten metal (molten aluminum), the additive elements shown in Table 1 with respective contents shown in Table 1 are added to produce a molten Al alloy. On the molten Al alloy with adjusted components, a hydrogen gas removal treatment and/or a foreign-matter removal treatment are/is preferably performed as appropriate.

(9) A belt-wheel-type continuous casting and rolling machine is used to continuously perform casting and hot rolling on the prepared molten Al alloy to produce a wire rod of 9.5 mm (continuously cast and rolled material). For the above-described continuous casting, a cooling mechanism or the like is adjusted to set the cooling rate to 4.5 C./sec. The DAS of the resultant cast material has been measured by means of a structure photograph and the measured DAS is approximately 20 m. Alternatively, the above-described molten Al alloy is poured into a predetermined fixed mold and cooled to produce a billet cast material, on which a homogenization treatment is performed and thereafter hot rolling is performed to produce a wire rod of 9.5 mm (rolled material). For samples containing Ti or containing Ti and B, Ti particle or TiB.sub.2 wire is fed to the molten Al alloy immediately before being cast so that the content(s) as shown in Table 1 is (are) satisfied.

(10) The above-described wire rod is subjected to cold wiredrawing to produce a wiredrawn material with a wire diameter of 0.3 mm. The wiredrawn material thus obtained is subjected to a softening treatment as shown in Table 1 to produce a softened material (Al alloy wire). For the softening treatment, a box-shaped furnace is used, and a batch treatment is performed in the atmosphere and at the heating temperature shown in Table 1 (holding time of each softening treatment is 3 hours, temperature decrease rate: 0.02 C./sec), or a continuous treatment is performed by means of a high-frequency induction heating method in the atmosphere shown in Table 1 (wire rate: 500 m/min, current value: 200 A, temperature decrease rate: 500 C./sec). Here, the continuous treatment has been performed on Samples No. 1-2 and No. 1-3, and the batch treatment has been performed on those samples other than samples No. 1-2 and No. 1-3 and having been softening-treated. The temperature in the continuous treatment has been measured with a non-contact infrared thermometer. For comparison's sake, untreated materials (Samples Nos. 1-102, 1-112) that are not softening-treated after being wiredrawn have also been prepared.

(11) TABLE-US-00001 TABLE 1 (AlFeMg) Conditions of Manufacture Softened Softening Softening Material Additive Elements (mass %) Temperature Treatment Sample No. Fe Mg Ti B Casting ( C.) Atmosphere 1-1 1.05 0.15 0.03 0.005 continuous 350 nitrogen gas casting 1-2 1.05 0.15 0.03 0.005 continuous 500 air casting 1-3 1.05 0.15 0.03 0.005 billet casting 1-4 1.05 0.15 0.03 0.005 billet casting 350 nitrogen gas (AlFeMg(Mn, Ni, Zr, Ag)) Softened Conditions of Manufacture Material Softening Softening Sample Additive Elements (mass %) Temperature Treatment No. Fe Mg Mn Ni Zr Ag Ti B Casting ( C.) Atmosphere 1-11 1.05 0.2 0.05 0.02 0.005 continuous 350 reducing gas casting 1-12 1.05 0.2 0.05 continuous 350 reducing gas casting 1-13 1.05 0.2 0.05 0.02 0.005 continuous 350 nitrogen gas casting 1-14 1.05 0.2 0.1 0.02 continuous 350 reducing gas casting 1-15 1.05 0.2 0.05 0.005 billet casting 350 reducing gas 1-16 0.8 0.05 0.05 continuous 350 reducing gas casting 1-101 3 0.8 3 continuous 350 reducing gas casting 1-102 1.05 0.2 0.05 0.02 0.005 continuous casting (AlFeCu) Softened Conditions of Manufacture Material Softening Softening Sample Additive Elements (mass %) Temperature Treatment No. Fe Cu Mg Si Ti B Casting ( C.) Atmosphere 1-21 1.05 0.2 continuous 350 argon gas casting 1-22 1.05 0.3 0.2 0.02 0.005 continuous 350 reducing casting gas 1-23 1.1 0.2 0.1 0.02 0.005 continuous 350 nitrogen gas casting 1-24 1.1 0.2 0.2 0.1 0.02 continuous 350 reducing casting gas 1-25 1.05 0.2 billet 350 reducing casting gas 1-26 0.8 0.02 continuous 350 reducing casting gas 1-111 3 0.8 continuous 350 reducing casting gas 1-112 1.05 0.2 0.2 0.02 0.005 continuous casting

(12) For the obtained softened materials with a wire diameter of 0.3 mm and the untreated materials, the tensile strength (MPa), the elongation (%), the 0.2% proof stress (MPa), and the electrical conductivity (% IACS) have been measured. The results are shown in Table 2.

(13) The tensile strength (MPa) and the elongation (%, fracture elongation), and the 0.2% proof stress (MPa) have been measured in compliance with JIS Z 2241 (method of tensile test for metallic materials, 1998) by means of a general-purpose tensile tester. The electrical conductivity (% TAGS) has been measured by the bridge method.

(14) TABLE-US-00002 TABLE 2 Material Characteristics Softened Tensile 0.2% Proof Material Strength Elongation Stress Conductivity Sample No. (MPa) (%) (MPa) (% IACS) (AlFeMg) 1-1 115 25 62 60 1-2 115 21 62 58 1-3 115 15 62 58 1-4 115 15 62 60 (AlFeMg(Mn, Ni, Zr, Ag)) 1-11 128 26 63 58 1-12 128 25 62 59 1-13 129 27 62 58 1-14 129 27 61 59 1-15 128 14 59 58 1-16 115 20 55 59 1-101 170 7 92 40 1-102 231 2 115 56 (AlFeCu) 1-21 123 30 58 61 1-22 143 19 57 58 1-23 126 28 59 60 1-24 147 15 60 58 1-25 123 18 56 61 1-26 118 29 52 61 1-111 146 8 75 55 1-112 252 2 116 56

(15) As shown in Table 1, Samples Nos. 1-1 to 1-4, 1-11 to 1-16, and 1-21 to 1-26 each made of an AlFe-based alloy having a specific composition and having undergone the softening treatment have an electrical conductivity of not less than 58% IACS, an elongation of not less than 10%, and further have a 0.2% proof stress of not less than 40 MPa and a tensile strength of not less than 110 MPa. Namely, Samples Nos. 1-1 to 1-4, 1-11 to 1-16, and 1-21 to 1-26 each have not only a high electrical conductivity and a high toughness but also a high strength. In particular, containing, in addition to Fe, of at least one additive element selected from Mg, Si, Cu, Zn, Ni, Mn, Ag, Cr, and Zr is likely to make the strength higher. A still higher strength is achieved by containing, in addition to Mg, of Mn, Ni, Zr, Ag, or containing, in addition to Cu, of Mg or Si or Mg and Si both. From a comparison between samples of the same composition, it is seen that a sample on which continuous casting and rolling has been performed tends to have a larger elongation than a sample on which billet casting has been performed. Depending on the composition, the elongation is 25% or more which means that the toughness is excellent.

(16) In contrast, Samples No. 1-102 and No. 1-112 which have not been softening-treated has a high strength while their elongation is very smaller resulting in lower toughness and their electrical conductivity is lower. As to a sample which has been softening-treated while it does not have a specific composition, specifically Samples No. 1-101 and 1-111 with higher contents of Fe and other additive elements have a high strength while their elongation and electrical conductivity are lower.

(17) [Softening Treatment Condition (Temperature) and Characteristics]

(18) Samples softening-treated under different conditions have been produced and the electrical conductivity (%) and the tensile strength (MPa) of the resultant samples have been examined. The results are shown in FIGS. 1 and 2. Here, the softening treatment has been performed on wiredrawn materials with the compositions of Sample No. 1-12 (FIG. 1) and Sample No. 1-22 (FIG. 2) and a wire diameter of 0.3 mm. The softening treatment has been performed on the withdrawn materials as a batch treatment using a box-shaped furnace (reducing gas atmosphere, temperature decrease rate: 0.02 C./sec) and a heating temperature (softening temperature) selected as appropriate from a range of 200 to 400 C. (holding time: 3 hours).

(19) As seen from FIGS. 1 and 2, the softening treatment can be performed at a heating temperature of 250 C. or more to obtain a softened material having an electrical conductivity of not less than 58% IACS and a tensile strength of not less than 120 MPa. The temperature of 200 C. appears to cause the tensile strength to be too high, resulting in a smaller elongation and a lower toughness.

(20) [Structure of Softened Material]

(21) FIG. 3 is a transmission electron microscope (TEM) photograph (45000) of a cross section of a produced softened material. Sample No. 1-1 (batch softening treatment) is shown in FIG. 3 (1), and Sample No. 1-2 (continuous softening treatment) is shown in FIG. 3 (2). In FIG. 3, the small dark gray dots represent precipitates, and the relatively larger black dots (dots having a circle-equivalent diameter exceeding 200 nm) are crystallizations. As shown in FIG. 3 (2), it is seen that the sample having undergone the continuous softening treatment includes less fine precipitates with a circle-equivalent diameter of 100 nm or less. As shown in FIG. 3 (1), it is also seen that the sample having undergone the batch softening treatment includes more fine precipitates with a circle-equivalent diameter of 100 nm or less than the sample having undergone the continuous softening treatment. Three observation fields of 2400 nm2600 nm have been taken from one cross section, and the number of precipitates that are present in each observation field and have a circle-equivalent diameter of 100 nm or less has been measured. It has been found that, in the sample having undergone the continuous softening treatment, the number of precipitates of 100 nm or less in the above-described observation field (average of the three observation fields) is 3 (less than 10) and, in the sample having undergone the batch softening treatment, the number is 18 (more than 10 and not more than 20). The size of a precipitate (circle-equivalent diameter) is the diameter of a circle into which the area of the precipitate is converted in an image-processed microscope photograph.

(22) [Characteristics of Covered Electric Wire]

(23) It is expected that an Al alloy wire made of an AlFe-based alloy having a specific composition and softening-treated as described above can suitably be used as a conductor for an electric wire of a wire harness. Thus, a covered electric wire has been produced to examine its mechanical characteristics.

(24) A plurality of wiredrawn materials (see Table 1 for the composition) with a wire diameter of 0.3 mm produced in the above-described manner are stranded together to produce a stranded wire. Here, 11 drawn wires in total consisting of three inner wires and eight outer wires are stranded together and thereafter subjected to compression working so that the profile of the cross section is circular so as to produce a compressed wire of 0.75 mm.sup.2. On the resultant compressed wire, a softening treatment (batch treatment by means of a box-shaped furnace, or continuous treatment by means of high-frequency induction heating method) is performed in the atmosphere and at the heating temperature shown in Table 1 basically under similar conditions to those for the softening treatment performed on the wiredrawn material of 0.3 mm as described above. On the outer periphery of the softened material thus obtained, an insulating material (here halogen-free insulating material) is used to form an insulating cover layer (0.2 mm in thickness) so as to produce a covered electric wire. For comparison's sake, untreated materials (Samples No. 2-102, No. 2-112) have also been prepared by stranding wiredrawn materials together and compressing the stranded wire into a compressed wire on which no softening treatment is performed.

(25) For the covered electric wires thus obtained, the impact resistance (J/m) and the terminal securing strength (N) have been examined. The results are shown in Table 3.

(26) The impact resistance (J/m or (N.Math.m)/m) has been evaluated in the following manner. FIG. 4 is an illustration for illustrating a test method for an impact resistance test. To an end of a sample S (point-to-point distance to be evaluated L: 1 m), a weight w is attached (FIG. 4 (1)), this weight w is raised by 1 m and thereafter let fall freely (FIG. 4 (2)). Then, a maximum weight (kg) of weight w that does not cause breakage of sample S is measured, the measured weight is multiplied by the gravitational acceleration (9.8 m/s.sup.2) and the fall distance 1 m, the product is divided by the fall distance, and the resultant value thus determined is used as an impact resistance (J/m or (N.Math.m)/m) for evaluation.

(27) The terminal securing strength (N) has been evaluated in the following manner. FIG. 5 is an illustration for illustrating a test method for a terminal securing strength test. For a sample S formed of a stranded wire 1 around which an insulating cover layer 2 is provided, cover layer 2 is stripped at the two opposite ends to expose stranded wire 1. A terminal portion 3 is attached to one end of stranded wire 1 and this terminal portion 3 is held in a terminal chuck 20. The other end of stranded wire 1 is held in a wire chuck 21. A general-purpose tensile tester is used to measure the maximum load (N) at the time of fracture of sample S held at its two ends by chucks 20, 21, and the maximum load (N) is used as a terminal securing strength (N) for evaluation.

(28) TABLE-US-00003 TABLE 3 Electric Wire Performance Softened Impact Terminal Securing Electric Wire Material Resistance Strength Sample No. Sample No. (J/m) (N) (AlFeMg) 2-1 1-1 12 70 2-2 1-2 11 71 2-3 1-3 10 71 2-4 1-4 10 70 (AlFeMg(Mn, Ni, Zr, Ag)) 2-11 1-11 12 72 2-12 1-12 12 71 2-13 1-13 12 72 2-14 1-14 12 72 2-15 1-15 10 71 2-16 1-16 14 60 2-101 1-101 6 105 2-102 1-102 2 123 (AlFeCu) 2-21 1-21 12 72 2-22 1-22 11 83 2-23 1-23 12 72 2-24 1-24 10 83 2-25 1-25 11 72 2-26 1-26 14 60 2-111 1-111 6 83 2-112 1-112 2 130

(29) As shown in Table 3, it is seen that the covered electric wires of Samples Nos. 2-1 to 2-4, 2-11 to 2-16, and 2-21 to 2-26 for which a stranded wire made of an AlFe-based alloy with a specific composition and having undergone the softening treatment is used have an excellent impact resistance and a high connection strength between the wire and a terminal portion.

(30) [Softening Treatment Condition (Method) and Characteristics]

(31) As the softening treatment, the batch treatment is performed on an Al alloy wire and the continuous treatment is performed on an Al alloy wire. The corrosion resistance and the mechanical characteristics of thus obtained Al alloy wires have been examined.

(32) The Al alloy wires are produced in a similar manner to the above-described Al alloy wire of 0.3 mm. Specifically, to molten pure aluminum similar to the above-described one, the additive elements shown in Table 4 are added at respective contents shown in Table 4 to produce a molten Al alloy. A belt-wheel-type continuous casting and rolling machine is used to produce a wire rod of 9.5 mm (cooling temperature for casting: 4.5 C./sec, DAS of cast material: about 20 m). This wire rod undergoes a cold wiredrawing treatment to produce a wiredrawn material with a wire diameter of 0.3 mm, which undergoes the softening treatment (batch treatment (bright softening treatment) or continuous treatment) under the conditions shown in Table 4 to produce a softened material of 0.3 mm (single wire). The conditions for the batch treatment at this time are basically similar to those for Sample No. 1-1 or 1-11, and the conditions for the continuous treatment are similar to those for Sample No. 1-2. 11 wiredrawn materials with a wire diameter of 0.3 mm thus obtained are stranded together to produce a compressed wire of 0.75 mm.sup.2. On the obtained compressed wire, the softening treatment (batch treatment or continuous treatment) is performed under the conditions shown in Table 4 to obtain a softened material (compressed wire) of 0.75 mm.sup.2. The conditions for the batch treatment at this time are basically similar to those for Sample No. 2-1 or 2-11, and the conditions for the continuous treatment are similar to those for Sample No. 2-2.

(33) TABLE-US-00004 TABLE 4 Softened Material Softening Treatment Sample Additive Elements (mass %) Temperature No. Fe Mg Mn Ni Zr Ag Cu Si, Cr, Zn Ti B Method ( C.) Atmosphere 3-1 1.00 0.03 0.005 continuous 500 air 3-2 1.00 0.03 0.005 bright 300 nitrogen gas 3-3 1.00 0.2 0.05 0.03 0.005 continuous 500 air 3-4 1.00 0.2 0.05 0.03 0.005 bright 350 nitrogen gas 3-5 1.00 0.2 0.05 0.03 0.005 continuous 500 air 3-6 1.00 0.2 0.05 0.03 0.005 bright 350 nitrogen gas 3-7 1.00 0.2 0.05 0.03 0.005 continuous 500 air 3-8 1.00 0.2 0.05 0.03 0.005 bright 350 nitrogen gas 3-9 1.00 0.2 0.1 0.03 0.005 continuous 500 air 3-10 1.00 0.2 0.1 0.03 0.005 bright 350 nitrogen gas 3-11 1.00 0.2 0.03 0.005 continuous 500 air 3-12 1.00 0.2 0.03 0.005 bright 350 nitrogen gas 3-13 1.00 0.2 0.2 Si: 0.05 0.03 0.005 continuous 500 air 3-14 1.00 0.2 Si: 0.05 0.03 0.005 bright 350 nitrogen gas 3-101 0.001 0.02 0.005 bright 250 reducing gas 3-15 0.2 0.02 0.005 bright 250 reducing gas 3-16 0.6 0.02 0.005 bright 350 reducing gas 3-17 1.7 0.02 0.005 bright 350 reducing gas 3-18 1.05 0.2 Cr: 0.05 0.02 0.005 bright 350 reducing gas 3-19 1.05 0.2 Cr: 0.05 0.02 0.005 bright 350 reducing gas 3-20 1.05 0.2 Zn: 0.05 0.02 0.005 bright 350 reducing gas 3-21 1.05 0.2 Zn: 0.05 0.02 0.005 bright 350 reducing gas 3-22 1.05 0.2 0.02 0.005 bright 350 reducing gas

(34) For the softened material thus obtained, the tensile strength (MPa), the 0.2% proof stress (MPa), the elongation (%, fracture elongation), the electrical conductivity (% IACS), the impact resistance (J/m), and the terminal securing strength (N) have been examined in a similar manner to the above-described one. The results are shown in Table 5.

(35) On a wiredrawn material with a wire diameter of 1.0 mm obtained in the process for producing the wiredrawn material with a wire diameter of 0.3 mm as described above, the softening treatment indicated in Table 4 is performed similarly to the softening treatment performed on the softened material of 0.3 mm, so as to produce a softened material. This softened material is used as a sample to measure the pitting potential (V) and the protective potential (V). The results are shown in Table 5.

(36) The pitting potential and the protective potential have been measured in the following manner. First, a sample is immersed in an aqueous solution of 5% by mass of NaOH (60 C.) for a predetermined time (one minute) to remove a passivation film. Next, the sample is immersed in an aqueous solution of 55% by mass of HNO.sub.3 for a predetermined time (about 10 seconds), washed and neutralized, and thereafter washed with water. The washed sample is immersed in an electrolytic solution (aqueous solution of 5% by mass of NaCl) and, for a predetermined time, a certain voltage is applied to cause reduction (1.5 V, 5 minutes). After this, the potential is swept to measure the pitting potential and the protective potential. The measurements are taken by forming a three-electrode electrochemical measurement cell. This cell includes a vessel into which an electrolytic solution is poured, a reference electrode (RE): Ag/AgCl, a counter electrode (CE): Pt, and a sample to be measured that are immersed in the electrolytic solution. Respective ends of the RE, CE and sample are connected to a commercially available potentiostat/galvanostat apparatus, and a certain potential is applied as described above to measure a change in electric current. Here, the pitting potential refers to the potential when the current having reached 100 A/cm.sup.2 continues increasing. Regarding the protective potential, when the current becomes 1 mA/cm.sup.2, the potential is swept in the opposite direction (here the cathode direction). The potential at which the current becomes zero is the protective potential. A smaller absolute value of the pitting potential and a smaller absolute value of the protective potential provide less pitting, namely superior corrosion resistance.

(37) TABLE-US-00005 TABLE 5 0.3 mm 0.75 mm.sup.2 Softened 1.0 mm 0.2% Terminal Material Pitting Protective Tensile proof Impact Securing Sample Potential Potential Strength stress Conductivity Elongation Resistance Strength No. (V) (V) (MPa) (MPa) (% IACS) (%) (J/m) (N) 3-1 0.69 1.09 112 50 60 30 12 59 3-2 0.82 1.15 111 51 62 34 12 58 3-3 0.71 1.13 127 56 58 23 13 72 3-4 0.82 1.14 128 55 58 26 15 73 3-5 0.70 1.13 127 57 58 22 14 73 3-6 0.82 1.16 128 56 59 25 14 72 3-7 0.72 1.14 126 50 58 21 13 71 3-8 0.85 1.16 129 63 58 27 16 74 3-9 0.65 1.08 130 62 58 22 13 75 3-10 0.75 1.12 129 64 59 27 16 75 3-11 0.68 1.09 123 61 58 25 14 72 3-12 0.73 1.13 123 62 61 30 15 72 3-13 0.65 1.07 142 71 58 17 11 83 3-14 0.71 1.13 143 68 58 19 11 85 3-101 0.77 1 108 50 62 17 12 66 3-15 0.73 1.01 112 45 61 22 12 65 3-16 0.72 1.09 111 56 62 20 13 69 3-17 0.68 1.2 125 73 60 25 16 72 3-18 0.71 1.09 124 60 58 24 17 73 3-19 0.73 1.08 124 59 60 30 15 75 3-20 0.69 1.07 123 56 58 23 16 74 3-21 0.71 1.07 124 57 59 29 18 76 3-22 0.71 1.11 126 59 59 28 19 78

(38) As shown in Table 5, the Al alloy wire made of an AlFe-based alloy having a specific composition and having undergone the softening treatment has an electrical conductivity of not less than 58% IACS, an elongation of not less than 10%, a 0.2% proof stress of not less than 40 MPa, and a tensile strength of not less than 110 MPa, and is accordingly of high electrical conductivity, high toughness, and high strength and also excellent in impact resistance and high in connection strength with a terminal portion. In particular, from a comparison between samples with the same composition, it is seen that a sample having undergone the batch softening treatment is superior to a sample having undergone the continuous softening treatment, in terms of electrical conductivity and mechanical characteristics such as elongation, strength, and impact resistance. In contrast, from a comparison between samples with the same composition, it is seen that the sample having undergone the continuous softening treatment is smaller in the absolute value of the pitting potential and the absolute value of the protective potential and superior in corrosion resistance as compared with the sample having undergone the batch softening treatment. Further, from a comparison for example between Sample No. 15 and Sample No. 16 in Table 5, it is seen that, of the samples that are almost identical in tensile strength, the sample having a higher 0.2% proof stress tends to have a higher terminal securing strength.

(39) As described above, a covered electric wire for which an Al alloy wire made of an AlFe-based alloy with a specific composition and having been softening-treated is used has a high electrical conductivity, a high toughness, and a high strength as well as an excellent connection strength with a terminal portion and an excellent impact resistance as well. Therefore, it is expected that this covered electric wire can be used suitably for a wire harness, particularly for a wire harness for a motor vehicle.

(40) It should be noted that the above-described embodiment may be modified as appropriate without going beyond the scope of the present invention, and is not limited to the above-described structure. For example, the content of Fe, Cu, Mg, Si, Zn, Ni, Mn, Ag, Cr, Zr each may be varied within a specific range. Further, the size and the shape of the wire and the number of wires to form a stranded wire may be changed.

INDUSTRIAL APPLICABILITY

(41) The wire harness of the present invention can suitably be used for applications where lightweight as well as high strength, high toughness, and high electrical conductivity are desired, specifically for a wiring of a motor vehicle, for example. The covered electric wire of the present invention, the aluminum alloy wire of the present invention, or the aluminum stranded wire of the present invention can suitably be used as an electric wire of this wire harness or a conductor for the electric wire. Further, the method of manufacturing an aluminum alloy wire of the present invention can suitably be used for manufacture of the above-described aluminum alloy wire of the present invention.

DESCRIPTION OF THE REFERENCE SIGNS

(42) 1 stranded wire; 2 insulating cover layer; 3 terminal portion; S sample; w weight; 20 terminal chuck; 21 wire chuck