Patent Application
20200181741
The present invention relates to an aluminum alloy wire, an aluminum alloy strand wire, a covered electrical wire, and a terminal-equipped electrical wire.
The present application claims priority to Japanese Patent Application No. 2016-213154 tiled on Oct. 31, 2016 and Japanese Patent Application No. 2017-074234 filed on Apr. 4, 2017, the entire contents of which are herein incorporated by reference.
PTL 1 discloses an extremely thin aluminum alloy wire which is composed of an Al—Mg—Si based alloy, high in strength and also in electrical conductivity, and excellent also in elongation.
PTL 1: Japanese Patent Laying-Open No. 2012-229485
An aluminum alloy wire in the present disclosure is an aluminum alloy wire composed of an aluminum alloy,
the aluminum alloy containing at least 0.03 mass % and at most 1.5 mass % of Mg, at least 0.02 mass % and at most 2.0 mass % of Si, and a remainder composed of Al and an inevitable impurity, a mass ratio Mg/Si being not lower than 0.5 and not higher than 3.5,
in a transverse section of the aluminum alloy wire, a rectangular surface-layer crystallization measurement region having a short side of 50 μm long and a long side of 75 μm long being taken from a surface-layer region extending by up to 50 μm in a direction of depth from a surface of the aluminum alloy wire, and
an average area of crystallized materials present in the surface-layer crystallization measurement region being not smaller than 0.05 μm2 and not greater than 3 μm2.
An aluminum alloy strand wire in the present disclosure is made by stranding together a plurality of the aluminum alloy wires in the present disclosure.
A covered electrical wire in the present disclosure includes a conductor and an insulation cover which covers an outer circumference of the conductor, the conductor including the aluminum alloy strand wire in the present disclosure.
A terminal-equipped electrical wire in the present disclosure includes the covered electrical wire in the present disclosure and a terminal portion attached to an end portion of the covered electrical wire.
[Problem to be Solved by the Present Disclosure]
An aluminum alloy wire excellent in impact resistance and also in fatigue characteristics is desired as a wire member to be used for a conductor equipped in an electrical wire.
Electrical wires for various applications such as a wire harness provided in equipment such as cars and aircrafts, wires for various electrical appliances such as industrial robots, and wires in buildings may receive impact or repeated bending when such equipment is used or installed. Specific examples (1) to (3) are given below.
(1) In an electrical wire equipped in a wire harness for cars, impact may be applied to the vicinity of a terminal portion in attaching the electrical wire to a connection target (PTL 1). In addition, sudden impact may be applied depending on a state of travel of a car, or repeated bending may be applied by vibration during travel of a car.
(2) An electrical wire routed in an industrial robot may repeatedly be bent or twisted.
(3) To an electrical wire routed in a building, impact may be applied due to sudden strong tension or inadvertent drop by an operator during installation, or the electrical wire may repeatedly be bent by waving for removing waviness of a wire member wound like a coil.
Therefore, the aluminum alloy wire to be used for a conductor equipped in an electrical wire is desirably less likely to break even though not only impact but also repeated bending is applied.
One of objects is to provide an aluminum alloy wire excellent in impact resistance and fatigue characteristics. Another of the objects is to provide an aluminum alloy strand wire, a covered electrical wire, and a terminal-equipped electrical wire excellent in impact resistance and fatigue characteristics.
[Advantageous Effect of the Present Disclosure]
An aluminum alloy wire in the present disclosure, an aluminum alloy strand wire in the present disclosure, a covered electrical wire in the present disclosure, and a terminal-equipped electrical wire in the present disclosure are excellent in impact resistance and fatigue characteristics.
[Description of Embodiment of the Invention of the Present Application]
The present inventors have manufactured aluminum alloy wires under various conditions, and studied aluminum alloy wires excellent in impact resistance and fatigue characteristics (less likeliness to break against repeated bending). A wire member composed of a specifically composed aluminum alloy containing Mg and Si within a specific range and subjected in particular to aging treatment is high in strength (for example, high in tensile strength or 0.2% proof stress), high in electrical conductivity, and also excellent in electrical conductive property. The present inventors have found that a certain amount of fine crystallized materials is present in particular in a surface layer of this wire member leads to excellent impact resistance and less likeliness of break in spite of repeated bending. The present inventors have found that an aluminum alloy wire containing fine crystallized materials in the surface layer can be manufactured, for example, by controlling within a specific range, a cooling rate in a specific temperature region in a casting process. The invention of the present application is based on such findings. Contents of an embodiment of the invention of the present application will initially be listed and described.
(1) An aluminum alloy wire according to one manner of the invention of the present application is an aluminum alloy wire composed of an aluminum alloy,
the aluminum alloy containing at least 0.03 mass % and at most 1.5 mass % of Mg, at least 0.02 mass % and at most 2.0 mass % of Si, and a remainder composed of Al and an inevitable impurity, a mass ratio Mg/Si being not lower than 0.5 and not higher than 3.5,
in a transverse section of the aluminum alloy wire, a rectangular surface-layer crystallization measurement region having a short side of 50 μm long and a long side of 75 μm long being taken from a surface-layer region extending by up to 50 μm in a direction of depth from a surface of the aluminum alloy wire, and
an average area of crystallized materials present in the surface-layer crystallization measurement region being not smaller than 0.05 μm2 and not greater than 3 μm2.
The transverse section of the aluminum alloy wire refers to a cross-section obtained by cutting along a surface orthogonal to an axial direction (a longitudinal direction) of the aluminum alloy wire.
The crystallized material representatively refers to a single element or a compound containing at least one of Mg and Si representing an additive element, and it herein refers to a material having an area not smaller than 0.05 μm2 in the transverse section of the aluminum alloy wire (a material having a Heywood diameter not smaller than 0.25 μm with an area being identical). A compound having an area smaller than 0.05 μm2 and a finer compound representatively having a Heywood diameter not greater than 0.2 μm and further not greater than 0.15 μm is defined as a precipitated material.
The aluminum alloy wire (which may be called an Al alloy wire below) is composed of a specifically composed aluminum alloy (which may be called an Al alloy below). The aluminum alloy wire is high in strength, less likely to break even though it is repeatedly bent, and excellent in fatigue characteristics, by being subjected to aging treatment in a manufacturing process. The aluminum alloy wire is high in breaking elongation and excellent also in impact resistance when it is high in toughness. In particular, in the Al alloy wire, a crystallized material present in a surface layer is fine. Therefore, even though impact is applied to the Al alloy wire or the Al alloy wire is repeatedly bent, a large crystallized material is less likely to be a starting point of cracking and surface cracking is less likely. Development of cracking through a large crystallized material also tends to be lessened, and development of cracking from a surface of a wire member to the inside or resultant breakage can also be lessened. Therefore, the Al alloy wire is excellent in impact resistance and fatigue characteristics. The Al alloy wire may contribute to suppression of growth of crystal grains of the Al alloy owing to presence of a crystallized material which is Fine but has a certain size. Improvement in impact resistance and fatigue characteristics can he expected also based on a fine crystal grain. In addition, since the Al alloy wire is less likely to suffer from cracking originating from a crystallized material, it tends to be higher in at least one selected from tensile strength, 0.2% proof stress, and breaking elongation in a tensile test, although depending on a composition or a condition for heat treatment. The Al alloy wire is excellent also in mechanical characteristics.
(2) An exemplary form of the Al alloy wire is such that the number of crystallized materials present in the surface-layer crystallization measurement region is greater than 10 and not greater than 400.
According to the form, the number of fine crystallized materials described above present in the surface layer of the Al alloy wire satisfies the specific range described above. Therefore, the crystallized material is less likely to be a starting point of cracking, development of cracking originating from the crystallized material also tends to be lessened, and excellent impact resistance and fatigue characteristics are achieved.
(3) An exemplary form of the Al alloy wire is such that, in the transverse section of the aluminum alloy wire, a rectangular inside crystallization measurement region having a short side of 50 μm long and a long side of 75 μm long is taken such that a center of this rectangle is superimposed on a center of the aluminum alloy wire and an average area of the crystallized materials present in the inside crystallization measurement region is not smaller than 0.05 μm2 and not greater than 40 μm2.
According to the form, the crystallized materials present in the inside of the Al alloy wire are also fine, breakage originating from a crystallized material is thus more readily lessened and excellent impact resistance and fatigue characteristics are achieved.
(4) An exemplary form of the Al alloy wire is such that the aluminum alloy has an average crystal grain size not greater than 50 μm.
The form includes fine crystal grains and is excellent in pliability in addition to the crystallized material being fine. Therefore, better impact resistance and fatigue characteristics are achieved.
(5) An exemplary form of the Al alloy wire is such that, in the transverse section of the aluminum alloy wire, a rectangular surface-layer void measurement region having a short side of 30 μm long and a long side of 50 μm long is taken from a surface-layer region extending by up to 30 μm in the direction of depth from the surface of the aluminum alloy wire, and a total cross-sectional area of voids present in the surface-layer void measurement region is not greater than 2 μm2.
In the form, in addition to fine crystallized materials present in the surface layer of the Al alloy wire, there are a small number of voids. Therefore, even when impact or repeated bending is applied, a void is less likely to be a starting point of cracking, and cracking originating from a void or development of cracking tends to be lessened. Therefore, the Al alloy wire is better in impact resistance and fatigue characteristics.
(6) An exemplary form of the Al alloy wire in (5) in which a content of voids is within a specific range is such that, in the transverse section of the aluminum alloy wire, a rectangular inside void measurement region having a short side of 30 μm long and a long side of 50 μm long is taken such that a center of this rectangle is superimposed on a center of the aluminum alloy wire, and a ratio of a total cross-sectional area of voids present in the inside void measurement region to the total cross-sectional area of the voids present in the surface-layer void measurement region is not lower than 1.1 and not higher than 44.
In the form, the ratio of the total cross-sectional area described above is not lower than 1.1. Therefore, though more voids are present inside than in the surface layer of the Al alloy wire, the ratio of the total cross-sectional area described above satisfies the specific range and hence it can be concluded that there are a small number of voids also in the inside. Therefore, the form is better in impact resistance and fatigue characteristics because cracking is less likely to develop from the surface of the wire member to the inside through the voids and break is less likely even though impact or repeated bending is applied.
(7) An exemplary form of the Al alloy wire in (5) or (6) in which a content of voids is within a specific range is such that a content of hydrogen is not more than 8.0 ml/100 g.
The present inventors have examined a gas component contained in an Al alloy wire which contains voids, and found that the Al alloy wire contains hydrogen. Therefore, hydrogen may be one factor for voids in the Al alloy wire. Since the form can be concluded as containing a small number of voids also based on a low content of hydrogen, the form is less likely to suffer from break originating from a void and is better in impact resistance and fatigue characteristics.
(8) An exemplary form of the Al alloy wire is such that a work hardening exponent is not smaller than 0.05.
Since the form satisfies a specific range of the work hardening exponent, improvement in force of fixing a terminal portion by work hardening at the time of attachment of the terminal portion by crimping can be expected. Therefore, the form can suitably be made use of for a conductor to which a terminal portion is to be attached such as a terminal-equipped electrical wire.
(9) An exemplary form of the Al alloy wire is such that a dynamic friction coefficient is not greater than 0.8.
For example, a strand wire is formed from the Al alloy wire in the form. Then, when the strand wire is bent, elemental wires are readily slid with respect to each other, the elemental wire can smoothly move, and each elemental wire is less likely to break.
Therefore, the form is better in fatigue characteristics.
(10) An exemplary form of the Al alloy wire is such that surface roughness is not greater than 3 μm.
Since the form is small in surface roughness, a dynamic friction coefficient tends to be low, and in particular fatigue characteristics are better.
(11) An exemplary form of the Al alloy wire is such that a lubricant is adhered to a surface of the aluminum alloy wire and an amount of adhesion of C derived from the lubricant is more than 0 and not more than 30 mass %.
In the form, the lubricant adhered to the surface of the Al alloy wire may be remainder of a lubricant which was used in wire drawing or stranding in a manufacturing process. Since such a lubricant representatively contains carbon (C), an amount of adhesion of the lubricant is expressed as an amount of adhesion of C. The form is better in fatigue characteristics because lowering in dynamic friction coefficient can be expected owing to the lubricant present on the surface of the Al alloy wire. The form is also excellent in corrosion resistance owing to the lubricant. The form can prevent increase in connection resistance due to excessive interposition of the lubricant because an amount of lubricant (an amount of C) present on the surface of the Al alloy wire satisfies a specific range and hence an amount of the lubricant (an amount of C) interposed between the terminal portion and the Al alloy wire when the terminal portion is attached is small. Therefore, the form can suitably be made use of for a conductor to which a terminal portion is to he attached such as a terminal-equipped electrical wire. In this case, a connection structure particularly excellent in fatigue characteristics and low in resistance and also excellent in corrosion resistance can he constructed.
(12) An exemplary form of the Al alloy wire is such that the aluminum alloy wire has a surface oxide film having a thickness not smaller than 1 nm and not greater than 120 nm.
In the form, a thickness of the surface oxide film satisfies a specific range. Therefore, less oxide (which forms a surface oxide film) is interposed between the aluminum alloy wire and the terminal portion when the terminal portion is attached. Increase in connection resistance due to excessive interposition of an oxide can be prevented. In addition, excellent corrosion resistance is also achieved. Therefore, the form can suitably he made use of for a conductor to which a terminal portion is to be attached such as a terminal-equipped electrical wire. In this case, a connection structure excellent in impact resistance and fatigue characteristics and in addition low in resistance and excellent also in corrosion resistance can be constructed.
(13) An exemplary form of the Al alloy wire is such that tensile strength is not lower than 150 MPa, 0.2% proof stress is not lower than 90 MPa, breaking elongation is not lower than 5%, and electrical conductivity is not lower than 40% IACS.
The form is high in each of tensile strength, 0.2% proof stress, and breaking elongation, hence excellent in mechanical characteristics and better in impact resistance and fatigue characteristics, and high in electrical conductivity and hence also in electrical characteristics. With high 0.2% proof stress, the form is excellent also in fixability to a terminal portion.
(14) An aluminum alloy strand wire according to one manner of the invention of the present application is made by stranding together a plurality of the aluminum alloy wires described in any one of (1) to (13).
Each elemental wire forming the aluminum alloy strand wire (which may be called an Al alloy strand wire below) is composed of a specifically composed Al alloy as described above and contains a fine crystallized material in a surface layer thereof. Therefore, it is excellent in impact resistance and fatigue characteristics. A strand wire is generally better in flexibility than a solid wire identical in conductor cross-sectional area. Even though impact or repeated bending is applied to the strand wire, each elemental wire is less likely to break and excellent in impact resistance and fatigue characteristics. In this regard, the Al alloy strand wire is excellent in impact resistance and fatigue characteristics. Since each elemental wire is excellent in mechanical characteristics as described above, the Al alloy strand wire tends to be higher in at least one selected from tensile strength, 0.2% proof stress, and breaking elongation, and it is also excellent in mechanical characteristics.
(15) An exemplary form of the Al alloy strand wire is such that a strand pitch is at least 10 times and at most 40 times as large as a pitch diameter of the aluminum alloy strand wire.
The pitch diameter refers to a diameter of a circle defined by a series of centers of all elemental wires included in each layer of a multi-layered structure of a strand wire.
According to the form, a strand pitch satisfies a specific range. Therefore, the form is less likely to suffer from breakage because elemental wires are less likely to twist in bending. In addition, electrical wires are less likely to be unbound in attachment of a terminal portion, and hence attachment of the terminal portion is facilitated. Therefore, the form is particularly excellent in fatigue characteristics and can suitably be made use of for a conductor to which a terminal portion is to be attached such as a terminal-equipped electrical wire.
(16) A covered electrical wire according to one manner of the invention of the present application includes a conductor and an insulation cover which covers an outer circumference of the conductor, the conductor including the aluminum alloy strand wire described in (14) or (15).
Since the covered electrical wire includes a conductor made of the Al alloy strand wire excellent in impact resistance and fatigue characteristics described above, it is excellent in impact resistance and fatigue characteristics.
(17) A terminal-equipped electrical wire according to one manner of the invention of the present application includes the covered electrical wire described in (16) and a terminal portion attached to an end portion of the covered electrical wire.
Since the terminal-equipped electrical wire includes as its component, the covered electrical wire including the conductor made of the Al alloy wire or the Al alloy strand wire excellent in impact resistance and fatigue characteristics described above, it is excellent in impact resistance and fatigue characteristics.
[Details of Embodiment of the Invention of the Present Application]
An embodiment of the invention of the present application will be described in detail below with reference to the drawings as appropriate. An identical reference in the drawings refers to objects identical in label. A content of an element in the description below is represented by mass %.
[Aluminum Alloy Wire]
(Overview)
An aluminum alloy wire (Al alloy wire) 22 in an embodiment is a wire member composed of an aluminum alloy (Al alloy) and representatively used for a conductor 2 of an electrical wire (
Further detailed description will be given below. Details of a method of measuring each parameter such as a size of a crystallized material and details of the effects described above will be described in a test example.
(Composition)
Al alloy wire 22 in the embodiment is composed of an Al—Mg—Si based alloy and it is excellent in strength because Mg and Si are present therein in a state of a solid solution and also as a crystallized material and a precipitated material. Mg is an element high in effect of improvement in strength. By containing Mg within a specific range simultaneously with Si, specifically by containing at least 0.03% of Mg and at least 0.02% of Si, strength can effectively be improved by age hardening. As a content of Mg and Si is higher, strength of the Al alloy wire is higher. By containing Mg within a range not higher than 1.5% and containing Si within a range not higher than 2.0%, lowering in electrical conductivity or toughness resulting from Mg and Si is less likely, electrical conductivity or toughness is high, break is less likely in wire drawing, and manufacturability is also excellent. In consideration of balance among strength, toughness, and electrical conductivity, a content of Mg can be not lower than 0.1% and not higher than 2.0%, further not lower than 0.2% and not higher than 1.5%, and not lower than 0.3% and not higher than 0.9%, and a content of Si can be not lower than 0.1% and not higher than 2.0%, further not lower than 0.1% and not higher than 1.5%, and not lower than 0.3% and not higher than 0.8%.
When a content of Mg and Si is set within the specific range described above and a mass ratio between Mg and Si is set within a specific range, one element is not excessive and Mg and Si can appropriately be present in a state of a crystallized material or a precipitated material. Therefore, excellent strength or electrical conductive property is preferably obtained. Specifically, a ratio of a mass of Mg to a mass of Si (Mg/Si) is preferably not lower than 0.5 and not higher than 3.5, not lower than 0.8 and not higher than 3.5, and more preferably not lower than 0.8 and not higher than 2.7.
The Al alloy which makes up Al alloy wire 22 in the embodiment can contain, in addition to Mg and Si, at least one element selected from among Fe, Cu, Mn, Ni, Zr, Cr, Zn, and Ga (which may collectively he called an element α below). Fe and Cu are less likely to cause lowering in electrical conductivity and can improve strength. Though Mn, Ni, Zr, and Cr are likely to lower electrical conductivity, they are high in effect of improvement in strength. Zn is less likely to lower electrical conductivity and has an effect of improvement in strength to some extent. Ga effectively improves strength. With improved strength, fatigue characteristics are excellent. Fe, Cu, Mn, Zr, and Cr are effective in making crystals finer. With fine crystal structure, toughness such as breaking elongation is excellent and pliability is excellent so that bending is facilitated. Therefore, improvement in impact resistance and fatigue characteristics can be expected. A content of each of listed elements is not lower than 0% and not higher than 0.5%, and a total content of the listed elements is not lower than 0% and not higher than 1.0%. In particular, when a content of each element is not lower than 0.01% and not higher than 0.5% and a total content of the listed elements is not lower than 0.01% and not higher than 1.0%, an effect of improvement in strength and an effect of improvement in impact resistance and fatigue characteristics described above are readily obtained. A content of each element is set, for example, as below. Within a range of the total content above and a range of a content of each element below, a higher content tends to lead to improvement in strength and a lower content tends to lead to higher electrical conductivity:
(Fe) Not lower than 0.01% and not higher than 0.25% and further not lower than 0.01% and not higher than 0.2%;
(each of Cu, Mn, Ni, Zr, Cr, and Zn) Not lower than 0.01% and not higher than 0.5% and further not lower than 0.01% and not higher than 0.3%; and
(Ga) Not lower than 0.005% and not higher than 0.1% and further not lower than 0.005% and not higher than 0.05%.
When pure aluminum employed as a source material is subjected to component analysis and it contains an element such as Mg, Si, and/or element α as an impurity in the source material, an amount of addition of each element is desirably adjusted such that a content of the element is set to a desired amount. The content of each additive element described above refers to a total amount inclusive of a content of the element in aluminum metal itself to be employed as a source material, and it does not necessarily mean an amount of addition.
An Al alloy which makes up Al alloy wire 22 in the embodiment can contain, in addition to Mg and Si, at least one of Ti and B. Ti or B is effective in making crystals of the Al alloy finer in casting. By adopting a cast material having fine crystal structure as a base material, crystal grains tend to be fine even though working such as rolling or wire drawing or heat treatment including aging treatment is performed after casting. Al alloy wire 22 having fine crystal structure is less likely to suffer from breakage in application of impact or repeated bending thereto than an Al alloy wire having coarse crystal structure, and it is excellent in impact resistance and fatigue characteristics. The effect of making crystal grains finer tends to increase in the order of an example containing B alone, an example containing Ti alone, and an example containing both of Ti and B. When a content of Ti is not lower than 0% and not higher than 0.005% and further not lower than 0.005% and not higher than 0.05% in an example containing Ti and when a content of B is not lower than 0% and not higher than 0.005% and further not lower than 0.001% and not higher than 0.005% in an example containing B, the effect of making crystals finer is obtained and lowering in electrical conductivity resulting from Ti or B can be lessened, in consideration of balance between the effect of making crystals finer and electrical conductivity, the content of Ti can be not lower than 0.01% and not higher than 0.04% and further not higher than 0.03%, and the content of B can be not lower than 0.002% and not higher than 0.004%.
A specific example of a composition containing element α described above and the like in addition to Mg and Si is shown below, in the specific example below, a mass ratio Mg/Si is preferably not lower than 0.5 and not higher than 3.5.
(1) Mg is contained by at least 0.03% and at most 1.5%, Si is contained by at least 0.02% and at most 2.0%, Fe is contained by at least 0.01% and at most 0.25%, and the remainder is composed of Al and an inevitable impurity.
(2) Mg is contained by at least 0.03% and at most 1.5%, Si is contained by at least 0.02% and at most 2.0%, Fe is contained by at least 0.01% and at most 0.25%, at least one element selected from among Cu, Mn, Ni, Zr, Cr, Zn, and Ga is contained by at least 0.01% and at most 0.3% in total, and the remainder is composed of Al and an inevitable impurity.
(3) In (1) or (2), at least one of at least 0.005% and at most 0.05% of Ti and at least 0.001% and at most 0.005% of B is contained.
(Structure)
Crystallized Material
Al alloy wire 22 in the embodiment contains a certain amount of fine crystallized materials in its surface layer. Specifically, in a transverse section of Al alloy wire 22, as shown in
In an example where Al alloy wire 22 is a round wire or regarded substantially as a round wire, a crystallized material measurement region in the surface layer described above can be in a shape of a sector as shown in
In addition to crystallized materials in the surface layer satisfying the specific size described above, in at least one of the rectangular surface-layer crystallization measurement region and the crystallization measurement region in the shape of the sector described above, the number of crystallized materials present in the measurement region is preferably greater than 10 and not greater than 400. As the number of crystallized materials which satisfy the specific size described above is not greater than 400 and not excessively great, cracking is less likely to originate from the crystallized material and development of cracking originating from the crystallized material is also readily suppressed. Therefore, Al alloy wire 22 is better in impact resistance and fatigue characteristics. As the number is smaller, occurrence of cracking is more likely to be lessened. In this regard, the number of crystallized materials is preferably not greater than 350 and further not greater than 300, not greater than 250, and riot greater than 200. When more than ten crystallized materials which satisfy the specific size described above are present, an effect of suppression of lowering in electrical conductivity and suppression of growth of crystal grains as described above can be expected. In this regard, the number of crystallized materials can also be not smaller than 15 and further not smaller than 20.
When many of crystallized materials present in the surface layer are not greater than 3 μm2, the crystallized materials are fine and cracking is less likely to originate therefrom. In addition, dispersion strengthening by presence of crystallized materials uniform in size can be expected. In this regard, in at least one of the rectangular surface-layer crystallization measurement region and the crystallization measurement region in the shape of the sector described above, a total area of crystallized materials each having an area not greater than 3 μm2 among crystallized materials present in the measurement region is preferably not lower than 50%, further not lower than 60%, and more preferably not lower than 70% with respect to a total area of all crystallized materials present in the measurement region.
An Al alloy wire which includes a certain amount of fine crystallized materials not only in the surface layer of Al alloy wire 22 but also in the inside represents one example of Al alloy wire 22 in the embodiment. Specifically, a rectangular region having a short side length of 50 μm and a long side length of 75 μm (which is called an inside crystallization measurement region) is taken in the transverse section of Al alloy wire 22. The inside crystallization measurement region is taken such that the center of this rectangle is superimposed on the center of Al alloy wire 22. In an example where Al alloy wire 22 is a shaped wire, the center of an inscribed circle is defined as the center of Al alloy wire 22 (to similarly be understood below). An average area of crystallized materials present in the inside crystallization measurement region is not smaller than 0.05 μm2 and not greater than 40 μm2. Though the crystallized material is formed in the casting process and the crystallized material may be split by plastic working after casting, a size thereof in a cast material tends to substantially be maintained also in Al alloy wire 22 having a final diameter. In the casting process, generally, solidification proceeds from a surface layer to the inside of a metal. Therefore, a high-temperature state tends to be maintained longer in the inside of the metal than in the surface layer, and a crystallized material in the inside of Al alloy wire 22 tends to be greater than a crystallized material in the surface layer. In contrast, in Al alloy wire 22 in this form, a crystallized material present in the inside is also fine. Therefore, breakage originating from a crystallized material is more likely to be lessened and better impact resistance and fatigue characteristics are obtained. Similarly to the surface layer described above, from a point of view of lessening of breakage, the average area is preferably smaller, and the average area is not greater than 20 μm2, further not greater than 10 μm2, not greater than 5 μm2, and preferably further not greater than 2.5 μm2. From a point of view of presence of a certain amount of crystallized materials, the average area can be not smaller than 0.08 μm2 and further not smaller than 0.1 μm2.
Crystal Grain Size
An Al alloy wire in which an Al alloy has an average crystal grain size not greater than 50 μm represents one example of Al alloy wire 22 in the embodiment. Al alloy wire 22 having fine crystal structure is readily bent, excellent in pliability, and less likely to break in application of impact or repeated bending. This form of Al alloy wire 22 in the embodiment, with a small crystallized material in the surface layer and preferably its small number of voids (which will be described later), is excellent in impact resistance and fatigue characteristics. The average crystal grain size is preferably not greater than 45 μm, further not greater than 40 μm, and not greater than 30 μm, because as the average crystal grain size is smaller, bending or the like is more readily performed and excellent impact resistance and fatigue characteristics are achieved. The crystal grain size tends to be fine, for example, when an element effective in making crystals finer among and element α is contained as described above, although depending on a composition or a manufacturing condition.
Voids
An Al alloy wire containing a small number of voids in its surface layer represents one example of Al alloy wire 22 in the embodiment. Specifically, in a transverse section of Al alloy wire 22, a rectangular region having a short side of 30 μm long and a long side of 50 μm long (which is called a surface-layer void measurement region) is taken from a surface-layer region which extends by up to 30 μm in a direction of depth from a surface of the Al alloy wire, that is, an annular region having a thickness of 30 μm. The length of the short side corresponds to a thickness of the surface-layer region. A total cross-sectional area of voids present in the surface-layer void measurement region is not greater than 2 μm2. In an example where Al alloy wire 22 is a round wire or regarded substantially as a round wire, in a transverse section of Al alloy wire 22, a region in a shape of a sector having an area of 1500 μm2 (which is called a void measurement region) is taken from the annular region having a thickness of 30 μm, and a total cross-sectional area of voids present in the void measurement region in the shape of the sector is not greater than 2 μm2. The rectangular surface-layer void measurement region and the void measurement region in the shape of the sector are desirably taken similarly to surface-layer crystallization measurement region 222 or crystallization measurement region 224 in the shape of the sector described above, by changing short side length S to 30 μm and changing long side length L to 50 μm, and changing thickness t to 30 μm and an area to 1500 μm2. When the rectangular surface-layer void measurement region and the void measurement region in the shape of the sector described above are both taken and the total area of voids present in each of them is not greater than 2 μm2, it is expected that reliability as a wire member excellent in impact resistance and fatigue characteristics is enhanced. With a small number of voids in the surface layer, cracking originating from a void in application of impact or repeated bending can readily be lessened. In addition, development of cracking from the surface layer to the inside can also be lessened and breakage originating from a void can be lessened. Therefore, Al alloy wire 22 is excellent in impact resistance and fatigue characteristics. When a total area of voids is large, large voids are present or a large number of small voids are present. Then, cracking originates from a void or cracking tends to develop. Consequently, impact resistance and fatigue characteristics become poor. As a total cross-sectional area of voids is smaller, there are a smaller number of voids. Breakage originating from a void is lessened and impact resistance and fatigue characteristics are excellent. Therefore, the total cross-sectional area is preferably not greater than 1.9 μm2, further not greater than 1.8 μm2, and not greater than 1.2 μm2 and preferably closer to 0. A smaller number of voids tends to be present, for example, when a relatively low temperature of a melt is set in the casting process. In addition, as a cooling rate during casting, in particular, a cooling rate in a specific temperature region which will be described later, is increased, voids tend to be fewer and smaller.
An Al alloy wire which includes a small number of voids also in the inside in addition to the surface layer represents one example of Al alloy wire 22 in the embodiment. Specifically, a rectangular region having a short side length of 30 μm and a long side length of 50 μm (which is called an inside void measurement region) is taken in the transverse section of Al alloy wire 22. The inside void measurement region is taken such that the center of this rectangle is superimposed on the center of Al alloy wire 22. In at least one of the rectangular surface-layer void measurement region and the void measurement region in the shape of the sector described above, a ratio of a total cross-sectional area Sib of voids present in the inside void measurement region to a total cross-sectional area Sib of voids present in the measurement region (Sib/Sfb) is not lower than 1.1 and not higher than 44. As described above, in a casting process, solidification proceeds from a surface layer of a metal toward the inside. Therefore, when gas in an atmosphere is dissolved in a melt, in the surface layer of a metal, gas is likely to escape to the outside of the metal, whereas in the inside of the metal, gas tends to remain as being confined. A wire member manufactured from such a cast material as a base material is considered to contain more voids in the inside than in the surface layer. When total cross-sectional area Sfb of voids in the surface layer is small as described above, a form low in ratio Sib/Sib contains a smaller number of voids in the inside. Therefore, this form is likely to lessen occurrence of cracking or development of cracking in application of impact or repeated bending, achieves lessened breakage originating from a void, and is excellent in impact resistance and fatigue characteristics. As the ratio Sib/Sfb is lower, there are a smaller number of voids in the inside and impact resistance and fatigue characteristics are better. Therefore, the ratio Sib/Sb is more preferably not higher than 40, further not higher than 30, not higher than 20, or not higher than 15. When the ratio Sib/Mb is equal to or higher than 1.1, Al alloy wire 22 containing a small number of voids can be manufactured without excessively lowering a temperature of a melt, and such an Al alloy wire is considered as suitable for mass production. When the ratio Sib/Sib is approximately from 1.3 to 6.0, it is considered that mass production is easily achieved.
(Hydrogen Content)
An Al alloy wire which contains at most 8.0 ml/100 g of hydrogen represents one example of Al alloy wire 22 in the embodiment. Hydrogen may be one of factors for voids as described above. When a content of hydrogen with respect to a mass of 100 g of Al alloy wire 22 is not more than 8.0 ml, this Al alloy wire 22 contains a small number of voids and breakage originating from a void as described above can be lessened. As a content of hydrogen is lower, there may be a smaller number of voids. Therefore, the content is preferably not more than 7.8 ml/100 g, further not more than 7.6 ml/100 g, and not more than 7.0 ml/100 g and preferably closer to 0. Hydrogen in Al alloy wire 22 is considered to remain as dissolved hydrogen, through such a process that casting is performed in an atmosphere containing water vapor such as the air atmosphere and water vapor in the atmosphere is dissolved in a melt. Therefore, a content of hydrogen tends to be low, for example, by lessening solution of gas from the atmosphere by setting a relatively low temperature of a melt. The content of hydrogen tends to be lower when Cu is contained.
(Surface Property and State)
Dynamic Friction Coefficient
An Al alloy wire having a dynamic friction coefficient not greater than 0.8 represents one example of Al alloy wire 22 in the embodiment. When Al alloy wire 22 having such a small dynamic friction coefficient is used, for example, for an elemental wire of a strand wire and when the strand wire is repeatedly bent, friction between elemental wires (Al alloy wires 22) is low, the elemental wires are readily slid with respect to each other, and each elemental wire can smoothly move. When the dynamic friction coefficient is large, friction between the elemental wires is high. When repeated bending is applied, the elemental wire tends to break due to friction and consequently the strand wire is readily broken. Al alloy wire 22 having the dynamic friction coefficient not greater than 0.8 can be low in friction between elemental wires when it is used in particular for a strand wire, the Al alloy wire is less likely to break even though it is repeatedly bent, and the Al alloy wire is excellent in fatigue characteristics. As the dynamic friction coefficient is smaller, breakage clue to friction can be lessened, arid the dynamic friction coefficient is preferably not greater than 0.7, further not greater than 0.6, and not greater than 0.5. The dynamic friction coefficient tends to be small, for example, by smoothening the surface of Al alloy wire 22, applying a lubricant to the surface of Al alloy wire 22, or satisfying both of these conditions.
Surface Roughness
An Al alloy wire having surface roughness not greater than 3 μm represents one example of Al alloy wire 22 in the embodiment. Al alloy wire 22 having such small surface roughness tends to have s small dynamic friction coefficient. Therefore, when the Al alloy wire is used for an elemental wire of a strand wire as described above, friction between elemental wires can be low and the Al alloy wire is excellent in fatigue characteristics. As the surface roughness is smaller, the dynamic friction coefficient tends to be smaller and friction between elemental wires tends to be lower. Therefore, the surface roughness is not greater than 2.5 μm, further not greater than 2 μm, and preferably not greater than 1.8 μm. Surface roughness tends to be smaller, for example, by manufacturing for producing a smooth surface by using a wire drawing die having surface roughness not greater than 3 μm or by adjusting an amount of lubricant during wire drawing to be slightly larger. Facilitated industrial mass production is expected by setting the lower limit of surface roughness to 0.01 μm and further to 0.03 μm.
C Amount
An Al alloy wire in which a lubricant is adhered to its surface and an amount of adhesion of C derived from the lubricant is more than 0 and not more than 30 mass % represents one example of Al alloy wire 22 in the embodiment. The lubricant adhered to the surface of Al alloy wire 22 is considered as remainder of a lubricant (representatively an oil solution) used in a manufacturing process as described above. Al alloy wire 22 in which an amount of adhesion of C satisfies the range tends to have a small dynamic friction coefficient owing to adhesion of the lubricant, and as the amount of adhesion is greater within the range, the dynamic friction coefficient tends to be smaller. With a small dynamic friction coefficient, friction between elemental wires can be low when Al alloy wire 22 is used for an elemental wire of a strand wire as described above, and the Al alloy wire is excellent in fatigue characteristics. The Al alloy wire is also excellent in corrosion resistance owing to adhesion of the lubricant. As the amount of adhesion is smaller within the range, an amount of lubricant interposed between conductor 2 and a terminal portion 4 can be smaller when terminal portion 4 (
Surface Oxide Film
An Al alloy wire including a surface oxide film having a thickness not smaller than 1 nm and not greater than 120 nm represents one example of Al alloy wire 22 in the embodiment When heat treatment such as aging treatment is preformed, an oxide film can be present on a surface of Al alloy wire 22. When the surface oxide film has a small thickness not greater than 120 nm, an oxide interposed between conductor 2 and terminal portion 4 when terminal portion 4 is attached to an end portion of conductor 2 formed from Al alloy wire 22 can be less. As an amount of interposed oxide which is an electrically insulating material between conductor 2 and terminal portion 4 is small, increase in connection resistance between conductor 2 and terminal portion 4 can be lessened. When the surface oxide film is equal to or greater than 1 nm, corrosion resistance of Al alloy wire 22 can be enhanced. As the thickness of the surface oxide film is smaller in the range above, increase in connection resistance can be lessened, and as the thickness is greater, corrosion resistance can be enhanced. In consideration of suppression of increase in connection resistance and corrosion resistance, the surface oxide film can be not smaller than 2 nm and not greater than 115 nm, further not smaller than 5 nm and not greater than 110 nm, and further not greater than 100 nm. A thickness of the surface oxide film can be adjusted, for example, based on a condition for heat treatment. For example, when a concentration of oxygen in the atmosphere is high (for example, the air atmosphere), the surface oxide film tends to be large in thickness, and when a concentration of oxygen is low (for example, an inert gas atmosphere or a reducing gas atmosphere), the surface oxide film tends to be small in thickness.
(Characteristics)
Work Hardening Exponent
An Al alloy wire having a work hardening exponent, not smaller than 0.05 represents one example of Al alloy wire 22 in the embodiment. When the Al alloy wire has a large work hardening exponent not smaller than 0.05, for example, Al alloy wire 22 is readily work-hardened in performing plastic working such as making a compressed strand wire obtained by compression forming a strand wire obtained by stranding together a plurality of Al alloy wires 22 or crimping terminal portion 4 to an end portion of conductor 2 made up of Al alloy wire 22 (which may be any of a solid wire, a strand wire, and a compressed strand wire). Even though a cross-sectional area is decreased by plastic working such as compression forming or crimping, strength can be enhanced by work hardening, and terminal portion 4 can firmly be fixed to conductor 2. Al alloy wire 22 thus large in work hardening exponent can make up conductor 2 excellent in fixability of terminal portion 4. As the work hardening exponent is larger, improvement in strength by work hardening can be expected. Therefore, the work hardening exponent is preferably not smaller than 0.08 and further not smaller than 0.1. The work hardening exponent tends to be large as breaking elongation is higher. Therefore, in order to increase the work hardening exponent, breaking elongation is enhanced, for example, by adjusting a type or a content of an additive element or a condition for heat treatment. Al alloy wire 22 having such a specific structure that a size of a crystallized material satisfies the specific range described above and an average crystal grain size satisfies the specific range described above tends to satisfy the work hardening exponent not smaller than 0.05. Therefore, the work hardening exponent can be adjusted also by adjusting a type or a content of an additive element or a condition for heat treatment with the structure of the Al alloy being defined as an indicator.
Mechanical Characteristics and Electrical Characteristics
Al alloy wire 22 in the embodiment is high in tensile strength and 0.2% proof stress, excellent in strength, high in electrical conductivity, and also excellent in electrical conductive property by being composed of the specifically composed Al alloy described above and subjected representatively to heat treatment such as aging treatment. Depending on a composition or a manufacturing condition, breaking elongation can be high and toughness can also be excellent. Quantitatively, Al alloy wire 22 satisfies at least one selected from tensile strength not lower than 150 MPa, 0.2% proof stress not lower than 90 MPa, breaking elongation not lower than 5%, and electrical conductivity not lower than 40% IACS. Al alloy wire 22 which satisfies two items, in addition, three items, and in particular, all four items of the listed items is better in impact resistance and fatigue characteristics and also in electrical conductive property. Such Al alloy wire 22 can suitably be made use of for a conductor of an electrical wire.
When tensile strength is higher within the range, strength is higher, and tensile strength can be not lower than 160 MPa, further not lower than 180 MPa, and not lower than 200 MPa. When tensile strength is low, breaking elongation or electrical conductivity is readily enhanced.
When breaking elongation is higher in the range above, flexibility and toughness are better and bending is more readily performed. Therefore, breaking elongation can be not lower than 6%, further not lower than 7%, and not lower than 10%.
Al alloy wire 22 is representatively made use of for conductor 2. Therefore, higher electrical conductivity is preferred, and the electrical conductivity is more preferably not lower than 45% IACS, further not lower than 48% IACS, and not lower than 50% IACS.
Al alloy wire 22 is preferably also high in 0.2% proof stress. When tensile strength is equal, as 0.2% proof stress is higher, fixability to terminal portion 4 tends to be better. 0.2% proof stress can be not lower than 95 MPa, further not lower than 100 MPa, and not lower than 130 MPa.
When a ratio of 0.2% proof stress to tensile strength of Al alloy wire 22 is not lower than 0.5, 0.2% proof stress is sufficiently high, strength is high, breakage is less likely, and fixability to terminal portion 4 is also excellent as described above. As the ratio is higher, strength is higher and fixability to terminal portion 4 is also better. Therefore, the ratio is preferably not lower than 0.55 and further not lower than 0.6.
Tensile strength, 0.2% proof stress, breaking elongation, and electrical conductivity can be modified, for example, by adjusting a type or a content of an additive element or a manufacturing condition (a condition for wire drawing and a condition for heat treatment). For example, when an amount of an additive element is large, tensile strength or 0.2% proof stress tends to be high, and when an amount of an additive element is small, electrical conductivity tends to be high.
(Shape)
A shape of the transverse section of Al alloy wire 22 in the embodiment can be selected as appropriate in accordance with an application. For example, a round wire of which shape of the transverse section is circular is given as an example (see
(Size)
A size of Al alloy wire 22 in the embodiment (an area of the transverse section or a diameter in an example of a round wire) can be selected as appropriate in accordance with an application. For example, when the Al alloy wire is used for a conductor of an electrical wire equipped in various wire harnesses such as a wire harness for cars, Al alloy wire 22 has a diameter not smaller than 0.2 mm and not greater than 1.5 mm. For example, when the Al alloy wire is used for a conductor of an electrical wire which constructs a wiring structure of a building, Al alloy wire 22 has a diameter not smaller than 0.1 mm and not greater than 3.6 mm. Since Al alloy wire 22 is a wire member high in strength, it is expected to suitably be used also for an application where a diameter is smaller, for example, not smaller than 0.1 mm and not greater than 1.0 mm.
[Al Alloy Strand Wire]
Al alloy wire 22 in the embodiment can be used for an elemental wire of a strand wire as shown in
The number of strands for Al alloy strand wire 20 can be selected as appropriate, and for example, it can be set to 7, 11, 16, 19, or 37. A strand pitch of Al alloy strand wire 20 can be selected as appropriate. When the strand pitch is at least ten times as large as a pitch diameter of Al alloy strand wire 20, the Al alloy strand wire is less likely to be unbound in attachment of terminal portion 4 to an end portion of conductor 2 made up of Al alloy strand wire 20 and workability in attachment of terminal portion 4 is excellent. When a strand pitch is at most forty times as large as a pitch diameter, the elemental wire is less likely to twist in bending, and hence breakage is less likely and fatigue characteristics are excellent. In consideration of prevention of being unbound and prevention of twisting, the strand pitch can be at least 15 times and at most 35 times and further at least 20 times and at most 30 times as large as a pitch diameter.
Al alloy strand wire 20 can be a compressed strand wire obtained by further performing compression farming. In this case, a diameter can be smaller than in an example of simple stranding together, or an outer shape can be in a desired shape (for example, a circular shape). When the work hardening exponent of Al alloy wire 22 as each elemental wire is large as described above, improvement in strength and hence improvement in impact resistance and fatigue characteristics can also be expected.
Specifications such as a composition and a structure, a thickness of a surface oxide film, a content of hydrogen, an amount of adhesion of C, a property and a state of a surface, and mechanical characteristics and electrical characteristics of Al alloy wire 22 before stranding together are substantially maintained as specifications of each Al alloy wire 22 which makes up Al alloy strand wire 20. For such reasons as use of a lubricant in stranding, or heat treatment or the like after stranding together, a thickness of a surface oxide film, an amount of adhesion of C, mechanical characteristics, and electrical characteristics may be varied. A condition for stranding together is desirably adjusted such that specifications of Al alloy strand wire 20 are set to a desired value.
[Covered Electrical Wire]
Al alloy wire 22 in the embodiment or Al alloy strand wire 20 in the embodiment (which may be a compressed strand wire) can suitably be made use of for a conductor of an electrical wire. A bare conductor without an insulation cover can be made use of for any conductor of a covered electrical wire including an insulation cover. A covered electrical wire 1 in the embodiment, includes conductor 2 and an insulation cover 3 which covers an outer circumference of conductor 2, and includes Al alloy wire 22 in the embodiment or Al alloy strand wire 20 in the embodiment as conductor 2. Since covered electrical wire 1 includes conductor 2 made up of Al alloy wire 22 or Al alloy strand wire 20 excellent in impact resistance and fatigue characteristics, it is excellent in impact resistance and fatigue characteristics. An insulating material which makes up insulation cover 3 can be selected as appropriate. Examples of the insulating material include polyvinyl chloride (PVC), a non-halogen resin, and a material excellent in flame resistance, and a known material can be made use of. A thickness of insulation cover 3 can be selected as appropriate so long as prescribed dielectric strength is achieved.
[Terminal-Equipped Electrical Wire]
Covered electrical wire 1 in the embodiment can be made use of for electrical wires in various applications such as a wire harness provided on equipment such as cars and aircrafts, wires for various electrical appliances such as industrial robots, and wires in buildings. When the covered electrical wire is equipped in a wire harness or the like, terminal portion 4 is representatively attached to an end portion of covered electrical wire 1. A terminal-equipped electrical wire 10 in the embodiment includes covered electrical wire 1 in the embodiment and terminal portion 4 attached to an end portion of covered electrical wire 1 as shown in
A crimp terminal is electrically and mechanically connected to conductor 2 by removing insulation cover 3 at an end portion of covered electrical wire 1 to expose an end portion of conductor 2 and crimping the crimp terminal to the end portion. When Al alloy wire 22 or Al alloy strand wire 20 which makes up conductor 2 is high in work hardening exponent as described above, a portion of attachment of the crimp terminal in conductor 2 is excellent in strength owing to work hardening, although a cross-sectional area thereof is locally small. Therefore, for example, even when impact is applied at the time of connection between terminal portion 4 and a connection target in covered electrical wire 1 or repeated bending is further applied after connection, breakage of conductor 2 in the vicinity of terminal portion 4 can be lessened and terminal-equipped electrical wire 10 is excellent in impact resistance and fatigue characteristics.
When an amount of adhesion of C is relatively small or a surface oxide film is small in thickness as described above in Al alloy wire 22 or Al alloy strand wire 20 which makes up conductor 2, an electrically insulating material (a lubricant containing C or an oxide which forms a surface oxide film) interposed between conductor 2 and terminal portion 4 can be reduced and a connection resistance between conductor 2 and terminal portion 4 can be lowered. Therefore, terminal-equipped electrical wire 10 is excellent in impact resistance and fatigue characteristics and in addition also low in connection resistance.
As shown in
[Method of Manufacturing Al Alloy Wire and Method of Manufacturing Al Alloy Strand Wire]
(Overview)
Al alloy wire 22 in the embodiment can representatively be manufactured by performing heat treatment (including aging treatment) at appropriate timing in addition to basic steps of casting, intermediate working such as (hot) rolling and extrusion, and wire drawing. Known conditions can be referred to as conditions in the basic steps and aging treatment. Al alloy strand wire 20 in the embodiment can be manufactured by stranding together a plurality of Al alloy wires 22. Known conditions can be referred to as conditions for stranding together.
(Casting Step)
In particular, Al alloy wire 22 in the embodiment in which a certain amount of fine crystallized materials is present in the surface layer is readily manufactured, for example, by setting a relatively high cooling rate in the casting process, in particular, a relatively high cooling rate in a specific temperature region from a temperature of the melt to 650° C. A liquidus region is mainly defined as the specific temperature region, and a crystallized material generated through solidification tends to be smaller with a higher cooling rate in the liquidus region. It is considered, however, that, when a temperature of the melt is lowered as described above and a cooling rate is too high, in particular, not lower than 25° C./second, generation of a crystallized material is less likely and an amount of solid solution of an additive element increases, which may cause lowering in electrical conductivity or difficulty in obtaining an effect of pinning of crystal grains by a crystallized material. In contrast, by setting a relatively low temperature of a melt and setting a rate of cooling in the temperature region to be high to some extent, a large crystallized material is less likely to be included and a certain amount of crystallized material fine and relatively uniform in size tends to be contained. Finally, Al alloy wire 22 containing a fine crystallized material to some extent can be manufactured.
Although depending on a content of Mg and Si and an additive element such as element α, with a cooling rate in the specific temperature region, for example, not lower than 1° C./second, further not lower than 2° C./second, and not lower than 4° C./second, the crystallized material tends to be finer, and an appropriate amount of crystallized materials is readily generated when the cooling rate is not higher than 30° C./second, further lower than 25° C./second, not higher than 20° C./second, lower than 20° C./second, not higher than 15° C./second, and not higher than 10° C./second. A not excessively high cooling rate is suitable also for mass production. Depending on a cooling rate, a supersaturated solid solution can be obtained. In this case, solution treatment does not have to be performed in a step after casting or it may be performed separately.
It has been found that Al alloy wire 22 including a small number of voids described above can be manufactured by setting a relatively low temperature of a melt as described above. By setting a relatively low temperature of a melt, solution of gas in an atmosphere into the melt can be lessened and a cast material can be manufactured with the melt containing less dissolved gas. Hydrogen represents an example of the dissolved gas as described above, and hydrogen is considered to have resulted from decomposition of water vapor in the atmosphere or to have been contained in the atmosphere. By adopting a cast material less in dissolved gas such as dissolved hydrogen as a base material, a state that an Al alloy contains a small number of voids originating from dissolved gas is readily maintained in casting or steps thereafter in spite of plastic working such as rolling or wire drawing or heat treatment such as aging treatment. Consequently, voids present in the surface layer or the inside of Al alloy wire 22 which has a final diameter can satisfy the specific range described above. Furthermore, Al alloy wire 22 low in content of hydrogen as described above can be manufactured. Positions of voids confined in the Al alloy may be varied or a size of voids may be made smaller to some extent by performing steps after the casting process such as stripping or working accompanying plastic deformation (rolling, extrusion, and wire drawing). It is considered, however, that, if a total content of voids in the cast material is high, a total content of voids present in the surface layer or the inside and a content of hydrogen tend to be high (substantially maintained) in the Al alloy wire having a final diameter in spite of position change or variation in size. In contrast, by sufficiently decrease voids contained in the cast material itself by setting a low temperature of the melt, Al alloy wire 22 containing a small number of voids can be manufactured. As the temperature of the melt is lower, dissolved gas can be reduced and voids in the cast material can be reduced. By setting a low temperature of the melt, an amount of dissolved gas can be reduced even in casting in an atmosphere containing water vapor such as the air atmosphere, and hence a total content of voids originating from dissolved gas or a content of hydrogen can be reduced. In addition to lowering in temperature of a melt, a rate of cooling in a specific temperature region described above in the casting process is increased to some extent as described above, so that increase in dissolved gas originating from the atmosphere is readily prevented. With not too high a rate of cooling, it is considered that dissolved gas in the inside of a metal which is being solidified is readily emitted into an atmosphere which is the outside. Consequently, a total content of voids originating from dissolved gas or a content of hydrogen can further be reduced.
An example of a specific temperature of a melt is not lower than a liquidus temperature of the Al alloy and lower than 750° C. As the temperature of the melt is lower, dissolved gas can be reduced and voids in the cast material can be reduced. Therefore, the temperature of the melt is preferably not higher than 748° C. and further not higher than 745° C. When a temperature of the melt is high to some extent, a solid solution of an additive element is readily obtained. Therefore, a temperature of the melt can be not lower than 670° C. and further not lower than 675° C. By setting a cooling rate in the specific temperature region described above to be within a specific range while a relatively low temperature of the melt is set, a certain amount of fine crystallized materials can be contained as described above, and in addition, voids in a cast material are readily made smaller and fewer. Hydrogen is readily dissolved and dissolved gas tends to increase in the temperature region up to 650° C. described above. By setting the cooling rate to be within the specific range described above, however, increase in dissolved gas can be suppressed. In addition, with not too high a rate of cooling, dissolved gas in the inside of a metal which is being solidified is readily emitted into an atmosphere which is the outside. From the foregoing, more preferably, a temperature of the melt is not lower than 670° C. and lower than 750° C. and a rate of cooling from a temperature of the melt to 650° C. is lower than 20° C./second.
Furthermore, by setting a relatively high cooling rate in the casting process within the range described above, such effects as readily obtaining a cast material having fine crystal structure, obtaining a solid solution of an additive element readily to some extent, and readily making dendrite arm spacing (DAS) smaller (for example, 50 μm or smaller or further 40 μm or smaller) can also be expected.
Any of continuous casting and a metal mold casting (billet casting) can be used for casting. Continuous casting allows continuous manufacturing of a long cast material, and in addition, facilitated increase in cooling rate. Such effects as suppression of a large crystallized material as described above, reduction in voids, reduction in size of crystal grains or DAS, preparation of a solid solution of an additive element, and formation of a supersaturated solid solution depending on a cooling rate can be expected.
(Step Up to Wire Drawing)
An intermediate work material obtained by subjecting a cast material representatively to plastic working (intermediate working) such as (hot) rolling or extrusion can be subjected to wire drawing. A continuous cast and rolled material (representing one example of an intermediate work material) can also be subjected to wire drawing by performing hot rolling in succession to continuous casting. Stripping or heat treatment can be performed before and/or after plastic working. By performing stripping, a surface layer where voids or a surface flaw may be present can be removed. Examples of heat treatment include heat treatment aiming at homogenization or solution of an Al alloy. Examples of conditions for homogenization include setting an atmosphere to the air atmosphere or a reducing atmosphere, setting a heating temperature approximately not lower than 450° C. and not higher than 600° C. (preferably not lower than 500° C.) and a retention time not shorter than 1 hour and not longer than 10 hours (preferably not shorter than 3 hours), and gradual cooling in which a cooling rate is not higher than 1° C./minute. By performing homogenization treatment under the conditions above onto the intermediate work material before wire drawing, Al alloy wire 22 high in breaking elongation and excellent in toughness is readily manufactured, and by employing the continuous cast and rolled material for the intermediate work material, Al alloy wire 22 better in toughness is readily manufactured. Conditions which will be described later can be made use of as conditions for solution treatment.
(Wire Drawing Step)
A wire-drawn member is formed by subjecting a base material (an intermediate work material) subjected to such plastic working as rolling described above to (cold) wire drawing until a prescribed final diameter is achieved. Wire drawing is performed representatively by using a wire drawing die. In addition, wire drawing is performed with the use of a lubricant. By using a wire drawing die having small surface roughness, for example, not greater than 3 μm, and by adjusting an amount of application of the lubricant as described above, Al alloy wire 22 with a smooth surface of which surface roughness is not greater than 3 μm can be manufactured. By replacing a wire drawing die with a wire drawing die small in surface roughness as appropriate, a wire-drawn member with a smooth surface can successively be manufactured. Surface roughness of the wire drawing die is readily measured, for example, by using surface roughness of a wire-drawn member as an alternative value. By adjusting an amount of application of the lubricant or adjusting a condition for heat treatment which will be described later, Al alloy wire 22 in which an amount of adhesion of C to the surface of Al alloy wire 22 satisfies the specific range described above can be manufactured. Then, Al alloy wire 22 having a dynamic friction coefficient satisfying the specific range described above can be manufactured. A degree of wire drawing is desirably selected as appropriate in accordance with a final diameter.
(Stranding Step)
In manufacturing Al alloy strand wire 20, a plurality of wire members (wire-drawn members or heat-treated members subjected to heat treatment after wire drawing) are prepared and these wire members are stranded together at a prescribed strand pitch (for example, 10 times to 40 times as large as a pitch diameter). A lubricant may be used in stranding. When Al alloy strand wire 20 is made into a compressed strand wire, it is compression-formed into a prescribed shape after stranding together.
(Heat Treatment)
A wire-drawn member can be subjected to heat treatment at any timing, for example, while it is being drawn or after the wire drawing step. Examples of intermediate heat treatment performed during wire drawing include heat treatment aiming to remove strain introduced during wire drawing and to enhance workability. Examples of heat treatment after the wire drawing step include heat treatment aiming at solution treatment and heat treatment aiming at aging treatment. Heat treatment aiming at least at aging treatment is preferred. By performing aging treatment, a precipitated material containing an additive element such as Mg and Si and element α (for example, Zr) in an Al alloy depending on a composition can be dispersed in the Al alloy to thereby improve strength through age hardening and improve electrical conductivity owing to reduction in element in a solid solution state. Consequently, Al alloy wire 22 or Al alloy strand wire 20 high in strength and toughness and also excellent in impact resistance and fatigue characteristics can be manufactured. Examples of timing to perform heat treatment include at least one of during wire drawing, after wire drawing (before stranding), after stranding (before compression forming), and after compression forming. Heat treatment may be performed at a plurality of timings. When solution treatment is performed, solution treatment is performed before aging treatment (it does not have to be performed immediately before aging treatment). When intermediate heat treatment or solution treatment described above is performed during wire drawing or before stranding, workability can be enhanced to facilitate wire drawing or stranding. A condition for heat treatment is desirably adjusted such that characteristics after heat treatment satisfy a desired range. By performing heat treatment to satisfy, for example, breaking elongation not lower than 5%, Al alloy wire 22 of which work hardening exponent satisfies the specific range described above can also he manufactured. An amount of lubricant before heat treatment can be measured and a condition for heat treatment can also be adjusted such that a remaining amount of lubricant after heat treatment, attains to a desired value. The remaining amount of lubricant tends to be smaller as a heating temperature is higher or a retention time is longer.
Any of continuous treatment in which objects to be subjected to heat treatment are successively supplied to a heating vessel such as a pipe furnace or an electrical furnace for heating and batch treatment in which an object to be subjected to heat treatment is heated as being sealed in a heating vessel such as an atmospheric furnace can he made use of for heat treatment. In continuous treatment, for example, a temperature of a wire member is measured with a contactless thermometer and a control parameter is adjusted such that characteristics after heat treatment are within a prescribed range. Specific conditions for batch treatment include, for example, the following,
(Solution treatment) A heating temperature is approximately not lower than 450° C. and not higher than 620° C. (preferably not lower than 500° C. and not higher than 6000° C.), a retention time is riot shorter than 0.005 second and not longer than 5 hours (preferably not shorter than 0.01 second and not longer than 3 hours), a cooling rate is not lower than 100° C./minute, and rapid cooling not lower than 200° C./minute is further performed.
(Intermediate heat treatment) A heating temperature is not lower than 250° C. and not higher than 550° C. and a duration of heating is not shorter than 0.01 second and not longer than 5 hours.
(Aging treatment) A heating temperature is not lower than 100° C. and not higher than 300° C. and further not lower than 140° C. and not higher than 250° C., and a retention time period is not shorter than 4 hours and not longer than 20 hours and further not longer than 16 hours.
Examples of the atmosphere during heat treatment include an atmosphere relatively high in content of oxygen such as the air atmosphere or a low-oxygen atmosphere lower in content of oxygen than the air atmosphere. With the air atmosphere being set, control of the atmosphere is not required, however, a surface oxide film large in thickness (for example, not smaller than 50 nm) tends to be formed. Therefore, when the air atmosphere is adopted, continuous treatment in which a retention time period is readily shortened is adopted so that Al alloy wire 22 including a surface oxide film having a thickness satisfying the specific range described above is readily manufactured. Examples of the low-oxygen atmosphere include a vacuum atmosphere (a pressure-reduced atmosphere), an inert gas atmosphere, and a reducing gas atmosphere. Examples of the inert gas include nitrogen and argon. Examples of the reducing gas include hydrogen gas, hydrogen-mixed gas containing hydrogen and inert gas, and a gas mixture of carbon monoxide and carbon dioxide. Though control of the atmosphere is required for the low-oxygen atmosphere, the surface oxide film is readily made smaller in thickness example, smaller than 50 nm). Therefore, when a low-oxygen atmosphere is adopted, batch treatment in which the atmosphere is readily controlled is adopted so that Al alloy wire 22 including a surface oxide film having a thickness satisfying the specific range described above or Al alloy wire 22 preferably smaller in thickness of the surface oxide film is readily manufactured.
As described above, by adjusting a composition of the Al alloy (preferably by adding both of Ti and B and an element effective in making crystals finer among elements α) and employing a continuous cast material or a continuous cast and rolled material as the base material, Al alloy wire 22 of which crystal grain size satisfies the range described above is readily manufactured. In particular, by setting a degree of wire drawing from a state of a base material or a continuous cast and rolled material obtained by subjecting the continuous cast material to plastic working such as rolling to a state of a wire-drawn member having a final diameter to 80% or higher and subjecting the wire-drawn member having the final diameter, a strand wire, or a compressed strand wire to heat treatment (in particular aging treatment) so as to achieve breaking elongation not lower than 5%, Al alloy wire 22 of which crystal grain size is not greater than 50 μm is further readily manufactured. In this case, heat treatment may be performed also during wire drawing. By controlling such crystal structure and controlling breaking elongation, Al alloy wire 22 having a work hardening exponent satisfying the specific range described above can also be manufactured.
(Other Steps)
In addition, examples of a method of adjusting a thickness of the surface oxide film include exposing a wire-drawn member having a final diameter to presence of hot water at a high temperature and a high pressure, applying water to the wire-drawn member having the final diameter, and providing a drying step after water cooling when water cooling is performed after heat treatment in continuous treatment in the air atmosphere. The surface oxide film tends to be greater in thickness by exposure to hot water or by application of water. By drying after water cooling, formation of a boehmite layer originating from water cooling is prevented and the surface oxide film tends to be smaller in thickness. By using coolant obtained by adding ethanol to water as coolant in water cooling, degreasing is also achieved simultaneously with cooling.
When an amount of lubricant adhered to the surface of Al alloy wire 22 is small or there is substantially no lubricant due to heat treatment described above or degreasing treatment or the like, a lubricant can be applied so as to achieve a prescribed amount of adhesion. The amount of adhesion of lubricant can be adjusted with an amount of adhesion of C or a dynamic friction coefficient being defined as an indicator. A known method can be used for degreasing treatment, and degreasing treatment can also serve as cooling as described above.
[Method of Manufacturing Covered Electrical Wire]
Covered electrical wire 1 in the embodiment can be manufactured by preparing Al alloy wire 22 or Al alloy strand wire 20 (which may be a compressed strand wire) in the embodiment which makes up conductor 2 and forming insulation cover 3 around the outer circumference of conductor 2 by extrusion or the like. Known conditions can be referred to as conditions for extrusion.
[Method of Manufacturing Terminal-Equipped Electrical Wire]
Terminal-equipped electrical wire 10 in the embodiment can be manufactured by removing insulation cover 3 at an end portion of covered electrical wire 1 to expose conductor 2 and attaching terminal portion 4 thereto.
[Test Example 1]
Al alloy wires were fabricated under various conditions and characteristics thereof were examined. Al alloy strand wires were made by using the Al alloy wires, and a covered electrical wire including the Al alloy strand wire as a conductor was further made. Characteristics of a terminal-equipped electrical wire obtained by attaching a crimp terminal to an end portion of the covered electrical wire were examined.
In this test, as shown in
(Manufacturing Method A) WR→wire drawing→heat treatment (solution→aging
(Manufacturing Method B) WR→heat treatment (solution)→wire drawing→aging
(Manufacturing Method C) WR→heat treatment (solution)→wire drawing→heat treatment (solution)→aging
(Manufacturing Method D) WR→stripping→wire drawing→intermediate heat treatment→wire drawing→heat treatment (solution)→aging
(Manufacturing Method E) WR→heat treatment (solution)→stripping→wire drawing→intermediate heat treatment→wire drawing→heat treatment (solution)→aging
(Manufacturing Method F) WR→wire drawing→aging
(Manufacturing Method G) WR→heat treatment (solution, batch)→wire drawing→aging
Samples Nos. 1 to 71, Nos. 101 to 106, and Nos. 111 to 119 are samples manufactured by manufacturing method C. Samples Nos. 72 to 77 are samples manufactured by manufacturing methods A, B, and D to G in this order. A specific manufacturing process in manufacturing method C will be described below, in each manufacturing method other than manufacturing method C, steps the same as in manufacturing method C are performed under similar conditions. Stripping in manufacturing methods D and E refers to removal of approximately 150 μm of a wire member from a surface thereof, and intermediate heat treatment refers to a continuous treatment by high-frequency induction heating (a temperature of a wire member being set to approximately 300° C.). Solution treatment in manufacturing method G refers to batch treatment under a condition of 540° C.×3 hours.
A melt of an Al alloy was prepared by preparing pure aluminum (at least 99.7 mass % of Al) as a base, melting pure aluminum, and introducing an additive element shown in Tables 1 to 4 into the obtained melt (molten aluminum) such that a content thereof was set to an amount shown in Tables 1 to 4 (mass %). A content of hydrogen was readily reduced or a foreign matter was readily reduced by performing treatment for removing hydrogen gas or treatment for removing a foreign matter onto the melt of the Al alloy of which component was modified.
A continuous cast and rolled material or a billet cast material was prepared by using the prepared melt of the Al alloy. The continuous cast and rolled material was made by continuously performing casting and hot rolling by using a belt-wheel type continuous casting roller and the prepared melt of the Al alloy, and a wire rod of ϕ9.5 mm was obtained. The billet cast material was fabricated by pouring the melt of the Al alloy into a prescribed fixed mold and cooling the melt. After the billet cast material was subjected to homogenization treatment, it was subjected to hot rolling to thereby make a wire rod (a rolled member) of ϕ9.5 mm. Tables 5 to 8 show a type of a casting method (the continuous cast and rolled material being denoted as “continuous” and the billet cast material being denoted as the “billet”), a temperature of the melt (° C.), and a cooling rate in the casting process (an average rate of cooling from the temperature of the melt to 650° C., ° C./second). The cooling rate was varied by adjusting a state of cooling by using a water cooling mechanism.
The wire rod was subjected to solution treatment (batch treatment) under a condition of 530° C.×5 hours and thereafter to cold wire drawing, to thereby make a wire-drawn member having a diameter of ϕ0.3 mm, a wire-drawn member having a diameter of ϕ0.25 mm, and a wire-drawn member having a diameter of ϕ0.32 mm. Wire drawing was performed by using a wire drawing die and a commercially available lubricant (an oil solution containing carbon). A wire drawing die to be used could be changed as appropriate by preparing wire drawing dice different in surface roughness, and surface roughness of a wire-drawn member of each sample was adjusted by adjusting an amount of use of a lubricant. For sample No. 115, a wire drawing die largest in surface roughness was used.
An aged member (the Al alloy wire) was made by subjecting the obtained wire-drawn member having a diameter of ϕ0.3 mm to solution treatment and thereafter to aging treatment. Continuous treatment by high-frequency induction heating was adopted as solution treatment, in which a temperature of the wire member was measured with a contactless infrared thermometer and a condition of power feed was controlled such that the temperature of the wire member was not lower than 300° C. Batch treatment by using a box-shaped furnace was adopted as aging treatment, and it was performed at a temperature (° C.) for a time period (time period (H)) in an atmosphere shown in Tables 5 to 8. Sample No. 116 was subjected to boehmite treatment (100° C.×15 minutes) after aging treatment in the air atmosphere (marked with “*” in the field of Atmosphere in Table 8).
(Mechanical Characteristics and Electrical Characteristics)
Tensile strength (MPa), 0.2% proof stress (MPa), breaking elongation (%), a work hardening exponent, and electrical conductivity (% IACS) of the obtained aged member having a diameter of ϕ0.3 mm were measured. A ratio of 0.2% proof stress to tensile strength (proof stress/tension) was also calculated. Tables 9 to 12 show these results.
Tensile strength (MPa), 0.2% proof stress (MPa), and breaking elongation (%) were measured with the use of a general-purpose tensile tester in conformity with JIS Z 2241 (metallic materials-tensile testing-method of test at room temperature, 1998). The work hardening exponent is defined as an exponent n of true strain ε in an expressions σ=C×εn where σ represents true stress and ε represents true strain in a plastic strain region when test force in the tensile test is applied in a uniaxial direction. In the expression, C represents a strength coefficient. Exponent n is calculated by drawing an S-S curve by conducting a tensile test by using the tensile tester (see also JIS G 2253, 2011). Electrical conductivity (% IACS) was measured by a bridge method.
(Fatigue Characteristics)
The obtained aged member having a diameter of ϕ0.3 mm was subjected to a bending test and the number of times until breakage was counted. The bending test was conducted by using a commercially available cyclic bending tester. Repeated bending was performed by applying a load of 12.2 MPa by using a jig capable of applying 0.3% bending strain to a wire member as each sample. Each sample was subjected to the bending test three or more times, and Tables 9 to 12 show an average (count) thereof. It can be concluded that a large number of times until breakage indicates less likeliness of breakage by repeated bending and excellent fatigue characteristics.
A strand wire was made by using the obtained wire-drawn member having a diameter of ϕ0.25 mm or a diameter of ϕ0.32 mm (the wire-drawn member not subjected to aging treatment described above and not subjected to solution treatment immediately before aging or the wire-drawn member not subjected to aging treatment in manufacturing methods B, F, and G). A commercially available lubricant (an oil solution containing carbon) was used as appropriate for stranding. A strand wire including seven wire members each having a diameter of ϕ0.25 mm was made. A compressed strand wire obtained by further compression-forming the strand wire including seven wire members each having a diameter of ϕ0.32 mm was made. The strand wire and the compressed strand wire both had a cross-sectional area of 0.35 mm2 (0.35 sq). A strand pitch was set to 20 mm (in an example of the wire-drawn member having a diameter of ϕ0.25 mm, the strand pitch was approximately 40 times as large as the pitch diameter, and in an example of the wire-drawn member having a diameter of ϕ0.32 mm, the strand pitch was approximately 32 times as large as the pitch diameter).
The obtained strand wire and compressed strand wire were sequentially subjected to solution treatment and aging treatment (only to aging treatment in manufacturing methods B, F, and G). Conditions for heat treatment were the same as the conditions for heat treatment applied to the wire-drawn member of 0.3 mm described above, continuous treatment by high-frequency induction heating was adopted as solution treatment, and batch treatment performed under conditions shown in Tables 5 to 8 (see above for * of sample No. 116) was adopted as aging treatment. A covered electrical wire was made by adopting the obtained aged strand wire as the conductor and forming an insulation cover (having a thickness of 0.2 mm) with an insulating material (a halogen-free insulating material) around the outer circumference of the conductor. An amount of use of at least one of a lubricant in wire drawing and a lubricant in stranding was adjusted such that the lubricant remained to some extent after aging treatment. In sample No. 29, a slightly more lubricant was used than in other samples, and sample No. 117 was largest in amount of use of the lubricant. Sample No. 114 was subjected to degreasing treatment after aging treatment. In sample No. 113, a temperature for aging was set to 300° C. and a retention time period was set to 50 hours, aging was performed for a longer time period and at a higher temperature than those for other samples.
Items below of the obtained covered electrical wire as each sample or a. terminal-equipped electrical wire obtained by attaching a crimp terminal to the covered electrical wire were examined. Items of both of an example including the strand wire as the conductor of the covered electrical wire and an example including the compressed strand wire as the conductor of the covered electrical wire were examined. Though Tables 13 to 20 show results in the example including the strand wire as the conductor, it was confirmed based on comparison with results in the example including the compressed strand wire as the conductor that there was no great difference therebetween.
(Observation of Structure)
Crystallized Material
A transverse section of the obtained covered electrical wire as each sample was taken and the conductor (the strand wire or the compressed strand wire formed from the Al alloy wire, to be understood similarly below) was observed with a metal microscope to examine a crystallized material in the surface layer and the inside. A rectangular surface-layer crystallization measurement region having a short side of 50 μm long and a long side of 75 μm long was taken from a surface-layer region extending by up to 50 μm in a direction of depth from a surface of each Al alloy wire which made up the conductor. For one sample, one surface-layer crystallization measurement region was taken from each of the seven Al alloy wires which formed the strand wire and thus seven surface-layer crystallization measurement regions in total were taken. Then, an area and the number of crystallized materials present in each surface-layer crystallization measurement region were found. For each surface-layer crystallization measurement region, an average area of crystallized materials was found. For one sample, an average area of crystallized materials in seven measurement regions in total was found. Tables 13 to 16 show a value obtained by further averaging average areas of crystallized materials in seven measurement regions in total for each sample as an average area A (μm2).
The number of crystallized materials in seven surface-layer crystallization measurement regions in total was determined for each sample, and Tables 13 to 16 show a value calculated by averaging the numbers of crystallized materials in the seven measurement regions in total as the number A (count).
Furthermore, a total area of crystallized materials each having an area not greater than 3 μm2 among the crystallized materials present in each surface-layer crystallization measurement region was determined, and a ratio of a total area of crystallized materials each having an area not greater than 3 μm2 to the total area of all crystallized materials present in each surface-layer crystallization measurement region was calculated. For each sample, a ratio of the total area in the seven surface-layer crystallization measurement regions in total was determined. Tables 13 to 16 show a value calculated by averaging the ratios of the total area in the seven measurement regions in total as an area ratio A (%).
Instead of the rectangular surface-layer crystallization measurement region described above, a crystallization measurement region in a shape of a sector having an area of 3750 μm2 was taken from an annular surface-layer region having a thickness of 50 μm, and an average area B (μm2) of crystallized materials in the crystallization measurement region in the shape of the sector was found as in the example of evaluation of the rectangular surface-layer crystallization measurement region described above. The number B (count) of crystallized materials in the crystallization measurement region in the shape of the sector and an area ratio B (%) of the total area of crystallized materials each having an area not greater than 3 μm2 were found as in evaluation of the rectangular surface-layer crystallization measurement region described above. Tables 13 to 16 show results.
An area of crystallized materials is readily measured by subjecting an observed image to image processing such as binary processing to extract crystallized materials from the processed image. This is also applicable to voids which will be described later.
In the transverse section, a rectangular inside crystallization measurement region having a short side of 50 μm long and a long side of 75 μm long was taken in each Al alloy wire which made up the conductor. The inside crystallization measurement region was taken such that the center of the rectangle was superimposed on the center of each Al alloy wire. Then, an average area of crystallized materials present in each inside crystallization measurement region was calculated. An average area of crystallized materials in seven inside crystallization measurement regions in total was calculated for each sample. A value calculated by further averaging the average areas in the seven measurement regions in total was defined as an average area (inside). The average areas (inside) of samples Nos. 20, 40, and 70 were 2 μm2, 3 μm2, and 1 μm2, respectively. The average areas (inside) of the samples except for the three samples among samples Nos. 1 to 77 were also riot smaller than 0.05 μm2 and not greater than 40 μm2, and the average area of many of them was not greater than 35 μm2.
A transverse section of the obtained covered electrical wire as each sample was taken and the conductor was observed with a scanning electron microscope (SEM) to examine voids in the surface layer and the inside as well as a crystal grain size. A rectangular surface-layer void measurement region having a short side of 30 μm long and a long side of 50 μm long was taken from a surface-layer region extending by up to 30 μm in a direction of depth from a surface of each Al alloy wire which made up the conductor. For one sample, one surface-layer void measurement region was taken from each of the seven Al alloy wires which formed the strand wire and thus seven surface-layer void measurement regions in total were taken. Then, a total cross-sectional area of voids present in each surface-layer void measurement region was found. A total cross-sectional area of voids in the seven surface-layer void measurement regions in total was examined for each sample. Tables 13 to 16 show a value obtained by averaging the total cross-sectional areas of voids in the seven measurement regions in total as a total area A (μm2).
Instead of the rectangular surface-layer void measurement region described above, a void measurement region in a shape of a sector having an area of 1500 μm2 was taken from an annular surface-layer region having a thickness of 30 μm, and a total area B (μm2) of voids in the void measurement region in the shape of the sector was found as in the example of evaluation of the rectangular surface-layer void measurement region described above. Tables 13 to 16 show results.
In the transverse section, a rectangular inside void measurement region having a short side of 30 μm long and a long side of 50 μm long was taken in each Al alloy wire which made up the conductor. The inside void measurement region was taken such that the center of the rectangle was superimposed on the center of each Al alloy wire. Then, a ratio “inside/surface layer” of the total cross-sectional area of voids present in the inside void measurement region to the total cross-sectional area of voids present in the surface-layer void measurement region was calculated. Seven surface-layer void measurement regions in total and seven inside void measurement regions in total were taken for each sample, and a ratio “inside/surface layer” was calculated. Tables 13 to 16 show a value obtained by averaging the ratios “inside/surface layer” of the seven measurement regions in total as a ratio “inside/surface layer A”. A ratio “inside/surface layer B” in the example of the void measurement region in the shape of the sector described above was calculated as in the example of evaluation of the rectangular surface-layer void measurement region described above, and Tables 13 to 16 show results.
Crystal Grain Size
In the transverse section, a test line was drawn on an image observed with the SEM in conformity with JIS G 0551 (steels-micrographic determination of the apparent grain size, 2013) and a length of interception of the test line in each crystal grain was defined as a crystal grain size (an intercept method). A length of the test line was set such that the test line intercepted ten or more crystal grains. Each crystal grain size was found by drawing three test lines in one transverse section, and Tables 13 to 16 show a value obtained by averaging these crystal grain sizes as an average crystal grain size (μm).
(Hydrogen Content)
The insulation cover was removed from the obtained covered electrical wire as each sample so as to leave only the conductor, and a content (ml/100 g) of hydrogen per 100 g of the conductor was measured. Tables 13 to 16 show results. The content of hydrogen was measured by an inert gas fusion method. Specifically, a sample was introduced into a graphite crucible while argon was flowing, to thereby melt the sample by heating, and hydrogen was extracted together with other gas. The content of hydrogen was found by passing the extracted gas through a separation column to separate hydrogen from other gas and conducting measurement with a thermal conductivity detector to quantify a concentration of hydrogen.
(Surface Property and State)
Dynamic Friction Coefficient
The insulation cover was removed from the obtained covered electrical wire as each sample to leave only the conductor, and the strand wire or the compressed strand wire which formed the conductor was unbound to elemental wires. The dynamic friction coefficient was measured as below with each elemental wire (Al alloy wire) being defined as a sample. Tables 17 to 20 show results. As shown in
Surface Roughness
The insulation cover was removed from the obtained covered electrical wire as each sample to leave only the conductor, and the strand wire or the compressed strand wire which formed the conductor was unbound to elemental wires. With each elemental wire (Al alloy wire) being adopted as a sample, surface roughness (μm) was measured with a commercially available three-dimensional optical profiler (for example, NewView 7100 manufactured by Zygo Corporation). Arithmetic mean roughness Ra (μm) of a rectangular region of 85 μm×64 μm of each elemental wire (Al alloy wire) was found. For each sample, arithmetic mean roughness Ra of seven regions in total was determined, and Tables 17 to 20 show a value calculated by averaging arithmetic mean roughness Ra of the seven regions in total as surface roughness (μm).
Amount of Adhesion of C
The insulation cover was removed from the obtained covered electrical wire as each sample to leave only the conductor, and the strand wire or the compressed strand wire which formed the conductor was unbound. An amount of adhesion of C derived from a lubricant adhered to a surface of a central elemental wire was determined. The amount of adhesion of C (mass %) was measured with an SEM-EDX (energy dispersive X-ray analysis) apparatus with an acceleration voltage of an electron gun being set to 5 kV. Tables 13 to 16 show results. In an example in which the lubricant was adhered to the surface of the Al alloy wire which formed the conductor equipped in the covered electrical wire, in removal of the insulation cover, the lubricant may be removed as being adhered to the insulation cover at a portion of contact with the insulation cover in the Al alloy wire, and the amount of adhesion of C may not appropriately be measured. In measurement of the amount of adhesion of C at the surface of the Al alloy wire which formed the conductor equipped in the covered electrical wire, it is expected that an amount of adhesion of C can accurately be measured by defining a portion of the Al alloy wire not in contact with the insulation cover as a portion of measurement. Therefore, the central elemental wire not in contact with the insulation cover is adopted as a portion of measurement of the strand wire or the compressed strand wire obtained by concentrically stranding together seven Al alloy wires. A portion not in contact with the insulation cover may be adopted as a portion of measurement of outer elemental wires which surround the outer circumference of the central elemental wire.
Surface Oxide Film
The insulation cover was removed from the obtained covered electrical wire as each sample so as to leave only the conductor, the strand wire or the compressed strand wire which formed the conductor was unbound, and the surface oxide film of each elemental wire was subjected to measurement as below. A thickness of the surface oxide film of each elemental wire (Al alloy wire) was determined. A thickness of the surface oxide film of each of the seven elemental wires in total was determined for each sample, and Tables 17 to 20 show a value obtained by averaging thicknesses of the surface oxide films of the seven elemental wires in total as a thickness (nm) of the surface oxide film. A cross-section of each elemental wire was taken by performing cross-section polisher (CP) treatment, and the cross-section was observed with the SEM. A thickness of the oxide film having a relatively large thickness exceeding approximately 50 nm was measured by using this image observed with the SEM. For an oxide film having a relatively small thickness not greater than approximately 50 nm as observed with the SEM, measurement was conducted by separately conducting analysis in the direction of the depth (repeated sputtering and analysis by energy dispersive X-ray analysis (EDX)) with the use of electron spectroscopy for chemical analysis (ESCA).
(Impact Resistance)
Impact resistance (J/m) of the obtained covered electrical wire as each sample was evaluated with reference to PTL 1. Generally, a weight was attached to a tip end of a sample in which a distance between evaluation points was set to I m, the weight was lifted upward by 1 m followed by freefall, and a maximum mass (kg) of the weight up to which the sample did not break was measured. A product of the mass of the weight and acceleration of gravity (9.8 μm/s2) and a drop of 1 m was calculated by multiplication, and a value calculated by dividing the product by the drop (1 m) was defined as an evaluation parameter (J/m or (N·m)/m) of impact resistance. Tables 17 to 20 show a value calculated by dividing the found evaluation parameter of impact resistance by the conductor cross-sectional area (0.35 mm2) as an evaluation parameter (J/m·mm2) of impact resistance per unit area.
(Terminal Fixing Force)
Terminal fixing force (N) of the obtained terminal-equipped electrical wire as each sample was evaluated with reference to PTL 1. Generally, a terminal portion attached to one end of the terminal-equipped electrical wire was held by a terminal chuck., and a conductor portion resulting from removal of the insulation cover at the other end of the covered electrical wire was held by a conductor chuck. Maximum load (N) at the time of breakage of the terminal-equipped electrical wire as each sample having opposing ends held by these chucks was measured with a general-purpose tensile tester and this maximum load (N) was evaluated as terminal fixing force (N). Tables 17 to 20 show a value calculated by dividing the found maximum load by the conductor cross-sectional area (0.35 mm2) as terminal fixing force (N/mm2) per unit area.
(Corrosion Resistance)
The insulation cover was removed from the obtained covered electrical wire as each sample to leave only the conductor, and the strand wire or the compressed strand wire which formed the conductor was unbound to elemental wires. Any one elemental wire as a sample was subjected to a salt water spray test and corrosion was visually examined. Table 21 shows results. Conditions for the salt water spray test include use of a NaCl aqueous solution at a concentration of 5 mass % and a test time period of 96 hours. Table 21 extracts and shows sample No. 43 in which an amount of adhesion of C was 15 mass %, sample No. 114 in which an amount of adhesion of C was 0 mass % and the lubricant was substantially not adhered, and sample No. 117 in which an amount of adhesion of C was 40 mass % and the lubricant was excessively adhered. Samples Nos. 1 to 77 exhibited results the same as the result of sample No. 43.
The Al alloy wires as samples Nos. 1 to 77 (which may collectively be called an aged sample group below) composed of a specifically composed Al—Mg—Si based alloy containing Mg and Si within a specific range and containing as appropriate specific element α or the like within a specific range and subjected to aging treatment were higher in evaluation parameter values of impact resistance as shown in Tables 17 to 19 than the Al alloy wires as samples Nos. 101 to 106 outside the range of the specific composition (which may collectively be called a comparative sample group below), and the evaluation parameter values thereof were not lower than 4 J/m. The Al alloy wire in the aged sample group was high in breaking elongation as shown in Tables 9 to 11 and also achieved the number of times of bending at a high level. It can thus be seen that the Al alloy wire in the aged sample group was excellent in impact resistance and fatigue characteristics in a more balanced manner than the Al alloy wire in the comparative sample group. The aged sample group was excellent in mechanical characteristics and electrical characteristics, that is, high in tensile strength, also high in electrical conductivity, also high in breaking elongation, and further also high in 0.2% proof stress here. Quantitatively, the Al alloy wire in the aged sample group satisfied tensile strength not lower than 150 MPa, 0.2% proof stress not lower than 90 MPa, breaking elongation not lower than 5%, and electrical conductivity not lower than 40% IACS. Furthermore, the Al alloy wire in the aged sample group was also high in ratio “proof stress/tension” between tensile strength and 0.2% proof stress and the ratio was not lower than 0.5. In addition, it can be seen that the Al alloy wire in the aged sample group was also excellent in fixability to the terminal portion as shown in Tables 17 to 19 (not lower than 40 N). One of the reasons may be because the Al alloy wire in the aged sample group was high in work hardening exponent which was not lower than 0.05 (Tables 9 to 11) and an effect of improvement in strength owing to work hardening in crimping a crimp terminal was satisfactorily obtained.
Results of evaluation by using rectangular measurement region A and results of evaluation by using measurement region B in the shape of the sector are referred to in connection with matters about a crystallized material below and matters about voids which will be described later.
In particular, as shown in Tables 13 to 15, a certain amount of fine crystallized materials was present in the surface layer of the Al alloy wire in the aged sample group. Quantitatively, the average area was not greater than 3 μm2, and the average area was not greater than 2 μm2 and further not greater than 1.5 μm2 in many samples. The number of such tine crystallized materials was greater than 10 and not greater than 400 and not greater than 350 here, the number of fine crystallized materials was not greater than 300 in many samples, and the number of fine crystallized materials was not greater than 200 or not greater than 100 in some samples. Based on comparison between sample No. 20 (Tables 10 and 18) and sample No. 112 (Tables 12 and 20) identical in composition, sample No. 20 in which a certain amount of tine crystallized materials was present in the surface layer was greater in number of bending and greater also in parameter value of impact resistance. It is thus considered that, with finer crystallized materials present in the surface layer, cracking is less likely to originate from the crystallized material and excellent impact resistance and fatigue characteristics are achieved. Presence of a certain amount of fine crystallized materials may have suppressed growth of crystals to facilitate bending or the like arid has become one factor for improvement in fatigue characteristics.
It can be concluded from this test that, in order to make crystallized materials finer and allow presence thereof to some extent, a relatively high cooling rate in a specific temperature region (higher than 0.5° C./second and further not lower than 1° C./second and preferably lower than 25° C./second and further lower than 20° C./second) is effective.
It can further be concluded from this test as follows.
(1) As shown in “area ratio” in Tables 13 to 15, cracking was less likely to originate from a crystallized material also based on the fact that many (at least 70%, at least 80% in many cases, and further at least 85%) of crystallized materials present in the surface layer were fine crystallized materials uniform in size not greater than 3 μm2.
It is further considered in this test that cracking originating from a crystallized material or development of cracking From the surface layer to the inside through a crystallized material can be lessened and excellent impact resistance and fatigue characteristics are achieved also based on the fact that crystallized materials present not only in the surface layer but also in the inside were small (not greater than 40 μm2) as described above.
(2) The Al alloy wire in the aged sample group as shown in Tables 13 to 15 had a total area of voids in the surface layer not greater than 2.0 μm2 which was smaller than that of the Al alloy wires as samples Nos. 111, 118, and 119 shown in Table 16. With attention being paid to voids in the surface layer, comparison between samples Nos. 20 and 111 identical in composition, between samples Nos. 47 and 118 identical in composition, and between samples Nos. 71 and 119 identical in composition was made. It can be seen that samples Nos. 20, 47, and 71 smaller in number of voids were better in impact resistance (Tables 18 and 19) and greater in number of times of bending and hence also excellent in fatigue characteristics (Tables 10 and 11). One of the reasons may be because the Al alloy wires as samples Nos. 111, 118, and 119 including many voids in the surface layer tend to break because of cracking originating from a void in application of impact or repeated bending. It can thus be concluded that impact resistance and fatigue characteristics can be improved by reducing voids in the surface layer of the Al alloy wire. The Al alloy wire in the aged sample group as shown in Tables 13 to 15 is lower in content of hydrogen than the Al alloy wires as samples Nos. 111, 118, and 119 shown in Table 16, it is thus considered that hydrogen is one of factors for voids. It is considered that a temperature of the melt is high in samples Nos. 111, 118, and 119 and much dissolved gas tends to be present in the melt, and considered that much hydrogen was derived from dissolved gas. It can thus be concluded that setting a relatively low temperature (lower than 750° C.) of the melt in the casting process is effective for reducing voids in the surface layer.
In addition, it can be seen that hydrogen is readily reduced by containing Cu, based on comparison between sample No. 10 (Table 13) and samples Nos. 22 to 24 (Table 14).
As shown in Tables 13 to 15, the Al alloy wire in the aged sample group is smaller in number of voids not only in the surface layer but also in the inside. Quantitatively, a ratio “inside/surface layer” of the total area of voids is not higher than 44, it is not higher than 35 here, and it is not higher than 20 and further not higher than 10 in many samples, which are smaller than the ratio of sample No. 112 (Table 16). Based on comparison between samples Nos. 20 and 112 identical in composition, sample No. 20 lower in ratio “inside/surface layer” was greater in number of times of bending (Tables 10 and 12) and also larger in parameter value of impact resistance (Tables 18 and 20). One of the reasons may be because, in the Al alloy wire as sample No. 112 including many voids in the inside, cracking developed from the surface layer to the inside through voids in application of repeated bending and breakage was likely. It can thus be concluded that impact resistance and fatigue characteristics can be improved by reducing voids in the surface layer and the inside of the Al alloy wire. It can be concluded from this test that, as a cooling rate is higher, the ratio “inside/surface layer” tends to be lowered. Therefore, it can be concluded that, in order to reduce voids in the inside, setting a relatively low temperature of the melt in the casting process and setting a cooling rate relatively high to some extent in a temperature region up to 650° C. (higher than 0.5° C./second and further not lower than 1° C./second and preferably lower than 25° C./second and further lower than 20° C./second) are effective.
(3) As shown in Tables 17 to 19, the Al alloy wire in the aged sample group was small in dynamic friction coefficient. Quantitatively, the dynamic friction coefficient was not greater than 0.8, and many samples had a dynamic friction coefficient not greater than 0.5. It is considered that, owing to the small dynamic friction coefficient, elemental wires which formed a strand wire easily slid with respect to each other and break was less likely in repeated bending. The number of times until breakage of a solid wire (having a diameter of 0.3 mm) having the composition of sample No. 41 and a strand wire below prepared by using the Al alloy wire having the composition of sample No. 41 was determined by using the cyclic bending tester described above. Conditions for the test include bending strain of 0.9% and an applied load of 12.2 MPa. An elemental wire having a diameter of ϕ0.3 mm prepared similarly to the Al alloy wire as the solid wire having a diameter of 0.3 mmϕ was prepared, seven elemental wires were stranded together, and thereafter the stranded elemental wires were compressed to obtain a compressed strand wire having a cross-sectional area of 0.35 mm2 (0.35 sq). The compressed strand wire was then subjected to aging treatment (conditions in Table 6 and No. 41). As a result of the test, the number of times until breakage of the solid wire was 3894 and the number of times until breakage of the strand wire was 12053, and the number of times of bending significantly increased. An effect of improvement in fatigue characteristics can thus be expected by adopting an elemental wire small in dynamic friction coefficient for a strand wire. As shown in Tables 17 to 19, the Al alloy wire in the aged sample group was small in surface roughness. Quantitatively, surface roughness was not greater than 3 μm, many samples had surface roughness not greater than 2.5 μm, and some samples had surface roughness not greater than 2 μm or 1 μm, which were smaller than that of sample No. 115 (Table 20). Based on comparison between sample No. 20 (Tables 18 and 10) and sample No. 115 (Tables 20 and 12) identical in composition, sample No. 20 was smaller in dynamic friction coefficient and also surface roughness, and in addition, it was larger in number of times of bending and tends to be better also in impact resistance. It is thus considered that a small dynamic friction coefficient contributes to improvement in fatigue characteristics and impact resistance. It can be concluded that smaller surface roughness is effective for lowering a dynamic friction coefficient.
The Al alloy wire in the aged sample group can he concluded to have a smaller dynamic friction coefficient as shown in Tables 17 to 19 when a lubricant is adhered to the surface thereof and in particular when the amount of adhesion of C is not lower than 1 mass % (see comparison between sample No. 41 (Tables 14 and 18) and sample No. 114 (Tables 16 and 20)) as shown in Tables 13 to 15. It can be concluded that the dynamic friction coefficient tends to be smaller with a more amount of adhesion of C even though surface roughness is relatively large (see, for example, sample No. 22 (Tables 14 and 18)). As shown in Table 21, it can be seen that corrosion resistance is excellent owing to adhesion of a lubricant to the surface of the Al alloy wire. It is considered that an amount of adhesion of the lubricant (an amount of adhesion of C) is preferably small to some extent, in particular, not higher than 30 mass %, because too large an amount of adhesion of lubricant (amount of adhesion of C) leads to increase in resistance of connection to the terminal portion.
(4) As shown in Tables 13 to 15, the Al alloy wire in the aged sample group was small in crystal grain size. Quantitatively, the average crystal grain size was not greater than 50 μm, and many samples had an average crystal grain size not greater than 35 μm and further not greater than 30 μm, and some samples also had an average crystal grain size not greater than 20 μm, which were smaller than that of sample No. 113 (Table 16). Based on comparison between sample No. 20 (Table 10) and sample No. 113 (Table 12) identical in composition, sample No. 20 was approximately two times larger in number of tunes of bending. Therefore, it is considered that a small crystal grain size contributes in particular to improvement in fatigue characteristics. In addition, it can be concluded from this test, that a crystal grain size is readily made smaller, for example, by setting a relatively low temperature for aging or setting a relatively short retention time.
(5) As shown in Tables 17 to 19, the Al alloy wire in the aged sample group had a surface oxide film, however, a thickness thereof was as small as 120 nm or less (see comparison with sample No. 116 in Table 20). Therefore, it is considered that the Al alloy wire can achieve suppressed increase in resistance of connection to the terminal portion and can construct a low-resistance connection structure. It can be considered that formation of a surface oxide film of an appropriate thickness (not smaller than 1 nm) contributes to improvement in corrosion resistance described above. In addition, it can be concluded from this test that the surface oxide film tends to be large in thickness when heat treatment such as aging treatment is performed in the air atmosphere or under a condition to allow formation of a boehmite layer and that the surface oxide film tends to be small in thickness in a low-oxygen atmosphere.
(6) As shown in Tables 11, 15, and 19, even though change to manufacturing methods A, B, and D to G is made (samples Nos. 72 to 77), it can be concluded that an Al alloy wire which contains a certain amount of fine crystallized materials and is excellent in impact resistance and fatigue characteristics is obtained. In particular, by appropriately setting a cooling rate in a specific temperature region in the casting process, an Al alloy wire containing a certain amount of fine crystallized materials in the surface layer and excellent in impact resistance and fatigue characteristics in spite of various changes in subsequent steps can be manufactured, and a degree of freedom in manufacturing condition is high.
An Al alloy wire composed of a specifically composed Al—Mg—Si based alloy, subjected to aging treatment, and including a certain amount of fine crystallized materials in the surface layer as described above achieved high strength, high toughness, and high electrical conductivity, also excellent strength of connection to the terminal portion, and also excellent impact resistance and fatigue characteristics. Such an Al alloy wire is expected to suitably be used for a conductor of a covered electrical wire, in particular, a conductor of a terminal-equipped electrical wire to which a terminal portion is attached.
The present invention is not limited to these exemplifications but is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
For example, a composition of an alloy in Test Example 1, a cross-sectional area of a wire member, the number of strands in a strand wire, and a manufacturing condition (a temperature of a melt, a cooling rate in casting, timing of heat treatment, and a condition for heat treatment) can be modified as appropriate.
[Additional Aspect]
An aluminum alloy wire excellent in impact resistance and fatigue characteristics can be configured as below. Examples of a method of manufacturing an aluminum alloy wire excellent in impact resistance and fatigue characteristics include the following.
[Additional Aspect 1]
An aluminum alloy wire composed of an aluminum alloy,
the aluminum alloy containing at least 0.03 mass % and at most 1.5 mass % of Mg, at least 0.02 mass % and at most 2.0 mass % of Si, and a remainder composed of Al and an inevitable impurity, a mass ratio Mg/Si being not lower than 0.5 and not higher than 3.5,
in a transverse section of the aluminum alloy wire, a crystallization measurement region in a shape of a sector having an area of 3750 μm2 being taken from an annular surface-layer region extending by up to 50 μm in a direction of depth from a surface of the aluminum alloy wire, and an average area of crystallized materials present in the crystallization measurement region in the shape of the sector being not smaller than 0.05 μm2 and not greater than 3 μm2.
[Additional Aspect 2]
The aluminum alloy wire described in [Additional Aspect 1], in which the number of crystallized materials present in the crystallization measurement region in the shape of the sector is greater than 10 and not greater than 400.
[Additional Aspect 3]
The aluminum alloy wire described in [Additional Aspect 1] or [Additional Aspect 2], in which, in the transverse section of the aluminum alloy wire, a rectangular inside crystallization measurement region having a short side of 50 μm long and a long side of 75 μm long is taken such that a center of this rectangle is superimposed on a center of the aluminum alloy wire and an average area of the crystallized materials present in the inside crystallization measurement region is not smaller than 0.05 μm2 and not greater than 40 μm2.
[Additional Aspect 4]
The aluminum alloy wire described in any one of [Additional Aspect 1] to [Additional Aspect 3], in which the aluminum alloy has an average crystal grain size not greater than 50 μm.
[Additional Aspect 5]
The aluminum alloy wire described in any one of [Additional Aspect 1] to [Additional Aspect 4], in which, in the transverse section of the aluminum alloy wire, a void measurement region in a shape of a sector of 1500 μm2 is taken from an annular surface-layer region extending by up to 30 μm in the direction of depth from the surface of the aluminum alloy wire, and a total cross-sectional area of voids present in the void measurement region in the shape of the sector is not greater than 2 μm2.
[Additional Aspect 6]
The aluminum alloy wire described in [Additional Aspect 5], in which, in the transverse section of the aluminum alloy wire, a rectangular inside void measurement region having a short side of 30 μm long and a long side of 50 μm long is taken such that a center of this rectangle is superimposed on a center of the aluminum alloy wire, and a ratio of a total cross-sectional area of voids present in the inside void measurement region to the total cross-sectional area of the voids present in the void measurement region in the shape of the sector is not lower than 1.1 and not higher than 44.
[Additional Aspect 7]
The aluminum alloy wire described in [Additional Aspect 5] or [Additional Aspect 6], in which a content of hydrogen is not more than 8.0 ml/100 g.
[Additional Aspect 8]
The aluminum alloy wire described in any one of [Additional Aspect 1] to [Additional Aspect 7], in which a work hardening exponent is not smaller than 0.05.
[Additional Aspect 9]
The aluminum alloy wire described in any one of [Additional Aspect 1] to [Additional Aspect 8], in which a dynamic friction coefficient is not greater than 0.8.
[Additional Aspect 10]
The aluminum alloy wire described in any one of [Additional Aspect 1] to [Additional Aspect 9], in which surface roughness is not greater than 3 μm.
[Additional Aspect 11]
The aluminum alloy wire described in any one of [Additional Aspect 1] to [Additional Aspect 10], in which a lubricant is adhered to a surface of the aluminum alloy wire and an amount of adhesion of C derived from the lubricant is more than 0 and not more than 30 mass %.
[Additional Aspect 12]
The aluminum alloy wire described in any one of [Additional Aspect 1] to [Additional Aspect 11], the aluminum alloy wire including a surface oxide film having a thickness not smaller than 1 nm and not greater than 120 nm.
[Additional Aspect 13]
The aluminum alloy wire described in any one of [Additional Aspect 1] to [Additional Aspect 12], in which the aluminum alloy further contains at least 0 mass % and at most 0.5 mass % of each of at least one element selected from among Fe, Cu, Mn, Ni, Zr, Cr, Zn, and Ga and contains at least 0 mass % and at most 1.0 mass % in total of the at least one element.
[Additional Aspect 14]
The aluminum alloy wire described in any one of [Additional Aspect 1] to [Additional Aspect 13], in which the aluminum alloy further contains at least one of at least 0 mass % and at most 0.05 mass % of Ti and at least 0 mass % and at most 0.005 mass % of B.
[Additional Aspect 15]
The aluminum alloy wire described in any one of [Additional Aspect 1] to [Additional Aspect 14], the aluminum alloy wire satisfying at least one selected from tensile strength not lower than 150 MPa, 0.2% proof stress not lower than 90 MPa, breaking elongation not lower than 5%, and electrical conductivity not lower than 40% IACS.
[Additional Aspect 16]
An aluminum alloy strand wire made by stranding together a plurality of the aluminum alloy wires described in any one of [Additional Aspect 1] to [Additional Aspect 15].
[Additional Aspect 17]
The aluminum alloy strand wire described in [Additional Aspect 16], in which a strand pitch is at least 10 times and at most 40 times as large as a pitch diameter of the aluminum alloy strand wire.
[Additional Aspect 18]
A covered electrical wire including a conductor and an insulation cover which covers an outer circumference of the conductor, the conductor including the aluminum alloy strand wire described in [Additional Aspect 16] or [Additional Aspect 17].
[Additional Aspect 19]
A terminal-equipped electrical wire including the covered electrical wire described in [Additional Aspect 18] and a terminal portion attached to an end portion of the covered electrical wire.
[Additional Aspect 20]
A method of manufacturing an aluminum alloy wire including:
a casting step of forming a cast material by casting a melt of an aluminum alloy composed of at least 0.03 mass % and at most 1.5 mass % of Mg, at least 0.02 mass % and at most 2.0 mass % of Si, and a remainder composed of Al and an inevitable impurity, a mass ratio Mg/Si being not lower than 0.5 and not higher than 3.5;
an intermediate working step of forming an intermediate work material by subjecting the cast material to plastic working;
a wire drawing step of forming a wire-drawn member by wire drawing the intermediate work material; and
a heat treatment step of performing heat treatment during wire drawing or after the wire drawing step,
in the casting step, a temperature of the melt being not lower than a liquidus temperature and lower than 750° C. and a cooling rate in a temperature region from the temperature of the melt to 650° C. being not lower than 1° C./second and lower than 25° C./second.
[Additional Aspect 21]
An aluminum alloy wire composed of an aluminum alloy,
the aluminum alloy containing at least 0.03 mass % and at most 1.5 mass % of Mg, at least 0.02 mass % and at most 2.0 mass % of Si, and a remainder composed of Al and an inevitable impurity, a mass ratio Mg/Si being not lower than 0.5 and not higher than 3.5,
in a transverse section of the aluminum alloy wire, a void measurement region in a shape of a sector of 1500 μm2 being taken from an annular surface-layer region extending by up to 30 μm in a direction of depth from a surface of the aluminum alloy wire, and a total cross-sectional area of voids present in the void measurement region in the shape of the sector being not greater than 2 μm2.
The aluminum alloy wire described in [Additional Aspect 21] is better in impact resistance and fatigue characteristics by further satisfying an item described in at least one of [Additional Aspect 1] to [Additional Aspect 15]. The aluminum alloy wire described in [Additional Aspect 21] can be used for the aluminum alloy strand wire, the covered electrical wire, or the terminal-equipped electrical wire described in any one of [Additional Aspect 16] to [Additional Aspect 19].
1 covered electrical wire
10 terminal-equipped electrical wire
2 conductor
20 aluminum alloy strand wire
22 aluminum alloy wire (elemental wire)
220 surface-layer region
222 surface-layer crystallization measurement region
224 crystallization measurement region
22S short side
22L long side
P contact
T tangential line
C straight line
g gap
3 insulation cover
4 terminal portion
40 wire barrel portion
42 fitting portion
44 insulation barrel portion
S sample
100 mount
110 weight
150 counterpart member
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-213154 | Oct 2016 | JP | national |
| 2017-074234 | Apr 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2017/030734 | 8/28/2017 | WO | 00 |
