Conductive wire, electric wire, and method for manufacturing conductive wire

Abstract

A conductive wire is made of a metal material and has a rectangular cross-section having a width and a thickness. The corner portion of the rectangular cross-section is a curve, and the ratio S / SV of the area SV of an imaginary rectangle circumscribed with the rectangular cross-section to the area S of the rectangular cross-section is 0.975 or more. A first rate of change based on a width W1 of a first cross-section and a width W2 of a second cross-section separated by a predetermined length along a longitudinal axis of the conductive wire, and a second rate of change based on a thickness T1 of the first cross-section and a thickness T2 of the second cross-section are both 0.5% or less. The first change rate is (W1-W2) / W1 * 100, and the second change rate is (T1-T2) / T1 * 100. The arithmetic average roughness Ra of the surface of the corner portion is 0.2 [mu] m or less.

Description

Technical Field

[0001] The present disclosure relates to a wire, an electric wire, and a method for manufacturing the wire. This application claims priority based on Japanese application No. 2022-158710 filed on September 30, 2022, and all the contents described in the Japanese application are cited. Background Art

[0002] In Patent Document 1, a wire having a rectangular cross section is produced by wire drawing using a plurality of dies. The metal wire as the raw material of the wire has a circular cross section. The metal wire is gradually processed into a wire material having an elliptical cross section, and then passes through a finishing die to become a wire having a rectangular cross section.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-4399 Summary of the invention

[0006] The wire disclosed herein is a wire made of a metal material, having a rectangular cross-section having a width and a thickness, wherein the corner of the rectangular cross-section is a curve, and the ratio S / SV of the area SV of an imaginary rectangle circumscribed with the rectangular cross-section to the area S of the rectangular cross-section is greater than or equal to 0.975, wherein a first cross-section of the wire is separated from a second cross-section of the wire along a longitudinal axis of the wire, a first change rate based on a width W1 of the first cross-section and a width W2 of the second cross-section is less than or equal to 0.5%, a second change rate based on a thickness T1 of the first cross-section and a thickness T2 of the second cross-section is less than or equal to 0.5%, and the first change rate is

[0007] |(W1-W2) / W1|×100, the second rate of change is |(T1-T2) / T1|×100, and the arithmetic mean roughness Ra of the surface of the corner portion is 0.2 μm or less. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] [ Figure 1 ] Figure 1 This is a schematic diagram of an electric wire according to an embodiment of the present invention.

[0009] [ Figure 2 ] Figure 2 for Figure 1 A cross-sectional view of a conductor included in the electric wire shown.

[0010] [ Figure 3 ] Figure 3 This is a first explanatory diagram of the method for producing a conductive wire according to the embodiment.

[0011] [ Figure 4 ] Figure 4 This is a second explanatory diagram of the method for producing a conductive wire according to the embodiment.

[0012] [ Figure 5 ] Figure 5 It is a third explanatory diagram of the method for producing a conductive wire according to the embodiment.

[0013] [ Figure 6 ] Figure 6 Graph showing the relationship between the processing ratio P of the corner portion and the cross-sectional area reduction rate of each sample of the test example.

[0014] [ Figure 7 ] Figure 7 This is a graph showing the relationship between the ratio S / SV and the arithmetic mean roughness Ra of the corner portion of each sample of the test example. DETAILED DESCRIPTION

[0015] [Problems to be Solved by the Present Disclosure]

[0016] The surface of the corners of the wire obtained by wire drawing tends to become rough, and sometimes defective parts where the insulating layer is not formed sufficiently are generated at the roughened corners. For example, in order to improve the space factor of the coil, a wire with a small radius of curvature at the corners is required, but the smaller the radius of curvature at the corners, the easier it is for the surface of the corners to become rough, and the more defective parts tend to increase. An insulating layer with many defective parts may not be able to fully insulate the wire.

[0017] One of the objects of the present disclosure is to provide a wire in which poor formation of an insulating layer is less likely to occur at the corners of the rectangular cross section of the wire. One of the objects of the present disclosure is to provide an electric wire with fewer poor locations in the insulating layer covering the corners of the rectangular cross section of the wire. One of the objects of the present disclosure is to provide a wire manufacturing method capable of manufacturing the wire of the present disclosure.

[0018] [Effects of the present disclosure]

[0019] When the insulating layer is formed on the outer periphery of the conductive wire of the present disclosure, the occurrence of defective portions in the insulating layer covering the corners is suppressed.

[0020] [Description of Embodiments of the Present Disclosure]

[0021] Hereinafter, embodiments of the present disclosure will be listed and described.

[0022] <1> The wire involved in the embodiment is a wire made of a metal material, having a rectangular cross-section with a width and a thickness, the corner of the rectangular cross-section is a curve, and the ratio S / SV of the area SV of an imaginary rectangle circumscribed with the rectangular cross-section to the area S of the rectangular cross-section is greater than 0.975, the first cross-section of the wire is separated from the second cross-section of the wire along the longitudinal axis of the wire, the first change rate based on the width W1 of the first cross-section and the width W2 of the second cross-section is less than 0.5%, the second change rate based on the thickness T1 of the first cross-section and the thickness T2 of the second cross-section is less than 0.5%, the first change rate is |(W1-W2) / W1|×100, the second change rate is |(T1-T2) / T1|×100, and the arithmetic mean roughness Ra of the surface of the corner is less than 0.2μm.

[0023] The conductor having a ratio S / SV of 0.975 or more contributes to an increase in the space factor in the coil. The space factor is the ratio of the cross-sectional area of ​​the conductor to the cross-sectional area of ​​the space occupied by the coil formed by winding the conductor.

[0024] The wire having the first rate of change and the second rate of change both being less than 0.5% has a uniform rectangular cross section along the longitudinal axis of the wire. The longitudinal axis of the wire is an axis along which the first end and the second end of the wire are connected. That is, the wire of the present disclosure is a wire having a small dimensional fluctuation in the direction along the longitudinal axis of the wire. The product made using the wire suppresses fluctuations in electrical or magnetic properties. Such a wire is obtained by wire drawing using a die.

[0025] When the arithmetic mean roughness Ra of the surface of the corner is 0.2 μm or less, the arithmetic mean roughness Ra of the surface of the portion other than the corner is generally about 0.02 μm to 0.1 μm, so the difference in arithmetic mean roughness between the corner and the portion other than the corner can be reduced. Therefore, when the insulating layer is formed on the periphery of the conductive wire, it is difficult to produce defective parts in the insulating layer covering the corner.

[0026] <2> In the above <1> In the conductive wire, the metal material may be oxygen-free copper.

[0027] Wires made of oxygen-free copper have excellent electrical conductivity. Oxygen-free copper is easy to process. Wires made of oxygen-free copper have excellent weldability.

[0028] <3> In the above <1> or <2> In the wire, the area S can be 2mm 2 Above 12mm 2 the following.

[0029] With 2mm 2 Above 12mm 2The following conductive wires with an area S are suitable as the constituent material of the coil. The larger the area S is, the larger the allowable current of the conductive wire is.

[0030] <4> In the above <1> to <3> In any one of the conductive wires, the aspect ratio of the rectangular cross section may be 1 to 10.

[0031] The aspect ratio is the value obtained by dividing the width of the rectangular cross section by the thickness of the rectangular cross section. A rectangular cross section with an aspect ratio of 1 is roughly square. A wire with an aspect ratio of a rectangular cross section exceeding 1 is a so-called flat wire. By edgewise bending the flat wire, the number of turns of the coil can be increased without extending the length of the coil along the axis of the coil. Flat wires are easy to be flatwise bent. Therefore, a coil obtained by flat bending the flat wire is easy to produce.

[0032] <5> In the above <1> to <4> In any one of the conductive wires, a difference between the width W1 and the width W2 and a difference between the thickness T1 and the thickness T2 may both be 16 μm or less.

[0033] Above <5> The conductor is a conductor having a uniform rectangular cross section along the longitudinal axis of the conductor. <5> The wire suppresses performance fluctuations of each turn of the coil made of the wire. According to the wire, coils that exhibit stable performance can be mass-produced.

[0034] <6> The electric wire according to the embodiment comprises: <1> to <5> The conductive wire described in any one of the preceding claims; and an insulating layer covering a surface of the conductive wire.

[0035] The wire having the conductive wire and the insulating layer can be used as the material of the coil, for example. Since the corners of the conductive wire are smooth, it is difficult to form defective parts in the insulating layer covering the corners. With such a conductive wire, a coil with stable performance can be made.

[0036] <7> The manufacturing method of the wire involved in the embodiment includes a step of performing a final wire drawing process on a raw material wire, the raw material wire is a metal wire immediately before the final wire drawing process, the cross section of the raw material wire has four corners, the cross section has a width W0, a thickness T0, and a diagonal length L0, the rectangular cross section has a width W, a thickness T, and a diagonal length L, the processing ratio P of the corners in the final wire drawing process is 20% or more, the processing ratio P is {(L0-L) / X}×100, X is the larger value between W0-W and T0-T, and the cross-sectional area reduction rate of the final wire drawing process is 35% or less.

[0037] The final wire drawing process is the so-called fine wire drawing process. If the cross-sectional area reduction rate of the final wire drawing process is 35% or less, the wire is unlikely to break. When the cross-sectional area reduction rate becomes smaller, the pulling force used to pull the raw wire from the die becomes smaller, and the stress acting on the raw wire becomes smaller. However, for wire drawing with a small cross-sectional area reduction rate, the contact area between the die and the raw wire becomes smaller, and the stress per unit area acting on the surface of the raw wire, that is, the surface pressure, becomes larger. When the surface pressure acting on the raw wire becomes high during wire drawing, the surface of the wire including the corners tends to become smooth. In addition, if the processing ratio P in the final wire drawing process is 20% or more, sufficient processing is applied to the corners of the raw wire, so the surface of the corners of the wire becomes smooth. As a result, a wire having a corner with an arithmetic mean roughness Ra of less than 0.2μm is obtained.

[0038] [Details of the embodiments of the present disclosure]

[0039] Hereinafter, a specific example of a conductor, a method for manufacturing the conductor, and an electric wire including the conductor according to an embodiment of the present disclosure will be described based on the accompanying drawings. The same symbols in the figures represent the same or equivalent parts. The sizes of the components shown in the drawings are presented for the purpose of clarifying the description and do not necessarily represent the actual sizes. It should be noted that the present invention is not limited to these examples, but is represented by the claims, and is intended to include all changes within the meaning and scope equivalent to the claims.

[0040] <Implementation Method 1>

[0041] "electric wire"

[0042] Figure 1 The electric wire 1 shown in the figure comprises: a conductor 2 made of a metal material, and an insulating layer 3 covering the surface of the conductor 2. Figure 2 As shown, the conductor 2 has a rectangular cross section 20. The rectangular cross section 20 is a cross section of the conductor 2 obtained by cutting the conductor 2 along a plane perpendicular to the longitudinal axis of the conductor 2. The conductor 2 has a substantially uniform rectangular cross section 20 along the longitudinal axis of the conductor 2.

[0043] [wire]

[0044] The metal material constituting the conductor 2 is, for example, copper, copper alloy, aluminum, or aluminum alloy. These metal materials are relatively cheap and have excellent electrical conductivity. In particular, the conductor 2 composed of oxygen-free copper has excellent electrical conductivity. Oxygen-free copper is pure copper containing more than 99.95% by mass of copper, with the remainder being inevitable impurities. The total content of inevitable impurities in oxygen-free copper is, for example, 0.03% by mass or less. The oxygen content of oxygen-free copper is, for example, 0.005% by mass (50 ppm by mass) or less, further 0.002% by mass (20 ppm by mass) or less, and further 0.001% by mass (10 ppm by mass) or less. The lower the oxygen content of oxygen-free copper, the higher the electrical conductivity of oxygen-free copper.

[0045] The corner 29 of the rectangular cross section 20 is a curve. The ratio S / SV of the area SV of the imaginary rectangle 25 circumscribing the rectangular cross section 20 to the area S of the rectangular cross section 20 is 0.975 or more. The area S and the area SV are obtained from a microscope photograph of the rectangular cross section 20. Specifically, the image analysis of the microscope photograph of the rectangular cross section 20 is performed to determine the outer contour of the rectangular cross section 20. The area of ​​the portion surrounded by the outer contour is the area S. Figure 2 The imaginary rectangle 25 shown by the double-dashed line is the smallest rectangle that circumscribes the outer contour of the rectangular cross section 20 in the microscope photograph of the rectangular cross section 20. The inner area of ​​the imaginary rectangle 25 in the microscope photograph is the area SV. A conductor having a ratio S / SV of 0.975 or more helps to increase the space factor in the coil. The space factor is the ratio of the cross-sectional area of ​​the conductor 2 to the cross-sectional area of ​​the space occupied by the coil formed by winding the conductor 2. The higher the ratio S / SV, the higher the space factor. In order to increase the space factor, the ratio S / SV may be, for example, 0.990 or more, and further may be 0.995 or more.

[0046] The area S of the rectangular cross section 20 is, for example, 2 mm 2 Above 12mm 2 Below. With 2mm 2 Above 12mm 2 The following area S of the wire 2 can be used as the constituent material of the coil. The larger the area S is, the larger the allowable current of the wire 2 is. The area S can be, for example, 3 mm 2 Above 10mm 2 Below, 5mm is also possible 2 Above 10mm 2 the following.

[0047] The corner 29 is an arc. The radius of curvature of the arc-shaped corner 29 is, for example, not less than 0.07 mm and not more than 0.50 mm. The corner 29 having a radius of curvature of not less than 0.07 mm is not too sharp and is therefore difficult to damage. In addition, the insulating layer 3 formed on the periphery of the not too sharp corner 29 is also difficult to damage. If the radius of curvature of the corner 29 is not more than 0.50 mm, the area SV of the rectangular cross section 20 will not become too small. The radius of curvature can be, for example, not less than 0.09 mm and not more than 0.40 mm, or not less than 0.10 mm and not more than 0.25 mm, or not less than 0.10 mm and not more than 0.15 mm.

[0048] The rectangular cross section 20 has a width W and a thickness T. The width W of the rectangular cross section 20 is equal to the length of the first side 251 of the imaginary rectangle 25. The thickness of the rectangular cross section 20 is equal to the length of the second side 252 of the imaginary rectangle 25 that is orthogonal to the first side 251. The width W and the thickness T may be the same or different. In this example, the width W is longer than the thickness T. The wire 2 having different widths W and thicknesses T is a so-called flat wire.

[0049] For the conductor 2, the first cross section 21 and the second cross section 22 separated along the longitudinal axis of the conductor 2 have almost the same shape and size. The first cross section 21 is Figure 1 The second cross section 22 is a rectangular cross section 20 at the position of arrow A. Figure 1 The rectangular cross section 20 at the position of the arrow B. For ease of explanation, Figure 1 The distance between the arrow A and the arrow B is shorter. The distance between the first section 21 and the second section 22 is, for example, 100 m.

[0050] The first change rate based on the width W1 of the first cross section 21 and the width W2 of the second cross section 22 is 0.5% (percent) or less, and the second change rate based on the thickness T1 of the first cross section 21 and the thickness T2 of the second cross section 22 is 0.5% or less.

[0051] First rate of change |(W1-W2) / W1|×100

[0052] Second rate of change |(T1-T2) / T1|×100

[0053] The wire 2 having the first change rate and the second change rate of 0.5% or less has a substantially uniform rectangular cross section 20 along the longitudinal axis of the wire 2. The wire drawing process using a die can produce a wire 2 having a small dimensional fluctuation along the longitudinal axis of the wire 2. Therefore, it can be considered that the wire 2 having the first change rate and the second change rate of 0.5% or less is obtained by the wire drawing process using a die. The first change rate and the second change rate may be 0.4% or less, or 0.2% or less, respectively.

[0054] The conductive wire 2 having the uniform rectangular cross section 20 along the longitudinal axis of the conductive wire 2 suppresses performance fluctuations in each turn of a coil made of the conductive wire 2. The conductive wire 2 enables mass production of coils that exhibit stable performance.

[0055] The dimensional fluctuation along the longitudinal axis of the wire 2 can be evaluated using an absolute value. For example, the difference W1-W2 between the width W1 of the first section 21 and the width W2 of the second section 22 can be 16 μm or less, and the difference T1-T2 between the thickness T1 of the first section 21 and the thickness T2 of the second section 22 can be 16 μm or less. The smaller the difference W1-W2 and the difference T1-T2 are, the more the performance fluctuation of each turn of the coil made of the wire 2 can be suppressed. The difference W1-W2 and the difference T1-T2 can be, for example, 12 μm or less, or 8 μm or less.

[0056] The surface of the corner 29 of the conductor 2 is very smooth. Specifically, the arithmetic mean roughness Ra of the surface of the corner 29 is less than 0.2 μm. The arithmetic mean roughness Ra of this example is the average of the measurement results obtained by measuring three locations at each of the four corners 29. That is, the arithmetic mean roughness Ra is the average of the measurement results of 12 locations. The arithmetic mean roughness Ra of this example is based on JIS B 0601:2013. The arithmetic mean roughness Ra is obtained, for example, by a commercially available non-contact roughness measuring device, specifically, LEXT OLS4100 manufactured by Olympus Corporation.

[0057] The surface of the corner 29 having the arithmetic mean roughness Ra is as smooth as the surface of the portion other than the corner 29. Therefore, when the insulating layer 3 is formed on the periphery of the conductive wire 2, it is difficult for a defective portion to be generated in the insulating layer 3 covering the corner 29. The arithmetic mean roughness Ra may be, for example, 0.15 μm or less, 0.1 μm or less, or 0.08 μm or less.

[0058] [Insulation layer]

[0059] The insulating layer 3 ensures insulation of the wire 2. The insulating layer 3 is, for example, enamel obtained by curing insulating varnish. In addition, the insulating layer 3 may be, for example, a resin with high electrical insulation properties such as polyimide resin, fluororesin, polyethersulfone, or polyetheretherketone.

[0060] The thickness of the insulating layer 3 can be, for example, 1 μm to 100 μm, or 10 μm to 50 μm. Here, the corner 29 of the wire 2 in this example is very smooth, and the insulating layer 3 formed on the periphery of the smooth corner 29 is unlikely to have defective parts. Therefore, even if the thickness of the insulating layer 3 is within the above range, it is unlikely to have defective parts in the insulating layer 3. The insulating layer 3 covers a part or all of the surface of the wire 2.

[0061] 《How to manufacture electric wires》

[0062] The method for producing the electric wire 1 includes: a step of obtaining the conductive wire 2 by drawing a metal wire; a step of heat-treating the conductive wire 2; and a step of forming the insulating layer 3 on the outer periphery of the conductive wire 2 after the heat treatment.

[0063] [Process of Obtaining Wire]

[0064] The wire 2 is obtained, for example, by the wire manufacturing method disclosed in the present invention. Figure 3 The wire drawing device 6 shown is implemented. The wire drawing device 6 includes, for example, a plurality of dies 61, 62, 63, 64. By passing the metal wire 9 through the dies 61, 62, 63, 64, the metal wire 9 can be gradually approached to a desired shape and wire diameter. At least the die 64 is a wire drawing die. The dies 61, 62, 63 can be roller dies.

[0065] One of the characteristics of the method for manufacturing the wire 2 is that a process under predetermined conditions is performed in the final drawing of the wire drawing device 6. Figure 4 The characteristic features of the method for producing the conductor wire 2 will be described. In the description, the metal wire 9 supplied to the final die 64 is referred to as a raw wire material 4.

[0066] Figure 4 The solid line in FIG. 4 represents the cross section of the raw material wire 4. The double-dotted line represents the cross section of the wire 2 obtained by drawing the raw material wire 4. Figure 4 Shadows are omitted.

[0067] The raw material wire 4 has a cross section 40 having four corners 49. The cross section 40 is a cross section of the raw material wire 4 obtained by cutting it with a plane orthogonal to the longitudinal axis of the raw material wire 4. The cross section 40 of this example has a shape that is symmetrical in both vertical and horizontal directions. The corner 49 may be a pointed shape formed by connecting two straight lines, or may be a curved line. The corner 49 of this example is a curved line. The contour line connecting two adjacent corners 49 along the periphery of the cross section may be a straight line, or may be a curved line that is convex in a direction away from the center of the cross section. The contour line of this example is a straight line. The cross section 40 has a width W0 and a thickness T0. The width W0 and the thickness T0 are respectively the same as the length of the first side and the length of the second side of the imaginary rectangle that circumscribes the cross section 40. The first side and the second side are two sides orthogonal to each other. The width W0 and the thickness T0 may be the same or different. In this example, the width W0 is longer than the thickness T0. The corner 49 is, for example, a portion that is 10% of the length of the entire length of the first side from each end of the first side. The corner portion 49 is, for example, a portion having a length corresponding to 10% of the entire length of the second side from each of the two end portions of the second side.

[0068] The method for manufacturing the wire 2 includes a step of obtaining the wire 2 having a rectangular cross section 20 by drawing the raw wire 4. As already described, the rectangular cross section 20 has a width W and a thickness T. It can be considered that Figure 4 The profile of the rectangular cross section 20 and the mold 64 ( Figure 3 The contours of the portion with the smallest inner diameter of the die hole of the die 64, that is, the sizing area (bearing) of the die 64, are substantially consistent. The rectangular cross section 20 has a shape that is symmetrical in both the top and bottom and in the left and right directions.

[0069] The cross-sectional area reduction rate of the final wire drawing process is 35% or less. The cross-sectional area reduction rate is more preferably 15% to 35%. The cross-sectional area reduction rate is an indicator of how much the area S of the rectangular cross section 20 becomes smaller relative to the area S0 of the cross section 40. Specifically, the cross-sectional area reduction rate is calculated by {(S0-S) / S0}×100. If the cross-sectional area reduction rate of the final wire drawing process is 35% or less, the surface of the corner 29 becomes smooth. The die 64 can be an angle type die, a circle type die, or a mixed die. Figure 5 As shown, an angled die is a die in which the shape of the approach area 641 of the die 64 in the longitudinal section of the die 64 is a straight line. An arc-shaped die is a die in which the shape of the approach area is a curve. A mixed die is a die in which the shape of the approach area is a combination of a straight line and a curve. The approach area angle θ of the die 64 can be constant or different at different positions in the approach area. In order to improve the degree of processing of the surface of the raw wire 4, it is preferred that the approach area angle θ is high. Figure 5As shown, the approach zone 641 is a tapered portion disposed at the entrance side of the sizing zone 642, which has the function of reducing the outer diameter of the raw wire 4. The sizing zone 642 is a hole on the inner side of the die that determines the size of the wire 2. The approach zone angle θ is an angle formed by the tapered approach zone 641 in the longitudinal section of the die 64, and is an angle obtained by adding the angle formed at the upper portion and the angle formed at the lower portion relative to the horizontal direction.

[0070] The processing ratio P of the corner 49 during the wire drawing process is 20% or more. The processing ratio P of the corner 49 is an index indicating whether the corner 49 is greatly deformed during the wire drawing process of the raw wire 4. Specifically, the processing ratio P is obtained by {(L0-L) / X}×100.

[0071] L0...diagonal length of the cross section 40 of the raw material wire 4

[0072] L···diagonal length of the rectangular cross section 20 of the conductor 2

[0073] X···Maximum deformation of the portion other than the corner 49

[0074] The diagonal length L is the length of the diagonal of the rectangular cross section 20, that is, the distance between the first corner 29 and the second corner 29 at the diagonal position in the rectangular cross section 20. As shown in this example, when the corner 29 is in the shape of an arc, the straight line connecting the midpoint of the first arc and the midpoint of the second arc is the diagonal of the rectangular cross section 20. On the other hand, the diagonal length L0 is the length of the diagonal of the cross section 40. In this example, the straight line connecting the first intersection point and the second intersection point of the cross section 40 is the diagonal of the cross section 40. The first intersection point and the second intersection point are the intersection points of the extension line of the diagonal of the rectangular cross section 20 and the contour line of the cross section 40, respectively. The value obtained by subtracting the diagonal length L from the diagonal length L0 can be regarded as the deformation amount of the corner 49 caused by the final wire drawing process.

[0075] The maximum deformation amount X is the larger value between W0-W and T0-T. The width W and the thickness T are substantially the same as the size of the portion having the smallest inner diameter of the die hole of the die 64. In the conventional final wire drawing process, the corner 49 is hardly deformed, and the portions other than the corner 49 are greatly deformed. That is, in the conventional final wire drawing process, the maximum deformation amount X is much larger than the deformation amount L0-L of the corner 49.

[0076] The processing ratio P in this example is 20% or more. According to the final wire drawing process with such a processing ratio P, the corner 49 is fully processed in the same manner as the parts other than the corner 49, and the surface of the corner 29 becomes smooth in the same manner as the parts other than the corner 29. As a result, the wire 2 having the corner 29 with the arithmetic mean roughness Ra of the surface being 0.2 μm or less is obtained. The larger the processing ratio P is, the higher the processing degree of the corner 49 is, and the smoother the surface of the corner 29 is. The processing ratio P may be, for example, 30% or more, 45% or more, or 60% or more.

[0077] [Process for heat treatment of wire]

[0078] The main purpose of the heat treatment after the final wire drawing is to remove the strain introduced into the wire 2 by the wire drawing process. By removing the strain, the conductivity and elongation of the wire 2 are improved. The atmosphere temperature of the heat treatment is, for example, about 100°C to 550°C, and the holding time is, for example, 0.2 seconds to 10 hours. The heat treatment can be carried out in an intermittent furnace or a continuous furnace. This heat treatment is not essential.

[0079] [Step of forming insulating layer]

[0080] The insulating layer 3 is formed, for example, by a known enamel wire coating device. In the coating device, a first step of coating the surface of the wire 2 with a resin constituting the insulating layer 3 and a second step of curing the resin coated on the wire 2 in a sintering furnace are performed. The first step and the second step are repeated until the insulating layer 3 reaches a desired thickness. The first step and the second step may be performed once each.

[0081] <Test example>

[0082] In the test example, a plurality of wires 2 having different cross-sectional area reduction ratios and processing ratios P ​​of the corners 49 in the final wire drawing process were produced. The die 64 used for the final wire drawing process of each wire 2 was an angle die or an arc die. Next, an insulating layer 3 was formed on the outer periphery of each wire 2, and defective portions of the insulating layer 3 were confirmed. The wire drawing conditions and the dimensions of the wire 2 are shown in Tables 1 and 2.

[0083] The "die hole size" in the table is the size of the portion of the die hole of the die 64 with the smallest inner diameter, that is, the size of the sizing zone of the die 64. The size of the sizing zone is approximately equal to the size of the rectangular cross section 20 of the wire 2. Therefore, the "thickness", "width", "radius of curvature of the corner", and "area" recorded in the "die hole size" column can be regarded as Figure 4 The “thickness T”, “width W”, “radius of curvature of the corner 29”, and “area S of the rectangular cross section 20” in “Aspect ratio” is “width / thickness”.

[0084] The "pre-processing degree" in the column of "final wire drawing conditions" in the table represents the processing amount applied to the metal wire 9 from the last heat treatment to the final wire drawing process in percentage. Specifically, the "pre-processing degree" is {(S9-S0) / S9}×100. S9 is the cross-sectional area of ​​the metal wire 9 just before it is supplied to the wire drawing device 6, that is, the cross-sectional area of ​​the metal wire 9 just before it approaches the die 61. S0 is the cross-sectional area of ​​the cross section 40 of the raw wire 4, that is, the cross-sectional area of ​​the metal wire 9 just before it approaches the die 64. "T0-T", "W0-W", "L0-L", and "processing ratio P of the corner portion" are as described in the above-mentioned item "manufacturing method of the wire".

[0085] The "Ratio S / SV" in the "Conductor" column in the table is as described in the above-mentioned item [Conductor]. The area S and the area SV are obtained by image analysis of the cross-sectional image of the conductor 2, which is taken by VHX-7000 manufactured by KEYENCE Corporation. The "Ratio S / SV" in the table is expressed as a percentage. The "uniformity of size" is the result of evaluating whether the conductor 2 has the same rectangular cross-section 20 along the longitudinal axis. The evaluation "A" means that the "first change rate" and the "second change rate" described in the item [Conductor] are both less than 0.5%. The distance between the first section 21 and the second section 22 used to measure the "first change rate" and the "second change rate" is 100m.

[0086] "Corner Ra" in the table is the arithmetic mean roughness Ra of the surface of the corner 29 of the conductor 2. The unit of the arithmetic mean roughness is micrometer. The arithmetic mean roughness Ra is measured by LEXT OLS4100 manufactured by Olympus Corporation. Specifically, the arithmetic mean roughness Ra is measured at three locations at each of the four corners 29, and the arithmetic mean roughness Ra is calculated by averaging the 12 measurement results. The three measurement locations of each corner 29 are locations separated from each other along the arc of the corner 29. In this example, each measurement location is measured at a length of 258 μm along the longitudinal axis of the conductor 2.

[0087] The "incidence rate of defective parts" in the table is the number of defective parts of the insulation layer 3 of 100 kg of the conductor 2. The defective parts of the insulation layer 3 of this example are measured by a commercially available flaw detector. When the surface of the conductor 2 is rough, defective parts such as air accumulation are generated between the rough part and the insulation layer 3. In this example, a commercially available flaw detector is attached to the coating equipment of the insulation layer 3, and the number of defective parts occurring is continuously counted during the formation of the insulation layer 3. The weight of the conductor 2 is calculated based on the specific gravity of the material of the conductor 2, the area S of the rectangular cross-section 20, and the feed speed of the conductor 2 in the coating equipment. In this example, only the defective parts corresponding to the corner 29 are counted among the measured defective parts.

[0088] Samples No. 1 to No. 15 are mainly samples with different cross-sectional area reduction rates. Mold 64 is an angled mold with a 32° approach angle. Samples No. 21 to No. 24 are mainly samples with different curvature radii of the corners 29 of the conductor 2. Mold 64 is an angled mold with a 32° approach angle. Samples No. 31 to No. 33 are mainly samples with different aspect ratios. Mold 64 is an angled mold with a 32° approach angle. Samples No. 41 and No. 42 are mainly samples with different areas S of the rectangular cross section 20 of the conductor 2. Mold 64 is an angled mold with a 32° approach angle. Samples No. 51 to No. 56 are mainly samples with different thicknesses T and widths W of the rectangular cross section 20. Mold 64 is an angled mold with a 32° approach angle. Samples No. 61 to No. 64 are samples with different configurations of mold 64. Mold 64 of sample No. 61 is an angled mold having an approach angle of 24°. Mold 64 of sample No. 62 is an angled mold having an approach angle of 16°. Mold 64 of sample No. 63 is an arc-shaped mold having an approach area with an arc-shaped curvature radius of 6 mm. Mold 64 of sample No. 64 is an arc-shaped mold having an approach area with a curvature radius of 12 mm. Samples No. 101 to No. 104 are samples in which the processing ratio P of the corner 29 is less than 20% or the cross-sectional area reduction rate exceeds 35%. Mold 64 is an angled mold having an approach angle of 32°.

[0089]

[0090]

[0091] As shown in Tables 1 and 2, Samples No. 1 to 64 having a cross-sectional area reduction rate of 35% or less and a processing ratio P of the corner 49 of 20% or more had smooth corners 29 and a defective portion occurrence rate of 0.8 or less.

[0092] Samples No. 101 to No. 103, in which the processing ratio P of the corner 49 was less than 20%, had corners 29 with an arithmetic mean roughness Ra exceeding 0.2 μm, and the occurrence rate of defective parts exceeded 1.2. In addition, sample No. 104, in which the cross-sectional area reduction rate exceeded 35%, had corners 29 with an arithmetic mean roughness Ra exceeding 0.2 μm, and the occurrence rate of defective parts exceeded 1.0.

[0093] Figure 6: This is a graph showing the relationship between the processing ratio P of the corner 49 of each sample of the test example and the cross-sectional area reduction rate. The horizontal axis is the processing ratio P of the corner 49 of each sample. The vertical axis is the cross-sectional area reduction rate of each sample. As shown in Table 2, samples No. 101 to No. 104 are samples with a high incidence of defective parts. Samples in the range excluding samples No. 101 to No. 104 are samples with a low incidence of defective parts. Therefore, it is believed that the incidence of defective parts is low in the range of the processing ratio P of the corner 49 being 20% ​​to 140% and the cross-sectional area reduction rate being 7% to 35%. It is believed that the incidence of defective parts is lower in the range of the processing ratio P of the corner 49 being 20% ​​to 140% and the cross-sectional area reduction rate being 15% to 35%. It is believed that the incidence of defective parts is further lower in the range of the processing ratio P of the corner 49 being 40% to 140% and the cross-sectional area reduction rate being 15% to 35%.

[0094] Figure 7 This is a graph showing the relationship between the ratio S / SV of each sample of the test example and the arithmetic mean roughness Ra of the corner. The horizontal axis is the ratio S / SV of each sample. The vertical axis is the arithmetic mean roughness Ra of the corner 29. The closer the ratio S / SV is to 100%, the smaller the radius of curvature of the corner 29, that is, the more pointed the corner 29 becomes. The closer the ratio S / SV is to 100%, the more pointed the corner 29 becomes, and it is difficult to make the surface of the corner 29 smooth. However, if the ratio S / SV is satisfied, Figure 6 The arithmetic mean roughness Ra of the corners 29 of samples No. 1 to No. 64 with the cross-sectional area reduction ratio and processing ratio P shown is 0.2 μm or less. Therefore, it is considered that the method of manufacturing the wire 2 according to the embodiment is effective in forming the corners 29 with smooth surfaces.

[0095] Explanation of symbols

[0096] 1 Wire

[0097] 2 Wires

[0098] 20 rectangular section, 21 first section, 22 second section

[0099] 25 imaginary rectangle, 251 first side, 252 second side

[0100] 29 corner

[0101] 3 Insulation layer

[0102] 4 Raw material wire

[0103] 40 Section

[0104] 49 corner

[0105] 6 Wire drawing device

[0106] 61, 62, 63, 64 molds

[0107] 641 Approach Area

[0108] 642 Sizing Zone

[0109] 9 Metal Wire

[0110] θ Approach zone angle

[0111] T, T0, T1, T2 thickness

[0112] W, W0, W1, W2 width

Claims

1. A conductor, which is made of metal material, having a rectangular cross-section having a width and a thickness, The corners of the rectangular cross section are curved. The ratio S / SV of the area SV of the imaginary rectangle circumscribing the rectangular cross section to the area S of the rectangular cross section is greater than 0.975, The first cross section of the wire is spaced apart from the second cross section of the wire along the longitudinal axis of the wire, A first change rate based on the width W1 of the first cross section and the width W2 of the second cross section is 0.5% or less, A second change rate based on the thickness T1 of the first cross section and the thickness T2 of the second cross section is 0.5% or less, The first rate of change is |(W1-W2) / W1|×100, The second rate of change is |(T1-T2) / T1|×100, The arithmetic mean roughness Ra of the surface of the corner portion is 0.2 μm or less.

2. The wire according to claim 1, wherein The metal material is oxygen-free copper.

3. The guide wire according to claim 1 or claim 2, wherein: The area S is 2 mm 2 Above 12mm 2 the following.

4. The wire according to any one of claims 1 to 3, wherein: The aspect ratio of the rectangular cross section is greater than or equal to 1 and less than or equal to 10.

5. The wire according to any one of claims 1 to 4, wherein: The difference between the width W1 and the width W2 and the difference between the thickness T1 and the thickness T2 are both 16 μm or less.

6. An electric wire having: The wire according to any one of claims 1 to 5; and An insulating layer covering the surface of the wire.

7. A method for manufacturing a wire, which is a method for manufacturing a wire having a rectangular cross section, It has the process of final drawing of raw wire. The raw wire material is a metal wire just before the final wire drawing process. The cross section of the raw material wire has four corners, The cross section has a width W0, a thickness T0, and a diagonal length L0, The rectangular cross section has a width W, a thickness T, and a diagonal length L, The processing ratio P of the corner portion in the final wire drawing process is 20% or more, The processing ratio P is {(L0-L) / X}×100, where X is the larger value between W0-W and T0-T. The cross-sectional area reduction rate of the final wire drawing process is 35% or less.

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