Copper-coated steel wire and insulated electric wire

Abstract

Provided is a copper-coated steel wire comprising: a core wire made of austenitic stainless steel; a covering layer covering the peripheral surface of the core wire and made of copper or a copper alloy; and an interlayer provided between the core wire and the covering layer and made of nickel. In a cross section of the copper-coated steel wire which is perpendicular to the longitudinal direction thereof, the difference between a maximum value tmax and a minimum value tmin of the thickness of the covering layer is 9% or less of the maximum value tmax.

Description

Copper-coated steel wire and insulated wire

[0001] TECHNICAL FIELD This disclosure relates to copper clad steel wire and insulated electrical wire.

[0002] This application claims priority based on Japanese Application No. 2023-152403 filed on September 20, 2023, and incorporates by reference all of the contents of the aforementioned Japanese application.

[0003] In some cases, electric wires are required to have both strength and conductivity. In such cases, a copper-coated steel wire having a steel core wire and a copper coating layer covering the outer surface of the core wire can be used as the electric wire. Furthermore, when the copper-coated steel wire is used in an environment requiring corrosion resistance, austenitic stainless steel may be used as the steel constituting the core wire.

[0004] A terminal may be attached to the end of an electric wire by crimping. When a terminal is attached to the end of an electric wire including a copper-coated steel wire by crimping, the core wire may break during crimping, reducing the connection strength (crimping strength) between the copper-coated steel wire and the terminal. When a tensile load is applied to the connection, the copper-coated steel wire may come off the terminal. In response to this, a solution to the above problem has been proposed by appropriately setting the hardness of the core wire and the coating layer, and the tensile strength of the core wire (see, for example, JP 2022-157046 A (Patent Document 1)).

[0005] Japanese Patent Application Laid-Open No. 2022-157046

[0006] The copper-clad steel wire according to the present disclosure is a copper-clad steel wire comprising a core wire made of austenitic stainless steel, a coating layer made of copper or a copper alloy and covering the outer circumferential surface of the core wire, and an intermediate layer made of nickel and disposed between the core wire and the coating layer. ｍａｘ and the minimum value t ｍｉｎ The difference between ｍａｘ This is less than 9%.

[0007] Fig. 1 is a schematic diagram showing the structure of a copper-coated steel wire. Fig. 2 is a schematic cross-sectional view showing an enlarged view of the vicinity of the boundary between the core wire and the coating layer in Fig. 1. Fig. 3 is a schematic diagram showing the structure of an insulated wire. Fig. 4 is a schematic cross-sectional view showing the structure of a copper-coated steel wire. Fig. 5 is a flowchart showing an outline of a method for manufacturing a copper-coated steel wire and an insulated wire. Fig. 6 is a schematic perspective view showing a state in which an insulated wire and a crimp terminal are connected. Fig. 7 is a schematic view for explaining a method for a tensile test.

[0008] [Problem to be Solved by the Present Disclosure] However, even when the hardness of the core wire and the covering layer, and the tensile strength of the core wire are adjusted, there are cases where further improvement in crimping strength is required to prevent breakage of the core wire during crimping.

[0009] Therefore, one object of the present disclosure is to provide a copper-coated steel wire and an insulated wire including the copper-coated steel wire that can suppress a decrease in crimping strength.

[0010] [Effects of the Present Disclosure] According to the above-described copper-coated steel wire, it is possible to provide a copper-coated steel wire capable of suppressing a decrease in crimp strength.

[0011] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. The copper-clad steel wire of the present disclosure is a copper-clad steel wire comprising: (1) an austenitic stainless steel core wire; a copper or copper alloy coating layer covering the outer surface of the core wire; and a nickel intermediate layer disposed between the core wire and the coating layer. This copper-clad steel wire has a maximum thickness t of the coating layer in a cross section perpendicular to the longitudinal direction of the copper-clad steel wire. ｍａｘ and the minimum value t ｍｉｎ The difference between ｍａｘ This is less than 9%.

[0012] The present inventors investigated the reason why a decrease in crimp strength due to breakage of the core wire during crimping cannot be sufficiently suppressed even when the hardness of the core wire and the coating layer and the tensile strength of the core wire are adjusted, and based on the findings obtained from the investigation, they considered measures to suppress the decrease in crimp strength. As a result, they obtained the following findings and found a measure to suppress the decrease in crimp strength.

[0013] According to the study by the inventors, the breakage of the core wire during crimping is greatly affected by the variation in the thickness of the coating layer of the copper-coated steel wire. ｍａｘ and the minimum value t ｍｉｎ The difference between the maximum value t ｍａｘ It has been found that the decrease in the crimping strength can be effectively suppressed by setting the value of the tensile strength to a range not exceeding a specific value, specifically not exceeding 9%.

[0014] In the copper-coated steel wire of the present disclosure, the maximum thickness t of the coating layer in a cross section perpendicular to the longitudinal direction of the copper-coated steel wire ｍａｘ and the minimum value t ｍｉｎ The difference between ｍａｘ As a result, the copper-clad steel wire of the present disclosure can suppress a decrease in crimp strength. ｍａｘ and the minimum value t ｍｉｎ is defined as the average of the 10 maximum values ​​and the average of the 10 minimum values ​​obtained by randomly examining 10 cross sections perpendicular to the longitudinal direction of the copper-coated steel wire and measuring the maximum and minimum values ​​of the thickness of the coating layer at each cross section.

[0015] (2) In the above (1), the Vickers hardness of the core wire is HV ＳＴ , the carbon content of the core wire expressed in mass% is C ＳＴ , the maximum thickness of the coating layer is t ｍａｘ , where D is the wire diameter of the copper-coated steel wire, and the following formula (1) is satisfied: 450≦HV ＳＴ ≦1660×C ＳＴ +2850 x t ｍａｘ / D (1) may be satisfied.

[0016] By setting the hardness of the core wire to 450 HV or more, it becomes easy to impart sufficient strength to the copper-coated steel wire. On the other hand, by setting the hardness of the core wire to a value calculated according to a specific calculation formula (Equation (1)) or less using the carbon content of the core wire and the ratio of the thickness of the coating layer to the wire diameter of the copper-coated steel wire as parameters, breakage of the core wire during crimping can be suppressed. More specifically, the austenitic stainless steel constituting the core wire is hardened by wiredrawing to obtain the desired strength. In this case, the lower the carbon content of the austenitic stainless steel, the greater the amount of processing required to obtain the desired strength. Therefore, the lower the carbon content, the closer the austenitic stainless steel is to being used in a state closer to its processing limit, resulting in a smaller tolerance for deformation during crimping and a greater susceptibility to core wire breakage. Furthermore, the greater the ratio of the thickness of the coating layer to the wire diameter of the copper-coated steel wire, the more the coating layer, which has high deformability, bears the deformation caused by crimping, thereby suppressing breakage of the core wire. According to the inventors' research, by setting the hardness of the core wire to a value equal to or less than the sum of these parameters multiplied by a specific coefficient, breakage of the core wire during crimping can be suppressed. In the present application, the wire diameter D of the copper-coated steel wire is defined as the average value of the wire diameter (diameter) measured at 10 points in the longitudinal direction of the copper-coated steel wire. ＳＴ can be measured on a cross section perpendicular to the longitudinal direction of the core wire using a micro Vickers hardness tester under conditions such as a load of 0.196 N. The measurement point can be a point on a line segment corresponding to the diameter of the cross section, corresponding to the midpoint of the line segment (the center of the cross section) and the midpoints between both ends of the line segment.

[0017] (3) In the above (2), the above t ｍａｘ / D may be 0.25 or less. This configuration makes it easy to impart sufficient strength to the copper-clad steel wire. ｍａｘ / D may be 0.23 or less.

[0018] (4) In any of the above (1) to (3), the copper-coated steel wire may have a wire diameter D of 200 μm or more and 400 μm or less. The copper-coated steel wire of the present disclosure, which can suppress a decrease in crimping strength, is particularly suitable for a copper-coated steel wire having a wire diameter of 200 μm or more and 400 μm or less.

[0019] (5) In any of the above (1) to (4), the austenitic stainless steel constituting the core wire may be JIS standard SUS301, SUS304, SUS310S, or SUS316. JIS standard SUS301, SUS304, SUS310S, and SUS316 are particularly suitable as materials constituting the core wire.

[0020] (6) In any of the above (1) to (5), the hardness of the coating layer may be 50 HV or more and 140 HV or less. This configuration makes it easy to suppress a decrease in the crimp strength of the copper-coated steel wire. In the present application, the hardness of the coating layer may be defined as the average value of measurements taken at four points in the center of the thickness of the coating layer in a cross section perpendicular to the longitudinal direction of the copper-coated steel wire.

[0021] (7) An insulated wire according to the present disclosure includes the copper-coated steel wire according to any one of (1) to (6) above and an insulating layer covering the outer surface of the copper-coated steel wire. By including the copper-coated steel wire according to the present disclosure, the insulated wire according to the present disclosure can suppress a decrease in crimp strength.

[0022] [Details of the embodiment of the present disclosure] Next, embodiments of the copper-clad steel wire and the insulated electric wire according to the present disclosure will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and their description will not be repeated.

[0023] (Embodiment 1) Fig. 1 is a schematic diagram showing the structure of a copper-coated steel wire. Fig. 2 is a schematic cross-sectional view showing an enlarged view of the vicinity of the boundary between the core wire and the coating layer in Fig. 1. With reference to Figs. 1 and 2, the copper-coated steel wire 1 in this embodiment includes a core wire 10, a coating layer 20, and an intermediate layer 40. The core wire 10 is made of austenitic stainless steel. The coating layer 20 is disposed so as to cover the outer peripheral surface 11 of the core wire 10. The intermediate layer 40 is disposed between the core wire 10 and the coating layer 20. The coating layer 20 is in contact with the intermediate layer 40 at the inner peripheral surface 21. The core wire 10 is in contact with the intermediate layer 40 at the outer peripheral surface 11. The intermediate layer 40 is interposed between the core wire 10 and the coating layer 20. The outer peripheral surface 22 of the coating layer 20 constitutes the outer peripheral surface of the copper-coated steel wire 1.

[0024] FIG. 3 is a schematic diagram showing the structure of an insulated wire. Referring to FIG. 3, an insulated wire 100 according to the present embodiment includes the copper-coated steel wire 1 according to the present embodiment and an insulating layer 30. The insulating layer 30 is disposed so as to cover the outer peripheral surface 1A of the copper-coated steel wire 1 (the outer peripheral surface 22 of the coating layer 20). The insulating layer 30 covers the entire outer peripheral surface 1A of the copper-coated steel wire 1. The insulating layer 30 contacts the outer peripheral surface 1A of the copper-coated steel wire 1 at an inner peripheral surface 31. The outer peripheral surface 32 of the insulating layer 30 constitutes the outer peripheral surface of the insulated wire 100. The insulating layer 30 is made of an insulator such as a resin. Examples of resins that can be used to form the insulating layer 30 include polyethylene and vinyl chloride.

[0025] Fig. 4 is a schematic cross-sectional view showing the structure of a copper-coated steel wire. Fig. 4 shows a cross section perpendicular to the longitudinal direction of the copper-coated steel wire 1. Referring to Fig. 4, the wire diameter D (diameter of the cross section perpendicular to the longitudinal direction) of the copper-coated steel wire 1 is not particularly limited, but is, for example, 200 µm or more and 400 µm or less. As the austenitic stainless steel constituting the core wire 10, for example, JIS standards SUS301, SUS304, SUS310S, or SUS316 can be adopted. The tensile strength of the core wire 10 can be, for example, 1500 MPa or more and 3000 MPa or less. The Vickers hardness HV of the core wire 10 ＳＴ can be, for example, 450 HV or more and 840 HV or less.

[0026] The coating layer 20 is made of copper (Cu) or a copper alloy. The coating layer 20 covers the outer circumferential surface 11 (surface) of the core wire 10. The coating layer 20 may be a plated layer. The coating layer 20 may be a layer formed by plating. The hardness of the coating layer 20 is, for example, 50 HV or more and 140 HV or less. The maximum thickness t of the coating layer 20 in a cross section perpendicular to the longitudinal direction of the copper-coated steel wire 1 is ｍａｘ and the minimum value t ｍｉｎ The difference between the maximum value t ｍａｘ This is less than 9%.

[0027] Referring to Fig. 2, the intermediate layer 40 is made of nickel (Ni). The thickness of the intermediate layer 40 is not particularly limited, but can be set to be smaller than the thickness of the coating layer 20. The thickness of the intermediate layer 40 can be, for example, 0.0001 µm or more, preferably 0.005 µm or more. The thickness of the intermediate layer 40 can be, for example, 1 µm or less, preferably 0.8 µm or less. The intermediate layer 40 functions to improve adhesion between the core wire 10 and the coating layer 20. The intermediate layer 40 may be a plated layer. The intermediate layer 40 may be a layer formed by plating.

[0028] In the copper-coated steel wire 1 of this embodiment, as described above, the maximum thickness t ｍａｘ and the minimum value t ｍｉｎ The difference between these is the maximum value t ｍａｘ The variation in thickness of the coating layer 20 is suppressed to be 9% or less of the maximum thickness t of the coating layer 20. As a result, the copper-coated steel wire 1 of this embodiment is a copper-coated steel wire in which the decrease in crimping strength is suppressed. Furthermore, the insulated wire 100 including this copper-coated steel wire 1 is an insulated wire in which the decrease in crimping strength is suppressed. ｍａｘ and the minimum value t ｍｉｎ The difference between the maximum value t ｍａｘ By setting the ratio to 8% or less, 7% or less, 6% or less, or even 5% or less, the decrease in the crimping strength can be further suppressed.

[0029] In the copper-coated steel wire 1 of this embodiment, the Vickers hardness of the core wire 10 is HV ＳＴ , the carbon content of the core wire 10 expressed in mass% is C ＳＴ t is the maximum thickness of the coating layer 20 expressed in μm. ｍａｘ , where D is the wire diameter of the copper-coated steel wire 1 expressed in μm, and the following formula (1) is satisfied: 450≦HV ＳＴ ≦1660×C ＳＴ +2850 x t ｍａｘ / D (1) may be satisfied. By setting the hardness of the core wire 10 to 450 HV or more, it becomes easy to impart sufficient strength to the copper-coated steel wire 1. On the other hand, the hardness of the core wire 10 can be determined by the carbon content of the core wire 10 and the maximum value t ｍａｘBy setting the ratio of the core wire 10 to a value calculated according to the formula (1) as a parameter, breakage of the core wire 10 during crimping can be suppressed.

[0030] In the copper-coated steel wire 1 of this embodiment, the above t ｍａｘ When / D is 0.25 or less, it becomes easy to impart sufficient strength to the copper-coated steel wire 1.

[0031] Next, a method for manufacturing the copper-coated steel wire 1 and the insulated electric wire 100 according to the present embodiment will be described. FIG. 5 is a flowchart showing an outline of the method for manufacturing the copper-coated steel wire and the insulated electric wire. Referring to FIG. 5, the method for manufacturing the copper-coated steel wire 1 and the insulated electric wire 100 according to the present embodiment first performs a raw steel wire preparation step as step S10. In step S10, a raw steel wire is prepared. Specifically, a raw steel wire made of austenitic stainless steel, for example, JIS standard SUS301, SUS304, SUS310S, or SUS316 having a desired carbon content, is prepared. The outer diameter of the raw steel wire can be, for example, 0.3 mm or more and 1 mm or less.

[0032] Next, an intermediate layer forming step is carried out as step S20. In this step S20, an intermediate layer 40 is formed on the surface of the raw steel wire prepared in step S10. Specifically, for example, the intermediate layer 40 made of nickel is formed on the core wire 10 by plating. This results in a raw steel wire having the intermediate layer 40 formed on its surface. The thickness of the intermediate layer 40 formed in step S20 is determined so that the copper-coated steel wire 1 has a desired thickness in its finished state, taking into account that the thickness will be reduced by processing in the wiredrawing step described below.

[0033] Next, a wiredrawing step is carried out as step S30. In this step S30, the raw steel wire on which the intermediate layer 40 has been formed in step S20 is subjected to wiredrawing (drawing). The true strain in the wiredrawing in step S30 can be, for example, 1.3 or more and 2.6 or less. This adjusts the outer diameter of the raw steel wire to a desired value, and imparts desired hardness and tensile strength to the raw steel wire, turning the raw steel wire into a core wire 10 (see FIG. 1 ). The wiredrawing may be carried out in multiple steps.

[0034] Next, a coating layer forming step is carried out as step S40. In this step S40, a coating layer 20 is formed on the surface of the core wire 10 having the intermediate layer 40 obtained by carrying out steps up to S30. Specifically, for example, the coating layer 20 made of copper (pure copper) is formed by plating on the core wire 10 having the intermediate layer 40. Alternatively, a metal layer of tin (Sn), zinc (Zn), or the like may be formed by plating in addition to copper, and the copper alloy coating layer 20 may be formed by alloying these. In this way, a copper-coated steel wire 1 including the core wire 10 and the coating layer 20 is obtained. The coating layer 20 may be formed in multiple steps.

[0035] Next, a coating layer thickness uniformization step is carried out as step S50. In this step S50, the copper-coated steel wire 1 obtained by forming the coating layer 20 in step S40 is subjected to wiredrawing with a small amount of processing in order to reduce variations in the thickness of the coating layer 20. The true strain of the wiredrawing in step S50 can be, for example, 0.1 or more and 0.5 or less.

[0036] Next, a heat treatment step is carried out as step S60. In this step S60, the copper-coated steel wire 1 obtained by carrying out steps up to S50 is subjected to a heat treatment. Specifically, the copper-coated steel wire 1 is subjected to a heat treatment by, for example, holding it in a temperature range of 275°C to 450°C, preferably in a temperature range of 350°C to 450°C, for 30 minutes to 120 minutes, followed by air cooling to room temperature. This heat treatment recrystallizes the copper or copper alloy constituting the coating layer 20 and softens it to an appropriate hardness, and also removes internal stress in the core wire 10, thereby adjusting the hardness of the core wire 10 to an appropriate range. By the above procedure, the copper-coated steel wire 1 of this embodiment is obtained (see FIG. 1).

[0037] Furthermore, an insulating layer forming step is carried out as step S70. In this step S70, an insulating layer 30 is formed so as to cover the outer surface of the copper-coated steel wire 1 of this embodiment obtained by carrying out steps up to S60. The insulating layer 30 may be made of, for example, resin. Through the above procedure, the insulated electric wire 100 of this embodiment is obtained (see FIG. 3).

[0038] An experiment was conducted to confirm the effect of suppressing a decrease in crimp strength when connecting the copper-clad steel wire and the insulated electric wire of the present disclosure to a crimp terminal. The procedure of the experiment was as follows.

[0039] An insulated wire 100 was prepared according to the manufacturing method described in the above embodiment. JIS SUS301 and SUS304 steel wires were used as the raw steel wire material prepared in step S10. In step S20, an intermediate layer 40 was formed so that the finished product (i.e., the stage after step S70 was completed) would have a thickness of 0.6 μm. In step S40, a pure copper coating layer 20 was formed by plating. For comparison, an insulated wire was also prepared in which step S50 was omitted, thereby not achieving a uniform thickness for the coating layer 20. Samples A to Q were obtained in this manner. The strength of the crimped portions of the obtained samples when connected to crimp terminals was measured as follows.

[0040] Fig. 6 is a schematic perspective view showing the connection state between an insulated electric wire and a crimp terminal. Fig. 7 is a schematic view illustrating a method for a tensile test. Referring to Fig. 6, a crimp terminal 80 includes a main body 83, a conductor barrel 81 connected to the main body 83, and an insulation barrel 82 connected to the side of the conductor barrel 81 opposite the side connected to the main body 83. When connecting an insulated electric wire 100 to the crimp terminal 80, the insulation layer 30 at the end of the insulated electric wire 100 is first removed to expose the copper-coated steel wire 1. The conductor barrel 81 is then crimped to hold the exposed copper-coated steel wire 1, and the insulation layer 30 is held by the insulation barrel 82. If a crack occurs in the core wire 10 of the copper-coated steel wire 1 held by the conductor barrel 81, the strength (crimping strength) of the connection between the conductor barrel 81 and the copper-coated steel wire 1 decreases.

[0041] In this experiment, for each sample, the copper-clad steel wire 1 was held by the conductor barrel 81 as described above, but the insulation layer 30 was not held by the insulation barrel 82. The insulated wire 100 and the crimp terminal 80 were connected in this state. The compression ratio, expressed as 1 - (cross-sectional area of ​​the coating layer 20 before crimping) / (cross-sectional area of ​​the coating layer 20 after crimping), was set to 15%. This is the condition under which sufficient crimp strength can be obtained if the core wire 10 does not break. Then, as shown in FIG. 12 , a tensile test was conducted with the main body 83 of the crimp terminal 80 held by the first chuck 91 of a tensile tester and the insulated wire 100 held by the second chuck 92 of the tensile tester, and the load at break was investigated. The probability (pass rate) that the obtained load at break was 60% or more of the load at break without crimping was calculated. The experimental results are shown in Table 1.

[0042] Referring to Table 1, in samples A to F, I, J, M, and P produced by a process including the coating layer thickness uniformization step (S50), the maximum thickness t ｍａｘ and the minimum value t ｍｉｎ The difference between ｍａｘ On the other hand, in the samples G, H, K, L, N, O, and Q, which were produced by a process that did not include the coating layer thickness uniformization step (S50), the maximum thickness t ｍａｘ and the minimum value t ｍｉｎ The difference between ｍａｘ The maximum value t ｍａｘ and the minimum value t ｍｉｎ The difference between ｍａｘ The pass rates for samples A to F, I, J, M and P, which are 9% or less, are 90 to 100%, while the pass rates for samples G, H, K, L, N, O and Q, which are over 9%, are 40% or less. ｍａｘ and ｍｉｎ The difference between ｍａｘ It has been confirmed that the copper-coated steel wire and insulated electric wire of the present disclosure, in which the copper content is 9% or less, can suppress a decrease in crimp strength.

[0043] Furthermore, t ｍａｘ and the minimum value t ｍｉｎ The difference betweenｍａｘ Among the samples with a hardness of 9% or less, samples A to F that satisfy the condition of the above formula (1) have a pass rate of 100%. ＳＴ , the carbon content C of the austenitic stainless steel constituting the core wire ＳＴ and the maximum thickness t of the coating layer relative to the wire diameter D of the copper-coated steel wire ｍａｘ It has been confirmed that the decrease in the crimping strength can be further suppressed by adjusting the ratio of

[0044] It should be understood that the embodiments and examples disclosed herein are illustrative in all respects and are not limiting in any respect. The scope of the present invention is defined not by the above description but by the scope of the claims, and it is intended to include all modifications within the meaning and scope of the claims.

[0045] 1 Copper-coated steel wire, 1A Outer circumferential surface, 10 Core wire, 11 Outer circumferential surface, 20 Coating layer, 21 Inner circumferential surface, 22 Outer circumferential surface, 30 Insulating layer, 31 Inner circumferential surface, 32 Outer circumferential surface, 40 Intermediate layer, 80 Crimp terminal, 81 Conductor barrel, 82 Insulation barrel, 83 Main body, 91 First chuck, 92 Second chuck, 100 Insulated wire, C ＳＴ Carbon content of the core wire, D Diameter of the copper-coated steel wire, HV ＳＴ Core hardness, S10 to S70 Process, t ｍａｘ Maximum thickness of the coating layer, t ｍｉｎ The minimum thickness of the coating layer.

Claims

1. A copper-coated steel wire comprising: an austenitic stainless steel core; a copper or copper alloy coating layer covering the outer circumferential surface of the core; and a nickel intermediate layer disposed between the core and the coating layer; wherein the maximum thickness t of the coating layer in a cross section perpendicular to the longitudinal direction of the copper-coated steel wire is t ... ｍａｘ and the minimum value t ｍｉｎ The difference between the maximum value t ｍａｘ 9% or less of copper-coated steel wire.

2. The Vickers hardness of the core wire is HV ＳＴ The carbon content of the core wire is expressed in mass% as C ＳＴ The maximum thickness of the coating layer is t ｍａｘ The wire diameter of the copper-coated steel wire is D, and the following formula is satisfied: 450≦HV ＳＴ ≦1660×C ＳＴ +2850×t ｍａｘ 2. The copper-clad steel wire according to claim 1 , wherein:

3. T ｍａｘ 3. The copper-coated steel wire according to claim 2, wherein / D is 0.25 or less.

4. A copper-coated steel wire according to any one of claims 1 to 3, wherein the wire diameter D of the copper-coated steel wire is 200 μm or more and 400 μm or less.

5. The copper-clad steel wire according to any one of claims 1 to 4, wherein the austenitic stainless steel constituting the core wire is JIS standard SUS301, SUS304, SUS310S or SUS316.

6. A copper-coated steel wire according to any one of claims 1 to 5, wherein the hardness of the coating layer is 50 HV or more and 140 HV or less.

7. An insulated wire comprising: a copper-coated steel wire according to any one of claims 1 to 6; and an insulating layer covering the outer circumferential surface of the copper-coated steel wire.

Images