Wire, stranded wire, cable, and method for producing wire

Abstract

This wire comprises a core and a shell covering the outer circumference of the core. The core contains silver. The shell contains 33.0 to 37.0 mass% nickel, 9.0 to 10.5% molybdenum, 19.0 to 21.0% chromium, 0.5 to 1.2 mass% titanium, cobalt and inevitable impurities as the balance. The wire diameter is 100 μm or less, and the elongation of the wire is 12% or more.

Description

Wire, stranded wire, cable, and method for manufacturing wire

[0001] The present disclosure relates to wires, strands, cables, and methods for manufacturing wires. This application claims priority from Japanese Patent Application No. 2022-069119, filed April 19, 2022. The entire contents of the Japanese Patent Application are incorporated herein by reference.

[0002] Patent Document 1 discloses a wire having a core and a tubular shell surrounding the core. The core is made of silver. The shell is made of an alloy containing nickel, cobalt, molybdenum, and chromium.

[0003] U.S. Patent No. 7,015,392

[0004] The wire of the present disclosure is a wire comprising a core and a shell covering the outer periphery of the core, wherein the core contains silver, and the shell contains 33.0 mass% to 37.0 mass% nickel, 9.0 mass% to 10.5 mass% molybdenum, 19.0 mass% to 21.0 mass% chromium, and 0.5 mass% to 1.2 mass% titanium, with the remainder being cobalt and unavoidable impurities, and the wire has a diameter of 100 μm or less and an elongation of 12% or more.

[0005] The stranded wire of the present disclosure has a structure in which multiple wires of the present disclosure are twisted together.

[0006] The cable of the present disclosure comprises the stranded wire of the present disclosure and a sheath that covers the outer periphery of the stranded wire.

[0007] The wire manufacturing method of the present disclosure includes the steps of: fitting a core material and a shell material to produce a wire material; drawing the wire material; and heat treating the wire material that has been drawn. In the drawing step, intermediate heat treatments are performed between multiple drawing operations at a temperature of 850°C or higher and 960°C or lower for less than two hours, and the number of intermediate heat treatments is 20 or less.

[0008] FIG. 1 is a schematic cross-sectional view showing a transverse section of a wire according to an embodiment. FIG. 2 is a diagram illustrating a method for manufacturing a wire according to an embodiment, and is a schematic diagram showing an example of a process for producing a wire material. FIG. 3 is a schematic cross-sectional view showing a transverse section of a cable according to an embodiment. FIG. 4 is a diagram showing an SEM image of a longitudinal wire cross section of sample A. FIG. 5 is a diagram showing an SEM image of a longitudinal wire cross section of sample A, in which the vicinity of the outer peripheral surface of the shell is observed. FIG. 6 is a diagram showing an enlarged SEM image of a partial region of the outer peripheral surface of the shell shown in FIG. 5. FIG. 7 is a diagram showing an SEM image of a longitudinal wire cross section of sample B. FIG. 8 is a diagram showing an SEM image of a longitudinal wire cross section of sample B, in which the vicinity of the outer peripheral surface of the shell is observed. FIG. 9 is a diagram showing an enlarged SEM image of a partial region of the outer peripheral surface of the shell shown in FIG. 8.

[0009] [Problem to be Solved by the Present Disclosure] The above-mentioned wire is used in medical devices. Applications of this medical wire include catheters. In recent years, catheters have become thinner in diameter, and as a result, there is a demand for thinner wires used in catheters.

[0010] The basic properties required for wire are high elongation and high tensile strength. To reduce the diameter of a wire, it is necessary to repeatedly process it until the diameter reaches a predetermined value. Repeated processing causes work hardening of the wire, which reduces its elongation. Therefore, there is a demand for wires that have excellent elongation properties even when the wire diameter is small.

[0011] One object of the present disclosure is to provide a wire that is small in diameter and has good elongation. Another object of the present disclosure is to provide a stranded wire and cable that are small in diameter and flexible.

[0012] [Advantages of the present disclosure] The wire of the present disclosure has a small diameter and good elongation. The stranded wire and cable of the present disclosure have a small diameter and flexibility.

[0013] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0014] (1) A wire according to an embodiment of the present disclosure is a wire comprising a core and a shell covering the outer periphery of the core, wherein the core contains silver, and the shell contains 33.0% by mass or more and 37.0% by mass or less of nickel, 9.0% by mass or more and 10.5% by mass or less of molybdenum, 19.0% by mass or more and 21.0% by mass or less of chromium, and 0.5% by mass or more and 1.2% by mass or less of titanium, with the remainder being cobalt and inevitable impurities, and the wire has a diameter of 100 μm or less and an elongation of 12% or more.

[0015] The wire has a small wire diameter of 100 μm or less. The wire has good elongation of 12% or more. Therefore, the wire has a small wire diameter and good elongation.

[0016] The wire has electrical conductivity due to the silver core. The core may be composed of silver and inevitable impurities, or may be composed of an alloy containing silver, such as a silver alloy. The specific cobalt alloy containing nickel, molybdenum, chromium, and titanium has excellent mechanical properties. The wire has a shell made of the specific cobalt alloy, which provides both high tensile strength and high elongation.

[0017] (2) In the wire of the present disclosure described in (1) above, in a cross section of the wire, the ratio of the cross-sectional area of ​​the shell to the cross-sectional area of ​​the wire may be 50% or more and 90% or less.

[0018] The wire of the above embodiment has excellent electrical conductivity, tensile strength, and elongation. (3) In the wire of the present disclosure described in (1) or (2) above, the shell may have a precipitate layer containing titanium precipitates on the outer peripheral surface thereof, and the thickness of the precipitate layer may be 0.1 μm or more and 1.0 μm or less.

[0019] The wire of the above embodiment can suppress the decrease in elongation. As will be described in detail later, the inventors have found that by controlling the thickness of the deposit layer within the above specific range, the decrease in elongation of the wire can be significantly suppressed. For example, by setting the thickness of the deposit layer within the above specific range, the elongation of the wire can be made 12% or more.

[0020] (4) In the wire of the present disclosure described in any one of (1) to (3) above, the average crystal grain size of the metal constituting the shell in the longitudinal cross section of the wire may be 0.1 μm or more and 5.0 μm or less.

[0021] The wire of the above embodiment has a high tensile strength. (5) In the wire of the present disclosure described in any one of (1) to (4) above, the tensile strength of the wire may be 600 MPa or more.

[0022] The wire of the above embodiment has excellent tensile strength. (6) The wire of the present disclosure described in any one of (1) to (5) above may further include an insulating layer covering an outer periphery of the shell.

[0023] The wire of the above embodiment can ensure insulation from surrounding members by the insulating layer. (7) A stranded wire according to an embodiment of the present disclosure has a structure in which a plurality of wires according to any one of (1) to (6) above are twisted together.

[0024] The stranded wire of the present disclosure is made by twisting together the wires of the present disclosure, and is therefore thin in diameter and flexible.

[0025] (8) A cable according to an embodiment of the present disclosure comprises the stranded wire described in (7) above, and a sheath covering the outer periphery of the stranded wire.

[0026] The cable of the present disclosure includes the stranded wire of the present disclosure, and therefore has a small diameter and flexibility. (9) In the cable of the present disclosure described above in (8), a shielding layer may be provided between the stranded wire and the sheath.

[0027] The cable of the above embodiment can shield electromagnetic waves by the shielding layer. (10) A method for manufacturing a wire according to (1), comprising the steps of: fitting a core material and a shell material together to produce a wire material; drawing the wire material; and heat treating the drawn wire material, wherein intermediate heat treatments performed between multiple drawing operations in the drawing operation are performed at a temperature of 850°C to 960°C for less than two hours, and the number of intermediate heat treatments is 20 or less.

[0028] The above-described method for producing a wire can provide a wire having a small diameter and good elongation.

[0029] [Details of the embodiment of the present disclosure] Hereinafter, the embodiment of the present disclosure will be specifically described with reference to the drawings. The same reference numerals in the drawings denote the same objects.

[0030] It should be noted that the present invention is not limited to these examples, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0031] <Wire> A wire 1 according to an embodiment will be described with reference to Fig. 1 . The wire 1 includes a core 2 and a shell 3. Both the core 2 and the shell 3 are made of metal. The diameter of the wire 1 is 100 µm or less. The elongation of the wire 1 is 12% or more. The wire 1 will be described in detail below.

[0032] In the following description, elements are represented by their element symbols. Ag is silver. Co is cobalt. Ni is nickel. Mo is molybdenum. Cr is chromium. Ti is titanium. C is carbon. P is phosphorus. Si is silicon. Mn is manganese. S is sulfur. Fe is iron. Cu is copper. Al is aluminum.

[0033] <Shape> The shape of the wire 1 can be selected as appropriate. The wire 1 of this embodiment is a round wire. The cross-sectional shape of the wire 1 is circular as shown in FIG. 1. The cross-section is a cross section cut along a plane perpendicular to the longitudinal direction of the wire 1. The cross-sectional shape of the wire 1 may be non-circular. Examples of non-circular shapes include polygonal and elliptical shapes. Examples of polygonal shapes include rectangular and hexagonal shapes. Rectangles also include squares.

[0034] <Diameter> The diameter of the wire 1 is 100 μm or less. Here, "diameter" refers to the diameter of the cross section of the wire 1. When the cross section of the wire 1 is non-circular, the diameter of the wire 1 is the diameter of a circle having an area equal to the area of ​​the cross section of the wire 1. The diameter of the wire 1 is more preferably 80 μm or less, more preferably 60 μm or less. A wire 1 having a diameter of 100 μm or less can be suitably used for medical devices such as catheters. The lower limit of the diameter of the wire 1 is not particularly limited, but is, for example, 10 μm. The diameter of the wire 1 is, for example, 10 μm or more and 100 μm or less, further 15 μm or more and 80 μm or less, or 20 μm or more and 60 μm or less.

[0035] <Elongation> The elongation of the wire 1 is 12% or more. The "elongation" here refers to the breaking elongation when the wire 1 is pulled at a constant speed using a tensile tester and breaks. The elongation may be measured in accordance with JIS Z 2241:2011 "Methods for tensile testing of metallic materials." The elongation of the wire 1 is preferably 13% or more, more preferably 15% or more. In particular, when the elongation of the wire 1 is important, the elongation may be 17% or more, even 20% or more. The upper limit of the elongation of the wire 1 is not particularly limited, but is, for example, 30%. The elongation of the wire 1 is, for example, 12% to 30%, 13% to 27%, or 15% to 25%.

[0036] <Tensile Strength> The tensile strength of the wire 1 is preferably 600 MPa or more. The term "tensile strength" as used herein refers to the breaking strength when the wire 1 is pulled at a constant pulling rate using a tensile tester and breaks. The tensile strength may be measured in accordance with JIS Z 2241:2011 "Method for tensile testing of metallic materials." The tensile strength of the wire 1 may further be 700 MPa or more, or 800 MPa or more. The upper limit of the tensile strength of the wire 1 is not particularly limited, but is, for example, 1300 MPa. The tensile strength of the wire 1 is, for example, 600 MPa or more and 1300 MPa or less, 700 MPa or more and 1250 MPa or less, or 800 MPa or more and 1200 MPa or less.

[0037] <Conductivity> The conductivity of the wire 1 is preferably 10% IACS or more. The conductivity of the wire 1 may further be 20% IACS or more, or 25% IACS or more. In particular, when the conductivity of the wire 1 is important, the conductivity may be 30% IACS or more, or even 35% IACS or more. The upper limit of the conductivity of the wire 1 is not particularly limited, but is, for example, 60% IACS. The conductivity of the wire 1 is, for example, 10% IACS or more and 60% IACS or less, 20% IACS or more and 20% IACS or less, or 25% IACS or more and 55% IACS or less.

[0038] (Core) The core 2 may be made of Ag. The core 2 being made of Ag means that the metal constituting the core 2 contains 95% by mass or more of Ag, preferably 97% by mass or more, particularly 99% by mass or more or 99.9% by mass or more of Ag. The core 2 may be made of an Ag alloy containing Ag. In the case of an Ag alloy, for example, it is considered that the Ag content is 90% by mass or more. The core 2 is disposed at the center of the wire 1 as shown in FIG. 1 . The core 2 is a portion that mainly ensures the conductivity of the wire 1. The core 2 has higher conductivity than the shell 3. The wire 1 has conductivity due to the core 2. The larger the cross-sectional area of ​​the core 2, the lower the electrical resistance, and therefore the higher the conductivity of the wire 1. The contribution of the core 2 to the strength of the wire 1 is lower than that of the shell 3.

[0039] The core 2 is made of a single wire. In this embodiment, the cross-sectional shape of the core 2 is circular. The cross-sectional shape of the core 2 is not particularly limited. The cross-sectional shape of the core 2 may be non-circular.

[0040] (Shell) The shell 3 contains a specific Co alloy. The shell 3 covers the outer periphery of the core 2 as shown in Figure 1. The shell 3 has a pipe shape. The shell 3 is joined to the core 2. In other words, the shell 3 is in direct contact with the core 2. The shell 3 is the part that mainly ensures the strength of the wire 1. The shell 3 has a higher strength than the core 2. The wire 1 has a high tensile strength due to the shell 3. The larger the cross-sectional area of ​​the shell 3, the higher the tensile strength of the wire 1. The contribution of the shell 3 to the conductivity of the wire is lower than that of the core 2.

[0041] In this embodiment, the cross-sectional shape of the shell 3 is annular. That is, in the cross-section of the shell 3, the contour shapes of the inner and outer peripheries of the shell 3 are circular. The cross-sectional shape of the shell 3 is not particularly limited. At least one of the contours of the inner and outer peripheries of the shell 3 may be non-circular. The contour of the inner periphery of the shell 3 and the contour of the outer periphery of the shell 3 may have the same shape or different shapes.

[0042] The shell 3 contains Ni, Mo, Cr, and Ti, with the balance being Co and unavoidable impurities. The balance may be composed of Co and unavoidable impurities. The Ni content is 33.0 mass% or more and 37.0 mass% or less. The Mo content is 9.0 mass% or more and 10.5 mass% or less. The Cr content is 19.0 mass% or more and 21.0 mass% or less. The Ti content is 0.5 mass% or more and 1.2 mass% or less. Examples of unavoidable impurities include C, P, Si, Mn, S, Fe, etc. The total content of the unavoidable impurities is, for example, 2.0 mass% or less. A Co alloy having such a composition has excellent mechanical properties. Since the shell 3 is made of the above specific Co alloy, the wire 1 has both high tensile strength and high elongation. The above specific Co alloy is specified as F562 alloy in the American Society for Testing and Materials (ASTM) standard. An example of an F562 alloy is MP35N™ from SPS Technologies.

[0043] <Ratio of Cross-Sectional Area of ​​Shell> In the cross section of the wire 1, the ratio of the cross-sectional area of ​​the shell 3 to the cross-sectional area of ​​the wire 1 is preferably 50% or more and 90% or less. The cross-sectional area of ​​the wire 1 is the sum of the cross-sectional areas of the core 2 and the shell 3. The cross-sectional area ratio of the shell 3 is the proportion of the cross-sectional area of ​​the shell 3 when the cross-sectional area of ​​the wire 1 is 100%. Therefore, when the cross-sectional area ratio of the shell 3 is 50% or more and 90% or less, the cross-sectional area ratio of the core 2 is 10% or more and 50% or less. Hereinafter, the "cross-sectional area ratio of the shell" will be referred to as the "shell coverage rate."

[0044] By changing the coverage of the shell 3, the conductivity and tensile strength of the wire 1 can be controlled. The greater the coverage of the shell 3, the greater the proportion of the cross-sectional area of ​​the shell 3 in the cross-sectional area of ​​the wire 1. Therefore, the tensile strength of the wire 1 is likely to be high. When the coverage of the shell 3 is 50% or more, it is easy to ensure sufficient tensile strength of the wire 1. The smaller the coverage of the shell 3, the smaller the proportion of the cross-sectional area of ​​the shell 3 in the cross-sectional area of ​​the wire 1. In other words, the proportion of the cross-sectional area of ​​the core 2 increases. Therefore, the conductivity of the wire 1 is high. When the coverage of the shell 3 is 90% or less, it is easy to ensure the conductivity of the wire 1. Therefore, when the coverage is 50% or more and 90% or less, it is possible to obtain a wire 1 with excellent conductivity, tensile strength, and elongation. The proportion of the cross-sectional area of ​​the shell 3 may further be 55% or more and 85% or less, or 60% or more and 80% or less.

[0045] <Average Crystal Grain Size of Shell> The average crystal grain size of the metal constituting the shell 3 in the longitudinal cross section of the wire 1 is preferably 0.1 μm or more and 5.0 μm or less. The metal constituting the shell 3 is the specific Co alloy described above. Hereinafter, the "average crystal grain size of the metal constituting the shell" will be referred to as the "average crystal grain size of the shell." The smaller the average crystal grain size of the shell 3, the stronger the shell 3, and therefore the higher the tensile strength of the wire 1. When the average crystal grain size of the shell 3 is 5.0 μm or less, a wire 1 with high tensile strength can be obtained. The lower limit of the average crystal grain size of the shell 3 is not particularly limited, but is typically 0.1 μm. The average crystal grain size of the shell 3 may further be 0.15 μm or more and 4.0 μm or less, or 0.2 μm or more and 2.0 μm or less. The average crystal grain size of the metal constituting the shell 3 in the transverse cross section of the wire 1 is also the same as the average crystal grain size of the metal constituting the shell 3 in the longitudinal cross section.

[0046] The average crystal grain size of the shell 3 can be measured as follows. Of the longitudinal cross sections of the wire 1, the cross section of the shell 3 is observed with a scanning electron microscope (SEM). The longitudinal cross section is a cross section cut along a plane passing through the center of the wire 1 and along the longitudinal direction of the wire 1. The length of the wire 1 from which the longitudinal cross section is taken is, for example, 0.05 mm or more and 0.5 mm or less. An observation field is taken from the cross section of the shell 3. The observation field is preferably selected from a region near the center of the shell 3 in the thickness direction. The size of the observation field is preferably set so that 10 or more crystal grains are included within the observation field. The size of the observation field is, for example, 10 μm × 20 μm. The grain size of the crystal grains included within the observation field is measured. The grain size of the crystal grain is defined as the diameter of a circle having an area equal to the area of ​​the crystal grain. The area of ​​the crystal grain can be determined by image processing. The average value of the measured grain size of the crystal grains is defined as the average grain size in that observation field. The grain size of the crystal grains is measured in the same manner in multiple different observation fields to determine the average grain size. The average value of the average crystal grain size in all the observation fields is regarded as the average crystal grain size of the shell 3. The number of observation fields is set to, for example, five or more.

[0047] (Precipitation Layer) In this embodiment, the outer peripheral surface of the shell 3 has a precipitate layer 3a containing Ti precipitates. The precipitate layer 3a is a part of the shell 3. The precipitate layer 3a may be provided continuously or discontinuously along the outer peripheral surface of the shell 3. The shell 3 has the precipitate layer 3a on the outer peripheral side and an inner region inside the precipitate layer 3a. Typically, the amount of Ti precipitates in the precipitate layer 3a is greater than the amount of Ti precipitates in the inner region. For example, when a cross section of the shell 3 is observed in a given observation field of view, the number of Ti precipitates contained in the precipitate layer 3a is greater than the number of Ti precipitates contained in the inner region. In one example, the amount of Ti precipitates decreases from the outer periphery of the precipitate layer 3a toward the inner region. In another example, in the observation field, Ti precipitates are dispersed at a relatively high density in the precipitate layer 3a, and at a relatively low density in the inner region. In yet another example, within the observation field, the precipitate layer 3 a partially includes a region where Ti precipitates are dispersed at a high density. In this case, within the observation field, the inner region partially includes a region where Ti precipitates are dispersed at a low density, or does not include Ti precipitates. The Ti precipitates are second-phase particles where Ti is concentrated. The Ti contained in the precipitates originates from Ti contained in the specific Co alloy constituting the shell 3.

[0048] As a result of extensive research, the present inventors have made the following findings. When the specific Co alloy constituting the shell 3 contains Ti, Ti may precipitate during the manufacturing process of the wire 1, forming a precipitation layer 3a on the outer surface of the shell 3. The Ti precipitates in the precipitation layer 3a may serve as crack initiation sites, potentially resulting in reduced tensile strength and elongation. In particular, when the diameter of the wire 1 is 100 μm or less, the precipitation layer 3a has a significant effect on the mechanical properties, which is likely to result in reduced tensile strength and elongation. The present inventors have found that controlling the thickness of the precipitation layer 3a can significantly suppress the reduction in tensile strength and elongation of the shell 3. Specifically, they have found that setting the thickness of the precipitation layer 3a to 1.0 μm or less is effective in suppressing the reduction in the mechanical properties of the wire 1.

[0049] The thickness of the deposit layer 3a is preferably 0.1 μm or more and 1.0 μm or less. Here, the thickness of the deposit layer 3a refers to the radial thickness in the cross section of the shell 3. The thickness of the deposit layer 3a may vary along the outer periphery of the shell 3. In this case, the maximum thickness is preferably 0.1 μm or more and 1.0 μm or less. The smaller the thickness of the deposit layer 3a, the smaller the proportion of the deposit layer 3a in the shell 3. Therefore, a decrease in the tensile strength and elongation of the shell 3 can be suppressed. By ensuring that the thickness of the deposit layer 3a is 1.0 μm or less, a wire 1 with excellent tensile strength and elongation can be obtained. The lower limit of the thickness of the deposit layer 3a is not particularly limited, but is, for example, 0.1 μm. The thickness of the deposit layer 3a may further be 0.1 μm or more and 0.8 μm or less, or 0.2 μm or more and 0.6 μm or less. A method for measuring the thickness of the deposit layer 3a will be described in the test examples described below.

[0050] (Insulating Layer) The wire 1 may include an insulating layer 4 as shown in FIG. 1 . The insulating layer 4 covers the outer periphery of the shell 3. The insulating layer 4 is in direct contact with the shell 3. The insulating layer 4 may be provided as needed, and may also be omitted. The insulating layer 4 is made of a resin having electrical insulation properties. Examples of resins that make up the insulating layer 4 include polyurethane resin, polyester resin, polyesterimide resin, polyamideimide resin, and polyimide resin. By including the insulating layer 4, the wire 1 can ensure electrical insulation from surrounding components.

[0051] The insulating layer 4 may have a single layer structure or a multi-layer structure of two or more layers. In this embodiment, the insulating layer 4 is made of a polyesterimide resin. Unlike this embodiment, the insulating layer 4 may be made of two or more layers made of different resins.

[0052] <Method for Manufacturing Wire> The wire 1 of the present embodiment described above can be manufactured by a manufacturing method including the following first, second, and third steps.

[0053] The first step is to fit a core material and a shell material together to produce a wire material, and the second step is to draw the wire material.

[0054] The third step is a step of heat treating the wire material that has been subjected to the wire drawing process. Each step will be described in detail below.

[0055] (First Step) In the first step, a wire material is produced by inserting a wire-shaped core material into a pipe-shaped shell material and fitting the core material and shell material together. The core material is made of Ag. The core material will ultimately become the core 2 of the wire 1. The shell material is made of the specific Co alloy containing Ni, Mo, Cr, and Ti. The shell material will ultimately become the shell 3 of the wire 1. The diameter of the core material is, for example, 3 mm or more and 10 mm or less. The inner diameter of the shell material is slightly larger than the diameter of the core material to allow the core material to be inserted. The outer diameter of the shell material is, for example, 5 mm or more and 35 mm or less. The coverage of the shell 3 in the final wire 1 varies depending on the ratio of the cross-sectional area of ​​the core material to the cross-sectional area of ​​the shell material and the processing method used to fit the core material and shell material together. The diameter of the core material and the outer diameter of the shell material may be selected appropriately so that the coverage of the shell 3 falls within a predetermined range.

[0056] The core material and the shell material can be fitted together by, for example, drawing or rotary swaging. An example of fitting the core material and the shell material using drawing will be described with reference to FIG. 2 . In the case of drawing, the core material 200 is inserted into the shell material 300 and drawn through a die 500 to obtain the wire material 100. The cross-sectional shape of the core material 200 shown in FIG. 2 is circular. The cross-sectional shape of the shell material 300 is annular. The cross-sectional shape of the wire material 100 is also circular. The drawing process brings the core material 200 and the shell material 300 into close contact, bonding the core material 200 and the shell material 300 together. The diameter of the wire material 100 is smaller than the outer diameter of the shell material before drawing. The diameter of the wire material 100 is preferably 4.5 mm or more and 32 mm or less. If the diameter of the wire material 100 is large, repeated wire drawing will be required in the subsequent second process.

[0057] (Second step) In the second step, the wire material is drawn to have a predetermined diameter. The drawing is repeated multiple times until the diameter of the wire material reaches the predetermined diameter. When the drawing is repeated, intermediate heat treatment is performed between multiple drawing steps. The main purpose of this intermediate heat treatment is to soften the wire material during the drawing process and improve its workability.

[0058] The intermediate heat treatment is one of the factors that cause the formation of the above-mentioned precipitation layer 3a. As a result of extensive research, the inventors have found that the thickness of the precipitation layer 3a can be suppressed by controlling the conditions of the intermediate heat treatment. Specifically, the thickness of the precipitation layer 3a can be suppressed by controlling the temperature, time, number of times, and cooling rate among the conditions of the intermediate heat treatment. In particular, in order to suppress the thickness of the precipitation layer 3a, it is effective to appropriately manage the temperature and time of the intermediate heat treatment. The conditions of the intermediate heat treatment should be appropriately selected so that the thickness of the precipitation layer 3a is 1.0 μm or less. Preferred conditions of the intermediate heat treatment for suppressing the thickness of the precipitation layer 3a will be described below.

[0059] The temperature of the intermediate heat treatment is, for example, 850°C or higher and 960°C or lower. When the temperature of the intermediate heat treatment is 850°C or higher, the wire material is easily softened. Furthermore, when the temperature of the intermediate heat treatment is 850°C or higher, the wire material is easily softened in a short time. When the temperature of the intermediate heat treatment is 960°C or lower, the core material made of Ag can be prevented from melting and expanding in volume. Therefore, problems such as the shell material being broken due to the volume expansion of the core material are less likely to occur. The temperature of the intermediate heat treatment is further preferably 860°C or higher and 950°C or lower, or 880°C or higher and 940°C or lower.

[0060] The duration of the intermediate heat treatment is, for example, 5 seconds or more and less than 2 hours. The duration of the intermediate heat treatment is the time for which the wire material is maintained at the above temperature. When the duration of the intermediate heat treatment is 1 second or more, the wire material is easily softened. The shorter the duration of the intermediate heat treatment, the smaller the thickness of the precipitation layer 3a tends to be. When the duration of the intermediate heat treatment is less than 2 hours, the thickness of the precipitation layer 3a is easily suppressed. The duration of the intermediate heat treatment is preferably 10 seconds or more and less than 2 hours, 15 seconds or more and 1.5 hours or less, or 30 seconds or more and 1 hour or less. The duration of the intermediate heat treatment is preferably varied depending on the diameter of the wire material. This is because a larger diameter of the wire material requires more time for the entire wire material to soften. For example, when the diameter of the wire material is 3 mm or more, the duration of the intermediate heat treatment is preferably 1 minute or more, and even 10 minutes or more. Furthermore, when the diameter of the wire material is 1 mm or less, the duration of the intermediate heat treatment may be less than 1 minute.

[0061] The number of intermediate heat treatments is, for example, 20 or less. The fewer the number of intermediate heat treatments, the smaller the thickness of the precipitation layer 3a tends to be. By setting the number of intermediate heat treatments to 20 or less, it is easier to suppress the thickness of the precipitation layer 3a. The number of intermediate heat treatments is preferably 15 or less. The number of intermediate heat treatments depends on the number of wire drawing processes, but is, for example, 4 or more. The number of intermediate heat treatments is preferably, for example, 4 to 20 times, and more preferably 5 to 15 times.

[0062] After the intermediate heat treatment, the wire material is cooled. The cooling rate after the intermediate heat treatment is, for example, 1.5°C / second or more. The faster the cooling rate, the smaller the thickness of the precipitate layer 3a tends to be. A cooling rate of 1.5°C / second or more makes it easier to suppress the thickness of the precipitate layer 3a. The cooling rate is preferably 10°C / second or more. The faster the cooling rate, the more preferable it is. The cooling rate may even be 100°C / second or more.

[0063] In addition, the atmosphere for the intermediate heat treatment is preferably an inert gas atmosphere or a reducing gas atmosphere to suppress oxidation of the wire material. Examples of the inert gas include argon gas and nitrogen gas. Examples of the reducing gas include hydrogen gas and carbon monoxide gas.

[0064] (Third Step) In the third step, the drawn wire material is heat-treated to obtain a wire. The main purpose of this heat treatment is to soften the drawn wire material and adjust the mechanical properties of the final wire. This heat treatment is called the final heat treatment.

[0065] Like the intermediate heat treatment, the final heat treatment is also one of the factors that contribute to the formation of the precipitate layer 3a. Even if the conditions of the intermediate heat treatment are controlled in the second step so that the thickness of the precipitate layer 3a is 1.0 μm or less, the thickness of the precipitate layer 3a may exceed 1.0 μm depending on the conditions of the final heat treatment. Therefore, in order to suppress the thickness of the precipitate layer 3a, it is necessary to control not only the conditions of the intermediate heat treatment but also the conditions of the final heat treatment. The following describes the preferred conditions of the final heat treatment for suppressing the thickness of the precipitate layer 3a.

[0066] The temperature of the final heat treatment is, for example, 900° C. or higher and 950° C. or lower. When the temperature of the final heat treatment is 900° C. or higher, the elongation of the wire is improved, and a wire having an excellent balance between tensile strength and elongation can be obtained. When the temperature of the final heat treatment is 950° C. or lower, the thickness of the precipitation layer 3 a can be easily suppressed.

[0067] The time for the final heat treatment is, for example, 2 seconds to 3 minutes. The time for the final heat treatment is the time for which the wire material is held at the above temperature. When the time for the final heat treatment is 2 seconds or more, it is easy to improve the elongation of the wire. When the time for the final heat treatment is 3 minutes or less, it is easy to suppress the thickness of the deposition layer 3a. It is further preferable that the time for the final heat treatment be 2 seconds to 60 seconds, or 4 seconds to 30 seconds.

[0068] The atmosphere for the final heat treatment is preferably an inert gas atmosphere or a reducing gas atmosphere, similar to the intermediate heat treatment.

[0069] (Other Steps) When manufacturing the wire 1 having the insulating layer 4 shown in FIG. 1 , in addition to the above steps, a fourth step of coating the outer periphery of the wire that has been subjected to the final heat treatment with the insulating layer 4 may be included after the third step.

[0070] (Fourth Step) In the fourth step, for example, a resin constituting the insulating layer 4 is applied to the outer periphery of the wire, and then the resin is baked. This allows the insulating layer 4 to be formed so as to cover the shell 3 of the wire 1, as shown in FIG. 1. If the insulating layer 4 has two or more layers, two or more layers of resin may be applied and baked. For example, when forming an insulating layer 4 having a two-layer structure, a first resin is applied and baked, and then a second resin different from the first resin is applied and baked.

[0071] <Cable> A cable 10 according to an embodiment will be described with reference to Fig. 3. The cable 10 includes a stranded wire 1s and a sheath 40. The cable 10 of this embodiment further includes a shielding layer 30.

[0072] (Stranded Wire) The stranded wire 1s is formed by twisting together a plurality of wires 1. As shown in FIG. 3, the stranded wire 1s of this embodiment has a structure in which four wires 1 are twisted together. The number of wires 1 constituting the stranded wire 1s can be appropriately selected as needed. The number of wires 1 may be two, three, or five or more. The stranded wire 1s may have intervening wires that fill the spaces between the twisted wires 1, i.e., the twisting grooves. In this embodiment, no intervening wires are provided.

[0073] The wire 1 of this embodiment includes an insulating layer 4. Therefore, in the twisted wire 1s, the insulating layer 4 of each wire 1 ensures electrical insulation between the twisted wires 1.

[0074] In this embodiment, a film 20 is wound around the twisted wires 1 s. The film 20 is made of an electrically insulating resin. The film 20 is disposed between the twisted wires 1 s and the shielding layer 30. The film 20 prevents the twisted wires 1 s and the shielding layer 30 from coming into direct contact with each other, thereby preventing damage to the twisted wires 1 s and the shielding layer 30.

[0075] (Shield Layer) The shield layer 30 is provided around the stranded wire 1s. The shield layer 30 is disposed between the stranded wire 1s and the sheath 40. The shield layer 30 is a member that shields electromagnetic waves. In this embodiment, the shield layer 30 is formed by horizontally winding a plurality of strands 31. In the shield layer 30, the strands 31 are horizontally wound so that adjacent strands 31 are in contact with each other. The material that constitutes the strands 31 is, for example, a Cu alloy, an Ag alloy, or an Al alloy. In this embodiment, the strands 31 of the shield layer 30 are made of a Cu alloy.

[0076] (Sheath) The sheath 40 covers the outer periphery of the stranded wire 1s. In this embodiment, the sheath 40 is provided so as to cover the shielding layer 30. In other words, the stranded wire 1s and the sheath 40 are not in direct contact with each other. The sheath 40 is a member that mechanically protects the stranded wire 1s. The sheath 40 is made of, for example, a resin. Examples of resins that make up the sheath 40 include fluororesin, polyester resin, and polyurethane resin. Specific examples of fluororesin include polytetrafluoroethylene resin. In this embodiment, the sheath 40 is made of a fluororesin. The sheath 40 is formed by, for example, extrusion molding.

[0077] <Test Example> A wire sample having a core and a shell was prepared, and the prepared sample was evaluated.

[0078] The wires for each sample were prepared as follows. A wire made of Ag was prepared as the core material. The cross-sectional shape of the core material was circular. A pipe made of a Co alloy was prepared as the shell material. The Co alloy constituting the shell material was commercially available MP35N. The cross-sectional shape of the shell material was annular. The core material was inserted into the shell material, and the core material and the shell material were fitted together to produce the wire material. The core material and the shell material were fitted together using a drawing process. The cross-sectional shape of the wire material was circular.

[0079] The diameter of the core material used in Samples No. 1 and No. 11 was 12.2 mm. The inner diameter of the shell material used in Samples No. 1 and No. 11 was 13.3 mm and the outer diameter was 18.3 mm. The diameter of the core material used in Samples No. 2, No. 3, and No. 12 was 8.4 mm. The inner diameter of the shell material used in Samples No. 2, No. 3, and No. 12 was 9.5 mm and the outer diameter was 15.3 mm. The diameter of the core material used in Samples No. 4, No. 5, and No. 13 was 7.2 mm. The inner diameter of the shell material used in Samples No. 4, No. 5, and No. 13 was 8.1 mm and the outer diameter was 15.3 mm. The diameter of the core material used in Sample No. 6 was 4.5 mm. The shell material used in Sample No. 6 had an inner diameter of 5.0 mm and an outer diameter of 14.8 mm. The core material used in Sample No. 14 had a diameter of 11.2 mm. The shell material used in Sample No. 14 had an inner diameter of 12.0 mm and an outer diameter of 15.3 mm. The core material used in Sample No. 15 had a diameter of 4.0 mm. The shell material used in Sample No. 15 had an inner diameter of 5.0 mm and an outer diameter of 18.3 mm.

[0080] In Samples No. 1, No. 11, and No. 15, the diameter of the wire material in which the core material and the shell material were fitted together was 16 mm. In Samples No. 2 to No. 6, No. 12, No. 13, and No. 14, the diameter of the wire material was 13.5 mm.

[0081] The prepared wire material was drawn until its diameter reached 0.040 mm, i.e., 40 μm, or 0.055 mm, i.e., 55 μm. The drawing was performed cold. The drawing was repeated multiple times, with intermediate heat treatment performed during the drawing. After the drawing was completed, the wire material was subjected to final heat treatment. The intermediate heat treatment and final heat treatment conditions were varied for each sample. The heat treatment conditions were Condition A shown in Table 1 for Samples No. 1 and No. 15. Condition B shown in Table 1 for Samples No. 2, No. 3, No. 4, No. 6, and No. 14. Condition C shown in Table 1 for Sample No. 5. Condition D shown in Table 2 for Sample No. 11. Condition E shown in Table 2 for Sample No. 12. Condition F shown in Table 2 for Sample No. 13.

[0082] Each of the conditions A to F shown in Tables 1 and 2 indicates the timing of the heat treatment, as well as the temperature and time of the heat treatment. For each condition, the "Diameter" column indicates the diameter of the wire material. The top of the "Diameter" column indicates the diameter of the wire material before wiredrawing. The bottom of the "Diameter" column indicates the diameter of the wire material after wiredrawing. The diameter of the wire material after wiredrawing is 0.05 mm. The "Diameter" columns indicate the diameters of the wire material during wiredrawing, starting from the second column from the top. When the diameter of the wire material was the diameter entered in the "Diameter" column, heat treatment was performed at the "temperature" and "time" shown in the "Heat Treatment Conditions" column. When the "Diameter" column indicates 0.040 mm or 0.055 mm, the "Heat Treatment Conditions" column indicates the conditions of the final heat treatment. The other "Heat Treatment Conditions" columns indicate the conditions of the intermediate heat treatment. The number of intermediate heat treatments for Condition A was 10. The number of times of intermediate heat treatment is 9 under conditions B, C, and F. The number of times of intermediate heat treatment is 22 under condition D. The number of times of intermediate heat treatment is 20 under condition E.

[0083] For example, in condition A, when the "Diameter" column is 12.5 mm, this means that the wire material was drawn to a diameter of 12.5 mm and then subjected to intermediate heat treatment at 900°C for 1 hour. In condition A, when the "Diameter" column is 0.20 mm, this means that the wire material was drawn to a diameter of 0.20 mm and then subjected to intermediate heat treatment at 920°C for 15 seconds. In condition B, when the "Diameter" column is 0.055 mm, this means that the wire material after drawing was subjected to final heat treatment at a temperature range of 900°C to 940°C for 7 seconds.

[0084] The heat treatment was carried out in a batch furnace for a heat treatment time of 0.5 hours or more, i.e., 30 minutes or more. The heat treatment was carried out in a continuous softening furnace for a heat treatment time of less than 0.5 hours, i.e., less than 30 minutes. The heat treatment atmosphere was an inert gas atmosphere or a reducing gas atmosphere.

[0085]

[0086]

[0087] The wires of the prepared samples were all round wires. The wire diameters of Samples No. 1, No. 15, No. 5, No. 11, and No. 13 prepared under Conditions A, C, D, or F were each 40 μm. The wire diameters of Samples No. 2, No. 3, No. 4, No. 6, No. 14, and No. 12 prepared under Conditions B or E were each 55 μm.

[0088] (Shell Coverage) The shell coverage of the wire of each sample was determined. １ and the cross-sectional area of ​​the shell S ３ The coverage was measured. ３ / S １ ) × 100. The shell coverage of each sample is shown in Table 3.

[0089] (Thickness of Deposit Layer) The thickness of the deposit layer on the wire of each sample was measured. The thickness of the deposit layer was measured as follows: A longitudinal section of the wire was taken, and the cross section of the shell was observed using an SEM. Of the cross section of the shell, the area near the outer peripheral surface of the shell was observed at a magnification of 20,000x. From this observation field, five areas of the outer peripheral surface of the shell were selected. The selected areas were observed at a magnification of 100,000x. It was determined whether or not precipitates were present in the observation field. The observation field was scrolled from the outer peripheral surface of the shell toward the center of the shell until no precipitates were present in the observation field. The distance to the precipitate located farthest from the outer peripheral surface of the shell was measured. The same operation was performed for the other selected areas, and the distance to the precipitate located farthest from the outer peripheral surface of the shell was measured. The average of the measured distances was considered to be the thickness of the deposit layer. The thickness of the deposit layer for each sample is shown in Table 3.

[0090] The average crystal grain size of the shell in each sample wire was measured by the method described above in the section <Average crystal grain size of the shell>.

[0091] (Mechanical Properties) The mechanical properties of the wires of each sample were evaluated, specifically, the tensile strength and elongation were measured.

[0092] The tensile strength and elongation of the wire were measured as follows. The wire was cut to prepare a test piece with a length of 100 mm. The test piece was pulled at a pulling rate of 50 mm / min, and the tensile strength of the wire was determined as the tensile strength at the time the test piece broke. The elongation of the wire was determined by measuring the length at which the test piece broke, subtracting the length of the test piece before pulling from the length at break, and dividing the result by the length of the test piece before pulling, and expressed as a percentage. The tensile strength and elongation of the wire for each sample are shown in Table 3.

[0093] (Conductivity) Furthermore, the conductivity of the wire of each sample was measured. The measurement results are shown in Table 3.

[0094]

[0095] The wires of Samples No. 1 to No. 6 have excellent elongation properties, with elongation of 12% or more. Furthermore, the wires of Samples No. 1 to No. 6 have tensile strengths of 600 MPa or more, and even 700 MPa or more, combining high tensile strength and high elongation. The wires of Samples No. 1 to No. 6 all have precipitate layer thicknesses of 1.0 μm or less, and even 0.5 μm or less. Furthermore, the wires of Samples No. 1 to No. 6 all have average crystal grain sizes of 0.8 μm or less. Samples No. 1, No. 2, No. 4, and No. 6 all have average crystal grain sizes of 0.5 μm or less. In contrast, the wires of Samples No. 11 to No. 13 have elongations of less than 12%, which means they have inferior elongation properties compared to the wires of Samples No. 1 to No. 6. All wires of Samples No. 11 to No. 13 had precipitate layer thicknesses exceeding 1.0 μm. These results suggest that the thickness of the precipitate layer adversely affects the elongation of the wire. It can be seen that controlling the precipitate layer thickness to 1.0 μm or less effectively suppresses the deterioration of elongation. The wire of Sample No. 14 had a precipitate layer thickness equivalent to that of the wires of Samples No. 1 to No. 6, and also had the same elongation (12% or more), but due to the low coverage of 40%, the tensile strength was 590 MPa, which did not reach 600 MPa. The wire of Sample No. 15 had a precipitate layer thickness equivalent to that of the wires of Samples No. 1 to No. 6, and also had the same elongation (12% or more), but due to the high coverage of 95%, the electrical conductivity was low (4.9% IACS).

[0096] The reason why the thickness of the precipitate layer in Samples No. 1 to No. 6 could be suppressed to 1.0 μm or less is believed to be due to the control of the heat treatment conditions. For Samples No. 1 to No. 6, as shown in Conditions A to C in Table 1, the temperature of all intermediate heat treatments was controlled to 850°C or higher and 960°C or lower, and the duration of all intermediate heat treatments was controlled to less than 2 hours, particularly 1 hour or less. Furthermore, for Samples No. 1 to No. 6, the number of intermediate heat treatments was 20 or less, and even 15 or less. In particular, for Samples No. 1 to No. 6, the number of times that heat treatments were performed for 1 hour or more was low. Specifically, the number of times that intermediate heat treatments were performed for 1 hour or more was 5 or less, and even 3 or less. Heat treatment Condition A applied to Sample No. 1 involved two 1-hour intermediate heat treatments. For Samples No. 2 to No. 6, the number of intermediate heat treatments was 10 or less, and even 15 or less. In the heat treatment conditions B or C applied to sample No. 6, all intermediate heat treatment times were less than 1 hour, and even 0.5 hours or less. Sample No. 14, which was subjected to heat treatment condition B for sample No. 2, and sample No. 15, which was subjected to heat treatment condition A for sample No. 1, also achieved a precipitation layer thickness of 1.0 μm or less. In contrast, samples No. 11 and No. 12 were subjected to intermediate heat treatment for 2 hours or more at least once, as shown in Table 2 under conditions D and E, which is thought to be the reason for the thicker precipitation layer. Furthermore, samples No. 11 and No. 12 were subjected to intermediate heat treatment for 1 hour or more 10 times or more, and even 15 times or more. Furthermore, samples No. 11 and No. 12 were subjected to intermediate heat treatment for 2 hours or more twice or more. In Sample No. 13, the final heat treatment time was set to 2 hours, as shown in Condition F in Table 2, which is thought to have increased the thickness of the precipitate layer and the average crystal grain size of the shell. Note that the mechanical properties of the wires differ between Sample No. 2 and No. 3, which is thought to be due to the difference in the final heat treatment temperature, which was in the range of 900°C to 940°C.

[0097] In addition, the test results reveal the following: (1) A comparison of Samples No. 1 to No. 6 reveals that the smaller the shell coverage, the higher the wire conductivity. This is because the smaller the shell coverage, the greater the area ratio of the core in the wire cross section. (2) A comparison of Samples No. 2, No. 4, and No. 6, which were subjected to the same heat treatment conditions, reveals that the larger the shell coverage, the higher the tensile strength. This is because the larger the shell coverage, the greater the area ratio of the shell in the wire cross section.

[0098] Two wires were produced by varying the conditions for the intermediate heat treatment and the final heat treatment. One of the two wires was Sample A, and the other was Sample B. The elongation of each sample wire was measured, and Sample A had an elongation of 29.3%. Sample B had an elongation of 11.6%. Figure 4 shows an SEM image of the longitudinal cross section of the wire of Sample A, observed at 1000x magnification. In the SEM image of Figure 4, the light gray central portion is the core 2, and the dark gray portions sandwiching the core 2 from above and below are the shell 3. The black portions located above and below the shell 3 are the background. This is also true for the SEM image of Figure 7. Figure 5 shows an SEM image of the longitudinal cross section of the wire of Sample A, observed at 20,000x magnification near the outer surface of the shell 3. In Figure 5, the lower dark gray portion is the shell 3, and the upper black portion is the background. This is also true for the SEM images of Figures 6, 8, and 9. FIG. 6 shows an SEM image of the outer peripheral surface region of the shell 3 in the SEM image shown in FIG. 5 , observed at a magnification of 100,000 times. FIG. 7 shows an SEM image of the longitudinal cross section of the wire of sample B, observed at a magnification of 1,000 times. FIG. 8 shows an SEM image of the longitudinal cross section of the wire of sample B, observed at a magnification of 20,000 times, near the outer peripheral surface of the shell 3. FIG. 9 shows an SEM image of the outer peripheral surface region of the shell 3 in the SEM image shown in FIG. 8 , observed at a magnification of 100,000 times. The SEM images of FIGS. 5 and 8 show a precipitate layer 3a. In the SEM images of FIGS. 6 and 9 , the round granular objects are precipitates 3b. When the thickness of the precipitate layer in the wire of each sample was measured, the thickness of the precipitate layer in sample A was 0.27 μm, and the thickness of the precipitate layer in sample B was 1.9 μm.

[0099] 1 wire, 1s stranded wire, 2 core, 3 shell, 3a precipitate layer, 3b precipitate, 4 insulating layer, 10 cable, 20 film, 30 shield layer, 31 strand, 40 sheath, 100 wire material, 200 core material, 300 shell material, 500 die.

Claims

1. A wire comprising a core and a shell covering the outer periphery of the core, the core comprises silver; The shell is Nickel: 33.0% by mass or more and 37.0% by mass or less; Molybdenum: 9.0% by mass or more and 10.5% by mass or less; Chromium: 19.0% by mass or more and 21.0% by mass or less; Contains titanium in an amount of 0.5% by mass or more and 1.2% by mass or less, The balance comprises cobalt and inevitable impurities, The wire has a diameter of 100 μm or less; The elongation of the wire is 12% or more. Wire.

2. 2. The wire according to claim 1, wherein in a cross section of the wire, the ratio of the cross-sectional area of ​​the shell to the cross-sectional area of ​​the wire is 50% or more and 90% or less.

3. a precipitate layer including titanium precipitates on an outer peripheral surface of the shell; The wire according to claim 1 or 2, wherein the thickness of the deposition layer is 0.1 μm or more and 1.0 μm or less.

4. The wire according to claim 1 or 2, wherein the average crystal grain size of the metal constituting the shell in the longitudinal cross section of the wire is 0.1 μm or more and 5.0 μm or less.

5. 3. The wire according to claim 1 or claim 2, wherein the tensile strength of the wire is 600 MPa or more.

6. The wire according to claim 1 or 2, further comprising an insulating layer covering an outer periphery of the shell.

7. A structure in which a plurality of wires according to claim 1 or 2 are twisted together. Stranded wire.

8. The stranded wire according to claim 7; and a sheath covering the outer periphery of the stranded wire. cable.

9. 9. The cable of claim 8, further comprising a shielding layer between the strands and the sheath.

10. A method for producing the wire according to claim 1, comprising the steps of: A step of producing a wire material by fitting a core material and a shell material; A step of drawing the wire material; and performing a heat treatment on the wire material that has been subjected to the wire drawing process. In the wire drawing process, intermediate heat treatment is performed between multiple wire drawing processes at a temperature of 850°C or higher and 960°C or lower for less than 2 hours, and the number of intermediate heat treatments is 20 or less.