JP2011146352A - Cu-Ag ALLOY WIRE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrafine Cu-Ag alloy wire suitable for a shield conductor of a coaxial cable and method for manufacturing the same, and also to provide a coaxial cable. <P>SOLUTION: The Cu-Ag alloy wire is used for a shield conductor of a coaxial cable, and contains 1-20 mass% of Ag, with the rest being Cu and an impurity, and has a conductivity of 82%IACS or above, a tensile strength of 800 MPa or above, and a wire diameter of 0.05 mm or below. By using the Cu-Ag alloy wire for the shield conductor, a coaxial cable having a superior shield property can be obtained. In manufacturing the Cu-Ag alloy wire, an intermediate heat treatment is applied at a heating temperature of 350-550°C to a rolling material in the middle of a rolling process. For the intermediate heat treatment, a relationship between the wire diameter of the rolling material to be applied with the intermediate heat treatment and the conductivity and tensile strength of a final wire obtained by applying a rolling process to the heat-treated material applied with the intermediate heat treatment is preliminarily found. The intermediate heat treatment is conducted when the wire has a predetermined diameter inversely calculated from the final wire diameter based on the relationship so that the Cu-Ag alloy wire having the final wire diameter may have a conductivity of 82%IACS or above and a tensile strength of 800 MPa or above. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ultrafine Cu-Ag alloy wire, a coaxial cable including a shield conductor made of the ultrafine wire, and a method for producing the Cu-Ag alloy wire. In particular, the present invention relates to an ultrafine Cu—Ag alloy wire suitable for a shield conductor of a coaxial cable.

  As an electric wire used in various devices such as an electronic device and a medical device, there is a coaxial cable including a shield conductor (outer conductor) provided on an outer periphery of a central conductor (inner conductor) via an insulating layer. The shield conductor is configured by, for example, winding a plurality of strands around the outer periphery of the insulating layer. Conventionally, a copper wire is used as the element wire.

  In recent years, further downsizing of the coaxial cable has been demanded with the demand for downsizing and weight reduction of the equipment. However, if the copper wire has a low strength and is a very fine wire of 0.1 mm or less, it is easy to break when stress due to repeated bending or twisting is applied. In particular, when a shield conductor is formed by winding a wire around the outer periphery of an insulating layer as described above, not only bending during use but also twisting (for example, lateral winding in a spiral shape) when forming a shield conductor For example, it is desirable that the wire used for the shield conductor has high breaking strength and fatigue strength. Therefore, Patent Document 1 proposes to use a Cu—Ag alloy wire having higher strength than a copper wire as a shield conductor.

JP2003-132745A

  Conventionally, wire rods that are ultrafine wires of 0.05 mm or less and that have characteristics suitable for shield conductors of coaxial cables have not been sufficiently studied. As described above, the shield conductor is desired to be excellent in breaking strength and fatigue characteristics (flexibility / twist resistance).

  Furthermore, it is desired that the shield conductor of the coaxial cable has excellent shielding characteristics so that it is not easily affected by external noise. The shield characteristics are affected by the conductivity, and when the conductivity is lowered, the shield characteristics are lowered. Therefore, it is desirable that the shield conductor has high conductivity. However, a wire for a shield conductor that is an extremely fine wire as described above and has both high strength and high conductivity has not been obtained.

  Here, conventionally, when improving the characteristics of the coaxial cable, the center conductor has been mainly studied, and the shield conductor has not been sufficiently studied. In general, the electrical conductivity required for the central conductor of the coaxial cable is sufficient to be 65% IACS or more, and approximately 70% IACS to 80% IACS, and such a strand is also used as a shield conductor. However, by further increasing the conductivity of the shield conductor, a coaxial cable having excellent shielding characteristics can be obtained.

  On the other hand, Patent Document 1 discloses a Cu—Ag alloy wire having excellent bending resistance. In general, a copper alloy can be increased in strength by an increase in additive elements, but its conductivity is lowered. Therefore, it is considered difficult to further improve the electrical conductivity of the Cu—Ag alloy wire described in Patent Document 1.

  Accordingly, one of the objects of the present invention is to provide an ultrafine Cu—Ag alloy wire that is excellent in both conductivity and strength and suitable for a shield conductor. Another object of the present invention is to provide a method for producing a Cu-Ag alloy wire that can produce an ultrafine Cu-Ag alloy wire having both high conductivity and strength. Furthermore, the other object of this invention is to provide the coaxial cable which provides the shield conductor comprised with the said Cu-Ag alloy wire.

(Cu-Ag alloy wire)
[overall structure]
The Cu—Ag alloy wire of the present invention contains 1% by mass or more and 20% by mass or less of Ag, and the balance is composed of Cu and impurities. This Cu-Ag alloy wire has a conductivity of 82% IACS or more, a tensile strength of 800 MPa or more, and a wire diameter of 0.05 mm or less (excluding 0 mm). And this Cu-Ag alloy wire is used for the shield conductor of a coaxial cable.

  The Cu-Ag alloy wire of the present invention contains Ag in a specific range, so that even if the wire diameter is as fine as 0.05 mm or less, the strength is high and the fracture strength and fatigue characteristics are excellent. And the Cu-Ag alloy wire of the present invention has high electrical conductivity. When such a Cu-Ag alloy wire of the present invention is used as a constituent wire of a shield conductor of a coaxial cable, (1) it is difficult to break when wound around the outer periphery of an insulating layer in forming a shield conductor, (2 ) Even when repeated bending or twisting is applied during use of the coaxial cable, it is difficult to break, and (3) it has excellent shielding properties.

[composition]
The Cu-Ag alloy constituting the Cu-Ag alloy wire of the present invention is a binary alloy having an Ag content of 1% by mass to 20% by mass. When the Ag content is less than 1% by mass, it is difficult to obtain the effect of improving the strength due to the solid solution of Ag. Even if the conditions are adjusted, it is difficult to satisfy a tensile strength of 800 MPa or more. If it exceeds 20% by mass, the electric conductivity decreases due to excessive dissolution of Ag, and it is difficult to satisfy the electric conductivity of 82% IACS or more. It is more preferable that the Ag content is 1% by mass or more and 15% by mass or less because high strength and high electrical conductivity can be provided in a balanced manner. A raw material is prepared so that it may become a predetermined composition.

[Shape and size]
The Cu-Ag alloy wire of the present invention typically includes a round wire having a circular cross section, and the wire diameter is 0.05 mm (50 μm) or less. A Cu—Ag alloy wire having a wire diameter of 0.01 mm (10 μm) to 0.03 mm (30 μm) can also be obtained by appropriately changing the degree of processing during wire drawing.

[Tensile strength]
The Cu-Ag alloy wire of the present invention has high strength and a tensile strength of 800 MPa or more. The tensile strength can be further increased by appropriately changing the composition (Ag content), the processing degree during wire drawing, the intermediate heat treatment conditions described later, and the like. In particular, the tensile strength is preferably 800 MPa or more and 1600 MPa or less. When the tensile strength satisfies the above range, for example, even if the Cu-Ag alloy wire of the present invention is wound to form a shield conductor, or a coaxial cable including the shield conductor is repeatedly bent or twisted, The inventive Cu-Ag alloy wire is difficult to break.

[conductivity]
The Cu-Ag alloy wire of the present invention has high conductivity and satisfies 82% IACS or more. Although it depends on manufacturing conditions and composition, a Cu—Ag alloy wire satisfying an electrical conductivity of 85% IACS or more can be obtained. Since the shield conductor which is excellent in a shield characteristic is obtained, so that electrical conductivity is high, the upper limit of electrical conductivity is not provided in particular.

[Plating layer]
The Cu—Ag alloy wire of the present invention preferably has a form in which a plating layer is provided on the surface thereof. Here, when attaching a connector or a terminal to the end of the coaxial cable, solder is used. Cu-Ag alloy has poor wettability with solder. On the other hand, when the Cu-Ag alloy wire of the present invention having a plating layer is used as a shield conductor of a coaxial cable, wettability with the solder can be improved. Further, when attaching the connector or the like, the shield conductor may be removed by a laser in order to expose the end portion of the central conductor of the coaxial cable. When the element wire constituting the center conductor and the element wire constituting the shield conductor have the same composition, there is a possibility that not only the shield conductor but also the center conductor is cut by the laser. On the other hand, the wire constituting the shield conductor has a plating layer so that the laser absorption characteristics of the center conductor and the laser absorption characteristics of the shield conductor are different, and the center conductor is appropriately exposed. be able to. Moreover, the corrosion resistance of a Cu-Ag alloy wire can be improved by having a plating layer.

  Examples of the plating layer include one or more selected from Ag, Ag alloy, Sn, and Sn alloy. The plating layer may be a single layer or a plurality of layers. The thickness of the plating layer can be selected as appropriate, and is preferably about 0.1 μm to 0.4 μm because of excellent solderability.

[Application (coaxial cable)]
The Cu-Ag alloy wire of the present invention is used as a constituent wire of a shield conductor of a coaxial cable. Therefore, the coaxial cable of the present invention comprises, in order from the center, a central conductor, an insulating layer, and a shield conductor, and the shield conductor is configured by winding a plurality of fine wires around the outer periphery of the insulating layer. Then, it is proposed that the fine wire is composed of the Cu-Ag alloy wire of the present invention. The Cu-Ag alloy wire of the present invention has high conductivity as described above. Therefore, the coaxial cable of the present invention can have excellent shielding characteristics by including a shield conductor composed of the Cu-Ag alloy wire of the present invention. Moreover, the Cu-Ag alloy wire of the present invention is excellent in bending resistance and twisting resistance due to its high strength as described above. Therefore, when forming the shield conductor by winding the Cu-Ag alloy wire of the present invention around the outer periphery of the insulating layer, it is difficult to break even if stress such as bending or twisting is applied, and the shield conductor can be formed with high productivity. In addition, it is difficult to break even when stress is applied due to bending or twisting when using a coaxial cable. Therefore, it is expected that the coaxial cable of the present invention can be used for a long time.

(Production method)
The said Cu-Ag alloy wire of this invention can be manufactured with the manufacturing method of the following this invention Cu-Ag alloy wire, for example. The method for producing a Cu-Ag alloy wire of the present invention relates to a method for producing a Cu-Ag alloy wire used for a shield conductor of a coaxial cable, and includes the following casting step, wire drawing step, and heat treatment step. Prepare.
Casting process: A process for producing a cast material using a molten metal in which Ag and Cu as raw materials are dissolved.
Wire drawing process: A Cu-Ag alloy wire in which the above cast material is drawn, Ag is contained in an amount of 1% by mass to 20% by mass, the balance is Cu and impurities, and the final wire diameter is 0.05mm or less. The process of producing.
Heat treatment step: A step of performing an intermediate heat treatment on the wire drawing material in the middle stage until the Cu—Ag alloy wire having the final wire diameter is obtained.
In particular, the intermediate heat treatment is performed at a heating temperature of 350 ° C. or higher and 550 ° C. or lower. Further, the relationship between the wire diameter of the drawn wire subjected to the intermediate heat treatment and the electrical conductivity and tensile strength of the final wire obtained by subjecting the heat treated material subjected to the intermediate heat treatment to the wire drawing up to the final wire diameter. Obtained in advance and set retrospectively from the final wire diameter based on the above relationship so that the conductivity of the Cu-Ag alloy wire with the final wire diameter is 82% IACS or higher and the tensile strength is 800 MPa or higher. The intermediate heat treatment is performed at a predetermined wire diameter.

  The present inventors examined the relationship between wire drawing and intermediate heat treatment in producing the above-described high conductivity and high strength Cu—Ag alloy wire. Here, when manufacturing a very fine wire having a final wire diameter of 0.05 mm or less, drawing is usually performed in multiple stages (multi-pass). Further, during the drawing process (between passes), an intermediate heat treatment may be performed for the purpose of removing the strain introduced into the wire by the drawing process and improving the drawing property. This intermediate heat treatment has been conventionally performed at an arbitrary stage. However, it is not an arbitrary stage, and an intermediate heat treatment is performed when a specific wire diameter is reached, and the condition of the intermediate heat treatment is set to the above-mentioned specific conditions, so that an ultrafine Cu- The knowledge that an Ag alloy wire is obtained was obtained. The reason why such a high conductivity and high strength Cu—Ag alloy wire is obtained is considered as follows.

  When the Cu-Ag alloy is heat-treated and Ag is precipitated from the parent phase Cu, the conductivity can be improved. However, when there is too much precipitation amount of Ag, the strength improvement effect by the solid solution of Ag will reduce. Moreover, the strength can be improved by drawing the precipitated Ag into a fibrous shape by drawing. However, if the Ag is not sufficiently stretched (long fiber), that is, if the wire drawing after the heat treatment is insufficient, the precipitated Ag is the starting point of fracture during the subsequent wire drawing. There is a risk of becoming. Therefore, heat treatment is performed before wire drawing to the final wire diameter, that is, before wire drawing or in the middle of wire drawing so that an appropriate amount of Ag is precipitated, and the precipitated Ag is in an appropriate state (fibrous ) Is drawn. As described above, when appropriate heat treatment and wire drawing are performed, a Cu-Ag alloy wire having high conductivity and high strength can be obtained.

  On the other hand, when wire drawing is used as an index, the electrical conductivity and tensile strength are in a trade-off relationship. That is, if a lot of wire drawing is performed (the degree of work is increased), the tensile strength is increased, but strain accompanying the processing is accumulated in the wire drawing material, and the electrical conductivity of the wire drawing material tends to decrease. On the other hand, if there is little wire drawing (if the degree of work is small), the strain associated with the work will not be introduced much into the wire drawing material, so that the electrical conductivity of the wire drawing material can remain high, but due to work hardening etc. It is difficult to obtain an improvement in strength and the tensile strength is lowered.

  On the other hand, when the wire drawing material is subjected to a heat treatment after the wire drawing, the electrical conductivity can be improved by removing the strain as described above. For this reason, even when wire drawing with the same degree of processing is performed, when heat treatment is performed, a wire with higher conductivity can be obtained as compared with the case where heat treatment is not performed. In addition, as the number of intermediate heat treatments increases, the amount of accumulated strain is reduced, so even if the same degree of wire drawing is performed, if heat treatment is performed multiple times, the heat treatment is performed once. Compared with the case where it did, it exists in the tendency for a wire material with higher electrical conductivity to be obtained. And, when the number of intermediate heat treatment is constant, when the intermediate heat treatment is applied to a wire rod having a small wire diameter (hereinafter referred to as a thin diameter treatment material) by drawing to a size close to the final wire diameter, Compared with the case where intermediate heat treatment is applied to a wire with a large wire diameter (hereinafter referred to as a large diameter treatment material) that has not been subjected to much wire drawing, it is more conductive when the intermediate heat treatment is applied to the thin diameter treatment material. The rate tends to be high. Since the electrical conductivity and the tensile strength are in a trade-off relationship as described above, the above-mentioned large diameter treated material tends to have a higher tensile strength. From these facts, it can be said that it is preferable to perform heat treatment at an appropriate time during the wire drawing for improving the electrical conductivity.

  From the above, for example, when the intermediate heat treatment is performed once, if the intermediate heat treatment is performed when the wire diameter is thin, a wire with high conductivity is obtained, and when the heat treatment is performed a plurality of times, the conductivity can be further improved. By conducting an intermediate heat treatment when the wire diameter is large, a wire with high tensile strength can be obtained. By designing the stage and number of times of intermediate heat treatment according to the wire diameter of the wire to be subjected to intermediate heat treatment, a Cu-Ag alloy wire satisfying a conductivity of 82% IACS or higher and a tensile strength of 800 MPa or higher. Is obtained. Therefore, in the production method of the present invention, the intermediate heat treatment applied in the middle of the wire drawing process is not performed at an arbitrary stage, but the wire diameter of the drawn wire subjected to the intermediate heat treatment as described above, the conductivity and tensile strength of the final wire. It is prescribed that the timing (wire diameter) for performing the intermediate heat treatment is set based on this relationship.

  The intermediate heat treatment may be performed once or a plurality of times. In the case of multiple times, the relationship between the wire diameter of the drawn wire subjected to each intermediate heat treatment and the electrical conductivity and tensile strength of the wire obtained by subjecting the heat treated material subjected to the intermediate heat treatment to the next drawing. Based on the relationship of each time, the wire is drawn each time so that the conductivity of the Cu-Ag alloy wire of the final wire diameter is 82% IACS or more and the tensile strength is 800 MPa or more. The intermediate heat treatment may be performed at a predetermined wire diameter set retrospectively from the processed wire diameter.

  In addition, you may heat-process with respect to the raw material before a wire drawing in order to remove the distortion introduce | transduced by the processes (rolling etc.) before a wire drawing.

Alternatively, the Cu-Ag alloy wire of the present invention can be manufactured by the following manufacturing method. This production method is a method of producing a fine wire having a final wire diameter of 0.05 mm or less by drawing a material containing 1 mass% or more and 20 mass% or less of Ag. Prepare.
Surface layer removal step: The surface layer of the wire in the middle of drawing until reaching the final wire diameter is removed. This surface layer removing step particularly includes a thin wire processing step of removing a surface layer of a thin wire having a wire diameter of 1.0 mm or less.
In the fine wire processing step, the removal of the surface layer is performed so that the thickness t of the surface layer to be removed satisfies t / r ≧ 0.02 when r is 1/2 of the wire diameter of the wire before the removal of the surface layer. . The thickness t of the surface layer is a distance along the radial direction of the wire from the surface of the wire. Moreover, the cross-sectional shape of a wire is typically circular.

  In the above manufacturing method, a specific amount of surface layer is not applied to the wire before the wire drawing process, but to a specific size in the middle of wire drawing, specifically 1.0 mm or less, not just before the material before wire drawing or the final wire diameter. By removing, disconnection during wire drawing can be effectively reduced. Therefore, in the above manufacturing method, an ultrafine Cu—Ag alloy wire of 0.05 mm or less can be continuously produced, and a long Cu—Ag alloy wire can be obtained. In addition, the Cu-Ag alloy wire of the present invention having high conductivity and high strength can also be obtained by the above production method.

  The above manufacturing method is excellent in productivity of ultrafine Cu-Ag alloy wires because there are few disconnections. In particular, the constituent wire of the shield conductor in the coaxial cable is disposed outside the center conductor. For this reason, in forming the shield conductor, it is necessary to use more strands than the constituent wires of the center conductor or to use strands longer than the constituent wires of the center conductor. Therefore, it is desired that the constituent wire of the shield conductor uses a method capable of continuously producing a long wire without breaking. The above manufacturing method can sufficiently meet this requirement. In addition, the production method of the present invention in which the intermediate heat treatment is performed at a specific time during the wire drawing process described above includes the above-mentioned surface layer removal step, thereby producing an ultrafine Cu-Ag alloy wire with high conductivity and high strength. It can be manufactured with good performance.

  If the surface layer is removed so that the total t / r in each step is 0.08 or more, particularly 0.12 or more when the surface layer removal step is performed multiple times, the amount of removal of the surface layer increases. And foreign matter can be sufficiently removed, and occurrence of disconnection can be reduced. Therefore, in this embodiment, the productivity of the ultrafine Cu—Ag alloy wire is further improved.

  Furthermore, in the two manufacturing methods described above, it is preferable to use a cast material manufactured as follows. The prepared raw material Cu and raw material Ag are melted in a crucible made of high-purity carbon, and this mixed molten metal is kept at a temperature higher than the liquidus temperature of the mixture of Cu and Ag for 30 minutes or more, so that impurities are introduced on the surface of the mixed molten metal. Separate. Thereafter, a cast material is produced from the molten metal from which the impurities are separated, using a mold made of high purity carbon. This cast material has few foreign substances that can be involved in disconnection. By using such a cast material as a material for wire drawing, wire breakage during wire drawing can be further effectively reduced, and the productivity of ultrafine Cu-Ag alloy wire is further improved.

  In the production of the Cu-Ag alloy wire of the present invention, as a material used for wire drawing, for example, a material obtained by cold rolling a cast material can be used. In order to reduce foreign substances contained in this material, it is preferable to use raw material Cu or raw material Ag having a high purity, for example, a four-nine class (purity 99.99%) or higher.

  The wire drawing (typically cold) is performed over a plurality of passes until the final wire diameter is reached. The degree of processing of each pass may be appropriately adjusted in consideration of the composition (Ag content), final wire diameter, tensile strength, conductivity, and the like. In particular, the cold wire drawing performed first is preferably 70% or more, since the subsequent wire drawing is easily performed at a predetermined degree of processing.

  In the manufacturing method of the present invention, at least one intermediate heat treatment is performed during the wire drawing process, particularly at a predetermined wire diameter set based on the above-described relationship. By this intermediate heat treatment, processing strain introduced into the material before the intermediate heat treatment is removed to improve the conductivity and facilitate subsequent wire drawing. Further, the strength of the ultrafine wire is improved by precipitating Ag by an intermediate heat treatment and making the Ag precipitate into a fibrous form by subsequent wire drawing. The conditions for the intermediate heat treatment are heating temperature: 350 ° C. to 550 ° C. If the temperature is lower than 350 ° C, Ag cannot be sufficiently precipitated, and the strain cannot be removed sufficiently, making it difficult to improve the electrical conductivity. If the temperature exceeds 550 ° C, Ag is excessively precipitated, resulting in improved strength due to solid solution strengthening. It becomes difficult to obtain the effect. In particular, the heating temperature is preferably 400 ° C to 450 ° C. The holding time is preferably 0.5 hours to 10 hours.

  When the surface layer is removed during the wire drawing process, it is preferable to use chemical treatment or electrochemical treatment for the removal. Since the target to remove the surface layer is a thin wire with a wire diameter of 1.0 mm or less, if you try to remove the surface layer with a peeling die used for normal skinning, the center of the wire will be at the center of the die hole. It is difficult to match, leading to a decrease in productivity. On the other hand, chemical treatment and electrochemical treatment can be easily applied to a wire having an arbitrary wire diameter, and the surface after the treatment is very smooth and hardly causes wrinkles that cause disconnection. Accordingly, when the drawn wire is further drawn, it is difficult to break and excellent in drawability. Typical processing includes chemical polishing and electrolytic polishing. A known process may be used. The wire material for removing the surface layer preferably has a wire diameter of 0.2 mm or more from the viewpoint of reducing the manufacturing cost. Also in the embodiment in which the surface layer is removed as described above, at least one intermediate heat treatment is performed at any stage before the final wire diameter. That is, it may be before or during drawing. The intermediate heat treatment conditions are preferably the same as those in the above-described production method of the present invention.

  When producing a Cu—Ag alloy wire having a plated layer, the plated layer may be formed during the drawing process or after the final drawing. When the surface layer is removed during the wire drawing process, the plating layer can be formed at any time after the surface layer is removed.

  The Cu-Ag alloy wire of the present invention has high conductivity and high strength. The coaxial cable of the present invention is excellent in shielding properties and excellent in breaking strength and fatigue strength. According to the method for producing a Cu-Ag alloy wire of the present invention, it is possible to produce an ultrafine Cu-Ag alloy wire having a wire diameter of 0.05 mm or less and having a high conductivity and high strength.

Fig. 1 (I) is a graph showing the relationship between the wire diameter subjected to the intermediate heat treatment and the conductivity of the finally obtained Cu-Ag alloy wire, and Fig. 1 (II) is a wire subjected to the intermediate heat treatment. It is a graph which shows the relationship between a diameter and the tensile strength of the Cu-Ag alloy wire finally obtained. FIG. 2 is an explanatory diagram showing a state of the bending test.

(Test Example 1)
Several ultrafine wires made of Cu-Ag alloy were manufactured and the tensile strength and electrical conductivity were investigated. The results are shown in FIG.

  The extra fine wire was produced as follows. Prepare copper as the raw material Cu with a purity of 99.99% or more, and silver grains (Ag) with a purity of 99.99% or more as the raw material Ag, put them in a high-purity carbon crucible, and vacuum-melt them in a continuous casting machine. A mixed molten metal was dissolved. In addition, the addition amount of the silver grain was adjusted so that Ag content with respect to mixed molten metal might be 2 mass%.

  Using the resulting mixed molten metal, a high-purity carbon mold is used to produce a round wire casting with a diameter of φ22.0 mm, and this casting is subjected to multiple passes of cold drawing to obtain a final wire diameter of φ0. A .025 mm (25 μm) Cu—Ag alloy wire was obtained. In particular, an intermediate heat treatment was performed on the wire drawing material in the middle of the wire drawing. Here, a sample subjected to intermediate heat treatment once, a sample subjected to intermediate heat treatment twice, and a sample subjected to three times heat treatment were prepared. Samples that were subjected to an intermediate heat treatment (shown by ▲ in Fig. 1) were prepared by applying an intermediate heat treatment: 450 ° C x 3 hours once when the wire diameter φ was 0.9 mm or 0.32 mm. Cu-Ag alloy wire. Samples subjected to intermediate heat treatment twice (indicated by □ in FIG. 1) are subjected to intermediate heat treatment: 450 ° C x 3 hours once when the wire diameter φ is 8 mm, and then when the wire diameter φ is 0.9 mm A Cu—Ag alloy wire produced by subjecting the second intermediate heat treatment: 450 ° C. × 3 hours to either 0.32 mm or 0.12 mm. Samples that were subjected to intermediate heat treatment three times (indicated by ♦ in FIG. 1) were subjected to intermediate heat treatment: 450 ° C. × 3 hours once when the wire diameter φ was 8 mm and 2.6 mm, respectively, and then the wire diameter φ A Cu—Ag alloy wire produced by subjecting the third intermediate heat treatment: 450 ° C. × 3 hours to either 0.92 mm or 0.32 mm.

  About each obtained Cu-Ag alloy wire, electrical conductivity and tensile strength were measured. Tensile strength was measured in accordance with JIS Z 2241 (1998) (marking distance GL: 10 mm). The conductivity was measured by the bridge method.

  As shown in Fig. 1, even when using a Cu-Ag alloy material with the same composition (in this case, Ag: 2% by mass), the conductivity is different due to the difference in the wire diameter for intermediate heat treatment during wire drawing. It can be seen that the tensile strength is different. Specifically, a Cu-Ag alloy wire with higher conductivity is obtained when the intermediate heat treatment is performed when the wire diameter becomes smaller, and a tensile strength is higher when the intermediate heat treatment is performed when the wire diameter is larger. It can be seen that a high Cu-Ag alloy wire tends to be obtained. Moreover, it turns out that it exists in the tendency which is easy to raise electrical conductivity by increasing the frequency | count of intermediate heat processing.

  From the above test results, the relationship between the wire diameter of the drawn wire subjected to the intermediate heat treatment and the electrical conductivity and tensile strength of the final wire obtained by subjecting the heat treated material subjected to the intermediate heat treatment to the final wire diameter. Based on this relationship, the timing for performing the intermediate heat treatment is determined, and the intermediate heat treatment is performed at the determined predetermined wire diameter, whereby the conductivity is 82% IACS or more and the tensile strength is 800 MPa. It turns out that the above ultrafine Cu-Ag alloy wire is obtained.

(Test Example 2)
A number of ultrafine wires made of Cu-Ag alloy were manufactured, and the mechanical properties, electrical conductivity, and wire drawability were investigated.

<Sample No.2-0>
Electrolytic copper having a purity of 99.99% or more was prepared as a raw material Cu, and silver grains (Ag) having a purity of 99.99% or more were prepared as a raw material Ag. After pickling the prepared electrolytic copper and removing foreign matter adhering to the surface of the electrolytic copper, the pickled electrolytic copper and the silver particles are put into a high-purity carbon crucible and vacuum-dissolved in a continuous casting apparatus. Thus, a mixed molten metal in which Cu and Ag were dissolved was produced. In addition, the addition amount of the silver grain was adjusted so that Ag content with respect to mixed molten metal might be 2 mass%.

  After the silver melt was added, the mixed molten metal was held at a temperature higher than the liquidus temperature of the mixture of Cu and Ag for 30 minutes to separate impurities including foreign matters on the surface of the mixed molten metal in the crucible.

  After separating the impurities, a round wire (cast material) having a wire diameter of φ8.0 mm was manufactured using a high purity carbon mold. The amount of Al and the amount of Si in the obtained cast material were measured. Here, 200 g of the cast material was separated and dissolved in an aqueous solution containing 6.4 mol or more of nitric acid. This solution was filtered with a filter having a pore size of 0.2 μm, and the residue was collected with a filter. The collected residue was dried in a platinum crucible to incinerate the filter, and then melted by adding a flux to give a glassy substance. The obtained glassy substance was dissolved in an aqueous solution containing hydrochloric acid. The work from the melting of the cast material to the melting of the glassy substance was carried out in a clean booth. The amount of Si and Al was quantified by inductively coupled plasma (ICP) emission spectroscopic analysis of the solution in which the glassy substance was dissolved. As a result, the Si content was 0.1 mass ppm and the Al was 0.3 mass ppm, both of which were 1 mass ppm or less. In addition, about 100-200g is sufficient for the quantity of the casting material utilized for the measurement of Si amount and Al amount.

The obtained cast material (wire diameter φ8 mm) was subjected to cold drawing of multiple passes to obtain a wire material having a wire diameter φ of 2.6 mm. This intermediate wire was subjected to an intermediate heat treatment at 400 ° C. for 8 hours and then subjected to chemical polishing to remove the surface layer. Chemical polishing was performed using an aqueous hydrogen sulfate solution as the polishing liquid, with an immersion time of 150 min and a temperature of 30 ° C. The thickness t ₁ of the removed surface layer was t ₁ = 0.15 mm. If 1/2 of the wire diameter φ ₁ is r ₁ , r ₁ = 1.30 and t ₁ / r ₁ ≈0.115. Furthermore, this sample No. 2-0 was subjected to the chemical polishing similar to the above when the wire diameter φ ₂ was 0.9 mm (≦ 1.0 mm), which was an intermediate stage of wire drawing, and the surface layer was Removed. The thickness t ₂ of the removed surface layer was changed by varying the immersion time, and t ₂ = 0.01 mm. When 1/2 of the wire diameter φ ₂ is r ₂ , r ₂ = 0.45, t ₂ / r ₂ ≈0.022 (≧ 0.02). The sum of r ₁ / t ₁ and t ₂ / r ₂ in the removal of the surface layer twice is 0.115 + 0.022 = 0.137 (≧ 0.08).

  After the surface layer was removed for the second time, cold drawing was further performed to obtain wires having final wire diameters φ of 0.021 mm (21 μm) and 0.04 mm. Sn plating was applied to the wire having a final wire diameter of 0.021 mm (plating thickness: 0.1 μm) to obtain a plated Cu—Ag alloy wire. This plated Cu—Ag alloy wire and a Cu—Ag alloy wire having a final wire diameter of φ0.04 mm are designated as sample No. 2-0. In this test, for wire drawing, a die of American Wire Gage standard (AWG standard) was used for all samples.

<Sample No.2-1 to 2-6,100>
Electrolytic copper similar to Test Example 1 was prepared as the raw material Cu, and silver grains (Ag) similar to Test Example 1 were prepared as the raw material Ag. The prepared electrolytic copper was vacuum-melted in a continuous casting apparatus. After electrolytic copper is completely dissolved, the inside of the chamber of the continuous casting apparatus is replaced with argon gas, the prepared silver particles are put into a crucible and melted, and a molten mixture of Cu and Ag is cast and cast. A material (round wire having a wire diameter of φ22 mm or a wire diameter of φ16 mm) was produced. The amount of silver grains added was adjusted so that the Ag content relative to the molten mixture would be the amount shown in Table 1.

  The obtained cast material was subjected to multiple passes of cold drawing, and Cu-Ag alloy wires having final wire diameters of 0.021 mm (21 μm) and 0.04 mm (40 μm) were obtained for each sample. In particular, the wire drawing material in the middle of the wire drawing was subjected to an intermediate heat treatment: 450 ° C. × 3 hours for the wire diameters marked with “◯” in Table 2. For sample Nos. 2-1, 2-3 to 2-6, when the wire diameter was 0.9 mm, the wire was subjected to the same chemical polishing as sample No. 2-0 to remove the surface layer. (t / r ≒ 0.022).

  For comparison, Cu-Ag alloy wires with a high Ag content (final wire diameter φ 0.021 mm (21 μm), 0.04 mm (40 μm), sample No. 100), and Cu without intermediate heat treatment during wire drawing -Ag alloy wires (final wire diameter φ0.021 mm (21 μm), 0.04 mm (40 μm), sample No. 110) were prepared. Sample No. 100 was prepared in the same manner as Sample Nos. 2-1 to 2-6 described above with a cast material having a wire diameter of φ22 mm made of a Cu-Ag alloy having the composition shown in Table 1. Intermediate heat treatment: 450 ° C. × 3 hours was applied to the attached wire diameter. Sample No. 110 is a cast material having a wire diameter of φ22 mm made of a Cu-Ag alloy having the composition shown in Table 1, and is prepared in the same manner as Sample Nos. 2-1 to 2-6 described above. The wire was drawn without being subjected to wire drawing.

<Characteristics of Cu-Ag alloy wire>
About each obtained sample No.2-0-2-6,100,110, tensile strength (MPa), electrical conductivity (% IACS), the frequency | count of bending, the frequency | count of twisting, horizontal winding property, and wire drawing property were investigated. The results are shown in Table 1.

[Tensile strength, conductivity]
In each sample, the tensile strength and conductivity were measured for a wire having a final wire diameter φ of 0.021 mm. The tensile strength was measured in accordance with JIS Z 2241 (Gage distance GL: 10 mm). The conductivity was measured by the bridge method.

[Number of flexion]
The number of bendings in each sample was measured for a wire having a final wire diameter of φ0.04 mm. The number of bendings was measured according to the JIS G 3522 bending test. Here, as shown in FIG. 2, the sample S is arranged between a pair of mandrels m arranged opposite to each other, a weight w (load load: 12.5 g) is attached to one end of the sample S, and the other end is a lever l of the testing machine. The sample S is bent along the outer periphery of the mandrel m, the sample S is bent with a bending radius R (= 2 mm), bent in the repetition direction, and the number of times until the sample breaks is obtained. Count as one iteration. This number of times is defined as the number of bending times. The bending speed is 30 times / min.

[Number of twists]
In each sample, the number of twists was measured for a wire having a final wire diameter of φ0.04 mm. The number of twists is fixed by applying a load of 25 g to one end of the sample, and twisting in one direction by gripping the other end, then twisting in the other direction, that is, twisting in the repeat direction, Obtain the number of twists until the sample breaks. Count one iteration. In this test, the gauge distance GL = 10 mm.

[Horizontal winding]
For samples No. 2-0, 2-1, 2-2, and 110, the lateral rollability was examined. For horizontal winding, 20kg of wire rod with a final wire diameter of 0.021mm is prepared for each sample, and the number of breaks that occur until the entire 20kg is spirally wound at a predetermined pitch is measured. The value was divided by the number of disconnections (kg / time).

[Evaluation of drawability]
With respect to Sample Nos. 2-0, 2-1, 2-2, and 110, the drawability when a material having a wire diameter of φ22 mm was drawn to a final wire diameter of φ0.021 mm was examined. The wire drawing property was evaluated by a value (kg / time) obtained by preparing 20 kg of each of the above materials, measuring the number of wire breaks that occurred until the entire 20 kg wire was drawn, and dividing 20 kg by the number of wire breaks.

  As shown in Tables 1 and 2, by applying an intermediate heat treatment at a specific wire diameter during wire drawing, it has high conductivity, high strength, and extremely fine resistance to bending and twisting. It can be seen that a Cu-Ag alloy wire is obtained. In particular, even for Cu-Ag alloys with the same composition, a wire rod with higher electrical conductivity can be obtained by reducing the wire diameter for intermediate heat treatment during wire drawing or by performing multiple intermediate heat treatments. You can see that Thus, it can be seen that by performing the intermediate heat treatment at a specific wire diameter, a Cu—Ag alloy wire having a good balance between high conductivity and high strength can be obtained. Moreover, it turns out that a wire drawing property can be improved by removing a surface layer further in the middle of a wire drawing process. Therefore, it can be said that by removing such a surface layer, it is possible to produce the above-described high-strength, high-conductivity ultra-fine Cu-Ag alloy wire with high productivity.

  Furthermore, all of the obtained sample Nos. 2-0 to 2-6 have a high number of twists and are excellent in lateral winding, so that they can be wound around the outer periphery of the insulating layer when used as a shield conductor for coaxial cables. It is expected that there will be little disconnection etc. In addition, all of the obtained sample Nos. 2-0 to 2-6 have high conductivity, and have a large number of flexing and twisting times. -A coaxial cable with a shield conductor made of an Ag alloy wire is expected to have excellent shielding properties and resistance to twisting and bending applied during use.

  In Sample Nos. 2-1 to 2-6, as in Sample No. 2-0, a step of forming a plating layer at an appropriate time during the drawing process or after the drawing process may be added. A Cu—Ag alloy wire having a plating layer is obtained. When the surface layer is removed, the intermediate heat treatment is performed at an appropriate time after the surface layer is removed. When the intermediate heat treatment is performed, the plating layer is preferably formed at an appropriate time after the intermediate heat treatment.

  The above-described embodiment can be appropriately changed without departing from the gist of the present invention, and is not limited to the above-described configuration. For example, the Ag content, conductivity, tensile strength, final wire diameter, wire diameter subjected to intermediate heat treatment, and the like can be appropriately changed.

  The coaxial cable of the present invention can be suitably used as an electric wire for various electronic devices such as portable electronic devices such as mobile phones, electronic parts mounted on automobiles, medical devices, and industrial robots. The Cu-Ag alloy wire of the present invention can be suitably used for the shield conductor of the coaxial cable of the present invention. The method for producing a Cu-Ag alloy wire of the present invention can be suitably used for producing an ultrafine Cu-Ag alloy wire having high electrical conductivity and high strength.

  l Lever S Specimen w Weight m Mandrel R Bending radius

Claims (4)

Cu-Ag alloy wire used for the shield conductor of coaxial cable,
Contains 1% by mass to 20% by mass of Ag with the balance being Cu and impurities,
Conductivity is 82% IACS or higher,
Tensile strength is 800MPa or more,
A Cu-Ag alloy wire characterized by a wire diameter of 0.05 mm or less. It has a plating layer on the surface of the Cu-Ag alloy wire,
2. The Cu—Ag alloy wire according to claim 1, wherein the plating layer is made of at least one selected from Ag, Ag alloy, Sn, and Sn alloy. A coaxial cable comprising, in order from the center, a central conductor, an insulating layer, and a shield conductor,
The shield conductor is configured by winding a plurality of fine wires around the outer periphery of the insulating layer,
3. The coaxial cable according to claim 1, wherein the extra fine wire is a Cu—Ag alloy wire according to claim 1 or 2. A method for producing a Cu-Ag alloy wire used for a shield conductor of a coaxial cable,
A casting process for producing a cast material using a mixed molten metal in which Ag and Cu as raw materials are dissolved,
The cast material is drawn to produce a Cu-Ag alloy wire containing Ag in an amount of 1% by mass to 20% by mass, the balance being Cu and impurities, and a final wire diameter of 0.05 mm or less. Wire process,
A heat treatment step of performing an intermediate heat treatment on the wire drawing material in the middle stage until the final wire diameter Cu-Ag alloy wire is obtained,
The intermediate heat treatment
The heating temperature is 350 ° C or higher and 550 ° C or lower,
The relationship between the wire diameter of the drawn wire subjected to the intermediate heat treatment and the conductivity and tensile strength of the final wire obtained by subjecting the heat treated material subjected to the intermediate heat treatment to the wire drawing up to the final wire diameter is obtained in advance. In addition, based on the above relationship, a predetermined value set retrospectively from the final wire diameter so that the conductivity of the Cu-Ag alloy wire having the final wire diameter is 82% IACS or more and the tensile strength is 800 MPa or more. A method for producing a Cu-Ag alloy wire, which is performed at a wire diameter.

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