JP2011111634A - Copper wire and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copper wire formed from pure copper and having high strength and high toughness; a coated electrical wire which uses the copper wire as a conductor; and a method for manufacturing the copper wire. <P>SOLUTION: This manufacturing method includes: subjecting a base material containing 99.9 mass% or more Cu to cold working; then subjecting the base material to intermediate heat treatment; subjecting the obtained intermediate heat-treated material to final cold working to produce a drawn wire having a final wire diameter of 0.1-2.0 mm; and subjecting the drawn wire to final heat treatment. The intermediate heat treatment is conducted when the working degree of the final cold working which is conducted right after the intermediate heat treatment satisfies 85-95%. The copper wire having a fine structure with an average crystal grain size of 20 μm or less can be obtained by conducting the intermediate heat treatment so as to control the working degree of the final cold working within a particular range and also conducting the final heat treatment after the final cold working. The copper wire has high strength, high toughness, a tensile strength of 240 MPa or more and an elongation of 20% or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a copper wire used as a conductor, a method for producing the copper wire, and a covered electric wire including the copper wire as a conductor. In particular, the present invention relates to a copper wire made of pure copper and having high strength and high toughness.

  Conventionally, copper wires made of pure copper having excellent conductivity have been used for conductor wires such as power supply wires of various electric devices.

  Pure copper has high electrical conductivity and excellent toughness, but generally has low strength. On the other hand, Patent Document 1 discloses a copper wire material having excellent strength by containing a trace amount of an additive element in oxygen-containing copper such as tough pitch copper.

JP 2008-202104 A

  By containing an additive element as described above, the strength of the conductor wire can be increased. However, the inclusion of the additive element causes a decrease in properties such as toughness such as conductivity and elongation. Therefore, it is desired to develop a copper wire that has high electrical conductivity and can achieve both high strength and high toughness.

  Accordingly, one of the objects of the present invention is to provide a copper wire made of pure copper and having high strength and high toughness. Moreover, the other object of this invention is to provide the manufacturing method of this copper wire. Furthermore, the other object of this invention is to provide the covered electric wire which makes the said copper wire material a conductor.

  The inventors of the present invention produced copper wires made of pure copper by various production methods, and examined the obtained copper wires that had high tensile strength and high elongation, and found that the copper wires had high strength and high toughness. Has obtained the knowledge that it has a microstructure composed of fine crystal grains. In order to obtain a copper wire having this fine structure, it is necessary to prepare a material at a specific time during the cold working in the manufacturing process of material preparation → cold working (typically wire drawing) → final heat treatment. It was found that heat treatment is preferable. The present invention is based on these findings.

The manufacturing method of the copper wire of this invention is a method of manufacturing the copper wire which consists of 99.9 mass% or more of Cu, Comprising: The following processes are provided.
A process of cold working a material consisting of 99.9% by mass or more of Cu.
A step of performing an intermediate heat treatment on the cold worked material subjected to the cold working.
The step of subjecting the intermediate heat treatment material subjected to the intermediate heat treatment to final cold working to form a wire drawing material having a final wire diameter of 0.1 mm to 2.0 mm.
A step of subjecting the wire drawing material to a final heat treatment to produce a copper wire material having an average crystal grain size of 20 μm or less, a tensile strength of 240 MPa or more, and an elongation of 20% or more.
The intermediate heat treatment is performed when the workability of the final cold working performed immediately after the intermediate heat treatment satisfies 85% or more and 95% or less.

  The following copper wire of the present invention is obtained by the manufacturing method of the present invention. In the copper wire of the present invention, 99.9% by mass or more is made of Cu, the wire diameter is 0.1 mm or more and 2.0 mm or less, the average crystal grain size is 20 μm or less, the tensile strength is 240 MPa or more, and the elongation is 20% or more.

  In the case of producing an ultrafine copper wire made of pure copper and having a final wire diameter of less than 0.1 mm, an intermediate heat treatment is conventionally performed during cold working (drawing). By removing the processing strain associated with the wire drawing before the intermediate heat treatment by the intermediate heat treatment, the wire heat workability of the intermediate heat treated material after the intermediate heat treatment can be improved, and the above ultrafine copper wire is manufactured. be able to. In particular, when an ultrafine wire is manufactured, since copper is insufficient in strength, a copper alloy is generally used. In copper alloys, since the strength is too high, if the intermediate heat treatment is not performed during the wire drawing process, disconnection frequently occurs and the productivity is lowered. Therefore, the intermediate heat treatment is often performed during the wire drawing process. On the other hand, when producing a copper wire having a diameter larger than the above-mentioned ultrafine copper wire having a final wire diameter of 0.1 mm or more, it is stretched by the ductility of the copper itself even if an intermediate heat treatment is not performed during the drawing process as described above. Wire processing is possible. By not performing the intermediate heat treatment in the middle of the wire drawing process, for example, productivity can be improved. For this reason, the intermediate heat treatment is often not performed.

  From the background described above, conventionally, when producing a copper wire material having a final wire diameter of 0.1 mm to 2.0 mm, the timing for performing an intermediate heat treatment during wire drawing has not been sufficiently studied.

  In contrast, the manufacturing method of the present invention is high strength and high toughness when compared with a copper wire having the same final wire diameter manufactured by a conventional manufacturing method by performing an intermediate heat treatment at a specific time as described above. Copper wire can be manufactured. Moreover, according to this invention manufacturing method, the copper wire material from which tensile strength and elongation differ can be manufactured by selecting the time of intermediate heat processing in the specific range as mentioned above. For example, when producing a copper wire having the same final wire diameter, a copper wire having a higher tensile strength and elongation can be produced by performing an intermediate heat treatment when the cold-worked material is thinner than when the diameter of the cold-worked material is thick. In this way, even with a copper wire having the same final wire diameter, a copper wire having different tensile strength and elongation can be produced depending on the timing of the intermediate heat treatment. Therefore, the production method of the present invention uses a copper wire having characteristics according to various demands. It can be manufactured and is expected to be industrially useful.

  Since the copper wire of the present invention is made of pure copper and has high conductivity, and is excellent in both strength and toughness as described above, it is preferably used for conductor wires such as electric wires, electrode wires, and welding wires. Can do. Hereinafter, the present invention will be described in more detail.

[Copper wire]
"composition"
<Mother phase>
Pure copper constituting the copper wire of the present invention contains 99.9% by mass or more of Cu, and allows elements other than Cu to be contained in a total range of 0.1% by mass or less. Examples of such pure copper include oxygen-free copper (alloy number: C1020), tough pitch copper (alloy number: C1100), and phosphorous deoxidized copper (alloy number: C1201, C1220) as defined in JIS H 3100 (2006). Is mentioned. If elements other than Cu are contained in total exceeding 0.1% by mass, the strength is increased, but this leads to a decrease in conductivity and a decrease in toughness. It can utilize suitably for the conductor for electric wires as content of Cu is about 99.92 mass%-99.98 mass%.

<Other elements: Metal elements>
When at least one element of Sn, Pb, Fe, Ag, Ni, and Zn is contained in a mass ratio as the element other than Cu, the total strength is further increased to 0 ppm to 100 ppm (0.01 mass% or less), and the strength can be further increased. Depending on the desired properties, the above elements can be added in the above range. However, when the content of the above elements exceeds 100 ppm in terms of mass ratio, the conductivity and toughness are reduced as described above. In particular, Sn, Pb, Fe, and Ni are liable to lower the electrical conductivity. Therefore, Sn: 50 ppm or less, Pb: 20 ppm or less, Fe: 30 ppm or less, and Ni: 20 ppm or less are preferable. Since these metal elements may not be contained, there is no lower limit of the content.

<Other elements: Oxygen>
As an element other than the metal element, oxygen may be contained in a mass ratio of more than 0 ppm to 650 ppm or less (0.065 mass% or less). By containing oxygen in the above range, an impurity element can be precipitated as an oxide, and a decrease in conductivity can be suppressed. In order to obtain this effect, it is more preferable that oxygen is contained in a mass ratio of about 200 ppm to 400 ppm. On the other hand, when the oxygen content is small, for example, at the oxygen-free copper level (about 10 ppm by mass ratio), a copper wire excellent in hydrogen embrittlement resistance can be obtained. Oxygen is mainly present in copper as copper oxide, and if the content is large, the copper oxide becomes coarse, and disconnection is likely to occur during cold working starting from this coarse copper oxide. And The oxygen content may be selected according to desired characteristics.

<Other elements: Inevitable impurities>
Elements other than the above metal elements and oxygen are inevitable impurities. Inevitable impurities include As, Bi, Sb, and the like, and the content is desirably 30 ppm or less in total by mass ratio, and it is desirable that the impurities are not contained, so there is no lower limit.

<Average crystal grain size>
One feature of the copper wire of the present invention is that the average crystal grain size is small, and the average crystal grain size is 20 μm or less. By being comprised from such a fine structure, the copper wire of the present invention is excellent in toughness while having high strength. The average crystal grain size can be adjusted according to the degree of final cold working and the final heat treatment conditions. For example, a copper wire having a finer structure such as an average crystal grain size of 10 μm or less can be obtained.

"shape"
The copper wire of the present invention has a wire diameter (diameter) of 0.1 mm or more and 2.0 mm or less. Since the wire diameter satisfies this range, the effect of improving strength and toughness due to the intermediate heat treatment performed at a specific time during cold working can be sufficiently obtained. The wire diameter may be appropriately selected depending on the application. For example, when used as a conductor of a covered electric wire, a copper wire having a wire diameter of about 0.3 mm or more and 1.0 mm or less can be preferably used. This wire diameter is substantially equal to the final wire diameter in the manufacturing process.

<< Tensile strength and elongation >>
The copper wire of the present invention has a high tensile strength of 240 MPa or higher and a high elongation of 20% or higher. The copper wire of the present invention is excellent in toughness as described above, and can be easily bent without causing cracks, for example, even when it is bent into a coil shape.

  Tensile strength and elongation can be adjusted, for example, by the degree of work at the time of final cold working. The higher the degree of work, the greater the tensile strength. The lower the degree of work, the greater the elongation. Tend to be. In particular, according to the present invention, the copper wire according to the present invention has a tensile strength and an elongation when compared with a conventional copper wire having the same final wire diameter by selecting the timing for performing the intermediate heat treatment in a specific range as described above. Is big. It is advisable to select the degree of final cold working and the timing for performing the intermediate heat treatment so as to satisfy desired characteristics. For example, a copper wire with higher strength and toughness having a tensile strength of 250 MPa or more and an elongation of 30% or more can be obtained.

"conductivity"
Since the copper wire of the present invention is made of pure copper as described above, it has high conductivity and satisfies 98% IACS or more. In particular, depending on the composition, a copper wire material satisfying 99% IACS or more, and further 100% IACS or more can be obtained.

<< Usage form >>
The copper wire of the present invention can be suitably used as a conductor wire. As the conductor, any form of a single wire, a stranded wire obtained by twisting a plurality of copper wires of the present invention, and a compressed wire obtained by further compressing the stranded wire can be selected as appropriate. The conductor may be used as it is, or may be a covered electric wire having an insulating coating layer made of an insulating material on the outer periphery of the conductor.

[Production method]
《Preparing the material》
In the manufacturing method of the present invention, first, a material made of pure copper satisfying the above-described composition is prepared. Typically, high-purity electrolytic copper is used as a raw material, this raw material is melted in an appropriate atmosphere, and the resulting pure copper melt is cast to produce a cast material. The thing which gave the rolling is mentioned. The oxygen concentration in the finally produced copper wire can be adjusted by adjusting the oxygen concentration in the dissolving atmosphere or by appropriately performing the oxidation-reduction treatment after dissolving the raw material in the air atmosphere. For casting, when continuous casting methods such as a twin belt method and a belt and wheel method are used, the productivity of the cast material is excellent. Moreover, it is good also as a continuous cast rolling material by performing hot rolling continuously to continuous casting. A material having a wire diameter of about 8 mm to 12 mm can be suitably used.

《Cold processing》
Next, a cold-worked material is prepared by subjecting the material to cold working, typically wire drawing. In this cold working performed before the intermediate heat treatment described later, the total degree of work can be appropriately selected according to the final wire diameter. In producing the cold-worked material, a heat treatment may be appropriately performed during the cold work, and distortion due to the cold work before the heat treatment may be removed to improve the cold workability of the material.

《Intermediate heat treatment》
An intermediate heat treatment is applied to the cold worked material. This intermediate heat treatment removes distortion due to cold working before the intermediate heat treatment and softens it to enhance toughness, thereby facilitating the final cold working with a specific degree of work performed after the intermediate heat treatment. In the manufacturing method of the present invention, the final wire diameter is set in advance, and when the degree of work of the final cold working performed immediately after the intermediate heat treatment reaches 85% to 95%, the intermediate diameter is traced back from the final wire diameter. One of the characteristics is to perform heat treatment. By performing the intermediate heat treatment at a specific time as described above, the copper wire of the present invention having a fine structure with a small average crystal grain size and high strength and toughness can be produced.

  For the intermediate heat treatment and the final heat treatment described later, any of the following batch treatment and continuous treatment can be used.

<Batch processing>
Batch processing is a processing method in which a heating target is previously placed in a softening machine (atmosphere furnace, for example, a box furnace), and the heating state of the entire heating target is limited although the amount of processing at one time is limited. Since it is easy to manage, it is a processing method that makes it easy to obtain a particularly high elongation wire. Conditions when the intermediate heat treatment and final heat treatment are performed by batch treatment, heating temperature (atmosphere temperature in the container): 200 ° C. or higher and 600 ° C. or lower, holding time: 30 minutes or longer. When the heating temperature is less than 200 ° C. or the holding time is less than 30 minutes, distortion cannot be sufficiently removed in the case of intermediate heat treatment, and the effect of improving strength and toughness cannot be sufficiently obtained in the case of final heat treatment. If it exceeds 600 ° C, the crystal grains become coarse and the toughness is impaired. More preferable conditions are heating temperature: 200 ° C. or more and 400 ° C. or less, holding time: 1 hour or more and 5 hours or less.

<Continuous processing>
The continuous treatment is a treatment method in which a heating object is continuously supplied into the softening machine and the heating object is continuously heated, and the treatment method is excellent in workability in that it can be continuously heated. For continuous processing, direct energization method that heats the object to be heated by direct energization, indirect energization method that heats the object to be heated indirectly by using electromagnetic induction, etc. A furnace type in which an object to be heated is introduced into the furnace and heated by heat conduction. In particular, the direct energization method and the indirect energization method can achieve high productivity because the production rate can be maintained at a high speed even when the heat treatment is performed continuously after the cold working process.

  In the case of continuous processing, control parameters that can be involved in desired characteristics (here, strength and elongation) are appropriately changed, the characteristics at that time are measured, and such measurement data is created in advance. Based on this data, the parameters may be adjusted so that desired characteristic values (final tensile strength: 240 MPa or more and elongation: 20% or more) can be obtained. In the case of the energization method, the control parameters include the supply speed (linear speed) into the softener, the size of the heating target (wire diameter), the current value, and the like. In the case of the furnace type, the control parameters are the feed rate into the furnace (linear speed), the size of the heating target (wire diameter), the size of the furnace (pipe furnace length), the temperature of the heating atmosphere (400 to 600 ° C. is preferable). For example, when an energizing type softening machine is disposed on the wire drawing material discharge side of the wire drawing machine, the above-mentioned fine structure can be easily obtained by setting the wire speed to several hundred m / min or more, particularly 600 m / min or more.

《Final cold working》
The intermediate heat treatment material subjected to the intermediate heat treatment is subjected to final cold working to form a wire drawing material having a final wire diameter of 0.1 mm to 2.0 mm. The final cold working degree (cross-sectional reduction rate) is 85% to 95%. If the degree of work is less than 85% or more than 95%, the copper wire after the final heat treatment cannot be expected to have both high strength and high toughness.

《Final heat treatment (softening treatment)》
A final heat treatment is applied to the wire drawing material that has been subjected to the final cold working. The final heat treatment can utilize the same conditions as the intermediate heat treatment described above. The above-mentioned final cold working and the final heat treatment with a specific degree of processing provide the copper wire of the present invention having a microstructure and high strength and high toughness.

  The copper wire of the present invention has high electrical conductivity, high strength and high toughness. The manufacturing method of the copper wire of the present invention can manufacture the copper wire of the present invention with high productivity. The coated electric wire of the present invention can be suitably used for power supply lines in various fields where electrical conductivity is high and high strength and high toughness are desired.

  Copper wires made of pure copper were produced under different production conditions, and mechanical properties and structures were examined. Each sample was prepared in the order of preparation of raw material → cold working → (intermediate heat treatment → final cold work →) final heat treatment.

  Prepare copper copper as a raw material (pure copper containing 99.95 mass% or more of Cu and the remaining inevitable impurities) to produce a molten pure copper, and continuously cast and roll this molten metal to obtain a copper A drawn line (material) was obtained. The molten metal was prepared in a continuous melting furnace (shaft furnace), and the oxygen concentration was adjusted by adjusting the air-fuel ratio of the burner of the furnace. The twin belt method was used for continuous casting.

  The copper rough wire was subjected to cold working (cold drawing). Sample Nos. 1-5, 100, and 110 were subjected to intermediate heat treatment on the cold worked material when the wire diameter (mm) shown in Table 1 was reached during cold working, and then the final wire diameter shown in Table 1 on the intermediate heat treated material Final cold working (cold drawing) was performed up to (mm). Samples Nos. 1 and 2 were batch-processed with intermediate heat treatment (heating temperature: 300 ° C., holding time: 3 hours), and Samples Nos. 1 to 5 were subjected to continuous heat-treatment. On the other hand, Sample Nos. 200 and 210 were subjected to cold working (cold wire drawing) up to the final wire diameter (mm) shown in Table 1 on the copper rough drawing wire, and no intermediate heat treatment was performed during the cold working.

  A final heat treatment was applied to the wire drawing material subjected to the final cold working to prepare each sample. The intermediate heat treatment and final heat treatment of sample Nos. 1 to 5 are energized continuous processing, and correlation data between the control parameter values and measurement data described above are created in advance, and desired characteristics ( Control parameters (linear speed, current value, etc.) were adjusted so that the elongation and tensile strength were obtained. In both the intermediate heat treatment and the final heat treatment, the linear velocity was set to 600 m / min or more.

  For each sample obtained by the final heat treatment, the tensile strength (MPa), elongation (%), and average crystal grain size were measured. The results are shown in Table 1.

  Tensile strength and elongation were measured by preparing a test piece according to the description of JIS Z 2201 (1998) and conducting a tensile test. The test conditions were a distance between gauge points GL: 250 mm, a tensile speed: 50 mm / min, and room temperature. The average crystal grain size is obtained by taking an arbitrary cross section for each sample, wrapping this cross section, and performing crystal analysis using a commercially available EBSD (Electron Back-Scatter Diffraction Patterns) apparatus (magnification: 260). In this analysis image, the crystal grains in the region of 300 μm × 300 μm were obtained.

  As shown in Table 1, sample Nos. 1 to 5 that were subjected to intermediate heat treatment when the degree of final cold working satisfied 85% or more and 95% or less were intermediate when the above degree of processing did not satisfy the above range. It can be seen that the tensile strength and elongation are high and the average crystal grain size is fine when the wire diameter is the same as that of Samples Nos. 100 and 110 subjected to heat treatment. In addition, these sample Nos. 1 to 5 have higher tensile strength and elongation when the wire diameter is the same as those of sample Nos. 200 and 210 not subjected to intermediate heat treatment, and the average crystal grain size is fine. I understand that. Furthermore, when the conductivity of these samples No. 1 to 5 was measured by the 4-terminal method, all the samples were 99% IACS or more.

  Therefore, an intermediate heat treatment is performed when the degree of workability of the final cold working satisfies a specific range, and after this final cold working, the final heat treatment is performed, so that the electrical conductivity is high, and the copper wire has high strength and high toughness. It can be seen that The obtained copper wire, a stranded wire obtained by twisting a plurality of the copper wires, and a compressed wire obtained by compressing the stranded wire are expected to be suitably used for a conductor wire such as a conductor of a covered electric wire.

  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. The composition of pure copper, the timing of performing the intermediate heat treatment (wire diameter of the material), the intermediate heat treatment conditions, the final heat treatment conditions, the final wire diameter, and the like can be appropriately changed.

  The copper wire of the present invention can be suitably used for conductor wires such as conductors of various electric wires, electrode wires used for electric discharge machining, and welding wires used for welding materials. The coated wire of the present invention can be suitably used for power supply lines in various fields. The production method of the present invention can be suitably used for the production of the copper wire of the present invention.

Claims (6)

A copper wire made of 99.9% by mass or more of Cu,
Wire diameter is 0.1mm to 2.0mm,
The average grain size is 20 μm or less,
Tensile strength is 240 MPa or more,
A copper wire characterized by an elongation of 20% or more.   2. The copper wire according to claim 1, wherein the copper wire contains at least one element of Sn, Pb, Fe, Ag, Ni, and Zn in a mass ratio of 100 ppm or less in total.   3. The copper wire according to claim 1, wherein the copper wire contains oxygen in a mass ratio of 650 ppm or less.   The copper wire according to any one of claims 1 to 3, or a stranded wire formed by twisting a plurality of the copper wire materials, or a compressed wire obtained by compressing the stranded wire as a conductor, and the outer periphery of the conductor. A covered electric wire comprising an insulating covering layer. A copper wire manufacturing method for manufacturing a copper wire made of 99.9% by mass or more of Cu,
A process of cold working a material composed of 99.9% by mass or more of Cu,
A step of performing an intermediate heat treatment on the cold worked material subjected to the cold working;
Subjecting the intermediate heat treatment material subjected to the intermediate heat treatment to final cold working to form a wire drawing material having a final wire diameter of 0.1 mm or more and 2.0 mm or less;
Subjecting the wire rod to a final heat treatment, comprising a step of producing a copper wire rod having an average crystal grain size of 20 μm or less, a tensile strength of 240 MPa or more, and an elongation of 20% or more,
The method of manufacturing a copper wire, wherein the intermediate heat treatment is performed when a degree of work of the final cold working performed immediately after the intermediate heat treatment satisfies 85% or more and 95% or less.   6. The method for producing a copper wire according to claim 5, wherein at least one of the intermediate heat treatment and the final heat treatment is an energization-type continuous treatment, and a wire speed is 600 m / min or more.