JP2008115423A - Conductor for flexible cable, its manufacturing method, and flexible cable using the conductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductor which has ≥98% IACS electric conductivity and ≥15% elongation percentage and in which flexibility is improved without reducing productivity, its manufacturing method, and a flexible cable using the conductor. <P>SOLUTION: The conductor for flexible cable is composed of copper of single composition or copper alloy. Wire drawing to a diameter close to final wire diameter and annealing are carried out to prepare a conductor wire. Then, the conductor wire is subjected to cold working to the final wire diameter in such a way that elongation percentage at fracture becomes ≥15%, and hereby hardness in the surface part of a final wire is made higher than that in the central part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cable used for an industrial robot, an automatic machine tool, and the like, and relates to a conductor having improved bending resistance, a manufacturing method thereof, and a bending resistant cable using the conductor.

  Components (cables) used in drive units of industrial robots and automatic machine tools are required to have excellent repeated bending characteristics, that is, bending resistance, in view of the usage environment.

  Conventionally, tough pitch copper (conforming to JIS C3102) is generally used as a conductor of this type of cable (hereinafter referred to as a flex-resistant cable). However, tough pitch copper has insufficient bending resistance, and in applications where bending resistance is particularly important, solid solution strengthened Cu-Sn alloys (Patent Documents 1 to 3), precipitation strengthened Cu-Zr. Alloys (Patent Documents 4 and 5), Cu-Fe-P alloys (Patent Documents 6 and 7), and the like are also used.

  Further, there is a method of improving the strength, elasticity, conductivity, and stress relaxation resistance characteristics of a copper alloy by combining cold working with a cold working rate of 30% or less and final aging treatment (Patent Document 8). Furthermore, there is a method of adjusting the characteristics of 0.2% proof stress, tensile strength, elongation, and conductivity by adding a wire drawing process by light reduction of 10% or less to the electric copper wire after wire drawing and annealing ( Patent Document 9).

JP-A-6-76640 Japanese Patent Laid-Open No. 11-172391 JP 2004-179151 A JP-A-5-20208 JP 2000-242139 A JP-A-5-20207 JP-A-6-283038 JP-A-1-309948 Japanese Patent Laid-Open No. 60-24284

  However, when a Cu—Sn solid solution strengthened alloy is used, although the flex resistance is improved as the Sn solid solution amount is increased, there is a problem that the conductivity is lowered. For example, when the Sn solid solution amount is 0.3% by mass, the conductivity is 80% IACS. However, when the Sn solid solution amount is 0.7% by mass, the conductivity decreases to 65% IACS.

  Further, precipitation-strengthened alloys such as Cu-Zr and Cu-Fe-P have excellent electrical conductivity and bending resistance, but they have a long time to refining to a predetermined tensile strength after wire drawing. Therefore, there is a problem that productivity is inferior.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a flexible cable conductor that satisfies an electrical conductivity of 98% IACS or higher and an elongation of 15% or higher and has improved flex resistance without reducing productivity, and a method for manufacturing the same. It is another object of the present invention to provide a bend-resistant cable using the conductor.

  In order to achieve the above object, the invention according to claim 1 is a conductor wire material in which a conductor for a flexible cable made of copper or a copper alloy having a single composition is drawn to near the final wire diameter and annealed. The conductor wire was cold-worked to the final wire diameter so that the elongation at break was 15% or more, and the surface portion of the final wire was made harder than the central portion. It is a conductor for a flexible cable.

  A second aspect of the present invention is the flexible cable conductor according to the first aspect, wherein the ratio of the hardness of the surface portion to the central portion of the final wire is 1.09 to 1.11.

  The invention according to claim 3 is the flexible cable conductor according to claim 1 or 2, wherein the final wire has a 0.2% yield strength of 160 MPa or more and 245 MPa or less and an electrical conductivity of 98% IACS or more.

  The invention according to claim 4 is the flexible cable conductor according to any one of claims 1 to 3, wherein the final wire has a plated film of Sn, Ni, or Ag on the surface thereof.

  A fifth aspect of the present invention is the flexible cable conductor according to any one of the first to fourth aspects, wherein the conductor is formed of a stranded wire formed by twisting a plurality of the final wires.

  The invention of claim 6 is a bend-resistant cable characterized in that the periphery of the bend-resistant cable conductor according to any one of claims 1 to 5 is covered with an insulating layer.

  The invention of claim 7 is a method for producing a flexible cable conductor composed of copper or a copper alloy having a single composition. In the method for producing a conductor for a flexible cable, the wire is drawn to near the final wire diameter and annealed to produce a conductor wire. The conductor wire is cold-worked to the final wire diameter so that the elongation at break is 15% or more, and the surface portion of the final wire is formed to be harder than the central portion. It is a manufacturing method of the conductor for flexible cables.

  The invention according to claim 8 is the method for producing a flexible cable conductor according to claim 7, wherein the cold working rate is 0.8% or more and 6.0% or less.

  A ninth aspect of the present invention is the method for producing a flexible cable conductor according to the seventh or eighth aspect, wherein the cold working is a skin pass working.

  A tenth aspect of the present invention is the method for producing a flexible cable conductor according to the seventh or eighth aspect, wherein the cold working is peening.

  Based on this invention, the conductor for bending-resistant cables which is excellent in electrical conductivity and elongation rate and has favorable bending resistance can be obtained.

  Embodiments of the present invention will be described below.

  In the present invention, as a measure for improving the flex resistance of the flex-resistant cable conductor, surface processing (cold processing) is performed instead of alloying as in the prior art. Specifically, surface hardening is performed by adding (introducing) compressive residual stress to the surface of the wire or by surface plastic processing (that is, skin pass processing, shot peening processing, laser peening processing, or jet peening processing). Skin pass processing is mild rolling and drawing (described in JIS H0500) for surface polishing or distortion correction of plate materials, strip materials, pipe materials, wire materials, and the like.

  That is, the flexible cable conductor according to the preferred embodiment of the present invention is characterized in that the conductor wire is cold worked at a low working rate. Specifically, a wire composed of a single composition of copper (or copper alloy) is drawn to near the final wire diameter (R1), annealed to produce a conductor wire, and the final wire diameter is applied to the conductor wire. The surface portion of the final wire is made harder than the central portion by cold working so that the elongation at break is 15% or more until (R2 <R1).

  The ratio of the hardness of the surface portion to the central portion (surface portion / central portion) of the final wire rod (flexible cable conductor) is around 1.1 (1.09 to 1.11), and the 0.2% proof stress is 160 MPa. As described above, 245 MPa or less, preferably 200 MPa or more and 225 MPa or less, and the conductivity is 98% IACS or more. The 0.2% yield strength depends on the working rate of cold working described later, and the upper limit value and lower limit value of the 0.2% yield strength are determined from the upper limit value and lower limit value of the working rate.

  A tough pitch copper is mentioned as copper of the single composition which comprises the conductor for flexible cables. In addition, examples of the copper alloy that constitutes the cable conductor for bending resistance include those obtained by adding a small amount of an element that improves bending resistance to tough pitch copper to improve bending resistance compared to tough pitch copper. Except for flexibility, copper alloys have the same properties (conductivity and elongation) as tough pitch copper. Examples of the copper alloy include a Cu—Sn alloy, a Cu—Ni alloy, and a Cu—Ag alloy. Further, the flexible cable conductor may have a Sn, Ni, or Ag plating film on its surface. That is, the wire rod may be made of tough pitch copper, and a Sn, Ni, or Ag plating film may be provided on the surface of the wire rod.

  The conductor for a flexible cable is not limited to a single wire, and may be a stranded wire formed by twisting a plurality of single wires.

  The conductor for a flexible cable according to the present embodiment is particularly targeted for a conductor conforming to JIS C3102, and the conductor diameter is 0.1 mm or more and 0.7 mm or less, preferably 0.1 mm or more and 0.26 mm or less. And 0.29 mm or more and 0.7 mm or less.

  Next, the manufacturing method of this embodiment will be described.

  The method for manufacturing a flexible cable conductor according to the present embodiment is to produce a conductor wire by drawing a wire composed of copper (or copper alloy) having a single composition to near the final wire diameter and annealing. The conductor wire is subjected to skin pass processing (cold working) until the final wire diameter and the elongation at break is 15% or more, and the surface portion of the final wire is made harder than the central portion. It is. The processing rate (area reduction rate) of this skin pass processing is 0.8% or more and 6.0% or less, preferably 2.0% or more and 3.8% or less.

  A bend-resistant cable is obtained by covering the periphery of the bend-resistant cable conductor according to the present embodiment thus obtained with an insulating layer. As the constituent material of the insulating layer, those conventionally used as the insulating layer of the bending resistant cable can be applied.

  The reason why the lower limit of the skin pass processing rate is set to 0.8% or more is that it is difficult to control the processing rate at a processing rate lower than this. The lower limit of the processing rate is preferably set to 2.0% or more because the bending resistance is 1.1 times or more compared to a conventional bending-resistant cable conductor (hereinafter referred to as a conventional conductor). Because. The reason why the standard of bending resistance is 1.1 times is that the variation in bending resistance is about ± 10% (0.1) with respect to the average value (1.0). Here, the conventional conductor is a wire made of copper (or copper alloy) having a single composition, drawn to the final wire diameter and annealed.

  On the other hand, the reason why the upper limit of the skin pass processing rate is set to 6.0% or less is that when the processing rate is larger than this, the elongation rate is less than 15%. Moreover, the upper limit of the processing rate is preferably set to 3.8% or less because the elongation is less than 20% when the upper limit is increased.

  The standard value of the elongation rate is determined from JIS C3102, and the elongation rate of 20% or more is preferable in order to satisfy a wider range of wire diameter standards. Specifically, when the elongation rate is 15% or more, the wire diameter is 0.1 mm or more and 0.26 mm or less, and when the elongation rate is 20% or more, the wire diameter is 0.1 mm or more, 0.26 mm or less, 0.29 mm or more, 0. Meets JIS C3102 standards within a range of 7 mm or less.

  Next, the operation of the present embodiment will be described.

  In the method for producing a flexible cable conductor according to the present embodiment, the skin pass processing that has been performed for surface polishing or distortion correction of a wire or the like is drawn to near the final wire diameter, and the annealed conductor wire It is given. Specifically, the skin pass processing is performed on the conductor wire in the range of the processing rate of 0.8 to 6.0% so that the elongation to the final wire diameter is 15% or more. As a result, compressive stress due to plastic working remains on the surface of the obtained final wire (flexible cable conductor), and work hardening occurs on the surface of the final wire. Even if this work hardening occurs, the tensile strength of the final wire is hardly (or not much) improved.

  Even if an external stress such as repetitive bending is applied to the work-hardened final wire and a tensile stress acts on the surface of the final wire, the tensile stress is offset by the compressive residual stress. The bending-resistant cable conductors have significantly improved fatigue strength.

  In addition, since work hardening occurs only on the surface of the final wire, if the processing rate is in the range of 0.8 to 6.0%, the elongation of the final wire is not significantly reduced, resulting in breakage. An elongation rate of 15% or more can be ensured. For the same reason, if the processing rate is in the range of 0.8 to 6.0%, a large amount of distortion is not introduced into the final wire, and as a result, a conductivity of 98% IACS or more is ensured. can do.

  In the present embodiment, description has been made by taking skin pass processing as an example of cold processing to be applied to a conductor wire, but shot peening processing, laser peening processing, or jet peening processing is performed instead of skin pass processing. May be. Even in this case, the compressive residual stress is introduced to the surface of the final wire due to the impact energy of the shot grains, and work hardening occurs on the surface of the final wire, so that the same effect as skin pass processing can be obtained.

(Conventional example)
A wire rod having a wire diameter of 8 mm made of tough pitch copper (oxygen content of 300 to 350 ppm) was cold drawn to a wire diameter of 0.9 mm, and then annealed by energization to produce an intermediate material. The intermediate material thus obtained was cold-drawn to a wire diameter of 0.262 mm, and then subjected to annealing again by energization to produce a conductor A (conductor wire).
(Example 1)
The conductor A was subjected to skin pass processing to a wire diameter of 0.261 mm to obtain the conductor of Example 1. The processing rate (area reduction rate) of this skin pass is 0.8%.
(Example 2)
The conductor A was subjected to skin pass processing to a wire diameter of 0.260 mm to obtain a conductor of Example 2. The processing rate of this skin pass is 1.5%.
(Example 3)
The conductor A was subjected to skin pass processing to a wire diameter of 0.259 mm to obtain a conductor of Example 3. The processing rate of this skin pass is 2.3%.
Example 4
The conductor A was subjected to skin pass processing to a wire diameter of 0.258 mm to obtain a conductor of Example 4. The processing rate of this skin pass is 3.0%.
(Example 5)
The conductor A was subjected to skin pass processing to a wire diameter of 0.257 mm to obtain a conductor of Example 5. The processing rate of this skin pass is 3.8%.
(Example 6)
The conductor A was subjected to skin pass processing to a wire diameter of 0.256 mm to obtain a conductor of Example 6. The processing rate of this skin pass is 4.5%.
(Example 7)
The conductor A was subjected to skin pass processing to a wire diameter of 0.255 mm to obtain a conductor of Example 7. The processing rate of this skin pass is 5.3%.
(Example 8)
The conductor A was subjected to skin pass processing to a wire diameter of 0.254 mm to obtain a conductor of Example 8. The processing rate of this skin pass is 6.0%.
(Comparative Example 1)
The conductor A was subjected to skin pass processing to a wire diameter of 0.253 mm to obtain a conductor of Comparative Example 1. The processing rate of this skin pass is 6.8%.
(Comparative Example 2)
The conductor A was subjected to skin pass processing to a wire diameter of 0.247 mm to obtain a conductor of Comparative Example 2. The processing rate of this skin pass is 11.1%.

  Table 1 shows the wire diameters of the conductors of Examples 1 to 8, Comparative Examples 1 and 2 and the conventional example before and after skin pass processing and the processing rate at that time.

  Here, the processing rate is expressed as a percentage by standardizing the difference in the cross-sectional area (surface perpendicular to the drawing direction) before and after drawing with the cross-sectional area before drawing (JIS H0500). ). The processing rate was calculated from the wire diameter measured with a micrometer.

  Next, the tensile strength, 0.2% proof stress, elongation, conductivity, flex resistance, and Vickers hardness were evaluated for the conductors of Examples 1 to 8, Comparative Examples 1 and 2, and the conventional example. . This evaluation method is described below.

  In the tensile test, the test piece length was 100 mm and the strain rate was 20 mm / min, and the tensile strength, 0.2% proof stress, and elongation rate were evaluated from the results.

  The conductivity was calculated according to JIS C3002 from the electric resistance value measured by the double bridge method. The measurement conditions of the electrical resistance value by the double bridge method were a sample length of 500 mm and a measurement temperature of 20 ° C. As a result, all the conductors had excellent conductivity of 100% IACS or higher and satisfied J1S C3102.

  The bending resistance was evaluated using the number of times until the conductor was subjected to fatigue fracture after repeated 90 ° right and left bending. The bending conditions were a bending radius of 40 mm and a bending speed of 13 times / minute. In this test, a load is applied to the conductor. In this evaluation, a load of 28 to 29 g is applied. This load corresponds to 2% of the tensile breaking load of each conductor.

  The Vickers hardness was measured under test conditions of a pressing load of 10 g and a pressing time of 15 seconds.

  Table 2 shows the processing rate, tensile strength, 0.2% yield strength, elongation rate, and bending resistance of the conductors of Examples 1 to 8, Comparative Examples 1 and 2, and the conventional example.

  According to Table 2, since the bending resistance and the 0.2% proof stress are improved with the increase of the processing rate, when the bending resistance is improved, the range of the processing rate of the present invention (0.8 to 6.0%). ), It is desirable to increase the processing rate as much as possible.

  On the other hand, the elongation decreases as the processing rate increases. For this reason, the upper limit of the processing rate is a range where the elongation rate satisfies 15% or more, that is, a processing rate of 6.0% or less, and preferably a range where the elongation rate satisfies 20% or more, that is, a processing rate of 3.8%. It was as follows. The rules for the elongations of 15% and 20% are as described above.

  Further, the lower limit of the processing rate is set to 0.8% or more, preferably 2.0% or more, because of difficulty in controlling the processing rate. This is because the values of the bending resistance in Table 2 are average values, and the actual bending resistance is considered to vary by about ± 10% with respect to the average value. Therefore, in order to satisfy the bending resistance (1.0) or more of the conductor of the conventional example, the bending resistance is 1.1 or more, and the conductors of Examples 3 to 8 satisfy this. Based on this, a preferable lower limit (2.0% or more) of the processing rate was determined.

  Table 3 shows the hardness of the conductor surface based on the processing rate and the hardness of the conductor center of the conductors of Examples 1 to 8, Comparative Examples 1 and 2 and the conventional example (ratio of the hardness of the surface portion to the center portion). Indicates.

  According to Table 3, the hardness of the conductor surface based on the processing rate and the hardness of the conductor center is larger than that of the conventional example in both the examples and comparative examples, and the conductor surface portion is 10% higher than the conductor center portion. It turns out that it is hard (surface part hardness / center part hardness: 1.1).

  From the above, it is possible to achieve an improvement in flexural properties and an elongation rate of 15% or more by subjecting the conductor wire material to skin pass processing in a range of 0.8% or more and 6.0% or less. The conductivity can be 100% IACS or more.

Claims (10)

  In a flexible cable conductor composed of copper or copper alloy of a single composition, drawn to near the final wire diameter, annealed to produce a conductor wire, to the conductor wire, to the final wire diameter, and A flex-resistant cable conductor characterized in that a cold working is performed so that an elongation at break is 15% or more, and a surface portion of a final wire is formed harder than a central portion.   The conductor for a flexible cable according to claim 1, wherein the ratio of the hardness of the surface portion to the central portion of the final wire is 1.09 to 1.11.   The flexible cable conductor according to claim 1 or 2, wherein the final wire has a 0.2% proof stress of 160 MPa or more and 245 MPa or less and an electrical conductivity of 98% IACS or more.   The conductor for bending-resistant cables according to any one of claims 1 to 3, wherein the final wire has a Sn, Ni, or Ag plating film on a surface thereof.   The conductor for bend-resistant cables according to any one of claims 1 to 4, wherein the conductor is a twisted wire formed by twisting a plurality of the final wires.   A bend-resistant cable, wherein the conductor for a bend-resistant cable according to any one of claims 1 to 5 is covered with an insulating layer.   In a method for manufacturing a flexible cable conductor composed of copper or copper alloy having a single composition, a wire is drawn to near the final wire diameter, annealed to produce a conductor wire, and the final wire is applied to the conductor wire. Production of a flexible cable conductor characterized by forming the surface portion of the final wire rod harder than the center portion by cold working so that the elongation at break is 15% or more up to the diameter Method.   The method for producing a conductor for a flexible cable according to claim 7, wherein a processing rate of the cold working is 0.8% or more and 6.0% or less.   The method for producing a flexible cable conductor according to claim 7 or 8, wherein the cold working is a skin pass working.   The method for manufacturing a conductor for a flexible cable according to claim 7 or 8, wherein the cold working is peening.