JPS6056432A - Method for removing residual stress of solid wire or twisted wire of hard drawn copper wire - Google Patents

Abstract

PURPOSE:To remove residual stress of a hard drawn copper wire using a relatively simple means by passing the wire through a rotating device having bending members arranged at small spaces to give bending distortion to the wire and rotating the rotating device. CONSTITUTION:A rotary box 2 is rotated while pulling the hard drawn copper wire 1 in the direction of the arrow through a through hole 3, recessed parts 4', 5', 6' and a through hole 3'. When the copper wire 1 passes through the rotating device while rotating on its own axis, the bending distortion is given to the copper wire by the action of the recessed part 5' positioned at the deviated position of a bending member 5. Accordingly, the bending distortion that generates plastic deformation in all radial direction of the twisted wire is given by the presence of bending members 4, 5, 6, and the residual stress of the wire is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing residual stress from solid or stranded hard copper wire. In particular, the present invention relates to a method for removing residual stress by applying plastic deformation (or plastic strain) to a hard 81 wire, either a single wire or a stranded wire, either directly or with an insulating layer applied thereto.

Conventionally, in the field of overhead insulated wires, hard copper wires in particular have been used as conductors. Hard copper wire has high residual stress on its surface during its manufacturing process and overhead wire process, which causes stress corrosion cracking of overhead insulated wires. Therefore, in order to prevent stress corrosion cracking, it is conceivable to remove residual stress generated on the surface of solid copper wires, stranded wires, or coated conductors thereof.

Conventionally, compressed electric wires have been used to remove this L or residual stress, but there have been economical problems such as the need to develop new fittings. Furthermore, it has been proposed to remove residual stress by a roll straightening method, but in this method, residual stress is removed over the entire circumference of the conductor constituting the solid copper wire, stranded wire, and their coated wires. There was a drawback that stress could not be completely removed.

As a result of various studies, the inventors of the present invention have found that in curves where plastic deformation occurs in the entire radial direction of the wire, residual stress can be effectively removed over the entire circumference of the conductor surface of the hard copper wire by providing a cup. The present invention has been achieved based on the discovery that the present invention can be obtained.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for removing residual stresses in solid or stranded hard copper wire without the drawbacks of the prior art described above.

Another object of the present invention is to eliminate residual stress in hard copper wires and prevent stress corrosion cracking in overhead insulated wires.

The above objects of the present invention have been achieved by the method of the present invention shown below.

That is, the present invention provides for bends that cause plastic deformation in the entire radial direction of a solid copper wire or a stranded wire, directly or covered, to be arranged at small intervals to cause strain to the wire. A method for removing residual stress from a solid or stranded hard copper wire is characterized in that the method comprises rotating a rotating device having at least three bending members while passing the rotating device.

The present invention will be described below with reference to all the accompanying drawings.

FIG. 1 is a perspective view showing an example of a rotary bending device used in the present invention, and FIG. 2 is an explanatory diagram showing a rotary bending situation using a bending tool.

As shown in FIG. 1, the rotary bending device includes a hollow rotating national polity 2, and three bending members 4. '5.6. Through holes 3 and 3' are provided in both walls of the rotating national polity for passing hard copper wires (single wire, stranded wire, or these O-insulated wires, hereinafter simply referred to as hard copper wires) 1. is through hole 6,
3' can be rotated about the center line connecting 3'. The bending member 4.5.6 has a height and a length that is half the width in the lateral direction of the national polity 2, and has a rounded cutout or recess 4/, s1. b and y are provided respectively.

The cutout parts 4' and 6' of members 4 and 6 are through holes 3.3'
is on the same axis as the bending member 4,5.
6 is fixed within the country.

The size of the through hole 3.3' and the size of the cutout portions 4/, S/, and 6/ vary depending on the diameter or thickness of the wire to be processed.
Therefore, it is necessary to prepare a rotary bending device suitable for each wire. In addition, it is preferable that the hollow part provided on each bending member be in a saddle shape as shown in the figure so that the hard copper wire can pass through and the bending strain can be carried out smoothly. A bending strain is applied to the hard copper wire 1 in a state as shown in FIG.

As shown in the figure, the hard copper wire 1 is passed through the above-mentioned rotary bending device and taken in the direction of the arrow through the through hole 6, the missing part 4' + 5' + 6' +, and the through hole 6', and the rotating national polka dot 2 is rotated. When the hard copper wire 1 itself rotates and passes through the rotating device, bending strain is applied to the hard copper wire by the action of the notch 5' located at the biased position of the bending member 5, as shown in FIG. Therefore, the presence of the bending members 4, 5.degree. 6 imparts a bending strain that causes plastic deformation in all directions of the wire, thereby removing residual stress in the wire.

The rotating national polity and bending members can be made of metal, wood, plastic, etc., but wood or plastic can be used if they are lightweight and do not damage the conductor surface.

Although the above example describes the case where there are six bending members, the number may be six or more.

In addition, if both side walls of the rotating national polity with through holes are used as bending members, only one bending member having a biased section is sufficient, and the term "at least three bending members" is used in the present invention. also includes such aspects. Furthermore, although a box-shaped one was used as the rotating national polity, it is not limited to this, and may be cylindrical or the like.

The degree of bending and strain imparted to hard copper wire is determined by the material of the wire, the number and spacing of bending members, the degree of deviation of the missing parts, the rotational speed of the rotating device, the wire take-up speed, etc. However, it is preferable that the bending strain finally imparted to the hard copper wire is 0.15 to 6.0 cm as a bending strain on the wire surface. The bending strain is (11
If the bending strain is less than 5%, the amount of plastic deformation will be small and the residual stress removal effect will be small, and if the bending strain is more than 6 inches, the hard copper wire will be damaged, the deformation of the conductor will be uneven, and the formation of pits will be accelerated. Corrosion resistance becomes a problem.

According to the present invention, the residual stress of the hard copper wire can be removed using relatively simple means, and the following effects are also achieved.

(1) Residual stress is removed in the entire radial direction of solid copper wire and stranded wire.

(2) Manufacturing technology is easy to manage because relatively simple equipment is used.

(3) The equipment used in this method can handle wire rods with the same shape as conventional round stranded wires, so accessories for installing wires can be used, which is economically advantageous and reduces the need for existing equipment. It can be implemented by improving the system and does not require large capital investment.

(4) It can be processed in the form of insulated wires, and the equipment used is simple and convenient, making it easy to work at the wire installation site, and winding up the coated wires with residual stress removed. It can be used as is for overhead lines.

Hereinafter, the present invention will be described with reference to examples.

Example 1 As shown in FIG. 1, three types of rotary bending apparatuses were used, each having three members: one for a single wire, one for a stranded wire, and one for an insulated stranded wire.

2.0φ (diameter 2 籟) solid copper wire at 200 rpm
After passing the rotary curve for 2.0φ single wire through the device at a wire drawing speed of 20 m/min, the 19 wires were twisted together to form a twisted wire conductor (19/2.Q) (diameter 2.0 ms O, 19 lines) were created. Next, the stranded wire conductor (19/2.0) was passed through a rotary bending device for stranded wire (19/2.0) under the same conditions as before. Next, after applying insulation coating to this, the insulation coating twisted @ (1972, 0) is further insulated coating twisted wire (19/2.0
) was passed through the rotary bending device under the same conditions as before to obtain a straight insulated wire with a conductor cross-sectional area of 60 cm2 from which residual stress was removed.

In this example, the rotational speed and wire drawing speed of each rotary bending device were selected so that the bending strain imparted to the finally obtained insulated wire would result in a wire surface curve of 5 degrees. The obtained sample was designated as Sample 1.

Example 2 A stranded wire (19
/2.0) and insulation coated stranded wire (19/20) were passed through their respective rotary bending machines to remove residual stress6.
A straight insulated wire (19/20) of 0fi2 was obtained. In this example, a bending strain of 3 inches was applied as the line surface bending strain. (Sample 2).

Example 5 In Example 1, passing the 2.0φ hard copper wire single wire and stranded wire through the rotary bending device was omitted, and the insulation coated stranded wire (19/2.
0) is passed through a rotary bending device for stranded wires to remove residual stress from 60-2 straight insulated wire (1ci/2
．． 0) was obtained. In this example, the linear surface bending strain is 3.
% bending strain was given. (Sample 3).

Comparative Example 1 Using a ZOφ hard copper wire, it was
)made. This was used as a comparison sample.

7 for each sample obtained in Examples 1 to 3 and Comparative Example 1
A corrosion test and a stress corrosion cracking test were conducted in a mutton solution at 0°C for 200 hours. The stress condition was tensile milling, and the material was wound around a drum with a diameter of 220 m+, and a stress of 55 mm σ3 was applied.

The corrosion test results obtained are shown in Table 1.

The results in Table 1 show that the insulated wire subjected to bending strain according to the present invention has fewer bits that are caused by corrosion than the comparison sample ((number of pits per 100 m of 2,0φ hard copper wire). Comparison), therefore, the occurrence of bits, which are considered to be the incubation period of stress corrosion cracking, is suppressed, and it is considered that the stress corrosion cracking resistance effect is achieved.

The above effect is most remarkable in Sample 1, in which a single hard copper wire, a stranded hard copper wire, and a stranded insulated wire are all subjected to rotational bending strain according to the present invention.

Further, the results of the stress corrosion cracking test described above are shown in Table 2.

As is clear from the results in Table 2, the insulated wires obtained according to the present invention (samples 1 to 5) have a lower number of cracked sibits than the comparative samples and insulated wires that are not subjected to rotational bending strain (
The effectiveness of the present invention was confirmed by comparing the number of cracks per 100 wires of 2,0φ hard copper wire. In addition, in this test, Samples 1 and 2 showed the most excellent effect.

Table 1 Corrosion test results (after 200h) Table 2 Stress corrosion test results (after 200h)

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a rotary bending device used in the practice of the present invention, and FIG. 2 is an explanatory diagram showing a state in which rotational bending strain is applied. 1...Hard copper wire 2...Rotating box 3.5'...Through hole 4,5.6...Curve is member 4',
5', 6'...O missing part

Claims (2)

[Claims] (1) A solid or stranded hard copper wire directly or 4 coated with at least 3 wires spaced at small enough intervals to impart bending strain to the wire that causes plastic deformation in the entire radial direction of the wire. 1. A method for removing residual stress in a solid or stranded hard copper wire, which comprises rotating a rotating device having a plurality of curved members while passing the rotating device. (2) For the given song, the strain is 0.0 as the bending strain on the surface of the line.
The method for removing residual stress according to claim (1), wherein the residual stress is 15% to 6%.