JPS62160609A - Manufacture of conductor for covered wire - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention relates to a method for manufacturing a conductor for a covered electric wire that is insulated with polyethylene or the like, and particularly for a method for manufacturing a conductor for a covered electric wire that is installed between utility poles. Seki Juru.

[Prior Art 1] Hard copper wire has conventionally been used as a conductor for overhead distribution lines installed between utility poles. A plurality of assembled hard copper wires are twisted together, and an insulating coating made of polyethylene, polyvinyl chloride, or the like is applied to the twisted wires.

[Problems to be Solved by the Invention] On the surface of each stranded hard copper wire, a stranded wire repulsive force that tends to untwist is inevitably generated.

This twisted wire repulsive force appears as tensile residual stress on the surface of each hard copper wire. Further, each hard copper wire may have residual stress due to curling curls formed when it was wound around a drum.

In conventional coated electric wires, the residual stress as described above may be one of the causes of wire breakage.

That is, when rainwater enters the covered wire, the interior of the coating layer becomes a corrosive environment, and an oxide film is formed on the surface of the hard copper wire. When such a corrosive environment and the above-mentioned residual stress interact with each other, stress corrosion cracking occurs in the hard copper wire, resulting in wire breakage.

If annealed copper wire is used as the conductor for the covered electric wire, the residual stress as described above is small, so the possibility of stress corrosion cracking occurring is reduced. However, on the other hand, the tensile strength inevitably decreases, and therefore, in practice, annealed copper wire cannot be used as a conductor for coated wires.

Therefore, an object of the present invention is to provide a manufacturing method capable of obtaining a conductor for a coated electric wire that maintains tensile strength and does not cause corrosion under a stress of 11 g.

[Means for Solving the Problems] and [Effect 1] The method for manufacturing a conductor for a covered electric wire according to the present invention continuously produces a copper wire that has been cold-worked at a degree of cold working of 60 to 99.5%. The conductor strands constituting the stranded wire are obtained by rapidly heating the surface and immediately cooling it.

FIG. 1 is a diagram schematically showing this method.

The cold-worked copper wire 1 is continuously fed in one direction by a feeding roller 2 or the like. Then, on the way, the laser beam 3
The surface of the copper wire 1 is rapidly heated by such radiation. The copper wire 1 is then immediately passed through cooling water 4 and cooled.

FIG. 2 is a diagram showing the internal crystal structure of a conductor strand obtained by carrying out the above method.

As shown in the figure, the outer layer portion 5 of the conductor strand 5 has a recrystallized structure, and the center portion thereof has a drawn structure extending in the longitudinal direction.

Since the outer layer of each conductor strand constituting the stranded wire has a recrystallized structure, the outer layer of each strand is plastically deformed when the strands are twisted together. Therefore, residual stress as described above is less likely to occur on the surface of each strand, and the possibility of stress corrosion cracking occurring is also reduced.

On the other hand, since the central portion of each conductor strand has a drawn structure, its tensile strength is relatively high. Therefore, each conductor strand can maintain sufficient tensile strength to withstand use as a conductor for a covered electric wire.

The reason why the surface of the copper wire is rapidly heated continuously and then immediately cooled is to make it exhibit the above-mentioned crystal structure. Further, the reason why a copper wire cold-worked at a degree of cold working of 60 to 99.5% is used is based on the following reason. That is, if the degree of cold working is less than 60%, the central portion of the conductor strand does not have the desired tensile strength. In addition, the higher the degree of cold working, the lower the recrystallization temperature, and therefore the second
It becomes difficult to obtain the crystal structure shown in the figure. Taking this into consideration, the upper limit for the degree of cold working is 9. 5
%.

When using laser light as the heating means, the wavelength of the laser light is preferably within the range of 1 μm to 15 μm. If one attempts to produce 1 q of laser light with a wavelength of less than 1 μm, it will be industrially difficult to develop a high-output laser generating means.

On the other hand, when a laser beam with a wavelength exceeding 15 μl is used, the reflection of the laser beam from the surface of the copper wire becomes large, and the function of applying heat to the surface of the copper wire decreases.

The heating means is not limited to laser light, but infrared irradiation, high frequency induction heating, etc. may also be employed.

[Example] A rough-drawn tough pitch copper wire with a diameter of 8Iφ was made to have a diameter of 2mmφ by cold wire drawing. Cold working degree (area reduction rate) is 9
It is 4%. Then, the surface of the copper wire was heated with a carbon dioxide laser beam having a wavelength of 10.degree. 6 .mu.m and immediately cooled. The outer layer of the conductor wire thus obtained was softer than the center.

After collecting 19 of the above conductor strands into a twisted wire, a polyethylene coating was applied. Then, when a stress corrosion cracking test was performed by injecting diluted ammonia water between the coating layer and the conductor, no breakage of the conductor was observed even after 3 months had passed.

For comparison, a similar test was conducted on a coated wire using hard copper wire as the conductor wire, and the conductor suffered stress corrosion cracking and disconnection at a timely period of one month.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically illustrating the method according to the invention. FIG. 2 is a diagram showing the internal crystal structure of a conductor wire obtained by implementing the present invention. In the figure, 1 is a copper wire, 2 is a feed roller, 3 is a laser beam, 4 is a cooling water, 5 is an outer layer portion, and 6 is a center portion. Figure 7

Claims (3)

[Claims] (1) A covered electric wire that obtains conductor wires constituting a stranded wire by continuously rapidly heating a copper wire cold-worked at a degree of cold working from 60 to 99.5% from the surface and cooling it immediately. Method of manufacturing conductors for use. (2) The method for manufacturing a conductor for a covered electric wire according to claim 1, wherein the surface of the copper wire is rapidly heated by radiation of a laser beam. (3) The method for manufacturing a conductor for a covered electric wire according to claim 2, wherein the wavelength of the laser beam is within a range of 1 μm to 15 μm.