JPH0351794B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for manufacturing an insulated conductor in which a film made of cupric oxide (CuO) is formed on the surface of a strand of copper stranded wire.

BACKGROUND TECHNOLOGY Twisted copper wire used as power cables is made by twisting a large number of wires together and then compression-molding the wires to increase the space factor.
Due to the skin effect in which the power transmission current mainly flows near the surface of the stranded wire as a whole, the power transmission capacity does not increase in proportion to the cross-sectional area. Therefore, in order to increase the power transmission capacity, attempts have been made to provide an insulating layer on the surface of the wires to insulate them from each other.

A known method for manufacturing such insulated conductors is to generate a cupric oxide (CuO) film on the surface of the wire, but such an oxide film is formed on the wire in advance and then If twisting and compression molding are performed, there is a high possibility that the oxide film will peel off during the twisting process or compression molding process. Therefore, for example, as shown in Japanese Patent Publication No. 57-59608,
A known method is to immerse a compression-molded copper stranded wire in an oxidizing solution to chemically oxidize the surface layer of the wire. However, simply immersing stranded copper wire in an oxidizing solution does not cause sufficient oxidation, and
Because the wires are in close contact with each other due to compression molding, it is difficult for the oxidation treatment liquid to enter between the wires on the center layer side. This took a long time and caused problems with poor productivity.

Therefore, as already proposed in Japanese Patent Publication No. 58-23470, a method is known in which the copper strands are heated in an inert atmosphere in order to promote oxidation before being immersed in the oxidizing solution. .

Problems to be Solved by the Invention As shown in the above-mentioned Japanese Patent Publication No. 58-23470, the method of heating stranded copper wire before immersing it in an oxidation treatment solution has the following problems. Ta.
In other words, although heating in this case is supposed to be carried out in an inert gas atmosphere, in reality, the replacement with inert gas may not be sufficient, or the heating may be immersed in the oxidation treatment solution after heating in an inert gas atmosphere. Until then, the high-temperature stranded copper wire may come into contact with the outside air, and cuprous oxide (Cu ₂ O) may be generated on the surface of the strands of the stranded copper wire. This cuprous oxide not only has poor insulating properties, but also is difficult to change into cupric oxide (CuO) in the subsequent chemical oxidation treatment. A problem arises in that sufficient cupric oxide with good properties is no longer produced.

In view of the above-mentioned circumstances, the present invention provides a method for producing a copper oxide film strand insulated conductor that uniformly, sufficiently, and quickly forms a cupric oxide film over the entire surface layer of the strands of a stranded copper wire. The purpose is to

Means for Solving the Problems In order to achieve the above object, the present invention provides 1 to 10% NaClO ₂ to compression-molded copper stranded wire.
A step in which a mixed aqueous solution of an aqueous solution and a 1-10% NaOH aqueous solution is held at 80-105°C and press-injected, and steam or hot water at about 100°C is injected into the copper stranded wire to wash and remove the mixed aqueous solution. heating the cleaned copper stranded wire to 100-300°C in an inert atmosphere, and adding 1-10% NaClO2 aqueous solution and 1-10% _NaClO2 aqueous solution.
This method is characterized by including the step of again press-fitting the mixed aqueous solution with the NaOH aqueous solution into the stranded copper wire.

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a copper stranded wire with a high compression ratio can be targeted, for example, a copper stranded wire with a space factor of about 90% can be targeted. The copper strands have
As in the case of ordinary oxidation treatment, it is preferable to perform alkaline degreasing treatment, washing the degreasing solution with water, and draining water prior to the oxidation treatment.

After performing such preliminary treatment, a first oxidation treatment is performed. The main purpose of this is to generate a cupric oxide film on the surface of the wire in the outer layer, and the oxidizing agent is 1 to 10%.
A mixed aqueous solution of a NaClO ₂ aqueous solution and a 1 to 10% NaOH aqueous solution is used, and the mixed aqueous solution is maintained at 80 to 105°C and press-fitted into the target copper stranded wire. This operation is carried out, for example, by placing the mixed aqueous solution in a closed tank, inserting the targeted copper stranded wire into the closed tank while maintaining water solubility, and pressurizing the inside of the closed tank.

Following the oxidation treatment described above, the stranded copper wire is subjected to a cleaning treatment to remove the mixed aqueous solution. This prevents NaClO ₂ from decomposing and generating ClO ₂ gas, as well as the formation and adhesion of NaClO ₂ crystals during heating in the next process, and also prevents roughening of the conductor surface. This is done by injecting steam or hot water at about 100°C into the stranded copper wire. More specifically, a method can be adopted in which a stranded copper wire is inserted into a sealed tank in which steam or hot water is pressurized and sealed while maintaining airtightness or watertightness.

Next, the copper stranded wire is heated to 100 to 300
Heat and raise temperature to ℃. The purpose of this is to promote the oxidation of the strands on the center layer side during the oxidation treatment in the next step. The purpose of heating in an inert atmosphere is to prevent the formation of _cuprous oxide due to air oxidation. For this purpose, a high frequency induction heating device may be used. When the stranded copper wire is heated as described above, the wires expand thermally, the gaps between the wires widen, and the gas in the gaps expands thermally and is discharged to the outside.
In order to contract and reduce the pressure when cooled by the oxidation treatment liquid in the next process, by maintaining the above temperature until the next process, the oxidation treatment liquid can enter between the strands in the center layer. , and the high temperature accelerates the oxidation reaction. Furthermore, if the heating temperature is 200℃ or higher, an annealing effect will occur, which will correct the work hardening associated with compression molding, increase the electrical conductivity of the wire, especially on the center layer side, and reduce its electrical resistance. .
In this heating process, even if the replacement with an inert atmosphere is insufficient, or even if the high-temperature stranded wire comes into contact with the outside air when transferring the copper stranded wire to the next process, oxidation, which has poor insulation properties, may occur. Cuprous ( _Cu2O )
There is very little possibility that this will be generated. In other words, since a certain amount of cupric oxide film is already formed on the surface in the first step (the first oxidation treatment described above), the cupric oxide film protects against the progress of oxidation during the heating process. It functions as a film and can therefore effectively prevent cuprous oxide from being produced by heating.

The copper stranded wire heated to an elevated temperature as described above is sent to the second oxidation step and subjected to oxidation treatment while maintaining that temperature. The purpose of this second oxidation step is to oxidize the strands on the center layer side, and the conditions and operations are the same as those of the first oxidation treatment step described above.
This is carried out by press-fitting a mixed aqueous solution of ~10% _NaClO2 aqueous solution and 1~10% NaOH aqueous solution into the copper stranded wire while maintaining the temperature at 80~105°C. Note that this second
In the oxidation treatment process, the copper stranded wire is heated in the previous stage, so as mentioned above, the mixed aqueous solution as the oxidation treatment liquid easily enters the gap between the strands on the center layer side. In the heating process, the production of cuprous oxide, which is difficult to convert into cupric oxide, is prevented, so the oxidation reaction that produces cupric oxide proceeds rapidly, and as a result, the above-mentioned
In the oxidation treatment step, the strands in the outer layer are mainly oxidized, and the surface of the strands of the entire twisted copper wire is oxidized almost uniformly to form a film of cupric oxide.

Finally, the mixed aqueous solution is removed by washing with water, and the stranded copper wire is drained and dried before being wound up. In addition, it is preferable that the above-mentioned series of treatments be carried out in a so-called continuous process, in which the stranded copper wire, which has been compression-molded in advance, is fed out from a drum and is run. The tanks or heating devices may be arranged in sequence, and the targeted copper stranded wire may be inserted and run through these closed tanks or devices. Further, the copper stranded wire to which this invention is directed may be a final product itself, or may be a segment formed by combining a plurality of them into a single conductor.

Effects of the Invention As is clear from the above explanation, according to the method of the present invention, although the oxidation reaction is carried out at a relatively high temperature, there is no room for the production of cuprous oxide due to air oxidation, and moreover, the heating step is not required. This process promotes the penetration of the oxidation treatment liquid into the center layer side and the oxidation reaction, so that the entire strand of compression-molded copper stranded wire is uniformly oxidized and the cupric oxide film is sufficiently and quickly removed. can be generated.

Claims (1)

[Claims] 1 1 to 10% of the pre-compression molded copper stranded wire
(wt%, same below) _NaClO2 aqueous solution and 1-10%
A mixed aqueous solution with NaOH aqueous solution is maintained at 80 to 105°C and then press-injected, and then water vapor or hot water at about 100°C is press-injected into the copper strands to clean them, and then the copper strands are placed in an inert atmosphere. heated to 100 to 300℃, and further heated to 1 to 10% of the stranded copper wire.
A method for manufacturing a copper oxide coated strand insulated conductor, which comprises press-fitting a mixed aqueous solution of a NaClO ₂ aqueous solution and a 1-10% NaOH aqueous solution at a temperature of 80-105°C.