JPH0135451B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a molded stranded or braided superconducting wire with high current density.

Conventionally, a method for manufacturing this type of superconducting wire is to twist together a plurality of strands 3 in which a plurality of superconductors 1 are embedded in a stabilizing material 2 as shown in FIG. 1a, and then form and twist them as shown in FIG. 1b. This is a linear superconducting wire. In the case of a braided superconducting wire, a braiding machine is used to manufacture it.

However, in the conventional method, since the wires are round bars, when the wires are twisted in this state, the linear density is as low as about 78%. Furthermore, even if the strands are compression molded and twisted in the state shown in Figure 1b, the linear density increases by only a few percent; This can cause wire breakage and other problems, significantly impeding its performance as a superconducting wire. Also, the linear density of the braided wire is
The limit is set at around 70%.

Furthermore, in superconducting wires in which round strands are formed into rectangular shapes, the ends (edges) are severely deformed and may break. As a result, the wire at the edge becomes thinner and a critical current is defined. In addition, in the case of a braided wire, since the strands intersect with each other in point contact, the compression process causes cracking, which leads to breakage of the strands.

The present invention has been made as a result of intensive research aimed at improving these drawbacks, and as a result has discovered a manufacturing method for obtaining a superconducting wire with high linear density. That is, the method of the present invention is a method for manufacturing a molded stranded or braided superconducting wire by twisting a desired number of superconducting strands, which includes the steps of: pre-forming the superconducting strands into a rectangular shape with an aspect ratio in the range of 1 to 2; This method is characterized by comprising a step of twisting these rectangular wires and a step of compressing the twisted wires.

The method of the present invention has an aspect ratio of 1 as shown in FIG.
The two strands 3 are used to form a twisted wire or a braided wire using a conventional twisting machine or braiding machine. Note that, if necessary, the wires may be twisted while compression molding using a compressor or a tursk head.

FIG. 3 shows the concept of manufacturing a shaped stranded wire according to the method of the present invention, in which a superconductor 1 is built-in,
A molded stranded superconducting wire 5 is obtained by preparing seven strands of wire 3 and guiding them to a Turk's head 4 while aligning and twisting them and compression molding them.

In the method of the present invention, wires having an aspect ratio of 1 to 2 are used. The reason for this limitation is that deformation of the strands at the edge portion or strand intersection portion can be significantly reduced, and in stranded or braided superconducting wires that do not have a core material, the aspest ratio is 1 to 2. That is, the dimensions of the material to be used are from the same to about 1/2 the thickness of the stranded or braided superconducting wire. On the other hand, in a stranded or braided superconducting wire provided with a core material, the aspest ratio of the wire is determined by the size of the core material, and it is not possible to select a general aspest ratio. In any case, it is included in the concept of using a rectangular wire as a wire.

Note that the method of the present invention can be applied to alloy superconducting wires such as NbTi alloys and compound superconducting wires such as V ₃ Ga and Nb ₃ Sn. Of course, in the case of a compound superconducting wire, a compound superconductor is formed by forming a stranded or braided wire and then performing a diffusion heat treatment.

Next, examples of the present invention will be described.

Example 1 In order to mold Nb ₃ Sn, 505 Nb cores are built into a CuSn matrix, and the outer sheath is made of OFHC copper.
Seven wires of 0.4 mm ² (R=0.05) were prepared and subjected to the forming stranding process shown in FIG. 3 to obtain a stranded superconducting wire of 0.39×1.38 mm ² . The linear density of the superconducting wire thus obtained was 96.5%.

Furthermore, the linear density of the formed stranded superconducting wire obtained by twisting the above wires using the conventional method is 85%.
It was hot.

Example 2 Seven rectangular wires of 0.35 x 0.7 mm ² with 820 cores of NbTi alloy embedded in a Cu matrix were prepared and processed using a braiding machine to obtain a braided superconducting wire of 0.85 x 4.4 mm ² . . The linear density of this superconducting wire was 51%, but it was also compression molded using a Turks head.
A molded braided wire superconducting wire measuring 0.69×3.1 mm ² was obtained, and the density of this wire was 81%.

For comparison, 13 strands of 0.35 mmφ with NbTi alloy embedded in a 420-core Cu matrix were prepared, and a 0.85 x 5.5 mm ² braided superconducting wire was obtained using a braiding machine. The linear density of this line was 43%. When this was further rolled to a size of 0.62 x 5.4 mm ² , the linear density increased to 58%, but two strands were broken.

As described in detail above, the method of the present invention makes it possible to obtain a high-density superconducting wire, making it extremely useful not only for solenoid magnets but also for unusual magnets such as saddle-shaped magnets.

[Brief explanation of drawings]

Figure 1 is a schematic explanatory diagram of a conventional stranded superconducting wire.
FIG. 2 is a schematic explanatory diagram of a stranded superconducting wire according to the method of the present invention, and FIG. 3 is a schematic explanatory diagram showing the stranded wire method according to the present invention. 1... Superconductor, 2... Stabilizing material, 3... Superconducting wire, 4... Turks head, 5... Molded stranded superconducting wire.

Claims (1)

[Claims] 1. A method for manufacturing a molded stranded or braided superconducting wire by twisting a desired number of superconducting wires, a step of pre-forming superconducting strands into a rectangular shape with an aspect ratio in the range of 1 to 2, and forming these rectangular strands. A method for producing a superconducting wire, comprising the steps of twisting wires and compressing the twisted wires.