JPH04298917A - Manufacture of compound superconductor - Google Patents

Abstract

PURPOSE:To easily machine superconductor strands into the preset rectangular cross section shape without deforming them into a flat shape when manufacturing a flat rectangular superconductor. CONSTITUTION:Many strands 15 containing compound superconductor materials, e.g. Nb11 and Sn12, are buried in a Cu matrix 14 heat-treated at the temperature 500 deg.C-700 deg.C. A reinforced copper layer such as alumina-dispersed/reinforced copper 16 is integrated on the outer periphery side of the Cu matrix 14. This integrated body structure is draw-machined 17 to the preset diameter then cold-machined into a rectangular cross section shape 18. It is then heat-treated in the formation temperature region of a compound superconductor, and a compound superconductor layer is formed.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a compound superconducting conductor.

0003

[Prior Art] Superconductors currently in practical use include those using compound-based superconductors such as Nb3Sn and Nb3Al, and those using alloy-based superconductors such as Nb-Ti and Nb-Zr. This technology is well known, and efforts are being made to put it to practical use in superconducting coils, etc., which can generate strong magnetic fields without consuming power transmission cables or electricity. As methods for manufacturing superconducting conductors using the above-mentioned compound superconductors, the bronze method, tube method, internal diffusion method, jelly roll method, etc. are known.

For example, a superconducting conductor to which the Nb tube method is applied is manufactured, for example, as shown below. Taking Nb3Sn multi-superconducting wire as an example of a superconducting conductor, first, a Cu tube into which a Cu-Sn alloy or Sn rod is inserted is filled into an Nb tube, and the outer periphery of this Nb tube is coated with Cu. The parts are integrated using a swaging machine, etc., and the area is reduced to a predetermined outer diameter. Next, a large number of these strands are inserted into a Cu tube, integrated, and then subjected to surface reduction processing to obtain a predetermined wire diameter. After this,
By performing heat treatment at the formation temperature of Nb3Sn,
Sn in the Nb tube is diffused and reacted with Nb, and the Nb
b Form a Nb3Sn superconductor layer on the surface of the tube.

[0005] Furthermore, superconducting wires using Nb3Sn etc. have the disadvantage that superconducting properties such as critical current density tend to deteriorate when longitudinal tensile force or bending strain is applied. A superconducting wire with a rectangular cross section is less likely to deteriorate its superconducting properties due to the above deformation than a superconducting wire with a circular cross section, so superconducting wires with a rectangular cross section are generally used when manufacturing superconducting coils. It is being Such a rectangular superconducting wire is produced in the above-mentioned Nb tube method by rolling a round wire to a predetermined wire diameter through area reduction processing using a pressure roller or the like before heat treatment at the temperature for forming a compound superconductor. , the cross-sectional shape is made into a rectangular shape such as a square or a rectangle, and then heat treatment is performed at the temperature at which a compound superconductor is formed.

[0006]

[Problems to be Solved by the Invention] By the way, in the rectangular superconducting wire as described above, when processing the round wire into a rectangular cross-section, as shown in FIG. The filled Nb tube 3 itself also deforms into a flat shape. Although not shown in the figure, a superconductor layer such as Nb3Sn is formed on the inner circumferential side of the deformed Nb tube 3, so when the Nb tube 3 is deformed into a flat shape, the critical current density of the superconducting wire ( Anisotropy occurs in Jc). This situation is shown in FIG. As is clear from Fig. 5, compared to Jc (indicated by △ in the figure) when a magnetic field is applied in the short side direction of the cross section of the superconducting wire, the magnetic field is applied in the long side direction of the cross section of the superconducting wire. Jc (indicated by ○ in the figure) decreases significantly. This significantly limits the degree of freedom in using superconducting wires.

Furthermore, when manufacturing a superconducting magnet, the rectangular superconducting wire is wound so that the long side of the cross section is in contact with a winding jig in order to reduce the ease of winding and to suppress a decrease in Jc due to strain and load. That is, the rectangular superconducting wire is wound in the direction in which the Jc decreases more with respect to the direction of the magnetic field formed by the superconducting magnet. Therefore, in order to obtain a predetermined magnetic field, it is necessary to take measures such as increasing the number of turns or increasing the diameter of the wire, resulting in a large and heavy superconducting magnet.

[0008] The present invention has been made to address the above-mentioned problems of the prior art, and when manufacturing a rectangular superconducting conductor, it is possible to easily shape the superconducting wire into a predetermined rectangular cross-sectional shape without deforming the superconducting wire. The purpose of the present invention is to provide a method for manufacturing a compound superconducting conductor that can be processed into a compound superconducting conductor.

[Configuration of the invention]

0010

[Means and Effects for Solving the Problems] That is, the method for manufacturing a compound superconducting conductor of the present invention is to heat a large number of wires containing a compound superconductor material that reacts to form a compound superconductor by heat treatment at a temperature of 500°C to embedding in a Cu-based matrix heat-treated at a temperature in the range of 700°C;
A step of integrating a reinforcing copper layer on the outer peripheral side of the Cu-based matrix, a step of cold working this integrated structure into a predetermined external shape, and a step of applying the compound superconductor to the processed body. The method is characterized by comprising a step of performing heat treatment in the formation temperature range.

[0011] The compound superconductor material that reacts to form a compound superconductor by heat treatment used in the present invention includes Nb and Sn, which are the forming materials of Nb3 Sn, and Nb3
Nb and Al, which are forming materials for Al, are exemplified. For example, a superconductor wire is formed by filling a Nb tube with a material containing Sn or Al. Furthermore, it is also possible to use Nb, Sn, or Al as separate wires.

[0012] Such superconductor wires are embedded in a Cu-based matrix. Further, a reinforcing copper layer is integrated on the outer peripheral side of this Cu-based matrix, thereby forming a structure that is a prototype of the compound superconducting conductor of the present invention. here,
The Cu-based matrix is made of Cu that has been heat-treated at a temperature of 500°C to 700°C. Cu subjected to such heat treatment causes a softening phenomenon by cold working such as area reduction processing, and is therefore very effective in preventing deformation of the superconductor strands. If the temperature during the heat treatment is less than 500°C, the above-mentioned softening phenomenon cannot be sufficiently obtained, and if it exceeds 700°C, softening becomes difficult. The atmosphere during the heat treatment is not particularly limited, but is preferably a vacuum or an inert atmosphere in order to prevent oxidation of Cu. However, when the heat treatment is performed in an oxidizing atmosphere such as the air, the oxide layer may be removed after that. In addition, the heat treatment time is 10 hours ~
It is preferable to set it as about 50 hours. In addition, the above C
Examples of the reinforced copper integrated on the outer peripheral side of the U-based matrix include particle dispersion strengthened copper alloys using alumina particles, solid solution strengthened copper alloys using Cr, Zr, Ti, Zn, etc.
Examples include work-hardened copper, and alumina dispersion-strengthened copper is particularly preferred. This alumina dispersion strengthened copper has A in Cu.
It is a reinforced Cu alloy that is dispersion-strengthened by dispersing l2O3 particles in a range of about 1 to 2% by weight, and is obtained, for example, by reducing and sintering a mixture of copper oxide powder and alumina powder. This alumina dispersion-strengthened copper exhibits extremely small decrease in tensile strength even when heat treated at the temperature at which compound superconductors are formed, and is effective as a strong member of compound superconducting conductors, as well as preventing deformation of superconductor strands. is very effective.

In the manufacturing method of the present invention, the above-described structure is subjected to cold wire drawing to form a round wire of a predetermined wire diameter, and then this round wire is drawn using a pressure roller or the like. The external shape of the compound superconducting conductor is processed into a rectangular cross-section by rolling. Here, the pressure applied to the round wire is absorbed by the outermost reinforcing copper layer, and the internal Cu-based matrix is softened by wire drawing, and the superconductor strands in the matrix are softened. Since movement is more likely to occur, the load applied to the superconductor strands is dispersed and reduced. Therefore, even if the external shape of the compound superconducting conductor itself is processed to have a rectangular cross-section, the shape of the superconductor strand can be maintained to have an approximately circular cross-section.

[0014] Then, a compound superconductor layer is formed by heat-treating the processed body having a predetermined rectangular cross-sectional shape in the compound superconductor formation temperature range as described above. A compound superconducting conductor is obtained. For example, in the case of Nb3Sn, the heat treatment conditions are 650°C to 770°C for 10 hours to 40°C.
Approximately 0 hours, in the case of Nb3 Al, 750°C ~ 9
The time is about 1 hour to 100 hours at a temperature of 50°C.

[0015] When the compound superconducting conductor obtained according to the present invention is applied to a heat-treatable product, the heat treatment of the present invention may be performed during the assembly process of the product. For example, when forming a superconducting magnet using a superconducting wire manufactured according to the present invention, the wire before heat treatment is wound around a coil winding frame, and in this state, a compound superconductor and a diffusion prevention layer are formed. Heat treatment may also be performed for this purpose.

[0016]

EXAMPLES Next, examples of the method for manufacturing a compound superconducting conductor of the present invention will be described with reference to the drawings.

Example 1 FIGS. 1 and 2 are diagrams showing the manufacturing process of a compound superconducting conductor according to an example of the present invention. The method for manufacturing the multi-superconducting wire of this example will be described below with reference to these figures.

First, a tubular member made of pure copper was heat treated at 600° C. for 16 hours in the atmosphere. Then,
In order to brighten the blackened surface due to the formation of copper oxide,
Further, heat treatment was performed in a vacuum at 600°C. The Cu tube subjected to such heat treatment was used as a matrix component, and a superconductor wire was produced in the following manner.

As shown in FIG. 1(a), an Nb tube 1
After inserting the Cu tube 13 filled with the Sn rods 12 into the Cu tube 14, this was further inserted into the Cu tube 14 which had been subjected to the heat treatment, and the superconductor wire 15 was produced by integrating the Cu tube 13 into the Cu tube 14. The Cu tube 14 subjected to the above heat treatment becomes a constituent member of the Cu matrix.

Next, as shown in FIG. 1(b), a large number of the superconductor wires 15 are bundled and alumina dispersion strengthened copper (1
．． 1wt% Al2O3-Cu) was inserted into the tube 16. This alumina dispersion-strengthened copper tube 16 constitutes the outermost layer of the intended superconducting wire.

[0021] The alumina dispersion-strengthened copper tube 16 into which a large number of superconducting wires 15 are inserted is integrated by a swaging machine to form a prototype of the desired superconducting wire, as shown in FIG. 2(a). A structure was created. In this integration step, the Cu tube 14 subjected to the heat treatment forms a Cu matrix. After this, the integrated structure was subjected to a cold area reduction process (wire drawing process) to a diameter of 1.1 mm.
A 2 mm round wire 17 was obtained.

Next, the round wire 17 is rolled with a pressure roller and processed to have a rectangular cross-sectional shape of 0.7 mm x 1.4 mm, so as to form a rectangular wire as shown in FIG. 2(b). 1
8 was produced. When the cross-sectional structure of this rectangular wire 18 was observed under a microscope, the shape of the superconductor strand 15 maintained a roughly round shape, as shown in FIG. 2(b). this is,
As shown in FIG. 2(a), the pressure applied to the round wire 17 (indicated by arrow A in the figure) is received by the outermost alumina dispersion-strengthened copper tube 16, which has high mechanical strength. This is because the internal Cu matrix 14 has undergone a softening phenomenon due to the wire drawing process, and the superconductor wires 15 within the matrix 14 are likely to move.

[0023] After that, the above rectangular wire 18 is 7
Heat treatment was performed at 00° C. for 30 hours to cause the Nb tube 11 to react with the Sn that had diffused in the internal Cu tube 13. Although not shown in FIG. 2(b), the Nb tube 11
A Nb3Sn layer was formed on the inner peripheral side of the wire to obtain the desired rectangular superconducting wire.

The critical current density of the rectangular superconducting wire thus obtained was measured in a state in which a magnetic field was applied in the short side direction of the cross section and in a state in which a magnetic field was applied in the long side direction. The results are shown in FIG. As is clear from FIG. 3, the anisotropy of the critical current density with respect to the direction of magnetic field application is significantly improved compared to the conventional rectangular superconducting wire (see FIG. 5). For example, when a magnetic field was applied in the direction of the short side of the cross section, it was 850 A/mm2 at 15 Tesla, and when the magnetic field was applied in the direction of the long side, it was 800 A/mm2 at 15 Tesla. Further, a round wire before being processed into a rectangular shape was produced in the same manner, and the critical current density of the superconducting wire obtained by subjecting it to the same heat treatment was measured and found to be 935 A/mm2. From this, it can be seen that by processing the superconductor strand into a rectangular shape without flattening it, a critical current density value itself close to that of a round superconducting wire can be obtained.

[0025]

[Effects of the Invention] As explained above, according to the method for producing a compound superconducting conductor of the present invention, when producing a rectangular superconducting conductor, a predetermined shape can be obtained without deforming the superconducting wire into a flat shape. Since it can be easily processed into a rectangular cross-sectional shape, it is possible to provide a compound superconducting conductor with small anisotropy in superconducting properties such as critical current density with respect to the direction of application of a magnetic field. This makes it possible to greatly improve the degree of freedom when using rectangular superconducting conductors.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a part of the manufacturing process of a superconducting wire according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the superconducting wire manufacturing process following FIG. 1;

FIG. 3 is a diagram showing the critical current density of a rectangular superconducting wire obtained according to an example of the present invention with respect to the direction of an applied magnetic field.

FIG. 4 is a diagram showing a cross-sectional structure of a conventional rectangular superconducting wire.

FIG. 5 is a diagram showing the critical current density of a conventional rectangular superconducting wire with respect to the direction of an applied magnetic field.

[Explanation of symbols]

11...Nb tube 12...Sn rod 13...Cu tube 14...Cu matrix (heat-treated Cu tube) 15...Superconductor wire 16...Alumina dispersion-strengthened copper tube 17...Round shape Line 18...Flat line

Claims (1)

[Claims] Claim 1: A large number of strands containing a compound superconductor material that reacts with heat treatment to form a compound superconductor,
C heat treated at a temperature ranging from 500℃ to 700℃
a step of embedding in a u-based matrix, a step of integrating reinforcing copper on the outer peripheral side of the Cu-based matrix, a step of cold working this integrated structure into a predetermined external shape, and a step of said processing. A method for manufacturing a compound superconducting conductor, comprising the step of subjecting the body to a heat treatment in a temperature range in which the compound superconductor is formed.