JPH06223653A - Manufacture of nb 3 sn compound superconducting wire - Google Patents

Abstract

PURPOSE:To make it easy to manufacture a superconducting wire and to reduce the manufacturing cost thereof by improving the hysteresis loss of the wire to a lower value while keeping critical current density high, and reducing the heating value of the superconducting wire when used in a pulse coil, for example, and forming the superconducting wire from a soft, pure metal without use of any hard bronze matrix in manpufacturing the same. CONSTITUTION:A plurality of composite wires, each comprising one or plural Nb, or Nb-group, alloy rods 1 arranged in close contact with one another, Sn, or Sn-group, alloy rods 2 disposed around the Nb, or Nbgroup, alloy rods 1, and when necessary a Cu, or Cu-group, alloy disposed around the rods 1, 2, are bound together and inserted into a sheath 3. Thereafter, cross section reduction machining is carried out to obtain an element wire which is then heat treated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a Nb ₃ Sn compound superconducting wire. More specifically, the present invention relates to a method for producing a Nb ₃ Sn compound superconducting wire while maintaining a very high critical current density. superconducting wire minimum hysteresis loss can be obtained, a method of manufacturing a Nb ₃ Sn compound superconducting wire.

[0002]

2. Description of the Related Art Nb ₃ Sn compound superconducting wires have excellent superconducting characteristics such as critical temperature, critical magnetic field and critical current, and are therefore used as winding materials for electromagnets for generating high magnetic fields.

Generally, in Nb ₃ Sn compound superconducting wire, a complex of a large number of Nb ₃ Sn filaments and a bronze matrix existing around the filaments is stabilized with copper or Ta-based alloy or Nb or Nb-based alloy. Has a cross-section that contacts. FIG. 11 shows an example of a cross section of a conventional Nb ₃ Sn compound superconducting wire after heat treatment and cross-section reduction processing. In FIG. 11, 3 is stabilized copper, 4 is Ta
Alternatively, a diffusion barrier made of Ta-based alloy, Nb or Nb-based alloy, 5 is an Nb ₃ Sn filament, and 6 is a bronze matrix. The outer shape may be circular or rectangular. Of course, the Nb ₃ Sn filament 5 is a superconducting phase.

However, since the Nb ₃ Sn compound superconductor is an intermetallic compound and mechanically fragile, it is difficult to form a composite wire by a plastic working method like an alloy superconductor. Therefore, as one of the manufacturing methods of the Nb ₃ Sn compound superconducting wire, as shown in FIG. The composite of 6 and the diffusion barrier 4 and the stabilized copper 3 for preventing the diffusion of Sn are further combined, and these are composite-processed into a desired cross-sectional shape and then heat-treated to obtain a Nb ₃ Sn compound. Method to generate (Bronze method)
Was taken. However, according to this method, since the Sn concentration in the bronze matrix is as high as about 13% in cold surface reduction processing, the work hardening of the Cu-Sn bronze matrix is extremely large, and a large number of softening heat treatments are required during processing. However, the softening heat treatment requires much cost and time, and the Sn concentration in the bronze is about 13
%, There is an upper limit, so it is difficult to obtain a large amount of Sn, and therefore the amount of Nb ₃ Sn compound produced is small,
For example, the critical current was as low as 650 A / mm ^{2 at} 12T. If the Sn concentration is 13% or more, a compound is generated in the bronze matrix, which makes it extremely difficult to process the bronze matrix.

In order to solve such a drawback, as an example thereof, the following method has been adopted as shown in FIG. Cu / N from extruded composite billet consisting of Cu and Nb
b Create a composite pipe. Sn is inserted into the vertical hole in the central portion, and cross-sectional reduction processing is performed by swaging, rolling, drawing, or another method to obtain a wire having a small diameter. A plurality of these are bundled, put in another Cu pipe, and this is subjected to a drawing process or the like to obtain a superconducting element wire. When this is subjected to Nb ₃ Sn formation heat treatment, Sn diffuses to form an Nb ₃ Sn matrix, which can be used as an Nb ₃ Sn compound superconducting wire. Unlike the bronze method, this method does not have a Sn content limit of 13% or less, so that the Sn content can be increased, and thus the amount of Nb ₃ Sn compound produced can be increased. A very high critical current density can be obtained as compared with the method.

[0006]

However, even if a high critical current density (Jc) is obtained as described above, the fact that Nb cannot be arranged in the Sn in the central portion is accompanied by the Nb filament spacing. Is smaller, the adjacent filaments of the Nb ₃ Sn compound are likely to be connected to each other, and an increase in hysteresis loss has been observed.
For example, with a wire rod having a Jc of 950 A / mm ² at 12T, the effective filament diameter is 15 to 15 in terms of hysteresis loss.
It was 20 μm. A superconducting pulse coil using such a superconducting wire generates a large amount of heat and requires a powerful refrigerator. Furthermore, Nb is contained in Sn in the central portion.
_A so-called dead zone occurs because no Sn compound is produced.

The present invention has been made in order to solve the above-mentioned problems, and the Nb ₃ Sn compound superconducting wire which is adjacent to Nb ₃ S is maintained while maintaining a very high critical current density.
It is an object of the present invention to provide a method for producing a Nb ₃ Sn compound superconducting wire, which can obtain a superconducting wire with minimal hysteresis loss in which filaments of an n compound are not connected to each other.

[0008]

As a result of earnest studies, the present inventors were able to solve the above-mentioned conventional problems.

That is, according to the present invention, one Nb or Nb is used.
Base alloy rod or closely arranged Nb or Nb
A plurality of composite wire rods consisting of a base alloy rod, Sn or Sn base alloy rods arranged around the Nb or Nb base alloy rod and, if necessary, Cu or Cu base alloy arranged around these are bundled and inserted into a sheath material. After that, a cross-section reduction process is performed to obtain a wire, and the wire is heat-treated.
The present invention provides a method for producing an Nb ₃ Sn compound superconducting wire.

The present invention also includes a first Nb or Nb-based alloy rod or a plurality of closely arranged Nb or Nb-based alloy rods and, if necessary, Cu or a Cu-based alloy disposed around them. Composite wire and 1 Sn
Or Sn-based alloy rods or closely arranged Sn
Alternatively, a Sn-based alloy rod and, if necessary, a second composite wire made of Cu or a Cu-based alloy that is placed around these rods are placed so as to be dispersed and inserted into a sheath material,
The present invention provides a method for producing an Nb ₃ Sn compound superconducting wire, which comprises subjecting an element wire to a cross-section reduction process and heat-treating the element wire.

Further, according to the present invention, one Nb or Nb-based alloy rod or a plurality of Nb or Nb-based alloy rods closely arranged in a plurality of vertical holes provided in a copper or copper-based alloy rod material and one Of Sn or Sn-based alloy rods or a plurality of Sn or Sn-based alloy rods closely arranged are separately or integrally inserted, a cross-section is reduced to obtain a wire, and the wire is heat-treated. And a method for producing a Nb ₃ Sn compound superconducting wire.

[0012]

In the present invention, the arrangement of Sn is not concentrated, and is distributed around each Nb, so that there is no dead zone for the arrangement of Nb rods (Nb filaments), and therefore the Nb filaments are eliminated. interval can improve long, even if there is expansion of the filament due to Nb ₃ Sn compound produced, no longer connected the filaments of Nb ₃ Sn compound, as a result it is possible to reduce the hysteresis loss, high-performance superconducting wire is manufacturable.

[0013]

EXAMPLES The present invention will be described below with reference to examples. Example 1. Figure 1 shows Sn around the Nb rod as a composite wire.
It shows an embodiment in which a bar is arranged. In FIG. 1, 1
Is an Nb rod, 2 is an Sn rod, and 3 is a Cu tube. Diameter 10mm
A Sn plate having a thickness of 1.5 mm was sprinkled on the Nb rod 1 of No. 1 and inserted into a Cu tube 3 having a concave groove on the inner surface. This is drawn, and a hexagonal bar (composite wire) with a distance between opposite sides of 3.0 mm and a length of 1.0 m is 2
53 pieces were produced. The cross-sectional shape of the bundled hexagonal rods at this time is as shown in FIG. 1, and the Sn rods 2 are embedded in the concave groove on the inner surface of the Cu pipe 3. Next, bundle these 253 pieces and put them in another circular Cu tube (sheath material),
After drawing, 55 hexagonal rods with a distance of 3.5 mm and a length of 1.0 m were manufactured. This was inserted into another circular Cu tube together with a Ta barrier, and a superconducting wire having an outer diameter of 0.95 mm was produced by drawing. The processing could be favorably carried out without softening heat treatment during processing.

Both ends of a sample having a length of about 1.5 m, which was cut out from the prepared wire, was heated to perform Sn sealing treatment, and Nb
₃ Sn compound formation heat treatment was performed. Heat treatment is 675 ° C
It was 100 hours. As a result of measuring the critical current of the Nb ₃ Sn compound superconducting wire obtained by this, the critical current density was 1040 A / mm ² per non-copper in a magnetic field of 12 T at a temperature of about 4.2 ° K. Met. In addition, Nb ₃ S produced as a result of scanning electron microscope observation
It was found that there was no part where the n compounds were connected to each other, and the hysteresis loss was minimal. The result of measurement of the effective filament diameter in the coil shape of the sample subjected to the same heat treatment was 5 μm, and it was found that the Nb ₃ Sn compound superconducting wire has excellent performance in both critical current density and hysteresis loss characteristics.

The cross-section reduction process is not particularly limited, and may be swaging, rolling, drawing,
Other methods can be selected appropriately. further,
Although the above heat treatment was performed at 675 ° C. for 100 hours, the present invention is not limited to this heat treatment condition and can be performed, for example, at 500 to 900 ° C. for 1000 hours or less. Preferably, it is 600 to 750 ° C. × 300 hours or less.

Example 2. Nb rod with a diameter of 10 mm has an outer diameter of 1
A hexagonal bar (first composite wire) having a distance of 3.0 mm and a length of 1.0 m was manufactured by placing it in a Cu tube of 5.5 mm and an inner diameter of 10.5 mm and drawing it. Also, a Sn rod with a diameter of 10 mm was put into another Cu pipe with an outer diameter of 15.5 mm and an inner diameter of 10.5 mm and was drawn, and a hexagonal rod with the opposite side distance of 3.0 mm and a length of 1.0 m (second composite wire rod) was also used. ) Were produced. Total 2 above
53 pieces are bundled so as to be dispersed, put into another circular Cu tube (sheath material), and drawn, and the distance between opposite sides is 3.5 mm and the length is 1.0.
55 hexagonal rods of m were produced. This was further inserted into a circular Cu tube prepared separately, together with a Ta barrier, and drawn out,
A superconducting wire having an outer diameter of 0.95 mm was obtained. An enlarged view of the cross-sectional shape of the wire is shown in FIG. As can be seen from FIG. 2, the first composite wire and the second composite wire are evenly distributed and arranged. During the processing, the softening heat treatment unlike the bronze method was not necessary, and the processing could be favorably performed. A part of this strand was cut out and subjected to a heat treatment for forming a Nb ₃ Sn compound at 675 ° C. for 100 hours. The critical current of this coil-heat-treated sample was measured at a temperature of 4.2 ° K in a magnetic field of 12 T, and a high critical current density of 1010 A / mm ² was obtained. In the same manner as in Example 1, in the scanning electron microscope observation, there was no connection between the produced Nb ₃ Sn compounds, and regarding the hysteresis loss, the effective filament diameter was about 5 μm, and both the critical current density and the hysteresis loss characteristics were found. It has been proved that it has excellent performance in.

Embodiment 3. In the above and below examples, the metals used are pure metals such as Nb, Sn, Cu, and Ta, respectively. However, in order to improve the critical current density or to improve workability, another element is used. Even if added, the same effect can be obtained. For example, as an Nb-based alloy,
Sn-Ti (Ti 5% or less), Sn-In (In 10% or less), Sn-Ta (T 5% or less), Nb-Ta (Ta 7% or less), Sn-In (In 10% or less), Sn-Ta (T
a7% or less) or the like can be used.

Example 4. In addition, regardless of the finished wire diameter of the Nb ₃ Sn compound superconducting wire, the presence or absence of stabilizing copper, and the material of the diffusion barrier, Nb which basically constitutes the superconducting compound or the above Nb-based alloy, Sn or the above If the Sn-based alloy as described above and the composition of Cu are as in the present invention, the same effect can be obtained.

Example 5. In Examples 1 and 2, 1
The example of bundling 253 times and 55 times of the second time and putting it in a Cu pipe (sheath material) has been described, but the same effect can be obtained if the focusing is performed only once or three times or more. To be Furthermore, the number of bundles is not particularly limited, and the same effect can be obtained regardless of the number of bundles.

Example 6. Further, in the first embodiment, 1
Only one example of the arrangement of Sn or Sn-based alloy around the Nb or Nb-based alloy rod of the book is described, and another arrangement may be adopted. For example, not one Nb or Nb alloy rod,
It is also possible to use a plurality of closely arranged ones. Also,
Similar effects can be obtained by disposing the Nb or Nb-based alloy rod 1 and the Sn or Sn-based alloy rod 2 in the circular Cu tube 3 as shown in FIG.

Example 7. In the second embodiment, the first and second
Although the case where the composite wire rod of (1) is formed into a hexagonal shape and then bundled is described, another wire shape is similarly effective. For example,
Similar effects can be obtained by arranging each of the first and second composite wires in the circular Cu tube 3 as shown in FIG. In addition, Nb or N contained in the first and second composite wires
The b alloy rod and the Sn or Sn alloy rod may be a plurality of rods arranged in close contact with each other.

Example 8. Further, even if the arrangement of the first and second composite wire rods in the second embodiment is changed to the arrangement in which the second composite wire rod is surrounded by the first composite wire rod as shown in FIG. 5, the same effect is obtained. can get.

Example 9. ~ 13. Further, as shown in FIG. 6, a plurality of circular vertical holes are formed in a copper or copper-based alloy rod material (sheath material), for example, a circular rod material, and Nb rods 1 and Sn rods 2 are respectively formed therein. It may be inserted and subjected to the same heat treatment and cross-section reduction processing as in the above-mentioned embodiment. In FIG. 6, seven circular vertical holes of the same size are provided, and Nb rod 1 and Sn rod 1 are provided.
In addition to the above, the case where seven adjacent circular vertical holes having the same size are provided, and a rod provided with Sn around the Nb rod is inserted therein (FIG. 7) is the same. If you insert 19 circular holes of the same size and insert Sn around the Nb bar (Fig. 8), you will create 19 circular holes of the same size and insert the Nb bar into them. 1 and Sn
When the rods 1 are inserted adjacent to each other (Fig. 9), the Nb rod 1 is inserted in the large circular vertical hole in the center, and the Sn rods are inserted in the small circular vertical holes around it (Fig. 10). The same effect can be obtained. In the above,
Although the vertical hole of the sheath material is circular, its shape is not particularly limited and can be various shapes. Further, in the above, the case where the number of vertical holes is 7 or 19 has been described, but this number is not particularly limited, and may be any other number as necessary.

[0024]

As described above, according to the present invention, the arrangement of Sn is not concentrated but distributed around Nb, so that the dead zone for Nb arrangement is eliminated, and Nb is eliminated. The filament interval could be lengthened. Therefore, since the Nb ₃ Sn compound concatenation of filaments does not occur, the effective filament diameter is reduced, while maintaining a high critical current density, hysteresis loss can improve low, suppress small the amount of heat generated in the superconducting wire, for example a pulse coil There is an effect that can be. Further, also in the production of the superconducting wire, since it is made of soft pure metal without using a hard bronze matrix or the like, there is an effect that the production is easy and inexpensive.

[Brief description of drawings]

FIG. 1 is a partially enlarged cross-sectional view of a bundle of Nb ₃ Sn compound superconducting composite wires according to an embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view of a Nb ₃ Sn compound superconducting element wire according to an embodiment of the present invention.

FIG. 3 is a partially enlarged cross-sectional view of a bundle of Nb ₃ Sn compound superconducting composite wires according to an embodiment of the present invention.

FIG. 4 is a partially enlarged cross-sectional view of a Nb ₃ Sn compound superconducting element wire according to an embodiment of the present invention.

FIG. 5 is a partially enlarged cross-sectional view of a Nb ₃ Sn compound superconducting element wire according to an embodiment of the present invention.

FIG. 6 is a partially enlarged cross-sectional view of a Nb ₃ Sn compound superconducting wire according to an embodiment of the present invention.

FIG. 7 is a partially enlarged cross-sectional view of a Nb ₃ Sn compound superconducting element wire according to an example of the present invention.

FIG. 8 is a partially enlarged cross-sectional view of a Nb ₃ Sn compound superconducting element wire according to an example of the present invention.

FIG. 9 is a partially enlarged cross-sectional view of a Nb ₃ Sn compound superconducting element wire according to an example of the present invention.

FIG. 10 is a partially enlarged cross-sectional view of a Nb ₃ Sn compound superconducting element wire according to an example of the present invention.

FIG. 11 is a cross-sectional view of a Nb ₃ Sn compound superconducting wire manufactured by a conventional method.

FIG. 12 is a cross-sectional view of a Nb ₃ Sn compound superconducting element wire in the middle of processing by a conventional method.

FIG. 13 is a cross-sectional view of a Nb ₃ Sn compound superconducting element wire in the middle of processing by a conventional method.

[Explanation of symbols]

1 Nb or Nb alloy rod 2 Sn or Sn alloy rod 3 Cu tube 4 Diffusion barrier 5 Nb ₃ Sn filament 6 Bronze matrix

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[Procedure amendment]

[Submission date] June 1, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

However, even if a high critical current density (Jc) is obtained as described above, the fact that Nb cannot be arranged in the Sn in the central portion is accompanied by the Nb filament spacing. Is smaller, the adjacent filaments of the Nb ₃ Sn compound are likely to be connected to each other, and an increase in hysteresis loss has been observed.
For example, with a wire rod having a Jc of 950 A / mm ² at 12T, the effective filament diameter is 15 to 15 in terms of hysteresis loss.
It was 20 μm. A superconducting pulse coil using such a superconducting wire generates a large amount of heat and requires a powerful refrigerator.

Claims (3)

[Claims] 1. One Nb or Nb-based alloy rod or a plurality of closely arranged Nb or Nb-based alloy rods, said N
Sn or Sn arranged around b or Nb-based alloy rod
Base alloy rods and, if necessary, Cu placed around them
Alternatively, a plurality of composite wire rods made of a Cu-based alloy are bundled and inserted into a sheath material, and then a cross-section reduction process is performed to obtain a wire, and the wire is heat-treated, which is a Nb ₃ Sn compound superconducting wire. Production method. 2. A first composite wire comprising one Nb or Nb-based alloy rod or a plurality of closely arranged Nb or Nb-based alloy rods and, if necessary, Cu or a Cu-based alloy disposed around them. Dispersing one Sn or Sn-based alloy rod or a plurality of closely arranged Sn or Sn-based alloy rods and, if necessary, a second composite wire made of Cu or a Cu-based alloy disposed around them. And then inserted into the sheath material, the cross-section is reduced to obtain a wire, and the wire is heat-treated.
₃ Method for producing Sn compound superconducting wire. 3. One Nb or Nb-based alloy rod or a plurality of closely arranged Nb or Nb-based alloy rods and one Sn or Nb in a plurality of vertical holes provided in a copper or copper-based alloy rod material. Characterized in that a Sn-based alloy rod or a plurality of Sn or Sn-based alloy rods arranged in close contact with each other are separately or integrally inserted, a cross-section is reduced to obtain a strand, and the strand is heat-treated. A method for producing a Nb ₃ Sn compound superconducting wire.