JP3059570B2 - Superconducting wire and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting wire and a method for manufacturing the same.

[0002]

Conventionally, Nb ₃ Sn compound superconducting wire of a multi-core structure in which a plurality inborn an Nb ₃ Sn compound superconducting filaments is produced by the method of example described below (1) to (5).

(1) Bronze method In this method, as shown in FIG. 6 (a), a composite 3 in which a large number of Nb rods 2 are inserted into a CuSn alloy matrix 1 is formed into a linear shape by drawing and annealing. Then, the Nb ₃ Sn compound superconducting wire is manufactured by performing diffusion heat treatment to form a ring-shaped Nb ₃ Sn compound superconductor 4.

(2) External diffusion method In this method, as shown in FIG. 6 (b), a composite 6 in which a number of Nb rods 2 are inserted into a Cu matrix 5 is linearly processed by drawing or the like. After the wire is covered with the Sn layer 7, a diffusion heat treatment is performed to generate an annular Nb ₃ Sn compound superconductor 4, thereby manufacturing an Nb ₃ Sn compound superconducting wire.

(3) Internal diffusion method As shown in FIG. 6 (c), this method comprises a composite 9 in which a Sn matrix 8 is inserted into a Cu matrix 5 and a large number of Nb rods 2 are inserted therearound. Is subjected to a diffusion heat treatment to form a ring-shaped Nb ₃ Sn compound superconductor 4, thereby producing a Nb ₃ Sn compound superconducting wire.

(4) Tube method As shown in FIG. 7 (a), a first Cu tube 10, a Nb tube 11, and a second Cu tube 11 are arranged around a Sn rod 8 in a Cu matrix 5. A large number of composite rods 13 in which 12 are sequentially arranged are inserted to form a composite 14. This composite 14 is processed into a linear shape by wire drawing or the like, and then subjected to a diffusion heat treatment to produce an annular Nb ₃ Sn compound superconductor 4. By doing so, an Nb ₃ Sn compound superconducting wire is manufactured.

(5) In-situ method As shown in FIG.
A copper rod 17 is inserted through a barrier layer 18 into a Cu tube 16 in which an Nb alloy rod 15 is embedded to form a composite 19, and the composite 19 is processed into a linear shape by wire drawing or the like. After the Sn layer 7 is plated, a diffusion heat treatment is performed to generate the Nb ₃ Sn compound superconductor 4 and the CuSn alloy matrix 1, thereby producing an Nb ₃ Sn compound superconducting wire.

However, the above-described conventional annular Nb ₃
In the production of an Nb ₃ Sn compound superconducting wire having a superconducting filament made of a Sn compound superconductor, Sn diffuses from one direction into an Nb body to produce a cyclic Nb ₃ Sn compound superconductor. The cyclic Nb ₃ Sn thus generated
Since the compound superconductor has a large Sn concentration difference in the thickness direction, the stoichiometric composition of Nb and Sn is impaired. As a result, there is a problem that it is difficult to sufficiently increase the critical current density. When the thickness of the Sn diffusion reaction is reduced, a cyclic Nb ₃ Sn compound superconductor having a similar stoichiometric composition can be generated, but the proportion of Nb ₃ Sn in the wire cross-sectional area decreases. As a result, the conductor current density is reduced, so that an essential solution cannot be achieved.

In the above-described conventional tube method and the like,
Since the composite processing is performed in a state where the Sn concentrations of the metal layers inside and outside the Nb tube are extremely different, the difference in deformation resistance between the respective substrates is large. As a result, there is also a problem that the Nb tube is deformed non-uniformly, leading to disconnection.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems, and it is an object of the present invention to provide a superconducting wire having improved superconducting characteristics such as a critical current density and a method of manufacturing the same. It is.

[0011]

SUMMARY OF THE INVENTION The present invention provides a cyclic Nb ₃
A Sn compound superconductor, and an inner CuSn alloy adjacent to the inside of the Nb ₃ Sn compound superconductor of said annular, outer adjoining the outside of the Nb ₃ Sn compound superconductor of the annular Cu
A multi-core Nb ₃ Sn compound superconducting wire comprising an Sn alloy, wherein the annular Nb ₃ Sn compound superconductor is formed by diffusion of Sn from both the inner and outer CuSn alloys, A superconducting wire characterized in that the outer CuSn alloy has a higher Sn concentration than the inner CuSn alloy.

The above-described Nb ₃ Sn compound superconducting wire can be manufactured, for example, by the method described below.

First, a CuSn alloy is arranged so as to be adjacent to the outer side of the annular Nb or Nb alloy, and the outer C is arranged so as to be adjacent to the inner side of the annular Nb or Nb alloy.
After arranging a CuSn alloy having a Sn concentration higher than that of the uSn alloy, complex processing such as drawing and surface reduction is performed. Next, an Nb ₃ Sn compound superconducting wire is manufactured by performing diffusion heat treatment while supplying Sn to the outer CuSn alloy to generate an annular Nb ₃ Sn compound superconductor. In this manufacturing process, in order to perform diffusion heat treatment while supplying Sn to the outer CuSn alloy, Sn may be arranged so as to be in contact with the outer CuSn alloy before the diffusion heat treatment.

It is desirable to use an outer CuSn alloy having a Sn concentration of 3 to 13% by weight.
The reason is that if the Sn concentration is less than 3% by weight, it may be difficult to improve the superconducting characteristics such as the critical current density. On the other hand, if the Sn concentration exceeds 13% by weight, the workability of the outer CuSn alloy itself deteriorates, which may lead to disconnection or the like.

It is desirable to use an inner CuSn alloy having a Sn concentration of 80% by weight or more.

[0016]

According to the present invention, the annular Nb ₃ Sn compound superconductor is formed by diffusion of Sn from both the inner and outer adjacent CuSn alloys, whereby Sn in the thickness direction is obtained. The concentration becomes uniform and becomes close to the stoichiometric composition. As a result, a superconducting wire with improved superconducting characteristics and particularly with an increased critical current density can be obtained. Further, since the Sn concentration of the outer CuSn alloy is higher than that of the inner CuSn alloy, the annular Nb
₃ since towards the outside than the inside of Sn compound superconductor electric resistance is increased electrical resistance between the Nb ₃ Sn compound filaments is increased, it is possible to suppress the deterioration of the superconducting characteristics due to the proximity effect. As a result, it is possible to obtain a superconducting wire in which superconducting characteristics are further improved, and in particular, an AC loss such as a hysteresis loss is reduced.

According to the method of the present invention, first,
CuS to be adjacent to the outside of the annular Nb or Nb alloy
n alloy, and the outer CuSn alloy is positioned closer to the inner side of the annular Nb or Nb alloy than the outer CuSn alloy.
After arranging a CuSn alloy having a high n concentration, composite processing is performed. Next, a diffusion heat treatment is performed while supplying Sn to the outer CuSn alloy. As a result, the annular Nb ₃ Sn compound superconductor is brought into contact with both the inner and outer adjacent Cu conductors.
It can be generated by the diffusion of Sn from the Sn alloy. In the inner CuSn alloy, Sn is only reduced by the Nb ₃ Sn generation reaction, whereas the outer CuSn is reduced.
In the alloy, Sn is supplied from the outside while Sn is reduced by the Nb ₃ Sn generation reaction, so that the Sn concentration of the outer CuSn alloy can be higher than that of the inner CuSn alloy. As a result, a superconducting wire having improved superconducting characteristics such as critical current density can be manufactured. In addition, in this method, an alloy containing Sn is arranged on both the inner side and the outer side of the ring-shaped Nb or Nb alloy to perform a composite processing. As a result, deformation of the annular Nb or Nb alloy or disconnection can be prevented.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Example 1 First, as shown in FIG.
mm of annealed Cu-5 wt% Sn alloy
12.9 mm outside diameter, 5 m inside diameter in CuSn alloy tube 21
m Nb tube 22 is inserted into the Nb tube 22, and CuS made of Cu-95 wt% Sn alloy having a diameter of 4.9 mm is further inserted into the Nb tube 22.
The n bar 23 is inserted. Subsequently, these were drawn at room temperature to form a composite material 24 having a diameter of 3 mm as shown in FIG. 1 (b).

Next, as shown in FIG.
In the center of the second CuSn alloy tube 25 made of an annealed Cu-5 wt% Sn alloy having an inner diameter of 25 mm and an inner diameter of 25 mm, a Cu rod 26 having a diameter of 9.9 mm is provided with an outer diameter of 12 mm and an inner diameter of 10 m.
Then, the composite material 24 is inserted into the space between the second Cu-5 wt% Sn alloy tube 25 and the Ta tube 27. Then,
These were subjected to surface reduction using a swaging machine to form a wire rod 28 having a diameter of 1 mm as shown in FIG.

Next, a thickness of 20 μm is
An m-th Sn plating layer is formed. Next, this is set to temperature 4
Diffusion heat treatment is performed by heating at 00 ° C. for 100 hours and further heating at 690 ° C. for 30 hours to diffuse Sn from the CuSn alloy 29 adjacent on the inside and the CuSn alloy 30 adjacent on the outside as shown in FIG. To form an annular Nb
An Nb ₃ Sn compound superconducting wire in which the ₃ Sn compound superconductor 31 was generated was manufactured.

Examples 2 to 4, Comparative Example 1 and Reference Example 1 The following Table 1 replaces the first and second CuSn alloy tubes 21 and 25 made of Cu-5% by weight Sn alloy used in Example 1. A CuSn alloy rod having a Sn concentration of CuSn or a material made of Cu was used, and the CuSn alloy rod 2 used in Example 1 was used.
3 in place of the Sn concentration CuSn alloy or S shown in Table 1
An Nb ₃ Sn compound superconducting wire was manufactured in the same manner as in Example 1, except that a material made of n was used. Reference example 1
In the case of Nb ₃ S
An n-compound superconducting wire could not be manufactured.

In the manufacturing steps of the superconducting wires of Examples 1 to 4, Comparative Example 1 and Reference Example 1, the composite workability was as shown in Table 1 below.

With respect to the obtained superconducting wires of Examples 1 to 4 and Comparative Example 1, the Sn concentration of the CuSn alloy adjacent to the inside and outside of the annular Nb ₃ Sn compound superconductor was examined.
The results are shown in Table 1 below.

Further, the obtained Examples 1 to 4 and Comparative Example 1
Of superconducting wire in liquid helium (4.2K)
The critical current (Ic value) under a magnetic field of 0T was measured. The results are shown in Table 1 below.

[0026]

[Table 1] As is clear from Table 1, the superconducting wires of Examples 1 to 4 have a larger Ic value under a high magnetic field than the superconducting wire of Comparative Example 1. This is because the diffusion of Sn from both the inner and outer adjacent CuSn alloys has produced an annular stoichiometrically improved Nb ₃ Sn compound superconductor, and the Sn concentration of the outer CuSn alloy is CuS
This is because the electric resistance value between the Nb ₃ Sn compound filaments is higher than that of the n alloy and the electric resistance value between the Nb ₃ Sn compound filaments is increased.

The reason why the Sn concentration of the outer CuSn alloy in the superconducting wires of Examples 1 to 4 is higher than that of the inner CuSn alloy is that the inner CuSn alloy during the diffusion heat treatment is used.
In the alloy, Sn only decreased by the Nb ₃ Sn generation reaction, whereas in the outer CuSn alloy, Sn was reduced by the Nb ₃ Sn generation reaction while Sn was diffused and supplied from the external Sn plating layer. It is because of that.

Example 5 First, as in Example 1, an Nb tube having an outer diameter of 12.9 mm and an inner diameter of 5 mm was placed in an annealed CuSn alloy tube 21 having an outer diameter of 15 mm and an inner diameter of 13 mm made of a Cu-5 wt% Sn alloy. 2
Then, a CuSn rod 23 made of a Cu-95 wt% Sn alloy having a diameter of 4.9 mm is inserted into the Nb tube 22. Subsequently, these were drawn at room temperature to obtain a composite material 24 having a diameter of 3 mm similar to that of Example 1.
(FIG. 1).

Next, as shown in FIG.
22.9 m outside diameter in Cu tube 41 with 23 mm inside diameter
m, a Ta tube 42 having an inner diameter of 18 mm is inserted.
25 composite materials 24 are inserted into the tube 42. Subsequently, a particle size of 1 between the Ta tube 42 and the composite material 24 is formed.
A Sn powder 43 of 00 μm is filled. Subsequently, these were subjected to surface reduction while being annealed at a temperature of 300 ° C. for 20 hours, so that a diameter of 0.3 mm as shown in FIG.
A 9 mm wire 44 was formed.

Next, the wire 44 is heated at a temperature of 400.degree.
Then, the CuSn alloy 45 adjacent to the inside and the CuSn adjacent to the outside are heated as shown in FIG.
An Nb ₃ Sn compound superconducting wire in which an annular Nb ₃ Sn compound superconductor 47 was generated by diffusion of Sn from the alloy 46 was manufactured.

Examples 6 and 7 and Comparative Example 2 Cu made of the Cu-5% by weight Sn alloy used in Example 5
In place of the Sn alloy tube 21, the Sn concentration Cu shown in Table 2 below was used.
Using a material made of Sn alloy or Cu,
C made of Cu-95% by weight Sn alloy used in Example 5
In place of the uSn alloy rod 23, the Sn concentration Cu shown in Table 2 was used.
An Nb ₃ Sn compound superconducting wire was manufactured in the same manner as in Example 5, except that a material made of a Sn alloy or Sn was used.

In the manufacturing steps of the superconducting wires of Examples 5 to 7 and Comparative Example 2, the composite workability was as shown in Table 2 below.

With respect to the obtained superconducting wires of Examples 5 to 7 and Comparative Example 2, the Sn concentration of the CuSn alloy adjacent to the inside and outside of the annular Nb ₃ Sn compound superconductor was examined.
The results are shown in Table 2 below.

The obtained Examples 5 to 7 and Comparative Example 2
Of superconducting wire in liquid helium (4.2K)
The critical current (Ic value) under a magnetic field of 0T was measured, and the hysteresis loss of one cycle under a magnetic field of 0.5T was measured. These results are also shown in Table 2 below.

[0035]

[Table 2] As is clear from Table 2, the superconducting wires of Examples 5 to 7 have a larger Ic value under a high magnetic field and a smaller hysteresis loss than the superconducting wires of Comparative Example 2. This is due to the cyclic Nb with improved stoichiometry due to Sn diffusion from both the inner and outer adjacent CuSn alloy.
_This is because the 3Sn compound superconductor is generated, and the Sn concentration of the outer CuSn alloy is higher than that of the inner CuSn alloy, and the electric resistance value between the Nb ₃ Sn compound filaments is increased.

In the superconducting wires of Examples 5 to 7, the Sn concentration of the outer CuSn alloy is higher than that of the inner CuSn alloy because Sn is reduced in the inner CuSn alloy by Nb ₃ Sn formation reaction during diffusion heat treatment. On the other hand, in the outer CuSn alloy, Sn is reduced by the Nb ₃ Sn generation reaction while Sn is diffused and supplied from the Sn powder.

[0037]

As described above in detail, according to the present invention, it is possible to provide a superconducting wire having improved superconducting characteristics such as a critical current density and a method for manufacturing the same.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a manufacturing process of an Nb ₃ Sn compound superconducting wire of Example 1.

FIG. 2 is an explanatory view showing a manufacturing process of the Nb ₃ Sn compound superconducting wire of Example 1.

FIG. 3 is an explanatory view showing an Nb ₃ Sn compound superconducting wire of Example 1.

FIG. 4 is an explanatory view showing a manufacturing process of an Nb ₃ Sn compound superconducting wire of Example 5.

FIG. 5 is an explanatory view showing an Nb ₃ Sn compound superconducting wire of Example 5.

FIG. 6 is an explanatory view showing a manufacturing process of a conventional Nb ₃ Sn compound superconducting wire.

FIG. 7 is an explanatory view showing a manufacturing process of a conventional Nb ₃ Sn compound superconducting wire.

[Explanation of symbols]

21, 25: CuSn alloy tube, 22: Nb tube, 23: C
uSn rod, 24 ... composite material, 26 ... Cu rod, 27, 42 ...
Ta tube, 28, 44 ... wire, 29, 45 ... inner CuSn
Alloy, 30, 46: outer CuSn alloy, 31, 47: annular Nb ₃ Sn compound superconductor, 41: Cu tube, 43: S
n powder.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01B 12/00-13/00

Claims (3)

(57) [Claims] 1. A and Nb ₃ Sn compound superconducting ring, and an inner CuSn alloy adjacent to the inside of the Nb ₃ Sn compound superconductor of said annular, outer adjoining the outside of the Nb ₃ Sn compound superconductor of the annular CuSn a multi-core Nb ₃ Sn compound superconducting wire comprising the alloy, the annular Nb ₃
The Sn compound superconductor has both the inner and outer CuS
n produced from the diffusion of Sn from the n alloy,
And the Sn concentration of the outer CuSn alloy is equal to the inner CuS
A superconducting wire characterized by being higher than an n alloy. 2. A method for producing a multi-core Nb ₃ Sn compound superconducting wire, comprising: disposing a CuSn alloy so as to be adjacent to an outer side of an annular Nb or an Nb alloy;
Alternatively, the outer CuSn is adjacent to the inner side of the Nb alloy.
After placing a CuSn alloy with a higher Sn concentration than the alloy,
A method for manufacturing a superconducting wire, comprising: a step of performing a composite working; and a step of performing a diffusion heat treatment while supplying Sn to the outer CuSn alloy to generate an annular Nb ₃ Sn compound superconductor. 3. The method of manufacturing a superconducting wire according to claim 2, wherein an Sn having an Sn concentration of 3 to 13% by weight is used as the outer CuSn alloy.