JPS6044836B2 - Compound superconducting wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stable compound-based superconducting wire without AC loss.

The main manufacturing method for compound-based ultrafine multicore superconducting wires is to compositely process the constituent elements of the target compound superconducting wire into desired dimensions and shapes in the form of an easy-to-process alloy or single metal, followed by heat treatment. It consists of producing a compound superconducting material by causing the constituent elements to react with each other.

Taking a Nb, Sn ultrafine multicore superconducting wire as an example, to explain it specifically, Nb or Nb is present in the Cu-Sn alloy matrix.
After creating a composite wire consisting of a large number of thin alloy wires, a final heat treatment is performed to form a layer of Nb and Sn, which are reactants with Nb and Sn in the matrix, on the surface of the Nb or Nb alloy thin wire.

The same applies to the V3Ga ultra-fine multifilament wire, in which the reaction between the Cu--Ga alloy matrix and the V-thin wire takes place.

Since an alloy with high electrical resistance is used in the matrix, there is a risk that the wire will burn out if the superconductor quenches, ie, transitions from a superconductor to a normal conductor for some reason. As a protection law against this, N
b. As shown by taking Sn as an example, a method of providing a partition wall 3 made of Ta, Nb, etc. between the Cu-Sn alloy 2 and the stabilizing high-purity Cu 4 to prevent the purity of 4 from decreasing due to heat treatment. There is. This method is effective in improving stability, but when this wire is used in a pulsed magnetic field, it causes eddy current loss, which is undesirable. An object of the present invention is to provide a compound-based ultrafine multicore superconducting wire that is free from AC loss and is stable. According to the invention, the purpose is to make the partition wall discontinuous and to diffuse one of the constituents of the superconducting compound into the high-purity metal through the discontinuity, thereby partially alloying the high-purity metal. This can be achieved by dividing the high-purity metal by the alloy portion and the partition wall.

The alloy part is produced when a superconducting compound is produced by the final heat treatment, and the composite before and after producing the target superconducting compound by the final heat treatment is manufactured as follows. In other words, a composite is created in which one of the constituent materials of the superconducting compound is made into a fine wire and is embedded in an alloy containing other constituent materials, and a partition wall is provided around the alloy to discontinuously surround it. As a unit, a large number of these unit composites are independently buried in a stabilizing material made of high-purity metal and subjected to area reduction processing to obtain a composite prior to heat treatment. Then, a final heat treatment is performed to form a superconducting compound, but through this heat treatment, the components in the alloy containing the constituent materials of the superconducting compound diffuse, and the surface of the thin wire made of the constituent materials of the compound becomes superconducting. At the same time as a compound is generated, it also diffuses into the high-purity metal for stabilization through the discontinuous part of the partition wall and partially forms an alloy. On the other hand, since the part where the partition wall is continuous is not alloyed, the high purity metal is finely divided by the partition wall and the alloy part, that is, the high electrical resistance part. In this way, it is possible to provide a wire rod that is stabilized by high-purity metal and can eliminate loss in an alternating current magnetic field by dividing the high-purity metal. FIGS. 1 and 2 show examples of conventional compound superconducting wires, taking Nb3Sn as an example. In FIG. 1, 1 is an Nb wire, 2 is a Cu-Sn alloy provided to surround Nbl, and 3 is a partition wall to prevent a reaction between the Cu-Sn alloy 2 and the stabilizing high-purity CU4. . After forming into such a shape and reducing the area, heat treatment is performed to cause the Sn in the Cu-Sn alloy 2 to react with Nb to form a compound layer of Nb3Sn on the surface of the Nb wire 1.
At this time, the partition wall 3 prevents Sn from diffusing into the stabilizing high-purity Cu4 and contaminating it. FIG. 2 shows another example of a Nb3Sn compound superconducting wire, in which a large number of Nb thin wires 1 are formed using a Cu--Sn alloy 2 as a matrix. Further, the stabilizing high-purity CU 4 is surrounded by the partition wall 3 and buried therein. In this case too, it is final. As a result of the heat treatment, an Nb3Sn layer is formed on the surface of the Nb thin wire 1, and the high purity Cu4 is not contaminated. In the conventional example shown in FIG. 1, high-purity CU4 for stabilization is sufficient in quantity, but has the drawback of high eddy current loss when used in an alternating magnetic field. On the other hand, the example in Figure 2 shows high purity! Since the degree Cu4 is divided, the AC loss is small, but there are concerns about stability. The structure of the wire rod according to the present invention is shown in Figure 3.
As shown using an n-compound superconducting wire as an example, an Nb wire 1 is surrounded by a Cu-Sn alloy 2, and a 4N alloy discontinuously surrounds the Nb wire 1.
b. ．． Partition wall 3 made of Ta etc. and high purity Cu4 for stabilization
It becomes more.

With this structure, after the area is reduced to the specified wire diameter, NY
) 3Sn compound, the Sn in the Nb wire 1 and the Cu-Sn alloy 2 is removed as shown in Figure 4.
reacts to form a Nb3Sn layer 5 on the surface of the Nb wire 1,
Further, Sn in the Cu-Sn alloy 2 is diffused into the stabilized Cu 4 through the discontinuous portion 31 of the partition wall 3 to form a Cu-Sn diffusion portion 6. This Cu-Sn diffusion part 6 works to electrically divide the stabilized high-purity CU 4 together with the partition wall 3, and can eliminate AC loss due to eddy current loss. To show one example of the method of manufacturing a wire rod according to the present invention, first, a Cu-Sn alloy 2 is coated around an Nb wire 1 as shown in FIG.
Furthermore, a composite material 9 is prepared in which a discontinuous partition wall 3 is provided around the composite material 9 and the whole is covered with high purity CU7. This composite material can be easily obtained by composite processing of a high-purity Cu pipe, a plate-shaped partition material, a Cu-Sn alloy pipe, and a Nb wire. Next, a large number of composite materials 9 shown in FIG. 5 are inserted into the high-purity Cu pipes 8, and subjected to surface reduction processing to a predetermined wire diameter using an ordinary method, including intermediate annealing if necessary. By this processing, the high-purity chains U7 and 8 around the composite material 9 can be brought into close contact with each other as if they were a single piece, and the cross-sectional shape as shown in FIG. 3 can be obtained.

An example of manufacturing the wire rod of the present invention has been given, but in short, the present invention provides a discontinuous partition wall and electrically divides the high purity metal stabilized by the partition wall and a diffusion layer that diffuses from the discontinuous point of the partition wall in the final heat treatment. The purpose is to eliminate alternating current loss, and it is not limited to the exemplified N1)3Sn, but can also be applied to 3Ga, Nb3Ge, NFA1, etc.

As is clear from the above description, the present invention provides discontinuous partition walls that prevent one of the components of the superconducting compound from diffusing into the high-purity stabilizing metal. One of the constituent materials is diffused into a high-purity stabilizing metal to partially form an alloy portion that becomes an electrical resistance portion, and the high-purity stabilizing metal is divided by the alloy portion and the partition wall. Therefore, even if this wire is used in a pulsed magnetic field, AC loss due to eddy current loss can be eliminated, and its practical value is extremely large.

Note that the discontinuous portion in the partition preferably extends in the longitudinal direction of the wire, and may be present in either a linear or helical form.

Of course, it is desirable for the partition walls to be made of a material that does not melt during the final heat treatment and does not easily react with each constituent material, but it may also be made of the same material as one of the constituent materials of the superconducting compound, in which case the compound will not form on the inner surface of the partition wall. , it would be possible to increase the current capacity of the entire wire.

[Brief Description of the Drawings] Figures 1 and 2 are cross-sectional views of a compound superconducting wire according to the conventional method, Figure 3 is a cross-sectional view of the wire according to the present invention before final heat treatment, and Figure 4 is a cross-sectional view after heat treatment. , 5 and 6 are cross-sectional views showing an example of the method for manufacturing the wire rod of the present invention. DESCRIPTION OF SYMBOLS 1... Nb wire, 2... Cu-Sn alloy, 3... Partition wall, 31... Discontinuous part, 4
and 7...High purity Cul5 for stabilization...
・Nb3Sn layer, 6...Cu-Sn diffusion part, 8
...High purity Cll/Guip, 9...complex.

Claims (1)

[Claims] 1. In a compound-based superconducting wire, a discontinuous partition wall and a stabilizing high-purity metal are provided to surround the constituent materials of the superconducting compound arranged so as to generate the superconducting compound during the final heat treatment, and the stabilizing high-purity metal is disposed in the final heat treatment. A compound-based superconducting wire characterized in that a metal is divided by a partition wall and a high electrical resistance part which is an alloy part diffused into a high purity metal through a discontinuous part of the partition wall.