JPH0313686B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an Nb ₃ Sn-based ultrafine multifilamentary superconducting wire.

As an intermetallic compound-based superconducting material, Nb ₃ Sn
Besides, Nb ₃ Ga, Nb ₃ Ge, Nb ₃ Al, V ₃ Ga, etc. are known. This type of intermetallic compound-based superconducting material is generally superior to alloy-based superconducting materials in terms of superconducting properties, but on the other hand, it has problems with workability, particularly low malleability and ductility, and therefore Since it is difficult to process compounds such as rods, it is common to process them in a composite state that has not yet become an intermetallic compound, and then apply diffusion heat treatment after that process to generate an intermetallic compound.

By the way, the conventional method for manufacturing intermetallic compound-based ultrafine multicore superconducting wires will be explained using a typical Nb ₃ Sn-based ultrafine multicore superconducting wire as an example.
Conventional methods are broadly divided into the bronze method and the Sn plating method. As shown in Fig. 1, the former bronze method involves forming a large number of Cu-Sn alloys (bronze) in a base 1 of Cu-Sn alloy (bronze), which preferably has an Sn concentration of about 10 to 15 wt%.
Nb filament 2 is arranged to make an ultra-fine multicore composite wire with a predetermined wire diameter, and then diffusion heat treatment is applied to Cu.
− Diffusion of Sn in the Sn alloy base 1 to create a large number of
This is a method for obtaining ultrafine multicore Nb ₃ Sn superconducting wires having Nb ₃ Sn filaments, and the latter Sn plating method involves arranging a large number of Nb filaments 2 in a base 3 of pure Cu, as shown in Figure 2. After adjusting the wire diameter to a predetermined wire diameter, Sn plating 4 is applied on the outer periphery of the Cu base, and then diffusion heat treatment is performed to remove the wire from the outer Sn plating layer 4.
This is a method of manufacturing an ultrafine multicore Nb ₃ Sn superconducting wire similar to that described above by diffusing Sn through the Cu base 3. However, each of these conventional methods has advantages and disadvantages, and the reality is that none of them is satisfactory.

In other words, in the former bronze method, Nb ₃ Sn can be produced by relatively simple heat treatment,
Moreover, it has advantages such as not requiring Sn plating, but on the other hand, it has a serious problem of poor workability in diameter reduction processing. In other words, in the bronze method, in order to generate a sufficient amount of Nb ₃ Sn,
It is necessary to use a Cu-Sn alloy with a fairly high Sn concentration of about 10 to 15% as a base;
Work hardening is extremely likely to occur in Cu-Sn alloys with a high Sn concentration, so intermediate annealing must be performed frequently.Especially in the production of ultrafine multifilamentary superconducting wires, the diameter of one Nb core material is approximately several μm. Since diameter reduction processing must be performed until the filament becomes a filament, the number of annealing operations is significantly increased, resulting in a significant increase in the number of work steps and a problem in that productivity is significantly reduced. On the other hand, in the latter Sn plating method, since pure copper with good workability is used as the base, the number of annealing times during diameter reduction processing can be significantly reduced compared to the bronze method. On the other hand, in order to generate a sufficient amount of Nb ₃ Sn, a fairly thick Sn plating layer is required, and in order to generate such a thick plating layer, plating requires a considerable amount of time, and the plating thickness is There is a problem that it is difficult to control the
_Sn to generate Nb ₃ Sn is quite far away from the Nb filament and requires a long diffusion distance. In addition to the need to make various adjustments to the heat treatment conditions, there is also the problem that Sn on the outer periphery melts down or sneaks into the bottom during heat treatment. Such drawbacks of the Sn plating method become particularly noticeable when manufacturing ultrafine multicore Nb ₃ Sn superconducting wires with large diameters. In other words, as the wire diameter becomes thicker, a larger amount of Sn is required, so the thickness of the Sn plating layer needs to be significantly thicker, and the distance between the Nb filament in the center and the Sn plating layer increases. As the size increases, the distance that Sn must diffuse and move becomes longer, so in order to diffuse and move a large amount of Sn over a long distance and generate a sufficient amount of Nb ₃ Sn, preliminary heat treatment is required before normal diffusion heat treatment. However, there are disadvantages in that the preliminary heat treatment must be carried out in several stages.
Moreover, during such preliminary heat treatment, a brittle Sn-rich Cu-Sn intermetallic compound is generated, which may deteriorate the properties. Furthermore, the biggest drawback of the Sn plating method, as will be explained in detail later, is that it is a superconducting wire with stabilized copper, in which pure copper is placed on the outermost periphery for stabilization and a diffusion barrier is placed inside. This cannot be applied to manufacturing.

In order to solve the above-mentioned problems, the present inventors have already proposed an improved method that combines the bronze method and the Sn plating method. The first improvement method is to use a Cu-Sn alloy base with a low Sn concentration of less than 10wt% in place of the pure copper base 1 (see Figure 2) in the Sn plating method described above, and use the Cu-Sn alloy base with a low Sn concentration of less than 10 wt%. This is a method in which a large number of Nb filaments are arranged in an alloy matrix, the diameter is reduced to a predetermined diameter, and then Sn plating is applied to the outer peripheral surface of the filament. A second improvement method is to arrange a large number of Nb filaments 2 in a Cu-Sn alloy base 5 and to arrange pure copper 6 around the Cu-Sn alloy base 5, as shown in FIG. After reducing the wire diameter to a wire diameter of , Sn plating 4 is applied to the outer circumferential surface of the wire, and then diffusion heat treatment is performed in the same manner as described above. Furthermore, the third improvement method is a Cu-Sn alloy base 7 with a high Sn concentration comparable to that of the conventional bronze method, as shown in Figure 4.
A large number of Nb filaments 2 are placed inside the
A low Sn concentration Cu-
In this method, a Sn alloy base 8 is arranged, the wire diameter is reduced to a predetermined wire diameter, a thin Sn plating 4 is applied to the outer circumferential surface of the wire, and then a diffusion heat treatment is performed in the same manner as described above.

Compared to the bronze method mentioned above, these improved methods are relatively easy to reduce the diameter and require a relatively small number of annealing operations during the diameter reduction process, and compared to the Sn plating method mentioned above, the Sn plating process and the Nb Although the heat treatment process for producing _3Sn is relatively simple, it has not yet reached a fully satisfactory level. That is, in the first improvement method, a low Sn concentration Cu-Sn alloy with relatively good workability is used as the base, and in the second improvement method, a low Sn
The outside of the concentrated Cu-Sn alloy base has good workability.
Since it is covered with Cu, the workability is better than in the case of the bronze method mentioned above, and the number of annealing is reduced, but it is necessary to form a Sn plating layer with a certain thickness, and in that case, it is necessary to form a Sn plating layer with a certain thickness. If so, in order to sufficiently diffuse Sn in the outer Sn plating layer, it is necessary to perform a more sufficient heat treatment than in the case of the bronze method. In addition, in the third improved method, a Cu-Sn alloy base with a high Sn concentration and poor workability is covered with a Cu-Sn alloy with a low Sn concentration that has relatively good workability. The workability is only slightly improved compared to the case of , and therefore the number of annealing times is not significantly reduced.

Furthermore, the Sn plating method and the first to third
A common drawback of these improvement methods is that they all require Sn plating and diffusion heat treatment after the wire diameter has been reduced to a predetermined diameter, making it difficult to manufacture ultrafine multicore superconducting wires with stabilized copper and diffusion barriers. There are some problems that cannot be applied. That is, in the case of the bronze method, a diffusion barrier layer 9 made of Ta or Nb is conventionally formed on the outside of a Cu-Sn alloy base 1 in which a large number of Nb filaments 2 are arranged, as shown in FIG. A stabilized copper layer 10 made of oxygen-free copper is formed on the outside of the layer 9, and a high purity Cu layer for stabilization is provided by performing diffusion heat treatment after reducing the wire diameter to a desired wire diameter. There is a known method for manufacturing ultrafine multicore superconducting wires, and in this method, Sn is not diffused into the outer Cu layer due to the presence of a diffusion barrier layer, so the purity of the Cu layer is kept high.
It can play a sufficient role in stabilization. However, even if an attempt is made to manufacture an ultrafine multicore superconducting wire with stabilized copper accompanied by a diffusion barrier as described above using the Sn plating method or the improved method described above, it is impossible to diffuse Sn from the outside because of the existence of the diffusion barrier. However, it also contaminates the stabilizing oxygen-free copper placed outside the barrier, so the production of this type of ultrafine multicore superconducting wire is actually limited to the bronze method. In addition, in each of the above improvement methods, as with the Sn plating method, Sn may melt off from the Sn plating layer during diffusion heat treatment or its preliminary treatment, making it impossible to generate a sufficient amount of Nb ₃ Sn. Ta.

This invention has been made in view of the above circumstances, and aims to improve workability during diameter reduction processing, reduce the number of annealing operations, and easily perform diffusion heat treatment. The object is to provide a method which is advantageous for the production of wires and is suitable for the production of Nb ₃ Sn based superconducting wires with stabilized copper with a diffusion barrier.

In other words, in the conventional Sn plating method and each of the improved methods mentioned above, especially when manufacturing ultrafine multicore superconducting wires with a large number of core wires, assembling the composite strands and reducing the diameter (wire drawing) as described above is repeated multiple times. In contrast, in the method of this invention, for example, when manufacturing Nb ₃ Sn superconducting wire, the final number of cores is assembled to the desired wire diameter and number of cores. Sn plating is applied to the strands that are not assembled, and Sn plating is not applied to the outside of the wires when they are finally assembled.

In other words, the method for manufacturing a compound-based ultrafine multicore superconducting wire of the present invention involves
Among the metal elements Nb and Sn, one or more core materials made of Nb are placed in a copper alloy containing Sn or a base made essentially of copper to make a composite wire, and the composite wire is Plating Sn on the surface of the wire to create a plating composite wire, then collecting multiple plating composite wires, and adding a Cu layer or Cu layer to the outside of the assembly line.
- Forms a Sn alloy layer and outside of that layer.
A diffusion barrier layer is formed to prevent the diffusion of Sn to the outside, and a pure copper layer is formed on the outer peripheral surface of the diffusion barrier layer for stabilization. After reducing the wire diameter to a predetermined wire diameter, diffusion heat treatment is performed. It is a superconducting intermetallic compound. This is to obtain an Nb ₃ Sn-based ultrafine multicore superconducting wire.

The method of this invention will be specifically explained below.

First, as shown in FIG.
It is inserted into a Cu hollow pipe 11A, and subjected to diameter reduction processing such as swaging, wire drawing and drawing as necessary, to form a Cu-Sn alloy or Cu base 11 as shown in Fig. 6B. A composite wire 12 in which the Nb core material 2 is embedded is created. Or again, Figure 7A
As shown in the figure, a plurality of holes 13 are formed in a bar material 11B made of Cu-Sn alloy or Cu, and a Nb core material 2 in the form of a rod, wire, or powder is inserted into each hole 13, and extrusion processing and rolling are performed. After performing diameter reduction processing such as aging processing, drawing and wire drawing processing, it becomes as shown in Fig. 7B.
Multiple Nb in Cu-Sn alloy or Cu base 11
A composite wire 12' in which the core material 2 is embedded is created.
Next, as shown in FIG. 6C or FIG. 7C, a Sn plating layer of a required thickness is applied to the outside of the composite wires 12, 12', that is, the outside surface of the base 11 made of Cu-Sn alloy or Cu, by electroplating or the like. 13 to obtain a plating composite line 14. Next, as shown in FIG. 6D or FIG. 7D, a plurality of the plated composite wires 14 are assembled and inserted into a pipe 11C made of Cu-Sn alloy or Cu, and are further coated with Nb or Nb to form a diffusion barrier layer. It is inserted into a pipe 16 made of Ta, and the whole is inserted into an oxygen-free copper pipe 17 which is to become a stabilized copper layer, and then subjected to diameter reduction processing such as swaging, wire drawing, and drawing to obtain the desired shape. The diameter is reduced to the wire diameter, that is, the diameter of the superconducting wire to be finally obtained, and the ultrafine multicore composite wire 15 as shown in FIG. 6E or FIG. 7E is produced.
get. As shown in an enlarged view in FIG. 8 or 9, this ultra-fine multifilamentary composite wire 15 has a large number of extremely thin Nb core materials (Nb filaments) 2 arranged at intervals in a base 11 made of Cu-Sn alloy or Cu. Furthermore, a Sn plating layer 13 is arranged in a mesh pattern inside the base 11, and furthermore, a layer 11 made of Cu or Cu-Sn alloy is disposed on the outside of the entire base 11.
C', and a diffusion barrier layer 16' and a stabilizing copper layer 17' are respectively formed outside the layer 11C'. After obtaining the ultrafine multifilamentary composite wire 15 in this way, diffusion heat treatment is performed to remove the Sn plating layer 13 inside the base 11.
Sn is diffused around Nb filament 2.
Nb ₃ Sn is generated and becomes an ultrafine multicore superconducting wire.

According to the method of the present invention, the above-mentioned diffusion heat treatment can be as simple as the diffusion heat treatment in the conventional bronze method. In other words, since the Sn plating layer 13 is arranged in a mesh pattern inside the base 11 as shown in FIG. 8 or 9 at the stage of ultra-fine multicore composite wire, the conventional Sn plating method and the conventional improvement method are not possible. The distance between the Sn plating layer 13, which is the main Sn supply source, and the Nb filament 2 is significantly shorter than in the case where the Sn plating layer is located at the outermost circumferential side. In other words, the distance that Sn must diffuse to generate Nb ₃ Sn is longer than the conventional distance.
It is significantly shorter than the Sn plating method, and therefore there is no need to perform preheat treatment during diffusion heat treatment or to perform the preheat treatment in multiple stages. ₃ Sn
can be generated. Such an effect is
This is particularly noticeable when the wire diameter is large, that is, when the number of Nb filaments is large. In other words, conventional
In the Sn plating method, as the wire diameter increases, the distance between the outer plating layer and the central Nb filament increases, but with the method of this invention, the Nb filament diameter can be maintained even when the wire diameter increases. This does not happen because the wires are finished to almost the same small diameter, and the diffusion migration distance of Sn is always short, so even if the wire is thick, a sufficient amount of Nb ₃ Sn can be produced with a simple heat treatment, just like in the case of a thin wire. can be generated. Specifically, the diffusion heat treatment may be performed by heating at a temperature of about 650 to 850° C. for about 20 to 150 hours in a vacuum or an inert gas atmosphere.

As mentioned above, Cu or Cu-Sn alloy may be used for the pipes 11A, 11C or the rod 11B that will become the base 11 in which the Nb core material is embedded, but the amount of Sn required to generate Nb ₃ Sn is Since the metal is supplied from the plating layer, even if a Cu-Sn alloy is used, it is sufficient that the Cu-Sn alloy has a low Sn concentration. Therefore, in order to improve workability and reduce the number of intermediate annealing operations during diameter reduction processing,
It is desirable to use a Cu-Sn alloy with a Sn concentration of less than 10 wt%, more optimally about 8 wt% or less. Moreover, as this Cu-Sn alloy, one containing a small amount of P, that is, phosphor bronze can also be used.

Here, in the diffusion barrier layer 16', Sn diffuses into the outer stabilizing copper layer 17', reducing the Nb ₃ Sn generation efficiency, or reducing the purity of the stabilizing copper layer 17', increasing its electrical resistance. Contributes to preventing deterioration. Then, Cu is deposited on the inside of this diffusion barrier layer 16'.
By disposing the Cu-Sn alloy layer 11C', the diffusion barrier layer 16'
Good workability can be ensured by compensating for the deterioration in workability due to the formation of Nb ₃ Sn.

In the above explanation, the composite wire is the final Nb
Composite strands can be assembled intermediately even before they are assembled to the number of filaments. In other words, multiple composite strands that are not assembled at all (hereinafter referred to as primary composite strands) are assembled to create a secondary composite strand, and multiple secondary assembled strands are further assembled to reduce the diameter. However, an ultrafine multifilamentary composite wire with the final number of Nb filaments may be obtained. In this case, Sn plating may be performed either at the stage of the primary composite strand or at the stage of the secondary composite strand, or the Sn plating may be performed at both the stage of the primary composite strand and the stage of the secondary composite strand. It's okay,
In short, Sn plating should be performed at a stage before the final number of filaments is assembled.

For example, as shown in Figure 10A, Cu or Cu
- The Nb core material 2 is inserted into the pipe 11A made of Sn alloy, the diameter is reduced, and the Cu
Alternatively, after obtaining the primary composite wire 12A in which the Nb core material 2 is arranged in the base 11 of Cu-Sn alloy, and forming the Sn plating layer 13 on the outer surface of the primary composite wire 12A as shown in FIG. 10C, A plurality of the Sn-plated primary composite wires 12A are assembled into a pipe 11D made of Cu or Cu-Sn alloy as shown in FIG. 10D, and the diameter is reduced. E
A secondary composite wire 12B having a desired diameter as shown in FIG. 10F is obtained, and as shown in FIG. Pipe 1 made of Nb or Ta to be inserted and to serve as a diffusion barrier layer
6, and the entirety thereof is inserted into the oxygen-free copper pipe 17 which is to become a stabilized copper layer, and the diameter is reduced again to form the ultra-fine multifilamentary composite wire 1 as shown in FIG. 10G.
All you have to do is get a 5. Alternatively, the primary composite wire 12A shown in FIG. 10B is not plated with Sn, and the primary composite wire 12A shown in FIG. 10H is
A plurality of pipes 2 are assembled and inserted into a pipe 11D made of Cu or Cu-Sn alloy, and the diameter is reduced to form the 10th pipe.
Secondary composite wire 12 of desired wire diameter as shown in Figure I
B was obtained, and then, as shown in FIG. 10J, a Sn plating layer 13' was formed on the surface of the secondary composite wire 12B,
Next, as shown in FIG. 10K, a plurality of the Sn-plated secondary composite wires 12B are assembled.
The oxygen-free copper pipe 17 is inserted into a pipe 11C made of Cu or Cu-Sn alloy and is inserted into a pipe 16 made of Nb or Ta which is to serve as a diffusion barrier layer, and further whose entirety is to be a stabilizing copper layer.
The wire may be inserted into the wire and the diameter reduction process may be performed again to obtain an ultrafine multifilamentary composite wire 15 as shown in FIG. 10L. Furthermore, as shown in FIGS. 10A to 10C, the primary composite wire 1
After forming the Sn plating layer 13 on the surface of the wire 2A, the secondary composite wire 12B is assembled and diameter-reduced as shown in FIG. The Sn plating layer 13' may also be formed on the surface of the composite wire 12B, and then the wires may be assembled and diameter-reduced in the same manner as described above. Of course, even if the assembly and diameter reduction process are repeated two or more times before the final assembly process, Sn plating may be applied in accordance with each of the above-mentioned examples. The ultrafine multifilamentary composite wire obtained as described above may be subjected to diffusion heat treatment in the same manner as described above.

Examples of this invention are described below.

Example 1 A Nb rod with an outer diameter of 6.5 mm was inserted into a phosphor bronze pipe with an outer diameter of 10 mm and a wall thickness of 1.5 mm with an Sn concentration of 6 wt%, and wire drawing and intermediate annealing were repeated to create a primary composite with an outer diameter of 0.75 mm. I got a bare wire. After forming a Sn plating layer with a thickness of 10 μm on the outer peripheral surface of this primary composite wire by electroplating, the primary composite wire with the Sn plating was
This assembly was inserted into a phosphor bronze pipe containing 6 wt% Sn with an outer diameter of 10 mm and a wall thickness of 0.5 mm, and wire drawing and intermediate annealing were repeated to obtain a secondary composite wire with an outer diameter of 0.75 mm. . Furthermore, after forming a Sn plating layer with a thickness of 10 μm on the surface of this secondary composite strand by electroplating, 91 secondary composite strands were assembled to form an outer diameter of 10 mm.
Insert it into a phosphor bronze pipe containing 6wt% Sn with a wall thickness of 0.5 mm, and then insert it into a phosphor bronze pipe with an outer diameter of 12 mm and a wall thickness of 0.5 mm.
The whole is inserted into an oxygen-free copper pipe with an outer diameter of 17 mm and a wall thickness of 2 mm, and the wire drawing process and intermediate annealing are repeated. Created a core compound line. Next, diffusion heat treatment was performed at 800°C for 50 hours in this manner to obtain an Nb ₃ Sn-based ultrafine multifilamentary superconducting wire with stabilized copper. The superconducting properties of the superconducting wire are measured at a temperature of 4.2K and an external magnetic field.
When measured under the condition of 100KG, the critical current value
Got 250A. This value corresponds to 3×10 ³ A/mm ² when viewed as a critical current value of only Nb ₃ Sn, and can be said to be a good characteristic.

Example 2 Ninety-one 13 mmφ billet holes of Cu-Sn alloy (Sn3wt%) with an outer diameter of 200 mm were formed, and a hole with an outer diameter of 12 mm was formed in each hole.
A billet for extrusion was created by inserting a Nb rod.
After extruding the billet, wire drawing and intermediate annealing were repeated to obtain a composite wire with an outer diameter of 6.5 mm. After forming a Sn plating layer with a thickness of 160 μm on the surface of the composite wire by melt plating,
Oxygen-free copper pipe with inner diameter 160mm, outer diameter 150mm, inner diameter
140mm Nb pipe, and outer diameter 130mm, inner diameter 120mm
A billet with 19,747 cores was created by inserting a collection of 217 wires into a composite pipe made of stacked Cu-Sn alloys (Su3wt%). After extruding the billet, wire drawing and intermediate annealing are repeated to obtain an outer diameter of 2.0.
An ultrafine multicore composite wire with stabilized copper of mm was obtained. After that, diffusion heat treatment was performed at 755°C for 100 hours to create a Nb ₃ Sn-based ultrafine multicore superconducting wire with stabilized copper. The superconducting properties of this superconducting wire are measured at a temperature of 4.2K and an external magnetic field.
When measured at 120KG, a critical current value of 370A was obtained. This value is 1.5×10 ³ A/mm ² when converted to the critical current value of only Nb ₃ Sn, which is recognized as having good characteristics.

As is clear from the above explanation, in the method of the present invention, the composite strands are plated with Sn or the like before they are assembled to have the desired number of cores, so diffusion heat treatment is performed. In the immediately preceding stage of ultra-fine multicore composite wire, the plating layer made of one of the metals constituting the intermetallic compound is inside the composite wire and at the very edge of the core filament made of the other metal constituting the intermetallic compound. Since the intermetallic compounds are located nearby and it is therefore easy to generate the intermetallic compound by diffusion, diffusion heat treatment can be easily performed, and even in the case of thick wire diameters, the diffusion can be easily performed without being affected by the diameter. Heat treatment can be performed, and the base in which the core material is embedded can be made of copper, which has good workability, or copper alloy with a low alloy concentration.
The required number of intermediate annealing during diameter reduction processing is also lower than conventional
The amount can be reduced to the same level as the Sn plating method.
Furthermore, as mentioned above, diffusion heat treatment is easy and does not require any preliminary heat treatment, so Cu-Sn can be removed during heat treatment.
There is little risk of generating harmful compound phases such as intermetallic compounds, and since the plating layer of low melting point metals such as Sn is located inside the composite wire, there is no risk of Sn etc. melting through during diffusion heat treatment. Various effects can be obtained, such as reducing the amount of water used.

Furthermore, according to the present invention, it is possible to produce an Nb ₃ Sn-based ultrafine multifilamentary superconducting wire with stabilized copper accompanied by a diffusion barrier without using the bronze method, and therefore, due to the presence of the diffusion barrier, the stabilized copper layer By preventing Sn from diffusing into the stabilized copper layer, it is possible to prevent a decrease in electrical resistance of the stabilized copper layer and to prevent a decrease in Nb ₃ Sn generation efficiency. By using copper or a copper alloy with a low alloy concentration, which has good workability, and by disposing copper or a copper alloy on the inner periphery of the stabilizing barrier layer, the workability is extremely good, and therefore diameter reduction processing is possible. This is advantageous because it is easy to perform and the number of intermediate annealing can be reduced.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a composite wire in the conventional bronze method, Figure 2 is a cross-sectional view of a composite wire in the conventional Sn plating method, and Figures 3 and 4 are cross-sectional views of a composite wire in the conventional improved method. , FIG. 5 is a sectional view of a conventional stabilized composite wire with copper, FIGS. 6 and 7 are explanatory diagrams showing step-by-step an example of the method of the present invention, and FIG. 8 is a cross-sectional view of a conventional stabilized composite wire with copper. FIG. 9 is an enlarged sectional view of the composite wire shown in E of FIG. 7, and FIG. 10 is an enlarged sectional view of the composite wire shown in E of FIG. It is an explanatory diagram showing an example of a method step by step. 2...Nb core material, 11...Base, 12...Composite strand, 12A...Primary composite strand, 12B...Secondary composite strand, 13, 13'...Sn plating layer, 14...
...Metsuki compound wire, 15...Extra-fine multicore compound wire.

Claims (1)

[Claims] 1. One or more core materials made of Nb are arranged in a Cu-Sn alloy or a base substantially made of Cu to make a composite wire, and the surface of the composite wire is plated with Sn to form a plated composite wire. Then, a plurality of the plated composite wires are assembled, and a Cu or Cu-Sn alloy layer is formed on the outside of the assembled wire, and a diffusion barrier layer is formed on the outside to prevent Sn from diffusing outward. , and a pure copper layer is formed on the outer circumferential surface of the diffusion barrier layer for stabilization, and after reducing the wire diameter to a predetermined diameter, a diffusion heat treatment is performed to generate Nb ₃ Sn as a superconducting intermetallic compound inside. A method for producing a compound-based ultrafine multicore superconducting wire, characterized by the following.