JPH11250747A - Manufacture of nb3sn based superconducting wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and efficiently insert an Nb core material into high SnCu-Sn alloy and to prevent Sn segregation by solidifying Cu-Sn molten alloy, while feeding a plurality of Nb wires in a mold of a continuous casting device and by heat treating the obtained composite conductor material after depressive working. SOLUTION: Cu-Sn molten alloy 1 is poured from a tundish 8 into a mold for a belt type continuos casting device constituted of an upper belt 4a and a lower belt 4b, which are synchronously moved, and a pair of side dams 5. A plurality of Nb wires fed via a guide 7 are fixed to a starting block 6 whose one end is moved along with the belt 4 to be fed in the mold and moved in such a state as dipped in the molten metal in the mold. Pressurized water is injected into the mold from a cooling water jet 9 and the molten metal in the mold is cooled and solidified, while being pressurized. A composite conductor material having an Nb core material arranged in the inside of the obtained Cu-Sn alloy is degressively worked into a prescribed wire diameter and then heat treated so that Nb3 Sn intermetallic compound is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an Nb ₃ Sn-based superconducting wire.

[0002]

Nb ₃ Sn based superconducting material is [Prior Art] intermetallic compound is superior in superconducting properties compared to other compounds superconductive material and an alloy-based superconducting material, alloy material for fragile Nb ₃ Sn is hard Cannot be directly processed into a wire rod. Therefore, an Nb ₃ Sn-based superconducting wire is generally manufactured by the following method. Bronze method A number of holes are provided in a Cu-Sn alloy (bronze) material, and a core material of pure Nb is inserted into these holes to form a composite wire material. Next, a method of forming a Nb ₃ Sn layer on the surface of the Nb core material by applying a heat treatment (diffusion treatment of Sn) to a surface of the composite conductor material to reduce the surface thereof to make the wire thinner. The Sn concentration of the Cu—Sn alloy used at this time is usually 10 to
It is about 15% by mass. Further, if necessary, the Cu
Ti may be added to the Sn alloy in an amount of about 0.02 to 0.03% by mass. External diffusion method A number of holes are provided in a pure Cu material, and a core material of pure Nb is inserted into these holes to form a composite conductor material. Next, a method of reducing the surface area of the composite conductor material to reduce the thickness thereof, coating the surface of the Cu with Sn, and then performing a heat treatment to form Nb ₃ Sn on the surface of the Nb core material.

The bronze method and the external diffusion method have advantages and disadvantages. One of the disadvantages of the bronze method is that Sn
Segregation. The critical current density of nb ₃ Sn based superconducting wire, it is high tends higher the Sn concentration in the Cu-Sn alloy, the higher the Sn concentration in the Cu-Sn alloy, significant Sn segregation during solidification is liable to occur In some cases, it is difficult to cast a uniform ingot. For this reason,
When a Sn-diffusion treatment is performed using a Cu-Sn alloy in which Sn segregation has occurred, the Nb formed on the surface of the Nb core material
The crystal grain size and the chemical composition of the b ₃ Sn layer become non-uniform, and as a result, a problem occurs that the critical current density decreases.

On the other hand, in the external diffusion method, Cu after surface reduction is used.
It is necessary to apply Sn plating to the outer peripheral surface of
The thickness of the n-plated layer must be sufficient to generate Nb ₃ Sn. When such a thick plating layer is formed, it is difficult to control the thickness of the plating layer, and there is a problem that a considerable time is required for plating. Further, in this method, since Sn for forming Nb ₃ Sn is supplied from the Sn plating layer separated from the Nb core material, the generation efficiency of Nb ₃ Sn is low, and a sufficient amount of Nb ₃ Sn is obtained.
There is a problem that it takes a long time to generate b ₃ Sn.

For this reason, a method combining these bronze method and external diffusion method has been proposed (Japanese Patent Publication No. 55-1).
No. 8565). In this method, the Sn concentration in the Cu—Sn alloy is slightly lowered (for example, Sn: 4 to 7% by mass), a large number of holes are provided in the Cu—Sn alloy, and a pure Nb core material is provided in the holes. The composite wire material is formed by insertion. Then, after coating the Sn on the surface of the Cu-Sn alloy after the thinning and reduction process to the composite wire material, it is a method of forming a Nb ₃ Sn on the surface of the Nb core material by heat treatment . This method is expected to suppress the Sn segregation of the Cu-Sn alloy which is a problem of the bronze method, control the thickness of the Sn plating layer which is a problem of the external diffusion method, and shorten the plating time.

[0006]

However, what is particularly problematic in these bronze methods and external diffusion methods is that Nb ₃
The production of Sn-based superconducting wires involves many steps and involves complicated steps, resulting in an increase in equipment costs and running costs. In particular, the process of providing a large number of holes in a Cu—Sn alloy or a pure Cu material and inserting a core material of pure Nb into these holes is complicated and requires a lot of time.

For this reason, a simplified method of inserting a pure Nb core into a Cu—Sn alloy or pure Cu material has been proposed (see Japanese Patent Application Laid-Open No. 61-195538). In this method, as shown in FIG. 6, a Nb metal melt 13 for an Nb ₃ Sn compound superconductor is continuously cast into a matrix Cu metal 14 which is melted at a temperature lower than its melting point. The Nb metal rod 15 is formed, and the Cu metal melt 14 is continuously cast together with the plurality of Nb metal rods 15 to form the composite material 12 in which the plurality of Nb metal rods 15 are embedded in the Cu metal 16. How to get. Then, Sn is coated on the surface of the Cu which has been reduced in surface area and thinned, and is subjected to a heat treatment so that the surface of the Nb metal rod is Nb ₃ Sn.
Is formed. Thus, a multi-core composite material for an Nb ₃ Sn compound superconductor can be manufactured in one step by continuous casting.

However, in this method, a high melting point (melting point: 2447 ° C.), expensive Nb melting equipment is required for dissolving active Nb, and a large number of Nb molten metal flows are continuously applied to the dissolved Cu. The continuous casting equipment is also complicated because of the continuous casting. If the dissolved Cu-Sn
Assuming that Nb is continuously cast in the alloy melt, Sn segregation may occur in the cast Cu-Sn alloy. That is, since a high-temperature Nb rod is continuously cast in a Cu-Sn molten metal, and further a Nb rod and a Cu-Sn alloy are continuously cast, a high-temperature Nb rod is present in the Cu-Sn molten metal, and Cu- The cooling speed of the Sn ingot decreases,
The occurrence of remarkable segregation cannot be prevented.

As a simple method of inserting a pure Nb core material into another Cu—Sn alloy or pure Cu material, hollow Cu
A method using a pipe has been proposed (JP-A-59-2).
19812). In this method, a bronze tape is wound around the outer periphery of an Nb wire, inserted into a Cu pipe and integrated by surface reduction processing, and then a large number of the obtained single wires are bundled to provide a diffusion barrier inside. This is a method in which the surface is reduced by inserting it into a pipe and then subjected to a heat treatment for generating Nb ₃ Sn. Nb stabilized with Cu
It is described that a ₃ Sn superconducting wire can be manufactured inexpensively and efficiently.

However, in this method, it is necessary to wind a bronze tape around the outer periphery of a large number of Nb wires, and after reducing the area, further bundle a number of single wires and insert them into a Cu pipe to further reduce the area. Is complicated. For this reason, the running cost may be increased, and the cost may not be reduced.

The present invention has been made in view of the above circumstances, and simplifies the step of inserting a Nb core material into a Cu—Sn alloy material, and particularly provides a high critical current density. and to provide a method for manufacturing a Nb ₃ Sn based superconducting wire composite conductor material inserted core material of Nb in the Cu-Sn alloy of Sn concentration can be efficiently produced by a simple method.

[0012]

To achieve SUMMARY OF for the foregoing and other objects, the present invention, Nb ₃ subjected to heat treatment after processing area reduction composite wire material which arranged Nb core inside a Cu-Sn alloy the method of manufacturing a Nb ₃ Sn based superconducting wire to produce Sn intermetallic compound, the composite wire material is supplied into the mold of a continuous casting apparatus a plurality of Nb wires, Cu-Sn
It is characterized by being manufactured by solidifying a molten alloy. Since a plurality of Nb wires are supplied into the mold of the continuous casting apparatus to solidify the molten Cu—Sn alloy, a composite wire material in which the core material of Nb is inserted in one step of continuous casting can be manufactured. Further, the Cu—Sn molten metal is
Since it is also cooled from the b-line, the cooling rate is faster than in the conventional method, and it is possible to prevent Sn segregation of the Cu-Sn alloy having a high Sn concentration. At this time, the temperature rise of the Nb line can be suppressed low by releasing the heat by the guide.

[0013] Further, when manufacturing the composite conductor material,
When supplying a number of Nb lines into the mold of the continuous casting apparatus,
A plurality of Nb lines are provided on a guide provided on the entrance side of the mold.
The starter provided in the mold through the guide hole
It is preferable to fix to the block. Multiple Nb lines
Guides located on the inlet side of the mold and provided inside the mold
Placed at predetermined intervals by the starting block
It is possible to solidify the molten Cu-Sn alloy in the state
It is necessary to uniformly distribute the Nb core material in the composite conductor material.
Nb heat-treated by reducing the surface area_ThreeSn-based
Nb in conductive wire _ThreeSn filaments do not contact each other
Therefore, AC loss can be reduced.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a belt-type continuous casting apparatus used in an embodiment of the present invention, and FIG. 2 is a schematic view of a vertical cross section of a composite wire material manufactured according to the embodiment of the present invention. As shown in FIG. 1, the belt-type continuous casting apparatus used in the embodiment of the present invention includes a pair of upper belts 4a and lower belts 4b rotating in opposite directions, and a pair of side dams 5 on the lower belt 4b. Have been. The pair of side dams 5 are configured to move in synchronization with the lower belt.

The molten metal 1 in the tundish 8 is supplied between a pair of side dams 5 on the lower belt 4b, and the supplied molten metal solidifies between the upper belt 4a, the lower belt 4b and the pair of side dams 5. Thus, an ingot is continuously produced. At this time, the upper surface belt 4a and the lower surface belt 4b always press the ingot by the cooling water pressure of the cooling water jet 9, thereby preventing the cooling effect from being reduced by the air gap.

The size of the ingot to be cast in the belt-type continuous casting apparatus is determined by the thickness of the side dam 5 and the distance between both side dams 5. That is, the thickness of the ingot is determined by the thickness of the side dam 5, and the width of the ingot is determined by the interval between both side dams. In this embodiment, the thickness is 60 mm and the width is 1
The thickness of the side dam 5 was set to 60 mm and the interval between the side dams was set to 120 mm so that a 20 mm ingot could be cast.

Next, a method of manufacturing the composite conductor material of the present embodiment will be described. Starting block 6 is 120m wide
It was a block made of Cu having a length of m, a thickness of 60 mm and a length of 100 mm, and 133 drill holes having a diameter of 5 mm were formed in the block. The guide 7 was made of Cu, and 133 through holes (guide holes) having a diameter of 6 mm were provided in the guide 7 so as to correspond to the through holes of the starting block 6. This guide was provided on the inlet side of the mold of the belt type continuous casting apparatus, that is, on the side where the upper belt 4a, the lower belt 4b and the pair of side dams 5 were fed into the belt type continuous casting apparatus.

Then, 133 Nb wires 2 (outer diameter 5 m
m, 5 m in length) were passed through the guide holes of the guide 7 and were fixed in the drill holes of the starting block 6, respectively. The starting block 6 to which the Nb line 2 is fixed is sandwiched between the upper belt 4a, the lower belt 4b, and the pair of side dams 5. The guide 7 is provided on the inlet side of the casting mold of the belt-type continuous casting apparatus so that the Nb wire 2 is parallel to the casting direction during casting so as not to hinder pouring.

At this time, if there is a possibility that the guide is melted or deformed, the guide near the molten metal may be made of steel (including stainless steel) instead of Cu. Also,
In this embodiment, a plurality of guides 7 are provided, but one guide may be provided.

The composition of the molten Cu—Sn alloy used for continuous casting is Cu—14.5% by mass Sn—0.03% by mass T
i. Here, the reason for adding Ti is to improve the superconducting characteristics, refine the crystal grains, and promote the diffusion of Sn. The molten Cu-Sn alloy is composed of Sn and Cu-Ti
Was dissolved in the above composition and supplied to the tundish 8. Cu-S supplied to tundish 8
The n alloy melt 1 (melt temperature: 1200 ° C.) is fed into the mold region 10 between the upper belt 4a and the lower belt 4b and the pair of side dams 5 of the belt type continuous casting apparatus, and at the same time, the upper belt 4a and the lower belt. The rotation of 4b was started. At this time, the starting block 6 sandwiched between the upper belt 4a, the lower belt 4b and the pair of side dams 5 also starts to move in the casting direction, and the Nb wire 2 fixed to the starting block 6 also moves into the mold area 10. I was drawn in.

By solidifying the molten Cu—Sn alloy in the belt-type continuous casting apparatus by the above method, FIG.
The billet (width 120 mm, thickness 60 mm, length 5000 mm) of a composite conductor material obtained by casting an Nb wire in a Cu-Sn alloy matrix (bronze matrix) shown in FIG. The Nb wires in this composite conductor material are uniformly arranged in the Cu-Sn alloy matrix, and the Cu-Sn
No Sn segregation in the alloy matrix was observed.

This billet is cast in the casting direction, ie, Nb
In the arrangement direction of the wire, repeatedly performing surface reduction processing such as forging, rolling, swaging, drawing / drawing, etc.
The outer diameter of the Nb wire in the -Sn alloy was reduced from 5 mm to 0.5 mm to produce a composite superconducting baseline. Subsequently, the composite superconducting baseline was placed at 725 ° C. × 10
Nb ₃ Sn was generated by performing a diffusion heat treatment for 0 hour. As an atmosphere for the diffusion heat treatment, not only a nitrogen gas atmosphere but also an inert gas atmosphere or a vacuum atmosphere can be used.

The superconducting characteristics of the thus obtained Nb ₃ Sn-based ultrafine multifilamentary superconducting wire were measured and found to be 4.2.
The overall Jc in the magnetic field of K and 12T is 5.5 × 10
^{It was 4} A / cm ² . This value is the overall Jc of Nb ₃ Sn-based ultrafine multicore superconducting wire manufactured by the conventional bronze method.
(4.5 × 10 ⁴ A / cm ² ).

The Nb ₃ Sn-based ultrafine multifilamentary superconducting wire manufactured by the conventional bronze method is manufactured by the following method.
First, Cu-1 having an outer diameter of 100 mm and a length of 1000 mm was used.
After producing a 4.5 mass% Sn ingot, 133 holes having a diameter of 5 mm were provided in the longitudinal direction of the ingot, and a wire diameter of 5 m was formed in this hole.
m Nb lines were inserted. Thereafter, the ingot into which the Nb wire has been inserted is subjected to surface reduction processing so that the wire diameter of the Nb wire in the ingot is reduced to 0.
It was 5 mm. Continuously at 725 ° C x 10 in a nitrogen atmosphere
A diffusion heat treatment for 0 hour is performed to make Nb ₃ Sn and Nb ₃ S
This is an n-type ultrafine multicore superconducting wire manufactured. And
When the superconducting characteristics of the Nb ₃ Sn-based ultrafine multifilamentary superconducting wire were measured, overall
Jc was 4.5 × 10 ⁴ A / cm ² .

As described above, by using the method of the present invention, a plurality of Nb wires are supplied into the mold of the continuous casting apparatus to solidify the molten Cu—Sn alloy. A composite conductor material having a core material inserted therein can be manufactured.
Since it is also cooled from the wire, the cooling rate is faster than in the conventional method, the Sn segregation of the Cu—Sn alloy having a high Sn concentration can be prevented, and the superconductivity is stably high.

In the present invention, the Nb wire is supplied into the mold without a high temperature in order to release heat from the guide. In this embodiment, the temperature of the Nb wire on the inlet side of the mold was about 400 ° C. The temperature of the Nb line is the peritectic temperature of the Cu-Sn alloy (780
° C) or less, there is a cooling effect, but the lower the temperature of the Nb wire, the greater the cooling effect on the molten Cu-Sn alloy. In order to lower the temperature of the Nb line, a guide case shown in FIG. 3 can be used instead of the guide. The guide case 11 has a box shape and an inlet 21 for introducing a cooling gas in addition to a guide hole and an outlet 2 for discharging a cooling gas.
2 are provided. The cooling gas cools the Nb line to lower the temperature of the Nb line.

Using a belt type continuous casting apparatus, Cu-Sn
Although the embodiment in which the composite wire having the Nb wire as the core material is cast in the alloy matrix has been described, a continuous casting device such as a block type continuous casting device or a DC casting device can be used for casting the composite wire.

An embodiment of the present invention using a block type continuous casting apparatus will be described with reference to the drawings. FIG. 4 is a schematic diagram of a block type continuous casting apparatus. The block-type continuous casting apparatus is composed of a pair of casting blocks 1 rotating in opposite directions.
7, 17 are provided, and this pair of casting blocks 17, 1
7 are connected in a caterpillar shape. This block type continuous casting apparatus includes the pair of casting blocks 1
On both sides 7 and 17, the pair of casting blocks 17,
A side dam (not shown) is provided so as to cover the space between the two, and the mold region 10 is configured. A guide 7 is disposed on the inlet side of the mold, and a plurality of Nb wires 2 are passed through the guide holes of the guide 7 to the starting block 9.
It is fixed to. The molten Cu-Su alloy 1 is supplied to the mold region 10 in which the starting block 9 is disposed, and the pair of casting blocks 17 and 17 are rotated to form the Cu-Sn alloy in the same manner as the belt-type continuous casting apparatus. A composite conductor having an Nb wire as a core material is cast inside a matrix.

Next, another embodiment of the present invention using a DC casting apparatus will be described with reference to the drawings. FIG. 5 is a schematic diagram of a DC casting apparatus. In the DC casting apparatus, a water-cooled mold 1
The header 18 is disposed on the top of the melt 9 to supply the molten Cu-Su alloy 1. The guide 7 is disposed above the mold 19, and a plurality of Nb wires 2 are fixed to the bottom block 20 through the guide holes of the guide 7. The Cu—Su alloy melt 1 is supplied to a mold region constituted by the bottom block 20 and the mold 19 and is sequentially solidified in the mold 19, while the bottom block is lowered, and Cu The present invention is to cast a composite conductor having an Nb wire as a core material inside a Sn alloy matrix.

The present invention is not limited to the Cu--Sn alloy composition, but a Cu--Sn alloy having a Sn concentration close to the limit of solid solution of Sn in Cu (15.8% by mass) can be used. . In particular, C having a high Sn concentration of 13.0% by mass or more
This is effective in suppressing Sn segregation in the u-Sn alloy. Also,
If necessary, a small amount of an additional element such as Ti may be added.

[0031]

As described above, according to the present invention, Cu
Since an Nb wire serving as a core rod is cast together at the stage of producing a Sn alloy ingot, an insertion hole is formed in the ingot, and N
The step of passing the b core rod can be omitted, and the Nb ₃ Sn superconducting wire can be manufactured inexpensively and efficiently. Further, the present invention provides a method for producing a high Sn concentration Cu-
Even if an Sn alloy is used, the occurrence of Sn segregation, which is a problem in the bronze method, can be prevented, and an Nb ₃ Sn-based superconducting wire having stable and high superconductivity can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic view of a belt type continuous casting apparatus used in an embodiment of the present invention.

FIG. 2 is a schematic view of a vertical cross section of a composite conductor material manufactured according to an embodiment of the present invention.

FIG. 3 is a schematic view of a guide case.

FIG. 4 is a schematic diagram of a block type continuous casting apparatus used in an embodiment of the present invention.

FIG. 5 is a schematic view of a DC casting apparatus used in another embodiment of the present invention.

FIG. 6 shows a conventional example (first example of Japanese Patent Application Laid-Open No. 61-19573).
FIGS. 2A and 2B) are diagrams illustrating a), a) is a cross-sectional view, and b) is a cross-sectional view taken along line xx of a).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cu-Sn alloy molten metal 2 Nb wire 3 Cu-Sn alloy matrix 4a Upper surface belt 4b Lower surface belt 5 Side dam 6 Starting block 7 Guide 8 Tundish 9 Cooling water jet 10 Mold area 11 Guide case 12 Composite material 13 Nb molten metal 14 Cu metal for matrix 15 Nb metal rod 16 Cu metal 17 Cast block 18 Header 19 Mold 20 Bottom block 21 Cooling gas inlet 22 Cooling gas outlet

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22C 27/02 102 C22C 27/02 102A H01B 12/10 ZAA H01B 12/10 ZAA

Claims (2)

[Claims] 1. A heat treatment is performed by subjecting a composite wire material having a Nb core material arranged in a Cu—Sn alloy to a heat treatment after reducing the surface area.
The method of manufacturing a ₃ Sn intermetallic compound Nb ₃ Sn based superconducting wire to produce the composite conductor material is supplied into the mold of a continuous casting apparatus a plurality of Nb wires, solidifying the Cu-Sn alloy melt A method for producing an Nb ₃ Sn-based superconducting wire, characterized by being produced. 2. The method according to claim 1, wherein when the plurality of Nb wires are supplied into the mold of the continuous casting apparatus, the plurality of Nb wires are disposed on the inlet side of the mold. through the guide of the guide hole, Nb ₃ Sn-based method of manufacturing a superconducting wire, characterized in that it is fixed to the starting block provided in said mold.