JPH04294008A - Manufacture of compound superconductive wire - Google Patents

Abstract

PURPOSE:To obtain a manufacturing method having an A3B type compound approximate to stoichiometry composition by winding and enhancing pinning force together an A metal foil and a B metal foil, and then coating these with a high melting point metal, and further performing wire drawing thereon. CONSTITUTION:An Nb sheet (A metal foil) 1 having the prescribed thickness and an Sn sheet (B metal foil) 2 having the prescribed thickness are overlapped to have a prescribed ratio of an atomic ratio and to be spirally multiple-winded. These are put into a Ta tube (high melting point metallic tube) 3 having a prescribed diameter. These are put inot a Cu-Ni alloy-made tube 4 and subjected to wire drawing processing followed by melting removal of the tube 4 by nitric acid. Thereby, the sheet 1 and the sheet 2 are covered with a tube 3 so as to form a wire-drawn composite material 5. Further, prescribed pieces of obtained composite material 5 are collected to be subjected to a plurality of times of drawing processing and finally subjected to heat treatment at a prescribed temperature and for a prescribed time. Thereby, a compound superconductive wire having an A3B type compound layer approximate to stoichiometry composition and heightened pinning force can be obtained.

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 compound superconducting wire.

0002

[Prior art] As superconducting wires, Nb3 Sn, V3
Superconducting wires made of A3 B type compounds (A15 type compounds) such as Ga and Nb3 Al are known. Such a superconducting wire is made of A metal made of Nb or V, etc., and Sn, Ga, or A metal.
It is manufactured by bonding a metal containing a B metal such as L and the like, and then performing a heat treatment to cause a diffusion reaction between the A metal and the B metal at the interface to form an A3 B-type compound layer. For example, in manufacturing Nb3Sn compound superconducting wire by the bronze method, multiple Nb cores or Nb alloy cores are embedded in a bronze base material made of a Cu-Sn alloy, and then heat treated to form an Nb3Sn layer at the interface. Do the method. In addition, Nb3S by internal diffusion method (tube method, etc.)
In manufacturing an n-compound superconducting wire, a method is used in which an Nb tube or a Nb alloy tube is placed around a Sn-rich alloy core and then heat treated to form an Nb3Sn layer at the interface.

However, in the above-mentioned bronze method,
Sn diffusion determines the rate of the entire reaction, and the stoichiometric composition of Nb and Sn depends on the diffusion of Sn in the bronze and Nb3Sn layers, so Sn deficiency tends to occur on the center side of the Nb core or Nb alloy core. Become. As a result, the superconducting properties deteriorate, particularly in Hc2 (critical magnetic field) under high magnetic fields.

[0004] For this reason, in order to manufacture a superconducting wire having an A3B type compound layer having a stoichiometric composition, it is necessary to carry out sufficient heat treatment. This A
3 In the B-type compound layer, the pinning center is the crystal grain interface, and the pinning force fp due to the crystal grain interface is essentially not larger than the pinning force fp due to the normal conductive phase. Moreover, the pin density also depends on the reciprocal of the crystal grain size. As mentioned above, if sufficient heat treatment is applied for the purpose of forming an A3 B type compound layer with a stoichiometric composition, the crystal grains will become enlarged.
The pinning force is reduced, that is, the pin density is reduced. Therefore, the high magnetic field characteristics, especially the critical current density (
There were limits to the improvement of Jc).

[0005]

OBJECTS OF THE INVENTION The present invention has been made in order to solve the problems of the conventional art, and provides a compound having an A3 B type compound layer with a similar stoichiometric composition and an increased pinning force. The present invention aims to provide a method for manufacturing superconducting wires.

[0006]

[Means for Solving the Problems] In the production of A3B type compound superconducting wire, the present invention involves winding A metal foil and B metal foil together, coating them with a high melting point metal, and then stretching them. A3 B
A method for manufacturing a compound superconducting wire, comprising a step of forming a mold compound layer.

[0007] As the A3 B type compound, for example, N
b3 Sn, V3 Ga, Nb3 Al, Nb3 (A
l, Sn), Nb3 Si, Nb3 Ge, Nb3 (
Al, Ge), etc. Examples of the metal forming the metal foil A include Nb and V. The metals forming the B metal foil include Sn, Ga, Al, and Ge.
, Si, etc.

It is possible to add Ti, Ta, Mg, Hf, Ga, Mn, etc. to at least one of the A metal foil and the B metal foil. If such A and B metal foils are used, the additives are introduced into the A3 and B type compound layers, making it possible to further increase Jc under a high magnetic field. The ratio of winding the A metal foil and the B metal foil together is
Usually, the atomic ratio (number of atoms of metal A: number of atoms of metal B) is 3.
: It should be about 1.

[0009] Examples of the high melting point metal include Ta and N.
b, Ti, Hf, etc. M in the high melting point metal
It is possible to add g, Ga, Mn, etc. If such a high melting point metal is used, the high melting point metal acts as a pinning center at the grain boundary of the A3 B type compound, and the additive is diffused during heat treatment and introduced into the crystal grains of the A3 B type compound. Since it acts as a pinning center, it is possible to further increase Jc under a high magnetic field.

0010

According to the manufacturing method of the present invention, metal foil A and metal foil B are wound together, coated with a high melting point metal, and then wire drawn. In this step, since the A metal foil and the B metal foil have been made into thin films by the wire drawing process, the diffusion between the A metal and B metal can be achieved with a relatively short heat treatment, and the stoichiometric amount A3 approximating the theoretical composition
A B-type compound layer can be easily formed, and enlargement of crystal grains can be suppressed. Further, in the step, the A3
The high melting point metal can be introduced into the interface of the B-type compound layer. Therefore, the pinning force can be improved by suppressing the enlargement of the crystal grains of the A3 B type compound layer and introducing the high melting point metal to the interface. Therefore, the superconducting properties, especially Hc2 under high magnetic field.
, Jc can be manufactured.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Example 1

First, as shown in FIG. 1(a), a 90μ thick
A Nb sheet (metal foil A) 1 with a thickness of m and a Sn sheet (metal foil B) 2 with a thickness of 30 μm are stacked so that the atomic ratio (number of Nb atoms: number of Sn atoms) is 3:1 and formed into a spiral shape. Make multiple windings. This is put into a Ta tube (high melting point metal tube) 3 having an outer diameter of 25 mmφ and an inner diameter of 20 mmφ. Subsequently, these are put into the Cu-Ni alloy tube 4 and subjected to wire drawing processing using a swager and die.
Dissolve and remove with nitric acid. Thereby, as shown in FIG. 1(b), the Nb sheet 1 and the Sn sheet 2 are covered with the Ta tube 3 to form a composite material 5 drawn to an outer diameter of 2.3 mmφ.

Next, as shown in FIG. 2(a), 240 pieces of the composite material 5 are assembled into an outer diameter of 45 mmφ and an inner diameter of 35 mm.
The wire is placed in a Cu--Ni alloy tube 6 having a diameter of .phi., and after wire drawing is performed using a swager and a die, the Cu--Ni alloy tube 6 is dissolved and removed with nitric acid. As a result, the 240 composite materials 5 are bundled and integrated, and as shown in FIG. 2(b), the composite wire bundle 7 is drawn to an outer diameter of 3.3 mmφ.
form.

Next, as shown in FIG. 3(a), 85 wire bundles 7 of the composite material are assembled into a bundle having an outer diameter of 45 mmφ and an inner diameter of 35 mm.
It is placed in a tube 8 made of a Cu-Ni alloy having a diameter of mm, and subjected to wire drawing by hydrostatic extrusion. As a result, the 85 bundled wires 7 are further bundled and coated with Cu-Ni alloy, as shown in FIG.
As shown in (b), a hexagonal wire 9 drawn in a hexagonal shape with a diagonal distance of 4 mmφ is formed.

Next, as shown in FIG. 4(a), the 55 hexagonal wires 9 are assembled into a shape having an outer diameter of 45 mmφ and an inner diameter of 35 mmφ.
The wire is placed in a tube 10 made of a Cu-Ni alloy, and subjected to wire drawing by hydrostatic extrusion. As a result, 55 hexagonal wires 9 are bundled and coated with the Cu-Ni alloy to form a wire rod 11 drawn to an outer diameter of 0.2 mm as shown in FIG. 4(b). Subsequently, the wire rod 11 was heated at a temperature of 780° C. for 12
By performing heat treatment under conditions of 0 hours, the Nb sheet and the Sn sheet are caused to undergo a diffusion reaction to form Nb3Sn.
A compound superconducting wire with layers formed thereon was manufactured. Example 2

[0016] Outer diameter 25 mmφ and inner diameter 2 used in Example 1
Instead of Ta tube 3 with 0mmφ, outer diameter 25mmφ and inner diameter 22
．． A compound superconducting wire was manufactured in the same manner as in Example 1 except that a 5 mmφ Ta tube was used. Comparative Example 1 A compound superconducting wire having the same structure as in Example 1 was manufactured by a bronze method.

The compound superconducting wires of Examples 1 and 2 and Comparative Example 1 were tested in liquid helium at 10T and 16T, respectively.
The critical current density (Jc) under a high magnetic field was measured. The results are shown in Table 1 below.

As is clear from Table 1, the compound superconducting wires of Examples 1 and 2 have a larger Jc value under a high magnetic field than the compound superconducting wire of Comparative Example 1. This is due to Nb during heat treatment.
This is because the sheet and the Sn sheet are extremely thin and easily diffused, so that an Nb3Sn layer having a composition close to the stoichiometric composition is formed, and the Ta tube functions as a pinning center.

[0019]

Effects of the Invention As detailed above, the present invention has an A3B type compound layer having a composition close to the stoichiometric composition, increases the pinning force, and further improves Hc2, J under a high magnetic field.
A method for manufacturing a compound superconducting wire with improved c can be provided.

[Brief explanation of drawings]

[Fig. 1] Explanatory diagram showing the manufacturing process of the compound superconducting wire of Example 1

[Fig. 2] Explanatory diagram showing the manufacturing process of the compound superconducting wire of Example 1

[Fig. 3] Explanatory diagram showing the manufacturing process of the compound superconducting wire of Example 1

[Fig. 4] Explanatory diagram showing the manufacturing process of the compound superconducting wire of Example 1

[Explanation of symbols]

1... Nb sheet (metal foil A), 2... Sn sheet (metal foil B), 3... Ta tube (high melting point metal tube) 5... composite material.

Claims (1)

[Claims] [Claim 1] In the production of A3 B-type compound superconducting wire, a metal foil A and a metal foil B are wound together, then coated with a high melting point metal, and then drawn to form a composite material. A method for manufacturing a compound superconducting wire, comprising: a step of bundling and integrating a plurality of the composite materials; and a step of performing heat treatment to form an A3 B-type compound layer.