JPH03274612A - Manufacture of nb3 sn superconductive wire - Google Patents

Abstract

PURPOSE:To enable uniform deformation of an Nb group metal tube and improve its characteristic such as critical current density by arranging a copper alloy having big mechanical strength between the Nb group metal tube and a tin group metal in a central part. CONSTITUTION:A plurality of Nb group metal tubes are arranged in a copper or copper alloy matrix, and area reduction processing is applied to a complex body housing a tin group metal wire coated with a copper alloy having big mechanical strength inside said metal tube followed by heat treatment. An Nb radical alloy, to which pure Nb and Ti for improving workability, is used as the material of the Nb group metal tube to be arranged in the matrix. Heat treatment after area reduction is applied within a temperature range from 550 to 755 deg.C. As a copper alloy having big mechanical strength, Ti alloy including (0.1 to 2.0)wt.% of Cu, Sn alloy including (0.1 to 10)wt.% of Cu and Ni alloy including (1.0 to 40)wt. of Cu are used.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a superconducting wire, and in particular, in a method for manufacturing a Nb3Sn superconducting wire by a tube method, it enables uniform deformation of a Nb-based metal tube, and Critical current density (''
This invention relates to improvements in manufacturing methods that can improve properties such as C).

[Prior Art] A tube method is known as one of the methods for manufacturing Nb3Sn superconducting wire.

In this method, a plurality of composite wires in which the outer periphery of an Sn rod is sequentially coated with Cu tubes and Nb tubes is arranged in a Cu matrix to form a composite, and after cold working this composite, heat treatment is performed. (Japanese Patent Publication No. 55-18547).

Compared to the bronze method using a Cu-Sn alloy as a matrix, the above method (a) allows processing without requiring intermediate annealing.

(b) High Jc value.

(c) By allowing the Nb-based metal tube to remain after heat treatment, it is not necessary to add stabilizing copper when Cu (pure copper) is used for the matrix.

It has the following advantages.

[Problem II to be Solved by the Invention] However, in the above-mentioned tube method, when the degree of cold working exceeds 104, breakage or disconnection of the tube wall of the Nb tube is likely to occur, and heat treatment is required. In this case, 1: Sn diffuses into the matrix, causing problems such as a decrease in C and destabilization of cooling.

Further, when the Nb tube is processed to have an average diameter of about 80 μm or more, there is a problem that the remaining amount of unreacted Nb portion increases and Jc decreases.

The above problem is caused by the fact that the Nb tube is not deformed uniformly due to the highly processed molding, resulting in a significant difference in the shape of the Nb tube between the central portion and the peripheral portion.

Figure 3 shows an example of a cross section of a filament after heat treatment. In the filament near the center shown in Figure (a), an Nb3Sn layer 2 is uniformly generated around the Cu-Sn alloy 1, and Although the thickness of the remaining Nb tube 3 on the outside is almost uniform, the deformation of the filament in the peripheral part shown in FIG. Note that 1a is a Cu-Sn alloy, and 2a is N
b shows the NbHSn layer formed inside the tube 3a.

The present invention was made to solve the above problems, and it enables uniform deformation of Nb-based metal tubes, reduces the amount of Nb remaining after heat treatment, and reduces the critical current density ('C).
It is an object of the present invention to provide a method for manufacturing a Nb3Sn superconducting wire that can improve properties such as the following.

[Means for Solving the Problems] The method for manufacturing an Nb3Sn superconducting wire of the present invention includes arranging a plurality of Nb-based metal tubes in a copper or copper alloy matrix,
After subjecting the composite body containing a tin-based metal wire coated with a copper alloy with high mechanical strength in the metal tube to reduce its area, 5
The above object is achieved by performing heat treatment at a temperature of 50 to 755°C.

Copper or a copper alloy is used as the matrix material in the present invention, but oxygen-free copper is suitable when the matrix is to function as a stabilizing material.

As the material for the Nb-based metal tube disposed in the matrix, pure Nb or an Nb-based alloy to which TI or the like is added to improve workability is used.

Further, the heat treatment after the area reduction processing is carried out at a temperature of 550 to 755°C, because properties such as Jc deteriorate outside the above temperature range. In this heat treatment, in order to prevent Sn from diffusing into the matrix, it is preferable to select conditions such that a portion of the Nb tube remains.

In the present invention, when manufacturing a superconducting wire with a multicore structure, for example, a metal tube made of a copper alloy with high mechanical strength, a Nb tube, and a Cu tube are sequentially coated on the outer periphery of an Sn rod to form a hexagonal cross-section. It is preferable to use a composite formed by filling a plurality of molded composite wires into a Cu tube with their sides in contact.

The above-mentioned copper alloy with high mechanical strength includes Cu-(0
,1~2.0) wt% TI alloy, Cu-(0,1~10
)wt%sn alloy, Cu-(1,0-40)wt%N1
Preferably, alloys are used. If the added amount of TI, Sns Nl is less than the above range, the difference in strength with the Nb metal tube will become large and the deformation of the Nb metal tube will become uneven.On the other hand, if it exceeds the above range, processing will be difficult. The properties of the steel decrease and intermediate annealing becomes necessary. In addition to the above additive elements, it is also possible to use a copper alloy to which Be, Cr, etc. are added.

Furthermore, in addition to the above-mentioned copper alloys, alumina-dispersed copper containing about 0.1 to 0.2 vt% of Al2O3 can also be used. In this case, the mechanical strength of the bronze portion within Nb also increases due to the dispersion of alumina after heat treatment.

[Function] In the present invention, by disposing a copper alloy with high mechanical strength between the Nb-based metal tube and the tin-based metal in the center, the difference in strength between the Nb-based metal tube and the Nb-based metal tube is reduced. Significant non-uniform deformation of the tube can be prevented, and characteristics such as Jc can be improved.

That is, if the thickness of the Nb tube becomes uneven as shown in FIG.
is not generated, the amount of residual Nb increases and the C value decreases. This means that the amount of Nb3Sn produced is rate-determined by the thinner Nb portion.

[Example code] An example of the present invention and a comparative example will be described below.

Nb-1vt with exception diameter 8.0m*φ, inner diameter 5.6+u+φ
A Sn rod coated with Cu-0.3vt%Ti alloy was housed inside the Nb-Ti alloy tube, and a Cu tube with an outer diameter of 10.3 mg + φ and an inner diameter of 8.1 amφ was placed outside the Nb-Ti alloy tube. The distance between opposite sides is 2.52.
A composite wire with a hexagonal cross section of mg+ was manufactured. The above Nb-
Cu and Sn inside the Ti alloy tube were mixed to have a composition of Cu-30wt%Sn.

Next, seven of the above composite wires were housed in a Cu tube with an outer diameter of 1033 mm and an inner diameter of 8.1 am to form a composite.
This composite was subjected to wire drawing to produce a wire rod with an outer diameter of 0.51 mm. The copper ratio (copper/valve copper) of this wire is 1.98, and the filament diameter (in terms of yen) is 109 μm.

The thus obtained wire was heat treated at 725° C. for 72 hours to produce a superconducting wire. As a result of measuring the Jc of the valve copper of this superconducting wire, it was 600A/as at 15T.
A value of 2 was obtained.

FIG. 1 shows the cross-sectional structure of the above superconducting wire before heat treatment.

In the same figure, seven Nb-1vt% TI alloy tubes 10 are arranged in a Cu matrix 11, and Sn wires 13 coated with Cu-0,3vt% Ti alloy 12 are housed inside these Nb-Ti alloy tubes 10. has been done.

Comparative Example Cu-0,3vt%Ti alloy 12 in the above example
A composite body was formed in the same manner as in the example except that a Cu tube of the same size was used in place of the composite body, and subjected to wire drawing and heat treatment.

As a result of measuring the Jc of the valve copper of the superconducting wire thus obtained, a value of 550 A/cm2 was obtained at 15T.

FIG. 2 shows the cross-sectional structure of the above superconducting wire before heat treatment.

In the figure, seven Nb-1wt%T1 alloy tubes 10a are arranged in a Cu matrix 11a, and inside these Nb-Ti alloy tubes 10a are Sn wires 13 coated with Cu12a.
a is accommodated, and compared to FIG. 1, Nb-
It is clear that the thickness of the T1 alloy tube is significantly non-uniform.

[Effects of the Invention] As described above, according to the present invention, by disposing a copper alloy having high mechanical strength between the Nb-based metal tube and the tin-based metal in the center, the Nb-based metal tube has a remarkable Non-uniform deformation can be prevented, and as a result, the characteristics of the superconducting wire after heat treatment can be improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of the structure of a superconducting wire before heat treatment using the tube method of the present invention, FIG. 2 is a cross-sectional view showing the structure of a superconducting wire before heat treatment using the conventional tube method, and FIG. (a) and (b) are cross-sectional views showing the shape of a filament after heat treatment at the center and periphery of a superconducting wire by a conventional method, respectively. 1, l a-Cu-Sn alloy 2...Nb3 Sn layer 2a...Nb3 Sn layer 3.3a...Remaining Nb tube 10, 10 a ・Nb -1vt% Ti alloy tube 11.
11a...Cu matrix 12-----Cu-0,3 wt% Ti alloy 12a
...Cu 13 Sl 3 a = Sn line 1-562 Figure 69- (6) j13 (1))

Claims (2)

[Claims] (1) A composite body in which a plurality of Nb-based metal tubes are arranged in a copper or copper alloy matrix and a tin-based metal wire coated with a copper alloy with high mechanical strength is housed inside the metal tube is subjected to area reduction processing. A method for producing a Nb_3Sn superconducting wire, which comprises performing heat treatment at a temperature of 550 to 755°C. (2) Copper alloys with high mechanical strength are Cu-(0.1~
2.0)wt%Ti alloy, Cu-(0.1-10)wt
The method for producing a Nb_3Sn superconducting wire according to claim 1, wherein the Nb_3Sn superconducting wire is one of a %Sn alloy and a Cu-(1.0-40)wt%Ni alloy.