JPS61116711A - Manufacture of nb-ti multicore flat superconductor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention reduces disconnection of Nb-Ti strands during wire drawing, improves characteristics such as critical current density, and improves performance after wire drawing. Nb is used when manufacturing flat wires by rolling.
- N that does not cause disorder or separation of the arrangement of Ti wire groups
The present invention relates to a method for manufacturing a b-Ti multicore rectangular superconducting wire.

[Technical background of the invention and its problems 1 Conventionally, as a manufacturing method for superconducting wires, especially fine multi-superconducting wires, the outer periphery of Nb-Ti wire is coated with Cu,
A large number of core rods formed with a regular hexagonal cross section are tightly inserted into a Cu vibe, and a CuCl lot with a circular cross section to serve as a spacer is placed in the gap between the CIJI tube and the core rod, and is then processed by hydrostatic extrusion and wire drawing. There is a known method in which a superconducting wire is subjected to an area reduction process, and if necessary, the superconducting wire subjected to this area reduction process is formed into a regular hexagonal cross section, and the same operation is repeated to obtain a superconducting wire with a desired outer diameter. There is.

However, with such conventional methods, the Nb-Ti element wire is likely to break during area reduction processing, resulting in a problem that the properties of the obtained superconducting wire may deteriorate, and in some cases, the entire wire may break.・There was a desire for improvement. It was also desired to improve the properties of superconducting wires, such as critical current density.

As a method for manufacturing a superconducting wire that does not easily cause wire breakage as described above, the present applicant has developed
? *Nb-Ti alloy wire covered? 1! Textbook and Cl lot,
The Cu-coated Nb-Ti alloy wires are gathered in the center and C1
We previously filed an application for a method for manufacturing superconducting wire that is filled into a single tube and subjected to area reduction processing (Japanese Patent Application No. 58-201957).

However, although this method improves the frequency of wire breakage during wire processing and the above-mentioned characteristics related to this, it does It has been found that the arrangement of the Nb-Ti alloy strands is disturbed during rolling and drawing during wire manufacture, making it difficult to maintain the above-mentioned improved wire characteristics.

In order to prevent the arrangement of the superconducting strands from being disturbed during rectangular processing as described above, it is necessary to have a matrix of an appropriate area in the center of the wire, and this cannot be achieved with the above-mentioned method.

(Object of the invention) The present invention has been made to improve the above-mentioned difficulties.
By arranging composite wires having a matrix ratio in a predetermined range in a cylindrical shape, keeping the thickness of the matrix on the outer periphery below a certain level, and setting the cold working rate after heat treatment below a certain percentage, rectangular workability and superconductivity can be improved. It is an object of the present invention to provide a method for manufacturing a Nb-Ti multicore rectangular superconducting wire having a multicore structure with excellent properties.

(Summary of the Invention) The method for manufacturing a rectangular superconducting wire in which a large number of Nb-Ti alloy wires are arranged in an ε11 or C11-based alloy (hereinafter referred to as CI-based metal) matrix of the present invention is as follows: ) The outer periphery of the Nb-Ti alloy is coated with CIJI metal,
Matrix ratio (matrix cross-sectional area/1'Jb-Ti
(b) arranging a large number of said composite wires in a substantially cylindrical shape, and forming a composite wire inside the cylinder or inside and outside the cylinder; arranging 011 metal wires having the same cross-sectional shape as the composite wire on the outside and filling them into a CI gold metal tube; (c) placing the composite wire and Cu
A step of manufacturing a wire in which a Cu-based metal having a thickness of at least 12% of the wire diameter is arranged on the outer periphery of the wire by subjecting a 011-based metal tube filled with the 011-based metal wire to a cross-sectional reduction process;
d) A step of subjecting this wire to heat treatment to improve superconducting properties; (e) A step of subjecting the wire after heat treatment to cold working with a reduction in area of 70% or less; (f) After this cold working The method is characterized in that it consists of a step of rolling a wire rod with an aspect ratio of 1.8 or more.

In the present invention, the matrix ratio of the composite wire, the thickness of the matrix at the outer periphery of the superconducting wire, and the cross-sectional reduction rate after heat treatment are limited as described above for the following reasons.

In other words, when the cross-section reduction rate in cold working after heat treatment is high, about 75% or more, the smaller the matrix ratio of the composite wire is, the lower the filament breakage rate is, but the aspect ratio during subsequent rolling into a rectangular wire is If the aspect ratio is 1.8 or more, the Nb-Ti filament group may be disarranged or broken in the cross section of the flat wire after rolling, or voids may be formed inside. In order to form the composite wire by processing, the matrix of the composite wire should be within the above range, and the matrix thickness should be 12% of the wire diameter.
In addition to the following, it is necessary to suppress the area reduction rate after heat treatment to 70% or less.

In the present invention, by increasing the matrix ratio of the composite wire as much as possible and suppressing the cold working after heat treatment to a range where wire breakage does not occur, it is possible to perform rectangular rolling with a large aspect ratio.

If the matrix ratio of the composite wire exceeds 3.5, the wire breakage rate during wire drawing will increase, so it is necessary to set the matrix ratio in the range of 0.7 to 3.5.

The above heat treatment is carried out at 300 to 500°C for 80 to 180 hours, but especially at 300 to 370°C for 90 to 180 hours.
A range of 150 hours is suitable.

Examples of the invention] Example 1 A GOO127 Cu-coated Nb-Ti alloy wire was processed to have a regular hexagonal cross section, and 18 of the 336 Cu wires with the same cross-sectional shape were processed.
One tube was housed in a Cu tube with an outer diameter of 80 nφ and an inner diameter of 72 nφ. At this time, is the CD covered inside the Cu tube? The JNtl-Ti alloy wires are arranged in a substantially cylindrical shape, and the Cu tube and Cu
Cu wire was filled between the coated Nb-Ti alloy wires. This C
After the front and rear ends of the U-tube were sealed with a Cu alloy, hydrostatic extrusion was performed to obtain a composite rod with an outer diameter of 38 mm. This composite rod undergoes wire drawing and heat treatment (300℃~370℃X9
0 to 150 hours), the wire is further drawn to an outer diameter of 1. Onφ superconducting wire was manufactured.

For this wire, the relationship between the processing rate after heat treatment and the disconnection rate of the Nb-Ti filament, and the relationship between the critical current density ratio normalized by the value of processing rate 0% and the processing rate after heat treatment were determined.

The matrix ratio of this superconducting wire is 4.3, Nb-Ti
The filament diameter was 23.7 μm and the matrix thickness at the outer periphery of the superconducting wire was 5% of the wire outer diameter.

Next, a wire rod with a wire diameter of 1.85 m1φ was obtained by cold working after heat treatment, and then precision roll rolling was performed to produce rectangular wires with different aspect ratios, and their cross-sectional structures were investigated.

Example 2 Ike manufactured a superconducting wire in the same manner as in Example 1 using 336 pieces of Cu-coated Nb-Tr alloy wire with a Cu ratio of 0.73 and 487 pieces of Cu wire with the same cross-sectional shape.

The matrix ratio of this superconducting wire is 4.6, Nb-Ti
The filament diameter was 23.1 μm diameter, and the matrix thickness at the outer periphery of the superconducting wire was 11.7% of the wire outer diameter.

Comparative Example 1 336 Cu-coated Nb-Ti alloy wire with CIJ ratio of 0.50
A superconducting wire was manufactured in the same manner as in Example 1 except for using a book and 595 Cu wires having the same cross-sectional shape.

The matrix ratio of this superconducting wire is 4.4, Nb-T
i The filament diameter is 23.5μlφ, which is super? li
The matrix thickness at the outer periphery of the l-wire is 12.8% of the wire outer diameter.
Met.

Comparative Example 2 336 of Cu 1iNb-Ti alloy wire with Cu ratio of 0.29
A superconducting wire was manufactured in the same manner as in Example 1 except for using a book and 709 Cu wires having the same cross-sectional shape as the book.

The matrix ratio of this super N conducting wire is 4.1, Nb-Ti
The filament diameter was 24.2 μm, and the matrix thickness at the outer peripheral portion of the ultra-g1 wire was 13.3% of the wire outer diameter.

The cross-sectional states of the above examples and comparative examples after rolling are shown in the following table.

The arrangement of the filaments is shown in Figure 1 (a) (Example 1. Aspect ratio 1.92>, (b) (Example 2. Aspect ratio 2.03), (C) (Comparative example). 1. Aspect ratio 2.11) and (d) (Comparative example 2. Aspect ratio 2)
．． 11>, the relationship between the processing rate after heat treatment and the filament breakage rate is shown in FIG. 2, and the relationship between the processing rate after heat treatment and the critical current density ratio is shown in FIG. 3 (external magnetic field 8T).

The breakage rate of the filament was determined by dissolving the CU stabilizing material with nitric acid, then immersing the Nb-Ti wire in running water.
The percentage of the number of b-Ti wires and the number of Nb-Ti wires used is determined.

As is clear from FIGS. 1 to 3, the rectangular superconducting wire obtained by the method of the present invention has fewer disconnections and disordered arrangement of Nb--Ti strands, and has excellent properties such as critical current density.

[Effect of the invention] As is clear from the above examples, according to the present invention,
Wire breakage during wire drawing is reduced, workability is improved, and a rectangular superconducting wire with excellent critical current density and alignment after rectangular processing can be obtained.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are cross-sectional views showing the arrangement of filaments in a rectangular superconducting wire obtained by the method of the present invention, and FIGS. FIG. 2 is a cross-sectional view showing the filament arrangement state of the flat rectangular FF1TL wire, and FIG. FIG. 3 is a graph showing the relationship between processing rate and critical current density ratio after heat treatment of a multicore superconducting wire manufactured by a similar method.

Claims (1)

[Claims] A method for manufacturing a rectangular superconducting wire in which a large number of Nb-Ti alloy wires are arranged in a Cu or Cu-based alloy (hereinafter referred to as Cu-based metal) matrix, comprising (a) Nb
-The outer periphery of the Ti alloy is coated with a Cu-based metal, and the matrix ratio (matrix cross-sectional area/Nb-Ti alloy cross-sectional area) is 0.
(b) arranging a large number of the composite wires in a substantially cylindrical shape, and placing the composite wires on the inside of the cylinder, or on the inside and outside of the cylinder; arranging Cu-based metal wires with the same cross-sectional shape and filling them into a Cu-based metal tube; and (c) performing cross-sectional reduction processing on the Cu-based metal tube filled with the composite wire and the Cu-based metal wire. (d) manufacturing a wire in which a Cu-based metal having a thickness of at least 12% or less of the wire diameter is disposed on the outer periphery of the wire;
A step of subjecting this wire to heat treatment to improve superconducting properties; (e) a step of cold working the wire after heat treatment with a reduction in area of 70% or less; and (f) a step of cold working the wire after this cold working. 1. A method for producing a rectangular Nb-Ti multicore rectangular superconducting wire, comprising the step of rolling the wire to an aspect ratio (width/height) of 1.80 or more.