JPH0580283B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is directed to the production of superconducting wires that have less disconnection of Nb-Ti strands during wire drawing and that have improved characteristics such as critical current density and AC loss. Regarding the method.

[Technical background of the invention and its problems] Conventionally, as a manufacturing method for superconducting wires, especially fine multi-superconducting wires, the outer periphery of Nb-Ti wire is coated with Cu, and a large number of core rods formed to have a regular hexagonal cross section are coated with Cu. A Cu rod with a circular cross section is inserted into the gap between the Cu pipe and the core rod to serve as a spacer, and is then subjected to area reduction processing using hydrostatic extrusion and wire drawing, and further processed as necessary. A method is known in which a superconducting wire subjected to this surface reduction process is formed into a regular hexagonal cross section, and the same operation is repeated to obtain a superconducting wire having a desired outer diameter.

However, with such conventional methods, disconnection of the Nb-Ti strands is likely to occur during area reduction processing.
There is a problem in that the characteristics of the resulting superconducting wire deteriorate, or in some cases, the entire wire is broken, and an improvement has been desired. It was also desired to improve the properties of superconducting wires, such as critical current density, specific resistance value, and AC loss.

As a method for manufacturing a superconducting wire that is unlikely to cause wire breakage as described above, the present applicant has developed a method for manufacturing a superconducting wire that does not easily cause wire breakage.
We previously filed an application for a method for manufacturing superconducting wire in which the Cu-coated Nb-Ti alloy wires are collected in the center and filled into a Cu tube, and then subjected to area reduction processing (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, the space factor during coil forming,
During the rolling and drawing processes during the manufacturing of rectangular wires that have excellent winding workability and mechanical stability, the arrangement of Nb-Ti alloy strands becomes disordered, making it difficult to maintain the improved properties mentioned above. It turns out that there are some drawbacks.

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 in order to improve the above-mentioned difficulties, and includes arranging composite wires having a matrix ratio within a predetermined range in a cylindrical shape, making the thickness of the matrix on the outer periphery a certain value or more, and By setting the cold working rate after heat treatment to a predetermined percentage or higher, Nb-Ti with a multi-core structure has excellent workability and superconducting properties.
The purpose of the present invention is to provide a method for manufacturing multicore superconducting wire.

(Summary of the Invention) The method for manufacturing a 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 of the present invention includes: (a) Nb -The outer periphery of the Ti alloy is coated with Cu-based metal, and the matrix ratio (matrix cross-sectional area/Nb-Ti
(b) arranging a large number of said composite wires in a substantially cylindrical shape;
A Cu-based metal wire having the same cross-sectional shape as the composite wire is placed inside the cylinder, or inside and outside the cylinder,
(c) filling the composite wire and the Cu-based metal wire into a Cu-based metal tube;
A step of manufacturing a wire in which a Cu-based metal tube with a thickness of at least 10% of the wire diameter is arranged on the outer periphery of the wire by subjecting a Cu-based metal tube to a cross-sectional reduction process; It is characterized by consisting of a step of applying heat treatment for improvement, and (e) a step of cold working the wire rod after the heat treatment with a cross-section reduction rate of 50% or more.

In the present invention, the matrix ratio of the composite wire and the thickness of the matrix at the outer periphery of the superconducting wire are limited as described above because the effects of the present invention cannot be substantially obtained outside the above ranges. According to the present invention, breakage of the superconducting wire is reduced, workability is improved, and the characteristics of the superconducting wire are thereby further improved.

In the heat treatment of the present invention, the precipitates (mainly α-Ti) and the dislocations introduced by the cold working prevent the penetration of magnetic flux, thereby improving the superconducting properties. Since increasing the processing rate increases the filament breakage rate, the effect of this processing rate has not been sufficiently studied in the past.

In the present invention, the superconducting properties can be improved by making the wire material have a structure that has an extremely low wire breakage rate and can therefore be cold worked at a high processing rate, and by increasing the cold working rate after heat treatment to 50% or more. can.

The above heat treatment is carried out at 300-500℃ for 80-180 hours, but especially at 300-370℃ for 90-150 hours.
The time range is appropriate.

[Embodiments of the invention] Example 1 A Cu-coated Nb-Ti alloy wire with a Cu ratio of 0.29 was processed into a regular hexagonal cross section, and 336 Cu wires with the same cross-sectional shape were
709 tubes were housed in a Cu tube with an outer diameter of 80 mmφ and an inner diameter of 72 mmφ. At this time, the Cu wire was arranged inside and at the center of the Cu tube, and the Cu-coated Nb-Ti alloy wire was filled so as to be arranged in a substantially cylindrical shape. The front and rear ends of this Cu tube are
After sealing with alloy, the outer diameter is made by isostatic extrusion.
A composite rod with a diameter of 38 mm was obtained. After wire drawing and heat treatment (300°C to 370°C x 90 to 150 hours) is performed on this composite rod, further wire drawing is performed to determine the outer diameter.
A superconducting wire with a diameter of 1.0 mm was manufactured.

Processing rate and Nb-Ti after heat treatment for this wire
The relationship between the wire breakage rate of the filament and the relationship between the critical current density ratio normalized to the value of the working rate of 0% and the working rate after heat treatment was determined.

The matrix ratio of this superconducting wire is 4.1, Nb−
The diameter of the Ti filament was 24.2 μmφ, and the matrix thickness at the outer periphery of the superconducting wire was 13.3% of the outer diameter of the wire.

Example 2 A superconducting wire was manufactured in the same manner as in Example 1 except for using 336 pieces of Cu-coated Nb-Ti alloy wire with a Cu ratio of 0.50 and 595 pieces of Cu wire having the same cross-sectional shape.

The matrix ratio of this superconducting wire is 4.4, Nb−
The diameter of the Ti filament was 23.5 μmφ, and the matrix thickness at the outer periphery of the superconducting wire was 12.8% of the outer diameter of the wire.

Comparative Example 1 A superconducting wire was manufactured in the same manner as in Example 1 except for using 336 pieces of Cu-coated Nb-Ti alloy wire with a Cu ratio of 0.73 and 487 pieces of Cu wire having the same cross-sectional shape.

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

Comparative Example 2 A superconducting wire was manufactured in the same manner as in Example 1 except for using 336 pieces of Cu-coated Nb-Ti alloy wire with a Cu ratio of 1.7 and 181 pieces of Cu wire having the same cross-sectional shape.

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

Figure 1 shows the relationship between the processing rate after heat treatment and the filament breakage rate for the above examples and comparative examples, and Figure 2 (external magnetic field 4T) and the relationship between the processing rate after heat treatment and the critical current density ratio Figure 3 (external magnetic field
8T).

The breakage rate of the filament was determined by dissolving the Cu stabilizing material in nitric acid, then immersing the Nb-Ti wire in running water.
The percentage of the number of Nb-Ti strands falling and the number of Nb-Ti strands used is calculated.

As is clear from the graphs in Figures 1 to 3, the superconducting wire obtained by the method of the present invention is Nb-
Ti wire has less disconnection and has excellent characteristics such as critical current density.

[Effects 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 superconducting wire with excellent critical current density can be produced. Obtainable.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the processing rate after heat treatment and the filament breakage rate of multicore superconducting wires manufactured by the method of one example of the present invention and the comparative example, and FIGS. 2 and 3 is a graph showing the relationship between the processing rate after heat treatment and the critical current density ratio of a multicore superconducting wire manufactured by a similar method.

Claims (1)

[Claims] 1 Cu or Cu-based alloy (hereinafter referred to as Cu-based metal)
In a method for manufacturing a superconducting wire consisting of a large number of Nb-Ti alloy wires arranged in a matrix, (a) the outer periphery of the Nb-Ti alloy is coated with a Cu-based metal, and the matrix ratio (matrix cross-sectional area/Nb- Ti
(b) arranging a large number of said composite wires in a substantially cylindrical shape;
A Cu-based metal wire having the same cross-sectional shape as the composite wire is placed inside the cylinder, or inside and outside the cylinder,
(c) filling the composite wire and the Cu-based metal wire into a Cu-based metal tube;
A step of manufacturing a wire in which a Cu-based metal tube with a thickness of at least 10% of the wire diameter is arranged on the outer periphery of the wire by subjecting a Cu-based metal tube to a cross-sectional reduction process; A process characterized by comprising a step of applying heat treatment for improvement, and (e) a process of cold working the wire rod after the heat treatment with a cross-sectional area reduction rate of 50% or more.
A method for manufacturing Nb-Ti multicore superconducting wire.