JPH0252365B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a compound superconducting wire.

[Conventional technology]

Superconducting wire has become an indispensable material for devices that require high magnetic fields, such as nuclear fusion, accelerators, energy storage, or materials research.
Can be used in high magnetic fields of 10T (tesla) or more, and
There is a demand for highly reliable wire rods. Therefore, recently, so-called continuous fiber compound superconducting wires, which have a structure in which a large number of superconducting compounds such as Nb ₃ Sn and V ₃ Ga are embedded as continuous fibers in a normal conducting matrix, have been developed as this type of material. Although it is used,
Although it has excellent superconducting properties, it is extremely brittle against mechanical tension and bending. For this reason, this wire has the drawback of poor reliability during manufacturing and coil winding operations.

Therefore, recently, a large number of ultra-fine superconducting compound fibers are embedded in the matrix in a state in which they are necessarily continuously and very close to each other, and a superconducting current flows due to the proximity effect or filament effect. So-called discontinuous fiber superconducting wires have been proposed, but they have not been put into practical use because their superconducting properties are lower than conventional ones, and their manufacturing reliability is also low, making them impossible to mass-produce.

[Problem to be solved by the invention]

That is, taking as an example a discontinuous fiber superconducting wire made of Nb ₃ Sn compound, first, Nb powder is
A porous Nb rod is formed by pressure firing at an ultra-high temperature of 2400℃, and this Nb rod is immersed in a molten Sn bath to allow Sn to penetrate into the pores of the Nb rod from the outside.Then, this Nb rod is stretched. Nb by wire and heat treatment in final dimensions
It is produced by reacting Nb 3 Sn with Sn to obtain Nb ₃ Sn. However, unless the surface of the Nb powder used is chemically clean and the average diameter is as small as possible (approximately 20 μm or less), the wire will often break during the subsequent wire drawing process. In addition, the pressure firing process has very high temperatures, which promotes oxidation of the Nb powder surface, making sintering and later wire drawing difficult. The size is also limited to an extremely small size, making it unsuitable for mass production. Furthermore, Nb ₃ Sn compound wire has Nb and Sn
When Cu is simultaneously involved in the reaction,
It is known that the critical current density is also high because the Nb ₃ Sn formation temperature is lower and the formation rate is faster. However, since the conventional manufacturing method described above does not involve Cu, the critical current density is low.

The present invention has been made in view of the above points, and
It is an object of the present invention to provide a manufacturing method capable of obtaining a compound superconducting wire that has high mechanical strength, excellent superconducting properties, and excellent mass productivity.

[Means to solve the problem]

That is, the present invention includes a step of obtaining a composite consisting of a plurality of short wires in which Nb-based or V-based metal core wires are embedded in a Cu-based metal matrix, and
The Cu-based metal is adhered to the Nb-based or V-based metal core wire by maintaining the temperature above the melting temperature of the Cu-based metal and below the melting temperature of the Nb-based or V-based metal, and the remaining Cu-based metal is melted. A step of obtaining a porous rod-like body by cooling to room temperature after removal, and molten Sn, Ga, A, or Sn
- A method for producing a compound superconducting wire characterized by including the steps of: -Cu, Ga-Cu, A-Cu alloy infiltration and subsequent cross-sectional reduction processing and compound generation heat treatment.

[Effect]

Since the present invention is configured as described above, the Nb surface is almost covered with Cu, and oxidation does not occur.
Furthermore, there is no wire breakage during the wire drawing process.

〔Example〕

A detailed explanation will be given below based on examples.

Example 1 As shown in Fig. 1, 19 metal core wires 1 made of Nb core wires were buried in a matrix 2 made of Cu.
Nb, composite multi-core wire is obtained, and this composite multi-core wire is 0.18mm
The average diameter and spacing of the Nb core wire 1 when drawn to φ were 0.02 mm and 0.01 mm. Next, this core wire 1 is cut into short composite wires with a length of about 1 to 3 mm, and then the short composite wires are collected and pressed to form a rod-shaped material with a diameter of 30 mm and a length of 300 mm. I got it. Next, this rod-shaped body 3 made of Cu and Nb core wires is placed in a crucible 4 as shown in Fig. 2, and only Cu is removed from among the constituent components of the rod-shaped body made of Cu and Nb at a temperature of 1200°C in vacuum. Melt. (The melting temperature of Nb is about 2450°C) The molten Cu adheres to the surface of the Nb core wire and flows down into the molten metal reservoir 5. The Nb core wires in the rod-shaped body 3 are fixed by the Cu, and there are many small voids inside. A porous rod-shaped body with pores is formed (FIG. 3). Here, 6 is a porous rod-shaped body made of Cu and Nb core wires, and 7 is Cu. By immersing this porous rod-shaped body in a Sn bath maintained at approximately 500°C for 5 minutes, Sn is infiltrated into its interior.
A composite rod-shaped body 8 consisting of Cu, Nb and Sn was obtained.
As shown in the cross section in Fig. 4, a Ta pipe with an outer diameter of 34 mm and an inner diameter of 31 mm is coated on this composite rod-shaped body, and a Cu pipe 10 with an outer diameter of 50 mm and an inner diameter of 35 mm is placed outside the Ta pipe 9 for stabilization purposes. coated and cold-reduced to a diameter of 0.5 mm and a length of approx.
Obtained 1800m of wire. No wire breakage occurred during this wire drawing process. Nb in porous rods
Most of the core wire is coated with Cu, and the temperature is 1200°C, compared to 2000°C in the conventional method.
Since it is lower than 2400℃, there is less oxidation of the Nb core wire. In addition, because the Nb core wires are firmly bonded together by the coated Cu wires, the drawability was significantly improved compared to the conventional method. It also has the advantage of being able to be mass-produced using simple vacuum melting equipment. When the cross section of the obtained wire was observed under a microscope, Nb was formed by being stretched in the longitudinal direction of the wire.
The Cu and Sn fibers constituted the wire rod in a mixed state.

Finally, the wire rod obtained through the above process is heated to 750°C.
After heat treatment for 30 minutes, _Nb3Sn was added to the surface of the Nb fiber.
A Nb 3 Sn compound superconducting wire was produced by producing Nb ₃ Sn compound superconducting wire.

The obtained superconducting wire was placed in liquid helium under various conditions and without bending strain, and the critical current value was measured while changing the bias magnetic field. As a result, the critical current density at 8T was
The values were 900A/mm ² for 8T and 680A/mm ² for 10T, which are approximately 30% higher than wire rods manufactured by conventional methods.
Further, when the critical current density was measured while applying bending strain to the wire according to the present invention, it showed good results with almost no decrease until the strain reached about 2%. As described above, the wire according to the present invention had very excellent superconducting properties and mechanical properties.

In this example, the
By changing the number of Nb core wires, or using Cu−Sn, Cu−Ga, Cu−In, Cu−
Make it into A alloy or infiltrate it into a porous rod-shaped body
It is also effective to add Cu, Ga, ln, A, Pb, etc. to Sn.

Example 2 Nb powder and Cu powder with an average diameter of about 80 μm at a ratio of 2:1
Mixed and molded at a ratio of 30 mm in diameter and length
A rod-shaped body of 300 mm was obtained. It is also very effective to attach a Cu layer to the surface of the Nb powder in advance.
Next, as in Example 1, this rod-shaped body made of Cu and Nb was placed in a crucible 4 as shown in Fig. 2, and only Cu was melted at a temperature of 1300°C in a vacuum.
A porous rod-like structure was obtained. By immersing this in a Sn bath maintained at about 500°C, Sn penetrates into the inside of it to form a composite rod consisting of Cu, Nb, and Sn.This composite rod is used as an example. Similarly, in combination with a Cu pipe for stabilization and a Ta pipe for a diffusion barrier, the wire was drawn to a diameter of 0.5 mm and the final dimensions were
A heat treatment was performed to generate Nb ₃ Sn. As a result, wire drawing was carried out very easily, and the superconducting properties were also very good compared to the conventional method, as in Example 1.

Other compound wires V ₃ Ga, Nb ₃ A, manufactured by a similar method to the Nb ₃ Sn wire described in the examples
Of course, it can also be applied to Nb ₃ Ga, etc., and similar effects can be obtained.

In addition, in the above embodiments, the materials Nb, V,
Adding non-toxic ingredients to Cu, Sn, Ga, A, etc., short composite wires, powder composition and mixing methods, rod-shaped body forming methods,
Although various methods for infiltrating Sn etc. can be considered, the effects of the present invention are not impaired in any of them.

〔Effect of the invention〕

As explained above, according to the present invention, superconducting properties and mechanical properties such as bending resistance and tensile resistance are excellent, and in addition, high-purity Cu or A for stabilization is made into a pipe shape or the like to form a porous structure. It can be easily attached to a rod-shaped body. In addition, wire rods with excellent characteristics can be mass-produced on an industrial scale without the need for special equipment that limits the dimensions of the wire rods, and wire rod drawability has been significantly improved compared to conventional methods, making it possible to manufacture extremely stably. It has features. Compound wires that can be mass-produced and have excellent superconducting and mechanical properties can be used, for example, in superconducting magnets to produce economical and high-performance magnets, so the fields of their use will expand dramatically. increase

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a short composite wire in an example of the present invention, Fig. 2 is a diagram of the structure of the crucible before melting, Fig. 3 is a diagram of the structure of the crucible after melting, and Fig. 4 is a diagram of the structure of the crucible with stabilized Cu attached.
FIG. 3 is a cross-sectional view of a Nb ₃ Sn wire. 1...Nb core wire, 2...Cu matrix, 3...Cu and
Rod-shaped body made of Nb core wire, 4... Crucible, 5...
Molten metal reservoir, 6...Porous rod-shaped body, 7...Cu,
8...Composite rod-shaped body, 9...Ta pipe, 10...
Cu pipe.

Claims (1)

[Scope of Claims] 1. A step of obtaining a composite consisting of a plurality of short wires in which Nb-based or V-based metal core wires are embedded in a Cu-based metal matrix, and adding this composite to the Cu-based metal. The Cu-based metal is adhered to the Nb-based or V-based metal core wire by maintaining the temperature above the melting temperature of the Nb-based or V-based metal, and melts and removes the remaining Cu-based metal. and then cooling to room temperature to obtain a porous rod-like body, and molten Sn, Ga, Al or Sn-Cu,
1. A method for manufacturing a compound superconducting wire, the method comprising the steps of reducing the cross section after infiltrating Ga-Cu or Al-Cu alloy and subjecting it to heat treatment for compound formation. 2. In the step of obtaining the composite, the Nb-based or V-based metal core wire is in the form of a fiber, and the Cu-based metal is at least partially adhered to the Nb-based or V-based metal core wire. A method for manufacturing a compound superconducting wire according to claim 1. 3. In the step of obtaining the above composite, the Nb-based or V-based metal core wire is in a powder form, and the Cu-based metal is at least partially in close contact with the Nb-based or V-based metal core wire. A method for manufacturing a compound superconducting wire according to claim 1.