JPH0737453A - Superconducting wire manufacturing method - Google Patents

Abstract

(57) [Summary] [Purpose] To establish a means for stably producing high-performance Nb ₃ Al superconducting wire with good workability. [Structure] Nb and Al are clad with a Nb thin plate and a JIS6061Al alloy thin plate that has been solution-treated and then age hardened.
After making a laminated plate whose ratio is the target chemical composition ratio, cut this into strips, then gather these together and press-mold them, then make a wire rod by plastic working, and then perform diffusion heat treatment .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for industrially stably producing Nb ₃ Al superconducting wire.

[0002]

BACKGROUND ART The intermetallic compound Nb ₃ Al is known to be an excellent superconducting material because of its high critical magnetic field, critical current density, and critical temperature. It was bad, and it was also extremely difficult to process it into a fine wire or the like.

Therefore, conventionally, in order to obtain a wire rod made of this difficult-to-process intermetallic compound Nb ₃ Al, a) powder mixing method: a mixed powder of Nb powder and Al powder is extruded to form a billet, which is Nb ₃ Al wire rods are made into Nb ₃ Al wire rods by thinning them by a drawing method such as wire drawing, b) Liquid infiltration method: Nb powder is hydrostatically pressed and sintered, and then immersed in an Al molten bath to form Al Impregnated, re-extruded as a billet, groove-rolled or wire-drawn, then subjected to diffusion heat treatment to form Nb ₃ Al wire rod, c) Jerry roll method: Nb plate and Al plate Clad so as to have a stoichiometric ratio, and this is tightly wound into a billet, and the billet is drawn and then subjected to diffusion heat treatment.
Nb ₃ How to Al wire, d) Chu - Bed Method: nb Ju - packed Al in Bed, subjected to a diffusion heat treatment after subjecting it to the extrusion and drawing Nb ₃ Al
Special means such as the method of using wire rods have been tried.

However, in the above methods a) and b),
Since active metal powder must be handled, pay close attention to "absorption of gas in the atmosphere that causes deterioration of superconducting characteristics and workability", "avoid explosion hazard", "prevent inhalation of metal powder into the human body", etc. In addition, it has been pointed out that homogeneous mixing of powder is extremely difficult and the composition ratio becomes unstable. In particular, in order to obtain a uniform powder mixture before diffusion heat treatment, it is necessary to make the particle size of the raw material powder as fine as possible, but the finer the particle size of the raw material metal powder, the easier the surface oxidation occurs. As a result, the workability is impaired, and it is difficult to limit the molded shape and dimensions.

Further, in the method c), the winding start of the clad plate is apt to be loose, and if this is formed into a wire rod, the composition ratio of the central portion is difficult to reach a predetermined value, and it becomes non-uniform. Nb ₃ A that is uniform throughout even after heat treatment
The inconvenience of not becoming l was pointed out. Furthermore, the above c)
In the method of d) and d), the metal flow of the material is
However, there is also a problem that the central part and the outer peripheral part are in a different state, and a difference in density is likely to occur, and it is difficult to obtain an Nb ₃ Al wire rod having a uniform composition overall by these methods.

As described above, the conventionally known “method for producing Nb ₃ Al superconducting wire” is not only costly, but also is not a sufficiently reliable method, and the product properties and dimensions to be obtained. In terms of the above, there was a limit, and mass production on an industrial scale was extremely difficult.

Therefore, the inventors of the present invention firstly conducted high-quality Nb ₃ Al.
Based on the results of research carried out to establish a simple manufacturing method for superconducting wire, "after cutting composite materials of Nb and Al laminated at the target composition ratio into strips, these are gathered together and rolled or extruded. Nb ₃ Al superconducting wire is produced with high productivity by creating a wire material by pressure molding, etc., and then applying plastic processing such as drawing to this wire material to obtain a wire with a desired size and then performing diffusion heat treatment. Manufacturing method ”(Japanese Patent Application No. 63-
No. 234256). And this method was evaluated to be extremely advantageous for industrially manufacturing Nb ₃ Al superconducting wire,
It is called the "clad chip method" and has come to the forefront.

However, in recent years, the demand for improving the performance of superconducting materials has become more and more urgent day by day. Therefore, it is an urgent issue to improve the quality and performance of superconducting wires, not to mention the ease of manufacturing. It's coming.

[0009]

From the above-mentioned viewpoints, the inventors of the present invention particularly obtained Nb ₃ obtained by the clad chip method capable of ensuring stable quality under good workability.
As a result of further research to further improve the performance of the Al superconducting wire, “When the Nb ₃ Al wire is manufactured by the clad chip method, it is used as an Al material for creating a laminated composite material.
When heat treatment and age hardening material of 6061 aluminum (Al) alloy specified in IS is used, the difference in flow stress with Nb material is reduced and the workability as a composite material is improved. As a result, molding and diffusion heat treatment are performed. The Nb ₃ Al superconducting wire obtained by the above process will show further improved superconducting properties. ”

The present invention has been completed on the basis of the above-mentioned findings and the like. "Nb thin plate and a JIS 6061 Al alloy thin plate which has been subjected to solution hardening followed by age hardening are clad with Nb,
After creating a laminated plate in which the ratio of Al is the target chemical composition ratio,
This is cut into strips, which are then pressed together to form a wire by plastic working, and then subjected to diffusion heat treatment to make a high-performance Nb ₃ Al superconducting wire easy and stable. It has a major feature in that it can be manufactured by the above method.

Hereinafter, the present invention will be described in detail with reference to the drawings together with the operation of each step.

OPERATION FIG. 1 is a schematic diagram showing an example of the manufacturing process of the Nb ₃ Al superconducting wire according to the present invention.
A 61 Al alloy thin plate is laminated so that the ratios of Nb and Al are appropriate ratios (stoichiometric composition ratios) to form a multilayer clad forming material plate. In this case, the applied 6061 Al alloy thin plate is used after being subjected to solution heat treatment and then age hardening treatment. By applying such a treatment, 6061 Al
Although alloy thin plate increases strength without decreasing elongation,
As a result, the difference in flow stress from the Nb thin plate is reduced, which has an advantageous effect on the subsequent processing.

When the multilayer clad molding material plate is prepared as described above, the multilayer clad molding material plate is then finely cut into chips (including punching and the like). The cutting shape may be any of a circle, an ellipse, a triangle, a polygon, a star, etc., in addition to the quadrangle as shown in FIG. The appropriate size is about 1 to 50 mm in terms of diameter, length of side or diagonal, but appropriate size can be adopted depending on, for example, the capacity of the press used in the densification process of the next process. There is no limit.

Next, these chip-shaped strips are gathered together, and are collectively pressure-molded with a sufficient degree of processing by extrusion, rolling, etc., where is the molding raw material composed of the gathered body of chip-shaped laminated strips. Even if it is taken, it has a compatible composition and no segregation state, so that a dense body having a fine and uniform connective structure can be obtained. Further, in this dense body, the constituent metals are still in a mixed state without diffusing each other, so that the workability is very good, and further processing can be performed very easily. Incidentally, when the chip-shaped strips are pressed, it is suitable to fill them in a hollow tube which is a sheath material, but they may be directly filled in, for example, an extruding container to be a rod material or the like. . However, when using a sheath material, the selection of the material is important,
As the mechanical property, a material with a small difference in deformation resistance from the chip-shaped strip is selected, and when the chemical removal (corrosion, evaporation, etc.) of the sheath material is finally performed, it differs from the chip-shaped strip. A metal or alloy having chemical properties is selected.

Then, the dense body obtained by pressure molding is made into a wire rod by ordinary plastic working (drawing, rolling, swaging, etc.) to obtain a desired size. In this case, since the dense material as the molding material is in a state of being mixed without being diffused, the workability is good and smooth processing is performed as described above.

Subsequently, when the dense body processed into a desired size is subjected to the diffusion heat treatment which is the final step, the constituent metals constituting the dense body undergo the diffusion reaction as described above, and any portion is removed. It becomes an Nb ₃ Al intermetallic compound wire with a uniform composition and exhibits excellent superconducting properties.

Next, the present invention will be described more specifically by way of examples.

EXAMPLE First, a 0.145 mm-thick 6061 Al alloy plate was prepared.
After solution heat treatment for 15 minutes at 30 ° C., it was quenched in ice water and aged at room temperature. This 6061 Al alloy plate sandwiches a 1 mm thick Nb plate and performs clad rolling to obtain 0.15 mm thick Al-Nb-Al 3
A layer clad plate was created.

Next, the above clad plate is cut into strips of about 5 mm square and these are cut with a copper alloy sheath (inner diameter 30 mm, outer diameter 40 mm).
After being filled in, the mixture was extruded and drawn to obtain a Nb-Al composite dense wire rod. At this time, the plastic workability in the wire rod forming process was good, and the wire rod forming work could be easily performed up to the workability R = 7.3 × 10 ⁶ (where R = initial cross-sectional area / final cross-sectional area).

Then, the obtained wire rod was marked with "(900 ° C x 1
6 minutes) + (750 ° C. × 4 days) ”, a heat treatment under the conditions of A15 type intermetallic compound wire was performed, and then the superconducting characteristics were measured. The results of these measurements are summarized in Table 1 by the main chemical components of the 6061 Al alloy, the critical current density Jc under the conditions of a load magnetic field of 14.4 Tesla and a temperature of 4.2K.

[0019]

As is clear from the results shown in Table 1, N having sufficiently excellent Jc characteristics according to the method of the present invention.
It can be confirmed that a b ₃ Al superconducting wire can be obtained.

For comparison, the case of using "pure Al" as the Al material for producing the laminated composite material and "Al-3at"
% Mg alloy ”was used to prepare Nb ₃ Al wire rods by the same method, and the conductive properties were measured after heat treatment under the following conditions. Pure Al applied Nb ₃ Al wire rods: [1000 ° C x 2 minutes] + [ 750 ° C x 4
Sun], Al-3at% Mg alloy applied Nb ₃ Al wire: [900 ℃ × 16min] +
[750 ° C x 4 days].

These measurement results are used as a load magnetic field of 14.4 Tesla.
, The average Nb layer thickness converted from the critical current density Jc and the workability under the condition of temperature 4.2K, and the N
It is shown in comparison with that of the b ₃ Al wire rod in FIG. This Figure 2
As is clear from the above, according to the method of the present invention, the heat treatment temperature required is 900 because of good workability and a practically preferable heat treatment temperature.
It can be confirmed that a sufficiently excellent Nb ₃ Al superconducting wire can be obtained even at a low temperature of about ℃.

[0023]

[Summary of Effects] As described above, according to the present invention, it is possible to mass-produce the Nb ₃ Al superconducting wire having excellent performance easily and stably, and it is possible to bring about an extremely useful effect in industry. .

[Brief description of drawings]

FIG. 1 is a conceptual diagram illustrating a production example of a Nb ₃ Al superconducting wire according to the present invention.

FIG. 2 is a graph showing the Jc characteristics of the Nb ₃ Al superconducting wire produced in the example in comparison with the comparative material.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Ei Saito 2-2-11 Izumi-ku, Sendai-shi, Miyagi Prefecture (72) Inventor Takashi Wachi 8-2 Honshiocho, Shinjuku-ku, Tokyo 2 Japan Stainless Co., Ltd. Inside the technical laboratory

Claims (1)

[Claims] 1. A Nb thin plate and a JIS6061 aluminum alloy thin plate which has been subjected to a solution treatment followed by an age hardening treatment are clad to form a laminated plate in which the ratio of Nb and Al is the target chemical composition ratio. A method for producing a Nb ₃ Al superconducting wire, which comprises cutting into pieces, then gathering these together and press-molding them, making them into a wire by plastic working, and then subjecting them to diffusion heat treatment.