JP2000090754A - Method for producing Nb3Al compound superconducting wire and superconducting wire obtained by the method - Google Patents

Abstract

(57) [Summary] (Problem corrected) [Problem] Nb capable of compounding a stabilizing material layer having excellent adhesion
Method for producing a ₃ Al compound superconducting wire to provide the wire. SOLUTION: A pure Nb sheet 1 and a pure Al sheet 2 are overlapped to produce a jelly roll laminated composite. After the composite is formed into a single core billet, it is processed into a hexagonal cross section wire, and the Cu layer is removed to produce a single wire 6. This single wire 6 is incorporated into a plurality of separate Nb tubes 7 and
The multi-core billet 9 is inserted into the u-Ni alloy tube 8. Next, the Cu—Ni alloy layer of the outer skin is removed to obtain the composite multi-wire 10. The obtained Nb / Al composite wire has Nb-
An Al supersaturated solid solution is generated, a first stabilizer layer 11 is formed on the surface of the supersaturated solid solution wire, and a second stabilizer layer is formed thereon. The wire is heated again in a vacuum for a predetermined time to precipitate an Nb ₃ Al phase, thereby obtaining a Nb ₃ Al compound superconducting wire 12 provided with a stabilizing material layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an Nb ₃ Al compound based superconducting wire, and more particularly to a method for producing an Nb ₃ Al compound based superconducting wire, which comprises providing a strong stabilizing material layer around the periphery thereof. The present invention relates to a superconducting wire obtained.

[0002]

2. Description of the Related Art Nb ₃ Al compound based superconducting wires are superior to Nb ₃ Sn and NbTi, which are general superconducting wires, in the critical current density characteristics in a high magnetic field. It is expected to be put to practical use as a superconducting material such as a magnet. The Nb ₃ Al compound superconducting wire is generally composed of a plurality of single wires in which a composite material composed of Nb or an Nb alloy and Al or an Al alloy is surrounded by a high melting point metal or an alloy matrix thereof, and the outer periphery thereof is formed of a high melting point metal or It has a multi-structure surrounded by the alloy matrix, and a Nb ₃ Al compound is generated in the wire by the manufacturing method described below so that a predetermined superconducting property can be obtained.

At present, the main methods for producing Nb ₃ Al compound superconducting wires are the diffusion method and the rapid heating / quenching / transformation method.
One. The diffusion method combines Nb and Al with a predetermined composition,
After reducing the mutual diffusion distance to the order of submicrons, a heat treatment is performed at about 600 to 1050 ° C. to generate an Nb ₃ Al compound by solid-phase diffusion (“Jelly roll method of Nb ₃ Al superconducting wire rod”). development of",
Sumitomo Electric, No. 139 (1991)). Another rapid heating quenching / transformation method uses a composite wire with a predetermined composition.
Nb-
An Al supersaturated solid solution is formed, and then 600 to 1050
This is a method of precipitating an Nb ₃ Al phase by performing a heat treatment again at a temperature of about ° C. (Japanese Patent Publication No. 6-44427, Science and Technology Agency, Institute of Metals Technology).

[0004] By the way, the Nb ₃ Al compound is 1500 ° C.
These compounds are stable only at high temperatures. At lower temperatures, the deviation from the stoichiometric composition becomes large, and there is a disadvantage that the wire properties such as the critical current density deteriorate. In the case of the wire by the former diffusion method, since the heat treatment temperature is low, a deviation from the stoichiometric composition causes a high magnetic field N
Assuming application to an MR magnet or the like, the critical current density in a high magnetic field of 20 T or more is low and the required characteristics cannot be satisfied.

[0005] Therefore, in consideration of application to conductors for high-field NMR magnets and the like, among the current various metal-based superconducting wires, the latter wire by the rapid heating / quenching / transformation method is the only material.

[0006] A conventional production method based on the rapid thermal quenching / transformation method, for example, in the case of the jelly roll method is as follows.
After the Nb or Nb alloy sheet and the Al or Al alloy sheet are laminated and densely wound, they are packed into an Nb or Nb alloy pipe, and a single wire is produced through extrusion or drawing.
In the production of the single wire, the core rod at the time of dense winding may or may not be used. Next, a plurality of single wires are used again and incorporated into an Nb or Nb alloy pipe to obtain an Nb / Al composite multi-wire material serving as a base material through extrusion or drawing. When incorporating a composite multi-wire, N
In addition to the b / Al composite single wire, a combination of a dummy wire made of Nb or an Nb alloy is also incorporated. The Nb / Al composite multi-wire is rapidly heated and quenched to generate a Nb-Al supersaturated solid solution, and then subjected to a transformation heat treatment to precipitate an Nb ₃ Al compound.

In the conventional method of manufacturing a single wire for a base material, in addition to the above-mentioned jelly roll method, an Al or Al alloy rod is inserted into an Nb or Nb alloy pipe and extruded or drawn. There is a method of manufacturing, and conversely, a method of inserting an Nb or Nb alloy rod into an Al or Al alloy pipe and extruding or drawing.

[0008]

When a superconducting wire is used as a conductor for a superconducting magnet, it is necessary to provide a stabilizing material layer on the outermost periphery of the wire so as not to burn the wire even during quench during operation. . However, the wire produced by the rapid heat quenching / transformation method has a wire temperature of 1 during the rapid heat quenching treatment.
500 ° C. or higher. For example, the melting point of copper (Cu) is 1,
Since the temperature exceeds 083 ° C., copper as a stabilizing material cannot be previously applied to the surface. Therefore, in the rapid heating / quenching / transformation method Nb ₃ Al wire, the stabilizing material layer is not combined with the wire, and the wire surface is composed of Nb.

By the way, the conventional practical superconducting wire N
In the case of a b-Ti wire or a Nb ₃ Sn wire, a composite of Cu and Nb or an Nb-based alloy is subjected to a large wire drawing (a deformation rate of about 10 ⁶ ) to break an oxide film on the Nb surface.
Good Cu / Nb bonding is obtained.

On the other hand, when copper is compounded after the rapid heating and quenching treatment, it is very difficult to form copper due to the strong oxide film on the Nb surface. Furthermore, in air or water, an oxide film is immediately formed on the Nb surface. Nb
It is also difficult to form a composite by strong working like Ti wire or Nb ₃ Sn wire. For this reason, for example, even if copper is applied to the wire surface by electroplating or the like,
The adhesion between the coating layer and the wire is poor, and the wire is easily peeled off at the time of coil winding or the like at the time of manufacturing a magnet.

Accordingly, an object of the present invention is to provide an Nb ₃ Al compound superconducting wire which can solve the above-mentioned disadvantages of the prior art and can form a stabilizing material layer having excellent adhesion even in a so-called rapid heating / quenching / transformation method. An object of the present invention is to provide a manufacturing method and a wire obtained by the method.

[0012]

In order to solve the above-mentioned problems, according to the present invention, Nb or Nb alloy and Al or Al
After combining a plurality of single wires in which a composite material made of an alloy is surrounded by a high melting point metal or an alloy matrix thereof, and heating the multi-wire material whose outer periphery is surrounded by a matrix made of a high melting point metal or an alloy thereof to a predetermined temperature or more, Immediately cooled to form a Nb-Al supersaturated solid solution,
Then, in the method for producing a Nb ₃ Al compound based superconducting wire in which the Nb ₃ Al phase is precipitated by heat treatment again, when the stabilizing material is compounded on the outermost periphery of the multi-wire, after cooling immediately after energizing heating, or again. A method for producing an Nb ₃ Al compound-based superconducting wire, comprising forming a stabilizing material layer by a physical vapor deposition method after a heat treatment.

Here, the physical vapor deposition method referred to in the present invention is:
Ion plating method, which refers to a method in which a deposition substance is collided with a target substance as high-energy particles in a high vacuum and deposited, and is appropriately classified according to a deposition condition, an evaporation source, and the like, an ion plating method,
Including ion beam evaporation, sputtering, electron beam heating, high frequency heating, and resistance heating. Among them, the ion plating method is a method in which a vapor deposition material is excited and ionized by passing it through plasma to collide with a target object as high-energy particles to be precipitated, and can be suitably used in the present invention. By forming a stabilizing material layer by physical vapor deposition, even in the case of a multi-wire material in which a material that forms an oxide film immediately in air or liquid with an active metal such as Nb as a matrix, Since the treatment is performed in a vacuum, an oxide film is hardly generated on the surface of the multi-wire material, and the oxide film is also destroyed by the collision of the coating material particles, so that it is easy to obtain contact between the metals, and at the same time, to the surface of the multi-wire material due to the collision. Since the anchor effect of the wire is increased, the adhesion between the stabilizing material layer and the multi-wire is very strong.

In a preferred embodiment of the present invention, the stabilizer layer comprises
Consisting of one of copper, copper alloy, silver or silver alloy,
The physical vapor deposition method is an ion plating method.

The stabilizer layer by physical vapor deposition may itself constitute the entire stabilizer layer, while forming it as the first stabilizer layer of a relatively thin film, A second stabilizing material layer may be formed on the outer periphery of the ground layer.
The second stabilizer layer may be formed by a physical vapor deposition method, another electroplating method, or a similar film forming method.

In the method for producing an Nb ₃ Al compound-based superconducting wire according to the present invention, an Nb—Al supersaturated solid solution is produced by immediately heating after heating to 1500 ° C. or higher,
After that, it is heat-treated again at a temperature of 600 to 1,050 ° C. to precipitate an Nb ₃ Al phase, which is a method particularly suitable for a so-called rapid thermal quenching / transformation method. here,
The temperature of the heat treatment again can be appropriately selected from the range of 600 to 1,050 ° C. according to the material of the stabilizer layer and the heat treatment time as long as the temperature does not exceed the melting point of the material constituting the stabilizer layer. For example, in the case of a stabilizing material layer made of silver (Ag), heat treatment may be performed at a temperature slightly lower than the melting point of silver (962 ° C.), preferably at 950 ° C.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a method for producing an Nb ₃ Al compound-based superconducting wire of the present invention will be described with reference to the drawings. Note that the present invention is not limited to this.

FIG. 1 and FIG. 2 are a process explanatory view and a detailed flowchart showing a method for producing an Nb ₃ Al compound-based superconducting wire of the present invention. A pure Nb sheet 1 having a predetermined thickness and a pure Al sheet 2 having a predetermined thickness are overlapped and wound around the pure Nb bar 3 without any gap, thereby producing a jelly roll laminated composite (step 1). The composite is inserted into the Nb tube 4 and further inserted into the Cu tube 5 to form a single core billet, and then processed into a hexagonal cross-section wire rod by surface reduction processing (hydrostatic extrusion, die drawing). The hexagonal cross section wire is removed from the outer Cu layer to produce a single wire 6 (step 2). The single wire 6 is incorporated into a plurality of separate Nb tubes 7 and further inserted into a Cu-Ni alloy tube 8 to form a multi-core billet 9 (step 3). Next, the multifilament billet 9 is processed into a predetermined wire diameter by surface reduction processing (hydrostatic extrusion, die drawing), the Cu—Ni alloy layer of the outer skin is removed, and a circular section Nb / Al of a predetermined wire diameter is formed. A composite multi-wire 10 is obtained (step 4).

The Nb / Al composite wire produced by the above process is heated immediately after heating to 1500 ° C. or more, and immediately cooled to produce an Nb—Al supersaturated solid solution (rapid heat quenching / transformation treatment). Next, a stabilizing material layer (Cu layer) 11 having a predetermined thickness is formed on the surface of the supersaturated solid solution wire by a physical vapor deposition method, preferably an ion plating method. In addition, this stabilizing material layer is used as a first stabilizing material layer (that is, an underlayer), and a second stabilizing material layer (Cu
The second stabilizer layer may be formed by a method other than the physical vapor deposition method, for example, by electroplating. The wire thus obtained was placed in a vacuum at 600
Heat treatment again at a constant temperature of ~ 1,050 ° C for Nb
₃ By precipitating the Al phase, the stabilizing material layer 1
The Nb ₃ Al compound superconducting wire 12 to which No. 1 is applied is obtained (step 5).

The ion plating method preferably used in the present invention is to evaporate a substance to be coated in a vacuum and pass it through plasma to excite and ionize high-energy particles to a target substance (object to be coated). This is a technology for forming a film by colliding with a film. According to this ion plating method, since the energy of the particles is very large, the surface of the target object is sputter-cleaned and becomes relatively high in temperature.
The surface diffusion mobility is large on a clean and high temperature target surface, crystal growth is promoted, and a film having strong adhesive force is formed. Therefore, even when a target material is an active metal such as Nb, which immediately forms an oxide film in air or liquid, the surface of the target material is oxidized due to the treatment in a vacuum. The film is hardly generated, and the oxide film is destroyed by the collision of the coating substance ions, so that it is easy to obtain contact between the metals, and at the same time, the effect of anchoring to the surface of the target object due to the collision is increased. It has the feature that the adhesion to the film becomes very strong.

In the Nb ₃ Al compound based superconducting wire, a stabilizing material layer on the surface of the multi-wire Nb, for example, copper (Cu)
In applying Nb / Cu, the Cu layer hardly forms a solid solution in the combination of Nb / Cu, so that a method of simply coating the surface, for example, depending on electroplating, the adhesion between the plating layer and the target object Low power,
The effect as a stabilizer is also low. Further, the plating layer is cracked or peeled off even by a slight bending, so that it cannot withstand machining after forming the stabilizing material layer.

On the other hand, according to the method using the ion plating method of the present invention, a stabilizing material layer exhibiting strong adhesion to an object can be formed. Even if only the layer or the layer formed by the ion plating method is used as a base layer and the second stabilizer layer is coated thereon by electroplating or the like and the entire stabilizer layer is thickened, A good stabilizing material layer can be formed without lowering the adhesion to the material. Further, such a strong adhesive force has a characteristic of withstanding plastic working such as die drawing after forming the stabilizing material layer.

The physical vapor deposition can be performed by accommodating the entire target wire in the vapor deposition chamber or by continuously passing a part of the wire in the longitudinal direction into the vapor deposition chamber. is there.

[0024]

EXAMPLES The fact that the production method of the present invention is suitable for applying a stabilizing material to an Nb ₃ Al compound-based superconducting wire will be more clearly understood from the following examples and comparative examples.

Example 1 A pure Nb sheet having a thickness of 75 μm and a pure Al sheet having a thickness of 25 μm were superposed on each other to form φ1.
Wrap it tightly around a 5mm pure Nb rod, insert it into the Nb tube,
Furthermore, after inserting into a Cu tube, after processing into a hexagonal cross-section wire by surface reduction processing, Cu of the outer skin was removed to produce a single wire. This was assembled into a plurality of Nb tubes, further inserted into a Cu alloy tube, processed to a predetermined wire diameter by surface reduction processing, the outer Cu alloy was removed, and a Nb / Al composite multi-wire wire having a wire diameter of 1.25 mm was used. did.

Electric current is applied to the Nb / Al composite wire manufactured by the above-described process, and after rapidly heating to 2,000 ° C.
By cooling to ℃, a Nb / Al supersaturated solid solution wire was obtained. Next, an ion plating treatment was performed on this wire to form an underlying Cu layer (first stabilizing material layer) having a thickness of about 1 μm on the surface. Furthermore, electroplating is performed on this for about 4
A Cu layer (second stabilizing material layer) having a thickness of 9 μm was formed.

Embodiment 2 Nb / Al in Embodiment 1
An ion plating treatment was performed on the supersaturated solid solution wire to form a base Cu layer (first stabilizing material layer) having a thickness of about 0.1 μm on the surface. Further, a Cu layer (second stabilizing material layer) having a thickness of about 50 μm was formed thereon by electroplating.

Embodiment 3 Nb / Al in Embodiment 1
The supersaturated solid solution wire is deposited by sputtering,
An underlying Cu layer (first stabilizing material layer) having a thickness of about 1 μm was formed on the surface. Approximately 49 μm by electroplating
A thick Cu layer (second stabilizing material layer) was formed.

Comparative Example 1 Nb / Al in Example 1
Approximately 50 surfaces of supersaturated solid solution wire
A Cu layer (stabilizing material layer) having a thickness of μm was formed.

Comparative Example 2 Nb / Al in Example 1
The supersaturated solid solution wire was subjected to ion plating to form an underlying Cu layer (first stabilizing material layer) having a thickness of about 0.05 μm on the surface. Further, a Cu layer (second stabilizing material layer) having a thickness of about 50 μm was formed thereon by electroplating.

Each of the wires of Examples 1, 2, 3 and Comparative Examples 1 and 2 was subjected to a heat treatment at 800 ° C. for 10 hours in a vacuum to obtain a final Nb ₃ Al compound superconducting wire.

The critical current characteristics of the wires obtained by the methods of Examples and Comparative Examples were evaluated in a magnetic field of 21 to 15 T. Table 1 shows the wire specifications of the material of the present invention and the comparative material, and the critical current value of each wire at 4.2 K at each magnetic field. Here, the critical current value is a result obtained on the basis of 1 μV / cm. In the measurement result at 18T of Comparative Example 2, although a quench was finally generated, a slight increase in voltage was initially observed, and a transition from the superconducting state to the normal conducting state was observed. Quench.

As can be seen from the results, according to the method of the present invention, the stabilizing material layer applied wires (Examples 1 to 3) by the ion plating method or the sputtering method as the applying method of the stabilizing material layer are 17 T or less. The critical current value can be measured without generating a quench (that is, stabilized), while the wire with a stabilizer layer provided by simple electroplating (Comparative Example 1) can be measured at 18T. Quench occurred (that is, it was destabilized) and the critical current value could not be measured.
Further, as is apparent from a comparison between Examples 1 to 3 and Comparative Example 2, if the thickness of the stabilizing material layer by the ion plating method or the sputtering method is also 0.1 μm or more, the magnetic field of quench generation can be reduced. Also shown. That is, it is shown that the method of applying the stabilizing material layer using the ion plating method or the sputtering method is superior as the method of stabilizing the wire.

[0034]

[Table 1]

In the above embodiment, the thickness of the stabilizing material layer formed by the ion plating method or the sputtering method was set to 0.1 μm or more. This is because if the superconducting wire having the specific structure described in the embodiment is used as a high-field magnet conductor, it is considered sufficient if the superconducting wire is stabilized at 17 T or more, so that stability can be maintained in a magnetic field of 17 T or more. The thickness is specified by the applicant as the thickness, and the present invention is not limited to this. The thickness can be appropriately determined according to various structures of the superconducting wire. However, if this layer is too thin, the oxide film may not be sufficiently destroyed by the ion plating method or the sputtering method, and a stabilizing material layer with high adhesion may not be obtained.

In the embodiment, Cu is used as the material of the stabilizing material layer formed by the ion plating method or the sputtering method. However, a Cu alloy may be used. Also, C
u, a material other than the Cu alloy, for example, Ni, is used as a first stabilizing material layer, that is, an underlayer, and C
It may be a composite layer coated with a second stabilizing material layer made of u. For example, according to the combination of the Ni underlayer and Cu, it is considered that a solid solution is formed between Nb and Ni and between Ni and Cu, and the adhesion is further strengthened.

The material of the stabilizing material layer may be Ag or an Ag alloy whose electrical conductivity and thermal conductivity are similar to Cu.

As a matrix material, it is possible to use a matrix material having a sufficient strength at a temperature of 1500 ° C. or more during rapid heating and quenching treatment, a low reactivity with Nb, and a workability as long as it has a workability. In addition, for example, Ta and Ta alloy are promising.

The superconducting wire obtained by the method of the present invention is suitable for applications requiring a high critical current density in a magnetic field, for example, as a conductor for a high-field NMR magnet.

[0040]

Effect of the Invention Conventionally, a composite of stabilizing material layer to obtain the superconducting wire surface in a so-called rapid heating and quenching-transformation method has been difficult from the restrictions imposed by its special production method, Nb ₃ A of the present invention
The manufacturing method of l-compound superconducting wire is the first one that has made this possible.The superconducting properties in a high magnetic field, especially the critical current density, are superior to other metallic superconducting wires. For practical use of the obtained superconducting wire,
It opens the way greatly, and its industrial significance is extremely great.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a manufacturing process of an Nb ₃ Al compound-based superconducting wire according to the present invention.

FIG. 2 is a detailed flowchart of a manufacturing process of the Nb ₃ Al compound-based superconducting wire according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 Nb sheet 2 Al sheet 3 Nb rod 4 Nb tube 5 Cu tube 6 Hexagonal section wire 7 Nb tube 8 Cu alloy tube 9 Multifilament billet 10 Multi wire 11 Stabilizing material layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ryo Inoue 1-2-1, Sengen, Tsukuba, Ibaraki Pref., National Institute of Metals Science and Technology (72) Inventor Katsuo Fukutomi 1-2-1, Sengen, Tsukuba, Ibaraki No. 72, Metallurgical Materials Research Laboratory, Agency for Science and Technology (72) Inventor Genzo Iwaki, 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Hitachi Cable, Ltd. F-term (reference) in Hitachi Cable, Ltd. System Materials Laboratory 5G321 AA11 BA03 CA09 CA36 CA41 CA42 DC04 DC32 DC33 DC35

Claims (8)

[Claims] A composite material comprising Nb or a composite material comprising Nb alloy and Al or an Al alloy is surrounded by a high melting point metal or an alloy matrix thereof. A plurality of single wires are combined, and the outer periphery thereof is formed by a matrix comprising a high melting point metal or an alloy thereof. A method for producing an Nb ₃ Al compound superconducting wire, in which an encircled multi-wire is cooled to a predetermined temperature or more and immediately cooled after heating to generate an Nb-Al supersaturated solid solution and then heat-treated again to precipitate an Nb ₃ Al phase. in, upon complexing the stabilizing material on the outermost periphery of the multi-wire, after the energization heating immediately after cooled after or again heated, and forming a stabilizing material layer by a physical vapor deposition Nb ₃ A method for producing an Al compound superconducting wire. 2. The method according to claim 1, wherein the stabilizing material layer is made of any one of copper, copper alloy, silver and silver alloy, and the physical vapor deposition method is an ion plating method. Production method of Nb ₃ Al compound based superconducting wire. 3. The Nb according to claim 1, wherein a first stabilizing material layer formed by the physical vapor deposition method is used as a base layer, and a second stabilizing material layer is further formed around the first stabilizing material layer.
_{3 A} method for producing an Al compound superconducting wire. 4. A plurality of single wires each comprising Nb or a composite material composed of Nb alloy and Al or Al alloy surrounded by a high melting point metal or its alloy matrix, and the outer periphery thereof is surrounded by a high melting point metal or its alloy matrix. The multi-structured wire is heated by heating to 1500 ° C. or more and then immediately cooled, and the wire obtained is further heated at a temperature of 600 to 1,050 ° C. to obtain Nb.
_{In the} method for producing a Nb ₃ Al compound-based superconducting wire that produces a 3Al compound, when the stabilizing material is compounded on the outermost periphery of the multi-wire, after cooling immediately after the electric heating or after additional heat treatment, physical vapor deposition is performed. A method for producing an Nb ₃ Al compound-based superconducting wire, comprising forming a stabilizing material layer by a method. 5. The method according to claim 4, wherein the stabilizing material layer is made of any one of copper, copper alloy, silver and silver alloy, and the physical vapor deposition method is an ion plating method. Production method of Nb ₃ Al compound based superconducting wire. 6. The Nb according to claim 4, wherein a first stabilizing material layer formed by the physical vapor deposition method is used as an underlayer, and a second stabilizing material layer is further formed around the first stabilizing material layer.
_{3 A} method for producing an Al compound superconducting wire. 7. The Nb _{3 according} to claim 5, wherein the thickness of the stabilizing material layer by the physical vapor deposition method is 0.1 μm or more.
A method for producing an Al compound superconducting wire. 8. An Nb ₃ Al compound-based superconducting wire obtained by the method according to claim 1.