JPH06196030A - Manufacture of nb3 al compound - Google Patents

Abstract

PURPOSE:To improve a characteristic of high temperature heat resistance excellent in ferromagnetic field and AC characteristic by heat treating a compound, composed of Ag-Al group solid solution and Nb(alloy), after wire drawing work. CONSTITUTION:An Nb or Nb-alloy bar, adding lat% or less Ag and 0.1 to 10at% Ge or Si, is inserted into an Ag-Al group solid solution pipe of 0.1 to 20at% Al content, to obtain a compound. This compound, after wire drawing work, is heat treated at 600 to 960 deg.C in a vacuum, inert gas or the atmosphere.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an Nb ₃ Al compound. More specifically, the present invention is useful as a Nb ₃ Al superconducting wire excellent in strong magnetic field and AC characteristics and a structural material excellent in high temperature heat resistance.
_{The present} invention relates to a new production method capable of simply and easily producing an Al compound.

2. Description of the Related Art Conventionally, for superconducting wire rods for strong magnetic fields and alternating magnetic fields, two types of Nb ₃ Sn and V ₃ Ga have been used.
One A15 type compound wire is manufactured by utilizing the diffusion promoting action of copper, as represented by the bronze method,
It has been put to practical use. In the bronze method, Cu-
A composite processed wire composed of an Sn (Cu-Ga) alloy matrix and an Nb (V) core is heat-treated at a low temperature of, for example, 800 ° C or lower. As a result, Nb ₃ Sn (V ₃ Ga) having a fine grain structure and a high critical current density can be directly diffused without passing through an intermediate phase rich in Sn (Ga). However, for the Nb ₃ Al superconducting wire belonging to the same A15 type compound Nb ₃ Sn and V ₃ Ga, Applying the bronze process described above for its production, preferentially the Nb-Al-Cu3 element compound containing copper in a large amount However, there is a drawback in that the target Nb ₃ Al is not formed by diffusion. Even when Nb and Al are directly diffused at a low temperature of, for example, 1000 ° C. or less, an Al-rich intermediate layer such as NbAl ₃ or Nb ₂ Al is usually stably formed, and Nb ₃
Al is not generated. On the other hand, it is known that Nb ₃ Al can be thickly formed by heat-treating a composite wire of Nb and Al at high temperature. However, in this case, since the crystal grains are coarsened, there is a problem that the critical current density becomes extremely small. Therefore, after reacting at high temperature by laser / electron beam irradiation method or melt quenching method,
Although a rapid cooling manufacturing method has been proposed, this manufacturing method requires a large-scale and special rapid heating / cooling device, and at the present time, there is a large variation in performance in the longitudinal direction, leading to practical application. Not up to. On the other hand, a powder metallurgy method of filling Nb powder and Al powder into an Nb pipe and cold working, stacking Nb foil and Al foil, winding them around a copper rod, and cold working by compounding this with a copper pipe Jelly roll method, liquid infiltration method in which Al melt is infiltrated into the gap between sintered bodies of Nb powder and then cold working, Al-Nb-Al three-layer clad thin plate is cut into chips, filled into billets, and then extruded Nb / Al by various methods such as a cold-worked clad chip extrusion method or a cold-worked niobium tube method in which an Al alloy rod is inserted into an Nb tube.
By making the diffusion pair extremely thin, for example, to about 0.1 μm or less, it is possible to manufacture an Nb ₃ Al wire having a large critical current density even in a high magnetic field even at a low temperature heat treatment of 1000 ° C. or less. However, in these methods, in order to realize an extremely thin Nb / Al diffusion pair,
In order to obtain a very large cold drawing work rate of 10 ⁵ to 10 ¹⁰ and to secure such a large drawing work rate, and to make a multi-core wire structure that is stable against electromagnetic disturbance. For this reason, a stacking step of bundling and inserting a large number of strands into a tube is required several times during processing. In order to promote the integration of the stacked wires, generally, diffusion bonding such as hydrostatic extrusion or intermediate annealing is effective, but in the above method, the diffusion pair is thinned to some extent. However, there is a drawback in that NbAl ₃ is generated by working heat and the like, which causes wire breakage in the subsequent wire drawing, if extruded or the like. For this reason,
There is a problem that it is substantially difficult to integrate the individual wires in the stacking process, and it is difficult to manufacture a long multifilamentary wire. Also, it was difficult to coat copper as a stabilizing material. Furthermore, regarding the heat treatment atmosphere, Nb and Cu are also used.
Since it is easily oxidized, heat treatment in the atmosphere is impossible, and heat treatment in a vacuum or an inert gas atmosphere is indispensable. Further, the Nb ₃ Al compound has been attracting attention as a next-generation high-temperature structural material that substitutes for a Ni-based alloy or the like. However, when a bulk material is manufactured by melting, it is difficult to adjust the target composition because the melting point of Nb ₃ Al is as high as around 2000 ° C. and the Al evaporates violently. Since the ingot obtained is brittle, it was not easy to shape it into an arbitrary shape. The present invention has been made in view of the above circumstances, and solves the drawbacks of the conventional method for producing an Nb ₃ Al compound and accelerates the diffusion reaction of Nb and Al by interposing silver (Ag). , Nb excellent in strong magnetic field and AC magnetic field characteristics
It is an object of the present invention to provide a new production method capable of easily and easily producing an Nb ₃ Al compound useful as a ₃ Al superconducting wire or a structural material excellent in high temperature heat resistance.

[Means for Solving the Problems] In order to solve the above problems, the present invention linearly draws a composite composed of an Ag-Al based solid solution and Nb or an Nb alloy and heat-treats the composite. A method for manufacturing an Nb ₃ Al superconducting wire, which is characterized by the above. That is, this invention is Ag-
Various shapes of composites composed of an Al-based solid solution and Nb or Nb alloy are subjected to linear wire drawing by repeating intermediate annealing, cold working, etc., and Nb and A are intercalated by interposing silver (Ag).
Nb ₃ A, which promotes the diffusion reaction of 1, and has excellent strong magnetic field characteristics and AC characteristics even in heat treatment at a relatively low temperature of about 1000 ° C.
l Superconducting wire and the like can be manufactured. When a composite of an Ag-Al based solid solution and Nb or an Nb alloy is used in the present invention, the shape, size, arrangement, etc. of each material forming the composite are not particularly limited. For example, a composite processing method of inserting an Nb rod or an Nb-Ag alloy rod into an Ag-Al base solid solution tube, a niobium tube method of inserting an Ag-Al base solid solution rod into an Nb pipe or an Nb-Ag alloy pipe, an Ag-Al base Jelly roll method in which solid solution foil and Nb foil or Nb-Al alloy foil are alternately stacked and wound around a core material such as a copper rod, Nb powder or Nb-Al
Powder metallurgical method of mixing alloy powder and Ag-Al-based solid solution powder and filling the pipe material such as Nb pipe, Ag-Al-based solid solution plate and Nb
A composite can be prepared by various methods such as a clad chip extrusion method in which a plate or an Nb-Al alloy plate is roll-bonded, cut into chips, filled in a pipe material such as an Nb pipe and extruded. The Al concentration in the Ag-Al based solid solution is set to 0.1 at.% Or more in order to obtain excellent superconducting properties, and 20 at.% Or less from the viewpoint of maintaining good cold workability. The addition of Ge or Si to Ag-Al based solid solution or Nb alloy improves the high magnetic field characteristics of the Nb ₃ Al group compound. The amount of addition is 0.1 at.% Or more for improving the characteristics, and 10 at.% Or less for maintaining good cold workability. As a method of interposing silver (Ag), not only the use of Ag-Al-based solid solution but also
It is also possible to use an Nb-Ag alloy in which Ag is added on the Nb side. When Ag is added to Nb, the amount of Ag added must be 1 at.% Or less in order to maintain good cold workability. Then, in the present invention, for example, the composite shown above is repeatedly subjected to intermediate annealing, cold working, etc., drawn into a linear shape, and heat-treated to generate Nb ₃ Al. The heat treatment temperature is in the range of 600 ° C. or higher for the diffusion formation of Nb ₃ Al, and 960 ° C. or lower for not exceeding the melting point of the silver alloy. Further, the heat treatment atmosphere may be a vacuum atmosphere, an inert gas atmosphere, or an air atmosphere. This is because Nb, which is easily oxidized, has a structure coated with a silver (Ag) alloy having excellent oxidation resistance.

In the manufacturing method of the present invention, it is not necessary to prepare an extremely thin Nb / Al diffusion pair as in the conventional method due to the above characteristics, so that strong wire drawing is not required. When an Ag-Al based solid solution is used as a matrix material or a stack material for forming a multifilamentary wire, it is possible to perform intermediate annealing for hydrostatic extrusion, diffusion bonding, etc. Wire drawing is extremely easy, and the hysteresis loss is small, for example, the core diameter is 1
It is possible to manufacture a multifilamentary wire having a size of μm or less. Also, Al
By adjusting the concentration and the like, the matrix material and the stack material of the silver-based alloy can also serve as the high electrical resistance material between the filaments and reduce the coupling loss. Further, it is not necessary to introduce cupro-nickel or the like as the high-conductivity resistance material, the conductor manufacturing process is simplified, and the manufacturing cost can be reduced. Since the Nb-Al superconducting wire manufactured by the manufacturing method of the present invention has a higher critical temperature than the conventional Nb-Ti superconducting wire, it is possible to design with a margin and to downsize the superconducting magnet. Therefore, it is possible to reduce the cooling cost. Moreover, since the heat treatment can be performed at a low temperature of 1000 ° C. or less and in the atmosphere, a large-scale special device such as a continuous melt quenching device or an electron beam generator is not required. For a superconducting coil that needs to be heat-treated (Wind & React method) after being wound into a coil, for example, conventional superconducting wire cannot be heat-treated in the atmosphere and requires a large vacuum heat treatment furnace. Therefore, although it was limited to a special application, it becomes possible to perform heat treatment in the atmosphere from the present invention,
Applications of superconducting coils will be expanded. Furthermore, when a melt containing a small amount of Al in Ag (Ag-Al-based solid solution) is used as a diffusion source of Al, the structure is the same as that of a composite used in conventional Nb ₃ Sn, V ₃ Ga superconducting wire production. Since it has a similar structure, it is also possible to use the melting, wire drawing, and heat treatment equipment that has been conventionally used as it is. Thus, Nb ₃ Al can be easily and easily
A superconducting wire can be manufactured. If the composite is heat-treated after being formed into an arbitrary shape, the diffusion reaction of Nb and Al is completed at a relatively low temperature within a short time, and the Nb ₃ Al-based compound is synthesized in an arbitrary shape. Therefore, the manufacturing method of the present invention is promising as a manufacturing method of a structural material having excellent high temperature heat resistance.

EXAMPLES Examples are given below to illustrate the Nb ₃ Al of the present invention.
The method for manufacturing the superconducting wire will be described in more detail. Examples 1 to 4 Nb was processed into a 3.8 mmφ round bar to prepare a core material, which was melted in a Tammann furnace and then processed into 7.6 / 3.9 mmφ Ag-2,
Composite with 5, 10, 15 at.% Al alloy matrix (Examples 1, 2, 3 and 4) and wire drawing to 0.7 mm φ (Nb core diameter: 350 μm) while applying intermediate annealing at 500 ° C. For the sample in which the matrix was Ag-5 at.% Al (Example 2), the stacking process was repeated to obtain 5
9 cores (31 μm), 59 x 59 cores (3 μm), 59 x 5
The 9 × 60 core (0.3 μm) multi-drawn wire was able to be drawn without any breakage. When heat-treated under the conditions shown in Table 1, for the single-core wire, Ag-5 at.% Al
The highest Tc of 15.0K was obtained when using (Example 2). The Hc ₂ (4.2 K) of this sample is 16T
Met. For comparison, Nb ₃ A was used by the niobium tube method.
1 superconducting wire was manufactured under the conditions shown in Table 1 (Comparative Examples 1 and 2), but in order to obtain Tc comparable to the samples of Examples 1 to 4, the diffusion distance of Nb / Al was set to Example 1. It was necessary to shorten to about 1/100 of the samples of ~ 4. On the other hand, according to the SEM view, the compound layer thickness of the samples of Examples 1 to 4 is 1 μm or less, and therefore the overall Jc of the single core wire is
Although was small, with Ag-5at.% Al in Table 2, as shown for superconducting wire was multifilamentary wire, Nb ₃ Al it is possible to increase the core / matrix interface density produced by a multi-wire of , Overall Jc was confirmed to be significantly improved.

[Table 1]

[Table 2] Example 5 A wire made in the same manner as in Example 2 with a wire diameter of 0.7 mm and an Nb core count of 3500 (core diameter 2.9 μm) Ag-5 at.% Al /
When the Nb composite wire was heat-treated in the air at 825 ° C for 1 hour, the Tc was about the same as that of the sample heat-treated in the vacuum atmosphere.
And overall Jc were obtained. Example 6 In order to improve the high magnetic field characteristics, Ge or Si was changed to silver (A
g) Added to alloy matrix material. Using this matrix material, in the same manner as in Example 2, Ag-5 at.% Al-
A 2 at.% Ge (Si) / Nb composite wire was prepared and heat-treated at 850 ° C. Tc and H due to addition of Ge and Si
c ₂ (4.2 K) was 16.0 K and 18 T, which were improved by 1 K and 2 T as compared with the case of no addition. Example 7 An Ag-5 at.% Al alloy rod (3.8 mmφ) prepared in the same manner as in Example 2 was inserted into a Nb tube (7.6 / 3.9 mmφ) to be compounded, and an intermediate annealing (500 ° C.) was performed. 0.7mm φ while adding
(Ag-Al alloy core diameter: 350 μm) was drawn and then heat-treated at 825 ° C. for 1 hour in the atmosphere. As a result, the same Tc and overall Jc as those of the single core wire sample of Example 2 (Nb core diameter: 350 μm) were obtained. Of course, the present invention is not limited to the above examples, and it goes without saying that various aspects are possible in details.

As described in detail above, according to the present invention, the diffusion reaction of Nb and Al is promoted by the interposition of silver (Ag), and Nb ₃ excellent in strong magnetic field and AC magnetic field characteristics is obtained.
It is possible to easily and easily manufacture an Al superconducting wire and a promising Nb ₃ Al compound as a structural material having excellent heat resistance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsuyoshi Kiyoshi 1-2-1 Sengen, Tsukuba-shi, Ibaraki Prefectural Government, Science and Technology Agency, Research Institute for Metals, Tsukuba Branch (72) Inventor Ren Inoue 1-1, Sengen, Tsukuba-shi, Ibaraki 2-1, No. 1 within the Tsukuba Branch of the Research Institute for Metals, Science and Technology Agency

Claims (7)

[Claims] 1. A method for producing an Nb ₃ Al compound, which comprises subjecting a composite composed of an Ag—Al-based solid solution and Nb or an Nb alloy to linear drawing and heat treatment. 2. Ag-containing 0.1-20 at.% Al
The manufacturing method according to claim 1, wherein an Al-based solid solution is used. 3. The method according to claim 1, wherein an Nb alloy added with 1 at.% Or less of Ag is used. 4. The method according to claim 1, wherein an Ag--Al based solid solution or Nb alloy added with 0.1-10 at.% Ge or Si is used. 5. Nb or Nb is added to the Ag-Al based solid solution tube.
-Ag alloy rod inserted composite, Nb or Nb-Ag
Composite body in which Ag-Al based solid solution rod is inserted in alloy tube, Ag
-A composite body in which an Al-based solid solution foil and Nb or Nb-Ag alloy foil are alternately stacked and wound around a core material, Nb or N
A composite in which b-Ag alloy powder and Ag-Al-based solid solution powder are mixed and filled in a pipe material, or an Ag-Al-based solid solution plate and N
The manufacturing method according to claim 1, 2, 3 or 4, wherein a composite of b or Nb-Ag alloy sheet rolled and adhered, cut into chips, filled into a tubular material and extruded is used. 6. A heat treatment at 600 to 960 ° C. in a vacuum, an inert gas or an air atmosphere,
4 or 5 of the manufacturing method. 7. A method for producing an Nb ₃ Al superconducting wire, which comprises producing an Nb ₃ Al compound by the method according to any one of claims 1, 2, 3, 4, 5 or 6.