JPH0760620B2 - Nb3 Al Extra-fine multi-core superconducting wire manufacturing method - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing Nb ₃ Al ultrafine multifilamentary superconducting wire. More specifically, the present invention relates to Nb ₃ excellent in high magnetic field characteristics and strain resistance characteristics.
Al superconducting material, without losing its features,
The present invention relates to a method for producing an Nb ₃ Al extra-fine multi-core superconducting wire which can produce an ultra-fine multi-core superconducting wire having excellent stability and AC characteristics.

2. Description of the Related Art Currently, Nb ₃ Sn, V ₃ Ga extra fine multifilamentary wire is used as a superconducting conductor for high magnetic field, Nb-Ti extra fine multifilamentary wire is used for low magnetic field, and Nb- is used for alternating current. Ti ultra-fine multifilamentary wires have been put into practical use. On the other hand, Nb ₃ Al has a higher critical temperature and an upper critical magnetic field than Nb ₃ Sn and V ₃ Ga, and is attracting attention as a promising superconducting material for high magnetic fields. This Nb ₃ Al
For, for example, powder metallurgy that mixes and presses niobium and aluminum powder, and then wire-draws and heat-treats, or jerry roll method that superimposes niobium foil and aluminum foil and wire-draws and heat-treats the composite. It has been reported that the short wire rods produced by the laboratory-level method described above have excellent properties, but it is difficult to completely solve the problem of oxidation from the surface of the raw material powder or the raw material foil material, and the long wire material is difficult to solve. However, it has not yet been put to practical use. On the other hand, the inventors of the present invention previously compounded Nb and an Al alloy having work hardening characteristics similar to those of Nb, and repeatedly performed wire drawing and recomposition to produce Nb / Al alloy composite ultra-fine particles. It proposes a method for producing a long Nb ₃ Al superconducting wire by producing a core wire, heat-treating the core wire at a relatively low temperature of 1000 ° C. or lower, and causing mutual diffusion reaction. However, in the Nb ₃ Al superconducting wire produced by this method, although the crystal grains are fine, Nb ₃ Al having a composition deviated from the stoichiometric composition is generated, and J _C becomes high, but T _C And H _C2 is slightly low. When this wire is heat-treated at a high temperature of 1500 ° C. or higher, Nb ₃ Al having a crystal grain becomes coarse but a stoichiometric composition is formed, and T _C
And H _C2 are high, but J _C is low. Also, Nb-Al supersaturated solid solution bc stable only at high temperature
It is generated by the pseudo-steady state by the c alloy quenching after high temperature heat treatment, which was heat-treated at a low temperature, to precipitate Nb ₃ Al near stoichiometric composition with a fine grain, T _C, with H _C2 J _C A method for manufacturing a highly expensive wire rod has been studied so far. For example, IEEE Transactions on M
agnetics, Vol. MAG-13, No.1, January 1977, a composite wire in which a pure aluminum rod was inserted into a niobium tube was heat-treated at high temperature by electric heating, then the electric current was cut off and a helium gas jet was blown onto the wire. A method of quenching has been disclosed, and it is reported that a supersaturated bcc solid solution is formed and further Nb ₃ Al short wires can be obtained by low-temperature heat treatment. Similarly, in U.S. Pat. No. 4,088,512, Nb / Al composite single core wire is electrically heated, rapidly quenched with a helium gas jet, and additionally heat treated at low temperature.
_{3 A} method for manufacturing an Al wire is disclosed. However,
No report has been made so far that a long Nb ₃ Al wire can be continuously produced by this method. This is because the Al core diameter of the composite wire used is 100 μ.
It is considered that it is too thick as about m, so that the heat treatment takes too long, the wire can be moved only slowly, and continuous rapid cooling is actually impossible. Further, in order to realize an Nb / Al composite having a small Al core diameter, the hardness of Al is too soft as compared with the hardness of Nb, abnormal deformation occurs during processing, and it is impossible to process to 10 μm or less. This is considered to be one reason. The present invention has been made in view of the circumstances as described above, solves the drawbacks of the conventional method, and has a high J _C , a high H _C2, and a high T _C characteristic, and is an extremely fine multicore shape useful for practical use. It is an object of the present invention to provide a new manufacturing method capable of obtaining the long Nb ₃ Al superconducting wire.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is 2 to 15 at% Mg, 2 to 10 at% Z.
n, 2 to 10 at% Li, 1 to 8 at% Ag or 0.1 to 7
A composite of an aluminum alloy containing at least one of at% Cu and niobium was prepared, and the composite was cold drawn until the thickness of the aluminum alloy was 10 μm or less, and then while moving the composite wire. After conducting heat treatment for 5 seconds or less at a temperature of 1500 ° C. or more by electric heating, introducing into liquid metal and quenching, a composite wire in which Nb-Al supersaturated solid solution alloy filaments are arranged in a niobium matrix is formed, and then 650-
An additional heat treatment at 950 ° C. is performed to transform an Nb-Al supersaturated solid solution alloy filament into an A15 phase compound filament to obtain an ultrafine multicore superconducting wire, and a method for producing an Nb ₃ Al ultrafine multicore superconducting wire. . In addition, the present invention is applicable to aluminum or the above aluminum alloys 2 to
Nb ₃ Al for producing a composite from an aluminum alloy and niobium prepared by making an ingot to which one or more kinds of 8 at% Si or 2 to 25 at% Ge is added and heat treating at 350 to 450 ° C. for 1 to 30 hours It also provides a method for manufacturing an ultrafine multicore superconducting wire. As described above, since the composite workability of the composite of pure aluminum (Al) and niobium (Nb) is poor, the Al core diameter (thickness) of the composite is 10 μm.
Cannot be less than Therefore, Al is alloyed,
It is possible to make the work hardening characteristics similar to Nb,
In this case, the components to be added are required to appropriately increase the hardness of Al and not to deteriorate the superconducting property of Nb ₃ Al. In order to satisfy this, in the present invention, 2-15 at% Mg, 2-10 at% Zn, 2-1
One or more of 0 at% Li, 1 to 8 at% Ag, or 0.1 to 7 at% Cu is added to Al. This trace amount of Mg, Zn, L
Al alloys containing one or more of i, Ag or Cu are
The work hardening characteristics are similar to Nb, and the composite workability with Nb is greatly improved. Therefore, an Nb / Al composite wire having an Al alloy core diameter of 10 μm or less can be easily manufactured. Moreover, the additive element hardly deteriorates the superconducting property of the Nb ₃ Al that is formed. Further, 2 to 8 at% Si or 2 to 25 at% Ge is used as Al or above A
It is also effective to add it to the 1-alloy. In this case, the superconducting property of Nb ₃ Al is particularly improved. The addition of Si or Ge is known so far,
Since the addition of Si or Ge remarkably hinders the plastic workability of Al and Nb, very few examples have actually been tried for long Nb ₃ Al wires. In the present invention, the Al alloy ingot added with Si or Ge is temporarily heated to a temperature of 350 to 100 ° C. immediately below the melting point.
Heat treatment is performed at 450 ° C. for 1 to 30 hours to make the precipitated particles of Si or Ge in the ingot spherical. In this way, this alloy can be made to have plastic workability. The Nb ₃ Al extra-fine multifilamentary wire produced using this alloy exhibits superconducting properties superior to those using other alloys. On the other hand, if the above-mentioned additional elements deviate from the composition range, complex processing becomes difficult. It is essential that the core diameter (thickness) of the Al alloy core in the present invention immediately before heat treatment is 10 μm or less, and preferably 5 μm or less. 10 μm
When the size is larger than the above, rapid cooling is not performed well, a uniform Nb-Al supersaturated solid solution is difficult to be generated, and there is a problem that the diffusion reaction between the Al alloy core and the Nb matrix takes time. In order to sufficiently carry out the diffusion reaction, the heat treatment time may be lengthened, but in this case, even the compound phase layer other than the Nb-Al supersaturated solid solution layer is diffused and generated, and the wire becomes brittle, which makes handling difficult. There is a problem of becoming. Thus, the thickness of the Al alloy core is 10
If it is more than μm, the superconducting property and mechanical property of the Nb ₃ Al extra fine multifilamentary wire are deteriorated. Further, the heat treatment for electric conduction is performed for 5 seconds or less. For example, as a typical example, the wire moving speed is set to 1
When the distance between the electrodes is 10 cm in m / sec, the heat treatment time at this time can be 0.1 seconds. If the distance between the electrodes is made too long, the high-temperature elongation of the wire rod caused by the high-temperature heat treatment becomes remarkable, and the wire rod becomes slack and is easily detached from the reel that moves the wire rod. Therefore, in order to increase the distance between the electrodes and continuously heat treat the long wire, a mechanical mechanism for absorbing the slack is required. However,
In reality, since the heat treatment is performed at a high temperature near 1900 ° C, the wire becomes extremely soft and it is impossible to apply a strong tensile force, and it is extremely difficult to realize an absorption mechanism. On the other hand, 10 cm
If the distance between the electrodes is shortened to such an extent, such a special slack absorbing mechanism is not necessary. As described above, since the distance between the electrodes is limited, it may be possible to slow the wire moving speed in order to perform the heat treatment sufficiently. However, if the wire moving speed is reduced to 0.02 m / sec, the heat treatment time will be shortened. Although it can be set to 5 seconds, the cooling rate becomes 1/50, so that the quenching conditions are not satisfied, the supersaturated bcc solid solution phase of the metastable phase is less likely to be generated, and a superconducting wire with good characteristics I can't get it. Further, if the heat treatment time is increased by 5 seconds or more, Nb
Since Al atoms are diffused in the matrix and a large amount of Al is dissolved in the Nb matrix at a low concentration, an undesired low-concentration solid solution is generated, and Al is wastefully used. The amount of Nb ₃ Al generated in the inside decreases, and J _C per cross-sectional area of the wire decreases. It is not possible to obtain a wire with good superconducting properties. The temperature of electric heat treatment is
The characteristics are best when the temperature is 1500 ° C or higher and about 1700 to 2000 ° C. The rapid cooling after the electric heating is performed by quenching into the molten metal. Water quenching, oil quenching, or quenching in liquid nitrogen cannot obtain a sufficient cooling rate.
Further, the quenching operation is easier than the case of spraying a low temperature gas such as helium. The type of molten metal is not particularly limited, but a metal or alloy having a melting point near room temperature and not so active is desirable. For example, Ga, Hg, In,
Rose alloy (Bi-Pb-Sn alloy), wood alloy (B
i-Pb-Sn-Cd alloy) and the like. Sufficient Nb-Al supersaturated solid solution is formed in the heat-treated composite wire. Since this Nb-Al supersaturated solid solution has plastic workability, it is suitable, for example, when it is compounded with Cu as a stabilizer. As a method of compounding Cu, for example, N
For example, the surface of the b / Al composite wire may be coated with Cu by plating, or a large number of composite wires may be braided around the Cu wire. There is no particular limitation. The use of Cu as a stabilizing material in this way takes advantage of the fact that the Nb matrix is less likely to undergo a diffusion reaction with Cu. In the present invention, the Nb-Albcc solid solution filament is finally transformed into a fine crystal grain A15 phase compound filament by additional heat treatment at a temperature of 650 to 950 ° C. If this additional heat treatment temperature is set to 950 ° C. or higher, the crystal order of Nb ₃ Al deteriorates and the crystal grains become coarse, so that the superconducting characteristics deteriorate. When manufacturing an Nb ₃ Al extra-fine multi-core superconducting wire, for example, as shown in FIG. 1, an Al alloy rod (1) is fitted into an Nb pipe (2) for composite processing, and a single-core composite wire (3) is formed. Nb / Al extra fine multifilamentary wires can be produced by preparing a plurality of the single cored composite wires (3) and bundling them in a Nb pipe (4). In order to obtain a thinner Al alloy core diameter, it is also possible to bundle them and re-compound them in the Nb pipe (4).
This composite wire is subjected to continuous energization heat treatment and continuous quenching treatment in the apparatus shown in FIG. The liquid Ga bath (5) in the apparatus serves both as a current-carrying electrode and as a coolant for rapid cooling. Nb / Al extra fine multi-core composite wire (6)
Is rapidly heated by electric heating while continuously moving, and reaches a maximum temperature of about 1700 to 2000 ° C. immediately before the liquid Ga bath (5) electrode. Immediately thereafter, it is immersed in a low temperature liquid Ga bath (5) and rapidly cooled. The Nb matrix in the wire is Nb for forming the Nb-Al supersaturated solid solution.
In addition to the role of supply source, it also plays the role of maintaining the ultra-fine multi-core wire structure during the heat treatment by electric current. In the composite wire after the electric current treatment, ultrafine multicore Nb-Al supersaturated bcc solid solution filaments are formed in the Nb matrix. In this state, almost no A15 type compound Nb ₃ Al is formed, and the wire has plastic workability to some extent. In this state, Cu can be stabilized by compounding Cu having excellent electric conductivity by Cu plating or compounding with Cu. Then, the composite wire is used as it is or after being composited with Cu as a stabilizing material, and then subjected to additional heat treatment at 650 to 950 ° C. to form a Nb-Al supersaturated bcc solid solution filament with A1.
It is transformed into a 5 type Nb ₃ Al filament. The Nb ₃ Al wire thus produced has a composition ratio close to the stoichiometric composition, has a small crystal grain size, and has a fine metal structure.
Shows excellent superconducting properties. The critical current density in a high magnetic field also has a large value. A superconducting magnet can generate a higher magnetic field. Further, according to the present invention, a large amount of Nb ₃ Al filaments having a core diameter of 1 μm or less can be generated in the wire without intermediate annealing during processing, and the AC loss of the wire is extremely small, which is used for AC at commercial frequencies. It becomes possible. Further, it is possible to freely change the volume ratio of Cu as a stabilizing material, and it is possible to supply a wire rod having a stability most suitable for various applications. Currently, the only practically used Nb-Ti AC wire rod has a critical temperature of 9K,
When used in 4.2 K liquid helium, the temperature margin is only 4.8 K. On the other hand, T _C of the Nb ₃ Al superconducting wire is 16～19K, temperature margin can take more than 10K. A wire rod having such a large temperature margin is also advantageous for alternating current. It can be used as a wire for high magnetic field and alternating current superconducting magnets used in high-field magnets for NMR-analyzers, nuclear fusion reactors, energy storage, electromagnetic propulsion vessels, superconducting generators, superconducting transformers, magnetic lenses, etc. it can. The present invention will be described in more detail with reference to the following examples.

EXAMPLES Example 1 According to the procedure illustrated in FIG. 1, first, pure A having an outer diameter of 7 mm was used.
1, Al-2 at% Mg, Al-6 at% Mg, Al-10
A round bar of at% Mg and Al-15at% Mg is inserted into an Nb pipe with an outer diameter of 14 mm and an inner diameter of 7 mm, respectively, to make a composite, and cold drawn to form a composite wire with an outer diameter of 1.14 mm. did. 121 single-core composite wires are bundled and the outer diameter is 20 mm,
The composite was prepared by inserting it into an Nb pipe having an inner diameter of 14 mm, and processed into a 121-core composite wire having an outer diameter of 1.14 mm by cold drawing. An additional 121 pieces of this 121-core composite wire are bundled to form an outer diameter of 20
mm, inner diameter 14mm Nb pipe inserted into a composite body, and cold drawn to form outer diameter 2mm, 1mm, 0.7mm and
It was processed into a 121 x 121 core composite wire of 0.35 mm. The Al alloy core diameters of these composite wires are 4 μm, 2 μm,
It was set to 1.4 μm and 0.7 μm. In the above, some 121
For core composite wire, bundle 19 wires, outer diameter 8.3 mm, inner diameter 5.
Inserted into an 8mm Nb pipe and wire drawn, the outer diameter is 3mm,
1 mm, 0.7 mm and 0.35 mm 19 × 121 core composite wire (Al
Alloy core diameters are 14μm, 4.8μm, 3.4μm,
1.7 μm). Further, a part of the 121-core composite wire was further drawn to an outer diameter of 0.7 mm and 0.35 mm (Al alloy filament core diameters of 24 μm and 12 μm, respectively). In the apparatus illustrated in FIG. 2, these composite wire rods were electrically heated while moving in a vacuum, passed through a liquid Ga bath, and continuously quenched. This Ga bath also serves as a collecting electrode for electric heating, and the distance between the electrodes was 10 cm. Then, the superconducting critical temperature T _C and the critical current density J _C of the wire rod in this state and the wire rod subjected to the additional heat treatment at 600 to 1000 ° _C. were measured. The results are as shown in Table 1. In addition, according to the temperature measurement by the optical thermometer, the wire temperature at the time of energization heating becomes the highest temperature immediately before the Ga bath. That temperature
Ultimately, excellent superconducting properties were obtained at temperatures above 1500 ° C. The best properties were obtained at 1700-2000 ° C.

[Table 1] In the wire material using pure Al as the core material, when the Al filament core diameter was 30 μm or less, the shape of the core was broken and the processing was not successful. On the other hand, Al-2 at% Mg and Al-
In the case of wire material using 15at% Mg alloy, the core diameter is 1μ
Although it was possible to machine up to about m, some core diameters were abnormally deformed and some were broken. Al-6 at% M
In the case of a wire material using g and Al-10 at% Mg alloy, it was possible to manufacture an ultrafine multicore wire having a core diameter of 1 μm or less. The measurement of T _C was performed by the resistance method. In the case of a wire rod that is not subjected to additional heat treatment, it mainly shows T _C similar to T _C (~ 9K) of Nb, and J _C (4.2 _{C in} a magnetic field of 2T or more).
K) was zero. In the case of wire rods that have undergone additional heat treatment at 650 to 950 ° C, a high T _{C of} 13K or higher, often 16K or higher.
was gotten. J _C (4.2 K, 15T) strongly depends on the core diameter, and has a high value of 1 × 10 ⁴ A / cm ² or more when the core diameter is 10 μm or less. Example 2 In the same manner as in Example 1, a 121 × 121 core composite wire rod (outer diameter 0.7 mm, Al alloy filament core diameter 1.4 μm) using an Al-6 at% Mg alloy core material was prepared, and this was moved. 300 A x 0.05 sec, 150 A x 0.1 se by changing the speed
c, 50A × 0.3sec, 18A × 1sec, 15A × 1sec
, 9A × 2sec, 8A × 2sec, 5A × 4sec, 4A
Conductive heating and quenching treatment were performed for × 4 sec, 3 A × 6 sec and 2.5 A × 6 sec. And 850 ℃ × 2hr
T _C and J _C were measured after the additional heat treatment was performed. The results are as shown in Table 2.

[Table 2] Excellent superconducting properties were obtained only in the case of current heat treatment for 4 seconds or less. Further, the sample which was electrically heated at 150 A × 0.1 sec was subjected to additional heat treatment under various conditions. FIG. 3 shows the relationship between the heat treatment conditions and T _C. Although the optimum time varies, good T _C was obtained by adding a heat treatment temperature of 650 to 950 ° C.. Example 3 Al-0.05 at% Cu, Al-0.1 at% C having an outer diameter of 7 mm
u, Al-2 at% Cu, Al-5 at% Cu, Al-8 at
% Cu, Al-1 at% Zn, Al-2 at% Zn, Al-
4 at% Zn, Al-8 at% Zn, Al-12 at% Zn,
Al-1 at% Li, Al-2 at% Li, Al-4 at% L
i, Al-8 at% Li, Al-12 at% Li, Al-1
at% Ag, Al-2 at% Ag, Al-4 at% Ag, Al
Using alloy round bars of -8 at% Ag and Al-12 at% Ag, repeating the compounding and processing in the same manner as in Example 1,
A composite wire having an outer diameter of 0.7 mm and having 121 × 121 Al alloy cores (Al alloy core diameter 1.4 μm) was produced. In addition, Al-0.
05 at% Cu, Al-8 at% Cu, Al-1 at% Zn,
Al-12 at% Zn, Al-1 at% Li, Al-12 at
In the case of a wire using% Li, Al-1 at% Ag and Al-12 at% Ag alloy as the core material, abnormal deformation occurs when the Al alloy filament core diameter becomes 15 μm or less, and the multi-core wire structure cannot be maintained. In some cases, wire breakage occurred during wire drawing, making further processing impossible. The processed composite wire was subjected to electric current heating and quenching treatment under the condition of 150 A × 0.1 sec, and then subjected to additional heat treatment of 850 ° C. × 2 hr. T _C and J _C of the obtained wire rod were measured. The results are as shown in Table 3.

[Table 3] Good superconducting properties were obtained. Example 4 Al-2 at% Mg-2 at% Cu-2 at% Li having an outer diameter of 7 mm
-2 at% Ag and Al-3 at% Mg-3 at% Cu-3
At% Li-3 at% Ag alloy round bars, each with an outer diameter of 1
A composite body was prepared by inserting it into an Nb pipe having a diameter of 4 mm and an inner diameter of 7 mm, and processed into a composite wire having an outer diameter of 1.14 mm by cold drawing. 121 single-core composite wires are bundled and the outer diameter is 20 mm and the inner diameter is 1
The composite was prepared by inserting it into a 4 mm Nb pipe, and processed into a 121-core composite wire with an outer diameter of 1.14 mm by cold drawing. this
121 more 121-core composite wires are bundled, outer diameter 20 mm, inner diameter 1
A composite body inserted in a 4 mm Nb pipe was prepared and processed into a 121 × 121 core composite wire (Al alloy filament core diameter 1.4 μm) having an outer diameter of 0.7 mm by cold drawing. This composite wire was continuously energized and heated in the same manner as in Example 1 and quenched. The superconducting critical temperature T _C and the critical current density J _C of added heat-treated wire in the wire further 600 to 1000 ° C. were measured. If you do not additional heat treatment, mainly Nb of T _C (~
But it showed only T _C that matches the 9K), 650 ~950
High T of 16K or more for wire rod additionally heat treated at ℃
_C was obtained. J _C (4.2 K, 15T) also showed excellent characteristics of 6 × 10 ⁴ A / cm ² or more similar to those of Example 1. Example 5 Al-1 at% Ge, Al-2 at% Ge, Al-10 at%
Ge, Al-25 at% Ge, Al-28 at% Ge, Al
-1 at% Si, Al-2 at% Si, Al-6 at% Si,
Al-8 at% Si and Al-10 at% Si alloy ingots were prepared in a Tammann melting furnace and cold worked. Al-1at% Ge and Al-1at% Si could be directly cold worked, but other alloy ingots cracked,
Could not be cold worked. The alloys that could not be cold worked were heat treated at 350 ° C for 6 hours for Al-Ge alloys and 450 ° C for 6 hours for Al-Si alloys to remove Al-28at% Ge and Al-10at% Si alloys. It became possible to cold work. However, Al
Since the cold workability of -25 at% Ge and Al-8 at% Si alloy was not good, 6% was added at the stage of 10% workability.
A heat treatment of time was applied. By such heat treatment, the Ge or Si precipitation phase in the alloy is spheroidized, and Al-28at% G
All alloy ingots except e and Al-10 at% Si alloy could be cold worked. The Al-Ge and Al-Si alloy round rods with an outer diameter of 7 mm produced by cold working were inserted into Nb pipes with an outer diameter of 14 mm and an inner diameter of 7 mm, respectively, to produce a composite, which was then drawn by cold drawing. It was processed into a composite wire with a diameter of 1.14 mm. 121 single-core composite wires are bundled and the outer diameter is 20 m
A composite was prepared by inserting it into an Nb pipe having an inner diameter of 14 mm and an inner diameter of 14 mm, and was processed into a 121-core composite wire having an outer diameter of 1.14 mm by cold drawing. Bundling 121 more of this 121-core composite wire with an outer diameter of 2
A composite body inserted into an Nb pipe having an inner diameter of 0 mm and an inner diameter of 14 mm was prepared and processed into a 121 × 121 core composite wire (Al alloy filament core diameter 1.4 μm) having an outer diameter of 0.7 mm by cold drawing. In the case of a wire having Al-1at% Ge and Al-1at% Si as the core material, abnormal deformation occurs when the Al alloy core diameter becomes 15 μm or less, and the multi-core wire structure cannot be maintained, and in some cases, wire drawing Sometimes the wire was broken, and further wire drawing became impossible. In the case of a wire using an Al alloy having another composition, it was possible to perform wire drawing while maintaining the multi-core structure up to an Al alloy core diameter of about 1.4 μm. On the other hand, when the core diameter was 1 μm or less, abnormal deformation occurred, the multi-core wire structure could not be maintained, and in some cases, the wire was broken during wire drawing, and further wire drawing became impossible.
These composite wires were continuously subjected to electrical heating and quenching in the same manner as in Example 1. Then another 600-10
Further heat treatment was carried out at 00 ° C., and the superconducting critical temperature T _C and the critical current density J _C of the obtained wire rod were measured. If no additional heat treatment, primarily although not shown T _C (~9K) and comparable only from T _C of niobium, 650-950 having been subjected to the additional heat treatment ℃ is higher than 17.5 K T Showed _C. J _C (4.2 K, 15T) also had excellent characteristics of 8 × 10 ⁴ A / cm ² or more, which was slightly higher than that of Example 1. It is considered that this is because the superconducting property was improved by the effect of adding Ge or Si. Example 6 Al-10 at% Ge-2 at% Mg-2 at% Zn-2 at%
Li-2 at% Ag-2 at% Cu alloy and Al-6 at%
Si-2 at% Mg-2 at% Zn-2 at% Li-2 at% A
A g-2 at% Cu alloy was prepared by Tamman melting. This alloy is not cold workable, but if the former alloy is heat treated at 350 ° C for 6 hours and the latter alloy at 450 ° C for 6 hours,
Spheroidization of the precipitate occurred and cold working became possible.
Using this Al alloy, a composite wire with Nb was produced in the same manner as in Example 4. This composite wire is formed of Al- shown in Example 5.
The composite workability was superior to the composite wire using Ge alloy and Al-Si alloy, and it was possible to perform wire drawing while maintaining the ultrafine multicore shape even when the Al alloy core diameter was about 0.4 μm. These composite wires were continuously subjected to electrical heating and quenching in the same manner as in Example 1. And 600-1000
The superconducting critical temperature T _C and the critical current density J _C of the obtained wire rod were measured after additional heat treatment at ℃. The obtained superconducting properties were similar to those of the wire rod shown in Example 5, but the alloy used for this wire rod had better composite workability than the alloy shown in Example 5, It is considered promising in practice. Of course, the present invention is not limited to the above examples. It goes without saying that various details are possible.

As described above in detail, according to the present invention, Nb ₃ Al having a composition close to the stoichiometric composition (high in T _C and H _C2 ) and having a fine crystal grain size (high in J _C) ) Extra fine multi-core shape (high stability and low AC loss)
It is possible to continuously manufacture the long wire. Such superconducting wires are used for high magnetic field and alternating current superconducting magnets used in high-field magnets for NMR-analyzers, fusion reactors, energy storage, electromagnetic propulsion ships, superconducting generators, superconducting transformers, magnetic lenses, etc. Effective for wire rods.

[Brief description of drawings]

FIG. 1 is a flow chart exemplifying a manufacturing process of an Nb ₃ Al extra fine multi-core superconducting wire according to the present invention.

FIG. 2 is a cross-sectional view illustrating an apparatus configuration that can be used in the present invention.

FIG. 3 is a correlation diagram showing a change in T _c according to an additional heat treatment temperature of an Nb ₃ Al ultrafine multicore superconducting wire manufactured by using a core material having a composition of Al-6 at% Mg and a core diameter of 1.4 μm.

[Explanation of symbols]

 1 Al alloy rod 2 Nb pipe 3 Single core composite wire 4 Nb pipe 5 Liquid Ga bath 6 Nb / Al Extra fine multi-core composite wire

Claims (3)

[Claims] 1. A 2-15 at% Mg, 2-10 at% Zn,
2-10 at% Li, 1-8 at% Ag or 0.1-7 at%
A composite of an aluminum alloy containing at least one kind of Cu and niobium was prepared, and the composite was prepared so that the thickness of the aluminum alloy was 1 or less.
Cold wire drawing is performed until it becomes 0 μm or less, then, while moving the composite wire, heat treatment is performed for 5 seconds or less at a temperature of 1500 ° C. or more by electric heating while it is introduced into a liquid metal and rapidly cooled, and Nb-Al After forming a composite wire in which supersaturated solid solution alloy filaments are arranged in a niobium matrix, 650-95
A method for producing an Nb ₃ Al ultrafine multicore superconducting wire, which is characterized in that the Nb-Al supersaturated solid solution alloy filament is transformed into an A15 phase compound filament to obtain an ultrafine multicore superconducting wire by additional heat treatment at 0 ° C. 2. 2 to 15 at% Mg, 2 to 10 at% Zn,
2-10 at% Li, 1-8 at% Ag or 0.1-7 at%
One or more Cu, 2-8 at% Si or 2-25 at%
The method according to claim 1, wherein an aluminum alloy ingot containing at least one of Ge is produced, heat-treated at 350 to 450 ° C. for 1 to 30 hours, and then a composite is produced from cold-worked aluminum alloy and niobium. 3. 2-8 at% Si or 2-25 at% Ge
An aluminum alloy ingot containing at least one of the above, and heat-treated at 350 to 450 [deg.] C. for 1 to 30 hours, and then cold-worked to form a composite from niobium,
This composite is subjected to cold wire drawing until the thickness of the aluminum alloy is 10 μm or less, and then, while moving the composite wire, a heat treatment is performed for 5 seconds or less at a temperature of 1500 ° C. or more by electric heating to obtain a liquid metal And quench, Nb-Al
After forming the composite wire in which the supersaturated solid solution alloy filament is arranged in the niobium matrix, additional heat treatment is performed at 650 to 950 ° C., and the Nb-Al supersaturated solid solution alloy filament is made into A15.
A method for producing an Nb ₃ Al ultra-fine multi-core superconducting wire, which comprises transforming into a phase compound filament to obtain an ultra-fine multi-core superconducting wire.