JPS62278253A - Manufacture of nb3al superconducting wire - Google Patents

Abstract

PURPOSE:To manufacture a long-size Nb3Al superconducting wire excellent in superconducting characteristics, by subjecting a rod of an Nb-Al alloy with a specific composition to heating to a high temp. to allow it to enter into solid solution, to rapid cooling, and then to heating again to a specific temp. so as to precipitate Nb3Al in the solid solution. CONSTITUTION:An alloy rod 20 which has a composition consisting of 7-8.8wt% Al and the balance Nb and in which Nb3Al layers 20a, NbAl2 layers 20b, and NbAl3 layers 20c are present as a mixture is prepared by an arc melting method, etc. This rod is subjected to heating at 1,700-1,980 deg.C for several - several tens minutes and then to very rapid cooling at >=10<5> deg.C/sec cooling rate to undergo solution heat treatment so as to be formed into an Nb solid solution structure 22. The rod with this solid solution structure is covered with a barrier tube 23 composed of Ta or Nb, whose outside is further covered with a stabilizing material 24 composed of Cu tube so as to be formed into a composite tube 25. This tube 25 is subjected to diameter reduction working by wiredrawing so as to be formed into a wire 26. Then, the plural pieces of the above wires 26 are assembled, which is covered with a casing tube 27 made of pure copper to undergo multilandifying. Subsequently, the resulting wire is subjected to diameter reduction until the final diameter is reached and then to heating up to 600-1,000 deg.C to precipitate Nb3Al, so that superconducting wire 28 having high critical temp. can be manufactured.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention "Field of Industrial Application" The present invention uses Nb, which is known as a superconducting material with a high critical temperature.
The present invention relates to a method for manufacturing a 3A1-based superconducting wire.

"Conventional technology" Conventionally, the second method for manufacturing Nb3Al-based superconducting wires was
Two methods are known, which will be explained below with reference to FIG.

The first conventional method shown in FIG. 2 is to first use Nb powder and Al
A mixed powder 1 made of powder is sealed inside a reinforcing tube 2 made of Ta or the like as shown in FIG. A composite rod 4 is produced. Next, the composite rod 4 is reduced in diameter as shown in FIG. 2(B), and the metal tube 3 is chemically removed with a solution such as nitric acid solution as shown in FIG. 2(C). , heat treatment is performed to a temperature of 1200°C or higher for several tens of minutes to generate a Nb3Al phase, and furthermore, carbon is added to the outer periphery.
This is a method of manufacturing a Nb5Al based superconducting wire 6 shown in FIG. 2(D) by forming a stabilizing material 5 such as a U plating layer.

In addition, in the second conventional method shown in FIG. 3, first, a Nb rod 7 is covered with an Al pipe 8 to produce a composite rod 9 shown in FIG. 3(A), and then this composite rod 9 is reduced in diameter. A reinforcing tube 10 made of a high melting point material such as Nb and Ta is assembled into a plurality of reinforcing tubes 10
A multi-core composite rod 11 is produced by inserting the rod into the inside of the rod as shown in FIG. 3(B).

Subsequently, after reducing the diameter of this multi-core composite rod 11,
In this method, a Nb3Al-based superconducting wire is produced by performing heat treatment at a temperature of .degree. C. or higher for several minutes to several tens of minutes to generate a Nb3Al phase.

"Problems to be Solved by the Invention" In each of the above-mentioned methods, because the heat treatment temperature for NbffAl production is high, the crystal grains of the produced Nb3Al tend to become coarse, and the resulting superconducting There may have been a problem with the wire's poor superconducting properties.

In addition, when trying to manufacture a superconducting magnet using an NbaAl-based superconducting wire, the wire before being heat-treated to generate Nb and Al is wound around a winding drum, and then heat-treated to generate an Nb5Al phase to form a superconducting magnet. There is a way to manufacture it. However, when this method is adopted, it is necessary to heat the wire and the winding drum all at once to a high temperature of over 1,200°C, so a special heat-resistant material must be used for the structural material that makes up the winding drum. There was an interlayer.

On the other hand, in the first conventional method, when the diameter of the long reinforcing tube 2 is reduced in order to manufacture a long superconducting wire, there is a problem in that the reinforcing tube 2 is partially deformed such as constriction. Therefore, the first conventional method has the disadvantage that it is not possible to manufacture long superconducting wires.

The present invention has been made in view of the above problems, so that it is possible to manufacture a long NbjAl-based superconducting wire with excellent superconducting properties, and when manufacturing a superconducting magnet,
It is an object of the present invention to provide a method for manufacturing an NbjAl-based superconducting wire that has fewer restrictions on structural materials such as the winding drum of a superconducting magnet.

"Means for Solving the Problems" In order to solve the above problems, the present invention provides Al7-8.
Nb-Al containing 8% by weight, with the balance being Nb
An alloy rod made of an alloy is made, and this alloy rod is
A solid solution rod is produced by heating to a temperature of 700 to 1980°C and rapidly cooling at a cooling rate of 105°C/second or more, and then this solid solution lot is heated to a temperature of 600 to 10
Nb3A inside the solid solution lot by heating to a temperature of 00°C.
1 is precipitated, and it is a cellulose.

"Function" A solid solution single-phase deaf solid solution rod is produced by rapidly cooling a rod in which various intermetallic compound phases have disappeared by solid solution formation, and then heated to 600 to 1000°C to form a N b 3 A l is precipitated.

"Example" Figure 1 is for explaining an example of the present invention in the order of steps. In order to manufacture a Nb3Al based superconducting wire,
An alloy rod 20 having a composition of 7 to 8.8% by weight of Al and the balance being Nb is produced by performing a known arc melting method or an induction heating melting method.

In the alloy rod 20 produced in this way, the first
As shown in Figure (A), it has a cross-sectional structure in which the Nb s A 1 layer 20a, the NbAl 2 layer 20b, and the NbA 13 layer 20c are mixed inside, and the alloy rod 20 itself is very brittle and has low workability. It is organized.

Next, the alloy iron 20 is subjected to solution treatment.

This solution treatment is performed by heating the alloy Rondo 20 to a temperature of 1700° C. or higher and 1980° C. or lower for several minutes to several tens of minutes, and then rapidly cooling it at a cooling rate of 105° C./second or higher. Note that the rapid cooling treatment is carried out by a method such as putting it into a Pb5n solder bath with good wettability.

As a result of the heating operation, the interior of the alloy rod 20 becomes as shown in FIG.
The Nb solid solution structure as shown in B) is obtained, and the Nb solid solution structure is transferred to a room temperature state by the quenching operation to obtain the solid solution rod 22 having the Nb solid solution single-phase structure having the structure shown in FIG. 1(C). be able to. In the solid solution rod 22 created in this way, a single phase of Nb solid solution with excellent workability is used. ■It has excellent workability due to its woven structure.

In addition, in the alloy rod 20, the upper limit of the Al content is limited to 8.8% by weight or above because the solid solution temperature is 1700 to 19806C in the NbAl binary alloy.
In this case, the solid solubility limit of Al in Nb is 8.8% by weight.
This is because. Furthermore, when the tooth striking rate of Al is made larger than the above value, the amount of NbA13 phase protruding increases and the melting point of the alloy rod decreases, causing the problem that the rod melts at the solid solution temperature. On the other hand, the reason why the lower limit of the Al content is set to 7% by weight is that if the content is lower than this, Nb5Al
This is due to insufficient precipitation.

In addition, the reason why the cooling rate was limited to 10'C/sec or more is because if the cooling rate is set to about 10'C/sec, the NbAL phase will precipitate and the solid solution rod will become brittle.
A1. This is to prevent the appearance of the phase.

The solid solution rod 22 prepared as described above is shown in FIG.
As shown in D), a barrier W23 for a diffusion barrier made of a metal such as Ta or Nb is covered, and a copper tube 24 serving as a stabilizing material is further placed on the outside thereof to create a composite tube 25.

Next, the composite tube 25 is subjected to a diameter reduction process such as extrusion or wire drawing to produce a wire 26 shown in FIG. 1(E).
A plurality of superconducting wires are gathered together and covered with a jacket tube 27 made of pure copper to form a multi-strand, and the base wire 28 is created by reducing the diameter to the same diameter as the diameter of the superconducting wire to be finally obtained.

Next, this base line 28 is subjected to heat treatment in which it is heated to a temperature of 600° C. or more and 1000° C. or less for several hours to several tens of hours.

Through this heat treatment, an NbaA+superconducting intermetallic compound phase emerges from the Nb solid solution inside the base line 28, and the base line 28
8 is a superconducting wire.

In addition, in the above heat treatment, since the Nb5Al phase can be precipitated by heating to 600 to 1000 °C, the heat treatment temperature is lower than that in the conventional method, which requires heating to about 1200 °C. be able to.

Therefore, coarsening of Nb1A1 crystal grains can be prevented, and a superconducting wire having a fine crystal structure and good superconducting properties can be manufactured. In addition, the baseline 28
Since the solid solution rod 22 arranged inside the wire has excellent workability, the workability of the base line 28 is also good, and therefore a long superconducting wire can be manufactured.

On the other hand, when manufacturing a superconducting magnet using Nb3Al superconducting wire, the base line 28 with good workability before the heat treatment is wound around the winding drum, and the base line 28 is heat-treated together with the winding drum to form a bond between the Nb5A1 superconducting metals. A superconducting magnet is manufactured by precipitating a compound phase. In this case, the winding drum is 60
Since the Nb3Al phase can be precipitated by heating to 0 to 1000°C, there is no need for the winding drum to be made of a special heat-resistant material, and the winding drum can be made of stainless steel or the like.

Incidentally, in the above embodiment, an example was explained in which the gathering of the strands 26 and the diameter reduction process are performed only once, but the gathering of the strands 26 and the diameter reduction process may be performed multiple times, and the number of strands to be gathered can be set arbitrarily. can be selected.

"Production Example" A small lump of high-purity Al (purity of 99.99% or more) and a small lump of Nb (purity of 99.5% or more) are placed inside a crucible such that the composition is 115% by weight of A and the balance is Nb. It was inserted, melted by induction heating in a vacuum, and cast to create an alloy rod with an outer diameter of 10 mm. (The reason why Al is contained at 15% by weight here is that when the inside of the crucible is heated to the melting temperature of Nb and each small lump is melted, a part of At will evaporate and be damaged. (In order to make the manufactured alloy rod contain a specified amount of Al, the Al content is increased.) The alloy rod thus manufactured contains 18% by weight of A, and the balance has a composition of Nb. As a result of X-ray diffraction analysis, N
The presence of three compound phases, b3Al phase, NbAL phase, and NbA13 phase, was confirmed.

Next, using a vertical tube furnace, in an Ar gas atmosphere, the alloy rod was heated to 1800°C for 10 minutes to turn it into a solid solution, and then immediately put into a Pb-5n solder bath to be rapidly cooled to form a solid solution. It was created. In this rapid cooling process, the cooling rate was approximately 05°C/sec.

After the rapid cooling treatment, a part of the rod was cut out and subjected to X-ray diffraction analysis, and it was possible to observe a diffraction pattern of Nb solid solution and a trace amount of Nb3Al.

Next, the surface of the solid solution rond was subjected to surface treatment by cutting, and finished to an outer diameter of 8 mm. Next, this solid solution rod was made into a material with an outer diameter of 10 mm and an inner diameter of 9 mm, which will become an Al diffusion barrier layer.
Further, a stabilized copper pipe with an outer diameter of 15 mm and an inner diameter of 11' mm was fatigued and subjected to diameter reduction processing to create a wire with a diameter of 1 mm. Nineteen of these strands were assembled and inserted into a pure Cu vibrator, and further diameter-reduced to create a base line with a diameter of 1 mm.

Next, by heating the baseline to 750°C for 10 hours, f'Jb3A+ is precipitated from the Nb solid solution, and Nb
A 5A+ superconducting wire was manufactured.

"Effects of the Invention" As explained above, the present invention makes an alloy rod containing Al and Nb into a solid solution and then rapidly cools it to create a solid solution rod with a single phase of Nb solid solution.
NbzAl-based superconducting wire is manufactured by applying heat treatment to ooo°C to precipitate Nb3Al, and 12
Since the heating temperature can be set lower than in the conventional method, which heated to around 00°C, it is possible to prevent coarsening of Nb3Al crystal grains, which has the effect of producing a superconducting wire with excellent superconducting properties. .

In addition, since the alloy rod is heated to 1700 to 1980°C to undergo solid solution treatment, it is possible to reliably turn the alloy rod into a solid solution, and the alloy rod can be heated to 105°C/
In order to cool at a cooling rate of seconds or more, the solid solution phase generated as described above can be transferred to room temperature to reliably obtain a solid solution rod having a Nb solid solution single phase structure. system superconducting wire can be manufactured.

Furthermore, since the solid solution rod having the Nb solid solution single-phase structure is highly workable, the workability of the rod is improved and diameter reduction processing becomes easy. Therefore, it becomes possible to process a long solid solution rod, and there is an effect that a long Nb5Al-based superconducting wire can be manufactured.

[Brief explanation of the drawing]

FIGS. 1(A) to (G) are for explaining one embodiment of the present invention in the order of steps. FIG. 1(A) is a cross-sectional view of an alloy rod, and FIG. 1(B) is a solid solution treatment. Figure 1 (C) is a cross-sectional view of the rod after cooling, Figure 1 (D) is a cross-sectional view of the composite wire, and Figure 1 (E) is a cross-sectional view showing the assembled state of the composite wire. , Figure 1 (F) is a cross-sectional view of the multi-core composite wire, 1st
Figure (G) is a cross-sectional view of the base line, Figures 2 (A) to (D) show the first example of the conventional method, and Figure 2 (A) is a horizontal cross-sectional view of the composite rod. , Figure 2(B) is a cross-sectional view showing the composite rod after diameter reduction, Figure 2(C) is a cross-sectional view showing the state with the metal tube removed, and Figure 2(D) is a cross-sectional view of the superconducting wire. The top view and Figure 3 show the second example of the conventional method, and Figure 3 (
A) is a cross-sectional view of the composite rod, and FIG. 3(B) is a cross-sectional view of the multicore composite rod. 20... Alloy rod, 21...
Compound layer, 22...Solid solution rod, 23.
...Barrier pipe, 24...Copper pipe,
25...Composite pipe, 26...Element wire,
27...Sheath tube, 28...
・Baseline.

Claims (1)

[Claims] An alloy rod made of a Nb-Al alloy containing 7 to 8.8% by weight of Al and the balance being Nb was prepared, and this alloy rod was heated to a temperature of 1700 to 1980°C to produce Nb.
At the same time as turning into a solid solution, a solid solution rod is created by rapidly cooling at a cooling rate of 10^5°C/second or more, and then this solid solution rod is heated to a temperature of 600 to 1000°C to precipitate Nb_3Al inside the solid solution rod. A method for manufacturing a Nb_3Al-based superconducting wire, characterized by the following.