JP3108496B2 - Superconducting wire manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting N
The present invention relates to a method for manufacturing a b ₃ Sn superconducting wire.

[0002]

2. Description of the Related Art In the production of Nb ₃ Sn superconducting wires,
Since the Nb ₃ Sn compound is brittle, a production method based on forming an Nb ₃ Sn phase in the final step, for example, a composite processing method, an internal Sn method, a tube method, and the like have been developed.

[0003] Among the above-mentioned processing methods, in the composite processing method, first, as shown in FIG. 1A, a through hole is formed in a billet 1 made of a Cu-Sn alloy, and a bar 2 made of Nb is inserted into the through hole. The composite billet 3 is inserted to form a composite billet 3, and then the composite billet 3 is subjected to elongation to produce a composite wire 5. At this time, as shown in FIG. 1B, the cross section of the composite wire 5 is covered with a bronze layer 4 made of a Cu—Sn-based alloy around the Nb bar 2. Finally, this composite wire 5
To the Sn in the bronze layer 4 with Nb
By diffusing into the bar 2, the bronze layer 4 and Nb
An Nb ₃ Sn phase 6 is generated at the interface of the bar 2 to obtain an Nb ₃ Sn superconducting wire 7 as shown in FIG. 1C. The superconducting wire obtained by this method is electromagnetically stable because the Nb ₃ Sn phase is compounded in the bronze layer. Therefore, this superconducting wire has an advantage that it can be rapidly excited, and is widely used in practice.

[0004]

However, the amount of Sn in the Cu—Sn based alloy billet used in the above-mentioned combined working method is an amount within the range of solid solution in Cu in consideration of workability, that is, 15%. 0.0% by weight or less, and as a result, there is a problem that the Nb ₃ Sn phase to be formed is limited in quantity and a high value of superconductivity such as critical current density (Jc) cannot be obtained. Was.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method of manufacturing an Nb ₃ Sn superconducting wire capable of efficiently obtaining an Nb ₃ Sn superconducting wire exhibiting higher superconducting characteristics. And

[0006]

Means for Solving the Problems The present inventors have proposed Cu-S
After hot-working the n-based alloy, by performing elongation while dividing the intermetallic compound in the Cu-Sn-based alloy into smaller pieces, Cu-containing Cu in an amount exceeding the solid solution limit is obtained.
The inventor has found that the composite wire has sufficient deformability even with the use of the Sn-based alloy, and has further studied to complete the present invention.

That is, according to the present invention, a composite billet is prepared by compounding a desired number of bars made of Nb or Nb alloy in a matrix of a Cu—Sn alloy, and then the composite billet is subjected to elongation processing to form a composite billet. After getting the wire,
The method of manufacturing a composite wire subjected to a predetermined heat treatment to Nb ₃ Sn superconducting wire, the Cu-Sn-based alloy 15.
Contains 1 to 24.6% by weight of Sn, and the elongation is performed by repeating cold reduction processing or warm reduction processing after hot working, and annealing treatment in the Cu-Sn based alloy. A process for producing an Nb ₃ Sn superconducting wire, characterized in that the process is performed while dividing the intermetallic compound into smaller pieces.

[0008] The present invention also provides a composite billet by compounding a desired number of bars made of Nb or Nb alloy in a matrix of a Cu-Sn alloy to produce a composite billet, and then subjecting the composite billet to elongation processing. A wire rod is obtained, a large number of the composite wire rods are inserted into a pipe made of Cu or a Cu alloy to be composited to produce a multi-core composite billet, and then the multi-core composite billet is subjected to elongation processing to obtain a multi-core composite billet. A method for producing an Nb ₃ Sn superconducting wire in which a composite wire is obtained and then a predetermined heat treatment is performed on the multi-core composite wire, wherein the Cu-S
The n-based alloy contains 15.1 to 24.6% by weight of Sn, and the elongation is performed by repeating cold reduction processing or warm reduction processing and annealing after hot working.
to provide a method of manufacturing a Nb ₃ Sn superconducting wire, characterized in that the processing performed while divided smaller intermetallic compound of u-Sn-based alloy.

In the method of the present invention, the Cu—Sn based alloy serving as the matrix contains 15.1% by weight of Sn to 24.
In addition to the Cu-Sn binary alloy containing 6% by weight, an alloy containing about 0.1% to 0.4% by weight of Ti in this binary alloy is used. Further, as the Nb alloy of the rod-shaped Nb or Nb alloy compounded in the matrix, Nb − containing about 7.5% by weight of Ta is used.
A Ta-based alloy or the like is used.

In the method of the present invention, Cu-Sn
A composite billet in which a bar material made of Nb is compounded in a system alloy matrix is hot worked by a method such as extrusion or rolling, and then cold worked into a composite wire having a predetermined shape by a working method such as rolling, swaging or drawing. Is done. Note that the warm working means working at a temperature lower than the recrystallization temperature, and working at 350 ° C. or more is preferable. Further, the cold working is not necessarily limited to the working at room temperature, and may be carried out while slightly heating.

The hot working temperature for the above-mentioned extrusion, rolling, etc. is N
To prevent precipitation of b ₃ Sn phase, it is necessary to suppress the low and 700 to 750 ° C.. In addition, cold working such as drawing,
The area reduction rate is set to 40% or less, and preferably, the intermediate annealing treatment at 500 to 650 ° C. is performed every time processing is performed to 10 to 20%. If the area reduction ratio exceeds 40%, cold working becomes difficult. Further, if the intermediate annealing temperature is lower than 500 ° C., the material does not soften, and if the intermediate annealing temperature exceeds 650 ° C., N
This is because b ₃ Sn is generated. The intermediate annealing time is preferably 30 minutes to 3 hours.

The composite wire thus obtained is
By performing heat treatment for a long time at a high temperature of about
Diffusion reaction between Sn and Nb in the Sn-based alloy causes Nb ₃ Sn
A phase is formed to form an Nb ₃ Sn superconducting wire.

In the method of the present invention, the amount of Sn in the Cu—Sn alloy serving as the matrix is adjusted to 15.1% by weight to 2%.
The reason for limiting to the range of 4.6% by weight is that the amount of Sn is 15.
If it is less than 1% by weight, the amount of the Nb ₃ Sn phase generated by the heat treatment is not sufficient, and the superconducting properties such as Jc (critical current density) are not improved. If it exceeds 24.6% by weight, Cu—S
This is because the workability of the n-type alloy is reduced, and defects such as cracks occur in the bronze layer during the elongation process.

In the method of the present invention, the multifilament superconducting composite billet is manufactured by placing an Nb or Ta barrier in a pure Cu pipe and filling the superconducting element wire therein. The method of extending the multifilament superconducting composite billet into a multifilament composite wire and the heat treatment method applied to the composite wire are as described above.

According to the present invention, Cu serving as a source of Sn
Since the amount of Sn in the -Sn-based alloy, that is, the bronze layer is large, the Cu-Sn-based alloy is in a state in which the δ phase is precipitated in the α phase. This precipitate is Nb _{3 in the} last heat treatment step.
Since Sn is formed, it diffuses and disappears.

[0016]

According to the present invention, cold working or warm working and annealing are repeated after hot working so that the intermetallic compound phase (δ phase) in the Cu—Sn alloy is divided into smaller pieces. . That is, the metal compound phase is split by cold working, and a new interface is formed between the metal compound phase and the α phase. In the vicinity of the new interface of the α phase, since Sn in the α phase is less than the solid solution limit, Sn diffuses from the metal compound phase to the α phase, and the metal compound phase becomes smaller by that amount, and both phases become Join each other. Therefore, the metal compound phase is divided into smaller portions in combination with the division of the metal compound phase by cold working.

For this reason, Sn in the Cu—Sn alloy of the composite billet composed of the Cu—Sn alloy material and the Nb bar is used.
Even when the content is as large as 15.1% to 24.6% by weight, the composite billet can be subjected to elongation processing. Thereafter, by subjecting the obtained composite wire to heat treatment at a predetermined temperature, a large amount of Nb ₃ Sn phase is generated. Therefore,
An Nb ₃ Sn superconducting wire having higher superconducting properties such as Jc can be obtained.

[0018]

The present invention will be described below in detail with reference to examples.

Example 1 Cu-containing 15% by weight of Sn and 0.2% by weight of Ti
The Sn-based alloy is melted in vacuum, cast into a mold to form an ingot, and the ingot is externally cut to remove the Sn-rich layer, and then subjected to HIP treatment to blow holes and shrinkage inside the ingot. The nest was extinguished to form a billet having an outer diameter of 60 mmφ. Next, a through-hole having a diameter of 30 mm was formed in the center of the billet, and a bar made of Nb-7.5 wt% Ta-based alloy was inserted into the through-hole. Before insertion, a single layer of oxygen-free copper tape having a thickness of 0.5 mm was wrapped around the bar. Next, a lid made of oxygen-free copper at one end of the billet,
The other end was covered with a lid made of the same material as that of the billet, evacuated and evacuated, and then each of the lids was sealed by welding with an electron beam to produce a composite billet. Thereafter, the composite billet was extruded from the end of the oxygen-free copper lid to produce a rod having an outer diameter of 14 mmφ. The extrusion temperature was 7
The extrusion die was 30 ° C., and the taper angle was 60 degrees.

After extrusion, the structure of the outermost bronze layer was examined. As a result, although the δ phase was elongated in the extrusion direction and dispersed, no defects such as cracks were observed.

Next, the extruded rod material was subjected to cold groove roll rolling to form a superconducting hexagonal wire having a distance between opposing sides of 2 mm. In addition, the above-mentioned cold working has a reduction in area of 4%.
Each time the 0% processing was performed, it was performed while performing an intermediate annealing treatment at 600 ° C. to 650 ° C. × 1 Hr. Observation of the inside of the superconducting wire revealed that Sn was diffused on the bronze side of the oxygen-free copper tape interposed between the bronze layer and the Nb rod. However, no Nb ₃ Sn phase was confirmed on the Nb surface.

The superconducting hexagonal element wire thus produced was treated with a Cu-14 wt% S having an outer diameter of 230 mm and an inner diameter of 200 mm.
By inserting 5,000 pieces into an n-type alloy pipe, a multi-core composite billet was produced. In the center of the pipe, an oxygen-free copper rod as a stabilizing material was placed in a barrier Nb pipe having an outer diameter of 50 mm and an inner diameter of 46 mm.

Next, the composite billet is subjected to hot extrusion at 650 ° C. to form an extruded material having an outer diameter of 60 mmφ. Then, the extruded material is formed at a temperature of 500 to 550 ° C. × 1H for every 15% reduction in area.
While the intermediate annealing process of r is performed, a multi-core composite wire having an outer diameter of 0.7 mm is formed by swaging and wire drawing. Finally, a heat treatment at 700 ° C. × 48 hr is performed to convert Sn to Nb.
The multi-core Nb ₃ Sn superconducting wire of Example 1 was manufactured.

Examples 2 and 3 The multi-core Nb ₃ Sn superconducting wires of Examples 2 and 3 were prepared in the same manner as in Example 1 except that a Cu—Sn-based alloy containing the amount of Sn shown in Table 1 below was used. Was manufactured. In addition, about the sample whose Sn content is 24 weight%, it heated at 400 degreeC at the time of groove | channel roll rolling and wire drawing, and was drawn by graphite lubrication. At this time, the intermediate annealing treatment was unnecessary.

Comparative Example 1 S in the Cu-Sn alloy of the billet made of the Cu-Sn alloy
A multi-core Nb ₃ Sn superconducting wire of a comparative example was manufactured in the same manner as in Example 1 except that the content of n was set to 14% by weight.

Each of the Nb ₃ Sn superconducting wires obtained in Examples 1 to 3 and Comparative Example 1 obtained in this manner was
Jc was measured under a magnetic field of 12 Tesla. The results are shown in Table 1 below.

[0027]

[Table 1] Table 1 As is apparent, Nb ₃ Sn superconducting wire obtained by the method of the present invention (Examples 1-3) were of Jc high value. Jc showed a higher value for a billet made of a Cu-Sn alloy, that is, for a bronze layer containing a larger amount of Sn, and for a HIP-treated one in the final step.

On the other hand, N obtained by the conventional method
b ₃ Sn superconducting wire (Comparative Example 1), since a small amount of Sn in the bronze layer less the amount of Nb ₃ Sn phase, Jc was intended much lower.

Examples 5-7 Cu-Sn based alloys containing 16.3% by weight, 18.3% by weight, and 20.3% by weight of Sn were respectively melted to obtain ingots. Examination of the structures of these ingots confirmed that all of them had an α phase and a δ phase. These ingots were subjected to the same processing and processing as in Example 1 to produce respective composite billets, and further subjected to hot extrusion to produce rods having an outer diameter of 14 mmφ. At this time, when the structure of the bronze layer was examined, it was found that all of the δ phase was fibrous in the extrusion direction.

Next, the extruded rod material was subjected to cold groove roll rolling to form a superconducting hexagonal wire having a distance between opposing sides of 2 mm. The cold working is performed at a working temperature and a surface reduction rate shown in Table 2 below.
This was performed while an intermediate annealing treatment at 1 ° C. × 1 hr was performed. At this time, the δ phase is stretched in the extrusion direction by hot working, the amount of Sn is brought into equilibrium at the interface with the newly formed α phase at the time of annealing, and they are joined together. Together, they are divided into smaller pieces.

Using the superconducting hexagonal wires thus produced, multifilamentary Nb ₃ Sn superconducting wires of Examples 5 to 7 were produced in the same manner as in Example 1. Example 7
As for (Sn content: 20.3% by weight), cold working could not be performed at room temperature.

Comparative Examples 2 and 3 The multi-core Nb ₃ of Comparative Examples 2 and 3 was prepared in the same manner as in Examples 5 to 7, except that the Sn content was 14.3% by weight and 25.0% by weight, respectively. A Sn superconducting wire was manufactured. In addition,
In Comparative Example 3, since the content of Sn in the Cu-Sn-based alloy was too large, processing could not be performed even at a cold processing temperature of 400 ° C.

Each of the Nb ₃ Sn superconducting wires obtained in Examples 5 to 7 and Comparative Example 2 obtained as described above was
Jc was measured under a magnetic field of 12 Tesla. The results are shown in Table 2 below.

[0034]

[Table 2] Table 2 As apparent from, Nb ₃ Sn superconducting wire obtained by the method of the present invention (Examples 5-7) were of Jc high value.

On the other hand, N obtained by the conventional method
b ₃ Sn superconducting wire (Comparative Example 2), since a small amount of Sn in the bronze layer less the amount of Nb ₃ Sn phase was achieved, Jc is low. Further, those using a Cu-Sn-based alloy containing Sn outside the scope of the present invention (Comparative Example 3)
Could not be processed because the content of was too large.

[0036]

As described above, according to the method of the present invention,
Nb ₃ Sn superconducting wire having excellent superconducting properties such as Jc is obtained, it exhibits the industrially remarkable effects.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional perspective views for explaining a process of manufacturing an Nb ₃ Sn superconducting wire.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Billet made of Cu-Sn alloy, 2 ... Bar made of Nb, 3
... composite billet, 4 ... bronze layer, 5 ... composite wire, 6 ...
Nb ₃ Sn phase, 7 ... Nb ₃ Sn superconducting wire.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kyota Susai 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (56) References JP-A-61-264164 (JP, A) 2-112113 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01B 12/00-13/00 C22F 1/00

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein Nb is contained in a matrix of a Cu--Sn alloy.
Or bar member made of Nb alloy to prepare a desired number of composite to composite billet, then said to the composite billet is subjected to distraction process to obtain a composite wire, then, Nb ₃ for performing predetermined heat treatment to the composite wire In the method for manufacturing a Sn superconducting wire, the Cu-Sn-based alloy contains 15.1 to 24.6% by weight of Sn, and the elongation is performed by cold reduction of 40% or less after hot working. And annealing treatment at 500 to 650 ° C. was repeated to obtain Cu— in the Cu—Sn alloy.
Nb 3 _Sn method of manufacturing a superconducting wire, characterized in that the processing performed while divided smaller Sn based intermetallic compound. 2. The method according to claim 1, wherein Nb is contained in a matrix of a Cu—Sn alloy.
Alternatively, a composite billet is prepared by compounding a desired number of bars made of an Nb alloy, and then the composite billet is subjected to elongation processing to obtain a composite wire.
Or, it is inserted into a pipe made of a Cu alloy and composited to produce a multi-core composite billet, and then the multi-core composite billet is subjected to elongation to obtain a multi-core composite wire, and thereafter, the multi-core composite wire is In the method for producing a Nb ₃ Sn superconducting wire in which a predetermined heat treatment is performed on the Cu—Sn based alloy,
The steel contains 5.1 to 24.6% by weight of Sn. In the elongation, after the hot working, a cold area reduction process of 40% or less and an annealing process at 500 to 650 ° C. are repeated to obtain the Cu-
Nb characterized by being a process performed while dividing the Cu-Sn-based intermetallic compound in the Sn-based alloy into smaller pieces.
_{3. A} method for producing a Sn superconducting wire.