JPH07254317A - Manufacture of nb3sn superconducting wire - Google Patents

Abstract

PURPOSE:To manufacture a Nb3Sn superconducting wire having high superconducting characteristics with high productivity. CONSTITUTION:A composite wire material 2 having an Nb filament embedded in a Cu-Sn alloy material (bronze material) is drawn into the prescribed length of a composite element wire, while being subjected to an intermediate annealing process. Then, the element wire is subjected to the prescribed heating treatment, and Sn and Nb in the bronze material are made to react to each other, thereby generating a Nb3Sn phase. Regarding this method for manufacturing a Nb3Sn superconducting wire, the intermediate annealing process applied to the composite wire material 2 is continued without any interruption in an electrical heating system 5. As a result, an annealing time is substantially shortened and high productivity is provided, as electric heat is used for the intermediate annealing of the composite material 2 having the Nb filament embedded in the bronze material. Also, an invalid Nb3Sn phase is not generated, because of the short duration of the intermediate annealing process, and an obtainable Nb3Sn superconducting wire has high superconducting characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to N having excellent superconducting properties.
The present invention relates to a method for producing a b ₃ Sn superconducting wire with high productivity.

[0002]

2. Description of the Related Art Nb ₃ Sn-based superconducting wires are manufactured, for example, according to the following steps. Cu-10 with embedded Nb rod
~ 15wt% Sn alloy material (hereinafter referred to as bronze material)
A step of assembling a primary billet by winding an Nb strip or a Ta strip for preventing Sn diffusion around the outer periphery and inserting it into a copper pipe.
The process of drawing the primary billet into a composite wire with a predetermined size, drawing the composite wire into a composite material (usually
Round wire with a diameter of 2 to 5 mmφ, hexagonal wire with opposite side length of 3 to 9 mm, etc., the process of filling a composite material into a copper tube that serves as a stabilizer to assemble a secondary billet, a secondary billet Of drawing the composite wire into a composite wire having a predetermined size, drawing the composite wire into a composite wire having a predetermined size, subjecting the composite wire to a predetermined heat treatment, and Sn and Nb filaments in the bronze material To produce Nb ₃ Sn-based superconducting filaments.

[0003]

In the above-mentioned composite wire rod, when cold drawing is carried out, the bronze material hardens and becomes difficult to work. Therefore, intermediate annealing is inserted during the drawing work to form the bronze material. Need to be softened. Intermediate annealing reduces surface area by 40%
Since the number of times of application is large and the batch method is performed by using an electric furnace, it takes a lot of manpower and time and is inferior in productivity.

Further, since the batch type intermediate annealing using the electric furnace described above is performed under a condition of high temperature and long time, there is a problem that Nb ₃ Sn phase is generated. The Nb ₃ Sn phase generated at this time is called an ineffective Nb ₃ Sn phase and has a low superconducting property, and it is finely broken in the subsequent wire drawing to contribute to the formation of the Nb ₃ Sn superconducting filament in the final heating. Without doing so, it was a cause of deteriorating the characteristics of the obtained superconducting wire.

[0005]

Under the circumstances, the present invention has conducted earnest research on efficiency improvement of intermediate annealing and improvement of superconducting properties, and has found that the object can be achieved by electric heating. Through the progress of research, the present invention was completed. That is, according to the invention of claim 1, a composite wire in which a Nb filament is embedded in a Cu-Sn alloy material is subjected to an intermediate annealing and is stretched to form a composite wire having a predetermined size. Heat treatment is performed to react Sn in the Cu—Sn alloy material with the Nb filament to produce Nb ₃ S.
In a method for producing an Nb ₃ Sn-based superconducting wire that produces an n-phase, the intermediate annealing to be applied to the composite wire is continuously performed by electric heating.

According to a second aspect of the present invention, a composite wire in which Nb filaments are embedded in a Cu-Sn alloy material is subjected to intermediate annealing and stretched at room temperature to form a composite material having a predetermined size. The material is filled into a copper tube that serves as a stabilizing material to form a composite billet, and this composite billet is stretched to form a composite wire rod, and this composite wire rod is stretched at room temperature while undergoing intermediate annealing. With or without a composite wire of dimensions,
This composite wire is subjected to a predetermined heat treatment to react Sn in the Cu—Sn alloy material with the Nb filament to form Nb ₃
In the method for producing an Nb ₃ Sn-based superconducting wire that produces an Sn phase, the intermediate annealing applied to the composite wire is continuously performed by electric heating.

In the inventions of claims 1 and 2, the composite wire is a Cu-Sn alloy material (bronze material).
A wire rod in which a Nb metal rod is embedded in a wire and drawn into a predetermined size, a wire rod in which a large number of composite billets filled in a copper tube having the wire as a stabilizer are drawn into a predetermined size, C
An arbitrary wire rod in which a Nb filament is embedded in a u-Sn alloy material, including a composite of a stabilized copper material in the core portion is also included. The wire diameter of the composite wire is generally a wire diameter that enables wire drawing.

In the inventions of claims 1 and 2, the energization heating is a method of applying a current to the wire to be annealed, and heating the wire itself by Joule heat generated by the electric resistance of the wire. It is possible to anneal for a short time by properly selecting the conditions such as. In the electric heating according to the invention, the amount of electric power Q applied to the composite wire rod (however,
Q = (I × V × t) / C, where I is the conduction current (ampere),
V is voltage (volt), t is energization time (sec), and C is the volume (mm ³ ) of the composite wire material between the electrodes. ] Adversely affects wire drawability after generates the Nb ₃ Sn phase exceeds 5joule / mm ^3, also Nb ₃ Sn phase formed in the intermediate annealing is inferior in superconducting properties, of the resulting superconducting wire characteristics Is reduced. On the other hand, if the applied power amount Q is less than 0.5 joule / mm ³ , the annealing is not sufficiently performed and the wire drawing workability in the subsequent step is deteriorated. Therefore 5joule /
mm ³ ≧ Q ≧ 0.5joule / mm ³ condition, especially 2joule / mm ³
It is preferable to satisfy the condition of ≧ Q ≧ 0.8 joule / mm ³ . It is preferable that the electric heating is performed continuously after the cold drawing process or in the middle of the continuous drawing process. By doing so, the manufacturing time can be greatly reduced to 10 to 30% of the conventional time. The drawing process including the electric heating is usually a wire drawing process.

[0009]

In the present invention, since the intermediate annealing of the composite wire in which the Nb filament is embedded in the bronze material is performed by electric heating, the annealing time and the number of personnel can be reduced and the productivity is excellent. The productivity is further improved by introducing the electric heating continuously after the cold stretching process or in the middle of the continuous stretching process.

Further, according to the present invention, since the intermediate annealing is performed by the electric current heating, the annealing is performed in a very short time, therefore, the Nb ₃ Sn phase is not generated in the intermediate annealing step, and the superconducting property of the obtained Nb ₃ Sn based superconducting wire is obtained. Can be improved.

[0011]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 A bronze rod having an outer diameter of 45.5 mmφ is provided with a plurality of through holes of 7.2 mmφ at equal intervals, Nb wire rods of 7 mmφ are inserted into each of the through holes, and a bronze lid is electron beam welded to the front and rear ends. After vacuum sealing and covering, a HIP process was performed to form a primary billet, and the primary billet was sequentially subjected to hot extrusion and cold drawing to produce a hexagonal wire having an opposite side length of 4 mm. Next, attach a large number of these hexagonal wires to an oxygen-free copper tube (inner diameter 125 mmφ, outer diameter 2
(05 mmφ) was filled with a Ta strip interposed, and a lid made of oxygen-free copper having Ta strips coated on both ends was electron beam welded in a vacuum container to cover the lid. Next, this was hydrostatically compressed and then externally cut to a predetermined size to prepare a secondary billet. This secondary billet was hot extruded to 10.3 mmφ to form a composite wire rod, and this composite wire rod was drawn to form a 0.42 mmφ composite wire. When wire-drawing the composite wire, an electric heating was applied at an area reduction rate of about 40%. Further, a peeling wire was appropriately inserted to remove surface defects.

The electric heating was performed according to the steps shown in FIG. That is, the composite wire 2 supplied from the uncoiler 1
Is drawn through a die 4 in a continuous wire drawing machine 3, and the composite wire rod 2 produced from the wire drawing machine 3 is directly heated by an electric heating machine 5
It was annealed by continuously passing it through and was wound on a coiler 6.
The energizing heater 5 has three electrode wheels 7, 17, 27 and a guide pulley 8 arranged in a zigzag pattern in the vertical direction. The composite wire 2 sequentially contacts the peripheral surfaces of the three electrode wheels 7. Then, the power was received and the electrodes 7 and 17 were electrically heated. It was cooled after electrode wheel 27. A tensile test was performed on the composite wire 2 after the electric heating to examine the annealed state. The results are shown in Table 1 and Table 2.
It was shown to.

[0013]

[Table 1]

[0014]

[Table 2]

As is clear from Tables 1 and 2, the applied power Q in the range of 5 joule / mm ³ ≧ Q ≧ 0.5 joule / mm ³ (No. 1 to 12) is in a good annealed state. there were. Among them, the applied power amount Q within the range of 2 joule / mm ³ ≧ Q ≧ 0.8 joule / mm ³ (Nos. 7 to 9) was particularly excellent. Applied power Q
Exceeding 5 joule / mm ³ (No.13,14,16,17,20,22,2
4,26,28,30), some Nb ₃ Sn phase was generated, and the crystal grains of the bronze material were slightly coarsened, so that the elongation was somewhat reduced. Applied power Q less than 0.5 joule / mm ³ (No.15,18,19,2
1,23,25,27,29) had a rather low tensile strength and elongation, and the annealing was somewhat insufficient.

1.3 ton composite wire from 8mmφ to 0.42mmφ
Up to 10 times of electric heating was applied and wire drawing was performed, but the time required was 7 hours. Since the conventional method of batch-type intermediate annealing using an electric furnace required 64 hours, the method of the present invention significantly reduced the wire drawing time.

Example 2 The 10.3 mmφ composite wire used in Example 1 was wire-drawn to 0.42 mmφ while being annealed by electric heating in the middle. The wire diameter and wire speed for electric heating were the same as in Example 1. The applied power amount Q was set to be the same for all wire diameters. The obtained 0.42 mmφ composite wire was heat treated at 650 ° C for 150 hours to react Sn and Nb filaments in the bronze with N
b ₃ Sn phase to generate and to produce Nb ₃ Sn based superconducting wire. The critical current density Jc of the obtained Nb ₃ Sn based superconducting wire was measured under a magnetic field of 6 T (Tessler). The results are shown in Table 3. The Nb ₃ Sn superconducting wire had a stabilized copper: bronze: Nb cross-sectional area ratio of 5.25: 2.5: 1, a filament diameter of 5.8 μmφ, and a filament number of 12103.

[0018]

[Table 3]

As is clear from Table 3, all of the method products of the present invention (Nos. 31 to 38) subjected to intermediate annealing by electric heating exhibited excellent values of Jc. Above all, the applied power Q is 2.0-
The value of 0.8 joule / mm ³ showed a particularly high value of Jc. No.
No. 31 had a high applied power Q and a slight precipitation of Nb ₃ Sn phase during energization heating, and No. 38 had a low applied power Q and was not sufficiently annealed and had a small amount of Nb filaments broken during wire drawing. In each case, Jc was somewhat lowered.

Example 3 Hot extruded material of the secondary billet produced in Example 1 (10.3 mm
(φ) was cold drawn to 8 mmφ, and then continuously drawn to 0.42 mmφ. 10 online heating processes during wire drawing
I put it in. For comparison, intermediate annealing was performed batchwise in an electric furnace to produce a 0.42 mmφ material. The batch-type intermediate annealing was performed with the same wire diameter as in the case of electric heating. The obtained 0.42 mmφ material was heat-treated at 630 ° C. for 100 hours to react and generate a Nb ₃ Sn superconductor phase. The critical current density (Jc) of the obtained superconducting wire was measured under a magnetic field of 12T. The results are shown in Table 4.
It was shown to.

[0021]

[Table 4]

As is clear from Table 4, the product of the present invention (N
o.39 to 50) all showed high values of Jc. Of these, No. 49 has a large amount of heating power Q and is ineffective Nb ₃ Sn
Since the phase was precipitated in a small amount, and in No. 50, the Q was small and the annealing was slightly insufficient, the wire drawability was slightly deteriorated, and defects were generated although they were fine. On the other hand, the one annealed batchwise in an electric furnace has an ineffective Nb
_{Since a} large amount of ₃ Sn phase was generated, the Jc of the obtained Nb ₃ Sn based superconducting wire was significantly reduced.

The case where the composite wire of the secondary billet is heated by electric current has been described above. However, even if the present invention is applied to the intermediate annealing of the composite wire of the primary billet, the superconducting wire of another system such as Nb ₃ Al can be used. Similar effects can be obtained even when applied during manufacturing.

[0024]

[Effect] As described above, according to the method for producing a Nb ₃ Sn superconducting wire of the present invention, since the intermediate annealing of the composite wire material in which the Nb filament is embedded in the bronze material is performed by the electric current heating, the productivity and the superconducting characteristics are improved. Excellent and has a remarkable industrial effect.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a wire drawing process and an electric heating process in a method of the present invention.

[Explanation of symbols]

 1 Uncoiler 2 Composite wire 3 Continuous wire drawing machine 4 Die 5 Electric heating machine 6 Coiler 717,27 Electrode wheel 8 Guide pulley

Claims (4)

[Claims] 1. A composite wire in which Nb filaments are embedded in a Cu—Sn alloy material is subjected to intermediate annealing and stretched at room temperature to form a composite wire having a predetermined size. subjected to heat treatment, in the manufacturing method of the Nb ₃ Sn based superconducting wire by reacting Sn and Nb filaments of the Cu-Sn-based alloy material in to produce Nb ₃ Sn phase, by electrically heating the intermediate annealing applied to the composite wire A method for producing an Nb ₃ Sn-based superconducting wire, which is characterized in that it is continuously performed. 2. A composite wire in which a Nb filament is embedded in a Cu—Sn alloy material is subjected to intermediate annealing and stretched at room temperature to form a composite material having a predetermined size, and the composite material is used as a stabilizer. It is filled into an eggplant copper tube to form a composite billet, and this composite billet is drawn to form a composite wire rod.This composite wire rod is subjected to intermediate annealing and drawn at room temperature to form a composite wire with a predetermined size. None, by subjecting this composite wire to a predetermined heat treatment, Sn and N in the Cu-Sn alloy material
b and filaments was reacted in the method for manufacturing a Nb ₃ Sn based superconducting wire to produce Nb ₃ Sn phase, the Nb ₃ Sn based superconducting wire which is characterized in that the intermediate annealing is subjected to a composite wire continuously energized heating Production method. 3. The amount of electric power Q applied to the composite wire material by electric heating
Is the following equation, 5joule / mm ³ ≧ Q ≧ 0.5joule / mm ³ [however,
Q = (I × V × t) / C, where I is the conduction current (ampere),
V is the voltage (volt), t is the energization time (sec), and C is the volume (mm ³ ) of the composite wire between the electrodes. The method according to claim 1 or claim 2 Nb ₃ Sn based superconducting wire according to, characterized by satisfying the]. 4. The method for producing an Nb ₃ Sn-based superconducting wire according to claim 1, wherein energization heating is performed continuously after the drawing process or during the continuous drawing process.