JP3454550B2 - Method for producing Nb3Sn superconducting wire - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to Nb which is excellent in superconducting properties.
_{3 It} relates to a method for manufacturing a Sn superconducting wire.

[0002]

2. Description of the Related Art A Nb ₃ Sn superconducting wire has a low tin concentration bronze material 2 in which a large number of Nb ₃ Sn superconducting filaments 1 are embedded, as shown in the sectional view of FIG.
The layer 3 is compounded with the Ta layer 4 interposed. In manufacturing such Nb ₃ Sn superconducting wire, since the Nb ₃ Sn superconductor is brittle and difficult to process, for example, a Ta tube is filled with a large number of bronze materials in which Nb wire is embedded, and the outer circumference of the Ta tube is surrounded. After forming a composite billet by compounding a copper tube with a stabilizing material, the composite billet is drawn into a superconducting wire rod having a predetermined shape, and the wire rod is subjected to a predetermined heat treatment to obtain N.
b ₃ Sn phase is generated. When the superconducting wire is used as a twisted wire or a winding wire, the superconducting wire material is processed into a twisted wire or a winding wire and then subjected to heat treatment.

As shown in the sectional view of FIG. 2, the above-mentioned composite billet has a Ta tube 7 filled with a large number of hexagonal bronze wire rods 6 having Nb wires 5 embedded therein. A Cu tube 8 serving as a stabilizing material is compounded around the outer periphery of the. A copper wire having a Nb wire and a tin wire embedded therein is also applied to the wire filled in the Ta tube. As shown in FIG. 3, this copper wire has a thick Sn wire 10 embedded in the center of the Cu wire 9 and a large number of Nb wires 5 embedded in the peripheral portion of the Cu wire 9. . The role of the Ta tube in the composite billet is to prevent the Sn in the bronze material from diffusing into the outer copper tube during the annealing process during the drawing process or the heat treatment for forming the Nb ₃ Sn phase. It will be. When the Sn content in the bronze material decreases, the amount of Nb ₃ Sn phase produced in the final heat treatment decreases, leading to deterioration in characteristics.
Further, the electric resistance of the copper tube used as the stabilizing material at a low temperature is increased, and the stabilizing action is reduced. In order to interpose this Ta material, a method of winding a Ta strip around a bundle of bronze wire embedded with Nb wire has been used easily and often, but the overlapping portion of the Ta strip slips during the drawing process. There is a problem that the processed material deforms abnormally and causes a disconnection in the subsequent wire drawing.

[0004]

Therefore, a method using a Ta tube has been proposed. The Ta tube is manufactured by an extrusion method or a method of punching a Ta rod and striking a meat portion with a swager to reduce the wall thickness. Because it was expensive. Further, the Nb ₃ Sn superconducting wire using the Ta material for diffusion prevention has a problem that the superconducting characteristics vary from lot to lot.

[0005]

In view of such a situation, the present invention has investigated various methods for manufacturing Ta tubes and investigated in detail the factors of the characteristic fluctuation of the obtained superconducting wire. Regarding the latter characteristic fluctuation, it was determined that the Ta layer was thinned and broken by wire drawing, and the Sn diffusion preventing effect could not be fulfilled, and further research was conducted to complete the present invention. I arrived.

That is, according to the present invention, a composite billet that can be an Nb ₃ Sn superconducting wire is drawn into a composite wire having a predetermined shape, and then this composite wire is subjected to a predetermined heat treatment to obtain Nb ₃
In a method for manufacturing an Nb ₃ Sn superconducting wire that forms an Sn phase, a Ta tube for diffusion prevention that constitutes a composite billet is formed by using a welded tube in which a Ta strip is rolled into a tubular shape and an edge portion is welded.
A method for manufacturing an Nb3Sn superconducting wire, characterized in that the cross-sectional area ratio of the tube to the composite billet is ₃ to 15%.

The Ta tube used in the present invention is manufactured by rolling a Ta strip into a cylindrical shape with a forming roll, abutting the edge portions, and welding the abutting portions. This manufacturing method has excellent productivity and inexpensive processing equipment. In the present invention, the sectional area ratio of the Ta tube to the composite billet is 3 to 15
The reason for limiting to 10% is that when the cross-sectional area ratio of the Ta layer is less than 3%, the Ta layer breaks during wire drawing, and when the cross-sectional area ratio exceeds 15%, the occupancy of the superconductor is relatively increased. This is because the product rate decreases and the superconducting characteristics such as Jc deteriorate.

In the present invention, the composite billet that can be an Nb ₃ Sn superconducting wire includes a large number of bronze wire rods embedded with Nb wire or a large number of copper wire rods embedded with Nb wire and tin wire (FIG. 3). A composite billet or the like in which a Ta tube is filled with a book and a copper tube serving as a stabilizer is compounded is applied to the outer circumference of the Ta tube.

[0009]

In the method of manufacturing the Nb ₃ Sn superconducting wire of the present invention,
A Ta tube produced by an inexpensive welding method is interposed between a bronze wire rod having Nb wire embedded therein and a copper tube of the composite billet, and the sectional area ratio of the Ta tube to the composite billet is 3 to 15%.
Since it is limited to the above range, the breakage of the Ta layer during wire drawing can be prevented, the space factor of the superconductor can be maintained at a high level, and a superconducting wire with excellent characteristics such as Jc and stability can be manufactured at low cost. it can.

[0010]

EXAMPLES The present invention will be described in detail below with reference to examples. A hexagonal bronze wire (Cu-14% Sn-0.2% Ti alloy, with one Nb wire embedded in a Ta welded pipe with an inner diameter of 110 mmφ,
1540 pieces of the opposite side (3 mm) were filled, and this was inserted into an oxygen-free copper tube. Oxygen-free copper lids were attached to both ends of the oxygen-free copper tube, Ta lines were attached to the inner surfaces, and electron beam welding was performed in a vacuum container.
Next, this was subjected to HIP (hot isostatic pressing) treatment and externally cut to obtain a composite billet. The wall thickness of the Ta tube was variously changed. The outer diameter of the oxygen-free copper tube was changed according to the wall thickness of the Ta tube so that the copper ratio was 1.5. Then heat the composite billet to 50
Extruded into a rod with a diameter of mmφ and wire-drawing this rod to 0.7 mmφ
It was made into a composite wire rod. In the wire drawing, annealing was performed at 500 ° C for 2 hours for each 50% reduction in area. Then, this composite wire is heat-treated at 650 ° C for 150 hours to obtain Nb and S in bronze.
and n are reacted yielding Nb ₃ Sn phase Nb ₃ Sn
It is a multi-core superconducting wire. Ten samples were taken every 2500m from the 0.7mmφ superconducting wire, and the magnetic field strength was 12T, 4.2K.
Jc was measured under the conditions of. The residual resistance ratio of the stabilized copper was measured under the condition of 0T. The results are shown in Table 1.

[0011]

[Table 1] # Cross-sectional area ratio of Ta tube in composite billet, * per total cross-sectional area of superconducting wire.

As is clear from Table 1, the product of the present invention (N
All of o.1 to 5) showed high values of Jc and RRR.
On the other hand, the comparative products (No. 6 to 7) are all Jc and RR.
R has decreased. The reason for the decrease in Jc is that the space factor of the Ta pipe is low, so the wall thickness of the Ta pipe becomes thin during wire drawing, causing local fracture, and during annealing during wire drawing or the final Nb ₃ Sn phase. During the heat treatment for formation, S
This is because n diffused and disappeared in the oxygen-free copper pipe on the outer periphery, and as a result, the amount of Nb ₃ Sn phase produced in the heat treatment step decreased. Further, the reason why the RRR of the stabilized copper is lowered is that Sn in the bronze diffuses into the stabilized copper.

As described above, in the case where a Ta tube is filled with a large number of bronze wire rods in which Nb wires are embedded in the composite billet, and a composite billet in which a copper tube serving as a stabilizing material is compounded is used around the Ta tube. Although described, the same effect can be obtained in the case of a composite billet using a copper wire material in which Nb wire and Sn wire are embedded instead of the bronze wire.

[0014]

As described above, in the present invention, the Sn diffusion preventing Ta tube of the composite billet is made of an inexpensive welded tube, and
Since the space factor of the a-tube is 3 to 15%, Ta does not break during wire drawing and the conductive area is secured, so that the Nb ₃ Sn superconducting wire having excellent characteristics can be manufactured at low cost, Has a remarkable effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an aspect of a Nb ₃ Sn superconducting wire.

FIG. 2 is a cross-sectional view showing an aspect of a composite billet.

FIG. 3 is a transverse cross-sectional view showing a mode of a copper wire material in which Nb wires and Sn wires are embedded.

[Explanation of symbols]

1 Nb ₃ Sn Superconducting Filament 2 Low Tin Concentration Bronze Material 3 Cu Layer 4 Ta Layer 5 Nb Wire 6 Bronze Wire Material 7 Ta Tube 8 Cu Tube 9 Cu Wire Material 10 Sn Wire

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-159106 (JP, A) JP-A-56-112016 (JP, A) JP-A-63-218106 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01B 12/00-13/00

Claims (2)

(57) [Claims] [Claim 1] After stretching the composite billet can be made with the Nb ₃ Sn superconducting wire in composite wire having a predetermined shape, Nb ₃ Sn superconducting wire to form the Nb ₃ Sn phase is subjected to predetermined heat treatment to the composite wire In the manufacturing method of 1., a Ta pipe for diffusion prevention constituting a composite billet is formed by using a welded pipe in which a Ta strip is rolled into a tubular shape and an edge portion is welded, and a sectional area ratio of the Ta pipe in the composite billet is 3 to 15%. A method of manufacturing an Nb ₃ Sn superconducting wire, characterized in that 2. A composite billet, which can be an Nb ₃ Sn superconducting wire, has a Ta tube filled with a large number of bronze wires embedded with Nb wires or a large number of copper wires embedded with Nb wires and tin wires. 2. The N according to claim 1, which is a composite billet in which a copper tube serving as a stabilizing material is compounded on the outer circumference of the Ta tube.
b ₃ Sn superconducting wire manufacturing method.