JPH01183102A - Manufacture of superconducting oxide coil - Google Patents

Abstract

PURPOSE:To increase the critical current density, by forming a wire rod into a coil shape through application of a pressure to obtain a specified area- reduction factor. CONSTITUTION:Wire rod 4 is obtained by filling and sealing superconducting oxide powder in a pipe made of metal or an alloy, and then by extending or rolling the pipe. After that, the wire rod 4 is formed into a coil shape, drafting the wire rod 4 by an area reduction factor of more than {100(d/2D)+3} with a pair of rolls 2, 3 with grooves whose peripheral speeds are different from each other. In the equation, D is the coil diameter prescribed by the central axis of the wire rod 5 which has gone out of the rolls 2, 3, and (d) is the diameter of the part which the superconducting oxide occupies in the wire rod 5. This prevents the superconducting oxide of the coil periphery from cracking after the formation. Accordingly, the cutting of a path having superconductivity can be avoided, and the critical current density can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a superconducting oxide coil for manufacturing a superconducting coil used in a superconducting magnet or the like.

[Prior Art] Conventionally, as a method for manufacturing a superconducting coil using a superconducting oxide, powder of a superconducting oxide such as YBa2 Cu30 fu δ is filled and sealed in a silver vibrator, and then a wire drawing machine or a swaging machine is used. There is a wire drawing method used to reduce the diameter. During this diameter-reducing wire drawing process, the superconducting oxide powder filled and sealed in the silver pipe is simultaneously compressed, increasing its density and improving the bond between the powders. Next, the drawn wire is wound around a mandrel of a predetermined diameter and formed into a coil of a predetermined diameter.

[Problem to be solved by the invention] However, when a silver sheath-coated superconducting oxide wire that has been drawn to reduce its diameter and has an increased density is wound around a mandrel and formed into a coil of a predetermined diameter, a tensile force is generated on the outer periphery of the coil. This causes cracks to form in the powder compact of ceramic oxide, which has low ductility.

For this reason, there is a problem in that a path exhibiting superconductivity is cut off, resulting in a decrease in critical current density.

The present invention has been made in view of such problems, and includes:
An object of the present invention is to provide a method for manufacturing a superconducting oxide coil that can manufacture a superconducting oxide coil having a high critical current density.

[Means for Solving the Problems] The method for manufacturing a superconducting oxide coil according to the present invention includes a step of filling and enclosing superconducting oxide powder in a metal or alloy pipe, and a step of drawing or rolling it. In the process of obtaining the wire rod, a pair of grooved rolls with mutually different circumferential speeds (100 (d
/2D)+3)% or more of reduction in area while forming the wire into a coil shape.

[Function] In the present invention, the wire rod is formed into a coil shape while applying reduction at a predetermined area reduction rate, so that deformation strain due to rolling and bending strain due to bending deformation are simultaneously applied to the wire rod.

Therefore, even if a crack is generated in the green compact due to bending deformation, the superconducting oxide powder is moved and replenished by rolling deformation, so that the wire can be bent and deformed without cracking.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a front view showing an embodiment of the method of the present invention, and FIG. 2 is a side view seen from the direction of arrow 1 in FIG.

A pair of grooved rolls 2 and 3 are installed with their rotating shafts 6 horizontal. The grooved roll 2 has a larger diameter than the grooved roll 3, and the grooved rolls 2.3 are placed opposite each other with an appropriate distance between them, with their rotating shafts 6 parallel to each other, and rotate at the same time. It is designed to be rotationally driven at a speed (rpm). Therefore, the circumferential speed of the grooved roll 2 is greater than the circumferential speed of the grooved roll 3.

A superconducting oxide wire 4 coated with a metal sheath is fed between the grooved rolls 2 and 3.

The wire 4 is, for example, a silver pipe filled with superconducting oxide powder and encapsulated, and then wire-drawn to reduce its diameter. This diameter reduction compresses the superconducting oxide powder inside, increasing its density. Note that the superconducting oxide powder may be compressed by rolling instead of wire drawing.

This wire rod 4 is rolled by grooved rolls 2 and 3. Then, the wire rod 4 is rolled by the grooved rolls 2 and 3 to reduce its diameter and undergoes bending deformation.

Since the grooved roll 2 has a larger diameter than the grooved roll 3, when the shaft 6 rotates at the same rotation speed, the peripheral speed of the larger diameter roll 2 is higher, so the wire 4 has a larger diameter on the roll 2 side. On the other hand, the small diameter roll 3 side undergoes small processing deformation.

Therefore, the deformed wire 5 that comes out from between the rolls 2 and 3 is
The wire rod 5 is subjected to a rolling process in which it is largely stretched on the large-diameter roll 2 side, and the wire 5 is bent and formed into a coil shape with the side rolled by the large-diameter roll 2 being the outer peripheral side.

As described above, in this embodiment, the wire rod 4 (or 5) is formed into a coil shape while being rolled by the rolls 2 and 3, so that the deformation strain due to rolling and the bending strain due to bending deformation are applied at the same time. Even if cracks are to occur in the superconducting oxide compact due to bending deformation, the superconducting oxide material moves and is replenished by rolling deformation, so that cracks are prevented from occurring.

In addition, it is preferable that the thickness of the rolls 2 and 3 (length in the roll axis direction) be close to the diameter of the wire rod 4, and that the thickness of the portion other than the semicircular groove portion is not thick. The wire 4 comes out in a plane perpendicular to the rotational axes of the rolls 2 and 3, that is, in a straight direction from the caught rolls 2 and 3, and tries to curve into a coil shape. In this case, if the roll 2.3 is thick, this wire 4
A force is applied in a direction equal to the thickness of the rolls 2 and 3, that is, in the axial direction of the rolls 2 and 3. the result,
This is because some bending stress will be applied to the wire 4, which is not preferable. On the other hand, for example, if the incident direction of the wire 4 on the inlet side is shifted and a process is performed that involves bending to change the roll thickness in advance, the pitch of the coil will become longer, resulting in poor magnetic efficiency in applications such as magnets. Undesirable.

When forming the wire 4 into a coil, the wire 4 is reduced in diameter by an area reduction rate of (100(d/2D)+3)% or more. However, D is the coil diameter defined by the central axis of the wire 5 exiting the roll 2.3, and d is the diameter of the portion of the wire 5 occupied by the superconducting oxide.

When forming into a coil, tensile force is applied to the outer part of the wire with respect to its central axis, and this strain (%) is (100X
It is expressed as (d/2D)l.

Therefore, the size of the area reduction rate is (100X(d/2D)+α
), and investigated the relationship between area reduction rate and critical current density by setting various values of D, d, and α. In this case, the improvement rate of critical current density was extremely high.

Table 1 (Part 1) Table 1 (Part 2) In other words, the area reduction rate is (,100X (d/2D) + 3)%
In the above cases, a significant improvement in critical current density was observed.

However, the improvement rate of critical current density is expressed as the ratio of the critical current density to that of the conventional example, assuming that the critical current density of the conventional example (when a sheathed wire is wound around a mandrel) is 1. It is. Note that even if α is increased beyond 3, the critical current density does not increase significantly. Therefore,
The area reduction rate is preferably (100X (d/2D)'+3)%.

Next, the results of actually manufacturing a superconducting oxide coil using the example method of the present invention will be explained.

A silver pipe with an inner diameter of 10 mm and an outer diameter of 12 mm, YBa2
It has a composition of Cug 07-a and an average particle size of about 1μ.
m superconducting oxide powder was filled and sealed.

Then, the silver pipe was swaged using a swaging machine.
Order, 9.7 balls, 8.7 fins, 7.8 dragons, 7.0 dragons, 6.3
Dragon, 5.7mm, 5, 1mm, 4,6 Dragon, 4.1
After wire drawing to diameters of 5 mm, 3.72 mm, and 3.35 mm was performed sequentially, the wire was rolled by 0.40 mm in one direction to form an oval cross-section with a major axis of 3.40 mm and a minor axis of 2.95 mm. Next, using a pair of grooved rolls with a semicircular groove with a radius of 1.5 mm (the diameter of the large diameter roll is 150 mm, and the diameter of the small diameter roll is 100 m + n), the long diameter was cut at a rotation speed of 40 rpm. When it was rolled by rolling down the side, it was formed into a coil with a cross-sectional diameter of 3 mm and a coil diameter of 75 mm. The pitch of this coil was 5 dragons.

The silver sheath of the formed coil was dissolved in a nitric acid-methanol solution containing 250 g/Jl of nitric acid, and then heated to 900° C. for 10 hours in an oxygen gas flow (0.2 J/min) to sinter it. When the critical current density of the sintered coil was measured in liquid nitrogen, it was 8000 A /
A high value of crA was obtained. On the other hand, when the wire was processed to a predetermined diameter and then formed into a coil, the coil shape could not be maintained when the silver sheath was melted.

In the above embodiment, different circumferential speeds are obtained by varying the diameters of the grooved rolls, but the present invention is not limited to this, and rolls with the same diameter are used and the rotational speeds are varied. The circumferential speed may be changed accordingly.

In this case as well, the same effects as in the above embodiment can be obtained.

[Effects of the Invention] As explained above, according to the present invention, the wire rod is rolled and formed while applying an area reduction rate of (100X (d/2D) + 3)% or more using grooved rolls having different circumferential speeds. This prevents cracks from forming in the superconducting oxide on the outer circumferential side of the coil after molding, avoids cutting of superconducting paths, and improves critical current density.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of the method of the present invention, and FIG. 2 is a side view seen from the direction of the arrow 1 in FIG. 2.3; Grooved roll, 4,5; Wire rod

Claims (1)

[Claims] (1) A process of filling and enclosing superconducting oxide powder into a metal or alloy pipe, a process of drawing or rolling to obtain a wire rod, and a pair of grooved rolls with mutually different circumferential speeds. A method for manufacturing a superconducting oxide coil, comprising the step of forming the wire into a coil shape while applying rolling reduction with an area reduction rate of {100(d/2D)+3}% or more. However, D: the coil diameter defined by the central axis of the wire; d: the diameter of the portion of the wire occupied by the superconducting oxide.