JPH0353902A - Manufacture of oxide superconductive coil - Google Patents

Abstract

PURPOSE:To prevent the occurrence of cracks in the outside of a coil by rolling a composition in making it pass through between a pair of different diameter rolls, at the same time, plastic-deforming it into a coil form. CONSTITUTION:Provisional baked powders 6 for a superconductor, in which a polycrystalline substance of YBa2Cu3O7-delta obtained by mixing with each predetermined material powder and provisionally baking them is ground and finely powdered, are filled into a metallic sheath 3, and they are elongation-worked into a composite wire by swaging process, furthermore, rolled into a tape form by rolling. And, it is rolled by a rolling process in use of a pair of different diameter rolls 1, 2, at the same time, molded into a spiral coil from. A composition 4 molded herein is wound up by a guide rod 7 immediately and wound over into 5 layers. Next, in order to ceramic-bake the provisionally baked powders 6 of a superconductor in the coil, a heat treatment therefor is conducted in an oxidizing atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing an oxide-based superconducting coil suitable for application to, for example, manufacturing a strong magnetic field generating coil used in a generator.

[Conventional technology Bi system including L n-B a-C u-O
Alloy oxides that have been discovered in recent years, such as the T1 system, that transition to a superconducting state at relatively high temperatures are called oxide-based high-temperature superconductors.
Due to its high superconducting transition temperature, it is expected to be applied in a wide range of fields. In particular, the application to coils for generating strong magnetic fields in generators, motors, etc. is attracting attention, and various wire processing methods and coil forming methods for these materials are being devised and put into practical use.

By the way, oxide-based high-temperature superconductors are a type of so-called ceramics that do not have metallic bonds that facilitate mutual movement between crystal lattices and cannot be expected to undergo plastic deformation as explained by Ili movement, and are extremely brittle. Because of these properties, it is almost impossible to process the wire into a coil by rolling or drawing to reduce its area like general metal wire materials. In addition, oxide-based high-temperature superconductors have a relatively unstable crystal structure, and physical properties such as superconducting transition temperature change easily due to oxygen and moisture in the atmosphere, so the coil surface must be sealed from the atmosphere. There is a need.

Therefore, the manufacturing method for oxide-based superconducting coils is to apply the metal sheath method, fill a metal pipe with a fine powdered raw material preparation, and then shape the pipe and the final coil shape. A common method is to sinter the raw material conditioning body inside the metal sheath by heat-treating it.

In addition, this raw material preparation body is prepared by finely powdering the raw materials for each component of the superconductor, mixing them in appropriate proportions, and heat-treating them in an appropriate temperature and atmosphere to form an alloy oxide, for example. It is generally made into a polycrystalline body such as Y B , 2c u30 7-6, etc., which is then ground again to form a fine powder. In some cases, a mixture of raw materials for each component prepared in appropriate proportions is used directly, but this is not common because the molded product may break due to the change in volume accompanying the formation of an alloy oxide.

A specific method for manufacturing oxide-based superconducting coils using the metal sheath method involves filling a silver or silver alloy pipe with a raw material conditioning body to form a composite, and then processing the composite into a wire by reducing its area. A method is known in which the obtained wire is wound around the surface of a cylinder having a predetermined diameter and then heat treated as it is.

[Problems to be Solved by the Invention] When manufacturing oxide superconducting coils by the metal sheath method, the raw material conditioning body in the metal sheath is diametrically and axially modified in accordance with area reduction processing and coil winding processing. It must move smoothly and fill the metal sheath with uniform density without any gaps. However, since there is a limit to the fluidity of powder, in the above-mentioned manufacturing method of oxide-based superconducting coils in which a wire is wound around a cylinder, the stretching of the outer part of the coil due to winding causes the raw material adjustment body in the metal sheath to This creates minute gaps (cracks). This reduces the effective cross-sectional area of the oxide superconductor after heat treatment, impairing the current capacity of the coil, and becomes a stress concentration point, reducing the strength of the coil.

The present invention provides a method for manufacturing an oxide-based superconducting coil, which provides a superconducting coil with a high current capacity and little variation, and also reduces occurrence of cracks in the outer portion of the coil.

[Means for Solving the Problems] The method for manufacturing an oxide superconducting coil according to claim (1) of the present invention includes forming a composite body in which a powdered raw material preparation body is loaded into a metal sheath into a coil shape; A method for manufacturing an oxide superconducting coil by a metal sheath method, which performs heat treatment, characterized by comprising a roll rolling step in which the composite is rolled and simultaneously plastically deformed into a coil shape through a pair of rolls having different outer diameters. It is something.

Further, the method for manufacturing an oxide superconducting coil according to claim (2) of the present invention is such that the composite body has a coil pitch as a pair of rolls in the method for manufacturing an oxide superconducting coil according to claim (1) of the present invention. It is characterized by the use of a pair of rolls whose facing distances are different in the width direction so that they can be plastically deformed in both directions at the same time.

[Function] In the method for manufacturing an oxide superconducting coil according to claim (1) of the present invention, a raw material preparation body adjusted to have increased fluidity, for example, by pulverization, is loaded into a metal sheath and then composited. body.

Next, this composite is passed between a pair of rolls having different outer diameters, and simultaneously rolled and bent to form it into a coil shape all at once. At this time, the elongation of the metal sheath on the roll side with a smaller outer diameter is smaller than the elongation on the roll side with a larger outer diameter, so the J composite is bent with a constant curvature toward the roll with a smaller outer diameter. This curvature is controlled by adjusting the diameter and facing distance of each roll in accordance with the shape and mechanical properties of the metal sheath of the composite. In addition, in the process of bending the composite through a pair of rolls with different outer diameters, the outer part of the coil of the raw material conditioning body in the metal sheath of the composite is tightened with the same rolling force as the inner part of the coil, as described in the conventional example. This method is less likely to cause cranking than the method of wrapping wire around a cylinder. However, before performing this roll rolling process, it is desirable to perform an appropriate area reduction process (wire process) to tighten the raw material adjusting body to some extent uniformly within the metal sheath.

Next, heat treatment is performed to sinter the original adjustment body formed into a coil shape together with the metal sheath to form a ceramic material, thereby obtaining an oxide superconducting coil as a final product. on the other hand,
When a mixture of each component raw material is directly used as a raw material preparation body, alloy oxide formation is performed here.

Next, in the method for manufacturing an oxide superconducting coil according to claim (2) of the present invention, the opposing distance between the pair of rolls is wedge-shaped, which differs in the width direction, and the rolled composite is shaped like a wedge, which is different in the width direction. Because of the escape to the wide side, in addition to the bending in the coil diameter direction as described above, plastic deformation occurs simultaneously in the coil pitch direction perpendicular to this bending, and each strip of the formed coil automatically bends at a predetermined pitch in the coil pitch direction. Align.

Here, since the amount of plastic deformation in the coil pitch direction depends on the degree of opening of the wedge-shaped opposing gaps, the coil pitch can be adjusted and controlled by adjusting the inclination angle of the opposing gaps (roll axis crossing angle, etc.) .

[Embodiments of the invention] Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a roll rolling process for forming a coil in a method for manufacturing an oxide superconducting coil according to an embodiment of the present invention.

YB obtained by mixing specified raw material powders and calcining
7
, a silver alloy pipe with an inner diameter of 15 mm was used) 3, which was drawn into a composite wire with an outer diameter of 5 mm by swaging, and further rolled into a wire with a thickness of 0.5 mm.
It was rolled into a tape shape. This is shown in Figure 1, a pair of rolls with different outer diameters (each with an outer diameter of 100 mm).
The sample was rolled to a thickness of 0.3 mm and simultaneously formed into a spiral coil shape by rolling using rolls 1 and 2 (with a diameter of 40 mm and a facing interval 5 of 0.3 mm). Here, the molded composite 4 is immediately wound around a guide rod (diameter 50 mm) 7, and the molded composite 4 is wrapped around the guide rod 7.
Layered. Next, in order to ceramically sinter the superconductor pre-sintered powder 6 in this spiral coil, it was heat-treated for 10 hours in an oxidizing atmosphere at 9°C to obtain a test coil.

When this test coil was immersed in liquid nitrogen and its characteristics were measured, the critical current density JC was 3400A/cm2 (
LN20G), and the generated magnetic field at a coil current of 1c30A was 240G.

Next, the same composite (0.5 mm thick tape) was rolled to 0.3 mm using another roller rolling device, and then this straight tape was rolled in 5 layers onto another guide rod (50 mm in diameter). It was rolled up and formed into a spiral coil shape. This spiral coil was similarly heat-treated for 10 hours in an oxidizing atmosphere at 900'C, and was used as a comparison coil.

When this comparison coil was immersed in liquid nitrogen and its characteristics were measured, the critical current density J was found. is 98OA/Cm'(L
N2 0G), and the generated magnetic field at a coil current of 1c 9A was 70G.

Further, as a result of X-ray fluoroscopic observation, many fine cracks were observed in the oxide superconductor inside this comparative coil.

FIG. 2 shows a roll rolling process for forming a coil in a method for manufacturing an oxide superconducting coil according to another embodiment of the present invention. Here, members having the same configuration and function as those in the embodiment shown in FIG. 1 are given the same reference numerals.

In the embodiment of FIG. 2, 'f. A guide jig 8 is provided on the exit side of the rolling roller of the first embodiment, and the rolled composite is plastically deformed so as to be shifted by a predetermined amount in the coil pitch direction. As a result, even if the composite body 3 is rolled as in the embodiment shown in FIG. 1, for example, each strip of the spirally formed composite body 4b is guided in a spiral shape without overlapping, and is shaped like a straight solenoid. becomes a coil.

FIG. 3 shows a roll rolling process for forming a coil in a method for manufacturing an oxide superconducting coil according to yet another embodiment of the present invention. Here again, the same reference numerals are given to the members having the same structure and function as those in the embodiment shown in FIG.

In the embodiment shown in FIG. 3, the axes of the opposing rolls 1b and 2 are shifted from parallel (crossing angle θ), and the facing interval 5b between the rolls 1b and 2 is made into a tapered shape. As a result, even if the composite is sent in the direction indicated by the arrow 9 and rolled in the same manner as in the embodiment of FIG. Each strip is guided spirally without overlapping to form a linear solenoid-like coil.

In the embodiments shown in FIGS. 2 and 3, the pitch of the cylindrical coil can be adjusted freely by adjusting the position of the guide jig 8 or the intersection angle of each roll 1b, 2, for example, the pitch of each strip may be partially overlapped. Can be set. In addition, there is a winding frame (core material) in the center of the coil.
If the winding frame is installed and rotated together, and the winding frame is moved in the axial direction while being wound, the coil pitch and diameter can be controlled more precisely. In this case, it is preferable to insert a spacer between each strip to form a gap in which an insulating layer can be formed later.

In each of the above embodiments, the case where the thin plate-like composite body 3 is coil-formed is described.
You can freely select the cross-sectional shape of the composite such as polygon. Also,
The oxide superconductor layer (pre-sintered powder 6) can be formed into a coil with either a single core or multi-core, and the raw material and metal cis material for the oxide superconductor layer (pre-sintered powder 6) can be freely selected. However, in order to prevent the occurrence of cracks after coil forming, it is desirable that the coil forming according to the present invention be the final forming step of the metal sheath plastic working.

[Effects of the Invention] In the method for manufacturing an oxide superconducting coil according to the present invention, a composite body in which a powdered raw material preparation body is loaded into a metal sheath is rolled and simultaneously formed into a coil, and then heat-treated to form a raw material preparation body. Since it is made into a molded ceramic, even oxide-based superconductors without plasticity can be formed into coils. Furthermore, the surface of the coil is shielded from the atmosphere by a metal sheath, so that the influence of moisture and oxygen in the atmosphere on the J oxide superconductor is reduced.

In the method for manufacturing an oxide superconducting coil according to claim (1) of the present invention, a pair of rolls having different outer diameters 1 2 is applied so that the raw material adjusting body in the sheath applies a rolling force that is equal to the rolling force on the outer side of the coil than on the inner side of the coil. Since the coil is formed while being tightened, cracks are less likely to occur compared to the method of wrapping around a cylinder as described in the conventional example.

Next, in the method for manufacturing an oxide superconducting coil according to claim (2) of the present invention, plastic deformation occurs in the coil pitch direction at the same time as rolling, so each coil coil can be formed in a predetermined manner without a special guide. Automatically align by pitch.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating an embodiment of the method for manufacturing an oxide superconducting coil of the present invention. FIG. 2 shows the method for manufacturing an oxide superconducting coil of the present invention.
It is a typical perspective view explaining another example. FIG. 3 shows the method for manufacturing an oxide superconducting coil of the present invention.
It is a typical perspective view explaining still another example. [Explanation of symbols of main parts] l...Roll 2...Roll 3...Composite 4...Molded composite 5...Opposing interval 6...Calcined component powder

Claims (2)

[Claims] (1) In a method for producing an oxide superconducting coil in which a composite body in which a powdered raw material preparation body is loaded into a metal sheath is formed into a coil shape and then heat-treated, the composite body is rolled between a pair of rolls having different outer diameters. A method for manufacturing an oxide superconducting coil, comprising a roll rolling step of simultaneously rolling and plastically deforming it into a coil shape. (2) Manufacturing the oxide superconducting coil according to claim (1), characterized in that a pair of the rolls are used with opposing intervals different in the width direction so as to simultaneously plastically deform the composite in the coil pitch direction. Method.