JPH04337213A - Manufacture of multi-layer ceramic superconductor - Google Patents

Abstract

PURPOSE:To manufacture a wiry multi-core multi-layer ceramic superconductor with excellent superconductor characteristic, particularly high critical current density, by applying the cross section reduction machining for each layer of a composite tape on a metal core material. CONSTITUTION:Butt sections of both edge sections of a composite tape with the width about 32mm are seam-welded on a round bar made of Ag with the outer diameter 4mm, for example, to form a composite body. This composite body is heated for a preset period at the preset temperature in the atmosphere, and swage machining is applied by roll machining to reduce the cross section until the outer diameter of the composite body becomes 10mm, for example. This process is repeated multiple times, and the outer diameter of the composite body is made 5mm, for example, by the final swaging machining. The heat treatment under the same condition is then applied to obtain a ceramic superconductor with eight-layer ceramic superconductor layer, for example. A wiry multi-core multi-layer ceramic superconductor with more excellent superconductor characteristic, particularly high critical current density, as compared with the multi-core multi-layer ceramic superconductor manufactured in the conventional method is manufactured.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a multilayer ceramic superconducting conductor in which ceramic superconductors are arranged in multicore or concentric cylindrical layers inside a metal, and in particular, a multilayer ceramic superconductor that can be used for magnets, cables, etc. The present invention relates to a method of manufacturing a body.

0002

[Prior Art] As so-called high-temperature superconductors whose critical temperature (Tc) exceeds liquid nitrogen temperature, Y-BaCu-O system,
Bi-(Pb)-Sr-Ca-Cu-O system,
Ceramic superconductors such as those based on Tl-Ba-Ca-Cu-O have been developed. In order to put such ceramic superconductors into practical use, methods for molding ceramic superconductors into various shapes have been studied. For example, when making wire rods, a metal sheath method is generally used. In this method, a ceramic superconductor or a raw material that can be made into a superconductor is filled into a metal pipe, processed to reduce its cross section to obtain the desired shape and dimensions, and then heat treated to form a ceramic superconducting wire. be. As the cross-section reduction processing method, conventional plastic processing methods such as extrusion, rolling, swaging, and drawing are applied depending on the desired shape of the wire rod. Materials for metal pipes include materials with excellent thermal conductivity and electrical conductivity, such as Ag, Ag alloy, and C.
U, Cu alloys, etc. can be used, but Ag and Ag alloys are often used because of their good oxygen permeability.

Ceramic superconducting conductors generally have a round, elliptical, square, or tape-shaped cross section. The arrangement of superconductors is seen in a cross section perpendicular to the longitudinal direction,
Multicore wires in which multiple wire bundles of superconducting wire bodies are arranged, and multilayer wires in which ceramic superconductors are arranged inside a metal in a concentric cylindrical or spiral shape have also been prototyped or proposed. ing. The present inventor has already proposed the following method for manufacturing a multicore multilayer superconductor. For example, when producing a multicore multilayer superconductor as shown in Figures 1(a) and (b), a composite tape with a cross-sectional shape as shown in Figures 2(a) and (b), respectively, is prepared in advance. The composite tape is then wound around the outer periphery of a metal core material in a spiral or concentric cylindrical shape as required, and the wound tape is inserted into a metal pipe to form a composite billet. Furthermore, this composite billet is subjected to cross-section reduction processing and heat treatment to form a superconductor, thereby forming a ceramic superconductor.

0004

[Problems to be Solved by the Invention] Incidentally, one of the measures for evaluating the characteristics of superconducting conductors is the critical current density, and it is necessary to increase its value in order to put superconducting conductors into practical use. In order to achieve a high critical current density (Jc) of an oxide superconductor such as a ceramic superconductor, it is generally important to improve the crystal orientation of the superconductor. As a means for this, pressurization, that is, applying pressure to the superconductor, is effective, especially for Bi-Pb-Sr-Ca-C.
This is effective in the case of u-O based superconductors. However, conventional methods, such as Bi-Pb-Sr-Ca-
When producing a Cu-O based multilayer superconducting conductor, even if a composite billet is subjected to pressing, pressure is not sufficiently applied near the center of the composite billet. That is, since pressure is applied only to a very small portion near the surface, there is a drawback that orientation of the crystals of the superconductor does not proceed to the inside. Therefore, the degree of increase in Jc was low. The purpose of the present invention is to provide a method for manufacturing a multicore multilayer ceramic superconducting conductor having a high critical current density, particularly a method for manufacturing a multicore multilayer ceramic superconducting conductor having a high critical current density.
The object of the present invention is to provide an optimal manufacturing method for O-based multicore multilayer superconductors.

[0005]

[Means for Solving the Problems] As a result of various experimental studies to improve the problems of the conventional method described above, the present inventor found that
The above object could be achieved by the method for manufacturing a superconductor according to the present invention having the following characteristics. Its characteristics are (
a) forming a composite by wrapping a composite tape consisting of a ceramic superconductor or its raw material layer and a metal layer around a metal core material in a layered manner and seam welding; (b) forming a superconductor in the composite; (c) Next, a cross-section reduction process is performed, and (d) another composite tape consisting of a ceramic superconductor or its raw material layer and a metal layer is wrapped around the heat-treated composite in a layered manner to form a seam. welded to form a composite comprising laminated composite tape layers;
e) heat-treating the composite comprising the laminated composite tape layers to make it a superconductor; (f) then subjecting it to cross-section reduction processing; and performing steps (d) to (f) as desired.
This process is repeated as many times as desired to form a predetermined number of superconductor layers, and finally heat treatment is performed to form a superconductor.

[0006] The details and implementation of each step of the method for manufacturing a superconductor according to the present invention will be explained below. in advance,
A composite tape 10 made of a ceramic superconductor or its raw material layer 6 and a metal layer 8 as shown in FIG. 2(a) is produced. Conventional means can be applied as is to produce the composite tape. For example, a ceramic superconductor or its raw material powder is filled into a metal pipe, and the metal pipe filled with the ceramic superconductor or its raw material powder is subjected to cross-sectional reduction processing to form a tape-shaped composite billet, that is, a composite tape. The billet shape may be either round or square. In the production of the composite tape 10, a plurality of composite tapes with different widths are produced, and in the composite formation process described below, the narrow composite tape is first wrapped around a metal core material in a layered manner.
After seam welding, wide composite tapes are sequentially wrapped to perform seam welding. An example of a method for producing composite tapes with different widths is a method in which a comparatively wide tape is first produced and then slitted in the longitudinal direction to a predetermined width to obtain composite tapes with different widths. Ceramic superconductors or their raw materials and metal materials for composite tapes include:
There are no particular restrictions for both, and known ceramic superconductors or their raw materials and metals can be used.

The composite tape produced by the conventional method as described above is wrapped in layers around a metal core 12, such as a metal round bar or metal pipe 12, as shown in FIG. 1(a), and seam welded. A composite body 14 is formed. Figure 1
1 shows a composite formed by a longitudinal attachment method in which the longitudinal direction of the composite tape 10 is aligned with the longitudinal direction of the metal core material 12, but the present invention is not limited to this method. Tape 10 may be wrapped around metal core 12 to form a composite. In order to prevent the composite tape from peeling off even when the composite is lengthened, preferably the abutting portions of the longitudinal edges of the composite tape are welded as shown in FIG. Seam welding or the like is applied as the welding method. The metal core material 12 is made of the same metal used for forming the composite tape. Preferably, a metal core material made of the same material as the metal of the composite tape is used. The shape of the metal core material 12 does not need to be particularly circular in cross section, and can be shaped in accordance with the workability of the subsequent cross-section reduction process.

[0008] The composite body 14 is subjected to heat treatment to form a superconductor using a conventionally known method and conditions. Next, the heat-treated composite 14 is subjected to cross-section reduction processing. The cross-sectional shape is
Although there are no particular limitations, it is preferable to process the shape into a shape similar to the shape before the cross-section reduction process. There are no particular restrictions on the cross-section reduction processing method, and conventional methods can be used. Preferably, compression processes such as swaging, roller dies, etc. are used. Although there are no particular restrictions on the area reduction rate, it is not necessary to make the area reduction rate too high, preferably 10 to 20%.
That's about it. Due to the cross-sectional reduction process performed in this way, the ceramic superconductor layer is pressurized and the orientation of the crystals is improved. Next, use the same material as composite tape 10 again.
A composite tape 16 having the same structure but slightly wider is wrapped in layers around the composite 14 whose cross section has been reduced as shown in FIG. 1(b) and seam welded to form a composite 14 with laminated composite tapes. do. In this case as well, the composite tape 10
Preferably, the abutting portions of the longitudinal edges of the composite tape 16 are welded in the same manner as when the composite tape 16 is wound around the metal core material 12. Next, heat treatment was performed to form a superconductor using the same method and conditions as before, and then cross-section reduction processing was performed in the same way as before.
Improve the crystal orientation of the ceramic superconductor layer. In this case, the crystal orientation of the first layer of ceramic superconductor is maintained. The multilayer ceramic superconducting conductor according to the present invention can be obtained by repeating such steps a plurality of times as required to form a composite body with a predetermined number of superconductor layers, and then performing heat treatment to form the final superconductor. can get.

[0009] Up to now, an example has been described in which a composite tape is used in which a ceramic superconductor or its raw material layer is arranged inside a metal layer, but the present invention is not limited to this. For example, a composite tape 2 shown in FIG. 3(a) in which a ceramic superconductor or its raw material layer 20 is adhered to one side of a metal tape 18.
2 can also be used. Applying a ceramic superconductor or its raw material powder onto a metal tape by thermal spraying, coating, etc., or applying a paste prepared by kneading a ceramic superconductor or its raw material and a binder onto a metal tape. Thus, such a composite tape can be produced. In addition, when a composite tape is formed by applying a paste made by kneading a ceramic superconductor or its raw material and a binder onto a metal tape, the composite formed by wrapping the composite tape around a metal core material is heat-treated. A known debinding treatment is required to volatilize the binder component.

On the other hand, when producing a multicore multilayer ceramic superconductor according to the present invention, a multicore composite tape as shown in FIG. 2(b) or FIG. 3(b) is used to produce a superconductor. Multi-core and multi-layered. Also,
In this example, a method for manufacturing a multilayer, multicore ceramic superconducting conductor with a round cross section has been described, but it goes without saying that the method can also be applied to manufacturing a ceramic superconducting conductor having an elliptical or square cross section, for example. As described above, according to the method of the present invention, the pressing force in the cross-section reduction process is applied to the radial center of the ceramic superconductor, so that the orientation of the crystals of the ceramic superconductor is maintained even in the center of the ceramic superconductor. improves. Therefore, the Jc characteristic is significantly improved compared to the conventional method. Ceramic superconductors suitable for the method of the present invention include ceramic superconductors whose crystals are significantly oriented by pressure, such as B
Examples include i-Pb-Sr-Ca-Cu-O-based superconductors.

[0011]

EXAMPLES Next, the present invention will be explained in more detail based on examples. Example 1 Bi2O3, PbO, SrC
Ceramic superconductor primary raw material powders of O3, CaCO3, and CuO in a molar ratio of 1.6:0.4:2:2:3
After blending and mixing so that
The resulting calcined body was then pulverized to produce calcined powder with an average particle size of about 5 μm. The obtained calcined powder is compacted into a cross section with a length of 5 mm and a width of 5 mm and a length of 40 mm.
A large number of rod-shaped samples with a diameter of mm were prepared. Ag
They were placed in series in a rectangular pipe, and the ends of the rod-shaped samples were welded with electron beams to form a composite billet. The dimensions of the Ag square pipe were as follows: the outside of the pipe wall was 10 mm high, 50 mm wide, and 100 mm long; the inside of the wall was approximately 5 mm high, 40 mm wide, and 90 mm long. The composite billet formed as described above was subjected to cross-sectional reduction processing by rolling to a width of approximately 70 mm and a thickness of 0.3 m.
The composite tape was made into a composite tape with a thickness of approximately 1. This composite tape was slit in the longitudinal direction to obtain a composite tape with a width of about 32 mm.

Next, a composite tape with a width of about 32 mm is wrapped around an Ag round bar with an outer diameter of 10 mm as shown in FIG. was formed. Next, the obtained composite was heat treated in the atmosphere at a temperature of 830° C. for 50 hours, and then swooped to reduce the cross section by rolling until the outer diameter of the composite was 10 mm. Next, another composite tape made of the same material and structure as the previous composite tape was wrapped around the composite in a layered manner as shown in Figure 3(b), and then heat treated under the same conditions as before. After that, the outer diameter is 10
Swaging process was performed to mm. Repeat the above process 8 times and use the final swaging process to reduce the outer diameter of the composite to 5
mm, and then heat-treated under the same conditions as before to obtain a ceramic superconductor having eight ceramic superconductor layers as Example Product 1 according to the present invention. As a result of measuring Ic in an O magnetic field in liquid nitrogen for the multilayer ceramic superconducting conductor of Example Product 1, excellent characteristics of 85 (A) were obtained.

Example 2 The ceramic superconductor raw material calcined powder prepared in the same manner as the ceramic superconductor raw material calcined powder prepared in Example 1 and a binder were kneaded to form a paste, which was made into a paste having a width of about 32 mm. A composite tape was prepared by coating eight stripes each having a width of 2 mm and a thickness of 0.1 mm on an Ag sheet having a thickness of approximately 0.3 mm. The composite tape thus obtained was wound vertically around an Ag round bar with an outer diameter of 10 mm with the ceramic superconductor raw material layer side facing inside, and the butt portions of both edges of the composite tape were seam welded. A complex was formed. Next, this composite was subjected to a binder removal treatment in which the composite was held at a temperature of 500° C. for 5 hours to volatilize the binder component, and then a heat treatment was performed by maintaining the composite at a temperature of 830° C. for 50 hours in the atmosphere. Subsequently, the heat-treated composite was swaged to an outer diameter of 10
Finished in mm. Furthermore, another composite tape obtained in the same manner as the previous composite tape was wrapped around the composite having an outer diameter of 10 mm, and the butt portions of both edges of the composite tape were seam welded.
Heat treatment was performed in the same manner and under the same conditions as last time, and swaging was performed in the same manner as last time to increase the outer diameter to 10 mm. The same process was repeated 8 times, and the final swaging process resulted in an outer diameter of 5
mm, and heat-treated using the same method and conditions as before to produce a multicore ceramic superconductor having eight ceramic superconductor layers as Example 2 according to the present invention. As a result of measuring the Ic of this multicore multilayer ceramic superconductor in an O magnetic field in liquid nitrogen, an excellent characteristic of 68 (A) was obtained.

Comparative Example 1 A composite tape obtained in the same manner as the composite tape obtained in Example 1 was spirally wound in eight layers around an Ag round rod having an outer diameter of 10 mm to form a composite. This composite was inserted into an Ag pipe with an inner diameter of 15.5 mm and an outer diameter of 20 mm to form a composite billet. This was swaged and finished to an outer diameter of 5 mm. This is heated in the atmosphere at a temperature of 830°C.
A multilayer ceramic superconductor was produced as Comparative Example Product 1 by heat treatment at a temperature of 50 hours. The Ic of this multilayer ceramic superconducting conductor in an O magnetic field was measured in liquid nitrogen and was found to be 24 (A). Comparative Example 2 When the outer diameter of a composite obtained in the same manner as Comparative Example 1 reached 15 mm during the swaging process, the composite was temporarily held in the atmosphere at a temperature of 830°C for 50 hours and subjected to intermediate heat treatment. A multilayer ceramic superconductor of Comparative Example 2 was obtained in the same manner as Comparative Example 1 except for the following steps. The Ic of this multilayer ceramic superconductor in an O magnetic field was measured in liquid nitrogen and was found to be 28 (A). Comparative Example 3 When the outer diameter of a composite obtained in the same manner as Comparative Example 1 became 15 mm during the swaging process, the composite was once swaged in the atmosphere at 830 mm.
Comparative example except that the composite was held at ℃ for 50 hours and subjected to a first intermediate heat treatment, and when the outer diameter reached 10 mm, the composite was subjected to a second intermediate heat treatment under the same conditions as the first. A multilayer ceramic superconductor of Comparative Example Product 3 was obtained in the same manner as Product 1. As a result of measuring the Ic of this multilayer ceramic superconductor in an O magnetic field in liquid nitrogen, it was found to be 33 (
A).

Comparing the multilayer ceramic superconducting conductors of Example Product 1 and Comparative Example Products 1 to 3, it is clear that the Example product has a larger critical current, and the multilayer ceramics manufactured by the manufacturing method according to the present invention The superconductor was confirmed to have a higher critical current density than multilayer ceramic superconductors produced by conventional methods. Furthermore, it was confirmed that the multicore multilayer ceramic superconducting conductor of Example Product 2 also recorded a large critical current, and therefore had a high critical current density.

[0016]

Effects of the Invention As explained in detail above, the manufacturing method according to the present invention reduces the cross-section of each layer of the composite tape on the metal core material, thereby reducing the cross-section of the multi-core multi-layered composite tape manufactured by the conventional method. It is possible to produce a multi-core, multi-layered ceramic superconducting conductor made into a wire, which has much superior superconducting properties compared to ceramic superconductors, especially a high critical current density. The ceramic superconductor made into a wire by the manufacturing method according to the present invention can be applied as a conductor for magnets, cables, etc., and the present invention promotes the practical use of the ceramic superconductor.

[Brief explanation of the drawing]

FIG. 1(a) is a schematic perspective view of a composite formed by wrapping one layer of composite tape around a metal core material in an intermediate step in implementing the method for manufacturing a ceramic superconductor according to the present invention. , FIG. 1(b) is a schematic perspective view of a composite body formed by winding two layers of composite tape around a metal core material.

[Fig. 2] Fig. 2(a) is a cross-sectional view of the composite tape;
(b) is a sectional view of the multi-core composite tape.

FIG. 3(a) is a cross-sectional view of a composite tape formed by applying a kneaded paste of ceramic superconductor raw material powder and a binder to one side of a metal tape, and FIG. FIG. 3 is a cross-sectional view of the formed multicore composite tape.

FIG. 4(a) is a cross-sectional view of a multilayer ceramic superconductor manufactured by a conventional manufacturing method, and FIG. 4(b) is a cross-sectional view of a multilayer ceramic superconductor manufactured by a conventional manufacturing method.
1 is a cross-sectional view of a multicore multilayer ceramic superconductor manufactured by a conventional manufacturing method.

[Explanation of symbols]

6 Ceramic superconductor raw material layer 8 Metal layer 10 Composite tape 12 Metal core material 14 Complex 16 Another composite tape 18 Ceramic superconductor raw material layer 20 Metal tape 22 Composite tape

Claims (1)

[Claims] Claim 1: (a) A composite tape consisting of a ceramic superconductor or its raw material layer and a metal layer is wrapped in layers around a metal core material and seam welded to form a composite;
b) subjecting the composite to a heat treatment to make it a superconductor;
(c) Next, a cross-section reduction process is performed, and (d) another composite tape consisting of a ceramic superconductor or its raw material layer and a metal layer is wrapped around the heat-treated composite in layers and seam welded to laminate. (e) heat-treating the composite including the laminated composite tape layers to make it a superconductor;
f) Next, perform a cross-section reduction process, repeat the steps (d) to (f) as desired as desired to form a predetermined number of superconductor layers, and finally form a superconductor. A method for producing a multilayer ceramic superconducting conductor characterized by subjecting it to heat treatment.