JPH0215514A - Manufacture of oxide superconductor and superconductive magnet - Google Patents

Abstract

PURPOSE:To enable it to be used while letting flow refrigerant into inside of a metallic sheath by burying an oxide superconductor inside the peripheral wall of a pipe-shaped metallic sheath. CONSTITUTION:A tape material 1 which is constituted by covering a tape-shaped consolidated substance 3 consisting of a superconductor or a precursor of the oxide superconductor with a metallic sheath 2 is formed, and this tape material 1 is formed in pipe shape, and the butting parts are welded so as to make a pipe body 4. At the same time, this pipe body 4 is applied with heat treatment after being wound around a drum so as to produce an oxide superconductor 6 inside the consolidated substance 3. Hereby, a part of defective parts such as cracks, etc., which occurred in the consolidated substance during winding or before winding disappears by sintering actions by heat treatment, and the lowering of the critical current density of the oxide superconductor can be prevented. Also, the oxide superconductor 6 can be cooled efficiently from the inside of the metallic sheath 2 by letting flow refrigerant into inside of the metallic sheath 2.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Field of Application" /l) 庭0日E+ 纭0日 E+ PAPZE's Static Articles Introduction The present invention relates to a superconducting conductor and a method for manufacturing a superconducting magnet using this oxide superconductor.

"Prior Art" Oxide superconductors that have been discovered in recent years are known to have an extremely high critical temperature at which they transition from a normal conducting state to a superconducting state. This type of oxide superconductor has an extremely high critical temperature compared to conventionally known alloy-based or intermetallic compound-based superconductors.
-B a-Cu-0 system, B i-S r-Ca-Cu
Oxide superconductors such as -0 series and Tica-B a-Cu-0 series are known to exhibit critical temperatures exceeding liquid nitrogen temperature.

Conventionally, in order to manufacture superconducting wire using this type of oxide superconductor, a metal tube is filled with a mixed powder containing the elements constituting the oxide superconductor, and the diameter of the metal tube is reduced. A method is used in which the powder inside is compacted, and after diameter reduction, heat treatment is performed to cause a solid phase reaction inside the compacted body to produce an oxide superconductor.

``Problems to be Solved by the Invention'' By the way, as mentioned above, new oxide superconductors with high critical temperatures have been discovered. Attempts are being made to apply this.

A widely known example of this application is a superconducting magnet. This superconducting magnet is constructed by winding a superconducting wire around a drum. However, when manufacturing superconducting magnets using oxide superconducting wire, there is a problem with oxidation occurring during winding around the drum. The problem is mechanical strain added to superconducting wires.

As is well known, since oxide superconducting wires include sintered oxide superconductors, they are extremely brittle and have poor strength. Therefore, when a superconducting magnet is manufactured by winding an oxide superconducting wire having the above structure around a winding drum, there is a problem that defects such as cracks occur in the oxide superconductor, and the critical current density of the oxide superconductor decreases significantly. For this reason, there has conventionally been a problem that it has not been possible to manufacture oxide superconducting magnets that exhibit good characteristics.

The present invention has been made in order to solve the problem No. 11, and is to provide a pipe-shaped oxide superconducting conductor having a novel structure, and further, to provide a superconducting magnet with excellent characteristics using the oxide superconducting conductor. )・The purpose is to provide a method for manufacturing.

"Means for solving the problem" In order to solve the problem, the invention stated in claim I,
An oxide superconductor is embedded inside the peripheral wall of a pipe-shaped metal source.

In order to solve the above problem, the invention described in claim 2 has the following features:
A tape material is formed by covering a tape-shaped compacted body made of an oxide superconductor or a precursor of an oxide superconductor with a metal sheath, and this tape material is formed into a pipe shape, and the butted parts are joined to form a pipe. After the pipe body is wound around a winding drum, it is heat-treated to produce an oxide superconductor inside the consolidated body.

1. Since the oxide superconductor is embedded in the peripheral wall of the pipe-shaped metal sheath, it is possible to efficiently cool the oxide superconductor from the inside of the metal source by flowing a coolant inside the metal sheath. Become. In addition, by applying heat treatment after winding around the drum, some of the defects such as cracks that occurred in the consolidated body during or before winding disappear due to the sintering effect of the heat treatment, making the oxide superconductor Increases current flow through the body. Furthermore, if heat treatment is performed while oxygen gas is flowing through the pipe wound around the drum, oxygen can be efficiently supplied to the consolidated body over the entire length of the pipe. Oxygen is also supplied efficiently to the compacted body of the pipe wound around the pipe.

"Example" Figures 1 to 3 are for explaining an example of the present invention.In order to carry out the present invention and manufacture an oxide superconducting wire, first, starting materials are prepared. .

As this starting material, an oxide superconductor, a material containing an element constituting the oxide superconductor (precursor), or a mixture thereof (precursor) is used.

As the oxide superconductor, A-B-Cu-0
system (however, A is one or more elements of group 11a of the periodic table such as La, Ce, Y, Yb, Dy, and Ho, or one or more elements of group Vb of the periodic table such as Bi, or TI, etc.) Represents one or more elements of group IIIb of the periodic table, B is Ca
.

One or more elements of group 11a of the periodic table, such as Sr and Ba. ) are used.

In addition, materials containing elements constituting the oxide superconductor include powders containing elements of group Ma of the periodic table, elements of group Va of the periodic table, or elements of group 111b of the periodic table, and powders containing elements of group 111 of the periodic table.
A mixed powder consisting of a powder containing a group A element and a copper oxide powder, a calcined powder of this mixed powder, a mixed powder of the above mixed powder and calcined powder, etc. are used. The powder of a group Ia group element of the periodic table used here includes compound powder or alloy powder of group Ila elements such as carbonate powder, oxide powder, chloride powder, sulfide powder, and fluoride powder. In addition, the periodic table IIra group element powder, VB group element powder, and Ib group element powder include compound powders or alloys such as oxide powders, carbonate powders, chloride powders, sulfide powders, and fluoride powders of each element. Powder etc. are used. Furthermore, as copper oxide powder, CuO, CutO, Cu
3C12, Cu40z, etc. are used.

By the way, to prepare the mixed powder, the powder method described above is usually used, but it is not limited to this method. Each element is coprecipitated as oxalate, and the precipitate is dried to form a powder. It is also free to apply a coprecipitation method to obtain a mixed powder.

In addition, if the above-mentioned necessary elements such as alcokind compounds, oxyketone compounds, cyclopentadienyl compounds, etc. are mixed in a predetermined ratio to form a mixed solution, water is added to this mixed solution and hydrolyzed to form a sol. Alternatively, a sol-gel method may be applied in which this sol-like substance is heated to gel, and the gel is further heated to form a solid phase, which is then pulverized to obtain a mixed powder.

Next, the powder prepared as described above is filled into a metal tube to create a composite. The tubular body is preferably made of a metal material such as Ag that has excellent oxygen permeability. Note that the constituent material of the tube is not limited to metal materials as long as it can be plastically worked.

Furthermore, what is filled in the tube may be an oxide superconductor obtained by compacting and sintering the powder, or superconducting powder obtained by pulverizing this superconductor, or superconducting granules.

Once the tube body is filled with powder, forging or rolling is repeated as many times as necessary to compact the powder and form the entire body into a tape shape, creating tape material l whose cross-sectional structure is shown in Figure 1. . The tape 111 is composed of a plate-shaped metal sheath 2 formed by compressing and deforming a metal tube, and a plate-shaped compacted body 3 embedded inside the metal sheath 2. In this example, the tape material 1 was formed by filling a metal tube with powder and processing it, but the tape material 1 was also formed by coating the outer periphery of a compacted body obtained by pressure forming in advance. It's okay.

Next, this tape material 1 is rolled into a pipe shape as shown in FIG. 2 by means such as roll forming, and the abutting portions of the pipes are joined by a joining means such as welding to create a pipe body 4.

Next, this pipe body 4 is subjected to heat treatment.

This heat treatment is preferably carried out in an oxygen-present atmosphere for 8
This is carried out by heating to 00 to 1100°C for several minutes to several tens of hours and then cooling. In addition, when using an oxide superconductor such as Y-BaCu-0 series or Tica-Ba-Cu-0 series, it is preferable to perform the heat treatment while flowing oxygen gas inside the pipe during this heat treatment. .

Through the above processing, a solid phase reaction occurs inside the compacted body 3 of the pipe body 4 to generate an oxide superconductor, and as shown in the cross-sectional structure of FIG. It is possible to obtain an oxide superconducting conductor A in which a shaped oxide superconductor 6 is embedded.

Furthermore, during the heat treatment, oxygen in the atmosphere diffuses into the compact through the metal sheath 5, so that an oxide superconductor with good properties is produced without oxygen deficiency. Also,
When heat treatment is performed while flowing oxygen gas inside the pipe, oxygen also permeates from the inner peripheral surface of the pipe and reaches the compacted body, making it possible to supply oxygen more efficiently and lowering the critical current density. An excellent oxide superconductor with high properties can be produced.

The +M-made oxide superconducting conductor A shown in FIG. 3 can be used by flowing a coolant such as liquid nitrogen into the hollow part to cool it below the critical temperature. When used in this manner, the oxide superconductor inside the peripheral wall of the metal sheath 5 can be cooled without providing a separate coolant flow path or the like.

Next, a method for manufacturing a superconducting magnet will be explained.

To manufacture a superconducting magnet, a pipe body 4 shown in FIG. 2 is prepared, and the pipe body 4 is wound around a winding drum 11 a necessary number of times as shown in FIG. 4 before heat treatment.

Once the required length of pipe 4 is wound around the winding drum If, the pipe 4 wound around the winding drum 11 is heat treated together with the winding drum II. It is preferable that the heat treatment conditions be set to be the same as in the above-mentioned example. When performing this heat treatment, it is preferable to perform the heat treatment while flowing oxygen gas inside the pipe 4.

In the pipe 4 wound around the winding drum 11, an oxide superconductor is generated inside the metal sheath 2 by heat treatment,
A superconducting coil can be obtained.

In addition, when winding the pipe 4 around the winding drum ll, the pipe 4
Due to the stress acting on the consolidated body 3 inside the surrounding wall of
Defects such as fine racks may occur. However, even when such defects occur, these defects disappear due to the diffusion of elements through the sintering reaction, and the sintered density of the compact improves slightly, increasing the current path in the sintered compact. do. Therefore, superconducting magnets can be manufactured without being affected by the distortion caused by winding.
An oxide superconducting magnet with high critical current density and excellent superconducting properties can be obtained.

Also, the winding trunk! When performing heat treatment after winding the pipe 4 around the metal sheath 2 several times, the constituent material of the metal sheath 2 may be
Even when a material with excellent oxygen permeability is used and heat treatment is performed in an oxygen gas atmosphere, oxygen in the atmosphere does not reach the compacted body 3 of the tape 4 wound around the inner circumference of the winding drum 11. There is a possibility that it cannot be done. In this respect, if the heat treatment is carried out while flowing oxygen gas into the inside of the pipe 4, the heat treatment can also be carried out while supplying sufficient oxygen to the compacted body 3 inside the pipe 4 wound around the inner circumferential side of the winding drum 11. This has the effect of producing an oxide superconductor with a high critical current density in the compacted body 3 of the pipe 4 on the inner peripheral side of the winding drum 11.

FIG. 5 shows another example of the oxide superconducting conductor of the invention described in claim 1, and the oxide superconducting conductor B of this example is
The structure is such that a ring-shaped oxide superconductor 2I buried inside the peripheral wall of the pipe-shaped metal sheath 20 is provided in a portion close to the inner peripheral surface of the metal sheath 20. That is, the metal sheath 20 provided on the inner side of the oxide superconductor 21 is formed thinner than the thickness of the metal sheath 20 provided on the outer side of the oxide superconductor 21.

In the structure of this example, when sintering is performed by flowing oxygen gas into the hollow part, the thickness of the metal sheath 20 on the inner side of the ring-shaped oxide superconductor 21 is smaller than in the previous example. Therefore, oxygen can be more actively permeated through the metal sheath 20 from the inner peripheral side to supply oxygen. Therefore, an oxide superconductor 2I with more excellent properties can be produced. Further, when the oxide superconducting conductor B is used by cooling the oxide superconducting conductor B by flowing a refrigerant into the hollow portion, the cooling efficiency is improved because the metal sheath 20 on the inner side of the oxide superconducting conductor 21 is thin.

FIG. 6 shows still another example of the invention set forth in claim 1. In the oxide superconducting conductor C of this example, an oxide superconductor 31 is embedded inside the peripheral wall of a pipe-shaped metal sheath 30. The metal sheath 30 has a structure in which a large number of fine through holes 32 reaching the oxide superconductor 3I are formed on the inner circumferential surface of the metal sheath 30.

In the oxide superconducting conductor C of this example, when oxygen gas is flowed into the hollow part during heat treatment, the oxygen gas can easily reach the compacted body from the inside of the pipe through the through holes 23, so that a sufficient amount of oxygen can be supplied. This has the effect of allowing heat treatment to be performed while being supplied. Also,
When the oxide superconducting conductor C is used after being cooled with a refrigerant or the like, the refrigerant comes into direct contact with the oxide superconductor 32 through the through holes 23, so that the oxide superconductor 32 can be efficiently cooled.

"Production example!" Y2O3 powder, B a CO3 powder, and CuO powder Y:
A mixed powder was prepared by mixing Ba:Cu=1:2:3, and this mixed powder was calcined at 900°C for 12 hours, further crushed, and then molded using a rubber press into a rod shape with a diameter of 8 mm. I got a body. Thereafter, this rod-shaped body was heat-treated at 890°C for 5 hours in an oxygen atmosphere, and the rod-shaped body after heat treatment was further reduced to a diameter of 10 mm and an inner diameter of 9 m.
The tape material was inserted into a silver pipe of 1 mm in thickness, and after being reduced to a diameter of 8 mm, a tape material with a thickness of 1 mm and a width of 10 m+n was formed using a rolling machine.

Next, this tape material was formed into a pipe shape with a diameter of 3.2 mm, and the butted portions were TIG welded to create a long pipe body, which was then expanded to a diameter of 2.5 mm to obtain a pipe. Next, a quartz cross tape was wrapped around the outer periphery of the pipe to insulate it. Next, a winding diameter of 20 mm made of ceramic (made of boron nitride),
A winding drum with a collar diameter of 50 mm and an axial length of 50 I was prepared, and the pipes were laminated in 5 layers each with 17 turns to form a coil. Next, the entire pipe is inserted into an electric furnace maintained in a nitrogen atmosphere, both ends of the pipe wound around the winding drum are taken out of the furnace, and one tube is placed inside the pipe.
A heat treatment was performed in which the magnet was heated at 890° C. for 5 hours while flowing oxygen gas at a rate of 1/2 min, and then slowly cooled, thereby producing an oxide superconducting magnet.

The completed superconducting magnet was placed in a vacuum container, both terminals were taken out of the container, and an energization experiment was conducted while liquid nitrogen was flowing inside the pipe, and the critical current density (Jc) and critical temperature (Tc) were measured. Ta. In addition, the critical current density (Jc) and critical temperature (Tc) of a pipe-shaped superconducting conductor obtained by heat-treating a short pipe sample prepared in the same manner as the pipe wound around the drum were measured.

In a short sample, Jc at 77 K in the absence of a magnetic field.
=3000A/cm', Tc=92. He indicated OK.

The superconducting coil was able to conduct a current of 30 A at 77 K, and was able to generate an IT (Tesla) magnetic field.

“Production Example 2” BLOs powder, SrCO3 powder, CaCO5 powder, and Cu
B i:S r:Ca:Cu = 2:2:
Mix at a ratio of 2:3 and 8:3 in the atmosphere.
After calcining at 70°C and pulverizing, a rod-shaped body with a diameter of 8m+n was created using a rubber press, and further heat-treated by heating at 870°C for 10 hours in oxygen gas.

This sintered body was inserted into a silver pipe having an outer diameter of 12 mm and an inner diameter of 9 mm, which was further reduced in diameter to 8 n+m, and then rolled into a tape shape with a thickness of 2 m+n and a width of 10 mm using a rolling mill. Thereafter, one side of this tape was continuously immersed in a nitric acid solution to adjust the thickness of the silver layer on one side to 0.1-0.2 mm. The thickness of the silver layer on the other side is 0°3+n+n.

Next, the tape was rounded by forming into a pipe shape so that the side with the smaller thickness of the silver layer became the inner surface, and the abutted portions were joined by TIG welding to create a pipe body. Next, this pipe body was expanded using a plug to create a pipe with an outer diameter of 2.5 mm.
A 0.15 mm alumina tape was wrapped around the surface to insulate it.

Next, the insulated pipe was wound around a ceramic drum having a winding diameter of 25 mm, a collar diameter of 60 mm, and an axial length of 60 mm, and the same heat treatment as in Production Example 1 was performed to obtain a superconducting magnet. This heat treatment is performed while flowing oxygen gas inside the pipe, and the metal sheath on the inner circumferential side of the pipe has a thickness of 0.1 to 0.2 mm as described above.
Since the magnet is formed to be relatively thin, oxygen is sufficiently supplied, and an oxide superconducting magnet with excellent characteristics can be obtained.

For short samples, J c= at 77K in no magnetic field.
It showed 4000 A/cm' and Tc=105K.

In the superconducting magnet, a current of 40 A could be applied at 77 K, and a magnetic field of 2.5 T could be generated.

"Production Example 3" A calcined powder was prepared by mixing BaC0:+ powder and CuO powder at a ratio of 2:3 and calcining the mixture at 880°C in the atmosphere, and adding CaO powder and TI to the calcined powder.

03 powder as TI:Ca:Ba:Cu=2:2:2
:3 to obtain a mixed powder, which was calcined at 880° C. for 1 hour in oxygen gas. This calcined powder was crushed and rolled to obtain a rod-shaped body with a diameter of 8 mm, which was heat-treated at 880°C for 1 hour in an oxygen atmosphere, and then inserted into a silver pipe with an outer diameter of 10 mm and an inner diameter of 9+nn+. The overall diameter was reduced to 8 mm. Next, this wire was rolled into a tape with a thickness of 1 mm and a width of 10 mm, and then a large number of slits were made on one side of the tape at 2 mm intervals in the width direction and at 10 mm intervals in the length direction using a roll with protrusions. After that, the pipe body was formed by forming the pipe body so that the surface on which the slits were formed faced the inner surface. This pipe body was wound around a winding drum to produce a superconducting magnet in the same manner as in the previous manufacturing example.

The critical current density and critical temperature of a short sample obtained by heat treating this superconducting magnet and the pipe were measured.

For short samples, Jc= at 77K in no magnetic field
It showed 4000 A/cm' and Tc=123K.

In the superconducting magnet, a current of 40 A could be applied at 77 K, and a magnetic field of 2.5 T could be generated.

"Effects of the Invention" As explained above, in the oxide superconductor of the present invention, the oxide superconductor is embedded in the peripheral wall of the pipe-shaped metal sheath, so there is no need to provide a separate coolant passage. The oxide superconductor can be used while being cooled by flowing a coolant inside. Moreover, if the above structure is adopted,
When performing heat treatment to generate an oxide superconductor, heat treatment can be performed while flowing oxygen gas inside and outside the pipe body.
Oxide superconductors can be generated while supplying sufficient oxygen to the compacted body inside the metal sheath from both the inner and outer circumferential sides of the metal sheath, producing oxide superconductors with excellent superconducting properties.
can be made.

Furthermore, according to the method of the present invention, after the pipe body is wound around the winding drum, heat treatment is performed to generate an oxide superconductor in the compacted body inside the pipe body peripheral wall, so that the metal sheath is removed during or before winding. To manufacture a superconducting magnet that has few defective parts and does not cause deterioration of superconducting properties because defective parts such as cracks that have occurred in the internal compact body can be partially eliminated by the sintering action of heat treatment and the current path can be increased. I can do it. Furthermore, if heat treatment is performed while flowing oxygen gas inside the pipe body, an oxide superconductor with excellent superconducting properties can be produced without causing oxygen deficiency during heat treatment over the entire length of the pipe body. be.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the invention as claimed in claim 1, in which FIG. 1 is a sectional view showing a tape material having a structure in which powder is filled inside a metal sheath, and FIG. 3 is a cross-sectional view of the oxide superconducting conductor, and FIG. 4 is a cross-sectional view of the tape material being formed into a pipe shape. , a perspective view showing a state in which a pipe is wound around a winding drum; FIG. 5 is a sectional view showing another example of the invention set forth in claim 1; FIG. 6 is a perspective view showing yet another example of the invention. It is a diagram. A, B, C... Oxide superconducting conductor, l... Tape material, 2.5... Metal sheath, 3... Consolidated body, 4... Pipe body, 6... Oxide superconducting body,! l... Winding drum, 20.30... Metal sheath, 21.31... Oxide superconductor.

Claims (2)

[Claims] (1) An oxide superconductor characterized in that an oxide superconductor is embedded inside the peripheral wall of a pipe-shaped metal sheath. (2) A tape material is formed by covering a tape-shaped compacted body made of an oxide superconductor or a precursor of an oxide superconductor with a metal sheath, and this tape material is formed into a pipe shape,
A method for manufacturing a superconducting magnet, which comprises: creating a pipe body by joining the butted parts, and then heat-treating the pipe body after winding it around a winding drum to generate an oxide superconductor inside the consolidated body. .