JP2006059757A - Method for manufacturing nb3x compound superconducting wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method which facilitates the roll-up of a raw material on a core material in a Jelly-roll method and manufactures an Nb<SB>3</SB>X compound superconducting wire having a stable and high super conducting property throughout the length. <P>SOLUTION: A process for manufacturing the Nb<SB>3</SB>X compound superconducting wire by the Jelly-roll method includes a step for forming the superconducting wire where an Nb including sheet made of Nb or an Nb alloy and a sheet made of an alloy including an element X are used, the element X reacts with Nb to form the superconducting compound, the sheets are lapped over with one another, rolled up on the core material the surface of which is not smooth in the circumferential direction throughout the length, and formed into a roll shape lamination, and the roll shape lamination is inserted into a pipe made of Cu or a Cu alloy and squeezed out by static water pressure for the sheets to be formed into a shape of folds. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for producing a Nb ₃ Al-based or Nb ₃ Sn-based (hereinafter sometimes abbreviated as “Nb ₃ X compound-based”) superconducting wire by the jelly roll method, and in particular, nuclear fusion. The present invention relates to a useful method for producing a Nb ₃ X compound-based superconducting wire useful as a material for a superconducting magnet used in a device, a power storage device, physical property research, and the like. In the following description, a typical Nb ₃ Al-based superconducting wire will be taken as an example of the Nb ₃ X compound system, and the description will proceed.

In superconducting wires used in the field of high magnetic field applications, in addition to high critical current density under high magnetic fields, the development of materials with high strain resistance that can withstand mechanical strain stress caused by electromagnetic force acting on superconducting wires Is desired. Under these circumstances, Nb ₃ Al-based intermetallic compounds are expected to be used in superconducting magnets used for fusion devices, power storage devices, physical properties research, etc., because of their high strain resistance in high magnetic fields. .

As a method for producing an Nb ₃ Al-based intermetallic compound, (A) a rapid heating and quenching method in which a wire is heated and held at a high temperature of 1600 ° C. or higher and then rapidly cooled to obtain an Nb ₃ Al phase; (B) Nb and Al There is known a method (diffusion method) or the like in which Nb ₃ Al phase is obtained by a diffusion reaction between Nb and Al by performing a heat treatment at a temperature of 1000 ° C. or less in a state in which is finely dispersed.

Among the above methods, the Nb ₃ Al phase when the rapid thermal quenching method is applied can stably have a compound having a stoichiometric composition of Nb: Al = 3: 1, and has extremely high superconducting characteristics (under a high magnetic field). High critical current density). However, under a high temperature condition of 1600 ° C. or higher, a stabilizing metal such as Cu or Al that is arranged to enhance the stability of the superconducting wire is melted, so that there is a problem that it is difficult to combine the stabilizing metals. Yes, it has become a big obstacle for practical use.

On the other hand, when the diffusion method is applied, since the heat treatment is performed at a temperature of 1000 ° C. or lower, the composite of the stabilized metal is relatively easy. However, since the treatment temperature is low, the stoichiometric composition (Nb: A compound deviating from Al = 3: 1) is likely to be produced, and the superconducting properties are often inferior. However, in this method, when the diffusion distance into Nb is short, it is known that a good quality Nb ₃ Al phase is generated even at a processing temperature of 1000 ° C. or less. Development of Nb ₃ Al-based superconducting wires is underway.

Various manufacturing methods such as a powder metallurgy method, a tube method, a clad chip extrusion method, and a jelly roll method have been proposed as a method for manufacturing an Nb ₃ Al-based superconducting wire that shortens the diffusion distance of Al to Nb. Among them, the jelly roll method is considered to be the most suitable method for practical use since it is relatively easy to increase the length of the superconducting wire and lengthen it.

  In this jelly roll method, an Nb-containing sheet made of Nb or an Nb alloy and an Al-containing sheet made of Al or an Al alloy are wound around a core material made of Cu or a Cu alloy (or Nb or Nb alloy). After being inserted into a pipe made of Cu or Cu alloy, a primary superconducting wire is created by reducing the diameter (reducing surface area) and bundled together with Cu wires having the same cross-sectional shape. A wire rod having a multi-core filament is manufactured by inserting into a pipe made of Cu or Cu alloy and reducing the diameter. In such a method, by reducing the surface, the thicknesses of the laminated Nb sheet and Al sheet can be reduced, and the diffusion distance of Al into Nb can be shortened.

  By the way, in the lap winding process at the initial stage of processing, increasing the winding density and introducing more reaction interfaces directly improves the superconducting properties, so the winding density is increased while suppressing the spread of the raw material sheet wound around the core material. It is necessary to perform the winding operation.

In addition, the Nb ₃ Al phase formation reaction when the Nb ₃ Al-based superconducting wire is produced by the jelly roll method occurs only at the Nb / Al laminated interface, so the reaction rate is slow, and the heat treatment conditions allow Nb and Al to completely react. Then, the coarsening of the Nb ₃ Al crystal formed at an early stage proceeds remarkably, and the critical current density deteriorates due to the decrease of the Nb ₃ Al crystal grain boundary as the magnetic flux pinning point.

On the other hand, under the heat treatment conditions in which the coarsening of Nb ₃ Al crystal grains does not proceed, unreacted Nb and Al are present, so that a sufficient critical current density cannot be obtained. As described above, when an Nb ₃ Al phase is produced by the diffusion method for the Nb ₃ Al-based superconducting wire manufactured by the jelly roll method, there is a problem that a critical current density as expected cannot be obtained. . In order to solve such problems, various techniques have been proposed so far.

For example, in Patent Document 1, Nb ₃ Al whose critical current density is improved by adjusting the crystal structure of an Nb-containing sheet and making the Nb / Al composite structure a structure in which an Al phase is dispersed in a fibrous form in a matrix. -Based superconducting wires have been proposed. In Patent Document 2, the Nb-containing sheet is heat-treated prior to winding to adjust the crystal orientation so that the interface between the Nb-containing sheet and the Al-containing sheet has a dense zigzag shape. Nb ₃ Al-based superconducting wires with improved resistance have been proposed.

  In these techniques, the principle of improving the critical current density is to use an Nb crystal structure having anisotropy for processing. However, with these techniques, it is difficult to strictly control the crystal grain structure of the long Nb-containing sheet used for lengthening the wire, and it is difficult to partially deform the sheet into an intended shape. There is a problem that variations occur in the characteristics of the superconducting wire.

  By the way, when the Nb-containing sheet and the Al-containing sheet are alternately wound on the core material by the jelly roll method, it is common to use a round metal core as the core material, but between the core material and the sheet. Since a sufficient frictional force does not work, the core material is idle, and the sheet is liable to be loosened. When such looseness is generated, the superconducting characteristics are deteriorated. In order to eliminate such winding slack, it is necessary to perform rewinding, but there is a problem that manufacturing time is required. In fact, the inconvenience caused by the loosening of the winding has not been solved by the conventional technology.

Such a problem is not limited to the above-described Nb ₃ Al-based superconducting wire, but is a common problem that occurs in the same manner even when elements (Sn, Ge, Ga, etc.) that react with Nb to form a superconducting phase are used.
Japanese Patent No. 3438271 Patent Claims etc. JP, 6-290651, A Claims etc.

The present invention has been made under such circumstances, and the object thereof is to easily perform the winding operation of the raw material sheet around the core material in the jelly roll method, and to achieve a stable high over the entire length. An object of the present invention is to provide a method for producing a Nb ₃ X compound-based superconducting wire exhibiting superconducting characteristics.

The Nb ₃ method for producing X compound superconducting wire of the present invention which could achieve the above object, in producing a Nb ₃ X compound superconducting wire by a jelly roll method, a Nb sheet consisting of Nb or Nb alloy , A sheet made of an element X that reacts with Nb to form a superconducting compound or an alloy containing the element X, and is superposed and wound around a core whose surface is not smooth in the circumferential direction over its entire length The roll-shaped laminate is inserted into a pipe made of Cu or Cu alloy, and is hydrostatically pressed to form a primary superconducting wire having a sheet-like shape. .

In the manufacturing method of the present invention, a plurality of the primary superconducting wires are bundled, inserted into a pipe made of Cu or Cu alloy, subjected to heat treatment after reducing the diameter, and then subjected to heat treatment to form a multi-core Nb ₃ X compound superconducting wire. Can be obtained.

  In the production method of the present invention, the element X that forms a superconducting compound by reacting with Nb includes one or more elements selected from the group consisting of Al, Sn, Ge, and Ga.

In the production method of the present invention, when producing a Nb ₃ X compound superconducting wire by the jelly roll method, a core material whose surface is not smooth in the circumferential direction is used over the entire length, and a sheet is wound around the core material. By inserting the constructed roll-shaped laminate into a pipe made of Cu or Cu alloy and extruding the sheet into a pipe by hydrostatic pressure, the sheet is formed into a metal core by using the primary superconducting wire formed into a bowl shape. The winding work can be facilitated, and a superconducting wire exhibiting desired superconducting characteristics can be obtained. Also, it is possible to effectively realize the multi-core of the wire by bundling a plurality of primary superconducting wires as described above, inserting them into a pipe made of Cu or Cu alloy, reducing the diameter of this, and then performing heat treatment. it can.

  In order to solve the problems in the prior art, the inventors of the present invention (1) adopt a configuration that increases the frictional force between the metal core and the sheet, and (2) lengthen each interface of the stack. The contact area between Nb and element X is increased, and the diffusion reaction between Nb and element X must be completed before the coarsening of crystal grains proceeds. Thought. Based on these ideas, we examined from various angles. As a result, the inventors have found that the above object can be achieved brilliantly by adopting the configuration as described above, thereby completing the present invention. Hereinafter, the configuration of the present invention will be described in detail with reference to the drawings.

  In the present invention, an Nb-containing sheet made of Nb or Nb alloy and a sheet made of an element X or an alloy containing the element X that reacts with Nb to form a superconducting compound (hereinafter referred to as “Al-containing sheet”) are stacked. Although it is necessary to wind up around a core material collectively, the example of the shape of the core material used at this time is typically shown in FIG.

  In the core material 1 shown in FIG. 1, the unevenness | corrugation 1a is formed along the axial center direction full length of the core material surface. For such a core material, the Nb-containing sheet 2 and the Al-containing sheet 3 are superposed on the surface (Nb / Al laminated portion 4), and the cross-sectional structure (primary composite material) after winding on the core material 1 is illustrated. It is shown in 2.

  As shown in FIG. 2, voids 5 are formed in the core material recess where the core material 1 and the Nb / Al laminated portion 4 do not contact. When the primary composite material 6 having such a configuration is loaded into a Cu or Cu alloy case 7 and then subjected to isostatic pressing and wire drawing, a single-core composite material (primary superconducting wire) 10 as shown in FIG. 3 can be obtained.

  In the single-core composite material 10, the Nb / Al laminated portion 4 is deformed and enters the gap 5 by the isotropic pressure applied during the hydrostatic pressure extrusion and the surface reduction by the wire drawing die. As shown in the A region partial enlarged view of FIG. 3, the Nb / Al laminated portion 4 deformed into a bowl shape can be obtained.

In order to prevent fouling of the stabilized copper during the heat treatment for generating the Nb ₃ Al phase when Cu (stabilized copper) for stabilization is disposed as the core material 1 when constituting the primary composite material. In addition, before the Nb-containing sheet and the Al-containing sheet are overwrapped, the diffusion barrier layer may be provided by winding the Nb sheet around the core material a plurality of times. Further, in order to prevent contamination of the outer Cu-stabilized copper (the Cu or Cu alloy case 7), the Nb / Al laminated portion is covered with an Nb tube (Nb-containing material processed into a pipe shape), Alternatively, after winding the Nb / Al laminated portion, it is possible to wind the Nb sheet a plurality of times to provide a diffusion barrier layer.

Next, the primary superconducting wire 10 is made into a hexagonal cross-sectional shape by wire drawing, and bundled together with a Cu or Cu alloy spacer (not shown) having the same hexagonal cross-sectional shape, and as shown in FIG. It is inserted into the pipe 8 and subjected to extrusion processing and wire drawing processing to obtain a Nb ₃ Al multi-core superconducting wire 12 having a cross-sectional shape as shown in FIG.

Finally, the Nb ₃ Al-based multicore superconducting wire 12 is heat-treated at a relatively low temperature (for example, about 700 to 800 ° C.), whereby the reaction proceeds between the Nb-containing sheet 2 and the Al-containing sheet 3. A Nb ₃ Al-based superconductor phase is formed, and an Nb ₃ Al-based superconducting wire can be obtained.

  In such a configuration, since the core material 1 whose surface is not smooth in the circumferential direction is used, the friction between the core material 1 and the raw material sheet directly wound around the core material is improved, and the winding workability is good. Thus, the winding work can be performed while improving the winding density in a short time.

Further, after winding the composite material (Nb / Al laminated portion 4) around the core material 1 having the above-described configuration, the wound Nb sheet 2 and Al sheet 3 are directly bonded by applying an isotropic hydrostatic pressure. Nb ₃ Al-based superconductivity with high superconducting properties that can increase the reaction interface between Nb and Al reliably and easily over the entire length of the wire without the need for prior heat treatment, etc. Wire can be realized. Further, with such a configuration, the reaction interface can be greatly increased as compared with the conventional case.

  In the configuration of the core material 1 shown in FIG. 1, the cross-sectional shape of the convex portion of the core material 1 is a tapered shape, but this convex shape is not limited to that shown in FIG. As shown in FIG. 8, a gear type having a rectangular section, a corrugated section as shown in FIG. 8, and the like can be formed. Further, the uneven shape does not have to be constant along the axial direction, and may be an uneven shape having a planar lattice shape as shown in FIG. Furthermore, the surface may be diamond-like or heptagonal notched by knurling (knurling). In short, as long as the surface properties are not smooth in the circumferential direction, any can be used as the core material 1 of the present invention. Since the height of the concave portion and the convex portion in the surface property can be freely selected, the Nb / Al laminated portion 4 having an arbitrary shape (cross-sectional shape) can be formed.

  As the Nb-containing sheet 2 used in the present invention, an Nb alloy containing alloy elements such as Ti, Ta, Zr, and Hf can be used in addition to industrial pure Nb. Examples of the element X that reacts with Nb to form a superconducting compound include one or more elements selected from the group consisting of Al, Sn, Ge, and Ga, and a sheet made of these single elements, or these A sheet obtained by alloying two or more of these, and further containing an alloy element such as Mg, Be, Ag, or Cu can be used as a sheet containing the element X.

  Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are not of a nature that limit the present invention, and any design changes may be made in accordance with the gist of the present invention. It is included in the technical scope.

As an example core material 1, a Cu rod knurled so that the difference in diameter between the concave portion and the convex portion is 1.0 mm is used, and an Nb sheet 2 having a thickness of 0.1 mm and an Al having a thickness of 0.03 mm are used. The sheet 3 was laminated and wound up to produce a primary composite material 6 as shown in FIG. At this time, the time required for winding the Nb sheet 2 and the Al sheet 3 was about 2 hours.

The obtained primary composite material was loaded into the Cu case 7 (FIG. 3) and then subjected to hydrostatic pressure extrusion and wire drawing to prepare a hexagonal cross-section single-core composite material (Nb / Al / Cu composite). 102 hexagonal cross-section single core composites were bundled and incorporated in a Cu case, drawn, and processed to φ1.00 mm to produce a multicore composite (Nb ₃ Al multicore superconducting wire 12).

  In order to investigate the shape of the Nb / Al laminated portion in the produced multicore composite material, the multicore composite material was divided into 50 equal parts and the cross sections thereof were observed. As shown schematically in Fig. 1, it had a bowl shape with a very fine curved part.

This multi-core composite was subjected to Nb ₃ Al phase generation heat treatment at 750 ° C. for 50 hours, and the critical current density was measured at a temperature of 4.2 k and a magnetic field of 12 T. As a result, it was 690 A / mm ² .

As a comparative example core material 1, a Cu bar having a smooth surface is used, and a Nb sheet having a thickness of 0.1 mm and an Al sheet having a thickness of 0.03 mm are laminated and wound, and a primary composite material as shown in FIG. 15 was produced. At this time, the time required for winding the Nb sheet 2 and the Al sheet 3 was about 5 hours.

  After the obtained primary composite material 15 was loaded into the Cu case 7, it was subjected to hydrostatic extrusion and wire drawing to produce a single-core composite material 16 as shown in FIG. Further, the single-core composite material 16 was processed to prepare a hexagonal cross-section single-core composite material (Nb / Al / Cu composite). 102 hexagonal cross-section single-core composite materials were bundled and incorporated in a Cu case, wire drawing was performed, and processing was performed to φ1.00 mm to prepare a multicore composite material.

  In order to investigate the shape of the Nb / Al laminated portion in the produced multicore composite material, the multicore composite material was divided into 50 equal parts and the cross-sections were observed. 11 and a slightly curved shape as schematically shown in FIG.

This multi-core composite was subjected to Nb ₃ Al phase generation heat treatment at 750 ° C. for 50 hours, and the critical current density was measured at a temperature of 4.2 k and a magnetic field of 12 T. As a result, it was 630 A / mm ² .

It is the schematic which shows an example of the core material 1 used by this invention. It is the schematic sectional drawing which showed one structural example of the primary composite material 6 produced by this invention. It is the schematic of the single core composite material 10 produced by this invention. FIG. 4 is an enlarged view of a portion A in FIG. 3. It is a schematic view of making the Nb ₃ Al-based multi-core superconducting wire in the present invention. It is a schematic cross-sectional view of a Nb ₃ Al-based multi-core superconducting wire manufactured in this invention. It is a schematic sectional drawing which shows the other example of the core material 1 used by this invention. It is a schematic sectional drawing which shows the further another example of the core material 1 used by this invention. It is a schematic sectional drawing which shows the other example of the core material used by this invention. It is the schematic sectional drawing which showed the structural example of the primary composite material 15 as a comparative example. It is a schematic sectional drawing which shows one structural example of the single core composite material 16 as a comparative example. It is the B area | region partial enlarged view in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Core material 2 Nb containing sheet 3 Al containing sheet 4 Nb / Al lamination | stacking part 5 Space | gap 6,15 Primary composite material 10,16 Single core composite material (primary superconducting wire)
12 Nb ₃ Al multi-core superconducting wire

Claims (3)

In producing an Nb ₃ X compound-based superconducting wire by the jelly roll method, an Nb-containing sheet made of Nb or an Nb alloy, and a sheet made of an element X or an alloy containing the element X that reacts with Nb to form a superconducting compound A roll-shaped laminate formed by superimposing and winding these around a core material whose surface is not smooth in the circumferential direction over the entire length is inserted into a pipe made of Cu or Cu alloy, and this is hydrostatically extruded. method for producing a Nb ₃ X compound superconducting wire which comprises the step of the primary superconducting wire forming the sheet into pleated by. 2. The method of producing a Nb ₃ X compound-based superconducting wire according to claim 1, wherein a plurality of the primary superconducting wires are bundled, inserted into a pipe made of Cu or a Cu alloy, and subjected to heat treatment after diameter reduction processing. The element X that reacts with Nb to form a superconducting compound is at least one element selected from the group consisting of Al, Sn, Ge, and Ga. _3. The Nb ₃ X-based superconducting wire according to claim 1 or 2, Production method.

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