JPH11353961A - Precursor wire material of nb3sn compound superconductor and its manufacture, manufacture of nb3sn compound superconductor, and manufacture of nb3sn compound superconducting coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate wire stranding and coil formation by forming a Cu-Sn base matrix, many Nb base filaments separately embedded on the side outer than the central part of the Cu-Sn base matrix, and an Nb-Sn base compound layer formed in the outer periphery of the Nb base filaments. SOLUTION: A precursor wire material 10 of a Nb3 Sn compound superconductor has a Cu-Sn base matrix 11, a plurality of Nb base filaments 12 separately embedded in the matrix 11, and an Nb-Sn base compound layer 13 formed in the peripheral layer of the Nb base filaments 12. By this constitution, even if heat higher than the melting point of Sn is applied in a process for forming a conductor or a coil, generation of a shrinking cavity caused by melting of Sn is suppressed because pure Sn does not exist because the matrix 11 is formed in bronze. The production reaction of normal Nb3 Sn compound superconductor occurs in the following heat treatment, and deterioration in critical density characteristics in high magnetic field is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention, Nb ₃ Sn compound precursor wire and a method of manufacturing a superconductor, Nb ₃ Sn
The present invention relates to a method for producing a compound superconducting conductor and a method for producing an Nb ₃ Sn compound superconducting coil.

[0002]

2. Description of the Related Art As superconducting application fields in which a large current can flow or a strong magnetic field can be generated without power loss, (1) energy saving development by superconducting a power system such as a generator, a transmission cable, and energy storage; ) Fusion, M
Development of new energy such as HD (magnetohydrodynamic) power generation, (3) high energy accelerator,
Maglev train, electromagnetic propulsion ship, magnetic separation, medical MRI
(Magnetic resonance imagi
ng) and other new technologies utilizing high magnetic fields.
For the development of such superconducting applied technologies, the development of superior superconducting wire technology is indispensable.
Under a magnetic field of 8T and 9T or less, NbTi-based alloy superconductors are used, and under a high magnetic field higher than that, Nb ₃ Sn and V ₃
Ga-based compound superconductors have been developed. In order to stabilize these superconductors, a large number of superconducting filaments having a diameter of several tens of μm or less are buried in a metal matrix having a small resistivity, such as Cu, and the superconducting filaments have a twisted structure. . Such a superconductor is called an ultrafine multifilamentary wire.

[0003] Among these superconducting superconducting materials, compound superconducting materials have the characteristic that their critical temperature and upper critical magnetic field are considerably higher than alloy-based materials such as NbTi, but they are extremely brittle. have. Therefore, since the compound-based superconductor itself does not have workability, various ideas have been proposed for a manufacturing method for obtaining this ultrafine multifilamentary wire. At present, a production method which is industrially established utilizes a solid-phase reaction, and as a main method, for example, "Material Science" Vol. 2
0, No. 2, Aug. 1983, p. 82-P. 83
Bronze method, tube method, internal diffusion method,
There is an external diffusion method.

FIG. 4 is a cross-sectional view showing a precursor wire of an Nb ₃ Sn compound superconductor before heat treatment by a conventional internal diffusion method described in, for example, Japanese Patent Publication No. 61-16141. In FIG. 4, reference numeral 1 denotes a precursor wire of an Nb ₃ Sn compound superconductor before heat treatment, 2 denotes an Nb-based metal material which becomes a superconductor by a heat treatment performed later, 3 denotes a Cu-based matrix, and 4 denotes a Sn-based metal material.

[0005] Nb ₃ Sn by the internal diffusion method shown in FIG.
The precursor wire 1 of the compound superconductor is manufactured as follows. First, an Nb-based metal material 2 that becomes a superconductor by heat treatment after manufacturing the precursor wire 1 is inserted into a Cu tube, and the diameter is reduced to a predetermined diameter. The Nb-based metal rod covered with the reduced diameter Cu tube is cut into an appropriate length, and a large number of Cu containers are filled. However, C in the center
A u-bar or a Cu portion composed of a number of Cu lines is arranged. By arranging a Cu lid and sealing the lid by welding while excluding the air in the container,
A composite billet in which a number of Nb-based metal materials are embedded in u is obtained. After extruding the composite billet, a hollow portion is formed by drilling a hole in the center of the Cu portion by mechanical cutting, and the Sn alloy material 4 is inserted into the hollow portion, as shown in FIG.
A composite having a Sn alloy material 4 and a large number of Nb-based metal materials 2 embedded in a Cu-based matrix 3 at the center having the cross-sectional shape shown in FIG. By further reducing the diameter of this composite, a precursor wire 1 of an Nb ₃ Sn compound superconductor is obtained. In the precursor wire 1, a large number of Nb-based metal materials 2 embedded in a Cu-based matrix 3
It may be called a filament 5.

[0006] Nb ₃ Sn by the internal diffusion method shown in FIG.
The compound superconductor precursor wire 1 is manufactured as described above, and then subjected to a preliminary heat treatment for bronze formation (temperature range: 550 to 580 ° C., holding time: 100 to 200 hours).
And final heat treatment for Nb ₃ Sn generation (temperature range 60
(0 to 800 ° C., holding time: 30 to 300 hours), most or all of the surface layer of the Nb filament 5 is changed to Nb ₃ Sn, and an Nb ₃ Sn compound superconductor is obtained. Here, the reason for performing the preliminary heat treatment is that Sn diffuses into the surrounding Cu to form a Cu—Sn phase (bronze formation), so that Sn in the Cu—Sn phase becomes This is for reacting with all the Nb filaments 5 and for reacting the Nb filaments 5 with the homogeneous Nb ₃ Sn superconductor. Therefore, the conventional Nb ₃ Sn
The precursor wire 1 of the compound superconductor refers to a wire in which the Nb filament 5 becomes an Nb ₃ Sn compound superconductor in a heat treatment (preliminary heat treatment and final heat treatment) after the production of the precursor wire 1.

As described above, Nb ₃ Sn by the internal diffusion method is used.
A method for producing a compound superconductor has been industrially established. Recently, Nb ₃ Sn compounds have been replaced by _third compounds such as Ti and Ta.
By adding an element, a critical current density (hereinafter, referred to as Jc) in a high magnetic field is improved, and a high magnetic field magnet of 17 T or more has been put to practical use. In addition, for AC applications or pulse magnet applications, a stranded wire type superconducting conductor is used to reduce AC loss and secure current capacity.

[0008]

Since the Nb ₃ Sn compound superconductor has the disadvantage of being extremely brittle as described above, the superconducting characteristics against external load strain, particularly Jc
There is a problem that the characteristics are significantly deteriorated. For this reason,
There is a problem that it is difficult to form a superconducting conductor by twisting the Nb ₃ Sn compound superconductor generated by heat treatment, or to form a superconducting coil by winding using this superconducting conductor. there were.

In the production of a relatively small superconducting coil, a precursor wire before heat treatment, or a conductor in which several to several tens of precursor wires are twisted, may be subjected to an appropriate insulation treatment in some cases. After forming a coil in a desired shape in advance, a so-called Wind & React method (hereinafter referred to as W & R) in which a heat treatment for generating an Nb ₃ Sn compound superconductor is performed.
This is called a method). For relatively small superconducting coils, the W & R method avoids distortion problems associated with coil formation.

On the other hand, as seen in, for example, a superconducting coil for a fusion reactor, the current capacity is several tens of kA, and the coil diameter is several tens.
Production of large superconducting coils reaching 0 m has been started, and problems that have not been a major problem have appeared. That is, in order to secure a current capacity, a metal pipe called a conduit, such as stainless steel, is used.
Manufacture a conductor (cable-in-conduit (hereinafter referred to as CIC)) containing more than one twisted precursor wire and connect multiple conductors to each other to secure the conductor length. When connecting only by drawing in and welding together conduits, there are cases where a plurality of conductors are welded or soldered together).

However, when the W & R method is adopted for a large superconducting coil, Nb ₃ Sn by the conventional internal diffusion method is used.
The precursor wire of the compound superconductor has the following problems because the Cu matrix of the precursor wire is not bronze (the Cu matrix becomes a Cu-Sn based matrix). (1) In a processing step of forming a conductor or a coil, for example, a welding step of conduits, the melting point of Sn (about 200
℃) or more, the S inside the precursor wire at that portion
n is melted, and voids (so-called “hink cavities”) are generated inside the precursor wire, so that in the subsequent heat treatment, the Sn diffusion reaction and the Nb3Sn generation reaction in that portion of the precursor wire do not proceed well, and as a result, The Jc characteristic of the Nb ₃ Sn compound superconductor is deteriorated. Therefore,
During such a processing step, heat above the melting point of Sn cannot be applied. (2) Before heat treatment, S from the precursor wire during heat treatment
An end sealing process for preventing Sn from flowing out due to melting of n is required for each precursor wire. Further, after the heat treatment, after removing these end sealing portions, it is necessary to form a conductor or coil having a final shape. (3) The material strength of the matrix is weak.

In order to solve these problems, the precursor wire of the Nb ₃ Sn compound superconductor by the internal diffusion method before the heat treatment is preliminarily subjected to only the preliminary heat treatment which has been conventionally performed, so that the matrix of the precursor wire is bronze-formed. I tried to try. However, in the method in which this precursor wire is subjected to stranded wire processing and then the final heat treatment, there is a problem that the Jc characteristics are deteriorated due to the stranded wire processing.

The cause of the deterioration of the Jc characteristic due to the twisted wire processing is explained as follows. That is, as shown in FIG. 5, an electron beam microanalyzer (hereinafter, EPMA)
), It was found that the Nb-Sn-based compound layer 6 was formed on the outer periphery of the Nb filament 5 by the preliminary heat treatment. This Nb-Sn group compound layer 6
In EPMA, a strain is applied during the subsequent stranded wire processing, so that a part thereof is cracked or broken, and even a final heat treatment performed thereafter does not recover a normal Nb ₃ Sn compound. Became clearer.
Therefore, it was found that even if only the preliminary heat treatment performed conventionally and the final heat treatment was performed after the stranded wire processing, the Nb ₃ Sn compound having good Jc characteristics was not obtained, so that the Jc characteristics were significantly reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is resistant to external load distortion and has a melting point higher than the melting point of Sn during a processing step of forming a conductor or a coil. It is an object of the present invention to obtain a precursor wire of an Nb ₃ Sn compound superconductor to which heat of the above can be applied, that is, easy to form a stranded wire or form a coil, and a method for producing the precursor wire. It is another object of the present invention to provide a precursor wire of an Nb ₃ Sn compound superconductor which can suppress the deterioration of the Jc characteristic even when an external load strain is applied, and a method of manufacturing the same. Furthermore, it is strong against external load distortion during the manufacturing process, can suppress the deterioration of the Jc characteristic even when external load distortion is applied, and has a melting point higher than the melting point of Sn during the processing step of forming a conductor or a coil. Heat can be applied, and as a result, N has good characteristics that facilitates stranded wire processing or coil formation.
Method for producing b ₃ Sn compound superconductor, and Nb ₃ Sn
An object is to obtain a method for manufacturing a compound superconducting coil.

[0015]

[MEANS FOR SOLVING THE PROBLEMS] Nb ₃ S according to claim 1
The precursor wire of the n-compound superconductor includes a Cu-Sn-based matrix, a number of Nb-based filaments separated and embedded outside the center of the Cu-Sn-based matrix,
And a Nb-Sn-based compound layer formed on the outer periphery of the base filament.

Further, the precursor wire of the Nb ₃ Sn compound superconductor according to the second aspect is such that the thickness of the Nb—Sn based compound layer is 20% or less of the diameter of the Nb based filament.

The precursor wire of the Nb ₃ Sn compound superconductor according to claim 3 is one in which the average Sn concentration of the Cu—Sn based matrix is 14 to 30 wt%.

According to a fourth aspect of the present invention, there is provided a precursor wire of the Nb ₃ Sn compound superconductor, wherein the Cu—Sn based matrix includes an alpha phase bronze alloy, and at least one phase in a gamma phase, a delta phase, and an epsilon phase bronze. And a mixed phase.

According to a fifth aspect of the present invention, in the precursor wire of the Nb ₃ Sn compound superconductor, a central portion of the Cu—Sn based matrix is formed only of the Cu—Sn based matrix, and a large number of Nb based filaments are separated outside the matrix. It was buried.

According to a sixth aspect of the present invention, there is provided a method for producing a precursor wire of a Nb ₃ Sn compound superconductor, wherein a plurality of Nb-based filaments are separated and embedded outside a central portion of a Cu-based matrix. Extruding the composite billet, then drilling a hole in the center of the Cu-based matrix, inserting a Sn-based metal material into the hole to form a composite, and drawing at least one composite. And a step of forming a Cu-Sn-based matrix by performing a preliminary heat treatment after the wire-drawing step, whereby the Cu-based matrix and the Sn-based metal material of the composite undergo a diffusion reaction.
Forming a Nb-Sn-based compound layer having a thickness of 20% or less of the diameter of the Nb-based filament by causing Sn of the Cu-Sn-based matrix to undergo a diffusion reaction on the outer periphery of the Nb-based filament.

According to a seventh aspect of the present invention, in the method for producing a precursor wire of an Nb ₃ Sn compound superconductor, the step of performing the preliminary heat treatment is performed in a temperature range of 500 to 580 ° C. and a holding time of 60 hours or less. is there.

Further, the method of manufacturing an Nb ₃ Sn compound superconductor according to claim 8 comprises a step of forming a composite billet in which a large number of Nb-based filaments are separated and embedded outside the center of the Cu-based matrix, After extruding the composite billet, a hole is formed in the center of the Cu-based matrix, a Sn-based metal material is inserted into the hole to form a composite, and at least one composite is subjected to wire drawing. A step of forming a Cu-Sn-based matrix by performing a preliminary heat treatment after the step of wire drawing to perform a diffusion reaction between the Cu-based matrix and the Sn-based metal material of the composite to form a Cu-Sn-based matrix;
Sn of -Sn group matrix is subjected to a step of forming a Nb-Sn based compound layer with 20% or less of the thickness of the Nb-based filament diameter by diffusion reaction to the outer periphery of the Nb-based filaments Nb ₃ Sn compound superconducting A step of forming a precursor wire, a step of twisting a precursor wire of at least one Nb ₃ Sn compound superconductor to form a stranded wire conductor,
Forming a Nb ₃ Sn compound at the Nb-based filament portion of the stranded conductor by final heat treatment.

In the method for manufacturing a Nb ₃ Sn compound superconductor according to the ninth aspect, the step of performing the preliminary heat treatment may include:
The holding time is within 60 hours at a temperature range of 0 to 580 ° C, and the holding time is 3 hours at a temperature range of 600 to 800 ° C for the final heat treatment.
0 to 300 hours.

Still further, the Nb ₃ Sn according to claim 10 may be used.
The method of manufacturing the compound superconducting coil includes a step of forming a composite billet in which a large number of Nb-based filaments are separated and embedded outside a central portion of the Cu-based matrix, and extruding the composite billet, and then forming a center of the Cu-based matrix. Forming a composite by inserting a Sn-based metal material into the hole, performing a wire drawing process on at least one composite, and performing a preliminary heat treatment after the wire drawing process. A step of forming a Cu—Sn based matrix by a diffusion reaction between the Cu-based matrix and the Sn-based metal material of the composite, and a step of causing a diffusion reaction of Sn of the Cu—Sn-based matrix to the outer periphery of the Nb-based filament to form a Nb-based matrix. Base filament diameter of 20
Twisting% forming a precursor wire of Nb ₃ Sn compound superconductors subjected to the step of forming a Nb-Sn based compound layer having a thickness of, at least one of Nb ₃ Sn compound superconductor precursor wire Wire processing to form a stranded conductor,
The method includes a step of forming a coil by winding the stranded wire conductor, and a step of forming an Nb ₃ Sn compound formed on the Nb-based filament portion of the coil by final heat treatment.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a cross-sectional view showing a configuration of a precursor wire of an Nb ₃ Sn compound superconductor by an internal diffusion method according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 10 denotes a precursor wire of an Nb ₃ Sn compound superconductor,
Reference numeral 1 denotes a Cu-Sn-based matrix, 12 denotes a plurality of Nb-based filaments separately embedded in a Cu-Sn-based matrix 11, and 13 denotes an Nb-Sn-based compound layer formed on an outer peripheral layer of the Nb-based filament 12. .

The precursor wire 10 of the Nb ₃ Sn compound superconductor by the internal diffusion method according to the present invention shown in FIG. 1 and the precursor wire 1 of the Nb ₃ Sn compound superconductor by the conventional internal diffusion method shown in FIG. The main difference is that the precursor wire 1 of the conventional Nb ₃ Sn compound superconductor is not subjected to the preliminary heat treatment, whereas the precursor wire 10 of the Nb ₃ Sn compound superconductor according to the present invention is subjected to the preliminary heat treatment. It is. Hereinafter, a method for producing the precursor wire 10 of the Nb ₃ Sn compound superconductor by the internal diffusion method will be described.

First, an Nb round bar is inserted into a Cu tube,
A wire drawing is performed to obtain an Nb-based metal material covered with a Cu tube whose diameter has been reduced to a hexagonal shape, and the Nb-based metal material covered with the Cu tube is cut into a predetermined length. next,
A Cu rod or a Cu-based matrix composed of a large number of Cu wires is arranged at the center of the Cu container, and an Nb-based metal material covered with a large number of Cu tubes is embedded outside the central portion of the Cu-based matrix. . Therefore, the Nb-based metal materials are separated from each other by the Cu-based matrix. By arranging a Cu lid and eliminating air in the container, welding the lid and sealing it,
A composite billet having a number of Nb-based metal rods, ie, Nb-based filaments 12, embedded in a Cu-based matrix is formed.

The composite billet is extruded and processed, the both ends of the composite billet are cut transversely, and the center of the cut surface is cut to form a hole. A Sn-based metal material is inserted into the hole to form a composite. In some cases, a Ta tube serving as a Sn diffusion barrier is further placed over the outer peripheral portion of the composite, and an oxygen-free copper tube is placed over the outside thereof.

The composite thus obtained is subjected to wire drawing or, if necessary, a plurality of the above-mentioned composites are further compounded before wire drawing. After that, the end portion is melted by arc melting to perform the end portion treatment.

The thus formed product is kept in a nitrogen gas atmosphere at a temperature range of 500 to 580 ° C. and a holding time of up to 60 hours or less, preferably at a temperature range of 520 to 5
By performing a preliminary heat treatment at 80 ° C. to keep the holding time within 30 hours, bronzing, that is, Cu
The base matrix and the Sn-based metal material undergo a diffusion reaction to cause Cu-
The Sn-based matrix 11 is formed. In particular, Cu-
The central portion of the Sn-based matrix 11 is formed only of the Cu-Sn-based matrix.

Further, Sn in the Cu—Sn based matrix 11 diffuses and reacts to the outer periphery of the Nb based filament 12 to form N 2.
20% or less, preferably 15% of the diameter of the b-based filament
The Nb-Sn group compound layer 13 having the following thickness is formed to
The precursor wire 10 of the ₃ Sn compound superconductor is formed.
The precursor wire 10 is subjected to a final heat treatment in a subsequent step, for example, a temperature range of 600 to 800 ° C. and a holding time of 30 to 30.
By performing 0 hours, an Nb ₃ Sn compound superconductor is formed.

In a conventional precursor wire of an Nb ₃ Sn compound superconductor, Sn is partially formed on the precursor wire in a processing step of forming a conductor or a coil, for example, a welding step of conduits.
When the heat above the melting point is applied, Sn inside the precursor wire at that portion is melted, and “hink cavities” are generated inside the precursor wire, so that the diffusion reaction of Sn in the precursor wire at that portion in the subsequent heat treatment. And the formation reaction of Nb ₃ Sn did not proceed well, and as a result, the Jc characteristic of the Nb ₃ Sn compound superconductor was deteriorated.

However, according to the precursor wire 10 of the Nb ₃ Sn compound superconductor by the internal diffusion method of the first embodiment, the pre-heat treatment is performed to form a bronze, that is, a Cu-based matrix of a composite and a Sn-based metal material. And the Cu-Sn based matrix 11 is formed by a diffusion reaction. Therefore, even if heat equal to or higher than the melting point of Sn is applied to the precursor wire in a subsequent processing step of forming a conductor or a coil, the matrix is bronze-formed. Since pure Sn does not exist, it is possible to suppress the occurrence of “sink cavities” due to the melting of Sn. Therefore, a normal Nb ₃ Sn compound superconductor generation reaction does not occur in the subsequent heat treatment, and the Jc characteristics do not deteriorate. Therefore, during the process of forming a conductor or a coil, S
It is possible to obtain a precursor wire of an Nb ₃ Sn compound superconductor which can apply heat of not less than the melting point of n, that is, is easy to form a stranded wire or form a coil, and has good characteristics, and a method for producing the same.

Further, in the conventional precursor wire of the Nb ₃ Sn compound superconductor, an end sealing process (a process of melting the end portion by arc melting) for each precursor wire for the purpose of preventing the loss of Sn during the heat treatment. ), And removal of the end sealing portion after heat treatment. On the other hand, since the precursor wire 10 of the Nb ₃ Sn compound superconductor of the present invention has already been subjected to the preliminary heat treatment, the Cu matrix is bronze, so that the edge sealing treatment during the subsequent heat treatment, and The step of removing the end sealing portion after the heat treatment can be omitted. For this reason, it is possible to obtain a precursor wire of an Nb ₃ Sn compound superconductor and a method of manufacturing the same, which can simplify the process of stranded wire processing or coil formation.

Further, since the precursor wire 10 of the Nb ₃ Sn compound superconductor has already been subjected to the preliminary heat treatment,
Since the matrix is bronze, that is, the Cu-based matrix of the composite and the Sn-based metal material undergo a diffusion reaction to form the Cu-Sn-based matrix 11, the components of Cu, Sn, and Nb are charged in a pure metal state. Material strength can be improved as compared with the case where For this reason, N is resistant to external load distortion, that is, easy to form a stranded wire or form a coil.
b ₃ Sn compound superconductor precursor wire and it is possible to obtain a method of manufacturing.

Further, Sn in the Cu—Sn based matrix 11 diffuses and reacts on the outer periphery of the Nb based filament 12, and the Nb—Sn having a thickness of 20% or less, preferably 15% or less of the diameter of the Nb based filament. Since the base compound layer 13 is formed, if the thickness is such a thickness, the unreacted N
Since it is strengthened by b, distortion resistance is improved.
Further, even if a part of the Nb—Sn base compound layer 13 is cracked or broken by external load strain,
Since the rate of destruction of the Nb-Sn-based compound layer 13 with respect to the entire Nb-based filament is low, deterioration of the Jc characteristics can be suppressed.

In the precursor wire 10 of the Nb ₃ Sn compound superconductor of the present invention, unlike the wire made by the bronze method, the average Sn concentration of the Cu—Sn based matrix 11 is 1%.
The content can be as high as 4 wt% or more, whereby it is possible to form a mixed phase with at least one of the gamma phase, the delta phase, and the epsilon phase bronze in addition to the alpha phase bronze alloy. With such a configuration of the Cu—Sn based matrix 11, the characteristics of Jc can be improved.

The reason will be described with reference to FIG. FIG. 3 shows “Binary Alloy Phase Diagr”.
ams "2ndEdition, Vol. 2, ASM
International (1990), p. 1
481-P. 1483 is a Cu-Sn binary system diagram shown in FIG. In FIG. 3, the horizontal axis represents the solid solubility of Sn in Cu by weight% (lower axis) and the atomic weight% (upper axis), and the vertical axis represents the temperature in ° C. L indicates a liquid phase. In other indications, for example, alpha-phase bronze (the range indicated by α (Cu) in the figure) indicates the solid solubility of Sn in Cu at each temperature of 100 to 1084.87 ° C., and the highest is Cu-1.
It is shown as 5.8 wt% Sn (520 ° C.). Also,
For example, the delta phase (the range indicated by the δ phase in the figure) is 350
It shows the solid solubility of Sn in Cu at each temperature of ５８586 ° C., and the highest is indicated by Cu−32.55 wt% Sn (582 ° C.).

In the case of a bronze wire in which the matrix is bronze in advance and the wire is processed, C
Precipitation of the compound phase in the u-Sn-based matrix is not preferable due to the problem of workability, and there is a limitation that the average Sn concentration of the matrix must be in this alpha phase bronze alloy region. For this reason, in a wire rod by the bronze method, a bronze matrix of about 14% by weight or less is usually used. Therefore, finally Nb ₃ S
Nb amount to be n compound superconductor also can not be charged only meet the Sn amount, after all, Nb ₃ S generated
There is also a limit on the amount of n-compound superconductor.

However, in the internal diffusion method, Nb, Sn, C
Since each component of u is charged in the state of a pure metal, there is no limitation on the amounts of Nb and Sn due to workability restrictions. Therefore, C
The average Sn concentration of the u-Sn based matrix can be as high as 14 wt% or more. In other words, the amount of the Nb ₃ Sn compound superconductor can be increased, and the characteristics of Jc can be improved. Also, preferred practical Cu-
The average Sn concentration at the upper limit of the Sn-based matrix is 27.9 wt% in actual measurement, but can be further increased (about 40 wt%) in calculation, so it is preferably 30 wt%.

The embodiment of the present invention shown in FIG.
Cu is used as the precursor wire 10 of the Nb ₃ Sn compound superconductor.
As an example, a precursor wire of a superconductor having no stabilizing material typified by No. and a diffusion barrier material typified by Nb and Ta has been described. However, since these stabilizers and diffusion barrier materials are not affected by the heat treatment of the present invention, the present invention is also effective for precursor wires of Nb ₃ Sn compound superconductors having stabilizers and diffusion barrier materials. That is clear.

In the precursor wire 10 of the Nb ₃ Sn compound superconductor of the present invention shown in FIG. 1, at least one of the Nb-based filament and the Sn-based metal material includes Ti,
In, Ge, Si, Al, Ta, Hf, Zr, W, Mo
By adding an element represented by or a component containing at least one element among them, it is possible to improve the superconducting characteristics obtained by the subsequent heat treatment, particularly the Jc characteristics in a high magnetic field. The present invention does not prevent such element addition.

As the precursor wire 10 of the Nb ₃ Sn compound superconductor of the present invention shown in FIG. 1, the Cu—Sn based matrix 11 is composed of Ti, Mn, Ge, besides the binary bronze of Cu and Sn. , Si, In, Mg, etc., into a ternary or higher bronze phase by adding a small amount thereof, to obtain superconducting properties obtained by a subsequent heat treatment,
The c characteristics can be improved, and the present invention does not prevent such element addition.

Further, as the precursor wire 10 of the Nb ₃ Sn compound superconductor of the present invention shown in FIG. 1, an example in which a composite of an Nb filament and a Cu—Sn bronze matrix is made into a single wire has been described. In order to increase the current capacity, a large number of the obtained composites may be filled in a Cu tube or the like to form a secondary composite, and the diameter may be reduced. The precursor wire of such a secondary composite superconductor may be used. Needless to say, the present invention is effective also in the case of (1).

Furthermore, as the first embodiment, the explanation has been given by taking as an example the precursor wire of the Nb ₃ Sn compound superconductor by the internal diffusion method. However, in addition to the internal diffusion method, an Nb group such as the external diffusion method or the Nb tube method, It includes other precursor wires of Nb ₃ Sn-based compound superconductors composed of the respective metal components of base and Cu groups, and it cannot be overemphasized that the present invention is effective also in the precursor wires by these manufacturing methods.

Embodiment 2 The Nb ₃ Sn compound superconductor by the internal diffusion method according to the second embodiment and a method for manufacturing the same will be described. First, a precursor wire 10 of an Nb ₃ Sn compound superconductor is formed in the same manner as in the first embodiment.

Next, at least one precursor wire 10 of the Nb ₃ Sn compound superconductor is stranded to form a stranded conductor, for example, at a temperature range of 600 to 800 ° C. and a holding time of 30 to 300. By performing a final heat treatment for a long time in a nitrogen gas atmosphere, a portion of the Nb-based filament 12 in the precursor wire 10 of the Nb ₃ Sn compound superconductor is Nb ₃
An Sn compound is formed to form an Nb ₃ Sn compound superconductor.

Nb ₃ S by the internal diffusion method according to the second embodiment
According to the n-compound superconductor and the method of manufacturing the same, since the precursor wire 10 of the Nb ₃ Sn compound superconductor of the first embodiment is used, the same operation and effect as in the first embodiment can be obtained. That is, during the manufacturing process, it is strong against external load strain, and even if external load strain is applied, it is possible to suppress the deterioration of the Jc characteristic. As a result, it is easy to process the conductor, and the Nb ₃ Sn compound superconducting conductor having good characteristics and The manufacturing method can be obtained.

Further, particularly when a conductor is formed, the conventional conductor using a precursor wire and its manufacturing method require an end sealing process for each precursor wire and removal of the end sealing process. On the other hand, according to the Nb ₃ Sn compound superconductor by the internal diffusion method and the method for manufacturing the same according to the second embodiment, the Cu matrix of the wire is already bronze. and a sealing process, becomes its ends sealing treatment portion removal step and is not required at all, easily conductor processing as a result, and simplification of a process can be achieved Nb ₃ S
An n-compound superconductor and a method for producing the same can be obtained.

Embodiment 3 The Nb ₃ Sn compound superconducting coil by the internal diffusion method according to the third embodiment and a method for manufacturing the same will be described. First,
The precursor wire 10 of the Nb ₃ Sn compound superconductor is formed in the same manner as in the first embodiment.

Next, at least one precursor wire 10 of the Nb ₃ Sn compound superconductor is stranded to form a stranded conductor, and the stranded conductor is wound to form a coil. By subjecting the coil thus formed to a final heat treatment at a temperature range of 600 to 800 ° C. and a holding time of 30 to 300 hours in a nitrogen gas atmosphere P, the Nb-based filament 12 of the precursor wire 10 to form a ₃ Sn compound to form a Nb ₃ Sn compound superconducting coils.

Nb ₃ S by the internal diffusion method according to the third embodiment
According to the n-compound superconducting coil and the method of manufacturing the same, the precursor wire 10 of the Nb ₃ Sn compound superconductor of the first embodiment is used.
Is used, the same operation and effect as those of the first embodiment can be obtained. That is, it is strong against external load distortion during the manufacturing process, and can suppress the deterioration of the Jc characteristic even when external load distortion is applied. As a result, it is easy to perform stranded wire processing or coil processing, and Nb ₃ Sn with good characteristics is obtained. A compound superconducting coil and a method for producing the same can be obtained.

In particular, when a coil is formed, in a conductor using a conventional precursor wire and a method for manufacturing the same, the end sealing process and the removal of the end sealing portion are performed for each precursor wire. On the other hand, according to the Nb ₃ Sn compound superconducting coil by the internal diffusion method and the method of manufacturing the same according to the third embodiment, since the Cu matrix of the precursor wire is already bronze, the end sealing treatment is performed. A step of removing the Nb ₃ Sn compound superconducting coil and its end sealing treatment portion is not required at all, and as a result, a Nb ₃ Sn compound superconducting coil which can be easily processed by stranded wire or coil and can be simplified can be obtained.

Further, after the stranded wire processing, a CIC in which a number of stranded wires are drawn into a conduit (a metal tube represented by stainless steel) or the like, or a coil having a manufacturing process of forming a large coil using the CIC. It is self-evident that the present invention is effective also in the manufacturing method described above, and it is needless to say that this case is included as one of the embodiments.

[0055]

[Embodiment 1] Embodiment 1 will be described based on a specific production example. 180mm outside diameter, 15 inside diameter
In a 6 mm oxygen-free copper container, 91 pieces of oxygen-free copper rods having a hexagonal cross section of 3.5 mm on a side are arranged at the center, and 91 pieces of 306 copper-coated Nb single-core wires of the same size are arranged around the rod. (Occupancy rate of Nb: 53.7%) with the highest packing density
To further increase the packing density, the gaps were filled with fine wires of oxygen-free copper. A composite billet was formed by welding and sealing the lid while evacuating the air in the container by disposing a Cu lid on such a material.

The composite billet thus formed is
After extruding to a diameter of 50 mm and cutting both ends, the outer periphery was cut to 46 mm. 19mm on the central copper part
Is drilled, and a 18.8 mm Sn rod is inserted into the hole to form a composite. This complex was further added to 9.
Drawing was performed to 8 mm. After cleaning the surface, a Ta tube serving as a diffusion barrier of Sn having an outer diameter of 11 mm and an inner diameter of 10 mm is provided on the outside, and an outer diameter of 16 is further provided on the outside thereof.
The tube was covered with an oxygen-free copper tube for stabilization having a diameter of 11.2 mm and an inner diameter of 11.2 mm, and was drawn to a final diameter of 0.2 mm. At this time, the Nb filament diameter was about 3 μm.

The end of the composite thus obtained is
Perform edge processing by melting by arc melting,
After performing a preliminary heat treatment in a nitrogen gas atmosphere at a temperature range of 520 to 580 ° C. and a maximum holding time of 60 hours, the end treated portion was removed to form a precursor wire of the Nb ₃ Sn compound superconductor. The precursor wire thus formed is referred to as Sample 1-1. At this time, as shown in FIG. 2, the Nb—Sn-based compound layer formed on the outer periphery of the Nb filament is about 0.2 to 0.4 μm, which corresponds to about 15% of the filament diameter. Thinness was confirmed by EPMA analysis.

Next, _three precursor wires (sample 1-1) of the Nb ₃ Sn compound superconductor were prepared, and the pitch was 8 mm.
With a stranded wire. The obtained stranded wire is kept in a nitrogen gas atmosphere at a temperature range of 600 to 800 ° C. and a holding time of 30 to 3 hours.
A final heat treatment of 00 hours was performed. At this time, the end treatment of the stranded wire was not performed. The stranded wire thus obtained is referred to as Sample 1-2.

For comparison, three strands of the same precursor wire before the preliminary heat treatment were processed into a stranded wire, and the ends of the stranded wire were treated for each of the three strands. A retention time of 10 in the temperature range of 580 ° C
Preliminary heat treatment for 0 to 200 hours and temperature range of 600 to 8
After the final heat treatment was continuously performed at 00 ° C. for a holding time of 30 to 300 hours, an end-treated portion was also removed. The stranded wire thus obtained is referred to as Sample 1-3.

For Samples 1-2 and 1-3, Jc was measured in liquid helium (4.2 K) under a magnetic field of 12 T. As shown in Table 1, the results were both Jc = 750A.
/ Mm ^{2, which} is a good value.

[0061]

[Table 1]

Embodiment 2 FIG. In the same manner as in Example 1, a composite having a final diameter of 0.2 mm was produced. After subjecting the obtained composite body to edge treatment in the same manner as in Example 1, after performing preliminary heat treatment in a nitrogen gas atmosphere at a temperature range of 520 to 580 ° C. and a maximum holding time of 60 hours. Then, the end treated portion was removed to prepare a precursor wire of the Nb ₃ Sn compound superconductor. A part of the precursor wire of the Nb ₃ Sn compound superconductor,
Heat was applied by pressing an electric iron over the entire surface in an area of about 5 cm. The surface temperature at this time is about 250 to 350
° C. This wire including the heated part was subjected to a final heat treatment in a nitrogen gas atmosphere at a temperature range of 600 to 800 ° C. and a holding time of 30 to 300 hours. At this time, the wire end processing was not performed. The wire thus obtained is referred to as Sample 2-1.

For comparison, the same precursor wire before the preliminary heat treatment was subjected to an end treatment in the same manner as in Example 1, and then a part of the precursor wire was cut in the same manner as above. 5c
Heat was applied by pressing an electric iron over the entire surface of the m area. The surface temperature at this time was about 250 to 350 ° C. The pre-heated wire including the heated portion is preliminarily heat-treated in a nitrogen gas atmosphere at a temperature range of 550 to 580 ° C., which is a conventional heat treatment condition, for a holding time of 100 to 200 hours, and at a temperature range of 600 to 800 ° C. And holding time is 30 ~ 3
After the final heat treatment was continuously performed for 00 hours, an end-treated portion was also removed. The wire thus obtained is referred to as Sample 2-2.

For samples 2-1 and 2-2, Jc was measured in liquid helium (4.2K) under a magnetic field of 12T. As shown in Table 1, the results are as follows.
= 740 A / mm ^{2, which} is a good value,
In the case of -2, Jc was 450 A / mm ² , which was an inferior value.
The reason for this is that as a result of cross-sectional observation of the wire, heat above the melting point of Sn was applied to a part of the precursor wire, so that "a sinkhole" was generated in that part of the precursor wire. It was found that the Sn diffusion reaction did not proceed well, and as a result, the formation of the Nb ₃ Sn compound superconductor in that portion did not proceed well.

Comparative Example 1 In the same manner as in Example 1, a composite having a final diameter of 0.2 mm was produced. After the obtained composite was subjected to edge treatment in the same manner as in Example 1, the composite was subjected to conventional pre-heat treatment conditions of 550 to 580 in a nitrogen gas atmosphere.
After performing a preliminary heat treatment in a temperature range of 100C for 100 to 200 hours, the end treated portion was removed. The precursor wire thus obtained is referred to as Sample 3-1. With respect to this precursor wire, the Nb-Sn compound layer formed on the outer periphery of the Nb filament was subjected to EPMA analysis,
As shown in FIG. 5, over about 0.6 μm and about 0.8 μm
The length of the filament exceeded about 20% of the filament diameter and reached about 30%, and it was confirmed that the filament was very thick as compared with Example 1.

Next, three samples 3-1 were prepared and stranded at a pitch of 8 mm. The stranded wire is placed in a nitrogen gas atmosphere at a temperature range of 600 to 800 ° C. and a holding time of 3 hours.
A final heat treatment was performed for 0-300 hours. At this time, the end treatment of the stranded wire was not performed. The stranded wire thus obtained is referred to as Sample 3-2. For this stranded wire, Jc was measured in liquid helium (4.2K) under a magnetic field of 12T. The results were as shown in Table 1, Jc = 250 A / m
m ² was inferior value.

Comparative Example 2 In the same manner as in Example 1, a composite having a final wire diameter of 0.2 mm was produced. After subjecting this composite to end treatment in the same manner as in Example 1, the composite was subjected to conventional preliminary heat treatment conditions of 550 to 580 ° C. in a nitrogen gas atmosphere.
After performing a preliminary heat treatment for a holding time of 10 hours in the above temperature range, the end treated portion was removed. The precursor wire thus obtained is referred to as Sample 4-1. When the cross section of this precursor wire was subjected to EPMA analysis, Sn was not diffused up to the outermost periphery of the matrix, and Cu remained at the outer periphery of the matrix.

Next, three samples 4-1 were prepared.
The stranded wire was processed at a pitch of 8 mm. The stranded wire was subjected to a final heat treatment in a nitrogen gas atmosphere at a temperature range of 600 to 800 ° C. and a holding time of 30 to 300 hours. At this time, the end treatment of the stranded wire was not performed. The stranded wire thus obtained is referred to as Sample 4-2. About this stranded wire,
Jc was measured in liquid helium (4.2K) under a magnetic field of 12T. As shown in Table 1, the results were Jc = 200 A /
It was a poor value as mm ^2.

Comparative Example 3 In the same manner as in Example 1, a composite having a final wire diameter of 0.2 mm was produced. After subjecting this composite to end treatment in the same manner as in Example 1, preliminary heat treatment in a nitrogen gas atmosphere at a temperature range of 550 to 580 ° C., which is the conventional preliminary heat treatment condition, for a holding time of 100 to 200 hours. After performing a final heat treatment of a temperature range of 600 to 800 ° C. and a holding time of 30 to 300 hours,
The edge treatment was removed. The Nb thus obtained
_The sample of ₃ Sn superconductor is referred to as Sample 5-1. Next, this N
_Three b ₃ Sn superconductor wires were prepared and stranded at a pitch of 8 mm. The stranded wire thus obtained is referred to as Sample 5-2.

For these samples 5-1 and 5-2, J was measured under a magnetic field of 12 T in liquid helium (4.2 K).
c was measured. As shown in Table 1, the sample 5-1 before the stranded wire had a good value of Jc = 760 A / mm ² , but the stranded wire processed sample 5 after the heat treatment was used.
With respect to −2, Jc = 100 A / mm ² , which was a value inferior to Comparative Example 1 or more.

As shown in the above examples, the sample 1-2 of Example 1 according to the present invention, that is, the preliminary heat treatment in which the edge treatment was performed, the temperature range was 520 to 580 ° C., and the maximum holding time was 60 hours. After the end treatment, the end treated portion was removed to form a three-strand wire, and the final heat treatment was performed without end treatment at a temperature range of 600 to 800 ° C. and a holding time of 30 to 300 hours. In this case, the sample 5-1 of Comparative Example 3 was used.
And the sample of Example 1 (in the case where the pre-heat treatment and the final heat treatment were continuously performed on the precursor wire subjected to the end treatment, and then the end treatment part was removed), and the conventional Nb ₃ Sn compound superconductor indicated by The conventional process shown in 1-3 (after three precursor wires are stranded, three end wires are each subjected to an end treatment, a preliminary heat treatment and a final heat treatment are successively performed, and then the end treatments are performed. Jc value did not deteriorate.

On the other hand, in the case where the end treatment was performed and the preliminary heat treatment was performed, the end treatment portion was removed, the three strands were processed, and the final heat treatment was performed without the end treatment. The preliminary heat treatment conditions as shown in Sample 3-2
When the holding time is as long as 100 to 200 hours at 50 to 580 ° C, or when the holding time is as short as 10 hours at 550 to 580 ° C as shown in Sample 4-2 of Comparative Example 2, In each case, the Jc value was reduced to 1/3 or less.

Further, as shown in Sample 5-2 of Comparative Example 3, after the pre-heat treatment and the final heat treatment were continuously performed on the end-treated precursor wire, the end-treated portion was removed.
When the stranded wire was processed, the Jc value was deteriorated to 14% or less.

Therefore, it is understood that controlling the thickness of the Nb-Sn compound layer formed on the outer periphery of the Nb-based filament is important for preventing the deterioration of the Jc value. Therefore, the precursor wire is used, for example, in a temperature range of 500 to 58.
Preliminary heat treatment may be performed at 0 ° C. and a holding time of 60 hours or less, preferably in a temperature range of 520 to 580 ° C. and a holding time of 30 hours or less. At this time, if the heat treatment temperature is high or the heat treatment time is too long, the thickness of the Nb-Sn compound layer increases, so that the Nb-
It is not preferable because the amount of the Sn compound layer increases, and
If the heat treatment temperature is low or the heat treatment time is too short, bronzing of the matrix becomes difficult to proceed, which is not preferable.

Further, sample 2 of Example 2 according to the present invention was used.
-1, that is, the edge treatment is performed and the temperature range is 520 to 580.
After performing a preliminary heat treatment at 60 ° C. for a maximum holding time of 60 hours, a heat treatment having a surface temperature of about 250 to 350 ° C. is applied to a part of the precursor wire formed by removing the end treated portion. In the case where the wire including the portion to which is added is subjected to the final heat treatment of the final heat treatment having a temperature range of 600 to 800 ° C. and a holding time of 30 to 300 hours in a nitrogen gas atmosphere, the sample 5-1 of Comparative Example 3 is used. The Jc value of the indicated conventional Nb ₃ Sn compound superconductor (in the case where the pre-heat treatment and the final heat treatment were continuously applied to the end-treated precursor wire and the end-treated portion was removed) was obtained. There was no deterioration.

On the other hand, after subjecting the precursor wire of the conventional Nb ₃ Sn compound superconductor shown in Sample 2-2 of Example 2 to end treatment, a part of the precursor wire had a surface temperature of about 250.
After applying a heat load of up to 350 ° C., the wire containing the heated portion is kept in a nitrogen gas atmosphere at a temperature range of 550 to 580 ° C., which is the conventional heat treatment condition, for a holding time of 100 to 20 ° C.
When the pre-heat treatment for 0 hour and the final heat treatment for a temperature range of 600 to 800 ° C. and a holding time of 30 to 300 hours were continuously performed, and the edge treatment portion was removed, the Jc value was about 6%.
Degraded to 0%.

Therefore, it is necessary to bronze the Cu matrix so as to prevent the wire rod from forming “a sinkhole” due to the melting of Sn even if heat applied to a part of the wire rod is higher than the melting point of Sn during processing. It is understood that it is important for preventing the deterioration of the Jc value. For this reason, for example, a temperature range of 500 to 580 ° C. and a holding time of 60 hours or less, preferably a temperature range of 520 to 580 ° C. and a holding time of 30 ° C.
Preliminary heat treatment may be performed so as to be within an hour.

Embodiment 3 FIG. The second embodiment is the same as the third embodiment except for a part where a coil is formed. Therefore, the third embodiment will be described based on a specific manufacturing example. Final wire diameter 0.2 mm in the same manner as in Example 1.
Was prepared. This composite was subjected to edge treatment in the same manner as in Example 1, and then subjected to preliminary heat treatment in a nitrogen gas atmosphere at a temperature range of 520 to 580 ° C. and a maximum holding time of 60 hours. The treated part was removed to obtain a precursor wire. Next, the precursor wire rod is divided into six parts to have a wire diameter of 0.1 mm.
A 2 mm stainless steel wire (made of SUS304) was used as a core wire and stranded at a pitch of 10 mm to obtain a stranded conductor.

The stranded conductor was made to have an outer diameter of 50 mm and a height of 5 mm.
A small coil was produced by winding a single layer of solenoid around a 0 mm SUS304 winding frame for 50 turns so that the stranded conductors did not come into contact with each other. The obtained coil was placed in a nitrogen gas atmosphere at a temperature range of 600 to 800 ° C. and a holding time of 30 to
A final heat treatment of 300 hours was performed. At this time, the end treatment of each wire of the stranded conductor was not performed. A current lead for excitation and a voltage terminal for voltage monitoring were connected to the coil, and the coil was set in a cryostat, cooled with liquid helium, and an energization test of the coil under a magnetic field was performed. As a result, the result of Jc of this conductor excluding the SUS core material under a magnetic field of 12 T is Jc = 740 A / mm 2
And good values as in Example 1.

Also, in this experiment, before performing the above-mentioned six-strand wire, a low-melting glass was applied to the precursor wire at 450 ° C. and baked to perform insulation coating. We also considered doing. This method cannot be performed at a temperature exceeding the melting point of Sn because Sn leaks out from the precursor wire of the internal diffusion method before the conventional heat treatment, and the baking treatment of the insulating film could not be performed. It has been found that the present invention makes it possible to use a precursor wire rod, and that the present invention greatly expands the degree of freedom or tolerance of the processing process in conductor processing and insulation processing.

[0081]

As described above, according to the present invention, Nb ₃ S
According to the precursor wire of the n-compound superconductor, since the Cu-Sn based matrix is formed, even if heat above the melting point of Sn is applied to a part of the precursor wire in the subsequent processing step of forming a conductor or a coil. Since the matrix is bronze and there is no pure Sn, the occurrence of "sink cavities" due to the melting of Sn can be suppressed. Therefore, a normal Nb ₃ Sn compound superconductor generation reaction occurs in the subsequent heat treatment,
Jc characteristics do not deteriorate. Therefore, during the processing step of forming the conductor or the coil, heat that is higher than the melting point of Sn can be applied, that is, stranded wire processing or coil formation is facilitated. Further, since a Cu-Sn based matrix is formed, the end sealing process for each precursor wire rod for the purpose of preventing the Sn from flowing out during the subsequent heat treatment, and the heat treatment of the end sealing treatment portion after the heat treatment. The removal process can be omitted, and the process can be simplified. Further, Cu
Since a Sn-based matrix is formed, Cu, Sn,
The material strength can be improved as compared with the case where each component of Nb is charged in a pure metal state. For this reason, it is strong against external load distortion, that is, stranded wire processing or coil formation is facilitated.

Further, according to the precursor wire of the Nb ₃ Sn compound superconductor according to the present invention, the Nb—Sn based compound layer having a thickness of 20% or less of the diameter of the Nb based filament is formed. Since the thickness is strengthened by unreacted Nb inside, the strain resistance is improved. Further, even if a part of the Nb-Sn-based compound layer is cracked or broken due to external load strain, the ratio of destruction of the Nb-Sn-based compound layer to the entire Nb-based filament is low. Deterioration of characteristics can be suppressed.

According to the precursor wire of the Nb ₃ Sn compound superconductor according to the present invention, the average Sn concentration of the Cu—Sn based matrix can be increased to 14 wt% to 30 wt%, and the Nb amount corresponding to this can be increased. As a result, the amount of the Nb ₃ Sn compound superconductor can be increased, and the characteristics of Jc can be improved.

Further, according to the precursor wire of the Nb ₃ Sn compound superconductor according to the present invention, the average Sn concentration of the Cu—Sn based matrix can be as high as 14 wt% or more. In addition to the bronze alloy, a mixed phase with at least one of a gamma phase, a delta phase, and an epsilon phase bronze can be obtained. Accordingly, the average concentration of Sn Cu-Sn based matrix can be as high as more than 14 wt%, since the Nb content of commensurate thereto as a result can be ensured, Nb ₃ S
The amount of the n-compound superconductor can be increased, and the Jc characteristics can be improved.

Further, according to the precursor wire of the Nb ₃ Sn compound superconductor according to the present invention, since the central portion of the Cu—Sn based matrix is formed only of the Cu—Sn based matrix, the respective constituents of Cu, Sn and Nb are formed. The material strength can be improved as compared with the case where the components are charged in a pure metal state.
For this reason, it is strong against external load distortion, that is, stranded wire processing or coil formation is facilitated.

According to the method for producing a precursor wire of an Nb ₃ Sn compound superconductor according to the present invention, the Cu-based matrix and the Sn-based metal material undergo a diffusion reaction to form a Cu—Sn-based matrix. Since the Sn-based matrix is formed, the matrix is bronze and pure Sn does not exist even if heat at or above the melting point of Sn is applied to a part of the precursor wire in a subsequent processing step of forming a conductor or a coil. For this reason, the occurrence of a "sink cavity" due to the melting of Sn can be suppressed. Therefore, a normal Nb ₃ Sn compound superconductor generation reaction occurs in the subsequent heat treatment,
Jc characteristics do not deteriorate. Therefore, heat at or above the melting point of Sn can be applied during the processing step of forming the conductor or coil, that is, stranded wire processing or coil formation is facilitated. In addition, after the Cu-Sn-based matrix is formed, the end sealing process is performed for each precursor wire for the purpose of preventing the Sn from flowing out during the subsequent heat treatment, and after the heat treatment of the end sealing treatment portion. Can be eliminated, and the process can be simplified. Also, C
The step of forming the u-Sn group matrix allows C
The material strength can be improved as compared with the case where the respective components of u, Sn, and Nb are charged in a pure metal state. For this reason, it is strong against external load distortion, that is, stranded wire processing or coil formation is facilitated.

Further, the Sn of the Cu—Sn based matrix
Reacts with the outer periphery of the Nb-based filament to form a Nb-Sn-based compound layer having a thickness of 20% or less of the diameter of the Nb-based filament. Since the Nb—Sn-based compound layer is formed, if the thickness is such, it is strengthened by unreacted Nb inside, so that the strain resistance is improved. Also, suppose that Nb-Sn
Even if a part of the base compound layer is cracked or broken, the ratio of destruction of the Nb-Sn base compound layer to the whole Nb-based filament is low, so that the deterioration of the Jc characteristic can be suppressed.

Further, according to the method for producing a precursor wire of an Nb ₃ Sn compound superconductor according to the present invention, 500 to 580
A pre-heat treatment at a temperature range of 60 ° C. for a holding time of 60 hours or less results in bronzing, that is, C
The u-based matrix and the Sn-based metal material undergo a diffusion reaction to cause Cu
A Sn-based matrix is formed, and Sn in the Cu-Sn-based matrix diffuses and reacts with the outer periphery of the Nb-based filament to form an Nb-Sn-based compound layer having a thickness of 20% or less of the diameter of the Nb-based filament. Can be formed.

Further, according to the method for producing an Nb ₃ Sn compound superconductor according to the present invention, the Cu-based matrix and the S
Since the Cu-Sn-based matrix is formed by the step of forming a Cu-Sn-based matrix by a diffusion reaction with the n-based metal material, in a subsequent processing step of forming a conductor or a coil, the melting point of Sn or more is obtained. Even if heat is applied to a part of the precursor wire, the matrix is bronze and pure S
Since n does not exist, it is possible to suppress the occurrence of "a sinkhole" due to the melting of Sn. For this reason, normal N
The formation reaction of the b ₃ Sn compound superconductor does not occur, and the Jc characteristics do not deteriorate. Therefore, heat higher than the melting point of Sn can be applied during the processing step of forming the conductor, that is, stranded wire processing is facilitated. In addition, after the Cu-Sn-based matrix is formed, the end sealing process is performed for each of the precursor wires to prevent the Sn from flowing out during the subsequent heat treatment, and after the heat treatment of the end sealing treatment portion. Can be eliminated, and the process can be simplified. Further, by the step of forming the Cu—Sn based matrix, the material strength can be improved as compared with the case where the respective constituent components of Cu, Sn, and Nb are charged in a pure metal state. For this reason, it is strong against external load distortion, that is, stranded wire processing is easily performed.

Further, the Sn of the Cu—Sn based matrix
Forms a Nb-Sn-based compound layer having a thickness of 20% or less of the Nb-based filament diameter by a diffusion reaction on the outer periphery of the Nb-based filament, whereby Nb having a thickness of 20% or less of the diameter of the Nb-based filament is formed. Since the -Sn-based compound layer is formed, if the thickness is such, it is strengthened by unreacted Nb inside, so that the strain resistance is improved. Also, suppose that Nb-Sn
Even if a part of the base compound layer is cracked or broken, the ratio of destruction of the Nb-Sn base compound layer to the whole Nb-based filament is low, so that the deterioration of the Jc characteristic can be suppressed. That is, it is strong against external load distortion during the manufacturing process, and the deterioration of the Jc characteristic can be suppressed even when external load distortion is applied.

Further, in a temperature range of 500 to 580 ° C.,
By performing the preliminary heat treatment for a holding time of 60 hours or less, bronzing, that is, the Cu-based matrix of the composite and the Sn-based metal material undergo a diffusion reaction to form a Cu-Sn-based matrix. Further, Sn in the Cu—Sn-based matrix diffuses and reacts to the outer periphery of the Nb-based filament, and Nb having a thickness of 20% or less of the diameter of the Nb-based filament.
-A Sn group compound layer can be formed.

According to the method of manufacturing the Nb ₃ Sn compound superconducting coil according to the present invention, the Cu-Sn based matrix is formed by the step of forming a Cu-Sn based matrix by a diffusion reaction between the Cu based matrix and the Sn based metal material. Since a matrix is formed, even if heat above the melting point of Sn is applied to a part of the precursor wire in a subsequent processing step of forming a conductor or a coil, the matrix is bronze and pure S is formed.
Since n does not exist, it is possible to suppress the occurrence of "a sinkhole" due to the melting of Sn. For this reason, normal N
The formation reaction of the b ₃ Sn compound superconductor does not occur, and the Jc characteristics do not deteriorate. Therefore, during the processing step of forming the conductor or the coil, heat that is higher than the melting point of Sn can be applied, that is, stranded wire processing or coil formation is facilitated. In addition, after the Cu-Sn-based matrix is formed, the end sealing process is performed for each precursor wire for the purpose of preventing the Sn from flowing out during the subsequent heat treatment, and after the heat treatment of the end sealing treatment portion. Can be eliminated, and the process can be simplified. In addition, Cu-
Depending on the process in which the Sn-based matrix is formed, Cu,
The material strength can be improved as compared with the case where the respective components of Sn and Nb are charged in a pure metal state. For this reason, it is strong against external load distortion, that is, stranded wire processing or coil formation is facilitated.

Further, Sn of the Cu—Sn based matrix
Forms a Nb-Sn-based compound layer having a thickness of 20% or less of the Nb-based filament diameter by a diffusion reaction on the outer periphery of the Nb-based filament, whereby Nb having a thickness of 20% or less of the diameter of the Nb-based filament is formed. Since the -Sn-based compound layer is formed, if the thickness is such, it is strengthened by unreacted Nb inside, so that the strain resistance is improved. Also, even if a part of the Nb-Sn base compound layer is cracked or broken due to external load strain,
Since the rate of destruction of the Nb-Sn-based compound layer with respect to the entire Nb-based filament is low, deterioration of the Jc characteristics can be suppressed. That is, it is resistant to external load distortion during the manufacturing process, and the deterioration of the Jc characteristic can be suppressed even when external load distortion is applied.

Further, in a temperature range of 500 to 580 ° C.,
By performing the preliminary heat treatment for a holding time of 60 hours or less, bronzing, that is, the Cu-based matrix of the composite and the Sn-based metal material undergo a diffusion reaction to form a Cu-Sn-based matrix. Further, Sn in the Cu-Sn-based matrix diffuses and reacts to the outer periphery of the Nb-based filament,
Nb-S having a thickness of 20% or less of the diameter of the Nb-based filament
An n-based compound layer can be formed.

[Brief description of the drawings]

FIG. 1 shows N by an internal diffusion method according to a first embodiment of the present invention.
b ₃ is a cross-sectional view showing the configuration of a precursor wire of Sn compound superconductor.

FIG. 2 is a photograph of a cross section of a main part of FIG. 1, showing an Nb-Sn-based compound layer formed on an outer peripheral layer of an Nb-based filament embedded in a Cu-Sn-based matrix.

FIG. 3 shows Cu—S of the Cu—Sn based matrix of FIG.
FIG. 4 is an n2 system phase diagram.

FIG. 4 is a cross-sectional view showing a configuration of a precursor wire of an Nb ₃ Sn compound superconductor by a conventional internal diffusion method.

5 is a photograph of a cross-sectional view of a main part of FIG. 4, showing an Nb-Sn-based compound layer formed on an outer peripheral layer of an Nb-based filament embedded in a Cu-Sn-based matrix.

[Explanation of symbols]

10 Nb ₃ Sn compound superconductor precursor wire, 11 Cu-Sn based matrix, 12 Nb based filament, 13 Nb-Sn based compound layer

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁶ Identification code FI C22F 1/00 661 C22F 1/00 661A 680 680 685 685Z 686 686 686Z 691 691B 691C (72) Inventor Mitsunobu Wakata Marunouchi, Chiyoda-ku, Tokyo 2-3-2, Mitsubishi Electric Corporation (72) Inventor, Osamu Taguchi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation

Claims (10)

[Claims] 1. A Cu-Sn-based matrix, a large number of Nb-based filaments embedded separately from the center of the Cu-Sn-based matrix, and an Nb-Sn-based compound formed on the outer periphery of the Nb-based filament A precursor wire of a Nb ₃ Sn compound superconductor having a layer. Wherein Nb-Sn claim 1 Nb ₃ according thickness of the base compound layer is 20% or less of Nb-based filament diameter
Precursor wire for Sn compound superconductor. 3. The N according to claim 1, wherein the Cu—Sn based matrix has an average Sn concentration of 14 to 30 wt%.
b ₃ Sn compound superconductor precursor wire. 4. The method according to claim 1, wherein the Cu—Sn based matrix comprises an alpha phase bronze alloy and is a mixed phase with at least one phase in a gamma phase, a delta phase and an epsilon bronze. Nb ₃ S described
Precursor wire for n-compound superconductor. 5. The central part of the Cu—Sn based matrix is C
It formed from only u-Sn based matrix, Nb ₃ Sn compound superconductor precursor wire according to any one of to a large number of Nb-based filaments on the outside claims 1 embedded in isolation 4. 6. A step of forming a composite billet in which a number of Nb-based filaments are separated and buried outside a central portion of the Cu-based matrix. After extruding the composite billet, holes are formed in the central portion of the Cu-based matrix. Forming a composite by inserting a Sn-based metal material into the hole, performing a wire drawing process on at least one of the composites, and performing a preliminary heat treatment after the wire drawing process. A step of forming a Cu-Sn-based matrix by a diffusion reaction between the Cu-based matrix and the Sn-based metal material of the composite, and a diffusion reaction of Sn of the Cu-Sn-based matrix to the outer periphery of the Nb-based filament; Of a precursor wire for an Nb ₃ Sn compound superconductor comprising a step of forming an Nb—Sn based compound layer having a thickness of 20% or less of the Nb based filament diameter Method. 7. The step of performing a preliminary heat treatment is performed in a range of 500 to 58.
In a temperature range of 0 ° C., 60 hours within the manufacturing method of the precursor wire of Nb ₃ Sn compound superconductor according to claim 6, wherein the retention time. 8. A step of forming a composite billet in which a large number of Nb-based filaments are separated and buried outside a central part of the Cu-based matrix, extruding the composite billet, and forming a composite billet at a central part of the Cu-based matrix. Forming a composite by drilling a hole and inserting a Sn-based metal material into the hole; performing wire drawing on at least one of the composites; performing a preliminary heat treatment after the wire drawing process Forming a Cu-Sn-based matrix by a diffusion reaction between the Cu-based matrix and the Sn-based metal material of the composite, and a diffusion reaction of Sn of the Cu-Sn-based matrix to the outer periphery of the Nb-based filament. form a precursor wire of performing a step of forming a Nb-Sn based compound layer Nb ₃ Sn compound superconductor having 20% or less of the thickness of the Nb-based filament diameter and Forming a stranded conductor by twisting at least one precursor wire of the Nb ₃ Sn compound superconductor to form a stranded conductor; and applying a Nb ₃ A method for producing an Nb ₃ Sn compound superconductor comprising a step of forming a Sn compound. 9. The step of performing a preliminary heat treatment is performed in a range of 500 to 58.
The holding time is within 60 hours at a temperature range of 0 ° C, and the holding time is 30 to 30 at a temperature range of 600 to 800 ° C for the final heat treatment.
The method for producing an Nb ₃ Sn compound superconductor according to claim 8, wherein the time is 0 hour. 10. A step of forming a composite billet in which a large number of Nb-based filaments are separated and buried outside a central part of the Cu-based matrix, and extruding the composite billet, and then forming a composite billet at a central part of the Cu-based matrix. Drilling a hole, inserting a Sn-based metal material into the hole to form a composite, wire-drawing at least one of the composites, performing a preliminary heat treatment after the wire-drawing process Forming a Cu-Sn-based matrix by a diffusion reaction between the Cu-based matrix and the Sn-based metal material of the composite, and a diffusion reaction of Sn of the Cu-Sn-based matrix to the outer periphery of the Nb-based filament. the Nb ₃ Sn compound superconductor precursor wire is subjected to a step of forming a Nb-Sn based compound layer with 20% or less of the thickness of the Nb-based filament diameter and Forming a stranded wire conductor by twisting at least one precursor wire of the Nb ₃ Sn compound superconductor to form a stranded wire conductor, winding the stranded wire conductor to form a coil, and forming the coil. N comprising a step of forming an Nb ₃ Sn compound formed on the Nb-based filament by the final heat treatment.
Method for producing b ₃ Sn compound superconducting coil.