JPH06325643A - Nb3sn superconducting wire and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain an Nb3Sn superconducting wire useful as a magnet material for a nuclear magnetic resonance device without generating a problem such as attenuating a permanent current by performing operation so as to satisfy at least one of specific three important matters. CONSTITUTION:A compound billet 11 for satisfying one of (I) to (III) is subjected to wire drawing work and heat treatment to produce Nb3Sn in an interface between a Cu-Sn group alloy-made wire base material 1a and an Nb wire 2. (I) The Nb wire 2 buried in the wire base material 1a is constituted so that a space Ds of the most adjacent Nb3Sn after producing Nb3Sn obtains 0.5 to 1.0mum. (II) Ratio of a mean distance dout between the outermost surfaces of the compound billet 11 and a wire group 10 to a mean distance din between internal surfaces of a diffusion barrier layer 6 and a wire group 10 is constituted to 1.5 to 4.0. (III) A Ta wire 12 is constituted to be buried in an axial center part of each Nb wire 2 buried in a plural quantity in the wire base material 1a.

Description

Detailed Description of the Invention

[0001]

The present invention relates to relates to a Nb ₃ Sn superconducting wire and its manufacturing method used for a superconducting magnet structure material, Nb ₃ Sn superconducting wire and a Such having a particularly stable high field critical current characteristics The present invention relates to a useful method for obtaining a wire rod.

[0002]

2. Description of the Related Art A superconducting magnet which utilizes a permanent current phenomenon realized by a superconducting material and allows a large current to flow without consuming electric power to generate a magnetic field in a coil is known as a nuclear magnetic resonance (NMR) device. In addition to various physical property measurement devices, application to magnetic levitation trains, nuclear fusion devices, etc. is being promoted. As a constituent material of the above-mentioned superconducting magnet, a superconducting wire such as Nb ₃ Sn or V ₃ Ga has been conventionally used.

Among the above-mentioned superconducting wire rods, Nb ₃ Sn superconducting wire rods for practical use are mainly manufactured by a so-called composite processing method called a bronze method. The general method of the bronze method will be described in more detail with reference to the drawings.

First, as shown in FIG. 2, a Nb wire 2 is embedded in a billet case 1 (a linear base material) made of a Cu--Sn alloy, and the ends are electron beam welded to form a composite billet 3 (single core type). Assemble the composite billet). The composite billet is integrated by hot isostatic pressing and surface-reducing at the same time, and is further drawn by cold working to a predetermined size. At this time, since the Cu-Sn alloy is significantly work-hardened by cold drawing, an intermediate annealing for removing work-hardening strain is required in the wire-drawing step at each working with a working ratio of about 30 to 60%. . Then, by heat treatment (600 to 700 ° C.), N is formed on the interface between the Cu—Sn alloy linear base material 1 and the Nb wire 2.
b ₃ Sn to produce the a Nb ₃ Sn superconducting wire.

The above is the case of the single core type superconducting wire.
In the case of a multifilamentary superconducting wire, as shown in FIG. 3, a plurality of Nb wires 2 are embedded in a billet case 1a made of Cu-Sn alloy (a linear base material) to form a primary multifilament billet 8. 4 are bundled into a cylindrical shape to form a wire rod group 10, and as shown in FIG.
Cylindrical outer layer case 9 made of Cu or Cu-Sn alloy
(Outermost layer), drawn in the same manner as in the case of the single core type, and 3000 to 10000 Nb in the final shape.
Secondary multi-core billet 11 containing wire 2 (composite billet)
Make up. In the secondary multi-core billet 11, as shown in FIG. 4, a linear / rod-shaped oxygen-free copper 7 (stabilized copper), which is a stabilizing material, is incorporated in the central portion thereof. Between the wire rod group 10 of the core billet 8 and the oxygen-free copper 7, Cu
Cylindrical inner layer 5 consisting of -Sn alloy, and Nb ₃ Sn
A cylindrical Nb layer or Ta layer 6 to be a diffusion barrier layer for Sn during the diffusion heat treatment for formation is formed. Among them, the diffusion barrier layer 6 has an action of preventing the oxygen-free copper 7 from being contaminated with Sn. Finally, a Cu-Sn alloy linear at the interface of the base material 1a and the Nb line 2 to generate Nb ₃ Sn multi-core Nb ₃ Sn superconducting wire by heat treatment.

Each Nb ₃ Sn superconducting wire obtained as described above is Cu--S when the superconducting wires are connected to each other.
Since the n-alloy can be chemically removed with nitric acid or the like and the exposed superconducting filaments can be directly connected, the superconducting connection is easy and stable. Therefore, the Nb ₃ Sn superconducting wire has an optimum structure for an NMR apparatus that requires very high magnetic field stability.

[0007]

By the way, the superconducting magnet used in the NMR apparatus is required to have extremely high precision in the spatial homogeneity and temporal stability of the magnetic field. The former is a subject that depends on the design of the magnet, and the latter is a subject that largely depends on the performance of the superconducting wire used. That is,
This is because the temporal instability of the magnetic field is caused by the decay of the persistent current flowing in the superconducting wire. Such a phenomenon is more remarkable in the Nb ₃ Sn wire rod used in a higher magnetic field than in the NbTi superconducting wire rod. About 0.1 to 100p in commonly used Nb ₃ Sn superconducting wire
Attenuation of about pm / h has not been a serious problem for the applied equipment up to now, but even in the case of an NMR apparatus, even a slight attenuation would significantly deteriorate the performance as an analytical instrument. , A very serious problem.

The cause of the decay of the persistent current is current shunting caused by the nonuniformity of the Nb ₃ Sn producing filament in the wire and magnetic flux creep due to the proximity effect. The former will lead to current decay as follows.
First, in the processing step, irregularities may be generated on the surface of the filament, and as a result, the critical current in the portion where the filament cross-sectional area is locally small becomes smaller than the average critical current per filament. At this time, the current is shunted to another filament having a margin of critical current, and at this time resistance is generated, which leads to attenuation of the permanent current. The latter is a phenomenon in which when the spacing between superconducting filaments is narrow, weak superconducting parts also exist between filaments due to exudation of superconducting conductors in the normal conducting parts between filaments, and the magnetic flux in this part easily creeps and moves. As a result, resistance is generated and the current is attenuated.

On the other hand, when a magnetic field is generated by a superconducting magnet, an outward force called a hoop force acts on the superconducting wire material that constitutes the magnet. The entire Nb line 2 is N
When reacted with b ₃ Sn, this Nb ₃ Sn is brittle due to an intermetallic compound, so sometimes cracks occur in Nb ₃ Sn due to the hoop force, which may greatly deteriorate the properties of the wire and thus the magnet. To prevent such deterioration, N
Nb line 2 without completely converting all of b line 2 into Nb ₃ Sn
A method of leaving a ductile and high-strength Nb core in the central part of and making Nb ₃ Sn only in the periphery is used. And this N
Generally, it is desirable that the residual amount of the b core is uniform in the cross section of the wire.

However, in the multi-core type Nb ₃ Sn superconducting wire manufactured as described above, the amount of Sn around the Nb wire 2 is greatly different in the vicinity of the central portion of the wire and the outer peripheral portion thereof.
In the central part where the amount of n is small, the residual amount of the Nb core is large, whereas in the peripheral part where the amount of Sn is large, the Nb core does not remain and the Nb filament is completely converted into Nb ₃ Sn. It has been found that this defect appears in the superconducting magnet of the NMR apparatus as decay of the permanent current, that is, slight decay of the magnetic field (about 0.1 to 100 ppm / h). However, as described above, this attenuation greatly deteriorates the performance as an analytical instrument, and the multi-core type superconducting wire has some problems as a superconducting wire for an NMR apparatus.

Further, each Nb ₃ Sn superconducting wire produced by the bronze method is subjected to a heat treatment at about 600 to 700 ° C. to form an Nb wire 2 and a Cu-Sn alloy linear base material 1.
Since the Nb ₃ Sn compound is generated at the interface of (or 1a) and then cooled to the liquid helium temperature before use, Nb ₃ Sn in the wire is under compressive strain at the helium temperature, and the critical current and critical temperature Is in a slightly deteriorated state as compared with the unstrained state.

The present invention has been made in order to solve the technical problems of the conventional Nb ₃ Sn superconducting wire as described above, and its purpose is to avoid problems such as decay of permanent current. , Nb ₃ Sn superconducting wire useful as a material for a superconducting magnet for an NMR apparatus, and such Nb
₃ To provide a useful method for manufacturing a Sn superconducting wire.

[0013]

Means for Solving the Problems The present invention, which has achieved the above objects, includes: wire / rod-shaped stabilized copper; a cylindrical diffusion barrier layer; a cylindrical Cu-Sn-based alloy inner layer; A wire rod group in which a plurality of linear base materials made of Cu-Sn base alloy in which Nb wires are embedded are bundled in a cylindrical shape, and a cylindrical outermost layer made of Cu or Cu-Sn base alloy is outwardly radiated from the center side toward the outside. The composite billets are arranged in the above-mentioned mounting order to form a composite billet, and after the composite billet is drawn, heat treatment is performed to add Nb ₃ Sn to the interface between the Cu-Sn-based alloy linear base material and the Nb wire. the method of manufacturing a Nb ₃ Sn superconducting wire to produce a method for producing a Nb ₃ Sn superconducting wire having the gist in that perform operations in the manner to satisfy at least one of the following requirements (I) ~ (III). Further, the Nb ₃ Sn superconducting wire obtained by such a method exhibits desired characteristics as a constituent material of the superconducting magnet.

(I) An Nb wire embedded in a Cu-Sn-based alloy linear base material has a distance Ds of 0.5 to 1.0 μm between Nb ₃ Sn nearest neighbors after Nb ₃ Sn is generated. It is configured to be within the range of. (II) and the average distance d _out from the outermost surface of the composite billet to said wire group outermost surface, the ratio of the average distance d _in the diffusion barrier layer to the wire group in the surface (d _out / d _in) is 1 ．
It is configured to be 5 to 4.0. (III) Each N embedded in a plurality of Cu-Sn based alloy linear base materials
The Ta line is embedded in the axis of the b line.

[0015]

The present invention is constructed as described above, but it has been found that the operation corresponding to each of the requirements (I) to (III) described above can exert the effect corresponding to each requirement. The present invention has been completed. The above (I) to (III)
The requirements of 1 above can obtain the respective effects if they are operated so as to satisfy each requirement independently, but it is also possible to perform the operation by combining 2 or 3 of the above requirements. Multiple effects can be obtained. The action of each requirement (I) to (III) will be described in more detail.

First, in the requirement of (I), the Nb line 2 is connected to Nb ₃
Interval Ds of Nb ₃ Sn that is the most adjacent to Sn after generation of Sn
(See FIG. 1) is specified to be within the range of 0.5 to 1.0 μm. The reason why the distance Ds is set to 0.5 μm or more is that if the distance is less than 0.5 μm, the mutual distance between Nb ₃ Sn becomes too narrow and the proximity effect becomes remarkable. That is, the current due to the proximity effect is easily flux-creped, and this creep leads to current attenuation. Further, the reason why the distance Ds is set to 1.0 μm or less is that if it is larger than this, it is difficult to uniformly process the Nb wire 2. That is, unevenness may occur on the surface of the Nb wire 2 in the processing step, and the critical current of the portion of the Nb wire 2 having a small cross-sectional area becomes smaller than the average critical current per Nb wire 2. At this time, the current is shunted to another Nb ₃ Sn having a margin for the critical current, and at this time, resistance is generated and the permanent current is attenuated. After all, the requirement of (I) above is that the configuration point is that the proximity effect and the shunting of the current that cause the current attenuation can be reduced by setting the distance Ds within a predetermined range. is there.

Next, in the requirement of (II), the wire rod group 10 is formed from the outermost surface of the composite billet (the secondary multi-core billet 11).
The ratio (d _out / d _in ) of the average distance d _out to the outermost surface of the above and the average distance d _in (see FIG. 5) from the diffusion barrier layer 6 to the inner surface of the wire rod group 10 is 1.5 to It is set to 4.0. By optimizing the average distance d _in with respect to the average distance d _{out as} described above, the amount of Sn in the cross section of the wire is controlled. As a result, Nb ₃ S
Nb ₃ Sn can be uniformly generated during the heat treatment for generating n, and the residual amount of the Nb core can be made constant. In order to adjust the above average distances d _out and d _in, as shown in Examples described later, on the inner peripheral side and / or the outer peripheral surface of the wire rod group 10,
A Cu—Sn wire may be interposed in place of some of the primary multi-core billets 8, but in such a case the average distance d
_out and d _in are values including the distance in which the Cu—Sn wire rod is interposed.

Further, as will be described in more detail in the examples below,
Ratio of each residual Nb core diameter (RD) in the Nb ₃ Sn generation filament in the outermost layer portion and the innermost layer portion, RD _out / R
FIG. 6 shows the relationship between D _in and the d _out / d _in . R
Residual N in the cross section of the wire when D _out / RD _in is 1
Although the b core amount can be considered to be completely uniform, by setting d _out / d _in within the above range, it is almost 0.
The range of 8 <RD _out / RD _in ≦ 1.2 is satisfied, which can be considered to be almost constant. That is, d _out / d _in is 1.5 to 4.
By setting it to 0, Nb having an Nb core in which the residual amount in the cross section of the wire is uniformly equal after the Nb ₃ Sn generation heat treatment.
₃ It shows that a Sn superconducting wire can be formed.

The reason why d _out / d _in is limited as described above is due to the following reasons in addition to the above-mentioned reasons. First,
When d _out / d _in is larger than 4.0, the yield stress is small, so that cracking is likely to occur in Nb ₃ Sn and permanent current is likely to be attenuated. Also, when it becomes smaller than 1.5, the critical current becomes substantially low, and the operating current of a magnet that generates a general magnetic field of 12T (example: 100A).
This is because there is a possibility that resistance due to the magnetic flux flow will occur.

Further, by setting the requirement of (III) as described above, the yield stress is substantially increased, and Nb ₃ S
The critical strain in which n is cracked increases. That is, N of the present invention
The superconducting magnet for NMR using the b ₃ Sn superconducting wire has a large tolerance to the hoop force, and has an effect that it can be stably operated without permanent current attenuation.

The requirement of (III) is C as shown in FIG.
Each Nb wire 2 embedded in a plurality of u-Sn alloy linear base materials 1a
The primary multi-core material 8a in which the Ta wire 12 is embedded in the shaft core part of
It is operated by incorporating it into the next multi-core billet 11 (composite billet). By embedding the Ta wire in the axial center portion of each Nb wire 2 as described above, the point of the structure is that a uniform Ta core can be secured in the entire cross section of the wire regardless of any heat treatment. is there. That is, the above
If the requirement of (III) is adopted, the yield stress of Ta is Nb
Because of greater than the yield stress, the resulting Nb ₃ Sn superconducting wire, substantially the yield stress increases, with Nb ₃ limits distortion Sn cracking superconducting wire enters increases effect.
That is, the superconducting magnet for an NMR apparatus using the above Nb ₃ Sn superconducting wire according to the present invention has a large tolerance for the hoop force, and can be stably operated without decay of the permanent current. it can. Furthermore, by introducing Ta, the residual thermal strain is reduced, so that the effect of increasing the critical temperature can be obtained. As shown in FIG. 8, such an effect is obtained when the Cu-Sn alloy linear base material 1 is used.
A similar so-called single-core type composite billet 3a in which the Nb wire 2 is embedded and the Ta wire 12 is embedded in the axial center portion of the Nb wire 2 is similarly obtained. Further, in a superconducting magnet that generates a magnetic field exceeding 15 T, the above-mentioned hoop force is further increased. Therefore, the strengthening by burying Ta is not only applied to the superconducting magnet for an NMR apparatus but also as a wire for a high magnetic field magnet of other apparatuses. It is valid.

The linear base material 1 in which the Nb wire 2 is embedded according to the present invention
(Or 1a), the inner layer 5 and the outermost layer 9 are pure Cu-
Although Sn alloy is generally used, the same effect can be obtained by using an alloy in which a third element or a fourth element is added to Cu-Sn. In the present invention, these are collectively Cu-Sn.
It is a base alloy.

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and any modification of the design can be made in view of the gist of the preceding and the following. It is included in the target range.

[0024]

【Example】

Example 1 First, Cu- having a composition of Cu-13% Sn and having an outer diameter of 65 mm
The Sn alloy linear base material 1a was subjected to drilling at a diameter of 17 mm at 7 locations, Nb wires 2 having an outer diameter of 17 mm were embedded therein, and the primary multicore billet 8 as shown in FIG. 1 was assembled. 50%
The outer diameter was 1.
Wire drawing was performed up to 8 mm. At this time, the primary multi-core billet 8
Produced five types of Nb wires 2 having different intervals.

Next, the primary multi-core billet 8 is prepared as shown in FIG.
As shown in, secondary multi-core billet 11 (composite billet)
Assembled to Here, the three-layer structural member at the center has an outer diameter of 4
Insert a Ta pipe (diffusion barrier layer 6) with an outer diameter of 35 mm and an inner diameter of 32 mm and an oxygen-free copper (stabilized copper 7) with an outer diameter of 32 mm into a Cu-13% Sn alloy pipe (inner layer 5) of 0 mm and an inner diameter of 35 mm. The composite material is processed to have an outer diameter of 18 mm, which is hereinafter referred to as a Ta barrier stabilizing member.

Outside the Ta barrier stabilizing member, an outer diameter 6
A Cu-13% Sn alloy pipe (outermost layer 9) having a diameter of 5 mm and an inner diameter of 55 mm is arranged, and a primary multi-core billet 8 in which the Nb wire 2 has the same interval and is drawn to the outer diameter of 1.8 mm in the gap between them. 8
34 pieces are inserted (wire group 10) and the composite billet 11 is Nb.
Five types were assembled at every interval. Then, all the composite billets were wire-drawn to an outer diameter of 0.8 mm while performing intermediate annealing at 600 ° C. for 1 hour at every 50% processing rate. The obtained wire rod was twisted at a pitch of 50 mm and finished. These wires were subjected to a heat treatment for Nb ₃ Sn formation at 700 ° C. for 50 hours, and the critical current at 12 T was changed to a magnetic field history of (1) 0.
Critical current Ic1 for T → 12T and (2) 0T → 1
It was measured with the critical current Ic2 in the case of 4T → 12T. Furthermore, the attenuation of the permanent current at 12T was investigated when the wire was a small coil having an outer diameter of 45 mm and an inner diameter of 38 mm. These results are shown in Table 1 along with the spacing between the Nb ₃ Sns that are the most adjacent.

[0027]

[Table 1]

From the results of Table 1, the following can be considered. Table 1
In the case where Ic1 / Ic2 exceeds 1, it is indicated that the proximity effect is occurring. Therefore, it is speculated that the large current attenuation in the comparative example of Sample No. 1 is caused by this effect. Further, in order to examine the large current attenuation in the comparative example of Sample No. 5, the Cu—Sn alloy portion of the sample was removed with nitric acid and the filament was observed with a scanning electron microscope. As a result, irregularities were observed at a period of several tens of μm. It was In contrast, those of the sample No. 2 to 4 satisfying the requirements of the present invention has a small current decay showed a very excellent properties as a Nb ₃ Sn superconducting wire for NMR apparatus.

Example 2 In the same manner as in Example 1, a Ta barrier stabilizing member was produced. A Cu-13% Sn alloy pipe (outermost layer 9) having an outer diameter of 65 mm and an inner diameter of 55 mm is arranged on the outer side of the Ta barrier stabilizing member in the same manner as in Example 1, and the gap between the two is formed in the same manner as in Example 1. 834 for the primary multi-core billet 8 with an outer diameter of 1.8 mm
The secondary multi-core billet 11 which was fully inserted was assembled. At this time, the Ta pipe (diffusion barrier layer 6) and the innermost layer Nb ₃ S
Six types of composite billets were assembled by replacing the primary multi-core billet 8 on the center side with a bronze alloy wire having a diameter of 1.8 mm in order to adjust the average distance between n filament groups and d _in . All billets were wire-drawn to an outer diameter of 0.8 mm while performing intermediate annealing at 600 ° C. for 1 hour at every 50% working rate. The obtained wire rod was twisted at a pitch of 50 mm and finished.

The wire thus obtained was subjected to Nb at 700 ° C. for 50 hours.
₃ Sn heat treatment is applied, and the critical current Ic at 12T,
The attenuation of the persistent current at 12T was investigated when the wire was a small coil having an outer diameter of 45 mm and an inner diameter of 38 mm. In addition, a tensile test was performed at 4.2K to obtain a 0.2% proof stress. The results are shown in Table 2. At this time, the distances Ds between the Nb ₃ Sns that are closest to each other were all 0.8 μm. Further, the cross section of each sample was polished, and the residual Nb core diameter (RD) in the Nb ₃ Sn filaments in the outermost layer portion and the innermost layer portion was observed with a scanning electron microscope, and the ratio of the RD of the outermost layer portion and the innermost layer portion was compared. (RD _out / RD
_in ) is summarized in FIG. 6 in relation to d _out / d _in .

[0031]

[Table 2]

Here, d _in is the average distance between the Ta pipe (diffusion barrier 6) at the time of assembling the secondary multi-core billet 11 and the inner surface of the wire rod group 10, and d _out is the secondary multi-core billet 1.
1 is the thickness (5.3 mm) of the Cu-13% Sn alloy pipe (outermost layer 9) at the time of assembly. As is clear from these results, adjusting (d _out / d _in ) to an appropriate range (N
It can be seen that o. 8 to 10) are effective in reducing the current attenuation.

Example 3 A composite of Nb and Ta was prepared by inserting a Ta wire 12 having an outer diameter of 8.5 mm into an Nb wire 2 having an outer diameter of 17 mm and an inner diameter of 8.5 mm, and a composition of Cu-13% Sn. A Cu-Sn alloy linear base material 1a having an outer diameter of 65 mm is punched at a diameter of 17 mm at seven locations, and the composite is inserted therein to form a primary multi-core billet 8a as shown in FIG. I assembled it. The primary multi-core billet 8a was wire-drawn to an outer diameter of 0.3 mm while performing intermediate annealing at 600 ° C. for 1 hour at every 50% working rate. Also, as a comparative material, C was similarly drilled at 7 locations.
A sample was also prepared in which a Nb rod having an outer diameter of 17 mm was inserted into a u-Sn alloy column and wire-drawn to an outer diameter of 0.3 mm in the same processing step.

These samples were heat-treated in vacuum at 700 ° C. for 50 hours, and the critical current (Ic) was measured under tensile stress at 12T and 4.2K. Also, the critical temperature (Tc) of both samples
It was measured by the resistance method. FIG. 9 shows the results of critical current measurement under tensile stress. The critical current without tensile stress was 66 A for the material of the present invention and 73 A for the comparative material. This decrease in Tc is due to the Nb generated by the insertion of Ta.
_This is because the amount of ₃ Sn compound was reduced, and the Ic per compound layer was equal to or higher than that. However, as shown in FIG. 9, the strain having the maximum critical current was 0.27% in the comparative material, while it was 0.18% in the material of the present invention. This indicates that the residual thermal strain after heat treatment is small. Further, the critical temperature (resistance 0) was 17.2K for the comparative material, whereas it was 17.5K for the material of the present invention.

Example 4 A composite of Nb and Ta was prepared by embedding a Ta wire 12 having an outer diameter of 8.5 mm in an Nb wire 2 having an outer diameter of 17 mm and an inner diameter of 8.5 mm. On the other hand, an outer diameter of 65 mm with a composition of Cu-13% Sn
The Cu-Sn alloy linear base material 1a was subjected to drilling with a diameter of 17 mm at 7 locations, and the composite was inserted therein to assemble a primary multi-core billet 8a. 6 for every 50% processing rate
Wire drawing was performed to an outer diameter of 1.8 mm while performing intermediate annealing at 00 ° C for 1 hour. In addition, as a comparative material, a Cu / Sn alloy cylinder similarly drilled at 7 locations was inserted with an Nb rod with an outer diameter of 17 mm, and a primary multi-core billet 8 was drawn to the outer diameter of 1.8 mm in the same processing step. (See FIG. 3) was prepared.

Cu-1 having an outer diameter of 40 mm and an inner diameter of 35 mm
3% Sn alloy pipe (inner layer 5), Ta pipe (diffusion barrier layer 6) with an outer diameter of 35 mm and an inner diameter of 32 mm was inserted, and oxygen-free copper (stabilizer) with an outer diameter of 32 mm was inserted to stabilize the Ta barrier. The assembled member was assembled and the outer diameter was reduced to 18 mm.

Outside the Ta barrier stabilizing member, an outer diameter of 6
A Cu-13% Sn alloy pipe (outermost layer 9) having a diameter of 5 mm and an inner diameter of 55 mm is arranged, and the primary multi-core billet 8a is placed in the gap between the two.
Was inserted (wire rod group 10), and the composite billet 11 was assembled. Further, the composite billet 11 was similarly assembled for the comparative material. 60 for both billets every 50%
Wire drawing was performed to an outer diameter of 0.8 mm while performing intermediate annealing at 0 ° C for 1 hour.

The wire thus obtained was finished by twisting with a pitch of 50 mm. 50 at 700 ° C for these wires
The heat treatment for Nb ₃ Sn generation was performed for a period of time to examine the critical current Ic at 12T and the decay of the permanent current at 12T when the wire was made into a small coil having an outer diameter of 45 mm and an inner diameter of 38 mm. Also,
The 0.2% proof stress at 4.2K was also examined. The results are shown in Table 3.

Although the material of the present invention has a lower critical current than that of the comparative material, the current attenuation is small, and Nb ₃ Sn for an NMR apparatus is used.
It can be seen that the superconducting wire has extremely excellent characteristics. Further, since it has high mechanical strength, it can be used for a superconducting wire used for generating a higher magnetic field.

[0040]

[Table 3]

[0041]

As described above, the present invention can realize an Nb ₃ Sn superconducting wire which can be a constituent material of a superconducting magnet having an extremely excellent magnetic field stability, and can be used in a wide range of fields such as analysis and medical treatment. It can be expected that the performance of the equipment will be improved.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an average interval Ds defined in the present invention.

FIG. 2 is a view showing a cross section of a single-core type composite billet by a bronze method.

FIG. 3 is a view showing a cross section of a primary multi-core billet 8 produced by a bronze method.

FIG. 4 is a view showing a cross section of a secondary multi-core billet 11 by the bronze method.

FIG. 5 is a diagram for explaining distances d _out and d _in specified in the present invention.

FIG. 6 is a graph showing the relationship between (d _out / d _in ) and RD _out / RD _in .

FIG. 7 is a view showing a cross section of a primary multicore billet 8a in which a plurality of Ta wires are embedded in an Nb wire.

FIG. 8 is a view showing a cross section of a single core type composite billet 3a in which one Ta wire is embedded in an Nb wire.

FIG. 9 is a graph showing the strain dependence of the critical current of the invention material and the comparative material.

[Explanation of symbols]

 1 Billet case (Cu-Sn alloy linear base material) 2 Nb wire 3,3a Mixed billet (single core composite billet) 5 Inner layer 6 Nb or Ta layer (diffusion barrier layer) 7 Oxygen-free copper (stabilized copper ) 8,8a Primary multi-core billet 9 Outer layer case (outermost layer) 10 Wire group 11 Secondary multi-core billet (composite billet) 12 Ta wire

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiko Inoue 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Prefecture Kobe Steel Works, Ltd. Kobe Research Institute (72) Inventor Kazukazu Hakurakura Kobe, Hyogo Prefecture 1-5-5 Takatsukadai, Nishi-ku Inside the Kobe Research Institute of Kobe Steel, Ltd. (72) Inventor Hidefumi Kurahashi 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Inside the Kobe Research Institute of Kobe Steel ( 72) Inventor Yukihiro Maeda 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Prefecture Kobe Steel Works, Ltd. Kobe Research Institute

Claims (4)

[Claims] 1. A wire / rod-shaped stabilized copper, a cylindrical diffusion barrier layer, a cylindrical Cu—Sn based alloy inner layer, and a plurality of Nb.
A wire rod group formed by bundling a plurality of Cu-Sn base alloy linear base materials in which wires are embedded in a cylindrical shape, and a cylindrical Cu or Cu-Sn base alloy outermost layer from the center side in the radial direction to the outer side. disposed in people placing order to constitute a composite billet, generates an interface Nb ₃ Sn with the after the composite billet wire drawing, the Nb line and the Cu-Sn based alloy linear base material by heat treatment the method of manufacturing a cause Nb ₃ Sn superconducting wire, manufacturing method of Nb ₃ Sn superconducting wire and performing operations in the manner to satisfy at least one of the following requirements (I) ~ (III). (I) Cu-Sn and Nb wire group embedded in alloy linear base material, Nb ₃ is the closest after to generate Nb ₃ Sn Sn
The distance Ds is within the range of 0.5 to 1.0 μm. (II) and the average distance d _out from the outermost surface of the composite billet to said wire group outermost surface, the ratio of the average distance d _in the diffusion barrier layer to the wire group in the surface (d _out / d _in) is 1 ．
It is configured to be 5 to 4.0. (III) Each N embedded in a plurality of Cu-Sn based alloy linear base materials
The Ta line is embedded in the axis of the b line. 2. A Nb ₃ Sn superconducting wire obtained by the method according to claim 1. 3. A single core type composite billet is constructed by burying one Nb wire concentrically in the axial center of a Cu-Sn base alloy linear base material, and extending the single core type composite billet. After line processing,
The method of manufacturing a heat treatment to the Cu-Sn based alloy linear base material and the interface Nb ₃ Sn superconducting wire to produce Nb ₃ Sn with Nb lines, as the Nb lines, the Ta wire in the axial center portion A method for manufacturing an Nb ₃ Sn superconducting wire, which is characterized in that the embedded structure is used for operation. 4. A Nb ₃ Sn superconducting wire obtained by the method according to claim 3.