JPH065130A - Composite multi-core nbti superconductive wire - Google Patents

Abstract

PURPOSE:To provide a composite multi-core NbTi superconductive wire having high stability and high strength and excellent in workability. CONSTITUTION:In a composite multiple core NbTi superconductive wire where a plurality of NbTi filaments 1 are embedded in a normal conductive metal matrix, a part or the whole of the normal conductive metal matrix is made of a Cu-Ag alloy 4 including 0.1-5wt.% of Ag and the remainder of Cu.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite multicore NbTi superconducting wire used for a superconducting magnet or the like.

[0002]

2. Description of the Related Art As shown in FIG. 3, a composite multi-core NbTi superconducting wire used for a superconducting magnet or the like is made by converting NbTi alloy which is a superconducting material into a filament.
It has a structure in which a large number of (1) are embedded in a normal-conducting metal matrix such as oxygen-free copper (2), (2 ') which is a stabilizer.

The basic manufacturing method of this composite multifilamentary NbTi superconducting wire is as follows. First, if necessary, the NbTi ingot is wrapped with an Nb sheet around it, inserted into an oxygen-free Cu tube, and covered at both ends with an electron in a vacuum. Beam welding is included. This was hot extruded and then thinned into a predetermined hexagonal or round shape, then this composite wire was inserted again into the oxygen-free Cu tube, and both ends were covered with lids in the same manner as described above. Enclosed by beam welding, then extruded and thinned,
A composite multi-core NbTi superconducting wire having NbTi filaments of ten to several hundreds of thousands is obtained.

As described above, the composite multi-core NbTi superconducting wire has a structure in which a plurality of NbTi filaments are embedded in a normal conducting metal matrix. Among the normal conducting metal matrix, NbTi alloy rods are used in the manufacturing process. The oxygen-free copper pipe into which the oxygen-free copper is inserted serves as the peripheral portion of the NbTi filament (2 in FIG. 3), and the copper tube into which the oxygen-free copper / NbTi composite element wire is inserted serves as the sheath portion (2 'in FIG. 3).

Further, recently, a composite multi-core NbTi superconducting wire which can be used with an alternating current at a commercial frequency has been put into practical use. Since this reduces AC loss, high resistance Cu-
The Ni alloy is used for a part or all of the metal matrix, and if one example is shown, Cu-Ni as shown in FIG.
It has a three-layer structure of / Cu / Nb-Ti. That is, Cu-N with an oxygen-free copper filament (2) embedded in the center
The i-alloy tube (3) was arranged, and the assembly in which the Cu-Ni alloy tube (3) in which the NbTi filament (1) was embedded was arranged on the periphery thereof was further covered with the Cu-Ni alloy sheath part (3 '). It is a thing. As a method for manufacturing the composite multicore NbTi superconducting wire for alternating current, among the above manufacturing methods, NbT in the initial step
Instead of inserting the i alloy rod into the oxygen-free copper pipe, Cu-Ni
The other steps are almost the same except that they are inserted into the alloy pipe.

[0006]

By the way, in order to improve the stability of the superconducting wire, it is necessary to increase the residual resistance ratio of the metal matrix which is a stabilizing material. In the final step, annealing is performed to improve the residual resistance ratio. However, this annealing causes a problem that the residual resistance ratio increases and the stability improves but the mechanical strength decreases. Therefore, in the case of a wire having a large current capacity or when high strength is required such as a superconducting wire for alternating current in which a filament having a small wire diameter is twisted, it is necessary to additionally compound a reinforcing material such as a stainless wire.
In addition, in order to improve the critical current density (Jc) of the NbTi superconducting wire during processing, the aging heat treatment is repeated 400 times.
The oxygen-free copper matrix is completely annealed during this aging heat treatment, while NbTi is used.
The filament is age hardened. This makes NbTi
The yield strength ratio of filament to matrix copper is 10
There is also a problem that uniform deformation becomes difficult in the subsequent composite processing (drawing, etc.), and the Nb-Ti filaments and the entire superconducting wire are likely to be broken.

In the case of a superconducting wire for alternating current, when only a Cu--Ni alloy is used as a matrix, the strength is not remarkably decreased due to the softening of the metal matrix due to annealing as in the case of an oxygen-free copper matrix, but usually the Cu--Ni alloy Since only the matrix has low conductivity and has a problem in stability, a part of the matrix is often made of oxygen-free copper. As shown in FIG. 4, the structure is such that an Nb-Ti alloy filament coated with a Cu-Ni alloy is arranged around the oxygen-free copper filament coated with a Cu-Ni alloy,
A structure in which this assembly is sheathed with a Cu-Ni alloy is often adopted. In this case, the oxygen-free copper filament in the central portion has a wire diameter of about several μm, but this oxygen-free copper has a problem that it is softened by annealing as described above and its strength is lowered.

[0008]

SUMMARY OF THE INVENTION The present invention has been developed as a result of intensive studies in view of the above situation.
In a composite multicore NbTi superconducting wire in which a Ti filament is embedded in a normal-conducting metal matrix, a part or all of the normal-conducting metal matrix is a Cu-Ag alloy containing 0.1 to 5 wt% of Ag and the balance Cu. Is a composite multi-core NbTi superconducting wire.

Here, in the composite multi-core NbTi superconducting wire having the structure shown in FIG. 3, it is effective to arrange the Cu-Ag alloy only around the NbTi filament as shown in FIG.

Further, in the composite multicore NbTi superconducting wire for alternating current having the structure as shown in FIG. 4, as shown in FIG. 2, the oxygen-free copper filament in the central portion is replaced by a Cu--Ag alloy filament. It is effective.

[0011]

In the present invention, a Cu-Ag alloy is used in place of oxygen-free copper for a part or all of the metal matrix, because the Cu-Ag alloy is a NbTi superconducting wire if the Ag content is 0.1 wt% or more. 200 to 4 for annealing and aging treatment
It has the property that it does not soften even if it is heated to a temperature of 00 ° C, and its strength is less reduced by aging treatment, and if the Ag content is 5 wt% or less, the residual resistance ratio is 10 or more even in the unannealed working state. Indicates a value. Therefore, some or all of the oxygen-free copper that is the matrix metal has an Ag content of 0.1.
This is because a high strength NbTi superconducting wire can be obtained without lowering the residual resistance ratio, that is, without losing stability, even if it is replaced with a Cu-Ag alloy of 5 wt%. Further, the Cu-Ag alloy has a small decrease in strength during the aging treatment of the superconducting wire and does not have a large difference in strength with the NbTi alloy filament, so that the plastic deformation as a composite becomes uniform and the filament breakage or the entire superconducting wire breakage occurs. Can be prevented.
And, the Ag content of the Cu-Ag alloy is 0.1 to 5 wt%
If less than 0.1 wt%, the softening resistance does not change much from oxygen-free copper, and the strength after heat treatment is insufficient.
This is because if it exceeds 5 wt%, the residual resistance ratio decreases, the effect of improving the softening resistance is saturated, and the cost increases.

In the present invention, as shown in FIG. 1, NbTi
It is effective to replace only the peripheral part of the filament (1) with the Cu-Ag alloy (4). In recent NbTi superconducting wires, the NbTi filament is often thinned to 10 μm or less, and the oxygen-free part around the NbTi filament is oxygen-free. Copper is thinned to a thickness of several μm or less. Such a thin oxygen-free copper has a limited mean free path of electrons, and the residual resistance ratio recovers only to about several tens even if an annealing treatment is performed. Therefore, even if it is replaced with a Cu-Ag alloy, the entire matrix is reduced. The residual resistance ratio is not significantly affected, and the softening resistance is improved. Also, since the amount of Cu-Ag alloy used is small, it is advantageous in terms of cost.

When a Cu-Ni alloy is used as a matrix, as shown in FIG. 2, a Cu-Ni alloy is formed in the central portion.
A Cu-Ag alloy filament (4) coated with (3) (which replaces the oxygen-free copper in Fig. 4) is placed, and Cu-
Nb-Ti alloy filament coated with Ni alloy (3)
(1) is arranged, and a structure in which these aggregates are sheathed with a Cu-Ni alloy (3 ') is effective, but it is effective that the oxygen-free copper filament is annealed even if it becomes thin to a few μm. Since the residual resistance ratio is not sufficiently recovered and the strength is lowered, even if it is replaced with a Cu-Ag alloy, the residual resistance ratio of the entire matrix is little affected, and the softening resistance can be improved. is there.

[0014]

EXAMPLES The present invention will now be described in more detail with reference to Examples. Example 1 A 155 mmφ NbTi rod was inserted into an oxygen-free copper tube having an outer diameter of 200 mm and an inner diameter of 157 mm or various Cu-Ag alloy tubes, and both ends were vacuum-sealed to form a primary billet. This primary billet was subjected to hot extrusion, cold drawing, and peeling to obtain a hexagonal wire having an opposite side length of 2.5 mm. 4200 hexagonal wires were inserted into an oxygen-free copper tube or a Cu-Ag alloy tube having an outer diameter of 200 mm and an inner diameter of 175 mm, and both ends were vacuum-sealed to form a secondary billet. The billet was again subjected to hot extrusion and appropriate intermediate annealing to carry out cold drawing to obtain a 0.5 mmφ composite multicore NbTi superconducting wire having various metal matrices shown in Table 1. Here, the equivalent diameter of the NbTi filament was 5.5 μm. The sheath portion of the metal matrix shown in Table 1 was formed from the oxygen-free copper tube or Cu-Ag alloy tube in the secondary billet, and the NbTi filament peripheral portion was formed from the oxygen-free copper tube or Cu-Ag alloy tube in the primary billet. It is a thing. And N
The metal matrix around the bTi filament is 1.2
It was thinned to a thickness of μm. In addition, the ratio of the occupied area of the NbTi filament, the metal matrix of the sheath portion and the metal matrix around the NbTi filament in the cross-sectional area of the superconducting wire is 1.0: 0.5:
It is 0.5. After this superconducting wire was heated at 250 ° C. for 1 hour and annealed, the residual resistance ratio and the tensile strength were measured and the values are shown in Table 1. Table 1 also shows the number of wire breaks that occurred during processing up to 0.5 mmφ.

[0015]

[Table 1]

As is apparent from Table 1, the invention example No. 1 to
No. 4 is the conventional example No. Compared with No. 7, the strength is high, and the number of disconnection during manufacturing is small. Further, the residual resistance ratio is also within a range where there is no practical problem. On the other hand, Comparative Example No. 1 in which the Ag content in the Cu-Ag alloy is less than the range of the present invention. In Comparative Example No. 5, the strength was not improved and the Ag content was larger than the range of the present invention.
6 shows that the strength is high, but the residual resistance ratio is small.

[Example 2] Outer diameter 200 mm, inner diameter 157 mm
Insert a 155 mmφ NbTi rod into a Cu-10% Ni alloy tube of, and seal both ends in vacuum to form an NbTi / CuNi composite billet. This NbTi / CuNi composite billet is subjected to hot extrusion and intermediate annealing as needed while cooling. Hexagonal NbTi / Cu-Ni with opposite side length of 3 mm after thinning and peeling
It was a bare wire. On the other hand, Cu- with an outer diameter of 200 mm and an inner diameter of 157 mm
Various Cu-Ag alloy rods having a diameter of 155 mm were inserted into a 10% Ni alloy tube, and both ends were vacuum-sealed to form a Cu-Ag / Cu-Ni composite billet. This Cu-Ag / Cu-Ni composite billet was hot extruded, and Hexagonal Cu-Ag / C with opposite side length of 3 mm, with cold drawing and peeling while appropriately performing intermediate annealing on the way
The u-Ni strand was used. Next, 200 mm outer diameter and 175 mm inner diameter
Cu-10% Ni alloy tube with Cu-Ag / Cu
-2000 Ni strands and Nb-Ti / C around it
By inserting 930 u-Ni strands, 2930 in total, and vacuum-sealing both ends to form a secondary billet, by hot extruding this secondary billet and performing cold annealing while appropriately performing intermediate annealing. The composite multicore NbTi superconducting wire of 0.5 mmφ having various metal matrices shown in Table 2 was used. Here, the equivalent diameter of the NbTi filament was 6.8 μm, and the equivalent diameter of the Cu—Ag filament was 6.8 μm. After this superconducting wire was heated at 250 ° C. for 1 hour and annealed, the residual resistance ratio and the tensile strength were measured, and the values are shown in Table 2. Table 2 also shows the number of wire breaks that occurred during processing up to 0.5 mmφ. Further, as a conventional example, a composite multi-core NbTi superconducting wire in which the central filament is not oxygen-free Cu-Ag alloy but oxygen-free copper was manufactured and compared in the same manner as above.

[0018]

[Table 2]

As is apparent from Table 2, the invention sample No. 11
Nos. 13 to 13 are conventional examples. Compared with No. 16, the tensile strength is high and the number of breaks is small. Further, the residual resistance ratio is also within a range where there is no practical problem. On the contrary, Cu-Ag of the central filament
Comparative Example N in which the Ag content in the alloy is less than the range of the present invention
o. In No. 14, the tensile strength was not improved and the number of wire breaks was not reduced. Also, the Ag in the Cu-Ag alloy of the central filament
Comparative Example No. with a content higher than the range of the present invention. It can be seen that No. 15 has a high strength but a small residual resistance ratio.

[0020]

As described above, according to the present invention, a composite multifilamentary NbTi superconducting wire having high stability, high strength and good workability can be obtained, and the industrially remarkable effect is exhibited.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a composite multicore NbTi superconducting wire showing an embodiment of the present invention.

FIG. 2 is a composite multi-core NbTi showing another embodiment of the present invention.
Sectional drawing of a superconducting wire.

FIG. 3 is a cross-sectional configuration diagram of a conventional composite multi-core NbTi superconducting wire.

FIG. 4 is a cross-sectional configuration diagram of a conventional composite multi-core NbTi superconducting wire.

[Explanation of symbols]

 1 NbTi filament 2 Oxygen-free copper 3 Cu-Ni alloy 4 Cu-Ag alloy

Claims (3)

[Claims] 1. In a composite multi-core NbTi superconducting wire in which a plurality of NbTi filaments are embedded in a normal conducting metal matrix, a part or all of the normal conducting metal matrix contains Ag of 0.1 to 5 wt% and the remaining Cu. -A
A composite multi-core NbTi superconducting wire characterized by being a g-alloy. 2. C only in the peripheral portion of the NbTi filament
The composite multicore NbTi superconducting wire according to claim 1, further comprising a u-Ag alloy. 3. The composite multicore NbTi superconducting wire according to claim 1, wherein a plurality of NbTi filaments and a plurality of Cu—Ag alloy filaments are embedded in a Cu—Ni alloy matrix.