JP5117166B2 - NbTi superconducting multi-core wire for pulse and NbTi superconducting molded stranded wire for pulse - Google Patents

Description

  The present invention relates to a pulse NbTi superconducting multi-core wire and a pulse NbTi superconducting shaped twisted wire.

In general, the NbTi superconducting wire is composed of a plurality of NbTi filaments and a stabilized copper covering the NbTi filaments, for increasing the current carrying capacity, improving the current density, mechanical stability, and winding workability. It becomes a molded stranded wire structure. When this formed stranded wire is used under a pulse-varying magnetic field, an AC loss is generated, resulting in a decrease in cooling efficiency. As AC loss at this time, in addition to hysteresis loss occurring in the NbTi filament part in the superconducting element wire and coupling loss (including eddy current loss) occurring in the stabilized copper part which is a normal conducting metal, between the superconducting element wires There is a coupling loss between strands due to the flowing current.

Normally, the hysteresis loss in the NbTi filament portion can be reduced by reducing the filament diameter, but the manufacturing cost increases as the filament diameter decreases, so that it is within a range that satisfies the required characteristics as a device. Therefore, it is customary to design as large a value as possible. On the other hand, the coupling loss at the stabilized copper portion can be reduced by arranging a copper alloy such as a CuNi alloy at the outer periphery of each filament, between the filaments, or at the outer periphery of the strand. In particular, the coupling loss can be further reduced by arranging the CuNi alloy on the outer periphery of the filament, between the filaments, and on the entire outer periphery of the strand.

Based on this concept, an NbTi superconducting wire having a structure in which the stabilizing copper portion is completely eliminated and the matrix portion is entirely a CuNi alloy is used as an AC wire generally used in an empirical magnetic field of 1 to 2 T or less. . In the AC wire having such a configuration, the critical current density Jc is extremely high in a low magnetic field, and the loss due to the change in the magnetic field becomes large, so that it lacks stability. For this reason, in AC wires, the wire diameter is made as thin as possible to improve heat dissipation, or stabilized copper finely partitioned by a CuNi alloy barrier layer is incorporated in the center of the wire, so that stability in a low magnetic field is achieved. Has improved.

However, in such an AC wire rod, the NbTi filament diameter is reduced to 0.1 to 0.5 μm in order to reduce hysteresis loss and improve stability, so Jc in a magnetic field is small, The critical current capacity per strand is small. For this reason, when using for a large current wire, these strands must be twisted in multiple.

On the other hand, NbTi wires for pulses used on the high magnetic field side of 2T or more are used in equipment such as magnets for physics and chemistry research used in, for example, generator coils, SMES, elementary particle accelerators, nuclear fusion experimental reactors, etc. Since a large current capacity exceeding several kA to 10 kA is required in a high magnetic field region near 5T, a stranded wire structure is used. However, in order to increase mechanical rigidity, a pulse wire preferably has a small number of stranded wires. .

Therefore, it is necessary to increase the critical current capacity per one strand, and the outside diameter of the strand naturally increases. When the outer diameter of the strand increases, the heat loss becomes worse. For these reasons, it is not possible to employ an AC wire configuration in which the matrix portion is entirely made of a CuNi alloy for the pulse wire. That is, when the pulse wire is used for a large-sized device, if the strand is quenched, it will lead to a major accident, so the amount of copper in the material covering the NbTi filament must be increased for stabilization.

Pulse wire has a lower magnetic field change rate experienced than AC wire, but reduction of AC loss is indispensable in order to suppress the decrease in cooling efficiency and to improve instability caused by heat generation due to AC loss. It is.

Conventional pulse superconducting wire has a three-layer structure in which an NbTi filament is coated with a stabilizing material made of copper and CuNi alloy and is embedded in a copper matrix for the purpose of ensuring stability and reducing AC loss. The wire is used.

However, in this three-layer structure wire, when copper is interposed between NbTi filaments, the deformation resistance of copper is smaller than that of NbTi or CuNi, so NbTi or CuNi during hot extrusion or wire drawing The deformability differs between copper and copper, causing deformation of the filament shape and, in extreme cases, filament breakage.

In addition, since the copper outside the NbTi filament is generally thin, nickel atoms diffuse from CuNi into copper by heat treatment in the wire manufacturing process. For this reason, the electrical resistance of copper increases, and conversely, the thermal conductivity decreases and the function as a stabilizing material is reduced.

In Patent Document 1, as means for solving this problem, a filament assembly in which at least three NbTi filaments are embedded in a first matrix made of a copper alloy, and a plurality of filament assemblies are embedded. A pulse NbTi superconducting wire comprising a second matrix made of copper is disclosed.
JP-A-6-295626

However, a filament aggregate formed by embedding at least three NbTi filaments in a first matrix made of a copper alloy, and a second matrix made of copper in which a plurality of filament aggregates are embedded. In NbTi superconducting wire, the essential stabilization criteria were satisfied, but the effect of sufficiently satisfying the required characteristics as a device was not obtained, and it was never put into practical use due to the problem of manufacturing cost. It was.

  The present invention has been made in view of the above points, and has an NbTi superconducting multi-core wire for pulse and a NbTi superconducting molding for pulse using the same, which has low current cost and realizes energization stability, low AC loss, and high critical current density. It is to provide a stranded wire.

The first aspect of the NbTi superconducting multifilamentary wire for pulse according to the first invention is embedded in a substantially circular core section made of a stabilizing material and a copper alloy containing at least one of Ni, Mn and Si. N
bTi consists only of filaments Tona Ru 1 Tsugimotosen, and a plurality of the one and the filament assembly Tsugimotosen is disposed on the outer periphery of the core, the core formed on the outer periphery of the filament assemblies And a stabilizing layer made of the same stabilizing material as the portion, wherein the volume of the copper alloy in which the NbTi filament is embedded is 0.3 to 0.6 times that of the NbTi filament. .
Here, when the volume of the copper alloy in which the NbTi filament is embedded is less than 0.3 times that of the NbTi filament, the thickness of the copper alloy existing around the NbTi filament is too small. The copper alloy is damaged during the production of the primary strand of the superconducting multicore wire, and the NbTi filament is exposed. Therefore, the process to a multi-core wire cannot be performed, and the problem that a manufacturing yield falls will arise.
Further, when the volume of the copper alloy in which the NbTi filament is embedded is larger than 0.6 times the NbTi filament, when manufacturing the pulse NbTi superconducting multi-core wire using the primary strand, NbTi filaments are likely to be deformed abnormally. Thus, practical higher is better and is the n value - decrease (current index n when the voltage characteristic was VarufaI ⁿ⁾ is further embedded portion of the NbTi filaments in (filament aggregate) The problem arises that the current density itself becomes small.

The second aspect of the NbTi superconducting multifilamentary wire for pulse according to the first aspect of the present invention is that the total volume of the stabilizing material forming the core and the stabilizing layer is 1.5 to the total volume of the NbTi filament. It is characterized by 4.5 times. When the total volume of the stabilizing material is less than 1.5 times, the volume ratio of the stabilizing material disposed in the sheath portion (stabilizing layer) of the pulse NbTi superconducting multicore wire is reduced, and the pulse NbTi superconducting multi The NbTi filament is exposed during the manufacture of the core wire, making it difficult to manufacture a multi-core wire. Furthermore, when the NbTi superconducting multi-core wire is a stranded wire, there is a problem that deformation of the filament in the NbTi superconducting multi-core wire becomes large and Ic deteriorates. On the other hand, if it is larger than 4.5 times, the superconductor portion of the NbTi filament is reduced, resulting in a problem that Je is lowered.

A third aspect of the NbTi superconducting multifilamentary wire for pulse according to the first invention is characterized in that the stabilizing material is copper or a copper alloy having a residual resistance ratio of 50 or more and 350 or less. In addition, when the residual resistance ratio of the stabilizing material is less than 50, there is a problem that the stability during energization is deteriorated, and when it is larger than 350, not only the AC loss (coupling loss) increases. In addition, since it is necessary to select oxygen-free copper having a higher purity such as a residual resistance ratio of 400 or more in the raw material stage, there arises a problem that the yield of raw material reception is reduced.

  The first aspect of the pulse NbTi superconducting molded stranded wire according to the second aspect of the invention is that after forming at least one of a metal plating layer, a resin insulating layer and an oxide film on the surface of the pulse NbTi superconducting multi-core wire, More than 40 and not more than 40 NbTi superconducting multi-core wires for pulses are twisted and formed into a rectangular cross section. At this time, if the number of twisted NbTi superconducting multi-core wires for pulses is 5 or less, there is a problem that the winding property to the coil shape deteriorates, and if it exceeds 40, the flatness of the NbTi superconducting molded twisted wires for pulses There is a problem that it is difficult to secure.

ADVANTAGE OF THE INVENTION According to this invention, the NbTi superconducting multi-core wire for pulses and the NbTi superconducting shaping | molding twisted wire for pulses which are low in manufacturing cost compared with the former which implement | achieved energization stability, low alternating current loss, and high critical current density can be provided.

  A pulse NbTi superconducting multi-core wire and a pulse NbTi superconducting stranded wire in a preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, about each structural part which has the same function, the same code | symbol is attached | subjected and shown for simplification of illustration and description.

FIG. 1 shows a cross-sectional configuration diagram of a pulse NbTi superconducting multicore wire according to an embodiment of the present invention. This pulse NbTi superconducting multi-core wire 10 is composed of an NbTi filament 13 and a copper alloy layer 12 formed on the outer periphery of the NbTi filament 13 on the outer periphery of a core portion 16 having a substantially circular cross section made of a stabilizing material of copper or copper alloy. A filament assembly 15 is provided in which a plurality of primary strands 14 having a substantially hexagonal cross section are arranged in a matrix, and the filament assembly 15 is made of a stabilizer made of the same material as the core 16 on the outer periphery. An insulating layer 17 is formed.

The stabilizing material for forming the core portion 16 and the stabilizing layer 17 preferably has a residual resistance ratio (ratio of electrical resistance just above the temperature 27K and the superconducting critical temperature) of 50 or more and 300 or less. It is preferable that Further, when the stabilizing material forming the core portion 16 and the stabilizing layer 17 has a volume of 1.5 or more and 4.5 or less with respect to the total volume of the NbTi filament 13 in the filament assembly 15, the NbTi filament The processability is even better. The cross-sectional area of the stabilization layer 17 is more preferably 1 to 4 times the cross-sectional area of the core portion 16.

At this time, the thickness tb of the filament aggregate 15 is determined by the adiabatic stabilization criterion or the dynamic stabilization criterion. The thickness tb of the filament assembly 15 is determined by the average specific heat of the filament assembly 15, the volume ratio of the copper alloy layer 12 to the NbTi filament 13, and the critical current density Jc of the NbTi filament 13 according to the adiabatic stabilization standard, According to the dynamic stabilization standard, the volume ratio between the core 16 made of the stabilizing material and the stabilization layer 17 is taken into consideration, and is determined by the balance between diffusion of heat and magnetic flux caused by external disturbance and AC loss. To do. At this time, both tb determined by the adiabatic stabilization criterion or the dynamic stabilization criterion have similar values.

Further, the copper or copper alloy that forms the core 16 and the stabilization layer 17 may be divided by a barrier layer made of a CuNi alloy or the like. It is desirable not to arrange the barrier layer.

FIG. 2 is a cross-sectional configuration diagram of a pulse NbTi superconducting molded stranded wire according to an embodiment of the present invention. After forming the coating layer 18 on the surface of the NbTi superconducting multi-core wire 10 for pulses, the NbTi superconducting multi-stranded wire 11 for pulses is formed into 6 or more and 40 or less twisted rectangular cross sections of the NbTi superconducting multi-core wire 10 for pulses. Has been.

As the coating layer 18, a metal plating layer, a resin insulating layer, or an oxide film can be used. For example, Cr, Ni, Sn, or an alloy thereof can be used as the metal plating layer, and polyvinyl formal or polyvinyl acetal can be used as the resin insulating layer. When the stabilization layer 17 is copper or a copper alloy, copper oxide can be used for the oxide film. Among these, from the viewpoint of cost, a metal plating layer is preferably used, and Cr plating is more preferably used.

Below, the manufacturing method of the NbTi superconducting multi-core wire 10 for pulses is demonstrated. First, the manufacturing method of the primary strand 14 is demonstrated. A NbTi rod is inserted into the copper alloy tube to produce a primary composite billet. By subjecting the composite billet to hot extrusion and cold processing, a rod-shaped primary strand 14 (NbTi / copper alloy composite hexagon) is produced.

Next, a method for producing the pulse NbTi superconducting multi-core wire 10 using the primary strand 14 will be described. In order to form the core part 16, the stabilization rod-shaped body (stabilization material hexagon) which consists of a stabilization material is produced. Further, a copper tube or a copper alloy tube made of the stabilizing material and serving as the stabilizing layer 17 is manufactured, and the primary strand 14 and the stabilizing rod-like body are inserted into the tube of a predetermined size to obtain a secondary composite. Make a billet. Thereafter, hot extrusion processing is performed on the secondary composite billet, and then heat treatment and cold processing are repeated. Further, twisting and final wire drawing are performed to produce a pulse NbTi superconducting multi-core wire 10 having a predetermined size.

A method for producing the pulse NbTi superconducting shaped stranded wire 11 using the pulse NbTi superconducting multifilamentary wire 10 will be described. After the surface of the NbTi superconducting multi-core wire 10 for pulse is subjected to metal plating, resin insulation or oxide film formation, it is twisted 6 or more and 40 or less and subjected to forming processing such as biaxial roll rolling. The NbTi superconducting molded stranded wire 11 is produced.

In the above manufacturing method, depending on the material of the stabilizing material, the residual resistance ratio decreases due to work hardening. Therefore, an annealing step may be included in the intermediate step or the final step as necessary.

A method for producing a pulse NbTi superconducting multi-core wire 10 according to an embodiment of the present invention will be described with reference to FIG. First, in order to produce the primary strand 14, a Nb-47 wt% Ti rod was inserted into a Cu-10 wt% Ni tube to produce a composite billet. The composite billet is composed of a CuNi copper alloy layer 12 having a CuNi ratio of 0.5 formed on the outer periphery of the NbTi filament 13 and the NbTi filament 13 by subjecting the composite billet to hot extrusion and cold processing. A hexagonal rod-shaped primary strand 14 (NbTi / CuNi composite hexagon) having an opposite side dimension of 1.8 mm was produced.

Further, a hexagonal rod-shaped stabilizing rod-shaped body (Cu hexagon) 16a having an opposite side dimension of 1.8 mm to be the core portion 16 was manufactured by hot extrusion and cold processing of an oxygen-free copper ingot. Further, a Cu tube having an inner diameter of 150 mm / an outer diameter of 200 mm to be the stabilization layer 17 is manufactured, and the primary strand 14 (about 4,000 pieces) and the stabilizing rod-like body (Cu hexagonal) 16a (about 3,600 pieces). Was inserted into the copper tube to obtain a secondary composite billet. The secondary composite billet is subjected to repeated heat treatment and cold working after hot extrusion, and after twisting and final wire drawing, a pulse NbTi superconducting multi-core wire 10 having a diameter of 1.0 mmφ did. At this time, as shown in the enlarged view of part A of the NbTi superconducting multicore wire 10 for pulse shown in FIG. 1, a plurality of stabilizing rods (Cu hexagonal) 16a are combined and integrated to form the core portion 16, Similarly, a plurality of primary strands 14 are combined and integrated to form a filament assembly 15. The residual resistance ratio between the stabilizing rod-shaped body (Cu hexagon) 16a and the stabilizing layer 17 was 250.

Next, a method for producing the NbTi superconducting molded stranded wire 11 for pulses according to an embodiment of the present invention will be described with reference to FIG. After the surface of the pulse NbTi superconducting multi-core wire 10 was subjected to Cr plating, twelve strands were twisted and formed to obtain a pulse NbTi superconducting formed twisted wire 11.

Comparative example

  FIG. 3 is a cross-sectional configuration diagram of a pulse NbTi superconducting multicore wire according to a comparative embodiment. A method for producing the NbTi superconducting multicore wire 20 according to the comparative example will be described with reference to FIG. The NbTi superconducting multi-core wire 20 was produced as follows. First, a Cu tube serving as an internal stabilization layer 29 is inserted inside a Cu-10 wt% Ni tube serving as a copper alloy layer 22, and an Nb-47 wt% Ti rod serving as an NbTi filament 23 is further inserted inside the Cu tube. A primary composite billet was obtained. A primary strand 24 (NbTi / Cu / CuNi three-layer hexagon) having an opposite side dimension of 1.6 mm was manufactured by subjecting this primary composite billet to hot extrusion and cold processing. Next, a first hexagonal rod-shaped body (Cu hexagon) 26a having an opposite side dimension of 1.6 mm, which becomes the core portion 26 and the stabilization layer 27, was manufactured by subjecting the oxygen-free copper ingot to hot extrusion processing and cold processing. Further, a Cu-10 wt% Ni ingot is subjected to hot extrusion and cold working to form a copper alloy coating layer 28-1 and a copper alloy coating layer 28-2. ) 28-1a was produced. Then, a CuNi tube having an inner diameter of 180 mm / an outer diameter of 200 mm is manufactured, and the primary strand 24, the first hexagonal rod (Cu hexagon) 26a, and the second hexagonal rod (CuNi hexagon) 28-1a are connected to the outermost copper alloy. It inserted in the CuNi pipe | tube used as the coating layer 30, and obtained the secondary composite billet. After hot extrusion processing is performed on the secondary composite billet, heat treatment and cold processing are repeated, and after twisting processing and final wire drawing processing, copper formed from the first hexagonal rod-shaped body (Cu hexagonal) 26a A copper alloy coating layer 28-1 formed of a second hexagonal rod-shaped body (CuNi hexagonal) 28-1a is formed on the outer periphery of the core portion 26 having a substantially circular cross section made of the above stabilizing material, and the copper alloy coating layer 28 is further formed. -1 on the outer periphery of NbTi filament 23, inner stabilization layer 29 formed on the outer periphery of NbTi filament 23, and copper alloy layer 22 further formed on the outer periphery of inner stabilization layer 29. A filament assembly 25 formed by arranging a plurality of strands 24 in a matrix is provided, and a copper alloy formed of a second hexagonal rod (CuNi hexagon) 28-1a on the outer periphery of the filament assembly 25. A coating layer 28-2 is formed, and a stabilizing layer 27 made of a first hexagonal rod (Cu hexagon) 26a is formed on the outer periphery of the coating layer 28-2. An outermost copper alloy coating layer 30 made of the CuNi tube is formed on the outermost layer. An NbTi superconducting multicore wire 20 having a diameter of 1.0 mmφ was obtained. At this time, as shown in the enlarged view of the portion B of the NbTi superconducting multicore wire 20 shown in FIG. 3, the plurality of first rod-shaped bodies (Cu hexagonal) 26a are combined and integrated to form the core portion 26, and the outer periphery thereof. A plurality of second hexagonal rod-shaped bodies (CuNi hexagonal) 28-1a are combined and integrated to form a copper alloy coating layer 28-1, and a plurality of primary strands 24 are similarly combined on the outer periphery thereof. The filament aggregate 25 is formed by being integrated. The residual resistance ratio in the comparative example was 250 as in the example.

FIG. 4 is a cross-sectional view of a NbTi superconducting molded stranded wire according to a comparative embodiment. A method for producing the NbTi superconducting molded stranded wire 21 according to the comparative example will be described with reference to FIG. Sixteen NbTi superconducting multi-core wires 20 were twisted together and molded to obtain an NbTi superconducting shaped twisted wire 21 as a comparative example.

(Evaluation of superconducting stranded wire)
As characteristics of the superconducting molded stranded wires of Examples and Comparative Examples, Ic (critical current, defined as a specific resistance of 10 ⁻¹⁴ Ωm per NbTi area at 4.2 K), Je (engineering critical current density, Ic / NbTi superconducting multifilamentary wire cross-sectional area), n value (V = K (I / Ic) ⁿ , defined as 10 μV / m to 100 μV / m, V is a generated voltage, I is a conduction current, and K is a constant) , Hysteresis loss, coupling time constant (coupling current time constant, coupling loss is proportional to coupling time constant), current-carrying stability, workability and manufacturing cost. Table 1 describes the specifications of the examples and comparative examples and the above-described various characteristic evaluation results. NbTi / CuNi / Cu indicates a volume ratio in a superconducting formed stranded wire.

Ic and Je were measured under a magnetic field of 5T. The n value was obtained from current-voltage characteristics. For hysteresis loss, a triangular magnetic field with a magnetic field amplitude of ± 3T and 0.04T / s is applied in the direction perpendicular to the longitudinal direction of the wire, the magnetization is measured, and the area is integrated from each magnetization-applied magnetic field curve. It was calculated by doing. On the other hand, the coupling time constant (the sum of the coupling time constant within the strands and the coupling time constant between the strands) has a magnetic field amplitude ± in the direction perpendicular to the wide surface of the NbTi superconducting molded stranded wire 11 and the NbTi superconducting stranded strand 21. After applying a varying magnetic field with a sine waveform of 0.01 T and 1 to 25 Hz and measuring each magnetization, the AC loss is calculated by integrating the area from each magnetization-applied magnetic field curve, and its frequency dependence Sought from sex.

In addition, the stability of the NbTi superconducting stranded wire for pulse 11 and the NbTi superconducting stranded wire 21 for energization is up to 95% of the Ic of the wire in a 5 T static magnetic field. Heat was locally applied to the wire 11 and the NbTi superconducting shaped twisted wire 21, and the energization stability was confirmed with the amount of heat input until the pulse NbTi superconducting shaped twisted wire 11 and the NbTi superconducting shaped twisted wire 21 were quenched. At this time, equivalent stability was obtained in the example and the comparative example. Regarding the workability, confirmation was performed at a disconnection frequency per 20 km. In the comparative example, disconnection occurred once, but in the example, disconnection did not occur. Regarding the raw material cost and processing cost, according to the example, it was possible to realize a cost reduction of about 10% compared to the conventional example.

  From the above, the main superconducting performance of the NbTi superconducting molded stranded wire for pulse 11 of the present invention is higher in Je and n values and slightly larger in AC loss than the comparative example, but the current carrying stability and workability are the same. there were. In addition, the manufacturing cost can be reduced.

This is because the CuNi ratio in the NbTi superconducting multi-core wire 10 for pulses is kept low, the critical current per strand is increased, the number of strands is kept lower than that of the comparative example, and the raw material cost is reduced. This is because the ratio of (NbTi + CuNi) to Cu in the chemical material is small and the deformation resistance is small, so that the processing becomes easy and the manufacturing cost is reduced.

(Volume ratio of copper alloy layer to NbTi filament)
In the above embodiment, when the volume ratio of the copper alloy layer 12 made of CuNi of the primary wire 14 to the NbTi filament 13 (hereinafter referred to as CuNi volume ratio) is changed from 0.2 to 0.7, 1 The presence or absence of exposure of the NbTi filament 13 at the time of manufacturing the secondary strand 14 (NbTi single-core wire) and the deformation state of the NbTi filament 13 when the produced primary strand 14 was formed on the NbTi superconducting multicore wire 10 for pulse were examined. . Further, the n value was also measured under the same conditions as in Table 1. The results at this time are shown in Table 2.

  As shown in Table 2, when the CuNi volume ratio is 0.2, the thickness of the copper alloy 12 existing around the NbTi filament 13 is too small when the primary strand 14 is formed, so that the NbTi filament 13 is exposed. After that, the multi-core processing for forming the NbTi superconducting multi-core wire 10 for pulses could not be performed. When the CuNi volume ratio is 0.7, the NbTi filament 13 was not exposed when the primary strand 14 was formed, but abnormal deformation of the NbTi filament 13 of the primary strand 14 occurred during multi-core processing. In many cases, the n value was lower than when the CuNi volume ratio was 0.3 to 0.6. As described above, in the present invention, the CuNi volume ratio is preferably 0.3 to 0.6.

(Volume ratio of stabilizer to NbTi filament)
Next, the number of hexagonal bar-shaped stabilizing rod-shaped bodies (Cu hexagonal) 16a having an opposite side dimension of 1.8 mm serving as the core portion 16 and the inner diameter of the Cu tube serving as the stabilizing layer 17 are adjusted, and the stabilizing rod-shaped body 16a The NbTi superconducting multifilamentary wire 10 for pulse when the total volume of the Cu tube was changed to be 1 to 5 times the total volume of the NbTi filament 13 of the primary strand 14 was produced. The NbTi superconducting multi-core wire 10 for each pulse was examined for intra-element coupling loss time constant, critical current density Je, and whether the NbTi filament 13 was exposed. Hereinafter, the volume ratio of the stabilizing rod-shaped body 16a to the total volume of the NbTi filament 13 of the Cu tube is referred to as a copper volume ratio. In the examples of Table 1, the CuNi ratio is 0.5, the strand diameter is 1.0 mm, and the twist pitch is 10 mm, and the conditions are changed as described above. Also, the coupling loss time constant in the wire was evaluated at a magnetic field amplitude of ± 0.5 T, unlike Table 1. The critical current density Je was measured under the same conditions as in Table 1. The results at this time are shown in Table 3.

As shown in Table 3, when the copper volume ratio is 1, the NbTi filament 13 is exposed, and it becomes difficult to manufacture the NbTi superconducting multicore wire 10 for pulses, and there is a problem that the manufacturing yield is lowered. On the other hand, when the copper volume ratio is 5, the superconductor portion of the NbTi filament is reduced, resulting in a problem that not only Je is lowered but also the coupling time constant is increased.
From the above, in the present invention, the copper volume ratio is desirably 1.5 to 4.5. From the numerical values of Je and the binding time constant, a more preferable copper volume ratio is 1.5-3.

(Residual resistance ratio of stabilizing material)
Furthermore, the NbTi superconducting multi-core wire 10 for pulse which changed the annealing conditions in process so that the residual resistance ratio of the stabilization rod-shaped body (Cu hexagon) 16a and the stabilization layer 17 might be 30-350 was created. For each pulse NbTi superconducting multi-core wire 10, the intra-element coupling loss time constant and the conduction stability were examined. In the examples in Table 1, the CuNi ratio is 0.5, the copper volume ratio (NbTi / Cu) is 2.0, the strand diameter is 1.0 mm, and the twist pitch is 10 mm. The conditions are changing. In addition, the coupling loss time constant in the strand is measured under the same conditions as in Table 2. For the evaluation of energization stability, the NbTi superconducting multi-core wire for pulse 10 is energized to the critical current (Ic). , Ic was confirmed whether energization was possible. The results at this time are shown in Table 4.

  As shown in Table 4, when the residual resistance ratio was 30, it was not possible to energize up to the critical current value (Ic), and sufficient energization stability could not be obtained. In addition, when the residual resistance ratio is 400, the coupling time constant increases, so that the AC loss increases and it is necessary to select high-purity oxygen-free copper. The problem of a decrease in yield occurs. From the above, in the present invention, the residual resistance ratio is desirably 50 to 350, and 100 to 300 is preferable from the viewpoint of the coupling time constant and the conduction stability.

  As described above, a primary element formed from a NbTi filament and a copper alloy layer containing one or more of Ni, Mn, and Si between the core made of the stabilizing material and the stabilizing layer formed in the outermost layer. Since only the wires are embedded, there is no stabilizing material having a large deformation resistance difference from NbTi in the filament aggregate. That is, the copper alloy layer containing one or more of Ni, Mn and Si in the filament assembly and NbTi have a small deformation resistance difference, and thus cause filament deformation and filament breakage during hot extrusion and wire drawing. Can be prevented. Further, the copper alloy layer is a copper alloy containing one or more of Ni, Mn and Si, and the volume ratio with respect to the NbTi filament is 0.3 to 0.6. It is possible to suppress quenching of the filament region that tends to become unstable during pulse energization and to maintain high stability near the outer periphery of the filament and the inner periphery of the stabilization layer formed on the outer periphery of the filament assembly. Therefore, it is particularly suitable for pulse applications.

In addition, since the total volume of the stabilizing material is 1.5 to 4.5 copper or a copper alloy with respect to the total volume of the NbTi filament in the filament assembly, the dynamic stabilization standard can be satisfied. The standard stabilization standard. Similarly, by making the total volume of the stabilizing material 1.5 to 4.5 with respect to the total volume of the NbTi filament in the filament assembly, it is possible to suppress disconnection and surface quality in wire drawing. Can be secured. Furthermore, since the CuNi ratio (volume ratio of CuNi to NbTi) in the NbTi superconducting multicore wire can be kept low, the critical current value per NbTi superconducting multicore wire can be improved, and the raw material cost and assembly of the multicore billet can be improved. Machining costs can be reduced by reducing the total number of manufacturing steps and shortening the manufacturing lead time by reducing the number of members, reducing the combined deformation resistance, and increasing the extrusion ratio and the drawing splitting.

After forming a metal plating layer, a resin insulating layer or an oxide film on the surface of the pulse NbTi superconducting multi-core wire in the present invention, the pulse NbTi superconducting multi-core wire is formed into a rectangular cross section twisted by 6 or more and 40 or less. This suppresses the variation in contact resistance between the NbTi superconducting multicore wires for pulses and the contact between the NbTi superconducting multicore wires for pulses as compared with the case where there is no metal plating layer, resin insulating layer or oxide film on the surface of the NbTi superconducting multicore wires for pulses. Since resistance becomes high, the coupling loss between strands can be reduced. Here, the metal plating layer can increase the contact resistance between NbTi superconducting multicore wires for pulses by using high resistance Cr or Ni other than Cu, and by using a metal harder than Cu. The contact area between the NbTi superconducting multi-core wires for pulses can be made smaller than when Cu is used. The same effect can be obtained even if the NbTi superconducting multicore wire surface for pulses is a copper alloy layer.

It is a section lineblock diagram of the NbTi superconducting multi-core wire for pulses concerning one embodiment of the present invention. It is a section lineblock diagram of the NbTi superconductivity fabrication twisted wire for pulses concerning one embodiment of the present invention. It is a cross-sectional block diagram of the NbTi superconducting multi-core wire which concerns on comparative embodiment. It is a cross-sectional block diagram of the NbTi superconductivity shaping | molding twisted wire which concerns on comparative embodiment.

Explanation of symbols

10 NbTi superconducting multi-core wire for pulse 11 NbTi superconducting stranded wire for pulse 12 Copper alloy layer 13 NbTi filament 14 Primary strand 15 Filament assembly 16 Core portion 17 Stabilizing layer 18 Covering layer 20 NbTi superconducting multi-core wire 21 NbTi superconducting wire Stranded wire 22 Copper alloy layer 23 NbTi filament 24 Primary strand 25 Filament assembly 26 Core 27 Stabilization layer 28-1 Copper alloy coating layer 28-2 Copper alloy coating layer 29 Internal stabilization layer 30 Outermost copper alloy coating layer

Claims (4)

A substantially circular core section made of a stabilizing material,
Ni, consists only of NbTi filaments Tona Ru 1 Tsugimotosen embedded in a copper alloy containing one or more of Mn and Si, and, arranged a plurality of said 1 Tsugimotosen is on the outer periphery of the core portion Filament assembly,
A stabilizing layer made of the same stabilizing material as the core portion formed on the outer periphery of the filament assembly,
The NbTi superconducting multifilamentary wire for pulses, wherein the volume of the copper alloy in which the NbTi filament is embedded is 0.3 to 0.6 times that of the NbTi filament.
2. The pulse according to claim 1, wherein the total volume of the stabilizing material forming the core and the stabilization layer is 1.5 to 4.5 times the total volume of the NbTi filament. NbTi superconducting multicore wire. The pulse NbTi superconducting multi-core wire according to claim 1 or 2, wherein the stabilizing material is copper or a copper alloy having a residual resistance ratio of 50 or more and 350 or less.   After forming at least one of a metal plating layer, a resin insulating layer, and an oxide film on the surface of the NbTi superconducting multi-core wire for pulse according to any one of claims 1 to 3, 6 or more and 40 or less The NbTi superconducting stranded wire for pulses, wherein the NbTi superconducting multi-core wire is twisted and formed into a rectangular cross section.

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