JP2007172978A - Superconductive electric wire, method for manufacturing same, and superconductive electromagnet device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost superconductive magnet reducing surplus performance of a superconductive electric wire in a superconductive coil. <P>SOLUTION: In this superconductive electric wire, a cross sectional area ratio in the radial direction of a filament, which is formed of a Cu matrix and a superconductive material, to the superconductive wire is varied along in the axial direction of the superconductive wire. This superconductive wire having a copper ratio successively varied along the wire length direction is manufactured by drawing a combination of a Cu-base material 2 with varied diameter and an NbTi rod 7 with a fixed diameter or a combination of a Cu material 22 with a fixed diameter and an NbTi rod 27 with varied diameter into a wire with a fixed diameter. Using the superconductive wire, the copper ratio inside the coil is varied without superconductive connection for reducing excessive performance of the superconductive wire, and consequently, the superconductive magnet can be provided at a low cost. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting wire used in an image diagnostic apparatus mainly based on magnetic resonance imaging (MRI) using nuclear magnetic resonance, a method for manufacturing the superconducting wire, and a superconducting electromagnet apparatus using the superconducting wire. It is.

  In order for the conventional superconducting wire to function stably as a superconducting wire, a large number of thin NbTi, Nb3Sn, and the like are included in a stabilizing material made of a normal conducting metal having a low electrical resistance such as oxygen-free copper or aluminum. It has a structure in which a filament made of a superconducting material is embedded.

  In such a superconducting wire, the radial cross-sectional area ratio between the stabilizing material matrix and the superconducting material filament is referred to as a stabilizing material ratio, and when the stabilizing material is copper, it is particularly referred to as a copper ratio. In the superconducting wire, the value of the stabilizing material ratio increases as the cross-sectional area of the stabilizing material is large and the cross-sectional area of the filament is small. If the stabilizing material is copper, the value of the copper ratio is large. Conversely, the smaller the cross-sectional area of the stabilizing material and the larger the cross-sectional area of the filament, the smaller the value of the stabilizing material, and if the stabilizing material is copper, the value of the copper ratio is small. And in the conventional superconducting wire, the stabilizer ratio is constant over the entire wire length.

  As a method of manufacturing a superconducting wire having such a structure, a method of manufacturing a composite billet by extruding the composite billet by arranging a filament and a stabilizing material in the composite billet for extrusion so that there is a gap (for example, Patent Documents). 1) and a manufacturing method (for example, see Patent Document 2) in which the filament diameter range and the copper ratio range in the radial cross section (transverse section) of the wire are limited to ensure the integrity of the filament. .

  In general, the critical current of a superconducting wire is as follows: (1) the higher the magnetic field, the lower the critical current, and the lower the magnetic field, the higher the critical current. (2) Compared with superconducting wires of the same diameter, The critical current is low, and the smaller the stabilizing material ratio, the higher the critical current.

  On the other hand, in a solenoid type coil, the magnetic field generally becomes maximum near the center of the innermost layer of the coil, but the magnetic field in the coil becomes lower as the outer layer is reached. In the conventional superconducting electromagnet apparatus, the line type (diameter and stabilizing material ratio) of the superconducting wire is selected according to the condition of the high magnetic field near the innermost layer of the coil. In this case, a superconducting wire having an excessively high superconducting substance ratio and a small stabilizing material ratio, that is, an excessively high performance superconducting wire is used. However, from the viewpoint of cost, the superconducting material is more expensive than the stabilizing material, and it is desirable to reduce its usage as much as possible.

  Usually, a superconducting electromagnet apparatus forms a coil by winding a single superconducting wire whose diameter and stabilizing material ratio are constant in the axial direction (length direction). However, a coil may be formed by using a superconducting wire having a small stabilizing material ratio for the inner layer of the coil and using a superconducting wire having a large stabilizing material ratio for the outer layer (see, for example, Patent Document 3).

  The superconducting coil shown in Patent Document 3 is formed using two types of superconducting wires having a constant copper ratio in order to change the radial stress in the coil from a stress to a compressive stress. Using two types of superconducting wires having a constant copper ratio, the excessive performance of the coil upper layer can be corrected. That is, since the magnetic field in the coil is low in the upper layer portion of the coil, excessive performance can be corrected by using a superconducting wire having a large stabilizing material ratio without reducing the critical current.

JP-A-6-68725 (FIG. 1, pages 2 to 3 of the specification) JP 2002-304924 A (FIGS. 1-5, specifications 2-6) Japanese Patent Laid-Open No. 9-232130 (FIG. 1, pages 2 to 3 of the specification)

  However, when one coil is configured using a plurality of superconducting wires as described above, there arises a problem that the number of superconducting connections between the superconducting wires increases. The superconducting connection portion is more susceptible to quenching than a normal superconducting wire, and the manufacturing process is complicated and causes a cost increase due to processing. Therefore, it is desirable that the number of superconducting connections is as small as possible.

  Furthermore, in order to achieve a more appropriate distribution of stabilizing material ratio, it is desirable to divide the stabilizing material ratio in the superconducting coil more finely, but many types of superconducting wires with different stabilizing material ratios are used. There is a need. However, if the number of types of superconducting wires is increased, the number of superconducting connections increases, which increases the weakness against quenching, and increases the cost due to complicated processes. Conversely, if there are few types of superconducting wires with different stabilizing material ratios, it will not be possible to follow changes in the magnetic field in the coil, so the effect of changing the stabilizing material ratio will be small.

  As described above, the conventional superconducting wire has only one stabilizing material ratio in one superconducting wire, and therefore the stabilizing material ratio is changed in the superconducting wire coil using this superconducting wire. I can't. Further, if the stabilizer ratio of the superconducting wire is changed in accordance with the part of the superconducting coil, it is necessary to use a plurality of superconducting coils having different stabilizer ratios as described above. The number of points will increase, and weak points against quenching will be provided. Therefore, in order to correct the excessive performance of the upper layer portion of the coil, it is necessary to take a method other than the method of increasing the kind of the wire.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a continuous superconducting wire in which the value of the stabilizing material ratio changes along the axial direction of the superconducting wire. Is.

  Another object of the present invention is to provide a continuous superconducting wire manufacturing method in which the value of the stabilizing material ratio varies along the axial direction of the superconducting wire.

  Furthermore, an object of the present invention is to provide a superconducting electromagnet apparatus that suppresses excess performance of a superconducting coil and is low in cost.

  A superconducting wire according to the present invention is a superconducting wire in which a filament made of a superconducting material is embedded in a matrix made of a stabilizing material made of metal, and the superconducting wire of the matrix and the filament The cross-sectional area ratio in the radial direction is configured to change along the axial direction of the superconducting wire.

  Moreover, the superconducting wire according to the present invention is configured such that the cross-sectional area ratio is changed only by increasing or decreasing along the axial direction of the superconducting wire.

  Further, the superconducting wire according to the present invention is configured such that the cross-sectional area ratio is continuously increased and decreased alternately along the axial direction of the superconducting wire.

  Furthermore, the superconducting wire according to the present invention is the superconducting wire constructed as described above, wherein the stabilizing material is composed of Cu or Al.

The superconducting wire according to the present invention is the superconducting wire constructed as described above, wherein the superconducting material is composed of an NbTi alloy or Nb ₃ Sn.

  Furthermore, the method of manufacturing a superconducting wire according to the present invention includes a superconducting wire in which a radial cross-sectional area ratio between a matrix made of a metal stabilizing material and a filament made of a superconducting material varies continuously along the axial direction. A first step of forming a superconducting single core wire covered with a metal-stabilized material, and a radial cross-sectional area formed along the axial direction, the metal-made stabilizer. A second step of forming a composite billet by accommodating a plurality of the superconducting single core wires inside a continuously changing tube, and a third step of subjecting the composite billet to a cross-sectional reduction process Is.

  Furthermore, in the method of manufacturing a superconducting wire according to the present invention, the superconducting single core wire is covered with a metal stabilizing material, and the radial cross-sectional area ratio between the stabilizing material and the superconducting material continuously changes along the axial direction. A second step of forming a composite billet by accommodating a plurality of the superconducting single core wires inside a tubular body made of a metal-stabilizing material, and forming the composite billet And a third step of performing cross-sectional reduction processing.

  In the superconducting wire manufacturing method according to the present invention, the cross-sectional area ratio in the radial direction between the matrix made of the metal stabilizing material and the filament made of the superconducting material alternately increases and decreases along the axial direction. A method of manufacturing a continuously changing superconducting wire, comprising a first step of forming a superconducting single core wire coated with a metal-stabilizing material, and a radial direction composed of a metal-stabilizing material. A second step of forming a composite billet by accommodating a plurality of the superconducting single core wires inside a tubular body in which the cross-sectional area increases and decreases alternately in the axial direction; and a cross-section in the composite billet And a third step for performing reduction processing.

  Furthermore, in the method of manufacturing a superconducting wire according to the present invention, the radial cross-sectional area ratio between the stabilizing material and the superconducting material is alternately increased and decreased along the axial direction. A first step of forming a superconducting single-core wire that changes in length, and a second step of forming a composite billet by accommodating a plurality of the superconducting single-core wires inside a tubular body made of a metal stabilizing material. A step and a third step of subjecting the composite billet to a cross-sectional reduction process.

  The superconducting electromagnet apparatus according to the present invention is a superconducting electromagnet apparatus comprising a solenoidal superconducting coil formed by winding a superconducting wire, wherein the superconducting wire is a matrix made of a stabilizing material made of metal. A filament made of a superconducting material is embedded therein, and the radial cross-sectional area ratio between the matrix and the filament is continuously changed along the axial direction. In the part where the magnetic field in the coil is high, the cross-sectional area ratio of the superconducting wire is composed of a small part, and in the part where the magnetic field in the coil is lower than the high part, the superconducting wire is formed in a part where the cross-sectional area ratio is large. Is.

  Furthermore, the superconducting electromagnet apparatus according to the present invention is a superconducting electromagnet apparatus in which a plurality of solenoidal superconducting coils formed by winding a superconducting wire are connected in series, wherein the superconducting wire is a stabilizing material made of metal. A filament made of a superconducting material is embedded in a matrix constituted by the above, and the radial cross-sectional area ratio between the matrix and the filament is alternately increased and decreased along the axial direction. The plurality of superconducting coils are constituted by a single continuous superconducting wire, and in each of the superconducting coils, the portion of the superconducting wire has a high magnetic field in the coil. The cross-sectional area ratio is configured with a small part, and the superconducting wire has a large cross-sectional area ratio at a part where the magnetic field in the coil is lower than the high part. It is those that have been.

  According to the superconducting wire according to the present invention, the radial sectional area ratio of the matrix and the filament to the superconducting wire changes along the axial direction of the superconducting wire. A continuous superconducting wire in which the stabilizing material ratio changes can be obtained.

  Further, according to the superconducting wire according to the present invention, the cross-sectional area ratio is configured to change only by increasing or decreasing along the axial direction of the superconducting wire. The copper ratio increases continuously along the direction, and a superconducting wire having the largest copper ratio at the rear end can be obtained.

  Further, according to the superconducting wire according to the present invention, the cross-sectional area ratio is configured so that the increase and decrease are alternately and continuously changed along the axial direction of the superconducting wire, so that the copper ratio is arbitrarily increased or decreased. A superconducting wire can be manufactured.

  Furthermore, according to the superconducting wire according to the present invention, in the superconducting wire constructed as described above, since the stabilizing material is composed of Cu or Al, it is relatively inexpensive and stable in the axial direction of the superconducting wire. A continuous superconducting wire in which the chemical ratio changes can be obtained.

Further, according to the superconducting wire according to the present invention, since the superconducting material is composed of NbTi alloy or Nb ₃ Sn in the superconducting wire configured as described above, the axial length direction of the superconducting wire is relatively inexpensive. In this way, a continuous superconducting wire in which the stabilizer ratio changes can be obtained.

  Further, according to the method of manufacturing a superconducting wire according to the present invention, a first step of forming a superconducting single-core wire covered with a metal-stabilizing material, and a radial disconnection composed of the metal-stabilizing material. A second step of forming a composite billet by accommodating a plurality of the superconducting single core wires inside a tubular body whose area continuously changes along the axial direction; and a third step of subjecting the composite billet to a cross-sectional reduction process The superconducting wire with the smallest copper ratio at the front end, the copper ratio continuously increasing along the axial direction, and the largest copper ratio at the rear end can be easily and inexpensively provided. Can be manufactured.

  Further, according to the method of manufacturing a superconducting wire according to the present invention, the superconducting unit is coated with a metal stabilizing material, and the radial cross-sectional area ratio between the stabilizing material and the superconducting substance continuously changes along the axial direction. A first step of forming a core wire, a second step of forming a composite billet by accommodating a plurality of the superconducting single core wires inside a tubular body made of a metal stabilizing material, and the composite And a third step of reducing the cross-section of the billet, the distance between the filaments inside the superconducting wire after drawing is constant throughout the wire length, the copper ratio is the smallest at the tip, and along the axial direction Thus, the superconducting wire having the largest copper ratio at the rear end can be manufactured easily and inexpensively.

  Furthermore, according to the method of manufacturing a superconducting wire according to the present invention, a first step of forming a superconducting single core wire coated with a metal stabilizing material, and a radial direction constituted by the metal stabilizing material. A second step of forming a composite billet by accommodating a plurality of the superconducting single core wires inside a tubular body in which the cross-sectional area increases and decreases alternately in the axial direction; and a cross-section in the composite billet And the third step of performing reduction processing, it is possible to easily and inexpensively manufacture a superconducting wire in which the copper ratio is arbitrarily increased or decreased.

  Further, according to the method of manufacturing a superconducting wire according to the present invention, the radial cross-sectional area ratio between the stabilizing material and the superconducting material, which is covered with the metal stabilizing material, alternately increases and decreases along the axial direction. A first step of forming a continuously changing superconducting single core wire, and a first step of forming a composite billet by accommodating a plurality of superconducting single core wires inside a tubular body made of a metal stabilizing material. 2 and the third step of reducing the cross section of the composite billet, the spacing between the NbTi filaments inside the superconducting wire after wire drawing is constant throughout the entire wire length, and the copper ratio is arbitrarily set The superconducting wire which increases or decreases can be manufactured easily and inexpensively.

  Further, according to the superconducting electromagnet apparatus according to the present invention, the superconducting wire is formed by embedding a filament made of a superconducting substance in a matrix made of a stabilizing material made of metal, and between the matrix and the filament. The superconducting coil is configured in a portion where the cross-sectional area ratio of the superconducting wire is small at a portion where the magnetic field in the coil is high, and the cross-sectional area ratio in the radial direction is continuously changed along the axial direction. The superconducting wire having an appropriate copper ratio corresponding to the portion of the superconducting coil without increasing the superconducting connection because the cross-sectional area ratio of the superconducting wire is formed at a portion where the magnetic field in the coil is lower than the high portion. Therefore, it is possible to avoid using a superconducting wire having a low copper ratio and to obtain a superconducting electromagnet apparatus having a low cost.

  Furthermore, according to the superconducting electromagnet apparatus according to the present invention, the superconducting wire is constructed by embedding a filament made of a superconducting substance in a matrix made of a stabilizing material made of metal, and the matrix, the filament, The radial cross-sectional area ratio of the plurality of superconducting coils is constituted by a single continuous superconducting wire. In each of the superconducting coils, a portion where the magnetic field in the coil is high is constituted by a portion where the cross-sectional area ratio of the superconducting wire is small, and in a portion where the magnetic field in the coil is lower than the high portion, the superconducting wire Since the cross-sectional area ratio is large, the superconducting wire with the appropriate copper ratio is used for each part of multiple superconducting coils without increasing the number of superconducting connections. Rukoto can excessively it is unavoidable to use a low superconducting wire of copper ratio, it is possible to further obtain a low superconducting electromagnet apparatus cost.

Embodiment 1
A superconducting wire according to Embodiment 1 of the present invention is a superconducting wire formed by embedding a filament made of an NbTi alloy as a superconducting substance in a matrix using CU as a stabilizing material, and the radial direction of the matrix and the filament The cross-sectional area ratio continuously changes along the axial direction of superconducting wires having the same diameter.

That is, the copper ratio, which is the stabilizing material ratio, is configured to continuously change along the axial direction of one continuous superconducting wire. The method of changing the copper ratio increases continuously along the axial direction from one end of the superconducting wire to the other end, in other words, continuously decreases axially from the other end to the one end. It has changed.
The stabilizing material may be a metal other than CU, and the filament may be a superconducting material other than an NbTi alloy.

  Next, a method for manufacturing the superconducting wire according to the first embodiment will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view of a composite billet for extrusion, and FIG. 2 is a longitudinal sectional view of a superconducting single core wire before drawing. First, as shown in FIG. 2, the NbTi rod 7 and the Nb sheet 8 are incorporated inside the Cu pipe 6 to form the superconducting single core wire 11 before drawing. In this superconducting single core wire 11, the diameter of the Cu pipe 6 on the outer surface and the inner surface does not change along the axial direction. Therefore, the thickness of the Cu pipe 6 is made constant along the axial direction. In addition, the diameters of the NbTi rod 7 and the Nb sheet 8 are constant without changing along the axial direction. The superconducting single core wire 11 thus drawn before drawing is subjected to a drawing process to form a Cu-coated NbTi alloy single core wire 1 having a constant diameter.

  Next, as shown in FIG. 1, a large number of Cu-coated NbTi alloy single core wires 1 are inserted into the hollow portion of the large-diameter Cu pipe 2, and the tip member 3 and the rear end member 4 are attached to both ends, and these are integrated. To form a composite billet 5 for extrusion. In the first embodiment, the large-diameter Cu pipe 2 has a cylindrical shape whose inner surface has a uniform diameter along the axial direction, and a tapered shape whose outer surface continuously changes in diameter along the axial direction. Have. Accordingly, the outer diameter and the thickness of the CU pipe 2 continuously change along the axial direction.

  In the extruded composite billet 5 having a tapered shape, the radial cross-sectional area of the CU continuously changes along the axial direction, but the radial cross-sectional area of NbTi does not change along the axial direction and is the same. It is. Accordingly, the ratio of the cross-sectional area of the CU to the cross-sectional area of the NbTi in the radial direction in the composite billet 5 for extrusion is the smallest immediately after the tip member 3 in FIG. 1, and the left direction in FIG. 1 along the axial direction. As it goes, it continuously increases and becomes largest immediately before the rear end member 4.

  Next, the composite billet 5 for extrusion is subjected to hydrostatic pressure extrusion, and the shape whose outer shape is tapered along the axial direction is deformed into a cylindrical shape having the same diameter along the axial direction. Further, the composite billet deformed into a cylindrical shape with a constant diameter in this way is subjected to drawing and heat treatment a plurality of times to produce a long filament NbTi superconducting wire.

  When the composite billet 5 is drawn in this manner to produce a superconducting wire, the copper ratio of the superconducting wire continuously changes in accordance with the thickness of the large-diameter Cu pipe 2. The thin part of the Cu pipe 2 becomes a superconducting wire with a small copper ratio, and the thick part of the Cu pipe 2 becomes a superconducting wire with a large copper ratio. That is, according to the first embodiment, it is possible to obtain a superconducting wire having the smallest copper ratio at the front end, the copper ratio continuously increasing along the axial direction, and the largest copper ratio at the rear end. it can.

Embodiment 2
In the first embodiment, a superconducting wire in which the copper ratio changes is obtained by changing the thickness of the large-diameter Cu pipe 2 along the axial direction. However, in the second embodiment, the Cu-coated NbTi alloy is obtained. By continuously changing the copper ratio of the single core wire in the axial direction, a superconducting wire in which the copper ratio continuously changes along the axial direction is obtained. 3 and 4 show a method of manufacturing a superconducting wire according to Embodiment 2, FIG. 3 is a longitudinal sectional view of a composite billet for extrusion, and FIG. 4 is a longitudinal sectional view of a superconducting single core wire before drawing.

  In the second embodiment, first, as shown in FIG. 4, the NbTi rod 27 and the Nb sheet 28 are incorporated in the Cu pipe 26 to form the superconducting single core wire 211 before drawing. In this superconducting single core wire 211, the Cu pipe 26 has a cylindrical shape whose outer surface is uniform in diameter along the axial direction, and a tapered shape whose inner surface is continuously variable in diameter along the axial direction. . Accordingly, the outer diameter of the Cu pipe 26 is uniform and does not change along the axial direction, but the thickness continuously changes. Further, the NbTi rod 27 is formed in a tapered shape in accordance with the inner surface of the Cu pipe. The superconducting single core wire 211 thus drawn before drawing is subjected to a drawing process to make a Cu-coated NbTi alloy single core wire 21.

  In this Cu-coated NbTi alloy single core wire 21, the inner diameter of the Cu pipe 26 before processing changes continuously in the axial direction, and the diameter of the NbTi rod 27 also extends along the axial direction corresponding to the inner diameter of the Cu pipe. Continuously changing. Accordingly, the cross-sectional area ratio of Cu and NbTi in the radial direction, that is, the copper ratio is continuously changed along the axial direction. A portion with a small diameter of the NbTi rod 27 becomes a Cu-coated NbTi alloy single core wire with a large copper ratio, and a portion with a large diameter of the NbTi rod 27 becomes a Cu-coated NbTi alloy single core wire with a small copper ratio.

  Next, as shown in FIG. 3, a large number of Cu-coated NbTi alloy single core wires 21 are inserted into the hollow portion of the large-diameter Cu pipe 22, and a tip member 23 and a rear end member 24 are attached to both ends, and these are integrated. To form a composite billet 25 for extrusion. In the second embodiment, the large-diameter Cu pipe 22 has a cylindrical shape having a uniform diameter along the axial direction on both the inner surface and the outer surface. Therefore, the CU pipe 22 has the outer diameter and The wall thickness does not change along the axial direction and is constant.

  Next, the composite billet 25 for extrusion constructed as described above is subjected to isostatic pressing to obtain a composite rod, which is subjected to drawing and heat treatment a plurality of times to produce a long NbTi superconducting wire.

  According to the method of manufacturing a superconducting wire according to the second embodiment, the copper ratio is small at the front end, the copper ratio is continuously increased along the axial direction, and the copper ratio is the largest at the rear end. Can be manufactured. In the superconducting wire according to the first embodiment, since the extruded composite billet 5 in which the thickness of the outer copper changes is processed into a constant diameter, the spacing between the NbTi filaments in the superconducting wire becomes narrower as the copper ratio increases. However, in this Embodiment 2, since the large-diameter Cu pipe 22 has a constant outer shape, the interval between the NbTi filaments inside the superconducting wire after wire drawing is made constant throughout the entire wire length. Can do.

Embodiment 3
In the second embodiment, the outer surface has a cylindrical shape whose diameter is uniform along the axial direction, the inner surface has a tapered shape whose diameter changes continuously along the axial direction, and the tapered shape of the inner surface of this Cu pipe. The copper ratio of the superconducting wire was changed using an NbTi rod having a tapered outer surface adapted to the above, but in Embodiment 3, the diameter of the NbTi rod was made uniform along the axial direction, and the inner surface of the Cu pipe was A superconducting wire in which the diameter is made uniform along the axial direction according to the outer surface of the NbTi rod, and the outer surface is tapered so that the diameter continuously changes along the axial direction. It is designed to be manufactured. The third embodiment of the present invention will be described below with reference to FIG.

  First, an NbTi rod 37 and an Nb sheet 38 are inserted into the Cu pipe 36 and combined as shown in FIG. In Embodiment 3, the inner surface of the Cu pipe has a uniform cylindrical shape along the axial direction, and the outer surface has a tapered shape with the diameter continuously changing along the axial direction. The pipe thickness changes continuously. The NbTi rod 37 has a straight cylindrical shape whose diameter is uniform along the axial direction. The Nb sea and 38 are arranged on the inner surface of the outer surface Cu pipe 36 of the NbTi rod 37.

  Next, a Cu-coated NbTi alloy single core wire is made by subjecting the unconducted superconducting single core wire 311 formed by combining the Cu pipe 36, the NbTi rod 37, and the Nb sheet 38 to a drawing process. In this Cu-coated NbTi alloy single core wire, the outer diameter of the Cu pipe 36 before processing changes continuously in the axial direction, and accordingly, the cross-sectional area ratio in the radial direction of Cu and NbTi, that is, the copper ratio is It changes continuously along the axial direction. A portion with a small outer surface diameter of the Cu pipe 36 becomes a Cu-coated NbTi alloy single core wire with a small copper ratio, and a portion with a large outer surface diameter of the Cu pipe 36 becomes a Cu-coated NbTi alloy single core wire with a large copper ratio.

  Thereafter, the direction of the end portion having a large copper ratio and the end portion having a small copper ratio were aligned with a large number of Cu-coated NbTi alloy single core wires, and the right end side in FIG. Combined with the direction of the front end member 23 and inserted into the large-diameter Cu pipe 22, the front end member 23 and the rear end member 24 are attached to both ends and welded to form a composite billet for extrusion. Then, the composite billet for extrusion is subjected to an isostatic extrusion process, a plurality of drawing processes and a heat treatment to produce a long NbTi superconducting wire.

  As described above, according to the third embodiment of the present invention, it is possible to manufacture a superconducting wire in which the copper ratio continuously changes along the axial direction. In the superconducting wire of the first embodiment, since the composite billet for extrusion whose outer copper thickness changes is processed into a uniform diameter, the spacing between NbTi filaments in the superconducting wire becomes narrower as the copper ratio increases. However, in the third embodiment, since the large-diameter Cu pipe having a uniform diameter on both the inner surface and the outer surface is used, the distance between the NbTi filaments inside the superconducting wire after the drawing is set through the entire wire length. Can be constant.

Embodiment 4
The change in the copper ratio of the superconducting wires manufactured according to the first, second, and third embodiments is a change that is monotonously increased or decreased monotonically along the axial direction. The present invention provides a superconducting wire in which the copper ratio is arbitrarily increased or decreased. Hereinafter, the fourth embodiment will be described.

  First, in the same manner as in the first embodiment, the superconducting single-core wire before drawing shown in FIG. 2 is drawn, and the Cu-coated NbTi alloy single-core wire that has a constant diameter and does not change the copper ratio along the axial direction. 41 is formed.

  Next, a large number of Cu-coated NbTi alloy single core wires 41 having a constant diameter are arranged and inserted into a large-diameter Cu pipe 42 as shown in FIG. Then, the front end member 43 is combined with the front end portion, and the rear end member 44 is combined with the rear end portion, and these are welded to form an extrusion composite billet 45.

  Next, the composite billet 45 for extrusion is subjected to isostatic pressing, deformed into a cylindrical shape with a constant diameter, and the extrusion composite billet 45 transformed into a cylindrical shape with a constant diameter is further subjected to a drawing process. Heat treatment is performed a plurality of times to form a striated body, and an NbTi superconducting wire is manufactured.

  In the extruded composite billet 45 according to the fourth embodiment, the cross-sectional area of Cu changes along the axial direction, but the cross-sectional area of NbTi does not change. In order to manufacture a superconducting wire by drawing this, the copper ratio of the superconducting wire continuously increases or decreases corresponding to the thickness of the large-diameter Cu pipe 42. A superconducting wire having a small copper ratio is formed in a portion having a small diameter on the outer surface of the Cu pipe 42, that is, a portion having a small thickness, and a superconducting wire having a large copper ratio in a portion having a large diameter on the outer surface, that is, a portion having a large thickness. It becomes.

  Therefore, the thickness distribution of the wall thickness of the large-diameter Cu pipe 42 is adjusted as appropriate, and the cross-sectional area ratio of Cu and NbTi in the radial direction is increased or decreased in the axial direction to match the increase or decrease in the desired copper ratio of the superconducting wire Thus, a superconducting wire having an arbitrary copper ratio distribution can be manufactured. In the example shown in FIG. 6, after repeating the increase / decrease of the copper ratio twice from the front end to the rear end, a superconducting wire having the largest copper ratio at the rear end can be finally manufactured.

  As described above, according to the fourth embodiment of the present invention, the radial cross-sectional area ratio between the matrix made of Cu that is the stabilizing material and the filament made of the superconducting material is set along the axial direction. As a result, it is possible to manufacture a superconducting wire in which increase and decrease are alternately continued, and as a result, the copper ratio is arbitrarily increased or decreased.

Embodiment 5
In the fourth embodiment, an NbTi superconducting wire in which the copper ratio increases or decreases in the axial direction is manufactured by increasing or decreasing the outer diameter of the large-diameter Cu pipe. The present invention provides a superconducting wire in which the copper ratio increases or decreases in the axial direction by increasing or decreasing the copper ratio of the core wire in the axial direction. Hereinafter, the manufacturing method of the superconducting wire which concerns on Embodiment 5 is demonstrated.

  First, as shown in FIG. 7, an NbTi rod 57 and an Nb sheet 58 are inserted into the Cu pipe 56. The Cu pipe 56 has a cylindrical shape whose inner surface has a uniform diameter along the axial direction, and the outer surface is configured such that the diameter increases and decreases along the axial direction. Such a Cu pipe can be manufactured, for example, by subjecting the outer surface of a normal pipe to arbitrary shaving. These are combined as shown in FIG. 7 to form a superconducting single core wire 511 before drawing, and by drawing it, a Cu-coated NbTi alloy single core wire having a constant cross-section is made.

  The copper ratio of the Cu-coated NbTi alloy single core wire formed in this way continuously increases or decreases in the axial direction corresponding to the thickness of the Cu pipe 56 before processing. That is, a portion where the thickness of the Cu pipe 56 is thin becomes a Cu-coated NbTi alloy single core wire having a small copper ratio, and a portion where the Cu pipe 56 has a large thickness becomes a Cu coated NbTi alloy single core wire having a large copper ratio.

  Next, as in the second embodiment, as shown in FIG. 3, the superconductivity of FIG. 7 is formed in the hollow portion of the cylindrical large-diameter Cu pipe 22 having a uniform outer surface and inner diameter along the axial direction. A large number of Cu-coated NbTi alloy single core wires formed by pulling out the single core wires 511 are inserted, and a front end member 23 and a rear end member 24 are attached to both ends and welded to form a composite billet 25 for extrusion. And the NbTi superconducting wire is manufactured by subjecting the composite billet 25 for extrusion to an isostatic extrusion process, a plurality of drawing processes, and a heat treatment to form a filament.

  According to the fifth embodiment, the thickness distribution is appropriately adjusted by changing the diameter of the outer surface of the Cu pipe 56 along the axial direction, and the radial sectional area ratio of Cu and NbTi is increased or decreased along the axial direction. Thus, a superconducting wire having an arbitrary copper ratio distribution can be manufactured by matching the increase / decrease of the desired copper ratio. For example, after repeating the increase / decrease of the copper ratio twice from the front end to the rear end, a superconducting wire that finally has the largest copper ratio at the rear end can be manufactured.

  In the superconducting wire of the fourth embodiment, the extrusion composite billet 45 in which the thickness of the outer copper changes is processed to a constant diameter, so that the spacing between the NbTi filaments in the superconducting wire becomes narrower as the copper ratio increases. However, in the fifth embodiment, since a large-diameter Cu pipe having a constant diameter is used, the interval between NbTi filaments inside the superconducting wire after wire drawing may be constant throughout the entire wire length. it can.

Embodiment 6
Next, a superconducting electromagnet apparatus according to the present invention relating to Embodiment 6 will be described. FIG. 8 shows a superconducting electromagnet apparatus using a superconducting wire manufactured by the method of the first to third embodiments according to the present invention and having a copper ratio that continuously changes in the axial direction of the superconducting wire. It is a block diagram to explain.

  As shown in FIG. 8, the superconducting magnet according to the sixth embodiment is a superconducting magnet device for MRI, and includes side coils 61a and 61b that are superconducting coils installed at the inner peripheral end of the electromagnet device, and these side coils. Middle coils 62, 63a, 63b, 64a and 64b which are superconducting coils installed on the inner peripheral side of the electromagnet device between the coils 61a and 61b, and shield coils 65a and 66b which are superconducting coils installed on the outer peripheral side of the electromagnet device A superconducting coil group consisting of

  In the present embodiment, the side coils 61a and 61b are formed by winding the superconducting wire manufactured by any of the methods of the first to fifth embodiments, and the middle coils 62, 63a, 63b, 64a. , 64b and shield coils 65a and 65b are formed by winding a normal superconducting wire.

  Each of these superconducting coil groups is formed in an annular shape, and is coaxially arranged on the central axis X of the superconducting electromagnet apparatus and arranged in the axial direction with a predetermined interval. These superconducting coils are housed in a cylindrical helium container together with liquid helium. The helium vessel is equipped with a heat insulating structure and a cooling device, and is installed in a cryostat 66 provided with a cylindrical opening for inserting a subject (not shown). The cryostat 66 corresponds to a container and has a substantially cylindrical shape. In FIG. 8, the heat insulating structure and the cooling device are omitted.

  The superconducting electromagnet apparatus configured as described above generates a required magnetic field inside the cylindrical shape of the superconducting electromagnet apparatus by passing a current through the superconducting coil group. At this time, the side coils 61a and 61b mainly generate a magnetic field, and the middle coils 62, 63a, 63b, 64a, and 64b form a magnetic field uniform space 67 (magnetic field uniformity of 10 ppm or less) mainly around the center of the magnetic field. The shield coils 65a and 66b generate a magnetic field opposite to the side coil and the middle coil to reduce the leakage magnetic field to the outside of the superconducting electromagnet apparatus. The superconducting electromagnet apparatus according to the sixth embodiment shown in FIG. 8 is designed to generate a magnetic field of about 1.5 [T] at the center of the magnetic field by flowing a current of about 400 [A].

  The cross section of the side coil 61a is shown enlarged on the right side of FIG. The side coil 61b has the same configuration. In the sixth embodiment, a superconducting wire 68 having a diameter of 1.5 [mm] is wound from the first layer to the 58th layer as 59 turns for each layer, and has a cross section of 100 [mm] × 100 [mm]. A side coil 61a is configured. In addition, the said cross-sectional dimension contains an insulator etc. (not shown). The side coil 61a starts to be wound from the first layer, which is the innermost layer, and advances to the upper layer every time 59 turns are wound.

  When the side coil 61a configured with the above dimensions is energized, the magnetic field distribution inside the coil is as shown in FIG. As shown in FIG. 9, the place where the maximum magnetic field in the coil is 5.5 [T] is near the center of the inner surface of the annular superconducting coil, and the magnetic field in the coil is 5.0 [T]. The area exceeding the limit is limited to a small area near the inner periphery of the coil as viewed from the whole coil. Further, the locations of the magnetic fields 2.5 [T], 3.0 [T], 3.5 [T], and 4.5 [T] in the coil are as shown in FIG.

  Thus, according to the magnetic field distribution shown in FIG. 9, it can be seen that the magnetic field is high in the inner layer of the side coil 61a, which is a superconducting coil, and the magnetic field is low in the outer layer. On the other hand, the winding sequence starts from the inner layer and gradually goes to the outer layer, so that the magnetic field is high at the start of winding of the superconducting coil, and the magnetic field is lowered later.

  Therefore, the superconducting electromagnet apparatus according to the sixth embodiment of the present invention includes a superconducting wire manufactured by the method described in any one of the first to third embodiments and having a copper ratio continuously increasing or decreasing in the axial direction. The part of the superconducting wire with a small copper ratio is used at the beginning of the winding with a high magnetic field, and the part of the superconducting wire with a large copper ratio is used in the part after the low magnetic field.

  With this configuration, it is possible to use a superconducting wire with an appropriate copper ratio corresponding to the portion of the superconducting coil without increasing the superconducting connection, and avoid using a superconducting wire with an excessively low copper ratio. Therefore, the amount of NbTi used can be suppressed. Since NbTi has a higher cost than Cu, reducing the amount of NbTi used leads to a reduction in cost.

  In the sixth embodiment, in order to maintain a constant quench resistance with a coil having a magnetic field distribution as shown in FIG. 9 and to minimize the amount of NbTi to be used, the coil has a copper ratio distribution shown by a solid line in FIG. A superconducting wire may be used for the side coil. The copper ratio distribution shown in FIG. 10 is inversely correlated with the change in the maximum magnetic field for each layer of the coil indicated by the broken line in FIG. 10, and in each layer of the coil, the MQE (minimum quench energy; quenching the superconducting electromagnet apparatus is performed. The minimum thermal energy required to make the superconductivity the higher the MQE, the higher the stability of superconductivity).

  At this time, since the average value of the copper ratio of the superconducting wire is 5.9, the amount of NbTi used for manufacturing the side coil 61a is about 73% as compared with the case where all of the wires having a copper ratio of 4 are used. Can be suppressed. Although the amount of Cu used is about 1.5 times, the price per unit volume of NbTi is about 14 times higher than that of Cu. Therefore, in the sixth embodiment, all the wires having a copper ratio of 4 are used. Compared to the above, the cost related to the material of the superconducting wire of the side coil 61a can be reduced by about 25%.

  In addition, since the copper ratio of the superconducting wire changes continuously, the copper ratio slightly changes even in the turn direction in the same layer of the superconducting coil. However, since winding is performed sequentially for each layer, the copper ratio change in the same layer turn direction is extremely small compared to the change in the copper ratio in the layer direction, and the copper ratio in the same layer may be considered to be constant. .

  In the sixth embodiment, the superconducting wire manufactured by any of the methods of the first to third embodiments is applied only to the side coils 61a and 61b. Generally, the solenoid type coil is a coil near the innermost layer. Since the internal magnetic field is the highest and the magnetic field in the coil becomes lower as the outer layer becomes the same, the magnetic field distribution in the coil is the same as that of the side coil of the present embodiment, so the middle coils 62, 63a, 63b, 64a, and 64b By applying the same technique as that of the side coils 61a and 61b of the sixth embodiment to the shield coils 65a and 65b, the cost can be reduced by reducing the amount of NbTi used.

Embodiment 7
In the sixth embodiment, a superconducting electromagnet apparatus in which the superconducting wire in which the copper ratio manufactured according to any of the first to third embodiments is monotonously increased or decreased is applied to a single coil is shown. In the superconducting electromagnet apparatus, the superconducting wire with the copper ratio manufactured according to the fifth or sixth embodiment arbitrarily increased or decreased is applied to continuous winding of a plurality of coils. According to the seventh embodiment, a superconducting electromagnet apparatus with further reduced costs can be obtained. Hereinafter, a superconducting electromagnet apparatus according to Embodiment 7 will be described.

  The overall configuration of the superconducting electromagnet apparatus according to the seventh embodiment is the same as that of the sixth embodiment, and as shown in FIG. 8, side coils 61a and 61b, which are superconducting coils, and the inner circumference of the superconducting electromagnet apparatus between the side coils. A superconducting coil group including middle coils 62, 63a, 63b, 64a, and 64b that are superconducting coils installed on the side, and shield coils 65a and 66b that are superconducting coils installed on the outer peripheral side of the superconducting electromagnet apparatus.

  Usually, the middle coils 62, 63a, 63b, 64a, and 64b are manufactured by continuously winding a plurality of coils using a single superconducting wire since the wire length per coil is short. In the seventh embodiment, as indicated by the arrows in FIG. 11 in the middle coils 62, 63a and 64a, the innermost layer of the middle coil 62 → the outermost layer of the middle coil 62 → the innermost layer of the middle coil 63a → the middle coil. The superconducting wire is wound in the order of the outermost layer 63a → the innermost layer of the middle coil 64a → the outermost layer of the middle coil 64a to produce three coils with one superconducting wire.

  Each middle coil is a superconducting wire having a diameter of 1.2 [mm], the middle coil 62 has 10 turns for each layer 34 layers, the middle coil 63a has 49 turns for each layer, and the middle coil 64a has 10 turns for each layer 61 turns. It is manufactured by turning.

  The magnetic field inside the coil increases rapidly near the innermost layer of the coil, and the magnetic field in other locations does not increase that much. Specifically, the distribution of the magnetic field in the coil generated when 400 [A] is energized through the middle coils 62, 63a, 64a having the above-mentioned number of turns is as shown in FIG. From the winding sequence shown in FIG. 11 and the magnetic field distribution shown in FIG. 12, the superconducting wire used for continuous winding in the seventh embodiment alternately passes through places where the magnetic field is high and places where the magnetic field is low.

  At this time, in order to use a superconducting wire having an appropriate performance according to the magnetic field strength at each position in the coil and to minimize the amount of expensive NbTi used, the copper ratio of the superconducting wire is set to the value of each coil. It is necessary to increase or decrease appropriately so that it is small near the innermost layer and large at other places. Specifically, in the case of the magnetic field distribution and winding sequence shown in FIGS. 11 and 12, if the superconducting wire has a copper ratio distribution as shown in FIG. 13, the MQE is substantially constant. A superconducting wire having such a copper ratio distribution is realized by the method described in the fourth and fifth embodiments.

  The cost when the middle coil of the electromagnet device of FIG. 8 is manufactured using the superconducting wire with the copper ratio distribution shown in FIG. 13 is compared with the case where the same coil is manufactured with all the superconducting wires having a copper ratio of 4. In the copper ratio distribution of FIG. 13, since the average value of the copper ratio is about 6.2, the amount of NbTi used is suppressed to about 69%. At this time, the amount of Cu used is about 1.6 times, but the price per unit volume of NbTi is about 14 times higher than that of Cu. Therefore, in this example, all wires with a copper ratio of 4 are used. Compared to the conventional case of manufacturing a middle coil, the cost of the superconducting wire material can be reduced by about 28%.

It is a cross-sectional view which shows the composite billet for extrusion in Embodiment 1 of this invention. It is a cross-sectional view which shows the Cu covering NbTi alloy single core wire before drawing in Embodiment 1 of this invention. It is a cross-sectional view which shows the composite billet for extrusion in Embodiment 2 of this invention. It is a cross-sectional view which shows the Cu covering NbTi alloy single core wire before drawing in Embodiment 2 of this invention. It is a cross-sectional view which shows the Cu covering NbTi alloy single core wire before drawing in Embodiment 3 of this invention. It is a cross-sectional view which shows the composite billet for extrusion in Embodiment 4 of this invention. It is a cross-sectional view which shows the Cu covering NbTi alloy single core wire before drawing in Embodiment 5 of this invention. It is a block diagram which shows the superconducting electromagnet apparatus in Embodiment 6 of this invention. It is explanatory drawing which shows the cross-section of a coil and the magnetic field distribution in a coil in Embodiment 6 of this invention. It is a graph which shows the copper ratio distribution of the superconducting wire in Embodiment 6 of this invention. It is a figure which shows the winding order of the multiple coil continuous winding in Embodiment 7 of this invention. It is explanatory drawing which shows the magnetic field distribution in a middle coil in Embodiment 7 of this invention. It is a graph which shows the copper ratio distribution of the superconducting wire in Embodiment 7 of this invention.

Explanation of symbols

1 Cu-coated NbTi alloy single core wire 2, 22, 42 Large-diameter Cu pipe 3, 23, 43 End member 4, 24, 44 Rear end member 5, 25, 45 Extrusion composite billet 6, 26, 36, 56 Cu pipe 7, 27, 37, 57 NbTi rod 8, 28, 38, 58 Nb sheet 11, 211, 311, 511 Superconducting single core wire before drawing 65a, 65b Side coil 62, 63a, 63b, 64a, 64b Middle coil 65a, 65b Shield coil 66 Cryostat 67 Magnetic field uniform space 68 Superconducting wire

Claims (11)

  A superconducting wire in which a filament made of a superconducting material is embedded in a matrix made of a stabilizing material made of a metal, and the cross-sectional area ratio of the superconducting wire in the radial direction between the matrix and the filament is A superconducting wire configured to change along the axial direction of the superconducting wire.   2. The superconducting wire according to claim 1, wherein the cross-sectional area ratio changes only by increasing or decreasing along the axial direction of the superconducting wire.   2. The superconducting wire according to claim 1, wherein the cross-sectional area ratio alternately and continuously increases and decreases along the axial direction of the superconducting wire.   The superconducting wire according to any one of claims 1 to 3, wherein the stabilizing material is made of Cu or Al. The superconducting wire according to any one of claims 1 to ₃ , wherein the superconducting substance is made of an NbTi alloy or Nb ₃ Sn.   A method of manufacturing a superconducting wire in which the ratio of the cross-sectional area in the radial direction between a matrix made of a stabilizing material made of metal and a filament made of a superconducting material varies continuously along the axial direction. A first step of forming a superconducting single-core wire coated with a chemical material, and the inside of a tubular body constituted by a metal-stabilized material and having a radial cross-sectional area that continuously changes along the axial direction. A method of manufacturing a superconducting wire, comprising: a second step of forming a composite billet by accommodating a plurality of superconducting single core wires; and a third step of subjecting the composite billet to a cross-sectional reduction process.   A method of manufacturing a superconducting wire in which the ratio of the cross-sectional area in the radial direction between a matrix made of a stabilizing material made of metal and a filament made of a superconducting material varies continuously along the axial direction. A first step of forming a superconducting single core wire covered with a chemicalizing material and having a radial cross-sectional area ratio between the stabilizing material and the superconducting material continuously changing along the axial direction; and a metal stabilizing material A second step of forming a composite billet by accommodating a plurality of the superconducting single core wires inside the constructed tube body, and a third step of subjecting the composite billet to cross-sectional reduction processing are provided. A method of manufacturing a superconducting wire.   A method of manufacturing a superconducting wire in which the ratio of the cross-sectional area in the radial direction between a matrix made of a metal stabilizing material and a filament made of a superconducting material is alternately increased and decreased along the axial direction. The first step of forming the superconducting single core wire covered with the metal stabilizing material, and the radial cross-sectional area constituted by the metal stabilizing material alternately increasing and decreasing in the axial direction. A second step of forming a composite billet by accommodating a plurality of the superconducting single core wires inside a tube body that continuously changes, and a third step of subjecting the composite billet to a cross-sectional reduction process. A method of manufacturing a superconducting wire, characterized in that   A method of manufacturing a superconducting wire in which the ratio of the cross-sectional area in the radial direction between a matrix made of a metal stabilizing material and a filament made of a superconducting material is alternately increased and decreased along the axial direction. In addition, a superconducting single-core wire is formed which is covered with a metal-stabilizing material and in which the radial cross-sectional area ratio between the stabilizing material and the superconducting substance changes alternately and continuously increases and decreases along the axial direction. A second step of forming a composite billet by accommodating a plurality of the superconducting single core wires inside a tubular body made of a metal stabilizing material, and reducing the cross section of the composite billet A superconducting wire manufacturing method comprising: a third step of performing processing.   A superconducting electromagnet apparatus having a solenoidal superconducting coil formed by winding a superconducting wire, wherein the superconducting wire is embedded with a filament made of a superconducting substance in a matrix made of a metal stabilizing material. The superconducting coil is configured such that the ratio of the cross-sectional area in the radial direction between the matrix and the filament changes continuously along the axial direction. A superconducting electromagnet apparatus comprising: a portion having a small cross-sectional area ratio of a wire; and a portion having a large cross-sectional area ratio of the superconducting wire at a portion where the magnetic field in the coil is lower than the high portion.   A superconducting electromagnet apparatus in which a plurality of solenoidal superconducting coils formed by winding a superconducting wire are connected in series, wherein the superconducting wire is formed from a superconducting substance in a matrix made of a metal stabilizing material. A plurality of filaments are embedded, and the ratio of the cross-sectional area in the radial direction between the matrix and the filaments is alternately and continuously increased and decreased along the axial direction. The superconducting coil is composed of one continuous superconducting wire, and each superconducting coil is composed of a portion where the cross-sectional area ratio of the superconducting wire is small at a portion where the magnetic field in the coil is high. The superconducting electromagnet apparatus, wherein the superconducting wire is formed at a portion where the cross-sectional area ratio of the superconducting wire is large at a portion where the magnetic field in the coil is lower than the high portion.

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