Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – Superconductive type
Reexamination Certificate
1996-10-25
2001-02-27
Donovan, Lincoln (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
Superconductive type
C174S125100
Reexamination Certificate
active
06194985
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an oxide-superconducting coil, and especially, to a wind-and-react type coil using a metal sheathed oxide superconducting wire, and a method for manufacturing the same.
As methods for manufacturing an oxide superconducting wire, a powder-in-tube method, wherein superconducting powder, or a precursor of the superconducting powder, is filled in a metallic sheath, such as a silver tube, and the powder filled sheath is manufactured by a processing such as wire drawing, rolling, and other processes, or a dip-coat method, wherein a substrate is dipped into a suspended liquid containing superconducting powder continuously for coating both planes of the substrate with the suspended liquid, have been conventionally utilized. A superconducting coil using the superconducting wire manufactured by any one of the above methods, and manufactured by a wind-and-react (W & R) method, wherein a heat treatment is performed after fabrication of the coil, or a react-and-wind (R & W) method, wherein a heat treatment is performed prior to fabrication of the coil, has been reported to be able to generate a magnetic field of 3-4 T class under a condition of no backup magnetic field (Ookura et al.: Proceedings of The 53rd. 1995 Annual Meeting (Spring time) of the Cryogenic Engineering and Superconductor Society: D2-2 (1995)), and a magnetic field of 1-2 T under a backup magnetic field exceeding 20 T at 4.2 K (N. Tomita et al.: Appl. Phys. Lett., 65 (7), Aug. 15, 1994, p 898-900).
An oxide superconducting coil had problems such that high performance of the oxide superconducting coil estimated from characteristics of its short sample wire element could not be realized practically, on account of a large electromagnetic force under a strong magnetic field, a creep deformation by its own weight occurring during a heat treatment after fabrication of the coil, a thermal reaction of the superconducting core with an insulating material, and the like.
In detail, there were problems such as (1) breakage of the coil by the effect of an electromagnetic force of 40 MPa when the oxide superconducting coil was installed in an external magnetic field of 20 T and an electric current of 200 A was supplied thereto, (2) thermal creep deformation of the coil due to its own weight when a large scale coil was fabricated using the W & R method, and (3) deterioration of the superconductor in characteristics of the critical current density (Jc) caused by a reaction of the superconductor in the wire material core with a ceramic insulator, which was wound together with the superconductor in the wire material core, during heat treatment.
SUMMARY OF THE INVENTION
The present invention has been developed in consideration of the above problems. One of the objects of the present invention is to provide an oxide-superconducting coil in which can be deterioration of the characteristics in critical current density (Jc) by an electromagnetic force under a strong magnetic field can be prevented along with deformation and other reactions generated during heat treatment, and another object is to provide a method of manufacturing a coil having such qualities.
In order to manufacture a high performance oxide-superconducting coil, it is necessary to improve the mechanical strength of the superconducting coil at a temperature at which the coil is used, or which occurs during heat treatment of the coil, and to investigate the insulating material used in manufacturing the oxide-superconducting coil.
After serious investigation in consideration of the problems described above, the inventors of the present invention have developed an oxide-superconducting coil having the following composition.
The method of manufacturing the oxide-superconducting coil according to the present invention is characterized in the use of a heat resistant alloy, whereon an oxide film is previously formed by a heat treatment, as an insulating material when the coil is manufactured by the wind-and-react method, wherein heat treatment is performed after winding an oxide-superconducting powder filled metallic sheath and the insulating material together to form the coil.
Further, the method of manufacturing an oxide-superconducting coil according to the present invention is characterized in that the heat resistant alloy has a sufficient mechanical strength at an elevated temperature for preventing creep deformation by the weight of the coil itself during the heat treatment, and a sufficient mechanical strength to withstand hoop stress by an electromagnetic force after cooling.
Furthermore, the method of manufacturing the oxide-superconducting coil according to the present invention is characterized in that silver or a silver alloy is arranged at an intermediate layer between the oxide-superconducting wire material and the heat resistant alloy of the oxide-superconducting coil, which is manufactured by winding an oxide-superconducting powder filled metallic sheath and an insulating material together.
Furthermore, the method of manufacturing an oxide-superconducting coil according to the present invention is characterized in that the heat resistant alloy used as the insulating material contains at least one of the metals selected from a group consisting of Ni, Cr, Cu, Nb, Mn, Co, Fe, Al, Mo, Ta, W, Be, Ti, and Sn, all of which have a low reactivity with the oxide-superconducting wire material.
Furthermore, the method of manufacturing an oxide-superconducting coil according to the present invention is characterized in that it can be used in a condition under an electromagnetic force exceeding 40 MPa.
Furthermore, the method of manufacturing the oxide-superconducting coil according to the present invention is characterized in that the widths of the oxide-superconducting wire material, the silver or the silver alloy, and the heat resistant alloy, which are wound together, coincide within a range of 5%.
Furthermore, the method of manufacturing an oxide-superconducting coil according to the present invention is characterized in that a heat treatment is performed, wherein a temperature difference between the inner plane and the outer plane of the coil is kept within a range of 2 degrees by providing a heater at the inside of the bobbin of the coil when the oxide-superconducting coil is manufactured by the method comprising the steps of winding the metallic sheathed oxide-superconducting wire material in a pan-cake shape, or a solenoid shape, and subjecting it to heat treatment.
Furthermore, the method of manufacturing an oxide-superconducting coil according to the present invention is characterized in that a heat resistant alloy or an insulating material composed of Al
2
O
3
as a main component is wound in a spiral shape together after winding a silver tape or a silver alloy tape onto a surface of the metallic sheathed oxide-superconducting flat square shaped wire material, or tape shaped wire material.
Furthermore, the method of manufacturing an oxide-superconducting coil according to the present invention is characterized in winding the heat resistant alloy or an insulating material composed of Al
2
O
3
as a main component together in a spiral shape after adhering or joining a silver tape or a silver alloy tape onto a surface of the metallic sheathed oxide-superconducting flat square shaped wire material, or tape shaped wire material for forming a body.
Furthermore, the method of manufacturing an oxide-superconducting coil according to the present invention is characterized in that a heat resistant alloy is used as a material for the core of the coil.
The wire material used in manufacturing the oxide-superconducting coil according to the present invention is characterized in that it is manufactured by alloying an oxide-superconducting wire material coated with at least two kinds of different metals to each other by a heat treatment.
When the oxide-superconducting coil according to the present invention is used in a strong magnetic field, forming a complex superconducting magnet with a metallic group superconducting magnet
Fukushima Keiji
Okada Michiya
Tanaka Kazuhide
Antonelli Terry Stout & Kraus LLP
Donovan Lincoln
Hitachi , Ltd.
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