JPH03241706A - Manufacture of superconducting coil - Google Patents

Abstract

PURPOSE:To provide a high performance coil by heating a combined cylinder held between an internal frame cylinder and an external cylinder both specified in their linear expansion coefficients. CONSTITUTION:A superconducting coil is manufactured by pressurizing a coil 2 formed with a superconducting wire material by heating a combined cylinder held between an internal frame cylinder 1 having a linear expansion coefficient greater than that of the coil 2 and an external cylinder 3 having a linear expansion coefficient smaller than that of the coil 2. Namely, by heating the combined cylinder held between the internal and external frame cylinders 3, the coil 2 is compressed by the internal and external frame cylinders, etc., pressurized simultaneously with the heating, owing to a difference between the linear expansion coefficients of the internal frame cylinder 1, coil 2, and external cylinder 3. Accordingly, superconducting ceramics in the superconducting coil is densified, and crystal grain are oriented in the direction where a current is liable to flow. Hereby, a high performance superconducting coil is yielded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a superconducting coil that has a high critical current density and operates stably.

(Prior Art) Conventionally, methods for producing oxide superconducting wire used in superconducting coils include metal sheath method, doctor blade method, thermal spray method, thin film method, and the like. Using superconducting wires made by these methods, various superconducting coils such as solenoid coils, pancake coils, and bitter coils are made. Oxide superconducting wire is made by melting or sintering superconducting raw material powder.
It has low deformability and cracks easily. Furthermore, it is known that the critical current density (hereinafter referred to as Jc) is significantly reduced by bending strain. Therefore, when making a coil using these wires, a method called the wind-and-react method is generally used, in which the wire is first processed into a coil shape before or after heat treatment, and then the final heat treatment is performed.

However, even with coils made by the wind-and-react method, the current value that can be passed through simply heat treatment is low.In order to further increase Jc, the wire after heat treatment is pressurized by pressing or rolling, and the inside of the wire is It is necessary to densify the structure of the ceramic and at the same time orient the crystal grains in a direction that facilitates the flow of current. Therefore, CIP (cold isostatic pressing) and the like are currently being implemented as a method for pressurizing wire rods that have been heat-treated after winding.

(Problems to be Solved by the Invention) Conventional pressurization methods such as CIP used in the wind-and-react method described above use low pressure and cannot sufficiently densify the ceramics within the wire. Further, the wire rods have the disadvantage that the position of the wire rods moves during processes such as heat treatment and pressurization, and the wire rods may become deformed or loosened.

In the present invention, when manufacturing a coil using an oxide superconducting wire,
The purpose is to obtain a coil with higher performance than conventional ones by solving problems such as how to press the wire after winding and how to fix the wire after winding.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, a coil formed of a superconducting wire is formed into an inner frame cylindrical body having a coefficient of linear expansion greater than or equal to the coefficient of linear expansion of the coil. A superconducting coil is manufactured by pressurizing the coil by heating the combination cylinder sandwiched between the outer frame cylinder and the outer frame cylinder having a coefficient of linear expansion smaller than that of the coil.

(Function) By heating the combined cylindrical body sandwiched between the outer frame cylindrical body having a linear expansion coefficient smaller than that of the coil,
Due to the difference in the linear expansion coefficients of the inner frame, coil, and outer frame, the coil is compressed by the inner frame and outer frame, and
Pressure treatment is performed simultaneously with heat treatment.

The inner frame cylinder and the outer frame cylinder used in the present invention are required to have strength in addition to the above-mentioned linear expansion coefficient condition.

Ceramics are one suitable material. For example, 81
3N4, S i C, A l 203, Z r 02
(including Y20a), MgO, etc. can be used. The order of linear expansion coefficients of these materials is shown in the following inequality.

S 1aN4<S i C<A 1203<Zr02(
(including Y2O2)<MgO (1) These materials may be used in combination depending on the linear expansion coefficient of the coil.

(Example) An example of the superconducting coil manufacturing method of the present invention will be described below based on the drawings.

(2) As shown in FIG. 1, a coil 2 is formed by winding insulated oxide superconducting wire in multiple layers around the inner cylindrical body 1 of the winding frame.

(2) As shown in FIG. 2, an outer frame cylindrical body 3 is fitted as an outer frame onto the outside of the coil 2 by shrink fitting, cold fitting, press fitting, or the like. At this time, the materials of the inner frame cylindrical body 1, coil 2, and outer frame cylindrical body 3 have linear expansion coefficients α1, α2, and α, respectively.
The relationship of 3 is αTomi≧ α2〉 α3
・・・・・・ Select the material so that (2) is achieved.

(2) Next, as shown in FIG. 3, this combined cylindrical body is placed in a heat treatment furnace 4 and heat treated at a heat treatment temperature for oxide superconducting wires, usually 800° C. or higher.

Thermal expansion occurs due to the temperature rise due to this heat treatment, but since the linear expansion coefficients of each member, α1, α2, and α3, have the relationship shown in (2) above, the coil 2 is compressed due to the difference in linear expansion coefficients. be done.

When the furnace temperature is lowered after the Φ heat treatment, a gap is created between the coil 2 whose diameter has increased due to deformation and the inner frame cylindrical body 1. Fig. 4 shows the cane with the inner frame cylindrical body 1 removed.

(2) Combination of coil 2 and outer ceramic cylindrical body 3 The cylindrical body is pressurized by CIP (cold isostatic pressing) as shown in FIG.

(2) In order to further compress the coil 2, fit the inner frame cylindrical body 5 inside the coil 2 by shrink fitting, cold fitting, or press fitting as shown in FIG. As this inner frame cylindrical body 5,
A material is selected whose linear expansion coefficient α5 satisfies the following relationship with the linear expansion coefficients α2 and α3 of the coil 2 and the outer frame cylindrical body 3.

α5≧α2>α3 ・・・・・・(3)
■As shown in Figure 7, this combined cylindrical body is placed in a heat treatment furnace.
and heat treatment temperature of oxide superconducting wire (usually 800℃).
heat treatment at temperatures above ℃). At this time, due to the difference in coefficient of linear expansion between the inner cylindrical frame 5 and the outer cylindrical frame 3, the coil 2 is subjected to a large compressive force in a high temperature state and is hot pressed. This further increases (improves) the critical current density.

If it is possible to remove the inner frame cylindrical body 5 after the heat treatment,
By repeating the steps (1) to (2) above, the performance of the coil 2 is further improved. Even if the inner frame cylindrical body 5 does not come out, it is sufficient to leave it as is and repeat steps ① to ②. Incidentally, if the inner frame cylindrical body 3 is not ultimately required, it can be easily removed by cooling it to a low temperature.

Note that the pressurizing method of the present invention can be used not only for manufacturing a superconducting coil device but also for manufacturing a magnetic shield body using an oxide superconductor.

[Effects of the Invention] According to the manufacturing method of the present invention, strong pressure can be applied to the superconducting coil in a stable fixed state without causing deformation or cracking, so that the superconducting wire forming the superconducting coil can be A superconducting coil with high critical current density and high performance can be obtained by densifying the superconducting ceramic inside the coil and orienting the crystal grains in a direction in which current flows easily.

[Brief explanation of drawings]

1 to 7 are explanatory views showing an example of the manufacturing method of the present invention. 1.5... Inner frame cylindrical body, 2... Oxide superconducting coil, 3... Outer frame cylindrical body, 4... Heat treatment furnace. Figure 4 Figure 5 Figure 6 Figure 7

Claims (2)

[Claims] (1) In a method for manufacturing a superconducting coil using an oxide superconducting wire, a coil formed of a superconducting wire is connected to an inner frame cylinder having a linear expansion coefficient greater than or equal to the linear expansion coefficient of the coil, and a linear expansion coefficient of the coil. A method for manufacturing a superconducting coil, comprising a heating compression step of heating a combination cylinder sandwiched between outer frame cylinders having a coefficient of linear expansion smaller than the coefficient of linear expansion. (2) Either one of the inner frame tube and the outer frame tube body is shrink-fitted, cold-fitted, or press-fitted to sandwich a coil formed of a superconducting wire material to form a combined tube body. A method of manufacturing the superconducting coil described above.