JPH03241797A - Manufacture of magnetic shield body - Google Patents

Abstract

PURPOSE:To eliminate the problem of crack generated in production and at the same time enable shielding performance to be improved by allowing a linear expansion coefficient to be increased in an inner side second layer compared with that of an outer side second layer and by performing press treatment with working compression force. CONSTITUTION:By setting combination columns 1 and 2 to be an inner mold, setting a rubber column 3 to be an outer mold, filling an oxide superconductive powder 4 between them, performing pressing and then removing the rubber column mold 3, and then performing heat treatment, the oxide superconductive powder formed body is formed at an oxide superconductor 4'. On the other hand, a combination cylinder of a metal thin-film cylinder 5 is separately prepared at a ceramic cylinder 6 and is fit by pressing. At this time, a metal material which is of the same type as the metal thin-film cylinder 2 or that with a small difference in linear expansion coefficient is used for the metal thin-film cylinder 5 and a ceramic cylinder 6 with a smaller linear expansion coefficient than that of the ceramic cylinder 1 is selected, thus enabling a strong pressure to be applied to a superconductive coil without generating deformation or crack in a stably fixed state. Therefore, an intricate and high- performance magnetic shield body without any crack can be stably produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a method of manufacturing a magnetic shield using an oxide superconductor.

(Prior Art) Conventionally, methods for making a cylindrical magnetic shield using an oxide superconductor include a thermal spraying method and a powder method.

Thermal spraying is done from the outside of a ceramic or metal cylindrical body.
This is a method of manufacturing by repeating various heat treatments after melting and spraying an oxide superconductor.

The powder method is a method in which oxide superconducting raw material powder is formed into a cylindrical shape and then heat treated to produce a cylindrical magnetic shielding body.

(Problems to be solved by the invention) Among the above-mentioned conventional methods for manufacturing magnetic shielding bodies, thermal spraying tends to cause unevenness in the sprayed film, and it is extremely difficult to make the entire cylindrical surface superconducting. be.

In contrast, the powder method can relatively easily produce a uniform superconducting film. A drawback of this powder method is that cracks are likely to occur during heat treatment and during cooling to room temperature or below. Therefore,
In general, the thickness of the superconducting cylinder is increased, usually several millimeters or more, or a pressure step is provided during heat treatment to densify the structure using CIP (cold isostatic pressing), etc. Prevents cracking of the superconductor. However, increasing the thickness of the superconducting cylinder will conversely impede densification, lowering the critical current density and lowering the magnetic shielding performance. Additionally, intermediate pressure may also promote cracking depending on how pressure is applied, making stable production difficult.

The present invention aims to solve the problem of cracks that occur when manufacturing a magnetic shield cylinder using an oxide superconductor by a powder method, and at the same time improve shielding performance.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides that the first outer layer of the cylindrical oxide superconducting material is a metal tube, and the second outermost layer is a metal cylinder. is a ceramic tube, the inner first layer is a metal tube, and the innermost layer is a second layer.
A combination body having a structure in which the layers are ceramic cylinders or pillars, and in which the linear expansion coefficient of the outer second layer is smaller than that of the inner second layer, is heat-treated.

(Function) When a combination of the above structures is heated, a compressive force acts between the inner second layer and the outer second layer because the inner second layer has a larger coefficient of linear expansion than the outer second layer. . Due to this compressive force, the oxide superconducting material sandwiched between the inner second layer and the outer second layer is subjected to heat treatment and pressure treatment.

The inner frame cylindrical body and the outer frame cylindrical body used in the present invention are required to have strength in addition to the above-mentioned coefficient of linear expansion. Ceramics are one suitable material.

For example, Si3N4.5iC1A1203, Zr02(
Y2O3), MgO, etc. can be used. The order of linear expansion coefficients of these materials is shown in the inequality below.

S i3N4<S i C<A 1203<Zr02(
(including Y2O3)<MgO These materials may be used in appropriate combinations depending on their linear expansion coefficients.

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

■A thin metal cylinder 23 is fitted to the outside of the ceramic cylinder 1 by shrink fitting, cold fitting, or press fitting. The metal used here includes, for example, AulAg1C
u1Ni1Fe or an alloy thereof is used. Moreover, a ceramic cylinder may be used instead of the ceramic cylinder 1.

■As shown in Figure 1, this combined cylinder serves as the inner mold, the rubber cylinder 3 serves as the outer mold, and oxide superconducting powder (
Fill with raw material powder or calcined powder) 4.

Then, cold isostatic pressing (CIP) is applied to this to form the oxide superconducting powder 4 under pressure. After molding, the rubber cylindrical mold is easily removed due to springback, and a molded body of oxide superconducting powder is formed on the outside of the thin metal cylinder 2.

(2) Next, by heat-treating this, the oxide superconducting powder compact forms an oxide superconductor 4' in the form of a sintered body, a partially melted body, or a molten solidified body.

■On the other hand, as shown in Fig. 3, a combination cylinder is separately prepared in which the thin metal cylinder 5 is shrink-fitted, cold-sealed, or press-fitted into the ceramic cylinder 6, and this is shrunk-fitted or cold-fitted to the outside of the combination cylinder shown in Fig. 2. Fit by crimping or press fitting.

FIG. 4 is a diagram showing a fitted state.

Note that the thin metal cylinder 5 is made of the same type as the thin metal cylinder 2 or a metal material with a small difference in coefficient of linear expansion.

Further, the ceramic cylinder 6 is selected to have a coefficient of linear expansion smaller than that of the ceramic cylinder 1. Ceramics include structural ceramics with high high temperature strength, such as SiC, 5i3N41 A 1203. Z r 02
(including Y2O3) + MgO, etc. can be used.

■This is the heat treatment temperature for oxide superconductors, usually 800℃.
Heat treatment is performed as above. At this time, due to the difference in coefficient of linear expansion between the ceramic cylinder 6 and the ceramic cylinder 1, the oxide superconductor 4' of the oxide superconductor powder is compressed during heat treatment or temperature raising/lowering, and its structure becomes dense.

■After cooling, pull out the ceramic cylinder 1. In order to further densify the oxide superconductor 4', as shown in FIG. All you have to do is

(2) By cooling the assembled cylindrical body after processing to below room temperature, the outer ceramic cylinder 6 is removed, and a thin magnetic shield cylinder wrapped in metal is completed as shown in FIG.

In addition, in the case of the outer ceramic cylinder and the inner ceramic cylinder, they may be left in the final state.

[Effects of the Invention] The manufacturing method of the present invention makes it possible to apply strong pressure to the superconducting coil while it is stably fixed without causing deformation or cracking. This has the effect of stably manufacturing a high-performance magnetic shield body.

[Brief explanation of drawings]

FIGS. 1 to 6 are explanatory diagrams showing an example of the manufacturing method of the present invention. 1... Ceramic cylinder, 2, 5... Metal cylinder,
3... Rubber cylinder, 4... Oxide superconducting powder, 4'
...Oxide superconductor, 6.7... Ceramic circle Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] (1) In a method for manufacturing a magnetic shield using an oxide superconducting material, the first outer layer of the oxide superconducting material is a metal tube, the second outermost layer is a ceramic tube, and the inner first layer is a metal tube.
Heat treatment of a combination body having a structure in which the layer is a metal tube and the innermost second layer is a ceramic tube or column, and the linear expansion coefficient of the inner second layer is larger than the linear expansion coefficient of the outer second layer. A method for manufacturing a magnetic shielding body, comprising the step of: