JP2960251B2 - Method of forming helical coil conductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a helical coil conductor having high strength and high electrical conductivity for generating a strong magnetic field.

[0002]

It is anticipated that the magnetic field required for a magnetically confined fusion device will be in excess of 10-20 Tesla.
Conventional nuclear fusion devices consume a huge amount of electric power because they use coils of a normal conductor (copper wire).
Therefore, it is essential to develop a coil using a superconducting wire that consumes no power.

In order to develop a high-performance superconducting conductor that can withstand a strong magnetic field, various conductors are developed and put into a strong magnetic field generator, and the critical current density ( _Jc ), upper critical magnetic field, AC loss, etc. Need to find out.

Therefore, a strong magnetic field generator is required,
In order to generate a magnetic field of 30 terraces or more, as shown in FIG. 5, a superconducting magnet 8 (outside) and a water-cooled magnet 7 (inside) are combined so that the central part of the magnetic field at which the sum of the magnetic fields of both becomes maximum The resulting hybrid magnet is used.

There are three types of this water-cooled magnet coil, a polyhelix type, a bitter type, and a monohelix type. The present invention relates to a method for forming a polyhelix type coil conductor.

The polyhelical coil conductor is a multilayer coil in which a single-layer helical coil conductor is formed by a rectangular wire, and a plurality of helical coil conductors are concentrically combined and electrically connected in parallel and in series. A structure for cooling by flowing cooling water through the layer gap is generally adopted. Assuming that the multilayer coil conductors are independently supported, the circumferential tensile stress generated in each coil conductor is proportional to the product of the current density, coil radius and magnetic field. Therefore, as the coil conductor, a conductor having high strength in the circumferential direction as much as possible, particularly, high proof strength and high conductivity is required.

There are many Cu and Cu alloys subject to these specifications. For example, as shown in FIGS. 7 (J) to 7 (M), there is a method of increasing the yield strength and tensile strength of pure copper by ring rolling forging.
kg / mm ² , Tensile strength 40kg / mm ² Is the limit. In addition, Cr-Cu, Cr-Zr-
There are Cu and the like, but all of them are insufficient in strength. Further, although the alumina dispersion strengthened copper alloy has sufficient strength and electric properties, it is difficult to produce a large crystal.
As shown in FIGS. 6G and 6H, it is possible to wind the plate-shaped material 4 and provide a welded portion 6 to produce the cylinder 5, but the mechanical and electrical characteristics of the welded portion 6 are also possible. Is inferior,
Not a valid method.

[0008]

In order to obtain a strong magnetic field, for example, 40 to 50 Tesla in the hybrid magnet, the circumferential stress acting on the water-cooled magnet becomes extremely high. 50kg
/ Mm ² The above must be satisfied. To achieve further compactness, a conductivity of 80% (IACS) or more is required. Therefore, an object of the present invention is to provide a method for forming a helical coil conductor having higher strength and higher electrical conductivity.

[0009]

According to the present invention, there is provided a wire having a rectangular cross section, which is spirally wound around a cylinder, and a compression force is applied in the axial direction of the wound cylinder to form the wire into a trapezoidal cross section. The cross section was corrected to a rectangular shape again, and then the inner and outer surfaces of the drawn wire were finished.

[0010]

In the helical coil conductor, a large tensile stress acts in the circumferential direction due to the electromagnetic force, and 1/5 to 1 in the axial direction.
A compressive stress of about / 10 occurs. For this reason, in the trapezoidal cross section as it is wound, since the contact between the coil conductor layers is not uniform, not only does the overall dimensional accuracy deteriorate,
Buckling is likely to occur due to uneven contact, and the insulator around the coil conductor may be destroyed. However, by making the contact between the coil conductor layers uniform by forced deformation as in the present invention, all of these disadvantages are eliminated.
In addition, since the cold-drawn wire can be used as it is without heat treatment, excellent mechanical properties can be used.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for forming a helical coil conductor according to the present invention will be described below with reference to the drawings.

In this embodiment, the alumina particle dispersion strengthened copper 12 shown in FIG. 3E is used, and the rod-shaped copper copper 10 shown in FIG.
Then, a long flat rectangular copper strip 11 shown in FIG. 3 (F) is obtained by cold plastic drawing. The surface of the copper strip 11 is coated with 0.05 to 0.1 mm of pure copper.

Next, the copper strip 11 is mechanically wound while applying tension to the cylindrical inner mold 13 shown in FIG. 1A so that the gap between the copper strips 11 is as small as possible. Coil 14
Get. After winding, if the tension is removed, the coil diameter increases by the elastic deformation of the coil. Next, an outer mold 15 is inserted into the increased coil diameter in addition to the inner mold 13, and a load as shown in FIG.
The trapezoidal cross section of each layer is forcibly deformed so that it becomes the original rectangular shape. The load to be applied is determined by the plastic deformation resistance of the coil cross section. For high strength, it is necessary to apply a large force as the wire is drawn. Thereafter, the inner mold 13 is removed to obtain a coil conductor 17 shown in FIG.
~ 18h is machine finished to make the final shape interlayer 20
The coil conductor 19 having a to 20h can be shown in FIG.

A major feature of the present invention is that, after winding, only a compressive load is applied to improve the accuracy of a rectangular cross section and deformed. Therefore, machining for forming a spiral coil, wire cutting or electric discharge machining is performed. Is unnecessary, and the manufacturing process becomes extremely simple. Further, a coil having an arbitrary diameter can be manufactured by changing the diameter of the inner die, and the yield of the material is very good as compared with a method of cutting out from an integrated ingot. Furthermore, since the heat treatment is not performed after the winding, the excellent properties of the cold working can be utilized as it is without any deterioration of the material during heating.

FIG. 4 shows the degree of deformation of the inner and outer cross sections when a rectangular wire is wound around the inner mold. In normal winding, the ratio (t / D) of the coil conductor thickness to the diameter shown in FIG.
Up to about 15 As shown in FIG. 3, the cross section thus deformed can be easily deformed by applying a relatively small load corresponding to a surface pressure to approximate the original rectangular shape. This is because pure copper coated on the surface of the alumina particle dispersion strengthened copper used is easily deformed by a small load.

In FIG. 3, W is the dimension when the coil conductor is not deformed, and Δa is the amount of deformation when the lower bottom portion of the coil conductor expands and contracts. In FIG. 4, Δb indicates the amount of deformation when the upper bottom portion of the coil conductor expands and contracts, respectively.

As described above, in this embodiment, a rectangular wire is used as the initial flat rectangular wire.
It is also possible to process into a trapezoidal shape in anticipation of deformation after winding and to form a rectangular cross section after winding. Also in this case, it is possible to obtain the same effect as the above-described embodiment. Further, although wire drawing of alumina particle dispersion strengthened copper is used, metal wire drawing to which reinforcing materials such as long and short fibers, whiskers, particles and the like are added, or pure metal or alloy may be used.

[0018]

According to the present invention, a metal-based drawn wire having improved mechanical properties by cold working is wound around a cylinder to form a helical coil, and then the deformed coil section is corrected by a load from the axial direction. Since mechanical finishing is performed on the inner and outer surfaces of the coil and further between the respective layers, the cold-worked properties do not deteriorate, and a heat treatment step is not required. Therefore, any metal-based wire drawing can be used. Therefore, it is possible to manufacture a helical coil conductor having high strength and high conductivity and excellent machining accuracy. This makes it possible to increase the performance, reliability and compactness of the water-cooled magnet for the strong magnetic field.

[Brief description of the drawings]

FIGS. 1A and 1B are conceptual diagrams showing a forming process of a helical coil conductor according to the present invention, wherein FIG. 1A shows that a compressive force is applied to a spirally wound coil conductor, and FIG. (C) shows the coil conductor formed by the initial compressive force, and (D) shows the coil conductor that has been machined after applying the compressive force again.

FIG. 2 is a conceptual diagram showing a material shape of a coil conductor;
Indicates a material in the shape of a round bar, and (F) indicates a material processed into a rectangular shape.

FIG. 3 is a graph showing characteristics of each cross-sectional shape when a coil conductor obtained by the present invention is formed into a rectangular cross-section from a trapezoidal cross-section.

FIG. 4 is a graph showing the amount of deformation of a coil conductor obtained according to the present invention.

FIG. 5 is a diagram showing a configuration example of a hybrid magnet.

FIG. 6 is a conceptual diagram showing a conventional coil conductor forming process, in which (G) shows that the coil conductor has a flat plate shape;
(H) shows that a flat coil conductor is wound around a cylinder.

FIG. 7 is a conceptual diagram showing a conventional coil conductor molding process, in which (J) shows that the coil conductor is a cylindrical material,
(K) shows ring rolling forging on a coil conductor that is a cylindrical body, (L) shows a work-hardened cylindrical material, and (M) shows a helical coil conductor as a final shape.

[Explanation of symbols]

 11 Copper strip 12 Alumina particle dispersion strengthened copper 13 Inner mold 14 Helical coil 15 Outer mold 17 Coil conductor 19 Final shape coil conductor

Claims (1)

(57) [Claims] 1. A copper strip having a rectangular cross section is spirally wound around a cylinder, and a compressive force is applied from the axial direction of the wound cylinder to correct the copper strip into a trapezoidal cross section again into a rectangular cross section. Thereafter, the inner and outer surfaces of the copper strip are finished to form a helical coil conductor.