JPH05267044A - Formation of helical conductor - Google Patents

Abstract

PURPOSE:To manufacture a high strength and high conductivity helical coil conductor by coiling a wire whose cross section is straight angle-shaped around a cylinder spirally, applying compression force to the wire drawing from the longitudinal direction of the cylinder and correcting the trapezoid-shaped wire drawing in its cross section and correcting the shape into straight angle in its cross section and then finishing both the inner and outer surfaces of the wire drawing. CONSTITUTION:With tensile force applied to a cylinder-shaped inner mold, a copper belt is mechanically coiled in such a fashion that the clearance between the copper belts may be minimized, thereby obtain a spirally-shaped coil 2114. After its winding, if tensile force is removed, the size of the coil will be increased by the portion of resultant elastic deformation. Then, an outer mold 15 in addition to the inner mold is inserted into the enlarged coil. The trapezoid-shaped cross section of each layer of the spirally-shaped coils 14 is subjected to forced deformation and returned to the original straight angle. Then, the inner mold 13 is removed and a coil conductor 17 is obtained. Furthermore, all the surfaces between the inner and outer molds and each layer are mechanically finished, thereby producing a coil conductor 19 having a finally-shaped inner layers 20a to 20h.

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 conductivity for generating a strong magnetic field.

[0002]

BACKGROUND OF THE INVENTION The magnetic field required for magnetic confinement fusion devices is expected to be 10-20 Tesla or more.
Since various nuclear fusion devices so far use a coil of a normal conductor (copper wire), a huge amount of power is consumed.
For this reason, it is essential to develop a coil of superconducting wire that does not consume power.

In order to develop a high-performance superconducting conductor that can withstand a strong magnetic field, various conductors are developed and placed in 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, by combining the superconducting magnet 8 (outer side) and the water-cooled magnet 7 (inner side), the central part of the magnetic field where the sum of the two magnetic fields becomes maximum The resulting hybrid magnet is used.

There are three types of water-cooled magnet coils, 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 poly-helix type coil conductor is a multi-layer coil in which a single-layer helical coil conductor is made of a rectangular wire and a plurality of helical coil conductors are concentrically combined and electrically connected in parallel and in series. A structure in which cooling water is flowed through the layer gap to cool it is generally adopted. If 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, the coil radius and the magnetic field. Therefore, as the coil conductor, a conductor having a strength in the circumferential direction as much as possible, particularly a high yield strength and a high conductivity is required.

There are many Cu and Cu alloys that are subject to these specifications. For example, as shown in (J) to (M) of FIG. 7, 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 to these, precipitation hardening Cu alloys such as Cr-Cu and Cr-Zr-
Although there are Cu and the like, they are insufficient in strength. Further, although the alumina dispersion strengthened copper alloy has sufficient strength and electrical characteristics, it is difficult to produce large crystals.
Further, as shown in (G) and (H) of FIG. 6, it is possible to wind the plate-shaped material 4 and provide the welded portion 6 to manufacture the cylinder 5, but the mechanical and electrical characteristics of the welded portion 6 Is inferior,
Not a valid method.

[0008]

As described above, when a strong magnetic field, for example, 40 to 50 Tesla is obtained in the hybrid magnet, the circumferential stress acting on the water-cooled magnet becomes very high. 50 kg
/ Mm ² The above must be satisfied. To make it more compact, a conductivity of 80% (IACS) or higher 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 conductivity.

[0009]

According to the present invention, a wire 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 so that the wire has a trapezoidal cross section. The cross-section was again corrected to a rectangular shape, and then the inner and outer surfaces of the wire were finished.

[0010]

[Operation] A large tensile stress acts on the helical coil conductor in the circumferential direction by the electromagnetic force, and 1/5 to 1 of the tensile stress is exerted in the axial direction.
A compressive stress of about / 10 occurs. For this reason, in the trapezoidal section as wound, the contact between the coil conductor layers is not uniform, which not only deteriorates the overall dimensional accuracy, but also
Due to the uneven contact, buckling is likely to occur and the insulator around the coil conductor may be destroyed. However, as in the present invention, all of these problems are eliminated by making the contact between the coil conductor layers uniform by forced deformation.
Further, since the cold-drawn wire can be used as it is without heat treatment, excellent mechanical properties can be utilized.

[0011]

Embodiments of the 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. 3 (E) is used, and the rod-shaped rolled copper 10 shown in FIG. 3 (E) is used.
From the above, a long rectangular copper strip 11 shown in FIG. 4F is obtained by cold plastic drawing. The surface of the copper strip 11 is coated with pure copper of 0.05 to 0.1 mm.

Next, the copper strips 11 are mechanically wound so as to minimize the gap between the copper strips 11 while applying tension to the inner mold 13 having a cylindrical shape shown in FIG. Coil 14
To get When the tension is removed after winding, the coil diameter increases by the amount of elastic deformation of the coil. Next, in addition to the inner die 13, the outer die 15 is inserted into the increased coil diameter, and a load as shown in FIG.
Even if the trapezoidal section of each layer is forcibly deformed, the original rectangular shape is obtained. 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 in the wire drawing process. After that, the inner mold 13 is removed to obtain a coil conductor 17 shown in FIG. 1B, and a surface 18a between the inner and outer circumferences and each layer is obtained.
By machine finishing ~ 18h, the final shape of the 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, a compressive load is only applied and deformed in order to improve the precision of the rectangular cross section, so that machining, wire cutting or electric discharge machining for forming a spiral coil is performed. Is unnecessary, and the manufacturing process is extremely simple. Also, by changing the diameter of the inner die, it is possible to manufacture a coil of any diameter, and the material yield is very good compared to the method of cutting out from an integrated ingot. Furthermore, since no heat treatment is performed after winding, heating does not cause deterioration of the material at all, and the excellent properties of cold working can be utilized as they are.

FIG. 4 shows the degree of deformation of the inner and outer cross sections when a rectangular wire is wound around the inner die. In normal winding, the ratio of coil conductor thickness to diameter (t / D) shown in the figure is 0.05 to 0.
Up to about 15. As shown in FIG. 3, the cross section thus deformed can be easily deformed by applying a comparatively small surface pressure-equivalent load, and can be made close to the original rectangular shape. This is because the pure copper coated on the surface of the used alumina particle dispersion strengthened copper is easily deformed by a small load.

In FIG. 3, W is a dimension when the coil conductor is not deformed, and Δa is a deformation amount when the lower bottom portion of the coil conductor is expanded or contracted. Further, in FIG. 4, Δb represents the amount of deformation when the upper bottom portion of the coil conductor expands and contracts.

As described above, in this embodiment, a rectangular wire was used as the initial flat wire, but at the time of drawing,
It is also possible to anticipate the deformation after winding and process it into a trapezoidal shape, and to make a rectangular cross section after winding. Even in this case, it is possible to obtain the same effect as that of the above-described embodiment. Further, although the wire drawing of alumina particle dispersion strengthened copper was used, a metal wire drawing added with a reinforcing material such as long / short fibers, whiskers, particles, or a pure metal or alloy may be used.

[0018]

According to the present invention, a metallic wire drawing having improved mechanical properties by cold working is wound around a cylinder to form a spiral coil, and the deformed coil cross 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 layers, the cold-worked characteristics are not deteriorated and a heat treatment step is not required, so that any metal wire drawing can be used. Therefore, it is possible to manufacture a helical coil conductor having high strength and high electrical conductivity and excellent machining accuracy. As a result, the water-cooled magnet for a strong magnetic field can have high performance, high reliability, and a compact size.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a forming process of a helical coil conductor according to the present invention, where (A) shows that a compressive force is applied to a spirally wound coil conductor, and (B) shows that the conductor coil is compressed again. It shows that a force is applied, (C) shows the coil conductor formed by the initial compression force, and (D) shows the coil conductor machined after applying the compression force again.

FIG. 2 is a conceptual diagram showing a material shape of a coil conductor, (E)
Shows a material in the form of a round bar, and (F) shows a material processed into a rectangular shape.

FIG. 3 is a graph showing the characteristics of each cross-sectional shape when the coil conductor obtained according to 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 the coil conductor obtained by 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 winding a flat coil conductor around a cylinder.

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

[Explanation of symbols]

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

Claims (1)

[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 reshape the copper strip having a trapezoidal cross section into a rectangular cross section, Then, a method for forming a helical coil conductor, characterized by finishing the inner and outer surfaces of the copper strip.