JP2003007149A - Manufacturing method of superconductive wire material and superconductive wire material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method which enables high current density characteristic and does not require powdering of Mg to form a MgB2 superconductive wire material and to provide a MgB2 superconductive wire obtained there by. SOLUTION: A composite rod 6 is formed by winding a core Nb material with a composite sheet 4 consisting of Mg sheets 2a and 2b and a powder layer B. The rod 6 is successively treated by following processes of forming a single billet (d), extruding (e), stretching (f), forming multiple billets and stretching process (i) to form a wire like product having a specific size. Finally a heat-treatment (j) is applied to the above wire to form a MgB2 superconductive wire material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of manufacturing a superconducting wire, and to a superconducting wire, in particular, high manufacturing method of MgB ₂ superconducting wire having a critical current density characteristic, MgB ₂ superconducting wire obtained from this Regarding

[0002]

_2. Description of the Related Art MgB ₂ has attracted attention as a superconductor having a high critical temperature and capable of being processed into a wire. This Mg
As a standard manufacturing method for obtaining a wire having B ₂ as a superconducting constituent member, a metal pipe filled with superconducting powder composed of reacted MgB ₂ is drawn into a hexagonal cross section, After incorporating a plurality of these into a metal pipe to form a multi-core structure, wire drawing to a predetermined size is performed, and finally, heat treatment at about 600 to 800 ° C. is performed to solidify the MgB ₂ powders into a solid phase. A method of binding by a reaction is generally used.

Another standard manufacturing method is M
After the powder of Mg and B (boron), which is the raw material of gB ₂ , is filled in a metal pipe and drawn into a hexagonal cross section, a plurality of this is incorporated into the metal pipe to make a multi-core structure, and then a predetermined size A method is conceivable in which MgB ₂ is produced by subjecting the wire to a wire drawing process and subjecting this to a heat treatment at the above temperature.

[0004]

However, according to the manufacturing method described above, in the case of the former method, if an oxide film is present on the surface of the MgB ₂ powder, a different phase is formed at the boundary portion of the powder particles during the final heat treatment. Therefore, even if the individual particles exhibit superconductivity, the current flow is hindered at the boundary portion of the particles, and the improvement of the overall critical current density characteristics cannot be obtained.

For this reason, although there are many reports regarding bulk bodies of MgB ₂ superconductors, regarding the superconductors of wire material construction, the critical currents comparable to those of the Nb-Ti based superconducting wire materials or Nb3Sn based superconducting wire materials already in practical use. In fact, the fact that density characteristics have been reported has not yet been reported.

On the other hand, in the case of the latter method, since the Mg powder has a property of easily forming an oxide film on the surface,
In addition to having the same problem as the former, further, in the case of this method, since the powder particle size is on the order of μm, it is difficult to manufacture the Mg powder as a raw material, and dust explosion occurs in the Mg powder. It is highly dangerous and not a preferable method from the viewpoint of safety.

Accordingly, it is an object of the present invention, with a high critical current density characteristics can be obtained, provides a method for producing a MgB ₂ superconducting wire which does not require powder of Mg, a MgB ₂ superconducting wire obtained from this To do.

[0008]

The present invention has the above-mentioned object.
In order to achieve, MgB as a constituent member showing superconductivity ₂
In a method of manufacturing a superconducting wire having
A composite sheet material that combines a powdery B layer
And wrapping the composite sheet material on a metal core.
To form a composite rod, and draw wire on the composite rod.
The heat treatment should be applied to the filaments obtained by
By MgB₂Is characterized by generating
The present invention provides a method for manufacturing a conductor.

Further, in order to achieve the above object, the present invention is a superconducting wire having MgB ₂ as a constituent member exhibiting superconducting property, wherein a composite sheet material obtained by combining a Mg sheet and a powdery B layer is used as a metal. MgB ₂ produced by subjecting a composite rod-shaped body wound on the core
The present invention provides a superconducting wire rod.

In many cases, the above-mentioned filamentous body is formed on the basis of the above-mentioned assembly of composite rod-shaped bodies. Specifically, after extruding a composite rod-shaped body, swaging, drawing, and the like, a plurality of processed bodies processed by surface-reducing processing means such as wire gathering together, and then subjecting this to surface-reduction processing It is a linear body, and copper pipes, etc. are used for the assembly of the surface-reduced products of the composite rod-shaped body, and extrusion processing etc. are performed with a plurality of the surface-reduced products inserted in it. After that, the surface is reduced to obtain a linear body having a predetermined size.

As the composite sheet material of the Mg sheet and the powdery B layer in the above manufacturing method, for example, Mg
The sheet B may be formed by coating or spreading the layer B, or the sheet B may be sandwiched on both sides by a Mg sheet in a sandwich form. It can be said that this is a practical structure because it has the effect of preventing the powder from separating and stably holding the layer B.

The ratio of Mg and B is preferably such that the latter is 2 ± 0.2 mol with respect to the former 1. This is MgB ₂
From the stoichiometric ratio of, the molar ratio of the two is Mg: B =
The molar ratio should be 1: 2, but the melting point of Mg should be 65
Although it is as low as 0 ° C., that of B is as high as 2300 ° C. Therefore, at the final heat treatment temperature of 600 to 800 ° C., B component that does not react with Mg may remain in the wire. In order to prevent the above and increase the space factor of MgB ₂ , it is recommended that the ratio of B is 0.2 mol less at the maximum as a preferable form.

On the other hand, when the molar ratio of B is 0.2 mol more, which is the opposite of the above, the surface area of powder B is larger than that of sheet Mg, and therefore the thickness of the composite sheet material of Mg and B is large. When the thickness is large or when the thickness of the Mg layer and the B layer when processed into the final wire before heat treatment is on the order of several tens of μm, there is a possibility that unreacted Mg will remain. The molar ratio of B is increased by 0.2 mol at maximum.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of a method for manufacturing a superconducting wire according to the present invention and a superconducting wire obtained by the method will be described. FIG. 1 shows a manufacturing procedure. First,
In the step (a), the average particle size is 0.9 μm,
A powdery B having a purity of 99.9% is prepared, and the slurry 1 is prepared by mixing this with glycerin serving as a binder.

Then, this slurry 1 was treated with 0.
After being coated on a Mg sheet 2a having a thickness of 2 mm by a screen printing method, it is dried in an Ar gas atmosphere at 200 ° C., and glycerin is evaporated as described above to form a powdery layer 3 of B. .

Next, after confirming that the molar ratio of Mg and B in the obtained composite is Mg: B = 1: 1.1, in the step (b), the same Mg content as that of the sheet 2a is obtained. Sheet 2b is laminated on layer 3 so that the molar ratio is M
A composite sheet material 4 having a predetermined configuration in a sandwich shape of g: B = 1: 2.2 is manufactured.

(C) shows the composite sheet material 4 having a diameter of 8 mm.
Shows a step of manufacturing a composite rod-shaped body by winding 10 layers of Nb core material 5 of FIG.
The process of assembling into a single billet that is performed after that is shown.

In the step (d), first, the step (c)
The inner diameter of the composite rod 6 obtained in step 25 mm x the outer diameter 27 mm
Insert it into the copper pipe 7 of
Insert into the copper pipe 8 of 7.1 mm x 29 mm outer diameter,
Further, a single billet is constructed by attaching a copper plug and an iron plug to the front and rear ends of the pipe 8.

(E) shows an extrusion step using a hydrostatic extruder, in which the single billet obtained in step (d) is extruded to have an outer diameter of 12 mm. Then, in the step (f), the extruded billet was adjusted to have an opposite side dimension of 1.4.
After drawing into hexagonal wire 9 having a hexagonal cross section of mm, (g)
In the process of, these are assembled and made into a multi-billet.

The multi billet is produced by setting the hexagonal wire 9 to 150 m.
Cut into m length, which is 29mm inner diameter x 32 outer diameter
By inserting 349 pieces of hexagonal sides in close contact with each other in a copper pipe 10 of mm × 150 mm in length, and attaching a copper plug and an iron plug to the front and rear ends of the pipe 10, respectively. Done.

The multi-billet 11 is then subjected to the step (h).
In the step (i), the wire is extruded to a predetermined diameter by a hydrostatic extruder, and then wire drawing is performed in the step (i) until a filament having an outer diameter of 0.8 mm is obtained. Heat treatment is carried out at 700 ° C. for 5 hours, whereby MgB ₂ is produced.

FIG. 2 shows the mutual relationship between the magnetic field and the critical current density of the MgB ₂ type superconducting wire obtained as described above. According to the figure, it is possible for the MgB ₂ -based superconducting wire manufactured according to the present embodiment to obtain a critical current density characteristic comparable to that of Nb-Ti at a temperature of 10K, and a 10K-class conduction cooling method can be used to obtain 7- It is shown that it is possible to manufacture a magnet showing a magnetic field generation of 8T.

In order to reduce the load on the refrigerator based on the originally high critical temperature of the MgB ₂ system superconductor, and to provide a quench-free superconducting magnet based on the ultra-fine multicore structure, the embodiment shown in FIG. It can be said that the obtained superconducting wire is very useful.

[0024]

As described above, according to the method for manufacturing a superconducting wire according to the present invention, the Mg sheet and the powder B are coated by applying the powder B onto the Mg sheet.
To form MgB ₂ by constructing a composite sheet material that combines the above, and subjecting the composite rod-shaped body wound around a metal core material to predetermined processing such as wire drawing and heat-treating the obtained filamentous body. Therefore, it is possible to provide a practical manufacturing method that does not require pulverization of Mg. Since the MgB ₂ -based superconducting wire thus obtained has high critical current density characteristics, it is possible to construct a superconducting magnet or the like with high practicality.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a method for manufacturing a superconducting wire according to the present invention, in which (a) to (j) show the procedure.

FIG. 2 is an explanatory diagram showing the mutual relationship between the magnetic field and the critical current density of the MgB ₂ -based superconducting wire obtained from the embodiment of FIG.

[Explanation of symbols]

1 slurry 2a, 2b Mg sheet 3 Layers of powdered B 4 Composite sheet material 5 Nb heartwood 6 composite rods 7,8,10 copper pipes 9 Hexagonal line 11 multi billets

Claims (5)

[Claims] 1. A method of manufacturing a superconducting wire having MgB ₂ as a constituent member exhibiting superconductivity, comprising a composite sheet material in which a Mg sheet and a powdery B layer are combined, and the composite sheet material is made of metal. A composite rod-shaped body is formed by winding it around a core material, and MgB ₂ is generated by heat-treating a filament obtained by subjecting the composite rod-shaped body to a predetermined surface-reducing process such as wire drawing. A method for manufacturing a superconducting wire. 2. The heat treatment step is performed on a plurality of surface-reduced bodies of the composite rod-shaped body that are assembled and processed into the linear body. Manufacturing method of superconducting wire. 3. The step of constructing the composite sheet material comprises:
2. The method for producing a superconducting wire according to claim 1, wherein the composite sheet material is formed so that the powdery B layer is sandwiched by the Mg sheets from both sides. 4. The step of forming the composite rod-shaped body is performed so that a molar ratio of the Mg and the B is Mg: B = 1: 2 ± 0.2. A method for producing the superconducting wire described. 5. A superconducting wire having MgB ₂ as a constituent member exhibiting superconductivity, said MgB ₂ comprising Mg sheet and said powder B by applying powder B on Mg sheet or the like. M produced by heat-treating a composite rod-shaped body obtained by winding a composite sheet material in which layers of
A superconducting wire which is gB ₂ .