KR102002372B1 - Manufacturing method for superconducting wires using taping type and superconducting wire MgB2 and apparatus for making them - Google Patents

Abstract

The present invention relates to a method for manufacturing an MgB_2 superconducting multi-core wire rod, comprising: a step of coupling a plurality of multi-core wire rods through taping; a step of inserting the coupled plurality of multi-core wire rods into a tube; and a step of drawing and processing the inserted tube. Therefore, the method for manufacturing an MgB_2 superconducting multi-core wire rod can manufacture a wire rod having a uniform cross section shape and no distortion by applying taping to a drawn and processed single-core wire rod and, accordingly, can manufacture a superconducting wire rod with excellent physical characteristics such as critical current density.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a MgB2 superconducting wire manufactured by a taping method, and a MgB2 superconducting wire and a superconducting multi-

The present invention relates to a method for manufacturing MgB ₂ superconducting wire by taping, a MgB ₂ superconducting wire manufactured by the method, and a manufacturing apparatus for manufacturing the same. More particularly, the present invention relates to a method for manufacturing a MgB ₂ superconducting wire, in the manufacturing apparatus for preventing the distortion, and the diffusion barrier layer damage, and the threshold field density, etc. the manufacturing superior, MgB ₂ superconducting wire production method MgB ₂ superconducting wire according to the taping method can be produced, whereby the MgB ₂ superconducting wire and prepared by this .

Since the discovery of the superconducting phenomenon of MgB ₂ , many studies have been made, but studies for practical use thereof have been actively conducted. Generally, a superconducting wire having a possibility of practical use generally uses a superconducting wire of a multi-core type rather than a single core in view of improvement of thermal stability and reduction of AC loss. In the case of multi-core superconducting wire, if the integrity of the module can not be secured, the critical current characteristic is low, and a large number of disconnection occurs.

In order to secure uniform module assembly position in multi-core wire assembly process and taping process to prevent twisting during wire rod processing, MgB ₂ multi-core wire material is excellent in critical current characteristics and can manufacture more than 6km of wire rods.

However, in order to fabricate MgB _double- layered wire, it is necessary to increase the initial assembly diameter of the multi-core wire or to increase the length of the assembly. If the assembly wire diameter is increased, the total processing amount increases, .

1 and 2 is an assembly process and the photo of the MgB ₂ multi-core wire material made according to the conventional assembly process.

Referring to FIG. 1, after the single core wire is drawn, the single core wire is wound into a Cu tube, and then drawn again.

The problem is that the single core wire to be loaded in the Cu tube is not fixed and rotation of the swaging module in the drawing process is caused to deteriorate the integrity of the wire and cause the breakage to occur (see FIG. 2).

That is, when the assembly length is increased by 2 m or more due to the necessity of increasing the assembly length in a certain wire diameter, the straightness of the single wire becomes worse, and there is a problem in the soundness of the wire in the drawing process due to the unevenness of the module position . Therefore, it is necessary to secure the assembly integrity of the multi-core wire at a length of 2 m or more for manufacturing of the wire.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for manufacturing a wire rod, which is capable of preventing module damage (module shape distortion, damage to the diffusion preventing layer, and sausaging phenomenon) the properties such as density to provide a superconducting wire excellent MgB _2.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a method of manufacturing an MgB ₂ superconducting multi-core wire, comprising: taping and binding a plurality of multi-core wires; Charging a plurality of bundled multi-core wires into a tube; And drawing the loaded tube.

Here, the tube and the taping tape may be formed of copper (Cu) or a copper alloy (Cu alloy).

Here, the taping may be performed at an angle of 10 to 30 degrees with respect to the longitudinal direction of the multi-core wire.

Here, the step of taping and binding the plurality of multi-core wire materials can be performed by dividing a plurality of multi-core wire materials charged into the tube into the same number.

Here, the center of the tube may be provided with a circular rod capable of fixing the module.

The MgB ₂ is a superconducting wire produced by the MgB ₂ superconducting multi-core wire rod manufacturing method according to an embodiment of the invention.

An apparatus for manufacturing an MgB ₂ superconducting multi-core wire according to an exemplary embodiment of the present invention includes a multi-core wire guide unit having a hole formed therein to seat a plurality of multi-core wire materials along a hole to guide movement of the multi-core wire material in one direction; And a taping portion for taping a plurality of multi-core wires with a copper tape by turning the multi-core wire moving along the multi-core wire guide portion at a predetermined angle.

Here, the taping portion may include a taping angle adjusting portion for adjusting the tapping angle by turning the multi-core wire guide portion by a predetermined angle, A support plate extending upward from an upper surface of the tapping angle adjusting portion; A copper tape supply portion rotatably coupled to the support plate and supplying a copper tape; And a tension adjusting unit for adjusting the tension of the copper tape supplied to the copper tape supply unit and supplied to the copper tape supply unit.

The method for manufacturing MgB ₂ superconducting wire according to the present invention, the MgB ₂ superconducting wire and the superconducting multi-core wire manufacturing apparatus manufactured by the taping method according to the present invention can be applied to a single wire drawing process for taping, As a result, it is possible to manufacture a superconducting wire having excellent physical properties such as critical current density and the like.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 and 2 are photographs and a process of assembling the MgB ₂ multi-core wire manufactured according to the conventional assembling process.
3 is a flowchart of a method for manufacturing an MgB ₂ superconducting wire by taping according to an embodiment of the present invention.
4 is a conceptual diagram of a method of taping MgB ₂ superconducting wire by taping according to an embodiment of the present invention.
5 is a photograph of a state of being processed through a taping method according to the first embodiment of the present invention and a state of being drawn and processed.
6 is a photograph of a state of being processed through a taping method according to a second embodiment of the present invention and a state of being drawn and processed.
7 is a graph comparing threshold current densities according to the present invention and a comparative example.
8 is a comparative photograph according to the taping angle according to the embodiment of the present invention.
9 is a perspective view of a manufacturing apparatus for manufacturing a superconducting multi-core wire according to an embodiment of the present invention.
10 is a graph showing a change in critical current density according to the length of a MgB ₂ wire according to another embodiment of the present invention.
11 is a graph showing a change in critical current density of an MgB ₂ wire according to another embodiment of a diffusion preventing layer according to another embodiment of the present invention.
12 is a photograph showing the cross-sectional shape of MgB ₂ according to the type of the diffusion preventing layer according to another embodiment of the present invention, wherein (a) is Nb as the diffusion preventing layer and (b) is the Ti alloy.
FIG. 13 is a photograph showing the cross-sectional shape of the MgB ₂ wire using the Ti alloy as the diffusion preventing layer according to another embodiment of the present invention. FIG.
FIG. 14 is a photograph showing the cross-sectional shape of MgB ₂ after drawing according to another embodiment of the diffusion preventing layer according to another embodiment of the present invention. FIG. 14 (a) is a photograph showing Nb as a diffusion preventing layer and FIG.
15 shows the results of EDX analysis according to another embodiment of the present invention, wherein (a) shows Nb as the diffusion preventing layer and (b) shows the Ti alloy.
FIG. 16 is a result of surface roughness test of the diffusion preventing layer according to another embodiment of the present invention, wherein (a) shows Nb as a diffusion preventing layer and (b) shows a Ti alloy.
17 is a graph showing changes in hardness of the diffusion preventing layer according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that, in the drawings, the same components are denoted by the same reference symbols as possible. Further, the detailed description of known functions and configurations that may obscure the gist of the present invention will be omitted. For the same reason, some of the components in the drawings are exaggerated, omitted, or schematically illustrated.

Also, throughout the specification, when an element is referred to as " including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise. Also, throughout the specification, the term " on " means located above or below a target portion, and does not necessarily mean that the target portion is located on the upper side with respect to the gravitational direction.

Referring to FIG. 3, the MgB ₂ superconducting multi-core wire manufacturing method according to an embodiment of the present invention can be performed in the following sequential order and will be described with reference to FIGS. 4 to 8.

First, a plurality of multi-core wires 110 are tied with a copper tape 120 and bound (S100).

At this time, the method of bundling a plurality of multi-core wires 110 can be combined in two ways. 4 (a), a method of taping a plurality of multi-core wire materials 110 with a copper tape 120 at one time and charging them into the tube T (hereinafter referred to as first embodiment) 4 (b), a plurality of multi-core wire materials 110 charged into the tube T are divided into the same number (hereinafter, referred to as a second embodiment). 4 (b), three multi-core wires 110 are bundled and taped to the copper tape 120a and taped to the copper tape 120b. However, when the multi core wire 110 is wound around the copper wire 120a, When taping with the tape 120a, the number of the multi-core wires 110 is not limited to three.

In the present invention, a tape refers to any type of member that physically binds a wire as a foil, a strip, or a sheet, and can be fused when a tube is manufactured, and this is also within the scope of the present invention. Also, even if the tape is fused and can not be distinguished, it is at least within the scope of the present invention to use it at least during the manufacturing process. Further, the copper tape may include a different material as a tape including copper.

At this time, when taping the multi-core wire 110 with the copper tape 120, taping is performed with a predetermined angle as shown in Fig. At this time, the turned angle may be taped at an angle of 10 to 30 degrees with respect to the longitudinal direction of the multi-core wire.

If the taping angle is set to 10 degrees, the tape may be fed in a distorted state due to the right flange interference at the time of supplying the copper tape, so that a distorted portion may remain after taping. On the other hand, if the taping angle is set to be as large as 50 degrees, the left flange is interfered with, and the lifting shape is generated while the copper tape is transported.

Most preferably, when the copper tape is supplied while maintaining the taping angle at 20 degrees, interference between the flanges does not occur, and the taping overlap width can be kept constant.

A plurality of multi-core wire bundled through the above-mentioned fixation is charged into the tube T (S200). At this time, a circular rod 130 for fixing the module may be provided at the center of the tube. The tube T may be formed of the same copper material as the copper tape.

Finally, the loaded tube is drawn (300). The drawing process may be repeated several times.

Comparison Review

For the comparative example, the first embodiment and the second embodiment formed without taping, the assembly shape and straightness, cross-sectional shape observation using an optical microscope, and critical current density were compared and evaluated.

(1) Experimental conditions

In order to compare the first embodiment with the second embodiment, the following experimental procedure was preceded. First, in the first embodiment, a module is assembled in the form of 18 + 1 (a round rod of a multi core wire + copper material), and taping is performed once at the outermost portion. In the second embodiment, three tapes of single core wire are taped, and six taped tapes are assembled together with a center copper spacer, and additional taping is performed at the outermost periphery. MgB ₂ was mixed with Mg (75 μm) and B powder (<400 nm) together with media for 4 hours or more using a wet mixing process, dried and sieved, (OD21 x ID 16 x L2,000 mm) tube with a relative density of 0.3 or higher.

Tough pitch copper was used for the copper alloy tape used for taping. During taping, the tension was given a tension suitable for binding between the copper alloy tape and the module. The thickness of the copper alloy tape may vary depending on the taping tension, but a suitable 0.1 to 0.25 mm is applied. After assembling the taped bundle into a Cu sheath, MgB ₂ multi-core wire with a final wire diameter of 1.03 mm or less was manufactured using a drawing process with a metal tube tube with a unit reduction rate of 15%. The MgB ₂ multi core wire was heat treated at 700 ㅀ C temperature for 1 hour in Ar atmosphere to form final MgB ₂ phase.

(2) Assembly shape and straightness

(Comparative Example) assembled at regular intervals without taping, the assembled shape of the multi-core wire subjected to the first embodiment (taping once) and the second embodiment (twice taping) .

In the comparative example, module detachment occurred in the process of inserting into the copper tube, and the module shape was not constant due to the straightness difference of the module and the tolerance between the tube and the module. Also, module unevenness occurred due to the rotation of the module in the swaging process when drawing the assembled multi-core wire.

On the other hand, in the assembly result of the first embodiment, the assembled shape of the line and the rear was different from the hexagonal shape and the circular shape, and twist of the module was confirmed (see Fig. 5 (a)). It is considered that this is because 12 single core wire modules are additionally arranged and taped along the circumferential direction in the state that the straightness of six single core wires arranged around the copper circular rod is lacked. Accordingly, it was found that further fixing of the inner module by taping is further preferable.

As a result of the assembly of the second embodiment, the assembled shape of the multi-core wire was kept from the front to the back of the assembled multi-core wire, and the module position was the same even when the length was 3,000 mm (see FIG. The multi-core wire with the same module shape and position was uniformly maintained in the drawing process.

(3) Observing the cross-sectional shape

The cross section of the wire rod for each of the first and second embodiments was observed through an optical microscope on the MgB ₂ multi-core wire (1.03 mm) produced through the drawing process.

The first embodiment was taped with a copper alloy tape having a thickness of 0.1 mm, and a cross section of a final wire diameter of 1.03 mm was observed. As a result, it was confirmed that a taped section was present in the outermost module, Respectively.

The taping thickness of the second embodiment was 0.1 mm for the inside and 0.2 mm for the outside. The copper alloy tape was used for taping, and the section of the final wire diameter was drawn to 1.03 mm. As a result, The internal tape thickness was 6.9 ~ 7.4 ㎛ and the external tape thickness was 14.8 ~ 16.1 ㎛ in the final wire diameter. The outer tape was 0.2 mm thick and the inner tape thickness was 0.1 mm, resulting in thicker outer tape. If the thickness of the inner tape is the same as that of the outer tape, the taping becomes difficult and the assembly line diameter becomes large. Therefore, as described above, it is preferable to use a relatively thinner inner tape than the outer tape.

(4) Critical current density

The critical current density was measured by the energization method. To prepare the critical current measurement, MgB ₂ wire of about 1 m or more is wound around a barrel made of a Cu ring and a Ti alloy, and then soldered to a MgB ₂ wire and a copper ring, a copper ring and a measuring probe current- lead) were electrically connected and a voltage tap interval of 50 cm was given.

The comparison example in which taping is not applied and the wire material of MgB ₂ of the first embodiment and the second embodiment are compared in Table 1 as described above.

[Table 1]

As shown in Table 1, the second embodiment shows that the critical current density Jc can be increased by 55% or more as compared with the comparative example. Compared with the first embodiment, the critical current density Jc Respectively. This is shown in the graph of FIG. As described above, the critical current density of the second embodiment is increased as compared with the comparative example and the first embodiment because the multi-core wire 120 is divided into a plurality of the same number, and uniformity of the module shape by taping, Is improved and the wire diameter can be formed more compactly.

9 is a perspective view of a manufacturing apparatus for manufacturing a superconducting multi-core wire according to an embodiment of the present invention.

Referring to FIG. 9, an apparatus for manufacturing an MgB ₂ superconducting multi-core wire according to an embodiment of the present invention includes a multi-core wire guide unit 210 and a taping unit 220.

The multi-core wire guiding part 210 has a hole formed therein to seat a plurality of multi-core wire materials along the hole, thereby guiding the movement of the multi-core wire material in one direction.

The taping portion 220 is provided with a taping angle adjusting portion 221, a support plate 222, a copper tape supply portion 223, and a copper tape supply portion 223, which tapes a plurality of multi- And a tension adjusting unit 224.

The tapping angle adjusting unit 221 adjusts the taping angle by turning the multi-core wire guide unit at a predetermined angle. The tapping angle adjusting unit 221 may be provided with a driving motor for adjusting the angle of the lower portion and may be adjusted to a corresponding angle according to a user's input condition.

The support plate 222 extends upward from the upper surface of the tapping angle adjusting part 221 and is coupled to the copper tape supply part 221 and formed with a hole to be coupled with the copper tape supply part 223. The bearings can be coupled to the holes for smooth rotation of the copper tape supply part 223.

The copper tape supply unit 223 is rotatably coupled to the support plate 222 to supply the copper tape. At this time, the copper tape supply unit 223 can be detachably coupled to the copper tape.

The tension adjusting portion 224 is coupled to the copper tape supply portion 223 to adjust the tension of the supplied copper tape. The tension adjusting unit 224 adjusts the pressure transmitted to the copper tape supply unit 223 through the strength of the spring inserted along the axial direction of the copper tape supply unit 223 to adjust the pressure of the supplied copper tape.

Meanwhile, the wire rod according to another embodiment of the present invention can be manufactured by the following method.

Hereinafter, the MgB ₂ superconducting multi-core wire can be formed by molding the superconducting wire material MgB ₂ formed of copper as described above and applying the taping method according to the first and second embodiments described above to the molded superconducting wire material The MgB ₂ superconducting wire will be described more specifically.

The MgB ₂ superconducting wire according to another embodiment of the present invention includes a tube; At least one MgB ₂ filament wire loaded into the tube; And a diffusion preventing layer surrounding the MgB ₂ filament wire and preventing reaction between the tube metal and Mg. The diffusion preventing layer has a hardness increasing index of not more than 0.3 with respect to strain (?) And an initial hardness value of not more than Hv 140 .

The tube prevents the superconductivity from deteriorating due to contact with the outside, and is used for fixing Mg and B powder to be filled in the drawing process, and forms the outermost of the superconducting wire. The tube can block external contact of the superconducting wire and can be used without any limitation as long as it is made of a material which can be easily drawn and drawn. Preferably, stainless steel, copper, nickel, iron or brass can be used. When the superconducting superconducting structure has a double structure or a multiple structure, it is possible to use a plurality of coaxial tubes or a plurality of tube assemblies each having a plurality of tubes for separating the layers. In this case, each tube may be made of the same material, Tube.

The MgB ₂ is a material known to have superconductivity at 39 K, which is a relatively high temperature, and is charged into the tube in the form of a filament wire to be produced as a wire by drawing. The superconductivity of MgB ₂ has a critical temperature of the highest temperature among the non-oxide superconductors, and conventionally, a method of manufacturing superconductors by using Nb as a barrier metal (diffusion barrier) is well known. However, in the present invention, Ti is used in place of Nb, and since superconducting core wire is made of MgB ₂ , it is possible to manufacture superconducting wire using the existing substrate as it is.

The MgB ₂ may be used alone, but may be used by mixing MgB ₂ powder, Mg + B powder, MgB ₂ + X powder, Mg + B + X powder, It is also possible. Here, X means elements for increasing the flux pinning effect or reducing the porosity of MgB ₂ .

The diffusion preventing layer is used to prevent Mg powder from diffusing into the tube metal during the drawing process. It has been common to use Nb in the past, but in the present invention, it is preferable to use an alloy containing Ti or Ti.

The Ti alloy to be used at this time may be an alloy of Ti and a suitable metal, but may preferably further include Nb. More preferably, an alloy containing 20 to 60 wt.% Nb and the balance Ti can be used.

The diffusion prevention layer may have a hardness increase index of not more than 0.3, preferably not less than 0.2 and not more than 0.3, and an initial hardness value of Hv 140 or less.

It is known that Nb, which has been used in the past, is very expensive, and the irregularities of Nb and powder interface are generated to lower the critical current density characteristic. Particularly, in the case of the diffusion preventive layer, the higher the hardness increase index with respect to the strain (?), The more likely damage is caused by the drawing process. In the case of the diffusion preventive layer using Nb, the hardness increase index with respect to the strain (ε) is as high as 0.49. Therefore, in the case of drawing with a low wire diameter, not only the shape of the module becomes uneven, but also the inner surface of the Nb tube , The intergranular current density characteristics of the deep MgB ₂ wire are lowered and the occurrence frequency of the disconnection is increased and it is difficult to manufacture the wire rods.

The diffusion preventing layer may have a reduced initial hardness value by heat treatment. If an alloy containing Ti or Ti is used, additional heat treatment may be required since disconnection may occur as the initial hardness increases. If Mg is oxidized and preventing Mg and B by a reaction temperature and a low vacuum of less than 500 ℃ to prevent the MgB ₂ is not formed that the MgO is formed: in (degree of vacuum less than ^10-3), and an inert gas atmosphere It is preferable to perform heat treatment.

According to the use of the alloy containing Ti or Ti, the MgB ₂ superconducting wire has a high critical current density of at least 2.0 × 10 ⁵ A / cm 2 (4.2 K, 4 T) or more compared to the superconducting wire using Nb as the diffusion preventing layer Lt; / RTI &gt;

The superconducting wire may be manufactured by a drawing process, and the surface roughness Ra of the superconducting wire in the circumferential direction may be 5 탆 or less, preferably 4.5 탆 or less.

In the case of conventional Nb diffusion preventive layer, the hardness is low, and as the processing progresses, the irregularity of the internal interface deepens due to the friction with the powder, and the critical current density of the material decreases. This irregularity can be measured by observing the surface roughness and the surface roughness in the circumferential direction of the conventional Nb diffusion preventing layer is measured to be about 14 탆. However, when the alloy containing Ti or Ti as described in the present invention is used, the surface roughness (Ra) in the circumferential direction is reduced to 5 μm or less, preferably 4.5 μm or less Lt; / RTI &gt;

Example

Mg and B were weighed in a molar ratio of 1: 2 to 2.1, and then mixed with ZrO ₂ ball and media for 4 hours or longer and dried to prepare a mixture.

(OD 21 x ID 16 x L 2 000 mm) having a Vickers hardness value of Hv 130 and Cu, which is a microstructure in which recrystallization occurs by heat treatment of an alloy containing 45 wt.% Of Nb and a balance of Ti The matrix tube (OD25 x ID 22 x L2,000 mm) was used for each tube.

The mixture of Mg and B was charged into the Ti alloy tube at a relative density of 0.3 or more, and the Ti alloy tube was inserted into the tube. Ti alloy / Cu tube was cut at a reduction ratio of 15% to prepare MgB ₂ single core wire.

In order to confirm the effect depending on the type of the diffusion preventing layer, a single core wire using Nb, Fe and Ti was prepared in place of the Ti alloy, and the change in critical current density was measured. The results are shown in Table 2 below.

[Table 2]

The critical current density was measured by the energization method. To prepare the critical current measurement, MgB ₂ wire of about 1 m or more is wound around a barrel made of a Cu ring and a Ti alloy, and then soldered to a MgB ₂ wire and a copper ring, a copper ring and a measuring probe current- lead) were electrically connected and measured at 50 cm length with voltage taps.

As shown in Table 2, when the Ti alloy and pure-Ti were used as the diffusion preventing layer, it was confirmed that they had a high critical current density.

In order to confirm the critical current characteristics of the MgB ₂ wire according to the type and thickness of the diffusion preventing layer, the critical current density according to each diameter of the single core wire made of the Ti alloy and Nb as the diffusion preventing layer was measured, Respectively.

[Table 3]

As shown in Table 3, it was confirmed that all the wire diameters using the Ti alloy have a higher critical density current than the single core wire using Nb.

The cross - sectional shape of the MgB ₂ wire was examined by using a single core wire made of Ti alloy and Nb as a diffusion barrier.

[Table 4]

As shown in FIG. 14, when the diffusion preventive layer was Nb, it was confirmed that a breakage occurred in a part of the wire due to the friction with the powder, resulting in the phenomenon of small sagging. However, in the case of using Ti alloy, it was confirmed that the wire material was uniformly produced and the n-value was also high (Table 4).

Preparation of Multi-core Wire The MgB ₂ single-core wire and the single center Cu spacer, which were prepared by cutting and cutting 18 pieces of the above-mentioned Ti alloy as a diffusion barrier layer, were assembled into a 1 + 18 bundle shape after pickling and washing.

The bundle was inserted into a Cu tube tube as a stabilizer material. Then, the MgB ₂ multiwall wire having a final cumulative strain of 9.1 or more and a final diameter of 1.03 mm or less was manufactured using the drawing process at a unit reduction rate of 15%. The prepared MgB ₂ multi-core wire was heat-treated at 700 ° C for 1 hour in an Ar atmosphere to form a final MgB ₂ phase (FIG. 13).

As a comparative example, an MgB ₂ multi-core wire of 1.03 mm or less was manufactured without using a single tube by using a tube tube using Nb instead of the Ti alloy

MgB of 1.03, 0.90, 0.84mm wire diameter to determine the critical current of the wire diameter variation _second wire critical current measurement results as shown in Figure 11, MgB ₂ wires is spread Nb with Ti alloy as diffusion barrier layer at each wire diameter compared with the MgB ₂ wire with a layer it showed a high critical current density in at least ^{2.0X10 5 a / ㎠ (4.2K,} 4T).

Filament barrier surfaces having the same length were observed to confirm the cause of the improvement of the critical current density in terms of the soundness of the wire.

In order to evaluate the integrity of the module of the diffusion barrier layer, the Cu tube was removed from the nitric acid solution after manufacturing the multi core wire using the drawing process, and the shape of the module was observed using an optical microscope and a scanning electron microscope. The composition of the diffusion barrier layer was analyzed by EDX line analysis.

As a result, the wire using the Ti alloy diffusion barrier layer was relatively less defective and the interface uniformity with the MgB ₂ core was also good (FIG. 12).

The interfacial state between the wire rod (Example) in which the Ti alloy was used as the diffusion preventing layer (Example) and the MgB ₂ core in the wire rod (Comparative Example) using the barrier inner surface from which the Mg and B powders were removed was measured, It was confirmed that the roughness in the transverse direction and the damage of the diffusion preventing layer were low in the species generated by the friction with the powder during the drawing process (Fig. 12 and Table 5).

At this time, the cross section of the wire according to the machining direction was observed with a scanning electron microscope, and the surface roughness Ra was measured using a non-contact surface roughness measuring device (OLYMPUS, OLS4100) using a laser.

[Table 5]

In order to confirm the change of physical properties by the heat treatment, the wire rod of the example, the wire rod before the heat treatment and the wire rod using the existing Nb as the diffusion barrier layer (comparative example) were tested.

In order to observe the change in the hardness of the diffusion preventing layer as the total deformation amount of the wire rod was increased, the hardness of the diffusion preventing layer was measured using a micro Vickers hardness tester (applied load: 300 g) at the wire rod section.

As shown in FIG. 17, when the MgB ₂ wire was manufactured using Nb as the diffusion preventing layer, the hardness increase index was as high as 0.49 as the wire rod was drawn. As a result, when the wire is drawn with a low wire diameter, the module shape is uneven and the interfacial irregularity of the inner surface of the Nb tube due to the friction with the powder is severe, so that the critical current density characteristic of the MgB ₂ wire becomes low and the frequency of disconnection becomes high, .

The initial hardness reached Hv 170 when the wire was manufactured using Ti alloy without heat treatment and the hardness increase index according to the drawing process was 0.21. In this case, although the hardness increase index due to the drawing process was low, the initial hardness was high and the total cumulative deformation increased to 9.0 or more, resulting in hardness value of Hv 260 or more.

The initial hardness was Hv 130 when the heat treated Ti alloys were used and the hardness increase index according to the drawing process was 0.26. This indicates that the increase in the hardness increase index due to the drawing process is higher than that of the Ti alloy without heat treatment, but the hardness value according to the initial hardness and initial low hardness and total deformation amount did not exceed 260, , It was confirmed that the critical current density of MgB ₂ wire was improved and the incidence of disconnection was lowered.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative of the present invention in order to facilitate description of the present invention and to facilitate understanding of the present invention and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

110: Multi-core wire
120: Copper tape
130: round rod
210: Multi-core wire guide
220:

Claims (8)

As a method for manufacturing an MgB ₂ superconducting multi-core wire,
Forming a plurality of bundles by taping a plurality of multi-core wire materials into strip-shaped inner tapes;
Taping the plurality of bundles with a strip-shaped outer tape to bind the plurality of bundles to form a bundle;
Charging the multi-core wire formed of the bundled bundle into a tube; And
And drawing the loaded tube,
Preferably,
The tape is taped so as to overlap the plurality of the multi-core wires, and advances at an angle of 10 to 30 degrees with respect to the longitudinal direction of the multi-
The inner tape
MgB ₂ superconducting multi-core wire rod production method characterized in that the relatively thin layer is formed thick relative to the external tape. The method according to claim 1,
MgB ₂ superconducting multi-core wire material producing method for a tape is characterized in that the copper (Cu) or a copper alloy to the taping and the tube. delete The method according to claim 1,
The step of taping and binding the plurality of multi-core wire is, MgB ₂ superconducting multi-core wire rod production method of a plurality of multiple-strand wire that is charged into the tube characterized in that the progress divided by the same number. The method of claim 1, wherein
Center of MgB ₂ superconducting multi-core wire rod manufacturing method being provided with a round rod to secure the multi-core wire is formed with one of said bundles in said tube. An MgB2 superconducting wire produced by any one of claims 1 to 2 and 4 to 5. A manufacturing apparatus for manufacturing a superconducting multi-core wire according to any one of claims 1 to 4,
A multi-core wire guide portion having a hole formed therein and seating a plurality of multi-core wire materials along the hole to guide movement of the multi-core wire material in one direction; And
And a taping portion for tapping the plurality of multi-core wire materials with a copper tape by turning the multi-core wire material moving along the multi-core wire guide portion by a predetermined angle of 10 to 30 degrees. _{2. The} manufacturing method of a MgB ₂ superconducting multi- . 8. The method of claim 7,
The taping portion,
A taping angle adjusting unit for adjusting the tapping angle by turning the multi-core wire guide unit by 10 to 30 degrees;
A supporting plate extending upward from an upper surface of the tapping angle adjusting portion;
A copper tape supply unit rotatably coupled to the support plate and supplying the copper tape; And
MgB ₂ production apparatus for producing a multi-core superconducting wire comprising the; tension adjusting unit for adjusting the tension of the copper tape to be supplied is coupled to the copper tape supply.

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