JPH06333450A - Manufacture of superconductive material and nb-al group superconductive wire - Google Patents

Abstract

PURPOSE:To obtain a superconductive material, with which a Nb-Al superconductive wire having the excellent cross-section occupying factor of a Nb3Al group superconductive phase and the excellent superconductivity such as critical current density or the like even in the case where a primary element wire is formed with multiple cores and this operation is repeated to form a high-order compound element wire can be formed with the excellent workability. CONSTITUTION:An Al group layer 2 is provided in the periphery of a secondary or more-order compound element wire having multiple Al group core wires 13, which is coated with a Nb layer 12, inside of a Nb surrounding layer 14, and the outside thereof are provided with at least one pair of layers 3, which consists of a Nb layer 31 and an Al group layer 32, and plural compound element wires 4 are housed inside of a support tube 6, and drawing is performed to form a high-order compound multi- core wire. This compound multi-core wire is used for the next element wire and the similar operation is repeated at a required time to form a superconductive material. Since this superconductive material includes the Al group material, which contributes to the generation of superconductive phase, at a large ratio, the generation of disconnection can be restricted remarkably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a superconducting material which has a large occupation area of Nb ₃ Al type superconducting phase and is excellent in superconducting properties such as critical current density and the like, and a method for producing the superconducting material. Nb-Al system superconducting wire.

[0002]

2. Description of the Related Art Conventionally, a bundle of primary wires made of an Al-based core made of Al or its alloy coated with an Nb layer is housed in an Nb tube and then drawn to form a secondary composite element wire having a multi-core structure, There has been known a method for manufacturing a superconducting material in which a wire bundle is housed in a Nb tube and a wire drawing process is repeated as necessary as a starting wire. Such tube accommodation method (composite processing method or niobium tube method)
Has the advantage that the multifilamentary strands can be easily made higher, and the superconducting wire can be obtained by heat-treating a multifilarized material to generate a Nb ₃ Al-based superconducting phase.

However, when the superconducting phase is generated, the Nb layer located on the outer periphery of each of the secondary composite wires or more, especially the tertiary composite wires or more does not contribute to the formation of the Nb ₃ Al type superconducting phase, Therefore, the Nb layer that does not contribute to the formation of the superconducting phase increases as the wire bundle is housed in the Nb tube and the wire drawing process is repeated to increase the number of cores in the higher order, and the Nb ₃ Al occupying the cross-sectional area of the superconducting wire increases. There was a problem that the area of the superconducting phase of the system was drastically reduced.

By the way, in a quaternary composite superconducting material using a tertiary composite element wire, Nb which does not contribute to the formation of a superconducting phase
The cross-sectional area of the layer may reach as high as about 90%, so that the cross-sectional area of the superconducting phase is about 10%.

[0005]

DISCLOSURE OF THE INVENTION The present invention has an advantage in that the cross-sectional occupancy area of the Nb ₃ Al-based superconducting phase is excellent and the superconductivity of the critical current density or the like is excellent even if a high-order composite element wire is obtained by repeating the multicore of the primary element wire. It is an object of the present invention to develop a method for producing a superconducting material capable of forming an Nb-Al superconducting wire having excellent characteristics with good workability.

[0006]

According to the present invention, an Al-based layer is provided on the outer periphery of a secondary or more composite element wire having an Al-based core wire coated with an Nb layer in a multi-core state in the Nb surrounding layer. Nb on the outside
Of a superconducting material, characterized in that at least one pair layer consisting of a layer and an Al-based layer is provided, a plurality of the layers are accommodated in a support tube, and the wire is drawn into a high-order composite multicore wire. Manufacturing method and Al-based layer is provided on the outer periphery of the elemental wire with the composite wire of the secondary or higher order as the starting elemental wire, and at least one pair layer of Nb layer and Al-based layer is provided outside the Al-based layer A plurality of wires are housed in a support tube, which is drawn to form a higher-order composite multicore wire, and the composite multicore wire is used for the next strand, and the above-mentioned operation is repeated a required number of times. It is intended to provide a Nb-Al-based superconducting wire comprising a method for producing a material and a heat-treated product of the above-mentioned superconducting material.

[0007]

By the above-described method in which the wire is surrounded by the Al-based layer and the paired layer of the Nb layer and the Al-based layer and accommodated in the support pipe and wire-drawn, excellent wire drawability through the support pipe is achieved. The strands can be easily made high-order, and the primary strands can be made multi-core efficiently, and at the time of making the strands higher-order,
The system layer and the pair layer can contribute to the formation of the Nb ₃ Al-based superconducting phase.

Therefore, it is possible to reduce the interposition of the portion that does not contribute to the formation of the superconducting phase, and to repeat the multi-core of the primary elemental wire to form a higher-order elemental wire, which is excellent in the cross-sectional occupying area of the Nb ₃ Al-based superconducting phase and is critical. A superconducting material capable of forming an Nb-Al-based superconducting wire having excellent superconducting properties such as current density can be obtained, and the superconducting phase ratio in the cross-sectional area of the superconducting wire can be easily controlled.

The method of attaching the Al-based layer or the pair layer to the above-mentioned strand itself has particularly excellent wire drawing workability as compared with the method of attaching them to the bundle of strands.
It shows good wire drawability comparable to the conventional method of making Al-based core wire multi-core through a tube.

[0010]

EXAMPLES The manufacturing method of the present invention is such that an Al-based layer is provided on the outer periphery of a secondary or higher-order composite element wire, and at least one pair layer consisting of a Nb layer and an Al-based layer is provided on the outer side of the Al-based layer, and a plurality of such A book is loaded into a Nb tube as needed and accommodated in a support tube, and then drawn to form a higher-order composite multicore wire, and the outer support layer is removed from the composite multicore wire as needed to obtain a superconducting material. I will get it.

In another manufacturing method of the present invention, the high-order composite multifilamentary wire obtained above is used as the next strand to be surrounded by the Al-based layer and the paired layer, and a plurality of the layers are surrounded by Nb as necessary. The superconducting material is obtained by repeating the operation of loading the tube into the support tube and the operation of wire drawing.

1 (A) and 1 (B) show a state during the manufacturing process of the present invention. FIG. 1 (A) shows that the outer circumference of the wire 1 is Al.
This is an exemplification of a system layer 2 and a pair layer 3 having a pair of an Al system layer 31 and a Nb layer 32 provided on the outer side thereof. In the present invention, 4 is the object to be housed in the support tube. Al
The system layer 2 may be omitted and replaced with the Al system layer 31 in the pair layer 3 as illustrated in FIG.

On the other hand, FIG. 1 (B) shows an example of a state in which a plurality of wires 4 to be housed are housed inside a support tube 6, and in this way, an Al series layer and a pair layer are formed on the outer circumference. In the present invention, a plurality of strands provided with a plurality of strands are accommodated in a support tube, and in the present invention, a higher-order composite multicore wire is made by drawing.

Reference numeral 5 in FIG. 1 (B) is an Nb tube. This remains as a matrix in the obtained superconducting wire and contributes to improvement of mechanical strength and stability and prevention of AC loss. Further, when the support tube is removed and is used as an elemental wire for forming a composite multifilamentary wire according to the present invention, it reacts with the Al-based layer (2) provided on the outer periphery thereof to contribute to the formation of a superconducting phase. Therefore, the Nb tube is used as necessary for loading the wire when the wire is housed in the support tube.

As an element wire used for forming a composite multifilamentary wire according to the present invention, an Al-based core wire (primary wire) in which an Al-based core 11 made of Al or an alloy thereof is covered with an Nb layer 12 as in the example shown in FIG. A secondary or higher-order composite strand having multiple strands 13 inside the Nb envelope layer in a multi-core state is used.

Therefore, the composite strand may be a secondary composite strand 1 having the primary strand 13 inside the Nb surrounding layer 14 in a multi-core state as illustrated in FIG. 1 (A). A third-order composite wire having the secondary composite wire in the Nb envelope layer in a multi-core state, and a quaternary composite wire having the tertiary composite wire in the Nb envelope layer in a multi-core state. It may be an appropriate stage such as a composite strand.

On the other hand, even when the operation according to the method of the present invention is repeated, the starting strand may be one having an appropriate composite order of a composite strand of the second or higher order. Generally, since a quaternary composite wire is a superconducting wire, a composite wire below the tertiary composite wire, especially a secondary composite wire is regarded as a starting wire.

The composite wire may have an appropriate cross-sectional outer shape other than the circular shape. A cross-sectional profile, such as the hexagonal cross-section illustrated in FIG. 2, that can be accommodated in the support tube with as little void space as possible is advantageous. In the composite wire 41 of FIG. 2, 17 is a composite wire composed of the multi-core layer 15 of the Al-based core wire and the Nb layer 16, and 18 is an Nb surrounding layer.

The primary wire 13 can be obtained by, for example, a method of accommodating an Al-based wire in an Nb tube and a wire drawing treatment, or a method of filling an Al-based melt in the Nb tube. The secondary composite element wire 1 can be obtained by, for example, a method in which a large number of primary element wires 13 are housed inside an Nb tube and a wire drawing process is performed. Further, a composite wire of the third order or higher having Al-based core wires in the multi-core state inside the Nb envelope layer is obtained by, for example, accommodating a large number of the composite wires of the second order or higher obtained according to the above in an Nb tube. It can be obtained by a method of wire drawing.

The Al-based layer or the paired layer of the Nb layer and the Al-based layer provided on the outer periphery of the composite element wire may be surrounded by a roll winding method, a vertical attachment method, or a horizontal winding method using foil. It may be formed by any method. In the pair layers, an alternate arrangement in which the Al-based layers including the Al-based layers provided immediately above the wires are inside and the Nb layers are outside is preferable from the viewpoint of generation of the superconducting phase.

When the composite according to the present invention is applied to the secondary composite wire and its tertiary composite wire a plurality of times until the desired superconducting material is obtained, It is advantageous for the generation of the superconducting phase that the Nb layer and the Al-based layer in the paired layer are unified in the same material.

In the above, the Al-based layer provided immediately above the strand is Nb ₃ due to the reaction with the Nb layer in the inner strand.
It is intended to mainly contribute to the generation of the Al-based superconducting phase. Therefore, the Al-based layer has a main purpose of converting the Nb layer portion, which has not contributed to the formation of the superconducting phase in the conventional method, to the superconducting phase. The Al-based layer may be replaced with the Al-based layer in the pair layer as described above.

On the other hand, the pair layer is an Nb layer and Al forming a pair.
The purpose is to mainly contribute to the generation of the Nb ₃ Al-based superconducting phase by the reaction of the system layer. Therefore, the occupancy rate of the superconducting phase in the cross section of the superconducting wire can be controlled efficiently depending on the number of the pair layers. Therefore, the pair layer can be provided with an appropriate number of layers such as one layer or two or more layers. When two or more pair layers are provided, a roll winding method of winding, for example, a superposed foil of Al-based foil 31 and Nb foil 32 in a roll shape as shown in FIG. 3 is advantageous in terms of work efficiency. Is.

In the above description, the thickness of the Nb layer is preferably 10 to 2000 μm, especially 150 to 1100 μm, since the thinner it is, the more preferable it is when the superconducting phase is generated. However, the thickness is not limited to this. On the other hand, the thickness of the Al-based layer is 1/2 or less of the Nb layer to be reacted, and especially 1/3 to 1/1 / from the viewpoint of efficient formation of the Nb ₃ Al-based superconducting phase with the Nb layer.
4 is preferable.

A particularly preferred method is a method in which each Al-based layer has the same thickness as the Al-based core diameter of the primary wire in the wire to be composited. As a result, the heat treatment conditions for producing the Nb ₃ Al-based superconducting phase can be unified within the material.

By the way, in the case of the Al-based layer having a thickness different from the Al-based core diameter, the heating conditions for generating the superconducting phase are different between the Al-based core portion and the Al-based layer portion. It is easy to induce a problem of non-generation of Nb ₃ Al based superconducting phase due to insufficient heat treatment, or a problem of deterioration of superconducting properties due to coarsening of crystal grains of Nb ₃ Al based superconducting phase due to excessive heat treatment.

In the present invention, the Al-based core and the Al-based layer are, in addition to Al, Al-Mg, Al-Ag, Al-Cu, and Al-Ge.
It may be formed of an Al alloy such as. Also Nb tube and N
The b (enveloping) layer is made of Ti, Si, Hf, Ta, Zr, Mg, Be,
It may contain elements such as W and Mo, and may form an alloy with these elements.

The support tube for accommodating a plurality of composite strands is for efficiently performing wire drawing without damaging the strands or the surrounding layer thereof, and has excellent wire drawing workability. Thus, the strands can be easily made high-order, and the primary strands can be efficiently multicore. The number of strands accommodated in the support tube may be appropriately determined, but is generally about 10 to 300.

As the support tube, an appropriate tube that can withstand wire drawing may be used. A support tube that can be preferably used in view of wire drawability and removability as needed after wire drawing is made of copper, copper alloy, or the like. If necessary, the support tube after the wire drawing process may be removed by an appropriate method such as an etching method, an elution method with a chemical such as nitric acid, or a cutting method.

The drawing of the support tube accommodating a plurality of strands may be carried out by an appropriate method, but in general, a material that inhibits the workability such as NbAl ₃ or Nb ₂ Al by heating and the superconducting property is used. A cold wire drawing method that can prevent generation is preferable. Examples of the cold wire drawing method include a die method, a groove roll method, a cold forging method such as a swaging method and a hosing method, and a method using them in combination.

In the wire drawing process, the wire or the like is usually thinned in sequence through a plurality of dies, a cold forging machine, etc., and the area reduction rate per one process may be appropriately determined. Generally, the area reduction rate is 5 to 25%. Although the degree of thinning may be appropriately determined, it is generally 0.1 to 3 mm, which is used as a wire for the next wire drawing or as a superconducting material for forming an Nb-Al superconducting wire. It

FIG. 4 exemplifies the wire drawing process by the die method. According to this, while the wire drawing target 7 is sequentially supplied from the delivery roll 8, the wire drawing target 7 is thinned through the dice 76, 77, 78, 79 to the thin wires 71, 72, 73, and the thin wire 73 is formed. Cold forging is carried out via the forging machine 74 to form a wire 75, which is wound on a winding roll 81.

The wound wire 81 is used as a wire for the next wire drawing as described above, or as a superconducting material when a predetermined number of primary wires have been multicore.
It is used to form b-Al superconducting wires.

As described above, the support tube after wire drawing is removed if necessary, but the removal is generally performed according to the composite order of the wires in the target superconducting material, and It is preferable to perform it in the step, and it can be omitted in the step of the higher-order strands close to the order of the final composite purpose.

By the way, when the desired superconducting material is obtained by compounding the quaternary element wire, it is generally preferable to do so in the compounding step of the secondary compound element wire from the viewpoint of generation efficiency of the superconducting phase. However, the degree of deterioration of the superconducting phase generation efficiency is not great at the stage of compounding the third-order composite element wire, and its presence contributes to the formation of a matrix that is advantageous in improving mechanical strength and stability and preventing AC loss. For this reason, it is generally preferable to leave it unremoved. FIG. 5 illustrates a state in which the support tube after wire drawing is removed. 42 is an element wire compounded by wire drawing, and 51 is a Nb tube after wire drawing (Nb envelope layer)
Is.

In the manufacturing method of the present invention, the composite wire of the secondary or higher order is surrounded by the Al-based layer and the pair layer, and a plurality of the wires are housed in the support pipe through the Nb pipe, if necessary, The operation of removing the support layer of the outer layer from the formed wire drawing product as necessary may be repeated twice or more as necessary. Therefore, in that case, the method of the present invention is applied to compound the starting element wire, and the obtained elemental wire is then used for the next elemental wire for compounding.

The superconducting material produced by the present invention may be directly used for forming a superconducting wire, or may be further used for a higher-order composite strand by a method other than the method of the present invention. is there. In the latter case, the composite strands according to the present invention are bundled to form a composite fine wire to achieve a higher multicore, and a superconducting material having a desired Al-based core number or an Al-based core diameter is obtained. It

Therefore, the superconducting material formed according to the present invention can be arbitrarily determined, and the number of repetitions of the operation according to the present invention can be arbitrarily determined as required. The cross-sectional shape is also arbitrary.
The general superconducting material to be made into a superconducting wire by heat treatment is about 10 to 300 wires from the viewpoint of prevention of deterioration of mechanical strength and stability due to lack of matrix part which is not Nb-Al superconducting phase or AC loss. The number of cores is 10 to 10,000 cores, the diameter is 0.1 to 10 mm, and the secondary composite strand part / Nb layer occupies the cross-sectional area with the secondary composite strand made of multiple primary strands as a unit. Area ratio of additional parts such as 1/9 to 9/1, Al system / Nb area ratio of cross section 2 to 20% / 90 to 80%
It is considered as a degree.

The Al system / Nb area ratio in the cross section of the secondary composite wire itself is generally 0.2 to 20% / 99.
It is about 8 to 80%. Therefore, in the present invention, the addition of an Al-based layer or a pair layer is adjusted so that the above-mentioned numerical values are achieved.

The Nb-Al superconducting wire can be obtained by processing the superconducting material into a desired cross-sectional shape such as a circle, a rectangle, or a tape, if necessary, and then heat-treating it. The heating conditions are appropriately determined depending on the Al-based core diameter of the primary strand of the superconducting material, the thickness of the Al-based layer, and the like, but heating is generally performed in the temperature range of 700 to 1600 ° C. By the heat treatment, a Nb ₃ Al-based superconducting phase is formed.

FIG. 6 illustrates the Nb-Al type superconducting wire. 9
Is a heat-treated body of a wire-drawing work of a wire having a higher number of cores, 1
Reference numeral 0 is the heat-treated body of the outer layer such as the Nb layer finally enclosed. The Nb ₃ Al-based superconducting phase is generated in a portion where the Nb layer and the Al-based layer were adjacent to each other in the superconducting material in a state in which all or part of these layers participate in the reaction.

The Nb ₃ Al type superconducting phase produced by the heat treatment is usually about 4 times as much as the contained Al type component. Therefore, the content of the Nb ₃ Al-based superconducting phase in the obtained superconducting wire can be controlled by adjusting the Al-based portion in the cross-sectional area of the superconducting material. For example, assuming that the Al content ratio due to the secondary composite wire itself is 2% and the Al content ratio after the addition of the Al-based layer or the pair layer is 20%, the addition ratio of the Al-based layer or the pair layer. The content ratio of Al in the third-order composite element wire can be changed within the range of 2 to 20% by controlling the above, and correspondingly, the Nb ₃ Al superconducting phase can be changed from 8 to 8%.
It can be adjusted in the area of 80% cross section.

[0043]

EFFECTS OF THE INVENTION According to the present invention, wire drawing can be easily carried out, wire breakage can be greatly suppressed, and higher-order multi-filarization of the wire can be carried out efficiently and stably. In addition, the content of the Al-based substance that contributes to the formation of the superconducting phase is high, and even if the primary wire is repeatedly multicore, the area occupied by the Nb ₃ Al-based superconducting phase is excellent and the critical current density etc. It is possible to obtain a Nb-Al-based superconducting wire having excellent superconducting properties.

[Brief description of drawings]

FIG. 1 (A) is an explanatory sectional view showing a state in which an Al-based layer and a pair layer are provided.

FIG. 1 (B) is an explanatory cross-sectional view of a state in which the support tube is accommodated

FIG. 2 is an explanatory cross-sectional view showing an example of a composite wire.

FIG. 3 is an explanatory sectional view of a pair layer forming method.

FIG. 4 is an explanatory view of a wire drawing process.

FIG. 5 is an explanatory sectional view showing a state in which a support layer is removed.

FIG. 6 is an explanatory cross-sectional view illustrating the structure of an Nb-Al-based superconducting wire.

[Explanation of symbols]

 4, 41: Elementary wire for compounding 1: Secondary elemental wire 13: Primary elemental wire (Al-based core wire) 11: Al-based core 12: Nb layer 14, 18: Nb surrounding layer 17: Secondary or higher Composite wire 15: Multi-core layer of Al-based core wire 16: Nb layer 2: Al-based layer 3: Pair layer 31: Al-based layer 32: Nb layer 5: Nb tube 6: Support tube 9: Higher number Heat-treated body of cored wire drawn product 10: Heat-treated body of outer layer finally enclosed

Claims (6)

[Claims] 1. An A-based core wire coated with an Nb layer is provided on the outer periphery of a composite wire of a secondary or more order having a multi-core state in the Nb surrounding layer.
An l-type layer is provided, and at least one pair layer of Nb layer and Al-type layer is provided on the outer side of the l-type layer, and a plurality of them are accommodated in a support pipe. A method of manufacturing a superconducting material, comprising: 2. An Al-based layer is provided on the outer circumference of a strand of which a secondary or higher-order composite wire having an Al-based core wire coated with an Nb layer in a Nb surrounding layer in a multicore state is used as a starting wire. Nb on the outside
Layer and at least one pair of Al-based layers are provided, and a plurality of them are accommodated in a support pipe, which is wire-drawn to form a higher-order composite multicore wire, and the composite multicore wire is the next strand. A method for manufacturing a superconducting material, characterized in that the above operation is repeated a required number of times. 3. The manufacturing method according to claim 1, wherein the pair layer is formed by winding it in a roll shape. 4. The manufacturing method according to claim 1, wherein a plurality of strands of wire are loaded into the Nb tube and the Nb tube is housed in the support tube. 5. The manufacturing method according to claim 1, further comprising a step of removing an outer support layer after wire drawing. 6. An Nb-Al-based superconducting wire comprising a heat-treated product of a superconducting material obtained by the manufacturing method according to claim 1.