JP7032783B2 - A method for heat-treating a precursor wire for Nb3Al superconducting wire, and a method for manufacturing an Nb3Al superconducting wire using this precursor wire. - Google Patents

Description

The present invention relates to a method for heat-treating a precursor wire for Nb ₃ Al superconducting wire and a method for producing an Nb ₃ Al superconducting wire using this precursor wire . More specifically, a method for heat-treating a precursor wire for an Nb ₃ Al superconducting wire having a filament region containing Nb and Al and a plurality of single wires having a barrier layer surrounding the filament region, and the precursor wire. The present invention relates to a method for producing a Nb ₃ Al superconducting wire rod using the above.

In order to provide Nb ₃ Al superconducting wire rods with excellent characteristics and close to the stoichiometric composition ratio, rapid heating and quenching treatment, in which short-time energization heating and rapid cooling with liquid metal gallium are continuously performed in vacuum, is an effective means. (See, for example, Patent Documents 1 to 4). In the rapid heating and quenching treatment, high-temperature heating at around 2000 ° C. is performed for a short time, and then the mixture is immersed in a liquid metal gallium bath maintained at a temperature of about 50 ° C. and rapidly cooled to obtain the stoichiometric composition ratio of Nb ₃ Al. Produces a preserved supersaturated solid solution. After that, it is phase _- transformed into an A15 type Nb3Al superconducting compound close to the stoichiometric composition ratio by an additional heat treatment at about 800 ° C. Until now, the rapid heating and quenching treatment is usually performed in a vacuum because it is expected that the wire rod will be burnt out due to a remarkable oxidation reaction due to the high temperature heating of 2000 ° C. For example, in many non-patent documents such as a document first reported on this manufacturing method (Non-Patent Document 1) and a document reported on the same manufacturing method by an Italian group (Non-Patent Document 2), the rapid heating ^/ quenching treatment is 10-. There is a clear statement that it will be carried out in a high vacuum of ⁵ Torr or less.

Furthermore, since the energization heating temperature far exceeds the melting point of copper, it is difficult to quench and quench the wire containing stabilized copper, which is indispensable for practical use. Therefore, usually, stabilized copper is applied after the rapid heating and quenching treatment, and specifically, methods such as clad rolling of copper foil, copper ion plating, and copper electrolytic plating are used. In any method for imparting stabilized copper, the most important factor in ensuring strong adhesion is the surface condition of the wire before composite.

In the rapid heating and quenching treatment, the wire rod rushes into the metallic gallium at a high temperature, so that the surface material niobium and gallium react remarkably, and Nb-Ga compounds are formed in the form of granules on the surface of the wire rod. The Nb-Ga compound that contaminates the surface of the wire must be removed in order to combine stabilized copper, but since it is extremely hard, it has been mechanically scraped off with a wire brush or abrasive paper, or hydrofluoric acid, etc. It required complicated work such as chemical removal. In addition, these complicated operations have become one of the factors that raise the manufacturing cost of the Nb ₃ Al superconducting wire.

Japanese Patent No. 2021986 Japanese Patent No. 4005713 Japanese Unexamined Patent Publication No. 2004-20701 Japanese Unexamined Patent Publication No. 2000-090754

Yasuo Iijima, et. Al., “Superconducting properties of Nb3Al multifilamentary wires quenched continuously by rapid-quenching”, Advances in Cryogenic Engineering, Vol. 42, 1996, p.p. 1447-1454. S. Ceresara, et. Al., “Manufacture of Nb3Al superconducting wires by the rapid heating and quenching technique”, Physica C 386 (2003) p.p. 384-937. Akihiro Kikuchi, et. Al., “Fabrication of Cu Stabilizer into Long-Length RHQT-Processed Nb3Al Round Wire”, IEEE Trans. Appl. Supercond., Vol. 16, No. 2, 2006, p.p.1224-1227.

INDUSTRIAL APPLICABILITY The present invention is for Nb ₃ Al superconducting wire rod, which prevents the Nb-Ga compound from being formed in the form of granules on the wire rod surface even if the precursor wire rod rushes into the metal gallium in the rapid heat quenching treatment. It is an object of the present invention to provide a method for heat-treating a precursor wire of the above, and a method for producing an Nb ₃ Al superconducting wire using the precursor wire .

[1] In the heat treatment method for the precursor wire for Nb ₃ Al superconducting wire of the present invention, the precursor wire having a refractory metal coating formed around the composite of Nb and Al is subjected to rapid heating and quenching treatment. In the heat treatment method of the precursor wire for the Nb ₃ Al superconducting wire , which produces an Nb-Al supersaturated solid solution based on the complex.
In the rapid heat treatment of the rapid heating and quenching treatment, a step of forming a thin oxide film on the surface of the precursor wire by performing a rapid heat treatment at 1700 ° C to 2100 ° C in the atmosphere, and
The rapid cooling treatment of the rapid heating and quenching treatment is characterized by comprising a step of preventing the formation of granular Nb-Ga compounds on the surface of the precursor wire rod.

[2] In the heat treatment method for the precursor wire rod for Nb ₃ Al superconducting wire rod of the present invention, preferably, the complex is a jelly roll method, a RIT method (rod-in-tube method), or a CCE method (clad tip). It may be produced by either an extrusion method) or a PIT method (powder filling method).
[3] In the heat treatment method for the precursor wire for the Nb ₃ Al superconducting wire of the present invention, the refractory metal preferably consists of Nb or Ta and Ni, Al, Ti, Co, Gd as additive elements. Alternatively, it may contain an element or alloy selected from the group consisting of Fe or an alloy of any of these elements or a Cu alloy.

[4] In the method for producing the Nb ₃ Al superconducting wire of the present invention, the precursor wire heat-treated by the heat treatment method of the precursor wire for the Nb ₃ Al superconducting wire according to [1] to [3] is subjected to transformation heat treatment. This is characterized by precipitating the Nb ₃ Al phase based on the Nb-Al supersaturated solid solution .

In the present invention, by performing the rapid heating and quenching treatment in the atmosphere, a thin oxide film is formed on the surface of the precursor wire rod, and the formation of hard granular Nb-Ga compound is prevented. The present invention not only eliminates the complicated work for removing the Nb-Ga compound, but also dramatically simplifies the apparatus by eliminating the need for the expensive vacuum chamber and exhaust system of the rapid heating and quenching treatment apparatus itself. The price will also be significantly cheaper.

It is a processing process explanatory drawing of the precursor wire rod manufacturing of the Nb ₃ Al superconducting wire rod by this invention, and shows the case of the jelly roll method. A shows a partially enlarged view. It is a block diagram which shows an example of the rapid heat quenching processing apparatus used in the embodiment of FIG. It is a manufacturing process diagram in the embodiment of FIGS. 1 and 2. It is a figure which shows the surface state of the Nb / Al precursor wire rod before the rapid heat quenching process. It is a figure which shows one Embodiment of this invention, and shows the surface state of the Nb / Al precursor wire rod which was subjected to rapid heat quenching treatment in the atmosphere. It is a block diagram which shows an example of the rapid heat quenching processing apparatus used in the heat treatment method of the precursor wire | former for Nb ₃ Al superconducting wire which shows the comparative example of this invention. It is a figure which shows the comparative example of this invention, and shows the surface state of the Nb / Al precursor wire rod which was subjected to rapid heat quenching treatment in vacuum.

Next, an embodiment in the Nb ₃ Al-based superconducting wire according to the present invention and the method for producing the same will be described. FIG. 1 is an explanatory diagram of the processing process of manufacturing a precursor wire rod of the Nb ₃ Al superconducting wire rod according to the present invention, and shows the case of the jelly roll method.

In FIG. 1 (a), 1 is a jelly roll type configured by laminating an industrial pure Nb sheet 2 and an industrial pure Al sheet 3 and winding the industrial pure Nb center material 4 without a gap. Shows a complex. Reference numeral 5 shows a coating made of industrial pure Nb provided by covering the composite 1 with an Nb tube by hydrostatic extrusion, and a Cu coating 6 is similarly formed on the coating 5, whereby the composite is formed. It is a wire 7.

FIG. 1 (b) shows the structure of the single wire rod 8 manufactured by reducing the surface of the composite wire 7 into a hexagonal cross section by drawing a die and then removing the Cu coating 6. It has a structure that allows close assembly by.

FIG. 1 (c) shows the structure of the composite wire rod 11 obtained by forming the batch coating 9 made of Nb and the Cu—Ni alloy coating 10 on the aggregate bundle of the single wire rod 8. The composite wire 11 is surface-reduced to a predetermined size by die drawing, and then the Cu—Ni alloy coating 10 on the outer periphery is removed, whereby a multi-composite wire having a predetermined size is obtained.

FIG. 1 (d) shows the cross-sectional structure of the Nb3 Al _- based superconducting wire produced by heating, cooling, and reheating the multi-composite wire rod 16 obtained as described above. Heating and subsequent cooling were performed using the equipment described below. In the figure, 12 is an Nb ₃ Al superconducting portion, and 13 and 14 are both a central material matrix and an outer peripheral matrix composed of Nb.

FIG. 2 shows an outline of the equipment used for heating and cooling, in which 15 is a supply reel for sending out a multi-composite wire rod 16, 17 and 18 are electrode rollers, and 19 is a liquid Ga20 as a cooling agent inside. The cooling tank containing the above is shown, and the electrode roll 18 is immersed in the liquid Ga 20. 21 is a take-up reel, 22 is a power supply, and 23 is a current value measuring lead wire 24 for measuring a current from a potential difference between both ends of a resistor R, and a voltage measuring lead wire 25 for measuring a voltage between the electrode rollers 17 and 18. The recorder, 26, indicates a guide roller.

The multi-composite wire 16 delivered from the supply reel 15 was energized and heated at 2000 ° C. for 0.1 seconds while passing through the electrode rollers 17 and 18, and then subsequently cooled by the liquid Ga 20 at a cooling rate of 5000 K / sec. After that, it is wound on the take-up reel 21. Here, the rapid heating and quenching treatment is preferably carried out by heating at 1800 to 2100 ° C. for 0.1 to 10 seconds and then quenching to 500 ° C. or lower. As a result, Al and Nb constituting the multi-composite wire rod react with each other to form a supersaturated solid solution.

The wound multi-composite wire 16 is reheated at 800 ° C. for 10 hours in the transformation heat treatment step, whereby Nb ₃ Al is precipitated to become a predetermined Nb ₃ Al superconducting wire. The transformation heat treatment step can be carried out by heat treatment at preferably 600 to 1000 ° C., typically 800 ° C. for about 10 hours. The transformation heat treatment is a reheat treatment of a multi-composite wire having a supersaturated solid solution, whereby an Nb ₃ Al superconducting wire having a final shape is produced.
FIG. 3 summarizes the above superconducting wire manufacturing process in a flowchart.

(Example)
FIG. 4 is a diagram showing the surface state of the Nb / Al precursor wire rod before the rapid heating and quenching treatment, which shows one embodiment of the present invention. The surface material of the precursor wire is niobium, and the outer diameter is 1.37 mm.
FIG. 5 is a diagram showing the surface state of the Nb / Al precursor wire rod that has been subjected to rapid heating and quenching treatment in the atmosphere. The applied voltage during rapid heating and quenching was 10.5 V, and the wire was heated to about 2000 ° C. No formation of niobium-gallium compounds is observed in the surface state of the Nb / Al precursor wire rod that has been subjected to the rapid heating and quenching treatment.

(Comparative example)
FIG. 6 is a block diagram showing an example of a rapid heating / quenching treatment apparatus used in a conventional heat treatment method for a precursor wire for Nb ₃ Al superconducting wire, which shows a comparative example of the present invention. In FIG. 6, those having the same operation as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.
Here, the entire rapid heating / quenching processing apparatus is in a vacuum state of, for example, about ^2x10-5 Torr.

FIG. 7 is a diagram showing the surface state of the Nb / Al precursor wire rod that has been subjected to rapid heating and quenching treatment in vacuum. The applied voltage during rapid heating and quenching was 10.5 V, and the wire was heated to about 2000 ° C. The surface of the wire reacts with the metal gallium of the refrigerant to form hard niobium-gallium compounds in some places, which partially erode the surface layer of the wire and adhere firmly.
Therefore, as a post-step, an additional step of peeling off the niobium-gallium compound on the surface layer of the wire rod is required.

Although the embodiments and examples of the present invention have been described above, the above-described embodiments and examples do not limit the invention according to the claims. It should also be noted that not all combinations of features described in the embodiments and examples are essential to the means for solving the problems of the present invention.
For example, in the above embodiment, the jelly roll method is shown as the manufacturing process of the precursor wire for the Nb ₃ Al superconducting wire, but the RIT method (rod-in-tube method) and the CCE method ( Other conventional manufacturing methods such as clad tip extrusion method) and PIT method (powder filling method) may be used.
Further, in the above embodiment, an industrial pure Nb sheet and an industrial pure Al sheet are laminated as a precursor wire having a refractory metal coating formed around a composite of Nb and Al, and this is used for industrial purposes. The present invention shows a case where an Nb tube is covered as a coating of a refractory metal on a jelly roll type alloy constructed by winding it around a center material made of pure Nb without gaps, but the present invention is not limited to this. For example, an element or alloy selected from the group consisting of Nb or Ta as a refractory metal and Ni, Al, Ti, Co, Gd or Fe or an alloy of any of these elements or a Cu alloy as an additive element. A barrier layer including the barrier layer may be provided.

According to the heat treatment method for the precursor wire for Nb ₃ Al superconducting wire of the present invention, a thin oxide film is formed on the surface of the precursor wire by performing the rapid heating and quenching treatment in the atmosphere, and the hard granular Nb- The formation of Ga compound can be prevented. The present invention not only eliminates the complicated work for removing the Nb-Ga compound, but also dramatically simplifies the apparatus by eliminating the need for the expensive vacuum chamber and exhaust system of the rapid heating and quenching treatment apparatus itself. The price can also be significantly cheaper.

1 Composite 2 Nb sheet 3 Al sheet 4 Center material 5 Coating 6 Cu coating 7 Composite wire 8 Single wire 9 Collective coating 10 Cu-Ni alloy coating 11 Composite wire 12 Nb3 Al Superconducting part 13 Center material matrix 14 Outer peripheral matrix 15 Supply reel 16 Multi-composite wire rod 17, 18 Electrode roller 19 Cooling tank 20 Liquid Ga
21 Take-up reel 22 Power supply 23 Recorder 24 Current value measurement lead wire that measures current from the potential difference across the resistor R 25 Voltage measurement lead wire that measures the voltage between the electrode rollers 17 and 18 26 Guide roller

Claims (4)

For Nb3Al superconducting wire that produces an Nb-Al supersaturated solid solution based on the composite by subjecting a precursor wire having a refractory metal coating around the composite of Nb and Al to a rapid heat treatment. In the heat treatment method for precursor wire,
In the rapid heat treatment of the rapid heating and quenching treatment, a step of forming a thin oxide film on the surface of the precursor wire by performing a rapid heat treatment at 1700 ° C to 2100 ° C in the atmosphere, and
In the rapid cooling treatment of the rapid heating and quenching treatment, a step of preventing the formation of granular Nb-Ga compounds on the surface of the precursor wire and
A method for heat-treating a precursor wire for Nb ₃ Al superconducting wire. The rapid heating and quenching treatment for the Nb ₃ Al superconducting wire according to claim 1, wherein the complex is produced by any one of a jelly roll method, a RIT method, a CCE method, and a PIT method. Method of heat treatment of precursor wire rod. The refractory metal is composed of Nb or Ta, and an element or alloy selected from the group consisting of Ni, Al, Ti, Co, Gd or Fe, an alloy of any of these elements, or a Cu alloy as an additive element. The method for heat-treating a precursor wire having been subjected to rapid heating and quenching treatment for an Nb ₃ Al superconducting wire according to claim 1 or 2, wherein the method comprises. The Nb ₃ Al phase based on the Nb-Al supersaturated solid solution is precipitated by performing a transformation heat treatment on the precursor wire heat-treated by the heat treatment method for the precursor wire for the Nb ₃ Al superconducting wire according to claims 1 to 3. A method for producing a Nb ₃ Al superconducting wire .

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