JP2002033025A - Nb3Al superconducting multi-core wire and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Nb ₃ Al superconducting multi-core wire excellent in high magnetic field characteristics and having mechanical strength not hindering forming such as coil forming, and a method for producing the same. SOLUTION: Ag coated with a Nb jacket at the center part
A stabilizing material 1 is disposed, and an inner peripheral portion of Al-2
An Nb / Al-2at% Cu-RIT sub-multi wire 2 of at% Cu alloy is arranged, and the outer periphery has a composition of Nb-25at% Al as an outer peripheral portion, and the layer thickness of Al is 1
A 00 nm JRNb / Al submulti wire 3 was arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to Nb ₃ Al superconducting multifilamentary wire and a manufacturing method thereof, in particular, Nb ₃ on Al superconducting multifilamentary wire and a manufacturing method thereof excellent in moldability such as high magnetic field characteristics and the coil.

[0002]

2. Description of the Related Art An Nb ₃ Al compound superconducting wire is superior in critical current density characteristics in a high magnetic field as compared with general superconducting wires Nb ₃ Sn and NbTi. It is expected to be used for large and applied superconducting equipment in which a large electromagnetic force is applied to superconducting wires such as accelerators.

As a conventional method for producing a Nb ₃ Al compound-based superconducting wire, there is a rapid heating, rapid cooling and transformation (RHQT) method. In the RHQT method, for example, Jelly-R
oll; hereinafter referred to as JR) method.
/ Al multifilamentary composite wire is heated at a speed of 1 m / sec while being heated by heating to 2000 ° C. in 0.1 second, and immersed in liquid Ga which also serves as a coolant and an electrode, so that the body-centered cubic (bcc ) Form Nb (Al) ss in which 25 at% Al is supersaturated with Nb in the phase. The Nb (Al) ss is subjected to a transformation heat treatment at 700 ° C. to 800 ° C., thereby transforming the bcc phase into an A15 type compound heavily, thereby obtaining a Nb ₃ Al having a stoichiometric composition.
Form a compound superconducting wire.

[0004] Nb (Al) based on the above RHQT method
Since ss is excellent in cold workability, a wind-and-react method of performing transformation heat treatment in a state of being wound in a coil shape can be applied. For this reason, it is effective for forming an inner layer coil for a high magnetic field having a small winding diameter. However, generation of stacking faults by transformation heat treatment is inevitable, and the critical temperature Tc is 17.9K and the critical magnetic field Bc2 (4.2K) is The superconductivity is limited to 27T.

[0005] In order to improve such superconducting characteristics, the A15 type compound is directly produced by lowering the ultimate temperature during rapid heating and quenching, or by adding a third element such as Cu, Ge, Si, etc. Stoichiometric Nb ₃
It has been confirmed that an Al compound is formed. This A
The type 15 compound has a feature of irregularity with reduced long-range order, and is subjected to a heat treatment at 700 ° C. to 800 ° C. for ordering to have a critical temperature Tc of 18.5 K and B
c2 (4.2K) is improved up to 29T, and the critical current density Jc in a high magnetic field is improved.

[0006]

However, the conventional A15
In an Nb ₃ Al compound-based superconducting wire in which a type compound is directly generated, when the disordered A15 type compound is ordered by heat treatment, the critical current density Jc in a high magnetic field is improved, but the critical current density Jc in a low magnetic field is reduced. . In addition, it becomes brittle, and the formability such as the winding property at the time of coil forming and the use of a stranded wire conductor is reduced. The mechanical strength can be reinforced by increasing the ratio of the Nb matrix to the superconducting portion, but in this case, there is a problem that overallJc is greatly reduced.

Accordingly, it is an object of the present invention to provide an Nb ₃ Al superconducting multifilamentary wire having excellent high magnetic field characteristics and mechanical strength that does not hinder molding such as coil molding, and a method for producing the same.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an Nb transformed from a supersaturated solid solution to an A15 phase.
₃ Al filaments and Nb ₃ having a Nb ₃ Al filaments obtained by ordering the disordered A15 phase in the same cross-section
An Al superconducting multi-core wire is provided.

[0009] In order to achieve the above object, the present invention provides a method in which Nb ₃ Al transformed from a supersaturated solid solution has a volume ratio of 5%.
Provided is an Nb ₃ Al superconducting multifilamentary wire having a structure in which 0% or more of Nb ₃ Al filaments and Nb ₃ Al filaments ordered from an irregular A15 phase are dispersed and mixed with the Nb ₃ Al filaments.

Further, in order to achieve the above object, the present invention provides a method for forming a laminate by laminating a plurality of sub-multi wires coated with a matrix of Nb on an inner peripheral portion and an outer peripheral portion, and forming the laminate on the Nb matrix. Forming a multi-wire by coating with a matrix; primary heating the multi-wire at a predetermined temperature; cooling the primary-heated multi-wire with a metal material for cooling; An irregular A15 phase is generated in the inner peripheral portion, and after cooling, Nb ₃ Al filament transformed from a supersaturated solid solution to an A15 phase is formed on the outer peripheral portion by secondary heating at a predetermined temperature, and an irregular A15 phase is formed in the inner peripheral portion. To form Nb ₃ Al filaments in which
b ₃ to provide a method of manufacturing Al superconducting multifilamentary wire.

According to the above-described Nb ₃ Al superconducting multifilamentary wire and the method for producing the same, A1 is converted from a supersaturated solid solution rich in ductility.
By arranging the Nb ₃ Al filaments obtained by ordering a good irregular A15 phase transformation the Nb ₃ Al filaments and superconductivity in 5 phases within the same cross section, irregular due to the mechanical strain of bending, such as A15 Phase Nb ₃ Al filaments to prevent breakage and superconductivity, especially overal
lJc can be increased.

In order to form a supersaturated solid solution Nb (Al) ss, it is necessary to form a solid solution at a high temperature. When the filament at the outer periphery satisfies such a condition, it is essential that the diffusion reaction between Nb and Al is not completed in order to generate an irregular A15 phase filament at the center of the wire / cross section. Requires that the thickness (thickness) of the single wire Al or Al alloy be twice or more as large as that of the single wire rod in the outer peripheral portion. On the other hand, the ratio is 100
If Nb exceeds Nb, a large amount of unreacted Nb remains, and the volume ratio of Nb ₃ Al becomes low, and overall Jc becomes small. In addition, Nb (A
l) Since the solid solubility limit of ss increases with increasing temperature,
By increasing the nominal Al concentration of the sub-multi wire arranged at the center by 1 at% or more as compared with that arranged at the outer periphery, there is a heating temperature range in which supersaturated solid solution filaments and irregular A15 phase filaments coexist. . Nominal Al
When the concentration becomes higher than 5 at%, a large amount of Nb ₂ Al phase is generated, and eventually, the volume ratio of the irregular A15 phase becomes low, and
lJc becomes small.

The solid solubility limit of Nb (Al) ss is Cu, G
e, It is reduced by adding a third element of Si. If an Al alloy is used for the sub-multi wire arranged at the center and pure Al is used for the outer periphery, irregular A15 phase filaments and supersaturated solid solution filaments can be produced simultaneously.
For this purpose, it is necessary to add 0.5 at% of Cu, 5 at% of Ge, and 5 at% or more of Si to Al to destabilize the supersaturated solid solution. However, when the added amount exceeds 2 at%, 20 at%, and 15 at%, respectively, A
1 alloy becomes brittle, and the workability of the Nb / Al composite decreases. When the supersaturated solid solution and the irregular A15 phase are mixed to form a filament, the volume fraction of the supersaturated solid solution is set to 50%.
By doing so, the minimum workability of the filament can be ensured.

[0014]

Table 1 DETAILED DESCRIPTION OF THE INVENTION The configuration of the Nb ₃ Al superconducting multifilamentary wire formed in Examples 1 to 4 described below shows mechanical properties, and the superconducting properties.

[Table 1] The Nb ₃ Al superconducting multi-core wire of the present invention is formed by incorporating a plurality of sub-multi wires into a multi-structure wire. There are many methods for manufacturing a sub-multi wire, but in the present invention, the JR method and the rod tube (RIT) are used.
The sub-multi wire manufactured by the method will be described.

Example 1 FIG. 1 shows a cross section of a Nb ₃ Al superconducting multifilamentary wire, wherein (a) is a multi-wire according to an embodiment of the present invention, and (b) is a standard sample as a comparative example. Multi-line. In the multi-wire of (a), seven Ag stabilizers 1 covered with an Nb jacket are arranged in the center, and the number of filaments of the Al-2 at% Cu alloy is 7999 (421 × 19) as an inner periphery around the Ag stabilizer. Book Nb / Al-2a
One layer of t% Cu-RIT sub-multi wire 2 (12 wires in total)
And Nb-25at as an outer periphery on the outside.
% Al having a composition of 100 nm and an Al layer thickness of 100 nm
The b / Al sub-multi wires 3 are arranged in three layers (a total of 66 wires) to form a multi wire 4, and the multi wire 4 is subjected to rapid heat quenching (RH).
Q) Processing was performed.

In the multi-wire (b), seven Ag stabilizers 1 covered with an Nb jacket are arranged in the center, a filamentous Nb5 is arranged as an inner periphery around the Ag stabilizer 1, and an outer periphery is arranged around the Nb5. As the outer peripheral portion, three layers (a total of 66) of JRNb / Al submulti wires 3 having a composition of Nb-25 at% Al and an Al layer thickness of 100 nm are arranged, and the standard samples 1 and 2 having different rapid heating and quenching conditions are provided. It is 2. This multi-wire was also subjected to rapid heating and rapid cooling.

FIGS. 2A and 2B show the critical temperature Tc after the transformation heat treatment with respect to the flowing current in the rapid heating and quenching treatment. FIG. 2A shows the change in the critical temperature Tc of the multi-wire of Example 1, and FIG. Is the change in the critical temperature Tc of the multi-line. After the RHQ treatment, a transformation heat treatment was performed at 800 ° C. for 10 hours based on the rapid heating and quenching treatment conditions based on the current value supplied from the constant current power supply. Only the submulti (filament) is a supersaturated solid solution, and an irregular A15 phase occurs in the RIT submulti (filament) arranged on the inner periphery. The critical temperature Tc has a value exceeding 18.2K. Table 1
As shown in the figure, the critical current density Jc in a low magnetic field is slightly reduced, but the critical current density Jc in a high magnetic field is improved, and good bending workability is maintained. In addition, high critical temperature Tc
Is wide.

In the comparative example, the critical temperature Tc of the standard sample 1 is high under the RHQ condition where the irregular A15 phase is generated, and the critical current density Jc in a high magnetic field is large as shown in Table 1. However, even when the magnetic field becomes low, the critical current density Jc does not improve, and the bending workability after quenching decreases. The standard sample 2 has a low critical temperature Tc under RHQ conditions under which a supersaturated solid solution is formed, but has extremely good bending workability after rapid cooling as shown in Table 1. Although the critical current density Jc increases when the magnetic field decreases, the critical current density Jc increases on the high magnetic field side.
c degrades rapidly. As described above, the characteristics greatly differ depending on the RHQ conditions.

[Example 2] Seven Ag stabilizers coated with an Nb jacket were disposed at the center, and the inner periphery was composed of Nb-25 at% Al and the thickness of the Al layer was 1 μm. JRNb / Al submulti wire
A JRNb / Al submulti line having a composition of Nb-25 at% Al as an outer peripheral portion and an Al layer thickness of 100 nm was arranged on the outer side to form a multi line. The Al layer thickness of the JRNb / Al submultiple wire arranged on the inner peripheral portion is formed to be 10 times thicker than the outer layer portion.

When the multi-wire was subjected to rapid heating and quenching, the JRNb / Al sub-multi (filament) disposed on the outer periphery became a supersaturated solid solution, and the JRNb / Al sub-multi (filament) disposed on the inner periphery. ) Resulted in an irregular A15 phase. When the multi-wire was subjected to transformation heat treatment at 800 ° C. for 10 hours, as shown in Table 1, although the critical current density Jc in a low magnetic field was slightly reduced, the critical current density Jc in a high magnetic field was improved, and Bending workability was obtained.

Example 3 A coated with Nb jacket
g, seven JNb / A1 sub-multi lines having a composition of Nb-27.5 at% Al and an Al layer thickness of 100 nm are arranged around the periphery of the seven stabilizing materials, and , Nb-25 at% A as an outer peripheral portion
JRNb / having a composition of 1 and an Al layer thickness of 100 nm
Al sub-multi lines were arranged to form multi lines. The nominal Al concentration of the sub-multi wire arranged on the inner peripheral portion was higher by 2.5 at% than the nominal Al concentration on the outer peripheral portion.

When the multi-wire was subjected to rapid heating and quenching treatment, the JRNb / Al sub-multi (filament) disposed on the outer periphery became a supersaturated solid solution, and the JRNb / Al sub-multi (filament) disposed on the inner periphery. ) Resulted in an irregular A15 phase. When the multi-wire was subjected to transformation heat treatment at 800 ° C. for 10 hours, as shown in Table 1, although the critical current density Jc in a low magnetic field was slightly reduced, the critical current density Jc in a high magnetic field was improved, and Bending workability was obtained.

Example 4 A coated with Nb jacket
g. Seven stabilizing materials are arranged at the center, and 40 Rb 7-wires of Nb / Al-2at% Cu and 81 7-wires of Rb of Nb / Al-5at% Mg are provided around the stabilizing material. The multi-line was formed by arranging the sub-multi lines prepared by mixing, and arranging the same sub-multi lines on the outer side of the sub-multi lines.

When the multi-wire was subjected to rapid heating and quenching, a supersaturated solid solution and an irregular A15 phase were mixed in each filament at a ratio of about 7: 3. This multi line is 8
When the transformation heat treatment is performed at 00 ° C. for 10 hours, as shown in Table 1, the critical current density Jc in a low magnetic field is slightly reduced, but the critical current density Jc in a high magnetic field is improved. Even in this case, the bending workability required for coil forming is ensured.

According to the above-described Nb ₃ Al superconducting multifilamentary wire, the irregular A15 phase and the supersaturated solid solution are formed at the same time by controlling the arrangement or mixing ratio in the cross section. Is mechanically supported. This improves high magnetic field characteristics while maintaining good moldability without increasing the extra Nb matrix. For example, the innermost layer coil of a 1 GHz class NMR superconducting magnet having a small winding diameter based on the Wind and React method can be formed. In addition, it is possible to increase the current capacity by using stranded wires, and it is suitable for the superconducting magnet conductor of the next-generation fusion reactor, which increases the maximum experienced magnetic field. In terms of superconductivity, Nb ₃ Sn used as a practical wire rod
It has a critical current density Jc that is more than twice as large as that of the above, and has excellent strain resistance characteristics. Therefore, it is necessary to realize a large superconducting system such as a fusion reactor and a high energy accelerator, and to reduce the size of the entire system. And the cost of the apparatus can be reduced.

The manufacturing parameters such as the nominal Al concentration, the diffusion distance between Nb and Al, the presence or absence of alloy addition, etc. applied in the above embodiment are other manufacturing methods than the JR method and the RIT method. The same can be applied to the clad tip extrusion method and the powder extrusion method.

[0027]

As described above, according to the present invention, the Nb ₃ Al
According to superconducting multifilamentary wire and a manufacturing method thereof, an Nb ₃ Al filaments obtained by ordering a good irregular A15 phase transformation the Nb ₃ Al filaments and superconductivity in A15 phase from a supersaturated solid solution which is rich in ductility in the same cross-section Because of the arrangement, it is possible to provide a mechanical strength that is excellent in high magnetic field characteristics and does not hinder molding such as coil molding.

[Brief description of the drawings]

FIG. 1 shows an Nb ₃ Al superconducting multifilamentary wire according to an embodiment of the present invention, in which (a) is a cross-sectional view of the multiwire of the present invention, and (b) is a multiwire of a standard sample as a comparative example. Sectional view

FIG. 2 is an explanatory diagram showing a critical temperature Tc after a transformation heat treatment with respect to an energizing current in a rapid heat quenching treatment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Ag stabilizer 2 Nb / Al-2at% Cu ・ RIT submulti wire 3 JRNb / Al submulti wire 4 Multi wire 5 Nb

Continuing from the front page (72) Inventor Shinya Banno 1-2-1 Sengen, Tsukuba, Ibaraki Pref., National Institute for Metals Science and Technology Agency (72) Inventor Hitoshi Wada 1-1-2 Sengen, Tsukuba, Ibaraki Scientific Technology (72) Inventor Kohei Tagawa 3550, Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Within Hitachi Cable Advanced Research Center (72) Inventor Eizumi Morai, 3550 Kida Yomachi, Tsuchiura City, Ibaraki Hitachi Electric Wire Advanced Research Center Co., Ltd. (72) Inventor Kazuhiko Nakagawa 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Hitachi Cable Co., Ltd. Tsuchiura Plant F-term (reference) 5G321 AA11 BA03 DC32 DC36

Claims (15)

[Claims] 1. N transformed from a supersaturated solid solution to an A15 phase
An Nb ₃ Al superconducting multifilamentary wire having b ₃ Al filaments and Nb ₃ Al filaments in which irregular A15 phases are ordered in the same cross section. 2. The Nb ₃ Al superconducting multifilamentary wire according to claim 1, wherein the Nb ₃ Al filament transformed from the supersaturated solid solution to the A15 phase is arranged on an outer peripheral portion of the cross section. 3. Nb in which the irregular A15 phase is ordered
₃ Al filaments, Nb ₃ Al superconducting multifilamentary wire structure as in claim 1 wherein disposed on the inner peripheral portion of the cross section. 4. The Nb ₃ Al filament transformed from the supersaturated solid solution to the A15 phase is from 22 at% to 25 at%.
2. The composition according to claim 1, wherein the composition has a nominal Al concentration of 0.1%.
b ₃ Al superconducting multi-core wire. 5. Nb in which said irregular A15 phase is ordered
_2. The Nb ₃ Al superconducting multi-core wire according to claim 1, wherein the ₃ Al filament has a nominal Al concentration of 1 at% to 5 at% higher than a nominal Al concentration of the Nb ₃ Al filament transformed from the supersaturated solid solution to the A15 phase. . 6. Nb in which said irregular A15 phase is ordered
₃ Al filaments, when the composition based on the addition of the element M is denoted by _{Nb y (Al 1-x M} x) 1-y, the addition amount x of the element Cu is 0.005-0.02, elemental Ge Is 0.05-0.2, and the amount x of elemental Si is 0.05-0.2.
2. The Nb ₃ Al superconducting multi-core wire according to claim 1, wherein said Nb ₃ Al superconducting wire has a configuration of 0.15. 7. A Nb ₃ Al filaments transformed into A15 phase from the supersaturated solid solution, Al, expressed in pure Al, or added composition on the basis of the element M is _{Nb y (Al 1-x M} x) 1-y when it is, Nb ₃ Al superconducting multifilamentary wire of the first of claims configuration amount x of element Mg is 0-0.1. 8. A Nb ₃ Al filaments transformation the Nb ₃ Al is more than 50% by volume from a supersaturated solid solution, and the Nb ₃ Al filaments ordered from a disordered A15 phase in the Nb ₃ Al filaments were dispersed and mixed An Nb ₃ Al superconducting multifilamentary wire having a configuration. 9. An Nb diffusion burr at an arbitrary position on the cross section.
Ag covered with a layer is arranged as an internal stabilizing material.
Nb according to claim 1 or claim 8 _ThreeAl superconductivity
Conducting multi-core wire. 10. A multilayer body is formed by laminating a plurality of sub-multi wires covered with a matrix of Nb on an inner peripheral portion and an outer peripheral portion, and forming a multi-line by covering the laminate with a matrix of Nb. The multi-wire is primarily heated at a predetermined temperature, and the first-heated multi-wire is cooled with a cooling metal material to produce a supersaturated solid solution filament on the outer periphery and an irregular A15 phase on the inner periphery. is, Nb ₃ was transformed into A15 phase from a supersaturated solid solution in the outer peripheral portion after cooling to secondary heating at a predetermined temperature Al filaments, Nb ₃ obtained by ordering the disordered A15 phase in the inner peripheral portion
Nb ₃ for producing an Al filament
Manufacturing method of Al superconducting multi-core wire. 11. The Al of the sub-multi wire of the inner peripheral portion
The method for producing a Nb ₃ Al superconducting multi-core wire according to claim 10, wherein the size is 2 to 100 times larger than the Al size of the outer peripheral portion. 12. The nominal Al concentration of the sub-multi line excluding Nb sheath is 22 at% to 25 a at the outer peripheral portion.
t%, and the inner peripheral part is at 1 at from the outer peripheral part.
The Nb ₃ A according to claim 10, wherein the Nb ₃ A is in the range of 5 to 5 at%.
(1) A method for manufacturing a superconducting multi-core wire. 13. When the composition with element M is added to the Nb ₃ Al filaments portion of the inner peripheral portion is denoted by _{Nb y (Al 1-x M} x) 1-y, the addition amount x of the elements Cu 0.005-
0.02, the addition amount x of the element Ge is 0.05-0.2, the production of Nb ₃ Al superconducting multifilamentary wire added amount x wherein 10 claims is 0.05-0.15 element Si Method. 14. Nb and A constituting said sub-multi line
1 is a mixture of different Al sizes, nominal Al concentrations, and the presence or absence of element addition, wherein the Al size is 2 to 100 times smaller and the nominal Al concentration is 1
The Nb _{3 according} to claim 10, wherein the inner peripheral portion and the outer peripheral portion are bound without distinguishing between the inner peripheral portion and the outer peripheral portion, wherein the volume ratio of at least 5 at% to 5 at% or no element addition is 50% or more.
Manufacturing method of Al superconducting multi-core wire. 15. The method for producing a Nb ₃ Al superconducting multi-core wire according to claim 10, wherein Ag coated with a Nb diffusion barrier is disposed at an arbitrary position in the laminate as an internal stabilizing material.