JPH09310161A - Production of nb-ti superconductive multilayer sheet and nb-ti superconductive multilayer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize the production and to reduce the cost by executing hot rolling, cold rolling and final heat treatment under prescribed conditions. SOLUTION: In this method, a raw material is subjected to hot rolling at 500 to 1000 deg.C at 30 to 98% working ratio, is thereafter subjected to cold rolling at 30 to 70% working ratio and is next held at 600 to 800 deg.C for 30min to 5hr. This treatment is for refining the crystal grains of Nb-Ti. Then, it is subjected to cold rolling at 30 to 98% working ratio and is subjected to heat treatment at 300 to 450 deg.C in which holding time per time is regulated to 1 to 168hr and cold rolling in which working ratio per time is regulated to 30 to 98% alternately for <=6 times to form into a sheet or foil shape. In this way, dislocations and pores to form the driving force of precipitation are introduced therein to precipitate a sufficient amt. of α-Ti. Furthermore, it is subjected to final heat treatment at 300 to 450 deg.C for 1 to 1000hr. This is executed for moreover increasing the density of the α-Ti precipitated by the repetition of the cold working and heat treatment in the process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a superconducting multilayer plate and a superconducting multilayer plate which are mainly used as magnetic shields in superconducting devices such as MRI (magnetic resonance medical image diagnostic apparatus) and superconducting linear motor cars. In particular, the present invention relates to a thermo-mechanical treatment method in which the α-Ti precipitation phase in NbTi is dispersed at high density and a precipitation morphology of normal-conducting precipitates.

[0002]

2. Description of the Related Art A method for producing a superconducting multilayer board used in MRI, a linear motor car, etc.
As shown in Japanese Patent No. 36400, after hot rolling, 30
Holding time per time at a temperature of 0 to 450 ° C 1 to 16
After repeating the heat treatment for 8 hours and the cold rolling with the working rate of 30 to 98% per time alternately 6 times or less, 300 to 45
The final heat treatment is performed for 1 to 1000 hours at a temperature of 0 ° C. to obtain N
There is a method of depositing α-Ti as a superconducting pinning point in bTi. This is a method in which lattice defects such as dislocations and vacancies, which act as a driving force for precipitation, are introduced by cold working and combined with heat treatment to cause sufficient precipitation.

Also in the superconducting multifilamentary wire, a good critical current density is obtained by precipitating α-Ti by the same combination of processing and heat treatment (Japanese Patent Laid-Open No. 57-210516).
In the case of a superconducting multi-core wire, since the processing rate can be largely obtained by the square of the wire diameter in the case of a wire, the superconducting multilayer board can obtain only the rate of change of the plate thickness. It is necessary to devise the processing and heat treatment methods more than before.

[0004]

In the material manufactured by the manufacturing method of the prior art, the critical current density is 100,000 to 120,000 A / cm ² under a strong magnetic field of 5 Tesla, but a general superconducting multifilamentary wire is used. Has a critical current density of about 270,000 A / cm ^{2 under the} same magnetic field environment (“Seminar text of the Institute of Metals, Nano / Mesostructure control and development of high-performance materials” p.93), which is almost double that of the superconducting plate. There is. When a superconducting multilayer board is used as a magnetic shield material, the magnitude of the magnetic field that can be magnetically shielded is approximately proportional to the critical current density and the thickness of the magnetic shield material ("The Institute of Electrical Engineers of Japan, Superconductivity Engineering, The Institute of Electrical Engineers," p.
52). Therefore, if the critical current density is low, many materials have to be used, and there is a problem that the material has low shielding performance and low cost performance in comparison with the weight.

Further, Jc (critical current density) of the conventional method is
There is a problem that the heat treatment time is long, although it is as small as 100,000 to 120,000 A / cm ² under a magnetic field of 5 Tesla. The fact that the heat treatment time can be shortened when obtaining Jc of the same level as that of the conventional method is also very significant from the viewpoint of reducing the manufacturing cost.

The NbTi superconducting multilayer plate is a superconducting plate in which one or more plate-shaped NbTi layers are present in a Cu or Cu alloy base material which is a good electric conductor via Nb layers. The critical current density of such a superconducting plate is determined by normal-conducting Ti deposited in the NbTi layer. JP-A-2-9449
N of the conventional NbTi superconducting multilayer board as shown in Japanese Patent No. 8
The Ti precipitate existing in the bTi layer has a major axis of 200 nm to
It had an ellipsoidal shape with a diameter of 2 μm and a minor axis of 100 nm to 1 μm. These precipitates are deposited as a result of repeated rolling and heat treatment (JP-A-3-136400). The normal-conducting precipitates in the NbTi layer maintain the superconducting state by pinning the magnetic flux quanta that enter the superconductor in a regularly arranged array (triangular array) in a magnetic field of the upper critical magnetic field Hc 2 or more (this Is called an intermediate state). The lattice spacing of the magnetic flux quantum is about 49 nm in a 1 Tesla magnetic field, 5
It is about 22 nm in the Tesla magnetic field. The size of the normal-conducting precipitate that can pin the magnetic flux quantum most efficiently is about the same as the size of the interface (coherence length; 5.5 nm in the case of NbTi) of the superconducting normal-conducting region in the intermediate state and the magnetic flux. It is said that they are dispersed in the same degree as the quantum lattice spacing (tens of nm). From this viewpoint, the Ti precipitate in the NbTi layer of the conventional NbTi alloy-based superconducting plate has a minor axis of 100 to 200 nm and a major axis of 200 nm to 500.
It has an ellipsoidal shape of nm and is considerably larger than the ideal size of Ti precipitates, and the critical current density is 100 to 120,000 A / cm ² at 5 Tesla as described above, which is a commercially available Nb.
The value was lower than that of the Ti alloy-based superconducting wire (when a magnetic field was applied parallel to the plate).

The present invention has been made in view of these problems, and optimizes the method for producing a superconducting multilayer board to produce a material having a large critical current density and heat-treating such a material in the shortest possible time to reduce the cost. A method of manufacturing and specifying the morphology of normal conducting precipitates in the NbTi layer of a superconducting multilayer board.

[0008]

According to a first aspect of the present invention, at least one layer of an NbTi alloy and a high-conductivity metal are alternately stacked, and NbTi alloy and a high-conductivity metal are interposed between the NbTi alloy and the high-conductivity metal.
A method for producing a superconducting multilayer board having a barrier layer of b or Ta, wherein the processing rate is 30 at a temperature of 500 to 1000 ° C.
~ 98% hot rolling, cold rolling at a working rate of 30 to 70%, then holding at a temperature of 600 to 800 ° C for 30 minutes to 5 hours, and then cold rolling at a working rate of 30 to 98%. Rolled,
Holding time per time at a temperature of 300 to 450 ° C is 1 to
Heat treatment for 168 hours and processing rate of 30 to 98
% Cold rolling is repeated 6 times or less alternately to form a plate or foil, and a final heat treatment is performed at a temperature of 300 to 450 ° C. for a holding time of 1 to 1000 hours. The high conductivity metal refers to copper, aluminum and the like.

Since the material of the present invention is used in a DC strong magnetic field, it must be superconductingly stable. The reason for using a composite material of a superconducting material and a metal of high conductivity as the magnetic shield material is to improve the superconducting stability. The superconducting material has zero electrical resistance in the superconducting state, but if it partially transitions to normal conduction for some reason, it generates heat due to the large electric resistance in the normal conducting state, and the normal conducting portion expands to increase the overall material. A phenomenon occurs in which the superconducting state is broken at once (quench phenomenon).

On the other hand, in a composite material in which a high-conductivity material is adjacent to a superconducting material, even if a partial normal-conduction transition occurs, the current flowing in the superconducting material flows through the high-conductivity metal and is once The part that has been transferred to the conductive state can be returned to the superconducting state, and the superconducting state can be kept stable. In order to maintain the superconducting state even under a direct magnetic field of 1 Tesla or more, it is necessary that the superconducting material has a high critical magnetic field Hc2 (1 Tesla or more) and the workability such as rolling is good. Therefore, NbTi alloy was selected as the superconducting material. The reason why the Nb or Ta barrier layer is disposed between the NbTi layer and the high conductivity material layer is that the highly conductive metal such as copper and Ti in NbTi do not form an intermetallic compound in the hot rolling step in the manufacturing process. That's why.

After the hot rolling, cold rolling of 30 to 70% is performed, and the cold rolling is continued at 600 to 800 ° C. for 30 minutes to 5 hours and then the cold rolling is continued again. This is because When a type II superconductor such as NbTi is placed in a magnetic field, the magnetic field is divided into quantized magnetic flux lines having a magnetic flux quantum φ 0 and penetrates into the superconductor. When an electric current is passed through the superconductor in this state, Lorentz force acts on the quantized magnetic flux line. Here, if the quantized magnetic flux lines move, electromotive force is generated, and eventually the superconducting state with zero electric resistance is broken. In the case of NbTi, which blocks the motion of the quantized magnetic flux lines against the Lorentz force, titanium (α-T) precipitated in the alloy is used.
It is the precipitate of i). There are defects, impurities, etc. in the material as well as precipitates such as α-Ti that play a role in stopping the movement of the quantized magnetic flux lines, and these are collectively referred to as magnetic flux pinning points. The research conducted by the present inventor so far has revealed that α-Ti in NbTi is likely to precipitate at the grain boundaries. Therefore, if the crystal grain size of NbTi is small, a large amount of precipitates can be obtained quantitatively, so that pinning efficiency is good and a large critical current density can be obtained.

The lower limit of the heating temperature during hot rolling is set to 500 ° C. because NbTi and Nb or T are lower than 500 ° C.
This is because a is not sufficiently softened and the adhesion to copper is insufficient.
The reason why the upper limit is set to 1000 ° C. is that if the temperature exceeds 1000 ° C., the temperature is close to the melting point of copper and the material is excessively softened. The working ratio of hot rolling is set to 30 to 98% because if it is less than 30%, it is difficult to obtain sufficient adhesion even if the temperature is high, and if it exceeds 98%, the subsequent cold working ratio becomes too small. Is. The reason why the reduction ratio of the first cold rolling was set to 30 to 70% was 30.
If the rolling reduction is less than%, the driving force for recrystallization does not remain in the material, so that recrystallization does not occur unless the heating temperature is considerably raised. The upper limit of 70% is the material used in cold working after recrystallization. This is to leave a sufficient reduction margin in which dislocations can be sufficiently introduced. The lower limit of the first heat treatment temperature is 600 ° C. because it does not recrystallize even if the material contains many dislocations at a temperature lower than this, and the upper limit is 800 ° C. at a temperature higher than this. This is because the risk of coarsening of the recrystallized grains is great.

The crystal grains become fine by cold rolling after recrystallization. Since a large amount of α-Ti finally precipitated is precipitated at the grain boundaries, the density of precipitation is greatly improved by refining the crystal grains. The reduction ratio of the cold rolling after recrystallization is set to 30 to 98% because when the amount is less than 30%, the amount of lattice defects introduced is insufficient and the heat treatment effect cannot be utilized, and when it exceeds 98%. This is because some or all of the material is destroyed and processing defects occur. The temperature of the subsequent intermediate heat treatment is 300 to 450.
℃ is below 300 ℃, the flux pinning point α-
This is because the precipitation rate of Ti is too small and it takes too much time, and if it exceeds 450 ° C., the precipitates become coarse and hinder the subsequent cold working. The holding time per heat treatment is set to 1 to 168 hours, because the amount of precipitation is insufficient if it is less than 1 hour, and if it exceeds 168 hours, the precipitates become coarse, and the subsequent cold working is performed. This is because it causes trouble.

Introducing dislocations and vacancies that act as a driving force for precipitation,
In order to precipitate a sufficient amount of α-Ti, it is even more effective to repeat cold working and heat treatment alternately. The reason for repeating this 6 times or less is that if it exceeds 6 times, the cold reduction ratio during each heat treatment cannot be sufficiently obtained and the effect on the amount of precipitation is saturated. The reason why the cold working ratio between each heat treatment and until reaching the final shape is 30 to 98% is as follows.
This is the same as in the case of cold rolling after recrystallization. The reason why the final heat treatment is performed with the final plate thickness is to further increase the density of α-Ti precipitated by repeating cold working and heat treatment during the process. The temperature range of this heat treatment is set to 300 to 450 ° C. as in the case of the heat treatment described above. The holding time is set to 1 to 1000 hours because the effect of increasing the amount of precipitation cannot be obtained when the time is less than 1 hour, and the precipitation is saturated when the time exceeds 1000 hours.

Before explaining the second invention, a device within the scope of the conventional invention (Japanese Patent Laid-Open No. 3-136400) will be described. The conventional invention described above (Japanese Patent Laid-Open No. 3-13
No. 6400) 300-45 in the final heat treatment.
0 ℃, hold for 1 to 1000 hours in the first half of 300 ℃ or more,
When the heat treatment of the latter half is carried out at a temperature of 350 ° C. or higher and 450 ° C. or lower for a total time of 1000 hours or shorter,
Higher J than heat treated at the same temperature for the same time
c is obtained. For example, after holding at 800 ℃ for 1 hour, 50
After hot rolling at a reduction rate of 5%, heat treatment at 380 ° C. for 5 hours and cold rolling at a reduction rate of 50% were repeated 4 times, and the final heat treatment was held at 350 ° C. for 700 hours and the final heat treatment. The Jc of the material that was retained at 310 ° C for 400 hours and then continuously retained at 360 ° C for 300 hours was 5 for the former.
Whereas T is about 1200 A / mm ² , the latter is improved to about 1600 A / mm ² by 30% or more.

The reason why Jc is improved by performing the final heat treatment at a relatively low temperature in the first half and at a relatively high temperature in the second half is as follows. Phase diagram of NbTi alloy (L. Kaufman and B. Bemste
in: Computer calculatin of Phase Diagrams, Academic
Looking at Press 1970), α-Ti precipitates due to Ti supersaturated in the β solid solution region by holding in the α + β region at low temperature, but the amount of precipitation nuclei generated at relatively low temperature. Therefore, in the final heat treatment process, the first half is heat-treated at a relatively low temperature to generate a large amount of precipitation nuclei, and then heat-treated at a relatively high temperature to grow α-Ti precipitated in the previous process. The reason why the lower limit of the heat treatment temperature in the first half is 300 ° C. is that the precipitation rate is too low to prevent the generation of precipitation nuclei at a temperature lower than that, and the upper limit is less than 350 ° C. Then, there is a risk that α-Ti grows rapidly and becomes coarse. The first half heat treatment time is 10
The reason for setting it to 500 hours is that a sufficient amount of precipitation nuclei is not generated in less than 10 hours, and the amount of precipitation nuclei is saturated in more than 500 hours. The latter half heat treatment temperature is set to 35
The reason why the temperature is higher than or equal to 0 ° C. and lower than or equal to 450 ° C. is that a temperature lower than 350 ° C. is too low to promote the growth of precipitation nuclei.
This is because if the temperature exceeds 0 ° C., the precipitate will become coarse.
The second invention is a method of combining the first invention for atomizing NbTi and the manufacturing method by devising the final heat treatment in the above-mentioned conventional invention to disperse a large amount of α-Ti and disperse it densely. .

The third invention is to provide at least one layer of NbTi.
The alloy and the high conductivity metal are alternately laminated, and the NbT
A method for manufacturing a composite superconducting plate in which a barrier layer of Nb or Ta is present between the i alloy and the high conductivity metal, after hot rolling at a working rate of 30 to 98% at a temperature of 500 to 1000 ° C. , Cold rolling at a working rate of 30 to 98%, 300
Hold time of 1 to 168 at a temperature of ~ 450 ° C
After heat treatment for a period of time and cold rolling with a working rate of 30 to 98% per time are alternately repeated 6 times or less to form a plate or foil, a holding time of 1 to 300 at 450 to 450 ° C.
This is a method in which after performing heat treatment for 1000 hours, cold rolling of 30 to 90% is performed.

The reasons for limiting the processing rate and the temperature time of the heat treatment are the same as those described in the first invention. The particle size of the α-Ti precipitates deposited up to the final heat treatment step of the present invention is about several hundreds nm. In the present invention, this precipitate is made even thinner by rolling and the precipitation interval is made smaller, so that α-Ti
The size and distribution of pinning points are set to a particle size of several tens nm and a distribution interval of several tens nm, which are suitable for pinning the quantized magnetic flux lines. The lower limit of the rolling reduction after the final heat treatment is set to 30% because the effect of downsizing of α-Ti is small when it is less than 30%, and the upper limit is set to 90% when the workability deteriorates when it exceeds 90%. This is because disorder occurs in the layered structure of NbTi. From the viewpoint of miniaturizing α-Ti to a theoretically optimum size and the viewpoint of not disturbing the layered structure, the final cold working rate is preferably in the range of 50% to 75%.

The fourth aspect of the present invention is the same as the third aspect of the invention.
A method of manufacturing an NbTi superconducting multilayer plate, characterized by performing a heat treatment at a temperature of 50 ° C. for a holding time of 1 second to 5 hours. In the third invention, the material is work hardened by the final cold rolling. This is not a problem in the case where the NbTi superconducting multilayer plate is used as a plate, but it is inconvenient in the case where press working is necessary because the material is hard. Also, Cu
Since many dislocations are also introduced in the layer portion, the residual resistance ratio is small, and therefore there is a slight problem from the viewpoint of superconducting stability. In order to solve this problem, after the final cold rolling, heat treatment was performed at a temperature of 300 to 450 ° C. for 1 second or more and 5 hours or less. The heat treatment temperature is set to 300 ° C. because the material does not soften sufficiently at a lower temperature, and the heat treatment temperature is set to 450 ° C. or lower at a higher temperature.
This is because α-Ti, which has been miniaturized by the final cold rolling, starts to grow. The time of 1 second or longer means that the material softens when the temperature reaches the set temperature, and the minimum time is set to 1 second. The time is set to 5 hours or less because if it exceeds this time, α-Ti, which has been downsized in the final cold rolling, becomes large again.

A fifth aspect of the present invention is an NbTi superconducting multilayer plate in which a plate-shaped NbTi alloy layer is arranged in a Cu or Cu alloy base material with the Nb layer interposed therebetween. Is deposited in a plate shape in parallel with, and the thickness is 1 nm or more and 100 nm or less, and the distance in the plate thickness direction is 1
The NbTi superconducting multilayer plate is characterized in that normal conductive precipitates having a volume fraction of 3 nm or more and 500 nm or less and a volume fraction of 3% or more and 50% or less with respect to the entire NbTi alloy layer are present.

This will be described in detail with reference to FIG. Figure 1 shows Nb
The morphology of the NbTi layer of a Ti superconducting multilayer board is shown. NbTi
Assuming that the normal-conducting precipitates 2 having a thickness t are present in the layer 1 at an interval d, 1 nm ≦ t ≦ 100 nm, 1 nm ≦ d ≦ 500 nm, and the volume fraction of the normal-conducting precipitates in the NbTi layer is v. Then, 3% ≦ v ≦ 50%. Here, the width w and the length L of the normal-conducting precipitate are not particularly limited and may be any size.

With this structure, when the applied magnetic field is in the direction B or B'and a current is passed in the direction I or I ', the normal conducting precipitate 2 overcomes the Lorentz force F or F'. Effectively pin the magnetic flux and increase the critical current density.

The thickness of the normal-conducting precipitate is set to 1 nm or more because if it is smaller than this, it becomes too small as compared with the size of the region of the superconducting and normal-conducting interfaces of NbTi and the pinning of the magnetic flux quantum cannot be sufficiently performed. The reason for setting the thickness of the normal conducting precipitate to 100 nm or less is that if it is larger than this, it becomes larger than the interval of the magnetic flux quanta, and many magnetic flux quanta enter into the normal conducting precipitate and cannot be sufficiently pinned. Is.

The spacing between the normal conducting precipitates is set to 1 nm or more. If the spacing is smaller than this, there are many normal conducting deposits that do not contribute to pinning in the spacing of the magnetic flux quantum.
This is because the cross-sectional area of the NbTi superconductor is unnecessarily reduced, and the distance between the normal-conducting precipitates is 500 nm.
The reason for this is that the number of unpinned magnetic flux quanta becomes too large when the distance is further.

The reason why the volume fraction of the normal-conducting precipitate in the NbTi layer is 3% or more is that the flux quantum cannot be sufficiently pinned if the volume fraction is smaller than this, and the volume fraction is set to 50% or less. This is because if is too large, the cross-sectional area of superconductivity becomes small and the increase in critical current density is meaningless.

When the normal-conducting precipitates extend long in the direction parallel to the applied magnetic field, the magnetic flux quanta are mostly trapped in the energetically stable normal-conducting precipitates, so that the normal-conducting precipitates pinning point is reached. A large force is required to separate the magnetic flux quanta, resulting in a strong pinning. Further, the width W of the normal-conducting precipitate is not related to the pinning force, whether it is large or small as long as the directions of the magnetic field and the current are the same as in FIG. Therefore, the width and length of the normal-conducting precipitate may be arbitrary.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION

[Example 1] Table 1 shows the measurement results of the critical current density (Jc) of the superconducting multilayer plate manufactured by the present invention and the superconducting multilayer plate manufactured by the conventional method, and the total time of the intermediate heat treatment and the final heat treatment after hot rolling. The ratio of Jc (8T) to The larger this ratio, the higher the Jc can be obtained without incurring the cost of heat treatment. Jc is a value at 5T (tesla) and a value at 8T (tesla). The superconducting multilayer plates shown in the examples have the same multilayer structure. The final plate thickness was 1 mm in the examples of Inventions 1 and 2, and Jc was measured for the materials having the plate thicknesses of 0.5 mm, 0.2 mm, and 0.1 mm in the examples of Invention 3. The structure of the superconducting multilayer plate having a total thickness of 1 mm is as follows. The outermost layer is a copper layer with a thickness of about 0.11 mm, and an NbTi layer with a thickness of about 11 μm is 30
Layers, alternating with layers of copper of the same thickness. further,
An Nb layer of about 1 μm is inserted between the NbTi layer and the copper layer. The superconducting multilayer plates with total thicknesses of 0.5, 0.2 and 0.1 mm are obtained by rolling 1 mm plates at 50%, 80% and 90% reduction rates, respectively.

The critical current density is the critical current value which is the current value that can be applied until the inter-terminal voltage becomes 1 μV by attaching voltage terminals to the test piece having a width of 0.5 mm and a width of 0.5 mm at intervals of 10 mm. (Ic) and the value obtained by dividing this by the total cross-sectional area of NbTi was taken as the critical current density (Jc). The rolling direction was fixed in both hot and cold rolling, and the sample for measuring the critical current density was taken in the direction perpendicular to the rolling direction. A current was passed through the sample while it was immersed in liquid helium, and the critical current was measured. No. 1 of the present invention. 1 to No. 9 and No. 9 12, N
o. No. 13 of the manufacturing process and the comparative example. 10, No. 1
1 and No. 1 The manufacturing process of 14 is as follows.

No. 1 (Invention 1): Hot rolling (800
After holding at ℃ for 1 hour, rolling reduction 60% → cold rolling (rolling reduction 5
0%) → heat treatment (750 ° C, hold for 30 minutes) → cold rolling (rolling reduction: 50%) → heat treatment (380 ° C, hold for 5 hours) → cold rolling (rolldown: 50%) → heat treatment (380 ° C, hold for 5 hours) →
Cold rolling (75% reduction) → heat treatment (350 ° C 336 hours), final plate thickness 1 mm. Total heat treatment time after hot rolling: 34
6.5 hours.

No. 2 (Invention 1): Hot rolling (550
After holding at ℃ for 3 hours, reduction ratio 35%) → cold rolling (reduction ratio 3
0%) → Heat treatment (700 ° C. hold for 1 hour) → Cold rolling (reduction of 50%) → Heat treatment (380 ° C. hold for 168 hours) → Cold rolling (reduction of 95%) → Heat treatment (370 ° C.168 hours), Final plate thickness 1mm. Total heat treatment time after hot rolling: 33
7 hours.

No. 3 (Invention 1): Hot rolling (950
After holding for 1 hour at ℃, reduction rate 85%) → cold rolling (reduction rate 3
0%) → heat treatment (holding at 600 ° C for 4 hours) → cold rolling (rolling rate 50%) → heat treatment (430 ° C 10 hours) → cold rolling (rolling rate 75%) → heat treatment (330 ° C 500 hours), final Plate thickness 1 mm. Total heat treatment time after hot rolling: 514 hours.

No. 4 (Invention 2): Hot rolling (800
After holding at ℃ for 1 hour, rolling reduction 50%) → cold rolling (rolling reduction 5
0%) → heat treatment (holding at 750 ° C for 30 minutes) → cold rolling (holding rate at 50%) → heat treatment (holding at 430 ° C for 1 hour) → cold rolling (holding rate at 50%) → heat treatment (holding at 380 ° C for 5 hours) →
Cold rolling (80% reduction) → heat treatment (300 ° C 168 hours → 370 ° C 168 hours), final plate thickness 1 mm. Total heat treatment time after hot rolling: 342.5 hours.

No. 5 (Invention 2): Hot rolling (550
After holding at ℃ for 3 hours, reduction ratio 35%) → cold rolling (reduction ratio 3
0%) → heat treatment (holding at 700 ° C for 1 hour) → cold rolling (50% rolling reduction) → heat treatment (holding at 380 ° C 168 hours) → cold rolling (95% rolling reduction) → heat treatment (72 hours at 340 ° C →
380 ° C for 264 hours), final plate thickness 1 mm. Total heat treatment time after hot rolling: 505 hours.

No. 6 (Invention 2): Hot rolling (950
After holding for 1 hour at ℃, reduction rate 85%) → cold rolling (reduction rate 3
0%) → Heat treatment (holding at 600 ° C. for 4 hours) → Cold rolling (reduction of 50%) → Heat treatment (320 ° C. for 168 hours) → Cold rolling (reduction of 75%) → Heat treatment (320 ° C. for 264 hours → 4)
40 ° C for 72 hours), final plate thickness 1 mm. Total heat treatment time after hot rolling: 508 hours.

No. 7 (Invention 3): Hot rolling (800
After holding at ℃ for 1 hour, rolling reduction 50%) → cold rolling (rolling reduction 5
0%) → heat treatment (400 ° C, hold for 2 hours) → cold rolling (rolldown: 50%) → heat treatment (380 ° C, hold for 5 hours) → cold rolling (rolldown: 50%) → heat treatment (380 ° C, hold for 5 hours) →
Cold rolling (80% reduction) → heat treatment (240 ° C for 240 hours) → cold rolling (50% reduction), final plate thickness 0.5 mm.
Total heat treatment time after hot rolling: 252 hours.

No. 8 (Invention 3): Hot rolling (550
After holding at ℃ for 3 hours, reduction ratio 35%) → cold rolling (reduction ratio 3
0%) → heat treatment (400 ° C. hold for 3 hours) → cold rolling (roll reduction of 50%) → heat treatment (380 ° C. hold for 168 hours) → cold rolling (roll reduction of 95%) → heat treatment (340 ° C.336 hours) → Cold rolling (80% reduction), final thickness 0.2mm.
Total heat treatment time after hot rolling: 507 hours.

No. 9 (Invention 3): Hot rolling (950
After holding for 1 hour at ℃, reduction rate 85%) → cold rolling (reduction rate 3
0%) → heat treatment (holding at 320 ° C for 96 hours) → cold rolling (50% reduction) → heat treatment (96 hours at 320 ° C) → cold rolling (75% reduction) → heat treatment (168 hours at 400 ° C)
→ Cold rolling (reduction rate 90%), final plate thickness 0.1mm. Total heat treatment time after hot rolling: 360 hours.

No. 10 (Comparative Example 1): Hot rolling (80
After holding at 0 ° C for 1 hour, rolling reduction 50%) → heat treatment (380 ° C
Hold for 5 hours) → Cold rolling (50% reduction) → Heat treatment (3
80 ° C for 5 hours) → cold rolling (50% reduction) → heat treatment (380 ° C, 5 hours retention) → cold rolling (50% reduction)
→ Heat treatment (holding at 380 ° C for 5 hours) → Cold rolling (reduction rate 8
5%) → heat treatment (350 ° C. 700 hours), final plate thickness 1.
0mm. Total heat treatment time after hot rolling: 720 hours.

No. 11 (Comparative Example 2): Hot rolling (80
After holding at 0 ° C for 1 hour, rolling reduction 50%) → heat treatment (380 ° C
Hold for 5 hours) → Cold rolling (50% reduction) → Heat treatment (3
80 ℃ hold for 5 hours) → cold rolling (50% reduction) → heat treatment (hold at 380 ℃ for 5 hours) Illama rolling (50% reduction)
・ Heat treatment (holding at 380 ° C for 5 hours), one cold rolling (reduction rate 8
5%) → heat treatment (310 ° C 400 hours → 360 ° C 300)
Time), final plate thickness 1.0 mm. Total heat treatment time after hot rolling: 720 hours.

No. 12 (Invention 1): Hot rolling (80
After holding at 0 ° C for 1 hour, reduction rate 50%) → cold rolling (reduction rate 50%) → heat treatment (750 ° C 30 minutes retention) → cold rolling (reduction rate 50%) → heat treatment (380 ° C 5 hours retention) → Cold rolling (reduction of 50%) → Heat treatment (holding at 380 ° C for 5 hours) → Cold rolling (reduction of 85%) → Heat treatment (350 ° C 7
20 hours), final thickness 1mm. Total heat treatment time after hot rolling: 730.5 hours.

No. 13 (Invention 2): Hot rolling (80
After holding at 0 ° C for 1 hour, rolling reduction 50%) → cold rolling (rolling reduction 50%) → heat treatment (750 ° C 30 minutes holding) → cold rolling (rolling reduction 50%) → heat treatment (430 ° C 1 hour holding) → Cold rolling (50% reduction) → Heat treatment (380 ° C, hold for 5 hours) → Cold rolling (80% reduction) → Heat treatment (300 ° C 1
68 hours → 370 ° C. 504 hours), final plate thickness 1 mm. Total heat treatment time after hot rolling: 678.5 hours.

No. 14 (Comparative Example 3): Hot rolling (80
After holding at 0 ° C for 1 hour, rolling reduction 50%) → heat treatment (380 ° C
Hold for 5 hours) → Cold rolling (50% reduction) → Heat treatment (3
80 ° C for 5 hours) → cold rolling (50% reduction) → heat treatment (380 ° C, 5 hours retention) → cold rolling (50% reduction)
→ Heat treatment (holding at 380 ° C for 5 hours) → Cold rolling (reduction rate 8
5%) → heat treatment (350 ° C 1000 hours), final plate thickness 1.0 mm. Total heat treatment time after hot rolling: 1020 hours.

[0043]

[Table 1]

[Embodiment 2] No. 1 of the first embodiment. The material of the present invention 4 obtained by heat treating the material of No. 8 at 350 ° C. for 1 hour is
o. Set to 15. No. Table 1 shows the critical current densities under 15 and 5 Tesla and 8 Tesla. 3% under 5 Tesla, 8
About 5% under Tesla Although it is smaller than No. 8, comparing the critical current densities under 1 Tesla, No. In 8, 39
It was 45 A / mm ² , whereas No. In 15, 408
It was 5 A / mm ² and increased by about 3.5%. It is considered that this is because the superconducting stability was improved due to the increase in the residence resistance ratio of Cu, and the effect was exhibited particularly in the low magnetic field side. In addition, No. 8
And No. No. 15 was measured when the mechanical elongation of the material of No. 15 in the rolling direction was measured. 8 was about 1%, while N
o. At 15, it was about 11%. For applications where the plate is used without processing, use No. No. 8 is sufficient, but when press working is performed, No. 8 is used. 15 (Invention 4) is more suitable.

[Example 3] A total thickness of 1 mm and 30 layers of NbT
An NbTi / Nb / Cu multilayer plate having a structure in which i layers (about 12 μm in thickness) and Nb layers (about 1 μm in thickness) and copper layers (about 12 μm in thickness) were alternately laminated was produced. The manufacturing process is shown below, following the example of Example 1.

No. 16 (Invention 5): Hot rolling (83
After holding at 0 ° C for 2 hours, rolling reduction 60%) → cold rolling (rolling reduction 50%) → heat treatment (380 ° C 5 hours) → cold rolling (rolling reduction 50%) → heat treatment (380 ° C 5 hours) → cooling Cold rolling (50% reduction) → heat treatment (380 ° C 5 hours) → cold rolling (80% reduction) → heat treatment (370 ° C 500 hours) → cold rolling (60% reduction) → heat treatment (350 ° Cl) time).
Normal conductivity T in the NbTi layer seen from the cross section in the rolling direction of this material
i The average thickness of precipitates is 30 nm, the average interval is 100 n
m, a superconducting plate of the present invention 5 having an NbTi layer as shown in FIG. 2 having a volume fraction of 10% was obtained.

As a comparative example, No. 1 was manufactured by the following manufacturing process. Seventeen materials were produced. No. 17 (Comparative Example 4): Hot rolling (holding at 830 ° C. for 2 hours, rolling reduction 60%) → cold rolling (rolling reduction 50%) → heat treatment (380 ° C. 5 hours) → cold rolling (rolling reduction 50%) ) →
Heat treatment (380 ° C 5 hours) → cold rolling (rolling reduction 50%)
→ Heat treatment (380 ° C for 5 hours) → Cold rolling (Reduction rate 80
%) → heat treatment (370 ° C. 500 hours).

NbTi as seen from the section in the rolling direction of Comparative Example 4.
In the layer, elliptical normal-conducting Ti precipitates having an average major axis of 250 nm and an average minor axis of 150 nm were precipitated with an average interval of 250 nm and a volume fraction of 10% (FIG. 3). No. 16 (Invention 5) and No. Table 2 shows the results of measuring the critical current density in the width direction of the rolled material of No. 17 (Comparative Example 4).

[0049]

[Table 2]

[0050]

The superconducting multilayer board manufactured by the manufacturing process of the present invention has a maximum critical current density twice as high as that manufactured by the conventional manufacturing process, and when the same magnetic field is shielded. The thickness of the plate to be used can be reduced, and the weight of the magnetic shield can be reduced and the manufacturing cost can be significantly reduced. As can be seen by comparing Jc (at 8T) per unit heat treatment time, the manufacturing method was more efficient than the conventional technology, and the manufacturing cost could be reduced.

Further, in the fifth invention, plate-shaped normal-conducting precipitates thinly extending in the rolling direction to a thickness comparable to the size of the superconducting / normal-conducting interface are arranged at intervals close to the magnetic flux quantum intervals. Therefore, it is possible to obtain a large critical current density because the magnetic flux quantum that has entered in the intermediate state is efficiently captured and pinned with a large force.

[Brief description of drawings]

FIG. 1 is an overall view showing an NbTi alloy layer in a superconducting plate according to the present invention.

FIG. 2 is a rolling direction sectional view of an NbTi alloy layer in a superconducting plate showing an example of the present invention.

FIG. 3 is a sectional view in the rolling direction of an NbTi alloy layer in a conventional superconducting plate.

[Explanation of symbols]

 1 NbTi 2 Normal Conductive Ti Precipitate 3 Grain Boundary

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical location H05K 9/00 ZAA H05K 9/00 ZAAW (72) Inventor Mitsuru Sawamura 3 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa No.35-1 Nippon Steel Co., Ltd. Technology Development Division

Claims (5)

[Claims] 1. A method for producing a superconducting multilayer plate, wherein at least one layer of NbTi alloy and high conductivity metal are alternately laminated, and a barrier layer of Nb or Ta is present between the NbTi alloy and the high conductivity metal. And a temperature of 500 to 1
After hot rolling at a working rate of 30 to 98% at 000 ° C.,
Cold rolling at a working rate of 30-70%, then temperature of 600-8
After holding at 00 ° C for 30 minutes to 5 hours, processing rate 30 to 98
% Cold rolling, heat treatment at a temperature of 300 to 450 ° C. for a holding time of 1 to 168 hours per time, and cold rolling at a working rate of 30 to 98% per time of 6 times or less alternately. Repeatedly applied to form a plate or foil, then 300 to 45
A method for producing an NbTi superconducting multilayer plate, which comprises performing a final heat treatment at a temperature of 0 ° C. and a holding time of 1 to 1000 hours. 2. A method for manufacturing a superconducting multilayer plate, wherein at least one layer of NbTi alloy and high conductivity metal are alternately laminated, and a barrier layer of Nb or Ta is present between the NbTi alloy and the high conductivity metal. And a temperature of 500 to 1
After hot rolling at a working rate of 30 to 98% at 000 ° C.,
Cold rolling at a working rate of 30-70%, then temperature of 600-8
After holding at 00 ° C for 30 minutes to 5 hours, processing rate 30 to 98
% Cold rolling, heat treatment at a temperature of 300 to 450 ° C. for a holding time of 1 to 168 hours per time, and cold rolling at a working rate of 30 to 98% per time of 6 times or less alternately. After being repeatedly applied into a plate shape or a foil shape, it is applied at a temperature of 300 ° C. or higher and lower than 350 ° C. for 10 to 500 hours, and subsequently, a holding time of 1 to 1 at a temperature of 350 ° C. or higher and lower than 450 ° C.
NbT characterized by being subjected to a final heat treatment of 000 hours
i A method for manufacturing a superconducting multilayer board. 3. A method for producing a superconducting multilayer plate, wherein at least one layer of NbTi alloy and high conductivity metal are alternately laminated, and a barrier layer of Nb or Ta is present between the NbTi alloy and the high conductivity metal. And a temperature of 500 to 1
After hot rolling at a working rate of 30 to 98% at 000 ° C.,
Cold rolling at a working rate of 30 to 98%, heat treatment at a temperature of 300 to 450 ° C. for a holding time of 1 to 168 hours per time, and cold rolling at a working rate of 30 to 98% for 6 times. Repeatedly repeated less than once to make a plate or foil,
A method for producing an NbTi superconducting multilayer plate, which comprises performing a heat treatment at a temperature of 300 to 450 ° C. for a holding time of 1 to 1000 hours and then performing a cold rolling of 30 to 90%. 4. A superconducting multilayer plate comprising at least one layer of NbTi alloy and high conductivity metal alternately laminated, and a Nb or Ta barrier layer being present between said NbTi alloy and said high conductivity metal. After performing hot rolling with a processing rate of 30 to 98% at a temperature of 500 to 1000 ° C., a processing rate of 30
~ 98% cold rolling, heat treatment at a temperature of 300 ~ 450 ° C for a holding time of 1 ~ 168 hours per time, and cold rolling with a working rate of 30 ~ 98% per time alternate up to 6 times. Repeatedly plate-shaped or foil-shaped, then 300-450 ℃
After the heat treatment at the temperature of 1 to 1000 hours, the cold rolling of 30 to 90% is performed, and further 300 to 4
A method for producing an NbTi superconducting multilayer plate, which comprises performing heat treatment at a temperature of 50 ° C. for 1 second to 5 hours. 5. A plate-shaped NbT in a Cu or Cu alloy substrate.
In the NbTi superconducting multilayer plate in which the i alloy layer is arranged via the Nb layer, in the NbTi layer of the NbTi superconducting multilayer plate, a plate shape is deposited parallel to the plate surface, and a thickness of 1 nm or more and 100 nm or less, Distance in the plate thickness direction is 1 nm or more, 5
An NbTi superconducting multilayer plate, which has a normal-conducting precipitate having a volume fraction of 3% to 50% with respect to the entire NbTi alloy layer of 00 nm or less.