U.S. patent application number 17/069479 was filed with the patent office on 2021-07-22 for superconducting wire and superconducting coil.
This patent application is currently assigned to MITSUBISHI MATERIALS CORPORATION. The applicant listed for this patent is MITSUBISHI MATERIALS CORPORATION. Invention is credited to Kosei FUKUOKA, Yuki ITO, Kazunari MAKI.
Application Number | 20210225560 17/069479 |
Document ID | / |
Family ID | 1000005507895 |
Filed Date | 2021-07-22 |
United States Patent
Application |
20210225560 |
Kind Code |
A1 |
FUKUOKA; Kosei ; et
al. |
July 22, 2021 |
SUPERCONDUCTING WIRE AND SUPERCONDUCTING COIL
Abstract
The present invention is a superconducting wire including: a
wire formed of a superconducting material; and a superconducting
stabilization material disposed in contact with the wire, in which
the superconducting stabilization material is formed of a copper
material which contains: one or more types of additive elements
selected from Ca, Sr, Ba, and rare earth elements in a total of 3
ppm by mass to 400 ppm by mass; a balance being Cu and inevitable
impurities, and in which a total concentration of the inevitable
impurities excluding O, H, C, N, and S which are gas components is
5 ppm by mass to 100 ppm by mass.
Inventors: |
FUKUOKA; Kosei;
(Okegawa-shi, JP) ; ITO; Yuki; (Cambridge, MA)
; MAKI; Kazunari; (Saitama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUBISHI MATERIALS CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
MITSUBISHI MATERIALS
CORPORATION
Tokyo
JP
|
Family ID: |
1000005507895 |
Appl. No.: |
17/069479 |
Filed: |
October 13, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15540928 |
Jun 29, 2017 |
10964454 |
|
|
PCT/JP2015/085765 |
Dec 22, 2015 |
|
|
|
17069479 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22D 11/005 20130101;
C22C 9/00 20130101; Y02E 40/60 20130101; H01B 12/04 20130101; H01F
6/06 20130101; H01B 12/00 20130101; B22D 11/12 20130101; H01B 12/02
20130101; H01B 12/06 20130101; B22D 11/00 20130101 |
International
Class: |
H01B 12/04 20060101
H01B012/04; C22C 9/00 20060101 C22C009/00; H01F 6/06 20060101
H01F006/06; H01B 12/02 20060101 H01B012/02; B22D 11/12 20060101
B22D011/12; B22D 11/00 20060101 B22D011/00; H01B 12/00 20060101
H01B012/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 7, 2015 |
JP |
2015-001510 |
Claims
1. A superconducting wire comprising: a wire formed of a
superconducting material; and a superconducting stabilization
material disposed in contact with the wire, wherein the
superconducting stabilization material is formed of a copper
material which contains: one or more additive elements selected
from rare earth elements in a total of 3 ppm by mass to 400 ppm by
mass; and a balance being Cu and inevitable impurities, and in
which a total concentration of the inevitable impurities excluding
O, H, C, N, and S which are gas components is 5 ppm by mass to 100
ppm by mass.
2. The superconducting wire according to claim 1, wherein the
inevitable impurities comprise; Fe in a range of 10 ppm by mass or
less, Ni in a range of 10 ppm by mass or less, As in a range of 5
ppm by mass or less, Ag in a range of 50 ppm by mass or less, Sn in
a range of 4 ppm by mass or less, Sb in a range of 4 ppm by mass or
less, Pb in a range of 6 ppm by mass or less, Bi in a range of 2
ppm by mass or less, and P in a range of 3 ppm by mass or less.
3. The superconducting wire according to claim 1, wherein the
superconducting stabilization material is formed of the copper
material in which a ratio Y/X of the total amount of the one or
more additive elements (Y ppm by mass) to a total amount of S, Se,
and Te (X ppm by mass) is in a range of
0.5.ltoreq.Y/X.ltoreq.100.
4. The superconducting wire according to claim 1, wherein the
superconducting stabilization material is formed of the copper
material in which a compound, which contains the one or more
additive elements and one or more elements selected from S, Se, and
Te, is present.
5. The superconducting wire according to claim 1, wherein the
superconducting stabilization material has a residual resistance
ratio (RRR) of 250 or more.
6. The superconducting wire according to claim 1, wherein the
superconducting stabilization material is manufactured by a
continuous casting rolling method.
7. A superconducting coil comprising: a winding wire part formed by
winding the superconducting wire according to claim 1 around an
outer surface of a winding frame.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application is a Continuation of the U.S. patent
application Ser. No. 15/540,928 filed Jun. 29, 2017, which is a
U.S. National Phase Application under 35 U.S.C. .sctn. 371 of
International Patent Application No. PCT/JP2015/085765 filed on
Dec. 22, 2015 and claims the benefit of Japanese Patent Application
No. 2015-001510, filed Jan. 7, 2015, all of which are incorporated
herein by reference in their entirety. The International
Application was published in Japanese on Jul. 14, 2016 as
International Publication No. WO/2016/111159 under PCT Article
21(2).
FIELD OF THE INVENTION
[0002] The present invention relates to a superconducting wire
provided with a wire formed of a superconducting material and a
superconducting stabilization material disposed in contact with the
wire, and a superconducting coil formed of the superconducting
wire.
BACKGROUND OF THE INVENTION
[0003] The superconducting wire described above is used in fields
such as MRI, NMR, particle accelerators, maglev, and electric power
storage apparatuses.
[0004] This superconducting wire has a multi-core structure in
which a plurality of wires formed of a superconducting material
such as Nb--Ti alloy and Nb.sub.3Sn are bundled with a
superconducting stabilization material interposed therebetween. In
addition, a tape-shaped superconducting wire in which a
superconducting material and a superconducting stabilization
material are laminated is also provided.
[0005] Here, in the superconducting wire described above, in a case
where the superconducting state is destroyed in a part of the
superconducting material, there is a concern that the resistance
partially increases greatly, in which the temperature of the
superconducting material rises and the temperature of the entire
superconducting material becomes higher than the critical
temperature, transitioning the superconducting state to a normal
conducting state. Therefore, the superconducting wire has a
structure in which a superconducting stabilization material having
a relatively low resistance such as copper is disposed so as to be
in contact with the superconducting material and, in a case where
the superconducting state is partially destroyed, the electric
current flowing through the superconducting material is temporarily
diverted to the superconducting stabilization material and in the
meantime the superconducting material is cooled to return to the
superconducting state.
[0006] In the superconducting stabilization material described
above, in order to effectively divert the electric current, it is
required that the resistance at extremely low temperatures be
sufficiently low. Residual resistance ratio (RRR) is widely used as
an indicator of electric resistance at extremely low temperatures.
The residual resistance ratio (RRR) is the ratio
.rho..sub.293K/.rho..sub.4.2K of the resistance .rho..sub.293K at
normal temperature (293 K) to the resistance .rho..sub.4.2K at
liquid helium temperature (4.2 K), and the higher the residual
resistance ratio (RRR), the better the performance as a
superconducting stabilization material.
[0007] Therefore, for example, Japanese Unexamined Patent
Application, First Publication No. 2011-236484 and Japanese
Unexamined Patent Application, First Publication No. H05-025565
propose a Cu material having a high residual resistance ratio
(RRR).
[0008] Japanese Unexamined Patent Application, First Publication
No. 2011-236484 proposes a high purity copper having an extremely
low impurity concentration in which the amounts of specific
elements (Fe, P, Al, As, Sn, and S) are defined.
[0009] In addition, Japanese Unexamined Patent Application, First
Publication No. H05-025565 proposes a Cu alloy in which small
amount of Zr is added to high purity copper having a low oxygen
concentration.
Technical Problem
[0010] It is known that the residual resistance ratio (RRR) is
sufficiently high in an ultrahigh purity copper where the
concentrations of the impurity elements are reduced to an extreme
level. However, in order to purify copper to such high degree of
purity, there are problems in that the manufacturing process
becomes extremely complicated, and the manufacturing cost greatly
increases.
[0011] Here, in Japanese Unexamined Patent Application, First
Publication No. 2011-236484, the amounts of specific elements (Fe,
P, Al, As, Sn, and S) are limited to less than 0.1 ppm; however, it
is not easy to reduce these elements to less than 0.1 ppm, and
there is also the problem in that the manufacturing process becomes
complicated.
[0012] In addition, although the amounts of oxygen and Zr is
defined in Japanese Unexamined Patent Application, First
Publication No. H05-025565, there are problems in that it is
difficult to control the amounts of oxygen and Zr and it is
difficult to stably produce a copper alloy having a high residual
resistance ratio (RRR).
[0013] The present invention has been made in view of the above
circumstances, and has an objective of providing a superconducting
wire, which is able to be stably used and which is provided with a
superconducting stabilization material which is able to be
manufactured with a relatively simple and inexpensive manufacturing
process and has a sufficiently high residual resistance ratio
(RRR), as well as a superconducting coil formed of this
superconducting wire.
SUMMARY OF THE INVENTION
Solution to Problem
[0014] In order to solve this problem, as a result of extensive
research conducted by the present inventors, it was confirmed that
among the inevitable impurities, S, Se, and Te in particular exert
a negative influence on the residual resistance ratio (RRR), and it
was found that it is possible to manufacture a superconducting
stabilization material having a high residual resistance ratio
(RRR) by adding small amounts of Ca, Sr, Ba, and rare earth (RE)
elements to pure copper and fixing S, Se, and Te as a compound.
[0015] Based on the above findings, according to a first aspect of
the present invention, there is provided a superconducting wire
including: a wire formed of a superconducting material; and a
superconducting stabilization material disposed in contact with the
wire, in which the superconducting stabilization material is formed
of a copper material which contains: one or more types of additive
elements selected from Ca, Sr, Ba, and rare earth elements in a
total of 3 ppm by mass to 400 ppm by mass; and the balance being Cu
and inevitable impurities, and in which the total concentration of
the inevitable impurities excluding O, H, C, N, and S which are gas
components is 5 ppm by mass to 100 ppm by mass.
[0016] Here, in the present invention, the rare earth (RE) elements
are La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc,
and Y.
[0017] According to the superconducting wire having the
configuration described above, the superconducting stabilization
material is formed of a copper material in which one or more types
of additive elements selected from Ca, Sr, Ba, and rare earth
elements are contained in a total of 3 ppm by mass to 400 ppm by
mass in copper where a total concentration of inevitable impurities
excluding O, H, C, N, and S which are gas components is 5 ppm by
mass to 100 ppm by mass. Therefore, S, Se, and Te in copper are
fixed as a compound and it is possible to improve the residual
resistance ratio (RRR) of the superconducting stabilization
material. In addition, even in a case where the superconducting
state is destroyed in a part of the superconducting material, due
to the superconducting stabilization material being electrically in
contact with the wire formed of a superconducting material, it is
possible to divert the electric current flowing in the
superconducting material to the superconducting stabilization
material and to suppress the transition of the entire
superconducting wire to the normal conducting state. Therefore, it
is possible to stably use the superconducting wire.
[0018] In addition, in the superconducting stabilization material,
since copper with the total concentration of inevitable impurities
excluding O, H, C, N, and S which are gas components being 5 ppm by
mass to 100 ppm by mass is used, there is no need to excessively
increase the purity level of the copper, thus the manufacturing
process is simplified and it is possible to reduce the
manufacturing cost.
[0019] Here, in the superconducting wire according to the first
aspect of the present invention, the superconducting stabilization
material is preferably formed of the copper material with the
inevitable impurities in which an Fe content is 10 ppm by mass or
less, a Ni content is 10 ppm by mass or less, an As content is 5
ppm by mass or less, a Ag content is 50 ppm by mass or less, a Sn
content is 4 ppm by mass or less, an Sb content is 4 ppm by mass or
less, a Pb content is 6 ppm by mass or less, a Bi content is 2 ppm
by mass or less, and a P content is 3 ppm by mass or less.
[0020] Among inevitable impurities, specific elements such as Fe,
Ni, As, Ag, Sn, Sb, Pb, Bi, and P have an effect of decreasing the
residual resistance ratio (RRR). Therefore, defining the amount of
these elements as described above makes it possible to effectively
improve the residual resistance ratio (RRR) of the superconducting
stabilization material.
[0021] In addition, in the superconducting wire according to the
first aspect of the present invention, the superconducting
stabilization material is preferably formed of the copper material
in which a ratio Y/X of a total amount of additive elements of one
or more types selected from Ca, Sr, Ba, and rare earth elements (Y
ppm by mass) to a total amount of S, Se, and Te (X ppm by mass) is
in a range of 0.5.ltoreq.Y/X.ltoreq.100.
[0022] In this case, since a ratio Y/X of a total amount of
additive elements of one or more types selected from Ca, Sr, Ba,
and rare earth elements (Y ppm by mass) to a total amount of S, Se,
and Te (X ppm by mass) is in the range described above, it is
possible for S, Se, and Te in copper to be effectively fixed as a
compound with one or more types of additive elements selected from
Ca, Sr, Ba, and rare earth elements, and to effectively suppress
decreases in the residual resistance ratio (RRR) caused by S, Se,
and Te.
[0023] Furthermore, in the superconducting wire according to the
first aspect of the present invention, the superconducting
stabilization material is preferably formed of the copper material
in which a compound which contains one or more types of additive
elements selected from Ca, Sr, Ba, and rare earth elements and one
or more types of elements selected from S, Se, and Te is
present.
[0024] In this case, S, Se, and Te present in copper are
effectively fixed as a compound with one or more types of additive
elements selected from Ca, Sr, Ba, and rare earth elements, and it
is possible to effectively suppress decreases in the residual
resistance ratio (RRR) caused by S, Se, and Te.
[0025] In addition, in the superconducting wire according to the
first aspect of the present invention, the superconducting
stabilization material preferably has a residual resistance ratio
(RRR) of 250 or more.
[0026] In this case, since the residual resistance ratio (RRR) of
the superconducting stabilization material is relatively high at
250 or more, meaning the resistance at extremely low temperatures
is sufficiently low, it is possible to sufficiently divert the
electric current when the superconducting state of the
superconducting material is destroyed, and it is possible to
suppress the normal conducting state from propagating to the entire
superconducting material.
[0027] Furthermore, in the superconducting wire according to the
first aspect of the present invention, the superconducting
stabilization material is preferably manufactured by a continuous
casting rolling method.
[0028] In this case, since casting and rolling are carried out
continuously, it is possible to obtain a long superconducting
stabilization material with high production efficiency.
[0029] A superconducting coil according to a second aspect of the
present invention has a winding wire part formed by winding the
superconducting wire according to the first aspect around an outer
surface of a winding frame.
[0030] In the superconducting coil with this configuration, since
the superconducting wire provided with a superconducting
stabilization material having a high residual resistance ratio
(RRR) is used as described above, it is possible to stably use the
superconducting coil.
Advantageous Effects of Invention
[0031] According to the present invention, it is possible to
provide a superconducting wire which is able to be stably used and
which is provided with a superconducting stabilization material,
which is able to be manufactured with a relatively simple and
inexpensive manufacturing process and has a sufficiently high
residual resistance ratio (RRR), and to provide a superconducting
coil formed of this superconducting wire.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a cross-sectional schematic diagram of a
superconducting wire according to the present embodiment.
[0033] FIG. 2 is a longitudinal sectional schematic diagram of a
filament used for the superconducting wire shown in FIG. 1.
[0034] FIG. 3 is a schematic diagram of a superconducting wire
according to another embodiment.
[0035] FIG. 4 is diagrams showing (a) SEM observation result and
(b) analysis result of the compound of the superconducting
stabilization material of Invention Example 4 in the Examples.
[0036] FIG. 5 is diagrams showing (a) SEM observation result and
(b) analysis result of the compound of the superconducting
stabilization material of Invention Example 10 in the Examples.
[0037] FIG. 6 is diagrams showing (a) SEM observation result and
(b) analysis result of the compound of the superconducting
stabilization material of Invention Example 19 in the Examples.
DETAILED DESCRIPTION OF THE INVENTION
[0038] Description will be given below of a superconducting wire 10
according to one embodiment of the present invention with reference
to the accompanying drawings.
[0039] As shown in FIG. 1, the superconducting wire 10 in the
present embodiment is provided with a core portion 11, a plurality
of filaments 12 disposed on the outer peripheral side of the core
portion 11, and an outer shell portion 13 disposed on the outer
peripheral side of the plurality of filaments 12.
[0040] In the present embodiment, as shown in FIG. 1 and FIG. 2,
the filaments 12 described above have a structure in which a wire
15 formed of a superconducting material is surrounded by a
superconducting stabilization material 20 in a state of being
electrically in contact therewith. In other words, the wire 15
formed of a superconducting material and the superconducting
stabilization material 20 are in a state in which it is possible to
conduct electricity.
[0041] Here, as shown in FIG. 2, in the superconducting
stabilization material 20, in a case where the superconducting
state is destroyed in part of the wire 15 formed of a
superconducting material, a normal conducting area A is generated
and an electric current I flowing through the wire 15 formed of a
superconducting material is temporarily diverted.
[0042] Then, in the present embodiment, the superconducting
stabilization material 20 is formed of a copper material which
contains one or more types of additive elements selected from Ca,
Sr, Ba, and rare earth elements in a total of 3 ppm by mass to 400
ppm by mass, the balance being Cu and inevitable impurities, and a
total concentration of the inevitable impurities excluding O, H, C,
N, and S which are gas components being 5 ppm by mass to 100 ppm by
mass.
[0043] In addition, in the present embodiment, the copper material
forming the superconducting stabilization material 20 contains
inevitable impurities in which an Fe content is 10 ppm by mass or
less, a Ni content is 10 ppm by mass or less, an As content is 5
ppm by mass or less, an Ag content is 50 ppm by mass or less, an Sn
content is 4 ppm by mass or less, an Sb content is 4 ppm by mass or
less, a Pb content is 6 ppm by mass or less, a Bi content is 2 ppm
by mass or less, and a P content is 3 ppm by mass or less.
[0044] Furthermore, in the superconducting stabilization material
20 of the present embodiment, a ratio Y/X of a total amount of
additive elements of one or more types selected from Ca, Sr, Ba,
and rare earth elements (Y ppm by mass) to a total amount of S, Se,
and Te (X ppm by mass) is in a range of
0.5.ltoreq.Y/X.ltoreq.100.
[0045] In addition, in the present embodiment, the copper material
forming the superconducting stabilization material 20 includes a
compound which contains: one or more types of additive elements
selected from Ca, Sr, Ba, and rare earth elements; and one or more
types of elements selected from S, Se, and Te.
[0046] Furthermore, in the present embodiment, the superconducting
stabilization material 20 has a residual resistance ratio (RRR) of
250 or more.
[0047] Here, description will be given below of the reasons for
defining the component composition of the superconducting
stabilization material 20, the presence or absence of compounds,
and the residual resistance ratio (RRR) as described above.
(One or More Types of Additive Elements Selected from Ca, Sr, Ba,
and Rare Earth Elements)
[0048] Among the inevitable impurities contained in the copper, S,
Se, and Te are elements which form solid solutions in copper,
greatly decreasing the residual resistance ratio (RRR). Therefore,
in order to improve the residual resistance ratio (RRR), it is
necessary to eliminate the influence of S, Se, and Te.
[0049] Here, since one or more types of additive elements selected
from Ca, Sr, Ba, and rare earth elements are elements which are
highly reactive with S, Se, and Te, by creating a compound with S,
Se, and Te it is possible to suppress S, Se, and Te from forming a
solid solution in copper. Due to this, it is possible to
sufficiently improve the residual resistance ratio (RRR) of the
superconducting stabilization material 20.
[0050] Here, since one or more types of additive elements selected
from Ca, Sr, Ba, and rare earth elements are elements which do not
easily form a solid solution in copper and which have a small
effect of decreasing the residual resistance ratio (RRR) even in a
case of forming a solid solution in copper, the residual resistance
ratio (RRR) of the superconducting stabilization material 20 does
not decrease greatly even in a case where these additive elements
are excessively added with respect to the amount of the S, Se, and
Te.
[0051] Here, in a case where the amount of one or more types of
additive elements selected from Ca, Sr, Ba, and rare earth elements
is less than 3 ppm by mass, there is a concern that it will not be
possible to sufficiently fix S, Se, and Te. On the other hand, in a
case where the amount of one or more types of additive elements
selected from Ca, Sr, Ba, and rare earth elements exceeds 400 ppm
by mass, there is a concern that coarse precipitates or the like of
these additive elements will form, which deteriorates the
workability. From the above description, in the present embodiment,
the amount of one or more types of additive elements selected from
Ca, Sr, Ba, and rare earth elements is defined within the range of
3 ppm by mass to 400 ppm by mass.
[0052] Here, in order to effectively fix S, Se, and Te, the amount
of one or more types of additive elements selected from Ca, Sr, Ba,
and rare earth elements is preferably 3.5 ppm by mass or more, and
more preferably 4.0 ppm by mass or more. On the other hand, in
order to effectively suppress decrease in workability, the amount
of one or more types of additive elements selected from Ca, Sr, Ba,
and rare earth elements is preferably 300 ppm by mass or less, and
more preferably 100 ppm by mass or less.
(Inevitable Impurity Elements Excluding Gas Components)
[0053] Lowering the concentrations of inevitable impurities
excluding gas components (O, H, C, N, and S) improves the residual
resistance ratio (RRR). On the other hand, in a case where there is
an attempt to reduce the concentration of inevitable impurities
more than necessary, the manufacturing process becomes complicated
whereby the manufacturing cost drastically increases. Therefore, in
the present embodiment, the concentrations of inevitable impurities
excluding gas components (O, H, C, N, and S) are set within the
range of 5 ppm by mass to 100 ppm by mass in total.
[0054] In order to set the concentration of inevitable impurities
excluding the gas components (O, H, C, N, and S) within a range of
5 ppm by mass to 100 ppm by mass in total, it is possible to use
high purity copper with a purity of 99 to 99.9999 mass % or oxygen
free copper (C10100 and C10200) as a raw material. However, since
Ca, Sr, Ba, and rare earth elements react with O in a case there is
a high 0 concentration, the O concentration is preferably 20 ppm by
mass or less, and more preferably 10 ppm by mass or less. The O
concentration is even more preferably 5 ppm by mass or less.
[0055] Here, in order to effectively suppress the increase in the
manufacturing cost of the superconducting stabilization material
20, the inevitable impurities is preferably 7 ppm by mass or more,
and more preferably 10 ppm by mass or more. On the other hand, in
order to effectively improve the residual resistance ratio (RRR) of
the superconducting stabilization material 20, the inevitable
impurities is preferably 90 ppm by mass or less, and more
preferably 80 ppm by mass or less.
[0056] Here, inevitable impurities in the present embodiment are
Fe, Ni, As, Ag, Sn, Sb, Pb, Bi, P, Li, Be, B, F, Na, Mg, Al, Si,
Cl, K, Ti, V, Cr, Mn, Nb, Co, Zn, Ga, Ge, Br, Rb, Zr, Mo, Ru, Pd,
Cd, In, I, Cs, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Th, and
U.
(Fe, Ni, As, Ag, Sn, Sb, Pb, Bi, and P)
[0057] Since specific elements such as Fe, Ni, As, Ag, Sn, Sb, Pb,
Bi, and P among the inevitable impurities have an effect of
decreasing the residual resistance ratio (RRR) of the
superconducting stabilization material 20, defining the amount of
each of these elements makes it possible to effectively suppress
decreases in the residual resistance ratio (RRR) of the
superconducting stabilization material 20. Therefore, in the
present embodiment, the Fe content is defined as 10 ppm by mass or
less, the Ni content as 10 ppm by mass or less, the As content as 5
ppm by mass or less, the Ag content as 50 ppm by mass or less, the
Sn content as 4 ppm by mass or less, the Sb content as 4 ppm by
mass or less, the Pb content as 6 ppm by mass or less, the Bi
content as 2 ppm by mass or less, and the P content as 3 ppm by
mass or less.
[0058] In order to more effectively suppress decreases in the
residual resistance ratio (RRR) of the superconducting
stabilization material 20, it is preferable to define the Fe
content as 4.5 ppm by mass or less, the Ni content as 3 ppm by mass
or less, the As content as 3 ppm by mass or less, the Ag content as
38 ppm by mass or less, the Sn content as 3 ppm by mass or less,
the Sb content as 1.5 ppm by mass or less, the Pb content as 4.5
ppm by mass or less, the Bi content as 1.5 ppm by mass or less, and
the P content as 1.5 ppm by mass or less, and more preferably the
Fe content as 3.3 ppm by mass or less, the Ni content as 2.2 ppm by
mass or less, the As content as 2.2 ppm by mass or less, the Ag
content as 28 ppm by mass or less, the Sn content as 2.2 ppm by
mass or less, the Sb content as 1.1 ppm by mass or less, the Pb
content as 3.3 ppm by mass or less, the Bi content as 1.1 ppm by
mass or less, and the P content as 1.1 ppm by mass or less. The
lower limit of the amount of Fe, Ni, As, Ag, Sn, Sb, Pb, Bi, and P
is 0 ppm by mass. In addition, since there is a concern that
excessive reduction of the above may result in an increase in the
manufacturing cost, it is preferable to set the Fe content as 0.1
ppm by mass or more, the Ni content as 0.1 ppm by mass or more, the
As content as 0.1 ppm by mass or more, the Ag content as 0.1 ppm by
mass or more, the Sn content as 0.1 ppm by mass or more, the Sb
content as 0.1 ppm by mass or more, the Pb content as 0.1 ppm by
mass or more, the Bi content as 0.1 ppm by mass or more, and the P
content as 0.1 ppm by mass or more, without being limited
thereto.
(Ratio Y/X of Total Amount of Additive Elements to Total Amount of
S, Se, and Te)
[0059] As described above, one or more types of additive elements
selected from Ca, Sr, Ba, and rare earth elements form compounds
with elements such as S, Se, and Te. Here, in a case where the
ratio Y/X of the total amount of additive elements (Y ppm by mass)
to the total amount of S, Se, and Te (X ppm by mass) is less than
0.5, the amount of additive elements is insufficient, and there is
a concern that it may not be possible to sufficiently fix the
elements such as S, Se, and Te.
[0060] On the other hand, in a case where the ratio Y/X of the
total amount of additive elements to the total amount of S, Se, and
Te exceeds 100, there may be an excess of additive elements not
reacting with S, Se and Te, and this causes a concern that the
workability may be deteriorated.
[0061] From the above, in the present embodiment, the ratio Y/X of
the total amount of additive elements to the total amount of S, Se,
and Te is defined within the range of 0.5 to 100.
[0062] Here, in order to effectively fix the elements such as S,
Se, and Te as a compound, the ratio Y/X of the total amount of
additive elements to the total amount of S, Se, and Te is
preferably 0.75 or more, and more preferably 1.0 or more. In
addition, in order to effectively suppress decreases in
workability, the ratio Y/X of the total amount of additive elements
to the total amount of S, Se, and Te is preferably 75 or less, and
more preferably 50 or less. Here, the total amount of S, Se, and Te
in the superconducting stabilization material 20 is preferably more
than 0 ppm by mass and 25 ppm by mass or less, without being
limited thereto.
(Compound Containing Additional Element and One or More Types of
Elements Selected from S, Se, and Te)
[0063] As described above, one or more types of additive elements
selected from Ca, Sr, Ba, and rare earth elements form compounds
with elements such as S, Se, and Te so as to suppress elements such
as S, Se, and Te from forming solid solutions in the copper. Thus,
compounds containing one or more types of additive elements
selected from Ca, Sr, Ba, and rare earth elements and one or more
types of elements selected from S, Se, and Te are present, and
thereby it is possible to effectively improve the residual
resistance ratio (RRR) of the superconducting stabilization
material 20.
[0064] Here, when compounds containing one or more types of
additive elements selected from Ca, Sr, Ba, and rare earth elements
and elements such as S, Se, and Te are present in a number density
of 0.001/.mu.m.sup.2 or more, it is possible to effectively improve
the residual resistance ratio (RRR). In addition, in order to
further improve the residual resistance ratio (RRR), it is
preferable to set the number density of the compounds to
0.005/.mu.m.sup.2 or more. The number density is more preferably
0.007/.mu.m.sup.2 or more. In the present embodiment, the number
density described above relates to a compound having a particle
diameter of 0.1 .mu.m or more.
[0065] In the present embodiment, since the amount of elements such
as S, Se, and Te is sufficiently small, the number density of the
compound described above (particle diameter of 0.1 .mu.m or more)
is 0.1/.mu.m.sup.2 or less, and more preferably 0.09/.mu.m.sup.2 or
less. The n number density is even more preferably 0.08/.mu.m.sup.2
or less.
(Residual Resistance Ratio (RRR))
[0066] Since the residual resistance ratio (RRR) of the
superconducting stabilization material 20 according to the present
embodiment is 250 or more, the resistance value is low at extremely
low temperatures and it is possible to effectively divert the
electric current. The residual resistance ratio (RRR) is preferably
280 or more, and more preferably 300 or more. The residual
resistance ratio (RRR) is even more preferably 400 or more. Here,
it is preferable to set the residual resistance ratio (RRR) to
10000 or less, without being limited thereto.
[0067] Here, the superconducting stabilization material 20
described above is manufactured by a manufacturing process
including a melting casting process, a plastic working process, and
a heat treatment process.
[0068] A copper wire rod having the composition shown in the
present embodiment may be manufactured by a continuous casting
rolling method (for example, Southwire Continuous Rod (SCR) system)
or the like, and the superconducting stabilization material 20 may
be manufactured using this rod as a base material. In this case,
the production efficiency of the superconducting stabilization
material 20 is improved, and it is possible to greatly reduce the
manufacturing cost. The continuous casting rolling method referred
to here is a process in which a copper wire rod is manufactured
using a continuous casting rolling facility provided with a
belt-wheel type continuous casting apparatus and a continuous
rolling device, and a drawn copper wire is manufactured using this
copper wire rod as a material.
[0069] The superconducting wire 10 of the present embodiment formed
as described above includes: the wire 15 formed of a
superconducting material; and the superconducting stabilization
material 20 disposed in contact with the wire 15, and the
superconducting stabilization material 20 is formed of a copper
material in which one or more types of additive elements selected
from Ca, Sr, Ba, and rare earth elements are contained in a total
of 3 ppm by mass to 400 ppm by mass in copper where the total
concentration of inevitable impurities excluding O, H, C, N, and S
which are gas components is 5 ppm by mass to 100 ppm by mass. Thus,
S, Se, and Te in copper are fixed as a compound and it is possible
to improve the residual resistance ratio (RRR) of the
superconducting stabilization material 20. In addition, by the
superconducting stabilization material being electrically in
contact with the wire formed of the superconducting material, even
in a case where the normal conducting area A in which the
superconducting state is destroyed is generated in the wire 15
formed of the superconducting material, it is possible to
effectively divert the electric current to the superconducting
stabilization material 20. Therefore, it is possible to suppress
the transition of the entire superconducting wire 10 to the normal
conducting state, and it is possible to stably use the
superconducting wire 10 according to the present embodiment.
[0070] In addition, since copper where the total concentration of
inevitable impurities excluding O, H, C, N, and S which are gas
components is 5 ppm by mass to 100 ppm by mass is used, there is no
need to excessively increase the purity level of the copper, the
manufacturing process is simplified, and it is possible to reduce
the manufacturing cost of the superconducting stabilization
material 20.
[0071] Further, in the present embodiment, since the amounts of Fe,
Ni, As, Ag, Sn, Sb, Pb, Bi, and P which influence the residual
resistance ratio (RRR) are defined such that the Fe content is 10
ppm by mass or less, the Ni content is 10 ppm by mass or less, the
As content is 5 ppm by mass or less, the Ag content is 50 ppm by
mass or less, the Sn content is 4 ppm by mass or less, the Sb
content is 4 ppm by mass or less, the Pb content is 6 ppm by mass
or less, the Bi content is 2 ppm by mass or less, and the P content
is 3 ppm by mass or less, it is possible to effectively improve the
residual resistance ratio (RRR) of the superconducting
stabilization material 20.
[0072] In addition, in the present embodiment, since a ratio Y/X of
a total amount of additive elements of one or more types selected
from Ca, Sr, Ba, and rare earth elements (Y ppm by mass) to a total
amount of S, Se, and Te (X ppm by mass) is within the range of
0.5.ltoreq.Y/X.ltoreq.100, it is possible to effectively fix S, Se,
and Te in copper as a compound with additive elements, and it is
possible to effectively suppress decreases in the residual
resistance ratio (RRR). In addition, without large amounts of
excess additive elements which do not react with S, Se and Te, it
is possible to ensure the workability of the superconducting
stabilization material 20.
[0073] Furthermore, in the present embodiment, since there is a
compound which contains one or more types of additive elements
selected from Ca, Sr, Ba, and rare earth elements and one or more
types of elements selected from S, Se, and Te, the S, Se, and Te
present in copper are effectively fixed by a compound with one or
more types of additive elements selected from Ca, Sr, Ba, and rare
earth elements, and it is possible to effective suppress decreases
in the residual resistance ratio (RRR) of the superconducting
stabilization material 20 caused by S, Se, and Te.
[0074] In particular, in the present embodiment, since the number
density of the compounds having a particle diameter of 0.1 .mu.m or
more is 0.001/.mu.m.sup.2 or more, it is possible to effectively
fix S, Se, and Te as a compound, and to sufficiently improve the
residual resistance ratio (RRR) of the superconducting
stabilization material 20.
[0075] In addition, in the present embodiment, since the residual
resistance ratio (RRR) of the superconducting stabilization
material 20 is relatively high at 250 or more, the resistance value
at extremely low temperatures is sufficiently low. Therefore, even
in a case when the superconducting state is destroyed and a normal
conducting area A is generated in the wire 15 formed of the
superconducting material, it is possible to effectively divert the
electric current to the superconducting stabilization material
20.
[0076] Although the superconducting wire according to the
embodiment of the present invention was described above, the
present invention is not limited thereto but is able to be
appropriately modified in a range not departing from the technical
idea of the invention.
[0077] For example, the core portion 11 and the outer shell portion
13 forming the superconducting wire 10 may also be formed of a
copper material having the same composition as that of the
superconducting stabilization material 20 of the present
embodiment.
[0078] In addition, in the embodiment described above, as shown in
FIG. 1, the superconducting wire 10 having a structure in which the
plurality of filaments 12 are bundled is described as an example,
but the present invention is not limited thereto, for example, as
shown in FIG. 3, the superconducting wire may be a superconducting
wire 110 having a structure in which a superconducting material 115
and a superconducting stabilization material 120 are laminated and
disposed on a tape-like substrate 113.
Example
[0079] Description will be given below of the results of
confirmatory experiments conducted to confirm the effect of the
present invention.
[0080] In the examples, as a laboratory experiment, high purity
copper having a purity of 99.9999 mass % and a master alloy of Ca,
Sr, Ba, and rare earth (RE) elements were used as raw materials,
and adjustments were carried out to obtain the compositions shown
in Table 1. In addition, for Fe, Ni, As, Ag, Sn, Sb, Pb, Bi, P, and
other impurities, a master alloy of each element was prepared from
Fe, Ni, As, Ag, Sn, Sb, Pb, Bi, and P having a purity of 99.9 mass
% or more and pure copper having a purity of 99.9 mass % and
adjustments were carried out using the master alloys. First, high
purity copper was melted using an electric furnace in a reducing
atmosphere of N.sub.2+CO and master alloys of various additive
elements and impurities were added thereto thereby adjusting the
concentrations thereof to be a predetermined concentration, and
then the resultant was casted into a predetermined mold. Thereby,
an ingot with a diameter of 70 mm and a length of 150 mm was
obtained. Mischmetal was used as part of the raw material for a
rare earth master alloy. Square material having cross-sectional
size of 25 mm.times.25 mm was cut out from this ingot and subjected
to hot rolling at 850.degree. C. to obtain a hot rolled wire having
a diameter of 8 mm, and a thin wire with a diameter of 2.0 mm was
formed from this hot-rolled wire by cold rolling, and subjected to
strain relief annealing of being maintained at 500.degree. C. for 1
hour to produce the evaluation wire shown in Table 1. Here, in this
example, the mixing in of impurity elements was also observed in
the process of melting and casting.
[0081] Using these evaluation wires, the following items were
evaluated.
(Residual Resistance Ratio (RRR))
[0082] Using the four terminal method, the electrical specific
resistance (.rho..sub.293 K) at 293 K and the electrical specific
resistance (.rho..sub.4.2 K) at the temperature of liquid helium
(4.2 K) was measured and RRR=.rho..sub.293K/.rho..sub.4.2 K was
calculated.
(Composition Analysis)
[0083] Using the sample from which the residual resistance ratio
(RRR) was measured, component analysis was carried out as follows.
For elements excluding gas components, glow discharge mass
spectrometry was used in a case of being less than 10 ppm by mass
and an inductively coupled plasma atomic emission spectrometry was
used in a case of being 10 ppm or more. In addition, an infrared
absorption method was used for analysis of S. The measured O
concentrations were all 10 ppm by mass or less. Here, for the
analysis of O, the infrared absorption method was used.
(Observation of Compound Particles)
[0084] In order to confirm the presence or absence of compound
particles containing one or more types of additive elements
selected from Ca, Sr, Ba, and rare earth elements and one or more
types of S, Se, and Te, particle observation was performed using a
scanning electron microscope (SEM), and energy dispersive X-ray
spectrometry (EDX).
[0085] In addition, in order to evaluate the number density
(number/.mu.m.sup.2) of the compounds, an area where the dispersion
state of the compounds is not unique was observed at 10000 times
magnification (observation field: 2.times.10.sup.8 nm.sup.2), and
10 observation fields (total observation field: 2.times.10.sup.9
nm.sup.2) were analyzed. The particle diameter of the compound was
the average length along the major axis of the compound (the
maximum length of a straight line which could be drawn in the
particle on the condition of not coming into contact with the
particle boundary while being drawn) and the minor axis (the
maximum length of a straight line which could be drawn in the
direction orthogonal to the major axis on the condition of not
coming into contact with the particle boundary while being drawn).
Then, the number density (number/.mu.m.sup.2) of the compounds
having a particle diameter of 0.1 .mu.m or more was determined.
[0086] The evaluation results are shown in Table 1. In addition,
FIG. 4 shows (a) SEM observation results and (b) analysis results
(EDX analysis results) of the compound of Invention Example 4, FIG.
5 shows (a) SEM observation results of the compound and (b)
analysis results (EDX analysis results) of Invention Example 10,
and FIG. 6 shows (a) SEM observation results and (b) analysis
results (EDX analysis results) of the compound of Invention Example
19. Also, FIG. 4(b), FIG. 5(b), and FIG. 6(b) show the spectra of
the compounds marked with "+" in each of FIG. 4(a), FIG. 5(a), and
FIG. 6(b).
TABLE-US-00001 TABLE 1 Total Additive Elements (ppm by mass)
concentration Impurities (ppm by mass) Total of inevitable Total
amount Y impurities amount of Ca, Sr, excluding O, X of S, Ca Sr Ba
RE Ba, and RE H, C, N, and S S Se Te Se, and Te Invention 1 3 -- --
-- 3 13.3 5.5 1.1 1.2 7.8 Example 2 4 -- -- -- 4 32.8 5.0 0.6 0.4
6.0 3 12 -- -- -- 12 15.6 4.2 1.0 0.8 6.0 4 26 -- -- -- 26 40.4 5.2
0.5 1.0 6.7 5 53 -- -- -- 53 28.0 5.8 0.6 1.0 7.4 6 66 -- -- -- 66
15.7 4.4 0.9 0.5 5.8 7 95 -- -- -- 95 75.7 5.1 0.9 0.6 6.6 8 233 --
-- -- 233 92.0 5.5 1.1 0.9 7.5 9 384 -- -- -- 384 66.1 5.6 0.9 0.7
7.2 10 -- 13 -- -- 13 46.0 4.3 0.8 1.1 6.2 11 -- 35 -- -- 35 25.3
7.5 0.7 0.6 8.8 12 -- 71 -- -- 71 20.0 5.4 0.8 0.2 6.4 13 -- 164 --
-- 164 32.0 7.2 1.3 0.9 9.4 14 -- -- 11 -- 11 33.9 4.5 0.6 0.8 5.9
15 -- -- 54 -- 54 20.1 5.2 1.1 0.5 6.8 16 -- -- 102 -- 102 87.5 4.6
0.9 0.9 6.4 17 -- -- 135 -- 135 46.0 7.7 1.2 1.0 9.9 18 -- -- --
Ce: 13 13 27.7 7.5 0.5 0.6 8.6 19 -- -- -- *3MM: 51 51 19.8 7.3 1.2
0.9 9.4 20 -- -- -- Nd: 89 89 50.2 3.7 1.2 1.1 6.0 21 32 -- -- La:
32 32 5.5 0.9 0.2 0.2 1.3 22 -- 18 -- -- 18 5.7 0.4 0.1 0.1 0.5
Comparative 1 15 5 -- -- 20 171.4 5.0 1.0 0.4 6.4 Example 2 -- --
-- -- 0 48.2 4.6 0.8 0.9 6.3 3 1030 -- -- -- 1030 41.4 3.6 0.4 0.4
4.4 Impurities (ppm by mass) *2 Specific impurities *1 Number Fe Ni
As Ag Sn Sb Pb Bi P Cu Y/X density RRR Invention 1 1.2 1.1 1.0 6
0.1 0.1 0.1 0.1 0.1 Balance 0.4 0.00188 365 Example 2 6.8 2.8 1.2
13 0.8 1.2 1.2 0.4 1.4 Balance 0.7 0.00250 255 3 0.6 1.0 0.5 9 0.1
0.3 0.8 0.2 0.1 Balance 2.0 0.00750 452 4 2.3 2.4 1.2 21 1.1 0.5
4.8 0.8 1.5 Balance 3.9 0.01625 482 5 1.5 2.8 0.8 13 1.8 1.0 1.8
0.7 0.8 Balance 7.2 0.01872 639 6 0.6 1.0 0.5 9 0.1 0.3 0.7 0.2 0.1
Balance 11.4 0.01470 732 7 7.0 5.7 3.4 39 2.6 3.2 3.3 1.3 1.8
Balance 14.4 0.01672 310 8 9.9 8.7 4.3 42 3.9 3.2 4.9 1.9 2.8
Balance 31.1 0.01900 282 9 3.0 1.8 0.6 48 0.4 1.2 1.2 1.0 1.2
Balance 53.4 0.01822 324 10 2.5 2.8 1.5 28 1.1 1.2 1.8 0.7 0.7
Balance 2.1 0.00813 355 11 0.6 6.6 0.5 12 0.1 0.3 0.7 0.9 0.1
Balance 4.0 0.02188 547 12 1.1 1.0 1.4 10 0.1 0.2 1.4 0.9 1.1
Balance 11.1 0.01619 643 13 1.9 2.6 2.3 15 0.5 0.8 1.6 1.7 0.9
Balance 17.5 0.02379 424 14 2.4 2.0 1.3 20 0.3 0.8 1.6 0.4 1.0
Balance 1.9 0.00688 353 15 0.6 1.0 4.8 9 0.1 0.3 0.8 0.2 0.1
Balance 8.0 0.01720 503 16 8.7 6.8 3.9 44 2.9 3.2 4.4 1.5 2.3
Balance 15.9 0.01622 293 17 2.6 1.3 2.1 25 1.3 3.9 1.9 0.8 1.1
Balance 13.7 0.02506 438 18 4.1 0.9 1.8 13 1.3 0.4 1.5 1.0 0.5
Balance 1.5 0.00813 319 19 0.7 0.8 0.4 9 3.3 0.3 0.9 0.3 0.2
Balance 5.4 0.02379 677 20 6.0 1.1 0.6 31 0.4 0.7 1.0 0.3 2.6
Balance 14.9 0.01518 452 21 0.6 0.2 0.1 3 0.2 0.2 0.4 0.1 0.4
Balance 25.4 0.00319 969 22 2.1 0.1 0.2 2 0.2 0.1 0.1 0.1 0.2
Balance 33.4 0.00137 1181 Comparative 1 4.1 27.0 5.9 85 3.3 3.1 4.1
3.8 5.1 Balance 3.1 0.01250 106 Example 2 2.1 2.5 2.5 30 0.5 0.9
1.3 0.7 2.0 Balance 0.0 0.00000 218 3 2.6 0.9 1.8 25 0.8 0.7 1.8
0.7 2.9 Balance 234.6 -- -- *1 Y/X: Ratio of a total amount of
additive elements (Y ppm by mass) to a total amount of S, Se, and
Te (X ppm by mass) *2 Number density (number/.mu.m.sup.2) of
compounds with a particle diameter of 0.1 .mu.m or more *3MM:
Mischmetal
[0087] In Comparative Example 1, the total amount of inevitable
impurities excluding the gas components (O, H, C, N, and S)
exceeded 100 ppm by mass and the residual resistance ratio (RRR)
was relatively low at 106.
[0088] In Comparative Example 2, one or more types of additive
elements selected from Ca, Sr, Ba, and rare earth (RE) elements
were not added, and the residual resistance ratio (RRR) was
relatively low at 218.
[0089] In Comparative Example 3, the added amount of Ca exceeded
the range of the present invention at 1030 ppm by mass, and
breaking occurred during plastic working. For this reason,
measurement of the residual resistance ratio (RRR) and observation
of the particles were not performed.
[0090] In contrast, in Invention Examples 1 to 22, the residual
resistance ratio (RRR) was 250 or more, and it was confirmed that
Example 1 to 22 is particularly suitable as a superconducting
stabilization material.
[0091] In addition, as shown in FIG. 4, in a case where Ca was
added, a compound containing Ca and S was observed.
[0092] Furthermore, as shown in FIG. 5, in a case where Sr was
added, a compound containing Sr and S was observed.
[0093] Furthermore, as shown in FIG. 6, in a case where rare earth
elements were added, a compound of rare earth elements and S was
observed.
[0094] From the above, it was confirmed that, according to the
present invention, it was possible to provide a superconducting
wire which was provided with a superconducting stabilization
material which was able to be manufactured with a relatively simple
and inexpensive manufacturing process and which had a sufficiently
high residual resistance ratio (RRR).
INDUSTRIAL APPLICABILITY
[0095] According to the present invention, it is possible to
provide a superconducting wire which is able to be stably used and
which is provided with a superconducting stabilization material,
which is able to be manufactured with a relatively simple and
inexpensive manufacturing process and has a sufficiently high
residual resistance ratio (RRR).
REFERENCE SIGNS LIST
[0096] 10, 110 SUPERCONDUCTING WIRE [0097] 20, 120 SUPERCONDUCTING
STABILIZATION MATERIAL
* * * * *