JP2517597B2 - Manufacturing method of oxide superconducting wire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an oxide superconducting wire that can be used, for example, in a power transmission cable that performs large-capacity power transmission.

[Prior Art and its Problems] Recently, various oxide-based superconductors have been found which have a very high critical temperature (Tc) at which a normal-conducting state changes to a superconducting state. Since such an oxide superconductor has a higher critical temperature than conventional alloy-based or intermetallic compound-based superconductors, it is regarded as a very promising superconducting material in practical use.

By the way, conventionally, in order to manufacture an oxide superconducting wire, a method in which a raw material powder containing an element constituting an oxide superconductor is filled in a metal sheath, and then this whole metal sheath is subjected to a diameter reduction process and then heat treatment is performed. is there.

However, in such a method, when an oxidizing metal such as copper, a copper alloy, or stainless steel is present around the raw material powder of the oxide superconductor in a state of being in contact with the oxide superconductor, the oxidizing metal is oxidized during heat treatment to Oxygen in the raw material powder may be deprived. In this case, in the raw material powder of the portion in contact with the oxidizing metal, the amount of oxygen tends to be insufficient,
As a result, there is a problem that a superconductor having a low critical temperature and a low critical current density is partially generated in the metal sheath, and in the worst case, the outer peripheral portion of the superconductor becomes an insulator.

[Means for solving problems]

In the present invention, a powder made of at least one of an oxide superconductor and a material containing an element forming the oxide superconductor is compression-molded to form a rod-shaped molded body, and then this molded body is made of a non-oxidizing metal. After being coated with a primary metal layer consisting of, a large number of the molded bodies are assembled, and the obtained assembly is coated with a secondary metal layer made of a metal harder than the non-oxidizing metal, and then subjected to wire drawing. Then, heat treatment was used as a solution.

 Hereinafter, the present invention will be described in detail.

In this invention, first, a raw material powder is prepared. As the raw material powder, one containing an element forming an oxide superconductor is used, and specifically, a mixture of an alkaline earth metal element powder, a Group IIIa element powder of the periodic table, a copper oxide powder, and the like. A powder, a powder obtained by calcining this mixed powder, a mixed powder of the mixed powder and the calcined powder, or the like is used. As the alkaline earth metal element powder here,
A compound powder such as a carbonate powder, an oxide powder, a chloride powder, a sulfide powder, or a fluoride powder of each element of Be, Sr, Mg, Ba, and Ra or an alloy powder is used. Also, the periodic table
IIIa group element powders include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, E
u, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu Carbonate powders, oxide powders, chloride powders, sulfide powders, compound powders such as fluoride powders or alloy powders are used. To be Further, as the oxide powder, powder of copper oxide such as CuO, Cu ₂ O, Cu ₂ O ₃ and Cu ₄ O ₃ is used.

The mixing ratio of these powders was such that the obtained oxide superconductor was AxByCuzO _{9- δ} (where A represents an element of Group IIIa of the periodic table such as Sc, Y, La, and Yb, and B represents Be, It is desirable that x, y, z, and δ be determined in the following ranges when expressed by the composition formula of (representing an alkaline earth metal element such as Sr and Ba).

0.1 ≦ x ≦ 2, 0.1 ≦ y ≦ 3, 1 ≦ z ≦ 3, 0 ≦ δ ≦ 7 Then, a raw material powder is prepared from each of these powders. One kind may be selected from each of the metal element powder and the group IIIa element powder of the periodic table, or two or more kinds may be selected from each of the alkaline earth metal element powder and the group IIIa element powder of the periodic table. Good. In the case of the former, it becomes possible to prepare a raw material powder as a raw material of a La-Sr-Cu-O-based or Y-Ba-Cu-O-based superconductor, and in the latter case, for example, Ba-Sr. It is possible to prepare a raw material powder of a superconductor such as a -Cu-O type or a La-Y-Cu-O type.

When such raw material powder contains a carbonate or a carbon content, the raw material powder is pre-baked. This preliminary calcination is carried out in order to thermally decompose the carbonate or carbon content in the powder to form an oxide, and it is preferable to carry out the calcination at a temperature of 650 to 750 ° C. and a calcination time of 1 to 10 hours. . After such preliminary calcination, the presence or absence of carbonate or carbon content in the powder is analyzed and examined, and if the carbonate or carbon content remains, the preliminary calcination is repeated for this powder a necessary number of times.

Then, when the carbon content in the raw material powder is completely removed in this way, the powder is pre-baked. This calcination is preferably performed under conditions of a calcination temperature of 850 to 950 ° C. and a calcination time of 1 to 30 hours. By such calcination, the alkaline earth metal oxide in the powder and the oxide of the Group IIIa element of the periodic table react with copper oxide, and at least a part of the powder has an oxide exhibiting superconducting properties. Become.

Next, the raw material powder thus obtained is sufficiently pulverized to make the particle diameter uniform, and then the powder is subjected to a hydraulic press such as an ordinary rubber press to form the powder into a cylindrical molded body as shown in FIG. Mold to 1. The molding pressure of the hydraulic press depends on the composition of the raw material powder, the composition ratio, the size of the molded body to be obtained, etc., and is usually determined in the range of about 1.5 to 10 ton / cm ² .

Next, the molded body 1 is heat-treated. This heat treatment is carried out in an oxygen stream, and the treatment temperature is usually 800 to 1
It is carried out under the conditions of 100 ° C. and a treatment time of 1 to 300 hours. By this heat treatment, the alkaline earth metal oxide in the compact 1 sufficiently reacts with the oxide of the Group IIIa element of the periodic table and the copper oxide, and the compact 1 as a whole is, for example, a layered perovskite type oxide superconducting material. Become a body.

Then, the molded body 1 is coated with a primary metal layer 1a made of a non-oxidizing metal. Here, as the non-oxidizing metal, for example, noble metals such as Ag, Au, Pt, Ir, Os, Pd, Rh and Ru, and alloys thereof are preferably used. As a method of forming the primary metal layer 1a, a cladding method in which the compact 1 is inserted into a pipe made of the non-oxidizing metal, or the compact 1 is immersed in a molten non-oxidizing metal and then baked. Various methods such as a dipping method, a thin film forming method such as a sputtering method and a vacuum deposition method are used.

Next, a large number of the formed bodies 1 are assembled into an assembly 2 as shown in FIG. 2, and then a metal pipe 3 made of a material harder than the material forming the primary metal layer 1a on the assembly 2.
The composite body 4 is covered with the composite material 4 and the composite material 4 is reduced in diameter to form a wire 5 as shown in FIG. 3. A secondary metal layer 6 is formed on the wire 5. Here, in order to collect a large number of molded bodies 1, for example, one molded body 1 is centered
It is desirable to arrange a large number of molded bodies 1 ... Further, the secondary metal layer 6 is for reliably transmitting the processing pressure to the aggregate 2 in order to uniformly reduce the diameter of the aggregate 2 during the wire drawing in the subsequent step. The material for forming the secondary metal layer 6 is appropriately determined according to the material for forming the primary metal layer 1a, and for example, SUS3
04, stainless steel such as SUS316 is used.

Next, as shown in FIG. 4, a stabilizing pipe 7 made of copper or the like is placed on the secondary metal layer 6 of the wire 5 and wire drawing is carried out to obtain a desired wire diameter, followed by heat treatment. The oxide superconducting wire 8 shown in FIG. 5 is manufactured. The stabilizing pipe 7 is provided for the purpose of easy workability of wire drawing and stabilization of the finally obtained oxide superconducting wire. As a material for forming the stabilizing pipe 7, a metal such as copper, a copper alloy, or aluminum, which has excellent wire drawing workability, is used. The processing temperature of the above-mentioned heat treatment is almost the same as that of the above-mentioned heat treatment for the molded body 1, and the heat treatment time is determined according to the previous heat treatment time and the like. By such wire drawing and heat treatment, the plurality of compacts 1 ... Are uniformly reduced in diameter and heat-treated to form superconducting thin wires 1b.

In the oxide superconducting wire 8 thus obtained, the primary metal layer 1a made of a non-oxidizing metal is provided outside the superconducting thin wires 1b ... Oxygen in the superconducting thin wires 1b ... Can be surely prevented from being deprived of the oxidizing metal by the 1a. Therefore, the oxide superconducting wire 8 is a superconducting thin wire inside the oxide superconducting wire 8.
Since the good superconducting properties of 1b are maintained respectively, good superconducting properties are exhibited as a whole. Such an oxide superconducting wire 8 can be suitably used, for example, as a power transmission cable for performing large-capacity power transmission.

According to this method, since the material forming the secondary metal layer 6 on the aggregate 2 is harder than the material forming the primary metal layer 1a on the compact 1, the processing pressure during wire drawing is reduced. The secondary metal layer 6 can be surely transmitted to the aggregate 2, and the diameter of the entire aggregate 2 can be uniformly reduced, so that the multi-strand type oxide superconducting wire 8 can be manufactured in a long size.

Moreover, according to this method, the obtained oxide superconducting wire 8
Each of the superconducting thin wires 1b ... Is covered with the primary metal layer 1a of a non-oxidizing metal.
Oxygen in 1b can be surely prevented from being deprived of the oxidizing metal, so that good superconducting characteristics of the oxide superconducting wire 8 can be stabilized.

In the above examples, the powder containing the element forming the oxide superconductor was used as the raw material powder for forming the molded body 1. However, the powder made of the oxide superconductor already showing the superconducting characteristics, or the powder made of this superconductor. You may use the mixed powder of a powder and the said element powder. In this case, the conditions for calcination of the raw material powder and heat treatment of the compact 1 can be made gentle.

〔Example〕

The composition ratio of each element is Y: Ba: Cu: O = 1: 2: 3: 7 obtained as a (atomic weight ratio), Y ₂ O ₃ powder and BaCO ₃ powder and a mixed powder by mixing CuO powder It was Next, 700 ° C. for this mixed powder,
Pre-baking was performed for 3 hours, and then temporary baking was performed at 900 ° C. for 12 hours. Next, the mixed powder was pulverized into a fine powder, and then a rubber press was used to obtain a cylindrical molded body having an outer diameter of about 10 mm. Then, heat treatment was performed at 900 ° C. for 24 hours in an oxygen stream.

Next, this molded body was inserted into a silver pipe having an outer diameter of about 15 mm and a wall thickness of 2 mm, and then the entire diameter was reduced to prepare a wire rod having an outer diameter of about 4 mm.

Next, 7 such wire rods are prepared, and 6 wire rods are aligned around the outer periphery of this wire rod around the center of one wire rod to form an aggregate, and then this aggregate is formed to have an outer diameter of about 14 mm and a wall thickness. 0.5 mm
Insert it into a stainless steel (SUS304) pipe, and then insert it into a copper pipe with an outer diameter of about 20 mm and a wall thickness of 2.5 mm to make a composite, and then wire drawing it to a wire diameter of about 1.5 mm. After that, heat treatment was performed to obtain a multi-strand type oxide superconducting wire. This heat treatment was performed under the conditions of a treatment temperature of 900 ° C. and a treatment time of 3 hours.

When the critical temperature of the oxide superconducting wire thus obtained was measured, it was about 91K. The critical current was about 500 A / cm ² at liquid nitrogen temperature. Therefore, it was found that this oxide superconducting wire exhibits good superconducting properties.

〔The invention's effect〕

As described above, according to the manufacturing method of the present invention,
Since each superconducting wire of the resulting multi-strand type oxide superconducting wire is covered with a primary metal layer made of a non-oxidizing metal, it is ensured that oxygen in the oxide superconducting wire is deprived of the oxidizing metal. It is possible to prevent the oxide superconducting wire from being stabilized, and thus the excellent superconducting property of the oxide superconducting wire can be stabilized.

Further, according to this method, since the material forming the secondary metal layer on the aggregate is harder than the material forming the primary metal layer on the compact, the processing pressure during wire drawing is not The metal layer allows reliable transmission to the aggregate, and the diameter of the entire aggregate can be uniformly reduced. Therefore, a multi-strand type oxide superconducting wire can be manufactured in a long size.

Therefore, since the oxide superconducting wire obtained by this method is long and has excellent superconducting properties,
For example, it is possible to perform large-capacity power transmission by using the power transmission cable.

[Brief description of drawings]

1 to 5 are for explaining an example of a method for producing an oxide superconducting wire of the present invention, and FIG. 1 is an example of a molded body provided with a primary metal layer used in the present invention. 2 is a schematic sectional view showing a composite body in which a metal pipe is combined with the assembly obtained by collecting the molded bodies of FIG.
FIG. 3 is a schematic cross-sectional view showing a wire rod obtained by reducing the diameter of the composite of FIG. 2, and FIG. 4 is a schematic cross-sectional view showing a composite wire in which a stabilizing pipe is combined with the wire rod of FIG. FIG. 5 is a schematic sectional view showing an oxide superconducting wire obtained by subjecting the composite wire of FIG. 4 to diameter reduction processing and heat treatment. 1 ... Molded body, 1a ... Primary metal layer, 1b ... Superconducting thin wire,
2 ... Aggregate, 6 ... Secondary metal layer, 8 ... Oxide superconducting wire.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yu Sugimoto 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (72) Inventor Mikio Nakagawa 1-1-5, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Incorporated (56) References JP-A-63-257128 (JP, A)

Claims (1)

(57) [Claims] 1. A rod-shaped molded body is produced by compression-molding a powder made of at least one of an oxide superconductor and a material containing an element constituting the oxide superconductor, and the molded body is then made of a non-oxidizing metal. After coating with a primary metal layer consisting of
An oxide characterized in that a large number of the formed bodies are assembled, and the obtained assembly is covered with a secondary metal layer made of a metal harder than the non-oxidizing metal, followed by wire drawing and then heat treatment. Superconducting wire manufacturing method.