JPS63179032A - Alloy for superconducting material and its production - Google Patents

Abstract

PURPOSE:To improve critical current density and workability, by restricting impurities in Cu-Nb or Cu-V alloy to specific amounts of O and C and specifying a dendritic diameter. CONSTITUTION:This alloy has a composition consisting of, by weight, 10-60% Nb or V, <=250ppm O, 10-500ppm Ca, and the balance Cu and, in this alloy, the dendritic diameter is regulated to 50-300mu. In order to obtain this alloy, first refining is carried out in vacuum or under a nonoxidizing atmosphere by the use of a vessel in which at least internal surface is constituted of calcia refractory material of >=95wt.% CaO content so as to prepare an alloy containing Cu and Nb or V. Then the resulting molten alloy is cast in a calcia mold. This alloy has extremely excellent workability and mechanical properties and, moreover, it provides high critical current density owing to its dendritic size and also has superior superconductivity.

Description

Detailed Description of the Invention [Field of Application in Industry A] The present invention relates to an alloy for superconducting materials and a method for producing the same, and particularly relates to an alloy for superconducting materials and a method for manufacturing the same. It relates to its manufacturing method.

[Prior Art] Metal materials exhibiting a superconducting phenomenon in which a high-density current flows without power consumption in a superconducting state can economically generate a high magnetic field, and an extremely wide range of uses have been proposed.

Among superconducting materials, NbaSn multicore wires and the like have conventionally been manufactured by a composite processing method called the bronze method. The bronze method is a method for bronze, that is, Cu-3n (~8at, %
) A composite with a Nb core in an alloy matrix is wire-drawn and heat-treated at approximately 700°C, and this heat treatment produces a layer of Nb3Sn on the surface of the Nb core ("Solid State Physics J. VoJ2.14.No.

6.1979).

Among the superconducting materials obtained in this way, some small-scale applications have already entered the practical stage. Furthermore, research is currently being actively conducted on the use of superconductivity in superconducting power generators, superconducting high-energy accelerators, nuclear fusion devices, large-scale electronic computers, and the like. In order to expand such applications, it is desired to comprehensively improve basic technologies such as superconducting materials, refrigeration/cooling technology, and superconducting electromagnet manufacturing technology.In particular, in the field of superconducting materials, there is a need for improvements that have already been put into practical use. The properties of superconducting materials currently available are expected to further improve through research into materials and manufacturing methods. Therefore, at present, especially in compound wire rods, the In 5 Ittu method, Infiltration method, and Powder Metallurgy method are attracting attention as new manufacturing methods.

In 5itu method, Cu-Nb-5n or Cu-
This method uses a V-Ga ternary alloy ingot to produce a wire containing a large amount of discontinuous ultrafine fibers of Nb3Sn or V2Ga compounds. Cu-Nb-5 with appropriate composition
In n alloy or Cu-V-Ga alloy ingot, C
It has a phase structure in which Nb or V dendrites are dispersed in the matrix of the u-based alloy. Both of these two phases can be cold-worked, and when they are strongly worked to a fine wire by rolling and drawing, a wire rod in which a large number of Nb or V fibers are closely arranged in a Cu alloy can be obtained. When this is subjected to diffusion heat treatment at an appropriate temperature, an Nb3Sn or V3Ga layer is generated. Superconducting proximity effects and partial contact between fibers are considered to be the reason why discontinuous superconducting fibers exhibit zero electrical resistance in In 5 itu type wires.

In the In 5 itu method, Cu-V (or Cu-Nb)2
After making an original alloy ingot and drawing it into a thin wire, the surface is plated with Ga (Sn) and heat treated at an appropriate temperature to diffuse Ga (Sn) into the wire, and V3
Methods for producing Ga(NbsSn) fibers have also been developed. According to this method, not only the processing of the alloy becomes extremely easy, but also a large critical current density (Jc) can be obtained because the amount of Ga (Sn) can be increased arbitrarily.

In particular, the Vs Ga In 5 itu wire exhibits a Jc per total area of 2×10'A/cm' in a magnetic field of 20 Stella (T), which exceeds that of an ultrafine multifilamentary wire produced by a composite processing method.

With the In 5 itu method, ultra-fine multi-filament wires can be easily produced using a composite processing method, and since the fine fibers themselves mechanically strengthen the wire, superconducting properties are maintained against stresses such as bending and tension. It has excellent effects such as less deterioration,
This is an industrially extremely advantageous method ([Japanese Science and Technology J'82/Superconductivity P81-88).

In order to manufacture superconducting materials using the In 5 itu method, it is first necessary to manufacture Cu-V alloys and Cu-Nb alloys, and the methods include: (1) induction heating melting using high-frequency induction heating in a refractory container; Then, cast into a water-cooled Cu mold.

■ Cast by arc melting method using consumable electrode method or non-consumable electrode method. (Currently, the consumable electrode method is mainly adopted due to its low segregation, and Cu/Nb composite material is used as the electrode, and this method is advantageous for industrial mass production.) .

[Problems to be Solved by the Invention]However, both (1) and Nb have extremely high melting points.
℃), and has a strong affinity with oxygen, nitrogen, carbon, etc., and is highly reactive.

It is extremely difficult to melt an alloy containing Nb, and in the method (2), good melting cannot be achieved by melting using a normal refractory container.

That is, for furnace materials such as magnesia, alumina, and zirconia, which are generally known refractory materials for melting, 175
The upper limit of melting is about 0°C, and it has not been possible to melt metals and alloys with higher melting points than that. Further, even if it can be melted, it has a high content of impurities such as O and N.

In addition, there is a graphite refractory material used as a high-frequency furnace material for high-temperature melting, but V and Nb react very easily with carbon, and contamination inevitably deteriorates the superconducting properties of the alloy.

Moreover, when the Cu-Nb alloy or Cu-V alloy used in the In 5 itu method is to be made into a superconducting material, as described above, after processing this alloy into a wire rod, it can be coated with Sn or Ga. However, in order to obtain an alloy with excellent workability into wire rods, it is important that the amount of oxygen, nitrogen, carbon, etc. mixed into the alloy system is extremely small. .

However, conventionally, low-oxygen Cu--Nb alloys or Cu--V alloys with excellent workability suitable for use as superconducting materials have not been obtained by the high-frequency conductive heating method (2).

On the other hand, with the arc melting method (■), there is no problem such as the contamination of impurities from the fireproof container as in (■), but with this method, the initial dendrite diameter of the alloy is too small, 1 to 20 μm, and it cannot be used as is. There was a problem in that an alloy that could be used as an alloy could not be obtained, and that some kind of post-treatment was required.

The present applicant has proposed a Cu-Nb alloy or a Cu-V alloy having excellent properties suitable as an alloy for superconducting materials and a method for producing the same, which solves such problems. Weight %, AJZ and/or Ti
0.01 to 0.5% by weight, 0 to 250 ppm or less, C
An alloy for a superconducting material, characterized in that it contains 10 to 500 ppm of a, the remainder being substantially Cu, and a container in which at least the inner surface is composed of fused calcia.
A method for producing an alloy for superconducting materials, characterized in that the above alloy is obtained by making A1 and/or Ti exist in a molten alloy containing u and Nb or V in a vacuum or a non-oxidizing atmosphere. I filed a patent application for it first (Japanese Patent Application No. 1064/1983).

(hereinafter referred to as "prior application").

According to the above-mentioned prior application, an alloy is provided that fully satisfies the workability and mechanical properties required as a superconducting material.
In the field of superconducting materials, there is always a demand for materials with better properties, and the emergence of technology that can further improve critical current density (Jc), workability, etc. is desired.

[Means for Solving the Problems] The present invention provides an alloy for superconducting materials that has further improved Jc, workability, etc., and a method for producing the same. %, contains 250 ppm or less of O, 10 to 500 ppm of Ca, and the remainder is substantially Cu.
A container made of an alloy for superconducting material characterized by having a dendrite diameter of 50 to 300 μm, and a calcia refractory material having at least an inner surface of 95% by weight or more of CaO, is used in a vacuum or By casting a molten alloy containing Cu and Nb or V obtained by melting in a non-oxidizing atmosphere in a calcia mold,
Contains 10 to 60% by weight of Nb or V, 250 ppm or less of 0, 10 to 500 ppm of Ca, and the remainder is substantially Cu.
The gist of the present invention is a method for producing an alloy for superconducting material, which is characterized by obtaining an alloy ingot having a dendrite diameter of 50 to 300 μm.

That is, the present inventors have determined that the critical current density (Jc
) and other properties, we discovered that the initial dendrite size in the alloy is very important, and that the wire drawability of the alloy is affected by the amount of Ca in the alloy. , completed the present invention.

The present invention will be explained in detail below.

In addition, in this specification, "%" represents "weight %".

The superconducting material alloy of the present invention contains 10 to 60% Nb or V.
, 250 ppm or less of 0, 10 to 500 ppm of Ca, the remainder being substantially Cu, and the dendrite diameter is 50 to 300 μm.

If the Ca content in the alloy exceeds 250 ppm, or if the Ca content is less than 10 ppm or more than 500 ppm, good workability cannot be obtained. In the present invention, it is particularly preferable that the 0 content is 100 to 200 ppm and the Ca content is 200 to 400 ppm.

On the other hand, the dendrite diameter of the alloy ingot is less than 50 μm or 3
If it exceeds 00 μm, a high critical current density cannot be obtained. In the present invention, the dendrite diameter is particularly 100~
Preferably, it is 300 μm.

By the way, the larger the content of (■) or Nb, the greater the amount of VsCa or Nb3Sn produced by heat treatment, but if it is too large, V or Nb will act as a diffusion barrier for Ca or Sn, and may also reduce the Jc value and impair workability. lead to deterioration. Therefore, the content of V or Nb is 10 to 60%, preferably 20 to 40%.

Such an alloy for superconducting materials of the present invention can be easily manufactured according to the method of the present invention described below.

In the method of the present invention, first, (1) or an alloy containing Nb is placed in a vacuum or non-oxidizing atmosphere (for example, argon , helium, etc.) under
It is heated and melted using a conventional method such as a high frequency or low frequency induction heating method.

As the calcia refractory material constituting the container, one with a higher CaO content is more suitable. Other components contained in the calcia refractory material include Z ro2. MgO, Y203
Other high melting point oxides such as In addition, S to2
．． AfL203.

Components that lower the melting point of the refractory material, such as Fe2O3, B203, and TiO2, lower the heat resistance and make high-temperature melting impossible, so the total amount is preferably 3% or less, particularly 1% or less.

Such calcia refractory materials with high CaO content easily adsorb oxides and sulfides, absorbing oxides and sulfides in molten metal, and greatly reducing the amount of oxide and sulfide-based nonmetallic inclusions. It is also thermodynamically stable and Nb
, V and other easily oxidizable metals, and can be melted at high temperatures. In the present invention, especially fused calcia is used as the calcia refractory material, and the CaO content thereof is preferably 98% or more.

In order to produce the refractory material according to the present invention, for example, fused calcia powder and, if necessary, ZrO2°MgO, Y2O3
etc. in an appropriate ratio, and mold this into a crucible shape using die molding, slip casting, rubber press, etc.
Fire. In addition, a shaped refractory or an unshaped refractory may be made according to a conventional method, and the inner surface of the container may be made of fused calcia using such a refractory.

In the present invention, A1 and/or Ti is cooled and solidified in a molten alloy of Cu and V or Nb in a container whose inner surface is made of such a calcia-based material.
And/or it may be added so that the residual amount of Ti is 0.001 to 0.5%.

By making A2 and/or Ti exist in the molten metal,
The 0 content in the molten metal is reduced by the O removal action of Aλ and/or T1, and the 0 content in the resulting alloy is easily reduced to 25
It can be set to 0 ppm or less.

In this case, by making the inner surface of the container used for melting into fused calcia, contamination of Ca into the molten metal can be prevented by adding Aλ and/or Ti, and the Ca content in the resulting alloy can be easily reduced to 10 It becomes possible to set it as the range of 500 ppm.

In addition, in the method of the present invention, in order to improve the superconducting properties and processing properties of the alloy, Y, Hf, T,
One or more of a, Mo, Zr, and rare earth elements may be added. Rare earth elements include Ce, Pr, Nd,
Pm, Sm, En.

Gd, Tb, Dy, Ho, Er, Tm, Yb.

Although any of Ln may be used, Ce is usually used.

The amounts of Y, Hf, Ta, Mo, Zr, and rare earth elements to be added are preferably such that the amount remaining in the alloy is 2% or less. Y, Hf, Ta.

By adding Mo, Zr, and rare earth elements, the deoxidizing effect and superconducting properties are further improved.

The Cu-V or Cu-Nb alloy molten metal thus obtained is then poured into a calcia mold and cast.

In this case, it is preferable that the CaO content of the calcia mold used is higher, and the CaO content is 95% or more, especially 98%.
The above are preferred.

Casting using a calcia mold makes it possible to set appropriate casting conditions, and prevents contamination of the molten metal during casting. Diameter 5
Cu-V or Cu-Nb alloys of 0 to 300 μm are easily obtained.

The alloy for superconducting materials of the present invention is extremely useful as a raw material for producing superconducting materials, particularly by the In 5 itu method.

[Function] CaO has a high melting point and is extremely stable at high temperatures, and has extremely high stability with respect to molten alloys containing easily oxidizable high melting point metals such as Nb and (2), and can be melted at high temperatures. Therefore, during melting and casting, metal oxides are not generated and the molten metal is not contaminated with impurities. Moreover, CaO
Refractories mainly composed of oxides and sulfides easily react with so-called furnace walls, and can absorb oxides and sulfides in the molten metal, greatly reducing the amount of nonmetallic inclusions. Prevent contamination by oxygen, hydrogen, nitrogen, etc.

Therefore, according to the method of the present invention, specific O content, C
An alloy with a specific dendrite diameter and a content can be easily cast.

Therefore, the alloy for superconducting materials of the present invention obtained by such a method is highly clean, has extremely excellent workability, and has extremely excellent superconducting properties.

[Example] The present invention will be explained in more detail with reference to Examples below.
The present invention is not limited to the following examples unless it exceeds the gist thereof.

Example I K A calcia crucible was manufactured using fused calcia (CaO content: 99%). Using this, Cu-4 under Ar7 atmosphere
0%Nb alloy or Cu-40%■ alloy is melted, and the obtained molten metal is cast in a mold made of fused calcia (CaO content 99%), with a content of 0% of 250ppm or less and a content of Ca of 10 to 5o. .

A Cu-Nb or Cu-V alloy of the present invention having a P P m s dendrite diameter of 50 to 300 μm was obtained.

For comparison, melting and casting were performed with different refractory materials and mold materials, and alloys were produced in which any of the zero content, Ca content, and dendrite diameter was outside the range of the present invention.

Using each alloy, dendrite diameter and critical current density (Jc
H external magnetic field ITc), the relationship between the Ca content and the drawable diameter, and the relationship between the 0 content and the drawable diameter were investigated.

The results are shown in FIGS. 1 to 3.

From FIGS. 1 to 3, it is clear that the alloy for superconducting materials of the present invention is J
It is clear that the c value is high and the workability is also extremely good.

[Effects of the Invention] As detailed above, the alloy for superconducting materials of the present invention contains Nb
or 10 to 60% by weight of V, 250 ppm or less of 0, C
It contains 10 to 500 ppm of a, the remainder is substantially Cu, and the dendrite diameter is 50 to 300 ppm, and has low 0 content and low Ca content, and has extremely excellent workability and mechanical properties. In addition, a high Jc value can be obtained from its dendrite size, and it has excellent superconducting properties.

Such an alloy for superconducting materials of the present invention is particularly suitable for In 5
It is extremely useful as a raw material for producing superconducting materials using the itu method.

Therefore, the alloy for superconducting materials of the present invention must be melted in a container whose inner surface is made of a calcia refractory with a CaO content of 95% or more, and cast in a calcia mold. easily manufactured by the method of the invention.

[Brief explanation of the drawing]

Figures 1 to 3 are graphs showing the results obtained in Example 1. Figure 1 shows the relationship between dendrite diameter and Jc value, and Figure 2 shows the relationship between Ca content and drawable diameter. Figure 3 shows the relationship between the zero content and the drawable diameter. Agent Patent Attorney Tsuyoshi Shigeno Figure 1 Dendrite diameter (μm) Figure 2 0 content (ppm)

Claims (2)

[Claims] (1) 10 to 60% by weight of Nb or V, 250pp of O
An alloy for superconducting material, characterized in that it contains 10 to 500 ppm of Ca, the remainder is substantially Cu, and has a dendrite diameter of 50 to 300 μm. (2) Contains Cu and Nb or V obtained by melting in a vacuum or non-oxidizing atmosphere using a container whose inner surface is made of a calcia refractory material with a CaO content of 95% by weight or more. By casting the molten alloy in a calcia mold, 10 to 60% by weight of Nb or V and 250pp of O are added.
1. A method for producing an alloy for superconducting materials, the method comprising obtaining an alloy ingot containing 10 to 500 ppm of Ca, the remainder being substantially Cu, and having a dendrite diameter of 50 to 300 μm.