JPH0355530B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an alloy for superconducting materials and a method for producing the same, and in particular to an alloy for superconducting materials and its production method that has extremely high critical current density (Jc) and workability. Regarding the 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, Nb ₃ Sn multicore wires, etc.
It is manufactured using a composite processing method called the bronze method. Bronze method is bronze, that is, Cu-Sn
(~8 at.%) A composite with a Nb core in an alloy matrix is wire-drawn and heat treated at approximately 700℃.
It produces a layer of Nb ₃ Sn ("Solid State Physics")
Vol.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, there is a need for a comprehensive level-up of fundamental 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 to improve the level of fundamental technologies 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. However, currently, there are new manufacturing methods, especially for compound wires, such as the in-situ method.
Infiltration method and powder metallurgy method are attracting attention.
In Situ method is Cu-Nb-Sn or Cu-V-
Using Ga ternary alloy ingot, Nb ₃ Sn or
This is a method for producing a wire containing a large amount of discontinuous ultrafine fibers of V ₃ Ga compound. Cu-Nb with appropriate composition
-Sn alloy or Cu-V-Ga alloy ingots contain Nb or V in the Cu-based alloy matrix.
It has a phase structure with dispersed dendrites. This 2
Both phases can be cold-worked, and if they are strongly worked to a fine wire by rolling and drawing, a wire rod in which many Nb or V fibers are closely arranged in a Cu alloy can be obtained. When this is diffused heat treated at an appropriate temperature,
A Nb ₃ Sn or V ₃ Ga layer is generated. Superconducting proximity effects and partial contact between fibers are thought to be the reason why discontinuous superconducting fibers exhibit zero electrical resistance in in-situ wires.

In the In Situ method, a Cu-V (or Cu-Nb) binary alloy ingot is made, which is drawn into a fine wire.The surface is then plated with Ga (Sn) and heat treated at an appropriate temperature. Diffusion of Sn) into the wire,
Methods have also been developed to produce V ₃ Ga (Nb ₃ Sn) fibers. 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 V ₃ Ga In Situ wire has a 20-stellar (T) performance that exceeds that of ultra-fine multi-filament wires produced using composite processing methods.
Jc per total cross-sectional area of 2×10 ⁴ A/cm ² in a magnetic field of
shows. With the in-situ 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, it is resistant to stress such as bending and tensile stress. It has excellent effects such as little deterioration of superconducting properties, and is an extremely advantageous method industrially (Japanese Science and Technology '82/Superconductivity
P81-88).

In order to manufacture superconducting materials using such an in-situ method, it is first necessary to manufacture a Cu-V alloy or a Cu-Nb alloy, which is accomplished by 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.) There are two methods.

[Problems to be solved by the invention] However, both V and Nb have extremely high melting points (the melting point of V is 1900±25°C, and the melting point of Nb is 2468±25°C).
10℃) and have a strong affinity with oxygen, nitrogen, carbon, etc., and are highly reactive, making it extremely difficult to melt alloys containing V and Nb.
Good melting cannot be achieved by melting using a normal refractory container.

In other words, the upper limit for furnace materials such as magnesia, alumina, and zirconia, which are commonly known refractory materials for melting, is around 1750℃, and metals and alloys with higher melting points cannot be melted. I couldn't do it. Moreover, even if it can be melted, it has a high content of impurities such as O and N.

In addition, graphite refractory materials are available as high-frequency furnace materials for high-temperature melting, but V and Nb react very easily with carbon, and the superconducting properties of the alloy inevitably deteriorate due to contamination. .

Moreover, the Cu-Nb alloy used in the In Situ method or
When Cu-V alloy is used as a superconducting material, as mentioned above, after processing this alloy into a wire rod,
It is necessary to perform Sn or Ga diffusion treatment by applying Sn or Ga plating, but in order to obtain an alloy with excellent workability into wire rods, it is necessary to
An important requirement is that the amount of carbon etc. mixed in is extremely small.

However, conventional high-frequency induction heating methods have not yielded low-oxygen Cu--Nb alloys or Cn--V alloys that have excellent workability and are suitable for use as superconducting materials.

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

The applicant has developed an alloy that has excellent properties and is suitable as an alloy for superconducting materials to solve these problems.
Cu-Nb alloy or Cu-V alloy and its melting method include 10 to 60% by weight of Nb or V and Al and/or Ti.
0.01~0.5% by weight, O 250ppm or less, Ca 10~
An alloy for superconducting material containing 500 ppm and the remainder being substantially Cu, and a molten alloy containing Cu and Nb or V in a container whose at least inner surface is composed of fused calcia,
A patent application was previously filed for a method for producing an alloy for superconducting materials, which is characterized in that the above alloy is obtained by making Al and/or Ti exist in a vacuum or non-oxidizing atmosphere. No. (hereinafter referred to as the "first application").

According to the above-mentioned prior application, an alloy that fully satisfies the workability and mechanical properties required for a superconducting material is provided, but in the field of superconducting materials, there is always a demand for materials with even better properties. has been
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. %, O below 250ppm,
A superconducting material alloy characterized by containing 10 to 500 ppm of Ca, the remainder being substantially Cu, and having a dendrite diameter of 50 to 300 μm, and a calcia refractory whose inner surface has at least a CaO content of 95% by weight or more. Nb or V is produced by casting a molten alloy containing Cu and Nb or V in a calcia mold, which is obtained by melting in a vacuum or non-oxidizing atmosphere using a container made of Nb or V. 10-60% by weight,
Contains 250 ppm or less of O, 10 to 500 ppm of Ca, and the remainder is substantially Cu, and the dendrite diameter is 50 to 50 ppm.
The gist of the present invention is a method for producing an alloy for superconducting materials, which is characterized by obtaining an alloy ingot with a thickness of 300 μm.

In other words, as a result of intensive studies to improve the properties of superconducting materials such as critical current density (Jc), the inventors have discovered that the initial dendrite dimensions in the alloy are extremely important, and that the It was discovered that the drawability is affected by the amount of Ca in the alloy, and the present invention was completed.

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 10% of Nb or V.
It is an alloy containing 60%, 250 ppm or less of O, and 10 to 500 ppm of Ca, with the remainder being substantially Cu and having a dendrite diameter of 50 to 300 μm.

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

On the other hand, if the dendrite diameter of the alloy ingot is less than 50 μm or more than 300 μm, a high critical current density cannot be obtained. In the present invention, the dendrite diameter is particularly preferably 100 to 300 μm.

By the way, the higher the content of V or Nb, the greater the amount of V ₃ Ca or Nb ₃ Sn produced by heat treatment, but if it is too large, V or Nb becomes a diffusion barrier for Ca or Sn, and the Jc value decreases. , leading to deterioration of workability. 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, an alloy containing V or Nb is prepared such that at least the inner surface has a CaO content of 95%.
% or more of calcia refractory material, and melt it by heating in a vacuum or a non-oxidizing atmosphere (e.g. argon, helium, etc.) using a conventional method such as high frequency or low frequency induction heating. make

The calcia refractory material that makes up the container is
The higher the CaO content, the more suitable it is. Other components contained in calcia refractory materials include ZrO ₂ ,
Other high melting point oxides such as MgO, Y ₂ O ₃ etc. may be mentioned. Note that components that lower the melting point of refractory materials, such as SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , B ₂ O ₃ , and TiO ₂ , lower the heat resistance and make high-temperature melting impossible. 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. You can also
It is thermodynamically stable, has high stability against easily oxidizable metals such as Nb and V, and can be melted at high temperatures. In the present invention, especially fused calcia is used as the calcia refractory material, and its CaO content is
It is preferably 98% or more.

To produce the refractory material according to the present invention, for example, fused calcia powder and, if necessary, ZrO ₂ ,
MgO, Y ₂ O ₃ , etc. are mixed in an appropriate ratio, and this is formed into a crucible shape using die molding, slip casting, rubber pressing, etc., and then fired. In addition, it is also possible to use a regular method to make a shaped refractory or an unshaped refractory, and use such a refractory to make the inner surface of the container made of fused calcia.

In the present invention, Al and/or Ti remains after cooling and solidifying Al and/or Ti in a molten alloy of Cu and V or Nb in a container whose inner surface is made of such a calcia refractory material. The amount is 0.01~0.5
%.

By allowing AI and/or Ti to exist in the molten metal, the O content in the molten metal is reduced by the O removal effect of Al and/or Ti, and the O content in the resulting alloy can be easily reduced to 250 ppm or less. be able to.

In this case, by using fused calcia as the inner surface of the container used for melting, the addition of Al and/or Ti can prevent Ca contamination into the molten metal and easily reduce the Ca content in the resulting alloy. It becomes possible to set it as the range of 10-500 ppm.

In addition, in the method of the present invention, one or more of Y, Hf, Ta, Mo, Zr, and rare earth elements are added to the molten metal during melt production in order to improve the superconducting characteristics and processing characteristics of the alloy. Also good. Rare earth elements include Ce, Pr, Nd, Pm, Sm, En, Gd, Tb,
Any of Dy, Ho, Er, Tm, Yb, and Ln may be used, but Ce is usually used. These Y, Hf, Ta,
The amounts of Mo, Zr, and rare earth elements added are preferably such that the amount remaining in the alloy is 2% or less. By adding Y, Hf, Ta, 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, the higher the CaO content of the calcia template used, the more preferable it is, and the CaO content of 95% or more, particularly 98% or more is preferable.

Casting using a calcia mold makes it possible to set appropriate casting conditions, and prevents contamination of the molten metal during casting. A Cu-V or Cu-Nb alloy with a diameter of 50 to 300 μm can be 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 Situ 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 Nb and V, which are easily oxidized high melting point metals, 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, refractories mainly composed of CaO easily react with oxides, sulfides, etc. on the furnace wall, and can absorb oxides, sulfides, etc. in the molten metal, greatly reducing the amount of non-metallic inclusions. Moreover, it prevents contamination by oxygen, hydrogen, nitrogen, etc.

Therefore, according to the method of the present invention, it is possible to easily cast an alloy having a specific O content, a specific Ca content, and a specific dendrite diameter.

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.

[Examples] The present invention will be explained in more detail by Examples below, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Example 1 A calcia crucible was manufactured using fused calcia (CaO content 99%). Using this, under Ar atmosphere
Cu-40%Nb alloy or Cu-40%V alloy is melted, and the resulting molten metal is molten calcia (CaO content 99%).
%) Cast in a manufacturing mold, O content 250ppm or less,
Ca content 10~500ppm, dendrite diameter 50~300μ
A Cu-Nb or Cu-V alloy of the present invention of m was obtained.

For comparison, melting and casting were performed with different refractory materials and mold materials, and the O content and Ca
An alloy was produced in which either the content or the dendrite diameter was outside the range of the present invention.

Using each alloy, we investigated the relationship between the dendrite diameter and the critical current density (Jc) (in the case of an external magnetic field of 1Tc), the relationship between the Ca content and the drawable diameter, and the relationship between the O content and the drawable diameter. Examined.

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 has a high Jc value and has extremely good workability.

[Effects of the Invention] As detailed above, the alloy for superconducting materials of the present invention contains 10 to 60% by weight of Nb or V, 250 ppm or less of O, 10 to 500 ppm of Ca, and the balance is substantially Cu.
The dendrite diameter is 50 to 300 ppm, and the O content and Ca content are both low.
In addition to having extremely excellent workability and mechanical properties,
Due to its dendrite size, a high Jc value can be obtained, and it has excellent superconducting properties. Such an alloy for superconducting materials of the present invention is extremely useful as a raw material for producing superconducting materials, particularly by the in-situ method.

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

[Brief explanation of drawings]

Figures 1 to 3 are graphs showing the results obtained in Example 1, where 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 O content and the drawable diameter.

Claims (1)

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