JP3893729B2 - Spherical powder of Nb / Al based metal material and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, when manufacturing a wire or tape material (ribbon) from a superconducting material such as Nb ₃ Al which is brittle and poor in workability, a spherical powder of A2 type Nb / Al metal material with good workability is used. The present invention relates to a manufacturing method and a manufacturing apparatus. In addition, the present invention relates to a method for obtaining Nb ₃ Al wires or tapes (ribbons) having excellent superconducting properties after being processed from spherical powder with improved processability into wires and then further heat-treated. Or a block body in which the spherical powder is used as a heat-resistant material as a molded sintered body.
[0002]
[Prior art]
As a superconducting material which is processed into a tape material (ribbon), a wire, etc. and used for a winding of a superconducting magnet, a Ni-Ti metal material having high plasticity is used. However, the Nb—Ti metal material has a limit of 9 Tesla magnetic field generation in 4.2 K liquid He. On the other hand, in order to put a superconductor into practical use, a critical current density of 4 × 10 ⁴ A / cm ² is required in a liquid He at 4.2 K under a magnetic field of 10 Tesla. Therefore, a material having superconducting properties superior to that of the Nb—Ti metal material is required for a higher magnetic field superconducting magnet, and an A15 type metal material such as Nb ₃ Al has recently been attracting attention.
[0003]
However, the Nb ₃ Al usually has an A15 type crystal structure in the melted and solidified state, and since the A15 type is hard and brittle, it cannot be directly processed into a wire or the like. Has not been converted.
[0004]
On the other hand, it is known that A15 type Nb ₃ Al is phase-transformed to A2 type (bcc supersaturated solid solution of Nb · Al) by melting and quenching to improve workability. As a method of melting and quenching, many studies such as a hammer quenching method have been carried out (K. Schulze, et al. Journal of the Less-Common Metals, vol. 139, (1988) P97 to 106, etc.).
[0005]
[Problems to be solved by the invention]
However, in the conventional hammer quenching method, since a spherical body is not obtained, the moldability is poor, and the productivity is inferior due to batch operation. In addition, the conventional atomizing method that rapidly cools when atomizing with a jet gas is difficult to control the particle size, requires high energy, complicates the device, and increases the contamination because the molten metal contacts the nozzle. There is a problem.
[0006]
Therefore, an object of the present invention is to provide a production method and apparatus for producing a spherical powder of an A2 type Nb / Al-based metal material at low cost by melting and quenching with powder as a raw material.
[0007]
In addition, if the powder is used as a raw material, it becomes possible to produce a spherical powder of A2 type Nb / Al-based metal material having a particle size suitable for the molding method, which improves the moldability of the powder and improves the workability. A high-conductivity wire rod, tape material (ribbon), etc. can be obtained by re-heat-treating the formed body into a wire rod. Or it becomes easy to sinter to a block body after shaping | molding and to use as a heat-resistant material.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the method for producing a spherical powder of Nb / Al-based metal material having an A2-type body-centered cubic structure according to the present invention uses Nb / Al-based metal material powder having an A15-type crystal structure as a raw material. The raw material powder particles are heated and melted into a spherical shape by a plasma flame, and the molten particles are rapidly cooled at a cooling rate of 10 ⁴ K / s or more by gas jet cooling in the plasma apparatus to transform into an A2 type body-centered cubic structure. It is characterized by making it.
[0009]
That is, the spherical powder manufacturing method of the present invention heats and melts the raw material powder of the Nb / Al-based metal material as a powder particle in a plasma flame and rapidly cools it at a cooling rate of 10 ⁴ K / s or more by gas jet cooling . A2 type powder having good processability can be obtained from A15 type raw material powder, which is difficult to process, only by a melting process using a plasma flame. In addition, by changing the particle size of the raw material powder , a product powder having a desired particle size can be freely obtained. When the particle size is reduced, rapid cooling is facilitated, and a stable and uniform A2 type product powder can be obtained. As a result, a uniform particle size and a rapid cooling rate, which were difficult with the conventional centrifugal powder method and the like, can be obtained, and a stable A2-type powder can be obtained.
[0010]
In addition, if the raw material powder is prepared by pulverizing an Nb / Al metal material, the particle size of the raw material powder can be freely selected by pulverization, so that a fine product powder having a particle size of 300 μm or less and good moldability can be easily obtained. It is done.
[0011]
In the production method of the present invention, the raw material powder is heated and melted with a plasma flame. For example, the melting point of Nb.Al based metal material is very high, for example, the melting point of Nb ₃ Al is 2253K. The heating by is most suitable as a clean high-temperature heating energy source as compared with other heating methods.
[0012]
Further, by rapidly cooling the melted particles obtained by plasma-heating the raw material powder of the A15 type Nb / Al-based metal material which is difficult to process, it is transformed into the A2 type having good workability which is a spherical particle having a body-centered cubic structure. Since thereby improving the workability of Nb · Al-based metal material powder, wire from the powder, it becomes easy to process such as a tape material (ribbon). It is necessary to obtain a product powder of a stable A2 type Nb / Al-based metal material with a rapid cooling rate of 10 ⁴ K / s or more .
[0013]
In order to obtain Nb ₃ Al having excellent superconductivity, it is desirable that the spherical powder of the Nb · Al-based metal material has an Al content of 7 to 14 wt%. That is, in the stoichiometric composition of Nb ₃ Al, the Al amount is 8.8 wt%, but excellent superconductivity can be obtained if it is 7 to 14 wt%.
[0014]
The spherical powder of the Nb / Al-based metal material is Nb ₃ (Al _1-x , M _x ), where x = 0.01 to 0.5, and M = (Ga, Ge, Si, In 1). Or an excellent superconductor can be obtained.
[0015]
According to the method of the present invention, it is easy to make the spherical powder have a particle size of 300 μm or less, preferably 50 μm, and by making the particle size 50 μm or less, the moldability is further improved and A2 has good workability. A powder of type Nb ₃ Al is obtained.
[0016]
In addition, a method for manufacturing a superconducting material of Nb / Al-based metal material having excellent superconductivity according to the present invention is an Nb / Al having an A2 type body-centered cubic structure manufactured by the manufacturing method according to claim 1. A spherical powder of a metallic metal material is formed, the formed body is cold or warm processed, and is heat-treated at a temperature of 900 K or higher after the processing to retransform into an A15 type crystal structure. It is.
[0017]
That is, an Nb / Al-based metal material obtained by melting or the like has an A15 type crystal structure and has superconductivity but is difficult to process. By immediately cooling it at a cooling rate of 10 ⁴ K / s or more from a high temperature immediately after melt spheroidization by plasma of the present invention, it is possible to obtain a workable A2 type intermetallic compound. Meanwhile, the A2 type intermetallic compound obtained by the method of the present invention, the intact since good workability but has no superconductivity, by re-heating for a short time at a relatively low temperature above 900K Retransformation is performed from A2 type to A15 type. Thereby, superconductivity can be recovered . Thus, the powder of the workability good type A2 intermetallic compound wire, re-heating treatment Shoyo after processed into a tape material (ribbon), the superconducting by re transformed into A15 type from type A2 It is easy to obtain a product such as an excellent wire rod or tape (ribbon) . In contrast, in the conventional method of sheath processed and sintered remain A15 type raw material powder of a method of manufacturing a superconducting wire were required industrially disadvantageous temperature above 1500 K.
[0018]
In addition, the manufacturing method of the heat-resistant material of the Nb.Al-based metal material having the A2 type body-centered cubic structure according to the present invention is an Nb.Al having the A2 type body-centered cubic structure manufactured by the manufacturing method according to claim 1. after forming the spherical powder systems metallic material, it is characterized in that the block body by sintering.
[0019]
Since the Nb / Al metal material has high heat resistance, it has been studied to be used for a member of nuclear power or a gas turbine. However, since the melting point is high, melting and precise casting are difficult, and thus powder molding is performed. However, since the powder as melt is hard and brittle, it is difficult to mold and practical use is limited.
[0020]
Since the spherical powder obtained by the method of the present invention has good moldability, a complicated product can be obtained by sintering after molding, and can be used as a heat-resistant member.
[0021]
The apparatus for producing a spherical powder of Nb / Al-based metal material having an A2 type body-centered cubic structure according to the present invention is a plasma apparatus in which raw powder particles are heated and melted to form a molten spheroid. It is characterized by comprising a quenching means for rapidly transforming the particles of the Nb / Al-based metal material having a transformation into an A2 type body-centered cubic structure by quenching at a cooling rate of 10 ⁴ K / s or more by gas jet cooling. .
[0022]
Thus, by providing the plasma apparatus with a means for rapidly cooling spherical particles, which was not available in the conventional apparatus, it is possible to easily obtain a spherical powder of Nb / Al-based metal material of A2 type body-centered cubic structure with good workability. .
[0023]
By quenching the quenching means with a cooling nozzle that injects gas , clean cooling can be performed at a desirable cooling rate of 10 ⁴ K / s or more.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described with reference to an illustrated embodiment. FIG. 1 is a cross-sectional view of an apparatus for producing a spherical powder of Nb / Al-based metal material according to the present invention.
[0025]
First, the overall configuration of the manufacturing apparatus of the present invention will be described with reference to FIG. The manufacturing apparatus of the present invention includes a plasma torch 11, a raw material supply means 21, a chamber 31, and a rapid cooling means 41.
[0026]
In the plasma torch 11, a high frequency induction coil 17 is wound around an outer periphery of a quartz tube 12 having a double tube structure to be cooled by water, and a high frequency current is applied from a high frequency power source 40 through terminals 17a and 17b. A core gas supply pipe 13 and a sheath gas supply pipe 14 are provided above the quartz pipe 12 so that Ar gas is supplied from a gas cylinder 15. The periphery of these gas supply pipes is cooled by a torch head 16. The lower part of the quartz tube 12 is fixed to a water cooling jacket 18, and a cooling gas supply pipe 19 is provided in the water cooling jacket 18, and Ar gas is supplied from a gas cylinder 15.
[0027]
The supply means 21 includes a raw material hopper 22, a raw material supply pipe 23, and a raw material supply nozzle 24, and the tip of the raw material supply nozzle 24 is opened on the blowing side of the plasma frame 1. A carrier gas pipe 20 branched from the cooling gas supply pipe 19 is connected to the raw material hopper 22.
[0028]
The cooling means 41 comprises a cooling gas supply pipe 43 connected to the gas cylinder 15 and a cooling gas nozzle 42 connected thereto, and the tip of the cooling gas nozzle 42 gas-cools the heated and melted molten particles immediately below the plasma flame. Is open at the position.
[0029]
The chamber 31 has a cylindrical box shape, and the water cooling jacket 18 below the plasma torch 11 is fixed to the upper lid 34 of the cylindrical portion 32 so that the plasma torch 11 is mounted on the upper lid 34. The lower part of the cylindrical part 32 is opened and connected to the collection container 33. The gas in the chamber 31 is exhausted by a cyclone 35, a filter 36, and an air pump 37 connected to the side surface of the cylindrical portion 32.
[0030]
The operation of the manufacturing apparatus having the above configuration will be described below. First, when high-frequency power is applied to the high-frequency induction coil 17 while flowing Ar gas from the core gas supply tube 13 and the sheath gas supply tube 14 of the plasma torch 11, the plasma 1 indicated by a chain line in the figure is generated in the quartz tube 12 and the quartz tube. 12 is ejected from the lower side.
[0031]
Next, the raw material powder 3 of the raw material hopper 22 is supplied from the raw material supply nozzle 24 to the heating part 2 of the plasma flame through the raw material supply pipe 23 by the Ar gas in the carrier gas supply pipe 20. Since the heating part of the plasma flame is set so that the raw material powder is heated to a temperature equal to or higher than its melting point, the raw material powder is heated and melted as it is and the molten particles fall into the chamber 31.
[0032]
At this time, Ar gas supplied from the cooling gas supply pipe 43 is ejected from the tip of the cooling gas nozzle 42, and the molten particles heated and melted by the plasma flame are rapidly cooled by gas cooling. At this time, the gas injection such that the cooling rate is equal to or greater than 10 ⁴ K / s. As a result, the powder is spheroidized by melting, and the raw material powder of A15 type is transformed into A2 type spherical particles having a bcc body-centered cubic structure by a rapid cooling effect.
[0033]
The product powder 4 melted and rapidly cooled and transformed into A2 type falls into the chamber 31 and is stored in the collection container 33.
[0034]
Thus, according to the production method and production apparatus of the present invention, an arbitrary particle size can be selected by selecting the pulverized particle size of the raw material powder, and a fine product powder of 50 μm or less can be freely obtained. In addition, continuous operation is easy if the material hopper and the collection container are switched.
[0035]
【Example】
The following experiment was performed using the manufacturing apparatus having the configuration shown in FIG.
a. Metals Nb and Al have an Al content of 12 wt. % And melted by an arc melting method to prepare an Nb ₃ Al ingot.
b. This ingot was pulverized with a ball mill to obtain a raw material powder of Nb ₃ Al having a maximum diameter of 50 μm or less.
c. This raw material powder is charged into the raw material hopper 22, heated under plasma conditions of 13.5 MHz, Ep = 9.75 kV, Ip = 1.2 A, Ig = 0.4 A, rapidly cooled by Ar gas injection, Obtained.
d. Moreover, this product powder was heat-treated at 1123 K × 3.6 ks to prepare a heat-treated powder.
[0036]
X-ray analysis was performed on each of the raw material powder, product powder, and heat-treated powder. The XRD figure is shown in FIGS. The raw material powder in FIG. 2 is Nb ₂ Al + A15 type Nb ₃ Al because Al is expected in view of evaporation of Al. As can be seen from the XRD figure of the figure, the melted and quenched product powder in FIG. It turns out that it has transformed into a mold. Further, it is recognized that the heat-treated powder subjected to the reheating treatment in FIG. 4 is again transformed into the A15 type.
[0037]
The raw material powder, product powder, and heat-treated powder were each formed into pellets of 10 mmφ × 1 mmt by applying a pressure of 500 Mpa by press working.
[0038]
The result of having observed the cross section of the pellet of a raw material powder, a product powder, and the heat processing powder with SEM in FIG.
[0039]
In the pellet of the raw material powder of FIG. 5, it is difficult to see because the powder is crushed and not spheroidized, but many cracks are observed in the granule. On the other hand, in the pellet of the product powder shown in FIG. 6, no cracks were observed in the granules, and it was confirmed that the workability was improved. Moreover, in the pellet of the heat-treated powder of FIG. 7, many cracks are recognized at the edges of the granules, and it can be seen that the particles are cracked by pressing.
[0040]
From the above results, the raw material powder and the heat-treated powder transformed into A15 type have poor workability and are cracked by processing. However, the melt-quenched A2-type product powder of the present invention has no crack and has improved workability. I found out.
[0041]
Next, a tape material (ribbon) for superconducting property evaluation was manufactured under the following conditions using the product powder.
[0042]
a. A Ta sheath with an inner diameter of 5 mmφ and an outer diameter of 8 mmφ is filled with the product powder,
b. Processing to 2.4mm square using groove roll,
c. 873K × 1hr of annealing,
d. It was processed into a tape of 0.63 mmt with a flat roll.
[0043]
Above the critical current density Jc under a magnetic field of 10 Tesla the tape at 4.2K in a liquid ^{He 4 × 10 4 A / cm} 2 was obtained. That is, the powder of type A2 of Nb · Al-based metallic material according to the production method of the present invention, by reheating treatment after working the wire, 4 in the above conditions are required to practical application of superconductors It was found that the critical current density Jc of × 10 ⁴ A / cm ² can be sufficiently satisfied.
[0044]
Further, as a result of press-molding and sintering a 10 mm × 10 mm × 10 mm cube using the above product powder, it was found that the required moldability and sintering strength were obtained.
[0045]
As described above, according to the spherical powder of the Nb / Al-based metal material of the embodiment of the present invention and its manufacturing method and manufacturing apparatus, an A2 type Nb / Al-based metal material with good workability is obtained, It became easy to process wires, tapes (ribbons), etc., and if the heat treatment was performed after the processing, superconductivity was recovered, so it was found that high superconducting tapes (ribbons) could be obtained. .
[0046]
Further, by selecting the particle size of the raw material powder, the particle size of the powder of the obtained A2 type Nb / Al-based metal material can be arbitrarily changed, so that fine powder with good moldability can be obtained. It was found that heat-resistant parts and the like can be easily produced by sintering this spherical powder into a compact.
[0047]
【The invention's effect】
As described above, according to the spherical powder of the Nb / Al-based metal material of the present invention and the method and apparatus for producing the same, it is possible to obtain the powder of the A2 type Nb / Al-based metal material having good moldability continuously. Therefore, mass production processing of a wire material, a tape material (ribbon) or the like becomes easy, and a superconductor wire material or the like can be obtained by improving the superconducting characteristics by reheating after the processing. Thereby, a superconducting magnet with higher performance than before can be put into practical use. In addition, the application of Nb / Al-based metal powders to heat-resistant parts was opened.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an apparatus for producing a spherical powder of an Nb / Al-based metal material according to an embodiment of the present invention.
FIG. 2 is an XRD pattern of an X-ray analysis of a raw material powder according to an embodiment of the present invention.
FIG. 3 is an XRD pattern of X-ray analysis of a product powder according to an embodiment of the present invention.
FIG. 4 is an XRD diagram of an X-ray analysis of a heat-treated powder according to an embodiment of the present invention.
FIG. 5 is a photograph obtained by SEM observation of a cross section of the raw material powder pellet of the embodiment of the present invention.
FIG. 6 is a photograph obtained by SEM observation of a cross section of the product powder pellet of the embodiment of the present invention.
FIG. 7 is a photograph obtained by SEM observation of a cross section of the heat-treated powder pellet of the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Plasma flame 2 Plasma flame heating part 3 Raw material powder 4 Product powder 11 Plasma torch 12 Quartz tube 13 Core gas supply pipe 14 Sheath gas supply pipe 15 Gas cylinder 16 Torch head 17 High frequency induction coil 18 Water cooling jacket 19 Cooling gas supply pipe 20 Carrier gas pipe 21 Raw material supply means 22 Raw material hopper 23 Raw material supply pipe 24 Raw material supply nozzle 31 Chamber 32 Cylindrical portion 33 Collection container 34 Upper lid 35 Cyclone 36 Filter 37 Air pump 40 High frequency power supply 41 Rapid cooling means 42 Cooling gas nozzle 43 Cooling gas supply pipe

Claims (4)

A powder of an Nb.Al-based metal material having an A15 type crystal structure is used as a raw material, and the particles of the raw material powder are heated and spheroidized by a plasma flame , and the molten particles are cooled by gas jet cooling in a plasma apparatus at 10 ⁴ K / A method for producing a spherical powder of an Nb.Al based metal material having an A2 type body-centered cubic structure, characterized by rapidly cooling at a cooling rate of s or more to transform into an A2 type body centered cubic structure. A spherical powder of an Nb / Al-based metal material having an A2 type body-centered cubic structure manufactured by the manufacturing method according to claim 1 is formed, and the formed body is cold or warm processed. A method for producing a superconducting material of an Nb / Al-based metal material excellent in superconductivity, characterized by being retransformed into an A15 type crystal structure by heat treatment at a temperature. After forming the spherical powder of Nb · Al-based metallic material having a A2 type body-centered cubic structure manufactured by the method according to claim 1, A2 type body-centered, characterized in that the block body by sintering A method for producing a heat-resistant material of an Nb / Al-based metal material having a cubic structure. In a plasma apparatus that melts and spheroidizes raw material powder particles by heating, the particles of the Nb / Al-based metal material having an A15 type crystal structure that has been melted and spheroidized are heated to 10 ^Four An apparatus for producing a spherical powder of an Nb / Al-based metal material having an A2 type body-centered cubic structure, comprising quenching means for rapidly cooling at a cooling rate of K / s or more to transform into an A2 type body-centered cubic structure .

Images