JPH0310008A - Method and apparatus for manufacturing metal fine powder - Google Patents

Abstract

PURPOSE:To economically manufacture high purity metal fine powder with good efficiency by executing the manufacturing operation in inert gas atmosphere under pressurized condition, cooling the gas used to cooling with a heat exchanger and reusing the gas at the time of manufacturing the metal fine powder by focusing ultrasonic wave to the molten metal and cooling as fine drip-state. CONSTITUTION:A holding vessel 10 charged with the molten metal 12 in a vessel 13 of the inert gas atmosphere of Ar gas, etc., is arranged and the ultrasonic wave from an ultrasonic wave generator 1 is focused onto the surface of molten metal 12 with a radiating direction converter 18, and the molten metal 12 is spattered as the fine drips 24, and cooled and solidified with the low temp. Ar gas from a cooling gas supplying device 19, and the fine drips 24 is recovered into a recovering vessel 23 as the metal fine powder. In this case, the pressure in the vessel 13 is measured with the pressure detector 20, and by controlling a pressure control valve 21 with this measured value, the atmospheric pressure in the vessel 13 is made higher than the outer air pressure, and the fine drips are prevented from being oxidized by invation of the outer air and the high purity metal fine powder is manufactured. Further, after cooling the Ar gas for cooling, which becomes high temp., with the heat exchanger 25, the Ar gas is returned back to a cooling gas supplying device 19 through a guide pipe 26 and reused.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing fine metal powder and an apparatus therefor.

[Prior Art] Conventionally, as a method and apparatus for manufacturing fine metal powder using ultrasonic vibration, for example, Japanese Patent Application Laid-Open No. 58-110604
No. 61-295306 is disclosed. These conventional techniques will be explained with reference to the drawings. FIGS. 5(A) and 5(B) both show a conical resonator 51.
The molten metal 52 is made to flow down from above, and the molten metal 52 is atomized by the ultrasonic vibration of the resonator 51 and becomes minute particles 53, which are cooled by the cooling gas 55 ejected from the cooling gas supply pipe 54. Fine metal powder is produced. FIG. 6 shows a method in which a resonator 61 is crushed by a molten metal 62, and the ultrasonic vibrations generated from this cause minute metal particles 63 to be generated from the surface of the molten metal 62, which are then transferred to a chamber 63 held in an inert atmosphere. Cooling gas inlet 6 inside
It is cooled by the cooling gas introduced from 5, and a fine metal powder is produced.

[Problems to be Solved by the Invention] However, the above-mentioned conventional technology has the following problems.

■The temperature of the molten metal flowing down or immersed into the resonator is generally high, so when the molten metal comes into contact with the resonator, alloying elements or impurities contained in the resonator mix into the molten metal, resulting in pure metal fine powder. is not obtained.

■If a heat-resistant ceramic material is used to withstand the temperature of molten metal, the vibration characteristics will be poor and the desired vibration will not be obtained.

(2) Fluctuations in the thickness of the molten metal formed on the resonator result in variations in the directly produced fine metal powder, but it is difficult to control the thickness.

The present invention has been made in view of the above, and an object of the present invention is to provide a method and apparatus for producing fine metal powder, which can easily produce fine metal powder of high purity.

[Means for Solving the Problems] The present invention includes a process of melting a metal material to create a metal AK liquid, and focusing ultrasonic waves on the surface of the metal melt to atomize the metal melt into minute droplets. This is a method for producing a fine metal powder, which comprises a step of solidifying the fine droplets by cooling them using a cooling gas. Here, it is preferable that the step of atomizing the metal melt into minute droplets by focusing ultrasonic waves on the surface of the metal melt is performed under pressure. Also,
The step of collecting the cooling gas after cooling and solidifying the microdroplets, lowering the temperature of the cooling gas to a predetermined temperature, and then adding it to the cooling gas is performed after the step of cooling and solidifying the microdroplets using the cooling gas. It is preferable that it is provided.

The present invention also provides a holder for holding a metal material, a heating means disposed adjacent to the holder to heat the metal material to produce a metal melt, and an ultrasonic generation means for generating a predetermined ultrasonic wave. ,
a focusing means provided between the ultrasonic generating means and the holding body for focusing the ultrasonic waves on the surface of the metal melt to atomize the metal melt into minute droplets; and a focusing means for atomizing the metal melt into minute droplets; This is an apparatus for manufacturing fine metal powder, characterized in that it is equipped with a cooling gas supply means for supplying cooling gas. here,
It is preferable that a pressurizing means is provided to maintain the pressure of the atmospheric gas in contact with the metal melt at a predetermined pressurized state. Also,
It is preferable to include a cooling gas temperature lowering means for lowering the temperature of the cooling gas after cooling and solidifying the micro droplets to a predetermined temperature and then adding it to the cooling gas supply means.

Any heating means may be used as long as it can easily melt the metal material into a metal melt. Examples of such devices include heater radiant tubes, lasers, and the like.

In addition, heating and melting of metal materials can be done by placing the metal material in a container that is a holder and heating the container to melt the entire metal material, or by holding a metal plate, rod, wire, etc. with a holder. , by heating only the tips of these. Therefore, the holder is a cold crucible 4 as shown in FIG. 4(A).
0 and the holding container 41 shown in FIG. Furthermore, a holding body for the metal melt may be provided above the chamber, and the metal melt may flow down from the holding body.

The ultrasonic wave generating means may be any device that can generate ultrasonic waves having energy that can atomize the metal melt into minute droplets by focusing. An example of such a device is an ultrasonic generator that uses a normal high-frequency power source.

Further, as the ultrasonic focusing means, one is used that concentrates the ultrasonic waves on the surface of the metal melt and increases the energy. in this case,
It is preferable to focus the ultrasonic waves on a single point or line. Furthermore, during the operation of pulverizing metal, a combination of a point focusing type and a line focusing type may be used.

The pressurizing means may be of any type as long as it can maintain a pressure state that improves the transmission efficiency of ultrasonic waves. An example of such a method is one in which the atmospheric gas pressure of the metal melt is directly adjusted. Further, the atmospheric gas may be replaced with one having a higher density. These things may be provided directly within the device, or badge-type chambers may be provided separately from the device and connected to the device.

The cooling gas supply means may be any means as long as it can stably supply the cooling gas used for cooling, solidifying and collecting the micro droplets into the apparatus.

The cooling gas temperature lowering means may be any device that efficiently lowers the temperature of the cooling gas that has absorbed heat when micro droplets obtained by atomizing a metal melt are cooled and solidified to a predetermined temperature. Examples of such devices include finned heat exchangers and the like.

[Operation] According to the method and apparatus for producing fine metal powder according to the present invention, ultrasonic waves are generated, the phases of the ultrasonic waves are aligned, and the ultrasonic waves are focused on the surface of the metal melt. The metal melt is atomized into minute droplets by the energy of this ultrasonic wave.

Therefore, since the ultrasonic resonator is not in contact with the metal melt, it is possible to produce high-purity fine particles without introducing impurities into the atomized metal melt, and to extend the life of the resonator. .

Furthermore, by atomizing the metal melt while keeping the atmospheric gas in a pressurized state, the density of the gas medium can be increased, and as a result, the transmission efficiency of ultrasonic waves can be sufficiently increased. Fine metal powder can be efficiently produced.

Further, by lowering the temperature of the cooling gas used for cooling, solidifying and collecting the micro droplets to a predetermined temperature and adding it to the cooling gas supply means, the cooling gas can be used efficiently. Furthermore, the amount of cooling gas supplied can be easily adjusted.
The ambient temperature can be maintained at a predetermined value. Therefore, it is possible to prevent the phase shift of the ultrasonic waves that occurs due to the rise in ambient temperature, and the radiated ultrasonic waves can always be focused at the predetermined surface of the metal melt with the optimum energy for atomization. I can do it. As a result, fine metal powder can be produced continuously, stably, and efficiently.

[Examples] Examples of the present invention will be described below with reference to the drawings. Note that the explanation of the manufacturing method of the present invention includes the explanation of the operation of the apparatus of the embodiment.

Embodiment 1 FIG. 1 is an explanatory diagram showing the configuration of an embodiment of the present invention.

In the figure, 10 is a holding container that holds molten metal.

A heater 11 for melting the metal material is installed outside the holding container 10, and a metal melt 12 is held inside the holding container 10. This holding container 10 and heater 11 are provided below a chamber 13 maintained in an inert gas atmosphere. An ultrasonic generator 1 is provided above the chamber 13 . The ultrasonic generator 1 includes a high-frequency power source 14 and a high-frequency vibrator 15 provided outside a chamber 13, a resonator 17 provided inside the chamber 13, and an ultrasonic generator provided surrounding the resonator 17. It is composed of a radial direction converter 18 for focusing sound waves, and an amplitude expander 16 inserted between the chamber 13 and the radial direction converter 18 and connected between the vibrator 15 and the resonator 17.

Here, the material of the resonator 17 is preferably titanium alloy or aluminum alloy. In addition, since the radiation direction converter 18 has opposite phases on the vibrator side and the anti-vibrator side of the resonator 17, it is possible to superimpose these opposite phase radiated sound waves in the same phase on the surface of the metal melt. is set up.

Further, the radiation direction converter 18 has a reflecting surface set in a parabolic shape in order to efficiently cause the sound waves to reach the surface of the metal melt.

Further, a device 19 that communicates with the inside of the chamber 13 and supplies cooling gas is provided. This device 19 has a pressure detector 20 , a pressure regulating valve 21 based thereon, and a compressor 22 that causes cooling gas to flow into the chamber 13 . Further, a recovery device 23 is connected to the chamber 13 for recovering the manufactured fine metal powder.

Next, the operation of the apparatus for manufacturing fine metal powder constructed as described above will be explained.

First, the ultrasonic transducer 15 is vibrated by the high frequency power supply 14, and the resonator 17 connected to the transducer 15 is vibrated. By appropriately selecting the frequency of this ultrasonic wave, the particle size of the fine metal powder can be changed. Resonator 17
Ultrasonic waves are emitted using the atmospheric gas as a medium due to the vibrations. This radiated ultrasonic wave is focused on the surface of the metal melt 12 by a radiation direction converter 18 installed so that the ultrasonic waves are in phase and overlapped on the surface of the metal melt 12. When the focused ultrasonic waves act on the surface of the metal melt 12, capillary waves are created on the surface of the metal melt 12, which overcomes the surface tension and causes the micro droplets 24 to fly up from the surface of the metal melt 12.

The flying micro droplets 24 are cooled and solidified by the cooling gas, and are carried to the collector 23 and collected by the flow of the cooling gas. In this way, metal fine particles can be obtained.

Next, an experimental example conducted to confirm the effects of the present invention will be described.

Using the apparatus shown in Figure 1, the argon gas atmosphere was maintained at an absolute pressure of 1 kg/cd, and the resonator was vibrated at a frequency of 20 KHz to produce vibrations of approximately 12 microns with a single amplitude. , 172d near the surface of the metal melt
Ultrasonic waves with a sound pressure level of B were obtained. A titanium alloy was used as the resonator, and an aluminum alloy was used as the molten metal.

The ultrasonic waves were applied to the surface of the aluminum alloy liquid.

The obtained aluminum alloy powder was spherical particles with a particle size of 40 to 100 microns and an average particle size of 70 microns. There was no oxidation of the particle surface and no contamination of impurity elements, and extremely pure metal powder was obtained. Note that the amount of particles produced was approximately 700 grams/hour.

Embodiment 2 FIG. 2 is an explanatory diagram showing the configuration of an embodiment of the present invention. Note that explanations of parts that overlap with those of the device of Example 1 will be omitted.

In the figure, 13 is a chamber. A cooling gas supply device 19 that communicates with the inside of the chamber 13 and supplies cooling gas is provided at a side end of the chamber 13 . This device 19 includes a pressure detector 20 and a pressure regulating valve 2 based on the pressure detector 20.
1 and a compressor 22 for flowing cooling gas into the chamber 13.

Next, the operation of the apparatus for manufacturing fine metal powder constructed as described above will be explained.

First, the metal melt 12 held in the holding container 10 is maintained at a temperature equal to or higher than the melting point of the metal material by the heater 11. The inside of the chamber 13 is maintained in an inert atmosphere using an inert gas such as Ar gas. This prevents oxidation or other chemical reactions of the metal melt 12. Further, the pressure inside the chamber 13 is maintained at a predetermined pressurized state at least at atmospheric pressure by adjusting the inert gas pressure by the pressurizing means 2.

Next, the ultrasonic wave generator 1 emits ultrasonic waves to the metal melt 12.
is focused on the surface of When the focused ultrasonic waves act on the surface of the metal melt 12, capillary waves are generated on the surface of the metal melt 12, which overcomes the surface tension and scatters minute droplets 24 from the surface of the metal melt 12. The scattered minute droplets 24 are cooled and solidified by the cooling gas, and are carried to the collector 23 and collected by the flow of the cooling gas. In this way, clean metal particles free of impurities can be obtained.

Next, an example of an experiment conducted to confirm the effects of this example will be described.

Using the apparatus shown in Figure 2, the argon gas atmosphere was maintained at an absolute pressure of 3 kg/e♂, and the frequency was set to 20 KHz.
When the resonator set to
Ultrasonic waves with a sound pressure level of 2 dB were obtained. A titanium alloy was used as the resonator, and an aluminum alloy was used as the molten metal.

Ultrasonic waves with such characteristics were applied to the surface of the aluminum alloy liquid to pulverize it.

The obtained aluminum alloy powder was spherical particles with a particle size of 40 to 100 microns and an average particle size of 70 microns.

In addition, there was no oxidation on the particle surface or any contamination of impurity elements, and the metal powder was of extremely high purity. Note that the amount of particles produced was approximately 1100 grams/hour.

Embodiment 3 FIG. 3 is an explanatory diagram showing the configuration of an apparatus for manufacturing fine metal powder according to an embodiment of the present invention. Note that explanations of parts that overlap with those of the device of Example 1 will be omitted.

In the figure, 13 is a chamber. One cooling gas supply device that communicates with the inside of the chamber 13 and supplies cooling gas is provided. This device has a pressure detector 20 , a pressure regulating valve 21 based thereon, and a compressor 22 for introducing cooling gas into the chamber 13 . Further, a recovery device 23 is connected to the chamber 13 for recovering the manufactured fine metal powder. Further, a heat exchanger 25 is connected to the recovery device 23 as a cooling gas temperature lowering means for lowering the temperature of the cooling gas after unrecovered metal fine powder to a predetermined temperature. The heat exchanger 25 is in communication with the cooling gas supply device 19 by a conduit 26 in order to add the cooled gas to the cooling gas supply means. Further, the heat exchanger 25 is provided with a refrigerant inlet 25a and a refrigerant outlet 25b, so that the refrigerant can circulate therein.

Next, the operation of the apparatus for manufacturing fine metal powder configured as described above will be explained.

Ultrasonic waves are focused on the surface of the metal melt 1 (k12) by the ultrasonic generator 1. Then, minute droplets 24 are atomized from the surface of the metal melt 12. In this way, during atomization,
During operation, ultrasonic waves with optimal energy are always applied to the surface of the metal melt 12. As a result, the metal melt 12
Capillary waves are formed on the surface of the metal melt 12, which overcomes the surface tension and causes the minute droplets 24 to fly up from the surface of the metal melt 12. The flying micro droplets 24 are cooled and solidified by the gas, and are carried to the collector 23 and collected by the flow of the cooling gas. The cooling gas after collecting the fine metal powder is sent to the heat exchanger 25. heat exchanger 25
It is cooled by the refrigerant circulating from the refrigerant inlet 25a to the refrigerant outlet 25b. The cooled cooling gas is passed through conduit 2
6, the cooling gas 0 (is sent to the supply device 19 and reused. In this way, high purity metal particles can be obtained continuously, stably and efficiently.

Next, an example of an experiment conducted to confirm the effects of this example will be described.

Using the apparatus shown in Figure 3, the argon gas atmosphere was maintained at an absolute pressure of 1 kg/cj, and the resonator was vibrated at a frequency of 20 KHz to produce vibrations with a single amplitude of approximately 12 microns. , 172d near the surface of the metal melt
Ultrasonic waves with a sound pressure level of B were obtained. A titanium alloy was used as the resonator, and an aluminum alloy was used as the molten metal. This ultrasonic wave was applied to the surface of the aluminum alloy liquid to generate micro droplets. In addition, the flow rate and supply temperature of the cooling gas used for cooling solidification and recovery of the micro droplets were 180 m3/h and 50°C.

In this way, aluminum alloy spherical particles with a particle size of 40 to 100 microns and an average particle size of 70 microns were obtained. There was no oxidation of the particle surface or contamination of impurity elements, and extremely high purity metal fine powder was obtained. Note that the amount of particles produced was 800 grams/hour.

[Effects of the Invention] As explained above, according to the method and apparatus for producing fine metal powder according to the present invention, fine metal powder of high purity can be efficiently and easily produced.

[Brief explanation of drawings]

1, 2, and 3 are explanatory diagrams showing the configuration of an apparatus for manufacturing fine metal powder according to an embodiment of the present invention, and FIG. 4(A) is
FIG. 4(B) is an explanatory diagram of a cold crucible, and FIG. 5(A) is an explanatory diagram of a holding container for a metal material. (B) is an explanatory diagram showing a conventional metal fine particle manufacturing technique in which molten metal flows down into a resonator, and FIG. 6 is an explanatory diagram showing a conventional metal fine particle manufacturing technique in which a resonator is immersed in molten metal. be. 1... Ultrasonic generator, 2... Pressurizing means, 10...
- Holding container, 11... Heater 12... Metal melt, 13... Chamber 14... High frequency power supply, 15
... Vibrator, 16... Amplitude expander, 17... Resonator, 18... Radial direction converter, 19... Cooling gas supply device, 20... Pressure detector, 21...・Pressure adjustment valve, 22... Compressor, 23... Recovery device, 24... Micro droplet, 25... Heat exchanger, 25a... Refrigerant inlet, 25b... Refrigerant outlet , 26... Conduit.

Claims (6)

[Claims] (1) A process of melting a metal material to create a metal melt, a process of focusing ultrasonic waves on the surface of the metal melt to atomize the metal melt into minute droplets, and a process of atomizing the metal melt into minute droplets. 1. A method for producing fine metal powder, comprising a step of cooling and solidifying using a cooling gas. (2) The method for producing fine metal powder according to claim 1, wherein the step of atomizing the metal melt into minute droplets by focusing ultrasonic waves on the surface of the metal melt is performed under pressure. (3) The step of collecting the cooling gas after cooling and solidifying the microdroplets, lowering the temperature of the cooling gas to a predetermined temperature, and then adding it to the cooling gas is to cool and solidify the microdroplets using the cooling gas. The method for producing fine metal powder according to claim 1, which is provided after the step. (4) a holder that holds a metal material; a heating means that is installed adjacent to the holder and heats the metal material to produce a metal melt;
an ultrasonic generating means for generating a predetermined ultrasonic wave, and an ultrasonic generating means provided between the ultrasonic generating means and the holding body to focus the ultrasonic wave on the surface of the metal melt and atomize the metal melt into minute droplets. 1. An apparatus for producing fine metal powder, comprising: a focusing means for cooling and solidifying the micro droplets; and a cooling gas supply means for supplying a cooling gas for cooling and solidifying the micro droplets. (5) The apparatus for producing fine metal powder according to claim 4, further comprising pressurizing means for maintaining the pressure of the atmospheric gas in contact with the metal melt at a predetermined pressurized state. (6) The apparatus for manufacturing fine metal powder according to claim 4, further comprising a cooling gas temperature lowering means for lowering the temperature of the cooling gas after cooling and solidifying the micro droplets to a predetermined temperature and then adding the cooling gas to the cooling gas supply means.