JPH0310004A - Method and apparatus for manufacturing metal fine powder - Google Patents

Abstract

PURPOSE:To stably manufacture metal powder by detecting surface position of molten metal and always focusing ultrasonic wave onto the surface of molten metal with this detected signal at the time of manufacturing the metal fine powder by focusing the ultrasonic wave on the surface of molten metal to atomize the molten metal and cooling. CONSTITUTION:The metal 12 in a holding vessel 10 is heated and melted with a heater 11, and an ultrasonic vibrator 17 is vibrated with a high frequency electric source 16, and a resonator 19 is vibrated through an amplitude magnifier 18 to radiate the ultrasonic wave through atmospheric gas as medium. The ultrasonic wave is reflected with directional converter 20 and focused onto the surface of molten metal 12, and the molten metal at this part is finely atomized, and cooling gas from a cooling gas generator 21 is compressed wit a compressor 24, and the atomized metal drips are cooled and collected into a recovering vessel 25 as the fine metal powder 26. During this working, variation of surface position of the molten metal 12 is detected with detecting means 13 and by inputting the detected signal into control means 14, the holding vessel 10 is vertically moved, and by always focusing the ultrasonic wave on the surface of molten metal, the metal fine powder is stably manufactured.

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. Figure 6 (A).

In both cases (B), molten metal 52 is made to flow down from above into a conical resonator 51, and the molten metal 52 atomized by the ultrasonic vibration of the resonator 51 becomes microparticles 53, and the cooling gas supply pipe It is cooled by cooling gas 55 ejected from 54 to produce fine metal powder. In FIG. 7, a resonator 61 is immersed in molten metal 62, and the ultrasonic vibrations generated from this generate minute metal particles 63 from the surface of molten metal 62, which are then deposited in a chamber 64 maintained in an inert atmosphere. The metal powder is cooled by the cooling gas introduced from the cooling gas inlet 65, 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 high-purity fine metal 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 that can stably and easily produce fine metal powder of high purity. do.

[Means for Solving the Problems] The present invention includes the steps of melting a metal material to create a metal melt, holding the metal melt, and controlling the position of a focal point on the surface of the metal melt. A step of atomizing the metal melt into micro droplets by focusing ultrasonic waves on the surface of the metal melt while controlling the position of a focusing point, and a step of cooling and solidifying the micro droplets. It is characterized by Here, the step of controlling the position of the focusing point on the surface of the metal melt includes a step of detecting the position of the surface of the metal melt and controlling the position of the focusing point based on the detection signal, and a step of controlling the position of the focusing point on the surface of the metal melt, and Preferably, the steps include a step of measuring the particle size and the amount of produced n1, and a step of controlling the position of the focal point of the ultrasonic wave based on the constant signal of the particle size and the amount of produced n1. Furthermore, the step of melting a metal material to create a metal melt and holding the metal melt is performed by setting the distance between the surface of the metal melt and the end face of the opening to a predetermined value in a deep holding container having an opening. It is preferable to carry out the step of maintaining the temperature above.

The present invention also provides a holder for holding a metal material, a heating means installed adjacent to the holder to heat the metal material to produce a metal melt, and an ultrasonic wave generator that generates an ultrasonic wave to the metal material. a focusing means for atomizing the metal melt into micro droplets by focusing on the surface of the melt; a focusing point position control means for controlling the position of a focusing point of the ultrasonic waves focused by the focusing means; It is characterized by comprising a cooling means for cooling the droplets. Here, the focusing point position control means controls the position of the metal melt surface based on a detection signal, and measures the particle size and production amount of the micro droplets, and measures the particle size and production amount. It is preferable that the control is performed based on a signal of. Furthermore, it is preferable that the holder is a dip holding container having an opening and a metal melt non-accommodating part extending from the end face of the opening to a predetermined depth.

Here, the heating means may be of any type 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 3 as shown in FIG. 4(A).
0, a holding container 31 as shown in FIG.

The ultrasonic wave generator generates microscopic particles M and W of the metal melt by focusing.
Any device that can generate ultrasonic waves with enough energy to atomize can be used. An example of such a device is an ultrasonic generator that uses a normal high-frequency power source.

The ultrasonic focusing means is one that concentrates the ultrasonic waves on the surface of the metal melt and increases its energy.

In this case, it is preferable to focus the ultrasonic waves on one point or a negative line. Furthermore, during operation when pulverizing metal, -
A combination of point focusing type and line focusing type focusing means may be used.

The focusing point control means controls the focusing point of the ultrasonic waves to always be at a predetermined position even if the metal melt is atomized into minute droplets and the position of the metal melt surface changes. Good to have. For example, in response to the signal of the position of the metal melt surface,
Examples include those that move the holding body or focusing means up and down. Further, as the position of the metal melt surface changes, the distance from the focusing means to the focusing point may be changed by the focusing means, and as the amount of metal melt decreases, the metal material is replenished and the metal surface The position of may be kept constant. Note that when using a holding container, the surface of the metal melt is detected using a level meter, etc. When using a holding container such as a metal plate, rod, wire, etc., the position of the surface of the metal melt is detected using image processing, etc. Then, the information is fed back to the control means for control.

In addition, the focusing point control means controls the position of the ultrasonic focusing point to a predetermined position so that the atomized microdroplets always have the desired particle size and production amount, and is necessary for atomization. It may also be possible to set the energy to the optimum value. For example, there is a method that adjusts the frequency of ultrasonic waves according to the particle size/production amount signal.

As the particle size/production amount measuring means, a particle size distribution measuring device called a particle sizer, a production amount measuring device using optical means, etc. can be used.

The deep holding container used includes, for example, a metal melt non-accommodating portion 42 extending from the end surface 41 of the opening 40 to a predetermined depth (L), as shown in FIG. This end face 41
The depth (L) is set to an arbitrary distance depending on the two particle sizes to be collected. That is, by providing the metal melt non-accommodating portion 42 extending to a predetermined depth (L) from the end surface 41 of the opening 40, it is possible to easily collect only small metal fine powder of a given particle size or less at any time. It is something. This is because when the particle size of fine metal powder becomes large, it cannot float above a certain height due to its own weight. Therefore, the specific value of the depth (L) of the metal melt non-accommodating portion 42 is preferably set appropriately depending on the particle size of the fine metal powder to be obtained.

[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 detecting the changing position of the metal melt surface and controlling the position of the ultrasonic focusing point accordingly, it is possible to always focus the emitted ultrasonic waves on a predetermined surface of the metal melt. .

In addition, by measuring the particle size and production amount of atomized microdroplets and controlling the frequency and focus point position of the ultrasonic waves according to the particle size and production amount signals, the radiated ultrasonic waves are constantly atomized. The optimum energy can be focused on a predetermined surface of the metal melt.

Furthermore, by positioning the surface of the metal melt just below the metal melt non-containing part that extends from the end face of the opening at a predetermined depth and performing ultrasonic atomization, we can always produce small particles with a desired particle size or less. Only fine metal powder can be easily recovered.

Therefore, fine metal powder can be produced continuously and stably.

[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 15 maintained in an inert gas atmosphere. A detection means 13 for detecting the position of the surface of the metal melt 12 is installed above the surface of the metal melt 12 in the holding container 10 . This detection means 13 is connected to a control means 14 provided outside the chamber 15 and connected to the holding container. An ultrasonic generator 1 is provided above the chamber 15.

The ultrasonic generator 1 includes a high-frequency power source 16 and a high-frequency vibrator 17 provided outside a chamber 15, a resonator 19 provided inside the chamber 15, and an ultrasonic generator provided surrounding the resonator 19. It is composed of a radial direction converter 20 for focusing sound waves, and an amplitude expander 18 inserted between the chamber 15 and the radial direction converter 20 and connected between the vibrator 17 and the resonator 19.

Here, the material of the resonator 19 is preferably a titanium alloy or an aluminum alloy. Furthermore, since the radiation direction converter 20 has opposite phases on the vibrator side and anti-vibrator side of the resonator 19, it is possible to superimpose the radiated sound waves with the opposite phases in the same phase on the surface of the metal melt. is set up.

Further, the radiation direction converter 20 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 21 that communicates with the inside of the chamber 15 and supplies cooling gas is provided. This device 21 has a pressure detector 22 , a pressure regulating valve 23 based thereon, and a compressor 24 that causes cooling gas to flow into the chamber 15 . Further, a recovery device 25 is connected to the chamber 15 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 17 is vibrated by the high frequency power source 16, and the resonator 19 connected to the transducer 17 is vibrated. By appropriately selecting the frequency of this ultrasonic wave, the particle size of the fine metal powder can be changed. Resonator 19
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 20 installed so that the ultrasonic waves are in phase and overlapped on the surface of the metal melt 12. The surface of which metal melt 12 is detected by the detection means 13, and information on the position of the surface is fed back to the control means 14. The control means 14 moves the holding container 10 up and down based on this information. In this way, during operation, the position of the focal point of the ultrasonic waves can always be set at a predetermined metal melt surface. 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 minute droplets 26 to form from the surface of the metal melt 12.
make it fly. The flying micro droplets 26 are cooled and solidified by the cooling gas, and are carried to the collector 25 and collected by the flow of the cooling gas. In this way, metal fine particles can be obtained.

Next, an example of an experiment conducted to confirm the effect of Yoshiaki Moto will be explained.

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 focal position of the ultrasound waves was varied by moving the position of the holding container in response to the changing position of the aluminum alloy liquid surface. The moving speed of the holding container is
It was 1 cm/h.

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 or contamination of impurity elements, and extremely high purity metal fine 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 apparatus for manufacturing fine metal powder according to an embodiment of the present invention. Note that explanations of parts that overlap with those of Example 1 will be omitted.

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 15 maintained in an inert gas atmosphere. Above the surface of the metal melt 12 in the holding container 10, a particle size/production amount measuring means 27 is installed to measure the particle size and production amount of minute droplets generated by atomization. The particle size/production amount measuring means 27 includes a particle size Minl meter 27a consisting of a particle sizer, and a generation JI Hil consisting of a light receiving element and a light emitting element.
It is composed of an FI regulator 27b. Further, the particle size/production ff1lpI determining means 27 is electrically connected to the control means 14 provided outside the chamber 15 in connection with the holding container.

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

First, the ultrasonic transducer 17 is vibrated by the high frequency power source 16, and the resonator 19 connected to the transducer 17 is vibrated. Ultrasonic waves are emitted by the vibration of the resonator 19 using the atmospheric gas as a medium. This radiated ultrasonic wave is transmitted to the metal melt 12
The ultrasonic waves are focused on the surface of the metal melt 12 by the radiation direction converter 20 installed so that they are in phase and overlapped on the surface of the metal melt 12 . Then, minute droplets 26 are atomized from the surface of the metal melt 12. The particle size and production amount of the micro droplets 26 are measured by the particle size distribution measuring device 27a and the production amount measuring device 27b of the particle size/production amount measuring means 27. The particle size/production amount measuring means 27 supplies this particle size/production amount M11 signal to the control means 14. The control means 14 moves the holding container 10 up and down to a predetermined position based on the particle size/production amount measurement signal.

That is, the position of the holding container 10 is set so that the radiated ultrasonic waves always have the optimum energy for atomization and are focused on a predetermined surface of the metal melt 12. In this way, during operation, the focused ultrasonic wave is always set at the optimal position to act on the surface of the metal melt 12. by this,
Capillary waves are formed on the surface of the metal melt 12, which overcome the surface tension and cause micro droplets 26 of desired particle size and production amount to fly up from the surface of the metal melt 12. The flying micro droplets 26 are cooled and solidified by the cooling gas, and are carried to the collector 25 and collected by the flow of the cooling gas. In this way, metal fine particles having a desired particle size and production amount can be obtained continuously and stably.

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

Using the apparatus shown in Figure 2, 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.

This ultrasonic wave was applied to the surface of the aluminum alloy liquid to generate micro droplets. When the particle size and production amount of these microdroplets were measured, the average particle size was 70 μm, and the production amount was 800 grams/hour. In order to keep the particle size and production amount constant, the position of the holding container was moved to adjust the focusing position of the ultrasonic waves. Note that the moving speed of the holding container is 1. It was 2cm/h.

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

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

In the figure, 28 is a deep holding container for holding molten metal. The deep holding container 28 has a metal melt non-accommodating portion 28c extending from the end surface 28b of the opening 28a to a depth (L) of about 10 cm. Deep holding container 2
8, there is a heater 11 for melting the metal material.
is installed, and the metal melt 12 is held in the deep holding container 28. The deep holding container 28 and the heater 11 are provided below the chamber 15 maintained in an inert gas atmosphere.

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

First, the ultrasonic transducer 17 is vibrated by the high frequency power source 16, and the resonator 19 connected to the transducer 17 is vibrated. Ultrasonic waves are emitted by the vibration of the resonator 19 using the atmospheric gas as a medium. This radiated ultrasonic wave is transmitted to the metal melt 12
The ultrasonic waves are focused on the surface of the metal melt 12 by the radiation direction converter 20 installed so that they 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 minute droplets 26 to fly up from the surface of the metal support 12. At this time, since the deep holding container 28 is provided with a metal melt non-accommodating part 28c extending from the end surface 28b of the opening 28a to a depth (L) of approximately 10 cm, the metal melt may be scattered upward by more than 10 cm. Only small minute droplets 26 smaller than the particle size fly toward the collector 25 side.

The flying micro droplets 26 are cooled and solidified by the cooling gas, and are carried to the collector 25 by the flow of the cooling gas and collected daily. In this way, only fine metal particles having a desired small particle size can be easily obtained.

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

Using the apparatus shown in Figure 3, the argon gas atmosphere was maintained at an absolute pressure of 1 kg/c, and the frequency was set to 20 KHz.
When a 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.

The ultrasonic waves were applied to the surface of the aluminum alloy liquid. Note that the deep holding container is approximately 1 inch from the end surface of the opening.
The one having a metal melt non-accommodating part extending to a depth (L) of 0c+g was used.

The obtained aluminum alloy powder was spherical particles with a particle size of 70 microns or less and an average particle size of 60 microns. There was no oxidation of the particle surface or contamination of impurity elements, and extremely high purity metal fine powder was obtained. The amount of particles recovered was approximately 250 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 stably and easily produced. .

[Brief explanation of drawings]

1 to 3 are explanatory diagrams showing the configuration of a manufacturing apparatus for fine metal powder according to an embodiment of the present invention, FIG. 4(A) is an explanatory diagram of a cold crucible, and FIG. 4(B) is an explanatory diagram of a holding container for metal materials, FIG. 5 is an explanatory diagram of a deep holding container, and FIGS. 6 (A) and (B) are conventional metal particle manufacturing techniques in which molten metal flows down into a resonator. FIG. 7 is an explanatory diagram showing a conventional metal particle manufacturing technique in which a resonator is immersed in molten metal. 10... Holding container, 11... Heater 12...
Metal melt, 13... detection means, 14... control means,
15...Chamber 16...High frequency power supply, 17.
... Vibrator, 18... Amplitude expander, 19... Resonator, 20... Radial direction converter, 21... Cooling gas supply device, 22... Pressure detector, 23... pressure regulating valve,
24... Compressor, 25... Collector, 26... Micro droplet, 27... Particle size/production amount 1111 constant means, 27a
...Particle size distribution measuring device, 27b...Production amount Ap1 constant device, 28...Deep holding container, 288°40...Opening part of deep holding container, 28b, 41...End face of deep holding container , 28c, 42...Metal melt non-accommodating part.

Claims (8)

[Claims] (1) A step of melting a metal material to create a metal melt and holding the metal melt, a step of controlling the position of a focusing point on the surface of the metal melt, and a step of controlling the position of the focusing point. A method of producing fine metal powder, comprising the steps of: focusing ultrasonic waves on the surface of the metal melt to atomize the metal melt into minute droplets; and cooling and solidifying the minute droplets. Production method. (2) The step of controlling the position of the focusing point on the surface of the metal melt is a step of detecting the position of the surface of the metal melt and controlling the position of the focusing point based on the detection signal. A method for producing fine metal powder. (3) The step of controlling the position of the focusing point on the surface of the metal melt includes the step of measuring the particle size and amount of microdroplets produced, and focusing the ultrasonic waves based on the particle size and amount measurement signal. 2. The method for producing fine metal powder according to claim 1, wherein the step is controlling the position of the points. (4) The step of melting a metal material to create a metal melt and holding the metal melt is performed by setting a predetermined distance between the surface of the metal melt and the end face of the opening in a deep holding container having an opening. The method for producing fine metal powder according to any one of claims 1 to 3, wherein the step is to maintain the metal powder at or above a certain value. (5) 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;
A focusing means for atomizing the metal melt into minute droplets by focusing the ultrasonic waves generated from the ultrasonic generating means on the surface of the metal melt, and a position of a focal point of the ultrasonic waves focused by the focusing means. 1. An apparatus for producing fine metal powder, comprising: a focusing point position control means for controlling the micro droplets; and a cooling means for cooling the micro droplets. (6) Claim 5, wherein the focusing point position control means performs control based on a detection signal obtained by detecting the position of the surface of the metal melt.
The apparatus for producing the metal fine powder described above. (7) The production of metal fine powder according to claim 5, wherein the focusing point position control means measures the particle size and production amount of the micro droplets, and performs control based on the signal of the measurement of the particle size and production amount. Device. (8) Any one of claims 5 to 7, wherein the holding body is a deep holding container having an opening and a metal melt non-accommodating portion extending to a predetermined depth from the end face of the opening. The apparatus for producing fine metal powder according to item 1.