JP2808835B2 - Powder manufacturing apparatus and powder manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a powder production apparatus and a powder production method for producing powders of various metallic and non-metallic materials, and in particular, to reducing the particle size of powder. Related to improvements.

"Prior art" As a method for producing this kind of powder, a centrifugal spray method is well known. The centrifugal spraying method is a general term for a method in which a melt of a material to be powderized is scattered by centrifugal force and powdered, and is roughly classified into the following methods.

i. A rotating disk method in which a melt is dripped onto a high-speed rotating dish and scattered from an outer peripheral edge of the dish into an inert gas.

ii. While fixing the material to the rotating shaft, disposing an electrode facing this material, discharging between the material and the electrode, heating the material, and transferring the melt into the inert gas from the outer periphery of the tip of the material. Rotating electrode method to scatter. As a heating method, plasma or the like may be used in some cases.

iii. A rotating crucible method in which a crucible to be cooled with water is provided at the tip of a rotating shaft, and the crucible receives a melt generated from a consumable electrode (material) and scatters the melt into an inert gas from the outer periphery of the crucible.

Also, for low melting point metals such as Sn, a molten metal is dropped on a horn that is ultrasonically vibrated by a piezo element or the like,
An ultrasonic spraying method has also been developed in which droplets are generated from the crest of a standing wave to make powder.

"Problems to be Solved by the Invention" By the above-mentioned rotary spraying method, it is necessary to increase the number of rotations of the material in order to make the obtained powder finer. There is a danger that the rotational balance is likely to deteriorate due to wear and thermal deformation of the device, causing severe vibration. Therefore, there is an upper limit on the number of revolutions, and there is a problem that the minimum particle size of the powder that can be produced is limited by the upper limit.

In addition, increasing the number of rotations of the material increases the initial velocity of the droplets accordingly, increasing the size of the collection container required to sufficiently cool the droplets during flight, and increasing the size of the device. There was also.

On the other hand, in the ultrasonic spraying method, since the output of the oscillator is generally small, the amount of melt that can be processed per unit time is small and the productivity is low, and the temperature of the horn must be raised to the melting point of the material or higher. It could only be used for powder production of low melting point materials such as Sn.

"Means for solving the problem" The present invention has been made to solve the above problems,
First, a powder manufacturing apparatus of the present invention comprises a rotating shaft supported rotatably and axially displaceable by a bearing mechanism, a rotation drive mechanism for rotating the rotating shaft axially displaceable, and A vibration mechanism for vibrating, a material to be powdered coaxially supported at one end of the rotating shaft, a heating means for heating the tip of the material to a temperature higher than its melting point, and collecting powder scattered from the tip of the material; And a collection container.

Further, in the powder production method of the present invention, the material to be powdered is coaxially supported at one end of a rotating shaft, the rotating shaft is rotated and vibrated in the axial direction, and the tip of the material is heated using heating means. The method is characterized in that the material is heated to a temperature equal to or higher than the melting point, and the molten material is scattered from the front end of the material by centrifugal force and vibration force to be powdered.

[Operation] In the powder manufacturing apparatus and the powder manufacturing method, the material to be powderized is rotated and vibrated in the axial direction, and the tip is melted, so that the generated melt flows to the outer peripheral edge of the material due to centrifugal force. Furthermore, the melt undulates due to the vibration at the outer peripheral edge, and a splash is generated from the wave front and scatters radially by centrifugal force. At this time, the waveform formed on the outer peripheral edge is a composite waveform of the waveform due to the centrifugal force and the waveform due to the exciting force, and the acting force is a combined vector. As described above, since fine droplets are generated from the melt by the excitation force and the centrifugal force acting in directions orthogonal to each other, the particle diameter is much larger at the same rotation speed than in the conventional method in which the droplets are shaken only by the centrifugal force. Small powders can be produced.

In addition, even in the case of producing powder having a small particle size, the rotation speed can be relatively low. Therefore, deterioration of the rotation balance due to consumption of materials and thermal deformation does not easily occur, and the risk of generation of vibration can be reduced.

When powder is produced only by vibrating force, the initial velocity of the scattered powder is on the order of several tens to several hundred cm / s, and the flight time required for cooling is small due to the long flight time during scattering. It can be reduced but the cooling rate is reduced. On the other hand, in the apparatus and method of the present invention, the powder generated by the centrifugal force and the excitation force has a large initial velocity of several tens to several hundreds m / s determined by the centrifugal force. When the fine powder scatters at a high speed, the initial cooling rate (solidification rate) increases and the drag coefficient increases. Therefore, the deceleration is large, the space required for cooling can be reduced, and the apparatus can be downsized.

As a result, the resulting powder becomes to have a fine infrastructure undergoing quenching 10 ⁵ ~10 ⁶ ℃ / s, also increases the solid solubility of the solute atoms.

Embodiments FIGS. 1 and 2 are a vertical sectional view and a sectional view taken along line II-II, respectively, showing an embodiment of a powder producing apparatus according to the present invention.

In the figure, reference numeral 1 denotes a vertically arranged rotating shaft. The rotating shaft is provided with a rotation drive mechanism 2 at the center, and a magnetic levitation bearing mechanism 3 is provided above and below the rotation drive mechanism 2, and a bearing is further provided above it. A vibration mechanism 4 is provided.

The rotation drive mechanism 2 is the same as a normal motor, and includes a rotor 5 fixed to the rotating shaft 1 and a plurality of electromagnets 6 spaced from the outer peripheral surface of the rotor 5. Each is connected to a drive circuit (not shown).

On the other hand, the magnetic levitation type bearing mechanism 3 includes a ferromagnetic rotor 7 fixed coaxially to the rotating shaft 1 and a circumferential direction 90 at equal intervals toward the outer peripheral surface of the rotor 7 as shown in FIG. And four electromagnets 8 arranged at every ° C.
The separated electromagnets 8 form a pair, and each pair is connected to an independent radial direction control circuit 9.

At both ends of the rotating shaft 1, four radial sensors 10 are arranged at equal intervals toward the outer peripheral surface of the rotating shaft 1, at locations corresponding to the respective electromagnets 8 in the axial direction. Of these, a pair of sensors 10 separated by 180 ° is a radial control circuit 9 to which a corresponding electromagnet 8 is connected.
It is connected to the. Each radial control circuit 9 increases or decreases the amount of electricity to the corresponding pair of electromagnets 8 in accordance with the radial deviation of the rotating shaft 1 detected by the pair of radial sensors 10, and rotates by the electromagnetic force. The shaft 1 is sucked, and the position of the axis of the rotating shaft 1 is always kept constant.

The vibrating mechanism 4 includes a disk-shaped drive plate 11 fixed to the rotating shaft 1 and a pair of electromagnets 12A and 12B arranged on both surfaces of the drive plate 11 to face each other. 12B is connected to the axial drive circuit 13.

A disk-shaped reference plate 14 is fixed to the rotating shaft 1 in the vicinity of the drive plate 11, and an axial sensor 15 is provided facing the lower surface of the reference plate 14. It is connected to the.

The axial drive circuit 13 averages the output signal of the axial sensor 15 over a unit time longer than the excitation cycle to be described later (or simply lowers the temporal resolution), and this average value is set in advance. If it is larger than the reference value, the lower electromagnet 12B
In this case, the center of the amplitude of the drive plate 11 is kept at a fixed position by increasing the amount of power to the upper electromagnet 12A.

The axial drive circuit 13 is also connected to a high-frequency generator 16 that can change the transmission frequency steplessly, and the high-frequency current from the high-frequency generator 16 causes the above-described electromagnets 12A,
The currents to 12B are modulated in opposite phases, and the driving plate 11 vibrates up and down in synchronization with the high-frequency current. The amplitude can be adjusted by increasing or decreasing the output current of the high-frequency generator 16.

Further, if the frequency exceeds the natural frequency of the longitudinal vibration of the rotating shaft, it becomes impossible to vibrate. Therefore, the shape of the fixing jig 17 of the material 18 resonates at a harmonic such as a triple frequency. By designing this part, it is possible to amplify the amplitude 3 to 10 times and reduce the power consumption of the vibration mechanism 4.

On the other hand, at the upper end of the rotating shaft 1 is provided an openable and closable collection container 19 for covering the same.
A cylindrical material 18 to be powdered is fixed coaxially via 17. In the collection container 19, an electrode 20 is arranged coaxially opposite the material, and can be displaced in the axial direction by a feed mechanism (not shown).

The collection container 19 is provided with an inlet and an outlet for an inert gas (both not shown), and a nitrogen gas, an Ar gas, or the like is introduced into the collection container 19 from an inert gas supply device (not shown).

Next, a method for producing a powder using the apparatus having the above configuration will be described.

First, the feed mechanism of the electrode 20 is operated to set the distance between the electrode 20 and the material 18, and then an inert gas is introduced into the collection container 19.

Next, the rotation drive mechanism 2 is operated to rotate the rotation shaft 1, and when the rotation speed reaches a predetermined rotation speed, a current is supplied between the material 18 and the electrode 20 to start discharging, thereby melting the front end surface of the material 18.

Then, the generated melt moves to the outer peripheral edge of the material 18 that rotates at a high speed, and at the same time, vibrates at the outer peripheral edge due to vibration, and fine droplets are generated from the crest. The droplets scatter radially due to centrifugal force, are cooled by contact with the inert gas, become spherical solid particles, collide with the inner surface of the collection container 19, fall, and accumulate in the collection container 19.

Preferred powdering conditions are the type of material 18, material 19
Depends on the outside diameter of the powder, the desired particle size of the powder, etc.
In the case of a Ti alloy, powder having an average particle size of 100 μm or less can be produced in the following range.

Rotation speed: 6000-15000rpm Frequency: 1000-20000Hz Amplitude: 5-50μm Fine particle size up to 100-40μm by selecting the particle size and cooling condition by adjusting the combination of the relationship between rotation speed, frequency and amplitude Quenched powder can be produced.

Although the magnetic levitation bearing 3 is used in the above embodiment, other bearing mechanisms can be used as long as the rotating shaft can be axially displaceable. For example, an air bearing, an oil bearing, a hydraulic bearing, and the like can be used. Can be changed.

Further, the heating means is not limited to discharge heating, and a plasma heating method such as Ar or a method using an electron gun is also possible.

Further, the rotation axis may be arranged horizontally as shown in FIG. 3, or the heating means may be arranged vertically toward the tip of the material 18 as shown in FIG. Can be used not only for metals but also for intermetallic compounds such as TiAl.

“Experimental example” In a method of producing a Ti alloy powder by a general rotating electrode method, a buret having a diameter of 120 mm was rotated at 12000 rpm and an average of 86
A μm powder was obtained.

On the other hand, the apparatus having the configuration shown in FIG. 1 was actually assembled, and a burette of the same diameter and the same material as above was vibrated at a frequency of 20 kHz and an amplitude of 10 μm while rotating at the same speed. A powder was obtained at the production rate, and the particle size of the powder was measured to be 45 μm on average.

When the frequency was changed to 10 kHz under the above conditions, the average particle size of the obtained powder was 64 μm.

In addition, by applying 20kHz vibration,
At 0 rpm, a powder having an average of 94 μm, which is almost the same as the conventional powder, was produced. As a result of the reduction in the number of revolutions, a long billet can be used, and the productivity was improved.

[Effects of the Invention] As described above, in the powder manufacturing apparatus and the powder manufacturing method of the present invention, the material to be powdered is vibrated in the axial direction while rotating, and the tip is melted. After flowing to the outer peripheral edge of the material due to the force, the melt undulates at the outer peripheral edge, and splashes are generated from the wave front and scatter radially by centrifugal force.

As described above, the micro-droplets are generated from the melt by the excitation force and the centrifugal force acting in the directions orthogonal to each other. Small powders can be produced.

In addition, even in the case of producing powder having a small particle size, the rotation speed can be relatively low. Therefore, deterioration of the rotation balance due to consumption of materials and thermal deformation does not easily occur, and the risk of generation of vibration can be reduced.

Further, since the initial speed of the droplets can be reduced by the lower rotation speed, the space required for cooling the droplets can be reduced and the size of the device can be reduced.

[Brief description of the drawings]

1 and 2 are a vertical sectional view and a sectional view taken along line II-II of an embodiment of the powder producing apparatus according to the present invention. FIG. 3 is a front view showing a method of heating a material according to another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Rotating shaft, 2 ... Rotation drive mechanism, 3 ... Magnetic levitation type bearing, 4 ... Vibration mechanism, 9 ... Radial direction control circuit, 10 ...
Radial direction sensor, 11 Drive plate, 12A, 12B Electromagnet, 13 Axial drive circuit, 14 Reference plate, 15
... Axial direction sensor, 16 ... High frequency generator, 17 ... Fixing jig, 18 ... Material to be powdered, 19 ... Collection container, 20 ...
Discharge electrode.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B01J 2 / 00,2 / 18 B22F 9 / 04,9 / 14,9 / 10 B29B 9/10

Claims (2)

(57) [Claims] 1. A rotating shaft rotatably and axially displaceably supported by a bearing mechanism, a rotation driving mechanism for rotating the rotating shaft so as to be axially displaceable, and a vibrator for vibrating the rotating shaft in an axial direction. A mechanism, a material to be powdered coaxially supported at one end of the rotating shaft, a heating means for heating the tip of the material to a temperature higher than its melting point, and a collection container for collecting powder scattered from the tip of the material. A powder production apparatus comprising: 2. A material to be powdered is coaxially supported at one end of a rotating shaft, and the rotating shaft is rotated and vibrated in the axial direction, and the tip of the material is heated to a temperature equal to or higher than its melting point by using a heating means. A powder manufacturing method, wherein a melted material is scattered from the front end of the material by centrifugal force and vibration force and powdered.