JPH1017909A - Production of metal powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size distribution of the obtained metal powder and to improve its yield by radialy forming plural projections on the surface of a rotary body on which molten metal is dropped and stopping the molten metal accumulated on a disk by the projected parts. SOLUTION: Molten metal continuously drops on the opening parts 7 of a rotary body 3 rotating at a high speed and is sprayed on the inside of a chamber by centrifugal force. The scattered misty molten metal is cooled and solidified in an atmosphere of an inert gas or the like and is formed into irregular shaped metal powder. At this time, the plural projecting parts 5 radialy extending to the outer circumferential side edge faces from the cinter side of the rotary body 3 are formed at equal intervals. In this way, the molten metal accumulated on the face of the rotary body 3 is stopped, and the further delay to the back side (the direction reverse to the rotating direction) is prevented. By this clogging and checking effect, the delay of the moving rate in the molten body is relaxed, and the difference in the moving rates between the upper and lower artscan be reduced. Thus, the releasing rate of the molten metal can be uniformized, and the size number in the metal powder cam be suppressed to a nallow low range 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a metal powder capable of producing a metal powder having a narrow particle size distribution.

[0002]

2. Description of the Related Art Conventionally, as an apparatus for producing this kind of metal powder, a molten metal is continuously dropped on a conical or V-shaped disk which rotates at a high speed (for example, 2000 to 40000 rpm) in a chamber. A method of scattering and solidifying molten metal accumulated on a disk by a centrifugal force during rotation is well known (Japanese Utility Model Application Laid-Open No. 58-32929).

[0003]

However, as shown in FIG. 6, if the surface of the rotating body 3 on which the molten metal is dropped is flat, the height of the molten metal accumulated in a layer by high-speed rotation is increased. Slip occurs in the (thickness) direction, and a difference occurs in the rotation speed (moving speed) between the rotating body 3 and the molten metal.

Further, as shown in FIG. 7, the moving speed of the molten metal becomes slower toward the upper part of the molten layer, so that there is a difference in the discharge speed from the rotating body 3 and the size of the scattered fluid is increased. And the particle size of the obtained metal powder is distributed over a wide range.

In order to obtain a metal powder having a desired particle size,
The metal powder produced in the subsequent process must be once sorted through a mesh or the like, but if the particle size distribution is wide as described above, the yield of the metal powder deteriorates.

An object of the present invention is to provide a metal powder manufacturing apparatus which solves the above-mentioned drawbacks and improves (reduces) the particle size distribution of the metal powder to improve the yield.

[0007]

According to the first aspect of the present invention, a metal powder is produced by dropping a molten metal (4) onto a rotating body (3) rotating at a high speed to produce a metal powder (8). In the manufacturing apparatus of (1), the rotating body (3) has a cylindrical, conical or V-shaped disk shape, and the rotating body (3)
A plurality of projections (5) extending radially from the central part of the disk to the outer peripheral end face are cut off from the central part of the surface on the side where the molten metal (4) is dropped to form an open part (7). It is characterized by having been formed.

According to the second aspect of the present invention, a curved surface (R) is formed on the end surface of the projection (5) on the outer peripheral side of the disk in the height direction.
Is provided.

Further, according to the present invention, the metal powder (8) is an irregular-shaped zinc powder used as an active material for a negative electrode of an alkaline battery.

[0010]

FIG. 1 is a diagram showing a schematic configuration of an apparatus for producing metal powder according to the present invention.

In FIG. 1, reference numeral 1 denotes a closed chamber to which an inert gas is introduced as the case may be. A crucible 2 for melting metal is provided at the top of the chamber 1,
A nozzle 9 for dropping the molten metal 4 is provided at the bottom of the crucible 2. The rotating body 3 is disposed substantially directly below the nozzle 9. Reference numeral 8 denotes metal powder accumulated at the bottom of the chamber 1, and reference numeral 10 denotes an outlet for taking out the metal powder 8.

FIG. 2 is an external perspective view of the rotating body 3.
The rotating body 3 is a disk having an outer diameter of about 40 mm and a V-shaped cross section, and its inclination angle is, for example, about 13 ° to 2 ° with respect to the center line.
The angle is set in the range of 0 °, and a refractory material such as graphite is used for the material in view of the relationship with the physical properties of the molten metal 8 to be dropped.

Also, the rotating body 3 is provided on the rotating body 3 shaft 6.
A rotating device (not shown) for rotating at high speed is mounted.

Although the rotating body 3 having such a shape is known, in the present embodiment, the height of the rotating body 3 extending from the center side to the outer peripheral side end surface on the surface of the rotating body 3 on which the molten metal 4 is dropped is 0.7 to 0.7 mm.
It is characterized in that four elongated prism-shaped projections 5 of about 2 mm are formed radially and at equal intervals.

The central portion of each of the radial projections 5 is cut off to form a circular opening 7 into which the molten metal 4 is dropped from the nozzle 9, and as shown in FIG. A curved surface R is provided on an end surface on the outer peripheral side of the protrusion 5 in the height direction.

FIG. 3 is a view showing how molten metal 4 dropped from the nozzle 9 scatters from the rotating body 3.

A metal (for example, zinc or a zinc alloy) is melted in the crucible 2, and the molten metal 4 in the crucible 2 is opened from a nozzle 9 provided at the bottom of the crucible 2 by an opening of the rotating body 3 located almost directly below the nozzle 9. Drops are continuously dropped on the seven portions at a predetermined flow rate determined by the hole diameter of the nozzle 9. At this time, the rotating body 3 is rotating at a high speed by the rotating device connected to the shaft portion 6, and the molten metal 4 dropped from the central portion of the V-shaped disk which rotates at a high speed due to its viscosity is located on the outer peripheral side. And is sprayed into the chamber 1 sequentially from the end face by centrifugal force at the time of rotation.

The mist-like molten metal 4 scattered in the chamber 1 is cooled and solidified in an atmosphere of an inert gas or the like to form an irregularly shaped metal powder 8 and accumulates at the bottom of the chamber 1. In this case, the size of the chamber 1 is set so that the scattered molten metal particles 4 do not collide with the inner wall of the chamber 1 before cooling and solidifying.

The molten metal 4 on the rotating body 3 that rotates at high speed rotates (moves) together with the rotating body 3 due to the frictional force due to its viscosity. A difference in rotational speed (moving speed) occurs in the height direction of the molten metal 4 (melt), and the difference in speed increases as the layer becomes higher.

Therefore, in the present invention, as shown in FIG. 2, four protrusions 5 extending radially from the center side of the rotating body 3 to the outer peripheral end face are formed at equal intervals. With such a configuration, the molten metal 4 accumulated on the surface of the rotating body 3 is blocked by the protrusions 5, and there is no further delay behind (in the direction opposite to the rotation direction). Due to such a blocking effect, the delay of the moving speed in the melt is reduced, and as shown in FIG. 4, the difference in the moving speed between the upper and lower portions of the melt can be reduced as compared with the conventional example (see FIG. 7). . For this reason, the particle size distribution of the metal powder 8 produced by making the discharge speed of the molten metal 4 uniform can be suppressed to a narrow range.

Also, as shown in the partially enlarged view of FIG.
By subjecting the outer peripheral end face of the projection 5 to R processing in the height direction, the molten metal 4 is evenly distributed along the edge of the curved surface R, and the scattering direction of the molten material is the radius of the rotating body 3. As a result, the particle size distribution of the produced metal powder 8 is further improved.

In other words, if the outer peripheral end surface of the protrusion 5 is not R-processed in the height direction and has a right-angled shape, a large amount of molten metal 4 is concentrated at this corner, and the molten metal 4 is randomly distributed vertically therefrom. Since the molten particles are scattered, the molten particles collide with the inner wall of the chamber 1 before solidifying to form a powder having a large particle diameter. For this reason, the particle size distribution of the metal powder 8 deteriorates.

As described above, in the embodiment, the rotating body 3 has a V-shaped cross section, but the rotating body 3 may have a cylindrical or conical shape. The shape is not limited to the above embodiment as long as the protrusions 5 provided on the rotating body 3 are arranged radially, and the number of rotations of the rotating body 3 is not limited as long as the number is two or more. It may be set as appropriate according to the type of metal to be melted.

[0024]

EXAMPLES Next, zinc powder was produced using the apparatus for producing metal powder of the present invention and a conventional apparatus for producing metal powder, and the state of particle size distribution was examined.

The rotating body 3 used has a disk diameter of 40 m.
m, the shape was a V-shaped cross section at an angle of 13 °, and in the case of the device of the present invention, four protrusions 5 having a height of 2 mm were formed on the device.

The centrifugal atomization conditions for both the conventional example and the present invention were such that the zinc melting temperature was about 500 ° C., the number of revolutions of the rotating body 3 was 10,000 rpm, and the diameter of the nozzle 9 was 1.5 mm. The atomizing atmosphere was about 21% oxygen (atmosphere).

The zinc powder 8 produced under the above conditions was sifted through a mesh, and the weight ratio (%) of each particle size group to the total weight was measured. The distribution is shown in FIG.

According to FIG. 5, in the conventional product shown by the broken line, the particle size distribution is widely distributed on the large particle side (particle size of 125 μm or more).
It is difficult to efficiently obtain zinc powder having a desired particle size.
On the other hand, in the product of the present invention indicated by the solid line, the particle size distribution having a sharp peak in the desired particle size range of 125 to 250 μm due to a decrease in the large particle side is obtained.

As described above, in the apparatus for producing metal powder of the present invention, the protrusions 5 are arranged radially on the surface of the rotating body 3 to block the dropped molten metal 4 and to prevent the molten metal 4 accumulated in a layer form. By reducing the difference in the moving speed of the metal 4 in the height direction, the diameter of the melt particles at the time of scattering is kept constant, and the outer peripheral end face of the protrusion 5 is subjected to R processing in the height direction,
It is possible to stabilize the scattering direction of the melt particles.
Since the particle size distribution of the obtained metal powder 8 is greatly improved, it is possible to produce a metal powder with a high yield.

[0030]

As described above, according to the first aspect of the present invention, since a plurality of projections are radially formed on the surface of the rotating body on which the molten metal is dropped, a circular shape is obtained. The molten metal accumulated on the plate is blocked by these projections, and reduces the difference in moving speed between the upper and lower layers of the molten material. For this reason, the discharge speed from the rotating body is made uniform, and the particle size distribution of the produced metal powder can be narrowed.

According to the second aspect of the present invention, since the projection has a curved surface in the height direction on the outer peripheral end surface,
The scattering direction of the melt particles is concentrated in the radial direction of the rotating body, and the particle size distribution of the produced metal powder is further improved.

Further, according to the third aspect of the present invention,
If the apparatus for producing a metal powder of the present invention is used for producing the amorphous zinc powder used for the negative electrode active material of the alkaline battery, the particle size distribution is good, so that the yield is good and the productivity is greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an apparatus for producing metal powder according to the present invention.

FIG. 2 is a view showing a rotating body of the same metal powder manufacturing apparatus;
(a) is an external perspective view, (b) is a side view and a partially enlarged view, (c)
Is a plan view.

FIG. 3 is a view showing a state where molten metal is scattered from a rotating body.

FIG. 4 is a view showing a difference in a moving speed in a height direction of molten metal accumulated on a rotating body of the metal powder manufacturing apparatus.

FIG. 5 is a diagram showing a particle size distribution of zinc powder.

6A and 6B are views showing a rotating body of a conventional metal powder manufacturing apparatus, wherein FIG. 6A is an external perspective view and FIG. 6B is a side view.

FIG. 7 is a view showing a difference in a moving speed in a height direction of the molten metal accumulated on a rotating body of the metal powder producing apparatus.

[Explanation of symbols]

 3 Rotating Body 4 Molten Metal (Molten Zinc) 5 Projection 7 Open Section 8 Metal Powder (Zinc Powder) R Curved Surface

Claims (3)

[Claims] 1. A metal powder manufacturing apparatus for manufacturing a metal powder (8) by dropping a molten metal (4) onto a rotating body (3) rotating at high speed, wherein the rotating body (3) is cylindrical or conical. And a plurality of protrusions extending radially from the center of the disk to the outer peripheral end surface on the surface of the rotating body (3) on which the molten metal (4) is dropped. An apparatus for producing a metal powder, characterized in that the part (5) is formed by cutting off the central part and providing an open part (7). 2. The metal powder producing apparatus according to claim 1, wherein a curved surface (R) is provided in a height direction on an end surface of the protrusion (5) on the outer peripheral side of the disk. 3. The apparatus for producing a metal powder according to claim 1, wherein the metal powder (8) is an irregular-shaped zinc powder used as an active material for a negative electrode of an alkaline battery.