JPH0428762B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to a uniform spherical material used, for example, to replenish metal ions lost in a plating bath or for surface treatment such as shot blasting. The present invention relates to a method and apparatus for producing spherical metal particles.

[Prior Art] The conventional method and apparatus for producing spherical metal particles are as follows:
As shown in the figure, the molten metal 2 contained in the molten metal container 1 is transferred to the passage 3 of the molten metal dripping nozzle 3.
a, the cooling medium 5 such as cooling water stored in a cooling medium container 4 is dripped into the cooling medium 5 such as cooling water and solidified, and the passage 3a of the nozzle 3 is formed so that its cross-sectional area becomes smaller as it approaches the outlet. The temperature of the molten metal 2, the depth of the molten metal, the diameter d0 of the outlet 3b of the nozzle 3, the distance l0 between the tip of the nozzle and the liquid level of the cooling medium 5, etc. are selected as appropriate. As a result, the dripping amount and dripping state of the molten metal 2 are adjusted to the optimum state, so that the metal particles solidified in the cooling medium 5 have a uniform spherical shape (for example, as disclosed in Japanese Patent Application Laid-Open No. 1983-1999).
(See Publication No. 192205).

[Problems to be Solved by the Invention] However, in the above-mentioned conventional example, the temperature of the molten metal 2 or the diameter d0 of the outlet 3b of the nozzle 3
and it is difficult to select various conditions such as the distance l0 between the tip of the nozzle and the liquid level of the cooling medium 5, and
If the conditions are even slightly different from the optimal conditions found through trial and error, the metal grains obtained will be needle-shaped, crushed, petal-shaped, or flattened, making it impossible to obtain uniform spherical metallic properties. Ta.

SUMMARY OF THE INVENTION The object of the present invention is to provide a method and apparatus for producing spherical metal particles that eliminate the above-mentioned drawbacks.

[Means for Solving the Problems] The method for producing spherical metal particles according to the present invention includes first passing molten metal through a first passage having a small cross-sectional area;
Thereafter, the droplet is passed through a second passage having a larger cross-sectional area than the first passage, and the apparatus for producing spherical metal particles according to the present invention includes a nozzle for dropping molten metal. The molten metal distribution passage includes a first passage located on the interior side of the container and a second passage located on the exit side of the molten metal,
The cross-sectional area of the first passage is formed to be smaller than the cross-sectional area of the second passage, so that even if the conditions are slightly different, the spherical metal particles are always stable and uniform. Specifically, (1) a method for producing spherical metal particles in which spherical metal particles are produced by dropping a solution metal into a cooling medium and solidifying it, comprising: A structure characterized in that the metal is first passed through a first passageway having a small cross-sectional area, and then passed through a second passageway having a larger cross-sectional area than the first passageway so as to drip. 2) It has a container for storing molten metal, and the molten metal dripping nozzle provided at the bottom of the container, and a cooling medium prepared below is passed from the dropping nozzle to the molten metal contained in the container. In the apparatus for producing spherical metal particles by dropping and solidifying molten metal, the molten metal distribution passage of the molten metal dropping nozzle is arranged in a first tube located inside the container. and a second passage located on the exit side of the molten metal, the cross-sectional area of the first passage being smaller than the cross-sectional area of the second passage, have each.

[Function] In the above configuration, the cross-sectional areas of the first passage and the second passage are appropriately selected depending on the type of the molten metal, the diameter of the spherical metal to be obtained, etc., and the molten metal is passed through these passages. Spherical metal particles can be obtained by dropping the powder into a cooling medium.

In this case, the molten metal first passes through a first passage with a small cross-sectional area, and then passes through a second passage with a large cross-sectional area and drips. For this reason, first, the amount of molten metal that can be dropped per unit time is regulated by the first passage. Moreover, the viscosity of the molten metal flowing through the first passage is significantly higher than that of water, and the cross-sectional area of the first passage is sufficiently small, so that the flow rate is approximately equal to the cross-section of the first passage. It depends only on the size of the area and changes little even if other factors such as, for example, the depth of the molten metal vary slightly. Therefore, the molten metal flows through the first passage in a continuous flow while maintaining a stable and relatively small flow rate, and reaches the second passage having a large cross-sectional area. When the second passage is filled with the molten metal that has reached the second passage, the molten metal begins to protrude outward from the outlet end of the second passage in a spherical shape. As the molten metal is supplied from the passage 1, the diameter of the sphere is gradually increased, and the specific gravity of the molten metal,
When it reaches a certain size depending on factors such as viscosity or surface tension, it separates and drops, and solidifies in the cooling medium to become spherical metal particles. This results in
Spherical metal particles having an almost perfect spherical shape and an extremely uniform particle size can be stably obtained.

[Example] FIG. 1 is a partial sectional view showing an example of the apparatus for manufacturing spherical metal particles according to the present invention.

Hereinafter, with reference to FIG. 1, an embodiment of the method for producing spherical metal particles according to the present invention and an embodiment of the apparatus for producing spherical metal particles according to the present invention will be described.

In FIG. 1, reference numeral 10 denotes a container, and inside this container 10 are zinc, cadmium, gold, silver, copper, or alloys containing one or more of these metals (for example, two types of zinc alloy ingots for die casting). There are products with the following compositions that are used as

Composition; Al: 3.9-4.3%, Mg: 0.003-0.06%,
Cu: 0.03% or less, Cd: 0.002% or less, Pb: 0.003%
Below, Fe: 0.075% or less, Sn: 0.001% or less, Zn
The container 10 contains a molten metal 20 such as the remainder of the container 10, and a molten metal dripping nozzle 30 made of a material such as ceramic that has excellent heat retention and has poor leakage to the molten metal is attached to the bottom of the container 10. It is being This nozzle 30 is provided with a first passage 30a located on the inside side of the container, and a second passage 30b provided in communication with the first passage and located on the exit side of the molten metal. ing. In this case, the diameter d1 of the first passage 30a is larger than the diameter d1 of the first passage 30a.
The diameter d2 of the passage is large, and therefore the cross-sectional area of the first passage 30a is larger than that of the second passage 30b.
It is formed smaller than the cross-sectional area of . in this case,
Under normal conditions, the diameter of the passage of the nozzle 30 is 1 mm.
For example, if the molten metal is zinc, natural dripping (dropping by gravity) will be difficult.
On the other hand, it has been experimentally confirmed that if the thickness is 3 mm or more, it becomes difficult to obtain uniform spherical metal particles. Therefore, for example, if d1=1mm, d2=
It is said to be 2.5mm. Note that at this time, the lengths of the first passage 30a and the second passage 30b are respectively
Selected as 20mm and 105mm. Cooling water 50, which is a cooling medium, is positioned so that the liquid level is located at a distance l (usually l = 30 mm or less, preferably 10 to 20 mm) from the tip of the nozzle 30.
(Water temperature should be below 80℃, preferably below 35℃.80
If the temperature exceeds °C, the resulting metal grains may become flattened). Therefore, the molten metal first passes through the first passage 30a having a small cross-sectional area, and then passes through the second passage 30b having a large cross-sectional area.
It passes through and drips. Thereby, uniform spherical metal particles can be stably obtained due to the above-described effect. In this case, the risk of deformation of the molten metal dropped into the cooling medium can be further reduced by using, for example, a solution in which salts are dissolved and the viscosity, density, surface tension, etc. have been adjusted as the cooling medium. However, in that case, a water washing step is required, and in the above embodiment, even if water (e.g., tap water) is used as the cooling medium, uniform spherical metal particles can always be obtained. This has been confirmed.

FIG. 2 is a partial sectional view showing another embodiment of the apparatus for producing spherical metal particles according to the present invention.

This embodiment differs from the previous embodiment only in the melting point metal dropping nozzle. That is, in the figure, the molten metal dropping nozzle 31 is
A first hole 32 having a relatively large diameter is formed downward in the figure from the molten metal side, and a relatively large diameter ( d2) is inserted into the first hole 32, has an outer diameter slightly smaller than the inner diameter of the first hole 32, and has a tapered tip. The adjustment rod 34 is configured to include an adjustable rod 34. That is, in the case of this nozzle, the first passage is formed between the gap 31a formed between the first hole 32 and the adjustment rod 34 (between the tapered part 33 of the first hole 32 and the gap 31a). (including a gap formed between the adjustment rod 34 and the tapered end of the adjustment rod 34), and the second passageway is constituted by the second hole 31b. In addition, FIG. 3 shows the above-mentioned second
It is a perspective view of the molten metal dripping nozzle 31 in a figure.

In this embodiment, in addition to having the same advantages as the one embodiment described above, the adjustment rod 34 is
As shown, by moving up and down, the size of the gap 31a constituting the second passage can be adjusted, and the amount of dripping can be freely adjusted according to the type of molten metal. This has the advantage of making it possible to save the effort of replacing the nozzle depending on the type of molten metal.

Next, the present inventors actually manufactured spherical metal particles using the method and apparatus of each of the above-mentioned Examples, and some of the results are listed below.

Manufacturing Example 1 In this example, using the apparatus of the embodiment shown in FIG.
It was manufactured by heating and maintaining the temperature at 500°C and dropping it dropwise from a nozzle. Other manufacturing conditions are as follows.

Nozzle material for dropping molten metal...Diameter of ceramic first and second passages d1=1mm d2=2.5mm Cooling medium Type...Tap water Temperature...35℃ Dripping distance l=15mm Dripping amount...15~20Kg/ Time This produces spherical metal particles with a diameter of 4-6 mm.
Obtained with a yield of 90%. Details of the particle size distribution in this case are as follows.

Diameter 6 mm or more...3.0% 〃 4-6 mm...90.2% 〃 3-4 mm...5.2% 〃 2-3 mm...1.5% 〃 2 mm or less...0.1% Manufacturing example 2 In this example, Al :4.0%, Mg:
A die-casting zinc alloy having a composition of 0.04% and Zn: the balance was used, and was produced under the same conditions as Production Example 1, except that the temperature was maintained at 480°C. The particle size distribution of the obtained spherical metal particles was as follows.

Diameter 6 mm or more...5.2% 〃 4-6 mm...83.1% 〃 3-4 mm...9.3% 〃 2-3 mm...2.2% 〃 2 mm or less...0.2% Manufacturing example 3 This example is shown in Figure 2 above. Using the device of the other embodiment shown, a stainless steel rod is used as the adjustment rod 34, and the diameter d2 of the second hole 31b as the second passage is set to 2 mm to adjust the dripping amount to the adjustment rod. The production was carried out by adjusting the rate to 15 kg/hour using the No. 34. Note that other conditions were the same as in Production Example 1 above. The particle size distribution of the obtained spherical metal particles was as follows.

Diameter 6 mm or more...3.1% 〃 4-6 mm...94.8% 〃 3-4 mm...2.0% 〃 2-3 mm...0.1% 〃 2 mm or less...0.0% Manufacturing example 4 This example uses Cd as the molten metal. : Manufactured under the same conditions as in Manufacturing Example 3 above, except that 99.99% cadmium metal was used and maintained at 400°C. The particle size distribution of the obtained spherical metal particles was as follows.

Diameter 6 mm or more...2.8% 〃 4-6 mm...93.6% 〃 3-4 mm...3.4% 〃 2-3 mm...0.2% 〃 2 mm or less...0.0% (Comparative example) The present inventors, Using the conventional apparatus shown in FIG. 4, other conditions were set as in Manufacturing Example 3.
and the diameter d0 of the outlet part 3b of the nozzle 3 is
I tried some manufacturing experiments by changing several types of , but as long as the control accuracy of the manufacturing conditions (conditions such as temperature, depth of molten metal, etc.) was kept at the same level as in Manufacturing Example 3,
Almost no spherical metal particles could be obtained.

[Effects of the Invention] As detailed above, the present invention allows molten metal to first pass through a first passage having a small cross-sectional area, and then passes through a second passage having a larger cross-sectional area than the first passage. The metal particles are allowed to drip through the metal particles, thereby making it possible to obtain stable and uniform spherical metal particles at all times.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view showing one embodiment of the apparatus for producing spherical metal particles according to the present invention, and FIG. 2 is a partial cross-sectional view showing another embodiment of the apparatus for producing spherical metal particles according to the present invention. 3 is a perspective view of the molten metal dropping nozzle 31 shown in FIG. 2, and FIG. 4 is a diagram showing a conventional apparatus for producing spherical metal particles. DESCRIPTION OF SYMBOLS 10... Container, 20... Molten metal, 30... Molten metal dripping nozzle, 30a... First passage, 3
0b...Second passage, 50...Cooling water as a cooling medium.

Claims (1)

[Scope of Claims] 1. A method for producing spherical metal particles by dropping molten metal into a cooling medium and solidifying it, comprising: first passing the molten metal through a first passage having a small cross-sectional area; A method for producing spherical metal particles, characterized in that the particles are allowed to pass through, and then allowed to drop through a second passageway having a larger cross-sectional area than the first passageway. 2 comprising a container containing molten metal and the molten metal dripping nozzle provided at the bottom of the container,
In an apparatus for producing spherical metal particles, which produces spherical metal particles by dropping the molten metal contained in the container from the molten metal dropping nozzle into a cooling medium prepared below the nozzle and solidifying the molten metal, The molten metal distribution passage of the molten metal dripping nozzle has a first passage located inside the container and a second passage located on the exit side of the molten metal,
An apparatus for producing spherical metal particles, characterized in that the cross-sectional area of the first passage is smaller than the cross-sectional area of the second passage.