JP2915117B2 - Manufacturing method of metal particles - Google Patents

Description

The present invention relates to a method for producing metal particles.

(Prior art) As a method for producing metal particles, a drum containing cooling water is rotated at a high speed, and the cooling water is formed into a high-speed rotating liquid layer by centrifugal force. The jet is injected toward the wall of the rotating cooling water layer, and the continuous flow contacts the wall of the cooling water layer to apply a shearing force to break the droplet into small droplets. It is known to form particles (Japanese Patent Application Publication No. Hei 1-49769).

However, in this method, the continuous flow of molten metal
In order to apply a shearing force at the time of contact with the rotating cooling water layer, the peripheral velocity of the rotating cooling water layer needs to be larger than the velocity component of the continuous flow of the molten metal along the water layer surface. At the moment when the flow comes into contact with the surface of the rotating cooling water layer, an impact is generated on the contact surface due to a steep change in kinetic energy based on the difference between the two velocities, and the droplets become needle-like, and the droplets become needle-like. Difficulty spheroidizing the body.

Conventionally, the molten metal flow is formed at a temperature higher than the melting point of the metal by 600 ° C. or more, and the peripheral speed of the rotating cooling water layer and the velocity component along the water layer surface of the continuous flow of the molten metal are set to be substantially the same, and the metal is formed. It is known to produce granules (Patent Application Publication
2-122009). According to this method, the difference between the peripheral velocity of the rotating cooling water layer and the velocity component of the continuous flow of the molten metal along the surface of the water layer is substantially eliminated, and the above impact can be avoided, and the particles can be made spherical. It is.

(Problem to be Solved) However, the metal must be heated to a high temperature that is higher than its melting point by 600 ° C. or more, and an increase in equipment cost is inevitable due to the high temperature, and work is not easy.

As described above, when the peripheral velocity of the rotating cooling water layer and the velocity component of the continuous flow of the molten metal along the water layer surface are substantially the same, the continuous flow of the molten metal is divided into small droplets by air. The surface energy of the molten metal under contact and the surface energy of the molten metal under water contact are different, so that the continuous flow of molten metal becomes spherical by surface tension when it comes into contact with water,
It can be inferred that fragmentation occurs due to the spheroidization. In the present inventor, when the peripheral velocity of the rotary cooling water layer and the velocity component of the continuous flow of the molten metal along the water layer surface are made equal, the particle diameter of the metal particles is 2 times the injection diameter of the molten metal injection nozzle. ~
We observe that it becomes three times, and from this observation result,
This may support the validity of the above assumption.

In the present inventor, when various experiments were performed in the process leading to the above inference, it was found that if a liquid having a higher volatility than water at room temperature was added to the cooling water, the temperature of the molten metal was 100 to 600 ° C. higher than the melting point of the metal. It has been found that the spheroidization of the granules can be sufficiently achieved even if the range is kept as high as possible. Thus, the reason that the spheroidization of the granules can be promoted is that the surface energy of the molten metal under contact with the cooling liquid increases due to the volatile liquid, and the surface tension of the molten metal increases, It is considered that the divided molten metal droplets are covered with the volatile gas vaporized gas, the cooling speed of the droplets is relaxed, spheroidization by surface tension progresses well, and solidification ends.

The object of the present invention is to make the peripheral speed of the cooling water layer and the speed of the continuous flow of the molten metal substantially the same speed, and set the temperature of the molten metal within the range of 100 to 600 ° C. higher than the melting point of the metal based on the above findings. It is an object of the present invention to provide a method capable of producing substantially spherical metal particles under the condition that the metal particles are kept at a minimum.

(Means for Solving the Problems) In the method for producing metal particles according to the present invention, the metal is melted at a temperature lower than the melting point.
At a high temperature of 100 ° C to 600 ° C, the injection nozzle injects the injection speed component along the liquid surface at the temperature higher than the rotation peripheral speed of the cooling liquid from the injection nozzle, almost equal to the rotation peripheral speed of the cooling liquid. The present invention is characterized in that a mixture with a liquid which is volatile at normal temperature is used.

In the above, methanol, ethanol, 2-propanol (isopropyl alcohol), 2-methyl-2-propanol, n-propanol, or the like can be used as a liquid that is more volatile than water at normal temperature. The mixing ratio of the volatile liquid is preferably 5 to 50% (% by weight).

As the metal, a metal having a relatively low melting point (for example, a Sn-Ag alloy, a liquidus temperature of 221 ° C.) to a metal having a relatively low melting point (for example, a Cu—Zn alloy, liquidus temperature of 955 ° C.) can be used. In the case of a metal which is easily oxidized, it is effective to fill a rotary drum described later with an inert gas and to blow the inert gas to a nozzle orifice and its vicinity.

As the production apparatus, an existing apparatus used in the spinning-in-rotating liquid yarn method can be used.

FIG. 1 is an explanatory view showing an example of a manufacturing apparatus used in the present invention, and FIG. 2 is a sectional view taken along the line II-II in FIG.

In FIG. 1 and FIG. 2, reference numeral 1 denotes a rotating drum, which has a weir plate 11, is supported by a rotating shaft 12, and is rotated by the electric motor 2. Reference numeral 4 denotes an injection nozzle, which has a heater 41, and in which the molten metal 6 is injected in a continuous flow jet by the gas pressure from the inert gas injection pipe 5.

In order to produce metal particles according to the present invention, a cooling liquid 3 in which a liquid more volatile than water at room temperature is mixed with water is applied to a drum 1.
The cooling liquid 3 is formed into a layer by centrifugal force and the nozzle 4
The metal inside is heated by a heater 41 to a temperature
The molten metal 6 is heated in a temperature range higher by 0 to 600 ° C., and the molten metal 6 is jetted toward the cooling liquid layer 3 by a gas pressure from the inert gas injection pipe 5 by a continuous flow jet. The velocity component of this continuous flow along the surface of the cooling water layer (Vcosθ, where V is the injection velocity of the continuous flow and θ is the angle between the continuous flow and the cooling liquid layer) and the peripheral velocity v of the rotating cooling liquid layer are approximately Are equal (v / Vcosθ = 1.
1-0.9). Therefore, even if the continuous flow of the molten metal comes into contact with the rotary cooling liquid layer, the continuous flow of the molten metal does not receive an impact due to the above-mentioned uniform velocity, and the molten metal under the contact with the cooling liquid is not affected. Surface energy, i.e., due to surface tension, the continuous flow of molten metal becomes spherical and breaks into droplets,
The droplets are surrounded by the vaporized gas of the volatile liquid generated by the contact between the molten metal and the cooling liquid, and the droplets are gradually cooled by the surroundings of the vaporized gas, and are solidified with the progress of spheroidization.

As described above, according to the present invention, the continuous flow of the molten metal can be divided into small droplets without generating impact, and the droplets can be solidified while the spheroidization of the droplets proceeds. Can be achieved.

 Hereinafter, examples of the present invention will be described in comparison with comparative examples.

Example 1 The metal used was a Cu—Zn alloy having a liquidus temperature of 955 ° C., the temperature of the molten metal in the nozzle was 1060 ° C., and the water: isopropyl alcohol ratio was 70:30 ( (Weight ratio).

When the aspect ratio of the obtained metal particles was measured,
1.08. The particle diameter of the granules was about twice the hole diameter at the nozzle outlet.

Example 2 The metal used was an Sn-Ag alloy having a liquidus temperature of 221 ° C., the temperature of the molten metal in the nozzle was 800 ° C., and the water: ethanol ratio was 70:30 (weight ratio) in the cooling liquid. ) Was used.

When the aspect ratio of the obtained metal particles was measured,
1.02. The particle size of the granules was about three times the hole diameter at the nozzle outlet.

Comparative Example 1 The conditions were the same as in Example 1 except that only water was used as the cooling liquid. It did not become granules but became fine lines.

Comparative Example 2 The conditions were the same as in Example 2 except that only water was used as the cooling liquid. It did not become granules but became fine lines.

(Effects of the Invention) The method for producing metal granules according to the present invention has the above-described configuration, and only by mixing a liquid that is more volatile than water at room temperature in cooling water, heats molten metal injected from a nozzle. The temperature is relaxed from the conventional condition of `` 600 ° C or higher than the melting point '' to a range of 100 to 600 ° C higher than the melting point, and the continuous flow of molten metal from the nozzle is brought into contact with the rotating cooling liquid layer without impact. It is possible to make the droplets small and solidify them spherically with a cooling liquid. Therefore, the heating temperature of the molten metal can be reduced, which is advantageous in terms of equipment costs and work.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a manufacturing apparatus used in the present invention, and FIG. 2 is a sectional view taken along the line II-II in FIG. 1 ... rotating drum, 3 ... cooling liquid, 4 ... nozzle, 6 ...
... Molten metal.

Claims (1)

(57) [Claims] 1. Injecting a metal at a temperature 100 ° C. to 600 ° C. higher than a melting point from an injection nozzle toward a rotary cooling liquid with an injection velocity component along the liquid surface substantially equal to the rotational peripheral velocity of the cooling liquid;
A method for producing metal particles, wherein a mixture of water and a liquid that is more volatile at room temperature than water is used as the cooling liquid.