JP4264873B2 - Method for producing fine metal powder by gas atomization method - Google Patents

Description

[0001]
[Industrial application fields]
  The present invention relates to a method for producing a fine metal powder by a gas atomizing method.InRelated.
[0002]
[Prior art]
Metal powders are widely used for battery electrode materials, hydrogen storage alloys, metal powders for conductive pastes, metal powder fillers, metal powders for compression molding and injection molding, and the like.
In recent years, the characteristics of metal powders used in these applications have been required to improve filling properties, moldability, and reactivity in order to improve performance in various application fields. When the demand for higher performance of these metal powders is seen from the viewpoint of powder characteristics, the powder is made finer or spherical, and the cost reduction is required.
As typical methods for producing metal powders, a stirring method in a polar solvent, a mechanical pulverization method, a reduction method, an electrolysis method, a thermal decomposition method, a gas phase condensation method, an atomization method, and the like are known.
[0003]
The conventional stirring method in a polar solvent is a method of atomizing In or an In alloy by stirring a low melting point metal in a polar solvent under a condition higher than the melting point (see Patent Document 1). The stirring method in a polar solvent has lower productivity per unit time than the atomizing method, and a metal having a melting point of 250 ° C. or higher does not have a suitable polar solvent.
[0004]
The conventional mechanical pulverization method is a method in which a block of a metal material is mechanically pulverized into a powder using a pulverizer such as a jaw crusher, a block mill, or an attritor. In this method, since the particle shape of the metal powder becomes indefinite and the low melting point metal aggregates due to heat generated in the pulverization process, a fine metal powder cannot be obtained.
[0005]
Among these methods, the atomizing method is capable of producing metal powder having an average particle diameter of several μm to several hundred μm, and also in terms of production cost, the stirring method in the above-mentioned conventional method in a polar solvent, It is widely used industrially because it is more advantageous than mechanical pulverization, reduction, electrolysis, thermal decomposition, gas phase condensation, and the like. Typical atomization methods include a disk atomization method, a water atomization method, and a gas atomization method.
[0006]
In the conventional disk atomization method, a molten body of a molten metal such as a disk, a cylinder, or a wheel is poured directly onto a disk, that is, a method in which the poured molten metal is pulverized on the disk and powdered. is there. The rotational speed of the disk is usually 400 revolutions / minute to 20,000 revolutions / minute. In order to obtain a fine metal powder, tens of thousands of revolutions / minute are required as the number of revolutions of the disk. Therefore, there are limitations on the material of the disk rotation shaft, and it is difficult to obtain a fine metal powder. .
[0007]
Moreover, the conventional water atomization method is a method of obtaining metal powder by spraying water on a molten metal stream (see Patent Document 2). The water atomization method involves the use of water as a cooling medium in the production of metal powder, which involves oxidation due to the reaction between metal and water, and because of the large cooling capacity of water, only powder with an irregularly shaped irregular shape can be obtained. I can't. In addition, in the water atomization method, in order to recover the metal powder in water, there is a problem that the surface of the metal powder is oxidized, and a drying process of water attached to the surface of the metal powder is required, which increases costs. It was unsuitable for the manufacturing method of the fine metal powder by a gas atomizing method.
[0008]
In contrast to the above method, the gas atomization method is a method in which a metal powder is directly generated by spraying, dispersing, and solidifying a molten metal by injecting an inert gas at a high speed into the molten metal stream. It is. The metal powder produced using the gas atomization method has an excellent feature that the shape thereof is spherical and the surface thereof has few metal oxide layers. For this reason, the gas atomizing method is advantageous because a fine metal powder with high quality can be obtained as compared with the above-described disk atomizing method and water atomizing method.
[0009]
Next, the manufacturing method of the conventional gas atomizing method is demonstrated.
In an example of a conventional method for producing metal powder by gas atomization, room temperature Ar (argon) gas is used as the atomization gas, and 400 kgf / cm.²(40 MPa / cm²), The average particle size is about 10 μm, and 20 kgf / cm²~ 55kgf / cm²Ni-based superalloy powder having an average particle size of about 44 μm to 74 μm is obtained at an Ar gas pressure (see Patent Document 3).
[0010]
As another example, Ar gas at room temperature is used as atomizing gas, and Ar gas pressure is 15 kgf / cm.²Under the above high Ar gas pressure conditions, a hydrogen storage alloy powder having an average particle size of about 27 to 185 μm is obtained (see Patent Document 4).
[0011]
As another example, similarly, room temperature Ar gas is used as the atomizing gas, and 20 kgf / cm 2 is used.²The hydrogen storage alloy powder having an average particle diameter of about 35 μm to 100 μm is obtained at an Ar gas pressure (see Patent Document 5).
[0012]
Various empirical formulas have been reported for the average particle diameter of the metal powder obtained by the gas atomization method. For example, according to Lubanska, it is represented by the following formula (1) (see Non-Patent Document 1).
d = K · D · [(1 + Qm / Qg) · νm / (νg · We)]^0.5  (1)
Here, d is the average particle diameter of the metal powder, K is a constant term, D is the diameter of the molten metal, Qm is the mass flow rate of the molten metal, Qg is the mass flow rate of the atomized gas, νm is the kinematic viscosity coefficient of the molten metal, νg Is the kinematic viscosity coefficient of atomized gas.
In the above equation, We is the Weber number and is represented by the following equation (2).
We = ρm · Vg²・ D / γm (2)
Here, ρm is the density of the molten metal, Vg is the linear velocity of the atomized gas, and γm is the surface tension of the molten metal.
[0013]
From the above formulas (1) and (2), the main factors that determine the average particle size of the metal powder obtained by the gas atomization method are the diameter D of the molten metal that determines the flow rate of the molten metal and the collision energy of the atomized gas. I understand. If the diameter D of the molten metal is reduced, fine metal powder can be easily obtained, but the production amount of fine metal powder per unit time decreases.
Therefore, the refinement of the metal powder is to increase the diameter D of the molten metal to some extent so as to prevent the production amount of the fine metal powder per unit time from decreasing, and to secure the molten metal flow. In order to increase the pressure, the atomizing gas pressure is increased to increase the flow velocity of the atomizing gas.
In the above-described conventional method for producing metal powder by the gas atomizing method, a method of increasing the atomizing gas pressure is adopted exclusively, and 10 kgf / cm.²~ Several tens kgf / cm²The above pressure was necessary.
[0014]
[Patent Document 1]
JP-A-6-346118 (pages 2 to 3)
[Patent Document 2]
Japanese Patent Laid-Open No. 11-323411 (pages 2 to 4, FIG. 2)
[Patent Document 3]
JP 61-266506 A (pages 3 to 5, Tables 1 and 2)
[Patent Document 4]
JP-A-6-192712 (Page 5)
[Patent Document 5]
JP-A-10-204507 (pages 6-8, Table 7)
[Non-Patent Document 1]
M. Randall, translated by Hideshi Miura and Kenichi Takagi, “Science of Powder Metallurgy”, Uchida Otsukaku, June 25, 1996, p. 108
[0015]
[Problems to be solved by the invention]
Compared with conventional methods other than the gas atomization method, the conventional gas atomization method is more easily obtained, and the reactivity between the molten metal and the atomized gas Ar is low, so that it is clean without oxidation. There is an advantage that a metal powder surface is easily obtained.
[0016]
However, in order to obtain fine metal powder in the conventional gas atomization method, if the atomizing gas pressure is low, the shearing force applied to the molten metal is weak, so the atomizing gas pressure is set to several tens kgf / cm.²~ Several hundred kgf / cm²It was necessary to apply an extremely high pressure as described above. For this reason, the ability of the compressor to increase the atomizing gas pressure needs to be strong.
Therefore, in the production of the gas atomization method for obtaining fine metal powder, the cost required for equipment such as a compressor and piping that match the specifications of Ar gas pressure, and the operating cost for consuming a large amount of expensive Ar gas There is a problem that the manufacturing cost is high.
[0017]
In addition, when the average particle size of the fine metal powder is controlled by the Ar gas pressure, the metal sprayed into the atomizing gas container of the gas atomizing device at the time of collision between the molten metal flow and the Ar gas as the Ar gas pressure increases. The spread of the molten metal into the atomizing container, that is, the dispersion area becomes wide. For this reason, the molten metal disperse | distributed to the wide area in the pouring nozzle which is a jet nozzle of a molten metal, or an atomization container was easy to fly. For this reason, the fixation of the metal to the inside of the atomization container and the increase of the irregularly shaped particles are generated, and the yield of the fine metal powder is lowered, so that there is a problem that the cost is increased.
[0018]
As described above, realization of a gas atomizing method capable of producing a fine metal powder at a low cost is desired. However, in reality, it is impossible to produce a fine metal powder at a low cost.
[0019]
  In view of the above points, the present invention can produce a fine metal powder at a low cost by reducing the pressure of the atomizing gas, and a method for producing a fine metal powder by a gas atomization methodTheIt is intended to provide.
[0020]
[Means for Solving the Problems]
As a result of various studies, the inventors of the present invention have made it possible to reduce the atomizing gas pressure and the atomizing gas flow rate by heating the atomizing gas to a temperature higher than the melting point of the metal in the gas atomizing method. As a result, the present inventors have completed the present invention.
[0021]
  In order to solve the above-mentioned problems, the method for producing a fine metal powder by the gas atomization method of the present invention is a method for producing a fine metal powder by injecting an atomized gas heated to a melting point or higher of a metal to a molten metal flow. 3kgf / cm² -10kgf / cm² At a constant pressure in the range of0.6 Nm³ /Min~1.5Nm³ / MinControl the flow rate in the range ofThe supplied atomizing gas is heated and injected so that the collision angle is 15 ° or more and 30 ° or less with respect to the molten metal flow of 1 kg / min to 2 kg / min.The average particle size was controlled to 30 μm to 100 μmIt is characterized by producing fine metal powder.
  Here, the fine metal powder is preferably cooled by a cooling means.
  MoneyAs the genus, any one metal of Bi, Cd, Ga, In, Sn, and Zn, or an alloy made of two or more kinds of metals selected from these metals may be used. The metal may be an In alloy obtained by adding one or more metals selected from Ag, Bi, Cd, Cu, Ga, Hg, Sb, Sn, and Zn to In.
[0022]
According to this configuration, by atomizing the atomized gas heated to a temperature equal to or higher than the melting point of the metal to the molten metal, the atomized gas is substantially reduced even in a state where the pressure of the atomized gas is lower than when not heated. The flow rate can be increased, and the atomized gas flow rate can be reduced to produce fine metal powder with a small average particle size.
In addition, since the inside of the atomizing container is cooled, it is possible to efficiently disperse, spheroidize, solidify, and collect the molten metal particles with heat injected into the atomizing container. Aggregation of the powder can be prevented.
As a result, the dispersed molten metal particles can be recovered with high yield as a fine metal powder without agglomerating in the recovery container at a low atomizing gas pressure. Accordingly, it is possible to produce fine metal powder suitable for the purpose of using various industrial materials at a low cost.
[0023]
  Furthermore, the present inventionIsA crucible containing molten metal, an atomizing container connected to the crucible,It is installed inside the atomized container,A pouring nozzle to introduce molten metal from the crucibleAn atomizing gas injection means for injecting atomized gas supplied via an atomizing gas pipe, and the atomizing gas injection means as the atomizing gas injection means from the periphery of the pouring nozzle to the tip of the pouring nozzle An atomizing gas injection port is provided so that the angle formed with the pouring nozzle toward the molten metal outlet at 15 ° to 30 ° is less than the melting point of the metal material accommodated in the crucible. A heating means for heating the gas is provided, and a fine atomized metal is produced by injecting a heated atomizing gas onto the molten metal that passes through the pouring nozzle and flows down from the molten metal outlet.It is characterized by that.Preferably, the apparatus for producing fine metal powder further includes a cooling means for cooling the inside of the atomizing container. More preferably, a collection container for collecting the fine metal powder is connected to the atomization container.
[0026]
With the above configuration, a fine metal powder having a small average particle size can be produced with high yield by reducing the pressure and flow rate of an expensive atomizing gas used in the gas atomizing method. Therefore, fine metal powder suitable for the purpose of using various industrial materials can be produced at low cost, and an excellent production apparatus for fine metal powder by gas atomization can be provided.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a cross-sectional view showing a configuration of a fine metal powder production apparatus used in a fine metal powder production method using a gas atomization method.
In FIG. 1, the fine metal powder production apparatus 1 includes a crucible 3 for containing a molten metal 2, an atomizing container 4 provided below the crucible 3, and a collection container 5 provided below the atomizing container 4. The gantry 6 that holds these components is configured.
[0028]
The fine metal powder manufacturing apparatus 1 includes a metal heating means for heating the metal material to a temperature equal to or higher than its melting point in order to use the metal material accommodated in the crucible 3 as the molten metal 2. This metal heating means is composed of a crucible heating heater 8 surrounding the crucible 3.
Furthermore, the crucible 3 includes a through hole 3a on the bottom surface, and a pouring nozzle 9 is connected to the through hole 3a. The pouring nozzle 9 is inserted into a flow path portion 4b (shown in FIG. 2) of the atomizing container 4 to be described later without any gap, and the molten metal outlet 9a at the tip of the pouring nozzle 9 is at the upper end of the atomizing container 4. , And are arranged to open downward.
[0029]
In addition, although illustration is abbreviate | omitted as a metal heating means, in the case of a metal with high melting | fusing point, the crucible 3 and the crucible heating heater 8 are metal to induction heating apparatus, its heating coil, and a heating coil, such as a high frequency You may replace with the other heating apparatus by the moving apparatus etc. which insert material and move it below. In this case, since the lower part of the metal is melted by the heating coil to form a molten metal, the lower part of the metal is held at the upper end of the atomizing container 4 and disposed inside the atomizing container.
[0030]
The first feature of the fine metal powder production apparatus 1 of the present invention is that the atomizing gas 10 is heated to a temperature equal to or higher than the melting point of the metal to be melted.
As illustrated, the atomizing gas 10 is supplied at room temperature by two atomizing gas pipes 11 connected to the atomizing gas flow path 4 d of the atomizing container 4. The atomizing gas 10 supplied to the atomizing gas pipe 11 is pressurized by a compressor or the like which is a pressurizing device (not shown).
The atomizing gas 10 is heated to a temperature equal to or higher than the melting point of the metal to be melted by a heating means such as an atomizing gas heating heater 12 disposed around the atomizing gas pipe 11 to become a heated atomizing gas 13. The temperature of the heated atomizing gas 13 is equal to or higher than the melting point of the metal material, but this temperature may be about the temperature of the molten metal 2.
Here, the atomizing gas 10 is also called a dispersion medium, and nitrogen gas which is an inert gas can be used. Ar gas, helium (He) gas, or the like can also be used. In terms of cost, nitrogen gas is the cheapest and advantageous.
[0031]
FIG. 2 is an enlarged cross-sectional view showing the configuration of the injection port portion of the atomizing gas injection means in the fine metal powder manufacturing apparatus 1 of FIG.
As shown in the drawing, a channel portion 4 b into which a pouring nozzle 9 is inserted is provided on the upper portion of the atomizing container 4. The pouring nozzle 9 passes through the flow path portion 4 b and is fitted into the atomizing container 4, and the molten metal outlet 9 a at the tip of the pouring nozzle 9 opens toward the lower side of the atomizing container 4.
Further, the atomizing container 4 is provided with an atomizing gas injection port 4c at the periphery of the pouring nozzle 9, and an atomizing gas pipe 11 is provided in communication with the atomizing gas injection port 4c. The atomizing gas heater 12 is provided. The atomizing gas injection port 4c is formed in a circular slit shape from the periphery of the pouring nozzle 9 toward the molten metal outlet 9a at the tip thereof, passes through the hole in the pouring nozzle 9 and passes from the molten metal outlet 9a. An atomizing gas 13 heated to a melting point of the metal or higher is injected to the molten metal 2 flowing down.
[0032]
Since the atomized gas injection port 4c has a shorter flow rate until the heated atomized gas 13 collides with the molten metal 2, the loss of the flow velocity of the heated atomized gas 13 becomes smaller, and the shear force of the molten metal increases. The structure is arranged in the immediate vicinity of the molten metal nozzle 9.
Here, an angle formed by the atomizing gas injection port 4c and the pouring nozzle 9 is shown in FIG. 2 as a collision angle θ. By setting the collision angle θ to 15 ° or more and 30 ° or less, the molten metal can be effectively sprayed, and a fine metal powder can be obtained efficiently.
[0033]
FIG. 3 is an enlarged plan view of the atomized gas injection port portion of FIG. 2 viewed from below. As shown in the drawing, the inside of the opening tip of the pouring nozzle 9 is a molten metal outlet 9a, and the outer periphery of the pouring nozzle 9 is an atomizing gas injection port 4c.
If the diameter of the molten metal outlet 9a, the diameter of the pouring nozzle 9, and the diameter of the outer peripheral portion of the atomizing gas injection port 4c are D1, D2, and D3, respectively, the dimensions of D1, D2, and D3 are, for example, 2 mm and 4 mm. , 6 mm.
[0034]
Next, the inside of the atomizing container 4 will be described.
As shown in FIG. 1, the upper side surface of the atomizing container 4 is a cylindrical shape, and the lower part is a cone portion 4 a having a truncated cone shape. An opening provided at the lowermost portion of the cone portion 4 a is connected to the recovery container 5. The atomization container 4 and the recovery container 5 are configured to be airtight in order to prevent oxidation of the molten metal, and are maintained below a predetermined oxygen concentration by nitrogen gas being sealed in advance. Here, the atomized container 4 is sprayed with an atomized gas 13 heated to a melting point or higher of the metal, so that the atomized molten metal particles 14 fall in the atomized container 4 and are appropriately formed in the cone portion 4a. It is high enough to be cooled. The collection container 5 may be disposed outside the atomizing container 4 or separately from the atomizing container 4, but may be provided integrally with the inside of the atomizing container 4.
[0035]
As shown in FIG. 1, the fine metal powder manufacturing apparatus 1 of the present invention is provided with a cooling means 7 for cooling the cone portion 4a of the atomizing container 4. As the cooling means 7, a water-cooled jacket for cooling by circulating cooling water can be used.
[0036]
Bi, Cd, Ga, In, Sn, Zn, etc. are applicable as the metal material of the fine metal powder. Or the alloy which consists of two or more types of metals selected from these metals may be sufficient.
Further, for example, an In alloy or Sn alloy in which one or more metals selected from Ag, Bi, Cd, Cu, Ga, Hg, Sb, Sn, Zn, etc. are added to In or Sn. Is also applicable.
[0037]
Next, with reference to FIG. 1 thru | or FIG. 3, the manufacturing method of the fine metal powder by the gas atomizing method of this invention is demonstrated.
First, a raw metal material is put into the crucible 3 and heated to a melting point of the metal or higher by the crucible heater 8 to form the molten metal 2.
Next, the molten metal 2 in the crucible 3 flows down through the pouring nozzle 9 and the atomized gas 13 heated to a temperature equal to or higher than the melting point of the metal material from the atomized gas injection port 4c flows into the molten metal flow. Against.
FIG. 1 schematically shows a state in which the molten metal particles 14 sprayed and atomized by the heated atomizing gas 13 spread in a conical shape downward in the atomizing container 4.
[0038]
In this way, the atomized molten metal particle stream 14 is sprayed in the atomizing container 4, flows in a sufficient residence time, floats in the air, and gradually drops up and down repeatedly. . The molten metal particle flow 14 is solidified in the atomizing container 4 by flowing and dropping in this sufficient residence time. Further, the heat possessed by the solidified fine metal powder collides with the cone portion 4 a cooled by the water cooling jacket 7 and is removed by being cooled until it falls into the collection container 5. In FIG. 1, the fine metal powder 15 which collides with the cone part 4a is shown typically. Thereby, since the particles of the fine metal powders 14 and 15 do not aggregate in the collection container 5, the fine metal powder 16 is efficiently collected in the collection container 5.
[0039]
According to the method for producing fine metal powder by the gas atomizing method of the present invention, when the flow rate of the molten metal flow is 1 kg / min to 2 kg / min, the pressure of the atomizing gas 10 before heating the atomizing gas 10 is 3 kgf / cm²-10kgf / cm²And a flow rate of 0.6 Nm^Three/Min~1.5Nm^ThreeBy supplying the atomized gas 10 at a temperature equal to or higher than the melting point of the metal material and injecting it, the fine metal powder 16 having an average particle size of 30 μm to 100 μm can be efficiently produced regardless of the type of metal. can do.
Here, the average particle diameter is d50 particle diameter. The d50 particle size is a particle size at which the cumulative weight is 50% by measuring the weight of fine metal powder in each particle size classification classified by sieving.
The pressure of the atomizing gas 10 may be an atomizing gas pressure that is 1/3 to 1/2 or less that of the conventional gas atomizing method, so that the manufacturing apparatus can be realized at low cost. Further, since the consumption of the atomizing gas 10 is reduced, a fine metal powder can be produced at a low cost.
[0040]
Next, according to the present invention, when the fine metal powder is produced at a flow rate of the molten metal of 1 kg / min to 2 kg / min, the atomizing gas 13 heated at a temperature equal to or higher than the melting point of the metal material is used. The pressure of 10 is 3kgf / cm²-10kgf / cm²The reason for this will be described.
First, the reason for heating the atomized gas will be described. By heating the atomizing gas 10 using the atomizing gas heating heater 12, the volume of the heated atomizing gas 13 is constant because the pressure of the atomizing gas (10, 13) before and after the heating is constant. From the law, the ratio is increased by the ratio of the heated temperature T2 (absolute temperature: K) to the room temperature T1 (K) before heating, that is, T2 / T1. For example, when the atomizing gas 10 is heated from room temperature 25 ° C. to 500 ° C. and 1000 ° C., the volume of the heated atomizing gas 13 increases 2.6 times and 4.2 times, respectively. When the volume of the atomizing gas 10 is increased by heating, the flow velocity of the heated atomizing gas 13 injected from the atomizing gas injection port 4c is increased. Therefore, 7 kgf / cm at room temperature 25 ° C.²The flow rate when the atomized gas 10 was heated to 500 ° C. was 18 kgf / cm without heating the atomized gas 10 at room temperature.²This corresponds to the flow rate obtained when the value is increased. From this, even when the pressure of the atomizing gas 10 is lowered, the flow rate of the heated atomizing gas 13 injected at the atomizing gas injection port 4c is increased by increasing the temperature of the atomizing gas 10.
[0041]
Moreover, the molten metal flow colliding with the heated atomizing gas 13 goes through the steps of thin plate → string shape → dividing → sphericalization. If cooling is too early at the stage where the molten metal stream is spheroidized, the solidification time required for spheronization cannot be obtained, resulting in irregular particles. However, by using the heated atomizing gas 13, It becomes possible to take a sufficient time for the spheroidization of the molten metal flow.
Therefore, by heating the atomizing gas 10 to a temperature equal to or higher than the melting temperature of the metal, the flow rate of the heated atomizing gas 13 is increased, and the particle diameter of the metal proceeds in the direction of decreasing. The spheroidization is sufficiently advanced, and the fine metal powder 16 can be efficiently produced.
[0042]
Next, the pressure range of the atomizing gas 10 is 3 kgf / cm.²-10kgf / cm²As a fine metal powder is manufactured. The pressure of the atomizing gas 10 is 10 kgf / cm²If it becomes above, equipment costs, such as a compressor and piping which manufacture compression atomized gas, will start. On the other hand, the pressure of the atomizing gas 10 is 3 kgf / cm.²In the following, it is necessary to increase the flow rate of the atomizing gas 10 for forming metal fine particles, which increases the cost, which is not preferable.
In addition, in the manufacturing apparatus 1 of the fine metal powder used for this invention, the atomizing gas 10 before a heating is 0.6 Nm.^Three/Min~1.5Nm^ThreeThe flow rate is about / min. Where 1 Nm^Three/ Min is 1 m at 0 ° C. and 1 atm (atmospheric pressure)^ThreeFlow rate per minute.
In the apparatus for producing fine metal powder according to the present invention, since the atomizing gas 10 can be at a low pressure, the equipment of the high-pressure atomizing gas compressor used in the conventional gas atomizing method can be used even if the equipment cost of the heater 12 for atomizing gas heating is added. The cost is lower than the cost.
[0043]
Next, the reason why the fine metal powder is manufactured with the collision angle in the range of 15 ° to 30 ° will be described. When the collision angle θ is 30 ° or more, the heated atomizing gas 13 flows backward from the molten metal nozzle 9, so-called blowing occurs, and the molten metal 2 cannot be sprayed. On the other hand, when the collision angle θ is 15 ° or less, the average particle diameter of the fine metal powder 16 becomes large, which is not preferable. This is because when the collision angle θ is 15 ° or less, the collision distance between the heated atomizing gas 13 and the molten metal flow becomes longer, the flow velocity of the heated atomized gas 13 becomes slower, and the force that breaks the molten metal flow. This is presumably because the metal melt 2 cannot be atomized efficiently.
[0044]
Next, the cooling means installed in the cone part 4a of the atomizing container 4 will be described. After the atomized gas 13 is sprayed and dispersed in the molten metal stream and solidified, the fine metal powder 16 is recovered in the recovery container 5. By installing the water-cooling jacket 7 in the portion 4a and cooling only the cone portion 4a, the fine metal powder adhering thereto is sufficiently cooled, effectively aggregating the fine metal particles inside the collection container 5 Can be prevented. Further, even when the metal material is a low-melting-point metal, by increasing the cone portion 4a, the heat dissipation effect is further improved and the residence time in the atomizing container 4 is optimized, so that the low-melting-point metal having a slow solidification rate. However, since it can be sufficiently dispersed and solidified, the fine metal powder 16 of low melting point metal can be recovered with good yield. Thereby, the fine metal powder 16 can be efficiently recovered in the recovery container 5 without being aggregated in the atomization container 4 or the recovery container 5 from the dispersed molten metal stream 14 at the time of recovery.
[0045]
Examples of the method for producing fine metal powder by the gas atomizing method described above will be described.
Example 1
Using the fine metal powder production apparatus 1, fine metal powder of zinc (Zn) was produced. The diameter of the molten metal outlet 9a is 2 mmφ, and the sectional area of the atomizing gas injection port 4c is 35 mm.²It was. The molten metal temperature of zinc was 500 ° C. Moreover, nitrogen gas was used as the atomizing gas 10 and the nitrogen gas was heated to 500 ° C., which is the same as the zinc melt temperature.
The flow rate of the molten zinc flow rate is 1.2 kg / min, the nitrogen gas pressure before heating is 3 kgf / cm²Assuming that the flow rate of nitrogen gas is 0.6, 0.8, 1.4 Nm^ThreeThe fine zinc powder was prepared by changing the temperature within a range of / min. The fine metal powder of zinc thus obtained was measured for particle size with a dry laser particle size distribution analyzer (HELOS) to determine the d50 particle size.
[0046]
FIG. 4 is a table showing the d50 particle size of the fine zinc powder when the nitrogen gas flow rate is changed. Nitrogen gas flow is 0.6, 0.8, 1.4 Nm^ThreeThe d50 particle size at / min was 96 μm, 67 μm, and 59 μm, respectively. The d50 particle size decreases inversely with increasing nitrogen gas flow rate. Thereby, the nitrogen gas pressure before heating is, for example, 3 kgf / cm.²It can be seen that the d50 particle size, which is the average particle size of the fine zinc powder, can be controlled by changing the flow rate of the nitrogen gas at a constant value.
[0047]
FIG. 5 is a scanning electron microscope (SEM) photograph of fine zinc powder produced using the method for producing fine metal powder by the gas atomization method of the present invention. The electron acceleration voltage is 30 kV and the magnification is 150 times. From this SEM photograph, it can be seen that spherical fine zinc powder is obtained.
Thereby, since the nitrogen gas heated to the same temperature as the zinc melt was used as the heated atomizing gas 13, the nitrogen gas pressure before heating was 3 kgf / cm.²At such a low pressure, fine zinc powder having a d50 particle size of about 60 μm to 100 μm could be produced.
[0048]
(Example 2)
Using the fine metal powder production apparatus 1, indium (In) fine metal powder was produced. The diameter of the molten metal outlet 9a is 1.5mmφ, and the sectional area of the atomizing gas injection port 4c is 35mm.²It was. The melt temperature of indium was 200 ° C. Further, nitrogen gas was used as the atomizing gas 10 and the nitrogen gas was heated to 200 ° C., which is the same as the temperature of the indium melt. The flow rate of the indium melt flow rate is 1.1 kg / min, and the nitrogen gas pressure is 3 kgf / cm.²Or 5kgf / cm²The nitrogen gas flow rate is 0.6 to 1.2 Nm^ThreeThe fine indium powder was produced by changing the temperature in a range of / min. The d50 particle size of the fine indium powder thus obtained was measured in the same manner as described in Example 1.
[0049]
FIG. 6 is a table showing the d50 particle size of the fine indium powder when the nitrogen gas flow rate is changed. Nitrogen gas pressure before heating is 3 kgf / cm²And the nitrogen gas flow rate is 0.6, 1.0.0, 1.2 Nm^ThreeThe d50 particle size of the fine indium powder at / min was 90 μm, 54 μm, and 31 μm, respectively.
In this case as well, it can be seen that the d50 particle size of the fine indium powder decreases in inverse proportion to the increase in the nitrogen gas flow rate, as in the above zinc example. Thereby, the nitrogen gas pressure before heating is, for example, 3 kgf / cm.²It can be seen that the d50 particle size, which is the average particle size of the fine indium powder, can be controlled by changing the nitrogen gas flow rate at a constant value.
[0050]
Nitrogen gas pressure before heating is 5 kgf / cm²And the nitrogen gas flow rate is 0.6 Nm^ThreeThe d50 particle size of the fine indium powder at / min was 33 μm. The d50 particle size is such that the nitrogen gas pressure before heating is 3 kgf / cm.²And the nitrogen gas flow rate is 1.2 Nm^ThreeIt is almost the same as the d50 particle size at / min.
Therefore, if the d50 particle size is the same, increasing the nitrogen gas pressure before heating can reduce the nitrogen gas flow rate and reduce the consumption of nitrogen gas. In this way, the manufacturing cost can be further reduced. Thereby, since the nitrogen gas heated to the same temperature as the molten indium was used as the heated atomizing gas 13, the nitrogen gas pressure before heating was 3 kgf / cm.²Or 5kgf / cm²At such a low pressure, fine indium powder having a d50 particle size of about 60 μm to 100 μm could be produced.
[0051]
(Example 3)
Using the fine metal powder production apparatus 1, a fine metal powder of bismuth (Bi) was produced. The diameter of the molten metal outlet 9a is 1.5mmφ, and the sectional area of the atomizing gas injection port 4c is 35mm.²It was. The molten bismuth temperature was 300 ° C. Moreover, nitrogen gas was used as the atomizing gas 10 and the nitrogen gas was heated to 300 ° C., which is the same as the molten bismuth temperature. The bismuth melt flow rate is 1 kg / min, and the nitrogen gas pressure before heating is 3 kgf / cm.²The flow rate of nitrogen gas is 0.6, 1.4 Nm^ThreeThe fine bismuth powder was produced by changing the temperature within a range of 1 minute. The fine bismuth powder thus obtained was measured for d50 particle size in the same manner as described in Example 1.
[0052]
FIG. 7 is a table showing the d50 particle size of the fine bismuth powder when the nitrogen gas flow rate is changed. Nitrogen gas flow before heating is 0.6, 1.4 Nm^ThreeThe d50 particle size of the fine bismuth powder at / min was 65 μm and 30 μm, respectively.
Also in this case, as in the examples of zinc and indium, the d50 particle size of the fine bismuth powder is inversely proportional to the increase in the nitrogen gas flow rate, and the nitrogen gas pressure is set to 3 kgf / cm, for example.²It can be seen that the d50 particle size, which is the average particle size of the fine bismuth powder, can be controlled by changing the nitrogen gas flow rate while keeping the flow rate constant. Thereby, since the nitrogen gas heated to the same temperature as the molten bismuth was used as the heated atomizing gas 13, the nitrogen gas pressure before heating was 3 kgf / cm.²At such a low pressure, a fine bismuth powder having a d50 particle size of about 30 to 65 μm could be produced.
[0053]
(Example 4)
Using the fine metal powder production apparatus 1, a fine metal powder of tin (Sn) was produced. The diameter of the molten metal outlet 9a is 1.5mmφ, and the sectional area of the atomizing gas injection port 4c is 35mm.²It was. The molten metal temperature of tin was 300 ° C. Moreover, nitrogen gas was used as the atomizing gas 10 and the nitrogen gas was heated to 300 ° C., which is the same as the temperature of the molten tin. The molten metal flow rate is 1 kg / min, and the nitrogen gas pressure before heating is 3 kgf / cm.², The nitrogen gas flow rate is 1 Nm^ThreeFine tin powder was produced as / min. The fine tin powder thus obtained was measured for d50 particle size in the same manner as described in Example 1.
[0054]
FIG. 8 is a table showing the d50 particle size of the fine tin powder. Nitrogen gas flow rate is 1 Nm^ThreeThe d50 particle size of the fine tin powder at / min was 44 μm.
Thereby, since the nitrogen gas heated to the same temperature as the molten tin was used as the heated atomizing gas 13, the nitrogen gas pressure before heating was 3 kgf / cm.²A fine tin powder having a d50 particle size of 44 μm could be produced at such a low pressure.
[0055]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these are also included in the scope of the present invention. . For example, in the above embodiment, examples of the molten metal flow rate, the pressure and flow rate of the atomized gas, the heating temperature, etc. have been shown, but these parameters change depending on the cross-sectional area of the atomized gas injection port, etc. Needless to say, the value can be appropriately changed. Further, the metal material is not limited to the above embodiment, but can be applied to other metals and intermetallic alloys.
[0056]
【The invention's effect】
As understood from the above description, according to the present invention, in the gas atomization method, by atomizing the atomized gas heated to a temperature equal to or higher than the metal melting point by heating the atomized gas at a low pressure and a low flow rate, Fine metal powder can be produced with good yield. At this time, since the consumption amount of the atomizing gas is small, the fine metal powder can be produced at a low cost.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a fine metal powder production apparatus suitable for a fine metal powder production method by a gas atomization method of the present invention.
2 is an enlarged cross-sectional view showing a configuration of an atomizing gas injection port portion in the fine metal powder manufacturing apparatus of FIG. 1; FIG.
FIG. 3 is an enlarged plan view of the atomized gas injection port portion of FIG. 2 as viewed from below.
FIG. 4 is a table showing the d50 particle size of fine zinc powder when the nitrogen gas flow rate is changed.
FIG. 5 is a scanning electron microscope (SEM) photograph of fine zinc powder produced using the method for producing fine metal powder by the gas atomization method of the present invention.
FIG. 6 is a table showing the d50 particle size of fine indium powder when the nitrogen gas flow rate is changed.
FIG. 7 is a table showing the d50 particle size of fine bismuth powder when the nitrogen gas flow rate is changed.
FIG. 8 is a table showing the d50 particle size of fine tin powder.
[Explanation of symbols]
1 Fine metal powder production equipment
2 Molten metal
3 crucible
3a Through hole
4 Atomized containers
4a Cone part
4b Channel part
4c Atomizing gas injection port
4d atomizing gas flow path
5 collection containers
6 frame
7 Cooling means
8 Heater for crucible heating
9 Pouring nozzle
9a Metal melt outlet
10 Atomized gas
11 Atomized gas piping
12 Heater for atomizing gas heating
13 Heated atomized gas
14 Molten metal particle flow
15 Fine metal powder colliding with cone
16 Fine metal powder

Claims (4)

  A method for producing a fine metal powder by injecting an atomized gas heated above the melting point of a metal against a molten metal flow,
  3kgf / cm² -10kgf / cm² At a constant pressure in the range of0.6 Nm³ /Min~1.5Nm³ / MinControl the flow rate in the range ofThe supplied atomizing gas is heated and injected so that the collision angle is 15 ° or more and 30 ° or less with respect to the molten metal flow of 1 kg / min to 2 kg / min.The average particle size was controlled to 30 μm to 100 μmA method for producing a fine metal powder by a gas atomizing method, comprising producing a fine metal powder.   The method for producing a fine metal powder according to claim 1, wherein the fine metal powder is cooled by a cooling means. Said metals, Bi, Cd, Ga, In , Sn, any one metal of Zn or, characterized in that an alloy consisting of two or more metals selected from these metals, claim 1 Or the manufacturing method of the fine metal powder by the gas atomizing method of 2 . The metal is an In alloy obtained by adding one or more metals selected from Ag, Bi, Cd, Cu, Ga, Hg, Sb, Sn, and Zn to In . 4. A method for producing a fine metal powder by the gas atomizing method according to any one of 3 above.

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