JP7328796B2 - METHOD AND APPARATUS FOR MANUFACTURING METAL POWDER - Google Patents

Description

The present invention relates to methods and apparatus for producing metal powders, and more particularly to the production of fine metal powders.

Metal powder is an important material in industry, and depending on its characteristics, it is used in various applications such as electronic materials, catalysts, battery active materials, tools, medicines, and jewelry. Among these, in applications such as electronic materials, the miniaturization of products such as electronic devices manufactured in recent years and the integration of product components have progressed rapidly. A method that can produce small metal powder with high yield is desired.

Conventionally, as a method for producing fine metal powder, for example, the water atomization method disclosed in Patent Document 1 is known, in which high-pressure water is sprayed on molten metal at a temperature of 1100° C. or higher to pulverize and rapidly cool the metal. Therefore, according to this method, metal powder can be provided at low cost.

In addition, there are a gas atomization method (eg Patent Document 2), a method of spraying a plasma jet onto a metal material (eg Patent Document 3), and a method of injecting a flame jet onto molten metal (eg Patent Document 4). Further, for example, Patent Document 5 suggests using both the water atomization method and the gas atomization method. This is considered to be a method in which the molten metal is first pulverized by the gas atomization method and then further pulverized by the water atomization method.

Further, for example, Patent Document 6 describes a method for producing metal powder in which a flame jet is injected into molten metal and the molten metal powder obtained by the injection of the flame jet is cooled with a cooling medium. Focusing on the cost, this is intended to reduce the cost of various equipment and devices required in the water atomization method and the like, and to provide a metal powder at a low cost.

JP 2016-141817 A JP-A-56-146804 JP-A-5-179316 WO2012/157733 JP 2010-245460 A JP 2014-136807 A

As described above, further miniaturization of metal powder is required.
In the water atomization method described in Patent Document 1, high-pressure water collides with the molten metal to apply a shearing force (this causes the molten metal to pulverize), and at the same time, rapid cooling occurs and solidifies, so that the powder obtained is There is a limit to miniaturization.

In addition, in any of the methods of Patent Documents 2 to 4, the force for pulverizing the molten metal is weak, and the particle size of the obtained metal powder is at most the same level as that of the water atomization method. Furthermore, in the method of using both the water atomization method and the gas atomization method as described in Patent Document 5, since the molten metal is cooled and solidified when it comes into contact with the gas, pulverization by water atomization is insufficient. However, there is still a problem that there is a limit to the fineness of the powder.

Patent Document 6 described above does not require a high-pressure pump such as that used in the water atomization method, and the injection of the cooling medium in Patent Document 6 is intended only for cooling. Therefore, the particle size of the metal powder obtained by the method described in Patent Document 6 is considered to be about the same as that of the metal powder obtained by the methods described in Patent Documents 1 to 5.

On the other hand, as a method for producing metal powder, a wet reaction is also known in which metal powder is synthesized by reducing metal ions in a solution. The wet reaction process is known to produce finer metal powder than the water atomization process, but the use of various chemicals in the reaction causes the problem of contamination of the metal powder with impurities. There is In addition, wet reactions are more costly than water atomization methods.

In order to solve the problems associated with the above-described conventional techniques, the present invention provides a method for producing, at a low cost, a metal powder with a reduced amount of impurities, which is finer than the metal powder obtained by the conventional water atomization method or the like, and The object is to provide an apparatus for

In order to solve the above problems, the present invention has a water atomization step of spraying high-pressure water at a water pressure of 90 MPa to 400 MPa to the molten metal particles to crush the molten metal particles, and the molten metal particles are turned into molten metal. On the other hand, the molten metal particles are supplied by jetting a high-temperature fluid having a temperature higher than the melting point of the molten metal and coarsely pulverizing the molten metal. The hot fluid is a frame, and the hot fluid is jetted from a plurality of positions symmetrical with respect to the centerline of the flow on the outer peripheral side of the cross section of the flow of the molten metal. , flames are jetted at the same inclination angle from the outer peripheral side with respect to the center line, and the high-pressure water is sprayed at a plurality of positions symmetrical with respect to the center line on the outer peripheral side of the cross section of the flow of the molten metal particles. Assuming that the flames are jetted in a straight line, the imaginary intersection point where the frames first collide with each other and the high-pressure water is in a straight line A value A (mm / MPa) obtained by dividing the distance between the virtual intersection where the high-pressure water first collides by the water pressure of the high-pressure water is 1.25 mm / MPa or more. A method for producing metal powder is provided.

The jet speed of the flame may be 500 m/s or more. Also, the flame ejection speed may be 1200 m/s or less. The water atomizing step may be performed by spraying high-pressure water at a water pressure of 90 MPa to 400 MPa and a water flow rate of 100 L/min or more onto the molten metal grains.

More preferably, the value A is 1.25 mm/MPa to 1.60 mm/MPa.

The present invention also provides an apparatus for producing metal powder from molten metal grains using a water atomization method, comprising: a feeding means for feeding molten metal grains ; a high-pressure water injection mechanism for spraying high-pressure water of 90 MPa to 400 MPa to pulverize the molten metal grains , wherein the supply means includes molten metal supply means for supplying molten metal, and the molten metal supply means supplied by the molten metal supply means. a high-temperature fluid injection mechanism for injecting a high-temperature fluid having a temperature equal to or higher than the melting point of the molten metal, wherein the high-temperature fluid injection mechanism is a flame jet injection mechanism, and the flame jet injection mechanism is the molten metal. A plurality of jet burners are installed on the outer peripheral side of the cross section of the flow of the molten metal supplied by the supply means so as to be symmetrical with respect to the center line of the flow. Flames are jetted at the same angle of inclination from the outer circumference side with respect to the line, and the high-pressure water injection mechanism is positioned symmetrically with respect to the center line on the outer circumference side of the cross section of the flow of the molten metal particles. It was assumed that a plurality of water injection nozzles were installed, and from each water injection nozzle, high-pressure water was injected at the same inclination angle from the outer peripheral side with respect to the center line, and flames were injected in a straight line from each jet burner. In this case, the distance between the virtual intersection where the frames first collide and the virtual intersection where the high-pressure water first collides, assuming that the high-pressure water is injected in a straight line from each water injection nozzle, is defined as the high-pressure water A value A (mm/MPa) divided by the water pressure of is 1.25 mm/MPa or more .

The molten metal supply means may have, at its bottom, a nozzle for pouring out and dropping the molten metal.

The value A is preferably 1.25 mm/MPa to 1.60 (mm/MPa).

Advantageous Effects of Invention According to the present invention, fine metal powder with a reduced amount of impurities can be produced at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the outline of the manufacturing apparatus of the metal powder concerning embodiment of this invention. FIG. 5 is an explanatory diagram of a distance X between virtual intersections;

Embodiments of the present invention will be described below.

[Method for producing metal powder]
First, the method for producing the metal powder of the present invention will be explained. The present invention is a method for producing metal powder from molten metal particles using an atomizing method. In the conventional atomizing method, etc., it was difficult to obtain fine metal powder efficiently due to insufficient pulverization force. In addition, in the combined use of the water atomization method and the gas atomization method, although it is formally a two-stage pulverization, the molten metal is pulverized and cooled and solidified when the gas atomization, which is the first pulverization, is performed. Subsequent comminution by water atomization is unsatisfactory.

Thus, even if the number of pulverizations is increased, fine metal powder cannot be obtained unless each pulverization is effectively performed. Therefore, in the present invention, by performing the water atomizing process on metal particles in a molten state, it is possible to more effectively pulverize metal particles having a relatively small particle size and produce fine metal powder. .

There is no particular limitation on the type of metal targeted by the method for producing a metal powder of the present invention. is suitable as a target. Specific examples of such metals include one or more of the elements of Groups 2 to 15 of the periodic table, and from the viewpoint that the method for producing a metal powder of the present invention can be suitably applied, Au, Ag, Cu, Pd, Ni, Co, Al, Si, P, B, Ti, Cr, Fe, Zn, In, Sn, Te, Bi, Mg, and Mn. These metals may be used singly to form a metal powder, or a plurality of these metals may be used to form an alloy powder. Furthermore, one or more metals may be used as the main material, and other metals may be added in small amounts to impart desired properties to the resulting metal (alloy) powder.

<Supply of Molten Metal Particles (Coarse Grinding Step)>
In the present invention, molten metal particles can be supplied by known methods. For example, a metal is heated to a temperature higher than its melting point to form a molten metal, and a high-temperature fluid having a temperature higher than the melting point of the metal is jetted to the molten metal, thereby imparting a shearing force to the molten metal and coarsely pulverizing it. The method of injecting the high-temperature fluid to the molten metal is not particularly limited, but from the viewpoint of the production efficiency of the molten metal grains, the metal melted in a furnace or the like is dropped from the opening at the bottom, and the high-temperature fluid is injected into it. Coarse pulverization is preferred.

Although the type of high-temperature fluid that can be used in such a coarse pulverization step is not particularly limited, flame, plasma, and gas are preferred as high-temperature fluids that can be jetted at high speed from the viewpoint of pulverization force. These may be used singly or in combination of two or more. Further, the molten metal may be coarsely pulverized multiple times by injecting these in multiple stages. As a result, the grain size of the molten metal grains supplied to the subsequent water atomization step is reduced, and the finally obtained metal powder is considered to be finer. From the viewpoint of cost, a flame is particularly preferable as the high-temperature fluid.

The temperature of the high-temperature fluid should be higher than the melting point of the metal to be coarsely pulverized. prevent it from solidifying. That is, the temperature of the high-temperature fluid is set to the extent that the molten metal granules can be given enough energy to maintain the molten state until the molten metal particles shift to the water atomization process, taking into consideration the specific heat of the molten metal, the contact time with the high-temperature fluid, and the like.

The injection speed of the high-temperature fluid is not particularly limited as long as it can impart an appropriate shearing force to the molten metal. from the viewpoint of 100 m/s to 2500 m/s. More preferably, it should be 150 m/s to 2000 m/s.

When a flame is used as the high-temperature fluid, the injection velocity (flow velocity) of the flame-forming gas (hereinafter also referred to as "flame-forming gas") is usually 240 m/s to 1500 m/s. In the present invention, when the hot fluid is a flame, the injection velocity of the flame forming gas is considered to be the injection velocity of the flame. From the viewpoint of reducing the particle size of the metal powder to be obtained, it is preferable that the injection speed of the flame forming gas, that is, the injection speed of the flame is 500 m/s or more. From the same point of view, the flame injection speed is preferably 1200 m/s or less, more preferably 630 m/s or less.

Also, the flame forming gas is a mixed gas of fuel gas and oxygen gas. As the fuel gas, any gas conventionally used for combustion can be used without particular limitation, and examples thereof include acetylene, propane, ethylene and methane. Among these, propane is preferable from the viewpoint of cost. In addition, for example, the theoretical combustion ratio of propane and oxygen is 1 (propane): 5 (oxygen) in molar ratio, but in actual combustion, part of the oxygen gas may not be used for combustion, or may be incomplete. To avoid burning, it is preferable to mix more oxygen than the stoichiometric burning rate.

In the coarse pulverization step, from the viewpoint of pulverization efficiency and equipment cost, it is preferable to prepare the molten metal in a furnace or the like, drop it from the opening at the bottom, and then spray the flame as follows. . That is, from a plurality of positions symmetrical with respect to the center line of the molten metal flow on the outer peripheral side of the cross section of the falling molten metal flow, from the outer peripheral side with respect to the center line of the molten metal flow. Shoot the flame at an angle of inclination. The details of this configuration will be described later with reference to FIGS. Note that the center line means a straight line passing through the center of the flowing molten metal in the direction of flow.

Molten metal grains are supplied by the coarse pulverization process described above.

<Water atomization process>
Next, the water atomizing process will be explained. For example, by spraying high-pressure water onto the molten metal particles supplied in the coarse pulverization step, the molten metal particles are further pulverized into powder, producing fine metal powder.

In the water atomizing step, the molten metal particles are preferably subjected to a water pressure of 90 MPa to 400 MPa (more preferably 100 MPa to 350 MPa, still more preferably 120 MPa to 280 MPa) and a water amount of 100 L/min or more (more preferably 130 L/min to 400 L). /min) to spray water. The pH of the water used for this is not particularly limited, but the pH range that corrodes or dissolves metals should be avoided.

The molten metal particles are sheared by being sprayed with high-pressure water to further reduce the particle size and rapidly solidify. The metal powder thus obtained is fine. Furthermore, according to the present invention, since the powder is produced without using various chemicals as in the wet reaction, the amount of impurities in the obtained metal powder is small, and various disadvantages resulting from this (for example, powder Gas generation at the time of firing) is improved. Due to these characteristics, the metal powder produced by the method for producing metal powder of the present invention can be used in various applications such as electronic materials, catalysts, battery active materials, tools, medicines, and jewelry, depending on the type of metal. available for use.

As described above, in the coarse pulverization step, the molten metal is dropped from a plurality of symmetrical positions on the outer peripheral side of the cross section of the flow of the molten metal at approximately the same inclination angle from the outer peripheral side with respect to the center line of the flow. It is preferred to jet the flame. From the viewpoint of the uniformity of the particle size of the metal powder to be produced, it is preferable that the high-pressure water jetting in the water atomizing step is performed concentrically with the flame jetting. That is, the high-pressure water is supplied from a plurality of positions symmetrical with respect to the center line of the molten metal flow on the outer peripheral side of the cross section of the flow of molten metal particles, and from the outer peripheral side with respect to the center line of the flow of molten metal. It is preferable to jet at substantially the same inclination angle. The details of this configuration will be described later with reference to FIGS.

In the case of this configuration, if the water pressure of the high-pressure water and the interval between the coarse pulverization by the flame and the water atomization by the high-pressure water satisfy a predetermined relationship, finer metal powder can be obtained. . Specifically, first, the above-mentioned interval is the virtual intersection point where the frames first collide, assuming that the flames are jetted in a straight line, and the point of intersection, assuming that the high-pressure water is jetted in a straight line. , is defined as the distance from the virtual intersection where the high-pressure water collides first (distance between virtual intersections). It should be noted that the assumption that both the flame and the high-pressure water were jetted "in a straight line" is because of the effects of gravity and negative pressure caused by the jetting of high-pressure water, and that they are not jetted in a perfect straight line. Because it is possible. In addition, "injected in a straight line" here means that each of the flame (flame-forming gas) and water is injected with the same diameter as the diameter of the injection port, and is injected without bending. to do). Furthermore, when the molten metal is coarsely pulverized multiple times, the above "virtual intersection point where the frames first collide" is the first flame to be sprayed against the molten metal (granulated) at the end. Let it be a virtual intersection that collides with

In this configuration, the value A (mm/MPa) obtained by dividing the virtual inter-intersection distance by the water pressure of the high-pressure water is preferably 1.25 mm/MPa or more. Due to the negative pressure caused by the injection of high-pressure water, the upper frame of the high-pressure water is sucked into the high-pressure water side. is smaller than the distance between virtual intersections. The degree of this decrease increases as the water pressure of the high-pressure water increases. In order for the molten metal to be sufficiently pulverized by the flame, it is considered desirable that there is a certain distance between the collision of the molten metal with the flame and the collision with the high-pressure water. Since the virtual intersection distance, which is an index thereof, is affected by the water pressure of high-pressure water as described above, the influence of water pressure was eliminated by dividing the former by the latter. The value A is more preferably 1.25 mm/MPa to 1.60 mm/MPa from the viewpoint of making the particle size of the metal powder to be produced particularly fine.

By carrying out the water atomization process, a slurry in which metal powder is dispersed in water is obtained. This slurry may be filtered to recover the metal powder, which may then be washed with water, dried, pulverized, and classified.

In the metal powder production method of the present invention described above, the metal particles are effectively pulverized by water atomizing the molten metal particles. can be manufactured.

[Metal powder manufacturing equipment]
Next, a specific embodiment of the metal powder manufacturing method of the present invention will be described with reference to an example of a metal powder manufacturing apparatus according to an embodiment of the present invention. FIG. 1 is a cross-sectional view showing a metal powder manufacturing apparatus according to an embodiment of the present invention, and schematically showing a state during metal powder manufacturing. Note that the ring-shaped portions denoted by reference numerals 4 and 5 are shown three-dimensionally.

The manufacturing apparatus 1 has a supply means 2 for supplying molten metal particles 12 and a high-pressure water injection mechanism 5 for spraying high-pressure water 13 onto the molten metal particles 12 supplied by the supply means 2 to pulverize the molten metal particles 12. are doing. Specifically, the supply means 2 includes a molten metal supply means 3 (for example, a tundish) for supplying the molten metal 10, and a high temperature fluid injection mechanism 4 (for example, a flame jet injection mechanism) for injecting a high temperature fluid having a temperature higher than the melting point of the molten metal 10. mechanism). In the following description, the molten metal supply means is the tundish 3 and the hot fluid injection mechanism is the flame jet injection mechanism 4 .

The tundish 3, which is a means for supplying the molten metal 10, can melt the metal by heating it to a temperature above its melting point, accommodates the molten metal 10, and has a nozzle 3a at the bottom for discharging the molten metal 10. there is The molten metal 10 in the tundish 3 is heated to a temperature equal to or higher than the melting point and maintained at that temperature, so that the molten metal 10 can drop downward through the nozzle 3a.

A jet burner as a flame jet injection mechanism 4 is provided below the tundish 3 . A plurality of jet burners are preferably installed on the outer peripheral side of the cross section of the flow of the molten metal 10 dropping from the nozzle 3a so as to be symmetrical with respect to the center line of this flow. Each jet burner uniformly jets a flame 11 having a high temperature equal to or higher than the melting point of the molten metal 10 toward the falling molten metal 10 obliquely downward from the outer peripheral side of the molten metal 10 .

Here, reference numeral 4a shown in FIG. 1 indicates the arrangement of injection ports of the jet burner as the flame jet injection mechanism 4 (hereinafter referred to as "flame injection port array 4a"). A plurality of jet burners are installed on the outer peripheral side of the cross section of the flow of the molten metal 10 falling from the nozzle 3a so as to be symmetrical with respect to the center line of this flow. Centered on the center line L of the flow of the molten metal 10 falling from 3a (a straight line passing through the center of the flow of the molten metal 10 in the flow direction), they are arranged in a ring shape that is mutually in the horizontal plane. In addition, from each jet burner, a flame 11 having a high temperature higher than the melting point of the molten metal 10 is applied to the falling molten metal 10 obliquely downward from the outer peripheral side of the molten metal 10 at the same angle of inclination with respect to the center line L. spray toward. As a result, the flame 11 is jetted downward from a plurality of jet burners (flame jet array 4a) in a substantially conical shape.

The injection speed of the flame 11 (the injection speed at the injection port of each jet burner) is higher than the drop speed of the molten metal 10. For example, when the drop speed of the molten metal 10 is about 2.0 m/s, the injection speed is It is about 100 m/s to 2500 m/s, preferably about 150 m/s to 2000 m/s. By such a flame jet injection mechanism 4, a roughly conical flame is jetted downward toward the molten metal 10 falling from the nozzle 3a, thereby performing a coarse pulverization step of coarsely pulverizing the molten metal 10. , the molten metal grains 12 that are coarsely pulverized fall further downward. A barrel with a predetermined diameter may be installed between the flame jet injection mechanism 4 and the high-pressure water injection mechanism 5 so as to wrap the molten metal particles 12 so that the molten metal particles 12 formed by coarse pulverization do not spread (Fig. not shown). The apex angle θ of the conical shape formed by the flame 11 is preferably 15° to 60°, assuming that the flame 11 jets in a straight line. In this case, the conical shape is the inner surface of the flame 11 in the injection direction when it is assumed that the inner edge of the injection port of each jet burner (the inner edge of the flame injection port array 4a) is the bottom surface and the flame 11 is injected in a straight line. Define. The meaning of "linearly injected" is the same as that explained in relation to the embodiment of the metal powder manufacturing method of the present invention.

A high-pressure water injection mechanism 5 for spraying high-pressure water is provided below the flame jet injection mechanism 4, and the high-pressure water 13 is sprayed toward the molten metal particles 12 coarsely pulverized by the flame jet injection mechanism 4 to melt the molten metal. A water atomizing step is performed to further pulverize the grains 12 . The high-pressure water injection mechanism 5 has a high-pressure pump and a plurality of water injection nozzles, and the water injection nozzles are positioned symmetrically with respect to the center line of the molten metal flow on the outer peripheral side of the cross section of the flow of the molten metal particles 12. It is preferable that a plurality of such devices are installed. Each water injection nozzle is installed to inject high-pressure water 13 obliquely downward toward the falling molten metal grains 12, and uniformly injects the falling molten metal grains 12 obliquely downward from the outer peripheral side. do.

Here, reference numeral 5a shown in FIG. 1 indicates the arrangement of injection ports of the water injection nozzle as the high-pressure water injection mechanism 5 (hereinafter referred to as “water injection injection port array 5a”). The center line L' of the flow of the molten metal particles 12 (the center of the flow of the molten metal 10 dropping from the nozzle 3a By arranging a plurality of water injection nozzles so as to be symmetrical with respect to the line L, the water injection nozzle array 5a is coarsely pulverized by the frame 11 and drops molten metal particles. 12 are arranged in a ring shape centered on the center line L' of the flow and in a horizontal plane with respect to each other. Further, from each water injection nozzle, high-pressure water 13 is jetted obliquely downward from the outer peripheral side of the molten metal grains 12 to the center line L' at the same inclination angle to the falling molten metal grains 12 . As a result, the high-pressure water 13 is jetted downward from the plurality of water injection nozzles (the water injection nozzle array 5a) in a substantially conical shape. Also in this case, the conical shape assumes that the inner edge of the injection port of each water injection nozzle (the inner edge of the water injection injection port array 5a) is the bottom surface, and the injection direction of the high pressure water 13 when it is assumed that the high pressure water 13 is injected in a straight line. defined by the inner surface of The meaning of "linearly injected" is the same as that explained in relation to the embodiment of the metal powder manufacturing method of the present invention.

As shown in FIG. 2, it is preferable that the high-pressure water 13 is injected concentrically with the injection of the flame 11 by the flame jet injection mechanism 4 from the viewpoint of the uniformity of the particle size of the metal powder 14 . That is, both the flame injection port array 4a and the water injection injection port array 5a are arranged in a ring shape around the center line L of the flow of the molten metal 10 falling from the nozzle 3a. In addition, when it is assumed that the flames 11 are jetted in a straight line, the apex of the conical shape formed by this (assuming that the flames 11 are jetted in a straight line from each jet burner, the frames 11 first collide with each other) A virtual intersection point 11a) and a cone-shaped apex formed by this when it is assumed that the high-pressure water 13 is injected in a straight line (when it is assumed that the high-pressure water 13 is injected in a straight line from each water injection nozzle, A value A (mm/MPa) obtained by dividing the distance between the virtual intersection 13a) where the high-pressure water 13 first collides with each other (hereinafter, “distance between virtual intersections X”) by the water pressure of the high-pressure water 13 is the metal to be manufactured. In order to enhance the effect of making the powder 14 finer, it is preferably 1.25 mm/MPa or more, and more preferably 1.25 mm/MPa to 1.60 mm/MPa.

The high-pressure water injection mechanism 5 injects the high-pressure water 13 toward the molten metal grains 12 under the water pressure and water volume conditions described above to further pulverize the molten metal grains 12 coarsely pulverized by the frame 11. The molten metal grains 12 are pulverized by being made finer and rapidly solidified at the same time.

The flame jet injection mechanism 4 and the high-pressure water injection mechanism 5 of the manufacturing apparatus 1 as described above are provided, for example, in the chamber 21, and the metal powder 14 is deposited on the bottom of the chamber 21 together with water as a slurry. The obtained slurry of the metal powder 14 is used as a product through processes such as filtering, washing with water, drying, pulverization, and classification.

Although the embodiments of the present invention have been described above, the present invention is not limited to such examples. It is obvious that a person skilled in the art can conceive various modifications or modifications within the scope of the technical idea described in the claims, and these are also within the technical scope of the present invention. be understood to belong to

[Example 1]
Copper powder was produced from molten copper using the apparatus for producing metal powder described with reference to FIG.

Specifically, copper was heated to 1300° C. in the tundish furnace 3 to form a molten metal, which was discharged from a nozzle 3 a provided at the bottom of the tundish furnace 3 .

A flame 11 is jetted from a plurality of jet burners installed at symmetrical positions with respect to the center line of the flow of the molten metal 10 on the outer peripheral side of the cross section of the flow of the molten copper 10 against the molten copper 10 discharged, The molten metal 10 was coarsely pulverized. Here, as the flame forming gas, a mixed gas of propane gas, oxygen gas and compressed air is used. The flow velocity was set to 510 m/s. By injecting these gases in the same direction, the flow velocity of the flame-forming gas is increased (the flow velocity as the flame-forming gas is 615 m/s) and the injection velocity of the flame 11 is increased. merged with The temperature of the frame 11 was measured by bringing a manual immersion optical fiber thermometer FIMTHERM-HMII manufactured by Materials Eco-Refine Co., Ltd. close to the nozzle of the jet burner.

Subsequently, high-pressure water 13 was sprayed from the high-pressure water injection mechanism 5 onto the molten metal grains 12 that had been coarsely pulverized by the frame 11 to pulverize them. Specifically, water was sprayed onto the molten metal grains 12 at a water pressure of 115 MPa and a water flow rate of 160 L/min in an air atmosphere to rapidly cool and solidify, thereby obtaining a slurry in which copper powder was dispersed in water. The slurry was filtered, and the resulting solid was washed with water and dried to obtain copper powder. The virtual inter-intersection distance X was 204.4 mm, and the value A obtained by dividing this by the water pressure of the high-pressure water 13 was 1.777 mm/MPa.

The BET specific surface area, tap density, particle size distribution, oxygen content and carbon content of the obtained copper powder were measured. Specifically, it is as follows.

BET specific surface area: Using a BET specific surface area measuring instrument (4Sorb US manufactured by Yuasa Ionics Co., Ltd.), nitrogen gas was flowed into the measuring instrument at 105°C for 20 minutes to deaerate, and then nitrogen and helium were mixed. It was measured by the BET one-point method while flowing gas (N ₂ : 30% by volume, He: 70% by volume).

Tap density: In the same manner as the method described in JP-A-2007-263860, a copper powder layer was formed by filling a bottomed cylindrical die with an inner diameter of 6 mm and a height of 11.9 mm up to 80% of the volume. A pressure of 0.160 N/m ² is uniformly applied to the upper surface of this copper powder layer, and after compressing the copper powder layer with this pressure until the copper powder is no longer densely packed, the copper powder layer is The height was measured, and the density of the copper powder was obtained from the measured value of the height of the copper powder layer and the weight of the filled copper powder, and this was taken as the tap density of the copper powder.

Particle size distribution: Measured at a dispersion pressure of 5 bar using a laser diffraction particle size distribution analyzer (HELOS & RODOS (airflow dispersion module) manufactured by SYMPATEC).

Oxygen content: Measured with an oxygen/nitrogen analyzer (EMGA-920 manufactured by Horiba, Ltd.).

Carbon content: Measured with a carbon/sulfur analyzer (EMIA-220V manufactured by Horiba, Ltd.).

The manufacturing conditions of the above copper powder are summarized in Table 1 below, and the measurement results are summarized in Table 2 below.

[Examples 2 to 6]
Propane gas flow rate (m/s), oxygen gas flow rate (m/s), compressed air flow rate (m/s), and virtual intersection distance X (mm) were changed as shown in Table 1 below. produced copper powder in the same manner as in Example 1, and carried out various measurements. The measurement results are shown in Table 2 below.

[Comparative Example 1]
Using a water atomizer, copper powder was produced under the same conditions as the water atomization process of Example 1. Specifically, copper is heated to 1,300° C. in an air atmosphere and molten metal is dropped from the bottom of a tundish furnace, and water is sprayed at a water pressure of 115 MPa and a water volume of 160 L/min in an air atmosphere from a water atomizer. The resulting slurry was filtered, and the resulting solid was washed with water and dried to obtain copper powder. Various measurements were carried out in the same manner as in Example 1 for the obtained copper powder.

The above results are shown in Tables 1 and 2 below.

In Table 2, the BET diameter is the particle diameter in terms of true spheres calculated from the BET specific surface area of the copper powder, and the formula "BET diameter = 6/(BET specific surface area x density of copper (8.94 g/cm ³ ) )”.

From the comparison of Comparative Example 1 and Example 1, it can be seen that the D90 of the resulting copper powder was reduced by combining coarse pulverization with a flame and further pulverization by water atomization, compared to the case where only water atomization was performed. .

Regarding the flow velocity of the flame-forming gas, that is, the flame injection velocity, from a comparison of Examples 2 to 5, when the flame-forming gas flow velocity was in the range of 615 m/s to 627 m/s, (compared to the copper powder obtained in the comparative example), ) A fine copper powder with small D50 and D90 was obtained. In Example 5, in which the flow rate of the flame forming gas was not within this range, the D50 of the copper powder was almost the same as that of the comparative example, but the D90 was smaller.

[Examples 7 to 10]
Using silver as a molten metal raw material, propane gas flow rate (m / s), oxygen gas flow rate (m / s), compressed air flow rate (m / s), virtual intersection distance X (mm), and water atomization Silver powder was produced in the same manner as in Example 1 except that the conditions (water pressure of high-pressure water and molten metal temperature) were changed as shown in Table 3 below, and various measurements were performed. The measurement results are shown in Table 4 below.

[Comparative Example 2]
Using a water atomizer, silver powder was produced under the same conditions as the water atomization process of Example 7. Specifically, silver was melted by heating it to 1600°C in an air atmosphere, and the molten metal was dropped from the bottom of the tundish furnace, and water was sprayed at a water pressure of 150 MPa and a water volume of 160 L/min in an air atmosphere from a water atomizer. The resulting slurry was filtered, and the resulting solid was washed with water and dried to obtain silver powder. Various measurements were carried out in the same manner as in Example 1 for the obtained silver powder.

The above results are shown in Tables 3 and 4 below.

From the comparison of Comparative Example 2 and Example 7, it can be seen that the D90 of the resulting silver powder was reduced by combining coarse pulverization with a flame and further pulverization by water atomization, compared to the case where only water atomization was performed. .

Regarding the relationship between the virtual intersection distance X and the water pressure of high-pressure water, from a comparison between Example 7 and Examples 8 to 10, by setting the value A to 1.25 mm / MPa or more, D50 and D90 are small, fine A silver powder was obtained.

Further, from a comparison between Examples 1 to 6 and Examples 8 to 10, when the value A is 1.25 mm/MPa to 1.60 mm/MPa, D50 is much smaller than when only water atomization is performed. It can be seen that a fine metal powder was obtained.

INDUSTRIAL APPLICABILITY The present invention is applicable to the production of fine metal powder from molten metal.

1 manufacturing apparatus 2 supply means 3 molten metal supply means (tundish)
3a Nozzle 4 High-temperature fluid injection mechanism (flame jet injection mechanism)
4a Frame injection port array 5 High pressure water injection mechanism 5a Water injection injection port array 10 Molten metal 11 Frame 11a Virtual intersection 12 Molten metal particles 13 High pressure water 13a Virtual intersection 14 Metal powder 21 Chamber X Distance between virtual intersections

Claims (8)

a water atomizing step of pulverizing the molten metal particles by spraying high-pressure water at a water pressure of 90 MPa to 400 MPa against the molten metal particles ;
The molten metal particles are supplied to the molten metal by injecting a high-temperature fluid having a temperature higher than the melting point of the molten metal to coarsely pulverize the molten metal,
The supply of the molten metal particles is performed by injecting the high-temperature fluid at a higher speed than the falling speed of the molten metal while dropping the molten metal,
The high-temperature fluid is a frame, and from a plurality of positions on the outer peripheral side of the cross section of the flow of the molten metal, symmetrical with respect to the center line of the flow, the same inclination angle from the outer peripheral side with respect to the center line. to fire the frame with
the high-pressure water is jetted from a plurality of positions on the outer peripheral side of the cross section of the flow of the molten metal particles symmetrically with respect to the center line at the same inclination angle from the outer peripheral side with respect to the center line;
A virtual intersection where the frames first collide with each other assuming that the flames are jetted in a straight line, and a virtual intersection where the high-pressure waters first collide with each other assuming that the high-pressure water is jetted in a straight line. is 1.25 mm/MPa or more . 2. The method for producing metal powder according to claim 1 , wherein the flame spray speed is 500 m/s or more. 3. The method for producing metal powder according to claim 2 , wherein the flame spray speed is 1200 m/s or less. The method for producing metal powder according to any one of claims 1 to 3 , wherein the value A is 1.25 mm/MPa to 1.60 mm/MPa. The method for producing metal powder according to any one of claims 1 to 4 , wherein the water atomizing step is carried out by spraying high-pressure water at a water pressure of 90 MPa to 400 MPa and a water flow rate of 100 L/min or more onto the molten metal particles. An apparatus for producing metal powder from molten metal particles using a water atomization method,
a supply means for supplying molten metal grains; and a high-pressure water injection mechanism for spraying high-pressure water at a water pressure of 90 MPa to 400 MPa onto the molten metal grains supplied by the feeding means to pulverize the molten metal grains ;
The supply means comprises a molten metal supply means for supplying molten metal, and a high-temperature fluid injection mechanism for injecting a high-temperature fluid having a temperature equal to or higher than the melting point of the molten metal to the molten metal supplied by the molten metal supply means. have
the high-temperature fluid injection mechanism is a flame jet injection mechanism,
The flame jet injection mechanism has a plurality of jet burners installed on the outer peripheral side of the cross section of the flow of the molten metal supplied by the molten metal supply means so as to be symmetrical with respect to the center line of the flow. and from each jet burner, flames are jetted at the same angle of inclination from the outer peripheral side with respect to the center line,
The high-pressure water injection mechanism has a plurality of water injection nozzles installed on the outer peripheral side of the cross section of the flow of the molten metal particles so as to be symmetrical with respect to the center line, and from each water injection nozzle, the High-pressure water is jetted at the same angle of inclination from the outer circumference with respect to the center line,
The imaginary intersection point where flames collide first when it is assumed that flames are jetted in a straight line from each jet burner, and the high-pressure water when it is assumed that high-pressure water is jetted in a straight line from each water injection nozzle. An apparatus for producing metal powder, wherein a value A (mm/MPa) obtained by dividing a distance from the first colliding imaginary intersection by the water pressure of the high-pressure water is 1.25 mm/MPa or more. 7. The apparatus for producing metal powder according to claim 6 , wherein said molten metal supply means has a nozzle at its bottom for discharging and dropping said molten metal. 8. The apparatus for producing metal powder according to claim 7 , wherein the value A is 1.25 mm/MPa to 1.60 mm/MPa.

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