JP2018095915A - Metal powder production method and production apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a fine metal powder in which the amount of impurities is reduced, at low cost, and to provide an apparatus therefor.SOLUTION: The metal powder production method includes a water atomization process of blowing a high pressure water 13 to a molten metal particle 12 to pulverize the molten metal particle 12. The molten metal particle 12 is supplied by, for example, ejecting a high-temperature fluid of a melting point of the molten metal 10 or higher to the molten metal 10 to coarse-pulverize the molten metal 10. By executing the water atomization process on the metal particle in the molten state, it is possible to effectively pulverize the metal particles having a small particle size, and thereby producing a fine metal powder.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method and an apparatus for producing a metal powder, and more particularly to the production of a fine metal powder.

  Metal powder is an important material in the industry, and is used in various applications such as electronic materials, catalysts, battery active materials, tools, pharmaceuticals, and jewelry depending on the characteristics. Among these, in applications such as electronic materials, miniaturization and integration of products such as electronic devices manufactured in recent years have rapidly progressed, and further miniaturization of metal powder has been demanded, and fine metals of 1 μm or less are required. There is a need for powder.

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

  In addition, there are a gas atomizing method (for example, Patent Document 2), a method for spraying a plasma jet onto a metal material (for example, Patent Document 3), and a method for injecting a flame jet onto molten metal (for example, Patent Document 4). Furthermore, for example, Patent Document 5 suggests that the water atomization method and the gas atomization method are used in combination. 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 metal powder manufacturing method in which a flame jet is jetted onto a molten metal and the molten metal powder obtained by the jet of the flame jet is cooled with a cooling medium. This is an attempt to reduce the cost of various facilities and apparatuses by using a water atomizing method, and to provide metal powder at a lower cost.

Japanese Patent Laid-Open No. 2006-141817 JP 56-146804 A JP-A-5-179316 International Publication No. 2012/157733 JP 2010-245460 A JP, 2014-136807, A

  However, in the water atomization method described in Patent Document 1, cooling is performed simultaneously with the pulverization of the molten metal, and the viscosity of the molten metal is increased. Therefore, the particle size of the metal powder obtained by the water atomization method is usually about several μm to several tens of μm, and a powder having a submicron particle size cannot be obtained.

  Further, in any of the methods described in 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, as described in Patent Document 5, the water atomization method and the gas atomization method are also used in combination, because the molten metal is cooled and solidified when it comes into contact with the gas or the viscosity of the molten metal increases. There is a problem that pulverization by atomization becomes insufficient and there is a limit to refinement of pulverization.

  Patent Document 6 describes that a high-pressure pump used in the water atomization method is unnecessary, and the injection of the cooling medium in Patent Document 6 is intended only for cooling. As described above, the particle diameter of the metal powder obtained by independently jetting either the frame as in Patent Document 6 or gas or water is about several μm to several tens of μm. It is not possible to meet the needs for future refinement of metal powder in applications.

  On the other hand, as a method for producing metal powder, a wet reaction in which metal powder is synthesized by reducing metal ions in a solution is also known. According to the wet reaction process, it is known that finer metal powders can be obtained than with the water atomization method, etc., but since various chemicals are used in the reaction, these are mixed into the metal powder as impurities. There is. Furthermore, the wet reaction is more expensive than the water atomization method.

  In order to solve the above problems, an object of the present invention is to provide a method for manufacturing a fine metal powder with a reduced amount of impurities at a low cost, and an apparatus therefor.

  In order to solve the above problems, the present invention provides a method for producing a metal powder, which includes a water atomization step of pulverizing the molten metal particles by spraying high-pressure water onto the molten metal particles.

  The molten metal particles may be supplied by jetting a high-temperature fluid having a melting point of the molten metal or higher to roughly pulverize the molten metal. The high-temperature fluid is preferably at least one selected from the group consisting of a flame, plasma, and high-temperature gas. The supply of the molten metal particles may be performed by ejecting the high-temperature fluid at a higher speed than the falling speed of the molten metal while dropping the molten metal.

  The water atomization step may be performed by spraying the molten metal particles with high-pressure water having a water pressure of 90 to 160 MPa and a water amount of 100 L / min or more.

  Further, the present invention is an apparatus for producing metal powder from molten metal particles using a water atomizing method, the supply means for supplying molten metal particles, and a high pressure on the molten metal particles supplied by the supply means Provided is a metal powder manufacturing apparatus having a high-pressure water injection mechanism for spraying water.

  The supply means includes a molten metal supply means for supplying a molten metal, and a high-temperature fluid injection mechanism for injecting a high-temperature fluid having a melting point of the molten metal or higher with respect to the molten metal supplied by the molten metal supply means. You may have. The high temperature fluid ejecting mechanism may be a frame jet ejecting mechanism.

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

It is a figure which shows the outline of the manufacturing apparatus of the metal powder concerning embodiment of this invention.

  Embodiments of the present invention will be described below.

[Production method of metal powder]
First, the manufacturing method of the metal powder of this invention is demonstrated. The present invention is a method for producing metal powder from molten metal particles using an atomizing method. In the conventional atomizing method or the like, the pulverization force is insufficient, and as described above, a metal powder having a particle size of about several μm is obtained. In addition, the combined use of the water atomization method and the gas atomization method results in two-stage pulverization, but when the first atomization, gas atomization, is performed, the molten metal is pulverized and cooled to solidify or melt. Even if the state is maintained, the viscosity increases, and the subsequent pulverization by water atomization becomes insufficient.

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

  There are no particular limitations on the metal species targeted by the method for producing a metal powder of the present invention. However, according to the present invention, a fine metal powder can be provided, so that the metal used in applications where a fine powder is required. Is suitable as a target. Specific examples of such metals include one or more elements from Group 2 to Group 15 of the Periodic Table of Elements, and preferably from the viewpoint that the method for producing a metal powder of the present invention can be suitably applied. One or more of Au, Ag, Cu, Pd, Ni, Co, Al, Si, P, B, Ti, Cr, Fe, Zn, In, Sn, Te, Bi, Mg, and Mn may be mentioned. These metals may be used alone to form a metal powder, or a plurality of these metals may be used to form an alloy powder. Furthermore, a desired characteristic may be imparted to the obtained metal (alloy) powder by adding one or more metals as a main component and adding a small amount of other metals thereto.

<Supply of molten metal particles (coarse grinding step)>
In the present invention, the molten metal particles can be supplied by a known method. For example, the metal is heated to form a molten metal, and a high-temperature fluid having a melting point of the metal or higher is sprayed on the metal, whereby a shearing force is applied to the molten metal and coarsely pulverized. The method for 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 particles, the metal melted in the furnace or the like is dropped from the opening at the bottom, and the high-temperature fluid is injected into this. It is preferable to coarsely pulverize.

  The kind of the high-temperature fluid that can be used in such a coarse pulverization step is not particularly limited, but from the viewpoint of pulverization force, flame, plasma, and high-temperature gas are preferable as the high-temperature fluid that can be jetted at high speed. These may be used alone or in combination of two or more. Further, the molten metal may be coarsely pulverized a plurality of times by spraying them in multiple stages. As a result, the particle diameter of the molten metal particles supplied to the next water atomization step is reduced, and the metal powder finally obtained is considered to be finer. From the viewpoint of cost, a frame is particularly preferable as the high-temperature fluid.

  The temperature of the high-temperature fluid may be higher than the melting point of the metal to be coarsely pulverized, but since the molten metal particles generated thereby undergo a certain amount of cooling before moving to the next water atomization process, the molten metal particles are cooled by this cooling. It is desirable not to increase the viscosity. That is, it is desirable that the temperature of the high-temperature fluid be set to such an extent that energy sufficient to prevent the viscosity of the molten metal particles from increasing is taken into consideration from 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 an appropriate shearing force can be applied to the molten metal. However, when the molten metal is dropped from a furnace or the like as described above, it is preferably faster than the dropping speed. From the viewpoint, it is more preferably 100 m / s to 2500 m / s. More preferably, it is good in it being 150m / s-2000m / s. Molten metal particles are supplied by the above coarse pulverization step.

<Water atomization process>
Next, a water atomization process is demonstrated. For example, the molten metal particles are pulverized by spraying high-pressure water on the molten metal particles supplied by the coarse pulverization process as described above, and a fine metal powder is produced.

  In the water atomization step, the molten metal particles are preferably filled with water at a water pressure of 90 to 160 MPa (more preferably 120 MPa to 160 MPa), preferably at least 100 L / min (more preferably 130 L / min to 160 L / min). Spray. The pH of the water used for this is not particularly limited, but a pH range that corrodes or dissolves the metal is 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, and the average primary particle size is about submicron to 1 μm. Furthermore, according to the present invention, since the powder is produced without using various chemical agents as in the wet reaction, the amount of impurities in the obtained metal powder is small, and various disadvantages (for example, the powder is reduced). Gas generation during firing) is improved. Because of these characteristics, the metal powder produced by the method for producing metal powder of the present invention depends on the metal species, but various electronic materials, catalysts, battery active materials, tools, pharmaceuticals, jewelry, and the like. Available for use.

  In addition, although the slurry which metal powder disperse | distributed in water is obtained by water atomization, this slurry is filtered, metal powder is collect | recovered, Furthermore, this may be washed with water, dried, pulverized, classified.

  Even with the conventional atomization method, the metal powder produced may contain submicron size particles, and it is possible to recover only that by a method such as classification, but the collection from the starting material is not possible. The rate is less than 1% and is not practical. On the other hand, in the present invention, the metal particles are effectively pulverized by water atomization of the molten metal particles, so that it is possible to produce a metal powder having a submicron size with a higher yield than conventional. Can be industrially useful.

[Metal powder production equipment]
Next, with reference to the example of the manufacturing apparatus of the metal powder concerning embodiment of this invention, specific embodiment of the manufacturing method of the metal powder of this invention is described. FIG. 1: is sectional drawing which shows the manufacturing apparatus of the metal powder concerning embodiment of this invention, and shows the mode at the time of manufacture of a metal powder.

  The manufacturing apparatus 1 includes a supply unit 2 that supplies molten metal particles 12 and a high-pressure water injection mechanism 5 that blows high-pressure water 13 onto the molten metal particles 12 supplied by the supply unit 2. Specifically, the supply unit 2 includes a molten metal supply unit 3 (for example, a tundish) that supplies the molten metal 10 and a high-temperature fluid injection mechanism 4 (for example, a frame jet injection) that injects a high-temperature fluid having a melting point of the molten metal 10 or higher. Mechanism). Hereinafter, the molten metal supply means will be described as the tundish 3, and the high-temperature fluid injection mechanism will be described as the frame jet injection mechanism 4.

  The tundish 3 serving as a means for supplying the molten metal 10 can melt the metal by heating it to a melting point or higher. The tundish 3 accommodates the molten metal 10 and has a nozzle 3a for discharging the molten metal 10 on the bottom surface. Yes. The molten metal 10 in the tundish 3 is heated to a temperature equal to or higher than the melting point and the temperature is maintained, and the molten metal 10 can be dropped downward through the nozzle 3a.

  Below the tundish 3, a jet burner as a frame jet injection mechanism 4 is provided. 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 falling from the nozzle 3a so as to be symmetrical. The jet burner injects a high-temperature frame 11 equal to or higher than the melting point of the molten metal 10 from the outer peripheral side of the molten metal 10 to the falling molten metal 10 obliquely downward. The injection speed of the frame 11 is higher than the falling speed of the molten metal 10. For example, when the falling speed of the molten metal 10 is about 2.0 m / s, the injection speed is about 150 to 2500 m / s. By such a frame jet injection mechanism 4, a coarse pulverization step of coarsely pulverizing the molten metal 10 falling from the nozzle 3 a is performed, and the molten metal particles 12 that have been coarsely pulverized fall further downward. In addition, although it is preferable to inject the flame | frame 11 at a small angle with respect to the molten metal 10 which falls, the flame jet injection mechanism 4 and the high-pressure water injection mechanism 5 Between them, you may install the barrel of a predetermined diameter so that the molten metal particle 12 may be wrapped (not shown).

  A high-pressure water injection mechanism 5 that blows high-pressure water is provided below the frame jet injection mechanism 4, and a water atomization process that blows high-pressure water 13 toward the molten metal particles 12 that are coarsely pulverized by the frame jet injection mechanism 4. I do. The high-pressure water injection mechanism 5 has a high-pressure pump and a plurality of water injection nozzles, and the water injection nozzles preferably inject the high-pressure water 13 obliquely downward on the outer peripheral side of the cross section of the flow of the molten metal particles 12. The molten metal particles 12 that are installed and fall are sprayed evenly over the entire outer periphery of the molten metal particles 12 from the outer peripheral side toward the obliquely downward direction. The injection of the high-pressure water 13 is preferably performed concentrically with the injection of the frame jet injection mechanism 4 from the viewpoint of the uniformity of the particle size of the metal powder 14. In this water atomizing step, the molten metal particles 12 are pulverized by jetting the high-pressure water 13 toward the molten metal particles 12 and rapidly solidifying them under the conditions of the water pressure and the amount of water described above.

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

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this example. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

  From the copper melt, the particle size of the copper powder obtained only by the water atomization method, and the copper powder obtained by the manufacturing method according to an example of the embodiment of the present invention, which is a combination of the pulverization process by the frame jet and the water atomization process The particle size was determined by simulation. The simulation was performed using the following formula (1) based on “Masazumi Hirai, viscosity estimation formula of molten alloy”.

ｄ：平均粒径（μｍ）
Ｋ：定数
η_Ｍ：溶湯の粘性（ｍＮ・ｓ／ｍ^２）
η_Ｇ：銅の動粘性係数（ｍ^２／ｓ）
Ｖ：溶融金属粒の速度（ｍ／ｓ）
ρ_Ｍ：溶湯の密度（ｋｇ／ｍ^３）
γ_Ｍ：銅の表面張力（ｍＮ／ｍ）
Ｄ：出湯ノズル径（ｍ）
Ｘ：溶融金属粒流量（ｋｇ／ｍｉｎ）／水流量（ｋｇ／ｍｉｎ）

d: Average particle diameter (μm)
K: constant η _M : viscosity of molten metal (mN · s / m ² )
η _G : Kinematic viscosity coefficient of copper (m ² / s)
V: Speed of molten metal particles (m / s)
ρ _M : Density of molten metal (kg / m ³ )
γ _M : copper surface tension (mN / m)
D: Hot water nozzle diameter (m)
X: Molten metal particle flow rate (kg / min) / water flow rate (kg / min)

Formula (1) is an empirical formula for the particle size of the powder obtained by the gas atomization method, and this was applied to determine the particle size of the powder obtained by the water atomization method. That is, by collecting a plurality of data on the average particle diameter d of the copper powder by water atomization and determining the numerical value of the constant K so as to match it, the equation (1) was adapted so that it could be used for the water atomization method. η _M , ρ _M , and γ _M were obtained when the temperature was 1600 ° C., and V = 1000 m / s, D = 0.002 m, and X = 0.0125.

  According to this calculation formula, the particle size of the copper powder obtained only by the water atomization method is about 3.0 μm, whereas in the manufacturing method according to the embodiment of the present invention, the particle size is 0.5 μm.

  The present invention can be applied when producing a fine metal powder from a molten metal.

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 2 Supply means 3 Tundish 4 Flame jet injection mechanism 5 High pressure water injection mechanism 10 Molten metal 11 Frame 12 Molten metal particle 13 High pressure water 14 Metal powder 21 Chamber

Claims (8)

  The manufacturing method of metal powder which has a water atomization process which sprays high pressure water with respect to a molten metal particle, and pulverizes the said molten metal particle.   The method for producing metal powder according to claim 1, wherein the molten metal particles are supplied to the molten metal by spraying a high-temperature fluid having a melting point of the molten metal or higher to roughly pulverize the molten metal.   The method for producing a metal powder according to claim 2, wherein the high-temperature fluid is at least one selected from the group consisting of a flame, plasma, and high-temperature gas.   4. The metal according to claim 2, wherein the supply of the molten metal particles is performed by ejecting the high-temperature fluid at a speed higher than a falling speed of the molten metal while dropping the molten metal. Powder manufacturing method.   The said water atomization process is a manufacturing method of the metal powder as described in any one of Claims 1-4 performed by spraying the high pressure water with a water pressure of 90-160 MPa and the amount of water of 100 L / min or more to the said molten metal particle. An apparatus for producing metal powder from molten metal particles using a water atomization method,
An apparatus for producing metal powder, comprising: a supply unit that supplies molten metal particles; and a high-pressure water injection mechanism that blows high-pressure water onto the molten metal particles supplied by the supply unit.   The supply means includes a molten metal supply means for supplying a molten metal, and a high-temperature fluid injection mechanism for injecting a high-temperature fluid having a melting point of the molten metal or higher with respect to the molten metal supplied by the molten metal supply means. The apparatus for producing metal powder according to claim 6.   The metal powder manufacturing apparatus according to claim 7, wherein the high-temperature fluid injection mechanism is a frame jet injection mechanism.

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