JPS60500872A - Method of producing ultrafine metal powder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Method for producing ultra-fine metal powder field of invention The present invention relates to a method of manufacturing quenched fine metal powder.

Background of the invention U.S. Pat. No. 464 to 177 to Thompson The use of a flowing jet to atomize molten metal to form individual envelopes of metal. Discloses a method for producing oxidation-free powder metals and alloys by a method involving There is. The jet is directed into a reservoir outside the inert refrigerant stream to solidify and cool the particles. Prevents oxidation during cooling.

U.S. Patent No. 4,069,045 to Lnadgren describes a method for impinging a jet of molten metal on a rotating flat disk. . Relatively thin, brittle, easily crushed and virtually dendrite-free metal foil You will get a rake. These flakes are also described in U.S. Patent No. 4.064942. It is listed.

U.S. Pat. No. 4,221,587 to Ray describes a rotating cylinder Powder is produced by impinging a molten alloy jet at an acute angle on the inner surface of a shaped cooling rod. It is related to the method of As shown in column 5, the colliding molten metal is separated by individual liquids. broken up into a stream of drops, these bounce off the surface and move towards the cooling surface. Ru. Upon impact with a cold surface, the droplet solidifies rapidly. As shown in column 6 ``Glass-like metal powder Tateko... is capable of interlocking the particles during compaction.'' It has a relatively sharp notched edge that allows for ” Presented in the first example The particle size of the powder is as follows: 90% of the particles fall within the particle size range of approximately 25 to 50 microns. It's like waiting. In the second example, the particle size of the powder is 1oo~1000 In the micron range. Herbert Hermann and Haresh Bartha, 1980 AIM'FJ held October 5th-9th in Biffuppag, Pennsylvania. TMS-AIME Aloif was at the fall meeting of Metal Radio Rusocity. ``Plasma Spraying'' published in the newsletter of a symposium held by the In a paper entitled ``Metastable Phases Generated by Plasma Melt Particles onto a Substrate'' describes high-speed adhesion. On page 118, the paper describes solidifying liquid and This indicates that there should be good physical and thermal contact with the substrate. point of impact Are you completely separated? F! i. The expansion of dedication occurs. As shown in the drawing, the grains are the substrate. It has a flat surface next to it, drawing a central ridge area and a circular marginal area. FIG. 1 is a schematic diagram of an apparatus including a plasma spray apparatus and a drum.

Figure 2 is a schematic diagram of the equipment including the plasma spray equipment, substrate and air extraction equipment. be.

Figure 3 shows a plasma spray device, an endless belt, and a discharge device for substrate material. FIG.

Summary of the invention Atomized metal or metal alloy powder with a sheath circumference of 1 to 10 μm is suitable for It is desired for many applications such as and for rapid solidification processes. but, Particles in this size range are very difficult to obtain. Qi or liquid from Oriais The standard atomization technology that makes the flow of molten metal flow out produces particles within the above range. It is not effective to do so. Agglomeration and plasma melting are also not effective. Because It is possible to start the operation with an aggregate of approximately the same size as the final particle. This is because it is necessary. Agglomerates of very small dimensions are difficult to form and grain composition Uniformity in is even more difficult to obtain. In general, very fine powders are often atmospheric impurities such as oxygen, nitrogen or the grinding grain used to obtain small dimensions. It often contains a high content of impurities from

In accordance with the present invention, a substantial portion of the particles have a smooth curved surface and a flat surface of less than about 1 opm. A fine powder having a uniform particle size is provided.

Further, according to the present invention, a method of manufacturing ultrafine metal powder is provided. molten metal Two high streams of drops are directed onto the counter-Qianjiang surface. The melting threat collides with the surface and This causes the droplets to break apart and form broken droplets that are still in a molten state, and these rapidly is cooled to form a fine metal powder. The produced powder has a curved surface of about 1Q/ It consists of particles smaller than jfi.

detailed description High-speed flow of molten metal droplets is heat! It can be formed by lFl atomization. organic and non-organic A wide range of materials can be thermally atomized, including both machines. Typical ladders, as materials Examples include heat-resistant, high-density polymers such as aromatic polyester plastics. Ru. An example of such a polymer is the product name Econol by Bonrandom. Sold under (EKONOL). Ceramic materials are non-porous materials for thermal atomization and cermets.

Preferred powders are metals and metal alloys. Low melting point metals or alloys include zinc, lead, May contain silver or gold. Higher concentrations typically include copper, cobalt, iron and nickel. Metals and alloys with low melting points can also be used. Typically has a melting point of over 1800℃ Of particular interest are refractory metals and alloys that are Molyb is a heat-resistant metal. Examples include den, niobium, tungsten, tantalum, chromium alloys and mixtures thereof. Ru. The term "metal" refers to elemental metals, alloys, pure or mixed oxides of metals, borides, carbons, oxides and nitrides (with or without additives).

Due to the forces generated by the quenching, at least a portion of the dispersion is an amorphous phase or It also contains an f-shaped structure that includes metastable crystal lateral movement. By rapid cooling or by layering technique The most easily obtained metal alloys in the amorphous state are mixtures of transition metals. It is a thing. 5 required to achieve an amorphous state The cooling rate depends on the composition of the alloy.

In general, there is a small composition range in which an amorphous state can be obtained around each of the known compositions. exists. However, apart from quenching the alloy, among the many different alloys To predict with certainty which will produce amorphous metal according to given processing conditions There are no known practical guidelines.

Examples of amorphous alloys formed by rapid cooling are given in U.S. Pat. 2S No. 154, No. 198t No. 722, and others.

Amorphous and crystalline states are easily separated due to differences in X-melting diffraction measurements. Ru. The diffraction pattern of amorphous materials shows a wide halo similar to a liquid droplet. crystalline material lines Alternatively, a wide line diffraction pattern is produced. The amorphous alloy provided by the present invention Although it appears to be liquid when studied from the fold pattern, there are no observations regarding hardness and viscosity. Then, the nonalloy is solid. Amorphous alloy structures are inherently metastable, i.e. the state is non- It is in a state of equilibrium. Because atoms in an amorphous structure are not arranged in a periodic arrangement , the amorphous structure is in equilibrium at a given temperature through diffusion or segregation of alloy components. There is a tendency to transform into the crystal structure of

The quenched powder particles of the present invention preferably have at least about 80% particles of about 10 microns. It has a particle size distribution such that it has a smaller average particle size. Accurate composition and powder formation Depending on conditions, at least 90% of the particles have an average particle size of less than about 10 microns. Even smaller particle size distributions can be formed, such as those having Another particle distribution is approximately More than 80% of the particles are larger than about 0.5 microns and smaller than about 8 microns An example having an average particle size of

The particles of the present invention preferably include ultrafine portions of the molten material to give the particles a characteristic curved surface. It is cooled from a minute. Due to surface tension, the floating molten material will move to the best position that matches its Boosts the tendency to shrink until a small surface area is occupied. Due to the repellent properties of the anti-Yuee surface, Droplet formation is aided. The tendency of the molten material is to form spheres. If quenched 3 children If solidifies before assuming a spherical shape, or if the molten particles collide with the cooler, the molten part becomes Form round or elongated particles with rounded edges.

The powder of the present invention is characterized by an irregularly shaped profile that may have loose or rough edges. This is different from crushed or crushed powder.

Brunauer, Kmmett and Teller According to the (Te1ler) (BET) method and formulas for determining surface area and diameter. For example, particles of the present invention exhibit a BET diameter of about 172 ptrb to about 10 p''m. Ru.

The scanning electronics e, m (SE'M) photograph of the molybdenum powder book of the present invention is substantially smooth. A particle with a surface that has been milled is shown. Particles have arcuate and curved surfaces It is seen as a small prob or glob that is spherical and sinus. The particles are approximately 00 It consisted of cells of 1 to 11 μm, indicating that it was rapidly cooled.

In preparing the powder of the present invention, a high velocity stream of molten metal droplets is formed. instructor The flow is electric arc spraying, combustion spraying and plasma spraying. It can be formed by any thermal atomization technique such as atomization. Typically, the velocity of the droplet is about 1 o yx/sec or more, preferably about 2 o am/sec or more, more preferably 2 s am/sec or more. Speeds on the order of 9oom/sec or higher Under certain conditions to facilitate these speeds, which may include spraying in a vacuum It can be realized.

In a preferred method of the invention, the powder is fed through a thermal atomization device. Sending The feed powder is entrained in a carrier gas and then passed through the high temperature reactor. inside the reactor The temperature is preferably adjusted to allow for relatively short residence times in the reactor. higher than the melting point of the component with the highest melting point of the material, more preferably the vaporization temperature of the component with the lowest vaporization temperature of the material It is more than a degree.

The stream of dispersed entrained molten metal droplets is produced by a conventional plasma jet torch or can be generated by a mining device.

Typical plasma jet devices are of the resistance arc or induction type. in general, A source of metal powder is coupled to a source of propellant gas. Mixing gas and powder and transporting powder means for propelling the gas through the conduit communicating with the nozzle passage of the plasma atomizer; There are steps. With the arc i device, the conveyed powder passes through the center of the nozzle and sprouts. It is fed into a vortex chamber that communicates with and is coaxial with the perforated nozzle passage. a In arc-type plasma equipment, there is a gap between the inner wall of the nozzle passage and the electrode because it is inside the passage. An electric arc is maintained. The electrode is smaller than the nozzle passageway with which it is coaxial. Due to its small diameter, the gas is ejected from the nozzle in the form of a plasma jet. Ru. A power supply is usually a DC source suitable for carrying very large currents at relatively low voltages. It is. By adjusting the magnitude of arc power and gas flow rate, the torch temperature can be adjusted. It can range from 150°C to 1s, ooo°C. The device generally sprays It must be adjusted according to the melting point of the powder being used and the gas used. general When a low melting point powder is used with an inert gas such as nitrogen, the electrode The high melting point powder can be drawn into the chamber together with an inert gas such as argon. When used, the electrode can be fully extended within the nozzle.

In an induced plasma atomizer, the metal powder entrained in the inert gas is It is passed through a strong magnetic field at high speed to generate a voltage. Power source is IQ, 0 Adapted to carry very high currents on the order of OOA, but with voltages on the order of IQV. It can be made relatively low. These currents generate very strong direct magnetic fields. And it is required to create plasma. These plasma devices Additional means for assisting in the initiation of laser generation, for the torch in the form of an annular chamber around the nozzle It may include cooling means.

In plasma processes, the ionized gas inside the torch is ionized as it exits the nozzle. The ionization heat is recovered and an extremely powerful flame is created. In general, plas The flow of gas through the atomizer is provided at a velocity at least close to the speed of sound. teenager The superficial torch consists of conduit means with a converging portion converging downstream to the throat.

Since the convergence part communicates with the adjacent outlet openings, the ejection of plasma from the exit openings is prevented. It is caused by

Other types of engines, such as oxygen-acetylene types, flow high-pressure fuel gas through a nozzle. can be used. The powder can be introduced into the gas by suction. fuel is nozzle ignited at the outlet of the tube to provide a high temperature flame.

Preferably, the powder used for the torch is uniform in size and composition. and should be relatively free-flowing. Fluidity is powder into plasma flame desirable for aiding in the migration and infusion of Generally, fine powder (4 opm average diameter (below) do not exhibit good flow properties.

Under set flame conditions the largest particles may not completely melt and the smallest particles may A narrow size distribution is desired since there is a risk of heating to the point of oxidation. incomplete melting is detrimental to product uniformity, while vaporization and decomposition reduce process efficiency.

Typically, the size range of plasma-delivered powders is such that 80% of the particles are in the 30μ diameter range. and virtually all particles are within the 60μ range. .

U.S. Pat. A method is described for preparing dense, smooth, virtually spherical particles. spray drying By densifying the aggregates obtained by drying with plasma, they are typically combined into a molten material. Nongoldenable metals can be intimately mixed in a non-equilibrium phase to form a uniform powder composition .

The flow of conveyed molten metal droplets ejected from the nozzle tends to spread outwards, so the flow The droplet density inside decreases with increasing distance from the nozzle. Impact on repellent surfaces Prior to the drop, the flow typically passes through a gaseous atmosphere, which cools the droplet and cools it down. tends to reduce the speed of Cooling and velocity losses as the atmosphere approaches vacuum becomes smaller. The nozzle is placed firmly on the recalcitrant surface so that the droplet is in a molten state during impact. It is desired that they be located in close proximity.

If the nozzles are too far apart, the droplets may solidify before impact. If the nozzle If they get too close, the droplets will collide on top of the previously sprayed droplets, forming a pool of molten material. or increase droplet size. If the repulsive surface is curved, the flow will be directed toward the surface. Flow in the radial direction and, if the surface is flat, in the orthogonal direction is generally desired.

The repellent surface is preferably a molten material that increases the tendency of the material to form droplets on the surface. The surface is not wetted by the melting material. Wettability and relative surface energy of molten metal and surface Gee is the measurement of the contact angle through the liquid phase between the liquid phase of molten metal and the surface. It can be determined by In order to favor drop formation and wetability, a contact angle of greater than approximately 90° is used. It is preferable to have it. Typical surfaces include materials such as alumina, nitrided purple, and quartz. Lamic, aluminum, metal surfaces such as pots and dry ice (CO2) or contains an inert solid that can be liquid or solid at room temperature, such as ordinary ice (H2O). be caught. Preferably, the surface is smooth.

If the droplet impinges on the surface of the repellent method, it is typically the original. ; a solution that is at least about the volume of the It is divided into 9 fusion sections. After the collision, the molten part solidifies and bends into a substantially clean sword 1. A non-inventive powder is formed with a beveled surface. The melted part is a stirring surface. or by the atmosphere near the surface. repellent surface or Any cooling medium in the atmosphere is preferably below the freezing temperature of the molten material.

When a cooling atmosphere is used, the separated part will be free from rebound or re-rebound from the surface. It may also solidify. When the antiphlegm surface is the main cooling agent, the main quenching effect is It can occur on or near the surface.

The molten fragments on the surface tend to assume a spherical shape due to the repellency of the surface. The rebounding molten fragment tends to shrink to the minimum surface area corresponding to its volume. It is theorized that Tarizako tries to become spherical due to the fact that it has a spherical shape. be kicked. It is believed that high speed tends to increase fragmentation of particles. The droplet appears When colliding with a surface, the velocity component in the flying direction is parallel to the surface or relative to the surface. It is immediately converted into a velocity component in a direction that makes a slight angle. This force causes the droplet to Attempts to promote fragmentation.

The splitting, melting part and solidified particles that bounce back remove the splitting part from the path of the next flying droplet. Therefore, it is preferable to have a velocity component in a certain direction perpendicular to the flow direction. if If the nozzle is fixed against a repellent surface, this will allow the inert gas to This can be achieved by flowing the material along the surface at the original velocity. division The nozzle or surface is moved relative to the part of the particle entrained stream n that follows. sell. In order to prevent the droplets from colliding on the divided part, in other words, the divided droplets are separated from the flying droplets. It is desirable to take n out of the range of n.

FIG. 1 shows an apparatus for carrying out the method of the invention.

A plasma gun, shown schematically at 15, is shown. Gun 15 is a dragon It includes a nozzle radially directed at a repellent surface 17 in the form of a drum.

A high pressure gas source 19 communicates with a powder source 21 for transporting metal powder.

The end of the conveyance 8 is fed to the nozzle 15. D, C, power supply 26 connects nozzle 15 and plasma The element 23 for forming the matrix 25 is electrically connected to the element 23 . After impacting surface 17 , the fragmented particle portion is collected in a container 27. The drum is rotated and the particles bounce off The melting method gives the same rate of growth 7 and removes the divided portion 31 from the path of the incoming transport droplet. .

FIG. 2 illustrates yet another implementation of the invention, in which nozzle 51 is connected to a plasma stream. 53 to the rotating disk repellent surface 55. Another nozzle 57 rebounds and breaks off. The impingement location is directed to direct an inert gas flow 61 into portion 65 . divided part are exterminated towards N.59 and collected here.

FIG. 3 shows that the plasma from the nozzle 71 is transferred to a repellent material 75 such as dry ice. A specific example of another type of botanicals to be sent to a moving bed is shown below. The material 75 is the moving endless belt 7 9 is deposited from the bopper 7 at one end. The plasma 70 forms a divided portion 85. The divided part is placed on the other end of the endless belt 79. and collected in the container 81.

In Figures 1-3, the droplets in each plasma flow 25.53.70 The velocity is such that the droplets break off upon impacting the respective repellent surfaces 17.55 and 75. It is sufficient to form a minute. Surfaces 17.55 and 75 mm favor drop formation It is sufficiently repellent to allow for smoothing.

Higher particle size droplets will require higher speeds to break up the droplets.

It is believed that a turbulent gaseous medium next to a repellent surface can assist in solidification of repelled particles. It will be done. Allow a turbulent gas medium or a bouncing section to fall from a surface under the influence of gravity. Tightening can cause solidification of the separated portion away from the surface, thus making it less repellent. Allows the use of hard surfaces. Use of vacuum and separate the melted part back onto the repellent surface. Dropping may enhance solidification of the disconnected portion on the surface. In the latter case, high A highly repellent surface would be desired.

Implementation @1 Baystate, PG120-4, plasma gun fired indoors It was placed approximately 4 to 6 inches from the block of rice ice. Approximately 56%-2 70 to +325 mesh and has a size distribution of about 44% -'525 mesh Straw molybdenum e-bed (9″9.9% molybdenum) at approximately 1of3/hour The argon gas was supplied at a flow rate of &85 pints/hour. Al - Plasma gas was delivered to the torch at =1 of approximately 6of3/hour. torch Electric power G: about 30V at 600A.

The room had a nitrogen atmosphere. For the powder book, move the nozzle back and forth across the block. Dry ice was sprayed in a perpendicular direction onto a four-wheeled cart. Approximately 859 molybdenum powder were collected. Scanning electron micrographs show that about 90% of the particles are smaller than about 1θμ snow. and showed. At least some of the particles have been shown to have a cellular structure, with cells approximately α The dimensions were o1 to α1 μm. The particles had smooth curved surfaces that tended to be spherical. . However, the rapidly cooled particles were thought to be amorphous.

Example 2 In a similar manner to @1, the copper powder with starting dimensions of 0 to 40 pfn is about 1 to 1 The copper grain size was reduced to a grain size of Qpm. Starting powder is 1'00% 270 meth It had a smaller size distribution than S. The device used had a powder supply flow rate of 5.7 bons. powder/hour, plasma gas supply flow rate is 60 ft3/hour, and approximately 4052 powders per hour. Same as described in Example 1 except that was recovered. The final powder is the same as in Example 1. It showed a curved structure similar to the powder structure.

Example 6 In the same manner as in Example 2, powders consisting of nickel, chromium and boron were plasma blasted. Ta. The stamen powder, which was close to spherical in shape, had an amorphous diverticulate structure.

medicinal alms f114 In a similar manner to Example 1, the dry ice bed is made of quartz with high thermal shock resistance. The substrate surface is smooth and cooled with a ceramic substrate made of nitrogen. The gas was directed into the impingement zone tangentially to the plasma flow at the surface.

The collected rebound particles have a spherical shape and an average particle size of less than about 10 μm. It had

Engraving (no changes to the content) 7 Procedural amendment (formality) March 28, 1985 Mr. Manabu Boga, Commissioner of the Patent Office person who makes corrections Relationship to the incident: Patent applicant Name: GTE Predakku Corporation Agent 〒103 Address: Oil and Fat Industry Hall, 3-13-11 Nihonbashi, Chuo-ku, Tokyo \ζ−three,′ Target of correction Translation of drawing 1 Reverse Contents of the amendment as shown in the attached sheet An engraving of the translation of the drawings (no changes to the content) International “inspection report”

Claims (1)

[Claims] 1. The substantial part of the particles has a smoothly curved surface and a flat surface smaller than about 10 μm. Fine powder with uniform particle size. The fine powder according to claim 1, wherein the λ particles are made of metal. 5. Claims in which at least about 80% of the particles have an average particle size of less than about 10 μm The fine powder described in main item 1. 4. The fine powder according to claim 1, wherein the particles have a fusion temperature exceeding about 1800°C. The end. 5. Claim 1, wherein the powder is plasma densified and solidified from a molten powder. Fine powder as described. &　The fine powder according to claim 1, wherein the powder consists of amorphous particles. 2- The fine powder according to claim 1, wherein the powder is made of a high melting point metal. 8. Forming a high-velocity stream of molten metal droplets and directing the stream onto a repellent surface, collide with a repellent surface to form a divided section, and cool the divided section to make it slippery. Forms a powder consisting of particles smaller than about 10 μm with a curved surface A method for producing a fine powder comprising: 9. The fine particles according to claim 8, wherein the flow is formed by thermal spraying. Powder manufacturing method. 1α The method for producing fine powder according to claim 9, wherein the flow is plasma spray. Law. Claim 10, wherein said flow has a velocity greater than about 2 oorn/sec. The fine powder manufacturing method described in Section 1. 12. The method for producing fine powder according to claim 11, wherein the droplets are made of metal. 1B. Fine powder production according to claim 12, wherein the repellent surface promotes droplet formation. Device. 14. The method for producing fine powder according to #3, item 13, wherein the divided particles are rapidly cooled. . means for forming a high-velocity stream n of 15 droplets; and a repellent surface, the flow forming means A fine powder manufacturing apparatus in which a stage is directed against the counter-reactive surface. 1 & said flow forming means propels the flow at a velocity greater than about 1 aom/sec. 16. The device according to claim 15, adapted to