JPS59208005A - Production of alloy powder fines - Google Patents

Abstract

PURPOSE:To mass-produce alloy fines having uniform grain sizes with good efficiency by cooling quickly, by adiabatic expansion or the like, the gaseous mixture formed by mixing two kinds of metallic vapors and inert gas dividedly in two stages including adiabatic expansion. CONSTITUTION:A metallic material charged into a metallic vapor chamber 5 is melted to form a molten metal 8. The metallic vapor of the metal 8 is mixed with inert gas to form the 1st gaseous mixture. The gaseous mixture is passed through the 1st nozzle 12 and is cooled quickly by adiabatic expansion. The quickly cooled gas and the other one metallic vapor are mixed to form the 2nd gaseous mixture. The 2nd gaseous mixture is passed through the 2nd nozzle 2 and is quickly cooled by adiabatic expansion. The jet 26 from the nozzle 22 is further introduced into an oil 32. The alloy fines having uniform grain sizes are thus mass-produced with good efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing fine alloy powder, and in detail, a method for producing fine alloy powder with a particle size of several hundred A or less by rapidly cooling metal vapor. Pertains to.

Fine powders of pure metals and alloys used as dispersing materials in sintered materials and particle-dispersed composite materials are generally produced by mechanically crushing solid metals, or by spraying molten metal or colliding it with other low-temperature objects. The fine powder produced by these methods has a particle size of about 10 to 500 μm.

In general, the smaller the particle size of the fine metal powder, the higher the density of the sintered body, and the better the mechanical properties of the particle-dispersed composite material. Various attempts have been made to produce fine metal powder. For example, when a metal is heated in a vacuum, it becomes atoms and evaporates, and when cooled on the surface of a low-temperature object, it becomes a solid. This phenomenon is known as vacuum evaporation, and attempts have been made to utilize this phenomenon to produce fine metal powder. Also, instead of a vacuum atmosphere, 1/10 to 1/100
When a metal is evaporated in an inert gas at atmospheric pressure, the metal vapor is cooled by the inert gas, reaches a supersaturated state, and condenses into a liquid phase or a fine powder in the same phase. This method is called the gas evaporation method, and fine metal powder has been experimentally produced in small quantities by this method.

According to these methods, metal fine powder with a particle size of 1 μm or less can be produced, but all of these methods utilize a gentle thermal light-condensation phenomenon. There is a large variation in the particle size of the fine powder, and the productivity is extremely low. In order to increase productivity in these methods, it is necessary to quickly and continuously take out the generated metal vapor from the metal vapor chamber and avoid cooling it. Several methods have been proposed, including a method in which metal vapor is collided with a water-cooled copper plate and a method in which metal vapor is absorbed into dripping oil, but the former method requires expensive and large-scale equipment, while the latter method requires However, it is difficult to efficiently mass-produce fine metal powder with a uniform particle size in a low location using these methods due to the fact that the absorption efficiency is not necessarily sufficient.

The inventors of the present application, in view of various problems such as I was asked to improve my sexuality. Initially, we conducted experimental production of fine metal powder using a normal nozzle (a tapered nozzle), and succeeded in producing 100° of fine metal powder per hour. .

As a result of further intensive studies, the inventors of the present application discovered that productivity could be further improved by using a wide-divergent nozzle (also called a Laval tube), which is used in rocket propulsion devices such as the cold 711 nozzle. We have found that it is possible to efficiently produce fine metal powder with uniform particle size.

In addition, the inventors of the present application have proposed a method in which metal vapor is rapidly cooled by self-adiabatic expansion through a nozzle. The inert gas acts as a carrier gas, and the inert gas guides the gold vapor generated from the liquid surface of the molten metal to the nozzle more quickly, and also suppresses the growth of metal vapors due to their aggregation. By doing so, fine metal powder with even particle size can be produced more efficiently, and furthermore, the pressure ratio before and after the nozzle can be easily controlled, so it is possible to easily control the pressure ratio before and after the nozzle. We have found that the particle size of fine metal powder can be easily controlled and reduced.

According to the results of various experimental studies conducted by the inventors of this application, it is possible to efficiently produce fine metal powders with a particle size of several hundred amps or less, but in general, metals are made from two or more elements. As for metal fine powder, alloy fine powder is preferable to pure metal fine powder, and the actual demand for alloy fine powder is much larger.First
The figure shows the vapor pressure of various metals, and from this figure 1 it can be seen that the vapor pressure of metals varies greatly depending on the type of metal.

For example, the vapor pressures of Al, Cl, and Ni at 1800°C (12 Torr, 5, 6 Torr, respectively)
r, (J, 3 TOrr. Also, the boiling point of the metal varies greatly depending on its type. Therefore, the composition of Al-
Ni alloy was heated to 1800°C under reduced pressure.
1゛, most of the backside is illuminated only by aluminum vapor,
It was not until some time later that nickel vapor was produced.
Ru.

Therefore, by heating an alloy of a desired composition, the respective metal vapors are generated, and from the beginning of the throughput 1! [!
It is difficult to produce fine alloy powder with a uniform composition throughout the process, and the composition of the fine alloy powder is determined by the vapor pressure ratio of the metals that make up the powder. Accordingly, it is difficult to set the composition to the desired ratio.

The inventors of the present application (as a result of conducting various experimental studies in view of the above points) have found that one metal vapor and an inert gas are mixed to form a first mixed gas, and the second mixed gas is mixed with the first mixed gas. The first nozzle is passed through a first nozzle to rapidly cool the gas by adiabatic expansion, and this is combined with a pond of metal vapor to form a second mixed gas, and the second mixed gas is passed through a second nozzle. It has been found that fine alloy powder with a desired uniform composition can be easily produced by rapidly cooling the alloy by adiabatic expansion.

In general, the finer the alloy powder, the larger the surface area compared to its mass and the stronger its activity.If the alloy powder is taken out into the atmosphere under reduced pressure, it may ignite even at room temperature F. often observed. For this reason, conventionally, before the alloy fine powder is taken out into the atmosphere, a post-treatment is carried out to form an oxide film on the surface of the alloy fine powder under controlled conditions. In this method, low quality of the alloy fine powder and increased cost cannot be avoided.

The inventor's office has conducted various experimental studies on this point, and has found that oils that have fluidity directly under the nozzle and less evaporation even under vacuum, such as vacuum oil and electrical insulation oil, If an oil bath is installed and the jet jet ejected from the nozzle collides with the oil, the fine metal particles ejected from the nozzle in a mixed state of gas phase and liquid phase will be dispersed in the oil without grain growth due to aggregation. In addition, since the metal particles are present in the oil in the form of small particles, there is almost no aggregation of the metal particles, which makes it possible to produce extremely fine alloy powder with even more uniform particle size. Can you do it again?
The fine alloy powder introduced into the oil is stabilized by the substances that make up the oil and the moisture contained therein, so at! It has been found that there is almost no risk of igniting even if the oil is degreased by a t-ton or by vacuum distillation.

The present invention is based on the findings obtained from various experimental studies by the present invention, etc., as described above, and enables efficient production of extremely fine alloy powder with uniform particle size in a low process using human labor. The object of the present invention is to provide a method for manufacturing fine alloy powder that can be produced.

Such a purpose, according to the invention, is to mix a metal vapor and an inert gas to form a first gas mixture, and to pass the first gas mixture through a first nozzle for adiabatic expansion. quenching by mixing this with another metal vapor to form a second mixed gas, and passing the second mixed gas through a second nozzle for adiabatic expansion. A method for producing fine alloy powder, and mixing one metal vapor and an inert gas to form a first mixed gas;
The mixed gas is quenched by passing it through a first nozzle and expanding adiabatically. A method for producing an alloy powder comprising passing it through a second nozzle and adiabatically expanding it (quickly cooling it from the second and then blowing it out from the second nozzle and guiding the second 'd? mixture gas into oil) achieved by.

According to the present invention, non? The metal vapor is suppressed from grain growth due to aggregation by the i'i gas, the metal vapor is rapidly cooled by adiabatic expansion by the nozzle, and the metal vapor is rapidly and continuously guided to the nozzle by the inert gas. In addition, since it is possible to mix two or more metal vapors in any ratio, it is possible to create a fine alloy powder with a uniform particle size of several hundred A or less, with a uniform composition. It is possible to efficiently and inexpensively produce a fine alloy powder by hanging from a ceiling.Especially when it is rapidly cooled by a nozzle!: According to the method of introducing a mixed gas into oil, the collective growth of fine metal particles after being ejected from a nozzle is possible. This effectively suppresses the increase in particle size due to oxidation, and stabilizes the fine alloy powder, making it possible to produce even finer, more uniformly sized, and stable alloy fine powder by hanging from the ceiling more efficiently and in fewer turns. can do.

Further, according to the present invention, since a mixed gas of metal vapor and inert gas is passed through the nozzle, the pressure ratio of the mixed gas in front of the nozzle can be adjusted relatively easily by controlling the flow rate of the inert gas. This makes it possible to easily control the cooling rate of the mixed gas and the particle size of the fine alloy powder.

The nozzle for the cold 7J11 used in the present invention may be either a wide-spread nozzle or a tapered nozzle, but it is possible to increase the flow rate of the flfi gas mixture passing through the nozzle. In order to increase the cooling rate and thereby efficiently produce fine alloy powder with fine particle size and high quality, it is preferable to use a wide-end nozzle.

Now, the pressure and temperature of the mixed gas upstream from the cooling nozzle are P+ (Torr 〉, T+ ('K), respectively, and the pressure and temperature downstream from the nozzle are P2 (
If the nozzle is a divergent nozzle, the flow velocity of the mixed gas passing through the divergent nozzle will be supersonic when the pressure ratio PI/P2≧2゜1. 1.However, even if the pressure ratio is in the above range, if the value of the gas is relatively small (for example, PI/P2 = 2.5), the temperature of the gas body after passing through the wide-spread nozzle will be very low. 2 is relatively high, and when collecting fine alloy powder in an oil bath, some of it may burn or evaporate depending on the type and quality of the oil used. The pressure ratio PI/P2 is set to 4.0 so that the temperature of the gas 1 immediately before it collides with the liquid surface is below the flash point of the mail.
In particular, it is preferably set to 5.0 or more, more preferably 10 or more. Note that the approximate value of temperature T2 can be estimated using the following equation.

-7 to 'T'2= T'+ X (P2 / P+ > (to -
Specific Heat Ratio of Gas Body) When the cooling nozzle is a tapered nozzle, if the pressure ratio PI/P2 is set to 2.1 or more, the flow velocity of the gas body passing through the tapered nozzle becomes the sonic velocity. In the case of a tapered nozzle, it is not possible to increase the flow rate of the mixed gas to a speed higher than t), but in the future, even if the flow rate is 1-1 nozzle, the cold 7Jl im! The cooling rate is much faster than jl.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Figure 2 is a schematic diagram of the alloy powder manufacturing apparatus used in Example 1. In the figure, reference numeral 1 indicates a furnace shell which is a substantially airtight container, and a first crucible 2 is disposed within the furnace shell 1.

Is the crucible 2 a gas preheater for the gas introduction boat 3? 1′
4 and a first metal vapor chamber 5 communicating with the gas preheating chamber. A heater 7 is arranged around the crucible 2 to maintain the inside of the gas preheating chamber 4 and the metal vapor chamber 5 at a predetermined temperature.The heater 7 melts the metal charged into the crucible 2. The molten metal 8 is converted into molten metal, and is further evaporated into metal vapor.

Is there metal vapor on the bottom wall 9 of the crucible 2? A conduit 10 is fixed which communicates the conduit 5 with the outside of the crucible 2, and the second crucible disposed below the conduit +SL crucible 2 extends downward through the conduit 11. A diverging nozzle 12 is provided at its lower end. The crucible 11 defines a second metal vapor chamber 14 with a gas introduction boat 13. Crucible 1
Around 1, the metal vapor Ti 1 /l is heated to a predetermined temperature a.
A heater 15 is disposed to maintain the temperature at T'2, and the heater 15 melts the metal charged into the crucible 11 to form a molten metal 16, and further evaporates it into metal vapor. It has become. A heat insulating material 17 is placed between the first crucible 2 and the second crucible 11. The temperatures can be set to arbitrary temperatures 97 independently of each other.

Furthermore, a conduit 21 connecting the second metal vapor chamber 171 and the recovery zone 20 in the furnace shell 1 is fixed to the bottom wall 19 of the second crucible 11. The second diverging nozzle 22 is stepped.

The lower end of conduit 10 is received within the upper end of conduit 21, thereby forming diverging nozzles 12 and 22 (which together form a T-shaped nozzle).

A space 27'I is defined between the lower end of the first divergent nozzle 12 and the throat 23 of the first divergent nozzle 22.

In the recovery zone 20, water-cooled copper is placed at a position spaced apart from the tip of the first and second wide-spread nozzle 22. & J, sorptive plate 2
5 is arranged, and the housing 6 is tentatively a second diverging nozzle 2.
The alloy fine powder 27 is collected on the surface of the sorption plate 25 by the collision of the jet stream 26 ejected from the sorption plate 25 . , j:/, : The recovery zone 20 is connected by a conduit 28 to a vacuum pump 30 via an on-off valve 29, and this vacuum pump connects the recovery zone 20' to the space 24, the second metal vapor chamber 111, and the second metal vapor chamber 111. The inside of the first metal vapor chamber 5 is reduced L [(P4't P8't Pg 't
The pressure is maintained at a predetermined pressure of Pτ.

In addition, in the case shown in the illustration made of fine alloy powder wood
The gas introduction boat 13 spaced apart from the upper ring of 1 may be omitted, but if the alloy finely powdered wood @ device is constructed as shown, the inside of the second metal steam chamber 1/I may be omitted. The temperature and pressure in the space 24 and the temperature and pressure in the space 24 can be arbitrarily controlled independently of each other, and the pressure ratio before and after the first and second diverging nozzles can be easily controlled.

Using the thus configured alloy fine powder manufacturing apparatus, Ni--Cu fine powder was manufactured in the following manner.

First, 30% of metallic copper (99.9% C1, balance impurities) is charged into the first metal vapor chamber 5, and argon gas is introduced from the gas introduction bow [3], passes through the gas preheating chamber 4, and then enters the metal vapor chamber 5. The heater 7 rapidly heats the Ruppo 2 to raise the temperature T1 in the metal vapor chamber 5 to approximately 1700°C, thereby melting the metal copper to form a molten copper 8, and removing copper from the molten copper. Steam was generated. 30 g of metallic nickel (9
9.8% Ni, balance impurities) is charged into the second metal vapor chamber 14, argon gas is introduced into the metal vapor chamber 14 from the gas introduction boat 13, and the second crucible 11 is heated by the heater 15. is rapidly heated to bring the temperature in the metal vapor chamber 14 to about 2100° C., thereby melting the metal nickel to form molten nickel 16, and generating nickel vapor from the molten nickel.

Furthermore, by operating the vacuum pump 30 and controlling the argon gas guides from the gas introduction boats 3 and 13,
The pressure in the first metal vapor chamber 1)1, the pressure in the second metal vapor chamber 14, the pressure P3 in the space 24, and the pressure 14 in the recovery zone 20 are each about 10 Torr.
, 6-7-r-orr, 4=5 forr, 1-2
l-orr, and the distance 1I111 between the tip of the divergent nozzle 22 and the sorption plate 25 was set to about 10 cm.

In this case, 8J of molten copper is mixed with argon gas in the metal vapor chamber 5 of the generated copper vapor (31J), and the first mixed gas is passed through the first wide-spread nozzle. Temperature TO = 1100 ~ due to self-adiabatic expansion due to 12
It is rapidly cooled to about 1,200°C (estimated), and during the rapid cooling, the copper vapor becomes fine particles in the liquid phase and is mixed with the nickel vapor supplied from the first metal vapor chamber 14 in the space 24 to form copper. J, due to the combination of the fine particles and nickel vapor.
The argon introduced from the gas introduction boat 13 is mixed with sulfur to produce a second mixed gas, and the sulfur is self-absorbed by the wide-spread nozzle 22. Temperature -14= due to adiabatic expansion
The N1-CLI is rapidly cooled to about 700°C (estimated) to about 800°C (estimated), and during the rapid cooling, the Ni-C1 fine powder roars and collides with the sorption plate 25 together with the argon gas.
Fine powder 27 was collected on the sorption plate 25''.

All gold @ 5 & B] and metal nickel 1! I! It took about 13 minutes to remove the produced Ni −
The particle size range of the CU fine powder was 80-300A, and the average particle size was 1150A.

J, a nozzle and a conduit 2 arranged at the lower end of the conduit 10
The nozzles 12a and 22a provided at the lower end of the nozzle 1 are tapered nozzles 12a and 22a as shown in FIGS. 4 and 5, respectively.
N1-(:
, U fine powder is produced, and the particle size range of the produced fine powder is 130 to 350△, and the average particle size is 190△.
Both the variation in particle size and the average particle size were a little more crowded than the lifting platform of Example '1 of Kami+Ji, and the processing time was about 22 minutes, resulting in a slight decrease in productivity.

Embodiment 2 FIG. 3 is a schematic 4t4 diagram C similar to FIG. 2 showing an apparatus for producing fine powder of ft 2 alloy used in this embodiment 2. In this FIG. 3, parts that are substantially the same as those shown in FIG. 2 are designated by the same reference numerals ζ1.

The alloy fine powder TjlJ manufacturing apparatus used in this example is the same as that in Example 1 described above, except that an A-il storage tank 31 is arranged in the recovery zone 20 instead of the sorption zone. It is constructed in the same way as the 1J alloy powder production equipment used.

Using the thus configured alloy fine powder manufacturing apparatus, N1-cu fine powder was manufactured in the following manner.1. :,.

First, the initial temperature in the oil storage tank 31 is 20°C250.
0cc of vacuum oil (Matsumura Sekiyu Co., Ltd. NeA-bag)
MR-200>32 and then 30 g each of metallic copper and metallic nickel having the same composition as the metallic copper and metallic nickle used in Example 1 described above were added to the metallic vapor chamber.
4, and in the same manner as in Example 1 described above, the Onmaro T+ in the first metal vapor chamber 5 and the second metal vapor chamber 1 are charged.
The temperature 1-2 in /I, the temperature T3 in space 2/I, and the temperature T4 in the recovery zone 20 are 1700°C and 2100°C, respectively.
℃, 1100-1200℃, maintained at 30 = -50℃, and the pressure P1 in the first metal vapor chamber 5, the pressure 1]2 in the second metal vapor chamber 14, the pressure P9 in the space 24, The pressure P4 in the recovery zone 20 is set to about 10 Torr, respectively.
, 6~7-[old゛]゛, 4~51-orr, 1~
2- Maintaining the temperature at 15 cm, the distance between the tip of the wide-spread nozzle 22 and the liquid level of the vacuum oil 32 is approximately 15 cm, and the jet 26 ejected from the second wide-spread nozzle 22 collides with the liquid surface of the vacuum oil 32. The Ni-Cu fine powder is produced by introducing the Ni-Cu fine powder into vacuum oil.

In this example, the time required to process all of the metal copper and metal nickel was about 13 minutes, and the produced Ni-
The particle size range of the Cu fine powder was 50 to 20 OA, and the average particle size was 90△, and it was observed that the agglomeration of the recovered Ni-Cu fine powder was smaller than in the case of Example 1 described above. 1 and the lower ends of the conduits 10 and 21 ← The bifurcated nozzles are shown in Figures 4 and 5, respectively.
-L by changing to tapered nozzles 12a and 228 as shown in
Fine iron powder was produced under the same conditions as in Example 2.
As a result, the particle size range of the produced Ni-C1 fine V) powder was 90 ~ Soo, and the average particle size was 150Δ. The processing time was about 22 minutes, which was shorter than in Example 2.
Productivity was somewhat low.

Example 3 - [330g in the same manner as in Examples 1 and 2 above
of metallic nickel (99.8% Ni, remainder impurities) was charged into the metal vapor chamber 5 of the first crucible 2, and 30° of metallic aluminum (99.9% AI, remainder impurities) was charged into the second crucible 11. A fine powder of AI-Ni was produced under the following conditions using a wide-tailed nozzle.

Temperature T+: 2100℃ 1-2: 1600℃ T3: 1500-1600℃ 1-4: 600・-1000℃ Pressure P purchase:
10Torr P2: 5-6-rorr P3: 4-5Torr P4: 1-2T'orr In this example, the time taken to process all the metal nickel and metal aluminum was about 15 minutes, and the sorption plate The particle size range of the fine AI-Nt powder recovered above is 80
...-250 particles, and the average particle size is 120 particles, and the particle size range of the Al-Ni fine powder recovered by introducing it into vacuum oil is 60 to 180 particles, and the average particle size is It was 100A.

Further, the nozzles installed at the lower ends of the conduits 10 and 21 were changed to tapered nozzles 12a and 22a as shown in FIGS. 4 and 5, respectively, and Al - When fine Ni powder was produced, the particle size range of △l-, Ni fine powder collected on the sorption plate was 1a.
The average particle size is 170 particles, and the particle size range of the powder recovered by introducing it into vacuum oil is 90 to 230 particles. The diameter was 130A, and both the variation in particle size and the average particle size were larger than those in Example 3, and the processing time was about 19 minutes, resulting in a slight decrease in productivity.

Although the present invention has been described above in detail with reference to several embodiments, the present invention is not limited to these embodiments, and various embodiments are possible within the scope of the present invention. This should be obvious to the IJ.

[Brief explanation of the drawing]

Figure 1 is a J graph showing the relationship between vapor pressure and temperature of various metals, and Figures 2 and 3 are alloy fines suitable for carrying out the method for producing fine alloy powder according to the present invention. 4 and 5 are longitudinal sectional views showing the tapered nozzle. DESCRIPTION OF SYMBOLS 1... Furnace shell, 2... First ρ pot, 3... Gas introduction port t-, 4... Gas preheating chamber, 5... First metal vapor chamber. 7... Heater, 8... Molten metal, 9... Bottom wall, 1
0... Conduit, 11... Second crucible, 12... First diverging nozzle, 12a... Taper nozzle, 13...
Gas introduction port. 14... Second metal vapor chamber, 15... Heater, 16
...Metal molten metal, 17...1I7i heat material, 19...
Bottom wall, 20... Recovery zone, 21... Conduit, 22.
...Second wide end nozzle. 22a... Tapered nozzle, 23-... Throat, 24...
·space. 25... Sorption plate, 2G... Jet stream, 27... Alloy fine powder. 28...Conduit, 29...Opening/closing valve, 30...Vacuum pump. 31...A-il storage tank, 32...Vacuum oil special edition Applicant: Toyota Motor Corporation Representative Patent Attorney Masaki Akashi Figure 2 Ar Figure 3 Ar <ij formula) (self-motivated) 1. Incident Indication of 1981 weight [Application No. 081537 2, name of invention 'F! of alloy fine powder! Construction method 3, the person making the amendment (' + Which relationship Special Y
20) I~Yota Jidosha Co., Ltd. 4, Agent Address: 104 1-5-19-6 Shinkawa, Chuo-ku, Tokyo, Subject of amendment: Drawings

Claims (2)

[Claims] (1) One metal vapor and an inert gas are mixed to form a first mixed gas, and the first mixed gas is passed through a first nozzle to be adiabatically expanded to rapidly cool it. with one metal vapor to form a second mixed gas;
A method for producing a fine alloy powder, the method comprising passing the second mixed gas through a second nozzle to cause adiabatic expansion and quenching the second mixed gas. (2) One metal vapor and an inert gas are mixed to form a first mixed gas, and the first mixed gas is passed through a first nozzle to avoid adiabatic expansion, thereby rapidly cooling the gas. and one of the metal vapors to form a second mixed gas, and the second mixed gas is passed through a second nozzle to be rapidly cooled by adiabatic expansion, and the second mixed gas is rapidly cooled by adiabatic expansion. A method for producing fine alloy powder, the method comprising introducing the second mixed gas ejected from the second mixed gas into oil.