JPS5871306A - Production of powder - Google Patents

Abstract

PURPOSE:To obtain metallic powder which causes less segregation and contains no impurities with a device of simple construction and a cooling medium of small consumptions by plunging the molten metal particles which are atomized by centrifugal forces into the liquid cooling medium held centrifugally in a rotating vessel. CONSTITUTION:In a hermetic vessel 1 maintained in a gaseous Ar atmosphere under reduced pressure, liquefied Ar 12 as a cooling medium introduced through a supply pipe 14 for liquid cooling medium is held in a rotating vessel 11 which consists of a material having good heat conductivity such as copper and is rotated by a motor 25 via gears 24, 23, 19, 18, etc. On the other hand, molten metal 3 is supplied from a high frequency induction melting furnace 2 through a tundish 4 onto a rotating body 5. The molten metal 3 is atomized by the centrifugal forces of the body 5 which is rotated at about 12,000 (rpm) by an air motor 6, and the particles 13 of the molten metal formed by this atomization are plunged into the liquefied Ar 12, whereby the particles are cooled and solidified at about 10<5> deg.C/sec. cooling rate and the metallic powder of less segregation is obtained.

Description

[Detailed description of the invention] This invention utilizes centrifugal force (thus atomizing molten metal; be.

In recent years, powder metallurgy methods for producing high-performance heat-resistant alloys have been developed and are being put into practical use. The raw materials used for wheel metallurgy of such heat-resistant alloys are: 1. Contamination by oxygen is sufficiently low, for example, 50 ppm or less; 2. The content of inert gas is extremely low, for example, 1 ppm or less. ■segregation is sufficient.

It is necessary to satisfy the following conditions:

In order to satisfy these O conditions, it goes without saying that one molten raw material should be selected in case 1. In case 1, oxygen can be prevented from being mixed in during melting and spraying, and in case 1, molten metal should be disturbed by inert gas. In the case of ①, it is necessary to set the cooling rate high, for example, to 10″°C/+s@a or more.

As a method for producing powder that can approximate these conditions, the Isshin Futsunobu method is recommended. In this centrifugal atomization method, for example, molten metal is made to flow down onto a rotating disc, atomized by centrifugal force, and solidified into powder. In this case, the atomized metal particles fly in a molten state due to centrifugal force, so
Furthermore, the fusion of these metal particles requires a sufficient flight distance for cooling, which poses a problem in that the apparatus becomes extremely large. Therefore, various improvement measures have been attempted in the past to reduce the size of the device and prevent the fusion of molten metal particles. For example, attempts have been made to use water as a cooling medium to prevent fusion tubes of molten metal particles. An example of this is a method in which molten gold W4 is made to flow down onto a rotating disc, the molten metal is atomized by centrifugal force, and then the molten metal particles are cooled by hitting water dripping down on the inner wall of the container. There is,
The molten metal particles are rapidly cooled.

However, this method has the problem of not being able to fully satisfy the various conditions required for the raw material powder used in powder metallurgy of heat-resistant alloys as described above.

In particular, in order to reduce the segregation of powder, it is necessary to rapidly cool the metal from a completely molten state to a temperature at which the atoms cannot diffuse before solidifying and causing segregation. In the case of superalloys, this cooling rate 1
It is said that it is necessary to set the speed to 10' to 1 G''C/s or more.

Therefore, the above-mentioned 104-b method of using s He as a method of obtaining a cooling rate meeting (If
#Refer to Publication No. 107259/1983).

This method cools molten metal particles of 10 to 50P by flying them in a high-speed He fluid at high speed.In addition to using H, which is a scarce resource and expensive, In addition, in order to make molten metal particles of 10 to 50 microns fly at high speed, the number of revolutions of the rotating body must be considerably increased (for example, about 20,000 Or, p, m, etc.). have.

The present invention has been developed by focusing on the above-mentioned conventional problems, so that the cooling rate for molten metal particles is sufficiently high and powder with small segregation can be obtained, and at the same time, liquid cooling is possible. It is an object of the present invention to provide a method for producing powder that requires less consumption of a medium and can prevent contamination of the powder with impurities.

This invention relates to a method for producing powder by atomizing molten metal (including alloys) by centrifugal force, in which molten metal particles atomized by centrifugal force are centrifugally held in a rotating container and placed in a liquid cooling medium. It is characterized in that it is immersed in the liquid cooling medium, quenched in the liquid cooling medium, and then mixed to form a powder.

Next, the implementation of this invention will be explained.

FIG. 1 shows an example of the structure of an apparatus used for producing powder according to the present invention, in which 1 is connected to a vacuum evacuation device (not shown) to enable vacuum evacuation of the inside, and 2 is a container 1.
6 is a molten metal melted in the high frequency induction melting furnace 2; 4 is a tundish that receives the molten metal W43; A rotating body, 6 is an air motor that rotates the rotating body 5 at high speed via a rotating shaft 6IL;
7 is an air supply pipe that supplies pressurized air to the air motor 6.

t, 11 is arranged substantially concentrically with the rotating body 5, and 6-.

and retains the liquid cooling medium 12 by centrifugal force;
Molten metal particles 1st- atomized by the rotating body 5
A rotating container to be plunged into the liquid cooling medium 12, 14 a cooling medium supply pipe for supplying the liquid cooling medium 12, 15 a heat insulating material provided on the bottom side of the rotating container 11, and 16 a heat insulating material 15f:
A bearing, 17F, rotatably supports the rotating container 11 through the
A support that supports the rotating container 11 via the i-bearing 16, 18
11C) is a companion gear installed on the outer periphery of the rotating container 11C, and 19 is a gear 1.
A gear 20m meshes with 8, 20b is a rotating wheel 21t of the gear 19 - a bearing that rotatably holds the gear 19, and 22 is a bearing 20.
a holding member, 26 a gear fixed to the other end of the rotating shaft 21, 24 a binion gear meshing with the gear 26, 25
is a motor that rotates the rotary container 11 via the gear mechanism described above.

Next, the operation will be described. First, the inside of the container 1 is evacuated using a vacuum evacuation device (not shown), and then an inert gas pipe is appropriately introduced to create a non-globalizing atmosphere inside the container. Further, the master alloy is melted in the high frequency induction melting furnace 2 to obtain the molten metal 6, and the motor 251h is operated to rotate the rotating container 11, and the liquid cooling medium 12 is supplied from the cooling medium supply pipe 14. This liquid cooling medium 12 is centrifugally held in the rotating container 11. Next, the rotary body 5 is rotated at high speed by the air motor 6, and the molten metal 3 flows down from the tundish 4 onto the rotary body 5, and the molten metal 3 is atomized on the rotary body 5 by centrifugal force. The nine molten metal particles 1!1 atomized by the centrifugal force fly into the liquid cooling medium 12 centrifugally held in the rotating container 11, reach the rotating container 11, and become powder. In this case, reduced pressure is more effective to reduce cooling during flight.

Next, an example of implementation will be described. First, the inside of the container 1 is evacuated to about 10-' Torr using a vacuum evacuation device IK (not shown), and then Ar gas is introduced and replaced to bring the inside of the container 1 to about atmospheric pressure. shall be. Next, the master alloy (IN 100) is melted by the high-frequency induction furnace melting 2, and the rotating vessel 11 is heated to about 20 Orpm by the motor 25.
Then, liquefied Arf is supplied from the cooling medium supply pipe 14, and liquefied M%tS8-7130G(3) Ar cooling medium 12t is centrifugally held in the rotating container 11. Also, air
The rotary body 5 is rotated at a speed of about 1200 rpm by operating the rotary body 5, and the molten metal 6 is caused to flow down onto the rotary body 5 and atomized by centrifugal force. The nine molten metal particles 1M that are atomized fly into the liquefied Ar cooling medium 12, but at this time,
The liquefied At rapidly vaporizes and removes vaporization heat from the molten metal particles 16, thereby solidifying the particle surfaces. Subsequently, the metal particles 16 whose surfaces have been solidified reach the steel 110 surrounding vessel 11 cooled by liquefied Ar, where they are further rapidly cooled and become heat-resistant metal powder with less segregation. A scanning electron micrograph (x
As a result of checking with LOOOOO), it was as shown in Fig. 2. As is clear from FIG. 2, the structure was extremely fine and there was no macroscopic segregation, making it a heat-resistant superalloy with an ideal microstructure. Furthermore, the cooling rate is estimated to be 106°C/sec from the spacing of the secondary dendrites.

FIG. 3 shows another structural example of a rotating container. In the rotating container 11 shown in FIG. The holding capacity is relatively small.

Therefore, as shown in FIG. 3(1), the holding portion of the liquid cooling medium 12 may be formed into a rectangular shape. However, from the point of view of bringing the metal particles 16 whose surfaces have solidified by contacting the liquid cooling medium 12 into contact with the steel rotating container 11 km to further rapidly solidify them, the structure shown in Fig. 3 (&) does not improve much. There isn't. Therefore, Fig. 3(b).

As shown in (C), the rotating container 11 has an inclined surface 11 at
The structure is such that the metal particles 13 are brought into contact with the inclined surface 11aK of the rotating container 11 and further rapidly solidified, and then rapidly cooled.
If the solidified powder is allowed to enter the storage chamber 11b, the subsequent metal particles 15 can be easily rotated even when the amount of powder is large! The inclined surface 11aK of No. 11 contacts and is rapidly solidified. In this case, it is desirable that the rotating passenger device 11 be made of a material with good thermal conductivity, but the inclined surfaces 1 and 1
Only the storage chamber 11b is made of a steel material with good thermal conductivity, and the storage chamber 11b is made of relatively inexpensive and strong material such as stainless steel.

It can also be formed from materials.

FIG. 4 is a diagram showing another example of the structure of the rotating body 5, in which the first
Since the rotating body 5 shown in the figure has a structure in which the rotating shaft 6aK is directly attached, the heat of the molten metal 6 is directly transmitted to the rotating shaft 6a side. Therefore, in the rotating body 5 shown in FIG.
The structure is such that a fibrous heat insulating material 54 is arranged between these to prevent the heat of the molten metal 6 from being transmitted to the rotating shaft 6 side.

In the embodiments described above, a high-frequency induction furnace is used as the melting furnace, but it is also possible to use a plasma melting furnace, an electron beam melting furnace, etc., which have a low degree of contamination. In addition, as a liquid cooling medium, At(), t(e
@N2 etc. can be used, and the atmosphere inside the container 1 can be Ar, H, N! # Can be used for vacuum, etc. Furthermore, in order to reduce the Ar content in the powder, it is recommended to use liquefied N as a liquid cooling medium. 1+. It is desirable to determine the layer thickness of the liquid cooling medium appropriately depending on the material, temperature, size, etc. of the flying molten metal particles, and to supply the liquid cooling medium in an amount corresponding to the amount to be vaporized by the supply pipe. It is desirable to keep the layer thickness constant by replenishing from 14.

As explained above, in this invention, in a method of atomizing molten metal by centrifugal force, molten metal particles atomized by centrifugal pressure are plunged into a liquid cooling medium centrifugally held in a rotating container. I gave K so that it would coagulate and coagulate.
Since the atomized molten metal particles can be flown into the liquid cooling medium over a very short flight distance, it is possible to achieve a significant miniaturization of the equipment, and after passing through this liquid cooling medium, the rotating tube can be realized. By quickly reaching the container, the cooling rate of the molten metal particles II! It is possible to significantly increase the metal powder segregation, and the liquid cooling medium is centrifugally held in a rotating container, unlike the conventional method in which it flows down. Therefore, by replenishing the amount of liquid coolant that evaporates, the amount of liquid coolant consumed can be reduced.
It has many excellent benefits such as being able to easily prevent contamination of the powder with impurities and allowing the device to have a simple structure, and has four great industrial utility values. .

[Brief explanation of drawings]

Fig. 1 is an explanatory cross-sectional view showing an example of the structure of a companion powder manufacturing apparatus for carrying out the present invention, Fig. 2 is a photograph of a molded metal powder obtained in one embodiment, Fig. 3 (a), (6), (
C) is an explanatory cross-sectional view showing another example of the structure of the rotating container shown in FIG. 1, and FIG. 4 is an explanatory cross-sectional view showing another example of the structure of the rotating body shown in FIG. 1.-container, 2.. melting furnace, 6.. molten metal, 5.
... Rotating body, 6... Motor, 11... Rotating container, 1
2... Liquid cooling medium, 16... Molten metal particles, 14
...Liquid coolant supply pipe, 25...Motor. Figure 1. . ...°. -1, 14 0゜〆4 - 2 - 11, +2-' -1,2,18 \1, 13 18, 1 61116 ・ m-17,,7 ri [■ P 2″″″/l+'
='l-,7 Figure 3(b) (C)

Claims (4)

[Claims] (1) In a method of atomizing molten metal by centrifugal force, the molten metal particles atomized by centrifugal force are
A powder characterized by being centrifugally held and immersed in a liquid cooling medium! 1 method. (2) The method for producing powder according to claim (1), wherein the rotating container is made of a thermally conductive and malleable material. (3) Claim 1f, in which the rotating container has an inclination with respect to the direction of the molten metal particles.
F. is the method for producing the powder described in item (2). (4) The method for producing OII powder according to claim (1), (2) or (3), wherein the liquid cooling medium is liquefied inert gas i or liquefied nitrogen.