DE2063779B - Use of liquid inert gases in an atomization system for the production of metal powder - Google Patents

Description

refractory lined. With the funnel 20 attached to the top of the container 12 (see arrangement in the drawing) the container 12 is against the atmosphere through the O-ring closure26 closed. Is the inside of the container flushed using an inert gas or with If a pump is brought to negative pressure, the non-oxidizing atmosphere obtained can in this way therein during the subsequent atomization of the molten metal from the funnel be maintained. Below the upper part of the container 12 extends through the walls of the Container and inside a plurality of gas nozzles 28. The nozzles 28 are on the axis of the Nozzle 22 of the funnel directed a short distance below its end.

In practicing the invention, hopper 20 is filled with molten metal 24, that in one. Stream 30 oozes out of nozzle 22. An inert gas 32 is brushed from the gas nozzles 28 the stream of molten metal 30 and atomizes it into molten metal particles 34. The Particles 34 fall to the bottom of the container and into the reservoir 14. Those cooled to cryogenic temperature liquid inert gases in the supply rapidly cool and protect the particles 34 before they agglomerate furthermore during cooling against oxidation. Since inside the container a non-oxidizing If the atmosphere is present, the particles are also removed from the atmosphere during their passage Funnel nozzle 22 to the supply 14 protected against oxidation.

When all of the metal from the funnel has been atomized, the funnel is removed from the collecting container 12 removed to open it to the atmosphere. At this point in time, the valve 18 of the drain 16 becomes opened to withdraw the liquid inert gases cooled to the lowest possible temperature from the container. Any liquid remaining on the particles will be removed by volatilization when the inside of the container 12 is opened to the atmosphere. The cooled powder is now used subsequent storage and use in the compaction of powder metallurgy products from the Container removed.

The term "inert" used in the present means that the coming to be used on Liquid gases cooled at low temperatures do not have a harmful effect on the respective metal or have the alloy that is quenched in it.

As a specific example of practicing the invention, a tool steel (REX 71) and a nickel-based superalloy (ASTROLOY) is used, which has the following composition had:

REX 71

C.
Mn
S ..
P ..
Si ..
Cr.

1.20
0.30
0.02
0.02
0.30
4.10

V.,
W,
Mon
Co.
Fe.

1.25 10.0 5.2 12.2 remainder

C ..
Al.
Ti.
Mon
Cr.

ASTROLOY
Co

0.10
4.35
3.35
5.25
15.0

18.5

Fe 1.0 max.

B 0.030

Ni rest

These alloys were subjected to the following conventional treatment and equivalent The amount of alloys was the treatment according to the invention, described below subject.

Separate amounts of the two alloys listed above were placed in an induction crucible heated to melt and poured into a funnel; then you let them through a refractory nozzle in the bottom of the funnel into an atomization container. The to use The upcoming device was similar to the device shown in the drawing and described herein. The atomization and collection container had been purged with gaseous nitrogen. The Molten metal coming out of the funnel nozzle was injected into a gaseous nitrogen stream brought into contact at a rate sufficient to atomize the metal and so melt it To produce metal particles. The lower part of the atomization and collection container was in the case of the conventional process with water and in the case of the invention with liquid nitrogen filled. In both cases the molten metal particles were quenched in the respective liquid. After completion of the experiments, the metal particles were analyzed for the oxygen content to determine; the results are given below:

Quenching medium

Oxygen content

(Parts / million)

REX 71 ASTROLOY

Water 500 400

Liquid nitrogen 90 170

From this it can be concluded that the particles quenched in liquid nitrogen form one have much lower oxygen content than the particles quenched in water.

1 sheet of drawings

Claims (2)

1 2, which characteristically leads to a low patent claim ■ Quality of the product, especially from the point of view of cleanliness. As a result, it has hitherto been necessary to 1. Use of powder that has been chilled to the lowest possible temperature 5 and quenched by water, cooled liquid inert gases as cooling liquid to be subjected to a cleaning process before they in the collecting container of an atomization system for the production of WUR compressed according to the powder metallurgy process of metal powder. the. Such cleaning methods are pretty 2. Embodiment according to claim 1, thereby cumbersome and time-consuming; therefore they increase characterized in that the process costs and thus the costs of the final refrigerated product are reduced to the lowest temperature liquid inert gas nitrogen, argon or product considerably. Helium is used. The invention was therefore based on the object in the collecting tank of an atomization system for production of metal powder to use a cooling liquid, on the one hand a sintering and agglomeration the atomized metal particles prevented and on the other hand also the particles in front of a Oxidation protects. This object is achieved according to the invention through the use of cooled to the lowest possible temperature liquid inert gases dissolved. The drawing explains the invention; it represents a vertical section through one for implementation The present invention relates to apparatus suitable for use with the invention.
In the implementation of the invention, a gas is used as a cooling liquid in the collecting container of a quantity of molten metal or an alloy atomization system for the production of metal powder. In powder metallurgy, it is known to bring a stream of metal into contact with one another in order to produce it into powder, which is then compacted and thus atomized to form individual particles. A stream of molten metal 3 ° The particles are glued into a collecting container with a jet of inert gas, for example tet, in which there is a supply of cryogenic nitrogen, coated so that the stream of molten, cooled liquid inert gases is located vorzenem metal with the formation of particles atomized, preferably consist of nitrogen; Argon and helium will. These particles can also be used for subsequent use. The particles are deposited in the liquid treatment and use at room temperature for cooling; scared off. As a result of the increased specific time they are protected by the liquid inert gases against surfaces of the molten metal, the metal is protected from oxidation. The liquid or alloy after atomization and before jet is preferably also an inert gas, and the chamber, which is highly susceptible to cooling to room temperature, preferably has a non-oxidizing chamber for extreme surface oxidation. This oxy-4 ° atmosphere, either by evacuating to susceptibility to subdation, is further intensified when atmospheric pressure or by purging with an alloy has metal components that are obtained from the inert gas, which preferably belong to the strongly oxidizable types, such as, for example Liquid inert gases titanium and zirconium cooled to the lowest possible temperature. The reserve obtained after atomization is obtained. Once the molten metal particles are completely attenuated, they must be cooled to room temperature as low as possible so that they do not sinter or agglomerate, making them unsuitable for opening the container to the atmosphere and for subsequent use the compaction- the rest of the liquid is removed from the powder by volatilization into objects according to the conventional methods. The only figure of the drawing process will be powder metallurgy. 50 tion explains an embodiment of the device For cooling, inert or reduction, which is generally designated by 10, and the decorative gases or vapors under pressure or is also suitable for the invention. The device 10 uses the same circulating pressurized gas, e.g. B. helium, as consists of a closed collecting container 12, used for atomization. In this case, however, the amount of liquid inert gas cooled down to the lowest temperature, such as an undesired sintering or agglomeration of liquid nitrogen, is often too low.
the particle entered. In order to cool down more quickly, next to the bottom of the collecting container 12 To achieve and prevent agglomeration, an outlet or a drain 16 is in connection water has also already been used as a quenchant with a valve 18 which, when it is open, the uses, which in some cases still includes ice and / or draining the liquid salts cooled to the lowest possible temperature, Acids or bases were added. The inert gases from the container are allowed. Above that stirring the atomized metal particles with water open upper part of the container 12 is a funnel 20 However, it caused a rapid and strong oxidation, which was attached to a floor nozzle in its center Particle. But if the metal or alloy has opening 22. Molten metal 24 for the oxidized during cooling to room temperature 65 atomization is made from a trowel or another, is, then this contamination in the transport device, not shown here in the poured all powder metallurgy funnels made from the powder. The funnel 20 is customary products have a correspondingly high oxygen content with a corresponding one, not shown here