EP2421997B1 - Production of spheroidal metal particles - Google Patents

Description

The invention relates to a device for producing roundish metal particles of high size and shape uniformity; Process for producing roundish metal particles of high size and shape uniformity and the use of the method.

The granulate particles produced in this way are particularly suitable, for example, for applications in which a particular flowability of the granulate is desired as far as possible without the formation of abrasion or particles of smaller particle size, as in thixomolding.

Melting of metals with impurities such as metal oxides, metal nitrides, metal silicides, mixed compounds thereof or foreign metal moieties as well as common additives are common raw starting materials for producing metal granules. In particular, magnesium and similar base metals form reactions with the atmosphere in the melting furnace and the crucible material, if this is dissolved by the melt or material thereof flakes off, oxides, nitrides, which inter alia clog the outlets for the melt. Further, some impurities, magnesium, for example, its oxides, are heavier than the liquid metal, so that they sink in the melt and settle to the bottom and to flow restrictions, such as an outlet, or to cooler areas of a plant. Reactions with the crucible material of the melting furnace can also lead to the formation of intermetallic phases, which also accumulate in this sump. All of these plug outlets, expose ducts and result in an uneven composition of the granules.

1. a) mechanische Verfahren, bei denen durch Zerspanung oder Granulierung von Gussteilen Partikel hergestellt werden, und
2. b) Schmelzverfahren, bei denen Tröpfchen der Schmelze erstarren und dann die Partikel bilden.

Fundamentally, there are two possibilities for the production of metal powders:

1. a) mechanical processes in which particles are produced by machining or granulating castings, and
2. b) Melting processes in which droplets of the melt solidify and then form the particles.

Mechanical procedures

A mechanical granulating apparatus or cutting apparatus can produce particles of fine structure, but it lacks the roundness, which causes a low internal friction of the granules in the dumping, conveying and pressing. Such particles often have poor uniformity of grain size and grain shape, and of course are not spheroidal. Furthermore, it is complicated, if not impossible, to produce granules with as large a grain as possible by mechanical granulation. Finally, the process itself is expensive, since the mechanical machining of billets and the like. Is expensive and much remains unzerspantes residual material that must be returned to the casting process. Also, metal granules produced by the cutting process generally suffer from uneven composition in general since irregularities such as inclusions are transferred from the billet to the powder.

In particular, a high fines content (<0.8 mm) is produced. These small particles may jam in the injection molding machine between the flights of the extruder screw and the cylinder. The result is uneven turning of the worm due to torque fluctuations. It comes to uneven metering. This can lead to impairments in process stability. In addition, there is an increased risk of explosion due to the fines. When transporting the granules, it can lead to segregation of the granules, so that fines enriched. Further fines may be generated by friction of the angularly shaped granules, which aggravates the above problem. It also large grains, which may be greater than the depth of the snail in the catchment area. This too can lead to jamming of the screw.

melt process

Conventional devices and processes for the production of granules or powder from the melt apply either atomization, wherein molten Metal - often in mixture with gas - is explosively atomised from a nozzle at high speed, which leads to rather chunky parts, or produce roundish grains by the so-called rotating-disc process, wherein molten metal from a melt container or furnace on a rotating disk drips and is thrown there with cooling - preferably against an ascending gas flow, which slows down the falling velocity of the droplets and thus flattening their elongated drop shape in the case. By the method, relatively roundish particles are obtained. It has also been found that the spheres produced by melting form a substantially finer grain structure compared to the particles produced from pulverized cast masses, which has proven to be advantageous in particular in metal injection molding ( Czerwinski F .; Materials Science and Engineering A 367, 2004, pp. 261-271 ).

Metals that are very reactive in the melt, such as magnesium and its alloys, which are becoming increasingly desirable as lightweight materials, and which are often derived from magnesium die casting scrap, are problematic in that they are highly reactive in melt. For example. It is problematic that the outlets for liquid magnesium from melt tanks - be it a nozzle or a simple outlet pipe - easily clogged by the oxides formed from the melt and then lead to an interruption of production.

Conventional turntable devices for making metal spheres include means for melting the metal and casting the metal on a rotating base which tosses the molten metal to form spheroidal particles. S. for example. JP 51-64456 . JP 07-179912 . JP 63-33508 JP 07054019 and JP 07-173510 , Such typical rotary disc devices produce spheroidal powders of relatively poor sphericity, limited micro dimensions, and improved uniformity of composition and shape.

It is therefore an object of the invention to improve the production of spheroidal metal granules, such as light metal and in particular alkaline earth metal.

The object is achieved by a device with the features of Claim 1 and a method according to claim 8 and the use according to claim 13 solved.
Advantageous developments emerge from the dependent claims.

According to the invention, molten metal is conveyed from a melting furnace in a granulating tube (5) to melt outlet openings (16) in a granulation chamber (20). Furthermore, the device has a granulating turntable (1) below the granulating tube (5), which has at least one outlet for a molten metal jet on the turntable (1), wherein the rotating turntable (1) from the at least one outlet of the granulating tube (5 dripping molten metal in the form of roundish droplets. The melt drops solidify on the cold surface of the turntable to granules particles (12). An inert gas supply means (15) supplies specially selected gas to the molten metal discharged from the melt outlets (16) into a granulation chamber (20) in a manner preventing contact of the molten metal jet with air and oxidation of the metal. The gas supply can be done in countercurrent, perpendicular to the melt jet and obliquely to parallel to the melt jet. Possibly. a pulsating upward and downward movement of the granulating tube (5) for separating the melt jet into drops can be provided.

Advantageously, the granulating turntable (1) is cooled. To avoid precipitation in the granulation tube (5), etc., it may be useful for the granulation tube (5) to be heated. The granulation tube (5) has a blind flange in one embodiment. As a result, a high pressure can easily be built up and the melt is applied as quickly as possible. In another embodiment, the granulating tube (5) is returned to the melting furnace (3), whereby a regular mixing of the melt and high reproducibility of the particle composition is ensured. Often it makes sense that a feed pump in / on the melting furnace (3) for conveying the molten metal to / in the granulation (5) is provided.

• Schmelzen des metallischen Ausgangsmaterials;
• Transportieren der Metallschmelze in ein Granulierrohr mit mindestens einem Schmelzeauslaß für einen Schmelzestrom;
• Dispergieren der Metallschmelze zu kleinen sphäroiden Tröpfchen durch Leiten mindestens eines Schmelzestroms aus dem Granulierrohr unter Schutzatmosphäre auf einen Drehteller;
• Abkühlen und Unterstützen der Vereinzelung des Metallstahles zu Metalltröpfchen durch Leiten eines kühlenden Inert-Gases in den Schmelzestrom gegebenenfalls unter pulsierender Auf- und Abwärtsbewegung des Granulierrohres (5), und
• Abkühlen und dispergieren der Metalltropfchen durch den rotierenden Drehteller unter Erstarren derselben zu diskreten Granulatpartikeln;

A method according to the invention for producing roundish metal particles of high size and sphericity uniformity has the following steps:

• Melting the metallic starting material;
• Transporting the molten metal into a granulation tube having at least one melt outlet for a melt stream;
• Dispersing the molten metal into small spheroidal droplets by passing at least one melt stream from the pelletizing tube under protective atmosphere onto a turntable;
• Cooling and assisting the separation of the metal steel into metal droplets by passing a cooling inert gas into the melt stream, optionally with pulsating up and down movement of the granulation pipe (5), and
• Cooling and dispersing the metal droplets through the rotating turntable, solidifying them to form discrete granule particles;

Typical metals which are processed by the granulation method according to the invention for high reactivity in the melt, are selected from the group consisting of Al, Mg, Ca, Zn and their alloys - but the method can also be used for other metals.

Due to the high reactivity of the molten metal, it makes sense that the melting of the metal and the handling of the melt takes place under a controlled gas atmosphere. Also, the cooling of the dispersed droplets by gas is advantageously accomplished by means of a predetermined cooling gas of one or more inert gases in an open or closed granulation chamber 20 which provides the controlled atmosphere.

By the method according to the invention, the production of spherical particles of fine grain structure of high shape and size uniformity from the melt is possible. Such particles having a fine grain structure are particularly suitable for applications such as thixomolding, sintering, metal injection molding and similar powder metallurgy processes.

The inventive method is particularly suitable for the production of granules of magnesium or magnesium alloys.

definitions:

The term "metal" below also refers to their respective alloys as well as the metal with minor impurities.

By spheroid is meant any round shape, such as, for example, balls, lens shapes, elliptical shapes, etc., which has no sharp or angular edges.

The fact that now the production of granules takes place directly from the melt by draining the melt from openings on a turntable, the additional cutting can be saved and thereby effort is avoided. Furthermore, a very narrow particle size distribution can be achieved in the case of a round to lenticular grain shape, for which previously expensive separation processes were necessary goods and also a lot of rejects were produced. Thus, according to the invention, waste can be avoided and process steps can be saved.

In the case of very base alkaline earth metals, such as magnesium or calcium, or their alloys known rotating disc methods can not be easily transferred to these metals, but it must also special measures to protect the highly reactive molten metal, especially for crucibles with a large surface, are made ,

According to the invention the access of reacting with the melt gases, such as water vapor, oxygen, nitrogen is avoided as possible. For this purpose, the melting takes place under a protective cover or protective atmosphere and the transport of the melt through a closed pipe system to the outlet openings or nozzles.

The invention will be explained in more detail below with reference to magnesium alloys, but it is also suitable for other highly reactive metals in the melt.

As a gas in the furnace itself, a wide variety of gases, either inert or reactive gas, such as mixtures of dry air, nitrogen or carbon dioxide with sulfur dioxide, sulfur hexafluoride or R134a, above the melt, resulting in the formation of a protective layer on the melt surface. The transport tube, the molten metal from the melting furnace for Promotes sputtering station, is heated to prevent deposition of magnesium or its compounds by convection in the heat transfer tube, while ensuring the most uniform possible heat distribution in the longitudinal direction of the tube. Corresponding measures are familiar to the person skilled in the art. In this case, the melt can be circulated, whereby a constant return does not take place on the turntable ejected melt in the furnace and thus a permanent mixing of the melt volume is achieved while maintaining a high homogeneity of the product and a homogeneous temperature distribution. The high flow velocity in the pipe is advantageous, so that impurities (eg oxides) are permanently transported, are not deposited in the pipe and clog it from the inside.

But it is also possible to work with a Granulationsrohr without return, resulting in the construction of higher pressures in the pipe with faster throughput.

Also possible are mixed forms in which the return of the melt in the melting furnace is decelerated by a valve and so the pressure in the granulation tube at the discharge openings or nozzles can be regulated. The pressure at the discharge openings can also be changed dynamically during the granulation process, whereby clogging of the outlet openings is prevented or an already formed precipitate can be released again. When using a metal pump, such a pressure control can be realized not only via a valve on the return but also by regulating the delivery line of the pump.

The pipe itself can be heated over the whole area or only over part of the area, for example only in the lower area, in order to increase the convection there and to avoid settling of reaction products of the melt.

To shape the resulting particles, it is essential to consider the differences in velocity between the droplet and the surrounding gas. Furthermore, the shape and size of the particles are influenced inter alia by density, viscosity, surface tension and diameter of the jet emerging from the discharge opening (nozzle diameter, nozzle material).

With increasing speed occur: dripping, Rayleigh decay, wave decay, sputtering (these terms are in Schubert, Manual of Mechanical Process Engineering, Volume 1, Publisher Wiley VCH, 2001 which is referred to in its entirety to avoid repetition). The dependence of the droplet size has already been determined by Schmidt ( Schmidt, P .: "Atomization of Liquids" - Overview lecture Apparatus Engineering, University of Essen 1984 which is also incorporated by reference in its entirety). The maximum static pressure that a drop can withstand before decay was determined by Schmidt 1984 and Vauck 2000 ( Vauck, WRA: Basic Operations of Chemical Process Engineering, DVG Verlag, 11th Edition, 2000 to which full reference is made). As soon as the dynamic pressure exceeds the static pressure, Rayleigh decays. Thus, the droplet size can be calculated for certain alloys and plant parameters and, in part, the particle size can be controlled.

The problem is that it has also been observed that the outlet nozzles clog from the outside, ie form deposits on exit of the molten metal from the nozzle. Therefore, the formation of oxides, nitrides, etc. must be avoided. This can be achieved by working under inert gas. In a fully enclosed plant any inert gas is possible, in (partially) open plants it makes sense that the shielding gas is lighter than air and thus directed against the falling drops, so that access of undesirable gases such as oxygen / nitrogen to the nozzles, which leads to the formation of unwanted deposits is prevented. This can be achieved with open chambers in which the metal drips into the light protective gas, for example. By baffles on the granulation tube.

But it is also important to avoid the formation of undesirable compounds already in the furnace - either by selecting a suitable crucible material, as is known in the art, which can not dissolve through the melt or by filter measures before the melt feed pump, which coarse Withhold particles.

It is particularly surprising that the particle size variation in the method according to the invention is low, which can only be achieved in the case of machining processes by means of expensive further sieving / sifting operations.

In the production of spherical particles according to the invention, it was observed that the process yielded particles of the same and better properties during thixomolding than granules conventionally produced by machining and grain fractionation with a lower production outlay.

1. 1) niedrigere Herstellungskosten durch Einsparen des Zerspanens
2. 2) weniger Rückstand gegenüber Zerspanen (die Barren können nicht vollständig zerspant werden)
3. 3) Einsparung von Fraktionierungsstufen
4. 4) Reduktion von das Förderverhalten und Reaktionsverhalten der Partikel änderndem Abrieb, der bei Transport des durch Zerspanen hergestellten scharfkantigen Granulats entsteht, durch runde Form
5. 5) feinere Mikrostruktur der Granulatpartikel mit entsprechend besseren Eigenschaften von mit dem Granulat herstellten Bauteilen.

Among other things, the following advantages are achieved by the method according to the invention:

1. 1) lower manufacturing costs by saving the cutting
2. 2) less residue compared to machining (the ingots can not be machined completely)
3. 3) Savings of fractionation levels
4. 4) reduction of the conveying behavior and reaction behavior of the particle-changing abrasion, which results from transport of the sharp-edged granules produced by machining, by round shape
5. 5) finer microstructure of the granule particles with correspondingly better properties of produced with the granules components.

Adjusting the relationships between devices and methods according to the invention enables the production of relatively round, spheroidal, ellipsoidal or lenticular particles of various sizes and various applicability, such as in sintering, thixomolding (metal injection molding), pressing, etc.

The invention provides methods, devices and systems for producing granular particles of uniform spheroidal shape and high sphericity consisting of metal and its alloys by use of an improved rotating disc apparatus.

• FIG. 1 eine Ausführungsform der erfindungsgemäßen Anlage mit der Granulationsvorrichtung;
• Fig. 2A und 2B Gefüge eines mechanischen Granulates und eines schmelzmetallurgisch hergestellten Granulates (AZ 91).
• FIGS. 3A und 3B schematisch verschiedene Ausführungsformen des Transportrohrs
• Fig. 4 erfindungsgemäß hergestelltes Granulat der Magnesiumlegierung AZ 91.

In the following, the invention will be explained in more detail by means of exemplary embodiments, which serve only for explanation and are by no means restrictive. It shows:

• FIG. 1 an embodiment of the system according to the invention with the granulation device;
• FIGS. 2A and 2B Structure of a mechanical granulate and a melt-metallurgically produced granulate (AZ 91).
• FIGS. 3A and 3B schematically different embodiments of the transport tube
• Fig. 4 granules of the magnesium alloy AZ 91 produced according to the invention.

In Fig. 1 is schematically illustrated the system of the invention. From a melting furnace 3, melt 6 is fed into the granulating tube 5 with nozzles 16 by means of a feed pump 2. The melt exits the nozzles 16 into the inert gas-filled granulation chamber 20 and forms drops 8. The drops fall on the turntable 1, solidify to particles 12 and are passed through a scraper 13 in a container 2. Inert gas 14 is passed through lines 15 to the emerging from the nozzle 16 melt, which prevents the formation of oxides, nitrides and the like to the nozzle 16 of the granulation tube 5 and the granules, and promotes the disintegration of the melt jet to 8 drops.

Figure 3 schematically shows various embodiments of the course of the granulation tube 5. In Fig. 3a schematically a granulator with return 7 is shown. Within the pipe run a pump P is arranged, which ensures regular promotion of the melt. The return of non-discharged melt through the return pipe 7 in the furnace is apparent. In Fig. 3b For example, a non-return embodiment in which the granulation tube 5 terminates in a blind flange is shown. Again, there is a pump P, which pressure in the granulating tube 5 can build up for faster deployment of the melt and also pressure surges, for example. For blowing out of the nozzles 16, can exercise.

Fig. 4 shows various granules from a plant according to the invention. Clearly here is a roundish lens shape of the present invention produced from the melt Mg granules visible.

FIG. 2a shows a light micrograph of the microstructure of a step by a melt produced according to the invention particles of magnesium alloy AZ91 and Fig. 2b the microstructure of a particle made from Gußmasseln particles of the same alloy. It is clearly evident that the particles produced from the melt solidify rapidly and thus have a remarkably fine grain according to the invention, whereby their mechanical properties are favorably influenced.

The invention provides methods, devices and systems for producing metal granules wherein the particles have a uniform spheroidal shape - such as Fig. 4 seen.

For this purpose, at least one jet of molten metal, which has been broken down into droplets, is directed onto a rotating dish. The molten steel is supplied with inert gas, here predominantly helium. A bell made of baffles below the Granulierrohres prevented as a granulation chamber outflow of the protective gas and maintains an atmosphere that prevents oxidation of the exiting the nozzle melt, upright. The droplets hit the cold, preferably cooled turntable. The turntable removes heat from the melt droplet so quickly that a rapid solidification of the melt results in a granular particle with a fine-grained microstructure. The rotational movement of the plate prevents the melting droplets from meeting / coalescing, thus ensuring solidification of the droplets into discrete particles. The particles are pushed here by the trained here as a strip scraper over the edge of the plate in a container. Also conceivable are other means for removing the solidified particles such as brushes, blowers, etc.

The pressure in the granulation tube 5 is generated in this embodiment by a centrifugal pump. In general, all known pumping methods and systems for building up the melt pressure or the melt flow in the pouring tube suitable, such as piston pumps, induction pumps, pneumatic pumping systems, but also for pressurizing the furnace chamber and pump-free delivery systems, which work, for example, on the principle of communicating tubes can be used.

The shape and size of the granulate particles can be influenced by various system parameters. These include, inter alia, the distance of the pouring tube to the turntable so the drop height of emerging from the nozzle melt; the nozzle diameter, the melt pressure, the melt temperature and the design of the granulation tube (with or without return). In addition, determine temperature, flow velocity, composition and angle of attack of the protective gas and the temperature of the turntable, the shape and size of the granular particles. Depending on the combination of parameters, the particle shape is different spheroid z. B. platelet, lens, spherical or cylindrical. For example, increasing the rotational speed of the plate causes a more elongate shape of the formed particle.

Prior to granulation, the metallic starting materials, for example magnesium die-cast scrap, are selected under a protective gas atmosphere from the group consisting of noble gases such as argon, neon and helium or nitrogen, carbon dioxide or dry air with additions of sulfur dioxide, sulfur hexafluoride or r-134a or Mixtures thereof melted in the melting furnace 3. But it is also possible to carry out the melting with the addition of salts, which leads to the formation of a protective layer of liquid salt on the melt surface and thus prevents a reaction of the melt with the air. For this process step, all known protective measures for melts from the respective metal in this example of magnesium or magnesium alloys are suitable.

• ▪ Schmelzen des metallischen Ausgangsmaterials;
• ▪ Leiten des geschmolzenen Metalls in einem beheizten Granulierrohr über einen Drehteller.
• ▪ Austritt des geschmolzenen Metalls aus Düsen im Granulierohr auf den Drehteller.
• ▪ Erstarren des Metalls auf einem Drehteller zu sphäroiden Partikeln.

A method of the invention for producing small spheroidal particles of fine crystalline composition and uniform size and shape comprises the following steps:

• ▪ melting of the metallic starting material;
• ▪ passing the molten metal in a heated granulating tube through a turntable.
• ▪ Outflow of molten metal from nozzles in the granulating tube to the turntable.
• ▪ Solidification of the metal on a turntable to spherical particles.

1. 1) Vereinzeln des als Strahl aus den Düsen im Granulierrohr austretenden geschmolzenen Metalls durch Strahlzerfall in Tröpfchen.
2. 2) Austreten des geschmolzenen Metalls aus den Düsen unter Schutzgasanströmung.
3. 3) Rückführung des Schmelzestromes im Granulierrohr in den Ofen
4. 4) Kühlung des Drehtellers von unten z. B. mit Wasser

Embodiments may include, for example:

1. 1) Separation of the molten metal emerging as a jet from the nozzles in the granulation tube by jet disintegration into droplets.
2. 2) leakage of the molten metal from the nozzles under inert gas flow.
3. 3) Return of the melt stream in Granulierrohr in the oven
4. 4) cooling of the turntable from below z. B. with water

Metal powders made by the machining process also generally suffer from uneven composition in general.
When dispersing the molten metal, the external gas pressure on the circumference of the dispersed droplets is preferably atmospheric pressure.

As a result, small spherical particles of fine crystalline grain structure and highly uniform size and high sphericity are obtained, the size and shape of which can be controlled by the exit velocity of the molten metal, the melt temperature at the outlet, the rotation speed of the turntable, and the shape of the turntable.

example Production and Characteristics of Spheroid Mg Particles with General Fine Crystalline Character:

Magnesium die casting scrap of the alloy AZ91 is melted in an electrically heated melting furnace under nitrogen with 0.20% r-134 a at 680 ° C. In the melting furnace is a centrifugal pump, which at 5500 revolutions per minute, the magnesium melt in a from the melt furnace promotes leading, blind ending, closed, heated granulation tube with 16 dispensing nozzles. Under the dispensing nozzles runs a water-cooled turntable. When the melt emerges from the nozzles, a melt jet forms, which decays to droplets at a drop height of 120 mm. Helium is conducted as a protective gas against the melt jet. Guiding plates around the granulation tube form a bell, which prevent the escape of helium upwards and forms a granulation chamber 20 and a helium atmosphere for protecting the melt from oxidation between the granulation tube and turntable. Upon impact of the melt droplets on the plate, these solidify into particles before they leave the open granulation chamber 20 formed by the baffles by the rotational movement of the plate. The rotation of the plate is carried out according to the requirements of the particle shape at a speed of 4-10 revolutions per minute. The result is lenticular particles high form uniformity. The particles are guided with a scraper from the turntable into a container. By subsequent sieving large, sometimes not dimensionally stable particles can be separated. Fig. 4 shows 3 sieve fractions of so produced granules of the magnesium alloy AZ91.

A light microscopic picture of a cross section of the particles thus produced is shown in FIG Fig. 2a shown in comparison with a cross-section of particles from the conventional machining process. It is noticeable that the section through the particles produced by machining shows considerably larger grains and transition zones than the fine-crystalline structure of the casting particles produced by the granulation method from the melt.

Thus, the Mg particles produced according to the invention are superior to the particles produced by machining processes both in terms of their microstructure and their external shape.

While the invention has been explained in more detail with reference to an embodiment, it is obvious to the person skilled in the art that various modifications of this teaching are obvious within the scope of the invention. The scope of protection is therefore limited only by the appended claims.

LIST OF REFERENCE NUMBERS

1

turntable

2

melt pump

3

melting furnace

5

Granulierrohr

6

melt

7

Return pipe

8th

droplet

12

thrown particles

14

inert gas

16

Outlet opening in the granulation tube

20

granulation

Claims (13)

1. Device for manufacturing rounded metal particles having a high uniformity in size and shape from a molten mass, comprising:

   - a granulation chamber (20) which is substantially filled with inert gas and which has a closed granulation tube (5) with at least one molten mass exit opening (16), with the granulation tube (5) guiding the molten mass to the exit openings;

   - a rotary disc (1) which is located at a distance below the molten mass exit opening (16) of the granulation tube (5) and which can be operated with a selected speed, so that the molten metal that is dripping from the molten mass exit opening (16) solidifies in discrete particles on the surface of the disc, and

   - a gas introducing device for creating a controlled incident flow of protective gas within the counter flow that is impinging on the molten mass which exits from the exit opening and for creating a protective atmosphere in the granulation chamber (20).
2. Device according to claim 1, characterized in that the granulating rotary disc (1) is cooled.
3. Device according to claim 1 or 2, characterized in that the granulation tube (5) is heated.
4. Device according to one of the preceding claims, characterized in that the granulation tube (5) comprises a blank flange.
5. Device according to one of the claims 1 - 3, characterized in that the granulation tube (5) is guided back into the melting furnace (3).
6. Device according to claim 5, characterized in that a valve device for controlling the throughflow is provided inside the granulation tube.
7. Device according to one of the preceding claims, characterized in that a feed pump is provided in/at the melting furnace (3) for the purpose of feeding the molten metal mass to/into the granulation tube (5).
8. Device for manufacturing rounded metal particles from a highly reactive molten metal mass that have a high uniformity with regard to their size and shape, comprising the following steps:

   - melting the metallic source material under the exclusion of air;

   - transporting the molten metal mass in a closed granulation tube from the melting furnace to at least one molten mass exit

   - exit of the molten mass from the molten mass exit above a rotary disc in the form of discrete droplets as a molten mass jet, which breaks up into droplets by the time it impinges on the rotary disc

   - guiding a stream of protective gas against the molten mass which is exiting from the molten mass exit,

   - collecting the molten mass in the form of discrete molten mass drops on the rotary disc,

   - solidifying of the molten mass drops into granulate particles through their contact with the colder surface of the rotary disc, and

   - guiding of the granulate particles from the rotary disc for packaging/further processing.
9. Device according to claim 8, characterized in that the source material of the method is chosen from the group that consists of Al, Mg, Ca, Zn as well as their alloys.
10. Device according to claim 8 or 9, characterized in that melting of the metal is carried out under a controlled gas atmosphere.
11. Device according to the claims 8 - 10, characterized in that the stream of protective gas for the molten mass which is exiting from the molten mass exit includes helium.
12. Device according to claims 8 - 11, characterized in that the breaking up of the melt jet which is exiting from the molten mass exit opening is supported by a pulsating up-and-down movement of the granulation tube.
13. Use of the method according to claim 8 - 12 for the purpose of manufacturing spheric particles having a fine micro structure as well as a high uniformity with regard to their shape and size from the molten mass.

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