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EP0124023B1 - Process and apparatus for atomising molten metal for producing fine powder material - Google Patents

Process and apparatus for atomising molten metal for producing fine powder material Download PDF

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Publication number
EP0124023B1
EP0124023B1 EP84104377A EP84104377A EP0124023B1 EP 0124023 B1 EP0124023 B1 EP 0124023B1 EP 84104377 A EP84104377 A EP 84104377A EP 84104377 A EP84104377 A EP 84104377A EP 0124023 B1 EP0124023 B1 EP 0124023B1
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EP
European Patent Office
Prior art keywords
gas
jet
annular
gas jet
liquid metal
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
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EP84104377A
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German (de)
French (fr)
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EP0124023A1 (en
Inventor
Thomas Dr. Duerig
Marcel Dr. Escudier
Jakob Dr. Keller
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BBC Brown Boveri AG Switzerland
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BBC Brown Boveri AG Switzerland
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
    • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
    • B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
    • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
    • B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
    • B22F2009/088—Fluid nozzles, e.g. angle, distance

Definitions

  • the invention relates to a device for atomizing liquid metals according to the preamble of claim 1 and to a method according to the preamble of claim 2.
  • Metal atomization for the production of a powder for powder metallurgical and other applications has been published for a long time and is known from a wide range of specialist literature.
  • the process of atomization using a gas jet is preferred.
  • gas jet air, nitrogen, noble gas
  • Known devices for gas jet atomization have, as an essential tool, a centrally symmetrical body for guiding the liquid metal to be atomized (metal jet) and the atomizing medium (gas jet), a so-called nozzle. Such devices are intended to achieve the most complete possible resolution of the liquid metal jet into individual small droplets.
  • a device has already been proposed (cf., for example, US Pat. No. 2,997,245) which, in a rotationally symmetrical body, has an annular inlet channel for the gaseous atomizing medium, which is directed obliquely upwards against the body axis an imaginary cone-shaped taper (circumferentially distributed) (tapered nozzles with a circular cross-section) or in a single cone-shaped, also sloping upwards (as a nozzle). Opposite the individual nozzles or the annular gap there are recesses arranged symmetrically to the latter and so-called resonance chambers on both sides of these recesses.
  • the structure of this device is comparatively complicated, unclear and therefore hardly accessible to the gas dynamic calculation.
  • the abrupt deflection of the gas jet, the series connection of confusors and diffusers is also associated with considerable energy losses.
  • the metal powders produced with such a device leave something to be desired in various respects.
  • the invention has for its object to provide a device and a method for atomizing liquid metals, by means of which extremely high cooling rates of the melt and extremely fine-grained powder particles can be achieved.
  • the gas dynamic conditions in the atomization chamber should be simple and clear and should be optimized to ensure the greatest possible disintegration of the metal.
  • 1 shows a schematic longitudinal section through a device for atomizing liquid metals.
  • 1 is a rotationally symmetrical housing with preferably cylindrical boundary surfaces.
  • the housing 1 has an annular cooling channel 2 for receiving a liquid or gaseous coolant.
  • annular chamber 3 is provided, which serves for the gas supply (atomizing agent).
  • the chamber 3 merges into a conical narrow annular gap nozzle 4 which runs coaxially with the longitudinal axis of the housing 1.
  • the housing 1 On the outlet side of the annular gap nozzle 4, the housing 1 is closed off with a stepped flange (end plate) 5.
  • the latter has a sharp annular edge 6 and an annular resonance chamber 7 on its inner (bore) side.
  • a sleeve 8 In the central longitudinal bore of the housing 1 there is a sleeve 8, the outlet end of which is conical is cut and has a sharp trailing edge 9.
  • the sleeve 8 provided with a bore 10 for receiving the liquid metal to be atomized has a thread 11 at its inlet end, via which it is held on the housing 1 by means of a round nut 12.
  • the sleeve 8 is displaceable in its longitudinal direction with respect to the housing 1 and can thus be clamped in any position relative to the latter.
  • exit edge 9 can be varied with respect to the position of the annular gap nozzle 4 and the annular edge 6.
  • the components 1, 5, 8 and 12 are advantageously made of metallic materials with graded heat resistance and different thermal conductivity.
  • the sleeve 8 can also consist of a heat-resistant material such as ceramic material.
  • the invention is in no way material-specific; their characteristic geometry can in principle be transferred to all suitable material combinations.
  • Fig. 2 shows a longitudinal section through an atomization zone of the device on an enlarged scale.
  • the reference numerals correspond exactly to those in FIG. 1.
  • the exit edge 9 of the sleeve 8 is set back advantageously compared to the imaginary continuation of the conical movement surface of the annular gap nozzle 4, so that the exit cone of the sleeve 8 is not in alignment with the cone of the annular gap nozzle.
  • FIG 3 shows a diagram of the gas dynamic conditions in the atomization zone.
  • the sound intensity in decibels is plotted as a function of frequency in kHz.
  • Nitrogen under a pressure of 80 bar was used as the atomizing agent.
  • the components 1, 5, 8 and 12 according to FIG. 1 were made of steel, the actual dimensions being approximately half as large as shown in FIG. 1.
  • the sleeve 8 was set in such a way that its exit edge 9 was set back approximately 1.2 mm with respect to the imaginary section of the extension of the conical jacket corresponding to the annular gap nozzle 4 with the jacket of the cylindrical bore 10 of the sleeve 8 (see FIG. 2! .
  • the annular cooling channel 2 of the housing 1 was cooled with water, while the annular chamber 3 serving for gas supply was pressurized with nitrogen at 80 bar pressure as an atomizing agent. As can be seen from the diagram in FIG.
  • the invention is not exhausted in the description of the figures or in the aforementioned exemplary embodiment.
  • an inert gas e.g. B. argon or helium can be used.
  • the average total opening angle of the imaginary cone of the gas jet should be approximately 35 to 55 °.
  • the advantageous effect of the new atomization device consists in the generation of a gas jet which moves at least at the speed of sound against the liquid metal jet and which, in addition to a more or less continuous band, has clearly perceptible, high-intensity discrete sound frequencies. This is achieved by special training of a resonance room and a targeted guidance of the gas emitters.

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  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
  • Nozzles (AREA)
  • Glanulating (AREA)

Description

Die Erfindung geht aus von einer Vorrichtung zur Zerstäubung von flüssigen Metallen nach der Gattung des Oberbegriffs des Anspruchs 1 und von einem Verfahren nach der Gattung des Oberbegriffs des Anspruchs 2.The invention relates to a device for atomizing liquid metals according to the preamble of claim 1 and to a method according to the preamble of claim 2.

Die Metallzerstäubung zwecks Herstellung eines Pulvers für pulvermetallurgische und andere Anwendungen wird seit längerer Zeit publiziert und ist aus einer umfangreichen Fachliteratur bekannt. Dabei nimmt das Verfahren der Zerstäubung mittels eines Gasstrahls (Luft, Stickstoff, Edelgas) eine Vorzugsstellung ein. Bekannte Vorrichtungen zur Gasstrahl-Zerstäubung besitzen als wesentliches Werkzeug einen zentralsymmetrischen Körper zur Führung des flüssigen zu zerstäubenden Metalls (Metallstrahl) sowie des zerstäubenden Mediums (Gasstrahl), eine sogenannte Düse. Mit derartigen Vorrichtungen soll eine möglichst vollständige Auflösung des flüssigen Metallstrahls in einzelne kleine Tröpfchen erreicht werden.Metal atomization for the production of a powder for powder metallurgical and other applications has been published for a long time and is known from a wide range of specialist literature. The process of atomization using a gas jet (air, nitrogen, noble gas) is preferred. Known devices for gas jet atomization have, as an essential tool, a centrally symmetrical body for guiding the liquid metal to be atomized (metal jet) and the atomizing medium (gas jet), a so-called nozzle. Such devices are intended to achieve the most complete possible resolution of the liquid metal jet into individual small droplets.

Es ist bereits eine Vorrichtung vorgeschlagen worden (vgl. z. B. US-A-2 997 245), welche in einem rotationssymmetrischen Körper einen ringförmigen Zulaufkanal für das gasförmige zerstäubende Medium aufweist, der gegen die Körperachse zu in schräg nach oben gerichtete, auf einem gedachten Kegelmantel sitzende, am Umfang verteilt angeordnete Verjüngungen (Einzeldüsen mit kreisförmigem Querschnitt) oder in einen einzigen kegelförmigen, ebenfalls nach schräg oben gerichteten Ringspalt (als Düse) ausläuft. Gegenüber den Einzeldüsen bzw. dem Ringspalt befinden sich zu letzteren symmetrisch angeordnete Vertiefungen und zu beiden Seiten dieser Vertiefungen sogenannte Resonanzkammern. Im rechten Winkel zu den besagten ersten Düsen steht - ebenfalls auf einem gedachten Kegelmantel angeordnet, ein zunächst schroff sich erweiternder, dann verjüngender Ringspalt als zweite "Düse", die schlussendlich den Gasstrom in einem flachen, nach unten zulaufenden Kegel von ca. 120° totalem Öffnungswinkel in den freien Raum und auf den senkrecht nach unten fliessenden zylindrischen flüssigen Metallstrahl schleudert.A device has already been proposed (cf., for example, US Pat. No. 2,997,245) which, in a rotationally symmetrical body, has an annular inlet channel for the gaseous atomizing medium, which is directed obliquely upwards against the body axis an imaginary cone-shaped taper (circumferentially distributed) (tapered nozzles with a circular cross-section) or in a single cone-shaped, also sloping upwards (as a nozzle). Opposite the individual nozzles or the annular gap there are recesses arranged symmetrically to the latter and so-called resonance chambers on both sides of these recesses. At right angles to the first nozzles in question - also arranged on an imaginary cone shell - is an initially abruptly widening, then tapering annular gap as a second "nozzle", which in the end gasses the gas flow in a flat, downwardly tapering cone of approximately 120 ° total Throw angle into free space and hurls onto the cylindrical liquid metal jet flowing vertically downwards.

Diese Vorrichtung ist in ihrem Aufbau vergleichsweise kompliziert, wenig übersichtlich und deshalb der gasdynamischen Berechnung kaum zugänglich. Die schroffe Umlenkung des Gasstrahles, die Hintereinanderschaltung von Konfusoren und Diffusoren ist überdies mit beträchtlichen Energieverlusten verbunden. Die mit einer derartigen Vorrichtung erzeugten Metallpulver lassen in verschiedener Hinsicht zu wünschen übrig.The structure of this device is comparatively complicated, unclear and therefore hardly accessible to the gas dynamic calculation. The abrupt deflection of the gas jet, the series connection of confusors and diffusers is also associated with considerable energy losses. The metal powders produced with such a device leave something to be desired in various respects.

In der Pulvermetallurgie gibt es nun Anwendungsfälle, die es als wünschenswert erscheinen lassen, die Abkühlungsgeschwindigkeit während der Erstarrung der Tröpfchen bis zu extrem hohen Werten zu steigern, um ganz bestimmte, gezielte Strukturen zu verwirklichen. Insbesondere sollen auf diese Weise Seigerungen aus gesättigten oder übersättigten Schmelzen vermieden und homogene Gefüge erreicht werden. Dies bedingt wiederum spezielle Vorrichtungen, welche ganz bestimmte gasdynamische Bedingungen im Zerstäubungsbereich zu verwirklichen gestatten. Die bereits bekannten Vorrichtungen und Düsen erfüllen diese Bedingungen nicht oder nur in unzureichendem Masse.In powder metallurgy there are now applications that make it appear desirable to increase the cooling rate during the solidification of the droplets to extremely high values in order to achieve very specific, targeted structures. In particular, segregations from saturated or supersaturated melts are to be avoided in this way and homogeneous structures are to be achieved. This in turn requires special devices which allow certain gas-dynamic conditions to be achieved in the atomization area. The already known devices and nozzles do not meet these conditions, or do so only inadequate.

Es besteht daher ein grosses Bedürfnis, die bekannten Vorrichtungen zur Metallzerstäubung sowie deren Methoden dermassen zu verbessern, dass die vorgenannten Mängel möglichst weitgehend behoben werden können.There is therefore a great need to improve the known devices for metal atomization and their methods to such an extent that the aforementioned deficiencies can be eliminated as far as possible.

Der Erfindung liegt die Aufgabe zugrunde, eine Vorrichtung und ein Verfahren zur Zerstäubung von flüssigen Metallen anzugeben, mittels welchem extrem hohe Abkühlungsgeschwindigkeiten der Schmelze und äusserst feinkörnige Pulverpartikel erzielt werden können. Dabei sollen die gasdynamischen Verhältnisse im Zerstäubungsraum einfach und übersichtlich sein und optimiert gestaltet werden, um eine möglichst weitgehende Desintegration des Metalls zu gewährleisten.The invention has for its object to provide a device and a method for atomizing liquid metals, by means of which extremely high cooling rates of the melt and extremely fine-grained powder particles can be achieved. The gas dynamic conditions in the atomization chamber should be simple and clear and should be optimized to ensure the greatest possible disintegration of the metal.

Diese Aufgabe wird durch die im kennzeichnenden Teil der Ansprüche 1 und 2 angegebenen Merkmale gelöst.This object is achieved by the features specified in the characterizing part of claims 1 and 2.

Die Erfindung wird anhand des nachfolgenden, durch Figuren näher erläuterten Ausführungsbeispiels beschrieben.The invention is described with reference to the following exemplary embodiment, which is explained in more detail by means of figures.

Dabei zeigt:

  • Fig. 1 einen schematischen Längsschnitt durch eine Vorrichtung zur Zerstäubung von flüssigen Metallen,
  • Fig. 2 einen Längsschnitt durch die Zerstäubungszone der Vorrichtung gemäss Fig. 1 in vergrössertem Massstab,
  • Fig. 3 ein Diagramm der gasdynamischen Verhältnisse in der Zerstäubungszone: Schallintensität des Gasstrahls in Funktion der Frequenz.
It shows:
  • 1 shows a schematic longitudinal section through a device for atomizing liquid metals,
  • 2 shows a longitudinal section through the atomization zone of the device according to FIG. 1 on an enlarged scale,
  • 3 shows a diagram of the gas dynamic conditions in the atomization zone: sound intensity of the gas jet as a function of frequency.

In Fig. 1 ist ein schematischer Längsschnitt durch eine Vorrichtung zur Zerstäubung von flüssigen Metallen dargestellt. 1 ist ein rotationssymmetrisches Gehäuse mit vorzugsweise zylindrischen Begrenzungsflächen. Das Gehäuse 1 weist einen ringförmigen Kühlkanal 2 zur Aufnahme eines flüssigen oder gasförmigen Kühlmittels auf. Im mittleren Teil des Gehäuses 1 ist eine ringförmige Kammer 3 vorgesehen, welche der Gaszuführung (Zerstäubungsmittel) dient. Die Kammer 3 geht in eine konisch ausgebildete, zur Längsachse des Gehäuses 1 koaxial verlaufende schmale Ringspalt-Düse 4 über. Auf der Austrittseite der Ringspalt-Düse 4 ist das Gehäuse 1 mit einem abgesetzten Flansch (Endplatte) 5 abgeschlossen. Letzterer weist auf seiner innenliegenden (Bohrungs-) Seite eine scharfe ringförmige Kante 6 sowie einen ringförmigen Resonanzraum 7 auf. In der zentralen Längsbohrung des Gehäuses 1 befindet sich eine Hülse 8, deren Austrittsende konisch zugeschnitten ist und eine scharfe Austrittskante 9 aufweist. Die mit einer Bohrung 10 zur Aufnahme des flüssigen, zu zerstäubenden Metalls versehene Hülse 8 besitzt an ihrem eintrittseitigen Ende ein Gewinde 11, über welches sie mittels einer Rundmutter 12 am Gehäuse 1 festgehalten ist. Mittels dieses Mechanismus ist die Hülse 8 in ihrer Längsrichtung gegenüber dem Gehäuse 1 verschiebbar und kann somit in jeder relativen Lage zum letzteren festgeklemmt werden. Dadurch kann insbesondere ihre Austrittskante 9 gegenüber der Lage der Ringspalt-Düse 4 und der ringförmigen Kante 6 variiert werden. Die Bauelemente 1,5,8 und 12 werden vorteilhafterweise aus meta!lischen Werkstoffen mit abgestufter Warmfestigkeit und unterschiedlicher Wärmeleitfähigkeit gefertigt. Je nach Schmelztemperatur des zu zerstäubenden Metalls kann jedoch insbesondere die Hülse 8 auch aus einem hitzebeständigen Werkstoff wie beispielsweise Keramikmaterial bestehen. Die Erfindung ist jedoch in keiner Weise werkstoffspezifisch; ihre charakteristische Geometrie lässt sich prinzipiell auf alle geeigneten Werkstoffkombinationen übertragen.1 shows a schematic longitudinal section through a device for atomizing liquid metals. 1 is a rotationally symmetrical housing with preferably cylindrical boundary surfaces. The housing 1 has an annular cooling channel 2 for receiving a liquid or gaseous coolant. In the central part of the housing 1, an annular chamber 3 is provided, which serves for the gas supply (atomizing agent). The chamber 3 merges into a conical narrow annular gap nozzle 4 which runs coaxially with the longitudinal axis of the housing 1. On the outlet side of the annular gap nozzle 4, the housing 1 is closed off with a stepped flange (end plate) 5. The latter has a sharp annular edge 6 and an annular resonance chamber 7 on its inner (bore) side. In the central longitudinal bore of the housing 1 there is a sleeve 8, the outlet end of which is conical is cut and has a sharp trailing edge 9. The sleeve 8 provided with a bore 10 for receiving the liquid metal to be atomized has a thread 11 at its inlet end, via which it is held on the housing 1 by means of a round nut 12. By means of this mechanism, the sleeve 8 is displaceable in its longitudinal direction with respect to the housing 1 and can thus be clamped in any position relative to the latter. As a result, in particular their exit edge 9 can be varied with respect to the position of the annular gap nozzle 4 and the annular edge 6. The components 1, 5, 8 and 12 are advantageously made of metallic materials with graded heat resistance and different thermal conductivity. Depending on the melting temperature of the metal to be atomized, in particular the sleeve 8 can also consist of a heat-resistant material such as ceramic material. However, the invention is in no way material-specific; their characteristic geometry can in principle be transferred to all suitable material combinations.

Fig. 2 zeigt einen Längsschnitt durch eine Zerstäubungszone der Vorrichtung in einem vergrösserten Masstab. Die Bezugszeichen entsprechen genau denjenigen der Fig. 1. Aus der Fig. 2 ist insbesondere ersichtlich, dass die Austrittskante 9 der Hülse 8 mit Vorteil gegenüber der gedachten Fortsetzung der konischen Bewegungsfläche der Ringspalt-Düse 4 zurückversetzt ist, so dass der Austrittskegel der Hülse 8 nicht mit dem Kegel der Ringspalt-Düse in einer Flucht liegt.Fig. 2 shows a longitudinal section through an atomization zone of the device on an enlarged scale. The reference numerals correspond exactly to those in FIG. 1. In particular, it can be seen from FIG. 2 that the exit edge 9 of the sleeve 8 is set back advantageously compared to the imaginary continuation of the conical movement surface of the annular gap nozzle 4, so that the exit cone of the sleeve 8 is not in alignment with the cone of the annular gap nozzle.

In Fig. 3 ist ein Diagramm der gasdynamischen Verhältnisse in der Zerstäubungszone dargestellt. Die Schallintensität in Dezibel ist in Funktion der Frequenz in kHz aufgetragen. Als Zerstäubungsmittel wurde Stickstoff unter einem Druck von 80 bar verwendet.3 shows a diagram of the gas dynamic conditions in the atomization zone. The sound intensity in decibels is plotted as a function of frequency in kHz. Nitrogen under a pressure of 80 bar was used as the atomizing agent.

Ausführungsbeispiel:Design example: Siehe Fig. 1 bis 31See Figs. 1 through 31

Aus Stahl wurden die Bauelemente 1, 5, 8 und 12 gemäss Fig. 1 gefertigt, wobei die wirklichen Dimensionen ungefähr halb so gross waren wie in der Fig. 1 eingezeichnet. Die Hülse 8 wurde derart eingestellt, dass ihre Austrittskante 9 ca. 1,2 mm gegenüber dem gedachten Schnitt der Verlängerung des der Ringspalt-Düse 4 entsprechenden Kegelmantels mit dem Mantel der zylindrischen Bohrung 10 der Hülse 8 zurückversetzt war (siehe Fig. 2!). Der ringförmige Kühlkanal 2 des Gehäuses 1 wurde mit Wasser gekühlt, während die der Gaszuführung dienende ringförmige Kammer 3 mit Stickstoff von 80 bar Druck als Zerstäubungsmittel beaufschlagt wurde. Wie aus dem Diagramm der Fig. 3 hervorgeht, traten neben einem annähernd kontinuierlichen, als "Geräusch" zu interpretierenden Frequenzband von durchschnittlich ca. 30 Dezibel Schallintensität noch 3 weitere charakteristische diskrete Frequenzen im Ultraschallbereich von ca. 40, 80 und 130 kHz auf, welche in ihrer Intensität das kontinuierliche Band um ca. 15 bis 25 Dezibel überragten. Diese diskreten "Töne" können hauptsächlich für den vorteilhaften Desintegrationsmechanismus in der Zerstäubungszone des flüssigen Metalls herangezogen werden.The components 1, 5, 8 and 12 according to FIG. 1 were made of steel, the actual dimensions being approximately half as large as shown in FIG. 1. The sleeve 8 was set in such a way that its exit edge 9 was set back approximately 1.2 mm with respect to the imaginary section of the extension of the conical jacket corresponding to the annular gap nozzle 4 with the jacket of the cylindrical bore 10 of the sleeve 8 (see FIG. 2!) . The annular cooling channel 2 of the housing 1 was cooled with water, while the annular chamber 3 serving for gas supply was pressurized with nitrogen at 80 bar pressure as an atomizing agent. As can be seen from the diagram in FIG. 3, in addition to an approximately continuous frequency band to be interpreted as "noise" of an average of approximately 30 decibels of sound intensity, there were also 3 further characteristic discrete frequencies in the ultrasound range of approximately 40, 80 and 130 kHz, which the intensity of the continuous band exceeded by about 15 to 25 decibels. These discrete "tones" can mainly be used for the advantageous disintegration mechanism in the atomization zone of the liquid metal.

Die Erfindung erschöpft sich nicht in der Figurenbeschreibung noch im vorgenannten Ausführungsbeispiel. Bei der Durchführung des Verfahrens ist wesentlich, dass mindestens eine diskrete Schallfrequenz vorhanden ist, deren Intensität um mindestens 5 Dezibel über dem Durchschnitt des kontinuierlichen Bandes liegt, wobei die Druckamplitude mindestens den gleichen Wert erreichen soll wie der zur Erzeugung des Gasstrahles aufgewendete Stillstandsdruck des treibenden Gases. Als letzteres kann neben Stickstoff selbstverständlich auch ein Edelgas, z. B. Argon oder Helium verwendet werden. Vorteilhafterweise sollen mindestens 3 diskrete Schallfrequenzen mit mindestens 10 Dezibel Überhöhung gegenüber dem kontinuierlichen Band im Frequenzbereich von ca. bis 200 kHz vorhanden sein. Der mittlere totale Öffnungswinkel des gedachten Kegels des Gasstrahles soll dabei ca. 35 bis 55° betragen.The invention is not exhausted in the description of the figures or in the aforementioned exemplary embodiment. When carrying out the method, it is essential that at least one discrete sound frequency is present, the intensity of which is at least 5 decibels above the average of the continuous band, the pressure amplitude being to reach at least the same value as the standstill pressure of the driving gas used to generate the gas jet . As the latter, of course, in addition to nitrogen, an inert gas, e.g. B. argon or helium can be used. Advantageously, there should be at least 3 discrete sound frequencies with at least 10 decibels exaggeration compared to the continuous band in the frequency range from approx. The average total opening angle of the imaginary cone of the gas jet should be approximately 35 to 55 °.

Die vorteilhafte Wirkung der neuen Zerstäubungsvorrichtung besteht in der Erzeugung eines mindestens unter Schallgeschwindigkeit sich gegen den flüssigen Metallstrahl hin fortbewegenden Gasstrahls, welches ausser einem mehr oder weniger kontinuierlichen Band deutlich wahrnehmbare diskrete Schallfrequenzen hoher Intensität besitzt. Dies wird durch eine besondere Ausbildung eines Resonanzraumes sowie eine gezielte Führung der Gasstrahler erreicht.The advantageous effect of the new atomization device consists in the generation of a gas jet which moves at least at the speed of sound against the liquid metal jet and which, in addition to a more or less continuous band, has clearly perceptible, high-intensity discrete sound frequencies. This is achieved by special training of a resonance room and a targeted guidance of the gas emitters.

Claims (3)

1. Device for the atomization of liquid metals for the purpose of producing a fine-grained powder, consisting of a centrally symmetrical body which contains channels for supplying the liquid metal to be atomized and the gas serving for atomization and which is equipped with an annular cooling channel (2) and with an annular chamber (3) serving for the gas supply, characterized in that in a housing (1) limited by cylindrical outer surfaces there is an annular- clearance nozzle (4) having conical limiting faces narrowing in the flow direction, with a mean total opening angle of the imaginary cone of 35 to 55° for generating a gas jet in the form of a hollow cone tapering in the direction of flow of the liquid metal, in that, furthermore, the housing (1), on its end face confronting the gas outflow from the nozzle (4), is closed off, at the point after the narrowest gas cross-section in the flow direction, by means of a flange (5) having an annular resonance space (7) in the form of a hollow cone, which is approximately perpendicular to the gas jet on the outside and which has an outer sharp annular edge (6), and in that located in the central longitudinal bore of the housing (1) is a longitudinally displaceable, adjustable sleeve (8) which is equipped at its lower end with an outflow edge (9) having a conical limiting face and at its upper end with a thread (11) and is retained on the housing (1) by means of a round nut (12) and which is intended for receiving the jet of liquid metal flowing through the bore (10).
2. Process for the atomization of liquid metals for the purpose of producing a fine-grained powder, in which a jet of liquid metal is disintegrated by an annular gas jet which flows concentrically relative to it and is directed towards its interior and which forms an enveloping jacket and has acoustic vibrations superposed on it, characterized in that the gas jet contains not only a continuous band of acoustic frequencies, but also at least one discrete acoustic frequency, the intensity of which is at least 5 decibels above the average of that of the continuous band and the pressure amplitude of which attains at least the same value as the static standstill pressure of the propellent gas exerted in order to generate the gas jet, and in that the gas jet is guided in the form of a fan round an imaginary cone shell tapering in the flow direction, towards its vertex and towards the axis of the jet of liquid metal, the imaginary cone having a total opening angle of 35 to 55°.
3. Process according to Claim 2, characterized in that the gas jet contains at least 3 discrete acoustic frequencies at least 10 decibels higher in relation to the continuous band in the frequency range of 10 kHz to 200 kHz.
EP84104377A 1983-05-03 1984-04-18 Process and apparatus for atomising molten metal for producing fine powder material Expired EP0124023B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH238983 1983-05-03
CH2389/83 1983-05-03

Publications (2)

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EP0124023A1 EP0124023A1 (en) 1984-11-07
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EP84104377A Expired EP0124023B1 (en) 1983-05-03 1984-04-18 Process and apparatus for atomising molten metal for producing fine powder material

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EP (1) EP0124023B1 (en)
JP (1) JPS59206067A (en)
CA (1) CA1228459A (en)
DE (2) DE3319508A1 (en)

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Also Published As

Publication number Publication date
US4640806A (en) 1987-02-03
JPH049105B2 (en) 1992-02-19
DE3467726D1 (en) 1988-01-07
JPS59206067A (en) 1984-11-21
CA1228459A (en) 1987-10-27
DE3319508A1 (en) 1984-11-08
EP0124023A1 (en) 1984-11-07
US4575325A (en) 1986-03-11

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