EP0457674B1 - Verfahren und Vorrichtung zur Herstellung von Pulverlegierungen durch schnelle Erstarrung - Google Patents

Verfahren und Vorrichtung zur Herstellung von Pulverlegierungen durch schnelle Erstarrung Download PDF

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Publication number
EP0457674B1
EP0457674B1 EP19910401246 EP91401246A EP0457674B1 EP 0457674 B1 EP0457674 B1 EP 0457674B1 EP 19910401246 EP19910401246 EP 19910401246 EP 91401246 A EP91401246 A EP 91401246A EP 0457674 B1 EP0457674 B1 EP 0457674B1
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Prior art keywords
nozzle
dish
cup
crucible
opening
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English (en)
French (fr)
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EP0457674A1 (de
Inventor
Philippe Arcade
Georges Champier
Gérard Michot
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SOCIETE NOUVELLE DE METALLISATION INDUSTRIES SNMI
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NOUVELLE DE METALLISATION INDUSTRIES SNMI Ste
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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
    • B22F9/10—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 using centrifugal force

Definitions

  • the present invention relates to a device and a method for the preparation of powdered alloys, by rapid solidification.
  • the rapid solidification makes it possible to develop alloys whose chemical compositions differ widely from those imposed by the phase diagrams at equilibrium.
  • Heat treatment of the supersaturated solid solution obtained makes it possible, by controlling the precipitation of the second phase, to optimize the mechanical properties of the alloys.
  • the resulting microstructures are very fine, which limits the importance of the chemical segregations inherent in any solidification and avoids the formation of large precipitates capable of reducing the ductility of the material by blocking the plastic deformation.
  • the cooling can be fast enough to prevent crystallization and lead to the formation of a metallic glass.
  • Spraying with a gas jet consists in dividing a jet of molten metal by a jet of subsonic or ultrasonic gas.
  • the cooling rate is of the order of 102 to 104 ° K.s ⁇ 1 with an average particle size of 40 to 70 ⁇ m.
  • the cooling rate is higher by 104 to 105 ° K.s ⁇ 1 and the average particle size is smaller, of the order of 20 ⁇ m.
  • the alloy In the method of spraying by rotating electrode, the alloy is in the form of a cylindrical bar rotating around its axis. It is melted at one of its ends by an arc or a beam of electrons; the molten alloy is projected in the form of droplets under the effect of centrifugal force.
  • the cooling rate is estimated at 102 ° K.s ⁇ 1 with an average particle size of the order of 200 ⁇ m.
  • centrifugal spraying a jet of molten alloy falls in the center of a cup rotating at very high speed. Under the effect of centrifugal force, the liquid expelled towards the periphery is subdivided into fine particles.
  • the cooling rate is estimated at 105 ° K.s ⁇ 1 and the average particle size is around 75 ⁇ m.
  • the molten alloy is supersaturated with pressurized gas. It is then exposed to the vacuum; the gas then escapes from the liquid, producing fine particles.
  • the cooling rate is estimated at 102 ° K.s ⁇ 1; the average particle size varies from 40 to 70 ⁇ m.
  • the surface of the molten metal is subjected to an intense electric field. There appear small protrusions with tearing of liquid in the form of very fine charged droplets which are solidified and collected.
  • the cooling rate is estimated at 106-107 ° K.s ⁇ 1 with an average particle size of the order of a micron.
  • These devices include a pre-crucible into which the molten metal is poured.
  • the molten metal is then poured back into the main crucible from where it can be projected onto a rotating cup via a nozzle.
  • the possible application of an overpressure above the molten metal, allowing the rupture of the oxide layer, facilitates the flow of the metal through the nozzle.
  • the overpressure-nozzle diameter pair best suited to casting.
  • the flow is more or less important. We can therefore only measure an average flow, ratio of the mass ejected to the ejection time.
  • the flow of molten metal can be disturbed either by a hydrodynamic instability which offsets the jet, or by a rebound on the cup. In both cases, the liquid film covering the cup breaks, disturbing the thermal balance and the size distribution of the ejected droplets.
  • the droplets must leave the cup at the temperature T L of the liquidus and reach the walls of the enclosure at a temperature T ⁇ T s , temperature of the solidus, cooling intervening in a period of the order of 10 ms.
  • the temperature difference can be reduced if some supercooling occurs.
  • the temperature T c at which the drop leaves the cup a temperature which in fact fixes the microstructure of the powder, should be kept constant during spraying. This condition is very restrictive because if the initial temperature T co of the cup is imposed, it is not possible to avoid the cooling due to the starting of the turbine nor the subsequent heating at the start of the casting.
  • the present invention relates to a device for the preparation of metal powders by centrifugal spraying making it possible to eliminate the aforementioned drawbacks.
  • the invention also relates to a process for the preparation of metal powders by centrifugal spraying.
  • metal is meant pure metals and metal alloys in the present text.
  • the device for the production of metallic powders by centrifugal spraying comprising a crucible provided with a nozzle at its lower part, a cup associated with means capable of putting said cup in rotation and means for heating said crucible and said cup, the aforementioned elements being placed in a sealed enclosure provided with the openings necessary for the supply of liquid metal, for the passage of various measurement or control means, and for the extraction of the powder obtained, is characterized in that it further comprises means making it possible to adjust the distance between the lower opening of the nozzle and the upper face of the cup, and in that the external diameter ⁇ e of the face bottom of the nozzle is such that ⁇ i +2 mm ⁇ ⁇ e ⁇ ⁇ VS , ⁇ VS being the diameter of the cup and ⁇ i the internal diameter of the nozzle.
  • the means for adjusting the distance between the nozzle and the cup are preferably mechanical means.
  • the nozzle has an internal channel having a length l and an internal diameter ⁇ i .
  • the outside diameter of the underside of the nozzle is designated by ⁇ e . l and ⁇ i are chosen so that the crucible can be emptied by gravity in the absence of a cup and that the clogging phenomena which occur on conventional spraying devices are avoided. Indeed, these blocking phenomena cause a discontinuous supply of the cup and, consequently, a rapid drop in its temperature, inducing additional dispersions in the process.
  • ⁇ i is preferably greater than 2 mm.
  • the process for producing metal powders by centrifugal spraying consisting in supplying molten metal to a rotating cup, the molten metal being contained in a crucible provided at its lower part with a nozzle, the upper face of the cup and the lower opening of the nozzle being opposite and substantially parallel, the opening of the nozzle being centered on the cup, is characterized in that the distance between the lower opening of the nozzle and the face is adjusted upper part of the cup as a function of the surface of the nozzle facing the cup, and the liquid metal is extracted from said crucible by the vacuum created by the cup rotating around a vertical axis.
  • the method of the invention can advantageously be implemented using a device of the present invention, in which the distance H between the upper face of the cup and the lower opening of the nozzle is adjusted so that that in static condition, the molten metal contained in the nozzle does not flow.
  • the liquid film is then subjected to a much more intense shearing than that encountered in conventional centrifugal spraying since here the upper part of the film remains fixed while the lower part takes on the speed of drive of the cup.
  • This shearing specific to the process of the present invention, can have significant metallurgical incidences since the destruction of the solid germs as they are formed can lower the temperature of the bath below the temperature.
  • solidification T S the supercooling thus achieved allows very high solidification rates.
  • the diameter of the particles obtained by centrifugal spraying varies as where D E is the material flow, ⁇ C the diameter of the cup and V the speed of rotation of the cup.
  • Exhibitors obtained experimentally [Cf. Champagne B., Angers R., Modern Developments in Powder Metallurgy, 12, Proc. Conf. Washington (1980), 83; Friedman SJ, Gluckert FA, Marshall WR, Chem. Eng. Prog., 48 , (1952), 181; Kozlov VA, Golubkov VG, Sov. Powder Metall. Met. Ceram, 20 , (1981), 159; Wentzel JM, Powder Metall.
  • the molten metal is brought to the cup without significant loss of heat, the overheating of the bath is minimized, bet, which is appreciable in the case of reactive alloys such as Al-Li alloys for example.
  • the internal diameter ⁇ i of the nozzle is not a critical parameter. Only count the surface of the nozzle opposite the cup, that is to say the surface S where the capillary forces are exerted, and the distance H busecoupelle. It is no longer necessary to create and modulate an overpressure in the crucible during ejection, because the cup always carries the same amount of metal, the device is self-regulating. Consequently, the thermal regime of the assembly remains stable during the experiment, an improvement in the spraying efficiency is observed and a slight narrowing of the particle size distribution spectrum.
  • the internal diameter ⁇ i of the nozzle being no longer critical, it is then possible to substantially increase its dimension in order to avoid the plugging phenomenon which occurs in known devices. Indeed, an unpowered cup, even for a very short time, cools down very quickly, which leads to the beginning of cooling of the metal on its surface: the experiment is then disturbed.
  • FIG. 1 represents a spraying installation according to the invention.
  • Figure 2 shows part of the actual spraying device.
  • FIG. 3 represents the device for driving and adjusting the cup.
  • Figure 4 shows a sectional view of the nozzle and the cup.
  • FIG. 5 represents the variation of the extraction rate D E as a function ⁇ e .
  • the actual spraying device is placed in an enclosure comprising an upper part (1), an intermediate part (2) and a lower part (15).
  • the actual spraying device comprises a graphite crucible (6) provided at its lower part with a nozzle (12) and a cup (3) associated with a turbine.
  • the nozzle (12) has an internal channel of length l and diameter ⁇ i .
  • the outside diameter of the underside of the nozzle opposite the cup is ⁇ e .
  • H is the distance between the underside of the nozzle and the top face of the cup.
  • Two rails (5) fixed inside the part (2) of the enclosure serve to support the crucible (6) by means of two discs, one (26) integral with the rails, the other ( 27) adjustable so that the axis of the crucible-nozzle assembly coincides with that of the cup.
  • the graphite crucible (6) and its insulation (7) are placed inside a high frequency induction coil (8) which provides heating.
  • An alumina tube (20) is placed between the crucible (6) and the insulation (7).
  • the crucible (6) is closed at its upper part by a refractory stainless steel disc (9) surmounted by a control device (10) with a graphite pin (11) which allows the hole to be closed. ejection during the heating period. In fact, it is preferable not to let the metal come to wet the cup as long as the turbine is not in rotation because there would then form an oxide layer which would appreciably decrease the apparent diameter of the nozzle.
  • the device is sealed by graphite seals, an opening allowing either to balance the pressures between the crucible and the enclosure, or to apply an overpressure in the crucible to clean it at the end of the experiment.
  • the crucible ends at its lower part with a nitride nozzle (12) boron; the crucible nozzle seal is ensured by a graphite seal (13).
  • thermocouple (14) which makes it possible to measure the temperature of the molten metal, is placed in an alumina tube closed at one end; this tube passes through the crucible cover, sealing is ensured by a high temperature adhesive.
  • the rotation of the cup (3) is ensured by a gas turbine whose maximum speed of 30,000 rpm is reached for a gas pressure of 0.7 MPa.
  • the turbine is extended by a hollow axis (28) of refractory material mounted on rigid bearings and provided with cooling discs to prevent the heating of certain moving parts.
  • the graphite cup (3) which will receive the flow of molten metal; the bottom of the cup is flat while the shape and height of the edge vary according to the experiment to be carried out.
  • the cup (3) is heated by the induction coil (29) placed around the graphite jacket (4).
  • the cup (3) and the graphite jacket (4) are thermally insulated by kaolin wool (19), the assembly is held in an alumina cylinder (18) surmounted by a graphite crown to avoid wool dispersion during operation.
  • the temperature of the cup is controlled by means of a not shown thermocouple introduced on the side and retracted just before the rotation.
  • the impeller and the axis ball bearings (28) are mounted in a cylindrical sleeve (22) ( Figure 3).
  • the gas supplying the turbine At the lower part of the sheath is introduced the gas supplying the turbine.
  • the cylindrical sheath passes through the spray tank via an airlock (23) provided with isolation solenoid valves. Cylindrical seals placed at the entrance and at the exit of the airlock guarantee the sealing and ensure the displacement in height of the sleeve and consequently the variation of the distance H between the cup and the nozzle.
  • a comparator needle (24) allows to precisely control this distance adjusted by the device (21).
  • the upper part (1) of the enclosure has two lateral openings used for lighting the tank and a large central opening (25) provided for possible supply of liquid metal from the outside.
  • the lower part (15) has two lateral openings for the recovery of the powder (16) and for the connection with a pumping unit, a central opening closed by a disc (17) which supports the turbine-cup assembly ( Figure 3 ).
  • FIGS. 1 to 4 An installation as shown in FIGS. 1 to 4 was used to prepare various powders of alloys or pure metal (examples 1 to 8).
  • the useful internal diameter of the enclosure was 1350 mm, the useful internal height of 800 mm.
  • the internal diameter ⁇ i of the nozzle was 2 mm.
  • the external diameter ⁇ e of the nozzle was 8 mm, and variable for example 8.
  • the gas turbine used can reach a speed of 30,000 rpm for a gas pressure of 0.7 MPa.
  • the spraying then takes place.
  • the powder is collected through the opening (16).
  • Example 6 corresponds to the composition of an amorphizable alloy.
  • the diffraction lines of the crystallized phase very weak for small particle sizes (less than 125 ⁇ m), are reinforced for particles between 125 and 200 ⁇ m.
  • the crystallized fraction is evaluated at less than 1% for 50-100 ⁇ m and 100-125 ⁇ m powders and at less than 5% the crystallized fraction for 125-200 ⁇ m powders.
  • the particle size of the powders obtained essentially depends on the size of the cup and its speed of rotation.

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  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)

Claims (6)

  1. Vorrichtung zur Herstellung von Metallpulvern durch Zentrifugalzerstäubung, umfassend einen Schmelztiegel, der in seinem unteren Abschnitt mit einer Düse ausgestattet ist, eine Kupelle, die mit Mitteln verbunden ist, die die Kupelle in Drehung versetzen können, und Mittel zur Beheizung des Schmelztiegels und der Kupelle, wobei diese Elemente in einem dichten Raum untergebracht sind, der mit Öffnungen versehen ist, die für die Zufuhr von flüssigem Metall, für das Einbringen verschiedener Meß- oder Kontrolleinrichtungen und für die Entnahme des erhaltenen Pulvers notwendig sind,
    wobei die Vorrichtung dadurch gekennzeichnet ist, daß sie außerdem Mittel aufweist, mit denen man den Abstand zwischen der unteren Öffnung der Düse und der oberen Stirnfläche der Kupelle einstellen kann und daß der Außendurchmesser Φe der unteren Stirnfläche der Düse solcherart ist, daß Φ i + 2 mm ≦ Φ e ≦ Φ c
    Figure imgb0007
    Figure imgb0008
     , wobei Φc der Durchmesser der Kupelle und Φi der Innendurchmesser der Düse ist.
  2. Vorrichtung nach Anspruch 1, worin die Mittel zum Ermöglichen der Regulierung des Abstands zwischen der unteren Öffnung der Düse und der oberen Stirnfläche der Kupelle mechanische Mittel sind.
  3. Vorrichtung nach einem der Ansprüche 1 bis 2, worin der Innendurchmesser Φi der Düse größer oder gleich 2 mm ist.
  4. Verfahren zur Herstellung von Metallpulvern durch Zentrifugalzerstäubung, umfassend das Einbringen von geschmolzenem Metall in eine sich drehende Kupelle, wobei das geschmolzene Metall in einem Schmelztiegel enthalten ist, der in seinem unteren Abschnitt eine Düse aufweist, wobei die obere Stirnfläche der Kupelle und die untere Öffnung der Düse einander zugewandt und im wesentlichen parallel zueinander sind, wobei die Öffnung der Düse mit Bezug auf die Kupelle mittig angeordnet ist, dadurch gekennzeichnet, daß man den Abstand zwischen der unteren Öffnung der Düse und der oberen Stirnfläche der Kupelle als Funktion der Oberfläche der der Kupelle zugewandten Düse einstellt und daß das flüssige Metall infolge des Unterdrucks, der durch die sich um eine vertikale Achse drehende Kupelle ensteht, aus dem Schmelztiegel abgegeben wird.
  5. Verfahren nach Anspruch 4, das mit Hilfe der Vorrichtung nach einem der Ansprüche 1 bis 3 durchgeführt wird, wobei der Abstand zwischen der oberen Stirnfläche der Kupelle und der unteren Öffnung der Düse solcherart eingestellt wird, daß im statischen Zustand das in der Düse enthaltene geschmolzene Metall nicht abfließt.
  6. Verfahren nach einem der Ansprüche 4 oder 5, worin die Abgabemenge durch die Wahl des Außendurchmessers der unteren Stirnfläche der der Kupelle zugewandten Düse bestimmt wird.
EP19910401246 1990-05-16 1991-05-15 Verfahren und Vorrichtung zur Herstellung von Pulverlegierungen durch schnelle Erstarrung Expired - Lifetime EP0457674B1 (de)

Applications Claiming Priority (2)

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FR9006104A FR2662102B1 (fr) 1990-05-16 1990-05-16 Dispositif pour la preparation d'alliages en poudre, par solidification rapide.
FR9006104 1990-05-16

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EP0457674A1 EP0457674A1 (de) 1991-11-21
EP0457674B1 true EP0457674B1 (de) 1995-10-18

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CN110961640B (zh) * 2019-12-27 2023-12-01 深圳微纳增材技术有限公司 一种制备3d打印用金属粉末的装置及方法
CN113399674B (zh) * 2021-06-18 2023-02-03 唐山市嘉恒实业有限公司 一种颗粒更均匀的金属粒化装置和制备方法

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JPS5940054B2 (ja) * 1978-08-29 1984-09-27 株式会社佐藤技術研究所 融体から特定サイズの球形粒子を製造する方法
DE3326831A1 (de) * 1983-07-26 1985-03-07 Bayer Ag, 5090 Leverkusen Verfahren und vorrichtung zur zerteilung von schmelzen
US4648820A (en) * 1985-11-14 1987-03-10 Dresser Industries, Inc. Apparatus for producing rapidly quenched metal particles

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FR2662102A1 (fr) 1991-11-22
FR2662102B1 (fr) 1992-07-31
DE69113861D1 (de) 1995-11-23
EP0457674A1 (de) 1991-11-21

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