EP0048713A1 - Process for manufacturing metal pellets, product obtained thereby and device for implementing such process. - Google Patents

Process for manufacturing metal pellets, product obtained thereby and device for implementing such process.

Info

Publication number
EP0048713A1
EP0048713A1 EP81900066A EP81900066A EP0048713A1 EP 0048713 A1 EP0048713 A1 EP 0048713A1 EP 81900066 A EP81900066 A EP 81900066A EP 81900066 A EP81900066 A EP 81900066A EP 0048713 A1 EP0048713 A1 EP 0048713A1
Authority
EP
European Patent Office
Prior art keywords
metal
bath
jet
mass
molten metal
Prior art date
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.)
Granted
Application number
EP81900066A
Other languages
German (de)
French (fr)
Other versions
EP0048713B1 (en
Inventor
Gerard Bienvenu
Bernard Chaleat
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Extramet SA
Original Assignee
Extramet SA
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Extramet SA filed Critical Extramet SA
Priority to AT81900066T priority Critical patent/ATE5690T1/en
Publication of EP0048713A1 publication Critical patent/EP0048713A1/en
Application granted granted Critical
Publication of EP0048713B1 publication Critical patent/EP0048713B1/en
Expired legal-status Critical Current

Links

Classifications

    • 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
    • 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
    • B22F2009/086—Cooling after atomisation
    • B22F2009/0864—Cooling after atomisation by oil, other non-aqueous fluid or fluid-bed cooling
    • 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
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

  • the present invention relates to the manufacture of metallic granules. Its main object is a method for manufacturing metallic granules and it extends to the products obtained in accordance with this method as well as to a device particularly suitable for implementing this method.
  • the invention is applicable for putting any metal in the form of granules, by including in this concept, not only pure or almost pure metals, but also metal compositions or alloys.
  • the objective is to obtain practically spherical grains, of diameter for example of the order of 0.1 to 5 mm, together forming a powder which is pourable, easy to transport by pneumatic means, and which has a relatively apparent density. high, without great porosity, with in addition the possibility of obtaining a uniform grading of the grains, possibly after an easy sorting.
  • the invention provides a method of manufacturing metal granules of the type in which the metal in the form of granules is solidified from the molten metal, characterized in that a jet of molten metal, it is passed through a vibrating orifice to divide the jet into individual drops, and the cooling causes the solidification of these drops into granules.
  • the method according to the invention can be applied to the manufacture of metallic granules from molten metal baths of any composition. It will however be observed that most often the treated metals are in the molten state at a temperature of between 200 and 1500 ° C. and that the vibrating orifice through which the jet of molten metal exits generally opens into an atmosphere cooled by heat loss. in the ambient air, the temperature of which can therefore be between 20 and 9 ⁇ ° C. for example. In practice, operation is advantageously carried out under conditions such that the temperature difference between the molten metal when the jet is formed and the atmosphere in which the vibrating orifice opens is at least of the order of 200 ° C., and preferably between 300 and 1300 ° C, and more particularly between 500 and 1000 ° C.
  • the drops of the jet are made to fall by gravity through an atmosphere of inert gas maintained at a temperature below the ternpéra-ture of solidification of the molten metal.
  • the inert gas atmosphere can be chosen according to the nature of the metal, the diameter of the jet and the pressure conditions at the level of the vibrating orifice, so that the drops formed quickly reach the limit fall speed, over a drop height left available in the atmosphere which is sufficient to allow complete solidification of the granules before their collection.
  • the fall speed can for example be of the order of 2 to 30 meters per second and, depending on the thermal conditions, solidification can take a time corresponding to a fall height of the order of 10 cm to 20 m, or preferably 20 cm to 10 m.
  • the metal drops are subjected to internal forces which result from the vibrations communicated at the time of the division of the jet into drops at the outlet of the vibrating orifice.
  • the invention thus makes it possible to obtain powders of granules in which the diameters of the granules can be for example of the order of 0.2 to 3 mm, with dispersions relative to the average size which can remain less than + 0 , 5 mm, or even not to exceed approximately + 0.01 mm.
  • the powders obtained also have surface qualities which are generally favorable to the properties which are sought in this type of granules, in particular a surface hardness and a resistance which contribute to the good conservation of the powder and its flowability.
  • the inert gas can be for example helium, argon or mixtures of these gases. In certain cases, it may be advantageous to further ensure a dispersion of the metal drops during solidification with respect to the direction of fall of the jet, so as to prevent individual drops from being able to merge during solidification.
  • the bath used can advantageously consist of a molten halide of at least one metal of the molten metal mass. It can also consist of a molten halide of at least one additional metal more reducing than the essential metal of the granules and incorporated in small proportion in said mass.
  • Such an additional metal may in particular be calcium, a metal whose oxide readily dissolves in a bath of fluoride and / or calcium chloride.
  • a proportion of calcium of the order of 0.5 to 10% by weight is generally sufficient in metals such as aluminum or magnesium for example.
  • metals such as aluminum or magnesium for example.
  • the additional metal can be found in the granules obtained in accordance with the invention, while the recommended processing conditions make it possible to prevent the molten salts being found there other than in the trace state, detectable but not annoying, and in particular the invention makes it possible to produce granules of reactive metals such as calcium, magnesium or aluminum which, despite the use of a bath of molten salts, do not exhibit any hygroscopicity which is detrimental to preservation and. flowability of powders.
  • the manufacture of metallic granules involves the use of a device comprising a metal melting furnace in a receptacle for receiving a mass of molten metal, means for forming a jet of metal taken from said mass, through a vibrating orifice, means for causing the vibration of said orifice and thus ensuring the division of the jet into individual drops, and a chamber for cooling and solidifying the metal coming from said orifice, over at least the distance traveled by the drops during their solidification.
  • the device comprises a siphon for removing metal from a mass of molten metal separated from a bath of molten salts by decantation in said container.
  • said container and. said cooling chamber are preferably sealed and means are advantageously provided for separately adjusting the pressure of an inert gas in said container and in said cooling chamber.
  • FIG. 1 shows schematically in section the various organs of the device according to the invention in a first embodiment
  • FIG. 2 represents such a device, also in vertical section, in a second embodiment
  • Figure 3 shows in more detail the device of Figure 2 in its upper part.
  • the device comprises a heating cell provided with a sealed enclosure forming a container and heating means, a member for introducing raw materials into the cell, a cooling in communication with the cell by a conduit comprising a siphon and a zone pierced with at least one vibrating orifice, a first pneumatic means for establishing and controlling the pressure of the atmosphere in the enclosure, a vibrator connected to the zone comprising the vibrating orifice and arranged so as to make it vibrate continuously, a second pneumatic means for establishing and controlling the pressure of the atmosphere contained in the cooling chamber, and a device for evacuating the solid from this chamber .
  • the device shown in FIG. 1 comprises a closable member for introducing material 1 for bringing the metal into a heating cell 2 from which the molten metal is injected into a cooling chamber or tower 3 through a conduit 4
  • a closable evacuation device 5 makes it possible to evacuate the solid metal granules formed in the cooling tower 3.
  • the heating cell 2 comprises a sealed enclosure 6 forming a container for containing the molten metal.
  • This enclosure 6 is heated by an oven 7 surrounding its side walls and maintaining inside the enclosure a temperature higher than the melting temperature of the metal.
  • the molten metal 8 occupies the lower part of the enclosure 6; it is surmounted by a gaseous atmosphere 9, the pressure of which is controlled by a first pneumatic means 10 to which it is connected by a pipe 23.
  • This pressure in the atmosphere 9 can be increased or decreased, causing more or less rapid injection of the molten metal 8 through the conduit 4.
  • This conduit consists of a curved tube 11, one end 12 of which is immersed in the molten metal 8 and the other end of which 13 penetrates vertically into the upper part of the cooling tower 3.
  • the upper part of the tube, near the end 12, is bent to form a siphon, the elbow protruding from the level of the molten metal.
  • the end 12, the mouth of which is turned towards the bottom 14 of the enclosure 6, is provided with a filter 15 intended to retain the impurities contained in the molten metal.
  • the area of the enclosure 6 in the vicinity of the bottom 14 is a settling area where impurities of higher density can accumulate than the rest of the liquid.
  • the filter can be placed just above this settling zone of the molten metal to prevent suspended solid inclusions from quickly clogging the filter.
  • the heating cell 2 further comprises a mechanical stirring means diagrammatically represented by the propeller 18, ensuring stirring and homogenization of the liquid.
  • the end 13 of the tube 11 ends in at least one orifice for the injection of the molten metal into the cooling tower 3.
  • the filiform flow of molten metal thus obtained forms a jet in vertical drop to which vibrations are applied to produce uniform liquid drops.
  • the end 13 of the tube is driven by vibrations by a vibrator 16 and a connecting device schematically represented by the rod 17.
  • the drops of molten metal formed at the end 13 of the conduit 4 are dispersed in the cooling tower by a dispersing means 19. It is for example an annular electrode surrounding the jet and electrically charged with respect to the end 13 of the tube 11, which causes on the drops the appearance of electrical charges all of the same sign.
  • the drops of liquid disperse away from the vertical direction of the jet and they solidify before falling back to the bottom 20 of the tower 3.
  • the latter contains a gaseous atmosphere allowing the rapid cooling of the metal and inert with respect to of it. It may include different means for accelerating the cooling of the metal, for example means for circulating the gas.
  • the cooling rate of the drops can condition the nature of the phase of the material. riau solidified and, thus, the quality of the product obtained.
  • the use of a sealed cooling tower prevents communication of its internal atmosphere with the ambient air.
  • the pressure of the gaseous atmosphere of the tower can be controlled by a second pneumatic means 25 to which it is connected by a pipe 24.
  • the metal introduction member 1 includes a communication lock 21 and the evacuation device 5 includes a lock 22, to allow the continuous operation of the installation.
  • the raw material supply device 1 makes it possible to bring into the heating cell either molten metal or metal in the solid state; in the latter case, the melting takes place in the heating cell, and the metal is only injected into the cooling tower when it is fully molten and homogeneous. It is possible to treat metals which react with oxygen, since the hermetic assembly comprising the heating cell 6, the pressure control means 10 and 25, the communication conduit 4 and the cooling tower 3 can be subjected to a controlled atmosphere of gas which does not react with the metal.
  • the implementation of the invention by means of the device of FIG. 1 consists in introducing the metal into the heating enclosure 6, either in solid form or in liquid form, through the airlock 21, to maintain its temperature slightly above of its melting temperature by the heating means 7, and to homogenize the molten mass by stirring or by bubbling by the stirring means 18.
  • the molten mass is homogeneous, it is injected into the cooling tower 3 to through the tube 11 and the vibrating orifice.
  • the siphon is primed, for example, by an overpressure of the order of 5 g to 500 g / cm in the enclosure 6, produced by the pneumatic device 10.
  • the drops thus formed are dispersed if the elec- annular trode of the dispersing means 19 is under tension, and cooled by the atmosphere of the tower until forming solid spherical granules.
  • the injection speed of the molten metal through the vibrating orifices is regulated by the difference in gas pressure between the atmosphere 9 which overcomes this molten metal in the heating enclosure and the atmosphere of the tower 3. This injection speed is controlled and set allows to take into account the nature of the metal, the vibration frequency of the vibrating orifices, and various physical parameters of the molten metal such as its temperature.
  • the pneumatic means 10 and 25 thus make it possible to establish, adjust, and stop the flow of injected liquid metal.
  • the homogenization of the molten mass can be achieved in different ways. If the inclusions are sufficiently fine, a homogeneous suspension of these particles can be achieved by effective mixing by means 18. If on the contrary the inclusions are large and risk clogging the filter and / or the orifice (s) too quickly injection, a decantation is carried out which is carried out in the lower part of the enclosure 6.
  • a bottom 14 may be provided which is substantially and / or partially conical, the top of the cone being directed downward, to cause the accumulation of decantation products in a removable basket, not shown in the figure, placed at the bottom of the cone, the basket can be removed for the evacuation of these decantation products.
  • the passage of the basket may be facilitated by an offset, asymmetrical arrangement of the conical bottom 14 and / or of the communication conduit 4 relative to the enclosure 6 to allow the vertical release of the basket without abutting the siphon or the filter 15.
  • the device of FIGS. 2 and 3 comprises for the most part the same essential organs as the previous one, but it is designed to allow better than it the manufacture of reactive metal granules, easily oxidized.
  • the furnace 31 makes it possible to heat the cell 32 so as to melt and keep the materials introduced therein, as well the metal intended to constitute the granules produced as metal halides constituting the purification bath.
  • the cell 32 is equipped to define 1 interior of the oven two separate compartments communicating with each other by a filter 35.
  • the embodiment shown in detail in Figure 3 corresponds to the case where a bath of purification salts more dense than molten metal.
  • a tubular chimney 36 is disposed vertically in the enclosure 32, the cover 37 of which it passes in leaktight manner, to open to the outside via an airlock 38 for loading the solid products.
  • the filter 35 is arranged across the lower end of the chimney 36, above the bottom 39 of the cell 32.
  • a first compartment 41 is thus formed by the volume internal to the chimney 36.
  • the metal is introduced into solid pieces through the airlock 38 and that its fusion is ensured.
  • the metal is protected from oxidation by an inert gas which is admitted into this compartment at 42.
  • the other compartment 4 is constituted by the intermediate volume between the chimney 36 and the container limiting the cell 32. Its role is to allow the separation between the molten metal by decantation and the purification bath after it has passed through this bath. I1 thus makes it possible to create in the cell 32 a mass of molten metal 44 in which the sampling will be carried out for the formation of the liquid metallic jet. In the case of the figure, the mass of liquid metal 44 is decanted above the bath of molten salts 45 and it is surmounted by an atmosphere of inert gas introduced into cell 32 at 46.
  • the purification salt is present in quantity suf-fisante so that the filter 35 remains always immersed in the bath 45.
  • liquids can be forced through the filter 35, either to cause the transfer of the molten metal from the melting compartment 41 to the settling compartment 43, that is to circulate the molten salt through the holes of the filter for cleaning purposes.
  • the siphon-forming duct 34 comprises two vertical coaxial tubes sliding the one inside the other.
  • the internal tube 4 ⁇ crosses the bottom 39 of the cell 32.
  • I1 opens at its upper end into the atmosphere of inert gas which overcomes the mass of molten metal 44, at 47, and it ends at its lower end with l vibrating orifice 48 through which it opens vertically at the top of the tower 33.
  • a vibrator has been shown at 49 which acts on the end of the tube 46 and thus causes the jet to be divided into liquid drops as soon as it leaves the orifice 48
  • the external tube 51 of the siphon can be moved from outside the cell by means of a rod 52.
  • I1 is closed at its upper end and when it is completely lowered it opens by its lower end at ground level fondue 44. Its operation thus makes it possible to prime the siphon and cause the liquid metal to flow through the internal tube 46.
  • the jet of liquid metal divided into drops falls into the tower 33 which is filled with an inert gas admitted in 51 and extracted in 52 (figure 2 ).
  • the internal atmosphere in the tower cools by heat loss in the ambient air through its walls.
  • the height of the tower is sufficient for the drops of liquid metal to solidify completely during their fall.
  • the solid granules thus obtained are collected at the bottom of the tower 33 and they are extracted therefrom by an airlock 53.
  • the filter 35 having the aim of preventing the passage of any solid inclusion which could block the vibrating orifice 48, has holes of dimension less than or at most equal to that of this orifice, and for example less than 200 microns, for vibrating orifices of diameters which may vary between 200 microns and 3 mm.
  • the positive say according to the invention can be constituted differently in other embodiments.
  • the shape of the chimney 36 and that of the siphon 34 can be modified to adapt the cell 32 to receive a bath of molten salts of lower density than that of the molten metal.
  • the removal of liquid metal then takes place in the mass which settles below the bath of molten salts.
  • the production yield of granules can be increased, in an industrial manufacture, by replacing the single orifice 48 by a vibrating plate provided with holes which form separate jets. It is thus possible to form a series of jets in the same cooling atmosphere and at the end of the same sampling device.
  • a halide of the metal to be granulated generally a fluoride or a chloride, or a mixture of such salts, or a halide of a more reducing metal, the oxide of which forms preferentially to that of metal to be granulated.
  • a halide of the metal to be granulated generally a fluoride or a chloride, or a mixture of such salts, or a halide of a more reducing metal, the oxide of which forms preferentially to that of metal to be granulated.
  • a halide of the metal to be granulated generally a fluoride or a chloride, or a mixture of such salts, or a halide of a more reducing metal, the oxide of which forms preferentially to that of metal to be granulated.
  • a powder intended for use in aluminothermy was produced from molten aluminum brought to 850 ° C., using in addition a bath of molten cryolite (Na 3 AlF 6 ) to dissolve the alumina.
  • the molten aluminum is denser than this bath and is therefore taken from the bottom of the cell.
  • the cooling gas was helium.
  • magnesium for example, a mixture of magnesium chloride and fluoride is used as the molten salt bath.
  • Calcium is widely used for example in refining of cast irons and steels.
  • the invention makes it possible to have it in the form of a regular powder of spherical granules which are easy to transport and to dose, without having to incorporate undesirable constituents therein.
  • the addition of magnesium to calcium lowers the melting point of the alloy. From 11.5% by weight of magnesium in the eutectic alloy to 28% by weight of magnesium, the temperature to be imposed on the molten alloy is in fact determined by the melting temperature of the salts: 645 ° C. for the CaCl 2 -CaF 2 eutectic. The fusion cell is therefore brought to 700 ° C. for example.
  • the same salt bath is used in the context of aluminum granulation.
  • calcium in an amount at least stoichiometric for the reduction of the oxygen which it may contain, ie for example 0.5% by weight of calcium for commercial aluminum metal.
  • a greater proportion of calcium has been added, so that this calcium is mainly found in the granulated magnesium produced, for example in a proportion of 8% by weight.
  • the frequency of the vibrations imposed on the outlet of the jet was 1500 Hz, but we can increase this frequency to 6000 Hz, or use any frequency between 1000 and 16000 Hz.
  • the height of fall in the cooling gas was chosen to be sufficient so that there was always complete solidification of the drops during the fall, starting immediately at the outlet of the vibrating orifice, to benefit from the effect produced by the vibration on the drops.
  • the following data were used to evaluate the temperature of the cooling gas at 50 ° C and for the temperature of the metal at the vibrating orifice of 70 ° C above the melting point: Limiting speed Solidification height

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  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)

Abstract

Procede de fabrication de granules metalliques, suivant lequel on forme les granules par solidification a partir de metal fondu, caracterise en ce que l'on forme un jet de metal fondu, on le fait passer a travers un orifice vibrant (13, 48) pour diviser le jet en gouttes individuelles, et l'on provoque par refroidissement la solidification de ces gouttes en granules. Pour ce faire, on fait tomber les gouttes du jet par gravite a travers une atmosphere de gaz inerte maintenue a une temperature inferieure a la temperature de solidification du metal fondu. Pour des metaux reactifs, on forme ledit jet par prelevement a partir d'une masse de metal en fusion maintenue en contact avec un bain non miscible avec elle, dissolvant selectivement les derives resultant de son oxydation eventuelle.Method for manufacturing metallic granules, according to which the granules are formed by solidification from molten metal, characterized in that a jet of molten metal is formed, it is passed through a vibrating orifice (13, 48) for divide the jet into individual drops, and the solidification of these drops into granules is caused by cooling. To do this, the drops of the jet are dropped by gravity through an atmosphere of inert gas maintained at a temperature below the solidification temperature of the molten metal. For reactive metals, said jet is formed by sampling from a mass of molten metal maintained in contact with a bath immiscible with it, selectively dissolving the derivatives resulting from its possible oxidation.

Description

Procédé de fabrication de granulés métalliques, produits obtenus et dispositif pour la mise en oeuyre de ce procédé.Method for manufacturing metallic granules, products obtained and device for implementing this method.
La présente invention concerne la fabrication de granulés métalliques. Elle a principalement pour objet un procédé de fabrication de granulés métalliques et elle s'étend aux produits obtenus conformément à ce procédé ainsi qu'à un dispositif particulièrement adapté à la mise en oeuvre de ce procédé.The present invention relates to the manufacture of metallic granules. Its main object is a method for manufacturing metallic granules and it extends to the products obtained in accordance with this method as well as to a device particularly suitable for implementing this method.
L'invention est applicable pour mettre tout métal sous forme de granulés, en englobant dans cette notion, non seulement les métaux purs ou quasiment purs, mais aussi les compositions ou alliages métalliques. L'objectif est d'obtenir des grains pratiquement sphériques, de diamètre par exemple de l'ordre de 0,1 à 5 mm, formant ensemble une poudre qui soit coulable, facile à véhiculer par voie pneumatique, et qui présente une densité apparente relativement élevée, sans grande porosité, avec en outre la possibilité d'obtenir un calibrage uniforme des grains, éventuellement après un tri facile à réaliser.The invention is applicable for putting any metal in the form of granules, by including in this concept, not only pure or almost pure metals, but also metal compositions or alloys. The objective is to obtain practically spherical grains, of diameter for example of the order of 0.1 to 5 mm, together forming a powder which is pourable, easy to transport by pneumatic means, and which has a relatively apparent density. high, without great porosity, with in addition the possibility of obtaining a uniform grading of the grains, possibly after an easy sorting.
Dans ce but, on est conduit nécessairement à partir d'un bain de métal en fusion. Mais les propriétés des métaux, à l'état liquide, au passage de l'état liquide à l'état solide, puis à l'état solide, représentent des conditions spécifiques qui font que les procédés de granulation utilisés de manière classique dans le traitement de produits d'un autre genre, tels que des produits pâteux, ne leur sont pas applicables d'une manière générale. D'autre part, les procédés de production de granulés que l'on a pu appliquer à ce jour en partant de bains métalliques fondus, ne donnent pas encore satisfaction du point de vue de la régularité des formes et des dimensions, et les procédés s ' apparentant à 1 ' atomisation que l'on a cherché à appliquer à des produits à base de métaux réactifs comme le calcium conduisent à des poudres réactive et hygroscopiques qui se conservent mal et dont les possibi lités d'emploi sont finalement limitées.For this purpose, one is necessarily led from a bath of molten metal. However, the properties of metals, in the liquid state, on passing from the liquid state to the solid state, then to the solid state, represent specific conditions which make the granulation methods conventionally used in the treatment products of another kind, such as pasty products, are not generally applicable to them. On the other hand, the granule production processes that have been applied to date starting from of molten metal baths, are not yet satisfactory from the point of view of the regularity of shapes and dimensions, and the processes resembling atomization which it has been sought to apply to products based on reactive metals such as calcium lead to reactive and hygroscopic powders which do not keep well and whose possibilities of use are ultimately limited.
Pour s'affranchir de ces inconvénients, l'invention propose un procédé de fabrication de granulés métalliques du type dans lequel on assure la solidification du métal en forme de granulés à partir du métal fondu, caractérisé en ce que l'on forme un jet de métal fondu, on le fait passer à trave un orifice vibrant pour diviser le jet en gouttes individuelles, et l'on provoque par refroidissement la solidification de ces gouttes en granulés.To overcome these drawbacks, the invention provides a method of manufacturing metal granules of the type in which the metal in the form of granules is solidified from the molten metal, characterized in that a jet of molten metal, it is passed through a vibrating orifice to divide the jet into individual drops, and the cooling causes the solidification of these drops into granules.
Le procédé selon l'invention peut s'appliquer à la fabrication de granulés métalliques à partir de bains de métau en fusion de toute composition. On observera cependant que le plus souvent les métaux traités sont à l'état fondu à un température comprise entre 200 et 1500°C et que l'orifice vibrant par lequel sort le jet de métal fondu débouche en général dans une atmosphère refroidie par déperdition thermique dans l'air ambiant, dont la température peut donc se trouver comprise entre 20 et 9θ°C par exemple. En pratique, on opère avantageusement dans des conditions telles que la différence de température entre le métal fondu à la formation du jet et l'atmosphère dans laquelle s'ouvre l'orifice vibrant soit au moins de l'ordre de 200°C, et de préférence comprise entre 300 et 1300°C, et plus particulièrement entre 500 et 1000°C.The method according to the invention can be applied to the manufacture of metallic granules from molten metal baths of any composition. It will however be observed that most often the treated metals are in the molten state at a temperature of between 200 and 1500 ° C. and that the vibrating orifice through which the jet of molten metal exits generally opens into an atmosphere cooled by heat loss. in the ambient air, the temperature of which can therefore be between 20 and 9θ ° C. for example. In practice, operation is advantageously carried out under conditions such that the temperature difference between the molten metal when the jet is formed and the atmosphere in which the vibrating orifice opens is at least of the order of 200 ° C., and preferably between 300 and 1300 ° C, and more particularly between 500 and 1000 ° C.
Selon un mode de mise en oeuvre préféré de l'invention, à la sortie de l'orifice vibrant on fait tomber les gouttes du jet par gravité à travers une atmosphère de gaz inerte maintenue à une température inférieure à la ternpéra-ture de solidification du métal fondu. L'atmosphère de gaz inerte peut être choisie en fonction de la nature du métal, du diamètre du jet et des conditions de pression au niveau de l'orifice vibrant, de manière que les gouttes formées atteignent rapidement la vitesse de chute limite, sur une hauteur de chute laissée disponible dans l'atmosphère qui soit suffisante pour permettre une solidification complète des granulés avant leur collecte. En pratique, la vitesse de chute peut être par exemple de l'ordre de 2 à 30 mètres par seconde et, suivant les conditions thermiques, la solidification peut demander un temps correspondant à une hauteur de chute de l'ordre de 10 cm à 20 m, ou de préférence 20 cm à 10 m. Pendant cette solidification, ou au moins à son début, les gouttes de métal sont soumises à des efforts internes qui résultent des vibrations communiquées au moment de la division du jet en gouttes à la sortie de l'orifice vibrant. L'invention permet ainsi d'obtenir des poudres de granulés dans lesquelles les diamètres des granulés peuvent être par exemple de l'ordre de 0,2 à 3 mm, avec des dispersions par rapport à la dimension moyenne qui peuvent rester inférieures à + O, 5 mm, ou même ne pas dépasser environ + 0,01 mm. En liaison avec les conditions de refroidissement appliquées, les poudres obtenues présentent de plus des qualités de surface qui sont en général favorables aux propriétés que l'on recherche dans ce genre de granulés, en particulier une dureté superficielle et une résistance qui contribuent à la bonne conservation de la poudre et à sa coulabilité. Le gaz inerte peut être par exemple de l'hélium, de l'argon ou des mélanges de ces gaz. Dans certains cas, on peut avoir intérêt à assurer en outre une dispersion des gouttes métalliques en cours de solidification par rapport à la direction de chute du jet, de manière à éviter que des gouttes individuelles puissent fusionner pendant la solidification.According to a preferred embodiment of the invention, at the outlet of the vibrating orifice, the drops of the jet are made to fall by gravity through an atmosphere of inert gas maintained at a temperature below the ternpéra-ture of solidification of the molten metal. The inert gas atmosphere can be chosen according to the nature of the metal, the diameter of the jet and the pressure conditions at the level of the vibrating orifice, so that the drops formed quickly reach the limit fall speed, over a drop height left available in the atmosphere which is sufficient to allow complete solidification of the granules before their collection. In practice, the fall speed can for example be of the order of 2 to 30 meters per second and, depending on the thermal conditions, solidification can take a time corresponding to a fall height of the order of 10 cm to 20 m, or preferably 20 cm to 10 m. During this solidification, or at least at its beginning, the metal drops are subjected to internal forces which result from the vibrations communicated at the time of the division of the jet into drops at the outlet of the vibrating orifice. The invention thus makes it possible to obtain powders of granules in which the diameters of the granules can be for example of the order of 0.2 to 3 mm, with dispersions relative to the average size which can remain less than + 0 , 5 mm, or even not to exceed approximately + 0.01 mm. In connection with the cooling conditions applied, the powders obtained also have surface qualities which are generally favorable to the properties which are sought in this type of granules, in particular a surface hardness and a resistance which contribute to the good conservation of the powder and its flowability. The inert gas can be for example helium, argon or mixtures of these gases. In certain cases, it may be advantageous to further ensure a dispersion of the metal drops during solidification with respect to the direction of fall of the jet, so as to prevent individual drops from being able to merge during solidification.
Selon une autre caractéristique de l'invention, on peut prévoir de former le jet métallique liquide par prélèvement à partir d'une masse de métal en fusion maintenue en contact avec un bain non miscible avec elle, dissolvant sélectivement les dérivés résultant de son oxydation éventuelle. On peut avantageusement faire fondre le métal, le faire passer à 1 ' état fondu à travers le bain de dissolution sélective des dérivés d'oxydation et l'en séparer par décantation pour constituer la masse dans laquelle est prélevé le jet, et prévoir que le métal fondu soit alors conduit sans plus aucun contact avec l'air ou une atmosphère oxydante jusqu'à la sortie du jet dans une atmosphère inerte de refroidissement telle que décrite précédemment, de préférence par l'intermédiaire d'un tronçon de conduite verticale se terminant par l'orifice vibrant. Suivant un mode de mise en oeuvre particulièrement avantageux du procédé objet de l'invention, on peut prévoir de forcer la masse de métal en fusion à travers un filtre de retenue des particules solides, que l'on maintient immergé dans le bain de dissolution des dérivés oxydés et séparer ladite masse de ce bain par décanta-tion préalablement à la formation du jet.According to another characteristic of the invention, provision may be made to form the liquid metallic jet by sampling from a mass of molten metal maintained in contact with a bath immiscible with it, selectively dissolving the derivatives resulting from its possible oxidation . It is advantageous to melt the metal, the passing the molten state through the selective dissolution bath of the oxidation derivatives and separating it by decantation to constitute the mass from which the jet is taken, and providing that the molten metal is then conducted without any contact with air or an oxidizing atmosphere up to the exit of the jet in an inert cooling atmosphere as described above, preferably by means of a vertical pipe section ending in the vibrating orifice. According to a particularly advantageous embodiment of the process which is the subject of the invention, provision may be made to force the mass of molten metal through a filter for retaining solid particles, which is kept immersed in the dissolution bath of the oxidized derivatives and separate said mass from this bath by decanting prior to the formation of the jet.
I1 est ainsi possible de traiter selon l'invention des métaux réputés réactifs en évitant aisément toutes les difficultés que pourrait poser la présence de dérivés d'oxydation solides capables d'obstruer les trous du filtre ou l'orifice de sortie du jet et d'entraîner ainsi une irrégularité dans la formation des gouttes. Le bain utilisé peut être avantageusement constitué d'un halogénure fondu d'au moins un métal de la masse métallique fondue. Il peut aussi être constitué d'un halogénure fondu d'au moins un métal additionnel plus réducteur que le métal essentiel des granulés et incorporé en faible proportion dans ladite masse. Un tel métal additionnel peut être notamment le calcium, métal dont l'oxyde se dissout aisément dans un bain de fluorure et/ou chlorure de calcium. Une proportion de calcium de l'ordre de 0,5 à 10 % en poids est en général suffisante dans des métaux comme l'aluminium ou le magnésium par exemple. On remarquera que le métal additionnel peut se retrouver dans les granulés obtenus conformément à l'invention, alors que les conditions de mise en oeuvre préconisées permettent d' éviter que les sels fondus s'y retrouvent autrement qu'à l'état de traces, décelables mais non gênantes, et en particulier l'invention permet de produire des granulés de métaux réactifs comme le calcium, le magnésium ou l'aluminium qui, malgré l'emploi d'un bain de sels fondus, ne présentent aucun caractère d'hygroscopicité nuisible à la conservation et à la. coulabilité des poudres. La fabrication de granulés métalliques suivant le procédé objet de l'invention implique l'utilisation d'un dispositif comportant un four de fusion de métal dans un récipient de réception d'une masse de métal fondu, des moyens de formation d'un jet de métal prélevé dans ladite masse, à travers un orifice vibrant, des moyens pour provoquer la vibration dudit orifice et assurer ainsi la division du jet en gouttes individuelles, et une chambre de refroidissement et solidification du métal issu dudit orifice, sur au moins la distance parcourue par les gouttes pendant leur solidification. De préférence, le dispositif comporte un siphon de prélèvement de métal dans une masse de métal fondu séparée d'un bain de sels fondus par décantation dans ledit récipient. I1 peut aussi avantageusement comporter un filtre à trous de dimensions inférieures ou au plus égales à celles de l'orifice vibrant, et des moyens pour forcer le métal fondu à travers ce filtre immergé dans le bain de sels fondus. D'autre part, ledit récipient et. ladite chambre de refroidissement sont de préférence étanches et il est avantageusement prévu des moyens pour régler séparément la pression d'un gaz inerte dans ledit récipient et dans ladite chambre de refroidissement.It is thus possible according to the invention to treat metals known to be reactive, easily avoiding all the difficulties which the presence of solid oxidation derivatives could pose, capable of obstructing the holes of the filter or the outlet of the jet and of thus lead to an irregularity in the formation of the drops. The bath used can advantageously consist of a molten halide of at least one metal of the molten metal mass. It can also consist of a molten halide of at least one additional metal more reducing than the essential metal of the granules and incorporated in small proportion in said mass. Such an additional metal may in particular be calcium, a metal whose oxide readily dissolves in a bath of fluoride and / or calcium chloride. A proportion of calcium of the order of 0.5 to 10% by weight is generally sufficient in metals such as aluminum or magnesium for example. It will be noted that the additional metal can be found in the granules obtained in accordance with the invention, while the recommended processing conditions make it possible to prevent the molten salts being found there other than in the trace state, detectable but not annoying, and in particular the invention makes it possible to produce granules of reactive metals such as calcium, magnesium or aluminum which, despite the use of a bath of molten salts, do not exhibit any hygroscopicity which is detrimental to preservation and. flowability of powders. The manufacture of metallic granules according to the process which is the subject of the invention involves the use of a device comprising a metal melting furnace in a receptacle for receiving a mass of molten metal, means for forming a jet of metal taken from said mass, through a vibrating orifice, means for causing the vibration of said orifice and thus ensuring the division of the jet into individual drops, and a chamber for cooling and solidifying the metal coming from said orifice, over at least the distance traveled by the drops during their solidification. Preferably, the device comprises a siphon for removing metal from a mass of molten metal separated from a bath of molten salts by decantation in said container. It can also advantageously include a filter with holes of dimensions less than or at most equal to those of the vibrating orifice, and means for forcing the molten metal through this filter immersed in the bath of molten salts. On the other hand, said container and. said cooling chamber are preferably sealed and means are advantageously provided for separately adjusting the pressure of an inert gas in said container and in said cooling chamber.
D'autres caractéristiques de l'invention apparaîtront à la lecture de la description qui suit, et en particulier de la description plus détaillée d'un dispositif de fabrication de granulés métalliques, faite en référence aux figures 1 à 3 des dessins annexés dans lesquels :Other characteristics of the invention will appear on reading the following description, and in particular the more detailed description of a device for manufacturing metallic granules, made with reference to FIGS. 1 to 3 of the appended drawings in which:
La figure 1 représente schématiquement en coupe les divers organes du dispositif selon l'invention dans un premier mode de réalisation ; la figure 2 représente un tel dispositif, également en coupe verticale, dans un second mode de réalisation ; et la figure 3 représente d ' une manière plus détaillée le dispositif de la figure 2 dans sa partie supérieure.Figure 1 shows schematically in section the various organs of the device according to the invention in a first embodiment; FIG. 2 represents such a device, also in vertical section, in a second embodiment; and Figure 3 shows in more detail the device of Figure 2 in its upper part.
Tel qu'il est décrit ci-après, le dispositif selon 1 ' invention comprend une cellule de chauffe munie d'une enceinte étanche formant récipient et de moyens de chauffe, un organe d'introduction de matières premières dans la cellule, une chambre de refroidissement en communication avec la cellule par un conduit comportant un siphon et une zone percée d'au moins un orifice vibrant, un premier moyen pneumatique pour établir et commander la pression de l'atmosphère dans l'enceinte, un vibrâteur relié à la zone comportant l'orifice vibrant et agencée de manière à le faire vibrer de façon continue, un second moyen pneumatique pour établir et commander la pression de l'atmosphère contenue dans la chambre de refrodissement, et un dispositif d'éva-cuation du solide de cette chambre.As described below, the device according to the invention comprises a heating cell provided with a sealed enclosure forming a container and heating means, a member for introducing raw materials into the cell, a cooling in communication with the cell by a conduit comprising a siphon and a zone pierced with at least one vibrating orifice, a first pneumatic means for establishing and controlling the pressure of the atmosphere in the enclosure, a vibrator connected to the zone comprising the vibrating orifice and arranged so as to make it vibrate continuously, a second pneumatic means for establishing and controlling the pressure of the atmosphere contained in the cooling chamber, and a device for evacuating the solid from this chamber .
Ainsi, le dispositif représenté sur la figure 1 comprend un organe obturable d'introduction de matière 1 pour amener le métal dans une cellule de chauffe 2 d'où le métal fondu est injecté dans une chambre ou tour de refroidissement 3 à travers un conduit 4. Un dispositif d'évacuation obturable 5 permet d'évacuer les granulés de métal solide formés dans la tour de refroidissement 3.Thus, the device shown in FIG. 1 comprises a closable member for introducing material 1 for bringing the metal into a heating cell 2 from which the molten metal is injected into a cooling chamber or tower 3 through a conduit 4 A closable evacuation device 5 makes it possible to evacuate the solid metal granules formed in the cooling tower 3.
La cellule de chauffe 2 comprend une enceinte étanche 6 formant récipient pour contenir le métal en fusion. Cette enceinte 6 est chauffée par un four 7 entourant ses parois latérales et maintenant à l'intérieur de l'enceinte une température supérieure à la température de fusion du métal. Le métal en fusion 8 occupe la partie inférieure de l'enceinte 6 ; il est surmonté par une atmosphère gazeuse 9 dont la pression est commandée par un premier moyen pneumatique 10 auquel elle est reliée par une canalisation 23. Cette pression dans l'atmosphère 9 peut être augmentée ou diminuée, provoquant l'injection plus ou moins rapide du métal fondu 8 à travers le conduit 4. Ce conduit est constitué par un tube recourbé 11 dont une extrémité 12 est immergée dans le métal fondu 8 et dont l'autre extrémité 13 pénètre verticalement dans la partie supérieure de la tour de refroidissement 3. La partie supérieure du tube, voisine de l'extrémité 12, est recourbée pour former siphon, le coude dépassant du niveau du métal fondu. L'extrémité 12, dont l'embouchure est tour-née vers le fond 14 de l'enceinte 6, est munie d'un filtre 15 destiné à retenir les impuretés contenues dans le métal fondu. La zone de l'enceinte 6 au voisinage du fond 14 est une zone de décantation ou peuvent s'accumuler les impuretés de densité supérieure au reste du liquide. Le filtre pourra être placé juste au-dessus de cette zone de décantation du métal fondu pour empêcher les inclusions solides en suspension de colmater rapidement le filtre. La cellule de chauffe 2 comprend en outre un moyen mécanique de brassage schéma-tiquement représenté par l'hélice 18, assurant le brassage et l'homogénéisation du liquide. L'extrémité 13 du tube 11 se termine par au moins un orifice pour l'injection du métal fondu dans la tour de refroidissement 3. L'écoulement filiforme de métal fondu ainsi obtenu forme un jet en chute verticale auquel on appliqué des vibrations pour produire des gouttes de liquide uniformes. Selon un mode de réalisation, l'extrémité 13 du tube est animée de vibrations par un vibrateur 16 et un dispositif de liaison schématiquement représenté par la tige 17. Les gouttes de métal fondu formées à l'extrémité 13 du conduit 4 sont dispersées dans la tour de refroidissement par un moyen de dispersion 19. I1 s'agit par exemple d'une électrode annulaire entourant le jet et chargée électriquement par rapport à l'extrémité 13 du tube 11, qui provoque sur les gouttes l'apparition de charges électriques toutes de même signe. Les gouttes de liquide se dispersent en s 'écartant de la direction verticale du jet et elles se solidifient avant de retomber au fond 20 de la tour 3. Cette dernière contient une atmosphère gazeuse permettant le refroidissement rapide du métal et inerte vis-à-vis de celui-ci. Elle peut comprendre différents moyens pour accé-lérer le refroidissement du métal, par exemple des moyens de mise en circulation du gaz. La vitesse de refroidissement des gouttes peut conditionner la nature de la phase du maté- riau solidifié et, ainsi, la qualité du produit obtenu. L'emploi d'une tour de refroidissement étanche permet d'empêcher la communication de son atmosphère interne avec l'air ambiant. La pression de l'atmosphère gazeuse de la tour peut être commandée par un second moyen pneumatique 25 auquel elle est raccordée par une canalisation 24.The heating cell 2 comprises a sealed enclosure 6 forming a container for containing the molten metal. This enclosure 6 is heated by an oven 7 surrounding its side walls and maintaining inside the enclosure a temperature higher than the melting temperature of the metal. The molten metal 8 occupies the lower part of the enclosure 6; it is surmounted by a gaseous atmosphere 9, the pressure of which is controlled by a first pneumatic means 10 to which it is connected by a pipe 23. This pressure in the atmosphere 9 can be increased or decreased, causing more or less rapid injection of the molten metal 8 through the conduit 4. This conduit consists of a curved tube 11, one end 12 of which is immersed in the molten metal 8 and the other end of which 13 penetrates vertically into the upper part of the cooling tower 3. The upper part of the tube, near the end 12, is bent to form a siphon, the elbow protruding from the level of the molten metal. The end 12, the mouth of which is turned towards the bottom 14 of the enclosure 6, is provided with a filter 15 intended to retain the impurities contained in the molten metal. The area of the enclosure 6 in the vicinity of the bottom 14 is a settling area where impurities of higher density can accumulate than the rest of the liquid. The filter can be placed just above this settling zone of the molten metal to prevent suspended solid inclusions from quickly clogging the filter. The heating cell 2 further comprises a mechanical stirring means diagrammatically represented by the propeller 18, ensuring stirring and homogenization of the liquid. The end 13 of the tube 11 ends in at least one orifice for the injection of the molten metal into the cooling tower 3. The filiform flow of molten metal thus obtained forms a jet in vertical drop to which vibrations are applied to produce uniform liquid drops. According to one embodiment, the end 13 of the tube is driven by vibrations by a vibrator 16 and a connecting device schematically represented by the rod 17. The drops of molten metal formed at the end 13 of the conduit 4 are dispersed in the cooling tower by a dispersing means 19. It is for example an annular electrode surrounding the jet and electrically charged with respect to the end 13 of the tube 11, which causes on the drops the appearance of electrical charges all of the same sign. The drops of liquid disperse away from the vertical direction of the jet and they solidify before falling back to the bottom 20 of the tower 3. The latter contains a gaseous atmosphere allowing the rapid cooling of the metal and inert with respect to of it. It may include different means for accelerating the cooling of the metal, for example means for circulating the gas. The cooling rate of the drops can condition the nature of the phase of the material. riau solidified and, thus, the quality of the product obtained. The use of a sealed cooling tower prevents communication of its internal atmosphere with the ambient air. The pressure of the gaseous atmosphere of the tower can be controlled by a second pneumatic means 25 to which it is connected by a pipe 24.
Selon un mode de réalisation, l'organe d'introduction de métal 1 comporte un sas de communication 21 et le dispositif d'évacuation 5 comporte un sas 22, pour permettre le fonctionnement en continu de l'installation. Le dispositif d'alimentation en matière première 1 permet d'amener dans la cellule de chauffe soit du métal fondu soit du métal à l'état solide ; dans ce dernier cas, la fusion se fait dans la cellule de chauffe, et le métal n'est injecté dans la tour de refroidissement que lorsqu'il est entièrement fondu et homogène. Il est possible de traiter des métau qui réagissent avec l'oxygène, puisque l'ensemble hermétique comprenant la cellule de chauffe 6, les moyens de commande en pression 10 et 25, le conduit de communication 4 et la tour de refroidissement 3 peut être soumis à une atmosphère contrôlée de gaz ne réagissant pas avec le métal.According to one embodiment, the metal introduction member 1 includes a communication lock 21 and the evacuation device 5 includes a lock 22, to allow the continuous operation of the installation. The raw material supply device 1 makes it possible to bring into the heating cell either molten metal or metal in the solid state; in the latter case, the melting takes place in the heating cell, and the metal is only injected into the cooling tower when it is fully molten and homogeneous. It is possible to treat metals which react with oxygen, since the hermetic assembly comprising the heating cell 6, the pressure control means 10 and 25, the communication conduit 4 and the cooling tower 3 can be subjected to a controlled atmosphere of gas which does not react with the metal.
La mise en oeuvre de l'invention au moyen du dispositif de la figure 1 consiste à introduire le métal dans l'enceinte chauffante 6, soit sous forme solide soit sous forme liquide, par le sas 21, à maintenir sa température légèrement au-dessus de sa température de fusion par les moyens de chauffe 7, et à homogénéiser la masse en fusion par brassage ou par bullagc par les moyens de brassage 18. Lorsque la masse en fusion est homogène, on l'injecte dans la tour de refroidissement 3 à travers le tube 11 et l'orifice vibrant. Le siphon est amorcé par exemple par une sur- 2 pression de l'ordre de 5θ à 500 g/cm dans l'enceinte 6, produite par le dispositif pneumatique 10. Pendant leur chute les gouttes ainsi formées sont dispersées si l'élec-trode annulaire du moyen de dispersion 19 est sous tension, et refroidies par l'atmosphère de la tour jusqu'à former des granulés sphériques solides. La vitesse d'injection du métal fondu à travers les orifices vibrants est réglée par la différence de pression de gaz entre l'atmosphère 9 qui surmonte ce métal en fusion dans 1 ' enceinte chauffante et l'atmosphère de la tour 3. Cette vitesse d'injection con-trôlée et réglée permet de tenir compte de la nature du métal, de la fréquence de vibration des orifices vibrants, et de divers paramètres physiques du métal fondu tels que sa température. Les moyens pneumatiques 10 et 25 permettent ainsi d'établir, de régler, et d'arrêter le débit de métal liquide injecté. Ils permettent aussi, en fin d'opération, d'inverser la différence de pression entre les deux enceintes 6 et 3, ce qui permet de nettoyer le filtre sans avoir à ouvrir l'enceinte et à mettre celle-ci en contact avec 1 ' oxygène. L'homogénéisation de la masse en fusion peut être réalisée de différentes façons. Si les inclusions sont suffisamment fines, on peut réaliser une suspension homogène de ces particules grâce à un brassage efficace par le moyen 18. Si au contraire les inclusions sont grosses et risquent de colmater trop rapidement le filtre et/ou le ou les orifices d'injection, on procède à une décantation qui est effectuée dans la partie inférieure de l'enceinte 6. Pour faciliter notamment le nettoyage de 1 ' enceinte après décantation, on pourra prévoir un fond 14 sensiblement et/ou par-tiellement conique, le sommet du cône étant dirigé vers le bas, pour provoquer l'accumulation des produits de décantation dans un panier amovible, non représenté sur la figure, placé à la partie inférieure du cône, le panier pouvant être retiré pour l'évacuation de ces produits de décantation. Le passage du panier pourra être facilité par une disposition décalée, asymétrique, du fond conique 14 et/ou du conduit de communication 4 par rapport à 1 ' enceinte 6 pour permettre le dégagement vertical du panier sans buter contre le siphon ou le filtre 15. Le dispositif des figures 2 et 3 comprend en grande partie les mêmes organes essentiels que le précédent, mais il est conçu pour permettre mieux que lui la fabrication de granulés de métaux réactifs, s ' oxydant facilement. I1 permet en effet de purifier le métal déjà fondu, juste avant la formation du jet et des gouttes liquides, par réaction avec un bain de sels fondus capable de dissoudre les produits d'oxydation et de les retenir dans ce bain, évitant ainsi l'entraînement d'inclusions solides dans le jet métallique et des solidifications intempestives lors de la formation des gouttes.The implementation of the invention by means of the device of FIG. 1 consists in introducing the metal into the heating enclosure 6, either in solid form or in liquid form, through the airlock 21, to maintain its temperature slightly above of its melting temperature by the heating means 7, and to homogenize the molten mass by stirring or by bubbling by the stirring means 18. When the molten mass is homogeneous, it is injected into the cooling tower 3 to through the tube 11 and the vibrating orifice. The siphon is primed, for example, by an overpressure of the order of 5 g to 500 g / cm in the enclosure 6, produced by the pneumatic device 10. During their fall the drops thus formed are dispersed if the elec- annular trode of the dispersing means 19 is under tension, and cooled by the atmosphere of the tower until forming solid spherical granules. The injection speed of the molten metal through the vibrating orifices is regulated by the difference in gas pressure between the atmosphere 9 which overcomes this molten metal in the heating enclosure and the atmosphere of the tower 3. This injection speed is controlled and set allows to take into account the nature of the metal, the vibration frequency of the vibrating orifices, and various physical parameters of the molten metal such as its temperature. The pneumatic means 10 and 25 thus make it possible to establish, adjust, and stop the flow of injected liquid metal. They also allow, at the end of the operation, to reverse the pressure difference between the two chambers 6 and 3, which makes it possible to clean the filter without having to open the chamber and put it in contact with 1 ' oxygen. The homogenization of the molten mass can be achieved in different ways. If the inclusions are sufficiently fine, a homogeneous suspension of these particles can be achieved by effective mixing by means 18. If on the contrary the inclusions are large and risk clogging the filter and / or the orifice (s) too quickly injection, a decantation is carried out which is carried out in the lower part of the enclosure 6. To facilitate in particular the cleaning of the enclosure after decantation, a bottom 14 may be provided which is substantially and / or partially conical, the top of the cone being directed downward, to cause the accumulation of decantation products in a removable basket, not shown in the figure, placed at the bottom of the cone, the basket can be removed for the evacuation of these decantation products. The passage of the basket may be facilitated by an offset, asymmetrical arrangement of the conical bottom 14 and / or of the communication conduit 4 relative to the enclosure 6 to allow the vertical release of the basket without abutting the siphon or the filter 15. The device of FIGS. 2 and 3 comprises for the most part the same essential organs as the previous one, but it is designed to allow better than it the manufacture of reactive metal granules, easily oxidized. It in fact makes it possible to purify the already molten metal, just before the formation of the jet and of the liquid drops, by reaction with a bath of molten salts capable of dissolving the oxidation products and of retaining them in this bath, thus avoiding the entrainment of solid inclusions in the metallic jet and untimely solidifications during the formation of the drops.
On retrouve ainsi sur la figure 2 un four 31, entourant une cellule étanche 32 qui est montée au-dessus d'une tour 33 fermant une chambre étanche séparée de la cel lule 32. La communication entre les deux a lieu seulement par l'intermédiaire d'un siphon 34 (figure 3).Thus found in Figure 2 an oven 31, surrounding a sealed cell 32 which is mounted above a tower 33 closing a sealed chamber separate from the cell 32. Communication between the two takes place only through a siphon 34 (Figure 3).
Le four 31 permet de chauffer la cellule 32 de manière à faire fondre et maintenir en fusion les matériaux qui y sont introduits, aussi bien le métal destiné à constituer les granulés produits que des halogénures métalliques constituant le bain de purification. La cellule 32 est équipée pour définir à 1 ' intérieur du four deux compartiments distincts communiquant entre eux par un filtre 35. La réalisation représentée en détail sur la figure 3 correspond au cas où l'on utilise un bain de sels de purification plus dense que le métal fondu. Une cheminée tubulaire 36 est disposée verticalement dans l'enceinte 32, dont elle traverse de manière étanche le couvercle 37, pour s'ouvrir à l'extérieur par l'intermédiaire d'un sas 38 pour le chargement des produits solides. Le filtre 35 est disposé en travers de l'extrémité inférieure de la cheminée 36, au-dessus du fond 39 de la cellule 32. Un premier compartiment 41 est ainsi constitué par le volume interne à la cheminée 36.The furnace 31 makes it possible to heat the cell 32 so as to melt and keep the materials introduced therein, as well the metal intended to constitute the granules produced as metal halides constituting the purification bath. The cell 32 is equipped to define 1 interior of the oven two separate compartments communicating with each other by a filter 35. The embodiment shown in detail in Figure 3 corresponds to the case where a bath of purification salts more dense than molten metal. A tubular chimney 36 is disposed vertically in the enclosure 32, the cover 37 of which it passes in leaktight manner, to open to the outside via an airlock 38 for loading the solid products. The filter 35 is arranged across the lower end of the chimney 36, above the bottom 39 of the cell 32. A first compartment 41 is thus formed by the volume internal to the chimney 36.
C'est là qu'en fonctionnement on introduit le métal en morceaux solides par le sas 38 et que l'on assure sa fusion. Le métal est protégé de l'oxydation grâce à un gaz inerte qui est admis dans ce compartiment en 42. L'autre compartiment 4 est constitué par le volume intermédiaire entre la cheminée 36 et le récipient limitant la cellule 32. Il a pour rôle de permettre par décantation la séparation entre le métal fondu et le bain de purification après qu'il ait traversé ce bain. I1 permet ainsi de créer dans la cellule 32 une masse de métal fondu 44 dans laquelle s'effectuera le prélèvement pour la formation du jet métallique liquide. Dans le cas de la figure, la masse de métal liquide 44 se décante au-dessus du bain de sels fondus 45 et elle est surmontée par une atmosphère de gaz inerte introduite dans la cellule 32 en 46. Le sel de purification est présent en quantité suf-fisante pour que le filtre 35 reste toujours immergé dans le bain 45. Par action sur les pressions de gaz inerte en 42 et 46, on peut forcer des liquides à travers le filtre 35, soit pour provoquer le transfert du métal fondu depuis le compartiment de fusion 41 jusqu'au compartiment de décantation 43, soit pour faire circuler le sel fondu à travers les trous du filtre à des fins de nettoyage.It is there that in operation the metal is introduced into solid pieces through the airlock 38 and that its fusion is ensured. The metal is protected from oxidation by an inert gas which is admitted into this compartment at 42. The other compartment 4 is constituted by the intermediate volume between the chimney 36 and the container limiting the cell 32. Its role is to allow the separation between the molten metal by decantation and the purification bath after it has passed through this bath. I1 thus makes it possible to create in the cell 32 a mass of molten metal 44 in which the sampling will be carried out for the formation of the liquid metallic jet. In the case of the figure, the mass of liquid metal 44 is decanted above the bath of molten salts 45 and it is surmounted by an atmosphere of inert gas introduced into cell 32 at 46. The purification salt is present in quantity suf-fisante so that the filter 35 remains always immersed in the bath 45. By acting on the inert gas pressures at 42 and 46, liquids can be forced through the filter 35, either to cause the transfer of the molten metal from the melting compartment 41 to the settling compartment 43, that is to circulate the molten salt through the holes of the filter for cleaning purposes.
La constitution des moyens de prélèvement de métal liquide, de formation du jet, et de division de celui-ci en gouttes, apparaît aussi sur les détails de la figure 3. Le conduit formant siphon 34 comprend deux tubes verticaux co-axiaux coulissant l'un dans l'autre. Le tube interne 4θ traverse le fond 39 de la cellule 32. I1 s'ouvre à son extrémité supérieure dans l'atmosphère de gaz inerte qui surmonte la masse de métal fondu 44, en 47, et il se termine à son extrémité inférieure par l'orifice vibrant 48 par lequel il débouche verticalement en haut de la tour 33. On a représenté en 49 un vibrateur qui agit sur l'extrémité du tube 46 et provoque ainsi la division du jet en gouttes liquides dès sa sortie de l'orifice 48. Le tube externe 51 du siphon peut être déplacé depuis l'extérieur de la cellule au moyen d'une tige 52. I1 est fermé à son extrémité supérieure et lorsqu'il est abaissé complètement il débouche par son extrémité inférieure au niveau de la masse fondue 44. Sa manoeuvre permet ainsi d'amorcer le siphon et de faire s'é-cόuler le métal liquide par le tube interne 46. Le jet de métal liquide divisé en gouttes tombe dans la tour 33 qui est remplie d'un gaz inerte admis en 51 et extrait en 52 (figure 2). L'atmosphère interne à la tour se refroidit par déperdition thermique dans l'air ambiant à travers ses parois. La hauteur de la tour est suffisante pour que les gouttes de métal liquide se solidifient complètement au cours de leur chute. Les granulés solides ainsi obtenus sont recueillis au fond de la tour 33 et ils en sont extraits par un sas 53. Le filtre 35, ayant pour but d'empê cher le passage de toute inclusion solide qui pourrait venir boucher l'orifice vibrant 48, a des trous de dimension inférieure ou au plus égale à celle de cet orifice, et par exemple inférieure à 200 microns, pour des orifices vibrants de diamètres pouvant varier entre 200 microns et 3 mm.The constitution of the means for withdrawing liquid metal, for forming the jet, and for dividing the latter into drops, also appears in the details in FIG. 3. The siphon-forming duct 34 comprises two vertical coaxial tubes sliding the one inside the other. The internal tube 4θ crosses the bottom 39 of the cell 32. I1 opens at its upper end into the atmosphere of inert gas which overcomes the mass of molten metal 44, at 47, and it ends at its lower end with l vibrating orifice 48 through which it opens vertically at the top of the tower 33. A vibrator has been shown at 49 which acts on the end of the tube 46 and thus causes the jet to be divided into liquid drops as soon as it leaves the orifice 48 The external tube 51 of the siphon can be moved from outside the cell by means of a rod 52. I1 is closed at its upper end and when it is completely lowered it opens by its lower end at ground level fondue 44. Its operation thus makes it possible to prime the siphon and cause the liquid metal to flow through the internal tube 46. The jet of liquid metal divided into drops falls into the tower 33 which is filled with an inert gas admitted in 51 and extracted in 52 (figure 2 ). The internal atmosphere in the tower cools by heat loss in the ambient air through its walls. The height of the tower is sufficient for the drops of liquid metal to solidify completely during their fall. The solid granules thus obtained are collected at the bottom of the tower 33 and they are extracted therefrom by an airlock 53. The filter 35, having the aim of preventing the passage of any solid inclusion which could block the vibrating orifice 48, has holes of dimension less than or at most equal to that of this orifice, and for example less than 200 microns, for vibrating orifices of diameters which may vary between 200 microns and 3 mm.
Par rapport à la description qui précède, le dis positif selon l'invention peut être constitué différemment dans d'autres formes de réalisation. Ainsi par exemple, au niveau du four de fusion, la forme de la cheminée 36 et celle du siphon 34 peuvent être modifiées pour adapter la cellule 32 à recevoir un bain de sels fondus de densité in férieure à celle du métal fondu. Le prélèvement de métal liquide a alors lieu dans la masse qui se décante en-dessous du bain de sels fondus. D'autre part, le rendement de production en granulés peut être augmenté, dans une fabrication industrielle, en remplaçant l'orifice unique 48 par une plaque vibrante munie de trous qui forment des jets distincts. On peut ainsi former une série de jets dans la même atmosphère de refroidissement et à l'extrémité d'un même dispositif de prélèvement. On peut aussi multiplier le nombre des dispositifs de prélèvement par siphonnage dans la même masse de métal liquide et ces différents dispositifs de pré lèvement peuvent conduire à des jets formés soit dans la même tour de refroidissement soit dans des tours différentes. On décrira maintenant des exemples de mise en oeuvre de l'invention dans la fabrication de différents granulés métalliques. Dans le cas de métaux réactifs, la granulation est effectuée en utilisant un dispositif tel que celui des figures 2 et 3 , avec purification par un bain de sels fondus. Dans certains cas, on y ajoute un dispositif de dispersion des gouttes de métal, tel que celui qui a été décrit pour le dispositif de la figure 1.Compared to the above description, the positive say according to the invention can be constituted differently in other embodiments. Thus, for example, at the melting furnace, the shape of the chimney 36 and that of the siphon 34 can be modified to adapt the cell 32 to receive a bath of molten salts of lower density than that of the molten metal. The removal of liquid metal then takes place in the mass which settles below the bath of molten salts. On the other hand, the production yield of granules can be increased, in an industrial manufacture, by replacing the single orifice 48 by a vibrating plate provided with holes which form separate jets. It is thus possible to form a series of jets in the same cooling atmosphere and at the end of the same sampling device. One can also multiply the number of sampling devices by siphoning in the same mass of liquid metal and these different sampling devices can lead to jets formed either in the same cooling tower or in different towers. We will now describe examples of implementation of the invention in the manufacture of different metal granules. In the case of reactive metals, the granulation is carried out using a device such as that of FIGS. 2 and 3, with purification by a bath of molten salts. In some cases, a device for dispersing metal drops is added to it, such as that which has been described for Figure 1 device.
Comme bain de purification on utilise suivant les cas soit un halogénure du métal à granuler, généralement un fluorure ou un chlorure, ou un mélange de tels sels, soit un halogénure d'un métal plus réducteur dont l'oxyde se forme préférentiellement à celui du métal à granuler. On apprécie notamment d'avoir à dissoudre les oxydes de calcium ou de lanthane dans 1 ours hal oqόnures . Pour ce faire, on peut ajouter par exemple du calcium à un métal tel que l'aluminium ou le magnésium, en utilisant une proportion de calcium suffisante pour pouvoir réduire sensiblement tout l'oxyde éventuellement présent dans le métal à granuler, et retenir les oxydes par réaction de la chaux avec un bain de fluorure et/ou chlorure de calcium à travers lequel on fait passer le mélange métallique fondu.As the purification bath, use is made, depending on the case, of either a halide of the metal to be granulated, generally a fluoride or a chloride, or a mixture of such salts, or a halide of a more reducing metal, the oxide of which forms preferentially to that of metal to be granulated. We particularly appreciate having to dissolve the oxides of calcium or lanthanum in 1 halide bears. To do this, it is possible, for example, to add calcium to a metal such as aluminum or magnesium, using a proportion of calcium sufficient to be able to substantially reduce any oxide which may be present in the metal to be granulated, and to retain the oxides. by reaction of lime with a fluoride and / or calcium chloride bath through which the molten metal mixture is passed.
Dans par exemple la fabrication de granulés d'étain, utilisables comme matériau de soudure, il ' ny a pas de problème d'oxydation important à résoudre. On a cependant protégé la masse de métal fondu dans la cellule de fusion par un bain de couverture formé de l'eutectique LiCl-KCl, l'ensemble étant porté à 35θ°C. La tour de refroidissement contenait de l'argon introduit dans les conditions normales de température et pression et le jet sortant de l'orifice vibrant passait à travers une électrode annulaire portée à 5000V. On a ainsi obtenu des granulés de spectre granulomé-trique 1 mm + 0,01 mm.In, for example, the production of tin granules, which can be used as solder material, there is no significant oxidation problem to be solved. However, the mass of molten metal in the fusion cell was protected by a covering bath formed from the LiCl-KCl eutectic, the whole being brought to 35 ° C. The cooling tower contained argon introduced under normal conditions of temperature and pressure and the jet leaving the vibrating orifice passed through an annular electrode brought to 5000V. We thus obtained granules of granulometric spectrum 1 mm + 0.01 mm.
Dans des conditions analogues, on a produit une poudre destinée à être utilisée en aluminothermie, à partir d'aluminium fondu porté à 850°C en utilisant en outre un bain de cryolithe fondue (Na3AlF6) pour dissoudre l'alumine. L'aluminium fondu est plus dense que ce bain et il est donc prélevé au fond de la cellule. Le gaz de refroidissement était l'hélium.Under analogous conditions, a powder intended for use in aluminothermy was produced from molten aluminum brought to 850 ° C., using in addition a bath of molten cryolite (Na 3 AlF 6 ) to dissolve the alumina. The molten aluminum is denser than this bath and is therefore taken from the bottom of the cell. The cooling gas was helium.
Pour du magnésium, on utilise par exemple comme bain de sels fondus un mélange de chlorure et fluorure de magnésium.For magnesium, for example, a mixture of magnesium chloride and fluoride is used as the molten salt bath.
Le calcium est largement utilisé par exemple dans l'affinage des fontes et aciers.Calcium is widely used for example in refining of cast irons and steels.
L'invention permet d'en disposer sous la forme d'une poudre régulière de granulés sphériques faciles à véhiculer et à doser, sans devoir pour autant y incorporer des constituants non désirables.The invention makes it possible to have it in the form of a regular powder of spherical granules which are easy to transport and to dose, without having to incorporate undesirable constituents therein.
A partir de calcium fondu à 880°C, purifié à travers un filtre à trous de O, 2 mm imergé dans un bain de l'eutectique chlorure de calcium/fluorure de calcium (à 13,76 % en poids de fluorure de calcium) et, après dé- cantation du métal au-dessus de ce bain, en formant le jet à travers une buse de O, 4 mm de diamètre, vibrée à 1500 hertz, et en faisant chuter les gouttes, sans dispersion, dans l'hélium utilisé comme gaz de refroidissement, on a obtenu une poudre de grains sphériques à surface lisse, de diamètre compris entre O, 6 et 1,6 mm, très peu réactive vis-à-vis de l'air, l'oxygène, l'eau.From molten calcium at 880 ° C, purified through a 0.2 mm hole filter immersed in a bath of eutectic calcium chloride / calcium fluoride (at 13.76% by weight of calcium fluoride) and, after the metal has been deposited above this bath, by forming the jet through a 0.4 mm diameter nozzle, vibrated at 1500 hertz, and by dropping the drops, without dispersion, in helium used as cooling gas, a powder of spherical grains with a smooth surface was obtained, with a diameter of between 0.6 and 1.6 mm, very little reactive with respect to air, oxygen, water.
L'addition de magnésium au calcium permet d'abaisser le point de fusion de l'alliage. De 11,5 % en poid de magnésium dans l'alliage à l'eutectique à 28 % en poids de magnésium, la température à imposer à l'alliage fondu est en fait déterminée par la température de fusion des sels : 645 °C pour l'eutectique CaCl2-CaF2. On porte donc la cellule de fusion à 700°C par exemple.The addition of magnesium to calcium lowers the melting point of the alloy. From 11.5% by weight of magnesium in the eutectic alloy to 28% by weight of magnesium, the temperature to be imposed on the molten alloy is in fact determined by the melting temperature of the salts: 645 ° C. for the CaCl 2 -CaF 2 eutectic. The fusion cell is therefore brought to 700 ° C. for example.
Dans un autre exemple, on utilise le même bain de sels dans le cadre de la granulation d'aluminium. On ajout alors à l'aluminium solide introduit, du calcium en quantité au moins stoechiométrique pour la réduction de l'oxygène qu'il peut contenir, soit par exemple 0,5 % en poids de calcium pour de l'aluminium métal du commerce. Dans les mêmes conditions, mais pour la granulation de magnésium, on a ajouté une plus grande proportion de calcium, de sorte que ce calcium se retrouve en majeure partie dans le magnésium en granulés produit, par exemple en proportion de 8 % en poids. Pour une teneur initiale de l'ordre de 0, 1 % d'oxygène, seule une proportion de l'ordre de 0, 25 % du mélange métallique est consommée dans le bain de sels, dont la quantité nécessaire est d'environ 50 g de bain par kilogramme de magnésium à traiter.In another example, the same salt bath is used in the context of aluminum granulation. Then added to the solid aluminum introduced, calcium in an amount at least stoichiometric for the reduction of the oxygen which it may contain, ie for example 0.5% by weight of calcium for commercial aluminum metal. Under the same conditions, but for the granulation of magnesium, a greater proportion of calcium has been added, so that this calcium is mainly found in the granulated magnesium produced, for example in a proportion of 8% by weight. For an initial content of the order of 0.1% of oxygen, only a proportion of the order of 0.25% of the metallic mixture is consumed in the salt bath, the necessary quantity of which is approximately 50 g. of bath per kilogram of magnesium to be treated.
Dans tous ces exemples, la fréquence des vibrations imposées à l'orifice de sortie du jet était de 1500 Hz, mais on peut augmenter cette fréquence à 6000 Hz, ou utili-ser toute fréquence comprise entre 1000 et 16000 Hz. D'autre part, la hauteur de chute dans le gaz de refroidissement était choisie suffisante pour qu'il y ait toujours solidification complète des gouttes au cours de la chute, en commençant aussitôt à la sortie de l'orifice vibrant, pour bénéficier de l'effet produit par la vibration sur les gouttes. On s'est basé sur les données suivantes en évaluant la température de gaz de refroidissement à 50°C et pour température du métal à l'orifice vibrant de 70°C au-dessus du point de fusion : Vitesse limite Hauteur de solidificationIn all these examples, the frequency of the vibrations imposed on the outlet of the jet was 1500 Hz, but we can increase this frequency to 6000 Hz, or use any frequency between 1000 and 16000 Hz. , the height of fall in the cooling gas was chosen to be sufficient so that there was always complete solidification of the drops during the fall, starting immediately at the outlet of the vibrating orifice, to benefit from the effect produced by the vibration on the drops. The following data were used to evaluate the temperature of the cooling gas at 50 ° C and for the temperature of the metal at the vibrating orifice of 70 ° C above the melting point: Limiting speed Solidification height
Calcium dans l'héliumCalcium in helium
Diamètre 0,5 mm 4,5 m/s 15 cm Diamètre 1 mm 9,8 m/s 85 cm Diamètre 2 mm 21,0 m/s 4 m Calcium dans 1 ' argonDiameter 0.5 mm 4.5 m / s 15 cm Diameter 1 mm 9.8 m / s 85 cm Diameter 2 mm 21.0 m / s 4 m Calcium in 1 'argon
Diamètre 0,5 mm 2 m/s O , . 4 m Diamètre 1 mm 4,7 m/s 2 m Diamètre 1,6 mm 8 m/s 5 , 6 m Magnésium dans l'hélium Diamètre 0,5 mm 4,8 m/s 0 , 4 m Diamètre 1 mm 10,7 m/s 2 , 2 m Diamètre 2 . mm 23 m/s 11 m Ca 88,5 % + Mg 11,5 % dans l'hélium Diamètre 0,5 mm 4,5 m/s 0 , 25 m Diamètre 1 mm 10 m/s 1 , 4 m Diamètre 2 mm 22 m/s 7 m Diamètre 2,5 mm 28 m/s 11 , 5 m Aluminium dans l'héliumDiameter 0.5 mm 2 m / s O,. 4 m Diameter 1 mm 4.7 m / s 2 m Diameter 1.6 mm 8 m / s 5.6 m Magnesium in helium Diameter 0.5 mm 4.8 m / s 0.4 m Diameter 1 mm 10 , 7 m / s 2, 2 m Diameter 2. mm 23 m / s 11 m Ca 88.5% + Mg 11.5% in helium Diameter 0.5 mm 4.5 m / s 0.25 m Diameter 1 mm 10 m / s 1, 4 m Diameter 2 mm 22 m / s 7 m Diameter 2.5 mm 28 m / s 11.5 m Aluminum in helium
Diamètre 0,5 mm 6,6 m/s O , 9 m Diamètre 1 mm 15 m/s 4 , 3 mDiameter 0.5 mm 6.6 m / s O, 9 m Diameter 1 mm 15 m / s 4.3 m
Naturellement, l'invention n'est pas limitée à la description ni aux exemples qui précèdent, pas plus qu'au dessins les accompagnant, et toute variante imaginée par l'homme de l'art fait partie de la présente invention. Naturally, the invention is not limited to the description or to the preceding examples, any more than to the accompanying drawings, and any variant imagined by a person skilled in the art forms part of the present invention.

Claims

REVENDICATIONS
1. Procédé de fabrication de granulés métalliques, suivant lequel on forme les granulés par solidification à partir de métal fondu, caractérisé en ce que l'on forme un jet de métal fondu, on le fait passer à travers un orifice vibrant pour diviser le jet en gouttes individuelles, et l'on provoque par refroidissement la solidifica tion de ces gouttes en granulés.1. Method of manufacturing metallic granules, according to which the granules are formed by solidification from molten metal, characterized in that a jet of molten metal is formed, it is passed through a vibrating orifice to divide the jet in individual drops, and the solidification of these drops in granules is caused by cooling.
2. Procédé selon la revendication 1, caractérisé en ce qu'à la sortie de l'orifice vibrant, on fait tomber les gouttes du jet par gravité à travers une atmosphère de gaz inerte maintenue à une température inférieure à la température de solidification du métal fondu.2. Method according to claim 1, characterized in that at the outlet of the vibrating orifice, the drops of the jet are dropped by gravity through an atmosphere of inert gas maintained at a temperature below the solidification temperature of the metal molten.
3. Procédé selon la revendication 2, caractérisé en ce que l'on assure en outre une dispersion des gouttes en cours de solidification par rapport à la direction de chute du jet.3. Method according to claim 2, characterized in that one also ensures a dispersion of the drops during solidification with respect to the direction of fall of the jet.
4. Procédé selon l'une quelconque des revendications 1 à 3, caractérisé en ce que l'on forme ledit jet par prélèvement à partir d'une masse de métal en fusion maintenue en contact avec un bain non miscible avec elle dissolvant sélectivement les dérivés résultant de son oxydation éventuelle.4. Method according to any one of claims 1 to 3, characterized in that said jet is formed by sampling from a mass of molten metal maintained in contact with a bath immiscible with it selectively dissolving the derivatives resulting from its possible oxidation.
5. Procédé selon la revendication 4, caractérisé en ce que l'on force la masse de métal en fusion à travers un filtre de retenue des particules solides maintenu immergé dans le bain de dissolution des dérivés oxydés et l'on sépare ladite masse de ce bain préalablement à la formation du jet .5. Method according to claim 4, characterized in that the mass of molten metal is forced through a solid particle retaining filter kept immersed in the dissolution bath of the oxidized derivatives and said mass is separated from this bath prior to the formation of the jet.
6. Procédé selon la revendication 4 ou 5 , caractérisé en ce que le bain est constitué d'un halogénure fondu d'au moins un métal de ladite masse. 6. Method according to claim 4 or 5, characterized in that the bath consists of a molten halide of at least one metal of said mass.
7. Procédé selon la revendication 4 ou 5, caractérisé en ce que le bain est constitué d'un halogénure fondu d'un métal additionnel plus réducteur qu'un métal essentiel, des granulés et incorporé en faible proportion dans ladite masse.7. Method according to claim 4 or 5, characterized in that the bath consists of a molten halide of an additional metal more reducing than an essential metal , granules and incorporated in small proportion in said mass.
8. Procédé selon la revendication 6 ou 7, caractérisé en ce que ledit métal est le calcium et ledit bain est constitué de fluorure et/ou chlorure de calcium.8. Method according to claim 6 or 7, characterized in that said metal is calcium and said bath consists of fluoride and / or calcium chloride.
9. Dispositif de fabrication de granulés métalliques pour la mise en oeuvre du procédé selon l'une quelconque des revendications 1 à 8, caractérisé en ce qu'il comporte un four (7, 31) de fusion de métal dans un récipient (2, 32) de réception d'une masse de métal fondu, des moyens (4, 11, 34) de formation d'un jet de métal prélevé dans ladite masse à travers un orifice vibrant (13, 48), des moyens (16, 49) pour provoquer la vibration dudit orifice et assurer ainsi la division du jet en gouttes individuelles, et une chambre (3, 33) de refroidissement et solidification du métal issu dudit orifice sur au moins la distance parcourue par les gouttes pendant leur solidification.9. Device for manufacturing metallic granules for implementing the method according to any one of claims 1 to 8, characterized in that it comprises a furnace (7, 31) for melting metal in a container (2, 32) for receiving a mass of molten metal, means (4, 11, 34) for forming a jet of metal taken from said mass through a vibrating orifice (13, 48), means (16, 49 ) to cause the vibration of said orifice and thus ensure the division of the jet into individual drops, and a chamber (3, 33) for cooling and solidifying the metal coming from said orifice over at least the distance traveled by the drops during their solidification.
10. Dispositif selon la revendication 9, caractérisé en ce qu'il comprend un siphon (4, 34) de prélèvement de métal fondu dans une masse de métal fondu (44) séparée d'un bain de sels fondus (45) par décantation dans ledit récipient.10. Device according to claim 9, characterized in that it comprises a siphon (4, 34) for sampling molten metal in a mass of molten metal (44) separated from a bath of molten salts (45) by decantation in said container.
11. Dispositif selon la revendication 10, caractérisé en ce qu'il comprend un filtre (35) à trous de dimension inférieure ou au plus égale à celle de l'orifice vibrant, et des moyens pour forcer le métal fondu à travers ce filtre immergé dans ledit bain. REVENDICATIONS MODIFIEES (reçues par le Bureau International le 9 juin 1981 (09.06.81)) (modifiée) 1. Procédé de fabrication de granulés métalliques, suivant lequel on forme les granulés par solidification à partir de métal fondu, caractérisé en ce que l'on fait passer le métal fondu à 1 ' état divisé à travers un bain de purification, on le réunit en une masse de métal fondu séparée dudit bain par décantation, on forme un jet de métal fondu, par prélèvement à partir de ladite masse, on le fait passer à travers un orifice vibrant pour diviser le jet en gouttes individuelles, et l'on provoque par refroidissement la solidification de ces gouttes en granulés.11. Device according to claim 10, characterized in that it comprises a filter (35) with holes of dimension less than or at most equal to that of the vibrating orifice, and means for forcing the molten metal through this submerged filter in said bath. MODIFIED CLAIMS (received by the International Bureau on June 9, 1981 (09.06.81)) (modified) 1. Method of manufacturing metallic granules, according to which the granules are formed by solidification from molten metal, characterized in that the molten metal is passed in the divided state through a purification bath, it is combined into a mass of molten metal separated from said bath by decantation, a jet of molten metal is formed, by taking it from said mass, passes it through a vibrating orifice to divide the jet into individual drops, and the solidification of these drops into granules is caused by cooling.
2. Procédé selon la revendication 1, caractérisé en ce qu'à la sortie de l'orifice vibrant, on fait tomber les gouttes du jet par gravité à travers une atmosphère de gaz inerte maintenue à une température inférieure à la température de solidification du métal fondu.2. Method according to claim 1, characterized in that at the outlet of the vibrating orifice, the drops of the jet are dropped by gravity through an atmosphere of inert gas maintained at a temperature below the solidification temperature of the metal molten.
3. Procédé selon la revendication 2, caractérisé en ce que l'on assure en outre une dispersion des gouttes cours de solidification par rapport à la direction de chute du jet.3. Method according to claim 2, characterized in that one also ensures a dispersion of the drops during solidification relative to the direction of fall of the jet.
(modifiée) 4. Procédé selon l'une quelconque des revendications 1 à 3, caractérisé en ce que ledit bain de purification est maintenu en contact avec ladite masse de métal fondu et constitué par un bain non miscible avec elle dissolvant sélectivement les dérivés résultant de son oxydation éventuelle.(modified) 4. Method according to any one of claims 1 to 3, characterized in that said purification bath is kept in contact with said mass of molten metal and constituted by a bath immiscible with it selectively dissolving the derivatives resulting from its possible oxidation.
(modifiée) 5. Procédé selon la revendication 4, caractérisé en ce que 1 ' on force la masse de métal en fusion à travers un filtre de retenue des particules solides maintenu immergé dans ledit bain de purification.(modified) 5. Method according to claim 4, characterized in that one forces the mass of molten metal through a solid particles retaining filter kept immersed in said purification bath.
(modifiée) 6. Procédé selon l'une quelconque des revendications 1 à 5, caractérisé en ce que le bain est constitué d'un halogénure fondu d'au moins un métal de ladite masse.(modified) 6. Method according to any one of claims 1 to 5, characterized in that the bath consists of a molten halide of at least one metal of said mass.
(modifiée) 7. Procédé selon l'une quelconque des revendications 1 à 5, caractérisé en ce que le bain est constitué d'un halo génure fondu d'un métal additionnel plus réducteur qu'un métal essentiel des granulés et incorporé en faible proportion dans ladite masse.(modified) 7. Method according to any one of claims 1 to 5, characterized in that the bath consists of a halo genus molten from an additional metal more reducing than an essential metal of the granules and incorporated in small proportion in said mass.
8. Procédé selon la revendication 6 ou 7, caractérisé en ce que ledit métal est le calcium et ledit bain est constitué de fluorure et/ou chlorure de calcium.8. Method according to claim 6 or 7, characterized in that said metal is calcium and said bath consists of fluoride and / or calcium chloride.
(modifiée) 9. Dispositif de fabrication de granulés métalliques pour la mise en oeuvre du procédé selon 1 ' une quelconque des revendications 1 à 8, caractérisé en ce qu'il comporte un four (7, 31) de fusion de métal dans un récipient (2, 32) de réception d'une masse de métal fondu, et d'un bain de purification, des moyens pour faire passer le métal fondu à 1 ' état divisé à travers le bain de purification et séparer ladite masse par décantation dans ledit récipient, des moyens (4, 11, 34) de formation d'un jet de métal prélevé dans ladite masse à travers un orifice vibrant (13, 48) , des moyens (16, 49) pour provoquer la vibration dudit orifice et assurer ainsi la division du jet en gouttes individuelles, et une chambre (3, 33) de refroidissement et solidification du métal issu dudit orifice sur au moins la distance parcourue par les gouttes pendant leur solidification.(modified) 9. Device for manufacturing metallic granules for implementing the method according to any one of claims 1 to 8, characterized in that it comprises a furnace (7, 31) for melting metal in a container (2, 32) receiving a mass of molten metal, and a purification bath, means for passing the molten metal in the divided state through the purification bath and separating said mass by decantation in said container, means (4, 11, 34) for forming a jet of metal taken from said mass through a vibrating orifice (13, 48), means (16, 49) for causing the vibration of said orifice and thus ensuring dividing the jet into individual drops, and a chamber (3, 33) for cooling and solidifying the metal coming from said orifice over at least the distance traveled by the drops during their solidification.
(modifiée) 10. Dispositif selon la revendication 9, caractérisé en ce qu'il comprend un siphon (4, 34) de prélèvement de métal fondu dans ladite masse de métal fondu (44) pour former ledit jet.(modified) 10. Device according to claim 9, characterized in that it comprises a siphon (4, 34) for withdrawing molten metal from said mass of molten metal (44) to form said jet.
11. Dispositif selon la revendication 10, caractérisé en ce qu'il comprend un filtre (35) à trous de dimension inférieure ou au plus égale à celle de l'orifice vibrant, et des moyens pour forcer le métal fondu à travers ce filtre immergé dans ledit bain. 11. Device according to claim 10, characterized in that it comprises a filter (35) with holes of dimension less than or at most equal to that of the vibrating orifice, and means for forcing the molten metal through this submerged filter in said bath.
EP81900066A 1979-12-21 1980-12-22 Process for manufacturing metal pellets, product obtained thereby and device for implementing such process Expired EP0048713B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT81900066T ATE5690T1 (en) 1979-12-21 1980-12-22 METHOD AND DEVICE FOR THE MANUFACTURE OF METAL PARTICLES AND PARTICLES OBTAINED THEREFORE.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR7932115A FR2471827A1 (en) 1979-12-21 1979-12-21 DEVICE FOR THE PRODUCTION OF UNIFORM METAL PELLETS
FR7932115 1979-12-21

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EP0048713A1 true EP0048713A1 (en) 1982-04-07
EP0048713B1 EP0048713B1 (en) 1983-12-28

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EP (1) EP0048713B1 (en)
JP (1) JPH0135881B2 (en)
AU (1) AU543715B2 (en)
DE (1) DE3066037D1 (en)
FR (1) FR2471827A1 (en)
IT (1) IT1134864B (en)
WO (1) WO1981001811A1 (en)

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EP0048713B1 (en) 1983-12-28
AU543715B2 (en) 1985-04-26
JPH0135881B2 (en) 1989-07-27
IT1134864B (en) 1986-08-20
JPS56501850A (en) 1981-12-17
WO1981001811A1 (en) 1981-07-09
DE3066037D1 (en) 1984-02-02
AU6643581A (en) 1981-07-22
FR2471827A1 (en) 1981-06-26
IT8026884A0 (en) 1980-12-22
US4428894A (en) 1984-01-31

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