EP0636848B1 - Smelting process of electrically-conductive materials in an induction smelting furnace with a cold crucible and furnace therefor - Google Patents

Smelting process of electrically-conductive materials in an induction smelting furnace with a cold crucible and furnace therefor Download PDF

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Publication number
EP0636848B1
EP0636848B1 EP94401703A EP94401703A EP0636848B1 EP 0636848 B1 EP0636848 B1 EP 0636848B1 EP 94401703 A EP94401703 A EP 94401703A EP 94401703 A EP94401703 A EP 94401703A EP 0636848 B1 EP0636848 B1 EP 0636848B1
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Prior art keywords
electroconductive material
electromagnetic
jet
mass
crucible
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EP94401703A
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German (de)
French (fr)
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EP0636848A1 (en
Inventor
Pascal Colpo
Jean Driole
Sylvain Witzke
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TECPHY
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TECPHY
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B14/00—Crucible or pot furnaces
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B14/00—Crucible or pot furnaces
    • F27B14/06—Crucible or pot furnaces heated electrically, e.g. induction crucible furnaces with or without any other source of heat
    • F27B14/061—Induction furnaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/10—Supplying or treating molten metal
    • B22D11/11—Treating the molten metal
    • B22D11/114—Treating the molten metal by using agitating or vibrating means
    • B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D39/00—Equipment for supplying molten metal in rations
    • B22D39/003—Equipment for supplying molten metal in rations using electromagnetic field
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/34—Arrangements for circulation of melts
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2213/00—Aspects relating both to resistive heating and to induction heating, covered by H05B3/00 and H05B6/00
    • H05B2213/02—Stirring of melted material in melting furnaces

Definitions

  • the subject of the present invention is a method for melting an electroconductive material in an oven induction melting in a cold crucible and a furnace fusion for the implementation of this process.
  • This process is generally used for make a stabilized casting of a molten metal with a variable flow rate for the production of powders metallic by atomization.
  • melting furnaces by induction in which one uses a crucible intended to receive an electroconductive material and which is called a cold crucible because it is constantly cooled.
  • fusion is caused partial or total of a mass of the electrically conductive material liquid by electromagnetic confinement of so as to separate from the wall of the crucible the mass of said liquid electroconductive material.
  • the crucible is composed of several metallic sectors electrically isolated from each other from others and surrounded by a means of heating by electromagnetic induction of the electroconductive material contained in said crucible.
  • the crucible is for example of cylindrical shape having a substantially hemispherical bottom or conical with a pouring hole to which is fixed a mass pouring tube of the electroconductive material liquid.
  • Induction crucible melting furnaces metallic cold are preferred to crucible furnaces refractories that pollute the mass of electrically conductive material liquid by contact of said material with refractory walls of the crucible.
  • Pollution is due to the formation of inclusionary particles of compounds for example oxidized.
  • this pollution incorporates into the powders of numerous inclusions and it is notably recognized that the presence of such inclusions in rotating parts aeronautical engine, for example based on nickel, may be the cause of defects in service performance of these parts subjected to fatigue stresses and lead in particular to premature parts ruptures subject to high stresses at high temperature.
  • an electromagnetic nozzle comprising a coil inductor associated with a device magnetic field concentrator located between the inductor with turns and the walls of the pouring orifice.
  • Such a nozzle has the disadvantage to be conditioned, in its functioning, by the choice of specific dimension parameters, as well as parameters for defining the applied magnetic field such as the frequency and intensity of said field magnetic.
  • this nozzle has a strong size and low efficiency.
  • This centripetal movement at the level of the upper surface of the molten charge allows materials not yet perfectly melted floating on the surface of the load, to be brought to the center and to be then engulfed in this charge, and thereby allows mixing of the mass of molten materials without take into account the inclusions present in said mass fondue.
  • two phenomena are used which are electromagnetic mixing allowing to bring inclusions within the mass of molten metal towards the electromagnetic skin area and a capture of inclusions in the skin area, said inclusions being offset to the wall of the crucible and the surface of the molten metal mass under the effect of magnetic pressure forces.
  • the object of the invention is to propose a method for melting an electroconductive material in an oven of melting by induction in cold crucible which allows to ensure a dynamic purification in volume of the mass of the liquid electroconductive material before and during casting, by settling of inclusions.
  • the invention also relates to an oven of melting an electrically conductive material by induction in a cold crucible, for implementing the process mentioned above, said melting furnace comprising a crucible intended to contain said electroconductive material and formed of several metal sectors electrically isolated from each other, means of cooling of metal sectors, means of electromagnetic induction heating of the material electroconductive arranged around the crucible, a tube for pouring the arranged liquid electroconductive material vertically below the crucible and electromagnetic means confinement of the jet of electroconductive material liquid in the pouring tube, said electromagnetic means being arranged around the tube and powered by a generator, characterized in that the electromagnetic means of containment of the jet of electroconductive material are formed by an extra-flat electromagnetic coil and that includes means for centering said electromagnetic coil extra flat with respect to the vertical axis pouring tube and crucible and centering means and positioning of the crucible sectors by compared to electromagnetic induction heating means of electroconductive material and relative electromagnetic means for confining the jet of liquid electroconductive material.
  • Fig. 1 there is shown schematically a melting furnace 10 by induction in a cold crucible intended in particular for the purification of a mass 1 of a electroconductive material before atomization for the manufacture of powders.
  • the melting furnace 10 comprises a crucible 11 intended to contain the electroconductive material 1 and formed of several isolated metal sectors 12 electrically from each other and each provided with a water cooling means no shown in Fig. 1.
  • the number of metal sectors 12 is by example of new.
  • the crucible 11 is for example of shape cylindrical extending by a bottom substantially hemispherical or conical with a pouring orifice 13 the mass of the liquid electroconductive material 1.
  • the melting furnace 10 also includes electromagnetic induction heating means 14 of the electroconductive material 1 arranged around the crucible 10.
  • These means 14 of induction heating electromagnetic are composed for example of eight turns.
  • the melting furnace 10 also includes a tube pouring 15 of the electroconductive material 1 liquid arranged vertically below the crucible 11 and in the axis of the pouring orifice 13 and the means 16 of confinement of the jet of electroconductive material 1 liquid in said pouring tube 15.
  • Electromagnetic means 16 of containment of the jet of liquid electroconductive material are arranged around the pouring tube 15 and supplied by a generator not shown in the figures.
  • the tube casting 15 is formed by eight cylinder sectors 15a cooled by a fluid circulation circuit 17 such as water.
  • the means 16 for confining the jet of electroconductive material 1 liquid in the tube casting 15 are formed by an electromagnetic coil extra flat 16, such as a BITTER coil, comprising for example ten turns 16a in the form of copper plates, spread over a height of 30mm, for a jet of electroconductive material of approximately 12mm of diameter.
  • an electromagnetic coil extra flat 16 such as a BITTER coil, comprising for example ten turns 16a in the form of copper plates, spread over a height of 30mm, for a jet of electroconductive material of approximately 12mm of diameter.
  • Each of the copper plates is pierced with thirty-six 2.5mm diameter holes connected to a circuit 18 of transverse water circulation for cooling of the electromagnetic coil 16.
  • the melting furnace 10 comprises means 20 for centering the electromagnetic coil 16 for confining the jet of electroconductive material liquid relative to the vertical axis of the pouring tube 15 and crucible 11 and means 25 for centering and positioning of the sectors 12 of the crucible 11 relative to to the means 14 of heating by electromagnetic induction of the electroconductive material 1 and with respect to the electromagnetic coil 16.
  • the means of centering the electromagnetic coil 16 are formed by an envelope 20 in insulating material for example from PERMAGLAS inserting the turns 16a of said electromagnetic coil 16.
  • Centering and positioning means sectors 12 of the crucible 11 are formed by a shell 25 of insulating material, for example from PERMAGLAS arranged around said sector 12 and inserting the means 14 electromagnetic induction heating of electrically conductive material 1 and the cooling means sectors 12.
  • This coating keeps the turns means 14 for induction heating of the material electroconductive 1 and crucible 11 which avoids hydrodynamic disturbances in the mass of material liquid electroconductive.
  • the induction furnace 1 comprising crucible 11 and tube 15 can be placed in an enclosure under controlled atmosphere and the material flow jet electrically conductive is subjected to bursting in the form of a powder.
  • the perfect vertical cylindrical geometry of the casting jet of the electroconductive material is a important or even essential characteristic of good quality of the powders obtained by atomization.
  • the mass of electroconductive material 1 consisting of a steel 5 cm radius superalloy is placed in the crucible 11 and the power transmitted by the means 14 of electromagnetic induction heating and order of 50 KW for a current of 1000 A at the frequency of 20KHz.
  • the Applicant has found that the non-conductive particles, contained in the mass of electroconductive material 1 to be treated, were subjected, in an electromagnetic vortex medium, to a series forces such as drag force, virtual mass, Archimedes thrust, hydrodynamic pressure, force of lorentz which allowed to deduce the behavior of inclusions in a particular electromagnetic patch.
  • the Applicant has determined a configuration the more favorable for the separation of inclusionary particles nonconductive contained in the mass of the molten and confined electrically conductive material and their decantation on the surface of this mass.
  • the method according to the invention consists, during electromagnetic mixing, to create in the mass of the electrically conductive material 1 liquid at minus a vortex 30 in which the inclusionary particles solids or liquids are entrained in a swirling spiral and decanted when they reach the surface of this mass of electrically conductive material 1 liquid.
  • This coaxial alignment requires that the electromagnetic coil 16 means for confining the jet generates an electromagnetic field in symmetry cylindrical with the vertical axis of the melting furnace 10.
  • a classic spiral coil with a conductor of circular tubular cross section only may not be suitable for containment of the pouring jet, because each of the turns forms a current path which is moves in an inclined plane with respect to the vertical axis, directly dependent on the pitch of the propeller of the electromagnetic coil.
  • an electromagnetic coil classic generates a magnetic field creating instabilities jet casting.
  • the means of confinement of the pouring jet of the mass of the material electroconductive are formed by a extra flat electromagnetic coil 16 of the type described previously.
  • the electromagnetic field generated by the electromagnetic coil 16 is determined so that the magnetic pressure jump is maximum, for a given power of the generator supplying said coil electromagnetic 16.
  • Fig. 3 there is shown diagrammatically, the mass movement of the electroconductive material 1 liquid which is materialized by the two vortices 30 overlays with a travel speed of approximately 0.2m / s.
  • Figs. 4 and 5 represent two diagrams materializing the displacement of the inclusionary particles non-conductive respectively in the vortex superior and in the inferior vortex.
  • Measuring the settling time allows control the minimum melting time of the mass of the electroconductive material and mixing this mass which ensures the purification by settling of the particles inclusions of given size.
  • Particle separation time inclusions is maximum for particles located initially near the center of the vortex (s) 30 and the settling time is very important for particles small inclusions.
  • the Applicant has found that the efficiency of the electromagnetic confinement of the casting of the mass of the electroconductive material 1 is all the greater as the magnetic pressure jump between the axis and the surface of the casting jet is high.
  • the pressure jump is a function of applied electromagnetic force and depth of penetration of the magnetic field into the casting jet.
  • Fig. 6 represents three curves showing the variation of the value of the pressure jump ⁇ Pm in function of the ratio of the radius R of the casting jet to the penetration depth ⁇ of the magnetic field, for different electrical resistivities ⁇ of the material electroconductive.
  • the method according to the invention allows, thanks to the electromagnetic confinement of the associated casting jet to the coaxiality of the magnetic fields of the means of confinement of the pouring jet, heating means by induction of the mass of the electroconductive material, crucible and said mass of the electrically conductive material to obtain a control of the electromagnetic mixing of this liquid mass, while ensuring the separation into continuous solid inclusion impurities contained in the electroconductive material also allowing to obtain improved product quality.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Engineering & Computer Science (AREA)
  • Crucibles And Fluidized-Bed Furnaces (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Furnace Details (AREA)

Description

La présente invention a pour objet un procédé de fusion d'un matériau électroconducteur dans un four de fusion par induction en creuset froid et un four de fusion pour la mise en oeuvre de ce procédé.The subject of the present invention is a method for melting an electroconductive material in an oven induction melting in a cold crucible and a furnace fusion for the implementation of this process.

On connaít un procédé de fusion d'un matériau électroconducteur dans un four de fusion par induction en creuset froid, dans lequel on chauffe une masse d'un matériau électroconducteur jusqu'à sa température de fusion, on décante les particules inclusionnaires solides contenues dans le matériau électoconducteur liquide et on coule une partie de la masse dudit matériau électroconducteur liquide par un conduit de coulée disposé au-dessous dudit four de fusion.We know a method of melting a material electroconductive in an induction melting furnace in a cold crucible, in which we heat a mass of one electroconductive material up to its temperature of fusion, the solid inclusionary particles are decanted contained in the liquid electrically conductive material and a part of the mass of said electroconductive material is poured liquid through a pouring duct arranged below of said melting furnace.

Ce procédé est généralement utilisé pour réaliser une coulée stabilisée d'un métal fondu avec un débit de coulée variable pour l'élaboration de poudres métalliques par atomisation.This process is generally used for make a stabilized casting of a molten metal with a variable flow rate for the production of powders metallic by atomization.

A cet effet, on connaít des fours de fusion par induction dans lesquels on utilise un creuset destiné à recevoir un matériau électroconducteur et qui est appelé creuset froid car il est en permanence refroidi.For this purpose, there are known melting furnaces by induction in which one uses a crucible intended to receive an electroconductive material and which is called a cold crucible because it is constantly cooled.

Dans de tels fours, on provoque la fusion partielle ou totale d'une masse du matériau électroconducteur liquide par confinement électromagnétique de façon à écarter de la paroi du creuset la masse dudit matériau électroconducteur liquide.In such ovens, fusion is caused partial or total of a mass of the electrically conductive material liquid by electromagnetic confinement of so as to separate from the wall of the crucible the mass of said liquid electroconductive material.

Pour cela, le creuset est composé de plusieurs secteurs métalliques isolés électriquement les uns des autres et entourés d'un moyen de chauffage par induction électromagnétique du matériau électroconducteur contenu dans ledit creuset.For this, the crucible is composed of several metallic sectors electrically isolated from each other from others and surrounded by a means of heating by electromagnetic induction of the electroconductive material contained in said crucible.

Le creuset est par exemple de forme cylindrique comportant un fond sensiblement hémisphérique ou conique muni d'un orifice de coulée sur lequel est fixé un tube de coulée de la masse du matériau électroconducteur liquide.The crucible is for example of cylindrical shape having a substantially hemispherical bottom or conical with a pouring hole to which is fixed a mass pouring tube of the electroconductive material liquid.

Les fours de fusion par induction à creuset froid métallique sont préférés aux fours à creuset réfractaires qui polluent la masse de matériau électroconducteur liquide par le contact dudit matériau avec les parois réfractaires du creuset.Induction crucible melting furnaces metallic cold are preferred to crucible furnaces refractories that pollute the mass of electrically conductive material liquid by contact of said material with refractory walls of the crucible.

La pollution est due à la formation de particules inclusionnaires de composés par exemple oxydés.Pollution is due to the formation of inclusionary particles of compounds for example oxidized.

Dans des applications particulières, notamment dans l'élaboration de poudres par atomisation de métaux, cette pollution incorpore dans les poudres de nombreuses inclusions et il est notamment reconnu que la présence de telles inclusions dans des pièces tournantes de moteur aéronautique, par exemple à base de nickel, peut être à l'origine de défauts de tenue en service de ces pièces soumises à des sollicitations en fatigue et entraínent notamment des ruptures prématurées des pièces soumises à de fortes contraintes à haute température.In particular applications, in particular in the development of powders by atomization of metals, this pollution incorporates into the powders of numerous inclusions and it is notably recognized that the presence of such inclusions in rotating parts aeronautical engine, for example based on nickel, may be the cause of defects in service performance of these parts subjected to fatigue stresses and lead in particular to premature parts ruptures subject to high stresses at high temperature.

Pour éviter ces inconvénients, des solutions, ne donnant par entièrement satisfaction, ont été proposées sur la base de l'utilisation d'une busette électromagnétique formant l'orifice de coulée de la masse du matériau électoconducteur liquide sans que celui-ci soit en contact avec les parois de ladite busette.To avoid these drawbacks, solutions, not entirely satisfactory, have been proposed based on the use of an electromagnetic nozzle forming the mass pouring hole of the liquid electrically conductive material without it being in contact with the walls of said nozzle.

Dans le domaine de la régulation d'un débit d'écoulement d'un métal liquide à travers un tube de coulée, les brevets FR-A-2 316 026, FR-A-2 396 612 et FR-A-2 397 251 décrivent également des dispositifs électromagnétiques fonctionnant à haute fréquence dans lesquels un écran de cuivre est nécessaire pour obtenir le confinement souhaité.In the field of flow regulation flow of liquid metal through a tube casting, the patents FR-A-2 316 026, FR-A-2 396 612 and FR-A-2 397,251 also describe electromagnetic devices operating at high frequency in which a copper screen is required to obtain the containment desired.

La mise en oeuvre industrielle d'un tel dispositif, tel que sur une installation d'atomisation de poudres de superalliage à base de nickel présente toutefois de sérieuses difficultés.The industrial implementation of such device, such as on an atomization installation of nickel-based superalloy powders present however serious difficulties.

Pour éviter ces difficultés, on connaít dans le brevet FR-A-2 649 625 une busette électromagnétique comprenant un inducteur à spires associé à un dispositif concentreur de champ magnétique disposé entre l'inducteur à spires et les parois de l'orifice de coulée.To avoid these difficulties, we know in FR-A-2 649 625 an electromagnetic nozzle comprising a coil inductor associated with a device magnetic field concentrator located between the inductor with turns and the walls of the pouring orifice.

Une telle busette présente l'inconvénient d'être conditionnée, dans son fonctionnement, par le choix de paramètres spécifiques de dimension, ainsi que des paramètres de définition du champ magnétique appliqué comme par exemple la fréquence et l'intensité dudit champ magnétique.Such a nozzle has the disadvantage to be conditioned, in its functioning, by the choice of specific dimension parameters, as well as parameters for defining the applied magnetic field such as the frequency and intensity of said field magnetic.

D'autre part, cette busette présente un fort encombrement et un faible rendement.On the other hand, this nozzle has a strong size and low efficiency.

Par ailleurs, on connaít également dans le brevet FR-A-2 665 249 un four à creuset froid associé à une culasse magnétique qui permet de provoquer un resserrement des lignes de champ au niveau de la surface supérieure de la charge en fusion contenue dans le creuset.Furthermore, we also know in the patent FR-A-2,665,249 a cold crucible furnace associated with a magnetic breech which makes it possible to cause a tightening of field lines at surface level the molten charge contained in the crucible.

Ce resserrement des lignes de champ provoque un entraínement centripète de la matière en fusion au niveau de la surface du matériau fondu, ce qui entraíne en conséquence un brassage de la charge en fusion dans un sens inverse au sens naturel de brassage qui se produit en absence d'une telle culasse.This tightening of the field lines causes a centripetal drive of the molten material at level of the surface of the molten material, which results consequently a mixing of the molten charge in an opposite direction to the natural direction of mixing which is produced in the absence of such a cylinder head.

Ce mouvement centripète au niveau de la surface supérieure de la charge en fusion permet aux matières non encore parfaitement fondues flottant sur la surface de la charge, d'être amenées au centre et d'être englouties ensuite dans cette charge, et de ce fait permet un brassage de la masse de matériaux fondus sans tenir compte des inclusions présentes dans ladite masse fondue.This centripetal movement at the level of the upper surface of the molten charge allows materials not yet perfectly melted floating on the surface of the load, to be brought to the center and to be then engulfed in this charge, and thereby allows mixing of the mass of molten materials without take into account the inclusions present in said mass fondue.

On connaít également dans le brevet FR-A-2 646 858 un procédé de décantation des inclusions d'une masse métallique fondue, dans lequel on utilise un déplacement des particules inclusionnaires vers la surface, dans l'épaisseur de la peau électromagnétique, puis un piégeage des particules par les parties les plus froides du creuset.We also know in patent FR-A-2 646 858 a process for decanting the inclusions of a molten metallic mass, in which a displacement of the inclusionary particles towards the surface, in the thickness of the electromagnetic skin, then a trapping of the particles by the most cold from the crucible.

Dans ce procédé, on utilise deux phénomènes qui sont un brassage électromagnétique permettant d'amener au sein de la masse de métal fondu les inclusions vers la zone de peau électromagnétique et une capture des inclusions dans la zone de peau, lesdites inclusions étant déportées vers la paroi du creuset et la surface de la masse métallique fondue sous l'effet des forces de pression magnétiques.In this process, two phenomena are used which are electromagnetic mixing allowing to bring inclusions within the mass of molten metal towards the electromagnetic skin area and a capture of inclusions in the skin area, said inclusions being offset to the wall of the crucible and the surface of the molten metal mass under the effect of magnetic pressure forces.

L'invention a pour but de proposer un procédé de fusion d'un matériau électroconducteur dans un four de fusion par induction en creuset froid qui permet d'assurer une purification dynamique en volume de la masse du matériau électroconducteur liquide avant et pendant la coulée, par décantation des inclusions.The object of the invention is to propose a method for melting an electroconductive material in an oven of melting by induction in cold crucible which allows to ensure a dynamic purification in volume of the mass of the liquid electroconductive material before and during casting, by settling of inclusions.

L'invention a donc pour objet un procédé de fusion d'un matériau électroconducteur dans un four de fusion par induction en creuset froid, procédé dans lequel :

  • on confine électromagnétiquement dans le four de fusion, une masse du matériau électroconducteur jusqu'à sa température de fusion,
  • on décante les particules inclusionnaires contenues dans le matériau électroconducteur liquide,
  • on coule une partie de la masse du matériau électroconducteur liquide par un tube de coulée disposé au-dessous dudit four de fusion,
  • on soumet le jet de coulée du matériau électroconducteur liquide à un confinement électromagnétique radial,
caractérisé en ce que :
  • ou soumet le jet de coulée du matériau électroconducteur liquide à ce confinement à l'aide d'une bobine électromagnétique extraplate,
  • on assure un alignement coaxial vertical du champ électromagnétique agissant sur la masse du matériau électroconducteur liquide et sur le jet de coulée de ladite masse,
  • et on crée dans la masse du matériau électroconducteur liquide par brassage électromagnétique, au moins un vortex dans lequel les particules inclusionnaires sont entraínées dans un mouvement tourbillonnaire et décantées en atteignant la surface de ladite masse du matériau électroconducteur liquide.
The subject of the invention is therefore a method of melting an electroconductive material in a cold crucible induction melting furnace, method in which:
  • electromagnetically confining in the melting furnace, a mass of the electroconductive material up to its melting temperature,
  • the inclusionary particles contained in the liquid electroconductive material are decanted,
  • a part of the mass of the liquid electroconductive material is poured through a pouring tube placed below said melting furnace,
  • the pouring jet of the liquid electroconductive material is subjected to a radial electromagnetic confinement,
characterized in that:
  • or subjects the pouring jet of the liquid electroconductive material to this confinement by means of an extra-flat electromagnetic coil,
  • ensuring a vertical coaxial alignment of the electromagnetic field acting on the mass of the liquid electroconductive material and on the casting jet of said mass,
  • and creating in the mass of the liquid electroconductive material by electromagnetic stirring, at least one vortex in which the inclusionary particles are entrained in a vortex movement and decanted while reaching the surface of said mass of the liquid electroconductive material.

Selon une autre caractéristique de l'invention, on crée, dans la masse du matériau électroconducteur en fusion soumise au brassage électromagnétique, au moins deux vortex superposés.According to another characteristic of the invention, we create in the mass of electrically conductive material in fusion subjected to electromagnetic stirring, at least two superimposed vortices.

L'invention a également pour objet un four de fusion d'un matériau électoconducteur par induction en creuset froid, pour la mise en oeuvre du procédé mentionné ci-dessus, ledit four de fusion comprenant un creuset destiné à contenir ledit matériau électroconducteur et formé de plusieurs secteurs métalliques isolés électriquement les uns des autres, des moyens de refroidissement des secteurs métalliques, des moyens de chauffage par induction électromagnétique du matériau électroconducteur disposés autour du creuset, un tube de coulée du matériau électroconducteur liquide disposé verticalement au-dessous du creuset et des moyens électromagnétiques de confinement du jet de matériau électroconducteur liquide dans le tube de coulée, lesdits moyens électromagnétiques étant disposés autour du tube de coulée et alimentés par un générateur, caractérisé en ce que les moyens électromagnétiques de confinement du jet de matériau électroconducteur sont formés par une bobine électromagnétique extraplate et en ce qu'il comporte des moyens de centrage de ladite bobine électromagnétique extraplate par rapport à l'axe vertical du tube de coulée et du creuset et des moyens de centrage et de positionnement des secteurs du creuset par rapport aux moyens de chauffage par induction électromagnétique du matériau électroconducteur et par rapport aux moyens électromagnétiques de confinement du jet de matériau électroconducteur liquide.The invention also relates to an oven of melting an electrically conductive material by induction in a cold crucible, for implementing the process mentioned above, said melting furnace comprising a crucible intended to contain said electroconductive material and formed of several metal sectors electrically isolated from each other, means of cooling of metal sectors, means of electromagnetic induction heating of the material electroconductive arranged around the crucible, a tube for pouring the arranged liquid electroconductive material vertically below the crucible and electromagnetic means confinement of the jet of electroconductive material liquid in the pouring tube, said electromagnetic means being arranged around the tube and powered by a generator, characterized in that the electromagnetic means of containment of the jet of electroconductive material are formed by an extra-flat electromagnetic coil and that includes means for centering said electromagnetic coil extra flat with respect to the vertical axis pouring tube and crucible and centering means and positioning of the crucible sectors by compared to electromagnetic induction heating means of electroconductive material and relative electromagnetic means for confining the jet of liquid electroconductive material.

Selon d'autres caractéristiques de l'invention :

  • les moyens de centrage de la bobine électromagnétique extraplate sont formés par une enveloppe en matériau isolant électrique et thermique insérant lesdits moyens électromagnétiques de confinement du jet,
  • les moyens de centrage et de positionnement des secteurs du creuset sont formés par une coquille en matériau isolant électrique et thermique disposée autour desdits secteurs et insérant les moyens de chauffage par induction électromagnétique du matériau électroconducteur et les moyens de refroidissement desdits secteurs,
  • la bobine électromagnétique comporte dix spires sous forme de plaques de cuivre, reparties sur une hauteur de 30mm, pour un jet de matériau électroconducteur d'environ 12mm de diamètre,
  • le tube de coulée est formé par un cylindre métallique sectorisé à double paroi, refroidi par circulation d'un fluide,
  • le générateur d'alimentation de la bobine électromagnétique extraplate délivrent un signal à une fréquence déterminée pour que le rapport entre le rayon de la section du jet de matériau électroconducteur et la profondeur de pénétration du champ électromagnétique soit supérieur à 1,7.
According to other characteristics of the invention:
  • the means for centering the extra-flat electromagnetic coil are formed by an envelope of electrical and thermal insulating material inserting said electromagnetic means for confining the jet,
  • the means for centering and positioning the sectors of the crucible are formed by a shell of electrical and thermal insulating material placed around said sectors and inserting the means of heating by electromagnetic induction of the electroconductive material and the means for cooling said sectors,
  • the electromagnetic coil has ten turns in the form of copper plates, distributed over a height of 30mm, for a jet of electroconductive material of approximately 12mm in diameter,
  • the pouring tube is formed by a double-walled sectored metal cylinder, cooled by circulation of a fluid,
  • the power generator of the extra-flat electromagnetic coil deliver a signal at a determined frequency so that the ratio between the radius of the section of the jet of electroconductive material and the penetration depth of the electromagnetic field is greater than 1.7.

D'autres caractéristiques et avantages de l'invention apparaítront à la lecture de la description qui va suivre donnée uniquement à titre d'exemple et faite en se référant aux dessins annexés, sur lesquels:

  • la Fig. 1 est une vue schématique en coupe d'un four de fusion par induction en creuset froid selon l'invention,
  • la Fig. 2 est une vue schématique en coupe et à plus grande échelle du tube de coulée disposé au-dessous du four de fusion,
  • la Fig. 3 est une schéma de la masse du matériau électroconducteur confinée électromagnétiquement,
  • les Figs. 4 et 5 sont deux schémas matérialisant le déplacement des particules inclusionnaires dans la masse du matériau électroconducteur,
  • la Fig. 6 est une courbe représentant une variation du saut de pression magnétique entre l'axe du jet de coulée et sa surface en fonction de la fréquence du signal délivré par le générateur d'alimentation des moyens électromagnétiques de confinement du jet de coulée.
Other characteristics and advantages of the invention will appear on reading the description which follows, given solely by way of example and made with reference to the appended drawings, in which:
  • Fig. 1 is a schematic sectional view of an induction melting furnace in a cold crucible according to the invention,
  • Fig. 2 is a schematic sectional view on a larger scale of the pouring tube arranged below the melting furnace,
  • Fig. 3 is a diagram of the mass of the electro-conductive material confined electromagnetically,
  • Figs. 4 and 5 are two diagrams showing the movement of the inclusionary particles in the mass of the electroconductive material,
  • Fig. 6 is a curve representing a variation of the magnetic pressure jump between the axis of the pouring jet and its surface as a function of the frequency of the signal delivered by the generator supplying the electromagnetic means for confining the pouring jet.

Sur la Fig. 1, on a représenté schématiquement un four de fusion 10 par induction en creuset froid destiné notamment à la purification d'une masse 1 d'un matériau électroconducteur avant son atomisation pour la fabrication de poudres.In Fig. 1, there is shown schematically a melting furnace 10 by induction in a cold crucible intended in particular for the purification of a mass 1 of a electroconductive material before atomization for the manufacture of powders.

Le four de fusion 10 comprend un creuset 11 destiné à contenir le matériau électroconducteur 1 et formé de plusieurs secteurs métalliques 12 isolés électriquement les uns des autres et pourvus chacun d'un moyen de refroidissement par circulation d'eau non représenté sur la Fig. 1.The melting furnace 10 comprises a crucible 11 intended to contain the electroconductive material 1 and formed of several isolated metal sectors 12 electrically from each other and each provided with a water cooling means no shown in Fig. 1.

Le nombre de secteurs métalliques 12 est par exemple de neuf.The number of metal sectors 12 is by example of new.

Le creuset 11 est par exemple de forme cylindrique se prolongeant par un fond sensiblement hémisphérique ou conique muni d'un orifice 13 de coulée de la masse du matériau électroconducteur 1 liquide.The crucible 11 is for example of shape cylindrical extending by a bottom substantially hemispherical or conical with a pouring orifice 13 the mass of the liquid electroconductive material 1.

Le four de fusion 10 comprend également des moyens 14 de chauffage par induction électromagnétique du matériau électroconducteur 1 disposés autour du creuset 10.The melting furnace 10 also includes electromagnetic induction heating means 14 of the electroconductive material 1 arranged around the crucible 10.

Ces moyens 14 de chauffage par induction électromagnétique sont composés par exemple de huit spires.These means 14 of induction heating electromagnetic are composed for example of eight turns.

Le four de fusion 10 comporte aussi un tube de coulée 15 du matériau électroconducteur 1 liquide disposé verticalement au-dessous du creuset 11 et dans l'axe de l'orifice de coulée 13 et des moyens 16 de confinement du jet de matériau électroconducteur 1 liquide dans ledit tube de coulée 15.The melting furnace 10 also includes a tube pouring 15 of the electroconductive material 1 liquid arranged vertically below the crucible 11 and in the axis of the pouring orifice 13 and the means 16 of confinement of the jet of electroconductive material 1 liquid in said pouring tube 15.

Les moyens 16 électromagnétiques de confinement du jet de matériau électroconducteur liquide sont disposés autour du tube de coulée 15 et alimentés par un générateur non représenté sur les figures.Electromagnetic means 16 of containment of the jet of liquid electroconductive material are arranged around the pouring tube 15 and supplied by a generator not shown in the figures.

Comme représenté sur la Fig. 2, le tube de coulée 15 est formé de huit secteurs de cylindre 15a refroidis par un circuit 17 de circulation d'un fluide comme par exemple de l'eau.As shown in Fig. 2, the tube casting 15 is formed by eight cylinder sectors 15a cooled by a fluid circulation circuit 17 such as water.

Les moyens 16 de confinement du jet de matériau électroconducteur 1 liquide dans le tube de coulée 15 sont formés par une bobine électromagnétique extraplate 16, comme par exemple une bobine de BITTER, comportant par exemple dix spires 16a sous forme de plaques de cuivre, réparties sur une hauteur de 30mm, pour un jet de matériau électroconducteur d'environ 12mm de diamètre.The means 16 for confining the jet of electroconductive material 1 liquid in the tube casting 15 are formed by an electromagnetic coil extra flat 16, such as a BITTER coil, comprising for example ten turns 16a in the form of copper plates, spread over a height of 30mm, for a jet of electroconductive material of approximately 12mm of diameter.

Chacune des plaques de cuivre est percée de trente-six trous de 2,5mm de diamètre reliés à un circuit 18 de circulation d'eau transversale pour le refroidissement de la bobine électromagnétique 16.Each of the copper plates is pierced with thirty-six 2.5mm diameter holes connected to a circuit 18 of transverse water circulation for cooling of the electromagnetic coil 16.

D'autre part, le four de fusion 10 comporte des moyens 20 de centrage de la bobine électromagnétique 16 de confinement du jet de matériau électroconducteur liquide par rapport à l'axe vertical du tube de coulée 15 et du creuset 11 et des moyens 25 de centrage et de positionnement des secteurs 12 du creuset 11 par rapport aux moyens 14 de chauffage par induction électromagnétique du matériau électroconducteur 1 et par rapport à la bobine électromagnétique 16.On the other hand, the melting furnace 10 comprises means 20 for centering the electromagnetic coil 16 for confining the jet of electroconductive material liquid relative to the vertical axis of the pouring tube 15 and crucible 11 and means 25 for centering and positioning of the sectors 12 of the crucible 11 relative to to the means 14 of heating by electromagnetic induction of the electroconductive material 1 and with respect to the electromagnetic coil 16.

Les moyens de centrage de la bobine électromagnétique 16 sont formés par une enveloppe 20 en matériau isolant par exemple de PERMAGLAS insérant les spires 16a de ladite bobine électromagnétique 16.The means of centering the electromagnetic coil 16 are formed by an envelope 20 in insulating material for example from PERMAGLAS inserting the turns 16a of said electromagnetic coil 16.

Les moyens de centrage et de positionnement des secteurs 12 du creuset 11 sont formés par une coquille 25 en matériau isolant par exemple de PERMAGLAS disposée autour dudit secteur 12 et insérant les moyens 14 de chauffage par induction électromagnétique du matériau électroconducteur 1 et les moyens de refroidissement des secteurs 12.Centering and positioning means sectors 12 of the crucible 11 are formed by a shell 25 of insulating material, for example from PERMAGLAS arranged around said sector 12 and inserting the means 14 electromagnetic induction heating of electrically conductive material 1 and the cooling means sectors 12.

Cet enrobage permet de maintenir les spires des moyens 14 de chauffage par induction du matériau électroconducteur 1 et le creuset 11 ce qui évite des perturbations hydrodynamiques dans la masse de matériau électroconducteur liquide.This coating keeps the turns means 14 for induction heating of the material electroconductive 1 and crucible 11 which avoids hydrodynamic disturbances in the mass of material liquid electroconductive.

Dans le cas d'élaboration par atomisation du matériau électroconducteur sous forme d'une poudre, le four à induction 1 comprenant le creuset 11 et le tube de coulée 15 peut être placé dans une enceinte sous atmosphère contrôlée et le jet d'écoulement du matériau électroconducteur est soumis à éclatement pour la mise en forme de la poudre. In the case of preparation by atomization of the electroconductive material in the form of a powder, the induction furnace 1 comprising crucible 11 and tube 15 can be placed in an enclosure under controlled atmosphere and the material flow jet electrically conductive is subjected to bursting in the form of a powder.

La parfaite géométrie cylindrique verticale du jet de coulée du matériau électroconducteur est une caractéristique importante, voire essentielle de la bonne qualité des poudres obtenues par atomisation.The perfect vertical cylindrical geometry of the casting jet of the electroconductive material is a important or even essential characteristic of good quality of the powders obtained by atomization.

Selon un exemple d'application, la masse de matériau électroconducteur 1 constituée par un acier superalliage de 5 cm de rayon est placée dans le creuset 11 et la puissance transmise par les moyens 14 de chauffage par induction électromagnétique et de l'ordre de 50 KW pour un courant de 1000 A à la fréquence de 20KHz.According to an example of application, the mass of electroconductive material 1 consisting of a steel 5 cm radius superalloy is placed in the crucible 11 and the power transmitted by the means 14 of electromagnetic induction heating and order of 50 KW for a current of 1000 A at the frequency of 20KHz.

Le procédé de fusion du matériau électroconducteur 1 dans le four de fusion 10 consiste :

  • à confiner électromagnétiquement, dans le four de fusion 10, la masse du matériau électroconducteur 1 jusqu'à sa température de fusion,
  • à décanter les particules inclusionnaires solides ou liquides contenues dans le matériau électroconducteur 1 liquide,
  • à couler une partie de la masse du matériau électroconducteur 1 liquide par le tube de coulée 15, à soumettre le jet de coulée du matériau électroconducteur liquide 1 à un confinement électromagnétique radial,
  • à assurer un alignement coaxial vertical des champs électromagnétiques agissant sur la masse du matériau électroconducteur 1 liquide et sur le jet de coulée de ladite masse,
  • et à créer, dans la masse du matériau électroconducteur 1 liquide par brassage électromagnétique, au moins un vortex 30 (Fig. 3) dans lequel les particules inclusionnaires solides sont entraínées dans un mouvement tourbillonnaire et décantées en atteignant la surface de ladite masse du matériau électroconducteur 1 liquide.
The method of melting the electroconductive material 1 in the melting furnace 10 consists of:
  • electromagnetically confining, in the melting furnace 10, the mass of the electroconductive material 1 to its melting temperature,
  • decanting the solid or liquid inclusion particles contained in the liquid electroconductive material 1,
  • pouring part of the mass of the liquid electroconductive material 1 through the pouring tube 15, subjecting the pouring jet of the liquid electroconductive material 1 to radial electromagnetic confinement,
  • ensuring a vertical coaxial alignment of the electromagnetic fields acting on the mass of the liquid electroconductive material 1 and on the casting jet of said mass,
  • and creating, in the mass of the electrically conductive material 1 liquid by electromagnetic stirring, at least one vortex 30 (FIG. 3) in which the solid inclusion particles are entrained in a vortex movement and decanted while reaching the surface of said mass of the electrically conductive material 1 liquid.

De préférence, on crée, dans la masse du matériau électroconducteur 1 liquide soumise au brassage électromagnétique, au moins deux vortex 30 superposés.Preferably, one creates, in the mass of the electroconductive material 1 liquid subjected to stirring electromagnetic, at least two superimposed vortices 30.

En effet, la Demanderesse a constaté que les particules non conductrices, contenues dans la masse de matériau électroconducteur 1 à traiter, étaient soumises, en milieu tourbillonnaire électromagnétique, à une série de forces telles que force de traínée, masse virtuelle, poussée d'Archimède, pression hydrodynamique, force de lorentz ce qui a permis d'en déduire le comportement des inclusions dans un brassage électromagnétique particulier.Indeed, the Applicant has found that the non-conductive particles, contained in the mass of electroconductive material 1 to be treated, were subjected, in an electromagnetic vortex medium, to a series forces such as drag force, virtual mass, Archimedes thrust, hydrodynamic pressure, force of lorentz which allowed to deduce the behavior of inclusions in a particular electromagnetic patch.

En tenant compte de ces différents paramètres, la Demanderesse a déterminé une configuration la plus favorable à la séparation des particules inclusionnaires non conductrices contenues dans la masse du matériau électroconducteur fondue et confinée et à leur décantation en surface de cette masse.Taking into account these different parameters, the Applicant has determined a configuration the more favorable for the separation of inclusionary particles nonconductive contained in the mass of the molten and confined electrically conductive material and their decantation on the surface of this mass.

La configuration la plus favorable à cette décantation est assurée par la forme de la surface libre de la masse du matériau électroconducteur liquide, la dimension de cette masse, l'épaisseur de la peau électromagnétique, la morphologie du brassage électromagnétique et la géométrie du jet de coulée.The most favorable configuration for this decantation is ensured by the shape of the free surface of the mass of the liquid electroconductive material, the dimension of this mass, the thickness of the electromagnetic skin, the morphology of electromagnetic stirring and the geometry of the casting jet.

C'est pourquoi, le procédé selon l'invention consiste, lors du brassage électromagnétique, à créer dans la masse du matériau électroconducteur 1 liquide au moins un vortex 30 dans lequel les particules inclusionnaires solides ou liquides sont entraínées dans un mouvement tourbillonnaire en spirale et décantées lorsqu'elles atteignent la surface de cette masse du matériau électroconducteur 1 liquide.This is why the method according to the invention consists, during electromagnetic mixing, to create in the mass of the electrically conductive material 1 liquid at minus a vortex 30 in which the inclusionary particles solids or liquids are entrained in a swirling spiral and decanted when they reach the surface of this mass of electrically conductive material 1 liquid.

Cela est obtenu en assurant en particulier, un alignement coaxial entre l'axe du creuset 11 contenant la masse du matériau électroconducteur 1 liquide et l'axe longitudinal du tube de coulée 15. This is achieved by ensuring in particular, a coaxial alignment between the axis of the crucible 11 containing the mass of the liquid electroconductive material 1 and the axis longitudinal of the pouring tube 15.

Cet alignement coaxial nécessite que la bobine électromagnétique 16 des moyens de confinement du jet génère un champ électromagnétique en symétrie cylindrique avec l'axe vertical du four de fusion 10.This coaxial alignment requires that the electromagnetic coil 16 means for confining the jet generates an electromagnetic field in symmetry cylindrical with the vertical axis of the melting furnace 10.

Alors que jusqu'à présent la géométrie de la bobine électromagnétique de confinement du jet semblait négligeable, la Demanderesse a constaté que cette géométrie avait un rôle primordial.While so far the geometry of the electromagnetic jet containment coil seemed negligible, the Applicant has found that this geometry had a primary role.

En effet, une bobine classique en spirale avec un conducteur de section tubulaire circulaire ne peut pas convenir pour le confinement du jet de coulée, car chacune des spires forme un chemin de courant qui se déplace dans un plan incliné par rapport à l'axe vertical, dépendant directement du pas de l'hélice de la bobine électromagnétique.Indeed, a classic spiral coil with a conductor of circular tubular cross section only may not be suitable for containment of the pouring jet, because each of the turns forms a current path which is moves in an inclined plane with respect to the vertical axis, directly dependent on the pitch of the propeller of the electromagnetic coil.

De ce fait, une bobine électromagnétique classique génère un champ magnétique créant des instabilités de coulée du jet.Therefore, an electromagnetic coil classic generates a magnetic field creating instabilities jet casting.

Pour éviter cette perturbation, les moyens de confinement du jet de coulée de la masse du matériau électroconducteur, selon l'invention, sont formés par une bobine électromagnétique extraplate 16 du type décrit précédemment.To avoid this disruption, the means of confinement of the pouring jet of the mass of the material electroconductive, according to the invention, are formed by a extra flat electromagnetic coil 16 of the type described previously.

De façon à assurer la symétrie cylindrique du jet de coulée, le champ électromagnétique généré par la bobine électromagnétique 16 est déterminé de façon que le saut de pression magnétique soit maximum, pour une puissance donnée du générateur alimentant ladite bobine électromagnétique 16.In order to ensure the cylindrical symmetry of the casting jet, the electromagnetic field generated by the electromagnetic coil 16 is determined so that the magnetic pressure jump is maximum, for a given power of the generator supplying said coil electromagnetic 16.

Sur la Fig. 3, on a représenté schématiquement, le mouvement de la masse du matériau électroconducteur 1 liquide qui est matérialisé par les deux vortex 30 superposés dont la vitesse de déplacement est d'environ de 0,2m/s.In Fig. 3, there is shown diagrammatically, the mass movement of the electroconductive material 1 liquid which is materialized by the two vortices 30 overlays with a travel speed of approximately 0.2m / s.

Les Figs. 4 et 5 représentent deux schémas matérialisant le déplacement des particules inclusionnaires non conductrices respectivement dans le vortex supérieur et dans le vortex inférieur.Figs. 4 and 5 represent two diagrams materializing the displacement of the inclusionary particles non-conductive respectively in the vortex superior and in the inferior vortex.

On sait que les particules inclusionnaires solides sont décantées dès qu'elles atteignent la surface de la masse du matériau électroconducteur 1 liquide, sans tenir compte du mécanisme de capture de ces particules aux alentours des surfaces libres ou d'une paroi froide, par des phénomènes interfaciaux comme la pression magnétique.We know that the inclusionary particles solids are decanted as soon as they reach the surface of the mass of the liquid electroconductive material 1, without take into account the mechanism of capture of these particles around free surfaces or a cold wall, by interfacial phenomena like pressure magnetic.

La mesure du temps de décantation permet de maítriser le temps minimum de fusion de la masse du matériau électroconducteur et de brassage de cette masse qui assure la purification par décantation des particules inclusionnaires de taille donnée.Measuring the settling time allows control the minimum melting time of the mass of the electroconductive material and mixing this mass which ensures the purification by settling of the particles inclusions of given size.

Le temps de séparation des particules inclusionnaires est maximum pour les particules situées initialement près du centre du ou des vortex 30 et le temps de décantation est très important pour les particules inclusionnaires de petites tailles.Particle separation time inclusions is maximum for particles located initially near the center of the vortex (s) 30 and the settling time is very important for particles small inclusions.

Par ailleurs, la Demanderesse a constaté que l'efficacité du confinement électromagnétique du jet de coulée de la masse du matériau électroconducteur 1 est d'autant plus grande que le saut de pression magnétique entre l'axe et la surface du jet de coulée est élevé.Furthermore, the Applicant has found that the efficiency of the electromagnetic confinement of the casting of the mass of the electroconductive material 1 is all the greater as the magnetic pressure jump between the axis and the surface of the casting jet is high.

En effet, le saut de pression est fonction de la force électromagnétique appliquée et de la profondeur de pénétration du champ magnétique dans le jet de coulée.Indeed, the pressure jump is a function of applied electromagnetic force and depth of penetration of the magnetic field into the casting jet.

A puissance de générateur constante, il existe une fréquence optimale qui permet d'obtenir le saut de pression le plus élevé.At constant generator power, it exists an optimal frequency which allows to obtain the highest pressure jump.

La Fig. 6 représente trois courbes montrant la variation de la valeur du saut de pression ΔPm en fonction du rapport du rayon R du jet de coulée sur la profondeur de pénétration Δ du champ magnétique, pour différentes résistivités électriques ρ du matériau électroconducteur.Fig. 6 represents three curves showing the variation of the value of the pressure jump ΔPm in function of the ratio of the radius R of the casting jet to the penetration depth Δ of the magnetic field, for different electrical resistivities ρ of the material electroconductive.

On voit sur cette figure que l'optimum du saut de pression ΔPm est atteint pour un rapport du rayon R du jet de coulée sur la profondeur de pénétration δ du champ magnétique, égal à environ 1,7 ce qui correspond pour un rayon du jet de coulée de 7mm d'un alliage de 130 10-8 Ωcm de résistivité à une fréquence d'environ 20KHz.We see in this figure that the optimum of the pressure jump ΔPm is reached for a ratio of the radius R of the casting jet to the penetration depth δ of the magnetic field, equal to about 1.7 which corresponds to a radius of the jet of 7mm casting of an alloy of 130 10 -8 Ωcm resistivity at a frequency of about 20KHz.

Le procédé selon l'invention permet, grâce au confinement électromagnétique du jet de coulée associé à la coaxialité des champs magnétiques des moyens de confinement du jet de coulée, des moyens de chauffage par induction de la masse du matériau électroconducteur, du creuset et de ladite masse du matériau électroconducteur d'obtenir un contrôle du brassage électromagnétique de cette masse liquide, tout en assurant la séparation en continue des impuretés inclusionnaires solides contenues dans le matériau électroconducteur en permettant également d'obtenir une qualité améliorée des produits.The method according to the invention allows, thanks to the electromagnetic confinement of the associated casting jet to the coaxiality of the magnetic fields of the means of confinement of the pouring jet, heating means by induction of the mass of the electroconductive material, crucible and said mass of the electrically conductive material to obtain a control of the electromagnetic mixing of this liquid mass, while ensuring the separation into continuous solid inclusion impurities contained in the electroconductive material also allowing to obtain improved product quality.

Claims (8)

  1. Method of smelting of an electroconductive material (1) in a smelting furnace (10) by induction in a cold crucible, a method in which:
    there is electro-magnetically confined in the smelting furnace (10) a mass of the electroconductive material (1) up to its smelting temperature,
    the inclusion particles contained in the liquid electroconductive material (1) are decanted,
    a portion of the mass of liquid electroconductive material (1) is cast through a casting tube (15) disposed beneath said smelting furnace (10),
    the casting jet of the liquid electroconductive material (1) is subjected to a radial electro- magnetic confinement,
    characterised in that:
    the casting jet of liquid electroconductive material (1) is subjected to this confinement with the aid of an extra-flat electromagnetic coil,
    coaxial vertical alignment of the electromagnetic fields acting on the mass of liquid electroconductive material (1) is ensured as well as on the casting jet of the said mass,
    and there is created in the mass of liquid electroconductive material (1) by means of electromagnetic agitation, at least one vortex (30) in which the inclusion particles are set in a turbulent movement and are decanted on reaching the surface of the said mass of liquid electroconductive material (1).
  2. Method according to claim 1, characterised in that there is created in the mass of liquid electroconductive material (1) subjected to electromagnetic agitation, at least two superimposed vortices (30).
  3. Smelting furnace for an electroconductive material (1) by induction in a cold crucible, for putting into effect the method according to claims 1 and 2, said smelting furnace (10) comprising a crucible (11) intended to contain the said conductive material (1) and formed from a plurality of metallic sectors (12) electrically insulated from one another, means of cooling the said metallic sectors (12), means (14) of heating by electromagnetic induction of the electroconductive material (1), and disposed around the crucible (11), a casting tube (15) for the liquid electroconductive material (1) and disposed vertically beneath the crucible (11), and electromagnetic means (16) for confining the jet of liquid electroconductive material in the casing tube (15), the said electromagnetic means (16) being disposed around the casting tube (15) and supplied by a generator, characterised in that the electromagnetic means for confinement of the jet of electroconductive material (1) are formed by an extra-flat electromagnetic coil (16), and in that it comprises means (20) of centering said extra-flat electromagnetic coil (16) with respect to the vertical axis of the casting tube (15) and of the crucible (11), and means (25) of centering and positioning the sectors (12) of the crucible (11) with respect to the means (14) of heating by electromagnetic induction the electroconductive material (1), and with respect to the electromagnet means (16) for confining the jet of liquid electroconductive material (1).
  4. Smelting furnace according to claim 3, characterised in that the means of centering the extra-flat electromagnetic coil (16) are formed by an envelope (20) of electrical and thermal insulating material embedding the said extra-flat coil (16).
  5. Smelting furnace according to claim 3, characterised in that the means of centering and positioning the sectors (12) of the crucible (11) are formed by a shell (25) of electrical and thermal insulating material disposed around the sectors (12) and embedding the means (14) of heating by electromagnetic induction the electroconductive material and the means of cooling of the sectors (12).
  6. Smelting furnace according to claim 3, characterised in that the electro-magnetic coil (16) comprises ten windings (16a) in the form of copper plates, distributed at a height of 30 mm, for a jet of electroconductive material of a diameter of about 12 mm.
  7. Smelting furnace according to one of claims 3 to 6, characterised in that the casting tube (15) is formed by a double-walled, sub-divided metallic cylinder, cooled by circulation of a fluid.
  8. Smelting furnace according to claim 3, characterised in that the generator supplying the extra-flat electromagnetic coil (16) provides a signal at a determined frequency so that the ratio between the radius of the section of the jet of electroconductive material (1) and the depth of penetration of the electromagnetic field is above 1.7.
EP94401703A 1993-07-29 1994-07-25 Smelting process of electrically-conductive materials in an induction smelting furnace with a cold crucible and furnace therefor Expired - Lifetime EP0636848B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9309366 1993-07-29
FR9309366A FR2708725B1 (en) 1993-07-29 1993-07-29 Process for melting an electroconductive material in a melting furnace by induction in a cold crucible and melting furnace for the implementation of this process.

Publications (2)

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EP0636848A1 EP0636848A1 (en) 1995-02-01
EP0636848B1 true EP0636848B1 (en) 1998-09-30

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EP94401703A Expired - Lifetime EP0636848B1 (en) 1993-07-29 1994-07-25 Smelting process of electrically-conductive materials in an induction smelting furnace with a cold crucible and furnace therefor

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US (1) US5563904A (en)
EP (1) EP0636848B1 (en)
JP (1) JP3696903B2 (en)
KR (1) KR950003779A (en)
CA (1) CA2128936C (en)
DE (1) DE69413621T2 (en)
FR (1) FR2708725B1 (en)

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US6104742A (en) * 1997-12-23 2000-08-15 General Electric Company Electroslag apparatus and guide
US6097750A (en) * 1997-12-31 2000-08-01 General Electric Company Electroslag refining hearth
US6221123B1 (en) 1998-01-22 2001-04-24 Donsco Incorporated Process and apparatus for melting metal
US6144690A (en) * 1999-03-18 2000-11-07 Kabushiki Kaishi Kobe Seiko Sho Melting method using cold crucible induction melting apparatus
US6219372B1 (en) * 1999-12-29 2001-04-17 General Electric Company Guide tube structure for flux concentration
TWI265198B (en) 2002-12-02 2006-11-01 Univ Nat Taiwan The method and equipments for controlling the solidification of alloys in induction melting using cold crucible
US20060291529A1 (en) * 2005-05-26 2006-12-28 Haun Robert E Cold wall induction nozzle
KR101218923B1 (en) * 2010-09-15 2013-01-04 한국수력원자력 주식회사 Cold Crucible Induction Melter Using United Inductor and Crucible
WO2013183031A1 (en) * 2012-06-08 2013-12-12 Imp Automation (Pty) Ltd Separating system and method
RU2543022C1 (en) * 2013-11-11 2015-02-27 Общество с ограниченной ответственностью "Научно-производственный центр магнитной гидродинамики" Holding furnace
JP6146319B2 (en) * 2014-01-17 2017-06-14 トヨタ自動車株式会社 Metal melting equipment
US10898949B2 (en) 2017-05-05 2021-01-26 Glassy Metals Llc Techniques and apparatus for electromagnetically stirring a melt material
CN109253622A (en) * 2018-08-03 2019-01-22 荆门它山之石电子科技有限公司 A kind of smelting furnace preparing the aluminium alloy containing micropore
RU189343U1 (en) * 2018-09-27 2019-05-22 Федеральное Государственное Бюджетное Образовательное Учреждение Высшего Образования "Новосибирский Государственный Технический Университет" DEVICE OF MAGNETIC HYDRODYNAMIC MIXING OF LIQUID METAL IN CYLINDRICAL BATH
RU2708036C1 (en) * 2018-10-05 2019-12-03 Евгений Анатольевич Головенко Method of metal melt mixing and electromagnetic mixer for its implementation (versions)
RU207347U1 (en) * 2021-07-23 2021-10-25 Федеральное Государственное Бюджетное Образовательное Учреждение Высшего Образования «Новосибирский Государственный Технический Университет» DEVICE FOR MAGNETIC HYDRODYNAMIC MIXING OF LIQUID METAL IN A CYLINDRICAL BATH
CN117628900B (en) * 2024-01-22 2024-03-29 中信戴卡股份有限公司 Three-chamber melting furnace for aluminum alloy regeneration

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Also Published As

Publication number Publication date
DE69413621D1 (en) 1998-11-05
FR2708725B1 (en) 1995-11-10
JP3696903B2 (en) 2005-09-21
DE69413621T2 (en) 1999-04-29
US5563904A (en) 1996-10-08
JPH07207351A (en) 1995-08-08
KR950003779A (en) 1995-02-17
EP0636848A1 (en) 1995-02-01
FR2708725A1 (en) 1995-02-10
CA2128936A1 (en) 1995-01-30
CA2128936C (en) 2004-06-22

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