EP3386659A1 - Injection tip for casting machine, casting machine and method using such a tip - Google Patents

Injection tip for casting machine, casting machine and method using such a tip

Info

Publication number
EP3386659A1
EP3386659A1 EP16808684.1A EP16808684A EP3386659A1 EP 3386659 A1 EP3386659 A1 EP 3386659A1 EP 16808684 A EP16808684 A EP 16808684A EP 3386659 A1 EP3386659 A1 EP 3386659A1
Authority
EP
European Patent Office
Prior art keywords
liquid metal
injection
mold
electromagnetic
pipe
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
EP16808684.1A
Other languages
German (de)
French (fr)
Other versions
EP3386659B1 (en
Inventor
Victor Shribman
Ori Ben David
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.)
ADM28 SARL
Original Assignee
ADM28 SARL
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 ADM28 SARL filed Critical ADM28 SARL
Publication of EP3386659A1 publication Critical patent/EP3386659A1/en
Application granted granted Critical
Publication of EP3386659B1 publication Critical patent/EP3386659B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
    • B22D17/20—Accessories: Details
    • B22D17/2015—Means for forcing the molten metal into the die
    • B22D17/2023—Nozzles or shot sleeves
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
    • B22D17/02—Hot chamber machines, i.e. with heated press chamber in which metal is melted
    • B22D17/04—Plunger machines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
    • B22D17/20—Accessories: Details
    • B22D17/2015—Means for forcing the molten metal into the die
    • B22D17/2038—Heating, cooling or lubricating the injection unit
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
    • B22D17/20—Accessories: Details
    • B22D17/30—Accessories for supplying molten metal, e.g. in rations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
    • B22D17/02—Hot chamber machines, i.e. with heated press chamber in which metal is melted

Definitions

  • the invention relates to a magnetic necking injection nozzle for a machine for casting under pressure of metal, and more particularly to such a nozzle that can be used for the metal die casting of metal parts.
  • the invention also extends to a machine and a casting process using this tip.
  • Metal die-casting machines are generally used for the die-casting of metal parts, aluminum, zinc, magnesium, etc. and their alloys. This molding process allows high production rates and high accuracy of the parts obtained.
  • One of the most important parameters of the process is the pressure at which the molten metal in the liquid state is injected into the mold, particularly at the end of the injection. This pressure ranges from 5 to 30 MPa for machines called hot chamber and from 25 to 200 MPa, or even 350 MPa for machines called cold room.
  • liquid metal will be used to designate a molten metal in the liquid state, without prejudging the nature and / or the melting temperature of said metal.
  • WO02 / 30596 discloses a pressurized injection machine comprising a tubular injection nozzle comprising a resistor wound on the major part of this nozzle in order to maintain the temperature of the molten metal.
  • JP2005-28429 also discloses an analogous injection machine having a heating sleeve in which metal bars are inserted and fused by a resistive coil surrounding the sleeve.
  • a shutter secured to the mold can be actuated to close the supply channel.
  • the injection pressure depends on the general supply pressure of the machine.
  • the invention therefore aims to provide an injection nozzle adapted to be associated with a casting machine, which allows a simple adjustment of the amount of injected metal and a high pressure at the end of injection.
  • the invention also relates to a casting machine comprising such a nozzle, particularly adapted to allow to obtain high performance.
  • the invention also relates to a metal casting process, implemented by a casting machine equipped with an injection nozzle according to the invention, a method particularly suitable for die-casting.
  • the invention relates to a tube-shaped pressurized metal injection nozzle made of electrically insulating refractory material adapted to be inserted between a liquid metal feed pipe and an injection port of a mold, comprising an injection channel adapted for the circulation of liquid metal between a first end, said upstream end, adapted to be connected to said pipe and a second end, said downstream end adapted to be connected to the mold, characterized in that said tip comprises an electromagnetic coil, placed between said ends, of coinciding axis with at least one channel portion of the channel, adapted to be powered by a current pulse from a high-voltage generator and generate an electromagnetic necking in the injection channel.
  • this tip and particularly to the channel within which the liquid metal circulates, it is possible to fill the mold placed at the downstream end of the tip.
  • the material of the tip being refractory, for example ceramic, it is little degraded by the heat of the metal flowing in the channel.
  • the electromagnetic coil which surrounds this duct when it is traversed by a pulse of electric current of high amperage, the liquid metal flowing in the channel is subjected on the one hand to a magnetic field oriented axially relative to the coil and the channel and secondly to an induced current opposite to the direction of the current in the coil.
  • the combination of these two phenomena generates Lorentz forces, oriented radially to the duct, in the direction of its axis.
  • the coil is adapted to be connected to the terminals of a current pulse generator.
  • a generator for example a Marx generator, is capable, by means of one or more spark gaps discharging a capacitor bank, of developing an electrical current of the order of several tens of thousands of amperes at a voltage of several thousands of volts in a very short time, of the order of a few milliseconds.
  • the channel has a diameter comprising a narrowing between the upstream end and the coil. Due to this narrowing which forms a convergent nozzle, the velocity of the liquid metal at the outlet of the metal supply line is increased to the right of the electromagnetic coil due to the narrowing of the cross section of the channel.
  • the necking made in the channel, in line with the coil, in the narrowed portion of the channel projects the liquid metal with a speed which is added to the initial speed of circulation of the metal towards the injection orifice of the mold whereas, in the opposite direction, this speed is reduced by the effect of the narrowing which behaves in this direction as a divergent nozzle and subtracts from the initial velocity of circulation of the liquid metal.
  • the necking reaction in the direction of the supply line of the liquid metal is greatly attenuated.
  • the coil is embedded in the material of the tip.
  • the electromagnetic coil is placed as close as possible to the circulation channel of the liquid metal by embedding it in the refractory material forming the tip. Moreover, being thus maintained on all sides, the electromagnetic coil is less subject to reaction forces acting on its or its turns during necking. It remains possible, however, especially when the metal injection conditions (temperature, pressure, etc.) allow it, to use a tip having a thinner wall and thus to place the electromagnetic coil around and outside the tip nozzle. In this variant, the maintenance of the coil is facilitated.
  • the coil is multi-turns.
  • the coil is single turn.
  • the electromagnetic coil is made to have a plurality of turns extending from the narrow end of the narrowing of the channel towards its downstream end connected to the injection orifice of the mold in order to increase the width of the the zone of necking of the liquid metal in the tip and therefore the volume of metal propelled towards the mold.
  • the coil may be a single coil coil, which achieves, for the same output stage of the current pulse generator, higher frequencies (respectively shorter pulses) thus increasing the instantaneous power of the impulse, better energy transfer and improved life.
  • the invention also extends to a casting machine comprising a liquid metal reservoir, a liquid metal feed pipe connected to said reservoir and provided with an electromagnetic pump adapted to circulate the liquid metal in the pipe towards the a mold, characterized in that that the machine comprises a tip having at least one of the above characteristics between said pipe and an injection port of said mold.
  • the electromagnetic pump comprises a plurality of coaxial induction coils to the pipe, adapted to inductively heat the metal flowing in the pipe.
  • the induction coils are fed with polyphase current so as to generate a movable magnetic field and drive the liquid metal towards the endpiece.
  • Induction coils fed by alternating currents for induction heating may form a magnetohydrodynamic induction accelerator when energized by currents having a phase shift from one coil to the other. Therefore, in addition to heating the liquid metal in the supply line, the coils can generate an axial magnetic field in the pipe and communicate a movement to the liquid metal in the direction of the tip.
  • the machine comprises a cooling device of the induction coils interposed between said coils and the pipe.
  • a cooling device of the induction coils interposed between said coils and the pipe.
  • they are isolated from the pipe by an air or water cooling device, for example, for water cooling, by circulation of cooling liquid inside the coil.
  • a copper tube serving as winding ..
  • the invention further extends to a method of casting liquid metal under pressure in a metal mold, wherein: a casting machine comprising a liquid metal reservoir is used, a pipe connected to said reservoir provided with an electromagnetic pump adapted to circulate the liquid metal in the pipe towards a mold,
  • the electromagnetic pump is fed with a polyphase current so as to move the liquid metal from the reservoir to the injection orifice of the mold,
  • the casting machine comprises a nozzle comprising an electromagnetic coil surrounding an injection channel between said pipe and an injection port of said mold and that at the end of the injection, the electromagnetic coil of the nozzle with an electric current pulse from a high voltage generator to generate an electromagnetic necking in the injection channel and propel the liquid metal under pressure to the injection port of the mold.
  • the resulting flow velocity, in the direction of the pipe, is further reduced by the presence of the divergent formed by the narrowing of the section of the channel traveled in the opposite direction. It is thus possible to obtain at least a temporary stop of the circulation of the liquid metal in the supply line.
  • the invention also relates to a nozzle, a casting machine and a casting process characterized in combination by all or some of the characteristics mentioned above or below.
  • FIG. 1 represents a schematic sectional view of a casting machine according to the invention
  • FIG. 2 is a diagrammatic sectional view of a mouthpiece according to the invention.
  • FIG. 3 is a sectional view of a mouthpiece according to the invention during a necking of the flow of the metal
  • FIG. 1 represents a longitudinal section of a casting machine 10 comprising a reservoir 11, adapted to contain liquid metal to be injected into a mold 30.
  • the reservoir 11 may comprise heating means (not shown) for holding the metal at its melting temperature, or be shaped hopper in which the liquid metal is poured from a crucible.
  • the liquid metal is then conveyed into a pipe 12 for feeding the metal towards a tip 20 fixed between the pipe 12 and the mold 30.
  • the pipe 12 is equipped with an electromagnetic pump 50 comprising a plurality of induction coils 51 regularly spaced along the pipe 12.
  • Each of the induction coils 51 is connected to an inverter 53 adapted to feed the coils 51 with a alternating current.
  • the induction coils 51 fulfill a double role: on the one hand, they function in induction heating coils making it possible to keep the liquid metal vein flowing in the pipe 12 in the liquid state, and on the other hand, fed polyphase alternating current adapted to the number and order of the coils 51, they generate a moving magnetic field flowing from the tank 11 towards the tip 20, this magnetic field for circulating the liquid metal in the pipe towards the mold 30 with a speed V0.
  • the induction coils are supplied with three-phase current at a voltage of 400V at a voltage of frequency of the order of 50 Hz to 10 kHz with a current that can vary between 50 A and 10 000 A.
  • the coils 51 also comprise a cooling circuit 52 for example using a cooling liquid flowing in copper tubes forming the coils 51, to limit their heating.
  • a cooling circuit 52 for example using a cooling liquid flowing in copper tubes forming the coils 51, to limit their heating.
  • a forced convection air cooling system implementing one or more fans and cooling fins integral windings.
  • the tip 20 is attached to the end of the pipe 12 by its upstream end 23 (thus marked with respect to the direction of flow of the liquid metal in the pipe and in the tip) by means of flanges 25.
  • the tip 20 is also fixed at its opposite end, said downstream end 24, to the mold 30 by flanges 25.
  • the tip 20 comprises a body 21 of refractory material and electrically insulating, preferably ceramic, and more particularly alumina / zirconium nitride.
  • Other refractory materials may also be used, for example ceramics based on alumina, zirconium, yttrium, titanium or nickel oxide, or a mixture of these constituents in various proportions.
  • the body 21 of the nozzle is traversed by a channel 22 from the upstream end 23 to the downstream end 24 at which the channel 22 opens into the injection port 33 of the mold 30.
  • the channel 22 is preferably of cylindrical shape of revolution and comprises at the upstream end 23 a conical portion forming a narrowing 27 between a large section of a diameter corresponding to the end of the pipe 12 and a smaller section of the channel 22 corresponding to the section of the injection orifice 33 of the mold 30.
  • the body 21 also comprises, downstream of the narrowing 27, an electromagnetic coil 26, surrounding the channel 22 and overmolded in the body 21.
  • the coil 26 is preferably a multi-turn coil made of copper or other highly conductive material, for example aluminum, cupro -berylium alloy copper-chromium-zirconium, tungsten or tungsten-copper alloy ...
  • the coil 26 is adapted to be connected to a generator 40 of current pulses generally comprising a battery 41 of capacitors charged by an external DC power source (no shown) and discharged into the electromagnetic coil 26 via a spark gap 42.
  • the coil 26 may also be formed of a single coil.
  • the coil 26 has an axis of revolution substantially coincident with at least a portion of the axis of the channel 21, on the part thereof that surrounds.
  • the coil 26 thus delimits in the channel 21 a zone, called the necking zone 28, within which the electromagnetic field created by the coil 26 when it is fed by the generator 40 is developed.
  • the injection conditions allow it, that is to say if the injection pressure and / or the temperature and / or the metal to be injected are compatible with a tip whose body 21 comprises walls sufficiently thin, it is possible to place the coil 26 around the body 21.
  • the coil 26 For example, for the injection of zinc alloys (without aluminum) having a melting point below 450 ° C, it is possible to use a nonmagnetic refractory austenitic stainless steel tip that allows satisfactory resistance with thicknesses reduced to a few millimeters.
  • a single or multi-turn electromagnetic coil 26 can then be threaded onto the body 21 and fixed by any appropriate means. This variant allows easy disassembly of the coil while retaining the body 21 of the tip.
  • the tank 11 is filled with a liquid metal, for example a zinc or magnesium alloy.
  • the liquid metal flows from the tank 11 into the pipe 12.
  • the inverter 53 supplies the induction coils 51 with a polyphase alternating current (for example three-phase) so as to inductively heat the liquid metal in the pipe 12 to avoid any primer solidification or formation of lumps.
  • Each coil induction 51 also develops a magnetic field whose field lines are oriented along the axis of the induction coils and the pipe 12.
  • the phase shift of the magnetic field of the induction coils generates a movable magnetic field in the pipe 12 which moves the liquid metal contained therein towards its opposite end to the tank 11, with a substantially constant velocity V0.
  • the passage section of the liquid metal decreases in the constriction 27 and thus the speed of movement of the metal increases as a function of the section ratio between the upstream end 23 of the nozzle and the section of the channel 22 to reach a speed VI at the end of the narrowing, at the entrance to the necking zone 28 located below the electromagnetic coil 26.
  • the liquid metal progresses at the speed VI in the channel 22 and then in the injection orifice 33 of the mold 30 to fill one or more cavities 32 formed between the shells 31 of the mold 30.
  • the pulse generator 40 When the cavities 32 are filled, for example with end of a predetermined injection time as a function of the speed VI, the section of the channel 22 and / or the injection orifice 33 which define the metal flow rate and the volume of the fingerprint or fingerprints 32, the pulse generator 40 is activated and delivers a current pulse, for example of an intensity of the order of 20 kA to 1 MA, with a duration of 40 to 2 ms which circulates in the coil 26.
  • a current pulse for example of an intensity of the order of 20 kA to 1 MA, with a duration of 40 to 2 ms which circulates in the coil 26.
  • the liquid metal 13 is thus compressed radially and, because of its incompressibili tee, is ejected axially on either side of the necking zone 28 with an ejection speed V2.
  • the combination of this ejection velocity V2 with the circulation velocity VI of the liquid metal towards the mold 30 imparts a velocity corresponding to V1 + V2 to the metal.
  • this speed V1 + V2 is transformed into an increase in the injection pressure in the mold 30.
  • the coil generates a magnetic field of 40 T.
  • this magnetic field is applied to the liquid metal, it can reach a maximum speed (V1 + V2) of the order of 30 m / s in the nozzle and a maximum pressure of 700 MPa.
  • the circulation velocity of the metal following the combination of the circulation and ejection velocities is V1-V2.
  • the ejection velocity V2 is greater in absolute value than the circulation velocity VI which imparts to the liquid metal a movement towards the pipe 12 of the machine. Due to the narrowing 27 which behaves divergently in this direction, the speed of the liquid metal is reduced in the ratio of the sections and does not generate a large shock wave in the pipe 12 may damage the machine but simply a pressure wave which promotes the mixing of the metal in the pipe.
  • the dosage of the amount of metal to be injected into the mold cavities may be adjusted by an injection time before the pulse generator is triggered or by the adjustment of the transfer rate of the liquid metal by the frequency and supply phase of the induction coils.

Abstract

The invention concerns an injection tip (20) for injecting liquid metal under pressure, suitable for being inserted between a liquid metal supply conduit (12) and an injection opening (33) of a mould (30), characterised in that it is tubular in shape, made from electrically insulating refractory material and in that it comprises a channel (22) suitable for the flow of liquid metal between a first end referred to as the upstream end (23), suitable for being connected to said conduit, and a second end, referred to as the downstream end (24), suitable for being connected to the mould, and an electromagnetic coil (26), positioned between said ends, the axis of which merges with at least a portion of the axis of the channel. The invention also concerns a casting machine using such a tip and a method for casting metal using said machine.

Description

EMBOUT D'INJECTION POUR MACHINE DE COULÉE, MACHINE ET PROCÉDÉ DE COULÉE FAISANT USAGE D'UN TEL EMBOUT  INJECTION TIP FOR CASTING MACHINE, MACHINE AND CASTING METHOD USING SAME
L'invention concerne un embout d'injection à striction magnétique pour machine de coulée sous pression de métal, et plus particulièrement un tel embout utilisable pour le moulage métallique sous pression de pièces métalliques. L'invention s'étend également à une machine et un procédé de coulée mettant en œuvre cet embout.  The invention relates to a magnetic necking injection nozzle for a machine for casting under pressure of metal, and more particularly to such a nozzle that can be used for the metal die casting of metal parts. The invention also extends to a machine and a casting process using this tip.
Les machines de coulée sous pression de métal sont en général utilisées pour le moulage métallique sous pression de pièces métalliques, en aluminium, zinc, magnésium, etc. et leurs alliages. Ce procédé de moulage permet des cadences de production élevées et une grande précision des pièces obtenues. L'un des paramètres les plus importants du procédé est la pression à laquelle le métal fondu à l'état liquide est injecté dans le moule, particulièrement en fin d'injection. Cette pression s'étend de 5 à 30 MPa pour des machines dites à chambre chaude et de 25 à 200 MPa, voire même 350 MPa pour des machines dites à chambre froide.  Metal die-casting machines are generally used for the die-casting of metal parts, aluminum, zinc, magnesium, etc. and their alloys. This molding process allows high production rates and high accuracy of the parts obtained. One of the most important parameters of the process is the pressure at which the molten metal in the liquid state is injected into the mold, particularly at the end of the injection. This pressure ranges from 5 to 30 MPa for machines called hot chamber and from 25 to 200 MPa, or even 350 MPa for machines called cold room.
Dans le présent texte et à des fins de simplification, on utilisera les termes de "métal liquide" pour désigner un métal fondu à l'état liquide, sans préjuger de la nature et/ou de la température de fusion dudit métal.  In the present text and for purposes of simplification, the terms "liquid metal" will be used to designate a molten metal in the liquid state, without prejudging the nature and / or the melting temperature of said metal.
La plupart de ces machines de coulée utilisent un vérin comprenant un piston qui pousse le métal liquide dans un cylindre dont l'extrémité opposée au piston est reliée à l'orifice d'injection d'un moule. Ces machines présentent cependant divers inconvénients : le piston s'use rapidement, en particulier lors d'injection d'alliages d'aluminium qui dissolvent le fer à haute température, le réglage de la quantité de matière injectée dépend du volume utile de la chambre du vérin qu'il est nécessaire de changer lorsqu'on change le volume de la pièce à mouler, l'énergie à fournir pour conserver la température du métal en fusion est élevée du fait de la dissipation de chaleur au travers du cylindre et du piston, etc. On connaît, par exemple de WO02/30596 une machine d'injection sous pression comportant un embout d'injection tubulaire comprenant une résistance bobinée sur la majeure partie de cet embout afin de conserver la température du métal en fusion. JP2005-28429 décrit également une machine d'injection analogue comportant un manchon de chauffage dans lequel des barres de métal sont insérées et mises en fusion par une bobine résistive entourant le manchon. Afin de stopper l'alimentation du moule en métal liquide, un obturateur solidaire du moule peut être actionné pour obturer le canal d'alimentation. Cependant, dans ces exemples, la pression d'injection dépend de la pression d'alimentation générale de la machine. Most of these casting machines use a ram comprising a piston that pushes the liquid metal into a cylinder whose opposite end to the piston is connected to the injection port of a mold. These machines, however, have various disadvantages: the piston wears quickly, especially when injecting aluminum alloys that dissolve the iron at high temperature, the adjustment of the amount of material injected depends on the useful volume of the chamber of the cylinder that it is necessary to change when changing the volume of the workpiece, the energy to be provided to maintain the temperature of the molten metal is high due to the heat dissipation through the cylinder and the piston, etc. WO02 / 30596, for example, discloses a pressurized injection machine comprising a tubular injection nozzle comprising a resistor wound on the major part of this nozzle in order to maintain the temperature of the molten metal. JP2005-28429 also discloses an analogous injection machine having a heating sleeve in which metal bars are inserted and fused by a resistive coil surrounding the sleeve. In order to stop the supply of the liquid metal mold, a shutter secured to the mold can be actuated to close the supply channel. However, in these examples, the injection pressure depends on the general supply pressure of the machine.
Il a donc été proposé, par exemple dans le document FR 2 668 967, des machines dans lesquelles l'alimentation en métal liquide est réalisée par une pompe électromagnétique. Cependant, les performances de ces machines en matière de pression d'injection, notamment en fin d'injection, sont relativement faibles.  It has therefore been proposed, for example in document FR 2,668,967, machines in which the supply of liquid metal is carried out by an electromagnetic pump. However, the performance of these machines in terms of injection pressure, especially at the end of injection, are relatively low.
Il subsiste donc un besoin pour des machines de coulée de mise en œuvre et d'entretien simplifié, permettant des réglages simples et étendus tout en conservant des performances de haut niveau.  There is therefore a need for simplified casting and maintenance casting machines, allowing simple and extensive adjustments while maintaining high level performance.
L'invention vise donc à fournir un embout d'injection adapté pour être associé à une machine de coulée, qui permet un réglage simple de la quantité de métal injectée et une forte pression en fin d'injection.  The invention therefore aims to provide an injection nozzle adapted to be associated with a casting machine, which allows a simple adjustment of the amount of injected metal and a high pressure at the end of injection.
L'invention vise également une machine de coulée comportant un tel embout, particulièrement adaptée pour permettre d'obtenir des performances élevées.  The invention also relates to a casting machine comprising such a nozzle, particularly adapted to allow to obtain high performance.
L'invention vise en outre un procédé de coulée de métal, mis en œuvre par une machine de coulée équipée d'un embout d'injection selon l'invention, procédé particulièrement adapté au moulage métallique sous pression.  The invention also relates to a metal casting process, implemented by a casting machine equipped with an injection nozzle according to the invention, a method particularly suitable for die-casting.
Pour ce faire, l'invention concerne un embout d'injection de métal sous pression, de forme tubulaire, en matériau réfractaire électriquement isolant, adapté pour être inséré entre une conduite d'amenée de métal liquide et un orifice d'injection d'un moule, comportant un canal d'injection adapté pour la circulation de métal liquide entre une première extrémité, dite extrémité amont, adaptée pour être reliée à ladite conduite et une deuxième extrémité, dite extrémité aval adaptée pour être reliée au moule, caractérisé en ce que ledit embout comporte une bobine électromagnétique, placée entre lesdites extrémités, d'axe confondu avec au moins une portion d'axe du canal, adaptée pour être alimentée par une impulsion de courant issue d'un générateur à haute tension et générer une striction électromagnétique dans le canal d'injection. Grâce à cet embout et particulièrement au canal à l'intérieur duquel circule le métal liquide, il est possible de remplir le moule placé à l'extrémité aval de l'embout. De plus, le matériau de l'embout étant réfractaire, par exemple en céramique, il est peu dégradé par la chaleur du métal circulant dans le canal. Grâce en outre à la bobine électromagnétique qui entoure ce conduit, lorsqu'elle est parcourue par une impulsion de courant électrique de fort ampérage, le métal liquide circulant dans le canal est soumis d'une part à un champ magnétique orienté axialement par rapport à la bobine et au canal et d'autre part à un courant induit opposé au sens du courant dans la bobine. La combinaison de ces deux phénomènes génère des forces de Lorentz, orientées radialement au conduit, en direction de son axe. Ces forces entraînent une violente striction du métal liquide dans le canal, projetant le métal de part et d'autre de la zone de striction. La projection du métal liquide en direction de l'orifice d'injection du moule permet ainsi de générer une surpression dans le métal, particulièrement utile pour la qualité de finition des pièces ainsi moulées. To this end, the invention relates to a tube-shaped pressurized metal injection nozzle made of electrically insulating refractory material adapted to be inserted between a liquid metal feed pipe and an injection port of a mold, comprising an injection channel adapted for the circulation of liquid metal between a first end, said upstream end, adapted to be connected to said pipe and a second end, said downstream end adapted to be connected to the mold, characterized in that said tip comprises an electromagnetic coil, placed between said ends, of coinciding axis with at least one channel portion of the channel, adapted to be powered by a current pulse from a high-voltage generator and generate an electromagnetic necking in the injection channel. Thanks to this tip and particularly to the channel within which the liquid metal circulates, it is possible to fill the mold placed at the downstream end of the tip. In addition, the material of the tip being refractory, for example ceramic, it is little degraded by the heat of the metal flowing in the channel. Thanks also to the electromagnetic coil which surrounds this duct, when it is traversed by a pulse of electric current of high amperage, the liquid metal flowing in the channel is subjected on the one hand to a magnetic field oriented axially relative to the coil and the channel and secondly to an induced current opposite to the direction of the current in the coil. The combination of these two phenomena generates Lorentz forces, oriented radially to the duct, in the direction of its axis. These forces cause a violent necking of the liquid metal in the channel, throwing the metal on both sides of the necking zone. The projection of the liquid metal towards the injection port of the mold thus makes it possible to generate an overpressure in the metal, which is particularly useful for the quality of finishing of the parts thus molded.
Avantageusement et selon l'invention, la bobine est adaptée pour être connectée aux bornes d'un générateur d'impulsions de courant. Un tel générateur, par exemple un générateur de Marx, est capable, au moyen d'un ou plusieurs éclateurs déchargeant une batterie de condensateurs, de développer un courant électrique de l'ordre de plusieurs dizaines de milliers d'ampères sous une tension de plusieurs milliers de volts en un temps très bref, de l'ordre de quelques millisecondes.  Advantageously and according to the invention, the coil is adapted to be connected to the terminals of a current pulse generator. Such a generator, for example a Marx generator, is capable, by means of one or more spark gaps discharging a capacitor bank, of developing an electrical current of the order of several tens of thousands of amperes at a voltage of several thousands of volts in a very short time, of the order of a few milliseconds.
Avantageusement et selon l'invention, le canal présente un diamètre comportant un rétrécissement entre l'extrémité amont et la bobine. Grâce à ce rétrécissement qui forme une buse convergente, la vitesse du métal liquide en sortie de la conduite d'amenée du métal est augmentée au droit de la bobine électromagnétique du fait du rétrécissement de la section droite du canal. Dès lors, lorsqu'on injecte un courant dans la bobine, la striction réalisée dans le canal, au droit de la bobine, dans la partie rétrécie du canal, projette le métal liquide avec une vitesse qui s'ajoute à la vitesse initiale de circulation du métal en direction de l'orifice d'injection du moule alors que, dans la direction opposée, cette vitesse est diminuée par l'effet du rétrécissement qui se comporte dans ce sens comme une tuyère divergente et se retranche de la vitesse initiale de circulation du métal liquide. De ce fait, la réaction à la striction en direction de la conduite d'amenée du métal liquide est fortement atténuée. Advantageously and according to the invention, the channel has a diameter comprising a narrowing between the upstream end and the coil. Due to this narrowing which forms a convergent nozzle, the velocity of the liquid metal at the outlet of the metal supply line is increased to the right of the electromagnetic coil due to the narrowing of the cross section of the channel. Therefore, when a current is injected into the coil, the necking made in the channel, in line with the coil, in the narrowed portion of the channel, projects the liquid metal with a speed which is added to the initial speed of circulation of the metal towards the injection orifice of the mold whereas, in the opposite direction, this speed is reduced by the effect of the narrowing which behaves in this direction as a divergent nozzle and subtracts from the initial velocity of circulation of the liquid metal. As a result, the necking reaction in the direction of the supply line of the liquid metal is greatly attenuated.
Avantageusement et selon l'invention, la bobine est noyée dans le matériau de l'embout. Afin de minimiser les pertes d'énergie, la bobine électromagnétique est placée au plus près de la veine de circulation du métal liquide en la noyant dans le matériau réfractaire formant l'embout. De plus, étant ainsi maintenue de tous les côtés, la bobine électromagnétique est moins soumise aux forces de réaction s'exerçant sur sa ou ses spires lors de la striction. Il reste néanmoins possible, particulièrement lorsque les conditions d'injection du métal (température, pression...) le permettent, d'utiliser un embout comportant une paroi plus mince et donc de placer la bobine électromagnétique autour et à l'extérieur de la buse de l'embout. Dans cette variante, la maintenance de la bobine est facilitée.  Advantageously and according to the invention, the coil is embedded in the material of the tip. In order to minimize the energy losses, the electromagnetic coil is placed as close as possible to the circulation channel of the liquid metal by embedding it in the refractory material forming the tip. Moreover, being thus maintained on all sides, the electromagnetic coil is less subject to reaction forces acting on its or its turns during necking. It remains possible, however, especially when the metal injection conditions (temperature, pressure, etc.) allow it, to use a tip having a thinner wall and thus to place the electromagnetic coil around and outside the tip nozzle. In this variant, the maintenance of the coil is facilitated.
Avantageusement et selon l'invention, la bobine est multi spires. Alternativement et selon l'invention, la bobine est mono spire. Préférentiellement, la bobine électromagnétique est réalisée de manière à présenter une pluralité de spires s'étendant de l'extrémité étroite du rétrécissement du canal en direction de son extrémité aval reliée à l'orifice d'injection du moule afin d'augmenter la largeur de la zone de striction du métal liquide dans l'embout et donc le volume de métal propulsé vers le moule. Alternativement, la bobine peut être une bobine mono spire, qui permet d'atteindre, pour un même étage de sortie du générateur d'impulsions de courant, de plus hautes fréquences (respectivement des impulsions plus brèves) augmentant ainsi la puissance instantanée de l'impulsion, un meilleur transfert de l'énergie et une durée de vie améliorée.  Advantageously and according to the invention, the coil is multi-turns. Alternatively and according to the invention, the coil is single turn. Preferably, the electromagnetic coil is made to have a plurality of turns extending from the narrow end of the narrowing of the channel towards its downstream end connected to the injection orifice of the mold in order to increase the width of the the zone of necking of the liquid metal in the tip and therefore the volume of metal propelled towards the mold. Alternatively, the coil may be a single coil coil, which achieves, for the same output stage of the current pulse generator, higher frequencies (respectively shorter pulses) thus increasing the instantaneous power of the impulse, better energy transfer and improved life.
L'invention s'étend également à une machine de coulée comportant un réservoir de métal liquide, une conduite d'amenée de métal liquide reliée audit réservoir et munie d'une pompe électromagnétique adaptée pour faire circuler le métal liquide dans la conduite en direction d'un moule, caractérisée en ce que la machine comporte un embout présentant l'une au moins des caractéristiques ci-dessus, entre ladite conduite et un orifice d'injection dudit moule. Grâce à l'utilisation d'un tel embout, la machine de coulée est plus fiable et plus facile à maintenir. En effet, c'est dans l'embout que se produisent les plus fortes variations de pression et donc les phénomènes d'usure. Dès lors, un embout démontable permet un temps d'immobilisation réduit lors de la maintenance. The invention also extends to a casting machine comprising a liquid metal reservoir, a liquid metal feed pipe connected to said reservoir and provided with an electromagnetic pump adapted to circulate the liquid metal in the pipe towards the a mold, characterized in that that the machine comprises a tip having at least one of the above characteristics between said pipe and an injection port of said mold. Through the use of such a nozzle, the casting machine is more reliable and easier to maintain. Indeed, it is in the tip that occur the strongest pressure variations and therefore the phenomena of wear. Therefore, a removable tip allows a reduced downtime during maintenance.
Avantageusement et selon l'invention, la pompe électromagnétique comporte une pluralité de bobines d'induction coaxiales à la conduite, adaptées pour chauffer par induction le métal circulant dans la conduite. En installant des bobines d'induction hélicoïdales régulièrement réparties sur la longueur de la conduite d'amenée du métal liquide depuis le réservoir jusqu'à l'embout, il est possible de maintenir la température du métal et d'éviter la formation de grumeaux.  Advantageously and according to the invention, the electromagnetic pump comprises a plurality of coaxial induction coils to the pipe, adapted to inductively heat the metal flowing in the pipe. By installing helical induction coils regularly distributed along the length of the liquid metal supply line from the tank to the nozzle, it is possible to maintain the temperature of the metal and to avoid the formation of lumps.
Avantageusement et selon l'invention, les bobines d'induction sont alimentées en courant polyphasé de manière à générer un champ magnétique mobile et entraîner le métal liquide en direction de l'embout. Les bobines d'induction alimentées par des courants alternatifs pour le chauffage par induction peuvent former un accélérateur magnétohydrodynamique à induction lorsqu'elles sont alimentées par des courants présentant un déphasage d'une bobine à l'autre. Dès lors, outre le chauffage du métal liquide dans la conduite d'amenée, les bobines permettent de générer un champ magnétique axial dans la conduite et de communiquer un mouvement au métal liquide en direction de l'embout.  Advantageously and according to the invention, the induction coils are fed with polyphase current so as to generate a movable magnetic field and drive the liquid metal towards the endpiece. Induction coils fed by alternating currents for induction heating may form a magnetohydrodynamic induction accelerator when energized by currents having a phase shift from one coil to the other. Therefore, in addition to heating the liquid metal in the supply line, the coils can generate an axial magnetic field in the pipe and communicate a movement to the liquid metal in the direction of the tip.
Avantageusement et selon l'invention, la machine comporte un dispositif de refroidissement des bobines d'induction intercalé entre lesdites bobines et la conduite. Afin de limiter réchauffement des bobines d'induction, celles-ci sont isolées de la conduite par un dispositif de refroidissement à air ou à eau, par exemple, pour un refroidissement à eau, par une circulation de liquide de refroidissement à l'intérieur d'un tube de cuivre servant de bobinage..  Advantageously and according to the invention, the machine comprises a cooling device of the induction coils interposed between said coils and the pipe. In order to limit heating of the induction coils, they are isolated from the pipe by an air or water cooling device, for example, for water cooling, by circulation of cooling liquid inside the coil. 'a copper tube serving as winding ..
L'invention s'étend en outre à un procédé de coulée de métal liquide sous pression dans un moule métallique, dans lequel : - on utilise une machine de coulée comportant un réservoir de métal liquide, une conduite reliée audit réservoir munie d'une pompe électromagnétique adaptée pour faire circuler le métal liquide dans la conduite en direction d'un moule, The invention further extends to a method of casting liquid metal under pressure in a metal mold, wherein: a casting machine comprising a liquid metal reservoir is used, a pipe connected to said reservoir provided with an electromagnetic pump adapted to circulate the liquid metal in the pipe towards a mold,
- la pompe électromagnétique est alimentée par un courant polyphasé de manière à déplacer le métal liquide du réservoir vers l'orifice d'injection du moule,  the electromagnetic pump is fed with a polyphase current so as to move the liquid metal from the reservoir to the injection orifice of the mold,
caractérisé en ce que la machine de coulée comprend un embout comportant une bobine électromagnétique entourant un canal d'injection entre ladite conduite et un orifice d'injection dudit moule et en ce qu'en fin d'injection, on alimente la bobine électromagnétique de l'embout avec une impulsion de courant électrique issue d'un générateur de haute tension pour générer une striction électromagnétique dans le canal d'injection et propulser le métal liquide sous pression vers l'orifice d'injection du moule. characterized in that the casting machine comprises a nozzle comprising an electromagnetic coil surrounding an injection channel between said pipe and an injection port of said mold and that at the end of the injection, the electromagnetic coil of the nozzle with an electric current pulse from a high voltage generator to generate an electromagnetic necking in the injection channel and propel the liquid metal under pressure to the injection port of the mold.
En faisant circuler une impulsion de courant en fin d'injection dans la bobine électromagnétique de l'embout, on génère une force électromagnétique radiale qui s'exerce sur le métal liquide qui circule dans le canal d'injection. Cette force de striction repousse le métal de part et d'autre de la section du canal autour de laquelle est installée la bobine électromagnétique. Le métal est ainsi repoussé vers l'orifice d'injection du moule avec une vitesse qui s'ajoute à la vitesse de circulation du métal dans le canal sous l'effet de la pompe électromagnétique et génère une surpression à l'intérieur de l'empreinte du moule, améliorant ainsi le remplissage de celle-ci. De l'autre côté de la section dans laquelle se développe la force de striction, le métal est repoussé en direction de la conduite d'amenée avec une vitesse qui se retranche de la vitesse de circulation du métal. La vitesse de circulation résultante, en direction de la conduite, est encore diminuée par la présence du divergent formé par le rétrécissement de la section du canal parcouru en sens inverse. Il est ainsi possible d'obtenir un arrêt au moins temporaire de la circulation du métal liquide dans la conduite d'amenée. L'invention concerne également un embout, une machine de coulée et un procédé de coulée caractérisés en combinaison par tout ou partie des caractéristiques mentionnées ci-dessus ou ci-après. By circulating a current pulse at the end of the injection into the electromagnetic coil of the nozzle, a radial electromagnetic force is generated which is exerted on the liquid metal circulating in the injection channel. This necking force pushes the metal on both sides of the section of the channel around which the electromagnetic coil is installed. The metal is thus pushed back towards the injection orifice of the mold with a speed which is added to the speed of circulation of the metal in the channel under the effect of the electromagnetic pump and generates an overpressure inside the mold cavity, thus improving the filling thereof. On the other side of the section in which the necking force develops, the metal is pushed back towards the feed line with a speed which is subtracted from the speed of circulation of the metal. The resulting flow velocity, in the direction of the pipe, is further reduced by the presence of the divergent formed by the narrowing of the section of the channel traveled in the opposite direction. It is thus possible to obtain at least a temporary stop of the circulation of the liquid metal in the supply line. The invention also relates to a nozzle, a casting machine and a casting process characterized in combination by all or some of the characteristics mentioned above or below.
D'autres buts, caractéristiques et avantages de l'invention apparaîtront au vu de la description qui va suivre et des dessins annexés dans lesquels :  Other objects, features and advantages of the invention will become apparent from the following description and the appended drawings in which:
- la figure 1 représente une vue schématique en coupe d'une machine de coulée selon l'invention,  FIG. 1 represents a schematic sectional view of a casting machine according to the invention,
- la figure 2 est une vue schématique en coupe d'un embout selon l'invention,  FIG. 2 is a diagrammatic sectional view of a mouthpiece according to the invention,
- la figure 3 est une vue en coupe d'un embout selon l'invention pendant une striction de l'écoulement du métal  FIG. 3 is a sectional view of a mouthpiece according to the invention during a necking of the flow of the metal
La figure 1 représente une coupe longitudinale d'une machine de coulée 10 comportant un réservoir 11, adapté pour contenir du métal liquide à injecter dans un moule 30. Le réservoir 11 peut comporter des moyens de chauffage (non représentés) pour maintenir le métal à sa température de fusion, ou être conformé en forme de trémie dans laquelle le métal liquide est versé à partir d'un creuset. Le métal liquide est ensuite acheminé dans une conduite 12 d'amenée du métal en direction d'un embout 20 fixé entre la conduite 12 et le moule 30.  FIG. 1 represents a longitudinal section of a casting machine 10 comprising a reservoir 11, adapted to contain liquid metal to be injected into a mold 30. The reservoir 11 may comprise heating means (not shown) for holding the metal at its melting temperature, or be shaped hopper in which the liquid metal is poured from a crucible. The liquid metal is then conveyed into a pipe 12 for feeding the metal towards a tip 20 fixed between the pipe 12 and the mold 30.
La conduite 12 est équipée d'une pompe électromagnétique 50 comportant une pluralité de bobines d'induction 51 régulièrement espacées le long de la conduite 12. Chacune des bobines d'induction 51 est reliée à un onduleur 53 adapté pour alimenter les bobines 51 avec un courant alternatif. Les bobines d'induction 51 remplissent un double rôle : d'une part, elles fonctionnent en bobines de chauffage par induction permettant de conserver à l'état liquide la veine de métal liquide circulant dans la conduite 12, et d'autre part, alimentées en courant alternatif polyphasé adapté au nombre et à l'ordre des bobines 51, elles génèrent un champ magnétique mobile circulant du réservoir 11 en direction de l'embout 20, ce champ magnétique permettant de faire circuler le métal liquide dans la conduite en direction du moule 30 avec une vitesse V0. À titre d'exemple, les bobines d'induction sont alimentées en courant triphasé sous une tension de 400V à une fréquence de l'ordre de 50 Hz à 10 kHz avec un courant pouvant varier entre 50 A et 10 000 A. The pipe 12 is equipped with an electromagnetic pump 50 comprising a plurality of induction coils 51 regularly spaced along the pipe 12. Each of the induction coils 51 is connected to an inverter 53 adapted to feed the coils 51 with a alternating current. The induction coils 51 fulfill a double role: on the one hand, they function in induction heating coils making it possible to keep the liquid metal vein flowing in the pipe 12 in the liquid state, and on the other hand, fed polyphase alternating current adapted to the number and order of the coils 51, they generate a moving magnetic field flowing from the tank 11 towards the tip 20, this magnetic field for circulating the liquid metal in the pipe towards the mold 30 with a speed V0. For example, the induction coils are supplied with three-phase current at a voltage of 400V at a voltage of frequency of the order of 50 Hz to 10 kHz with a current that can vary between 50 A and 10 000 A.
Les bobines 51 comportent également un circuit de refroidissement 52 par exemple utilisant un liquide de refroidissement circulant dans des tubes de cuivre formant les bobines 51, permettant de limiter leur échauffement. Bien entendu, il peut être également envisagé d'utiliser un système de refroidissement à air par convection forcée, mettant en œuvre un ou plusieurs ventilateurs et des ailettes de refroidissement solidaires des bobinages.  The coils 51 also comprise a cooling circuit 52 for example using a cooling liquid flowing in copper tubes forming the coils 51, to limit their heating. Of course, it may also be envisaged to use a forced convection air cooling system, implementing one or more fans and cooling fins integral windings.
On se réfère à la figure 2 pour détailler la structure préférentielle de l'embout 20. L'embout 20 est fixé à l'extrémité de la conduite 12 par son extrémité amont 23 (repérée ainsi par rapport au sens de circulation du métal liquide dans la conduite et dans l'embout) au moyen de brides 25. L'embout 20 est également fixé à son extrémité opposée, dite extrémité aval 24, au moule 30 par des brides 25. L'embout 20 comporte un corps 21 en matériau réfractaire et isolant électriquement, de préférence en céramique, et plus particulièrement en nitrure d'alumine/zirconium. D'autres matériaux réfractaires peuvent également être utilisés, par exemple des céramiques à base d'alumine, de zirconium, d'yttrium, de titane ou d'oxyde de nickel, ou encore d'un mélange de ces constituants en diverses proportions.  Referring to Figure 2 to detail the preferred structure of the nozzle 20. The tip 20 is attached to the end of the pipe 12 by its upstream end 23 (thus marked with respect to the direction of flow of the liquid metal in the pipe and in the tip) by means of flanges 25. The tip 20 is also fixed at its opposite end, said downstream end 24, to the mold 30 by flanges 25. The tip 20 comprises a body 21 of refractory material and electrically insulating, preferably ceramic, and more particularly alumina / zirconium nitride. Other refractory materials may also be used, for example ceramics based on alumina, zirconium, yttrium, titanium or nickel oxide, or a mixture of these constituents in various proportions.
Le corps 21 de l'embout est traversé par un canal 22 allant de l'extrémité amont 23 à l'extrémité aval 24 au niveau de laquelle le canal 22 débouche dans l'orifice d'injection 33 du moule 30. Le canal 22 est préférentiellement de forme cylindrique de révolution et comporte au niveau de l'extrémité amont 23 une partie conique formant un rétrécissement 27 entre une grande section d'un diamètre correspondant à l'extrémité de la conduite 12 et une section plus faible du canal 22 correspondant à la section de l'orifice d'injection 33 du moule 30.  The body 21 of the nozzle is traversed by a channel 22 from the upstream end 23 to the downstream end 24 at which the channel 22 opens into the injection port 33 of the mold 30. The channel 22 is preferably of cylindrical shape of revolution and comprises at the upstream end 23 a conical portion forming a narrowing 27 between a large section of a diameter corresponding to the end of the pipe 12 and a smaller section of the channel 22 corresponding to the section of the injection orifice 33 of the mold 30.
Le corps 21 comporte également en aval du rétrécissement 27 une bobine 26 électromagnétique, entourant le canal 22 et surmoulée dans le corps 21. La bobine 26 est préférentiellement une bobine multi spire, en cuivre ou autre matériau très conducteur, par exemple en aluminium, cupro-berylium, alliage cuivre-chrome-zirconium, tungstène ou alliage tungstène-cuivre... La bobine 26 est adaptée pour être connectée à un générateur 40 d'impulsions de courant comportant généralement une batterie 41 de condensateurs chargés par une source d'alimentation continue externe (non représentée) et déchargée dans la bobine 26 électromagnétique par l'intermédiaire d'un éclateur 42. La bobine 26 peut également être formée d'une spire unique. Qu'elle soit multi ou mono spire, la bobine 26 présente un axe de révolution sensiblement confondu avec au moins une portion de l'axe du canal 21, sur la partie de celui-ci qu'elle entoure. La bobine 26 délimite ainsi dans le canal 21 une zone, dite zone de striction 28, à l'intérieur de laquelle se développe le champ électromagnétique créé par la bobine 26 lorsque celle-ci est alimentée par le générateur 40. The body 21 also comprises, downstream of the narrowing 27, an electromagnetic coil 26, surrounding the channel 22 and overmolded in the body 21. The coil 26 is preferably a multi-turn coil made of copper or other highly conductive material, for example aluminum, cupro -berylium alloy copper-chromium-zirconium, tungsten or tungsten-copper alloy ... The coil 26 is adapted to be connected to a generator 40 of current pulses generally comprising a battery 41 of capacitors charged by an external DC power source (no shown) and discharged into the electromagnetic coil 26 via a spark gap 42. The coil 26 may also be formed of a single coil. Whether multi or single turns, the coil 26 has an axis of revolution substantially coincident with at least a portion of the axis of the channel 21, on the part thereof that surrounds. The coil 26 thus delimits in the channel 21 a zone, called the necking zone 28, within which the electromagnetic field created by the coil 26 when it is fed by the generator 40 is developed.
Selon une variante, utilisable lorsque les conditions d'injection le permettent, c'est-à-dire si la pression d'injection et/ou la température et/ou le métal à injecter sont compatibles avec un embout dont le corps 21 comporte des parois suffisamment minces, il est possible de placer la bobine 26 autour du corps 21. Par exemple, pour l'injection d'alliages de zinc (sans aluminium) présentant un point de fusion inférieur à 450°C, il est possible d'utiliser un embout en acier inoxydable austénitique réfractaire non magnétique qui permet une résistance satisfaisante avec des épaisseurs réduites à quelques millimètres. Une bobine 26 électromagnétique mono ou multi spire peut être alors enfilée sur le corps 21 et fixée par tout moyen approprié. Cette variante permet un démontage facile de la bobine tout en conservant le corps 21 de l'embout.  According to a variant, usable when the injection conditions allow it, that is to say if the injection pressure and / or the temperature and / or the metal to be injected are compatible with a tip whose body 21 comprises walls sufficiently thin, it is possible to place the coil 26 around the body 21. For example, for the injection of zinc alloys (without aluminum) having a melting point below 450 ° C, it is possible to use a nonmagnetic refractory austenitic stainless steel tip that allows satisfactory resistance with thicknesses reduced to a few millimeters. A single or multi-turn electromagnetic coil 26 can then be threaded onto the body 21 and fixed by any appropriate means. This variant allows easy disassembly of the coil while retaining the body 21 of the tip.
On se réfère maintenant aux figures 1 et 3 pour décrire le fonctionnement de la machine 10 et de l'embout 20, ainsi que le procédé de coulée selon l'invention.  Referring now to Figures 1 and 3 to describe the operation of the machine 10 and the tip 20, and the casting method according to the invention.
Lors d'une opération de coulée, on remplit le réservoir 11 avec un métal liquide, par exemple un alliage de zinc ou de magnésium. Le métal liquide coule du réservoir 11 dans la conduite 12. L'onduleur 53 alimente les bobines d'induction 51 avec un courant alternatif polyphasé (par exemple triphasé) de manière à réchauffer par induction le métal liquide dans la conduite 12 pour éviter toute amorce de solidification ou la formation de grumeaux. Chaque bobine d'induction 51 développe également un champ magnétique dont les lignes de champ sont orientées selon l'axe des bobines d'induction et de la conduite 12. Le déphasage du champ magnétique des bobines d'induction génère un champ magnétique mobile dans la conduite 12 qui déplace le métal liquide contenu dans celle-ci vers son extrémité opposée au réservoir 11, avec une vitesse sensiblement constante V0. During a casting operation, the tank 11 is filled with a liquid metal, for example a zinc or magnesium alloy. The liquid metal flows from the tank 11 into the pipe 12. The inverter 53 supplies the induction coils 51 with a polyphase alternating current (for example three-phase) so as to inductively heat the liquid metal in the pipe 12 to avoid any primer solidification or formation of lumps. Each coil induction 51 also develops a magnetic field whose field lines are oriented along the axis of the induction coils and the pipe 12. The phase shift of the magnetic field of the induction coils generates a movable magnetic field in the pipe 12 which moves the liquid metal contained therein towards its opposite end to the tank 11, with a substantially constant velocity V0.
À l'entrée dans l'embout 20, la section de passage du métal liquide diminue dans le rétrécissement 27 et donc la vitesse de déplacement du métal augmente en fonction du rapport de section entre l'extrémité amont 23 de l'embout et la section du canal 22 pour atteindre une vitesse VI au bout du rétrécissement, à l'entrée dans la zone de striction 28 située sous la bobine 26 électromagnétique. Le métal liquide progresse à la vitesse VI dans le canal 22 puis dans l'orifice d'injection 33 du moule 30 pour remplir une ou plusieurs empreintes 32 formées entre les coquilles 31 du moule 30. Lorsque les empreintes 32 sont remplies, par exemple au bout d'un temps d'injection prédéterminé en fonction de la vitesse VI, de la section du canal 22 et/ou de l'orifice d'injection 33 qui définissent le débit de métal et du volume de la ou des empreintes 32, le générateur d'impulsions 40 est activé et délivre une impulsion de courant, par exemple d'une intensité de l'ordre de 20 kA à 1 MA, d'une durée de 40 à 2 ms qui circule dans la bobine 26. L'importante variation du flux du champ magnétique généré par la bobine 26 lorsqu'elle est traversée par cette impulsion de courant donne lieu à une force magnétique radiale qui s'exerce sur le métal liquide 13 dans la zone de striction 28. Le métal liquide 13 est ainsi comprimé radialement et, du fait de son incompressibilité, est éjecté axialement de part et d'autre de la zone de striction 28 avec une vitesse d'éjection V2. La combinaison de cette vitesse d'éjection V2 avec la vitesse de circulation VI du métal liquide en direction du moule 30 imprime au métal une vitesse correspondant à V1+V2. Compte tenu du fait que l'empreinte 32 est remplie, cette vitesse V1+V2 se transforme en une augmentation de la pression d'injection dans le moule 30. À titre d'exemple, pour une bobine 26 mono spire en aluminium présentant une zone de travail (zone de striction 28) d'une longueur de 15 mm, alimentée par une impulsion de courant Imax= 500 kA à 500 Hz (2 ms), la bobine génère un champ magnétique de 40 T. Lorsque ce champ magnétique est appliqué au métal liquide, celui-ci peut atteindre une vitesse maximum (V1+V2) de l'ordre de 30 m/s dans l'embout et une pression maximale de 700 MPa. At the entrance to the nozzle 20, the passage section of the liquid metal decreases in the constriction 27 and thus the speed of movement of the metal increases as a function of the section ratio between the upstream end 23 of the nozzle and the section of the channel 22 to reach a speed VI at the end of the narrowing, at the entrance to the necking zone 28 located below the electromagnetic coil 26. The liquid metal progresses at the speed VI in the channel 22 and then in the injection orifice 33 of the mold 30 to fill one or more cavities 32 formed between the shells 31 of the mold 30. When the cavities 32 are filled, for example with end of a predetermined injection time as a function of the speed VI, the section of the channel 22 and / or the injection orifice 33 which define the metal flow rate and the volume of the fingerprint or fingerprints 32, the pulse generator 40 is activated and delivers a current pulse, for example of an intensity of the order of 20 kA to 1 MA, with a duration of 40 to 2 ms which circulates in the coil 26. The important variation of the flux of the magnetic field generated by the coil 26 when traversed by this current pulse gives rise to a radial magnetic force acting on the liquid metal 13 in the necking zone 28. The liquid metal 13 is thus compressed radially and, because of its incompressibili tee, is ejected axially on either side of the necking zone 28 with an ejection speed V2. The combination of this ejection velocity V2 with the circulation velocity VI of the liquid metal towards the mold 30 imparts a velocity corresponding to V1 + V2 to the metal. Given the fact that the cavity 32 is filled, this speed V1 + V2 is transformed into an increase in the injection pressure in the mold 30. For example, for a coil 26 single-turn aluminum having a zone working piece (necking zone 28) with a length of 15 mm, fed by a current pulse Imax = 500 kA at 500 Hz (2 ms), the coil generates a magnetic field of 40 T. When this magnetic field is applied to the liquid metal, it can reach a maximum speed (V1 + V2) of the order of 30 m / s in the nozzle and a maximum pressure of 700 MPa.
De l'autre côté de la zone de striction 28, la vitesse de circulation du métal suite à la combinaison des vitesses de circulation et d'éjection est V1-V2. En général, la vitesse d'éjection V2 est supérieure en valeur absolue à la vitesse de circulation VI ce qui imprime au métal liquide un mouvement en direction de la conduite 12 de la machine. Grâce au rétrécissement 27 qui se comporte en divergent dans ce sens, la vitesse du métal liquide est diminuée dans le rapport des sections et ne génère pas une onde de choc importante dans la conduite 12 susceptible d'endommager la machine mais simplement une onde de pression qui favorise le mélange du métal dans la conduite.  On the other side of the necking zone 28, the circulation velocity of the metal following the combination of the circulation and ejection velocities is V1-V2. In general, the ejection velocity V2 is greater in absolute value than the circulation velocity VI which imparts to the liquid metal a movement towards the pipe 12 of the machine. Due to the narrowing 27 which behaves divergently in this direction, the speed of the liquid metal is reduced in the ratio of the sections and does not generate a large shock wave in the pipe 12 may damage the machine but simply a pressure wave which promotes the mixing of the metal in the pipe.
Bien entendu, cette description est donnée à titre d'exemple illustratif uniquement et l'homme du métier pourra y apporter de nombreuses modifications sans sortir de la portée de l'invention, par exemple en adaptant les dimensions des différents éléments de la machine de coulée en fonction du métal à couler, du volume des empreintes du moule, etc. De même, le dosage de la quantité de métal à injecter dans les empreintes du moule pourra être réglé par une durée d'injection avant déclenchement du générateur d'impulsion ou par le réglage de la vitesse de transfert du métal liquide par la fréquence et la phase d'alimentation des bobines d'induction.  Of course, this description is given as an illustrative example only and the skilled person can make many modifications without departing from the scope of the invention, for example by adapting the dimensions of the various elements of the casting machine depending on the metal to be cast, the volume of mold impressions, etc. Similarly, the dosage of the amount of metal to be injected into the mold cavities may be adjusted by an injection time before the pulse generator is triggered or by the adjustment of the transfer rate of the liquid metal by the frequency and supply phase of the induction coils.

Claims

REVENDICATIONS
1/ - Embout (20) d'injection de métal (13) liquide sous pression, de forme tubulaire, en matériau réfractaire électriquement isolant, adapté pour être inséré entre une conduite (12) d'amenée de métal liquide et un orifice d'injection (33) d'un moule (30), comportant un canal (22) d'injection adapté pour la circulation de métal liquide entre une première extrémité, dite extrémité amont (23), adaptée pour être reliée à ladite conduite et une deuxième extrémité, dite extrémité aval (24), adaptée pour être reliée au moule,  1 / - Tube-shaped liquid injection nozzle (13) made of electrically insulating refractory material adapted to be inserted between a pipe (12) for feeding liquid metal and an orifice injection (33) of a mold (30), comprising an injection channel (22) adapted for the circulation of liquid metal between a first end, said upstream end (23) adapted to be connected to said pipe and a second end, said downstream end (24), adapted to be connected to the mold,
caractérisé en ce que ledit embout comporte une bobine (26) électromagnétique, placée entre lesdites extrémités, d'axe confondu avec au moins une portion d'axe du canal, adaptée pour être alimentée par une impulsion de courant issue d'un générateur (40) à haute tension et générer une striction électromagnétique dans le canal (22) d'injection. characterized in that said tip comprises an electromagnetic coil (26) placed between said ends, of axis coincident with at least one axis portion of the channel, adapted to be powered by a current pulse from a generator (40). ) at high voltage and generate an electromagnetic necking in the injection channel (22).
21 - Embout selon la revendication 1, caractérisé en ce que le canal (22) d'injection présente un diamètre comportant un rétrécissement (27) entre l'extrémité amont (23) et la bobine (26) électromagnétique.  21 - nozzle according to claim 1, characterized in that the channel (22) of injection has a diameter having a narrowing (27) between the upstream end (23) and the coil (26) electromagnetic.
3/ - Embout selon l'une quelconque des revendications 1 ou 2, caractérisé en ce que la bobine (26) électromagnétique est noyée dans le matériau de l'embout.  3 / - nozzle according to any one of claims 1 or 2, characterized in that the coil (26) electromagnetic is embedded in the material of the tip.
4/ - Embout selon l'une quelconque des revendications 1 à 3, caractérisé en ce que la bobine (26) électromagnétique est multi spires.  4 / - nozzle according to any one of claims 1 to 3, characterized in that the coil (26) electromagnetic is multi turns.
5/ - Embout selon l'une quelconque des revendications 1 à 3, caractérisé en ce que la bobine (26) électromagnétique est mono spire.  5 / - nozzle according to any one of claims 1 to 3, characterized in that the coil (26) electromagnetic is single turn.
6/ - Machine (10) de coulée comportant un réservoir (11) de métal liquide, une conduite (12) d'amenée de métal liquide reliée audit réservoir et munie d'une pompe électromagnétique (50) adaptée pour faire circuler le métal liquide dans ladite conduite en direction d'un moule (30), caractérisée en ce que la machine comporte un embout (20) selon l'une quelconque des revendications 1 à 6 entre ladite conduite et un orifice d'injection (33) dudit moule.  6 / - casting machine (10) comprising a reservoir (11) of liquid metal, a pipe (12) supplying liquid metal connected to said reservoir and provided with an electromagnetic pump (50) adapted to circulate the liquid metal in said pipe towards a mold (30), characterized in that the machine comprises a nozzle (20) according to any one of claims 1 to 6 between said pipe and an injection port (33) of said mold.
11 - Machine selon la revendication 6, caractérisée en ce que la pompe électromagnétique (50) comporte une pluralité de bobines d'induction (51) coaxiales à la conduite (12) d'amenée de métal liquide, adaptées pour chauffer par induction le métal circulant dans ladite conduite. 11 - Machine according to claim 6, characterized in that the electromagnetic pump (50) comprises a plurality of induction coils (51) coaxial with the conduit (12) supplying liquid metal, adapted to inductively heat the metal flowing in said pipe.
8/ - Machine selon la revendication 7, caractérisée en ce que les bobines d'induction (51) sont alimentées en courant polyphasé de manière à générer un champ magnétique mobile et entraîner le métal liquide en direction de l'embout (20).  8 / - Machine according to claim 7, characterized in that the induction coils (51) are supplied with polyphase current so as to generate a movable magnetic field and drive the liquid metal towards the tip (20).
91 - Machine selon l'une des revendications 7 ou 8, caractérisée en ce qu'un dispositif de refroidissement (52) des bobines d'induction (50) est intercalé entre lesdites bobines et la conduite (12).  91 - Machine according to one of claims 7 or 8, characterized in that a cooling device (52) of the induction coils (50) is interposed between said coils and the pipe (12).
10/ - Procédé de coulée de métal liquide sous pression dans un moule (30) métallique, dans lequel :  10 / - Process for casting liquid metal under pressure in a metal mold (30), in which:
- on utilise une machine (10) de coulée comportant un réservoir (11) de métal liquide, une conduite (12) d'amenée de métal liquide reliée audit réservoir munie d'une pompe électromagnétique (50) adaptée pour faire circuler le métal liquide dans ladite conduite en direction d'un moule (30),  a casting machine (10) comprising a reservoir (11) of liquid metal, a conduit (12) for supplying liquid metal connected to said reservoir provided with an electromagnetic pump (50) adapted to circulate the liquid metal, is used. in said pipe towards a mold (30),
- la pompe électromagnétique (50) est alimentée par un courant polyphasé de manière à déplacer le métal liquide du réservoir vers l'orifice d'injection du moule,  the electromagnetic pump (50) is fed with a polyphase current so as to move the liquid metal from the reservoir to the injection orifice of the mold,
caractérisé en ce que la machine (10) de coulée comprend un embout (20) comportant une bobine (26) électromagnétique entourant un canal (22) d'injection entre ladite conduite et un orifice d'injection (33) dudit moule et en ce qu'en fin d'injection, on alimente la bobine (26) électromagnétique de l'embout (20) avec une impulsion de courant électrique issue d'un générateur (40) de haute tension pour générer une striction électromagnétique dans le canal (22) d'injection et propulser le métal liquide sous pression vers l'orifice d'injection (33) du moule. characterized in that the casting machine (10) comprises a nozzle (20) having an electromagnetic coil (26) surrounding an injection channel (22) between said pipe and an injection port (33) of said mold and in that at the end of the injection, the electromagnetic coil (26) of the tip (20) is fed with an electric current pulse from a high voltage generator (40) to generate an electromagnetic necking in the channel (22). ) of injection and propel the liquid metal under pressure to the injection port (33) of the mold.
EP16808684.1A 2015-12-11 2016-12-09 Injection tip for casting machine, casting machine and method using such a tip Active EP3386659B1 (en)

Applications Claiming Priority (2)

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FR1562245A FR3044943B1 (en) 2015-12-11 2015-12-11 INJECTION TIP FOR A CASTING MACHINE, MACHINE AND CASTING PROCESS USING SUCH A TIP
PCT/EP2016/080396 WO2017097961A1 (en) 2015-12-11 2016-12-09 Injection tip for casting machine, casting machine and method using such a tip

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WO2017097961A1 (en) 2017-06-15
JP2018537296A (en) 2018-12-20
EP3386659B1 (en) 2020-12-02
FR3044943B1 (en) 2020-12-04
US20190001407A1 (en) 2019-01-03
FR3044943A1 (en) 2017-06-16
JP6840166B2 (en) 2021-03-10
CN108367344A (en) 2018-08-03

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