EP0050578B1 - Apparatus for the treatment of a molten metal bath by gas injection - Google Patents

Apparatus for the treatment of a molten metal bath by gas injection Download PDF

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Publication number
EP0050578B1
EP0050578B1 EP81420150A EP81420150A EP0050578B1 EP 0050578 B1 EP0050578 B1 EP 0050578B1 EP 81420150 A EP81420150 A EP 81420150A EP 81420150 A EP81420150 A EP 81420150A EP 0050578 B1 EP0050578 B1 EP 0050578B1
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EP
European Patent Office
Prior art keywords
liquid metal
agitator
metal bath
plug
treatment apparatus
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Expired
Application number
EP81420150A
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German (de)
French (fr)
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EP0050578A1 (en
Inventor
François Bucourt
Henri Fetaud
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Rio Tinto France SAS
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Aluminium Pechiney SA
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Publication of EP0050578A1 publication Critical patent/EP0050578A1/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/09—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure
    • B22D27/13—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure making use of gas pressure
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B21/00—Obtaining aluminium
    • C22B21/06—Obtaining aluminium refining
    • C22B21/064—Obtaining aluminium refining using inert or reactive gases
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B21/00—Obtaining aluminium
    • C22B21/06—Obtaining aluminium refining
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
    • C22B9/05—Refining by treating with gases, e.g. gas flushing also refining by means of a material generating gas in situ

Definitions

  • the present invention relates to a device for treating a bath of liquid metal and, in particular, of aluminum or its alloys by gas injection.
  • the first consists in passing the liquid metal through inert or active filtration media which retain impurities either mechanically, or following chemical reactions, or by exerting the two effects;
  • the second way resorts to the use of inert or reactive gases or their mixtures, which are more or less intensely stirred with the liquid metal, in the presence or not of products such as fluxes.
  • gases are injected in the form of small discrete bubbles by means of a device consisting of a rotary shaft secured to a finned rotor, of a fixed sleeve surrounding said shaft and connected at its lower end to a finned stator; shaft and sleeve are separated by an axial passage in which the gases are transported and introduced at the level of the fins where they are subdivided into small bubbles and brought into intimate contact with the metal stirred by the rotor.
  • This device for treating a bath of liquid metal contained in a container by gas injection is characterized in that it comprises a free rotary agitator in vertical translation comprising a lower part and an upper part whose lower surface of the lower part rests, when stationary, on the upper surface of a gas injection plug placed at the bottom of the container and which, under the action of the pressure of the gas emitted by the plug rises and, thus supported by a bearing fluid, can, under the effect of an external torque applied to the upper part of the agitator, freely rotate around its axis and let escape by the space which separates it from the stopper, a multitude of gas bubbles regularly dispersed .
  • the device according to the invention is therefore formed by the combination of two means, a rotary agitator, on the one hand, and a gas injection plug, on the other hand.
  • the rotary agitator consists of a massive piece of cylindrical-conical shape, the upper part of which is provided with a cylindrical opening in which engages the shaft on which an external torque is exerted.
  • the lower part of this agitator may have a smooth surface or have several radial notches of increasing depth towards the periphery, so as to facilitate the entrainment of the injection gases. These notches extend for example in length over about a third of the diameter of the agitator and can be extended on the lateral face by forming sorts of propellers oriented to the right or to the left and whose pitch is more or less great depending on the processing conditions.
  • the agitator shaft is equipped with a system antivortex placed at the bath-atmosphere interface, so as to limit the movements of the liquid metal which could hinder proper dispersion of the gases.
  • the external torque is preferably exerted by a variable speed motor fixed on a support arranged at the top of the container.
  • the shaft of this motor is integral with the shaft of the agitator by means of any connection system which allows the agitator to be able to describe a vertical translational movement over a distance of several millimeters.
  • the gas injection plug is made up of a cylindrical piece, the upper surface of which is pierced with holes of small diameter, which can be arranged in crowns and which are connected inside the plug to channels which form a channel. central which leads to an expansion chamber supplied with gas by a pipe external to the container.
  • the mass of the plug located above the expansion chamber can be produced with a porous material.
  • the agitator and the stopper are arranged, with respect to each other, so that the vertical axes of symmetry of each of them are coincident.
  • the lower surface of the lower part of the agitator and the upper surface of the stopper are adapted to one another so that, when at rest, they are in contact with each other and cause an obstruction of the orifices of gas injection.
  • This adaptation can be achieved for example by giving said surface of the stopper a conical shape and by providing in said surface of the stirrer a cavity of similar shape.
  • the gas pressure admitted at the level of the plug raises the agitator and produces a fluid bearing so that, when the drive motor is put into service, said agitator can rotate freely without contact with the cap.
  • the agitator and the stopper are preferably composed of graphite, but any other material having sufficient resistance to liquid metal is also suitable.
  • the gas admitted by the plug is a neutral gas such as argon, nitrogen or a reactive gas such as chlorine or their mixtures, or any other gas capable of treating the metal.
  • a neutral gas such as argon, nitrogen or a reactive gas such as chlorine or their mixtures, or any other gas capable of treating the metal.
  • Such a device is placed on a container containing the metal bath to be treated. It can be, for example, a pocket through which the metal passes continuously before being cast.
  • This container may comprise, in a conventional manner, a partition and, then, the device is placed in the upstream compartment.
  • the bottom of this pocket can be provided with a filtration bed or not.
  • This pocket is equipped with means which make it possible to maintain a neutral atmosphere on the surface of the liquid metal and thus avoid any oxidizing action of the outside air.
  • This container can also be provided with heating means intended to maintain the metal in the liquid state.
  • Figure 2 shows the arrangement of the notches (5) on the conical surface (4) of the lower part of the agitator.
  • the pocket is supplied with liquid metal by the channel (25) and flows towards the bottom of the upstream compartment, then below the partition (19) towards the downstream compartment before leaving the pocket through the channel (27).
  • the metal bath delimited by the walls of the pocket and the surface (28) is intimately stirred by the agitator with the formation of a multitude of finely dispersed gas bubbles which escape through the space (29) forming under pressure gases between the lower part of the agitator and the upper part of the cap.
  • the metal to be treated was an aluminum alloy of the 6000 series, which was brought to the liquid state, at a temperature close to 720 ° C., at a flow rate of 5 tonnes per hour in a ladle where the bath height was 80 cm.
  • the plug of the channel type, was supplied with argon at a rate of approximately 2 m 3 / h under a pressure of between 1.2 and 1.4 bar.
  • the agitator was rotating at a speed of 400 rpm.
  • the alloy presented 10 bubbles in the vacuum solidification test; after passing through the pocket, the number of bubbles was zero. This shows the effectiveness of the treatment obtained by means of the claimed device.
  • the present invention finds its application in the treatment of liquid metals with a gas, and in particular in the treatment of aluminum or its alloys for the removal of hydrogen and non-metallic impurities.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
  • Coating With Molten Metal (AREA)

Description

La présente invention est relative à un dispositif de traitement d'un bain de métal liquide et, notamment, d'aluminium ou de ses alliages par injection de gaz.The present invention relates to a device for treating a bath of liquid metal and, in particular, of aluminum or its alloys by gas injection.

L'homme de l'art sait qu'avant de procéder à la mise en forme de produits métallurgiques semi finis, il est nécessaire de traiter le métal brut d'élaboration pour le débarrasser des gaz dissous et des impuretés non métalliques qu'il contient et dont la présence nuirait aux propriétés souhaitées et à la facilité de solidification des pièces fabriquées.Those skilled in the art know that before proceeding to the shaping of semi-finished metallurgical products, it is necessary to treat the raw metal for processing in order to rid it of dissolved gases and of the non-metallic impurities which it contains. and the presence of which would adversely affect the desired properties and the ease of solidification of the parts produced.

Deux voies principales de traitement sont connues actuellement : la première consiste à faire passer le métal liquide à travers les milieux de filtration inertes ou actifs qui retiennent les impuretés soit mécaniquement, soit à la suite de réactions chimiques, soit en exerçant les deux effets ; la deuxième voie recourt à l'utilisation de gaz inertes ou réactifs ou de leurs mélanges, lesquels sont brassés plus ou moins intensément avec le métal liquide, en présence ou non de produits tels que des flux. Ces deux voies peuvent, d'ailleurs, être combinées entre elles.Two main ways of treatment are currently known: the first consists in passing the liquid metal through inert or active filtration media which retain impurities either mechanically, or following chemical reactions, or by exerting the two effects; the second way resorts to the use of inert or reactive gases or their mixtures, which are more or less intensely stirred with the liquid metal, in the presence or not of products such as fluxes. These two routes can, moreover, be combined together.

Suivant la deuxième voie, de nombreuses réalisations ont été faites portant, entre autres, sur la manière d'introduire le gaz dans le bain de métal liquide et sur la façon d'obtenir une plus ou moins grande dispersion des gaz dans le métal. C'est ainsi que, dans le brevet français n° 1 555 953, le gaz est amené dans le bain par un plongeur dont la partie inférieure est équipée d'un dispositif rotatif assurant le brassage et la répartition du gaz à travers une grande surface de bain.According to the second path, numerous embodiments have been made relating, inter alia, to the manner of introducing the gas into the bath of liquid metal and to the manner of obtaining a greater or lesser dispersion of the gases in the metal. Thus, in French patent No. 1,555,953, the gas is brought into the bath by a plunger, the lower part of which is equipped with a rotary device ensuring the mixing and distribution of the gas over a large area. of bath.

Dans le brevet français n° 2 063 916, le gaz est insufflé dans le métal fondu au moyen d'une lance à double enveloppe refroidie par eau.In French Patent No. 2,063,916, the gas is blown into the molten metal by means of a water-cooled double jacket lance.

Dans le brevet français n° 2 166 014, on injecte des gaz sous forme de petites bulles discrètes au moyen d'un dispositif constitué d'un arbre rotatif solidaire d'un rotor à ailettes, d'un manchon fixe entourant ledit arbre et relié à son extrémité inférieure à un stator à ailettes ; arbre et manchon sont séparés par un passage axial dans lequel les gaz sont transportés et introduits au niveau des ailettes où ils sont subdivisés en petites bulles et amenés en contact intime avec le métal agité par le rotor.In French Patent No. 2,166,014, gases are injected in the form of small discrete bubbles by means of a device consisting of a rotary shaft secured to a finned rotor, of a fixed sleeve surrounding said shaft and connected at its lower end to a finned stator; shaft and sleeve are separated by an axial passage in which the gases are transported and introduced at the level of the fins where they are subdivided into small bubbles and brought into intimate contact with the metal stirred by the rotor.

Dans le brevet français n° 2 200 364, le gaz est introduit au centre de rotation d'un agitateur à turbine et mis en contact avec le métal liquide dans des conditions d'agitation évitant toute émulsification.In French Patent No. 2,200,364, the gas is introduced into the center of rotation of a turbine agitator and brought into contact with the liquid metal under stirring conditions avoiding any emulsification.

De nombreuses solutions ont été proposées. Toutefois, chacune d'elles présente des inconvénients. Ainsi, les dispositifs d'injection de gaz, par l'intermédiaire d'un agitateur, recourent à l'utilisation de canaux de distribution de gaz placés au sein dudit agitateur, ce qui en complique la réalisation et conduit à des systèmes fragiles et d'un entretien coûteux ; de plus, ces canaux sont la source de pertes de charge importantes qui limitent la vitesse d'injection de gaz dans le bain. En outre, la vitesse de rotation de tels dispositifs et, par suite, leur pouvoir de dispersion des gaz et d'agitation du bain, est limitée par l'apparition de balourds et de phénomènes d'abrasion. Certes, on peut parer à ces balourds en fixant les arbres des agitateurs par leur extrémité inférieure, mais il est alors nécessaire soit de monter des paliers supports travaillant au contact de métal liquide, à température relativement élevée, soit de prolonger ces arbres en dehors du récipient de métal et de les équiper de joints tournants. Ce sont autant de solutions qui entraînent des difficultés technologiques souvent insurmontables.Many solutions have been proposed. However, each of them has drawbacks. Thus, gas injection devices, by means of an agitator, resort to the use of gas distribution channels placed within said agitator, which complicates the production thereof and leads to fragile and d '' costly maintenance; in addition, these channels are the source of significant pressure drops which limit the speed of gas injection into the bath. In addition, the speed of rotation of such devices and, consequently, their power to disperse gases and agitate the bath, is limited by the appearance of imbalances and abrasion phenomena. Admittedly, these unbalances can be countered by fixing the shafts of the agitators by their lower ends, but it is then necessary either to mount support bearings working in contact with liquid metal, at relatively high temperature, or to extend these shafts outside the metal container and equip them with rotating joints. These are all solutions that lead to often insurmountable technological difficulties.

C'est pourquoi, la demanderesse a cherché et mis au point un dispositif de traitement d'un bain de métal liquide par injection de gaz dans lequel on supprime l'alimentation en gaz par l'arbre de l'agitateur et toutes les complications de réalisation qui en résultent ; on limite les phénomènes de balourd et d'abrasion et on obtient un effet de laminage et de dispersion des bulles de gaz tel que l'efficacité de traitement du métal s'en trouve sensiblement amélioré.This is why, the applicant has sought and developed a device for treating a bath of liquid metal by gas injection in which the gas supply by the agitator shaft and all the complications of gas are eliminated. resulting achievement; the phenomena of unbalance and abrasion are limited and a rolling and dispersing effect of the gas bubbles is obtained such that the processing efficiency of the metal is appreciably improved.

Ce dispositif de traitement d'un bain de métal liquide contenu dans un récipient par injection de gaz est caractérisé en ce qu'il comprend un agitateur rotatif libre en translation verticale comportant une partie inférieure et une partie supérieure dont la surface inférieure de la partie inférieure repose, à l'arrêt, sur la surface supérieure d'un bouchon d'injection de gaz placé au fond du récipient et qui, sous l'action de la pression du gaz émis par le bouchon se soulève et, ainsi supporté par un palier fluide, peut, sous l'effet d'un couple extérieur appliqué à la partie supérieure de l'agitateur, tourner librement autour de son axe et laisser échapper par l'espace qui le sépare du bouchon, une multitude de bulles de gaz régulièrement dispersées.This device for treating a bath of liquid metal contained in a container by gas injection is characterized in that it comprises a free rotary agitator in vertical translation comprising a lower part and an upper part whose lower surface of the lower part rests, when stationary, on the upper surface of a gas injection plug placed at the bottom of the container and which, under the action of the pressure of the gas emitted by the plug rises and, thus supported by a bearing fluid, can, under the effect of an external torque applied to the upper part of the agitator, freely rotate around its axis and let escape by the space which separates it from the stopper, a multitude of gas bubbles regularly dispersed .

Le dispositif selon l'invention est donc formé par la combinaison de deux moyens, un agitateur rotatif, d'une part, et un bouchon d'injection de gaz, d'autre part.The device according to the invention is therefore formed by the combination of two means, a rotary agitator, on the one hand, and a gas injection plug, on the other hand.

L'agitateur rotatif est constitué d'une pièce massive de forme cylindrotronconique dont la partie supérieure est pourvue d'une ouverture cylindrique dans laquelle s'engage l'arbre sur lequel est exercé un couple extérieur. La partie inférieure de cet agitateur peut avoir une surface lisse ou présenter plusieurs échancrures radiales de profondeur croissante vers la périphérie, de manière à faciliter l'entraînement des gaz d'injection. Ces échancrures s'étendent par exemple en longueur sur un tiers environ du diamètre de l'agitateur et peuvent se prolonger sur la face latérale en formant des sortes d'hélices orientées vers la droite ou vers la gauche et dont le pas est plus ou moins grand suivant les conditions de traitement.The rotary agitator consists of a massive piece of cylindrical-conical shape, the upper part of which is provided with a cylindrical opening in which engages the shaft on which an external torque is exerted. The lower part of this agitator may have a smooth surface or have several radial notches of increasing depth towards the periphery, so as to facilitate the entrainment of the injection gases. These notches extend for example in length over about a third of the diameter of the agitator and can be extended on the lateral face by forming sorts of propellers oriented to the right or to the left and whose pitch is more or less great depending on the processing conditions.

L'arbre de l'agitateur est équipé d'un système antivortex placé à l'interface bain-atmosphère, de façon à limiter les déplacements du métal liquide qui pourraient nuire à une dispersion convenable des gaz.The agitator shaft is equipped with a system antivortex placed at the bath-atmosphere interface, so as to limit the movements of the liquid metal which could hinder proper dispersion of the gases.

Le couple extérieur est exercé de préférence par un moteur à vitesse variable fixé sur un support disposé à la partie supérieure du récipient.The external torque is preferably exerted by a variable speed motor fixed on a support arranged at the top of the container.

L'arbre de ce moteur est solidaire de l'arbre de l'agitateur par l'intermédiaire d'un système de liaison quelconque qui permet à l'agitateur de pouvoir décrire un mouvement de translation vertical sur une distance de plusieurs millimètres.The shaft of this motor is integral with the shaft of the agitator by means of any connection system which allows the agitator to be able to describe a vertical translational movement over a distance of several millimeters.

Le bouchon d'injection de gaz est constitué d'une pièce cylindrique dont la surface supérieure est percée de trous de petit diamètre, qui peuvent être disposés en couronnes et qui sont reliés à l'intérieur du bouchon à des canaux se regroupant en un canal central qui débouche sur une chambre de détente alimentée en gaz par une tuyauterie extérieure au récipient.The gas injection plug is made up of a cylindrical piece, the upper surface of which is pierced with holes of small diameter, which can be arranged in crowns and which are connected inside the plug to channels which form a channel. central which leads to an expansion chamber supplied with gas by a pipe external to the container.

Suivant un autre mode de réalisation de l'invention, la masse du bouchon située au-dessus de la chambre d'expansion, peut être réalisée avec un matériau poreux.According to another embodiment of the invention, the mass of the plug located above the expansion chamber can be produced with a porous material.

L'agitateur et le bouchon sont disposés, l'un par rapport à l'autre, de façon que les axes de symétrie verticaux de chacun d'eux soient confondus.The agitator and the stopper are arranged, with respect to each other, so that the vertical axes of symmetry of each of them are coincident.

La surface inférieure de la partie inférieure de l'agitateur et la surface supérieure du bouchon sont adaptées l'une à l'autre afin qu'au repos, elles soient en contact l'une avec l'autre et provoquent une obstruction des orifices d'injection de gaz.The lower surface of the lower part of the agitator and the upper surface of the stopper are adapted to one another so that, when at rest, they are in contact with each other and cause an obstruction of the orifices of gas injection.

Cette adaptation peut être réalisée par exemple en donnant à ladite surface du bouchon une forme conique et en ménageant dans ladite surface de l'agitateur une cavité de forme semblable.This adaptation can be achieved for example by giving said surface of the stopper a conical shape and by providing in said surface of the stirrer a cavity of similar shape.

Lors du fonctionnement du dispositif, la pression de gaz admise au niveau du bouchon soulève l'agitateur et réalise un palier fluide de sorte que, lorsque le moteur d'entraînement est mis en service, ledit agitateur peut tourner librement sans contact avec le bouchon.During operation of the device, the gas pressure admitted at the level of the plug raises the agitator and produces a fluid bearing so that, when the drive motor is put into service, said agitator can rotate freely without contact with the cap.

On peut ainsi obtenir de grandes vitesses de rotation sans risque d'usure du palier ; de plus, l'adaptation réalisée notamment avec des faces coniques, combinée à l'injection de gaz, assure un centrage de l'agitateur et limite le balourd. Dans ces conditions, on a un dispositif robuste qui assure un brassage intense du bain et un laminage du gaz dans l'espace compris entre le bouchon et l'agitateur, de façon à le laisser s'échapper dans le métal sous la forme d'une multitude de bulles régulièrement dispersées. Il en résulte un contact intime entre gaz et métal et une efficacité de traitement remarquable.It is thus possible to obtain high rotational speeds without risk of wear of the bearing; in addition, the adaptation carried out in particular with conical faces, combined with gas injection, ensures centering of the agitator and limits the unbalance. Under these conditions, there is a robust device which ensures intense mixing of the bath and a rolling of the gas in the space between the plug and the agitator, so as to let it escape into the metal in the form of a multitude of regularly dispersed bubbles. This results in intimate contact between gas and metal and remarkable treatment efficiency.

L'agitateur et le bouchon sont composés, de préférence, de graphite mais, toute autre matière ayant une tenue suffisante au métal liquide convient également.The agitator and the stopper are preferably composed of graphite, but any other material having sufficient resistance to liquid metal is also suitable.

Le gaz admis par le bouchon est un gaz neutre tel que l'argon, l'azote ou un gaz réactif comme le chlore ou leurs mélanges, ou tout autre gaz susceptible de traiter le métal.The gas admitted by the plug is a neutral gas such as argon, nitrogen or a reactive gas such as chlorine or their mixtures, or any other gas capable of treating the metal.

Un tel dispositif est mis en place sur un récipient contenant le bain de métal à traiter. Ce peut être, par exemple, une poche à travers laquelle passe le métal en continu avant d'être coulé. Ce récipient peut comporter, de façon classique, une cloison et, alors, le dispositif est placé dans le compartiment amont. Le fond de cette poche peut être pourvu d'un lit de filtration ou non. Cette poche est équipée de moyens qui permettent de maintenir à la surface du métal liquide une atmosphère neutre et d'éviter ainsi toute action oxydante de l'air extérieur.Such a device is placed on a container containing the metal bath to be treated. It can be, for example, a pocket through which the metal passes continuously before being cast. This container may comprise, in a conventional manner, a partition and, then, the device is placed in the upstream compartment. The bottom of this pocket can be provided with a filtration bed or not. This pocket is equipped with means which make it possible to maintain a neutral atmosphere on the surface of the liquid metal and thus avoid any oxidizing action of the outside air.

Ce récipient peut aussi être pourvu de moyens de chauffage destinés à maintenir le métal à l'état liquide.This container can also be provided with heating means intended to maintain the metal in the liquid state.

La présente invention sera mieux comprise à l'aide des dessins qui accompagnent la demande et qui représentent un type particulier et non limitatif de dispositif.

  • La figure 1 représente, en coupe verticale, le dispositif agitateur-bouchon.
  • La figure 2 représente une vue de dessous de l'agitateur.
  • La figure 3 représente, en coupe verticale, le dispositif installé sur une poche de coulée en continu.
The present invention will be better understood with the aid of the drawings which accompany the application and which represent a particular and non-limiting type of device.
  • Figure 1 shows, in vertical section, the agitator-stopper device.
  • Figure 2 shows a bottom view of the agitator.
  • Figure 3 shows, in vertical section, the device installed on a continuous casting ladle.

Sur la figure 1, on distingue :

  • - l'agitateur (1) maintenu par un filetage (2) sur l'arbre (3) et dont la partie inférieure présente une surface conique (4) pourvue d'échancrures (5) ;
  • le bouchon d'injection (6) qui a une surface conique vers laquelle aboutissent des canaux (7) issus d'un canal central (8) débouchant d'une chambre de détente (9) alimentée en gaz par une tuyauterie (10). Ce bouchon est inséré dans le revêtement (11) d'une poche de coulée par l'intermédiaire d'un joint isolant (12) et tenu en place par une plaque (13) boulonnée en (14) sur l'armature métallique (15) de la poche.
In Figure 1, we distinguish:
  • - the agitator (1) held by a thread (2) on the shaft (3) and the lower part of which has a conical surface (4) provided with notches (5);
  • the injection plug (6) which has a conical surface towards which lead channels (7) from a central channel (8) emerging from an expansion chamber (9) supplied with gas by a pipe (10). This plug is inserted into the coating (11) of a ladle by means of an insulating seal (12) and held in place by a plate (13) bolted at (14) on the metal frame (15 ) from the pocket.

La figure 2 montre la disposition des échancrures (5) sur la surface conique (4) de la partie inférieure de l'agitateur.Figure 2 shows the arrangement of the notches (5) on the conical surface (4) of the lower part of the agitator.

Sur la figure 3, on voit le dispositif de l'invention équipant une poche de coulée (16) partagée en deux compartiments amont (17) et aval (18) par une cloison (19). Sur un support (20) placé à la partie supérieure de la poche, repose le moteur (21) dont l'arbre de rotation (22) est relié à l'arbre (3) de l'agitateur par un système (23) au moyen duquel l'arbre (3) peut se déplacer verticalement. Cet arbre peut être équipé d'un système antivortex (24).In Figure 3, we see the device of the invention fitted to a ladle (16) shared in two upstream (17) and downstream (18) compartments by a partition (19). On a support (20) placed at the upper part of the pocket, rests the motor (21) whose rotation shaft (22) is connected to the shaft (3) of the agitator by a system (23) at the means by which the shaft (3) can move vertically. This tree can be equipped with an antivortex system (24).

La poche est alimentée en métal liquide par le chenal (25) et s'écoule vers le fond du compartiment amont, puis en dessous de la cloison (19) vers le compartiment aval avant de quitter la poche par le chenal (27).The pocket is supplied with liquid metal by the channel (25) and flows towards the bottom of the upstream compartment, then below the partition (19) towards the downstream compartment before leaving the pocket through the channel (27).

Au cours de son passage dans le compartiment amont, le bain de métal délimité par les parois de la poche et la surface (28), est brassé intimement par l'agitateur avec formation d'une multitude de bulles de gaz finement dispersées qui s'échappent par l'espace (29) se formant sous la pression des gaz entre la partie inférieure de l'agitateur et la partie supérieure du bouchon.During its passage through the upstream compartment, the metal bath delimited by the walls of the pocket and the surface (28) is intimately stirred by the agitator with the formation of a multitude of finely dispersed gas bubbles which escape through the space (29) forming under pressure gases between the lower part of the agitator and the upper part of the cap.

La présente invention est illustrée par les résultats obtenus au cours d'essais mettant en oeuvre le dispositif décrit ci-dessus, ces résultats étant donnés à titre indicatif et ne pouvant en aucune façon limiter la portée de l'invention.The present invention is illustrated by the results obtained during tests using the device described above, these results being given for information only and cannot in any way limit the scope of the invention.

Le métal à traiter était un alliage d'aluminium de la série 6 000, qui a été amené à l'état liquide, à une température voisine de 720 °C, suivant un débit de 5 tonnes par heure dans une poche de coulée où la hauteur de bain était de 80 cm.The metal to be treated was an aluminum alloy of the 6000 series, which was brought to the liquid state, at a temperature close to 720 ° C., at a flow rate of 5 tonnes per hour in a ladle where the bath height was 80 cm.

Le bouchon, du type à canaux, était alimenté avec de l'argon à raison de 2 m3/h environ sous une pression comprise entre 1,2 et 1,4 bar.The plug, of the channel type, was supplied with argon at a rate of approximately 2 m 3 / h under a pressure of between 1.2 and 1.4 bar.

L'agitateur tournait à une vitesse de 400 t/minu- tes.The agitator was rotating at a speed of 400 rpm.

A l'entrée de la poche, l'alliage présentait 10 bulles au test de solidification sous vide ; après passage dans la poche, le nombre de bulles était nul. Ceci montre l'efficacité du traitement obtenu au moyen du dispositif revendiqué.At the entrance of the pocket, the alloy presented 10 bubbles in the vacuum solidification test; after passing through the pocket, the number of bubbles was zero. This shows the effectiveness of the treatment obtained by means of the claimed device.

La présente invention trouve son application dans le traitement des métaux liquides par un gaz, et notamment dans le traitement de l'aluminium ou de ses alliages pour l'élimination de l'hydrogène et des impuretés non métalliques.The present invention finds its application in the treatment of liquid metals with a gas, and in particular in the treatment of aluminum or its alloys for the removal of hydrogen and non-metallic impurities.

Claims (15)

1. Apparatus for treating a bath of liquid metal contained in a container, by injecting gas, characterised in that it comprises a rotary agitator which is free in respect of vertical translatory movement, comprising an upper portion and a lower portion, in which the lower surface (4) of the lower portion rests, in the stopped condition, on the upper surface of a gas injection plug (6) positioned at the bottom of the container (1) and which, under the action of the pressure of gas emitted by the plug rises and, thus supported by a fluid bearing, can, under the effect of an outside torque applied to the upper portion of the agitator, rotate freely about its axis and allow a multitude of regularly dispersed gas bubbles to escape through the space (29) which separates it from the plug.
2. A liquid metal bath treatment apparatus according to claim 1 characterised in that the plug is fixed with respect to the bottom of the container.
3. A liquid metal bath treatment apparatus according to claim 1 characterised in that the agitator and the plug are of materials which are not corroded by liquid aluminium.
4. A liquid metal bath treatment apparatus according to claim 3 characterised in that the material which is not corroded by liquid aluminium is graphite.
5. A liquid metal bath treatment apparatus according to claim 1 characterised in that the vertical axes of symmetry of the plug and the agitator are aligned.
6. A liquid metal bath treatment apparatus according to claim 1 characterised in that the outside torque is applied by means of a variable speed motor.
7. A liquid metal bath treatment apparatus according to claim 1 characterised in that the outside torque is applied to the agitator by means of a system (23) which permits a vertical translatory movement.
8. A liquid metal bath treatment apparatus according to claim 1 characterised in that the upper surface of the plug and the lower surface of the agitator are of a conical shape.
9. A liquid metal bath treatment apparatus according to claim 1 characterised in that the shaft (3) of the agitator is provided with an antivortex system (24) positioned at the metal-atmosphere interface.
10. A liquid metal bath treatment apparatus according to claim 1 characterised in that the lower surface of the agitator has a plurality of radial notches (5).
11. A liquid metal bath treatment apparatus according to claim 10 characterised in that said notches (5) are extended over the side face of the agitator, forming kinds of helices.
12. A liquid metal bath treatment apparatus according to claim 1 characterised in that the upper surface of the plug is apertured with holes which are connected inside the plug to ducts (7).
13. A liquid metal bath treatment apparatus according to claim 1 characterised in that the plug is internally provided, on the path of flow of the gases, with an expansion chamber (9).
14. A liquid metal bath treatment apparatus according to claim 13 characterised in that the mass of the plug which is disposed above the expansion chamber is made with a porous material.
15. Use of the apparatus according to any one of the preceding claims in one of the compartments (17) of a casting ladle provided with two compartments (17, 18).
EP81420150A 1980-10-14 1981-10-13 Apparatus for the treatment of a molten metal bath by gas injection Expired EP0050578B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8022193 1980-10-14
FR8022193A FR2491954A1 (en) 1980-10-14 1980-10-14 DEVICE FOR TREATING A LIQUID METAL BATH BY INJECTING GAS

Publications (2)

Publication Number Publication Date
EP0050578A1 EP0050578A1 (en) 1982-04-28
EP0050578B1 true EP0050578B1 (en) 1984-03-21

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US (1) US4372541A (en)
EP (1) EP0050578B1 (en)
JP (1) JPS5792146A (en)
KR (1) KR830007187A (en)
AU (1) AU540945B2 (en)
CA (1) CA1165117A (en)
DE (1) DE3162821D1 (en)
ES (1) ES506075A0 (en)
FR (1) FR2491954A1 (en)
GR (1) GR75823B (en)
IN (1) IN155192B (en)
NO (1) NO813447L (en)
OA (1) OA06917A (en)
RO (1) RO83654B (en)
YU (1) YU243581A (en)

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Also Published As

Publication number Publication date
EP0050578A1 (en) 1982-04-28
ES8207229A1 (en) 1982-09-01
FR2491954A1 (en) 1982-04-16
CA1165117A (en) 1984-04-10
AU540945B2 (en) 1984-12-06
AU7628281A (en) 1982-04-22
YU243581A (en) 1983-10-31
RO83654A (en) 1984-03-15
ES506075A0 (en) 1982-09-01
DE3162821D1 (en) 1984-04-26
GR75823B (en) 1984-08-02
IN155192B (en) 1985-01-12
JPS5792146A (en) 1982-06-08
OA06917A (en) 1983-05-31
NO813447L (en) 1982-04-15
RO83654B (en) 1984-03-30
KR830007187A (en) 1983-10-14
US4372541A (en) 1983-02-08
JPS6160904B2 (en) 1986-12-23
FR2491954B1 (en) 1982-10-22

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