EP0296074B1 - Method and apparatus for sand casting composite parts with a fibre insert in a light alloy matrix - Google Patents

Method and apparatus for sand casting composite parts with a fibre insert in a light alloy matrix Download PDF

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Publication number
EP0296074B1
EP0296074B1 EP88420187A EP88420187A EP0296074B1 EP 0296074 B1 EP0296074 B1 EP 0296074B1 EP 88420187 A EP88420187 A EP 88420187A EP 88420187 A EP88420187 A EP 88420187A EP 0296074 B1 EP0296074 B1 EP 0296074B1
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Prior art keywords
pressure
bath
mould
cavity
mold
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German (de)
French (fr)
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EP0296074A1 (en
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Jean Charbonnier
François Goliard
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Constellium Issoire SAS
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Pechiney Rhenalu SAS
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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
    • B22D19/00—Casting in, on, or around objects which form part of the product
    • B22D19/14—Casting in, on, or around objects which form part of the product the objects being filamentary or particulate in form
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D18/00—Pressure casting; Vacuum casting
    • B22D18/08—Controlling, supervising, e.g. for safety reasons

Definitions

  • the invention relates to a method and a device for molding in sand of composite parts with a light alloy matrix and a fibrous insert according to the preambles of claims 1 and 5.
  • alloys based on light metals such as aluminum or magnesium for example, for the production of parts intended to equip means of land or air transport is more and more widespread because it allows in particular to reduce the energy consumption necessary for their propulsion.
  • the first of these methods makes it possible to produce highly reinforced parts and achieve high characteristics, but the shape and size of the parts are limited.
  • the second is intended for the manufacture of composites with reinforcement of particles or short fibers dispersed throughout the mass of the part.
  • the third is the only one which makes it possible to make parts of complicated shape, of large dimensions, reinforced locally but the applicable pressures are limited.
  • the Applicant is more particularly interested in the manufacture of composite parts reinforced with long fiber inserts in a traditional sand mold provided with an imprint, associated with a supply pipe plunging into a liquid metal bath contained in an oven. , association described for example in French Patent No. 2,147,827, and applying the principle of infiltration.
  • This process in which a sand mold is used containing in its imprint a preform of a fibrous insert and fed by means of a tubing immersed in a liquid metallic bath contained in an oven is characterized in that a depression is created in the mold and above the bath, then the pressure is increased above the bath so as to obtain a positive pressure difference ⁇ P relative to the mold and thus to repress the metal in the mold, then the pressure above atmospheric pressure is simultaneously increased both in the mold and above the bath while maintaining the same difference ⁇ P until the part solidifies.
  • the invention therefore consists first of all in bringing the pressure which prevails in the mold and above the bath to a value lower than atmospheric pressure. Because of the permeability of the sand, it suffices to put the outside of the mold under vacuum to obtain this result inside the cavity and consequently within the naturally permeable gas preform. Preferably, it is sought to reach a residual pressure at most equal to 3 ⁇ 103 Pa.
  • this residual pressure is increased above the bath by making an air inlet for example in the oven so that under the difference of the positive pressure ⁇ P thus created above the bath compared to the mold, the metal rises into the tube and enters the mold cavity.
  • the preform having no contact with the walls of the cavity is thus completely surrounded by the liquid metal which shields any passage of gas.
  • the invention also relates to a device for implementing the method described above.
  • this device comprises a sand mold produced from the usual materials such as silica, alumina, zircon, olivine, etc., in the divided state and linked together by means of either a organic resin, or a mineral binder of the sodium silicate, colloidal silica, ethyl silicate or phosphate type, for example.
  • this mold In the imprint of this mold is placed a mass of long ceramic fibers preferably and of the graphite, silicon carbide, alumina, etc. type, to which a suitable shape has been given to the reinforcement of the part.
  • This preform is placed inside the cavity and kept away from the walls of the mold by any suitable means. In this way, it is possible to make a complete coating of its walls by the metal during the casting of the part and to ensure its tightness with respect to the mold, an essential condition for carrying out the process described above.
  • This mold is enclosed in a sealed chamber provided with a pipe in communication for example with a vacuum pump or a compressor. From this chamber also opens a pipe integral with the mold which connects the impression to the metal bath to be molded and allows the impression to be fed.
  • the mold can be equipped with heating means intended to perform preheating before the introduction of the metal; this makes it possible to slow down the solidification of the part and thus to facilitate the impregnation of the preform and the obtaining of thin walls.
  • the device according to the invention also comprises an electrically heated oven containing the metal to be molded and placed below the mold.
  • This oven can also be placed in a chamber similar to that of the mold. However, it is also possible to enclose it as it is in a sealed enclosure with the mold surrounded by its chamber.
  • the first pipe is that of the mold chamber
  • the second is related to the atmosphere from the oven.
  • the enclosure In operation, having set up the preform in the cavity, closed the mold and heated and filled the metal oven, the enclosure is closed by means of a cover and then puts the two pipes in communication with means of placing under depression.
  • the pressure gauge remains at 0.
  • the enclosure pipe is then isolated from the vacuum means and open to the atmosphere for the time necessary for the pressure gauge to indicate a pressure equal to ⁇ P.
  • the metal is forced back from the oven to the mold.
  • the venting being closed and the pipe of the chamber being isolated from the vacuum means, the two pipes are put in communication with the pressurization means and by means of adjustment valves, the pressure gauge at value ⁇ P.
  • the two pipes are isolated from the pressurizing means and placed in the atmosphere.
  • the enclosure and the mold are then opened successively and the part is extracted.
  • a particular means for sealing between the preform and the mold by means of the metal consists in providing the imprint of housings equipped on their faces with metal sheets juxtaposed between them and which lie inside the footprint. The ends of the preform are then placed in contact with these sheets. Thus, when the metal fills the mold, it seals the sheets together and the housings become gas tight; the preform thus has no contact with the walls of the mold through which the gases could penetrate when pressurized.
  • the fibrous preform 17 Inside the impression is placed the fibrous preform 17, the ends of which are placed in housings formed by metal sheets 18 which extend along 19 inside the impression.
  • the invention finds its application in the production by sand molding of parts having good cohesion between the insert and the matrix.

Abstract

The invention relates to a method and apparatus for sand molding composite articles formed of a light alloy metal and fibrous insert. A sand mold is formed containing a fibrous preform separated from the walls of the mold cavity. The mold is fed by means of a tube dipping into a liquid metallic bath therebelow. In the molding process, the pressure in the mold cavity and above the bath are reduced, and the pressure above the bath is increased to create a positive pressure differential DELTA P, thereby forcing molten metal from the bath into the mold cavity. The pressure in the mold cavity and above the bath are then increased to above atmospheric, and the pressure differential DELTA P is maintained until the metal in the mold cavity solidifies.

Description

L'invention est relative à un procédé et à un dispositif de moulage en sable de pièces composites à matrice en alliage léger et insert fibreux selon les préambules des revendications 1 et 5.The invention relates to a method and a device for molding in sand of composite parts with a light alloy matrix and a fibrous insert according to the preambles of claims 1 and 5.

L'utilisation d'alliages à base de métaux légers tels que l'aluminium ou le magnésium, par exemple, pour la réalisation de pièces destinées à équiper des moyens de transport terrestres ou aériens est de plus en plus répandue parce qu'elle permet notamment de réduire la consommation d'énergie nécessaire à leur propulsion.The use of alloys based on light metals such as aluminum or magnesium, for example, for the production of parts intended to equip means of land or air transport is more and more widespread because it allows in particular to reduce the energy consumption necessary for their propulsion.

Cependant, ces alliages présentent certains défauts tels que:

  • une mauvaise tenue à température élevée,
  • une résistance faible à la fatigue,
  • une médiocre résistance à l'usure par frottement,
  • un petit module d'élasticité.
However, these alloys have certain defects such as:
  • poor resistance to high temperature,
  • low resistance to fatigue,
  • poor resistance to wear by friction,
  • a small modulus of elasticity.

C'est pourquoi l'homme de l'art a cherché à améliorer fortement les propriétés de ces pièces en renforçant ces alliages au moyen de fibres ou de particules céramiques de manière à former des pièces composites à matrice métallique.This is why a person skilled in the art has sought to greatly improve the properties of these parts by reinforcing these alloys by means of ceramic fibers or particles so as to form composite parts with a metallic matrix.

Ces pièces peuvent être obtenue à partir de plusieurs procédés dont trois d'entre eux passent par la voie du moulage en phase liquide. Ce sont:

  • le moulage-forgeage ou squeeze casting,
  • le compocasting,
  • l'infiltration sous pression gazeuse.
These parts can be obtained from several processes, three of which pass through the liquid phase molding process. Those are:
  • molding-forging or squeeze casting,
  • the compocasting,
  • gas pressure infiltration.

Le premier de ces procédés permet de réaliser des pièces fortement renforcées et d'atteindre des caractéristiques élevées mais la forme et la taille des pièces sont limitées.The first of these methods makes it possible to produce highly reinforced parts and achieve high characteristics, but the shape and size of the parts are limited.

Le deuxième est destiné à la fabrication de composites à renfort de particules ou de fibres courtes dispersées dans toute la masse de la pièce.The second is intended for the manufacture of composites with reinforcement of particles or short fibers dispersed throughout the mass of the part.

Le troisième est le seul qui permette de faire des pièces de forme compliquée, de grandes dimensions, renforcées localement mais les pressions applicables sont limitées.The third is the only one which makes it possible to make parts of complicated shape, of large dimensions, reinforced locally but the applicable pressures are limited.

La demanderesse s'est interessée plus particulièrement à la fabrication de pièces composites renforcées par des inserts en fibres longues dans un moule traditionnel en sable muni d'une empreinte, associé à une tuyauterie d'alimentation plongeant dans un bain métallique liquide contenu dans un four, association décrite par exemple dans le brevet français n° 2 147 827, et en appliquant le principe de l'infiltration.The Applicant is more particularly interested in the manufacture of composite parts reinforced with long fiber inserts in a traditional sand mold provided with an imprint, associated with a supply pipe plunging into a liquid metal bath contained in an oven. , association described for example in French Patent No. 2,147,827, and applying the principle of infiltration.

Elle s'est heurtée à deux types de problèmes:

  • le premier est d'éviter le déplacement de l'insert à l'intérieur du moule sous l'effet de la poussée exercée par le métal liquide lors de la coulée. Ceci peut être obtenu en réalisant une préforme rigide qui est fixée en certains points de la paroi de l'empreinte du moule comme les noyaux classiques destinés à réaliser les creux à l'intérieur des pièces;
  • le second problème est celui de la pression à exercer sur le métal liquide pour le forcer à pénétrer dans les mèches des fibres, cette pression devant être d'autant plus grande que le diamètre des fibres est petit, que le taux de renforcement est élevé et que la tension interfaciale métal-fibres est forte. La solution envisagée consiste alors à couler les pièces sous basse pression en augmentant la pression d'injection.
She encountered two types of problems:
  • the first is to avoid displacement of the insert inside the mold under the effect of the thrust exerted by the liquid metal during casting. This can be obtained by producing a rigid preform which is fixed at certain points on the wall of the mold cavity like the conventional cores intended to produce the hollows inside the parts;
  • the second problem is that of the pressure to be exerted on the liquid metal to force it to penetrate into the wicks of the fibers, this pressure having to be all the greater the smaller the diameter of the fibers, the higher the rate of reinforcement and that the metal-fiber interfacial tension is high. The envisaged solution then consists in casting the parts under low pressure by increasing the injection pressure.

Mais ces solutions présentent néanmoins deux inconvénients graves:

  • d'une part, l'imprégnation des fibres ne peut pas être totale car le métal commence par enrober complétement la préforme avant de pénétrer en son sein et de ce fait de l'air est emprisonné à l'intérieur de la préforme de sorte que l'infiltration du métal cesse quant la pression de cet air est égale à celle qui est exercée sur le métal liquide;
  • d'autre part, la pression exercée ne peut être trop élevée car le moule et les noyaux réalisés en sable étant poreux, risquent d'être imprégnés par le métal, même en présence de certains revêtements, ce qui conduit à un mauvais état de surface des pièces ainsi obtenues.
However, these solutions have two serious drawbacks:
  • on the one hand, the impregnation of the fibers cannot be total since the metal begins by completely coating the preform before penetrating therein and therefore air is trapped inside the preform so that metal infiltration ceases when the pressure of this air is equal to that which is exerted on the liquid metal;
  • on the other hand, the pressure exerted cannot be too high because the mold and the cores made of sand being porous, risk being impregnated with the metal, even in the presence of certain coatings, which leads to a poor surface condition parts thus obtained.

Pour surmonter ces difficultés, la demanderesse a été amenée à inventer un procédé et un dispositif permettant d'appliquer une forte pression sur la préforme tout en limitant la pression exercée par le métal sur le moule.To overcome these difficulties, the applicant has been led to invent a method and a device making it possible to apply high pressure to the preform while limiting the pressure exerted by the metal on the mold.

Ce procédé dans lequel on utilise un moule en sable renfermant dans son empreinte une préforme d'un insert fibreux et alimenté au moyen d'une tuyauterie plongeant dans un bain métallique liquide contenu dans un four est caractérisé en ce que l'on crée une dépression dans le moule et au-dessus du bain, puis on augmente la pression au-dessus du bain de manière à obtenir une différence de pression ΔP positive par rapport au moule et à refouler ainsi le métal dans le moule, ensuite on augmente simultanément la pression au-dessus de la pression atmosphérique à la fois dans le moule et au-dessus du bain tout en maintenant la même différence ΔP jusqu'à la solidification de la pièce.This process in which a sand mold is used containing in its imprint a preform of a fibrous insert and fed by means of a tubing immersed in a liquid metallic bath contained in an oven is characterized in that a depression is created in the mold and above the bath, then the pressure is increased above the bath so as to obtain a positive pressure difference ΔP relative to the mold and thus to repress the metal in the mold, then the pressure above atmospheric pressure is simultaneously increased both in the mold and above the bath while maintaining the same difference ΔP until the part solidifies.

L'invention consiste donc d'abord à amener la pression qui règne dans le moule et au-dessus du bain à une valeur inférieure à la pression atmosphérique. En raison de la perméabilité du sable, il suffit de mettre l'extérieur du moule sous dépression pour obtenir ce résultat à l'intérieur de l'empreinte et par suite au sein de la préforme naturellement perméable aux gaz. De préférence, on cherche à atteindre une pression résiduelle au plus égale à 3 × 10³ Pa.The invention therefore consists first of all in bringing the pressure which prevails in the mold and above the bath to a value lower than atmospheric pressure. Because of the permeability of the sand, it suffices to put the outside of the mold under vacuum to obtain this result inside the cavity and consequently within the naturally permeable gas preform. Preferably, it is sought to reach a residual pressure at most equal to 3 × 10³ Pa.

Puis, cette pression résiduelle est augmentée au-dessus du bain en faisant une entrée d'air par exemple dans le four de sorte que sous la différence de la pression ΔP positive ainsi créée au-dessus du bain par rapport au moule, le métal monte dans le tube et pénètre dans l'empreinte du moule. La préforme n'ayant aucun contact avec les parois de l'empreinte se trouve ainsi complètement entourée par le métal liquide qui vient faire écran à tout passage de gaz.Then, this residual pressure is increased above the bath by making an air inlet for example in the oven so that under the difference of the positive pressure ΔP thus created above the bath compared to the mold, the metal rises into the tube and enters the mold cavity. The preform having no contact with the walls of the cavity is thus completely surrounded by the liquid metal which shields any passage of gas.

De préférence, la valeur de ΔP est comprise entre 5 × 10³ Pa et 1,5 × 10⁵ Pa. Ensuite, la pression est augmentée simultanément au-dessus du bain et autour du moule tout en maintenant la différence ΔP. De préférence, cette augmentation se fait jusqu'à une valeur comprise entre 3 et 20 fois la pression atmosphérique. Dans ces conditions, le gaz pénètre à travers les parois perméables du moule et la pression d'infiltration exercée par le métal sur le moule conserve sa valeur ΔP. Par contre, du fait que l'intérieur de la préforme est toujours sous dépression et n'a pas de communication avec l'extérieur, la pression d'infiltration de cette dernière a une valeur P beaucoup plus grande que ΔP. On obtient ainsi les résultats recherchés à savoir:

  • une pénétration à coeur de la préforme par le métal d'où une meilleure cohésion entre l'insert et la matrice;
  • une faible pression d'infiltration du moule ce qui permet d'éviter l'abreuvage du moule et des noyaux et d'obtenir un meilleur état de surface des pièces;
  • une solidification de la pièce sous pression isostatique d'où une homogénéité de structure plus grande.
Preferably, the value of ΔP is between 5 × 10³ Pa and 1.5 × 10⁵ Pa. Then, the pressure is increased simultaneously above the bath and around the mold while maintaining the difference ΔP. Preferably, this increase takes place up to a value between 3 and 20 times atmospheric pressure. Under these conditions, the gas penetrates through the permeable walls of the mold and the infiltration pressure exerted by the metal on the mold retains its value ΔP. On the other hand, because the interior of the preform is always under vacuum and has no communication with the exterior, the infiltration pressure of the latter has a value P much greater than ΔP. The desired results are thus obtained, namely:
  • penetration of the preform through the metal, resulting in better cohesion between the insert and the matrix;
  • a low mold infiltration pressure which makes it possible to avoid watering the mold and the cores and to obtain a better surface condition of the parts;
  • solidification of the part under isostatic pressure, hence greater structural homogeneity.

L'invention concerne également un dispositif pour la mise en oeuvre du procédé décrit ci-dessus.The invention also relates to a device for implementing the method described above.

Il comprend un moule en sable muni d'une empreinte, un four chauffé électriquement placé en dessous du moule et contenant un bain de métal à mouler et une tuyauterie solidaire du moule et communiquant avec l'empreinte par l'une de ses extrémités et plongeant dans le bain par l'autre extrémité caractérisé en ce que:

  • le moule renferme dans son empreinte une préforme fibreuse dont toutes les faces sont situées à l'écart des parois de l'empreinte et est placé dans une chambre étanche reliée à une canalisation en communication avec des moyens de mise sous pression ou sous dépression,
  • le moule, le four et la tuyauterie sont contenus dans une enceinte étanche munie d'une canalisation en communication avec des moyens de mise sous pression, les deux canalisations étant reliées entre elles par l'intermédiaire d'un manomètre différentiel.
It includes a sand mold fitted with an imprint, an electrically heated oven placed below the mold and containing a bath of metal to be molded and a pipe integral with the mold and communicating with the imprint by one of its ends and plunging in the bath by the other end, characterized in that:
  • the mold contains in its imprint a fibrous preform, all the faces of which are located away from the walls of the imprint and is placed in a sealed chamber connected to a pipe in communication with pressurization or vacuum means,
  • the mold, the oven and the piping are contained in a sealed enclosure provided with a pipe in communication with pressurizing means, the two pipes being interconnected by means of a differential pressure gauge.

Ainsi, ce dispositif comprend un moule en sable réalisé à partir des matériaux usuels tels que la silice, l'alumine, le zircon, l'olivine etc..., à l'état divisé et liés entre eux au moyen soit d'une résine organique, soit d'un liant minéral du type silicate de soude, silice colloïdale, silicate d'éthyle ou phosphate par exemple.Thus, this device comprises a sand mold produced from the usual materials such as silica, alumina, zircon, olivine, etc., in the divided state and linked together by means of either a organic resin, or a mineral binder of the sodium silicate, colloidal silica, ethyl silicate or phosphate type, for example.

Dans l'empreinte de ce moule est placée une masse de fibres céramiques longues de préférence et du type graphite, carbure de silicium, alumine, etc..., à laquelle on a donné une forme convenable au renforcement de la pièce. Cette préforme est disposée à l'intérieur de l'empreinte et maintenue à l'écart des parois du moule par tout moyen convenable. De cette façon, il est possible de faire un enrobage complet de ses parois par le métal lors de la coulée de la pièce et d'assurer son étanchéité vis à vis du moule, condition indispensable pour réaliser le procédé décrit ci-dessus.In the imprint of this mold is placed a mass of long ceramic fibers preferably and of the graphite, silicon carbide, alumina, etc. type, to which a suitable shape has been given to the reinforcement of the part. This preform is placed inside the cavity and kept away from the walls of the mold by any suitable means. In this way, it is possible to make a complete coating of its walls by the metal during the casting of the part and to ensure its tightness with respect to the mold, an essential condition for carrying out the process described above.

Ce moule est enfermé dans une chambre étanche munie d'une canalisation en communication par exemple avec une pompe à vide ou un compresseur. De cette chambre débouche également une tuyauterie solidaire du moule qui relie l'empreinte au bain de métal à mouler et permet l'alimentation de l'empreinte.This mold is enclosed in a sealed chamber provided with a pipe in communication for example with a vacuum pump or a compressor. From this chamber also opens a pipe integral with the mold which connects the impression to the metal bath to be molded and allows the impression to be fed.

Le moule peut être équipé de moyens de chauffage destinés à réaliser un préchauffage avant l'introduction du métal; cela permet de ralentir la solidification de la pièce et ainsi de faciliter l'imprégnation de la préforme et l'obtention de parois minces.The mold can be equipped with heating means intended to perform preheating before the introduction of the metal; this makes it possible to slow down the solidification of the part and thus to facilitate the impregnation of the preform and the obtaining of thin walls.

Le dispositif selon l'invention comprend également un four chauffé électriquement contenant le métal à mouler et placé au dessous du moule. Ce four peut être placé également dans une chambre analogue à celle du moule. Toutefois, il est également possible de l'enfermer tel quel dans une enceinte étanche avec le moule entouré de sa chambre.The device according to the invention also comprises an electrically heated oven containing the metal to be molded and placed below the mold. This oven can also be placed in a chamber similar to that of the mold. However, it is also possible to enclose it as it is in a sealed enclosure with the mold surrounded by its chamber.

De cette enceinte débouchent deux canalisations qui sont mises en communication avec des moyens de mise sous pression ou sous dépression par l'intermédiaire de vannes de réglage: la première canalisation est celle de la chambre du moule, la seconde est en relation avec l'atmosphère du four.From this enclosure open two pipes which are placed in communication with pressurization or vacuum means by means of adjustment valves: the first pipe is that of the mold chamber, the second is related to the atmosphere from the oven.

Ces deux canalisation sont reliées entre elles par l'intermédiaire d'un manomètre différentiel.These two pipes are interconnected via a differential pressure gauge.

En fonctionnement, ayant mis en place le préforme dans l'empreinte, fermé le moule et chauffé et rempli le four de métal, on ferme l'enceinte au moyen d'un couvercle puis met les deux canalisations en communication avec des moyens de mise sous dépression. Le manomètre reste au 0. La canalisation de l'enceinte est alors isolée des moyens de mise sous dépression et ouverte vers l'atmosphère pendant le temps nécessaire pour que le manomètre indique une pression égale à ΔP. Durant ce temps, le métal est refoulé du four vers le moule. La mise à l'atmosphère étant fermée et la canalisation de la chambre étant isolée des moyens de mise sous dépression, les deux canalisations sont mises en communication avec les moyens de mise sous pression et à l'aide des vannes de réglage, on maintient le manomètre à la valeur ΔP.In operation, having set up the preform in the cavity, closed the mold and heated and filled the metal oven, the enclosure is closed by means of a cover and then puts the two pipes in communication with means of placing under depression. The pressure gauge remains at 0. The enclosure pipe is then isolated from the vacuum means and open to the atmosphere for the time necessary for the pressure gauge to indicate a pressure equal to ΔP. During this time, the metal is forced back from the oven to the mold. The venting being closed and the pipe of the chamber being isolated from the vacuum means, the two pipes are put in communication with the pressurization means and by means of adjustment valves, the pressure gauge at value ΔP.

Après solidification de la pièce dans le moule, les deux canalisations sont isolées des moyens de mise sous pression et mises à l'atmosphère.After the part has solidified in the mold, the two pipes are isolated from the pressurizing means and placed in the atmosphere.

L'enceinte et le moule sont alors ouverts successivement et on extrait la pièce.The enclosure and the mold are then opened successively and the part is extracted.

Un moyen particulier pour réaliser l'étanchéité entre la préforme et le moule par l'intermédiaire du métal consiste à munir l'empreinte de logements équipés sur leurs faces de tôles métalliques juxtaposées entre elles et qui s'allongent à l'intérieur de l'empreinte. Les extrémités de la préforme sont alors placées au contact de ces tôles. Ainsi, au moment où le métal remplit le moule, il vient sceller les tôles entre elles et les logements deviennent étanches aux gaz; la préforme n'a ainsi aucun contact avec les parois du moule par l'intermédiaire desquelles pourraient pénétrer les gaz lors de la mise sous pression.A particular means for sealing between the preform and the mold by means of the metal consists in providing the imprint of housings equipped on their faces with metal sheets juxtaposed between them and which lie inside the footprint. The ends of the preform are then placed in contact with these sheets. Thus, when the metal fills the mold, it seals the sheets together and the housings become gas tight; the preform thus has no contact with the walls of the mold through which the gases could penetrate when pressurized.

L'invention peut être illustrée à l'aide des dessins ci-joints qui représentent:

  • · figure 1, les courbes d'évolution des pressions en fonction du temps au cours d'une opération de moulage
  • · figure 2, une coupe verticale d'un dispositif de moulage
The invention can be illustrated by means of the attached drawings which represent:
  • · Figure 1, the evolution curves of pressures as a function of time during a molding operation
  • · Figure 2, a vertical section of a molding device

Plus précisément:

  • · La figure 1 montre en traits pleins la courbe A de la pression absolue en Pa appliquée à l'empreinte et en tirets la courbe B de la pression absolue en Pa appliquée au-dessus du bain au cours des quatre phases du procédé: I mise sous dépression du four et du moule _ II aspiration du métal dans le moule _ III infiltration de l'insert par le métal IV solidification de la pièce.
More precisely:
  • · Figure 1 shows in solid lines the curve A of the absolute pressure in Pa applied to the impression and in dashes the curve B of the absolute pressure in Pa applied above the bath during the four phases of the process: I setting under vacuum of the oven and the mold _ II aspiration of the metal in the mold _ III infiltration of the insert by the metal IV solidification of the part.

Au cours de la dernière phase, la pression exercée sur la préforme, qui est pratiquement équivalente au maximum de la courbe B, est beaucoup plus élevée que celle exercée sur les parois du moule qui est égale à ΔP.

  • · La figure 2 représente l'enceinte 1 étanche dans laquelle est placée le four 2 contenant le bain métallique 3 dans lequel plonge le tube 4 relié à l'empreinte 5 du moule 6 enfermé dans la chambre étanche 7. De la chambre 7 débouche la canalisation 8 et de l'enceinte 1 la canalisation 9 qui sont reliées entre elles par l'intermédiaire du manomètre différentiel 10 et communiquent chacune séparément avec des moyens de mise sous pression ou sous dépression 11 et 12 par l'intermédiaire de vannes d'isolement 13 et 14 et de mise à l'atmosphère 15 et 16.
During the last phase, the pressure exerted on the preform, which is practically equivalent to the maximum of curve B, is much higher than that exerted on the walls of the mold which is equal to ΔP.
  • FIG. 2 represents the sealed enclosure 1 in which the oven 2 is placed containing the metal bath 3 in which the tube 4 connected to the imprint 5 of the mold 6 is enclosed in the sealed chamber 7. From the chamber 7 opens the pipe 8 and enclosure 1 the pipe 9 which are interconnected by means of the differential pressure gauge 10 and each communicate separately with pressurization or vacuum means 11 and 12 by means of isolation valves 13 and 14 and venting 15 and 16.

A l'intérieur de l'empreinte est diposée la préforme 17 fibreuse dont les extrémités sont placées dans des logements constitués par des tôles métalliques 18 qui s'allongent suivant 19 à l'intérieur de l'empreinte.Inside the impression is placed the fibrous preform 17, the ends of which are placed in housings formed by metal sheets 18 which extend along 19 inside the impression.

L'invention trouve son application dans l'obtention par moulage en sable de pièces présentant une bonne cohésion entre l'insert et la matrice.The invention finds its application in the production by sand molding of parts having good cohesion between the insert and the matrix.

Claims (6)

1. A method of sand moulding composite articles with a die made of light alloy and a fibrous insert, in a mould 6 containing in its cavity 5 a preforming tool of said insert and fed by means of a tube 4 which dips into a liquid metallic bath 3 contained in a furnace, characterised in that low pressure is created in the mould and above the bath, the pressure above the bath is increased to give a positive pressure difference ΔP relative to the mould and thus force the metal into the mould, then the pressure is increased to above atmospheric in the mould and above the bath simultaneously, and the same difference ΔP is maintained until the article solidifies.
2. The method of claim 1, characterised in that when the low pressure is created, the residual pressure in the mould or above the bath is at most equal to 3 × 10³ Pa.
3. The method of claim 1, characterised in that the value of ΔP is from 5 × 10³ Pa to 1.5 × 10⁵ Pa.
4. The method of claim 1, characterised in that the pressure is increased to a value between 3 and 20 times atmospheric pressure.
5. Apparatus for carrying out the method of claim 1, comprising a sand mould 6 with a cavity 5; an electrically heated furnace 2 placed below the mould and containing a bath 3 of metal to be moulded; and a tube 4 rigidly connected to the mould, communicating with the cavity at one end and dipping into the bath at the other, characterised in that:
the mould 6 contains in its cavity 5 a fibrous preforming tool 17 with all its surfaces separated from the walls of the cavity, and is placed in a sealed chamber 7 connected to a pipe 8 in communication with means 11 for putting under pressure or under low pressure, and that the mould 6, the furnace 2 and the pipe 4 are contained in a sealed enclosure 1 fitted with a pipe 9 in communication with means 12 for potting under pressure, the two pipes (8 and 9) being interconnected by a differential manometer 10.
6. The apparatus of claim 5, characterised in that the cavity is fitted with seats equipped on their surfaces with metal sheets 18, which are juxtaposed and extend along 19 inside the cavity, the ends of the preforming tool being placed in contact with them.
EP88420187A 1987-06-11 1988-06-09 Method and apparatus for sand casting composite parts with a fibre insert in a light alloy matrix Expired - Lifetime EP0296074B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT88420187T ATE62161T1 (en) 1987-06-11 1988-06-09 METHOD AND APPARATUS FOR SANDING COMPOSITES FROM A FIBER INSERT AND A LIGHT METAL ALLOYED MASS.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8708749 1987-06-11
FR8708749A FR2616363B1 (en) 1987-06-11 1987-06-11 METHOD AND DEVICE FOR MOLDING SAND INTO LIGHT ALLOY MATRIX COMPOSITES AND FIBROUS INSERT

Publications (2)

Publication Number Publication Date
EP0296074A1 EP0296074A1 (en) 1988-12-21
EP0296074B1 true EP0296074B1 (en) 1991-04-03

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EP88420187A Expired - Lifetime EP0296074B1 (en) 1987-06-11 1988-06-09 Method and apparatus for sand casting composite parts with a fibre insert in a light alloy matrix

Country Status (9)

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US (1) US4889177A (en)
EP (1) EP0296074B1 (en)
JP (1) JPH0734986B2 (en)
AT (1) ATE62161T1 (en)
CA (1) CA1326586C (en)
DE (1) DE3862247D1 (en)
ES (1) ES2021460B3 (en)
FR (1) FR2616363B1 (en)
GR (1) GR3001726T3 (en)

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Also Published As

Publication number Publication date
EP0296074A1 (en) 1988-12-21
FR2616363A1 (en) 1988-12-16
DE3862247D1 (en) 1991-05-08
FR2616363B1 (en) 1991-04-19
ES2021460B3 (en) 1991-11-01
US4889177A (en) 1989-12-26
GR3001726T3 (en) 1992-11-23
JPS63317246A (en) 1988-12-26
ATE62161T1 (en) 1991-04-15
JPH0734986B2 (en) 1995-04-19
CA1326586C (en) 1994-02-01

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