EP0968064B1 - Method and installation for low pressure die casting in a mould with ceramic casting die - Google Patents
Method and installation for low pressure die casting in a mould with ceramic casting die Download PDFInfo
- Publication number
- EP0968064B1 EP0968064B1 EP98964545A EP98964545A EP0968064B1 EP 0968064 B1 EP0968064 B1 EP 0968064B1 EP 98964545 A EP98964545 A EP 98964545A EP 98964545 A EP98964545 A EP 98964545A EP 0968064 B1 EP0968064 B1 EP 0968064B1
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- European Patent Office
- Prior art keywords
- pressure
- value
- casting
- liquid metal
- space
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- 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.)
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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
- B22D18/00—Pressure casting; Vacuum casting
- B22D18/04—Low pressure casting, i.e. making use of pressures up to a few bars to fill the mould
Definitions
- the invention relates to a method and a low pressure casting installation of a metallic composition in liquid state, in a mold comprising a ceramic shell, one side of which delimits a casting space and a mass of sand without binder in contact with the other face of the shell, the mold being placed in a box having at its base a access connected to the pouring space and connected by a line for supplying liquid metal to a metal source liquid below, for example a casting furnace.
- the source of metal liquid such as a casting furnace is set communication with a pressurized gas source of such that is applied to the liquid metal contained in the liquid metal source, a first value of pressure by which the liquid metal is brought in and maintained in the area of the caisson access for this liquid metal.
- the level of liquid metal is raised above the mold threshold where it was, increasing the pressure to a second value slightly higher than the value necessary to bring the liquid metal to fill the casting space, in order to have a margin of security and to be certain that all the crevices of the mold, even the tallest ones, are filled with metal liquid, and the pressure is maintained at this second value for enough time to leave establish a rest regime, and a metallo-static pressure weak on the shell walls in ceramic.
- the pressure is further increased to a third value to fill the cavities or possible shrinkage, and the pressure is maintained at this third value for a period allowing to obtain the desired solidification of the metal contained in the mold, after which we decrease the pressure of such so that the level of unused liquid metal drops approximately at the initial level, and we maintain this pressure for the time required for example to remove the mold, unmold the piece, and put a mold allowing the manufacture of another part.
- the ceramic shells of these molds generally have an extremely thick weak and thus a certain flexibility which their confers, when subjected to pressure from the liquid metal, a tendency to undergo deformations which affect their dimensional stability.
- the box has a second access connected to the space where the mass of sand is, connected by a suction line to a delivery device depression.
- the object of the invention is to remedy these disadvantages and to this end relates to a method of low pressure casting in a mold comprising a ceramic shell, one side of which defines a space of casting and. a space containing a mass of sand without binder in contact with the other face of the shell, the mold being placed in a box having at its base a access connected to the pouring space and connected to a source of liquid metal below, process in which applies to the liquid metal of the source a first pressure value suitable for supplying liquid metal in the region of said access, the pressure is increased up to a second value slightly higher than a value needed to fill the casting space and we maintains this second value for a first predetermined duration, then the pressure is increased to a third value and we maintain this third value for a second predetermined duration, then we decreases the pressure so that the level of the liquid metal descend approximately in the region of said access or below, characterized in that, approximately when the pouring space becomes completely filled with liquid metal, the pressure in the space of the mass of sand below atmospheric pressure up
- the invention also relates to an installation for the implementation of the above process, comprising a mold comprising a ceramic shell, one side of which delimits a casting space, and a space containing a mass of sand without binder in contact with the other face of the shell, the mold being placed in a box presenting at its base an access connected to the space of poured and connected to a source of liquid metal in below, installation characterized in that the box internally has a vacuum chamber provided with less an air permeable wall region having an access opening provided with a vacuum outlet to be connected to a suction device via a solenoid valve controlled by a programmable controller also controlling a device for regulating source pressure of liquid metal.
- the installation according to the invention can moreover feature the fact that the room vacuum extends annularly in the box against a base wall and side walls thereof.
- the molding process can be implemented very quickly and can be controlled precisely with an investment in remaining material despite everything moderate.
- the installation according to the invention comprises a box 1 in which is formed a mold 2 comprising a ceramic shell 21 which may be of the type "Consumable" of which one side delimits a space of casting 22 whose shape corresponds to the outside shape of the part to be cast, and a mass 23 of sand without binder in the space of the box delimited between the walls of this one and the other side of the shell and so in contact with this other side.
- a mold 2 comprising a ceramic shell 21 which may be of the type "Consumable" of which one side delimits a space of casting 22 whose shape corresponds to the outside shape of the part to be cast, and a mass 23 of sand without binder in the space of the box delimited between the walls of this one and the other side of the shell and so in contact with this other side.
- the thickness of the shell 21 may be small, for example a thickness of 2 mm can be reached.
- the thickness is in the range of 2 to 4 mm, but the process is also suitable for greater thicknesses.
- the box 1 has a base wall 11 and side walls 12 having a common edge with the base wall and top edge bent outwards so as to constitute a flange 13 extending parallel to the base wall.
- the base wall has an access opening 14 connected to the casting space 22 by a seal 15 tubular with a part fitted into the opening of the base wall and a part serving as worn on the inside, of conjugate shape, of the mouth (lower) of the shell 21.
- Case 1 has a vacuum chamber 3 annular extending against the peripheral region of its base wall 11 and the side wall regions 12 which end up at this base wall.
- This room vacuum has at least one wall 31 in contact with the mass of sand 23; this wall 31 includes at least one region breathable but sandproof.
- One of the walls sides of the box 1 and of the vacuum chamber 3 comprises a second access opening 16 opening into the vacuum chamber, fitted with a vacuum outlet 17.
- the mass of sand 23 fills the space of the box 1 between the walls thereof and the shell 21, at with the exception of the vacuum chamber 3.
- the box is placed on a support plate (not shown) having an opening opposite the access opening of its base wall.
- the support plate is everything first placed on a vibrating device (also not shown) comprising for example rollers eccentrics.
- the box 1 when the shell 21 is positioned on the seal 15, the box 1 can be filled with soft sand, that is to say without binder, while being vibrated to obtain maximum densification.
- the sand level is then equalized with the rule to obtain a level regular on the upper surface of the box.
- the box 1 filled with sand is then ready to be transported near a casting furnace 4, arranged below the box.
- the box is positioned so that the access opening 14 of its base wall lined with the gasket 15 is opposite an outlet neck 41 of a metal supply pipe 42 liquid from the oven, so that the neck can be secured to the box and that the supply line thus connects the mold casting space to the interior space of the oven.
- a movable plate 5 under which is fixed a seal 51 is attached to the box for example by clamping to constitute the cover of the latter, the seal 51 then being interposed between the plate and the flange 13 formed on the side walls of the caisson.
- the seal crushed between the plate and the flange, following the shape of these, so lets do the empty inside the box.
- the vacuum outlet 17 is tightly connected to a pipe 61 connecting this socket to a device suction 6 comprising a vacuum manifold 62 setting vacuum by a pump 63 such as a pallets.
- a solenoid valve 64 controlled by a PLC programmable 7 is inserted between the vacuum manifold 62 and the vacuum outlet 17 of the box; a pressure gauge 65 measures the pressure at the inlet of the box.
- the casting furnace 4 comprises, above the mass 43 of liquid metal, a vault 44 connected by a pressure line 45 to a pressure device pressure regulation 8 also controlled by the programmable controller 7.
- the liquid metal of the casting furnace 4 is applied, by means of the pressurization line 45, a pressure of value P1 for example of the order of 1.15 absolute bars, which brings the liquid metal by a movement ascending in the region of access opening 14 of the base of the box 1, at the threshold of the mouth of the mold 2.
- phase AB increase the pressure (phase AB), until a P2 value for example of approximately 1.4 bar absolute, and more generally a value slightly greater than that necessary to fill completely so ascending the casting space with a safety margin ⁇ h sufficient, and we maintain this value to let establish a rest regime (BC phase).
- the reduction of the pressure in space of the mass of sand quickly, because the duration of this phase of decrease below atmospheric pressure up to the vacuum value chosen must be shorter than that of phase BC where the mass of liquid metal is subjected to the pressure of P2 value.
- the liquid metal pressure at the P2 value here of 1.4 bars not only until the cavity 22 is filled, but also as long as the depression in the mass of sand did not reach the chosen level.
- the shell 21 being stiffened by the compaction of the mass of sand due to depression, we further increases the pressure applied to the liquid metal (CD phase) up to a value P3 for example of the order 1.7 bars to fill cavities or shrinkage possible, and we maintain this value P3 of overpressure for a period allowing to obtain everything first a solidified crust against the shell, then the solidification of the metal contained in the mold (phase DE).
- a value P3 for example of the order 1.7 bars to fill cavities or shrinkage possible
- the depression in the mass of sand is maintained at a value corresponding to the pressure absolute from 0.5 to 0.9 bar here approximately up to point E, and in any case the "vacuum” must not be “Broken” before the metal crust formed against the shell 21.
- phase EF liquid metal
- the depression being applied to the mass of sand after filling of the shell it does not affect the flow of the metal in the latter, and this flow remains controlled by pressure, while the depression in the mass of sand ensures the stiffening of the shell in the overpressure phase at pressure P3, which is the most critical, at least as long as the shell is not stiffened by a metal crust.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Casting Devices For Molds (AREA)
- Other Liquid Machine Or Engine Such As Wave Power Use (AREA)
- Molds, Cores, And Manufacturing Methods Thereof (AREA)
Description
L'invention concerne un procédé et une installation de coulée sous basse pression d'une composition métallique à l'état liquide, dans un moule comprenant une coquille en céramique dont une face délimite un espace de coulée et une masse de sable sans liant en contact avec l'autre face de la coquille, le moule étant placé dans un caisson présentant à sa base un accès raccordé à l'espace de coulée et relié par une conduite d'amenée de métal liquide à une source de métal liquide en contrebas, par exemple un four de coulée.The invention relates to a method and a low pressure casting installation of a metallic composition in liquid state, in a mold comprising a ceramic shell, one side of which delimits a casting space and a mass of sand without binder in contact with the other face of the shell, the mold being placed in a box having at its base a access connected to the pouring space and connected by a line for supplying liquid metal to a metal source liquid below, for example a casting furnace.
On connaít déjà des procédés et des installations de coulée de ce type, dans lesquels la source de métal liquide telle qu'un four de coulée est mise en communication avec une source de gaz sous pression de telle manière que soit appliquée au métal liquide contenu dans la source de métal liquide, une première valeur de pression grâce à laquelle le métal liquide est amené et maintenu dans la région de l'accès du caisson pour ce métal liquide.We already know processes and facilities of this type, in which the source of metal liquid such as a casting furnace is set communication with a pressurized gas source of such that is applied to the liquid metal contained in the liquid metal source, a first value of pressure by which the liquid metal is brought in and maintained in the area of the caisson access for this liquid metal.
Lorsque l'on désire couler une pièce en introduisant du métal liquide dans le moule, le niveau du métal liquide est élevé au-dessus du seuil du moule où il se trouvait, en augmentant la pression jusqu'à une deuxième valeur légèrement supérieure à la valeur nécessaire pour amener le métal liquide à remplir l'espace de coulée, afin de posséder une marge de sécurité et d'être certain que toutes les anfractuosités du moule, même les plus hautes, sont remplies de métal liquide, et on maintient la pression à cette deuxième valeur pendant une durée suffisante pour laisser s'établir un régime de repos, et une pression métallo-statique faible sur les parois de la coquille en céramique. Puis on augmente encore la pression jusqu'à une troisième valeur afin de combler les cavités ou retassures éventuelles, et on maintient la pression à cette troisième valeur pendant une durée permettant d'obtenir la solidification désirée du métal contenu dans le moule, après quoi on diminue la pression de telle sorte que le niveau du métal liquide inutilisé descende approximativement au niveau initial, et on maintient cette pression pendant le temps nécessaire par exemple pour retirer le moule, démouler la pièce, et remettre un moule permettant la fabrication d'une autre pièce.When you want to cast a piece in introducing liquid metal into the mold, the level of liquid metal is raised above the mold threshold where it was, increasing the pressure to a second value slightly higher than the value necessary to bring the liquid metal to fill the casting space, in order to have a margin of security and to be certain that all the crevices of the mold, even the tallest ones, are filled with metal liquid, and the pressure is maintained at this second value for enough time to leave establish a rest regime, and a metallo-static pressure weak on the shell walls in ceramic. Then the pressure is further increased to a third value to fill the cavities or possible shrinkage, and the pressure is maintained at this third value for a period allowing to obtain the desired solidification of the metal contained in the mold, after which we decrease the pressure of such so that the level of unused liquid metal drops approximately at the initial level, and we maintain this pressure for the time required for example to remove the mold, unmold the piece, and put a mold allowing the manufacture of another part.
Cependant, les coquilles en céramique de ces moules présentent en général une épaisseur extrêmement faible et ainsi une certaine flexibilité qui leur confère, lorsqu'elles sont soumises à la pression du métal liquide, une tendance à subir des déformations qui nuisent à leur stabilité dimensionnelle.However, the ceramic shells of these molds generally have an extremely thick weak and thus a certain flexibility which their confers, when subjected to pressure from the liquid metal, a tendency to undergo deformations which affect their dimensional stability.
Afin de remédier aux instabilités dimensionnelles qui surviennent dans le cas du procédé de coulée décrit ci-dessus, il a été proposé de maintenir en dépression la masse de sable en contact avec la coquille, afin d'assurer une stabilité dynamique aux grains de sable et ainsi la stabilité dimensionnelle de la coquille. A cette fin, le caisson est doté d'un deuxième accès raccordé à l'espace où se trouve la masse de sable, relié par une conduite d'aspiration à un dispositif de mise en dépression.In order to remedy dimensional instabilities which occur in the case of the casting process described above, it has been proposed to maintain in depression the mass of sand in contact with the shell, so provide dynamic stability to the grains of sand and thus the dimensional stability of the shell. At this end, the box has a second access connected to the space where the mass of sand is, connected by a suction line to a delivery device depression.
Mais cette mise en dépression de la masse de sable a pour inconvénient de perturber la montée et la bonne répartition du métal liquide dans l'espace de coulée, par l'intermédiaire de la porosité de la céramique (remplissage « par le vide »), ce qui conduit à un remplissage trop rapide générant des défauts dans les pièces coulées.But this depression of the mass of sand has the disadvantage of disturbing the rise and good distribution of liquid metal in the space of casting, through the porosity of the ceramic ("vacuum" filling), which leads to overfilling, generating faults in the castings.
L'invention a pour but de remédier à ces inconvénients et concerne à cet effet un procédé de coulée sous basse pression dans un moule comprenant une coquille céramique dont une face délimite un espace de coulée et. un espace contenant une masse de sable sans liant en contact avec l'autre face de la coquille, le moule étant placé dans un caisson présentant à sa base un accès raccordé à l'espace de coulée et relié à une source de métal liquide en contrebas, procédé dans lequel on applique au métal liquide de la source une première valeur de pression adaptée pour amener du métal liquide dans la région dudit accès, on augmente la pression jusqu'à une deuxième valeur légèrement supérieure à une valeur nécessaire pour remplir l'espace de coulée et on maintient cette deuxième valeur pendant une première durée prédéterminée, puis on augmente la pression jusqu'à une troisième valeur et on maintient cette troisième valeur pendant une deuxième durée prédéterminée, puis on diminue la pression pour que le niveau du métal liquide descende approximativement dans la région dudit accès ou au-dessous, caractérisé en ce que, approximativement lorsque l'espace de coulée devient entièrement rempli de métal liquide, on diminue la pression dans l'espace de la masse de sable au-dessous de la pression atmosphérique jusqu'à une valeur de dépression prédéterminée, on maintient cette valeur de dépression au moins jusqu'à ce que soit obtenue contre la coquille une croûte solidifiée, et on remonte approximativement à la pression atmosphérique la pression dans l'espace de la masse de sable.The object of the invention is to remedy these disadvantages and to this end relates to a method of low pressure casting in a mold comprising a ceramic shell, one side of which defines a space of casting and. a space containing a mass of sand without binder in contact with the other face of the shell, the mold being placed in a box having at its base a access connected to the pouring space and connected to a source of liquid metal below, process in which applies to the liquid metal of the source a first pressure value suitable for supplying liquid metal in the region of said access, the pressure is increased up to a second value slightly higher than a value needed to fill the casting space and we maintains this second value for a first predetermined duration, then the pressure is increased to a third value and we maintain this third value for a second predetermined duration, then we decreases the pressure so that the level of the liquid metal descend approximately in the region of said access or below, characterized in that, approximately when the pouring space becomes completely filled with liquid metal, the pressure in the space of the mass of sand below atmospheric pressure up to a predetermined vacuum value, we maintains this depression value at least until let a crust be obtained against the shell solidified, and we go up approximately to the pressure atmospheric pressure in space the mass of sand.
Le procédé selon l'invention peut de plus présenter une ou plusieurs des caractéristiques suivantes :
- la durée de la phase au cours de laquelle on diminue la pression dans l'espace où se trouve la masse de sable, au-dessous de la pression atmosphérique, jusqu'à une valeur de dépression prédéterminée, est plus courte que la première durée prédéterminée ;
- la phase au cours de laquelle on augmente la pression dans l'espace où se trouve la masse de sable, approximativement jusqu'à la pression atmosphérique, est menée à son terme avant le terme de la phase au cours de laquelle on diminue la pression à laquelle est soumis le métal liquide contenu dans la source de métal liquide de telle sorte que le niveau du métal liquide descende approximativement dans la région dudit accès ou au-dessous ;
- la valeur de dépression prédéterminée correspond à une pression absolue dans la gamme approximativement de 0,5 à 0,9 bar ;
- la première valeur de pression est d'environ 1,15 bars absolus ;
- la deuxième valeur de pression est d'environ 1,4 bars absolus ;
- la troisième valeur de pression est d'environ 1,7 bars absolus.
- the duration of the phase during which the pressure is reduced in the space where the mass of sand is located, below atmospheric pressure, up to a predetermined depression value, is shorter than the first predetermined duration ;
- the phase during which the pressure in the space where the mass of sand is increased, approximately up to atmospheric pressure, is completed before the end of the phase during which the pressure is reduced to which is subjected to the liquid metal contained in the source of liquid metal so that the level of the liquid metal drops approximately in the region of said access or below;
- the predetermined vacuum value corresponds to an absolute pressure in the range approximately from 0.5 to 0.9 bar;
- the first pressure value is approximately 1.15 bar absolute;
- the second pressure value is approximately 1.4 bar absolute;
- the third pressure value is approximately 1.7 bar absolute.
Grâce au fait que c'est seulement lorsque l'espace de coulée est rempli de métal liquide que l'on diminue la pression dans l'espace de la masse de sable, le remplissage n'est pas perturbé par la dépression.Thanks to the fact that it's only when the pouring space is filled with liquid metal which is decreases the pressure in space of the mass of sand, the filling is not disturbed by the vacuum.
L'invention concerne également une installation pour la mise en oeuvre du procédé ci-dessus, comportant un moule comprenant une coquille céramique dont une face délimite un espace de coulée, et un espace contenant une masse de sable sans liant en contact avec l'autre face de la coquille, le moule étant placé dans un caisson présentant à sa base un accès raccordé à l'espace de coulée et relié à une source de métal liquide en contrebas, installation caractérisée en ce que le caisson comporte intérieurement une chambre à vide munie d'au moins une région de paroi perméable à l'air et présentant une ouverture d'accès munie d'une prise de vide pour être reliée à un dispositif d'aspiration par l'intermédiaire d'une électrovanne commandée par un automate programmable commandant également un dispositif de régulation de pression de la source de métal liquide.The invention also relates to an installation for the implementation of the above process, comprising a mold comprising a ceramic shell, one side of which delimits a casting space, and a space containing a mass of sand without binder in contact with the other face of the shell, the mold being placed in a box presenting at its base an access connected to the space of poured and connected to a source of liquid metal in below, installation characterized in that the box internally has a vacuum chamber provided with less an air permeable wall region having an access opening provided with a vacuum outlet to be connected to a suction device via a solenoid valve controlled by a programmable controller also controlling a device for regulating source pressure of liquid metal.
L'installation selon l'invention peut de plus présenter pour caractéristique le fait que la chambre à vide s'étend annulairement dans le caisson contre une paroi de base et des parois latérales de celui-ci.The installation according to the invention can moreover feature the fact that the room vacuum extends annularly in the box against a base wall and side walls thereof.
Grâce à cette installation, le procédé de moulage peut être mis en oeuvre très rapidement et être contrôlé avec précision avec un investissement en matériel restant malgré tout modéré.Thanks to this installation, the molding process can be implemented very quickly and can be controlled precisely with an investment in remaining material despite everything moderate.
D'autres caractéristiques et avantages de l'invention ressortiront de la description qui va suivre d'un exemple de réalisation de l'invention illustré par les dessins joints dans lesquels :
- la figure 1 est un schéma général d'une installation pour la mise en oeuvre du procédé selon l'invention, et
- la figure 2 est un diagramme illustrant la succession des phases du procédé selon l'invention.
- FIG. 1 is a general diagram of an installation for implementing the method according to the invention, and
- FIG. 2 is a diagram illustrating the succession of the phases of the method according to the invention.
L'installation selon l'invention comporte un
caisson 1 dans lequel est constitué un moule 2 comprenant
une coquille 21 en céramique pouvant être du type
« consommable » dont une face délimite un espace de
coulée 22 dont la forme correspond à la forme extérieure
de la pièce à couler, et une masse 23 de sable sans liant
dans l'espace du caisson délimité entre les parois de
celui-ci et l'autre face de la coquille et ainsi en
contact avec cette autre face.The installation according to the invention comprises a
Grâce à l'invention, l'épaisseur de la coquille
21 peut être faible, et par exemple une épaisseur de 2 mm
peut être atteinte.Thanks to the invention, the thickness of the
En général, l'épaisseur est dans la gamme de 2 à 4 mm, mais le procédé convient également pour des épaisseurs plus importantes. In general, the thickness is in the range of 2 to 4 mm, but the process is also suitable for greater thicknesses.
Le caisson 1 comporte une paroi de base 11 et des
parois latérales 12 présentant un bord commun avec la
paroi de base et un bord supérieur coudé vers l'extérieur
de manière à constituer une bride 13 s'étendant
parallèlement à la paroi de base.The
La paroi de base présente une ouverture d'accès
14 raccordée à l'espace de coulée 22 par un joint 15
tubulaire présentant une partie emmanchée dans
l'ouverture de la paroi de base et une partie servant de
portée à la face intérieure, de forme conjuguée, de
l'embouchure (inférieure) de la coquille 21.The base wall has an access opening
14 connected to the
Le caisson 1 comporte une chambre à vide 3
annulaire s'étendant contre la région périphérique de sa
paroi de base 11 et les régions des parois latérales 12
qui aboutissent à cette paroi de base. Cette chambre à
vide a au moins une paroi 31 en contact avec la masse de
sable 23 ; cette paroi 31 comporte au moins une région
perméable à l'air mais étanche au sable. L'une des parois
latérales du caisson 1 et de la chambre à vide 3 comporte
une deuxième ouverture d'accès 16 débouchant dans la
chambre à vide, munie d'une prise de vide 17.
La masse de sable 23 emplit l'espace du caisson 1
entre les parois de celui-ci et la coquille 21, à
l'exception de la chambre à vide 3.The mass of
Le caisson est disposé sur un plateau support (non représenté) présentant une ouverture en face de l'ouverture d'accès de sa paroi de base.The box is placed on a support plate (not shown) having an opening opposite the access opening of its base wall.
En vue du remplissage en sable du caisson au moyen par exemple d'une trémie dont l'orifice de base débouche dans le caisson, le plateau support est tout d'abord disposé sur un dispositif de vibration (également non représenté) comportant par exemple des rouleaux excentriques.With a view to filling the caisson with sand at means for example of a hopper whose base orifice opens into the box, the support plate is everything first placed on a vibrating device (also not shown) comprising for example rollers eccentrics.
Ainsi, lorsque la coquille 21 est positionnée sur
le joint 15, le caisson 1 peut être rempli de sable flou,
c'est-à-dire sans liant, tout en étant vibré pour obtenir
une densification maximale. Le niveau de sable est
ensuite égalisé à la règle pour obtenir un niveau
régulier à la surface supérieure du caisson.Thus, when the
Le caisson 1 rempli de sable est alors prêt à
être transporté à proximité d'un four de coulée 4,
disposé en contrebas du caisson. Le caisson est
positionné de telle sorte que l'ouverture d'accès 14 de
sa paroi de base garnie du joint 15 soit en vis-à-vis
d'un col de sortie 41 d'une conduite 42 d'amenée de métal
liquide du four, afin que le col puisse être solidarisé
au caisson et que la conduite d'amenée relie ainsi
l'espace de coulée du moule à l'espace intérieur du four.The
Egalement, un plateau mobile 5 sous lequel est
fixé un joint d'étanchéité 51 est attaché sur le caisson
par exemple par bridage pour constituer le couvercle de
celui-ci, le joint 51 étant alors interposé entre le
plateau et la bride 13 formée sur les parois latérales du
caisson. Le joint, écrasé entre le plateau et la bride,
épousant la forme de ceux-ci, permet donc de faire le
vide à l'intérieur du caisson.Also, a
Approximativement simultanément à l'application
du plateau mobile 5 sur le caisson, la prise de vide 17
est raccordée de manière étanche à une conduite
d'aspiration 61 reliant cette prise à un dispositif
d'aspiration 6 comprenant une nourrice de vide 62 mise en
dépression par une pompe 63 telle qu'une pompe à
palettes.Approximately simultaneously with the application
of the
Une électrovanne 64 commandée par un automate
programmable 7 est insérée entre la nourrice de vide 62
et la prise de vide 17 du caisson ; un manomètre 65
mesure la pression à l'entrée du caisson.A
Le four de coulée 4 comporte, au-dessus de la
masse 43 de métal liquide, une voûte 44 reliée par une
conduite 45 de mise en pression à un dispositif de
régulation de pression 8 également commandé par
l'automate programmable 7.The casting furnace 4 comprises, above the
mass 43 of liquid metal, a
Grâce à cette installation, et sous la commande de l'automate programmable 7, on peut mettre en oeuvre le procédé selon l'invention qui va être décrit ci-après et qui est illustré par la figure 2.Thanks to this installation, and under the command of the programmable logic controller 7, it is possible to implement the process according to the invention which will be described below and which is illustrated in Figure 2.
On applique au métal liquide du four de coulée 4,
au moyen de la conduite de mise en pression 45, une
pression de valeur P1 par exemple de l'ordre de 1,15
bars absolus, qui amène le métal liquide par un mouvement
ascendant dans la région de l'ouverture d'accès 14 de la
base du caisson 1, au seuil de l'embouchure du moule 2.The liquid metal of the casting furnace 4 is applied,
by means of the
Puis, on augmente la pression (phase AB), jusqu'à une valeur P2 par exemple d'environ 1,4 bars absolus, et plus généralement une valeur légèrement supérieure à celle nécessaire pour emplir entièrement de manière ascendante l'espace de coulée avec une marge de sécurité Δh suffisante, et on maintient cette valeur pour laisser s'établir un régime de repos (phase BC).Then, increase the pressure (phase AB), until a P2 value for example of approximately 1.4 bar absolute, and more generally a value slightly greater than that necessary to fill completely so ascending the casting space with a safety margin Δh sufficient, and we maintain this value to let establish a rest regime (BC phase).
De plus, lorsque la pression a atteint
approximativement sa valeur permettant le remplissage du
moule, et de préférence sa valeur P2 avec la marge de
sécurité, (point B), on diminue rapidement, par
l'intermédiaire de la conduite d'aspiration, et par suite
de l'ouverture de l'électrovanne 64 commandée par
l'automate programmable 7, la pression dans la masse de
sable ; la diminution est poursuivie jusqu'à ce que l'on
atteigne une valeur de dépression par rapport à la
pression atmosphérique, correspondant à une pression
absolue prédéterminée de préférence dans la gamme
approximativement de 0,5 à 0,9 bar, et on maintient cette
valeur de dépression pendant une certaine durée comme on
le verra dans la suite.In addition, when the pressure has reached
approximately its value allowing the filling of the
mold, and preferably its P2 value with the margin of
security, (point B), we decrease rapidly, by
through the suction line, and therefore
the opening of the
De préférence, on effectue la diminution de la
pression dans l'espace de la masse de sable rapidement,
car la durée de cette phase de diminution au-dessous de
la pression atmosphérique jusqu'à la valeur de dépression
choisie doit être plus courte que celle de la phase BC où
la masse de métal liquide est soumise à la pression de
valeur P2. Selon l'invention, on maintient donc la
pression du métal liquide à la valeur P2 ici de 1,4 bars,
non seulement tant que la cavité 22 n'est pas emplie,
mais également tant que la dépression dans la masse de
sable n'a pas atteint le niveau choisi.Preferably, the reduction of the
pressure in space of the mass of sand quickly,
because the duration of this phase of decrease below
atmospheric pressure up to the vacuum value
chosen must be shorter than that of phase BC where
the mass of liquid metal is subjected to the pressure of
P2 value. According to the invention, therefore, the
liquid metal pressure at the P2 value here of 1.4 bars,
not only until the
Après quoi, la coquille 21 étant rigidifiée par
le compactage de la masse de sable dû à la dépression, on
augmente encore la pression appliquée au métal liquide
(phase CD) jusqu'à une valeur P3 par exemple de l'ordre
de 1,7 bars afin de combler les cavités ou retassures
éventuelles, et on maintient cette valeur P3 de
surpression pendant une durée permettant d'obtenir tout
d'abord une croûte solidifiée contre la coquille, puis la
solidification du métal contenu dans le moule (phase DE).After which, the
La dépression dans la masse de sable est
maintenue à une valeur correspondant à la pression
absolue de 0,5 à 0,9 bar ici approximativement jusqu'au
point E, et en tout cas le « vide » ne doit pas être
« cassé » avant la formation de la croûte de métal contre
la coquille 21.The depression in the mass of sand is
maintained at a value corresponding to the pressure
absolute from 0.5 to 0.9 bar here approximately up to
point E, and in any case the "vacuum" must not be
"Broken" before the metal crust formed against
the
Lorsque la solidification désirée du métal de
l'espace de coulée 22 est obtenue, on diminue la pression
sur le métal liquide (phase EF) de telle sorte que le
niveau de celui-ci descende approximativement au niveau
initial (valeur de pression P1 égale ici à 1,15 bars
environ), et on maintient cette pression pendant le temps
nécessaire par exemple pour retirer le moule et en
remettre un autre en vue de la fabrication d'une autre
pièce. Comme on l'a vu, on peut casser le « vide »
(augmenter la pression) dans la masse de sable à partir
du moment où la croûte solide est formée, mais
généralement on n'effectue cette opération
qu'immédiatement avant le relâchement de la pression
appliquée au métal liquide ou au moment de ce
relâchement ; cependant, cette phase d'augmentation de la
pression dans l'espace où se trouve la masse de sable
approximativement jusqu'à la pression atmosphérique est
effectuée suffisamment tôt et/ou rapidement pour qu'elle
soit menée à son terme avant le terme F de la phase EF au
cours de laquelle on diminue la pression sur le métal
liquide pour assurer son retour à la pression P1 ou même
au-dessous. La masse de sable n'étant plus en dépression,
le métal liquide peut redescendre librement dans la
conduite d'amenée 42, son niveau revenant alors
approximativement dans la région de l'accès 14 ou au-dessous,
et on peut retirer aisément le caisson sans
craindre des retours de métal liquide.When the desired solidification of the metal of
the
Ainsi, grâce à l'invention, la dépression étant appliquée à la masse de sable à l'issue du remplissage de la coquille, elle n'intervient pas sur l'écoulement du métal dans cette dernière, et cet écoulement reste piloté par la pression, tandis que la dépression dans la masse de sable assure la rigidification de la coquille dans la phase de surpression à la pression P3, qui est la plus critique, au moins tant que la coquille n'est pas rigidifiée par une croûte de métal.Thus, thanks to the invention, the depression being applied to the mass of sand after filling of the shell, it does not affect the flow of the metal in the latter, and this flow remains controlled by pressure, while the depression in the mass of sand ensures the stiffening of the shell in the overpressure phase at pressure P3, which is the most critical, at least as long as the shell is not stiffened by a metal crust.
Claims (9)
- Process for low pressure die casting in a mould (2) comprising a ceramic casting die (21) one side of which delimits a casting space (22), and a space containing a mass of sand (23) without any binder, in contact with the other side of the casting die, the mould being placed in a box (1) having in its base an access point (14) communicating with the casting space and connected to a source (4) of liquid metal below, in which process a first pressure value (P1) is applied to the liquid metal of the source, adapted to bring the liquid metal into the region of said access point, the pressure is increased to a second value (P2) slightly higher than a value needed to fill the casting space and this second value is maintained for a first predetermined length of time (BC), then the pressure is increased to a third value (P3) and this third value is maintained for a second predetermined length of time (DE), then the pressure is reduced so that the level of liquid metal falls to approximately the region of said access point (14) or below it, characterised in that, approximately when the casting space becomes totally filled with liquid metal, the pressure in the space for the mass of sand (23) is reduced below atmospheric pressure to a predetermined underpressure value, this underpressure value is maintained at least until a solidified crust is obtained against the casting die (21), and the pressure in the space for the mass of sand is raised to approximately atmospheric pressure.
- Die casting process according to claim 1, characterised in that the duration of the phase during which the pressure in the space where the mass of sand (23) is located is reduced below atmospheric pressure to a predetermined underpressure value, is shorter than the first predetermined length of time (BC).
- Die casting process according to claim 1, characterised in that the phase during which the pressure in the space where the mass of sand (23) is located is raised approximately to atmospheric pressure is brought to an end before the end (F) of the phase (EF) during which the pressure to which the liquid metal contained in the source (4) of liquid metal is reduced so that the level of the liquid metal falls to approximately the region of said access point (14) or below.
- Die casting process according to any one of claims 1 to 3, characterised in that the predetermined underpressure value corresponds to an absolute pressure approximately in the range from 0.5 to 0.9 bar.
- Die casting process according to any one of claims 1 to 4, characterised in that the first pressure value (P1) is about 1.15 bars of absolute pressure.
- Die casting process according to any one of claims 1 to 5, characterised in that the second pressure value (P2) is about 1.4 bars of absolute pressure.
- Die casting process according to any one of claims 1 to 6, characterised in that the third pressure value (P3) is about 1.7 bars of absolute pressure.
- Apparatus for carrying out the process according to any one of claims 1 to 7, comprising a mould (2) having a ceramic casting die (21) one side of which delimits a casting space (22), and a space containing a mass of sand (23) without any binder, in contact with the other side of the casting die, the mould being placed in a box (1) having at its base an access point (14) communicating with the casting space and connected to a source (4) of liquid metal below, and comprising on the inside a vacuum chamber (3) provided with at least one wall portion (31) which is air-permeable and having an access opening (16) provided with a vacuum connector (17) for connecting to a suction device (6), the apparatus being characterised in that the vacuum connector (17) is connected to the suction device (6) via an electromagnetic valve (64) controlled by a process controller (7) which also controls a device for regulating the pressure (8) of the source (4) of liquid metal.
- Apparatus according to claim 8, characterised in that the vacuum chamber (3) extends annularly in the box against a base wall (11) and side walls (12) thereof.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9800091A FR2773337B1 (en) | 1998-01-07 | 1998-01-07 | LOW PRESSURE CASTING PROCESS AND INSTALLATION IN A CERAMIC SHELL MOLD |
| FR9800091 | 1998-01-07 | ||
| PCT/FR1998/002908 WO1999034945A1 (en) | 1998-01-07 | 1998-12-29 | Method and installation for low pressure die casting in a mould with ceramic casting die |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0968064A1 EP0968064A1 (en) | 2000-01-05 |
| EP0968064B1 true EP0968064B1 (en) | 2002-10-23 |
Family
ID=9521572
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP98964545A Expired - Lifetime EP0968064B1 (en) | 1998-01-07 | 1998-12-29 | Method and installation for low pressure die casting in a mould with ceramic casting die |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US6422293B1 (en) |
| EP (1) | EP0968064B1 (en) |
| CA (1) | CA2282673A1 (en) |
| DE (1) | DE69808892T2 (en) |
| ES (1) | ES2186248T3 (en) |
| FR (1) | FR2773337B1 (en) |
| WO (1) | WO1999034945A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6766850B2 (en) * | 2001-12-27 | 2004-07-27 | Caterpillar Inc | Pressure casting using a supported shell mold |
| DE10352179B4 (en) * | 2003-11-05 | 2007-09-06 | Dihag Deutsche Giesserei- Und Industrie-Holding Ag | Low pressure casting process for the production of a casting |
| DE102006045267A1 (en) * | 2006-09-22 | 2008-03-27 | Kurtz Gmbh | Casting device for producing open-pored foam structures made of metal, metal alloys, plastic or ceramic with or without closed outer shell |
| CN102962433A (en) * | 2012-12-06 | 2013-03-13 | 淄博宏泰防腐有限公司 | Magnesium alloy low-pressure casting equipment |
| JP6406510B2 (en) * | 2014-12-26 | 2018-10-17 | 日産自動車株式会社 | Casting method and casting apparatus |
| JP6406509B2 (en) * | 2014-12-26 | 2018-10-17 | 日産自動車株式会社 | Casting apparatus and casting method |
| CN107107180B (en) * | 2015-01-15 | 2022-03-29 | 日产自动车株式会社 | Low-pressure casting method and low-pressure casting device |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57139465A (en) * | 1981-02-24 | 1982-08-28 | Fuji Electric Co Ltd | Control method for pressure charging furnace |
| FR2534167B1 (en) * | 1982-10-11 | 1985-06-07 | Pont A Mousson | METHOD FOR THE FOUNDRY MANUFACTURE OF MOLDED PARTS IN OXIDIZABLE METAL ALLOYS |
| FR2556996B1 (en) * | 1983-12-26 | 1988-03-11 | Pont A Mousson | METHOD FOR SUPPLYING FOUNDRY MOLDS WITH METAL ALLOYS UNDER CONTROLLED DIFFERENTIAL PRESSURE |
| JPH0357549A (en) * | 1989-07-25 | 1991-03-12 | Daido Steel Co Ltd | Pressure reduction/suction casting method |
| US5069271A (en) * | 1990-09-06 | 1991-12-03 | Hitchiner Corporation | Countergravity casting using particulate supported thin walled investment shell mold |
| JPH04187359A (en) * | 1990-11-21 | 1992-07-06 | Hitachi Ltd | Low pressure casting equipment |
-
1998
- 1998-01-07 FR FR9800091A patent/FR2773337B1/en not_active Expired - Fee Related
- 1998-12-29 CA CA002282673A patent/CA2282673A1/en not_active Abandoned
- 1998-12-29 WO PCT/FR1998/002908 patent/WO1999034945A1/en active IP Right Grant
- 1998-12-29 DE DE69808892T patent/DE69808892T2/en not_active Expired - Lifetime
- 1998-12-29 US US09/380,463 patent/US6422293B1/en not_active Expired - Fee Related
- 1998-12-29 EP EP98964545A patent/EP0968064B1/en not_active Expired - Lifetime
- 1998-12-29 ES ES98964545T patent/ES2186248T3/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| FR2773337A1 (en) | 1999-07-09 |
| CA2282673A1 (en) | 1999-07-15 |
| DE69808892T2 (en) | 2003-02-20 |
| EP0968064A1 (en) | 2000-01-05 |
| US6422293B1 (en) | 2002-07-23 |
| ES2186248T3 (en) | 2003-05-01 |
| WO1999034945A1 (en) | 1999-07-15 |
| FR2773337B1 (en) | 2000-02-11 |
| DE69808892D1 (en) | 2002-11-28 |
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