EP0971805B2 - Method and casting device for precision casting - Google Patents
Method and casting device for precision casting Download PDFInfo
- Publication number
- EP0971805B2 EP0971805B2 EP98906787A EP98906787A EP0971805B2 EP 0971805 B2 EP0971805 B2 EP 0971805B2 EP 98906787 A EP98906787 A EP 98906787A EP 98906787 A EP98906787 A EP 98906787A EP 0971805 B2 EP0971805 B2 EP 0971805B2
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- European Patent Office
- Prior art keywords
- casting
- gas
- mould
- mold
- container
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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
- B22D27/003—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using inert gases
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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
- B22D18/06—Vacuum casting, i.e. making use of vacuum to fill the mould
Definitions
- the invention relates to a method for casting metallic objects in a casting device for investment casting with at least one mold, a device for pouring liquid metal into the mold and with means for generating vacuum and pressure and a casting device for performing this method.
- Investment casting is understood to mean the casting of pieces of jewelery, works of art or ornaments, as well as precision small parts for industry, in particular gold, silver, platinum, bronze and other metals.
- casting devices in which a crucible and a mold are arranged in a container.
- the crucible is equipped with an internal cavity for receiving raw material and equipped with a heater, e.g. an electrical induction device provided.
- a heater e.g. an electrical induction device provided.
- the known possibilities can be used, wherein the known example has a bottom spout with a stopper.
- the mold is positioned, which consists of gas-permeable, porous material.
- the mold has a mold cavity, which usually allows the casting of a plurality of individual parts in the same casting process, i. the mold cavity has a tree structure with a pouring funnel.
- the production of the mold is usually done with the help of a plastic or wax model, and the form is used only once.
- the method for casting metallic objects in this known casting device is composed of several steps. For the time being, when the container is open, the crucible is filled with raw material and the casting mold is inserted into the lower part of the container. The lower part of the container is separated from the upper part.
- the upper container part is connected to a device for generating an overpressure and the lower container part to a device for generating negative pressure.
- the container is sealed gas-tight and initiated the melting process in the crucible.
- the stopper By opening the stopper, the liquid melt flows by falling casting into the mold cavity of the mold until it is completely filled.
- the lower container part, in which the mold is is exposed to a negative pressure, which also expands via the porosity of the mold material into the mold cavity.
- a negative pressure which also expands via the porosity of the mold material into the mold cavity.
- an overpressure is generated in the upper container space, so that this pressure also acts on the mirror of the melt in the pouring funnel of the mold.
- the liquid melt may spread too little in the mold cavity.
- partial fine ramifications are not filled, or different structures of the solidified metal occur, since the cooling rate and the solidification time are different in different areas of the mold cavity.
- the mold cavity of the mold and the surrounding space of the mold is exposed to a negative pressure before the start of the casting process, ie before pouring liquid melt into the mold cavity.
- the openings and passages in the at least partially porous and gas-permeable wall of the mold are evacuated and air or other gas residues are sucked out of these porous openings.
- the mold cavity and the surrounding space of the mold is purged with a light gas of low density, which provides the advantage that this gas penetrates into the pores in the wall of the mold and fills them.
- a gas is selected as the light gas, which in the periodic table of the elements has an atomic number between 1 and 10 and which causes the highest possible flow rate of this gas through the pores in the wall of the mold.
- a special suitable gas from this group is helium. After rinsing the mold cavity and the ambient space of the mold with this light gas, a negative pressure is again generated at least in the mold cavity and then filled the liquid melt in the mold cavity. This filling process is now extremely fast, because the light gas, such as helium, is very easily and quickly displaced by the pores in the wall of the mold and can flow to the outside. This advantage is brought about by the high flow rate of the selected light gas through pores and capillary openings.
- the advantage is that no partial overpressure is built up in the individual regions of the mold cavity and between the inflowing liquid metal, so that the liquid metal can flow quickly and unhindered into the finest branches of the mold cavity. This alone achieves improved form accuracy and a higher casting speed. This also has the consequence that in all parts of the mold cavity, a better structure of the cast objects arises.
- the heavy gas As a heavy gas with a higher density while a gas is selected, which has an atomic number of at least 7 in the periodic table of the elements and in any case has a higher atomic number than the light gas with which is purged in the previous process step.
- the heavy gas may also be a gas mixture which has the same properties.
- a particularly suitable gas from this group is argon, since it has the property of flowing through the pores of the wall of the mold only at a relatively low flow rate.
- a casting device which has two sources for different gases of different density. Further advantages arise when the mold is arranged in a first gas-tight container and the crucible and the pouring device are arranged in a second, separate from the first container.
- the two containers are connected via connecting lines and control valves to the first or second gas source and there are pumps for generating a partial negative or positive pressure, and corresponding control devices. If a third gas space is formed in the region between the spout opening on the crucible and the sprue opening on the casting mold, there is the advantage that this space is relatively small and thus the pressure build-up above the sprue can be faster after the casting mold has been filled and less gas is required becomes.
- corresponding control and connection devices to the gas sources and / or to the first or second gas-tight container are provided.
- the region of the pouring opening of the crucible and the region of the pouring opening of the casting mold are displaceable relative to one another in the direction of the casting axis.
- this allows better accessibility to the casting mold and crucible and, on the other hand, joining or separating the first or second or third container from one another.
- This by moving the device parts with the crucible or the device parts with the mold against each other. For sealing, at least one gas-tight seal is formed between these parts of the device.
- the operation of the inventive casting device and the application of the inventive method in this device is carried out in an expedient manner with a controller which contains a control program for performing the method.
- This control controls the appropriate control valves and controls between the gas sources and the gas tight containers.
- This control can also take over the control of the known melting and Abgussvortician.
- a mold 2 is positioned with a mold cavity 3.
- This mold 2 serves to drain metallic objects, in the example shown, jewelry.
- a plurality of objects are arranged around a central sprue with a sprue area 17 and biiden a tree-like structure.
- the mold 2 consists of a porous molding material which is gas-permeable. The mold is produced in a known manner with the aid of a wax model which is melted out after the casting mold 2 has been produced.
- a crucible 1 is positioned on an intermediate carrier.
- This crucible 1 comprises a collecting space 25 for raw material or molten metal and a spout opening 14 in the bottom region of the crucible 1.
- This spout 14 is closed with a stopper 15 and can be opened by an actuator 16 by not shown, but known actuators and getting closed.
- a heating device in the form of an induction coil is arranged, which is also not shown in the example shown, but is known per se.
- the stopper 15 and the spout opening 14, as well as the actuator 16 form the spout 4.
- the interior 26 of the container 5 is sealed gas-tight by means of the lid 24. The interior 26 simultaneously forms the ambient space to the mold 2.
- a connecting line 19 connects this interior space 26 with a first gas source 6, for example a compressed gas cylinder containing helium.
- a valve 22 is arranged, which has actuators and is connected via control lines 23 to a controller 10.
- the interior 26 of the first container 5 is connected to a vacuum pump 8, which is also connected via a control line 23 to the controller 10.
- a valve 21 with actuators and control lines to the controller 10 is also installed.
- the vacuum pump 8 may additionally be supplemented with a vacuum tank, not shown.
- the interior 26 of the container 5 is connected to a second gas source 7, which contains argon in the example described.
- a second gas source 7 which contains argon in the example described.
- an overpressure device 9 for example in the form of a pressure pump and a valve 20 is installed, these elements in turn being connected via control lines 23 to the controller 10.
- the mold cavity 3 of the mold 2 is filled with metal and in the runner 17, the mirror 18 of the cast melt is visible.
- the filling of the mold cavity 3 with liquid melt takes place according to the following method.
- the mold 2 is inserted into the container 5 and the collecting space 25 of the crucible 1 filled with the necessary amount of raw material.
- raw materials such as gold, silver or platinum use, whereby other materials used and other objects, such as art objects or small industrial parts can be poured.
- the volume of the crucible 1 is approximately between 5 to 2000 cm 3 .
- the container 5 is sealed gas-tight with the lid 24 and melted in the crucible 1 metal using the heating device, not shown.
- the entire interior 26 of the container 5 is evacuated with the aid of the vacuum pump 8 to a negative pressure of at least 100 mbar.
- a negative pressure of at least 100 mbar.
- the air which has entered during the filling of the container 5 is drawn off from the interior space 26 and the mold cavity 3 and also the pores in the wall of the casting mold 2 are evacuated.
- a light gas is introduced via the valve 22 from the first gas source 6 with a low density, helium in the example described in the interior 26 of the container 5 and in particular the mold cavity 3 rinsed with this light gas ,
- a small negative pressure can continue to be maintained via the pump 8, so that the rinsing of the entire casting mold 2 is ensured.
- an overpressure of 1000 mbar is applied and this overpressure acts directly on the mirror 18 of the melt in the mold cavity 3.
- the melt in the mold cavity 3 is pressed into the outermost regions of the mold cavity 3 and the light gas helium is completely forced out of the mold cavity 3 displaced.
- the heavy gas argon has the property that it only very poorly penetrates into the pores of the mold 2 and therefore the pressure build-up initially acts only on the mirror 18 of the melt in the mold cavity and only reduced over the wall as a back pressure.
- the device for a new casting process with a new, empty mold 2 is ready.
- the control of the entire casting process via a controller 10, for example, a control computer, which is equipped with a corresponding control program and an input device.
- the program and thus the casting process can be adapted to the corresponding boundary conditions.
- other gases in the first or second gas source 6, 7 are used, these changes are also taken into account by the controller 10.
- Fig. 2 shows an example of a casting device for investment casting, which compared to the example according to Fig. 1 having advantageous supplements.
- the casting device consists of two containers, namely a first container 5 ', which receives the mold 2 and a second container 13, which receives the crucible 1.
- the two containers 5 'and 13 are gas-tight connected to each other, wherein the corresponding connection means are not shown.
- a lid 24 is arranged, which is connectable via not shown connecting means gas-tight with the container 13.
- the container 13 has a bottom 27, in which at least one connecting channel 28 is arranged.
- the bottom 27 of the second container 13 rests on a seal 29 on the upper surface 30 of the mold 2.
- the mold 2 is turned off in the example shown on a lifting and lowering device 31, by means of which the mold 2 against the bottom 27 and thus driven against the spout opening 14 or can be moved away from it.
- This makes it possible to connect the interior of the first container 5 'with the interior of the second container 13 via the connecting channels 28 with each other when the mold 2 is lowered down and no longer abuts the seal 29.
- the crucible 1 not yet melted raw material is filled in the example shown, ie it is the initial state before the start of the melting process and the Abgiessvorganges shown.
- the two inner spaces of the first container 5 'and the second container 13 are evacuated via the vacuum pump 8 and the connecting pipe 11 to a predetermined pressure.
- the interior of the container 5 ' forms the surrounding space to the mold 2.
- a second valve 32 is arranged, which connects the pump 8 with the interior of the second container 13.
- both valves 21 and 32 are opened to evacuate both in the first container 5 'as well as in the second container 13 to generate the desired negative pressure and to suck the unwanted gases from the mold cavity 3 .
- the evacuation can also be done with lowered mold 2, in which case only one of the two valves 21, or 32 must be open.
- the mold 2 is moved in this case by means of the device 31 against the seal 29.
- the valve 22 is opened and from the first gas source 6, a light gas in the container 5 'and 13 is admitted.
- helium is used as a light gas with a low density.
- the time required for the light gas to flow through and fill the pores of the casting mold 2 depends on the size of the casting mold 2 and the molding material selected.
- the purging operation is stopped by closing the valve 22.
- an additional valve 33 can be installed.
- the valve 32 is closed during the flushing process and continues to generate a negative pressure in the ambient space of the mold 2 via the valve 21.
- the light gas helium then flows into the second container 13 and via the connecting channels 28 in the mold cavity 3 and penetrates from the inside to the outside of the mold 2.
- the valve 21 is closed before the start of Abgiessvorganges and only via the valve 32 a maintained predetermined negative pressure in the mold cavity 3.
- the valve 32 is closed and the valve 20 is opened.
- the heavy gas, again argon, in the interior of the second container 13 is admitted and this heavy gas argon charged via the connecting channels 28, the mirror of the melt in the gate 17 of the mold cavity.
- an overpressure built is now in the second container 13 with respect to the ambient space of the mold 2 in the first container 5 ', an overpressure built.
- This causes the liquid melt in the mold cavity 3 to penetrate into the outermost regions of the mold cavity 3, since the light gas drains off helium without great resistance via the pores of the mold 2 into the surrounding space.
- the heavy gas argon acts only on the sprue area 17 of the mold cavity 3, the outflow of the lighter gas helium from the mold cavity 3 into the surrounding space of the container 5 'is facilitated since no overpressure is built up around the mold 2.
- Fig. 3 shows an additionally improved embodiment in which a third gas space 34 is formed between the first container 5 "and the second container 13.
- This third gas space 34 is formed between the bottom 27 of the second container 13 and an intermediate wall 35 on the first container 5".
- This intermediate wall 35 seals the upper surface 30 of the casting mold 2 against the surrounding space in the first container 5 ".
- the first container 5" and the second container 13, as well as the cover 24, are also not shown in this embodiment connection means connected in a gastight manner.
- this embodiment has the additional advantage that the air or other gases present in the mold cavity 3 are sucked outwards in any case
- the valve 22 is opened, and from the first gas source 6 via the conduit 19, the light gas in the form of helium in the interior of the container 13 and the third gas space 34.
- connection line 36 between the line 19 and the third gas space 34 at The valve 21 remains open, so that due to the negative pressure in the ambient space to the mold 2 in the first container 5 ", the helium from the third gas space 34 flows through the mold cavity 3 to the outside in the surrounding space of the mold 2. This ensures complete purging of the pores and capillary openings in the walls of the mold 2, so that they are completely filled with helium.
- the valve 22 is closed in the conduit 19 and the pouring of the liquid melt into the mold cavity 3 can be carried out in the manner already described. As soon as the mold cavity 3 is filled with liquid melt, the heavy gas in the form of argon is fed directly to the third gas space 34 via the connecting line 12 '.
- the desired overpressure in this example of 3000 mbar, compared to the ambient space to the mold 2 in the first container 5 "is thereby built only in the third gas space 34. Since this Only a small amount of argon is required for the third gas space 34, and the construction of the desired overpressure can also take place very quickly and with little expenditure of energy even the light gas is reduced to a minimum.
- helium / argon In place of the gas exchange combinations helium / argon mentioned for the examples, various other combinations are possible. If pure gases are used, combinations such as nitrogen / argon or helium / nitrogen are possible, for example. With mixed gases, for example, a combination of nitrogen can be used as a light gas, with carbon dioxide as a heavy gas.
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Description
Die Erfindung betrifft ein Verfahren zum Giessen von metallischen Objekten in einer Giesseinrichtung für Feinguss mit mindestens einer Giessform, einer Einrichtung zum Eingiessen von flüssigem Metall in die Giessform und mit Einrichtungen zum Erzeugen von Vakuum und Druck und eine Giesseinrichtung zur Durchführung dieses Verfahrens.The invention relates to a method for casting metallic objects in a casting device for investment casting with at least one mold, a device for pouring liquid metal into the mold and with means for generating vacuum and pressure and a casting device for performing this method.
Unter Feinguss wird das Giessen von Schmuckstücken, Kunstobjekten oder Ziergegenständen, sowie von präzisen Kleinteilen für die Industrie, insbesondere aus Gold, Silber, Platin, Bronze und anderen Metallen verstanden. Es sind Giesseinrichtungen bekannt, bei welchen ein Schmelztiegel und eine Giessform in einem Behälter angeordnet sind. Der Schmelztiegel ist mit einem Innenhohlraum zur Aufnahme von Rohmaterial ausgestattet und mit einer Heizeinrichtung, z.B. einer elektrischen Induktionseinrichtung versehen. Als Ausgussvorrichtungen können die bekannten Möglichkeiten eingesetzt werden, wobei das bekannte Beispiel einen Bodenausguss mit einem Stopper aufweist. Unterhalb des Schmelztiegels ist die Giessform positioniert, welche aus gasdurchlässigem, porösem Material besteht. Dabei weist die Giessform einen Formhohlraum auf, welcher zumeist das Giessen einer Mehrzahl von Einzelteilen im gleichen Giessvorgang ermöglicht, d.h. der Formhohlraum hat eine Baumstruktur mit einem Eingusstrichter. Die Herstellung der Giessform erfolgt zumeist mit Hilfe eines Kunststoff- oder Wachsmodelles, und die Form ist nur einmalig verwendbar. Das Verfahren zum Giessen von metallischen Objekten bei dieser bekannten Giesseinrichtung setzt sich aus mehreren Schritten zusammen. Vorerst wird bei offenem Behälter der Schmelztiegel mit Rohmaterial gefüllt und die Giessform in den unteren Teil des Behälters eingesetzt. Dabei ist der untere Teil des Behälters vom oberen Teil abgetrennt.Investment casting is understood to mean the casting of pieces of jewelery, works of art or ornaments, as well as precision small parts for industry, in particular gold, silver, platinum, bronze and other metals. There are known casting devices, in which a crucible and a mold are arranged in a container. The crucible is equipped with an internal cavity for receiving raw material and equipped with a heater, e.g. an electrical induction device provided. As pouring devices, the known possibilities can be used, wherein the known example has a bottom spout with a stopper. Below the crucible, the mold is positioned, which consists of gas-permeable, porous material. In this case, the mold has a mold cavity, which usually allows the casting of a plurality of individual parts in the same casting process, i. the mold cavity has a tree structure with a pouring funnel. The production of the mold is usually done with the help of a plastic or wax model, and the form is used only once. The method for casting metallic objects in this known casting device is composed of several steps. For the time being, when the container is open, the crucible is filled with raw material and the casting mold is inserted into the lower part of the container. The lower part of the container is separated from the upper part.
Der obere Behälterteil ist mit einer Einrichtung zum Erzeugen eines Überdruckes und der untere Behälterteil mit einer Einrichtung zum Erzeugen von Unterdruck verbunden. Zum Einleiten des Giessvorganges wird der Behälter gasdicht verschlossen und der Schmelzvorgang im Schmelztiegel eingeleitet. Durch Öffnen des Stoppers fliesst die flüssige Schmelze durch fallendes Giessen in den Formhohlraum der Giessform, bis diese vollständig gefüllt ist. Vor und/oder während des Giessvorganges wird der untere Behälterteil, in welchem die Giessform steht, einem Unterdruck ausgesetzt, welcher sich über die Porosität des Giessformmateriales auch in den Formhohlraum ausdehnt. Am Ende des Giessvorganges, d.h. wenn der Formhohlraum gefüllt ist, wird im oberen Behälterraum ein Überdruck erzeugt, so dass dieser Druck auch auf den Spiegel der Schmelze im Eingusstrichter der Giessform wirkt. Diese Kombination von Unterdruck, welcher auf den Boden und den Mantel der Giessform wirkt, und von Überdruck, welcher auf die Schmelze im Formhohlraum wirkt, bewirkt gegenüber Giessverfahren mit beidseitig gleichem Druck eine bessere Füllung des Formhohlraumes und eine bessere Ausformung von feinen Details.The upper container part is connected to a device for generating an overpressure and the lower container part to a device for generating negative pressure. To initiate the casting process, the container is sealed gas-tight and initiated the melting process in the crucible. By opening the stopper, the liquid melt flows by falling casting into the mold cavity of the mold until it is completely filled. Before and / or during the casting process, the lower container part, in which the mold is, is exposed to a negative pressure, which also expands via the porosity of the mold material into the mold cavity. At the end of the casting process, i. When the mold cavity is filled, an overpressure is generated in the upper container space, so that this pressure also acts on the mirror of the melt in the pouring funnel of the mold. This combination of negative pressure, which acts on the bottom and the shell of the mold, and of overpressure, which acts on the melt in the mold cavity, compared to casting methods with equal pressure on both sides a better filling of the mold cavity and a better formation of fine details.
Aus
Trotz der an sich guten Giessergebnisse mit diesen bekannten Einrichtungen, treten immer wieder Probleme auf, insbesondere bei komplizierten und feingliedrigen Giessobjekten. Die flüssige Schmelze kann sich beispielsweise zu wenig schnell im Formhohlraum verteilen. Dies hat zur Folge, dass teilweise feine Verästelungen nicht ausgefüllt werden, oder unterschiedliche Strukturen des erstarrten Metalls auftreten, da die Abkühlungsgeschwindigkeit und der Erstarrungszeitpunkt in verschiedenen Bereichen des Formhohlraumes unterschiedlich sind.Despite the good casting results with these known devices, there are always problems, in particular with complicated and delicate casting objects. For example, the liquid melt may spread too little in the mold cavity. As a result, partial fine ramifications are not filled, or different structures of the solidified metal occur, since the cooling rate and the solidification time are different in different areas of the mold cavity.
Es ist deshalb Aufgabe der vorliegenden Erfindung, ein Verfahren und eine Einrichtung zu schaffen, mit welcher die Abformgenauigkeit und der Füllgrad des Formhohlraumes noch weiter erhöht werden können und auch die Struktur der abgegossenen Objekte verbessert wird.It is therefore an object of the present invention to provide a method and a device with which the accuracy of molding and the degree of filling of the mold cavity can be further increased and also the structure of the cast objects is improved.
Diese Aufgabe wird bei einem Verfahren nach dem Patentanspruch 1 erfindungsgemäss durch die Merkmale dieses Patentanspruches und bei einer Vorrichtung nach dem Patentanspruch 5 nach den Merkmalen dieses Patentanspruches 5 gelöst. Vorteilhafte Weiterbildungen der Erfindung ergeben sich nach den Merkmalen der abhängigen Patentansprüche.This object is achieved in a method according to claim 1 according to the invention by the features of this claim and in a device according to
Entsprechend dem erfindungsgemässen Verfahren wird vor dem Beginn des Giessvorganges, d.h. vor dem Eingiessen von flüssiger Schmelze in den Formhohlraum, der Formhohlraum der Giessform und der Umgebungsraum der Giessforrn einem Unterdruck ausgesetzt. Dadurch werden auch die Öffnungen und Durchlässe in der mindestens teilweise porösen und gasdurchlässigen Wandung der Giessform evakuiert und Luft- oder andere Gasrückstände werden aus diesen porösen Öffnungen abgesaugt. Anschliessend wird der Formhohlraum und der Umgebungsraum der Giessform mit einem leichten Gas mit geringer Dichte gespült, was den Vorteil erbringt, dass dieses Gas in die Poren in der Wandung der Giessform eindringt und diese ausfüllt. Dabei wird als leichtes Gas ein Gas gewählt, welches im Periodensystem der Elemente eine Ordnungszahl zwischen 1 und 10 aufweist und welches eine möglichst hohe Durchflussrate dieses Gases durch die Poren in der Wandung der Giessform bewirkt. Ein besonders geeignetes Gas aus dieser Gruppe ist Helium. Nach dem Spülen des Formhohlraumes und des Umgebungsraumes der Giessform mit diesem leichten Gas wird mindestens im Formhohlraum erneut ein Unterdruck erzeugt und dann die flüssige Schmelze in den Formhohlraum eingefüllt. Dieser Füllvorgang erfolgt nun ausserordentlich schnell, da das leichte Gas, z.B. Helium, sehr leicht und schnell durch die Poren in der Wandung der Giessform verdrängt wird und nach aussen abfliessen kann. Dieser Vorteil wird durch die hohe Durchflussrate des gewählten leichten Gases durch Poren und Kapillaröffnungen bewirkt. Für den Giessvorgang besteht der Vorteil darin, dass in den Einzelbereichen des Formhohlraumes und zwischen dem einfliessenden flüssigen Metall kein partieller Überdruck aufgebaut wird, sodass das flüssige Metall rasch und ungehindert in die feinsten Verästelungen des Formhohlraumes fliessen kann. Allein dadurch wird bereits eine verbesserte Formgenauigkeit und eine höhere Abgussgeschwindigkeit erreicht. Dies hat auch zur Folge, dass in allen Teilen im Formhohlraum eine bessere Struktur der abgegossenen Objekte entsteht. Sobald der Formhohlraum vollständig mit flüssigem Metall gefüllt ist, wird der Spiegel der Schmelze im Eingussbereich des Formhohlraumes mit einem anderen schweren Gas mit höherer Dichte beaufschlagt. Dieses Gas weist gegenüber dem Umgebungsraum der Giessform einen Überdruck auf. Als schweres Gas mit höherer Dichte wird dabei ein Gas gewählt, welches im Periodensystem der Elemente eine Ordnungszahl von mindestens 7 aufweist und in jedem Fall eine höhere Ordnungszahl hat als das leichte Gas, mit welchem im vorgängigen Verfahrensschritt gespült wird. Das schwere Gas kann auch ein Gasgemisch sein, welches die gleichen Eigenschaften aufweist. Ein besonders geeignetes Gas aus dieser Gruppe ist Argon, da es die Eigenschaft aufweist, nur mit einer relativ geringen Durchflussrate durch die Poren der Wandung der Giessform zu fliessen. Versuche zeigen, dass der Druckausgleich zwischen der Innenwand der Giessform und der Aussenwand der Giessform bei Beaufschlagung einer Seite mit Argon 8-10 mal langsamer erfolgt als bei Beaufschlagung mit Helium. Dies bringt nun den Vorteil, dass die flüssige Schmelze im Formhohlraum der Giessform einem erhöhten Druck ausgesetzt werden kann, ohne dass der Unterdruck im Umgebungsraum der Giessform merklich reduziert wird. Dies führt zu einer noch besseren Füllung der Formhohlräume und einer verbesserten Struktur der abgegossenen Objekte.According to the inventive method, the mold cavity of the mold and the surrounding space of the mold is exposed to a negative pressure before the start of the casting process, ie before pouring liquid melt into the mold cavity. As a result, the openings and passages in the at least partially porous and gas-permeable wall of the mold are evacuated and air or other gas residues are sucked out of these porous openings. Subsequently, the mold cavity and the surrounding space of the mold is purged with a light gas of low density, which provides the advantage that this gas penetrates into the pores in the wall of the mold and fills them. In this case, a gas is selected as the light gas, which in the periodic table of the elements has an atomic number between 1 and 10 and which causes the highest possible flow rate of this gas through the pores in the wall of the mold. A special suitable gas from this group is helium. After rinsing the mold cavity and the ambient space of the mold with this light gas, a negative pressure is again generated at least in the mold cavity and then filled the liquid melt in the mold cavity. This filling process is now extremely fast, because the light gas, such as helium, is very easily and quickly displaced by the pores in the wall of the mold and can flow to the outside. This advantage is brought about by the high flow rate of the selected light gas through pores and capillary openings. For the casting process, the advantage is that no partial overpressure is built up in the individual regions of the mold cavity and between the inflowing liquid metal, so that the liquid metal can flow quickly and unhindered into the finest branches of the mold cavity. This alone achieves improved form accuracy and a higher casting speed. This also has the consequence that in all parts of the mold cavity, a better structure of the cast objects arises. Once the mold cavity is completely filled with liquid metal, the mirror of the melt in the gate region of the mold cavity is charged with another heavy gas of higher density. This gas has over the ambient space of the mold on an overpressure. As a heavy gas with a higher density while a gas is selected, which has an atomic number of at least 7 in the periodic table of the elements and in any case has a higher atomic number than the light gas with which is purged in the previous process step. The heavy gas may also be a gas mixture which has the same properties. A particularly suitable gas from this group is argon, since it has the property of flowing through the pores of the wall of the mold only at a relatively low flow rate. Experiments show that the pressure equalization between the inner wall of the mold and the outer wall of the mold takes place when applied to a side with argon 8-10 times slower than when charged with helium. This now has the advantage that the liquid melt in the mold cavity of the mold can be exposed to an increased pressure without the negative pressure in the surrounding space of the mold is markedly reduced. This leads to an even better filling of the mold cavities and an improved structure of the cast objects.
Diese Vorteile des beschriebenen erfindungsgemässen Verfahrens werden durch eine Giesseinrichtung erreicht, welche zwei Quellen für je unterschiedliche Gase mit unterschiedlicher Dichte aufweist. Weitere Vorteile ergeben sich, wenn die Giessform in einem ersten gasdichten Behälter angeordnet ist und der Schmelztiegel und die Ausgussvorrichtung in einem zweiten, vom ersten getrennten Behälter angeordnet sind. Die beiden Behälter sind über Verbindungsleitungen und Steuerventile mit der ersten, bzw. zweiten Gasquelle verbunden und es sind Pumpen zum Erzeugen eines partiellen Unter-, bzw. Überdruckes, sowie entsprechende Steuereinrichtungen vorhanden. Wird im Bereich zwischen der Ausgussöffnung am Schmelztiegel und der Eingussöffnung an der Giessform ein dritter Gasraum ausgebildet, so ergibt sich der Vorteil, dass dieser Raum relativ klein ist und dadurch der Druckaufbau über der Eingussöffnung nach dem Füllen der Giessform schneller erfolgen kann und weniger Gas benötigt wird. Auch hier sind entsprechende Steuer- und Verbindungseinrichtungen zu den Gasquellen und/oder zum ersten, bzw. zweiten gasdichten Behälter vorgesehen.These advantages of the described method according to the invention are achieved by a casting device which has two sources for different gases of different density. Further advantages arise when the mold is arranged in a first gas-tight container and the crucible and the pouring device are arranged in a second, separate from the first container. The two containers are connected via connecting lines and control valves to the first or second gas source and there are pumps for generating a partial negative or positive pressure, and corresponding control devices. If a third gas space is formed in the region between the spout opening on the crucible and the sprue opening on the casting mold, there is the advantage that this space is relatively small and thus the pressure build-up above the sprue can be faster after the casting mold has been filled and less gas is required becomes. Here too, corresponding control and connection devices to the gas sources and / or to the first or second gas-tight container are provided.
Weitere Vorteile ergeben sich, wenn der Bereich der Ausgussöffnung des Schmelztiegels und der Bereich der Eingussöffnung der Giessform in Richtung der Giessachse gegeneinander verschiebbar sind. Dies ermöglicht einerseits eine bessere Zugänglichkeit zur Giessform und zum Schmelztiegel und andererseits ein Verbinden oder Trennen des ersten oder zweiten oder dritten Behälters voneinander. Dies durch Verschieben der Geräteteile mit dem Schmelztiegel oder der Geräteteile mit der Giessform gegeneinander. Zur Abdichtung ist zwischen diesen Geräteteilen mindestens eine Gasdichtedichtung ausgebildet.Further advantages result if the region of the pouring opening of the crucible and the region of the pouring opening of the casting mold are displaceable relative to one another in the direction of the casting axis. On the one hand, this allows better accessibility to the casting mold and crucible and, on the other hand, joining or separating the first or second or third container from one another. This by moving the device parts with the crucible or the device parts with the mold against each other. For sealing, at least one gas-tight seal is formed between these parts of the device.
Der Betrieb der erfindungsgemässen Giesseinrichtung und die Anwendung des erfindungsgemässen Verfahrens in dieser Einrichtung erfolgt in zweckmässiger Weise mit einer Steuerung, welche ein Steuerprogramm zur Durchführung des Verfahrens enthält. Über diese Steuerung werden die entsprechenden Steuerventile und Steuereinrichtungen zwischen den Gasquellen und den gasdichten Behältern gesteuert. Diese Steuerung kann auch die Kontrolle der an sich bekannten Schmelz- und Abgussvorgänge übernehmen.The operation of the inventive casting device and the application of the inventive method in this device is carried out in an expedient manner with a controller which contains a control program for performing the method. This control controls the appropriate control valves and controls between the gas sources and the gas tight containers. This control can also take over the control of the known melting and Abgussvorgänge.
Im folgenden wird die Erfindung anhand von Ausführungsbeispielen unter Bezugnahme auf die beiliegenden Zeichnungen näher erläutert. Es zeigen:
- Fig. 1
- Eine erfindungsgemässe Giesseinrichtung in schematischer Darstellung,
- Fig. 2
- eine erfindungsgemässe Giesseinrichtung mit einem ersten und einem zweiten Behälter, und
- Fig. 3
- eine erfindungsgemässe Giesseinrichtung mit einem zusätzlichen dritten Gasraum.
- Fig. 1
- An inventive casting device in a schematic representation,
- Fig. 2
- a casting device according to the invention with a first and a second container, and
- Fig. 3
- an inventive casting device with an additional third gas space.
Die in
Über eine weitere Verbindungsleitung 12 ist der Innenraum 26 des Behälters 5 mit einer zweiten Gasquelle 7 verbunden, welche im beschriebenen Beispiel Argon enthält. Zwischen der zweiten Gasquelle 7 und dem ersten Behälter 5 ist eine Überdruckeinrichtung 9, beispielsweise in der Form einer Druckpumpe und ein Ventil 20 eingebaut, wobei diese Elemente wiederum über Steuerleitungen 23 mit der Steuerung 10 verbunden sind.Via a further connecting
In dem in
Nach dem Schmelzen des rohen Metalls im Schmelztiegel 1 werden die beiden Innenräume des ersten Behälters 5' und des zweiten Behälters 13 über die Vakuumpumpe 8 und die Verbindungsleitung 11 auf einen vorbestimmten Druck evakuiert. Der Innenraum des Behälters 5' bildet dabei den Umgebungsraum zur Giessform 2. Der Aufbau des Unterdruckes im Formhohlraum 3 erfolgt über den Innenraum des zweiten Behälters 13 und die Verbindungskanäle 28, welche in den Eingussbereich 17 der Giessform 2 münden. Bei dieser Anordnung ist zusätzlich zum Ventil 21 in der Verbindungsleitung 11 ein zweites Ventil 32 angeordnet, welches die Pumpe 8 mit dem Innenraum des zweiten Behälters 13 verbindet. Wenn die Giessform 2 an der Dichtung 29 am Boden 27 anliegt, sind zum Evakuieren beide Ventile 21 und 32 geöffnet, um sowohl im ersten Behälter 5' wie auch im zweiten Behälter 13 den gewünschten Unterdruck zu erzeugen und die unerwünschten Gase aus dem Formhohlraum 3 abzusaugen. Das Evakuieren kann auch bei abgesenkter Giessform 2 erfolgen, wobei dann nur eines der beiden Ventile 21, bzw. 32 geöffnet sein muss. Vor Beginn des Abgiessvorganges wird in diesem Fall die Giessform 2 mit Hilfe der Einrichtung 31 gegen die Dichtung 29 gefahren. Nach Erreichen des gewünschten Unterdruckes wird das Ventil 22 geöffnet und aus der ersten Gasquelle 6 wird ein leichtes Gas in die Behälter 5' und 13 eingelassen. Auch in diesem Beispiel wird Helium als leichtes Gas mit einer geringen Dichte verwendet. Die Zeit, welche benötigt wird, bis das leichte Gas die Poren der Giessform 2 durchflossen und gefüllt hat, ist von der Grösse der Giessform 2 und dem gewählten Formmaterial abhängig. Sobald die Poren gespült und mit Helium gefüllt sind, wird der Spülvorgang abgebrochen, indem das Ventil 22 geschlossen wird. Zur Verbesserung des Spülvorganges kann ein zusätzliches Ventil 33 eingebaut werden. In diesem Fall wird während des Spülvorganges das Ventil 32 geschlossen und über das Ventil 21 weiterhin ein Unterdruck im Umgebungsraum der Giessform 2 erzeugt. Das leichte Gas Helium strömt dann in den zweiten Behälter 13 und über die Verbindungskanäle 28 in den Formhohlraum 3 und durchdringt von innen nach aussen die Giessform 2. Bei beiden Varianten wird vor Beginn des Abgiessvorganges das Ventil 21 geschlossen und nur noch über das Ventil 32 ein vorbestimmter Unterdruck im Formhohlraum 3 aufrechterhalten. Sobald der Formhohlraum 3 mit flüssiger Schmelze gefüllt ist, wird auch das Ventil 32 geschlossen und das Ventil 20 geöffnet. Aus der zweiten Gasquelle 7 und über die Verbindungsleitung 12 wird das schwere Gas, im dargestellten Beispiel wiederum Argon, in den Innenraum des zweiten Behälters 13 eingelassen und dieses schwere Gas Argon beaufschlagt über die Verbindungskanäle 28 den Spiegel der Schmelze im Eingussbereich 17 des Formhohlraumes 3. Über die Überdruckeinrichtung 9 wird nun im zweiten Behälter 13 gegenüber dem Umgebungsraum der Giessform 2 im ersten Behälter 5' ein Überdruck aufgebaut. Dies bewirkt wiederum, dass die flüssige Schmelze im Formhohlraum 3 in die äussersten Bereiche des Formhohlraumes 3 dringt, da das leichte Gas Helium ohne grossen Widerstand über die Poren der Giessform 2 in den Umgebungsraum abfliesst. Da hier das schwere Gas Argon nur den Eingussbereich 17 des Formhohlraumes 3 beaufschlagt, ist das Abströmen des leichteren Gases Helium aus dem Formhohlraum 3 in den Umgebungsraum des Behälters 5' erleichtert, da um die Giessform 2 kein Überdruck aufgebaut wird.After melting the raw metal in the crucible 1, the two inner spaces of the first container 5 'and the
An Stelle der zu den Beispielen erwähnten Gaswechselkombinationen Helium/ Argon sind verschiedene andere Kombinationen möglich. Wenn Reingase eingesetzt werden, sind beispielsweise Kombinationen wie Stickstoff/Argon oder Helium/Stickstoff möglich. Mit Mischgasen ist beispielsweise eine Kombination von Stickstoff als leichtem Gas, mit Kohlendioxid als schwerem Gas einsetzbar.In place of the gas exchange combinations helium / argon mentioned for the examples, various other combinations are possible. If pure gases are used, combinations such as nitrogen / argon or helium / nitrogen are possible, for example. With mixed gases, for example, a combination of nitrogen can be used as a light gas, with carbon dioxide as a heavy gas.
Claims (11)
- Method for casting metallic objects in a casting device for investment casting, with at least one porous casting mould (2), a device (4) for pouring liquid metal into the casting mould (2) and with devices for producing vacuum and pressure, wherein an underpressure is produced in the mould cavity (3) and in the surrounding space of the casting mould (2) before the casting operation commences, the mould cavity (3) and the surrounding space of the casting mould (2) are then flushed with a light gas, of a low density, the pores in the walls of the casting mould (2) are filled at least partly with the light gas during flushing, an underpressure is subsequently again produced at least in the mould cavity (3), the liquid melt is then fed into the mould cavity (3) and the mould cavity (3) is filled, after the mould cavity (3) has been filled another, heavy gas, of a higher density, acts on the surface (18) of the melt in the pouring region (17) of the mould cavity (3) and an overpressure with respect to the cavities in the pores of the casting mould (2) is produced in the gas space with the heavy gas, wherein hydrogen or helium or nitrogen or oxygen or fluorine or neon is used as the light gas.
- Method according to Claim 1, characterized in that the light gas which is used is a gas whose density is lower than the density of the heavy gas by a factor of 1.2.
- Method according to Claim 1 or 2, characterized in that the heavy gas which is used is a gas from the periodic table having the atomic number of at least 7, for example argon, wherein the heavier gas has a higher atomic number than the lighter one.
- Method according to any one of Claims 1 to 3, characterized in that an underpressure of at least 100 mbar is produced before the casting operation commences, and an overpressure of at least 10 mbar with respect to the pressure in the cavities of the pores of the casting mould (2) is produced in the heavy gas at the end of the casting operation.
- Casting device for carrying out the method according to Claim 1, comprising a crucible (1) with a discharge appliance (4) and at least one casting mould (2) with a mould cavity (3), wherein the casting mould (2) consists of a material which is at least partly porous and gaspermeable, this casting mould (2) is disposed in a gastight vessel (5), this vessel (5) is connected to a first source (6) for the light gas and to a second source (7) for the heavy gas, respectively, there is a connecting line (11) to a pump (8) for producing underpressure in the vessel (5), and a device (9) for producing overpressure is additionally disposed in the connecting line (12) between the vessel (5) and the second gas source (7) and furthermore the casting device is set up so that the casting mould (2) is connected with the first source (6) for the light gas during flushing, so that the pores in the walls of the casting mould (2) are filled at least partly with the light gas during flushing.
- Casting device according to Claim 5, characterized in that the crucible (1) and the discharge appliance (4) are disposed in a second gastight vessel (13), and this vessel (13) is connected via a valve (20) and a connecting line (12) to the device (9) for producing overpressure.
- Casting device according to Claim 5 or 6, characterized in that a third gas space (34) is formed between the discharge opening (14) in the crucible (1) and the pouring opening (17) in the casting mould (2).
- Casting device according to any one of Claims 5 to 7, characterized in that the region of the discharge opening (14) in the crucible (1) and the region of the pouring opening (17) in the casting mould (2) can be displaced relative to one another in the direction of the casting axis.
- Casting device according to Claim 8, characterized in that at least one gastight seal (29) is disposed between the region of the discharge opening (14) in the crucible (1) and the region of the pouring opening (17) in the casting mould (2).
- Casting device according to Claim 7, characterized in that the third gas space (34) is connected via a connecting line (12') to the device (9) for producing overpressure and/or via a connecting line (36) to the first gas source (6).
- Casting device according to any one of Claims 5 to 10, characterized in that the device is provided with a control (10) with a control program corresponding to the method according to Claim 1 and with control valves (20, 21, 22, 32) in the connecting lines (11, 12, 19) for the gases.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CH76597 | 1997-04-03 | ||
CH76597 | 1997-04-03 | ||
PCT/CH1998/000103 WO1998045071A1 (en) | 1997-04-03 | 1998-03-17 | Method and casting device for precision casting |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0971805A1 EP0971805A1 (en) | 2000-01-19 |
EP0971805B1 EP0971805B1 (en) | 2001-11-28 |
EP0971805B2 true EP0971805B2 (en) | 2009-06-03 |
Family
ID=4194659
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP98906787A Expired - Lifetime EP0971805B2 (en) | 1997-04-03 | 1998-03-17 | Method and casting device for precision casting |
Country Status (6)
Country | Link |
---|---|
US (1) | US6253828B1 (en) |
EP (1) | EP0971805B2 (en) |
JP (1) | JP4275195B2 (en) |
CN (1) | CN1072071C (en) |
DE (1) | DE59802238D1 (en) |
WO (1) | WO1998045071A1 (en) |
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DE10327165B4 (en) * | 2003-06-15 | 2008-08-07 | Kern Gmbh Magnesium-Giesstechnik | Apparatus for producing light metal castings |
US7258158B2 (en) | 2004-07-28 | 2007-08-21 | Howmet Corporation | Increasing stability of silica-bearing material |
JP4689342B2 (en) * | 2005-05-09 | 2011-05-25 | 株式会社Ihi | Precision casting and precision casting |
US8030082B2 (en) | 2006-01-13 | 2011-10-04 | Honeywell International Inc. | Liquid-particle analysis of metal materials |
RU2312738C1 (en) * | 2006-02-09 | 2007-12-20 | Открытое акционерное общество "Новосибирский завод химконцентратов" | Investment casting method at pressure crystallization and apparatus for performing the same |
AT503391B1 (en) * | 2006-04-04 | 2008-10-15 | O St Feingussgesellschaft M B | METHOD FOR MEASURING METALLIC SHAPES AND DEVICE THEREFOR |
JP4442598B2 (en) * | 2006-10-12 | 2010-03-31 | トヨタ自動車株式会社 | Vacuum casting method and vacuum casting apparatus |
US20090065354A1 (en) * | 2007-09-12 | 2009-03-12 | Kardokus Janine K | Sputtering targets comprising a novel manufacturing design, methods of production and uses thereof |
GB2454010B (en) * | 2007-10-26 | 2009-11-11 | Castings Technology Internat | Casting a metal object |
KR101225429B1 (en) * | 2010-09-29 | 2013-01-22 | 현대제철 주식회사 | Method for purging of a upper nozzle for tundish |
CN102107259A (en) * | 2010-12-08 | 2011-06-29 | 山东梦金园珠宝首饰有限公司 | Method for pouring bowl-shaped ornament |
US8151865B1 (en) | 2011-03-30 | 2012-04-10 | General Electric Company | Method and apparatus for casting filaments |
US8590595B2 (en) | 2011-03-30 | 2013-11-26 | General Electric Company | Casting methods and apparatus |
JP5328998B1 (en) * | 2013-01-25 | 2013-10-30 | 株式会社石原産業 | Metal glass casting apparatus and casting method using the same |
US9381569B2 (en) | 2013-03-07 | 2016-07-05 | Howmet Corporation | Vacuum or air casting using induction hot topping |
CN103433479B (en) * | 2013-09-12 | 2015-07-08 | 河南正旭精密制造有限公司 | Thin-wall part casting process and casting cabin |
CN103706778A (en) * | 2013-12-31 | 2014-04-09 | 大连福岛精密零部件有限公司 | Method for utilizing non-vacuum furnace to produce high temperature alloy parts of Stirling engine |
KR101647205B1 (en) * | 2014-11-20 | 2016-08-09 | 두산중공업 주식회사 | Blowing-in Device of Inert Gas for Vacuum Casting |
CN105033200A (en) * | 2015-09-18 | 2015-11-11 | 山东钢铁股份有限公司 | Vacuum smelting-casting equipment and process |
WO2017217733A1 (en) * | 2016-06-13 | 2017-12-21 | 한국기계연구원 | Casting mold for metal sheet |
CN108555256A (en) * | 2018-06-11 | 2018-09-21 | 江苏集萃先进金属材料研究所有限公司 | A kind of devices and methods therefor improving vacuum induction ingot solidification quality |
JP7367640B2 (en) * | 2020-09-02 | 2023-10-24 | トヨタ自動車株式会社 | Blast hole analysis method, program, and casting condition derivation method |
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- 1998-03-17 DE DE59802238T patent/DE59802238D1/en not_active Expired - Lifetime
- 1998-03-17 CN CN98803885A patent/CN1072071C/en not_active Expired - Fee Related
- 1998-03-17 US US09/381,734 patent/US6253828B1/en not_active Expired - Fee Related
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Also Published As
Publication number | Publication date |
---|---|
WO1998045071A1 (en) | 1998-10-15 |
CN1251543A (en) | 2000-04-26 |
JP2001518847A (en) | 2001-10-16 |
DE59802238D1 (en) | 2002-01-10 |
JP4275195B2 (en) | 2009-06-10 |
EP0971805A1 (en) | 2000-01-19 |
CN1072071C (en) | 2001-10-03 |
EP0971805B1 (en) | 2001-11-28 |
US6253828B1 (en) | 2001-07-03 |
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