EP0461306B1 - Induction smelting furnace - Google Patents

Induction smelting furnace Download PDF

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Publication number
EP0461306B1
EP0461306B1 EP90123415A EP90123415A EP0461306B1 EP 0461306 B1 EP0461306 B1 EP 0461306B1 EP 90123415 A EP90123415 A EP 90123415A EP 90123415 A EP90123415 A EP 90123415A EP 0461306 B1 EP0461306 B1 EP 0461306B1
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EP
European Patent Office
Prior art keywords
crucible
melt
melting furnace
induction melting
pressure piston
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Expired - Lifetime
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EP90123415A
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German (de)
French (fr)
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EP0461306A1 (en
Inventor
Franz Hugo
Erwin Wanetzky
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ALD Vacuum Technologies GmbH
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ALD Vacuum Technologies GmbH
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Publication of EP0461306A1 publication Critical patent/EP0461306A1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B14/00—Crucible or pot furnaces
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B14/00—Crucible or pot furnaces
    • F27B14/06—Crucible or pot furnaces heated electrically, e.g. induction crucible furnaces with or without any other source of heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B14/00—Crucible or pot furnaces
    • F27B14/06—Crucible or pot furnaces heated electrically, e.g. induction crucible furnaces with or without any other source of heat
    • F27B14/061—Induction furnaces

Definitions

  • the invention relates to an induction melting furnace for melting difficult-to-melt metals with an induction coil wrapping around the crucible and a molded container which is surrounded by an annular chamber for receiving coolant, the induction melting furnace being surrounded by a housing provided with a vacuum connection.
  • a precision casting device for dental use with a melting chamber and a casting chamber which, under normal operating conditions, are arranged coaxially one above the other in a frame and can be pulled horizontally out of the frame during maintenance for access to lighten her inside.
  • the working chamber is divided into two chambers, namely a melting and a casting chamber. These chambers are held separately on a support frame in a vertical, coaxial arrangement.
  • the casting chamber sits in a cup-shaped cavity of a holding element, which is also carried by the frame.
  • the arrangement is designed so that the casting chamber can be pushed upwards when a gas is to be pressed into the cavity.
  • the upward movement of the casting chamber causes the melting chamber and the casting chamber to touch and form a single chamber.
  • US-A 1,540,515 already shows a melting furnace for melting difficult-to-melt metals and a molding container, the molding container being surrounded by a housing provided with a vacuum connection.
  • a method for melting small amounts of metal which uses a cold crucible for this purpose.
  • the cold melting crucible consists of an upper crucible, which forms the crucible trough by means of appropriately shaped wall segments, and a base part. Cooling channels run along the wall segments, into which the supply lines for the coolant are introduced from below.
  • the base part also has a further flange for receiving a pressure vessel. Furthermore, the individual wall elements are surrounded by a high-frequency coil. This device is not suitable for small batches, because due to the surface tension and the viscosity of the melt, the melt is not sufficiently compressed in the crucible.
  • a casting process of the type mentioned at the outset is also known (DE 39 27 998), in which an inert gas atmosphere is used to cast a material.
  • tilt casting is used so that the melt runs into the mold in the presence of a gas atmosphere.
  • the melt entering the mold must displace the gas present in the mold, before it can penetrate the smallest mold spouts. So gas inclusions or bubbles in the metal can not be excluded.
  • the invention has for its object to design the induction melting furnace with the associated mold container such that even with very small batches in the mold container of the induction melting furnace and correspondingly large surface tension of the melt, the microporosity of the metal, especially titanium, obtained after the casting process is improved.
  • the object is achieved according to the invention in that above the inlet opening of the mold container an insertable pressure stamp is provided, with which the melt is pressed out of the upper crucible through an outlet opening provided in the crucible into the mold container, and the pressure stamp is provided in the interior of the crucible is.
  • the pressure stamp accommodated in the housing is arranged such that it can move vertically in the housing and that the pressure stamp is provided with a ceramic coating on its front end which can be immersed in the melt, in order in this way to make the pressure stamp resistant and also at To make metals with a very high melting point usable. Furthermore, with a pressure stamp designed in this way, the melt can be easily pushed out through the outlet opening of the crucible and ensure sufficient compression of the melt in the molding container.
  • the invention makes it possible in a simple manner that the mold container with its inlet opening can be moved up to the outlet opening of the crucible by means of a lifting device.
  • the mold container consists of an inner and an outer container, between which the annular space is formed, which is surrounded by a porous ceramic material through which liquid argon is passed in order to cool the casting faster to reach. It is particularly advantageous that the cast is cooled very quickly in order to obtain a fine-grained structure.
  • the argon supplied to the ceramic material is evaporated, thereby extracting thermal energy from the melt.
  • the argon then discharged to the outside causes a pressure increase in the interior of the housing and thus a re-compression of the melt in the molding container. It is also possible to spray the mold container with liquid argon.
  • the induction melting furnace for melting difficult-to-melt metals is equipped with a crucible and a mold container which is surrounded by an annular chamber for receiving coolant, the induction melting furnace being surrounded by a housing provided with a vacuum connection and above the inlet opening of the molding container there is a pressure ram which can be inserted into the molding tank and with which the melt is subsequently compressed into the molding tank and the pressure ram is provided in the interior of the crucible, a floating coil being provided above the molding tank, between which the melt is formed or is held. This ensures that the melt falls into the shape below the coil after the melt flow is switched off. It is particularly advantageous that the pressure ram for recompressing the melt immediately after the melt flow has been switched off is pressed into the mold for recompression.
  • the ceramic coating frozen in the mold head is advantageously separated from the casting with the lost mold.
  • the crucible with its discharge funnel provided at the lower end of the crucible is aligned coaxially with the mold container and that the crucible tapers downwards. It is also advantageous that the crucible is surrounded by an annular chamber and that the pressure stamp is preheated.
  • 1 denotes an induction melting furnace which consists of a housing 7 which has at its upper end a cover 18 with a flange 20 which can be pressed against a further flange 21 provided on the housing part 28 via a seal 19.
  • the cover 18 can be provided with a sight glass 23 in order to observe the pouring process or the solidification of the melt.
  • a sight glass 23 in order to observe the pouring process or the solidification of the melt.
  • in the cover 18 there is also an inlet opening 22 through which the melt is introduced.
  • the housing 7 consists of an upper and a lower housing part 28 and 30.
  • the two housing parts 28 and 30 are connected to one another by two flanges 25 and 27, a seal 26 being provided between the two flanges 25 and 27.
  • the housing 7 of the induction melting furnace 1 is placed on a base 31, which is only schematically indicated in the drawing.
  • the housing 7 has a base 29 with a connecting piece 32, to which a connecting line 33 is connected, via which argon is supplied.
  • the connecting line 33 is in flow connection via a reservoir (not shown in the drawing) for receiving argon.
  • the connecting line 33 is led into the interior of the housing 7 and connected to an inlet opening 34 of the molded container 4.
  • the molded container 4 has a can 35 in its interior. Between the can 35 and the outer wall 37 of the molded container 4, an annular space 5 is formed, which serves to receive a porous ceramic material. Argon can be passed through the porous ceramic material 36 in order to accelerate the cooling process during the solidification process of the melt. After the evaporation process, the argon is passed outside through the opening 44 into the interior of the housing 7, so that pressure can build up in the interior and therefore also above the melt. This ensures sufficient recompaction of the melt during the solidification process.
  • the mold container 4 there is a crucible 3 for melting metals which are difficult to melt, for example titanium.
  • the crucible or cold crucible 3 can be constructed in segments in its interior.
  • the crucible 3 tapers downward and has an outlet opening 11 at its lower end, so that the melt can be fed to the interior of the molded container 4 via the bottom tapping.
  • the upper end of the crucible 3 is designed as an inlet opening 40. It is also possible to close the inlet opening 40 of the crucible 3 with a pressure cap, not shown in the drawing, in order to conduct argon into the interior of the crucible via a corresponding inlet opening and thereby build up the desired pressure above the melt.
  • a pressure ram 9 in the interior of the crucible 3, which can be inserted through an inlet opening 40 of the crucible 3.
  • the pressure stamp 9 is made of high temperature resistant metal. It tapers towards the front and has a ceramic coating 10 at its downward end.
  • the melt is compressed again by pressing the melt by means of the pressure ram 9.
  • the pressure plunger 9 is guided through the outlet opening 11 and then into the inlet opening 13 of the mold container 4.
  • argon is passed into the annular space 5, as already explained. The rapid evaporation of the argon results in a rapid pressure increase when using a titanium melt of approx. 10 bar. Solidification under pressure improves microporosity.
  • a flange 41 connected to a vacuum pump (not shown in the drawing) with a nozzle 6, via which the housing 7 can be evacuated.
  • the melted material received in the crucible 3 is melted with an induction coil 2 wrapping around the crucible 3.
  • the induction coil 2 includes a yoke 24 which surrounds the induction coil 2 and which is at a sufficient distance from the outer wall of the crucible 3 so that thermal energy is not supplied to the wall but only to the melt.
  • the molded container 4 provided below the crucible 3 is arranged on a table 42 which is fastened on a lifting column 43.
  • the lifting column 43 is guided through the connecting piece 32 and is of hollow design. In its interior, it receives the connecting line 33 via which the argon is fed to the annular space 5 of the molded container 4.
  • the molded container 4 can be placed exactly below the crucible 3.
  • the melt is produced and tapped as described below.
  • the melting material is introduced into the housing 7 or into the melting crucible 3 and then the housing 7 is closed by means of the cover 18.
  • the induction melting furnace 1 is then evacuated via a vacuum pump connected to the flange 41 and not shown in the drawing. Now the melting material under the existing vacuum can be melted by means of the induction coil 2. After the melting material has completely melted, tapping takes place via the outlet opening 11 and the melting material is passed into the molding container 4. By means of the pressure ram 9, the entire melt material is pressed into the molding container without further notice. This ensures that the molding container is completely and evenly loaded.
  • argon is now fed into the annular space 5 via the connecting line 33 and thermal energy is removed from the melt by the rapid evaporation of the argon.
  • the pressure in the housing 7 is increased, since the annular space 5 is connected to the interior of the housing 7 via the opening 44.
  • the rapid rise in pressure to approx. 10 bar during the solidification process ensures good microstructure formation, since the normally occurring dendrites cannot form.
  • the gas pressure and the pressure ram 9 also ensure that even the finest ramifications of the form are filled with melt material.
  • the arrangement according to the invention is particularly suitable for very small batches, in particular for titanium in the gram range, that is to say for casting sizes such as are customary in dentures.
  • the embodiment shown in Figure 2 differs only slightly from the embodiment of Figure 1.
  • a coil 2 a is provided in the ring coil 2 according to FIG.
  • the melt falls into the mold container 4 provided below the crucible 3.
  • the pressure ram 9 can be preheated for post-compression and can be pressed into the mold immediately after the melt flow has been switched off.
  • the ceramic coating frozen in the stamp 9 is then separated from the casting with the lost shape.

Abstract

The invention relates to an induction melting furnace 1 for metals which are difficult to melt including an induction coil 2 surrounding the crucible 3 and a mold receptacle 4 surrounded by an annular chamber 5 to hold the cooling agent. The crucible 3 is disposed in a housing 7 provided with a vacuum connection 6. In order to improve the microporous nature, the melt contained in the mold receptacle 4 is compressed by means of a pressure which is build up in the mold receptacle 4 prior to the cooling.

Description

Die Erfindung bezieht sich auf einen Induktionsschmelzofen zum Schmelzen von schwer schmelzbaren Metallen mit einer den Schmelztiegel umschlingenden Induktionsspule und einem Formbehälter, der von einer Ringkammer zur Aufnahme von Kühlmittel umgeben ist, wobei der Induktionsschmelzofen von einem mit einem Vakuumanschluß versehenen Gehäuse umgeben ist.The invention relates to an induction melting furnace for melting difficult-to-melt metals with an induction coil wrapping around the crucible and a molded container which is surrounded by an annular chamber for receiving coolant, the induction melting furnace being surrounded by a housing provided with a vacuum connection.

Aus der DE A1 3 108 336 ist eine Präzisions - Gußvorrichtung für zahnärztliche Verwendung mit einer Schmelz- und einer Gießkammer bekannt, die unter normalen Betriebsbedingungen in einem Rahmen koaxial übereinander angeordnet sind und während der Wartung horizontal aus dem Rahmen herausgezogen werden können, um den Zugang zu ihrem Inneren zu erleichtern. Bei der bekannten Vorrichtung ist die Arbeitskammer in zwei Kammern unterteilt, nämlich in eine Schmelz- und eine Gießkammer. Diese Kammern werden gesondert auf einem Tragrahmen in vertikaler, koaxialer Anordnung gehalten. Die Gießkammer sitzt in einem becherförmigen Hohlraum eines Halteelementes, das ebenfalls vom Rahmen getragen wird. Die Anordnung ist so ausgebildet, daß die Gießkammer nach oben geschoben werden kann, wenn ein Gas in den Hohlraum gedrückt werden soll. Die Aufwärtsbewegung der Gießkammer führt dazu, daß sich die Schmelzkammer und die Gießkammer berühren und eine einzige Kammer bilden.From DE A1 3 108 336 a precision casting device for dental use with a melting chamber and a casting chamber is known which, under normal operating conditions, are arranged coaxially one above the other in a frame and can be pulled horizontally out of the frame during maintenance for access to lighten her inside. In the known device, the working chamber is divided into two chambers, namely a melting and a casting chamber. These chambers are held separately on a support frame in a vertical, coaxial arrangement. The casting chamber sits in a cup-shaped cavity of a holding element, which is also carried by the frame. The arrangement is designed so that the casting chamber can be pushed upwards when a gas is to be pressed into the cavity. The upward movement of the casting chamber causes the melting chamber and the casting chamber to touch and form a single chamber.

Die US-A 1,540,515 zeigt bereits einen Schmelzofen zum Schmelzen von schwer schmelzbaren Metallen und einem Formbehälter, wobei der Formbehälter von einem mit einem Vakuumanschluß versehenen Gehäuse umgeben ist.US-A 1,540,515 already shows a melting furnace for melting difficult-to-melt metals and a molding container, the molding container being surrounded by a housing provided with a vacuum connection.

Es ist bereits ein Verfahren (EP 345 541 A2) zum Schmelzen kleiner Metallmengen bekannt, das sich hierzu eines Kaltschmelztiegels bedient. Der Kaltschmelztiegel besteht aus einem oberen, die Tiegelmulde durch entsprechend geformte Wandsegmente bildenden Tiegel und einem Basisteil. An den Wandsegmenten laufen Kühlkanäle entlang, in die von unten die Zuführungsleitungen für das Kühlmittel eingebracht sind. Das Basisteil weist ferner einen weiteren Flansch zur Aufnahme eines Druckbehälters auf. Ferner werden die einzelnen Wandelemente von einer Hochfrequenzspule umgeben. Diese Vorrichtung ist nicht für kleine Chargen geeignet, da aufgrund der Oberflächenspannung und der Viskosität der Schmelze keine ausreichende Verdichtung der Schmelze im Tiegel erfolgt.A method (EP 345 541 A2) for melting small amounts of metal is already known, which uses a cold crucible for this purpose. The cold melting crucible consists of an upper crucible, which forms the crucible trough by means of appropriately shaped wall segments, and a base part. Cooling channels run along the wall segments, into which the supply lines for the coolant are introduced from below. The base part also has a further flange for receiving a pressure vessel. Furthermore, the individual wall elements are surrounded by a high-frequency coil. This device is not suitable for small batches, because due to the surface tension and the viscosity of the melt, the melt is not sufficiently compressed in the crucible.

Es ist ferner ein Gießverfahren der eingangs aufgeführten Art bekannt (DE 39 27 998), wobei zum Gießen eines Materials in einer inerten Gasatmosphäre gearbeitet wird. Bei diesem Gießverfahren wird im Kippguß gearbeitet, so daß die Schmelze bei vorhandener Gasatmosphäre in die Form einläuft. Die in die Form einlaufende Schmelze muß das in der Form vorhandene Gas verdrängen, bevor es in die kleinsten Formausläufe eindringen kann. So können Gaseinschlüsse bzw. Blasenbildung im Metall nicht ausgeschlossen werden.A casting process of the type mentioned at the outset is also known (DE 39 27 998), in which an inert gas atmosphere is used to cast a material. In this casting process, tilt casting is used so that the melt runs into the mold in the presence of a gas atmosphere. The melt entering the mold must displace the gas present in the mold, before it can penetrate the smallest mold spouts. So gas inclusions or bubbles in the metal can not be excluded.

Demgegenüber liegt der Erfindung die Aufgabe zugrunde, den Induktionsschmelzofen mit dem zugehörigen Formbehälter derart auszubilden, daß auch bei sehr kleinen Chargen im Formbehälter des Induktionsschmelzofens und entsprechend großer Oberflächenspannung der Schmelze die Mikroporosität des nach dem Gießvorgang gewonnenen Metalls, insbesondere Titan, verbessert wird.In contrast, the invention has for its object to design the induction melting furnace with the associated mold container such that even with very small batches in the mold container of the induction melting furnace and correspondingly large surface tension of the melt, the microporosity of the metal, especially titanium, obtained after the casting process is improved.

Gelöst wird die Aufgabe erfindungsgemäß dadurch, daß oberhalb der Einlaßöffnung des Formbehälters ein in den Formbehälter einführbarer Druckstempel vorgesehen ist, mit dem die Schmelze aus dem oberen Schmelztiegel durch eine im Schmelztiegel vorgesehene Auslaßöffnung in den Formbehälter gedrückt wird, und der Druckstempel im Innenraum des Schmelztiegels vorgesehen ist. Hierdurch wird sichergestellt, daß auch bei sehr kleinen Chargen, die in einen Formbehälter eingegeben werden, und trotz hoher Viskosität der Schmelze und der damit verbundenen Oberflächenspannung eine gute Verdichtung der Schmelze im Formbehälter erfolgt, da durch den oberhalb der Schmelze aufgebauten Druck sichergestellt wird, daß die Schmelze den Formbehälter bei Vermeidung von Gaseinschlüssen gleichmäßig ausfüllt. So wird einer Hohlraumbildung durch Dendritenwachstum vorgebeugt, da die Schmelze durch den entsprechenden Druck in kleinste, durch die Dendriten gebildete Hohlräume nachfließen kann. Durch den Einsatz eines Druckstempels ist es auf einfache Weise möglich, während des Erstarrungsvorgangs der Schmelze eine gute Verdichtung der Schmelze herbeizuführen. Auf diese Weise lassen sich auch sehr kleine Chargen vergießen. Die bei diesen kleinen Chargen bislang als problematisch dargestellte Oberflächenspannung der Schmelze braucht daher nicht beachtet zu werden, da mittels des Druckstempels ein Nachverdichten der in den Formbehälter abgegossenen Schmelze möglich ist.The object is achieved according to the invention in that above the inlet opening of the mold container an insertable pressure stamp is provided, with which the melt is pressed out of the upper crucible through an outlet opening provided in the crucible into the mold container, and the pressure stamp is provided in the interior of the crucible is. This ensures that even with very small batches that are fed into a mold container and despite the high viscosity of the melt and the associated surface tension, the melt in the mold container is well compacted, since the pressure built up above the melt ensures that the melt fills the mold container evenly while avoiding gas inclusions. Cavity formation by dendrite growth is thus prevented, since the melt can flow into the smallest voids formed by the dendrites due to the corresponding pressure. By using a pressure stamp it is simple possible to bring about a good compression of the melt during the solidification process of the melt. Even very small batches can be poured in this way. The surface tension of the melt, which has so far been shown to be problematic in these small batches, therefore need not be taken into account, since it is possible to recompress the melt poured into the mold container by means of the pressure stamp.

Gemäß eines besonderen Merkmals der erfindungsgemäßen Lösung ist schließlich vorgesehen, daß der im Gehäuse aufgenommene Druckstempel höhenbeweglich im Gehäuse angeordnet ist und daß der Druckstempel an seinem vorderen in die Schmelze eintauchbaren Ende mit einem Keramiküberzug versehen ist, um auf diese Weise den Druckstempel widerstandsfähig und auch bei Metallen mit sehr hohem Schmelzpunkt einsetzbar zu machen. Ferner läßt sich mit einem derart ausgebildeten Druckstempel die Schmelze ohne weiteres durch die Auslaßöffnung des Schmelztiegels herausdrücken und eine ausreichende Verdichtung der Schmelze im Formbehälter sicherstellen.According to a special feature of the solution according to the invention it is finally provided that the pressure stamp accommodated in the housing is arranged such that it can move vertically in the housing and that the pressure stamp is provided with a ceramic coating on its front end which can be immersed in the melt, in order in this way to make the pressure stamp resistant and also at To make metals with a very high melting point usable. Furthermore, with a pressure stamp designed in this way, the melt can be easily pushed out through the outlet opening of the crucible and ensure sufficient compression of the melt in the molding container.

Durch die Erfindung wird es auf einfache Weise möglich, daß der Formbehälter mit seiner Einlaßöffnung mittels einer Hubeinrichtung an die Auslaßöffnung des Schmelztiegels heranfahrbar ist.The invention makes it possible in a simple manner that the mold container with its inlet opening can be moved up to the outlet opening of the crucible by means of a lifting device.

Von besonderer Bedeutung ist bei der erfindungsgemäßen Vorrichtung, daß der Formbehälter aus einem inneren und einem äußeren Behälter besteht, zwischen denen der Ringraum gebildet ist, der von einem porösen Keramikstoff umgeben ist, durch den flüssiges Argon geleitet wird, um ein schnelleres Abkühlen des Gußstücks zu erreichen. Es ist besonders vorteilhaft, daß der Abguß sehr schnell abgekühlt wird, um ein feinkörniges Gefüge zu erhalten. Das dem Keramikwerkstoff zugeführte Argon wird verdampft und entzieht dadurch der Schmelze Wärmeenergie. Das dann nach außen abgeführte Argon verursacht eine Druckerhöhung im Inneren des Gehäuses und dadurch eine Nachverdichtung der Schmelze im Formbehälter. Ferner ist es möglich, den Formbehälter mit flüssigem Argon zu besprühen. Durch die ebenfalls rasche Verdampfung des Argons erfolgt ein schneller Druckanstieg bis auf den Argon-Versorgungsdruck (vorteilhafterweise von etwa 10 bar), zum Beispiel bei einer Titanschmelze. Durch die Erstarrung bei Überdruck wird ferner die Mikroporosität des Gießteils verbessert.It is of particular importance in the device according to the invention that the mold container consists of an inner and an outer container, between which the annular space is formed, which is surrounded by a porous ceramic material through which liquid argon is passed in order to cool the casting faster to reach. It is particularly advantageous that the cast is cooled very quickly in order to obtain a fine-grained structure. The argon supplied to the ceramic material is evaporated, thereby extracting thermal energy from the melt. The argon then discharged to the outside causes a pressure increase in the interior of the housing and thus a re-compression of the melt in the molding container. It is also possible to spray the mold container with liquid argon. Due to the likewise rapid evaporation of the argon, there is a rapid rise in pressure up to the argon supply pressure (advantageously of approximately 10 bar), for example in the case of a titanium melt. The microporosity of the cast part is also improved by the solidification under excess pressure.

In weiterer Ausgestaltung der Erfindung ist es vorteilhaft, daß der Induktionsschmelzofen zum Schmelzen von schwer schmelzbaren Metallen mit einem Schmelztiegel und einem Formbehälter ausgestattet ist, der von einer Ringkammer zur Aufnahme von Kühlmittel umgeben ist, wobei der Induktionsschmelzofen von einem mit einem Vakuumanschluß versehenen Gehäuse umgeben ist und oberhalb der Einlaßöffnung des Formbehälters ein in den Formbehälter einführbarer Druckstempel vorgesehen ist, mit dem die Schmelze in den Formbehälter nachverdichtet wird und der Druckstempel im Innenraum des Schmelztiegels vorgesehen ist, wobei oberhalb des Formbehälters eine Schwebespule vorgesehen ist, zwischen der die Schmelze gebildet bzw. gehalten wird. Hierdurch wird sichergestellt, daß die Schmelze nach Abschalten des Schmelzstroms in die unterhalb der Spule befindliche Form fällt. Dabei ist es besonders vorteilhaft, daß der Druckstempel zum Nachverdichten der Schmelze direkt nach Abschalten des Schmelzstroms in die Form zum Nachverdichten gedrückt wird. Der im Formenkopf eingefrorene Keramiküberzug wird in vorteilhafter Weise mit der verlorenen Form vom Gußteil getrennt.In a further embodiment of the invention, it is advantageous that the induction melting furnace for melting difficult-to-melt metals is equipped with a crucible and a mold container which is surrounded by an annular chamber for receiving coolant, the induction melting furnace being surrounded by a housing provided with a vacuum connection and above the inlet opening of the molding container there is a pressure ram which can be inserted into the molding tank and with which the melt is subsequently compressed into the molding tank and the pressure ram is provided in the interior of the crucible, a floating coil being provided above the molding tank, between which the melt is formed or is held. This ensures that the melt falls into the shape below the coil after the melt flow is switched off. It is particularly advantageous that the pressure ram for recompressing the melt immediately after the melt flow has been switched off is pressed into the mold for recompression. The ceramic coating frozen in the mold head is advantageously separated from the casting with the lost mold.

In weiterer Ausgestaltung der Erfindung ist es besonders vorteilhaft, daß der Schmelztiegel mit seinem am unteren Ende des Schmelztiegels vorgesehenen Auslauftrichter koaxial zum Formbehälter ausgerichtet ist und daß sich der Schmelztiegel nach unten hin verjüngt. Vorteilhaft ist ferner, daß der Schmelztiegel von einer Ringkammer umgeben ist und daß der Druckstempel vorgeheizt wird.In a further embodiment of the invention, it is particularly advantageous that the crucible with its discharge funnel provided at the lower end of the crucible is aligned coaxially with the mold container and that the crucible tapers downwards. It is also advantageous that the crucible is surrounded by an annular chamber and that the pressure stamp is preheated.

Weitere Merkmale der Erfindung sind in der Beschreibung der Figuren dargestellt, wobei bemerkt wird, daß alle Einzelmerkmale und alle Kombinationen von Einzelmerkmalen erfindungswesentlich sind.Further features of the invention are shown in the description of the figures, it being noted that all the individual features and all combinations of individual features are essential to the invention.

In den Figuren ist die Erfindung an einer Ausführungsform beispielsweise dargestellt, ohne auf diese Ausführungsform beschränkt zu sein. Es zeigt:

Figur 1
einen Induktionsschmelzofen mit einem Kalttiegel und einem darunter angeordneten Formbehälter zur Aufnahme des Schmelzguts,
Figur 2
ein weiteres Ausführungsbeispiel des Induktionsschmelzofens mit dem zugehörigen Formbehälter.
In the figures, the invention is shown in one embodiment, for example, without being limited to this embodiment. It shows:
Figure 1
an induction melting furnace with a cold crucible and a mold container arranged underneath for receiving the melting material,
Figure 2
another embodiment of the induction melting furnace with the associated mold container.

In der Zeichnung ist mit 1 ein Induktionsschmelzofen bezeichnet, der aus einem Gehäuse 7 besteht, das an seinem oberen Ende einen Deckel 18 mit einem Flansch 20 aufweist, der über eine Dichtung 19 gegen einen weiteren am Gehäuseteil 28 vorgesehenen Flansch 21 anpreßbar ist.In the drawing, 1 denotes an induction melting furnace which consists of a housing 7 which has at its upper end a cover 18 with a flange 20 which can be pressed against a further flange 21 provided on the housing part 28 via a seal 19.

Der Deckel 18 kann mit einem Schauglas 23 versehen sein, um den Gießvorgang bzw. die Erstarrung der Schmelze zu beobachten. Im Deckel 18 befindet sich ferner eine Einlaßöffnung 22, durch die die Schmelze eingeführt wird.The cover 18 can be provided with a sight glass 23 in order to observe the pouring process or the solidification of the melt. In the cover 18 there is also an inlet opening 22 through which the melt is introduced.

Das Gehäuse 7 besteht aus einem oberen und einem unteren Gehäuseteil 28 und 30. Die beiden Gehäuseteile 28 und 30 sind durch zwei Flansche 25 und 27 miteinander verbunden, wobei zwischen den beiden Flanschen 25 und 27 eine Dichtung 26 vorgesehen ist.The housing 7 consists of an upper and a lower housing part 28 and 30. The two housing parts 28 and 30 are connected to one another by two flanges 25 and 27, a seal 26 being provided between the two flanges 25 and 27.

Das Gehäuse 7 des Induktionsschmelzofens 1 ist auf einem in der Zeichnung nur schematisch angedeuteten Sockel 31 abgestellt. Das Gehäuse 7 weist einen Boden 29 mit einem Stutzen 32 auf, an den eine Anschlußleitung 33 angeschlossen ist, über die Argon zugeführt wird. Die Anschlußleitung 33 steht über ein in der Zeichnung nicht dargestelltes Reservoir zur Aufnahme von Argon in Durchflußverbindung. Die Anschlußleitung 33 ist in das Innere des Gehäuses 7 hineingeführt und an eine Einlaßöffnung 34 des Formbehälters 4 angeschlossen.The housing 7 of the induction melting furnace 1 is placed on a base 31, which is only schematically indicated in the drawing. The housing 7 has a base 29 with a connecting piece 32, to which a connecting line 33 is connected, via which argon is supplied. The connecting line 33 is in flow connection via a reservoir (not shown in the drawing) for receiving argon. The connecting line 33 is led into the interior of the housing 7 and connected to an inlet opening 34 of the molded container 4.

Der Formbehälter 4 weist in seinem Innenraum eine Kanne 35 auf. Zwischen der Kanne 35 und der äußeren Wand 37 des Formbehälters 4 ist ein Ringraum 5 gebildet, der zur Aufnahme eines porösen Keramikwerkstoffs dient. Durch den porösen Keramikwerkstoff 36 kann, um beim Erstarrungsprozeß der Schmelze den Abkühlungsvorgang zu beschleunigen, Argon geleitet werden. Das Argon wird nach dem Verdampfungsvorgang über die Öffnung 44 nach außen in den Innenraum des Gehäuses 7 geleitet, so daß sich im Innenraum und dadurch auch oberhalb der Schmelze Druck aufbauen kann. Hierdurch wird eine ausreichende Nachverdichtung der Schmelze während des Estarrungsvorgangs sichergestellt.The molded container 4 has a can 35 in its interior. Between the can 35 and the outer wall 37 of the molded container 4, an annular space 5 is formed, which serves to receive a porous ceramic material. Argon can be passed through the porous ceramic material 36 in order to accelerate the cooling process during the solidification process of the melt. After the evaporation process, the argon is passed outside through the opening 44 into the interior of the housing 7, so that pressure can build up in the interior and therefore also above the melt. This ensures sufficient recompaction of the melt during the solidification process.

Oberhalb des Formbehälters 4 befindet sich ein Schmelztiegel 3 zum Schmelzen von schwer schmelzbaren Metallen, beispielsweise Titan. Der Schmelztiegel bzw. Kalttiegel 3 kann in seinem Inneren segmentartig aufgebaut sein. Der Schmelztiegel 3 verjüngt sich nach unten und weist an seinem unteren Ende eine Auslaßöffnung 11 auf, so daß die Schmelze über den Bodenabstich dem Innenraum des Formbehälters 4 zugeführt werden kann.Above the mold container 4 there is a crucible 3 for melting metals which are difficult to melt, for example titanium. The crucible or cold crucible 3 can be constructed in segments in its interior. The crucible 3 tapers downward and has an outlet opening 11 at its lower end, so that the melt can be fed to the interior of the molded container 4 via the bottom tapping.

Das obere Ende des Schmelztiegels 3 ist als Einlaßöffnung 40 ausgebildet. Es ist auch möglich, die Einlaßöffnung 40 des Schmelztiegels 3 mit einer in der Zeichnung nicht dargestellten Druckkappe zu verschließen, um über eine entsprechende Einlaßöffnung Argon in den Innenraum des Schmelztiegels zu leiten und dadurch den gewünschten Druck oberhalb der Schmelze aufzubauen.The upper end of the crucible 3 is designed as an inlet opening 40. It is also possible to close the inlet opening 40 of the crucible 3 with a pressure cap, not shown in the drawing, in order to conduct argon into the interior of the crucible via a corresponding inlet opening and thereby build up the desired pressure above the melt.

Wie aus Figur 1 ferner hervorgeht, befindet sich während des Abstichs im Innenraum des Schmelztiegels 3 ein Druckstempel 9, der durch eine Einlaßöffnung 40 des Schmelztiegels 3 eingeführt werden kann. Der Druckstempel 9 besteht aus hochtemperaturbeständigem Metall. Er verjüngt sich nach vorne und weist an seinem nach unten gerichteten Ende einen Keramiküberzug 10 auf. Nach dem Vergießen des Schmelzmaterials in den Formbehälter 4 wird durch Andrücken der Schmelze mittels des Druckstempels 9 eine Nachverdichtung der Schmelze vorgenommen. Der Druckstempel 9 wird hierzu durch die Auslaßöffnung 11 geführt und dann in die Einlaßöffnung 13 des Formbehälters 4. Um ein schnelles Abkühlen der Form zu erreichen, wird - wie bereits erläutert - Argon in den Ringraum 5 geleitet. Durch die rasche Verdampfung des Argons erfolgt ein schneller Druckanstieg bei Verwendung einer Titanschmelze von ca. 10 bar. Durch Erstarrung unter Druck wird eine verbesserte Mikroporosität erzielt.As can also be seen from FIG. 1, during the tapping there is a pressure ram 9 in the interior of the crucible 3, which can be inserted through an inlet opening 40 of the crucible 3. The pressure stamp 9 is made of high temperature resistant metal. It tapers towards the front and has a ceramic coating 10 at its downward end. After the melt material has been poured into the mold container 4, the melt is compressed again by pressing the melt by means of the pressure ram 9. For this purpose, the pressure plunger 9 is guided through the outlet opening 11 and then into the inlet opening 13 of the mold container 4. To achieve rapid cooling of the mold, argon is passed into the annular space 5, as already explained. The rapid evaporation of the argon results in a rapid pressure increase when using a titanium melt of approx. 10 bar. Solidification under pressure improves microporosity.

Im Bereich des Bodens 29 des unteren Gehäuseteils 30 befindet sich ein an eine in der Zeichnung nicht dargestellte Vakuumpumpe angeschlossener Flansch 41 mit einem Stutzen 6, über den das Gehäuse 7 evakuiert werden kann.In the area of the bottom 29 of the lower housing part 30 there is a flange 41 connected to a vacuum pump (not shown in the drawing) with a nozzle 6, via which the housing 7 can be evacuated.

Das in dem Schmelztiegel 3 aufgenommene Schmelzgut wird mit einer den Schmelztiegel 3 umschlingenden Induktionsspule 2 geschmolzen. Zu der Induktionsspule 2 gehört ein Joch 24, das die Induktionsspule 2 umgibt und das einen ausreichenden Abstand zur Außenwand des Schmelztiegels 3 aufweist, damit nicht der Wand, sondern nur der Schmelze Wärmeenergie zugeführt wird.The melted material received in the crucible 3 is melted with an induction coil 2 wrapping around the crucible 3. The induction coil 2 includes a yoke 24 which surrounds the induction coil 2 and which is at a sufficient distance from the outer wall of the crucible 3 so that thermal energy is not supplied to the wall but only to the melt.

Der unterhalb des Schmelztiegels 3 vorgesehene Formbehälter 4 ist auf einem Tisch 42 angeordnet, der auf einer Hubsäule 43 befestigt ist. Die Hubsäule 43 ist durch den Stutzen 32 geführt und hohlförmig ausgebildet. Sie nimmt in ihrem Inneren die Anschlußleitung 33 auf, über die das Argon dem Ringraum 5 des Formbehälters 4 zugeführt wird. Mittels der Hubeinrichtung bzw. der Hubsäule 43 läßt sich der Formbehälter 4 genau unterhalb des Schmelztiegels 3 plazieren.The molded container 4 provided below the crucible 3 is arranged on a table 42 which is fastened on a lifting column 43. The lifting column 43 is guided through the connecting piece 32 and is of hollow design. In its interior, it receives the connecting line 33 via which the argon is fed to the annular space 5 of the molded container 4. By means of the lifting device or the lifting column 43, the molded container 4 can be placed exactly below the crucible 3.

Die Herstellung der Schmelze und der Abstich erfolgt wie nachstehend beschrieben.The melt is produced and tapped as described below.

Zuerst wird in das Gehäuse 7 bzw. in den Schmelztiegel 3 das Schmelzgut eingebracht und dann das Gehäuse 7 mittels des Deckels 18 verschlossen. Anschließend wird der Induktionsschmelzofen 1 über eine an den Flansch 41 angeschlossene, in der Zeichnung nicht dargestellte Vakuumpumpe evakuiert. Nun kann das Schmelzgut unter dem bestehenden Vakuum mittels der Induktionsspule 2 geschmolzen werden. Nachdem das Schmelzgut vollständig geschmolzen ist, erfolgt über die Auslaßöffnung 11 der Abstich, und das Schmelzgut wird in den Formbehälter 4 geleitet. Mittels des Druckstempels 9 wird das gesamte Schmelzgut ohne weiteres in den Formbehälter gedrückt. Hierdurch wird sichergestellt, daß der Formbehälter vollständig und gleichmäßig beschickt wird.First, the melting material is introduced into the housing 7 or into the melting crucible 3 and then the housing 7 is closed by means of the cover 18. The induction melting furnace 1 is then evacuated via a vacuum pump connected to the flange 41 and not shown in the drawing. Now the melting material under the existing vacuum can be melted by means of the induction coil 2. After the melting material has completely melted, tapping takes place via the outlet opening 11 and the melting material is passed into the molding container 4. By means of the pressure ram 9, the entire melt material is pressed into the molding container without further notice. This ensures that the molding container is completely and evenly loaded.

Um den Abkühlungsvorgang zu beschleunigen, wird nun Argon über die Anschlußleitung 33 in den Ringraum 5 geführt und durch die schnelle Verdampfung des Argons der Schmelze Wärmeenergie entzogen. Gleichzeitig wird der Druck im Gehäuse 7 erhöht, da der Ringraum 5 über die Öffnung 44 mit dem Innenraum des Gehäuses 7 in Verbindung steht. Durch den schnellen Druckanstieg auf ca. 10 bar während des Erstarrungsvorgangs wird eine gute Gefügeausbildung sichergestellt, da sich die normalerweise auftretenden Dendriten nicht bilden können. Durch den Gasdruck und durch den Druckstempel 9 wird außerdem sichergestellt, daß auch feinste Verästelungen der Form mit Schmelzgut ausgefüllt werden.In order to accelerate the cooling process, argon is now fed into the annular space 5 via the connecting line 33 and thermal energy is removed from the melt by the rapid evaporation of the argon. At the same time, the pressure in the housing 7 is increased, since the annular space 5 is connected to the interior of the housing 7 via the opening 44. The rapid rise in pressure to approx. 10 bar during the solidification process ensures good microstructure formation, since the normally occurring dendrites cannot form. The gas pressure and the pressure ram 9 also ensure that even the finest ramifications of the form are filled with melt material.

Nach dem Erstarrungsprozeß wird der Druck heruntergefahren, das Gehäuse 7 geöffnet und die Form entnommen. Danach wird eine neue Form eingesetzt, und der Gießvorgang kann wiederholt werden. Die erfindungsgemäße Anordnung eignet sich besonders für sehr kleine Chargen, insbesondere für Titan im Grammbereich, also für Gußstückgrößen, wie sie bei Zahnersatz üblich sind.After the solidification process, the pressure is reduced, the housing 7 is opened and the mold is removed. Then a new mold is inserted and the casting process can be repeated. The arrangement according to the invention is particularly suitable for very small batches, in particular for titanium in the gram range, that is to say for casting sizes such as are customary in dentures.

Das in Figur 2 dargestellte Ausführungbeispiel unterscheidet sich nur geringfügig vom Ausführungsbeispiel gemäß Figur 1. Im Induktionsschmelzofen 1 ist anstelle der Ringspule 2 gemäß Figur 1 eine Schwebespule 2a vorgesehen. Die Schmelze fällt bei diesem Gießverfahren nach Abschalten der Schwebespule 2a in den unterhalb des Schmelztiegels 3 vorgesehenen Formbehälter 4. Der Druckstempel 9 kann zum Nachverdichten vorgeheizt werden und direkt nach Abschalten des Schmelzstroms zum Nachverdichten in die Form eingepreßt werden. Der im Druckstempel 9 eingefrorene Keramiküberzug wird dann mit der verlorenen Form vom Gußteil getrennt.The embodiment shown in Figure 2 differs only slightly from the embodiment of Figure 1. In the induction melting furnace 1 is instead a coil 2 a is provided in the ring coil 2 according to FIG. In this casting process, after the floating coil 2a has been switched off, the melt falls into the mold container 4 provided below the crucible 3. The pressure ram 9 can be preheated for post-compression and can be pressed into the mold immediately after the melt flow has been switched off. The ceramic coating frozen in the stamp 9 is then separated from the casting with the lost shape.

BezugszeichenlisteReference list

11
InduktionsschmelzofenInduction melting furnace
22nd
InduktionsspuleInduction coil
2a2a
SchwebespuleFloating coil
33rd
SchmelztiegelMelting pot
44th
FormbehälterMolded container
55
RingraumAnnulus
66
StutzenSupport
77
Gehäusecasing
99
DruckstempelPressure stamp
1010th
KeramiküberzugCeramic coating
1111
AuslaßöffnungOutlet opening
1212th
HubeinrichtungLifting device
1313
EinlaßöffnungInlet opening
1818th
Deckelcover
1919th
Dichtungpoetry
2020th
Flanschflange
2121
Flanschflange
2222
EinlaßöffnungInlet opening
2323
SchauglasSight glass
2424th
Jochyoke
2525th
Flanschflange
2626
RingdichtungRing seal
2727
Flanschflange
2828
GehäuseteilHousing part
2929
Bodenground
3030th
GehäuseteilHousing part
3131
Sockelbase
3232
StutzenSupport
3333
AnschlußleitungConnecting cable
3434
EinlaßöffnungInlet opening
3535
KanneJug
3636
KeramikCeramics
3737
Wandwall
4040
EinlaßöffnungInlet opening
4141
Flanschflange
4242
Tischtable
4343
HubsäuleLifting column
4444
Öffnungopening

Claims (11)

  1. Induction melting furnace (1) for melting metals which are difficult to melt, with an induction coil surrounding the crucible (3) and a mold receptacle (4) surrounded by an annular chamber (5) for holding a coolant, whereby the induction melting furnace (1) is surrounded by a housing (7) provided with a vacuum connection (6), characterized in that, above the inlet opening (13) of the mold receptacle (4), there is a pressure piston (9) that can be inserted into the mold receptacle, and this pressure piston (9) can be used to push the melt out of the upper crucible (3) into the mold receptacle through an outlet opening (11) provided in the crucible (3), and the pressure piston (9) is provided in the interior of the crucible.
  2. Induction melting furnace according to Claim 1, characterized in that the pressure piston (9) is accommodated in the housing (7) so as to be height-adjustable in the housing (7).
  3. Induction melting furnace according to Claim 1, characterized in that the pressure piston (9) is provided with a ceramic coating (10) at its front end that can be immersed into the melt.
  4. Induction melting furnace according to one or more of the preceding claims, characterized in that the pressure piston (9) is accommodated in the crucible (3) and its lower end extends through the outlet opening (11) provided in the crucible (3), whereby the front end of the pressure piston is gradually tapered towards the front.
  5. Induction melting furnace according to one or more of the preceding claims, characterized in that the inlet opening (13) of the mold receptacle (4) can be moved to the outlet opening (11) of the crucible (3) by means of a lifting device (12).
  6. Induction melting furnace according to one or more of the preceding claims, characterized in that the mold receptacle (4) consists of an internal container (35) and an external container (37) between which the annular space (5) is formed that is surrounded by a porous ceramic material (36).
  7. Induction melting furnace (1) for melting metals which are difficult to melt with a crucible (3) and a mold receptacle (4) surrounded by an annular space (5) for holding a coolant, whereby the induction melting furnace (1) is surrounded by a housing (7) provided with a vacuum connection (6), characterized in that, above the inlet opening (13) of the mold receptacle (4), there is a pressure piston (9) that can be inserted into the mold receptacle (4), and this pressure piston (9) can be used to post-compress the melt in the mold receptacle (4) and the pressure piston (9) is provided in the interior of the crucible, whereby, above the mold receptacle (4), there is a suspended coil (2a) between which the melt is formed and/or held.
  8. Induction melting furnace according to Claim 1, characterized in that the outlet funnel located at the lower end of the crucible (3) is coaxially aligned with respect to the mold receptacle (4).
  9. Induction melting furnace according to Claim 1, characterized in that the crucible (3) is tapered towards the bottom.
  10. Induction melting furnace according to Claim 1, characterized in that the crucible (3) is surrounded by an annular space.
  11. Induction melting furnace according to one or more of Claims 2 through 6, 8 through 10, characterized in that the pressure piston (9) can be preheated.
EP90123415A 1990-06-13 1990-12-06 Induction smelting furnace Expired - Lifetime EP0461306B1 (en)

Applications Claiming Priority (2)

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DE4018925A DE4018925A1 (en) 1990-06-13 1990-06-13 INDUCTION MELTING OVENS
DE4018925 1990-06-13

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EP0461306A1 EP0461306A1 (en) 1991-12-18
EP0461306B1 true EP0461306B1 (en) 1997-04-16

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JP (1) JP2935281B2 (en)
KR (1) KR920001164A (en)
AT (1) ATE151862T1 (en)
DE (2) DE4018925A1 (en)

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CN102974802B (en) * 2012-12-19 2013-09-25 攀枝花市立宇矿业有限公司 Extrusion casting device and method using same to produce castings
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DE4018925C2 (en) 1993-04-15
US5121406A (en) 1992-06-09
JPH0510676A (en) 1993-01-19
JP2935281B2 (en) 1999-08-16
EP0461306A1 (en) 1991-12-18
KR920001164A (en) 1992-01-30
ATE151862T1 (en) 1997-05-15
DE4018925A1 (en) 1991-12-19
DE59010700D1 (en) 1997-05-22

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