DE2158115A1 - Metal casting device and metal casting process - Google Patents

Description

G 47 975

Dr. Arnold Daniel, 2219 Devonshire Drive,
CLEVELAND Heights, Ohio 44106 (USA)
Joseph Burdette Richey II, 2160 Demington Drive,
CLEVELAND Heights, Ohio 44106 (USA)

Metal grit device and metal casting process

The invention relates to a metal mold casting device, particularly for rapid melting and casting smaller Metal batches as well as a metal casting process.

In the manufacture of casting molds for the manufacture of jewelry, tooth inlays and bridges and the like, molding processes have long been used. In such applications it is particularly essential that a very precise control of the casting process is carried out so that the casting has the exact predetermined dimensions and the
Has prescribed alloy composition.

In the usual production of castings from dental alloys, a casting mold is made by means of a wax model and the casting mold is preheated to remove the wax
melt out and the mold to the required casting

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temperature to heat up. The setting and maintenance of this temperature during the casting process is of considerable importance Importance because both the Torah and the casting have the tendency to shrink while cooling, and around To produce a finished casting of the exact predetermined dimensions, it is essential that both the molten Both the metal and the form when the metal is introduced into the porm have the right temperatures. With a usual The procedure here is such that the mold is preheated in the manner mentioned and then placed in a centrifugal casting machine is used. The gold alloy batch is placed in the machine and then heated so far by means of an acetylene-oxygen burner that the charge becomes molten, whereupon the machine is switched on and the molten metal is pressed into the mold under the influence of centrifugal force. At a In such an operation it is obviously not possible to ensure that the temperature of the mold at the moment is optimally adjusted in that the molten metal penetrates into it, and it is also not possible ensure that the molten liquid charge itself the Has optimal temperature. The alloy composition and the charge can also be changed during the melting process can be by atmospheric or by using the burner generated gases are contaminated. Also must be alloy material can be used in excess, resulting in subsequent removal and grinding of the metallic sprues and risers requires, and the entire procedure requires a high level of skill and experience, so that most dental technicians Companies send such work to specialized laboratories and do not carry out such work themselves. This leads to a significant time delay and increased costs, especially when different castings are made must be made before a truly satisfactory casting for its intended purpose is produced.

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The invention is therefore based on the object of an assembled one To create unit in which the mold is in front or not out of the heating during the pouring process Environment must be removed. The device according to the invention is intended primarily for the casting of small molds and batches and suitable for use with a standard 110V or 220V AC source, as in all dental factories exist, with high to ensure an automatic production of castings Quality without special experience of the operator can be provided a corresponding control system.

To solve this problem it is essential that both the molten metal and the mold are at optimum Temperatures are heated, and that the casting process is carried out very quickly and so that the molten Metal is kept free of impurities and the proportions of the alloying elements are kept the same.

The molding device according to the invention is characterized by an insulated housing; Heating elements for heating the Inside the housing to a desired temperature; a mold disposed in the housing; one above the mold arranged metal crucible with a pouring channel in its bottom; one directly below the pouring channel of the crucible arranged and leading to the mold cavity inlet in the top of the mold; and by suction devices to create a negative pressure in the mold so that molten metal quickly flows out of the crucible into the mold cavity is sucked.

In the following description, in which further embodiments of the device according to the invention are described, the Invention explained in more detail with reference to the drawing of an embodiment of the device according to the invention, namely:

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Pig. 1 is a perspective view of a new one

Mold casting device including the associated Control devices for carrying out the method according to the invention;

FIG. 2 is an enlarged vertical sectional view taken along line 2-2 in FIG. 2, but with the control panel is omitted;

Figure 3 is a circuit diagram showing suitable control circuitry for operating the apparatus shows;

Fig. 4 is an enlarged perspective exploded view of the Schraelz crucible of the device; and

Fig. 5 is a circuit diagram of an optionally usable modified heater for the metal.

The molding device according to the invention has an insulated Housing or a muffle with heating elements for heating its interior to an elevated temperature. In the upper part A metal crucible is attached to the housing, and there are means for holding a casting mold directly below of the crucible is provided in clamping engagement therewith so that the metal melted in the crucible directly can be dispensed into the casting mold arranged below it. Suction devices are connected to the casting mold, which Suction of the molten metal charge from the crucible into the mold cavity assist, and electrical Control devices ensure that the various operations are carried out at the right times and at the appropriate times Temperatures are carried out. The crucible can be surrounded with an inert atmosphere to avoid any possibility of contamination of the molten batch

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The following is based on the drawings and in particular on the pig. 1 and 2 are referred to. The illustrated embodiment The invention shows a furnace 1, which preferably stands on supports 2 and an outer aluminum sheet cladding or a housing 3. This housing has a thick wall made of a refractory insulating material lining 4 lined, which encloses a fireproof ceramic inner lining 5. Between the outer lining 4 and the inner lining 5 are nichrome heating elements 6 arranged to bring the interior of the furnace to an elevated temperature bring. The front of the furnace is closed by means of an insulated hinged flap or door 7, which through a counterweight 8 is normally kept closed.

A control panel 9 is connected by means of brackets which fix it at a distance from the furnace wall and on the top A removable hood 10 is attached to the furnace. This hood can, if necessary, by means of a flexible Hoses 12 to a source of inert gas, e.g. B. be connected to a cylinder 11, the supply of this gas (e.g. helium, nitrogen or argon) to the hood by means of a manually operated valve 13.

The hood 10 serves to cover an opening in the top of the furnace in which a metal crucible is used and is attached. This crucible is a vertically divided, two crucible halves 14 and 15 (see also Fig. 4) exhibiting graphite crucible, the halves of which are covered by a layer of inert refractory material 16, (z. B. Asbestos) are separated, and with one as a pouring channel for the crucible serving, central opening of small cross-section can be provided in its lower edge. The two halves of the Crucibles are also electrically isolated from one another in this way. In the preferred one shown in FIG However, the pouring channel 17 is only shown in FIG

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a crucible half is provided, the inner surfaces of the other half and the asbestos release layer being inclined towards the pouring channel. This pouring channel can, for example, have a diameter of approximately 0.04 mm. When the crucible halves 14 and 15 are united with the insulating layer 16 lying between them, they form a crucible cavity, the upper end of which protrudes above the surface of the furnace 1 and the lower end of which protrudes into the interior of the furnace 1. The halves 14 and 15, which are made of graphite, are each covered with a heavy sheet of aluminum or with copper contact plates 19 and 20, to the upper edges of which feed lines 21 and 22 are connected. Electrical insulating layers 23 and 24 enclose the sides of the crucible and the contact plates, so that the two crucible halves are electrically insulated not only from one another but also from the upper furnace wall holding the crucible.

An optionally usable, but usually preferred V device is provided within the hood 10, which a charge to be melted in the crucible is pressurized in the downward direction, and thereby a better contact between the two crucible halves and the charge bridging them. This device can have a have on the surface of the furnace fastened holder 25, which has a vertically arranged plunger 26 directly above of the pouring channel of the melting level consisting of graphite in Axially back and forth displaceable carries. A compression spring 27 is used to hold this plunger normally in its depressed position Hold position so that the graphite rod 28 attached coaxially to the plunger tightly down onto the im Crucible batch is pressed. The plunger 26 and the rod 28 can by pressing down the operating lever 29 can be temporarily lifted by hand when a new batch has to be introduced into the crucible.

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Inside the furnace chamber or the muffle 31 is at the upper end of a metal tube that can be moved vertically back and forth 32 a circular, made of metal, e.g. B. corrosion-resistant steel, existing platform 30 attached. The top of the The tube is connected to a centrally located opening in the platform 30 and the lower end of the tube is connected to an elbow 33 Connected from a corrosion-resistant steel pipe, which is connected to a vacuum line 34. One The hand-rotatable nut is screwed onto the lower projecting end portion of the metal pipe 32 and axially by an upper washer 36 located between the nut and the underside of the oven and one between the Nut and a holder provided with a central opening inserted lower washer 37 set. The holder 38 is attached to the underside of the stove and protrudes from it. Therefore, when the nut 35 is turned by hand, the Platform 30 in the furnace chamber is raised or lowered accordingly.

The remaining components of the device are best considered in conjunction with the description of the operation below to explain the metal mold casting device.

The operation of the metal casting apparatus will first be described in general and then subsequently in detail with reference to FIG electrical control system described.

The usual wax model is prepared and made in the usual metallic mold ring 40 with a suitable casting mold 39 surrounded by porous molding material. This mold can first be laterally of the platform 30 in the manner shown at 40 ' placed inside the furnace to preheat them prior to performing the casting process. This preheating is used for liquefying and melting out the wax model, with the vapors produced through vents V from the furnace chamber

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are discharged , and for heating the mold 39 to the correct casting temperature. The oven door is then opened and the operator lifts the mold onto the platform 30, where it is placed on an annular asbestos sealing ring 41 that is used to hold the bottom of the mold slightly above the top of the platform 30, thereby allowing the Metal tube 32 then a vacuum can be applied to the entire underside of the mold. In those cases in which the mold is not sufficiently porous, it may be necessary to provide a small vent passage 42 which leads from the mold cavity 43 to a porous layer 44 of asbestos, which in turn is led to the underside of the mold 39 and thereby the application a vacuum (e.g. 71.1 to 73.7 cm Hg) is allowed in a more direct way to the mold cavity. The upper surface of the casting mold is recessed in the manner of a crater at 45 and thus forms a funnel-shaped cavity which leads into a small inlet 46 leading into the mold cavity 43. A centrally pierced sheet metal cover 47 and a sealing ring 48 made of asbestos is placed on the top of the mold and a smaller asbestos sealing ring 49 is inserted between the cover and the bottom of the crucible so that the pouring channel 17 of the crucible is directly connected to a closed vacuum system Connection.

The crucible arrangement is by means of a long locking screw 50 fixed in their position (which can be isolated from the contact plate 19 or which can only be grounded by of the outer aluminum housing 3 of the furnace is grounded. the Nut 35 is now rotated so that the platform 30 is raised and the mold moves upwards and thereby the cover 47 firmly against the sealing ring 49 between the cover and the underside of the divided crucible.

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The hood 10 is now raised, the actuating lever 29 is depressed to raise the rod 28 and one measured solid metal charge 51 is placed in the crucible. The operating handle 29 is then released so that the Rod 28 presses the batch downwards in close contact with the respective crucible halves. Via the feed line 21 and 22 can now feed the crucible halves for a period of time sufficient to melt the metal charge (e.g. 10th Seconds). The butt arrangement 26, 27 and 28 is usually dimensioned and dimensioned so that even when the crucible is completely empty, the lower end of the Rod 28 does not extend all the way to the bottom of the crucible, since it is only necessary that the lower end of the rod rests on the solid metal charge with sufficient force to establish adequate electrical contact between of the batch and the associated crucible halves. When the batch is molten and at the optimum temperature is brought (e.g. by a thermocouple or in connection with the circuit diagram described in more detail below Infrared radiation detector is determined), a vacuum is applied to the vacuum line 34, which over the knee 33, the support tube 32, the porous casting mold 39, the mold cavity 43 and the inlet 46 act on the casting channel, the surface tension of the molten metal overcomes and the latter rapidly down into the mold cavity sucks. The platform 30 can then be lowered, the door 7 opened and the casting mold removed from the furnace chamber 31 will. If it is necessary to cool the mold more slowly in order to control the solidification more precisely, which affects the core structure of the casting, the mold can alternatively remain in the chamber for a longer period of time, while the furnace chamber is gradually being cooled.

From the foregoing it can be seen that the molten metal in this way very quickly after reaching the optimum

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temperature is sucked into the mold cavity, with the possibility of picking up any impurities is almost impossible. As mentioned above, a can from the storage bottle 11 before the melting is carried out inert gas can be introduced into the hood 10, and this inert gas can, if necessary, also under sufficient Pressure to clean the hood and the crucible before lifting the casting mold in the clamping system on the underside of the crucible are fed. The pressure of the inert gas in the hood can then facilitate the removal of the molten metal from the Support the crucible in the evacuated mold cavity if the hood is clamped tightly and the crucible is in the appropriate position Way is sealed in the top of the furnace.

Referring now to FIG. 3, the operation of the metal mold casting apparatus of the invention in detail in connection with the electrical control system is described. After inserting the mold rings 40 and 40 »with the casting molds contained in them in the furnace chamber 31 and closing the door 7, the switch is closed by hand, generating a heating current (110 V AC) can flow from the main line 53, 54 to the lines 55 »56, which are connected to the nichrome heating elements 6 in the furnace 1 are connected. Line 56 runs through a standard temperature control unit 57, which can be preset in such a way that it interrupts the line when a desired temperature is reached inside the furnace. Temperature-sensitive devices in the form of the thermocouple 58 can be provided in the oven and connected to the temperature control unit 57 in order to trigger the latter. A neon indicator light 59 indicates the presence of a voltage. The nut 35 is rotated and lifts the platform 30 so that the mold is clamped in place under the split crucible, whereupon the metal charge 51 is inserted into the crucible and the rod 28 biased in the downward direction

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is applied to the batch under pressure. The skin 10 is closed, clamped and, if necessary, is inert gas introduced into them.

When the thermocouple 58 signals that the predetermined Temperature is reached in the furnace chamber 31, the temperature control unit 57 automatically switches off or limits the further power supply to the nichrome heating elements 6 to the to keep the preset temperature at a constant level. After the mold has sufficient time to reach the Optimum temperature is given, the operator can Trigger the melting process by putting the deferred Switch 60 on the crucible temperature controller 61 depresses. This energizes the coil of the contactor 62, which in turn leads mains voltage to the primary side of a transformer 63, whereby a high current through the Secondary side of the transformer is brought to flow, which over the two graphite crucible halves 14 and 15 and the Metal batch 51 is shorted. When the predetermined optimal melting temperature of the one embedded in the crucible, however, thermocouple 64 electrically isolated from it or measured by the infrared radiation detector D above the crucible and is reported, the temperature control device 61 de-energizes the coil of the contactor 62 and energizes the coil a time delay relay 65, which in turn is the coil of a normally closed solenoid valve 66 energized so that this is opened, the vacuum line 34 through the time delay relay for a certain period of time is connected to a vacuum. This sucks the molten liquid immediately in the manner described above Metal through the pouring channel in the crucible into the evacuated mold cavity 43. After that through the time delay relay 65 for a certain period of time, the valve 66 closes again automatically and switches the vacuum connection to the casting mold away.

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During the application of the vacuum, the pressure differential causes the surface tension of the molten liquid to be overcome Metal and sucks it through the thin pouring channel.

From the foregoing it can be seen that a method for dispensing molten metal from the Crucible is created in which the outlet or pouring channel emanating from it is of sufficiently small dimensions, that the surface tension of the molten metal normally has a discharge through the channel due to the action of gravity prevented, but at the appropriate moment the applied vacuum creates a pressure differential that is sufficient to overcome the effect of surface tension so that the molten metal flows through the pouring channel. The crucible must of course consist of a material which cannot be wetted by the molten metal.

The casting mold can be used in the production of cast dental fillings, Supports, crowns, bridges and connectors for removable prostheses in essentially known ways be produced, with dental gold casting alloys according to the American Dental Association Specification No. 5 (Spec No. 7 for dental gold casting alloys of the Federation Dentaire Internationale) is used.

The wax model is made and a 12 gauge (Brown & Sharpe) spout pen is used in the most extensive Part of the model is inserted and a conical sprue former is attached to the other end of the pin. Usually, the length of the pin from the model to the sprue former should not be greater than 9.53 mm. The order is carefully washed and dried.

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A cylindrical shaped ring made of brass or corrosion-resistant Steel is brought into alignment with a circularly laid asbestos strip, the ends of which slightly diverge overlap. This ring can, for example, be 38.1 mm long and have a diameter of 31.75 mm, and the Asbestos strip should now be about 3.175 shorter on each end than the ring.

The mold material (usually a plaster of paris mix), e.g. B. "Kerr Luster Cast" or cristobolite is mixed with water (e.g. 30 to 34 parts of water per 100 grams of powder), whereby the mold material is sifted into the water until a creamy consistency is achieved. The model is coated with the mixture, after usually first a light coating with a wetting agent is done, is then turned over and inserted into the ring, which then with the same Mixture is topped up. The firing process can begin after a hardening time of about one hour. The pouring agent and the sprue pin are removed and the mold ring and the mold can then be inserted into the furnace with the remaining gate facing down shows. When the mold is slowly heated to a temperature of about 260 ° C, it is turned over so that the sprue pointing upwards, and the furnace is brought to the casting temperature (approx. 700 ° G for cristobolite). There is a heat balance before the casting desirable for a period of about 20 minutes at this temperature.

The crucible is made from a gold alloy bar (approx. 3.11 g up to 6.22 g for insoles and crowns, and about 31.1 g to 46.65 g for larger prosthesis parts to be cast) Melting temperature heated, usually closer to the upper (liquidus) than to the lower (solidus) limit of the Melting range is heated.

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The mold is then clamped and vacuum applied in the manner described. The vacuum should be as high as possible, e.g. B. 71.1 to 73.7 cm Hg (0.844 to 0.914 kgf / cm ² ) if possible, and the crucible sprue can be 16 gauge (Brown & Sharpe) or less to prevent premature draining impede.

In the following, Pig. 5, in which an optionally usable embodiment of a hold-down device is shown, which has one of the rod 28 in the effect corresponding graphite electrode 67, which, however, in addition is electrically connected to the transformer 63. It must therefore, as shown at 68, in its holder be electrically isolated, and part of the heating current flows between the electrode and the crucible halves.

The temperature measuring thermocouple 64 (Fig. 3 and 4) can with its wires through an elongated ceramic Insulating piece 69 can be inserted into one of the graphite crucible halves, with the thermocouple itself in the vicinity the molten metal zone is embedded in refractory ceramic insulating material. Isolation plates 70 and 71 can be provided on crucible projections 72 and 73 to ensure that the crucible is against the furnace even then is isolated when the threaded tube 32 exerts the upward pressure, and also to a gas-tight seal to create around the crucible. The infrared radiation detector mentioned above as the preferred alternative to thermocouple 64 D is a commercially available unit shown semi-schematically in Fig. 2 on a projection of the holder 25 is shown attached. This detector (preferably silicon type) is clamped at such an angle that that its focus on the charge 51 is at the bottom of the crucible, whereby it depends on the temperature of this charge of the infrared radiation emitted by the metal (infrared radiation pyrometry). The lines

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from detector D are then instead of the wires coming from thermocouple 64 in FIG. 3 to the temperature control device 61 connected.

With the device and the method according to the invention, a metal casting system is thus created which maintains the integrity of the castings produced in terms of composition, physical properties and dimensions in one previously unattainable dimensions. The device is not excessively expensive and the method of operation is such that it can be mastered without extraordinary experience and practice.

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Claims (31)

Claims 1. Mold casting device characterized by an insulated Housing (3, 4, 5), heating elements (6) for heating the interior of the housing to a desired temperature; a casting mold (39 »40) arranged in the housing (3» 4, 5); a metal crucible arranged above the casting mold (39, 40) (14, 15) with a pouring channel (17) in its underside; one directly below the pouring channel (17) of the crucible (14, 15) and to the mold cavity (43) leading gate (46) in the top of the casting mold (39, 40); and by suction devices (32, 33, 34) for generating suction pressure in the casting mold (39, 40), so that molten metal from the crucible (14, 15) is quickly sucked into the mold cavity (43). 2. Apparatus according to claim 1, characterized in that the crucible (14, 15) is divided vertically, and its crucible halves (14; 15) are laterally spaced from one another have, so that a metal charge (51) to be melted in it bridges the crucible halves, and that one electrical power source is connected to the crucible halves (14; 15), so that they and the batch (51) of Electricity flows through it, the charge being caused by resistance heating is heated. 3. Apparatus according to claim 1 or 2, characterized by control devices (52 to 66) for the suction devices (32, 33, 34), which switch on the suction devices when a heating current is supplied to the crucible (14, 15) and a predetermined temperature is reached in the crucible. 209823/0783 4. Device according to one of claims 1 to 3 »characterized by a pressure device (25 to 29) which exerts a downward pressure on the charge (51) located in the crucible (14, 15) in order to press it against the crucible halves (14; 15) to be pressed, so that the charge (51) is heated quickly as a result of the improved current flow. 5. Device according to one of claims 1 to 4, characterized in that the crucible (14, 15) made of graphite consists. 6. Device according to one of claims 2 to 5, characterized in that the between the lateral distance mutually arranged crucible halves (14; 15) located essentially through refractory electrical insulating material is closed. 7. Device according to one of claims 1 to 6, characterized by a clamping device (35, 36, 37, 38) for 'Clamping the casting mold (39, 40) in close contact with the underside of the crucible (14, 15), whereby the Vacuum acts on the crucible pouring channel (17). 8. Device according to one of claims 1 to 7, characterized in that a melting crucible (14, 15) surrounding it Hood (10) and devices (11, 12, 13) for supplying an inert material with respect to the molten metal Gas are provided in the hood (10). 9. molding device according to claim 1, characterized in that the metal crucible (14, 15) has a thin, open, into the mold cavity (43) of a vacuum casting mold (39, 40) leading pouring channel (17) that means for rapid heating of the metal to above 209823/0783 Melting point to the desired casting temperature in the crucible (14 »15) are provided that the dimensions of the Gravel channel (17) is chosen so small that molten metal with regard to its surface tension below normal pressure conditions does not occur, and that the devices (32, 33, 34) for generating the vacuum so designed so that the vacuum overcomes the surface tension and the molten metal into the mold cavity (43) sucks. 10. The device according to claim 9, characterized by a first temperature monitoring device (58) for monitoring the temperature of the casting mold (39, 40) and a second temperature monitoring device (64) for monitoring the temperature of the molten metal; one with the first temperature monitoring device connected signaling device, which the achievement of the desired Reports temperature in the mold; Devices for switching on the metal heating devices; and through electrical control devices responsive to a signal from the second temperature monitoring device (64) (65, 66) which automatically switch off the actuation when the predetermined temperature of the molten metal is reached turn on the devices (32, 33, 34) for generating the vacuum. 11. Apparatus according to claim 9 or 10, characterized in that the heating elements (6) for heating the casting mold (39, 40) are provided in a furnace (1) surrounding the mold that the crucible (14, 15) into the upper Wall of the furnace (1) is inserted in such a way that it can be loaded from outside the furnace, and that the pouring channel (17) of the crucible gas-tight to the one in the mold cavity (43) leading inlet (46) is connected. 209823/0783 12. The device according to claim 11, characterized in that a detachable hood surrounding the crucible (14, 15) (10) Devices (11, 12, 13) for feeding an inert gas into the hood (10) and a vent (V) of the furnace (1) are provided. 13. Device according to one of claims 9 to 12, characterized in that a downward pressure Pressurizing device (25, 26, 27, 28, 29) that applies pressure to the metal in the crucible (14, 15) is provided. 14. The apparatus according to claim 13, characterized in that the crucible (14, 15) in the vertical direction in two essentially the same crucible halves (14; 15) is divided that electrical between the two halves Insulating material (16) lies in that power supply devices (19, 20, 21, 22) for supplying a heating current the crucible halves (14; 15) are provided, which flows through the metal in the crucible and is molten makes, and that the crucible halves and the part (28) acting on the metal of the pressurizing means (25 to 29) consist of graphite. 15. The device according to claim 1, characterized in that the crucible (14, 15) two substantially the same, electrically conductive crucible halves (14; 15) divided in the vertical direction and one between them lying layer (16) made of electrically insulating material that a pouring channel in the bottom of the crucible (17) is arranged that a hold-down part (28) for applying a downward pressure to a The charge (51) located in the crucible is provided, which makes good electrical contact with the charge 209823/0783 the two crucible halves ensures, and that power supply devices (19, 20, 21, 22) for supplying a charge (51) flowing through and making it molten making heating current to the two crucible halves (H; 15) are provided. 16. The device according to claim 15, characterized in that the hold-down part (28) is also electrically conductive and connected to an electrical power source, so that the heating current flows between the hold-down part (28) and the crucible (14, 15) through the charge (51), 17. Apparatus according to claim 15 or 16, characterized in that that the hold-down part (28) is arranged resiliently biased in the downward direction onto the charge (51), and that a stop device is provided which limits the downward movement of the hold-down part (28) in such a way; that direct contact of the hold-down part with the crucible halves (14; 15) is prevented. 18. The device according to claim 1, characterized in that the insulated housing (3, 4, 5) has an electrically heated Oven (1) represents the one with a door (7) closing the housing and one in the housing in the vertical direction reciprocally displaceable platform (30) for holding a casting mold (39, 40) is provided, which is on an in vertical direction back and forth displaceable support tube (32) is arranged, wherein the supporting tube penetrating The passage communicates with the surface of the platform (30) and the casting mold (39, 40) arranged thereon, that the devices (32, 33, 34) for generating the vacuum in the mold cavity (43) act on this passage, that a device (35, 36, 37) is provided for raising and lowering the support tube (32) and the platform (30), that in the upper part of the furnace housing immediately above 209823/0783 the PIaTTPORM (30) an opening is formed, and that in this opening the metal crucible (14, 15) is arranged, which has a pouring channel (17) on the bottom, the one with one in the mold cavity (43) of the casting mold (39, 40) leading inlet (46) can be curled when the platform (30) is raised so that the mold is pressed against the bottom of the crucible. 19. The device according to claim 18, characterized in that a heating device for melting the metal in the crucible (14, 15) is provided. 29, device according to claim 19, characterized in that an electrical control device (52 to 66) for monitoring the temperature of the molten metal in the crucible (14, 15) and for operating the devices (32, 33, 34) to create the vacuum so that the molten metal quickly out of the crucible in the mold cavity is sucked, is provided. 21. The device according to claim 20, characterized in that the crucible (14, 15) divided in the vertical direction is made of electrically conductive material and is divided by an insulating material layer (16), and that power supply devices (19, 20, 21, 22) are provided which carry an electrical heating current through the divided crucible halves and lead through a metal charge (51) contained in these, so that the charge melts. 22. Apparatus according to claim 20 or 21, characterized in that the pouring channel provided in the crucible (14, 15) (17) is designed so thin that a passage of molten metal under the influence of gravity takes so long is prevented as no additional vacuum acts. 209823/078 3 BATH 23. Apparatus according to claim 21, characterized in that the crucible (14, 15) is enclosed by a hood (10) is, and that a device (11, 12, 13) is provided for supplying an inert gas into the interior of the hood. 24. The device according to claim 15 »characterized in that the vertically divided, electrically conductive mold crucible halves (14, 15) and the layer in between (16) are clamped together from insulating material such that a common crucible cavity is formed, and that the grit channel (17) emanating from its bottom only in one the mold crucible halves (14; 15) is formed. 25. The device according to claim 1, characterized in that the metal crucible (14, 15) has a pouring channel (17) as an outlet in its bottom, that the casting mold (39 _f 40) which can be acted upon by vacuum has an inlet (46) on its upper side ) that a vertically displaceable back and forth holder for the casting mold and devices (32, 35, 36, 37, 38) for moving the holder in such a way that the casting mold (39, 40) is clamped against the underside of the crucible is provided, wherein the pouring channel (17) and the inlet (46) are aligned with each other, and that a vacuum line to the casting mold (39, 40) runs through the holder. 26. The device according to claim 25, characterized in that the holder and the casting mold (39, 40) in a heatable Housing (3) are arranged. 27. In a device according to one of claims 1 to 26 feasible casting process, characterized in that a casting mold that can be acted upon by a vacuum is brought to the optimum casting temperature, that then an electrical Current through one arranged above this casting mold 209823/0 7 83 Metal batch is passed, whereby the batch is quickly heated and converted into a molten state, that the molten metal is then brought to the optimum casting temperature, and that finally the vacuum is applied to the mold so that the molten metal is sucked into the mold. 28. The method according to claim 27, characterized in that the melting of the metal in an inert atmosphere is carried out. 29. The method according to claim 27 or 28, characterized in that the charge for generating a supply of molten Metal is melted, which has a surface tension, which a penetration of the metal in a of a crucible in which the melting process is carried out is prevented, outgoing pouring channel and penetration into the mold cavity of the casting mold, and that the surface tension is overcome by applying the vacuum. 30. The method according to claim 29, characterized in that the optimal casting temperature of the molten metal is scanned electrically, and that immediately thereafter the vacuum is brought into effect. 31. The method according to claim 27, characterized in that the supply of molten metal is melted in a vessel which has a pouring channel with a cross-section that is too small to allow the molten to pass through Metal easily, and that the molten metal suddenly experiences a substantial pressure differential which forces the metal through the passage into a mold cavity. 209823/0783 32 «Method according to claim 3t», characterized in that the passage is provided in the bottom of the vessel, and that the passage size and the surface tension of the molten metal are adjusted so that a. Flow of the metal through the passage is prevented only under the influence of gravity. 209 823/0783