WO1999059752A1

WO1999059752A1 - Device for casting molten metal

Info

Publication number: WO1999059752A1
Application number: PCT/EP1999/002818
Authority: WO
Inventors: Christian Baron; Michael Scheiwe; Hans Eugen BÜHLER; Stefan Köhler
Original assignee: Striko-Westofen Gmbh
Priority date: 1998-05-14
Filing date: 1999-04-27
Publication date: 1999-11-25
Also published as: AU3823699A; DE19980878D2; DE19821650A1

Abstract

The invention relates to a device for casting molten metal, comprising a metering vessel (1) which is connected to the hearth of a melting or holding furnace in terms of the flow by a closeable opening (2). Said metering vessel (1) can be emptied through a feed tube (3) using compressed gas. The opening is located in the floor (4) of the metering vessel (1) and can be closed off from inside by means of a valve body (6), the valve stem (5) being situated inside the metering vessel (1).

Description

Device for pouring molten metal

The invention relates to a device for casting molten metal, in particular light metal melt, such as aluminum melt, with a metering container which is in flow connection via a closable opening with the melting space of a melting or holding furnace and by means of pressurized gas exposure via a material which is resistant to the metal melt existing riser pipe can be emptied.

From EP-A-0 126 797 a device for casting metal, in particular light metal, by means of a compressed gas is known. It has a dosing crucible, which is connected to the melting chamber of a melting or holding oven via a closable opening and via a

Riser pipe is emptied, two probes being provided, of which one probe, which is preferably adjustable in height, when the level of the dosing crucible required for casting is reached, the other probe emits an electrical signal when the sump remaining after casting is reached. A stopper which closes the connection opening of the dosing crucible to the melting space of the furnace can be lifted by means of a working cylinder lowerable and guided at its lower end in preferably three ribs, each offset by 120 °. The upward-facing connection opening is provided in a temporal approach of the dosing crucible and the working cylinder with the plug attached to it is hung on the edge of the furnace outside the dosing crucible. The device therefore takes up a relatively large amount of space, due to the asymmetry of the dosing crucible there is a temperature-related asymmetrical stress distribution during operation and undesirable bending forces are exerted on the lateral approach of the dosing crucible when the stopper is moved into the closed position.

The object of the present invention is to propose a device of the type mentioned at the outset which, while avoiding the disadvantages mentioned above, allows a high metering accuracy in a compact design.

This object is achieved, for example, in that the opening, preferably centrally in the bottom of the preferably rotationally symmetrical, e.g. is located tubular metering container and can be closed from the inside by means of a valve body provided at the lower end of a valve rod and the valve rod, at least in a region adjoining the valve body, is arranged within the metering container.

Due to the circumstance that the valve rod for the most part is also arranged within the metering container and acts on a preferably central opening in the bottom of the metering container itself, a compact design is achieved without undesirable bending forces occurring during operation. The preferably rotationally symmetrical design of the metering container, whose shape is adapted to the shape of the riser tube, allows small wall thicknesses. During operation are unbalanced Stress distributions avoided. To prevent the entry of parts of the melt pool into the downward opening of the

Dosing container can be connected to this outward from the bottom of a U-shaped tube, the inlet opening at the tube end facing up or to the side.

Preferably the opening is at the deepest point of e.g. hemispherical or conical bottom of the metering container arranged. In this way, freezes can be counteracted.

According to a further advantageous embodiment, the opening has conical surfaces for receiving the valve body equipped with corresponding conical or hemispherical surfaces. In particular if the valve body has hemispherical surfaces which cooperate with the conical surfaces of the opening, the valve body catches itself without it having to be additionally guided.

Preferably, however, the valve rod, which may be ground in some areas for this purpose, is in the e.g. made of steel, pressure-tightly attached to the dosing container, if necessary with sealing e.g. with a graphite foil, and optionally guided axially for the up and down movement by means of a guide sleeve.

The dosing container can consist, for example, of Al-Ti, the valve rod in the area in contact with the melt and the valve body made of silicon nitride and the valve rod above the melt made of steel. This results in negligible abrasion for e.g. spherical ground valve body end achieved.

In a special embodiment of the invention, the valve rod is equipped with a controllable, for example an air pressure cylinder, drive for axial and / or rotary motion connected. While the axial movement ensures the opening and closing of the valve body; The rotational movement, which is preferably carried out simultaneously with the closing movement of the valve rod, ensures that the valve body catches and grinds better in its valve seat, that is to say the melt-tightness cannot be prevented by any approaches.

The device according to the invention can also have at least one e.g. have a sensor designed as a pivotable probe for determining the fill level in the dosing container.

The fill level in the dosing container is, inter alia, checked by means of sensor electronics having the sensor. continuous, e.g. through inductive measurement.

The sensor system preferably has electronics for signaling minimum, maximum, target and / or actual fill levels.

Another feature of the invention is that the metal melt when pressurized gas is applied to the metering container by means of e.g. inert gas can be converted into a trough or casting mold via the riser pipe with a lateral opening and recess.

To further improve the dosing accuracy, the dosing container can be operated at a constant pressure, e.g. can be acted upon by means of a storage container for providing a sufficiently large amount of gas.

If a holder is provided for receiving a clamping ring fastened to the dosing container, the dosing container in the melt can be cleaned quickly and safely. This reduces stresses and the risk of destruction of the ceramic components, in particular Al-Ti parts, by thermally induced stresses. Furthermore, a program control for the automatic execution of the

Pouring process largely independent of the level of the

Dosing container can be provided.

It is also proposed that the maximum fill level of the molten metal in the metering container be repeated repeatedly at intervals so that undesired deposits are avoided.

The target fill level of the molten metal in the metering container can preferably be set in a standardized manner before the start of metering.

Further objectives, features, advantages and possible uses of the invention result from the following description of exemplary embodiments with reference to the drawing. All of the described and / or illustrated features, alone or in any meaningful combination, form the subject matter of the invention, regardless of their combination in individual claims or their relationship.

It shows:

Fig. 1 in vertical section a device having the invention, and

Fig. 2 shows a similar representation for another embodiment of the device according to the invention.

The device for precisely metering small amounts of melt has a metering container 1 which is immersed in the melt present in the melting chamber of a melting or holding furnace and in which the amount to be metered is measured. The dosing tank 1 consists of Al-Ti and is tubular with a sealing surface on its top for receiving a lid 8. At the lower end, the tubular dosing container 1 is closed either by a conical (FIG. 1) or a hemispherical (FIG. 2) bottom 4. In the bottom 4 there is a central opening 2 with an internal conical section, which makes it possible for the valve body 6 made of silicon nitride to be attached (Fig. 1) or formed (Fig. 2) to the lower end of a valve rod 5 which can be moved up and down to record. The valve body 6 can be tapered towards its free end (FIG. 1) or hemispherical (FIG. 2). The valve rod 5 is, as best seen in FIG. 2, axially guided by means of a guide sleeve, which may be equipped with a sliding bushing 9 ", for example made of CuZn7SnPb. The sliding bushing 9 'can also have a graphite foil for sealing, for example.

The valve rod 5 is (in a manner not shown) outside the metering container 1 with a e.g. connected to an air pressure cylinder drive with which it can be raised, lowered and / or rotated, so that the valve body 6 catches and grinds better, for example, during lowering in the valve seat formed at the opening 2, that is to say the melt-tightness is not caused by any approaches is prevented.

A riser pipe 3, a gas supply pipe 7 and a pivotable sensor 10 for level measurement and monitoring are also held in the temperature-resistant cover 8, which is fixed pressure-tight on the metering container 1. The lid 8 is screwed according to FIG. 2 with nuts and with the aid of a clamping ring 11 placed around the dosing container 1 against the sealing surface of the dosing container 1. Thus, the dosing container 1 hangs on the cover 8, which is fixed with bolts to a holder adapted to the melting or holding furnace, so that the dosing container 1 is in the melting bath. 7 The gas supply takes place via a pre-store and a gas supply pipe 7 provided in the cover 8, so that a large volume is the desired one

Pressure delivers trouble-free and constant during the said casting process.

The sensor 10 inductively detects the respective fill level in the dosing container 1. The electronics of the sensor system are connected to the rest of the control electronics for the casting process in such a way that the desired target fill level is standardized before the start of dosing.

The dimensions of the riser pipe 3 are matched to the metering container 1 and largely of the same geometry. The upper outflow is formed by a lateral recess or opening in the riser tube 3, from which the melt laterally enters a casting trough or casting mold (not shown). In this case, for example, a sensor can be provided which, when the ascending pipe outflow through the melt is reached, sends a control signal to the overall control of the casting process.

The casting process proceeds as follows:

The dosing container 1 is filled through the opening 2 in the bottom 4, which is opened by the positively controlled valve body 6. At the beginning of the metering process, the previously defined working fill level in the metering container 1 is achieved in that the melt is pressed out of the metering container 1 by means of gas overpressure with the valve body 6 open. In this way, the work level is initially undercut by a certain amount. After venting the gas in the metering container 1, the melt level then rises again. When the desired working level is reached, the dosing container 1 is closed by lowering and rotating the valve body 6. In this way it becomes more reproducible Work level reached. After this leveling, the desired amount of melt is conveyed to the outside via the riser pipe 3 by means of a defined increase in gas pressure. When the melt has reached the outlet of the riser 3, the pivotable sensor 10 is pivoted away by an air pressure cylinder. At the same time, the control electronics register this time as a start signal for the selected pressure-time program. The melt then reaches a casting trough or directly into a casting mold or into a die casting chamber.

After the metering process has ended, the valve body 6 is raised. In this way, the fill level in the metering container 1 adjusts to the surrounding melt level. In this way, formation of deposits on the components located in the metering container 1, which is promoted by the cold compressed gas, is prevented or eliminated. Preferably, as

Compressed gas argon is used, which is inert and because of its density lies on the melt and protects it against air access during breaks in operation and venting processes. If downtimes or very long periods of use occur, maintenance and inspection of the dosing container 1 may become necessary. For this purpose, the dosing container 1 can be pushed into another holder with the aid of the clamping ring 11 in such a way that it is slightly higher than in the melt during operation.

The surrounding furnace is preferably filled in such a way that all of the batches are located in the upper region of the metering container 1 and are as soft as possible, ie the aluminum oxide which forms is impregnated with liquid aluminum. The cover 8 can then be removed and the components can be freed of approaches with a slide. Because this process is carried out directly in or very close to the melt, all batches can be removed without freezing. In the device according to the invention, the dosing container 1 can have an optimized shape due to its rotational symmetry, which allows small wall thicknesses and avoids asymmetrical stress distributions during the casting operation. Due to the valve body on the inside with the associated valve rod, the design is very compact. In contrast to impellers or worm drives, there are virtually no mechanically stressed parts in the melt. The geometry of the device according to the invention can be chosen so that various components can be taken from the normal program of the manufacturers of technical ceramics and do not have to be manufactured separately. The preferred geometry of the valve seat (conical) and valve body (hemispherical) according to the invention permits error-free closing of the metering container 1 without further guidance of the valve body 6. The inductively operating sensor 10 enables the sensor to be continuously detected

Level during the entire casting operation. This is an operating mode that is almost independent of the fill level of the surrounding crucible. Since the dosing container 1 has a special holder, it can be cleaned quickly and safely in the melt. In this way, tensions and the risk of destruction become more ceramic

Components, especially the Al-Ti parts, reduced by shrinkage stresses. With a suitable control electronics, the procedure enables reproducible accuracies down to ± 1.5% for weights <than 200 g even with large dosing series.

Reference list

1 dosing container

opening

Riser pipe

ground

Valve stem

Valve body

Gas supply pipe

cover

Guide sleeve 'sliding bush 0 probe 1 clamping ring

Claims

Patent claims

1. Device for casting metal melt, in particular light metal melt, such as aluminum melt, with a metering container (1), which has a closable opening (2) with the melting space of a melting or holding furnace in

Flow connection is established and can be emptied by means of pressurized gas through a riser pipe (3) consisting of material resistant to the molten metal, characterized in that the opening (2) is preferably centered in the bottom (4) of the preferably rotationally symmetrical, e.g. tubular metering container (1) and can be closed from the inside by means of a valve body (6) provided at the lower end of a valve rod (5) and the valve rod (5), at least in a region adjoining the valve body (6), inside the metering container ( 1) is arranged.

2. Device according to claim 1, characterized in that the opening (2) at the deepest point of e.g. hemispherical or conical bottom (4) of the metering container (1) is arranged.

3. Apparatus according to claim 1 or 2, characterized in that the opening (2) has conical surfaces for receiving the valve body (6) equipped with corresponding conical or hemispherical surfaces.

4. Device according to one of the preceding claims, characterized in that the regionally ground valve rod (5) in the e.g. made of steel, pressure-tightly attached to the dosing container (1)

Cover (8), if necessary with sealing e.g. is guided with a graphite foil and possibly by means of a guide sleeve (9).

5. Device according to one of the preceding claims, characterized in that the metering container (1) optionally made of Al-Ti, the valve rod (5) in the melt-contact area and the valve body (6) optionally made of silicon nitride and the valve rod (5) above the melt may consist of steel.

6. Device according to one of the preceding claims, characterized in that the valve rod (5) with a controllable, e.g. an air pressure cylinder drive is connected for axial and / or rotary movement.

7. Device according to one of the preceding claims, characterized by at least one e.g. Sensor (10) designed as a probe for determining the fill level in the dosing container (1).

8. The device according to claim 7, characterized in that by means of a sensor (10) having sensors, the level in the metering container (1) can be detected continuously, for example by inductive measurement.

9. The device according to claim 8, characterized in that the sensor system is equipped with electronics for signaling minimum, maximum, target and / or actual filling levels.

10. Device according to one of the preceding claims, characterized in that the molten metal when pressurized gas is applied to the metering container (1) by means of e.g. inert gas can be transferred into a trough or casting mold via the riser pipe (3) with a lateral opening or recess.

11. Device according to one of the preceding claims, characterized in that the metering container (1) with constant pressure over the casting process, e.g. can be acted upon by means of a storage container for providing a sufficiently large amount of gas.

12. Device according to one of the preceding claims, characterized by a holder for receiving a clamping ring (11) fastened to the dosing container (1).

13. Device according to one of the preceding claims, characterized by a programming control for the automatic execution of the casting process.

14. Device according to one of the preceding claims, characterized in that the maximum fill level of the molten metal in the container (1) can be repeatedly adjusted at intervals.

15. The device according to any one of the preceding claims, characterized in that the target fill level is adjustable before starting metering.