EP1786576B1 - Method and device for casting molten metal - Google Patents

Description

The invention relates to a method and a device for casting molten metal, in particular light metal melts, such as aluminum-based melts.

Usually, for the production of castings, a casting mold is provided, which has a mold cavity which images the casting to be produced. The molten metal is then poured from a melt container into the mold cavity. The melt container can be, for example, a casting furnace or another container filled with melt, in which the melt is kept at a temperature level required for casting. After the melt in the casting mold has solidified to the casting to be produced, casting mold and casting are separated from each other.

The properties of a casting are strongly influenced by the course of the solidification of the melt in the casting mold and the make-up required to compensate for the volume shrinkage. Thus, a particularly uniform distribution of properties shows when the mold filling is performed with melt in a continuous process while avoiding large melt flows in the mold and the solidification evenly distributed and used on the side opposite the feeder side of the mold.

For this purpose, methods are known in which the melt is conveyed against the effective direction of gravity in the mold. In some of these casting techniques, also known as "rising casting", the melt container is located under the mold. The melt is then forced by pressurizing the atmosphere above the melt in the melt container atmosphere via a riser into the mold cavity of the mold. This is usually done by introducing a gas under pressure into the free space of the melt of the melt container. Alternatively, a negative pressure can be applied to the mold cavity of the casting mold for conveying the melt or the molten metal can be conveyed into the casting mold by means of electromagnetic forces.

This filling of the casting mold with melt against the direction of gravity has the advantage that a smooth and controlled casting run is achieved with minimized turbulence of the melt. The risk of casting defects in the manufactured casting can be significantly reduced. A disadvantage of such methods, however, is that the molds must each remain for a long time in the casting plant, which is required for the complete solidification of each casting produced in them.

A device for carrying out the rising casting is for example from the DE 100 33 904 A1 known. In this known device, a slide closure is arranged between the mold and the melt container, which is formed of two superimposed and mutually displaceable plates, each having a passage opening. To fill the mold, the passage openings are brought into coincidence so that melt can flow through the riser from the melt container into the casting mold. Once the mold is filled, one of the slide plates is moved relative to the other, so that the passage openings are closed. Subsequently, the mold can be removed and another casting cycle can be started.

As soon as a plug of solidified melt has formed in the filling opening of the casting mold, the slide closure can be removed for use. In order to shorten the waiting time that has elapsed so far, a cooling device can be provided at the filling opening, which causes a targeted cooling of the melt present in the filling area.

Another method for rising casting and a device suitable for carrying out this method are known from the DE 100 33 903 C1 known. According to this known method, a casting mold with a lower pouring opening is used, which is equipped with a detachable shut-off device. The shut-off device comprises for this purpose a base frame, which is attached to the clamping frame made of molded parts screwed as a core package composite mold. The base frame carries a slidably mounted on the base frame plate, in which a passage opening is formed. By moving the plate whose passage opening can be brought into coincidence with the pouring opening of the mold or the inlet opening are closed again.

In order to further improve the quality of cast products, it has been proposed to turn the mold to be filled with melt. For this purpose is in the DE 100 19 309 A1 It has been proposed to dock a melt container containing molten metal with its upwardly directed opening to a downwardly pointing filling opening of a casting mold. Subsequently, the mold is rotated together with the firmly associated with her melt container by about 180 °. In the course of the rotation, the melt passes from the melt container into the casting mold. When the end position of the rotation is reached, the melt container is removed from the mold. The hot residual melt in the feeder area, which is now located at the top, can then continue to be effective under the action of gravity and compensate the volume loss associated with the solidification of the melt in a particularly effective manner.

Also from the WO 2004/039516 A Known method is based on the idea of filling a casting mold with the molten metal during the production of castings and then turning it. For this purpose, a melt container is used according to this known method, from which the melt against gravity on a the top of the melt container attached filling channel is conveyed in a staggered over the melt container mold. The lying outside of the mold part of the filling channel leads obliquely upwards and opens into the lower region of the side wall of the mold. The continuation of the filling channel within the mold is horizontal. From the filling channel branch up distribution channels and several risers in the overlying cavity of the workpiece from. On the signal of the weight sensors of the control device, the metal production is completed, the mold closed by a controlled by the controller sand slide and thereby separated from the outer part of the filling channel. Subsequently, the mold is rotated with the still liquid metal about a horizontal axis which extends approximately through the center of the mold. Since the filling of the mold takes place from the bottom side and the mold is separated from the filling device after closing the sand slide, the sand slider must keep the mold during the rotation permanently closed during this procedure. Otherwise, the melt would leak out of the mold. Accordingly, the sand slider is also destroyed during demoulding of the casting mold.

The rotation of the casting mold with the melt container achieves complete filling of the casting mold with molten metal. During the rotation, the melt passes through the molten metal poured into the casting mold during the mold rotation Gravity is exposed, safe in all areas of the mold cavity of the mold, which forms the casting to be cast. In addition, this casting technique, also known as "rotational molding", optimizes the microstructure as a result of directional solidification, which is brought about by the orientation of the casting mold associated with the rotation. In this way, geometrically complex castings of high quality can be produced.

However, in the known method, for example, the mold filling is not optimal if, in the case of cylindrical internal geometries, particularly homogeneous solidification morphologies are required.

In addition to the above-described prior art are from the DE 196 49 014 A1 In addition, a method and apparatus for producing aluminum alloy castings is known. In this case, it is provided to increase the productivity that the aluminum melt is pressed at a relatively low pressure via a riser from bottom to top in a mold made of a gasifiable foam. After casting, the casting mold is rotated together with the casting container about an approximately horizontal axis of rotation in the region of the inlet of the casting.

Object of the present invention was to produce castings with high productivity, which also meet further increased quality requirements safely.

• Bereitstellen einer Gießform mit einer in Schwerkraftrichtung weisenden Einfüllöffnung,
• Ankoppeln der Gießform mit der Einfüllöffnung an einen die Metallschmelze enthaltenden Schmelzenbehälter,
• Fördern der Metallschmelze aus dem Schmelzenbehälter in die Gießform entgegen der Schwerkraftrichtung,
• Verschließen der Gießform unmittelbar nach dem Befüllen mit Metallschmelze mittels einer Absperreinrichtung, die zumindest vorübergehend fest mit der Gießform verbunden ist,
• unmittelbar auf das Verschließen der Gießform folgendes Abkoppeln der Gießform von dem Schmelzenbehälter und
• Drehen der Gießform um eine horizontale Drehachse, wobei die Gießform von der während des Drehens mit ihr weiterhin fest verbundenen Absperreinrichtung verschlossen gehalten bleibt
• wobei die Absperreinrichtung nach dem Drehen der Gießform von der Gießform getrennt wird.

This object has been achieved on the one hand by a method for casting molten metal, comprising the following steps:

• Providing a casting mold with a feed opening facing in the direction of gravity,
• Coupling the casting mold with the filling opening to a melt container containing the molten metal,
• Conveying the molten metal from the melt container into the casting mold in the direction of the direction of gravity,
• Closing the casting mold immediately after filling with molten metal by means of a shut-off device which is at least temporarily fixedly connected to the casting mold,
• immediately following the closure of the casting mold, the following uncoupling of the casting mold from the melt container and
• Turning the mold about a horizontal axis of rotation, wherein the mold is kept closed by the shut-off while still firmly connected with it while turning
• wherein the shut-off device is separated from the casting mold after rotation of the casting mold.

On the other hand, the above object has also been achieved by a device for casting molten metal, with a mold having a filling opening, with a device for coupling the mold to a melt container, which is arranged in this operating position below the mold and contains the molten metal, with a device for conveying the molten metal from the melt container into the mold through the filling opening the direction of gravity, with a device for uncoupling the casting mold from the melt container, with a device for rotating the casting mold in the state uncoupled from the melt container about a horizontal axis associated with the casting mold, with a control device which emits a signal for rotating the casting mold about its axis of rotation, when the mold is filled with melt, and with a at least during rotation about its horizontal axis fixed to the mold connected shut-off device for closing the filling opening of the mold, which is releasably connected to the mold.

The invention combines rising casting with rotational molding. In order to achieve short cycle times, the invention provides a closure connected to the mold, which remains firmly attached to the mold during rotation and keeps it closed. In this way, it is no longer necessary to wait until the beginning of the rotational movement that a sufficient amount of solidified melt material has formed in the filling opening of the casting mold, but the rotational movement can begin immediately after the filling of the casting mold has ended. Already in this way will be considerably shorter Cycle times achieved when they are possible in the usual rising casting.

By the mold is sealed immediately after the filling with melt by at least during the turning operation firmly connected to the mold shut-off device, the mold can be decoupled from the melt container immediately after closing with still liquid molten metal.

Then, when an overhead position of the mold is reached, the shut-off device is separated from the mold according to the invention. In this position, in which the effect of gravity prevents leakage of melt from the mold, unlike in the filling position and during the turning process itself, there is no longer any risk of melt leakage. The separate from the mold shut-off can then be used again for closing subsequently to be filled molds.

Due to the fact that the casting mold can be turned immediately after filling by being kept closed by a shut-off device according to the invention during the turning process, the melt container is directly after pouring the molten metal into the casting mold for the next casting operation and, if necessary, for refilling Molten metal ready. This, too, leads to productivity, economic efficiency and increased productivity Availability of a device according to the invention over the prior art are increased.

In addition, it is easily possible by the inventive arrangement of at least for the period of rotation connected to the mold shut-off device to perform the rotation of the mold without a docked to the mold melt container. In the case of the procedure according to the invention, therefore, casting of cast parts can not only take place within short cycle times, but also proceeds in a mode of operation which can be implemented simply in terms of apparatus. In this case, the inventive method and the device according to the invention are operationally safe to carry out. Surprisingly, it has been shown that the shut-off device can be sufficiently firmly connected to the casting mold in order to securely hold the casting mold tightly closed during rotation despite the resulting loads and to reliably prevent the still molten metal melt from escaping from the mold. This was all the more surprising with the use of such shut-off devices which are released from the casting mold after being turned to be used again.

According to the invention, high-quality castings are thus obtained by a complete mold filling with optimized solidification of the molten metal, wherein at the same time the productivity is significantly increased compared to the prior art.

The melt container may be, for example, a casting furnace known per se for low-pressure casting.

The molten metal can be conveyed by pressurizing the melt surface from the melt container into the casting mold. For this purpose, a device according to the invention may comprise a device for pressurizing the melt surface in the melt container. The device for pressurizing may in particular be a compressed gas supply connected to the interior of the melt container via a valve, via which gas can be passed under pressure into the interior, which acts on the surface of the melt contained in the interior of the melt container. The gas can be air. If the risk of oxidation in the melt container is to be reduced, however, it is also possible to use a gas which is inert with respect to the molten metal, for example nitrogen or a noble gas.

A particularly robust embodiment of a device according to the invention results when the shut-off device is designed as a slide closure. Such a slide closure is usually characterized in that a first element of the closure can be displaced such that in a first position of the element a shut-off opening is opened and in a second position of the element, the opening is closed. Such a slide closure can be easily manufactured and takes up only a small amount of space. In this case, the slide closure according to the model of the prior art, in particular at least two plates each having a passage opening, wherein for closing the mold at least one of the plates from an open position in which the passages are in overlap, is moved to a closed position, in which the passage openings are completely offset from each other. Such a design of the slide closure is on the one hand robust and easy in the production technology application. On the other hand, this embodiment ensures in a particularly secure manner that no molten metal escapes from the casting mold during a rotation of the casting mold.

If the invention is to be used in mass production, the casting mold may be a permanent casting mold. However, in order to take advantage of lost shapes, such as high flexibility, it is also possible to make the mold from molded parts, such as molded sand parts. Such a mold, also referred to as a core package, is destroyed after the casting process and the solidification of the molten metal to the casting, so that then the finished casting is obtained. However, it is also conceivable that the casting mold has both permanent casting moldings and molding cores if, for example, complex internal shapes of the casting are to be produced.

Further embodiments of the invention are specified in the dependent claims and are explained in more detail with reference to an embodiment of the invention showing drawing.

The FIGS. 1 to 5 each show schematically a device for casting of light metal melt in four different operating positions in a partially broken side view.

The device V for casting an aluminum-based melt A comprises a casting mold 1, in whose wall 1a a filling opening 2 is formed. The filling opening 2 opens into a formed in the mold 1 feeder section 3, which feeds the mold cavity 4, through which the casting to be produced is imaged. In the mold cavity 4 cooling iron 5 are used. When the melt A is filled in the mold cavity 4, the cooling irons 5 effect a targeted solidification profile in order to form a specific microstructure in the regions of the cast part assigned to the cooling iron 5.

On the wall 1a of the mold 1, in which the filling opening 2 is formed, designed as a slide closure shut-6 is releasably attached. The shut-off device 6 has a first of the wall 1a directly associated slide plate 7, in which a through hole 8 is formed at a central location, and a second slide plate 9, which lies on the first slide plate 7 and in which also a through hole 10 is formed. Diameter and shape of the through holes 8,10 are on the diameter and the shape of the filling opening 2 adapted. By means of an adjusting device 11, the slide plates can be moved 7.9 against each other to bring their passage opening 8.10 in a passage position with each other and with the filling opening 2 and in a closed position in which the lying outside the passage opening 8 closed portion of the slide plate 7, the filling opening 2 closes and in which a closed, lying outside the passage opening 10 portion of the second slide plate 9 is disposed below the filling opening 2 and the filling opening 2 directly closing portion of the first slide plate 7 is supported.

The mold 1 is rotatably mounted in a rotary bearing, not shown, about a horizontally oriented axis of rotation X. To the rotation axis X, the mold 1 can be rotated by means also not shown. In addition, the mold 1 can be lifted by means of a likewise not shown adjusting device in the vertical direction Y.

Furthermore, the device 1 comprises a melt container 12, in which the aluminum melt A to be cast is stored. The melt container 12 has a lid 13, with which the melt container 12 can be sealed tightly against the environment U. Through the lid 13, a vertically aligned riser 14 is guided, the inlet opening 15 is arranged just above the bottom 16 of the melt container 12. In the operating position, the outlet opening 17 of the riser 14 is against positioned just above the lid 13. The melt container 12 is mounted on rollers 18 which are guided on rails 19.

The orientation and rotation of the mold 1 and the working positions of the shut-off devices 6 are controlled by a control device 20.

For discharging melt A from the melt container 12, the interior space enclosed by the melt container 12 with the cover 13 attached can be subjected to a compressed gas, for example air or nitrogen. For this purpose, a supply line 21 is guided through the cover 13 into the interior 12a of the melt container 12. The supply line 21 is connected to a compressed gas supply 22, which provides a required for the expulsion of each required amount of melt gas volume with sufficient pressure.

In the initial position for filling the empty mold 1 is oriented such that its filling opening 2 is directed downward in the direction S of gravity. The shut-off device 6 is opened by the passage openings 8.10 of its slide plates 7.9 are brought to cover each other and with the filling opening 2.

The mold sits with the outer slide plate 9 on the lid 13 of the positioned below the mold 1 and sealed by the lid melt container 12, wherein the Outlet opening 17 of the riser pipe 14 is aligned with the filling opening 2 of the mold 1 is aligned. In this way, the mold cavity 4 of the mold 1 is connected to the inner space 12a of the melt container 12 ( Fig. 1 ).

As a result, melt A rises through the riser 14 into the mold 1 and fills in a quiet flow the mold cavity 4 of the mold 1. The atmosphere contained in the mold cavity 4 escapes not over illustrated vents. By applying pressure, the melt A contained in the mold cavity 4 of the mold 1 is introduced uniformly and largely avoiding turbulence in all voids formed in the mold cavity 4, so that even complex moldings, such as engine blocks for internal combustion engines or the like, are generated safely and with optimum work result can ( Fig. 2 ).

As soon as the filling process is completed, the control device 20 gives a signal to close the shut-off device 6. For this purpose, while still maintaining the pressure in the melt container 12, the slide plates 7, 9 of the shut-off devices 6 are displaced relative to one another until their passage openings 8, 10 are closed by the closed section each other slide plate is closed 9.7. Once this process is completed, the mold 1 is lifted in the vertical direction Y and so separated from the melt container 12. The melt container 12 can now be moved on the rails 19 to another filling station, not shown here, where already another empty mold waiting for the filling ( Fig. 3 ).

Immediately after the separation of the casting mold 1 from the melt container 12, the control device 20 outputs a signal for rotating the casting mold 1 (FIG. Fig. 4 ).

The turning device, not shown, then rotates the casting mold 1 by 180 ° about the axis of rotation X, until its still closed by the shut-off device 6 filling opening 2 faces upwards. If this overhead position, which is directed counter to the direction of gravity, has been reached, the shut-off device 6 can be detached from the casting mold 1 and fed to a casting mold, which is not shown here, and subsequently filled with molten metal A ( Fig. 5 ).

According to the invention it is thus ensured that the castings obtained meet even the highest standards and there is no appreciable rejects in the course of casting production. At the same time, the production of castings according to the invention takes place in a simplified manner and with increased productivity.

reference numeral

A

aluminum smelter

U

Environment of the device V

S

Direction of gravity

V

Device for casting an aluminum-based melt A

X

Rotary axis of the mold 1

Y

vertically aligned adjusting axis of the casting mold 1

1

mold

1a

Wall of the mold 1

2

fill opening

3

feeder section

4

mold cavity

5

chills

6

shut-off

7

slide plate

8th

Through opening of the slide plate. 7

9

slide plate

10

Through opening

11

setting device

12

melt container

12a

Interior of the melt container 12

13

Lid of the melt container 12

14

riser

15

Entry opening of the riser 14th

16

Bottom of the melting tank

17

Outlet opening of the riser 14th

18

roll

19

rails

20

control device

21

supply line

22

Compressed gas supply

Claims (15)

1. Method for casting molten metal (A) including the following steps:

   - providing a casting mould (1) with a filling opening (2) pointing in the direction of gravity (S),

   - coupling the casting mould (1) with the filling opening (2) to a melt container (12) containing the molten metal (A),

   - conveying the molten metal (A) from the melt container (12) into the casting mould (1) counter to the direction of gravity (S),

   - sealing the casting mould (1) directly after filling with molten metal (A) using a reusable locking means (6) which is at least temporarily connected to the casting mould (1) in a fixed manner,

   - decoupling the casting mould (1) from the melt container (12) directly after closure of the casting mould (1),

   - rotating the casting mould (1) about a horizontal axis of rotation (X), wherein the casting mould (1) remains in a sealed position with respect to the locking means (6) which is firmly connected thereto during rotation,

   - the locking means (6) being separated from the casting mould (1) after rotation of the casting mould (1).
2. Method according to claim 1, characterised in that the locking means (6) is detached from the casting mould once it has reached an upper position.
3. Method according to any one of the preceding claims, characterised in that the molten metal (A) is conveyed from the melt container (12) into the casting mould (1) via a riser pipe (14).
4. Method according to any one of the preceding claims, characterised in that the molten metal (A) is conveyed from the melt container (12) into the casting mould (1) by the application of pressure to the surface of the melt.
5. Method according to any one of the preceding claims, characterised in that the locking means (6) is in the form of a slide closure which has at least two plates (7, 9) with a respective through-opening (8, 10), wherein for closing the casting mould (1) at least one of the plates (7, 9) is displaced from an opened position, in which the through-openings (8, 10) overlap, into a closed position, in which the through-openings (8, 10) are completely offset relative to each other.
6. Method according to any one of the preceding claims, characterised in that the molten metal cast is molten aluminium.
7. Device for casting molten metal (A),

   - with a casting mould (1) having a filling opening (2),

   - with a means for coupling the casting mould (A) to a melt container (12) which, in this operating position, is arranged below the casting mould (1) and contains the molten metal (A),

   - with a means for conveying the molten metal (A) from the melt container (12) into the casting mould (1) through the filling opening (2) counter to the direction of gravity (S),

   - with a means for decoupling the casting mould (1) from the melt container (12),

   - with a means for rotating the casting mould (1), when decoupled from the melt container (12), about a horizontal axis (X) associated with the casting mould (1), characterised in that the device comprises

   - a control means (20) which issues a signal for rotating the casting mould (1) about the axis of rotation (X) when the casting mould (1) is filled with melt (A), and

   - a reusable locking means (6), which is connected to the casting mould (1) in a fixed manner at least during rotation about the horizontal axis (X) thereof, for closing the filling opening (2) in the casting mould (1) which is detachably connected to the casting mould (1).
8. Device according to claim 7, characterised in that the locking means (8) is connected to the casting mould so as to be detachable from the casting mould (1) once it has reached an upper position on rotation of the casting mould (1) about the horizontal axis (X).
9. Device according to either claim 7 or claim 8, characterised in that the melt container (12) has a riser pipe (14) for conveying the molten metal (A) from the melt container (12) into the casting mould (1).
10. Device according to any one of claims 7 to 9, characterised in that the means for conveying the molten metal (A) comprises a means (22) for applying pressure to the surface of the melt in the melt container (12).
11. Device according to any one of claims 7 to 10, characterised in that the locking means (6) is a slide closure.
12. Device according to claim 11, characterised in that the locking means (6) has at least two plates (7, 9) with a respective through-opening (8, 10) and in that for closing the casting mould (1) at least one of the plates (7, 9) is displaceable from an opened position, in which the through-openings (8, 10) overlap, into a closed position, in which the through-openings (8, 10) are completely offset relative to each other.
13. Device according to any one of claims 7 to 12, characterised in that the casting mould (1) is a permanent casting mould.
14. Device according to any one of claims 7 to 13, characterised in that the casting mould (1) is formed from moulding material cores.
15. Device according to any one of claims 7 to 14, characterised in that the casting mould (1) has permanent casting mould parts and moulding material cores.

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