EP3089841B1 - Method for casting a cast part - Google Patents

Description

The invention relates to a method for casting a casting according to the Kippgießprinzip, according to the preamble of claim 1.

A method of the type mentioned is from the DE102009023881A1 known.

A method for Kippgießen is from the WO2010 / 058003A1 known. In the known method, the process of Umgießens by tilting the casting container is set in motion. In this case, the casting container or the level of the melt in the casting container is higher than the casting mold, so that the melt enters the casting container with relatively high kinetic energy. In the known solution, as is customary in such methods, the melt is scooped from a scoop with a ladle and then recast from the ladle into the casting container, with which then the mold is filled. Other casting methods are from the US2012 / 325424A1 , of the DE102006058142A1 , of the WO2010 / 068113A1 , of the US5704413A as well as the GB1164173 known.

A disadvantage of the known method, among other things, that it already before the start of the Umgießens the molten metal from the casting into the mold as a result of filling the casting container with the ladle to turbulence in the melt and to a mixing of metal oxide and molten metal and thus severe deterioration of the microstructure of the resulting casting may occur.

It is therefore an object of the invention to provide a new Kippgießverfahren, which does not have the disadvantages mentioned above.

This object is achieved by a method of the type mentioned according to the invention by the features of the characterizing part of claim 1

With the solution according to the invention, a particularly homogeneous and low-turbulence casting process can be realized. As a result, irregularities in the material structure of the casting can be avoided very well. Above all, by dispensing with the pouring of the melt from the ladle into the casting container, it is possible to achieve a particularly low swirling and transporting of the melt to the casting mold. Since the molten metal has calmed down before being transferred from the casting container into the casting mold, casting of the melt into the casting mold can also take place very evenly and without turbulence. The casting is carried out at such a speed that the metal oxide skin floats on the molten metal until the end of the overmolding. This ensures a uniform pouring of the molten metal into the casting mold.

A particularly low-turbulence encapsulation can be achieved by floating at least 80% of the metal oxide skin on the surface of the molten metal.

It has proven to be particularly advantageous if the metal oxide skin remains in the casting container until reaching the end position. In this case, it is particularly favorable if a region of the metal oxide skin facing away from the casting mold leaves the casting container last on reaching the end position and comes to rest on the surface of the molten metal in the casting mold.

Advantageously, more than 80%, preferably more than 95%, of the metal oxide skin come to rest in the region of a feeder of the casting mold in a setting position subsequent to time in the final position.

A variant of the invention, with which a particularly high quality of the casting can be achieved, provides that the encapsulation takes place at such a speed that the metal oxide skin remains elastic and undamaged until reaching the end position.

A particularly low-turbulence Umge, is achieved by the fact that the surface of the metal oxide skin located in the casting container during the pouring of the molten metal increased from the casting container into the mold. This embodiment ensures that the casting of the molten metal takes place at an optimum speed.

According to a preferred embodiment, which allows a very precise and defined encapsulation, it may be provided that the casting container is connected to the casting mold prior to casting and a relative position of the casting container with respect to the casting mold during the Umuzießens between the starting position and the end position is maintained ,

An optimal solidification behavior of the molten metal in the mold can be achieved in that the axis of rotation extends in the starting position through the mold and either lies under the mold cavity or viewed from the casting container behind the mold cavity or through the mold cavity or over the mold cavity.

In order to prevent damage to the casting by the metal oxide skin, it may be provided according to a development of the method according to the invention, that the metal oxide skin falls after reaching the end position on a feeder of the casting mold or slides into it over the entire width.

According to a variant of the invention, which is characterized by a particularly smooth and turbulence-free Umgeießen the molten metal from the casting into the mold, it may be provided that the casting container is brought after the ladling of molten metal from the scoop to the feeder of the mold, wherein the casting container has a pouring region, via which the molten metal is poured into the casting mold via the feeder, the contour of the pouring region corresponding to the contour of a section of the feeder lying below in the starting position in the vertical direction, the pouring region being directly and congruent with the feeder is connected.

To be particularly favorable, it has been found in the starting position, the contour of the feeder and the contour of the pouring are in a horizontal position or are pivoted by an angle of 30 ° maximum from the horizontal position.

Very good results with regard to the quality of the casting can be achieved in that in the end position, the contour of the feeder and the contour of the pouring area are rotated by an angle of at most 120 ° and at least 60 ° relative to the starting position.

It has proven to be particularly advantageous if the casting container is connected to the casting mold immediately after completion of the filling with the molten metal within a period of not more than 5 seconds, in particular within a period of at most 3.5 seconds, and brought into the starting position. Due to the short docking time of the casting container to the casting mold, an optimal casting temperature of the molten metal and an optimal flow behavior of the same can be ensured. Also, optimal elastic properties of the metal oxide skin can be achieved with the indicated periods.

An optimum condition of the metal oxide skin and the molten metal for casting can be achieved by filling the casting container with the molten metal in the scooping furnace within a period of time, the maximum duration of which is 3.5 seconds.

Very good results with regard to the microstructure of the casting can be achieved by moving the casting container and the casting mold from the starting position to the final position within a maximum period of 8 seconds, in particular within a maximum period of 6.5 seconds.

To be particularly advantageous, it has been found that an average temperature of the molten metal in the scooping furnace has a value derived from a range of values whose lower limit is 680 ° Celsius and its upper limit is 780 ° Celsius.

A particularly low-turbulence and gentle and low-oxide scooping of the molten metal from the scoop can be achieved in addition to the above-mentioned period for the scooping of the molten metal that the casting container at a remote in the starting position of the mold has a slot-shaped opening, wherein the casting container for scooping the molten metal is dipped from the scoop with the opening in advance in the molten metal in the scoop.

According to a further very advantageous variant of the invention, provision may be made for the casting container and the casting mold to be brought from the starting position into the end position in an overpressure atmosphere.

According to an optimal embodiment in terms of productivity and short process times, it can be provided that at least three molds are used, which are arranged on a carousel, wherein the carousel the three molds in turn from a casting position, in which a pouring the molten metal from the casting container into the casting mold, into a solidification position in which the molten metal solidifies in the casting mold, and then rotates to an operating position in which the casting mold is opened and a casting is removed from the casting mold and the casting mold is cleaned. It can be operated in parallel according to an advantageous development, two carousels.

A very high productivity with an optimum quality of the castings produced can be achieved by further turning the carousel at a constant rate having a value coming from a value range whose lower limit is 70 seconds and whose upper limit is 80 seconds.

For a better understanding of the invention, this will be explained in more detail with reference to the following figures.

Fig. 1

einen Gießbehälter, eine Gießform und einen Schöpfofen wie sie bei einem erfindungsgemäßen Verfahren verwendet werden;

Fig. 2

eine Ausgangsposition des Gießbehälters und der Gießform aus Fig. 1 vor einem Umgießen einer Metallschmelze aus dem Gießbehälter in die Gießform;

Fig. 3

eine Endposition des Gießbehälters und der Gießform aus Fig. 2 nach dem Umgießen der Metallschmelze aus dem Gießbehälter in die Gießform;

Fig. 4

eine perspektivische Ansicht des Gießbehälters und der Gießform aus Fig. 2;

Fig. 5

einen Schnitt durch den Gießbehälter und die Gießform aus Fig. 4;

Fig. 6

ein Karussell mit drei Gießformen.

In each case, in a highly simplified, schematic representation:

Fig. 1

a casting container, a casting mold and a scoop furnace as used in a method according to the invention;

Fig. 2

a starting position of the casting container and the mold from Fig. 1 prior to pouring a molten metal from the casting container into the casting mold;

Fig. 3

an end position of the casting container and the mold Fig. 2 after pouring the molten metal from the casting container into the casting mold;

Fig. 4

a perspective view of the casting container and the mold Fig. 2 ;

Fig. 5

a section through the casting container and the mold Fig. 4 ;

Fig. 6

a carousel with three molds.

By way of introduction, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numerals or the same component names, the disclosures contained in the entire description can be mutatis mutandis to the same parts with the same reference numerals or component names. Also, the location information chosen in the description, such as top, bottom, side, etc. related to the immediately described and illustrated figure and these position information in a change in position mutatis mutandis to transfer to the new location.

The embodiments show possible embodiments of the solution according to the invention, it being noted at this point that the invention is not limited to the specifically illustrated embodiments thereof, but rather various combinations of the individual embodiments are possible with each other and this variation possibility due to the teaching of technical action representational invention in the skill of those skilled in this technical field.

Furthermore, individual features or combinations of features from the different exemplary embodiments shown and described can also represent independent, inventive or inventive solutions.

The task underlying the independent inventive solutions can be taken from the description.

All information on ranges of values in objective description should be understood to include these arbitrary and all sub-ranges thereof, eg the indication 1 to 10 should be understood to encompass all sub-ranges, starting from the lower limit 1 and the upper limit 10 that is, all portions begin with a lower limit of 1 or greater and end at an upper limit of 10 or less, eg, 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

Especially in the Fig. 6 embodiment shown form the subject of an independent invention. The relevant objects and solutions according to the invention can be found in the detailed descriptions of this figure.

For the sake of order, it should finally be pointed out that in order to better understand the structure of the components of the casting apparatus used for carrying out the method, these or their components have been shown partially unevenly and / or enlarged and / or reduced in size.

According to the Figures 1 - 3 the casting takes place in a method according to the invention for casting a casting according to the Kippgießprinzip. In this case, a molten metal 1 is recast from a tiltable casting container 2 into a casting mold 3 with a mold cavity 4 depicting the casting. As the molten metal 1, an aluminum alloy is particularly preferably used, for example AC-Al Si 10 Mg (Cu), AC-Al Si8 Cu3, Al Si7 Cu3, Al Si6 Cu4. The casting mold 3 is particularly preferably a casting mold for highly stressed aluminum components, such as cylinder heads or other components of vehicle engines.

In the Figures 1 - 3 the casting container 2 and the casting mold 3 are shown in different temporally successive positions. The Umgießen can also be done by means of two or more parallel to each other, also referred to as a ladle, casting container 2.

The casting container 2 is preferably brought by a robot arm to the mold 3 and connected to this, for example hooked. The robot arm can release the casting container 2 after connecting the casting container 2 with the casting mold 3 and is available for another working process. Also, the filling of the casting container 2 is preferably carried out by means of the robot arm, which dips the casting container 2 into the molten metal 1 of the scoop 5. Here, the molten metal 1 is scooped with the casting 2 directly from a scoop 5. During the scooping or immediately thereafter, a metal oxide skin 6 forms in the casting container 2 on the surface of the molten metal 1. An average temperature of the molten metal in the scoop 5 6 has a value derived from a range of values whose lower limit is 680 ° Celsius and whose upper limit is 780 ° Celsius.

After it has been filled, the casting container 2 containing the molten metal 1 and the metal oxide skin 6 floating thereon is brought to the casting mold 3. Then, the molten metal 1 is poured from the casting container 2 into the casting mold 3 by a common rotation of the casting container 2 and the casting mold 3 from an initial position to an end position about a rotation axis a. During the overmolding, the metal oxide skin 6 floats predominantly, at least 80%, or even completely, on the molten metal 1 and remains essentially on the surface of the molten metal until it reaches the end position.

According to a variant of the invention, the metal oxide skin 6 can also remain in the casting container 2 until reaching the end position. A region of the metal oxide skin 6 facing away from the casting mold 3 leaves the casting container 2 last when it reaches the end position and comes to lie on the surface of the molten metal 1 in the casting mold 3. Conveniently, more than 80%, preferably more than 95%, of the metal oxide skin 6 come to rest in the region of a feeder 7 of the casting mold 3 in a solidification position subsequent to time in the final position.

The metal oxide skin 6 remains elastic and undamaged until reaching the end position. During the pouring over of the molten metal 1, the surface of the metal oxide skin 6 located in the casting container 2 can also increase, in particular in the direction of a pouring region of the pouring container 2. By enlarging the surface of the metal oxide skin during the casting, a particularly smooth flow of the molten metal is achieved.

The casting container 2 is connected to the casting mold 3 before casting. A relative position of the pouring container 2 with respect to the mold 3 is maintained during the overmolding between the starting position and the end position. That is, the casting container 2 follows a movement of the casting mold 3 about the axis of rotation a. To be particularly favorable, it has been found that the axis of rotation a runs in the starting position through the casting mold 3. In this case, the axis of rotation a can either be below the mold cavity 4 or from the casting container 2 Seen from behind the mold cavity 4 or through the mold cavity 4 or over the mold cavity 4.

On the pouring side, the casting mold 3 can have a feeder 7. The casting container 2 can be brought in this case after scooping the molten metal 1 from the scoop 5 to the feeder 7 of the mold 3 and connected to this feeder 7. The casting container 2 has a pouring region 8, via which the molten metal 1 flows into the feeder 7 and from there into the mold cavity 4. The contour of the pouring region 8 corresponds to the contour of a section of the feeder 7 which is located below in the starting position in the vertical direction. The pouring region 8 is preferably connected directly and congruently to the feeder 7. In the present context, the term "contour" is understood primarily to mean the shaping of a bottom region and the adjacent outer edges and outer surfaces of the feeder 7 and the pouring region 8 of the casting container 2.

After reaching the end position, the metal oxide skin 6 falls onto the feeder 7 of the casting mold 3 or slides into the feeder 7. The metal oxide skin preferably slides into the feeder 7 substantially over its entire width.

According to Fig. 4 For example, the casting container 2 may have a slot-shaped opening 9 at a region facing away from the starting position of the casting mold 3. To scoop the molten metal 6 from the scoop 5, the casting container 2 with the opening 9 is immersed in advance in the molten metal 6 located in the scooping furnace 5. Through the slot-shaped, during the scooping vertically in the molten metal 1 of the scoop 5 standing opening 9 ensures that only clean oxide-free metal flows into the casting container 2 during the scooping process. The filling of the casting container 2 in the scooping furnace 5 with the molten metal 6 takes place within a period of time whose maximum duration is 3.5 seconds.

Immediately after completion of the filling with the molten metal 6, the casting container 2 is connected to the casting mold 3 within a maximum period of 5 seconds, in particular within a maximum period of 3.5 seconds, and brought into the starting position.

How out FIG. 5 it can be seen, are in the initial position, the contour of the feeder 7 and the contour of the pouring 8 in a horizontal position. It should be noted at this point that the contours of the feeder 7 and of the pouring region in the starting position can also be pivoted about an axis of rotation a up to an angle of at most 30 ° from the horizontal position. In the end position, the contour of the feeder 7 and the contour of the pouring region 8 are rotated by an angle of at most 120 ° and at least 60 ° relative to the starting position. The casting container 2 and the casting mold 3 are moved from the starting position to the end position within a maximum period of 8 seconds, in particular within a maximum period of 6.5 seconds.

At this point it should also be pointed out that the entire process according to the invention or even only the step of pouring the molten metal 1 out of the casting container 2 into the casting mold 3 can be carried out in an overpressure atmosphere. To generate the overpressure, the casting container 2 and the casting mold 3 can be arranged in a closed space which can be filled with a gas or gas mixture, for example an inert protective gas, so that an overpressure relative to the ambient atmosphere arises outside the space. In principle, the scoop oven 5 could also be arranged in the room.

In the Fig. 6 illustrated embodiment has at least three molds 10,11, 12, which are arranged on a carousel. This embodiment constitutes an independent embodiment in its own right, which can also be used with other casting methods than those described above. The carousel rotates the three casting molds 10, 11, 12 in turn from a casting position I, in which the molten metal 6 is poured from the casting container 2 into the casting mold 10, 11, 12, into a solidification position II, in which the molten metal 1 in the casting Mold 10, 11, 12 solidifies, and then in an operating position III, in which the mold 10, 11, 12 is opened and removed a casting from the mold 10, 11, 12 and the mold 10, 11, 12 is cleaned. The carousel is further rotated at a constant rate having a value coming from a range of values whose lower limit is 70 seconds and whose upper limit is 80 seconds. In a preferred embodiment, this cycle is 75 seconds and is as follows: In the pouring position I, the docking of the pouring vessel 2 to the casting mold 11 takes 3.5 seconds, while the tilting of the pouring vessel 2 and the casting mold 11 from the starting position to the end position Takes 6.5 seconds. After reaching the end position of the casting is undocked from the mold and is available for a new scooping again. Another 56 seconds, the molten metal solidifies in the casting position I. For further rotation of the mold 11 in the position II 9 seconds are required.

In the solidification position II, the molten metal 1 or the casting in the casting mold 10 solidifies for a further 66 seconds, again requiring 9 seconds for further rotation into the operating position III. In the operating position the casting solidifies for another 10 seconds, for the opening of the casting mold it takes 9 seconds and for the removal of the casting by means of a robot 8 seconds are needed. The cleaning of the mold 3 takes 20 seconds and the insertion of new sand cores takes 10 seconds. For the closing of the mold 3 and the further rotation in the casting position I 9 seconds are required in each case. This results in a cycle time of 75 seconds for the further rotation of one of the positions I, II, III in the next position.

REFERENCE NUMBERS

1

molten metal

2

gooseneck

3

mold

4

mold cavity

5

ladle furnace

6

Metalloxidhaut

7

Speiser

8th

pouring zone

9

opening

10

mold

11

mold

12

mold

A

axis of rotation

I

casting position

II

solidification position

III

operating position

Claims (20)

1. A method for casting a cast part according to the tilt casting principle, wherein a metal melt (1) is cast out of at least one tiltable pouring flask (2) into a mold (3) with a mold cavity (4) that replicates the cast part, wherein the metal melt (1) is scooped directly out of a bale-out furnace (5) with the pouring flask (2), a metal oxide skin (6) forms in the pouring flask (2) on the surface of the metal melt (1), and the pouring flask (2) containing the metal melt (1) and metal oxide skin (6) floating thereon is moved toward the mold (3), and the metal melt (1) is poured from the pouring flask (2) into the mold (3) by jointly rotating the pouring flask (2) and mold (3) from an initial position into an end position around a rotational axis (a), characterized in that the pouring flask (2) has a slotted opening (9) at an area facing away from the mold (3) in the initial position, wherein the pouring flask is dipped into the metal melt (6) located in the bale-out furnace (5) with the opening in front (9) to scoop the metal melt (6) out of the bale-out furnace (5).
2. The method according to claim 1, characterized in that, during recasting, at least 80% of the metal oxide skin (6) floats on the surface of the metal melt (1), and remains on the surface of the metal melt (1).
3. The method according to claim 1 or 2, characterized in that the metal oxide skin (6) remains in the pouring flask (2) until the end position has been reached.
4. The method according to one of claims 1 to 3, characterized in that an area of the metal skin (6) facing away from the mold (3) exits the pouring flask (2) last once the end position has been reached, and comes to lie on the surface of the metal melt (1) in the mold (3).
5. The method according to one of claims 1 to 4, characterized in that more than 80% of the metal oxide skin (6) comes to lie in the area of a feeder (7) of the mold (3) in a solidification position that chronologically follows the end position.
6. The method according to one of claims 1 to 5, characterized in that the metal oxide skin (6) remains elastic and undamaged until the end position has been reached.
7. The method according to claims 1 to 6, characterized in that the surface of the metal oxide skin (6) located in the pouring flask (2) enlarges while pouring the metal melt (1) from the pouring flask (2) into the mold (3).
8. The method according to one of claims 1 to 7, characterized in that the pouring flask (2) is connected with the mold (3) before recasting, and a relative position of the pouring flask (2) is retained in relation to the mold (3) while recasting between the initial position and end position.
9. The method according to one of claims 1 to 8, characterized in that the rotational axis (a) runs through the mold (3) in the initial position, and either lies under the mold cavity (4) or runs behind the mold cavity (4) or through the mold cavity (4) or over the mold cavity as viewed from the pouring flask (2).
10. The method according to one of claims 1 to 9, characterized in that, once the end position has been reached, the metal oxide skin (6) falls onto a feeder (7) of the mold (3) or slides into the latter over the entire width of the feeder (7).
11. The method according to claim 10, characterized in that, once the metal melt (1) has been scooped out of the bale-out furnace (5), the pouring flask (2) is moved toward the feeder (7) of the mold (3), wherein the pouring flask has a pouring zone (8) via which the metal melt is poured by way of the feeder (7) into the mold (3), wherein the contour of the pouring zone (8) corresponds to the contour of a section of the feeder (7) that in the initial position lies at the bottom as viewed in the vertical direction, wherein the pouring zone (8) is directly and congruently connected with the feeder (7).
12. The method according to claim 11, characterized in that, in the initial position, the contour of the feeder (7) and contour of the pouring zone (8) lie in a horizontal position, or are pivoted out of the horizontal position by an angle of at most 30°.
13. The method according to claim 12, characterized in that, in the end position, the contour of the feeder (7) and contour of the pouring zone (8) are twisted by an angle of at most 120° and at least 60° relative to the initial position.
14. The method according to one of claims 1 to 13, characterized in that, immediately after filled with the metal melt (6) within a period of at most 5 seconds, the pouring flask (2) is connected with the mold (3) and brought into the initial position.
15. The method according to one of claims 1 to 14, characterized in that the pouring flask (2) in the bale-out furnace (5) is filled with the metal melt (6) within a period lasting at most 3.5 seconds.
16. The method according to one of claims 1 to 15, characterized in that the pouring flask (2) and mold (3) are moved from the initial position into the end position within a period lasting at most 8 seconds.
17. The method according to one of claims 1 to 16, characterized in that an average temperature of the metal melt (6) in the bale-out furnace (5) has a value originating from a range of values with a lower limit of 680 °C and upper limit of 780 °C.
18. The method according to one of claims 1 to 17, characterized in that the pouring flask (2) and mold (3) are brought from the initial position into the end position in an overpressure atmosphere.
19. The method according to one of claims 1 to 18, characterized in that use is made of at least three molds (10, 11, 12) arranged on a carousel, wherein the carousel turns the three molds (10, 11, 12) uniformly from a pouring position (I) in which the metal melt (6) is recast from the pouring flask (2) into the mold (10, 11, 12) into a solidification position (II) in which the metal melt (1) in the mold (10, 11, 12) solidifies, and then into an operating position (III) in which the mold (10, 11, 12) is opened, and a cast part is removed from the mold (10, 11, 12), and the mold (10, 11, 12) is cleaned.
20. The method according to claim 19, characterized in that the carousel continues to be turned at a constant rate having a value originating from a range of values with a lower limit of 70 seconds and an upper limit of 80 seconds.

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