Title:
METHOD AND SYSTEM FOR PRODUCING A CAST COMPONENT
Kind Code:
A1


Abstract:
The invention relates to a method for producing a cast component (10), in particular a diecast component, in particular made of an aluminium alloy, in which the cast component (10) is subjected, at least in part, to a heat treatment process following the casting process and removal of the cast component from its mould (12), wherein the cast component (10) is cooled immediately after reaching a target temperature (Ts) during the heat treatment or, before cooling, is heat-treated for a hold time (th) of up to 3 mins. The invention further relates to a system for producing a cast component (10) of this type.



Inventors:
Westerheide, Dirk E. O. (Versmold, DE)
Wuest, Juergen (Erding, DE)
Application Number:
12/467823
Publication Date:
11/26/2009
Filing Date:
05/18/2009
Assignee:
BDW TECHNOLOGIES GMBH (Markt Schwaben, DE)
Primary Class:
Other Classes:
164/270.1
International Classes:
C22F1/047; B22C9/00; C22F1/04
View Patent Images:



Primary Examiner:
MORILLO, JANELL COMBS
Attorney, Agent or Firm:
BARLOW, JOSEPHS & HOLMES, LTD. (PROVIDENCE, RI, US)
Claims:
1. Method for producing a cast component (10), in particular a diecast component, in particular made of an aluminium alloy, in which the cast component (10) is subjected, at least in part, to a heat treatment process following the casting process and removal of the cast component from its mould (12), characterised in that the cast component (10) is cooled immediately after reaching a target temperature (Ts) during the heat treatment or, before cooling, is heat-treated for a hold time (th) of up to 5 mins, and in particular of up to 3 mins.

2. Method according to claim 1, characterised in that, after reaching the target temperature (Ts) during the heat treatment and before cooling, the cast component (10) is heat-treated for a hold time (th) of up to 120 secs, and in particular for a hold time (th) of up to 90 secs.

3. Method according to claim 1, characterised in that, after reaching a target temperature (Ts) during the heat treatment and before cooling, the cast component (10) is heat-treated for a hold time (th) of up to 60 secs, and in particular for a hold time (th) of up to 30 secs.

4. Method according to claim 1, characterised in that the target temperature (Ts) during the heat treatment ranges from 420 to 560° C., and in particular ranges from 490 to 540° C.

5. Method according to claim 1, characterised in that the cast component (10) is at least substantially heated with a temperature gradient of 2 to 12 K/s, and in particular with a temperature gradient of 4 to 8 K/s until the target temperature (Ts) has been reached.

6. Method according to claim 1, characterised in that the cast component (10) is heated to the target temperature (Ts) by way of warm moving air.

7. Method according to claim 6, characterised in that the cast component (10) is heated by way of a plurality of warm air flows (nozzles 68).

8. Method according to claim 1, characterised in that the cast component (10) is heated to the target temperature (Ts) at a temperature ranging from 20 to 400° C., and in particular at a temperature ranging from 100 to 300° C. above the target temperature (Ts).

9. Method according to claim 1, characterised in that the cast component (10) is heated to the target temperature (Ts) at a temperature ranging from 500 to 750° C., and in particular at a temperature ranging from 600 to 720° C.

10. Method according to claim 1, characterised in that the cast component (10) is cooled from the target temperature (Ts) to a temperature (Ta) below 200° C., and in particular to a temperature ranging from 100 to 150° C.

11. Method according to claim 1, characterised in that the cast component (10) is cooled from the target temperature (Ts) by way of moving air.

12. Method according to claim 11, characterised in that the cast component (10) is cooled by way of a plurality of cool air flows (nozzles 68).

13. Method according to claim 1, characterised in that the heat treatment of the cast component (10) starts within a period of 15 mins after the cast component has been removed from its mould (12).

14. Method according to claim 1, characterised in that the heat treatment of the cast component (10) starts within a period of up to 2 mins, and preferably within a period of up to 15 secs after the cast component has been removed from its mould (12).

15. Method according to claim 1, characterised in that the heat treatment process starts when the cast component (10) is at a temperature (Ta) ranging from 50 to 400° C.

16. Method according to claim 1, characterised in that a T4, T6, T7 or O heat treatment is used as the heat treatment process.

17. Method according to claim 1, characterised in that a thermosettable aluminium alloy is used for the cast components (10), in particular the diecast components.

18. Method according to claim 16, characterised in that an aluminium alloy having an Mg content of 0.04 to 0.6% by weight, and in particular of 0.08 to 0.18% by weight is used for the cast components (10), in particular the diecast components.

19. Method according to claim 1, characterised in that the cast component (10) is heat-treated, at least in part.

20. System for producing a cast component (10), in particular a diecast component, in particular made of an aluminium alloy, comprising a heat treatment device (28), by means of which the cast component (10) is subjected, at least in part, to a heat treatment process following the casting process and removal of the cast component from its mould (12), characterised in that the heat treatment device (28) comprises a temperature, in at least one heat treatment section (40), which ranges from 20 to 400° C., and in particular ranges from 100 to 300° C. above the target temperature (Ts) of the heat treatment.

21. System according to claim 20, characterised in that the heat treatment device (28) comprises a temperature, in the at least one heat treatment section (40), which ranges from 500 to 750° C., and in particular ranges from 600 to 720° C.

22. System according to claim 20, characterised in that the cast component (10) is to be removed from the mould (12) and transported to the heat treatment device (28) by way of the same transport system (robot 24).

23. System according to claim 20, characterised in that the cast component (10) is to be removed from the mould (12) and transported to the heat treatment device (18), with no intermediate storage, by way of the transport system (robot 24).

24. System according to claim 20, characterised in that the heat treatment device (28) comprises a device (52) for heating the cast component (10) to the target temperature (Ts) by way of warm moving air.

25. System according to claim 24, characterised in that the device (52) for heating the cast component (10) comprises a plurality of nozzles (68) or the like for producing warm air flows.

26. System according to claim 20, characterised in that the heat treatment device (28) comprises a device (58) for cooling the cast component (10) from the target temperature (Ts) by way of moving air.

27. System according to claim 26, characterised in that the device (56) for cooling the cast component (10) comprises a plurality of nozzles (68) or the like for producing cool air flows.

28. System according to claim 20, characterised in that the heat treatment section (40) for heating the cast component (10) to the target temperature (Ts) comprises at least one chamber (42).

29. System according to claim 20, characterised in that the heat treatment section (40) for heating the cast component (10) to the target temperature (Ts) comprises a retaining chamber (44).

30. System according to claim 20, characterised in that the heat treatment device (28) comprises an input chamber (46) and/or an output chamber (48).

31. System according to claim 28, characterised in that the chambers (42, 44, 46, 48) of the heat treatment device (28) are separated from one another and from the outside by respective sluices (50).

32. System according to claim 20, characterised in that said system is configured for carrying out a method according to any one of claims 1 to 19.

Description:

The present invention relates to a method and system for producing a cast component, in particular a diecast component, in particular made of an aluminium alloy of the type disclosed in the preambles of claims 1 and 20.

With current conventional methods for producing a cast component, it is normal to remove the cast component from its mould together with the cast melt once cast and solidified. In this case, the cast component still has a demoulding temperature of, for example, from 50 to 400° C. The cast components are then normally cooled further by being quenched in still or moving air, or even in a reservoir, or by being sprayed with a liquid coolant, in particular with water. Once the cast component has been substantially cooled to a manageable temperature, the slugs, such as the sprue system, are separated and the cast component is roughly deburred. Should a subsequent heat treatment be carried out in order to increase the mechanical properties of the cast component, said component is normally stored temporarily for a few hours or days before the subsequent heat treatment is carried out.

The subsequent one-step or two-step heat treatment normally takes place in a separate system. The cast component is normally heated to a target temperature and kept at this temperature for a length of time. Subsequently, the cast component is correspondingly cooled from the target or hold temperature to a lower temperature, for example room temperature.

The object of the present invention is to provide a method and system of the aforementioned type, with which the cast component can be heat-treated in a particularly advantageous manner.

This object is achieved in accordance with the invention by a method and system for producing a cast component having the features of claims 1 and 20. Advantageous embodiments with useful and non-trivial developments of the invention are disclosed in the dependent claims.

In order to provide a method of the aforementioned type, by means of which the cast component can be heat-treated in a particularly advantageous manner, it is provided in accordance with the invention for the cast component to be cooled immediately after reaching a target temperature during the heat treatment or, before cooling, to be heat-treated for a hold time of up to five, in particular up to three minutes. In other words, in the case of the present method the heat treatment may be carried out in accordance with two variants. Either the cast component is immediately cooled after reaching the target or hold temperature, or after reaching the target temperature the cast component is kept at this hold temperature for up to a maximum of five, and in particular up to a maximum of three minutes. In particular, it has thus been found that in the case of a heat treatment process of this type, for example with cast components made of aluminium-silicon alloys, a yield point Rp0.2 ranging from 100 N/mm2 to 210 N/mm2 and an elongation at break A5 ranging from approximately 8% to 20% can be achieved. Depending on the field in which the cast component is to be used, particularly advantageous yield point Rp0.2 or elongation at break A5 values can be achieved by an extremely short heat treatment. Consequently, high elongation at break A5 values, for example above 15% of the present heat treatment, can be achieved if the cast components are to be used, for example, in crash structures of passenger vehicles and must therefore be resilient (in the case of energy absorption) if the respective vehicle structure is involved in a collision and is subjected to a high impact of force caused by the accident. Furthermore, correspondingly high strength properties of the yield point Rp0.2 of more than 180 N/mm2 can be achieved, for example by way of the present heat treatment if, for example, a cast component made of an aluminium-silicon alloy is used for body frame elements or the like of a motor vehicle and must exhibit correspondingly high levels of strength and rigidity.

A particular advantage of the extremely short heat treatment process further lies in that it can be particularly advantageously adapted to existing cycle times of the casting process. Normally, in the case of diecasting a cycle lasts for between 50 and 100 secs for example. The present heat treatment may thus optionally be set advantageously in such a way that once a diecast component has been demoulded it can be introduced into the heat treatment device, using the residual heat of the component, in order to subject said component to the subsequent short heat treatment. If, as in the present case, no hold time or only a short hold time is selected during the heat treatment, the cast component only remains substantially at the target temperature inside the heat treatment device during its heating phase. Heating to the target temperature may thus correspondingly be set to such a short time that the entire heat treatment is adapted to the cycle time of the diecasting process. It is thus possible to optionally dispense with buffer furnaces or the like.

In a further embodiment of the invention, after reaching the target temperature during heat treatment and before cooling, the cast component is heat-treated for a hold time of up to 120 seconds, and in particular for a hold time of up to 90 seconds. Another preferred embodiment further provides for the hold time to only be up to 60 seconds, and in particular only up to 30 seconds. The shorter this hold time can be, the more economically feasible the present method. If nothing else, reducing the hold time makes it possible to integrate the heat treatment into the above casting process in such a way that a method for producing the cast component is achieved, in which the cast components can be produced particularly quickly, without intermediate storage and in a particularly cost-effective manner.

In another preferred embodiment, the target temperature during the heat treatment is set in such a particular way that it ranges from 420° C. to 560° C., and in particular ranges from 490° C. to 540° C. In particular, solution annealing is consequently achieved which can be followed by age-hardening.

It has also proved to be advantageous if the cast component is heated, at least substantially, with a temperature gradient of 2 K/s (Kelvin/second) to 12 K/s, and in particular with a temperature gradient of 4 K/s to 8 K/s until the target temperature has been reached. The cast component can thus be brought to the target temperature in a relatively short space of time. In particular, if the casting heat of the cast component is also used, i.e. if the cast component is immediately or promptly subjected to the heat treatment once it has been cast and demoulded, extremely short heating times may be observed until the target temperature is reached. These heating times are, for example, approximately 30 to 180 secs. Furthermore, if no hold time or a relatively short hold time at the target temperature or hold temperature of up to five, or in particular up to three minutes is selected, the entire heat treatment can thus clearly be carried out within an extremely short space of time.

In a further embodiment of the invention, the cast component is heated to the target temperature by warm or hot moving air or another moving gas. The desired high-temperature gradients are thus achieved.

In a further embodiment of the invention it has proved to be advantageous to use a plurality of warm air flows, by which means the cast component is heated. The plurality of warm air flows may optionally be at different temperatures so a cast component having different thicknesses or the like can be evenly heated and the target temperature can be achieved consistently over the entire cast component.

In a further embodiment of the invention, the cast component is heated to the target temperature at a temperature ranging from 20° C. to 400° C., and in particular at a temperature ranging from 100° C. to 300° C. above the target temperature. In other words, the cast component is, for example, supplied with warm or hot moving air which is considerably warmer or hotter than the desired target or hold temperature of the cast component. In particular, it is thus possible to heat the cast component to the target temperature particularly quickly without this excessive temperature damaging the structure of the cast component.

In a further embodiment of the invention, it has proved to be advantageous if a temperature, for example of the warm or hot moving air, ranging from 500° C. to 750° C., and in particular a temperature ranging from 600° C. to 720° C. is used. It is thus ensured that a cast component consisting of an aluminium-silicon alloy, for example, is heated in a particularly quick manner.

It has also proved to be advantageous if the cast component is cooled from the target temperature to a temperature below 200° C., and in particular to a temperature ranging from 100° C. to 150° C. In another embodiment of the invention this may be achieved by way of moving air for example, said air being produced by a plurality of cool air flows for example. The plurality of cool air flows may in turn fluctuate in intensity or temperature so as to cool component regions of differing thickness equally for example. In any case, accelerated cooling is achieved by the cold moving air which, for example, has a negative temperature gradient which lies within the range of the temperature gradient when heating the cast component to the target temperature.

In order to be able to subject the cast component to a heat treatment in a much more energy-efficient manner and to be able to produce the cast component with a much quicker production time, it is provided in a further embodiment of the invention for the heat treatment of the cast component to begin immediately after removal from its mould or within a period of up to 15 mins after removal from its mould. In other words, it is thus provided for the cast component to no longer be cooled to ambient or room temperature after removal from its mould, but instead for the solidification heat or residual heat of the cast component to be used so as to again heat the cast component during heat treatment. In this case, the cast component is, in particular, again heated from a temperature close to its demoulding temperature and is subjected to the heat treatment. A further advantage is also that the time and costs needed to store the cast components between demoulding and the subsequent heat treatments can now be significantly reduced.

In an advantageous embodiment of the invention it is provided for the heat treatment process of the cast component to be started within a period of up to 2 mins, and preferably within a period of up to 15 secs after removal of the cast component from its mould. The cast component thus has the highest temperature possible close to its demoulding temperature. In a further advantageous embodiment of the invention it is provided for the heat treatment process to be started immediately or within a period of 3 to 8 secs after demoulding so the cast component can be heated, at least approximately, from its demoulding temperature. It is clear that in such a short space of time particularly quick cycle times and a particularly quick production of the cast components can be achieved.

It is also advantageous if the heat treatment process is started at a temperature of the cast component ranging from 50° to 400° C., and preferably above 150° C. of the cast component. The cast component may thus be heated in a particularly economically feasible manner to a temperature which generally ranges from 400° to 540° C. in the case of aluminium-silicon alloys, since the cast component must be heated by a considerably lower difference in temperature than would be necessary if heating from ambient or room temperature. Since only the difference in temperature between, for example, approximately 150° C. when demoulding and placing the cast component in the heat treatment device and approximately 490° C. when heat-treating the cast component must therefore be overcome, there is an extremely high potential to save energy and time in such a way that a production process can be achieved which is extremely economically feasible and also ecologically sound.

In a further embodiment of the invention, the T6 or T7 heat treatment which is usual for aluminium cast alloys and provides solution annealing, cooling and age-hardening is used as the heat treatment process. Alternatively, a T4 heat treatment may be used which only comprises solution annealing, or an O heat treatment may be used which only includes soft annealing. A soft annealing process of this type preferably takes place in a range from 280° C. to 440° C., and in particular at a temperature ranging from 340° C. to 420° C.

The production method according to the invention has thus proved to be advantageous, in particular when diecasting cast components made of an aluminium-silicon alloy, since in this case there is considerable potential to save time and energy. If, for example, a thermosettable aluminium-silicon alloy of the AlSi10MnMg type with an Mg content of 0.04 to 0.6% by weight, and in particular of 0.08 to 0.18% by weight is used, the aforementioned values for the yield point Rp0.2 ranging from approximately 100 to 210 N/mm2 and for elongation at break A5 ranging from approximately 8 to 20% can be achieved. Alternatively, an aluminium-silicon alloy for example, in particular of the AlSiMnMgFe type having a high silicon content of 4 to 12%, and in particular of 7 to 11% may be used.

As comprised within the scope of the invention, however, it should be noted that the production method according to the invention may of course also be used for cast components made of different alloys. In addition to use in the case of a diecasting process, it is thus in particular also conceivable to use the method according to the invention in the case of sand casting or chill casting.

Of course, the cast component does not have to be completely heat-treated during the heat treatment. It would of course also be conceivable to only heat-treat portions of a respective cast component correspondingly so as to change the properties of said component. It would also be conceivable to heat a component, for example by way of warm moving air, to different temperatures in different regions and to then heat and cool a component to different temperatures starting from the target temperature so as to thus achieve different material properties in different regions.

The cast components may be age-hardened immediately following solution annealing. Of course, age-hardening may also take place at a later point, provided that a corresponding subsequent treatment with a suitable thermal influence takes place, such as cathodic dip-coating, for example of the body-in-white of a motor vehicle.

The aforementioned advantages described in conjunction with the method according to the invention also apply to the system according to claim 20. The advantages described below also apply to the method according to claims 1 to 19.

The system according to claim 20 is characterised, in particular, in that the temperature thereof is a lot higher than the target temperature of the heat treatment or of the cast component to be heat-treated. The desired rapid heating of the cast component is thus achieved in such a way that the heat treatment can easily be integrated into the cycle times of the casting process of the cast component for example.

In a further embodiment of the invention, the production process is additionally shortened and simplified in that the cast component is removed from the mould and transported to the heat treatment device by way of the same transport system, for example in the form of a robot.

A particularly cost-effective and time-saving production process is thus achieved, in which the cast component is removed from the mould and transported to the heat treatment device by way of the transport system without intermediate storage. Furthermore, in this way the heat treatment can be started from a relatively high demoulding temperature of the cast component.

The heat treatment device preferably comprises a heat treatment section, in which the respective cast component is heated, for example from a temperature of, for example, approximately 150° C. (i.e. using the residual heat of the component) to the target temperature of the component of, for example, approximately 490° C. to 560° C. This heat treatment section may thus comprise at least one heat treatment chamber, in which this heating process to the target temperature is carried out. The heat treatment section may also optionally comprise a retaining chamber, namely if the cast component is not to be cooled immediately after reaching the target temperature, but instead is to be kept at the target temperature or hold temperature for a hold time of up to 3 minutes before a subsequent cooling process takes place.

Before the heat treatment section, the heat treatment device may also comprise an input chamber so that when opening the heat treatment chamber the temperature inside does not decrease excessively. In addition, the heat treatment device may comprise an output chamber so as to avoid an excessive decrease in temperature when the individual sluices between the heat treatment section and the output chamber are opened.

Further advantages, features and details of the invention will become clear from the following description of an embodiment, with reference to the drawings, in which:

FIG. 1 is a schematic and figurative construction of the system for producing a cast component which is formed in a diecasting process and subsequently treated in a heat treatment process inside a heat treatment device and, optionally, an ageing furnace;

FIG. 2 is a schematic diagram of the temperature curve over time of the cast component during the heat treatment;

FIG. 3 is a schematic view of the heat treatment device for carrying out the heat treatment of the cast component; and

FIG. 4 is a perspective view of a detail of a substantially identically constructed device for heating the cast component to the target temperature and for cooling the cast component from the target temperature by way of warm and cold moving air, the device comprising a plurality of nozzles or the like for producing warm air flows and cool air flows.

It can be seen from FIG. 1 that a cast component 10 is produced in a diecasting process, in which the liquid molten metal is quickly poured into a mould 12 configured as a metal die at a correspondingly high pressure and over a correspondingly short space of time. The mould 12 is thus held in a corresponding diecasting machine 14, via which two mould halves 16, 18 of the mould 12 are to be opened and closed. The mould 12 is provided from a casting chamber 22 with molten metal from a casting container 20. In the case of the present diecasting process, a thermosettable aluminium-silicon alloy, for example of the AlSi10MnMg type, is used which has an Mg content, for example, of 0.04 to 0.6% by weight, and in particular of 0.08 to 0.18% by weight. Specific alloys thus comprise an Mg content of 0.08, 0.12 and 0.18% by weight.

An aluminium diecasting alloy of this type is, for example, known from EP 0 997 550 B1, the disclosure of which is expressly contained herein. The Mg content of said alloy has been changed in accordance with the above details.

Once the molten metal has solidified, the cast component 10 is demoulded after the mould halves 16, 18 have been opened and the component has been removed via the ejector pins 23 by a robot 24. The robot 24 thus comprises a gripping means 26, with which it can receive the cast component 10, preferably at a slug 32, such as the sprue system or the like. It is thus ensured that substantial regions and the final moulding of the cast component 10 are not unnecessarily deformed by the retaining force exerted by the robot 24 or by its gripping means 26.

In the present embodiment, the cast component 10 is introduced into a heat treatment device 28, described hereinafter in greater detail and shown only figuratively in FIG. 1, immediately after having been removed from its mould 12.

Owing to the immediate or prompt heat treatment, the cast component 10 still has a temperature close to the demoulding temperature of approximately 50° to 400° C., and preferably above 150°to 180° C. when it is introduced into the heat treatment furnace 28. The cast component 10 must therefore only be heated by a relatively low difference in temperature until it reaches a target or hold temperature.

In the present case, the heat treatment process does not have to be carried out immediately once the cast component 10 has been removed from its mould. Instead, the heat treatment process may be started within a period of up to 15 mins after the cast component has been removed from its mould. In this case it is also possible for the cast component 10 to be stored in the meantime in a buffer furnace associated with the heat treatment device 28. Since the heat treatment is carried out either immediately or promptly after demoulding, the cast component 10 is removed from the mould 12 by a robot 24 and is passed to the heat treatment device 28. It is therefore obviously necessary for the heat treatment device 28 to be arranged in the vicinity of the diecasting machine 14 and the mould 12.

The heat treatment process described hereinafter in greater detail may be carried out relatively quickly owing to the fact that the cast component 10 introduced into the heat treatment device 28 already has a temperature close to the demoulding temperature. After the heat treatment, the cast component 10 may be guided from the heat treatment device 28. Since the slug 32 is still present on the cast component 10, the component is held via said slug 32 by the gripping means 26 of the robot 24 in a simple manner. Another advantage of the slug 32 is that it contributes to the stabilisation of the cast component 10 when said component is cooled by means of the fan 30 and thus reduces warping.

Since, in this case, the cast component 10 is still extremely soft after cooling, it may be mechanically processed in a simple manner in a further process step by way of a corresponding separation device 34. In the separation device 34, the slug 32 is removed from the cast component 10, whereby the relatively soft material is accounting for the fact that there is no major warping. In a further process step, the moulding of the cast component 10 may optionally be levelled. The cast component 10 may be transferred to the separation device 34 again via the gripping means 26 of the robot 24. Inside the separation device 34, the slug 32 may also be used as a stop or template for the cast component 10.

Once the mechanical processing inside the separation device 34 has been carried out, the cast component 10 is introduced into an ageing furnace 36, in which the cast component 10 is treated, for example at a temperature of 140° to 240° C., for an ageing time of approximately 15 mins to 10 hours. The cast component 10 may again optionally be transferred from the separation device 34 to the ageing furnace 36 by the robot 24.

As shown by the line 35, the ageing furnace 36 does not have to form part of the system, but instead may also be separate. Furthermore, the cast component 10 may also be age-hardened at a later point, provided there is a corresponding subsequent treatment with suitable thermal influence, such as cathodic dip-coating, for example of the body-in-white of a motor vehicle. Cathodic dip-coating and the age-hardening process associated therewith may be carried out over a period of from 15 to 30 mins at a temperature ranging from 80° to 240° C., and in particular ranging from 160° to 220° C.

As comprised in the invention, it is noted that, in particular, the slug 32 may be removed by way of the separation device 34 and the age-hardening process may be carried out by way of the ageing furnace 36 at a considerable time after the heat treatment which takes place inside the heat treatment device 28.

It is also provided within the scope of the invention that a human worker may be provided instead of the robot 24, who can remove the cast component 10 from its mould 12 and transfer the cast component in accordance with the other process steps.

FIG. 2 is a schematic diagram of the temperature curve over time of the cast component during the heat treatment inside the heat treatment device 28.

The temperature T of the cast component is thus plotted on the y-axis, whilst the curve over time t is shown on the x-axis.

In particular, a target temperature Ts is given on the y-axis, to which temperature the cast component 10 is to be heated during the heat treatment or during the present solution annealing process. In the present case, the starting point is a starting temperature Ta which, in the present case, ranges from 50° C. to 400° C. In other words, in the present case it is provided in particular to use the residual heat of the component (as already described) and to start the heat treatment of the cast component 10 relatively promptly after its removal from the mould 12. The cast component 10 thus still comprises the residual heat in the described temperature range in such a way that the cast component 10 does not have to be heated from room temperature. However, as comprised within the scope of the invention, it should be noted that this is also optionally possible.

Starting from the starting temperature Ta, the cast component is quickly heated to a target temperature Ts which ranges from 420° C. to 560° C., and in particular ranges from 490° C. to 540° C. In this case, a relatively high temperature gradient of approximately 2 K/s to 12 K/s, and in particular a temperature gradient of 4 K/s to 8 K/s is provided. In other words, in the present case the cast component 10 is heated by several Kelvins per second. This heating process takes place, in this case, at a temperature ranging from 500° C. to 750° C., and in particular at a temperature ranging from 600° C. to 720° C. In other words, a temperature is selected, for example inside a heat treatment furnace or a heat treatment chamber, which is considerably higher than the desired target temperature Ts of the cast component 10. The cast component 10 is thus heated in an accelerated manner. The time between starting the heat treatment ta and the point ts at which the cast component 10 has reached the target temperature Ts is thus shown on the x-axis.

The solid line thus shows a temperature curve which comprises a temperature, for example in the heat treatment device 28, which corresponds at least approximately to the target temperature Ts. If, in contrast, a temperature is set inside the heat treatment device 28 which is considerably higher than the target temperature Ts, a temperature curve H is obtained for example which is shown by way of a dashed line. This differs from the temperature curve shown with a solid line as it reaches the target temperature Ts quicker and consequently has a considerably more pronounced peak.

In the present heat treatment process, it is possible in extreme cases for the cooling process to be started immediately after the target temperature Ts has been achieved, as is shown by the corresponding temperature curve. In other words, in this case the cast component 10 is not kept, at least substantially, at the target temperature Ts, but instead is immediately cooled again after reaching this temperature. A saw-toothed temperature curve is thus obtained.

A further temperature curve according to FIG. 2 shows a heat treatment process, in which after reaching the target temperature Ts and before cooling, the cast component 10 is kept at the target temperature or hold temperature for a hold time th and is only then cooled. This hold time th may lie within a period between zero and five minutes, and in particular between zero and three minutes. In a preferred embodiment, this hold time lies within a range up to 120 seconds, and in particular in a range up to 90 seconds. A further specific embodiment provides a hold time of up to 60 seconds, and in particular of up to 30 seconds. Obviously, the shorter the hold time, the shorter the casting cycles of the previous casting process can be maintained.

It can also be seen from FIG. 2 that the cast component 10 is also cooled with a correspondingly negative temperature gradient which corresponds with the temperature gradient when heating the cast component 10 as regards its size.

In the present case, the cast component 10 is cooled to a temperature Tk in the range of below 200° C., and in particular ranging from 100° C. to 150° C. Cooling to room temperature is, of course, also possible.

FIG. 3 is a schematic view of the heat treatment device 28 shown schematically in FIG. 1 of a corresponding system for producing the cast component 10. In the present case, the heat treatment device 28 comprises a heat treatment section 40 which comprises in the present case at least one corresponding heating chamber 42. The cast component 10 is heated to a target temperature Ts in said heating chamber 42. If the cast component 10 is also to be kept at the target temperature Ts or the hold temperature for a specific hold time th, this may optionally take place in a separate retaining chamber 44.

The heating chamber 42 may be arranged after an input chamber 46 so as to avoid a considerable drop in temperature when introducing the cast component 10 into the heat treatment section 40. In addition, an output chamber 48 may be arranged after the heat treatment section 40, inside which chamber the cast component 10 may also be cooled for example.

In the present embodiment, the individual chambers 42, 44, 46, 48 are separated from one another by corresponding sluices 50. These sluices 50 may be correspondingly opened and closed in such a way that when a single sluice 50 is opened, there is a relatively low fall in temperature, in particular in chambers 42 and 44 of the heat treatment section 40.

Furthermore, the heat treatment device 28 comprises a plurality of devices 52, 54, 56 for producing moving air. Warm or hot moving air is thus produced inside the heat treatment section 40. In contrast, cool air is produced inside the output chamber 48.

A perspective view of a detail of a device of this type 52, 54, 56 is shown in FIG. 4, it being possible for the device to basically be configured in the same way, whether it is to be used for heating or cooling the cast component 10.

In the present case, respective air flows are thus achieved by way of a fan (not shown), which air flows travel via feed lines 58, 60 to respective exhaust beds 62, 64. Each of the exhaust beds 62, 64, which are arranged opposite one another and between which the cast component 10 to be heated or cooled respectively is arranged on a corresponding stand 66, comprises a plurality of nozzles 68, from which a respective air flow may be released. If warm or hot air is to be produced, respective burners may be provided in the region of the nozzles 68, which burners heat the respective air flow. Of course, other heating elements are also conceivable.

The distinctiveness of the present nozzles 68 lies in that a plurality of individual warm or cool air flows may be produced which may differ from one another in terms of heat and intensity.

In the case of the devices 52 and 54 for heating the cast components 10, it is also conceivable, for example, to use warm air flows of differing temperature and/or intensity in order to achieve the different intensity of warm air over the respective exhaust bed 62, 64. This different intensity and/or temperature may, for example, be adjusted to different shapes or wall thicknesses of the cast component 10 in such a way that the temperature distribution inside the cast component 10 is equal or, if desired, different at local points. This may, for example, be achieved by the nozzles 68 having exhaust cross-sections of differing size. In other words, targeted heating by means of the plurality of nozzles 68 may be achieved, optionally with different levels of heating at local points. Instead of arranging the nozzles 68 on opposite sides of the cast component 10 (in this case above and below), it is of course possible to arrange the nozzles 68 on more or fewer sides of the cast component 14.

In contrast, in the case of the device 56 for cooling the cast component 10, the cool moving air may be varied in that a respective cool air flow is released from the respective nozzles 68 with a different flow volume in each case. In this case also, the cast component 10 may be cooled uniformly or unevenly in parts, for example in order to cool the cast component 10 uniformly or unevenly at local points.

It is also possible to incorporate the ageing furnace 36 into the heat treatment device 28.

It can thus be seen from FIGS. 2 to 4 that with the present method and the present system, a heat treatment process is possible which is carried out extremely quickly and may optionally immediately follow a casting process. This rapid heat treatment process can be adapted to the cycle time of the casting process in such an advantageous manner that, for example, a buffer furnace is no longer needed. However, if there are different cycle times between the casting process and the heat treatment process, a circular furnace or the like may optionally be used if, for example, the cycle time of the casting process is shorter than that of the heat treatment process.

In conjunction with the aforementioned alloy, high values of elongation at break A5, for example ranging from 8% to 20%, and high values of yield point, for example ranging from 100 N/mm2 to 200 N/mm2 may optionally be achieved by way of the heat treatment process. The mechanical properties which can be achieved are highly dependent on the alloy. It is possible that the values could be higher. The setting of the values, in particular of the yield point Rp0.2 and the elongation at break A5, thus depends primarily on the Mg content used and the respective positive and negative temperature gradients when heating and cooling the cast component 10.

As comprised within the scope of the invention, it is to be noted that instead of heating by way of moving air, another way of heating is of course also possible. In particular, it is also possible to use another moving gas instead of moving air.

In addition, the cast component 10 may also be heated or cooled in an accelerated manner by bringing the cast component 10 into contact with one or more correspondingly warm or hot or cold elements. It is thus conceivable, for example, to cool the cast component 10 using correspondingly cool sand or water. It is also possible to carry out a heating process in this manner.

In the present case, the moving warm air flow is configured so as to be considerably warmer than the target temperature Ts of the cast component 10. For example, the temperature inside the furnace chamber 42 is set so as to range from 20° C. to 400° C., and in particular so as to range from 100° C. to 300° C. above the target temperature Ts. The cast component 10 is thus quickly heated and must optionally be duly removed from the heating chamber 42 so the target temperature Ts is not temporarily exceeded due to drag effects or inertia effects.