Method and device for heat treating a cast component for a motor vehicle
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- AUDI AG
- Filing Date
- 2024-06-12
- Publication Date
- 2026-05-06
Smart Images
Figure EP2024066232_02012025_PF_FP_ABST
Abstract
Description
[0001] Method and device for heat treating a cast component for a motor vehicle
[0002] DESCRIPTION:
[0003] The invention relates to a method for heat-treating a cast component for a motor vehicle, in which the heat treatment comprises solution annealing and age-hardening of the cast component. The cast component is removed from a casting mold and subjected to solution annealing to homogenize at least one alloy constituent of the cast component. Age-hardening increases the hardness of the cast component. Furthermore, the invention relates to a device for heat-treating a cast component for a motor vehicle.
[0004] DE 10 2010 009 118 A1 describes a method and apparatus for the heat treatment of light metal die-cast parts by solution annealing, cooling, and age-hardening. The castings are solution-annealed using infrared radiation immediately after removal from the mold or while still in the mold before removal, then quenched and subjected to artificial age-hardening.
[0005] Naturally hard alloys, which reach their final strength immediately after casting or pouring, can be used to produce aluminum die-cast components. Such naturally hard alloys do not become harder through subsequent heat treatment or exposure to heat. Furthermore, heat-treatable alloys can be used to produce aluminum die-cast components. These alloys undergo at least one heat treatment step after the casting process to achieve specific final properties. These heat-treatable alloys are significantly superior to naturally hard alloys in terms of achievable strength, but also in terms of formability. This is especially true when the alloy is a silicon-containing aluminum alloy.Hardenable alloys are therefore preferable when die-cast components with thin walls and the lowest possible weight are to be produced, as can be the case in particular in the production of cast components for motor vehicles.
[0006] There are various process routes for the heat treatment of cast components made of age-hardenable alloys. In the so-called T5 heat treatment, the cast component is simply aged in a separate step after casting, i.e., after removal from the mold. Solution annealing for the purpose of homogenizing the material is omitted. An advantage of this variant or process route is that it is a comparatively lean process, which nevertheless allows high strengths to be achieved. However, this variant does not exploit the maximum possible properties, particularly with regard to the formability of the manufactured cast component.In particular, when a silicon-containing aluminum alloy is subjected to the T5 heat treatment, the formability is significantly less than would be the case if solution annealing were carried out as an additional heat treatment step.
[0007] Another process route or variant is the so-called T6 or T7 heat treatment. Here, after the casting of the cast component, it is first solution annealed at high temperatures. Solution annealing, in particular, achieves the redissolution of certain alloy components, which enables increased formation of precipitates during subsequent ageing. In T6 / T7 heat treatment, the cast component is quenched after solution annealing and then artificially aged until the cast component has reached the desired final strength. While this type of heat treatment achieves very good properties of the cast component in terms of strength and formability, the separate solution annealing process requires an additional furnace. This is associated with higher process costs.
[0008] In addition, with T6 or T7 heat treatment, the high temperatures required for solution annealing are maintained for a relatively long period of time, for example, 10 to 40 minutes. Because aluminum alloys in particular are comparatively soft, undesirable deformations can occur during solution annealing during such a period due to the weight of the cast component. This, in turn, can lead to the finished cast component not meeting the desired dimensional accuracy requirements. In other words, deviations in dimensional accuracy can occur, especially significant ones. Therefore, T6 or T7 heat treatment are not suitable, especially for relatively large cast components.
[0009] With regard to the heat treatment steps of solution annealing and artificial ageing, there is therefore a conflict of objectives. To achieve good forming properties of the cast material, which can be achieved through solution annealing, high annealing temperatures are required, which, however, can be associated with reduced dimensional stability or distortion. Furthermore, a heat treatment facility for solution annealing is complex. Particularly in the production of voluminous die-cast components, a relatively large heat treatment facility is also required for solution annealing. This is expensive. In addition, such a large heat treatment facility for solution annealing requires a lot of space. Furthermore, it is difficult to achieve sufficiently rapid quenching following solution annealing in the production of voluminous or large cast components.To achieve good dimensional accuracy, which is particularly desirable for large cast components, solution annealing over a long period of time is not effective. Especially with a high component weight, increased distortion can occur due to creep effects over the comparatively long solution annealing period. Furthermore, rapid heating is hardly possible or impossible in a forced-air furnace due to system limitations if the component to be solution annealed is comparatively large or has a high mass.
[0010] The object of the present invention is to provide a method of the type mentioned at the outset which is particularly low-cost and to provide a device suitable for carrying out the method.
[0011] This object is achieved by a method having the features of patent claim 1 and by a device having the features of patent claim 10. Advantageous embodiments with expedient further developments of the invention are specified in the dependent patent claims and in the following description.
[0012] In the method according to the invention for heat-treating a cast component for a motor vehicle, the heat treatment comprises solution annealing and age-hardening of the cast component. In the method, the cast component is removed from a casting mold and subjected to solution annealing to homogenize at least one alloy constituent of the cast component. In addition, the age-hardening increases the hardness of the cast component. Before age-hardening, at least a portion of the cast component is provided with at least one coating material that can be hardened by applying heat. Age-hardening is effected at least partially by the heat applied to the cast component to harden the at least one coating material.This is based on the realization that the curing of coating materials, such as those used in a painting process during the production of cast components for a motor vehicle, requires heat anyway. This heat serves to cure at least one coating material. In this case, the heat used in the painting process, in particular the paint curing process, is used for aging and thus for increasing the hardness of the cast component. Consequently, the process is particularly low-cost.
[0013] Increasing the hardness of the cast component is particularly advantageous when the cast component is used for a body of the motor vehicle, for example as a cast node or similar connecting component which is used when connecting other body components of the motor vehicle.
[0014] During the age-hardening heat treatment step, phases known as precipitates are formed in a matrix within the previously single-phase material. This formation of precipitates, which can particularly be Mg2Si precipitates when using aluminum alloys containing silicon and magnesium, increases the hardness of the finished cast component.
[0015] Although the cast component undergoes the heat treatment steps of solution annealing and artificial ageing, no separate heat treatment facility is required for artificial ageing, as is typically required for T6 or T7 heat treatment. Thus, the lean, cost-effective T5 heat treatment process is supplemented with the heat treatment step of solution annealing, which is typically required for T6 or T7 heat treatment. Therefore, despite the lean and cost-effective process, the cast component can achieve the advantageous properties of high strength and high formability, which are typically reserved for T6 or T7 heat treatment.And advantageously, no separate heat treatment plant needs to be provided for the artificial aging, since the aging is effected at least partially, preferably predominantly, in particular completely, by the heat to which the cast component is exposed anyway for the purpose of curing the at least one coating material.
[0016] Furthermore, by means of the process in which the age-hardening is effected at least partially by the heat used to cure the at least one coating material, particularly good dimensional stability of the cast component can be achieved. This is because, if a complex heat treatment facility is dispensed with, in which the solution annealing is carried out over a comparatively long period of time, for example, 10 to 40 minutes, as in the T6 or T7 heat treatment, creep or creep processes do not occur or only occur to a minor extent. Particularly with large cast components, creep processes can occur during the solution annealing or annealing process due to the dead weight of the components. In particular, if the solution annealing is carried out with a rapid heating rate and short holding time, such creep processes are advantageously significantly reduced.
[0017] Accordingly, the process offers the possibility of cost-effectively heat-treating even relatively large cast components into a condition that would normally only be achievable through T6 or T7 heat treatment. This is advantageous. Due to the distortions that occur during T6 or T7 heat treatment, such large cast components could previously only be used in their naturally hardened condition or in the condition achievable through T5 heat treatment. The cast component obtained using the process is advantageously characterized by particularly high strength and very good formability. This results in significant savings potential with regard to the weight of the cast component. Even very thin wall thicknesses of the cast component can be realized.This is particularly advantageous in the presently preferred use of the cast component for the body of the motor vehicle.
[0018] Preferably, the cast component is removed from the casting mold by means of a handling device. The cast component is introduced into a heating device by means of the handling device, wherein the heating device heats the cast component to a temperature at which the solution annealing takes place. The handling device, which is provided anyway for removing the cast component from the casting mold, is therefore used to introduce the cast component into the heating device. This allows the heating of the cast component to the temperature at which the solution annealing takes place in close proximity to the casting mold. This is advantageous in view of the minimal space required for carrying out the process. In particular, a complex heat treatment system can be dispensed with.
[0019] The casting mold from which the cast component is removed by means of the handling device can be arranged in a casting cell which is secured from the surroundings by a fence or similar shielding device against unauthorized or unintentional access. In this case, the handling device and preferably also the heating device can be accommodated in the casting cell. However, it is also possible to arrange the heating device directly at the exit of such a casting cell, i.e. in close spatial proximity to the casting cell. This is also advantageous in view of the small space requirement of the device for carrying out the method. In addition, it can be ensured that the handling device can very easily remove the cast component from the casting mold and place it in the heating device.
[0020] Furthermore, it is advantageous that the heat present in the component resulting from the casting process can be utilized to advantage, so that the heating of the cast component to the temperature at which solution annealing takes place takes place particularly quickly in the heating device. It is therefore also advantageous if the handling device that has removed the cast component from the mold places the cast component directly into the heating device.
[0021] The handling device can, in particular, be provided by at least one robot. For example, one robot can grasp the cast component after the mold has been opened and remove it from the mold, and this robot can then place the cast component into the heating device. However, it can also be provided that a plurality of robots are used for these handling steps, forming the handling device.
[0022] Preferably, the cast component is heated by means of a heating device emitting infrared radiation to a temperature at which the solution annealing takes place. A receiving chamber of the heating device, into which the cast component is placed, is heated to a heating temperature that is at least 50 percent higher than the temperature at which the solution annealing takes place.
[0023] By means of the heating device emitting infrared radiation or such an infrared furnace, the cast component can be brought very quickly to the temperature at which solution annealing takes place. Accordingly, a very rapid heating rate can be achieved by means of the heating device emitting infrared radiation during operation. This is particularly advantageous because, despite the provision of the heat treatment step in the form of solution annealing, the production of the cast component can be designed to be neutral with regard to the cycle time. In other words, carrying out solution annealing does not lead to an undesirably long delay in the production of the cast component. Rather, the cast components removed from the casting mold according to the casting cycles can be subjected to solution annealing according to the casting cycle times.
[0024] For this purpose, the heating device can have several chambers into which the respective cast components can be placed after being removed from the casting mold.
[0025] Additionally or alternatively, the cast components can pass through the heating device, whereby the length of the heating device in the direction of production is sufficiently large that each cast component is subjected to solution annealing to the desired extent.
[0026] Both of these processes enable the production of cast components with a neutral cycle time. This is due, among other things, to the fact that the heating device emitting infrared radiation allows the respective cast component to heat up to the heating temperature particularly quickly.
[0027] By bringing the receiving chamber of the heating device, into which the cast component is placed, to a heating temperature that is at least 50 percent higher than the temperature at which solution annealing takes place, the cast component is heated with a high gradient. This can be achieved in particular by using infrared radiators in the heating device that emits infrared radiation. The associated advantages are particularly evident when the receiving chamber of the heating device is brought to a heating temperature that is at least 75 percent higher than the temperature at which solution annealing takes place. It can also be provided that the heating temperature is approximately twice the temperature to be set for solution annealing.
[0028] For example, in a cast component where the target temperature for solution annealing is in the range of approximately 500 °C, the chamber housing the infrared-emitting heating device can be heated to a temperature of approximately 900 °C. This allows the cast component to be heated particularly quickly to the temperature required for solution annealing.
[0029] The temperature to be set for solution annealing the respective cast component depends on the alloy used to manufacture the cast component. For cast components made from the respective alloys, it is particularly advantageous if the heating temperature achievable using the infrared radiation emitted by the heating device is significantly higher than the target temperature of the respective cast component, i.e., the temperature at which solution annealing takes place.
[0030] Preferably, a uniform heat distribution is achieved in the receiving space by operating a plurality of infrared radiators of the heating device and / or by means of reflection elements and / or convection elements of the heating device. Such a diffuse radiation chamber in the receiving space, into which the cast component is inserted, ensures a very uniform and at the same time rapid heating of the cast component to the temperature at which the solution annealing takes place.
[0031] In particular, the infrared radiators can be designed as high-performance radiators capable of providing a heating temperature of up to approximately 900°C. If a plurality of reflection elements, in particular in the form of nanoreflectors, and / or convection elements are additionally used, the high temperature can be provided particularly quickly and evenly in the receiving space. It can be provided that the cast component is kept at the temperature at which the solution annealing takes place for a predetermined, preferably short, period of time, for example for a period of time from approximately 2 minutes to approximately 5 minutes, by means of the heating device emitting the infrared radiation during operation. However, it is also possible for the cast component to be removed directly from the receiving space of the heating device emitting the infrared radiation as soon as the cast component has reached the temperature at which the solution annealing takes place.
[0032] In particular, if a period of a specific length is required to maintain the temperature at which the solution annealing takes place, i.e., to maintain the desired final temperature, the heat treatment device can comprise a separate temperature-maintaining device in addition to the heating device. In this way, rapid heating can be achieved in the infrared heating device, and the temperature-maintaining device can maintain the temperature at which the solution annealing takes place.
[0033] This is based on the finding that, using the heating device emitting infrared radiation, the cast component can be very quickly brought to the temperature at which solution annealing takes place. Once the cast component has been heated to the temperature required for solution annealing by the heating device, it can be placed in the temperature-maintaining device, where the temperature required for solution annealing is maintained.
[0034] This makes the process particularly efficient. The heating device, which emits infrared radiation during operation, can be used to heat the cast component, while the temperature-maintaining device is used solely to maintain this temperature. In particular, the temperature-maintaining device can be designed as a circulating air furnace. Preferably, the cast component is removed from the heating device by means of the handling device and placed into the temperature-maintaining device by means of the handling device. This makes handling of the cast component particularly easy during heat treatment, and the device for heat-treating the cast component requires a particularly small amount of space. This is advantageous.
[0035] Preferably, the cast component is subjected to solution annealing for a period of approximately 2 to approximately 5 minutes. This is based on the finding that such a comparatively short annealing process is particularly beneficial for preventing undesirable creep of the heated cast component during solution annealing.
[0036] Preferably, the cast component is heated to a temperature of approximately 300°C to approximately 530°C during this period. Depending on the alloy used for the cast component, solution annealing can take place at this temperature. The comparatively short and rapid heating of the cast component to the temperature at which solution annealing takes place is advantageous for ensuring high dimensional accuracy of the cast component. In particular, if the temperature at which solution annealing takes place is to be maintained after the rapid heating of the cast component by means of the infrared heating device, the temperature maintenance device can be used in addition to the infrared heating device.
[0037] It has also been shown to be advantageous if the cast component is made of a silicon-containing aluminum alloy. This is because the heat treatment in the form of solution annealing can ensure that the so-called eutectic silicon, i.e., needle-like, silicon-containing phases in the cast component, are transformed into phases with more rounded shapes. This forming of the eutectic silicon is beneficial for achieving high strength in the cast component. Subjecting the cast component to solution annealing also allows the so-called pi phase to be dissolved, the presence of which would be detrimental to the strength and formability of the cast component.This is because magnesium is incorporated into the pi phase, which, when a corresponding alloy is used for the cast component, has the composition AlFeMgSi, which is then no longer available to form magnesium-containing precipitates during aging. Therefore, it is advantageous to ensure that the eutectic silicon is incorporated and the pi phase is dissolved during heat treatment of the cast component.
[0038] The cast component, which is preferably made from the silicon-containing aluminum alloy, can in particular be a die-cast component, i.e. a cast component which is formed in the casting mold in a die-casting process.
[0039] It has also been shown to be advantageous if the cast component is cooled after solution annealing by exposing it to water and / or air. In particular, the cast component can be immersed in water and / or exposed to a cooling air stream for this purpose. This ensures that the at least one alloy component dissolved during solution annealing and distributed as homogeneously as possible does not simply slowly resolidify, but is available for the desired formation of precipitates during the subsequent aging process.
[0040] Preferably, the cast component is subjected to pre-aging by heating after cooling and before the at least one coating material is applied. This optional pre-aging or pre-hardening step can be preceded by mechanical processing of the cast component, for example in the form of punching and / or removal of excess projections and / or residues from the casting process that are not required for the function of the cast component. In particular, such mechanical processing of the cast component can remove or separate excess projections and / or residues, such as at least one sprue or the like.
[0041] Heating during pre-aging ensures that the cast component is kept in a metastable state, thereby advantageously preventing or avoiding cold ageing, i.e., ageing at room temperature. Preventing time-dependent cold ageing by subjecting the cast component to pre-aging through heating is beneficial for increasing the stability of the material used for the cast component.
[0042] The device according to the invention is designed for heat-treating a cast component for a motor vehicle. The device comprises means for carrying out the method according to the invention. Consequently, the device allows for a particularly low-cost heat treatment of the cast component.
[0043] The advantages and preferred embodiments described for the method according to the invention apply analogously to the device according to the invention for heat treating the cast component.
[0044] The invention therefore also includes further developments of the device according to the invention that have features already described in connection with the further developments of the method according to the invention. For this reason, the corresponding further developments of the device according to the invention are not described again here.
[0045] The motor vehicle in which the cast component is used is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus. The invention also encompasses combinations of the features of the described embodiments. The invention thus also encompasses implementations that each have a combination of the features of several of the described embodiments, unless the embodiments are described as mutually exclusive.
[0046] Exemplary embodiments of the invention are described below. Shown are:
[0047] Fig. 1 schematically shows a sequence of process steps in the production of a cast component which is subjected to heat treatment; and
[0048] Fig. 2 shows a highly schematic view of a handling device designed as a robot, by means of which the cast component removed from a casting mold is introduced into a heating device emitting infrared radiation, wherein by means of the robot the cast component can be introduced into a temperature maintenance device and / or into a device designed, for example, as a circulating air oven for pre-storage.
[0049] The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that can be considered independently of one another, each of which also develops the invention independently of one another. Therefore, the disclosure is intended to encompass combinations of the features of the embodiments other than those illustrated. Furthermore, the described embodiments can also be supplemented by further features of the invention already described. In the figures, identical reference numerals designate functionally identical elements.
[0050] Fig. 1 schematically shows process steps that can be used in the production of a cast component 10 (see Fig. 2). The cast component 10 can, in particular, be designed as a cast node, such as can be used for a motor vehicle body. For example, the respective cast component 10 can be designed as a connecting component by means of which other body components of the motor vehicle body are connected to one another. In particular, with such a design of the respective cast component 10, the cast component 10 can be comparatively large and thus referred to as a large cast component.
[0051] The cast component 10 is subjected to heat treatment steps in order to achieve, on the one hand, high strength of the cast component 10 and, on the other hand, high deformability of the cast component 10. In the present case, the heat treatment steps comprise solution annealing 12 (see Fig. 1 ) and age hardening 14. During solution annealing 12, at least one alloy component of the cast component 10 is homogenized. If an aluminum alloy containing magnesium and silicon is used to produce the cast component 10, then solution annealing 12 can, in particular, achieve dissolution and as uniform a distribution as possible of magnesium. During age hardening 14, the hardness of the cast component 10 is increased. If the aluminum alloy used to produce the cast component 10 contains magnesium and silicon, precipitates in the form of Mg2Si can, in particular, be formed during age hardening 14.Such precipitations increase the hardness of the cast component 10.
[0052] In the method to be explained with reference to Fig. 1, it is advantageously possible to combine, in a cycle time-neutral manner, the advantages of a heat treatment in which the solution annealing 12 is carried out with the lower process costs of a heat treatment in which the solution annealing is omitted and in which the cast component 10 is only subjected to the heat treatment of ageing 14 after being removed from a casting mold (not shown).
[0053] During the production of the cast component 10, the cast component 10 is first cast 16 in the casting mold (not shown) of the device, preferably using a die-casting process. After casting 16, the cast component 10 is removed from the casting mold by means of a handling device, for example in the form of a robot 18 shown highly schematically in Fig. 2. The cast component 10 can then be subjected to solution annealing 12 (see Fig. 1). For this purpose, the cast component 10 can be introduced into a heating device 20 (see Fig. 2), which emits infrared radiation during operation. The heating device 20 can thus be designed as an infrared oven. By means of the handling device, in this case in the form of the robot 18, the cast component 10 can be removed from the casting mold and introduced into a receiving space 22 of the heating device 20 (see Fig. 2).
[0054] Fig. 2 shows a highly schematic representation of several infrared radiators 24 of the heating device 20, which may be configured, in particular, as high-power infrared radiators. Such high-power infrared radiators may, in particular, be capable of providing a heating temperature of up to approximately 900°C in the receiving space 22.
[0055] If the cast component 10 is introduced into the receiving space 22 of the heating device 20 directly after casting 16, i.e. directly after removal from the casting mold (not shown), the casting heat still present in the cast component 10 can be used advantageously to very quickly reach the temperature of the cast component 10 at which the solution annealing 12 takes place.
[0056] Optionally, the cast component 10 can be quenched after casting 16 and before solution annealing 12, i.e., before being introduced into the receiving space 22 of the heating device 20 (see Fig. 2), for example, by immersion in a water bath. However, the heat from the casting process can then only be utilized to a limited extent to very quickly reach the temperature in the heating device 20 at which solution annealing 12 takes place.
[0057] When using the silicon-containing aluminum alloy for the cast component 10, the solution annealing 12 ensures that the eutectic silicon is formed and the pi phase is dissolved. However, this advantageously occurs without requiring a separate heat treatment system, in which both the solution annealing 12 and the age-hardening 14 take place, to be connected downstream of a casting cell 26 of the device for producing the cast component 10. Rather, the heating device 20 can be arranged in comparatively close proximity to the casting mold (not shown) in which the casting 16 takes place.
[0058] In particular, as shown schematically in Fig. 1, the solution annealing 12 can take place within the casting cell 26. However, it is also possible to carry out the solution annealing 12 in the immediate vicinity of the casting cell 26. The casting cell 26 can be a fenced-in area or an area otherwise separated from the surroundings 28 of the device or system in which the production of the cast component 10 takes place.
[0059] The heating device 20 (see Fig. 2), arranged within the casting cell 26 or at least in the vicinity of the casting cell 26, for performing the solution annealing 12 can be designed as an infrared furnace. The cast component 10 can pass through the infrared furnace in a flow process on a belt, onto which the cast component 10 is preferably placed by means of the handling device, for example in the form of the robot 18.
[0060] Additionally or alternatively, the heating device 20 can be provided by a plurality of heat treatment cells or heat treatment chambers, into whose respective receiving spaces 22 respective cast components 10 can be introduced. In both ways, it is possible to provide a small buffer, which enables cycle-time-neutral production of the cast components 10.
[0061] After the (preferably brief) solution annealing 12, the cast component 10 is quenched 30 (see Fig. 1). During this quenching 30, the cast component 10 can be cooled with water and / or air. The cast component 10 can still have projections caused by the casting 16, for example in the form of at least one sprue (not shown here) and / or burrs or the like. Such projections or appendages or the like can be removed in at least one subsequent mechanical processing step 32 (see Fig. 1). For example, the mechanical processing step 32 can be implemented by punching the cast component 10.
[0062] An (optional) pre-aging 34 can take place within the casting cell 26 or in a separate process step immediately following the casting cell 26. During this pre-aging 34, the cast component 10 is heated, for example, to a temperature between approximately 150°C and approximately 200°C, in order to prevent cold ageing. During cold ageing, in contrast, precipitations form at room temperature. If the (optional) pre-aging 34 is performed, the stability of the cast component 10 can be increased because cold ageing or cold hardening is avoided. During the pre-aging 34, metastable phases of the cast component 10 can advantageously be formed.
[0063] In the present case, the method for heat-treating the cast component 10 comprises a painting process 36, which takes place in a painting system (not shown in detail) of the device for producing the cast component 10. The painting process 36 comprises at least one coating step 38 (see Fig. 1). In this at least one coating step 38, at least a portion of the cast component 10 is provided with at least one coating material prior to the aging process 14.
[0064] For example, for cast components 10, such as those used for motor vehicles, a plurality of coating steps 38 can be provided, such as applying a cathodic dip coating (CDP), applying a PVC material (PVC = polyvinyl chloride), applying a filler, and applying a topcoat. In such coating steps 38, the respective coating material is cured by applying heat to the cast component 10 using at least one dryer (not shown in detail here).
[0065] In the present case, this heat is used to achieve the aging 14 (see Fig. 1) of the cast component 10. The aging 14 thus involves, on the one hand, an increase in the hardness of the cast component 10 and, on the other hand, the curing of the coating material that was previously applied to at least the partial area of the cast component 10 in the at least one coating step 38.
[0066] The cast component 10 undergoes the painting process 36 anyway if the cast component 10 is to be provided with the at least one coating material. Therefore, in this case, the curing in the form of aging 14 can be performed simultaneously with the curing of the coating material. This results in the overall process time for producing the cast component 10 not being increased. Rather, the painting process 36, which is to be carried out anyway, is advantageously used for aging 14. This leads to savings in costs, space, and process time.
[0067] Nevertheless, properties of the cast component 10 are achieved that accompany the heat treatment steps of solution annealing 12 and age-hardening 14, in this case particularly in the form of artificial age-hardening. The cast component 10 can then be installed in the body of the motor vehicle, whereby joining techniques such as punch riveting or the like can be used. Such joining techniques can be carried out particularly well when the cast component 10 is in the state it has after undergoing the painting process 36 (see Fig. 1).
[0068] According to Fig. 2, the cast component 10 can be introduced into the heat treatment cell in the form of the heating device 20 after removal from the casting mold, i.e. after casting 16 (see Fig. 1), which emits infrared radiation during operation. Prior quenching, for example by immersion in water, can be performed, but is not necessary. If the cast component 10 is not quenched before being introduced into the heating device 20, the heat of the casting process can be used to a particularly large extent to quickly bring the cast component 10 in the receiving space 22 of the heating device 20 to the temperature at which the solution annealing 12 (see Fig. 1) takes place.
[0069] In the receiving chamber 22, the cast component 10 can be brought to the annealing temperature, i.e., the temperature at which the solution annealing 12 takes place, within a period of less than 2 minutes to approximately 5 minutes. In particular, the cast component 10 can be brought to a temperature of approximately 300°C to approximately 530°C by means of the infrared radiators 24 during the aforementioned period.
[0070] According to Fig. 2, the heating device 20 can have a plurality of reflection elements 40 and / or convection elements (not shown in detail here) in order to achieve the fastest and most homogeneous heating possible of the cast component 10 in the receiving space 22 of the heating device 20. The reflection elements 40 can be designed, for example, as nanoreflectors. In particular, by combining the reflection elements 40 with the convection elements (not shown), a very uniform heat distribution in the receiving space 22 can be achieved, so that a diffuse radiation space is formed in the receiving space 22 during operation of the heating device 20.
[0071] If maintaining the desired final temperature over a specific period of time during the heat treatment of the cast component 10 is desirable, the cast component 10 can be introduced into a temperature-maintaining device 42, which is shown highly schematically in Fig. 2, after being introduced into the heating device 20. For example, the temperature-maintaining device 42 can be designed as a conventional circulating air furnace in which a temperature is set that essentially corresponds to the target temperature of the cast component 10. The target temperature of the cast component 10 is preferably the temperature at which the solution annealing 12 takes place.
[0072] In contrast, in the heating device 20, which, according to Fig. 2, has the infrared radiators 24, a heating temperature is preferably set in the receiving space 22 that is significantly higher than the target temperature of the cast component 10, i.e., the temperature at which the solution annealing 12 takes place. Thus, the temperature of the cast component 10 to be set for the solution annealing 12 can be reached very quickly when the cast component 10 is introduced into the receiving space 22 of the heating device 20.
[0073] According to Fig. 2, the handling device in the form of the robot 18 can introduce the cast component 10 into the temperature-maintaining device 42. After removing the cast component 10 from the heating device 20 or from the temperature-maintaining device 42, the quenching 30 of the cast component 10 preferably takes place (see Fig. 1).
[0074] According to Fig. 2, the optional step of pre-storage or pre-storage 34 (see Fig. 1 ), which can take place before the at least one coating step 38, can be carried out in a heating device designed as a circulating air oven 44. It can be provided that the cast component 10 can be introduced into this circulating air oven 44 by means of the handling device, in this case in the form of the robot 18, before the cast component 10 is subjected to the at least one coating step 38 as part of the painting process 36.
[0075] The forced-air furnace 44, in which the optional pre-storage 34 (see Fig. 1) can take place, can be designed as a continuous furnace. In such a continuous furnace, the respective cast components 10 can be heated briefly, for example, over a period of less than approximately 5 minutes, in particular to a temperature of approximately 80°C to approximately 250°C. Subsequently, the cast component 10 can be removed from the forced-air furnace 44 by a foundry employee or similar worker.
[0076] Instead of the circulating air oven 44 shown schematically and by way of example here, a further infrared oven (not shown) can be used for the optional pre-aging 34 (see Fig. 1). If the step of pre-aging or pre-aging 34 is provided, part of the increase in the hardness of the cast component 10 already takes place in the circulating air oven 44 and / or in the further infrared oven (not shown), which can be achieved by the heat treatment in the form of artificial aging. If the pre-aging 34 is omitted, in contrast, exclusively the heat used to cure the at least one coating material is used for the aging 14.
[0077] In particular, the in-line heat treatment, in which the solution annealing 12 can take place before the quenching 30, particularly within the casting cell 26, allows undesirable creep processes during the solution annealing 12 to be largely avoided. Furthermore, the use of the infrared radiators 24 in the heating device 20 ensures that the temperature of the cast component 10 to be set for the solution annealing 12 is reached very quickly. Cast components 10 in the form of large cast components, in particular, can therefore be manufactured cost-effectively and with high dimensional accuracy (i.e., without incurring undesirably large distortion) if the procedure described above is followed.
[0078] Overall, the examples show how a method for producing a cast component 10 formed from a die-cast material, which can in particular be designed as a large cast component and which has an increased deformability, can be provided.
Claims
PATENT CLAIMS:
1. A method for heat-treating a cast component (10) for a motor vehicle, wherein the heat treatment comprises solution annealing (12) and age-hardening (14) of the cast component (10), wherein the cast component (10) is removed from a casting mold and subjected to solution annealing (12) to homogenize at least one alloy constituent of the cast component (10), and wherein the age-hardening (14) increases the hardness of the cast component (10), characterized in that at least a partial region of the cast component (10) is provided with at least one coating material prior to age-hardening (14), which coating material is hardenable by application of heat, wherein the age-hardening (14) is brought about at least partially by the heat applied to the cast component (10) to harden the at least one coating material.
2. Method according to claim 1, characterized in that the cast component (10) is removed from the casting mold by means of a handling device, in particular provided by at least one robot (18), wherein the cast component (10) is introduced into a heating device (20) by means of the handling device, and wherein the heating device (20) heats the cast component (10) to a temperature at which the solution annealing (12) takes place.
3. Method according to one of the preceding claims, characterized in that the cast component (10) is heated by means of a heating device (20) emitting infrared radiation to a temperature at which the solution annealing (12) takes place, wherein a receiving space (22) of the heating device (20), into which the cast component (10) is introduced, is brought to a heating temperature which is at least 50 percent, in particular at least 75 percent, higher than the Temperature at which solution annealing (12) takes place.
4. Method according to claim 3, characterized in that by operating a plurality of infrared radiators (24) of the heating device (20), in particular providing a heating temperature of up to approximately 900 °C, and / or by means of reflection elements (40) and / or convection elements of the heating device (20) in the receiving space (22), a uniform heat distribution is set.
5. Method according to claim 3 or 4, characterized in that the cast component (10) brought to the temperature to be set for the solution annealing (12) by means of the heating device (20) is introduced into a temperature-maintaining device (42), in particular designed as a circulating air furnace, in which the temperature to be set for the solution annealing (12) is maintained.
6. Method according to claim 5 in its dependence on claim 2, characterized in that the cast component (10) is removed from the heating device (20) by means of the handling device and is introduced into the temperature-maintaining device (42) by means of the handling device.
7. Method according to one of the preceding claims, characterized in that the cast component (10) is subjected to solution annealing (12) for a period of time of approximately 2 minutes to approximately 6 minutes, wherein the cast component (10) is brought to a temperature of approximately 300 °C to approximately 530 °C during the period.
8. Method according to one of the preceding claims, characterized in that the cast component (10), in particular a die-cast component, is produced from a silicon-containing aluminum alloy.
9. Method according to one of the preceding claims, characterized in that the cast component (10) is cooled after the solution annealing (12) by exposure to water and / or air, wherein the cast component (10) is subjected to a pre-aging (34) by heating after cooling and before the cast component (10) is provided with the at least one coating material.
10. Apparatus for heat-treating a cast component (10) for a motor vehicle, the apparatus comprising means for carrying out the method according to one of the preceding claims.