Thermally treating a metallic component

Abstract

The invention relates to a method for thermally treating a metallic component (2), said method comprising: a) heating the entire component (2); b) transferring the component (2) to a temperature control station (4); c1) cooling a first region (10) of the component (2) in the temperature control station (4), wherein, at least after the cooling process, a temperature of the first region (10) is below the austenite reversion temperature (TAR) of the component (2); c2) in the temperature control station (4), using a laser unit (9) to heat a sub-region (12) of the first region (10), cooled in step c1), of the component (2) to a temperature above the Ac3 temperature (TAC3) of the component (2); d) transferring the component (2) to a second continuous furnace (5); and e) thermally treating the component (2) in the second continuous furnace (5), wherein, during method steps a) to e), a temperature of a second region (11) of the component (2) at least temporarily exceeds the Ac3 temperature (TAC3) of the component (2).

Description

[0001] Thermal treatment of a metallic component

[0002] The invention relates to a method and a device for thermally treating a metallic component, in particular a steel component for a motor vehicle.

[0003] In the automotive industry in particular, it is well known to specifically harden steel components through thermal treatment. For this purpose, steel components such as B-pillars are thermally treated differently in certain areas. This results in different ductility in certain areas, which is advantageous for the crash behavior of such components. For example, vehicle occupants can be protected by a hard section of the B-pillar at seat height, while soft sections in the upper and lower sections of the B-pillar absorb energy through deformation.

[0004] For the locally varied thermal treatment of components, methods have proven successful: first, the entire component is heated in a first furnace, then the component is subjected to locally varied thermal treatment in a temperature control station, and then the entire component is heated in a second furnace. In the temperature control station, one area of ​​the component is cooled, for example by exposure to a cooling fluid, while the rest of the component is kept approximately at its temperature. Excellent results can be achieved in this way for many applications. However, there is a growing need to obtain temperature distributions that are difficult or impossible to achieve using conventional methods. This particularly applies to components in which a small, hard sub-area is to be formed within a soft area. It is difficult to exclude a small sub-area when cooling with a cooling fluid.Similar difficulties generally arise when more than a simple division of the component into soft and hard areas is desired.

[0005] The object of the present invention is to provide a particularly flexible method for the locally varied thermal treatment of metallic components. A corresponding device is also to be presented. These objects are achieved by the method and device according to the independent claims. Further advantageous embodiments are specified in the dependent claims. The features presented in the claims and in the description can be combined with one another in any technologically expedient manner.

[0006] According to the invention, a method for thermally treating a metallic component is presented. The method comprises: a) heating the entire component in a first continuous furnace, b) transferring the component from the first continuous furnace to a tempering station, c) cooling a first region of the component in the tempering station, wherein a

[0007] Temperature of the first region is below the austenite re-transformation temperature of the component at least after cooling, c2) heating a sub-region of the first region of the component cooled in step c1) with a laser unit in the tempering station to a temperature above the AC3 temperature of the component, d) transferring the component from the tempering station into a second continuous furnace, e) thermally treating the component in the second continuous furnace, wherein the first region of the component outside the sub-region is heated in such a way that a temperature of the first region of the component outside the sub-region is below the AC3 temperature of the component even after heating, wherein a temperature of a second region of the component during process steps a) to e) at least temporarily exceeds the AC3 temperature of the component.

[0008] The described method can be used to thermally treat a metallic component. The metallic component is preferably a component made of steel. The steel is preferably 22MnB5. However, it is not necessary for the metallic component to meet the definition of steel. Therefore, reference is generally made herein to a metallic component. For example, a component for a motor vehicle, in particular a B-pillar, can be thermally treated using the described method. However, the method can also be used for any other applications. The component preferably has a material thickness of at least 0.7 mm, in particular in the range of 1 to 4 mm. Such a material thickness is useful for many applications. However, the described method can also be carried out with components of other material thicknesses. The material thickness of the component is preferably constant across the entire component.Alternatively, the component can also have a different material thickness in certain areas. For example, the component can be a "tailor rolled blank (TRB)," in which locally different material thicknesses are obtained through locally different rolling processes. The component can also be a "tailor welded blank (TWB)," in which locally different material thicknesses are obtained by welding several sheets together. A combination of TRB and TWB is also possible. Furthermore, the process can be applied equally to components with and without coatings. The component is particularly preferably coated with Al / Si.

[0009] After the thermal treatment, the component is preferably press-hardened in a press and thus hot-formed. The method preferably comprises the further steps of transferring the component from the second continuous furnace to the press (step f)) and press-hardening in the press (step g)). In this case, the described method is a method for the thermal treatment and press-hardening of a component. However, it is not necessary for the press-hardening of the component to be carried out as part of the described method. The described method can also serve as preparation for press-hardening carried out outside of the described method. In general, the component thermally treated with the described method can be subjected to further process steps which, together with other processes, can, for example, result in a finished motor vehicle.However, the thermal treatment of the component is a distinct sub-process within such an overall process. It is therefore useful to consider the thermal treatment separately from the subsequent process steps, especially separately from press hardening.

[0010] In step a), the entire component is heated in the first continuous furnace. A furnace is a device whose interior is heated to an adjustable temperature and into which a component can be inserted. Over time, the temperature of the component approaches the temperature prevailing inside the furnace. The heat is thus transferred from the gas in the furnace, which can in particular be air, to the component. A continuous furnace is a furnace through which the component can be moved, whereby the component is heated as it passes through the furnace.

[0011] The first continuous furnace is preferably a roller hearth furnace. In the first continuous furnace, the component is preferably heated by burners, in particular gas burners. This allows the component to achieve a particularly evenly distributed temperature. In the first continuous furnace, the entire component is heated. The component is completely absorbed by the first continuous furnace. In addition, a continuous furnace can achieve heating by a particularly large temperature difference. With a continuous furnace, a component can be heated, in particular, from room temperature to a temperature in the range of the component's AC3 temperature. Such extensive heating is not possible with many other heating methods, or at least not without disproportionately great effort.

[0012] In the case of a coated component, the first continuous furnace can also serve to diffuse the coating into the remaining material of the component. This applies in particular to an Al / Si coating. In the case of a coated component, it is preferred that the component is heated in step a) such that the coating material diffuses into the material of the remaining component in step a). The component is therefore preferably heated in step a) to a temperature that is above the temperature at which the coating material diffuses into the material of the remaining component. Preferably, the temperature of the component in step a) is above this temperature for at least 1 minute, in particular even at least 2 minutes. Preferably, the component is heated in step a) to a temperature of at least 700°C, in particular of at least 780°C. Satisfactory results have already been achieved at these temperatures.In order to increase process reliability, however, heating to at least 830 °C is preferred. Preferably, the temperature of the component in step a) is above a temperature of 700 °C, in particular 780 °C or even 830 °C for at least 1 minute, in particular even at least 2 minutes. In the case of a coated component, the component is particularly preferably heated in step a) to a temperature above the AC1 temperature of the component, in particular above the AC3 temperature of the component. Preferably, the temperature of the component in step a) is above the AC1 temperature of the component, in particular above the AC3 temperature of the component, for at least 1 minute, in particular even at least 2 minutes. In this respect, the heating in step a) can be used not only to diffuse the coating, but can also already make a contribution to the microstructure transformation.

[0013] Heating in a continuous furnace is particularly in contrast to heating by so-called "direct energization". This would make it difficult to heat the component evenly and to a sufficiently high degree. With direct energization, the speed of heating is more important. In addition, direct energization requires contact with the component. In step a) of the described process, heating is preferably carried out without contact. This does not preclude the component from being moved through the first continuous furnace on transport rollers and thus being in contact with the transport rollers. Heating is considered contactless if the heat is introduced into the component via a gas and / or thermal radiation.

[0014] In step b) of the process, the component is transferred from the first continuous furnace to the tempering station. This is preferably done using a first transfer device. In the tempering station, the component is thermally treated differently in certain areas. For this reason in particular, the described process is a process for the locally different thermal treatment of metallic components. However, this does not need to be explicitly mentioned, since the locally different thermal treatment is explicitly defined by steps c1) and c2).

[0015] The first continuous furnace and the tempering station are separate components that are spatially separated from one another. The transfer between the first continuous furnace and the tempering station facilitates the cooling of the component between heating in the first continuous furnace and thermal treatment in the tempering station. In the tempering station, the component is cooled as quickly as possible in certain areas. Rapid cooling can be achieved more efficiently outside the hot first continuous furnace. This allows cooling to begin during the transfer. In this respect, the spatial separation of the first continuous furnace from the tempering station accelerates the process. This contrasts with a solution in which all process steps are carried out in the same facility without having to transfer the component. Such solutions typically aim to minimize the effort required for component transfers or to avoid them altogether.The spatial separation between the first continuous furnace and the tempering station also simplifies the design because the requirements for the first continuous furnace and the tempering station are different.

[0016] In step d), the component is transferred from the tempering station to a second continuous furnace. This is preferably done using a second transfer device. In step e), the component is thermally treated in the second continuous furnace. For step e), the entire component is removed from the second continuous furnace.

[0017] The tempering station and the second continuous furnace are separate components that are spatially separated from each other. The transfer between the tempering station and the second continuous furnace facilitates the cooling of the component between the thermal treatment in the tempering station and in the second continuous furnace. This allows a part of the component that requires cooling to be cooled during the transfer. This reduces the required residence time in the tempering station and accelerates the process. This contrasts with a solution in which all process steps are carried out in the same facility, if possible, without having to transfer the component. Such solutions typically aim to minimize the effort required for component transfers or to eliminate them altogether.The spatial separation between the tempering station and the second continuous furnace also simplifies the design because the requirements for the tempering station and the second continuous furnace are different.

[0018] The second continuous furnace is preferably a roller hearth furnace. In the second continuous furnace, the entire component is thermally treated, preferably heated. The component is completely absorbed by the second continuous furnace. Thermal treatment in a continuous furnace contrasts particularly with heating by so-called "direct energization." Thermal treatment in the second continuous furnace serves, in particular, to promote microstructural transformation. Because the component is not cooled immediately after the tempering station, for example, in a press, sufficient time is provided for the desired microstructural distribution to develop within the component. In particular, in step e), carbon atoms can diffuse within the component, changing the microstructure of the component as desired.In addition, the thermal treatment in the second continuous furnace can serve to reduce thermal stresses in the component. This can reduce distortion during subsequent press hardening.

[0019] With the described method, three areas in particular can be thermally treated differently. First, a distinction can be made between a first area and a second area. Furthermore, a sub-area of ​​the first area is treated separately from the rest of the first area. Thus, the result is at least the sub-area of ​​the first area, the remaining part of the first area, and the second area.

[0020] The first region, the sub-region of the first region, and the second region are not necessarily each contiguous regions. In particular, it is possible for a central part of a B-pillar to represent the first region, while an upper and a lower part of the B-pillar together represent the second region. Within the first region, one or more parts can represent the sub-region. The component preferably, but not necessarily, has only the first region and the second region, i.e., no further regions. This also applies despite the sub-region, since this is part of the first region.

[0021] The sub-area represents a portion of the first area. The sub-area is smaller than the first area. Therefore, there is also a portion of the first area that does not belong to the sub-area.

[0022] With the described process, different areas of the component can be thermally treated differently. This allows the microstructure of the component to be influenced differently locally, resulting in locally different ductilities. The first area outside the sub-area becomes more ductile than the sub-area and the second area. The sub-area of ​​the first area and the second area can have the same ductility or different ductilities.

[0023] In step a), the entire component is heated in the first continuous furnace. All areas are treated equally in step a). Therefore, it is not necessary for the areas to be distinguishable from one another in step a).

[0024] The described process is multi-stage and includes, in addition to heating in the first continuous furnace, thermal treatment in the tempering station and heating in the second continuous furnace. Therefore, heating in the first continuous furnace can, in principle, be carried out to any desired temperature. If the component is only slightly heated in the first continuous furnace, it can be heated more intensively in the lower section and more intensively in the second section as the process progresses, and vice versa. In particular, heating of the component in the first continuous furnace can be carried out to a temperature above or below the component's AC3 temperature.

[0025] Particularly for energy reasons, it is advantageous to heat the component comparatively strongly in the first continuous furnace. This makes it possible to exploit the previously described advantage of heating in a continuous furnace compared to other heating methods, in particular compared to direct energization. The component is therefore preferably heated in step a) to at least 400 °C, in particular to at least 600 °C. The component is preferably heated in step a) to a temperature above the AC1 temperature of the component. Preferably, the component is heated in step a) to a temperature which is a maximum of 400 K below the AC3 temperature of the component, in particular a maximum of 200 K below the AC3 temperature of the component. Preferably, the component does not exceed a temperature of 200 K above the AC3 temperature of the component in step a). For example, the component can be heated to a temperature in the range 600 to 800 °C in step a).Alternatively, higher temperatures are preferred, in particular those above the AC3 temperature of the component. It is also preferred that the component be heated in step a) to a temperature of at least 900°C, in particular at least 1000°C. For example, the component can be heated in step a) to a temperature in the range of 850 to 1200°C.

[0026] The component is thermally treated differently locally in the tempering station downstream of the first continuous furnace. For this purpose, the first and second areas of the component are first subjected to different thermal treatments in the tempering station. The first area is cooled in step d) in the tempering station. This is preferably achieved by subjecting the first area to a cooling fluid, in particular compressed air. The compressed air preferably has a pressure in the range of 2 to 4.5 bar. This comparatively high pressure allows a large amount of compressed air to be directed onto the first area of ​​the component within a very short time, so that a sufficiently high cooling rate can be achieved. However, the method used to cool the first area is generally not important for the functioning of the described process.

[0027] In step c 1 ), the first region is cooled such that the temperature of the first region, at least after cooling, is below the austenite retransformation temperature of the component. This generally allows high ductility to be achieved in the first region.

[0028] If the entire component is heated to a temperature above the AC3 temperature in step a), austenite forms throughout the component. By cooling the first region in step c1) below the austenite re-transformation temperature of the component, this austenite in the first region decomposes again. The austenite re-transformation temperature is defined by the fact that austenite decomposes as soon as the temperature falls below the austenite re-transformation temperature. The austenite re-transformation temperature is a material property. The fact that the temperature of the first region is below the austenite re-transformation temperature of the component, at least after cooling, does not imply that austenite was previously formed in the component. If the entire component is not heated to a temperature above the AC3 temperature in step a), no austenite will form in this step.However, in this case, cooling the first region in step c1) below the austenite re-transformation temperature of the component can help ensure that no austenite is formed in the first region during the further course of the process, even if the component is subjected to further heating. If no austenite is formed in step a), the austenite re-transformation temperature in step c1) does not have to be undercut for the austenite to decompose. If the entire component is not heated to a temperature above the AC3 temperature in step a), any cooling of the first region in step c1) is sufficient. Nevertheless, it is still advisable to undercut the austenite re-transformation temperature in this case.This does not result from the fact of austenite retransformation below this temperature, but merely from the fact that the austenite retransformation temperature is generally significantly below the AC3 temperature.

[0029] Preferably, the first region is cooled in step c1) by at least 100 K, in particular by at least 250 K. The temperature of the first region after step c1) is preferably in the range from 400 to 700 °C, in particular in the range from 500 to 600 °C.

[0030] Regardless of the temperature reached in step a), there is no austenite in the first region after cooling in step c1). As long as the AC3 temperature of the component in the first region is not (again) exceeded after cooling in step c1, a ductile structure can be obtained in the first region. However, step c2) causes the AC3 temperature to be exceeded in part of the first region. This part of the first region is referred to as the sub-region of the first region. In step c2), the sub-region is heated using a laser unit in the temperature control station to a temperature above the AC3 temperature of the component. This allows austenite to form in the sub-region of the first region.

[0031] For the functioning of the described method, it is irrelevant whether the heating in step c2) is carried out with a single laser or with multiple lasers. Therefore, it is provided that the heating in step c2) is carried out with a laser unit. The laser unit can comprise one or more lasers. Electronics for supplying and controlling the at least one laser can be part of the laser unit or provided outside the laser unit, for example, in a control unit of a device used for the method.

[0032] Preferably, the subregion of the first region is heated in step c2) by at least 100 K, in particular by at least 250 K. The temperature of the subregion of the first region after step c2) is preferably in the range from 900 to 1100 °C.

[0033] It is preferred that, following heating in step c2), the temperature in the sub-region does not fall below the austenite re-transformation temperature of the component at least until the completion of step e). If press hardening is part of the described process, the austenite re-transformation temperature in the sub-region of the first region is preferably not fallen below until the press. However, it is not necessary to ensure that the austenite re-transformation temperature in the sub-region of the first region after step c2) is not fallen below until the completion of step e). Austenite does not decompose instantaneously. Acceptable results can also be obtained if some of the austenite in the sub-region of the first region has decomposed before press hardening.

[0034] In step e), a temperature of the sub-region of the first region preferably changes by a maximum of 200 K, in particular by a maximum of 100 K. This can also be referred to as maintaining the temperature, whereby a change in the temperature within a tolerance of 200 K or 100 K is accepted. For example, the sub-region of the first region in the second continuous furnace can be exposed to a temperature above the AC3 temperature of the component. Depending on the temperature of the sub-region of the first region upon entry into the second furnace and depending on the residence time of the component in the second furnace, the sub-region of the first region can be maintained at its temperature in the tempering station or heated, or cooling of the sub-region of the first region can be slowed down.

[0035] Outside the sub-region of the first region, the AC3 temperature of the component is not exceeded in steps c2) to e). This prevents austenite from forming outside the sub-region of the first region. In step e), the first region of the component outside the sub-region is heated in such a way that a temperature of the first region of the component outside the sub-region remains below the AC3 temperature of the component even after heating. The first region of the component outside the sub-region, i.e. the part of the first region that does not belong to the sub-region, is therefore no longer heated above the AC3 temperature of the component after cooling in step c1). Preferably, the temperature of the first region of the component outside the sub-region does not exceed the AC3 temperature of the component, at least in steps c2) to e).If press hardening is part of the claimed process, the temperature of the first region of the component outside the sub-region preferably does not exceed the AC3 temperature of the component up to and including the press hardening. This allows a ductile microstructure to be maintained in the first region outside the sub-region. However, strict attention need not be paid to ensuring that the AC3 temperature is not exceeded during the specified periods. Austenite is not formed instantaneously. Even with the formation of a small amount of austenite in the first region of the component outside the sub-region, acceptable results can be achieved.

[0036] In addition to the first region with the subregion, the component has a second region. The process is carried out in such a way that the temperature of the second region of the component exceeds the AC3 temperature of the component at least temporarily during process steps a) to e). This can lead to the formation of austenite in the second region. During press hardening, martensite can be formed from this, giving the second region a comparatively low ductility.

[0037] It is irrelevant at what point in time the temperature of the second region exceeds the AC3 temperature of the component. If in step a) the entire component is heated to a temperature above the AC3 temperature of the component, the aforementioned condition is already met in step a). If the second region is heated to less than the AC3 temperature in step a), the second region can be heated to a temperature above the AC3 temperature in the tempering station or in the second furnace. It is preferred that the temperature of the second region no longer falls below the austenite re-transformation temperature after heating to a temperature above the AC3 temperature of the component until the end of step e). Preferably, the temperature in the second region does not fall below the austenite re-transformation temperature until the press is completed. This prevents the austenite formed in the second region from decomposing before press hardening.

[0038] In steps b) to e), a temperature of the second region preferably changes by a maximum of 200 K, in particular by a maximum of 100 K. This can also be referred to as maintaining the temperature, whereby a change in the temperature within a tolerance of 200 K or 100 K is accepted. For example, in steps c1) and c2), the second region can be exposed to a temperature above the AC3 temperature of the component in the temperature control station and / or in step e) in the second furnace, it can be exposed to a temperature above the AC3 temperature of the component. Depending on the temperature of the second region upon entry into the temperature control station or into the second furnace and depending on the length of time the component spends in the temperature control station or in the second furnace, the second region can be maintained at its temperature in the temperature control station or heated, or cooling of the second region can be slowed down.In particular, the second area can also cool down in the ambient air in the temperature control station.

[0039] It is possible that the temperature of the second region in steps a) to e) initially rises above the AC3 temperature, then falls below the austenite retransformation temperature, and then rises above the AC3 temperature again. In this case, it is sufficient that the temperature of the second region does not fall below the austenite retransformation temperature after the second heating to above the AC3 temperature until the completion of step e). This is encompassed by the formulation that a temperature of the second region of the component during process steps a) to e) at least temporarily exceeds the AC3 temperature of the component and subsequently does not fall below an austenite retransformation temperature of the component.

[0040] With the method described, a ductile structure can be obtained in the first region outside the sub-region, while a less ductile structure is obtained in the sub-region of the first region and in the second region.

[0041] The sub-area can be created with particular precision by heating it with the laser unit. In particular, the sub-area can have a finer contour and / or be smaller than would be possible with other methods. This is especially true compared to a process in which the sub-area is excluded during cooling. In this respect, the process is particularly flexible.

[0042] In a preferred embodiment of the method, the first region of the component is cooled in step c 1 ) by exposure to a cooling fluid.

[0043] The cooling fluid is preferably compressed air. The cooling fluid is preferably discharged onto the first region using nozzles. This allows the first region to be cooled easily and quickly. However, the use of nozzles has the fundamental disadvantage that the cooling fluid does not allow a precise separation between the cooled and the uncooled part of the component. The described method overcomes this. First, in step d), the first region, including the lower region, is cooled. The lower region is then heated again using the laser unit. The result is basically the same as a method in which the lower region was left out during cooling. However, depending on the desired contour of the regions, this would be difficult or impossible to achieve using cooling with nozzles. The described method is simpler in comparison.

[0044] In a further preferred embodiment of the method, a temperature of the component in step a) does not exceed the AC3 temperature of the component.

[0045] In this embodiment, the subregion of the first region and the second region of the component are heated to above the AC3 temperature only in the tempering station or only in the second furnace. Preferably, the component is heated in step a) to a temperature above the AC1 temperature of the component. In this case, the component is heated in step a) to a temperature between the AC1 temperature and the AC3 temperature of the component. In a further preferred embodiment of the method, the entire component is heated in step a) to a temperature above the AC3 temperature of the component.

[0046] In a further preferred embodiment of the method, the sub-region of the first region of the component is heated locally to different degrees in step c2).

[0047] The laser unit allows the sub-region to be heated with particular precision. This not only means that a particularly precise contour of the sub-region can be achieved. The present embodiment also takes advantage of the fact that the sub-region can be heated to varying degrees locally. This allows for locally varying ductility to be achieved within the sub-region.

[0048] The locally different heating of the sub-area can be achieved by varying the power of the laser unit.

[0049] In a further preferred embodiment of the method, the sub-region of the first region of the component is heated locally to different degrees in step c2) such that a temperature gradient is obtained over the sub-region of the first region of the component.

[0050] By applying locally different heating, a temperature gradient can be achieved across the sub-region. For example, after step c2), the temperature of the sub-region can increase from one edge of the sub-region to an opposite edge. In this way, a precisely controlled transition region between different ductilities can be achieved.

[0051] In principle, it is preferred that regions of different ductility be separated as sharply as possible. A transition region between adjacent regions is therefore preferably as small as possible. In the present embodiment, however, the temperature gradient can be precisely adjusted. A resulting ductility gradient is therefore not merely random. There are applications in which a precisely adjusted ductility gradient is useful. As a further aspect of the invention, a device for thermally treating a metallic component is presented. The device comprises:

[0052] - a first continuous furnace for heating the entire component,

[0053] - a temperature control station with a cooling device for cooling a first region of the component and with a heating device with a laser unit for heating a sub-region of the first region of the component,

[0054] - a second continuous furnace for thermal treatment of the component,

[0055] - a first transfer device for transferring the component from the first continuous furnace to the tempering station, and

[0056] - a second transfer device for transferring the component from the tempering station to the second continuous furnace.

[0057] The described advantages and features of the method are applicable and transferable to the device, and vice versa. The device is preferably configured to operate according to the method. The method is preferably carried out with the device. The first continuous furnace serves step a), the first transfer device serves step b), the tempering station serves steps c1) and c2), the second transfer device serves step d), and the second continuous furnace serves step e).

[0058] Preferably, the device comprises a control device which is configured to control the device according to the described method.

[0059] Furthermore, the device preferably comprises a press for press hardening the component and a third transfer device for transferring the component from the second continuous furnace into the press.

[0060] In a preferred embodiment of the device, the laser unit comprises a VCSEL.

[0061] A vertical-cavity surface-emitting laser (VCSEL) is a laser diode that emits light perpendicular to its surface. A VCSEL can also be referred to as a surface emitter. It has been found that particularly good results can be achieved with a VCSEL in step c2). The invention is explained in more detail below with reference to the figures. The figures show a particularly preferred embodiment, to which the invention is not limited. The figures and the proportions depicted therein are only schematic. They show:

[0062] Fig. 1 : a device according to the invention for the thermal treatment of a metallic component,

[0063] Fig. 2: a temperature profile which can be obtained with the device of Fig. 1 by a method according to the invention, and

[0064] Fig. 3a to 3c: three examples of a component which has been treated with the method illustrated in Fig. 2.

[0065] Fig. 1 shows a device 1 for thermally treating a metallic component 2. The device 1 comprises a first continuous furnace 3, a tempering station 4, and a second continuous furnace 5, which are arranged successively in a transport direction r of the component 2. A control device 6 is configured, in particular, to control the first continuous furnace 3, the tempering station 4, and the second continuous furnace 5.

[0066] The temperature control station 4 has a cooling device 7 for cooling a first region 10 of the component 2 and a heating device 8 with a laser unit 9 for heating a sub-region 12 of the first region 10 of the component 2. The regions 10, 11, 12 of the component 2 are illustrated in Fig. 3. The laser unit 9 can, in particular, comprise a VCSEL.

[0067] Furthermore, the device 1 comprises a first transfer device 13 for transferring the component 2 from the first continuous furnace 3 to the tempering station 4 and a second transfer device 14 for transferring the component 2 from the tempering station 4 to the second continuous furnace 5.

[0068] Fig. 2 shows a temperature profile that develops in the component 2 when it is moved through the device 1 of Fig. 1. The representation of Fig. 2 is schematic. It shows a plot of temperature T over time t in arbitrary units. The component 2 is first heated in the first continuous furnace 3. The residence time of the component 2 in the first continuous furnace 3 is denoted by t. D1 In the example shown, the entire component 2 is heated in the first continuous furnace 3 to a temperature above the AC3 temperature T Ac3 of the component 2. Alternatively, the process could be carried out in such a way that the temperature of the component 2 in the first continuous furnace 3 reaches the AC3 temperature T AC3 of component 2.

[0069] Subsequently, component 2 is transferred to the temperature control station 4. The corresponding transfer time is t T1 During this transfer, component 2 can cool down.

[0070] In the tempering station 4, the component 2 remains for a residence time t TS During this time, a first region 10 of the component 2 is cooled, wherein a temperature of the first region 10 after cooling is below the austenite re-transformation temperature T AR of the component 2. The temperature of the first region 10 is shown as T q . After cooling, a sub-region 12 of the previously cooled first region 10 of the component 2 is heated with the laser unit 9 to a temperature above the AC3 temperature T AC3 of the component 2. The temperature of the sub-region 12 of the first region 10 is T 1A while the temperature of the remaining first area 10 is shown as T 1 B is marked.

[0071] A uniform temperature T is shown 1A for the sub-region 12 of the first region 10 of the component 2. However, in an alternative process, the sub-region 12 could also be heated to different local intensities. This could, in particular, create a temperature gradient across the sub-region 12. This is not shown in the figures.

[0072] After the thermal treatment of the component 2 in the tempering station 4, the component 2 is transferred to the second continuous furnace 5. The transfer time for this is t T 2. Component 2 can also cool down, which can vary depending on the area.

[0073] In the second continuous furnace 5, the component 2 is further thermally treated. The residence time of the component 2 in the second continuous furnace 5 is t D2 In the second continuous furnace 5, the first region 10 of the component 2 outside the sub-region 12 is heated such that the temperature T 1 B of the first area 10 of the component 2 outside the sub-area 12 even after heating below the AC3 temperature T AC3 of component 2.

[0074] A temperature T2 of the second region 11 of the component 2 exceeds the AC3 temperature T in the first continuous furnace 3 AC3 of component 2 and does not fall below this temperature again until the end of the process shown.

[0075] Fig. 3a shows a first example of the design of component 2 in a top view. In this example, component 2 is a B-pillar for a motor vehicle. The first region 10 and the second region 11 are visible. The sub-region 12 is shown within the first region 10. Fig. 3b shows a second example of the design of component 2 in a top view. In contrast to Fig. 3a, the sub-region 12 is composed of two non-connected parts.

[0076] Fig. 3c shows a third example of the design of component 2 in a top view. In contrast to Fig. 3a, the second region 11 and the sub-region 12 of the first region 10 are each composed of two parts.

[0077] The shapes shown for component 2 and regions 10, 11, and 12 are examples. The method shown in Fig. 2 can be used to process components of any geometry. The method is particularly flexible, particularly with regard to the design of subregion 12.

[0078] List of reference symbols

[0079] 1 device

[0080] 2 component

[0081] 3 first continuous furnace

[0082] 4 Tempering station

[0083] 5 second continuous furnace

[0084] 6 Control device

[0085] 7 Cooling device

[0086] 8 Heating device

[0087] 9 Laser unit

[0088] 10 first area

[0089] 11 second area

[0090] 12 Subsection

[0091] 13 first transfer facility

[0092] 14 second transfer facility

[0093] T Temperature

[0094] T A C3 AC3 temperature of the component

[0095] T AR Austenite retransformation temperature of the component

[0096] T q Temperature of the first area of ​​the component

[0097] T 1A Temperature of the sub-area of ​​the first area of ​​the component

[0098] T 1B Temperature of the remaining first area of ​​the component

[0099] T2Temperature of the second area of ​​the component t Time t D1 Residence time in the first continuous furnace t Ti Transfer time from the first continuous furnace to the tempering station t TS Residence time in the temperature control station t T 2 Transfer time from the tempering station to the second continuous furnace t D2 Residence time in the second continuous furnace r Transport direction of the component

Claims

Claims 1. A method for thermally treating a metallic component (2), comprising: a) heating the entire component (2) in a first continuous furnace (3), b) transferring the component (2) from the first continuous furnace (3) to a tempering station (4), c1) cooling a first region (10) of the component (2) in the tempering station (4), wherein a temperature of the first region (10) is below the austenite re-transformation temperature (T A R) of the component (2), c2) in the tempering station (4) heating a sub-region (12) of the first region (10) of the component (2) cooled in step c1) with a laser unit (9) to a temperature above the AC3 temperature (T AC3) of the component (2), d) transferring the component (2) from the tempering station (4) into a second continuous furnace (5), e) thermally treating the component (2) in the second continuous furnace (5), wherein the first region (10) of the component (2) outside the sub-region (12) is heated in such a way that a temperature of the first region (10) of the component (2) outside the sub-region (12) remains below the AC3 temperature (T AC3 ) of the component (2), wherein a temperature of a second region (11) of the component (2) during the method steps a) to e) at least temporarily exceeds the AC3 temperature (T AC3 ) of the component (2).

2. The method according to claim 1, wherein the first region (10) of the component (2) is cooled in step c1) by exposure to a cooling fluid.

3. Method according to one of the preceding claims, wherein a temperature of the component (2) in step a) is the AC3 temperature (T ACs) of the component (2). Method according to one of claims 1 or 2, wherein the entire component (2) in step a) is heated to a temperature above the AC3 temperature (T AC 3) of the component (2). Method according to one of the preceding claims, wherein the sub-region (12) of the first region (10) of the component (2) is heated locally to varying degrees in step c2). Method according to one of the preceding claims, wherein the sub-region (12) of the first region (10) of the component (2) is heated locally to varying degrees in step c2) such that a temperature gradient is obtained across the sub-region (12) of the first region (10) of the component (2). Device (1) for thermally treating a metallic component (2), comprising: - a first continuous furnace (3) for heating the entire component (2), - a tempering station (4) with a cooling device (7) for cooling a first region (10) of the component (2) and with a heating device (8) with a laser unit (9) for heating a sub-region (12) of the first region (10) of the component (2), - a second continuous furnace (5) for thermally treating the component (2), - a first transfer device (13) for transferring the component (2) from the first continuous furnace (3) to the tempering station (4), and - a second transfer device (14) for transferring the component (2) from the tempering station (4) to the second continuous furnace (5). The device (1) according to claim 7, wherein the laser unit (9) comprises a VCSEL.

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