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); d) 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 certain regions of the first region (10), cooled in step d), of the component (2) in such a way that a temperature gradient is set at least in a first sub-region (12) within the first region (10); 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, processes have proven effective. In these processes, the entire component is first heated in a first furnace, the component is then subjected to locally varied thermal treatment in a tempering station, and the entire component is finally heated in a second furnace. In the tempering station, an 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 processes. This particularly applies to components in which the ductility changes gradually. In particular, it is difficult to precisely adjust a temperature gradient when cooling with a cooling fluid.

[0005] The object of the present invention is to present a particularly flexible method for the locally varied thermal treatment of metallic components. Furthermore, a corresponding device is to be presented.

[0006] 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.

[0007] 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 1 ) cooling a first region of the component in the tempering station, wherein a

[0008] Temperature of the first region is below the austenite re-transformation temperature of the component at least after cooling, c2) heating the first region of the component cooled in step c1) in the tempering station with a laser unit in such a way that a temperature gradient is set at least in a first sub-region within the first region, d) transferring the component from the tempering station into a second continuous furnace, e) thermally treating the component in the second continuous furnace, 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.

[0009] 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. The described method is particularly well suited for so-called door rings. A door ring is a part for the body of a motor vehicle that encloses the opening for a door. A door ring can therefore be used instead of separate components for the A and B pillars as well as the parts of the floor and roof of the body located in between. It is preferred that the component is a door ring.However, the process can also be used for any other application in any technical field.

[0010] The component preferably has a material thickness of at least 0.7 mm, particularly in the range of 1 to 4 mm. This material thickness is appropriate for many applications. However, the described process 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 material thickness that varies 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 coating.The component is particularly preferably coated with Al / Si.

[0011] 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 separate sub-process within such an overall process. It is therefore sensible to consider the thermal treatment separately from the subsequent process steps, in particular also separately from press hardening. In step a), the entire component is heated in the first continuous furnace. A furnace is a device whose interior is brought to an adjustable temperature and into which a component can be placed. Over time, the temperature of the component approaches the temperature prevailing inside the furnace. The heat is therefore 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.

[0012] 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 taken up 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 high expenditure.

[0013] 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.However, to increase process reliability, 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 ACI 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 contribute to the microstructural transformation.

[0014] 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.

[0015] 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 d) and c2).

[0016] The first continuous furnace and the tempering station are separate components that are spatially separated from each other. 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.

[0017] 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.

[0018] 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 avoid 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. 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 is particularly in contrast to 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 allowed for the desired microstructural distribution to develop within the component.In particular, in step e), carbon atoms can diffuse within the component, changing the component's microstructure as desired. Furthermore, the thermal treatment in the second continuous furnace can serve to reduce thermal stresses within the component. This can reduce distortion during subsequent press hardening.

[0019] With the described method, three areas in particular can be thermally treated differently. Firstly, a distinction can be made between a first area and a second area. Furthermore, a first sub-area of ​​the first area is treated separately from the rest of the first area. As a result, there is at least the first sub-area of ​​the first area, the remaining part of the first area, and the second area. In addition to the first sub-area of ​​the first area, the first area can also have a second sub-area and optionally further sub-areas. In this case, the result is the first sub-area of ​​the first area, the second sub-area of ​​the first area, the remaining part of the first area, and the second area.

[0020] The first region, the sub-region(s) of the first region, and the second region are not necessarily each contiguous regions. In particular, it is possible for a middle 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 first 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 one or more sub-regions, since these are part of the first region.

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

[0022] With the described method, regions of the component can be thermally treated differently. This allows the microstructure of the component to be influenced differently locally, so that locally different ductilities are obtained. In particular, a ductility gradient can be set in the first sub-region of the first region. Outside the first sub-region, the first region is preferably more ductile than the second region. The ductility of the first sub-region can, in particular in this case, lie between the ductility of the remaining first region and the second region. In particular, the ductility in the first sub-region can gradually increase from the ductility of the second region to the ductility of the remaining first region. The first sub-region can therefore be designed as a transition region.Although a transition zone generally arises when a component undergoes different thermal treatments in different areas, the described process allows the transition zone to be deliberately and precisely adjusted.

[0023] The fact that a temperature gradient is set at least in a first sub-range within the first range does not rule out the temperature gradient extending beyond the first sub-range. It is therefore even conceivable for the temperature gradient to extend over the entire first range. In this case, the first sub-range can be defined as any part of the first range. The fact that a temperature gradient is set at least in a first sub-range within the first range therefore means that the temperature gradient is set in the entire first range or that the temperature gradient is set in a part of the first range - which is then referred to as the first sub-range. If the temperature gradient is set in the entire first range, there does not have to be a first sub-range that differs from the rest of the first range.This means that any part of the first region is identified as the first sub-region, even if this part is no different from the rest of the first region. Preferably, however, the temperature gradient is limited to the first sub-region. In this case, the first sub-region is delimited from the rest of the first region. A temperature gradient is then set only in the first sub-region within the first region.

[0024] 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).

[0025] 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 heated slightly in the first continuous furnace, it can be heated even more during the further course of the process, particularly in the second section, 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.

[0026] 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 AC3 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.

[0027] The temperature control station downstream of the first continuous furnace subjects the component to locally different thermal treatments. For this purpose, the first and second areas of the component are initially subjected to different thermal treatments in the temperature control station. The first area is cooled in step d) in the temperature control 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.

[0028] In step d), the first region is cooled such that, at least after cooling, the temperature of the first region is below the austenite retransformation temperature of the component. This generally allows for high ductility to be achieved in the first region.

[0029] 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 d) 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 d) 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 d) 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.

[0030] Preferably, the first region is cooled in step d) by at least 100 K, in particular by at least 250 K. The temperature of the first region after step c 1 ) is preferably in the range from 400 to 700 °C, in particular in the range from 500 to 600 °C.

[0031] Regardless of the temperature reached in step a), no austenite is present in the first region after cooling in step d). As long as the AC3 temperature of the component in the first region is not (again) exceeded after cooling in step d), a ductile microstructure can be obtained in the first region. However, step c2) heats at least part of the first region. This can result in lower ductility in this part. In particular, the AC3 temperature can be exceeded.

[0032] In step c2), the first region is heated in sections using a laser unit in the tempering station such that a temperature gradient is established at least in the first sub-region. The temperature gradient extends from a first end with a lower temperature to a second end with an upper temperature. Between the first end and the second end, the temperature of the component gradually increases from the lower temperature to the upper temperature. This increase can be linear or non-linear. The lower temperature is preferably below the AC3 temperature, in particular below the austenite re-transformation temperature. The upper temperature can also be below the AC3 temperature, in particular below the austenite re-transformation temperature. However, it is preferred that the upper temperature is above the austenite re-transformation temperature and even above the AC3 temperature.The upper temperature is preferably in the range from 900 to 1100°C. The upper temperature is preferably at least 100 K, in particular at least 250 K, higher than the temperature before step c2). Preferably, the first sub-region of the first region is thus at least partially heated in step c2) by at least 100 K, in particular by at least 250 K. The lower temperature is preferably at least 100 K, in particular by at least 200 K, or even by at least 400 K, lower than the upper temperature. In general, the effect of the temperature gradient is greater the further apart the lower temperature and the upper temperature are.

[0033] Austenite can form in one part of the first sub-region, from which martensite can be obtained through press hardening, while this is not the case in the remaining part of the first sub-region. In between, the microstructure composition can change gradually.

[0034] 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.

[0035] If martensite is to be obtained in a part of the first sub-region, it is preferred that, following the region-wise heating in step c2), the austenite re-transformation temperature of the component is not undercut in this part of the first sub-region, at least until the completion of step e). If press hardening is part of the described process, the austenite re-transformation temperature in this part of the first sub-region is preferably not undercut until the press. However, it is not necessary to ensure that the austenite re-transformation temperature in this part of the first sub-region is not undercut after step c2) until the completion of step e). Austenite does not decompose instantaneously. Acceptable results can also be obtained if part of the austenite in the first sub-region has decomposed before press hardening.

[0036] In step e), a temperature of the first 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, wherein a change in the temperature within a tolerance of 200 K or 100 K is accepted. For example, the first 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 first 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 first sub-region of the first region in the second continuous furnace can be maintained at its temperature or heated, or cooling of the first sub-region of the first region can be slowed down.Since the temperature of the first sub-area varies locally, the statements in this paragraph apply to each location in the first sub-area.

[0037] Outside the first sub-region of the first region, the component can be thermally treated in different ways in step e). Preferably, outside the first sub-region, there is a further sub-region of the first region in which the AC3 temperature of the component is not exceeded in steps c2) to e). This prevents austenite from forming in this sub-region of the first region. In step e), this part of the first region of the component is heated in such a way that a temperature remains below the AC3 temperature of the component even after heating. This part of the first sub-region is therefore no longer heated above the AC3 temperature of the component after cooling in step c1). Preferably, the temperature of this part of the first 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 this part of the first sub-range preferably does not exceed the AC3 temperature of the component until press hardening. This allows a ductile microstructure to be maintained in this part of the first sub-range. 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, acceptable results can be achieved.

[0038] In addition to the first region with the first 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.

[0039] It is irrelevant at what point in time the temperature of the second region exceeds the AC3 temperature of the component. If the entire component is heated to a temperature above the AC3 temperature of the component in step a), the aforementioned condition is already met in step a). If the second region is heated to below the AC3 temperature in step a), the second region can be heated to a temperature above the AC3 temperature in the temperature control station or in the second furnace.

[0040] It is preferred that the temperature of the second region, after heating to a temperature above the AC3 temperature of the component, no longer falls below the austenite retransformation temperature until the completion of step e). Preferably, the temperature in the second region does not fall below the austenite retransformation temperature until the press. This prevents the austenite formed in the second region from decomposing before press hardening.

[0041] 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.

[0042] 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.

[0043] The first subregion can be created with particular precision by heating with the laser unit. In particular, the subregion can have a finer contour and / or be smaller than would be possible with other methods. Cooling would make it difficult or even impossible to maintain the temperature gradient. In a preferred embodiment of the method, the first region of the component is cooled in step c1) by applying a cooling fluid.

[0044] 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 for 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 first sub-region, is cooled. At least the first sub-region is then reheated in regions using the laser unit so that the temperature gradient is maintained. In principle, this results in a method in which the first sub-region is cooled differently in regions. However, depending on the desired design of the temperature gradient, this would be difficult or impossible to achieve using cooling with nozzles.The procedure described is simpler.

[0045] 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.

[0046] In this embodiment, the AC3 temperature of the component is only exceeded in the tempering station or in the second furnace. Preferably, the component is heated in step a) to a temperature above the ACI temperature of the component. In this case, the component is heated in step a) to a temperature between the ACI temperature and the AC3 temperature of the component.

[0047] 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.

[0048] In a further preferred embodiment of the method, the first region of the component is heated in step c2) in regions with the laser unit such that a second sub-region of the first region arranged outside the first sub-region is brought to a temperature above the AC3 temperature of the component.

[0049] In the present embodiment, the component has a first region and a second region, wherein the first region has at least a first sub-region and a second sub-region. A temperature gradient is set at least in the first sub-region of the first region so that gradually variable ductility can be achieved. The temperature gradient preferably does not extend into the second sub-region. In the second sub-region of the first region and in the second region, the AC3 temperature is exceeded so that low ductility is obtained in these two regions. In principle, this could also be achieved by leaving out not only the second region but also the second sub-region of the first region during cooling. However, depending on the desired contour of the regions, this would be impossible or difficult to achieve by cooling, for example with nozzles.The described method, in contrast, is simpler and allows finer contours.

[0050] Preferably, the second 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 second subregion of the first region after step c2) is preferably in the range from 900 to 1100 °C.

[0051] It is preferred that, following heating in step c2), the temperature in the second 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 temperature in the second sub-region of the first region is preferably not fallen below until the press. However, it is not necessary to ensure that the temperature in the second sub-region of the first region does not fall below the austenite re-transformation temperature after step c2) until the completion of step e). Austenite does not decompose instantaneously. Acceptable results can also be obtained if part of the austenite in the second sub-region of the first region has decomposed before press hardening.

[0052] In a further preferred embodiment of the method, the first sub-region of the first region borders the second sub-region of the first region and / or the second sub-region of the first region borders the second region. The "and" case is preferred.

[0053] If the first sub-region of the first region borders on the second sub-region of the first region, it is preferred that, after step c2), the temperature in the first sub-region gradually decreases starting from the temperature of the second sub-region. In this respect, the first sub-region can be designed as a transition region. If the second sub-region of the first region borders on the second region, it is preferred that the second sub-region of the first region and the second region have the same temperature after step c2). In this respect, the second sub-region of the first region can be designed as a continuation of the second region.

[0054] As a further aspect of the invention, a device for thermally treating a metallic component is presented. The device comprises:

[0055] - a first continuous furnace for heating the entire component,

[0056] - 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, which is designed to heat the first region of the component in such a way that a temperature gradient is set at least in a first sub-region within the first region,

[0057] - a second continuous furnace for thermal treatment of the component,

[0058] - a first transfer device for transferring the component from the first continuous furnace to the tempering station, and

[0059] - a second transfer device for transferring the component from the tempering station to the second continuous furnace.

[0060] 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 using the device. The first continuous furnace serves step a), the first transfer device serves step b), the tempering station serves steps d) and c2), the second transfer device serves step d), and the second continuous furnace serves step e).

[0061] Preferably, the device comprises a control device which is configured to control the device according to the described method.

[0062] The laser unit is preferably further configured to heat a second sub-region of the first region, located outside the first sub-region, to a temperature above the AC3 temperature of the component. 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 to the press.

[0063] In a preferred embodiment of the device, the laser unit comprises a VCSEL

[0064] 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).

[0065] 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, however. The figures and the proportions depicted therein are merely schematic. They show:

[0066] Fig. 1 : a device according to the invention for the thermal treatment of a metallic component,

[0067] Fig. 2: a temperature profile which can be obtained with the device of Fig. 1 by a method according to the invention, and

[0068] Fig. 3: a component which has been treated with the method illustrated in Fig. 2.

[0069] 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.

[0070] 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. The laser unit 9 is configured to heat the first region 10 of the component 2 in regions such that a temperature gradient is established at least in a first sub-region 12 within the first region 10 and that a second sub-region 15 of the first region 10, arranged outside the first sub-region 12, is brought to a temperature above the AC3 temperature of the component 2. The regions 10, 11, 12, 15 of the component 2 are illustrated in Fig. 3. The laser unit 9 can, in particular, comprise a VCSEL.

[0071] 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.

[0072] 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. Di 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 AC 3 of component 2.

[0073] 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.

[0074] In the tempering station 4, the component 2 remains for a residence time t T s. 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 retransformation temperature T ARof the component 2. The temperature of the first region 10 is shown as Ti. After cooling, the previously cooled first region 10 of the component 2 is heated in sections with the laser unit 9. The second sub-region 15 is heated to a temperature above the AC3 temperature T AC 3 of the component 2. The temperature of the second sub-region 15 of the first region 10 is T 1A The part of the first region 10 which belongs neither to the first sub-region 12 nor to the second sub-region 15 has a temperature T 1 B . In the first sub-region 12, a temperature gradient is obtained. This extends from the temperature T 1 B as lower temperature up to temperature T 1A as the upper temperature. This is indicated by arrows in Fig. 2.

[0075] 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.

[0076] 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 D 2. In the second continuous furnace 5, the first region 10 of the component 2 outside the first sub-region 12 and the second sub-region 15 is heated such that the temperature T 1 B of the first area 10 of the component 2 in this area even after heating below the AC3 temperature T AC 3 of component 2.

[0077] 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.

[0078] Fig. 3 shows a plan view of component 2. In this example, component 2 is a B-pillar for a motor vehicle. The first region 10 and the second region 11 are visible. Within the first region 10, the first sub-region 12 and the second sub-region 15 are shown. The second sub-region 15 is composed of two non-connected parts. A temperature gradient is set in the first sub-region 12, as indicated by arrows. The shape of component 2 and regions 10, 11, 12, and 15 shown is exemplary. Components of any geometry can be treated using the method shown in Fig. 2. The method is particularly flexible, particularly with regard to the design of the first sub-region 12 and the second sub-region 15. 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 first sub-area

[0091] 13 first transfer facility

[0092] 14 second transfer facility

[0093] 15 second sub-area

[0094] T Temperature

[0095] T A C3 AC3 temperature of the component

[0096] T AR Austenite retransformation temperature of the component

[0097] T q Temperature of the first area of ​​the component

[0098] T 1ATemperature of the sub-area of ​​the first area of ​​the component

[0099] T 1B Temperature of the remaining first area of ​​the component

[0100] T2Temperature of the second area of ​​the component t Time t Di Residence time in the first continuous furnace t T1 Transfer time from the first continuous furnace to the tempering station t T s Residence time in the temperature control station t T2 Transfer time from the tempering station to the second continuous furnace t D 2 Residence time in the second continuous furnace r Transport direction of the component

Claims

Claims Method for the thermal treatment of 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), d) in the tempering station (4) cooling a first region (10) of the component (2), wherein a temperature of the first region (10) at least after cooling is below the austenite re-transformation temperature (T AR) of the component (2), c2) in the tempering station (4), heating the first region (10) of the component (2) cooled in step d) in regions with a laser unit (9) such that a temperature gradient is set at least in a first sub-region (12) within the first region (10), 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 a temperature of a second region (11) of the component (2) during method steps a) to e) at least temporarily exceeds the AC3 temperature (TAGS) of the component (2). Method according to claim 1, wherein the first region (10) of the component (2) is cooled in step d) by exposure to a cooling fluid. Method according to one of the preceding claims, wherein a temperature of the component (2) in step a) does not exceed the AC3 temperature (T GS) of the component (2).Method according to one of claims 1 or 2, wherein the entire component (2) is heated in step a) to a temperature above the AC3 temperature (TAGS) of the component (2). Method according to one of the preceding claims, wherein the first region (10) of the component (2) is heated in step c2) in regions with the laser unit (9) in such a way that a second sub-region (15) of the first region (10) arranged outside the first sub-region (12) is heated to a temperature above the AC3 temperature (T AC 3) of the component (2). The method according to claim 5, wherein the first subregion (12) of the first region (10) adjoins the second subregion (15) of the first region (12) and / or wherein the second subregion (15) of the first region (10) adjoins the second region (11). A device (1) for thermally treating a metallic component (2), comprising: - a first continuous furnace (3) for heating the entire component (2), - a temperature control 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), which is designed to heat the first region (10) of the component (2) in such a way that a temperature gradient is set at least in a first sub-region (12) within the first region (10), - 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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