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) in a first continuous furnace (3); b) transferring the component (2) from the first continuous furnace (3) to a temperature control station (4); c) cooling at least a first region (10) of the component (2) in the temperature control station (4); d) transferring the component (2) from the temperature control station (4) to a second continuous furnace (5); e) thermally treating the component (2) in the second continuous furnace (5), wherein: after completion of step c), at least sections of an edge (12) of the first region are heated with a laser unit (9); at least after the cooling process in step c), a temperature of the component (2) in a core (15) of the first region (10) enclosed by the edge (12) of the first region (10) is below the austenite reversion temperature (TAR) of the component (2) and, after step c), does not exceed the Ac3 temperature of the component (2); and, 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 that steel components can be specifically hardened 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 area of ​​the B-pillar at seat height, while soft areas in the upper and lower areas of the B-pillar absorb energy through deformation. In addition, a B-pillar can be specifically made soft at the points where the B-pillar is to be connected to other body parts. Such soft joining areas can also be referred to as soft spots. In soft spots, the B-pillar can be easily drilled through, for example, to create holes for rivets or screws.

[0004] For the locally varied thermal treatment of components, processes have proven successful. 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, 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 many applications with this method. However, known processes are not precise enough, particularly for the creation of soft spots. This is because the cooling cannot be limited locally, for example using nozzles, or is difficult to do. 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 method for the thermal treatment of metallic components that can produce a soft area with a particularly precise contour. 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) cooling at least a first region of the component in the tempering station, d) transferring the component from the tempering station to a second continuous furnace, e) thermally treating the component in the second continuous furnace, wherein, after completion of step c), an edge of the first region is heated at least in sections with a laser unit, wherein a temperature of the component in a core of the first region enclosed by the edge of the first region is below the austenite retransformation temperature of the component, at least after cooling in step c), and does not exceed the AC3 temperature of the component after step c).and 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 result in, for example, 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.However, in order to increase process reliability, heating to at least 830 °C is preferred. The temperature of the component in step a) is preferably 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. The temperature of the component in step a) is preferably 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 not only be used 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.

[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 means that cooling can begin during the transfer. In this respect, the spatial separation of the first continuous furnace from the tempering station accelerates the process. This is in contrast to 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 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 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] Using the described method, the first region can be given a particularly precise contour. To this end, an edge of the first region is heated, at least in sections, with a laser unit after completion of step c).

[0020] The edge is formed circumferentially around the remaining part of the first region. The edge thus encloses the remaining part of the first region. The fact that the edge is heated at least in sections means that at least a portion of the edge is heated. This portion is formed circumferentially around the remaining part of the first region, thus partially enclosing the remaining part of the first region. Preferably, the edge of the first region is completely heated with a laser unit after completion of step c).

[0021] In particular, three areas can be thermally treated differently. First, a distinction can be made between a first area and a second area. Furthermore, the edge of the first area is treated separately from the rest of the first area, i.e., the core of the first area.

[0022] There is at least one first region. There can therefore be exactly one first region or several first regions. Preferably there are a plurality of first regions. The following primarily deals with the case of exactly one first region by way of example. If several first regions are provided, the following statements apply accordingly to all first regions. The edge of the first region represents a two-dimensional part of the first region. The edge of the first region could therefore also be referred to as an edge region. The edge region represents a sub-region of the first region. The edge is therefore smaller than the first region. There is also a part of the first region that does not belong to the edge of the first region. This part is referred to as the core of the first region. The core of the first region is two-dimensional and could therefore also be referred to as a core region of the first region.If there are several first areas, each of the first areas has a core and an edge.

[0023] The component preferably, but not necessarily, has only the first region or the first regions and the second region, i.e., no further regions. Whether there is one second region or several second regions is irrelevant.

[0024] With the described process, different regions of the component can be thermally treated differently. This allows the structural composition of the component to be influenced differently locally, resulting in locally different ductilities. The first region outside the edge becomes more ductile than the edge of the first region and the second region. The edge of the first region and the second region can have the same ductility or different ductilities. Equal ductilities are preferred.

[0025] In particular, the core of the first region can be designed as a soft spot, via which the component can be connected to another component, for example, in the case of a B-pillar as a component to another body part. The first region is thus a soft joining area in which the component can be easily drilled, for example, to create a hole for a rivet or a screw. The first region is preferably circular.

[0026] In step a), the entire component is heated in the first continuous furnace. All areas are therefore treated equally in step a). It is therefore not necessary for the areas to be distinguishable from one another in step a). The described process is multi-stage and, in addition to heating in the first continuous furnace, also includes thermal treatment in the tempering station and heating in the second continuous furnace. Therefore, heating in the first continuous furnace can, in principle, take place to any temperature. If the component is only heated slightly in the first pass, the component can be heated more intensively in the edge of the first area and more intensively in the second area as the process progresses, and vice versa. In particular, heating of the component in the first continuous furnace can take place to a temperature above or below the AC3 temperature of the component.

[0027] 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.

[0028] 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 c) 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.

[0029] The cooling in step c) does not have to be precise. In particular, during cooling in step c), the desired soft spots do not have to be sharply demarcated from their surroundings. It is sufficient that in step c) the part of the component in which a soft spot is to be created is also cooled. This is the core of the first area or, in the case of several first areas, the cores of the first areas. This can be achieved, for example, by simply blowing compressed air onto it. If a small area of ​​the component is exposed to compressed air, the compressed air spreads over the surface of the component and thus cools the component in a weakened form even outside the area actually to be cooled - which, for example, is intended to form a soft spot. By subsequently heating the edge of the first area with the laser unit, the desired sharp contour of the core is achieved.The laser unit therefore completely or partially reverses the unwanted cooling outside the part of the component that is actually to be cooled.

[0030] The part of the component cooled in step c) is referred to as the first region. This also includes the part of the component that is undesirably cooled due to the described insufficient precision. This part represents the edge of the first region, which is subsequently reheated with the laser unit. The area that actually only needs to be cooled is the part of the first region that is not part of the edge of the first region. This part of the first region is referred to as the core of the first region. The edge of the first region encloses the core of the first region. A soft spot can therefore be created by the core of the first region. The fact that the contour of the first region can be sharpened with the described method can therefore be understood to mean that a sharply defined core is obtained from the first region by precisely heating its edge.Equivalently, it can be said that with the described method the contour of the core of the first area can be sharpened.

[0031] The high ductility in the core of the first region is achieved by thermal treatment using the described process. The temperature of the component in the core of the first region is below the austenite retransformation temperature of the component, at least after cooling in step c), and does not exceed the AC3 temperature of the component after step c).

[0032] If the entire component is heated to a temperature above the AC3 temperature in step a), austenite forms throughout the component. Cooling the core of the first region below the component's austenite retransformation temperature in step c) causes this austenite to decompose again in the core of the first region. The austenite retransformation temperature is defined by the fact that austenite decomposes as soon as the temperature falls below the austenite retransformation temperature. The austenite retransformation temperature is a material property. The fact that the temperature of the core of the first region is below the component's austenite retransformation temperature, at least after cooling, does not imply that austenite was previously formed in the component.

[0033] 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, cooling the core of the first region in step c) below the austenite re-transformation temperature of the component can help ensure that no austenite is formed in the core of 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 does not have to be undercut in step c) for the austenite to decompose. In the event that the entire component is not heated to a temperature above the AC3 temperature in step a), any cooling of the core of the first region in step c is sufficient. Nevertheless, it is still advisable to undercut the austenite re-transformation temperature in this case.This does not result from the fact that austenite retransformation occurs below this temperature, but merely from the fact that the austenite retransformation temperature is generally significantly below the AC3 temperature.

[0034] Preferably, the core of the first region is cooled in step c) by at least 100, in particular by at least 250 K. The temperature of the core of the first region after step c) is preferably in the range of 400 to 700 °C, in particular in the range of 500 to 600 °C.

[0035] Regardless of the temperature reached in step a), no austenite is present in the core of the first region after cooling in step c). As long as the AC3 temperature of the component is not (again) exceeded in the core of the first region after cooling in step c), a ductile structure can be maintained in the core of the first region. The AC3 temperature of the component is therefore not exceeded in the core of the first region in steps d) to e). This prevents austenite from forming in the core of the first region after cooling. In step e), the core of the first region of the component is heated in such a way that the temperature of the core of the first region of the component remains below the AC3 temperature of the component even after heating. The core of the first region of the component is therefore no longer heated above the AC3 temperature of the component after cooling in step c).

[0036] In addition to the at least one first region with the core and the edge, the component has a second region. The process is carried out such 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. 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 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.

[0038] 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.

[0039] 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 step c) 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) it can be exposed to a temperature above the AC3 temperature of the component in the second furnace. 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 in the temperature control station can be maintained at its temperature 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.

[0040] 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 re-transformation 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 re-transformation 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 re-transformation temperature of the component. With the described process, a ductile microstructure can therefore be obtained in the core of the first region, while a less ductile microstructure is obtained in the second region.

[0041] The core of the first region can be created with particular precision by heating with the laser unit. In particular, the core of the first region can have a finer contour and / or be smaller than would be possible with other methods. This makes the process particularly flexible.

[0042] There are only a few requirements for the thermal treatment of the edge of the first region. The edge is part of the first region and is therefore, by definition, cooled in step c). However, unlike the core of the first edge, the temperature to which this occurs is not important. The edge of the first region can, in particular, be the part of the component that is cooled in step c) only due to a lack of cooling precision. It is in the nature of things that no precise information can be given about the temperature to which this part of the component is cooled. The described method is intended to take into account the fact that the edge of the first region is cooled imprecisely during cooling.

[0043] Furthermore, it is sufficient that the core of the first region does not exceed the AC3 temperature of the component after step c). However, this is possible in the edge of the first region. It is even preferred that the AC3 temperature be exceeded by heating the edge of the first region with the laser unit. This allows austenite to form in the edge of the first region as well. The edge of the first region can thus be given low ductility, just like the second region.

[0044] Ideally, the edge of the first region will retain the same structure as the second region. It is therefore preferred that the edge of the first region be heated to the temperature of the second region by heating with the laser unit. Preferably, the edge of the first region and the second region have the same temperature after heating with the laser unit until the end of the process. In this respect, the edge of the first region is treated in the same way as the second region.

[0045] However, the method can also be used advantageously if the ideal case described is deviated from. Each heating of the edge of the first region causes a demarcation of the edge of the first region from the core of the first region. The contour of the core of the first region can therefore be sharpened by any desired heating of the edge of the first region. Each heating of the edge of the first region counteracts an undesired cooling effect caused by a lack of precision in the cooling in step c). Therefore, it is not necessary to heat the edge of the first region by a minimum amount or even to heat it exactly to the temperature of the second region. However, the more the edge of the first region is heated with the laser unit, the more sharply the core of the first region is demarcated from its surroundings. This applies at least until the edge of the first region exceeds the AC3 temperature.

[0046] It has proven advantageous to heat the edge of the first region with the laser unit by at least 100 K, in particular by at least 250 K. The temperature of the edge of the first region after heating is preferably in the range of 900 to 1100 °C.

[0047] It is preferred that, following heating of the edge of the first region with the laser unit, the temperature in the edge of the first region does not fall below the austenite retransformation temperature of the component at least until the completion of step e). If press hardening is part of the described method, the austenite retransformation temperature in the edge of the first region is preferably not fallen below until the press. However, it is not necessary that, after heating of the edge of the first region with the laser unit, the temperature in the edge of the first region does not fall below the austenite retransformation temperature until the completion of step e). Austenite does not decompose instantaneously. Good results can also be obtained if part of the austenite in the edge of the first region has decomposed before press hardening.Acceptable results can even be obtained if no austenite is formed at the edge of the first zone, or if it completely decomposes before press hardening. This is also due to the fact that any heating of the edge of the first zone counteracts an undesirable cooling effect caused by inaccurate cooling in step c).

[0048] If heating with the laser occurs before step e), the edge of the first region is already formed as such in step e). Whether and to what extent the temperature of the edge of the first region changes in step e) is irrelevant. Preferably, the temperature of the edge of the first region changes in step e) 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 edge 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 edge of the first region upon entry into the second furnace and depending on the residence time of the component in the second furnace, the edge of the first region can be maintained at its temperature in the tempering station or heated, or cooling of the edge of the first region can be slowed down.

[0049] For the functioning of the described method, it is also irrelevant whether the edge of the first region is heated with a single laser or with multiple lasers. Therefore, the heating is provided 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.

[0050] In a preferred embodiment of the method, the first region of the component is cooled in step c) by exposure to a cooling fluid.

[0051] The cooling fluid is preferably compressed air. The cooling fluid is preferably applied to 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 c), the first region, including the edge, is cooled. The edge is then reheated with the laser unit. The result is essentially a process in which the edge of the first region was left out during cooling. However, depending on the desired contour of the regions, this would be impossible or difficult to achieve using cooling with nozzles. The described method is simpler in comparison.

[0052] 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.

[0053] In this embodiment, the second region of the component and optionally the edge of the first region are heated 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 Ad temperature of the component. In this case, the component is heated in step a) to a temperature between the A temperature and the AC3 temperature of the component.

[0054] 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.

[0055] In a further preferred embodiment of the method, the edge of the first region is heated at least in sections in step c) or after step e).

[0056] If the edge of the first region is heated in step c), the laser unit is part of the tempering station. This is advantageous in that the tempering station offers comparatively plenty of space for a laser unit. Furthermore, it has proven advantageous to heat the edge of the first region with the laser unit immediately after cooling in step c). The undesired cooling of the edge of the first region can be counteracted particularly quickly. There is therefore very little time for an undesired microstructural transformation. Alternatively, the edge of the first region can be heated in the present embodiment after step e). In this case, the laser unit is arranged downstream of the second continuous furnace.Compared to arranging the laser unit, for example, inside the second continuous furnace, this has the advantage that the laser unit can be arranged relatively easily outside the second continuous furnace. Furthermore, the laser unit does not have to be designed for use inside a furnace. Maintenance is also easier when the laser unit is arranged outside the second continuous furnace. Heating the edge of the first region with the laser unit after step e) has the advantage that there is comparatively little time within which the achieved sharp contour of the core of the first region could be lost again, for example through thermal conduction within the component. This advantage can be achieved in particular if the component is subjected to a press hardening process after step e).

[0057] Both heating options in step c) and after step e) each have advantages. It's even conceivable to heat the edge of the first area in step c) with a first laser unit and then after step e) with a second laser unit. While this solution would be complex, it would combine the advantages of both options.

[0058] As an alternative to the two possibilities of the present embodiment, the heating of the edge of the first region can also take place at other times in the process, in particular between steps c) and d), in step d), between steps d) and e), or in step e). Even if the previously described advantages of heating in step c) or after step e) are not achieved in these cases, the purpose of heating, namely sharpening the contour of the first region, is nevertheless achieved.

[0059] As a further aspect of the invention, a device for thermally treating a metallic component is presented. The device comprises:

[0060] - a first continuous furnace for heating the entire component,

[0061] - a temperature control station with a cooling device for cooling at least a first area of ​​the component,

[0062] - a second continuous furnace for thermally treating the component, - a first transfer device for transferring the component from the first continuous furnace to the tempering station, and

[0063] - a second transfer device for transferring the component from the tempering station to the second continuous furnace,

[0064] - a laser unit for at least partially heating an edge of the first region of the component cooled by the temperature control station.

[0065] 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 step c), the second transfer device serves step d), and the second continuous furnace serves step e).

[0066] Preferably, the device comprises a control device which is configured to control the device according to the described method.

[0067] 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.

[0068] In a preferred embodiment of the device, the laser unit comprises a VCSEL.

[0069] 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 shown that particularly good results can be achieved with a VCSEL in step c2).

[0070] 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 merely schematic. They show:

[0071] Fig. 1: a device according to the invention for thermally treating a metallic component, Fig. 2: a temperature profile which can be obtained with the device from Fig. 1 by a method according to the invention,

[0072] Fig. 3: an example of a component which has been treated with the method illustrated in Fig. 2, and Fig. 4: an enlargement of a first area from Fig. 3.

[0073] 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.

[0074] The tempering 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 an edge 12 of the first region 10 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.

[0075] 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.

[0076] 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 AC 3 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. Component 2 is then transferred to the temperature control station 4. The corresponding transfer time is t T1 During this transfer, component 2 can cool down.

[0077] 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 re-transformation temperature T AR of the component 2. The temperature of the first region 10 is shown as T. After cooling, an edge 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 edge 12 of the first region 10 is T 1A while the temperature of the core 15 of the first region 10 is shown as T 1 B is marked.

[0078] A uniform temperature T is shown 1Afor the subregion 12 of the first region 10 of the component 2. In particular, Fig. 2 is schematic in this respect. In particular, the edge 12 of the first region 10 can have a locally varying temperature. For example, the temperature of the edge 12 of the first region 10 can increase radially from the inside to the outside after cooling. The same applies to the core 15 of the first region 10.

[0079] 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 T2 Component 2 can also cool down, which can vary depending on the area.

[0080] 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 D2In the second continuous furnace 5, the core 15 of the first region 10 of the component 2 is heated such that the temperature T 1B of the core 15 of the first region 10 of the component 2 even after heating below the AC3 temperature T AC3 of component 2.

[0081] 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. Fig. 3 shows an example of the design of component 2 in a plan view. In this example, component 2 is a B-pillar for a motor vehicle. A plurality of circular first regions 10 and the second region 11 can be seen.

[0082] In Fig. 4, a section of Fig. 3 is shown enlarged. One of the first areas 10 can be seen therein. The edge 12 and the core 15 of the first

[0083] Area 10.

[0084] The shapes shown for component 2 and regions 10, 11, 12, and 15 are examples. The method shown in Fig. 2 can be used to process components of any geometry.

[0085] List of reference symbols

[0086] 1 device

[0087] 2 component

[0088] 3 first continuous furnace

[0089] 4 Tempering station

[0090] 5 second continuous furnace

[0091] 6 Control device

[0092] 7 Cooling device

[0093] 8 Heating device

[0094] 9 Laser unit

[0095] 10 first area

[0096] 11 second area

[0097] 12 edges

[0098] 13 first transfer facility

[0099] 14 second transfer facility

[0100] 15 Core of the first area

[0101] T Temperature

[0102] T AC 3 AC3 temperature of the component

[0103] T A R Austenite retransformation temperature of the component

[0104] T -i Temperature of the first area of ​​the component

[0105] T 1A Temperature of the edge of the first area of ​​the component

[0106] T 1B Temperature of the core of the first area of ​​the component

[0107] 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 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 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), c) cooling at least a first region (10) of the component (2) in the tempering station (4), d) transferring the component (2) from the tempering station (4) to a second continuous furnace (5), e) thermally treating the component (2) in the second continuous furnace (5), wherein after completion of step c) an edge (12) of the first region is heated at least in sections with a laser unit (9), wherein a temperature of the component (2) in a core (15) of the first region (10) enclosed by the edge (12) of the first region (10) is below the austenite retransformation temperature (T AR) of the component (2) and after step c) does not exceed the AC3 temperature of the component (2), and 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). Method according to claim 1, wherein the first region (10) of the component (2) is cooled in step c) by exposure to a cooling fluid. Method according to one of the preceding claims, wherein a temperature of the component (2) in step a) exceeds the AC3 temperature (T AC3 ) 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 AC3 ) of the component (2) is heated. Method according to one of the preceding claims, wherein the at least partial heating of the edge (12) of the first region (10) takes place in step c) or after step e). 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 at least a 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) into the second continuous furnace (5), - a laser unit (9) for at least partially heating an edge (12) of the first region (10) of the Component (2). Device (1) according to claim 6, wherein the laser unit (9) comprises a VCSEL.

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