Heat treatment of metal parts
By locally cooling in the temperature control station and heating the edges with laser units, the problem of unclear soft area profiles in the heat treatment of metal parts is solved, and the precise heat treatment of metal parts is realized, especially suitable for B-pillars and other components of motor vehicles.
Patent Information
- Application Number
- CN202380079182.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-11-15
- Filing Date
- 2023-11-15
- Publication Date
- 2025-07-11
AI Technical Summary
In the prior art, when performing local heat treatment on metal parts, it is difficult to achieve precise contour division of soft and hard areas, especially in the formation of soft spots.
Using a method and device, precise heat treatment of the metal parts is achieved by heating the entire component in the first continuous furnace, then locally cooling in the temperature control station and heating the edges with a laser unit, combined with heat treatment in the second continuous furnace.
It can achieve a particularly accurate outline of the soft areas of metal parts, ensuring clear definition of soft points and effective protection of hard areas, and is suitable for parts such as B-pillars in motor vehicles, improving the accuracy and flexibility of heat treatment.
Smart Images
Figure CN120303416A_ABST
Abstract
Description
Field of the Invention
[0001] The present invention relates to a method and an apparatus for heat-treating metal components, in particular steel components of motor vehicles. Background Art
[0002] Especially in the automotive industry, it is known to selectively harden steel components by heat treatment. For this purpose, regions of the steel component (such as the B-pillar) are subjected to different heat treatments. Accordingly, regions with different ductilities are created, which is advantageous for the collision behavior of these components. For example, the occupants of a motor vehicle can be protected by the hard region of the B-pillar at the seat height, while the soft regions at the upper and lower parts of the B-pillar can absorb energy by deformation. In addition, for example, at the position where the B-pillar is to be connected to other body components, the B-pillar can be selectively softened. Such soft connection regions can also be referred to as soft spots. At the soft spots, for example, it is possible to drill through the B-pillar easily in order to provide holes for rivets or screws.
[0003] A successful method for locally different heat treatment of components has proven to be as follows: First, the entire component is heated in a first furnace, then the component is subjected to locally different heat treatment in a temperature control station, and then the entire component is heated in a second furnace. In the temperature control station, for example, a certain region of the component is cooled by applying a cooling fluid to that region, while the rest of the component remains substantially at its temperature. For many application cases, this can achieve excellent results. However, the known method is not precise enough, especially in forming soft spots. This is because the cooling, for example, through nozzles, cannot be locally limited or is difficult to locally limit. Similar difficulties usually also occur when the component needs to be simply divided into soft and hard regions. Summary of the Invention
[0004] The object of the present invention is to provide a method for heat-treating metal components that can obtain soft regions with particularly precise contours. The object is also to provide a corresponding apparatus.
[0005] These objects are achieved by the method and apparatus according to the independent claims. Other advantageous configurations are specified in the dependent claims. The features set forth in the claims and the description can be combined with each other in any technically meaningful way.
[0006] According to the present invention, a method for heat-treating metal components is provided. The method includes:
[0007] a) Heating the entire component in a first continuous furnace,
[0008] b) Transferring (conveying) the component from the first continuous furnace to a temperature control station,
[0009] c) Cooling at least a first region of the component in the temperature control station,
[0010] d) Transferring the component from the temperature control station to a second continuous furnace,
[0011] e) Heat-treating the component in the second continuous furnace,
[0012] wherein, after completion of step c), the edge of the first region is at least partially heated by a laser unit, wherein at least after cooling in step c), the temperature of the component in the core of the first region surrounded by the edge of the first region is lower than the austenite inversion temperature of the component and does not exceed the AC3 temperature of the component after step c), and wherein during method steps a) to e), the temperature of a second region of the component at least temporarily exceeds the AC3 temperature of the component.
[0013] The method described enables heat treatment of metal components. The metal components are preferably components made of steel. The steel is preferably 22MnB5. However, the metal components do not have to meet the definition of steel. Therefore, this document will generally refer to metal components. For example, components of a motor vehicle, in particular B-pillars, can be heat-treated by the method. However, the method can also be used for any other desired application.
[0014] The material thickness of the component is preferably at least 0.7 mm, in particular in the range from 1 to 4 mm. Such a material thickness is suitable for many applications. However, the method described is also applicable to components with different material thicknesses. The material thickness of the component is preferably constant over the entire component. Alternatively, the component can also have regionally different material thicknesses. For example, the component may be a "tailor rolled blank (TRB)", in which case locally different material thicknesses are obtained by locally different rolling processes. The component may also be a "tailor welded blank (TWB)", in which case locally different material thicknesses are obtained by welding together multiple metal sheets. A combination of TRB and TWB is also possible. The method is equally applicable to components with and without coatings. The component is particularly preferably coated with Al / Si.
[0015] After heat 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 the component in the press (step g)). In this case, the method is a method for heat-treating and press-hardening the component. However, the press-hardening of the component does not have to be carried out as part of the method. The method can also be a preparation for a press-hardening operation carried out outside the method. Generally speaking, the component heat-treated by the method can be subjected to further process steps, the result of which together with the further processes can be, for example, a finished motor vehicle. However, the heat treatment of the component is a defined sub-method in such an overall process. Therefore, it is advantageous to consider the heat treatment separately from the subsequent process steps, in particular separately from the press-hardening.
[0016] In step a), the entire component is heated in a first continuous furnace. A furnace is understood to be a device inside which a settable temperature can be achieved and into which the component can be introduced. Over time, the temperature of the component gradually approaches the actual (prevailing) temperature inside the furnace. Thus, heat is transferred to the component through the gas (especially air) inside the furnace. A continuous furnace is a furnace through which the component can move and is heated as it passes through the furnace.
[0017] The first continuous furnace is preferably a roller hearth furnace. In the first continuous furnace, the component is preferably heated by burners (especially gas burners). This enables a particularly uniformly distributed temperature to be provided for the component. In the first continuous furnace, the entire component is heated. The component is completely accommodated by the first continuous furnace. In addition, a continuous furnace can be used to obtain heating with a particularly large temperature difference. Using a continuous furnace, the component can in particular be heated from room temperature to a temperature within its AC3 temperature range. Such comprehensive heating is not achievable with many other heating methods; even if it were possible, it would be too costly.
[0018] In the case of a coated component, the first continuous furnace can also be used to diffuse the coating into the remaining material of the component. This is particularly applicable to Al / Si coatings. In the case of a coated component, preferably, in step a), the component is heated in such a way that the coating material diffuses into the remaining material of the component in step a). Thus, in step a), preferably the component is heated to a temperature higher than the temperature at which the coating material diffuses into the remaining material of the component. Preferably, in step a), the temperature of the component is higher than this temperature for at least 1 minute, especially even at least 2 minutes. Preferably, in step a), the component is heated to a temperature of at least 700 °C, especially a temperature of at least 780 °C. Satisfactory results have been obtained at these temperatures. However, for improved process reliability, it is preferably heated to at least 830 °C. Preferably, in step a), the temperature of the component is higher than 700 °C, especially 780 °C or even 830 °C, for at least 1 minute, especially even at least 2 minutes. Particularly preferably, in the case of a coated component, in step a), the component is heated to a temperature higher than the AC1 temperature of the component, especially higher than the AC3 temperature of the component. Preferably, in step a), the temperature of the component is higher than the AC1 temperature of the component, especially higher than the AC3 temperature of the component, for at least 1 minute, especially even at least 2 minutes. In this regard, the heating in step a) can not only be used to diffuse the coating, but also has contributed to the transformation of the microstructure.
[0019] Heating in a continuous furnace can in particular be contrasted with so-called "direct electrical heating". This heating method makes it difficult to heat the component evenly and with a sufficient amount of heat. Direct electrical heating focuses more on rapid heating. In addition, in the case of direct electrical heating, contact with the component is required. In step a) of the method, heating is preferably carried out non-contact. This does not exclude the component being moved through the first continuous furnace by conveyor rollers and being in contact with the conveyor rollers in this regard. When heat is introduced into the component through gas and / or thermal radiation, the heating is non-contact.
[0020] In step b) of the method, the component is transferred from the first continuous furnace to a temperature control station. This is preferably carried out by a first transfer device. In the temperature control station, different heat treatments are carried out on areas of the component. Thus, in particular, the described method is a method for carrying out locally different heat treatments on a metal component. However, this does not need to be explicitly mentioned as the locally different heat treatment has already been clearly defined.
[0021] The first continuous furnace and the temperature control station are components that are different from each other and spatially separated. The transfer between the first continuous furnace and the temperature control station makes it easier to cool the components between heating in the first continuous furnace and heat treatment in the temperature control station. In the temperature control station, the components are regionally cooled as quickly as possible anyway. Rapid cooling can be carried out more effectively outside the hot first continuous furnace. Therefore, cooling can already start during the transfer. In this regard, the spatial separation of the first continuous furnace from the temperature control station speeds up the method. This is in contrast to solutions where all method steps are carried out in the same device without transferring the components. The aim of such solutions is usually to keep the cost of component transfer low or even avoid it. The spatial separation between the first continuous furnace and the temperature control station also makes construction easier because the requirements for the first continuous furnace and for the temperature control station are different.
[0022] In step d), the component is transferred from the temperature control station to the second continuous furnace. This is preferably carried out by a second transfer device. In step e), the component is heat treated in the second continuous furnace. For step e), the entire component is accommodated by the second continuous furnace.
[0023] The temperature control station and the second continuous furnace are components that are different from each other and spatially separated. The transfer between the temperature control station and the second continuous furnace makes it easier to cool the components between heat treatments in the temperature control station and the second continuous furnace. Therefore, the parts of the component to be cooled can still be cooled during the transfer. This reduces the necessary residence time in the temperature control station and speeds up the method. This is in contrast to solutions where all method steps are carried out in the same device as much as possible without transferring the components. The aim of such solutions is usually to keep the cost of component transfer low or even avoid it. The spatial separation between the temperature control station and the second continuous furnace also makes construction easier because the requirements for the temperature control station and for the second continuous furnace are different.
[0024] The second continuous furnace is preferably a roller hearth furnace. In the second continuous furnace, the entire component is heat treated, preferably heated. The component is completely accommodated by the second continuous furnace. The heat treatment carried out in the continuous furnace can in particular be contrasted with so-called "direct electric heating". The heat treatment in the second continuous furnace is especially used to promote the transformation of the microstructure. Since the component is not directly cooled (e.g., in a press downstream of the temperature control station), there is sufficient time to establish the required microstructure distribution in the component. In particular, in step e), carbon atoms can diffuse inside the component, so that the microstructure of the component changes as expected. In addition, the heat treatment in the second continuous furnace can be used to reduce the thermal stress in the component. In the subsequent stamping hardening operation, warping of the component can be reduced.
[0025] The method can impart a particularly precise contour to the first region. To this end, after step c) is completed, the edge of the first region is at least partially heated using a laser unit.
[0026] This edge forms around the perimeter of the remainder of the first region. Thus, this edge encloses the remainder of the first region. The fact that the edge is at least partially heated means that at least one part of the edge is heated. This part forms around the perimeter of the remainder of the first region and thus partially encloses the remainder of the first region. Preferably, after step c) is completed, the edge of the first region is completely heated using a laser unit.
[0027] This makes it possible, in particular, to perform different heat treatments on three regions. First, a distinction can be made between the first region and the second region. In addition, the edge of the first region is treated separately from the remainder of the first region (i.e., from the core of the first region).
[0028] There is at least one first region. Thus, exactly one first region or multiple first regions can be provided. Preferably, there are multiple first regions. The following discussion mainly concerns the case of exactly one first region by way of example. If multiple first regions are provided, the following statements apply to all first regions, each case being applicable accordingly.
[0029] The edge of the first region constitutes a two-dimensional part of the first region. Thus, the edge of the first region can also be referred to as the edge region. The edge region constitutes a sub-region of the first region. Thus, the edge is smaller than the first region. Thus, there is also a part of the first region that does not belong to the edge part of the first region. This part is called the core of the first region. The core of the first region is two-dimensional and can thus also be referred to as the core region of the first region. If there are multiple first regions, each first region has its own core and its own edge.
[0030] The component preferably but not necessarily has only one first region, or multiple first regions and a second region, i.e., no other regions. Whether there is one second region or multiple second regions is not important.
[0031] The method enables different heat treatments to be performed on the individual regions of the component. Thus, the composition of the microstructure of the component may be locally differently affected, resulting in locally different ductility. The first region outside the edge is more ductile than the second region and the edge of the first region. The second region and the edge of the first region can be given the same ductility or different ductilities. Preferably, they are given the same ductility.
[0032] In particular, the core of the first region can be in the form of a soft spot through which the component can be connected to another component. For example, if the B-pillar is the component, it can be connected to another body component. Thus, the first region is a soft connection region where, for example, the component can be easily drilled through to provide holes for, for example, rivets or screws. The first region is preferably circular.
[0033] In step a), the entire component is heated in a first continuous furnace. Thus, in step a), all regions are treated in the same way. Therefore, it is not necessary to be able to distinguish these regions already in step a).
[0034] The method has multiple stages and, in addition to heating in the first continuous furnace, also includes heat treatment in a temperature control station and heating in a second continuous furnace. Thus, the heating in the first continuous furnace can in principle be carried out to any desired temperature. If the component is only slightly heated in the first passage, then in the subsequent course of the method, the component can be heated more in the edge of the first region and in the second region, and vice versa. In particular, the component can be heated in the first continuous furnace to a temperature above or below the AC3 temperature of the component.
[0035] In particular for energy-related reasons, it is advantageous to heat the component relatively strongly in the first continuous furnace. This makes it possible to utilize the above-mentioned advantages of heating in a continuous furnace compared to other types of heating (especially compared to direct electrification). Thus, preferably, the component is heated to at least 400 °C in step a), especially at least 600 °C. Preferably, the component is heated to a temperature above the AC1 temperature of the component in step a). Preferably, the component is heated to a temperature not more than 400 K below the AC3 temperature of the component in step a), especially not more than 200 K below the AC3 temperature of the component. Preferably, the temperature of the component in step a) does not exceed 200 K above the AC3 temperature of the component. For example, the component can reach a temperature in the range of 600 to 800 °C in step a). As an alternative, higher temperatures are preferred, especially above the AC3 temperature of the component. Thus, it is also preferred that the component is heated to at least 900 °C, especially at least 1000 °C in step a). Preferably, the component can be heated to a temperature in the range of 850 to 1200 °C in step a).
[0036] Due to the temperature control station downstream of the first continuous furnace, the component is subjected to locally different heat treatments. For this purpose, in the temperature control station, different heat treatments are first carried out on the first region and the second region of the component. In step c), the first region is cooled in the temperature control station. This is preferably achieved by applying a cooling fluid (especially compressed air) to the first region. The pressure of the compressed air is preferably in the range of 2 to 4.5 bar. Due to this relatively high pressure, a large amount of compressed air can be directed to the first region of the component in a very short time, so that a sufficiently high cooling rate can be achieved. However, for the operating mode of the method, it is generally not important which method is used to cool the first region.
[0037] The cooling in step c) does not have to be precise. In particular, during the cooling process of step c), the required soft spots do not need to be sharply defined from their surrounding areas. In any case, the part of the component to be given (or formed) soft spots is also cooled in step c). This is the core of the first region, or if there are multiple first regions, the cores of the respective first regions. For example, this can be done simply by blowing compressed air into it. However, if the compressed air is applied to a small area of the component, the compressed air will spread on the surface of the component, so that even the part of the component outside the actual area to be cooled (for example, the area intended to form soft spots) is cooled to a lesser extent. Subsequently, the edge of the first region is heated by a laser unit so that the core has the required sharp contour. Therefore, the laser unit can completely or partially reverse the undesired cooling outside the actually required cooling part of the component.
[0038] The part of the component cooled in step c) is called the first region. This also includes the part of the component that is undesirably cooled due to the lack of precision. This part constitutes the edge of the first region, which is subsequently reheated by a laser unit. The region that actually only needs to be cooled is the part of the first region that does not belong to the edge of the first region. This part of the first region is called the core of the first region. The edge of the first region surrounds the core of the first region. Therefore, the core of the first region can provide soft spots. The fact that the described method can sharpen the contour of the first region (or make the contour of the first region clear) can thus be understood as that by precisely heating the edge of the region, a clearly defined core can be obtained from the first region. It can be said synonymously that the described method can sharpen the contour of the core of the first region.
[0039] By the described method, high ductility of the core of the first region is obtained through heat treatment. At least after the cooling in step c), the temperature of the component in the core of the first region is lower than the austenite inversion temperature of the component and does not exceed the AC3 temperature of the component after step c).
[0040] If the entire component is heated to a temperature above the AC3 temperature in step a), austenite will form throughout the component. By cooling the core of the first region below the austenite transformation temperature of the component in step c), this austenite decomposes again in the core of the first region. The austenite transformation temperature is defined by the fact that once the temperature drops below the austenite transformation temperature, the austenite decomposes. The austenite transformation temperature is a material property. Thus, the fact that the temperature of the core of the first region is below the austenite transformation temperature of the component after cooling at least does not mean that austenite has previously formed in the component.
[0041] 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 below the austenite transformation temperature of the component in step c) will also result in the fact that in the subsequent process of the method, even if the component is further heated, no austenite will form in the core of the first region. If no austenite is formed in step a), there is no need to lower the temperature below the austenite transformation temperature in step c) to cause the austenite to decompose. If the entire component is not heated to a temperature above the AC3 temperature in step a), any required cooling of the core of the first region in step c) is sufficient. However, in this case, it is also advantageous to lower the temperature below the austenite transformation temperature. This is not derived from the fact that austenite transformation occurs below this temperature, but merely from the fact that the austenite transformation temperature is generally significantly lower than the AC3 temperature.
[0042] Preferably, in step c), the core of the first region is cooled by at least 100 K, especially at least 250 K. After step c), the temperature of the core of the first region is preferably in the range of 400 to 700 °C, especially in the range of 500 to 600 °C.
[0043] Therefore, regardless of the temperature reached in step a), no austenite exists in the core of the first region after cooling in step c). As long as the AC3 temperature of the component is not exceeded (again) in the core of the first region after cooling in step c), a ductile microstructure can be obtained in the core of the first region. Thus, in steps d) to e), the AC3 temperature of the component is not exceeded in the core of the first region. This avoids the formation of austenite in the core of the first region after cooling. In step e), the core of the first region of the component is heated such that even after heating, the temperature of the core of the first region of the component is below the AC3 temperature of the component. Therefore, after cooling in step c), in any case, the core of the first region of the component is no longer heated to a temperature above the AC3 temperature of the component.
[0044] In addition to at least one first region having a core and a periphery, the component also has a second region. The implementation of the method is such that during method steps a) to e), the temperature of the second region of the component is at least temporarily above the AC3 temperature of the component. This enables the formation of austenite in the second region. During the press hardening operation, martensite can be formed therefrom, and thus the second region has a relatively low ductility.
[0045] It is not important when the temperature of the second region exceeds the AC3 temperature of the component. If in step a), the entire component is heated to a temperature above the AC3 temperature of the component, then this condition is already met in step a). If the second region is heated to a temperature below the AC3 temperature in step a), then the second region can be heated to a temperature above the AC3 temperature in a temperature control station or in a second furnace.
[0046] Preferably, after heating to a temperature above the AC3 temperature of the component, until step e) is completed, the temperature of the second region does not drop below the austenite inversion temperature. Preferably, in the second region, the temperature first drops below the austenite inversion temperature in the press. This makes it possible to avoid the decomposition of the austenite formed in the second region before press hardening.
[0047] In steps b) to e), the temperature change of the second region is preferably at most 200 K, in particular at most 100 K. This can also be referred to as maintaining this temperature, where temperature changes within a tolerance range of 200 K or 100 K are acceptable respectively. For example, the second region can be exposed to a temperature above the AC3 temperature of the component in a temperature control station in step c), and / or the second region can be exposed to a temperature above the AC3 temperature of the component in a second furnace in step e). Depending on the temperature of the second region when it enters the temperature control station or the second furnace, and depending on the residence time of the component in the temperature control station or in the second furnace, in the temperature control station, the second region can be maintained at its temperature or heated, or the cooling of the second region can be slowed down. However, in particular, the second region can also be cooled in the temperature control station by exposure to ambient air.
[0048] In steps a) to e), the temperature of the second region can first rise above the AC3 temperature, then drop below the austenite inversion temperature, and then rise above the AC3 temperature again. In this case, it is sufficient that as long as after the second heating to a temperature above the AC3 temperature, until step e) is completed, the temperature of the second region does not drop below the austenite inversion temperature. This is included in the following statement: during method steps a) to e), the temperature of the second region of the component is at least temporarily above the AC3 temperature of the component and does not drop below the austenite inversion temperature of the component thereafter.
[0049] Thus, the method can obtain a ductile microstructure in the core of the first region while obtaining a less ductile microstructure in the second region.
[0050] Due to the heating of the laser unit, the core of the first region can be created particularly precisely. In particular, the core of the first region can have a finer profile and / or be smaller than by other methods. In this regard, the method can be applied particularly flexibly.
[0051] The heat treatment of the edge of the first region requires little. The edge is part of the first region and is thus, by definition, cooled in step c). However, compared to the core of the first edge, to what temperature it is cooled is not important. In particular, the edge of the first region can be the part of the component that is cooled only due to the lack of cooling precision in step c). Due to the nature of things, an accurate statement cannot be made about the temperature to which this part of the component is cooled. With the method described, it is particularly necessary to take into account the imprecise cooling of the edge of the first region during the cooling process.
[0052] In addition, after step c), it is sufficient that the core of the first region does not exceed the AC3 temperature of the component. In contrast, at the edge of the first region, this is possible. Even preferably, due to the heating of the edge of the first region by the laser unit, the AC3 temperature is exceeded in the edge of the first region. This also makes it possible to form austenite in the edge of the first region. Thus, the edge of the first region can have low ductility like the second region.
[0053] Ideally, the edge of the first region will have the same microstructure as the second region. Thus, preferably, the edge of the first region is brought to the temperature of the second region by heating with the laser unit. Preferably, after heating by the laser unit until the method is completed, the second region and the edge of the first region have the same temperature. In this regard, the edge of the first region is treated in the same way as the second region.
[0054] However, if there is a deviation from the ideal situation, the method can also be used advantageously. Any heating of the edge of the first region will cause the edge of the first region to be separated from the core of the first region. Thus, the profile of the core of the first region can be sharpened by any desired heating of the edge of the first region. Any heating of the edge of the first region will counteract the undesired cooling effect due to the insufficient cooling precision in step c). Thus, there is no need for a minimum amount of heating of the edge of the first region, or even to heat it to exactly the same temperature as the second region. The more the edge of the first region is heated by the laser unit, the clearer the boundary between the core of the first region and its surrounding area becomes. This applies in any case until the edge of the first region exceeds the AC3 temperature.
[0055] It has been found that it is advantageous to heat the edge of the first region by means of a laser unit to at least 100 K, in particular at least 250 K. The temperature of the edge of the first region after heating is preferably in the range from 900 to 1100 °C.
[0056] Preferably, after heating the edge of the first region by means of a laser unit, and at least until before step e) is completed, the edge temperature of the first region does not drop below the austenite inversion temperature of the component. If press hardening is part of the method, then preferably, in the press, the temperature of the edge of the first region first drops below the austenite inversion temperature. However, after heating the edge of the first region by means of a laser unit, and until before step e) is completed, the temperature in the edge of the first region does not need to drop below the austenite inversion temperature. Austenite does not decompose immediately. Good results can also be obtained when part of the austenite in the edge region of the first region has decomposed before press hardening. Acceptable results can even be obtained if no austenite is formed at all in the edge of the first region, or if the austenite has completely decomposed before press hardening. This is also because any heating of the edge of the first region counteracts the undesired cooling effect due to insufficient cooling accuracy in step c).
[0057] If heating is carried out by laser before step e), then the edge of the first region has been formed as such in step e). In this case, it does not matter whether and to what extent the edge temperature of the first region changes in step e). Preferably, in step e), the temperature change of the edge of the first region is at most 200 K, in particular at most 100 K. This can also be referred to as maintaining the temperature, where temperature changes within a tolerance of 200 K or 100 K respectively are acceptable. For example, the edge of the first region can be exposed to a temperature above the AC3 temperature of the component in a second continuous furnace. Depending on the temperature of the edge of the first region when entering the second furnace and depending on the residence time of the component in the second furnace, in the temperature control station, the edge of the first region can be maintained at its temperature or heated, or the cooling of the edge of the first region can be slowed down.
[0058] For the operating mode of the method, it does not matter whether the heating of the edge of the first region is carried out by a single laser or multiple lasers. Therefore, it is provided that the heating is carried out by a laser unit. The laser unit can comprise one or more lasers. The electronic device for supplying power to and controlling at least one laser can be part of the laser unit or can be arranged outside the laser unit, for example, in the control unit of the device for the method.
[0059] In a preferred embodiment of the method, the first region of the component in step c) is cooled by applying a cooling fluid.
[0060] The cooling fluid is preferably compressed air. The cooling fluid is preferably distributed onto the first region using a nozzle. This enables the first region to be easily cooled in a short time. However, the fundamental disadvantage of using a nozzle is that the cooling fluid does not allow for an exact separation between the cooled and non-cooled parts of the component. The method described avoids this. First, in step c), the first region including the edge is cooled. Then, the edge is reheated using a laser unit. Thus, it essentially corresponds to a method of not cooling the edge of the first region. However, depending on the contour of the required region, it is impossible or very difficult to achieve this by nozzle cooling. In contrast, the method described is easier.
[0061] In another preferred embodiment of the method, the temperature of the component in step a) does not exceed the AC3 temperature of the component.
[0062] In this embodiment, first, the second region of the component and optionally the edge of the first region are heated to a temperature above the AC3 temperature in a temperature control station or a second furnace. Preferably, in step a), the component is heated to a temperature above the AC1 temperature of the component. In this case, in step a), the component is thus heated to a temperature between the AC1 temperature and the AC3 temperature of the component.
[0063] In another preferred embodiment of the method, in step a), the entire component is heated to a temperature above the AC3 temperature of the component.
[0064] In another preferred embodiment of the method, at least part of the heating of the edge of the first region occurs in step c) or after step e).
[0065] If the edge of the first region is heated in step c), the laser unit is part of the temperature control station. This is advantageous because the temperature control station provides a relatively large space for the laser unit. Furthermore, it has been found that it is advantageous to heat the edge of the first region using the laser unit directly after cooling in step c). In this case, the undesired cooling of the edge of the first region can be compensated particularly quickly. Thus, the time for an undesired microstructural transformation to occur is particularly short.
[0066] As an alternative, in the present embodiment, the edge of the first region can be heated after step e). In this case, the laser unit is located downstream of the second continuous furnace. Compared to, for example, arranging the laser unit inside the second continuous furnace, the advantage of doing so is that the laser unit can be relatively easily arranged outside the second continuous furnace. In addition, the laser unit does not need to be designed for use inside the furnace. Maintenance is also easier if the laser unit is arranged outside the second continuous furnace. Heating the edge of the first region using the laser unit after step e) has the following advantages: the clear contour of the core of the obtained first region has a relatively short remaining time that may disappear again, for example, due to heat conduction within the component. In particular, this advantage can be obtained if a stamping hardening operation is performed on the component after step e).
[0067] Therefore, both heating options during step c) and after step e) have advantages. It is even conceivable to heat the edge of the first region using a first laser unit in step c) and by a second laser unit after step e). Although this solution is more complex, it combines the advantages of both options.
[0068] As an alternative to the two options of the present embodiment, the edge of the first region can also be heated at different times during the method, in particular between steps c) and d), in step d), between steps d) and e), or in step e). Even in these cases, although the above advantages of heating in step c) or after step e) are not obtained, the heating purpose of sharpening the contour of the first region can still be achieved.
[0069] Another aspect of the present invention proposes a device for heat-treating a metal component. The device includes:
[0070] - A first continuous furnace for heating the entire component,
[0071] - A temperature control station having cooling equipment for cooling at least one first region of the component,
[0072] - A second continuous furnace for heat-treating the component,
[0073] - A first transfer device for transferring the component from the first continuous furnace into the temperature control station, and
[0074] - A second transfer device for transferring the component from the temperature control station into the second continuous furnace,
[0075] - A laser unit for at least partially heating the edge of the first region of the component cooled by the temperature control station.
[0076] The advantages and features of the method can be applied and transferred to the device, and vice versa. The device is preferably designed to operate according to the method. The method is preferably implemented by the device. A first continuous furnace is used for step a), a first transfer device is used for step b), a temperature control station is used for step c), a second transfer device is used for step d), and a second continuous furnace is used for step e).
[0077] Preferably, the device has a control device which is designed to control the device according to the method.
[0078] Preferably, the device also has a press for press hardening the component and a third transfer device for transferring the component from the second continuous furnace to the press.
[0079] In a preferred embodiment of the device, the laser unit includes a VCSEL.
[0080] 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 obtained by using a VCSEL in step c). Description of the Drawings
[0081] The present invention will be described in more detail below with reference to the drawings. The drawings show particularly preferred exemplary embodiments, however, the present invention is not limited thereto. The drawings and the relative dimensions shown therein are only schematic. In the drawings:
[0082] Figure 1 : shows a device for heat treating a metal component according to the present invention;
[0083] Figure 2 : shows the temperature curve that can be obtained by using the device according to the method of the present invention, Figure 1 ;
[0084] Figure 3 : shows an example of a component treated by the method shown in Figure 2 ; and
[0085] Figure 4 : shows Figure 3 an enlarged view of the first region in Detailed Description of the Preferred Embodiments
[0086] Figure 1 Shows a device 1 for heat treating a metal component 2. The device 1 includes a first continuous furnace 3, a temperature control station 4, and a second continuous furnace 5, which are arranged one after another in the conveying direction r of the component 2. The control device 6 is specifically designed to control the first continuous furnace 3, the temperature control station 4, and the second continuous furnace 5.
[0087] 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 having a laser unit 9 for heating an edge 12 of the first region 10 of the component 2. These regions 10, 11, 12, 15 of the component 2 are shown in Figure 3 . The laser unit 9 can in particular comprise a VCSEL.
[0088] The apparatus 1 further comprises a first transfer device 13 for transferring the component 2 from the first continuous furnace 3 to the temperature control station 4, and a second transfer device 14 for transferring the component 2 from the temperature control station 4 to the second continuous furnace 5.
[0089] Figure 2 Shows the temperature profile established in the component 2 when the component 2 moves through Figure 1 the apparatus 1. Figure 2 The illustration in is a schematic view. It shows a graph of temperature T versus time t plotted 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 as t D1 . In the example shown, the entire component 2 is heated in the first continuous furnace 3 to a temperature above the AC3 temperature T AC3 of the component 2. As an alternative, the method can be implemented such that the temperature of the component 2 in the first continuous furnace 3 does not exceed the AC3 temperature T AC3 of the component 2.
[0090] Then, the component 2 is transferred to the temperature control station 4. The associated transfer time is denoted as t T1 . During this transfer, the component 2 can cool.
[0091] The component 2 stays in the temperature control station 4 for a residence time t TS . During this time, the first region 10 of the component 2 is cooled, and after cooling, the temperature of the first region 10 is lower than the austenite inversion temperature T AR of the component 2. The temperature of the first region 10 is denoted as T1. After cooling, the edge 12 of the previously cooled first region 10 of the component 2 is heated 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 denoted as T 1A , while the temperature of the core 15 in the first region 10 is denoted as T 1B .
[0092] Depicts the uniform temperature T 1A of the edge 12 of the first region 10 of the component 2. In particular in this regard, Figure 2It is a schematic diagram. In particular, the edge 12 of the first region 10 may have a locally variable temperature. For example, after cooling, the temperature of the edge 12 of the first region 10 may increase radially from the inside to the outside. The same applies to the core 15 of the first region 10.
[0093] After the component 2 has been heat-treated in the temperature control station 4, the component 2 is transferred to the second continuous furnace 5. This transfer time is denoted as t T2 . During this period, the component 2 can also cool down, and this cooling may vary from one region to the next.
[0094] In the second continuous furnace 5, the component 2 will be further heat-treated. The residence time of the component 2 in the second continuous furnace 5 is denoted as t D2 . In the second continuous furnace 5, the core 15 of the first region 10 of the component 2 is heated in such a way that even after heating, the temperature T 1B of the core 15 of the first region 10 of the component 2 is lower than the AC3 temperature T AC3 of the component 2.
[0095] In the first continuous furnace 3, the temperature T2 of the second region 11 of the component 2 exceeds the AC3 temperature T AC3 of the component 2 and will not drop below this temperature again before the end of the method shown.
[0096] Figure 3 A plan view showing an example of the configuration of the component 2 is presented. In this example, the component 2 is a B-pillar of a motor vehicle. A plurality of circular first regions 10 and second regions 11 are visible in the figure.
[0097] Figure 4 Shows Figure 3 a detail enlarged view. It shows one of the first regions 10. The edge 12 and the core 15 of the first region 10 are depicted.
[0098] The shapes of the component 2 and the regions 10, 11, 12, 15 shown are exemplary. Figure 2 The method in
[0099] List of reference numerals
[0100] 1 Device
[0101] 2 Component
[0102] 3 First continuous furnace
[0103] 4 Temperature control station
[0104] 5 Second continuous furnace
[0105] 6 Control device
[0106] 7 Cooling equipment
[0107] 8 Heating equipment
[0108] 9 Laser unit
[0109] 10 First area
[0110] 11 Second area
[0111] 12 Edge
[0112] 13 First transfer device
[0113] 14 Second transfer device
[0114] 15 Core of the first area
[0115] T Temperature
[0116] T AC3 AC3 temperature of the component
[0117] T AR Austenite inversion temperature of the component
[0118] T1 Temperature of the first area of the component
[0119] T 1A Temperature of the edge of the first area of the component
[0120] T 1B Temperature of the core of the first area of the component
[0121] T2 Temperature of the second area of the component
[0122] t Time
[0123] t D1 Residence time in the first continuous furnace
[0124] t T1 Duration of transfer from the first continuous furnace to the temperature control station
[0125] t TS Residence time in the temperature control station
[0126] t T2 Duration of transfer from the temperature control station to the second continuous furnace
[0127] t D2 Residence time in the second continuous furnace
[0128] r Conveying direction of the component
Claims
1. A method for heat-treating a metal component (2), characterized in that, 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 of the component (2) in the temperature control station, d) Transferring the component (2) from the temperature control station (4) to a second continuous furnace (5), e) Heat-treating the component (2) in the second continuous furnace (5), Wherein, after completion of the step c), the edge (12) of the first region is at least partially heated by the laser unit (9), wherein at least after cooling in the step c), the temperature of the component (2) in the core (15) of the first region (10) surrounded by the edge (12) of the first region (10) is lower than the austenite inversion temperature (T AR ) of the component (2), and does not exceed the AC3 temperature of the component after the step c), and wherein, during the method steps a) to e), the temperature of the second region (11) of the component (2) at least temporarily exceeds the AC3 temperature (T AC3 ) of the component (2).
2. The method according to claim 1, wherein In step c), the first region (10) of the component (2) is cooled by applying a cooling fluid to the first region (10).
3. The method according to any one of the preceding claims, characterized in that, In step a), the temperature of the component (2) does not exceed the AC3 temperature (T AC3 ) of the component.
4. The method according to any one of claims 1 and 2, characterized in that, In step a), the entire component (2) is heated to a temperature higher than the AC3 temperature (T AC3 ) of the component (2).
5. The method according to any one of the preceding claims, characterized in that, At least partial heating of the edge (12) of the first region (10) occurs in step c) or after step e).
6. An apparatus (1) for heat-treating a metallic component (2), characterized in that, Comprising: - A first continuous furnace (3) for heating the entire component (2), - A temperature control station having cooling means (7) for cooling at least a first region (10) of the component (2), - A second continuous furnace (5) for heat-treating the component (2), - A first transfer means (13) for transferring the component (2) from the first continuous furnace (3) to the temperature control station (4), and - A second transfer means (14) for transferring the component (2) from the temperature control station (4) to the second continuous furnace (5), - A laser unit (9) for at least partially heating the edge (12) of the first region (10) of the component (2) cooled by the temperature control station (4).
7. The device (1) according to claim 6, characterized in that, The laser unit (9) comprises a VCSEL.