Heat treatment of metal components
By cooling in a temperature control station and heating with laser units, the accuracy of local heat treatment of metal parts in the prior art is solved, flexible local differentiated heat treatment of metal parts is realized, and the collision performance and ductility control of the components are improved.
Patent Information
- Application Number
- CN202380079517.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-11-15
- Filing Date
- 2023-11-15
- Publication Date
- 2025-07-04
AI Technical Summary
The prior art is difficult to achieve precise heat treatment of local areas of metal components, especially the difficulty in setting up small hard proton areas in soft areas, making it difficult to meet complex collision performance requirements.
Using a method and apparatus, by heating the entire component in a first continuous furnace, then cooling the first area of the component in a temperature control station and heating its sub-regions with a laser unit, and then heat treatment in a second continuous furnace, different areas of the component achieve different microstructures and ductility.
It realizes flexible local differentiated heat treatment for metal parts, and can set up small hard proton areas in soft areas, improving the collision performance and ductility control accuracy of the components.
Smart Images
Figure CN120265794A_ABST
Abstract
Description
[0001] The present invention relates to a method and an apparatus for heat-treating metal components, in particular steel components of a motor vehicle.
[0002] Especially in the automotive industry, it is well-known to selectively harden steel components by heat treatment. For this purpose, different regions of a steel component (such as a B-pillar) are subjected to different heat treatments. Accordingly, regions with different ductilities are generated, which is very advantageous for the crash performance of such components. For example, vehicle occupants can be protected by the hard regions of the B-pillar at seat height, while the soft regions at the upper and lower parts of the B-pillar can absorb energy by deformation.
[0003] A successful method for locally differentially heat-treating a component is: first heating the entire component in a first furnace, then locally differentially heat-treating the component in a temperature control station, and finally heating the entire component in a second furnace. In the temperature control station, a certain region of the component is cooled by applying a cooling fluid to this region, while keeping the other parts of the component at a substantially constant temperature. In many cases, this method can achieve excellent results. However, there is an increasing need to obtain temperature distributions that cannot be achieved or are difficult to achieve by known methods. This especially applies to components that require small hard sub-regions to be provided within soft regions. In the case of cooling with a cooling fluid, it is difficult to precisely avoid the small sub-regions. Similar difficulties are usually encountered when the component needs to be divided not only into simple hard and soft regions.
[0004] The object of the present invention is to provide a particularly flexible method for locally differentially heat-treating metal components. The object of the present invention is also to provide a corresponding apparatus.
[0005] These objects can be achieved by the method and apparatus according to the independent claims. Further preferred definitions are specified in the dependent claims. The features in the claims and the description can be combined with each other in any technically meaningful way.
[0006] In the present invention, a method for heat-treating a metal component is first proposed, comprising:
[0007] a) heating the entire component in a first continuous furnace;
[0008] b) transferring the component from the first continuous furnace to a temperature control station;
[0009] c1) cooling a first region of the component in the temperature control station, and after cooling, the temperature of the first region is at least lower than the austenite restoration temperature of the component;
[0010] c2) in the temperature control station, heating a sub-region of the first region of the component cooled in step c1) to a temperature higher than the AC3 temperature of the component by a laser unit;
[0011] d) Transfer the component from the temperature control station to the second continuous furnace;
[0012] e) Heat-treat the component in the second continuous furnace, wherein a first region of the component outside the sub-region is heated such that, even after heating, the temperature of the first region of the component outside the sub-region remains below the AC3 temperature of the component;
[0013] Wherein, during method steps a) to e), the temperature of the second region of the component is at least temporarily higher than the AC3 temperature of the component.
[0014] The method can heat-treat metal components. The metal component is preferably a steel component. The steel is preferably 22MnB5. However, the metal component does not necessarily have to conform to the definition of steel. Therefore, metal components will be generally referred to herein. For example, automotive components, especially B-pillars, can be heat-treated by the method. However, the method can also be used for any other desired purpose.
[0015] The material thickness of the component is preferably at least 0.7 mm, especially in the range of 1 to 4 mm. Such a material thickness is suitable in many cases. However, the method can also be used for components with different material thicknesses. The material thickness of the entire component is preferably constant. As an alternative, the component can also have regionally different material thicknesses. For example, the component can be a "Tailored Rolled Blank (TRB)", with locally different material thicknesses obtained by locally different rolling. The component can also be a "Tailored Welded Blank (TWB)", in which case, by welding together multiple metal sheets, locally different material thicknesses can be obtained. It can also be a combination of TRB and TWB. The method is equally applicable to coated and uncoated components. The component is preferably coated with an aluminum / silicon coating.
[0016] After heat treatment, the component is preferably press-hardened in a press to thereby be hot-formed. The method preferably further includes the 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, press-hardening the component in the method is not necessary. The method can also be used as a preparation for press-hardening operations outside the method. Generally, the components heat-treated by the method can be subjected to subsequent processing steps, and the results of the combined action with other further processing can be, for example, a finished automotive product. However, during the entire process, the heat treatment of the component is a defined sub-process. Therefore, it is preferable to consider the heat treatment separately from subsequent process steps, especially separately from press-hardening.
[0017] In step a), the entire component is heated in a first continuous furnace. A furnace can be understood as a device within which a settable temperature can be achieved and into which the component can be placed. Over time, the temperature of the component gradually approaches the temperature inside the furnace. Heat is transferred to the component through the gas (especially air) inside the furnace. A continuous furnace is a furnace in which the component can be moved and is heated as it passes through the furnace.
[0018] Preferably, the first continuous furnace is a roller hearth furnace. In the first continuous furnace, it is preferred to heat the component using burners, especially gas burners, so that the component can obtain a particularly uniform temperature distribution. In the first continuous furnace, the entire component is heated. The first continuous furnace can completely accommodate the entire component. In addition, a continuous furnace can also be used to achieve heating with a large temperature difference. Using a continuous furnace, the component can be heated from room temperature to a temperature close to the AC3 temperature range of the component. With other heating methods, such comprehensive heating cannot be achieved, or otherwise a high cost would be incurred anyway.
[0019] For a component with a coating, the first continuous furnace can also diffuse the coating into the remaining material of the component. This is especially applicable to an aluminum / silicon coating. For a coated component, preferably in step a), a heating method that enables the coating material to diffuse into the remaining material of the component is adopted. Therefore, in step a), it is preferred to heat the component 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 component is maintained at this temperature for at least 1 minute, preferably at least 2 minutes. Preferably, the component in step a) is heated to at least 700 °C, preferably at least 780 °C. Satisfactory results have been obtained at this temperature. However, to improve the reliability of the process, it is preferred to heat to at least 830 °C. Preferably, in step a), the component is maintained at a temperature higher than 700 °C for at least 1 minute, preferably 780 °C, even 830 °C, preferably at least 2 minutes. Preferably, if it is a coated component, the component in step a) is heated to a temperature higher than the AC1 temperature of the component, preferably higher than the AC3 temperature of the component. Preferably, the temperature of the component in step a) is maintained at a temperature higher than the AC1 temperature of the component for at least 1 minute, preferably higher than the AC3 temperature of the component, and even preferably at least 2 minutes. Therefore, the heating in step a) can not only cause the coating to diffuse but also promote the transformation of the microstructure.
[0020] The heating in the continuous furnace is in sharp contrast to the so-called "direct electric heating". The latter heating method makes it difficult to achieve a large and uniform temperature rise of the component. Direct electric heating focuses more on rapid heating. In addition, in the case of direct electric heating, it is necessary to be in contact with the component. In step a) of the method, the heating is preferably carried out in a non-contact manner. This does not exclude the case where the component moves in the first continuous furnace through the conveyor rollers and is in contact with the conveyor rollers. When heat enters the component through gas and / or thermal radiation, the heating is non-contact.
[0021] In step b) of the method, the component is transferred from the first continuous furnace to the temperature control station. This is preferably done by the first transfer device. In the temperature control station, differential heat treatment is carried out on various regions of the component. Therefore, the method is especially a method for local differential heat treatment of metal components. However, this does not need to be explicitly mentioned, because the local differential heat treatment is clearly defined by steps c1) and c2).
[0022] The first continuous furnace and the temperature control station are independent components and are spatially separated. By transferring between the first continuous furnace and the temperature control station, it is easy to cool the component between the heating in the first continuous furnace and the heat treatment in the temperature control station. In the temperature control station, the component needs to be cooled in regions as quickly as possible anyway. Rapid cooling can be carried out more effectively outside the first continuous furnace at a high temperature. Therefore, cooling can start during the transfer process. In this regard, the spatial separation of the first continuous furnace and the temperature control station speeds up the method. This is in sharp contrast to the scheme where all process steps are carried out in the same equipment without transferring the component. The purpose of the latter scheme is usually to reduce or even avoid the cost of component transfer. The spatial separation between the first continuous furnace and the temperature control station also simplifies the equipment structure, because the requirements for the first continuous furnace and the temperature control station are different.
[0023] In step d), the component is transferred from the temperature control station to the second continuous furnace. This step is preferably done by the second transfer device. In step e), the component is heat-treated in the second continuous furnace. In step e), the second continuous furnace needs to accommodate the entire component.
[0024] The temperature control station and the second continuous furnace are independent components of each other and are spatially separated. By transferring between the temperature control station and the second continuous furnace, it is easy to cool the components between the heat treatment in the temperature control station and that in the second continuous furnace. Therefore, during the transfer process, the parts that need to be cooled in the components can also be cooled. This reduces the residence time required at the temperature control station and speeds up the method. This is in sharp contrast to the scenario where all process steps are carried out in the same equipment without transferring the components. The purpose of the latter scenario is usually to reduce or even avoid the cost of component transfer. The spatial separation between the temperature control station and the second continuous furnace also simplifies the equipment structure because the requirements for the temperature control station and the second continuous furnace are different.
[0025] 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 in the continuous furnace is different from the so-called "direct electric heating". The heat treatment in the second continuous furnace is mainly to promote the transformation of the microstructure. Since the component is not directly cooled, for example, cooled in a press downstream of the temperature control station, there is sufficient time to form the required microstructure distribution in the component. Especially in step e), carbon atoms can diffuse inside the component, thus causing the required changes in the microstructure of the component. In addition, the heat treatment carried out in the second continuous furnace can reduce the thermal stress in the component. During the subsequent stamping hardening operation, the deformation of the component can be reduced.
[0026] The method can particularly perform different heat treatments on three regions. First, the first region and the second region can be distinguished. In addition, a sub-region of the first region is treated separately from the other regions of the first region. Therefore, the result is at least the sub-region of the first region, the rest of the first region, and the second region.
[0027] The first region, the sub-region of the first region, and the second region are not necessarily all contiguous regions. Therefore, especially the central part of the B-pillar can constitute the first region, while the upper and lower parts of the B-pillar together constitute the second region. Within the first region, one or more components can constitute the sub-region. Preferably, there are only the first region and the second region for the components, that is, no other regions, but this is not necessary. This also applies to the sub-region as it is part of the first region.
[0028] The sub-region is part of the first region. The sub-region is smaller than the first region. Therefore, there is also a part of the first region that does not belong to the sub-region.
[0029] By means of the method described above, different heat treatments can be carried out on various regions of the component. Thus, the composition of the microstructure of the component can be locally differently affected, so that locally different ductilities are obtained. A first region outside the sub-region is more ductile than the sub-region and the second region. The second region and the sub-region of the first region can have the same ductility or different ductilities.
[0030] 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 distinguish between the regions in step a).
[0031] The method is divided into a plurality of stages. In addition to the heating in the first continuous furnace, it also includes heat treatment in a temperature control station and heating in a second continuous furnace. Thus, in principle, the heating in the first continuous furnace can reach any desired temperature. If only a small amount of heating of the component is carried out in the first continuous furnace, then in the subsequent process of the method, more heating of the component can be carried out in the sub-region and the second region, and vice versa. Preferably, the component can be heated in the first continuous furnace to a temperature above or below the AC3 temperature of the component.
[0032] Preferably, considering energy aspects, it is very advantageous to heat the component relatively strongly in the first continuous furnace. In this way, the advantages of heating in a continuous furnace compared to other heating methods, especially compared to direct electric heating, can be utilized. Therefore, it is preferred to heat the component in step a) to at least 400 °C, preferably at least 600 °C. Preferably, the component in step a) is heated to a temperature above the AC1 temperature of the component. Preferably, the component in step a) is heated to a temperature 400 K lower than the AC3 temperature of the component, preferably 200 K lower than the AC3 temperature of the component. The temperature of the component in step a) preferably does not exceed 200 K above the AC3 temperature of the component. For example, the component in step a) can reach a temperature range of 600 °C to 800 °C. As an alternative, a higher temperature is preferred, preferably a temperature above the AC3 temperature of the component. Thus, if the component in step a) is heated to at least 900 °C, preferably at least 1000 °C, it is also preferred. For example, the component in step a) can be heated to a temperature range of 850 °C to 1200 °C.
[0033] Since a temperature control station is provided downstream of the first continuous furnace, local differential heat treatment of the components can be carried out. Therefore, in the temperature control station, different heat treatments are first carried out on the first and second regions of the components. In step c1), the temperature control station cools the first region. Preferably, this is done by applying a cooling fluid, in particular compressed air, to the first region. The pressure of the compressed air is preferably between 2 and 4.5 bar. Since the pressure is relatively high, a large amount of compressed air can be introduced into the first region of the component in an extremely short time, thus achieving a sufficiently fast cooling rate. However, in terms of the operating mode of the method, which method is used to cool the first region generally does not matter.
[0034] In step c1), the first region is cooled. After cooling, the temperature of the first region is at least lower than the austenite restoration temperature of the component. In this way, a higher ductility can be achieved in the first region in principle.
[0035] If the entire component in step a) is heated to a temperature above the AC3 temperature, austenite is formed throughout the component. By cooling the first region in step c1) so that its temperature is lower than the austenite restoration temperature of the component, the austenite will decompose again in the first region. The austenite restoration temperature is defined as the temperature at which austenite decomposes once the temperature drops below it. The austenite restoration temperature is a material property. Therefore, the fact that at least the temperature of the first region after cooling is lower than the austenite restoration temperature of the component does not mean that austenite has been previously formed in the component.
[0036] If the entire component is not heated to a temperature above the AC3 temperature in step a), austenite will not be formed in this step. However, in this case, if the first region in step c1) is cooled to a temperature below the austenite restoration temperature of the component, austenite will not be formed in the first region even if the component is continuously heated. If austenite is not formed in step a), then in step c1), the temperature does not need to be lowered below the austenite restoration temperature for austenite to decompose. If the entire component is not heated to a temperature above the AC3 temperature in step a), then in step c1), any desired cooling of the first region can be carried out. However, in this case, lowering the temperature below the austenite restoration temperature is also an expedient measure. This is not because austenite restoration occurs below this temperature, but only because the austenite restoration temperature is generally significantly lower than the AC3 temperature.
[0037] Preferably, in step c1), the first region is cooled by at least 100 K, in particular at least 250 K. After step c1), the temperature of the first region is preferably between 400 °C and 700 °C, preferably between 500 °C and 600 °C.
[0038] Therefore, regardless of the temperature reached in step a), after cooling in step c1), austenite does not appear in the first region. As long as the component in the first region does not exceed the AC3 temperature (exceeded again) after cooling in step c1), a ductile microstructure can be obtained in the first region. However, due to the result of step c2), a part of the first region exceeds the AC3 temperature. This part of the first region is called a sub-region of the first region. In step c2), the sub-region of the first region is heated to a temperature higher than the AC3 temperature of the component by a laser unit in the temperature control station. This also makes it possible to form austenite in the sub-region of the first region.
[0039] In terms of the functional effect of the method, it does not matter whether the heating in step c2) is carried out by a single laser or multiple lasers. Therefore, the heating in step c2) is completed by a single laser unit. The laser unit may include one or more lasers. The electronic device for powering and controlling at least one laser may be part of the laser unit or may be provided outside the laser unit, for example, in the control unit of the application device for this method.
[0040] In step c2), the sub-region of the first region is preferably heated by at least 100 K, preferably at least 250 K. The temperature of the sub-region of the first region after step c2) is preferably in the range of 900 to 1100 °C.
[0041] More preferably, after heating in step c2), at least before step e) is completed, the temperature of the sub-region does not drop below the austenite restoration temperature of the component. If press hardening is part of the method, the temperature of the sub-region of the first region preferably drops below the austenite restoration temperature during the pressing process. However, before step e) is completed, it is not necessary to strictly ensure that the temperature of the sub-region of the first region after step c2) does not drop below the austenite restoration temperature. Austenite does not decompose immediately. Acceptable results can also be obtained if part of the austenite in the sub-region of the first region has decomposed before press hardening.
[0042] In step e), the temperature of the sub-region of the first region preferably changes by at most 200 K, preferably at most 100 K. This can also be called maintaining the temperature, and temperature changes within a tolerance of 200 K or 100 K respectively are acceptable. For example, the sub-region of the first region can be exposed to a temperature higher than the AC3 temperature of the component in the second continuous furnace. According to the temperature of the sub-region of the first region when it enters the second furnace and according to the residence time of the component in the second furnace, in the temperature control station, the first sub-region of the first region can maintain its temperature or be heated, or the cooling rate of the sub-region of the first region can be slowed down.
[0043] Outside the sub-region of the first region, the component does not exceed the AC3 temperature in steps c2) to e). This can avoid the formation of austenite outside the sub-region of the first region. In step e), the outside of the sub-region of the first region of the component is heated such that the temperature outside the sub-region of the first region of the component remains below the AC3 temperature of the component after heating. Therefore, the first region outside the sub-region of the component, i.e., the part of the first region that does not belong to the sub-region, should not be heated above the AC3 temperature of the component again under any circumstances after being cooled in step c1). Preferably, in steps c2) to e), the temperature of the first region outside the sub-region of the component does not exceed the AC3 temperature of the component. If the press hardening operation is part of the method, then preferably, before or during the press hardening operation, the temperature of the first region outside the sub-region of the component does not exceed the AC3 temperature of the component. In this way, a ductile microstructure can be obtained outside the sub-region of the first region. However, it is not necessary to strictly ensure that the AC3 temperature is not exceeded during these stages. Austenite does not form immediately. Even if a small amount of austenite forms outside the sub-region of the first region of the component, acceptable results can be obtained.
[0044] In addition to the first region containing the sub-region, the component also has a second region. When implementing the method, during method steps a) to e), the temperature of the second region of the component at least temporarily exceeds the AC3 temperature of the component. This makes it possible to form austenite in the second region. During the press hardening operation, it transforms into martensite, so that the second region has relatively low ductility.
[0045] It does not matter 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 has been met in step a). If the second region is heated to a temperature 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 the second furnace.
[0046] Preferably, after being heated to a temperature above the AC3 temperature of the component, the temperature of the second region does not drop below the austenite restoration temperature until the end of step e). Preferably, the temperature of the second region first drops below the austenite restoration temperature in the press. This can avoid the decomposition of the austenite formed in the second region before press hardening.
[0047] In steps b) to e), the temperature of the second region preferably changes by at most 200 K, more preferably by at most 100 K. This can also be referred to as maintaining the temperature, and temperature changes within a tolerance of 200 K or 100 K respectively are acceptable. For example, in steps c1) and c2), the second region can be exposed to a temperature higher than the AC3 temperature of the component in the temperature control station, and / or in step e), the second region can be exposed to a temperature higher than the AC3 temperature of the component in the second furnace. Depending on the temperature of the second region when it enters the temperature control station or the second furnace, and the residence time of the component in the temperature control station or the second furnace, in the temperature control station, the second region can maintain its temperature or be heated, or the cooling rate of the second region can be slowed down. However, preferably, the second region can also be cooled by exposure to ambient air in the temperature control station.
[0048] In steps a) to e), the temperature of the second region may first rise above the AC3 temperature, then drop below the austenite restoration temperature, and then rise above the AC3 temperature again. In this case, after the second heating to above the AC3 temperature, until step e) is completed, as long as it is satisfied that the temperature of the second region no longer drops below the austenite restoration temperature. This is included in the following description: during method steps a) to e), the temperature of the second region of the component is at least temporarily higher than the AC3 temperature of the component, and then no longer drops below the austenite restoration temperature of the component.
[0049] Therefore, the method can obtain a ductile microstructure outside the sub-region of the first region, while obtaining a less ductile microstructure in the second region and the sub-region of the first region respectively.
[0050] Due to the heating effect of the laser unit, the sub-region can be formed particularly precisely. In particular, the contour of the sub-region may be finer and / or smaller than other methods. Preferably, this is compared with the method of skipping the sub-region during the cooling process. In this regard, the application of the method is particularly flexible.
[0051] In a preferred example of the method, in step c1), a cooling fluid is applied to the first region of the component for cooling treatment.
[0052] The cooling fluid is preferably compressed air. The cooling fluid is preferably sprayed onto the first region using a nozzle. This can achieve easy cooling of the first region in a short time. However, the disadvantage of using a nozzle is that the cooling medium cannot precisely separate the cooled part and the non-cooled part of the component. The method avoids this problem. First, in step c1), the first region including the sub-region is cooled. Then the sub-region is reheated by the laser unit. Therefore, fundamentally speaking, this is consistent with the method of not cooling the sub-region. However, for the required region contour, cooling by nozzle is difficult or impossible to achieve. In contrast, the method is more convenient.
[0053] In another preferred example of the method, the component temperature in step a) does not exceed the AC3 temperature of the component.
[0054] In this embodiment, first, the second region and a sub-region of the first region of the component are heated above the AC3 temperature in a temperature control station or a second furnace. Preferably, the component in step a) is heated to a temperature higher than the AC1 temperature of the component. In this case, the component in step a) is heated to a temperature between the AC1 temperature and the AC3 temperature of the component.
[0055] In another preferred example of the method, the entire component in step a) is heated to a temperature higher than the AC3 temperature of the component.
[0056] In another preferred example of the method, in step c2), a sub-region of the first region of the component is heated to a locally differentiated degree.
[0057] The laser unit can achieve high-precision heating of the sub-region. Its advantages are not only reflected in that a particularly precise sub-region profile can be obtained. In the embodiment of the present invention, the fact that the sub-region can be locally differentially heated is also utilized. Therefore, local differential ductility can be obtained inside the sub-region.
[0058] Local differential heating of the sub-region can be achieved by changing the power of the laser unit.
[0059] In another preferred example of the method, in step c2), a sub-region of the first region of the component is heated to a locally differentiated degree, so as to obtain a temperature gradient on the sub-region of the first region of the component.
[0060] Locally differential heating enables a temperature gradient across the entire sub-region. For example, after step c2), it is possible for the temperature of the sub-region to increase from one edge of the sub-region to the opposite edge of the sub-region. In this way, a precise transition region can be obtained between various ductilities.
[0061] Fundamentally, the regions with different ductilities are preferably separated as clearly as possible. Therefore, the transition region between adjacent regions is preferably as small as possible. In contrast, in the embodiment of the present invention, the temperature gradient can be precisely controlled. Therefore, the subsequent ductility gradient is not randomly formed. In some cases, precisely establishing the ductility gradient is very advantageous.
[0062] Another aspect of the present invention is a device for heat-treating a metal component. The device includes:
[0063] - A first continuous furnace for heating the entire component;
[0064] - A temperature control station, with a cooling device for cooling a first area of the component and a heating device with a laser unit for heating a sub-area of the first area of the component;
[0065] - A second continuous furnace for heat-treating the component;
[0066] - A first transfer device for transferring the component from the first continuous furnace to the temperature control station; and
[0067] - A second transfer device for transferring the component from the temperature control station to the second continuous furnace.
[0068] The advantages and features of the method can be applied and transferred to the equipment, and vice versa. The equipment is preferably designed to operate the method according to the present invention. The method is preferably carried out using this equipment. The first continuous furnace is used for step a), the first transfer device is used for step b), the temperature control station is used for steps c1) and c2), the second transfer device is used for step d), and the second continuous furnace is used for step e).
[0069] The equipment preferably has a control device for controlling the equipment of the method according to the present invention.
[0070] The equipment preferably also has a press for stamping and hardening the component and a third transfer device for transferring the component from the second continuous furnace to the press.
[0071] In a preferred example of the equipment, the laser unit includes a VCSEL.
[0072] "Vertical-cavity surface-emitting laser" (VCSEL) is a type of laser diode that emits light perpendicular to its surface. VCSEL can also be referred to as a surface emitter. It has been found that very good results can be obtained by using VCSEL in step c2).
[0073] The present invention will be described in more detail below with reference to the accompanying drawings. What is shown in the figures is a particularly preferred embodiment, but the present invention is not limited thereto. The numbers and relative dimensions shown in the figures are only schematic. In the accompanying drawings:
[0074] Figure 1 : Shows the equipment for heat-treating metal components according to the present invention;
[0075] Figure 2 : Shows the Figure 1 temperature curve that can be obtained by the method according to the present invention using the equipment shown; and
[0076] Figures 3a to 3c : Shows three examples of components processed by the method shown Figure 2 .
[0077] 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 in sequence along the conveying direction r of the metal component 2. The control device 6 is mainly used to control the first continuous furnace 3, the temperature control station 4, and the second continuous furnace 5.
[0078] The temperature control station 4 has a cooling device 7 for cooling the first region 10 of the component 2; and a heating device 8, which has a laser unit 9 for heating a sub-region 12 of the first region 10 of the component 2. The regions 10, 11, 12 of the component 2 are shown in Figure 3. The laser unit 9 may in particular include a VCSEL.
[0079] The device 1 also includes 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.
[0080] Figure 2 Shows the temperature curve of the component 2 Figure 1 when moving in the device 1. Figure 2 Is a schematic diagram. In the figure, the relationship between temperature T and time t is represented 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 embodiment, the entire component 2 is heated to a temperature higher than the AC3 temperature T AC3 of the component 2 in the first continuous furnace 3. As an alternative method, the method may keep the temperature of the component 2 not exceeding the AC3 temperature T AC3 of the component 2 in the first continuous furnace 3.
[0081] Then, the component 2 is transferred to the temperature control station 4. The relevant transfer time is denoted as t T1 . During the transfer, the component 2 may cool down.
[0082] The component 2 stays in the temperature control station 4 for a period of time t TS . During this period, 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 restoration temperature T AR of the component 2. The temperature of the first region 10 is denoted as T1. After cooling, the sub-region 12 of the previously cooled first region 10 of the component 2 is heated to a temperature higher than the AC3 temperature T AC3 of the component 2 by the laser unit 9. The temperature of the sub-region 12 of the first region 10 is denoted as T 1A , while the temperature of the remaining part of the first region 10 is denoted as T 1B .
[0083] The figure depicts the uniform temperature T of the sub-region 12 of the first component 10 of the component 2. 1A . However, in another method, the sub-region 12 can also be heated to a locally differentiated degree. This makes it possible to form a temperature gradient on the sub-region 12. This is not shown in the figure.
[0084] After the component 2 is heat-treated at the temperature control station 4, the component 2 is transferred to the second continuous furnace 5. The transfer time is denoted by t T2 . During this period, the component 2 also cools down, and the cooling conditions in different regions may vary.
[0085] 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 by t D2 . In the second continuous furnace 5, the first region 10 of the component 2 outside the sub-region 12 is heated so that the temperature T 1B of the first region 10 of the component 2 outside the sub-region 12 remains lower than the AC3 temperature T AC3 of the component 2 after heating.
[0086] The temperature T2 of the second region 11 of the component 2 exceeds the AC3 temperature T AC3 of the component 2 in the first continuous furnace 3 and will not drop below this temperature again until the end of the method.
[0087] Figure 3a Shows a plan view of the first embodiment of the configuration of the component 2. In this embodiment, the component 2 is the B-pillar of a motor vehicle. The first region 10 and the second region 11 are obvious. The sub-region 12 is located inside the first region 10.
[0088] Figure 3b Shows a plan view of the second embodiment of the configuration of the component 2. Different from Figure 3a , the sub-region 12 consists of two non-contiguous parts.
[0089] Figure 3c Shows a plan view of the third embodiment of the configuration of the component 2. Different from Figure 3a , the second region 11 and the sub-region 12 of the first region 10 each consist of two parts.
[0090] The shapes of the component 2 and the regions 10, 11, 12 in the figure are exemplary. Figure 2 The method in
[0091] List of reference symbols
[0092] 1 Equipment
[0093] 2 Components
[0094] 3 First Continuous Furnace
[0095] 4 Temperature Control Station
[0096] 5 Second Continuous Furnace
[0097] 6 Control Device
[0098] 7 Cooling Device
[0099] 8 Heating Device
[0100] 9 Laser Unit
[0101] 10 First Region
[0102] 11 Second Region
[0103] 12 Sub-region
[0104] 13 First Conveyor
[0105] 14 Second Conveyor
[0106] T Temperature
[0107] T AC3 AC3 Temperature of the Component
[0108] T AR Austenite Restoration Temperature of the Component
[0109] T1 Temperature of the First Region of the Component
[0110] T 1A Temperature of the Sub-region of the First Region of the Component
[0111] T 1B Temperature of the Remaining Part of the First Region of the Component
[0112] T2 Temperature of the Second Region of the Component
[0113] t Time
[0114] t D1 Residence Time in the First Continuous Furnace
[0115] t T1 Duration of Transfer from the First Continuous Furnace to the Temperature Control Station
[0116] t TS Residence Time in the Temperature Control Station
[0117] t T2 Duration of Transfer from the Temperature Control Station to the Second Continuous Furnace
[0118] tD2 Residence time in the second continuous furnace
[0119] Transport direction of the r component
Claims
1. A method for heat-treating a metal 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 temperature control station (4); c1) Cooling the first region (10) of the component (2) in the temperature control station (4), at least after cooling, the temperature of the first region (10) being lower than the austenite restoration temperature (T AR ) of the component (2); c2) In the temperature control station (4), a sub-region (12) of a first region (10) of the component (2) cooled in step c1) is heated by a laser unit (9) to a temperature higher than the AC3 temperature (T AC3 ) of the component (2); d) transferring the component (2) from the temperature control station (4) to a second continuous furnace (5); e) Heat-treating the component (2) in a second continuous furnace (5), wherein a first region (10) of the component (2) outside the sub-region (12) is heated, and even after heating, the temperature of the first region (10) of the component (2) outside the sub-region (12) remains below the AC3 temperature (T AC3 ) of the component (2). Wherein, during method steps a) to e), the temperature of the second region (11) of the component (2) is at least temporarily higher than the AC3 temperature (T AC3 ) of the component (2).
2. The method according to claim 1, wherein In step c1), the component (2) is cooled by applying a cooling fluid to a first region (10) of the component (2).
3. The method according to any one of the preceding claims, characterized in that, In step a), the temperature of component (2) does not exceed the AC3 temperature (T AC3 ) of component (2).
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, In step c2), a sub-region (12) of the first region (10) of the component (2) is heated to a locally differentiated degree.
6. The method according to any one of the preceding claims, characterized in that, In step c2), the sub-region (12) of the first region (10) of the component (2) is heated to a locally differentiated degree, thereby obtaining a temperature gradient on the sub-region (12) of the first region (10) of the component (2).
7. An apparatus (1) for heat-treating a metal component (2), comprising: - a first continuous furnace (3) for heating the entire component (2); - a temperature control station (4) equipped with a cooling device (7) for cooling a first region (10) of the component (2); and simultaneously equipped with a heating device (8) including a laser unit (9) for heating a sub-region (12) of the first region (10) of the component (2); - a second continuous furnace (5) for heat-treating the component (2); - 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).
8. The device (1) according to claim 7, characterized in that, The laser unit (9) includes a VCSEL.