EP2993241A1 - Method and press for manufacturing cured sheet metal components, in sections at least - Google Patents

Abstract

A method is proposed for producing an at least partially hardened sheet metal component (27) in a press (1) comprising a press table (5), a press ram (6) and a plurality of tool stages (2; 3), comprising the following steps: € ¢ at least partially heating a sheet metal blank (26) to a temperature greater than the austenitizing temperature Ac3, Inserting the heated metal sheet (26) into a first forming tool stage (2) of the press (1), Hot forming of the sheet metal blank (26) to the sheet metal component (27) in the forming tool stage (2), whereby the press (1) executes a closing movement (Y), € ¢ holding the forming tool stage (2) for a first holding time (t 2 ') € ¢ cooling of the formed metal sheet (26) during the first holding time (t 2 '), and € ¢ transfer of the formed sheet metal blank (26) into a second tool stage (3), Hardening of the sheet metal blank (26) by cooling in the second tool stage (3) within at least a second holding time (t 4 ') wherein the forming die stage (2) is moved during the closing movement from an upper turning point to a lower turning point of the press (1) by at least one elastic actuator (7) relative to the press (1), so that the hot working is ended and stopping starts, before the press (1) reaches the lower reversal point (UP) and / or that the locking of the forming tool stage (2) by an elastic actuator (7) only during the upward movement of the press (1) is terminated after the lower reversal point of the press ( 1) was completely passed through.

Description

The invention relates to a method and a press for producing at least partially cured sheet metal components.

In the forming technique, it is known to perform sheet metal components made of metal strip material, in particular of steel, by at least one stage forming operation in a press. For this purpose, the sheet is unwound from the tape and sheet metal blanks of certain shape geometry are cut from the tape. Subsequently, the forming takes place in a press with at least one pressing tool stage.

Especially in the automotive industry, it is customary to produce complex geometries and to adjust the mechanical design of the component in addition to the shaping at the same time. For this purpose, the thermoforming, also known as press hardening or tempering, has been widely used for many years for the production of chassis and structural components of motor vehicles.

The DE 10 2008 034 596 A1 describes a method for producing at least partially hardened sheet metal components in two successive tool stages, wherein each tool stage has an upper tool and a lower tool arranged in a press and closed by closing movement of the press upper tool and lower tool and thereby hot-formed austenitizing a sheet metal blank to the sheet metal component. By holding and contacting the sheet metal blank with the tool halves, the formed sheet metal blank is rapidly cooled. In addition, only partially hardened sheet metal components are to be produced by providing gaps between the tool halves or by using different materials with different thermal conductivity in the upper tool or lower tool.

The DE 10 2009 057 382 A1 describes a multi-tooling process and press for thermoforming sheet metal blanks heated to austenitizing temperature to produce hardened sheet metal components. After thermoforming in a cooled forming tool stage, the sheet metal component is to be hardened in a further cooled tool stage and then cold-cut. The press is to be operated at high throughput, which is why it is proposed to close the tool stages with upper tool and lower tool as early as possible and open as late as possible.

The object of the invention, starting from the aforementioned prior art, is to propose a large-scale feasible and reliable method and a press for producing hardened sheet-metal components, which has an increased production throughput and a higher resulting product quality.

The problem is solved by the features of claim 1. The dependent claims 2 to 11 represent advantageous embodiments.

The object is further objectively solved by the characterizing part of claim 12. The dependent therefrom dependent claims 13 to 18 form advantageous embodiments.

• Wenigstens abschnittsweises Erwärmen einer Blechplatine auf eine Temperatur von größer als die Austenitisierungstemperatur Ac3,
• Einlegen der erwärmten Blechplatine in eine erste Umformwerkzeugstufe der Presse,
• Warmumformen der Blechplatine zum Blechbauteil in der Umformwerkzeugstufe, wobei dabei die Presse eine Schließbewegung ausführt,
• Zuhalten der Umformwerkzeugstufe für eine erste Haltezeit,
• Abkühlen der umgeformten Blechplatine während der ersten Haltezeit, und
• Transfer der umgeformten Blechplatine in eine zweite Werkzeugstufe,
• wenigstens abschnittsweises Härten der Blechplatine durch Abkühlen in der zweiten Werkzeugstufe innerhalb wenigstens einer zweiten Haltezeit.

A method is proposed for producing an at least partially hardened sheet-metal component, which is carried out in a press comprising a press table, a press ram and a plurality of tool stages. The following steps are performed:

• Heating a sheet metal blank to a temperature greater than the austenitizing temperature Ac3 at least in sections,
• Inserting the heated sheet metal blank into a first forming stage of the press,
• Hot forming of the sheet metal blank to the sheet metal component in the Umformwerkzeugstufe, in which case the press performs a closing movement,
• Holding the forming die stage for a first holding time,
• Cooling the formed sheet metal blank during the first holding time, and
• Transfer of the formed sheet metal blank into a second tool stage,
• at least partially hardening of the sheet metal blank by cooling in the second tool stage within at least a second holding time.

The method is characterized in that the forming die stage is moved during the closing movement from an upper reversal point to a lower reversal point of the press by at least one elastic actuator relative to the press, so that the hot forming is terminated and stopping begins before the press reaches the lower reversal point achieved, and / or that the locking of the Umformwerkzeugstufe is terminated by an elastic actuator only during the upward movement of the press after the lower reversal point of the press has been completely passed through, wherein the upper tool and the lower tool have cooling channels, whereby a cooling medium is passed.

This is a highly economical manufacturing process, especially for industrial mass production achieved while improving the Process and component quality causes. Specifically, the cycle time of the hot forming and hardening of the sheet metal component can be reduced by the transformation starts and ends very early and the holding time for quenching the formed sheet metal component in the individual tool stages is maximally utilized. In addition, can be compensated by the / the elastic actuators inaccuracies in the positioning of the upper and lower tool of Umformwerkzeugstufe and discontinuities in the surface finish and thickness of the sheet metal blank.

The sheet metal blank is further processed by hot forming the sheet metal component, in the following description, both terms are also used in parallel, if it is not about the evoked by the forming properties, but the process steps, in particular the heat treatment and the press are explained in more detail.

In the context of the invention, the sheet-metal plate is brought by at least partially heating means known per se to a temperature above the austenitizing temperature of the steel alloy used. It is useful in the context of the invention, the use of heaters high heating rate, such as by contact heating with inductively or conductively heated contact masses, direct burner heating or furnace heating with furnace room overtemperature. A combination thereof or with other known furnace types is possible, for example when using metallically coated sheet metal blanks.

The austenitizing temperature Ac3 is also referred to as the recrystallization temperature, the height of the austenitizing temperature depending on the exact alloy composition. For the process according to the invention, the use of manganese boron steels has proven successful which, after heating by rapid cooling or quenching, undergoes continuous hardening by transformation of the austenitic microstructure into martensite textures. With the hardness, the mechanical properties yield strength Rp0.2 and tensile strength Rm increase, while maximum bending angle and elongation A50 decrease.

Holding time according to the invention is that period to understand in which upper tool and lower tool at least the Umformwerkzeugstufe and the second tool stage are closed, so are at least partially in intimate contact with the shaped sheet metal plate or with the sheet metal component.

The term transfer includes any handling operation that causes the transport of the sheet metal component from a tool stage to the next-consecutive tool stage, including removal from the respective tool stage and insertion into the respective tool stage.

The reversal point of the press according to the invention is defined so that the press in the power stroke exactly an open position, the upper reversal point and exactly a maximum closed position, the lower reversal point reached. Of these, depending on the type of press, a maximum open position of the press that can be achieved for maintenance or conversion operations, which under certain circumstances may be greater than the upper reversal point, can be distinguished.

Preferably, during or after completion of the hot forming in the Umformwerkzeugstufe a edge trimming and / or perforation are performed, in particular before the press is completely closed. This has the advantage that a subsequent perforation or edge trim in the cold and cured state of the sheet metal component can be omitted and thus tool wear and additional handling processes are avoided. The fact that the punching or trimming takes place before the press is fully closed, the closing movement can be used to drive the cutting means, which are necessary for punching or trimming. Subsequently, the trimmed sheet metal component for further, at least in sections, rapid cooling is transferred to the second tool stage.

The second tool stage is also preferred, at least in regions, during the closing movement of the press by at least one elastic actuator moves relative to the press, so that the locking begins before the press reaches the lower reversal point. But it is also possible that the locking of the second Tool stage is at least partially terminated by an elastic actuator only during the upward movement of the press after the lower reversal point of the press has been completely passed through. Most preferably, by at least one elastic actuator, the second tool stage mounted to the press that remain closed during a significant portion of the closing time and during a significant portion of the time the upward movement of the upper tool and lower tool. The decisive factor here is a time share of more than 30 percent each of the closing movement and / or the upward movement of the press.

Furthermore, the Umformwerkzeugstufe and preferably also the second tool stage can be spring-loaded by the elastic actuator mechanically, hydraulically or pneumatically. The elastic actuators themselves can either passively purely mechanically effective by permanently applying a counteracting force of the press force on the upper tool or lower tool. To name a few would be coil springs or spring assemblies made of other mechanical springs. But it is also possible that at least one elastic actuator is actively driven to adjust a differentiated during the press movement force control of the actuator. The latter makes it possible to differentiate between a sufficient for the hot forming force level and a required for locking higher force level, but to spare the elastic actuator to the associated actuator. As a result, the holding time as a whole for carrying out the rapid cooling and for hardening the sheet metal component can be reduced.

The transfer of the sheet metal component is carried out according to the invention preferably by a transfer system, in particular by a linear guided transfer bar with grippers, in a transfer time of 1 to 4 seconds, preferably in 2 to 3 seconds, between at least two tool stages. It is thus possible to keep the heat losses during the movement of the sheet metal component between the tool stages as low as possible and ideally to dispense with complicated multi-axis handling devices. It can be provided that the grippers of the transfer system are already brought close to the sheet metal component, before the press has reached the upper reversal point. In particular, in the Tool steps recesses for collision-free implementation of the transfer system or for bringing the grippers are provided close to the sheet metal component, so that the sheet metal component immediately with the separation of upper tool and lower tool, ie after the end of the holding time, removed by the transfer system or by the gripper of Umformwerkzeugstufe and is moved on.

Furthermore, with the method according to the invention in a particularly simple and reliable manner only a partially cured sheet metal component can be produced. Sectionally means in the context of the invention that the sheet metal part at least a first section with relatively low strength and plug boundary with a structure which is preferably uncured or hardened only slightly, and at least a second section with high strength Rm and yield strength Rp0.2 but reduced Elongation A50 and has essentially a martensitic structure. This means that the first section of the sheet metal component has a tensile strength between 400 and 800 megapascals (MPa), in particular between 450 and 650 MPa, and predominantly ferrite-pearlitic constituents.

Preferably, in the Umformwerkzeugstufe a cooling temperature of the sheet metal component is set, which is in a first portion of the sheet metal plate is greater than the Martensitgefügelung required martensite Ms and in a second section is smaller than Ms, the sheet metal blank in the first section in particular to a cooling temperature of 540th is cooled to 660 ° C. In addition to the cooling temperature, it is important in the second sections to also maintain a high cooling rate above 25 Kelvin per second (K / s), in particular above 70 K / s, in order to ensure sufficient through-hardening of the microstructure in this section. The cooling of the first section of the sheet metal plate to a lesser extent and to a higher temperature compared to the cooling in the second section is achieved that a structural transformation is suppressed in the sheet metal from the austenitic state in martensite, but at the same time a structural transformation of austenite to ferrite and / or perlite begins.

In order to obtain a particularly expansible and reliably crack-free deformable, in particular deformable component in the first section, a cooling temperature of the sheet metal component can be set in the second tool stage, which is between 350 to 500 ° C at the end of the second holding time in the first section and in the second section is smaller than the martensite finish temperature Mf required for complete martensite structure transformation, wherein the sheet metal part in the second section is preferably cooled to less than 200 ° C., in particular to room temperature. This ensures that the steel structure in the first section has sufficient time at a temperature significantly higher than the first section in order to carry out the microstructure transformation to ferrite and / or perlite without bainite or even martensite being produced to any significant extent. In contrast, to be achieved by the temperature of the second section, that a completely martensitic structure is formed, whereby a tensile strength between 1400 and 2100 MPa, preferably 1450 and 1800 MPa, depending on the steel alloy, in particular depending on Kohlestoff- and manganese content adjusted.

Furthermore, it can be provided that the sheet metal component is held for a first holding time between 2 and 8 seconds and for a second holding time between 2 and 10 seconds. Thus, with an unchanged cycle time of the press, there is almost a doubling of the available time duration for the cooling of the shaped sheet metal blank and for the structural transformations associated therewith. The difference between the two holding times is mainly due to the required time for hot forming in the Umformwerkzeugstufe.

The cycle time of the press with a forming tool stage and a subsequent second tool stage between its upper reversal point and its lower reversal point is preferably between 3 and 11 seconds. This makes it possible to achieve an extremely high output quantity or a high throughput and thus very low production costs. In combination with the production of partially hardened sheet metal components, there is also the advantage that the component properties and quality do not suffer from the high production cycle. It should be stressed that the sheet metal components produced have a high dimensional stability, in contrast to a single-stage thermoforming and press hardening process for the production of sectional press-hardened sheet metal components with heated tool areas.

A further aspect of the invention provides that the hardening is terminated only in a third tool stage, after which the sheet metal component completely has a cooling temperature below 200 ° C. This has the advantage that the cycle time of the press can be reduced again and at the end of the press a cool and non-critical sheet metal component can be removed. A residual heat distortion is completely excluded in particular by the approximation of the cooling temperatures of the two sections of the sheet metal component.

Preferably, the cycle time of the press with a Umformwerkzeugstufe and a second tool stage and a third tool stage, and thus in a three-stage temporal successive process, between its upper reversal point and its lower reversal point between 3 and 9 seconds. In order to achieve this low cycle time of the press, it is preferable to use a mechanical crank or eccentric press or a servo-electric press, wherein in the case of the mechanical press the reversal points are passed through without substantial interruption of the press movement. A holding time by press standstill can be advantageously eliminated.

Another aspect of the invention relates to a press for producing at least partially cured sheet metal component. The press has several tool stages, a press ram and a press table, and can be used in particular for carrying out the method described above. According to the invention, it is provided that at least one tool stage is an at least partially coolable forming tool stage for the hot forming of sheet metal blanks, which comprises an upper tool and a lower tool, which form a mold cavity in a closed state.

The press is characterized in that at least one elastic actuator is arranged between press table and lower tool, so that either the lower tool can be raised relative to the press table, and / or the upper tool can be pressurized at a distance relative to the press ram, to produce the closed state of the Umformwerkzeugstufe before the press is fully closed, wherein the upper tool and the lower tool have cooling channels, whereby a cooling medium is conductive.

In other words, it is possible that the lower tool and / or the upper tool of the press table or press ram is spaced at least until the lower reversal point of the press is reached. The distance is adjustable by the elastic actuator and decreases during the hot forming and preferably during a time portion of the holding time in the closed state of the upper tool and lower tool. To compensate for the position of the upper tool and lower tool with each other and any discontinuities of the thickness of the sheet metal plate is a one-sided elastic actuator is sufficient. It is also conceivable, on both sides, therefore between the upper tool and press ram and between the lower tool and press table to provide appropriate actuators. If at the same time or after hot forming a trimming or punching takes place in the Umformwerkzeugstufe, it is also conceivable to provide a storable on an elastic actuator cutting means.

Preferably, a vertical travel is adjustable by the elastic actuator, wherein the travel is less than the maximum Pressenhubweg between the upper and lower reversal points of the press, but at least 100 mm. In combination with the predetermined by the press drive speed during the closing movement and during the upward movement of the press, it is thus advantageously possible to extend the holding time by contact between the sheet metal blank, upper tool and lower tool.

Further preferably, the elastic actuator has a force that increases at least over a part of a travel from the upper reversal point to the lower reversal point of the press, in particular the restoring force is at least 20 percent greater in the closed state of Umformwerkzeugstufe, whereby the contact and contact pressure between the tool stage and the sheet metal component increases and thus a high heat transfer or the fast Achieving at least a desired quenching temperature of the sheet metal component is possible.

In order to produce only partially hardened component, it is furthermore preferably provided that at least the Umformwerkzeugstufe is partially heated by a heat source to effect in a first section a reduced cooling rate in the sheet metal component, wherein unheated areas have cooling channels for carrying a cooling medium. Specifically, this is in the unheated area of the tool stage, a temperature near room temperature, in any case, but below 200 ° C adjustable. Due to the heat source, a temperature between 650 and 450 ° C can be set in the heated area. Thus, the upper tool and the lower tool are provided for cooling the shaped sheet metal component during the holding time with different cooling rate and thereby to different quenching temperature or to keep at these temperatures. As already described above, a first section with a lower tensile strength and at least a second section with high strength are thus adjustable in the sheet-metal component.

Alternatively or preferably in addition, it is also possible that both the Umformwerkzeugstufe and at least the subsequent second tool stage regions, in particular by a heating source, is heated to at least not completely hardened sheet metal component in a first section. This results in the same features and advantages as above in the method for producing only partially hardened sheet metal components for the second tool stage has already been performed.

Furthermore, the unheated region of the second tool stage may have an active cooling source at least corresponding to a transition section between the first section and the second section of the sheet metal component. The cooling source serves to reduce a heat transfer between the unterschlich tempered sections of the sheet metal blank to ensure the narrowest possible transition section. This has the advantage that designers have to consider only a small area in the design of sheet metal parts, especially for the automotive industry, which no mechanical parameters directly assigned or for which no mechanical characteristics can be guaranteed. It is also ensured that the second area has a homogeneous distribution of the structure and the mechanical properties throughout. The cooling source can be formed by the cooling medium itself, and / or comprise a heat exchanger arranged outside the press, which is in operative connection with the cooling medium and the cooling channels of at least the Umformwerkzeugstufe.

Finally, it is the first portion and the transition portion of the sheet metal component at least in the second tool stage form-fitting fixable by fixing. In the case of a three-stage press with Umformwerkzeugstufe, second tool stage and third tool stage, the sheet metal component is preferably also in the third tool stage form-fitting fixable by fixing. This results in a uniformity of the pressing force in all tool stages for the press according to the invention and in particular prevents the press table and press ram are aligned unevenly to each other.

Other objects, advantages, features and applications of the present invention will become apparent from the following description of several embodiments with reference to the drawings. All described and / or illustrated features alone or in any meaningful combination form the subject matter of the present invention, also independent of their summary in the claims or their dependency.

Figur 1

eine erste Ausführungsvariante der erfindungsgemäßen Presse im Querschnitt,

Figur 2a und 2b

eine zweite Ausführungsvariante einer Umformwerkzeugstufe der erfindungsgemäßen Presse im Querschnitt und Längsschnitt,

Figur 3

eine dritte Ausführungsvariante einer erfindungsgemäßen Presse im Längsschnitt,

Figur 4a und 4b

ein Ablaufschema für erfindungsgemäßes Verfahren anhand eines Längsschnitts durch die Umformwerkzeugstufe zu verschiedenen Zeitpunkten des Pressentaktes,

Figur 5

eine Ausführungsvariante einer Umformwerkzeugstufe einer erfindungsgemäßen Presse zur Herstellung abschnittsweise gehärteter Blechbauteile,

Figur 6

eine alternative Ausführungsvariante einer Umformwerkzeugstufe einer erfindungsgemäßen Presse zur Herstellung abschnittsweise gehärteter Blechbauteile im Längsschnitt,

Figur 7a und 7b

eine alternative Ausführungsvariante einer erfindungsgemäßen Presse zur Herstellung abschnittsweise gehärteter Blechbauteile 7a) im Längsschnitt und 7b) im Horizontalschnitt,

Figur 8a und 8b

eine alternative Ausführungsvariante einer erfindungsgemäßen Presse zur Herstellung abschnittsweise gehärteter Blechbauteile 8a) im Längsschnitt und 8b) im Horizontalschnitt,

Figur 9a

einen Zeit-Temperatur-Verlauf der Blechplatine für das erfindungsgemäße Verfahren in einer zweistufigen Presse und separater Kühlstufe und

Figur 9b

einen Zeit-Temperatur-Verlauf der Blechplatine für das erfindungsgemäße Verfahren in einer dreistufigen Presse.

Showing:

FIG. 1

a first embodiment of the press according to the invention in cross section,

FIGS. 2a and 2b

a second embodiment of a Umformwerkzeugstufe the press according to the invention in cross-section and longitudinal section,

FIG. 3

a third embodiment of a press according to the invention in longitudinal section,

FIGS. 4a and 4b

a flow chart for inventive method with reference to a longitudinal section through the Umformwerkzeugstufe at different times of the press cycle,

FIG. 5

a variant of a Umformwerkzeugstufe a press according to the invention for producing partially cured sheet metal components,

FIG. 6

an alternative embodiment of a Umformwerkzeugstufe a press according to the invention for producing partially hardened sheet metal parts in longitudinal section,

FIGS. 7a and 7b

an alternative embodiment of a press according to the invention for producing partially hardened sheet-metal components 7a) in longitudinal section and 7b) in horizontal section,

FIGS. 8a and 8b

an alternative embodiment of a press according to the invention for the production of partially hardened sheet metal components 8a) in longitudinal section and 8b) in horizontal section,

FIG. 9a

a time-temperature profile of the sheet metal blank for the inventive method in a two-stage press and separate cooling stage and

FIG. 9b

a time-temperature profile of the sheet metal blank for the inventive method in a three-stage press.

FIG. 1 1 shows a longitudinal section of a press 1 according to the invention with two tool stages, the forming tool stage 2 and a second tool stage 3. An initially unshaped sheet metal blank 26 first passes through the forming tool stage 2 and then the second tool stage 3 for forming into a sheet metal component 27. The press 1 has a press ram 6 and a press table 5, wherein arranged on the press table 5 two clamping plates 10 are. Each clamping plate 10 further comprises a plurality of elastic actuators 7, which extend from the clamping plate 10 in the direction of press ram 6, wherein on the press table 5 opposite ends of the press ram 6, a tool clamping plate 9 is fixed. The clamping plates 10 are each fixed via clamping elements 31 on the press table 5. In addition, the tool clamping plates 9 are fixed to the press table 5 facing away from the ends of the actuators 7.

At the tool clamping plates 9, a lower tool 12 is fixed via clamping elements 31 ', which comprises the forming tool stage 2 and the second tool stage 3. Corresponding to the lower tool 12, an upper tool 11 is fixed to the press ram 6, wherein a sheet metal blank 26 can be arranged between the upper tool 11 and the lower tool 12. Both upper tool 11 and lower tool 12 have cooling channels 17, whereby a cooling medium 18 can be conducted. Furthermore, the lower tool 12 on guide elements 32 ', which are designed to be insertable in a corresponding guide recess 32. The guide elements 32 'and guide recesses 32 are formed corresponding to each other and allow the guide of the upper tool 12 and the lower tool 11 to each other. As a result of the floating of the elastic actuators 7 storage of the lower tools 12 32 possibly occurring position deviations from the upper tools 11 are compensated transversely to the press movement by means of the guide elements 21 and guide recesses. The elastic actuators 7 are in FIG. 1 designed as pneumatic spring assemblies, ie it is acted upon by gas pressure actuators 7, which are actively controlled. Shown here is the state of the press in the upper reversal point OP, it being noted that the elastic actuators 7 raise the lower tool 12 relative to the press table 5, whereby the path of the closing movement Y of the Umformwerkzeugstufe 2 and the second tool stage 3 is shorter than the Pressenhubweg between upper reversal point OP and lower reversal point UP of the press 1.

FIG. 2a shows a further embodiment of the press 1 according to the invention, wherein the press 1 two tool stages, but here shown in longitudinal section only the double falling forming tool stage 2, has. Behind the Forming tool stage 2 is not shown, the second likewise falling falling tool stage 3, which receive the already hot-formed in the forming stage 2 sheet metal blanks 26 and continue to cool. The term double falling means that in the tool stage, two components can be thermoformed and cooled simultaneously in a press cycle. In contrast to the variant of the FIG. 1 Are also designed as an elastic actuator 7 mechanical spring assemblies 8, here as a plurality of coil springs.

Furthermore, the press 1 in the second embodiment, additional cutting means 33 on the upper tool 11 and cutting means 33 on the lower tool 12, which serve to trim the deformed sheet metal plate or the sheet metal component 27 in the still warm and uncured state. In particular, an edge trimming is carried out here, whereby, as an example, the upper cutting means 33 'are fixed via elastic actuators 34 on the upper tool 11. The elastic actuators 34, like the actuators 7, may be active or passive. The lower cutting means 33, however, are firmly and immovably connected to the lower tool 12. However, a reverse connection of the cutting means 33, 33 'to the forming tool stage 2 is also possible. On the left in the image plane, it is shown by way of example that the cutting means 33 are firmly but interchangeably connected to the upper tool 11 and the lower tool 12. Of course, in practice, the same type of connection can be made for both the right and the left halves of the forming tool stage 2.

FIG. 2b shows a cross-sectional view of the second embodiment of the press 1 by the Umformwerkzeugstufe 2, which in turn here on the mechanical spring assembly 8 is arranged movable relative to the press table 5. It can be seen here that the cooling channels 17 extend over the entire longitudinal extent of the upper tool 11 and the lower tool 12, wherein (not shown here) an inlet and outlet of the cooling channels 17 to a cooling source 19, for example in the form of a heat exchanger outside the Forming tool stage 2, preferably also outside the press 1, is located.

The FIG. 3 shows in a longitudinal section an alternative embodiment of the press 1 according to the invention with a Umformwerkzeugstufe 2 and a temporally in the process subsequent second tool stage 3. It can be seen that on a common press table 5 via a clamping plate 10 elastic actuators 7 are arranged in the form of mechanical spring assemblies 8 , The remote from the press table 5 ends of the elastic actuators 7 are coupled to a tool clamping plate 9, which in turn connected to the lower tool 12 or is an integral part of the lower tool 12. As in the previous embodiments, both upper tool 11 and lower tool 12 have cooling channels 17 for the passage of a cooling medium 18.

FIG. 4a shows in the center of the image on the left is the press in the upper reversing point OP, right at the time when the Umformwerkzeugstufe 2 just the sheet metal blank 26 completely in the mold cavity 13 between the upper tool 11 and the lower tool 12 and the hot forming takes place. The lower tool 12 is still fully raised by the elastic actuators 7 at this time. The closing movement Y of the press 1 is continued continuously. The travel W7 is the proportion of the Pressenhubweg, starting from the upper reversal point UP of the press, the upper tool 11 and the lower tool 12 are moved towards each other until the Umformwerkzeugstufe 2 is completely closed to form a mold cavity 13.

In FIG. 4b is again shown on the left the time in which the press 1 is in the upper reversal point OP, but the press 1 is now shown on the right at the time in which just the lower reversal point UP is passed through or adjustable by the actuators 7 distance A between the lower tool 12 and press table 5 is minimal. The press stroke W1 is the distance traveled by the press 1 from its upper reversing point OP to its lower reversing point UP.

FIG. 5 shows a variant of a Umformwerkzeugstufe 2 of the press 1 according to the invention for producing partially cured Sheet metal components 27. The forming tool stage 2 comprises an upper tool 11 and a lower tool 12, which each have an unheated area 22 and a heated area 21. Through the unheated region 22 extending cooling channels 17 for the passage of a cooling medium 18, wherein the cooling channels 17 are connected such that the cooling medium 18 can be supplied from the Umformwerkzeugstufe 2 to the outside in a cooling source, not shown, for example, a heat exchanger. The heated areas 21 are formed in this embodiment as mold inserts 15 and connected to the unheated areas 22 fixed but interchangeable. As a heat source 14 are used here by gas burners or electrical resistance heated heating cartridges. The forming tool stage 2 can be coupled via the clamping plate 10 on the press ram 6 and additionally via the tool clamping plate 9 and elastic actuators 7 on the press table 5 or on the clamping plate 10 fixed thereto.

In contrast to the aforementioned embodiment in FIG. 5 are in FIG. 6 a segmented upper tool 11 and lower tool 12 formed for producing partially hardened sheet metal components. A heated area 21 is arranged as a separate mold segment 16 separated by an insulation 20 from the unheated area 22 in the upper tool 11 and in the lower tool 12. This serves the more energy-efficient utilization of the heat sources 14 and cooling sources. After the tool closing time t ₂ and the first holding time t _{2 '} in the forming tool stage 2, a temperature profile with a relatively high temperature first section and a lower temperature second section is established in the sheet metal component. The microstructure transformation in martensite in the second section as well as in ferrite and / or perlite in the first section is thereby prepared. Between the first and second section there is a narrow transition section 30 with later relatively indefinite mechanical properties.

Of course, it is possible to provide more than one heated area 21 in the forming tool stage 2, as well as in the second tool stage 3.

Finally, in the FIGS. 7a and 7b a further embodiment of the entire press 1 for producing partially hardened sheet metal components 27th shown. First, in Figure 7a a longitudinal section through the press 1 shown. It comprises the forming tool stage 2 according to FIG. 6 and a second, partially heated tool stage 3 with fixing elements 24 for particular positive reception of the sheet metal component (not shown) and heated by heat sources 14 areas 21 in the form of another mold segment 16. The mold segment 16 may be formed identical in the Umformwerkzeugstufe 2, or at least be designed stronger or more robust than in the second tool stage 3 with respect to the material, the material quality, the heat capacity or the temperature resistance.

Furthermore, dashed lines indicate a transfer bar 25 and in the forming tool stage 2 gripper recesses 25 'which serve, when the sheet metal component 27 is removed, to approach grippers (not shown), which are connected to the transfer bar 25, as early as possible to the sheet metal component, without colliding with the lower tool 12 during the upward movement Z.

The second tool stage 3 is followed in terms of time, a further tool stage 4, which primarily serves the further cooling of the sheet metal component. Like the unheated region 23 of the second tool stage 3, it has fixing elements 24, as a result of which the sheet metal component can be fixed in a positionally accurate manner for further cooling. The cooling itself can by not shown cooling sources, for example by air ventilation, air or cooling medium shower or by immersion according to German patent DE 10 2005 028 010 B3 take place by a part of the third tool stage 4 with the sheet metal component 27 is immersed in the cooling medium.

As FIG. 7b illustrates, in this embodiment, each tool stage formed doppelfallend and has two tools respectively in the Umformwerkzeugstufe 2, the second tool stage 3 and the third tool stage 4. Not shown is the transfer bar for transporting the metal sheet or the sheet metal component in the tool stages 2, 3, 4 in or out of these. A heating device 35 is indicated, in which the sheet metal plates 26 are heated at least in sections to Ac3 temperature.

In the FIGS. 8a and 8b an alternative embodiment of the entire press 1 for producing partially hardened sheet metal components 27 is shown in FIG FIG. 8a as a longitudinal section and in FIG. 8b as a horizontal section through the lower tools 12. In contrast to FIG. 7 Here, the third tool stage 4 'is arranged separately in another press 36, which has the advantage that the final cooling of the high press cycle can be decoupled and in the press 1 more space for the Umformwerkzeugstufe 2 and second tool stage 3 remains. By way of example, a triple-falling forming tool stage 2 and a triple-falling second tooling stage 3 and a heating device 35 in front of the press 1 are shown here.

One of the sheet-metal components 27 produced is shown in the third tool stage 4 ', wherein the first section 28 and the second section 29 as well as the transition section 30 can be seen with different mechanical properties and different microstructure adapted to the component insert described above. Of course, can the sheet metal component 27 as shown here in the embodiment according to FIG. 7 make like that.

Finally, the shows FIGS. 9a and 9b The time-temperature profiles of the sheet metal blank 26 or sheet metal components 27 assigned during the execution of the method according to the invention are assigned to the last two variants.

Starting from a sheet metal plate 26 heated at least in regions to austenitizing temperature Ac3, a transfer takes place within 2 seconds from the heating device 35 into the forming tool stage 2 of the press 1. Then the closing movement of the press and the tool begins until the forming tool stage 2 is completely closed and the sheet metal blank 26 to the sheet metal component 27 is hot worked. Then, the first holding time t _{2 '} begins to cool the sheet metal component while the press 1 performs the lower reversing point UP and starts the upward movement. During the upward movement, the forming tool stage 2 is opened with a delay, wherein the sheet metal component 27 has cooled to different cooling temperatures T _1.1 and T _1.2 due to the different temperatures and / or tool material properties. This is followed by another transfer within the transfer time t ₃ from the forming tool stage 2 to the second Tool stage 3. Thereafter, the sheet metal component 27 is further cooled, while the second tool stage 3 is closed and the component 27 is held fixed in position. The temperature difference between the cooling temperature T _2.1 and T _2.2 in the sections 28, 29 of the sheet metal component 27 is again by different cooling rates through the heated and unheated areas 21, 23 of the second tool stage 3 (FIGS. FIG. 8b ).

Subsequently, the transfer follows within the transfer time t _{5 of} the sheet metal component 27 in the third tool stage 4, 4 ', which here is now the FIGS. 9a and 9b differ. FIG. 9a corresponds to the embodiment of the press according to FIG. 8 and FIG. 9b with the embodiment according to the FIGS. 7a and 7b , It can be seen that the cooling at the cooling time t ₆ in FIG. 9a lasts longer than in FIG. 9b because the last process is time-bound with the press 1. The cooling temperature T _3.1 and T _3.2 has closely approximated and is below 200 ° C in both sections.

Reference number :

1 -

Press

2 -

Umformwerkzeugstufe

3 -

Second tool level

4, 4 '-

Further tool level

5 -

press table

6 -

press ram

7 -

actuator

8th -

Mechanical spring package

9 -

Tool clamping plate

10 -

10Spannplatte

11 -

upper tool

12 -

lower tool

13 -

mold cavity

14 -

heating source

15 -

mold insert

16 -

mold segment

17 -

cooling channel

18 -

cooling medium

19 -

cooling source

20 -

insulation

21 -

Heated area

22 -

Unheated area to 2

23 -

Unheated area to 3

24 -

fixing

25 -

transfer bars

25 '-

Greiferausnehmung

26 -

sheet metal blank

27 -

sheet metal component

28 -

First section to 27

29 -

Second section to 27

30 -

Transitional section to 27

31 -

clamping element

32 -

guide recess

32 '-

guide element

33.33 '-

cutting means

34 -

actuator

35 -

heater

36 -

Press

D -

Thickness to 27

A -

Pressenhubweg

W7 -

Travel Range

t ₁ -

transfer time

t ₂ -

Mold closing time

t _{2 '} -

first holding time

t ₃ -

transfer time

t ₄ -

Mold closing time

t _{4 '} -

second holding time

t ₅ -

transfer time

t ₆ -

cooling

A -

distance

Ac3 -

austenitizing

M _s -

martensite

M _f -

martensite

OP -

Upper reversal point

UP -

Lower reversal point

RT -

room temperature

T _1.1 -

Cooldown

T _1.2 -

Cooldown

T _2.1 -

Cooldown

T _2.2 -

Cooldown

T _3.1 -

Cooldown

T _3.2 -

Cooldown

Y -

closing movement

Z-

upward movement

Claims (18)

Method for producing an at least partially hardened sheet metal component (27) in a press (1) comprising a press table (5), a press ram (6) and a plurality of tool stages (2; 3; 4), comprising the following steps: at least partially heating a sheet metal blank (26) to a temperature greater than the austenitizing temperature Ac3, Inserting the heated sheet metal blank (26) into a first forming tool stage (2) of the press (1), Hot forming of the sheet metal blank (26) to the sheet metal component (27) in the Umformwerkzeugstufe (2), wherein the press (1) performs a closing movement, Holding the forming tool stage (2) for a first holding time (t _{2 '} ), - cooling the formed sheet metal blank (26) during the first holding time (t _{2 '} ), and Transfer of the formed sheet metal blank (26, 27) into a second tool stage (3), Hardening of the sheet metal blank (26) by cooling in the second tool stage (3) at least in sections within at least a second holding time (t _{4 '} ), characterized in that the Umformwerkzeugstufe (2) during the closing movement of an upper reversal point (OP) to a lower reversal point (UP) of the press (1) by at least one elastic actuator (7) relative to the press (1) is moved so that hot forming is terminated and stopping begins before the press (1) reaches the lower reversal point (UP) and / or that the locking of the forming tool stage (2) by an elastic actuator (7) takes place only during the Upward movement of the press (1) is terminated after the lower reversal point (UP) of the press (1) has been completely passed through, wherein the upper tool (11) and the lower tool (12) cooling channels (17), whereby a cooling medium 18 is passed. A method according to claim 1, characterized in that in the Umformwerkzeugstufe (2) an edge trimming and / or perforation is performed, in particular before the press (1) is completely closed. A method according to claim 1 or 2, characterized in that the second tool stage (3) at least partially during the closing movement of the press (1) by at least one elastic actuator (7) is moved relative to the press (1), so that the holding begins, before the press (1) reaches the lower reversal point (UP) and / or that the locking of the second tool stage (3) is terminated at least in sections by an elastic actuator (7) only during the upward movement of the press (1) after the lower reversal point (UP) the press (1) was completely passed through. Method according to one of the preceding claims, characterized in that the Umformwerkzeugstufe (2) and preferably also the second tool stage (3) by the elastic actuator (7) is mechanically, hydraulically or pneumatically spring-loaded. A method according to at least one of the preceding claims, characterized in that the sheet metal component (27) via a transfer system, in particular a linearly guided transfer bars (25) with grippers, in a transfer time (t _3, t ₅₎ of from 1 to 4 seconds, preferably in 2 to 3 seconds, between at least two tool stages (2, 3, 4) is conveyed. Method for producing a partially hardened sheet metal component (27) according to one of the preceding claims, characterized in that a cooling temperature (T _1.1 , T _1.2 ) of the sheet metal component (27) is set in the forming tool stage (2), which in a first section (28 ) is larger martensite start temperature Ms required for the martensite texture transformation, and Ms in a second section (29), wherein the sheet metal blank (27) in the first section (28) is cooled in particular to a cooling temperature (T _2.1 ) of 540 to 660 ° C , A method according to claim 6, characterized in that in the second tool stage (3) a cooling temperature (T ₂ ) of the sheet metal component (27) is set at the end of the second holding time (t _{4 '} ) in the first section (28) between 350 is lower than the martensite finish temperature Mf required for complete martensite microstructure, wherein the sheet metal component (27) in the second section (29) is preferably cooled to less than 200 ° C., in particular to room temperature (RT) becomes. Method according to at least one of the preceding claims, characterized in that the sheet metal component (27) is held for a first holding time (t _{2 '} ), between 2 and 8 seconds and for a second holding time (t _4' ) between 2 and 10 seconds. Method according to at least one of the preceding claims, characterized in that the cycle time of the press (1) with a Umformwerkzeugstufe (2) and a second tool stage (3) between its upper reversal point (OP) and its lower reversal point (UP) between 3 and 11 Seconds. Method according to one of claims 1 to 8, characterized in that the curing is terminated only in a third tool stage, wherein thereafter the sheet metal component completely a cooling temperature (T _3.1 , T _3.1 ) below 200 ° C. A method according to claim 10, characterized in that the cycle time of the press (1) with a Umformwerkzeugstufe (2) and a second tool stage (3) and a third tool stage (4) between its upper reversal point (OP) and its lower reversal point (UP) between 3 and 9 seconds. Press (1) for producing an at least partially hardened sheet-metal component (27) with a plurality of tool stages (2; 3; 4), a press ram (6) and a press table (5), in particular for carrying out the method according to one of claims 1 to 11, wherein at least one tool stage (2, 3, 4) is an at least partially coolable Umformwerkzeugstufe (2) for hot forming of sheet metal blanks (26) comprising an upper tool (11) and a lower tool (12), which in a closed state, a mold cavity ( 13), characterized in that between the press table (5) and lower tool (12) at least one elastic actuator (7) is arranged, so that either the lower tool (12) relative to the press table (5) can be raised, and / or the upper tool (11) is pressurizable at a distance (A) relative to the press ram (6) to establish the closed state of the forming die stage (2) before the press (1) is fully closed is, wherein the upper tool (11) and the lower tool (12) cooling channels (17), whereby a cooling medium (18) is conductive. Press (1) according to claim 12, characterized in that by the elastic actuator (7) a vertical travel (W7) is adjustable, wherein the travel (W7) less than the maximum Pressenhubweg (W1) between the upper and lower reversal points (OP , UP) of the press (1), but at least 100mm. Press (1) according to claim 12 or 13, characterized in that the elastic actuator (7) has a force which at least over part of a travel (W7) from the upper reversal point (OP) to the lower reversal point (UP) of the press (1 ), in particular the actuating force in the closed state of the forming tool stage (2) is at least 20 percent greater. Press (1) for producing a partially hardened sheet metal component (27) according to one of claims 12 to 14, characterized in that at least the Umformwerkzeugstufe (2) in regions by a heat source (14) is heated to a reduced in a first section (28) Cooling speed in the sheet metal component (27) to cause, wherein unheated regions (22) cooling channels (17) for carrying a cooling medium (18). Press (1) according to one of claims 12 to 15, characterized in that both the forming tool stage (2) and at least the subsequent second tool stage (3) can be heated in regions, in particular by a heating source (14), in a first section (28) at least not obtain a completely hardened sheet metal component (27). Press (1) according to claim 16, characterized in that the unheated region (22) of the second tool stage (3) at least corresponding to a transition portion (30) between the first portion (28) and the second portion (29) of the sheet metal component (27) active cooling source (19). Press (1) according to claim 17, characterized in that the first portion (28) and the transition portion (30) of the sheet metal component (27) at least in the second tool stage (3) is positively fixable by fixing elements (24).

Images