EP2931453A1

EP2931453A1 - Hot forming device

Info

Publication number: EP2931453A1
Application number: EP13811422.8A
Authority: EP
Inventors: Manfred Beck; Michael Braun; Ralf Hund
Original assignee: Braun Manuela
Current assignee: Braun Manuela
Priority date: 2012-12-14
Filing date: 2013-12-13
Publication date: 2015-10-21
Anticipated expiration: 2033-12-13
Also published as: EP2931453B1; WO2014091014A1; DE102012112334A1

Abstract

The invention relates to a hot forming device (1) for hot forming and/or hot stamping workpieces (4), preferably consisting of steel sheets, said workpieces (4) having one tempered workpiece section and one ductile workpiece section following the hot stamping. The hot forming device (1) comprises a first forming station (2) with a first tool (3) and a second forming station (2') arranged behind said first forming station (2) and comprising a second tool (3') which is designed to have the shaped contour of the first tool (3). At least the first tool (3) comprises a first tool section (33) which is provided to form the tempered workpiece section, and a second tool section (34) which is provided to form the ductile workpiece section. The tools (3, 3') comprise temperature control devices (10) for adjusting the temperatures.

Description

Warmumformvorrichtung

The invention relates to hot forming apparatus for hot working and / or press hardening workpieces according to the subject matter of claim 1 and a method for hot working and / or press hardening after

The subject matter of claim 9.

Hot-forming devices for hot-forming or / and press-hardening of workpieces are known and described, for example, in DE 10 2007 047 314 A1. In a processing device for the production of

Sheet metal components from sheet metal blanks, which includes stations upstream and downstream of the hot forming device, the cycle time of the individual stations should be about the same to avoid dead times and thus to achieve optimum workpiece throughput. Hot forming devices in which workpieces are to be formed which, in addition to press-hardened regions, should also have ductile regions, require a significantly higher cycle time than the other stations if the workpiece in the tool cools down to such an extent that it no longer becomes distorted after removal from the mold suffers, thus forming a "bottleneck" in the technological process.

It is also possible to reduce the cycle time by the workpieces are already removed from the tool as soon as the press hardening

is completed. The disadvantage is that when cooling down further

Ambient temperature outside the tool may occur a delay of the workpiece because it is no longer fixed in the tool. This results in costly rework.

The object of the present invention is to specify an apparatus and a method for hot working or / and press hardening of workpieces which does not have the mentioned disadvantages.

According to the invention, this object is achieved with the subject matter of claim 1. A hot-forming device for hot-forming and / or press-hardening workpieces, preferably made of sheet steel, which after press hardening has a hardened workpiece section and a ductile workpiece section, is provided, wherein

in that the hot-forming device comprises a first forming station with a first tool and a second forming station arranged behind the first forming station with a second tool, wherein the second

The tool is formed with the shape contour of the first tool that at least the first tool, a first tool portion, which is provided for forming the hardened workpiece portion, and a second tool portion, which is for forming the ductile

Workpiece section is provided, and,

that the tools temperature control equipment for adjusting the

Include temperatures. In preferred embodiments, it may be provided that the second tool also has a first tool section, which is provided for forming the hardened workpiece section, and a second tool section

Tool section, which is used to form the ductile

Workpiece section is provided.

Particularly preferred embodiments of the hot forming device may have the advantage that the total cycle time required to two in the

Essentially identical tools is split, so a higher one

Workpiece throughput can be achieved with respect to a forming station with only one tool. Ideally, the workpiece throughput is doubled.

Another advantage is that due to the planned cooling in the tool no delay can occur. The delay can occur when cooled outside the tool, especially for workpieces that are made of different materials, for example, with different coefficients of expansion, or have areas of different material thickness. Rework may be required to ensure high dimensional accuracy

Achieve workpiece. In the treated in the proposed device workpiece no distortion occurs.

The first and second tool sections need not be contiguous. It can be provided, for example, that a first tool section is arranged between two second tool sections or vice versa. For example, so-called crumple zones, which can absorb impact energy, can be formed by second tool sections with ductile formation in workpieces intended for installation in motor vehicles. It can be provided that the setpoint temperature of the first tool in the first tool section about 20 ° C and in the second

Tool section 300 to 400 ° C. Under the temperature indication "approx. 20 ° C "here is understood that it is the ambient temperature of the tool.

It may further be provided that the first and the second

Tool section of the first tool are integrally formed. In this case, the two workpiece sections are only by

different setpoint temperatures are delimited from each other.

In an alternative embodiment it can be provided that the first and the second tool section of the first tool are separated by an expansion joint. By means of the expansion joint stresses in the tool can be avoided, which can occur due to differential thermal expansion in the two tool sections.

It can also be provided that between the first and the second tool portion of the first tool, a compensation element is arranged, which by expansion joints of the first and the second

Tool section is separated.

In a further advantageous embodiment, it can be provided that the second tool has a first tool section, which is provided for forming the hardened workpiece section, and a second tool section

Tool section for forming the ductile workpiece section is provided has. The two tool sections can be delimited analogously to the two tool sections of the first tool.

It may be provided that the inclination of the second tool in the first tool section about 20 ° C and in the second

Tool section 20 to 200 ° C. It may thus be provided, for example, that the setpoint temperature in the first tool section is 20 ° C and in the second tool section 200 ° C. The cooling time of the second

Workpiece section, which is formed ductile, is thus further increased and moved to the storage phase of the removed from the device workpiece. Under the temperature indication "approx. 20 ° C "here is understood that it is the ambient temperature of the tool.

The forming stations may comprise additional devices for processing the workpieces, for example punching and punching devices

Trimming. Preferably, these devices are in the second

Tool sections arranged in which the workpiece is formed ductile and / or in the first tool portion of the first tool. If the additional devices during hot forming before the

Press hardening act so occurs no increased wear of the cutting elements of the devices.

It can further be provided that between the first forming station and the second forming station, an industrial robot is arranged, which is designed such that it removes a machined workpiece from the first forming station and stores in the second forming station for further processing. The term "industrial robot" is understood here also transport devices that work, for example, with intermittently moving gripper bars or the like. For controlling the hot-forming device may be provided a control device, wherein the control device has inputs which are connected to temperature sensors, which are arranged on the tool sections of the tools, and having outputs that with

Tempering devices are connected, which cooperate with the tool sections of the tools. The control device can have further inputs and outputs and, for example, also be provided for controlling further stations which are upstream and / or downstream of the hot-forming device.

It can be provided that the tempering a

Cooling circuit with arranged in the tool sections of the tools cooling channels, a heat exchanger and a coolant compressor comprises.

The object of the invention is further with a method for

Hot working and / or press hardening of workpieces, preferably made of sheet steel, comprising the hot stamping and / or press hardening process steps, the workpieces having a hardened workpiece section and a ductile workpiece section after press hardening, and wherein

in that the press hardening process step is carried out in two time-sequential substeps, a first substep having a first cooling time in a first tool having a first tool portion provided to form the hardened workpiece portion and a second tool portion adapted to form the ductile one

Workpiece section is provided, is performed,

and a second substep having a second cooling time in a second Tool is performed.

The proposed method has the advantage that the cycle time corresponding to the cooling time, which is required for the Warmunnfornnen and / or press hardening in only one process step, is divided into two process steps with two cycle times, each of which is shorter in itself than the aforementioned cycle time. This achieves a higher workpiece throughput.

Another advantage of the proposed method is that due to the planned cooling in the tool no delay can occur. The delay can occur during cooling outside the tool, in particular for workpieces that are made of different materials, for example, with different coefficients of expansion, or regions of different material thickness, occur and require rework to achieve a high dimensional accuracy of the workpiece. In the proposed

Procedure, this rework is not required.

It can be provided that the setpoint temperature of the first tool in the first tool section to about 20 ° C and in the second

Tool section is set in the range of 300 to 400 ° C. Under the temperature indication "approx. 20 ° C "is understood here to mean that

Ambient temperature of the tool is.

It can further be provided that the setpoint temperature of the second tool in a first tool section, which is used to form the hardened

Workpiece section is provided, to about 20 ° C and in a second tool section, which is provided for forming the ductile workpiece section, is set in the range of about 20 to 200 ° C. Under the Temperature indication "ca. 20 ° C "is understood here to mean that

Ambient temperature of the tool is.

It can further be provided that the first cooling time for forming the hardened workpiece section, and that the sum of the first cooling time and the second cooling time for forming the ductile workpiece section is provided. The cooling time of the second workpiece section is thus further increased, and the storage phase of the workpiece removed from the device is used for complete cooling.

The invention will now be explained in more detail with reference to exemplary embodiments. Show it

1 shows a hot forming device according to the invention in one

schematic sectional view;

Fig. 2 shows a first embodiment of an inventive

Hot forming device in a schematic plan view;

3 shows a schematic temperature-time diagram of the process step

Fig. 4a shows a second embodiment of an inventive

Hot forming device in a schematic plan view;

4b, the hot forming device in Fig. 4a at the end of

Process step "press hardening";

5a shows a third embodiment of an inventive

Hot forming device in a schematic plan view;

5b, the hot forming device in Fig. 5a at the end of

Process step "press hardening"; Fig. 6 is a block diagram of the Hotumformvor rect.

Fig. 1 shows a hot forming device 1, which is called for the hot forming and / or press hardening of sheet metal blanks and / or sheet metal parts made of steel with different material thickness, hereinafter referred to as workpiece 4.

The workpiece is heated to a temperature above the Austenitisierungstemperatur for hot forming with respect to subsequent press hardening and fixed between a tool upper part and a lower tool part of a forming and / or pressing tool and subjected to a pressing pressure. That's the hot forming. Thereafter, the workpiece is in

Tool rapidly cooled below the Austenitisierungstemperatur, that is quenched. This is press hardening, which is also known as tempering because it takes place in a closed mold.

It can also be provided in the workpiece except hardened

Sections to form ductile sections. Ductile sections must be cooled considerably slower than during press hardening, so that no martensitic transformation takes place.

The hot forming device 1 has a frame-shaped frame 1 1, in which a first forming station 2 with a first tool 3 and a second forming station 2 'with a second tool 3', which is formed with the shape contour of the first tool 3, respectively. Between one

Tool upper part 31 and a lower tool part 32, the workpiece 4 can be arranged. In the embodiment shown in Fig. 1 is at the workpiece 4 to a plate-shaped sheet metal blank made of a high-strength hardenable steel. The upper tool part 31 is rigidly connected to a head plate 12. The top plate 12 is rigidly connected to an output of a supported on the frame 1 1 drive 13. The lower tool part 32 is arranged on a supported on the frame 1 1 base plate 14 and rigidly connected thereto. The tool top 31 may be formed as a die, and the tool base 32 may be formed as a die, or vice versa.

The tools 3 and 3 'and thus the upper tool parts 31 and

Tool lower parts 32 have a first tool portion 33, which is provided for forming the hardened workpiece portion, and a second tool portion 34, which is for forming the ductile

Workpiece section is provided on (see Fig. 2 to 4).

The tools 3 and 3 'further have means for regulating the

Temperature of the first and second tool sections 33, 34, as described in more detail in Fig. 6 below. In that shown in Fig. 1

Embodiment, the tool top 31 and the

Tool lower part 32 in its the workpiece 4 facing pressing surfaces near the tool surface cooling channels 35, which are connected to a cooling circuit, not shown in Fig. 1. The cooling channels 35 are flowed through by a cooling medium, which dissipates heat from the workpiece 4. The first tool sections 33 and the second tool sections 34 of the two tools 3 and 3 'have separate cooling circuits in order to be able to set different setpoint temperatures that are to be achieved

Sollendtemperatur the workpiece section after a predetermined cycle time correspond. In addition to the cooling circuits, heating means may be provided to preheat, if necessary, cold tools to a temperature above ambient temperature. For example, the first tool 3 in the second tool section 34 is heated to 300 to 400 ° C.

The workpiece 4 successively passes through a heating station 8, the first forming station 2 and the second forming station 2 '.

Between the two adjacent forming stations 2 and 2 'is a

Industrial robot 5 arranged, which in the first forming station. 2

machined workpiece 4 of the first forming station 2 removes and stores in the second forming station 2 'for further processing.

Further industrial robots 5 are between a storage station 6 for unprocessed workpieces and the heating station 8, the heating station 8 and the first forming station 2, and the second forming station 2 'and a

Storage station 7 arranged for machined workpieces.

Fig. 2 shows a schematic plan view of the tool lower parts 32 of the juxtaposed tools 3 and 3 'with launched

Workpieces 4. The tools 3 and 3 ', as mentioned above, each have a first and a second tool portion 33, 34, which are integrally formed in the embodiment shown in FIG. The second tool 3 'is formed with the shape contour of the first tool 3, that is, the inner contour of the second tool 3' corresponds to the outer contour of the first tool 3 removed workpiece 4. In this way it is ensured that in the second

Tool 3 'the press hardening of the workpiece 4 can be continued.

Fig. 3 shows a temperature-time diagram, the in the

Hot forming device 1 in the two forming stations 2 and 2 'carried out and explained in the following process steps illustrated.

In a first method step, a workpiece 4 is a on the

Storage station 6 removed for unprocessed workpieces formed workpiece stack and stored in the heating station 8.

In a second method step, the workpiece 4 stored in the heating station 8 is at a temperature above the

Austenitizing temperature of its steel material heated.

In a third method step, the heated workpiece 4 is the

Warming station 8 removed and stored in the open tool 3 of the first forming station 2.

In a fourth method step, the tool 3 of the forming station 2 is closed and the heated workpiece 4 is hot-formed.

In a fifth method step, the formed workpiece 4 is partially press-hardened when the tool 3 is closed. The workpiece 4 has in the temperature to be hardened workpiece portion at time ti a temperature Tu and in the ductile workpiece part to be formed a temperature T ₂ i on. The temperatures Tu and T ₂ i are equal and correspond to the temperature of the workpiece 4 after the forming, in which a small cooling of the workpiece 4 can occur. For example, Tu = T ₂ i = about 500 ° C. This is the temperature of a workpiece after hot forming, which was heated to about 950 ° C before hot forming and when inserting the

Workpiece in the tool still had a temperature of about 700 ° C. The workpiece 4 is now in a first period of time

Ati = t ₂ - ti

cooled in the part to be hardened to a temperature Ti ₂ and cooled in the ductile workpiece portion to a temperature T ₂₂ , wherein T _{22 is} above the transition temperature of austenite to ferrite and Tu is below the transition temperature of austenite to ferrite, because the target temperature of first tool section 33 is selected to about 20 ° C, and the target temperature of the second tool section 34 is selected in the range of 300 to 400 ° C. The temperature indication "approx. 20 ° C "means the ambient temperature, so it is not intended or necessary to choose a setpoint temperature below the ambient temperature.

For example, the duration of the period Ati about 10s, wherein at time t _2, the temperature Ti _{2 of} the workpiece 4 in the workpiece to be hardened portion in the range of 60 to 150 ° C and the temperature T _{22 of} the workpiece 4 in the ductile workpiece section to be formed in Range is from 400 to 500 ° C.

In a sixth method step, the first tool 3 is opened and the partially hardened workpiece 4 is removed by the industrial robot 5 and stored in the opened second tool 3 '. In the in Fig. 3 2, for the sake of simplification, it is assumed that in a second period of time provided for the transfer

At ₂ = t ₃ - 1 ₂

no further cooling of the workpiece 4 occurs.

In a seventh method step, the partially hardened workpiece 4 is finished hardened when the tool 3 'is closed. The workpiece 4 has the temperature Ti ₂ in the workpiece section to be hardened at the time t _3, and the temperature T ₂ 2 in the workpiece section to be formed in a ductile manner. Both workpiece sections are now in a third period of time

At ₃ = - 1 ₃

cooled to a temperature Ti ₃ and T ₂₃ , preferably. The

Target temperature of the second tool 3 'is in the first tool section 33 and in the second tool section 34 in the range of 20 to 200 ° C.

For example, the duration of the time period At _{2 is} about 10 s, wherein at time t, the temperature Ti _{2 of} the workpiece 4 in the workpiece section to be hardened and in the workpiece section to be formed in a ductile manner approximately

Ambient temperature is.

In a seventh method step, the second tool 3 'is opened and the finished hardened workpiece 4 is removed by the industrial robot 5 and stored in the storage station 7 for machined workpieces. By distributing the process step press hardening to two

Forming stations is compared to only one forming station, an increased throughput of workpieces possible because now the cycle times of the individual stations in the Ideally aligned. The period of time available for the slow cooling of the ductile workpiece section is the sum

S = Δίι + At ₃

the first and the third period. Advantageously, the first period Ati and the third period At _{3 are the} same as described above in the example. Since the stored in the storage station 7 workpieces 4 are already cooled, no more distortion occurs.

Figs. 4a and 4b show a second embodiment of a

Hot-forming device which is like that described in FIG

Hot forming device is formed, with the difference that the first and the second tool portion 33, 34 of the first tool 3 are separated by a expansion joint 3d. The expansion joint 3d prevents

Thermal stresses in the first tool 3, which may occur due to the different temperature of the first and second tool sections 33, 34.

FIG. 4 a shows the hot-forming device 1 at the time at which the first tool section 33 of the first tool 3 has a temperature of approximately 20 ° C. and the second tool section 34 has a temperature in the range from 300 to 400 ° C. The expansion joint 3d between the first tool section 33 and the second tool section 34 has a minimum width, which is preferably 0 mm. 4b shows the hot-forming device 1 at the time when the first tool section 33 and the second tool section 34 of the first tool 3 have cooled to ambient temperature. The expansion joint 3d has a maximum width, because the second tool section 34 of 300 cooled to 400 ° C to ambient temperature and therefore has a shortened length.

Figs. 5a and 5b show a third embodiment of a

Hot-forming device which is like that described in FIG

Hot forming device is formed, with the difference that between the first and the second tool portion 33, 34 of the first tool 3, a compensating element 3a is arranged. The compensating element 3a abuts in the illustrated embodiment on the first tool section 33, so that the two expansion joints 3d have a different width.

The forming stations 2 and 2 'may be additional devices for

Processing of the workpieces 4 include, for example, devices for punching and trimming. Preferably, these devices are arranged in the second tool sections 34, in which the workpiece 4 is formed ductile and / or in the first tool section 33 of the first tool 3, so that no increased wear due to high hardness occurs. Fig. 6 shows a block diagram of the hot forming device 1, the

Functionality of the hot forming device clarified.

For controlling the hot forming device 1, a control device 9 is provided. The control device 9 has inputs that with

Temperature sensors 9 s are connected, wherein the temperature sensors 9 s at the first and second tool sections 33, 34 of the first tool 3 and the second tool 3 'are arranged. The controller 9 has outputs connected to control inputs of Tempering devices 10 are connected, which may be formed, for example, as cooling circuits with heat exchanger and compressor pump, wherein as shown in Fig. 1, the tools 3, 3 'cross-cooling channels 35 form sections of the cooling circuits.

At least one further output of the control device 9 is connected to the robot 5 arranged between the two forming stations 2 and 2 ', which transports the workpieces 4 from the first forming station 2 into the second forming station 2'.

Advantageously, the control device 9 can have further inputs and outputs in order to control the storage station 6 and 7 shown in FIG. 1, the heating station 8 and the associated further robots 5 and to coordinate the process sequence described in FIG. Preferably, a computer-aided control device 9 is provided, in which the process flow is stored in a control software.

LIST OF REFERENCE NUMBERS

1 hot forming device

2 first forming station

2 'second forming station

3 first tool

3a compensation element

3d expansion joint

3 'second tool

4 workpiece

5 industrial robots

6 storage station for unprocessed workpieces

7 storage station for machined workpieces

8 warming station

9 control device

9s temperature sensor

10 tempering device

1 1 rack

12 head plate

13 drive of the top plate

14 base plate

31 Tool upper part

32 lower tool part

33 first tool section

34 second tool section

35 cooling channel

Claims

claims

Hot-forming device (1) for hot-forming and / or press-hardening workpieces (4), preferably made of sheet steel, which have a hardened workpiece section and a ductile workpiece section after press-hardening,

characterized,

in that the hot-forming device (1) comprises a first forming station (2) with a first tool (3) and a second forming station (2 ') arranged behind the first forming station (2) with a second tool (3'), wherein the second tool ( 3 ') with the shape contour of the first

Tool (3) is formed,

that at least the first tool (3) has a first

Tool section (33) used to form the hardened

Workpiece section is provided, and a second

Tool section (34), which is used to form the ductile

Workpiece section is provided, and,

that the tools (3, 3 ') tempering means (10) for Setting the temperatures include.

2. hot forming device according to claim 1,

characterized,

that the setpoint temperature of the first tool (3) in the first

Tool section (33) about 20 ° C and in the second

Tool section (34) is 300 to 400 ° C. 3. hot forming device according to claim 1 or 2,

characterized,

in that the first and second tool sections (33, 34) of the first tool (3) are integrally formed. 4. hot forming device according to claim 1 or 2,

characterized,

in that the first and second tool sections (33, 34) of the first tool (3) are separated by an expansion joint (3d). 5. hot forming device according to claim 4,

characterized,

in that between the first and the second tool section (33, 34) of the first tool (3) a compensating element (3a) is arranged which is separated from the first and the second tool section (33, 34) by expansion joints (3d).

6. hot forming device according to one of the preceding claims, dad u rch geken nzeich net, the second tool (3 ') has a first tool section (33), which is provided for forming the hardened workpiece section, and a second tool section (34), which is provided for forming the ductile workpiece section,

Hot forming device according to claim 6,

characterized,

that the setpoint temperature of the second tool (3 ') in the first tool section (33) about 20 ° C and in the second

Tool section (34) is 20 to 200 ° C.

Hot-forming device according to one of the preceding claims, characterized in that

that between the first forming station (2) and the second

Forming station (2 ') an industrial robot (5) is arranged, which is adapted to the first forming station (2) removes a machined workpiece (4) and stores in the second forming station (2') for further processing.

that for controlling the hot forming device (1) a

Control device (9) is provided, wherein the

Control device (9) has inputs that with

Temperature sensors (9s) are connected to the

Tool sections (33, 34) of the tools (3, 3 ') are arranged, and outputs having with temperature control means (10) connected to the tool sections (33, 34) of the

Tools (3, 3 ') interact.

10. hot forming device according to claim 9,

characterized,

in that the tempering device (10) comprises a cooling circuit with cooling channels (35) arranged in the tool sections (33, 34) of the tools (3, 3 '), a heat exchanger and a coolant.

1 1. Method for hot forming and / or press hardening of workpieces (4), preferably of sheet steel, comprising the process steps

Hot working and / or press hardening, the workpieces (4) having a hardened workpiece section and a ductile workpiece section after press hardening,

characterized,

in that the press hardening process step is carried out in two time-sequential substeps, wherein a first substep having a first cooling time Ati in a first tool (3) having a first tool portion (33) adapted to form the hardened

Workpiece section is provided, and a second

Tool section (34), which is used to form the ductile

Workpiece section is provided, is performed,

and a second sub-step is performed with a second cooling time At ₃ in a second tool (3 ').

12. The method according to claim 1 1,

characterized, that the setpoint temperature of the first tool (3) in the first

Tool section (33) to about 20 ° C and in the second

Tool section (34) is set in the range of 300 to 400 ° C, 13. The method of claim 1 1,

characterized,

the setpoint temperature of the second tool (3 ') in a first tool section (33) used to form the hardened

Workpiece section is provided, to about 20 ° C and in a second tool section (34), for forming the ductile

Workpiece section is provided, is set in the range of about 20 to 200 ° C.

14. The method according to any one of claims 1 1 to 13,

characterized,

that the first cooling time Ati to the training of the hardened

Workpiece section, and

the sum of first cooling time Ati and second cooling time At _{3 is provided} for forming the ductile workpiece section.