EP2427282B1 - Device and method for heating workpieces which are to be hot-formed - Google Patents

Description

The invention relates to a device and a method for heating hot to be formed metallic workpieces, for example, sheet metal parts of a vehicle body.

For hot forming of metallic workpieces, such as sheet metal parts, with a diffusion-based surface protection not only requires a heating of the sheet metal parts to the required final temperature for forming. So that a sufficient amount of the material forming the surface protection material can diffuse into the sheet surface, the sheet metal parts must also be kept at a predetermined minimum temperature over a predetermined minimum period, which requires a correspondingly long residence time in a heating device. Nevertheless, in order to be able to supply surface-protected sheet-metal parts in rapid succession to a hot-forming process, heretofore long roller hearth furnaces have been used, which pass through the sheet-metal parts over a period of several minutes in a long row. In addition to an extraordinary amount of space such ovens require a high investment and maintenance costs. The furnace interior is largely inaccessible during operation. Defects and faults inside the furnace inevitably lead to the shutdown of the entire system.

The invention has for its object to provide a new improved device and a new improved method for heating hot workpieces to be formed.

The solution of this object is achieved according to the invention with a heat treatment apparatus according to claim 1 and a Heat treatment method, preferably with such a heat treatment apparatus, according to claim 6 and for concrete applications of heat treatment of hot-to-form metallic workpieces, for example sheet metal parts of a vehicle body with a special heat treatment process according to claim 15.

• eine erste Wärmestation,
• eine nachgeschaltete zweite Wärmestation,
• gegebenenfalls eine oder mehrere weitere nachgeschaltete Wärmestation(en),
• eine Überführungsvorrichtung, um die Werkstücke den Wärmestationen zu und/oder abzuführen, und
• eine Steuerungseinrichtung für den Betrieb der Überführungsvorrichtung und/oder den Betrieb der Wärmestationen,
  wobei vorgesehen ist,
• dass die erste Wärmestation derart ausgebildet ist, dass das darin aufgenommene Werkstück oder die darin aufgenommenen Werkstücke jeweils innerhalb einer für die erste Wärmestation vorbestimmten Verweilzeit auf eine für die erste Wärmestation vorbestimmte Temperatur erwärmbar ist bzw. sind,
• dass die zweite Wärmestation mehr Werkstückaufnahmeplätze als die erste Wärmestation aufweist, und derart ausgebildet ist, dass die darin aufgenommenen Werkstücke jeweils innerhalb einer für die zweite Wärmestation vorbestimmten Verweilzeit, die größer ist als die für die erste Wärmestation vorbestimmte Verweilzeit, auf eine für die zweite Wärmestation vorbestimmte Temperatur erwärmbar und/oder auf dieser vorbestimmten Temperatur konstant haltbar sind, wobei die für die zweite Wärmestation vorbestimmte Temperatur ungefähr gleich oder höher ist als die für die erste Wärmestation vorbestimmte Temperatur.

The solution according to claim 1 provides a heat treatment device, possibly with downstream hot forming device, for example, with a press for metallic workpieces, preferably sheet metal parts of a vehicle body before. This heat treatment device comprises

• a first heat station,
• a downstream second heat station,
• optionally one or more further downstream heat stations
• a transfer device for feeding and discharging the workpieces to the heat stations, and
• a control device for the operation of the transfer device and / or the operation of the heat stations,
  being provided
• the first heat station is designed such that the workpiece accommodated therein or the workpieces accommodated therein can each be heated to a predetermined temperature for the first heat station within a predetermined residence time for the first heat station,
• the second heat station has more work piece receiving sites than the first heat station, and is configured so that the workpieces received therein in each case within a predetermined for the second heat station dwell time, which is greater than the predetermined for the first heat station dwell time, one for the second Heat Station predetermined temperature can be heated and / or kept constant at this predetermined temperature, wherein the predetermined for the second heat station temperature is approximately equal to or higher than the predetermined temperature for the first heat station.

In this heat treatment device according to the invention, one or more such first heat stations and one or more such second heat stations may be provided. Furthermore, further heat stations can be connected upstream and / or downstream and optionally interposed. The division into several different heat stations, the apparatus requirement is created to perform the heating of the workpieces in several different heat treatment phases. The different heat treatment phases may be a plurality of heating and / or temperature-preserving phases having preferably different temperatures in the heat stations and preferably different residence time in the heat stations.

In particularly advantageous applications of the heat treatment device according to the invention coated with a surface protection parts are used, it can be hot to be formed metallic workpieces, preferably sheet metal parts of a vehicle body. However, the heat treatment device according to the invention is not limited to these applications. In the case of the hot-formed metallic workpieces with surface protection, a rapid heating phase is carried out in the first heat station and a diffusion phase in the second heat station. In the diffusion phase, the diffusion of the coating material into the metallic workpiece takes place at a temperature required for the diffusion. The residence time in the heat station of the diffusion phase is set larger in comparison to the residence time in the upstream rapid heating station.

According to the invention, the different stations in conjunction with the different residence times may have a different number of workpiece receiving stations. With the number of workpiece receiving stations in the stations a multiple assignment and thus a parallel treatment of several workpieces in each case a heat station is possible.

It is essential in the case of the heat treatment apparatus according to the invention that the second heat station has more workpiece receiving places than the first heat station. This means that in the second heat station, a larger number of workpiece receiving stations is available. It is thus in the second heat station so a parallel treatment of several workpieces simultaneously or at least temporally overlapping possible. However, it is not always used in all versions of the heat treatment process all available workpiece receiving stations, that is occupied with workpieces.

Furthermore, according to the invention, the second heat station can effectively form a buffer memory. It is thus possible to provide relatively long residence times of the workpieces in the second heat station and to realize shorter residence times in the upstream and / or downstream heat station, wherein the cycle time can be determined by the shorter residence time, for example by a downstream heat station or the downstream hot forming device , The removal time of the heated in the stations workpieces can thus be compared to the conventional technique reduced by a multiple and can be tuned, for example, to the cycle time of the forming machine.

Due to the inventive concept of the device with the multiple occupancy or parallel heat treatment in the second heat station in conjunction with upstream and downstream heat stations with less number of workpiece receiving stations can be built relatively small and good accessibility and lower maintenance costs can be achieved.

Due to the high workpiece receiving capacity, that is, the plurality of workpiece receiving positions in the second heat station, a high variability and flexibility of the heat treatment apparatus can be achieved. Thus, the stations of different workpiece holding capacity or different residence time can be advanced and / or downstream of the second heat treatment station.

In preferred embodiments it is provided that a third heat station is provided downstream of the second heat station, which has fewer workpiece receiving stations than the second heating station and is designed such that the workpiece received therein or the workpieces received therein in each case within a predetermined residence time for the third heat station, which is smaller than the predetermined for the second heat station residence time heated to a predetermined temperature for the third heat station and / or stable to this predetermined temperature is durable, this predetermined temperature is approximately equal to or higher than that predetermined for the second heat station Temperature.

One or more such third heat stations may be provided. It is essential that the number of workpiece receiving stations of this third heat station is lower than that of the second heating station. In special embodiments, the number of workpiece receiving stations of the third heat station may be the same as the number of workpiece receiving stations of the first heat station. There are provided embodiments in which the first Heat station and / or the second station each having only one workpiece receiving station.

The type of heating equipment in the different heat stations can be different. This substantial advantages can be achieved because depending on the performance of the respective heating device, the number of workpiece receiving stations for the relevant heat station can be selected. It is particularly preferred if in the first heat station, an inductive heating device is present to obtain a particularly rapid heating of the workpieces. It can be provided that the first heat station has a heating device for inductive heating of the workpieces. However, embodiments with conductive heating of the workpieces in the first heat station are also conceivable.

As regards the heating device of the second heat station, it is advantageous if the second heat station has a heating device for heating the workpieces by means of fuel combustion and / or by electrical resistance heating. It is also possible to reduce the energy requirement by good insulation of the second heat station. This is of particular advantage in the second heat station, which provides a relatively long residence time. Preferably, well-insulated termination devices, such as end flaps or end covers, are provided which allow the workpieces to be fed and removed but minimize the heat losses during the residence time of the workpieces concerned.

As regards the third heat station, it is advantageous if the third heat station has at least one heating device for inductive heating of the sheet metal parts. In the third heat station may also be provided preferably a zone-wise heating. It can be provided that the third heat station at least two or more similar or different Having heating devices which form two or more zones for the third heat station predetermined temperatures zone by zone. For each of the zones may preferably be provided a separate inductor for adjusting the required different temperature, for. B. temperatures below or above the Austenitisierungstemperatur of the metallic material. But it is also possible to use the required different temperatures through an inductor with different heat generating zones. In connection with the multi-zone heating, a multi-zone hardening can take place. It can be achieved by different heating in the different zones predefined in the different zones strength. Particular advantages arise with the Mehrzonenheizeinrichtungen, even if the workpieces to be heated in the different zones have different material thicknesses,

The tuning in the different zones can also be done for material combinations with different melting points and different conductivity in the zones.

Schritt a:

Erwärmen des Werkstücks über einen ersten Zeitabschnitt,

Schritt b:

Warmhalten des Werkstückes durch Wärmeisolieren und/oder Beheizen auf einer Temperatur für das Eindiffundieren des Materials zur Oberflächenbeschichtung in das Werkstück über einen zweiten Zeitabschnitt,

Schritt c:

weiteres Erwärmen des Werkstückes auf eine Temperatur, die gleich oder höher ist als die Austenitisierungstemperatur des Werkstücks, und Halten der Temperatur auf mindestens der Austenitisierungstemperatur über einen dritten Zeitabschnitt,

wobei die Zeitdauer des Schrittes a und die Zeitdauer des Schrittes c jeweils kürzer ist als die Zeitdauer des Schrittes b und
wobei Werkstücke, die sukzessive nacheinander oder mit zeitlicher Überlappung dem Schritt a unterzogen werden, sodann gleichzeitig, d. h. zumindest überlappend, dem Schritt b unterzogen werden und sodann sukzessive ohne zeitliche Überlappung dem Schritt c unterzogen werden.As already mentioned above, particularly preferred applications of the heat treatment, if a protective material is applied to the workpieces before the heat treatment, it is particularly important in the heat treatment of hot-formed metallic workpieces with surface coating that prior to hot forming the material of the surface coating in the workpieces diffused. The heat treatment method may according to claim 15 preferably have the following steps:

Step a:

Heating the workpiece over a first period of time,

Step b:

Keeping the workpiece warm by heat-insulating and / or heating at a temperature for in-diffusion of the surface-coating material into the workpiece over a second period of time;

Step c:

further heating the workpiece to a temperature equal to or higher than the austenitizing temperature of the workpiece, and maintaining the temperature at least at the austenitizing temperature over a third period of time,

wherein the time duration of the step a and the duration of the step c are each shorter than the time duration of the steps b and
wherein workpieces which are successively successively or temporally overlapped with the step a, then simultaneously, ie at least overlapping, subjected to the step b and then successively subjected to step c without temporal overlap.

Preferably, inductive heating of the workpiece may be provided in step a, but it is also possible to provide other heating methods, for example, conductive heating. Preferably, in step b, the heating can be carried out by means of fuel combustion and / or by electrical resistance heating.

1. a) Übergabe eines Werkstücks an die erste Wärmestation,
2. b) Erhitzen des Werkstücks während einer für die erste Wärmestation vorbestimmten Verweilzeit auf eine für die erste Wärmestation vorbestimmte Temperatur,
3. c) Zuordnung der positionsverstellbaren ersten Wärmestation zu einem freien zweiten Werkstückaufnahmeplatz der zweiten Wärmestation,
4. d) Übergabe des Werkstücks nach Ablauf der für die erste Wärmestation vorbestimmten Verweilzeit an die zweite Wärmestation,
5. e) Erhitzen des Werkstücks auf eine für die zweite Wärmestation vorbestimmte Temperatur und Halten dieser Temperatur;
6. f) Zuordnung der positionsverstellbaren dritten Wärmestation zu einem belegten zweiten Werkstückaufnahmeplatz der zweiten Wärmestation, an dem eine die Verweilzeit größer oder gleich der für die zweite Wärmestation vorbestimmten Verweilzeit ist,
7. g) Übergabe des Werkstücks an die dritte Wärmestation,
8. h) Erhitzen des Werkstücks auf die für die dritte Wärmestation vorbestimmte Temperatur,
9. i) Positionieren der dritten Wärmestation, sodass das Werkstück an die stromabwärts hinter der dritten Wärmestation angeordnete Warmumformvorrichtung übergebbar ist,
10. j) Übergabe des Werkstücks an die Warmumformvorrichtung.

The heat treatment method may preferably be performed with a heat treatment apparatus having first, second, and third heat stations as described above. Such a solution is the subject of claim 6, after which the following process steps are cycled:

1. a) transfer of a workpiece to the first heat station,
2. b) heating the workpiece during a predetermined residence time for the first heat station to a temperature predetermined for the first heat station,
3. c) assignment of the positionally adjustable first heat station to a free second workpiece receiving location of the second heat station,
4. d) transfer of the workpiece after expiration of the predetermined for the first heat station dwell time to the second heating station,
5. e) heating the workpiece to a predetermined temperature for the second heat station and holding this temperature;
6. f) assignment of the positionally adjustable third heat station to an occupied second workpiece receiving location of the second heat station, at which a residence time is greater than or equal to the predetermined residence time for the second heat station,
7. g) transfer of the workpiece to the third heat station,
8. h) heating the workpiece to the temperature predetermined for the third heat station,
9. i) positioning the third heat station so that the workpiece can be transferred to the hot-forming device arranged downstream of the third heat station,
10. j) transfer of the workpiece to the hot forming device.

The following statements are directed to particularly preferred specifications of the method steps.

It can be provided that the method steps b) to d) and e) to g) and h) to j) are carried out simultaneously.

It can further be provided that in step h) at least two predetermined for the third heat station temperatures are provided, these two temperatures are assigned to different workpiece sections. In this way it is possible to have different crystal structures in the workpiece austenitic, such as austenitic and non-austenitic areas, so that the workpiece after cooling can have hardened and ductile areas. Austenite refers to γ mixed crystals of iron. Austenite is part of many stainless steels. The structure has a low hardness, but can be increased considerably by cold deformation.

It can be provided that the temperature or the temperatures in the third heat station is greater than or equal to the austenitizing temperature. It may be provided here that at least one of the temperatures predetermined for the third heat station is less than the austenitizing temperature.

With regard to the zone-wise different temperatures in the third heat station, the temperature of one of the workpiece sections may, for example, be above the austenitizing temperature, the temperatures in the other workpiece sections may be below the austenitizing temperature, the austenitizing temperature being readable, for example, from the state diagram of the steel alloy from which the Workpiece is formed. Thus, it is particularly easy for workpiece sections to be press-hardened in a press device after hot-forming, while other workpiece sections remain ductile. The ductile regions of the component produced from the workpiece can deform very plastically when overloaded and are therefore able to absorb impact energy, while the hardened areas contribute to the stability. The components formed in this way are particularly suitable for improving the safety of motor vehicles in rear-end collisions because the ductile regions can act as crumple zones and destroy impact energy through deformation.

It can further be provided that the residence time predetermined for the second heat station is at least equal to the time in which the diffusion process is completed. It is possible, the residence time in the third heat station the technological requirements and to choose larger ones, whereby the result of the diffusion is not questioned.

It is possible that the cycle time of the hot-forming device is greater than the predetermined for the first heat station residence time and / or the predetermined for the third heat station residence time. In this case, the cycle time of the hot-forming apparatus, taking into account the transfer time between the third heat station and the hot-forming device and the time for removal of the finished component from the hot-forming device, determines the smallest possible cycle time.

It can be provided that the cycle time of the hot forming device is much smaller than the second residence time, provided that the second heat station, which provides a relatively high residence time, has a sufficiently high number of workpiece receiving locations.

As stated above, the predetermined for the first and third heat station residence time are substantially smaller than the predetermined for the second heat station residence time. For example, if the residence time predetermined for the second heat station is 4 minutes, that is 240 seconds, and the predetermined residence time for the first and third heat stations is 4 seconds each, the residence time predetermined for the second heat station is (240/4) times ie, 80 times larger than the residence time predetermined for the first heat station. Consequently, the second heat station must have at least 80 second workpiece receiving locations to operate at the same rate as the first thermal station. This very rough estimate does not yet take into account the transfer times between the heat treatment stations. For example, if the transfer time between adjacent heat stations is 6 seconds, only at least 240 / (4 + 6) = 24 second workpiece slots are needed to achieve the same cycle time saving effect. As stated above, however, the cycle time of Hot forming device, taking into account the transfer time between the third heat station and the hot forming device and the time for the removal of the finished component from the hot forming device to determine the smallest possible cycle time, which is then used to calculate the minimum number of required second workpiece receiving positions. Assuming that the said sum of the cycle time of the hot forming device and the transfer times is 20 seconds, only at least 240/20 = 12 second workpiece receiving positions are required.

Further advantageous embodiments are directed to particularly preferred apparatus designs of the heat stations.

It can be provided that at least one of the heating stations and / or the tool receiving station and / or the tool receiving stations of at least one of the heat stations is / are positionally adjustable.

It can further be provided that the heat station and / or the workpiece receiving station and / or the workpiece receiving stations is or are positionally adjustable such that at least one workpiece receiving station of the adjustable heat station or the adjustable workpiece receiving station and / or the adjustable workpiece receiving stations can be assigned to a workpiece receiving station of a downstream or upstream heating station is or are for the supply of a workpiece from the upstream heat station or for the removal of a workpiece to the downstream heat station.

Further, it can be provided that the workpiece is arranged supported on a movable carrier, which is arranged resting and / or fixed during the residence time of the workpiece in a heat station on the workpiece holder position and during the supply of the workpiece from an upstream heat station or during the discharge of Workpiece to a downstream heat station is movably guided. The movable carrier may be, for example, a trolley on which the workpiece is stored and possibly fixed.

In particular, in inductive heating, the fixing of the workpiece on the workpiece receiving station or the movable carrier is advantageous because otherwise the workpiece could perform uncontrolled movements, such as flutter movements with inductive heating. It is provided in preferred embodiments of heat stations with inductive heating to fix the workpieces on the workpiece receiving stations or the movable carriers. Apart from this, the fixation of the workpieces can advantageously be provided in all versions with movable carriers or positionally adjustable workpiece receiving stations or heat storage stations which can be positioned in order to ensure that the workpieces are securely held in position during the heat treatment or during their transport through the heat treatment device. This is especially true when the heat station itself is positionally adjustable or has position-adjustable workpiece receiving positions.

In preferred embodiments, it may be provided that the positionally adjustable heat station and / or the positionally adjustable workpiece receiving station is adjustable in the vertical direction or is adjustable in the horizontal direction.

It can further be provided that one or more of the heat stations has vertically above one another or horizontally juxtaposed workpiece receiving positions. Horizontally juxtaposed workpiece receiving stations may be preferred to arrange more than one technological line for heat treatment and hot forming side by side, wherein the below-described embodiment of the second heating station with vertically stacked workpiece receiving stations may be preferred.

In a preferred embodiment, it is provided that the second heat station has workpiece receiving stations arranged vertically one above the other and the upstream first heating station or the downstream third heating station is positionally adjustable in the vertical direction or has at least one workpiece receiving position adjustable in the vertical direction,
or
in that the second heat station has workpiece receiving stations arranged horizontally next to one another and the upstream first heat station and / or the downstream third heat station is positionally adjustable in the horizontal direction or has at least one workpiece receiving position which can be adjusted in a horizontal direction.

In an advantageous development it can be provided that the first and / or third heat station are mounted on a vertically or horizontally movable lift.

It can further be provided that the workpiece receiving station forms a guideway section or is connected to a guideway section, which can be assigned to a guideway section of a workpiece receiving station of this upstream or downstream heating station for the supply of a workpiece from an upstream heat station or for the removal of a workpiece to a downstream heat station forming a guideway composed of the guideway sections. The guideway sections can each be designed as a platform. They can themselves be designed as a workpiece holder or support, preferably a movable carrier, on which the respective workpiece can be arranged. In order to supply the workpieces from the stations and remove, they can by the transfer device on the example formed as a platform guide track sections of the one be moved to the other station. The platforms of the workpiece receiving stations, between which the transfer takes place, thereby forming a composite of the platforms guideway for the workpieces to be transferred.

It can be provided that the transfer device has a drive device which acts with its output side on the workpiece and / or a workpiece receiving the movable carrier and / or on a movable component of a workpiece receiving station directly or indirectly pulse-like or permanent. The drive device can be designed, for example, as a rack drive, threaded rod drive or a push rod designed with a pneumatic, hydraulic or electric linear drive. These embodiments have the advantage that the drive motor or the drive member can be arranged outside of the heat stations and therefore are not subject to high-temperature wear.

The transfer device may also be designed as robotic engagement arms or the like in modified embodiments.

The above-mentioned control device for the operation of the transfer device and / or the operation of the heat stations can be advantageously designed as a computer-controlled electronic control device comprising at least all required for the operation of the heat treatment device measuring and control components, wherein in a computer, a control program can be stored, which coordinates and monitors the interaction of said components.

Fig. 1

eine schematische Darstellung (Seitenansicht) einer Vorrichtung nach der Erfindung in Verbindung mit einer Warmumformvorrichtung;

Fig. 2

eine Teildarstellung der Vorrichtung in Fig. 1;

Fig. 3

ein weiteres Ausführungsbeispiel für eine Vorrichtung nach der Erfindung in schematischer Darstellung (Draufsicht).

The invention will be explained in more detail with reference to embodiments and the accompanying drawings relating to these embodiments. Show it:

Fig. 1

a schematic representation (side view) of a device according to the invention in conjunction with a hot forming device;

Fig. 2

a partial view of the device in Fig. 1 ;

Fig. 3

a further embodiment of a device according to the invention in a schematic representation (plan view).

At the in FIG. 1 shown embodiment of a heat treatment device 1 is a device for heating warm-formed workpieces 11. This has in the illustrated case, three successive heat stations 12, 13 and 14 on. The heat station 14 is followed by a hot forming device 15. The workpieces 11 are metallic workpieces, for example cut sheet metal parts of a vehicle body. The sheet metal parts used are preferably sheet metal parts which have already been coated with a protective layer. However, provision may also be made for the workpieces 11 to be provided with a protective layer in a coating station (not shown) upstream of the heat treatment device, and then to be dried. The workpieces go through the in FIG. 1 represented stations, by being transferred in each case from one station to the other station in detail in the manner described below.

The first heat station 12 is used for rapid heating of the workpieces 11. In the downstream second heat station 13 takes place at a predetermined temperature in the case of the described embodiment with the precoated workpieces 11, the diffusion of the protective material into the metallic material of the workpiece. The predetermined temperature is hereby set as required for the diffusion of the protective material. In the downstream third heat station 14, the austenitization of the workpieces 11 takes place in the illustrated case. For this purpose, a temperature required for the desired austenitization is set. The structure of the individual stations and the operating conditions will be explained in more detail below.

As in FIG. 1 recognizable, the first heat station 12 has a workpiece receiving space 12a. This workpiece receiving station 12a can be heated by a first heating device 12e, which is designed for rapid heating of the workpiece as an inductive heating device. But it can also be provided a different heating method, for example, conductive heating.

This first heat station 12 has in the embodiment in FIG. 1 only one workpiece holder 12a on. He is trained as a platform on which, as in FIG. 1 recognizable, a trolley 16 is arranged. The trolley 16 has an in FIG. 1 not shown holding device for receiving and fixing the workpiece 11. The platform forming the workpiece receiving station 12a passes through the heat station 12 and thus forms a guide section 12f for the transfer of the workpiece, as will be explained in more detail below.

In the case shown, the first heat station 12 is arranged on a lift 17, which is vertically movable on a columnar stationary supporting and guiding body 17.

The second heat station 13 has a plurality of workpiece receiving stations 13a, which are arranged like a shelf in the illustrated embodiment, one above the other. These workpiece receiving stations 13a are each designed as platforms, on each of which a transport carriage 16 with the workpiece 11 can be arranged. The platforms each form the bottom of the receiving compartments. They each pass through the heat station 13 and thus form guideway sections 13f for the handover of the workpieces, which is explained in more detail below.

The workpiece receiving stations 13a of the second heat station are in the in FIG. 1 illustrated embodiment formed as a thermally insulated storage compartments. They have lockable inputs and outputs, which are designed for example as heat-insulated flaps.

The heating device of the heat station 13 may be a heating device operated by means of fuel combustion and / or electrical resistance heating. The heating device is designed as a common heating device for all workpiece receiving stations of the heat station 13. The workpiece receiving stations are therefore not mutually thermally insulated in the case shown, but only the outer walls and the lockable outputs and inputs are thermally insulated. In modified embodiments, it is also possible to provide for each of the workpiece receiving stations 13a a separate heating device, which may be formed, for example, as an inductive or other type of heating device. In another modification, it is possible to form the heat station 13 only as a pure heat insulation station without a heated heating device. In such embodiments, it is advantageous if the walls of the heat station are then correspondingly strongly insulated, and then preferably the workpiece receiving stations can also be designed as individual heat insulation compartments be.

The third heat station 14 has only one workpiece receiving station 14a in the illustrated embodiment. This one is in the in Fig. 1 The workpiece 11 is heated to temperatures required for the subsequent hot forming process, or preferably to various suitable temperatures, in sections, by heating means 14e, 14e 'and 14e dimensioned such that the temperature is separately adjustable or regulated, so that in the workpiece 11 temperature zones are formed. In this way it is possible to form different crystal structures in the workpiece, for example austenitic and non-austenitic regions, so that the workpiece can have hardened and ductile regions after cooling. Austenite refers to γ mixed crystals of iron. The term austenite is also applied to other cubic face centered structures, such as shape memory alloys. Austenite is part of many stainless steels. The structure has a low hardness, but can be increased considerably by cold deformation. In the in Fig. 1 The final temperature of the second heater 14e 'is above the austenitizing temperature, the end temperatures of the other two heaters 14e and 14e "are below the austenitizing temperature, the austenitizing temperature being readable, for example, from the state diagram of the steel alloy from which the workpiece 11 is formed but can also be provided that the third heat station 14 has only one heat treatment device and no different zone heating is performed.

The heat devices 14e to 14e "of the third heat station are advantageously designed as inductive heating devices, so that as in the heating device of the first heat station 12 may be provided a short heating time.

The workpiece receiving station 14a of the third heat station 14 is penetrated by a guideway section 14f, which is likewise designed as a platform, and can receive a transporting carriage 16.

The third heat station 14 is arranged in the same way as the first heat station 12 on a lift 18, which is vertically movable on a supporting and guiding body 18t.

The transport trolleys 16 and the guideway sections 12f, 13f and 14f are subassemblies of a transfer device which is provided for the supply of a workpiece 11 from an upstream heat station or for the removal of a workpiece 11 to a downstream heat station, wherein a guideway can be formed from associated guideway sections of the heat stations is on which the trolley 16 are movable.

Downstream of the third heat station 14, a hot forming device 15 is arranged. The hot-forming device 15 is a hot pressing device with a pressing tool 15p. The transfer of the stored on the trolley 16 workpiece 11, for example, by a in Fig. 1 not shown industrial robot done. In the hot forming device 15, a press hardening takes place in the area of the workpiece 11 heated by the heating device 14e 'while the area of the workpiece 11 heated by the heating devices 14e and 14e remains ductile.The workpiece 11 described by way of example can advantageously be a component of a motor vehicle which can increase the safety of the vehicle against collision accidents Portions of said component may undergo highly plastic deformation upon overstress and therefore are able to absorb impact energy while the hardened portions contribute to stability.

The heat stations, the transfer device and the hot-forming device are advantageously provided with an in Fig. 1 not shown control device connected. The control device may advantageously be designed as a computer-controlled electronic control device which comprises at least all measuring and control components required for operating the heat treatment device 1, wherein a control program is stored in a computer which coordinates and monitors the interaction of said components.

The workpiece 11 is placed on an empty trolley 16, secured and the trolley 16 then retracted into the workpiece receiving station 12a of the first heat station 12. In preferred embodiments, a clamping of the workpieces is provided on the trolley. For loading an empty trolley 16 in the first heat station 12, an industrial robot or other suitable feeding and equipping device may be provided. When stationary on the workpiece receiving place 12a stagnant trolley 16, the workpiece 11 is now heated by the heater 12e within a predetermined, relatively short residence time in this heat station to a first temperature, which is preferably above 600 ° C. This residence time may be, for example, about 4 seconds.

During this residence time of the workpiece on the receiving space 12a in the first heating station, an empty workpiece receiving station 13a in the second heat station 13 is determined by the control unit and the first workpiece receiving station 12a of the first occupied by the workpiece 11 Heat station 12 is assigned by means of the lift 17 to said empty second workpiece receiving station 13a. In this case, the guide track section 12f of the first heat station is aligned with the guide track section 13f of the second heat station, so that the two guide track sections 12f, 13f form a jointly assembled guide track on which the transport carriage 16 can be moved.

After the predetermined residence time in the first heat station, the drive of the transfer device is now activated, which is connected to the trolley 16 so that the trolley 16 is transferred to the empty workpiece receiving station 13a of the second heat station. Once the trolley 16 has come to a standstill in the workpiece receiving station 13a and possibly detected, the measurement of the residence time in the second heat station 13 is started, which is at least as large as a minimum residence time in which the diffusion process is completed. This minimum residence time in the second heat station 13 is substantially greater than the residence time in the first heat station 12. It may be, for example, about 4 minutes.

In parallel with the described process sequence, the control unit may have determined a occupied workpiece receiving station 13a of the second heat station 13, wherein the second residence time is greater than the Mindestverweilzeit and the third heat treatment station 14 has been assigned by means of the lift 18 this occupied workpiece receiving space 13a by moving into the relevant position be. In this case, the guide track section 13f is aligned with the guide track section 14f, so that the two guide track sections 13f, 14f form a common guide track on which the transport carriage 16 can be moved from the second heat station 13 into the third heat station 14.

Then, the drive of the transfer device is activated, which is connected to the trolley 16 so that the trolley 16 to the empty Workpiece receiving station 14 a of the third heat station 14 is passed. Once the trolley 16 has come to a standstill in the workpiece receiving station 14a and detected, the measurement of the residence time in the third heat station 14 is started, which is predetermined to be substantially smaller than the minimum residence time in the second heat station 13. Advantageously, it may also be provided to dispense with the time measurement in the third heat station and to end the residence time in this heat station when all three temperatures desired in this heat station have been reached. The residence time in the third heat station may preferably be chosen to be on the order of the residence time in the first heat station, for example about 4 seconds.

Alternatively it can be provided that the workpiece receiving station 12a of the first heat station 12 is assigned to a occupied workpiece receiving station 13a of the second heat station 13 whose minimum dwell time is exceeded and that the empty workpiece receiving station 14a of the third heat station 14 is assigned to the occupied workpiece receiving station 13a of the second heat station 13. In this case, the guide track sections 12f to 14f form a guide track, wherein the transport carriage 16 arranged in the workpiece receiving station 12a displaces the transport carriage 16 arranged in the occupied workpiece receiving station 13a and pushes it into the empty workpiece receiving station 14a (see FIG Fig. 2 ). In an analogous manner can be moved with empty trolley 16, wherein two empty trolley 16 are moved in the reverse direction of displacement. In this case, the drive of the trolley can be very easily designed as a rack drive, threaded rod drive or trained with a pneumatic, hydraulic or electric linear drive push rod.

Fig. 3 shows a second embodiment with a heat treatment device 2, which like the heat treatment device 1 in Fig. 1 and 2 is formed, with the difference that, instead of a heat treatment line for heat treatment, it has two heat treatment lines, which are arranged parallel to each other. For a better understanding, the heat treatment apparatus 2 is shown in a schematic plan view.

The first heat treatment line is formed from the first heat station 12, the second heat station 13 and the third heat station 14, wherein the second heat station 13 has two workpiece receiving sites arranged side by side in each processing plane. The second heat treatment line is formed from a further first heat station 12 ', the second heat station 13 and a further third heat station 14', so that in comparison to the in FIG Fig. 1 and 2 shown first embodiment, twice as many workpieces 11 are heat treated in the same time. It can preferably be provided that a common hot-forming device, as described above, is connected downstream of both heat treatment lines with high capacity. But it can also be provided that each of the two heat treatment lines is followed by a hot forming device. As stated above, the residence times in the first heat station and in the third heat station are substantially smaller than the residence time in the second heat station. If, as stated above, the residence time in the second heating station is 4 minutes, ie 240 seconds, and the residence time in the first heating station is 4 seconds, the second residence time is 240/4 times, ie 80 times greater than the residence time in the first heat station. Consequently, the second heat station 13 must have at least 80 workpiece receiving stations 13a in order to operate in the same cycle as the first heat station 12. The second heat station 13 thus fulfills the function of a buffer memory, so that the longest cycle time is reduced to the cycle time of the first heat station 12 by parallel operation of the second heat station 13. For example, when the transfer time between adjacent heat stations is 6 seconds, only at least 240 / (4 + 6) = 24 work receiving places 13a are required to achieve the same effect.

In a preferred embodiment, the cycle time of the hot forming apparatus 15, the transfer time between the third heat station 14 and the hot forming apparatus 15, and the removal time of the finished component from the hot forming apparatus in total in relation to the residence time in the second heat station determine the number of workpiece receiving sites 13a required. Assuming that said sum of the cycle time of the hot working device 15 and the transfer time is 20 seconds, at least 240/20 = 12 work receiving places 13a are required.

In the two embodiments described above in connection with the figures, the second heat station 13 had workpiece receiving stations 13a arranged one above the other. But it is also possible that the second heat station 13 has juxtaposed workpiece receiving stations 13a, wherein instead of the lifts 17 and 18 horizontally operating transport means may be provided which assign the workpiece receiving positions each other.

LIST OF REFERENCE NUMBERS

1

Heat treatment device

11

workpiece

12, 12 '

first heat station

12a

first workpiece holder

12f

first guideway section

12e

first heating device

13, 13 '

second heat station

13a

second workpiece holder

13f

second guideway section

14, 14 '

third heat station

14e - 14e "

third heating devices

14f

third guideway section

15

Warmumformvorrichtung

15p

press tool

16

Dolly

17, 17 '

lift

17T, 17T '

Support and guide body

18, 18 '

lift

18t, 18t '

Support and guide body

Claims (15)

1. Heat treatment device (1), where required having a downstream hot forming device (15), for example a press, for metallic workpieces(11), preferably sheet metal parts of a vehicle body, comprising

   - a first heating station (12),

   - a downstream second heating station (13),

   - where required, one or several further downstream heating station(s) (14),

   - a transfer device to lead the workpieces (11) to and/or from the heating stations (12-14), and

   - a control device for the operation of the transfer device and/or the operation of the heating stations (12-14),
   wherein it is provided that,

   - the first heating station (12) is formed in such a way that the workpiece (11) taken into it or the workpieces (11) taken into it can each be heated to a predetermined temperature for the first heating station (12) within a predetermined dwell time for the first heating station (12),

   - the second heating station (13) has more workpiece intake spaces (13a) than the first heating station (12), and is formed in such a way that the workpieces (11) taken into it can each be heated to a predetermined temperature for the second heating station (13) within a predetermined dwell time for the second heating station (13), which is greater than the predetermined dwell time for the first heating station (12) and/or can be kept constant at this predetermined temperature, wherein the predetermined temperature for the second heating station (13) is approximately equal to or higher than the predetermined temperature for the first heating station (12),

   characterised in that,
   at least one of the heating stations (12-14) and/or the workpiece intake space (12a-14a) and/or the workpiece intake spaces (12a-14a) of at least one of the heating stations (12-14) can be adjusted in terms of position.
2. Device according to claim 1,
   characterised in that,
   a third heating station (14) is provided downstream of the second heating station (13), which has fewer workpiece intake spaces (14a) than the second heating station (13) and is formed in such a way that the workpiece (11) taken into it or the workpieces (11) taken into it can each be heated to a predetermined temperature for the third heating station within a predetermined dwell time for the third heating station (14), which is lower than the predetermined dwell time for the second heating station (13) and/or can be kept constant at this predetermined temperature, wherein this predetermined temperature is approximately equal to or higher than the predetermined temperature for the second heating station.
3. Device according to one of the preceding claims,
   characterised in that,
   the intake capacity of the second heating station (13) is n times greater than the intake capacity of the first or the third heating station (12, 14), wherein n ≥ 2.
4. Device according to one of the preceding claims,
   characterised in that,
   the third heating station (14) has a heating device(14e) for inductive heating of the workpiece (11).
5. Device according to one of the preceding claims,
   characterised in that,
   the third heating station (14) has two or more homogeneous or heterogeneous heating devices (14e) which generate two or more different predetermined temperatures for the third heating station (14)in different zones.
6. Heat treatment method for workpieces (11) to be hot formed with a heat treatment device (1, 2) having a first heating station (12), a second heating station (13) and a third heating station (14), preferably a heat treatment device according to one of claims 1 to 5,
   wherein it is provided that,
   the following method steps are performed cyclically:

   a) transfer of a workpiece (11) to the first heating station (12),

   b) heating the workpiece (11) to a predetermined temperature for the first heating station (12) for a predetermined dwell time for the first heating station (12),

   c) assigning the first heating station (12) which is adjustable in terms of position to a free second workpiece intake space (13a) of the second heating station (13),

   d) transferring the workpiece (11) to the second heating station (13) after the predetermined dwell time for the first heating station (12) has ended,

   e) heating the workpiece (11) to a predetermined temperature for the second heating station and maintaining this temperature;

   f) assigning the third heating station (14) which is adjustable in terms of position to an occupied second workpiece intake space (13a) of the second heating station (13), for which the dwell time is greater than or equal to the predetermined dwell time for the second heating station (13),

   g) transferring the workpiece (11) to the third heating station (14),

   h) heating the workpiece (11) to one or more predetermined temperature(s) for the third heating station (14),

   i) positioning the third heating station (14) in such a way that the workpiece (11) can be transferred to a hot forming device (15) which is arranged downstream, behind the third heating station (14),

   j) transferring the workpiece (11) to the hot forming device (15).
7. Heat treatment method according to claim 6,
   characterised in that,
   method steps b) to d) and e) to g) and h) to j) are carried out simultaneously.
8. Heat treatment method according to claim 6 or 7,
   characterised in that,
   in step b, the predetermined temperature of the first heating station (12) is a temperature which is required for the diffusion of a protective material applied on the workpiece (11).
9. Heat treatment method according to one of claims 6 to 8,
   characterised in that,
   in step h), at least two predetermined temperatures for the third heating station (14) are provided, wherein these two temperatures are assigned to different workpiece sections.
10. Heat treatment method according to one of claims 6 to 9,
    characterised in that,
    the predetermined temperature for the third heating station (14) or at least one of the predetermined temperatures for the third heating station (14) is higher than or equal to the austenitising temperature.
11. Heat treatment method according to claim 9 or 10,
    characterised in that,
    at least one of the predetermined temperatures for the third heating station (14) is lower than the austenitising temperature.
12. Heat treatment method according to one of claims 6 to 11,
    characterised in that,
    the predetermined dwell time for the second heating station (13) is at least equal to the time in which the diffusion process is completed.
13. Heat treatment process according to one of claims 6 to 12,
    characterised in that,
    the cycle time of the hot forming device (15) is greater than the predetermined dwell time for the first heating station (12) and/or the predetermined dwell time for the third heating station (14).
14. Heat treatment process according to one of claims 6 to 13,
    characterised in that,
    the cycle time of the hot forming device (15) is much smaller than the predetermined dwell time for the second heating station (13).
15. Heat treatment method of metallic workpieces to be hot formed (11), for example, sheet metal parts of a vehicle body, having the following steps:

    Step a: heating the workpiece (11) over a first period,

    Step b: keeping the workpiece warm (11) by means of heat insulation and/or heating to a temperature for the diffusion of the material of the surface coating into the workpiece over a second period,

    Step c: further heating of the workpiece (11) to a temperature which is equal to or higher than the austenitising temperature of the workpiece (11), and keeping the temperature at at least the austenitising temperature over a third period,

    wherein the duration of step a and the duration of step c are both shorter than the duration of step b and
    wherein workpieces (11) which undergo step a successively after one another or with a time overlap, then simultaneously i.e. at least overlapping, undergo step b and then successively undergo step c without a time overlap.

Images