EP2182082B2 - Method and device for tempering a steel sheet body - Google Patents

Description

The invention relates to a method and a device for tempering a steel sheet body.

For weight reduction, metal sheets or sheet metal parts made of high-strength steel alloys are used, for example, in automobile bodies, which allow for the same strength a design with lower sheet thickness. However, high-strength sheets sometimes do not have sufficient dimensional flexibility when cold-formed. Therefore, for forming workpieces made of high-strength metal sheets forming processes at elevated temperatures, ie hot forming processes, such as the so-called press hardening used. Here, the sheet metal plates to be reshaped are fully austenitized by heating to a temperature above A _c3 (so-called austenitization) and then placed in a pressing tool, formed (so-called hot forming) and cooled in the tool and hardened (so-called direct press hardening).

In industrial production practice, roller pass furnaces are used to heat the sheet steel body during austenitizing. In this case, the steel sheet body is placed in the oven and heated relatively slowly during the passage through the Rollenendurchlaüfofen. The residence time of the steel sheet body within the furnace is typically about 5 to 10 minutes.
After the steel sheet body has passed through the oven or was heated by other heating methods, this is immediately inserted into a pressing tool. Then the forming phase of the process is initiated, with the two halves of the tool being closed. By contact with the usually water-cooled tool comes during the rapid cooling of the steel sheet body. The closure of the tool halves must be before cooling. of the steel sheet body to the temperature of the martensitic microstructure transformation (about 400 ° C). After this forming step is completed, the formed component remains in the mold and is further quenched, thereby completing the induced martensitic microstructure transformation and achieving the final properties of the component.
The transport between the furnace and the pressing tool represents a fault-prone process step. Thus, the temperature of the sheet material can be limited control and control during transport, since the temporal and thermal conditions during the transfer of the steel plate body from the oven into a subsequent forming tool not exactly defined and can be safely reproduced. This can lead to uncontrollable changes in the properties of the sheet material and thus the Umformverhaltens.
Also, the sheet materials when they come out of the oven, a relatively high temperature. This leads to an increased wear on the forming tool. On the other hand, the cycle times required for the hot forming increase, since a relatively long period of time is necessary for the cooling of the sheet material in the tool to a temperature that allows the demoulding.

DE 10 2007 009 937 A1 describes a method for tempering a sheet steel body between austenitizing and hot working. Initially, a heating to a predetermined temperature. Subsequently, a cooling takes place through the contact of the steel plate body with two mutually parallel contact plates. Here, the cooling takes place as quickly as possible. If the sheet steel body has been cooled to the desired temperature, the contact plate is removed immediately.

Further describes DE 10 2007 009 937 A1 a device with mutually parallel contact plates and a closing device for varying the distance of the contact plates to each other.

The object of the invention is to provide a method and a device for tempering at least one steel sheet body between the austenitizing and the hot forming, by means of which the material properties of the sheet steel body can be adjusted exactly and homogeneously.

This object is achieved by a method having the features of patent claim 1. Advantageous embodiments of the method are realized in the subclaims 2-9. For the device, the object is solved by the features of claim 10. Advantageous embodiments of the device are realized in the dependent claims 11-13.

In the method according to the invention for tempering at least one steel sheet body between the austenitizing and the hot forming, the steel sheet body located at austenitizing temperature is fixed in position, at least one first contact plate is brought into contact with at least one first surface portion of the steel sheet body and at least one second contact plate with at least one second Surface portion of the steel sheet body brought into contact. The contact plates are flat substantially or completely formed according to the contour of the surface portions of the sheet steel body and arranged in the state of contacting with the sheet steel body substantially parallel to each other. At least one contact plate has during the contacting of the steel sheet body with respect to the steel sheet body lower temperature. The temperature in at least a portion of the at least one lower temperature contact plate is controlled by a temperature control device during contacting of the steel sheet body with the contact plates. The temperature control of the contact plate with a lower temperature is carried out by an at least one of the contact plates in connection standing as an inductive or conductive heat source formed energy source, wherein the at least one heat source is integrated in one of the contact plates.
Under a sheet steel body here are both single substantially planar-shaped sheets and steel blanks, as well as three-dimensionally shaped sheet metal parts made of steel and also components that are composed of several such sheets understood.

The austenitizing temperature is understood to mean the temperature above A _c3 at which the steel sheet body was austenitized.

By the contact of the contact plates with the steel sheet body is a rapid tempering, i. cooling from the austenitizing temperature to a lower temperature. If the steel sheet body is subsequently shaped in a hot forming process, this transformation takes place temporally according to the temperature control method according to the invention. This reduces the heat load on the forming tools and reduces the cycle times.

By means of the method according to the invention, it is possible to introduce a precisely defined temperature into the regions of the steel sheet body which are in contact with the contact surfaces. As a result, the material properties that arise as a result of the temperature control can be adjusted very precisely and homogeneously.

The method according to the invention can be used variably. In particular, the temperature which the contact plate has or on which the steel sheet body is brought, as well as the period of time for which the contact between contact plates and steel sheet body, can be chosen almost arbitrarily. Thus, it is possible to variably adapt the method according to the invention to the desired parameters of the temperature control and to the material to be treated.

The contact between sheet steel body and contact plates may be formed such that the contact plates and the sheet steel body touch directly. However, it may also be an intermediate layer, such as a contact agent, which improves the temperature balance between the contact plate and sheet steel body, be present.

It can be detected both between the contact plates at the same time only a sheet steel body and several steel sheet body.

The area associated with the contact plates surface portions can both extend over large parts of the sheet steel body or completely cover this and form only small, localized areas of the sheet steel body. If only locally limited areas are connected to the contact plates, a local thermal treatment of the steel sheet body can be carried out.

In a preferred embodiment of the method, a sheet metal plate made of a steel of composition 22MnB5 and having an AlSi10 coating as steel sheet body located at austenitizing temperature is fixed between a first contact plate and a second contact plate. The contact plates have a temperature between 400 ° C and 600 ° C. After the sheet steel body has been contacted by the contact plates for a period of, for example, 10 seconds to 120 seconds, it is placed in a forming tool and hot worked.

• Mindestens eine Kontaktplatte kann während der Kontaktierung eine Temperatur zwischen 300 °C und 800 °C, vorzugsweise zwischen 400 °C und 600 °C, besitzen.
• Die Kontaktplatten können auf den Stahlblechkörper gepresst werden. Dies hat den Vorteil, dass ein Kontakt zwischen Kontaktplatten und Metallkörper besonders sicher gewährleistet wird. Darüber hinaus ist dadurch eine Minimierung der Verzüge besonders wirkungsvoll möglich.
• Die Temperatur der mindestens einen Kontaktplatte mit höherer Temperatur kann vor und/oder während der Kontaktierung des Stahlblechkörpers mit den Kontaktplatten durch eine Temperaturregeleinrichtung geregelt werden.
• Die Temperatur der mindestens einen Kontaktplatte mit höherer Temperatur kann vor und/oder während der Kontaktierung des Stahlblechkörpers mit den Kontaktplatten durch eine Temperaturkontrolleinrichtung kontrolliert werden.
• Die Temperatur kann in mindestens einem Teilbereich der mindestens einen Kontaktplatte mit höherer Temperatur vor und/oder während der Kontaktierung des Stahlblechkörpers mit den Kontaktplatten durch eine Temperaturregeleinrichtung geregelt werden.
• Es kann in einem weiteren Verfahrensschritt mindestens eine Kontaktplatte entfernt werden. Dadurch wird es möglich, die Ausbildung des Temperaturprofils des Metallkörpers durch das Entfernen einer oder mehrerer Kontaktplatten zu beeinflussen.
• Mindestens eine der Kontaktplatten kann gekühlt werden. Durch die aktive Kühlung der Kontaktplatten kann die Temperatur des Stahlblechkörpers exakt gesteuert werden. Insbesondere kann dadurch die Abkühlgeschwindigkeit des Stahlblechkörpers genau eingestellt werden.
• Der Stahlblechkörper kann eine Schutzschicht, insbesondere ein Al-Si-Schutzschicht oder eine Zinkschutzschicht, aufweisen. Insbesondere können hochfeste, verzinkte Bleche und Blechformteile aus dem Karosseriebau eingesetzt werden. Bei derartigen Metallkörpern mit einer Zinkschicht verhindert der Kontakt zwischen Metallkörper und Kontaktplatte die Beschädigung bzw. Zerstörung der Zinkschicht.

Further advantageous embodiments of the method may have the following additional features:

• At least one contact plate may have a temperature between 300 ° C and 800 ° C, preferably between 400 ° C and 600 ° C, during the contacting.
• The contact plates can be pressed onto the sheet steel body. This has the advantage that a contact between contact plates and metal body is ensured particularly secure. In addition, thereby minimizing the delays is particularly effective possible.
• The temperature of the at least one contact plate with a higher temperature can before and / or during the contacting of the Steel sheet body are controlled by the contact plates by a temperature control device.
• The temperature of the at least one contact plate with a higher temperature can be controlled before and / or during the contacting of the sheet steel body with the contact plates by a temperature control device.
• The temperature can be regulated in at least a portion of the at least one contact plate with a higher temperature before and / or during the contacting of the sheet steel body with the contact plates by a temperature control device.
• It can be removed in a further process step, at least one contact plate. This makes it possible to influence the formation of the temperature profile of the metal body by removing one or more contact plates.
• At least one of the contact plates can be cooled. By actively cooling the contact plates, the temperature of the sheet steel body can be controlled exactly. In particular, this allows the cooling rate of the steel sheet body to be set accurately.
• The steel sheet body may have a protective layer, particularly an Al-Si protective layer or a zinc protective layer. In particular, high-strength, galvanized sheets and sheet metal parts can be used from the body shop. In such metal bodies with a zinc layer, the contact between metal body and contact plate prevents the damage or destruction of the zinc layer.

The device according to the invention is designed to carry out the method according to the invention and has a first surface formed contact plate, a second flat contact plate, which is arranged substantially parallel to the first contact plate, at least one inductive or conductive heat source for temperature control of the contact plates, which communicates with at least one of the contact plates, a closing device for varying the distance of the mutually parallel Contact plates and a temperature control device for controlling the temperature in at least a portion of the at least one contact plate with a lower temperature during the contacting of the steel sheet body with the contact plates. The at least one heat source is integrated in one of the contact plates.

• Die Vorrichtung kann eine Temperaturkontrolleinrichtung aufweisen.
• Die Kontaktplatten können aus einem Metall und/oder aus Keramik bestehen.
• Mindestens eine Kontaktplatte kann Kühlkanäle aufweisen.

Advantageous embodiments of the device may have the following additional features:

• The device may have a temperature control device.
• The contact plates may be made of a metal and / or ceramic.
• At least one contact plate may have cooling channels.

The contact plates can both be made of the same material as well as of different materials. Preferably, contact plates that are heated, made of a metallic material, such as steel.

Contact plates that are not heated may preferably be made of both metallic and non-metallic materials. In a particularly advantageous manner, contact plates that are not heated, made of an insulating material. This has the advantage that the heat loss is reduced.

The contact plates may have an insulating layer. Also, the heat loss can be reduced thereby.

Fig. 1

eine schematische Schnittdarstellung einer Ausführungsform des erfindungsgemäßen Verfahrens,

Fig. 2

eine schematische Schnittdarstellung einer weiteren Ausführungsform des erfindungsgemäßen Verfahrens,

Fig. 3a

eine schematische Schnittdarstellung eines ersten Verfahrensschrittes zu einer Temperierung der Kontaktplatten,

Fig. 3b

eine schematische Schnittdarstellung eines zweiten Verfahrensschrittes zu einer Anwendung der Kontaktplatten,

Fig. 3c

eine schematische Schnittdarstellung eines dritten Verfahrensschrittes zu einer Anwendung der Kontaktplatten.

The invention is further explained by means of embodiments in the drawing figures. Show it:

Fig. 1

a schematic sectional view of an embodiment of the method according to the invention,

Fig. 2

a schematic sectional view of another embodiment of the method according to the invention,

Fig. 3a

1 is a schematic sectional view of a first method step for tempering the contact plates;

Fig. 3b

FIG. 2 is a schematic sectional view of a second method step for using the contact plates. FIG.

Fig. 3c

a schematic sectional view of a third method step for an application of the contact plates.

Fig. 1 shows a schematic sectional view of an embodiment of the method according to the invention. The steel sheet body 1 has been brought by the displacement of the first contact plate 2 by means of the closing device 11 in the direction 4 with the first contact plate 2 in contact. A first surface portion 6 of the sheet steel body 1 is in communication with the first contact plate 2. The first surface section 6 lies on the upper side of the sheet metal and the second surface section 7 is located on the underside of the sheet metal.

In the in Fig. 1 illustrated embodiment, the first surface portion 6 and the second surface portion 7 correspond to a portion of the top or bottom of the flat sheet steel body 1. However, embodiments are also possible in which the first surface portion 6 and the second surface portion 7 of the entire bottom or the entire top of a flat sheet steel body 1 correspond.

In addition, the steel sheet body 1 has been brought into contact with the second contact plate 3. A second surface portion 7 is in communication with the second contact plate 3.

In this case, the contact plates 2, 3 are formed flat in accordance with the contour of the surface sections 6, 7 of the steel sheet body 1 and are arranged running parallel to one another in the state of contacting with the metal body 1.

In the embodiment according to Fig. 1 is varied by the closing device 11, the contact plate 2 in their distance from the contact plate 3. As a result, the moving apart and moving together of the contact plates 2.3 and thus the contacting of a steel sheet body 1 introduced between these is possible.

For contacting the contact plates 2,3 with the sheet steel body 1 but also differently constructed locking devices are suitable. Thus, either only one contact plate or several contact plates can be displaced.

The contacting can be designed such that the first contact plate 2 and the second contact plate 3 are brought into contact with the steel sheet body 1 simultaneously. But it can also first a contact plate. 2 be brought into contact with the sheet steel body 1 and only later, a second contact plate 3 added.

The second contact plate 3 is or was brought by an energy source 5 to a relative to the steel sheet body 1 lowered temperature. In other words, the contact plate 3 is brought to a temperature which is above room temperature but below the austenitizing temperature. Energy source 5 is understood below to mean any device that can be used to heat objects.

Not shown in the figures is a cooling device. This can either be mounted in the immediate vicinity of one or both of the contact plates 2, 3 or integrated in them. For example, 2.3 cooling channels can be introduced into one or both master clock plates. This allows the Dutchleitung of liquid or gaseous coolants through the contact plates 2,3, was to a particularly accurate cooling leads.

In interaction with the power source 5, the cooling device can thus regulate the temperature of the contact plates 2.3 particularly precisely.

The contact plates 2, 3 are arranged running parallel to one another. The second contact plate 3 has an insulation layer 8. Through this insulating layer 8, the heat or Kühfverlust can be reduced.

During the contacting of the contact plates 2, 3 with the steel sheet body 1, the temperature of the steel sheet body 1 can be kept constant. However, it is also possible to vary the temperature of the steel sheet body 1 in the course of contacting by the defined change in the temperatures of the contact plates 2.3. Thus, a very variable adaptation of the temperature-time curve is possible.

The temperature profile along a contact plate 2, 3 can be designed such that an almost constant temperature is established over the entire contact plate 2, 3. However, the contact plate 2, 3 can also be heated or cooled in such a way that regions with different temperatures form within the contact plate 2, 3. Thus, it becomes possible to realize different temperature-time profiles in different areas of the steel sheet body 1 and thus to achieve a selective and individually adapted to the application temperature application of individual portions of the surface portions 6 and 7 of the sheet steel body 1.

The first surface portion 6 brought into contact with the contact plates 2, 3 and the second surface portion 7 of the sheet steel body 1 may be the same size. However, they can also have different sizes (not shown).

On the contact plate 2, a temperature control device 9 and a temperature control device 10 may be attached. Furthermore, a temperature sensor element (not shown) may also be attached. This allows the measurement of the temperature of the steel sheet body 1 and / or the contact plates 2,3. The temperature measured in this way can serve, for example, as an input variable for the temperature control device 9 and / or the temperature control device 10, which controls and / or controls or controls the temperature-time profile of the thermal treatment. The temperature control device 9 can in this case control both the energy source 5 and the cooling device and thus ensure a particularly accurate temperature control of the contact plates 2.3 and thus the sheet steel body 1.

The method can also be configured such that a plurality of steel sheet bodies 1 are simultaneously brought into contact with at least one first and / or one at least one second contact plate simultaneously.

Fig. 2 shows a schematic sectional view of another embodiment of the method according to the invention. The steel sheet body 1 was brought by moving the first contact plate 2 with this and a second contact plate 3 in contact. In this case, the displacement of the two contact plates 2, 3 arranged parallel to one another takes place through the closing device 11. The first contact plate 2 is or has been brought to a temperature reduced relative to the steel sheet body by an energy source 5 and a cooling device (not shown). The second contact plate 3 is or was brought by a further energy source 5 and a further cooling device (not shown) to a relative to the steel sheet body elevated temperature. In this case, the first contact plate 2 and the second contact plate 3 can be brought by the energy sources 5 and the cooling devices both to the same temperature and to different temperatures.

Fig. 3a shows a schematic sectional view of a first process step to a temperature of the contact plates. The first contact plate 2 and the second contact plate 3 are brought into mutual contact with each other before contacting with the steel sheet body. Subsequently, the second contact plate 3 is heated by the power source 5 to a temperature which is above room temperature and below the Austenitisierungstemperatur. The temperature is subsequently transferred to the first contact plate 2 which is in contact with the second contact plate 3.

Fig. 3b shows a schematic sectional view of a second method step to an application of the contact plates, which conform to the in Fig. 3a followed by the process step. The first contact plate 2 and the second contact plate 3 are separated from each other. The steel sheet body 1 located at austenizing temperature is introduced between the separate contact plates 2, 3.

Fig. 3c shows a schematic sectional view of a third method step for an application of the contact plates 2 and 3, which conform to the in Fig. 3b followed by the process step. The first contact plate 2 and the second contact plate 3 were brought into contact with the steel sheet body 1 by closing the closing device 11. In this case, both the first contact plate 2 and the second contact plate 3 have a relation to the steel sheet body 1 lowered temperature.

LIST OF REFERENCE NUMBERS

1. 1 sheet steel body
2. 2 first contact plate
3. 3 second contact plate
4. 4 direction
5. 5 energy source
6. 6 First section of the area
7. 7 Second surface section
8. 8 insulation layer
9. 9 temperature control device
10. 10 temperature control device
11. 11 closing device

Claims (13)

1. Method for controlling the temperature of at least one steel sheet body between austenitization and hot forming,
   wherein

   - the steel sheet body (1) which is at austenitization temperature is fixed in position,

   - at least one first contact plate (2) is brought into contact with at least one first surface portion (6) of the steel sheet body (1),

   - at least one second contact plate (3) is brought into contact with at least one second surface portion (7) of the steel sheet body (1),

   - the contact plates (2, 3) have an areal form substantially or entirely corresponding to the contour of the surface portions (6, 7) of the steel sheet body (1), and are arranged extending substantially parallel to one another when in contact with the steel sheet body (1), and

   - at least one contact plate (2, 3) is at a lower temperature than the steel sheet body (1) when it makes contact with the steel sheet body (1),

   characterized in that:

   - the temperature in at least one partial region of the at least one contact plate (2, 3) at a lower temperature is controlled by a temperature controlling device (9) during contact between the steel sheet body (1) and the contact plates (2, 3), and

   - the temperature of the contact plate (2, 3) at a lower temperature is controlled by an energy source which is connected to at least one of the contact plates (2, 3) and is in the form of an inductive or conductive heat source (5), wherein the at least one heat source (5) is integrated in one of the contact plates (2, 3).
2. Method according to Claim 1, wherein, during contact, the at least one contact plate (2, 3) at a lower temperature is at a temperature of between 300°C and 800°C, preferably of between 400°C and 600°C.
3. Method according to either of the preceding claims, wherein the contact plates (2, 3) are pressed onto the steel sheet body (1).
4. Method according to one of the preceding claims, wherein the temperature in at least one partial region of the at least one contact plate (2, 3) at a lower temperature is controlled by a temperature monitoring device (10) before and/or during contact between the steel sheet body (1) and the contact plates (2, 3).
5. Method according to one of the preceding claims, wherein at least one contact plate (2, 3) is removed in a further method step.
6. Method according to one of the preceding claims, wherein the steel sheet body (1) is formed in an immediately following working step, and the at least one first surface portion (6) and second surface portion (7) lie in or in the vicinity of the region to be formed.
7. Method according to one of the preceding claims, wherein the at least one contact plate is cooled.
8. Method according to one of the preceding claims, wherein the steel sheet body (1) has a protective layer, in particular an Al-Si protective layer or a zinc protective layer.
9. Method according to one of the preceding claims, wherein the temperature of the contact plate at a lower temperature is controlled by the energy source which is connected to at least one of the contact plates (2, 3) and is in the form of an inductive or conductive heat source (5) and by a cooling apparatus.
10. Apparatus for carrying out the method according to one of the preceding claims, having

    - a first contact plate (2) formed in an areal manner,

    - a second contact plate (3) which is formed in an areal manner and is arranged substantially parallel to the first contact plate (2),

    - a closing apparatus (11) for varying the distance between the contact plates (2, 3) arranged parallel to one another,

    characterized by:

    - a temperature controlling device (9) for controlling the temperature in at least one partial region of the at least one contact plate (2, 3) at a lower temperature during contact between the steel sheet body (1) and the contact plates (2, 3), and

    at least one inductive or conductive heat source (5) for controlling the temperature of the contact plates (2, 3), which is connected to at least one of the contact plates (2, 3), wherein the at least one heat source (5) is integrated in one of the contact plates (2, 3).
11. Apparatus according to Claim 10, wherein the apparatus has a temperature monitoring device (10).
12. Apparatus according to either of Claims 10 and 11, wherein the contact plates (2, 3) consist of metal and/or of ceramic.
13. Apparatus according to one of Claims 10-12,
    wherein at least one of the contact plates has cooling ducts.

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