DE102009050997B4 - Method and forming device for producing a form-hardened component - Google Patents

Abstract

A method of producing a thermoformed component from a steel board, wherein a board (15) cut to predetermined dimensions is heated in a furnace (42) within a predetermined time to a predetermined temperature above an austenite transformation temperature Taust and then mold hardened in a tool (52) wherein the blank (15) is flexibly hot rolled (120) prior to die hardening of the blank (15, 70) to achieve setting of different thicknesses along the length of the blank (15, 70), wherein the flexible hot rolling ( 120) at a temperature in a range between 500 ° C and 950 °, and wherein a rolling device (44) is arranged immediately downstream of the furnace (42).

Description

The invention relates to a method and a shaping device for producing a form-hardened component from a steel circuit board as well as a form-hardened component and a body with at least one form-hardened component.

Methods for producing a shape-hardened component from a semifinished product or a steel circuit board are known. The board is hereby usually made of a hot-workable steel sheet, which is preferably cut from an endless belt with rolled-up radiation sheet, the coil. The dimensions of the board correspond approximately to the dimensions of the final component. The endless belt is here cut before forming into a circuit board, which is formed with a mold hardening tool to the component, in particular form hardened. The forming of the board takes place at a temperature which is above the austenite transformation temperature. By subsequent accelerated cooling, the component is cured. As a result, the component has a significantly increased strength. At the austenite transformation temperature, the austenite is converted from the austenite area on cooling. The transformation can be to perlite if the diffusion of iron and carbon is possible. A transformation to martensite takes place during a rapid cooling in which no diffusion processes can take place. Conversion in the middle temperature range can lead to bainite where the carbon can still diffuse, but austenite-ferrite transformation occurs after a folding process similar to martensite.

The DE 10 2005 041 741 A1 describes a method for producing a press-hardened component. In the method, a component is produced from a semifinished product of uncured, hot-forming steel, wherein the semifinished product is heated and press-hardened. Here, the forming speed is so high that the transformation process is completed by an austenitic to a martensitic or bainitic structure only after completion of the forming process.

The DE 10 2006 032 617 A1 relates to a method for producing a semi-finished sheet metal, which is suitable for molding. A component is produced by means of form hardening, wherein the sheet semifinished product is coated before the form hardening.

The DE 10 2007 013 739 B3 describes a method for flexible rolling of steel strips, in which the steel strip is cut into individual boards after flexible rolling and then heated to austenitizing temperature and formed. The rolling mill can be fed here hot or cold strip.

In practice, the technology of form hardening / press hardening is used in series production for the manufacture of body components. The form hardening enables the production of ultra-high strength body parts in the lightweight construction of the automotive industry. In these processes, the boards are heated in a roller hearth furnace to 950 ° C and then cooled in a tool. The form hardening is carried out in two alternative methods, direct and indirect. In the direct method, the board is heated after cutting in a continuous furnace and the indirect method, the board is preformed after cutting in a press and then heated.

The direct hot forming process involves several consecutive production steps. The material is delivered directly to the steel suppliers in coils and cut to the required dimensions in a blanking center. Thereafter, the material is transported to the form hardening lines and stored in special containers. The hardening furnace is equipped with several robots with blanks. The boards are heated in the continuous furnace to 950 ° C in a fixed time. Thereafter, the boards are placed with a robot in a hot forming tool and reshaped. Subsequently, the shelf of the board is placed in special containers. In the indirect process, the boards are preformed before heating. The illustrated methods use boards of constant thickness.

The demands placed on automobile manufacturers in the field of lightweight construction have increased dramatically in recent years and will continue to increase in the near future. This includes on the one hand a determination to reduce CO ₂ emissions and on the other hand a demand for increasing the crash safety of the vehicle and increasing the safety of passers-by. In order to meet these requirements, alternative production concepts are being developed, including the production of body components for Taylored Rolled Blanks vehicles. Taylored Rolled Blanks are based on the original idea of Taylored Blanks. Taylored blanks are customized sheet metal blanks made up of two or more blanks of varying thickness, mechanical properties and surface finishes. The notations Tailored Rolled Blank and Taylored Rolled Blank are equivalent. The individual sheet metal blanks are usually connected to each other by laser welding. These custom-made boards can easily be conventionally reshaped in subsequent finishing steps. Furthermore, the Taylored Blanks used as hot-formed body parts as standard. The purpose of using the Taylored Blanks is to design the bodywork components according to their individual requirements in order to meet the above requirements in the best possible way. Taylored Rolled Blanks are specially made custom-made blanks which have varying sheet thicknesses in the rolling direction of the sheet metal strip. The production of such sheet metal blanks takes place in a cold rolling process, the flexible rolling. In this case, the sheet metal strip coming from the coil is cold-rolled again and adjusted at regular intervals, the required sheet thickness of the board. The sheet thickness distribution as well as the material selection takes place after agreement with the customer. The dimensions of the blanks can be adjusted according to the needs of the supplier after consultation with the supplier. These are cut to size immediately after rolling. By integrating special control and software, this manufacturing concept can be realized in the industry. The sheet thickness is monitored by a special measuring system. The advantages of this method are that the entire welding process is eliminated, as well as a homogeneous transition between areas with different thicknesses arises. Custom tailored properties of Taylored Rolled Blanks include corrosion resistance, crash safety, and weight reduction of manufactured components. The disadvantage of this production strategy, however, is the dependence on upstream production and delivery processes.

It is the object of the present invention to provide an improved method for producing a shape-hardened component. Furthermore, it is the object of the invention to provide a device with which a form-hardened component can be produced. In particular, it is the object to provide a method and / or a device in which and / or the components can be produced with optimized thickness distribution.

The object is achieved by the features of the independent claims. Advantageous developments of the invention can be found in the features of the dependent claims.

In the method according to the invention for producing a form-hardened component from a steel blank, it is provided that a blank cut to predetermined dimensions is heated in a furnace within a predetermined time to a predetermined temperature above an austenite transformation temperature T _aust and then mold-hardened in a mold, wherein the board is flexible-hot-rolled prior to die-setting of the board to achieve adjustment of different thicknesses along the length of the board, the flexible-hot-rolling at a temperature of between 500 ° C and 950 ° C, and wherein a rolling device is used Furnace is immediately downstream.

The dimensions of the board correspond essentially to the dimensions of the finished component. The steel may be a high-strength steel, in particular a boron-manganese-steel alloy. Preferably, the steel is a 22MnB5 material. The hot forming of the board takes place at a temperature which is suitable for allowing shaping of a sheet in a forming tool, in particular a press. The temperature is above the Austenisierungstemperatur T _aust for the steel alloy. Depending on the steel grade, the austenitizing temperature T _aust can vary between 700 ° C and 1100 ° C. The tool is preferably water-cooled, so that during or after the conversion of the board cooling of the component can take place. By cooling, a microstructure can form in which the component has a high hardness. The forming of the board can be done directly in a forming step or indirectly in two steps. The board is heated to the required temperature in an oven and passed through a flexible rolling apparatus in the tool prior to mold hardening to achieve adjustment of different thicknesses along the length of the board. The device for flexible hot rolling may be formed in a conventional manner, such as in the EP 1 074 317 B1 the entire contents of which are incorporated by reference into the disclosure of the present document. In flexible hot rolling, a nip can be selectively changed during rolling. The setting data for the rolls can be determined before the actual rolling process according to the requirements of the finished component and the rolling device can be controlled accordingly. In contrast to the prior art, the flexible rolling according to the invention takes place in the heated state of the board. The flexible hot rolling at a temperature below the austenite transformation temperature T _aust and above the ferrite transformation temperature T _fer is therefore referred to as flexible hot rolling.

Advantageously, the flexible hot rolling can be carried out with lower rolling forces than during cold rolling, since the sheet is softer due to the high temperature. In this case, bending of the rolls due to excessive roll forces can advantageously be avoided.

Advantageously, a Taylored Rolled Blank is thus produced after heating and before the form hardening of the board. Because the thickness of the sheet from which the components are molded is simple and can be set exactly, in each case the thickness of the component can be reduced in total or in areas and so the material consumption can be reduced overall. Thus, the weight of the component can be optimized. In addition, for a component to an expected requirement, such as a loading zone will be discussed. The stress zones in the component are designed to be stronger, so have a higher material thickness, and the unloaded zones can be made thinner, so have a lower material thickness.

In summary, the process of producing the form-hardened part can be described as follows: the material is delivered in steel strips called coils by a steel supplier and cut to the required dimensions in a blanking center. Thereafter, the cut blanks are transported to the Formhärtlinie having the mold hardening tool, and stored in special containers. A robot can equip the oven, which is also known as a form hardening oven, with the blanks. The blanks then pass through the furnace for a defined time, preferably a continuous furnace, preferably a roller hearth furnace, at a temperature of about 950 ° C. In the subsequent process of flexible hot rolling above a temperature of 500 ° C., the thickness of the board is adjusted. A downstream transfer system places the rolled board in the tool. Thereafter, the pressing of the board to the final component geometry can be done.

Preferably, a thickness adjustment of the board takes place first by means of a first roller and subsequently by means of at least one second roller with a different orientation of the first roller from the alignment of the second roller. In this case, the rolling is preferably carried out such that a thickness adjustment of the board takes place first in a first direction and subsequently in a second direction different from the first direction. In this case, flexible geometry variants are adjustable, which ensure optimum adaptation of the component to the required requirements. Here, the roll adjustment is preferably controlled and regulated automatically. The roll adjustment can be done periodically.

In a further preferred embodiment of the method, the board is tempered during the flexible hot rolling to keep the board at a temperature of 500 ° C to 950˚C. Furthermore, a transport of the flexible hot-rolled blank after the rolling step by means of a transport system or transfer system can be performed in the forming tool. The conveyor belt here is preferably a heated conveyor belt and has a heating device to keep the board at a temperature of 500 ° C to 950˚C.

A monitoring and control of the board thickness is preferably carried out during the flexible hot rolling, for example by an automatic control system. A measuring system can detect the thickness of the board and based thereon the rolling process can be controlled accordingly, preferably a roll gap.

The object is further achieved by a form-hardened component which is produced by means of the method according to the invention.

The object is further achieved by a body of a motor vehicle with at least one form-hardened component, wherein the component is produced by the method according to the invention.

The advantages of the component and the body essentially correspond to those of the method according to the invention, since the thickness of the sheet from which the components are formed, can be easily and accurately adjusted, in each case the thickness of the component can be reduced and thus the material consumption can be reduced ,

The object is further achieved by a forming apparatus having a furnace for heating a blank cut to predetermined dimensions within a predetermined time to a predetermined temperature above an austenite transformation temperature and having a mold hardening tool for curing between the furnace and the mold hardening tool a rolling device is arranged for flexible hot rolling, and wherein the device is adapted to flexibly hot roll the board at a temperature between 500 ° C and 950 ° C.

The advantages of the forming device correspond to those of the method according to the invention.

Advantageous developments and refinements of the method and the device for producing a form-hardened component from a steel circuit board can be taken from the dependent claims.

The invention will be described in more detail with reference to the figures of the drawing, from which, regardless of the summary in the claims further features, details and advantages of the invention.

In the figures, the same or similar objects or parts are provided with the same reference numerals.

Show it:

1 an apparatus for performing a direct mold hardening process according to the prior art;

2 an apparatus for performing an indirect mold hardening method according to the prior art;

3 a forming apparatus for performing a mold-hardening process with integrated rolling process;

4 a schematic representation of the rolling process, in particular the sheet thickness adjustment before forming;

5 a flow diagram of a method for producing a three-dimensional component.

1 shows a schematic representation of a device 10 for producing a shape-hardened component according to the prior art. The device 10 has a blanking device or cutting press 12 , An institution 14 for heating a circuit board 15 , one of the heating device 14 directly downstream hydraulic press 16 on. After the press 16 is a laser cutting device 18 arranged. The board 15 is also available as a semi-finished product 15 designated. In the board cutting device 12 becomes an endless band 20 that also as a coil 20 is called, inserted. The steel band in the endless band 20 includes a thermosetting steel. The device 10 is set up that a direct mold hardening process can be carried out. In the form hardening process of the steel, the forming takes place in a forming process in the heated state. Thereafter, the component is cooled quickly, thereby achieving a cure.

2 shows a device 22 containing a board cutting device 12 , a pre-forming press 24 , a continuous furnace 26 , a hydraulic press 28 and a laser cutter 30 and a storage device 32 having for the manufactured components. Between the facilities for processing the semi-finished product 15 are robots 34 . 36 . 38 arranged to perform the transfer from one device to another arranged after this device.

3 shows a forming device 40 for the production of form-hardened components according to the invention. The forming device 40 has a stove 42 in which a board (not shown) is heated to a temperature suitable for forming. In this case, the boards preferably have predetermined dimensions. This temperature is in particular above the austenite transformation temperature T _{aust of} the steel from which the board 15 consists. The temperature is preferably about 950 ° C. The temperature is also referred to as austenitizing temperature. The oven 42 immediately downstream is a rolling device 44 in which the heated board 15 can be flexibly hot-rolled. The rolling device 44 has a controller 46 and a measuring device 48 for thickness measurement of the rolled board. In the transport direction of the device 40 after the rolling device 46 For example, a circuit board may be provided which has areas of different thicknesses. By means of a transfer system 50 The rolled board is in the heated state in a press 52 transferred. The press 52 may preferably be a hydraulic press. The press 52 is a sinker device 53 downstream. The board depositing device 53 serves the intermediate storage of the form-hardened component or the form-hardened components, before assembly takes place in a mounting device (not shown) to a body of a motor vehicle.

The rolling device 44 is set up according to one in the control 46 fed setpoint and by the measuring device 48 determined measured value of the board thickness to set a nip. The nip may be formed by a distance of two rolls or a distance between a roll and a solid support. The measuring device 48 In particular, it comprises a board monitoring device with a special measuring system. The roll adjustment is preferably controlled automatically and the roll gap is preferably set to a nominal size.

The in the forming device 40 fed boards 15 in this case preferably have a uniform thickness and are in the forming device 40 prior to forming into Taylored Rolled Blanks with areas of different thickness flexible-hot rolled.

4 shows a schematic representation of a rolling device 44 out 3 in detail. The board 15 is on a transport device 54 arranged. The transport device 54 preferably has a heatable transport unit 56 on. The rolling device 44 has a first roller 58 and at least one second roller 60 on. The first roller 58 and the at least second roller 60 are in the direction of the transport movement, each with an arrow 62 is designated, arranged one behind the other. The arrow 62 denotes the direction of movement of the transport of the boards 15 , The board 15 designates the board, as seen from the oven 42 is delivered heated. The oven 42 is only schematic at the beginning 64 represented the process line. The board after the first rolling step 66 is with the reference number 68 designated.

Further shows 4 a circuit board 70 . 15 that in a first direction 72 and then in a second, different from the first direction 74 was rolled.

• – Schritt 110: Erwärmen einer auf vorgegebene Abmessungen zugeschnittenen Platine in einem Ofen, der eingerichtet ist, eine Temperatur oberhalb der Austenitumwandlungstemperatur T_aust, insbesondere von oberhalb ungefähr 950˚ C, einzustellen;
• – Schritt 120: flexibel-Warmwalzen der erwärmten Platine 15, bei einer Temperatur, die größer ist als die Ferritumwandlungstemperatur T_fer und niedriger ist als die Austenitumwandlungstemperatur T_aust, die zwischen 500˚ C–950˚ C liegt,
• – Schritt 130: Umformen der erwärmten und flexibel-warmgewalzten Platine 70 zu einem formgehärteten Bauteil.

In summary, the inventive method 100 in 5 and shows the steps:

• - Step 110 By heating a blank cut to predetermined dimensions in an oven adapted to set a temperature above the austenite transformation temperature T _aust , in particular above about 950 ° C;
• - Step 120 : flexible hot rolling of the heated board 15 , at a temperature greater than the ferrite transformation temperature T _fer and lower than the austenite transformation temperature T _aust , which is between 500˚ C-950˚ C,
• - Step 130 : Forming the heated and flexible hot-rolled blank 70 to a form hardened component.

The features described in connection with the method and the device can be used alone or in combination. Thus, features described in connection with the method may also be applicable to the device and vice versa.

Claims (11)

Method for producing a molded-hardened component from a steel circuit board, wherein a circuit board cut to predetermined dimensions ( 15 ) in an oven ( 42 ) within a predetermined time to a predetermined temperature above an austenite transformation temperature T _aust heated and in a tool ( 52 ) is then shape hardened, wherein the board ( 15 ) before molding the board ( 15 . 70 ) flexible-hot rolled ( 120 ) is used to set different thicknesses along the length of the board ( 15 . 70 ), wherein the flexible-hot rolling ( 120 ) at a temperature in a range between 500 ° C and 950 ° and wherein a rolling device ( 44 ) the oven ( 42 ) is immediately downstream. Method according to claim 1, characterized in that a thickness adjustment of the board ( 15 . 70 ) first by means of a first roller ( 58 ) and subsequently by means of at least one second roller ( 60 ), with one of an orientation of the first roller ( 58 ) different orientation of the second roller ( 60 ) he follows. Method according to one of the preceding claims, characterized in that the board ( 15 . 70 ) during flexible hot rolling ( 120 ) is tempered. Method according to one of the preceding claims, characterized in that during the flexible hot rolling ( 120 ) monitoring and / or regulating the thickness of the board ( 15 . 70 ) he follows. Method according to one of the preceding claims, characterized in that the heating of the board ( 15 ) to the temperature T _aust in a continuous furnace ( 42 ) he follows. Method according to one of the preceding claims, characterized in that after the flexible hot rolling ( 120 ) and before hardening ( 130 ) from the board ( 15 ) a Taylored Rolled Blank ( 70 ) will be produced.  A shape-hardened component produced by a method according to any one of claims 1 to 6.  Body of a motor vehicle, which comprises at least one form-hardened component according to claim 7. Forming device for producing a form-hardened component from a steel circuit board with a furnace ( 42 ) to a board cut to specified dimensions ( 15 ) within a predetermined time to a predetermined temperature above an austenite transformation temperature T _aust and a mold hardening tool ( 52 ) for shape hardening ( 130 ), characterized in that between the furnace ( 42 ) and the mold-hardening tool ( 52 ) a rolling device ( 44 ) for flexible hot rolling ( 120 ), wherein the device is set up, the circuit board ( 15 ) at a temperature between 500 ° C and 950 ° C flexible hot roll. Forming device according to claim 9, characterized in that the rolling device ( 44 ) with a first roller ( 58 ) and subsequently in the transport direction of the board with at least one second roller ( 60 ), with one of an orientation of the first roller ( 58 ) different orientation of the second roller ( 60 ) Is provided. Forming device according to claim 9 or 10, characterized in that a heatable transport device ( 54 ) for at least temporary tempering of the boards ( 15 . 70 ) during flexible hot rolling ( 120 ) is provided.

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