EP1888794B1 - Method for producing a metallic component comprising adjacent sections having different material properties - Google Patents

Abstract

The invention relates to a method for producing a metallic component (B), whereby adjacent regions (Z1, Z2, Z3) having different material properties can be produced on the metallic component (B) in a simple manner. According to said method, a sheet metal element (E) heated to a forming temperature is shaped in a form tool (1) into an end component (B). The form tool (1) comprises a tempering device for regulating the temperature of at least one of the sections (5,7,16) thereof that comes into contact with the sheet metal element (E) during the forming process. The forming speed is controlled in such a way that the component regions with the desired increased hardness come into contact with the cooled form tool faster than adjacent regions with the desired reduced hardness. The invention is especially suitable for shaping sheet metal elements of different thicknesses that are interconnected with a material fit (tailored blanks).

Description

The invention relates to a method for producing a metal component with adjoining sections of different material properties.

In practice, methods of this type are used to produce by press hardening, for example, manganese-boron steels components that have a uniform hardness profile of up to 1,500 MPa. Due to their low ductility remaining after the hardening process, components made of such steels are usually first preformed, then heated to austenitizing temperature and then rapidly cooled in a mold under high pressure. The parts obtained in this way, in addition to their high hardness on a good dimensional stability.

A method for producing a metal component, such as a safety strut for vehicle doors, with adjacent zones of different material properties, for example, from DE 197 23 655 A1 known. In this method, a heated to a forming temperature sheet metal element is formed in a forming tool into a final molded component, wherein the forming a tempering device for adjusting the temperature of at least one of his during forming with the sheet metal element coming into contact Sections has in the form of ceramic inserts that delay the cooling of their contacting section, in the form of recesses that reduce the cooling effect or in the form of induction elements with which the respective section can be actively heated so that in the course of Cooling in the respective areas no hardness structure sets. The forming itself should also be as fast as possible in this known method, so that the workpiece does not harden during the deformation. The sheet metal part, which is rapidly formed in this way, subsequently remains in the cooled forming tool, so that it is cured only in the already completely deformed state.

The Indian DE 24 52 486 A1 The prior art described has encouraged the person skilled in the art to carry out the forming process in such a way that it is completed before hardening structure has formed.

From the DE 100 49 660 It is also known that a patched composite sheet can be hot formed and defined cooled. As essential for the provided with a brazing composite sheet is considered a uniform cooling. This uniformity is to be achieved by cooling in two stages, with forced cooling to a target temperature of 500 ° C., in order to maintain a solidification point of the brazing alloy and thus the joining of the two sheets.

An example of the type of the above-mentioned prior art counting method for press hardening is, for example, from DE 103 41 867 A1 known. According to this method can be a hardened sheet metal profile in that first an intermediate shape is formed from a sheet metal blank, this sheet metal profile is then heated to hardening temperature and that the heated sheet metal profile is finally selectively cooled in a device similar to a deep drawing tool under the action of a predetermined pressure. The intermediate form produced in the first step of the method already corresponds approximately to the final shape of the component to be produced.

The device used for carrying out the known method has channel-like cooling arrangements, which, depending on the heat to be dissipated, are flushed through by oil, water, ice-water or saline solution. The cooling arrangements can be controlled separately from each other to form zones with mutually different degrees of hardness on the finished component.

In spite of this way with the example from the DE 103 41 867 A1 Advantages achieved by known methods, there is the requirement for a manufacturing technology simplified feasible method that allows you to produce molded from a sheet metal elements components with exact pre-definable zones of different material properties.

In order to meet this requirement, the invention proposes a method for producing a metal component designed according to claim 1.

According to the invention, in addition to the from DE 103 41 867 A1 or the DE 197 23 655 A1 known measures for producing a finished component with zones of different material properties, such as strength or deformability, the speed with which the deformation of the respectively processed sheet metal element is carried out in its final shape, adjusted so that with the tempered area of the tool, which have a relation to the adjacent sections different temperature within an optimal time for the desired work result with time the separately treated zones of the sheet metal element come into contact and that this contact is maintained under consideration of the other general forming conditions over an equally optimal period of time. In this way, with the method according to the invention, within a process time reduced to a minimum, a sheet-metal component can be produced which has precisely determined zones with different material properties compared to its other sections.

If, according to the invention, a zone of higher hardness than in the environment is to be produced on the finished component, the sheet metal element can be heated to a forming temperature according to the invention, from which it starts with a correspondingly rapid cooling to form hardened structures. In this case, the tempering device is designed as a cooling device, which cools its respectively assigned section of the forming tool to such a low temperature that the zone of the sheet metal element in contact with this cooled section is quenched with a speed sufficient for the formation of the desired hardened structure.

Conversely, however, it is also possible to form zones on the finished component which have a lower hardness than their surroundings. For this purpose, the invention provided tempering be designed as a heater that holds the portion of the tool that is associated with the less hard zone of the finished sheet metal component at such a high temperature that is maintained at a contact of the sheet with this section, a relatively soft structure.

If a plurality of tempering devices are present, then specifically cooled and heated sections of the tool can be arranged closely adjacent to one another with the aim of minimizing the spread of areas with undefined mixed structures at the transition between a zone of high hardness and its adjacent surroundings in the finished sheet metal part and thus to produce perfectly precisely defined zones with different material properties in the finished component.

The inventively provided coupling of the forming speed of the position and propagation of the generated in the finished component zones of different material properties is in this context of particular importance. Thus, in order to produce a particularly hard zone in the finished component, the forming speed can be selected according to the invention such that the zone in question comes into contact with the strongly cooled section of the tool as quickly as possible. Conversely, the forming speed is reduced, for example, when a particular zone of the component is to cool particularly slowly in order to produce a softer microstructure there.

The targeted expression of certain zones in which the finished sheet metal component special material properties can be additionally supported by the fact that during the forming on an edge region of the sheet metal element a controlled depending on the forming speed hold-down force is exercised.

Basically, all sheet metal elements made of metal materials are suitable for the application of the method according to the invention, the structure of which changes when heated or cooled. However, the method according to the invention can be used particularly advantageously for sheet metal elements which consist of steel. Especially with sheet metal elements made of steel material, the advantages of the invention can be used particularly targeted.

An embodiment of the invention which is particularly favorable from a production point of view is characterized in that the sheet metal element used as the starting material in the method according to the invention is a flat sheet metal blank. In this variant of the method according to the invention, unlike in the prior art, a not yet deformed, flat sheet metal part brought to the respective forming temperature, from which starting to be generated in the course of the subsequent forming process, locally different material properties of the sheet can be achieved. Subsequently, the heated sheet metal element is finished, for example, finished in the form of a deep-drawing process in the forming tool. At the same time the targeted, locally limited cooling or heating treatment of the zones of the sheet metal element in which the special properties are to be generated takes place in the forming tool. As a result, while saving at least one complete, discussed at the beginning State of the art always required operation, namely the preforming, received from a sheet finished molded component, the precisely certain, locally limited areas with special, with respect to the adjacent areas of the finished component differing material properties, such as a higher hardness having.

A further advantage of the procedure according to the invention is that they are particularly suitable for processing sheet metal elements having regions of different thickness. Especially when forming such sheet metal elements, the invention allows the formation of the desired, localized zones with certain material properties, which allow the forming speed and the respective temperature of the tool to adapt to the non-uniform thickness of the sheet metal element, that an optimal work result is obtained. This has a particularly advantageous effect when the sheet metal element is composed of different, materially joined together, in particular by welding, sheet metal pieces. Such sheet metal elements are commonly referred to as "tailored blanks". They are composed, for example, of pieces of sheet metal whose thickness or material properties, such as hardness and toughness, are adapted to the stresses to which the product produced from the tailored blank is exposed in practical use.

The forming tool can be any type of tool which, taking into account the respective shaping of the component to be produced, is suitable for exerting the required forming and pressing forces on the respective deformed sheet metal element. Suitable for this purpose In particular, such forming tools, which have a die and an adjustable for forming in the die stamp.

The inventive method is particularly suitable for the production of body parts that are exposed to changing loads in practical use. Thus, in the manner according to the invention, spring strut receptacles can be produced particularly well, in which, for example, high strengths are required in the region of the strut tower, while higher extensibilities are required in the region of the flanks of the receptacles. By means of the invention, a purely martensitic, particularly firm structure can be specifically produced in the region of the spring strut dome by rapidly cooling this region during the forming process according to the invention and at a high cooling rate. By a time-delayed contact of the tool with the other parts of the shock absorber receiving a bainitic, pearlitic, ferritic or a mixed structure can be generated there just as well that optimally satisfies the demands placed on the respectively required extensibility or strength.

Another particularly advantageous application of the method according to the invention is the production of crash-relevant vehicle components which, in the event of a collision, must have a high energy absorption capacity and at the same time optimum strength. In this case, the invention makes it possible by targeted heating of the forming tool in certain sections in the finished component to form zones in which particularly high residual strains are ensured.

Fig. 1

ein Umformwerkzeug in einer ersten Betriebsstellung in einer Schnittansicht;

Fig. 2

das Umformwerkzeug in einer zweiten Betriebsstellung in einer Schnittansicht;

Fig. 3

das Umformwerkzeug in einer dritten Betriebsstellung in einer Schnittansicht;

Fig. 4

das Umformwerkzeug in einer vierten Betriebsstellung in einer Schnittansicht;

Fig. 5

ein in dem Umformwerkzeug erzeugtes Bauteil.

The invention will be explained in more detail with reference to a drawing illustrating an exemplary embodiment. Each show schematically:

Fig. 1

a forming tool in a first operating position in a sectional view;

Fig. 2

the forming tool in a second operating position in a sectional view;

Fig. 3

the forming tool in a third operating position in a sectional view;

Fig. 4

the forming tool in a fourth operating position in a sectional view;

Fig. 5

a component produced in the forming tool.

The forming tool 1 is designed in the manner of a deep-drawing device and has a stationarily arranged die 2. In the die 2, a recess 3 is formed, which images the outer shape of the produced, forming a profile component B.

In addition, the forming tool 1 comprises a punch 4, which determines the inner shape of the component B to be produced. The punch 4 can by means of an adjusting device, not shown, from a remote from the die 2 starting position ( Fig. 1 ) are moved into its end position in which it is fully retracted into the recess 3 of the die 2 ( Fig. 3 ). The adjusting device comprises a control device that the Speed at which the punch 4 enters the recess 3 of the die 2, controlled.

The punch 4 has a trapezoidal in cross-section basic shape with an end face 5 and obliquely to the end face 5 tapered side surfaces 6,7. The stamp 4 is carried by an integrally connected thereto carrier 8, the lateral edge portions 9,10 are in the manner of a collar laterally beyond the side surfaces 6,7 of the punch 4 at the upper edge. The lower edge surfaces 11,12 of the edge regions 9,10 are connected in a horizontal orientation to the side surfaces 6,7 of the punch 4.

In the forming tool 1 planar, not preformed sheet metal elements E are processed in the embodiment described here, which are in the manner of tailored blanks of two welded together, consisting of a steel material sheet metal parts T1, T2 assembled. The first sheet metal part 1 is thinner than the second sheet metal part T2 for weight savings.

In the area of his first entering into the recess 3 of the die 2 in contact with the sheet metal element E end face 5 cooling channels 13 are introduced into the stamp. The cooling channels 13 are part of a further not shown as a cooling device first tempering. Depending on the respectively required degree of cooling, the cooling channels 13 are traversed by water, ice-water, a frozen salt solution, liquid nitrogen or another cooling medium which is suitable for the rapid removal of large amounts of heat.

In the thicker sheet metal part T2 of the sheet metal element E associated transition region at which merges the one side surface 7 of the punch 4 in the adjacent lower edge surface 12 of the carrier 8, are in the stamp 4 heating coils 14 of a second, designed as a heater and further also not shown tempering.

Similarly, in the die 2 in the region of the side surface 15 of the recess 3, which is associated with the side surface 6 of the punch 4, channels 16 of a third tempering device is formed, which is also not shown here in detail further. Through the channels 16 of the tempering a cooling oil is promoted, which causes a moderate cooling of the die in this area.

To produce the component B, the sheet metal element E is first heated to austenitizing temperature in an oven, not shown here. Subsequently, the sheet metal element E is placed in the forming tool 1, so that it lies with its edge on the upper side of the die 2. If this is necessary for the further deformation of the sheet metal element E carried out in the forming tool 1, hold-downs, not shown, are now used, which hold down the sheet metal elements E in its edge region during the subsequent forming. The Nierdehaltekraft exerted by the holddown can be adjusted depending on the particular deformation rate, to allow an optimized Nachfießen the material of the sheet metal element 4 in the recess 3.

Then the punch 4 is placed on the sheet metal element 4 at a high speed, so that the strongly cooled end face 5 of the punch 4 quickly comes into intensive contact with its associated surface portion E1 of the sheet metal element E. The sheet metal element E is quenched in this way in its section E1 so fast that there forms a zone with a hardness which is higher than the hardness of the other, adjacent to the section E1 sections E2 and E3 of the sheet metal element E.

Subsequently, the feed of the punch 4 is reduced in order not to cause cooling, in particular in the sections E2 and E3, which could lead to the formation of hardened structures. In this case, in particular in the region of the heating coils 14, only a reduced heat dissipation via the punch 4 takes place, so that a softer, tougher structure is retained in the regions of the sheet metal element E which comes into contact with this region of the punch 4. In the areas which are cooled only moderately cooled side surfaces via the cooling oil flowing through the channels 16, in the deformation in the section E2 of the sheet metal element E forms a zone in which the hardened portion E1 gradually merges into a softer, more compliant zone of the finished component B.

After the punch 4 has fully retracted into the receptacle 3 of the die 2 and there pressed the sheet metal element 4 so finished that it has adopted the final shape of the manufactured component B, the punch moves 4 back to its original position. Due to the fact that the sheet metal element E has contracted as a result of cooling, the finished component B is still held on the punch 4, so that it can be easily removed from the die 2 and then separated from the punch 4.

The component B produced in this way by forming the sheet metal element E has a first zone Z1 with a hardness which is higher than the hardness of the adjacent zones Z2 and Z3 of the component B. The zone Z3 is followed by a zone Z4 of markedly lower hardness, however higher extensibility. This zone Z4 corresponds to the region of the sheet metal element E, which has been cooled during the forming in the region of the heating coils 14 only to a small extent. The zone Z2 corresponds to the region of the sheet metal element E, which has been cooled only moderately during the forming in the region of the side surface 15 of the die 2 and accordingly has an average hardness.

REFERENCE NUMBERS

1

forming tool

2

die

3

recess

4

stamp

5

Face of the punch 4

6.7

Side surfaces of the punch 4

8th

carrier

9.10

lateral edge regions of the carrier 8

11.12

lower edge surfaces of the edge regions 9,10

13

cooling channels

14

heating coils

15

Side surface of the recess 3

16

channels

B

component

e

sheet metal element

E1, E2, E3

Sections of the sheet metal element E

T1, T2

Sheet metal parts of the sheet metal element E

Z1, Z2, Z3, Z4

Zones of the component B

Claims (11)

1. Method for producing a metallic component (B) comprising adjoining zones (Z1, Z2, Z3) having differing material properties, in which a sheet metal element (E) heated to a forming temperature is shaped in a forming tool (1) into an end-shaped component (B), wherein the forming tool (1) has a temperature adjustment means for adjusting the temperature of at least one of the portions (5, 7, 16) thereof that comes into contact with the sheet metal element (E) during the forming process, characterised in that, in consideration of the time for which the portion (5, 7, 16) of the forming tool (1) that is regulated with regard to the temperature thereof is in contact with the respective region (E1, E2, E3) of the sheet metal element (E) that rests against said portion, the forming speed is controlled such that the properties of the component to be produced which differ in portions already result during the shaping process.
2. Method according to claim 1, characterised in that the sheet metal element (E) consists of steel.
3. Method according to either of the preceding claims, characterised in that the sheet metal element (E) is a flat sheet metal blank.
4. Method according to any one of the preceding claims, characterised in that the sheet metal element (E) has regions (T1, T2) of differing thickness.
5. Method according to any one of the preceding claims, characterised in that the sheet metal element is composed of different sheet metal parts (T1, T2) which are interconnected with a material fit.
6. Method according to any one of the preceding claims, characterised in that the forming temperature corresponds to a hardening temperature, starting from which a hardened structure forms during cooling in the sheet metal element (E).
7. Method according to any one of the preceding claims, characterised in that the forming tool (1) has a female mould (2) and a male mould (4) which can be positioned in a recess (3) in the female mould (2) for the purposes of shaping.
8. Method according to any one of the preceding claims, characterised in that the temperature adjustment means is a cooling means (13, 16).
9. Method according to any one of claims 1 to 7, characterised in that the temperature adjustment means is a heater (14).
10. Method according to any one of claims 1 to 7, characterised in that a cooling means (13, 16), as a temperature adjustment means, is associated with at least one portion (7) of the forming tool (1) and a heater (14), as a temperature adjustment means, is associated with at least one other portion of the shaping tool.
11. Method according to any one of the preceding claims, characterised in that a holding-down force regulated as a function of the forming speed is exerted on an edge region of the sheet metal element during shaping.

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