EP3212346B1 - Molding tool for producing hot-formed components - Google Patents

Description

The invention relates to a mold for the production of hot-formed components.

In today's automotive industry, the comfort for vehicle occupants is increasing, due to the use of special equipment. These include many electromechanical components such as sensors, motors, actuators, and serve to make the driving task easier for the driver. At the same time as the increase in comfort, however, the vehicle weight also increases. In order to counteract this, the prior art attempts to reduce the weight of the structural components of the body.

The structural components of the body are not only significantly involved in the stability of the vehicle, but also play a decisive role in safety in the event of a crash. In order to resolve this conflict of objectives between reducing the component weight of structural components while maintaining or realizing high mechanical parameters, it has proven successful in the past to produce structural components using hot forming. Hot forming processes are also described in the literature as form hardening or press hardening.

Two fundamentally different methods are known for the production of form-hardened components, in particular for the production of body components. In the direct hot forming process, a blank is first heated in a furnace to a temperature above the austenitizing temperature of the steel and then simultaneously shaped and cooled, ie hardened, in a tool. In the indirect hot-forming process, a blank is first produced from a blank by cold forming and then a trimmed and trimmed steel component. This is then in one Heating system heated to a temperature above the austenitizing temperature of the steel and then hardened in a mold by rapid cooling. In both hot-forming processes, the blank or a component that has already been formed and trimmed from steel is thermomechanically deformed in the tool after heating to the austenitizing temperature, thermomechanical shaping being preferred at a temperature above the final austinization temperature Ac3 (approx. 830 ° C.) between 900 and 1100 ° C. The formed workpieces are cooled by means of cooling, which is located in a closed tool body. As a result, components with particularly high mechanical properties, in particular with high strengths, can be produced.

The patent DE 19723655 B4 shows a process for the manufacture of steel sheet products by heating a measured steel sheet, thermoforming the steel sheet in a pair of tools, hardening the product formed by rapid cooling from an austenitic temperature while it is still held in the tool pair and then processing the product.

From the JP 2007-075834 A a mold for hot press molding a hot, metallic, smooth material is known, the strength of the molded product being controllable by means of a cooling device with a heat insulating device. The heat insulating filing has first recessed portions that are formed on the mold surface of the tool.

On the basis of this prior art, it is the object of the present invention to provide a molding tool for the production of components, in particular vehicle components made of sheet metal, in which particularly good mechanical characteristics are achieved and at the same time the component weight is reduced.

This object is achieved with a molding tool according to independent claim 1. Advantageous embodiments of the method are specified in the subclaims.

To achieve this object, the invention proposes a molding tool for the production of hot-formed components, in particular sheet metal parts before, with a lower tool part and an upper tool part, which are relatively movable relative to one another and which are designed with corresponding active surfaces for shaping the component, at least the active surface of a tool part being at least partially coolable and cooling lines being provided in the tool part. At least one recess can be provided in at least one of the two tool parts, which, when the tool is closed, forms an air chamber with the component, which acts as a thermal insulator between the component and the tool part. The object of the invention is based on the effect that a workpiece heated in a furnace to a temperature above AC3 is introduced between the tool parts and is hot-formed in the direct method, the workpiece being simultaneously geometrically shaped and thermally cooled. In the area of the workpiece to which the recess adjoins, a medium enclosed in the chamber serves as an insulator, so that the workpiece is thereby cooled more slowly in the area of the chamber than in the remaining areas of the component. This results in a structure with lower mechanical strength values in this area of the workpiece than in the rest of the component. Gases, for example inert gases or ambient air, are particularly suitable as the medium.

The recess is variable in volume. As a result, the amount of air in the chamber can be increased or reduced as required and the degree of insulation with respect to the cooled tool part can be varied. The higher the amount of air in the chamber, the higher the insulation.
An insert can be arranged in the tool part in which the recess is formed, which forms a tool-side rear wall of the air chamber. In other words: the insert has a surface section facing the component, which forms part of the wall of the recess.

Furthermore, the insert can be arranged to be movable, in particular linearly displaceable, in the tool part. Depending on the desired degree of insulation, the insert can be transferred to a corresponding position and the volume of the air chamber can be defined.

In addition, channels can be provided in the insert for temperature control of the insert. Use with a temperature-controlled medium, in particular with a gas or with a liquid, for example oil or water, is preferably set to a predetermined temperature. The medium is tempered in a heating and / or cooling device and passed through the channels of the insert. This has the advantage that the insert can be heated or cooled as required. As a result, the volume in the chamber can also be tempered, whereby desired mechanical properties can be set in certain areas of the sheet metal part.

The insert can be in a retracted position when the tool is closed, in order to produce the recess. A chamber filled with medium / air is then formed in this position. When the tool is open, the insert can be in an advanced position in which the volume of the recess is at least reduced compared to the volume of the recess in the retracted position of the insert. As a result, the air is optionally removed from the chamber after each shaping process or after a predetermined number of shaping processes and thereby prevents the air in the chamber from being excessively heated. The recess or the chamber is consequently regularly flushed with the medium / air. The hot forming process - and not least the structure in this area of the workpiece - is not affected.

In an alternative embodiment, the recess can be actively flushed using a control or regulation.

The sheet metal parts can be formed from ferrous metal, in particular from steel and / or from non-ferrous metal, in particular from aluminum and / or magnesium.

The cooling lines can conduct a coolant essentially parallel to a surface of the component. The coolant in the cooling lines, which can be gaseous or liquid, does not come into direct contact with the component. The thermal energy of the coolant in the cooling lines acts on the component or workpiece through the material of the tool part, which is in contact with the tool part during forming. Individual areas of the component or the workpiece can thus be cooled at different speeds or with different degrees of strength, and various mechanical properties can thereby be realized in the component.

In addition, the cooling lines can be supplied with coolant via a common supply system. This offers the advantage that a uniform temperature control or supply with coolant of the same temperature is ensured in all cooling lines.

In a further alternative embodiment of the molding tool, the active surface of the upper tool part and / or the active surface of the lower tool part can be designed to be coolable, at least in sections. Due to the small thickness of the sheet metal component, which is in the range of 0.5 to 5 mm, one-sided cooling is sufficient. However, in order to achieve particularly rapid and strong cooling, it can be advantageous to implement cooling on both sides.

The invention is explained in more detail below on the basis of the description of the figures. The description of the figures, the claims and the drawings contain features which a person skilled in the art would possibly also consider in a different combination in order to adapt them to corresponding applications of the invention.

It shows in a schematic representation
Fig. 1 a sectional view through a mold.

Fig. 1 shows a molding tool 10, which can be used in presses for the hot forming of tools, in particular sheet metal blanks to sheet metal components 17. The molding tool 10 has a lower tool half 12u, which is seated on a base plate 11. The lower mold half 12u interacts with an upper mold half 12o. The mutually facing active surfaces of the upper mold half 12o and the lower mold half 12u are designed correspondingly, so that they function like the die and punch of a press tool. At the in Fig. 1 In the example shown, the tool half 12o is designed as a stamp and the tool half 12u as a die. Without leaving the scope of the invention, in alternative embodiments, not shown, the upper and lower mold halves can be interchanged with respect to their arrangement, so that the upper tool acts as a die and the lower tool acts as a punch. The upper tool half 12o and the lower tool half 12u are relatively movable with respect to one another. In the Fig. 1 Shown mold halves 12o, 12u can be moved apart and moved together again. When the mold halves move together, a piece of sheet metal or a sheet metal plate gets between the mold halves and is encompassed and shaped by the active surfaces. The in Fig. 1 The state shown corresponds to an end position of the tool halves 12u, 12o during a forming process in which the component 17 is completely formed.

An insert 16 is shown in the upper tool half 12o and is movable along the double arrow B relative to the tool half 12o. The insert 16 is thus linearly displaceable in the direction of the component 17 and away from the component 17. In Figure 1 the insert 16 performs a linear movement essentially perpendicular to the component surface. Alternatively, however, a movement at an angle to the Component surface are carried out. In the in Figure 1 shown closed state of the tool 10, the insert 16 forms a recess 15. The recess 15 acts as a chamber which is filled with air. This chamber 15 is bordered by a surface of the insert 16 which faces the component 17, an inner surface of the opening through the upper tool half 12o in which the insert 16 is inserted and a section of the surface of the component 17. The air in this chamber 16 isolates the warm sheet metal part 17 coming from the furnace from the upper tool half 12o and the insert 16 located therein. Thus, the heat transfer from the component 17 to the mold is slower at this point than in the other component areas in which the component 17 is directly involved the tool 10 is in touching contact. The component 17 cools more slowly in the area of the air chamber 15, so that a structure with low mechanical characteristics, in particular with low strength values, is established in this area. The air gap 15 thus covers exactly the area that is characterized in the later component or vehicle by low strength and thus high ductility. The properties of the component can thus be set in such a way that a targeted deformation of the ductile area results in the event of a vehicle crash.

The size of the air chamber 15 can be changed by moving the insert 16. Depending on the selected position of the insert 16 i.e. depending on the size of the air chamber 16, other desired strength values can be set accordingly in the area of the component. The air chamber 16 can also be designed as a gap, in particular with a small volume.

As an alternative to the medium air, other gases can also be used to fill the chamber 16.

According to one embodiment of the invention, 16 channels 18 can optionally be arranged in the insert, which are used for temperature control of the insert. For this purpose, the insert 16 is flushed with a temperature-controlled medium and set to a predetermined temperature. The medium is preheated in a heating and / or cooling device and passed through the channels 16 of the insert 18. The temperature of the insert 16 and thus the air in the chamber 15 can thus be controlled or regulated via the temperature of the medium. Gases, for example inert gases or liquids, for example oil or water, are particularly suitable as the medium. However, the provision of channels 18 is only optional. In other embodiments of the invention, the insert 16 can also be designed without the medium-carrying channels 18.

A mold insert 13 is provided in the lower mold half 12u, in which a cooling system which has a plurality of cooling lines 14 is integrated. The use of such cooling inserts 13 offers the advantage, on the one hand, that different component contours can be embossed with a lower molding tool 12u, in that the molding insert 13 can be exchanged in accordance with the desired component shape. The cooling lines 14 are fluidly connected to a distributor or connection system. The coolant is thus introduced via the connection system and distributed to the cooling lines 14.

In the Fig. 1 The cooling lines 14 shown run essentially parallel to the surface of the component 17 and thus also essentially parallel to the active surface of the mold halves 12u, 12o. The cooling lines 14 thus follow the component contour at a certain distance into the mold insert 13 of the lower mold half 12u.

Gaseous cooling media, liquid cooling media or a combination thereof are suitable as coolants for the cooling lines 14.

In Fig. 1 only a single insert 16 is shown, which is arranged in the upper tool part 12o. In a further embodiment of the invention, not shown, it can be used in the lower tool part 12u may be arranged. Alternatively, one or more inserts 13 can be positioned both in the upper and in the lower tool half 12o, 12u. In addition, only the lower tool half 12u is provided with cooling lines 14. In further embodiments of the invention, the arrangement of the cooling system, ie the connection system and the cooling lines 14, can alternatively also be arranged in the upper tool half 12o. In a further alternative embodiment, cooling lines 14 can be provided both in the upper tool half 12o and in the lower tool half 12u. In addition, a mold insert 13 can alternatively be arranged in the upper tool half 12o or in both tool halves.

Reference symbol list

10th

Molding tool

11

Tool base plate

12u

Lower part of the tool

12o

Upper part of the tool

13

Tool insert

14

Cooling pipes

15

Recess

16

commitment

17th

Component

18th

channels

Claims (8)

1. A forming die (10) for producing hot-formed components (17), especially shaped sheet metal parts, with a lower die part (12u) and an upper die part (12o) which are movable in relation to each other and which are formed with corresponding effective areas for shaping the component (17), wherein at least the effective area of one die part (12u, 12o) is formed to be coolable at least in portions and cooling lines (14) are provided in the die part (12u, 12o),
   wherein at least one recess (15) is provided in at least one of the two die parts (12u, 12o), which recess in a closed state of the die (10) forms with the component (17) an air chamber which acts as a thermal insulator between the component (17) and the die part (12o), characterised in that
   the recess (15) is formed to be variable in volume.
2. A forming die according to Claim 1, characterised in that an insert (16) is arranged in the die part (12u, 12o) in which the recess (15) is formed, which insert forms a die-side rear wall of the air chamber.
3. A forming die according to Claim 2, characterised in that the insert (16) is arranged movably, especially linearly displaceably, in the die part.
4. A forming die according to Claim 3, characterised in that the insert (16) in a closed state of the die (10) is in a retracted position in order to produce the recess (15).
5. A forming die according to Claim 3 or Claim 4, characterised in that in an opened state of the die (10) the insert is in an advanced position, in which the volume of the recess (15) is reduced compared with the volume of the recess (15) in the retracted position of the insert (16).
6. A forming die according to one of Claims 2 to 5, characterised in that ducts (18) are provided in the insert (16).
7. A forming die according to one of the preceding claims, characterised in that
   the shaped sheet metal parts are formed of ferrous metal, especially of steel, and/or of non-ferrous metal, especially of aluminium and/or magnesium.
8. A forming die according to one of Claims 2 to 7, characterised in that the insert (16) is formed from metal, non-metal, especially of concrete, wood or a combination of these materials.

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