EP2874765B1 - Method for producing a shaped and at least regionally hardened sheet metal component and quench press die for producing such a component - Google Patents

Description

The invention relates to a method for producing a deformed and at least partially cured sheet metal component, in particular a sheet steel component, with at least one introduced therein in which a blank heated to forming temperature, subsequently formed in a tool and then cured by appropriate cooling at least partially, wherein the at least one opening is introduced into the blank by means of a stamping process, before the blank is hardened. Furthermore, the invention relates to a press-hardening tool for producing a deformed and at least partially hardened sheet metal component with at least two mutually adjustable tool opening and closing tool parts and with a stamping punch comprehensive punching device for introducing an opening in a located between the tool parts blank.

Press hardening tools are tools with which metal blanks are reshaped and hardened. Depending on the configuration of the method, for the purposes of hardening, a blank preheated according to deformation temperature is supplied to the press-hardening tool, transformed therein and, after the forming has been completed, sufficiently rapidly cooled and thus tempered to cure. Such press-hardening tools are used, for example, for producing structural components of motor vehicles. Typically, the blanks are sheet steel parts, so that the structural components are sheet steel components. It is also possible to further reshape already preformed sheet steel blanks in a press-hardening tool and then to treat them in the press-hardening tool. A heating of the blank to its forming temperature, which typically corresponds to the austenitizing temperature in the case of a blank made of steel, can in principle be carried out within the pressing tool. In most cases, however, the blank will be heated to the forming temperature in an oven and then introduced into the open press-hardening tool. The Press hardening tool itself has at least two opening and closing the same adjustable tool parts, which are addressed as a rule as a die and stamp. In this case, the die represents the stationary tool part, against which the punch is moved by means of a press to close the tool and thus to reshape the blank inserted therein. For tempering the deformed blank within the press-hardening tool, the two tool parts have coolant channels through which coolant is pumped through for the purpose of the tempering or hardening process. After completion of the cooling process for at least partial hardening of the formed blank, the tool is opened and the steel sheet component removed.

There are applications in which such sheet metal components, which are produced according to the method described above using a press-hardening tool, one or more openings, sometimes addressed as passages, should have. Such breakthroughs can be introduced into the sheet steel component after the step of press hardening. This is done with a laser processing, since a punching of the hardened sheet metal component is not without problems due to the hardness set by the manufacturing process. However, laser processing for introducing the at least one opening can also be considered disadvantageous. This is due to the fact that it involves the equipment-related and handling-related expense. In addition, the set hardness is reduced again at least in the edge areas enclosing the opening by the heat input during lasering.

Out DE 10 2004 019 693 A1 For example, a method and a device for producing a hardened sheet steel component are known in which, within the pressing tool, the at least one opening in the blank is introduced into the blank during cooling by means of perforation. In this method, the at least one opening in the blank is introduced at a time in which this is not yet, at least not fully cured. It is emphasized in this document that the punch is brought out again immediately after the introduction of the opening from the opening to a shrinking of the blank to prevent the punch. In this way, damage to the punch to be avoided when removing or pulling it from the shrunk on it in the course of the cooling process blank.

As a disadvantage, however, in terms of the DE 10 2004 019 693 A1 It has become known methods that the circumferential geometry of the at least one introduced into the blank opening during the cooling process is not controlled. Although the blank is held between the closed tool parts during the cooling process. However, this can not prevent shrinkage, in particular uneven shrinkage of the opening width of the introduced opening. In principle, a shrinkage of the opening width of the opening must be accepted. However, it would be desirable if such shrinkage were uniform across the contour of the aperture. This is not guaranteed by the aforementioned prior art method. Different shrinkage rates can occur, especially in the case of apertures whose geometry deviates from the circular cross-sectional shape.

Another method for producing a hardened sheet metal profile with an opening is made EP 2 062 664 A1 known. In the method described in this document, a limited by at least one cutting edge area is first cut, the depth of cut is less than the material thickness of the board. The board is then hot formed and the cut area is pressed out along the cut edge after hot forming. The cutting and expressing of the area is carried out in the opposite direction, so that you get grading-free cutting contours. Also with this procedure can as already to DE 10 2004 019 693 A1 described shrinkage phenomena are not avoided.

Based on the pre-discussed prior art, the invention is therefore the object of developing an aforementioned method and a press-hardening tool mentioned above such that the above-described problem of uneven shrinkage introduced into a not yet final cured blank Breakthrough is counteracted.

The procedural object is achieved according to the invention by an initially mentioned, generic method in which the cut out by punching out of the blank punched back is returned to the opening, where it remains for the duration of the cooling process and only with or after removal of the sheet steel component from the Tool in which it is held during the cooling is pushed out.

The device-related object is achieved by an aforementioned, generic press-hardening tool, in which that tool part against which the punch for inserting the opening operates on a return ram has its actuating side to the punch and whose axis of movement corresponds to the axis of movement of the punch, so that a by means of the punch from a blank severed punching slug in the introduced by the punching process in the blank opening in the correct position or approximately in the correct position for filling the same is traceable.

In the method according to the invention-the same applies to the claimed press-hardening tool-the aperture is introduced into the blank which has not yet hardened, that is to say at a point in time in the sequence of the process steps in which the blank still has relatively soft material properties. Consequently, the aperture can be introduced into the blank by a cutting operation performed as punching. Thus, a separation of the Butzens takes place differently than when lasing without loss of material. To counteract an uneven shrinkage of the thus created opening the punching slug is now used, which is returned immediately after the punching of the aperture in this. In the opening of the punching remains at least until the decisive completion of the cooling process. Since the stamping fits snugly into the opening and this is correct position and thus returned in its original position or in a corresponding position to fill the opening in this, the slug forms the placeholder for the created Opening, whereby an uneven shrinkage and thus an undesirable change in the peripheral geometry of the aperture is effectively counteracted. The slug itself is naturally made of the same material as the blank. Consequently, this shrinks to the same extent as the blank. Therefore, in this process, no or at most only an insignificant shrinking on the stamped joint, which is why this can be pushed out of the opening readily after completion of the cooling process. Finally, there is no material composite between the stamped slug and the surrounding material of the sheet steel component.

Preferably, the method steps described above will be carried out in such a way that the punched slug cut out of the blank is returned to the opening with the return stroke of the punch immediately after completion of the punching stroke. This purpose is expediently a return ram, which is arranged in that tool part in which the punch is not arranged. It can be provided that by the punching stroke of the punch and the consequent translational movement of the Stanzbutzens which is located on the opposite side of the punch punching punch applied return ram is moved back to its original position to be activated after completion of the punching stroke, causing the punching in the Aperture is traced back. This return movement can be used to return the punch itself to its original position. It is expedient if, after returning the stamped plug into the aperture, both the stamping punch and the return punch bear against the stamped billet, since this fixes the position of the stamped billet within the aperture for the cooling process.

According to one embodiment, it is provided that the cross-sectional geometry of the return ram corresponds in its abutting on the punched portion of the opening geometry and thus the geometry of the punching. In such an embodiment, the return ram bears against the entire surface of the stamped slug, so that the stamped slug is exposed to the same or at least substantially the same cooling conditions as the adjoining edge regions of the opening. In such an embodiment, the press-hardening tool can also be used to produce sheet steel components that do not necessarily have an opening, thus the step of cutting out a punched, is not performed. Nevertheless, the area in which an opening could be introduced is also subject to the same or at least approximately the same cooling conditions for the adjoining areas, so that no appreciable differences in strength can be detected even in this area of the sheet metal component despite the provision of the punching and returning device. Thus, with the above-described concept, a press hardening tool can be provided with which, without having to change the tool geometry or certain inserts, sheet steel components with and without openings can be produced. It is understood that such a press-hardening tool can also have more than one punching device with one of these each associated return punch.

In addition to the advantages already shown, which brings the claimed concept with it, it becomes obvious that in this concept the punched slug does not need to be led out of the press-hardening tool. Butzenkanäle for taking out a punching bushing are therefore basically not needed. This, in turn, favors the above-described uniform cooling conditions across the aperture.

Fig. 1:

einen schematisierten Querschnitt durch ein Presshärtwerkzeug mit einer Einrichtung zum Einbringen einer Durchbrechung in ein in dem Presswerkzeug gehaltenes Werkstück,

Fig. 2:

eine vergrößerte Darstellung aus dem Bereich der Einrichtung zum Einbringen einer Durchbrechung des Presshärtwerkzeuges der Figur 1,

Fig. 3:

der Ausschnitt des Presshärtwerkzeuges der Figur 2 mit einem zwischen den Werkzeugteilen gehaltenen Rohling nach Abschluss des Umformvorganges,

Fig. 4:

die Darstellung der Figur 3 nach Einbringen einer Durchbrechung in den Rohling,

Fig. 5a, 5b:

das Presshärtwerkzeug in dem Ausschnitt der Figur 4 während und nach einem Schritt des Zurückführens des Stanzbutzens in die in den Rohling eingebrachte Durchbrechung und

Fig. 6:

in einer Querschnittsdarstellung das aus dem Presshärtwerkzeug entnommene Stahlblechbauteil nach Abschluss des Vergütungsprozesses und nach Herausdrücken des zuvor in der Durchbrechung befindlichen Stanzbutzens.

Further advantages and embodiments of the invention will become apparent from the following description of an embodiment with reference to the accompanying figures. Show it:

Fig. 1:

a schematic cross section through a press-hardening tool with a device for introducing an opening in a held in the pressing tool workpiece,

Fig. 2:

an enlarged view of the area of the device for introducing an opening of the press-hardening tool of FIG. 1 .

3:

the section of the press hardening tool of FIG. 2 with a held between the tool parts blank after Completion of the forming process,

4:

the representation of FIG. 3 after introducing an opening in the blank,

5a, 5b:

the press hardening tool in the cutout of FIG. 4 during and after a step of returning the blank to the blanking hole and into the blank

Fig. 6:

in a cross-sectional view taken from the press-hardening tool sheet steel component after completion of the annealing process and after pressing out of the previously located in the opening punching.

An in FIG. 1 only schematically represented press hardening tool 1 has two mutually adjustable tool parts 2, 3. The tool part 2 is a fixed tool part, which therefore can also be addressed as a die. The tool part 3 is translationally movable relative to the tool part 2. This tool part 3 can also be addressed as a stamp. Both tool parts 2, 3 each have a mold surface 4, 4.1. On the mold surfaces 4, 4.1, an inserted into the open press-hardening tool 1, previously heated to forming temperature in an oven blank, typically a steel plate, reshaped. The tool parts 2, 3 have coolant channels 5, 5.1, via which heat can be conducted away from the formed blank for carrying out a hardening process by correspondingly rapid cooling. If cooling is desired, the coolant channels 5, 5.1 are exposed to coolant. In that regard, the press-hardening tool 1 is a press-hardening tool, as is known per se.

In addition to the otherwise customary devices, which have a press-hardening tool, the press-hardening tool 1 additionally has a device 6 for introducing an opening into a blank held between the tool parts 2, 3. This device 6 comprises a punching device 7 with a punch 8, which punching device 7 assigned to the stamp 3 in the illustrated embodiment. The punch 8 is in by the double arrow in FIG. 1 indicated direction translatable in a manner not shown adjustable. The pointing into the mold cavity 9 end face of the punch serves for punching out a stamped from a held between the tool parts 2, 3 blank. In the illustrated embodiment, the punch 8 has a circular cross-sectional geometry. It is understood that the punch 8 may have any cross-sectional geometries. The device 6 is further associated with a return device 10 with a return ram 11. The return device 10 is assigned to the die 2 of the press-hardening tool 1. The double arrow indicates that the return punch 11 of the return device 10, which is not shown in any other detail, can also be moved in the translatory direction, on the same axis of movement as the punch 8. The return device 10 serves the purpose of removing one between a punching operation the tool parts 2, 3 located blank in the course of creating an opening herausgeschennten punched scraper immediately after the punching process in the created aperture.

The punching device 7 and the return device 10 are clearer from the enlarged detail view of FIG. 2 recognizable. The cross-sectional geometry of the return punch 11 corresponds to the cross-sectional geometry of the punch. The clear width of the movement channel 12, in which the return ram 11 is moved, is sufficiently large, so that the punch 8 can engage in performing a punching stroke therein.

FIG. 3 shows the press-hardening tool 1 in its enlarged view corresponding to that of FIG. 2 with a previously placed on forming temperature and already converted by moving the tool parts 2, 3 blank 13. The blank 13 is a sheet steel blank, which has been heated prior to the forming austenitizing temperature. After the forming process and before acting on the coolant channels 5, 5.1 of the tool parts 2, 3 with coolant, ie before actively initiating the hardening or tempering process is introduced into the blank 13 an opening. For this purpose, the punch 8 is pressed for punching a Stanzbutzens, as this by the block arrow in FIG. 3 is indicated. In the course of the punching stroke, the punched slug 14 is cut out of the blank 13 and pressed into the movement channel 12 of the return ram 11. At the same time, the return punch 11 is pushed back into its starting position by this punching stroke. This situation is in FIG. 4 shown. The punched slug 14 is completely inserted in the movement channel 12 with respect to its material thickness. It is clear from this that the punched slug 14 no longer has any material connection to the blank 13. Immediately after completion of the punching stroke of the punch 8, the return punch 11 of the return device 10 is activated, whereby the punched slug 14 is returned from the movement channel 12 in the introduced through the punching process in the blank 13 opening. Due to the leadership of Stanzbutzens 14 which rests flat on the front side of the Rückführstempels 11 and is held on the other side by the punch 8, this is in the correct position and thus in its original position, as this has been cut out of the blank 13 in the created Penetration inserted, in which the punched slug 14 fits snugly. The steps of returning the punch 14 into the aperture 16 are in FIG FIGS. 5a, 5b shown, where FIG. 5a shows the situation in which the punching slug 14 is inserted into the opening, while FIG. 5b the punched slug 14 inserted into the opening 16 shows.

Subsequently, the active cooling process is initiated by applying the coolant channels 5, 5.1 with coolant. Due to the snug fit of the punching 14 within the opening 16 this serves as a placeholder and therefore ensures a uniform shrinkage of the entire region of the opening and in particular of the opening bordering edge portions of the blank 13, whereby a retention of the opening geometry is guaranteed.

After completion of the cooling process, the press-hardening tool 1 is opened and the steel sheet component 15 produced therein is removed. The punched slug 14 can be pushed out of the opening 16 readily, especially manually. Subsequently, the sheet steel component provided with the desired aperture in the intended dimensional accuracy.

In the described embodiment, the opening 16 is introduced into the blank 13 after the forming step is completed. Similarly, it can be provided that the opening is introduced while the forming process is in its final phase. The machine cycle for introducing the aperture described can be provided very short, so that the usual machine cycle for producing the sheet steel components in question is not or only slightly increased.

In the embodiment described in the figures, the punching device is associated with the punch and the return means of the die. Likewise, the punching means may be associated with the die and the return means associated with the punch. With provision of a plurality of aperture insertion means, the punching means and the return means may each be associated with the same tool part. Likewise, it is possible to assign at least one punching device and one return device to each tool part. The assignment of punching device and return device will be made depending on the structural conditions of the tool. In addition, it can be provided that the punch and the return punch a Durchbrechungseinbringseinrichtung are executed so that both activities can exercise. Then the punching stroke and the return stroke of both punches can be equally exercised.

LIST OF REFERENCE NUMBERS

1

Presshärtwerkzeug

2

Tool part, die

3

Tool part, stamp

4,4.1

mold surface

5,5.1

Coolant channel

6

Facility

7

punch

8th

punch

9

mold cavity

10

Return means

11

Recirculation Temple

12

movement channel

13

blank

14

slug

15

Sheet steel component

16

perforation

Claims (9)

1. Method for producing a shaped and at least regionally hardened sheet metal component, particularly a sheet steel component (15), with at least one perforation (16) produced in it, in which method a blank (13) is heated to forming temperature, subsequently shaped in a tool (1) and then at least regionally hardened by corresponding quenching, wherein the at least one perforation (16) in the blank (13) is produced during the course of a punching process before the blank (13) is hardened, characterised in that the metal piece (14) separated from the blank (13) by punching is fed back into the perforation (16), remains there for the duration of the quenching process and is only pressed out during or after removal of the sheet steel component (15) from the tool (1), in which it is held during quenching.
2. The method of claim 1 characterised in that the perforation (16) is introduced into the blank (13) after the shaping step or in an end phase of the shaping step.
3. The method according to claim 1 or 2 characterised in that an active quenching of the shaped blank (13) is not effected until the steps of creating the perforation (16) and returning the metal piece (14) to the perforation (16) are complete.
4. The method according to any one of claims 1 to 3 characterised in that at least one perforation (16) is introduced into a region of the blank (13) which is subsequently hardened.
5. The method according to any one of claims 1 to 4 characterised in that the steps for producing the shaped and at least regionally hardened sheet metal component (13) are carried out in a quench press tool (1).
6. Quench press tool for producing a shaped and at least regionally hardened sheet metal component, particularly a sheet steel component (15), with at least two tool parts (2, 3) adjustable against one another for opening and closing the tool (1) and with a punching device (7) comprising a punching die (8) for producing a perforation (16) in a blank (13) located between the tool parts (2, 3), characterised in that the quench press tool is configured to perform the method according to any one of claims 1 to 5, with the tool part (2) against which the punching stamp (8) for producing the perforation (16) works, has a return stamp (11), the actuation side of which points to the punching stamp (8) and the axis of motion of which corresponds to the axis of motion of the punching stamp (8), such that a metal piece (14) separated from blank (13) by means of said punching stamp (8) can be returned to the correct position, or approximately to the correct position in the perforation (16) produced in the blank (13) to fill said perforation.
7. The quench press tool according to claim 6 characterised in that until the opening of the tool (1) for the removal of the sheet metal component (15), the return stamp (11) lies with its actuation side against the metal piece (14) returned to the created perforation (16).
8. The quench press die according to claim 6 characterised in that the return stamp (11) is brought into its initial position by the metal piece (14) moved by the punching stamp (8).
9. The quench press die according to any one of claims 6 or 7 characterised in that the punching stamp (8) is brought into its initial position by the operating of the return stamp (11) for returning the metal piece (14) into the perforation (16).

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