Method for producing a formed and at least regionally hardened sheet metal component

Abstract

The invention relates to a 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 preform (13) is heated to forming temperature, subsequently shaped and then at least regionally hardened by corresponding cooling, wherein the at least one perforation (16) in the preform (13) is produced during the course of a punching process before the preform (13) is hardened. According to the invention, the metal piece (14) separated from the preform (13) by punching is fed back to its original position or a corresponding position in 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 (13) from the die (1), in which it is held during quenching. The invention also describes a quench press die (1) for producing a shaped and at least regionally hardened sheet metal component, particularly a sheet steel component (15), with at least two die parts (2, 3) adjustable against one another for opening and closing the die (1) and with a punching device (7) comprising a punching die (8) for producing a perforation (16) in a preform (13) located between the die parts (2, 3). The die part (2), against which the punching die (8) for producing the perforation (16) works, has a return punch (11), the actuation side of which points towards the punching die (8) and the axis of motion of which corresponds to the axis of motion of the punching die (8), such that a metal piece (14) separated from a preform (13) by means of said punching die (8) can be returned to the correct position, or approximately to the correct position in the perforation (16) produced in the preform (13) by the punching process to fill said perforation.

Claims

1. Method for producing a formed and at least regionally hardened sheet steel component, with at least one perforation produced in it, the method comprising the steps of: heating a blank to forming temperature and subsequently forming the blank in a tool; forming at least one perforation in the blank by a punching process before the blank is hardened; feeding a punched out piece separated from the blank back to its original position in the perforation to remain there for the duration of a quenching process; at least regionally hardening by corresponding quenching the blank; and pressing out the punched out piece either at the time of or after removal of the sheet steel component from the tool in which it is held during the quenching.

2. The method of claim 1, wherein the perforation is produced in the blank after the forming step or in an end phase of the forming step.

3. The method of claim 1, wherein an active quenching of the formed blank occurs after the steps of producing a perforation and feeding back the punched out piece into the perforation have been completed.

4. The method of claim 1, wherein at least one perforation is produced in a region of the blank which is subsequently hardened.

5. The method of claim 1, wherein the steps of producing the formed and at least regionally hardened sheet component are carried out in a press hardening tool.

6. The method of claim 1, wherein the punched out piece and the blank adjacent to the punched out piece shrink to substantially the same extent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Additional advantages and embodiments of the invention result from the following description of an embodiment example in reference to the appended figures.

(2) FIG. 1: shows a diagrammatic cross section through a press hardening tool with a device for producing a perforation in a workpiece held in the press hardening tool.

(3) FIG. 2: shows an enlarged representation of the region of the device for producing a perforation of the press hardening tool of FIG. 1.

(4) FIG. 3: shows the section of the press hardening tool of FIG. 2 with a blank held between the tool parts after the completion of the forming process.

(5) FIG. 4: shows the representation of FIG. 3 after the introduction of a perforation into the blank.

(6) FIGS. 5a, 5b: show the press hardening tool in the section of FIG. 4 during and after a step of feeding the punched out piece back into the perforation produced in the blank.

(7) FIG. 6: shows, in a cross-sectional representation, the sheet steel component taken out of the press hardening tool, after the completion of the tempering process and after the pressing out of the punched out piece located previously in the perforation.

DETAILED DESCRIPTION

(8) A press hardening tool 1 represented only diagrammatically in FIG. 1 has two tool parts 2, 3 that can be adjusted relative to one another. The tool part 2 is a stationary tool part, which therefore can also be referred to as a die. The tool part 3 can be moved in translation relative to the tool part 2. This tool part 3 can also be referred to as a stamp. Each of the two tool parts 2, 3 has a forming surface 4, 4.1. A blank, typically a steel plate heated beforehand to forming temperature in an oven, is inserted onto the forming surfaces 4, 4.1, of the opened press hardening tool 1 and where it is formed. For carrying out a hardening process, the tool parts 2, 3 have coolant channels 5, 5.1, by means of which, heat can be removed from the formed blank by appropriate rapid quenching. If a quenching is desired, coolant is run through the coolant channels 5, 5.1. To that extent, the press hardening tool 1 is a press hardening tool as is known.

(9) In addition to the otherwise conventional devices that a press hardening tool has, the press hardening tool 1 moreover has a device 6 for producing a perforation in a blank held between the tool parts 2, 3. This device 6 comprises a punching device 7 with a punching stamp 8, punching device 7 which is associated in the represented embodiment example with the stamp 3. The punching stamp 8 can be moved in translation, as indicated with the double arrow in FIG. 1, in a manner which is not represented in further detail. The end side of the punching stamp, facing the forming cavity 9, is used for punching out a piece of the blank held between the tool parts 2, 3. In the represented embodiment example, the punching stamp 8 has a circular cross-sectional geometry. It is understood that the punching stamp 8 can have any cross-sectional geometries. The device 6 is moreover associated with a return device 10 with a return stamp 11. The return device 10 is associated with the die 2 of the press hardening tool 1. The double arrow indicates that the return stamp 11 of the return device 10, which is otherwise not represented in further detail, can also be moved in translation direction, namely on the same movement axis as the punching stamp 8. The return device 10 is used to feed the punched out piece, which in the course of the production of a perforation has separated from the blank located in the course of a punching process in between the tool parts 2, 3, back into the produced perforation immediately after the punching process has taken place.

(10) The punching device 7 and the return device 10 can be seen more clearly in the enlarged section representation of FIG. 2. The cross-sectional geometry of the return stamp 11 corresponds to the cross-sectional geometry of the punching stamp. The clear width of the movement channel 12 in which the return stamp 11 is moved is sufficiently large so that the punching stamp 8 can engage therein when the punch stroke is performed.

(11) FIG. 3 shows the press hardening tool 1 in an enlarged representation thereof corresponding to that of FIG. 2 with a blank 13 which has been brought beforehand therein to forming temperature and which has already been formed by moving the tool parts 2, 3 together. The blank 13 is a sheet steel blank which has been heated before the forming process to the austenitization temperature. After the forming process has been completed and before coolant has been run through the coolant channels 5, 5.1 of the tool parts 2, 3, that is to say before the start of the hardening or tempering process, a perforation is produced in the blank 13. For this purpose, the punching stamp 8 is actuated in order to punch out a punched out piece, as indicated by the block arrow in FIG. 3. In the course of the punch stroke, the punched out piece 14 is separated from the blank 13 and it is pressed into the movement channel 12 of the return stamp 11. By means of this punch stroke, the return stamp 11 is simultaneously pressed back into its starting position. This situation is shown in FIG. 4. In terms of its material thickness, the punched out piece 14, is introduced completely into the movement channel 12. From this it becomes evident that the punched out piece 14 no longer has any material connection with the blank 13. Immediately after the completion of the punch stroke of the punching stamp 8, the return stamp 11 of the return device 10 is activated, as a result of which the punched out piece 14 is moved from the movement channel 12 back into the perforation introduced by the punching process into the blank 13. Due to the guiding of the punched out piece 14, which is in contact with its surface with the end side of the return stamp 11 and which is held on its other side by the punching stamp 8, said piece is pushed into the produced perforation in the correct and initial position, as said piece is separated from the blank 13, perforation in which the punched out piece 14 sits with precise fit. The steps of feeding the punched out piece 14 back into the perforation 16 are shown in FIGS. 5a, 5b, wherein FIG. 5a shows the situation in which the punched out piece 14 is being introduced into the perforation, while FIG. 5b shows the punched out piece 14 inserted into the perforation 16.

(12) Subsequently, the active quenching process is started by running coolant through the coolant channels 5, 5.1. Due to the precise-fit seat of the punched out piece 14 within the perforation 16, said piece functions as a place holder and therefore ensures a uniform shrinkage of the entire region of the perforation and in particular of the marginal regions of the blank 13 encompassing the perforation, as a result of which preservation of the perforation geometry is ensured.

(13) After the completion of the quenching process, the press hardening tool 1 is opened and the sheet steel component 15 produced therein is removed. The punched out piece 14 can also be pressed out of the perforation 16, including in particular by hand without problem. Subsequently the sheet steel component with the desired perforation and the intended dimensional accuracy is provided.

(14) In the described embodiment example, the perforation 16 is produced in the blank 13 after the forming step has ended. Similarly, it is possible to provide for introducing the perforation while the forming process is in its end phase. The machine cycle for introducing the described perforation can be provided to be very short, so that the usual machine cycle for producing the sheet steel components in question is not increased or increased only barely noticeably.

(15) In the embodiment example described in the figures, the punching device is associated with the stamp and the return device with the die. It is equally possible to associate the punching device with the die and the return device with the stamp. When several perforation production devices are provided, the punching devices and the return device can each be associated with the same tool part. It is also possible to associate at least one punching device as well as a return device with each tool part. The association of punching device and return device is implemented as a function of the construction circumstances of the tool. In addition it is possible to provide for the punching stamp and the return stamp of a perforation production device to be implemented so as to be able to perform both activities. Then, the punch stroke and the return stroke of the two stamps can be performed in the same way.

LIST OF REFERENCE NUMERALS

(16) 1 Press hardening tool 2 Tool part, die 3 Tool part, stamp 4, 4.1 Forming surface 5, 5.1 Coolant channel 6 Device 7 Punching device 8 Punching stamp 9 Forming cavity 10 Return device 11 Return stamp 12 Movement channel 13 Blank 14 Punched out piece 15 Sheet steel component 16 Perforation