WO2005075279A1

WO2005075279A1 - Component with a joining region, method and tool for the production thereof

Info

Publication number: WO2005075279A1
Application number: PCT/EP2005/001019
Authority: WO
Inventors: Bernd Dreher; Andrea Gackenheimer; Guenther Schoenle; Timo Wieland
Original assignee: Daimlerchrysler Ag
Priority date: 2004-02-05
Filing date: 2005-02-02
Publication date: 2005-08-18
Also published as: DE102004005568A1

Abstract

The invention relates to a component (1, 2) of sheet metal, for joining to at least another component (10) of sheet metal in a joining region (9). The aim of said invention is to ensure a process-reliable joining of both components (1, 2, 10). Said aim is achieved, whereby one of these components (1, 2) is provided with a locally defined stamping (12) in the joining region (9) thereof, in the area of which the material thickness (4') of the component (1, 2) is locally reduced. Said component (1, 2) may be stamped by a cold- or hot-forming method.

Description

DaimlerChrysler AG

_B AUTEIL WITH A CONNECTING AREA, METHOD AND TOOL FOR ITS PRODUCTION

The invention relates to a connection area on a component which is provided for joining this component to at least one further component made of sheet metal using a thermal joining method, in particular spot welding.

In the course of weight savings on motor vehicle bodies, it is known to design and optimize structural parts of bodies in accordance with local loads. To achieve weight reductions, structural parts made of sheet metal can be designed as composite components; Such a composite component comprises a base plate which is provided with locally limited reinforcement plates in highly stressed areas. In this way, the entire structural component does not have to be produced from a thicker sheet, but the higher sheet thickness is provided only for the areas to be reinforced. Such a patchwork component is known for example from DE 43 07 563 AI.

Alternatively, the structural component can be produced from a Taylored blank, that is to say a circuit board which is assembled from several sheet metal sections of different material thickness. Furthermore, a flexibly rolled sheet can be used as a semifinished product for the production of the structural component, the distance between rolls being varied during its production. is while the sheet is transported through the space between the rollers; this produces a circuit board which has at least two surface sections with different material thicknesses. Such a flexibly rolled circuit board can also be used as a locally limited reinforcing plate for a composite component, as described, for example, in (unpublished patent application 103 53 479.2-14).

Cold forming processes, in particular deep drawing, can be used to produce the structural component. Alternatively, the structural component can be produced from a thermoformable sheet using a hot-forming process; Particularly high strengths of the component can be achieved if a heat-increasing heat treatment is carried out in the course of hot forming. The production of a hot-formed structural component from a locally reinforced board is described for example in DE 100 49 660 AI. - Furthermore, it is known from DE 196 53 543 AI to locally heat treat a circuit board in such a way that regions of different material expansion coefficients are generated; in a subsequent forming process, this leads to areas of different material thickness on the finished component.

A common feature of the described embodiments of weight-optimized structural components is that the material thickness of the component varies across the component, so that there is a higher material thickness in highly stressed areas than in less stressed areas.

The individual structural components made of sheet metal are joined with the aid of spot welding in order to produce a bodyshell. Two or more individual building parts welded to a single spot; A prerequisite for a good joining result, however, is that the total material thickness of the sheet metal parts to be joined lying on top of each other does not significantly exceed a thickness of 3 mm. If the (local) material thickness of one or more of the individual components to be joined is increased in such a way that the stack of the components lying on top of one another in the joining area is considerably thicker than 3 mm, the individual components can no longer be reliably processed using the Connect spot welding.

To solve this problem it is proposed in the generic DE 100 02 617 AI to design the patchwork component in such a way that the reinforcing plate has a recess in the joining area, so that the simple material thickness in the joining area (instead of the increased material thickness of the patchwork) of the base plate is present. However, such a recess in the reinforcement plate is associated with local weakening of the patchwork component, which is why the solution shown in DE 100 02 617 AI can only be used to a limited extent in highly stressed component areas.

The invention is therefore based on the object of proposing an alternative design for the connection region of a plurality of individual components to be joined, in which it is ensured that the individual components can be connected reliably with the aid of a thermal joining method, in particular spot welding. Furthermore, a method and a device for generating such a connection area are to be proposed.

The object is achieved by the features of claims 1, 3 and 9. The material thickness of at least one of the individual components to be connected is then locally reduced in the connection area by providing the component with a locally limited indentation. If the components are to be connected using spot welding, the depth of this impression is selected so that the total material thickness of the component stack to be connected does not exceed 3 mm in the joining area.

The invention makes it possible to join components whose material thickness has been locally increased in accordance with the load, even in the area of this increased material thickness, using the conventional thermal joining methods, in particular spot welding. The invention also makes it possible to reliably connect two sheets with very different material thicknesses with the aid of a thermal joining process by locally reducing the sheet thickness of the thicker sheet in the joining area and thus approximating the sheet thickness of the thinner sheet.

The invention is particularly applicable to metallic sheet metal components, the three-dimensional shape of which was generated by means of a cold forming process, for example deep drawing. The impression in the connection area can be produced, for example, in the course of the three-dimensional shaping of the component. For this purpose, the upper or lower tool is provided with a bulge at the point corresponding to the connection area, which protrudes into the metal sheet when the forming tool is closed - ie when the component contour is being shaped - and forces the component material out of this area. Since the pressures necessary for such macroscopic material displacement are very high, it may be advantageous to separate this indentation only after the three-dimensional component contour has been generated in a separate one Generate process step (ie preferably with a separate tool).

The pressures required to displace the component material from the connection area can be reduced if the embossments are provided on the component edge, so that the material displaced from the embossing area can be pushed out beyond the component edge. In this case, the three-dimensional component shape is advantageously first completely shaped and the component is trimmed before the embossing is produced.

If the connection area is located in a zone of the component remote from the edge, the material displaced from the embossing area cannot escape over the component edge. In this case, it is advantageous to surround the bulge of the tool - at least in sections - with an annular recess into which the displaced component material can flow. In the area of the component opposite the recess, a flat bead is formed which is adjacent to the embossing.

In order to achieve a long service life for the embossing tool, the strength of the tool in the region of the bulge is advantageously increased locally. This can be done, for example, by laser hardening. Alternatively, the tool can be provided with a ceramic insert (or an insert made of another suitable hard material) in the region of the bulge.

Furthermore, the forces or pressures required to generate the impression in the connection area can be reduced if the area of the impression and its surroundings are locally heated before the actual stamping process. The embossing process is advantageously carried out at a temperature which has already started to soften the component materials. The local heating of the component required for this can take place, for example, by induction heating.

As an alternative to the cold-formed components described so far, the invention can also be used in components made of a hot-formable steel sheet, the three-dimensional component contours of which are produced by means of a hot-forming process (“press hardening”). In this process, the blank from which the component is formed is first heated to a temperature above such a structural transformation temperature of the material - usually a certain temperature within the temperature range between 850 ° C and 930 ° C - above which the material structure is in the austenitic state. The blank is then placed in the hot forming tool and formed and heat-treated in it - targeted cooling can be used to adjust the (local) material strength. Since the board material is much softer when heated than at room temperature, it can be stamped in the same step as the molding g of the three-dimensional component contour. In this case, the bulges on one of the tool halves required to produce the impressions are advantageously part of the hot-forming tool, so that - in contrast to cold-forming - no further separate process step is required for producing the impressions.

The bulges of the tool advantageously have a round or oval outer contour and a size of 10-20 mm. In this way, impressions can be produced which, on the one hand, are adapted in terms of their shape to the geometry of the spot welding guns, but on the other hand have such a small lateral extension that they can only be neglected. significant effects on the strength and stiffness of the component to be produced. Alternatively, the bulge can have a rectangular outer contour. The corners or edges of the bulge are advantageously rounded in order to minimize weakening of the component due to notching.

The invention is explained in more detail below with reference to an exemplary embodiment illustrated in the drawings. Show:

Figure la is a perspective view of a B-pillar for a motor vehicle with local impressions.

Figure 1b shows an assembly of the B-pillar of Figure la with a reinforcing member in a sectional view along the line Ib - Ib of Figure la.

2a shows a half of a hot-forming tool for producing the B-pillar of FIG. 1a;

2b shows a detail of the hot-forming tool half of FIG. 2a in a detailed illustration;

Fig. 3 is a schematic sectional view through a hot forming tool according to the line III - III in Figure 2a ... Fig. 3a ... with the tool open Fig. 3b ... with the tool closed

Fig. 4 shows a section of a tool with different forms of characteristics.

FIG. 1 a shows a molded component 1, in the present case a B-pillar 2 for a motor vehicle, which was produced from a sheet steel plate by a hot-forming process. To manufacture this B-pillar 2, a patched composite sheet was used as the semi-finished product 3 with a base plate which was provided locally with a reinforcing sheet. This The design of the semi-finished product 3 has the result that the material thickness 4,4 'of the fully formed B-pillar 2 varies over the length of the B-pillar 2, so that the B-pillar 2 in the upper and lower transition area 5,6 has a lower material thickness 4 ', while the material thickness 4 is increased in a central region 7 lying between the transition regions 5, 6 in accordance with the stress. Details regarding the production of a composite sheet as a semifinished product 3 and its hot forming to produce such a B-pillar 2 are described in DE 100 49 660 AI, the content of which is hereby incorporated into the present application.

Along its edges 8, the B-pillar 2 of FIG. 1 a has connection areas 9 in which the B-pillar 2 is to be joined with further components 10. Figure Ib shows a sectional view of a section of the B-pillar 2 of Figure la in the assembled position with the other component 10. In the upper transition region 6, the total thickness 11 'of the sheets 2,10 lying on top of one another is sufficiently small (ie ≤ 3 mm) that the two sheets 2, 10 can be joined together by means of spot welding. In the central area 7, on the other hand, in which - as described above - the material thickness 4 of the B-pillar 2 was increased in accordance with the stress, the total thickness 11 of the sheets 2, 10 lying on top of one another is too large (ie> 3.5 mm), so that no reliable spot welding of the two sheets 2, 10 is possible in this area 7. In order to be able to spot weld the sheets 2, 10 in this central area 7 as well, the B-pillar 2 is provided according to the invention with locally limited impressions 12, so that the material thickness 4 ″ of the B-pillar 2 is locally reduced in this part of the connecting area 9. The total thickness 11 ″ of the two sheets 2, 10 lying on top of one another is sufficiently small in the region of these impressions 12 (ie ≤ 3 mm), so that the two sheets 2, 10 are process-reliable at the location of these impressions 12 using spot welding can be added. In order to be insensitive to inaccuracies in the positioning of the spot welding guns, the impressions 12 are designed in such a way that the material thickness 4 ″ is approximately constant across the impression 12.

FIG. 2a shows a tool half 13 of a hot-forming tool 14 for producing the B-pillar 2 in FIG. The border 8 of the B-pillar 2 produced with this tool 14 is indicated in FIG. 2a by a dash-dotted line. In order to produce the local impressions 12 in the connection area 9 of the B-pillar 2, the tool half 13 is provided with local bulges 15 at the corresponding points, which are shown in a detailed view in FIG. 2b.

The effect of the local bulges 15 of the tool half 13 on the semifinished product 3 is shown in a detailed illustration in FIGS. 3a and 3b: The semifinished product 3, from which the B-pillar 2 is to be formed, is inserted into the open hot-forming tool 14 (FIG 3a). When the hot-forming tool 14 is closed (FIG. 3b), the three-dimensional shape of the B-pillar 2 is shaped or deformed, since when the tool 14 is closed, the clear distance 16 between the two tool halves 13, 13 'in the region of the bulges 15 is less than that Original sheet thickness 4 in this area is displaced locally by the bulges 15 when the tool 14 is closed, which results in the permanent impressions 12 on the sheet 3. The size and shape of the embossments 12 therefore largely correspond to the size and shape of the bulges 15 on the tool part 13.

The bulges 15 on the tool part 13 are advantageously adapted in terms of their shape and size to the joining method, with the aid of which the finished component 2 in a subsequent step are to be connected to the further component 10. In addition to the rectangular bulges 15 shown in FIGS. 2a, 2b, the bulges 15 can in particular be round or oval (see FIG. 4) or have any other shape. The edges 17 of the bulges 15 are expediently rounded in order to ensure a continuous change in the material thickness 4.4 ″ in the edge region 17 and to avoid local weakening of the component 1 due to sharp edges.

Since the tool part 13 causes a local material displacement on the component 1 in the area of the bulges 15, these areas 15 of the tool half 13 (and the opposite tool half 13 ') are exposed to particularly high loads. In order to increase the service life of the tool 14, it is advantageous to locally increase the strength of the tool halves 13, 13 'in the region of the bulges 15. In the exemplary embodiment in FIGS. 2a and 2b, this was achieved in that the corresponding regions 15 were laser-hardened; the edges of these laser-hardened zones are indicated by dashed lines in FIG. 2b.

As shown in FIG. 1 a, the impressions 12 of the B-pillar 2 spatially overlap with the component edges 8. This has the advantage that the material (excess), which is forced out of these areas 12 in the course of the introduction of the impressions 12, is free can escape beyond the component boundary 8. For the production of the B-pillar 2 of FIG. 1 a, the use of the method described in (patent application 102 54 695.9-14) is recommended, in which a component blank 3 is first formed from the (unhardened) semi-finished product by a cold-forming process, which is then corresponding to the Boundary contour 8 is trimmed. This component blank 3 is then heated and in a hot forming Tool 14 is press-hardened, the final three-dimensional shape of the B-pillar 2 being produced and the local embossments 12 being introduced at selected points in the connection areas 9.

As an alternative or in addition to the indentations 12 near the edge, indentations 12 can also be provided in regions of the component 1 remote from the edge (corresponding to connection regions 9 in regions of the component 1 remote from the edge). In this case, it must be ensured that the excess material that is forced out of the area of the bulges 15 when the hot-forming tool 14 is closed can be absorbed in a targeted manner. For this purpose, the tool half 13 can be provided in the immediate vicinity of the bulges 15 with recesses 18 into which the excess material can flow. Examples for the design of such recesses 18 are shown in FIG. 4 and (dashed) in FIGS. 3a and 3b. These cutouts 18 are advantageously designed in such a way that they surround the bulges 15 in an annular manner, at least in sections; this ensures a uniform flow of material in all directions.

In the exemplary embodiment described so far, the local impressions 12 were introduced into the component 1 in the course of a hot forming process. Alternatively, the impressions 12 can also be pressed into the component 1 by a cold forming process.

As described above, the embossments 12 are used primarily on components 1 which have areas 7 with a material thickness 4 which is increased in accordance with the stress and are to be joined there in connection areas 9 with the aid of spot welding with other components 10. The invented The design of the connection areas 9 in accordance with the invention, in which local impressions 12 are provided, is also particularly suitable for components 1 which are to be connected by means of laser welding. It is known that during laser welding, the material thicknesses of the sheets 1, 10 to be welded must be precisely matched to one another in order to avoid burning through in the joining area. Here, the invention permits simple mutual adaptation of the local material thicknesses of the components 1, 10 to be connected in the connection areas 9.

If components 1 made of sheet steel have previously been considered, the impressions according to the invention can also be applied to sheet metal components made of any light metal alloys (for example aluminum) and other metals and alloys.

The invention is preferably used in structural and cladding components in vehicle construction, for example in the case of A and B pillars, longitudinal, transverse and integral beams, vehicle roofs etc. The invention can, however, also be applied to a wide range of other components which can be used with the aid of a thermal joining process, in particular with the aid of spot welding, to be connected to other components.

Claims

DaimlerChrysler AG patent claims

Connection area (9) on a component (1, 2) made of a metal sheet, which is provided for joining this component (1, 2) with at least one further component (10) made of sheet metal using a thermal joining process, in particular spot welding characterized in that the connection area (9) has a locally limited indentation (12), in the area of which the material thickness (4 ") of the component (1, 2) is locally reduced.

Connection area according to claim 1, characterized in that the embossing (12) overlaps the edge (8) of the component (1, 2).

Method for joining two or more components (1, 2, 10) made of sheet metal, the components (1, 2, 10) being joined in a connection area (9) by means of a joining method, in particular spot welding, characterized in that at least one the components (1, 2) are provided with a locally limited indentation (12) in the connection area (9), in the area of which the material thickness (4 ") of the component (1, 2) is locally reduced. Method according to claim 3, characterized in that the three-dimensional shape of the component (1, 2) is produced with the aid of a tensile pressure forming process in the cold state, in particular with the aid of deep drawing, and in that the embossing (12) as part of this forming process in the component ( 1,2) is introduced.

Method according to Claim 3, characterized in that the three-dimensional shape of the component (1, 2) is generated with the aid of a tensile pressure forming process in the cold state, in particular with the aid of deep drawing, and in that the impression (12) after the forming process is completed in the component ( 1,2) is introduced.

A method according to claim 4 or 5, characterized in that the area of the embossing (12) before the actual one

Embossing process is heated.

Method according to claim 3, characterized in that the three-dimensional shape of the component (1, 2) is produced with the aid of a hot-forming process, and in that the embossing (12) is introduced into the component (1, 2) during hot-forming.

Method according to one of claims 3 to 7, characterized in that the impression (12) is introduced into the component (1, 2) after trimming.

9. Forming tool (14) for producing a component (1, 2) from a semifinished product (3) from a metal sheet, with two tool halves (13, 13 '), between which the semifinished product (3) is formed at least in sections, characterized in that that at least one of the two tool halves (13) has a bulge (15) in the direction of the opposite tool half (13 '), in the area of which in the closed position of the tool (14) the distance (16) of the two tool halves (13, 13') is smaller is the local material thickness (4) of the semi-finished product (3).

10. Forming tool according to claim 9, characterized in that the strength of the tool half (13) in the region of the bulge (15) is increased.

11. Forming tool according to claim 10, characterized in that the strength of the tool half (13) in the region of the bulge (15) is increased by laser hardening.

12. Forming tool according to claim 10, characterized in that the tool half (13) in the region of the bulge (15) is provided with a strength-increasing insert made of a hard material, in particular a ceramic material.

13. Forming tool according to one of claims 9 to 12, characterized in that the bulge (15) has a round or oval outer contour.

4. Forming tool according to one of claims 9 to 13, characterized in that the bulge (15) is at least partially surrounded by an annular recess (18).