EP1658148B2 - Method for shaping metal sheets - Google Patents

Description

The invention relates to a method for hot forging of sheets, in particular circuit boards, in a forming tool, applied to a motherboard for partial reinforcement one or more reinforcing boards, the motherboard and the at least one reinforcing board fixed to each other and / or aligned by suitable means to each other and the motherboard and forming the at least one reinforcing board together, wherein a surface coating for forming a bonding layer is applied to the at least one reinforcing board prior to the hot forging operation, wherein the surface coating melts during the hot forging and forms a bond between the motherboard and the at least one reinforcing board.

Such methods are known in the art, especially in the manufacture of molded parts for vehicles. Especially in the vehicle sector, there is the fundamental requirement to design parts as lightweight as possible in lightweight construction. As a result, the fuel consumption of the vehicle can be reduced and its handling and driving characteristics can be significantly improved. At the same time, however, a good stability of the vehicle parts should be ensured, especially a crash stability. For the partially heavily loaded in such a crash moldings, such as vehicle uprights, it is known to locally strengthen these more stressed areas. Such a local reinforcement can be achieved by a cross-sectional enlargement, for example by doubling sheets. Previously, the base plate and the reinforcing plate were each deep-drawn by itself and subsequently assembled into a complete structural part. Since in the rarest cases, a precise fit between the aufzufügenden shaped reinforcing sheet and the separately shaped base plate can be achieved, arise when joining such moldings usually at least in the edge region gaps. In this moisture can penetrate and lead to corrosion. However, this is particularly to be avoided since the doublings are provided precisely where reinforcement of the sheet used is required. Occurring corrosion, however, leads to a weakening of such an area.

The DE 43 07 563 C2 suggests for the field of deep drawing of sheet metal, therefore, deep-draw base plate and reinforcing plate together or form-punching. The one or more reinforcing plates are attached to the base plate before the common deep-drawing or punching and connected inextricably after deep-drawing or punching with the base plate. In addition, this document discloses the provision of corrosion protection measures in the field of superimposed sheets. For this purpose, the provision of coated or galvanized steel sheets or the interposition of a plastic or metal foil or an adhesive layer (see also DE 101 20 121 A1 ) called.

As a thermoforming as Kaltverformvorgang the tools heavily loaded when doubling the deep-drawing sheets, is in the generic DE 100 49 660 A1 proposed to reform a patched composite sheet of a base plate and reinforcing sheet (s) in the hot state at 800 - 850 ° C in a desired shape and to cool defined on the forming tool with mechanical maintenance of the forming state. To connect the base plate and the reinforcing plates, the contact surface of at least one of the plates is provided with a brazing blanket area before being applied to the base plate. After the soldering and before heating, a connection point between the reinforcement plate and the base plate is set to ensure a clear positioning of the sheets together. Before the common forming, the patched composite sheet is heated to a temperature above the forming temperature of the material of the sheets, formed in the hot state into the desired shape and then cooled defined under mechanical fixation in the forming state in the closed held forming tool and / or fixing and cutting tool.

A similar procedure as the DE 100 49 660 A1 also reveals the DE 101 36 433 A1 , According to this publication, a local high reinforcement and rigidity increase with low additional weight in a sandwich construction of base plate and reinforcing plate is achieved in that between these two sheets, a molded body made of glass or a glass mat is inserted. Forming then takes place according to the DE 100 49 660 A1 by hot forming the entire patched composite sheet, initially again heating to temperatures above the forming temperature of the materials of the sheets, then the composite is placed in a hot state in a forming tool, formed into the desired shape and cooled with mechanical fixation of the desired forming state. To avoid leakage of the doughy glass from the gap between the base plate and the reinforcing plate, the edge of the reinforcing plate is connected to the base plate around the glass intermediate element, whereby a cavity is created for the intermediate glass element.

From the DE 101 35 647 C1 is a application of a non-metallic, inorganic sealant on a near-edge contact area of sheets, a stacking of the sheets, heating the patched composite sheet to a temperature above the forming temperature of the material, forming in the hot state and subsequent mechanical fixing of the forming state by cooling disclosed.

The DE 198 26 290 A1 discloses a method of manufacturing partial double sheet or multiple sheet metal structures formed from a base sheet and one or more reinforcing sheets which may be deep drawn, bent or die-stamped together. From the DE 199 57 910 A1 For example, a method is known for roll profiling two or more sheets that are brought together between oppositely rotating rolls. In the in the DE 199 19 783 A1 described method is a bonding of at least two sheets by a partial cross-linking of an adhesive before forming. A complete cross-linking of the adhesive takes place only after the forming. The EP 0 857 526 A1 relates to a forming part with a partially formed multiple sheet metal structure, wherein the reinforcing plates are welded overlapping each other with the base sheet.

The sheet forming processes discussed above provide either no hot working and thus high and partially differential stress on the thermoforming tool, or hot working, which, however, is cumbersome when applied in paste form due to the use of blanket brazing application. precise metering and positioning when sprayed on, sprinkled or applied in the form of chips or applied in the form of a solder foil is, where in such a prior accurate blank is required. The provision of a pocket or a cavity for a glass intermediate element or a glass mat has the disadvantage that on the one hand such a cavity must be created, on the other hand, the glass mat, if it does not have the dimensions of the reinforcing plate, the ingress of moisture at their edges allows and thus corrosion of the sheets used.

The present invention is an object of the invention to provide a method for hot forming of sheets or boards, which does not have the disadvantages mentioned above and allows the production of moldings in lightweight construction with provided for a partial higher stress reinforcement, with respect to the above Technique for even more effective corrosion protection in conjunction with a secure connection of motherboard and reinforcement board (s) is to be made possible.

According to claim 1, the object is achieved for a method of the type mentioned above in that the connecting layer consists of a coating applied to the motherboard and / or the at least one reinforcing board adhesive and the warm forging at temperatures between 500 ° C and 730 ° C, in particular 500 ° C and 700 ° C, in particular 500 ° C and 650 ° C.

This provides a process for hot forging sheet metal, particularly blanks, which combines the advantages of co-forming blanks to be joined and hot forging with those of optimum sealing and bonding of the blanks. Due to the use of a common hot forging of motherboard and reinforcing board (s), very good manufacturing accuracy and avoidance of gaps between the reshaped boards can be achieved in combination with the advantage of an arbitrarily high degree of forming due to the use of hot forging as opposed to cold forming, for example like deep drawing. As a result, in particular the press tools used can be spared, even when using almost any material thicknesses of boards and their combination with each other. In warm forging, lower temperatures are used than in hot forming, which generally does not harden the material. However, for example, high-strength materials can be used which already have high-strength properties. In this case, only a temperature increase in ranges between 500 and 730 ° C, more preferably between 500 and 700 ° C, in particular to 650 ° C to succeed.

According to the invention, a surface coating for forming a connecting layer is applied to the at least one reinforcing plate, wherein the surface coating is applied to the at least one reinforcing plate before the hot forging process, wherein the surface coating melts during forming and forms a connection between the motherboard and the at least one reinforcing plate , This makes it possible that already during the forming of the boards these are interconnected. By coating the reinforcement board (s), an optimal and uniform connection with the motherboard is possible up to the edge of the reinforcement board and, if necessary, of individual reinforcement boards. In this way, a full-surface connection of the boards can be achieved up to the edge region of the reinforcing board (s) even with very complex shapes. An additional application of a sealant bead in the edge region of the at least one reinforcing plate is therefore no longer necessary, but may, if desired, nevertheless be provided.

As the adhesive, a silicone, in particular epoxy resin adhesive, polyurethane adhesive, hot melt adhesive, PUR dispersion adhesive, etc., can be used. The coating can be done, for example, by rolling, dipping, printing, gumming, etc.

The tie layer may completely cover the surface of the reinforcing board (s). However, it can also be formed as a pattern or mask on the surface of the at least one reinforcing plate and / or the motherboard, in particular surrounding the edge region of the reinforcing board substantially gapless. In some cases, it is not absolutely necessary to provide the entire surface of the reinforcing board (s) with the respective bonding layer, since a connection of the molded boards is already supported by their shaping and sealing only in the edge region of the reinforcing board (s) for corrosion protection appropriate is. In the choice of the pattern or the mask, this (s) is advantageously matched to the forces acting on the finished molding during operation, so that unintentional release of the boards can be avoided from each other.

According to the invention, the connecting layer consists of a coating applied to the motherboard and / or the at least one reinforcing board adhesive, which melts during the forming process and forms a firm connection between motherboard and reinforcing board (s) during cooling. As a result of the warm forging, the adhesive melts and forms an adhesive coating on the reinforcing sheet (s). Upon cooling, a strong bond will form between the adjacent board surfaces. Corrosion protection is possible as well as a firm connection of the molded boards. In contrast to the provision of glass intermediate elements in cavities between a base plate and a reinforcing plate, as in DE 101 36 433 A1 discloses, it is possible to provide a very thin interconnecting layer which is much more resilient than the thick glass intermediate layer after DE 101 36 433 A1 , Cavities between motherboard and reinforcement board must also not be provided.

In the case of semi-hot forming of a tie-layer base board and at least one reinforcing board together, an adhesive will be used as the tie-layer. This can melt during the forming process, harden on cooling and form a firm connection between the motherboard and the at least one reinforcing board.

In a structural test made by the method of the invention, a bonding layer is provided between a molded motherboard and at least one reinforcing board in the form of an adhesive and / or molten and solidified glass material which interconnects the motherboard and the at least one reinforcing board and / or multiple reinforcing boards.

Preferably, a reinforcing board is arranged on the motherboard and fixed and / or aligned by suitable means to this or several reinforcing boards next to and / or one above the other on the motherboard arranged and fixed and / or aligned by suitable means to each other and / or to the motherboard. Particularly preferred is provided with the provision of only one gain board on the motherboard and fixed and / or aligned by suitable means to this or providing several reinforcing boards these are overlapping and / or abutting each other in a partial area and / or spaced from each other on the motherboard fixed and / or aligned with each other by suitable means. By providing multiple reinforcement boards Side by side with and without distance to each other stresses within a shaped workpiece or sheet metal structural part can be avoided or at least reduced, and stiffness increases are selectively carried out, especially when providing different material strengthen motherboard and reinforcement board (s). By providing a plurality of reinforcement boards one above the other, additional material reinforcements and thus greatly differing stiffnesses can be achieved over the surface of the structural part. By overlapping a plurality of reinforcement boards in their respective edge regions, stiffness differences can also be generated. However, in each case only one reinforcing plate can be provided, which if necessary was previously composed of several parts, in particular of different material thickness. Instead of providing a fixation or connection of the boards with each other before the forming process, it is also possible to position the boards only aligned with each other and without forming a connection with each other. To fix the position or to maintain the mutual positioning, stud bolts or the like may be particularly preferably provided in the forming tool or the forming press.

Preferably, the reinforcing boards are connected to each other abutting each other before the forming process, in particular by attaching a weld or other connecting seam. Depending on the forming temperature and forming mode, this butt seam can be leveled during forming, so that no uneven transition points remain.

Preferably, the boards are fixed to each other before the warm forging and / or after the warm forging by additional compounds, in particular by welding, riveting, clinching or another connection method. As a result, the unique position of the reinforcing plate (s) applied selectively at certain points on the surface of the motherboard is fixed, so that it does not substantially change during the forming, especially before forming. After reshaping, a fixation proves to be advantageous in itself otherwise by shearing off possibly easily releasing connections between motherboard and reinforcement board (s), since especially an additional punctiform connection can counteract unwanted shearing.

In contrast to the solder joints according to the DE 100 49 660 A1 proves the provision of an adhesive advantageous that the heating temperature does not need to be kept in a tolerable range for the area, but can be adjusted to a suitable in particular for warm forging range. In addition, the problem of corrosion by flux, which is commonly used for a soldering, avoided.

Figur 1 bis 4

eine schematische Ansicht des Ablaufs einer zweiten Ausführungsform eines erfindungsgemäßen Halbwarmumformvorgangs unter Vorsehen einer Oberflächenbeschichtung auf Verstärkungsplatinen.

For a more detailed explanation of the invention, an embodiment will be described below with reference to the drawings. These show in:

Figure 1 to 4

a schematic view of the process of a second embodiment of a warm forging process according to the invention under provision of a surface coating on reinforcing boards.

The shaped reinforcing boards serve e.g. as internal reinforcement, the molded motherboard as external reinforcement of a vehicle B-pillar.

FIG. 1 shows the first processing step of an alternative method for hot forging of blanks. Here, the reinforcing boards 2, 3, 4 are initially provided with a surface coating 20, 30, 40. This surface coating consists of an adhesive which melts under the influence of heat and at the latest on cooling of the molded blanks with these adhesively bonding adhesive. As an alternative to providing the surface coating only on the surfaces of the reinforcing boards, the surface 10 of the motherboard and / or both the surface of the motherboard and the reinforcing boards can be provided with a surface coating which also allows connection to the reinforcing boards when heated, eg in the manner of a multi-component adhesive.

With their coated surfaces 21, 31, 41, the reinforcing plates 2, 3, 4 are then placed on the motherboard 1 and fixed in the case shown in FIG. 7 at various points, for example by welding points 5.

This resulting unit of a composite board 60 is subsequently introduced into a furnace 7, such as FIG. 2 can be seen. In this, the composite board is heated to a suitable temperature for warm forging and forwarded to the forming press 8 ( FIG. 3 ). Therein, the warm forging takes place with corresponding temperatures. During the forming process, the surface coating of the boards melts and bonds to the respective adjacent board surface. Therefore, a bonding layer 12 is formed directly during the forming, which allows a dense and firmly connected unit of the molded blanks.

During annealing of the board material, the bonding layer 12 is cooled and thereby hardens. Any gaps between motherboard and reinforcing boards remaining or remaining during molding are filled by the bonding layer, thereby creating a dense corrosion prevention unit. In addition to the joints already existing and remaining during hot forging in the form of e.g.

Welding points, even more or these may be again provided for additional connection of the molded boards to each other. In principle, however, it is already possible to ensure a sufficiently firm hold of the molded blanks on one another by the combination of the fixing connecting points applied before forming and the connecting layer.

The forming press 8, as in FIG. 3 is shown, a finished molded part can be removed, which can be used as a structural part in vehicle construction after a customarily subsequent to the forming cutting.

LIST OF REFERENCE NUMBERS

1

motherboard

2

reinforcing plate

3

reinforcing boards

4

reinforcing boards

5

WeldingSpot

6

composite board

7

oven

8th

forming press

9

arrows

10

Surface of the motherboard

11

link layer

12

link layer

20

surface coating

21

coated surface

30

surface coating

31

coated surface

40

surface coating

41

coated surface

60

composite board

P

arrows

Claims (8)

1. A method for the warm forming of sheet metal, in particular plates (1, 2, 3, 4), in a forming die (8), wherein one or a plurality of reinforcement plates (2, 3, 4) are applied to a base plate (1) for the purposes of partial reinforcement, the base plate (1) and the at least one reinforcement plate (2, 3, 4) are fixed on top of one another and/or, by suitable means, are aligned with one another, and the base plate (1) and the at least one reinforcement plate (2, 3, 4) are formed together,
   wherein, before the warm forming process, a surface coating (20, 30, 40) is applied to the at least one reinforcement plate (2, 3, 4) for the formation of a bonding layer, or as a bonding layer,
   and wherein the surface coating melts during the warm forming and forms a bond between the base plate (1) and the at least one reinforcement plate (2, 3, 4),
   characterised in that
   the bonding layer consists of an adhesive applied as a coating on the base plate (1) and/or on the at least one reinforcement plate (2, 3, 4), and the warm forming takes place at temperatures between 500 and 730°C, in particular 500 and 700°C, in particular 500 and 650°C.
2. The method according to Claim 1,
   characterised in that
   the adhesive is an adhesive that is suitable for high or very high temperatures.
3. The method according to Claim 1 or 2,
   characterised in that
   the bonding layer is designed as a pattern or mask on the surface of the at least one reinforcement plate (2, 3, 4) and/or the base plate (1), in particular surrounding the edge region of the reinforcement plate.
4. The method according to one of the preceding claims,
   characterised in that
   a reinforcement plate is arranged and fixed on the base plate (1) and/or, by suitable means, is aligned with the latter, or in that a plurality of reinforcement plates (2, 3, 4) are arranged and fixed on the base plate (1) alongside one another and/or on top of one another and/or, by suitable means, are aligned with one another and/or with the base plate (1).
5. The method according to one of the preceding claims,
   characterised in that
   a reinforcement plate is arranged and fixed on the base plate (1) and/or, by suitable means, is aligned with the latter, or in that a plurality of reinforcement plates (2, 3, 4) are fixed on the base plate (1) overlapping one another in a sub-region, and/or abutting one another, and/or with a distance apart from one another, and/or, by suitable means, are aligned with one another.
6. The method according to Claim 5,
   characterised in that
   a plurality of reinforcement plates are bonded to one another in an abutting manner before the forming process, in particular by the application of a weld seam or another bonding seam.
7. The method according to one of the preceding claims,
   characterised in that
   the base plate (1) and the reinforcement plate(s) (2, 3, 4) have different material thicknesses.
8. The method according to one of the preceding claims,
   characterised in that
   the plates (1, 2, 3, 4), before the warm forming and/or after the warm forming, are fixed to one another by means of additional bonds, in particular by welding, riveting, clinching or another bonding method.

Images