DE102009038896B4 - Method for producing a structural component joined from a first and a second component, and device for carrying out the method - Google Patents

Abstract

Method for producing a structural component joined from a first and a second component (1, 2), in which the first component (1) is formed from a blank by means of a hot forming process and during the hot forming process in a joining region (3) the thickness (D) of the the first component (1) is reduced to a predetermined value (d) by embossing, and -the embossing of the first component (1) in the joining region (3) by means of an embossing stamp (7) generates a material accumulation (6) surrounding the embossed region characterized by the following method steps: a) punching of the first component (1) in the joining region (3) to produce a pre - hole (4), wherein between the material accumulation (6) encircling the pre - hole (4) and the edge surface of the pre - hole (4) narrow edge region runs, and b) inserting the pre-punched first component (1) with the second component (2) for producing a joining point (5) in the joining region (3) by means of a die (8) and a associated stamp (9), wherein the accumulation of material (6) is arranged on the die side.

Description

The invention relates to a method for producing a structural component joined from a first and a second component according to the preamble of patent claim 1 as well as a device for carrying out the method according to the invention according to the preamble of patent claim 8.

The generic DE 10 2004 005 568 A1 describes a component made of a metal sheet which is to be joined in a connection region with at least one further component made of sheet metal using a thermal joining method, in particular spot welding. There is the problem that with the help of the spot welding only a good joining result can be achieved if the total material thickness of the superposed and to be joined sheet metal parts does not significantly exceed a thickness of 3 mm. This problem will be according to this DE 10 2004 005 568 A1 achieved in that one of these components is provided in the connection region with a localized imprint, wherein in this connection region, the material thickness of the component is locally reduced. The impression is introduced in the course of a cold or a hot forming process in the component.

It is known by hot forming and press hardening of steel sheet of high-strength steels, such as. For example, 22MnB5 with a tensile strength of 1400-1600 MPa by heating in a furnace or by another method, for example. Induction heating sheet metal blanks to about 950 ⁰ and then with a cooled forming tool, which consists of die top and tool base with die, punches and Sheet holder is formed by hot forming into a molded part. Here, the steel sheet is cooled as a sheet metal blank in the cooled forming tool with a predetermined temperature gradient and cured by a structural transformation (martensite).

So is, for example, from the DE 10 2007 043 154 A1 a method for producing hardened profiles is known, in which a sheet metal strip is formed into a profile, the profile is heated to a temperature above the Austenitisierungstemperatur and cooled this previously heated profile with a speed above the critical hardness speed and then a device for embossing or Cutting recesses is supplied.

Such high-strength and press-hardenable steels are used in vehicle construction in crash-relevant areas of the vehicle steel body. Welding methods can be used as joining technologies, with the production of hybrid sheet metal structural components, for example aluminum-structural structural components, placing high demands on the joining technology.

It is known to add aluminum and steel components mechanically, possibly with gluing, with automatable, mechanical joining methods without pre-punching of the components, such as punched rivets, clinching (also called clinching) as well as hole- and thread-forming screws are economical. However, these joining methods can not be used economically for the above-described high-strength and press-hardenable steels, since they are not sufficiently formable in the cured state.

Also, clinching with a pre-hole is known as a reshaping joining method in which one of the joining partners is pre-punched in the joining area and only the non-pre-punched joining partner is reshaped. This makes it particularly suitable for clinching compounds in which one of the joining partners is not or only partially deformable and therefore they are not suitable as joining partners for the production of clinch connections without pre-hole, such as the compounds described above, high-strength press-hardenable steels and aluminum. In such hybrid compounds, the press-hardened steel usually has a greater thickness as a joining partner than the other aluminum joining partner. The press-hardened steels are perforated by means of a laser or by punching, also water-jet cutting is suitable for this purpose. Due to the high hardness or strength and the thickness of this joining partner, the laser and punching is technologically complex and often leads to low downtime, so that an economical production of such hybrid structural components is not always possible.

A clinching (clinching) is, for example, from the DE 101 51 659 A1 known, for joining at least partially overlapping components with a mold and a pressure fluid in a first joining step, wherein by means of the pressurized fluid material of the second component is plastically deformed by a formed in the first component Vorloch, and in a second joining step means a joining die of the molding tool is acted on in the opposite direction to a deformed in the first joining step portion of the deformed second component, wherein material from the deformed area in a mold cavity, which is formed in a molding of the mold, displaced and an undercut between the components is formed.

Furthermore, also describes the DE 20 2005 013 220 U1 the production of a Durchsetzfügeverbindung in an overlapping connection area two sheet metal parts.

The sake of completeness is on the DE 10 2005 032 113 B3 which describes a method and apparatus for hot working and partially curing a component. For this purpose, the forming tool consists of two tool halves in a press, wherein these tool halves are each divided into at least two segments, which are separated by a heat insulation. These segments can be heated or cooled by a temperature control, so that in different areas of the component different temperatures and thus different cooling curves are adjustable. With this known method, a component with areas of different hardness or strength and ductility can be produced.

The object of the invention is to provide an improved method, with the components joined inexpensively, in particular hybrid structural components can be produced economically.

The object is also to provide a device for carrying out the method according to the invention.

The object is achieved by a method having the features of patent claim 1.

• - das erste Bauteil mittels eines Warmumformprozesses aus einer Platine umgeformt und während des Warmumformprozesses in einem Fügebereich die Dicke des ersten Bauteils auf einen vorgegebenen Wert durch Prägen verringert wird, und
• - mit dem Prägen des ersten Bauteils im Fügebereich mittels eines Prägestempels eine den geprägten Bereich umgebende Materialanhäufung erzeugt wird,

werden erfindungsgemäß folgende Verfahrensschritte durchgeführt:

1. a) Lochen des ersten Bauteils im Fügebereich zur Erzeugung eines Vorloches, wobei zwischen der das Vorloch umlaufenden Materialanhäufung und der Randfläche des Vorloches ein schmaler Randbereich verläuft, und
2. b) Durchsetzfügen des ersten vorgelochten Bauteils mit dem zweiten Bauteil zur Herstellung wenigstens eines Fügepunktes im Fügebereich mittels einer Matrize und einem zugehörigen Stempel, wobei die Materialanhäufung matrizenseitig angeordnet ist.

In this method according to the invention are for producing a joined from a first and second structural component, in which

• - The first component is formed by means of a hot forming process from a circuit board and during the hot forming process in a joining region, the thickness of the first component is reduced to a predetermined value by embossing, and
• - By embossing the first component in the joining region by means of an embossing stamp, a material accumulation surrounding the embossed region is produced,

the following process steps are carried out according to the invention:

1. a) punching of the first component in the joining region to produce a pre-hole, wherein between the Vorloch surrounding material accumulation and the edge surface of the pre-hole is a narrow edge region, and
2. b) passing through the first pre-punched component with the second component for producing at least one joining point in the joining region by means of a die and an associated punch, wherein the material accumulation is arranged on the die side.

With this method according to the invention, an embossing process is carried out simultaneously with the hot forming process in the joining region, with which the thickness of the first component, which preferably consists of a high-strength and press-hardenable steel, is locally reduced such that the punching or lasering of the pre-hole can be carried out economically, d. H. In particular, the service life of the tools are extended.

In addition, the clinch connection thus produced leads to a significantly higher connection strength, in particular in the production of a hybrid structural component, preferably of high-strength press-hardened steel and aluminum. The connection strength depends essentially on the neck thickness of the clinch connection and u. a. determined by the sheet thicknesses to be joined, wherein a greater strength is achieved when the thickness of the punch-side first component is greater than the thickness of the die-side second component. Since usually in such hybrid clinch compounds, the sheet thicknesses of the high-strength and press-hardened steels are greater than the sheet thicknesses of aluminum, a known clinch connection would lead to a reduced strength of the compound due to their low neck thickness. Due to the inventive reduction of the sheet thickness in the joining area more material is available to form the neck of the clinch connection, as a result, the neck thickness is greater. In particular, in the case of the clinch connection, the engagement in the likewise reduced thickness of the edge region of the pre-hole, so that a solid form-fitting connection of the aluminum is achieved with the press-hardened steel.

Furthermore, embossing of the first component in the joining region by means of an embossing stamp, or in the case of two-sided embossing with two embossing stamps, generates a material accumulation surrounding the embossed region which, after punching, surrounds the pre-hole to form a narrow edge of the pre-hole. In this case, the first component is joined to the second component by means of a die and an associated stamp such that the material accumulation is arranged on the die side. This results in the pre-hole area to a voltage reduction, which when using such compounds in crashrelevanten areas of a vehicle body, the crash properties of the corresponding structural components are positively influenced. Furthermore, such a material accumulation, which has a funnel-shaped cross-sectional profile, as a positioning aid for the clinch tools in automated process of manufacturing the structural component can be used.

A high connection strength is achieved even if the thicknesses of the first and second components are equal or if the thickness of the second component is smaller than the thickness of the second component in the joining region.

It is particularly advantageous if the first component is hardened in the hot-forming process in such a way that a partially lower strength is produced in the joining region than in the remaining region of the first component. This also facilitates the introduction of the Vorloches by means of stamping, laser cutting or water jet cutting.

Furthermore, it has proven to be expedient that the perforation according to method step a) is carried out after cooling of the first component, in particular, this can be carried out in the same tool as in the forming tool.

The perforation of the second component arranged on the die side is preferably carried out by means of a laser or by means of punching or water jet cutting.

The inventive method can be advantageously used for the production of structural components, in which the first component of a press-hardenable steel and the second component made of a light metal, preferably aluminum, wherein the second component also profiled, for example. An aluminum press profile part may be.

Particularly stable clinch connections can be achieved even if the second component has a smaller thickness than the first component.

The object is also achieved with the features of claim 8.

Thereafter, the device for carrying out the method according to the invention consists of a forming tool with a tool base and a tool top, in particular with a punch and a die and in addition to the one-sided embossing comprises an embossing stamp or two-sided embossing a further die with preferably circular cross-section, which is provided according to the invention in that the device has a thermally insulated region in which the die (s) is / are arranged.

Thus, the embossing can be done simultaneously with the hot forming under heat, without requiring an additional process step. Furthermore, in the joining region of the first component, the material strength can be reduced to a desired value by influencing the temperature gradient during the cooling of the first component, in particular in the case of a high-strength and press-hardenable sheet metal blank as the first component. Preferably, this thermally insulated area can be heated individually to even better adjust the temperature profile during cooling can.

• 1 schematische Darstellungen möglicher Prägevorgänge gemäß des erfindungsgemäßen Verfahrens,
• 2 eine schematische Darstellung eines Clinch-Vorganges gemäß des erfindungsgemäßen Verfahrens, und
• 3 eine schematische Darstellung eines Umformwerkzeugs.

The invention will now be described in detail by means of an embodiment with reference to the accompanying figures. Show it:

• 1 schematic representations of possible embossing operations according to the method according to the invention,
• 2 a schematic representation of a clinch process according to the inventive method, and
• 3 a schematic representation of a forming tool.

In the following, the process steps of the method according to the invention for producing a hybrid structural component consisting of, for example, steel (for example 22MnB5) and aluminum will be explained and illustrated in detail.

First, a sheet metal blank made of the material 22MnB5 in a heating furnace (or in an induction furnace) is heated to about 950 ⁰ C and then as the first component 1 placed in a cooled forming tool by simultaneously pressing and cooling with high cooling rate to harden the sheet metal plate is carried out so as to increase the material strength or hardness of the material to about 800 MPa to 1400-1600 MPa.

This first component 1 has at least one joining area 3 on, in which a joining point 5 by clinching with a second component 2 is created as joining partner. For this purpose, an embossing punch is in the forming tool 7 provided in the 1a) and 1b) is shown schematically. This stamp 7 have a plane and a circular embossing surface 7a on, according to 1a) from one opposite the embossing surface 7a remote annular support surface 7b will circulate. In the intermediate area, ie between the embossing surface 7a and the circumferential support surface 7b becomes in the joining area during the embossing process 3 of the first component 1 Material for forming a material accumulation 6 pressed.

The stamp 7 to 1b on the other hand, it is slightly chamfered at the preg-sided end, being at a distance from the embossing die 7 a hold-down 7c is provided, the first component 1 is also chamfered. By the distance of the hold-down 7c to the embossing stamp 7 and the chamfers a gap is formed, so that by the embossing process in the joint area 3 of the first component 1 as well an accumulation of material 6 is generated in this gap, wherein the chamfering, especially on the punch side, this accumulation of material is shaped according to V-shaped.

The 1a and 1b show exemplary dies 7 with stamping surfaces 7a , This stamp 7 and their embossing surfaces 7a can also have other shapes and cross-sections and, for example, be formed annular, conical or spherical. Furthermore, the show 1a and 2 B one-sided embossing, the same applies to two-sided embossing, which another, from below against the first component 1 require guided dies to require.

This stamping process becomes the original sheet thickness D of the first component 1 , So the sheet metal plate used on a smaller sheet thickness d reduced. By reducing the sheet thickness in the joining area 3 the strength is lowered, so that the production of a Vorloches 4 in the joining area 3 of the first component 1 is relieved.

A further reduction of the strength in the joining area 3 can be achieved by the fact that the forming tool used be designed such that the area of the embossing punch 7 is thermally insulated from the surrounding area of the tool, as exemplified by 3 schematically shows. These 3 shows a lower and upper mold half 14 and 15 , which is thermally insulated as part of a forming tool, not shown, and possibly also can be heated. The lower half of the mold 14 carries the movable die 7 that has a stamping surface 7a with a center on the embossing surface 7a arranged cone-shaped elevation, which causes a reduction in the sheet thickness, when between the two mold halves 14 and 15 the first component 1 is inserted.

Thus, another cooling rate can be achieved in this thermally insulated area, which then also leads to a different hardness or material strength in this joining area and therefore additionally the production of a pre-hole 4 facilitated. This thermally insulated area can also be equipped with a heater, so that a certain temperature gradient can be set to cool the joint area. If the relevant parameters are set appropriately, local consolidation in the joint area could be avoided.

After cooling the first component 1 becomes known in the art a Vorloch 4 in the joining area 3 of the first component 1 inserted so that between the pre-hole 4 circulating material accumulation 6 and the peripheral surface of the pre-hole 4 a narrow edge area runs in the clinching material of the second component 2 engages behind.

Subsequently, the joining of the first pre-punched first component takes place 1 and the second component 2 by means of clinching known to those skilled in the art for producing a joining point 5 , This process shows 2 with the used clinching tools, a die 8th and an associated stamp 9 , In this tool, the two join partners, the pre-punched first component 1 and the second component 2 placed, with the first component 1 is inserted so that its accumulation of material 6 on a support surface 10 of the tool rests. The second component 2 is from a downholder 11 fixed. For positioning the first component 1 serves the accumulation of material 6 , In particular, the circumferential inclined surface, the example. By embossing after 1b) can be produced with a funnel-shaped cross-section.

The 2 shows the condition when the clinching punch 9 completely against the matrix 8th forming a residual soil 12 from the material of the second component 2 was pressed. It can be clearly seen that due to the reduced sheet thickness d in the joining area 3 the neck thickness 13 was significantly increased. Also, the amount of material for Hintergreifung of the first component 1 in the area of the peripheral edge of the Vorlochs 4 increased due to the thickness reduction, whereby the fit of the two joining partners is also improved.

For connecting two joining partners according to the description, it is also possible to produce a plurality of such joining regions with corresponding joining points.

The inventive method is particularly suitable for automatic production. In particular, clinching methods other than those described above can also be used to carry out the method according to the invention.

LIST OF REFERENCE NUMBERS

1

first component

2

second component

3

joining area

4

Pre-hole in the first component 1

5

joining point

6

Material accumulation at the pre-hole 4

7

dies

7a

Embossing surface of the embossing stamp 7

7b

supporting

7c

down device

8th

Matrix as a clinching tool

9

Stamp as a clinching tool

10

supporting

11

down device

12

residual base

13

neck thickness

14

Thermally insulated area on the lower mold half for receiving the stamping die

15

Thermally insulated area on the upper mold half

D

Sheet thickness of the first component 1

d

Sheet thickness in the joining area 3

Claims (9)

Method for producing a structural component joined from a first and a second component (1, 2), in which - the first component (1) is shaped from a blank by means of a hot forming process and during a hot forming process in a joining region (3) the thickness (D) of the the first component (1) is reduced to a predetermined value (d) by embossing, and - the embossing of the first component (1) in the joining region (3) generates a material accumulation (6) surrounding the embossed region by means of an embossing stamp (7) characterized by the following method steps: a) punching of the first component (1) in the joining region (3) to produce a pre - hole (4), wherein between the material accumulation (6) encircling the pre - hole (4) and the edge surface of the pre - hole (4) narrow edge region runs, and b) inserting the pre-punched first component (1) with the second component (2) for producing a joining point (5) in the joining region (3) by means of a die (8) and e ines associated punch (9), wherein the accumulation of material (6) is arranged on the die side. Method according to Claim 1 , characterized in that the first component (1) is hardened in the hot forming process such that in the joint region (3) a partially lower strength than in the remaining region of the first component (1). Method according to one of the preceding claims, characterized in that the perforation according to method step a) after cooling of the first component (1) is performed. Method according to Claim 3 , characterized in that the punching is carried out by means of a laser or by means of punching or water jet cutting. Method according to one of the preceding claims, characterized in that the first component (1) consists of a press-hardenable steel. Method according to one of the preceding claims, characterized in that the second component (2) consists of a light metal, preferably aluminum. Method according to one of the preceding claims, characterized in that the second component (2) has a smaller thickness than the first component (1). Device for carrying out the method according to one of the preceding claims, wherein the device consists of a forming tool with a tool base and a tool top, in particular with a punch and a die and in addition to one-sided embossing an embossing punch (7) or in two-sided embossing a further die with preferably comprises circular cross-section, characterized in that the device has a thermally insulated region (14, 15) in which the or the dies (7) is or are arranged. Device after Claim 8 , characterized in that the thermally insulated area (14, 15) is individually heated.

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