EP0934132B1 - Diffusion welding process and device for joining sheet metal parts - Google Patents

Abstract

In a diffusion welding process for joining superimposed sheet metal parts by welding, part of the material of the metal sheets is locally upset by means of a stamp and a die perpendicularly to the plane of the metal sheets, causing the material of the sheet metal parts to yield and diffusion welding the sheet metal parts at a weld. In order to achieve a sufficiently solid weld even when the parts to be joined are made of materials with a particular tendency to hardening at low temperatures or pre-hardened materials, the parts of the metal sheet surrounding the weld are pressed onto the die during welding with a force which is sufficient to prevent the material from yielding against the active direction of the stamp.

Description

The invention relates to a clinching method according to the preamble of claim 1 and a device intended for its implementation according to the preamble of claim 6.

EP 0 546 270 B1 describes a method for locally shaping brittle material known in which the sheets to be joined between the stamp and the anvil are clamped, whereby the sheet material is subjected to a pressure load according to the preload of the anvil by a spring. During joining this pressure load of the spring force increases accordingly, the anvil in the Die hole is pushed back. Finally the anvil sits on the lower one Stop, and the stamp pushes material into the space left by the anvil is released, whereby the bracketing takes place.

DE 37 26 392 A1 describes a method for connecting thin layers lying one on top of the other Known plates in which a cam is formed by deep drawing, the bottom of which a protruding curvature is freely formed. This curvature is then formed flat by an opposing upsetting stroke, the excess material is pushed aside. The deep-drawn wall thicknesses are retained, whereby the Plate material is protected because the side displacement is primarily due to bending and not done by squeezing.

The two plates are advantageously during the deep drawing and Compression process around the deep-drawing point from both sides using the hold-down device clamped. In this way, plate material can be in the area of the deep-drawing point move between the hold-down device and the die. Especially with the upsetting stroke only the thermoforming die can move backwards while lifting the plates is prevented.

EP 0 330 061 B1 describes a method and an apparatus for Assert two or more superimposed, planes Sheet metal parts known, in which a tool set consisting of stamp and die is used, the matrix of a central anvil and opposite one Anvil work surface has upstanding female moldings, preferably can dodge sideways during an upset and one Limit mold cavity into which is inserted.

In the known clinching, the sheet metal parts to be connected enforced jointly at a selectable joint and then cold compressed using such pressures that through a lateral flow of material a positive and non-positive seating of the sheet metal parts in the form of a cup-like joining element. That at the joint volume of material located under a stamp effective area initially only enforced. For this purpose, the sheet material is made from the Level of the sheet metal parts moved out, the bottom thickness of the resulting Addition still corresponds approximately to the total starting sheet thickness. at a further enforcement is between the bowl bottom of the joining element a stamp effective surface and the anvil clamped and by an increasing increasing punch force an upsetting process with radial material flow causes in the floor area, the so-called widths. The thickness of the floor panels is reduced by upsetting compared to the starting sheet thickness, what is necessary to create the necessary form fit by spreading.

To facilitate this upsetting process, the connecting sheet metal parts partially cut in the direction of penetration are, since then the cup bottom of the joining element largely during the upsetting process remains free of the bond to the other material or this Bond is at least reduced. However, it is disadvantageous that a cutting portion on the joining process, the strength of the penetration joint is reduced and the joining is not gas-tight, so that joining elements are preferred which can be produced without local cutting.

US-A-5 581 860 discloses a clincher for joining superimposed sheet metal parts with a die and in a mold cavity Die penetrable die, the die being an anvil and the like has upstanding, laterally swiveling fittings. The stamp is from a hold-down, and the anvil and stamp each have a pin having an active surface made of a hardened material, which in a Base body is pressed from a different material. A method according to the preamble of claim 1 can also be found in US Pat. No. 5,581,860.

This pushing through of sheet metal parts has so far not been economical can be used for sheet metal parts made of stainless steel with predominantly austenitic Basic structure. The same applies to others when the shape changes metals that are particularly prone to strain hardening, e.g. high-alloy stainless steel, titanium, or for pre-consolidated metals, e.g. higher strength steels. The material-related process forces for Forming joining is above the load limit of the joining tool or lead to failure after just a few joining processes thereof.

However, if the process forces are too low, the load-bearing behavior is the inadequacies. It was also found that at greatest possible cold compression only an insufficient form fit in the joining element is achieved. Such sheet metal materials are enforced therefore only at all with a cut in the sheet metal parts and with acceptance of the associated disadvantages possible, the also by the cutting achieved a reduction in process forces to no appreciable extent Leads to an increase in tool life.

A first object of the invention is therefore a clinching method to create the type mentioned at the outset, with which also for joining parts from materials that tend to work harden or or A sufficiently firm joint can be produced from pre-consolidated materials is.

A second object is an apparatus for this method to accomplish.

The first task is characterized by the characteristics of the Claim 1 solved.

The second task is characterized by the characteristics of the Claim 6 solved.

This creates a method in which an effective form fit is achieved with reduced introduction of joining force. this applies especially for the materials that tend to work harden. The joining forces to be applied are reduced so that the Tools can withstand this load.

It has been found that, especially in the case of strong work hardening agents Sheet materials that the width is difficult because the Tried to avoid material under compressive stresses and against The direction of the stamp flows back. By pressing the parts to be joined during This backflow is prevented during the joining process and the sheet metal material forced by the thus initiated broadening a positive Form the connecting element in the effective area of the die. With the too The process leads to materials that tend to work harden therefore also to a good positive fit not previously achieved.

The fact that the sheet metal parts lying around a joint with such a great force is pressed against the die, which is sufficient to hold the material to be pressed onto a base (here the die) in such a way that the joining material volume no longer against the direction of action of the stamp can flow back, namely it is achieved that the initiated Compression force in an early phase of compression to form a effective positive locking is used. Consequently, the result is more advantageous Wise a sufficiently firm disposition even if under Protection of the tools the necessary degree of deformation at the joint under reduced force transmission takes place. This is especially the enforcement more economical because the number of with a joining tool feasible additions increases considerably.

The pressure force acting on the sheet metal parts around the joint is one passive force, which must be higher than the reflux force of the material of the parts to be joined during the joining process. According to the invention, it was found that the pressure force then the skid flow force of the material exceeds if the pressing force is 5 times to 8 times the forces that only for stripping the parts to be joined are needed during the enforcement phase.

Furthermore, the pressure force is preferably applied to an effective pressure surface applied around the joint with a size such that the applied pressure does not leave an impression in the sheets and the moldings of the die can move laterally when compressed. The contact pressure effective area can therefore be dimensioned sufficiently large be so that the resulting pressure load does not become a plastic Deformation of the clamped parts to be joined, and if possible small so that it can be joined even in hard-to-reach places.

It was found that the deformation can still be improved if the Sheet metal parts at a higher temperature than the environment or the tools be joined; this results in a temperature difference of 10 ° C up to 50 ° C with the same joining force an improvement in load-bearing behavior the joining, or with the same load-bearing behavior as at ambient temperature Joining elements produced, the joining force can be reduced by up to Lower 15%. One reason for this is a reduction in work hardening, as they are particularly the case with austenitic sheet materials occurs.

Sheet metal materials can also be used with the clinching device according to the invention enforced with a pronounced tendency to work hardening be without causing plastic deformation of the stamp and anvil or a failure of the tool body. The modular stamp and die-side structure, in which the stamp and Anvil pin is supported on a flat base plate, a higher one Resilience of the tool set as cracks are anticipated. The The tool set can therefore accommodate higher joining pressures.

The anvil surface has a material flow-compatible design in the form of a circumferential bevel, with a better form fit at the same Sheet metal thickness is reached. At the same time, such a bevel leads to one Pressure relief of the edge, which increases the tool life.

Preferred high strength materials for the stamp and anvil pin are hard metal and high-strength ceramics.

The active surfaces of the stamp and anvil pen can have a star shape Have micrograph, which further increases their tool life and the Material flow is improved.

Further embodiments of the invention are the following description and the subclaims.

Fig. 1

zeigt schematisch eine teilgeschnittene Seitenansicht eines ersten Ausführungsbeispiels einer Durchsetzfügevorrichtung,

Fig. 2

zeigt eine teilgeschnittene Seitenansicht eines Stempels mit Anpreßelement gemäß einem weiteren Ausführungsbeispiel einer Durchsetzfügevorrichtung,

Fig. 3

zeigt eine Draufsicht einer Wirkfläche eines Stempels gemäß Fig. 2,

Fig.

4 zeigt eine Seitenansicht eines Ambosses gemäß einem weiteren Ausführungsbeispiel einer Durchsetzfügevorrichtung,

Fig. 5

zeigt eine Draufsicht einer Wirkfläche eines Amboßstiftes gemäß Fig. 4,

Fig. 6, 7 und 8

sind vergrößerte Seitenansichten weiterer Ausführungsformen des in Fig. 4 mit einem strichpunktierten Kreis markierten Bereiches.

Fig. 9a

zeigt im Teilschnitt eine mit der Vorrichtung nach Fig. 1 hergestellte Verbindung,

Fig. 9b

zeigt im Teilschnitt eine mit einer Vorrichtung ohne Anpreßelement hergestellte Verbindung bei gleicher Bodendicke des Fügeelements wie bei Fig. 9a,

Fig. 10a

zeigt die hergestellte Verbindung gemäß Fig. 9a,

Fig. 10b

zeigt im Teilschnitt eine mit einer Vorrichtung ohne Anpreßelement hergestellte Verbindung bei durch größere Fügekraft wie bei Fig. 9a, 9b und 10a verringerter Bodendicke des Fügeelementes.

The invention is explained in more detail below on the basis of the exemplary embodiments illustrated in the attached figures.

Fig. 1

schematically shows a partially sectioned side view of a first embodiment of a clinching device,

Fig. 2

shows a partially sectioned side view of a stamp with a pressing element according to a further embodiment of a clinching device,

Fig. 3

2 shows a plan view of an active surface of a stamp according to FIG. 2,

FIG.

4 shows a side view of an anvil according to a further exemplary embodiment of a clinching device,

Fig. 5

4 shows a top view of an active surface of an anvil pin according to FIG. 4,

6, 7 and 8

are enlarged side views of further embodiments of the area marked with a dash-dotted circle in Fig. 4.

Fig. 9a

1 shows a partial section of a connection produced with the device according to FIG. 1,

Fig. 9b

shows in partial section a connection made with a device without pressing element with the same bottom thickness of the joining element as in FIG. 9a,

Fig. 10a

shows the connection made according to FIG. 9a,

Fig. 10b

shows in partial section a connection made with a device without pressing element with a reduced bottom thickness of the joining element due to greater joining force as in FIGS. 9a, 9b and 10a.

Fig. 1 shows a first embodiment of a device for clinching from a tool set with a stamp 1 and a die 2, each arranged in a clinching tool holder 3, 4 are.

The die 2 has an anvil 5 as the central area, the head side an upsetting table 6 (anvil work surface) of a mold cavity 7 forms in the die 2. The mold cavity 7 limits the enforcement of a volume of material by compared to Upset table 6 upright die elements in the form of shaped pieces 8, 9, which can dodge sideways during an upsetting process. The shaped pieces 8, 9 also form with their respective top 10, 11 a die pad for sheet metal parts 12, 13 to be joined Joining process, the evaded fittings 8, 9 are reset and close the die 2 are preferably two return springs 42, 43 combined in a spring bonnet. Using a fastening screw 14, the die 2 can be fastened to the tool holder 4.

The stamp 1 has a stamp pin 15 with a stamp effective surface 16, which in the mold cavity 7 with a selectable joining force penetrates for a clinching process. During this joining process becomes a located at a joint under a stamping surface 16 Volume of material of sheet metal parts 12, 13 initially enforced, i.e. moved out of the plane of the sheet metal parts 12, 13 until a bottom 17 (see FIGS. 9a and 10a) of the resulting joint rests on the anvil 5, and then compressed with widths.

The stamp 1 is enclosed by a pressure element 18, the one Force transmission to the sheet metal parts 12, 13 around a joint, i.e. adjacent the stamp effective surface 16. The pressing element 18th For this purpose presses the sheet metal parts 12, 13 lying around the punch effective surface 16 against the die pad. The pressure element 18 should therefore have a counteraction exert a backward force on a material. The high of Force application or the pressure force is controllable. This control can be separate from or linked to the introduction of the joining force his.

Spring elements 19, 20 are preferably used to apply the pressure element force intended. Furthermore, the pressure element 18 is preferably over the spring elements 19, 20 guided on the tool holder 3 for the stamp 1. Such a guide allows the introduction of force in a simple manner increased by the pressure element 18 during the joining process become. For this purpose, the pressure element 18 can be provided with an active surface 21 against which the stamp 1 compresses the spring elements 19, 20 and increasing the pressure force works. The pressure element 18 is preferably designed as a press plate and can also be used as a stripping element at the end of a joining process.

To apply the pressure element force other pressure transmitters than Springs are used to generate the compressive forces. It is further not necessary that the pressure element 18 is guided on the stamp. By means of an external guide and an external drive, the pressing element 18 also perform its function.

The effective area 21 of the pressing element 18 is then dimensioned to be sufficiently large if the resulting pressure load does not become a plastic one Deformation of the surface of the sheet metal parts 12, 13 to be joined leads and the fittings 8, 9 of the die 2 can open during the joining process.

The stamp 1 and the die 2 are preferably of modular construction. To the stamp 1 comprises the stamp pin 15 at its head end the stamp effective surface 16 is formed and which is in a base body 23 is pressed. For this purpose, the base body 23 preferably has one Through hole 24. This modular structure allows the use of different Materials for the stamp pin 15 and the base body 23. The stamp pin 15 can be made of a first material, namely a Material of higher hardness or higher strength. Preferred materials for this are hard metal and high-strength ceramics. The basic body 23 can be made of a second material that is less hard but in return for example, is tougher than the first material. Is preferred as second material tempered tool steel.

At its end facing away from the working surface 16, the is supported Stamping pin 15 preferably continues on a plate 25 that is made of the same material as the stamp pin 15 and can be in turn in the tool holder 3 of a press, not shown supported. The transverse dimensions of the plate 25 are chosen so that the the tool holder 3 acting load of this without risk of breakage can be included. By means of a fastening screw 26 Stamp 1 to be attached to the tool holder 3.

The die 2 can have a modular design like the stamp 1. The anvil 5 is then formed by an anvil pin 22 from a first Material, namely a material of higher hardness or greater strength, such as hard metal or high-strength ceramics. The anvil pin 22 is pressed into a base body 27 made of a tough material, for which purpose this has a through hole 29. The material pairing can as with the stamp. The anvil 5 can also have a Support plate 28 on tool holder 4. The plate 28 can accordingly the plate 25 for the stamp 1 may be formed.

2 to 5 show a second embodiment of a clinching device, which is different from the embodiment described above differs only by the differences mentioned below. Otherwise, the above statements apply accordingly, so that for same parts same reference numerals are used.

Fig. 2 shows a stamp 1 in a modular design with a stamp pin 15, on which the stamp effective surface 16 is formed, which in one Base body 23 is pressed and is supported on a base plate. Partial circumferential grooves 30 are used for quick tool changes and thus for fastening of the stamp 1 to a tool acceptance. The effect of the stamp is as in the embodiment of FIG. 1 of a pressure element 18 comprises, which is supported by springs 19, 20 on the base body 23. About this pressure element 18, the stamp 1 as narrow as possible, but encloses with a sliding fit and the springs 19, 20 are now the invention Pressure forces initiated, the pressing element 18 so press firmly on the die so that the sheet metal material around the Stamp 1 is firmly clamped and thus prevents the material of the stamp-side sheet during upsetting, that is, against the effective direction of the stamp 1 can flow. Even before the start of enforcement, the stamp-side sheet metal can be pressed so that also feared no bending of the sheets during enforcement must become.

The pressure element 18 according to FIG. 2 differs from that of FIG. 1 in that the active surface 21 of the pressing element 18 runs continuously.

Fig. 4 shows the associated die 2 with an anvil 5, which in one Base body 27 is pressed and is supported on a base plate 28. The base body 27 has on its side facing the stamp 1 Inclined surfaces 32 on which die elements (not shown) support the spring-loaded on the anvil 5 and limit the cavity of the die together with the effective surface 6 of the anvil.

To prevent the danger that the anvil 5 and / or the stamp pin 15 breaking out at the edge under high pressure is a circumferential chamfer 31 provided, whose cross-sectional shape, as shown in Fig. 6 to 8, can be variable: rounded (Fig. 6), flat beveled (Fig. 7) or double beveled (Fig. 8). This chamfer also favors the material flow.

The facing active surfaces 16, 6 of stamp 1 and / or anvil 5 are with a favoring the flow of the material to be joined Provide surface finish as shown on the star-shaped micrograph in Fig. 3 and 5 recognizable. Accordingly, the active surfaces 16 and 6 in the 1 device.

A clinching method for joining superimposed ones Sheet metal parts 12, 13 comprises a joining process, in which by means of a stamp 1 and a die 2 at a joint a material volume of Sheet metal parts 12, 13 enforced locally and by upsetting perpendicular to Sheet level is added under material flow. The area surrounding the joint Sheet metal parts 12, 13 are on during this joining process the die 2 pressed with a pressure force sufficient to flow a material to prevent against the effective direction of the stamp 1.

The pressure force can be kept constant during the entire joining process become. Alternatively, the pressure force during the joining process be increased so that at least when compressing a pressure force in the surrounding area the joint that acts. Reflux force exceeds while it can be chosen lower beforehand. Also a first one Pressure force before or shortly before the joining process around the active surface of the stamp.

The sheet metal parts 12, 13 are essentially stationary on the die 2 pressed, with such a pressing force that a material flows back is prevented. This is especially true for the special Cold-hardening or pre-consolidated materials.

The pressing force is chosen in particular such that the sheet metal parts 12, 13 not during the joining process in the area surrounding the stamp 1 gap, i.e. the sheet metal parts 12, 13 lie flat against one another.

The pressing force for flat, flat sheet metal parts can also be selected in this way be that it is 5 times to 8 times the forces that only to prevent the parts to be bent during the enforcement phase are needed. An exemplary reference value for the The applied force with a joining element diameter of 5mm is 3000 N, if e.g. austenitic stainless steel sheets.

The pressure force is preferably applied to an effective pressure surface applied with such a size around the joint that the to be used Pressure does not leave an imprint in the sheet metal parts and the Die can open laterally.

Furthermore, the temperature of the sheet metal parts 12, 13 compared to the ambient temperature increase. Preferably 10 ° C to 50 ° C are higher Temperatures than the ambient temperature.

9a shows an example of one with the clinching devices described above manufactured joint, being that of the pressing element 18 pressing force exerted by the arrows during the joining process and the letter F is indicated. Sheet metal parts 12, 13 from a special work hardening material with a starting sheet thickness of each about 1 mm are positively connected by a joining element, the bottom 17 between the stamping surface 16 and the anvil work surface 6 in the mold cavity 7 while reducing the overall starting thickness is upset. A width 33 is formed by material flows, for which the fittings 8, 9 have moved outwards. The result is a coincidence with a good form fit. At the end of the joining process gap the sheet metal parts 12, 13 in the vicinity of the stamp not so that they lie flat against one another and without gap areas.

In comparison, Fig. 9b shows a joint with a stamp 1 and one Die 2 with a stamp collar but without pressure element. When achieved same floor thickness, i.e. approximately the same joining forces no effective positive locking achieved.

10a and 10b serve to further clarify the invention Process. 10a corresponds to that in FIG. 9a shown. The addition of Fig. 10b differs from that Fig. 9b in that increased joining forces have been used, leading to a have led to greater compression of the bottom 17 of the joint. But also the width 34 achieved in this way does not yet show sufficient Positive engagement.

9a, 9b and 10a, 10b illustrate that the invention Process allows the use of lower joining forces because of the effective Positive locking is achieved even with a small compression.

Claims (13)

1. Press-joining method for connecting sheet metal parts (12, 13) lying one upon another by means of a joining operation in which, by means of a punch (1) and a die (2) with an anvil face, at a joint location a volume of material of the sheet metal parts is displaced locally and, as a result of upsetting perpendicular to the plane of the sheet metal, is joined as the material flows, characterized in that sheet metal parts surrounding the joint location and made of materials tending to particular work-hardening or of previously work-hardened materials are pressed against the die (2) during the joining operation with a pressing force which prevents any flow of material counter to the direction of action of the punch (1) and which is five times to eight times the forces which are used merely for stripping, the material flow being made easier for this purpose by means of a circumferential chamfer (31), promoting material flow, on the anvil face, so that the joining force is reduced in such a way that the joining tools withstand this loading.
2. Press-joining method according to Claim 1, characterized in that the pressing force is applied to an effective contact area of such a size around the joint location that the pressing force to be used leaves behind no impression in the sheet metal parts, and the die can open sideways.
3. Press-joining method according to Claim 1 or 2, characterized in that a pressing force is applied to the surrounding sheet metal parts before the joining operation is started.
4. Press-joining method according to one of Claims 1 to 3, characterized in that the temperature of the sheet metals is increased above the ambient temperature.
5. Press-joining method according to Claim 4, characterized in that the sheet metal parts are heated to a temperature 10°C to 50°C higher than the ambient temperature.
6. Press-joining device for connecting sheet metal parts (12, 13) lying one upon another using a die (2) and a punch (1) that can penetrate into a mould cavity (7) in the die, the die (2) having an anvil (5) and mould pieces (8, 9) which project vertically from the said anvil, can pivot out sideways and are intended to limit the mould cavity (7), in which displacing takes place locally, and the punch (1) is enclosed by a pressing element (18) for applying force to the sheet metal parts (12, 13), the anvil (5) and the punch (1) each having a pin (15, 22) which has an active face and is made of a high-strength material, and which is pressed into a basic body made of another material, characterized in that the basic bodies (23, 27) of punch and anvil have through bores (24, 29) which accommodate the respective pins (15, 22) inside them, and the pins (15, 22) are each supported at the end opposite the respective active face (16, 6) on a planar supporting plate (25, 28), via which pressure loading can be introduced, at the anvil (5) and the punch (1), into a tool holder (3, 4), in that the pressing element (18) can apply a pressing force which is 5 times to 8 times the forces which are used merely for stripping, and the anvil (5) has a circumferential chamfer (31) which promotes material flow.
7. Press-joining device according to Claim 6, characterized in that the circumferential chamfer (31) is rounded.
8. Press-joining device according to Claim 6, characterized in that the circumferential chamfer (31) has a triangular cross section.
9. Press-joining device according to Claim 6, characterized in that the circumferential chamfer (31) has a broken cross-sectional shape that approximates to a rounding.
10. Press-joining device according to one of Claims 6 to 10, characterized in that the active faces (6, 16) of anvil (5) and/or punch (1) are provided with a surface finish which promotes material flow.
11. Press-joining device according to one of Claims 6 to 10, characterized in that the supporting plates (25, 28) consist of a high-strength material.
12. Press-joining device according to one of Claims 6 to 11, characterized in that the high-strength material used is hard metal or high-strength ceramic.
13. Press-joining device according to one of Claims 6 to 12, characterized in that the pressing element (18) is a pressure plate that is guided on the punch (1) and is supported by one or more prestressed springs (19, 20).

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