Mixed construction joint

Abstract

A hybrid construction joint comprising a metal casting (1) and a metal sheet part (3), wherein the metal sheet part (3) has a sheet flange (7) which is welded or brazed to the metal casting (1) via a connecting seam (19) extending over a seam length (l) between the metal casting (1) and the metal sheet part (3), wherein a bead (21) is formed in the metal sheet part (3) parallel to and offset from the connecting seam (19), by means of which component stresses in the metal sheet part (3) can be relieved, which form during the welding or brazing process due to thermal expansion or in the finished hybrid construction joint, so that a transfer of component stresses from the metal sheet part (3) to the metal casting (1) is reduced, characterized in that a flange bead (23) is formed in the sheet flange (7) which relieves component stresses in the metal sheet part (3) during the welding or brazing process.and that the flange groove (23) is completely in material bond with the weld or brazed material (17) after the formation of the joining seam (19).

Description

The invention relates to a hybrid construction connection according to the preamble of claim 1. In the mass production of automotive bodies, soldering processes are established in which the hard solder is melted using an industrial laser. Laser beam soldering can be used to join a hybrid component consisting of a metal casting and a metal sheet part. In contrast to a point-welded mixed-material connection, such a hybrid joint offers the following advantages: Laser beam brazing is a non-destructive joining process that does not affect the crystalline (i.e., non-formable) microstructure of the metal casting, thus eliminating the risk of notch formation that could lead to premature component cracking or fracture. Furthermore, the brazing seam creates a large-area, force-transmitting connection between the sheet metal part and the metal casting, allowing mechanical stresses from the sheet metal part to be distributed over a large area and transferred into the metal casting. This reduces the risk of stress cracks in the extremely brittle metal casting. A hybrid joint consists of a metal casting and a metal sheet component. The metal sheet component can be designed as an angle profile, with a base section and a flange extending from it. This flange, together with the metal casting, can define a joint gap that is filled with weld or solder material up to a certain depth during the welding or brazing process, forming a weld seam that extends along the length of the joint between the metal casting and the metal sheet component. Due to the high process temperature at the joint, mechanical stresses are generated in the metal sheet component, which are transferred via the weld seam to the brittle, non-formable metal casting with its crystalline microstructure. A generic method for joining a first component to a second component is known from DE 10 2011 006 364 A1. Further component connections are known from DE 11 2011 104 032 T5, DE 10 2018 128 402 A1, DE 10 2014 000 618 B4, DE 10 2020 215 071 A1, DE 10 2019 219 743 A1, and DE 10 2021 207 519 A1. DE 10 2014 000 618 B4 discloses a joint between two thin-walled sheet metal components. Both sheet metal components have flange sections that define a joining gap filled with solder. The flange sections have grooves that are completely covered with weld or brazing material after the welding or brazing process. A process arrangement is known from DE 10 2015 016 513 B4, by means of which two components are joined in a laser beam welding process.The welding system of the process arrangement is integrated into a control loop to ensure weld quality. The object of the invention is to provide a hybrid construction connection with a metal casting and a metal sheet part in which, compared to the prior art, the component stresses acting on the metal casting can be reduced in a simple manner. The problem is solved by the features of claim 1. Preferred embodiments of the invention are disclosed in the dependent claims. The following describes aspects of the invention relating to a soldering process. However, the invention is not limited to such a soldering process. Rather, all aspects are also transferable to a welding process. The invention is based on a hybrid construction connection consisting of a metal casting and a metal sheet component. The metal sheet component can be an angle profile with a sheet base section and a sheet flange attached to it. This flange, together with the metal casting, can define a joining gap which, during the welding or brazing process, is filled with weld or brazing material up to a certain depth, forming a weld seam that extends over a seam length between the metal casting and the metal sheet component. The welding or brazing process according to the invention is preferably a laser brazing process in which the laser beam is guided along the joining gap, where it melts the brazing alloy, for example, a copper-silicon wire. The molten brazing alloy flows into the joining gap, thereby forming the joint. Due to the high process temperature at the brazing joint, mechanical stresses arise in the metal sheet component.To reduce the transfer of these mechanical component stresses from the sheet metal part to the metal casting, a bead can be formed in the base section of the sheet metal part, parallel to and offset from the joint seam. This bead helps to dissipate the component stresses that develop during the brazing process, thereby reducing the transfer of these stresses to the metal casting. In one technical implementation, the base section bead formed in the sheet metal part's base section can run at a distance from the weld seam, so that the base section bead is out of contact with the weld seam. For further stress relief, not only is the base section bead provided in the base section of the sheet metal part, but also a flange bead in the sheet metal part's flange. This flange bead can also relieve component stresses in the sheet metal part during the brazing process. Unlike the base section bead, the flange bead is completely covered by the brazing material after the weld seam has formed. The base section bead and the flange bead run parallel to each other along the length of the weld seam. Furthermore, the base section bead (and, if applicable, the flange bead) is completely continuous and / or uninterrupted along the entire length of the weld seam.Unlike sheet metal parts, metal castings are free of beads to relieve component stresses. Due to their crystalline microstructure, metal castings cannot deform during welding or brazing processes; instead, they remain deformation-free. A process arrangement for producing the hybrid joint according to the invention can be implemented as follows: A soldering unit can be integrated into the process arrangement together with an electronic control unit and a detector in a control loop. Within the control loop, the detector can detect an actual process parameter during the welding or soldering process, which correlates with the joint quality. Depending on the detected actual process parameter, the electronic control unit can control the soldering unit with a control signal. Preferably, a comparator module is assigned to the electronic control unit, which compares the detected actual process parameter with a stored setpoint. Based on the difference between the actual process parameter and the setpoint, the electronic control unit can determine the control signal for controlling the soldering unit. In a preferred implementation, the detector can be a radiometric device. This can consist of a radiation source generating X-rays or gamma rays and an imaging acquisition module. During the welding or soldering process, the radiation source can be used as a transmitted light source that illuminates the joining area, i.e., the solder joint. The imaging acquisition module generates a radiation intensity image of this illuminated joining area. In an evaluation module, the actual process parameter is determined by analyzing the radiation intensity image. This parameter is then forwarded to the electronic control unit, where the setpoint / actual value comparison is performed. Preferably, the actual process parameter can be a seam depth, an offset of the joining seam to the joint path between the two components and / or a material cross-section of the soldered material in the joining gap. A riveting process – just like the welding process described above – is also a destructive joining process in which the crystalline microstructure of the metal casting is affected, creating the risk of notch formation, which leads to premature component cracking / fracture in the metal casting. In another embodiment, the sheet metal flange can be divided transversely to the weld seam into an overlap segment and a deformation segment. The overlap segment overlaps the metal casting and is joined to it by an overlap weld. The deformation segment of the sheet metal flange, which adjoins the overlap segment, does not overlap the metal casting and transitions into the base section of the sheet metal at a transition edge. The bead is formed in the deformation segment of the sheet metal flange. Exemplary embodiments of the invention are described below with reference to the accompanying figures. Figures 1, 2, 3 to 4 show different views illustrating the hybrid construction according to the invention. Figure 1 shows a completed hybrid joint consisting of a metal casting 1, for example, made of die-cast metal or, specifically, die-cast aluminum, and a metal sheet part 3, for example, an aluminum or steel sheet part. In the hybrid joint, the metal sheet part 3 is realized as a thin-walled angle profile, comprising a sheet base section 5 and an angled sheet flange 7. The metal casting 1 is also realized as a thin-walled angle profile, comprising a metal base section 9 and a metal flange 11. The base sections 5 and 9 of the two joining partners 1 and 3 merge flush at a joint, while a joining gap 15 is defined between the flanges 7 and 11 of the two joining partners 1 and 3, which is filled with solder 17. The soldered material 17 forms a connecting seam 19, which extends over a seam length l between the metal casting part 1 and the metal sheet part 3. This type of hybrid construction is primarily used in the manufacture of automotive bodies. For example, the metal casting 1 can be a body-side cast frame to which the metal sheet part 3 is attached. The metal sheet part 3 can be, for example, a side panel, a floor panel, an interior trim panel, or an outer skin of the vehicle. Alternatively, the metal sheet part 3 can be an intermediate support to which another add-on sheet metal part is attached using a spot riveting process. A direct connection of the add-on part to the metal casting 1 via the riveting connection would, however, potentially lead to notch formation, causing the metal casting 1 to crack or break prematurely. As further shown in Fig. 1, a base section bead 21 is formed in the sheet metal part base section 5, parallel to and offset from the joining seam 19. This bead allows component stresses in the sheet metal part 3, which arise during the brazing process, to be relieved. This reduces the transfer of component stresses from the sheet metal part 3 to the metal casting 1. The base section bead 21 can preferably be positioned in a concealed area to avoid any potential impairment of the external appearance of the composite joint. In Fig. 1 or Fig. 2, the base section bead 21 extends at a distance from the joining seam 19, so that the base section bead 21 remains out of contact with the joining seam 19 and is therefore freely deformable. In addition, a flange bead 23 is formed in the sheet metal flange 7 of the sheet metal part 3, which also relieves component stresses in the sheet metal part 3 during the welding or brazing process. Unlike the base section bead 21, however, the flange bead 23 is no longer deformable for stress relief after the brazing process has been completed. This is because, unlike the base section bead 21, the flange bead 23 is completely in material bond with the weld or braze material 17 after the joining seam 19 has been formed. Both the base section bead 21 and the flange bead 23 extend completely and without interruption over the entire seam length l of the connecting seam 19. The composite joint shown in Fig. 1 is produced by a laser beam soldering process, as indicated in Fig. 2. Accordingly, a laser beam 27 generated by a laser device 25 is guided along the joint, where it melts the brazing alloy 29, for example, a copper-silicon wire. The molten brazing alloy 29 flows into the joining gap 15, forming the weld seam 19. As shown in Fig. 2, the soldering device 25 is integrated into a control loop together with an electronic control unit 31 and a detector. In this control loop, the detector detects an actual process parameter x during the welding or soldering process, which correlates with the joint quality. The electronic control unit 31 is assigned a comparator module that compares the detected actual process parameter x with a setpoint z. Based on the difference between the actual process parameter x and the setpoint z, the control unit 31 determines a control signal y for controlling the laser device 25. In Fig. 2, the detector is designed as a radiometry device. This device comprises a radiation source 35, which generates X-rays or gamma radiation, and an imaging acquisition module 37. During the soldering process, the radiation source 35 is used as a transmitted light source, illuminating the joining area. The imaging acquisition module 37 generates a radiation intensity image of the illuminated joining area. In a downstream evaluation module 39, the actual process parameter is determined by evaluating the radiation intensity image and is then transmitted to the electronic control unit 31. For example, the actual process parameter x can be a seam depth, an offset of the joint seam to the joint line and / or a material cross-section of the solder material 17 located in the joining gap 15. Figures 3 and 4 show further comparative examples of a hybrid construction not covered by the invention, in which the metal casting 1 and the metal sheet 3 are welded together by welds 19, namely a lap weld and a parallel fillet weld. According to Figures 3 and 4, the sheet flange 7 is divided transversely to the two welds 19 into an overlap segment 41 and a deformation segment 43. The overlap segment 41 overlaps the metal casting 1 and is welded to it. The deformation segment 43 of the sheet flange 7, adjoining the overlap segment 41, does not overlap the metal casting 1 and transitions into the sheet base section 5 at a transition edge 45. The freely deformable bead 21 is formed in the deformation segment 43 of the sheet metal flange 7. Reference symbol list 1 Metal casting 3 Metal sheet part 5 Sheet metal part base section 7 Sheet metal part flange 9 Metal casting part base section 11 Metal casting part flange 15 Joining gap 17 Weld or braze material 19 Joining seam 21 Base section bead 23 Flange bead 25 Brazing unit 27 Laser beam 29 Brazing alloy 31 Control unit 35 Radiation source 37 Imaging acquisition module 39 Evaluation module 41 Overlap segment 43 Deformation segment 45 Transition edge l Seam length

Claims

A hybrid construction joint comprising a metal casting (1) and a metal sheet part (3), wherein the metal sheet part (3) has a sheet flange (7) which is welded or brazed to the metal casting (1) via a connecting seam (19) extending over a seam length (l) between the metal casting (1) and the metal sheet part (3), wherein a bead (21) is formed in the metal sheet part (3) parallel to and offset from the connecting seam (19), by means of which component stresses in the metal sheet part (3) can be relieved, which form during the welding or brazing process due to thermal expansion or in the finished hybrid construction joint, so that a transfer of component stresses from the metal sheet part (3) to the metal casting (1) is reduced, characterized in that a flange bead (23) is formed in the sheet flange (7) which relieves component stresses in the metal sheet part (3) during the welding or brazing process.and that the flange groove (23) is completely in material bond with the weld or brazed material (17) after the formation of the joining seam (19). Mixed construction connection according to claim 1, characterized in that the bead (21) runs at a distance from the connecting seam (19), so that the bead (21) is out of contact with the connecting seam (19). Mixed construction connection according to one of the preceding claims, characterized in that the sheet metal part (3) has an angle profile with a sheet metal part base section (5) and the sheet metal part flange (7) set off therefrom, and that the sheet metal part flange (7) together with the metal casting part (1) defines a joining gap (15) which can be filled with welding or soldering material (17) in the welding or brazing process up to a seam depth, forming the joining seam (19). Mixed construction connection according to one of the preceding claims, characterized in that the metal casting (1) is an angle profile with a metal casting base section (9) and the metal casting flange (11) set off therefrom, and that the metal casting flange (11) together with the sheet metal part flange (7) limits the joining gap (15), and / or that the welding or brazing process is a laser process. Mixed construction connection according to claim 4, characterized in that the sheet metal part flange (7) is divided transversely to the joining seam (19) into an overlap segment (41) which overlaps with the metal casting (1) and is joined to it by an overlap weld / braze connection, and into an adjoining deformation segment (43) which is without overlap with the metal casting (1) and transitions into the sheet metal part base section (5) at a transition edge (45), and that the bead (21) is formed in the deformation segment (43) of the sheet metal part flange (7). Mixed construction connection according to one of the preceding claims, characterized in that the bead (21) and / or the flange bead (23) run completely continuously and / or without interruption over the seam length (l) of the connecting seam (19). Mixed construction connection according to one of the preceding claims, characterized in that the metal casting (1) is free of beads for reducing component stresses.

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