DE102018128402A1 - Process for producing a laser welded joint - Google Patents

Abstract

The invention relates to a method for producing a laser welded connection, comprising the steps:
- Bringing together a joining section (11, 31, 61) of a first component (10, 30, 60) with a second component (20, 40, 70), wherein a projection (12, 32, 65, 66) protruding from the rest of the joining section the first component (10, 30, 60) comes into contact with the second component (20, 40, 70),
- Force-fitting pressing together of the components at at least two fixing points (15, 16; 35, 36; 62, 63) of the joining section, which are arranged on both sides of the projection (12, 32, 65, 66), whereby a spring element section (12, 32) of the first component (10, 30) or a spring element section (72) of the second component (70) is elastically deformed,
- Joining the components pressed together at the fixing points (15, 16; 35, 36; 62, 63) and
- Welding the components on the spring element section (12, 32, 72) using a laser beam.

Description

The invention relates to a method for producing a laser welding connection, in particular by means of remote laser beam welding.

In laser beam welding, a focused beam of high power density is directed onto a joint, which melts the irradiated material. The weld pool is moved by a relative movement between the laser beam and the components to be joined. The cooling melt solidifies and cohesively connects the components that are welded together. Laser beam welding is characterized by a high welding speed and high component flexibility. In addition, laser beam welding only requires unilateral component access.

The welding speeds and flexibility can be increased even further if the laser welding is carried out as remote laser welding. The laser beam is directed onto the components via a scanner system and guided over them. The scanner system allows single or multi-axis deflection of the laser beam. Remote laser beam welding usually takes place with a large working distance of e.g. more than 0.4 m to the welding point. Due to the large working distance and the high welding speeds, remote laser beam welding is carried out without additional material. This results in only a small gap bridging ability and the need to weld at the technical zero gap. This usually makes complex clamping systems necessary, with which the components are pressed together at the joint.

The components used in body construction often have an anti-corrosion coating, e.g. a zinc coating. Due to the low boiling temperature of the coating, the coating material evaporates during welding. Without adequate precautions for directional zinc degassing, spatter and the resulting seam defects or necessary reworking occur, which means that laser beam welding compared to e.g. resistance welding.

Due to this problem and the high acquisition costs of laser welding systems, laser beam welding has so far only been used cautiously in body construction. Against this background, it is the object of the present invention to provide a possibility of how the potentials in laser beam welding, in particular in body construction, can be better used. Another object of the invention is to provide a method in which it is ensured in a simple manner that the components are laser-compatible, i.e. can be clamped and welded at the technical zero gap and with a targeted degassing option.

The object is achieved by a method according to claim 1. Further advantageous refinements result from the subclaims and the following description.

• - Aneinanderbringen eines Fügeabschnitts eines ersten Bauteils mit einem zweiten Bauteil, wobei ein gegenüber dem restlichen Fügeabschnitt vorstehender Vorsprung des ersten Bauteils mit dem zweiten Bauteil in Kontakt kommt,
• - Aneinanderpressen der Bauteile an mindestens zwei Fixierstellen des Fügeabschnitts, die beidseitig des Vorsprungs angeordnet sind, wodurch ein Federelementabschnitt des ersten Bauteils oder des zweiten Bauteils elastisch verformt wird,
• - Fügen der aneinandergepressten Bauteile an den Fixierstellen und Verschweißen der Bauteile an dem Federelementabschnitt mittels Laserstrahl.

A method for producing a welded connection is specified, with the following steps:

• Bringing together a joining section of a first component with a second component, a projection of the first component protruding from the rest of the joining section coming into contact with the second component,
• Pressing the components together at at least two fixing points of the joining section which are arranged on both sides of the projection, as a result of which a spring element section of the first component or of the second component is elastically deformed,
• - Joining the components pressed together at the fixing points and welding the components to the spring element section using a laser beam.

The invention is based on the idea of tensioning the components in a laser-compatible manner by introducing structural elements into the joining section when they are fixed within the assembly. The joining section is a section of the first component in which the fixing points and the projection are arranged and which is joined to the second component by subsequent joining processes.

If the components are brought together, the projection first comes into contact with the second component. If the components are then pressed together at the fixing points, an increased pressing force acts between the projection and the second component. This acts on the spring element section. The spring element section is a section of the joining section which, due to its geometric configuration, e.g. Shape and / or wall thickness, is able to deform elastically under the specified force. When the components are pressed together at the fixing points, there is consequently an elastic deformation of the spring element section, which in turn exerts a spring force counteracting the deformation on the opposite component. By joining the components at the fixing points, this deformation and the resulting spring force are practically “frozen”. The two components are clamped to each other and there is a defined contact.

The method described ensures that there is a technical zero gap on the spring element section, regardless of other tensioning devices. The spring element sections, which are also referred to as component-integrated laser-compatible clamping features, make it possible to weld the assembly with a laser beam after fixing it to the fixing points without using any other clamping technology.

The first and second components are pressed together at the fixing points and joined. The joining of the components can e.g. by screwing or riveting. The two components are particularly preferably connected at the fixing points by spot welding. The spot weld connection can preferably be designed as a conventional resistance spot weld connection. Resistance spot welding is particularly suitable due to the force exerted on both sides, to compensate for component inaccuracies when joining and to press the components together at the fixing points. In addition, a large number of resistance points are usually provided, in particular on body components. Advantageously, some of these points can serve as fixation at the fixing points, while further resistance points are replaced by the welding on the spring element sections.

The joint connections formed at the fixing points can be designed as pure geopoints, i.e. they can be used to fix the components to one another geometrically, but alone are not sufficient to achieve sufficient strength. The laser seam on the spring element section is a weld seam, by means of which a sufficiently high strength of the component assembly is brought about.

In one embodiment of the invention, the spring element section is formed by the projection, i.e. When the components are pressed together, the above projection protrudes. Such a projection can be produced in a simple manner and without additional effort directly during component production, e.g. in the press shop for a sheet metal component or when casting a cast component. The necessary accuracy for the protrusion can be easily mapped.

In one configuration, such a spring element section is designed as a sheet metal section spaced apart from the rest of the joining section by at least one bead. For example, the spring element section can be surrounded by a circular bead. In an alternative embodiment, the spring element is web-shaped and laterally e.g. limited to two or more beads. This configuration advantageously enables the use of beads already inserted in the component, such as KTL beads, as component-integrated clamping features by skillful tolerance of the contact surfaces against each other. This reduces the effort for producing the spring element sections and enables simple integration into existing production processes. It is also advantageous that the open cavity of the bead also serves as a degassing gap, which is why further precautions for zinc degassing are not necessary.

This advantage is particularly evident when, in a preferred embodiment, the laser beam welding takes place in the radius outlet of the at least one bead. In the present case, the first component has an almost flat section which merges into a section bent away from the second component. The transition from a flat to a curved section is called a radius outlet.

A method with which reliable welding can be carried out in the radius outlet of a curve is, for example, in the not previously published German patent application 102018213297.6 described, which is hereby incorporated in full by reference. In the process, the components are arranged in an overlap joint and welded at a predetermined welding position using an I-seam. In the joining area, the top plate (first component) is bent away from the bottom plate (second component) with a radius. The top plate is optically measured to determine at least one characteristic value characterizing the bend and the welding position for the processing laser beam is specified on the basis of the at least one characteristic value. Here, the method is based on the consideration that the bending of the top plate provides a continuously widening gap that can be used for the purpose of zinc degassing. The invention now makes use of the fact that the course of the top plate also reflects the course of the gap. In the flat area of the top plate, ie before the bend, it lies on the bottom plate. At the beginning of the bend, the top plate moves away from the bottom plate and a gap is created between the two components. Assuming a constant component thickness, the height of the gap increases as the distance between the surface of the top plate and the bottom plate increases. The height profile of the surface of the top plate thus reproduces the height profile of the gap very precisely.

The welding position is now selected so that the gap height at this point on the one hand enables sufficient zinc degassing and on the other hand ensures an adequate connection of the components through the seam. This is done by an optical measurement of the component surface and a positioning of the laser beam depending on the measured component shape achieved. The optical measurement can take place immediately before the welding of the components, which gives a possibility to position the processing laser beam in real time during the welding process.

The optical measurement can be carried out using a light section method. In the light section method, a laser line is projected onto the object to be measured using a light section sensor. This light plane intersects the measurement object along a profile line, the course of which is more or less curved depending on the object height. An image sensor observes the scene and, using the known spatial geometry of this arrangement, the height information about the object is calculated from the shape of the profile line according to the triangulation principle.

Because of the directional independence, the method of optical coherence tomography (OCT) is particularly suitable for optical measurement. The OCT is an optical measurement and imaging method and offers the possibility of obtaining contact information and non-destructive height information of the respective measurement point using measurement light. The height information can be linked to the location of the measuring point, which enables topographical information on the component surface to be obtained. In this way, a line-like or relief-like height profile of the surface of the top plate can be created.

The characteristic value for determining the welding position is then e.g. determines a radius of the bend and the position of the radius outlet. As long as the component is measured in the flat area, the distance to the sensor fluctuates only slightly. The distance between the surface of the top plate and the sensor only decreases steadily when the bend begins. This can be determined by means of an algorithm and the start of the bend, i.e. the position of the radius outlet on the component, can be detected. Knowing the radius run-out, the radius itself can be obtained from the further data of the height profile. The radius in turn provides information about the course of the gap between the two components and in particular allows the gap height to be determined as a function of the distance from the radius outlet.

For example, an offset value can be determined based on the radius. The offset value indicates at which distance from the radius outlet the gap height assumes the optimum value for welding and zinc degassing. Then the welding position is specified by adding the offset value to the position of the radius outlet.

Alternatively, the height profile of the component can be determined and a position is specified as the welding position at which the height profile of the top plate reaches a predetermined value. Assuming a constant component thickness, the height profile compared to the flat top section also reflects the height of the gap between the components. This procedure enables the welding position to be determined in a particularly simple manner.

In a further preferred embodiment, the spring element section is designed as a flange which is inclined relative to the remaining joining section and runs between the two fixing points. In other words, the component between the two fixing points is shaped such that a flange section is inclined with respect to the rest of the joining section, preferably at an acute angle and e.g. at an angle of less than 20 degrees. This employed flange forms a cavity for the resulting zinc vapors while at the same time ensuring the technical zero gap.

It is particularly preferred if the employed flange only comes into contact with the second component on its end face, more precisely with an edge of its end face. In this embodiment, the welding of the first and second component takes place as a fillet weld along the end face of the flange. In addition to the possibility of degassing on both sides, the method also has the advantage of simple seam tracking using known methods for edge detection. In particular, contactless edge tracking is possible.

If welding is carried out with such a flange, the cavity between the flange and the second component can also be used as a reservoir and for holding e.g. serve excess adhesive. In one embodiment it is therefore provided that an adhesive is still arranged between the first and second component in the region of the joining section. If the components are pressed together, excess adhesive can escape into the cavity without influencing the subsequent laser welding process. Rather, it is ensured by the cavity that emerging adhesive cannot reach the front face of the flange made and thus in the area of the laser weld seam.

Such a reservoir can advantageously be enlarged in a simple manner by, in one embodiment, the second component having a recess opposite the flange.

In the embodiments described so far, the projection in the first component also takes on the function of the spring element section. In an alternative embodiment, the spring element section is arranged in the second component and is deflected by the projection in the first component. It is a preferred embodiment here if the projection in the first component is formed by a bead and the welding takes place in the bead. The bead is visible on the top of the component arrangement, which enables exact positioning of the laser beam in a simple manner. This configuration also enables the use of beads that are already present or provided in the component, such as, for example, KTL beads.

Laser beam welding is not limited to any particular process. Due to the defined technical zero gap generated by the method and the possibility of providing defined degassing options, remote laser beam welding is preferably used.

Because of the advantages mentioned, the method described above is particularly suitable for welding body components. It is possible to replace welding spots that were previously formed by resistance welding spots with remote laser beam welding seams. The geopoints in the body shop are already tacked as resistance points so that they can be used as fixing points and the process can be integrated into existing processes with only minor changes to the components.

Because of the integrated degassing options described above, the method can preferably be used for welding coated sheet metal components. For example, at least one component can be provided with an anti-corrosion coating. Both sheet metal components and cast components can be used as components. All laser-weldable materials are suitable as materials, e.g. Steel or aluminum materials.

In this respect, the terms top plate and bottom plate are to be understood to mean only the arrangement of the components relative to one another. The component facing the laser beam is referred to as the top plate, and the component facing away from the laser beam is correspondingly referred to as the bottom plate.

The above-mentioned advantages in combination theoretically enable the joining of a maximum component spectrum as well as further processing steps in the same laser cell only by adapting the welding and robot programs. Compared to pure resistance spot welding, no large pliers are required, there is greater material flexibility and a reduced machining time with the same component strength.

Further advantages, features and details of the invention emerge from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination. If the term "can" is used in this application, it is both the technical possibility and the actual technical implementation.

• 1 eine perspektivische Ansicht einer Bauteilanordnung gemäß eines ersten beispielhaften Verfahrens,
• 2A bis C eine Schnittansicht A-A der Bauteilanordnung aus 1 zu verschiedenen Stadien des Verfahrens,
• 3 eine perspektivische Ansicht einer Bauteilanordnung gemäß eines zweiten beispielhaften Verfahrens,
• 4A bis C eine Schnittansicht B-B der Bauteilanordnung aus 3 zu verschiedenen Stadien des Verfahrens,
• 5A bis C eine Schnittansicht der Bauteilanordnung aus 3 mit zusätzlicher Klebstoffschicht
• 6 eine perspektivische Ansicht einer Bauteilanordnung gemäß eines dritten beispielhaften Verfahrens und
• 7A bis C eine Schnittansicht C-C der Bauteilanordnung aus 6 zu verschiedenen Stadien des Verfahrens.

Exemplary embodiments are explained below with reference to the accompanying drawings. In it show:

• 1 2 shows a perspective view of a component arrangement according to a first exemplary method,
• 2A to C. a sectional view AA the component arrangement 1 at different stages of the process,
• 3rd 2 shows a perspective view of a component arrangement according to a second exemplary method,
• 4A to C. a sectional view BB the component arrangement 3rd at different stages of the process,
• 5A to C. a sectional view of the component assembly 3rd with additional layer of adhesive
• 6 a perspective view of a component arrangement according to a third exemplary method and
• 7A to C. a sectional view CC the component arrangement 6 at different stages of the process.

1 shows a first exemplary component arrangement 1-1 to carry out the procedure. The component arrangement includes a first component 10th and a second component 20th in the form of a sheet metal component. The first component 10th has a flange-like joining section 11 for welding to the second component 10th . In the joining section 11 is a spring element section 12th trained by beading 13 , 14 from neighboring fixing points 15 , 16 is delimited. In the direction of joining the second component 20th stands the spring element section 12th opposite the fixing points 15 , 16 before as in 2A recognizable, and thus forms a head start. The components are used for joining 10th , 20th now brought together in the correct position and at the fixing points 15 , 16 pressed together non-positively and by resistance welding points SP fixed, shown in 2 B . By the supernatant of the Spring element section 12th this gets in front of the fixing points 15 , 16 in contact with the second component 20th and is elastically deformed when the components are brought together again. As a result, the spring element section 12th with a defined spring force against the second component 20th curious; excited.

After fixing the components with the welding points SP the components are at the fixing points 10th , 20th geometrically fixed to each other in a given position. A technical zero gap is ensured without the need for additional tensioning devices. The component assembly is then welded out using laser radiation L . 2C shows an example of a weld 17th , 18th in the radius of the bead 13 , 14 is set. The radius outlet provides a defined degassing cavity 19th ready, so that sheets with an anti-corrosion coating can be welded particularly preferably.

3rd shows an alternative component arrangement 1-2 to carry out the method with a first component 30th and a second component 40 in the form of a sheet metal component. The first component 30th has a joining section 31 on with a spring element section 32 between two fixing points 35 , 36 is arranged. The spring element section is formed by a web-shaped flange with a free end 33 which is opposite the remaining joining section 31 and in particular the fixing points 35 , 36 is inclined, see also 4A . The slanted component flange 32 protrudes with its free end 33 towards the second component 40 in front and forms a projection over the fixing points 35 , 36 .

4 B shows that the two components 30th , 40 aligned in a given position and by pressing together at the fixing points 35 , 36 brought together. Here, the above spring element section 32 spring loaded and with a spring force against the second component 40 tense. The fixation is in turn preferably carried out by forming a resistance welding spot SP at the fixing points 35 , 36 . The components are now permanently fixed to each other and the spring element section 32 is with the second component 40 tense. This will create an edge 34 the end face of the spring element section 32 with a defined zero gap to the second component 40 positioned. In the next step, shown in 4C , the spring element section is welded 32 by means of laser radiation L , why a fillet weld 37 between the free end 33 and the second component 40 is trained. The slanted flange 32 enables defined degassing on both sides, so that sheets with an anti-corrosion coating can be welded particularly preferably.

5A to C. illustrates an alternative embodiment with a component arrangement 1-3 , in the in the component arrangement 1-2 from that to 4A to C. described method additionally an adhesive layer 50 is introduced between the first and second component. If the components are pressed together and welded at the fixing points by welding spots (not shown), excess adhesive is pressed out. Through the employed flange 32 becomes a cavity 38 formed into which the excess glue can escape, ensuring that there is no interference between glue 50 and laser seam 37 is coming. Depending on the expected amount of adhesive, the cavity can 38 can be enlarged in that in the second component 40 one, the employed flange 32 opposite depression 42 (due to the dashed course of the component 40 shown) is provided.

6 and 7 show an alternative component arrangement in a further exemplary embodiment 1-4 to carry out the method with a first component 60 and a second component 70 in the form of a sheet metal component. In a joining section 61 of the first component 60 are between the fixing points 62 , 63 , 64 one lead each 65 and 66 formed by pressing in beads. These ledges 65 , 66 stand towards the second component 70 before, see 7A . Will the components 60 , 70 now at the fixing points 62 , 63 , 64 pressed together, so the protrusions press 65 , 66 on the area of the second component 70 between the fixing points 62 , 63 , 64 . This area is elastically deformed as a spring element section and a corresponding spring force acts between the two components. This ensures a defined contact and a technical zero gap.

7B shows the deformation of a spring element section 72 in the area of the projection 65 . At the fixing points 62 , 63 , 64 the components are permanently fixed, preferably by forming welding spots SP , e.g. by resistance spot welding. The component assembly is then welded out 1-4 , why at the contact point between the projection 65 , 66 and second component 70 is welded. 4C shows that by means of laser radiation L trained I-seam 67 on the ledge 65 . If the lead, as in 6 and 7 shown, provided by a bead, the position of the bead provides an optically detectable marking for the location of the laser welding, which moreover enables the laser beam to be positioned precisely and quickly.

Laser beam welding is preferably carried out as remote laser beam welding.

Although in the figures the fixation is carried out by resistance spot welding, other fixations, for example by alternative welding methods or by screw or rivet connections, are also possible.

Similarly, for example, spring element sections - in particular in connection with the in the 1 and 2nd shown example - are used, which are formed by a sheet metal section and a circumferential bead around the sheet metal section.

Reference symbol list

1-1, 1-2, 1-3, 1-4

Component arrangement

10, 20, 30, 40, 60, 70

Components

11, 31, 61

Joining sections

12, 32

Spring element section and projection

13, 14

Beads

15, 16, 35, 36, 62, 63, 64

Fixing points

17, 18, 37, 67

Laser seams

19, 38

Degassing cavity

33

free end

34

Edge

42

deepening

65, 66

head Start

72

Spring element section

SP

Spot weld

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102018213297 [0016]

Claims (13)

Method for producing a laser welded connection, comprising the steps: - Bringing together a joining section (11, 31, 61) of a first component (10, 30, 60) with a second component (20, 40, 70), wherein a projection (12, 32, 65, 66) protruding from the rest of the joining section the first component (10, 30, 60) comes into contact with the second component (20, 40, 70), - Force-fitting pressing together of the components at at least two fixing points (15, 16; 35, 36; 62, 63) of the joining section, which are arranged on both sides of the projection (12, 32, 65, 66), whereby a spring element section (12, 32) of the first component (10, 30) or a spring element section (72) of the second component (70) is elastically deformed, - Joining the components pressed together at the fixing points (15, 16; 35, 36; 62, 63) and - Welding the components on the spring element section (12, 32, 72) using a laser beam. Procedure according to Claim 1 , in which the first and second component are connected at the fixing points (15, 16; 35, 36; 62, 63) by means of resistance spot welding. Procedure according to Claim 1 or 2nd , in which the spring element section is formed by the projection (12, 32). Procedure according to Claim 3 , in which the spring element section (12) is designed as a sheet metal section spaced apart from the rest of the joining section (11) by at least one bead (13). Procedure according to Claim 4 , in which the welding takes place in the radius outlet of the at least one bead (13). Procedure according to Claim 3 , in which the spring element section (32) is designed as a flange which is inclined relative to the remaining joining section (31). Procedure according to Claim 6 , in which the welding takes place as a fillet weld (37) along an end face (33) of the flange. Procedure according to Claim 6 or 7 , in which an adhesive (50) is also arranged between the first component (30) and the second component (40) in the joining section (31). Procedure according to Claim 6 , in which the second component (40) has a recess (42) opposite the flange (32). Procedure according to Claim 1 or 2nd , in which the spring element section (72) is arranged in the second component (70), the projection (65, 66) is formed by a bead and the welding takes place in the bead. Method according to one of the preceding claims, in which the laser beam welding is a remote laser beam welding. Method according to one of the preceding claims, in which the components (10, 20, 30, 40, 60, 70) are body components. Method according to one of the preceding claims, in which at least one component (10, 20, 30, 40, 60, 70) is a sheet metal component with an anti-corrosion coating.

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