Method of traversing a weld contour multiple times with multiple laser spots

Abstract

The invention relates to a method for welding at least two aluminum-containing components, wherein the components each have an aluminum content of at least 75 percent by weight, wherein the welding is carried out as laser welding in a deep-penetration welding system, wherein an output laser beam (6) is split into a plurality of sub-beams (8), the sub-beams are directed at the components, and a plurality of laser spots is produced on the surface of the components, wherein the plurality of laser spots is moved over a welding contour on the surface of the components, wherein the laser spot centers of at least three laser spots of the plurality of laser spots are arranged in an annular array, wherein the output laser beam (6) is produced by means of a multiple fiber, in particular a two-in-one fiber (2a), such that the plurality of laser spots on the surface of the components each has a core portion and a ring portion, wherein the welding contour is at least partially walked over a second time after the first time.

Description

Technical Field

[0001] The present invention relates to a method for welding at least two aluminum-containing components, wherein the components each have an aluminum content of at least 75% by weight, wherein the welding is performed as laser welding in a deep welding system, wherein an output laser beam is split into multiple sub-beams and directed at the components to generate multiple laser spots on the surface of the components, wherein the multiple laser spots pass through a welding profile on the surface of the components, and wherein at least three of the multiple laser spots are arranged in a ring array at their center.

[0002] The present invention also relates to a component assembly manufactured using the method described above. Background Technology

[0003] The method mentioned at the beginning is known from DE 10 2016 124 924 A1.

[0004] In electric vehicles, components must be joined for various applications, and these components are constructed to be sealed to different media. Typical media that need to be sealed to provide a suitable atmosphere for sensitive components include coolants or protective gases.

[0005] In electric vehicles, aluminum-based components are particularly important due to their low density. To date, brazing has been the primary method used to join aluminum-containing components in a medium-sealing manner. Brazing requires the supply of solder to create a brazed joint. Brazing is relatively costly and difficult; furthermore, brazed joints can be susceptible to corrosion. Alternatively, aluminum-containing components can be bonded together to achieve a medium-sealing connection. Bonding is also relatively costly and typically requires a long curing process, and the bonded areas can be sensitive to high temperatures.

[0006] Welding is a joining method that permanently connects two workpieces to each other. Laser welding is mostly used when welding requires high speeds, long and narrow weld shapes, and low heat deformation. In laser welding, energy is supplied by a laser beam. To achieve high welding speeds, laser welding is preferably performed in deep welding systems, where vapor capillaries (orifices) are formed in the component material.

[0007] However, laser welding of medium-sealed welds in aluminum-containing components is challenging. Aluminum-containing workpieces can cause intense turbulence in the molten pool during laser welding. This turbulence leads to uneven solidification of the weld. As a result, this can cause weld undercut, edge notches, or porosity. Due to the aforementioned problems associated with cracks and porosity at the weld, insufficiency may occur at the weld, making the welded component unsuitable for applications dependent on medium sealing. Furthermore, the intense turbulence of the molten pool during laser welding often results in the formation of severe weld spatter, which contaminates the surrounding environment and causes material loss at the weld.

[0008] As known from DE 10 2010 003 750 A1, the beam profile characteristics of a laser beam can be altered by using multi-clad optical fibers. Here, a laser beam having a core portion and a ring portion can be generated.

[0009] A laser welding apparatus is known from DE 10 2016 124 924 A1. This apparatus can be used to weld a sealing plate onto a battery casing, wherein the casing and the sealing plate are made of aluminum. A collimated laser beam is guided through a forming device comprising a diffractive optical element (DOE) with an opening. The DOE can split the incident laser beam into multiple sub-beams, for example, four sub-beams, which can be arranged in a square angular configuration. Depending on the overlap between the collimated laser beam and the DOE and its opening, a portion of the collimated laser beam can be split into sub-beams by means of the DOE, or kept undistorted as it passes through the opening.

[0010] Therefore, it has been shown in practice that welded aluminum-containing components often have defective parts and are not sealed to the medium. Summary of the Invention

[0011] Therefore, the object of the present invention is to provide a method for rapidly and cost-effectively creating a welded connection that provides a particularly reliable medium-sealing seal. A further object of the present invention is to provide a component assembly having the aforementioned medium-sealing welded connection.

[0012] According to the present invention, this task is accomplished by a method according to one technical solution and a component assembly according to another technical solution.

[0013] Therefore, the task is accomplished by the method mentioned at the beginning, characterized by generating an output laser beam by means of multiple optical fibers, especially a two-in-one optical fiber, so that multiple laser spots on the surface of the component have core portions and ring portions respectively, wherein the laser beam passes through the welding profile at least partially a second time after passing through the welding profile for the first time.

[0014] The second pass serves as a strategic safeguard for process reliability by remelting the already welded profile. While remelting the welded profile is generally disadvantageous, as the second pass typically introduces more defects into the weld profile rather than eliminates them, it has been surprisingly shown that the multiple laser spots according to the invention homogenize the weld profile during the second pass. This eliminates potential porosity and voids from the first pass, improving process reliability and enabling media-sealing welding at high process speeds (welding speeds) and short cycle times. Thus, the first pass is used to achieve the desired weld depth and consequently, the required strength, while the additional second pass is used to repair potential, material-dependent, and unavoidable defects and to produce a media-sealing, particularly hermetically tight, weld profile.

[0015] This invention proposes a method for welding aluminum-containing components by splitting an output laser beam into multiple sub-beams and correspondingly into multiple laser spots on the workpiece surface. At least a portion of the laser spots (in most cases, all laser spots or all laser spots except one) are arranged in a ring array on the workpiece surface. Furthermore, beam shaping is employed on the output laser beam, which has multiple optical fibers, preferably a two-in-one optical fiber. Through beam shaping, the laser power is correspondingly divided into a core portion with higher power density and a ring portion with lower power density in the output laser beam, in the sub-beams, and thus in each individual laser spot (in the case of a two-in-one optical fiber, this is referred to as "two-in-one technology"). The multiple optical fibers include a central core fiber and one or more ring fibers that circumferentially surround the core fiber. The core portion is generated from the core fiber, and the ring portion is generated from one or more ring fibers (in the case of multiple ring fibers, the ring portion here comprises multiple individual ring portions, which together constitute the ring portion). Through all these measures, according to the invention, high-quality laser welding of aluminum-containing components can be achieved, and in particular, welds with low porosity and media-sealed properties can be obtained.

[0016] While the two-in-one technique using a single laser spot (single spot) reduces spatter formation to some extent compared to single-spot techniques using a common (non-deformable) laser beam in the case of aluminum-containing components, the instabilities retained in aluminum-containing components still result in welds that are typically not sealed against the medium. This also leads to intense turbulence in the molten pool during welding due to the unique properties of aluminum in the component material. The aperture during a single spray may be too small compared to the resulting molten pool. In particular, the creation of multiple pores allows the medium to penetrate the weld.

[0017] Surprisingly, however, particularly stable pinholes can be obtained when laser welding aluminum-containing components, especially when using a combination of multiple optical fibers or multiple laser spots arranged in a ring array, as is typically the case with the present invention. Within the framework of this invention, larger pinholes (compared to single pinholes with a single laser spot) can be achieved; these pinholes are more stable and do not collapse. Instead, the molten material can pass through the larger pinhole more reliably. Uniform weld solidification can be achieved.

[0018] The centers of the individual laser spots (which are successive / adjacent to each other in the ring array) can be conceptually connected to each other in a polygonal manner, forming an inner surface (polygonal face) within the polygon. Deep welding according to the invention can be performed substantially within the region of the polygonal face in aluminum-containing components.

[0019] The laser welding according to the invention produces a particularly large volume of molten material, especially upstream of the corresponding vapor capillary (orifice); in particular, the outer sub-regions of the annular portion (with respect to the annular array) can increase the molten material volume. Here, the laser spot can form a common molten material. The particularly large upstream molten material volume can reduce molten material flow and thus reduce turbulence.

[0020] Within the framework of this invention, particularly large pinholes can be provided, and the geometry of the pinholes (compared to those in the case of a single spot) is altered, and the absorption characteristics of the laser beam are changed accordingly. A common pinhole can be formed, in particular, by all laser spots or sub-beams together. During the continued welding process, the molten material can flow around the corresponding vapor capillary. Overall, particularly high pinhole stability can be achieved. High welding speeds can be achieved with good weld quality, and particularly, aluminum-containing welds that provide medium sealing can be produced without problems, especially at butt joints. Particularly preferably, the cap is inserted into the component and welded at the butt joint.

[0021] By arranging at least three laser spots in a ring array, the orientation dependence of the welding process can be reduced. With four or more laser spots arranged in a ring array (in the case of symmetrical laser spot arrangement), the welding process becomes largely orientation-independent. Furthermore, the ring array can very effectively stabilize common keyholes in aluminum-containing components. The total number of laser spots on the workpiece surface is referred to herein as the welding pattern.

[0022] The generation of the laser beam is typically achieved by guiding the output laser beam between collimating and focusing optics through one or more optical elements that extend into at least a portion of the beam cross-section of the output laser beam. A typical optical element for this purpose is a wedge; however, other diffractive and refractive optical elements can also be used. In a preferred variant, two bifocal inserts are used, arranged at a 90° angle relative to each other. It is also possible to use prism panels as optical elements, which provide annularly arranged facets (outer facets) corresponding to the desired number of laser spots in the annular array. These facets are curved (tilted) at an angle β relative to a base plane extending transversely to the beam propagation direction, typically 0 < β ≤ 0.50°, and usually β ≤ 0.25°. The outer facets typically rotate relative to each other at 360° / N about a central axis (the optical axis of the prism panel, corresponding to the beam propagation direction), where N: the number of laser spots in the annular array. If a central laser spot is desired, additional facets (central facets) can be provided, parallel to the base plane, with outer facets radially inwardly adjacent to the central facet. The central facet is typically constructed as a regular polygon. If a central laser spot is not desired, the outer facets can simply meet radially inwardly at a common center point. Using facets, any number of laser spots can be generated, in principle, corresponding to the configuration of the facets.

[0023] Laser spots typically have the same size. Typically, the same laser power is assigned to each of the circular array laser spots. The circular array laser spots typically have the same spacing (radius) with respect to the common center (centroid) of all the laser spots.

[0024] The method is preferably characterized in that the average power density in the core portion is higher than the average power density in the ring portion.

[0025] The power components of the core and ring portions in the corresponding laser spot can be set using the components of the output laser beam, which are respectively guided into the core fiber and one or more ring fibers of the multi-fiber array. In most cases, the average power density in the core portion is at least twice, and typically at least four times, the average power density in the ring portion. In the case of multiple ring fibers in the outermost single ring portion, the (outer) boundary between the core and ring portions can be defined as a location where the local power density is less than half the average power density in either the core or ring portion; this corresponds to the FWHM (half-width, half-height) standard, where the power density in the core portion is approximately the same as that in the ring portion. The diameter or proportion of the core fiber and the (outermost) ring fiber at the mapped fiber end determines the diameter or proportion of the ring portion of the core portion in the corresponding laser spot. The imaging ratio and absolute size of the laser spot can be selected and set using collimating and focusing optics.

[0026] The laser spot continuously traverses the welding profile (without jitter) along its path, typically at a constant feed rate (welding speed). This produces a weld (sealed against the medium). It should be noted that the local feed direction (welding direction) can be changed while traversing the welding profile, and thus the orientation of the weld pattern relative to the local feed direction can also be altered. Due to the invention's at least largely orientation-independent nature of the weld pattern, such changes in the local feed direction are largely non-critical when welding components according to the invention.

[0027] The weld profile can be constructed as a fillet weld or a lap weld at the butt joint. Laser welding can be performed as a grommet weld or also as a through weld. Preferably, welding of aluminum-containing components is performed as a grommet weld at the lap joint or butt joint, and particularly preferably as a grommet weld at the butt joint. It should be noted that the term "component" can be understood here in relation to the laser welding process in which the components are welded to each other within the framework of the invention; correspondingly, the components to be welded may be independent prior to laser welding, or may have already been connected to each other independently of the connection to be welded.

[0028] Preferably, the weld profile is completely traversed during the second pass. This achieves a weld profile that completely seals the medium in a simple manner and simplifies the process.

[0029] The component preferably has at least 90% by weight of aluminum.

[0030] The components may be made of die-cast aluminum or forged aluminum alloy. Preferably, the components are made of die-cast aluminum or forged aluminum alloy. More preferably, one component is made of die-cast aluminum while the other component is made of forged aluminum alloy. The assembly of these components cannot be welded together in a practically effective manner and method to seal against the medium without the method according to the invention.

[0031] Preferably, 1XXX, 3XXX, 5XXX, and 6XXX series aluminum (Al) alloys are used as forging aluminum alloys.

[0032] The second pass should preferably melt less material than the first pass. In another preferred embodiment of the invention, the second pass is thus performed with a lower power and / or a higher feed rate than the first pass. The second pass is performed with a power that is preferably 2% to 20%, particularly 5% to 15%, and especially preferably 8% to 12% lower per laser spot than the first pass. The second pass is performed with a feed rate that is preferably 2% to 20%, particularly 5% to 15%, and especially preferably 8% to 12% higher than the first pass.

[0033] Compared to the first pass, the lateral offset during the second pass is preferably less than 20 mm, particularly less than 10 mm, and especially preferably less than 5 mm.

[0034] More preferably, the remaining parameters for the second pass are selected to be the same as those for the first pass. This ensures that the weld profile produced during the first pass is completely or almost completely melted and homogenized.

[0035] The weld penetration depth is preferably less than 10 mm. More preferably, it is less than 4 mm, particularly between 1 mm and 3 mm.

[0036] The welding profile, which has been traced twice, can be recorded by optical sensors, and defect locations can be detected. This allows for the identification and elimination of potential defects. By identifying the welding profile, time-consuming operations, especially the loosening, inspection, and re-clamping of components, can be avoided.

[0037] Optical sensors can be designed in the form of cameras or photodiodes.

[0038] A record can be created directly after the second pass over the welding profile. By creating a record directly after the second pass over the welding profile, the process luminescence during the second pass can be detected and evaluated.

[0039] Here, the optical path of the optical sensor can be extended coaxially with the optical path of the output laser beam, thus making the method particularly simple in structure.

[0040] After the second pass, the weld contour can be passed through at least partially a third time. The third pass allows for a weld connection that is particularly airtight and especially designed to be sealed to the medium.

[0041] Preferably, a third pass is only performed if at least one defective part is identified after the second pass.

[0042] To simplify the method, it is preferable to completely traverse the welding profile during the third pass.

[0043] The weld penetration depth is selected to be substantially the same during the third pass as during the second pass. Therefore, in a preferred embodiment of the invention, the third pass is performed with the same parameters as the second pass, except for a deviation of ±10%, particularly ±5%, and especially preferably ±2%. The third pass can also be performed with higher power than the second pass, however, it is preferably performed with a correspondingly higher feed rate.

[0044] In a particularly preferred variant of the method according to the invention, the first pass is performed with selected parameters, the second pass is performed with lower power but the same feed rate (thereby achieving a smaller weld penetration depth in the second pass than in the first pass), and the third pass is performed with a higher feed rate and higher power than the second pass (thereby obtaining substantially the same weld penetration depth as in the second pass).

[0045] An optical sensor can record the weld profile traversed three times and detect defects. Preferably, the same optical sensor records the weld profile traversed twice. Typically, no defects are detected after the third pass at the latest, allowing the welded component to be certified as acceptable by visual inspection.

[0046] Preferably, the record is created during the third pass over the welding profile. Particularly preferably, the record is created during the third pass over the welding profile in the same manner and method as during the second pass. This significantly reduces programming costs and process complexity.

[0047] A preferred variation of the method according to the invention for welding aluminum-containing components is that at least two components are welded together at a butt joint, and the laser welding is performed in the following manner: - As a veneer, the weld depth corresponds to the cap thickness or at least 75% of the cap thickness. Replacement as an overlap: - As a grommet weld, wherein the weld extends to at least 10% of the thickness of the lowest member of the lap joint, or - As a through weld that passes through all components of the lap joint. Welding in lap joints has proven particularly effective in practice for creating welds that seal against the medium, especially when the weld is performed as a through weld. Through a through weld, a reliable seal can be created by preserving the solid material of the lowest component.

[0048] A particularly preferred variant is in which a common vapor capillary is formed in the component for all laser spots, the common vapor capillary being surrounded by a common molten pool. The common vapor capillary is an interconnected space in the component to be welded, containing metal vapor and surrounded by liquid melt; the vapor capillaries of the individual laser spots (when they can be used separately) merge into this interconnected space. The common vapor capillary (common aperture) can be configured by implementing a suitable method, particularly with a moderately large spacing between the laser spots in a ring array. The common aperture is significantly larger than the aperture that could be produced by a single laser beam (single spot). The larger aperture, and the different geometric shapes, affect the absorption characteristics of the incident laser beam. The multiple intensity peaks of the multiple laser spots corresponding to the ring array are arranged in a ring-shaped distribution at the common aperture; furthermore, the intensity peaks of additional laser spots can be added at the center of the ring array. The aperture is particularly stable at the location of local intensity peaks; multiple intensity peaks at a common aperture can generally stabilize a common, larger aperture. Conversely, in the case of a single spot, the aperture can be stabilized only within the range of a single intensity peak. The common vapor capillary (in the case of an lap joint) preferably extends so deeply that its cross-section forms a connecting surface at the interface between the overlapping components to be welded. Furthermore, (typically) the common vapor capillary preferably extends so deeply that its cross-section forms a connecting surface at a height half the maximum depth of all its sub-segments. Here, the cross-section is perpendicular to the beam propagation direction.

[0049] A preferred variant is in which the plurality of laser spots are arranged in a rotationally symmetric manner, the rotational symmetry having multiplicity corresponding to the number of laser spots in the annular array. Rotational symmetry achieves significant direction independence in laser welding, meaning that the relative orientation of all laser spots with respect to the current feed direction has little or no effect on the welding process.

[0050] In one variant, all laser spots are arranged in a ring array. This is particularly easy to achieve, for example, with four laser spots in a ring array, using two dual-focal inserts. Especially noteworthy is that no laser spot is positioned at the center of the ring array. In the case of fewer laser spots in a ring array (e.g., 3 to 5 laser spots in a ring array), a stable, common aperture can often be set in this manner.

[0051] In an alternative variant, the laser spot centers are positioned at the center of the annular array. In other words, the annular array of laser spots is supplemented by another laser spot positioned at the center of the annular array. This can, particularly when multiple laser spots are arranged in annular arrays (e.g., four or more, preferably six or more laser spots in annular arrays), additionally stabilize the common aperture; in the case of multiple laser spots in annular arrays, in most cases, the radius of the laser spot centers of the annular array is also chosen to be larger than the radius of the common center of the laser spots to reduce the overlap of the annular portions of the laser spots. The centrally positioned laser spot can stabilize the central region of the common aperture and prevent localized depressions in the aperture within the central region.

[0052] One variant proposes a ring array consisting of exactly three laser spots, wherein the welding profile is extended in such a way that, during laser welding, at least primarily with respect to the local feed direction... - One laser spot in the ring array is upstream, and - The two laser spots in the ring array are located downstream at the same position with respect to the local feed direction.

[0053] By using three laser spots arranged in a ring array, the directional dependence on two (or more) laser spots arranged in a linear array can be significantly reduced. The preferred primary orientation of a weld pattern with one upstream laser spot and two downstream laser spots relative to the local weld direction / feed direction has proven effective in practice.

[0054] One variant is particularly preferred, in which the ring array consists of exactly four laser spots. This allows for a high degree of orientation independence in a simple manner. The exactly four laser spots of the ring array are preferably arranged in a square.

[0055] In a further embodiment of this variant, the weld profile is extended in such a way that, during laser welding, at least primarily with respect to the local feed direction, - One laser spot in the ring array is located upstream. - The two laser spots in the ring array are centrally located at the same position with respect to the local feed direction. - and a laser spot in a ring array is downstream.

[0056] By utilizing the orientation primarily adopted in the welding pattern (also known as the "trapezoidal" arrangement), relatively wide welds can be set with four laser spots arranged in a ring array, resulting in a particularly large and stable molten pool.

[0057] A further alternative is preferred, wherein the weld profile is extended in such a way that, during laser welding, at least primarily with respect to the local feed direction, - The two laser spots in the ring array are located upstream at the same position with respect to the local feed direction. - And the two laser spots in the ring array are located downstream at the same position with respect to the local feed direction.

[0058] By utilizing the primary orientation of the welding pattern (also known as a "square" arrangement), relatively long weld seams can be set up with four laser spots arranged in a circular array, thereby achieving particularly deep melting with high welding speeds and a stable molten pool. The primary local welding direction / feed direction can correspond to one of the principal coordinate axes of the laser welding equipment used. It should be noted that the orientation of the welding pattern is changed when turning, for example from a square arrangement to a trapezoidal arrangement and then back to a square arrangement when turning a 90° bend.

[0059] In another variant, the annular array consists of exactly five laser spots, wherein the welding profile is extended in such a way that, during laser welding, at least primarily with respect to the local feed direction, - One laser spot in the ring array is located upstream. - The two laser spots in the ring array are centrally located at the same position with respect to the local feed direction. - And the two laser spots in the ring array are located downstream at the same position with respect to the local feed direction.

[0060] This variant achieves better orientation independence. A particularly smooth weld pool is achieved by using one upstream laser spot, two centered laser spots, and two downstream laser spots in the preferred orientation of the weld pattern relative to the feed direction.

[0061] In another variation, the ring array consists of exactly six laser spots. Additionally, a third laser spot can be centrally located within the ring. This achieves a high degree of orientation independence. It should be noted that a number of 3 to 6 laser spots in a ring array is preferred within the framework of this invention; generally, a larger number only brings minor improvements in orientation independence or molten pool stability.

[0062] A particularly preferred variant is in which the annular portions of adjacent laser spots in the annular array are arranged in contact with each other. This allows for a very stable, common keyhole when laser welding aluminum-containing components. The annular portions of adjacent laser spots in the annular array are considered to be in contact with each other if the laser spots have a spacing between their centers corresponding to the sum of their respective half-diameters, wherein the tolerance is ±10% of this sum.

[0063] In an alternative variant, the annular portions of adjacent laser spots in the annular array are arranged to overlap each other, particularly wherein the core portion of the laser spots in the annular array does not overlap with the annular portions of adjacent laser spots in the annular array. Because the annular portions of the laser spots overlap, and especially where the annular portions and core portions do not overlap, it is generally possible to reduce localized protrusions and depressions in common keyholes with respect to depth toward the component to be welded.

[0064] A further embodiment of this variant is preferred, wherein, at each location, up to two ring portions of the annular laser spot overlap each other. This has proven effective for particularly stable molten pools in aluminum-containing components.

[0065] A further preferred embodiment is that the annular array of laser spots includes a common center at which the ring portions of the annular array of laser spots contact each other, and specifically, exactly four laser spots are arranged in an annular array. In a variant where a laser spot is typically not positioned at the center of the annular array, a smooth and large pinhole with only small local protrusions and depressions at the depth of the component to be welded can be provided.

[0066] A variant is also advantageous, wherein, in the central region, the ring portions of all the laser spots in the annular array overlap each other, particularly where exactly three laser spots are arranged in an annular array. Especially in the case of only a few laser spots, for example, when three laser spots are arranged in an annular array and there is no other laser spot at the center of the annular array, the overlap of the ring portions of the annularly arranged laser spots in the central region can generate an auxiliary intensity peak, which, in addition to the intensity peak of the core portion of the laser spots, can also stabilize the common aperture.

[0067] In a preferred variant, the following parameters are set for the core diameter DK and the ring diameter DR: 2 ≤ DR / DK ≤ 10, preferably 2.5 ≤ DR / DK ≤ 6, particularly preferably 3.5 ≤ DR / DK ≤ 5; and for the core power component LK relative to the total power in the corresponding laser spot: 10% ≤ LK ≤ 90%, preferably 30% ≤ LK ≤ 70%, particularly preferably 40% ≤ LK ≤ 60%. For the present invention, these parameter ranges have proven effective in practice for achieving stable pinholes and welds that seal the medium in aluminum-containing components.

[0068] In addition, a variant is preferred, which sets: - The component has a component thickness BD, wherein 0.5 mm ≤ BD ≤ 5.0 mm; and / or - The components are made of 3000, 5000 or 6000 series aluminum; and / or - The core portion of the laser spot has a diameter DK, wherein 11 µm ≤ DK ≤ 200 µm, preferably 50 µm ≤ DK ≤ 150 µm, and the ring portion of the laser spot has a diameter DR, wherein 50 µm ≤ DR ≤ 700 µm, preferably 200 µm ≤ DR ≤ 550 µm; and / or - The average laser power P of the output laser beam is such that: P ≥ 2 kW, preferably P ≥ 4 kW; and / or - The welding speed SG is ≥ 5 m / min, preferably SG ≥ 10 m / min.

[0069] The parameters have also proven effective in practice for laser welding of aluminum-containing components. In particular, exceptionally high welding speeds (SG) can be set within the framework of this invention.

[0070] The objective of the invention is also achieved by a component assembly manufactured by the method described herein, wherein the component assembly is configured to be sealed to the medium at the weld contour. The weld contour is preferably configured to be waterproof, particularly sealed to coolant, and especially preferably airtight. By using the method according to the invention, the component assembly can be manufactured in a simple and reliable manner, sealing it to the medium via the weld (or the welded weld contour).

[0071] Other advantages of the invention become apparent from the specification and drawings. Similarly, the features described above and further to be set forth can be used individually or in any combination thereof according to the invention. The embodiments shown and described should not be construed as a final enumeration, but rather as having exemplary features for illustrating the invention. Attached Figure Description

[0072] Figure 1a An exemplary welding optics device is shown in a schematic side view, by means of which the method according to the invention can be performed.

[0073] Figure 1b The source of the 90° rotation is shown. Figure 1a An exemplary welding optics device.

[0074] Figure 1c A schematic diagram of an exemplary two-in-one optical fiber used in the present invention is shown in cross-section. For example, this two-in-one optical fiber can be used as... Figure 1a The laser fiber in the fiber can provide an output laser beam for use in the method according to the present invention.

[0075] Figure 2 A weld pattern with four laser spots is shown as a variant of the method according to the invention; for example, this weld pattern may be derived from... Figure 1a Exemplary welding optics are produced.

[0076] Figure 3 Shown in Figure 2 The welding diagram is a schematic longitudinal section view of two components during welding to illustrate the method according to the invention.

[0077] Figure 4 Show Figure 3 A schematic cross-sectional view of the vapor capillary on planes AA, BB, and CC.

[0078] Figure 5a A welding diagram showing a variant of the method according to the invention is provided, in which the annular portions of four laser spots are arranged to partially overlap each other and to contact each other at their center points.

[0079] Figure 5b A welding diagram showing a variant of the method according to the invention is provided, in which the annular portions of three laser spots are arranged to partially overlap each other.

[0080] Figure 5c A welding diagram showing a variant of the method according to the invention is provided, in which the ring portions of five laser spots are arranged to partially overlap each other.

[0081] Figure 6aA schematic top view of an exemplary prism panel is shown, which may be used in welding optics to generate multiple sub-beams for use in the method according to the invention.

[0082] Figure 6b Showing from Figure 6a A schematic cross-sectional view of an exemplary prism panel.

[0083] Figure 6c The diagram illustrates a welding pattern of six laser spots arranged in a ring array and a central laser spot, representing a variant of the method according to the invention. For example, this welding pattern could be derived from... Figure 6a An exemplary prism panel is produced.

[0084] Figure 7 An experimental diagram showing the longitudinal grinding surfaces of two aluminum-containing components after the first pass according to the method of the present invention.

[0085] Figure 8 A schematic side view of an exemplary welding optics device is shown, which has an optical sensor for recording the welding profile.

[0086] Figure 9 The components are shown being welded at the butt joint.

[0087] Figure 10 The cross-sectional ground surfaces of two aluminum-containing components are shown after performing the method according to the invention. Detailed Implementation

[0088] Figure 1a An exemplary welding optics 1 is shown in a schematic side view, by means of which the method according to the invention can be performed in a preferred variant. Figure 1b The source of the 90° rotation is shown. Figure 1a 1. Welding optical devices.

[0089] The welding optical device 1 includes a laser cable 2 constructed as multiple optical fibers, of which a two-in-one optical fiber 2a is formed, a collimating lens 3, two bifocal inserts 4a and 4b constructed as glass wedges, and a focusing lens 5. The bifocal inserts 4a and 4b are arranged sequentially and rotated 90° relative to each other.

[0090] An output laser beam 6 is provided via laser cable 2, which exits at the fiber end of the laser cable 2. The fiber end is located at the focal point of collimating lens 3, and the output laser beam 6 is collimated by collimating lens 3, thereby transforming the output laser beam 6 into a collimated laser beam 7. The collimated laser beam 7 is guided to bifocal inserts 4a and 4b. The bifocal inserts 4a and 4b occupy, for example, half of the cross-section of the collimated laser beam 7. Thus, in the exemplary welding optics 1 shown here, the collimated laser beam 7 can be divided into four sub-beams 8. The sub-beams 8 are focused onto the surface of the component to be welded (not shown) through focusing lens 5, thereby creating a welding pattern on the surface of the component consisting of four equally sized laser spots.

[0091] The average laser power P of the output laser beam 6 can be selected, for example, P ≥ 2 kW, preferably P ≥ 4 kW.

[0092] Figure 1c An exemplary cross-section of a two-in-one fiber 2a is shown, by means of which an output laser beam can be provided for the method according to the invention.

[0093] The dual-fiber 2a includes a core fiber 9 with a core fiber diameter KFD and a ring fiber 10 with a ring fiber diameter RFD. Typically, the core fiber diameter KFD can be selected, for example, 11 µm ≤ KFD ≤ 200 µm, preferably 30 µm ≤ KFD ≤ 150 µm, and the ring fiber diameter RFD can be selected, for example, 30 µm ≤ RFD ≤ 700 µm, preferably 100 µm ≤ RFD ≤ 550 µm. (See also: Welding optics including dual-fiber optics (see...)) Figure 1a In this embodiment, the imaging ratio is selected as 1:1; in other embodiments, for example, the imaging ratio can be selected as >1:1.

[0094] A laser beam can be generated using a two-in-one optical fiber, which has a core and a ring (for example, see the laser spot). Figure 2 And used as the output laser beam in welding optics (see...) Figure 1a For this purpose, for example, by means of an optical wedge (not shown in detail) partially moved into the initial laser beam, the initial laser beam (not shown in detail) is partially fed into the core fiber 9 and partially fed into the ring fiber 10.

[0095] exist Figure 2 The diagram shows a schematic of a welding pattern 11 on the surface of the component to be welded. For example, this welding pattern can be derived from... Figure 1a Exemplary welding optics are produced.

[0096] The welding diagram 11 includes four laser spots 12 of the same size. Each of the four laser spots 12 has a core portion 13 and a ring portion 14, because the output laser beam is generated by a two-in-one fiber and accordingly has its own core and ring portions.

[0097] Each laser spot 14 has a laser spot center 15. The core portion 13 here has a diameter DK of 100 µm and the ring portion 14 here has a diameter DR of 400 µm. Accordingly, the ratio DR / DK is 4.

[0098] For the power component LK of the core portion 13 of a single laser spot 12, LK = 50% can be selected. In the variant shown here, the area of ​​the ring portion 14 is approximately 15 times the area of ​​the core portion 13. The average power density in the core portion 13 is, in this case, approximately 15 times the average power density in the ring portion 14.

[0099] The laser spot 12 is arranged in a ring array 16; the laser spot center 15 defines the vertices of a polygon (square in this case) that encloses the inner surface. The spacing between the two laser spot centers 15 of adjacent laser spots 12 in the ring array 16 (e.g., the laser spot centers 15 of laser spots 12' and 12'') is 400 µm. In the variant shown here, the annular portions 14 of adjacent laser spots 12 in the ring array 16 are in contact. The spacing between the laser spot centers 15 of adjacent laser spots 12 in the ring array 16 corresponds to the sum of half the respective diameter DR of the annular portions 14 of the laser spots 12 involved.

[0100] The welding diagram 11 here has fourfold rotational symmetry because the ring 16 is composed of four laser spots 12, which can be transferred to each other by rotating 90° around a common center (center of gravity) 17. The center 15 of the laser spots 12 of the ring 16 is here on the circumference line (shown as a dashed line) around the common center 17.

[0101] Regarding the local feed direction 18, the welding diagram 11 is arranged such that two laser spots 12a are upstream and two laser spots 12b are downstream.

[0102] Figure 3 Shown in such Figure 2 The welding diagram shown is a schematic longitudinal section of the two components 19 during welding to illustrate the method according to the invention in a preferred variant. The two components 19 are joined in a lap joint. Alternatively, and not shown here, the two components 19 may also be joined in a butt joint.

[0103] Component 19 is made of aluminum. The upper component 19a here has, for example, a component thickness BD or thickness D of 2 mm. ob The lowest member 19b here has, for example, a member thickness BD or thickness D of 3 mm. unt Welding is performed here as a grommets. The longitudinal section is chosen to pass through two laser spots side by side with respect to each other in the feed direction 18.

[0104] Figure 3 The sub-beams 8 contained in the longitudinal section originate from the welding optics (not shown) and point towards the surface 20 of the upper member 19a. The sub-beams 8 penetrate the member 19 from the surface 20 and cause aluminum to evaporate in the immediate surrounding environment of the member. Through the action of all the sub-beams 8 or all the laser spots, a common vapor capillary 21 (also called a common aperture or common metal vapor capillary) extending to the lowermost member 19b is formed. The common vapor capillary 21 forms a connected volume in the member 19. In the region near the core portion of the sub-beams 8, the common vapor capillary 21 has a deeper extending sub-segment 21a (“protrusion”). In the region between the sub-beams 8, the common vapor capillary 21 has a shallower extending sub-segment 21b (“recess”). The maximum depth T of the common vapor capillary 21 at the lowest point 23 is... max In this case, it is approximately 4 mm.

[0105] Through the combination of the two-in-one technology and multiple laser spots generated by the sub-beam 8, the common vapor capillary 21 is particularly stable.

[0106] Aluminum is melted in the environment surrounding the common vapor capillary 21, thereby forming a molten pool 24 of liquid aluminum. Because the sub-beam 8 moves relative to the component 19 along the weld profile 20a in the feed direction 18 during welding—moving to the left in the illustration shown here—the molten pool 24 sinks to the right in cross-section. Aluminum is melted at the left edge 24a and lower edge 24b of the molten pool 24, and then solidified again at the right edge 24c of the molten pool 24.

[0107] Welding is carried out in the lowest component 19b until the weld depth ET is reached. unt In the case shown, the weld depth is the component thickness D. unt Approximately 85%. This method allows for excellent and medium-sealed welding. In variations not shown, laser welding can also be performed as a through-weld across all components 19 of the lap joint.

[0108] The aluminum material used for component 19 can be selected from the 3000, 5000, or 6000 series. The welding speed SG can be selected as SG ≥ 5 m / min, preferably SG ≥ 10 m / min.

[0109] exist Figure 4 The middle shows Figure 3 A schematic cross-sectional view of the vapor capillary 21 on planes AA, BB, and CC.

[0110] The dotted line indicates the vapor capillary 21 in Figure 3 The profile 21a on the plane AA is located at the interface between the upper and lower components, that is, at a depth of approximately 2 mm. The vapor capillary 21 forms a connected surface here.

[0111] The dashed line shows the vapor capillary 21 in Figure 3 The profile 21b on the plane BB, which lies at a depth corresponding to the maximum depth T of the common vapor capillary. max Half of it, located at a depth of approximately 2.5 mm. The vapor capillary 21 forms a slightly smaller, but still always connected surface here.

[0112] The vapor capillary 21 is shown in solid line. Figure 3 The profile 21c on the plane CC at a depth of approximately 3.8 mm of the vapor capillary 21. At this depth, the vapor capillary forms four independent (unconnected) sub-regions in cross-section, each of which is constructed to be approximately circular. That is, the plane CC intersects the vapor capillary only in locally raised regions.

[0113] exist Figure 5a The diagram below shows a cross-section of a welding pattern 11 for another variant of the invention, wherein the welding pattern has four laser spots 12 arranged in a ring array.

[0114] Here, all laser spots 12 are the same size. The core portion 13 has a diameter DK of 100 µm, and the ring portion 14 has a diameter DR of 400 µm. Accordingly, the ratio DR / DK is 4.

[0115] The distance between the centers of the two (diagonally) opposed laser spots 12 is 400 µm. In the variant shown here, the annular portions 14 of the opposed laser spots 12 contact exactly at a common center 17. Adjacent laser spots 12 are arranged overlapping each other. The core portions 13 correspondingly do not overlap. Welding diagram 11 here has fourfold rotational symmetry because the annular array consists of four laser spots 12 that can be transferred to each other by rotating 90° around the common center 17.

[0116] Regarding the local feed direction 18 shown, welding diagram 11 is arranged such that two laser spots 12a are upstream and two laser spots 12b are downstream. The two laser spots 12a are in the same position with respect to the local feed direction 18. Similarly, the two laser spots 12b are in the same position with respect to the local feed direction 18.

[0117] exist Figure 5b The diagram shown in the middle is a schematic cross-section of a welding pattern 11 in another variant of the invention, wherein the welding pattern has three laser spots 12 arranged in a ring array.

[0118] Here, all laser spots 12 are the same size. The core portion 13 has a diameter DK of 300 µm, and the ring portion 14 has a diameter DR of 800 µm. Accordingly, the ratio DR / DK is 2.67.

[0119] Adjacent laser spots 12 are arranged overlapping each other with respect to the annular portion 14, and all three laser spots 12 overlap in the annular portion 14 within the central region 26. The core portions 13 do not overlap.

[0120] With respect to the local feed direction 18 shown, welding pattern 11 is arranged such that laser spot 12a is upstream and two laser spots 12b are downstream. The two laser spots 12b are in the same position with respect to the local feed direction 18. Here, the distance between the laser spots 12b and each of the downstream laser spots 12b is slightly smaller than the distance between the upstream laser spot 12a and each of the downstream laser spots 12b (correspondingly with respect to the center of the laser spot).

[0121] exist Figure 5c The diagram shown in the middle is a schematic cross-section of a welding pattern 11 in another variant of the invention, which has five laser spots 12 arranged in a ring array.

[0122] Here, all laser spots 12 are the same size. The core portion 13 has a diameter DK of 100 µm, and the ring portion 14 has a diameter DR of 400 µm. Accordingly, the ratio DR / DK is 4.

[0123] The spacing between the centers 15 of two adjacent laser spots 12 in the annular array is approximately 350 µm. In the variant shown here, adjacent laser spots 12 in the annular array are arranged with the ring portion 14 overlapping each other. Welding figure 11 here has fivefold rotational symmetry because the annulus is composed of five laser spots 12, which can be transferred to each other by rotating 72° around a common center 17.

[0124] Regarding the local feed direction 18 shown, the welding diagram 11 is arranged such that one laser spot 12a is upstream, two laser spots 12b are downstream, and two laser spots 12c are centrally located between laser spots 12a and 12b. The two downstream laser spots 12b are in the same position with respect to the local feed direction 18. Similarly, the two centrally located laser spots 12c are in the same position with respect to the local feed direction 18.

[0125] Figure 6a A schematic top view of an exemplary prism panel 27 is shown, which, for example, can be used in welding optics to generate multiple sub-beams for use in the method according to the invention.

[0126] In the form shown here, the prism panel 27 includes a central hexagonal facet 28 (“central facet”). The prism panel 27 includes six external facets 29 (“outer facets”) arranged around the central facet. A collimated laser beam 7 is incident on the prism panel 27.

[0127] Figure 6b Showing from Figure 6a A schematic cross-sectional view of an exemplary prism panel 27.

[0128] The outer facets 29 are wedge-shaped. The facet angle β is approximately 0.15°, measured relative to the base plane 25 perpendicular to the incident direction of the collimated laser beam 7. The collimated laser beam 7 is incident on the facet 27. In the region of the central facet 28, the collimated laser beam 7 is not deflected. In the regions of the six outer facets 29, the collimated laser beam 7 is deflected (refracted). This results in an undeflected sub-beam 8 and six deflected sub-beams 8.

[0129] Figure 6c A welding pattern 11, illustrating a variant of the method according to the invention, is shown, having six laser spots 12 arranged in a ring array and a central laser spot 12. For example, this welding pattern can be derived from... Figure 6a An exemplary prism panel 27 is generated. The central laser spot 12 is marked here as 12'''.

[0130] Here, all laser spots 12 are the same size. The core portion 13 has a diameter DK of 100 µm, and the ring portion 14 has a diameter DR of 400 µm. Accordingly, the ratio DR / DK is 4.

[0131] The spacing between the centers 15 of two adjacent laser spots 12 in the annular array is approximately 350 µm. In the variant shown here, adjacent laser spots 12 in the annular array are arranged with the annular portion 14 overlapping each other. The central laser spot 12''' overlaps with all other laser spots 12 with respect to the annular portion 14. The core portions 13 do not overlap. Welding figure 11 here has sixfold rotational symmetry because the annulus is composed of six laser spots 12, which can be transferred to each other by rotating 60° around a common center 17; the central laser spot 12''' is unaffected by rotation because its laser spot center overlaps with the common center 17.

[0132] Regarding the local feed direction 18, the welding diagram 11 is arranged such that two laser spots 12a are upstream, two laser spots 12b are downstream, and three laser spots 12c are centrally arranged between laser spots 12a and 12b.

[0133] Figure 7 Experimental images of two aluminum-containing components are shown, which, in a variation of the method of the invention, have been welded together at an lap joint. Cross-sectional surfaces have been prepared and photographed using an optical microscope.

[0134] The upper component has a thickness of approximately 1 mm, and the lower component has a thickness of approximately 2 mm. Welding is performed by welding approximately 40% into the lower component; the welding direction is perpendicular to the plane of the drawing. A virtually pore-free, medium-sealed weld has been obtained.

[0135] In this example, Figure 2 The welding diagram (see above) shows four laser spots arranged in a square, contacting manner. The chosen average laser power is P = 3 kW, and the welding speed is SG = 5 m / min. For each laser spot, the power component in the core is 70%, the core diameter DK is 100 µm, and the ring diameter DR is 400 µm. The aluminum-containing component is made of aluminum alloy AW-5083.

[0136] Figure 8 An apparatus 30 with welding optics 1 is shown, which is used for welding component 19 or for generating a weld profile 20a. According to the invention, the weld profile 20a is traversed multiple times, especially completely traversed multiple times. After traversing or (preferably) during traversal, it can be determined by an optical sensor 31 whether traversal is necessary again. The optical sensor 31 is preferably arranged coaxially with the optical path of the sub-beam 8.

[0137] Figure 9The welded components are shown, with a weld outline 20a formed at the butt joint. The cap-shaped component 19c was placed inside another can-shaped component 19d before welding.

[0138] Figure 10 The cross-sectional ground surfaces of two welded components are shown, where two passes can be seen from the weld profile 20a.

[0139] List of reference numerals 1 Welding optical components 2. Laser fiber optic cable 2a Two-in-one fiber optic cable 3. Collimating lens 4a, 4b Bifocal insertion devices 5. Focusing lens 6. Output laser beam 7 Collimated laser beam 8 beamlets 9-core optical fiber 10-ring fiber optic cable 11 Welding Diagram 12 laser spots 12' is the laser spot adjacent to laser spot 12''. 12'' is the laser spot adjacent to laser spot 12'. 12''' laser spot at the center 12a upstream laser spot 12b downstream laser spot 12c centered laser spot 13-core section 14-ring section 15. Center of laser spot 16. Circular Formation 17 Common Center 18 Feed direction 19 components 19a Upper component 19b Bottommost component 19c Cap-like component 19d Tank-shaped component 20 Surface 20a Welding Profile 21. Steam capillary 21a Protrusion 21b Depression 23 Lowest point 24 Molten Pool 24a Left edge 24b lower edge 24c Right edge 25 Base plane 26 Central Area 27-sided panel 28 Central facets 29. Outer facets 30 devices 31 Optical Sensors β facet angle BD component thickness The diameter of the DK core portion D ob Component thickness of the upper component Diameter of the DR ring section D unt Thickness of the lowest component ET unt Welding depth in the lowest component KFD core fiber diameter RFD ring fiber diameter T max Maximum depth of the vapor capillary.

Claims

1. A method for welding at least two aluminum-containing components (19), in, The components (19) each have an aluminum content of at least 75% by weight. The welding is performed as laser welding within a deep welding system. The output laser beam (6) is divided into multiple sub-beams (8), and the sub-beams are directed toward the component (19), thereby generating multiple laser spots (12) on the surface (20) of the component (19). The plurality of laser spots (12) pass over the welding profile (20a) on the surface (20) of the component (19). Among them, the laser spot centers (15) of at least three of the plurality of laser spots (12) are arranged in a ring array (16). Its features are, The output laser beam (6) is generated by means of multiple optical fibers, such that the plurality of laser spots (12) on the surface (20) of the component (19) each have a core portion (13) and a ring portion (14), wherein the welding profile (20a) is traversed at least partially a second time after the first traversal, wherein the second traversal is performed at a lower power and / or a higher feed rate than the first traversal.

2. The method according to claim 1, characterized in that, The component (19) contains die-cast aluminum or forged aluminum alloy.

3. The method according to any one of claims 1 to 2, characterized in that, Welding depth (ET) unt (less than 10mm) 4. The method according to any one of claims 1 to 2, characterized in that, The welding profile (20a) that has been passed twice is recorded by an optical sensor (31) and the defect location is detected.

5. The method according to claim 4, characterized in that, The record is created during the second pass through the weld profile (20a).

6. The method according to any one of claims 1 to 2, characterized in that, After the second traversal of the welding profile (20a), the welding profile (20a) is traversed at least partially for the third time.

7. The method according to claim 6, characterized in that, The welding profile (20a) that has been passed through three times is recorded by an optical sensor (31) and the defect location is detected.

8. The method according to claim 7, characterized in that, The record is created when the weld contour (20a) is traversed for the third time.

9. The method according to claim 1, characterized in that, The output laser beam (6) is generated by means of a two-in-one optical fiber (2a).

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