EP3274121A1

EP3274121A1 - Laser beam joining method and laser machining optics

Info

Publication number: EP3274121A1
Application number: EP16714221.5A
Authority: EP
Inventors: Steffen Walter
Original assignee: Scansonic MI GmbH
Current assignee: Scansonic MI GmbH
Priority date: 2015-03-24
Filing date: 2016-02-29
Publication date: 2018-01-31
Also published as: DE102015104411A1; US20180071848A1; DE102015104411B4; CN107405711A; WO2016150425A1

Abstract

The invention relates to a method for joining workpieces (12, 13) using a laser beam (7), wherein the laser beam (7) is focused onto a focal plane downstream of the machining plane in the beam propagation direction and subdivided into a plurality of partial beams (19) by means of a beam dividing device (6). The subdivision is effected in a geometric manner, i.e. the partial beam cross sections emerge from a division of the geometric form of the beam cross section of the laser beam (7). The partial beams (19) are guided onto the machining plane (8) in a crossed manner and with an offset from one another in such a way that an extended laser focus (18) is formed. The radiation intensity distribution of the superposed partial beams (19) in the machining plane (8) along a line perpendicular to the seam joint respectively has a maximum at the end regions thereof. As a result thereof and as a result of the spatially extended region of high radiation intensity on both sides along the seam joint compared to the prior art, there is, firstly, an improvement in the edge connection and hence in the quality of the seam joint and, secondly, an increase in the process efficiency.

Description

Laser beam joining process and laser processing optics

The invention relates to a method and a laser processing optics for welding or soldering workpieces by means of a laser beam. The process not only improves the edge connection of the soldering or welding seam, and thus the seam quality, but also increases process efficiency.

For joining two workpieces by means of a laser beam, laser welding and laser soldering are known. In both cases, workpieces are joined together at a joint while melting a material. While the workpieces, or their surfaces, are melted during laser welding, only a solder wire applied to the joint or introduced into the joint is melted during laser soldering.

The laser beam welding in turn can also be done using an additional wire, for example, with a large gap width of the joint. The filler wire is positioned in or on the gap of the joint; The laser beam then melts the edges of the two workpieces at the joint and the filler wire, forming a melt pool.

The energy input when joining two workpieces by means of laser is characterized by the spatial radiation intensity distribution, and thus the energy distribution of the laser focal spot (also called Laserspot) in the working plane. For example, in the case of a butt joint, the working plane is usually positioned at the joint on the surface of the two workpieces to be joined. Often laser spots are used which have either a rotationally symmetrical rectangular or Gauss-shaped profile of their radiation intensity distribution in cross section. But there are also, as described below, rectangular or line focus optics known to produce a non-rotationally symmetric laser spot. The energy distribution along a line in the cross section of the laser spot essentially follows a rectangular profile or a Gaussian distribution, ie the energy distribution along this line is largely homogeneous or has a maximum in the center of the laser spot. In laser beam welding using an additional wire, however, such an energy distribution is unfavorable, since the greater proportion of the laser light intensity is incident on the additional wire and only a small part on the workpieces to be joined. On the one hand, low-melting alloys are generally used for the additional wire, for which reason a small amount of energy compared to the workpieces is sufficient for melting; on the other hand, part of the laser power striking the additional wire is reflected unused.

To solve this undesirable effect z. B. two laser beams are used for joining or two laser spots in the working plane.

DE 10 201 1 016 579 A1 shows a method and a device for laser beam welding by means of two laser beams of different power density, wherein the laser focal spots are arranged one behind the other in the feed direction. For this purpose, two separate lasers or a laser whose laser beam is split can be used.

WO 98/51442 describes an apparatus for welding with two laser focal spots, wherein the two, in a variable distance parallel to each other extending laser partial beams are generated by means of mirrors from a laser beam. Here, the laser focal spots are arranged on a line perpendicular to the weld, i. h., Each of the two laser partial beams is imaged onto a workpiece associated with it.

DE 199 61 918 C2 describes a method and a device for beam splitting a laser beam with a variable lens system for producing at least two laser focal spots on a workpiece to be machined, wherein the distance and intensity of the laser focal spots can be changed continuously. Here, the laser focal spots are preferably arranged on a line perpendicular to the weld, by means of a rotating device, the arrangement of the laser focal spots can also be varied as desired with respect to the weld. DE 101 13 471 A1 discloses a method for hybrid welding by means of a laser double focus. DE 102 61 422 B4 shows a laser welding and soldering method and the corresponding apparatus in which a laser beam is divided by means of a variable optical arrangement with a prism and a lens system into at least two separately contactable partial laser beams of different intensities, wherein the partial laser beams with regard to their power distribution can be adjusted with respect to their focus position rotation with respect to the joint seam and / or with regard to their operating point separation, so that two separate laser burn spots can be used for joining. In this case, a first partial beam is focused on the processing plane, while a second is focused on a focal plane above the processing plane, so that this second partial beam is widened in the working plane and has a lower energy density compared to the first partial beam.

By means of the welding apparatus disclosed in JP H07-60 470 A, the division of a laser beam into partial beams is also provided, wherein the separate partial beams are used for simultaneous welding at different points of a component to reduce thermally induced stresses.

Further techniques for the production of two partial laser beams and their use for material processing are disclosed in DE 196 19 339 A1, WO 95/1 1 101 A1, DE 197 51 195 C1 and DE 43 16 829 A1, wherein in these techniques only limited adaptation possibilities to the Requirement of a material processing process possible or these are technically very complicated to implement.

The described method or devices have in common that at least two separate laser spots are used for processing, wherein the radiation intensity distribution in the laser or laser partial beams either the typical Gaussian profile or, z. B. in imaging a fiber end, a homogeneous, rectangular intensity distribution (also called Tophat) along a line through the respective cross section of the laser spots.

EP 1 525 972 A2 describes a laser beam welding method in which the laser beam is split into partial beams, the partial beams being used either separately or superimposed for welding. A specific design of the total intensity distribution of the superposed partial beams is not disclosed herein. It is also known the expansion of the laser spot on a rectangular surface in the working plane. DD 229 332 A1 shows an arrangement in which a laser beam with a circular cross-section and Gaussian radiation intensity distribution is focused or defocused rectangularly onto the weld area by means of one or two cylindrical lenses. But even with this method, the laser focal spot in its center shows the maximum of the radiation intensity, which serves the actual joining. The less intense radiation intensity at the focal spot edge is used for preheating or reheating the workpiece area to be joined or already joined.

A method for modifying the radiation intensity distribution in only one laser beam is described in DE 40 34 744 C2. Here, first a division of a laser beam into two partial beams, then a modification of the properties of a partial beam and finally a merger of the two partial beams to form a total beam. This also makes it possible to modify the radiation intensity distribution in the composite laser beam in such a way that two Gaussian profiles with respectively different parameters are added to form an overall profile, with the respective maxima of the individual Gaussian profiles coming to lie in the same spatial position. Thus, the compound laser spot is characterized by a light intensity falling towards the edge.

Also known to the person skilled in the art is the Powell lens, named after its inventor and described in detail in US Pat. No. 4,826,299 A, for producing a linear laser spot, the intensity distribution along the line being largely constant. This is achieved by a transformation of the laser beam by means of a cylinder in the direction of this line. Perpendicular to the line, the laser beam is focused on the working plane.

WO 2014/052239 A1 discloses a device using a Powell lens, in which the energy distribution along the projected linear laser spot is further homogenized. However, a Gaussian-like obtained intensity profile, ie, the energy density distribution over the line cross-section, ie perpendicular to the line, has a maximum in the middle, while falling continuously towards the edges.

Another limitation of the Powell lens is that the linewidth of the laser spot, i. H. the extent of the linear laser spot transverse to the line, is fixed by the beam cross section of the coupled laser beam. The effective spot width is also predetermined by the wedge angle used, the radiation intensity at the joint seam and the edges of the joint seam being identical. An increase of the integral energy input into the workpieces next to the seam would only be possible by an extension of the laser potential, but also - while reducing the energy density - the range of energy input is increased.

It would be desirable to have a laser joining method in which the geometrical shape of the laser spot and its energy distribution in the working plane can be modified in such a way that only one laser spot and the simplest possible optical structure is required for joining, the energy density in the edge region of the laser spot being preferred the joint, d. H. on the flanks of the seam - is highest.

The invention is based on the object laser beam joining by a - in comparison to the prior art - more effective (and within certain limits predefinable) distribution of radiation intensity in the focal spot to form sharper focal spot outer edges on the workpieces to be joined or the weld the edge connection and thus Improve the seam quality, while at the same time by increasing the energy input into the joining partners against the energy input at the position of the joint the energy balance of the laser beam joining process, especially in laser beam welding with filler wire to be improved. In addition, the spatial extent of the focal spot in the working plane should be variable along the joint, the region of high energy density of acting on the joining laser laser spot should have a length, in particular in the feed direction on the flanks of the seam, which in the ideal case of the extension of the laser focal spot in this direction equivalent. The solution of this object is achieved by a method having the features according to claim 1 and a laser processing optics according to claim 5; expedient embodiments of the invention can be found in the subclaims.

According to the invention, a more effective distribution of the radiation intensity in the laser focal spot (with formation of sharper focal spot outer edges in comparison with the prior art) in a working plane on the workpieces to be joined or the weld seam during laser beam joining is effected by a modification of the laser focal spot geometry and the radiation intensity distribution in the cross section of FIG the processing plane defocused laser beam. These modifications of the laser focal spot are achieved by a geometrical division of the laser beam into partial beams, an inventive deflection of the beam directions of the partial beams relative to each other and a local and orientation correct merging of the partial beams in the working plane, wherein in the working plane a combined of the partial beams laser focal spot with a through the Division and deflection defined radiation intensity distribution is formed.

The defocusing of the laser beam is preferably carried out in such a way that a use of the laser focal spot takes place in the so-called far field, d. h., The distance of the working plane from the focus is greater, preferably way much larger than the Rayleighlänge of the laser beam, the focus is in the laser beam direction below the working plane. In this case, the radiation intensity distribution (of the undivided laser beam) in the working plane has a Gaussian-shaped profile.

Geometric division of the laser beam is understood to mean the following method:

The laser beam, having a geometric shape of the beam cross-section in a plane perpendicular to the beam, is divided by cutting the beam cross-section such that the sub-beams formed by the division have a geometric shape of their beam cross-section which is a fraction (ie, a portion) of the geometric Shape of the beam cross section of the undivided laser beam is, wherein can be formed by a "joining" all generated by dividing sub-beam cross-sections in a plane again the geometric shape of the (undivided) beam cross-section.

By a z. B. single, preferably central parts of, for example, circular beam cross-section along the pitch direction arise in this way two partial beams whose partial beam cross sections each have the geometric shape of a semicircle. In the case of a Gaussian radiation intensity distribution in the beam cross section of the undivided laser beam, the two partial beams in the partial beam cross section along the direction of division also have a Gaussian radiation intensity distribution. In contrast to the division direction, the radiation intensity distribution in a sub-beam cross-section in the far field has a profile which corresponds to a maximum-cut Gaussian curve. Thus, the two sub-beams show a monotonically increasing from zero to a maximum value distribution of the radiation intensity in the sub-beam cross-section transverse to the division line of the circular laser beam cross-section with asymmetric and mirror image position of the maximum. The distance of the cut edges of the cut Gaussian curves transversely to the division direction, ie in the direction of the beam offset in the working plane, will be referred to below as "beam offset".

According to the invention, the geometrical division of the defocused laser beam preferably takes place in the manner just described, namely that the (round) cross section of the laser beam along one or more chords (which preferably extend in the vicinity of the laser beam axis) in sub-beams each having a partial beam cross-section, z. B. circle segments, is decomposed. In a sub-beam, the radiation intensity (in the far field) increases monotonically to a maximum value at the second outer edge opposite the first outer edge of the partial beam cross-section along a direction (arranged perpendicular to the division line) in the partial beam cross-section from a minimum value at a first outer edge of the partial beam cross-section ,

Due to the positioning of the laser beam dividing tendon or tendons within the laser cross section, a defined distribution of the laser power to the individual partial beams is possible. The superposition of the partial beams in the working plane then takes place in such a way that the partial beams impinge with a local offset of their beam axis to each other on the working plane, wherein the focal spot formed by the superposition of the partial beams in the working plane preferably represents a superposition of circle segments and a rectangular envelope having.

The sum profile of the radiation intensities of the superimposed partial beams in the working plane along a line which is defined by the offset of the beam axes of two partial beams in the working plane has a first maximum value at the first edge section of the laser focal spot, a minimum value arranged between the two edge sections and at the second, the first opposite edge portion of the laser focal spot on a second maximum value.

The first maximum value of the radiation intensity, i. H. the light intensity, may be identical to the second maximum value. The minimum value of the radiation intensity is dependent on the offset of the two combined partial beams and the defocusing of the undivided laser beam.

According to an embodiment of the method, the offset of the partial beams in the working plane is selected such that the spatial extent of the laser focal spot formed from the combination of the partial beams in the working plane in the direction defined by the offset of the two partial beams essentially corresponds to the diameter of a laser spot which would arise if the laser beam would strike the working plane undivided. In this case, with a Gaussian-shaped radiation intensity distribution present in the undivided, defocused laser beam, the above-mentioned minimum value of the radiation intensity in the center of the laser focal spot formed by the partial beams becomes approximately zero and is limited to only one point in the radiation intensity distribution. The beam offset should be according to the invention in the working plane between 30% and 100%, preferably 50% to 80%, of the beam diameter of the undivided laser beam. If, on the other hand, the beam offset between the partial beams in the machining plane is greater than the diameter of the (undivided) laser beam in the machining plane, an (extended) range with the minimum value of approximately zero arises in the radiation intensity distribution of the laser focal spot formed by the partial beams - it appears as it were a gap in the profile of intensity.

In the case of a beam offset smaller than the diameter and larger than the radius of the (undivided) laser beam in the processing plane, a radiation intensity distribution is produced in the laser focal spot on the processing plane along the direction defined by the offset of the two partial beams, in which the minimum value of the intensity is greater than zero.

Preferably, the geometric beam splitting (eg with a roof plate or a segmented mirror or a lens that contains a wedge angle in beam splitting zones) with generation of at least one deflection angle transverse to the feed direction in such a way that the sub-beams with respect to the original axis of the laser beam so crossing in the further course) be deflected, that the impact points of the respective partial beam axes, d. H. the beam offset in the working plane, are optimally spaced for the joining task.

The laser focal spot formed by the laser beam joining method has, as a rule, a rectangular envelope in the process. In a (one-time) geometric division of the laser beam along a line (i.e., chord in the circular beam cross-section) parallel to the feed direction is thereby formed, compared to an undivided laser beam, extended in the feed direction region of high light intensity left and right of the joint seam. Thus, a laser spot is produced with relatively sharp and long, high radiation intensity edges aligned along the machine direction (welding / soldering direction).

According to the invention, it is provided to divide the laser beam geometrically at least once, two partial beams being formed in the case of a geometric division of a (partial) beam, ie with each geometric division two partial beams are generated from one beam or partial beam. So it is also planned to to divide serstrahl several times geometrically. For example, four sub-beams can be formed, which are combined in such a way that a substantially rectangular laser focal spot is formed in the working plane whose radiation intensity distribution in each of the four corners of the rectangle has a maximum.

Preferably, the geometric division is carried out in such a way that the

Intensity of light of the (combined) laser focal spot in the working plane intensity maxima in the two areas of the laser focal spot next to the joint seam, or next to an additional wire arranged on the joint seam, wherein the absolute minimum of the intensity distribution in the laser focal spot is imaged on the joint.

An advantage of the laser beam joining method according to the invention is, for example, the possibility of increasing the light intensity and thus the energy density at the two edges along the joint of the joining seam forming during joining during the laser welding of two workpieces using an additional wire at a joint. Thus, a smaller laser power is applied to the additional wire than to the two workpiece surfaces directly next to the additional wire, two elongated regions of high radiation intensity being formed in the feed direction on the flanks of the seam. Therefore, the energy balance is improved by means of the invention, wherein only one laser focal spot is used.

By working in the far field, wherein the focus is below the working plane, the laser focal spot - in contrast to the beam splitting variants of the prior art - at its outer edge, in particular along the seam, a relatively straight edge.

The increase in intensity at the edges of the joint seam, in conjunction with the length of engagement of the laser focal spot which is increased in the feed direction compared to a laser burn spot according to the prior art, also improves the edge connection and thus the quality of the joint seam. A further advantage of the laser beam joining method according to the invention is a temperature distribution in the molten bath caused by the specific surface energy input, which results in improved degassing of the melt and thus, in comparison to prior art methods, a reduction in the number of pores in the solidified joint seam and a reduced roughness of the joint seam causes.

The laser beam joining method according to the invention can be used both in fixed laser processing optics and in scanning laser processing systems or systems with integrated seam guidance.

Preferably, for the method multimode laser radiation is used, the z. B. can be generated by means of fiber coupling of multi-kilowatt lasers, since at a laser radiation near the fundamental mode, the diffraction patterns affect the desired intensity distributions.

To carry out the laser beam joining method according to the invention, a laser processing optical system described below is provided for use in a laser joining device.

The laser processing optics comprises a collimation device, a focusing device and a beam splitting device, all of which are arranged along an optical axis. The beam splitting device can have one or more beam-splitting elements.

In the beam path of the laser beam, first the collimation device, behind the focusing device and finally the beam splitting device can be arranged. It can also be provided to arrange the beam splitting device in the laser beam path between the collimation device and the focusing device. Finally, it is also possible to arrange the beam splitting device in the beam path of the laser beam in front of the collimation device and the focusing device.

If the beam splitting device contains a plurality of separate elements, these individual elements can also be arranged separately from each other according to the above-mentioned positions in the beam path. The beam splitter may be formed by transmitting elements such as a wedge plate or a roof plate (ie a wedge plate with two wedge segments) or by reflective elements such as segmented mirrors (ie mirrors whose specular surface is subdivided into individual segments, with the normal vectors applied to the segments) Surfaces of the segments are each rotated by an angle), be realized.

The laser processing optics may further comprise one or more cylindrical lenses, which enable a scaling of the geometric dimensions or the geometric shape of the laser focal spot in the processing plane. For example, it can be provided to obtain an oblong rectangular shape of the laser focal spot by means of a suitable combination of convex and concave cylindrical lenses, wherein the extent of the laser focal spot along the feed direction is substantially greater than its extension transverse to the feed direction.

The beam splitting device can furthermore be equipped with an acylindrical transition zone, which enables a selective division of the laser intensity onto the individual sub-beams, in that a part of the laser radiation is deflected differently depending on the point of impact.

Furthermore, it can be provided that the beam splitting device and the focusing device are combined in a single optical element. For this purpose, this optical element can have, for example, a segmented, focussing interface between two optical media (eg air and glass). The segments of the interface each have a normal vector of the surface. The normal vectors of adjacent segments are in each case rotated by the angle through which the partial beams are tilted relative to one another, so that the partial beams are deflected accordingly when the laser beam is split up. The segments may have sharp boundaries to adjacent segments, but they may also merge into one another continuously to achieve a selectively adjusted intensity distribution into the individual sub-beams. The invention will be explained in more detail with reference to embodiments. These show in a schematic representation of the

1 shows a beam path in a laser processing optics in cross section and the radiation intensity distribution in the laser beam from the prior art.

2 shows a beam path in a laser processing optical system in cross section and the radiation intensity distribution in the laser focal spot according to the invention;

3 each a cross section through three variants of the laser processing optics according to the invention;

4 shows a plan view of the joining joint and the joining seam of two workpieces at the point of action during the implementation of the laser beam joining method according to the invention with two partial beams; and

Fig. 5 is a plan view of the joint and the joining seam of two workpieces at the point of action during implementation of the laser beam joining method according to the invention with four partial beams.

FIG. 1 shows the beam path of the laser beam 7 in a laser processing optical system according to the prior art. The laser beam 7, which has the Gaussian radiation intensity distribution 3.1 in its cross section, is focused by the focusing device 5 on the laser focus plane 9, whereby the (defocused) laser focal spot 18 is formed in the working plane 8, which in its cross section the radiation intensity distribution 3.2 having. The maximum of the two Gaussian radiation intensity distributions 3.1 and 3.2 respectively lies on the beam axis 10.

FIG. 2 shows the beam path of the laser beam 7 according to the invention. The laser beam 7, which has the radiation intensity distribution 3.1 in its cross section, is focused by the focusing device 5 on the Laserfokusebene 9 and divided by the beam splitting device 6, here in the form of a roof panel in two sub-beams 19 and deflected in the way that of the two Partial beams 19 in the processing plane 8 of the continuous laser focal spot 18 is formed. The distance of the working plane 8 from the laser focus plane 9 along the beam axis 10 is much greater than the Rayleigh length of the laser beam 7. The radiation intensity distribution 20 of this laser focal spot 18 along the direction y marked in FIG. 2 points at the two edges 21 of the laser focal spot 18 two sharp maxima, while it drops to zero in the area of the beam axis 10.

FIG. 3 shows three embodiment variants a, b and c of the laser processing optics according to the invention with respect to the arrangement of the collimation device 4, the focusing device 5 and the beam splitting device 6 along the beam axis 10. The coupling of the laser beam takes place by means of the optical fiber 2.

FIG. 4 shows a top view of the joint 1 1 or the weld seam 15 between the two workpieces 12 and 13 during the welding process with filler wire according to the laser beam joining method according to the invention. The additional wire 14 is brought to the joint 1 1 and melted in the laser focal spot 18. The laser beam is divided in this example once into two sub-beams, each forming the partial laser focal spot 18.1 and 18.2. The largely square laser spot 18 composed of the two partial laser burn spots 18.1 and 18.2 is characterized by the length 17 in the feed direction and the width 16 transversely to the feed direction. Clearly visible are the locations of intense laser irradiation on the two edges of the laser focal spot 18, which are arranged parallel to the joint 11, ie. on the edge regions of the arranged on both sides of the joint 1 1 workpieces 12 and 13, along the entire length 17 of the laser focal spot 18th

In an analogous manner, in Figure 5, the top view of the joint 1 1 between the two workpieces 12 and 13 during the welding process with additional wire according to the invention Laserstrahlfügeverfahren with geometric division of the laser beam into four partial beams, which are superimposed on the weld 15 to be created, too see. In this case, the square-shaped laser focal spot 18 formed in the working plane is composed of four quarter-circle partial laser burn spots 18.1 to 18.4 of the four partial beams. In this example, the radiation intensity in each of the four corners of the laser spot 18 reaches a maximum while it is practically zero in the center of the laser spot 18. List of reference numbers used

2 optical fiber

3 radiation intensity distribution

4 collimation device

5 focusing device

6 beam splitting device

7 laser beam

8 processing level

9 laser focus plane

10 beam axis of the laser beam

1 1 joint

12 workpiece 1

13 workpiece 2

14 additional wire

15 jointing

16 seam width

17 Einwirklänge the laser focal spot

18 laser stain

19 partial beam

20 Beam intensity distribution along the y-direction in the working plane

21 edge of the laser focal spot

x feed direction

y direction in the working plane transverse to the feed direction

Claims

claims

1 . A laser beam joining method for joining a first (12) and a second (13) workpiece to a joint (1 1) using a laser beam (7), wherein in a working plane (8) at the joint (1 1) and at the joint ( 1 1) positioned edge regions of the workpieces (12, 13) a laser focal spot (18) is formed, characterized by the following steps:

Defocusing the laser beam (7) in the processing plane (8) in such a way that the focus is positioned in the direction of the laser beam path at a distance greater than the Rayleigh length behind the processing plane (8);

Dividing the defocused laser beam (7) by means of a beam splitting device (6) into at least two partial beams (19) each having an intensity distribution along its partial beam cross section, wherein the division is carried out in such a way that the partial beams (19) in a region between the beam splitting device (6) and the working plane (8) intersect, and

Overlaying the partial beams (19), each with an offset to each other in the processing plane (8) to the laser focal spot (18), wherein the radiation intensity of the laser focal spot (18) in its outer edge region on at least two on the workpieces to be joined (12, 13) a line transverse to the joint (1 1) in each case next to the same oppositely disposed positions has a maximum.

2. Laserstrahlfügeverfahren according to claim 1, characterized in that the laser beam (7) is divided into two partial beams (19) with similar geometric shape and similar radiation intensity distribution of the two partial beam cross sections, wherein a first radiation intensity maximum of the laser focal spot (18) on the first workpiece (12 ) and a second radiation intensity maximum on the second workpiece (13) is arranged.

3. Laser beam joining method according to claim 1, characterized in that the laser beam (7) in four partial beams (19) with similar geometric shape and the same radiation intensity distribution of the four partial beam cross sections is divided, wherein the laser focal spot (18) has a rectangular shape in the working plane (8) each having a radiation intensity maximum in the four corners of the rectangle.

4. Laser beam joining method according to one of the preceding claims, characterized in that the extension (16) transversely to the joint (1 1) of the laser beam spot (18) generated by the superposition of the partial beams (18) 30% to 100% of the diameter of the beam cross section of the undivided Laser beam (7) in the working plane (8) corresponds.

5. laser processing optics for performing the laser beam joining method according to one of claims 1 to 4, characterized in that it comprises a collimation device (4), a focusing device (5) and a beam splitting device (6).

6. laser processing optics according to claim 5, characterized in that the beam splitting device (6) comprises transmitting elements for splitting the laser beam (7).

7. Laser processing optics according to claim 5, characterized in that the beam splitting device (6) comprises reflective elements for splitting the laser beam (7).

8. laser processing optics according to one of claims 5 to 7, characterized in that it comprises a scanner unit.

9. laser processing optics according to one of claims 5 to 8, characterized in that it comprises one or more cylindrical lenses for scaling the outer dimensions (16, 17) of the laser focal spot (18).

10. laser processing optics according to one of claims 5 to 9, characterized in that the focusing device (5) and the beam splitting device (6) in an optical element, comprising at least one segmented, fo-kussierende interface between two optical media, are summarized, wherein the respective normal vectors are inclined to the focusing interface in the segments relative to each other by an angle of the beam deflection.