Method and laser processing system for producing an integral joint between two workpieces

Abstract

The invention relates to a method for producing an integral joint between two workpieces (1, 2) by laser welding, wherein: a molten pool (4) is produced at a joint seam (3) of the workpieces (1, 2) by at least one laser beam (5) and a wire (7) is fed to the region of the molten pool (4) such that the wire melts in the region of the molten pool (4); the at least one laser beam (5) is shaped to form a laser beam pattern (51) which has a radiation gap (52), so that a wire feed region (8) is defined at the joint seam (3) by the radiation gap (52), and the joining wire (3) penetrates into the molten pool (4) in the wire feed region (8); the laser beam (5) and the laser beam pattern (51) are configured such that the point of melting (9) of the wire (7) lies below the outer surface (10) of the joint seam (3).

Description

[0001] Method and laser processing system for producing a material-bonded connection between two workpieces

[0002] The present invention relates to a method and a laser processing system for producing a material-jointed connection between two workpieces by means of laser welding, wherein a melt pool is generated at a joint seam of the workpieces by at least one laser beam and a wire is fed to the area of ​​the melt pool so that it melts in the area of ​​the melt pool.

[0003] Various processes and laser processing systems for creating a metallurgical bond between two workpieces using laser welding are known in the art, particularly with the use of filler wire. These processes offer numerous advantages, such as the ability to bridge component tolerances by using the wire as a filler material. Additionally, the use of wire allows for filling gaps and notches, as well as layering material to achieve greater material thicknesses. Another application is alloying, which is used especially with crack-prone materials, such as 6000 or 7000 series aluminum alloys or high-strength steels, to improve the weld properties. Furthermore, laser welding with wire offers high flexibility with regard to material selection, enabling its use in a variety of applications.

[0004] Nevertheless, the known processes and systems have some significant disadvantages that lead to problems in practice. Typically, the wire is melted above the component surface and then fed into the molten pool of the base material. This approach results in the bond between the wire and the base material occurring primarily in the near-surface layers. Especially at greater welding depths above 5 mm, this necessitates the layer-by-layer application of material, which is time-consuming and reduces the efficiency of the process. Furthermore, melting the wire at the surface often leads to an uneven material distribution in the weld, which can impair the mechanical properties of the joint.Another problem is that the weld quality is compromised by the limited penetration depth of the wire, which can lead to insufficient joint strength, especially with high-strength materials or thick workpieces. This can reduce the durability of the joint and increase its susceptibility to material defects such as cracks or porosity. Additionally, the layered application of material limits the geometric precision of the weld, making it more difficult to produce joints with more complex requirements.

[0005] The object of the invention is to avoid or at least reduce the disadvantages known from the prior art and to provide an optimized method and an improved laser processing system for producing a material-jointed connection between two workpieces.

[0006] This problem is solved by a method for producing a material-bonded connection between two workpieces by means of laser welding, wherein a melt pool is generated at a joint of the workpieces by at least one laser beam and a wire is fed into the area of ​​the melt pool so that it melts in the area of ​​the melt pool, wherein the at least one laser beam is shaped into a laser beam pattern which has a radiation gap, such that a wire feed area is defined by the radiation gap at the joint, and the connecting wire penetrates the melt pool in the wire feed area, wherein the laser beam and the laser beam pattern are configured such that the melting point of the wire lies below the outer surface of the joint.

[0007] This process offers the advantage that the wire is not only inserted into the weld seam but also selectively melted below the outer surface. This ensures a uniform distribution of the wire material even in deeper areas of the weld, resulting in improved mechanical properties. A reliable material transfer is achieved, especially with high laser power and greater material thicknesses. Furthermore, the process prevents the wire from melting only on the surface of the workpiece, significantly improving the quality of the joint and minimizing the formation of surface defects such as pores or spatter. This allows for the reliable production of demanding joints in high-strength materials or under challenging thermal conditions.

[0008] Furthermore, the uniform integration of the wire material across the entire weld depth, particularly at effective weld depths (EST) greater than 5 mm, allows for homogeneous alloying. This results in consistent weld properties that improve the mechanical strength and durability of the welded joint. Especially with demanding material requirements, such as high-strength steels or aluminum alloys, this ensures consistent weld quality.

[0009] Another advantage is that the wire is melted at a greater depth, resulting in better mixing of the base material with the filler wire. This allows for a deeper bond and reduces the risk of surface defects, such as pores or cracks, which often occur during near-surface melting processes.

[0010] Furthermore, the alloy composition can be precisely adjusted, allowing for customization of the weld's material properties. This enables precise control of the weld geometry, which is particularly advantageous in demanding applications where specific mechanical or chemical properties of the welded joint are required.

[0011] The invention thus solves several key challenges inherent in conventional methods and systems for producing metallurgical bonds by laser welding. A major problem with previous approaches was that the wire material was often only melted in near-surface layers during welding, leading to insufficient material penetration, particularly at effective weld depths (EST) greater than 5 mm. This impairs the weld quality, as the mechanical properties cannot be optimized in deeper weld areas. The present invention overcomes this challenge by transporting the wire material to greater depths and reliably melting it there. This allows for uniform mixing of the wire material with the base material even in deep layers of the weld, significantly improving the strength and durability of the joint.

[0012] Another challenge solved by the invention is to position the wire's melting point below the component surface. This results in the wire melting in deeper regions of the weld pool, optimizing material distribution and reducing the risk of surface defects such as pores or cracks. Precise control of the melting point achieves a uniform weld seam across the entire depth of the material, which is particularly advantageous for thicker workpieces.

[0013] Especially at laser powers exceeding 20 kW and effective welding depths of more than 5 mm, the welding process requires particularly good material transport into the material to ensure sufficient penetration and a homogeneous weld structure. The invention solves this challenge through the targeted configuration of the laser beam and the wire feed area, enabling the wire to be introduced into the weld pool efficiently and in a controlled manner. This allows for deeper mixing of the wire material with the base material and ensures a uniform distribution of the melt, resulting in significantly improved process stability and weld quality.

[0014] workpiece

[0015] For the purposes of this patent application, a workpiece is a component or assembly that is joined to another workpiece by means of a material bond using the laser welding process according to the invention. The workpiece serves as the starting material for producing a permanent, load-bearing connection in which the surfaces and, if applicable, deeper material layers are melted by a laser beam and subsequently fused together.

[0016] The workpiece can be made of various metallic materials, with aluminum, copper, or steel being preferred. Depending on the specific design requirements, the workpiece can have a simple geometry, such as a flat surface, or a more complex, three-dimensional shape. For example, the workpiece can have a homogeneous material structure or consist of multiple layers of different materials to provide specific functionalities such as corrosion protection or increased strength.

[0017] The laser welding process according to the invention is particularly advantageous for larger material thicknesses of over 5 mm.

[0018] Connecting seam

[0019] For the purposes of this patent application, a weld seam is a material-bonded connection that joins two or more workpieces along a common contact surface. The weld seam is created by a welding process in which the material of the workpieces in the seam area is melted and fused together by the use of laser radiation. Wire material is fed into the molten pool, which is also melted below the surface of the weld seam to ensure uniform mixing and a stable bond.

[0020] The design of the weld seam can vary depending on the application and workpiece geometry. One possible embodiment of the weld seam is the joining of adjacent workpieces, where the seam runs along the adjoining edges of the workpieces. Such an arrangement enables a surface-level connection, which is particularly advantageous for long workpieces or large-area joints. Another embodiment of the weld seam involves joining workpieces stacked on top of each other. Here, the weld seam extends through both workpieces to create a particularly strong and durable connection. This type of weld seam is especially suitable for applications requiring high load-bearing capacity in the vertical direction.

[0021] Melt bath

[0022] For the purposes of this patent application, a melt pool is the area of ​​a weld seam in which the material of the workpieces to be joined is melted by the energy input of the laser beam. The melt pool is created by the concentrated heat input of the laser onto the workpiece surface, causing the material to transition into a liquid state and enabling a metallurgical bond between the workpieces. The size and shape of the melt pool depend on the laser parameters, such as power and beam focus, as well as on the material properties of the workpieces.

[0023] The weld pool plays a central role in the welding process, as it enables the joining of the materials through the flow of the molten material. The weld pool ensures a uniform mixing of the base material with the supplied wire, resulting in a strong and homogeneous weld. Additionally, the weld pool can be configured to integrate the supplied wire symmetrically, leading to a uniform distribution of the wire material and increased weld homogeneity.

[0024] laser beam

[0025] For the purposes of this patent application, a laser beam is a highly focused electromagnetic radiation generated by a laser and used for the targeted application of energy to a workpiece.

[0026] The function of the laser beam is to heat the material at the weld seam sufficiently to melt it, thus creating a metallurgical bond between the workpieces. The laser beam is advantageously generated by a laser beam source such as a disk, fiber, or diode direct laser, wherein the laser preferably has a power output in the range of 20 to 500 kW, and particularly preferably between 20 and 200 kW. An infrared laser with a wavelength in the range of 800 to 1200 nm, particularly at 1030 nm or 1070 nm, is preferably used, which proves to be particularly advantageous for welding most metallic materials. Alternatively, a visible-vision (VIS) laser can also be used, particularly with wavelengths of 400 to 450 nm (blue) or 515 nm (green), with the green laser being particularly preferred for melting copper.

[0027] The beam diameter of the individual jets of the core jet is preferably in the range of 30 pm to 500 pm on the workpiece, and particularly between 60 pm and 300 pm. The diameter of the annular jet surrounding the core jet is advantageously 2 to 6 times larger than that of the core jet. This configuration allows for targeted shaping of the weld pool, with the core jet providing deep material penetration, while the larger annular jet heats the adjacent areas of the workpiece, thus ensuring a uniform weld geometry and controlled weld pool movement.

[0028] Preferably, the laser beam intensity in the wire feed area, i.e., above the component surface, can be reduced to less than 80% of the average intensity of the laser beam cross-section. This average intensity is determined using the 86% method or the second-moment method. Technically, this means that the laser beam is configured so that the intensity distribution along the laser beam cross-section is not homogeneous, but rather that there is a targeted reduction in laser intensity in the area where the wire is introduced into the melt pool. The average laser beam intensity describes the average energy input per unit area within the laser beam cross-section, which is defined by the 86% method or the second-moment method. The 86% method refers to the definition of the effective beam size, which comprises 86% of the total energy contained in the beam.The second-moment method determines the effective beam size based on the distribution of beam energy across the cross-section, with the beam width determined by the second moment of the intensity distribution. Both methods provide a precise measurement of the mean intensity, which serves as a reference for intensity reduction in the wire feed area. Reducing the laser intensity in this area to less than 80% of the mean intensity prevents the wire from being excessively melted at the workpiece surface. This allows for controlled heating of the wire and ensures that the melting of the wire material preferentially occurs in deeper regions of the weld.

[0029] The use of feed rates in the range of 50 mm / s to 3000 mm / s is preferred, with a range of 100 mm / s to 1000 mm / s being particularly favored. Technically, the feed rate refers to the speed at which the laser beam is guided along the weld seam relative to the workpiece surface.

[0030] Lower feed rates, around 50 mm / s, allow the laser beam to remain at a specific point on the workpiece for a longer period, resulting in a deeper and wider weld pool. This is advantageous for applications where thicker materials are being welded or a greater weld width is required. However, excessively slow feed rates can increase the risk of overheating the material and associated deformations or defects such as spatter or porosity. Higher feed rates, particularly in the range of 1000 mm / s to 3000 mm / s, enable the processing of thinner or high-strength materials at higher speeds without excessive weld depth. This increases the productivity of the welding process by allowing for shorter processing times.

[0031] Feed rates in the range of 100 mm / s to 1000 mm / s are preferred, as these offer an optimal compromise between weld pool depth, weld width, and process speed. This range enables controlled weld pool formation and uniform energy input, resulting in a stable weld with high strength and low thermal deformation. These feed rates are particularly well-suited for applications involving the welding of thicker or more demanding materials without significantly compromising process speed and efficiency.

[0032] Laser beam pattern

[0033] For the purposes of this patent application, a laser beam pattern is to be understood as a configuration of laser beams comprising several point-spaced partial beams and / or a modified beam profile, in both cases including a radiation gap. This radiation gap represents an area within the beam pattern where no laser radiation or laser radiation of lower intensity strikes the workpiece and serves to guide the welding wire precisely into the weld pool.

[0034] In the first variant of the laser beam pattern, the partial beams are arranged at defined intervals. These point-like partial beams precisely deliver energy to the workpiece, ensuring uniform heating of the weld. The gap between these point beams allows the wire to be guided into the weld pool without melting its surface. This arrangement results in better control over the penetration depth of the weld and promotes a more even mixing of the wire material with the base material.

[0035] In the second variant, where the laser beam pattern consists of a modified beam profile, the laser beam is shaped so that the intensity is at least reduced in the area of ​​the wire feed. Here, too, the radiation gap is present, allowing the wire to penetrate the weld pool. The modified beam profile offers the advantage of a continuous energy distribution around the weld seam, which ensures uniform heating and controlled shaping of the weld pool.

[0036] Radiation gap

[0037] For the purposes of this patent application, a radiation gap is an area within the laser beam pattern where the intensity of the laser beam is selectively reduced or completely interrupted. This radiation gap allows the wire to be introduced into the weld pool without being directly heated by the laser beam. The wire can thus penetrate deeper into the weld before melting. The radiation gap therefore serves, in particular, to temporarily protect the wire from direct laser radiation, preventing it from melting at the surface of the workpiece and allowing it to penetrate deeper into the weld pool. This ensures that the wire material is distributed evenly throughout the entire depth of the weld, resulting in improved mechanical properties of the weld.The radiation gap also controls the energy input into the melt pool, thereby reducing or completely preventing the formation of surface defects such as splashes or pores.

[0038] wire

[0039] For the purposes of this patent application, a wire is an additive material that is fed into the welding process to supplement the molten metal and influence the desired material properties of the weld. The wire preferably consists of a metallic material that is introduced into the weld pool and melted there to reinforce or enhance the joint between two workpieces. The wire serves to compensate for material losses during the welding process and / or to improve the weld mechanically and chemically. By selectively introducing the wire, specific alloy properties of the weld can also be adjusted, thereby influencing its strength, corrosion resistance, or other specific characteristics.

[0040] The wire's construction can vary depending on the application. Preferably, the wire is made of a material that exhibits good compatibility with the base material, resulting in a homogeneous bond. The wire can have a round, oval, or flat cross-sectional shape, depending on the requirements of the welding process and the weld seam shape.

[0041] Possible wire configurations include various diameters and material compositions, depending on the specific requirements of the material to be welded and the required weld geometry. The wire can be fed either by thrusting, dragging, or coaxially, with the feed direction and angle selected to ensure optimal integration of the wire into the weld pool.

[0042] wire feed area

[0043] For the purposes of this patent application, a wire feed zone is the area in the welding process into which the wire is fed to penetrate the weld pool in a controlled manner and fuse with the base material. The wire feed zone is defined by the specific laser beam pattern, which features a radiation gap that allows the wire to be integrated into deeper regions of the weld pool without causing undesirable surface phenomena such as spatter or porosity. In this low-radiation zone, the wire can be safely and precisely introduced into the weld pool without being melted directly at the surface. Therefore, the wire can be positioned so that its melting point lies below the outer surface of the weld seam, resulting in a uniform and deeper weld.

[0044] The function of the wire feed area is therefore to precisely introduce the wire into the weld pool, ensuring optimal mixing with the base material. This contributes to improved mechanical properties of the weld, particularly during alloying or when filling thicker material layers. The radiation gap and the defined wire feed area prevent the wire from melting too early or too close to the surface, enabling uniform mixing with the base material and resulting in a homogeneous and durable weld.

[0045] Melting point

[0046] For the purposes of this patent application, a melting point is the location in the weld pool where the fed wire begins to melt and is integrated into the weld. The melting point lies below the outer surface of the weld and marks the precise area where the temperature of the laser beam is high enough to melt the wire and introduce it into the weld pool. Placing the melting point below the surface ensures that the wire penetrates deeper into the weld, resulting in improved mixing and a stronger bond between the materials.

[0047] The melting point plays a crucial role in the entire welding process, as it directly influences the quality and homogeneity of the weld. The wire is guided through the gap in the laser beam pattern into the defined wire feed area and begins to melt at this point, allowing for precise control of the alloy composition and weld geometry. This precise control of the melting point ensures uniform strength across the entire weld, resulting in increased load-bearing capacity and durability of the welded joint.

[0048] Laser beam source

[0049] For the purposes of this patent application, a laser beam source is to be understood as a device that generates electromagnetic radiation in the form of a coherent laser beam. This laser beam source converts energy, for example electrical energy, into highly focused light beams characterized by a specific wavelength and high intensity. The laser beam serves to selectively melt materials in order to create metallurgical bonds between workpieces, as is the case in laser welding.

[0050] Preferably, the laser beam source is an infrared laser operating in the wavelength range of 800–1200 nm, particularly at 1030 nm or 1070 nm. These wavelengths are especially well-suited for welding metallic materials such as steel or aluminum, as they enable efficient energy transfer and stable weld pool formation. Alternatively, a visible-vision (VIS) laser operating in the visible spectral range can also be used, particularly at wavelengths of 400–450 nm (blue) or 515 nm (green). Green laser beams are advantageously particularly suitable for melting copper, as this wavelength offers improved absorption in copper alloys, thus ensuring higher efficiency in the welding process.

[0051] The laser beam source can advantageously provide a laser power in the range of 20 to 500 kW, with a power range of 20 to 200 kW being preferred. This power range enables the welding of both thin and thick materials and offers flexible adaptation to different welding requirements. By precisely controlling the laser power and selecting the appropriate wavelength, the laser beam source can be optimally adapted to the respective material properties and welding parameters to ensure high weld quality and process stability.

[0052] Advantageous embodiments of the invention

[0053] According to an advantageous embodiment of the invention, the wire can be fed into the weld pool at an angle greater than 10° to the weld seam, thereby ensuring particularly deep penetration of the wire material into the weld pool. This improves the material transport and distribution of the wire material in the weld pool, resulting in higher strength and homogeneity of the weld. Furthermore, material stresses can be reduced because the wire material is integrated more uniformly into the depth of the weld.

[0054] According to a further preferred embodiment of the invention, the wire feed speed can also be greater than or equal to the welding speed. This offers the advantage that a sufficient quantity of material is always introduced into the weld pool. This prevents material shortages in the weld and results in a continuous, uniform melt. The targeted control of the wire feed helps to stabilize the weld quality and avoid undesirable weld interruptions or inhomogeneities.

[0055] Furthermore, according to an equally advantageous embodiment of the invention, the wire can be fed in a penetrating, trailing, or coaxial manner. The flexibility in wire feeding (penetrating, trailing, or coaxial) allows the process to be adapted to various welding requirements. This offers the advantage that the weld geometry and the material entry zones can be individually influenced depending on the wire feeding method. The option of feeding the wire in a penetrating, trailing, or coaxial manner also offers the advantage of symmetrical mixing of the wire material into the weld pool. This symmetrical distribution leads to a uniform mixing of the wire and the base material, resulting in a homogeneous weld. Particularly in demanding applications where precise material properties and a uniform weld structure are required, this symmetrical feeding contributes to improved weld quality.Symmetrical mixing also reduces the risk of imbalances in the weld pool, which decreases the formation of defects such as pores or cracks and increases the mechanical strength of the weld. The uniform distribution of the material results in a stable and durable weld seam that exhibits greater resistance to external influences.

[0056] According to a further particularly preferred embodiment of the invention, it can be provided that the laser beam is guided through an in or in-fiber, so that two or three focus zones are generated, which have a core beam and one or two ring beams.

[0057] For the purposes of this patent application, a focus zone is the area on or near the surface of the workpiece where the energy of the laser beam is concentrated to melt the material and create a weld. The focus zone is created by selectively focusing the laser beam, for example, using optical elements, so that the laser energy is concentrated on a defined point or small area. By controlling the focus zone, the weld pool can be created at the desired depth and geometry, enabling an optimal weld between the workpieces. A particular advantage is that by adjusting the size and position of the focus zone, even deeper welds can be achieved without compromising the integrity of the material. The formation of the focus zone is advantageously determined by the interaction of the optical focusing elements, which concentrate the laser beam onto a point or area.Preferably, multiple focus zones are created, for example, by using a 2-in-1 or 3-in-1 fiber, which generates several beams, such as core and ring beams. These beams each create their own focus zones that address different areas of the weld pool. The core beam creates a focus zone with higher intensity, which is preferably used for deeper material penetration, while the ring beams create focus zones with lower intensity that contribute to the uniform heating of the surrounding areas of the weld pool. This structure enables precise and controlled weld pool formation, resulting in a more stable weld and improved material properties.

[0058] By using a 2-in-1 or 3-in-1 fiber, which creates multiple focus zones, precise and controlled energy distribution can be achieved in the welding process. This configuration allows for the effective melting and joining of both surface areas and deeper material layers. As a result, thicker materials can be processed with high precision, while simultaneously reducing the formation of weld defects such as pores or cracks. This leads to improved process stability and more uniform welds.

[0059] Another significant advantage is the reduction of spatter during the welding process. The targeted splitting of the laser beam into core and ring beams enables precise energy input, which stabilizes the weld pool and thus minimizes spatter formation. This not only results in a cleaner working environment but also in improved weld surface quality, as less rework is required.

[0060] Another advantage lies in the reduction of porosity. The controlled distribution of energy across the workpiece ensures uniform mixing of the weld pool, preventing the formation of gas bubbles and thus the development of pores. This significantly contributes to increasing the mechanical strength and structural integrity of the weld, as pores typically act as weak points. Reducing pores therefore improves the quality and durability of the joint, especially in safety-critical applications.

[0061] Furthermore, the invention can also be further developed such that the core jet has a higher intensity than the ring jet(s), resulting in more stable weld pool formation. The increased intensity in the core jet ensures deeper and more concentrated energy input, while the lower intensity of the ring jets supports the outer area of ​​the weld pool without overheating the material. This helps to minimize thermal deformation and leads to better penetration of the wire material into deeper weld areas.

[0062] The higher intensity of the core jet compared to ring jets offers the advantage of stabilizing the keyhole (vapor capillary) during the welding process. The concentrated energy input of the core jet ensures the keyhole opens uniformly and remains stable, resulting in controlled and deep weld penetration. This prevents keyhole collapse and reduces the risk of weld defects such as irregular weld pools or insufficient penetration depth. Keyhole stabilization also contributes to increased process reliability, as the energy input is precisely maintained, even at higher welding speeds or in thicker materials. This leads to consistent weld quality and minimizes the risk of weld defects, thus improving the mechanical strength and reliability of the joint.

[0063] In a further preferred embodiment of the invention, the beam parameter product of the core beam may also be ≤32 mm*mrad, in particular ≤6 mm*mrad, and the beam parameter product of the ring beam(s) ≤60 mm*mrad, in particular ≤20 mm*mrad. The specified beam parameter product ensures high precision and efficiency in the welding process. A low value of the beam parameter product for the core beam enables targeted energy input into smaller and more precise areas, while the higher value for the ring beams ensures uniform heating of the surrounding areas. This results in improved weld quality and allows welding at higher speeds without compromising material integrity.

[0064] The predefined beam parameter product of the core and ring beams offers the advantage of producing particularly thin welds with high precision. The tight focusing of the core beam and the targeted energy distribution to the welding area make it possible to minimize the weld width without compromising penetration depth or weld strength. This is especially beneficial in applications where aesthetics or material savings are important, as narrow welds enable a clean, precise joint. Another advantage of this beam parameter configuration is the increased welding speed. Thanks to efficient energy transfer and the low beam parameter product, higher welding speeds can be achieved without affecting weld quality.This leads to a significant increase in productivity and a reduction in processing times, which is of great economic advantage, especially for large-scale or series-produced welding tasks.

[0065] It can also be advantageous to further develop the invention by guiding the laser beam through a beam splitter to provide a laser beam pattern with at least two laser beams on the surface of the weld. Using a beam splitter to generate a multi-beam laser beam pattern offers the advantage of optimal energy distribution across the workpiece. This leads to better control of heat input and enables more uniform weld pool formation. Furthermore, the laser beam pattern allows the wire to be fed precisely and into deeper areas of the weld, significantly improving the quality of the weld.

[0066] According to a further preferred embodiment of the invention, the partial beams of the laser beam can be essentially identical, which ensures a homogeneous energy distribution on the workpiece. This leads to uniform weld pool formation and reduces the risk of local overheating or material deformation. The uniformity of the radiation sources improves process control and contributes to consistently high weld quality.

[0067] The invention can also be advantageously implemented such that the optical axes of the laser beams of the laser beam pattern are arranged parallel or at an angle of less than 3° to each other. This combination of features offers the advantage that the energy input is precisely controlled and the beams strike the workpiece uniformly. This minimizes the formation of welding defects and ensures consistent weld quality. The precise alignment of the laser beams further ensures that the weld pool is heated and mixed uniformly, resulting in consistent and homogeneous weld properties. Uniform heating of the weld pool reduces the risk of material distortion, uneven mixing, or local overheating, which could lead to defects such as cracks or pores. This significantly improves the mechanical properties of the weld, such as strength and fatigue resistance.These uniform weld properties are particularly advantageous in demanding applications where high loads and consistent joint quality are required.

[0068] Furthermore, the laser beam pattern can exhibit a continuous beam profile with reduced intensity in the wire feed area, deviating from a point or straight line. This continuous beam profile with reduced intensity in the wire feed area offers the advantage of precise and gentle wire integration into the weld seam. This configuration reduces the risk of material excess or spatter and ensures a uniform distribution of the wire material in the weld pool.

[0069] For the purposes of this patent application, a beam profile is a contour of the laser beam that deviates from the usual point shape. The beam profile describes the geometric shape of the laser beam, which can be not only point-like but also more complex, such as a ring, ring segment, crescent, or other advantageous geometries. This deviation from the point-like structure enables targeted control of the energy distribution and adaptation of the laser welding process to specific requirements.

[0070] The beam profile serves to project the laser energy onto the workpiece surface in such a way that specific process goals, such as uniform heating or precise melting of material, can be achieved efficiently. In the described invention, the beam profile is specifically designed to create an intensity gap. This gap in the beam cross-section creates an area with at least reduced laser intensity, through which the wire can be inserted into the melt pool without being completely melted at the surface due to excessive energy.

[0071] Preferably, the beam profile has a ring-shaped or segmented contour, which allows the energy to be directed precisely to different zones of the welding area. This non-point-shaped structure of the laser beam leads to improved control over the welding process and enables uniform processing both on the surface and in deeper layers of the material. The specific design of the beam profile, which is generated using optical elements such as beam shapers or beam splitters, allows for targeted manipulation of the weld geometry and the material distribution in the weld pool.

[0072] In this context, it is also advantageous if the laser beam profile is shaped as a ring segment, particularly a circular ring segment, which enables exceptionally uniform heating of the weld pool. The ring segment ensures that the intensity in the wire feed area is reduced, allowing the wire to be optimally integrated into deeper weld areas. This geometry contributes to minimizing thermal deformation and welding defects.

[0073] Furthermore, it can be advantageous if a laser beam is directed at a single

[0074] The radiation source is split into several individual laser beams and shaped into the laser beam pattern. The advantage of splitting a single laser beam into multiple beams lies in significant cost optimization. By using only one laser source, the need for additional, expensive laser beam sources is reduced, leading to a significant decrease in acquisition and maintenance costs. At the same time, the flexibility of the process is maintained, as the laser beam pattern is generated with multiple beams, ensuring precise energy distribution and high weld quality.

[0075] Alternatively, it would also be conceivable to shape the laser beams from multiple radiation sources into the laser beam pattern. Using multiple radiation sources to generate a laser beam pattern offers the advantage of greater flexibility in adjusting the energy distribution. Multiple radiation sources allow for independent control of the beam intensities and distribution, resulting in even better process control and optimized weld quality.

[0076] It is also preferred to use a camera-based image processing system to detect the weld position and correct the laser beam position. Using a camera-based image processing system to detect the weld position improves the accuracy of the welding process. This helps to reduce positioning tolerances and optimize weld quality. The system can also enable real-time monitoring and adjustment of the welding process.

[0077] Advantageously, the penetration depth of the laser beam can be measured using an OCT (Optical Coherence Tomography) method, enabling precise control of the welding process. This method allows for accurate monitoring of the weld pool depth and helps ensure consistent weld quality. It reduces the risk of material defects and improves process stability. Furthermore, it can be advantageous for the weld pool aspect ratio, calculated as the depth to width of the weld pool, to be greater than one. This offers the benefit of achieving a deep and strong bond between the workpieces, which can contribute to particularly high load-bearing capacity and durability of the weld, especially with thicker materials.A larger embedment area results in a stronger and more robust joint because more material penetrates deeper, thus achieving better mechanical interlocking between the workpieces. This increases the strength and durability of the weld, especially under high loads or when joining thick materials. Furthermore, the increased embedment area improves heat distribution and reduces local stresses that can occur during the welding process. This helps to reduce cracks, porosity, or other weld defects and ensures a more uniform and higher-quality joint. The increased embedment area is particularly advantageous in safety-critical applications where high load-bearing capacity and reliability of the weld are required.

[0078] The object of the invention is further achieved by a laser processing system for producing a material-bonded connection between two workpieces by means of laser welding, comprising at least one radiation source for providing at least one laser beam, optics for splitting the laser beam into a plurality of laser beams and / or for forming a laser beam pattern, and a machine control for controlling the radiation source and the optics, wherein the at least one radiation source, the optics, and the machine control are configured such that the at least one laser beam is formed into a laser beam pattern which has a radiation gap, such that a wire feed area is defined by the radiation gap at the joint seam, and the connecting wire penetrates the weld pool in the wire feed area, wherein the laser beam and the laser beam pattern are configured such thatthat the melting point of the wire lies below the outer surface of the joint.

[0079] For the purposes of this patent application, a laser processing system is a device used to generate and control one or more laser beams for joining workpieces together by laser welding. Such a system comprises essential components such as one or more radiation sources, optics for shaping and focusing the laser beam, and a machine control system for precisely regulating the entire welding process.

[0080] The laser beam source, preferably a fiber or disk laser source, supplies the necessary energy in the form of focused radiation to create the weld pool at the joint between the workpieces. Advantageously, the laser beam is shaped by the optics to produce a precise laser beam pattern that includes the beam gap through which the wire is inserted into deeper regions of the weld pool. The optics can utilize a 2-in-1 or 3-in-1 fiber to generate multiple focus zones, each consisting of a core beam and one or more ring beams, thereby achieving uniform energy distribution and a stable weld.

[0081] The machine control system performs the central task of coordinating the laser beam source and the optics, ensuring that the laser beam is precisely directed at the weld seam and adjusted in intensity and shape. Advantageously, the laser processing system features integrated image processing, which allows for monitoring the position of the workpieces and the weld seam and correcting the laser position in real time. Additionally, the penetration depth of the laser beam is preferably measured using an optical coherence tomography (OCT) method to guarantee the quality of the weld.

[0082] For the purposes of this patent application, an optic is a technical element or assembly used to shape, direct, and focus the laser beam onto the surface of the workpiece. The optic can be implemented in various embodiments, depending on the specific requirements of the welding process. One advantageous embodiment involves the use of a beam splitter, such as an optical wedge, a diffractive optical element (DOE), or a refractive optical element (ROE). These beam splitters generate at least two beams that are applied to the component surface to ensure uniform energy distribution and thus high process stability.

[0083] Preferably, scanner optics such as the PFO33-2, which have an imaging ratio of 1:1 to 5:1, and especially between 2:1 and 3:1, can also be used. These optics enable precise control of the laser beam across the entire weld seam and thus contribute to the accurate guidance of the weld pool. Another possible embodiment is the use of a so-called "flying optic," such as the BEO, which operates with the same imaging ratios. This type of optic is characterized by its flexibility in movement and enables quick and precise adaptation of the laser beam to different workpiece geometries, which is particularly advantageous in complex welding processes.

[0084] The use of a laser processing system, comprising a radiation source, optics, and machine control, offers the advantages of precise control of the laser beam pattern through the integration of these components, significantly improving weld quality. In particular, by creating a beam gap within the laser beam pattern, the wire can be selectively inserted into deeper areas of the weld seam, resulting in a uniform material distribution and increased joint strength. The system's flexibility allows the laser beam pattern to be adapted to different material requirements, increasing the system's versatility and enabling its use in various applications.

[0085] The invention will now be explained in more detail with reference to figures, without limiting the general concept of the invention.

[0086] It shows:

[0087] Figure 1 shows a first embodiment of the inventive method for producing a material-bonded connection between two workpieces by means of laser welding in a top view and a sectional view perpendicular to the welding direction; Figure 2 shows a second embodiment of the inventive method for producing a material-bonded connection between two workpieces by means of laser welding in a top view and a sectional view perpendicular to the welding direction.

[0088] Figure 3 shows a third embodiment of the inventive method for producing a material-bonded connection between two workpieces by means of laser welding in a top view and a sectional view perpendicular to the welding direction.

[0089] Figure 4 shows a fourth embodiment of the inventive method for producing a material-bonded connection between two workpieces by means of laser welding in a top view and a sectional view perpendicular to the welding direction.

[0090] Figure 5 shows a fifth embodiment of the inventive method for producing a material-bonded connection between two workpieces by means of laser welding in a top view and a sectional view perpendicular to the welding direction.

[0091] Figure 6 shows a first embodiment of a laser processing system according to the invention for producing a material-jointed connection between two workpieces by means of laser welding in a schematic representation.

[0092] Figure 7 shows a first embodiment of a laser processing system according to the invention for producing a material-jointed connection between two workpieces by means of laser welding in a schematic representation.

[0093] Figures 1-5 are used as a basis for discussing various possible scenarios below.

[0094] Embodiments of methods for producing a materially bonded

[0095] The joining of two workpieces 1, 2 by means of laser welding is explained. All illustrated embodiments have in common that a weld pool 4 is generated at a joint 3 of the workpieces 1, 2 by at least one laser beam 5, and a wire 7 is fed into the weld pool 4, causing it to melt within the weld pool. This occurs in a precisely controlled process in which both the temperature and the melting time are influenced by controlling the laser beams in order to achieve optimal weld quality.

[0096] The at least one laser beam 5 is shaped into a laser beam pattern 51, which has a radiation gap 52. This radiation gap 52 defines a wire feed area 8 at the weld seam 3, and the connecting wire 7 penetrates the weld pool 4 within this area. The radiation gap allows the wire to be guided into deeper regions of the weld seam without immediately melting near the surface due to the full laser intensity. The laser beam 5 and the laser beam pattern 51 are configured such that the melting point 9 of the wire 7 lies below the outer surface 10 of the weld seam 3, ensuring a uniform and deeper mixing of the material.

[0097] In the embodiments shown in Figures 1-5, the weld pool aspect ratio, formed by the depth 15 to the width 16 of the weld pool 4, is greater than one. This aspect ratio ensures that the weld penetrates deep enough into the material to create a strong, metallurgical bond, while simultaneously controlling the width of the weld to avoid deformation or undesirable material expansion.

[0098] The feed rate of the wire 7 is always greater than or equal to the welding speed. This ensures that sufficient material enters the weld pool to guarantee complete mixing and a homogeneous weld. An insufficient feed rate could lead to material shortages and impair weld quality. In the embodiments shown in Figures 2-3, the wire 7 is fed by a penetrating feed; in Figures 1 and 4, it is fed by a dragging feed; and in Figure 5, it is fed coaxially. The different feeding methods directly influence the geometry of the weld pool and the distribution of material within it. The penetrating feed introduces the material more directly and deeply into the weld pool, while the dragging feed promotes a more uniform surface expansion of the melt.

[0099] In the embodiments shown in Figures 1-4, the wire 7 is fed into the weld pool 4 at an angle 11 of greater than 10° to the weld seam 3. This angular orientation facilitates the penetration of the wire into deeper layers of the weld pool, resulting in a better bond between the wire material and the base material and improving the mechanical properties of the weld.

[0100] In the illustrated embodiments, the laser beam 5 is guided through a 2-in-1 fiber, creating two focus zones 12, each with a core beam 13 and an annular beam 14. The core beam 13 has a higher intensity than the annular beam 14. This configuration ensures that the main energy of the laser is directed into the core area of ​​the weld, while the annular beam provides additional energy input at the edges of the weld. This results in a uniform weld with a stable structure both in the center and at the edges of the weld pool.

[0101] In the embodiment shown in Figure 1, the laser beam 5 was guided through a beam splitter to provide a laser beam pattern 51 with four laser beams 5a, 5b, 5c, 5d on the surface of the weld seam 3. The partial beams 5a, 5b, 5c, 5d of the laser beam 5 are arranged at the vertices of an imaginary square and are essentially identical. This ensures a uniform energy distribution over the entire weld area, which is particularly advantageous for large-area joints or materials with high thermal conductivity. The optical axes of the laser beams 5a, 5b, 5c, 5d of the laser beam pattern 51 are parallel or arranged at an angle of <3° to each other, thus ensuring precise focusing and overlap of the beams without undesirable energy scattering. Figures 1-3 show that the two workpieces 1, 2 have a weld seam 3 that runs vertically.This means that the workpieces 1, 2 are in contact with each other at their respective contact surfaces, so that the weld seam 3 is oriented perpendicular to the workpiece surface. This vertical orientation of the weld seam 3 ensures that the laser beam is guided along the vertical seam in this direction to create a continuous and uniform weld. This arrangement of the workpieces 1, 2 allows the molten pool 4 to be generated uniformly along the entire vertical weld seam 3, and the fed wire 7 can be precisely introduced into the molten pool to achieve a metallurgical bond between the workpieces.

[0102] Figures 4 and 5 show that the two workpieces 1 and 2 have a horizontally extending weld seam 3. This indicates that the workpieces 1 and 2 are positioned one above the other in the area of ​​the weld seam 3. The horizontal weld seam 3 shows that the two workpieces 1 and 2 are in a welding position where the upper workpiece 1 rests on the lower workpiece 2. This arrangement is characteristic of certain welding processes in which the weld seam is formed by depositing the weld pool 4 along a horizontal plane. In this configuration, the weld pool 4 is produced uniformly along the weld seam 3, and the wire 7 is fed into the weld pool 4 to ensure a metallurgical bond between the superimposed workpieces 1 and 2.

[0103] Figures 2-5 show laser beam patterns 51 with a continuous beam profile 17 that deviates from a point or a straight line and has reduced intensity in the wire feed area 8. The beam profile 17 of the laser beam 5 is designed as a circular segment. This special beam profile ensures that there is a lower laser intensity in the wire feed area, allowing the wire to be fed into deeper areas of the weld without melting prematurely at the surface.

[0104] In Figure 5, the wire 7 is formed coaxially with the annular segment-shaped beam profile 17. This means that the wire 7 runs along the axis of the

[0105] The wire 7 is guided by a circular segment-shaped beam profile 17, so that it is centrally introduced into the melt pool 4 and uniformly surrounded by the reduced intensity of the laser beam 5. This coaxial feed ensures symmetrical melting of the wire 7 and a uniform distribution of the material in the melt pool 4. This arrangement achieves optimized mixing of the wire material with the base material, resulting in a particularly homogeneous and durable weld. With coaxial wire feed, it is also possible for the beam profile 17 to be formed as a closed circular ring.

[0106] In other embodiments, such as that shown in Figure 1, the wire 7 can be fed essentially parallel to the axis of the laser beam pattern 51. Here, the wire 7 is fed parallel to the optical axis of the laser beam 5, so that it does not enter the melt pool 4 coaxially, but at a specific distance from the individual partial beams 5a, 5b, 5c, 5d.

[0107] As can be seen from the combined representation of Figures 1-6, a laser beam 5 from a single radiation source 53 can be split into several individual laser beams 5 via optics 22 and shaped into the laser beam pattern 51. The optics perform the precise control and focusing of the beams to ensure a uniform distribution of the laser energy. As can be seen from the combined representation of Figures 1-5 and Figure 7, laser beams 5a, 5b from several radiation sources 53, 54 can also be shaped into the laser beam pattern 51. This makes it possible to flexibly adjust the power and energy distribution according to the requirements of the welding process.

[0108] Figures 6 and 7 each show a laser processing system 20 for producing a material-bonded connection between two workpieces 1 and 2 by means of laser welding. The laser processing system 20 in Figure 5 has one radiation source 53 for providing a laser beam 5a, while the laser processing system 20 in Figure 6 has two radiation sources 53 and 54 for providing two laser beams 5a and 5b. The use of multiple radiation sources allows for greater flexibility in adjusting the laser parameters and more efficient processing of workpieces with different laser energy requirements.

[0109] The laser processing systems of Figures 5-6 each have optics 22 for splitting the laser beam 5 into a plurality of laser beams 5 and / or for forming a laser beam pattern 51, as well as a machine control 23 for controlling the radiation source 53, 54 and the optics 22. The machine control plays a crucial role in the precise synchronization of the radiation source and the optics to ensure consistent welding quality.The at least one radiation source 53, 54, the optics 22 and the machine control 23 are configured such that the at least one laser beam 5 is shaped into a laser beam pattern 51 which has a radiation gap 52, such that a wire feed area 8 is defined by the radiation gap 52 at the joint 3, and the connecting wire 7 penetrates the melt bath 4 in the wire feed area 8, wherein the laser beam 5 and the laser beam pattern 51 are configured such that the melting point 9 of the wire 7 lies below the outer surface 10 of the joint 3.

[0110] A camera-based image processing system is used to detect the position of the weld seam 3 and to correct the position of the laser beam 5. This enables real-time monitoring of the weld seam and precise adjustment of the laser beam to compensate for any tolerance deviations. The penetration depth of the laser beam 5 is measured using a

[0111] OCT (Optical Coherence Tomography) method, which allows the quality and depth of the weld to be continuously checked and adjusted to ensure a consistent weld depth and material penetration.

[0112] The invention is not limited to the embodiments illustrated in the figures. The foregoing description is therefore not to be considered limiting, but rather explanatory. The following claims are to be understood as meaning that a named feature is present in at least one embodiment of the invention. This does not preclude the presence of further features. Where the claims and the foregoing description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing any hierarchy.

[0113] List of reference signs

[0114] 1 workpiece

[0115] 2 workpieces

[0116] 3. Joining seam

[0117] 4 Melt bath

[0118] 5 Laser beam

[0119] 7 wire

[0120] 8 Wire feed area

[0121] 9 Melting point

[0122] 10 surface

[0123] 11 angles

[0124] 12 focus zones

[0125] 13 Core beam

[0126] 14 ring rays

[0127] 15 depth

[0128] 16 width

[0129] 17 Beam profile

[0130] 20 laser processing systems

[0131] 22 Optics

[0132] 23 Machine control

[0133] 51 laser beam patterns

[0134] 52 radiation gap

[0135] 53 Laser beam source

[0136] 54 Laser beam source

Claims

1. Claims 1. A method for producing a material-bonded connection between two workpieces (1, 2) by means of laser welding, wherein a melt pool (4) is generated at a joining seam (3) of the workpieces (1, 2) by at least one laser beam (5) and a wire (7) is fed into the area of ​​the melt pool (4) so ​​that it melts in the area of ​​the melt pool (4), characterized in that the at least one laser beam (5) is formed into a laser beam pattern (51) which has a radiation gap (52) such that a wire feed area (8) is defined by the radiation gap (52) at the joining seam (3), and the connecting wire (3) penetrates the melt pool (4) in the wire feed area (8), wherein the laser beam (5) and the laser beam pattern (51) are configured such that the melting point (9) of the wire (7) lies below the outer surface (10) of the joining seam (3).

2. Method according to claim 1, characterized in that the wire (7) is oriented at an angle (11) of greater than 10° to the joining seam (3) and fed into the melt bath (4).

3. Method according to claim 1 or 2, characterized in that the feed rate of the wire (7) is greater than or equal to the welding rate. 32 4. Method according to one of the preceding claims, characterized in that the wire (7) is fed in by piercing, trailing or coaxial means.

5. Method according to one of the preceding claims, characterized in that the laser beam (5) is guided through a 2in1 or 3in1 fiber, so that two or three focus zones (12) are generated, which have a core beam (13) and one or two ring beams (14).

6. Method according to claim 5, characterized in that the core beam (13) has a higher intensity than the ring beam(s) (14).

7. Method according to claim 5 or 6, characterized in that the beam parameter product of the core beam (13) is <=32 mm*mrad, in particular <= 6 mm*mrad, and the beam parameter product of the ring beam(s) (14) is <=60 mm*mrad, in particular <= 20 mm*mrad.

8. Method according to one of the preceding claims, characterized in that the laser beam (5) is guided via a beam splitter to provide a laser beam pattern (51) with at least two laser beams (5) on the surface of the joining seam (3). 33 9. Method according to claim 8, characterized in that the partial beams of the laser beam (5) are essentially identical.

10. Method according to claim 8 or 9, characterized in that the optical axes of the laser beams (5) of the laser beam pattern (51) are arranged parallel or at an angle of <3° to each other.

11. Method according to one of claims 1-7, characterized in that the laser beam pattern (51 ) has a continuous beam profile (17) that deviates from a point or a straight line and has reduced intensity in the area of ​​the wire feed area (8).

12. Method according to claim 11 characterized in that the beam profile (17) of the laser beam (5) is designed as a ring segment, in particular a circular ring segment.

13. Method according to one of the preceding claims, characterized in that a laser beam (5) of a single radiation source (53) is split into several individual laser beams (5) and formed into the laser beam pattern (51 ).

14. Method according to one of the preceding claims 1-12, characterized in that the laser beams (5) of several radiation sources (53, 54) are shaped to form the laser beam pattern (51).

15. Method according to one of the preceding claims, characterized in that a camera-based image processing system is used to detect the position of the joining seam (3) and to correct the position of the laser beam (5).

16. Method according to one of the preceding claims, characterized in that the measurement of the penetration depth of the laser beam (5) is carried out using an OCT method.

17. Method according to one of the preceding claims, characterized in that the melt bath aspect ratio formed from the depth (15) to the width (16) of the melt bath (4) is greater than one.

18. Laser processing system (20) for producing a material-jointed connection between two workpieces (1, 2) by means of laser welding, comprising • At least one radiation source (53, 54) to provide at least one laser beam (50), • an optic (22) for splitting the laser beam (5) into a plurality of laser beams (5) and / or for forming a laser beam pattern (51) as well as • a machine control (23) for controlling the radiation source (53, 54) and the optics (22), characterized in that the at least one radiation source (53, 54), the optics (22) and the machine control (23) are configured such that the at least one laser beam (5) is formed into a laser beam pattern (51) which has a radiation gap (52) such that a wire feed area (8) is defined by the radiation gap (52) at the joint (3) and the connecting wire (3) penetrates the melt bath (4) in the wire feed area (8), wherein the laser beam (5) and the laser beam pattern (51) are configured such that the melting point (9) of the wire (7) is below the outer surface (10) of the joint (3). 36

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