Optical fiber laser device, laser beam machining system, and laser welding method

Abstract

The present application discloses an optical fiber laser device (1), a laser beam machining system, and a laser welding method. The optical fiber laser device (1) comprises a plurality of laser modules (101-10n), a laser output head (20), and a control device (30); output optical fibers of the plurality of laser modules (101-10n) are symmetrically bundled to form an array of optical fibers (2032); the array of optical fibers (2032) is coupled and connected to the laser output head (20); output laser of the plurality of laser modules (101-10n) is emitted by means of the laser output head (20) to form preset light spots; the control device (30) is separately connected to the plurality of laser modules (101-10n) and provides an editing interface; and the control device (30) is used for controlling light emission and the output power of the laser modules (101-10n) to modulate the shape and energy distribution of the preset light spots.

Description

Fiber laser equipment, laser processing system and laser welding method

[0001] This application claims priority to patent application number 202311829539.3 filed with the China Patent Office on December 28, 2023, priority to patent application number 202410994470.8 filed with the China Patent Office on July 24, 2024, priority to patent application number 202410127106.1 filed with the China Patent Office on January 30, 2024, priority to patent application number 202410127104.2 filed with the China Patent Office on January 30, 2024, and priority to patent application number 202410259265.7 filed with the China Patent Office on March 7, 2024. The entire contents of these five applications are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of laser processing technology, and in particular to fiber lasers and laser welding processing. Background Art

[0003] Laser processing technology (such as laser welding, laser cutting, laser marking, laser drilling, laser scribing, laser ablation, micromachining, etc.) is increasingly used in various industries. Different laser processing technologies have different requirements for the shape of the light spot, energy distribution and other characteristics. Some laser processing equipment platforms with relatively simple functions may not be able to meet the processing control requirements. Summary of the Invention

[0004] Based on the above, the purpose of this application is to provide a fiber laser device, a laser processing system and a laser welding method.

[0005] This application adopts the following technical solutions:

[0006] A fiber laser device, comprising: a plurality of laser modules, a laser output head and a control device; wherein,

[0007] The output optical fibers of the multiple laser modules are symmetrically bundled to form an optical fiber array;

[0008] The array optical fiber is coupled to the laser output head, and the output lasers of the multiple lasers are emitted through the laser output head to form a preset light spot;

[0009] The control device is connected to the multiple lasers respectively and provides a spot editing interface. The control device is used to control the light output and output power of the lasers and modulate the shape and energy distribution of the preset light spot.

[0010] A laser processing system, comprising:

[0011] Multi-beam laser and focus depth adjustment unit; wherein,

[0012] The multi-beam laser comprises a plurality of lasers, the output optical fibers of each laser are arranged in an array, and the laser beams output by each output optical fiber are combined to form a welding beam;

[0013] The focus depth adjustment unit includes a focus depth coarse adjustment module and a focus depth fine adjustment module; the focus depth coarse adjustment module is connected to each of the lasers to control the spot size of the welding beam; the focus depth fine adjustment module is connected to each of the lasers to control the energy distribution ratio of the welding beam.

[0014] A laser welding method, comprising:

[0015] Providing a material to be welded, the material comprising a first welding section and a second welding section having different welding thicknesses;

[0016] Providing a welding beam having a first focal depth, and welding along a welding path of the first welding section at the first focal depth;

[0017] While adjusting the output power of the welding beam, its spot diameter and / or spot energy distribution are adjusted so that the welding beam is converted from a first focal depth to a second focal depth, and welding is performed along the welding path of the second welding section at the second focal depth.

[0018] A laser welding method, comprising:

[0019] Configuring a laser combination according to the conditions of the workpieces to be welded, wherein the laser combination is composed of at least a first welding beam and a second welding beam;

[0020] The first welding beam and the second welding beam are output simultaneously or separately. The first welding beam is displaced relative to the material along a preset welding path to form a deep-melting keyhole in the material. The second welding beam acts on the rear wall of the keyhole to maintain the stability of the opening of the keyhole. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a schematic structural diagram of a fiber laser device provided in this embodiment;

[0022] FIG2 is a schematic structural diagram of the fusion bonding of an optical fiber bundling head and a quartz end cap provided in this embodiment;

[0023] FIG3 is a schematic diagram of a fiber end cap in which the output optical fibers of 19 lasers provided in this embodiment are arranged in a honeycomb pattern;

[0024] FIG4 is a schematic structural diagram of a laser output head provided in this embodiment;

[0025] FIG5 is a schematic structural diagram of an armored cable fixing assembly provided in this embodiment;

[0026] FIG6 is a three-dimensional assembly diagram of the armored cable fixing assembly provided in this embodiment;

[0027] FIG7 is a three-dimensional assembly diagram of the water-cooling head assembly provided in this embodiment;

[0028] FIG8 is a schematic diagram showing the structure of the limiting hole of the first limiting member provided in this embodiment;

[0029] FIG9 is a schematic diagram showing the assembly of the second limiting member and the first limiting member provided in this embodiment;

[0030] FIG10 is a schematic diagram of the control device provided in this embodiment controlling the rotation of the light spot to adapt to the processing path;

[0031] FIG11 is a diagram of a preset light spot having a circular shape and a Gaussian energy distribution obtained in one embodiment;

[0032] FIG12 is a diagram showing a preset light spot with a circular shape and a flat-top energy distribution obtained in one embodiment;

[0033] FIG13 is a diagram showing a preset light spot with a circular shape and an M-shaped energy distribution obtained in one embodiment;

[0034] FIG14 shows a preset light spot having a strip shape and a flat-top energy distribution obtained in one embodiment;

[0035] FIG15 is a diagram of a preset light spot with a multi-point light spot distribution obtained in one embodiment;

[0036] FIG16 is a preset light spot of a dual-wavelength light beam obtained in one embodiment;

[0037] FIG17 is a diagram of a preset light spot having a ring shape and a Gaussian energy distribution obtained in one embodiment;

[0038] FIG18 is a schematic structural diagram of a laser processing system with variable focal depth provided in this embodiment;

[0039] FIG19 is a schematic structural diagram of an optical fiber array provided in this embodiment arranged in a rectangular array;

[0040] FIG20 is a schematic diagram of the spot energy distribution of a square welding beam with a focal depth of 10 mm provided in this embodiment at defocus positions of 0 mm, -5 mm, and 5 mm;

[0041] FIG21 is a schematic diagram of the spot energy distribution of a square welding beam with a focal depth of 20 mm provided in this embodiment at defocus positions of 0 mm, -10 mm, and 10 mm;

[0042] FIG22 is a schematic diagram of the spot energy distribution of a square welding beam with a focal depth of 12 mm provided in this embodiment at defocus positions of 0 mm, -6 mm, and 6 mm;

[0043] FIG23 is a schematic diagram of welding beam control in which the output power varies with the thickness of the differential plate provided in this embodiment;

[0044] FIG24 is a schematic diagram of welding beam control in which output power and focal depth vary with plate thickness according to the embodiment;

[0045] FIG25 is a flow chart of a method for laser welding of differentially thick plates provided in this embodiment;

[0046] FIG26 is a schematic diagram showing the changes in the molten pool and keyhole morphology formed during laser welding of a high-reflectivity material;

[0047] 27 is a flow chart of a laser welding method for reducing keyhole collapse according to an embodiment;

[0048] FIG28 is a schematic diagram of a structure in which the morphology of the rear wall of a keyhole is changed by a second welding beam according to an embodiment;

[0049] FIG29 is a schematic diagram showing the distribution of heat-affected zones of the first welding beam, the second welding beam, and the third welding beam provided in an embodiment;

[0050] FIG30 is a microscopic image of the weld surface formed using the welding parameters described in the example;

[0051] FIG31 is a metallographic image of a cross section of a weld bead formed using the welding parameters described in the example;

[0052] FIG32 is a schematic diagram of the welding method of a medium-thick plate high-power laser welding method provided in an embodiment of the present application;

[0053] FIG33 is a schematic diagram of a laser assembly provided in an embodiment of the present application;

[0054] FIG34 is a schematic diagram of the operation of the laser welding head provided in an embodiment of the present application;

[0055] FIG35 is a microscope image of the front face of a weld formed using welding parameters in an example according to a specific embodiment of the present invention;

[0056] 36 is a metallographic image of a molten pool formed using welding parameters in an example according to a specific embodiment of the present invention.

[0057] Figure: 1. Fiber laser equipment; 10. Laser; 101-10n. Laser module; 11. Fiber bundle head; 20. Laser output head; 201. Armored cable fixing assembly; 2011. Fixing tube; 2012. Anti-bending spring; 2013. Teflon bushing; 2014. Fixing buckle; 202. Water cooling head; 2021. Cooling chamber; 2023. Metal dispensing ring; 20271, 20272, and 20273. First stopper; 2028. Second stopper; 203. Output armored cable; 2031. Armored cable; 20311. Teflon tube; 20312. Cable tube; 2032. Optical fiber array; 21. Quartz end cap; 22. Lens assembly; 30. Control device; 2. Laser processing system with variable focal depth; 60. Depth of focus adjustment unit; 61. Coarse depth of focus adjustment module; 62. Fine depth of focus adjustment module; 700. Plate with different thickness; 710. First welding section; 720. Second welding section; 730. Thickness gradient section; 100. Workpiece; 200. Butt joint gap; 110. Keyhole; 1110. Keyhole rear wall; 120. Molten pool; 130. Stable molten pool; 150. Weld; 3. Laser welding head; 160. Wire feeding structure; I0. Pre-processing beam; I1. First welding beam; I2. Second welding beam; I3. Third welding beam. DETAILED DESCRIPTION

[0058] The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary.

[0059] In the description of this application, the terms "center," "up," "down," "left," "right," "vertical," "horizontal," "inside," and "outside" and the like indicate positions or location relationships based on the positions or location relationships shown in the accompanying drawings. These terms are used solely to facilitate the description of this application and to simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions.

[0060] Unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," and "fixed" should be interpreted broadly. For example, they may refer to fixed or removable connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components or interactions between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0061] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first feature being in direct contact with the second feature, or may include the first feature being in contact with the second feature through another feature between them instead of being in direct contact. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature's horizontal height is higher than the second feature's horizontal height. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature's horizontal height is lower than the second feature's horizontal height.

[0062] The technical solution of the present application will be further explained below with reference to the accompanying drawings and through specific implementation methods.

[0063] As shown in FIG1 , the present application provides a fiber laser device 1 suitable for a precision laser processing system, which is used to solve the problem of high cost and large space occupied by the implementation scheme of the spot rotation. The fiber laser device 1 comprises: a laser 10, including a plurality of laser modules 101 to 10n, a laser output head 20, and a control device 30. Among them, the output optical fibers of the laser modules 101 to 10n are bundled and combined to form a fiber bundling head 11 as shown in FIG2 . The fiber bundling head 11 is directly end-face connected to the quartz end cap 21 by melting or gluing. The quartz end cap 21 is of a centrally symmetrical shape, and the end face shape is adapted to the fiber bundling head 11, and a quartz glass body with a circular cross-section is used.

[0064] As shown in FIG3 , the fiber bundler 11 is distributed in an axially symmetrical, centrally symmetrical, or rotationally symmetrical manner, and can be used to form composite lasers of various shapes, such as a honeycomb regular hexagonal array or a circular array. The laser modules 101 to 10n can be either fiber laser devices or semiconductor lasers. The output fibers of the laser modules 101 to 10n can be either single-mode or multi-mode. Multiple laser modules 101 to 10n can have the same laser output wavelength or different laser output wavelengths, for example, being divided into two groups, one with a central wavelength of 1064 nm for the output wavelength of the laser in one group and a central wavelength of 780 nm for the output wavelength of the laser in the other group, to form a dual-wavelength laser. Multiple laser modules 101 to 10n can use either the same size or different size output fibers. Using the same size output fibers to form a honeycomb regular hexagonal array maximizes the use of the array arrangement to achieve outputs of various spot shapes.

[0065] As shown in FIG4 , this embodiment provides a laser output head based on an array optical fiber. The structure of the laser output head is designed to be fixed to the array optical fiber to ensure the stability of the array optical fiber to prevent the end of the array optical fiber, that is, the fusion splice between the optical fiber bundle head and the end cap from breaking; simultaneously, the heat generated at the output part of the array optical fiber is dissipated.

[0066] As shown in FIG4 and FIG5, the laser output head 20 includes an armored cable fixing assembly 201 and a water cooling head 202. The output armored cable 203 fixed in the laser output head 20 is divided into two parts: an armored cable 2031 and an array optical fiber 2032 exposed after the cable tube and other components are stripped off.

[0067] As shown in Figure 5, the armor cable fixing assembly 201 includes a fixing tube 2011. The fixing tube 2011 is hollow inside and has a slot at the upstream position of the fixing tube 2011. The slot fixes the armor cable 2031 therein via a set screw. The tail end of the fixing tube 2011 is connected to the water cooling head 202 via a mechanical thread.

[0068] As shown in Figure 6 , the armored cable fixing assembly 201 also includes an anti-bending spring 2012, a Teflon bushing 2013, and a fixing buckle 2014, all disposed within the fixing tube 2011. The armored cable 2031 comprises a Teflon tube 20311 and a cable tube 20312, which are sequentially nested around the optical fiber array. The end of the Teflon tube 20311 is connected to the fixing buckle 2014. Referring to Figure 9 , the output armored cable 203 located to the left of the fixing buckle 2014 is the armored cable 2031, while the output armored cable 203 located to the right of the fixing buckle 2014 is the exposed optical fiber array 2032. An anti-bending spring 2012 and a Teflon bushing 2013 are nested outside the cable tube 20312. The tail end of the anti-bending spring 2012 is sleeved on the outer periphery of the Teflon bushing 2013 to prevent the armor cable fixing assembly 201 and the output armor cable 203 from breaking at the connection. The Teflon bushing 2013 is used to separate the anti-bending spring 2012 and the cable tube 20312 to reduce friction.

[0069] As shown in Figures 5 to 7, the water-cooled head 202 includes a shell, which is axially penetrated and has a hollow structure. A cooling cavity 2021 is provided therein. An independent cooling medium channel is provided on the outer periphery of the cavity wall of the cooling cavity 2021. The cooling medium channel is connected to the cooling water connector and connected to the cooling water. The circulation of the cooling water provides cooling for the cooling cavity 2021 to ensure the stability and service life of the laser output head.

[0070] As shown in Figure 7, a first fixing member and a second fixing member are respectively provided at the entrance and exit of the cooling chamber 2021, for securing the arrayed optical fiber at two points. In the present application, the first fixing member is a metal adhesive ring 2023. A mounting structure is provided at one end of the adhesive ring near the entrance of the cooling chamber 2021. The mounting structure directly secures the first fixing member to the housing and seals the cooling chamber 2021 via a sealing device such as a sealing ring. The mounting structure includes at least one of a flange, thread, connection hole, riveting, or snap-fitting structure. In this embodiment, the flange structure abuts the entrance of the cooling chamber and is fixed to the housing via fixing screws.

[0071] The glue ring has an extension at one end, facing away from the mounting structure. This extension is surrounded by multiple glue injection holes. The end face of the extension is also connected to a through-hole for the optical fiber array 2032. During installation, the optical fiber array 2032 is inserted into the through-hole and fixed in place with curing glue injected through the glue injection hole. In other words, the glue ring not only secures the optical fiber array 2032 but also seals the cooling chamber 2021, ensuring that external moisture and dust do not affect the optical path within the cooling chamber 2021.

[0072] Among them, the opening shape of the through hole can be selected to match the contour shape of the array optical fiber 2032, that is, when the array optical fiber 2032 adopts a regular hexagonal array, the opening shape of the through hole is correspondingly a regular hexagon, and when the array optical fiber 2032 adopts a rectangular array, the fixed opening shape is correspondingly a rectangle; the curing glue flows into the gap between the through hole and the array optical fiber 2032 as filling, and after solidification, the array optical fiber 2032 is fixed and the through hole is sealed to ensure the sealing of the cooling cavity 2021.

[0073] As shown in FIG7 , the fiber bundling head 11 is disposed near the outlet of the cooling chamber 2021 and serves as a second fixing member. The quartz end cap 21 is fused and fixed to one end of the array optical fiber 2032 . Thus, both ends of the array optical fiber are fixed.

[0074] Optionally, the second fixing member may also be an optical fiber connector, which is used to couple and connect the array optical fiber and the end cap pigtail, ie, the optical fiber bundling head, and fix the array optical fiber.

[0075] Since the laser spot formed by the array optical fiber is directional relative to the laser spot formed by a single optical fiber, taking the strip spot as an example, the spot formed is strip-shaped, so it is necessary to preset and mark the position of the wide side or narrow side of the strip spot. When the array optical fiber is assembled, as shown in FIG7 , the end cap is not a traditional cone-shaped column, and an alignment portion is provided on the inner wall of the cooling cavity 2021. An alignment matching portion is provided on the optical fiber bundling head 11, which can be aligned with the cooling cavity 2021 and can be aligned and calibrated to ensure that the strip spot is emitted in the preset direction.

[0076] Optionally, the fusion bonding portion of the quartz end cap 21 is conical, or may be a structure in which a small end face is provided at the top of the cone.

[0077] As shown in Figures 7 and 8 , at least one first stopper is provided between the entrance and exit of the cooling chamber 2021. In this embodiment, multiple first stoppers are provided, spaced apart at regular intervals and each having a through-hole for the array optical fiber to pass through. These multiple stoppers, spaced apart at multiple intervals, reduce the large oscillation amplitude of the array optical fiber 2032 to several smaller ones. This reduces stress at the fusion interface between the array optical fiber 2032 and the quartz end cap 21, ensuring that the fusion interface does not break.

[0078] Taking the setting of three first limiting members 20271, 20272 and 20273 as an example, the limiting holes of the first limiting members 20271, 20272 and 20273 are respectively opened in the axial direction, and the opening shape of the limiting hole is adapted to the contour shape of the array optical fiber 2032, and the opening size is slightly larger than the size of the array optical fiber 2032. When the array optical fiber 2032 passes through, it allows the array optical fiber 2032 to have a certain amount of shaking, while ensuring that the shaking amount is not too large. When the optical fiber array 2032 is fixed at two points in the cooling chamber 2021 through the through hole and the quartz end cap 21, the optical fiber array 2032 in the cooling chamber 2021 is not in a straightened and taut state. Therefore, the optical fiber array 2032 will produce a large swing amplitude. The first limiting members 20271, 20272 and 20273 in the cooling chamber 2021 are arranged at a certain interval, so that the large swing amplitude of the optical fiber array 2032 is decomposed and reduced to four smaller swing amplitudes, which greatly reduces the stress generated at the fusion surface between the optical fiber array 2032 and the quartz end cap 21, ensuring that the fusion surface does not break.

[0079] The first stopper 20273, adjacent to the quartz end cap 21, not only serves as a stop but also absorbs reflected light from the fusion bond between the array fiber 2032 and the quartz end cap 21, acting as a stop. The reflected light's energy is absorbed by the stopper 20272, causing a temperature increase. Therefore, using brass for the first stopper 20273 facilitates heat dissipation through the cooling chamber 221. Since the first stoppers 20271 and 20272 absorb relatively little reflected light, brass is unnecessary. Instead, ceramic can be used to reduce contamination of the cooling chamber by metal debris caused by friction.

[0080] In some embodiments, as shown in FIG9 , a second limiting member 2028 is further provided in the cooling chamber 2021. Since the second limiting member 2028 is longer and its outer wall shape matches the inner wall shape of the cooling chamber 2021, the second limiting member 2028 separates the first limiting member from the inner wall of the cooling chamber 2021, while allowing the first limiting members 20271, 20272 and 20273 to rotate slightly therein to allow slight deformation of the array optical fiber 2032. In addition, the first limiting member 127 is provided at a position where the second limiting member 2028 is adjacent to the optical fiber bundling head 11, and both receive the returned light. In order to reduce the attenuation of heat transfer on the medium surface, the second limiting member 2028 and the first limiting member 20273 adjacent to the optical fiber bundling head 11 can be set to the same material, or directly designed as an integrated structure.

[0081] In this embodiment, the second limiting member 2028 also has a through-hole formed therein. The internal diameter of the hole can be uniform or variable to provide a better aperture function. Furthermore, the second limiting member 2028 can be entirely disposed around the periphery of the first limiting members 20271, 20272, and 20273, meaning the first limiting member can be completely contained within the through-hole of the second limiting member 2028. Alternatively, the second limiting member 2028 can be partially disposed around the periphery of the first limiting members 20271, 20272, and 20273, meaning a portion of the first limiting members 20271, 20272, and 20273 can be contained within the second limiting member 2028, while a portion can extend beyond the second limiting member 2028, thereby enabling more flexible axial rotation.

[0082] In this embodiment, the first limiter is set as a buffer aperture to buffer the interaction between the array optical fiber and the second limiter. The second limiter is set to isolate the interaction between the array optical fiber and the inner cavity of the water-cooled head, avoiding the influence of the interaction between the array optical fiber and the internal parts of the laser, which is beneficial to the uniformity of the laser beam.

[0083] In this embodiment, optionally, the second limiter 2028 is made of a metal material or plastic material with good heat dissipation, such as copper, copper alloy, aluminum, aluminum alloy, or red copper. The first limiters 20271, 20272, and 20273 are made of high-temperature resistant ceramic material. High-temperature resistant ceramic has the characteristics of wear resistance and high temperature resistance. Even if the array optical fiber shakes, the friction dust generated is small, which helps to keep the inner cavity clean. The second limiter 2028 with better heat dissipation can quickly conduct the heat generated by the reflected light entering the inner cavity of the second limiter 2028. Optionally, the first limiters 20271, 20272, and 20273 can also be replaced by Teflon material, Teflon coating, or other compatible materials.

[0084] The laser output head 20 introduced above adopts the QBH type laser head structure. For the laser adapter structures of QCS, QD and other models, several first limiters matching the array optical fiber profile are also set in the cooling cavity. The specific structural structures are not described one by one.

[0085] The laser output head described in the present application is internally provided with a plurality of first limiting members, each of which is provided with a limiting hole. The shape of the limiting hole is the same as the contour shape of the array optical fiber. The plurality of limiting holes respectively limit the array optical fiber at a plurality of positions, so that the array optical fiber has a certain amount of shaking space inside the output head, and the fusion bonding surface will not be separated due to tension, and the fusion bonding surface can be prevented from being broken due to large shaking.

[0086] As shown in Figure 10, the control device 30 includes at least a first control module for controlling the translation of the preset light spot along the X-axis and a second control module for controlling the translation of the preset light spot along the Y-axis. Together, the first and second control modules work together to enable the preset light spot to move from the X-axis to the Y-axis, or to any angle, on a first processing plane defined by the X- and Y-axes.

[0087] Furthermore, the control device 30 may also include a third control module for controlling the focal position of the preset light spot (i.e., controlling the distance between the laser output head and the target work surface). Accordingly, through the interaction of the first, second, and third control modules, the preset light spot can be moved from the first processing plane to the second processing plane formed by the X-axis and Z-axis, or to the third processing plane formed by the Y-axis and Z-axis, and can be tilted to any angle on the second or third processing plane.

[0088] By means of the control device 30, the movement direction of the preset light spot can be changed without adjusting the emission angle of the laser output head 20. In this way, the preset light spot can be rotated on a planar or non-planar processing surface without setting a rotation axis, which reduces the equipment cost and does not occupy equipment space.

[0089] In this embodiment, the control device 30 is connected to the laser output head 20 and each laser module respectively. By opening an editing interface to the laser output head 20 or the laser, the light spot rotation can be realized through the editing interface. By controlling the on / off and output power of each laser, the shape and energy distribution of the preset light spot are modulated, thereby realizing the movement of the preset light spot on the processing surface to match the laser processing path.

[0090] Specifically, in this embodiment, the control device 30 controls the on / off of each laser module 101-10n, thereby controlling the spot shape of the laser beam output by the laser output head 20; and controls the output power of each laser module 101-10n, thereby controlling the spot energy distribution of the laser beam output by the laser output head 20. By tuning the on / off and output power of each laser module 101-10n, the laser emitted by the laser output head 20 can be formed into different spot shapes and energy distributions, such as circular, annular, strip, and multi-point shapes, and energy distributions such as Gaussian distribution, flat-top distribution, and M-shaped distribution. At the same time, when the laser operation requires rotating the processing direction, the control device 30 synchronously tunes each laser module 101-10n to complete the rotation of the preset spot, and the rotation method is simple and effective.

[0091] The specific structure of the laser 1 and the spot rotation control described in this embodiment are further described below through specific examples.

[0092] In one embodiment, the laser 1 provided in this embodiment includes 19 laser modules 101-119. Laser modules 101-119 all use fiber laser equipment with an output wavelength of 1080nm. The maximum output power of a single laser module reaches 1500W. The output fiber of a single laser module has a size of 50μm / 250μm and a core numerical aperture of 0.07. As shown in Figure 3, the output fibers of laser modules 102-119 are evenly spaced around the output fiber of laser module 101, and the output fibers of laser modules 108-119 are evenly spaced around the output fiber of laser modules 102-119, forming a honeycomb-shaped regular hexagonal fiber bundle head 11. The focal length of the lens group is set to 150mm.

[0093] As an example, the steering control device controls the laser modules 101 to 119 to output at the same power P0. As shown in FIG11 , the preset spot shape of the laser emitted by the lens group is circular, and the energy distribution is Gaussian. Since the spot is circular and the energy is Gaussian, when the laser 1 is performing a path direction conversion operation, the output of the laser modules 101 to 119 is not changed, and the effect of the preset spot rotation can be equivalently obtained.

[0094] As an example, the control device controls the laser modules 102 to 119 to output at the same power P0, and controls the laser module 101 to output at 0.8P0. As shown in FIG12 , the preset spot shape of the laser emitted by the lens group is circular, and the energy distribution is a flat-top distribution. Since the spot is circular and the energy is a flat-top distribution, when the laser 10 is performing a path direction conversion operation, the output of the laser modules 101 to 119 is not changed, and the effect of the preset spot rotation can be equivalently obtained.

[0095] As an example, the control device controls the laser modules 102 to 119 to output at the same power P0, and at the same time turns off the laser module 101. Then, as shown in FIG13 , the preset spot shape of the laser emitted by the lens group is circular, and the energy distribution is M-shaped. Since the spot is circular and the energy is flat-top distributed, when the laser 1 performs the path direction conversion operation, the output of the laser modules 101 to 119 is not changed, and the effect of the preset spot rotation can be equivalently obtained.

[0096] As an example, the steering control device controls the laser modules 108 to 119 to output at the same power P0 while turning off other lasers. As shown in FIG14 , the preset spot shape of the laser emitted by the lens group is annular, and the energy distribution is Gaussian.

[0097] As an example, the control device controls the laser modules 101, 102, and 105 to output at the same power P0, while turning off the other lasers. As shown in FIG15 , the preset spot shape of the laser emitted by the lens group is a stripe, and the energy distribution is a flat-top distribution. Since the spot is formed in a stripe shape and the energy is a flat-top distribution, when the laser 1 performs the path direction conversion operation, the output of the laser modules 101 to 119 must be changed. For example, if it rotates 60°, it is necessary to control the laser modules 103, 102, and 106 to output at the same power P0, while turning off the other lasers.

[0098] As an example, the control device controls laser modules 104 and 106 to output at the same power P0, controls laser module 102 to output at a power greater than P0, and simultaneously turns off other lasers. As shown in FIG16 , the preset spot shape of the laser light emitted by the lens assembly is a multi-point spot. Because the spot is formed as a multi-point spot and the energy is not uniformly distributed, when laser 1 performs a path direction change operation, the output of laser modules 101-119 must be changed. For example, if it rotates 60°, it is necessary to control laser modules 104 and 106 to output at the same power P0, control laser 1019 to output at a power greater than P0, and simultaneously turn off other lasers.

[0099] In another embodiment, the laser module 101 adopts a semiconductor laser, and the laser modules 102-119 adopt an optical fiber laser device; the output wavelength of the semiconductor laser is 915 nm, and the output wavelength of the optical fiber laser device is 1080 nm. The laser modules 101-119 have the same output power and output optical fiber model, wherein the maximum output power of a single laser reaches 1500 w, the size of the output optical fiber of a single laser is 50 μm / 250 μm, and the core numerical aperture is 0.07; the output optical fibers of the laser modules 102-119 are evenly spaced around the output optical fiber distribution of the laser module 101, and the output optical fibers of the laser modules 108-119 are evenly spaced around the output optical fibers of the laser modules 102-119, forming a honeycomb-shaped regular hexagonal optical fiber bundling head 11; the focal length of the lens group is set to 150 mm.

[0100] As an example, the control device controls the laser modules 102 to 119 to output at the same power P0, and controls the laser module 101 to output at a power greater than P0. Then, as shown in FIG17 , the preset spot shape of the laser emitted by the lens group is circular, and the focused spot is a dual-wavelength circular spot.

[0101] In summary, the fiber laser equipment described in the present application adopts an output fiber array of multiple laser modules that are fused and connected with a quartz end cap to form a preset light spot. In addition, the switching and power of these laser modules are regulated by a control device. When the processing direction needs to be changed, the direction of the light spot itself can be controlled by changing the switching and power of each laser module, and there is no need to set a rotating axis in the laser processing equipment. The light spot rotation method is simple, low-cost, and does not take up equipment space.

[0102] In order to adapt to welding scenarios of different thicknesses, the laser processing equipment needs to be able to adjust the depth of focus. The depth of focus adjustment scheme usually adopts the following two schemes: Scheme 1, adjust the distance between the collimating lens group and the focusing lens group in the welding head to adjust the depth of focus; Scheme 2, replace the focusing lens group with different magnifications to adjust the depth of focus. Adjusting the depth of focus using Scheme 1 requires a mechanical displacement structure to support the relative displacement of the lenses in each lens group. Due to the control accuracy and displacement speed limitations of the mechanical displacement, it is impossible to achieve fast and precise adjustment of the depth of focus (the adjustment speed of the depth of focus is limited, and the adjustment accuracy of the depth of focus is limited), nor can it achieve a jump adjustment of the depth of focus (for example, directly converting from a 10mm focal depth to a 20mm focal depth); Scheme 2 requires replacing the lens group module, which is more cumbersome. Usually, the welding head is only selected before welding to adapt to processing conditions within a certain focal depth range, and real-time adjustment of the depth of focus cannot be achieved.

[0103] To solve the above problems, as shown in FIG18 , this embodiment provides a laser processing system 2 with variable focal depth, the laser processing system 2 comprising: a multi-beam laser 10 and a focal depth adjustment unit 60.

[0104] The multi-beam laser 10 includes a plurality of laser modules 101 - 10n, and the laser beams output by the laser modules 101 - 10n are combined to form a welding beam Iz.

[0105] The depth of focus adjustment unit 60 is connected to the multi-beam laser 10, and the depth of focus adjustment unit 60 includes a coarse depth of focus adjustment module 61 and a fine depth of focus adjustment module 62. The coarse depth of focus adjustment module 61 is connected to each laser module 101~10n respectively, and can control the on and off of each laser module 101~10n; the fine depth of focus adjustment module 62 is connected to each laser module 101~10n respectively, and can control the output power of each laser module 101~10n.

[0106] In this embodiment, the focal depth coarse adjustment module 61 controls the on / off state of each laser module 101-10n to control the spot size of the welding beam formed by the laser beam combination output by these laser modules. It can be understood that for the output optical fibers arranged in an array, when the output optical fibers located at the periphery switch from emitting light to not emitting light, the spot diameter of the formed welding beam will be correspondingly reduced; as shown in the following formula: Wherein, DOF represents the focal depth; d represents the spot diameter of the welding beam; λ represents the wavelength of the welding beam; M 2 Expressed as the beam quality factor of the welding beam.

[0107] It can be seen from the above formula that when the spot diameter d decreases, the depth of focus DOF ​​will also change accordingly.

[0108] As an example, as shown in FIG19 , laser processing system 2 includes 25 laser modules 101-125. Laser modules 101-125 utilize fiber laser equipment with an output wavelength of 1080 nm and output fibers of 50 μm / 125 μm. The output fibers of laser modules 101-116 are evenly arranged on the outer square, while the output fibers of lasers 1017-125 are evenly arranged on the inner square. Laser 1025 is located at the center of quartz end cap 12. The resulting square fiber array is fused to quartz end cap 12. The collimating lens in the laser output head has a focal length of 100 mm, and the focusing lens has a focal length of 200 mm. Laser modules 101-116 are controlled to not emit light, while lasers 1017-125 are set to emit light at the same output power. The light spots at defocus points of 5 mm, 0 mm, and -5 mm are shown in FIG20 , respectively, with a focal depth of 10 mm. Controlling laser modules 101-125 to emit light at the same output power is equivalent to increasing the spot diameter, thereby increasing the depth of focus. The spots at defocus points of 10mm, 0mm, and -10mm, respectively, are shown in Figure 21, with a focal depth of 20mm, doubling the focus. Furthermore, because the output of laser modules 101-125 is controlled by switching them on and off, sudden changes in spot size and depth of focus can be achieved, making it suitable for welding in thickness-sharp machining scenarios. Because the depth of focus adjustment method, which controls the spot diameter, has a wide range of adjustment, it is primarily suitable for applications with focal depth differences of 10mm or greater.

[0109] In this embodiment, the depth of focus fine-tuning module 62 controls the output power of each laser module 101 to 10n to control the energy distribution of the welding beam formed by the laser beam group output by these laser modules. For the output optical fibers arranged in an array, when the energy distribution of the output welding beam is changed, the focal depth of the formed welding beam will change accordingly.

[0110] As an example, as shown in Figure 20, controlling lasers 1017-124 to emit light at the same output power, and controlling the output power of laser 1025 to be twice the output power of lasers 1017-124, compared to the case where lasers 1017-125 output at the same power, is equivalent to changing the power density distribution of the light spot formed by the welding beam, and thereby changing the focal depth. As shown in Figure 22, the light spots at defocus points of 6mm, 0mm, and -6mm are shown in the figure, and the focal depth is 12mm, an increase of 2mm. Moreover, since the output power of laser modules 101-125 can be adjusted separately, a sudden change in the light spot energy distribution can be achieved, thereby achieving a sudden change in the focal depth. The focal depth changes in a timely manner without affecting processing efficiency.

[0111] In actual application scenarios, the focal depth adjustment unit 60 can adjust the focal depth in a timely and accurate manner by synchronously coordinating the on / off and power of each laser based on the actual application scenario, and is suitable for welding scenarios where the thickness changes suddenly.

[0112] The focal depth coarse adjustment module 61 adjusts the focal depth of the welding beam over a large range by controlling the on and off of the laser, and its adjustment accuracy can reach within 10mm; the focal depth fine adjustment module 62 adjusts the focal depth of the welding beam over a small range by controlling the power distribution of the laser, and its adjustment accuracy can reach within 2mm; when the focal depth adjustment range is greater than 10mm, coarse adjustment is first performed through the focal depth coarse adjustment module 61, and then precise fine adjustment is performed through the focal depth fine adjustment module 62, so that stylish and accurate real-time adjustment of the focal depth can be achieved.

[0113] In summary, the present application describes a laser processing system with variable focal depth. The welding beam formed by the welding system is formed by combining multiple beams. A coarse depth of focus adjustment device and a fine depth of focus adjustment device are provided to adjust the spot diameter and energy distribution of the welding beam, respectively, thereby achieving adjustment of the focal depth. This adjustment method abandons the method of adjusting the focal depth based on the structural characteristics of the laser output head and output mirror, and instead adjusts the focal depth by changing the beam composition of the welding beam itself. This allows for accurate and rapid continuous adjustment of the focal depth, achieving high welding quality and high welding efficiency. Therefore, the present application effectively overcomes the various shortcomings of the related art and has high industrial application value.

[0114] During laser welding, the laser output power will cause changes in the state of weld penetration. Excessive output power will cause collapse and burn-through, while too low output power will result in incomplete penetration. Therefore, different thicknesses of plates are suitable for different laser output powers. In the laser welding process of the differential thickness plate 700, as shown in Figure 23, the horizontal axis direction is the welding direction. Along the welding direction, the thickness of the differential thickness plate changes. At the same time, when the thickness changes, the output power P also changes accordingly. In the welding process of the differential thickness plate 700, since the laser output power can be precisely controlled and quickly converted, the laser output power can be dynamically adjusted with the thickness change of the differential thickness plate 700, which is feasible. Ultimately, the laser welding of the differential thickness plate 700 can achieve good welding quality and welding rate. However, due to the limitation of the focal depth parameter of the laser beam, the laser power density at different thickness positions of the plate is different. As shown in Figure 24, when the thickness difference of the differential thickness plate 700 is large, the power density difference will significantly affect the welding quality.

[0115] Based on the above problems, the present application proposes a laser welding method, in which, while accurately controlling and quickly converting the output power of the welding beam, the focal depth DOF of the welding beam is also accurately controlled and quickly converted, so that when facing processing requirements with large thickness differences, the focal depth DOF can be adjusted quickly and accurately to avoid large differences in laser power density at different thickness positions of the plate, thereby affecting the welding quality.

[0116] As shown in FIG25 , this embodiment provides a laser welding method, which includes steps S1 to S3. Optionally, it also includes step S4.

[0117] Step S1: providing a plate with different thicknesses, wherein the plate with different thicknesses 700 includes a first welding section 710 and a second welding section 720 having different welding thicknesses.

[0118] In this embodiment, as shown in FIG24 , the differential thickness plate 700 includes at least two regions of different welding thicknesses, which are distinguished by thickness. The region that precedes the welding path sequence is defined as the first welding segment 710, and the region that follows the welding path sequence is defined as the second welding segment 720. It is understood that the differential thickness plate 700 typically has multiple regions of varying thicknesses, and the thickness difference between the first welding segment 710 and the second welding segment 720 is used as an example here. Furthermore, the differential thickness plate may also include at least one thickness gradient segment 730. The thickness of the thickness gradient segment 730 may vary at a uniform rate, forming a sloped topography as shown in FIG24 , or may have an irregular thickness, forming a concave-convex topography.

[0119] Step S2: providing a welding beam with a first focal depth, and performing welding along a welding path of the first welding section 710 at the first focal depth.

[0120] In this embodiment, the parameters of the welding beam output by the laser are set so that its output power P, the focal depth DOF of the beam, the spot movement speed and other parameters are adapted to the thickness and material density of the first welding section to achieve optimal welding quality and welding efficiency. Among them, when welding the first welding section, the focal depth of the welding beam is the first focal depth.

[0121] Step S3: While adjusting the output power of the welding beam, adjust the spot diameter and / or spot energy distribution so that the welding beam is converted from the first focal depth to the second focal depth, and weld along the welding path of the second welding section at the second focal depth.

[0122] In this embodiment, as shown in Figure 24, when the thickness changes and the welding path shifts from the first welding section 710 to the second welding section 720, the welding beam output power is adjusted simultaneously with the focal depth (DOF) to convert the welding beam's first focal depth to the second focal depth to accommodate the thickness of the second welding section. As shown in Figure 24, when the first welding section 710 and the second welding section 720 meet, the sudden change in thickness causes the welding beam's focal depth (DOF) to also change abruptly. Adjusting the spacing between the collimating and focusing lens assemblies cannot meet this sudden change in focal depth.

[0123] Step S4: Based on the thickness change rate of the thickness gradient section 730, while gradually adjusting the output power of the welding beam, gradually adjust the spot diameter size and / or spot energy distribution of the welding beam so that the focal depth of the welding beam changes synchronously with the thickness change rate.

[0124] In this embodiment, as shown in Figure 24, when the thickness changes gradually, it is necessary to gradually adjust the output power of the welding beam according to the change in thickness, and at the same time gradually adjust the focal depth of the welding beam, so that different focal depths are adapted at different thickness positions to obtain ideal welding quality and welding efficiency.

[0125] In summary, the laser welding method described in this application dynamically adjusts not only the output power of the welding beam but also the spot diameter and / or spot energy distribution of the welding beam when the thickness of the plates to be welded changes, thereby achieving dynamic adjustment of the focal depth. When the thickness of the plates differs significantly, the instantaneous change in the focal depth ensures that the focal depth matches the thickness even if the thickness changes significantly, thus ensuring the power density of the welding beam. Therefore, this application effectively overcomes the various shortcomings of the related art and has high industrial application value.

[0126] The traditional wavelength of fiber laser equipment is near-infrared laser. Copper, aluminum and other materials have very low absorption efficiency for infrared light at room temperature. Therefore, when using high-power laser welding (the high-power laser used in industry is mainly fiber laser equipment), if the initial power density during welding is not increased, it is easy to cause cold welding. Taking copper as an example, its absorption rate for 1060nm laser at room temperature is about 3%. Usually, it is necessary to ensure that the power density is as high as 106w / cm2 to ensure that the copper material absorbs enough heat to evaporate the material and form the keyhole 110 shown in Figure 26; as shown in Figure 26 (a) As shown, the molten metal at the location of the dotted oval frame (approximately at the intersection of the upper surface of the molten pool 120 and the keyhole rear wall 1110) has the fastest flow rate and is therefore more prone to spattering than other locations on the molten pool surface. Furthermore, when the laser enters the formed keyhole 110, its absorption efficiency soars due to refraction and absorption, exceeding 50%. This huge difference in absorption rate leads to drastic thermal fluctuations, as shown in Figure 26 (b). This thermal fluctuation increases the amount of metal vapor generated and accelerates the flow rate of the molten metal, ultimately causing the keyhole rear wall 1110 to collapse forward, forming the pores shown in Figure 26 (c). The generation of spatter and pores can affect welding quality.

[0127] Based on the aforementioned welding issues, this application proposes a laser welding method for reducing keyhole collapse. This method addresses the issue of high laser peak power, which can easily cause droplet splashing and poor weld quality when welding highly reflective materials. As shown in Figures 27 and 28, this welding method configures a laser assembly based on the conditions of the workpiece to be welded. The assembly includes at least: a first welding beam I1 with high power density, which vaporizes the material to form a keyhole 110; and a second welding beam I2, which irradiates the keyhole rear wall 1110 and has lower total power than the first welding beam. This vaporizes the molten metal located on the keyhole rear wall 1110, smoothing the corner between the upper surface of the molten pool 120 and the keyhole rear wall 1110. This effectively reduces the likelihood of spatter. Furthermore, after the molten metal on the keyhole rear wall 1110 is vaporized, the keyhole rear wall 1110 no longer tilts forward, reducing the risk of keyhole collapse. This effectively reduces the likelihood of porosity and ensures stable welding quality.

[0128] As shown in FIG27 , this embodiment provides a laser welding method for reducing keyhole collapse, which includes steps S1 to S2. In practical applications, it also includes a material pretreatment step S0.

[0129] Step S0: grinding the part of the workpiece 100 to be welded to remove oil stains on the surface of the material.

[0130] In step S1 , a first welding beam I1 is formed. The first welding beam I1 is displaced relative to the workpiece 100 along a preset welding path to form a keyhole 110 in the workpiece 100 .

[0131] In this embodiment, the first welding beam I1 moves relative to the material in direction Y, irradiating the surface of the workpiece 100 and forming a keyhole 110 within the workpiece 100, as shown in Figure 26(a). Simultaneously, air is coaxially blown toward the irradiation location. For example, the shielding gas flow rate is set to 15 L / min, and the gas pressure is set to 0.2 MPa. Laser welding is performed while the shielding gas is blown, effectively evacuating the gas within the keyhole 110 and forming a good weld. Furthermore, due to the high reflectivity of the workpiece 100 to near-infrared wavelengths, a plasma shielding effect is likely to occur on the surface during welding, affecting the workpiece 100's further absorption of the laser. The coaxial shielding gas can promptly blow away the surface plasma cloud, ensuring stable keyhole formation.

[0132] Step S2, forming a second welding beam I2, the second welding beam I2 acts on the keyhole rear wall 1110 of the keyhole 110 to maintain the stability of the keyhole opening; wherein the power of the second welding beam I2 is less than or equal to the power of the first welding beam I1.

[0133] In this embodiment, as shown in Figure 28, the second welding beam I2 acts on the keyhole rear wall 1110. Its power exceeds the material's evaporation threshold, vaporizing the melt on the keyhole rear wall 1110. This evaporation effectively widens the opening of the keyhole 110, smoothing the rear wall of the widened keyhole 110 and reducing the melt's flow rate at corners, thereby minimizing spatter. Furthermore, since some of the melt on the keyhole rear wall 1110 is evaporated, a greater force is required within the melt to force the melt on the keyhole rear wall 1110 forward, covering the keyhole bottom and forming bubbles. Therefore, the second welding beam I2 acting on the keyhole rear wall 1110 can effectively reduce spatter and bubbles, thereby improving welding quality.

[0134] In some embodiments, step S1 and step 2 are also considered to occur simultaneously.

[0135] Specifically, in S2, a third welding beam I3 is also formed, and the third welding beam I3 maintains a certain distance from the second welding beam I2; and the third welding beam I3 acts on the rear wall of the keyhole 110 to maintain the opening of the keyhole stable and not easy to collapse.

[0136] In this embodiment, as one beam arrangement, as shown in the dashed boxes (left) in Figures 28 and 29 , the first, second, and third welding beams I1, I2, and I3 are sequentially spaced apart to form a stripe arrangement. The first welding beam I1 forms a keyhole with a relatively deep depth. The second and third welding beams I2 and I3 act sequentially on the rear wall of the keyhole. The third welding beam I3 further vaporizes the molten metal located on the rear wall 1110 of the keyhole relative to the second welding beam I2, smoothing the keyhole 110 and stabilizing the opening of the keyhole 110, thereby improving weld quality. Furthermore, to maintain a stable fusion zone width and ensure that the second and third welding beams I2 and I3 do not increase the fusion zone width, the power of the second welding beam I2 can be controlled to be less than that of the first welding beam I1, and the power of the third welding beam I3 can be controlled to be less than that of the second welding beam I2. As an example, as shown in the dashed box (left) in Figure 29, the first, second, and third welding beams I1, I2, and I3 utilize near-infrared lasers with a power ratio of 900W:750W:600W. The heat-affected zones (HAZs) decrease in size, the relative distance between the beam centers is set at 500μm, and the welding speed is 80mm / s. A microscopic image of the weld bead surface, as shown in Figure 30, demonstrates a smooth surface, a fine molten pool, a metallic luster, and no welding defects. A cross-sectional metallographic image, as shown in Figure 31, demonstrates a weld bead free of pores, fine and uniform grains, and a penetration depth of approximately 1mm.

[0137] As another beam arrangement, as shown in the dotted box (right) of FIG29 , the first welding beam I1, the second welding beam I2, and the third welding beam I3 are arranged in a triangular array (the center points of the light spots are arranged in a triangular array). The second welding beam I2 and the third welding beam I3 are spaced the same as the first welding beam I1 and all act on the keyhole rear wall 1110. This provides a larger melt evaporation area in the width direction of the fusion zone, stabilizes the opening of the keyhole 110, and improves welding quality. Furthermore, for the application scenario of butt welding, where there is a weld seam in the middle of the welding material, the bilateral symmetry of the second welding beam I2 and the third welding beam I3 can ensure stable welding, especially when welding thin plates, where the edges are not easily shrunk or collapsed. In some embodiments, to maintain a stable fusion zone width and ensure that the second welding beam I2 and the third welding beam I3 do not increase the fusion zone width, the lateral action width of the second welding beam I2 and the third welding beam I3 is controlled to be smaller than the spot diameter of the first welding beam I1. That is, the spacing between the first welding beam and the second welding beam is adjusted to ensure that the fusion zone width is not increased.

[0138] When the power density is too high, the second welding beam I2 and the third welding beam I3 will vaporize the molten metal on the back wall 1110 of the keyhole, leaving a small keyhole with a relatively large depth and width. The spot energy distribution of the second welding beam 12 and the third welding beam 13 is controlled to be a flat-top distribution. Compared with the Gaussian spot distribution, the flat-top distribution has a wider effective area and forms a small keyhole with a relatively small depth and width, which can more effectively ensure the smoothness of the back wall 1110 of the keyhole.

[0139] This application uses a first welding beam with higher energy and power to overcome the initial resistance caused by the poor absorption performance of the material, and realizes high absorption efficiency laser welding. At the same time, a second welding beam is formed after the first welding beam. The second welding beam acts on the rear wall of the keyhole, changes the flow state of the molten pool on the rear wall of the keyhole, and slows down the fluid kinetic energy of the liquid metal located on the rear wall of the keyhole, so as to effectively improve the generation of pores and spatter, make the laser welding process stable, and have high welding quality.

[0140] Traditionally, narrow-gap arc welding has been used primarily for welding medium and thick plates, with narrow-gap submerged arc welding and narrow-gap TIG welding being the predominant methods. Narrow-gap laser welding and laser arc hybrid welding have also found application in medium and thick plate welding. However, both narrow-gap arc welding and narrow-gap laser welding with wire filler, as well as laser arc welding, which combines two heat sources, require pre-grooving and multiple weld passes to fill the gap. This results in low welding efficiency, significant weld distortion, and the potential for defects such as weld porosity, lack of fusion on the sidewalls, and unstable penetration during wire feeding.

[0141] This application replaces the traditional grinding pre-treatment step of the material with a direct output of a pre-processing beam without grinding. The width of the pre-processing beam completely covers the width of the weld seam, cleaning the oxide layer and dirt on the surface to be welded, and generating a stable molten pool with shallow penetration and large molten area on the surface of the workpiece to be welded.

[0142] As shown in Figures 32 to 36, the workpiece 100 to be welded can be various grades of carbon steel, stainless steel, alloy steel, and aluminum alloy disclosed in the related art, with a thickness of 4.5 mm to 25 mm. The method includes the following steps:

[0143] S1: measuring the width of the butt gap 200 between two workpieces 100 to be welded, and configuring a laser combination according to the width of the butt gap 200 , wherein the laser combination is composed of at least a pre-processing beam I0 and a first welding beam I1 .

[0144] S2: Output the pre-processing beam I0 and the first welding beam I1 simultaneously or separately; wherein, the width of the pre-processing beam I0 at least completely covers the butt gap 200, is used to clean the oxide layer and dirt on the surface of the workpiece 100 to be welded, and to generate a stable molten pool 130 with a shallow melting depth and a large melting area on the surface of the workpiece 100; the first welding beam I1 is arranged parallel to the pre-processing beam I0, and acts on the rear part of the stable molten pool 130 formed by the pre-processing beam I0 along the moving direction of the laser welding head 3, is used to further vaporize the material, and form a deep melting keyhole 110 on the surface of the workpiece 100.

[0145] Specifically, in this embodiment, the width of the pre-processing beam I0 at least completely covers the butt joint gap 200, cleaning the oxide layer and dirt on the surface of the workpiece 100 to be welded. It also forms a stable molten pool 130 with shallow penetration and a large melting area on the surface of the workpiece 100. The molten welding wire liquid and the workpiece 100 are fully fused in the stable molten pool 130 and then fill the butt joint gap 200. The first welding beam I1 is arranged parallel to the pre-processing beam I0 and acts on the rear portion of the stable molten pool 130 formed by the pre-processing beam I0 along the movement direction of the laser welding head 3 to vaporize the material and form a deep-penetrating keyhole 110 on the surface of the workpiece 100. Because the surface of the workpiece 100 and the welding wire are already molten after the pre-processing beam I0 acts on them, the energy of the first welding beam I1 can be fully utilized. Almost all of the laser energy can be absorbed by the molten metal, and a lower laser energy can achieve a greater penetration. The first welding beam I1 and the pre-processing beam I0 work together to form a deep-penetrating keyhole 110. Pre-processing beam I0 acts on the front wall of deep-penetration keyhole 110, maintaining a wide opening. Metal vapor within deep-penetration keyhole 110 escapes along the keyhole sidewalls, reducing laser shielding and improving laser energy utilization and welding efficiency. Pre-processing beam I0 and first welding beam I1 can be emitted simultaneously or separately at a preset interval. The timing of the emission depends on the time required for the stable molten pool 130 to stabilize. If the time required for the stable molten pool 130 to stabilize is short, simultaneous emission can be selected. If the time required for the stable molten pool 130 to stabilize is long, the pre-processing beam 10 and first welding beam I1 are emitted separately at a preset interval, with the preset time being greater than or equal to the stabilization time of the stable molten pool 130. The first welding beam I1 is emitted after the stable molten pool 130 stabilizes, ensuring that the laser energy of the first welding beam I1 is fully utilized, achieving greater penetration with lower energy.

[0146] 32 and 33 , the laser assembly further includes a second welding beam I2 for maintaining the open state of the rear wall of the deep penetration keyhole 110. Specifically, in this embodiment, the second welding beam I2 acts on the rear wall of the deep penetration keyhole 110. As the pre-processing beam I0 and the first welding beam I1 move along the extension direction of the butt gap 200, the metal behind the deep penetration keyhole 110 continuously solidifies to form a weld 150. The second welding beam I2 can maintain the open state of the deep penetration keyhole 110, and together with the pre-processing beam I0 and the first welding beam I1, form a large "Y"-shaped deep penetration keyhole 110. This can reduce the pressure of the metal vapor within the deep penetration keyhole 110, reduce the solidification rate of the stable molten pool 130, slow the cooling rate of the stable molten pool 130, and reduce the difficulty of gas escape, thereby effectively avoiding spatter during welding and the formation of pores in the weld 150, thereby facilitating the optimization of the formation of the weld 150.

[0147] Specifically, in this embodiment, the wire feeding method is either front-feed or rear-feed, with front-front feeding being preferred. With the welding wire in front and the laser in the rear, the welding wire absorbs the energy of the pre-processing beam I0 and melts. After the molten droplets enter the stable molten pool 130, the first welding beam I1 and the second welding beam I2 begin to act. This prolonged molten state results in more complete fusion of the workpiece 100 and the welding wire, and better weld 150 formation. In the rear-feed method, with the laser in front and the welding wire in the rear, the welding wire primarily absorbs the energy of the second welding beam I2. As the laser welding head 3 continues to move, the welding wire droplets begin to cool after entering the stable molten pool 130, resulting in a less favorable cladding effect. The type of welding wire can be selected as needed based on the material of the workpiece 100 to be welded. Specifically, the diameters of solid welding wires are generally 0.8 mm, 1.0 mm, 1.2 mm, and 1.6 mm. The diameter of the welding wire will also affect the wire feeding amount per unit time. If the workpiece 100 is thick or the butt gap 200 between the two workpieces 100 is large, the welding wire needs to be thickened accordingly. At the same time, the laser power required to melt the welding wire also needs to be increased.

[0148] Specifically, in this embodiment, the total width of the pre-processing beam I0 at least completely covers the butt joint gap 200, and the power of the pre-processing beam I0 can melt through the welding wire without melting through the workpiece 100; the light output mode, light output power, beam width and spot shape are determined in combination with the single spot shape, spot diameter, spacing and collimation and focusing ratio of the laser welding head 3 of the first welding beam I1, so that the total width of the first welding beam I1 is smaller than the pre-processing beam I0 but needs to completely cover the butt joint gap 200, and the power of the first welding beam I1 can reach the required welding depth, the spots are arranged linearly, the first welding beam I1 is set parallel to the pre-processing beam I0, and along the moving direction of the laser welding head 3, the first welding beam I1 is parallel to the pre-processing beam I0. Beam I1 is located 0.5mm-1mm behind the pre-processing beam I0; combined with the single spot shape, spot diameter, spacing of the second welding beam I2 and the collimation and focusing ratio of the laser welding head 3, the light output mode, light output power, beam width and spot shape of the second welding beam I2 are confirmed, so that the total width of the second welding beam I2 is slightly larger than the first welding beam I1. At the same time, the power of the second welding beam I2 is less than the power of the first welding beam I1, which can melt through the welding wire without melting through the workpiece 100. The spots are arranged linearly, the second welding beam I2 is set parallel to the first welding beam I1, and along the moving direction of the laser welding head 3, the second welding beam I2 is located 0.5mm-1mm behind the first welding beam I1.

[0149] It can be understood that the above-mentioned laser combination is composed of multiple lasers output by a laser based on an array fiber. The laser based on an array fiber includes several laser modules. The output fiber arrays of several laser modules are arranged to form a fiber array. Several laser modules are independently controlled and adjustable in real time.

[0150] Specifically, the pre-processing beam I0, the first welding beam I1, and the second welding beam I2 are formed by lasers from different output fibers. The single-point spot diameter and spacing of the pre-processing beam I0, the first welding beam I1, and the second welding beam I2 depend on the core and cladding diameters of the pigtail fiber ultimately outputted by the single laser path, as well as the collimation and focusing ratio of the laser welding head 3.

[0151] Optionally, the light emission modes of the pre-processing beam I0, the first welding beam I1 and the second welding beam I2 are continuous mode or pulse mode. Specifically, in this embodiment, they are all continuous mode, and the stable molten pool 130 has better stability in the continuous mode.

[0152] Optionally, the width of each welding beam is determined by the single-point spot diameter and spacing of the multi-channel laser; the single-point spot diameter and spacing of the multi-channel laser are determined by the core and outer cladding diameters of the output optical fibers of several laser modules and the collimation and focusing ratio of the laser welding head.

[0153] Specifically, the spot diameter = fiber core × (focusing lens focal length / collimating lens focal length), and the spot spacing = outer cladding diameter × (focusing lens focal length / collimating lens focal length). For example, the fiber core is typically 20 μm, 50 μm, or 100 μm, and the outer cladding is typically 250 μm or 400 μm. The collimation-focusing ratio of the laser welding head 3 is 1:2, 1:2.5, or 1:3, preferably 1:2.

[0154] Optionally, the width of the pre-processing beam I0 is greater than the width of the first welding beam I1; the width of the second welding beam I2 is greater than the width of the first welding beam I1, and / or, smaller than the width of the pre-processing beam I0.

[0155] Specifically, the total width of the pre-processing beam I0 needs to cover the butt gap 200 and, ideally, also cover the edges of the workpiece 100. This not only serves to clean the workpiece 100 before deep penetration, but also allows the molten droplets of the workpiece 100 and the welding wire to fully fuse. The total width of the first welding beam I1 is smaller than that of the pre-processing beam I0, but it also needs to cover the butt gap 200 to ensure a stable depth and width of the molten pool 130 and avoid issues with incomplete penetration at the edges of the weld 150. The width of the second welding beam I2 is generally slightly wider than that of the first welding beam I1 to effectively prevent the collapse of the deep penetration keyhole 110. For example, if the butt gap 200 is 1.5 mm wide and the spot spacing is 0.5 mm, then at least four pre-processing beams I0 need to be emitted simultaneously. Considering the relatively large gap, the first welding beam I1 is preferably two.

[0156] In addition, the number of paths for each laser combination is selected based on the requirements for the width of the weld 150 and whether the gap can be completely covered. The width of the laser combination can be changed by adjusting the number of paths, and the width of the weld 150 can be fine-tuned in combination with the welding angle of the laser combination. When adjusting the welding angle and width of the laser combination, the projection of the pre-processing beam I0 on the horizontal plane must be perpendicular to the butt gap 200, thereby ensuring that the first welding beam I1 and the second welding beam I2 are both perpendicular to the butt gap 200, so as to ensure that the two workpieces 100 can be welded together, and at the same time ensure that the projection width of the laser combination on the horizontal plane completely covers the gap.

[0157] Optionally, the power of the first welding beam I1 is greater than the power of the pre-processing beam I0 and the second welding beam I2; preferably, the power of the first welding beam I1 is configured to achieve the required welding depth, and the power of the pre-processing beam I0 and the second welding beam I2 is configured to melt through the welding wire without melting through the plate.

[0158] Specifically, the setting of a single laser power depends on the thickness of the workpiece 100 that actually needs to be welded. The pre-processing beam I0 and the second welding beam I2 are only auxiliary and need to melt the welding wire through without melting through the workpiece 100. The penetration depth only needs to reach one-third of the thickness of the workpiece 100; the first welding beam I1 is the main welding heat source and needs to reach the set welding depth.

[0159] It should be noted that, as one of the beam arrangement methods, on the basis of the second welding beam I2, a third welding beam I3 as shown in the dotted box (left) in Figures 28 and 29 can also be formed. The third welding beam I3 can maintain a certain distance from the second welding beam according to the requirements of the welding process, and act together on the rear wall of the keyhole 110 to maintain the stability of the opening of the keyhole.

[0160] Optionally, the pre-processing beam I0 and the second welding beam I2 together form a 'Y'-shaped large deep penetration keyhole 110 around the first welding beam I1 .

[0161] Specifically, the spacing between the pre-machining beam I0 and the first welding beam I1, and the spacing between the first welding beam I1 and the second welding beam I2, is generally 0.5 mm to 1 mm. The spacing setting is related to the stability of the deep penetration keyhole 110. If the spacing between the two sets of laser beams is too small, the opening at the top of the deep penetration keyhole 110 will be insufficient, and pores and spatter will still be obvious. If the spacing is too large, the deep penetration keyhole 110 will change from a "Y" shape to an independent "W" shape, and the deep penetration keyhole 110 will not form a complete deep penetration keyhole 110. In addition, the deep penetration keyholes 110 of the pre-machining beam I0 and the first welding beam I1 will interfere with each other.

[0162] Optionally, as shown in Figure 34, the laser welding head 3 and the wire feeding structure 160 are tilted, and the angle between the axis of the laser welding head 3 and the vertical direction is 5°-10° to ensure that during high-power welding, the reflected light will not directly enter the laser welding head 3 and damage the lens or laser.

[0163] Optionally, the welding process parameters of the laser welding head 3 are set, wherein the adjustment range of the welding defocus amount is from -10mm to +10mm. Increasing the welding defocus amount will result in a decrease in the penetration depth and an increase in the laser power density at the positive focus. Therefore, increasing the welding defocus amount can improve the stability of the welding process and optimize the formation of the weld 150. The welding speed is 0.3m / min-3m / min. The size of the welding speed can affect not only the width of the weld 150, but also the penetration depth. Too slow a welding depth will result in excessive heat input per unit time, making the welding state unstable; and too fast a welding speed may result in insufficient welding fusion. The specific welding speed needs to be adjusted according to the actual welding effect and welding rhythm.

[0164] In summary, the present application can solve the problems of low welding efficiency and energy utilization, and the easy occurrence of welding porosity, unfused side walls and unstable welding penetration in the existing laser welding process; in addition, the welding method does not require pre-grooving of the workpiece to be welded, nor does it require cleaning of the workpiece before welding, which can effectively improve the welding efficiency. Multiple groups of laser beams are welded in parallel, which improves the tolerance of the assembly gap.

Claims

1. A fiber laser device, comprising: Multiple laser modules, laser output heads and control devices; wherein, The output optical fibers of the multiple laser modules are symmetrically bundled to form an optical fiber array; The array optical fiber is coupled to the laser output head, and the output lasers of the multiple lasers are emitted through the laser output head to form a preset light spot; The control device is connected to the multiple lasers respectively and provides a light spot editing interface. The control device is used to control the light output and output power of the lasers and modulate the shape and energy distribution of the preset light spot.

2. The fiber laser device according to claim 1, wherein The laser output head comprises: A housing having an axially penetrating cooling cavity disposed therein; An end cap, wherein the end cap is partially or completely received at one end of the cooling cavity; A first fixing member is located at the other end of the cooling cavity and is fixedly mounted on the housing, wherein a through hole is formed on the first fixing member; One end of the array optical fiber is arranged in a predetermined shape and is fixedly connected to the end cap; one end of the array optical fiber away from the end cap passes through the through hole and the housing and is fixedly connected to the first fixing member; At least one first limiting member is accommodated in the cooling cavity, and the array optical fiber can be movably disposed through the first limiting member.

3. The fiber laser device according to claim 2, wherein The first limiting member is provided with an axially penetrating limiting hole, the limiting hole being adapted to the shape of the array optical fiber, and / or The first stopper is axially rotatably disposed between the end cap and the first fixing member, and / or The number of the first limiting members can be configured as multiple, and the multiple first limiting members are arranged at a preset distance from each other, so that the shaking amplitude of the array optical fiber is decomposed into a plurality of smaller shaking amplitudes, and / or A mounting structure and at least one glue point hole are provided at one end of the first fixing member, the mounting structure directly fixes the first fixing member on the housing, the glue point hole is communicated with the through hole, and is used to inject glue to fix the optical fiber array in the first fixing member, and cooperate with a sealing member to seal the cooling cavity and seal the cooling cavity through the sealing member, and / or Alignment structures are respectively arranged on the surface of the end cap and the inner wall of the cooling cavity accommodating the end cap, and the end cap is fixed to one end of the cooling cavity at a preset angle through the alignment structure.

4. The fiber laser device according to claim 2, wherein, The laser output head further comprises a second stopper which is axially penetrating, wherein at least a part or all of the second stopper is arranged around the outer periphery of the first stopper; The wear resistance of the material of the first limiting member is higher than that of the material of the second limiting member, and / or the first limiting member adjacent to the end cap is made of the same material as that of the second limiting member, or is integrally formed with the second limiting member.

5. The fiber laser device according to claim 1, wherein, The control device also includes a first control module and a second control module, the first control module is used to control the horizontal movement of the preset light spot in the X-axis direction of the processing surface, and the second control module is used to control the horizontal movement of the preset light spot in the Y-axis direction of the processing surface; the first control module and the second control module cooperate simultaneously to realize the oblique movement of the preset light spot at any angle on the first processing surface formed by the X-axis and the Y-axis.

6. The fiber laser device according to claim 5, wherein, The control device further includes a third control module for controlling the movement of the preset light spot in the Z-axis direction of the processing surface; the first control module, the second control module, and the third control module cooperate to achieve the oblique movement of the preset light spot at any angle on the second processing surface formed by the X-axis and the Z-axis or the third processing surface formed by the Y-axis and the Z-axis on the processing surface, or move from the first processing surface to the second processing surface or the third processing surface.

7. The fiber laser device according to claim 1, wherein, The array optical fibers formed by multiple output optical fibers are centrosymmetrically distributed, and the number of the output optical fibers is (2N - 1)×6 + 1, N≥1, and / or The shape of the preset light spot is one or more of a circular light spot, an annular light spot, a strip light spot, a multi-point light spot, and a special-shaped light spot; the energy distribution of the preset light spot is one or more of a Gaussian distribution, an annular distribution, and a multi-point distribution.

8. A laser processing system, comprising: A multi-beam laser and a focal depth adjustment unit; wherein, The multi-beam laser includes a plurality of laser modules, the output optical fibers of each laser module are arranged in an array, and the array lasers output by each output optical fiber are combined to form a processing beam; The focal depth adjustment unit includes a plurality of focal depth coarse adjustment modules and focal depth fine adjustment modules; each of the focal depth coarse adjustment modules is respectively connected to each of the laser modules, and the spot size of the processing beam is controlled by controlling the turning on and off of each laser; each of the focal depth fine adjustment modules is respectively connected to each of the laser modules, and the energy distribution ratio of the processing beam is controlled by controlling the power of each laser.

9. The laser processing system according to claim 8, wherein, The focal depth adjustment unit synchronously controls the focal depth coarse adjustment module and the focal depth fine adjustment module to control the focal depth change of the processing beam to be greater than or equal to 10 mm; and / or, The adjustment accuracy of the focal depth coarse adjustment module is less than or equal to 10 mm; the adjustment accuracy of the focal depth fine adjustment module is less than or equal to 2 mm.

10. The laser processing system according to claim 8, wherein, The depth of focus and the spot size satisfy the following formula: Among them, DOF represents the depth of focus; d represents the spot diameter of the processing beam; λ represents the wavelength of the processing beam; M 2 represents the beam quality factor of the processing beam.

11. A laser welding method, comprising: Providing a material to be welded, the material includes a first welding section and a second welding section with different welding thicknesses; Providing a welding beam with a first focal depth and welding along the welding path of the first welding section with the first focal depth; While adjusting the output power of the welding beam, adjusting its spot diameter size and / or spot energy distribution, so that the welding beam is converted from the first focal depth to the second focal depth, and welding along the welding path of the second welding section with the second focal depth.

12. The laser welding method according to claim 11, wherein, The material further includes a thickness gradient section; the laser welding method further includes: According to the thickness of the thickness gradient section, while gradually adjusting the output power of the welding beam, gradually adjusting the spot diameter size and / or spot energy distribution of the welding beam, so that the focal depth of the welding beam changes synchronously with the thickness of the thickness gradient section.

13. A laser welding method, comprising: Configuring a laser combination according to the condition of the workpiece to be welded, the laser combination is at least composed of a first welding beam and a second welding beam; Output the first welding beam and the second welding beam simultaneously or separately. The first welding beam displaces relative to the material along a preset welding path, acting on the material to form a keyhole with deep penetration. The second welding beam acts on the rear wall of the keyhole to maintain the stability of the keyhole opening.

14. The laser welding method according to claim 13, wherein the welding beam further includes a third welding beam; the third welding beam and the second welding beam act on the rear wall of the keyhole together to maintain the stability of the keyhole opening; the power of the second welding beam and the third welding beam is less than or equal to the power of the first welding beam, and both exceed the evaporation threshold of the material; and / or, the first welding beam, the second welding beam, and the third welding beam act on the material in a strip array; and / or, the first welding beam, the second welding beam, and the third welding beam act on the material in a triangular array, and the lateral acting width of the second welding beam and the third welding beam is less than the spot size of the first welding beam.

15. The laser welding method according to claim 13, before outputting the first welding beam and the second welding beam simultaneously or separately, further includes: outputting a preprocessing beam; the width of the preprocessing beam completely covers at least the weld width, for cleaning the oxide layer and dirt on the surface to be welded, and generating a stable molten pool with a shallow penetration depth and a large molten area on the surface of the workpiece to be welded; the width of the preprocessing beam is greater than the widths of the first welding beam and the second welding beam, and the power of the preprocessing beam is less than the powers of the first welding beam and the second welding beam. The preprocessing beam and the second welding beam jointly form a 'Y'-shaped large keyhole around the first welding beam.

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