Welding system and method for aluminum alloy laser welding

Abstract

The invention belongs to the technical field of laser welding, and particularly relates to a welding system and method for aluminum alloy laser welding. The system comprises a workbench, a six-axis industrial robot, a laser welding and surface treatment device, a gas protection device and a control unit. The workbench is used for bearing and fixing an aluminum alloy workpiece; a dual-wavelength laser generating unit, a light beam coupling and shaping unit, a plasma processing subunit, a laser micro-texture processing subunit, a spraying unit, a laser welding mechanism and a laser swinging mechanism are integrated in a shell of the laser welding and surface processing device. The gas protection device comprises a multi-stage annular gas knife protection device. The method sequentially comprises the steps of workpiece clamping and fixing, CCD visual welding seam positioning, plasma film removing, laser micro-texture machining, nano coating spraying, dual-wavelength swing laser welding and post-welding detection. The aluminum alloy laser absorptivity in the laser welding process is improved, the aluminum alloy welding defect rate is reduced, and the welding seam quality is improved.

Description

Technical Field

[0001] This invention belongs to the field of laser welding technology, specifically relating to a welding system and method for laser welding of aluminum alloys, particularly suitable for precision welding of high-reflectivity, high-thermal-conductivity, and hot-cracking-prone aluminum alloys such as the 2000 series (e.g., 2024, 2017), 6000 series (e.g., 6061, 6063), and 7000 series (e.g., 7075, 7050). This system and method can be widely applied in high-end manufacturing industries with stringent requirements for welding quality, production efficiency, and environmental protection, such as aerospace, new energy vehicles, 3C electronics, rail transportation, and shipbuilding. It can effectively solve the technical bottlenecks in welding key aluminum alloy components in these industries, improving product reliability and service life. Background Technology

[0002] In modern industrial manufacturing, aluminum alloys, with their comprehensive advantages such as low density, high strength, good corrosion resistance, excellent machinability, and good electromagnetic shielding performance, are seeing their application range continuously expand. From the traditional aerospace field, their applications are gradually extending to high-end manufacturing fields such as new energy vehicle bodies and battery packs, 3C electronic device housings and internal structural components, rail transit vehicle bodies, and lightweight ship components. Laser welding technology, as a typical high-energy-density welding technology, has outstanding characteristics such as narrow weld seams, small heat-affected zones, minimal welding deformation, high welding efficiency, and ease of automation and intelligent control. It has gradually replaced traditional arc welding technology and become one of the mainstream technologies for precision welding of aluminum alloys.

[0003] However, aluminum alloys have extremely high reflectivity to near-infrared lasers, with an initial reflectivity as high as 80%-90%, and very low absorption rate to commonly used lasers at room temperature. The significant amount of laser energy reflected results in energy waste and may also damage optical components, necessitating the use of higher-power lasers and increasing initial equipment investment costs.

[0004] Aluminum alloy surfaces readily form a dense Al2O3 oxide film with a melting point much higher than the substrate, making it prone to leaving residues and forming defects during welding. Existing treatment methods involve mechanical grinding, which easily leads to uneven surface roughness and secondary oxidation. Chemical corrosion pollutes the environment and may introduce hydrogen. Traditional plasma cleaning is incomplete in removing the oxide film, and laser cleaning alone is prone to secondary oxidation and may damage the substrate.

[0005] Aluminum alloys have high thermal conductivity, making it difficult to maintain the "keyhole" effect stably, which easily leads to porosity and incomplete penetration defects; the water absorption of the oxide film results in a high risk of hydrogen porosity; aluminum alloy welding has a crystallization temperature range, which easily leads to crystallization cracks and liquefaction cracks, and the defect rate of existing technologies is generally above 15%.

[0006] The extreme thermal cycle of laser welding destroys the original strengthening mechanism of aluminum alloys, and low-melting-point alloying elements evaporate and burn off, resulting in the formation of coarse cast structure in the weld. This leads to a significant decrease in weld hardness and strength. At the same time, weld defects can cause stress concentration, further reducing mechanical properties.

[0007] Existing welding systems are mostly open-loop controlled, which is highly dependent on the skills of operators; some detection components have insufficient accuracy in detecting micro-defects and cannot achieve closed-loop control; surface treatment and welding modules are independent and lack coordinated control; gas protection methods are singular and positioning and trajectory tracking accuracy is limited.

[0008] Existing technical solutions often only optimize for a single problem, making it difficult to achieve precise defect control from both the source and the process. It is also difficult to achieve the best balance between thorough porosity suppression, process stability, production efficiency, and environmental protection. Summary of the Invention

[0009] To address the technical problems of low near-infrared laser absorption rate of aluminum alloys, difficulty in removing surface oxide films and easy secondary damage, easy generation of porosity and cracks during welding, decline in weld mechanical properties, and lack of coordinated control and inability to achieve precise closed-loop regulation in existing welding systems, this invention provides a welding system and method for laser welding of aluminum alloys.

[0010] Therefore, the present invention provides the following technical solution:

[0011] A welding system for laser welding of aluminum alloys includes a worktable, a six-axis industrial robot, a laser welding and surface treatment device, a gas protection device, and a control unit. The worktable is used to support and fix aluminum alloy workpieces; The laser welding and surface treatment device includes a housing, which is fixedly connected to the output end of the six-axis industrial robot. The end of the housing facing the aluminum alloy workpiece is the execution end. The housing houses a dual-wavelength laser generating unit, a beam coupling and shaping unit, a plasma processing subunit, a laser micro-texturing subunit, a spraying unit, a laser welding mechanism, and a laser oscillation mechanism. The light outlets or output ports of the plasma processing subunit, the laser micro-texturing subunit, the laser welding mechanism, and the spraying unit are all oriented towards the execution end of the housing. The laser output end of the dual-wavelength laser generating unit is optically connected to the laser input end of the beam coupling and shaping unit. The laser output end of the beam coupling and shaping unit is connected to the optical paths of the laser micro-texturing subunit and the plasma processing subunit respectively through optical paths. The laser output end of the beam coupling and shaping unit is also connected to the input end of the laser oscillation mechanism through optical paths. The output end of the laser oscillation mechanism is connected to the optical path of the laser welding mechanism. The laser spots corresponding to the laser micro-texturing subunit and the plasma processing subunit are located in front of the welding spot of the laser welding mechanism along the welding direction (the oxide film is removed first, and then micro-texturing is done, which completely solves the problem of oxide film residue and secondary damage). The input end of the spraying unit is connected to the output end of an external spraying pressure pump through a fluid channel (to achieve controllable spraying of bio-based coatings, forming a dense barrier layer and reducing the risk of hydrogen porosity and oxidation). The actuator end of the housing is also equipped with a gas shield. The gas shield has a nozzle facing the aluminum alloy workpiece. The input end of the gas shield is connected to the output end of the gas protection device through a gas pipeline (to provide a local stable protective atmosphere and avoid secondary oxidation and porosity cracks during welding). The control unit is electrically connected to the six-axis industrial robot, the dual-wavelength laser generating unit, the beam coupling and shaping unit, the plasma processing subunit, the laser micro-texturing processing subunit, the spraying unit, the laser oscillation mechanism, the laser welding mechanism, and the gas protection device (to achieve unified control of multiple modules and solve the problem of open-loop control and inability to close-loop regulation in existing systems).

[0012] Furthermore, an XYZ three-axis ball screw moving platform is installed on the workbench. A cast iron base and a vacuum adsorption device are fixedly installed on the XYZ three-axis ball screw moving platform. The cast iron base is provided with a workpiece groove for positioning the aluminum alloy workpiece. The vacuum adsorption device is located below the aluminum alloy workpiece, and the suction nozzle of the vacuum adsorption device faces the aluminum alloy workpiece.

[0013] Furthermore, the gas protection device includes a protective gas storage unit, a gas purification unit, and several flow control valves; each flow control valve integrates a flow sensor and a proportional adjustment module, and the proportional adjustment module is electrically connected to the corresponding flow sensor and flow control valve respectively; the outlet of the protective gas storage unit is connected to the inlet of the gas purification unit, and the outlet of the gas purification unit is connected to the inlet of each flow control valve through a pipeline. The gas shield is equipped with a multi-stage annular gas knife protection device, which includes at least three concentric annular gas knives: an inner layer, a middle layer, and an outer layer. Each annular gas knife is connected to the outlet of a corresponding flow control valve through an independent gas supply branch, and the outlet of each annular gas knife is connected to the corresponding nozzle of the gas shield (forming a three-dimensional gradient protective atmosphere, effectively blocking air from entering the molten pool, and significantly reducing porosity and oxidation defects).

[0014] Furthermore, the control unit includes a detection unit, a data processing unit, and a central control system. The detection unit is fixedly mounted on the housing of the laser welding and surface treatment device via a bracket, and the signal output terminal of the detection unit is connected to the signal input terminal of the data processing unit. The data processing unit is connected to the central control system, which is connected to the six-axis industrial robot, the dual-wavelength laser generating unit, the beam coupling and shaping unit, the plasma processing subunit, the laser micro-texturing processing subunit, the spraying unit, the laser oscillation mechanism, the laser welding mechanism, and the gas protection device (to achieve real-time monitoring and closed-loop control throughout the entire process, solving the problem that existing welding systems cannot achieve precise process control and defect prediction).

[0015] Furthermore, the detection unit includes at least a CCD vision subunit for weld positioning, a laser triangulation subunit for surface quality detection, an optical coherence tomography subunit for real-time monitoring of the molten pool, and an infrared thermal imager subunit for temperature field monitoring (to achieve multi-dimensional micro-defect monitoring, improve weld quality detection accuracy, and solve the problem of micro-defects being unidentifiable).

[0016] Furthermore, the laser wavelengths output by the dual-wavelength laser generating unit include 1080nm and 915nm, and the power ratio of the two lasers is 1:4-4:1 (the dual wavelengths synergistically improve the absorption rate of the aluminum alloy, reduce energy reflection, and solve the energy waste and laser damage risk caused by high reflectivity).

[0017] A welding method for laser welding of aluminum alloys, applied to the aforementioned welding system for laser welding of aluminum alloys, includes the following steps: S1. Clean the surface of the aluminum alloy workpiece and then clamp it on the worktable (remove impurities and oil stains in advance to reduce the origin of pores and cracks). S2. Locate the weld area using the CCD vision sub-unit of the detection unit (achieve high-precision weld positioning, reduce trajectory deviation, and improve welding stability). S3. Under the local protective atmosphere formed by the gas shield, the surface treatment of the area to be welded is carried out. The plasma treatment subunit removes the oxide film of the workpiece area to be welded, the laser micro-texturing subunit processes the laser micro-texture of the area to be welded, and the spraying unit sprays a bio-based nano-coating on the area to be welded (completely removes the oxide film, increases surface wettability, forms a dense barrier layer, solves the problem of difficult oxide film removal and secondary oxidation, and improves the mechanical properties of the weld). S4. Within the set time interval after the surface treatment is completed, the dual-wavelength laser generation unit is activated. After the laser is processed by the beam coupling and shaping unit and the laser oscillation mechanism, it is oscillated and welded by the laser welding mechanism. During the welding process, the gas protection device provides multi-level gas protection. At the same time, based on the real-time monitoring data collected by the detection unit, the control unit executes closed-loop feedback control to ensure the stability of the welding parameters. S5. After welding, continue gas protection until the weld cools down, and then perform quality inspection on the workpiece (to ensure that the weld is not oxidized during the cooling process and to improve the density and strength of the weld).

[0018] Furthermore, in step S3, the plasma oxide film removal uses a mixture of Ar and H2 as the working gas; the texture type of the laser microtexturing is grid-like or striped, with a depth of 10-20 μm; and the thickness of the bio-based nanocoating is 50-100 nm.

[0019] Furthermore, the time interval after surface treatment in step S4 shall not exceed 5-8 seconds; the multi-stage gas protection uses a mixture of Ar, He, and O2, wherein the volume fraction of O2 is 1.0%-1.5%; The dual-wavelength laser employs a central spot, annular spot, or a central-annular composite spot mode; the oscillation frequency of the oscillation welding is 10-400Hz, and the oscillation amplitude is 0-5mm.

[0020] Furthermore, in step S4, the closed-loop feedback control involves real-time monitoring of the molten pool morphology and weld depth by an optical coherence tomography subunit, and monitoring of the heat-affected zone temperature by an infrared thermal imager subunit. When the monitoring data of the molten pool morphology, weld depth, or heat-affected zone temperature deviate from the preset process threshold, the data processing unit generates an adjustment command, and the central control system adjusts the laser power and welding speed in real time, or adjusts the protective gas flow parameters through a flow control valve.

[0021] Advantages and positive effects of the present invention: This invention performs sequential surface treatments on the welding area of ​​an aluminum alloy workpiece under a localized protective atmosphere created by a gas shield. First, a plasma treatment subunit removes the oxide film from the welding area. Then, a laser micro-texturing subunit adds micro-textures to the welding area, increasing its surface roughness. Finally, a spraying unit promptly applies a bio-based nano-coating to the treated area, forming a dense protective barrier layer. The surface treatment achieves excellent results, with high oxide film removal efficiency and no environmental pollution. The micro-textured structure effectively increases the surface roughness of the welding area, significantly improving the aluminum alloy's laser absorption rate. The nano-coating effectively inhibits secondary oxidation in the welding area. Experimental verification shows that this surface treatment method significantly improves the absorption rate of both wavelengths of laser light output from the dual-wavelength laser generator of this invention, reducing energy consumption during welding and eliminating the need for a higher-power laser, thus effectively lowering the initial investment cost of the equipment.

[0022] This invention employs a dual-wavelength laser generator unit in conjunction with a laser oscillation mechanism to achieve oscillating welding. Combined with multi-dimensional detection and closed-loop feedback control of the control unit, the detection unit collects data such as the molten pool and temperature field in real time. After analysis by the data processing unit, the central control system adjusts welding parameters in real time, achieving precise control throughout the entire process. This effectively suppresses various defects in aluminum alloy welding, such as porosity, cracks, and incomplete penetration, improving the welding qualification rate, significantly enhancing the stability and consistency of welding quality, reducing rework and scrap caused by defects, and further reducing production energy consumption and costs. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the overall structure of a welding system for laser welding of aluminum alloys according to the present invention.

[0025] Figure 2 This is a schematic diagram of the internal structure of the laser welding and surface treatment device of the present invention.

[0026] Figure 3 This is a schematic diagram of the internal structure of the gas protection device of the present invention.

[0027] Figure 4 This is a logic block diagram of the closed-loop feedback control of the present invention.

[0028] Figure 5This is a process flow diagram of the synergistic surface treatment and welding process of the present invention.

[0029] In the diagram: 1. Workbench; 2. Laser welding and surface treatment device; 3. Gas protection device; 4. Control unit; 5. Six-axis industrial robot; 6. Aluminum alloy workpiece; 7. Optical path; 8. Gas protective cover; 9. Plasma treatment subunit; 10. Laser micro-texturing processing subunit; 11. Spraying unit; 12. Multi-stage annular air knife protection device; 13. Protective gas storage unit; 14. Flow control valve; 15. Gas purification unit; 16. Housing; 17. Dual-wavelength laser generation unit; 18. Beam coupling and shaping unit; 19. XYZ three-axis ball screw moving platform; 20. Cast iron base; 21. Vacuum adsorption device. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0031] This invention provides a welding system for laser welding of aluminum alloys, such as... Figure 1 As shown, it includes a workbench 1, a six-axis industrial robot 5, a laser welding and surface treatment device 2, a gas protection device 3, and a control unit 4.

[0032] The worktable 1 is used to support and fix the aluminum alloy workpiece 6. An XYZ three-axis ball screw moving platform 19 is installed on the worktable 1. A cast iron base 20 and a vacuum adsorption device 21 are fixedly installed on the XYZ three-axis ball screw moving platform 19. The cast iron base 20 has a workpiece groove for positioning the aluminum alloy workpiece 6. The vacuum adsorption device 21 is located below the aluminum alloy workpiece 6, and its suction nozzle faces the aluminum alloy workpiece 6. The high-strength cast iron base is made of HT300 material and undergoes two artificial aging treatments to eliminate internal stress. The positioning accuracy of the XYZ three-axis moving platform can reach ±0.005mm, and the repeatability is ±0.002mm. The vacuum adsorption device generates a negative pressure of -0.08~-0.09MPa, forming a dual fixing method suitable for welding thin-walled aluminum alloy workpieces.

[0033] like Figure 2As shown, the laser welding and surface treatment device 2 includes a housing 16, which is fixedly connected to the output end of a six-axis industrial robot 5 via a flange. The end of the housing 16 facing the aluminum alloy workpiece 6 is the execution end. Inside the housing 16 are installed a dual-wavelength laser generating unit 17, a beam coupling and shaping unit 18, a plasma processing subunit 9, a laser micro-texturing subunit 10, a spraying unit 11, a laser welding mechanism, and a laser oscillation mechanism. The light output ports or output ports of the plasma processing subunit 9, the laser micro-texturing subunit 10, the laser welding mechanism, and the spraying unit 11 are all positioned facing the execution end of the housing 16. The laser output end of the dual-wavelength laser generating unit 17 is optically connected to the laser input end of the beam coupling and shaping unit 18. The dual-wavelength laser generator has an output power of 1000-6000W, and the laser wavelengths output by the dual-wavelength laser generating unit 17 include 1080nm and 915nm, with a power ratio of 1:4-4:1 between the two lasers.

[0034] The laser output end of the beam coupling and shaping unit 18 is connected to the laser micro-texturing subunit 10 and the plasma processing subunit 9 via optical path 7. The laser output end of the beam coupling and shaping unit 18 is also connected to the input end of the laser oscillation mechanism via optical path, and the output end of the laser oscillation mechanism is connected to the optical path of the laser welding mechanism. The laser spots corresponding to the laser micro-texturing subunit 10 and the plasma processing subunit 9 are located 0.5-2.0 mm ahead of the welding spot of the laser welding mechanism along the welding direction to avoid secondary oxidation. The coupling accuracy of the beam coupling and shaping unit is 0.01 mm.

[0035] The input end of the spraying unit 11 is connected to the output end of an external spraying pressure pump through a fluid channel.

[0036] The actuator end of the housing 16 is also equipped with a gas shield 8. The gas shield 8 has a nozzle facing the aluminum alloy workpiece 6. The input end of the gas shield 8 is connected to the output end of the gas protection device 3 through a gas pipeline.

[0037] like Figure 3 As shown, the gas protection device 3 includes a protective gas storage unit 13, a gas purification unit 15, and several flow control valves 14; each flow control valve 14 integrates a flow sensor and a proportional adjustment module, and the proportional adjustment module is electrically connected to the corresponding flow sensor and flow control valve 14 respectively; the outlet of the protective gas storage unit 13 is connected to the inlet of the gas purification unit 15, and the outlet of the gas purification unit 15 is connected to the inlet of each flow control valve 14 through a pipeline.

[0038] The gas shield 8 is equipped with a multi-stage annular air knife protection device 12, which includes at least three concentric annular air knives: an inner layer, a middle layer, and an outer layer. Each annular air knife is connected to the outlet of the corresponding flow control valve 14 through an independent gas supply branch, and the outlet of each annular air knife is connected to the corresponding nozzle of the gas shield 8.

[0039] The control unit 4 is electrically connected to the six-axis industrial robot 5, the dual-wavelength laser generating unit 17, the beam coupling and shaping unit 18, the plasma processing subunit 9, the laser micro-texturing processing subunit 10, the spraying unit 11, the laser oscillation mechanism, the laser welding mechanism, and the gas protection device 3, respectively.

[0040] like Figure 4 The control unit 4 includes a detection unit, a data processing unit, and a central control system. The detection unit is fixedly mounted on the housing 16 of the laser welding and surface treatment device 2 via a bracket, and its signal output terminal is connected to the signal input terminal of the data processing unit. The data processing unit is connected to the central control system, which is connected to the six-axis industrial robot 5, the dual-wavelength laser generating unit 17, the beam coupling and shaping unit 18, the plasma processing subunit 9, the laser micro-texturing processing subunit 10, the spraying unit 11, the laser oscillation mechanism, the laser welding mechanism, and the gas protection device 3. The central control system uses a PLC controller to achieve full closed-loop control and is equipped with a human-machine interface for visual management.

[0041] The detection unit includes at least a CCD vision subunit for weld positioning, a laser triangulation subunit for surface quality inspection, an optical coherence tomography subunit for real-time monitoring of the molten pool, and an infrared thermal imager subunit for temperature field monitoring.

[0042] A welding method for laser welding of aluminum alloys, such as Figure 5 As shown, it includes the following steps: S1. Clean the surface of the aluminum alloy workpiece, and then clamp and fix it on the worktable; S2. Locate the weld area using the CCD vision sub-unit of the detection unit; S3. Under the local protective atmosphere formed by the gas shield, the surface treatment of the area to be welded is carried out. The plasma treatment subunit removes the plasma oxide film from the area to be welded, the laser microtexturing subunit performs laser microtexturing on the area to be welded, and the spraying unit sprays a bio-based nano-coating onto the area to be welded. The plasma oxide film removal uses a mixture of Ar and H2 as the working gas. The texture type of the laser microtexturing is grid-like or striped, with a depth of 10-20μm. The thickness of the bio-based nano-coating is 50-100nm.

[0043] S4. Within the set time interval after surface treatment, the set time interval after surface treatment shall not exceed 5-8 seconds; the dual-wavelength laser generation unit shall be activated, and the laser shall be processed by the beam coupling and shaping unit and the laser oscillation mechanism, and then oscillated for welding by the laser welding mechanism; during the welding process, the gas protection device shall provide multi-level gas protection, which shall use a mixture of Ar, He and O2, wherein the volume fraction of O2 shall be 1.0%-1.5%; at the same time, based on the real-time monitoring data collected by the detection unit, the control unit shall execute closed-loop feedback control to ensure the stability of welding parameters; the dual-wavelength laser shall adopt a central spot, annular spot or central-annular composite spot mode; the oscillation frequency of oscillation welding shall be 10-400Hz, and the oscillation amplitude shall be 0-5mm.

[0044] The closed-loop feedback control uses an optical coherence tomography subunit to monitor the morphology and depth of the molten pool in real time, and an infrared thermal imager subunit to monitor the temperature of the heat-affected zone. When the monitoring data of the molten pool morphology, depth of molten pool, or temperature of the heat-affected zone deviate from the preset process threshold, the data processing unit generates an adjustment command, and the central control system adjusts the laser power and welding speed in real time, or adjusts the protective gas flow parameters through the flow control valve.

[0045] S5. After welding, continue gas protection until the weld cools down, and then perform quality inspection on the workpiece.

[0046] Working principle: When the system is working, it first completes the bearing and fixation of the aluminum alloy workpiece. The XYZ three-axis ball screw moving platform installed on the worktable surface can drive the cast iron base above and the vacuum adsorption device to achieve precise displacement in the X, Y and Z directions, which facilitates the adjustment of the workpiece position to adapt to the welding requirements. The workpiece groove on the cast iron base is used to perform preliminary mechanical positioning of the aluminum alloy workpiece and limit the horizontal displacement of the workpiece. At the same time, after the vacuum adsorption device is started, it generates negative pressure and adsorbs the bottom of the workpiece through the suction nozzle. This, together with the mechanical positioning of the cast iron base, forms a double fixation, effectively preventing the thin-walled aluminum alloy workpiece from shifting or deforming during the welding process.

[0047] Subsequently, the control unit activates the CCD vision subunit within the detection unit. The CCD vision subunit transmits the acquired weld seam image data to the data processing unit. The data processing unit analyzes and processes the image, identifying key information such as the weld seam location and bevel type, and feeds the positioning data back to the central control system. Based on the weld seam positioning data, the central control system automatically plans the motion trajectory and controls the six-axis industrial robot to move the housing of the laser welding and surface treatment device, ensuring that the actuator of the housing is precisely aligned with the area to be welded. CCD vision weld seam recognition, image data processing, and robot trajectory planning are all standard techniques in the existing fields of machine vision and industrial robot control, and therefore will not be elaborated upon here.

[0048] During the welding process, the dual-wavelength laser generating unit is activated first, outputting dual-wavelength lasers with wavelengths of 1080nm and 915nm. The two lasers are output in a power ratio of 1:4 to 4:1. By utilizing the complementary effect of different wavelength lasers on the absorption characteristics of aluminum alloys, the total absorption rate of laser energy by aluminum alloys is significantly improved, making up for the defects of low absorption rate and severe energy reflection of single-wavelength lasers, and improving energy utilization.

[0049] The laser emitted by the dual-wavelength laser is transmitted to the beam coupling and shaping unit. After being coupled and shaped by the optical elements inside the unit, a coaxial beam with uniform energy distribution is formed. On the one hand, it is transmitted to the plasma processing subunit and the laser micro-texturing processing subunit through the optical path to provide energy for surface treatment. On the other hand, it is transmitted to the laser oscillation mechanism to provide energy for laser welding.

[0050] Under the localized protective atmosphere created by the gas shield, the plasma treatment subunit utilizes the coupled laser, in conjunction with the externally supplied working gas, to generate highly active plasma, thoroughly removing the Al2O3 oxide film from the area to be welded on the aluminum alloy workpiece, eliminating welding defects caused by residual oxide film at the source. Subsequently, the laser micro-texturing subunit processes micro-textures on the surface of the workpiece after the oxide film has been removed, increasing the surface roughness of the workpiece and further improving the laser absorption rate and welding wettability. The spraying unit receives bio-based nano-coating material delivered by an external spraying pressure pump through a fluid channel and uniformly sprays it onto the treated area to be welded, forming a dense nano-barrier layer that effectively prevents secondary oxidation of the area to be welded and reduces the risk of hydrogen porosity.

[0051] After surface treatment, the laser oscillation mechanism is activated. This existing technology drives the laser spot output by the laser welding mechanism to oscillate periodically according to preset parameters. Its core function is to solve the instability problem of the "keyhole" effect caused by the high thermal conductivity of aluminum alloy. By oscillating the laser spot, the laser energy is evenly distributed in the area to be welded, driving the fluid flow in the molten pool, replenishing the liquid metal in the keyhole area, expelling residual gas, stabilizing the "keyhole" effect, and suppressing defects such as porosity and incomplete penetration. The existing laser welding mechanism is mainly used to focus the laser on the workpiece surface to form a weld pool. The dual-wavelength laser after oscillation is transmitted to the laser welding mechanism, which focuses the laser on the area to be welded. The high energy of the laser melts the aluminum alloy workpiece to form a weld pool. At the same time, a six-axis industrial robot moves the shell smoothly along the weld seam trajectory. After the weld pool cools and solidifies, a high-quality weld seam is formed. During the welding process, the dual-wavelength laser can use a central spot, an annular spot, or a central spot according to process requirements. The annular composite spot mode optimizes the formation and depth of the molten pool.

[0052] During welding, the protective gas stored in the protective gas storage unit is first delivered to the gas purification unit. Purification removes moisture and impurities from the gas, ensuring its purity and preventing impurities from being introduced into the molten pool and causing defects. The purified protective gas is then delivered through pipelines to various flow control valves. Each flow control valve integrates a flow sensor to monitor the gas flow rate in real time. The proportional adjustment module automatically adjusts the valve opening based on the monitoring data, achieving precise control of the gas flow rate. The multi-stage annular air knife protection device within the gas shield receives protective gas at corresponding flow rates through three concentric annular air knives. This forms a three-dimensional gradient protective atmosphere: an inner layer directly protects the molten pool, a middle layer provides transitional protection, and an outer layer isolates external air. This effectively prevents air from intruding into the molten pool, significantly reducing porosity and oxidation defects. Simultaneously, the He in the mixed protective gas optimizes the molten pool cooling rate, and trace amounts of O2 enhance plasma stability, further improving the protection effect.

[0053] Throughout the entire operation, in addition to the CCD vision subunit, the detection unit utilizes existing technology, including a laser triangulation subunit for real-time detection of the workpiece surface quality after surface treatment, ensuring that micro-texture dimensions and surface roughness meet requirements. The optical coherence tomography (OCT) subunit is also existing technology, used for real-time monitoring of the molten pool morphology and melt depth. An infrared thermal imager subunit is also existing technology, used for real-time monitoring of the heat-affected zone temperature. All detection data is transmitted to the data processing unit. The data processing unit compares and analyzes the detection data against preset process thresholds. When data deviates from the thresholds (e.g., abnormal molten pool morphology, insufficient melt depth, excessively high temperature, or deviation in protective gas flow), it immediately generates adjustment commands and transmits them to the central control system. Based on these adjustment commands, the central control system adjusts the six-axis industrial robot's motion trajectory, dual-wavelength laser power ratio, laser oscillation parameters, spraying parameters, and protective gas flow in real-time, ensuring stable operating parameters for each module. This achieves a complete closed loop of detection, analysis, command, execution, and feedback, solving the problem of open-loop control and inaccurate regulation in existing systems.

[0054] Example 1: Butt welding of 6061-T6 aluminum alloy thin plates for aluminum alloy workpieces (application in new energy vehicle body).

[0055] 1. Workpiece parameters The workpiece to be welded is a 6061-T6 aluminum alloy sheet. This material is mainly used for lightweight components in the bodies of new energy vehicles, requiring the welded joint to have high tensile strength and corrosion resistance. The workpiece is 2mm thick and has dimensions of 100mm×50mm×2mm. The weld type is a butt weld with an I-groove. The original oxide layer thickness is approximately 50nm, and the surface is free of obvious oil and impurities.

[0056] 2. System parameter settings (1) Synergistic composite surface treatment parameters The plasma processing subunit has an output power of 1000W, uses an Ar:H2 mixture (volume ratio 9:1) as the working gas, a flow rate of 15L / min, a plasma spray gun distance of 10mm from the workpiece surface, and a processing speed of 300mm / min. The laser microtexturing type is a mesh pattern with a depth of 10μm, a width of 30μm, a spacing of 100μm, a processing speed of 500mm / min, a pulse width of 50ns, a repetition frequency of 200kHz, and an output power of 300W. The bio-based nano-coating concentration is 0.3wt%, and the spraying amount is 1.5μL / cm². 2 The spraying pressure is 0.2 MPa; the pretreatment protective gas is high-purity argon (purity ≥99.999%), with a flow rate of 18 L / min; the laser spot of the laser microtexturing subunit and the plasma treatment subunit are 1.0 mm ahead of the welding spot.

[0057] (2) Laser welding parameters The 1080nm laser power is 3000W, and the 915nm laser power is 2000W, with a power ratio of 3:2; the welding speed is 300mm / min, and the defocusing amount is 0mm; the oscillation frequency is 200Hz, the oscillation amplitude is 2mm, and the oscillation trajectory is a sine wave; the central strong spot (spot diameter 0.8mm) is used in the initial welding stage, and the stabilization welding stage switches to an annular spot (inner ring diameter 0.6mm, outer ring diameter 1.2mm); the time interval between processing and welding is 8s.

[0058] (3) Protective gas parameters The welding shielding gas is an Ar-He-O2 mixture, with an Ar:He volume ratio of 8:2 and an O2 volume fraction of 1.0%. The total flow rate is 25 L / min, with the inner layer air knife flow rate at 12 L / min (48%), the middle layer air knife flow rate at 8 L / min (32%), and the outer layer air knife flow rate at 5 L / min (20%). The gas pressure monitoring threshold is 0.3 MPa, and the allowable deviation range for gas composition is ±0.2%.

[0059] (4) Positioning and detection parameters The CCD visual positioning subunit has a positioning accuracy of ±0.01mm, and the weld seam recognition algorithm adopts a deep learning model based on convolutional neural networks; the laser triangulation surface quality detection subunit has a measurement accuracy of ±1μm, and the surface roughness qualification threshold Ra≤2.0μm; the OCT welding process monitoring subunit has a detection frequency of 100Hz and a detection accuracy of ±10μm; the infrared thermal imager temperature monitoring subunit has a temperature measurement range of 0-800℃, and the maximum temperature control threshold of the heat-affected zone is ≤400℃.

[0060] 3. Welding process and results (1) Workpiece pretreatment and clamping Since the workpiece surface has little oil stains, it is initially cleaned by wiping with anhydrous ethanol. A lint-free cloth is used to wipe the workpiece surface and weld area in one direction to avoid impurities remaining. After wiping, the workpiece is placed on the cast iron base of the worktable, and the vacuum adsorption device is started. The vacuum pump generates a negative pressure of -0.08MPa to firmly adsorb the workpiece on the worktable. After clamping, the CCD vision positioning subunit detects the position of the workpiece. The detection result shows that the workpiece clamping deviation is 0.02mm, which meets the set requirements (≤±0.05mm).

[0061] (2) Weld positioning and parameter setting The CCD vision positioning subunit is activated, and the industrial camera acquires image data of the workpiece surface, which is then transmitted to the data processing unit. A deep learning-based weld recognition algorithm automatically identifies the butt weld and I-groove, generates the coordinate data of the weld, and transmits the positioning information to the central control system. Based on the coordinate data of the weld, the central control system automatically plans the motion trajectory of the composite surface treatment and welding integration module. The operator inputs the above-set collaborative composite surface treatment parameters, laser welding parameters, and shielding gas parameters through the human-machine interface, and the system completes the parameter loading.

[0062] (3) Synergistic composite surface treatment The central control system controls a six-axis industrial robot to move the laser welding and surface treatment device along the planned weld seam trajectory. Simultaneously, it activates the plasma pretreatment subunit, the laser microtexturing subunit, the bio-based nanocoating spraying unit, and the inert gas protection unit. First, the plasma pretreatment subunit generates highly active Ar-H2 plasma to decompose and remove the oxide film on the workpiece surface. During this process, the robot maintains a constant distance between the plasma spray gun and the workpiece surface to ensure uniform oxide film removal. Subsequently, the laser microtexturing subunit processes a grid-like microtexture on the oxide-removed workpiece surface, covering the weld seam area and 5mm areas on both sides. Within 0.3 seconds of completing the laser microtexturing, the bio-based nanocoating spraying unit sprays a bio-based nanocoating onto the workpiece surface, forming a barrier layer approximately 80nm thick. Throughout the entire process, the inert gas protection unit continuously sprays high-purity argon gas, creating a localized inert gas protective atmosphere. After the surface treatment is completed, the laser triangulation measurement surface quality detection subunit detects the surface roughness and micro-texture size of the workpiece. The detection results show that the surface roughness Ra=1.2μm, the micro-texture depth 10μm, width 30μm, and spacing 100μm all meet the set requirements.

[0063] (4) Multi-wavelength synergistic laser welding Within 8 seconds of surface treatment completion, the central control system activates the dual-wavelength laser generator, beam coupling and shaping unit, oscillating welding mechanism, and gas protection device to begin welding. After coupling and shaping, the dual-wavelength laser focuses a central strong spot onto the weld area during the initial welding stage, achieving rapid arc initiation. After initial welding, the spot mode automatically switches to an annular spot to improve the stability of the molten pool. The oscillating mechanism drives the welding head to oscillate along a sinusoidal trajectory, stirring the molten pool. The intelligent gas protection module's three-stage annular gas knife continuously sprays Ar-He-O2 mixed protective gas, forming a three-dimensional protective atmosphere. During welding, the OCT welding process monitoring subunit monitors the molten pool morphology and penetration depth in real time. When welding reaches the 30mm position, a tiny pore with a diameter of approximately 80μm is detected. The data processing unit analyzes that this is due to insufficient protective gas flow and immediately generates a parameter adjustment command, adjusting the total protective gas flow from 25L / min to 27L / min and the inner layer gas knife flow to 13L / min. After receiving the command, the central control system adjusts the protective gas flow in real time, and the pore defect subsequently disappears. The infrared thermal imager temperature monitoring subunit monitors the temperature of the heat-affected zone in real time. The monitoring results show that the highest temperature in the heat-affected zone is 380℃, which does not exceed the set threshold (400℃).

[0064] (5) Post-welding treatment and quality inspection After welding, the central control system stops the dual-wavelength laser generator from outputting laser light, while the intelligent gas protection module continues to spray protective gas for 8 seconds until the weld area cools to room temperature. Then, all modules are shut down, the vacuum adsorption and clamping are released, and the welded workpiece is removed. Quality inspection of the workpiece is performed: visual inspection shows that the weld surface is smooth and flat, without oxidation discoloration, undercut, incomplete penetration, or other defects, and the weld width is uniform (approximately 2.5 mm). Ultrasonic testing shows that there are no defects such as porosity, inclusions, or cracks inside the weld. Tensile strength testing using a universal testing machine shows that the weld tensile strength is 320 MPa, the base metal tensile strength is 345 MPa, and the weld joint tensile strength reaches 93% of the base metal. Hardness testing using a Vickers hardness tester shows that the weld hardness is 110 HV, the base metal hardness is 123 HV, and the weld hardness reaches 89% of the base metal. After a 500-hour salt spray test (ASTM B117 standard), there are no obvious corrosion marks on the weld surface, indicating good corrosion resistance. The test results show that the quality of the welded joints fully meets the requirements for use in new energy vehicle body components.

[0065] Example 2: Butt welding of 7075-T6 aluminum alloy thick plates (aerospace component application) 1. Workpiece parameters The workpiece to be welded is a 7075-T6 aluminum alloy thick plate. This material is mainly used in load-bearing components in the aerospace field, requiring the welded joint to have extremely high tensile strength and an extremely low defect rate. The workpiece thickness is 10mm, the dimensions are 200mm×100mm×10mm, the weld type is a butt weld, the bevel type is a V-groove, the bevel angle is 60°, the surface oxide layer thickness is >100nm, and there is a small amount of oil on the surface.

[0066] 2. System parameter settings (1) Synergistic composite surface treatment parameters The plasma treatment subunit has an output power of 2000W, uses an Ar:H2 mixture (volume ratio 9:1) as the working gas, a flow rate of 30L / min, a nozzle-to-workpiece surface distance of 15mm, and a processing speed of 100mm / min. The laser microtexturing subunit processes stripes with a microtexture depth of 20μm, a width of 50μm, a spacing of 200μm, a processing speed of 200mm / min, a pulse width of 100ns, a repetition frequency of 100kHz, and an output power of 500W. The bio-based nano-coating has a concentration of 0.4wt% and a coating amount of 2.0μL / cm³. 2 The spraying pressure is 0.3 MPa; the protective gas output by the gas protection device is high-purity argon (purity ≥99.999%), with a flow rate of 25 L / min; the laser spot of the laser micro-texturing subunit and the plasma processing subunit are 1.5 mm ahead of the welding spot.

[0067] (2) Laser welding parameters The 1080nm laser power is 6000W, and the 915nm laser power is 4000W, with a power ratio of 3:2; the welding speed is 100mm / min, and the defocusing amount is -3mm; the oscillation frequency is 100Hz, the oscillation amplitude is 5mm, and the oscillation trajectory is a square wave; a center-ring composite spot is used (center spot diameter 1.0mm, ring spot diameter 2.0mm), the center spot is responsible for forming a stable "small hole" to ensure the penetration depth, and the ring spot is responsible for widening the molten pool to improve the shape; the time interval between processing and welding is 5s.

[0068] (3) Protective gas parameters The welding shielding gas is an Ar-He-O2 mixture, with an Ar:He volume ratio of 7:3 and an O2 volume fraction of 1.5%. The total flow rate is 40 L / min, with the inner layer air knife flow rate at 18 L / min (45%), the middle layer air knife flow rate at 14 L / min (35%), and the outer layer air knife flow rate at 8 L / min (20%). The gas pressure monitoring threshold is 0.3 MPa, and the allowable deviation range for gas composition is ±0.2%.

[0069] (4) Positioning and detection parameters The CCD visual positioning subunit has a positioning accuracy of ±0.01mm, and the weld seam recognition algorithm adopts a deep learning model based on convolutional neural networks; the laser triangulation surface quality detection subunit has a measurement accuracy of ±1μm, and the surface roughness qualification threshold Ra≤3.0μm; the OCT welding process monitoring subunit has a detection frequency of 100Hz, a detection accuracy of ±10μm, and a penetration depth detection threshold ≥10mm (matching the workpiece thickness); the infrared thermal imager temperature monitoring subunit has a temperature measurement range of 0-1000℃, and the maximum temperature control threshold of the heat-affected zone ≤450℃.

[0070] 3. Welding process and results (1) Workpiece pretreatment and clamping Due to a small amount of oil on the workpiece surface, ultrasonic cleaning was used for initial cleaning: anhydrous ethanol was used as the cleaning solution, the cleaning power was set to 200W, and the cleaning time was 8 minutes. After cleaning, the workpiece was placed in a 60℃ constant temperature drying oven for 12 minutes to ensure that no moisture remained on the workpiece surface. The dried workpiece was then placed on the cast iron base of the worktable, and the vacuum adsorption device was activated. The vacuum pump generated a negative pressure of -0.09MPa, firmly adsorbing the workpiece onto the worktable. After clamping, the CCD vision positioning subunit detected the workpiece position. The detection result showed that the workpiece clamping deviation was 0.03mm, which met the set requirements (≤±0.05mm).

[0071] (2) Weld positioning and parameter setting The CCD vision positioning subunit is activated, and the industrial camera acquires image data of the workpiece surface and transmits it to the data processing unit. A deep learning-based weld recognition algorithm automatically identifies the butt weld and V-groove (groove angle 60°), accurately generating weld coordinate data and transmitting it to the central control system. Based on the weld coordinate data, the central control system automatically plans the motion trajectory of the laser welding and surface treatment devices, ensuring that the processing spot and welding spot always move along the center of the groove. The operator inputs the aforementioned collaborative composite surface treatment parameters, laser welding parameters, and shielding gas parameters through the human-machine interface. The system completes parameter loading and verification, and enters the standby state after confirming there are no parameter conflicts.

[0072] (3) Synergistic composite surface treatment The central control system controls the movement of a six-axis industrial robot, simultaneously activating the plasma treatment subunit, the laser micro-texturing subunit, the bio-based nano-coating spraying unit, and the inert gas protection unit. First, the plasma pretreatment subunit generates highly active Ar-H2 plasma to decompose and peel off the oxide film (greater than 100nm thick) on the surface of 7075-T6 aluminum alloy. During this process, the robot adjusts its posture in real time to ensure a constant distance of 15mm between the plasma spray gun and the workpiece surface (including the bevel side), guaranteeing uniform and thorough removal of the oxide film in the bevel area. Subsequently, the laser micro-texturing subunit processes striped micro-textures on the oxide-removed workpiece surface (including the weld area and 10mm areas on both sides, and the bevel side), with the micro-texture direction parallel to the weld direction. Within 0.5 seconds of the laser micro-texturing completion, the bio-based nano-coating spraying unit uniformly sprays a bio-based nano-coating onto the pretreated workpiece surface through a micro-pneumatic nozzle, forming a barrier layer approximately 100nm thick. Throughout the entire process, the inert gas protection unit continuously sprays high-purity argon gas, creating a localized inert gas protective atmosphere, which, in conjunction with the nano-coating, provides dual protection against secondary oxidation. After the surface treatment is completed, the laser triangulation measurement surface quality detection subunit detects the surface roughness and micro-texture size of the workpiece. The results show that the surface roughness Ra=2.2μm, the micro-texture depth 20μm, width 50μm, and spacing 200μm all meet the set requirements and no rework is required.

[0073] (4) Multi-wavelength synergistic laser welding Within 5 seconds of surface treatment completion, the central control system activates the dual-wavelength laser generation unit, beam coupling and shaping unit, oscillating welding mechanism, and intelligent gas protection module to begin multi-wavelength collaborative laser welding. The dual-wavelength laser, coupled into a coaxial beam by the beam coupling and shaping unit, forms a central-annular composite spot and is focused onto the weld area. The central spot quickly forms a stable "keyhole" to ensure penetration depth, while the annular spot widens the molten pool and improves its shape. The oscillating mechanism causes the welding laser to oscillate along a square wave trajectory, thoroughly stirring the molten pool and promoting the escape of gases and impurities. The intelligent gas protection module's three-stage annular gas knife continuously sprays a mixed Ar-He-O2 protective gas. The inner gas knife directly protects the molten pool area, the middle gas knife forms a transitional protective atmosphere, and the outer gas knife isolates external air, creating a stable three-dimensional protective atmosphere. During welding, the OCT welding process monitoring subunit monitors the molten pool morphology, penetration depth, and weld formation quality in real time, while the infrared thermal imager temperature monitoring subunit monitors the temperature distribution in the weld area and heat-affected zone in real time. When the welding reached the 80mm mark, OCT monitoring indicated that the penetration depth was slightly below the set threshold (10mm). The data processing unit analyzed the data and determined that the laser energy utilization was slightly insufficient. It immediately generated a parameter adjustment command, fine-tuning the 1080nm laser power to 6200W while keeping the 915nm laser power unchanged at 4000W. The central control system received the command and adjusted the parameters in real time. Subsequent penetration depth monitoring showed that the penetration depth stabilized at 10.2-10.5mm, meeting the requirements. Infrared thermal imaging showed that the highest temperature in the heat-affected zone was 430℃, which did not exceed the set threshold (450℃), thus avoiding grain coarsening and joint softening problems caused by high temperatures.

[0074] (5) Post-welding treatment and quality inspection After welding is completed, the central control system controls the dual-wavelength laser generator to stop outputting laser, and at the same time controls the gas protection device to continue spraying protective gas for 10 seconds until the weld area cools to room temperature to prevent oxidation of the weld when it comes into contact with air during the cooling process; then all functional modules are shut down, the vacuum adsorption and fixture clamping are released, and the welded workpiece is removed. A comprehensive quality inspection of the workpiece was conducted: Visual inspection revealed a smooth and even weld surface, free from defects such as oxidation discoloration, undercut, incomplete penetration, and cracks. The weld width was uniform (approximately 5.5 mm), and the V-groove was fully fused. Non-destructive testing employed an X-ray inspection system to examine the internal quality of the weld, showing no defects such as porosity, inclusions, or cracks, with a defect rate of 0%. Mechanical property testing included tensile strength testing using an Instron 5982 universal testing machine. The results showed a weld tensile strength of 545 MPa, a base metal tensile strength of 580 MPa, and the weld joint tensile strength reaching 94% of the base metal's. Hardness testing used an HV-1000 Vickers hardness tester, yielding a weld hardness of 170 HV and a base metal hardness of 185 HV, with the weld hardness reaching 92% of the base metal's. Corrosion resistance testing was conducted according to ASTM B117 standards, involving a 500-hour salt spray test. After the test, no obvious corrosion marks were observed on the weld surface, demonstrating excellent corrosion resistance. The test results show that the quality of the welded joints fully meets the stringent requirements for load-bearing components in the aerospace field.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A welding system for laser welding of aluminum alloys, characterized in that, It includes a workbench (1), a six-axis industrial robot (5), a laser welding and surface treatment device (2), a gas protection device (3), and a control unit (4); The worktable (1) is used to support and fix the aluminum alloy workpiece (6). The laser welding and surface treatment device (2) includes a housing (16), which is fixedly connected to the output end of the six-axis industrial robot (5). The end of the housing (16) facing the aluminum alloy workpiece (6) is the execution end. The housing (16) is equipped with a dual-wavelength laser generating unit (17), a beam coupling and shaping unit (18), a plasma processing subunit (9), a laser micro-texturing processing subunit (10), a spraying unit (11), a laser welding mechanism, and a laser oscillation mechanism. The light outlets or output ports of the plasma processing subunit (9), the laser micro-texturing processing subunit (10), the laser welding mechanism, and the spraying unit (11) are all set facing the execution end of the housing (16). The laser output end of the dual-wavelength laser generating unit (17) is optically connected to the laser input end of the beam coupling and shaping unit (18). The laser output end of the beam coupling shaping unit (18) is connected to the laser microtexturing subunit (10) and the plasma processing subunit (9) via the optical path (7), respectively. The laser output end of the beam coupling shaping unit (18) is also connected to the input end of the laser oscillation mechanism via the optical path. The output end of the laser oscillation mechanism is connected to the optical path of the laser welding mechanism. The laser spots corresponding to the laser microtexturing subunit (10) and the plasma processing subunit (9) are located in front of the welding spot of the laser welding mechanism along the welding direction. The input end of the spraying unit (11) is connected to the output end of an external spraying pressure pump through a fluid channel; The actuator end of the housing (16) is also equipped with a gas shield (8), which has a nozzle facing the aluminum alloy workpiece (6). The input end of the gas shield (8) is connected to the output end of the gas protection device (3) through a gas pipeline. The control unit (4) is electrically connected to the six-axis industrial robot (5), the dual-wavelength laser generating unit (17), the beam coupling and shaping unit (18), the plasma processing subunit (9), the laser micro-texture processing subunit (10), the spraying unit (11), the laser oscillation mechanism, the laser welding mechanism, and the gas protection device (3), respectively.

2. The welding system for laser welding of aluminum alloys according to claim 1, characterized in that, The workbench (1) is equipped with an XYZ three-axis ball screw moving platform (19). A cast iron base (20) and a vacuum adsorption device (21) are fixedly installed on the XYZ three-axis ball screw moving platform (19). The cast iron base (20) is provided with a workpiece groove for positioning the aluminum alloy workpiece (6). The vacuum adsorption device (21) is located below the aluminum alloy workpiece (6), and the suction nozzle of the vacuum adsorption device (21) faces the aluminum alloy workpiece (6).

3. The welding system for laser welding of aluminum alloys according to claim 1, characterized in that, The gas protection device (3) includes a protective gas storage unit (13), a gas purification unit (15), and several flow control valves (14); each flow control valve (14) integrates a flow sensor and a proportional adjustment module, and the proportional adjustment module is electrically connected to the corresponding flow sensor and flow control valve (14); the outlet of the protective gas storage unit (13) is connected to the inlet of the gas purification unit (15), and the outlet of the gas purification unit (15) is connected to the inlet of each flow control valve (14) through a pipeline. The gas shield (8) is equipped with a multi-stage annular air knife protection device (12), which includes at least three concentric annular air knives: an inner layer, a middle layer, and an outer layer. Each annular air knife is connected to the outlet of the corresponding flow control valve (14) through an independent gas supply branch, and the outlet of each annular air knife is connected to the corresponding nozzle of the gas shield (8).

4. The welding system for laser welding of aluminum alloys according to claim 1, characterized in that, The control unit (4) includes a detection unit, a data processing unit and a central control system. The detection unit is fixedly installed on the housing (16) of the laser welding and surface treatment device (2) by a bracket. The signal output terminal of the detection unit is connected to the signal input terminal of the data processing unit. The data processing unit is connected to the central control system. The central control system is connected to the six-axis industrial robot (5), the dual-wavelength laser generation unit (17), the beam coupling and shaping unit (18), the plasma processing subunit (9), the laser micro-texture processing subunit (10), the spraying unit (11), the laser oscillation mechanism, the laser welding mechanism and the gas protection device (3) respectively.

5. A welding system for laser welding of aluminum alloys according to claim 4, characterized in that, The detection unit includes at least a CCD vision subunit for weld positioning, a laser triangulation subunit for surface quality detection, an optical coherence tomography subunit for real-time monitoring of the molten pool, and an infrared thermal imager subunit for temperature field monitoring.

6. The welding system for laser welding of aluminum alloys according to claim 4, characterized in that, The laser wavelengths output by the dual-wavelength laser generating unit (17) include 1080nm and 915nm, and the power ratio of the two lasers is 1:4-4:

1.

7. A welding method for laser welding of aluminum alloys, applied to the welding system for laser welding of aluminum alloys as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Clean the surface of the aluminum alloy workpiece, and then clamp and fix it on the worktable; S2. Locate the weld area using the CCD vision sub-unit of the detection unit; S3. Under the local protective atmosphere formed by the gas shield, the surface treatment of the area to be welded is carried out by plasma treatment subunit to remove the plasma oxide film of the workpiece to be welded, laser microtexturing processing subunit to laser microtexture processing of the area to be welded, and bio-based nano-coating spraying of the area to be welded by spraying unit. S4. Within the set time interval after the surface treatment is completed, the dual-wavelength laser generation unit is activated. After the laser is processed by the beam coupling and shaping unit and the laser oscillation mechanism, it is oscillated and welded by the laser welding mechanism. During the welding process, the gas protection device provides multi-level gas protection. At the same time, based on the real-time monitoring data collected by the detection unit, the control unit executes closed-loop feedback control to ensure the stability of the welding parameters. S5. After welding, continue gas protection until the weld cools down, and then perform quality inspection on the workpiece.

8. A welding method for laser welding of aluminum alloys according to claim 7, characterized in that, In step S3, the plasma oxide film removal uses a mixture of Ar and H2 as the working gas; the texture type of the laser microtexturing is grid-like or striped, with a depth of 10-20 μm; and the thickness of the bio-based nanocoating is 50-100 nm.

9. A welding method for laser welding of aluminum alloys according to claim 7, characterized in that, The time interval after surface treatment in step S4 shall not exceed 5-8 seconds; the multi-stage gas protection uses a mixture of Ar, He and O2, wherein the volume fraction of O2 is 1.0%-1.5%; The dual-wavelength laser employs a central spot, annular spot, or a central-annular composite spot mode; the oscillation frequency of the oscillation welding is 10-400Hz, and the oscillation amplitude is 0-5mm.

10. A welding method for laser welding of aluminum alloys according to claim 7, characterized in that, In step S4, the closed-loop feedback control involves real-time monitoring of the molten pool morphology and weld depth by an optical coherence tomography subunit and monitoring of the heat-affected zone temperature by an infrared thermal imager subunit. When the monitoring data of the molten pool morphology, weld depth, or heat-affected zone temperature deviate from the preset process threshold, the data processing unit generates an adjustment command, and the central control system adjusts the laser power and welding speed in real time, or adjusts the protective gas flow parameters through a flow control valve.

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