CN-122007613-A - Welding system and method for aluminum alloy laser welding

CN122007613ACN 122007613 ACN122007613 ACN 122007613ACN-122007613-A

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, wherein the workbench is used for bearing and fixing an aluminum alloy workpiece, a dual-wavelength laser generating unit, a beam coupling shaping unit, a plasma treatment 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 treatment device, and the gas protection device comprises a multi-stage annular gas knife protection device. The method comprises the steps of workpiece clamping and fixing, CCD visual weld positioning, plasma film removal, laser micro-texture processing, nano coating spraying, dual-wavelength swing laser welding and post-welding detection. The invention improves the laser absorptivity of the aluminum alloy in the laser welding process, reduces the welding defect rate of the aluminum alloy and improves the quality of welding seams.

Inventors

ZHOU LIN
LV HAITING
Xiao Fengnan
JI XUE
ZHANG SIYU
Zuo Chenxin
LI ZHIQIANG

Assignees

大连科技学院

Dates

Publication Date: 20260512
Application Date: 20260313

Claims (10)

1. A welding system for aluminum alloy laser welding, which is characterized by comprising 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 workbench (1) is used for bearing and fixing an aluminum alloy workpiece (6); the laser welding and surface treatment device (2) comprises a shell (16), wherein the shell (16) is fixedly connected to the output end of the six-axis industrial robot (5), and one end of the shell (16) facing the aluminum alloy workpiece (6) is an execution end; The dual-wavelength laser generating unit (17), the beam coupling shaping unit (18), the plasma processing subunit (9), the laser micro-texture processing subunit (10), the spraying unit (11), the laser welding mechanism and the laser swinging mechanism are arranged in the shell (16), and the light outlets or the output outlets of the plasma processing subunit (9), the laser micro-texture processing subunit (10), the laser welding mechanism and the spraying unit (11) are all arranged towards the execution end of the shell (16); The laser output end of the beam coupling shaping unit (18) is respectively connected with the laser micro-texture processing subunit (10) and the plasma processing subunit (9) through the optical path (7), and the laser output end of the beam coupling shaping unit (18) is also connected with the input end of the laser swing mechanism through the optical path, and the output end of the laser swing mechanism is connected with the optical path of the laser welding mechanism; the input end of the spraying unit (11) is connected with the output end of an external spraying pressure pump through a fluid channel; The execution end of the shell (16) is also provided with a gas protection cover (8), the gas protection cover (8) is provided with a nozzle towards the aluminum alloy workpiece (6), and the input end of the gas protection cover (8) is connected with the output end of the gas protection device (3) through a gas transmission pipeline; The control unit (4) is respectively and electrically connected with the six-axis industrial robot (5), the dual-wavelength laser generating unit (17), the beam coupling shaping unit (18), the plasma processing subunit (9), the laser micro-texture processing subunit (10), the spraying unit (11), the laser swing mechanism, the laser welding mechanism and the gas protection device (3).
2. Welding system for laser welding of aluminium alloys according to claim 1, characterized in that the table (1) is provided with an XYZ three-axis ball screw moving platform (19), the XYZ three-axis ball screw moving platform (19) is fixedly provided with a cast iron base (20) and a vacuum suction device (21), the cast iron base (20) is provided with a workpiece groove for positioning the aluminium alloy workpiece (6), the vacuum suction device (21) is located below the aluminium alloy workpiece (6), and the suction nozzle of the vacuum suction device (21) faces the aluminium alloy workpiece (6).
3. Welding system for laser welding of aluminium alloys according to claim 1, characterized in that the gas protection device (3) comprises a protection gas storage unit (13), a gas purification unit (15) and a number of flow control valves (14), each flow control valve (14) being integrated with a flow sensor and a proportional adjustment module, the proportional adjustment module being electrically connected to the corresponding flow sensor and flow control valve (14), respectively, the gas outlet of the protection gas storage unit (13) being in communication with the gas inlet of the gas purification unit (15), the gas outlet of the gas purification unit (15) being in communication with the gas inlet of each flow control valve (14) respectively by means of a pipeline; The gas protection cover (8) is internally provided with a multistage annular gas knife protection device (12), the multistage annular gas knife protection device (12) at least comprises an inner layer, a middle layer and an outer layer, each layer of annular gas knife is communicated with the gas outlet of the corresponding flow control valve (14) through an independent gas transmission branch, and the gas outlet of each layer of annular gas knife is communicated with the corresponding nozzle of the gas protection cover (8).
4. The welding system for aluminum alloy laser welding according to claim 1, wherein the control unit (4) comprises a detection unit, a data processing unit and a central control system, the detection unit is fixedly arranged on a shell (16) of the laser welding and surface processing device (2) through a bracket, a signal output end of the detection unit is in signal connection with a signal input end of the data processing unit, the data processing unit is in signal connection with the central control system, and the central control system is respectively in control connection with the six-axis industrial robot (5), the dual-wavelength laser generating unit (17), the beam coupling shaping unit (18), the plasma processing subunit (9), the laser micro-texture processing subunit (10), the spraying unit (11), the laser swinging mechanism, the laser welding mechanism and the gas protecting device (3).
5. The welding system for laser welding of aluminum alloys of claim 4, wherein said detection unit comprises at least a CCD vision subunit for weld positioning, a laser triangulation subunit for surface quality detection, an optical coherence tomography subunit for molten pool real-time monitoring, and a thermal infrared imager subunit for temperature field monitoring.
6. The welding system for aluminum alloy laser welding according to claim 4, wherein the laser wavelength output by the dual-wavelength laser generating unit (17) comprises 1080nm and 915nm, and the power ratio of the two laser paths 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 according to any one of claims 1 to 5, characterized by comprising the steps of: s1, cleaning the surface of an aluminum alloy workpiece, and then clamping and fixing the aluminum alloy workpiece on a workbench; S2, positioning a welding line area through a CCD vision subunit of the detection unit; s3, carrying out surface treatment on the to-be-welded area under the local protective atmosphere formed by the gas shield, sequentially removing a plasma oxide film from the to-be-welded area of the workpiece through the plasma treatment subunit, carrying out laser micro-texture processing on the to-be-welded area through the laser micro-texture processing subunit, and carrying out bio-based nano coating spraying on the to-be-welded area through the spraying unit; S4, starting a dual-wavelength laser generating unit within a set time interval after finishing surface treatment, and performing swing welding by a laser welding mechanism after laser is processed by a beam coupling shaping unit and the laser swing mechanism; And S5, continuing gas protection until the welding line is cooled after welding is finished, and then carrying out quality detection on the workpiece.
8. The welding method for aluminum alloy laser welding according to claim 7, wherein in the step S3, the plasma oxide film is removed by using a mixed gas of Ar and H 2 as a working gas, the texture type of the laser micro-texture processing is in a grid shape or a stripe shape, the depth is 10-20 μm, and the thickness of the bio-based nano coating is 50-100nm.
9. The welding method for aluminum alloy laser welding according to claim 7, wherein the set time interval after finishing the surface treatment in the step S4 is not more than 5-8 seconds, wherein the multistage gas shield adopts mixed gas of Ar, he and O 2 , wherein the volume fraction of O 2 is 1.0% -1.5%; the dual-wavelength laser adopts a central light spot, an annular light spot or a central-annular composite light spot mode, the swing frequency of swing welding is 10-400Hz, and the swing amplitude is 0-5mm.
10. The welding method according to claim 7, wherein the closed loop feedback control in the step S4 is to monitor the molten pool morphology and penetration in real time by an optical coherence tomography subunit, monitor the heat affected zone temperature by a thermal infrared imager subunit, and when the monitored data of the molten pool morphology, penetration or heat affected zone temperature deviate from the preset process threshold, generate an adjustment command by a data processing unit, and the central control system adjusts the laser power, welding speed in real time, or adjusts the flow parameters of the shielding gas by a flow control valve.

Description

Welding system and method for aluminum alloy laser welding Technical Field The invention belongs to the technical field of laser welding, and particularly relates to a welding system and a method for aluminum alloy laser welding, which are particularly suitable for precisely welding aluminum alloy materials with high reflection, high heat conduction and high hot cracking tendency, such as 2000 series (such as 2024 and 2017), 6000 series (such as 6061 and 6063), 7000 series (such as 7075 and 7050) and the like. The system and the method can be widely applied to high-end manufacturing industries with severe requirements on welding quality, production efficiency and environmental protection, such as aerospace, new energy automobiles, 3C electronics, rail transit, ship manufacturing and the like, can effectively solve the technical bottleneck of welding of the key components of the aluminum alloy in the industries, and improve the reliability and the service life of products. Background In the field of modern industrial manufacturing, the aluminum alloy is continuously expanded in application range by virtue of comprehensive advantages of low density, high strength, good corrosion resistance, excellent processability, good electromagnetic shielding performance and the like, and gradually extends from the traditional aerospace field to a plurality of high-end manufacturing fields such as new energy automobile bodies and battery packs, 3C electronic equipment shells and internal structural members, rail transit vehicle bodies, ship lightweight members and the like. As a typical high-energy density welding technology, the laser welding technology has the outstanding characteristics of narrow welding line, small heat affected zone, small welding deformation, high welding efficiency, easy realization of automation and intelligent control and the like, and gradually replaces the traditional arc welding technology, thereby becoming one of the main stream technologies for aluminum alloy precision welding. However, aluminum alloys have very strong laser reflectivity in the near infrared band, initial reflectivity as high as 80% -90%, and very low absorptivity for common lasers at room temperature. A large amount of laser energy is reflected to cause energy waste, optical components can be damaged, enterprises need to use higher power lasers, and initial investment cost of equipment is increased. Compact Al2O3 oxide films are easy to form on the surface of the aluminum alloy, the melting point is far higher than that of a matrix, and defects are easy to remain and form during welding. The existing treatment method is that by mechanical polishing, uneven surface roughness and secondary oxidation are easy to cause, chemical corrosion pollutes the environment and hydrogen elements are possibly introduced, the traditional plasma cleaning and removal are not thorough, and single laser cleaning is easy to cause secondary oxidation and possibly damage a substrate. The aluminum alloy has high heat conductivity, the 'small hole' effect is difficult to stably maintain, air holes and incomplete penetration defects are easy to form, the risk of hydrogen holes caused by the water absorption of an oxide film is high, the aluminum alloy is easy to generate crystallization cracks and liquefaction cracks when being welded in a crystallization temperature range, and the defect rate in the prior art is generally more than 15%. The original strengthening mechanism of the aluminum alloy is damaged by the extreme thermal cycle of laser welding, the low-melting-point alloy elements are evaporated and burnt, a coarse as-cast structure is formed on the welding seam, the hardness and the strength of the welding seam are obviously reduced, meanwhile, stress concentration is formed on the defect of the welding seam, and the mechanical property is further reduced. The existing welding system is mainly controlled in an open loop mode, the dependence on the skill of operators is strong, the detection precision of part of detection components on microscopic defects is insufficient, closed loop control cannot be realized, the surface treatment and the welding module are independent, cooperative control is lacked, the gas protection mode is single, and the positioning and track tracking precision is limited. The prior art scheme is usually optimized for only a single problem, and is difficult to realize accurate defect control from the source and the process, and the optimal balance among the thoroughness of air hole inhibition, the process stability, the production efficiency and the environmental protection is difficult to obtain. Disclosure of Invention The invention provides a welding system and a method for aluminum alloy laser welding, aiming at solving the technical problems that the aluminum alloy near infrared laser absorptivity is low, a surface oxide film is difficult to remove and is easy to damage secondarily, pores and cracks are easy to ge