Aluminum-copper dissimilar metal composite laser welding method and aluminum-copper welding head

Abstract

The embodiment of the invention provides an aluminum-copper dissimilar metal composite laser welding method and an aluminum-copper welding head, and relates to the technical field of laser welding. The aluminum-copper dissimilar metal composite laser welding method comprises the following steps that S1, an aluminum metal plate and a copper metal plate are arranged in a stacked mode and relatively fixed, and a to-be-welded part is obtained; s2, blue laser, point infrared laser and ring infrared laser are combined and focused to a welding site on the surface of the to-be-welded part, and a composite laser beam is formed; and S3, the composite laser beam is kept in an oscillating swing mode to weld the to-be-welded part. According to the aluminum-copper dissimilar metal composite laser welding method and the aluminum-copper welding head, the porosity in a welding seam can be reduced, and the mechanical property and ductility of the welding seam are improved.

Description

Technical Field

[0001] The present application relates to the technical field of laser welding, and in particular to an aluminum-copper dissimilar metal composite laser welding method and an aluminum-copper welding joint. Background Art

[0002] The tabs in the power soft-pack batteries of new energy vehicles are usually made of highly conductive copper and connected to the busbar in parallel or series, which consumes a lot of copper resources in the battery manufacturing process. However, my country's existing copper resources are relatively scarce and it is difficult to meet the large demand for copper resources in the industrial field. Based on the advantages of aluminum and aluminum alloys, such as light weight, low cost, strong electrical conductivity, thermal conductivity and corrosion resistance, more and more industrial fields have begun to study the feasibility of replacing copper with aluminum.

[0003] After a lot of exploration, aluminum-copper welding joints have become the focus of attention in the application of the automotive power battery industry. However, aluminum and copper are dissimilar metals with very different chemical and physical properties such as thermal conductivity, thermal expansion coefficient, melting point, etc., and the limited mutual solubility leads to the formation of a large number of highly brittle intermetallic compound phases at the weld, which will reduce the strength and ductility of the weld. In addition, aluminum and copper metals have strong thermal conductivity and high reflectivity to infrared lasers. In conventional infrared laser welding, the laser energy acting on the weld area is very limited, and the minimum power of laser welding needs to be increased. The porosity in the weld also increases significantly.

[0004] Therefore, it is necessary to develop a laser welding method for aluminum-copper dissimilar metals that can reduce the porosity in the weld and improve the mechanical properties and ductility of the weld to meet the urgent needs of high-quality aluminum-copper welded joints. Summary of the invention

[0005] The purpose of the embodiments of the present application is to provide an aluminum-copper dissimilar metal composite laser welding method and an aluminum-copper welding joint, which can reduce the porosity in the weld and improve the mechanical properties and ductility of the weld.

[0006] In a first aspect, an embodiment of the present application provides an aluminum-copper dissimilar metal composite laser welding method, which comprises the following steps: S1. stacking and relatively fixing the aluminum metal sheet and the copper metal sheet to obtain a part to be welded; S2, combining the blue laser, the point infrared laser and the ring infrared laser, and focusing them to the welding position on the surface of the workpiece to be welded to form a composite laser beam; S3, welding the parts to be welded in a manner that the composite laser beam maintains an oscillating motion.

[0007] In the above technical scheme, a blue laser is used to preheat the surface of aluminum or copper metal, and the effect of blue light is used to improve the laser absorption rate of high-reflective metals to lasers; the high energy density characteristics of point infrared lasers (central infrared beams) are used to maintain deep fusion welding (also called keyhole welding) mode during the welding process of highly reflective metals; the compounding of ring infrared lasers (ring infrared beams) is used to reduce the temperature gradient on the surface of the material during single central infrared beam welding, stabilize the welding keyhole, and further improve the utilization rate of laser energy in the welding keyhole. The oscillation of the composite laser beam can provide stirring force for the molten pool, which is conducive to the floating of bubbles, thereby achieving the purpose of reducing pores, and is conducive to the mixing of dissimilar metal base materials and the refinement of the grains in the weld zone, thereby effectively eliminating the welding difficulties caused by the poor performance differences of dissimilar metals, thereby reducing the porosity in the weld and improving the mechanical properties and ductility of the weld.

[0008] In a possible implementation, the aluminum metal includes aluminum or an aluminum alloy, and the copper metal includes copper or a copper alloy.

[0009] In a possible implementation, in step S1, the aluminum metal sheet and the copper metal sheet are polished, cleaned, dried, and then stacked and fixed with a welding fixture; And / or, the aluminum metal plate and the copper metal plate are stacked up and down or stacked down and up.

[0010] In the above technical solution, a welding fixture is used to clamp and fix the stacked aluminum-copper metals to prevent thermal deformation during welding.

[0011] In a possible implementation, in step S2, a blue laser and an infrared tunable mode laser are used to emit a blue laser, a point infrared laser and a ring infrared laser, and the beams are combined through a welding head; And / or, the distance from the focus of each laser beam to the welding site is adjusted so that the beam waist position of each laser beam is located at the welding site to form the composite laser beam.

[0012] In a possible implementation, in the composite laser beam, the radius of the blue laser is 0.8-1 mm, the diameter of the point infrared laser is 0.01-0.05 mm, the diameter of the ring infrared laser is 0.1-0.3 mm, and the central energy density is >10 6 W / mm 2 .

[0013] In the above technical solution, the central energy density is greater than 10 6 W / mm 2 The keyhole welding mode is reached.

[0014] In a possible implementation, the oscillation mode of the composite laser beam includes at least one of an ∞ type, an 8 type, and an o type.

[0015] In the above technical solution, the composite laser beam in oscillating mode has a strong stirring effect on the welding molten pool, which can significantly refine the grains and suppress weld porosity, and is a feasible way to achieve high-quality welding.

[0016] In a possible implementation, the welding process parameters are: the power of the blue light laser is 100-300 W, the power of the point infrared laser is 500-1000 W, and the power of the ring infrared laser is 500-1000 W; the amplitude of the oscillation swing is 0.5-2 mm, and the frequency is 50-200 Hz; the welding speed is 10-100 mm / s, and the defocus is 0-0.5 mm.

[0017] In a possible implementation, in step S3, an inert medium is used to protect the welding area during the welding process; optionally, the flow rate of the inert medium is 5-15 L / min.

[0018] In the second aspect, an embodiment of the present application provides an aluminum-copper welded joint, which is manufactured by the aluminum-copper dissimilar metal composite laser welding method provided by the first aspect, wherein the aluminum-copper welded joint comprises an aluminum metal plate and a copper metal plate that are stacked and welded together, the porosity in the weld is <0.5 vol.%, the shear strength is 80-110 MPa, and the elongation is 6%-8%.

[0019] In the above technical solution, compared with the existing laser welding technology, the weld is well formed, free of welding defects such as cracks, pores, and lack of fusion, and the welding process performance is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic diagram of an aluminum-copper dissimilar metal composite laser welding method provided in an embodiment of the present application; Figure 2 This is a macroscopic morphology of the aluminum-copper welding joint at the weld of Example 1; Figure 3 This is a shear performance diagram of the weld of the aluminum-copper welded joint of Example 1; Figure 4This is a macroscopic morphology of the aluminum-copper welding joint at the weld of Example 2; Figure 5 This is a shear performance diagram of the weld of the aluminum-copper welded joint of Example 2; Figure 6 This is a macroscopic morphology of the aluminum-copper welding joint at the weld of Example 3; Figure 7 This is a shear performance diagram of the weld of the aluminum-copper welded joint of Example 3. DETAILED DESCRIPTION

[0022] Aluminum-copper welded joints have become a focus of attention in the application of the automotive power battery industry. However, aluminum and copper have very different chemical and physical properties such as thermal conductivity, thermal expansion coefficient, melting point, etc., and their limited mutual solubility leads to the formation of a large number of highly brittle intermetallic compound phases at the weld, thereby reducing the strength and ductility of the welded joint.

[0023] Aluminum and copper metals have strong thermal conductivity and high reflectivity to infrared lasers (1064 nm). In laser welding, the laser energy acting on the weld area is very limited, which increases the minimum power of laser welding of high-reflectivity dissimilar metals and significantly increases the porosity in the weld. The blue light and infrared laser composite technology can improve the laser absorption rate of high-reflectivity aluminum and copper metals, making the melting depth easy to control and improving the strength of the welded joint. However, due to the active nature of aluminum and copper metals and their easy oxidation, hydrogen pores and cavitation formed by the collapse of some keyholes are easily formed in the weld, reducing the performance of the welded joint.

[0024] At present, the method for reducing porosity in laser welding is mainly to increase the stirring effect of the molten pool. After analyzing the prior art, it can be found that there is a prior art that discloses a method of introducing ultrasonic vibration and pulse stirring in ultrasonic-assisted pulse laser-MIG composite heat source welding to increase the fluidity of the aluminum alloy molten pool, which effectively solves the problem of more pores being easily formed in the aluminum alloy laser-MIG composite heat source welding joint, but the introduction of an external auxiliary energy field device in the lap laser welding of aluminum-copper thin plates is not conducive to high-efficiency batch production. There is also a prior art that uses dual-focus laser-TIG composite welding technology, which uses two beams of laser and arc to act on the welding area, which can effectively eliminate welding porosity defects, but its welding speed is relatively slow. In addition, there is a prior art that introduces an oscillating scanning laser beam in laser-arc composite welding, which has a stronger weld porosity suppression ability and improves weld strength, but the oscillating laser beam is around the arc action point to achieve synergistic strengthening in a local micro-area, and the welding effect needs to be improved.

[0025] After extensive research, the applicant discovered that the development of a blue light-spot ring infrared composite laser oscillating welding method for aluminum-copper dissimilar metals can achieve in-situ preheating of a stable molten pool, while suppressing spatter, reducing porosity, preventing cracks, and improving weld mechanical properties, thereby overcoming the shortcomings of the prior art and meeting the urgent need for high-quality Al / Cu welds.

[0026] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0027] The aluminum-copper dissimilar metal composite laser welding method and the aluminum-copper welding joint according to the embodiment of the present application are described in detail below.

[0028] Please see Figure 1 The present invention provides a method for laser welding of aluminum-copper dissimilar metal composites, which comprises the following steps: S1. Stacking and relatively fixing aluminum metal plates and copper metal plates to obtain parts to be welded.

[0029] In some embodiments of the present application, the aluminum metal includes pure aluminum (such as 1050, 1060 and other grades) or aluminum alloys (such as 5052, 6061 and other grades), the aluminum metal plate is selected from the above-mentioned aluminum metal materials, the surface should be clean and free of oxide layer, the thickness of the aluminum metal plate is 0.1-1 mm, and the thickness tolerance is controlled within ±0.05 mm; the copper metal includes pure copper (such as T2) or copper alloys (such as brass H70, tin bronze QSn6.5-0.1), the surface should be clean and free of oil, the copper metal plate is selected from the above-mentioned copper metal materials, the thickness of the copper metal plate is 0.1-1 mm, and the thickness tolerance is controlled within ±0.05 mm.

[0030] In some embodiments of the present application, in step S1, the plates to be welded: aluminum metal plates and copper metal plates are polished, (scrubbed with acetone and ultrasonically) cleaned and dried, and then stacked and fixed with a welding fixture, wherein the polishing method may be sandpaper, and the cleaning method may be acetone scrubbed and ultrasonically cleaned; In step S1, the aluminum metal plate can be directly fixed on the top or bottom of the copper metal plate. Accordingly, the aluminum metal plate and the copper metal plate are stacked up and down or stacked up and down. The stacking of the aluminum metal plate and the copper metal plate is suitable for occasions with strict requirements on the heat affected zone, but the bonding strength between the two may be insufficient. The stacking of the copper metal plate and the aluminum metal plate is suitable for occasions where high bonding strength is required, but it is necessary to prevent aluminum from overheating. Figure 1It shows that the aluminum metal sheet and the copper metal sheet are stacked up and down, which can ensure that the welding joint has matching strength and plasticity.

[0031] S2. Combining the blue laser, the point infrared laser and the ring infrared laser, and focusing them to the welding position on the surface of the workpiece to be welded, to form a composite laser beam.

[0032] In some embodiments of the present application, in step S2, a blue laser and an infrared adjustable mode laser are used to emit a blue laser, a point infrared laser (central infrared beam) and a ring infrared laser (ring infrared beam), and the beams are combined through a welding head. Exemplarily, the laser used is a beam mode adjustable laser, Shanghai Feibo Laser Technology Co., Ltd., equipment model: YDFL-2000 / 4000-PAM+; and a blue laser, Guangdong Guangdong-Hong Kong-Macao Greater Bay Area Hard Technology Innovation Institute, model: BLF-455-800-2 (the subsequent embodiments and comparative examples use the same equipment, which will not be repeated). In other embodiments, other lasers that can emit blue lasers, point infrared lasers and ring infrared lasers can also be used, which can be a single laser or a combination of different lasers.

[0033] The focusing method is to adjust the distance from the focus of each laser beam to the welding site so that the waist position of each laser beam is located at the welding site on the same plane to form a composite laser beam. The "waist position" is a point where the energy and quality of the beam emitted by the laser are the best. The waists of the above three laser beams (blue laser, point infrared laser and ring infrared laser) overlap. Figure 1 The weld site shown is the upper surface of the aluminum sheet metal.

[0034] In some embodiments of the present application, the composite laser beam refers to the laser beam formed by combining and focusing the above three laser beams (blue laser, point infrared laser and ring infrared laser). During the welding process, the composite laser beam remains in the combined and focused state. In the composite laser beam formed, the radius of the blue laser is 0.8-1 mm, the diameter of the point infrared laser is 0.01-0.05 mm, the diameter of the ring infrared laser is 0.1-0.3 mm, and the central energy density is >10 6 W / mm 2 , in order to achieve the keyhole welding mode. The size of each laser beam mentioned above is based on the size of each laser beam on the same plane to be welded (such as the upper surface of the aluminum metal plate). The size refers to the outer diameter. The central energy density of the composite laser beam is mainly determined by the point infrared laser. The energy density of the other beams is much smaller than that of the point infrared laser. Therefore, the energy density of the point infrared laser can be adjusted to control the central energy density of the composite laser beam.

[0035] S3. The composite laser beam is kept in an oscillating manner to weld the workpiece. During the welding process, the surface of the aluminum metal sheet or the copper metal sheet is preheated by a blue light laser, a keyhole welding (also called keyhole welding) mode is formed by a central infrared laser, and a ring infrared laser is used to stabilize the keyhole and reduce spatter.

[0036] During the welding process, the oscillation frequency and amplitude of the composite laser beam are adjusted to keep the composite laser beam oscillating and swinging, and the welding speed is controlled by a robotic arm to form a continuous weld. The swing mode of the composite laser beam includes at least one of the ∞ type, 8 type, and o type, that is, the waist position of the three overlapping laser beams maintains a high-frequency vibration of "∞ type, 8 type, and o type".

[0037] During the welding process, the power of the three laser beams is set respectively, and the dissimilar metals are welded at a predetermined welding speed, wherein the process parameters include the welding speed and the power of the three laser beams.

[0038] In some embodiments of the present application, the welding process parameters are: the power of the blue light laser is 100-300 W, the power of the point infrared laser is 500-1000 W, and the power of the ring infrared laser is 500-1000 W; the amplitude of the oscillation swing is 0.5-2 mm, and the frequency is 50-200 Hz; the welding speed is 10-100 mm / s, and the defocus is 0-0.5 mm.

[0039] In some embodiments of the present application, in step S3, an inert medium is used to protect the welding area during the welding process; optionally, the flow rate of the inert medium is 5-15 L / min.

[0040] In addition, an embodiment of the present application provides an aluminum-copper welded joint, which is manufactured by the aluminum-copper dissimilar metal composite laser welding method of the aforementioned embodiment. The aluminum-copper welded joint includes an aluminum metal plate and a copper metal plate that are stacked and welded together. The porosity in the weld is <0.5 vol.%, the shear strength is 80-110 MPa, and the elongation is 6%-8%.

[0041] The features and performance of the present application are further described in detail below in conjunction with the embodiments.

[0042] Example 1 This embodiment provides an aluminum-copper dissimilar metal composite laser welding method, the steps are as follows: S1. The plates to be welded: the aluminum metal plate is polished on the copper metal plate with sandpaper, scrubbed with acetone, ultrasonically cleaned and dried, and fixed with a welding fixture, wherein the aluminum metal plate is overlapped on top of the copper metal plate.

[0043] S2. A semiconductor blue laser and an infrared spot-ring beam adjustable mode laser emit blue laser, spot infrared laser (central infrared beam) and ring infrared laser (ring infrared beam), which are combined through a welding head to focus multiple laser beams onto the upper surface of the aluminum metal sheet to form a composite laser beam.

[0044] S3. Control the welding head to keep the light beam oscillating for welding. The laser oscillation mode is "∞" type. The process parameters are as follows: blue light laser power is 100 W, central infrared laser power is 600 W, outer ring infrared laser power is 700 W, amplitude is 0.5 mm, oscillation frequency is 150 Hz, welding speed is 30 mm / s, defocus is 0 mm, and flow rate of inert medium is 15 L / min. The above process parameters are used to achieve high reflectivity aluminum-copper dissimilar metal connection to obtain an aluminum-copper welding joint.

[0045] The macrostructure and shear properties of the brazed joint at the weld are as follows: Figure 2 and Figure 3 As shown, the weld porosity is calculated using Image-ProPlus software (the ratio of the pore area to the weld area in the metallographic photograph). The weld of the aluminum-copper welded joint obtained in this embodiment has low porosity (<0.5 vol.%), fine grain structure, thin brittle layer at the aluminum-copper interface, low brittle phase content, maximum shear strength of 110 MPa, and elongation of 6%.

[0046] Example 2 This embodiment provides an aluminum-copper dissimilar metal composite laser welding method, the steps are as follows: S1. Grind the plate to be welded with sandpaper, scrub with acetone, clean and dry with ultrasonic cleaning, and fix the aluminum and copper dissimilar metals with a welding fixture, wherein the aluminum metal is above the copper metal.

[0047] S2, a semiconductor blue laser and an infrared spot ring beam adjustable mode laser emit blue laser, spot infrared laser (central infrared beam) and ring infrared laser (ring infrared beam), and combine the beams through a welding head so that multiple laser beams are focused onto the overlapping upper surface of the dissimilar metals.

[0048] S3. Control the welding head to keep the light beam oscillating and swinging. The laser swing mode is "8" type. The process parameters are composed of the following: blue light laser power is 200 W, central infrared laser power is 700 W, outer ring infrared laser power is 800 W, amplitude is 1.0 mm, oscillation frequency is 100 Hz, welding speed is 50 mm / s, defocus is 0.2 mm, and flow rate of inert medium is 10 L / min, to obtain an aluminum-copper welding joint.

[0049] The weld macrostructure and shear properties of the brazed joint at the weld are as follows Figure 4 and Figure 5 As shown, the weld porosity is calculated using Image-Pro Plus software (the ratio of the pore area to the weld area in the metallographic photograph). The weld porosity of the aluminum-copper welded joint obtained in this embodiment is low (<0.5 vol.%), the grain structure is fine, the brittle layer of the aluminum-copper interface layer is thin, the brittle phase content is small, the maximum shear strength is 105 MPa, and the elongation is 7%.

[0050] Example 3 This embodiment provides an aluminum-copper dissimilar metal composite laser welding method, the steps are as follows: S1, grinding the plate to be welded with sandpaper, scrubbing with acetone, and ultrasonically cleaning and drying, and fixing the aluminum and copper dissimilar metals with a welding fixture, wherein the aluminum metal is above the copper metal; S2, using a semiconductor blue laser and an infrared spot ring beam adjustable mode laser to emit a blue laser, a spot infrared laser (central infrared beam) and a ring infrared laser (ring infrared beam), and combining the beams through a welding head so that the multiple laser beams are focused onto the overlapping upper surface of the dissimilar metals; S3. Control the welding head to keep the light beam oscillating and swinging. The laser swing mode is "o" type. The process parameters are composed of the following: blue light laser power is 300 W, central infrared laser power is 600 W, outer ring infrared laser power is 800 W, amplitude is 1.5 mm, oscillation frequency is 70 Hz, welding speed is 70 mm / s, defocus is 0.4 mm, and the flow rate of inert medium is 5 L / min, to obtain an aluminum-copper welding joint.

[0051] The macrostructure and shear properties of the brazed joint at the weld are as follows: Figure 6 and Figure 7 As shown, the weld porosity is calculated using Image-ProPlus software (the ratio of the pore area to the weld area in the metallographic photograph). The weld of the aluminum-copper welded joint obtained in this embodiment has low porosity (<0.5 vol.%), fine grain structure, thin brittle layer at the aluminum-copper interface, low brittle phase content, maximum shear strength of 100 MPa, and elongation of 8%.

[0052] Comparative Example 1 This comparative example provides an aluminum-copper dissimilar metal composite laser welding method, and the steps are different from those in Example 1 in that a point infrared laser (central infrared beam) and a ring infrared laser (annular infrared beam) are emitted, but a blue light laser is not included, and finally an aluminum-copper welding joint is obtained.

[0053] The porosity of the weld of the obtained aluminum-copper welded joint is 7.5 vol.%, the maximum shear strength is 60 MPa, and the elongation is 2%.

[0054] Comparative Example 2 This comparative example provides an aluminum-copper dissimilar metal composite laser welding method, and the steps are different from those in Example 1 in that: blue light laser and ring infrared laser (ring infrared beam) are emitted, and point infrared laser (central infrared beam) is not included, and finally an aluminum-copper welding joint is obtained.

[0055] The porosity of the weld of the obtained aluminum-copper welded joint is 2.5 vol.%, the maximum shear strength is 90 MPa, and the elongation is 6%.

[0056] Comparative Example 3 This comparative example provides an aluminum-copper dissimilar metal composite laser welding method, and the steps are different from those in Example 1 in that: a blue light laser and a point infrared laser (central infrared beam) are emitted, but a ring infrared laser (annular infrared beam) is not included, and finally an aluminum-copper welding joint is obtained.

[0057] The porosity of the weld of the obtained aluminum-copper welded joint is 4.5 vol.%, the maximum shear strength is 80 MPa, and the elongation is 4%.

[0058] In summary, the aluminum-copper dissimilar metal composite laser welding method and the aluminum-copper welding joint of the embodiment of the present application can reduce the porosity in the weld and improve the mechanical properties and ductility of the weld.

[0059] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for laser welding of aluminum-copper dissimilar metal composites, characterized in that: It includes the following steps: S1. stacking and relatively fixing the aluminum metal sheet and the copper metal sheet to obtain a part to be welded; S2, combining the blue laser, the point infrared laser and the ring infrared laser, and focusing them to the welding position on the surface of the workpiece to be welded to form a composite laser beam; S3, welding the parts to be welded in a manner that the composite laser beam maintains an oscillating motion.

2. The aluminum-copper dissimilar metal composite laser welding method according to claim 1, characterized in that: The aluminum metal includes aluminum or an aluminum alloy, and the copper metal includes copper or a copper alloy.

3. The aluminum-copper dissimilar metal composite laser welding method according to claim 1, characterized in that: In step S1, the aluminum metal sheet and the copper metal sheet are polished, cleaned, dried, stacked, and fixed with a welding fixture; And / or, the aluminum metal plate and the copper metal plate are stacked up and down or stacked down and up.

4. The aluminum-copper dissimilar metal composite laser welding method according to claim 1, characterized in that: In step S2, a blue laser and an infrared tunable mode laser are used to emit a blue laser, a point infrared laser and a ring infrared laser, and the beams are combined through a welding head; And / or, the distance from the focus of each laser beam to the welding site is adjusted so that the beam waist position of each laser beam is located at the welding site to form the composite laser beam.

5. The aluminum-copper dissimilar metal composite laser welding method according to claim 1, characterized in that: In the composite laser beam, the radius of the blue laser is 0.8-1 mm, the diameter of the point infrared laser is 0.01-0.05 mm, the diameter of the ring infrared laser is 0.1-0.3 mm, and the central energy density is >10 6 W / mm 2 .

6. The aluminum-copper dissimilar metal composite laser welding method according to claim 1, characterized in that: The oscillation mode of the composite laser beam includes at least one of ∞ type, 8 type, and o type.

7. The aluminum-copper dissimilar metal composite laser welding method according to claim 1 or 6, characterized in that: The welding process parameters are as follows: the power of the blue laser is 100-300 W, the power of the point infrared laser is 500-1000 W, and the power of the ring infrared laser is 500-1000 W; the amplitude of the oscillation is 0.5-2 mm, and the frequency is 50-200 Hz; the welding speed is 10-100 mm / s, and the defocus is 0-0.5 mm.

8. The aluminum-copper dissimilar metal composite laser welding method according to claim 1, characterized in that: In step S3, an inert medium is used to protect the welding area during the welding process.

9. The aluminum-copper dissimilar metal composite laser welding method according to claim 8, characterized in that: The flow rate of the inert medium is 5-15 L / min.

10. An aluminum-copper welding joint, characterized in that: It is made by the aluminum-copper dissimilar metal composite laser welding method as described in any one of claims 1 to 9, the aluminum-copper welded joint comprises an aluminum metal plate and a copper metal plate that are stacked and welded together, the porosity in the weld is <0.5 vol.%, the shear strength is 80-110 MPa, and the elongation is 6%-8%.

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