A laser-arc hybrid welding method for high-strength aluminum alloy in different heat treatment states

Abstract

This invention relates to the field of composite welding technology, specifically to a laser-MIG arc composite welding method for high-strength aluminum alloys in dissimilar heat-treated states. The method includes the following steps: butt-assembling a first base material and a second base material in dissimilar heat-treated states, both the first and second base materials being high-strength aluminum alloys, with the first base material having a lower strength than the second base material; adjusting the centerlines of the two laser beams and the central axis of the MIG welding torch to be located on the welding surface, with the angle α formed by the line connecting the center of the first spot of the first laser beam and the center of the second spot of the second laser beam and the welding surface being 15° to 75°; and performing laser-MIG arc composite welding on the first and second base materials under inert gas protection conditions according to the set welding process parameters. The purpose of this laser-MIG arc composite welding method for high-strength aluminum alloys in dissimilar heat-treated states is to solve the problem of cracking easily occurring in high-strength aluminum alloys in dissimilar heat-treated states during laser-arc composite welding.

Description

Technical Field

[0001] This invention relates to the field of composite welding technology, and specifically to a laser-arc composite welding method for high-strength aluminum alloys in different heat treatment states. Background Technology

[0002] High-strength aluminum alloys, with the 7XXX series as a typical example, are used as primary structural materials in aerospace due to their excellent machinability, corrosion resistance, and high toughness. Taking aircraft fuselage structures as an example, thin-walled 7XXX series high-strength aluminum alloy structures are generally machined or riveted. In a few non-load-bearing areas, arc welding is used to achieve metallurgical connections in thin-walled structures. However, arc welding involves high heat input, leading to significant deformation of the weldment. Furthermore, arc-welded high-strength aluminum alloy structures are not only highly susceptible to welding cracks, but also exhibit relatively low mechanical properties of the weld joint.

[0003] Laser-arc hybrid welding combines the advantages of both laser welding and arc welding, achieving superior welding results through the coupling of energy from two heat sources, thus its application is becoming increasingly widespread. Compared to argon arc welding, laser-arc hybrid welding not only significantly reduces welding heat input, which is beneficial for grain refinement and improved joint performance, but also allows for further control of joint microstructure and properties through filler wire during the welding process. The use of laser-arc hybrid welding technology to replace conventional arc welding in the welding of thin-walled 7XXX series high-strength aluminum alloy structures is of significant importance, as it further reduces welding deformation, improves joint performance, and ultimately enhances the service reliability of the welded structures.

[0004] 7XXX high-strength aluminum alloys are typically manufactured in high-strength or high-hardness states (e.g., 7075-T6, 7075-T651, 7050-T7451, etc.) to produce thin-walled parts through machining, reducing tool sticking during processing. Conversely, 7XXX high-strength aluminum alloys may also be manufactured in lower-strength or lower-hardness states (e.g., 7075-O, 7050-O, etc.) to produce thin-walled parts through sheet metal fabrication, fully utilizing the material's ductility or plasticity in this state. When the machined parts are butt-welded to the sheet metal parts, cracks are more likely to form on the machined part side. To suppress cracking, welding wire (e.g., ER4043, ER4047) is added during welding to increase the amount of liquid metal in the molten pool and, to some extent, increase its fluidity. However, the length of the weld and the complexity of the welded structure are generally positively correlated with the restraint stress caused by the welding fusion process. When the weld length is long or the welded structure is complex, that is, when the restraint stress is large, it is easier to generate cracks on the side of the machined parts, and even long through cracks.

[0005] Therefore, the inventors have provided a laser-arc composite welding method for high-strength aluminum alloys with different heat treatment states. Summary of the Invention

[0006] (1) Technical problems to be solved

[0007] This invention provides a laser-arc composite welding method for high-strength aluminum alloys in dissimilar heat treatment states, which solves the technical problem that high-strength aluminum alloys in dissimilar heat treatment states are prone to cracking during laser-arc composite welding.

[0008] (2) Technical solution

[0009] This invention provides a laser-arc hybrid welding method for high-strength aluminum alloys in dissimilar heat treatment states, comprising the following steps:

[0010] The first and second base materials in different heat treatment states are butt-assembled. Both the first and second base materials are made of high-strength aluminum alloy, and the strength of the first base material is less than that of the second base material.

[0011] The centerlines of the two laser beams are aligned with the central axis of the MIG welding torch and located on the welding surface. The first laser beam forms a first spot on the base material surface, and the second laser beam forms a second spot on the base material surface. The angle formed between the line connecting the centers of the first and second spots and the welding surface is... α The angle is 15° to 75°.

[0012] Based on the set welding process parameters, laser-MIG arc hybrid welding is performed on the first base material and the second base material under inert gas protection conditions.

[0013] Furthermore, the maximum gap between the first base material and the second base material during assembly is ≤ △x, where △x is the minimum of 30%·δ and 0.5mm, and δ is the wall thickness of the thinner base material.

[0014] Furthermore, the misalignment of the first base material and the second base material during assembly is ≤ △y, where △y is the minimum of 20%·δ and 0.3mm, and δ is the wall thickness of the thinner base material.

[0015] Furthermore, the angle between the central axis of the first laser beam and the second laser beam and the normal to the surface of the base material is within ±10°.

[0016] Furthermore, the diameter of the first light spot is r1, the diameter of the second light spot is r2, and the difference between r1 and r2 is within 20%; the center distance between the first light spot and the second light spot is d, and the value of d ranges from (r1+r2) / 4 to (r1+r2)*2.

[0017] Furthermore, the energy ratio of the first laser beam to the second laser beam is 1:1 to 4:1.

[0018] Furthermore, the distance between the center point of the line connecting the centers of the first spot and the second spot and the center point of the theoretical landing point of the molten droplet entering the molten pool under the action of the MIG arc is 2 to 8 mm.

[0019] Furthermore, the welding wire used in MIG arc welding includes at least one of Er, Zr, and Sc.

[0020] Furthermore, the step of performing laser-MIG arc hybrid welding on the first base material and the second base material under inert gas protection conditions according to the set welding process parameters specifically includes the following steps:

[0021] Under the action of MIG power supply and DC pulse mode, the welding wire forms molten droplets, enters the molten pool in the form of droplet transfer, and acts on the landing point. The first spot and the second spot form an elongated welding keyhole.

[0022] In front of the elongated welding keyhole, the molten base material bypasses the elongated welding keyhole in a first split and a second split, respectively, and flows to the rear of the elongated welding keyhole, and the flow rate of the second split is greater than the flow rate of the first split;

[0023] Behind the elongated welding keyhole, under the impact of the molten droplets being injected into the molten pool at an angle and the magnetic blow-out force of the MIG arc, the liquid molten pool is diverted by the elongated welding keyhole, and flows to the rear of the elongated welding keyhole in the manner of a third diversion and a fourth diversion, respectively, and the flow rate of the third diversion is greater than the flow rate of the fourth diversion.

[0024] Furthermore, after performing laser-MIG arc hybrid welding on the first base material and the second base material, the process further includes:

[0025] The strength of the welded joint and the first base material is restored by solution aging heat treatment.

[0026] (3) Beneficial effects

[0027] In summary, this invention combines dual laser beams, spaced close together and at a certain angle to the welding direction, with a side-axis MIG arc to achieve a non-uniform flow of liquid metal on both the front and rear sides of the keyhole. On the front side, a portion of the higher-strength or harder base material transitions to a lower-strength or harder base material, improving or strengthening the weld performance on the lower-strength or harder base material side. On the rear side, more of the lower-strength matching welding wire transitions to the higher-strength or harder base material side, further improving the weld crack sensitivity on the higher-strength or harder side and achieving better crack suppression. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic flowchart of a laser-arc composite welding method for high-strength aluminum alloys in dissimilar heat treatment states provided in an embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram of the welding position for laser-arc composite welding of high-strength aluminum alloys under dissimilar heat treatment states, provided in an embodiment of the present invention.

[0031] Figure 3 This is a top view of the molten pool of a high-strength aluminum alloy laser-arc composite welding process under dissimilar heat treatment conditions, provided in an embodiment of the present invention.

[0032] In the picture:

[0033] 1-First base material; 2-Second base material; 3-Dual-spot laser head; 4-First laser beam; 5-Second laser beam; 6-Laser center line; 7-MIG welding torch; 8-Welding wire; 9-Inert gas shield; 10-Molten droplet; 11-First spot; 12-Second spot; 13-Drop point; 14-Molten pool; 15-First splitter; 16-Second splitter; 17-Third splitter; 18-Fourth splitter. Detailed Implementation

[0034] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention by way of example, but should not be used to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments, and any modifications, substitutions and improvements to the parts, components and connection methods are covered without departing from the spirit of the present invention.

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] Figure 1 This is a schematic flowchart of a laser-arc hybrid welding method for high-strength aluminum alloys in dissimilar heat treatment states provided by an embodiment of the present invention. The method may include the following steps:

[0038] S100. The first and second base materials in different heat treatment states are joined together and assembled. Both the first and second base materials are made of high-strength aluminum alloy, and the strength of the first base material is less than that of the second base material.

[0039] Specifically, the maximum gap between the first base material 1 and the second base material 2 during butt assembly is ≤ △x, where △x is the minimum of 30%·δ and 0.5mm, and δ is the wall thickness of the thinner base material; the misalignment between the first base material 1 and the second base material 2 during butt assembly is ≤ △y, where △y is the minimum of 20%·δ and 0.3mm, and δ is the wall thickness of the thinner base material. The first base material 1 is an aluminum alloy in a heat-treated state with lower strength or hardness, and the second base material 2 is an aluminum alloy in a heat-treated state with higher strength or hardness.

[0040] S200. Adjust the centerlines of both laser beams to be aligned with the central axis of the MIG welding torch on the welding surface. The first laser beam forms a first spot on the base material surface, and the second laser beam forms a second spot on the base material surface. The angle formed between the center line of the first and second spots and the welding surface is... α The range is 15° to 75°.

[0041] Specifically, such as Figure 2As shown, two laser beams (first laser beam 4 and second laser beam 5) are transmitted from the laser through the dual-spot laser head 3, forming a dual-beam laser-MIG arc composite welding with the off-axis MIG arc. The centerline 6 of the two laser beams and the central axis of the MIG welding torch 7 are in the same welding plane, and the angle between the central axis of the two laser beams and the normal to the base material surface is within ±10°. The defocusing amount of the two laser beams acting on the upper surface of the base material is -50%·δ~0mm. The first laser beam 4 forms a first spot 11 on the base material surface, and the second laser beam 5 forms a second spot 12 on the base material surface. The angle α formed by the line connecting the centers of the first spot 11 and the second spot 12 with the welding plane is α, and the value of α ranges from 15° to 75° (due to wire current shunting). The diameter of the first spot 11 is r1, and the diameter of the second spot 12 is r2, with the difference between r1 and r2 within 20%. The center distance between the first light spot 11 and the second light spot 12 is d, where d is in the range of (r1+r2) / 4 to (r1+r2)·2. More preferably, d is in the range of (r1+r2) / 2 to (r1+r2).

[0042] The pre-set arc spacing is D, which is the distance between the center point of the line connecting the centers of the first laser spot 11 and the second laser spot 12 and the center point of the theoretical landing point 13 of the molten droplet 10 falling into the molten pool 14 under the action of the MIG arc. D is in the range of 2mm to 8mm, and more preferably, D is in the range of 2mm to 4mm. The energy ratio of the first laser beam 4 and the second laser beam 5 is 1:1 to 4:1.

[0043] The angle between the MIG welding torch and the base material surface is: β , β The angle is between 30° and 60°. Driven by the wire guide wheel of the MIG welding torch 7, the welding wire 8 is continuously fed. The welding wire 8 is a low-strength matching welding wire. The diameter of the welding wire 8 is Φ1.0mm to Φ1.6mm, and the wire extension is 5mm to 15mm, more preferably 6mm to 10mm.

[0044] S300. Based on the set welding process parameters, laser-MIG arc hybrid welding is performed on the first base material and the second base material under inert gas protection conditions.

[0045] Specifically, other welding process parameters determined through process optimization experiments are set, such as welding speed, laser power, MIG welding current, wire feed speed, and inert shielding gas flow rate. This step S300 specifically includes the following steps:

[0046] S301. Under the action of MIG power supply and DC pulse mode, the welding wire forms molten droplets, enters the molten pool in the form of droplet transfer, and acts on the landing point. The first spot and the second spot form an elongated welding keyhole.

[0047] Specifically, when the first light spot 11 and the second light spot 12 are close together, the high-energy-density first light spot 11 and the second light spot 12 form an elongated welding keyhole at an angle α to the welding direction; when the first light spot 11 and the second light spot 12 are far apart, the first light spot 11 and the second light spot 12 form an elongated heat input (high energy at both ends), and the direction of the elongated shape is at an angle α to the welding direction. The welding wire 8 is low-strength matched with the base material, including ER4043 welding wire or ER4047 welding wire. When the first light spot 11 and the second light spot 12 are close together, the high-energy-density first light spot 11 and the second light spot 12 form an elongated welding keyhole at an angle α to the welding direction; when the first light spot 11 and the second light spot 12 are far apart, the first light spot 11 and the second light spot 12 form an elongated heat input (high energy at both ends), and the direction of the elongated shape is at an angle α to the welding direction. ER4043 or ER4047 welding wire may also include small amounts of trace elements such as Er, Zr, and Sc, or any combination thereof. When Er is added to welding wire 8, the mass percentage of Er ranges from 0.10% to 0.30%; when Zr is added, the mass percentage of Zr ranges from 0.10% to 0.30%; and when Sc is added, the mass percentage of Sc ranges from 0.10% to 0.20%. When these trace elements are added to welding wire 8, the transition to the liquid molten pool leads to a relatively increased probability of heterogeneous nucleation, which can further refine the grains and improve the strength of the weld joint, and to a certain extent, further suppress weld cracking. Under the premise that weld cracking is controllable, ER5356 welding wire can also be used for welding wire 8 to further improve the strength performance of the weld joint.

[0048] S302. In front of the elongated welding keyhole, the molten base material bypasses the elongated welding keyhole in the manner of first diversion and second diversion, and flows to the rear of the elongated welding keyhole, and the flow rate of the second diversion is greater than the flow rate of the first diversion.

[0049] In this process, in front of the inclined elongated welding keyhole or the elongated heat input, the molten base material bypasses the welding keyhole in the manner of the first diversion 15 and the second diversion 16, and flows to the rear of the keyhole. The flow rate of the second diversion 16 should be greater than the flow rate of the first diversion 15.

[0050] S303. Behind the elongated welding keyhole, under the impact of the molten droplets being injected into the molten pool at an angle and the magnetic blow-out force of the MIG arc, the liquid molten pool is diverted by the elongated welding keyhole, and flows to the rear of the elongated welding keyhole in the manner of the third diversion and the fourth diversion, respectively, and the flow rate of the third diversion is greater than the flow rate of the fourth diversion.

[0051] In this process, behind the inclined elongated welding keyhole or elongated heat input, under the impact of the molten droplet 10 being injected into the molten pool at an incline and the magnetic blow-out force of the MIG arc, the liquid molten pool is diverted by the elongated welding keyhole or elongated heat input, and flows to the rear of the keyhole in the manner of the third diversion 17 and the fourth diversion 18, respectively, and the flow rate of the third diversion 17 should be greater than the flow rate of the fourth diversion 18.

[0052] In the above embodiments, the second base material 2 has higher strength or hardness, meaning it is more susceptible to cracking. By allowing more of the low-strength matching welding wire 8 to flow towards the second base material 2, the weld crack sensitivity on the second base material 2 side is significantly improved, resulting in excellent crack suppression. Similarly, the first base material 1 has lower strength or hardness; the transition to the second base material 2, which has higher strength or hardness at the keyhole tip, also improves or strengthens the weld performance on the first base material 1 side.

[0053] Using high-strength aluminum alloy base material in dissimilar heat-treated states and low-strength matching welding wire, under the influence of dual laser beams and their keyholes, arc magnetic blow force and droplet impact force, and inert shielding gas flow, while maintaining a basically equal flow rate of molten metal to both sides and the rear of the molten pool, more welding wire metal flows to the higher strength or hardness base material side. This further promotes liquid backfilling during the solidification process of the molten pool on that side, reduces shrinkage stress, and thus fundamentally inhibits cracking. Using laser-arc hybrid welding instead of conventional arc welding for the metallurgical joining of 7XXX high-strength aluminum alloys in dissimilar heat-treated states can significantly reduce welding heat input, refine weld grains, reduce the width of the heat-affected zone, and significantly improve the mechanical properties of the welded joint.

[0054] As an optional implementation, after laser-MIG arc hybrid welding of the first and second base materials, step S400 is further included: strength recovery of the weld joint and the first base material through solution aging heat treatment. Before strength recovery, quality inspection is required, and non-destructive testing is performed on the weld joint. Non-destructive testing methods include X-ray inspection and penetrant testing.

[0055] Example 1

[0056] Taking the butt welding of a 7075-T6 aluminum alloy machined part and a 7075-O aluminum alloy sheet metal part with a weld thickness of 3.0mm as an example, the specific welding process includes the following steps:

[0057] S100: Base Material Assembly. Complete the butt joint assembly of the first base material 1 and the second base material 2, with a maximum assembly gap of no more than 0.5mm and an assembly misalignment of no more than 0.3mm.

[0058] S200: Welding posture adjustment and dual-beam welding parameter settings. Two laser beams (first laser beam 4 and second laser beam 5) are transmitted from the laser through the dual-spot laser head 3, forming a dual-beam laser-MIG arc composite welding with the off-axis MIG arc.

[0059] The centerlines 6 of the two laser beams and the central axis of the MIG welding torch 7 lie in the same welding plane, and the angles between the central axes of the two laser beams and the normal to the base material surface are within 8°. The defocusing amount of the two laser beams acting on the upper surface of the base material is 0 mm. The first laser beam 4 forms a first spot 11 on the base material surface, and the second laser beam 5 forms a second spot 12 on the base material surface. The angle between the center line of the first spot 11 and the second spot 12 and the welding plane is α = 45°. The diameter of the first spot 11 is r1 = 0.525 mm, and the diameter of the second spot 12 is r2 = 0.525 mm, r1 = r2. The center distance between the first spot 11 and the second spot 12 is d, where d = r1 + r2 = 1.05 mm.

[0060] The pre-set arc spacing is D, which is the distance between the center point of the line connecting the centers of the first laser spot 11 and the second laser spot 12 and the center point of the theoretical landing point 13 of the molten droplet 10 under the action of the MIG arc, where D = 4 mm. The energy ratio of the first laser beam 4 and the second laser beam 5 is 50:50.

[0061] The angle between the MIG welding torch and the base material surface is: β , β =45°. Driven by the wire guide wheel of the MIG welding torch, welding wire 8 is continuously fed. Welding wire 8 is a low-strength matching welding wire ER4043, with a diameter of Φ1.2mm and a wire extension of 8mm.

[0062] S300: Set other welding process parameters. Set other welding process parameters determined through process optimization experiments, such as welding speed, laser power, MIG welding current, wire feed speed, and inert gas flow rate.

[0063] S400: Welding is performed. Based on the set welding process parameters, laser-MIG arc hybrid welding of high-strength aluminum alloys in dissimilar heat treatment states is performed under inert gas protection conditions.

[0064] Under the action of MIG power supply and DC pulse mode, the welding wire 8 forms molten droplets 10, which enter the molten pool 14 in a droplet transfer manner and act on the landing point 13. Because the first spot 11 and the second spot 12 are close together, the high-energy-density first spot 11 and the second spot 12 form an elongated welding keyhole, perpendicular to the welding direction. αAt the angle, in front of the inclined elongated welding keyhole, the molten base material bypasses the welding keyhole in the manner of the first diversion 15 and the second diversion 16, and flows to the rear of the keyhole, with the flow rate of the second diversion 16 being greater than that of the first diversion 15. Simultaneously, behind the inclined elongated welding keyhole, under the impact force of the molten droplets 10 being injected into the molten pool at an angle and the magnetic blow-out force of the MIG arc, the liquid molten pool is diverted by the elongated welding keyhole, and flows to the rear of the keyhole in the manner of the third diversion 17 and the fourth diversion 18, with the flow rate of the third diversion 17 being greater than that of the fourth diversion 18.

[0065] The second base material 2 has higher strength or hardness, meaning it is more susceptible to cracking. By allowing more of the low-strength matching welding wire 8 to flow towards the second base material 2, the weld crack sensitivity on the second base material 2 side is significantly improved, resulting in excellent crack suppression. Similarly, the first base material 1 has lower strength or hardness, and the transition to the higher-strength or harder second base material 2 at the keyhole tip also improves or strengthens the weld performance on the first base material 1 side. After welding, solution aging heat treatment can be used to restore the strength of the weld joint and the low-strength base material.

[0066] S500: Quality Inspection. Non-destructive testing (NDT) is performed on welded joints, including X-ray inspection and penetrant testing. Welded joints can also undergo solution aging heat treatment to restore strength to the welded joints and the low-strength base material.

[0067] The laser-arc hybrid welding process of this invention has been verified to be reasonable and feasible. It not only further eliminates welding crack defects in 7XXX series high-strength aluminum alloys under dissimilar heat treatment states, reducing structural welding rework, but also replaces conventional arc welding. It significantly reduces welding heat input by 20%–50%, increases welding efficiency by approximately 30%–60%, refines weld grains, reduces the width of the heat-affected zone of the weld joint by approximately 50%–80%, and improves the mechanical properties of the weld joint (as-welded state) by approximately 10%–30%. After solution aging heat treatment, the tensile mechanical properties of the weld joint also improve by approximately 10%–30% compared to conventional arc welding. Therefore, this invention demonstrates outstanding inventiveness and can further promote the engineering application of high-strength aluminum alloy welded structures, especially suitable for welding long welds or complex structures of 7XXX series and other high-strength aluminum alloys under dissimilar heat treatment states.

[0068] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0069] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art without departing from the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A method of laser-arc hybrid welding of high-strength aluminum alloys in different heat treatment states, characterized in that, The method includes the following steps: The first and second base materials in different heat treatment states are butt-assembled. Both the first and second base materials are made of high-strength aluminum alloy, and the strength of the first base material is less than that of the second base material. The centerlines of the two laser beams are aligned with the central axis of the MIG welding torch and located on the welding surface. The first laser beam forms a first spot on the base material surface, and the second laser beam forms a second spot on the base material surface. The angle formed between the line connecting the centers of the first and second spots and the welding surface is... α The angle is 15° to 75°. Based on the set welding process parameters, under inert gas protection conditions, laser-MIG arc hybrid welding is performed on the first base material and the second base material, specifically including the following steps: Under the action of MIG power supply and DC pulse mode, the welding wire forms molten droplets, enters the molten pool in the form of droplet transfer, and acts on the landing point. The first spot and the second spot form an elongated welding keyhole. In front of the elongated welding keyhole, the molten base material bypasses the elongated welding keyhole in a first split and a second split, respectively, and flows to the rear of the elongated welding keyhole, and the flow rate of the second split is greater than the flow rate of the first split; Behind the elongated welding keyhole, under the impact of the molten droplets being injected into the molten pool at an angle and the magnetic blow-out force of the MIG arc, the liquid molten pool is diverted by the elongated welding keyhole, and flows to the rear of the elongated welding keyhole in the manner of a third diversion and a fourth diversion, respectively, and the flow rate of the third diversion is greater than the flow rate of the fourth diversion.

2. The laser-arc composite welding method for high-strength aluminum alloys in dissimilar heat-treated states according to claim 1, characterized in that, The maximum gap between the first base material and the second base material during assembly is ≤ △x, where △x is the minimum of 30%·δ and 0.5mm, and δ is the wall thickness of the thinner base material.

3. The laser-arc composite welding method for high-strength aluminum alloys with dissimilar heat treatment states according to claim 1 or 2, characterized in that, The misalignment between the first base material and the second base material is ≤ △y, where △y is the minimum of 20%·δ and 0.3mm, and δ is the wall thickness of the thinner base material.

4. The laser-arc composite welding method for high-strength aluminum alloys in dissimilar heat treatment states according to claim 1, characterized in that, The angle between the central axis of the first laser beam and the second laser beam and the normal to the surface of the base material is within ±10°.

5. The laser-arc composite welding method for high-strength aluminum alloys in dissimilar heat-treated states according to claim 1, characterized in that, The diameter of the first light spot is r1, and the diameter of the second light spot is r2. The difference between r1 and r2 is within 20%. The center distance between the first light spot and the second light spot is d, and the value of d ranges from (r1+r2) / 4 to (r1+r2)*2.

6. The laser-arc composite welding method for high-strength aluminum alloys in dissimilar heat-treated states according to claim 1, characterized in that, The energy ratio of the first laser beam to the second laser beam is 1:1 to 4:

1.

7. The laser-arc composite welding method for high-strength aluminum alloys in dissimilar heat-treated states according to claim 1, characterized in that, The distance between the center point of the line connecting the centers of the first spot and the second spot and the center point of the theoretical landing point of the molten droplet entering the molten pool under the action of the MIG arc is 2 to 8 mm.

8. The laser-arc composite welding method for high-strength aluminum alloys in dissimilar heat-treated states according to claim 1, characterized in that, The welding wire used in MIG arc welding includes at least one of Er, Zr, and Sc.

9. The laser-arc composite welding method for high-strength aluminum alloys in dissimilar heat-treated states according to claim 1, characterized in that, After performing laser-MIG arc hybrid welding on the first base material and the second base material, the method further includes: The strength of the welded joint and the first base material is restored by solution aging heat treatment.

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