Laser-electric arc hybrid welding method for thick plate aluminum alloy

Abstract

The invention provides a laser-electric arc hybrid welding method for a thick plate aluminum alloy, and relates to the technical field of welding. Comprising the following steps that S1, an aluminum alloy metal plate is selected and fixed to a welding operation table in a butt joint mode after being pretreated, and a welding focus is adjusted; s2, the included angle between a welding gun and the to-be-welded workpiece is adjusted to be 65-75 degrees, the distance between light wires is adjusted to be 2-3 mm, and a laser spot and the tip end of a welding wire are located on the same straight line; s3, a powder feeding system and a welding gun are associated, and scanning laser-electric arc welding process parameters are set; and welding of the aluminum alloy metal plate is completed according to the set process parameters. According to the invention, the zirconium powder is added to realize microalloying of the welding seam, and the heterogeneous nucleation effect is utilized to significantly refine the welding seam grains; meanwhile, in combination with the synergistic effect of the circular scanning laser, the fluidity of a welding pool and the stability of a laser keyhole are effectively enhanced, and the flowing and mass and heat transfer efficiency of the welding pool are further synergistically improved, so that gas exhaust is more effectively promoted, gas hole formation is inhibited, and the welding seam quality is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding, in particular to a laser-arc hybrid welding method for thick plate aluminum alloy. BACKGROUND

[0002] With the increasing demand for energy reduction in the fields of transportation and aerospace, lightweight design and manufacturing of transportation tools have been increasingly valued. As a lightweight metal material, aluminum alloy has the characteristics of low density (about 2.7 g / cm 3 ), good thermal stability, strong corrosion resistance and excellent plasticity, etc., and has shown significant advantages in the manufacturing of lightweight and high-strength parts, and has been widely used.

[0003] However, in the process of aluminum alloy welding, there are still problems such as porosity and joint softening, and with the increase of plate thickness, the welding difficulty is further increased. The welding techniques commonly used for aluminum alloy at present include friction stir welding (FSW), tungsten inert gas welding (TIG), metal inert gas welding (MIG) and laser welding (LW). As a solid-state welding process, although FSW can avoid defects such as cracks, inclusions and porosity, its process window is narrow, the welding efficiency is lower than that of fusion welding, and it is difficult to be applied to complex shape or small precision components, which limits its promotion in industry. TIG welding and MIG welding are the most widely used gas shielded welding methods, but they have large heat input, which can easily lead to poor weld formation and severe deformation. Laser welding has the advantages of high speed, narrow heat-affected zone and small deformation, but it requires high assembly precision, and has low energy utilization rate and serious porosity problem when welding high reflectivity aluminum alloy.

[0004] To integrate the advantages of laser and arc heat sources and make up for their shortcomings, laser-arc hybrid welding technology (LAHW) has emerged. This technology not only significantly improves the welding efficiency, but also effectively reduces the porosity of aluminum weld through the synergistic effect of laser-arc. However, in the process of LAHW of medium-thick plate aluminum alloy, the metallurgical reaction in the molten pool is intense and the flow is unstable, and the keyhole is prone to periodic collapse, which leads to increased porosity and decreased mechanical properties of the weld. Studies have shown that using a scanning laser beam can enhance the stability of the keyhole, reduce porosity, and improve weld formation and mechanical properties.

[0005] Currently, to improve the performance of aluminum alloy laser-arc hybrid welding joints, domestic and foreign researches are mostly focused on process parameter optimization, but the improvement effect is limited. In addition to process optimization, micro-alloying is considered as an effective way to improve the performance of aluminum alloy, and the grain can be refined and the structure can be improved by adding rare earth elements (such as Sc, Y) or transition elements (such as Zr, Er, Ag, etc.). The existing technology of micro-alloying to improve the performance of aluminum alloy welding joint mainly includes the following two types: one is to adjust the alloy composition of the base material, and the other is to change the alloy composition of the welding material. Although both methods can effectively improve the mechanical properties of the joint, they both rely on complex preparation process and need to add specific micro-alloying elements in the production stage. Although this method can be designed for specific performance requirements, it lacks flexibility and real-time control capability: once the material is prepared, its composition is fixed and cannot be dynamically adjusted according to the actual welding requirements. In addition, this method has a long preparation period and high cost, and its applicability is limited, making it difficult to achieve on-site micro-alloying on demand. SUMMARY

[0006] The purpose of the present application is to provide a laser-arc hybrid welding method for thick plate aluminum alloy, which realizes weld micro-alloying by adding zirconium powder, significantly refines the weld grain by utilizing heterogeneous nucleation, and effectively enhances the fluidity of the welding pool and the stability of the laser keyhole by combining the synergistic effect of circular scanning laser, thereby strengthening the heat / mass transfer process in the pool, promoting bubble escape, and greatly reducing porosity defects, and finally obtaining thick plate aluminum alloy with excellent mechanical properties.

[0007] In one aspect, embodiments of the present application provide a laser-arc hybrid welding method for thick plate aluminum alloy, comprising the following steps: S1: Selecting an aluminum alloy metal plate, fixing it in a butt joint form on a welding operation table after pretreatment, and adjusting the welding focal point; S2: Adjusting the included angle between the welding torch and the workpiece to be welded to 65-75°, the light wire spacing to 2-3mm, and making the laser spot and the welding wire tip on the same straight line; S3: Associating the powder feeding system and the welding torch, setting the scanning laser-arc welding process parameters; and completing the welding of the aluminum alloy metal plate according to the set process parameters.

[0008] Further, in step S1, the pretreatment method includes grinding and cleaning the welding surface of the aluminum alloy metal plate.

[0009] Further, the welding focal point is located on the surface of the workpiece to be welded, and the laser head is deflected by 10° along the welding direction.

[0010] Further, in step S2, the included angle between the welding torch and the workpiece to be welded is 70°, and the light wire spacing is 2.5mm.

[0011] Further, in step S3, the process parameters include a scanning pattern, a scanning frequency, a scanning amplitude, a laser power, a welding speed, a wire feeding speed, a carrier gas amount, and a rotating disc speed.

[0012] Further, the scanning pattern is a circular trajectory formed by the laser beam due to the galvanometer scanning, the scanning frequency is the number of cycles of the laser beam on the scanning pattern per unit time, and the scanning amplitude is the maximum distance of the scanning pattern in the direction perpendicular to the welding direction.

[0013] Further, the scanning pattern is a circle.

[0014] Further, the powder added in the powder feeding system is zirconium powder.

[0015] In another aspect, the embodiment of the present application also provides a powder feeding system, which comprises a powder box and a driving motor penetrating through the bottom of the powder box, and a powder feeding disc is arranged in the powder box, and a top surface of the powder feeding disc is provided with an annular powder groove; the powder feeding system also comprises a powder storage tank, an air inlet pipe, and a powder outlet pipe penetrating through the top of the powder box; the bottom end of the powder storage tank and the bottom end of the powder outlet pipe are both provided with a support disc, and the support discs extend into the annular powder groove.

[0016] Further, the bottom end of the air inlet pipe penetrates through the top surface of the powder box, and the bottom end is connected with a plurality of air guide pipes, and the other end of any air guide pipe is provided with an opening on the bottom surface of the powder box.

[0017] Compared with the prior art, the embodiment of the present application has at least the following advantages or beneficial effects: The present application realizes weld micro-alloying by adding zirconium powder, significantly refines the weld grain by using heterogeneous nucleation, effectively enhances the fluidity of the welding pool and the stability of the laser keyhole by combining the synergistic effect of the circular scanning laser, further synergistically improves the flow and mass and heat transfer efficiency of the pool, thereby more effectively promoting the gas discharge, inhibiting the pore formation, and improving the weld quality. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0019] Figure 1 It is a schematic diagram of the overall welding platform of the embodiment of the present application; Figure 2 It is a schematic diagram of the circular scanning path and the welding direction of the embodiment of the present application; Figure 3 It is a front view of the powder feeding system in the embodiment of the present application; Figure 4A perspective view of a powder feeding system of an embodiment of the present application; Figure 5 A schematic view of a metal plate welding appearance in Embodiments 1-3 of the present application; Figure 6 A schematic view of a grain appearance in a weld fusion zone in Embodiments 1-3 of the present application; Figure 7 A schematic view of a grain appearance in a weld fusion zone in Embodiments 4-6 of the present application; Figure 8 A schematic view of a grain appearance in a weld fusion zone in Embodiments 7-9 of the present application; Figure 9 A comparison chart of tensile strength and elongation of the metal plates after welding in Embodiments 1-9 of the present application; Figure 10 A schematic view of sub-micron pure zirconium cluster particles formed in the weld of the aluminum alloy after welding with zirconium powder; Figure 11 A schematic view of Al3Zr phase formed in the weld of the aluminum alloy after welding with zirconium powder.

[0020] Figure: 1 - laser oscillating head; 2 - laser beam; 3 - collimating mirror; 4 - welding torch; 5 - powder outlet tube; 6 - electric arc; 7 - laser keyhole; 8 - molten pool; 9 - laser; 10 - electric arc welding machine; 11 - powder feeding system; 12 - powder tank; 13 - driving motor; 14 - powder storage tank; 15 - air inlet pipe; 16 - support disc; 17 - air guide pipe; 18 - powder feeding disc; 19 - annular powder groove. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0023] Embodiment 1 This embodiment provides in detail a laser-arc hybrid welding method for thick plate aluminum alloy, such as Figure 1As shown, the operation platform used in the welding process is a six-axis robot system, an IPG laser, a Fronius welding, an IPG D50 swing laser head and a powder feeding system; specifically comprising the following steps: S1: Select two aluminum alloy metal plates with completely identical size specifications, polish the welding surfaces of the two aluminum alloy metal plates with sandpaper to remove the surface oxidation film of the plates, and wipe the polished surface with acetone to remove surface oil and dust, so as to ensure that there is no other contaminant between the two plates during butt joint; after cleaning, place the two metal plates in a butt joint form on the welding operation table and clamp them with a clamp to ensure that the relative position of the two plates is fixed during welding. After fixing, adjust the position of the laser head using the six-axis welding robot so that the laser focal point is located on the upper surface of the workpiece to be welded, and deflect the laser head in the welding direction to prevent the laser from being reflected in the original direction and burning out the laser head. The deflection angle is 10°.

[0024] S2: Adjust the included angle between the welding torch and the workpiece to be welded to 70°, and ensure that the light wire spacing is 2-3 mm, then make the laser spot and the tip of the welding wire on the same straight line, and the straight line direction is parallel to the welding direction.

[0025] In this step, the purpose of setting the light wire spacing of 2-3 mm is to make the laser and the electric arc have a synergistic effect.

[0026] S3: Associate the powder feeding system and the welding torch, set the scanning laser-arc welding process parameters, and the specific parameters are: using cap welding, the included angle between the laser beam and the electric arc welding torch is 70°, the light wire spacing is 2.5 mm, the laser beam defocusing amount is 0 mm, the laser power is 8000 W, the welding speed is 1.25 m / min, the wire feeding speed is 15 m / min, and the welding mode is non-scanning laser-arc composite welding; and complete the welding of the aluminum alloy metal plate according to the set process parameters.

[0027] Example 2 The steps of this example and example 1 are basically the same, the difference is only that: In step S3, using filling welding, the included angle between the laser beam and the electric arc welding torch is 70°, the light wire spacing is 2.5 mm, the laser beam defocusing amount is 0 mm, the laser power is 3000 W, the welding speed is 1 m / min, the wire feeding speed is 16 m / min, and the welding mode is non-scanning laser-arc composite welding.

[0028] Example 3 The steps of this example and example 1 are basically the same, the difference is only that: In step S3, the laser beam and the arc welding gun are at an angle of 70°, the light wire spacing is 2.5 mm, the laser beam defocusing amount is 0 mm, the laser power is 8000 W, the welding speed is 2 m / min, the wire feeding speed is 15 m / min, and the welding mode is no scanning laser-arc composite welding.

[0029] Example 4 The steps of this example and example 1 are basically the same, except that: In step S3, the laser beam and the arc welding gun are at an angle of 70°, the light wire spacing is 2.5 mm, the laser beam defocusing amount is 0 mm, the laser power is 8000 W, the welding speed is 2 m / min, the wire feeding speed is 15 m / min, and the welding mode is no scanning laser-arc composite welding. The scanning path and the welding direction are as shown in Figure 2 .

[0030] Example 5 The steps of this example and example 4 are basically the same, except that: In step S3, the laser beam and the arc welding gun are at an angle of 70°, the light wire spacing is 2.5 mm, the laser beam defocusing amount is 0 mm, the laser power is 3000 W, the welding speed is 1 m / min, the wire feeding speed is 16 m / min, and the welding mode is circular scanning laser-arc composite welding, the scanning radius is 0.6 mm, and the scanning frequency is 300 Hz; the scanning path is circular, and the scanning amplitude is the circular radius.

[0031] Example 6 The steps of this example and example 4 are basically the same, except that: In step S3, the laser beam and the arc welding gun are at an angle of 70°, the light wire spacing is 2.5 mm, the laser beam defocusing amount is 0 mm, the laser power is 8000 W, the welding speed is 2 m / min, the wire feeding speed is 15 m / min, and the welding mode is circular scanning laser-arc composite welding, the scanning radius is 0.6 mm, and the scanning frequency is 400 Hz; the scanning path is circular, and the scanning amplitude is the circular radius.

[0032] Example 7 The steps of this example and example 4 are basically the same, except that: In step S3, cover welding is used. The angle between the laser beam and the arc welding gun is 70°, the wire spacing is 2.5mm, the laser beam defocusing amount is 0mm, the laser power is 8000W, the welding speed is 1.25m / min, the wire feed speed is 15m / min, and the welding method is powder microalloying circular scanning laser-arc hybrid welding. The microalloying powder used is pure zirconium powder with a particle size of 15-52μm, the scanning radius is 0.6mm, the scanning frequency is 300Hz, the scanning path is circular, and the scanning amplitude is the radius of the circle.

[0033] In this embodiment, zirconium powder needs to be fed into the powder feeding system 11 before welding. For example... Figure 3 As shown, the powder feeding system includes a powder box 12 and a drive motor 13 penetrating the bottom of the powder box 12. A powder feeding disc 18 is provided inside the powder box 12, and the bottom surface of the powder feeding disc 18 is connected to the drive motor 13. An annular powder groove 19 is formed on the top surface of the powder feeding disc 18. The system also includes a powder storage tank 14 penetrating the top of the powder box 12, an air inlet pipe 15, and a powder outlet pipe 5. Support plates 16 are provided at the bottom ends of both the powder storage tank 14 and the powder outlet pipe 5, extending into the annular powder groove 19 via the support plates 16. The bottom end of the air inlet pipe 15 passes through the top surface of the powder box 12 and is connected to several air guide pipes 17. The other end of any one of the air guide pipes 17 opens onto the bottom surface of the powder box 12.

[0034] The working principle of the powder feeding system 11 is as follows: First, an appropriate amount of zirconium powder is added to the powder storage tank 14. During the welding process, by starting the drive motor 13 and the air inlet pipe 5, the drive motor 13 drives the powder feeding disc 18 to rotate at a constant speed of 2 r / min. At the same time, the zirconium powder in the powder storage tank 14 falls into the annular powder trough 19 and rotates together with the powder feeding disc 18. In addition, by supplementing gas into the air inlet pipe 15, the gas enters the bottom of the powder box 12 along the air guide pipe 17 and escapes from the powder outlet pipe 5. Since the powder outlet of the powder outlet pipe 5 is small, the flow rate of these gases will increase when passing through the powder outlet, and due to the difference in internal and external pressure, the powder in the annular powder trough will be carried out, so that the zirconium powder is sprayed out from the powder outlet pipe 5, thereby realizing continuous powder feeding during the welding process.

[0035] Example 8 The steps in this embodiment are basically the same as those in Embodiment 7, with the only difference being: In step S3, filler welding is used. The angle between the laser beam and the arc welding gun is 70°, the wire spacing is 2.5mm, the laser beam defocusing amount is 0mm, the laser power is 3000W, the welding speed is 1m / min, the wire feed speed is 16m / min, and the welding method is powder microalloying circular scanning laser-arc hybrid welding. The microalloying powder used is pure zirconium powder with a particle size of 15-52μm, the scanning radius is 0.6mm, the scanning frequency is 300Hz, the scanning path is circular, and the scanning amplitude is the radius of the circle.

[0036] Example 9 The steps of this example and example 7 are basically the same, with the only difference being: In step S3, the laser beam and the arc welding gun form an angle of 70°, the light wire spacing is 2.5 mm, the laser beam defocusing amount is 0 mm, the laser power is 8000 W, the welding speed is 2 m / min, the wire feeding speed is 15 m / min, the welding mode is powder micro-alloyed circular scanning laser-arc composite welding, the micro-alloyed powder used is pure zirconium powder with a particle size of 15-52 μm, the scanning radius is 0.6 mm, and the scanning frequency is 400 Hz; the scanning path is circular, and the scanning amplitude is the circular radius.

[0037] Result analysis: The metal plates after welding of example 1 to example 9 were analyzed, including comparative analysis of weld appearance, porosity defects, weld fusion zone grain morphology, size, and tensile strength and elongation. The experimental results are shown in Figures 5-9 Among them, Figure 5 (a) is the weld appearance of three welding modes of example 1 to example 3, and the porosity is 6.9%; Figure 5 (b) is the weld appearance of three welding modes of example 4 to example 6, and the porosity is 2.7%; Figure 5 (c) is the weld appearance of three welding modes of example 7 to example 9, and there is no obvious porosity, which indicates that circular oscillating laser-arc composite welding can effectively reduce porosity defects; and after adding zirconium powder, porosity defects can be further reduced.

[0038] In addition, Figures 6-8 is a comparison chart of weld fusion zone grain morphology of example 1 to example 9. It can be seen that the size will decrease accordingly by using different welding modes. Among them, the grain size of non-oscillating laser-arc composite welding is the largest, the grain size of circular oscillating laser-arc composite welding is the second, and the grain size of circular oscillating laser-arc composite welding with zirconium powder is the smallest. In addition, the welding mode will also have a certain influence on the size of the grain, and the grain size obtained by backing welding is relatively the largest, while the grain size obtained by filling welding and cap welding is relatively smaller.

[0039] Further, the tensile strength and elongation of the metal plates after welding of example 1 to example 9 were compared, and the comparison results are shown in Figure 9 It can be seen that the tensile strength and elongation of non-oscillating laser-arc composite welding are the lowest, the tensile strength and elongation of circular oscillating laser-arc composite welding are the second, and the tensile strength and elongation of circular oscillating laser-arc composite welding with zirconium powder are significantly improved, which are much higher than the other two welding modes. This indicates that the addition of zirconium powder can significantly improve the mechanical properties of the metal plate after welding.

[0040] In addition, in order to further verify the mechanism of the zirconium powder in the welding of the aluminum alloy, a part of the aluminum alloy sample welded by adding the zirconium powder is selected for analysis, and results are shown in Figures 10-11 As can be seen, due to the addition of the zirconium powder, submicron pure zirconium cluster particles and dispersedly distributed Al3Zr phases are formed in the weld. The pure zirconium particles can improve the heterogeneous nucleation rate of the weld, so that the grain of the weld is significantly refined, and the strength and toughness of the weld are improved. The dispersedly distributed precipitated phase (Al3Zr) can hinder the dislocation movement, and improve the strength of the weld.

[0041] In summary, the embodiment of the present application provides a laser-arc hybrid welding method for thick plate aluminum alloy, which realizes weld micro-alloying by adding zirconium powder, significantly refines the weld grain by using heterogeneous nucleation, and effectively enhances the fluidity of the welding pool and the stability of the laser keyhole by combining the synergistic effect of the circular scanning laser, further synergistically improves the flow and mass and heat transfer efficiency of the pool, so as to more effectively promote the gas discharge, inhibit the pore formation, and improve the weld quality.

[0042] The above is only the preferred embodiment of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A laser-arc hybrid welding method for thick aluminum alloy plates, characterized in that, Includes the following steps: S1: Select an aluminum alloy metal plate, pre-treat it, and fix it to the welding worktable in a butt joint manner, and adjust the welding focus; S2: Adjust the angle between the welding torch and the workpiece to be welded to 65-75°, the wire spacing to 2-3mm, and make the laser spot and the tip of the welding wire in the same straight line; S3: Connect the powder feeding system and welding torch, set the scanning laser-arc welding process parameters, and complete the welding of aluminum alloy metal plates according to the set process parameters.

2. The laser-arc hybrid welding method for thick aluminum alloy plates according to claim 1, characterized in that, In step S1, the pretreatment method includes grinding and cleaning the welding surface of the aluminum alloy metal plate.

3. The laser-arc hybrid welding method for thick aluminum alloy plates according to claim 1, characterized in that, The welding focus is located on the surface of the workpiece to be welded, and the laser head is deflected 10° along the welding direction.

4. The laser-arc hybrid welding method for thick aluminum alloy plates according to claim 1, characterized in that, In step S2, the angle between the welding torch and the workpiece to be welded is 70°, and the spacing between the optical fibers is 2.5 mm.

5. The laser-arc hybrid welding method for thick aluminum alloy plates according to claim 1, characterized in that, In step S3, the process parameters include scanning pattern, scanning frequency, scanning amplitude, laser power, welding speed, wire feed speed, carrier gas volume, and turntable speed.

6. The laser-arc hybrid welding method for thick aluminum alloy plates according to claim 5, characterized in that, The scanning pattern is a circular trajectory formed by the laser beam scanning through a galvanometer. The scanning frequency is the number of times the laser beam cycles through the scanning pattern per unit time. The scanning amplitude is the maximum distance of the scanning pattern perpendicular to the welding direction.

7. The laser-arc hybrid welding method for thick aluminum alloy plates according to claim 6, characterized in that, The scanned pattern is circular.

8. The laser-arc hybrid welding method for thick aluminum alloy plates according to claim 7, characterized in that, The powder feeding system contains zirconium powder.

9. The laser-arc hybrid welding method for thick aluminum alloy plates according to claim 1, characterized in that, The powder feeding system includes a powder box and a drive motor that penetrates the bottom of the powder box. The powder box is equipped with a powder feeding disc, and the top surface of the powder feeding disc has an annular powder groove. It also includes a powder storage tank, an air inlet pipe, and a powder outlet pipe that penetrate the top of the powder box. The bottom end of the powder storage tank and the bottom end of the powder outlet pipe are both equipped with support plates, which extend into the annular powder groove through the support plates.

10. The laser-arc hybrid welding method for thick aluminum alloy plates according to claim 9, characterized in that, The bottom end of the air inlet pipe passes through the top surface of the powder box, and the bottom end is connected to several air guide pipes, with the other end of any one of the air guide pipes opening on the bottom surface of the powder box.

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