Beam shaping laser seal welding method and system for aluminum alloy target piece

Abstract

The invention belongs to but not limited to the technical field of welding, and discloses a beam shaping laser seal welding method and system for an aluminum alloy target, which combines a power modulation technology on the basis of galvanometer laser mechanical swing and combines the advantages of a beam time shaping technology and a beam space shaping technology into a whole. And a novel beam shaping strategy of power modulation and galvanometer laser is realized. During beam shaping laser welding, a laser beam is welded by adopting a circular scanning track, power modulation is performed on 36 phase points in a circular scanning period, laser energy distribution is adjusted, and a corresponding energy field is matched for an aluminum alloy sealing welding joint; a welding seam formed by the aluminum alloy cladding pipe and the end plug is sealed in a beam shaping mode with the high middle and the two low sides, the maximum peak energy density of lasers on the two sides of the welding seam is reduced, the flowing stability of a molten pool is improved, and therefore welding seam undercuts are reduced, and welding seam surface forming is improved.

Description

Technical Field

[0001] The present invention belongs to but is not limited to the field of welding technology, and in particular relates to a beam shaping laser welding method and system for an aluminum alloy target. Background Art

[0002] Nuclear grade 6061-T6 aluminum alloy has good mechanical properties, radiation resistance (small thermal neutron absorption cross section, only 0.22×10 -24 cm 2 ), corrosion resistance and economy, and are often used to manufacture fuel element cladding and irradiation target cladding materials for low and medium temperature research and test reactors. Aluminum alloy targets usually consist of an upper end plug, a lower end plug, an inner cladding tube, an outer cladding tube and internal components. The sealing quality of the cladding and the upper and lower end plugs plays a key role in the safe operation of the aluminum alloy targets in the reactor. When the aluminum alloy targets are working in the reactor, they must withstand both the external coolant pressure and the internal pressure of the internal gas. In addition, they must withstand the fatigue stress caused by power changes in the reactor and the vibration caused by the flow of coolant. Therefore, the targets are required to have sufficient mechanical properties and avoid welding defects. Specifically, the weld must have a certain penetration depth and the penetration depth must be greater than 90% of the cladding tube wall thickness. In addition, cracks, pores larger than 0.2 mm and slag inclusions are not allowed in the weld, and the weld leakage rate is less than 1.33×10 -9 Pa·m 3 / s. However, due to the large thermal expansion coefficient, fast heat dissipation and strong sensitivity to thermal cracks of aluminum alloy, it is easy to produce welding defects such as pores and cracks, resulting in reduced weld sealing. In addition, aluminum alloy welded joints are prone to softening, resulting in reduced mechanical properties of sealed joints, which has become a welding problem that restricts the improvement of aluminum alloy target sealing quality and application. Therefore, the study of aluminum alloy target sealing technology has important theoretical significance and application value.

[0003] At present, aluminum alloy targets are mainly sealed by automatic TIG welding process, but there are many problems:

[0004] (1) Aluminum alloy TIG welding has high requirements for process and equipment, and requires good adaptability to assembly deviations. It is necessary to ensure high welding quality stability and good full-automatic operation capabilities;

[0005] (2) TIG welding process has a slow welding speed and low production efficiency;

[0006] (3) TIG welding of aluminum alloys causes defects such as joint softening, thermal cracks and pores that are difficult to avoid, affecting the sealing of the weld;

[0007] (4) Aluminum alloy has a large thermal expansion coefficient, the nuclear target tube structure has a large constraint force, and the cooling and shrinkage after welding produce large thermal stress, which is very easy to cause cracks.

[0008] Laser welding has the characteristics of high energy density, low welding heat input, and small weld deformation. It can effectively improve the softening of aluminum alloy joints and produce welded joints with relatively high quality and fewer welding defects. The use of galvanometer scanning laser welding can make the laser beam weld on the surface of the workpiece within a certain range and with a certain motion trajectory, and stir the molten pool, which can effectively reduce porosity defects and improve welding quality. In addition, the laser action range is expanded by laser beam scanning, which can increase the weld width and improve the adaptability of assembly gap errors. The use of laser welding technology to replace TIG welding technology for thin-walled container sealing has good technical prospects. Therefore, it is of great theoretical significance and application value to study the laser sealing process of aluminum alloy targets, improve welding efficiency and welding quality, and explore new technical approaches for the application of laser technology in the fields of nuclear material sealing.

[0009] However, galvanometer laser aluminum alloy welding still has problems such as low heat source efficiency and inability to flexibly control heat, which limits the further improvement of the quality and performance of aluminum alloy target welding. Beam shaping technology is an improved laser welding technology developed in recent years. It changes the laser energy distribution through beam shaping strategy to achieve heat source control, which can significantly improve the stability of the welding process, reduce welding defects, improve weld formation and improve joint performance. At the same time, it reduces welding heat input and improves the softening problem of welding joints, which has a good effect on improving the quality of aluminum alloy target welding.

[0010] In view of the above analysis, the technical problems that urgently need to be solved in the prior art are: the welding process of aluminum alloy targets is poorly stable, there are welding defects such as undercuts, pores, cracks, etc., the weld sealing is poor, the sealing quality is low, and the welding efficiency is low. Summary of the invention

[0011] In view of the problems existing in the prior art, the present invention provides a beam shaping laser sealing method and system for an aluminum alloy target.

[0012] The present invention is implemented as follows: a beam shaping laser sealing method for aluminum alloy target parts combines power modulation technology on the basis of mechanical swing of galvanometer laser, combines the dual advantages of beam time shaping and space shaping technology, and realizes a new beam shaping strategy of "power modulation + galvanometer laser". During beam shaping laser welding, the laser beam adopts a circular scanning trajectory for welding, and modulates the power of 36 phase points within a circular scanning cycle, adjusts the laser energy distribution, matches the corresponding energy field for the aluminum alloy sealing joint, and adopts a beam shaping mode with high middle and low sides to seal the weld formed by the aluminum alloy cladding tube and the end plug, reduces the maximum peak energy density of the laser on both sides of the weld, improves the flow stability of the molten pool, thereby reducing the weld edge biting and improving the weld surface formation.

[0013] The beam shaping laser sealing welding method of the aluminum alloy target comprises the following steps:

[0014] Step 1: clean the aluminum alloy end plug and the cladding tube, and assemble the dried aluminum alloy cladding tube and the end plug, with an interference fit between the end plug and the cladding tube;

[0015] Step 2, fixing the assembled aluminum alloy target on a rotating platform;

[0016] Step 3: Move the laser welding head so that the weld to be welded is located in the middle of the laser spot; adjust the height of the laser welding head so that the surface to be welded is located at the zero defocus position;

[0017] Step 4: Set laser welding parameters and optimize power modulation dynamically and in real time in combination with the intelligent control system;

[0018] Step 5: modulate the laser beam shaping mode, perform power modulation on 36 phase points within a circular scanning cycle, adjust the laser energy distribution, match the corresponding energy field for the aluminum alloy sealing joint, and adjust the circular beam shaping mode with high center and low sides to form a gap between the aluminum alloy cladding tube and the end plug for sealing welding;

[0019] Step 6: Introduce protective gas. During welding, the laser welding head is fixed and the rotating platform rotates clockwise at a speed of 20r / min, i.e. 3s / r;

[0020] Step seven, welding the end plug ring weld for 4 / 3r, that is, stopping the laser output after 4s of welding, the welding rotating platform continues to rotate, and continues to introduce shielding gas to protect the weld. When the weld cools to below 200°C, stop introducing shielding gas and the welding rotating platform stops rotating.

[0021] Furthermore, in step 1, the thickness of the aluminum alloy cladding tube is 2 mm, and the material is a nuclear grade 6061-T6 aluminum alloy tube.

[0022] Furthermore, in step one, the aluminum alloy end plug and the cladding tube are cleaned with a NaOH solution to remove surface dirt, oil and other impurities, and then cleaned with a hydrochloric acid solution, and then cleaned with distilled water, and finally cleaned with acetone and placed in a vacuum drying oven for 3 hours.

[0023] Furthermore, in step 2, the fitting clearance between the end plug and the cladding tube is 0.01-0.03 mm, and the gap of the weld to be welded after assembly should be less than 0.2 mm.

[0024] Furthermore, in step 4, the laser welding parameters are set: laser power 3.6 kW, scanning trajectory is set to a circle, scanning frequency is 200 Hz, and scanning amplitude is 0.8 mm.

[0025] Furthermore, in step 4, real-time sensor technology is used to monitor the temperature distribution, molten pool morphology and weld surface during the welding process online, and the power modulation parameters and scanning trajectory are adjusted in real time according to the feedback data.

[0026] Furthermore, in step five, the laser beam shaping mode is modulated to change the laser power at different positions within the laser circular scanning trajectory period to achieve laser energy distribution regulation in the molten pool, reduce the laser energy distribution at the edge of the molten pool, improve the stability of the molten pool, and thus improve the quality of weld formation.

[0027] Furthermore, the shielding gas in step six is ​​a special shielding gas mixing scheme for aluminum alloys, in which 25% helium is added to argon gas to improve thermal efficiency, improve molten pool fluidity, and improve welding efficiency while ensuring welding stability.

[0028] Furthermore, the gas flow rate of the protective gas is 15 L / min.

[0029] Another object of the present invention is to provide a beam shaping laser welding method for an aluminum alloy target and a beam shaping laser welding system for an aluminum alloy target, comprising:

[0030] The welding module is a global power modulation galvanometer laser welding system that combines a new beam shaping strategy with beam oscillation and power modulation dual beam shaping technologies;

[0031] The sensor module is used to monitor the temperature distribution, molten pool morphology and weld surface during welding online;

[0032] Intelligent control module, used for dynamic real-time optimization of power modulation, and real-time adjustment of power modulation parameters and scanning trajectory according to feedback data;

[0033] The shielding gas module is used to adjust the shielding gas type and mixing ratio, introduce shielding gas, and control the gas flow.

[0034] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0035] First, the purpose of the present invention is to provide a beam shaping laser welding method for an aluminum alloy nuclear target tube, and to improve the welding quality of aluminum alloy targets through a new beam shaping strategy;

[0036] By changing the laser energy distribution through beam shaping strategy, the corresponding energy field is matched for the aluminum alloy sealing joint, the stability of the welding process is improved, welding defects such as undercut and porosity are reduced, and the quality of weld formation is improved;

[0037] The beam shaping strategy is used to reduce welding heat input, improve the softening of the weld and heat-affected zone, and enhance the mechanical properties of the joint.

[0038] The new beam shaping strategy refines the weld grains, increases the proportion of equiaxed crystals, and improves the weld tightness.

[0039] Compared with the existing TIG welding method, the beam shaping laser sealing welding method increases the rotation speed during welding of the aluminum alloy nuclear target tube and improves the welding efficiency; in addition, the heat input is further reduced through the laser welding beam shaping strategy, which reduces the width of the heat affected zone of the aluminum alloy welding and improves the softening problem of the aluminum alloy joint, thereby improving the joint quality.

[0040] Second, the expected benefits and commercial value of the technical solution of the present invention after transformation are as follows: After transformation, the technical solution of the present invention can significantly improve the quality of aluminum alloy target welding and improve the sealing of welding joints. At the same time, it improves welding efficiency and saves time costs. The present invention adopts laser welding method to replace traditional automatic TIG welding, speeds up the rotation speed of target welding, and improves welding efficiency; in addition, it improves the softening problem of welding joints caused by large heat input during traditional TIG welding, and improves the mechanical properties of joints. The beam shaping strategy is used to improve the quality of weld formation and make the weld more beautiful.

[0041] The technical solution of the present invention solves a technical problem that people have been eager to solve but have never been successful: the domestic welding of aluminum alloy targets usually uses the automatic TIG welding method, the welding quality and welding efficiency are low, and the reliability of the sealing quality has not been completely and effectively solved, and there is a large gap with the international advanced level. The present invention realizes the laser welding process of aluminum alloy fuel targets, improves the softening of welding joints, reduces defects such as weld porosity and cracks, and improves the sealing quality and efficiency of aluminum alloy targets. Certain progress has been made in the field of nuclear fuel rod laser welding technology, narrowing the gap with the international advanced level. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a flow chart of a beam shaping laser sealing welding method for an aluminum alloy target provided by an embodiment of the present invention;

[0043] Figure 2 It is a structural diagram of a beam shaping laser welding system for an aluminum alloy target provided by an embodiment of the present invention;

[0044] Figure 3 It is a schematic diagram of the structure of a nuclear target tube provided by an embodiment of the present invention;

[0045] Figure 4 The scanning trajectory and beam shaping laser energy distribution diagram provided by the embodiment of the present invention are as follows: (a) circular scanning trajectory; (b) conventional galvanometer laser energy distribution; (c) beam shaping laser energy distribution;

[0046] Figure 53. The weld morphology of beam shaping laser sealing welding under different laser powers provided by the embodiment of the present invention;

[0047] Figure 6 is a cross-sectional morphology diagram of a beam shaping laser weld provided by an embodiment of the present invention;

[0048] Figure 7 It is a microstructure diagram at the weld fusion line provided by an embodiment of the present invention.

[0049] The following are the components and their corresponding numbers:

[0050] 1. Outer shell tube; 2. Inner shell tube; 3. Upper end plug; 4. Lower end plug; 5. Circumferential weld; 6. End weld; 7. Internal components. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0052] like Figure 1 As shown, an embodiment of the present invention provides a beam shaping laser welding method for an aluminum alloy target, comprising the following steps:

[0053] Step 1: clean the aluminum alloy end plug and the cladding tube, and assemble the dried aluminum alloy cladding tube and the end plug, with an interference fit between the end plug and the cladding tube;

[0054] Step 2, fixing the assembled aluminum alloy target on a rotating platform;

[0055] Step 3: Move the laser welding head so that the weld to be welded is located in the middle of the laser spot; adjust the height of the laser welding head so that the surface to be welded is located at the zero defocus position;

[0056] Step 4: Set laser welding parameters and optimize power modulation dynamically and in real time in combination with the intelligent control system;

[0057] Step 5: modulate the laser beam shaping mode, perform power modulation on 36 phase points within a circular scanning cycle, adjust the laser energy distribution, match the corresponding energy field for the aluminum alloy sealing joint, and adjust the circular beam shaping mode with high center and low sides to form a gap between the aluminum alloy cladding tube and the end plug for sealing welding;

[0058] Step 6: Introduce protective gas. During welding, the laser welding head is fixed and the rotating platform rotates clockwise at a speed of 20r / min, i.e. 3s / r;

[0059] Step seven, welding the end plug ring weld for 4 / 3r, that is, stopping the laser output after 4s of welding, the welding rotating platform continues to rotate, and continues to introduce shielding gas to protect the weld. When the weld cools to below 200°C, stop introducing shielding gas and the welding rotating platform stops rotating.

[0060] The aluminum alloy end plug and cladding tube are cleaned to remove surface oxides and contaminants to ensure that they are not affected by impurities during welding. The cleaned cladding tube is assembled with the end plug, using an interference fit to achieve a tight fit through mechanical stress, providing a good initial structure and stability for subsequent welding.

[0061] The assembled aluminum alloy target is fixed on the rotating platform to ensure that the target is stable and does not deviate during the rotation process. By adjusting the horizontal and height positions of the laser welding head, the weld to be welded is located at the center of the laser spot, while ensuring that the surface is in a zero defocus state. This precise positioning ensures uniform coverage of the weld by the welding beam and improves the welding quality.

[0062] According to the characteristics of aluminum alloy materials, laser welding parameters (such as power, scanning speed, etc.) are set, and the welding process is optimized in real time and dynamically in combination with the intelligent control system. The intelligent control system ensures that the laser energy is evenly distributed during the welding process by adjusting the power distribution in real time, effectively reducing the occurrence of weld defects.

[0063] Laser beam shaping technology is used to modulate the laser in a circular beam scanning mode, and the energy distribution is adjusted to a "high in the middle and low on both sides" distribution mode to adapt to the gap between the aluminum alloy cladding tube and the end plug. By modulating the power of 36 phase points in one scanning cycle, efficient energy coupling is achieved, improving the uniformity and reliability of sealing welding.

[0064] During the welding process, the laser welding head remains fixed, and the rotating platform rotates clockwise at a speed of 20r / min, completing the welding through relative motion. At the same time, protective gas is introduced into the welding area to prevent the aluminum alloy material from reducing its strength and corrosion resistance due to oxidation during the welding process. The welding speed and gas flow are strictly controlled throughout the welding process to ensure the quality of the weld.

[0065] When the weld reaches 4 / 3 of the end plug ring seam (about 4 seconds), the laser output is stopped, but the rotating platform continues to rotate while maintaining the flow of shielding gas. The shielding gas supply stops when the weld cools to below 200°C, and then the rotating platform stops moving. This step prevents excessive thermal stress and oxidation of the weld through continuous cooling and protection measures, ensuring welding quality and durability.

[0066] The thickness of the aluminum alloy cladding tube is 2mm and the material is nuclear grade 6061-T6 aluminum alloy tube.

[0067] Beam shaping technology is used to regulate and optimize the temperature distribution, molten pool morphology and weld formation quality during the welding process. The beam shaping strategy is adjusted in real time according to feedback data to further accurately control the energy distribution and improve the molten pool stability and weld formation quality.

[0068] On the basis of the existing galvanometer laser welding beam oscillation, the power modulation collaborative shaping method is explored. In step 5, the new beam shaping strategy of "power modulation + galvanometer laser" is used to adjust the laser energy distribution, match the corresponding energy field for the aluminum alloy sealing joint, improve the flow stability of the molten pool, and further optimize the weld surface formation and internal structure uniformity.

[0069] Develop a special shielding gas mixing solution for aluminum alloys, such as adding helium to argon to improve thermal efficiency and optimize the molten pool fluidity and protection effect during welding. By adjusting the gas ratio, not only can the porosity and weld oxidation be effectively reduced, but also the welding stability can be improved. Since nuclear aluminum alloy targets have high requirements for sealing quality and sealing, 25% helium can be added to further improve the stability of the molten pool, improve weld formation, and reduce weld porosity.

[0070] like Figure 2 As shown, an embodiment of the present invention provides a beam shaping laser welding method for an aluminum alloy target and a beam shaping laser welding system for an aluminum alloy target, comprising:

[0071] The welding module is a global power modulation galvanometer laser welding system that combines a new beam shaping strategy with beam oscillation and power modulation dual beam shaping technologies;

[0072] Sensor module, used for online monitoring of temperature distribution, molten pool morphology and weld surface during welding;

[0073] Intelligent control module, used for dynamic real-time optimization of power modulation, and real-time adjustment of power modulation parameters and scanning trajectory according to feedback data;

[0074] The shielding gas module is used to adjust the shielding gas type and mixing ratio, introduce shielding gas, and control the gas flow.

[0075] Example 1

[0076] A beam shaping laser sealing welding method for an aluminum alloy target comprises the following steps:

[0077] Step 1: Use NaOH solution to clean the aluminum alloy end plug and cladding tube to remove dirt, oil and other impurities on the surface, then clean them with hydrochloric acid solution, then with distilled water, and finally with acetone and put them in a vacuum drying oven for 3 hours;

[0078] Step 2: Assemble the cleaned and dried aluminum alloy cladding tube and the end plug. The end plug and the cladding tube are interference fit, and the fit clearance is 0.01-0.03mm. After assembly, the gap of the weld to be welded should be less than 0.2mm.

[0079] Step 3, fixing the assembled aluminum alloy target on a rotating platform;

[0080] Step 4: Move the laser welding head so that the weld to be welded is located in the middle of the laser spot; adjust the height of the laser welding head so that the surface to be welded is located at the zero defocus position;

[0081] Step 5, fixing the assembled aluminum alloy target on a rotating platform;

[0082] Step 6: Set the laser welding parameters: laser power 3.6kW, set the scanning trajectory to a circle, the scanning frequency to 200Hz, and the scanning amplitude to 0.8mm;

[0083] Step 7: modulate the laser beam shaping mode, perform power modulation on 36 phase points within a circular scanning cycle, adjust the laser energy distribution, match the corresponding energy field for the aluminum alloy sealing joint, and adjust the circular beam shaping mode with high center and low sides to form a gap between the aluminum alloy cladding tube and the end plug for sealing welding;

[0084] Step 8: The purity of the introduced argon gas is 99.99% and the gas flow rate is 15 L / min.

[0085] Step 9: During welding, the laser welding head is fixed and the rotating platform rotates clockwise at a speed of 20r / min, i.e. 3s / r;

[0086] Step 10, welding the end plug ring weld for 4 / 3r, that is, stopping the laser output after 4s of welding, continuing the rotation of the welding rotating platform, and continuing to introduce argon gas to protect the weld. When the weld cools to below 200°C, stopping the introduction of argon gas and the rotation of the welding rotating platform.

[0087] like Figure 3 As shown, the fuel rod is mainly composed of an outer cladding tube 1, an inner cladding tube 2, an upper end plug 3, a lower end plug 4, and an internal component 7, wherein the outer cladding tube 1, the inner cladding tube 2, the upper end plug 3, and the lower end plug 4 are all made of nuclear grade 6061-T6 aluminum alloy, and the upper and lower end plugs are interference fit with the cladding tube, with an interference amount of 0.01-0.03mm, respectively assembled at both ends of the inner and outer cladding tubes, and sealed by two welds. There is a girth weld 5 between the upper end plug 3 and the outer cladding tube 1, and an end weld 6 between the upper end plug 3 and the inner cladding tube 2.

[0088] like Figure 4As shown in the figure, compared with the conventional galvanometer laser welding mode, the laser energy distribution in the beam shaping laser welding mode is more uniform. At the same time, the beam shaping laser welding mode reduces the maximum peak energy density of the laser at the edge of the molten pool, reduces the degree of weld undercut, improves the stability of the welding process, and makes the weld surface forming more uniform; the uniformly distributed laser energy improves the stability of the welding keyhole, and the rotating laser beam stirs the molten pool to intensify the flow of the molten pool, which is conducive to promoting gas escape and reducing the porosity; in addition, the uniformly distributed laser energy can reduce the heat input on both sides of the weld, reduce the width of the heat-affected zone, and improve the softening problem of the heat-affected zone.

[0089] Figure 5 This is the weld surface morphology of aluminum alloy sheet laser sealing welding using the same parameters as aluminum alloy nuclear target tube beam shaping laser welding. Figure 5 It can be seen that the weld surface is relatively smooth, slightly concave, and has no undercut. The weld surface has a silvery white metallic luster and no oxidation.

[0090] like Figure 6 As shown in the figure, the cross-section of the weld was sampled for metallographic observation. The end plug and the cladding tube were well combined, the microstructure was uniform, the effective weld depth reached more than 90% of the wall thickness, and there were no defects such as pores, cracks and inclusions, which met the welding technical requirements. At the same time, due to the beam shaping strategy, the laser energy distribution on both sides of the weld was reduced, and the bottom of the weld was in a uniform semicircular shape, which avoided stress concentration and reduced the risk of cracks.

[0091] like Figure 7 As shown in the figure, the weld microstructure was observed and the grain size was measured. It was found that near the fusion line, the grains were columnar and grew toward the center of the weld. Compared with the conventional galvanometer laser welding mode, the grain size was smaller in the beam shaping laser welding mode, which had a fine grain strengthening effect and improved the weld performance.

[0092] The specific application field of the present invention is the field of nuclear technology, and the specific products are the welding of aluminum alloy nuclear target end plugs and cladding tubes for low and medium temperature research and test reactors. In addition, other aluminum alloy irradiation targets and structural materials in the nuclear industry, automobiles, chemicals, electronic products and other manufacturing fields involving the welding of aluminum alloy components can also be welded using this technical solution, such as welding of aluminum alloy body structural parts, sealing of aluminum alloy shells of power battery packs, aluminum alloy structural parts in electronic equipment and electrical appliances, etc.

[0093] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A beam shaping laser welding method for an aluminum alloy target, characterized in that: The following steps are involved: Step 1: clean the aluminum alloy end plug and the cladding tube, and assemble the dried aluminum alloy cladding tube and the end plug, with an interference fit between the end plug and the cladding tube; Step 2, fixing the assembled aluminum alloy target on a rotating platform; Step 3: Move the laser welding head so that the weld to be welded is located in the middle of the laser spot; adjust the height of the laser welding head so that the surface to be welded is located at the zero defocus position; Step 4: Set laser welding parameters and optimize power modulation dynamically and in real time in combination with the intelligent control system; Step 5: modulate the laser beam shaping mode, perform power modulation on 36 phase points within a circular scanning cycle, adjust the laser energy distribution, match the corresponding energy field for the aluminum alloy sealing joint, and adjust the circular beam shaping mode with high center and low sides to form a gap between the aluminum alloy cladding tube and the end plug for sealing welding; Step 6: Introduce protective gas. During welding, the laser welding head is fixed and the rotating platform rotates clockwise at a speed of 20r / min, i.e. 3s / r; Step seven, welding the end plug ring weld for 4 / 3r, that is, stopping the laser output after 4s of welding, the welding rotating platform continues to rotate, and continues to introduce shielding gas to protect the weld. When the weld cools to below 200°C, stop introducing shielding gas and the welding rotating platform stops rotating.

2. The beam shaping laser welding method for an aluminum alloy target according to claim 1, characterized in that: In step 1, the thickness of the aluminum alloy cladding tube is 2 mm, and the material is a nuclear grade 6061-T6 aluminum alloy tube.

3. The beam shaping laser welding method for an aluminum alloy target according to claim 1, characterized in that: In step 1, the aluminum alloy end plug and cladding tube are cleaned with NaOH solution to remove surface dirt, oil and other impurities, then cleaned with hydrochloric acid solution, then cleaned with distilled water, and finally cleaned with acetone and placed in a vacuum drying oven for 3 hours.

4. The beam shaping laser welding method for an aluminum alloy target according to claim 1, characterized in that: In step 2, the fitting clearance between the end plug and the cladding tube is 0.01-0.03mm, and the gap of the weld to be welded after assembly should be less than 0.2mm.

5. The beam shaping laser welding method for aluminum alloy target according to claim 1, characterized in that: In step 4, the laser welding parameters are set as follows: laser power 3.6 kW, scanning trajectory set to circular, scanning frequency to 200 Hz, and scanning amplitude to 0.8 mm.

6. The beam shaping laser welding method for an aluminum alloy target according to claim 1, characterized in that: In step 4, real-time sensor technology is used to monitor the temperature distribution, molten pool morphology and weld surface during the welding process online, and the power modulation parameters and scanning trajectory are adjusted in real time according to the feedback data.

7. The beam shaping laser welding method for an aluminum alloy target according to claim 1, characterized in that: In step five, the laser beam shaping mode is modulated to change the laser power at different positions within the laser circular scanning trajectory period to achieve laser energy distribution regulation in the molten pool, reduce the laser energy distribution at the edge of the molten pool, improve the stability of the molten pool, and thus improve the quality of weld formation.

8. The beam shaping laser welding method for an aluminum alloy target according to claim 1, characterized in that: The shielding gas in step six is ​​a special shielding gas mixing solution for aluminum alloys, which adds 25% helium to argon to improve thermal efficiency, improve molten pool fluidity, and improve welding efficiency while ensuring welding stability.

9. The beam shaping laser welding method for an aluminum alloy target according to claim 8, characterized in that: The gas flow rate of the protective gas is 15L / min.

10. A beam shaping laser welding system for an aluminum alloy target according to the beam shaping laser welding method for an aluminum alloy target as claimed in any one of claims 1 to 9, characterized in that: include: The welding module is a global power modulation galvanometer laser welding system that combines a new beam shaping strategy with beam oscillation and power modulation dual beam shaping technologies; Sensor module, used for online monitoring of temperature distribution, molten pool morphology and weld surface during welding; Intelligent control module, used for dynamic real-time optimization of power modulation, and real-time adjustment of power modulation parameters and scanning trajectory according to feedback data; The shielding gas module is used to adjust the shielding gas type and mixing ratio, introduce shielding gas, and control the gas flow.

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