CO2 laser and ultrafast laser hybrid welding system and method and welded quartz glass optical element

Abstract

The invention discloses a CO2 laser and ultrafast laser hybrid welding system and method and a welded quartz glass optical element. The method comprises the steps that S1, at least two to-be-welded materials are clamped so that to-be-welded interfaces can make close contact; s2, ultrafast laser is adopted to conduct instantaneous heating and melting on the local area of the interface to be welded in the action area of the low-flux CO2 laser, and meanwhile auxiliary heat is provided by the low-flux CO2 laser; s3, after ultrafast laser local welding is completed, low-flux CO2 laser is adopted for continuing heating in the action area; s4, the position of the to-be-welded material is adjusted, and the to-be-welded interface which is not welded enters the action area; the steps S2-S3 are repeated until all the to-be-welded interfaces are welded and annealed; and S5, the welding area is naturally cooled, and composite welding is completed. By applying double laser, the temperature gradient is remarkably reduced, and thermal deformation is reduced; and CO2 laser post-welding annealing is carried out, so that the interface stress is effectively eliminated.

Description

Technical Field

[0001] The present invention belongs to the field of welding, and in particular relates to a composite welding system and method of CO2 laser and ultrafast laser, and a welded quartz glass optical element. Background Art

[0002] In the manufacturing of high-precision optical components, the choice of welding technology is crucial to ensuring the quality and performance of the final product. Traditionally, flame welding is commonly used to manufacture quartz glass optical components. However, this method is prone to significant thermal stress and weld distortion during the welding process, and the consistency and reliability of the weld interface often struggle to meet high-precision requirements. These limitations severely impact the accuracy and stability of optical components, making it difficult to meet the stringent optical performance requirements of high-end optical systems.

[0003] With the development of laser technology, laser welding, as a precision welding technology, has demonstrated advantages such as high energy density, fast welding speed, and high welding quality. In particular, CO2 lasers and ultrafast lasers (such as femtosecond lasers and picosecond lasers) have been widely used in the field of material processing. Due to its longer wavelength, CO2 lasers can provide a deeper welding depth and are suitable for welding thick materials. However, the CO2 laser welding process faces the problem of thermal deformation, which affects the welding quality. In contrast, ultrafast lasers, due to their extremely high peak power and extremely short pulse width, can achieve high-precision material removal and processing while reducing the heat-affected zone. However, this high-precision welding method also places extremely stringent requirements on the state of the connection interface. If these requirements are not met, cracks are very likely to occur, affecting the overall welding effect.

[0004] In order to improve the cracks caused by femtosecond laser welding, CN116117322A discloses a glass welding method that couples a femtosecond laser with a low-flux CO2 laser. Based on a femtosecond laser processing system, the low-flux CO2 laser processing system is coupled to perform a local remelting treatment on the glass material after welding, thereby improving the problems of microcracks and poor airtightness caused by femtosecond laser welding and enhancing the strength of the weld. However, the existing composite welding method still has many shortcomings. First, the above scheme still belongs to the serial composite idea of first ultrafast laser and then CO2 laser. The CO2 laser mainly plays the role of annealing to eliminate the residual stress of the joint, and cannot achieve a synergistic effect. At the same time, the CO2 laser performs local remelting and annealing only after the femtosecond laser completes the weld formation. There is a significant lag in the action time between the two. The molten pool has basically solidified, and it is impossible to synchronously adjust the thermal field and stress field within the critical window of instantaneous melting and cooling of femtosecond welding. Therefore, it is still difficult to completely avoid the generation of microcracks and thermal residual stress, and the problem of thermal deformation cannot be solved. Secondly, in serial mode, the processing cycle is limited and the processing efficiency is low. For optical components with large sizes or multiple welds, the production capacity bottleneck is prominent. Finally, the errors in the transfer and repositioning of the two-station are large. After the femtosecond welding station completes the scan, the workpiece is moved to the CO2 station, which easily introduces system positioning errors, resulting in deviations in the action positions of the CO2 laser and the ultrafast laser, affecting the consistency and strength uniformity of the weld. To overcome these problems, an in-situ collaborative composite welding technology is urgently needed in a single station, in the same action area, and in the same time window to ensure weld quality and optical performance. Summary of the Invention

[0005] The purpose of this invention is to provide a welding technology that effectively improves weld quality and addresses the problems of weld deformation and poor joint consistency encountered by traditional welding methods in the manufacture of high-precision optical components. To address these issues, the present invention relates to a laser welding system and method, specifically a hybrid welding system and method utilizing a CO2 laser and an ultrafast laser, particularly suitable for the precision welding of quartz glass optical components.

[0006] The composite welding technology of the present invention combines the advantages of low-flux CO2 laser and ultrafast laser, and uses a single-station dual-beam coupling configuration. Specifically, in this configuration, the low-flux CO2 laser is precisely positioned by a mechanical device, preferably in an oblique incidence manner, and works in conjunction with the ultrafast laser controlled by a scanning galvanometer at the same welding point. The CO2 laser provides the necessary auxiliary heat for the welding process with its millimeter-level coverage, while the ultrafast laser performs precise scanning according to a preset path within this area, ensuring the precise formation and high-quality connection of the weld. Through the cooperation of the mechanical translation stage and the scanning galvanometer unit, the present invention not only achieves efficient composite welding, but also effectively combines the heating effect of the low-flux CO2 laser and the precision processing function of the ultrafast laser, and plays a role in each stage before, during and after welding, effectively reducing heat input, reducing deformation during welding, and greatly improving the strength and consistency of the weld.

[0007] To achieve the above objectives, the present invention provides the following technical solutions: The present invention provides a CO2 laser and ultrafast laser composite welding method, comprising the following steps: S1, clamping at least two pieces of materials to be welded so that the weld interfaces are in close contact; S2, using an ultrafast laser to instantaneously heat and melt a local area of the interface to be welded within the action area of a low-flux CO2 laser, while the low-flux CO2 laser provides auxiliary heat; S3, after the ultrafast laser local welding is completed, the low-flux CO2 laser is used to continue heating in the action area to perform annealing treatment on the welding area; S4, adjusting the position of the materials to be welded so that the unwelded interfaces to be welded enter the active area of the low-flux CO2 laser; repeating steps S2 to S3 for the interfaces to be welded after the positions are adjusted until all interfaces to be welded are welded and annealed; S5, after annealing, the welding area is allowed to cool naturally to complete the composite welding.

[0008] When the material to be welded is quartz glass, the power density of the CO2 laser is in the range of 10-3000 kW cm -2 .

[0009] Preferably, the ultrafast laser has a pulse width of 30 fs-50 ps and a repetition frequency range of 10-1000 kHz. As an example, the ultrafast laser is a femtosecond laser or a picosecond laser.

[0010] Preferably, the diameter of the CO2 laser beam is in the range of 1-8 mm, and the diameter of the ultrafast laser focus is in the range of 20-100 μm.

[0011] Before the processing in step S1, at least two pieces of materials to be welded are usually selected and their surfaces are pre-treated to remove impurities.

[0012] The CO2 laser provides necessary auxiliary heat to control the temperature gradient during welding and reduce thermal stress and deformation. In step S3, during the annealing process, the ultrafast laser irradiation is terminated.

[0013] Furthermore, the ultrafast laser is controlled to quickly scan within the action area of the CO2 laser through a galvanometer.

[0014] Furthermore, in step S2, the ultrafast laser and the CO2 laser are coupled to form a composite laser beam. The ultrafast laser focus in the composite laser beam acts within the CO2 laser spot envelope and scans within the CO2 laser's active area according to a preset path, thereby achieving instantaneous heating and melting of a localized area of the weld interface. The ultrafast laser preferably has a scanning speed of 10-4000 mm / s.

[0015] In the present invention, "low-flux CO2 laser" refers to a CO2 laser with an average power lower than 500W and a scanning speed lower than 300mm / s.

[0016] Furthermore, in step S3, by controlling the annealing time and the CO2 laser beam power, the internal structure of the weld joint is optimized, the residual stress is eliminated, and the mechanical properties of the weld joint are enhanced.

[0017] According to the composite welding method described above, it also includes a preferred step: before the step S2 process, a low-flux CO2 laser is used to preheat the welding area to reduce the welding interface gap. By using this preheating, the interface gap is reduced to below 3μm. The CO2 laser does not undergo preheating treatment before ultrafast laser welding, and the interface gap cannot be adjusted. The interface gap is one of the most important factors affecting ultrafast laser welding. Through CO2 laser preheating, the area to be welded can be evenly heated, and the local softening of the material to be welded can reduce the interface gap between the upper and lower layers of the material to be welded under the action of the clamping force provided by the fixture; effectively eliminate gap unevenness, improve joint consistency, and improve the overall welding quality. Especially in large gap welding, it breaks through the limitations of traditional welding methods and ensures that the material preparation before welding is more sufficient.

[0018] Furthermore, the welding area is uniformly heated by adjusting the power density and incident angle of the CO2 laser beam.

[0019] When the material to be welded is quartz glass, the power density of the CO2 laser is in the range of 10-3000 kW cm -2 Before welding, the CO2 laser heats the interface to be welded to 1200K-2000K to reduce the interface gap and avoid material melting.

[0020] Optionally, a CO2 laser and ultrafast laser composite welding method further includes: mechanically grinding and polishing the welded components after the composite welding is completed to eliminate microscopic defects that may be generated by the welding operation and ensure the surface finish of the components.

[0021] The present invention also provides a welding system for implementing the above-mentioned CO2 laser and ultrafast laser composite welding method, comprising: CO2 laser generator, used to generate CO2 laser; Ultrafast laser generator, used to generate ultrafast laser; Scanning galvanometer unit, used to guide the movement of ultrafast laser; Mechanical translation stage, used to fix the material to be welded; dynamic high-precision control of the welding area is achieved through high-precision motion control of the mechanical translation stage; The translation stage and the scanning galvanometer unit work together to enable the CO2 laser and the femtosecond laser to act on the same welding area.

[0022] Furthermore, the system also includes a beam coupling unit for coupling the CO2 laser and the ultrafast laser together to form a composite laser beam. In the composite laser beam, the CO2 laser acts on the surface of the material to be welded (such as quartz material), and the ultrafast laser focus acts within the CO2 laser spot envelope and scans according to a preset path.

[0023] Furthermore, the scanning galvanometer unit includes an X-axis scanning galvanometer, a Y-axis scanning galvanometer, and a Z-axis zoom module. The Z-axis zoom module is used to guide the ultrafast laser to be incident on the X-axis scanning galvanometer and the Y-axis scanning galvanometer. The X-axis scanning galvanometer and the Y-axis scanning galvanometer cooperate to guide the movement of the ultrafast laser on the interface to be welded. The Z-axis zoom module is also used to guide the focal plane of the ultrafast laser to match the interface to be welded. The Z-axis zoom module can change the focal plane of the ultrafast laser to match the position of the interface to be welded according to the thickness of the material to be welded.

[0024] Furthermore, the system also includes a CO2 laser beam homogenizer for homogenizing the CO2 laser, thereby converting the energy distribution of the CO2 laser beam from a Gaussian distribution to a flat-top distribution, producing a more consistent and uniform effect over the active area. The CO2 laser passes through the beam homogenizer to form a flat-top spot of a parallel beam.

[0025] Furthermore, the system also includes a beam diameter adjustment module for adjusting and controlling the diameter of the CO2 laser and / or ultrafast laser beam. The diameter range of the CO2 laser beam is 1-8 mm, and the ultrafast laser focus diameter is 20-100 μm.

[0026] Furthermore, the mechanical displacement stage includes a welding fixture for fixing the material to be welded.

[0027] The system further includes a control unit for controlling the coordinated motion of the laser generator and the scanning galvanometer unit. Furthermore, the control unit is also used to adjust welding parameters, including laser power, repetition rate, and welding speed.

[0028] The present invention also provides a welded quartz glass optical element obtained by implementing the above-mentioned CO2 laser and ultrafast laser composite welding method, which has high connection strength, small welding deformation and good joint consistency.

[0029] Compared with the prior art, the present invention has the following significant technical effects: 1. This invention uses a low-flux CO2 laser for preheating before welding, which can evenly heat the area to be welded, effectively reducing the gap at the weld interface, eliminating gap unevenness, and improving overall weld quality. Especially for large-gap welding, it breaks through the limitations of traditional welding methods and ensures more thorough material preparation before welding.

[0030] 2. By simultaneously applying low-flux CO2 lasers and ultrafast lasers, this invention significantly reduces the temperature gradient during welding, effectively minimizing thermal deformation and thereby improving the geometric accuracy and shape consistency of the weld. This optimized thermal management approach is particularly suitable for welding high-precision optical components.

[0031] 3. The present invention uses CO2 laser post-weld annealing to achieve precise control of the post-weld cooling rate, effectively eliminates the stress generated at the welding interface, improves the microstructure of the weld, further enhances the mechanical properties and long-term stability of the weld joint, and ensures the reliability of the optical component during use.

[0032] 4. This invention utilizes single-station dual-beam coupling technology to efficiently couple a low-flux CO2 laser beam with an ultrafast laser beam at the same processing location. The femtosecond pulse characteristics and high repetition rate of the ultrafast laser enable instantaneous heating and melting of the localized joining area while maintaining the original material properties and avoiding a significant heat-affected zone.

[0033] 5. The present invention and system allow for flexible adjustment of the scanning path and laser parameters (including power, frequency, and speed), enabling the welding process to be optimized for specific welding requirements. The coordinated motion of the high-precision mechanical translation stage and the scanning galvanometer unit further ensures the efficiency and accuracy of the welding process.

[0034] 6. By combining low-flux CO2 lasers with ultrafast lasers, and coordinating the welding process at each stage (pre-weld preheating, in-weld auxiliary heating, and post-weld annealing), this invention not only achieves controlled interfacial gaps and improves welding efficiency, but also significantly improves the microstructure and overall quality of the welded joint. This method is particularly well-suited for high-end optical applications, which require stringent weld quality and optical performance. These advantages contribute to the invention's superior performance in forming high-quality welded joints, meeting the demands of high-end optical applications such as quartz materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of a CO2 laser and ultrafast laser hybrid welding system according to an embodiment of the present invention.

[0036] Figure 2 This is a flow chart of a CO2 laser and ultrafast laser composite welding method according to an embodiment of the present invention.

[0037] Description of reference numerals: Figure 1 :1- CO2 laser generator, 2- Z-axis zoom module, 3- X-axis scanning galvanometer, 4- Y-axis scanning galvanometer, 5- upper layer of material to be welded, 6- lower layer of material to be welded, 7- ultrafast laser generator. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the technical solutions in this application, the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work should fall within the scope of protection of this application.

[0039] Reference Figure 2 , a CO2 laser and ultrafast laser composite welding method, comprising: (1) Pretreatment of the materials to be welded: Select two pieces of materials to be welded and perform surface pretreatment to remove surface impurities. For example, the materials to be welded are quartz glass optical elements. Clamp the two pieces of materials to be welded so that the weld interface is in close contact. (2) Preheating before CO2 laser welding: Use low-flux CO2 laser to preheat the welding area.

[0040] (3) Auxiliary heating in ultrafast laser welding and simultaneous CO2 laser welding: An ultrafast laser is used to perform local instantaneous heating and melting of the interface to be welded within the action area of the low-flux CO2 laser, while the low-flux CO2 laser provides auxiliary heat.

[0041] (4) Annealing after CO2 laser welding: After the ultrafast laser local welding is completed, the ultrafast laser is turned off, and the low-flux CO2 laser continues to heat the action area, thereby achieving annealing of the welding area.

[0042] (5) Completion of composite welding: Adjust the position of the materials to be welded by the mechanical displacement stage so that the unwelded interface to be welded enters the action area of the CO2 laser; repeat steps (2) to (4) for the interface to be welded after the position is adjusted until all interfaces to be welded are welded and annealed; after annealing, allow the welding area to cool naturally to complete the composite welding.

[0043] See also Figure 1 , a system for implementing the above-mentioned in-situ welding method, comprising: A CO2 laser generator 1, used for generating CO2 laser; An ultrafast laser generator 7, for generating ultrafast laser; when the ultrafast laser generator is a femtosecond laser generator, it is used to generate femtosecond laser; when the ultrafast laser generator is a picosecond laser generator, it is used to generate picosecond laser; A scanning galvanometer unit is used to guide the movement of the ultrafast laser. For example, the scanning galvanometer unit includes a Z-axis zoom module 2, an X-axis scanning galvanometer 3, and a Y-axis scanning galvanometer 4. The X-axis scanning galvanometer 3 and the Y-axis scanning galvanometer 4 are used to guide the ultrafast laser to scan a preset pattern on the interface to be welded. The Z-axis zoom module is used to guide the focal plane of the ultrafast laser to match the interface to be welded. Mechanical translation stage ( Figure 1 (not shown) for securing the components to be welded; the components to be welded comprise an upper layer of welded material 5 and a lower layer of welded material 6. The mechanical translation stage includes a welding fixture for securing the components to be welded. High-precision motion control of the mechanical translation stage enables dynamic, high-precision control of the welding area of the components to be welded.

[0044] The mechanical translation stage and the scanning galvanometer unit work together to enable the CO2 laser and the femtosecond laser to act on the same welding area.

[0045] In a specific embodiment, the components to be welded are two pieces of transparent quartz glass.

[0046] Example 1 Selection and clamping of transparent quartz glass: 1. Select two quartz glass optical components to be welded and perform surface pretreatment to remove surface impurities; 2. Use a welding fixture to fix the two pieces of quartz glass on the mechanical translation stage, and make the interfaces to be welded of the two pieces of quartz glass in close contact.

[0047] Preheating before welding: 1. Use a CO2 laser generator to generate CO2 laser, and use the generated CO2 laser to preheat the welding area. Use a high-precision mechanical translation stage to adjust the position of the quartz glass optical element to ensure that the interface to be welded is accurately aligned with the CO2 laser. By adjusting the power density of the beam to a range of 10-3000 kW cm -2 , uniformly heat the quartz glass, and before welding, use CO2 laser to heat the interface of the quartz glass to 1200K-2000K, optimize the interface gap between the upper and lower materials to be welded, and reduce the interface gap to below 3μm.

[0048] Hybrid laser welding: 1. Connect the outputs of the low-flux CO2 laser generator and the ultrafast laser generator to a beam coupling unit. The beam coupling unit includes optical components such as beam splitters and reflectors to achieve spatial overlap and optical path unification of the two beams, forming a single-station dual-beam coupling system. This system couples an ultrafast laser (wavelength 0.3-1.1μm) with a low-flux CO2 laser beam (average power <500W, scanning speed range 1-300mm / s) to form a composite laser beam.

[0049] 2. Control the coordinated movement of the mechanical translation stage and the scanning galvanometer unit to ensure that the CO2 laser and ultrafast laser accurately cross-act on the same welding point. The ultrafast laser is guided to the welding point by the scanning galvanometer unit, performing high-precision and rapid local melting of the welding point to achieve precision welding. The ultrafast laser follows a zigzag trajectory and a preset line interval at a scanning speed of 10-4000mm / s, rapidly scanning the envelope range of the CO2 laser beam. The flat-top distributed CO2 laser continues to provide the necessary auxiliary heat to maintain the temperature of the quartz glass at 1400K-1500K, control the temperature gradient during the welding process, and reduce thermal stress and deformation. In this way, the composite beam performs precise scanning welding according to the above-set path and parameters to form the weld.

[0050] Post-weld treatment: 1. After the composite laser welding, turn off the ultrafast laser generator and maintain a certain power output of the low-flux CO2 laser in the welding area to anneal the weld. By controlling the annealing time range of 1-50min and the beam power density range of 10-3000 kW cm -2 , maintain the quartz glass temperature at the annealing temperature of 1400K-1500K, optimize the internal structure of the welded joint, eliminate residual stress, and enhance the mechanical properties of the weld.

[0051] 2. After annealing, allow the welding area to cool naturally to complete the composite welding.

[0052] 3. If necessary, the weld can be subjected to subsequent treatment (such as re-annealing) to further enhance the strength and sealing of the weld.

[0053] Inspection and post-processing: 1. After welding is completed, visual and instrumental inspections are performed to evaluate the quality and uniformity of the weld joint. If necessary, mechanical grinding and polishing are performed to eliminate microscopic defects that may be caused by the welding operation and ensure the surface finish of the optical component.

[0054] 2. Final quality control: Evaluate the performance of welded optical components through optical or mechanical testing to ensure they meet design requirements and application standards.

Claims

1. A CO2 laser and ultrafast laser composite welding method, characterized in that: The following steps are involved: S1, clamping at least two pieces of materials to be welded so that the weld interfaces are in close contact; S2, using an ultrafast laser to instantaneously heat and melt a local area of the interface to be welded within the action area of a low-flux CO2 laser, while the low-flux CO2 laser provides auxiliary heat; S3, after the ultrafast laser local welding is completed, the low-flux CO2 laser is used to continue heating in the action area to perform annealing treatment on the welding area; S4, adjusting the position of the materials to be welded so that the unwelded interfaces to be welded enter the active area of the low-flux CO2 laser; repeating steps S2 to S3 for the interfaces to be welded after the positions are adjusted until all interfaces to be welded are welded and annealed; S5, after annealing, the welding area is allowed to cool naturally to complete the composite welding.

2. The method according to claim 1, characterized in that Also includes: Before the processing in step S2, a low-flux CO2 laser is used to preheat the welding area to reduce the welding interface gap.

3. The method according to claim 1 or 2, characterized in that The ultrafast laser has a pulse width of 30 fs-50 ps and a repetition frequency range of 10-1000 kHz.

4. The method according to claim 1 or 2, characterized in that In step S2, the ultrafast laser and the CO2 laser are coupled to form a composite laser beam. The ultrafast laser focus in the composite laser beam acts within the CO2 laser spot envelope and scans within the action area of the CO2 laser according to a preset path, thereby achieving instantaneous heating and melting of the local area of the interface to be welded.

5. The method according to claim 1 or 2, wherein The ultrafast laser is a femtosecond laser or a picosecond laser, and the ultrafast laser has a scanning speed of 10-4000 mm / s; the material to be welded is quartz glass; the power density range of the CO2 laser is 10-3000 kW cm -2 .

6. The method according to claim 2, wherein The material to be welded is quartz glass; the power density of the CO2 laser is in the range of 10-3000 kW cm -2 ; Before welding, the CO2 laser heats the interface to be welded to 1200K-2000K.

7. A welding system for implementing the method according to any one of claims 1 to 6, characterized in that: include: CO2 laser generator, used to generate CO2 laser; Ultrafast laser generator, used to generate ultrafast laser; Scanning galvanometer unit, used to guide the movement of ultrafast laser; Mechanical translation stage, used to fix the material to be welded; dynamic high-precision control of the welding area is achieved through high-precision motion control of the mechanical translation stage; The translation stage and the scanning galvanometer work in coordination so that the CO2 laser and the femtosecond laser act on the same welding area.

8. The system according to claim 7, characterized in that The system also includes a beam coupling unit, a beam diameter adjustment module, and a CO2 laser beam homogenizer. The beam coupling unit is used to couple the CO2 laser and the ultrafast laser together to form a composite laser beam. The CO2 laser beam homogenizer is used to homogenize the CO2 laser, thereby converting the energy distribution of the CO2 laser beam from a Gaussian distribution to a flat-top distribution. The beam diameter adjustment module is used to adjust and control the diameter of the CO2 laser and / or ultrafast laser beam. The CO2 laser beam diameter ranges from 1 to 8 mm, and the ultrafast laser focus diameter ranges from 20 to 100 μm.

9. The system according to claim 7, wherein: The scanning galvanometer unit includes an X-axis scanning galvanometer, a Y-axis scanning galvanometer and a Z-axis zoom module, wherein the Z-axis zoom module is used to guide the ultrafast laser to be incident on the X-axis scanning galvanometer and the Y-axis scanning galvanometer. The X-axis scanning galvanometer and the Y-axis scanning galvanometer are used to cooperate to guide the movement of the ultrafast laser on the interface to be welded. The Z-axis zoom module is also used to guide the focal plane of the ultrafast laser to match the interface to be welded.

10. A welded quartz glass optical component obtained by implementing the method according to any one of claims 1 to 6, characterized in that: It has high connection strength, small welding deformation and good joint consistency.

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