Laser welding method for T-shaped red copper structure

Abstract

The invention relates to a laser welding method for a T-shaped red copper structure, which comprises the following steps of: vertically assembling an upper cover plate and a lower plate made of a red copper material, forming a red-blue composite laser beam by coaxial infrared laser beam and blue laser beam, and welding along the outer surface of the upper cover plate corresponding to the lower plate by using the red-blue composite laser beam, during welding, the inclination angle between the red-blue composite laser beam and the vertical face of the outer surface of the upper cover plate is larger than or equal to 5 degrees, welding is conducted with the negative defocusing amount, a light spot formed by the infrared laser beam swings in a light spot formed by the blue laser beam, a welding seam is formed in the upper cover plate and penetrates through the upper cover plate, and after welding, the upper cover plate and the lower plate form a T-shaped red copper structure. The infrared laser provides large energy density to guarantee large fusion depth, the uniform energy distribution of the blue laser guarantees the stability of a molten pool, for a red copper thick plate with the upper cover plate smaller than or equal to 3 mm, the fusion depth can be larger than or equal to 2 mm, the thermal deformation of the upper cover plate is smaller than or equal to 0.5%, splashing is extremely low in the welding process, large-particle splashing is avoided, cost is low, and large-scale production is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-reflectivity metal welding, and particularly relates to a laser welding method for a T-shaped copper structure. Background Art

[0002] Due to its good thermal conductivity, electrical conductivity, corrosion resistance and other characteristics, copper is widely used in heat dissipation devices. In recent years, with the booming development of artificial intelligence, the demand for heat dissipation devices has increased day by day, and the demand for deep penetration welding of copper has also increased sharply, which involves vertically welding and connecting the upper cover plate and the lower plate of copper material to form a T-shaped structure. Therefore, it is necessary to develop a welding method for T-shaped copper structures with high welding quality, low cost and conducive to mass production.

[0003] Laser welding is a highly efficient and precise welding technology that uses a highly focused monochromatic light. After being focused by an optical system, the laser energy is converted into heat energy. When the laser beam irradiates the surface of the material to be welded, the material can absorb the laser energy, and the surface temperature rapidly rises to reach the melting point of the material, so that the material melts and fuses together. Compared with other welding methods, it has the advantages of high efficiency, small heat affected zone, precision, etc. However, there are still the following technical difficulties in applying it to the welding of T-shaped copper structures:

[0004] First, since non-ferrous metals have extremely low absorption rates for long-wavelength laser light, and copper, as a typical high-reflectivity material among non-ferrous metals, has an absorption rate of only 3% - 5% for infrared laser light. Therefore, in the prior art, short-wavelength lasers are mostly used for copper welding. Because the absorption rate of copper for blue light is as high as 65%, blue light lasers are mainly used. However, the maximum power of existing mainstream blue light lasers is generally below 3000W, and the energy density is relatively low, and the penetration depth into copper is basically less than 1mm, which cannot meet the effective penetration depth requirements of T-shaped copper structures.

[0005] II. Infrared lasers have a longer wavelength and have the advantage of strong deep penetration welding ability. Generally, single-mode fiber lasers or ring light source lasers are used. In order to improve the poor absorption rate of copper materials to infrared light and the problem of poor welding, although some dual-beam composite laser welding methods have been proposed in the prior art. For example, in a dual-beam composite laser welding device and method for red copper materials disclosed in Patent Publication No. CN114633022A, a blue laser oscillating welding head is vertically irradiated onto the weld of the red copper material, and the fiber laser outputs an annular light spot and irradiates the material surface at an angle of 45 degrees with the horizontal plane for composite welding. However, on the one hand, the welding of T-shaped red copper structures is more difficult than that of ordinary red copper welding specimens when using laser welding. The reason is that at the intersection of the T-shaped joint, that is, the joint between the upper cover plate and the lower plate, the heat dissipation area is larger than that when directly connecting the welds between two horizontal copper plates. The heat is quickly dissipated in multiple directions, and a higher heat input or a more concentrated heat source is required to maintain the molten pool. However, in order to obtain a large penetration welding effect, if the power of the infrared laser is increased sharply, it will lead to poor appearance formation of the weld, resulting in problems such as thermal cracks, thermal deformation, explosion holes on the weld surface, and large metal spatter. On the other hand, due to the influence of reflection, the vertical welding of blue light is easily affected by optical path pollution, which affects the beam quality and even causes the reflected light to damage the optical structure. Therefore, the existing dual-beam composite laser welding method is not suitable for the welding of T-shaped red copper structures.

[0006] III. In the prior art, for the welding position of the T-shaped structure, the contact positions on both sides of the lower plate and the upper cover plate are adopted. For example, in a dual-sided laser-CMT composite welding device and method for T-shaped joints of low-resistivity medium-thick plates disclosed in Patent Publication No. CN117697149A, laser-CMT composite welding is carried out symmetrically along the welding direction. There are also problems of many processes and equipment for the welding of T-shaped red copper structures, which affect the welding cost and efficiency. Summary of the Invention

[0007] The present invention aims to solve at least one of the above technical problems to some extent. The present invention provides a laser welding method for T-shaped red copper structures, which can effectively weld T-shaped red copper structures with an upper cover plate ≤ 3 mm, and has extremely low spatter during welding, no large particle spatter, small thermal deformation of the upper cover plate, low cost, and is conducive to mass production.

[0008] The technical solution adopted by the present invention to solve its technical problems is:

[0009] A laser welding method for T-shaped red copper structures, the method comprising:

[0010] After vertically assembling the upper cover plate and the lower plate made of copper material, a red-blue composite laser beam is formed by coaxial infrared laser beam and blue laser beam, and the red-blue composite laser beam is used to weld along the outer surface of the upper cover plate corresponding to the lower plate. During welding, the inclination angle between the red-blue composite laser beam and the vertical plane of the outer surface of the upper cover plate is ≥5°, and welding is carried out with a negative defocus amount. The spot formed by the infrared laser beam swings within the spot formed by the blue laser beam, forming a weld seam on the upper cover plate and penetrating the upper cover plate. After welding, the upper cover plate and the lower plate form a T-shaped copper structure.

[0011] In the preferred technical solution, a tooling is used to adsorb the upper cover plate until the assembly gap between the upper cover plate and the lower plate is ≤0.01mm. The upper cover plate and the lower plate are assembled in an adsorption flexible manner, which can further improve the assembly accuracy and production rate, and at the same time, compared with other rigid jigs, it can avoid damage or deformation to the upper cover plate made of copper material.

[0012] In order to further improve the efficiency of automated laser welding processing, in the preferred technical solution, the tooling includes a driving mechanism and an adsorption head. The driving mechanism is used to drive the adsorption head to reciprocate relative to the upper cover plate. When the adsorption head is driven close to the upper cover plate, the upper cover plate and the lower plate can be adsorbed and pressed together to ensure tight fit between them. After welding is completed, the adsorption head is driven to release adsorption and move away from the upper cover plate, and it can be prepared to press and fit the next group of upper cover plates and lower plates to be welded.

[0013] In order to further improve the efficiency of automated laser welding processing, in the preferred technical solution, a red-blue composite welding head with an infrared swing function is used. The red-blue composite welding head uses a single-mode infrared laser and a blue laser to generate a red-blue composite laser beam. During welding, the welding position of the red-blue composite welding head is controlled to weld along a preset trajectory to ensure the position of the weld seam on the lower plate and further ensure the welding quality.

[0014] In order to further avoid problems such as pore explosion on the weld surface and large metal spatter caused by too high power of the single-mode infrared laser, in the preferred technical solution, the power of the single-mode infrared laser is ≤6000W. In order to further improve the uniformity of the blue laser energy distribution and the stability of the molten pool, in the preferred technical solution, the power of the blue laser is ≥500W.

[0015] In order to further increase the penetration depth, and at the same time effectively control the heat accumulation during welding and reduce the thermal deformation of the upper cover plate, in the preferred technical solution, the welding speed during welding is 50-70mm / s, and the defocus amount is -1 to -3m. An appropriate welding speed can make the interaction between the composite laser energy and the copper material reach a better balance, and the penetration depth and width of the weld seam are relatively uniform. The weld seam has good formation, smooth surface and no obvious defects. An appropriate negative defocus amount can make the laser energy more concentrated on the upper cover plate, which is beneficial to increasing the penetration depth of the weld seam and avoiding defects such as overheating and pores at the bottom of the weld seam caused by too large negative defocus amount.

[0016] In order to further avoid the pool boiling and intense spattering caused by too high power during welding, and avoid reducing the weld penetration and the service life of the equipment due to too low laser power, in the preferred technical solution, the power of the single-mode infrared laser is 3600 - 5400W, and the power of the blue laser is 500 - 800W.

[0017] In order to further avoid problems such as excessive heat input, thermal cracks and thermal deformation caused by the delayed swing of the infrared laser beam during operation, in the preferred technical solution, the infrared swing is turned on in advance during welding.

[0018] In order to further keep the spot formed by the infrared laser beam swinging within the spot formed by the blue laser beam, in the preferred technical solution, the blue laser is turned on before the infrared laser during welding, and preferably the blue laser is turned on 200ms - 500ms in advance.

[0019] In order to further facilitate the control of the defocus amount and power density of the infrared laser to match the spot formed by the blue laser beam, and avoid reducing the effective weld penetration and increasing the welding spatter, in the preferred technical solution, the collimation focal length of the optical configuration of the red-blue composite welding head is 100mm, and the focusing focal length is 250mm.

[0020] In order to further facilitate the control of the swing trajectory of the infrared laser, in the preferred technical solution, a swing lens is added to the infrared collimation position of the red-blue composite welding head to control the swing of the infrared laser.

[0021] In order to further keep the molten pool stable, reduce the welding spatter and improve the weld quality, and optimize the protection lens replacement system, in the preferred technical solution, when the single-mode infrared laser and the blue laser are continuously welded with the same welding parameters and the laser brightness weakens, the protection lens of the red-blue composite welding head is replaced.

[0022] In order to further improve the welding stability, in the preferred technical solution, a chiller with a refrigeration power ≥ 6000W is used to cool the single-mode infrared laser and the red-blue composite welding head.

[0023] In order to further improve the welding stability, in the preferred technical solution, a chiller with a refrigeration power ≥ 2100W is used to cool the blue laser.

[0024] In order to further avoid damage to the tooling caused by the reflected light irradiating on the tooling due to too large an inclination angle, in the preferred technical solution, the inclination angle between the red-blue composite laser beam and the vertical plane of the outer surface of the upper cover plate during welding ≤ 10°.

[0025] In order to further improve the uniformity of heat distribution, reduce the concentration of thermal stress and spatter during welding, increase the acting area, and optimize energy utilization, in the preferred technical solution, the spot formed by the infrared laser beam swings in a circular shape.

[0026] In order to further adapt to the size of the lower plate and prevent the weld width from being too large, in the preferred technical solution, the swing radius of the infrared laser beam is 0.2 mm to 0.5 mm.

[0027] In order to further protect the solder joint from oxidation and reduce the spatter generated during welding, in the preferred technical solution, argon gas is blown coaxially with the red-blue composite laser beam for gas protection.

[0028] In order to further improve the quality of the weld seam, in the preferred technical solution, the argon gas flow rate > 20 L / min.

[0029] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0030] (1) The present invention uses a coaxial infrared laser beam and a blue laser beam to form a red-blue composite laser beam, and combines the spot formed by the infrared laser beam to swing and weld the T-shaped copper structure within the spot formed by the blue laser beam. The infrared laser provides high heat input and a more concentrated heat source to maintain the molten pool, ensuring an effective penetration depth. For a copper thick plate with an upper cover plate ≤ 3 mm, the penetration depth can reach ≥ 2 mm. Combining the uniform energy distribution of the blue laser ensures the stability of the molten pool, prevents problems such as thermal cracks and thermal deformation caused by excessive heat input, enables the weld seam appearance to be smooth, has a high welding efficiency, effectively controls the heat accumulation during welding, and makes the thermal deformation of the upper cover plate ≤ 0.5%. Compared with the ring-shaped infrared laser, it not only has low welding spatter and high energy absorption rate, but also reduces the light source cost, which is beneficial for mass production applications.

[0031] (2) The present invention uses a red-blue composite laser beam with an inclination angle ≥ 5° for laser welding. Compared with the existing welding method based on an infrared laser, it prevents more red light reflection from copper, improves the absorbed energy and thus the effective penetration depth, and at the same time protects the optical devices in the equipment. Compared with the vertical welding of the blue laser, it can reduce the influence of reflection on the blue laser.

[0032] (3) The red-blue composite laser beam of the present invention welds along the outer surface of the upper cover plate corresponding to the lower plate, forms a weld seam on the upper cover plate and penetrates through the upper cover plate, so that the upper cover plate and the lower plate are directly connected to form a T-shaped copper structure after welding. This welding position and penetration welding method can effectively improve the production efficiency, reduce the thermal deformation of the upper cover plate and the welding cost compared with the existing method of welding on both sides of the lower plate.

[0033] (4) The present invention adopts an adsorption tooling, appropriate welding parameters, an optical configuration, a chiller for temperature protection, coaxial gas protection, and a protective lens replacement system, which can further improve the processing efficiency and the stability of the metal molten pool, reduce welding spatter, and improve the weld quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, where:

[0035] Figure 1 is a welding schematic diagram of an embodiment of the present invention;

[0036] Figure 2 is a schematic diagram of the laser anti-reflection tilt angle of an embodiment of the present invention;

[0037] Figure 3 is a schematic diagram of the swing of the composite light source of an embodiment of the present invention;

[0038] Figure 4 Weld appearance diagram of Embodiment 1 of the present invention;

[0039] Figure 5 Weld metallographic diagram of Embodiment 1 of the present invention;

[0040] Figure 6 Weld appearance diagram of Embodiment 2 of the present invention;

[0041] Figure 7 Weld metallographic diagram of Embodiment 2 of the present invention;

[0042] Figure 8 Weld appearance diagram of Embodiment 3 of the present invention;

[0043] Figure 9 Weld metallographic diagram of Embodiment 3 of the present invention;

[0044] Figure 10 Weld appearance diagram of Comparative Example 1 of the present invention;

[0045] Figure 11 Weld metallographic diagram of Comparative Example 1 of the present invention;

[0046] Figure 12 Weld appearance diagram of Comparative Example 2 of the present invention;

[0047] Figure 13 Weld metallographic diagram of Comparative Example 2 of the present invention.

[0048] Reference numerals in the figures: red-blue composite welding head 1, infrared laser beam 2, blue laser beam 3, welding track 4, upper cover plate 5, lower plate 6, adsorption head 7, pneumatic slider 8, red-blue composite laser beam 9, machining surface 10, tilt angle θ, blue laser beam forming spot 11, near-infrared swing track 12 Detailed implementation manners

[0049] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals indicate the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0050] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "horizontal", "vertical", "upper", "lower", "level", "inner", "outer", etc. are based on the orientation or positional relationships shown in the accompanying drawings. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

[0051] For the existing blue laser, the penetration depth into copper is basically less than 1 mm. For the infrared laser, a single-mode fiber laser or a ring light source laser is adopted, which has problems such as the reflected light damaging the optical structure, poor appearance formation of the weld seam, explosion holes on the weld seam surface, and large metal spatter. The existing dual-beam composite laser welding method is not yet applicable to the welding of T-shaped copper structures, and the welding cost and efficiency of the T-shaped structure are relatively high. In view of this situation, the present invention considers adopting a welding strategy of a coaxial inclined red-blue composite laser beam + an infrared laser beam oscillating within the blue light spot.

[0052] In the following embodiments and comparative examples: The used laser welding equipment adopts a red-blue composite welding head with an infrared oscillation function. The model of the single-mode infrared laser of the red-blue composite welding head is the Chuangxin Laser MFSC-6000 single-module continuous fiber laser; the model of the blue laser of the red-blue composite welding head is the 1000W blue laser of Lanmu Laser; the optical configuration of the red-blue composite welding head has a collimation focal length of 100 mm and a focusing focal length of 250 mm. A swing lens is added to the infrared collimation position of the red-blue composite welding head to control the oscillation of the infrared laser.

[0053] In the following embodiments and comparative examples: During welding, the infrared oscillation is turned on in advance, the blue laser is turned on before the infrared laser, a chiller with a refrigeration power of 7200W is used to cool the single-mode infrared laser and the red-blue composite welding head, and a chiller with a refrigeration power of 2100W is used to cool the blue laser to ensure welding stability; Argon gas is blown coaxially with the red-blue composite welding head for gas protection, which can effectively protect the weld seam surface from oxidation and reduce the spatter generated during welding at the same time; For every 500 products produced, that is, 3000 weld seams, the protective lens on the red-blue composite welding head is replaced; The copper wire substrate is T1 copper.

[0054] In the following embodiments and comparative examples: As Figure 1As shown, the tooling includes a driving mechanism and a suction head 7. The driving mechanism includes a pneumatic slider 8 which can move up and down and is used to drive the suction head 7 to reciprocate relative to the upper cover plate 5. The suction head 7 can be provided in multiple numbers, and the end of the suction head 7 can be set as a disc shape for corresponding to multiple upper cover plates 5. When the suction head 7 is driven to approach the upper cover plate 5, the upper cover plate 5 and the lower plate 6 can be adsorbed and pressed together to ensure a tight fit between the two. After welding is completed, the suction head 7 is driven to release the adsorption and move away from the upper cover plate 5, and then it is ready to press and fit the next group of upper cover plates 5 and lower plates 6 to be welded.

[0055] Embodiment 1:

[0056] This is a preferred embodiment of the laser welding method for the T-shaped copper structure of the present invention, and its method includes:

[0057] Vertically assemble the upper cover plate 5 and the lower plate 6 made of copper material. Specifically:

[0058] As Figure 1 shown, the thickness of the upper cover plate 5 is 1.5 mm. There are multiple upper cover plates 5 and lower plates 6, and they are all made of copper material. Place the multiple upper cover plates 5 to be welded horizontally above the corresponding lower plates 6. The pneumatic slider 8 drives the suction head 7 to descend. The suction head 7 adsorbs the corresponding upper cover plate 5 and presses the upper cover plate 5 onto the corresponding lower plate 6. At this time, the upper cover plate 5 and the lower plate 6 are perpendicular, and the assembly gap between the upper cover plate 5 and the lower plate 6 ≤ 0.01 mm to ensure no gap between the copper plates.

[0059] After assembly, a red-blue composite laser beam 9 is formed by the coaxial infrared laser beam 2 and blue laser beam 3. Use the red-blue composite laser beam 9 to weld along the outer surface of the upper cover plate 5 corresponding to the lower plate 6. When welding, the red-blue composite laser beam 9 is inclined to the vertical plane of the outer surface of the upper cover plate 5 and is welded with a negative defocus amount. The spot formed by the infrared laser beam 2 swings within the spot 11 formed by the blue laser beam to form a weld seam on the upper cover plate 5 and penetrate the upper cover plate 5. After welding, the upper cover plate 5 and the lower plate 6 form a T-shaped copper structure. Specifically:

[0060] As Figure 1 shown, set the welding track 4 of the laser welding equipment along the outer surface of the upper cover plate 5 corresponding to the lower plate 6. The power of the single-mode infrared laser is turned on at 55% of the total power of 6000 W, the power of the blue laser is turned on at 60% of the total power of 1000 W, the welding speed is 70 mm / s, the defocus amount is -2 m, the red-blue composite welding head 1 of the laser welding equipment is located above the side of the upper cover plate 5, and the argon gas flow rate is 25 L / min. As Figure 2As shown, the red-blue composite welding head 1 uses a single-mode infrared laser and a blue laser to generate coaxial infrared laser beam 2 and blue laser beam 3, forming a red-blue composite laser beam 9. The inclination angle of the red-blue composite welding head 1 with respect to the vertical plane is 6°, that is, the inclination angle θ of the red-blue composite laser beam 9 with respect to the vertical plane of the machining surface 10 of the upper cover plate 5 is 6°. As Figure 3 shown, set the infrared swing function of the red-blue composite welding head 1 so that the spot formed by the infrared laser beam 2 swings within the spot 11 formed by the blue laser beam, forming an annular near-infrared swing trajectory 12. The swing radius of the spot formed by the infrared laser beam 2, that is, the inner diameter of the near-infrared swing trajectory 12, is 0.4 mm. Using a laser welding device under gas protection, laser welding is performed along the welding trajectory 4. As Figure 5 shown, a T-shaped weld is formed, that is, a weld is formed on the upper cover plate 5 and penetrates the upper cover plate 5. After welding, the upper cover plate 5 and the lower plate 6 form a T-shaped copper structure. After welding is completed, the suction head 7 releases the suction, and the pneumatic slider 8 drives the suction head 7 to automatically lift. The finished T-shaped copper structure, that is, the T-shaped copper plate, is blanked, and the next set of upper cover plates 5 and lower plates 6 to be welded is prepared for pressing.

[0061] Observe the surface and cross-section of the weld of the T-shaped copper plate under a microscope. As Figure 4 shown, the weld surface has a fusion width of 1.6 mm and no heat-affected zone. The weld is smooth, without splash particles and blowhole phenomena. The cross-section of the weld is as Figure 5 shown. It can be seen from the figure that the penetration depth of the weld is up to more than 2.5 mm, the effective fusion width is 1.1 mm, meeting the welding requirements of the T-shaped copper plate, and the thermal deformation of the upper cover plate 5 ≤ 0.5%.

[0062] Example 2:

[0063] This is another preferred embodiment of the laser welding method for the T-shaped copper structure according to the present invention. The method includes:

[0064] Vertically assemble the upper cover plate 5 and the lower plate 6 made of copper material. Specifically:

[0065] As Figure 1 shown, the thickness of the upper cover plate 5 is 2 mm. There are multiple upper cover plates 5 and lower plates 6, all made of copper material. Place the multiple upper cover plates 5 to be welded horizontally above the corresponding lower plates 6. The pneumatic slider 8 drives the suction head 7 to descend. The suction head 7 adsorbs the corresponding upper cover plate 5 and presses the upper cover plate 5 onto the corresponding lower plate 6. At this time, the upper cover plate 5 and the lower plate 6 are perpendicular, and the assembly gap between the upper cover plate 5 and the lower plate 6 ≤ 0.01 mm, ensuring no gap between the copper plates.

[0066] After assembly, a red-blue composite laser beam 9 is formed by the coaxial infrared laser beam 2 and blue laser beam 3. The red-blue composite laser beam 9 is used to weld along the outer surface of the upper cover plate 5 corresponding to the lower plate 6. During welding, the red-blue composite laser beam 9 is inclined with respect to the vertical plane of the outer surface of the upper cover plate 5 and welded with a negative defocus amount. The spot formed by the infrared laser beam 2 swings within the spot 11 formed by the blue laser beam, forming a weld seam on the upper cover plate 5 and penetrating through the upper cover plate 5. After welding, the upper cover plate 5 and the lower plate 6 form a T-shaped copper structure. Specifically:

[0067] As Figure 1 shown, the welding track 4 of the laser welding equipment is set along the outer surface of the upper cover plate 5 corresponding to the lower plate 6. The power of the single-mode infrared laser is turned on at 65% of the total power of 6000W, and the power of the blue laser is turned on at 60% of the total power of 1000W. The welding speed is 70mm / s, the defocus amount is -2m, the red-blue composite welding head 1 of the laser welding equipment is located above the upper cover plate 5 side, and the argon gas flow rate is 25L / min. As Figure 2 shown, the coaxial infrared laser beam 2 and blue laser beam 3 are generated by the single-mode infrared laser and blue laser in the red-blue composite welding head 1 to form a red-blue composite laser beam 9. The inclination angle of the red-blue composite welding head 1 with respect to the vertical plane is 6°, that is, the inclination angle θ of the red-blue composite laser beam 9 with respect to the vertical plane of the processing surface 10 of the upper cover plate 5 is 6°. As Figure 3 shown, the infrared swing function of the red-blue composite welding head 1 is set so that the spot formed by the infrared laser beam 2 swings within the spot 11 formed by the blue laser beam, forming an annular near-infrared swing track 12. The swing radius of the spot formed by the infrared laser beam 2, that is, the inner diameter of the near-infrared swing track 12, is 0.4mm. Using the laser welding equipment under gas protection, laser welding is carried out along the welding track 4. As Figure 7 shown, a T-shaped weld seam is formed, that is, a weld seam is formed on the upper cover plate 5 and penetrates through the upper cover plate 5. After welding, the upper cover plate 5 and the lower plate 6 form a T-shaped copper structure. After welding is completed, the suction head 7 releases the suction, and the pneumatic slider 8 drives the suction head 7 to automatically lift. The T-shaped copper structure finished product, that is, the T-shaped copper plate, is cut and prepared to press the next group of upper cover plates 5 and lower plates 6 to be welded.

[0068] Observe the surface and cross-section of the weld seam of the T-shaped copper plate under a microscope. As Figure 6 shown, the weld seam surface has a fusion width of 1.8mm and no heat-affected zone. The weld seam is smooth, without splash particles and blowhole phenomena; the cross-section of the weld seam is as Figure 7 shown. It can be seen from the figure that the penetration depth of the weld seam is about 2.8mm, the effective fusion width is 1.4mm, meeting the welding requirements of the T-shaped copper plate, and the thermal deformation of the upper cover plate 5 ≤ 0.5%.

[0069] Example 3:

[0070] Another preferred embodiment of the laser welding method for the T-shaped copper structure according to the present invention includes the following steps:

[0071] Vertically assemble the upper cover plate 5 and the lower plate 6 made of copper material. Specifically:

[0072] As Figure 1 shown, the thickness of the upper cover plate 5 is 3 mm. There are multiple upper cover plates 5 and lower plates 6, all made of copper material. Horizontally place the multiple upper cover plates 5 to be welded above the corresponding lower plates 6. Drive the suction head 7 to descend by the pneumatic slider 8. The suction head 7 adsorbs the corresponding upper cover plate 5 and presses the upper cover plate 5 onto the corresponding lower plate 6. At this time, the upper cover plate 5 is perpendicular to the lower plate 6, and the assembly gap between the upper cover plate 5 and the lower plate 6 is ≤ 0.01 mm, ensuring no gap between the copper plates.

[0073] After assembly, a red-blue composite laser beam 9 is formed by the coaxial infrared laser beam 2 and blue laser beam 3. Weld along the outer surface of the upper cover plate 5 corresponding to the lower plate 6 with the red-blue composite laser beam 9. During welding, the red-blue composite laser beam 9 is inclined with respect to the vertical plane of the outer surface of the upper cover plate 5 and is welded with a negative defocus amount. The spot formed by the infrared laser beam 2 swings within the spot 11 formed by the blue laser beam, forming a weld on the upper cover plate 5 and penetrating the upper cover plate 5. After welding, the upper cover plate 5 and the lower plate 6 form a T-shaped copper structure. Specifically:

[0074] As Figure 1 shown, set the welding track 4 of the laser welding equipment along the outer surface of the upper cover plate 5 corresponding to the lower plate 6. The power of the single-mode infrared laser is turned on at 65% of the total power of 6000 W, and the power of the blue laser is turned on at 85% of the total power of 1000 W. The welding speed is 70 mm / s, the defocus amount is -3 m. The red-blue composite welding head 1 of the laser welding equipment is located above the upper cover plate 5 side, and the argon gas flow rate is 25 L / min. As Figure 2 shown, the coaxial infrared laser beam 2 and blue laser beam 3 are generated by the single-mode infrared laser and blue laser in the red-blue composite welding head 1 to form a red-blue composite laser beam 9. The inclination angle of the red-blue composite welding head 1 with respect to the vertical plane is 6°, that is, the inclination angle θ of the red-blue composite laser beam 9 with respect to the vertical plane of the machining surface 10 of the upper cover plate 5 is 6°. As Figure 3 shown, set the infrared swing function of the red-blue composite welding head 1 to make the spot formed by the infrared laser beam 2 swing within the spot 11 formed by the blue laser beam, forming an annular near-infrared swing track 12. The swing radius of the spot formed by the infrared laser beam 2, that is, the inner diameter of the near-infrared swing track 12, is 0.2 mm. Use the laser welding equipment to perform laser welding along the welding track 4 under gas protection. As Figure 9As shown, a T-shaped weld seam is formed, that is, a weld seam is formed on the upper cover plate 5 and penetrates through the upper cover plate 5. After welding, the upper cover plate 5 and the lower plate 6 form a T-shaped copper structure. After welding is completed, the suction head 7 releases the suction, and the pneumatic slider 8 drives the suction head 7 to automatically lift. The finished product of the T-shaped copper structure, that is, the T-shaped copper plate, is blanked, and the next set of upper cover plates 5 and lower plates 6 to be welded are prepared for pressing.

[0075] Observe the surface and cross-section of the weld seam of the T-shaped copper plate under a microscope, as Figure 8 shown. The fusion width of the weld seam surface is 2.0 mm and there is no heat-affected zone. The weld seam is smooth, without splash particles and blowholes; the cross-section of the weld seam is as Figure 9 shown. It can be seen from the figure that the penetration depth of the weld seam is up to more than 3.3 mm, and the effective fusion width is 0.9 mm, meeting the welding requirements of the T-shaped copper plate, and the thermal deformation of the upper cover plate 5 is ≤0.5%.

[0076] It can be seen from the results of Examples 1 to 3 that the present invention adopts the method of coaxial inclined red-blue composite laser beam + infrared laser beam oscillating welding in the blue light spot, which has a lower light source cost than the ring infrared laser, and the weld seam appearance is smooth and the welding spatter is low. Compared with the vertical welding of the blue light laser or the double-beam composite laser welding method, it can reduce the influence of reflection on the blue light laser. For the copper thick plate with an upper cover plate ≤3 mm, the penetration depth can reach ≥2 mm, and the thermal deformation of the upper cover plate is ≤0.5%. At the same time, compared with the existing double-sided welding method, laser welding is accurate and has high welding efficiency, which can meet the welding requirements of the T-shaped thick copper plate structure and is conducive to mass production applications.

[0077] Comparative Example 1:

[0078] A laser welding method for a T-shaped copper structure, which is different from Example 3 in that: the power of the single-mode infrared laser is turned on at 45% of the total power of 6000 W, the power of the blue light laser is turned on at 40% of the total power of 1000 W, the welding speed is 50 mm / s, the defocus amount is +1 m, the inclination angle of the red-blue composite welding head 1 with the vertical plane is 10°, the spot formed by the infrared laser beam 2 does not swing, the gas protection flow is 20 L / min, and a T-shaped copper plate cannot be formed after welding. Observe the surface and cross-section of the weld seam of the upper cover plate 5 under a microscope, as Figure 10 shown. There are splash and perforation phenomena on the weld seam surface, and the forming is uneven; the cross-section of the weld seam is as Figure 11 shown. It can be seen from the figure that the penetration depth of the weld seam cannot penetrate the 3-mm upper cover plate 5, making it difficult to meet the welding of the T-shaped copper plate.

[0079] Comparative Example 2:

[0080] A laser welding method for a T-shaped copper structure, which is different from Example 3 in that: the power of the single-mode infrared laser is turned on at 85% of the total power of 6000W, the power of the blue laser is turned on at 60% of the total power of 1000W, the welding speed is 50mm / s, the defocus amount is +2m, the inclination angle of the red-blue composite welding head 1 with the vertical plane is 15°, the swing radius of the spot formed by the infrared laser beam 2, that is, the inner diameter of the near-infrared swing trajectory 12 is 0.8mm. After welding, a T-shaped copper plate cannot be formed. Observe the surface and cross-section of the weld of the upper cover plate 5 under a microscope, as Figure 12 shown. The weld surface has a large fusion width, uneven formation, and the reinforcement shifts to one side; the weld cross-section is as Figure 13 shown. It can be seen from the figure that the penetration depth of the weld cannot penetrate the 3mm upper cover plate 5, making it difficult to meet the welding requirements of the T-shaped copper plate.

[0081] From the comparison results of Example 3, Comparative Example 1, and Comparative Example 2, it can be seen that the present invention uses a red-blue composite laser beam 9 to weld along the outer surface of the upper cover plate 5 corresponding to the lower plate 6. During welding, the inclination angle of the red-blue composite laser beam 9 with the vertical plane of the outer surface of the upper cover plate 5 is ≥5°, and welding is performed with a negative defocus amount. The spot formed by the infrared laser beam 2 swings within the spot 11 formed by the blue laser beam. The rapid temperature rise can be achieved by blue laser welding, promoting the absorption of infrared laser by copper materials, avoiding the damage of infrared laser to the optical configuration, ensuring a large penetration depth by the large energy density provided by the infrared laser, and ensuring the stability of the molten pool by the uniform energy distribution of the blue laser. It can adapt to the characteristics of the upper cover plate being a thick plate, copper being a highly reflective metal, a large heat dissipation area at the T-shaped intersection, and heat being rapidly dissipated in multiple directions. There is no need for double-sided welding, and it can penetrate and weld at one time to meet the requirements of effective penetration depth. The weld quality is good, there are basically no spatter and bead explosions on the weld appearance, no large-particle spatter is generated, and at the same time, the thermal deformation of the upper cover plate is small, the cost is low, the production efficiency is high, and it is conducive to mass production.

[0082] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser welding method for a T-shaped copper structure, characterized in that: The methods include: After the upper cover plate (5) and the lower plate (6) made of copper material are vertically assembled, a red-blue composite laser beam (9) is formed by a coaxial infrared laser beam (2) and a blue laser beam (3), and the red-blue composite laser beam (9) is used to weld along the outer surface of the upper cover plate (5) corresponding to the lower plate (6). During welding, the inclination angle between the red-blue composite laser beam (9) and the vertical plane of the outer surface of the upper cover plate (5) is ≥5°, and welding is performed with a negative defocus amount. The light spot formed by the infrared laser beam (2) swings within the light spot (11) formed by the blue laser beam, forming a weld on the upper cover plate (5) and penetrating the upper cover plate (5). After welding, the upper cover plate (5) and the lower plate (6) form a T-shaped copper structure.

2. The laser welding method for T-shaped copper structure according to claim 1, characterized in that: The upper cover plate (5) is adsorbed by a tooling until the assembly gap between the upper cover plate (5) and the lower plate (6) is ≤0.01 mm.

3. The laser welding method for T-shaped copper structure according to claim 1, characterized in that: A red-blue composite welding head (1) with an infrared swing function is used. The red-blue composite welding head (1) uses a single-mode infrared laser and a blue light laser to generate a red-blue composite laser beam (9). The power of the single-mode infrared laser is ≤6000W, the power of the blue light laser is ≥500W, the welding speed is 50-70mm / s, and the defocusing amount is -1--3m.

4. The laser welding method for T-shaped copper structure according to claim 3, characterized in that: The power of the single-mode infrared laser is 3600-5400W, the power of the blue laser is 500-800W, and the infrared oscillation is turned on in advance during welding, and the blue laser is turned on before the infrared laser.

5. The laser welding method for T-shaped copper structure according to claim 3, characterized in that: The optical configuration of the red-blue composite welding head (1) has a collimation focal length of 100 mm and a focusing focal length of 250 mm.

6. The laser welding method for T-shaped copper structure according to claim 3, characterized in that: When the single-mode infrared laser and the blue laser are continuously welded using the same welding parameters and the laser brightness decreases, the protective lens of the red-blue composite welding head (1) is replaced.

7. The laser welding method for T-shaped copper structure according to claim 3, characterized in that: A water chiller with a cooling power of ≥6000W is used to cool the single-mode infrared laser and the red-blue composite welding head (1), and a water chiller with a cooling power of ≥2100W is used to cool the blue laser.

8. The laser welding method for T-shaped copper structure according to claim 1, characterized in that: During welding, the inclination angle between the red and blue composite laser beam (9) and the vertical plane of the outer surface of the upper cover plate (5) is ≤10°.

9. The laser welding method for T-shaped copper structure according to claim 1, characterized in that: The light spot formed by the infrared laser beam (2) swings in a circular shape, and the swing radius is 0.2 mm to 0.5 mm.

10. The laser welding method for T-shaped copper structure according to any one of claims 1 to 9, characterized in that: Argon gas is blown coaxially with the red-blue composite laser beam (9) for gas protection, and the gas flow rate is greater than 20 L / min.

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