Crack-controllable heterogeneous material ultrafast laser welding method and equipment

Abstract

The invention relates to the field of laser micro-nano machining, in particular to a crack-controllable heterogeneous material ultrafast laser welding method and equipment, and effectively solves the problems that when heterogeneous materials are welded under the non-optical contact condition, cracks are generated on transparent materials and joints due to the too high heat effect, and the strength of the welded joints is reduced. Through the ultrafast laser single-spot welding technology, the laser energy and spatial distribution are regulated and controlled, and high-quality heterogeneous material welding under non-optical contact is achieved. The method specifically comprises the steps that a transparent material and a metal material are fixed to a three-dimensional motion platform through a clamp, and single-point welding machining is conducted on the transparent material and the metal material through a galvanometer light path system shown in the figure 1. Parameters such as the laser energy, the welding dotting time and the distance between adjacent welding points are set, and then ultrafast laser sequentially completes single-point welding machining through a galvanometer. According to the method, the heat effect generated in the welding process can be effectively controlled, cracks on the transparent material and the welding joint are reduced, and therefore the strength of the welding joint is improved.

Description

Technical Field

[0001] This invention relates to the field of laser micro-nano processing, specifically to a method and equipment for ultrafast laser welding of heterogeneous materials with controllable cracks. Background Technology

[0002] Heterogeneous materials refer to two different materials with significant differences in physical and chemical properties. Currently, over 90% of industrial products are composed of heterogeneous materials, making heterogeneous material welding a hot topic in welding technology. Welding glass to metal is a crucial heterogeneous material welding problem that urgently needs to be solved. Connectors composed of highly ductile, tough, and impact-resistant metals and glass are widely used in industrial fields, including solar cells, medical devices, and sensor manufacturing. The miniaturization of these devices and the expansion of their applications will place even higher demands on the micro-connections between glass and metal.

[0003] Optical contact welding (material gap less than λ / 4) is a mature technology, but its high surface quality requirements make it difficult to apply in industrial production. Under non-optical contact conditions, the sample gap increases. If the laser energy is low, femtosecond laser welding can only melt a small amount of material at the focal point due to nonlinear absorption, failing to fill larger material gaps. If the laser energy is high, although it can fill the gaps, it generates excessive heat, leading to excessive residual stress. Both situations easily result in low joint strength. Achieving high-stability, high-quality welding under non-optical contact conditions is a major challenge for ultrafast laser welding technology to move towards practical industrial applications.

[0004] The published patent (CN119115205A) describes a method for welding dissimilar materials based on the burst output mode of ultrafast lasers. It divides the energy of a single pulse into multiple pulses and emits light in a pulse sequence, making it easier to achieve thermal accumulation effects. This increases processing speed, ablation efficiency, and the connection strength and stability between transparent and metallic dissimilar materials. While effectively addressing the issue of low weld strength, this method requires mirror polishing pretreatment of the materials, demanding high surface quality. Being within the scope of optical contact, it is difficult to apply practically.

[0005] The published patent (CN116900471A) uses beam shaping to extend the focal depth range while homogenizing the beam shape. This method reduces the distance requirement between materials by using a long focal depth laser beam, achieving non-optical contact, and also improves the uniformity of the weld pool by homogenizing the laser beam. While this method improves the quality of welding dissimilar materials under non-optical contact conditions to some extent, homogenizing the beam shape means that higher laser power is needed to reach the ablation threshold of the material. This can generate excessive heat during welding, leading to embrittlement of the weld joint and low strength.

[0006] The authorized patent (CN117564460B) provides a non-optical contact welding method. It involves pre-treating a transparent material and fabricating microgroove structures on its surface to provide space for the thermal expansion of the heterogeneous material. The molten material spreads evenly around the microgrooves in the transparent material, effectively improving the weld strength and airtightness. However, microgroove fabrication is not a simple process. Controlling the number and size of the microgrooves based on the volume of the molten material and its expansion is a major challenge in implementing this method. Furthermore, the additional pre-treatment steps increase processing costs.

[0007] In summary, non-optical contact welding of dissimilar materials often faces the problem of excessive heat and internal cracking when attempting to fill the gaps with molten material due to the large gaps between the materials. Existing welding methods frequently address this issue using pneumatic auxiliary fixtures, surface pretreatment, and beam shaping, but these methods often come with high processing costs and increased process complexity. To effectively control the thermal effects of welding dissimilar materials under non-optical contact conditions, this invention provides a crack-controllable ultrafast laser welding method and equipment for dissimilar materials. Specifically, the invention includes sequentially stacking a transparent material (after ultrasonic cleaning) and a metallic material on a three-dimensional platform, clamping them with a fixture, and adjusting the three-dimensional platform so that the focal plane of the laser coincides with the contact surface of the upper and lower workpieces. After setting the welding parameters and dot-mapping positions, the laser is turned on. The laser beam passes through a collimated optical path and perpendicularly enters the entrance aperture of a scanning galvanometer, exiting from the exit aperture. Focused by a field lens, the laser energy melts the transparent and metallic materials, forming a joint, thus completing a single-point welding process. A dot-mapping array is set using the galvanometer, and the laser sequentially completes the single-point welding process through the galvanometer. This method effectively reduces the spatial heat accumulation effect and decreases cracks in the transparent material, thereby improving the strength of the welded joint. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a method and equipment for ultrafast laser welding of dissimilar materials with controllable cracking. Through ultrafast laser single-point welding technology, high-quality, high-strength welding of dissimilar materials under non-optical contact conditions is achieved.

[0009] To achieve the above objectives, the present invention provides a method and equipment for ultrafast laser welding of heterogeneous materials with controllable cracking, comprising the following steps:

[0010] (1) The transparent material and metal material after ultrasonic cleaning are stacked on a three-dimensional platform in sequence and clamped by a fixture. The three-dimensional platform is adjusted so that the focal plane of the laser coincides with the contact surface of the upper and lower workpieces.

[0011] (2) After setting the parameters of the high-repetition-rate ultrafast laser and the dotting position, turn on the laser. The laser vertically enters the incident hole of the scanning galvanometer through the collimation optical path and exits from the exit hole of the scanning galvanometer, and is focused by the field lens. The laser energy melts the transparent material and the metal material to form a joint, thus completing the single-point welding process for a single time.

[0012] (3) Use the galvanometer to set the dotting array. The distance d between adjacent welding points and the radius r of the laser focus spot satisfy the mathematical relationship of 2r < d < 10r. The laser completes the single-point welding process through the single-point irradiation time t, and completes the array processing under the galvanometer scanning. Through the array, the effective connection between the transparent material and the metal material can be achieved. Under this specific spatial dotting welding method, the thermal effect generated during the welding process can be effectively controlled, and the transverse cracks on the transparent material and the welding joint can be reduced, thereby improving the strength of the welding joint.

[0013] Further, the metal material used has a rough surface, and the surface roughness Sa ranges from 0.3 to 2.5 μm. When it contacts the transparent material, the interface is in a non-optical contact state.

[0014] Further, under the spacing setting that satisfies 2r < d < 10r, the shear strength of the welding joint that can be obtained can be higher than 60 MPa. When the spacing d is less than 2r, cracks will be induced at the single-point laser welding, and the welding strength will be reduced to below 10 MPa. When using the traditional scanning welding method, that is, the spacing d is much less than 1r, the welding strength will be reduced to below 30 MPa.

[0015] Further, the laser power density used needs to make the laser energy density after focusing slightly higher than the ablation threshold of the transparent material.

[0016] Further, the transparent material is sapphire or fused quartz or transparent ceramic or silicon, and the metal material is Ivar alloy or titanium alloy or stainless steel or aluminum alloy or copper.

[0017] Further, the laser used is a high-repetition-rate femtosecond laser, the repetition frequency is 200 - 1000 kHz, and the dotting time is 2 - 20 ms.

[0018] Further, the above-mentioned ultrafast laser welding method for heterogeneous materials with crack controllability is used to reduce the cracks generated during the welding process of non-optical contact heterogeneous materials, and achieve high-quality welding and high strength.

[0019] Generally speaking, compared with the prior art solutions through the above technical solutions of the present invention, the following main advantages are mainly possessed:

[0020] Compared with the ultrafast laser processing method under optical contact, this method does not have too high requirements for the surface quality of the material. When the metal material is a rough sample, high-quality and stable welding of heterogeneous materials can be achieved through this method, effectively reducing the processing cost.

[0021] Compared to traditional non-optical contact ultrafast laser welding methods, this method eliminates the need for pneumatic auxiliary fixtures or surface pretreatment to reduce material gaps. By controlling the laser energy magnitude and spatial distribution, this method achieves high-quality and stable welding of heterogeneous materials, resulting in cost reduction and process optimization.

[0022] This method controls the magnitude and spatial distribution of laser energy to minimize the thermal effects during welding while ensuring the strength of the welded joint. It avoids defects such as transverse cracks in the transparent material and the joint caused by excessive thermal stress, resulting in a significantly improved joint strength compared to scanning welding. This method achieves high-quality welding of dissimilar materials under non-optical contact conditions.

[0023] This invention effectively solves the problem of excessive heat effect caused by excessive laser energy, resulting in cracks in transparent materials and joints, and reduced weld joint strength when welding dissimilar materials under non-optical contact conditions. By using ultrafast laser single-point welding, the magnitude and spatial distribution of laser energy can be controlled to achieve high-quality, high-strength welding of dissimilar materials under non-optical contact conditions. Attached Figure Description

[0024] Appendix Figure 1 Optical path diagram of the invention's crack-controllable ultrafast laser welding method for heterogeneous materials

[0025] Appendix Figure 2 Schematic diagram and top view of ultrafast laser single-point welding process.

[0026] Appendix Figure 3 Schematic diagram of single-point welding path

[0027] Appendix Figure 4 This includes microscopic images of single-point welded and scanned welded samples with normal and small pitches, including microscopic images of complete welded samples and microscopic images of the weld surfaces of sapphire and Invar alloy after the samples were broken.

[0028] Appendix Figure 5 Schematic diagram of crack defect induction mechanism

[0029] Figure label explanation: 1-High repetition rate ultrafast laser; 2-Collimating optical path; 3-Scanning galvanometer; 4-Field lens; 5-Sample; 6-Fixture; 7-Three-dimensional motion platform; 8-Transparent sample; 9-Metallic sample. Detailed Implementation

[0030] To make the technical problems, solutions, and points to be solved by this invention clearer, a detailed description will be provided below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the description of these embodiments is intended to aid in understanding the invention but does not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other.

[0031] This invention addresses the problem of reduced weld joint strength caused by excessive heat effects in non-optical contact welding of dissimilar materials, which leads to cracks in the transparent material and the joint. It provides a crack-controllable ultrafast laser welding method and equipment for dissimilar materials.

[0032] The structure of an example provided by the present invention is shown in the figure, which consists of a high repetition rate ultrafast laser 1; a collimating optical path 2; a scanning galvanometer 3; a field lens 4; a sample 5; a fixture 6; a three-dimensional motion platform 7; a transparent sample 8; and a metal sample 9.

[0033] In this example, the high-repetition-rate ultrafast laser 1, collimating optical path 2, scanning galvanometer 3, and field mirror 4 are located on the same optical path. After being emitted from the high-repetition-rate ultrafast laser, the laser first passes through the collimating optical path 2 for collimation, and then enters the scanning galvanometer 3. The scanning galvanometer 3 controls the two-dimensional movement of the optical path through an internal mirror to ensure that it enters the field mirror 4 perpendicularly. The laser is focused by the field mirror 4 onto the contact surface between the transparent sample 8 and the metal sample 9 in sample 5. During the single-point welding process, the workpiece remains stationary, while the scanning galvanometer and field mirror move the laser spot, thereby completing the ultrafast laser single-point welding of heterogeneous materials. Alternatively, a focusing mirror can be used instead of the scanning galvanometer 3 and field mirror 4. In this method, the laser spot remains stationary during the processing, and the workpiece is moved by the three-dimensional motion platform 6 to achieve single-point welding.

[0034] First, the surfaces of transparent sample 8 and metal sample 9 are ultrasonically cleaned. After adjusting the optical path, the cleaned transparent sample 8 and metal sample 9 are stacked together and fixed on the three-dimensional motion platform 6 using a clamp. The focal plane of the laser is adjusted so that it is at the height of the contact surface between the transparent sample 8 and metal sample 9. The welding point and welding time are set using a galvanometer, and the appropriate welding laser parameters are selected using a laser controller according to the ablation threshold curve of the transparent material. After all preparations are completed, laser 1 is turned on. The laser beam passes through the collimated optical path 2, enters vertically through the entrance hole of the scanning galvanometer 3, and exits through the exit hole of the scanning galvanometer 3. It is then focused by the field lens 4 at the height of the contact surface between the transparent sample 8 and metal sample 9, and single-point welding is performed on the transparent sample 8 and metal sample 9.

[0035] Specific examples

[0036] Example 1: This example uses sapphire as transparent sample 8 and Ivar alloy as metal sample 9. The size of the sapphire is approximately 8mm×10mm×2mm, and the size of the Ivar alloy is approximately 10mm×20mm×2mm. Welding is performed according to the steps of the ultrafast laser high-stability welding method for heterogeneous materials provided in the above embodiment.

[0037] In the single-point welding process, a laser power of 30W, a repetition frequency of 500kHz, a welding time of 10ms, 121 welding points, a laser focusing diameter of 33μm, and a spacing of 0.2mm between adjacent welding points were used. Sapphire and Ivar alloy were stacked together and fixed with a fixture. The displacement platform was adjusted so that the contact surface between the sapphire and Ivar alloy coincided with the focal plane. The welding point array was set at the center of the sapphire and Ivar alloy, and the ultrafast laser welded the sapphire and Ivar alloy according to the set welding points. The welded sample is shown in the attached image. Figure 4 As shown, the average shear strength of Ivar alloy and sapphire is 63.37 MPa.

[0038] Example 2: This example uses sapphire as the transparent sample 8 and Ivar alloy as the metal sample 9. The size of the sapphire is approximately 8mm×10mm×2mm, and the size of the Ivar alloy is approximately 10mm×20mm×2mm. Welding is performed according to the steps of the ultrafast laser high-stability welding method for heterogeneous materials provided in the above embodiment.

[0039] In the single-point welding process, a laser power of 30W, a repetition frequency of 500kHz, a welding time of 10ms, 121 welding points, a laser focusing diameter of 33μm, and a spacing of 0.06mm between adjacent welding points were used. Sapphire and Ivar alloy were stacked together and fixed with a fixture. The displacement platform was adjusted so that the contact surface between the sapphire and Ivar alloy coincided with the focal plane. The welding point array was set at the center of the sapphire and Ivar alloy, and the ultrafast laser welded the sapphire and Ivar alloy according to the set welding points. The welded sample is shown in the attached image. Figure 4 As shown, the average shear strength of Ivar alloy and sapphire is 9.71 MPa.

[0040] Example 3: This example uses sapphire as transparent sample 8 and Ivar alloy as metal sample 9. The size of the sapphire is approximately 8mm×10mm×2mm, and the size of the Ivar alloy is approximately 10mm×20mm×2mm. Welding is performed using the ultrafast laser scanning welding method.

[0041] During the scanning welding process, a laser power of 30W, a repetition rate of 500kHz, a laser focusing diameter of 33μm, a scanning speed of 4mm / s, a scanning interval of 0.2mm, and a welding area size of 2mm×2mm were used. Sapphire and Ivar alloy were stacked together and fixed with a fixture. The displacement platform was adjusted so that the contact surface between the sapphire and Ivar alloy coincided with the focal plane. The welding area was set at the center of the sapphire and Ivar alloy, and the ultrafast laser welded the sapphire and Ivar alloy according to the pre-set welding path. The welded sample is shown in the attached image. Figure 4 As shown, the average shear strength of Ivar alloy and sapphire is 25.75 MPa.

Claims

1. A method and equipment for ultrafast laser welding of heterogeneous materials with controllable cracking, used for laser welding of rough metallic materials and transparent materials, characterized in that, It includes the following steps: Step 1: Stack the transparent material and the metal material after ultrasonic cleaning on the three-dimensional platform in sequence, clamp them with a fixture, and adjust the three-dimensional platform to make the focal plane of the laser coincide with the contact surface of the upper and lower workpieces. Step 2: After setting the parameters of the high-repetition-rate ultrafast laser and the dotting positions, turn on the laser. The laser vertically enters the incident hole of the scanning galvanometer through the collimation optical path and exits from the exit hole of the scanning galvanometer, and is focused by the field lens. The laser energy causes the transparent material and the metal material to melt and form a joint, thus completing the single-point welding process for one time. Step 3: Adopt the single-point welding method, use the galvanometer to set the dotting array. The distance d between adjacent welding points and the radius r of the laser focusing spot satisfy the mathematical relationship of 2r < d < 10r. The laser completes the single-point welding process through the single-point irradiation time t, and completes the array processing under the scanning of the galvanometer. Through the array, the effective connection between the transparent material and the metal material is realized. Under this specific spatial dotting welding method, the thermal effect generated during the welding process can be effectively controlled, and the transverse cracks on the transparent material and the welding joint can be reduced, thereby improving the strength of the welding joint.

2. The welding method according to claim 1, characterized in that, The metal material used has a rough surface, and the surface roughness Sa ranges from 0.3 - 2.5 μm. When it contacts the transparent material, the interface is in a non-optical contact state.

3. The welding method according to claim 1, characterized in that, Under the spacing setting that satisfies 2r < d < 10r, the shear strength of the obtained welding joint is higher than 60 MPa. When the spacing d is less than 2r, cracks will be induced at the laser single-point welding position, and the welding strength is reduced to below 10 MPa. When the traditional scanning welding method is adopted, that is, the spacing d is much less than 1r, the welding strength is reduced to below 30 MPa.

4. The welding method according to claim 1, characterized in that, The laser power density used needs to make the laser energy density after focusing slightly higher than the ablation threshold of the transparent material.

5. The welding method according to claim 1, characterized in that, In Step 1, the transparent material is sapphire or fused quartz or transparent ceramic or silicon, and the metal material is Ivar alloy or titanium alloy or stainless steel or aluminum alloy or copper.

6. The welding method according to claim 1, characterized in that, The laser adopted is a high-repetition-rate femtosecond laser, the repetition frequency is 200 - 1000 kHz, and the dotting time t is 2 - 20 ms.

7. A crack-controllable ultrafast laser welding equipment for heterogeneous materials, characterized in that... Adopt the ultrafast laser welding method for heterogeneous materials with crack controllability described in Claim 1 above to reduce the cracks generated during the welding process of non-optical contact heterogeneous materials and achieve high-quality and high-strength welding.

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