Ultrafast laser welding method for sapphire sheet and stainless steel tube for endoscope

Abstract

An ultrafast laser welding method for a sapphire piece and a stainless steel pipe for an endoscope comprises the steps that firstly, to-be-welded faces of sapphire and the stainless steel pipe are cleaned, then the to-be-welded face of the stainless steel pipe is subjected to electrolytic polishing, then the surface of the sapphire piece is textured, then the sapphire piece is embedded into the to-be-packaged end of the stainless steel pipe, and finally the sapphire piece and the stainless steel pipe are welded. And then welding the to-be-welded area of the welding assembly by adopting ultrafast laser to obtain a welded assembly, and finally carrying out vacuum annealing treatment on the welded assembly. According to the method, the problems that stress is concentrated, the sapphire sheet and the stainless steel pipe are difficult to wet, and an optical area of the sapphire sheet is polluted can be solved, the appearance of a welded assembly is clean, the connecting strength of the sapphire sheet and the stainless steel pipe is guaranteed, and the method has the advantages of being simple in technological process, high in repeatability, small in deformation after welding, high in welding seam strength and the like. Ultrafast laser welding of the sapphire sheet and the stainless steel tube for the endoscope is achieved, and engineering is achieved conveniently.

Description

Technical Field

[0001] The present invention relates to the technical field of welding of dissimilar materials, and in particular to an ultrafast laser welding method of a sapphire sheet for an endoscope and a stainless steel tube. Background Art

[0002] The connection between the sapphire window and the stainless steel tube of a medical endoscope is a critical component affecting endoscope failure. It ensures tightness and prevents water and air leaks. Its resistance to high-temperature, high-humidity sterilization is crucial to the endoscope's performance and service life. Traditional endoscope windows often use epoxy or acrylic adhesives to bond the sapphire to the stainless steel substrate. After approximately 20 sterilization cycles at high temperature and humidity (134°C / 70% RH), the adhesive layer ages and debonds, leading to air leaks at the sapphire-stainless steel connection and ultimately rendering the endoscope inoperable.

[0003] Currently, the main solutions are brazing and laser welding. Laser welding can achieve metal-to-metal connection, but there are significant differences in physical properties between sapphire (Al2O3 single crystal) and stainless steel (Fe-Cr-Ni alloy). The thermal expansion coefficient of sapphire is 5.3×10 -6 / K, stainless steel is 17.3×10 -6 / K, which can easily lead to welding thermal stress concentration and low joint strength; at the same time, the transmittance of sapphire to 1064nm wavelength laser is greater than 80%, making it difficult to achieve surface melting.

[0004] Prior art attempts to use intermediate metal coatings (such as Ti / Au) to assist welding, but the process is complex, and the coating interface is prone to produce brittle intermetallic compounds (IMC). For brazing, in addition to the above-mentioned stress concentration, coating process and the problem of producing brittle intermetallic compounds, there is also the problem that the high-temperature flow of solder (such as Ag-Cu alloy) easily contaminates the light-transmitting area of ​​the sapphire bottom surface. As shown in the Chinese patent "Encapsulation method of stainless steel tube and quartz plate for endoscope" of patent application number CN201510043062.5 (authorization announcement number CN105982633B), the method carries out metallization pretreatment to the side of quartz plate, polishes the surface to be welded of stainless steel tube, assembles the two and fills solder between the two, and finally welds sapphire and stainless steel tube with laser as heat source. The connection strength and density are greatly improved compared with traditional bonding method, and effective endoscope packaging is achieved. However, the metallization treatment process for the side of the quartz sheet is very difficult, and the coating interface is also prone to produce hard and brittle metal compounds. The filled solder melts during the welding process, which easily contaminates the bottom surface of the quartz sheet, thereby affecting the light transmittance of the transparent window. Therefore, the entire process is difficult to apply to actual production. In addition, as shown in the Chinese patent "A Stereoscopic Hard Tube Endoscope" with patent application number CN202111680943.X (application publication number CN114176503A), this method fills the sapphire sheet and the side wall of the stainless steel tube with brazing solder, heats it to 230℃~280℃, and the molten solder fills the gap between the sapphire sheet and the stainless steel tube. After cooling, a brazing joint is formed, and a leak test of 3 atmospheres is leak-proof, thereby achieving a dense connection between the sapphire sheet and the stainless steel tube of the endoscope. However, this method will cause uncertainty in the direction of solder flow after melting the solder, thereby contaminating the optical area of ​​the sapphire lens.

[0005] Therefore, further improvements are needed in the welding method between sapphire sheets and stainless steel tubes for endoscopes. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an ultrafast laser welding method for sapphire sheets and stainless steel tubes for endoscopes with high weld strength and simple process flow in view of the above-mentioned existing technical status.

[0007] The technical solution adopted by the present invention to solve the above technical problems is: the ultrafast laser welding method of the sapphire sheet for endoscope and the stainless steel tube is characterized by comprising the following steps:

[0008] S1. Cleaning the surfaces of the sapphire sheet and the stainless steel tube to be welded;

[0009] S2, electrolytically polishing the end of the stainless steel pipe with the surface to be welded after being cleaned in S1;

[0010] S3, using a femtosecond laser to perform surface texturing on the sapphire sheet cleaned in S1, so that the surface to be welded of the sapphire sheet has micron-scale connection grooves, which are used to connect to the surface to be welded of the stainless steel tube;

[0011] S4. Loading the sapphire sheet obtained in S3 into the end to be packaged of the stainless steel tube obtained in S2, thereby obtaining a to-be-welded assembly, wherein the to-be-packaged end of the stainless steel tube is the end having the to-be-welded surface, and the to-be-welded surface of the sapphire sheet and the to-be-welded surface of the stainless steel tube overlap to form a to-be-welded area of ​​the to-be-welded assembly;

[0012] S5, welding the area to be welded in S4 using an ultrafast laser to obtain a welded assembly;

[0013] S6. Perform vacuum annealing on the assembly welded in S5.

[0014] Furthermore, in S1, the stainless steel tube is polished with sandpaper on its surface to be welded, and the sand is rinsed with clean water. The sapphire sheet and the stainless steel tube, after polishing and rinsing, are ultrasonically cleaned with ethanol on their respective surfaces to be welded. Ultrasonic cleaning can effectively remove water film and organic matter from the sapphire surface to be welded. Sanding the stainless steel tube surface to be welded removes oil stains, and the sand is then rinsed with clean water. Ultrasonic cleaning can penetrate and clean the gaps between the stainless steel tube surfaces to be welded, thereby improving production efficiency and results.

[0015] Furthermore, the femtosecond laser in S3 has a wavelength of 1060-1070 nm, a pulse width of 150-300 fs, a power of 15-20 W, a pulse frequency of 50-100 kHz, a spot diameter of 12-18 μm, and a scanning speed of 150-200 mm / s. This parameter range allows for the creation of suitable connection grooves on the surface of the sapphire sheet to be welded, resulting in a better connection between the sapphire sheet and the stainless steel tube.

[0016] Furthermore, the connecting grooves of the sapphire sheet in S3 are multi-annular grooves or concentric circular grooves. The mutual wetting of the sapphire sheet and the stainless steel tube is an important step in the welding process. The wettability mainly depends on the surface treatment and the properties of the liquid. The present application performs nano-level processing on the sapphire sheet so that the surface to be welded has multi-annular grooves or concentric circular grooves, thereby increasing the roughness of the sapphire sheet. The melted stainless steel will completely infiltrate the multi-annular grooves or concentric circular grooves and the rest of the surface to be welded of the sapphire sheet. This treatment can utilize the Wenzel effect to amplify the wettability of the stainless steel, thereby achieving a better interlocking effect between the stainless steel tube and the sapphire sheet. Among them, the manufacturing process of the multi-annular groove is simpler, which makes the utilization rate of the surface to be welded of the sapphire sheet higher; there are more design methods for the concentric circular grooves, and the parameters of the concentric circular grooves can be designed according to actual conditions, making the adaptability of the connecting groove wider.

[0017] Furthermore, the multi-annular groove is a plurality of annular grooves arranged at intervals along the thickness direction of the sapphire sheet, the width of the annular groove is 40 to 70 μm, the depth of the annular groove is 25 to 83 μm, and the distance between two adjacent annular grooves is 180 to 250 μm. If the width of the annular groove is too small or the depth is shallow, the surface to be welded of the sapphire sheet will not have the multi-annular groove or the size of the multi-annular groove will be small, thereby making the mutual wettability of the sapphire sheet and the stainless steel tube poor, thereby causing the connection strength of the sapphire sheet and the stainless steel tube to be poor, and even possible falling off; if the width of the annular groove is too large or the depth is too deep, the effective welding contact area is small, thereby failing to ensure the connection strength of the sapphire sheet and the stainless steel tube, and the utilization rate of the surface to be welded of the sapphire sheet with too large a width or a deep depth is low, and the melted stainless steel may not be able to fill an annular groove, thereby causing stress concentration problems; therefore, the annular groove within this parameter range can achieve a better connection effect between the sapphire sheet and the stainless steel tube.

[0018] Furthermore, multiple concentric grooves are arranged on the surface of the sapphire sheet to be welded at intervals along the circumference of the sapphire sheet, and the spacing between the centers of the multiple concentric grooves is 200 to 300 μm. The concentric grooves include multiple rings with the same center and different diameters, and a groove is formed between two adjacent rings. The width of the ring is 1.5 to 3.5 μm, and the depth between two adjacent rings is 15 to 20 μm. The diameter of the largest ring in each of the concentric grooves is 100 to 200 μm, and the diameter of the ring in each of the concentric grooves decreases by 10 μm starting from the largest diameter. Similarly, if the width of the ring is too large or the depth is too shallow, the surface of the sapphire sheet to be welded will not have concentric grooves or the size of the concentric grooves will be small, resulting in poor mutual wettability between the sapphire sheet and the stainless steel tube, which in turn leads to poor connection strength between the sapphire sheet and the stainless steel tube, and may even cause it to fall off; if the width of the ring is too small or the depth is too deep, the effective welding contact area is small, and the connection strength between the sapphire sheet and the stainless steel tube cannot be guaranteed. In addition, a ring with a small width or a deep depth will result in a low utilization rate of the surface of the sapphire sheet to be welded, and the melted stainless steel may not be able to fill a concentric groove, resulting in stress concentration problems; therefore, the concentric grooves within this parameter range can make the connection between the sapphire sheet and the stainless steel tube better.

[0019] Furthermore, the ultrafast laser in S5 has a wavelength of 530-540 nm, a pulse width of 10-15 ps, a power of 200-300 W, a pulse frequency of 300-500 kHz, a spot diameter of 12-18 μm, a scanning speed of 400-550 mm / min, an argon flow rate of 18-22 L / min, a spiral progressive scanning path, and a pitch of 8-12 μm. If the temperature of the melting stainless steel tube is too high or too low, the connection between the stainless steel tube and the sapphire sheet will be affected. Ultrafast lasers within this parameter range can keep the stainless steel tube in a suitable melt state, that is, the melted stainless steel can wet the sapphire without completely melting. Therefore, ultrafast lasers within this parameter range are reasonable.

[0020] Furthermore, the vacuum annealing in S6 is to place the assembly welded in S5 in a vacuum annealing furnace, heating it from room temperature to 240-250°C at a heating rate of 80-100°C / h, keeping it at this temperature for at least 2 hours, cooling it to below 100°C in the furnace, then taking it out and cooling it to room temperature, wherein the vacuum pressure of the vacuum annealing furnace is ≤1×10 -3 P. Annealing can release residual stress and prevent deformation or cracking at the connection between the sapphire sheet and the stainless steel tube.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] (1) The welding method of the present application texturizes the surface of the sapphire sheet so that the surface to be welded of the sapphire sheet has a connecting groove. The connecting groove can increase the roughness of the surface to be welded of the sapphire sheet, thereby making the stainless steel tube wet the sapphire sheet better, thereby enhancing the connection strength between the sapphire sheet and the stainless steel tube, and can also alleviate the problem of thermal stress concentration, thereby solving the problem of stress concentration caused by different thermal expansion coefficients;

[0023] (2) This application uses an ultrafast laser to weld the sapphire sheet and the stainless steel tube. Without using solder filling or performing metallization pretreatment, the stainless steel tube wets the surface of the sapphire sheet to be welded, thereby forming a mechanical interlocking effect between the stainless steel tube and the sapphire sheet, solving the problem of difficult wetting of the sapphire sheet and the stainless steel tube. This not only ensures the strength of the connection between the sapphire sheet and the stainless steel tube, but also prevents the molten solder from contaminating the optical area of ​​the sapphire sheet, making the appearance of the completed welded assembly clean.

[0024] (3) The present application performs vacuum annealing on the welded assembly, thereby releasing the residual stress in the assembly after welding, solving the problem of stress concentration caused by residual stress after welding;

[0025] (4) The method of the present application has the advantages of simple process flow, high repeatability, small deformation after welding, and high weld strength. It realizes ultrafast laser welding of sapphire sheets and stainless steel tubes for endoscopes, which is convenient for engineering. The completed welded assembly can meet the requirements of endoscopes to withstand high temperature and high humidity (134°C / 70% RH) sterilization for more than 2,000 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a cross-sectional view of an embodiment of the present invention;

[0027] Figure 2 Schematic diagram of the structure of the multi-annular groove in an embodiment of the present invention;

[0028] Figure 3 Schematic diagram of the structure of concentric circular grooves in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0030] like Figures 1-2 FIG. 1 is an embodiment 1 of the present invention.

[0031] Example 1

[0032] The ultrafast laser welding method of the sapphire sheet for endoscope and the stainless steel tube of the present embodiment comprises the following steps:

[0033] S1. Clean the surfaces to be welded of the sapphire sheet 1 and the stainless steel tube 2, i.e., place the sapphire sheet 1 in anhydrous ethanol and perform ultrasonic cleaning for 15 minutes at a frequency of 40 kHz and a power of 100 W to remove the water film and organic matter on the surface of the sapphire sheet 1, and then blow dry with nitrogen; and use 800-mesh sandpaper to polish the surface to be welded of the stainless steel tube 2 to remove the oxide layer and oil stains. After rinsing the sand with clean water, immerse the surface to be welded of the stainless steel tube 2 in alcohol and perform ultrasonic cleaning for 10 minutes at a frequency of 40 kHz and a power of 120 W, and blow dry for standby use.

[0034] S2. Electrolytic polishing is performed on the end of the stainless steel tube 2 with the surface to be welded after cleaning in S1, that is, a mixture of phosphoric acid and sulfuric acid with a volume ratio of 3:1 is used as the electrolyte, the voltage is 12V, and the current density is 0.5A / cm 2 , polishing time is 3 minutes, and a smooth surface with a roughness Ra≤0.2μm is obtained.

[0035] S3. Use a femtosecond laser to perform surface texturing on the sapphire sheet 1 cleaned in S1, so that the surface to be welded of the sapphire sheet 1 has multi-annular grooves 11 at the micron level. The multi-annular grooves 11 are used to connect with the surface to be welded of the stainless steel tube 2, wherein the laser wavelength of the femtosecond laser is 1064nm, the pulse width is 200fs, the power is 18w, the pulse frequency is 80kHz, the spot diameter is 15μm, and the scanning speed is 150mm / s; and the multi-annular grooves 11 of this embodiment are multiple annular grooves arranged at intervals along the thickness direction of the sapphire sheet 1, the width of the annular grooves formed by the femtosecond laser is 50μm, the depth of the annular grooves is 30μm, and the distance between two adjacent annular grooves is 200μm.

[0036] S4. The sapphire sheet 1 obtained in S3 is loaded into the end to be packaged of the stainless steel tube 2 obtained in S2, thereby obtaining an assembly to be welded, wherein the end to be packaged of the stainless steel tube 2 is an end portion having a surface to be welded, and the surface to be welded of the sapphire sheet 1 overlaps with the surface to be welded of the stainless steel tube 2 to form a welding area of ​​the assembly to be welded, and the setting direction of the multiple annular grooves in the multi-annular groove 11 is perpendicular to the laser scanning path.

[0037] S5. Use ultrafast laser to weld the area to be welded in S4 to obtain a completed welded assembly, wherein the laser wavelength of the ultrafast laser is 532nm, the pulse width is 12ps, the power is 250w, the pulse frequency is 400kHz, the spot diameter is 15μm, the scanning speed is 500mm / min, the scanning path is a spiral progressive trajectory, the pitch is 10μm, and argon protection is introduced at the same time, and the argon flow rate is 20L / min.

[0038] S6. Perform vacuum annealing on the assembly welded in S5, i.e., place the assembly welded in S5 in a vacuum annealing furnace, heat it from room temperature to 250°C at a heating rate of 100°C / h, keep it at this temperature for 2 hours, cool it down to 100°C, take it out, and cool it down to room temperature. The vacuum pressure of the vacuum annealing furnace is ≤1×10 -3 P.

[0039] The method of this embodiment realizes ultrafast laser welding of sapphire sheets and stainless steel tubes for endoscopes, which can meet the requirements of endoscopes to withstand high temperature and high humidity (134°C / 70% RH) sterilization for more than 2,000 times. The airtightness test result shows no leakage at 3 atmospheres of pressure.

[0040] Example 2

[0041] The ultrafast laser welding method of the sapphire sheet for endoscope and the stainless steel tube of the present embodiment comprises the following steps:

[0042] S1. Clean the surfaces to be welded of the sapphire sheet 1 and the stainless steel tube 2, i.e., place the sapphire sheet 1 in anhydrous ethanol and perform ultrasonic cleaning for 15 minutes at a frequency of 40 kHz and a power of 100 W to remove the water film and organic matter on the surface of the sapphire sheet 1, and then blow dry with nitrogen; and use 800-mesh sandpaper to polish the surface to be welded of the stainless steel tube 2 to remove the oxide layer and oil stains. After rinsing the sand with clean water, immerse the surface to be welded of the stainless steel tube 2 in alcohol and perform ultrasonic cleaning for 10 minutes at a frequency of 40 kHz and a power of 120 W, and blow dry for standby use.

[0043] S2. Electrolytic polishing is performed on the end of the stainless steel tube 2 with the surface to be welded after cleaning in S1, that is, a mixture of phosphoric acid and sulfuric acid with a volume ratio of 3:1 is used as the electrolyte, the voltage is 12V, and the current density is 0.5A / cm 2 , polishing time is 3 minutes, and a smooth surface with a roughness Ra≤0.2μm is obtained.

[0044] S3. Use a femtosecond laser to perform surface texturing on the sapphire sheet 1 cleaned in S1, so that the surface to be welded of the sapphire sheet 1 has multi-annular grooves 11 at the micron level. The multi-annular grooves 11 are used to connect with the surface to be welded of the stainless steel tube 2, wherein the laser wavelength of the femtosecond laser is 1064nm, the pulse width is 150fs, the power is 15w, the pulse frequency is 50kHz, the spot diameter is 15μm, and the scanning speed is 180mm / s; and the multi-annular grooves 11 of this embodiment are multiple annular grooves arranged at intervals along the thickness direction of the sapphire sheet 1, the width of the annular grooves formed by the femtosecond laser is 40μm, the depth of the annular grooves is 25μm, and the distance between two adjacent annular grooves is 180μm.

[0045] S4. The sapphire sheet 1 obtained in S3 is loaded into the end to be packaged of the stainless steel tube 2 obtained in S2, thereby obtaining an assembly to be welded, wherein the end to be packaged of the stainless steel tube 2 is an end portion having a surface to be welded, and the surface to be welded of the sapphire sheet 1 overlaps with the surface to be welded of the stainless steel tube 2 to form a welding area of ​​the assembly to be welded, and the setting direction of the multiple annular grooves in the multi-annular groove 11 is perpendicular to the laser scanning path.

[0046] S5. Use ultrafast laser to weld the area to be welded in S4 to obtain a completed welded assembly, wherein the laser wavelength of the ultrafast laser is 532nm, the pulse width is 10ps, the power is 200w, the pulse frequency is 300kHz, the spot diameter is 15μm, the scanning speed is 400mm / min, the scanning path is a spiral progressive trajectory, the pitch is 10μm, and argon protection is introduced at the same time, and the argon flow rate is 20L / min.

[0047] S6. Perform vacuum annealing on the assembly welded in S5, i.e., place the assembly welded in S5 in a vacuum annealing furnace, heat it from room temperature to 250°C at a heating rate of 90°C / h, keep it at this temperature for 2 hours, cool it to 100°C, take it out, and cool it to room temperature. The vacuum pressure of the vacuum annealing furnace is ≤1×10 -3 P.

[0048] The method of this embodiment realizes ultrafast laser welding of sapphire sheets and stainless steel tubes for endoscopes, which can meet the requirements of endoscopes to withstand high temperature and high humidity (134°C / 70% RH) sterilization for more than 2,000 times. The airtightness test result shows no leakage at 3 atmospheres of pressure.

[0049] Example 3

[0050] The ultrafast laser welding method of the sapphire sheet for endoscope and the stainless steel tube of the present embodiment comprises the following steps:

[0051] S1. Clean the surfaces to be welded of the sapphire sheet 1 and the stainless steel tube 2, i.e., place the sapphire sheet 1 in anhydrous ethanol and perform ultrasonic cleaning for 15 minutes at a frequency of 40 kHz and a power of 100 W to remove the water film and organic matter on the surface of the sapphire sheet 1, and then blow dry with nitrogen; and use 800-mesh sandpaper to polish the surface to be welded of the stainless steel tube 2 to remove the oxide layer and oil stains. After rinsing the sand with clean water, immerse the surface to be welded of the stainless steel tube 2 in alcohol and perform ultrasonic cleaning for 10 minutes at a frequency of 40 kHz and a power of 120 W, and blow dry for standby use.

[0052] S2. Electrolytic polishing is performed on the end of the stainless steel tube 2 with the surface to be welded after cleaning in S1, that is, a mixture of phosphoric acid and sulfuric acid with a volume ratio of 3:1 is used as the electrolyte, the voltage is 12V, and the current density is 0.5A / cm 2 , polishing time is 3 minutes, and a smooth surface with a roughness Ra≤0.2μm is obtained.

[0053] S3. Use a femtosecond laser to perform surface texturing on the sapphire sheet 1 cleaned in S1, so that the surface to be welded of the sapphire sheet 1 has multi-annular grooves 11 at the micron level. The multi-annular grooves 11 are used to connect with the surface to be welded of the stainless steel tube 2. The laser wavelength of the femtosecond laser is 1064 nm, the pulse width is 300 fs, the power is 20 W, the pulse frequency is 100 kHz, the spot diameter is 15 μm, and the scanning speed is 200 mm / s. The multi-annular grooves 11 of this embodiment are multiple annular grooves spaced apart along the thickness direction of the sapphire sheet 1. The width of the annular grooves formed by the femtosecond laser is 70 μm, the depth of the annular grooves is 83 μm, and the distance between two adjacent annular grooves is 250 μm.

[0054] S4. The sapphire sheet 1 obtained in S3 is loaded into the end to be packaged of the stainless steel tube 2 obtained in S2, thereby obtaining an assembly to be welded, wherein the end to be packaged of the stainless steel tube 2 is an end portion having a surface to be welded, and the surface to be welded of the sapphire sheet 1 overlaps with the surface to be welded of the stainless steel tube 2 to form a welding area of ​​the assembly to be welded, and the setting direction of the multiple annular grooves in the multi-annular groove 11 is perpendicular to the laser scanning path.

[0055] S5. Use ultrafast laser to weld the area to be welded in S4 to obtain a completed welded assembly, wherein the ultrafast laser has a laser wavelength of 532nm, a pulse width of 15ps, a power of 300w, a pulse frequency of 500kHz, a spot diameter of 15μm, a scanning speed of 550mm / min, a spiral progressive trajectory, a pitch of 10μm, and argon protection is introduced at the same time, and the argon flow rate is 20L / min.

[0056] S6. The assembly welded in S5 is subjected to vacuum annealing treatment, i.e., the assembly welded in S5 is placed in a vacuum annealing furnace, and the temperature is raised from room temperature to 240°C at a heating rate of 80°C / h, and the temperature is kept at this temperature for 2.5 hours. The assembly is then taken out of the furnace and cooled to room temperature, wherein the vacuum pressure of the vacuum annealing furnace is ≤1×10 -3 P.

[0057] The method of this embodiment realizes ultrafast laser welding of sapphire sheets and stainless steel tubes for endoscopes, which can meet the requirements of endoscopes to withstand high temperature and high humidity (134°C / 70% RH) sterilization for more than 2,000 times. The airtightness test result shows no leakage at 3 atmospheres of pressure.

[0058] Example 4

[0059] The ultrafast laser welding method of the sapphire sheet for endoscope and the stainless steel tube of the present embodiment comprises the following steps:

[0060] S1. Clean the surfaces to be welded of the sapphire sheet 1 and the stainless steel tube 2, i.e., place the sapphire sheet 1 in alcohol and ultrasonically clean it for 20 minutes at a frequency of 45 kHz and a power of 110 W to remove contaminants on the surface of the sapphire sheet 1, and then blow it dry with nitrogen; and use 1000-mesh sandpaper to polish the surface to be welded of the stainless steel tube 2 to remove the oxide layer and oil stains. After rinsing the sand with clean water, immerse the surface to be welded of the stainless steel tube 2 in ethanol and ultrasonically clean it for 15 minutes at a frequency of 45 kHz and a power of 130 W, and blow it dry for later use.

[0061] S2. Electrolytic polishing is performed on the end of the stainless steel tube 2 with the surface to be welded after cleaning in S1, that is, a mixture of nitric acid and hydrofluoric acid with a volume ratio of 5:1 is used as the electrolyte, the voltage is 10V, and the current density is 0.4A / cm 2, polishing time is 5 minutes, and a smooth surface with a roughness Ra≤0.15μm is obtained.

[0062] S3, using a femtosecond laser to perform surface texturing on the sapphire sheet 1 cleaned in S1, so that the surface to be welded of the sapphire sheet 1 has micron-scale concentric circular grooves 12, and the concentric circular grooves 12 are used to connect with the surface to be welded of the stainless steel tube 2, such as Figure 3 As shown, the laser wavelength of the femtosecond laser is 1064nm, the pulse width is 180fs, the power is 17w, the pulse frequency is 70kHz, the spot diameter is 15μm, and the scanning speed is 200mm / s; and the multiple concentric circular grooves 12 of this embodiment are arranged on the surface to be welded of the sapphire sheet 1 along the circumference of the sapphire sheet 1 at intervals, the spacing between the centers of the multiple concentric circular grooves 12 is 200μm, the concentric circular grooves 12 include multiple circular rings with the same center and different diameters, and a groove is formed between two adjacent circular rings. The width of the circular ring formed by the femtosecond laser is 2.0μm, and the depth between two adjacent circular rings is 20μm. The diameter of the largest circular ring in each concentric circular groove 12 is 100μm, and the diameter of the circular ring in each concentric circular groove 12 decreases by 10μm starting from the largest diameter.

[0063] S4. The sapphire sheet 1 obtained in S3 is loaded into the end to be packaged of the stainless steel tube 2 obtained in S2, thereby obtaining an assembly to be welded, wherein the end to be packaged of the stainless steel tube 2 is the end having the surface to be welded, and the surface to be welded of the sapphire sheet 1 overlaps with the surface to be welded of the stainless steel tube 2 to form a welding area of ​​the assembly to be welded, and the setting direction of the multiple rings in a concentric circular groove 12 is aligned with the laser scanning path.

[0064] S5. Use ultrafast laser to weld the area to be welded in S4 to obtain a completed welded assembly, wherein the laser wavelength of the ultrafast laser is 532nm, the pulse width is 14ps, the power is 220w, the pulse frequency is 350kHz, the spot diameter is 15μm, the scanning speed is 480mm / min, the scanning path is a spiral progressive trajectory, the diameter matches the area to be welded, the pitch is 10μm, and argon protection is introduced at the same time, and the argon flow rate is 20L / min.

[0065] S6. The assembly welded in S5 is subjected to vacuum annealing treatment, i.e., the assembly welded in S5 is placed in a vacuum annealing furnace, and the temperature is raised from room temperature to 240°C at a heating rate of 80°C / h, and the temperature is kept at this temperature for 2.5 hours. The assembly is then taken out of the furnace and cooled to room temperature, wherein the vacuum pressure of the vacuum annealing furnace is ≤1×10 -3 P.

[0066] The method of this embodiment realizes ultrafast laser welding of sapphire sheets and stainless steel tubes for endoscopes, which can meet the requirements of endoscopes to withstand high temperature and high humidity (134°C / 70% RH) sterilization for more than 2,000 times. The airtightness test result shows no leakage at 3 atmospheres of pressure.

[0067] Example 5

[0068] The ultrafast laser welding method of the sapphire sheet for endoscope and the stainless steel tube of the present embodiment comprises the following steps:

[0069] S1. Clean the surfaces to be welded of the sapphire sheet 1 and the stainless steel tube 2, i.e., place the sapphire sheet 1 in alcohol and ultrasonically clean it for 20 minutes at a frequency of 45 kHz and a power of 110 W to remove contaminants on the surface of the sapphire sheet 1, and then blow it dry with nitrogen; and use 1000-mesh sandpaper to polish the surface to be welded of the stainless steel tube 2 to remove the oxide layer and oil stains. After rinsing the sand with clean water, immerse the surface to be welded of the stainless steel tube 2 in ethanol and ultrasonically clean it for 15 minutes at a frequency of 45 kHz and a power of 130 W, and blow it dry for later use.

[0070] S2. Electrolytic polishing is performed on the end of the stainless steel tube 2 with the surface to be welded after cleaning in S1, that is, a mixture of nitric acid and hydrofluoric acid with a volume ratio of 5:1 is used as the electrolyte, the voltage is 10V, and the current density is 0.4A / cm 2 , polishing time is 5 minutes, and a smooth surface with a roughness Ra≤0.15μm is obtained.

[0071] S3, using a femtosecond laser to perform surface texturing on the sapphire sheet 1 cleaned in S1, so that the surface to be welded of the sapphire sheet 1 has micron-scale concentric circular grooves 12, and the concentric circular grooves 12 are used to connect with the surface to be welded of the stainless steel tube 2, such as Figure 3 As shown, the laser wavelength of the femtosecond laser is 1064nm, the pulse width is 150fs, the power is 15w, the pulse frequency is 50kHz, the spot diameter is 15μm, and the scanning speed is 150mm / s; and the multiple concentric circular grooves 12 of this embodiment are arranged on the surface to be welded of the sapphire sheet 1 along the circumference of the sapphire sheet 1, and the spacing between the centers of the multiple concentric circular grooves 12 is 250μm. The concentric circular grooves 12 include multiple circular rings with the same center and different diameters, and a groove is formed between two adjacent circular rings. The width of the circular ring formed by the femtosecond laser is 1.5μm, and the depth between two adjacent circular rings is 15μm. The diameter of the largest circular ring in each concentric circular groove 12 is 150μm, and the diameter of the circular ring in each concentric circular groove 12 decreases by 10μm starting from the largest diameter.

[0072] S4. The sapphire sheet 1 obtained in S3 is loaded into the end to be packaged of the stainless steel tube 2 obtained in S2, thereby obtaining an assembly to be welded, wherein the end to be packaged of the stainless steel tube 2 is the end having the surface to be welded, and the surface to be welded of the sapphire sheet 1 overlaps with the surface to be welded of the stainless steel tube 2 to form a welding area of ​​the assembly to be welded, and the setting direction of the multiple rings in a concentric circular groove 12 is aligned with the laser scanning path.

[0073] S5. Use ultrafast laser to weld the area to be welded in S4 to obtain a completed welded assembly, wherein the laser wavelength of the ultrafast laser is 532nm, the pulse width is 10ps, the power is 200w, the pulse frequency is 300kHz, the spot diameter is 15μm, the scanning speed is 400mm / min, the scanning path is a spiral progressive trajectory, the diameter matches the area to be welded, the pitch is 10μm, and argon protection is introduced at the same time, and the argon flow rate is 20L / min.

[0074] S6. Perform vacuum annealing on the assembly welded in S5, i.e., place the assembly welded in S5 in a vacuum annealing furnace, heat it from room temperature to 250°C at a heating rate of 100°C / h, keep it at this temperature for 2 hours, cool it down to 100°C, take it out, and cool it down to room temperature. The vacuum pressure of the vacuum annealing furnace is ≤1×10 -3 P.

[0075] The method of this embodiment realizes ultrafast laser welding of sapphire sheets and stainless steel tubes for endoscopes, which can meet the requirements of endoscopes to withstand high temperature and high humidity (134°C / 70% RH) sterilization for more than 2,000 times. The airtightness test result shows no leakage at 3 atmospheres of pressure.

[0076] Example 6

[0077] The ultrafast laser welding method of the sapphire sheet for endoscope and the stainless steel tube of the present embodiment comprises the following steps:

[0078] S1. Clean the surfaces to be welded of the sapphire sheet 1 and the stainless steel tube 2, i.e., place the sapphire sheet 1 in alcohol and ultrasonically clean it for 20 minutes at a frequency of 45 kHz and a power of 110 W to remove contaminants on the surface of the sapphire sheet 1, and then blow it dry with nitrogen; and use 1000-mesh sandpaper to polish the surface to be welded of the stainless steel tube 2 to remove the oxide layer and oil stains. After rinsing the sand with clean water, immerse the surface to be welded of the stainless steel tube 2 in ethanol and ultrasonically clean it for 15 minutes at a frequency of 45 kHz and a power of 130 W, and blow it dry for later use.

[0079] S2. Electrolytic polishing is performed on the end of the stainless steel tube 2 with the surface to be welded after cleaning in S1, that is, a mixture of nitric acid and hydrofluoric acid with a volume ratio of 5:1 is used as the electrolyte, the voltage is 10V, and the current density is 0.4A / cm 2, polishing time is 5 minutes, and a smooth surface with a roughness Ra≤0.15μm is obtained.

[0080] S3, using a femtosecond laser to perform surface texturing on the sapphire sheet 1 cleaned in S1, so that the surface to be welded of the sapphire sheet 1 has micron-scale concentric circular grooves 12, and the concentric circular grooves 12 are used to connect with the surface to be welded of the stainless steel tube 2, such as Figure 3 As shown, the laser wavelength of the femtosecond laser is 1064nm, the pulse width is 300fs, the power is 20w, the pulse frequency is 100kHz, the spot diameter is 15μm, and the scanning speed is 180mm / s; and the multiple concentric circular grooves 12 of this embodiment are arranged on the surface to be welded of the sapphire sheet 1 along the circumference of the sapphire sheet 1 at intervals, the spacing between the centers of the multiple concentric circular grooves 12 is 300μm, the concentric circular grooves 12 include multiple circular rings with the same center and different diameters, and a groove is formed between two adjacent circular rings. The width of the circular ring formed by the femtosecond laser is 3.5μm, and the depth between two adjacent circular rings is 18μm. The diameter of the largest circular ring in each concentric circular groove 12 is 200μm, and the diameter of the circular ring in each concentric circular groove 12 decreases by 10μm starting from the largest diameter.

[0081] S4. The sapphire sheet 1 obtained in S3 is loaded into the end to be packaged of the stainless steel tube 2 obtained in S2, thereby obtaining an assembly to be welded, wherein the end to be packaged of the stainless steel tube 2 is the end having the surface to be welded, and the surface to be welded of the sapphire sheet 1 overlaps with the surface to be welded of the stainless steel tube 2 to form a welding area of ​​the assembly to be welded, and the setting direction of the multiple rings in a concentric circular groove 12 is aligned with the laser scanning path.

[0082] S5. Use ultrafast laser to weld the area to be welded in S4 to obtain a completed welded assembly, wherein the laser wavelength of the ultrafast laser is 532nm, the pulse width is 15ps, the power is 300w, the pulse frequency is 500kHz, the spot diameter is 15μm, the scanning speed is 550mm / min, the scanning path is a spiral progressive trajectory, the diameter matches the area to be welded, the pitch is 10μm, and argon protection is introduced at the same time, and the argon flow rate is 20L / min.

[0083] S6. The assembly welded in S5 is subjected to vacuum annealing treatment, i.e., the assembly welded in S5 is placed in a vacuum annealing furnace, and the temperature is raised from room temperature to 240°C at a heating rate of 80°C / h, and the temperature is kept at this temperature for 2.5 hours. The assembly is then taken out of the furnace and cooled to room temperature, wherein the vacuum pressure of the vacuum annealing furnace is ≤1×10 -3 P.

[0084] The method of this embodiment realizes ultrafast laser welding of sapphire sheets and stainless steel tubes for endoscopes, which can meet the requirements of endoscopes to withstand high temperature and high humidity (134°C / 70% RH) sterilization for more than 2,000 times. The airtightness test result shows no leakage at 3 atmospheres of pressure.

Claims

1. A method for ultrafast laser welding of a sapphire sheet for endoscope and a stainless steel tube, characterized in that: The following steps are involved: S1, cleaning the surface to be welded of the sapphire sheet (1) and the surface to be welded of the stainless steel tube (2); S2, electrolytically polishing the end of the stainless steel tube (2) cleaned in S1, which has the surface to be welded; S3, using a femtosecond laser to perform surface texturing on the sapphire sheet (1) cleaned in S1, so that the surface to be welded of the sapphire sheet (1) has a micron-scale connection groove, and the connection groove is used to connect with the surface to be welded of the stainless steel tube (2); S4, loading the sapphire sheet (1) obtained in S3 into the end to be packaged of the stainless steel tube (2) obtained in S2, thereby obtaining a to-be-welded assembly, wherein the to-be-packaged end of the stainless steel tube (2) is an end portion having a to-be-welded surface, and the to-be-welded surface of the sapphire sheet (1) and the to-be-welded surface of the stainless steel tube (2) overlap to form a to-be-welded area of ​​the to-be-welded assembly; S5, welding the area to be welded in S4 using an ultrafast laser to obtain a welded assembly; S6. Perform vacuum annealing on the assembly welded in S5.

2. The method for ultrafast laser welding of a sapphire sheet for endoscope and a stainless steel tube according to claim 1, characterized in that: The stainless steel tube (2) in S1 is polished with sandpaper on its surface to be welded and the sand is rinsed with clean water, and the sapphire sheet (1) and the polished and rinsed stainless steel tube (2) are ultrasonically cleaned with ethanol on their respective surfaces to be welded.

3. The method for ultrafast laser welding of a sapphire sheet for endoscope and a stainless steel tube according to claim 1, characterized in that: The femtosecond laser in S3 has a laser wavelength of 1060-1070 nm, a pulse width of 150-300 fs, a power of 15-20 W, a pulse frequency of 50-100 kHz, a spot diameter of 12-18 μm, and a scanning speed of 150-200 mm / s.

4. The method for ultrafast laser welding of a sapphire sheet for endoscope and a stainless steel tube according to claim 1, characterized in that: The connection grooves of the sapphire sheet (1) in S3 are multi-annular grooves (11) or concentric circular grooves (12).

5. The method for ultrafast laser welding of a sapphire sheet for endoscope and a stainless steel tube according to claim 4, characterized in that: The multi-annular grooves (11) are multiple annular grooves spaced apart along the thickness direction of the sapphire sheet (1), the width of the annular grooves is 40 to 70 μm, the depth of the annular grooves is 25 to 83 μm, and the distance between two adjacent annular grooves is 180 to 250 μm.

6. The method for ultrafast laser welding of a sapphire sheet for endoscope and a stainless steel tube according to claim 4, characterized in that: A plurality of concentric circular grooves (12) are arranged on the surface to be welded of the sapphire sheet (1) at intervals along the circumference of the sapphire sheet (1); the spacing between the centers of the plurality of concentric circular grooves (12) is 200 to 300 μm; the concentric circular grooves (12) include a plurality of circular rings with the same center and different diameters; a groove is formed between two adjacent circular rings; the width of the circular rings is 1.5 to 3.5 μm; the depth between two adjacent circular rings is 15 to 20 μm; the diameter of the largest circular ring in each of the concentric circular grooves (12) is 100 to 200 μm; and the diameters of the circular rings in each of the concentric circular grooves (12) decrease by 10 μm starting from the largest diameter.

7. The method for ultrafast laser welding of a sapphire sheet for endoscope and a stainless steel tube according to claim 1, characterized in that: The ultrafast laser in the S5 has a laser wavelength of 530-540 nm, a pulse width of 10-15 ps, a power of 200-300 W, a pulse frequency of 300-500 kHz, a spot diameter of 12-18 μm, a scanning speed of 400-550 mm / min, an argon flow rate of 18-22 L / min, a spiral progressive trajectory, and a pitch of 8-12 μm.

8. The method for ultrafast laser welding of a sapphire sheet for endoscope and a stainless steel tube according to claim 1, characterized in that: The vacuum annealing in S6 is to place the assembled body welded in S5 in a vacuum annealing furnace, and heat it from room temperature to 240-250°C at a heating rate of 80-100°C / h, and keep it at this temperature for at least 2 hours. After cooling it to below 100°C, the assembled body is taken out and cooled to room temperature. The vacuum pressure of the vacuum annealing furnace is ≤1×10 -3 P.

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