A method for vacuum laser welding of thick titanium alloy cylinders

Abstract

This invention belongs to the field of vacuum laser titanium alloy welding, specifically a method for vacuum laser welding thick titanium alloy cylinders. The method involves first processing the thick titanium alloy cylinder to be welded onto a suitable substrate, then cleaning the welding surface and weld seam with acetone and alcohol, positioning and fixing it on a rotating mechanism, and finally evacuating the entire chamber before using a laser to weld the thick titanium alloy cylinder. This invention significantly suppresses the diffusion of plumes during the titanium alloy welding process, increases the weld penetration, reduces defects such as oxidation, porosity, and incomplete fusion during welding, improves the mechanical properties of the welded joint, and reduces residual stress at the weld seam. This invention can achieve high-performance welding of various structural components made of titanium alloys with thicknesses ranging from 20-100 mm, and is particularly suitable for welding thick titanium alloy cylinders. It can be applied to the welding of large titanium alloy structural components in fields such as nuclear power, deep-sea submersibles, ships, and aerospace.

Description

Technical Field

[0001] This invention belongs to the field of vacuum laser titanium alloy welding technology, specifically to a method for vacuum laser welding of thick titanium alloy cylinders. Background Technology

[0002] Titanium alloys, with their high strength, low density, and excellent corrosion resistance and high-temperature resistance, occupy a crucial position in cutting-edge technology fields such as aerospace, deep-sea submersibles, and petrochemicals. However, the welding of titanium alloys faces numerous challenges. Traditional welding methods often result in defects such as embrittlement, porosity, and cracks at the weld seam, which not only reduces the performance of the welded joint but also severely restricts the application of titanium alloys in a wider range of fields. To overcome these technical difficulties, laser welding technology has emerged. This technology uses a high-energy-density laser beam as a heat source to achieve efficient and precise welding of titanium alloys. Combining laser welding technology with a vacuum environment further improves the welding quality, effectively avoiding oxidation and nitriding of titanium alloys during the welding process, and ensuring the purity and excellent mechanical properties of the weld seam.

[0003] Currently, the thickness of welded cylindrical titanium alloy parts generally does not exceed 40mm. For welding thick-cylinder titanium alloys, the excessive thickness leads to decreased stability of the molten pool during the welding process. The greater the thickness, the higher the laser power required. Higher laser power results in a less stable molten pool, making defects such as porosity more likely. Furthermore, the use of higher laser power for thicker titanium alloys results in a very small state space between the welded and cut states, making it difficult to determine suitable process parameters.

[0004] In summary, a variety of factors make vacuum laser welding of thick titanium alloy cylinders extremely difficult, causing many products to give up at the design stage and hindering the application of titanium alloys in thicker materials. At present, significant breakthroughs are needed in solving the problems and solutions of vacuum laser welding of thick titanium alloy cylinders. Summary of the Invention

[0005] In view of the above-mentioned technical problems, the present invention provides a vacuum laser welding method for thick titanium alloy cylinders. This method ensures precise positioning of the workpiece before welding, guaranteeing a uniform weld gap; the process substrate ensures good shape and quality of the weld bottom during welding; the vacuum environment reduces the diffusion of plumes during welding, minimizing laser beam energy loss; the overall vacuum environment during welding allows for a more stable molten pool state, reducing internal defects such as porosity; tilting the laser head at a certain angle during welding reduces damage to the laser beam from high-reflection lasers and spatter.

[0006] To achieve the above objectives, the present invention provides the following technical solutions.

[0007] A method for vacuum laser welding of thick titanium alloy cylinders includes the following steps:

[0008] Step 1: Before welding, process a substrate is machined onto the welding surfaces of the two titanium alloy cylinders;

[0009] Step 2: When hoisting one of the titanium alloy cylinders, clamp it with two sets of lifting clamps. Then, set a lateral micro-motion mechanism above the connection between the two sets of lifting clamps. When the titanium alloy cylinder moves to the approximate position, release the micro-motion mechanism to achieve a short-distance precise movement of the titanium alloy cylinder and achieve accurate positioning of the titanium alloy cylinder. The micro-motion distance is ±5mm. Clamp the titanium alloy cylinder on the rotating chuck to ensure that the coaxial runout of the titanium alloy cylinder is within ±0.05mm and the end face runout is within ±0.05mm.

[0010] Step 3: First, wipe the welding surface and weld position of the clamped titanium alloy cylinder with alcohol, then wipe the welding surface and weld position with acetone. Wipe with alcohol and acetone until there are no obvious stains visible to the naked eye. Finally, use laser to clean the welding surface and weld position. After cleaning, use a cleanliness tester to test the cleanliness. The cleanliness test range is 5-60 RFU.

[0011] Step 4: Hoist another titanium alloy cylinder as in Step 2. After hoisting, clean the weld surface and welding position using the method in Step 3. After the cleaning index is qualified, move it above the first titanium alloy cylinder, adjust the micro-motion structure so that the second titanium alloy cylinder is aligned with the process substrate of the first titanium alloy cylinder, and lower the second titanium alloy cylinder to make the two process substrates join together and the welding surfaces meet.

[0012] Step 5: Press the two titanium alloy cylinders together, and use a torque wrench to lock them in place during the pressing process. The locking torque is 350-369N, and record the locking force each time.

[0013] Step 6: The vacuum welding chamber is equipped with both high- and low-precision vacuum gauges; the laser head mounting assembly is equipped with dual-angle adjustment function, with the X-axis angle adjustment range of ±15 degrees and the Z-axis angle adjustment range of ±10 degrees; the laser head protective lens is equipped with lens contamination monitoring and temperature monitoring; the laser head is equipped with a molten pool monitoring system and a post-weld surface morphology observation system.

[0014] Step 7: Place the two titanium alloy cylinders in the vacuum welding chamber, determine the weld start point of the two titanium alloy cylinders, and then perform low vacuum treatment followed by high vacuum treatment.

[0015] Step 8: Vacuum laser welding is performed on the titanium alloy cylinder. During the vacuum laser welding process, the overlap between the start and end points of the laser beam is controlled within a certain range, and finally a thick titanium alloy cylinder with vacuum laser welding is obtained.

[0016] Furthermore, the wall thickness of the titanium alloy cylinder is 20-100mm.

[0017] Furthermore, in step 1, the width of the process substrate is 3-8 mm and the thickness is 2-6 mm.

[0018] Furthermore, in step 3, the alcohol is high-purity alcohol of 98% or higher; the laser cleaning parameters are: 100W power, speed 1mm / s, width 20mm, and focal length 300mm.

[0019] Furthermore, in step 6, the low vacuum level ranges from 100 to 101000 Pa, with an accuracy of ±10 Pa; the high vacuum level ranges from -100 to 100 Pa, with an accuracy of ±0.1 Pa.

[0020] Furthermore, in step 6, the temperature monitoring range is -50℃ to 160℃; the molten pool monitoring system monitors the molten pool temperature range of 200℃ to 3000℃, and the molten pool morphology monitoring change range is 0.02-1mm.

[0021] Furthermore, in step 7, the vacuum degree is 0.01-100 Pa.

[0022] Furthermore, in step 7, the method for determining the welding start point of the titanium alloy cylinder weld is as follows: first, determine the highest point of the cylindrical surface of the titanium alloy cylinder, with the deviation of the highest point not exceeding ±0.2mm; then, after aligning the red light of the laser head with the highest point, set the distance between the laser head and the titanium alloy cylinder to 87mm; after setting, adjust the Z-axis up and down to ensure that the deviation of the red light aligned with the weld seam does not exceed ±0.02mm.

[0023] Furthermore, in step 8, the parameters for vacuum laser welding are: welding power 10-60KW, defocusing amount 0-50mm, and welding speed 0.1-1.5m / min.

[0024] Furthermore, in step 8, the rotation direction during welding of the titanium alloy cylinder is the direction corresponding to the X-axis deflection angle of the laser head; the overlap is 10-100mm in length.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0026] 1. The micro-motion structure enables rapid, stable, and precise docking of the titanium alloy welded cylinder during hoisting, reducing collisions and improving the overall hoisting efficiency and quality.

[0027] 2. By combining multiple cleaning methods in sequence and testing the surface cleanliness during the cleaning process, the cleaning efficiency and cleanliness of the welding surface can be greatly improved. The numerical records can facilitate subsequent data statistics.

[0028] 3. The process substrate not only enables precise positioning of the weld seam and welding surface of the titanium composite cylinder, but also improves the overall welding quality of the weld seam.

[0029] 4. The laser head is equipped with temperature and molten pool monitoring, which can monitor and control the welding process in real time to ensure welding quality.

[0030] 5. Precise positioning of the weld start point can ensure accurate control of the weld width and depth. Attached Figure Description

[0031] Figure 1 Example 1: Overall view of the thick titanium alloy cylinder after vacuum laser welding.

[0032] Figure 2 Partial view of the thick titanium alloy cylinder after vacuum laser welding in Example 1. Detailed Implementation

[0033] The technical solutions of this invention will now be clearly and completely described. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0034] Example 1.

[0035] The first step involves machining process substrates on the mating surfaces of the two titanium alloy cylinders before welding. After the process substrates of the two titanium alloy cylinders are fitted together, they are joined together. The width of the process substrate is 5mm and the thickness is 3mm. After the two titanium alloy cylinders are fitted together, the coaxiality deviation is guaranteed to be no more than 0.05mm and the gap between the mating surfaces is no more than 0.05mm.

[0036] The second step involves using two sets of clamps to hold the titanium alloy cylinder. A lateral micro-motion mechanism is then set above the connection between the two sets of clamps. When the titanium alloy cylinder moves to its approximate position, the micro-motion mechanism is released to achieve a short-distance precise movement of the titanium alloy cylinder, thus achieving accurate positioning of the titanium alloy cylinder. The micro-motion distance is ±5mm. After adjusting the position, the cylinder is placed on a rotating chuck and clamped for fixation.

[0037] The third step involves first applying a small amount of high-purity alcohol (98% or higher) to a non-woven fabric and wiping the welding surface and weld seam. After wiping until the non-woven fabric surface shows no obvious changes, apply a small amount of acetone and wipe the welding surface and weld seam in the same way. After wiping, use a handheld laser cleaning device to perform laser cleaning on the welding surface and weld seam. The laser cleaning parameters are: 100W power, speed 1mm / s, width 20mm, and focal length 300mm. After laser cleaning, use a cleanliness detector to test the cleanliness. The acceptable value range is 30 RFU.

[0038] Fourth, the second titanium alloy cylinder is hoisted using the method in the second step. After hoisting, the weld surface and welding position are cleaned using the method in the third step. After the cleaning indicators are qualified, it is moved above the first titanium alloy cylinder. The micro-motion structure is adjusted so that the second titanium alloy cylinder is aligned with the process substrate of the first titanium alloy cylinder. The second titanium alloy cylinder is slowly lowered to make the two process substrates join together and the welding surfaces are joined. The coaxiality is checked to ensure that the coaxiality deviation of the two cylinders does not exceed 0.05mm and the gap between the mating surfaces does not exceed 0.05mm.

[0039] The fifth step is to use a clamping fixture to press the two titanium alloy cylinders together. During the clamping process, a torque wrench is used to lock the cylinder with a locking torque of 366N, and the locking force is recorded each time.

[0040] Step 6: Adjust the laser head angle adjustment component. Adjust the X-axis angle to +15 degrees and the Z-axis angle to 0 degrees. After adjustment, use an angle meter to check the angle.

[0041] Step 7: After the titanium alloy cylinder is compressed, it is transported to a fixed position in the vacuum chamber by a conveyor vehicle. A dial indicator is fixed on the laser head, and the pressure pointer of the dial indicator is pressed against the arc surface of the titanium alloy cylinder. The X-axis of the welding head is moved, and the change of the dial indicator needle is observed until the needle stops. The point where the needle stops is the highest point of the arc surface. The deviation of the highest point should not exceed ±0.2mm. After marking the highest point, the Z-axis is moved vertically up and down to mark another highest point. A line is drawn between the two points using a steel ruler.

[0042] Step 8: Turn on the laser guide beam, move the laser head motion mechanism, and align the red light with the highest point line drawn in step 7. After aligning the laser head red light with the highest point, set the distance between the laser head and the highest point line of the titanium alloy cylinder to 87mm. After setting, adjust the Z-axis up and down to align the red light with the welding seam, with an up and down deviation not exceeding ±0.02mm. After alignment, record the initial point coordinate system in the equipment operating system.

[0043] Step 9: Close the vacuum chamber door and begin vacuuming. The vacuum chamber is equipped with two vacuum gauges: a low vacuum range of 100-101000 Pa with an accuracy of ±10 Pa, and a high vacuum range of -100-100 Pa with an accuracy of ±0.1 Pa. During the initial vacuuming, the low vacuum gauge is activated, and the pump unit starts high-power vacuuming. When the high vacuum range is reached, the high vacuum gauge is activated, and the pump unit uses low-power vacuuming to ensure a more stable welding environment. The final vacuum level is maintained at 10 Pa to prepare for welding.

[0044] Step 10: Before starting welding, set the vacuum laser welding parameters according to the 66mm titanium alloy welding thickness: welding power 1.8KW, negative defocusing amount after focusing 30mm, and welding speed 0.4m / min.

[0045] Step 11: During the welding process, activate the laser head temperature monitoring sensor and the molten pool monitoring sensor to monitor the laser head temperature and molten pool temperature. The laser head temperature should not exceed 45℃, the molten pool temperature should not exceed 2000℃, and the molten pool width deviation should not exceed 1mm.

[0046] Step 12: After welding a section of the weld and cooling for 20 minutes, open the vacuum chamber, rotate the rotary chuck to move the titanium alloy cylinder to the welding position, grind the protruding part of the position with an alloy rotary grinding head to make it smooth, and wipe the surface clean with alcohol; similarly, rotate the rotary chuck to the initial welding position, grind the weld to make it smooth using the same method, and wipe it clean with alcohol.

[0047] Step 13: Use a ruler to measure and mark two 100mm distances from the start point of the weld. Set the end point of the upper weld section as the start point of the lower weld section, and the other point as the end point. Calculate the length of the entire weld section based on the two marked points. After the machine tool records the coordinate points, adjust the rotary chuck to the initial position, close the vacuum chamber door, and prepare to start the second weld.

[0048] Step fourteen: During the welding process, the same welding method as steps nine, ten, and eleven was used. After welding, the chamber door was opened after holding the weld at a constant temperature for 20 minutes, yielding the vacuum laser-welded thick titanium alloy cylinder. The test results are shown in Table 1.

[0049] Example 2.

[0050] The first step involves machining process substrates on the mating surfaces of the two titanium alloy cylinders before welding. The process substrates on the two cylinders are then joined together. The width of the process substrates is 5mm, and the thickness is 3mm. After the two titanium alloy cylinders are fitted together, the coaxiality deviation must not exceed 0.05mm, and the gap between the mating surfaces must not exceed 0.05mm.

[0051] The second step involves using two sets of clamps to hold the titanium alloy cylinder. A lateral micro-motion mechanism is then set above the connection between the two sets of clamps. When the titanium alloy cylinder moves to its approximate position, the micro-motion mechanism is released to achieve a short-distance precise movement of the titanium alloy cylinder, thus achieving accurate positioning of the titanium alloy cylinder. The micro-motion distance is ±5mm. After adjusting the position, the cylinder is placed on a rotating chuck and clamped for fixation.

[0052] The third step involves first applying a small amount of high-purity alcohol (98% or higher) to a non-woven fabric and wiping the welding surface and weld seam. After wiping until the non-woven fabric surface shows no obvious changes, apply a small amount of acetone and wipe the welding surface and weld seam in the same way. After wiping, use a handheld laser cleaning device to perform laser cleaning on the welding surface and weld seam. The laser cleaning parameters are: 100W power, speed 1mm / s, width 20mm, and focal length 300mm. After laser cleaning, use a cleanliness detector to test the cleanliness. The acceptable value range is 30 RFU.

[0053] Fourth, the second titanium alloy cylinder is hoisted using the method in the second step. After hoisting, the weld surface and welding position are cleaned using the method in the third step. After the cleaning indicators are qualified, it is moved above the first titanium alloy cylinder. The micro-motion structure is adjusted so that the second titanium alloy cylinder is aligned with the process substrate of the first titanium alloy cylinder. The second titanium alloy cylinder is slowly lowered to make the two process substrates join together and the welding surfaces are joined. The coaxiality is checked to ensure that the coaxiality deviation of the two cylinders does not exceed 0.05mm and the gap between the mating surfaces does not exceed 0.05mm.

[0054] The fifth step is to use a clamping fixture to press the two titanium alloy cylinders together. During the clamping process, a torque wrench is used to lock the cylinder with a torque of 360N, and the locking force is recorded each time.

[0055] Step 6: Adjust the laser head angle adjustment component. Adjust the X-axis angle to +15 degrees and the Z-axis angle to 0 degrees. After adjustment, use an angle meter to check the angle.

[0056] Step 7: After the titanium alloy cylinder is compressed, it is transported to a fixed position in the vacuum chamber by a conveyor vehicle. A dial indicator is fixed on the laser head, and the pressure pointer of the dial indicator is pressed against the arc surface of the titanium alloy cylinder. The X-axis of the welding head is moved, and the change of the dial indicator needle is observed until the needle stops. The point where the needle stops is the highest point of the arc surface. The deviation of the highest point does not exceed ±0.2 mm. After marking the highest point, the Z-axis is moved vertically up and down to mark another highest point. A line is drawn between the two points using a steel ruler.

[0057] Step 8: Turn on the laser guide beam, move the laser head motion mechanism, and align the red light with the highest point line drawn in step 7. After aligning the laser head red light with the highest point, set the distance between the laser head and the highest point line of the titanium alloy cylinder to 87mm. After setting, adjust the Z-axis up and down to align the red light with the welding seam, with an up and down deviation not exceeding ±0.02mm. After alignment, record the initial point coordinate system in the equipment operating system.

[0058] Step 9: Close the vacuum chamber door and begin vacuuming. The vacuum chamber is equipped with two vacuum gauges: a low vacuum range of 100-101000 Pa with an accuracy of ±10 Pa, and a high vacuum range of -100-100 Pa with an accuracy of ±0.1 Pa. During the initial vacuuming, the low vacuum gauge is activated, and the pump unit starts high-power vacuuming. When the high vacuum range is reached, the high vacuum gauge is activated, and the pump unit uses low-power vacuuming to ensure a more stable welding environment. The final vacuum level is maintained at 10 Pa to prepare for welding.

[0059] Step 10: Before starting welding, set the vacuum laser welding parameters according to the 58mm titanium alloy welding thickness: welding power 1.6KW, negative defocusing amount after focusing 30mm, and welding speed 0.4m / min.

[0060] Step 11: During the welding process, activate the laser head temperature monitoring sensor and the molten pool monitoring sensor to monitor the laser head temperature and molten pool temperature. The laser head temperature should not exceed 45℃, the molten pool temperature should not exceed 2000℃, and the molten pool width deviation should not exceed 1mm.

[0061] Step 12: After welding a section of the weld and cooling for 20 minutes, open the vacuum chamber, rotate the rotary chuck to move the titanium alloy cylinder to the welding position, grind the protruding part of the position with an alloy rotary grinding head to make it smooth, and wipe the surface clean with alcohol; similarly, rotate the rotary chuck to the initial welding position, grind the weld to make it smooth using the same method, and wipe it clean with alcohol.

[0062] Step 13: Use a ruler to measure and mark two 100mm distances from the start point of the weld. Set the end point of the upper weld section as the start point of the lower weld section, and the other point as the end point. Calculate the length of the entire weld section based on the two marked points. After the machine tool records the coordinate points, adjust the rotary chuck to the initial position, close the vacuum chamber door, and prepare to start the second weld.

[0063] Step fourteen: During the welding process, the same welding method as steps nine, ten, and eleven was used. After welding, the chamber door was opened after holding the weld at a constant temperature for 20 minutes, yielding the vacuum laser-welded thick titanium alloy cylinder. The test results are shown in Table 2.

[0064] Example 3.

[0065] The first step involves machining process substrates on the mating surfaces of the two titanium alloy cylinders before welding. The process substrates on the two cylinders are then joined together. The width of the process substrates is 5mm, and the thickness is 3mm. After the two titanium alloy cylinders are fitted together, the coaxiality deviation must not exceed 0.05mm, and the gap between the mating surfaces must not exceed 0.05mm.

[0066] The second step involves using two sets of clamps to hold the titanium alloy cylinder. A lateral micro-motion mechanism is then set above the connection between the two sets of clamps. When the titanium alloy cylinder moves to its approximate position, the micro-motion mechanism is released to achieve a short-distance precise movement of the titanium alloy cylinder, thus achieving accurate positioning of the titanium alloy cylinder. The micro-motion distance is ±5mm. After adjusting the position, the cylinder is placed on a rotating chuck and clamped for fixation.

[0067] The third step involves first applying a small amount of high-purity alcohol (98% or higher) to a non-woven fabric and wiping the welding surface and weld seam. After wiping until the non-woven fabric surface shows no obvious changes, apply a small amount of acetone and wipe the welding surface and weld seam in the same way. After wiping, use a handheld laser cleaning device to perform laser cleaning on the welding surface and weld seam. The laser cleaning parameters are: 100W power, speed 1mm / s, width 20mm, and focal length 300mm. After laser cleaning, use a cleanliness detector to test the cleanliness. The acceptable value range is 30 RFU.

[0068] Fourth, the second titanium alloy cylinder is hoisted using the method in the second step. After hoisting, the weld surface and welding position are cleaned using the method in the third step. After the cleaning indicators are qualified, it is moved above the first titanium alloy cylinder. The micro-motion structure is adjusted so that the second titanium alloy cylinder is aligned with the process substrate of the first titanium alloy cylinder. The second titanium alloy cylinder is slowly lowered to make the two process substrates join together and the welding surfaces are joined. The coaxiality is checked to ensure that the coaxiality deviation of the two cylinders does not exceed 0.05mm and the gap between the mating surfaces does not exceed 0.05mm.

[0069] The fifth step is to use a clamping fixture to press the two titanium alloy cylinders together. During the clamping process, a torque wrench is used to lock the cylinder with a torque of 358N, and the locking force is recorded each time.

[0070] Step 6: Adjust the laser head angle adjustment component. Adjust the X-axis angle to +15 degrees and the Z-axis angle to 0 degrees. After adjustment, use an angle meter to check the angle.

[0071] Step 7: After the titanium alloy cylinder is compressed, it is transported to a fixed position in the vacuum chamber by a conveyor vehicle. A dial indicator is fixed on the laser head, and the pressure pointer of the dial indicator is pressed against the arc surface of the titanium alloy cylinder. The X-axis of the welding head is moved, and the change of the dial indicator needle is observed until the needle stops. The point where the needle stops is the highest point of the arc surface. The deviation of the highest point should not exceed ±0.2mm. After marking the highest point, the Z-axis is moved vertically up and down to mark another highest point. A line is drawn between the two points using a steel ruler.

[0072] Step 8: Turn on the laser guide beam, move the laser head motion mechanism, and align the red light with the highest point line drawn in step 7. After aligning the laser head red light with the highest point, set the distance between the laser head and the highest point line of the titanium alloy cylinder to 87mm. After setting, adjust the Z-axis up and down to align the red light with the welding seam, with an up and down deviation not exceeding ±0.02mm. After alignment, record the initial point coordinate system in the equipment operating system.

[0073] Step 9: Close the vacuum chamber door and begin vacuuming. The vacuum chamber is equipped with two vacuum gauges: a low vacuum range of 100-101000 Pa with an accuracy of ±10 Pa, and a high vacuum range of -100-100 Pa with an accuracy of ±0.1 Pa. During the initial vacuuming, the low vacuum gauge is activated, and the pump unit starts high-power vacuuming. When the high vacuum range is reached, the high vacuum gauge is activated, and the pump unit uses low-power vacuuming to ensure a more stable welding environment. The final vacuum level is maintained at 10 Pa to prepare for welding.

[0074] Step 10: Before starting the welding process, set the vacuum laser welding parameters according to the 50mm titanium alloy welding thickness: welding power of 1.2KW, negative defocusing amount after focusing of 30mm, and welding speed of 0.4m / min.

[0075] Step 11: During the welding process, activate the laser head temperature monitoring sensor and the molten pool monitoring sensor to monitor the laser head temperature and molten pool temperature. The laser head temperature should not exceed 45℃, the molten pool temperature should not exceed 2000℃, and the molten pool width deviation should not exceed 1mm.

[0076] Step 12: After welding a section of the weld and cooling for 20 minutes, open the vacuum chamber, rotate the rotary chuck to move the titanium alloy cylinder to the welding position, grind the protruding part of the position with an alloy rotary grinding head to make it smooth, and wipe the surface clean with alcohol; similarly, rotate the rotary chuck to the initial welding position, grind the weld to make it smooth using the same method, and wipe it clean with alcohol.

[0077] Step 13: Use a ruler to measure and mark two 100mm distances from the start point of the weld. Set the end point of the upper weld section as the start point of the lower weld section, and the other point as the end point. Calculate the length of the entire weld section based on the two marked points. After the machine tool records the coordinate points, adjust the rotary chuck to the initial position, close the vacuum chamber door, and prepare to start the second weld.

[0078] Step fourteen: During the welding process, the same welding method as steps nine, ten, and eleven was used. After welding, the chamber door was opened after holding the weld at a constant temperature for 20 minutes, yielding the vacuum laser-welded thick titanium alloy cylinder. The test results are shown in Table 3.

[0079] Table 1 shows the test results of Example 1.

[0080]

[0081] Note: The "-" in the residual stress test results indicates that the direction is opposite to the current test direction. It only represents the direction, and the final value is the absolute value.

[0082] Table 2 shows the test results of Example 2.

[0083]

[0084] Note: The "-" in the residual stress test results indicates that the direction is opposite to the current test direction. It only represents the direction, and the final value is the absolute value.

[0085] Table 3 shows the test results of Example 3.

[0086]

Claims

1. A method for vacuum laser welding of thick titanium alloy cylinders, characterized in that, Includes the following steps: Step 1: Before welding, process a process substrate on the welding surface of the two titanium alloy cylinders; the width of the process substrate is 3-8mm and the thickness is 2-6mm. Step 2: When hoisting one of the titanium alloy cylinders, clamp it with two sets of lifting clamps. Then, set a lateral micro-motion structure above the connection between the two sets of lifting clamps. When the titanium alloy cylinder moves to the position, release the micro-motion structure to achieve a short-distance precise movement of the titanium alloy cylinder and achieve accurate positioning of the titanium alloy cylinder. The micro-motion distance is ±5mm. Clamp the titanium alloy cylinder on the rotating chuck to ensure that the coaxial runout of the titanium alloy cylinder is within ±0.05mm and the end face runout is within ±0.05mm. Step 3: First, wipe the welding surface and weld position of the clamped titanium alloy cylinder with alcohol, then wipe the welding surface and weld position with acetone. Wipe with alcohol and acetone until there are no obvious stains visible to the naked eye. Finally, use laser to clean the welding surface and weld position. After cleaning, use a cleanliness tester to test the cleanliness. The cleanliness test range is 5-60 RFU. Step 4: Hoist another titanium alloy cylinder as in Step 2. After hoisting, clean the weld surface and welding position using the method in Step 3. After the cleaning index is qualified, move it above the first titanium alloy cylinder, adjust the micro-motion structure so that the second titanium alloy cylinder is aligned with the process substrate of the first titanium alloy cylinder, and lower the second titanium alloy cylinder to make the two process substrates join together and the welding surfaces meet. Step 5: Press the two titanium alloy cylinders together, and use a torque wrench to lock them in place during the pressing process. The locking torque is 350-369N, and record the locking force each time. Step 6: The vacuum welding chamber is equipped with both high- and low-precision vacuum gauges; the laser head mounting assembly is equipped with dual-angle adjustment functions, with the X-axis angle adjustment range being ±15 degrees and the Z-axis angle adjustment range being ±10 degrees; the laser head protective lens is equipped with lens contamination monitoring and temperature monitoring; the laser head is equipped with a molten pool monitoring system and a post-weld surface morphology observation system; the low vacuum range is 100-101000 Pa with an accuracy of ±10 Pa; the high vacuum range is -100-100 Pa with an accuracy of ±0.1 Pa. Step 7: Place the two titanium alloy cylinders in the vacuum welding chamber, determine the weld start point of the two titanium alloy cylinders, and then perform low vacuum treatment followed by high vacuum treatment. Step 8: Vacuum laser welding is performed on the titanium alloy cylinder. During the welding of the titanium alloy cylinder, the rotation direction is the direction corresponding to the X-axis deflection angle of the laser head. During the vacuum laser welding process, the overlap between the start and end points of the laser beam is controlled within the range of 10-100mm. Finally, a thick titanium alloy cylinder with vacuum laser welding is obtained. The wall thickness of the titanium alloy cylinder is 20-100mm.

2. The method for vacuum laser welding of thick titanium alloy cylinders according to claim 1, characterized in that, In step 3, the alcohol is high-purity alcohol of 98% or higher; the laser cleaning parameters are: 100W power, speed 1mm / s, width 20mm, and focal length 300mm.

3. The method for vacuum laser welding of thick titanium alloy cylinders according to claim 1, characterized in that, In step 6, the temperature monitoring range is -50℃ to 160℃; the molten pool monitoring system monitors the molten pool temperature range of 200℃ to 3000℃, and the molten pool morphology monitoring range is 0.02-1mm.

4. The method for vacuum laser welding of thick titanium alloy cylinders according to claim 1, characterized in that, In step 7, the vacuum degree is 0.01-100 Pa.

5. The method for vacuum laser welding of thick titanium alloy cylinders according to claim 1, characterized in that, In step 7, the method for determining the starting point of the titanium alloy cylinder weld is as follows: First, determine the highest point of the cylindrical surface of the titanium alloy cylinder, with a deviation of no more than ±0.2mm. Then, after aligning the red light of the laser head with the highest point, set the distance between the laser head and the titanium alloy cylinder to 87mm. After setting, adjust the Z-axis up and down to ensure that the deviation of the red light aligned with the weld seam does not exceed ±0.02mm.

6. The method for vacuum laser welding of thick titanium alloy cylinders according to claim 1, characterized in that, In step 8, the parameters for vacuum laser welding are: welding power 10-60KW, defocusing amount 0-50mm, and welding speed 0.1-1.5m / min.

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