Vacuum laser welding method for thick titanium alloy cylinder

Abstract

The invention belongs to the field of vacuum laser titanium alloy welding, and belongs to a vacuum laser welding method for a thick titanium alloy cylinder. According to the method, a proper process substrate is machined on a titanium alloy thick cylinder to be welded, then the welding surface and the welding seam position are wiped clean through acetone and ethyl alcohol, the titanium alloy thick cylinder is positioned, installed and fixed to a rotating mechanism, a whole cabin is vacuumized after fixing, and then the titanium alloy thick cylinder is welded through laser. According to the method, diffusion of plume in the titanium alloy welding process is obviously inhibited, the titanium alloy welding fusion depth is increased, the defects of oxidation, air holes, incomplete fusion and the like in the titanium alloy welding process are reduced, the mechanical property of a titanium alloy welding joint is improved, and the residual stress value of a welding seam after welding is reduced. The method can realize high-performance welding of various titanium alloy structural members with the thickness of 20-100mm, is particularly suitable for welding of thick titanium alloy cylinders, and is applied to welding of large titanium alloy structural members in the fields of nuclear power, underwater submersible, ships, aerospace and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of vacuum laser titanium alloy welding, and in particular belongs to a vacuum laser welding method for a thick titanium alloy cylinder. Background Art

[0002] Titanium alloys play an important role in cutting-edge science and technology fields such as aerospace, deep-water submersibles, and petrochemicals due to their high strength, low density, and excellent corrosion resistance and high temperature resistance. However, the welding of titanium alloys faces many challenges. Traditional welding methods often produce defects such as embrittlement, pores, and cracks at the weld, which not only reduces the performance of the welded joint, but also seriously restricts the application of titanium alloys in a wider range of fields. In order to overcome these technical difficulties, laser welding technology came into being. 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 the oxidation and nitridation of titanium alloys during the welding process, and ensuring the purity and excellent mechanical properties of the weld.

[0003] At present, the thickness of thick cylindrical titanium alloy parts welded is generally no more than 40mm. For thick cylindrical titanium alloy welding, the thickness is too thick, which leads to poor stability of the molten pool during welding. The thicker the welding thickness, the higher the laser power. The higher the laser power during welding, the more unstable the welding molten pool is, and defects such as pores are prone to occur. In addition, the thicker the titanium alloy, the higher the laser power is used during welding, which leads to a very small state space between the welding state and the cutting state, and it is difficult to find the appropriate process parameters.

[0004] In summary, a variety of factors make it extremely difficult to achieve vacuum laser welding of thick titanium alloy cylinders, causing many products to be discouraged at the design stage, hindering the application of titanium alloys in thicker materials. At present, the problems and solutions of vacuum laser welding of thick titanium alloy cylinders need major breakthroughs. 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 tubes. This method can ensure that the workpiece is accurately positioned before welding, and ensure that the weld gap before welding is uniform and consistent; during welding, the process substrate can ensure that the weld bottom has a good shape and quality; this method reduces the diffusion of the plume body during welding through a vacuum environment, minimizes the energy loss of the laser beam, and the overall welding is in a vacuum environment. The molten pool state can reach a relatively stable state, reducing defects such as internal pores; during welding, the laser head is tilted at a certain angle to reduce the damage of the laser to the laser due to the high opposition of the laser and reduce the damage of the laser head to the laser head due to splashing.

[0006] In order to achieve the above object, the present invention provides the following technical solutions.

[0007] A vacuum laser welding method for thick titanium alloy cylinders comprises the following steps: Step 1, processing the welding surfaces of two titanium alloy cylinders with a process substrate before welding; Step 2: One of the titanium alloy tubes is hoisted and clamped with two sets of lifting clamps, and then a transverse micro-movement structure is set above the connection between the two sets of lifting clamps. When the titanium alloy barrel moves to the approximate position, the micro-movement structure is released to achieve short-distance precise movement of the titanium alloy tube and precise positioning of the titanium alloy tube. The micro-movement distance is ±5mm; the titanium alloy tube is clamped on the rotating chuck to ensure that the coaxial runout of the titanium alloy tube is ±0.05mm and the end face runout is ±0.05mm; Step 3: Wipe the welding surface and weld position of the clamped titanium alloy cylinder with alcohol first, then with acetone, until there is no obvious stain observed by naked eye, and finally use laser to clean the welding surface and weld position. After cleaning, use a cleanliness detector to detect, and the cleanliness inspection range is 5-60RFU; Step 4, hoist another titanium alloy cylinder according to step 2, clean the weld surface and welding position using the method in step 3 after hoisting, move it to the top of the first titanium alloy cylinder after the cleaning index is qualified, adjust the micro-motion structure, align the second titanium alloy cylinder with the process substrate of the first titanium alloy cylinder, drop the second titanium alloy cylinder to combine the two process substrates, and butt the welding surfaces; Step 5, compress the two titanium alloy cylinders, and use a torque wrench to tighten them during the compression process, with a tightening torque of 350-369N, and record the tightening force each time; Step 6. Two types of vacuum gauges, high and low precision, are installed in the vacuum welding chamber; the laser head mounting assembly is equipped with a dual angle adjustment function, with the X-direction angle adjustment range of ±15 degrees and the Z-direction 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 post-weld surface morphology observation; Step 7, placing the two titanium alloy cylinders in a vacuum welding chamber, determining the welding starting points of the welds of the two titanium alloy cylinders, and then performing low vacuum treatment and then high vacuum treatment; Step 8: vacuum laser welding is performed on the titanium alloy cylinder. During the vacuum laser welding process, the overlap amount between the starting point and the end point of the laser beam is controlled within a certain range, and finally a thick titanium alloy cylinder that has been vacuum laser welded is obtained.

[0008] Furthermore, the wall thickness of the titanium alloy cylinder is 20-100 mm.

[0009] Furthermore, in step 1, the width of the process substrate is 3-8 mm and the thickness is 2-6 mm.

[0010] Furthermore, in step 3, the alcohol is high-purity alcohol of more than 98%; the laser cleaning parameters are: 100W power, 1mm / s speed, 20mm width, and 300mm focal length.

[0011] Furthermore, in step 6, the range of low vacuum degree is 100-101000Pa, with an accuracy of ±10Pa; the range of high vacuum degree is -100-100Pa, with an accuracy of ±0.1Pa.

[0012] Furthermore, in step 6, the temperature monitoring range is -50°C-160°C; the molten pool monitoring system monitors the molten pool temperature range is 200°C-3000°C, and the molten pool morphology monitoring change range is 0.02-1mm.

[0013] Furthermore, in step 7, the vacuum degree is 0.01-100Pa.

[0014] Furthermore, in step 7, the method for determining the starting point of the welding seam of the titanium alloy tube is as follows: first determine the highest point of the cylindrical surface of the titanium alloy tube, with the highest point deviation not exceeding ±0.2mm, then align the red light of the laser head with the highest point and set the distance between the laser head and the titanium alloy tube to 87mm. After setting, adjust the Z axis up and down so that the red light is aligned with the welding seam with a deviation not exceeding ±0.02mm.

[0015] Furthermore, in step 8, the parameters of vacuum laser welding are: welding power 10-60KW, defocusing amount 0-50mm, welding speed 0.1-1.5m / min.

[0016] Furthermore, in step 8, the rotation direction of the titanium alloy tube during welding is the direction corresponding to the X-axis deflection angle of the laser head; the overlap amount is 10-100 mm in length.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0018] 1. The micro-motion structure can achieve fast, stable and accurate docking of the titanium alloy welding cylinder during the hoisting process, reduce the collision during the hoisting process, and improve the efficiency and quality of the overall hoisting.

[0019] 2. Using a variety of cleaning methods in sequence and testing the surface cleanliness during the cleaning process can greatly improve the cleaning efficiency and cleanliness of the welding surface. Numerical records can facilitate subsequent data statistics.

[0020] 3. The process substrate not only realizes the precise positioning of the weld and welding surface of the titanium alloy tube, but also improves the overall welding quality of the weld.

[0021] 4. The temperature and molten pool monitoring system on the laser head can monitor and control the welding process in real time to ensure the welding quality.

[0022] 5. Accurate positioning of the weld starting point can ensure accurate control of the weld width and depth. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Example 1 Overall view of the thick titanium alloy cylinder after vacuum laser welding.

[0024] Figure 2 Partial view of the thick titanium alloy cylinder after vacuum laser welding in Example 1. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example 1.

[0027] In the first step, the two titanium alloy tubes are processed with process substrates on the butt welding surface before welding. The process substrates of the two titanium alloy tubes are matched and combined with each other. The width of the process substrate is 5mm and the thickness is 3mm. After the two titanium alloy tubes are matched, the coaxiality deviation is guaranteed to be no more than 0.05mm and the gap between the matching surfaces is no more than 0.05mm.

[0028] In the second step, two sets of lifting clamps are used to clamp the titanium alloy cylinder. Then a lateral micro-motion structure is set above the connection between the two sets of lifting clamps. When the titanium alloy barrel moves to the approximate position, the micro-motion structure is released to achieve precise short-distance movement of the titanium alloy cylinder. The precise positioning of the titanium alloy cylinder is achieved. The micro-movement distance is ±5mm. After adjusting the position, it is placed on the rotating chuck and clamped.

[0029] The third step is to first use non-woven fabric to dip a small amount of high-purity alcohol with a concentration of more than 98% to wipe the welding surface and weld position. After wiping until there is no obvious change on the surface of the non-woven fabric, dip a small amount of acetone and wipe the welding surface and weld position in the same way. After wiping, use a handheld laser cleaning device to laser clean the welding surface and weld. The laser cleaning parameters are: 100W power, 1mm / s speed, 20mm width, and 300mm focal length. After laser cleaning, use a cleanliness detector to detect, and the qualified value range of the detection is 30RFU.

[0030] The fourth step is to use the method in the second step to lift the second titanium alloy cylinder. After lifting, use the method in the third step to clean the weld surface and welding position. After the cleaning indicators are qualified, move it to the top of the first titanium alloy cylinder, adjust the micro-motion structure, align the second titanium alloy cylinder with the process substrate of the first titanium alloy cylinder, slowly drop the second titanium alloy cylinder to combine the two process substrates, butt the welding surfaces, and check the coaxiality to ensure that the coaxiality deviation of the two cylinders does not exceed 0.05mm, and the butt surface gap does not exceed 0.05mm.

[0031] The fifth step is to use a clamping tool to press the two titanium alloy cylinders together. During the clamping process, a torque wrench is used to tighten them with a locking torque of 366N, and the locking force is recorded each time.

[0032] Step 6: Adjust the laser head angle adjustment assembly. The X-direction angle is adjusted to +15 degrees and the Z-direction angle is adjusted to 0 degrees. After adjustment, use an inclinometer to check the angle.

[0033] In the seventh step, after the titanium alloy tube 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 so that the compression pointer of the dial indicator is pressed onto the arc surface of the titanium alloy tube. The X-axis of the welding head is moved to observe the changes in the dial indicator needle until the needle stops moving. The fixed point of the needle is the highest point of the arc surface, and the deviation of the highest point does not exceed ±0.2mm. After marking the highest point, move the Z axis vertically up and down to mark another highest point, and draw a line between the two points with a steel ruler.

[0034] The eighth step is to turn on the laser guide light and move the laser head movement mechanism to align the red light with the highest point line drawn in the seventh step. Then, after aligning the red light of the laser head with the highest point, set the distance between the laser head and the highest point line of the titanium alloy tube to 87mm. After setting, adjust the Z axis up and down to align the red light with the welding weld. The upper and lower deviations should not exceed ±0.02mm. After alignment, record the initial point coordinate system in the equipment operating system.

[0035] The ninth step is to close the vacuum chamber door and start to evacuate the vacuum chamber. The vacuum chamber is equipped with two range vacuum gauges. The low vacuum range is 100-101000Pa with an accuracy of ±10Pa, and the high vacuum range is -100-100Pa with an accuracy of ±0.1Pa. The low vacuum gauge is enabled during the initial vacuuming, and the pump group starts high-power vacuuming. When the vacuum reaches the set range of high vacuum, the high vacuum gauge is started. The pump group uses low-power vacuuming to make the welding environment more stable. The final vacuum degree of vacuuming is maintained at 10Pa to prepare for welding.

[0036] The tenth step, before starting welding, set the parameters of vacuum laser welding according to the welding thickness of 66mm titanium alloy: welding power is 1.8KW, negative defocus after focusing is 30mm, and welding speed is 0.4m / min.

[0037] Step 11. During welding, the laser head temperature monitoring sensor and the molten pool monitoring sensor are started to monitor the laser head temperature and the molten pool temperature. The laser head temperature does not exceed 45°C, the molten pool temperature does not exceed 2000°C, and the molten pool width deviation does not exceed 1mm.

[0038] Step 12. After welding a section of weld, cool it for 20 minutes and then open the vacuum chamber. Turn the rotary chuck to turn the titanium alloy cylinder to the welding technical position. Use the alloy rotary grinding head to grind the raised part of this position flat and wipe the surface clean with alcohol. Similarly, turn the rotary chuck to the initial welding position, use the same method to grind the weld flat and then wipe it clean with alcohol.

[0039] Step 13. Use a ruler to measure and mark two locations 100mm away from the starting point of the weld. Set the end point of the upper weld as the starting point of the lower weld and the other point as the end point. Calculate the length of the entire weld 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 cabin door, and prepare to start the second weld.

[0040] Step 14: During the welding process, the same method as in Steps 9, 10 and 11 is used. After the welding is completed, the hatch is opened after keeping warm for 20 minutes to obtain the thick titanium alloy cylinder welded by vacuum laser. The test results are shown in Table 1.

[0041] Example 2.

[0042] In the first step, the two titanium alloy cylinders are processed with a process substrate on the butt welding surface before welding. The process substrates processed by the two titanium alloy cylinders are matched and combined with each other. The width of the process substrate is 5mm and the thickness is 3mm. After the two titanium alloy cylinders are matched, the coaxiality deviation is guaranteed to be no more than 0.05mm and the clearance between the matching surfaces is no more than 0.05mm.

[0043] In the second step, two sets of lifting clamps are used to clamp the titanium alloy cylinder. Then a lateral micro-motion structure is set above the connection between the two sets of lifting clamps. When the titanium alloy barrel moves to the approximate position, the micro-motion structure is released to achieve precise short-distance movement of the titanium alloy cylinder. The precise positioning of the titanium alloy cylinder is achieved. The micro-movement distance is ±5mm. After adjusting the position, it is placed on the rotating chuck and clamped.

[0044] The third step is to first use non-woven fabric to dip a small amount of high-purity alcohol with a concentration of more than 98% to wipe the welding surface and weld position. After wiping until there is no obvious change on the surface of the non-woven fabric, dip a small amount of acetone and wipe the welding surface and weld position in the same way. After wiping, use a handheld laser cleaning device to laser clean the welding surface and weld. The laser cleaning parameters are: 100W power, 1mm / s speed, 20mm width, and 300mm focal length. After laser cleaning, use a cleanliness detector to detect, and the qualified value range of the detection is 30RFU.

[0045] The fourth step is to use the method in the second step to lift the second titanium alloy cylinder. After lifting, use the method in the third step to clean the weld surface and welding position. After the cleaning indicators are qualified, move it to the top of the first titanium alloy cylinder, adjust the micro-motion structure, align the second titanium alloy cylinder with the process substrate of the first titanium alloy cylinder, slowly drop the second titanium alloy cylinder to combine the two process substrates, butt the welding surfaces, and check the coaxiality to ensure that the coaxiality deviation of the two cylinders does not exceed 0.05mm, and the butt surface gap does not exceed 0.05mm.

[0046] The fifth step is to use a clamping tool to press the two titanium alloy cylinders together. During the clamping process, a torque wrench is used to tighten them with a locking torque of 360N, and the locking force is recorded each time.

[0047] Step 6: Adjust the laser head angle adjustment assembly. The X-direction angle is adjusted to +15 degrees and the Z-direction angle is adjusted to 0 degrees. After adjustment, use an inclinometer to check the angle.

[0048] In the seventh step, after the titanium alloy tube is compacted, it is transported to a fixed position in the vacuum chamber by a conveyor vehicle. A dial indicator is fixed on the laser head so that the compaction pointer of the dial indicator is pressed onto the arc surface of the titanium alloy tube. The X-axis of the welding head is moved to observe the changes in the dial indicator needle until the needle stops moving. The fixed point of the needle is the highest point of the arc surface, and the deviation of the highest point does not exceed ±0.2㎜. After marking the highest point, move the Z axis vertically up and down to mark another highest point. Use a steel ruler to draw a line between the two points.

[0049] The eighth step is to turn on the laser guide light and move the laser head movement mechanism to align the red light with the highest point line drawn in the seventh step. Then, after aligning the red light of the laser head with the highest point, set the distance between the laser head and the highest point line of the titanium alloy tube to 87mm. After setting, adjust the Z axis up and down to align the red light with the welding weld. The upper and lower deviations should not exceed ±0.02mm. After alignment, record the initial point coordinate system in the equipment operating system.

[0050] The ninth step is to close the vacuum chamber door and start to evacuate the vacuum chamber. The vacuum chamber is equipped with two range vacuum gauges. The low vacuum range is 100-101000Pa with an accuracy of ±10Pa, and the high vacuum range is -100-100Pa with an accuracy of ±0.1Pa. The low vacuum gauge is enabled during the initial vacuuming, and the pump group starts high-power vacuuming. When the vacuum reaches the set range of high vacuum, the high vacuum gauge is started. The pump group uses low-power vacuuming to make the welding environment more stable. The final vacuum degree of vacuuming is maintained at 10Pa to prepare for welding.

[0051] The tenth step, before starting welding, set the parameters of vacuum laser welding according to the welding thickness of 58mm titanium alloy: welding power is 1.6KW, negative defocus after focusing is 30mm, and welding speed is 0.4m / min.

[0052] Step 11. During welding, the laser head temperature monitoring sensor and the molten pool monitoring sensor are started to monitor the laser head temperature and the molten pool temperature. The laser head temperature does not exceed 45°C, the molten pool temperature does not exceed 2000°C, and the molten pool width deviation does not exceed 1mm.

[0053] Step 12. After welding a section of weld, cool it for 20 minutes and then open the vacuum chamber. Turn the rotary chuck to turn the titanium alloy cylinder to the welding technical position. Use the alloy rotary grinding head to grind the raised part of this position flat and wipe the surface clean with alcohol. Similarly, turn the rotary chuck to the initial welding position, use the same method to grind the weld flat and then wipe it clean with alcohol.

[0054] Step 13. Use a ruler to measure and mark two locations 100mm away from the starting point of the weld. Set the end point of the upper weld as the starting point of the lower weld and the other point as the end point. Calculate the length of the entire weld 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 cabin door, and prepare to start the second weld.

[0055] Step 14: During the welding process, the same method as in Steps 9, 10 and 11 is used. After the welding is completed, the hatch is opened after keeping warm for 20 minutes to obtain the thick titanium alloy cylinder welded by vacuum laser. The test results are shown in Table 2.

[0056] Example 3.

[0057] In the first step, the two titanium alloy cylinders are processed with a process substrate on the butt welding surface before welding. The process substrates processed by the two titanium alloy cylinders are matched and combined with each other. The width of the process substrate is 5mm and the thickness is 3mm. After the two titanium alloy cylinders are matched, the coaxiality deviation is guaranteed to be no more than 0.05mm and the clearance between the matching surfaces is no more than 0.05mm.

[0058] In the second step, two sets of lifting clamps are used to clamp the titanium alloy cylinder. Then a lateral micro-motion moving structure is set above the connection between the two sets of lifting clamps. When the titanium alloy barrel moves to the approximate position, the micro-motion moving structure is released to achieve precise short-distance movement of the titanium alloy cylinder. The precise positioning of the titanium alloy cylinder is achieved. The micro-movement distance is ±5mm. After adjusting the position, it is placed on the rotating chuck and clamped.

[0059] The third step is to first use non-woven fabric to dip a small amount of high-purity alcohol with a concentration of more than 98% to wipe the welding surface and weld position. After wiping until there is no obvious change on the surface of the non-woven fabric, dip a small amount of acetone and wipe the welding surface and weld position in the same way. After wiping, use a handheld laser cleaning device to laser clean the welding surface and weld. The laser cleaning parameters are: 100W power, 1mm / s speed, 20mm width, and 300mm focal length. After laser cleaning, use a cleanliness detector to detect, and the qualified value range of the detection is 30RFU.

[0060] The fourth step is to use the method in the second step to lift the second titanium alloy cylinder. After lifting, use the method in the third step to clean the weld surface and welding position. After the cleaning indicators are qualified, move it to the top of the first titanium alloy cylinder, adjust the micro-motion structure, align the second titanium alloy cylinder with the process substrate of the first titanium alloy cylinder, slowly drop the second titanium alloy cylinder to combine the two process substrates, butt the welding surfaces, and check the coaxiality to ensure that the coaxiality deviation of the two cylinders does not exceed 0.05mm, and the butt surface gap does not exceed 0.05mm.

[0061] The fifth step is to use a clamping tool to press the two titanium alloy cylinders together. During the clamping process, a torque wrench is used to tighten them with a locking torque of 358N, and the locking force is recorded each time.

[0062] Step 6: Adjust the laser head angle adjustment assembly. The X-direction angle is adjusted to +15 degrees and the Z-direction angle is adjusted to 0 degrees. After adjustment, use an inclinometer to check the angle.

[0063] In the seventh step, after the titanium alloy tube 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 so that the compression pointer of the dial indicator is pressed onto the arc surface of the titanium alloy tube. The X-axis of the welding head is moved to observe the changes in the dial indicator needle until the needle stops moving. The fixed point of the needle is the highest point of the arc surface, and the deviation of the highest point does not exceed ±0.2mm. After marking the highest point, move the Z axis vertically up and down to mark another highest point, and draw a line between the two points with a steel ruler.

[0064] The eighth step is to turn on the laser guide light and move the laser head movement mechanism to align the red light with the highest point line drawn in the seventh step. Then, after aligning the red light of the laser head with the highest point, set the distance between the laser head and the highest point line of the titanium alloy tube to 87mm. After setting, adjust the Z axis up and down to align the red light with the welding weld. The upper and lower deviations should not exceed ±0.02mm. After alignment, record the initial point coordinate system in the equipment operating system.

[0065] The ninth step is to close the vacuum chamber door and start to evacuate the vacuum chamber. The vacuum chamber is equipped with two range vacuum gauges. The low vacuum range is 100-101000Pa with an accuracy of ±10Pa, and the high vacuum range is -100-100Pa with an accuracy of ±0.1Pa. The low vacuum gauge is enabled during the initial vacuuming, and the pump group starts high-power vacuuming. When the vacuum reaches the set range of high vacuum, the high vacuum gauge is started. The pump group uses low-power vacuuming to make the welding environment more stable. The final vacuum degree of vacuuming is maintained at 10Pa to prepare for welding.

[0066] The tenth step, before starting welding, set the parameters of vacuum laser welding according to the welding thickness of 50mm titanium alloy: welding power is 1.2KW, negative defocus after focusing is 30mm, and welding speed is 0.4m / min.

[0067] Step 11. During welding, the laser head temperature monitoring sensor and the molten pool monitoring sensor are started to monitor the laser head temperature and the molten pool temperature. The laser head temperature does not exceed 45°C, the molten pool temperature does not exceed 2000°C, and the molten pool width deviation does not exceed 1mm.

[0068] Step 12. After welding a section of weld, cool it for 20 minutes and then open the vacuum chamber. Turn the rotary chuck to turn the titanium alloy cylinder to the welding technical position. Use the alloy rotary grinding head to grind the raised part of this position flat and wipe the surface clean with alcohol. Similarly, turn the rotary chuck to the initial welding position, use the same method to grind the weld flat and then wipe it clean with alcohol.

[0069] Step 13. Use a ruler to measure and mark two locations 100mm away from the starting point of the weld. Set the end point of the upper weld as the starting point of the lower weld and the other point as the end point. Calculate the length of the entire weld 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 cabin door, and prepare to start the second weld.

[0070] Step 14: During the welding process, the same method as in Steps 9, 10 and 11 is used. After the welding is completed, the hatch is opened after keeping warm for 20 minutes to obtain the thick titanium alloy cylinder welded by vacuum laser. The test results are shown in Table 3.

[0071] Table 1. Test results of Example 1. Note: The “-” in the residual stress test result represents the opposite direction of the current test direction. It only represents the direction, and the final value is the absolute value.

[0072] Table 2 Example 2 test results. Note: The “-” in the residual stress test result represents the opposite direction of the current test direction. It only represents the direction, and the final value is the absolute value.

[0073] Table 3 Example 3 test results.

Claims

1. A vacuum laser welding method for thick titanium alloy cylinders, characterized in that: The steps include: Step 1, processing the welding surfaces of two titanium alloy cylinders with a process substrate before welding; Step 2: One of the titanium alloy tubes is hoisted and clamped with two sets of lifting clamps, and then a transverse micro-movement structure is set above the connection between the two sets of lifting clamps. When the titanium alloy barrel moves to the approximate position, the micro-movement structure is released to achieve short-distance precise movement of the titanium alloy tube and precise positioning of the titanium alloy tube. The micro-movement distance is ±5mm; the titanium alloy tube is clamped on the rotating chuck to ensure that the coaxial runout of the titanium alloy tube is ±0.05mm and the end face runout is ±0.05mm; Step 3: Wipe the welding surface and weld position of the clamped titanium alloy cylinder with alcohol first, then with acetone, until there is no obvious stain observed by naked eye, and finally use laser to clean the welding surface and weld position. After cleaning, use a cleanliness detector to detect, and the cleanliness inspection range is 5-60RFU; Step 4, hoist another titanium alloy cylinder according to step 2, clean the weld surface and welding position using the method in step 3 after hoisting, move it to the top of the first titanium alloy cylinder after the cleaning index is qualified, adjust the micro-motion structure, align the second titanium alloy cylinder with the process substrate of the first titanium alloy cylinder, drop the second titanium alloy cylinder to combine the two process substrates, and butt the welding surfaces; Step 5, compress the two titanium alloy cylinders, and use a torque wrench to tighten them during the compression process, with a tightening torque of 350-369N, and record the tightening force each time; Step 6. Two types of vacuum gauges, high and low precision, are installed in the vacuum welding chamber; the laser head mounting assembly is equipped with a dual angle adjustment function, with the X-direction angle adjustment range of ±15 degrees and the Z-direction 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 post-weld surface morphology observation; Step 7, placing the two titanium alloy cylinders in a vacuum welding chamber, determining the welding starting points of the welds of the two titanium alloy cylinders, and then performing low vacuum treatment and then high vacuum treatment; Step 8: vacuum laser welding is performed on the titanium alloy cylinder. During the vacuum laser welding process, the overlap amount between the starting point and the end point of the laser beam is controlled within a certain range, and finally a thick titanium alloy cylinder that has been vacuum laser welded is obtained.

2. The vacuum laser welding method for thick titanium alloy cylinder according to claim 1 is characterized in that: The wall thickness of the titanium alloy cylinder is 20-100 mm.

3. The vacuum laser welding method for thick titanium alloy cylinder according to claim 1 is characterized in that: In step 1, the width of the process substrate is 3-8 mm and the thickness is 2-6 mm.

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

5. The vacuum laser welding method for thick titanium alloy cylinder according to claim 1 is characterized in that: In step 6, the range of low vacuum degree is 100-101000Pa, and the accuracy is ±10Pa; the range of high vacuum degree is -100-100Pa, and the accuracy is ±0.1Pa.

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

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

8. The vacuum laser welding method for thick titanium alloy cylinder according to claim 1 is characterized in that: In step 7, the method for locating the starting point of the titanium alloy tube weld is as follows: first determine the highest point of the cylindrical surface of the titanium alloy tube, with the highest point deviation not exceeding ±0.2mm, then align the red light of the laser head with the highest point and set the distance between the laser head and the titanium alloy tube to 87mm. After setting, adjust the Z axis up and down so that the red light is aligned with the welding seam with a deviation not exceeding ±0.02mm.

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

10. The vacuum laser welding method for thick titanium alloy cylinder according to claim 1, characterized in that: In step 8, the rotation direction of the titanium alloy tube during welding is the direction corresponding to the deflection angle of the laser head X axis; the overlap amount is 10-100mm in length.

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