Low-heat-input large-depth-to-width-ratio welding seam forming regulation and control method

Abstract

The invention discloses a low-heat-input large-depth-to-width-ratio welding seam forming regulation and control method, and belongs to the technical field of laser machining. The invention aims to solve the problems of cracks, grain coarsening and welding deformation during welding of a large-thickness heat input sensitive material and the problem that a low-heat input pulse laser welding technology is not applied to thick plate welding. The method comprises the steps of 1, tacking a workpiece; 2, placing on a welding platform of a vacuum laser welding device, adjusting the welding position and fixing; 3, welding; and fourthly, welding parts are taken out of the cabin. The method is used for forming regulation and control of the welding seam with the low heat input and the large depth-to-width ratio.

Description

Technical Field

[0001] This invention belongs to the field of laser processing technology. Background Technology

[0002] In fields like aerospace, nuclear energy, and shipbuilding, where structural stability is paramount, thick-walled structures with thicknesses exceeding 10 mm are widely used. These structures typically operate in extreme environments characterized by alternating high and low temperatures, high pressure, strong corrosion, or high radiation. Therefore, lightweight and low-cost welding techniques are commonly used to connect components, and the quality of these joints directly determines the overall reliability of the product. However, in recent years, with the continuous improvement in equipment carrying capacity and output power, higher demands have been placed on the quality of welded joints. Traditional welding methods are no longer sufficient to meet the high-quality weld requirements of new product models in terms of welding efficiency, heat input control, and joint performance. Therefore, breakthroughs in process technology are urgently needed.

[0003] For welding medium and thick plates, the available welding methods are multi-layer multi-pass welding and single-pass high-energy beam welding with large penetration depth. Multi-layer multi-pass welding requires pre-machining the bevel, followed by layer-by-layer stacking of filler metal to achieve full-thickness welding. This process suffers from problems such as high heat input, severe welding deformation, high residual stress, large heat-affected zone, coarsening of microstructure, and low production efficiency. It is also susceptible to human error. To improve welding efficiency and quality, many products are increasingly adopting high-energy beam welding technology for single-pass high-penetration welds, such as low-heat-input electron beam welding, laser welding, and vacuum environment laser welding. However, when welding heat-sensitive materials, continuous high-energy beam welding is prone to problems such as liquefaction cracks, coarsening of grains in the heat-affected zone, and welding deformation. Studies have shown that pulsed laser welding technology can achieve precise control of the molten pool morphology and thermal cycle characteristics through intermittent energy output, which can significantly reduce welding heat input. However, because the keyhole and molten pool behavior is very intense when welding deep welds, pulsed laser welding technology is prone to defects such as welding spatter and porosity. Therefore, this technology is only used for low heat input and small deformation welding of thin plates, and has not yet been applied to thick plate welding. Summary of the Invention

[0004] This invention aims to address the problems of cracking, grain coarsening, and welding deformation in the welding of thick heat-input sensitive materials, as well as the lack of application of low-heat-input pulsed laser welding technology in thick plate welding. It provides a method for controlling the formation of welds with a large aspect ratio and low heat input.

[0005] A method for controlling the formation of welds with low heat input and large aspect ratios, comprising the following steps:

[0006] 1. Clean the surface and mating surfaces of the workpiece, then fit the mating surfaces together to form a joint and laser fix it to obtain the workpiece after laser fixation;

[0007] 2. Place the spot-fixed workpiece on the welding platform of the vacuum laser welding device, adjust the welding position, and then use a clamp to fix it.

[0008] 3. First, evacuate the vacuum. Then, introduce horizontal and vertical shielding gases below the protective lens of the welding laser head. Next, introduce balancing gas to balance the chamber pressure to a welding pressure of 0.1 kPa to 10 kPa. Then, with a laser power of 3 kW to 15 kW, a welding speed of 0.3 m / min to 2 m / min, a defocusing amount of 0 mm to -24 mm, a welding pressure of 0.1 kPa to 10 kPa, a spot diameter of 0.2 mm to 0.8 mm, and a pulsed laser output mode, move along the preset welding path. After reaching the welding end position, stop moving and laser output. Finally, stop introducing horizontal shielding gas, vertical shielding gas, and balancing gas.

[0009] The waveform of the pulse is a trapezoidal wave; the inlet pressure of the horizontal protective gas is 0.1MPa~2.0MPa, and the inlet flow rate of the downward vertical protective gas is 10L / min~20L / min;

[0010] IV. Welded components are removed from the chamber, and a method for controlling the formation of welds with a large depth-to-width ratio and low heat input is implemented.

[0011] The beneficial effects of this invention are:

[0012] (1) Under the same heat input conditions, the present invention obtains a deeper weld than continuous wave laser welding in a vacuum environment, providing a new method for low heat input welding of welds with large aspect ratios;

[0013] (2) Compared with other welding methods, the present invention requires a lower welding heat input under the same weld penetration depth, which effectively avoids the problems of liquefaction cracks, grain coarsening and welding deformation caused by excessive heat input, and provides a new path for welding deep welds of heat-sensitive materials.

[0014] (3) The present invention effectively suppresses the spatter problem in the vacuum environment pulsed laser welding process and solves the "bulging" problem of the weld cross section in the vacuum environment pulsed laser welding, thus obtaining high-quality weld formation and realizing the application of low heat input pulsed laser welding technology in thick plate welding. Attached Figure Description

[0015] Figure 1 This is a diagram showing the positional relationship between the vertical and horizontal protective gas devices and the laser welding head in Specific Implementation Method 5;

[0016] Figure 2 This is a schematic diagram illustrating the control of the trapezoidal wave in this invention;

[0017] Figure 3 These are weld morphology images obtained in Example 1 and Comparative Experiment 1. a and c are from Comparative Experiment 1, and b and d are from Example 1.

[0018] Figure 4 To compare the solidification structure of the weld obtained in Experiment 1, a is the solidification structure near the center of the weld, b is the solidification structure between the center line of the weld and the fusion line, and c is the solidification structure near the fusion line.

[0019] Figure 5 The diagram shows the solidification structure of the weld obtained in Example 1. a is the solidification structure near the center of the weld, b is the solidification structure between the weld centerline and the fusion line, and c is the solidification structure near the fusion line.

[0020] Figure 6 The diagram shows the pulse waveform parameter control diagram and the resulting weld morphology diagram used in Example 2. a is the pulse waveform parameter control diagram, b is the weld surface morphology, and c is the weld cross-sectional morphology.

[0021] Figure 7 To compare the weld surface morphology obtained in Experiment 2, a represents a pulse period of 40ms, b represents a pulse period of 20ms, c represents a pulse period of 10ms, and d represents a pulse period of 5ms.

[0022] Figure 8 To compare the weld cross-sectional morphology obtained in Experiment 2, a is the longitudinal section of the weld with a pulse period of 40ms, b is the longitudinal section of the weld with a pulse period of 20ms, c is the longitudinal section of the weld with a pulse period of 10ms, d is the longitudinal section of the weld with a pulse period of 5ms, e is the cross-section of the weld with a pulse period of 40ms, f is the cross-section of the weld with a pulse period of 20ms, g is the cross-section of the weld with a pulse period of 10ms, and h is the cross-section of the weld with a pulse period of 5ms. Detailed Implementation

[0023] Specific implementation method one, combined with Figure 2 Detailed explanation: This embodiment describes a method for controlling the formation of welds with low heat input and large aspect ratio, which is carried out according to the following steps:

[0024] 1. Clean the surface and mating surfaces of the workpiece, then fit the mating surfaces together to form a joint and laser fix it to obtain the workpiece after laser fixation;

[0025] 2. Place the spot-fixed workpiece on the welding platform of the vacuum laser welding device, adjust the welding position, and then use a clamp to fix it.

[0026] 3. First, evacuate the vacuum. Then, introduce horizontal and vertical shielding gases below the protective lens of the welding laser head. Next, introduce balancing gas to balance the chamber pressure to a welding pressure of 0.1 kPa to 10 kPa. Then, with a laser power of 3 kW to 15 kW, a welding speed of 0.3 m / min to 2 m / min, a defocusing amount of 0 mm to -24 mm, a welding pressure of 0.1 kPa to 10 kPa, a spot diameter of 0.2 mm to 0.8 mm, and a pulsed laser output mode, move along the preset welding path. After reaching the welding end position, stop moving and laser output. Finally, stop introducing horizontal shielding gas, vertical shielding gas, and balancing gas.

[0027] The waveform of the pulse is a trapezoidal wave; the inlet pressure of the horizontal protective gas is 0.1MPa~2.0MPa, and the inlet flow rate of the downward vertical protective gas is 10L / min~20L / min;

[0028] IV. Welded components are removed from the chamber, and a method for controlling the formation of welds with a large depth-to-width ratio and low heat input is implemented.

[0029] Specific implementation steps: Step 1: Before assembly, clean the mating surfaces and the surfaces to be welded, removing the oxide layer, oil, and other contaminants from the surfaces; Step 2: Use laser spotting to locally melt the mating area to form a molten pool.

[0030] In the specific implementation method, step two involves clamping and fixing the components to prevent the relative positions of the components and the weld joint from shifting during the welding process.

[0031] In the third step of the specific implementation method, pre-welding teaching is performed. First, the welding defocusing amount, laser power, pulsed laser parameters, welding speed, and welding time are adjusted. Then, the laser head indicator spot is moved to the welding start position, and the welding start point is taught in the welding robot teaching system. After that, the spot is moved to the welding end position, and the welding end point is taught in the welding robot teaching system. The straight weld is determined by the welding start point and the welding end point. When the welding path is not a simple linear weld, the teaching method combines circular arc teaching and straight line teaching.

[0032] In the specific implementation method, step three achieves a vacuum environment in the chamber by using a two-stage vacuum system consisting of a mechanical pump and a Roots pump to reduce the environmental pressure inside the chamber, and reading the chamber pressure through a pressure gauge.

[0033] In the third step of the specific implementation method, protective gas for laser head protection is first introduced to form a horizontal and vertical downward high-pressure airflow below the protective lens of the welding laser head to prevent splashes from entering the laser head.

[0034] This specific implementation combines vacuum laser technology with pulse modulation to achieve heat input control and weld formation optimization for welds with large aspect ratios. Through precise pulse waveform control, it enables high-quality weld formation and defect-free deep-penetration welds, further improving weld penetration and quality stability. This provides a new solution for high-quality, low-heat-input welding of medium-thick plates and heat-sensitive materials. This method can be extended to welding various heat-sensitive materials to meet the demands of advanced manufacturing for high-performance welded joints.

[0035] The beneficial effects of this embodiment are:

[0036] (1) Under the same heat input conditions, this embodiment obtains a deeper weld than continuous wave laser welding in a vacuum environment, providing a new method for low heat input welding of welds with large aspect ratios;

[0037] (2) Compared with other welding methods, the present invention requires a lower welding heat input under the same weld penetration depth, which effectively avoids the problems of liquefaction cracks, grain coarsening and welding deformation caused by excessive heat input, and provides a new path for welding deep welds of heat-sensitive materials.

[0038] (3) This embodiment effectively suppresses the spatter problem in the vacuum environment pulsed laser welding process and solves the "bulging" problem of the weld cross section in the vacuum environment pulsed laser welding, thus obtaining high-quality weld formation and realizing the application of low heat input pulsed laser welding technology in thick plate welding.

[0039] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the workpiece material in step one is a high-temperature alloy with a thickness of 5mm to 40mm. Everything else is the same as in Specific Implementation Method One.

[0040] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the connector mentioned in step one is a flat butt joint or a lock-bottom butt joint, and the butt gap is ≤1.0mm. Everything else is the same as in Specific Implementation Method One or Two.

[0041] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the laser spotting described in step one is specifically performed as follows: The laser beam is aligned with the mating surface, and under conditions of a laser power of 1000W~2000W and a defocusing amount of -10mm~+10mm, the light is emitted for 200ms~1000ms, causing localized melting at the mating location to form a molten pool. Everything else is the same as in Specific Implementation Method Three.

[0042] Specific implementation method five, combined with Figure 1Specific Explanation: This embodiment differs from one of embodiments one to four in that: in step three, a horizontal protective gas and a downward vertical protective gas are introduced below the protective lens of the welding laser head. This is specifically achieved through a vertical protective gas device and a horizontal protective gas device. The vertical protective gas device is a circular air nozzle with a diameter that gradually decreases from top to bottom, and it is connected to the lower end face of the laser welding head via an adapter block. The horizontal protective gas device is an air cutter with a 0.1mm air groove, located on the side of the laser welding head. The horizontal protective gas device introduces horizontal protective gas, and the horizontal protective gas is located between the vertical protective gas device and the workpiece surface. The vertical protective gas device introduces downward vertical protective gas, and the downward vertical protective gas is coaxially introduced with the laser. Everything else is the same as in embodiments one to four.

[0043] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: in step three, the vacuuming process specifically involves first using a mechanical pump to reduce the chamber pressure to ≤3 kPa, and then starting a Roots pump to reduce the chamber pressure to below 20 Pa. Everything else is the same as in Specific Implementation Methods One to Five.

[0044] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: in step three, a fiber laser with a wavelength of 1064nm~1080nm is used for laser welding, and the focal length of the laser welding is ≥200mm. Everything else is the same as in Specific Implementation Methods One to Six.

[0045] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the rise time of the trapezoidal wave described in step three is ≥2ms, the high-frequency duration is ≥3ms, and the low-frequency pulse duration is ≤10ms. Everything else is the same as in Specific Implementation Methods One to Seven.

[0046] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the horizontal protective gas, the downward vertical protective gas, and the balancing gas mentioned in step three are all argon gas with a purity of 99.99%. Everything else is the same as in Specific Implementation Methods One to Eight.

[0047] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One through Nine in that: in step four, the Roots pump is turned off, and after an interval of 10 to 30 seconds, the mechanical pump is turned off. Then, air is introduced, and after the pressure inside and outside the cabin is equalized, the hatch is opened. After waiting for 1 to 5 minutes, the welded parts are removed from the cabin. Everything else is the same as in Specific Implementation Methods One through Nine.

[0048] The beneficial effects of the present invention are verified using the following embodiments:

[0049] Example 1:

[0050] A method for controlling the formation of welds with low heat input and large aspect ratios, comprising the following steps:

[0051] 1. Clean the surface and mating surfaces of the workpiece, then fit the mating surfaces together to form a joint. Center the laser beam on the mating surfaces and, under the conditions of laser power of 2000W and defocusing amount of -5mm, emit light for 500ms to locally melt the mating position and form a molten pool for laser spotting, thus obtaining the spot-fixed workpiece.

[0052] The workpiece is made of GH4169 nickel-based high-temperature alloy and has a thickness of 20mm; the cleaning process specifically involves first mechanically grinding the workpiece and then wiping it with a non-woven cloth soaked in acetone.

[0053] The joint described is a weld overlay joint, simulating a butt joint with a 0mm butt gap;

[0054] 2. Place the spot-fixed workpiece on the welding platform of the vacuum laser welding device, adjust the welding position, and then use a clamp to fix it.

[0055] 3. First, use a mechanical pump to pump the chamber pressure to 3 kPa, then start the Roots pump to pump the chamber pressure to 10 Pa. Then, introduce horizontal shielding gas and downward vertical shielding gas under the protective lens of the welding laser head. At this time, the chamber pressure is 0.08 kPa. Then, introduce balancing gas to balance the chamber pressure to the welding pressure of 0.1 kPa. Then, use a fiber laser with a wavelength of 1064 nm, with a laser power of 6 kW, a welding speed of 1 m / min, a defocusing amount of -6 mm, a welding pressure of 0.1 kPa, a spot diameter of 0.45 mm, and a laser output mode of pulse. Move according to the preset welding path. After reaching the welding end position, stop the movement and laser output. Finally, stop introducing horizontal shielding gas, downward vertical shielding gas, and balancing gas.

[0056] The waveform of the pulse is a trapezoidal wave; the inlet pressure of the horizontal protective gas is 1.0 MPa, and the inlet flow rate of the downward vertical protective gas is 10 L / min.

[0057] The focal length for laser welding is 247mm;

[0058] The rise time of the trapezoidal wave is 2ms, the high-frequency duration is 4ms, and the low-frequency pulse duration is 4ms; the laser power is 6kW at high frequency and 0kW at low frequency.

[0059] The horizontal protective gas, the downward vertical protective gas, and the balancing gas are all argon gas with a purity of 99.99%;

[0060] 4. Turn off the Roots pump, and after 10 seconds, turn off the mechanical pump. Then, introduce air and wait until the pressure inside and outside the cabin is the same before opening the hatch. After waiting for 1 minute, remove the welded parts from the cabin to complete the low heat input, high aspect ratio weld formation control method.

[0061] In step three, a horizontal protective gas and a downward vertical protective gas are introduced below the protective lens of the welding laser head. This is specifically achieved through a vertical protective gas device and a horizontal protective gas device. The vertical protective gas device is a circular gas nozzle with a diameter that gradually decreases from top to bottom, and it is connected to the lower end face of the laser welding head through an adapter block. The horizontal protective gas device is an air cutter with a 0.1mm gas groove, which is set on the side of the laser welding head. The horizontal protective gas device introduces horizontal protective gas, and the horizontal protective gas is located between the vertical protective gas device and the workpiece surface. The vertical protective gas device introduces downward vertical protective gas, and the downward vertical protective gas is introduced coaxially with the laser.

[0062] In step two of this embodiment, after fixing the laser with a fixture, the welding path is taught by demonstrating the welding start point and welding end point under the conditions of laser power of 6kW, welding speed of 1m / min, defocusing amount of -6mm, spot diameter of 0.45mm, rise time of trapezoidal wave of 2ms, high frequency duration of 4ms, and low frequency pulse duration of 4ms. The accuracy of the teaching results is then checked before proceeding to step three.

[0063] In step three of this embodiment, the heat input for the weld is 180 J / mm.

[0064] Comparative Experiment 1: This comparative experiment differs from Example 1 in that step three utilizes continuous wave laser welding in a vacuum environment. Specifically, the laser power is 3kW, the welding speed is 1m / min, the defocusing amount is -6mm, the welding pressure is 0.1kPa, and the spot diameter is 0.45mm. In this case, the weld heat input in step three is 180J / mm. Everything else is the same as in Example 1.

[0065] Example 2: This example differs from Example 1 in that the rise time of the trapezoidal wave in step 3 is 2ms, the high-frequency duration is 5ms, and the low-frequency pulse duration is 3ms. Everything else is the same as in Example 1.

[0066] Comparative Experiment 2: This embodiment differs from Embodiment 2 in that the waveform of the pulse in step 3 is a rectangular wave; the pulse period of the rectangular wave is 40ms, 20ms, 10ms, or 5ms, and the duty cycle is 50%. Everything else is the same as in Embodiment 2.

[0067] Figure 3The figures show the weld morphology obtained in Example 1 and Comparative Experiment 1, with a and c representing Comparative Experiment 1 and b and d representing Example 1. The weld formation of the continuous wave vacuum laser welding in Comparative Experiment 1 and Example 1 was compared under the same heat input. As shown in the figures, under the same heat input, the continuous laser welding in Comparative Experiment 1 achieved a penetration depth of 8.25 mm, a weld width of 1.18 mm, and a depth-to-width ratio of 6.99. In contrast, Example 1 achieved a weld penetration depth of 10.71 mm, a weld width of 1.36 mm, and a depth-to-width ratio of 13.4. Furthermore, the weld surface and cross-sectional formation quality were extremely high, with the penetration depth increase being 1.33 times that of continuous vacuum laser welding. This confirms that Example 1 can achieve welds with greater penetration depth under the same heat input. Figures c and d show that the weld surface formation quality is excellent, with a continuous and full weld surface and no spatter particles on either side of the weld.

[0068] Figure 4 To compare the solidification structure of the weld obtained in Experiment 1, a is the solidification structure near the center of the weld, b is the solidification structure between the center line of the weld and the fusion line, and c is the solidification structure near the fusion line. Figure 5 The diagram shows the solidification structure of the weld obtained in Example 1. Figure a shows the solidification structure near the weld center, figure b shows the solidification structure between the weld centerline and the fusion line, and figure c shows the solidification structure near the fusion line. As can be seen from the figure, the solidification structure of the weld obtained in Example 1 is similar to that of the vacuum laser weld in Comparative Experiment 1, both being dominated by columnar crystals. However, the columnar dendrites in the weld obtained in Example 1 are finer, and a wider fine-grained region appears near the weld fusion line. Under heat-affected zones, only a small amount of grain boundary liquefaction occurs, confirming that Example 1 has the beneficial effect of refining the weld solidification structure and suppressing crack initiation in heat-sensitive materials.

[0069] Figure 6 The figures show the pulse waveform parameter control diagram and the resulting weld morphology diagram used in Example 2. Figure a shows the pulse waveform parameter control diagram, figure b shows the weld surface morphology, and figure c shows the weld cross-sectional morphology. As can be seen from the figures, the weld formation quality is excellent, with no welding defects appearing on the weld surface or cross-section. The weld penetration depth is 11.32 mm, the weld width is 0.91 mm, and the depth-to-width ratio is 12.44, demonstrating that Example 2 has a significant effect on improving the formation of welds with large penetration depths.

[0070] Figure 7 To compare the weld surface morphology obtained in Experiment 2, a represents a pulse period of 40ms, b represents a pulse period of 20ms, c represents a pulse period of 10ms, and d represents a pulse period of 5ms. Figure 8To compare the weld cross-sectional morphology obtained in Experiment 2, a is the longitudinal section of the weld with a pulse period of 40ms, b is the longitudinal section of the weld with a pulse period of 20ms, c is the longitudinal section of the weld with a pulse period of 10ms, d is the longitudinal section of the weld with a pulse period of 5ms, e is the cross-section of the weld with a pulse period of 40ms, f is the cross-section of the weld with a pulse period of 20ms, g is the cross-section of the weld with a pulse period of 10ms, and h is the cross-section of the weld with a pulse period of 5ms. As shown in the figure, at a pulse period of 40ms, severe spatter defects appeared on the weld surface, and the cross-section and longitudinal section of the weld showed obvious porosity defects, and "nail-point" defects appeared at the root of the weld. When the pulse period was reduced to below 20ms, spatter defects existed on the weld surface, but the cross-section and longitudinal section of the weld were well formed, indicating that a continuous weld could be obtained with a low frequency time of less than 10ms. When the pulse period continued to decrease, the spatter on the weld surface turned into small particle spatter, and the cross-section of the weld showed obvious "bulging" defects, which easily induced defects and caused inconsistent mechanical properties in the depth direction of the weld. It was confirmed that conventional vacuum environment pulsed lasers could not achieve ideal deep-penetration weld joints, indicating that Example 2 has the beneficial effect of improving weld formation.

Claims

1. A method for controlling the formation of a high aspect ratio weld with low heat input, characterized in that... It is done in the following steps:

1. Clean the surface and mating surfaces of the workpiece, then fit the mating surfaces together to form a joint and laser fix it to obtain the workpiece after laser fixation; 2. Place the spot-fixed workpiece on the welding platform of the vacuum laser welding device, adjust the welding position, and then use a clamp to fix it.

3. First, evacuate the vacuum. Then, introduce horizontal and vertical shielding gases below the protective lens of the welding laser head. Next, introduce balancing gas to balance the chamber pressure to a welding pressure of 0.1 kPa to 10 kPa. Then, with a laser power of 3 kW to 15 kW, a welding speed of 0.3 m / min to 2 m / min, a defocusing amount of 0 mm to -24 mm, a welding pressure of 0.1 kPa to 10 kPa, a spot diameter of 0.2 mm to 0.8 mm, and a pulsed laser output mode, move along the preset welding path. After reaching the welding end position, stop moving and laser output. Finally, stop introducing horizontal shielding gas, vertical shielding gas, and balancing gas. The waveform of the pulse is a trapezoidal wave; the inlet pressure of the horizontal protective gas is 0.1MPa~2.0MPa, and the inlet flow rate of the downward vertical protective gas is 10L / min~20L / min; IV. Welded components are removed from the chamber, and a method for controlling the formation of welds with a large depth-to-width ratio and low heat input is implemented.

2. The method for controlling the formation of a high aspect ratio weld with low heat input according to claim 1, characterized in that... The workpiece mentioned in step one is made of high-temperature alloy and has a thickness of 5mm to 40mm.

3. The method for controlling the forming of a high aspect ratio weld with low heat input according to claim 1, characterized in that... The connector mentioned in step one is a flat butt joint or a lock-bottom butt joint, and the butt gap is ≤1.0mm.

4. The method for controlling the forming of a high aspect ratio weld with low heat input according to claim 1, characterized in that... The laser spotting described in step one is carried out in the following steps: the laser beam is aligned with the mating surface, and under the conditions of laser power of 1000W~2000W and defocusing amount of -10mm~+10mm, the light is emitted for 200ms~1000ms, so that the mating position is locally melted to form a molten pool.

5. The method for controlling the formation of a high aspect ratio weld with low heat input according to claim 1, characterized in that... In step three, a horizontal protective gas and a downward vertical protective gas are introduced below the protective lens of the welding laser head. This is specifically achieved through a vertical protective gas device and a horizontal protective gas device. The vertical protective gas device is a circular gas nozzle with a diameter that gradually decreases from top to bottom, and it is connected to the lower end face of the laser welding head through an adapter block. The horizontal protective gas device is an air cutter with a 0.1mm gas groove, which is set on the side of the laser welding head. The horizontal protective gas device introduces horizontal protective gas, and the horizontal protective gas is located between the vertical protective gas device and the workpiece surface. The vertical protective gas device introduces downward vertical protective gas, and the downward vertical protective gas is introduced coaxially with the laser.

6. The method for controlling the forming of a high aspect ratio weld with low heat input according to claim 1, characterized in that... Step 3 describes the vacuuming process, which involves first using a mechanical pump to reduce the chamber pressure to ≤3kPa, and then starting a Roots pump to reduce the chamber pressure to below 20Pa.

7. The method for controlling the forming of a high aspect ratio weld with low heat input according to claim 1, characterized in that... In step three, a fiber laser with a wavelength of 1064nm~1080nm is used for laser welding, and the focal length of the laser welding is ≥200mm.

8. The method for controlling the forming of a high aspect ratio weld with low heat input according to claim 1, characterized in that... The rise time of the trapezoidal wave described in step three is ≥2ms, the high frequency duration is ≥3ms, and the low frequency pulse duration is ≤10ms.

9. A method for controlling the formation of a high aspect ratio weld with low heat input according to claim 1, characterized in that... The horizontal protective gas, the downward vertical protective gas, and the balancing gas mentioned in step three are all argon gas with a purity of 99.99%.

10. A method for controlling the formation of a high aspect ratio weld with low heat input according to claim 1, characterized in that... In step four, turn off the Roots pump, and after an interval of 10 to 30 seconds, turn off the mechanical pump. Then, introduce air and wait until the pressure inside and outside the cabin is the same before opening the hatch. After waiting for 1 to 5 minutes, remove the welded parts from the cabin.

Images