Variable curvature circumferential weldment device based on laser-arc composite coaxial energy modulation

Abstract

This invention discloses a variable curvature circumferential weldment device based on laser-arc composite coaxial energy modulation. By rationally distributing and arranging the energy of three auxiliary lasers and the main laser, it effectively solves the problem of excessive energy focusing in variable curvature welding, significantly improving weld formation quality. Combined with a real-time monitoring system of temperature and vision sensors, the central controller rapidly and accurately adjusts welding parameters, achieving precise control of the welding process on complex curved surfaces. In the actual welding process, by activating each heat source system and wire feeding mechanism, welding parameters are initialized. The coaxial infrared thermometer and vision sensor continuously monitor the state of the molten pool and curvature changes. The central controller automatically adjusts the power of each laser and arc parameters based on real-time temperature data. Especially when welding areas with large curvature changes, the three auxiliary lasers compensate for the energy distribution, effectively suppressing defects such as poor weld formation and spatter.

Description

Technical Field

[0001] This invention belongs to the field of laser welding technology, specifically relating to a variable curvature circumferential seam welding device based on laser-arc composite coaxial energy modulation. Background Technology

[0002] With the rapid development of high-end equipment manufacturing technology, higher requirements are being placed on the welding quality and efficiency of large variable curvature structures in fields such as aerospace, shipbuilding, and energy and chemical engineering. Traditional welding methods often face problems such as insufficient process adaptability and inaccurate heat input control when dealing with variable curvature structures. In recent years, laser-arc hybrid welding technology has become an important development direction for solving high-requirement welding scenarios due to its advantages such as high energy density, controllable heat input, and good weld formation.

[0003] Against this backdrop, a multi-source laser-arc coaxial hybrid modulation welding device and method for variable curvature circumferential seams has emerged. Currently, traditional laser-arc hybrid welding technology still faces several key bottlenecks when dealing with variable curvature circumferential seam welding: On the one hand, dynamic changes in curvature easily lead to the laser focal point shifting relative to the weld trajectory and a decrease in arc morphology stability, resulting in a severe imbalance in energy distribution. The increased curvature on the outer side of the weld leads to a longer heat dissipation path and a faster heat dissipation rate, but often results in insufficient energy supply, while the limited heat dissipation space on the inner side makes heat accumulation easy, leading to excessive energy concentration. On the other hand, traditional welding parameters are mostly fixed and cannot be adjusted in real time according to sudden changes in curvature. This not only causes uneven weld penetration and irregular weld formation but also easily induces welding defects such as porosity, cracks, and spatter, making it difficult to meet the stringent requirements for welding accuracy and joint mechanical properties of complex curved surface components. Summary of the Invention

[0004] The purpose of this invention is to provide a variable curvature circumferential weld device based on laser-arc composite coaxial energy modulation to solve the above-mentioned problems.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a variable curvature circumferential weld device based on laser-arc composite coaxial energy modulation, comprising a three-part light-assisted welding heat source system, a laser heat source system, an in-light laser-arc composite welding head, and a monitoring and control system;

[0006] The three-beam auxiliary welding heat source system is used to split a laser beam emitted by a fiber laser heat source into three auxiliary laser beams, which act on the weld pool.

[0007] The laser heating system is used to generate the main laser beam, which is applied to the workpiece for welding.

[0008] The laser-arc hybrid welding head is connected to the monitoring and control system and can receive instructions from the control system to adjust the welding parameters in real time.

[0009] The monitoring and control system includes a coaxial infrared thermometer, a vision sensor, and a central controller. The coaxial infrared thermometer and vision sensor are used to monitor the temperature field and curvature changes of the molten pool, and feed the changes of the temperature field and curvature of the molten pool back to the central controller for regulation.

[0010] The adjustment is based on the system's preset curvature threshold K. th :

[0011] When |K(t)|≤K th At that time, the monitoring and control system operates in mode one, which is the constant parameter modulation mode.

[0012] When K(t) > K th At this time, the monitoring and control system switches to mode two, which is the high-frequency pulse modulation mode, suitable for outer welds with increased curvature.

[0013] When K(t) < −K th When the monitoring and control system switches to mode three, which is the gradual duty cycle modulation mode, it is suitable for inner welds with increased curvature or transitions to flat areas.

[0014] The curvature threshold K th The setting is based on the following: its core is to identify the critical point where changes in the workpiece's geometric curvature during welding cause a significant alteration in the thermo-mechanical behavior of the molten pool, necessitating a switch to the energy modulation mode. This is determined through the following steps:

[0015] Theoretical Analysis and Simulation Prediction: A three-dimensional transient thermal-fluid coupling model of variable curvature laser-arc hybrid welding is established for the target workpiece material and typical plate thickness. Through simulation calculations, the variation law of the symmetry of the molten pool temperature field, fluid flow state, and weld morphology with curvature is analyzed, and the quality-sensitive curvature range is preliminarily determined.

[0016] Process calibration and testing: A series of test pieces with known gradient curvature were prepared, and welding tests were conducted under selected baseline welding parameters (Mode 1). A coaxial vision sensor and infrared thermography system were used to simultaneously acquire images of the molten pool, temperature data, and subsequent weld formation quality at different curvature positions. The test data were analyzed, and the absolute value of curvature corresponding to when the weld formation began to deviate from the expected result (such as the appearance of undercut on the outside or collapse on the inside) was determined as the threshold K under this process condition. th。

[0017] Parameter correlation and optimization: Threshold K th It is related to the workpiece material, plate thickness, reference welding speed, and heat input. In practical applications, calibration is required for different main welding process windows, and the calibration values ​​can be stored in the process parameter database of the central controller for later use.

[0018] K is determined by the above method. th This ensures a precise match between the mode switching logic and the physical process, which is the foundation for achieving adaptive and precise control.

[0019] In modes two and three, the monitoring and control system redistributes the power of the three auxiliary laser beams based on the curvature K. The distribution principle is defined by the following mapping function:

[0020] ;

[0021] , , These are the auxiliary laser powers acting on the front, outer, and inner sides of the molten pool, respectively. , , The reference power is α, β, and γ, which are power-curvature coupling coefficients. α corresponds to the auxiliary laser at the front end of the molten pool, β corresponds to the outer side, and γ corresponds to the inner side. All of them are greater than zero.

[0022] Preferably, during the process of the monitoring and control system redistributing the power of the three auxiliary laser beams according to the curvature K, the instability in the welding process caused by stabilization mode switching or parameter jumps is addressed using the following formula:

[0023] ;

[0024] D(t) is the actual output value of the current period. set The target setpoint is calculated for the outer loop. Ts is the control period, and τ is the inertial time constant, with a value range of 0.1-0.5s. When the welding speed is ≤ mm / min, τ = 0.3-0.5s to avoid molten pool fluctuations caused by excessively rapid parameter adjustments; when the welding speed is > mm / min, τ = 0.1-0.3s to ensure rapid parameter response to curvature changes. The duty cycle D of the pulsed arc is adjusted according to the weld position.

[0025] Duty cycle of the outer side of the weld: ;

[0026] Duty cycle of the inner side of the weld: ;

[0027] Where D is the baseline duty cycle, and ζ,η are the duty cycle-curvature adjustment coefficients.

[0028] Preferably, the three-beam assisted welding heat source system includes a semiconductor laser, a transmission fiber 1, a three-beam optical device, and a reflector 1, a reflector 2, a reflector 3, a rotatable bracket 1, a rotatable bracket 2, a rotatable bracket 3, a telescopic bracket 1, a telescopic bracket 2, and a telescopic bracket 3. The semiconductor laser is connected to the three-beam optical device through the transmission fiber 1. The reflector 1, the reflector 2, and the reflector 3 are arranged on the same horizontal plane as the three-beam optical device to emit the split semiconductor laser beams 1, 2, and 3 to a specific area of ​​the molten pool.

[0029] The semiconductor laser beam generated by the semiconductor laser is divided into semiconductor laser beam one, semiconductor laser beam two, and semiconductor laser beam three after passing through a three-beam optical device. These beams are then focused onto the end of the welding wire by mirror one, mirror two, and mirror three in sequence. The split laser beam includes semiconductor laser beam one, semiconductor laser beam two, and semiconductor laser beam three.

[0030] Preferably, the laser heat source system includes a fiber laser, a second transmission fiber, a focusing lens, and a wedge lens. The fiber laser is connected to the optical laser-arc composite welding head through the second transmission fiber. The focusing lens is located below the first, second, and third reflectors, and the wedge lens is located below the focusing lens.

[0031] The main laser beam generated by the fiber laser is focused onto a wedge-shaped lens by a focusing lens. After passing through the wedge-shaped lens, the focused laser beam is deflected at a small angle and focused behind the welding wire.

[0032] Preferably, the optical laser-arc composite welding head includes an optical laser-arc composite welding head, welding wire, pulley, welding wire collimator, wire feeding mechanism, protective gas cylinder, rotatable support, and protective gas delivery pipe; the wire feeding mechanism feeds the welding wire into the optical laser-arc composite welding head through the pulley, and ensures that it is coaxial with the laser beam through the welding wire collimator; the protective gas cylinder delivers protective gas to the surface of the workpiece through the protective gas delivery pipe.

[0033] The technical effects and advantages of this invention are as follows: By rationally allocating and arranging the energy of the three auxiliary lasers and the main laser, the problem of excessive energy focusing in variable curvature welding is effectively solved, significantly improving the weld formation quality. Combined with a real-time monitoring system using temperature and vision sensors, the central controller enables rapid and precise control of welding parameters, achieving accurate control of the complex curved surface welding process and ensuring stable and reliable welding. In actual welding, welding parameters are initialized by activating each heat source system and wire feeding mechanism. During welding, a coaxial infrared thermometer and vision sensor continuously monitor the molten pool state and curvature changes. The central controller automatically adjusts the laser power and arc parameters based on real-time temperature data. Especially when welding areas with significant curvature changes, the three auxiliary lasers compensate for energy distribution, effectively suppressing defects such as poor weld formation and spatter, ensuring consistent weld depth and uniform formation throughout the circumferential weld. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the overall structure of the variable curvature circumferential weld device of the present invention;

[0035] Figure 2 This is a schematic diagram of the spatial position of the reflector assembly of the present invention;

[0036] Figure 3 This is a schematic diagram showing the application positions and laser positions of Mode 1, Mode 2, and Mode 3 of the present invention.

[0037] In the diagram: 12. Semiconductor laser; 11. Transmission fiber optic one; 13. Three-way beam optical device; 14. Reflector one; 15. Reflector two; 16. Reflector three; 131. Semiconductor laser beam one; 132. Semiconductor laser beam two; 133. Semiconductor laser beam three; 122. Rotatable support one; 124. Rotatable support two; 126. Rotatable support three; 121. Telescopic support one; 123. Telescopic support two; 125. Telescopic support three;

[0038] 21. Transmission fiber optic cable 2; 22. Fiber laser; 23. Focusing lens; 24. Main laser beam; 25. Fixed bracket 1; 26. Slide rail device; 27. Fixed bracket 2;

[0039] 3. In-light laser-arc welding joint; 31. Welding wire; 32. Pulley; 33. Welding wire collimator; 34. Wire feeding mechanism; 35. Shielding gas; 36. Rotatable support four; 37. Shielding gas delivery pipe;

[0040] 4. Monitoring and control system; 41. Coaxial infrared thermometer and vision sensor; 42. Rotatable bracket five; 43. Central controller. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] This invention provides, for example Figures 1-3 The variable curvature circumferential weldment device based on laser-arc composite coaxial energy modulation shown includes...

[0043] The three-beam auxiliary welding heat source system is used to split a laser beam emitted by the fiber laser heat source 12 into three auxiliary laser beams, which are then applied to the welding pool for control.

[0044] A laser heating system is used to generate a main laser beam 24, which is applied to the workpiece for welding.

[0045] The laser-arc hybrid welding head 3 is connected to the monitoring and control system 4, which can receive instructions from the control system to adjust the welding parameters in real time.

[0046] The monitoring and control system 4 includes a coaxial infrared thermometer and vision sensor 41 and a central controller 43. The coaxial infrared thermometer and vision sensor 41 are used to monitor the temperature field and curvature changes of the molten pool, and feed the signal back to the central controller 43 for regulation.

[0047] The device performs coaxial welding by combining the main laser 24, semiconductor laser beam 131, semiconductor laser beam 2 132, semiconductor laser beam 3 133 with a pulsed electric arc. The heat source at the variable curvature position is set by three large-diameter auxiliary laser beams with low power density intersecting at a 120° angle, with the intersection point on the welding wire 31, and the small-diameter but high-power-density main laser beam 24 in front of the intersection point of the welding wire 31, which is used to melt the base material in advance.

[0048] The adjustment of the device's heat source should be initiated by a visual sensor detecting changes in curvature and feeding this feedback to the control system. The visual sensor's sensing mechanism primarily involves the conversion of "light signal → electrical signal → digital signal." The lens captures scene light and focuses it onto the photosensitive element. The photosensitive element converts the light intensity into a weak electrical signal, which is then converted into a digital signal via an analog-to-digital converter (ADC). This signal is processed into structured data, providing a foundation for subsequent analysis. Curvature is calculated by taking pictures of areas of curvature change using a standard camera. From the acquired images, key feature points at these curvature points, such as the edges of welded parts, are selected. The pixel coordinates u and v are converted to precise coordinates in the real-world coordinate system through camera intrinsic parameter calibration. A mathematical model is then used to fit these feature points. The least squares method is commonly used to fit quadratic curves such as circles, parabolas, or higher-order curves such as B-spline curves, resulting in a curve equation such as a quadratic curve: ax² + bx + c = 0. The curvature is then calculated based on the mathematical expression of the fitted curve. Taking a quadratic curve as an example, the radius of curvature formula is used:

[0049] ;

[0050] In the above formula Let K be the radius of curvature, K be the curvature, and f(t) be the curve fitted by the least squares method for the feature points of the weld edge.

[0051] The adjustment is divided into three modes:

[0052] Mode 1, when the curvature does not change, adopts constant parameter modulation mode, which uses continuously output laser and fixed frequency pulsed arc.

[0053] Mode 2, when the curvature increases, adopts a high-frequency pulse modulation mode. This mode uses a continuously output laser and an adaptive frequency arc. When the heat dissipation is faster on the outside of the weld, a high duty cycle arc is used, and when the heat dissipation is slower on the inside of the weld, a low duty cycle arc is used.

[0054] Mode 3, when the curvature decreases, adopts a gradual duty cycle modulation mode. This mode uses continuously output laser and pulsed arc with gradually increasing duty cycle, so as to smoothly transition to mode 1.

[0055] Mode 1, Mode 2, and Mode 3 all use continuous output laser and pulsed electric arc.

[0056] Specifically, the three-beam assisted welding heat source system includes a semiconductor laser 12, a transmission fiber 11, a three-beam optical device 13, and reflectors 14, 25, 316, 122, 124, 126, 121, 123, and 125. The semiconductor laser 12 is connected to the three-beam optical device 13 via the transmission fiber 11. The reflectors 14, 215, and 316 are arranged on the same horizontal plane as the three-beam optical device 13 to emit the split semiconductor laser beams 131, 132, and 133 to a specific area of ​​the molten pool.

[0057] The semiconductor laser beam generated by the semiconductor laser 12 is divided into semiconductor laser beam one 131, semiconductor laser beam two 132 and semiconductor laser beam three 133 after passing through the beam splitting optical device 13. The beams are then focused onto the end of the welding wire by reflecting mirror one 14, reflecting mirror two 15 and reflecting mirror three 16 in sequence. The split laser beams include semiconductor laser beam one 131, semiconductor laser beam two 132 and semiconductor laser beam three 133.

[0058] Specifically, the laser heat source system includes a fiber laser 22, a second transmission fiber 21, a focusing lens 23, and a wedge lens. The fiber laser 22 is connected to the optical laser-arc hybrid welding head 3 via the second transmission fiber 21. The focusing lens 23 is located below the first reflector 14, the second reflector 15, and the third reflector 16. The wedge lens is located below the focusing lens 23 and is used to provide the main laser energy required for welding. Its components include the fiber laser 22, the second transmission fiber 21, the focusing lens 23, the first fixing bracket 25, the slide rail device 26, the second fixing bracket 27, the wedge lens, and the third fixing bracket. The high-power laser beam generated by the fiber laser 22 is transmitted to the interior of the optical laser-arc hybrid welding head 3 via the second transmission fiber 21. After being focused by the focusing lens 23 onto the wedge lens, the focused laser beam is deflected at a small angle and directly focused onto the surface of the workpiece behind the welding wire, achieving deep penetration welding. The focusing lens 23 is installed below the reflector group by a fixed bracket 25 and its left and right movement is controlled by a sliding rail device 26. The wedge lens is fixed below the focusing lens 23 by a fixed bracket 3, so that the wedge lens and the focusing lens can move synchronously, thereby ensuring that the main laser optical path and the auxiliary laser and arc heat source achieve true coaxial composite.

[0059] The main laser beam 24 generated by the fiber laser 22 is focused onto the wedge-shaped lens by the focusing lens 23. After passing through the wedge-shaped lens, the focused laser beam is deflected at a small angle and focused behind the welding wire.

[0060] Specifically, the monitoring and control system 4 includes a coaxial infrared thermometer and vision sensor 41 and a central controller 43. The coaxial infrared thermometer 41 is used to monitor the temperature field of the molten pool in real time, and the vision sensor 41 is used to observe whether the curvature changes. The coaxial infrared thermometer and vision sensor 41 are located on the right side of the laser-arc hybrid welding head 3 and can rotate at multiple angles to achieve multi-dimensional capture of multi-spatial information, real-time tracking of the dynamic process, and adaptability to complex working conditions. The central controller 43, based on the digital signals fed back from the coaxial infrared thermometer and vision sensor 41, dynamically adjusts the main laser power, auxiliary laser power, pulse arc parameters, and wire feed speed to achieve real-time monitoring and dynamic control of the welding process. It consists of the coaxial infrared thermometer and vision sensor 41, a rotatable bracket 5 42, and the central controller 43. The coaxial infrared thermometer and vision sensor 41 are mounted on one side of the laser-arc hybrid welding head 3 via the rotatable bracket 5 42 and can rotate at multiple angles to comprehensively capture the temperature field distribution of the molten pool. The collected temperature data is transmitted to the central controller 43 in real time via a signal line. The central controller 43 has a built-in control algorithm that can dynamically adjust key process parameters such as the main laser power, the energy ratio of the three auxiliary lasers, the pulse arc parameters current, voltage, and wire feed speed according to the temperature change of the molten pool, thereby realizing closed-loop control of the welding process.

[0061] The system presets a curvature threshold K. th The controller's mode switching logic is determined by the following condition function:

[0062] When |K(t)|≤K th At that time, the system operates in mode one constant parameter modulation mode.

[0063] When K(t) > K th When this occurs, the system switches to mode two, high-frequency pulse modulation mode, which is suitable for outer welds with increased curvature.

[0064] When K(t) < −K th When the system switches to mode three, the gradual duty cycle modulation mode is suitable for inner welds with increased curvature or transitions to flat areas.

[0065] In modes two and three, the system redistributes the power of the three auxiliary laser beams according to the curvature K, and the distribution principle is defined by the following mapping function:

[0066] ;

[0067] , , These are the auxiliary laser powers acting on the front, outer, and inner sides of the molten pool, respectively. , , The reference power is set below mode, where α, β, and γ are power-curvature coupling coefficients. α corresponds to the auxiliary laser at the front end of the molten pool, β corresponds to the outer side, and γ corresponds to the inner side; all are greater than zero. The calibration process is as follows: ① Select the target weldment material and fabricate 10 sets of different curvatures of 1 / 50 m. -1 ~1 / 200 m -1 ① Test block; ② Fix the basic parameters such as main laser power and welding speed, and only adjust the power of the three auxiliary lasers to record the power ratio without defects under different curvatures; ③ The method for determining the power-curvature coupling coefficient is as follows: First, based on the thermal-fluid coupling numerical model of laser-arc composite welding on variable curvature surfaces, simulate the adjustment amount ΔP of the three auxiliary lasers required to maintain the ideal molten pool morphology under different curvatures K. front ΔP out ΔP in By using linear regression of the ΔP-K data sequence, preliminary estimates and signs of the coupling coefficients α, β, and γ were obtained to guide experimental design. A series of specimens covering the working curvature range were prepared, and the response surface methodology was used to design experiments. Curvature K and the adjustment amount of the three laser beams were used as factors, and the symmetry of the molten pool morphology and the weld formation quality score were used as responses. After establishing the response surface model, for each discrete curvature value K... j Solve for the optimal power adjustment combination [ΔP] that maximizes the overall welding quality score. front (K j ), ΔP out (K j ), ΔP * in (K j A univariate linear regression is performed on the optimal adjustment sequence, and the slope of the regression line is the precisely calibrated power-curvature coupling coefficients α, β, and γ. The calculation process can be described as follows:

[0068] ;

[0069] Similarly, β and γ are calculated, where n is the number of experimental curvature levels. The value of n is determined by the staff based on the actual situation, and is generally 3 to 5 under the condition of equal intervals. The horizontal bar represents the average value.

[0070] In actual welding, the central controller monitors the feature length difference ΔL on both sides of the molten pool extracted by the vision sensor in real time. If ΔL continues to exceed the allowable range, the coupling coefficient is finely adjusted according to the preset rules. All coupling coefficients are stored in the process parameter library and are associated with the current material, plate thickness and main process parameters.

[0071] To avoid instability in the welding process caused by mode switching or parameter jumps, the system uses a first-order inertial element for smoothing filtering of key parameters such as duty cycle D. Its discretization implementation is as follows:

[0072] ;

[0073] D(t) is the actual output value of the current period. set The target setpoint is calculated for the outer loop. Ts is the control period, and τ is the inertial time constant, which ranges from 0.1 to 0.5 s. The specific value is determined based on the welding speed: when the welding speed is ≤300 mm / min, τ = 0.3-0.5 s, which can avoid the molten pool from fluctuating due to excessive parameter adjustment; when the welding speed is >300 mm / min, τ = 0.1-0.3 s, which can ensure that the parameters respond quickly to curvature changes.

[0074] The duty cycle D of the pulsed arc is adjusted according to the weld location.

[0075] Duty cycle of the outer side of the weld: ;

[0076] Duty cycle of the inner side of the weld: ;

[0077] Where D0 is the baseline duty cycle, and ζ,η are the duty cycle-curvature adjustment coefficients.

[0078] The determination of the reference duty cycle D0 requires first performing a thermophysical analysis of the material to determine the pulse frequency and base current range that allow the arc to burn stably and the droplet to transition smoothly under a given shielding gas and welding wire diameter. Then, a systematic experiment is conducted under the corresponding working condition of "Mode 1" to fix other parameters and only change the pulse arc duty cycle D to find the most suitable duty cycle, which is D0 (the most suitable here is determined based on actual needs and the needs of the staff).

[0079] Preferably, the determination of ζ and η requires experimental design, namely, conducting pulsed arc welding tests on specimens with the same curvature, fixing parameters such as arc current and voltage, and adjusting only the pulse duty cycle D. Experimental matrices are designed for both the outer and inner weld seams, recording arc stability, molten pool flow morphology, and weld formation data under different duty cycles. Next, data acquisition and modeling are performed, collecting arc voltage and current waveforms, and observing the dynamic behavior of the molten pool using high-speed cameras. Arc stability indices S(D,K) (such as arc drift rate and spatter quantity) and weld formation indices F(D,K) (such as undercut and collapse degree) are defined. Then, coefficient fitting is performed, and under a reference duty cycle D0, the optimal duty cycle adjustment for S and F is found.

[0080] ;

[0081] ;

[0082] When S ≥ 90 and F ≥ 90, the duty cycle adjustment is considered optimal. The F value is primarily determined by the following defect factors: For Class B welds, the diameter of a single pore is ≤ 10% of the weld width, and the total area does not exceed a certain percentage; exceeding this percentage results in an unacceptable F value. Undercut depth is ≤ 0.1mm (or a percentage of the plate thickness); exceeding this results in a deduction or disqualification. Any macroscopic crack results in a zero F value. Only when all sub-items of the F value meet or exceed the highest level requirements specified in the product design documents / industry standards can the F value be considered 90 or higher. The dynamic range of the S value: The statistical results of the S value sub-indicators, spatter number and arc voltage standard deviation, consistently falling within the top 20% of the data distribution are considered excellent. If the S value sub-indicators of the current welding process remain consistently within the excellent range with minimal fluctuation, the S value is considered 90 or higher.

[0083] The applicability of ζ and η under different welding speeds and material thicknesses was verified by fitting ζ and η using linear regression.

[0084] Specifically, the optical laser-arc composite welding head 3 includes an optical laser-arc composite welding head 3, welding wire 31, pulley 32, welding wire collimator 33, wire feeding mechanism 34, protective gas cylinder 35, rotatable support 36, and protective gas delivery pipe 37.

[0085] The wire feeding mechanism 3 feeds the welding wire 31 into the laser-arc hybrid welding head 34 via pulley 32, and ensures that the wire is coaxial with the laser beam via the wire collimator 33. The shielding gas cylinder 35 delivers shielding gas to the workpiece surface via the shielding gas delivery pipe 37, and provides inert gas protection to the welding area to prevent oxidation of the molten pool. The laser-arc hybrid welding head 3 can achieve multi-degree-of-freedom attitude adjustment under the support of the rotatable bracket 36 to adapt to the changes in the welding path of the variable curvature chamber.

[0086] Specifically, three auxiliary lasers are symmetrically arranged around the main laser axis, and their beam positions can be independently adjusted. They act on the front, rear, and sides of the molten pool, respectively, and their energy distribution can also be independently adjusted. The power ratio and position of each laser can be adjusted in real time according to the state of the molten pool. The three auxiliary lasers are distributed at an angle of 120°. Each reflector is mounted on a rotatable support, and the support is finely adjusted in space through a telescopic mechanism. This allows for independent control of the incident angle and position of each laser beam, achieving dynamic energy compensation for the front, rear, and side areas of the molten pool.

[0087] Specifically, the welding parameters include the pulsed arc current, voltage, main laser power, auxiliary laser power, and welding speed. The monitoring and control system 4 compares the molten pool temperature collected at time t+t0 with that at time t0, and adjusts the welding parameters according to the curvature of the workpiece to maintain uniform laser energy.

[0088] Working principle: Step 1: Start the three-part light-assisted welding heat source system, laser heat source system, light-in-light laser-arc composite welding head 3 and monitoring and control system 4;

[0089] Step 2: Weld the variable curvature circumferential seam using the laser-arc hybrid welding head 3, and adjust the welding path in real time according to the curvature change;

[0090] Step 3: Monitor the temperature field and curvature changes of the molten pool in real time using a coaxial infrared thermometer and a vision sensor 41;

[0091] Step 4: The central control system 43 provides real-time feedback based on the monitoring results and adjusts the energy distribution of the main laser power 24, semiconductor laser beam 131, semiconductor laser beam 2 132, semiconductor laser beam 3 133, and the welding parameters of the pulsed arc.

[0092] Step 5: Dynamically control the molten pool using three auxiliary lasers to compensate for uneven energy focusing caused by curvature changes and suppress welding defects. In the actual welding process, first, start each heat source system and wire feeding mechanism to initialize welding parameters. During welding, a coaxial infrared thermometer and vision sensor 41 continuously monitor the state of the molten pool and curvature changes. The central controller 43 automatically adjusts the power of each laser and arc parameters based on real-time temperature data. Especially when welding areas with large curvature changes, the energy distribution is compensated by three auxiliary lasers, effectively suppressing defects such as poor weld formation and spatter, ensuring consistent weld depth and uniform formation throughout the circumferential weld.

[0093] Example: Taking a typical TC4 titanium alloy variable curvature circumferential weld as the welding object in the aerospace field, a three-beam assisted welding heat source system is used. The semiconductor laser is a 1064nm fiber-coupled type with a maximum output power of 600W. It is connected to a fused silica beam splitter prism via a transmission fiber 1. The prism has a beam splitting ratio of 1:1:1 and a splitting angle of 120°±0.5°. The three split laser beams are reflected by a reflector supported by a rotatable and telescopic bracket. The final focused spot diameter φ of the three auxiliary laser beams is 3-5mm, with the focal point 2-3mm from the end of the welding wire. The power of each beam is independently adjustable from 80-200W, acting on the front, rear, and side of the molten pool respectively. The laser heat source system uses a 1080nm high-power fiber laser with a maximum output power of 2000W. It is connected to a focusing lens via a transmission fiber 2. The main laser beam has a focused spot diameter φ of 0.8-1.2mm, with the focal point located 1-1.5mm behind the welding wire, and a continuous output power of 1200-2500W. In the laser-arc hybrid welding head, the wire feeding mechanism is a servo motor with a wire feeding speed of 2-15 m / min and a control accuracy of ±0.1 m / min. It is compatible with TC4 titanium alloy welding wire with a diameter of 1.2-1.6 mm. The welding wire is transported via pulleys and protective pipelines. The protective gas cylinder provides 99.999% pure argon gas at a working pressure of 1.2 MPa and a flow rate of 5-25 L / min. The pulsed arc power supply has a rated current of 50-300 A, a voltage of 10-25 V, a pulse frequency of 10-200 Hz, and a duty cycle of 30%-80%. The monitoring and control system includes a coaxial infrared thermometer and a vision sensor, and the signals are processed by a central controller. During welding, preheat all systems for 10 minutes, calibrate the monitoring equipment, and preset the main laser power to 2000W, auxiliary lasers to 150W each, arc current to 180A, wire feed speed to 8m / min, shielding gas flow rate to 15L / min, and welding speed to 300mm / min. Calibrate the optical path to ensure coaxiality. During welding, maintain constant parameters at the beginning and end, and fine-tune the main laser power using temperature feedback. When the curvature increases to 1 / 100 m⁻¹, switch to high-frequency pulse mode, increasing the auxiliary laser power at the front to 180-200W, decreasing it to 100-120W at the tail, and 150-180W on the sides. The arc frequency is 100Hz with a duty cycle of 70% on the outer side and 80Hz with a duty cycle of 40% on the inner side. The welding speed is reduced to 250mm / min, and the curvature is reduced to 1 / 90. At m⁻¹, switch to gradual duty cycle mode, and the auxiliary laser and arc parameters gradually return to their initial values, increasing the welding speed to 300 mm / min; after welding, first turn off the main laser and arc, maintain wire feeding and shielding gas for 30 seconds, and then shut down other systems.

[0094] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A variable curvature circumferential weldment device based on laser-arc composite coaxial energy modulation, characterized in that: This includes a three-part optical-assisted welding heat source system, a laser heat source system, an in-optical laser-arc hybrid welding head, and a monitoring and control system; The three-beam auxiliary welding heat source system is used to split a laser beam emitted by a fiber laser heat source into three auxiliary laser beams, which act on the weld pool. The laser heating system is used to generate the main laser beam, which is applied to the workpiece for welding. The laser-arc hybrid welding head is connected to the monitoring and control system and can receive instructions from the control system to adjust the welding parameters in real time. The monitoring and control system includes a coaxial infrared thermometer, a vision sensor, and a central controller. The coaxial infrared thermometer and vision sensor are used to monitor the changes in the temperature field and curvature of the molten pool, and feed the changes in the temperature field and curvature of the molten pool back to the central controller for regulation. The curvature threshold K is preset according to the system th : When |K(t)|≤K th the monitoring and control system works in mode one, i.e. constant parameter modulation mode, When K(t) > K th When K(t) > K th When K(t) > K th When K(t) > K th When K(t) > K th When K(t) > K th When K(t) > K th When K(t) > K th When K(t) < −K th When the monitoring and control system switches to mode three, which is the gradual duty cycle modulation mode, it is suitable for inner welds with increased curvature or transitions to flat areas. K(t) represents the geometric curvature value of the weld trajectory, which is measured and calculated in real time over time t during the welding process. In modes two and three, the monitoring and control system redistributes the power of the three auxiliary laser beams acting on the front, outer, and inner sides of the molten pool, respectively, based on the curvature K. The distribution principle is defined by the following mapping function: ； , , These are the auxiliary laser powers acting on the front, outer, and inner sides of the molten pool, respectively. , , The reference power is defined as follows: α, β, γ are power-curvature coupling coefficients, α corresponds to the auxiliary laser at the front end of the molten pool, β corresponds to the outer side, γ corresponds to the inner side, α>0, β>0, γ<0, and α, β, γ are determined based on the slope of the regression line of the univariate linear regression equation.

2. The variable curvature circumferential weldment device based on laser-arc composite coaxial energy modulation according to claim 1, characterized in that: During the process of the monitoring and control system redistributing the power of the three auxiliary laser beams according to the curvature K, the welding process instability caused by stable mode switching or parameter jumps is addressed using the following formula: ； D(t) is the actual output value of the current period. set The target setpoint is calculated for the outer ring. Ts is the control period, and τ is the inertial time constant, which ranges from 0.1 to 0.5 s. When the welding speed is ≤300 mm / min, τ = 0.3-0.5 s to avoid molten pool fluctuations caused by excessively rapid parameter adjustments; when the welding speed is >300 mm / min, τ = 0.1-0.3 s to ensure rapid parameter response to curvature changes. The duty cycle D of the pulsed arc is adjusted according to the weld position. Duty cycle of the outer side of the weld: ; Duty cycle of the inner side of the weld: ; Where D0 is the baseline duty cycle, ζ,η are the duty cycle-curvature adjustment coefficients, ζ>0, η<0.

3. The variable curvature circumferential weldment device based on laser-arc composite coaxial energy modulation according to claim 1, characterized in that: The three-beam assisted welding heat source system includes a semiconductor laser, a transmission fiber 1, a three-beam optical device, and reflectors 1, 2, and 3, rotatable brackets 1, 2, and 3, and telescopic brackets 1, 2, and 3. The semiconductor laser is connected to the three-beam optical device through the transmission fiber 1. Reflectors 1, 2, and 3 are arranged on the same horizontal plane as the three-beam optical device to emit the split semiconductor laser beams 1, 2, and 3 to a specific area of ​​the molten pool. The semiconductor laser beam generated by the semiconductor laser is divided into semiconductor laser beam one, semiconductor laser beam two, and semiconductor laser beam three after passing through a three-beam optical device. These beams are then focused onto the end of the welding wire by mirror one, mirror two, and mirror three in sequence. The split laser beam includes semiconductor laser beam one, semiconductor laser beam two, and semiconductor laser beam three.

4. The variable curvature circumferential weldment device based on laser-arc composite coaxial energy modulation according to claim 1, characterized in that: The laser heat source system includes a fiber laser, a second transmission fiber, a focusing lens, and a wedge lens. The fiber laser is connected to the optical laser-arc composite welding head through the second transmission fiber. The focusing lens is located below the first, second, and third reflectors, and the wedge lens is located below the focusing lens. The main laser beam generated by the fiber laser is focused onto a wedge-shaped lens by a focusing lens. After passing through the wedge-shaped lens, the focused laser beam is deflected and focused behind the welding wire.

5. The variable curvature circumferential weldment device based on laser-arc composite coaxial energy modulation according to claim 1, characterized in that: The optical laser-arc hybrid welding head includes an optical laser-arc hybrid welding head, welding wire, pulleys, welding wire collimator, wire feeding mechanism, protective gas cylinder, rotatable support, and protective gas delivery pipe. The wire feeding mechanism feeds the welding wire into the optical laser-arc hybrid welding head through the pulleys, and the welding wire collimator ensures that it is coaxial with the laser beam. The protective gas cylinder delivers protective gas to the surface of the workpiece through the protective gas delivery pipe.

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