TC4 skin self-adaptive tailored blank laser welding method based on light beam scanning-pulse cooperation

Abstract

The invention discloses a TC4 skin self-adaptive tailored blank laser welding method based on light beam scanning-pulse cooperation, and belongs to the technical field of high-energy beam precision welding. The problems that in the batch production process of the aerospace thin-wall titanium alloy standardized cabin, due to skin assembly gap fluctuation, plate thickness misalignment, V-shaped notches and other shape and position deviations, the shape of a molten pool is unstable, and welding seam forming consistency is poor are solved. A collaborative matching method of a scanning path and pulse energy parameters is adopted to improve the bridging efficiency of a molten pool and the form stability of a bridging liquid film, and meanwhile, self-adaptive response adjustment of welding parameters is achieved by combining workpiece form and position deviation changes and real-time monitoring feedback of dynamic bridging behaviors of the molten pool. According to the technology, continuous and stable welding seam forming under the assembly working condition of a gap of 0.2-0.4 mm, a misalignment of 0.3-0.6 mm or a V-shaped notch of 20-30 degrees is achieved for the specification of a skin with the thickness larger than or equal to 1.5 mm, the tensile strength of a welding seam reaches 95% or above of a base material, and meanwhile high welding heat efficiency is maintained. According to the method, the adaptability of the laser welding technology to the workpiece form and position deviation is remarkably improved through the multi-parameter synergistic effect and process monitoring feedback regulation and control, and key technical support is provided for solving the high-quality and stable welding problem of a new-generation spaceflight standard general cabin structure in the development and batch production process.

Description

Technical Field

[0001] A TC4 skin adaptive laser welding method based on beam scanning - pulse cooperation proposed by the present invention belongs to the technical field of high - energy beam precision welding. It is applicable to the high - quality and stable welding forming of titanium alloy skins under the conditions of geometric deviations such as assembly gap fluctuations, plate thickness misalignment, and V - shaped notches. Background Technique

[0002] As the core structural material of the aerospace vehicle cabin section, the forming quality of the sheet - welded skin of TC4 titanium alloy directly determines the bearing strength and anti - overload performance of the cabin components. In actual manufacturing, affected by sheet metal tolerances, processing precision, and assembly errors, there are three typical geometric deviations in the skin splicing area: gaps, misalignment, and V - shaped notches. Among them, the gap deviation has the highest occurrence frequency and often forms compound defects with misalignment or notches.

[0003] In recent years, with the in - depth development of supersonic / hypersonic aircraft equipment towards generalization and modularization, the "geometry - sensitive - forming instability" problem exposed during the laser welding of TC4 titanium alloy skins has become a key common technical bottleneck in the forming and manufacturing process of cabin standard parts. Research shows that under conventional process conditions (single - mode / spot diameter 100 - 400μm / pulse frequency ≥5000Hz), the loss of laser energy caused by local assembly deviations of the skin will significantly weaken the gap - bridging efficiency of the molten pool and induce incomplete fusion problems; the instability effect caused by the surface tension gradient of the molten pool promotes the shrinkage and cracking of the bridging liquid film, forming characteristic chain - like button - hole defects, resulting in the interruption of weld continuity. Although existing research has improved the geometric deviation tolerance to far exceed the theoretical threshold of the spot radius or 10% of the plate thickness through process improvements such as filler wire multi - heat - source composite welding and non - filler wire defocused welding, it still faces technical limitations such as poor process stability, low heat - source utilization rate, and insufficient inclusiveness of geometric deviation characteristics, and it is difficult to meet the requirements of high - quality and stable welding manufacturing. Summary of the Invention

[0004] In view of the limitations of the background technique, this project proposes a TC4 skin adaptive laser welding method based on beam scanning - pulse cooperation. On the one hand, by customizing the energy density distribution through beam galvanometer scanning, while reducing the loss of thermal efficiency, the melting area of the workpiece is expanded, significantly improving the gap - bridging efficiency of the molten pool across the gap; at the same time, combined with the specific waveform pulse energy time - series collaborative matching, the keyhole morphology and the temperature gradient distribution of the molten pool are precisely regulated, thereby enhancing the morphological stability of the bridging liquid film and effectively suppressing the tendency of discontinuous forming. Through the reasonable matching of the scanning path and pulse energy, it is possible to achieve the dynamic gap - bridging of the longitudinal - seam molten pool of the TC4 titanium alloy skin under geometric deviation conditions such as assembly gap fluctuations, plate thickness misalignment, and V - shaped notches, while maintaining the morphological stability of the bridging liquid film, meeting the quality consistency requirements for batch production of standardized cabin skin components.

[0005] The technical solution of the present invention is as follows:

[0006] An adaptive laser welding method for TC4 skin based on beam scanning - pulse cooperation, which uses laser cutting to prepare TC4 titanium alloy skin longitudinal seam structure flat specimens and conducts pre - welding cleaning. Build a welding test platform integrating modules such as fiber / disc lasers, servo walking mechanisms, two - axis scanning galvanometers, and pulse modulation units. Design a fixture for the shape and position deviation assembly of butt joints, which can simulate a gap of 0.2 - 0.4 mm, an offset of 0.3 - 0.6 mm, or a 20 - 30° V - shaped notch. Use a circular scanning path to match the square - wave pulse energy, and design a parameter combination of laser peak power = 1.0 - 3.0 kW, welding speed = 1.2 - 2.4 m / min, scanning amplitude = 1 - 1.5 mm, scanning frequency = 100 - 300 Hz, pulse frequency = 50 - 100 Hz, and duty cycle = 0.5. Implement the scanning - pulse cooperative welding process test, and through the monitoring and analysis of multi - modal data during the welding process, output the real - time shape and position deviation of the skin and the thermodynamic state of the molten pool, and realize the adaptive matching of process parameters through the feedback system.

[0007] Furthermore, the shape and position deviation characteristics of the titanium alloy skin test pieces are set through a modular assembly fixture.

[0008] Furthermore, the laser welding equipment is a fiber laser with a rated laser power ≥ 2 kW, a central wavelength range of 1070 ± 10 nm, a modulation frequency of 0 - 5 kHz, and a beam quality not lower than 4 mm × mard.

[0009] Furthermore, during the welding process, a laser profiler and an infrared thermometer are used to synchronously collect the shape and position deviation of the skin and the thermal - flow state of the molten pool, and the scanning - pulse parameters are adaptively adjusted through special software and actuators.

[0010] Furthermore, after welding, the surface, cross - section morphology, metallographic structure, and tensile properties of the weld are systematically characterized and analyzed, and the weld quality is rated in combination with relevant industry standards.

[0011] The beneficial effects of the present invention are as follows: Through the dynamic cooperation mechanism of the beam scanning path and pulse energy, the problem of welding instability of aerospace titanium alloy thin - wall skins under complex shape and position deviations is effectively solved. The innovatively designed circular scanning - square - wave pulse cooperation process can significantly improve the dynamic bridging ability of the molten pool and the stability of the liquid bridge morphology. With the real - time feedback system of the molten pool thermodynamic state, it can realize the adaptive adjustment of parameters under extreme shape and position deviation conditions, greatly improving the welding process stability and the first - pass welding qualification rate compared with traditional processes, and providing an innovative solution for the development and mass production of general standard cabin sections of aerospace vehicles. Description of the Drawings

[0012] Figure 1Scanning-Pulse Synergistic Welding Process Design and Laser Energy Density Distribution.

[0013] Figure 2 Appearance and Cross-Section Morphology of the Skin Weld in the Embodiment.

[0014] Figure 3 Tensile Strength and Fracture Morphology of the Weld in the Embodiment. Detailed Implementation Manner

[0015] The present invention will be further described below in conjunction with specific embodiments.

[0016] Embodiment

[0017] TC4 titanium alloy sheets with a thickness of 1.5 mm are used as the welding base material, and are wire-cut into specimens with a length of 200 mm and a width of 100 mm. The butt joint assembly method is adopted, and the gap geometric deviation is set by using a limit tooling and a feeler gauge, and the gap amount is 0.3 mm. The main welding equipment includes an IPG YLS-5000-BR fiber laser (with a 0-5000 Hz analog pulse function), a Novanta LightningTM II two-axis scanning galvanometer, a servo walking mechanism, a flexible tooling and a test protection chamber, as Figure 1 shown. A circular scanning path is designed to match the square-wave pulse. The core welding process parameters include: laser peak power P = 1.3 kW, welding speed u = 1.2 m / min, scanning amplitude A = 1.2 mm, scanning frequency f osc = 100 - 200 Hz, pulse frequency f plu = 50 Hz, duty cycle r = 0.5; the shielding gas is pure Ar, and the supply flow rates on the front and back surfaces are both 20 L / min. During the welding process, a Keyence LJ-V7000 laser profiler and a Keyence FT-H40K infrared thermal camera are used to synchronously collect the geometric deviation of the skin and the thermal-fluid state of the molten pool. After welding, the cross-section morphology is obtained by metallographic sample preparation, and the tensile strength of the joint is tested by a universal testing machine.

[0018] The appearance and cross-section metallographic morphology of the weld obtained in the embodiment are as Figure 2 shown, and the tensile strength test results are as Figure 3 shown. It can be seen from the figure that under the condition of a 0.3 - 0.5 mm gap deviation, the weld formation is uniform and complete, the effective connection rate reaches 100%, and the problem of discontinuous formation caused by the buttonhole effect is significantly suppressed; the weld cross-section presents an inverted trapezoid, and due to the gap filling effect, there are slight depressions and undercuts on the surface. The average tensile strength of the welded joint exceeds 1000 MPa, slightly higher than that of the base material, the elongation is about 0.4%, and the fracture presents a typical microvoid coalescence ductile fracture morphology.

[0019] The analysis of the results of the embodiments shows that the laser tailor-welding method based on the coordinated deployment of the scanning path and the pulse waveform proposed by the present invention improves the molten pool bridging efficiency and the liquid film morphology stability synchronously, thereby improving the skin tailor-welding forming quality under the gap geometric perturbation. In addition, the scanning path breaks through the spot size limitation of the conventional diameter-through path, and compared with the defocusing method proposed in the past, the spot power is not lost, so it can adapt to the skin tailor-welding scenario with a plate thickness ≥ 1.5 mm. This invention provides theoretical support and a method system for the high-quality and consistent forming manufacturing requirements of the aerospace TC4 standard cabin section in the research and development / mass production links, and accelerates the transformation of technical achievements and the industrial application process.

[0020] The above are only some embodiments of the present invention, and do not impose any form of limitation on the present invention. Any person familiar with the technical field of this specialty, without departing from the scope of the technical solution of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiments according to the technical essence of the present invention shall still fall within the protection scope of the claims of the present invention.

Claims

1. An adaptive laser welding method for TC4 skin based on beam scanning - pulse cooperation, characterized in that, It includes the following steps: Step 1: Build a welding test platform integrating modules such as fiber / disc lasers, servo walking mechanisms, two-axis scanning galvanometers, and pulse modulation units; Step 2: Design a fixture for the shape and position deviation assembly of butt joints, which can simulate a gap of 0.2 - 0.4 mm, an offset of 0.3 - 0.6 mm, or a V-notch of 20 - 30°; Step 3: Adopt a circular scanning path to match the square-wave pulse energy, and design a parameter combination with a laser peak power of 1.0 - 3.0 kW, a welding speed of 1.2 - 2.4 m / min, a scanning amplitude of 1 - 1.5 mm, a scanning frequency of 100 - 300 Hz, a pulse frequency of 50 - 100 Hz, and a duty cycle of 0.5; Step 4: Carry out multi-modal data monitoring and analysis during the welding process, output the real-time shape and position deviation of the skin and the thermodynamic state of the molten pool, and realize the adaptive adjustment of scanning-pulse parameters through a dedicated software and an actuator.

2. The adaptive laser welding method for TC4 skin based on beam scanning - pulse cooperation according to claim 1, characterized in that The scanning path and pulse energy in Step 3 need to follow certain parameter adjustment principles, where the scanning amplitude ≥ 3 times the gap amount, and the ratio of the scanning frequency to the pulse frequency should be an integer ≥ 2, ensuring that the pulse interval appears after a complete scanning cycle.

3. The multi-modal data monitoring and analysis during the welding process according to Claim 1 mainly uses a laser profiler and an infrared camera to collect the shape and position deviation of the skin and the bridging morphology of the molten pool, and realizes the adaptive adjustment of scanning-pulse parameters through a dedicated control software and an actuator.

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