Ultrasonic soldering device and ultrasonic soldering method

Abstract

The application relates to the technical field of laser processing, in particular to an ultrasonic brazing coating device and an ultrasonic brazing coating method. A laser brazing coating unit and an ultrasonic vibration unit are arranged on the two sides of a curved workpiece; a brazing coating movement mechanism is connected with the laser brazing coating unit, so as to drive the laser brazing coating unit to walk along a brazing coating path of the curved workpiece, and in the process, the angle between the axial direction of the laser brazing coating unit and the normal direction of the curved workpiece is always not greater than a preset qualified angle; an ultrasonic movement mechanism is connected with the ultrasonic vibration unit, so as to drive the ultrasonic vibration unit to walk along the brazing coating path of the curved workpiece synchronously with the laser brazing coating unit, and in the process, the angle between the axial direction of the ultrasonic vibration unit and the normal direction of the curved workpiece is always not greater than the preset qualified angle. The application solves a series of technical problems existing in the mode of applying from the front surface of the workpiece to the brazing material / matrix interface through the molten brazing material layer.

Description

Technical Field

[0001] This application relates to the field of laser processing technology, and in particular to an ultrasonic brazing apparatus and ultrasonic brazing method. Background Technology

[0002] Brazing is a surface engineering technology that involves melting brazing filler metal and coating it onto the surface of a workpiece to form a functional coating. It is widely used for surface protection and functional modification of key components such as hot-end parts of aero-engines, mold cavities, and electronic heat dissipation devices. Laser brazing uses a laser as a heat source and has advantages such as concentrated heating, a small heat-affected zone, and good controllability, making it an important technical approach to achieving high-quality brazing.

[0003] Ultrasonic-assisted technology, by applying ultrasonic vibrations during the brazing process, utilizes the ultrasonic cavitation effect to break down oxide films, improve wettability, and refine microstructure, and has been proven to significantly improve brazing / brazing quality. In existing ultrasonic-assisted laser brazing / brazing technologies, ultrasonic vibrations are typically transmitted from the front (i.e., the same side as the laser) through the molten filler metal layer to the filler metal / base material interface. This "front-side application" mode has the following inherent drawbacks: (i) The ultrasonic transmission path is severely interfered with by the molten pool. Ultrasonic energy needs to pass through the molten solder layer to reach the interface. There are strong convection, bubble disturbances and temperature gradients in the molten solder. When ultrasonic waves propagate in the liquid medium, they are severely scattered and absorbed, and the energy attenuation can reach more than 50%, and the transmission state is extremely unstable.

[0004] (ii) The cavitation effect is constrained by the conditions of the molten pool. The intensity and stability of the ultrasonic cavitation effect depend on the static pressure, temperature and gas content of the liquid medium. The high temperature of the molten solder (usually 800-1200℃) and the open environment increase the cavitation threshold and decrease the cavitation intensity, thus limiting the efficiency and controllability of ultrasonic action.

[0005] (iii) Poor adaptability to curved surfaces. For irregular curved workpieces, when applying ultrasonic waves to the front, the tool head needs to maintain close contact with the curved surface and avoid the laser beam path, resulting in a complex structure and limited adaptability.

[0006] (iv) Ultrasonic tool heads are susceptible to high-temperature corrosion. When applied to the front, the ultrasonic tool head needs to be close to or in contact with high-temperature molten brazing filler metal, which poses a risk of corrosion and thermal damage, affecting the tool head's lifespan and ultrasonic transmission stability. Summary of the Invention

[0007] The purpose of this application is to provide an ultrasonic brazing apparatus and ultrasonic brazing method, thereby solving a series of technical problems existing in the current "front-side application" mode, where ultrasonic vibration is usually transmitted from the front of the workpiece through the molten brazing filler layer to the brazing filler / base material interface.

[0008] According to a first aspect of this application, an ultrasonic brazing apparatus is provided, comprising a brazing motion mechanism, a laser brazing unit, an ultrasonic motion mechanism, and an ultrasonic vibration unit; wherein, each position on the curved workpiece to be processed has a local normal; the laser brazing unit and the ultrasonic vibration unit are respectively disposed on opposite sides of the curved workpiece in the normal direction; the brazing motion mechanism is connected to the laser brazing unit to drive the laser brazing unit to move along the brazing path of the curved workpiece, and during the process, the angle between the axial direction of the laser brazing unit and the normal direction of the curved workpiece is controlled to never exceed a preset qualified angle; the ultrasonic motion mechanism is connected to the ultrasonic vibration unit to drive the ultrasonic vibration unit to move synchronously with the laser brazing unit along the brazing path of the curved workpiece, and during the process, the angle between the axial direction of the ultrasonic vibration unit and the normal direction of the curved workpiece is controlled to never exceed the preset qualified angle.

[0009] In any of the above technical solutions, the ultrasonic brazing device further includes a three-dimensional vision sensor, which is used to perform a full-domain scan of the curved workpiece, reconstruct the point cloud data into a curved digital model, generate the brazing path, and calculate the local normal of each position point on the curved surface on the brazing path.

[0010] In any of the above technical solutions, the laser brazing unit further includes a laser alignment transmitter, and the ultrasonic vibration unit further includes a laser alignment receiving target. The laser alignment transmitter and the laser alignment receiving target are used to monitor the coaxiality of the laser brazing unit and the ultrasonic vibration unit in real time.

[0011] In any of the above technical solutions, the laser brazing unit further includes: A laser rangefinder sensor is used to measure the distance between the laser focus and the surface of the curved workpiece in real time, and to feed back the measured distance data to the dynamic focusing module. A dynamic focusing module, comprising at least one lens movable along the optical axis, is configured to: determine whether the distance data exceeds a preset distance range based on the distance data; if it does, drive the lens to move along the optical axis to adjust the distance data to the preset distance range. A laser confocal displacement sensor is used to monitor the thickness of the solder coating in real time. A high-speed color camera is used to observe the spreading behavior of brazing filler metal on the curved workpiece in real time. A dual-color infrared pyrometer is used to monitor the temperature of the brazing area in real time.

[0012] In any of the above technical solutions, the ultrasonic brazing device further includes an acoustic emission sensor and an ultrasonic transmission efficiency monitoring module. The acoustic emission sensor is installed on the side of the ultrasonic vibration unit or the curved workpiece facing away from the laser brazing unit, and is used to collect the intensity of the ultrasonic cavitation signal after transmission through the curved workpiece in real time. The ultrasonic vibration unit also includes an ultrasonic generator, an amplitude transformer, and a tool head connected in sequence. The tool head is in contact with the surface of the curved workpiece. The tool head is a flexible part, or the tool head is in contact with the surface of the curved workpiece through a solid coupling medium.

[0013] According to a second aspect of this application, an ultrasonic brazing method of the ultrasonic brazing apparatus as described above is provided, wherein the curved workpiece is scanned in its entirety by a three-dimensional vision sensor and the point cloud data is reconstructed into a digital model of the curved surface, a brazing path is generated according to the digital model of the curved surface, and the tilt angle θ, radius of curvature R, and local normal vector n of each position point on the curved surface on the brazing path are calculated. The brazing motion mechanism drives the laser brazing unit to perform brazing from one side of the curved workpiece along the brazing path, and controls the axial angle between the laser brazing unit and the normal angle of the curved workpiece to be no greater than a preset qualified angle. The vibration motion mechanism drives the ultrasonic vibration unit to apply vibration from the other side of the curved workpiece along the soldering path, and controls the axial angle between the ultrasonic vibration unit and the normal of the curved workpiece to be no greater than a preset qualified axial angle. The laser brazing unit further includes a laser alignment transmitter, and the ultrasonic vibration unit further includes a laser alignment receiving target. The laser brazing unit and the ultrasonic vibration unit move synchronously along the brazing path of the curved workpiece. During the movement, the laser alignment transmitter emits a reference laser beam to the laser alignment receiving target.

[0014] In any of the above technical solutions, further, the brazing motion mechanism controls the axial angle between the laser brazing unit and the normal angle of the curved workpiece to be no greater than a preset qualified angle, and the vibration motion mechanism controls the axial angle between the ultrasonic vibration unit and the normal angle of the curved workpiece to be no greater than a preset qualified angle, further including: assuming the homogeneous transformation matrix of the laser brazing unit coordinate system relative to the world coordinate system is M. L The homogeneous transformation matrix of the ultrasonic vibration unit coordinate system relative to the world coordinate system is M. R Z L and Z R These are the axial vectors of the laser brazing unit and the ultrasonic vibration unit, respectively, expressed in the world coordinate system; wherein the origin of the laser brazing unit coordinate system is the center point of the laser brazing unit, and the origin of the ultrasonic vibration unit coordinate system is the center point of the ultrasonic vibration unit. Set an attitude alignment constraint, which satisfies: Z L =-Z R And Z L and -Z R The angle between the local normal vector n and the target vector n is never greater than the preset acceptable angle. The attitude alignment constraint is solved in real time, and the soldering motion mechanism and the ultrasonic motion mechanism are controlled to ensure that Z... L and -Z R The angle between the local normal vector n and the target vector n is never greater than the preset acceptable angle.

[0015] In any of the above technical solutions, further, during the synchronous movement of the laser brazing unit and the ultrasonic vibration unit along the brazing path of the curved workpiece, the laser centering transmitter emits a reference laser beam to the laser centering receiving target, which further includes; Let O0(0, 0) be the theoretical coincidence point of the axis between the center point of the laser centering receiving target and the center point of the laser centering transmitter, and let P1(x1, y1) be the coordinates of the measured light spot. Then the formula for calculating the real-time coaxiality deviation D is: ; A real-time coaxiality deviation D constraint is set, which satisfies: D ≤ deviation threshold; when D > deviation threshold, a compensation amount is calculated for the coaxiality deviation D and its direction, and the brazing motion mechanism and the ultrasonic motion mechanism are controlled so that D ≤ deviation threshold.

[0016] In any of the above technical solutions, the ultrasonic brazing method further includes: during the brazing process along the brazing path, the laser brazing unit dynamically adjusts the laser power according to the radius of curvature R of each position on the curved surface on the brazing path; The ultrasonic vibration unit controls the applied vibration mode according to the tilt angle θ of each position point on the curved surface on the brazing path; When θ≤30°, the ultrasonic vibration unit adopts a longitudinal-torsional composite mode, which satisfies the following: vibration frequency of 25~40kHz, longitudinal amplitude of 5~15μm, and torsional amplitude of 3~10μm. When 30°<θ≤75°, the ultrasonic vibration unit adopts a low-frequency longitudinal mode, which satisfies the following conditions: vibration frequency of 15~25kHz and amplitude of 10~20μm. When θ > 75°, the ultrasonic vibration unit adopts a combination of the longitudinal-torsional composite mode and the low-frequency longitudinal mode.

[0017] In any of the above technical solutions, the ultrasonic brazing method further includes: real-time acquisition of ultrasonic cavitation signals transmitted through the curved workpiece based on an acoustic emission sensor, and comparison of the output power P of the ultrasonic generator based on an ultrasonic transmission efficiency monitoring module. 输出 The ultrasonic cavitation signal intensity P collected by the acoustic emission sensor 界面 Real-time calculation of ultrasonic transmission efficiency η, η=P 界面 / P 输出 When the attenuation of η relative to the reference value exceeds 30%, the contact pressure between the ultrasonic vibration unit and the curved workpiece is increased.

[0018] During the brazing process along the brazing path, the laser brazing unit monitors the thickness of the brazing filler metal coating in real time based on the laser copolymerization displacement sensor. When the thickness of the brazing filler metal coating deviates from the set value, the linear velocity of the ultrasonic vibration unit along the brazing path is adjusted, or the supply speed of the brazing filler metal powder of the laser brazing unit is adjusted. The temperature of the brazing area is monitored in real time using a dual-color infrared pyrometer. When the detected temperature exceeds the temperature threshold, the laser brazing unit is controlled to further adjust the laser power.

[0019] The ultrasonic brazing apparatus of this application includes a brazing motion mechanism, a laser brazing unit, an ultrasonic motion mechanism, and an ultrasonic vibration unit. Each position on the curved workpiece to be processed has a local normal. The laser brazing unit and the ultrasonic vibration unit are respectively positioned on opposite sides of the curved workpiece in the normal direction. The brazing motion mechanism is connected to the laser brazing unit to drive the laser brazing unit along the brazing path of the curved workpiece, and during this process, the angle between the axial direction of the laser brazing unit and the normal direction of the curved workpiece is always controlled to be no greater than a preset acceptable angle. The ultrasonic motion mechanism is connected to the ultrasonic vibration unit to drive the ultrasonic vibration unit to move synchronously with the laser brazing unit along the brazing path of the curved workpiece, and during this process, the angle between the axial direction of the ultrasonic vibration unit and the normal direction of the curved workpiece is always controlled to be no greater than a preset acceptable angle.

[0020] Based on the above technical features, the beneficial effects of this application are as follows: This application places the laser brazing unit and the ultrasonic vibration unit on opposite sides of the curved workpiece, with the axial angles of both units relative to the normal of the workpiece never exceeding a preset acceptable angle (with tolerance, but the error is no greater than the preset acceptable angle). With this configuration, the application achieves front-side laser heating and back-side ultrasonic vibration. The laser heating direction of the laser brazing unit is aligned with the normal, and the incident direction of the ultrasonic vibration unit's sound beam is also aligned with the normal. This ensures that the sound waves are incident perpendicularly to the surface of the curved workpiece along the normal, minimizing energy loss. Furthermore, it does not rely on an ultrasonic coupling medium and can be directly applied to high-temperature brazing environments.

[0021] Furthermore, compared to existing technologies, this application has the following advantages: (1) Ultrasonic waves are transmitted from the back of the curved workpiece through the solid base material to the brazing interface, which fundamentally changes the ultrasonic transmission path, avoids the scattering and absorption of ultrasonic energy by the molten brazing layer, and greatly improves the ultrasonic transmission efficiency and stability.

[0022] (2) The laser brazing unit on the front and the ultrasonic vibration unit on the back are placed face to face, so that the laser focus and the ultrasonic action point are located on the same side of the curved workpiece, achieving optimal energy field spatial coordination of front heating and back vibration.

[0023] (3) The surface normal follows the movement of both sides in real time, so that the incident direction of the front laser beam and the back ultrasonic wave is always consistent with the surface normal, ensuring that the laser energy and ultrasonic energy act on the surface at the optimal angle, and ensuring the consistency of coating quality.

[0024] (4) Completely dehydrated design, eliminating liquid coupling medium, making the device suitable for high-temperature brazing environment.

[0025] (5) The laser brazing unit and the ultrasonic vibration unit are respectively set on both sides of the curved workpiece. The ultrasonic vibration unit does not need to contact the high-temperature molten brazing filler metal, thus avoiding the problem of high-temperature corrosion and thermal damage to the ultrasonic vibration unit in the front application method.

[0026] (6) The laser brazing unit and the ultrasonic vibration unit are respectively set on both sides of the curved workpiece. The back ultrasonic vibration unit does not need to compete for space with the front laser brazing unit, making the structural layout more flexible and the curved surface more adaptable.

[0027] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A schematic diagram of the overall structure of the ultrasonic brazing device of this application is shown; Figure 2 The schematic diagram of the principle structure of the laser brazing unit and the ultrasonic vibration unit of this application is shown.

[0030] Reference numerals: 100-Brushing motion mechanism; 200-Laser brushing unit; 300-Ultrasonic motion mechanism; 400-Ultrasonic vibration unit; 510-Laser centering transmitter; 520-Laser centering receiver target; 530-Acoustic emission sensor; 540-Laser confocal displacement sensor; 550-Dual-color infrared pyrometer; 560-High-speed color camera; 570-Connecting flange; 600-Curved workpiece. Detailed Implementation

[0031] The following detailed embodiments are provided to help the reader gain a comprehensive understanding of the methods, apparatus, and / or systems described herein. However, various changes, modifications, and equivalents of the methods, apparatus, and / or systems described herein will be apparent after understanding the disclosure of this application. For example, the order of operations described herein is merely illustrative and is not limited to the order set forth herein; changes that will be apparent after understanding the disclosure of this application are possible, except for operations that must occur in a specific order. Furthermore, for clarity and brevity, descriptions of features known in the art may be omitted.

[0032] The features described herein may be implemented in different forms and should not be construed as being limited to the examples described herein. Rather, the examples described herein have been provided merely to illustrate some of the many feasible ways of implementing the methods, apparatus, and / or systems described herein that will be apparent upon understanding the disclosure of this application.

[0033] This application provides an ultrasonic brazing apparatus and an ultrasonic brazing method, thereby solving a series of technical problems inherent in the existing "front-side application" mode, where ultrasonic vibration is typically transmitted from the front of the workpiece through the molten brazing filler metal layer to the brazing filler metal / base material interface. See below for reference. Figure 1 and Figure 2 This application describes an ultrasonic brazing apparatus according to some embodiments.

[0034] like Figure 1 and Figure 2As shown, the ultrasonic brazing apparatus of this application includes a brazing motion mechanism 100, a laser brazing unit 200, an ultrasonic motion mechanism 300, and an ultrasonic vibration unit 400; wherein, each position on the curved workpiece 600 to be processed has a local normal; the laser brazing unit 200 and the ultrasonic vibration unit 400 are respectively arranged on opposite sides of the curved workpiece 600 in the normal direction; the brazing motion mechanism 100 is connected to the laser brazing unit 200 through a connecting flange 570 to drive the laser brazing unit 200 along the brazing direction of the curved workpiece 600. The laser brazing unit 200 moves along the brazing path, and during the process, the angle between the axial direction (axial direction) of the laser brazing unit 200 and the normal direction (normal direction) of the curved workpiece 600 is always no greater than the preset qualified angle; the ultrasonic motion mechanism 300 is connected to the ultrasonic vibration unit 400 through the connecting flange 570 to drive the ultrasonic vibration unit 400 to move synchronously with the laser brazing unit 200 along the brazing path of the curved workpiece 600, and during the process, the angle between the axial direction of the ultrasonic vibration unit 400 and the normal direction of the curved workpiece 600 is always no greater than the preset qualified angle.

[0035] It should be noted that each position on the curved workpiece 600 has a corresponding local normal, and the normals at different positions are different, continuously changing with the position. The ultrasonic vibration unit 400 and the laser brazing unit 200 move synchronously, and during the process, it is ensured that the angle between the axis of the laser brazing unit 200 (ultrasonic vibration unit 400) at each position and the normal of the curved workpiece 600 is never greater than a preset qualified angle. For example, when the laser brazing unit 200 and the ultrasonic vibration unit 400 move synchronously to position A, it is ensured that the angle between the axis of the laser brazing unit 200 (ultrasonic vibration unit 400) at position A and the normal of the curved workpiece 600 at position A is never greater than a preset qualified angle.

[0036] With this configuration, the laser brazing unit 200 and the ultrasonic vibration unit 400 are respectively positioned on both sides of the curved workpiece 600, and the axial angles of both units relative to the normal of the curved workpiece 600 are always no greater than a preset acceptable angle (with tolerance, but the error is no greater than the preset acceptable angle). This configuration combines front-side laser heating with back-side ultrasonic vibration. The laser heating direction of the laser brazing unit 200 is aligned with the normal, and the incident direction of the sound beam from the ultrasonic vibration unit 400 is aligned with the normal. This ensures that the sound waves are incident perpendicularly to the surface of the curved workpiece 600 along the normal, minimizing energy loss. Furthermore, it does not rely on an ultrasonic coupling medium and can be directly applied to high-temperature brazing environments.

[0037] Furthermore, compared to existing technologies, this application has the following advantages: (1) Ultrasonic waves are transmitted from the back of the curved workpiece 600 through the solid base material to the brazing interface, which fundamentally changes the ultrasonic transmission path, avoids the scattering and absorption of ultrasonic energy by the molten brazing layer, and greatly improves the ultrasonic transmission efficiency and stability.

[0038] The conductive medium differs. In existing technologies, the ultrasonic conductive medium is molten solder (liquid, with an acoustic impedance of approximately 2–5 × 10⁻⁶). 6 kg / (m²·s)), the ultrasonic transmission medium in this application is a solid matrix (acoustic impedance approximately 30–50 × 10⁻⁶ kg / (m²·s)). 6 The acoustic impedance of the solid base material is about 10 times that of the liquid brazing filler metal, and the acoustic energy transmission efficiency is significantly improved.

[0039] The attenuation mechanisms differ. Ultrasonic waves attenuate primarily in liquid media due to viscous absorption and thermal conduction, with an attenuation coefficient αliquid ≈ 10–100 dB / (m·MHz²). In solid media, attenuation is mainly caused by lattice scattering and dislocations, with an attenuation coefficient αsolid ≈ 1–10 dB / (m·MHz²). Ultrasonic attenuation in solid substrates is an order of magnitude lower than that in liquid brazing filler metals.

[0040] The interface functions differently. When ultrasound is incident perpendicularly from the back to the interface between the solder and the base material, due to the acoustic impedance difference between the solid base material and the liquid solder (approximately 10 times), about 80% of the acoustic energy is reflected at the interface. The reflected sound waves form a standing wave field in the base material, and the standing wave effect can produce an additional cavitation enhancement effect at the interface.

[0041] Unaffected by molten pool disturbances, the ultrasound transmitted from the back side has already propagated in the solid base material before entering the interface, and is not affected by factors such as molten solder flow, bubble disturbances, and temperature gradients. The stability and controllability of the ultrasound action are significantly better than those of the front-side application method.

[0042] (2) The front laser brazing unit 200 and the back ultrasonic vibration unit 400 are placed face to face, so that the laser focus and the ultrasonic action point are located on the same side of the curved workpiece 600, achieving optimal energy field spatial coordination of front heating + back vibration.

[0043] (3) The surface normal follows the movement of both sides in real time, so that the incident direction of the front laser beam and the back ultrasonic wave is always consistent with the surface normal, ensuring that the laser energy and ultrasonic energy act on the surface at the optimal angle, and ensuring the consistency of coating quality.

[0044] (4) Completely dehydrated design, eliminating liquid coupling medium, making the device suitable for high-temperature brazing environment.

[0045] (5) The laser brazing unit 200 and the ultrasonic vibration unit 400 are respectively set on both sides of the curved workpiece 600. The ultrasonic vibration unit 400 does not need to contact the high-temperature molten brazing filler metal, thus avoiding the problem of high-temperature corrosion and thermal damage to the ultrasonic vibration unit 400 in the front application method.

[0046] (6) The laser brazing unit 200 and the ultrasonic vibration unit 400 are respectively set on both sides of the curved workpiece 600. The back ultrasonic vibration unit 400 does not need to compete for space with the front laser brazing unit 200, making the structural layout more flexible and the curved surface more adaptable.

[0047] According to a second aspect of this application, an ultrasonic brazing method using the ultrasonic brazing apparatus described above is provided. The ultrasonic brazing method of this application is as follows.

[0048] In the embodiments of this application, the specific methods for calculating the normal vectors at each position of the brazing path in real time and planning the optimal postures of the laser brazing unit 200 and the ultrasonic vibration unit 400 are as follows.

[0049] First, a 3D vision sensor (e.g., a structured light 3D scanner or a laser profilometer; for example, a structured light 3D scanner with an accuracy of ±0.03mm and a scanning speed ≥1 million points / second) projects coded structured light onto the surface of the curved workpiece 600, and simultaneously captures images of the deformation of the stripes modulated by the curved surface using a camera. After triangulation calculation, the control system directly acquires the original 3D point cloud data of millions of spatially discrete points on the surface of the curved workpiece 600. Each point cloud data contains spatial XYZ 3D coordinate values ​​(x, y, z) and the corresponding reflection intensity. In some embodiments, it also includes an initial estimate of the surface normal at each point calculated by the camera's built-in software.

[0050] Then, the data processing module reconstructs the original point cloud into a digital model according to the following standard steps.

[0051] Step (1) Filtering and denoising: The statistical outlier removal (SOR) algorithm is used to calculate the average distance between each point and its nearest neighbors, and to remove discrete noise points whose distance exceeds the set standard deviation (usually 3σ) to obtain a clean target point cloud.

[0052] Step (2) Data Simplification and Registration: A voxel filter is used to downsample and homogenize the high-density point cloud, reducing the computational load. If the curved workpiece 600 requires multi-angle scanning, multiple point cloud data are registered to the same coordinate system based on the Iterative Closest Point (ICP) algorithm.

[0053] Step (3) Surface Reconstruction (NURBS Fitting): Based on the filtered point cloud, the discrete point lattice is transformed into a continuous parametric surface (i.e., a digital surface model) with explicit mathematical expressions by using the well-known B-spline surface or NURBS surface fitting algorithm.

[0054] The surface digital model is mathematically expressed using standard non-uniform rational B-splines (NURBS) in computer-aided geometric design.

[0055] Its general formula is: Where u and v are the surface parameter domain coordinates, and the u-direction, v-direction, and normal are mutually perpendicular. P i,j To control the coordinates of grid points, w i,j N is the weighting factor. i,p (u) and N j,q (v) represents the p-th and q-th order B-spline basis functions along the u and v directions, respectively. After acquiring the point cloud using a structured light 3D scanner, the control points are solved by inverse parametric reconstruction to establish the digital model of the surface.

[0056] After obtaining the surface digital model, the path planning module generates trajectory points for motion control of the soldering motion mechanism 100 and the ultrasonic motion mechanism 300 according to the following logic.

[0057] Step (1) Path topology generation: According to the requirements of the brazing process, the control system first generates a snake-shaped scanning (reciprocating) or spiral two-dimensional basic trajectory in the parameter domain (u, v coordinate system) of the curved surface through a linear equidistant or equal arc length interpolation algorithm.

[0058] Step (2) Spatial 3D Coordinate Mapping: Map the basic trajectory points in the parameter domain back to the surface digital model one by one, and calculate the 3D physical space coordinates (x, y, z) corresponding to each trajectory point. i y i , z i ).

[0059] Step (3) Normal vector calculation and attitude calibration: Based on the conventional differential geometry algorithm in this field, calculate the tangential partial derivative of the surface and the normal vector n at each trajectory point. i The final output of the control system consists of a series of data units, including: "three-dimensional spatial coordinates P". i +Unit normal vector n i +path spacing d".

[0060] The method for calculating the local normal vector n at each position point on the surface of the soldering path after generating the soldering path is as follows.

[0061] After determining the coordinates (u0, v0) of a certain parameter on the soldering path, its coordinates in Cartesian space are S0(u0, v0). Calculate the unit normal vector n of this point on the surface using the standard partial derivative cross product formula in this field.

[0062] , of which S u and S v These are the first-order partial derivatives of the surface equations with respect to u and v, respectively. It should be noted that all coordinate systems mentioned above are world coordinate systems.

[0063] Finally, based on the local normal vector n calculated above, the attitude matrices of the laser brazing unit 200 and the ultrasonic vibration unit 400 are solved respectively using the standard algebraic analytical method or Jacobi matrix iteration method of the brazing motion mechanism 100 and the ultrasonic motion mechanism 300 (six-axis industrial robot or five-axis linkage platform, repeatability positioning accuracy ±0.05mm) to ensure that their respective center point (TCP) and axial vector meet the requirements.

[0064] Specifically, let M be the homogeneous transformation matrix of the laser soldering unit 200 coordinate system relative to the world coordinate system. L The homogeneous transformation matrix of the ultrasonic vibration element's 400 coordinate system relative to the world coordinate system is M. R Z L and Z R These are the axial vectors of the laser brazing unit 200 and the ultrasonic vibration unit 400, respectively, expressed in the world coordinate system; where the origin of the coordinate system of the laser brazing unit 200 is the center point of the laser brazing unit 200, and the origin of the coordinate system of the ultrasonic vibration unit 400 is the center point of the ultrasonic vibration unit 400.

[0065] Set attitude alignment constraints, which satisfy: Z L =-Z R And Z L and -Z R The angle between the local normal vector n and the target angle is always no greater than a preset acceptable angle (the preset acceptable angle is, for example, 3°). The control system solves for the attitude alignment constraint in real time (converting it into the joint angles of the soldering motion mechanism 100 and the ultrasonic motion mechanism 300), and controls the soldering motion mechanism 100 and the ultrasonic motion mechanism 300 to ensure that Z... L and -Z R The angle between the local normal vector n and the target vector n is never greater than the preset acceptable angle.

[0066] In the embodiments of this application, during the brazing process, the coaxiality (alignment accuracy ≤ 0.1 mm) of the laser brazing unit 200 and the ultrasonic vibration unit 400 is monitored in real time, and automatic correction is performed when the alignment deviation exceeds the set threshold.

[0067] Specifically, the ultrasonic brazing device also includes a laser alignment transmitter 510 and a laser alignment receiving target 520; the laser alignment transmitter 510 is mounted on the laser brazing unit 200, and the laser alignment receiving target 520 is mounted on the ultrasonic vibration unit 400; during the synchronous movement of the laser brazing unit 200 and the ultrasonic vibration unit 400 along the brazing path of the curved workpiece 600, the laser alignment transmitter 510 emits a reference laser beam to the laser alignment receiving target 520; assuming the theoretical coincidence point of the axis where the center point of the laser alignment receiving target 520 and the center point of the laser alignment transmitter 510 are located is O0(0,0), and the coordinates of the measured light spot are P1(x1,y1), then the formula for calculating the real-time coaxiality deviation D is: Set a real-time coaxiality deviation constraint D, which satisfies: D ≤ deviation threshold; when D > deviation threshold, the control system calculates compensation amount (ΔT) for the coaxiality deviation D and its direction. x ΔT y ΔR x ΔR y ΔR z The system controls the soldering motion mechanism 100 and the ultrasonic motion mechanism 300 to ensure that D ≤ deviation threshold, i.e., the system automatically corrects the position and orientation of the two motion mechanisms within ≤50ms to restore coaxial alignment.

[0068] In summary, this application calculates the normal vector of each path point in real time based on the surface digital model, and plans the optimal posture of the laser brazing unit 200 and the ultrasonic vibration unit 400 respectively, so that the axes of the two always coincide and are consistent with the normal of the surface at that point (deviation ≤ 3°).

[0069] Optionally, in the embodiments of this application, the inclination angle θ and radius of curvature R of each point on the surface along the brazing path are calculated based on the surface digital model. When θ ≤ 30°, the ultrasonic vibration unit 400 adopts a longitudinal-torsional composite mode, which satisfies the following conditions: vibration frequency of 25–40 kHz, longitudinal amplitude of 5–15 μm, and torsional amplitude of 3–10 μm, promoting rapid spread of the brazing filler metal. When 30° < θ ≤ 75°, the ultrasonic vibration unit 400 adopts a low-frequency longitudinal mode, which satisfies the following conditions: vibration frequency of 15–25 kHz and amplitude of 10–20 μm, generating a strong acoustic flow effect to counteract the downward flow of the brazing filler metal caused by gravity. When θ > 75°, the ultrasonic vibration unit 400 adopts a combination of the longitudinal-torsional composite mode and the low-frequency longitudinal mode, taking into account both cavitation film breaking and acoustic flow promotion. The laser power of the laser brazing unit 200 is dynamically adjusted according to the radius of curvature R.

[0070] Optionally, in embodiments of this application, the ultrasonic brazing apparatus further includes an acoustic emission sensor 530 (frequency response range 10kHz~1MHz, sensitivity ≥60dB) and an ultrasonic transmission efficiency monitoring module. The acoustic emission sensor 530 is mounted on the ultrasonic vibration unit 400 or on the side of the curved workpiece 600 facing away from the laser brazing unit 200 to collect the intensity of the ultrasonic cavitation signal after transmission through the curved workpiece 600 in real time, for evaluating the ultrasonic transmission efficiency. The ultrasonic transmission efficiency monitoring module compares the output power P of the ultrasonic generator... 输出 The ultrasonic cavitation signal intensity P collected by the acoustic emission sensor 530 界面 Real-time calculation of ultrasonic transmission efficiency η, η=P 界面 / P 输出 When the attenuation of η relative to the reference value exceeds 30%, it is determined that the ultrasonic coupling is poor. The control system increases the contact pressure between the ultrasonic vibration unit 400 and the curved workpiece 600 (increase by 10-30%) and adjusts the posture of the ultrasonic vibration unit 400. If it still cannot be restored, an alarm is triggered to check the contact status of the ultrasonic vibration unit 400.

[0071] Optionally, in embodiments of this application, the ultrasonic brazing apparatus further includes a laser confocal displacement sensor 540 (accuracy ±0.005mm, sampling frequency ≥5kHz). The laser confocal displacement sensor 540 is installed in the laser brazing unit 200 and monitors the thickness of the brazing filler coating in real time at a sampling frequency of ≥5kHz. When the thickness of the brazing filler coating is detected to deviate from the set value (e.g., exceeding ±10%), the control system adjusts the linear velocity of the ultrasonic vibration unit 400 along the brazing path or adjusts the supply speed of the brazing filler powder in the laser brazing unit 200 within ≤0.3s to compensate.

[0072] Optionally, in the embodiments of this application, the ultrasonic brazing device further includes a dual-color infrared pyrometer 550 (temperature range 250~2000℃, accuracy ±3℃, response time ≤1ms). The dual-color infrared pyrometer 550 is installed in the laser brazing unit 200 to monitor the temperature field of the brazing area in real time. When the detected temperature exceeds the temperature threshold, the control system controls the laser brazing unit 200 to adjust the laser power.

[0073] Optionally, in embodiments of this application, the ultrasonic brazing apparatus further includes a high-speed color camera 560 (frame rate ≥ 1000fps), which is mounted on the laser brazing unit 200 to observe the spreading behavior of the brazing filler on the curved workpiece 600 in real time.

[0074] The ultrasonic brazing method of this application includes the following steps: Step S1: Reconstruct the NURBS surface digital model (accuracy ±0.05mm), and calculate the radius of curvature R, tilt angle θ, and normal vector n at various points on the surface.

[0075] Step S2: Based on the surface digital model, automatically generate the soldering path (equidistant or equal arc length path, with a spacing of 2 to 10 mm).

[0076] Simultaneously, the axial angle between the laser brazing unit 200 and the normal of the curved workpiece 600 is always ≤3°, the axial angle between the ultrasonic vibration unit 400 and the normal of the curved workpiece 600 is always ≤3°, and the coaxiality (alignment accuracy ≤0.1mm) of the laser brazing unit 200 and the ultrasonic vibration unit 400 is also planned.

[0077] Generate dual-sided six-axis linkage control code to ensure that the front laser focus and the back ultrasonic action point are located on opposite sides of the same position on the curved surface in space and move synchronously in time.

[0078] Step S3: Select the solder type according to the target coating requirements and load it into the supply device, and set the feeding parameters.

[0079] Step S4: Move the laser brazing unit 200 and the ultrasonic vibration unit 400 to the starting positions on the front and back sides of the curved workpiece 600, respectively, and then perform brazing. During the brazing process, ensure that the axial angle between the laser brazing unit 200 and the normal of the curved workpiece 600 is always ≤3°, the axial angle between the ultrasonic vibration unit 400 and the normal of the curved workpiece 600 is always ≤3°, and the coaxiality (alignment accuracy ≤0.1mm) of the laser brazing unit 200 and the ultrasonic vibration unit 400 is maintained.

[0080] Step S5: During the brazing process, firstly, a high-frequency longitudinal ultrasonic mode (frequency 50–80 kHz, amplitude 5–8 μm) is applied. After the high-frequency ultrasound is transmitted through the solid substrate to the interface, a strong cavitation effect is generated at the interface, effectively breaking down the oxide film on the curved surface (oxide film removal rate ≥95%) and activating the interface. Furthermore, the laser power is set to 110–120% of the rated value to rapidly establish the molten pool.

[0081] Subsequently, the ultrasonic mode is selected based on the local tilt angle θ of the curved surface, and the laser power of the laser brazing unit 200 is dynamically adjusted according to the radius of curvature R.

[0082] Step S6: Real-time monitoring and adaptive control of ultrasonic transmission efficiency.

[0083] Step S7: Online monitoring and closed-loop compensation of coating thickness.

[0084] Step S8: After the brazing is completed, perform slow cooling treatment (1-5℃ / min) or stress-relief annealing.

[0085] In summary, compared with the prior art, this application has the following beneficial effects: (1) Significant improvement in ultrasonic transmission efficiency. In this application, ultrasonic waves are transmitted from the back side through the solid base material to the interface. The acoustic impedance of the solid base material is about 10 times that of the liquid solder, and the ultrasonic attenuation coefficient is an order of magnitude lower than that of the liquid solder. Ultrasonic energy can reach the solder / base material interface directly and efficiently, and the transmission efficiency and stability are significantly better than the existing method of transmission through molten solder on the front side.

[0086] (2) Optimal energy field synergy of "front heating + back vibration". This application achieves perfect synergy between the laser brazing unit 200 on the front and the ultrasonic vibration unit 400 on the back by arranging them face-to-face, so that the laser focus and the ultrasonic action point are strictly aligned in space (coaxiality ≤ 0.1 mm) and precisely synchronized in time (synchronization delay ≤ 10 ms). The laser heats and melts the brazing filler metal from the front, and the ultrasonic waves act perpendicularly on the interface from the back. The two coincide in space and are synchronized in time, achieving optimal synergy between the two energy fields of "heating" and "vibration".

[0087] (3) The surface normal is followed in real time to ensure the optimal incident angle of the energy field. This application uses the synchronous control of the dual six-axis motion mechanism and the real-time calculation of the normal to ensure that the front laser beam and the back ultrasonic wave are both incident in a direction perpendicular to the curved surface (normal deviation ≤ 3°), thus maximizing the laser energy density and ultrasonic energy transmission efficiency.

[0088] (4) The ultrasonic vibration unit 400 tool head is protected from high-temperature corrosion. Since the ultrasound is applied from the back, the ultrasonic vibration unit 400 tool head does not need to come into contact with the high-temperature molten brazing filler metal, which avoids the problem of high-temperature corrosion and thermal damage to the tool head in the front application method, greatly extends the service life of the tool head, and ensures the long-term stability of ultrasonic transmission.

[0089] (5) Applicable to thin-walled and complex curved surface workpieces 600. For thin-walled components, the back ultrasonic can directly penetrate the base material and act on the interface, with a short transmission path and small energy loss; for complex curved surface workpieces 600, the back ultrasonic vibration unit 400 tool head does not need to compete with the front laser for space, the structural layout is more flexible, and the surface adaptability is stronger.

[0090] Furthermore, it is worth mentioning that in the embodiments of this application, such as Figure 2 As shown, the laser brazing unit 200 of this application includes a dynamic focusing module and a laser rangefinder. The dynamic focusing module adjusts the focal length in real time according to the surface topography, with a focusing range of ±20mm. The laser rangefinder (accuracy ±0.02mm, sampling frequency ≥2kHz) measures the distance between the laser focal point and the surface in real time and feeds it back to the dynamic focusing module to achieve closed-loop focusing, so that the defocusing amount is controlled within ±0.5mm.

[0091] Specifically, the dynamic focusing module includes at least one lens (the lens is a focusing lens with a response frequency ≥1kHz) that can move along the optical axis. The laser range sensor measures the distance data between the laser focus and the surface of the curved workpiece 600 in real time and feeds it back to the dynamic focusing module. When the distance data exceeds a preset threshold, the dynamic focusing module adjusts the movement of the lens in real time so that the distance data is controlled within the preset threshold.

[0092] In the embodiments of this application, such as Figure 2 As shown, the ultrasonic vibration unit 400 of this application includes an ultrasonic generator, an amplitude transformer, and a tool head connected in sequence. The tool head contacts the surface of the curved workpiece 600. The working end face of the tool head is a flat, curved, or flexible conformal structure to adapt to the shape of the back side of the curved workpiece 600 with different curvatures. There is no liquid coupling medium between the tool head and the back side of the curved workpiece 600; dry coupling is used (e.g., the tool head is a flexible component, and contact coupling is achieved through elastic compression) or the tool head contacts the surface of the curved workpiece 600 through a solid coupling medium, such as a graphite gasket or metal foil. With this configuration, this application eliminates the need for liquid coupling media in ultrasonic processing / inspection, employing dry or solid coupling methods. This completely avoids the limitation that liquid media such as water cannot be used in high-temperature brazing environments (800–1200°C), successfully applying the structural advantages of a "double-sided" design to the field of high-temperature processing.

[0093] This application illustrates the specific implementation method as follows: Example 1: The curved workpiece 600 is an aluminum alloy curved shell with a wall thickness of 1.5–3 mm. The base material is 6061 aluminum alloy (Al-Mg-Si system), with a solidus temperature of approximately 582℃ and a liquidus temperature of approximately 652℃. The solder is a Zn-Al-Si paste solder with a solidus temperature of approximately 380℃ and a liquidus temperature of approximately 420℃. The target coating thickness is 250±30 μm.

[0094] Implementation steps: (1) The shell is clamped and the structured light 3D scanner is used to scan and obtain the full surface morphology.

[0095] (2) Set the laser parameters: semiconductor laser (wavelength 980nm, maximum output power 1000W), reference power P0=750W, reference scanning speed v0=25mm / s, reference spot D0=3mm. The laser power is selected based on the following criteria: to make the temperature of the brazing area reach 440~480℃ (about 20~60℃ higher than the liquidus temperature of Zn-Al-Si brazing filler metal), and at the same time about 100℃ lower than the solidus temperature of 6061 aluminum alloy (582℃), so as to avoid overheating of the base material and grain coarsening.

[0096] (3) The ultrasonic vibration unit 400 synchronously follows the corresponding position on the back of the curved workpiece 600. The tool head and the back of the aluminum alloy are dry coupled (elastic clamping) with a contact pressure of 0.10-0.15MPa.

[0097] (4) Temperature monitoring: The dual-color infrared pyrometer 550 monitors the brazing temperature throughout the process, with a target of 440-480℃. When the temperature approaches 500℃ (about 80℃ above the solidus line 582℃ of 6061), the laser power is automatically fine-tuned (response time ≤50ms) to ensure that the base material does not overheat.

[0098] Thickness monitoring: A laser confocal displacement sensor 540 (sampling frequency 5kHz, accuracy ±0.005mm) monitors the coating thickness in real time. In a certain tilted area (θ≈40°), the coating was found to be too thin (measured 128μm, target 150μm, deviation -15%). The control system reduced the scanning speed from 20mm / s to 17mm / s (a decrease of 15%) and increased the paste solder extrusion rate from 0.8mL / min to 0.95mL / min (an increase of 19%) within 0.25s. The thickness recovered to 152μm after about 1.0s.

[0099] (5) The acoustic emission sensor 530 (frequency response 10kHz~1MHz) showed that the cavitation signal intensity after being conducted through 2.0mm aluminum alloy on the back side was 68~76% of the generator output power (η=68~76%), which was significantly higher than the typical value (30~50%) conducted through molten solder on the front side, verifying the superiority of the solid-state conduction path on the back side.

[0100] (6) Stress-relief annealing: 180℃×2h, vacuum degree ≤5×10 - ²Pa, cooled with the furnace.

[0101] Test results: Coating thickness: 243~277μm, uniformity ±10.8%.

[0102] Bond strength (adhesive tensile test, referring to ASTM C633 principle): average 51 MPa (fracture surface located at the coating / substrate interface, which is an interfacial fracture mode), approximately 35% higher than the front ultrasonic test; Microhardness: 85~105HV (load 100g).

[0103] Salt spray test (ASTM B117, 5% NaCl solution, 35°C): No corrosion propagation after 1000h (compared to corrosion occurring after 720h under the same conditions without ultrasonic assistance coating, an improvement of approximately 39%).

[0104] SEM observation of the coating cross section: The interface is continuous and without pores, the thickness of the intermetallic compound layer is about 2-4 μm, and there is no continuous brittle phase.

[0105] Example 2: The curved workpiece 600 is an aero-engine turbine blade. The blade surface is a three-dimensional freeform surface with a radius of curvature of 30–800 mm, an inclination angle of 0–85°, a wall thickness of 2–4 mm, and a surface area of ​​approximately 80 cm². The base material is K418 nickel-based cast high-temperature alloy with a solidus temperature of approximately 1295 °C and a liquidus temperature of approximately 1345 °C. The solder is Ni-Cr-Si-B alloy powder (BNi-2) with a particle size of 45–106 μm, a solidus temperature of 971 °C, and a liquidus temperature of 999 °C. The target coating thickness is 300 ± 50 μm.

[0106] Implementation steps: (1) The blade is clamped on the six-axis robot worktable, and the structured light 3D scanner is used to scan and acquire the point cloud of the blade surface (acquisition density 200 points / mm²), and the NURBS surface digital model is reconstructed. The digital twin mirror module performs path pre-planning in the virtual environment and generates an initial process parameter library.

[0107] (2) Setting laser parameters: fiber laser (wavelength 1070nm, maximum output power 2000W), reference power P0=1600W, reference scanning speed v0=15mm / s, reference spot diameter D0=4mm (flat-top beam, uniformity 95%). The laser power is selected based on the following criteria: to make the temperature of the brazing area reach 1050~1120℃ (about 50~120℃ higher than the liquidus temperature of BNi-2), while being about 175℃ lower than the solidus temperature of K418 base material (1295℃), to avoid overheating of the base material.

[0108] (3) Start the brazing process along the planned path (equal arc length spiral, arc length interval 3mm), in the order of blade base → blade back → blade edge. The back ultrasonic vibration unit 400 synchronously follows from the back of the blade, and the ultrasonic tool head contact pressure is 0.20~0.35MPa.

[0109] (4) Dual-color infrared pyrometer 550, which displays the brazing temperature of 1050~1120℃, with a temperature fluctuation of ±8℃.

[0110] (5) The laser confocal displacement sensor 540 (sampling frequency 5kHz, accuracy ±0.005mm) monitored the coating thickness from 282 to 328μm with a deviation of <±8%; during this period, two fine-tuning compensations were triggered: the first time was in the leaf basin-leaf back transition zone (thickness 12%), the scanning speed was reduced from 15mm / s to 13mm / s, the powder feeding rate was increased from 6.5g / min to 7.8g / min (increase of 20%), and the response time was 0.25s; the second time was in the leaf edge high curvature zone (thickness 14%), the scanning speed was increased from 11mm / s to 13mm / s, the powder feeding rate was reduced from 5.2g / min to 4.4g / min (decrease of 15%), and the response time was 0.28s.

[0111] (6) The acoustic emission sensor 530 (frequency response 10kHz~1MHz) showed that the intensity of the cavitation signal conducted on the back side was stable (fluctuation <±12%), and the ultrasonic transmission efficiency η=78~84% (conducted on the back side through solid base material), which was significantly higher than the typical value (30~50%) conducted on the front side through molten solder. High-speed color camera 560 (1000fps) observation showed that the solder spread wetting angle was 12-22° and the spreading speed was uniform.

[0112] (7) After the brazing is completed, it is slowly cooled to room temperature at 3℃ / min, and then subjected to vacuum stress relief annealing at 550℃ for 2h.

[0113] Test results: Coating thickness: 278~332μm, uniformity ±8.8%.

[0114] Interface bonding strength: average 81 MPa, more than 30% higher than that of frontal ultrasound-assisted bonding.

[0115] Coating microhardness: 695~730 HV (load 500g, hold for 15s), hardness fluctuation <5%.

[0116] Finally, it should be noted that the above-described embodiments are merely specific implementations of this application, used to illustrate the technical solutions of this application, and not to limit them. The protection scope of this application is not limited thereto. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the scope of the technology disclosed in this application, or make equivalent substitutions for some of the technical features. Such modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be covered within the protection scope of this application.

Claims

1. An ultrasonic brazing device, characterized in that, It includes a brazing motion mechanism, a laser brazing unit, an ultrasonic motion mechanism, and an ultrasonic vibration unit; wherein, each position on the curved workpiece to be processed has a local normal; the laser brazing unit and the ultrasonic vibration unit are respectively arranged on both sides of the curved workpiece that are opposite to each other in the normal direction; The brazing motion mechanism is connected to the laser brazing unit to drive the laser brazing unit to move along the brazing path of the curved workpiece. During the process, the angle between the axial direction of the laser brazing unit and the normal direction of the curved workpiece is controlled to never be greater than a preset qualified angle. The ultrasonic motion mechanism is connected to the ultrasonic vibration unit to drive the ultrasonic vibration unit to move synchronously with the laser brazing unit along the brazing path of the curved workpiece. During the process, the axial angle between the ultrasonic vibration unit and the normal of the curved workpiece is controlled to never be greater than the preset qualified axial angle.

2. The ultrasonic brazing apparatus according to claim 1, characterized in that, The ultrasonic brazing device also includes a three-dimensional vision sensor, which is used to perform a full-domain scan of the curved workpiece, reconstruct the point cloud data into a digital model of the curved surface, generate the brazing path, and calculate the local normal of each position point on the curved surface along the brazing path.

3. The ultrasonic brazing apparatus according to claim 2, characterized in that, The laser brazing unit further includes a laser alignment transmitter, and the ultrasonic vibration unit further includes a laser alignment receiving target. The laser alignment transmitter and the laser alignment receiving target are used to monitor the coaxiality of the laser brazing unit and the ultrasonic vibration unit in real time.

4. The ultrasonic brazing apparatus according to claim 2, characterized in that, The laser brazing unit also includes: A laser rangefinder sensor is used to measure the distance between the laser focus and the surface of the curved workpiece in real time, and to feed back the measured distance data to the dynamic focusing module. A dynamic focusing module, comprising at least one lens movable along the optical axis, is configured to: determine whether the distance data exceeds a preset distance range based on the distance data; if it does, drive the lens to move along the optical axis to adjust the distance data to the preset distance range. A laser confocal displacement sensor is used to monitor the thickness of the solder coating in real time. A high-speed color camera is used to observe the spreading behavior of brazing filler metal on the curved workpiece in real time. A dual-color infrared pyrometer is used to monitor the temperature of the brazing area in real time.

5. The ultrasonic brazing apparatus according to claim 1, characterized in that, The ultrasonic brazing device also includes an acoustic emission sensor and an ultrasonic transmission efficiency monitoring module. The acoustic emission sensor is installed on the side of the ultrasonic vibration unit or the curved workpiece facing away from the laser brazing unit, and is used to collect the intensity of the ultrasonic cavitation signal after transmission through the curved workpiece in real time. The ultrasonic vibration unit further includes an ultrasonic generator, an amplitude transformer, and a tool head connected in sequence. The tool head is in contact with the surface of the curved workpiece. The tool head is a flexible component, or the tool head is in contact with the surface of the curved workpiece through a solid coupling medium.

6. An ultrasonic brazing method using the ultrasonic brazing apparatus as described in any one of claims 1-5, characterized in that, The curved workpiece is scanned across the entire area using a 3D vision sensor, and the point cloud data is reconstructed into a digital model of the curved surface. A soldering path is generated based on the digital model of the curved surface, and the tilt angle θ, radius of curvature R, and local normal vector n of each position point on the curved surface along the soldering path are calculated. The brazing motion mechanism drives the laser brazing unit to perform brazing from one side of the curved workpiece along the brazing path, and controls the axial angle between the laser brazing unit and the normal angle of the curved workpiece to be no greater than a preset qualified angle. The vibration motion mechanism drives the ultrasonic vibration unit to apply vibration from the other side of the curved workpiece along the soldering path, and controls the axial angle between the ultrasonic vibration unit and the normal of the curved workpiece to be no greater than a preset qualified axial angle. The laser brazing unit further includes a laser alignment transmitter, and the ultrasonic vibration unit further includes a laser alignment receiving target. The laser brazing unit and the ultrasonic vibration unit move synchronously along the brazing path of the curved workpiece. During the movement, the laser alignment transmitter emits a reference laser beam to the laser alignment receiving target.

7. The ultrasonic brazing method according to claim 6, characterized in that, The brazing motion mechanism controls the axial angle between the laser brazing unit and the normal angle of the curved workpiece to be no greater than a preset acceptable angle, and the vibration motion mechanism controls the axial angle between the ultrasonic vibration unit and the normal angle of the curved workpiece to be no greater than a preset acceptable angle. Further, it includes: setting the homogeneous transformation matrix of the laser brazing unit coordinate system relative to the world coordinate system as M. L The homogeneous transformation matrix of the ultrasonic vibration unit coordinate system relative to the world coordinate system is M. R Z L and Z R These are the axial vectors of the laser brazing unit and the ultrasonic vibration unit, respectively, expressed in the world coordinate system; wherein the origin of the laser brazing unit coordinate system is the center point of the laser brazing unit, and the origin of the ultrasonic vibration unit coordinate system is the center point of the ultrasonic vibration unit. Set an attitude alignment constraint, which satisfies: Z L =-Z R And Z L and -Z R The angle between the local normal vector n and the target vector n is never greater than the preset acceptable angle. The attitude alignment constraint is solved in real time, and the soldering motion mechanism and the ultrasonic motion mechanism are controlled to ensure that Z... L and -Z R The angle between the local normal vector n and the target vector n is never greater than the preset acceptable angle.

8. The ultrasonic brazing method according to claim 6, characterized in that, During the synchronous movement of the laser brazing unit and the ultrasonic vibration unit along the brazing path of the curved workpiece, the laser centering transmitter emits a reference laser beam to the laser centering receiving target, further including; Let O0(0, 0) be the theoretical coincidence point of the axis between the center point of the laser centering receiving target and the center point of the laser centering transmitter, and let P1(x1, y1) be the coordinates of the measured light spot. Then the formula for calculating the real-time coaxiality deviation D is: ; A real-time coaxiality deviation D constraint is set, which satisfies: D ≤ deviation threshold; when D > deviation threshold, a compensation amount is calculated for the coaxiality deviation D and its direction, and the brazing motion mechanism and the ultrasonic motion mechanism are controlled so that D ≤ deviation threshold.

9. The ultrasonic brazing method according to claim 6, characterized in that, The ultrasonic brazing method further includes: during the brazing process along the brazing path, the laser brazing unit dynamically adjusts the laser power according to the radius of curvature R of each position on the curved surface along the brazing path; The ultrasonic vibration unit controls the applied vibration mode according to the tilt angle θ of each position point on the curved surface on the brazing path; When θ≤30°, the ultrasonic vibration unit adopts a longitudinal-torsional composite mode, which satisfies the following: vibration frequency of 25~40kHz, longitudinal amplitude of 5~15μm, and torsional amplitude of 3~10μm. When 30°<θ≤75°, the ultrasonic vibration unit adopts a low-frequency longitudinal mode, which satisfies the following conditions: vibration frequency of 15~25kHz and amplitude of 10~20μm. When θ > 75°, the ultrasonic vibration unit adopts a combination of the longitudinal-torsional composite mode and the low-frequency longitudinal mode.

10. The ultrasonic brazing method according to claim 6, characterized in that, The ultrasonic brazing method further includes: real-time acquisition of ultrasonic cavitation signals transmitted through the curved workpiece using an acoustic emission sensor, and comparison of the output power P of the ultrasonic generator using an ultrasonic transmission efficiency monitoring module. 输出 The ultrasonic cavitation signal intensity P collected by the acoustic emission sensor 界面 Real-time calculation of ultrasonic transmission efficiency η, η=P 界面 / P 输出 When the attenuation of η relative to the reference value exceeds 30%, the contact pressure between the ultrasonic vibration unit and the curved workpiece is increased. During the brazing process along the brazing path, the laser brazing unit monitors the thickness of the brazing filler metal coating in real time based on the laser copolymerization displacement sensor. When the thickness of the brazing filler metal coating deviates from the set value, the linear velocity of the ultrasonic vibration unit along the brazing path is adjusted, or the supply speed of the brazing filler metal powder of the laser brazing unit is adjusted. The temperature of the brazing area is monitored in real time using a dual-color infrared pyrometer. When the detected temperature exceeds the temperature threshold, the laser brazing unit is controlled to further adjust the laser power.

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