A dual-wavelength composite laser welding pore suppression method

Abstract

The application relates to the technical field of laser welding, and discloses a double-wavelength composite laser welding pore inhibition method, which comprises the following steps: pre-treating and laser cleaning the workpiece to be welded through laser cleaning parameters; coaxially or spatially outputting first-wavelength laser and second-wavelength laser; controlling the first-wavelength laser to act on a welding position to form a small-hole structure, and controlling the second-wavelength laser to act on a molten pool surface region around the small hole; adjusting the first-wavelength laser power density according to small-hole depth data, and adjusting the second-wavelength laser power density according to molten pool width data; synchronously and periodically modulating the power of the first-wavelength laser and the second-wavelength laser, and adjusting a modulation period according to a small-hole depth fluctuation amplitude; and controlling the scanning speed and the defocusing amount of the composite laser beam. The application can make the pore inhibition process run through the whole process of pre-welding, welding and solidification.

Description

Technical Field

[0001] This invention relates to the field of laser welding technology, and more specifically, to a method for suppressing porosity in dual-wavelength composite laser welding. Background Technology

[0002] In the field of laser welding technology, especially in deep penetration welding, the high energy density creates a pinhole structure in the molten pool. The back pressure of the vapor inside the pinhole and the surface tension of the molten pool are in a dynamic equilibrium. When this equilibrium is disturbed, the pinhole is prone to periodic fluctuations or even local collapse, causing shielding gas or metal vapor to be drawn into the molten pool. During solidification, this results in porosity defects, affecting the weld's density and mechanical properties.

[0003] In existing technologies, porosity problems are usually improved by optimizing a single laser parameter (such as power, scanning speed or defocusing amount) or by simple pre-weld surface cleaning methods. However, the above methods are mostly for controlling a single process step and lack systematic and coordinated control of the pre-weld interface state, the behavior of pinholes during welding, and the flow state of the molten pool.

[0004] Therefore, it is necessary to provide a dual-wavelength composite laser welding porosity suppression method to address the problem that existing methods for improving porosity often focus on controlling a single process step and lack systematic and coordinated control over the pre-welding interface state, pinhole behavior during welding, and molten pool flow state. Summary of the Invention

[0005] In view of this, the present invention proposes a method for suppressing porosity in dual-wavelength composite laser welding, which aims to solve the problem that existing methods for improving porosity are mostly aimed at controlling a single process step and lack systematic and coordinated control of the interface state before welding, the behavior of pinholes during welding, and the flow state of the molten pool.

[0006] This invention proposes a method for suppressing porosity in dual-wavelength composite laser welding, comprising: Collect surface condition data of the workpiece to be welded, and determine laser cleaning parameters based on the surface condition data; wherein, the surface condition data includes surface roughness parameters and oxide film thickness parameters; The workpiece to be welded is pre-treated by laser cleaning parameters to remove the surface oxide film and contaminant layer. The first wavelength laser and the second wavelength laser are coaxially combined or spatially paralleled to form a composite laser beam, and the power ratio and spot diameter of the first wavelength laser and the second wavelength laser are set. The first wavelength laser is controlled to act on the welding position to form a keyhole structure, and the second wavelength laser is controlled to act on the surface area of ​​the molten pool around the keyhole; Data on the pinhole depth and weld pool width are collected during the welding process. The power density of the first wavelength laser is adjusted based on the pinhole depth data, and the power density of the second wavelength laser is adjusted based on the weld pool width data. The first and second wavelength lasers are synchronously periodically modulated, and the modulation period is adjusted according to the fluctuation amplitude of the pinhole depth. By controlling the scanning speed and defocusing amount of the composite laser beam, the molten pool is continuously formed along the welding path and solidified.

[0007] Furthermore, determining the laser cleaning parameters based on the surface condition data includes: The scanning speed and pulse frequency for laser cleaning are determined based on the surface roughness parameters. The power density and treatment time of laser cleaning are determined based on the oxide film thickness parameter.

[0008] Furthermore, when determining the scanning speed and pulse frequency of laser cleaning based on the surface roughness parameter, the process includes: The arithmetic mean deviation of the surface profile of the workpiece to be welded is obtained as the surface roughness parameter. When the arithmetic mean deviation of the profile is greater than the preset first roughness threshold, the scanning speed of laser cleaning is set to the first scanning speed and the pulse frequency is set to the first pulse frequency. When the arithmetic mean deviation of the profile is less than or equal to the preset first roughness threshold and greater than the preset second roughness threshold, the scanning speed is set to the second scanning speed and the pulse frequency is set to the second pulse frequency. When the arithmetic mean deviation of the profile is less than or equal to the preset second roughness threshold, the scanning speed is set to the third scanning speed and the pulse frequency is set to the third pulse frequency. Among them, the first scan speed is less than the second scan speed, the second scan speed is less than the third scan speed; the first pulse frequency is greater than the second pulse frequency, and the second pulse frequency is greater than the third pulse frequency.

[0009] Furthermore, when determining the power density and action time of laser cleaning based on the oxide film thickness parameter, the process includes: Obtain the oxide film thickness parameters on the surface of the workpiece to be welded; The oxide film thickness parameter is compared with a preset thickness threshold. When the oxide film thickness parameter is greater than the preset thickness threshold, the power density of laser cleaning is set to a first power density and the action time is set to a first action time. When the oxide film thickness parameter is less than or equal to the preset thickness threshold and greater than the preset secondary thickness threshold, the power density of laser cleaning is set to the second power density and the action time is set to the second action time. When the oxide film thickness parameter is less than or equal to the preset secondary thickness threshold, the power density of laser cleaning is set to the third power density and the action time is set to the third action time. Among them, the first power density is greater than the second power density, the second power density is greater than the third power density; the first action time is greater than the second action time, and the second action time is greater than the third action time.

[0010] Furthermore, the step of coaxially combining the first wavelength laser and the second wavelength laser or spatially paralleling them to form a composite laser beam, and setting the power ratio and spot diameter of the first wavelength laser and the second wavelength laser, includes: Obtain the material type and plate thickness parameters of the workpiece to be welded; Select the corresponding target power ratio from the preset material parameter table according to the material type; Select the corresponding first spot diameter and second spot diameter from the preset thickness parameter table according to the plate thickness parameter; The output power of the first wavelength laser and the output power of the second wavelength laser are determined according to the target power ratio and the set total output power; wherein, the ratio of the output power of the first wavelength laser to the output power of the second wavelength laser is equal to the target power ratio; Adjust the focusing lens positions of the first wavelength laser and the second wavelength laser respectively, so that the spot diameter of the first wavelength laser is equal to the first spot diameter, and the spot diameter of the second wavelength laser is equal to the second spot diameter.

[0011] Furthermore, the step of acquiring the keyhole depth data and molten pool width data during the welding process, and adjusting the power density of the first wavelength laser based on the keyhole depth data, includes: A coaxial imaging device is used to acquire pinhole images of the welding area, and pinhole depth data is extracted based on the pinhole images; Compare the hole depth data with a preset hole depth range; When the aperture depth data is less than the preset lower limit, the power density of the first wavelength laser is gradually increased according to the preset power adjustment step size; When the aperture depth data is greater than the preset upper limit value, the power density of the first wavelength laser is gradually reduced according to the preset power adjustment step size; When the aperture depth data is within the preset aperture depth range formed by the preset lower limit and the preset upper limit, the power density of the first wavelength laser remains unchanged.

[0012] Furthermore, adjusting the power density of the second wavelength laser based on the molten pool width data includes: A coaxial imaging device is used to acquire images of the molten pool in the welding area, and the width data of the molten pool is extracted based on the images. Compare the molten pool width data with a preset molten pool width range; When the molten pool width data is less than the preset minimum value, the power density of the second wavelength laser is gradually increased according to the preset power adjustment step size; When the molten pool width data is greater than the preset maximum value, the power density of the second wavelength laser is gradually reduced according to the preset power adjustment step size; When the molten pool width data is within the preset molten pool width range formed by the preset minimum and preset maximum values, the power density of the second wavelength laser remains unchanged.

[0013] Furthermore, the synchronous periodic power modulation of the first wavelength laser and the second wavelength laser includes: Set the reference power density for the first wavelength laser and the reference power density for the second wavelength laser; Set the modulation period and modulation amplitude; During the modulation period, the power density of the first wavelength laser is periodically varied between a preset first up modulation amplitude and a preset first down modulation amplitude, with the reference power density of the first wavelength laser as the center. During the modulation period, the power density of the second wavelength laser is periodically varied between a preset second up-modulation amplitude and a preset second down-modulation amplitude, with the reference power density of the second wavelength laser as the center. The power change start time of the first wavelength laser and the second wavelength laser is kept consistent in each modulation cycle, so that they enter the periodic power change process synchronously.

[0014] Furthermore, adjusting the modulation period based on the fluctuation amplitude of the aperture depth includes: Acquire the pinhole depth data during the welding process, and calculate the difference between the maximum and minimum pinhole depths within adjacent modulation cycles as the pinhole depth fluctuation amplitude. The fluctuation amplitude of the hole depth is compared with a preset fluctuation amplitude threshold. When the fluctuation amplitude of the hole depth is greater than the preset fluctuation amplitude threshold, the modulation period is reduced by adjusting the step size according to the preset period. When the fluctuation amplitude of the hole depth is less than or equal to the preset fluctuation amplitude threshold, the modulation period is increased by adjusting the step size according to the preset period. The modulation period is adjusted by gradually increasing or decreasing based on the current modulation period.

[0015] Furthermore, the control of the scanning speed and defocusing amount of the composite laser beam to ensure the continuous formation and solidification of the molten pool along the welding path includes: Obtain the geometric trajectory information of the welding path, and identify straight line segments and curvature change points based on the geometric trajectory information; When in a straight line segment, set the scanning speed to a fixed value and the defocus amount to a fixed value, and keep them unchanged. When entering the curvature change point, the scanning speed is adjusted once with a fixed adjustment step size, and the defocus amount is adjusted once simultaneously with a fixed adjustment step size. The direction of the scanning speed adjustment is determined based on the molten pool width data. When the molten pool width is greater than the upper limit of the molten pool width, a decrease adjustment is performed. When the molten pool width is less than the lower limit of the molten pool width, an increase adjustment is performed. The direction of defocus adjustment is determined based on the aperture depth data. When the aperture depth is greater than the upper limit of the aperture depth, an increase adjustment is performed. When the aperture depth is less than the lower limit of the aperture depth, a decrease adjustment is performed. Each adjustment is performed only once, based on the change amount corresponding to the adjustment step size.

[0016] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention constructs a continuous process chain of surface pretreatment, dual-wavelength composite energy construction, coordinated control of the orifice and molten pool, periodic power modulation, and scanning and defocusing coupling control, enabling the porosity suppression process to run through the entire process of pre-welding, welding, and solidification. Specifically, by quantifying surface roughness parameters and oxide film thickness parameters and determining laser cleaning parameters accordingly, standardized treatment of the welding interface state is achieved, reducing the source of interface gas. A first-wavelength laser forms the orifice structure, and a second-wavelength laser acts on the molten pool area around the orifice, achieving spatial division of labor between deep melting formation and surface energy control. Synchronous acquisition of orifice depth and molten pool width, and feedback adjustment of the power density of the two lasers, achieves coordinated control of orifice stability and molten pool morphology. Dynamic adjustment of the dual-wavelength synchronous periodic power modulation period based on the orifice depth fluctuation amplitude suppresses unstable orifice fluctuations. Coupled control of scanning speed and defocusing amount ensures continuous molten pool formation and stable solidification, thereby reducing gas entrapment and retention conditions and improving the porosity suppression effect of the weld. Attached Figure Description

[0017] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A flowchart of a dual-wavelength composite laser welding porosity suppression method provided in an embodiment of the present invention. Detailed Implementation

[0018] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] In some embodiments of this application, see Figure 1 As shown, this embodiment provides a method for suppressing porosity in dual-wavelength composite laser welding, including the following steps: S100. Collect surface condition data of the workpiece to be welded, and determine laser cleaning parameters based on the surface condition data; wherein, the surface condition data includes surface roughness parameters and oxide film thickness parameters; S200: The workpiece to be welded is pre-treated by laser cleaning parameters to remove the surface oxide film and contaminant layer. S300: The first wavelength laser and the second wavelength laser are coaxially combined or spatially paralleled to form a composite laser beam, and the power ratio and spot diameter of the first wavelength laser and the second wavelength laser are set. S400: Control the first wavelength laser to act on the welding position to form a keyhole structure, and control the second wavelength laser to act on the surface area of ​​the molten pool around the keyhole. S500: Collect the pinhole depth data and molten pool width data during the welding process, and adjust the first wavelength laser power density according to the pinhole depth data and the second wavelength laser power density according to the molten pool width data; S600: Synchronously periodically modulate the power of the first wavelength laser and the second wavelength laser, and adjust the modulation period according to the fluctuation amplitude of the pinhole depth. S700 controls the scanning speed and defocusing amount of the composite laser beam, so that the molten pool is continuously formed along the welding path and solidification is completed.

[0020] It is understood that this invention constructs a continuous process chain encompassing surface pretreatment, dual-wavelength composite energy generation, synergistic control of the orifice and molten pool, periodic power modulation, and scanning and defocusing coupling control, enabling the porosity suppression process to run through the entire process of pre-welding, welding, and solidification. Specifically, steps S100–S200 quantify surface roughness and oxide film thickness parameters and determine laser cleaning parameters accordingly, achieving standardized treatment of the welding interface state and reducing the source of interface gases. Steps S300–S400 use a first-wavelength laser to form a orifice structure, with a second-wavelength laser acting around the orifice. In the molten pool region, spatial division of labor is achieved between deep melt formation and surface energy regulation; S500 achieves coordinated control of aperture stability and molten pool morphology by synchronously acquiring aperture depth and molten pool width and separately feeding back and adjusting the power density of the two lasers; S600 achieves suppression of aperture instability fluctuations by dynamically adjusting the dual-wavelength synchronous periodic power modulation period based on aperture depth fluctuation amplitude; S700 ensures continuous molten pool formation and stable solidification through coupled control of scanning speed and defocusing amount, thereby reducing gas entrapment and retention conditions as a whole and improving the weld porosity suppression effect.

[0021] In some specific embodiments of this application, determining the laser cleaning parameters based on the surface state data includes: The scanning speed and pulse frequency for laser cleaning are determined based on the surface roughness parameters. The power density and treatment time of laser cleaning are determined based on the oxide film thickness parameter.

[0022] It is understandable that different surfaces to be welded with different roughness and oxide film thickness require different laser cleaning energy inputs and intensities. By quantitatively matching the corresponding cleaning parameters, it is possible to avoid gas sources caused by oxide film and impurity residue due to insufficient cleaning, as well as surface pit defects caused by over-cleaning. This reduces the space for gas residue during welding and further ensures that the welding interface is uniform and stable after pretreatment, laying the foundation for subsequent stable welding and suppression of porosity formation.

[0023] In some specific embodiments of this application, determining the scanning speed and pulse frequency of laser cleaning based on the surface roughness parameter includes: The arithmetic mean deviation of the surface profile of the workpiece to be welded is obtained as the surface roughness parameter. When the arithmetic mean deviation of the profile is greater than the preset first roughness threshold, the scanning speed of laser cleaning is set to the first scanning speed and the pulse frequency is set to the first pulse frequency. When the arithmetic mean deviation of the profile is less than or equal to the preset first roughness threshold and greater than the preset second roughness threshold, the scanning speed is set to the second scanning speed and the pulse frequency is set to the second pulse frequency. When the arithmetic mean deviation of the profile is less than or equal to the preset second roughness threshold, the scanning speed is set to the third scanning speed and the pulse frequency is set to the third pulse frequency. Among them, the first scan speed is less than the second scan speed, the second scan speed is less than the third scan speed; the first pulse frequency is greater than the second pulse frequency, and the second pulse frequency is greater than the third pulse frequency.

[0024] Understandably, a higher surface roughness means greater surface undulation, making it easier for contaminants and oxide films to adhere to the pits and crevices. Therefore, a lower scanning speed is needed to ensure the laser's action time per unit area, while a higher pulse frequency can provide more concentrated energy action, ensuring thorough cleaning of impurities in the crevices. Conversely, a smoother surface requires a faster scanning speed and a lower pulse frequency to avoid over-cleaning and damaging the surface, ensuring cleaning effectiveness while avoiding unnecessary damage to the workpiece surface.

[0025] Specifically, the preset first roughness threshold and the preset second roughness threshold are determined based on the distribution range of the arithmetic mean deviation value of the surface profile of similar materials in history. The roughness data in the historical samples are sorted from high to low, and the high quantile is taken as the first roughness threshold, and the median distribution point is taken as the second roughness threshold, so as to form three surface state ranges: high, medium, and low. The first scanning speed, the second scanning speed, and the third scanning speed are determined based on the effective cleaning coverage speed range under different roughness ranges in the historical cleaning process. The first scanning speed corresponds to the minimum coverage speed under high roughness conditions, the third scanning speed corresponds to the maximum efficiency speed under low roughness conditions, and the second scanning speed serves as an intermediate transition speed. The first pulse frequency, the second pulse frequency, and the third pulse frequency are determined based on the frequency range corresponding to the optimal uniformity of energy input per unit area in the historical cleaning process. High roughness corresponds to a higher pulse frequency to improve the energy superposition density, while medium and low roughness correspond to a gradually decreasing pulse frequency to achieve matching control between energy input and surface state.

[0026] In some specific embodiments of this application, determining the power density and action time of laser cleaning based on the oxide film thickness parameter includes: Obtain the oxide film thickness parameters on the surface of the workpiece to be welded; The oxide film thickness parameter is compared with a preset thickness threshold. When the oxide film thickness parameter is greater than the preset thickness threshold, the power density of laser cleaning is set to a first power density and the action time is set to a first action time. When the oxide film thickness parameter is less than or equal to the preset thickness threshold and greater than the preset secondary thickness threshold, the power density of laser cleaning is set to the second power density and the action time is set to the second action time. When the oxide film thickness parameter is less than or equal to the preset secondary thickness threshold, the power density of laser cleaning is set to the third power density and the action time is set to the third action time. Among them, the first power density is greater than the second power density, the second power density is greater than the third power density; the first action time is greater than the second action time, and the second action time is greater than the third action time.

[0027] It is understood that the present invention introduces the oxide film thickness parameter into the graded judgment mechanism and sets a preset thickness threshold and a preset secondary thickness threshold to form a three-segment interval division, so that different oxide film thicknesses correspond to different combinations of laser cleaning power density and action time, thereby achieving graded matching control of energy input and material removal requirements.

[0028] Specifically, when the oxide film thickness is large, the power density is increased and the action time is extended to increase the energy input per unit area and the cumulative action time simultaneously, ensuring sufficient oxide film removal. When the oxide film thickness is in the medium range, a combination of intermediate power density and action time is used to achieve a balance between removal efficiency and substrate protection. When the oxide film thickness is small, the power density is reduced and the action time is shortened to avoid excessive thermal impact on the substrate material. Through the above-mentioned graded control, the laser cleaning energy input and the change in oxide film thickness are matched accordingly, thereby improving cleaning consistency and providing stable and clean interface conditions for subsequent welding processes, reducing the risk of porosity formation.

[0029] Furthermore, the preset thickness threshold and the preset secondary thickness threshold are determined based on the statistical distribution of the oxide film thickness of historical workpieces to be welded. The historical oxide film thickness data are sorted from largest to smallest, and the highest quantile is taken as the preset thickness threshold. The median distribution point or the engineering acceptable removal thickness boundary is taken as the preset secondary thickness threshold, thus forming three categories: thick oxide film, medium oxide film, and thin oxide film. The first power density, the second power density, and the third power density are determined based on the energy input level that achieves complete removal without causing damage to the substrate under different oxide film thickness conditions during historical laser cleaning processes. The first power density corresponds to the maximum energy input per unit area required for thick oxide film removal, the third power density corresponds to the minimum effective energy input for thin oxide film cleaning, and the second power density is an intermediate transitional energy level. The first action time, the second action time, and the third action time are determined based on the shortest effective action time range required for complete oxide film removal during historical cleaning processes and are matched with the corresponding power density to ensure the integrity of oxide film removal while avoiding excessive thermal effects that could affect the substrate performance.

[0030] In some specific embodiments of this application, the step of coaxially combining and spatially paralleling the first wavelength laser and the second wavelength laser to form a composite laser beam, and setting the power ratio and spot diameter of the first wavelength laser and the second wavelength laser, includes: Obtain the material type and plate thickness parameters of the workpiece to be welded; Select the corresponding target power ratio from the preset material parameter table according to the material type; Select the corresponding first spot diameter and second spot diameter from the preset thickness parameter table according to the plate thickness parameter; The output power of the first wavelength laser and the output power of the second wavelength laser are determined according to the target power ratio and the set total output power; wherein, the ratio of the output power of the first wavelength laser to the output power of the second wavelength laser is equal to the target power ratio; Adjust the focusing lens positions of the first wavelength laser and the second wavelength laser respectively, so that the spot diameter of the first wavelength laser is equal to the first spot diameter, and the spot diameter of the second wavelength laser is equal to the second spot diameter.

[0031] Understandably, by introducing material type and plate thickness parameters as the basis for setting dual-wavelength composite laser parameters, the power ratio and spot diameter of the first and second wavelength lasers can be matched with the physical properties of the workpiece. Determining the target power ratio by material type allows for targeted compensation of differences in laser absorption rate and melting characteristics among different materials; determining the spot diameter of the two lasers by plate thickness parameters ensures that the energy distribution pattern matches the required melting depth, guaranteeing consistency between pinhole formation and molten pool stability; simultaneously, by setting the total output power and distributing it according to the power ratio, the dual-wavelength energy input remains generally stable and internally adjustable, thereby achieving a synergistic match between deep melting capability and surface control capability, improving welding process stability and reducing the probability of porosity.

[0032] Specifically, the preset material parameter table is established based on the laser absorption rate, melting point range, and porosity sensitivity of different materials in historical welding experiments. The energy distribution ratio of the first and second wavelengths corresponding to the same type of materials under stable welding conditions is statistically classified and categorized. The corresponding target power ratio range is formed according to the material type, thereby realizing the differentiated energy distribution reference for different materials. The preset thickness parameter table is constructed based on the spot diameter range corresponding to the formation of stable small hole structures under different plate thicknesses in historical welding processes. The plate thickness is segmented from thin to thick, and the combination relationship of the first and second spot diameters that achieve stable melt depth and molten pool morphology control in each plate thickness range is recorded, thereby forming a corresponding mapping relationship between plate thickness and spot size, so that workpieces of different thicknesses can obtain matching energy action scale and molten pool geometry control conditions.

[0033] In some specific embodiments of this application, the step of collecting pinhole depth data and weld pool width data during the welding process, and adjusting the power density of the first wavelength laser based on the pinhole depth data, includes: A coaxial imaging device is used to acquire pinhole images of the welding area, and pinhole depth data is extracted based on the pinhole images; Compare the hole depth data with a preset hole depth range; When the aperture depth data is less than the preset lower limit, the power density of the first wavelength laser is gradually increased according to the preset power adjustment step size; When the aperture depth data is greater than the preset upper limit value, the power density of the first wavelength laser is gradually reduced according to the preset power adjustment step size; When the aperture depth data is within the preset aperture depth range formed by the preset lower limit and the preset upper limit, the power density of the first wavelength laser remains unchanged.

[0034] It is understandable that by using a coaxial imaging device to image the welding area in real time and extracting pinhole depth data based on the image, the pinhole state can be continuously quantified and characterized. By setting a preset pinhole depth range, the pinhole depth is controlled within a stable range, thus constraining the pinhole stability. When the pinhole depth deviates from this range, the power density of the first wavelength laser is corrected step by step according to a uniform power adjustment step size, so that the energy input change has a controllable discrete adjustment characteristic, thereby avoiding violent pinhole oscillations caused by power mutations. Through the above methods, the pinhole depth is always maintained near the stable range, reducing gas entrainment caused by pinhole collapse or over-penetration, thereby reducing the probability of porosity formation.

[0035] Specifically, the preset pinhole depth range is determined based on the statistical distribution of pinhole depth during historical stable welding processes. After sorting and analyzing the pinhole depth data from a large number of stable welding samples, the lower boundary of the stable forming interval is taken as the preset lower limit and the upper boundary as the preset upper limit, thus forming an allowable fluctuation range for stable pinhole existence. The preset power adjustment step size is determined based on the sensitivity of pinhole depth to power density changes during historical welding processes. By statistically analyzing the average change in pinhole depth caused by a unit change in power density, it is converted into the minimum power adjustment increment that can cause a detectable change in pinhole depth. This ensures that each adjustment can effectively correct deviations while avoiding sudden changes in pinhole state due to excessive adjustment amplitude, thus achieving stable hierarchical closed-loop control.

[0036] In some specific embodiments of this application, adjusting the power density of the second wavelength laser based on the molten pool width data includes: A coaxial imaging device is used to acquire images of the molten pool in the welding area, and the width data of the molten pool is extracted based on the images. Compare the molten pool width data with a preset molten pool width range; When the molten pool width data is less than the preset minimum value, the power density of the second wavelength laser is gradually increased according to the preset power adjustment step size; When the molten pool width data is greater than the preset maximum value, the power density of the second wavelength laser is gradually reduced according to the preset power adjustment step size; When the molten pool width data is within the preset molten pool width range formed by the preset minimum and preset maximum values, the power density of the second wavelength laser remains unchanged.

[0037] It is understandable that by using a coaxial imaging device to image the weld pool in real time and extracting the weld pool width data based on the image, continuous quantitative monitoring of the weld pool geometry can be achieved. By setting a preset weld pool width range, the weld pool width is limited within a stable forming range, keeping the lateral expansion and contraction of the weld pool under control. When the weld pool width deviates from this range, the power density of the second wavelength laser is adjusted stepwise according to a uniform power adjustment step size, so that the energy input corrects the weld pool width change in a discrete and controllable manner. This avoids the weld pool from fluctuating violently due to excessively rapid energy adjustment, keeps the weld pool width within a stable range, improves the consistency of the weld pool morphology, and reduces gas retention and entrapment caused by a weld pool that is too wide or too narrow, thereby reducing the risk of porosity formation.

[0038] Specifically, the preset range of molten pool width is determined based on the statistical results of molten pool width during historical stable welding processes. After sorting and analyzing the molten pool width data from a large number of stable welding samples, the lower bound corresponding to the stable molten pool formation state is taken as the preset minimum value and the upper bound as the preset maximum value, thus forming the allowable fluctuation range for stable molten pool formation. The preset power adjustment step size is determined based on the influence relationship between the change in the power density of the second wavelength laser and the molten pool width during historical welding processes. By statistically analyzing the average change in molten pool width caused by a change in unit power density, the smallest increment that can cause a stable and detectable change is taken as the adjustment step size, thereby achieving gradual closed-loop control of the molten pool width and avoiding instability of the molten pool shape due to excessive adjustment amplitude.

[0039] In some specific embodiments of this application, the synchronous periodic power modulation of the first wavelength laser and the second wavelength laser includes: Set the reference power density for the first wavelength laser and the reference power density for the second wavelength laser; Set the modulation period and modulation amplitude; During the modulation period, the power density of the first wavelength laser is periodically varied between a preset first up modulation amplitude and a preset first down modulation amplitude, with the reference power density of the first wavelength laser as the center. During the modulation period, the power density of the second wavelength laser is periodically varied between a preset second up-modulation amplitude and a preset second down-modulation amplitude, with the reference power density of the second wavelength laser as the center. The power change start time of the first wavelength laser and the second wavelength laser is kept consistent in each modulation cycle, so that they enter the periodic power change process synchronously.

[0040] Understandably, by setting reference power densities for the first and second wavelength lasers respectively, and introducing a unified modulation period and modulation amplitude, the power of the two lasers is synchronously and periodically disturbed under stable reference energy input conditions. Specifically, the first and second wavelength lasers periodically change around their respective reference power densities between corresponding upward and downward modulation amplitudes, and by controlling the start time of their power changes to be consistent, the energy input of the two wavelengths remains synchronized in the time dimension. This synchronous periodic power change can periodically disturb and regulate the flow state of the molten pool within the orifice without changing the overall energy input level, thereby weakening the continuous accumulation effect of unstable fluctuations within the orifice, improving orifice stability, reducing the formation of gas stagnation conditions, and thus reducing the probability of porosity formation.

[0041] Specifically, the reference power density of the first wavelength laser and the reference power density of the second wavelength laser are determined based on the average power density corresponding to the conditions of no obvious keyhole collapse and molten pool fluctuation during historical stable welding processes, and are used as the center values ​​of the stable energy input of the two lasers, respectively. The modulation period and modulation amplitude are determined based on the statistical results of the keyhole depth fluctuation frequency and molten pool oscillation period during historical welding processes, so that the modulation period is on the same order of magnitude as the natural fluctuation period of the keyhole, and the modulation amplitude is taken within the energy change range that does not cause molten pool instability but can produce observable disturbance response. The preset first upward modulation amplitude and the preset first downward modulation amplitude are determined based on the sensitivity of the first wavelength laser to keyhole depth changes, so that its upward and downward adjustment amplitudes can cover the energy correction range required for keyhole stability maintenance. The preset second upward modulation amplitude and the preset second downward modulation amplitude are determined based on the influence characteristics of the second wavelength laser on the molten pool surface flow and width change, so that its adjustment amplitudes can correspond to the lateral stability control requirements of the molten pool, thereby realizing synchronous disturbance control of the two wavelengths under different action mechanisms.

[0042] In some specific embodiments of this application, adjusting the modulation period based on the fluctuation amplitude of the pinhole depth includes: Acquire the pinhole depth data during the welding process, and calculate the difference between the maximum and minimum pinhole depths within adjacent modulation cycles as the pinhole depth fluctuation amplitude. The fluctuation amplitude of the hole depth is compared with a preset fluctuation amplitude threshold. When the fluctuation amplitude of the hole depth is greater than the preset fluctuation amplitude threshold, the modulation period is reduced by adjusting the step size according to the preset period. When the fluctuation amplitude of the hole depth is less than or equal to the preset fluctuation amplitude threshold, the modulation period is increased by adjusting the step size according to the preset period. The modulation period is adjusted by gradually increasing or decreasing based on the current modulation period.

[0043] Understandably, by calculating the difference between the maximum and minimum pinhole depths within adjacent modulation cycles during the welding process, the pinhole depth fluctuation amplitude is obtained. A preset fluctuation amplitude threshold is then used as the criterion to quantitatively evaluate pinhole stability. When the fluctuation amplitude is large, the modulation period is reduced to increase the modulation frequency, thereby increasing the number of power disturbance responses per unit time and enhancing the ability to suppress pinhole instability. When the fluctuation amplitude is small, the modulation period is increased to reduce the disturbance frequency, allowing the system to tend towards a stable energy input state and avoiding over-modulation that introduces new fluctuations. Through a periodic adaptive adjustment method based on fluctuation amplitude feedback, dual-wavelength synchronous power modulation can be matched with the dynamic stability of the pinhole, thereby improving the pinhole structural stability and reducing gas retention and porosity formation caused by periodic fluctuation mismatch.

[0044] Specifically, the preset fluctuation amplitude threshold is determined based on the statistical results of pinhole depth fluctuation data during historical stable welding processes. After sorting and analyzing the pinhole depth fluctuation amplitude in a large number of stable forming welding samples, the upper limit of the fluctuation amplitude when in a stable welding state is taken as the judgment threshold to distinguish between stable fluctuation and unstable fluctuation states. The preset cycle adjustment step size is determined based on the response relationship of historical modulation cycle changes to the pinhole depth fluctuation suppression effect. By analyzing the change in pinhole fluctuation amplitude caused by unit modulation cycle change, the smallest cycle adjustment amount that can cause a detectable change in the fluctuation state is taken as the adjustment step size, so that the modulation cycle adjustment process is gradual and controllable, and avoids the enhancement of pinhole oscillation due to abrupt cycle changes.

[0045] In some specific embodiments of this application, controlling the scanning speed and defocusing amount of the composite laser beam to continuously form and solidify the molten pool along the welding path includes: Obtain the geometric trajectory information of the welding path, and identify straight line segments and curvature change points based on the geometric trajectory information; When in a straight line segment, set the scanning speed to a fixed value and the defocus amount to a fixed value, and keep them unchanged. When entering the curvature change point, the scanning speed is adjusted once with a fixed adjustment step size, and the defocus amount is adjusted once simultaneously with a fixed adjustment step size. The direction of the scanning speed adjustment is determined based on the molten pool width data. When the molten pool width is greater than the upper limit of the molten pool width, a decrease adjustment is performed. When the molten pool width is less than the lower limit of the molten pool width, an increase adjustment is performed. The direction of defocus adjustment is determined based on the aperture depth data. When the aperture depth is greater than the upper limit of the aperture depth, an increase adjustment is performed. When the aperture depth is less than the lower limit of the aperture depth, a decrease adjustment is performed. Each adjustment is performed only once, based on the change amount corresponding to the adjustment step size.

[0046] Understandably, a partitioned strategy for scanning and defocusing control is implemented by dividing the welding path into straight segments and curvature change points. Fixed scanning speed and defocusing amounts are used in the straight segments to maintain stable energy input and molten pool morphology, reducing unnecessary parameter fluctuations. Fixed adjustment step sizes are introduced at curvature change points for single-step discrete adjustments, ensuring deterministic and controllable parameter changes and preventing system oscillations caused by continuous adjustments. A control interval is established using the upper and lower limits of the molten pool width to directionally correct the scanning speed, keeping the lateral dimensions of the molten pool within a stable range. The upper and lower limits of the pinhole depth constrain the defocusing amount, maintaining the pinhole depth within a stable forming range. By combining partitioned control with interval constraints, the scanning speed and defocusing amount correspond to the geometric stability of the molten pool and the structural stability of the pinhole, respectively, achieving structured and stable control of the welding process, thereby reducing the risk of porosity formation caused by path changes and local instability.

[0047] Specifically, the fixed scanning speed value is determined based on the average scanning speed under the condition of stable molten pool width and minimal spatter during historical straight-line welding, ensuring that it meets the requirements of stable energy input and continuous molten pool formation. The fixed defocusing value is determined based on the average defocusing position when the keyhole depth remains stable during historical stable welding without collapse or over-penetration, ensuring a stable energy coupling state. The fixed adjustment step size is determined based on the minimum observable change in the impact of historical parameter adjustments on molten pool width and keyhole depth, ensuring that each adjustment provides effective control while avoiding abrupt state changes due to excessively large step sizes. The upper and lower limits of molten pool width are determined based on the statistical distribution range of molten pool width during historical stable welding, using the fluctuation boundary of the stable forming state as the constraint range. The upper and lower limits of keyhole depth are determined based on the stable range of keyhole depth during historical stable keyhole formation, limiting the allowable variation range of keyhole structure to maintain a stable through-hole state, thereby achieving dual constraint control of the geometric shape of the welding process.

[0048] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program goods. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program goods embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0049] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program goods according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0050] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0051] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for suppressing porosity in dual-wavelength composite laser welding, characterized in that, include: Collect surface condition data of the workpiece to be welded, and determine laser cleaning parameters based on the surface condition data; wherein, the surface condition data includes surface roughness parameters and oxide film thickness parameters; The workpiece to be welded is pre-treated by laser cleaning parameters to remove the surface oxide film and contaminant layer. The first wavelength laser and the second wavelength laser are coaxially combined or spatially paralleled to form a composite laser beam, and the power ratio and spot diameter of the first wavelength laser and the second wavelength laser are set. The first wavelength laser is controlled to act on the welding position to form a keyhole structure, and the second wavelength laser is controlled to act on the surface area of ​​the molten pool around the keyhole. Data on the pinhole depth and weld pool width are collected during the welding process. The power density of the first wavelength laser is adjusted based on the pinhole depth data, and the power density of the second wavelength laser is adjusted based on the weld pool width data. The first and second wavelength lasers are synchronously periodically modulated, and the modulation period is adjusted according to the fluctuation amplitude of the pinhole depth. By controlling the scanning speed and defocusing amount of the composite laser beam, the molten pool is continuously formed along the welding path and solidified.

2. The method for suppressing porosity in dual-wavelength composite laser welding according to claim 1, characterized in that, Determining the laser cleaning parameters based on the surface condition data includes: The scanning speed and pulse frequency for laser cleaning are determined based on the surface roughness parameters. The power density and treatment time of laser cleaning are determined based on the oxide film thickness parameter.

3. The method for suppressing porosity in dual-wavelength composite laser welding according to claim 2, characterized in that, Determining the scanning speed and pulse frequency for laser cleaning based on the surface roughness parameters includes: The arithmetic mean deviation of the surface profile of the workpiece to be welded is obtained as the surface roughness parameter. When the arithmetic mean deviation of the profile is greater than the preset first roughness threshold, the scanning speed of laser cleaning is set to the first scanning speed and the pulse frequency is set to the first pulse frequency. When the arithmetic mean deviation of the profile is less than or equal to the preset first roughness threshold and greater than the preset second roughness threshold, the scanning speed is set to the second scanning speed and the pulse frequency is set to the second pulse frequency. When the arithmetic mean deviation of the profile is less than or equal to the preset second roughness threshold, the scanning speed is set to the third scanning speed and the pulse frequency is set to the third pulse frequency. Among them, the first scan speed is less than the second scan speed, the second scan speed is less than the third scan speed; the first pulse frequency is greater than the second pulse frequency, and the second pulse frequency is greater than the third pulse frequency.

4. The method for suppressing porosity in dual-wavelength composite laser welding according to claim 2, characterized in that, Determining the power density and action time of laser cleaning based on the oxide film thickness parameter includes: Obtain the oxide film thickness parameters on the surface of the workpiece to be welded; The oxide film thickness parameter is compared with a preset thickness threshold. When the oxide film thickness parameter is greater than the preset thickness threshold, the power density of laser cleaning is set to a first power density and the action time is set to a first action time. When the oxide film thickness parameter is less than or equal to the preset thickness threshold and greater than the preset secondary thickness threshold, the power density of laser cleaning is set to the second power density and the action time is set to the second action time. When the oxide film thickness parameter is less than or equal to the preset secondary thickness threshold, the power density of laser cleaning is set to the third power density and the action time is set to the third action time. Among them, the first power density is greater than the second power density, the second power density is greater than the third power density; the first action time is greater than the second action time, and the second action time is greater than the third action time.

5. The method for suppressing porosity in dual-wavelength composite laser welding according to claim 1, characterized in that, The process of coaxially combining and spatially paralleling the first and second wavelength lasers to form a composite laser beam, and setting the power ratio and spot diameter of the first and second wavelength lasers, includes: Obtain the material type and plate thickness parameters of the workpiece to be welded; Select the corresponding target power ratio from the preset material parameter table according to the material type; Select the corresponding first spot diameter and second spot diameter from the preset thickness parameter table according to the plate thickness parameter; The output power of the first wavelength laser and the output power of the second wavelength laser are determined according to the target power ratio and the set total output power; wherein, the ratio of the output power of the first wavelength laser to the output power of the second wavelength laser is equal to the target power ratio; Adjust the focusing lens positions of the first wavelength laser and the second wavelength laser respectively, so that the spot diameter of the first wavelength laser is equal to the first spot diameter, and the spot diameter of the second wavelength laser is equal to the second spot diameter.

6. The method for suppressing porosity in dual-wavelength composite laser welding according to claim 1, characterized in that, The process of acquiring pinhole depth data and weld pool width data during the welding process, and adjusting the power density of the first wavelength laser based on the pinhole depth data, includes: A coaxial imaging device is used to acquire pinhole images of the welding area, and pinhole depth data is extracted based on the pinhole images; Compare the hole depth data with a preset hole depth range; When the aperture depth data is less than the preset lower limit, the power density of the first wavelength laser is gradually increased according to the preset power adjustment step size; When the aperture depth data is greater than the preset upper limit value, the power density of the first wavelength laser is gradually reduced according to the preset power adjustment step size; When the aperture depth data is within the preset aperture depth range formed by the preset lower limit and the preset upper limit, the power density of the first wavelength laser remains unchanged.

7. The method for suppressing porosity in dual-wavelength composite laser welding according to claim 6, characterized in that, When adjusting the power density of the second wavelength laser based on the molten pool width data, the following steps are included: A coaxial imaging device is used to acquire images of the molten pool in the welding area, and the width data of the molten pool is extracted based on the images. Compare the molten pool width data with a preset molten pool width range; When the molten pool width data is less than the preset minimum value, the power density of the second wavelength laser is gradually increased according to the preset power adjustment step size; When the molten pool width data is greater than the preset maximum value, the power density of the second wavelength laser is gradually reduced according to the preset power adjustment step size; When the molten pool width data is within the preset molten pool width range formed by the preset minimum and preset maximum values, the power density of the second wavelength laser remains unchanged.

8. The method for suppressing porosity in dual-wavelength composite laser welding according to claim 1, characterized in that, The synchronous periodic power modulation of the first wavelength laser and the second wavelength laser includes: Set the reference power density for the first wavelength laser and the reference power density for the second wavelength laser; Set the modulation period and modulation amplitude; During the modulation period, the power density of the first wavelength laser is periodically varied between a preset first up modulation amplitude and a preset first down modulation amplitude, with the reference power density of the first wavelength laser as the center. During the modulation period, the power density of the second wavelength laser is periodically varied between a preset second up-modulation amplitude and a preset second down-modulation amplitude, with the reference power density of the second wavelength laser as the center. The power change start time of the first wavelength laser and the second wavelength laser is kept consistent in each modulation cycle, so that they enter the periodic power change process synchronously.

9. The method for suppressing porosity in dual-wavelength composite laser welding according to claim 8, characterized in that, When adjusting the modulation period based on the fluctuation amplitude of the aperture depth, the following steps are included: Acquire the pinhole depth data during the welding process, and calculate the difference between the maximum and minimum pinhole depths within adjacent modulation cycles as the pinhole depth fluctuation amplitude. The fluctuation amplitude of the hole depth is compared with a preset fluctuation amplitude threshold. When the fluctuation amplitude of the hole depth is greater than the preset fluctuation amplitude threshold, the modulation period is reduced by adjusting the step size according to the preset period. When the fluctuation amplitude of the hole depth is less than or equal to the preset fluctuation amplitude threshold, the modulation period is increased by adjusting the step size according to the preset period. The modulation period is adjusted by gradually increasing or decreasing based on the current modulation period.

10. The method for suppressing porosity in dual-wavelength composite laser welding according to claim 1, characterized in that, The process of controlling the scanning speed and defocusing amount of the composite laser beam to ensure the continuous formation and solidification of the molten pool along the welding path includes: Obtain the geometric trajectory information of the welding path, and identify straight line segments and curvature change points based on the geometric trajectory information; When in a straight line segment, set the scanning speed to a fixed value and the defocus amount to a fixed value, and keep them unchanged. When entering the curvature change point, the scanning speed is adjusted once with a fixed adjustment step size, and the defocus amount is adjusted once simultaneously with a fixed adjustment step size. The direction of the scanning speed adjustment is determined based on the molten pool width data. When the molten pool width is greater than the upper limit of the molten pool width, a decrease adjustment is performed. When the molten pool width is less than the lower limit of the molten pool width, an increase adjustment is performed. The direction of defocus adjustment is determined based on the aperture depth data. When the aperture depth is greater than the upper limit of the aperture depth, an increase adjustment is performed. When the aperture depth is less than the lower limit of the aperture depth, a decrease adjustment is performed. Each adjustment is performed only once, based on the change amount corresponding to the adjustment step size.

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