A method and system for controlling the macroscopic forming of weld seams in high-power single-mode laser welding

Abstract

This invention discloses a method and system for macroscopic forming control in high-power single-mode laser welding, belonging to the field of laser welding quality monitoring and control technology. The method first establishes a complete quadratic polynomial mapping model between weld penetration depth and laser power, welding speed, and defocusing amount based on process experiments. Through time-scale analysis, a dimensionless number S is defined to characterize the relative magnitude of the evaporation and heat conduction effects at the top and bottom of the keyhole, establishing a keyhole stability criterion. Based on the threshold range of S and the penetration depth model, a process window for good macroscopic forming is defined. In actual welding, the S value is calculated according to process parameters, and combined with the process window, rapid judgment of weld forming quality is achieved. The dimensionless number S criterion provided by this invention quantitatively reflects keyhole stability from a physical mechanism perspective, avoiding the blindness of traditional empirical methods, and can efficiently achieve process parameter control, improving the forming quality and process development efficiency of thick plate laser welding.

Description

Technical Field

[0001] This invention belongs to the field of laser welding technology, and in particular relates to a method and system for controlling the macroscopic forming of weld seams in high-power single-mode laser welding. Background Technology

[0002] Laser welding is an advanced manufacturing technology that uses a high-energy-density laser beam to join materials. It features high welding speed, deep penetration, and a small heat-affected zone, and is widely used in aerospace, rail transportation, and high-end equipment manufacturing. High-power single-mode laser welding, with its higher energy concentration and smaller spot size, more easily forms the keyhole structure required for deep penetration welding, making it an important technical approach for thick plate welding. This type of welding process typically operates in keyhole mode, essentially forming a dynamic vaporization channel supported by metal vapor within the material. The laser energy is efficiently absorbed through multiple reflections, thus achieving deep penetration welding.

[0003] However, in the keyhole mode, the welding process exhibits obvious unsteady characteristics. The keyhole undergoes strong dynamic changes under the combined influence of multiple factors such as evaporation backpressure, surface tension, and molten pool flow, and its stability directly determines the weld formation quality. Related studies have shown that multiple competing mechanisms exist within the keyhole. For example, evaporation backpressure promotes keyhole expansion, while surface tension and fluid damping tend to cause it to collapse. This fluctuation in mechanical balance can trigger keyhole morphological oscillations and lead to defects ([PMC][2]). When the keyhole stability is insufficient, problems such as porosity, spatter, and weld discontinuity are easily generated, seriously affecting the performance of the welded joint.

[0004] In existing technologies, research on keyhole stability and weld quality largely focuses on analyzing the impact of different process parameters on weld morphology through experimental methods. For example, by adjusting laser power, welding speed, or beam mode, changes in weld cross-sectional morphology and surface quality are observed to determine the applicable range of process parameters. Some studies have indicated that the laser power distribution and its interaction with the material significantly affect keyhole stability and weld quality; however, such studies typically rely on high-speed imaging or cross-sectional analysis for post-hoc evaluation, lacking unified quantitative criteria. Furthermore, although existing models attempt to describe keyhole behavior from the perspectives of energy and pressure, they are primarily used to explain phenomena or for localized analysis, making them difficult to directly apply to rapid decision-making and control of process parameters.

[0005] Furthermore, existing technologies typically employ an "experiment-correction" approach to determine welding processes in practical applications, gradually approximating suitable parameter combinations through numerous experiments. While this method can guarantee welding quality to some extent, it has significant limitations: firstly, the experimental process is time-consuming and labor-intensive, making it difficult to cover the complete process space under multi-parameter coupling conditions; secondly, complex coupling effects exist between different parameters, making it difficult to accurately reflect the true state of the welding process by relying solely on single-variable analysis. In addition, the construction of existing process windows is mostly based on single indicators such as penetration depth or surface finish, lacking direct characterization of keyhole dynamic stability, resulting in insufficient reliability when parameters shift or operating conditions change.

[0006] In summary, while existing technologies have studied the laser welding process from the perspectives of experimental observation and local modeling, they still lack a quantitative analysis method that can simultaneously combine process parameters, penetration response, and keyhole stability mechanisms. This makes it difficult to achieve rapid prediction and unified judgment of the macroscopic weld formation quality. This problem has become a significant factor restricting the efficient optimization and engineering application of high-power single-mode laser welding processes. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a method and system for controlling the macroscopic forming of high-power single-mode laser welding.

[0008] This invention is implemented as follows: A method for controlling the macroscopic forming of high-power single-mode laser welding includes:

[0009] S1: Constructing a mapping model between weld penetration depth and process parameters: Based on single-mode laser welding process experiments, weld penetration depth data under different combinations of laser power, welding speed and defocusing amount were obtained; a complete quadratic polynomial model containing linear terms, quadratic terms and pairwise interaction terms was adopted, and a weld penetration depth prediction model was established by fitting the model using the least squares method.

[0010] S2: Establish keyhole stability criteria: Through time-scale analysis, define the dimensionless number 𝑆 to characterize the relative magnitude of the evaporation effect and the heat conduction effect at the top and bottom of the keyhole; based on the laser beam dwell time and heat diffusion characteristic time, combined with the beam radius and heat diffusion length, derive the expression for the dimensionless number 𝑆.

[0011] S3: Determine the process window for good macroscopic forming: Based on the threshold range of the dimensionless number 𝑆, and combined with the weld penetration prediction model, divide the process range for laser power, welding speed and defocusing amount, and establish the process window for good macroscopic forming of the weld.

[0012] S4: Macroscopic forming control of weld: In the actual welding process, the dimensionless value of the keyhole top and bottom is calculated according to the set laser power, welding speed and defocusing amount, and the macroscopic forming quality of the weld is determined according to the threshold range and process window.

[0013] Furthermore, the process for establishing the mapping relationship between the weld penetration depth and process parameters is as follows:

[0014] S1.1: Experiments were conducted on single-mode laser welding process. By changing the laser power P (1~5kW), welding speed V (10~50mm / s), and defocusing amount D (-4~4mm), the weld penetration depth under different combinations of process parameters was obtained. The penetration depth was measured by metallographic specimens of the weld cross-section.

[0015] S1.2: Considering the nonlinear effects of laser power, defocusing amount, and welding speed on weld penetration and their possible interactions, a complete quadratic polynomial model containing all linear terms, quadratic terms, and pairwise interaction terms is adopted:

[0016]

[0017] in, Indicates the predicted melting depth. ~ The regression coefficients are to be calculated.

[0018] S1.3: Using the Statistics and Machine Learning Toolbox in Matlab R2017a, the least squares method is employed for parameter estimation. The calculated and fitted melt depth prediction curve can be represented as follows:

[0019]

[0020] By comparing the fitting residuals with the measured values, the weld penetration prediction curve can effectively reflect the relationship between laser power, welding speed, defocusing amount, and weld penetration.

[0021] Furthermore, the keyhole stability criterion establishment process for the single-mode laser welding process is as follows:

[0022] S2.1: Through time-scale analysis, a dimensionless number is derived to establish a keyhole stability criterion. Here, the dimensionless number 𝑆 is defined as representing the relative magnitude of the evaporation effect and the heat conduction effect of the keyhole.

[0023] S2.2: Assuming the laser beam moves forward at a welding speed of , the time it spends at the bottom of the keyhole or a certain point on the bottom is approximately the time required for the laser spot to sweep across the characteristic length of the keyhole. Let the characteristic distance of the keyhole be , then the dwell time of the laser beam is:

[0024]

[0025] The characteristic time required for heat to diffuse a characteristic distance *t* within a material via thermal conduction can be expressed as:

[0026]

[0027] Where α is the thermal diffusivity of the material;

[0028] S2.3: Further assumptions when t s ≈t d At this point, the evaporation effect and the heat conduction effect reach a dynamic equilibrium, and the keyhole is in a relatively stable state. Therefore, the dimensionless number S can be expressed as:

[0029]

[0030] S2.4: Assume that the top and bottom opening diameters of the keyhole are linearly superimposed by the radius *r* of the beam-irradiated region and the radius of expansion caused by thermal conduction, where the radius of the beam-irradiated region can be calculated using the Gaussian beam propagation formula:

[0031]

[0032] Where w0 is the radius of the beam on the focal plane, z R Rayleigh length, It is equal to the absolute value of the defocusing amount. The lateral expansion diameter caused by thermal conduction is represented by the characteristic length of thermal diffusion α / V, then the characteristic radius of thermal diffusion is α / (2V). Therefore, the characteristic distance can be obtained, which can be expressed as:

[0033]

[0034] S2.5: Substituting the equation, we can derive the expression for the dimensionless number 𝑆 as follows:

[0035]

[0036] S2.6: To verify the reliability of the proposed keyhole stability criterion, the surface and internal formation of the weld were observed under multiple sets of process parameters, and the dimensionless number S corresponding to the top of the keyhole (height is considered to be the workpiece surface, h=0) and the bottom of the keyhole (height h is calculated by the penetration depth prediction formula) under each set of process parameters was calculated.

[0037] The process for establishing a good macroscopic forming process window for single-mode laser welding provided in this embodiment of the invention is as follows:

[0038] S3.1: Determine the judgment process of good macroscopic weld formation process parameters, and calculate the three process parameters of laser power, welding speed and defocusing amount respectively;

[0039] S3.2: The process ranges at power levels of 1kW, 2kW, 3kW, 4kW, and 5kW were calculated according to the judgment process. This yielded process ranges with welding speeds of 0~50mm / s and defocusing amounts of -10~10mm at fixed power. As laser power increases, the process range, composed of defocusing amount and welding speed, changes from a continuous state to an intermittent state. Increased laser power significantly increases energy density, enhancing the evaporation effect during material interaction, leading to a narrower keyhole stability process window. When targeting deep penetration welding, the laser power can be set to the highest level, simultaneously matching negative defocusing and a medium speed (10~30mm / s).

[0040] S3.3: For welding speeds of 10mm / s, 20mm / s, 30mm / s, 40mm / s, and 50mm / s, process ranges with laser power in the range of 0~5kW and defocusing amount in the range of -10~10mm were obtained. As the welding speed increases, the process range under the power-defocusing amount combination continuously shifts downward and shrinks. This is because excessively fast welding speeds weaken the evaporation effect and enhance the heat conduction effect, thus making the keyhole wall surface lack sufficient support from the metal vapor back pressure, which in turn makes it prone to instability.

[0041] S3.4: Under the conditions of defocusing amounts of -4mm, -2mm, 0mm, 2mm and 4mm, the process ranges with laser power in the range of 0~5kW and welding speed in the range of 0~50mm / s were obtained. The defocusing amount mainly affects the energy distribution of the keyhole along the depth direction. When the defocusing amount is -4mm and -2mm, the process range is relatively large. However, when the defocusing amount increases to 4mm, the process range narrows rapidly with the increase of laser power. This indicates that it is easier to obtain good macroscopic seam formation under negative defocusing conditions.

[0042] Furthermore, the verification process for the 20mm thick TC4 titanium alloy single-mode laser welding process is as follows:

[0043] S4.1: In the preliminary process experiments, when the laser power was set to the maximum laser power (5kW), the weld penetration depth in the incomplete penetration state could reach 10-12mm. In order to achieve a weld penetration depth of more than 10mm on one side, the laser welding power was fixed at 5kW.

[0044] S4.2: Based on the penetration depth fitting formula of the judgment process for good weld macro-forming, the weld penetration depth prediction curve under the conditions of variable welding speed and variable defocus under fixed laser power can be obtained. When the laser power is 5kW, a weld penetration depth of about 11mm can be obtained by adjusting the defocus amount to 5mm.

[0045] S4.3: Calculate the trend of the steady state of the welding process with the welding speed according to the judgment process, and select appropriate process parameters;

[0046] S4.4: Based on the selected welding process parameters, a double-sided butt welding experiment was carried out on 20mm thick TC4 titanium alloy. The macroscopic weld formation was good, the weld morphology was continuous and uniform, and there were no welding defects such as spatter or undercut. No non-fusion defects or obvious porosity defects were found in the weld cross-section. The longitudinal section morphology of the weld was obtained by cutting along the center of the weld and it was found that there were no porosity defects inside the weld.

[0047] S4.5: On the basis of achieving good macroscopic shape of the weld, hardness test and tensile property test are performed on the weld. The microhardness of the weld area is greater than the hardness of the base material.

[0048] Another object of the present invention is to provide a high-power single-mode laser welding macroscopic forming control system, comprising:

[0049] The weld penetration prediction module is equipped with a mapping model between weld penetration and process parameters, which is used to output the predicted weld penetration based on the input laser power, welding speed and defocusing amount.

[0050] The stability criterion calculation module is used to calculate the dimensionless value of the keyhole top and bottom based on the input process parameters and material properties.

[0051] A process window storage module is used to store good macroscopic forming process windows under various combinations of process parameters established based on the dimensionless number K threshold range;

[0052] The quality judgment module is used to compare the dimensionless value of the actual process parameters with the threshold range, and output the macroscopic forming control result of the weld seam based on the comparison result.

[0053] Another object of the present invention is to provide a computer device including a memory and a processor, the memory storing a computer program, which, when executed by the processor, causes the processor to perform the steps of the high-power single-mode laser welding macro-forming control method.

[0054] Another object of the present invention is to provide a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the high-power single-mode laser welding macro-forming control method.

[0055] Another objective of the present invention is to provide an information data processing terminal for implementing the high-power single-mode laser welding macroscopic forming control system.

[0056] Based on the above technical solutions and the technical problems solved, please analyze the advantages and positive effects of the technical solution to be protected by this invention from the following aspects: (Specific description follows)

[0057] (1) This invention proposes a dimensionless keyhole stability criterion based on physical mechanism. By analyzing the time scale, the evaporation effect and the heat conduction effect are quantitatively compared, which can accurately reflect the stability state of the top and bottom of the keyhole, providing a scientific quantitative judgment index for the macroscopic forming quality of the weld, and overcoming the blindness of traditional empirical methods.

[0058] (2) This invention establishes a weld penetration prediction model that includes laser power, welding speed and defocusing amount, and defines a process window with good macroscopic forming through stability criteria. This process window comprehensively considers penetration, surface forming and internal defects, and can provide clear process parameter guidance for different welding requirements (such as large penetration and high-speed welding), significantly improving process development efficiency.

[0059] (3) The reliability of the proposed criterion was verified by experiments and defect-free welding was achieved in double-sided welding of 20mm thick TC4 titanium alloy. The tensile strength of the weld reached 94.7% of the base material, proving the engineering application value of this method in high-power laser welding of thick plates. Attached Figure Description

[0060] Figure 1 This is a flowchart of the macroscopic forming control method for high-power single-mode laser welding provided in an embodiment of the present invention.

[0061] Figure 2 This is a cloud map showing the predicted penetration depth under different defocusing amounts and welding speeds when the laser power is 5 kW.

[0062] Figure 3 This is a comparison chart of the predicted and measured weld penetration values ​​provided in the embodiments of the present invention.

[0063] Figure 4 This is a diagram showing the verification results of the keyhole stability criterion provided in an embodiment of the present invention.

[0064] Figure 5This is a process window diagram showing the good macroscopic forming of weld seams under different laser powers provided in the embodiments of the present invention.

[0065] Figure 6 This is a process window diagram showing the good macroscopic forming of welds at different welding speeds provided in the embodiments of the present invention.

[0066] Figure 7 This is a process window diagram of good macroscopic forming of weld seam under different decoking amounts provided in the embodiments of the present invention.

[0067] Figure 8 This is a macroscopic forming quality diagram of a 20mm thick TC4 titanium alloy double-sided weld provided in an embodiment of the present invention. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0069] like Figure 1 As shown, the high-power single-mode laser welding macroscopic shaping control method provided by this embodiment of the invention includes the following steps:

[0070] S1: Constructing a mapping model between weld penetration depth and process parameters: Based on single-mode laser welding process experiments, weld penetration depth data were obtained under different combinations of laser power, welding speed, and defocusing amount; a complete quadratic polynomial model containing linear terms, quadratic terms, and pairwise interaction terms was adopted, and a weld penetration depth prediction model was established through least-multiplication fitting.

[0071] S2: Establishing a keyhole stability criterion: Through time-scale analysis, a dimensionless number S is defined to characterize the relative magnitudes of the evaporation and heat conduction effects at the top and bottom of the keyhole; based on the laser beam dwell time and thermal diffusion characteristic time, combined with the beam radius and thermal diffusion length, an expression for the dimensionless number S is derived;

[0072] S3: Determine the process window for good macroscopic forming: Based on the threshold range of the dimensionless number S, and combined with the weld penetration prediction model, divide the process range for laser power, welding speed, and defocusing amount to establish the process window for good macroscopic forming of the weld.

[0073] S4: Macroscopic forming control of weld: In the actual welding process, the dimensionless number S value of the top and bottom of the keyhole is calculated according to the set laser power, welding speed and defocusing amount, and the macroscopic forming quality of the weld is determined according to the threshold range and process window.

[0074] The process for establishing the mapping relationship between weld penetration and process parameters provided in this embodiment of the invention is as follows:

[0075] S1.1: Experiments were conducted on single-mode laser welding process. By changing the laser power P (1~5kW), welding speed V (10~50mm / s), and defocusing amount D (-4~4mm), the weld penetration depth under different combinations of process parameters was obtained. The penetration depth was measured by metallographic specimens of the weld cross-section.

[0076] S1.2: Considering the nonlinear effects of laser power, defocusing amount, and welding speed on weld penetration and their possible interactions, a complete quadratic polynomial model containing all linear terms, quadratic terms, and pairwise interaction terms is adopted:

[0077]

[0078] in, Indicates the predicted melting depth. ~ The regression coefficients are to be calculated.

[0079] S1.3: Using the Statistics and Machine Learning Toolbox in Matlab R2017a, the least squares method is employed for parameter estimation. The calculated and fitted melt depth prediction curve can be represented as follows:

[0080]

[0081] Comparison of fitted residuals with measured values Figure 5-8 As shown, where R 2 The value reached 0.931, indicating a good fitting effect. The weld penetration prediction curve can effectively map the relationship between laser power, welding speed, defocusing amount and weld penetration.

[0082] The keyhole stability criterion establishment process provided in this embodiment of the invention is as follows:

[0083] S2.1: Through time-scale analysis, a dimensionless number is derived to establish a keyhole stability criterion. Here, the dimensionless number 𝑆 is defined as representing the relative magnitude of the evaporation effect and the heat conduction effect of the keyhole.

[0084] S2.2: Assuming the laser beam moves forward at a welding speed of , the time it spends at the bottom of the keyhole or a certain point on the bottom is approximately the time required for the laser spot to sweep across the characteristic length of the keyhole. Let the characteristic distance of the keyhole be , then the dwell time of the laser beam is:

[0085]

[0086] The characteristic time required for heat to diffuse a characteristic distance *t* within a material via thermal conduction can be expressed as:

[0087]

[0088] Where α is the thermal diffusivity of the material;

[0089] S2.3: Assume that when t s ≈t d At this point, the evaporation effect and the heat conduction effect reach a dynamic equilibrium, and the keyhole is in a relatively stable state. Therefore, the dimensionless number S can be expressed as:

[0090]

[0091] S2.4: Assume that the top and bottom opening diameters of the keyhole are linearly superimposed by the radius *r* of the beam-irradiated region and the radius of expansion caused by thermal conduction, where the radius of the beam-irradiated region can be calculated using the Gaussian beam propagation formula:

[0092]

[0093] Where w0 is the radius of the beam on the focal plane, z R Rayleigh length, It is equal to the absolute value of the defocusing amount. The lateral expansion diameter caused by thermal conduction is represented by the characteristic length of thermal diffusion α / V, then the characteristic radius of thermal diffusion is α / (2V). Therefore, the characteristic distance can be obtained, which can be expressed as:

[0094]

[0095] S2.5: Substituting the equation, we can derive the expression for the dimensionless number 𝑆 as follows:

[0096]

[0097] S2.6: To verify the reliability of the proposed keyhole stability criterion, the surface and internal formation of the weld were observed under 25 sets of process parameters. The dimensionless number S corresponding to the top of the keyhole (height is considered to be the workpiece surface, h=0) and the bottom of the keyhole (height h is calculated by the penetration depth prediction formula) under each set of process parameters was calculated. When the S value of the top is high (e.g., 9#, 12# and 20#), severe spatter defects appear on the weld surface and dense porosity defects appear inside the weld. When the S values ​​of the top and bottom are low (e.g., 5#, 14# and 25#), problems such as drastic fluctuations in weld penetration depth and distortion of weld surface formation occur. When the top and bottom are close to 1 (e.g., 4#), the weld surface formation is good, there are no spatter defects, and there are no porosity defects inside the weld with slight fluctuations in penetration depth. The overall macroscopic formation of the weld is good.

[0098] The process for establishing a good macroscopic forming process window for single-mode laser welding provided in this embodiment of the invention is as follows:

[0099] S3.1: Determine the judgment process of good macroscopic weld formation process parameters, and calculate the three process parameters of laser power, welding speed and defocusing amount respectively;

[0100] S3.2: The process ranges at power levels of 1kW, 2kW, 3kW, 4kW, and 5kW were calculated according to the judgment process. This yielded process ranges with welding speeds of 0~50mm / s and defocusing amounts of -10~10mm at fixed power. As the laser power increases, the process range composed of defocusing amount and welding speed changes from a continuous state to an intermittent state. The increase in laser power significantly increases the energy density, enhancing the evaporation effect during material interaction, leading to a narrower keyhole stability process window. When targeting deep welds, the laser power can be adjusted to the highest level, simultaneously matching negative defocusing and a medium speed (10~30mm / s).

[0101] S3.3: For welding speeds of 10mm / s, 20mm / s, 30mm / s, 40mm / s, and 50mm / s, process ranges with laser power in the range of 0~5kW and defocusing amount in the range of -10~10mm were obtained. As the welding speed increases, the process range under the power-defocusing amount combination continuously shifts downward and shrinks. This is because excessively fast welding speeds weaken the evaporation effect and enhance the heat conduction effect, thus making the keyhole wall surface lack sufficient support from the metal vapor back pressure, which in turn makes it prone to instability.

[0102] S3.4: Under the conditions of defocusing amounts of -4mm, -2mm, 0mm, 2mm and 4mm, the process ranges with laser power in the range of 0~5kW and welding speed in the range of 0~50mm / s were obtained. The defocusing amount mainly affects the energy distribution of the keyhole along the depth direction. When the defocusing amount is -4mm and -2mm, the process range is relatively large. However, when the defocusing amount increases to 4mm, the process range narrows rapidly with the increase of laser power. This indicates that it is easier to obtain good macroscopic weld formation under negative defocusing conditions.

[0103] The verification process of the 20mm thick TC4 titanium alloy single-mode laser welding process provided in this embodiment of the invention is as follows:

[0104] S4.1: In the preliminary process experiments, when the laser power was set to the maximum laser power (5kW), the weld penetration depth in the incomplete penetration state could reach 10-12mm. In order to achieve a weld penetration depth of more than 10mm on one side, the laser welding power was fixed at 5kW.

[0105] S4.2: Based on the penetration depth fitting formula of the judgment process for good weld macro-forming, the weld penetration depth prediction curve under the conditions of variable welding speed and variable defocusing under fixed laser power can be obtained. When the laser power is 5kW, a weld penetration depth of about 11mm can be obtained by adjusting the defocusing amount to 5mm.

[0106] S4.3: Based on the judgment process, the trend of the steady state of the welding process with the welding speed was calculated. When the welding speed is 15 mm / s, the S values ​​of the keyhole top and bottom are 1.12 and 1.05, respectively. Under this process condition, the values ​​of the keyhole top and bottom are very close to 1. Therefore, the process parameters selected in the process verification stage are: laser power 5kW, welding speed 15 mm / s, defocusing amount -5 mm;

[0107] S4.4: Based on the selected welding process parameters, a double-sided butt welding experiment was carried out on 20mm thick TC4 titanium alloy. The macroscopic weld formation was good, the weld morphology was continuous and uniform, and there were no welding defects such as spatter or undercut. No non-fusion defects or obvious porosity defects were found in the weld cross-section. The longitudinal section morphology of the weld was obtained by cutting along the center of the weld and it was found that there were no porosity defects inside the weld.

[0108] S4.5: Based on achieving good macroscopic weld formation, hardness and tensile properties tests were conducted on the weld. The microhardness of the weld area was greater than that of the base material. The average hardness of the weld was 358 HV, while that of the base material was 312 HV, representing an increase of 46 HV (14.7% higher than the base material). In terms of tensile strength, the tensile strength of the base material was 990 MPa. The tensile strengths of the weld under the three test paths (characterizing the upper, middle, and lower regions of the weld, respectively) reached 933 MPa, 947 MPa, and 934 MPa, respectively, with an average tensile strength of 938 MPa, reaching 94.7% of the strength of the base material.

[0109] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high power single mode laser welding macroshaping regulation method, characterized in that, Includes the following steps: Sample data on the relationship between laser power, welding speed, defocusing amount and weld penetration depth were obtained, and a weld penetration depth prediction model was established. A keyhole stability criterion was established based on time-scale analysis, and the dimensionless number S at the top and bottom of the keyhole was calculated respectively. Based on the weld penetration prediction model and the determination range of the dimensionless number S, the combination of laser power, welding speed and defocusing amount is screened to establish a good macroscopic forming process window for the weld. In the actual welding process, the set laser power, welding speed and defocusing amount are input to predict the weld penetration depth and calculate the dimensionless number S at the top and bottom of the keyhole. The predicted weld penetration depth and the dimensionless number S at the top and bottom of the keyhole are compared with the judgment conditions corresponding to the process window to output the macroscopic forming quality judgment result of the weld.

2. The high-power single-mode laser welding macroscopic forming control method as described in claim 1, characterized in that, The weld penetration prediction model is a complete quadratic polynomial model containing linear terms, quadratic terms, and pairwise interaction terms. The independent variables of the model are laser power, defocusing amount, and welding speed, and the dependent variable is weld penetration. The least squares method is used to obtain the regression coefficients.

3. The high-power single-mode laser welding macroscopic forming control method as described in claim 1, characterized in that, The dimensionless number S is established by the relationship between the dwell time of the laser beam on the material surface and the time required for heat to diffuse to the characteristic distance in the material; The characteristic distance is determined by the radius of the beam irradiation area and the characteristic radius of thermal diffusion. The radius of the beam illumination area is determined based on the propagation relationship of the beam in the defocused state; The thermal diffusivity radius is determined based on the material's thermal diffusivity and the welding speed. The dimensionless number S is used to characterize the relative magnitudes of the keyhole evaporation effect and the thermal conduction effect.

4. The high-power single-mode laser welding macroscopic forming control method as described in claim 1, characterized in that, The process of establishing a good macroscopic forming process window for the weld includes: With a fixed laser power, the parameters of welding speed and defocusing amount are calculated to obtain the corresponding process range. By fixing the welding speed, the corresponding process range is obtained by iterating through the parameter combinations of laser power and defocusing amount. With a fixed defocusing amount, the parameters of laser power and welding speed are traversed and calculated to obtain the corresponding process range; By cross-comparing the various process intervals, a good macroscopic forming process window for the weld that meets the predicted penetration depth requirements and the stability requirements of the keyhole top and bottom is obtained.

5. A high-power single-mode laser welding macroscopic forming control system, characterized in that, The method for controlling the macroscopic forming of high-power single-mode laser welding as described in any one of claims 1 to 4 includes: The data modeling module is used to build a weld penetration prediction model based on sample data of laser power, welding speed, defocusing amount, and weld penetration depth. The stability criterion module is used to calculate the dimensionless number S at the top and bottom of the keyhole based on process parameters and material thermal diffusion properties. The process window generation module is used to generate a good macroscopic forming process window for the weld based on the weld penetration prediction model and the judgment interval of the dimensionless number S. The quality assessment module is used to receive actual welding parameters, call the calculation results of the weld penetration prediction model and the stability criterion module, and generate the macroscopic forming quality assessment result of the weld in combination with the process window.

6. The high-power single-mode laser welding macroscopic forming control system as described in claim 5, characterized in that, The stability criterion module includes a top criterion unit and a bottom criterion unit. The top criterion unit is used to calculate the dimensionless number S at the top of the keyhole, and the bottom criterion unit is used to calculate the dimensionless number S at the bottom of the keyhole. The quality judgment module makes a joint judgment based on the calculation results of the top criterion unit and the bottom criterion unit.

7. The high-power single-mode laser welding macroscopic forming control system as described in claim 5, characterized in that, The process window generation module generates multiple two-dimensional process intervals by fixing a single parameter and linking the other two parameters, and maps and merges the multiple two-dimensional process intervals to form a three-parameter coupled process window dataset. The quality assessment module maps the actual welding parameters to the process window dataset and outputs a judgment result on whether the weld is in a good macroscopic forming state.

8. A laser welding macroscopic forming control device, characterized in that, The device includes a processor and a memory, wherein the memory stores program instructions, and when the program instructions are executed by the processor, the device invokes the high-power single-mode laser welding macro-forming control system according to any one of claims 5 to 7 to implement the high-power single-mode laser welding macro-forming control method according to any one of claims 1 to 4.

9. The laser welding macroscopic forming control equipment as described in claim 8, characterized in that, When the processor executes the program instructions, it first predicts the weld penetration depth based on the input laser power, welding speed and defocusing amount, then calculates the dimensionless number S at the top and bottom of the keyhole, and then combines the predicted penetration depth and dimensionless number S with the judgment conditions in the process window to output the macroscopic forming control result.

10. The laser welding macroscopic forming control equipment as described in claim 8, characterized in that, The device is also used to update the calculation parameters of the dimensionless number S according to the properties of the material to be welded when switching welding tasks, and to call the process window generation module or quality judgment module again according to the updated calculation parameters to output the macroscopic forming judgment result of the weld corresponding to the current material.

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