A laser homogenization reshaping spot global temperature control preheating scanning welding method and system

Abstract

The application discloses a laser homogenization shaping spot global temperature control preheating scanning welding method and system, first, according to the workpiece spectral characteristics, a function solidified isolation double laser light source is matched, a multimodule composite homogenization assembly is selected and matched to output a flat-top spot global homogenization preheating of full coverage of the workpiece, and the temperature gradient of the plate surface is eliminated; the precision scanning welding of the galvanometer is completed through the coaxial double-layer wrapped double-spot under the workpiece constant temperature base, the global gradient tempering is used for slow release of the residual stress after welding, and the global array temperature measurement double-layer closed loop temperature control full process temperature stabilization is adopted. The traditional local preheating of the weld is abandoned, the wavelength matching of the material matching is relied on, the multi-stage homogenization, the global gradient tempering, the temperature field linkage compensation and the light source time sequence interlocking are adopted, the thin-walled part warping and springback are inhibited from the heat transfer mechanism, the uniformity and the mass production yield of the multi-material welding are improved, and the method is suitable for the precise welding of various metals with the thickness of 0.01-2 mm.

Description

Technical Field

[0001] This invention belongs to the field of laser scanning welding technology, and particularly relates to a laser homogenization and shaping spot temperature control preheating scanning welding method and system. Background Technology

[0002] Existing laser welding processes have several limitations that make it difficult to meet the mass production requirements for precision thin-walled workpieces with low deformation and high consistency:

[0003] Localized preheating leads to large temperature differences in the workpiece, resulting in prominent welding deformation defects in thin-walled parts. Currently, the industry commonly uses weld-following localized preheating, heating only a narrow area of ​​the weld. This results in a huge temperature gradient across the entire workpiece. Rapid localized cooling after welding easily causes warping, springback, and wavy deformation. It is impossible to eliminate the temperature difference across the entire plate from the heat transfer mechanism, leading to a low welding yield for thin-walled parts. At the same time, the lack of a post-weld full-area gradient tempering process further exacerbates forming defects due to the concentrated release of residual stress.

[0004] Traditional equipment is only equipped with a single uniform beam shaping module, which cannot be adapted to workpieces of different sizes. The beam spot is prone to hot spots in the center and energy attenuation at the edges. Moreover, it only collects the temperature of a single point of the weld for single-level power adjustment, and cannot monitor the temperature distribution of the entire workpiece. There is no means of fine-grained control of beam spot energy. The preheating temperature of the whole plate fluctuates greatly, and it is difficult to guarantee the consistency of weld width and depth in the same batch.

[0005] The light source lacks functional division and supporting intelligent collaborative control logic, resulting in weak adaptability to multiple materials. Existing equipment uses preheating and welding light sources interchangeably without hardware isolation and division of labor, making it impossible to balance large-area preheating efficiency with precision welding focusing accuracy. At the same time, it lacks supporting control methods such as galvanometer temperature field trajectory compensation, zoned gas protection, and dual-light source timing interlock. It is difficult to match the optimal light source combination with metals with different spectral absorption characteristics, and welding is prone to defects such as spatter, oxidation, and incomplete welding. The equipment has a low degree of versatility. Summary of the Invention

[0006] The purpose of this invention is to provide a laser homogenization and shaping spot global temperature control preheating scanning welding method and system to solve the problems mentioned in the background art.

[0007] In view of this, the present invention provides a laser homogenization and shaping spot global temperature control preheating scanning welding method, comprising the following:

[0008] S1. Working condition matching selection: Match the combination of dual independent laser light sources according to the spectral absorption characteristics of the workpiece material to be welded, and select the beam homogenization and shaping component according to the overall size of the workpiece, the target preheating coverage range, and the beam spot uniformity index.

[0009] The two laser light sources are hardware-defined functional zones. One light source is matched for global substrate preheating, and the other light source is matched for precision melting and scanning welding. The two light source paths are independent of each other and there is no cross-reuse.

[0010] S2, Full-area homogenization substrate preheating: Start the dedicated preheating light source. After the beam is modulated by the selected beam homogenization and shaping component, it outputs a large-size flat-top homogenization light spot that can completely cover the entire workpiece. It synchronously and homogenously heats the entire workpiece, equalizes the overall temperature field distribution of the workpiece, and eliminates the temperature gradient and initial residual stress before welding.

[0011] S3. Constant Temperature Coaxial Galvanometer Scanning Welding: Continuously maintain a large-size homogenized preheating spot to fully cover the workpiece to form a stable constant temperature processing substrate. Start the welding-specific light source. The preheating beam and the welding beam are coaxially combined to achieve coplanar and common focal point synchronous output.

[0012] The welding beam is focused to form a finely processed spot, which is dynamically scanned along the preset weld seam trajectory within the area covered by the preheated spot to complete the metal melting and welding process.

[0013] S4. Gradient heat preservation and tempering to relieve stress in the whole area: After the complete scanning and processing of the weld is completed, the welding-specific light source is turned off, and a large-size uniform light spot is continuously output to perform segmented gradient heat preservation and slow cooling on the whole area of ​​the workpiece. The residual thermal stress and structural stress generated by welding are gradually released by the uniform temperature field in the whole area.

[0014] S5. Full-domain multi-parameter temperature closed-loop control: Real-time acquisition of multi-point temperature field data of the workpiece throughout the welding process, and construction of a multi-parameter closed-loop adjustment loop based on the temperature distribution deviation of the whole domain, linking and controlling the output power of the preheating light source, the preheating duration, and the gradient heat preservation and tempering duration, so as to constrain the temperature fluctuation of the whole domain of the workpiece within the preset processing temperature zone threshold.

[0015] In a further embodiment of the present invention, the beam homogenization and shaping component is configured with multiple sets of standardized beam homogenization and shaping modules that can be independently activated and switched in series, which can automatically match a single module optical path or a multi-level composite beam homogenization optical path according to the workpiece width and beam spot uniformity requirements.

[0016] Multi-level composite uniform light path can eliminate the difference between light spot diffraction hotspots and the central energy peak, and improve the uniformity of preheating energy of the whole plate.

[0017] In a further embodiment of the present invention, the welding beam is focused by a high-speed digital galvanometer in conjunction with a telecentric flat-field focusing mirror to form a micron-level fine welding spot;

[0018] It also includes a galvanometer dynamic trajectory compensator, which synchronously corrects the galvanometer scanning trajectory and scanning speed based on the real-time global temperature field deviation of the workpiece.

[0019] In a further embodiment of the present invention, the S4 global gradient heat preservation and tempering stress relief adopts an adaptive variable temperature slow cooling strategy. The gradient temperature drop rate and the total heat preservation time are based on the workpiece thermal property parameters, substrate thickness and preheating reference temperature to construct a three-dimensional linkage matching model, and automatically output tempering process parameters that are suitable for the workpiece.

[0020] In a further embodiment of the present invention, the global multi-parameter temperature closed-loop control adopts a distributed array multi-point temperature measurement method to collect the two-dimensional global temperature field of the workpiece, and at the same time constructs a two-layer hierarchical closed-loop adjustment loop.

[0021] The first-level coarse adjustment circuit adjusts the overall output power of the preheating light source based on the average temperature deviation across the entire region, while the second-level fine adjustment circuit corrects the beam energy distribution parameters of the beam homogenization and shaping component based on the extreme values ​​of regional temperature differences.

[0022] In a further embodiment of the present invention, a full-area zoned inert gas protection process is also included, wherein inert protective media are delivered separately to the weld formation area and the stress concentration area at the edge of the workpiece during the welding process, and the protective gas flow rate and laminar flow pattern are independently controlled in each area to prevent the high-temperature substrate from undergoing an oxidation reaction with the air.

[0023] In a further embodiment of the present invention, a dual-light source timing linkage interlocking control process is set up, and a synchronous triggering logic for the preheating light source and the welding light source is established;

[0024] The system unlocks the welding light source output permission only when the temperature of the entire workpiece reaches the preset threshold, and locks the output power of the preheating light source throughout the welding process to avoid drastic changes in the workpiece temperature field during processing.

[0025] In a further embodiment of the present invention, the large-size flat-top homogenized light spot has the characteristic of full-area energy surface distribution, completely covering the entire processing substrate area of ​​the workpiece.

[0026] In a further embodiment of the present invention, in the S2 global homogenization substrate preheating, the overall preheating reference temperature of the workpiece is controlled within a fixed ratio range of the base material melting temperature, and the upper and lower limits of the range can be adaptively fine-tuned according to the material plastic deformation threshold and thermal expansion coefficient.

[0027] A laser homogenization and shaping spot full-domain temperature control and preheating scanning welding system is used to perform the laser homogenization and shaping spot full-domain temperature control and preheating scanning welding method. The system includes a dual-function partitioned laser source unit, a multi-mode composite beam homogenization and shaping unit, a galvanometer precision scanning welding unit with temperature compensation, a double-layer coaxial beam combining optical unit, a full-domain double-layer closed-loop temperature control unit, and a timing linkage control unit.

[0028] The dual-function zoned laser source unit is equipped with two types of lasers with fixed hardware functions, isolated optical paths and non-interchangeable use: a dedicated laser for full-area preheating and a dedicated laser for precision melting welding. The corresponding wavelength combination can be matched according to the spectral absorption characteristics of the workpiece material. The output power and working sequence of the two types of lasers can be independently controlled.

[0029] The multi-mode composite beam homogenization and shaping unit integrates multiple standardized homogenization and shaping modules and optical path switching slides, supporting free switching between single-module independent optical paths or multi-module serial composite optical paths, and performs multi-level homogenization modulation on the output beam of the preheated laser to generate a large-size flat-top beam with equal energy that can completely cover the entire workpiece.

[0030] The temperature-compensated galvanometer precision scanning welding unit includes a high-speed digital galvanometer, a telecentric flat field mirror group, and a trajectory compensation control sub-card. The welding laser output beam is focused to form a microscale processing spot. The trajectory compensation control sub-card receives global temperature field data and corrects the galvanometer scanning trajectory and running speed in real time.

[0031] The dual-layer coaxial beam combining optical unit is equipped with a 45° multilayer dielectric film beam combining mirror and a coaxial dynamic calibration component. It combines the preheated homogenized beam and the welding fine beam into a coplanar coaxial output optical path with a common focus, forming a dual-layer spatial optical path structure in which a large preheated spot wraps around the internal welding spot. The coaxial dynamic calibration component eliminates the coaxial offset of the two beams in real time.

[0032] The full-domain dual-layer closed-loop temperature control unit includes a distributed array infrared temperature measurement module and a dual-layer graded temperature controller. The array temperature measurement module collects the full-domain two-dimensional temperature field of the workpiece, and the temperature controller performs dual-loop coordinated control of coarse adjustment of the full-domain average temperature power and fine adjustment of the local temperature difference spot energy.

[0033] The timing linkage control unit establishes signal communication with the dual-function zone laser light source unit and the full-domain dual-layer closed-loop temperature control unit, respectively. It has built-in dual light source interlocking logic, which allows the welding laser to start output only when the temperature of the entire workpiece meets the preset threshold. The output state of the preheating light source is locked throughout the welding process to maintain a constant temperature processing substrate.

[0034] The beneficial effects of this invention are:

[0035] The integrated process of full-area homogenization preheating and gradient tempering suppresses workpiece welding deformation at the source. It abandons the local preheating mode of the weld seam and adopts a large-size flat-top homogenization spot that fully covers the workpiece to achieve synchronous and homogeneous heating of the whole plate, eliminating the temperature gradient in the whole area before processing. The galvanometer welding is completed under constant temperature, and the residual stress is released by full-area gradient heat preservation and slow cooling after welding. This greatly reduces the warping, springback and wave deformation of thin-walled parts and significantly improves the yield of batch processing.

[0036] Multi-mode composite uniform light path + dual-layer global closed-loop temperature control improves preheating uniformity and welding consistency. It is equipped with multiple sets of switchable composite uniform light shaping modules, which can combine the light path as needed to eliminate spot hotspots and adapt to workpieces of various sizes. It adopts a global array multi-point temperature measurement to construct a dual-layer hierarchical closed-loop control loop. By coarsely adjusting the power of the global average temperature and finely adjusting the spot energy of the light spot by the local temperature difference, the temperature fluctuation of the workpiece is controlled within a very small range, and the weld formation size of the same batch is highly uniform.

[0037] The light source hardware functional partitioning and multi-dimensional intelligent collaborative control improve material compatibility and processing stability. The preheating and welding light source hardware is isolated and the functions are fixed and divided. The corresponding light source combination can be matched according to the material spectral characteristics to improve the laser absorption rate of various metals and reduce welding spatter and porosity defects. With the addition of galvanometer temperature field trajectory compensation, partitioned inert gas protection, and dual light source timing interlock control, defects such as low temperature welding and weld oxidation are avoided. A single device can be adapted to the precision welding of various thin-walled metal parts, greatly improving versatility and mass production stability. Attached Figure Description

[0038] Figure 1 This is a flowchart of the method of the present invention;

[0039] Figure 2 It is the optical path diagram through which the reflector propagates the preheated flat-top light spot onto the working plane;

[0040] Figure 3 yes Figure 2 A simulated light spot effect formed by the optical path;

[0041] Figure 4 It is an optical path diagram that directly focuses a flat-top light spot onto the working plane through off-axis focusing, imaging, or projection.

[0042] Figure 5 yes Figure 4 A simulated light spot effect formed by the optical path. Detailed Implementation

[0043] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0044] In the description of this application, it should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. For ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0045] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and are not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0046] It should be noted that in the description of this application, the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0047] It should be noted that, in this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various additions, omissions, or combinations are also possible. Additionally, features described with reference to certain examples may be combined in other examples.

[0048] This embodiment provides a laser homogenization and shaping spot global temperature control preheating scanning welding method, including the following:

[0049] S1. Working Condition Matching Selection: Match the combination of dual independent laser light sources according to the spectral absorption characteristics of the workpiece material to be welded, and select the beam homogenization and shaping component according to the overall size of the workpiece, the target preheating coverage area, and the beam uniformity index; the two laser light sources have hardware-fixed functional partitions, one light source is matched for full-area substrate preheating, and the other light source is matched for precision melting scanning welding. The two light source optical paths are independent of each other and there is no cross-reuse.

[0050] This step employs a material-specific spectral matching approach combined with permanent hardware-based light source functionality, completely differentiating it from existing methods that allow for arbitrary mixing and use of light sources with uniform wavelengths. It distinguishes the core functions of preheating and welding light sources from the hardware level, eliminating the need for shared optical paths and power reuse. The two types of light sources have physically isolated optical paths and independent drive circuits, making them non-interchangeable. For different metal spectral absorption curves, two unchangeable matching wavelength matching systems are permanently fixed in hardware, forming two standardized operating condition solutions.

[0051] Option 1 (High-reflectivity metal system, gold / silver / copper / aluminum and their composite ultrathin substrates, such as 0.1mm VC heat sink): A 450nm multimode direct semiconductor laser is selected as the global preheating light source, and a 532nm narrow-linewidth green laser is selected as the precision welding light source. The intrinsic absorption rate of 450nm blue light for high-reflectivity metals such as copper and aluminum is much higher than that of the infrared band, and the multimode output beam has a naturally soft energy distribution, which can be easily shaped into a large-area flat-top spot by various homogenizing mirror groups. The photoelectric conversion efficiency exceeds 45%, which is suitable for long-term global whole-board preheating. The beam quality of 532nm green light is M²<1.2. After focusing, it can form a micron-level fine spot, which is specially used for high-precision weld melting and forming, and suppresses welding spatter, cold welds, and porosity defects in high-reflectivity metals.

[0052] Option 2 (Conventional metal systems, stainless steel / iron / nickel / titanium alloys and composite materials, such as 1.5mm titanium alloy thin-walled structural parts): A 915nm multimode semiconductor laser is selected as the global preheating light source, and a 1070nm single-mode fiber laser is selected as the precision welding light source. The 915nm semiconductor light source has low operating costs and stable high-power output, suitable for uniform heating of large-size titanium alloy plates. The 1070nm fiber laser has high energy density and controllable penetration depth, suitable for continuous scanning welding of medium-thickness and thin-walled metals. During the selection phase, the equipment has a built-in workpiece size-spot matching database, automatically matching the corresponding homogenization and shaping optical path based on the workpiece length, width, swath width, target preheating full coverage area, and spot uniformity index (in-plane energy difference ≤5%). For ultra-thin small parts with a swath width <100mm, a microlens array single-stage homogenization module is matched by default; for large plates with a swath width ≥200mm, an integrating mirror + homogenizing rod composite series homogenization optical path is automatically called, eliminating the need for repeated manual adjustment of optical components throughout the process.

[0053] In this embodiment, for the first time, "material spectral absorption characteristics" are used as the sole criterion for grouping light source hardware. At the same time, the functional boundaries of the light source are solidified at the circuit and optical path levels, completely eliminating the inherent defects of existing technologies that mix preheating and welding light sources and blindly use universal wavelengths. Therefore, matching wavelengths according to material greatly improves the laser absorption rate of various metals, and welding is free of large-area spatter. The division of labor of the light sources takes into account both high preheating efficiency and high welding precision. A single device is compatible with both high-reflectivity and conventional thin-walled metal parts, greatly improving the equipment's versatility and reducing the investment in equipment for production lines of multiple types of workpieces.

[0054] S2, Full-area homogenization substrate preheating: Start the dedicated preheating light source. After the beam is modulated by the selected beam homogenization and shaping component, it outputs a large-size flat-top homogenization light spot that can completely cover the entire workpiece. It synchronously and homogenously heats the entire workpiece, equalizes the overall temperature field distribution of the workpiece, and eliminates the temperature gradient and initial residual stress before welding.

[0055] This step abandons the existing industry-wide weld-following, localized, narrow-strip heating mode, and adopts a full-surface, flat-top, uniformly heated spot for synchronous and homogeneous heating. This eliminates the source of hot and cold zone variations on the workpiece surface, resolving warping, springback, and wavy deformation caused by concentrated localized heat input in thin-walled parts. The process is implemented with standardized quantitative standards: the overall preheating reference temperature is uniformly locked within 60%-80% of the base material's melting temperature. The system adaptively adjusts the threshold based on the material's thermoplasticity and coefficient of thermal expansion, precisely balancing the residual stress relief effect with the risk of high-temperature softening and collapse of the sheet material.

[0056] 1) Example 1 (0.1mm copper-aluminum VC heat sink, high reflectivity metal): The base material has a melting point of 660℃, the preheating range is locked at 400±20℃ (about 60% of the melting point), the microlens array shapes and outputs a 120mm×80mm full-coverage flat-top light spot, the in-plane energy difference is ≤3%, the whole board heats up synchronously, and there are no local hot spots.

[0057] 2) Example 2 (1.5mm titanium alloy thin-walled plate, conventional metal): The base material has a melting point of 1668℃, and the preheating range is locked at 460℃ (70% of the melting point range). A 300mm×200mm large-size homogenized light spot is output through a composite optical path of integrating mirror + homogenizing rod. The entire plate is uniformly heated under a nitrogen inert atmosphere, and the temperature difference between any two points on the plate surface is ≤15℃. During the processing, the large-size light spot completely covers the entire base material area of ​​the workpiece, and there is no local heating behavior only along the weld seam trajectory. The initial residual stress before forming caused by the rolling and stamping of the plate is released simultaneously, and a temperature difference-free constant temperature processing base is constructed, providing a foundation for subsequent constant temperature welding.

[0058] This step utilizes a full-area, synchronous, homogeneous preheating and heat transfer system, which differs from all existing localized trajectory preheating schemes. Therefore, it eliminates the temperature gradient and initial residual stress across the entire workpiece in advance, and the isothermal substrate welding significantly reduces warping, springback, and wave deformation in thin-walled parts, achieving a batch production yield of over 99.8%.

[0059] S3. Constant Temperature Coaxial Galvanometer Scanning Welding: The large-size homogenized preheating spot continuously covers the entire workpiece to form a stable constant temperature processing substrate. The welding-specific light source is activated, and the preheating beam and the welding beam are coaxially combined to achieve coplanar and common focal point synchronous output. The welding beam is focused to form a fine processing spot, which dynamically scans along the preset weld seam trajectory within the area covered by the preheating spot to complete the metal melting and welding.

[0060] In this step, the double-layer coaxial wrap-around dual-spot optical path structure is a completely new optical layout. Existing coaxial preheating equipment can only fit small-sized preheating spots onto the weld seam, and cannot achieve simultaneous processing of large-spot complete wrapping of the welding spot. Optical hardware implementation details: The coaxial beam combining unit adopts a 45° tilted multilayer dielectric film beam combining mirror, with anti-reflection / high-reflection coatings on both sides to match the wavelengths of the preheating light source and the welding light source. After the two beams are combined without loss, they achieve coplanar and confocal output. The matching coaxial dynamic calibration component monitors the coaxial offset of the two beams in real time, automatically fine-tunes the optical lenses to compensate for optical path drift, and always maintains that the large-sized global preheating spot completely wraps the internal micron-level welding spot. There is no spot misalignment or processing blind spot during the entire galvanometer scanning process. Galvanometer processing hardware details: The welding beam is focused by a high-speed digital galvanometer paired with a telecentric flat-field focusing lens to form a fine processing spot of 5-30μm. The galvanometer scanning speed can reach up to 3000mm / s, adaptable to high-speed scanning of straight lines, arcs, and irregular closed trajectories. The preheating light source output is never turned off throughout the process, and the workpiece is continuously maintained at the constant temperature substrate set in step S2, eliminating localized instantaneous high temperatures in the weld area during the welding process and avoiding cracks caused by sudden cooling of the molten pool. Therefore: the green laser welding spot of 0.1mm VC heat sink is small, and the weld width is uniform without spatter; the fiber laser weld of 1.5mm titanium alloy is smooth, without oxidation blackening or microcrack defects.

[0061] In this embodiment, a double-layer coaxial synchronous optical path is used to wrap a fine welding spot with a large preheating spot. The substrate is welded at a constant temperature throughout the process, resulting in high consistency in weld width and depth, and no defects such as incomplete welding or microcracks. The coaxial optical path does not require secondary positioning, which greatly reduces the difficulty of debugging the automated production line.

[0062] S4. Gradient heat preservation and tempering to relieve stress in the whole area: After the complete scanning and processing of the weld is completed, the welding-specific light source is turned off, and a large-size uniform light spot is continuously output to perform segmented gradient heat preservation and slow cooling on the whole area of ​​the workpiece. The residual thermal stress and structural stress generated by welding are gradually released by the uniform temperature field in the whole area.

[0063] In this step, a three-dimensional adaptive gradient tempering model linking material, thickness, and preheating temperature is adopted, whereas existing tempering processes only involve fixed-duration constant-temperature holding. Specifically: the model has a built-in database of full material thermal properties (thermal conductivity, coefficient of thermal expansion, phase transformation temperature). After inputting the workpiece material, plate thickness (0.01-2mm), and preheating reference temperature, it automatically outputs multi-level gradient cooling rates and segmented holding times, releasing welding thermal residual stress and metallographic stress in stages, avoiding the localized sudden cooling and shrinkage deformation caused by directly removing the heat source after welding in traditional methods: 1) 0.1mm ultra-thin VC copper-aluminum parts: three-stage gradient slow cooling, total holding time 70s, cooling rate 2℃ / s, quickly releasing surface stress of thin materials and avoiding plate warping; 2) 1.5mm thick titanium alloy thin-walled parts: five-stage gradient slow cooling, total holding time 240s, cooling rate 0.5℃ / s, slowly releasing titanium alloy welding phase transformation stress and suppressing plate shrinkage and springback. The preheating spot is continuously activated throughout the entire process, and the entire plate cools down synchronously and uniformly. The stress is released simultaneously at the weld and the edge of the plate, and there is no localized stress concentration phenomenon due to rapid cooling.

[0064] In this embodiment, by constructing a three-dimensional parameter-linked gradient tempering adaptive model, the residual welding stress is gradually released, the flatness and dimensional accuracy of the workpiece are stable after welding, and the subsequent shaping and rework processes of thin-walled parts are greatly reduced.

[0065] S5. Full-domain multi-parameter temperature closed-loop control: Real-time acquisition of multi-point temperature field data of the workpiece throughout the welding process, and construction of a multi-parameter closed-loop adjustment loop based on the temperature distribution deviation of the whole domain, linking and controlling the output power of the preheating light source, the preheating duration, and the gradient heat preservation and tempering duration, so as to constrain the temperature fluctuation of the whole domain of the workpiece within the preset processing temperature zone threshold.

[0066] This embodiment adopts a dual-layer hierarchical closed-loop temperature control architecture with full-domain array temperature measurement, which differs from the rudimentary temperature control schemes of existing technologies that only perform single-point temperature measurement of the weld and single-stage power adjustment. It is divided into a first-level coarse adjustment loop and a second-level fine adjustment loop for dual-layer coordinated control. Specifically, it uses a distributed coaxial infrared array multi-point temperature measurement module, with temperature measurement points evenly and densely distributed along the length and width of the workpiece, to collect the complete two-dimensional full-domain temperature field in real time at a sampling frequency of 100Hz.

[0067] First-level coarse adjustment loop: Using the average temperature of the entire workpiece as the control benchmark, when the average temperature deviates from the target range by ±20℃, the output power of the semiconductor preheating laser is significantly adjusted to quickly pull the temperature of the entire board back to the benchmark.

[0068] Secondary fine-tuning loop: The extreme temperature difference in a local area of ​​the workpiece plate is used as the control benchmark. When the temperature difference between two points in a local area exceeds 30℃, the output signal finely adjusts the optical path parameters of the beam homogenization and shaping component, corrects the energy distribution in the beam spot, and eliminates local hot spots / low temperature areas on the plate. The entire process is linked and synchronously controls the preheating power, preheating holding time, and tempering holding time to stably control the temperature fluctuation of the entire workpiece within ±20℃, adapting to the constant temperature requirements of both large and small workpieces.

[0069] Through a dual-layer hierarchical closed-loop collaborative temperature control logic, the full-domain two-dimensional array multi-point temperature measurement replaces the traditional single-point weld temperature measurement, resulting in a completely innovative control dimension. As a result, the workpiece temperature is highly stable throughout the entire process, the consistency of the weld depth, weld width, and deformation of the same batch of workpieces is significantly improved, and the processing dispersion of batch products is greatly reduced.

[0070] In this embodiment, the beam homogenization and shaping component is equipped with multiple sets of standardized beam homogenization and shaping modules that can be independently activated and switched in series. It can automatically match a single module optical path or a multi-level composite beam homogenization optical path according to the workpiece width and beam spot uniformity requirements. The multi-level composite beam homogenization optical path can eliminate the beam spot diffraction hotspots and the center energy peak difference, and improve the uniformity of the preheating energy of the entire plate.

[0071] Existing preheating and shaping optical paths use only a single fixed homogenizing module, which cannot adapt to workpieces of various sizes. This solution integrates four types of standardized homogenizing and shaping modules, supporting independent use of a single module and free switching between two or more series-connected composite optical paths, forming a multi-level hotspot elimination and homogenization system. The four types of standardized modules include an integrating mirror shaping module, a microlens array shaping module, a homogenizing rod shaping module, and a fiber beam shaping module; equipped with an electric optical path switching slide, the system automatically switches the optical path according to the workpiece width: 1) Small VC heat sink (width < 100mm): The microlens array shaping module is used alone, the optical path is lightweight, and a uniform small-sized flat-top light spot is output; 2) Large titanium alloy thin plate (width ≥ 200mm): Integrating mirror + homogenizing rod series-connected composite optical path, two-stage homogenization superposition eliminates the energy peak at the center of the light spot and the diffraction hotspot at the edge, and the energy uniformity within the light spot surface is improved to over 95%. The multi-level composite optical path, through two energy homogenization superpositions, completely solves the defects of uneven energy distribution and local high-temperature ablation of the workpiece on the plate surface in traditional single homogenizing optical paths.

[0072] Therefore, through a multi-module, serially combinable, and switchable multi-level uniform light shaping optical path, there is no similar integrated solution in the existing preheating and shaping structure; it brings a set of equipment that can adapt to extremely small and thin parts, large-size thin-walled plates and other workpieces of various specifications, with no hot spots in the light spot, greatly improving the uniformity of the preheating temperature of the whole plate, and suppressing the deformation and oxidation of the plate caused by local high temperature.

[0073] In this embodiment, the welding beam is focused by a high-speed digital galvanometer and a telecentric flat field focusing lens to form a micron-level fine welding spot; it also includes a galvanometer dynamic trajectory compensation sub-step, which synchronously corrects the galvanometer scanning trajectory and scanning speed based on the real-time global temperature field deviation of the workpiece.

[0074] Existing galvanometer welding only presets a fixed trajectory and a fixed scanning speed, lacking a dynamic compensation mechanism based on the real-time temperature field across the entire workpiece. This solution adds a global temperature field-linked adaptive compensation algorithm for the galvanometer trajectory. Through an array of infrared temperature measurement modules, the system transmits back a two-dimensional temperature field distribution map of the workpiece in real time. The system divides the plate surface into high-temperature and low-temperature zones and executes differentiated compensation strategies: 1) Local low-temperature areas of the workpiece: Automatically slightly offsets the galvanometer scanning trajectory, simultaneously reduces the scanning speed, extends the laser energy application time, and increases the melt pool depth; 2) Local high-temperature areas of the workpiece: Fine-tunes the trajectory to avoid high-temperature accumulation areas, simultaneously increases the scanning speed, reduces heat input, and avoids overheating and deformation of the plate; For high-reflectivity thin-walled copper and aluminum parts and titanium alloy plates, there are built-in matching compensation parameter libraries, eliminating the need for manual recalibration of the compensation curve.

[0075] Based on the dual-dimensional dynamic compensation process of galvanometer trajectory and scanning speed in the global two-dimensional temperature field, the weld formation difference caused by the small global temperature difference of the workpiece is offset, and the weld size consistency of the same batch of workpieces is further improved, reducing the number of defective welds.

[0076] In this embodiment, the S4 global gradient heat preservation and tempering stress relief adopts an adaptive variable temperature slow cooling strategy. The gradient temperature drop rate and total heat preservation time are based on the workpiece thermal property parameters, substrate thickness, and preheating reference temperature to construct a three-dimensional linkage matching model, and automatically output tempering process parameters that are suitable for the workpiece.

[0077] The 3D linkage matching model incorporates a complete database of thermal properties for industrial metals, including thermal conductivity, coefficient of thermal expansion, and critical high-temperature phase transformation temperatures for gold, silver, copper, aluminum, stainless steel, nickel, and titanium alloys. The model's computational logic uses plate thickness and preheating reference temperature as input variables to automatically and iteratively calculate the optimal segmented temperature drop gradient and holding time for each segment, completely replacing the traditional method of manually adjusting tempering process parameters repeatedly. Examples of differentiated parameter output: For 0.1mm ultra-thin copper-aluminum composite parts with low heat capacity, the model outputs rapid gradient slow cooling parameters; for 1.5mm titanium alloy plates with high heat capacity and high phase transformation stress, the model outputs multi-stage slow cooling and long-term holding parameters. The entire process is automated, requiring no manual recording or parameter correction.

[0078] By using a three-dimensional parameter-linked adaptive tempering intelligent model, fully automatic matching of process parameters is achieved, whereas existing tempering processes all require manual adjustment of fixed parameters. This significantly reduces the labor cost of process debugging on the production line, and there is no need to readjust the tempering process when switching production of workpieces of different materials and thicknesses, thus improving mass production efficiency.

[0079] In this embodiment, the global multi-parameter temperature closed-loop control adopts a distributed array multi-point temperature measurement method to collect the two-dimensional global temperature field of the workpiece, and at the same time constructs a two-layer hierarchical closed-loop adjustment loop; the first-level coarse adjustment loop adjusts the overall output power of the preheating light source according to the global average temperature deviation, and the second-level fine adjustment loop corrects the spot energy distribution parameters of the beam homogenization and shaping component according to the extreme value of regional temperature difference.

[0080] By coaxially integrating the distributed array infrared temperature measurement module into the beam combining optical path, there is no laser obstruction or processing interference, enabling synchronous parallel processing and temperature measurement; the dual-layer hierarchical closed-loop circuit sets the control priority: the first level power coarse adjustment is the basic control, and the second level spot energy fine adjustment is the fine optimization control. The two-level circuits operate independently and output control signals in a coordinated manner.

[0081] When the average temperature of the workpiece deviates from the target range of ±20℃, the first-level coarse adjustment circuit is activated first to significantly adjust the semiconductor preheating power; only when the average temperature reaches the target but the local temperature difference on the board surface still exceeds 30℃, the second-level fine adjustment circuit is activated to finely adjust the uniform light shaping module, correct the spot energy distribution, and simultaneously eliminate the dual problems of overall temperature deviation and local uneven heating and cooling, which is different from the rudimentary control method of existing technologies that only adjust the laser power.

[0082] By adopting a dual-layer collaborative closed-loop control system of coarse adjustment of average temperature and fine adjustment of local temperature difference spot, the control dimensions and control objects are different from the existing single-level temperature control schemes. It takes into account the overall temperature stability of the workpiece and the local uniformity of the plate surface, significantly narrows the temperature fluctuation range of the whole domain, and significantly improves the welding consistency.

[0083] In this embodiment, a full-area zoned inert gas protection process is also included. During the welding process, inert protective media are delivered separately to the weld formation area and the stress concentration area at the edge of the workpiece. The flow rate and laminar flow pattern of the protective gas are independently controlled in each area to prevent the high-temperature substrate from undergoing an oxidation reaction with the air.

[0084] Traditional welding protection uses only a single gas path for full coverage, and the gas flow parameters are uniform and cannot be adjusted. This solution sets up two physically independent inert gas delivery pipelines.

[0085] Specifically, the material-compatible gas selection is as follows: high-purity argon is used for high-reflectivity copper, aluminum, and silver substrates; a mixture of argon and 5% helium is used for titanium alloys and stainless steel. The gas path has two independent control strategies: 1) Gas path in the weld formation molten pool area: high-flow laminar gas, vertically aligned with the molten pool, isolating oxygen and nitrogen from the air to inhibit weld oxidation, blackening, and porosity; 2) Gas path in the stress concentration area at the workpiece edge: low-flow, slow-flow parallel laminar gas, covering the high-temperature edges of the plate to prevent high-temperature oxidation and embrittlement of thin-walled parts. The flow rate and laminar flow pattern of both gas paths are independently adjustable, with continuous synchronous gas supply throughout the welding process, and low-flow protection maintained synchronously during the tempering and heat preservation stage.

[0086] By using an independent and controllable inert gas layered protection process for weld seams and edges, and replacing the existing weld protection design which lacks differentiated control, this method specifically suppresses oxidation defects at the weld seam and plate edges, reduces porosity, slag inclusions, and weld blackening, and improves the mechanical properties and appearance quality of the weld seam.

[0087] In this embodiment, a dual-light source timing linkage interlock control process is also set up to establish synchronous triggering logic for the preheating light source and the welding light source; only when the temperature of the entire workpiece reaches the preset threshold, the system unlocks the output permission of the welding light source, and the output power of the preheating light source is locked throughout the welding process to avoid drastic changes in the workpiece temperature field during the processing.

[0088] The existing equipment lacks a mandatory interlocking timing sequence for preheating and welding light sources, allowing the welding light source to be triggered arbitrarily, which easily leads to batch defects such as low-temperature incomplete welds. This solution incorporates a built-in PLC underlying timing interlocking program.

[0089] Specifically, the temperature unlocking threshold is calibrated according to material: the welding light source can be unlocked only when the average temperature of the entire area of ​​the high-reflectivity VC metal workpiece is ≥400℃; the welding light source can be unlocked only when the average temperature of the entire area of ​​the titanium alloy workpiece is ≥460℃.

[0090] Timing priority control logic: 1) Preheating stage: Only the preheating light source is allowed to output, while the welding light source is forcibly blocked; 2) Constant temperature welding stage: The output power of the preheating light source is locked, and automatic power reduction is prohibited to continuously maintain a constant temperature substrate; 3) Tempering stage: The welding light source is turned off first, while the preheating light source continues to output and performs gradient slow cooling. The preheating light source is then turned off after tempering is completed. If the overall temperature of the workpiece does not reach the calibrated threshold, the welding light source drive circuit is forcibly powered off, completely eliminating batch defects such as insufficient penetration, incomplete welding, and lack of fusion caused by low-temperature welding.

[0091] Therefore, by adopting a full-domain temperature threshold linkage dual-light source timing interlock safety control logic, the existing equipment does not have a forced temperature unlocking light emission mechanism; from the control logic level, low-temperature welding defects are eliminated, the constant temperature processing substrate is stably maintained, the scrap rate of mass production is reduced, and the safety of mass production of the equipment is greatly improved.

[0092] In this embodiment, the large-size flat-top homogenized light spot has the characteristic of full-area energy surface distribution, completely covering the entire processing substrate area of ​​the workpiece.

[0093] The light spot, after multi-module composite homogenization and shaping, possesses a standard flat-top energy distribution with an energy uniformity of ≥95% within the spot surface. It exhibits no central energy peak, no edge energy attenuation, and no localized diffraction hotspots. The geometric contour of the light spot perfectly matches the length and width of the workpiece, achieving 100% full coverage of the entire substrate area. Even 0.1mm VC heat sinks and 1.5mm titanium alloy sheets can be completely covered by the light spot, allowing for simultaneous heating at any location on the workpiece surface without localized concentrated heat input. This completely eliminates warping and ablation defects caused by localized high temperatures.

[0094] By using a full-coverage, equal-energy, flat-top, large-spot optical path design, it differs from the existing narrow weld seam local preheating spot architecture, eliminating localized concentrated heat input on the workpiece surface, and suppressing warping and springback deformation of thin-walled parts from the root of the heat transfer mechanism.

[0095] In this embodiment, during the S2 global homogenization substrate preheating, the overall preheating reference temperature of the workpiece is controlled within a fixed ratio range of the base material melting temperature. The upper and lower limits of the range can be adaptively fine-tuned according to the material's plastic deformation threshold and thermal expansion coefficient.

[0096] The system adopts a unified and standardized preheating temperature range: 60%-80% of the base material's melting point, breaking the current industry status quo where there is no unified standard for preheating temperature and it is all set by manual experience. The system has built-in material adaptive fine-tuning logic, which automatically floats the upper and lower limits of the range according to the material's plastic deformation threshold and thermal expansion coefficient, balancing the stress elimination effect and the risk of high-temperature deformation of the sheet material: 1) High-reflectivity copper-aluminum VC parts have low plasticity thresholds, and the range is locked at the melting point of 60%-70% to avoid high-temperature softening and collapse; 2) Titanium alloys have excellent high-temperature plasticity, and the range is widened to 70%-80% of the melting point to fully release internal residual stress.

[0097] By adapting to the standardized preheating range of 60%-80% of the base material melting point for the full-range preheating process, and with the matching material adaptive fine-tuning logic, the initial residual stress of the workpiece is fully eliminated, while avoiding the softening and collapse of thin-walled plates caused by high temperature, making it suitable for processing metal thin-walled parts with a full thickness of 0.01-2mm.

[0098] Another embodiment provides a laser homogenization and shaping spot full-domain temperature control preheating scanning welding system. The system is used to perform the laser homogenization and shaping spot full-domain temperature control preheating scanning welding method, including a dual-function partitioned laser source unit, a multi-mode composite beam homogenization and shaping unit, a temperature-compensated galvanometer precision scanning welding unit, a dual-layer coaxial beam combining optical unit, a full-domain dual-layer closed-loop temperature control unit, and a timing linkage control unit.

[0099] The dual-function zoned laser source unit is equipped with two types of lasers with fixed hardware functions, isolated optical paths and non-interchangeable use: a dedicated laser for full-area preheating and a dedicated laser for precision melting welding. The corresponding wavelength combination can be matched according to the spectral absorption characteristics of the workpiece material. The output power and working sequence of the two types of lasers can be independently controlled.

[0100] This unit achieves dual isolation and solidification of the optical path and driving circuit at the hardware level, eliminating the cross-reuse of light sources from the physical structure. It features two independent wavelength light source hardware modules, with the system automatically switching based on the material: 1) High-reflectivity metal module: 450nm multimode direct semiconductor preheating laser + 532nm green welding laser; the semiconductor light source boasts high photoelectric conversion efficiency and supports long-term, high-power homogenization preheating; the green laser offers excellent beam quality and fine focused spot; 2) Conventional metal module: 915nm multimode semiconductor preheating laser + 1070nm single-mode fiber welding laser; suitable for high-efficiency whole-plate preheating and continuous scanning welding of large-size titanium alloy plates. Both types of lasers are equipped with independent power drives and independent timing control loops, ensuring that their output parameters do not interfere with each other. At the hardware level, the optical paths cannot be interchanged, completely different from the common design of existing equipment that reuses a single light source and shares the same optical path.

[0101] The hardware-based solidified light source partitioning architecture with dual optical and electrical isolation, the material-specific dual-wavelength standardized hardware modules, and the material-specific precise matching of light sources improve laser absorption rate. This eliminates the mutual constraints on preheating efficiency and welding precision caused by mixing light sources, and allows a single device to be compatible with multiple types of thin-walled metal parts.

[0102] The multi-mode composite beam homogenization and shaping unit integrates multiple standardized homogenization and shaping modules and optical path switching slides, supporting free switching between single-module independent optical paths or multi-module serial composite optical paths, and performs multi-level homogenization modulation on the output beam of the preheated laser to generate a large-size flat-top beam with equal energy that can completely cover the entire workpiece.

[0103] This system integrates four standardized homogenization modules: an integrating mirror, a microlens array, a homogenizing rod, and fiber shaping. It features a high-precision motorized optical path switching slide, automatically driven by the system program to switch optical paths without manual disassembly or assembly of optical lenses. It supports two operating modes: independent single-module operation and dual-module tandem multi-stage homogenization. It performs two or more stages of energy homogenization modulation on semiconductor multimode beams, eliminating energy peaks at the center of the beam and diffraction hotspots at the edges, outputting a flat-top beam with equal energy covering the entire workpiece. Hardware configuration differences: the VC small-part equipment uses a single-module microlens array optical path; the titanium alloy large-plate equipment uses an integrating mirror + homogenizing rod tandem composite optical path, adapting to the full-area preheating requirements of workpieces of different sizes.

[0104] By integrating a multi-module, electric switching slide, multi-level composite uniform light hardware unit, the existing preheating and shaping unit only has a single fixed optical path, making one optical unit adaptable to workpieces of multiple specifications. The light spot energy is uniform and there are no hot spots, which greatly suppresses welding deformation of thin-walled parts and significantly improves the equipment's versatility.

[0105] The temperature-compensated galvanometer precision scanning welding unit includes a high-speed digital galvanometer, a telecentric flat field mirror group, and a trajectory compensation control sub-card. The welding laser output beam is focused to form a microscale processing spot. The trajectory compensation control sub-card receives global temperature field data and corrects the galvanometer scanning trajectory and running speed in real time.

[0106] An independent trajectory compensation control sub-card is added. This sub-card communicates bidirectionally with the full-domain array infrared temperature measurement module in real time via a high-speed communication bus. It independently calculates the full-domain temperature field compensation algorithm and outputs coordinate and speed correction commands to the galvanometer driver board, achieving dynamic compensation in two dimensions: scanning trajectory and travel speed. A matching telecentric planar lens group ensures uniform focusing spot size across the entire processing area, eliminating edge spot distortion. The high-speed digital galvanometer supports high-speed scanning of arbitrary two-dimensional irregular weld seams. Matching compensation parameters are stored separately for copper and aluminum high-reflectivity thin-walled parts and titanium alloy thin plates, automatically recalled by the hardware without manual recalibration.

[0107] Through the independent temperature field trajectory compensation sub-card hardware architecture, real-time linkage compensation between the whole-domain temperature field and galvanometer scanning is achieved, which offsets the weld formation deviation caused by the small temperature difference in the whole workpiece. The weld width and depth of batch workpieces are highly uniform, and the welding consistency is greatly improved.

[0108] The dual-layer coaxial beam combining optical unit is equipped with a 45° multilayer dielectric film beam combining mirror and a coaxial dynamic calibration component. It combines the preheated homogenized beam and the welding fine beam into a coplanar coaxial output optical path with a common focus, forming a dual-layer spatial optical path structure in which a large preheated spot wraps around the internal welding spot. The coaxial dynamic calibration component eliminates the coaxial offset of the two beams in real time.

[0109] By using a 45° multilayer dielectric film combiner with a customized dielectric film system coated on both sides to adapt to two wavelength combinations, high-transmission / high-reflection non-destructive beam combining of the preheating and welding beams is achieved. The accompanying coaxial dynamic calibration component incorporates an optical path offset detection sensor and a fine-tuning motorized lens to monitor the coaxiality of the two beams in real time. It automatically compensates for optical path drift caused by temperature and vibration, maintaining a double-layer spatial optical path structure where the large-size, full-area preheating spot completely encloses the internal micron-sized welding spot. This ensures no spot misalignment or processing blind spots during arbitrary galvanometer scanning, eliminating the need for secondary positioning throughout the process. Existing coaxial beam combining equipment lacks a dynamic real-time calibration component, and the preheating spot size is too small to achieve a full-plate enveloping optical path layout.

[0110] By using a large spot to wrap a small spot in a double-layer coaxial optical path and real-time dynamic coaxial calibration hardware, the optical layout and calibration mechanism are completely new designs. The dual spots are processed synchronously and collaboratively, resulting in high optical path stability, simplifying the debugging process of automated production lines, and eliminating blind spots in constant temperature substrate processing.

[0111] The full-domain dual-layer closed-loop temperature control unit includes a distributed array infrared temperature measurement module and a dual-layer graded temperature controller. The array temperature measurement module collects the full-domain two-dimensional temperature field of the workpiece, and the temperature controller performs dual-loop coordinated control of coarse adjustment of the full-domain average temperature power and fine adjustment of the local temperature difference spot energy.

[0112] By coaxially integrating a distributed array infrared temperature measurement module into the beam combining optical path, the laser processing path is not obstructed, and the complete two-dimensional global temperature field of the workpiece is acquired synchronously. It is equipped with a dedicated dual-layer graded temperature controller, which has built-in independent coarse adjustment and fine adjustment operation chips. The two chips operate in parallel and output control signals to the preheating laser power supply and the beam homogenization and shaping unit, respectively. This achieves dual-loop coordinated control of "coarse adjustment of whole board power + fine adjustment of spot energy", which stably controls the temperature difference of the entire workpiece within an extremely small threshold, which is different from the rudimentary architecture of the existing single-chip single-level temperature controller.

[0113] It adopts a coaxial array full-domain temperature measurement hardware + dual-chip dual-layer graded dedicated temperature controller, and a dual-loop parallel collaborative control architecture, which ensures high temperature stability of the workpiece throughout the entire process and significantly reduces welding deformation and weld size dispersion of workpieces in the same batch.

[0114] The timing linkage control unit establishes signal communication with the dual-function zone laser light source unit and the full-domain dual-layer closed-loop temperature control unit, respectively. It has built-in dual light source interlocking logic, which allows the welding laser to start output only when the temperature of the entire workpiece meets the preset threshold. The output state of the preheating light source is locked throughout the welding process to maintain a constant temperature processing substrate.

[0115] The timing-linked control unit is an independent dedicated PLC control module, which communicates bidirectionally and at high speed with the light source unit and the dual-layer closed-loop temperature control unit. Internally, it has a material-specific temperature unlocking threshold program that distinguishes between two sets of temperature judgment standards for high-reflectivity metals and conventional metals. It features three-level timing priority control logic: preheating timing > welding timing > tempering timing. During the welding operation phase, the preheating light source output power is forcibly latched. During the tempering phase, the welding light source is automatically delayed and shut off, while continuously maintaining full-area preheating and heat preservation output. The entire timing system operates in a fully automatic closed-loop manner without manual intervention. At the hardware level, the welding light source output circuit is forcibly cut off when the temperature is not up to standard, preventing poor low-temperature welding from the equipment's core.

[0116] Through an independent dedicated timing PLC module and a dual-light source interlocking hardware control logic that links the temperature threshold across the entire range, the equipment avoids batch defects such as low-temperature soldering and insufficient penetration at the underlying level. The entire process is carried out with constant temperature substrate processing, and the deformation of thin-walled parts is controllable, which greatly improves the stability of mass production.

[0117] Furthermore, relevant demonstrations are provided for actual application scenarios. This embodiment's solution is adaptable to two scenarios: one is where a reflector propagates a preheated flat-top light spot onto the working plane, as shown in the attached diagram. Figure 2 As shown, the simulated light spot effect is Figure 3As shown.

[0118] Secondly, after off-axis focusing, imaging, or projection, the flat-top light spot is directly focused onto the working plane, as shown in the attached diagram. Figure 4 As shown, the simulated light spot effect is Figure 5 As shown.

[0119] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A laser homogenization and shaping spot global temperature control preheating scanning welding method, characterized in that, Including the following: S1. Working condition matching selection: Match the combination of dual independent laser light sources according to the spectral absorption characteristics of the workpiece material to be welded, and select the beam homogenization and shaping component according to the overall size of the workpiece, the target preheating coverage range, and the beam spot uniformity index. The two laser light sources are hardware-defined functional zones. One light source is matched for global substrate preheating, and the other light source is matched for precision melting and scanning welding. The two light source paths are independent of each other and there is no cross-reuse. S2, Full-area homogenization substrate preheating: Start the dedicated preheating light source. After the beam is modulated by the selected beam homogenization and shaping component, it outputs a large-size flat-top homogenization light spot that can completely cover the entire workpiece. It synchronously and homogenously heats the entire workpiece, equalizes the overall temperature field distribution of the workpiece, and eliminates the temperature gradient and initial residual stress before welding. S3. Constant Temperature Coaxial Galvanometer Scanning Welding: Continuously maintain a large-size homogenized preheating spot to fully cover the workpiece to form a stable constant temperature processing substrate. Start the welding-specific light source. The preheating beam and the welding beam are coaxially combined to achieve coplanar and common focal point synchronous output. The welding beam is focused to form a finely processed spot, which is dynamically scanned along the preset weld seam trajectory within the area covered by the preheated spot to complete the metal melting and welding process. S4. Gradient heat preservation and tempering to relieve stress in the whole area: After the complete scanning and processing of the weld is completed, the welding-specific light source is turned off, and a large-size uniform light spot is continuously output to perform segmented gradient heat preservation and slow cooling on the whole area of ​​the workpiece. The residual thermal stress and structural stress generated by welding are gradually released by the uniform temperature field in the whole area. S5. Full-domain multi-parameter temperature closed-loop control: Real-time acquisition of multi-point temperature field data of the workpiece throughout the welding process, and construction of a multi-parameter closed-loop adjustment loop based on the temperature distribution deviation of the whole domain, linking and controlling the output power of the preheating light source, the preheating duration, and the gradient heat preservation and tempering duration, so as to constrain the temperature fluctuation of the whole domain of the workpiece within the preset processing temperature zone threshold.

2. The laser homogenization and shaping spot global temperature control preheating scanning welding method according to claim 1, characterized in that, The beam homogenization and shaping component is equipped with multiple sets of standardized beam homogenization and shaping modules that can be independently activated and switched in series. It can automatically match a single module optical path or a multi-level composite beam homogenization optical path according to the workpiece width and beam spot uniformity requirements. Multi-level composite uniform light path can eliminate the difference between light spot diffraction hotspots and the central energy peak, and improve the uniformity of preheating energy of the whole plate.

3. The laser homogenization and shaping spot global temperature control preheating scanning welding method according to claim 1, characterized in that, The welding beam is focused by a high-speed digital galvanometer and a telecentric flat-field focusing lens to form a micron-level fine welding spot. It also includes a galvanometer dynamic trajectory compensator, which synchronously corrects the galvanometer scanning trajectory and scanning speed based on the real-time global temperature field deviation of the workpiece.

4. The laser homogenization and shaping spot global temperature control preheating scanning welding method according to claim 1, characterized in that, The S4 global gradient heat preservation and tempering stress relief adopts an adaptive variable temperature slow cooling strategy. The gradient temperature drop rate and total heat preservation time are based on the workpiece's thermal properties, substrate thickness, and preheating reference temperature to construct a three-dimensional linkage matching model, which automatically outputs tempering process parameters that are suitable for the workpiece.

5. The laser homogenization and shaping spot global temperature control preheating scanning welding method according to claim 1, characterized in that, The full-domain multi-parameter temperature closed-loop control adopts a distributed array multi-point temperature measurement method to collect the two-dimensional full-domain temperature field of the workpiece, and at the same time constructs a two-layer hierarchical closed-loop control loop. The first-level coarse adjustment circuit adjusts the overall output power of the preheating light source based on the average temperature deviation across the entire region, while the second-level fine adjustment circuit corrects the beam energy distribution parameters of the beam homogenization and shaping component based on the extreme values ​​of regional temperature differences.

6. The laser homogenization and shaping spot global temperature control preheating scanning welding method according to claim 1, characterized in that, It also includes a full-area zoned inert gas protection process, in which inert protective media are delivered separately to the weld formation area and the stress concentration area at the edge of the workpiece during the welding process. The flow rate and laminar flow pattern of the protective gas are independently controlled in each area to prevent the high-temperature substrate from undergoing an oxidation reaction with the air.

7. The laser homogenization and shaping spot global temperature control preheating scanning welding method according to claim 1, characterized in that, It also sets up a dual-light source timing linkage interlock control process and establishes synchronous triggering logic for preheating light source and welding light source; The system unlocks the welding light source output permission only when the temperature of the entire workpiece reaches the preset threshold, and locks the output power of the preheating light source throughout the welding process to avoid drastic changes in the workpiece temperature field during processing.

8. The laser homogenization and shaping spot global temperature control preheating scanning welding method according to claim 1, characterized in that, The large-size flat-top homogenized light spot has the characteristic of full-area energy surface distribution, completely covering the entire processing substrate area of ​​the workpiece.

9. The laser homogenization and shaping spot global temperature control preheating scanning welding method according to claim 1, characterized in that, In the S2 global homogenization substrate preheating, the overall preheating reference temperature of the workpiece is controlled within a fixed ratio range of the base material melting temperature. The upper and lower limits of the range can be adaptively fine-tuned according to the material's plastic deformation threshold and thermal expansion coefficient.

10. A laser homogenization and shaping spot global temperature control preheating scanning welding system, characterized in that, The system is used to perform the laser homogenization and shaping spot full-domain temperature control preheating scanning welding method according to any one of claims 1 to 9, including a dual-function partitioned laser source unit, a multi-mode composite beam homogenization and shaping unit, a galvanometer precision scanning welding unit with temperature compensation, a double-layer coaxial beam combining optical unit, a full-domain double-layer closed-loop temperature control unit, and a timing linkage control unit. The dual-function zoned laser source unit is equipped with two types of lasers with fixed hardware functions, isolated optical paths and non-interchangeable use: a dedicated laser for full-area preheating and a dedicated laser for precision melting welding. The corresponding wavelength combination can be matched according to the spectral absorption characteristics of the workpiece material. The output power and working sequence of the two types of lasers can be independently controlled. The multi-mode composite beam homogenization and shaping unit integrates multiple standardized homogenization and shaping modules and optical path switching slides, supporting free switching between single-module independent optical paths or multi-module serial composite optical paths, and performs multi-level homogenization modulation on the output beam of the preheated laser to generate a large-size flat-top beam with equal energy that can completely cover the entire workpiece. The temperature-compensated galvanometer precision scanning welding unit includes a high-speed digital galvanometer, a telecentric flat field mirror group, and a trajectory compensation control sub-card. The welding laser output beam is focused to form a microscale processing spot. The trajectory compensation control sub-card receives global temperature field data and corrects the galvanometer scanning trajectory and running speed in real time. The dual-layer coaxial beam combining optical unit is equipped with a 45° multilayer dielectric film beam combining mirror and a coaxial dynamic calibration component. It combines the preheated homogenized beam and the welding fine beam into a coplanar coaxial output optical path with a common focus, forming a dual-layer spatial optical path structure in which a large preheated spot wraps around the internal welding spot. The coaxial dynamic calibration component eliminates the coaxial offset of the two beams in real time. The full-domain dual-layer closed-loop temperature control unit includes a distributed array infrared temperature measurement module and a dual-layer graded temperature controller. The array temperature measurement module collects the full-domain two-dimensional temperature field of the workpiece, and the temperature controller performs dual-loop coordinated control of coarse adjustment of the full-domain average temperature power and fine adjustment of the local temperature difference spot energy. The timing linkage control unit establishes signal communication with the dual-function zone laser light source unit and the full-domain dual-layer closed-loop temperature control unit, respectively. It has built-in dual light source interlocking logic, which allows the welding laser to start output only when the temperature of the entire workpiece meets the preset threshold. The output state of the preheating light source is locked throughout the welding process to maintain a constant temperature processing substrate.

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