Laser beam machining treatment process for surface of steel bridge component

Abstract

The invention relates to the field of laser processing, and discloses a laser beam processing treatment process for the surface of a steel bridge component, which comprises the following steps: a laser beam deflection unit drives a laser beam to carry out area scanning on the surface of the component, and a photoelectric sensing unit is used for collecting a reflection intensity signal; the control unit extracts a signal amplitude mean value to construct a feature sequence and compares the feature sequence with an oxidation judgment benchmark; and when the amplitude is in a switching interval, bidirectional scanning is switched into unidirectional intermittent scanning by modulating a galvanometer motor driving signal, and a thermal relaxation gap is constructed by using a motor commutation dead zone so as to synchronously block laser energy. Transient heat at the edge of a processing area is effectively induced to diffuse, the interface peak temperature is maintained below the oxidation critical point of a base body, and the problems of base material ablation and oxidation caused by light spot reversing staying are solved on the basis of guaranteeing pollutant stripping.

Description

Technical Field

[0001] This invention belongs to the field of laser processing technology, and in particular relates to a laser beam processing technology for the surface of steel bridge components. Background Technology

[0002] Currently, laser beam processing technology has become a common technical solution for rust removal and coating removal on carbon steel substrates due to its high energy density, non-contact nature, and absence of chemical residues. It utilizes laser beam irradiation on the surface of components to cause transient vaporization or peeling of contaminants, thereby obtaining a clean metallurgical interface. The thermal parameters of the carbon steel component surface dynamically evolve with the deepening of the purification process. Under continuous scanning path, laser energy is concentrated and deposited within microseconds. If the longitudinal thermal conductivity of the component substrate is consistently lower than the energy injection rate, transient heat accumulation occurs at the processing interface. This heat accumulation effect is particularly evident during the window period when contaminants are almost completely peeled off and the substrate is exposed. Since traditional processes often use spatially symmetrical continuous filling trajectories, thermal interference between adjacent scanning lines can easily cause local peak temperatures to exceed the oxidation critical point of carbon steel.

[0003] At the hardware level, the acceleration and deceleration characteristics of the commutation point of the two-dimensional galvanometer scanning cause nonlinear energy density distribution, resulting in overheating damage in the edge area of ​​the component. In addition to hardware limitations, the control method also has shortcomings. For example, Chinese invention patent application CN119187888A discloses a welding device and method that integrates laser cleaning and laser arc welding. It achieves the integration of cleaning and welding stations through beam splitting technology and improves the molten pool formation by using oscillating scanning. However, the control logic relies on preset fixed light intensity ratio and static process parameters. When dealing with complex heat dissipation boundaries and randomly distributed rust thickness components such as steel bridge decks and U-shaped ribs, the open-loop control mode cannot sense the physical state change of the material surface from contaminant absorption to high-reflection transition of the matrix. It lacks a transient blocking mechanism for the critical energy threshold of substrate oxidation and does not consider nonlinear heat injection during commutation. When dealing with areas of abrupt thickness change or scanning boundaries, energy density overload causes secondary oxidation and embrittlement of the substrate.

[0004] Therefore, the technical problem to be solved by this invention is how to adjust the driving command of the two-dimensional galvanometer in real time based on the grayscale feature feedback of the processing interface, and construct the thermal relaxation gap at the physical level by switching the scanning mode, so as to suppress the oxidation of the substrate without reducing the overall processing efficiency. Summary of the Invention

[0005] This invention provides a laser beam processing technology for the surface of steel bridge components, comprising the following steps: Step S101: The beam deflection unit drives the laser beam to perform area filling scan on the surface of the steel bridge component, and the photoelectric sensing unit collects the reflection intensity signal value generated by the laser beam radiation in the area to be processed in real time. Step S102: The control unit extracts the average amplitude of the reflection intensity signal value and constructs a characteristic time sequence reflecting the evolution of the surface physical property state; the characteristic time sequence is compared with the preset oxidation judgment benchmark in real time, and the oxidation judgment benchmark is determined by the saturated reflectivity of the steel bridge component substrate when it is exposed. In step S103, when the average amplitude enters the preset switching range, the control unit switches the scanning trajectory of the laser beam from a bidirectional serpentine scanning mode to a unidirectional intermittent scanning mode by modulating the phase of the driving current of the galvanometer motor in the beam deflection unit. In the unidirectional intermittent scanning mode, the control unit reads the mechanical inertia time of the galvanometer motor when it performs the commutation action at the end of each scanning line in real time, and constructs a thermal relaxation gap that is synchronously matched with the mechanical inertia time in the laser beam projection sequence. Within the time range corresponding to the thermal relaxation gap, the control unit sends a laser energy blocking command, uses the physical commutation cycle of the galvanometer motor as the physical residence time of thermal diffusion on the substrate surface, and controls the total amount of transient heat injection at the edge of the area to be treated by the scanning trajectory to be below the oxidation critical energy threshold of the steel bridge component substrate, thereby maintaining the pollutant stripping dynamics while suppressing the secondary oxidation reaction of the exposed substrate.

[0006] Preferably, in step S103, the control unit performs the following closed-loop adjustment steps: obtaining the real-time deviation between the average amplitude and the oxidation judgment benchmark, and calculating the evolution slope of the characteristic time sequence; the control unit linearly extends the laser off-time in the unidirectional intermittent scanning mode according to the increase of the evolution slope; the laser off-time is set to 1.1 to 1.5 times the unidirectional swing response time of the galvanometer motor; by dynamically interlocking the duty cycle of the laser beam with the commutation acceleration of the galvanometer motor, the temporal proportion of the thermal relaxation gap increases with the improvement of the surface cleanliness of the area to be treated; the control unit uses the thermal relaxation gap to establish a thermal hysteresis buffer at the edge boundary of the area to be treated, balances the depth of the heat-affected zone between the center and the edge of the area to be treated, and maintains the metallurgical structure consistency of the processed surface of the steel bridge component.

[0007] Preferably, in step S102, the control unit performs mean filtering on the reflection intensity signal value and removes the noise amplitude generated by laser plasma plume radiation according to the preset optical spectrum envelope to generate a characteristic time sequence; the control unit determines the thinning rate of surface contaminants in the area to be treated by calculating the first derivative of the characteristic time sequence, and adjusts the pulse repetition frequency of the laser beam according to the absolute value of the first derivative.

[0008] Preferably, in step S103, the switching interval is defined as: the average amplitude reaches 85% to 95% of the oxidation judgment benchmark; when the average amplitude is lower than the lower limit of the switching interval, the control unit maintains the bidirectional serpentine scanning mode to maintain the macroscopic processing efficiency of the laser beam processing technology.

[0009] Preferably, when performing the unidirectional intermittent scanning mode in step S103, the control unit keeps the laser beam in an energy-off state during the physical cycle of the galvanometer motor performing the reverse return of the scan line, and restarts the laser beam at the starting trigger point of the next scan line, so as to ensure that the direction of heat flow field conduction of the laser beam on the surface of the area to be processed has unidirectional determinism.

[0010] Preferably, the control unit corrects the overlap spacing d between adjacent scan lines in the scan trajectory in real time based on the surface topography features fed back by the feature time sequence; the overlap spacing d follows the following quantization rules: ,in, The preset initial scan line spacing, This is the real-time feedback value of the reflection intensity signal. As the criterion for oxidation determination, This is the full-scale feedback value of the photoelectric sensing unit.

[0011] Preferably, the steel bridge components are made of carbon steel, and their component forms include bridge deck, U-shaped ribs and transverse diaphragms; before executing step S101, the control unit automatically compensates for the defocusing of the laser beam based on the obtained three-dimensional coordinate information of the surface of the steel bridge components, so that the energy density of the laser beam spot on the surface of the area to be processed is maintained between 5J / cm² and 15J / cm².

[0012] Preferably, in the unidirectional intermittent scanning mode, the duration of the thermal relaxation gap is limited to 5ms to 15ms, and is not less than 1.2 times the time consumed by a single physical reversal of the beam deflection unit.

[0013] Preferably, the process further includes step S104: after the processing of the area to be processed is completed, the control unit uses the photoelectric sensing unit to collect the surface features after cleaning and calculates the surface contrast value; when the surface contrast value meets the preset welding cleanliness level, the processing completion command is output and the energy output of the laser beam is stopped.

[0014] Preferably, the control unit establishes a closed-loop response circuit between the average amplitude and the output power of the laser beam; at the instant when the average amplitude reaches the oxidation judgment benchmark, the control unit performs a power reduction action to reduce the single pulse energy of the laser beam by 30% to 50% in order to limit the thermal penetration depth of the laser energy into the steel bridge component matrix.

[0015] Compared with existing technologies, the laser beam processing technology for the surface of steel bridge components of this invention has the following advantages: 1. In the laser beam processing of steel bridge components, a dynamic adjustment mechanism for the energy field driven by thermal properties is established to break through the physical limit of heat accumulation in continuous scanning. This invention switches the spatially continuous scanning path to a step-by-step scanning during the critical window period from rust layer peeling to substrate exposure, artificially lengthening the thermal relaxation time of adjacent heated areas. The cold substrate of the component itself is used as a natural heat sink to dissipate transient heat waves. This spatiotemporal dispersion energy injection method physically dismantles the heat congestion conduction chain caused by continuous scanning at the microscale, so that the local peak temperature is always controlled below the substrate oxidation threshold. While maintaining the predetermined overlap density to ensure thorough cleaning, it avoids secondary oxidation damage to the substrate caused by energy overload.

[0016] 2. Constructing a closed-loop underlying mechanism for optical features and motion control to eliminate the interference of working condition fluctuations on interface quality: This invention embeds the evolution depth of image grayscale mean into the trigger chain of galvanometer deflection logic, so that the projection sequence of the laser beam is dynamically reconstructed with the real-time changes in surface properties. Since the grayscale difference gating mechanism can directly sense the non-uniformity of rust layer thickness and distribution, the system is freed from dependence on preset fixed process parameters and switches between initial stripping and final finishing modes. This process closed loop driven by the microscopic state of the material ensures a high degree of metallurgical quality consistency at the processing boundary in complex engineering environments, eliminating defects such as insufficient cleaning or excessive ablation that are common in traditional open-loop processing.

[0017] 3. By coupling the energy field distribution with the mechanical motion law, the thermal accumulation effect at the endpoint of the scanning trajectory is eliminated. To address the energy accumulation problem at the bidirectional scanning reversal endpoint of the two-dimensional galvanometer, this invention performs unidirectional intermittent scanning in the gray-scale critical range and constructs a forced energy-injection-free shut-off interval using the time window of the mechanical idle jump. This transforms the mechanical reversal time, which originally restricted the processing accuracy, into a process redundancy that assists in heat dissipation of the substrate. This effectively offsets the risk of edge overheating caused by the nonlinear increase in the dwell time of the light spot at the reversal point. By reshaping the topology of the beam projection, the uniform control of the depth of the heat-affected zone in the central and edge regions of the component is achieved, ensuring the stability of the physical properties of the steel bridge component after surface cleaning. Attached Figure Description

[0018] Figure 1 This is a flowchart of the laser processing technology for the surface of a steel bridge controlled by thermal relaxation, as described in this invention. Figure 2 This is the closed-loop control logic diagram for laser scanning based on optical signal feedback in this invention. Detailed Implementation

[0019] 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 embodiments of this application, not all embodiments. 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.

[0020] It should be noted that all directional and positional terms used in this invention, such as: up, down, left, right, front, back, vertical, horizontal, inner, outer, top, bottom, transverse, longitudinal, center, etc., are only used to explain the relative positional relationship and connection between components in a specific state (as shown in the accompanying drawings). They are only for the convenience of describing this invention and do not require that this invention be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention. In addition, the descriptions of "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal connection of two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood in conjunction with the specific circumstances.

[0022] In the description of this specification, references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0023] A laser beam processing technology for the surface of steel bridge components includes the following steps: Step S101: The beam deflection unit drives the laser beam to perform area filling scan on the surface of the steel bridge component, and the photoelectric sensing unit collects the reflection intensity signal value generated by the laser beam radiation in the area to be processed in real time. Step S102: The control unit extracts the average amplitude of the reflection intensity signal value and constructs a characteristic time sequence reflecting the evolution of the surface physical property state; the characteristic time sequence is compared with the preset oxidation judgment benchmark in real time, and the oxidation judgment benchmark is determined by the saturated reflectivity of the steel bridge component substrate when it is exposed. In step S103, when the average amplitude enters the preset switching range, the control unit switches the scanning trajectory of the laser beam from a bidirectional serpentine scanning mode to a unidirectional intermittent scanning mode by modulating the phase of the driving current of the galvanometer motor in the beam deflection unit. In the unidirectional intermittent scanning mode, the control unit reads the mechanical inertia time of the galvanometer motor when it performs the commutation action at the end of each scanning line in real time, and constructs a thermal relaxation gap that is synchronously matched with the mechanical inertia time in the laser beam projection sequence. Within the time range corresponding to the thermal relaxation gap, the control unit sends a laser energy blocking command, uses the physical commutation cycle of the galvanometer motor as the physical residence time of thermal diffusion on the substrate surface, and controls the total amount of transient heat injection at the edge of the area to be treated by the scanning trajectory to be below the oxidation critical energy threshold of the steel bridge component substrate, thereby maintaining the pollutant stripping dynamics while suppressing the secondary oxidation reaction of the exposed substrate.

[0024] Preferably, in step S103, the control unit performs the following closed-loop adjustment steps: obtaining the real-time deviation between the average amplitude and the oxidation judgment benchmark, and calculating the evolution slope of the characteristic time sequence; the control unit linearly extends the laser off-time in the unidirectional intermittent scanning mode according to the increase of the evolution slope; the laser off-time is set to 1.1 to 1.5 times the unidirectional swing response time of the galvanometer motor; by dynamically interlocking the duty cycle of the laser beam with the commutation acceleration of the galvanometer motor, the temporal proportion of the thermal relaxation gap increases with the improvement of the surface cleanliness of the area to be treated; the control unit uses the thermal relaxation gap to establish a thermal hysteresis buffer at the edge boundary of the area to be treated, balances the depth of the heat-affected zone between the center and the edge of the area to be treated, and maintains the metallurgical structure consistency of the processed surface of the steel bridge component.

[0025] Preferably, in step S102, the control unit performs mean filtering on the reflection intensity signal value and removes the noise amplitude generated by laser plasma plume radiation according to the preset optical spectrum envelope to generate a characteristic time sequence; the control unit determines the thinning rate of surface contaminants in the area to be treated by calculating the first derivative of the characteristic time sequence, and adjusts the pulse repetition frequency of the laser beam according to the absolute value of the first derivative.

[0026] Preferably, in step S103, the switching interval is defined as: the average amplitude reaches 85% to 95% of the oxidation judgment benchmark; when the average amplitude is lower than the lower limit of the switching interval, the control unit maintains the bidirectional serpentine scanning mode to maintain the macroscopic processing efficiency of the laser beam processing technology.

[0027] Preferably, when performing the unidirectional intermittent scanning mode in step S103, the control unit keeps the laser beam in an energy-off state during the physical cycle of the galvanometer motor performing the reverse return of the scan line, and restarts the laser beam at the starting trigger point of the next scan line, so as to ensure that the direction of heat flow field conduction of the laser beam on the surface of the area to be processed has unidirectional determinism.

[0028] Preferably, the control unit corrects the overlap spacing d between adjacent scan lines in the scan trajectory in real time based on the surface topography features fed back by the feature time sequence; the overlap spacing d follows the following quantization rules: ,in, The preset initial scan line spacing, This is the real-time feedback value of the reflection intensity signal. As the criterion for oxidation determination, This is the full-scale feedback value of the photoelectric sensing unit.

[0029] Preferably, the steel bridge components are made of carbon steel, and their component forms include bridge deck, U-shaped ribs and transverse diaphragms; before executing step S101, the control unit automatically compensates for the defocusing of the laser beam based on the obtained three-dimensional coordinate information of the surface of the steel bridge components, so that the energy density of the laser beam spot on the surface of the area to be processed is maintained between 5J / cm² and 15J / cm².

[0030] Preferably, in the unidirectional intermittent scanning mode, the duration of the thermal relaxation gap is limited to 5ms to 15ms, and is not less than 1.2 times the time consumed by a single physical reversal of the beam deflection unit.

[0031] Preferably, the process further includes step S104: after the processing of the area to be processed is completed, the control unit uses the photoelectric sensing unit to collect the surface features after cleaning and calculates the surface contrast value; when the surface contrast value meets the preset welding cleanliness level, the processing completion command is output and the energy output of the laser beam is stopped.

[0032] Preferably, the control unit establishes a closed-loop response circuit between the average amplitude and the output power of the laser beam; at the instant when the average amplitude reaches the oxidation judgment benchmark, the control unit performs a power reduction action to reduce the single pulse energy of the laser beam by 30% to 50% in order to limit the thermal penetration depth of the laser energy into the steel bridge component matrix.

[0033] Example 1: In the cleaning of the weld seam at the bottom of the inner cavity of the large U-shaped rib of an orthotropic steel bridge deck, the laser beam processing technology faces dual physical constraints of limited space and highly asymmetrical heat flow field. The carbon steel substrate at the bottom of the U-shaped rib is covered with a composite contamination layer of rust and alkyd primer with an uneven distribution of thickness between 1.5mm and 2.5mm. Due to the physical shielding of the web structure, the heat diffusion channel at the processing interface is limited to a single longitudinal substrate conduction. When performing peeling in such areas with abrupt thickness changes using bidirectional serpentine continuous scanning, if the laser beam penetrates the local thin rust area and exposes the highly thermally conductive carbon steel substrate, the transient heat wave accumulated by the previous scan line cannot be fully dissipated along the confined interface within microseconds. The secondary heat injection superimposed by adjacent scan lines causes the local peak temperature to exceed the oxidation critical threshold of the carbon steel. The high energy density required to peel off the thick rust layer and the low heat input required for the exposed substrate to resist oxidation are used to resolve the thermodynamic contradiction between these two factors. The beam deflection unit drives the laser beam to perform a region-filling scan in the area to be treated. The photoelectric sensing unit collects the reflection intensity signal value in real time. The control unit extracts the average amplitude of the reflection intensity signal value to construct a characteristic time sequence reflecting the evolution of the surface physical state. This sequence is then compared in real time with the oxidation judgment benchmark determined by the saturated reflectivity of the exposed steel bridge component substrate. When the average amplitude value enters the preset switching range of 85% to 95% of the oxidation judgment benchmark, the control unit switches the laser beam scanning trajectory from a bidirectional serpentine scanning mode to a unidirectional intermittent scanning mode by modulating the phase of the driving current of the galvanometer motor.

[0034] Simultaneously, the mechanical inertia time of the galvanometer motor during the commutation action at the end of each scan line is read in real time, and a thermal relaxation gap synchronously matched with this mechanical inertia time is constructed in the laser beam projection sequence. The threshold jump of the reflection intensity characteristic sequence defines the critical time node of the abrupt change in the thermal properties of the material interface. The active reading of the physical commutation cycle of the galvanometer motor provides a cooling time window that matches the thermal diffusion rhythm of the substrate. The control unit sends a laser energy blocking command within the time range corresponding to the thermal relaxation gap, and uses the mechanical space delay to create a heat dissipation gap of 5ms to 15ms between adjacent high-energy injection lines. During this process, the control unit follows the quantization rules based on the real-time surface morphology features fed back by the characteristic time sequence. Real-time correction of the overlap spacing d between adjacent scan lines, where The preset initial scan line spacing, This is the real-time feedback value of the reflection intensity signal. As the criterion for oxidation determination, As the full-scale feedback value of the photoelectric sensing unit, this rule converts the optical reflection increment into the spatial sparsity of the spot overlap density, so that the laser input thermal flow field and the residual heat capacity of the substrate are dynamically matched. With the alternating execution of the unidirectional intermittent scanning mode and the dynamic correction command of the overlap spacing, the control unit limits the total amount of transient heat injection at the edge of the area to be processed to below the oxidation critical energy threshold of the steel bridge component substrate. The dense alkyd primer and thick rust layer on the carbon steel surface undergo vaporization and peeling. The exposed cold substrate surface does not produce overheated oxidation phase transformation characteristics. The heat flux blocking mechanism established based on the inherent thermal conduction and optical evolution gradient of the substrate eliminates the energy accumulation effect at the reversing endpoint while maintaining the pollutant peeling kinetic energy, and maintains the metallurgical structure consistency of the processed surface of the steel bridge component.

[0035] Example 2: To address the interface thermal control requirements of laser beam processing under confined space thermal flux field abrupt changes, a test platform was constructed, comprising a kilowatt-level continuous wave fiber laser, a two-dimensional galvanometer deflection system, and a coaxial broadband photodiode sensor. The raw optical data collected by the photoelectric sensing unit is superimposed with high-frequency noise from plasma plume radiation induced by laser vaporization of contaminants. The characteristic time sequence judgment threshold is set based on a physical trade-off between material removal rate and substrate thermal damage tolerance. When the judgment threshold is lower than the required value, the unidirectional intermittent scanning mode is prematurely triggered, leading to attenuation of peeling kinetic energy. When the judgment threshold is higher than the safety limit, transient heat waves penetrate the substrate, causing secondary oxidation damage. Accordingly, the preset switching range is defined as the range of 85% to 95% of the oxidation judgment benchmark. A Q345qD orthotropic steel bridge deck with an alkyd primer and a heavily corroded composite layer with a thickness gradient distribution of 1.0 mm to 3.0 mm was selected as the test sample.

[0036] The experiment established a control group 1 using a conventional bidirectional serpentine continuous scanning trajectory; a partial missing control group 2 that switched to a unidirectional intermittent scanning mode while maintaining a fixed scan line spacing when the 90% threshold was reached; and three control groups using a complete set of trajectory modulation and dynamic overlap spacing correction strategies. The determination threshold for control group 1 was set at 80% of the oxidation determination benchmark, for control group 2 at 90% of the oxidation determination benchmark, and for control group 3 at 98% of the oxidation determination benchmark. During the processing of control group 2, the control unit received high-frequency noise interference between 45mV and 120mV. The original reflection intensity peak fluctuates, and the control unit executes a one-dimensional moving average filtering algorithm to output a smooth amplitude mean sequence. In the later stage of rust layer peeling, it shows a stable step increase trend between 85mV and 92mV. When the amplitude mean reaches the preset 90% oxidation judgment benchmark, i.e., 88.5mV, the control unit changes the phase of the galvanometer motor drive current to switch the scanning trajectory to a unidirectional intermittent scanning mode. At this time, the control unit reads the mechanical inertia time of the galvanometer motor during the extreme acceleration and deceleration phase as 12.5ms, and inserts a 12.5ms thermal relaxation gap between adjacent unidirectional scanning line projection cycles. At the same time, the control unit executes a mathematical model based on the feedback signal. After substituting the calculation results into the measured values, the control unit dynamically amplifies the overlap spacing between adjacent scan lines from the initial 0.08mm to 0.11mm, with the physical meaning of each symbol remaining consistent with the above.

[0037] Test results show that in comparative sample group 1, the lack of thermal diffusion buffer when treating a 1.0mm thin rust area caused the edge peak temperature to climb to 685℃ and generate a blue oxide phase. In comparative sample group 2, after introducing a thermal relaxation gap, the edge peak temperature dropped to 490℃, but due to the lack of dynamic sparsity adjustment of the gap, local thermal discoloration occurred and the pollutant removal rate dropped to 92.4%. In the present invention sample group 1, the low judgment threshold caused heat input blockage, resulting in a residual rust layer ratio of 15.2%. In the present invention sample group 3, the high judgment threshold caused transient heat wave penetration, resulting in an edge peak temperature... When the temperature rises to 590℃, the peak temperature of the matrix extracted by sample group 2 of this invention, under the synergistic constraint of dynamic correction of thermal relaxation gap and overlap spacing of 12.5ms, converges to a steady-state range of 415℃ to 425℃ when dealing with non-uniform rust layers of 1.0mm to 3.0mm. Moreover, the pollutant removal rate reaches 99.6%. The temperature convergence and decontamination rate indicators confirm that the synchronous intervention of spatial sparsity adjustment of spot overlap density and mechanical space thermal relaxation mechanism can maintain the original metallurgical structure of the bottom layer of steel bridge components while blocking energy accumulation at the reversing endpoint.

[0038] Example 3: In the operation of laser beam processing of steel bridge components, when the laser scanning trajectory crosses the physical interface area of ​​a rust layer or primer with abrupt thickness changes, the vaporization and thinning rate of surface contaminants undergoes a nonlinear jump. The static mode switching mechanism relying on a fixed optical judgment threshold lacks prior judgment of the material removal kinetics evolution trend, making it difficult to effectively suppress the excessive injection of local transient heat waves before the reflected signal reaches the oxidation judgment benchmark. After extracting the amplitude mean sequence of the reflected intensity signal value, the control unit constructs a sliding data window in memory with a time span of Δt and containing N consecutive discrete sampling points. By reading the latest amplitude mean and the earliest amplitude mean within this sliding data window and performing a finite difference operation, it outputs the real-time first derivative of the characteristic time sequence. This first derivative characterizes the instantaneous thinning rate of surface contaminants in the area to be treated. The control unit sends instructions to the pulse control register according to this rate change, following mathematical rules. Update the pulse repetition frequency of the laser beam ,in The preset reference pulse frequency for the system, This is the frequency adjustment proportional coefficient. To calculate the first derivative; in the synchronous operation logic branch, the control unit obtains the deviation between the current amplitude mean and the oxidation judgment benchmark, and calculates the evolution slope of the characteristic time sequence approaching the oxidation threshold by combining the first derivative, and after the beam deflection unit enters the unidirectional intermittent scanning mode, according to the model Increase the laser off-time in the modulation signal ,in Basic shutdown parameters, This is the timing extension gain coefficient. The slope of the evolution.

[0039] Read the sensor data of the galvanometer motor or obtain the response peak of the drive signal at the current commutation point from the external monitoring equipment, and measure the mechanical commutation time of the beam deflection unit to perform the task; in the unidirectional intermittent scanning mode, the laser turn-off time is set to 1.1 to 1.5 times the mechanical commutation time; use this as a reference value to match the slope of the characteristic time sequence evolution. Adjust the gain; by adjusting the timing extension gain coefficient. The thermal hysteresis buffer zone at the edge of the area to be treated is widened; the physical commutation cycle of the galvanometer motor is used to compensate for the thermal diffusion time of the substrate material, ensuring that the metallurgical structure remains constant after the removal of contaminants from the processing interface; based on the dynamic adjustment steps of the sliding data window and algebraic mapping, the state evolution rate extracted from the optical sensor is converted into microsecond-level intervention on the laser pulse time density and mechanical idle time. The dynamically extended thermal relaxation gap is used to establish a thermal hysteresis buffer zone at the edge boundary of the area to be treated, with the time ratio increasing with the surface cleanliness. This weakens the peak value of the single-pulse heat input while matching the thermal diffusion rhythm of the substrate material, eliminating the difference in the depth of the heat-affected zone between the center and the edge commutation area of ​​the area to be treated, and blocking the metallurgical structure variation induced by the depletion of the substrate's heat capacity.

[0040] Example 4: When the laser beam processing technology faces the deployment conditions of steel bridge components with batch-to-batch variations in surface roughness and fluctuations in alloy composition, the control unit drives the beam deflection unit to guide the laser beam to a reference test area where surface contaminants have been pre-removed, and scans the reference test area with increasing linear energy density. The photoelectric sensing unit simultaneously collects the reflection intensity signal value generated in this area under continuous laser radiation. The control unit extracts the average amplitude of the reflection intensity signal value after it enters the nonlinear saturation range as the full-scale feedback value of the exposed substrate of the steel bridge component. The control unit is based on a mathematical model. Calculate and lock the oxidation judgment criteria Where η is the equipment calibration coefficient, the system establishes a baseline for judgment independent of ambient stray light based on the extracted optical response data of specific physical interfaces. A standard test block of the steel bridge component is selected, and within a preset energy density range, the laser beam is driven to perform a stepped power scan on the surface of the standard test block. The evolution of the reflection intensity signal is monitored using a photoelectric sensing unit. When the numerical increment tends to stabilize with increasing power and the fluctuation is less than 3%, the average value of the saturation state signal is confirmed to be the full-scale feedback value. Determine the oxidation criterion by combining the calibrated reflectivity constant. By calibrating the optical properties of the component surface, the judgment error caused by material fluctuations or ambient light interference can be eliminated.

[0041] After establishing the oxidation determination criteria, the control unit manipulates the beam deflection unit to transfer the laser beam to the calibration area with the target thickness of the corrosion layer for initial power scanning. The control unit simultaneously records the first derivative of the characteristic time sequence. The physical parameters for reaching the peak phase are determined, and the plasma plume radiation intensity value of this phase is converted into frequency domain control parameters and written into the underlying drive register to calibrate the reference pulse frequency. The initial operating values ​​are used, and the control unit extracts the frequency adjustment ratio coefficient based on the critical thermal boundary condition that the underlying substrate in the calibration area has not undergone a micro-phase change. With timing extension gain coefficient The limit control parameters are collected and converted into a parameter array, which is then stored in the controller's memory. The hardware system calls this parameter array to drive the galvanometer motor to perform scanning trajectory mode switching and dynamically insert microsecond-level thermal relaxation gaps during continuous area scanning operations. The system's transient heat injection rate and the substrate's own thermal diffusion rate form a quantitatively matched steady-state operating state.

[0042] Example 5: For the laser beam processing of the bottom of the inner cavity of the large U-shaped rib of orthotropic steel bridge deck, in order to eliminate the high-frequency physical interference objectively superimposed on the optical signal collected by the photoelectric sensing unit caused by the commutation jitter of the galvanometer motor and the sudden change in local airflow, the system deploys a pre-processed data smoothing and baseline locking procedure before the filling scan of the execution area; the control unit divides the internal storage space into sections of length [missing information]. A sliding data window, the capacity of which is determined by the formula Calculated, where The fixed sampling frequency for the photoelectric sensing unit. To match the time constant of the thermal response hysteresis characteristics of a specific carbon steel substrate, the control unit drives the laser beam to perform scanning in a pre-cleaned benchmark test area with an increasing linear energy density, and uses the sliding data window to perform continuous one-dimensional moving average filtering on the real-time input reflection intensity signal value to filter out high-frequency interference, thereby outputting a smooth amplitude mean sequence.

[0043] During this process, the control unit synchronously calculates the real-time first derivative of the filtered amplitude mean sequence and compares it with a preset small fluctuation range close to zero. When it is determined that the absolute value of the first derivative has not exceeded the small fluctuation range within M consecutive sampling periods, the control unit determines that the optical response of the material interface has reached a nonlinear saturation state limited by the inherent physical properties of the matrix. At this time, the control unit latches the steady-state amplitude mean recorded in the window and confirms it as the full-scale feedback value for the current surface state of the component. The decision period M is limited to a value range of 15 to 25, based on which the system establishes a bottom-level optical baseline that excludes random interference. By performing sliding window filtering based on time constant constraints and derivative convergence determination based on continuous period evaluation during the initial scanning phase, the control unit establishes a rigorous numerical mapping between the device calibration coefficients and the true optical saturation response after noise filtering, ensuring that subsequent data based on the mathematical model... The calculated oxidation criterion It can resist random fluctuations in external environmental parameters.

[0044] 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 of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A laser beam processing technology for the surface of steel bridge components, characterized in that, Includes the following steps: Step S101: The beam deflection unit drives the laser beam to perform area filling scan on the surface of the steel bridge component, and the photoelectric sensing unit collects the reflection intensity signal value generated by the laser beam radiation in the area to be processed in real time. Step S102: The control unit extracts the amplitude mean of the reflection intensity signal value and constructs a characteristic time series sequence reflecting the evolution of surface physical properties. The characteristic time sequence is compared with the preset oxidation judgment benchmark in real time. The oxidation judgment benchmark is determined by the saturated reflectance of the steel bridge component substrate when it is exposed. In step S103, when the average amplitude enters the preset switching range, the control unit switches the scanning trajectory of the laser beam from a bidirectional serpentine scanning mode to a unidirectional intermittent scanning mode by modulating the phase of the driving current of the galvanometer motor in the beam deflection unit. In the unidirectional intermittent scanning mode, the control unit reads the mechanical inertia time of the galvanometer motor when it performs the commutation action at the end of each scanning line in real time, and constructs a thermal relaxation gap that is synchronously matched with the mechanical inertia time in the projection sequence of the laser beam. Within the time range corresponding to the thermal relaxation gap, the control unit sends a laser energy blocking command, uses the physical commutation period of the galvanometer motor as the physical residence time of thermal diffusion on the substrate surface, and controls the total amount of transient heat injection at the edge of the area to be processed by the scanning trajectory to be below the oxidation critical energy threshold of the steel bridge component substrate.

2. The laser beam processing technology for the surface of steel bridge components according to claim 1, characterized in that, In step S103, the control unit performs the following closed-loop adjustment steps: obtaining the real-time deviation between the average amplitude and the oxidation judgment benchmark, and calculating the evolution slope of the characteristic time sequence; the control unit linearly extends the laser off-time in the unidirectional intermittent scanning mode according to the increase of the evolution slope; the laser off-time is set to 1.1 to 1.5 times the unidirectional swing response time of the galvanometer motor; by dynamically interlocking the duty cycle of the laser beam with the commutation acceleration of the galvanometer motor, the temporal proportion of the thermal relaxation gap increases with the improvement of the surface cleanliness of the area to be treated; The control unit utilizes the thermal relaxation gap to establish a thermal hysteresis buffer zone at the edge boundary of the area to be treated, balancing the depth of the heat-affected zone between the center and the edge of the area to be treated, and maintaining the consistency of the metallurgical structure on the machined surface of the steel bridge component.

3. The laser beam processing technology for the surface of steel bridge components according to claim 1, characterized in that, In step S102, the control unit performs mean filtering on the reflection intensity signal value and removes the noise amplitude generated by laser plasma plume radiation according to the preset optical spectrum envelope to generate a characteristic time sequence. The control unit determines the thinning rate of surface contaminants in the area to be treated by calculating the first derivative of the characteristic time sequence and adjusts the pulse repetition frequency of the laser beam according to the absolute value of the first derivative.

4. The laser beam processing technology for the surface of steel bridge components according to claim 1, characterized in that, In step S103, the switching range is defined as: the average amplitude reaches 85% to 95% of the oxidation judgment benchmark; when the average amplitude is lower than the lower limit of the switching range, the control unit maintains the bidirectional serpentine scanning mode to maintain the macroscopic processing efficiency of the laser beam processing technology.

5. The laser beam processing technology for the surface of steel bridge components according to claim 1, characterized in that, When executing the unidirectional intermittent scanning mode in step S103, the control unit keeps the laser beam in an energy-off state during the physical cycle of the galvanometer motor performing the reverse return of the scan line, and restarts the laser beam at the starting trigger point of the next scan line to ensure that the direction of heat flow field conduction of the laser beam on the surface of the area to be processed has unidirectional determinism.

6. The laser beam processing technology for the surface of steel bridge components according to claim 1, characterized in that, The control unit corrects the overlap spacing d between adjacent scan lines in the scan trajectory in real time based on the surface topography features fed back by the feature time sequence; the overlap spacing d follows the following quantization rules: ,in, The preset initial scan line spacing, This is the real-time feedback value of the reflection intensity signal. As the criterion for oxidation determination, This is the full-scale feedback value of the photoelectric sensing unit.

7. The laser beam processing technology for the surface of steel bridge components according to claim 1, characterized in that, The steel bridge components are made of carbon steel, and their component forms include bridge deck, U-shaped ribs and transverse diaphragms. Before executing step S101, the control unit automatically compensates for the defocusing of the laser beam based on the obtained three-dimensional coordinate information of the surface of the steel bridge components, so that the energy density of the laser beam spot on the surface of the area to be processed is maintained between 5J / cm² and 15J / cm².

8. The laser beam processing technology for the surface of steel bridge components according to claim 1, characterized in that, In the unidirectional intermittent scanning mode, the duration of the thermal relaxation gap is limited to 5ms to 15ms, and is no less than 1.2 times the time consumed by a single physical reversal of the beam deflection unit.

9. The laser beam processing technology for the surface of steel bridge components according to claim 1, characterized in that, The process also includes step S104: after the processing of the area to be processed is completed, the control unit uses the photoelectric sensing unit to collect the surface features after cleaning and calculates the surface contrast value; when the surface contrast value meets the preset welding cleanliness level, the processing completion command is output and the energy output of the laser beam is stopped.

10. The laser beam processing technology for the surface of steel bridge components according to claim 1, characterized in that, The control unit establishes a closed-loop response circuit between the average amplitude and the output power of the laser beam; at the instant when the average amplitude reaches the oxidation judgment benchmark, the control unit performs a power reduction action to reduce the single pulse energy of the laser beam by 30% to 50% in order to limit the thermal penetration depth of the laser energy into the steel bridge component matrix.

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