Rotary laser and trajectory internal feeding timing coordinated steel surface repair method and system

Abstract

The present application belongs to the field of laser surface modification, and relates to a steel surface repair method and system with rotation laser and in-track feeding time sequence cooperation, comprising: determining a to-be-processed area of a to-be-processed steel surface, and forming a closed curve scanning track on the to-be-processed steel surface after laser is deflected by a rotating optical deflection assembly; feeding additive material to a feeding area located in the closed curve scanning track through a feeding assembly; controlling the machining head and the feeding assembly to move in the same direction along the processing direction, and the areas of the closed curve scanning track located before and after the feeding area respectively constitute a forward action area and a backward action area; the present application utilizes the mutual cooperation of the forward action area, the feeding area and the backward action area of the rotation laser scanning track, so that the same to-be-processed area sequentially experiences cleaning or preheating, additive material feeding and subsequent cladding, melting or remelting, thereby reducing the risk of additive material deposition to the unclean interface, and reducing the secondary pollution, repeated positioning and unstable interface state problems caused by step-by-step cleaning and step-by-step cladding.

Description

Technical Field

[0001] This invention relates to the field of laser processing and steel structure corrosion repair technology, specifically to a method and system for steel surface repair that coordinates the timing of rotating laser and in-track material feeding. Background Technology

[0002] When steel structures are used in marine, atmospheric, bridge, port, and industrial environments, their surfaces are prone to corrosion, forming corrosion products, oxides, salts, or contaminants. Current repair and protection processes for in-service steel structures typically involve mechanical rust removal or sandblasting followed by painting, spraying, welding, or laser cladding. This step-by-step process suffers from problems such as repetitive positioning, secondary contamination between processes, low processing efficiency, and difficulty in maintaining a stable interface condition after cleaning.

[0003] With the development of laser processing technology, integrating laser cleaning and laser cladding into the same process has become a research hotspot. Laser cleaning can apply localized energy to the surface of corroded steel, causing corrosion products to peel off, volatilize, break down due to thermal shock, or desorb from the interface; laser cladding or laser additive repair can form a repair and protective layer on the surface of the steel substrate. However, when additive materials are directly deposited on a rusted surface that has not been sufficiently cleaned, corrosion products, salts, or oxides may be drawn into the molten pool, resulting in inclusions, porosity, lack of fusion, or insufficient interfacial bonding; if cleaning is performed first and then cladding is performed in steps, secondary contamination after the cleaned surface is exposed and repeated positioning errors may occur.

[0004] Patent CN111945153A discloses a multi-source laser multi-channel integrated repair method for metal surfaces, which adopts multi-source laser multi-channel coupling to achieve integrated "washing-repair" treatment of metal surfaces through simultaneous parallel operation or step-by-step operation mode. However, this solution has the following shortcomings: (1) It requires the configuration of multiple independent laser sources and optical channels, resulting in high equipment costs and complex structures; (2) The cleaning laser and the repair laser are independent beam systems, and precise spatial position calibration is required between them, making it difficult to ensure that the same area to be treated is accurately aligned with the repair position after cleaning; (3) In the parallel operation mode, cleaning and cladding act on different areas simultaneously, while in the step-by-step operation mode, it is necessary to switch between different workstations, making it impossible to ensure that the same area undergoes sequential cleaning, feeding and cladding during the continuous movement of the same processing head; (4) It does not disclose the technical concept of using a single laser to naturally form front and rear action zones on a closed trajectory through rotary scanning and feeding within the trajectory.

[0005] Patent CN115229212A discloses a broadband laser cladding synchronous laser cleaning and grinding composite additive manufacturing device and method. It uses a broadband laser cladding head, a wire wheel grinding head and a laser cleaning head mounted side by side on the same device. The three move synchronously along the cladding direction during the workpiece's rotational motion to achieve composite processing of grinding-cleaning-cladding. However, the following shortcomings exist in this scheme: (1) Multiple independent processing heads are arranged side by side, resulting in structural redundancy and a large space occupation, which makes it difficult to adapt to the on-site repair needs of narrow spaces or complex curved steel structures; (2) The cleaning spot and the cladding spot come from independent laser systems, and are not naturally formed by the same laser beam after rotation and deflection, resulting in difficulty in matching energy distribution and scanning characteristics; (3) The processing objects are mainly shaft-type rotating workpieces, which rely on the rotational motion of the workpiece to form a spiral trajectory, which is not suitable for continuous moving repair of planar steel surfaces; (4) There is a lack of precise timing coordination control methods based on parameters such as rotational phase difference, rotational frequency, and scanning trajectory size, which makes it impossible to adjust the time interval from forward cleaning to backward cladding in the same area in real time according to the forward speed of the processing head, and it is also difficult to ensure the timing coordination between the material feeding point and the backward cladding action area; (5) The introduction of the wire wheel grinding head increases the complexity of the equipment and may cause mechanical damage to the surface of the steel substrate, which is not conducive to the metallurgical bonding of the subsequent cladding interface.

[0006] In summary, while existing integrated laser cleaning-cladding technology reduces process changes to some extent, it still fails to solve the technical problem of how to sequentially complete cleaning / preheating, additive feeding, and cladding / remelting of the same area to be treated through temporal coordination during the continuous movement of a single processing head and the same continuous wave laser beam. Therefore, there is an urgent need for a steel surface repair method and system that can precisely control the spatial intervals or time intervals between the forward action zone, the feeding zone, and the backward action zone within the same closed-circuit scanning trajectory of a rotary laser. Summary of the Invention

[0007] This invention provides a method and system for steel surface repair that coordinates the timing of rotary laser scanning and in-track material feeding. By utilizing the forward action zone, in-track material feeding zone, and backward action zone of the rotary laser scanning trajectory in the treatment of rusted steel surfaces, the same area to be treated sequentially undergoes cleaning or preheating, additive material supply, and subsequent cladding, melting, or remelting. This reduces the risk of additive material deposition on uncleaned interfaces and minimizes secondary contamination, repositioning, and interface instability caused by step-by-step cleaning and step-by-step cladding.

[0008] The objective of this invention can be achieved through the following technical solutions: One objective of this invention is to provide a method for repairing steel surfaces by coordinating the rotational laser with the feeding timing within the trajectory, for laser surface treatment of rusted steel, comprising: S1. Determine the area to be treated on the steel surface. After the laser is deflected by the rotating optical deflection component, it forms a closed curve scanning trajectory on the steel surface. S2. Additive material is supplied to the feeding zone located within the closed curve scanning trajectory via the feeding assembly; S3. The control head and the feeding assembly move in the same direction along the processing direction. The area of ​​the closed curve scanning trajectory in front of the feeding area constitutes the forward action zone, and the area of ​​the closed curve scanning trajectory behind the feeding area constitutes the backward action zone. The forward action zone irradiates the area to be treated to remove adhering substances from the surface of the steel substrate and pre-treat the surface of the steel substrate. The backward action zone irradiates the area where additive material has been supplied, causing the additive material to bond with the surface of the steel substrate to form a fusion interface. In other words, the forward action zone irradiates the area to be treated to remove corrosive substances from the surface of the steel substrate and preheat or activate the surface of the steel substrate. The backward action zone irradiates the area where additive material has been supplied, causing the additive material to clad, melt, or remelt and form a fusion interface with the surface of the steel substrate. Specifically, based on at least two of the following parameters—the size of the closed curve scanning trajectory, the rotational phase difference between the forward and backward action zones, the rotational frequency of the forward and backward action zones, the forward speed of the processing head relative to the steel substrate to be treated, the feeding point position of the feeding assembly, and the feeding and transport time—the spatial interval or time interval between the forward action zone, the feeding zone, and the backward action zone is coordinated so that the completion time of irradiation of the forward action zone, the arrival time of the additive material in the feeding zone, and the start time of irradiation of the backward action zone in the same area to be treated sequentially satisfy the following: the completion time of irradiation of the forward action zone is earlier than the arrival time of the additive material in the feeding zone, and the arrival time of the additive material in the feeding zone is earlier than the start time of irradiation of the backward action zone.

[0009] Furthermore, by using the size of the closed-curve scanning trajectory and the forward speed of the processing head relative to the steel substrate to be processed, the spatial interval or time interval between the forward action zone, the feeding zone and the backward action zone are coordinated. The time interval between the forward action zone and the backward action zone of a certain area of ​​the steel substrate to be treated is denoted as Δ. t macro The effective span of the closed curve scanning trajectory is denoted as . D eff The forward speed of the processing head relative to the steel substrate to be processed is denoted as . v head ; Satisfy Δ t macro = D eff / v head .

[0010] Wherein, the effective span of the closed curve scanning trajectory D eff , refers to the projected distance along the machining direction between the forward action zone and the backward action zone, for example, between the foremost and rearmost regions of a closed curve scanning trajectory. For a circular closed curve scanning trajectory, when the machining direction is fixed, the effective span Deff is approximately equal to the outer dimension of the closed curve scanning trajectory in the machining direction, for example, it can be taken as the diameter Dring of the annular trajectory; when the machining head forward speed is vhead, the time interval Δtmacro required for a fixed point on the steel surface to travel from the forward action zone through the feeding zone to the backward action zone is Δtmacro = Deff / vhead. In another embodiment, for elliptical or other shaped closed curve scanning trajectories, the effective span Deff is taken as the maximum outer dimension distance of the trajectory along the machining direction.

[0011] Furthermore, the spatial interval or time interval between the forward action zone, the feeding zone and the backward action zone are coordinated by the rotation phase difference between the forward action zone and the backward action zone and the rotation frequency between the forward action zone and the backward action zone. The time interval between the forward action zone and the backward action zone of a certain area of ​​the steel substrate to be treated is denoted as Δ. t phase The rotational phase difference between the forward action region and the backward action region is denoted as Δ. Φ The rotational frequencies of the forward and backward action regions are denoted as... n rot ; Satisfy Δ t phase = Δ Φ / (2π× n rot ).

[0012] Furthermore, the feeding assembly feeds materials through at least one of the following methods: central axis powder feeding, central axis wire feeding, side powder feeding, side wire feeding, multi-path converging powder feeding, single-sided wire feeding, or double-sided wire feeding.

[0013] Furthermore, the diameter of the closed curve scanning trajectory is denoted as... D ring The distance from the outlet of the feed nozzle of the feeding assembly to the surface of the steel to be treated is denoted as . H nozzle The lateral dimension of the area formed by the additive material powder jet ejected from the feed nozzle outlet of the feeding assembly on the steel surface to be treated is denoted as . D feed ; satisfy, D ring It ranges from 10 to 50 mm.H nozzle It ranges from 5 to 50 mm. D feed ≤ D ring .

[0014] Furthermore, the additive material is at least one of Fe-based materials, Ni-based materials, stainless steel materials, Al / Zn-based materials, ceramic-reinforced composite materials, metal powders, alloy powders, cored wires, solid wires, slurries, or pre-formed particles.

[0015] Furthermore, the closed curve scanning trajectory is also provided with an avoidance sector, which is located in the upper and / or lower regions of the closed curve scanning trajectory. When the laser passes through the avoidance sector, the laser energy is reduced.

[0016] The second objective of this invention is to provide a steel surface repair system that coordinates the rotational laser with the timing of material feeding within the trajectory, comprising: The motion execution unit is used to drive the processing head to move continuously along the processing direction of the steel surface to be processed; The laser action unit includes a continuous wave laser and a rotating optical deflection assembly. The laser is used to output continuous laser light, and the rotating optical deflection assembly is used to form a closed curve scanning trajectory on the steel surface to be treated after the continuous laser light is rotated and refracted. The feeding unit supplies additive material to the feeding zone located in the middle of the closed curve scanning trajectory. The area of ​​the closed curve scanning trajectory before the feeding zone constitutes the forward action zone, and the area of ​​the closed curve scanning trajectory after the feeding zone constitutes the backward action zone. The area to be treated is irradiated by the forward action zone to remove corrosive substances from the surface of the steel substrate and to preheat or activate the surface of the steel substrate. The area to which additive material has been supplied is irradiated by the backward action zone to cause the additive material to clad, melt, or remelt and form a fusion interface with the surface of the steel substrate. The timing coordination control unit is used to coordinate the spatial interval or time interval between the forward action zone, the feeding zone and the backward action zone based on at least two of the following parameters: the size of the closed curve scanning trajectory, the rotation phase difference between the forward action zone and the backward action zone, the rotation frequency of the forward action zone and the backward action zone, the forward speed of the processing head relative to the steel substrate to be treated, the feeding landing point position of the feeding assembly and the feeding and transport time. This ensures that the completion time of irradiation of the forward action zone, the arrival time of the additive material in the feeding zone and the start time of irradiation of the backward action zone in the same area to be treated satisfy the following in sequence: the completion time of irradiation of the forward action zone is earlier than the arrival time of the additive material in the feeding zone, and the arrival time of the additive material in the feeding zone is earlier than the start time of irradiation of the backward action zone.

[0017] Furthermore, the system also includes a thermal state acquisition or prediction unit, which is connected to the timing coordination control unit. The thermal state acquisition or prediction unit is used to acquire or predict the background thermal state, surface temperature, steel substrate surface temperature, fusion depth, or heat-affected zone depth formed by the laser action unit in the forward action zone through temperature sensors or thermal conduction models, and send it to the timing coordination control unit to adjust the laser power, scanning speed, overlap rate, number of repeat passes, or processing head movement speed of the laser action unit in the backward action zone.

[0018] Furthermore, the system also includes a feedback detection unit connected to the timing coordination control unit. This feedback detection unit detects the surface morphology, layer thickness, fusion depth, heat-affected zone depth, porosity, cracks, residual corrosion, or rust recurrence status of the repair protective layer, and sends the detection results to the timing coordination control unit to update one or more of the following parameters: The laser power, scanning speed, or overlap rate of the laser action unit in the forward action zone; The feeding amount of the feeding unit; The laser power, scanning speed, or overlap rate of the laser action unit in the backward action zone; The motion speed of the motion execution unit.

[0019] Compared with the prior art, the present invention has the following advantages: (1) This invention utilizes a single-beam continuous wave laser to form a closed-curve scanning trajectory on the surface of the steel to be treated via a rotating optical deflection component. During the continuous movement of the processing head, three functional zones are naturally formed: a forward action zone, a material feeding zone within the trajectory, and a backward action zone. Through time-series coordinated control, the same area to be treated sequentially undergoes cleaning and preheating, additive material supply, and cladding and remelting. Compared with existing multi-source laser multi-channel or multi-processing head parallel schemes, this invention only requires a single processing head and a single-beam continuous wave laser to achieve integrated continuous processing of cleaning, material feeding, and cladding. The equipment structure is compact, and there is no need for precise spatial positioning calibration of multiple independent laser systems, fundamentally eliminating multi-optical path coupling errors. Compared to the traditional process of cleaning and cladding in stages, this invention ensures that the additive material is always deposited on the interface that has been thoroughly cleaned and preheated by the forward action zone, reducing the risk of corrosion products, salts or oxides being drawn into the molten pool and forming inclusions, pores and incomplete fusion defects. At the same time, since cleaning and cladding are completed sequentially during the continuous movement of the same processing head, secondary contamination caused by exposure of the cleaning surface between stages and repeated positioning errors caused by station switching are avoided, ensuring the metallurgical stability of the fusion interface and the consistency of the repair layer quality.

[0020] (2) This invention establishes a quantitative relationship between the macroscopic time interval, the effective span of the closed curve scanning trajectory, and the forward speed of the processing head. That is, the macroscopic time interval is equal to the ratio of the effective span of the scanning trajectory to the forward speed of the processing head, providing a clear basis for calculating the time window for the timing coordination control unit. Operators can flexibly control the time interval from cleaning and preheating to cladding and remelting of the same area to be treated without changing the laser source or rotating optical deflection components by adjusting the size of the closed curve scanning trajectory or the forward speed of the processing head. This allows the interval to be precisely matched with the material feeding and conveying time, adapting to the timing requirements of different corrosion degrees, different additive materials, and different processing conditions.

[0021] (3) This invention provides a microscopic means of precise timing control by establishing a quantitative relationship between the time interval and the rotational phase difference and rotational frequency of the forward and backward action zones, i.e., the time interval corresponding to the phase difference is equal to the rotational phase difference divided by the product of the rotational frequency and the complete circumferential angle. With the forward speed of the processing head remaining constant, the phase timing between forward cleaning and backward cladding in the same area can be precisely adjusted within milliseconds by changing the rotational frequency of the rotating optical deflection component, meeting the process requirements of high-precision timing coordination, and providing quantifiable control parameters for adaptive timing optimization under different workpiece surface temperature conditions. Attached Figure Description

[0022] Figure 1 This is a structural block diagram of a steel surface repair system that coordinates the timing of rotating laser and in-track material feeding in this invention. Figure 2 This is a schematic diagram of the material feeding head structure within the rotary laser trajectory in this invention; Figure 3 This is a top view schematic diagram of the forward action area, the backward action area, the material supply area within the trajectory, and the optional avoidance sector in this invention; Figure 4 This is a schematic diagram of the material feeding geometry parameters within the trajectory in this invention; Figure 5 This is a schematic diagram of the continuous processing and the formation of the repair and protective layer in this invention.

[0023] The markings in the figure are as follows: 1-Continuous wave laser; 2-Rotating optical deflection component; 3-Central shaft; 4-Central axis; 5-Continuous wave laser beam after deflection; 6-Feeding nozzle; 7-Feeding area; 8-Closed curve scanning trajectory; 9-Steel substrate to be treated; 10-Forward action area; 11-Backward action area; 12-Avoidance sector. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0025] Example 1 like Figures 1-3 As shown, this embodiment provides a basic implementation of a steel surface repair method that coordinates the timing of rotating laser and in-track material feeding.

[0026] The processing head is equipped with a laser and a rotating optical deflector assembly. The laser outputs a continuous wave laser 1. The rotating optical deflector assembly 2 can be a rotating prism, a rotating refractive optical element, or a refractive scanning assembly. The rotating optical deflector assembly 2 rotates under the drive of the central axis 3. After the continuous wave laser 1 is incident on the rotating optical deflector assembly 2, it is deflected by the assembly, and the output beam forms a fixed deflection angle relative to the central axis. When the rotating optical deflector assembly 2 rotates uniformly around the central axis 4, the deflected laser spot sweeps across the surface of the steel substrate 9 to be processed, forming a dynamic circular or near-circular closed curve scanning trajectory 8.

[0027] The feeding assembly is located inside or on the side of the processing head, with its feeding nozzle 6 exiting towards the area enclosed by the closed-curve scanning trajectory. Powder, filament, or other additive materials are supplied to the feeding zone 7 inside the closed-curve scanning trajectory via the feeding assembly. The feeding point can be set at the geometric center of the dynamic scanning trajectory, or it can be offset relative to the geometric center based on the feeding transport time, protective gas flow distribution, molten pool location prediction, or structural avoidance requirements.

[0028] The processing head is driven by an external motion execution unit and moves continuously along the processing direction of the steel surface to be processed. During the movement of the processing head, the position of the closed curve scanning trajectory 8 relative to the steel surface changes continuously, thus naturally forming two functional zones in the processing direction: with the processing direction as the reference, the trajectory segment located in front of the feeding area, that is, the forward side of the movement direction, constitutes the forward action zone 10; the trajectory segment located behind the feeding area, that is, the backward side of the movement direction, constitutes the backward action zone 11.

[0029] During processing, the forward action zone 10 first irradiates the area of ​​the steel substrate to be treated. The laser energy acts on the rusted surface, causing corrosion products, oxides, salts, or contaminants to peel off, volatilize, thermally shock break, or desorb at the interface, thus removing the rust layer. Simultaneously, the residual heat effect of the laser preheats or activates the surface of the steel substrate, improving the activity of the subsequent fusion interface. Subsequently, as the processing head moves forward relatively, the same area enters the feeding zone 7 within the trajectory, where additive material is precisely supplied to the surface of the steel substrate that has been derusted and preheated. After a brief transport and waiting period, the same area further enters the backward action zone 11, where the laser energy irradiates the supplied additive material and the surface of the steel substrate, causing the additive material to clad, melt, or remelt, forming a strong fusion interface with the surface of the steel substrate.

[0030] Therefore, as Figure 5 As shown, in this embodiment, the forward action area 10 and the backward action area 11 naturally formed on the closed curve scanning trajectory by the same rotating laser beam, together with the feeding area 7 in the trajectory, realize the continuous process of the same area to be treated undergoing cleaning / preheating-feeding-cladding / remelting in strict sequence, avoiding the direct deposition of additive materials onto the untreated rusted surface.

[0031] Example 2 Based on Example 1, this embodiment further provides a coordinated control method for the spatial interval or time interval between the forward action area, the feeding area and the backward action area, so as to ensure that the same area to be processed meets strict timing constraints during the switching process of each functional zone.

[0032] In one implementation, the effective span of the dynamic closed curve scanning trajectory along the processing direction is denoted as... D eff The forward speed of the processing head relative to the steel substrate to be processed is denoted as . v head The macroscopic time interval Δ during which the same region to be processed moves from the forward action zone to the backward action zone is then considered. t macro It can be calculated according to the following relationship: Δ t macro = D eff / v head Among them, effective span D eff This refers to the projected distance along the machining direction between the forward and backward action areas. For a circular closed curve scanning trajectory, when the machining direction is fixed, the effective span... D eff It can be approximated as the diameter of the circular trajectory.D ring For closed curve scanning trajectories of elliptical or other irregular shapes, the effective span is... D eff The maximum outer contour distance of the trajectory along the processing direction is taken as the reference value. The controller then uses this macroscopic time interval Δ... t macro By combining the feeding and conveying time of the feeding components with the feeding landing point, the forward speed or rotation frequency of the processing head is coordinated and adjusted so that the time when the additive material reaches the steel surface is later than the time when the forward action zone completes its action on the area, and earlier than the time when the backward action zone begins to clad the area.

[0033] In another embodiment, the timing relationship between the forward and backward acting regions can also be precisely determined by their rotational phase difference. Let the rotational phase difference between the forward and backward acting regions be ΔΦ, and the rotational frequency of the rotating optical deflector be... n rot Then the time interval Δ corresponding to the phase difference t phase It can be represented as: Δ t phase = ΔΦ / (2π × n rot ) When the forward action region and the backward action region differ spatially by half a rotation period (i.e., ΔΦ = π), the above relationship can be simplified to: Δ t phase = 1 / (2 × n rot ) This embodiment establishes a time window model for the same area to be processed from cleaning / preheating to cladding / remelting, providing a precise algorithmic basis for the timing collaborative control unit, thereby ensuring that the feeding action always occurs after the forward cleaning is completed and before the backward cladding begins during continuous high-speed movement.

[0034] Example 3 This embodiment provides various specific implementations of the feeding component based on embodiment 1 or embodiment 2.

[0035] The feeding method that the feeding assembly can adopt includes, but is not limited to, at least one of the following: central axis powder feeding, central axis wire feeding, side powder feeding, side wire feeding, multi-path converging powder feeding, single-sided wire feeding, or double-sided wire feeding.

[0036] In a preferred embodiment, the feeding nozzle is located within the area enclosed by the dynamic closed-curve scanning trajectory, employing a central or near-central feeding method to precisely supply powder to the feeding area within the trajectory under the action of carrier gas or protective gas. In this arrangement, the feeding point is located between the forward action zone and the backward action zone, facilitating the reception of preheating energy from the forward action zone and awaiting the cladding energy from the backward action zone.

[0037] In another preferred embodiment, the feeding assembly is designed as a replaceable modular structure. The first module is a powder feeding nozzle module, suitable for supplying powder-based additive materials; the second module is a filament feeding channel module, suitable for supplying filament-based additive materials. The replaceable modules are installed to the processing head housing via detachable connection structures, such as threaded connections, snap-fit ​​connections, or flange connections, allowing the same processing head to quickly switch between powder feeding mode and filament feeding mode according to the repair process requirements.

[0038] Furthermore, to protect the feeding assembly from the effects of the dynamic rotating laser thermal field, a heat insulation layer and a water-cooling channel can be installed on the outer wall of the feeding assembly. The heat insulation layer can be made of high-temperature resistant ceramic fiber or aerogel composite material; the water-cooling channel can be spirally arranged along the outer wall of the feeding assembly, using circulating cooling water to remove radiant heat. In addition, the feeding assembly also integrates a protective gas channel, which can be used for both long-distance stable transport of powder and inert gas protection of the molten pool surface to prevent oxidation of the high-temperature molten pool. A splash guard or splash cover can also be installed at the end of the feeding assembly to reduce the adhesion and contamination of molten droplets, splashed powder, or oxides to the feeding nozzle outlet, ensuring feeding accuracy and long-term operational stability.

[0039] Example 4 Based on any of the embodiments in Embodiments 1-3, this embodiment further defines the key geometric parameters and their preferred range between the dynamic closed curve scanning trajectory and the feeding component, so as to ensure that the additive material falls accurately within the feeding area of ​​the trajectory and to ensure that the forward action area and the backward action area have sufficient effective action distance.

[0040] like Figure 4 As shown, the following key geometric parameters are defined: The diameter of the dynamic closed curve scanning trajectory is denoted as D ring ; The vertical distance from the outlet of the feed nozzle of the feeding assembly to the surface of the steel to be treated is denoted as . H nozzle ; The lateral dimension of the supply area formed on the steel surface by the additive material powder or filament ejected from the feed nozzle is denoted as . D feed .

[0041] In a preferred embodiment, the above parameters satisfy the following relationship: D ring The value ranges from 10 mm to 50 mm; H nozzle The value ranges from 5 mm to 50 mm; D feed ≤ D ring .

[0042] The significance of the above geometric relationship lies in the fact that by setting the diameter of the closed-curve scanning trajectory within the range of 10 mm to 50 mm, it ensures that the forward action zone has sufficient laser dwell time to complete rust removal and preheating, while also ensuring sufficient energy input in the backward action zone to complete the cladding and metallurgical bonding of the additive material; feeding distance H nozzle The distance is controlled between 5 mm and 50 mm, balancing the focusing accuracy of the powder flow or filament and the thermal safety distance of the feeding components; D feed ≤ D ring The constraints ensure that the landing area of ​​the additive material is always completely surrounded by the closed curve scanning trajectory, avoiding the scattering of powder or filament outside the effective range of the laser, which would result in material waste or interface contamination.

[0043] In the powder feeding embodiment, the preferred powder particle size range is 50 micrometers to 150 micrometers. The powder material can be Fe-based, Ni-based, stainless steel, Al / Zn-based, ceramic-reinforced composite materials, or combinations thereof. In the wire feeding embodiment, the wire material can be solid wire, flux-cored wire, or other alloy wire that can be laser-melted to form a repair and protective layer.

[0044] Example 5 Based on any of the embodiments in Embodiments 1-4, this embodiment further provides an optional avoidance sector design to solve the problems of possible obstruction, interference, or lateral heat accumulation between the feeding pipeline, powder feeding nozzle, wire feeding component or its support structure and the deflected rotary laser optical path.

[0045] like Figure 3As shown, in one embodiment, the dynamic closed-curve scanning trajectory may be provided with at least one avoidance sector 12. The avoidance sector is located in the upper and / or lower region of the closed-curve scanning trajectory. Here, "upper" and "lower" are relative to the processing direction: if the processing direction is horizontal, then "upper" and "lower" correspond to the areas above and below the scanning trajectory, respectively. The feeding pipeline, powder nozzle, wire feeding component, or its supporting structure can extend into the feeding area within the trajectory through the spatial position corresponding to the avoidance sector, thereby achieving a structural layout that allows lateral entry into the feeding area from a non-processing direction, avoiding motion interference with the laser action area in the forward and backward directions.

[0046] Within the scanning phase range corresponding to the avoidance sector, the effective laser energy input can be reduced by at least one of the following methods: (1) Turn off laser output: Within the phase window corresponding to the avoidance sector, a gating signal is sent to the laser through the timing coordination control unit to temporarily turn off the laser output; (2) Reduce laser power: Reduce the laser power within the avoidance sector to a level that is insufficient to melt the substrate but can maintain the presence of the beam; (3) Skip the scanning phase: By increasing the rotation speed of the rotating optical deflector within the corresponding angle range of the avoidance sector, the region can be quickly skipped, shortening the dwell time of the laser in the region; (4) Deflecting the beam or changing the optical path: By using an additional tilting mirror or beam deflector, the main beam is deflected from the workpiece surface within the avoidance sector. (5) Set up a light-shielding structure: Set up a local light-shielding cover inside the processing head to block the laser at the mechanical position corresponding to the avoidance sector.

[0047] It should be noted that the energy reduction state formed within the avoidance sector after the continuous wave laser in this embodiment undergoes the aforementioned phase synchronization gating, power modulation, skip scan control, beam deflection, or shading control can be considered a quasi-continuous output state. This quasi-continuous output does not require the use of a specific type of quasi-continuous wave laser, but rather achieves local energy management through time-varying control of the continuous wave laser. Its purpose is to provide a safe mechanical path for the feeding component and reduce the risk of heat accumulation in the lateral region of the scanning trajectory.

[0048] Example 6 This embodiment provides a steel surface repair system that coordinates the rotational laser and the in-track feeding timing with the method described above, and describes the complete process of using this system to perform continuous processing and form a repair and protective layer.

[0049] The steel surface repair system includes: The motion execution unit is used to carry and drive the processing head to move continuously along the processing direction of the steel surface to be treated. The motion execution unit can be at least one of the following: a Cartesian coordinate robot, a multi-axis linkage robotic arm, a gantry-type walking mechanism, or a crawling mobile platform, specifically selected according to the size, shape, and on-site working conditions of the steel component to be repaired.

[0050] The laser processing unit includes a continuous-wave laser and a rotating optical deflector assembly. The continuous-wave laser is used to output high-power continuous laser light, and the power range is adjustable according to the thickness of the rust layer, the type of additive material, and the depth of the cladding layer. The rotating optical deflector assembly is installed downstream of the laser's optical path and is used to rotate and refract the continuous laser light to form a closed-curve scanning trajectory on the steel surface.

[0051] The feeding unit includes a feeding assembly, a powder feeder or wire feeder, a carrier gas / protective gas source, and its flow control valve. The feeding unit supplies additive material to the feeding zone located in the middle of the closed-curve scanning trajectory. The trajectory segment in front of the feeding zone constitutes the forward action zone, and the trajectory segment behind the feeding zone constitutes the backward action zone. The forward action zone is used to remove surface corrosion and preheat or activate the steel substrate surface; the backward action zone is used to clad, melt, or remelt the area where additive material has been supplied, forming a fusion interface between the additive material and the steel substrate surface.

[0052] The timing coordination control unit, as the core control module of the system, is connected to the motion execution unit, laser ablation unit, and feeding unit. The timing coordination control unit receives at least two of the following parameters: the size of the closed curve scanning trajectory, the rotational phase difference between the forward and backward ablation zones, the rotational frequency, the forward speed of the processing head relative to the steel substrate, the feeding point position of the feeding assembly, and the feeding and transport time. Through an internal algorithm, it coordinates the spatial or time intervals between the forward ablation zone, the feeding zone, and the backward ablation zone in real time. The timing coordination control unit ensures that the completion time of irradiation in the forward ablation zone of the same area to be processed is earlier than the arrival time of the additive material in the feeding zone, and that the arrival time of the additive material in the feeding zone is earlier than the start time of irradiation in the backward ablation zone.

[0053] In a further optimized embodiment, the system also includes a thermal state acquisition or prediction unit. This thermal state acquisition or prediction unit is connected to a timing-coordinated control unit. It can directly measure the background thermal state, surface temperature, and steel substrate surface temperature formed after the forward action zone is cleared / preheated using contact or non-contact temperature sensors, such as infrared thermal imagers or thermocouples. Alternatively, it can predict thermal parameters such as fusion depth and heat-affected zone depth using a built-in thermal conduction numerical model. The thermal state acquisition or prediction unit sends the acquired or predicted results to the timing-coordinated control unit in real time. Based on this, the timing-coordinated control unit dynamically adjusts the laser power, scanning speed, overlap rate, number of repeat passes, or processing head movement speed of the laser action unit in the backward action zone to compensate for fluctuations in the thermal state of the forward action zone and ensure the stability of the backward cladding process.

[0054] In another further optimized embodiment, the system also includes a feedback detection unit. This feedback detection unit is connected to the timing-coordinated control unit and can perform online detection of the formed repair protective layer using at least one of a laser displacement sensor, eddy current thickness gauge, ultrasonic non-destructive testing instrument, visual inspection system, or spectral analysis system. The detection content includes, but is not limited to: the surface morphology, layer thickness, fusion depth, heat-affected zone depth, porosity, crack state, and residual corrosion or rust re-emergence state of the repair protective layer. After the feedback detection unit sends the detection results to the timing-coordinated control unit, the timing-coordinated control unit executes a closed-loop control strategy, automatically updating one or more of the following parameters: Adjust the laser power, scanning speed, or overlap rate of the laser action unit in the forward action zone to optimize the rust removal and preheating effect; Adjust the feed rate of the feeding unit to match the molten pool requirements and layer thickness target; Adjust the laser power, scanning speed, or overlap rate of the laser action unit in the backward action zone to optimize the cladding quality; Adjust the speed of the motion execution unit to coordinate the macroscopic processing rhythm.

[0055] The complete process of continuous processing using the above system is described below: First, the processing head is positioned at the starting processing position of the steel substrate to be processed. The continuous wave laser is activated, and after being deflected by the rotating optical deflector, the laser beam forms a dynamic closed-curve scanning trajectory on the steel surface. The motion execution unit is then activated, causing the processing head to move at a constant speed along the preset processing direction.

[0056] As the processing head moves, the area of ​​the corroded steel substrate to be treated first enters the forward action zone. The rotating laser spot in the forward action zone sweeps the corroded surface with high energy density, causing the corrosion products to rapidly vaporize, peel off, or desorb, while the residual heat preheats and activates the underlying steel substrate.

[0057] Subsequently, the same area moves relative to the processing head and enters the feeding zone within the trajectory. The feeding unit precisely supplies powder or filament to the cleaned and preheated steel substrate surface according to the feeding rate and feeding point preset by the timing coordination control unit. Because there is a controlled time interval between the forward action zone and the feeding zone, the additive material will not be directly deposited on the untreated rusted surface, avoiding the risk of corrosion products being drawn into the molten pool.

[0058] Subsequently, the same region enters the backward-acting zone. The rotating laser spot in the backward-acting zone irradiates the supplied additive material and the steel substrate surface with a suitable energy density, causing the additive material to melt rapidly and form a molten pool. Under the influence of laser scanning motion and heat conduction, the molten pool spreads and solidifies, forming a metallurgically bonded fusion interface with the steel substrate surface.

[0059] As the processing head continues to advance along the processing path, the aforementioned forward cleaning / preheating-in-track feeding-backward cladding / remelting process is repeated continuously along the processing path. Appropriate overlap rates are achieved between adjacent closed-curve scanning trajectories by controlling the movement speed and rotation parameters of the motion execution unit, ultimately forming a continuous, uniform, and well-overlapping repair and protective layer on the steel surface.

[0060] Application Example 1 This application example refers to the method provided in Example 1 to perform in-situ repair on locally corroded areas of a vertical steel plate of a bridge. The steel plate to be treated is set vertically, and the area to be treated is 500 mm × 500 mm in size. The specific treatment process is as follows.

[0061] S1, Preprocessing of the area to be processed Manual tools were used to remove loose rust and adhering debris from the surface of the area to be treated. After pretreatment, a residual rust layer with a thickness of approximately 100 μm remained on the steel plate surface. The above treatment was mainly used to remove loose rust products and surface debris that were weakly bonded to the steel plate substrate. The remaining rust layer that was more tightly bonded to the steel plate substrate was further removed by a subsequent rotary laser, while the steel plate substrate was preheated and the metal powder was fused simultaneously.

[0062] S2, Arrangement of laser processing head and powder supply nozzle A laser processing head is positioned on the outer side of the steel plate to be treated, with a distance of 200 mm between the rotating prism inside the laser processing head and the surface of the steel plate. The laser beam is refracted and deflected by the rotating prism before being projected onto the steel plate surface. The rotating prism rotates continuously at 5000 rpm, causing the laser beam to form a 20 mm diameter annular scanning trajectory on the steel plate surface. A powder supply nozzle is positioned within the area enclosed by the annular scanning trajectory, with a 20 mm distance between the nozzle outlet and the steel plate surface. By adjusting the spray direction and powder supply range of the nozzle, a 15 mm diameter powder supply area is formed on the steel plate surface. This powder supply area is located within the area enclosed by a closed, annular scanning trajectory, and its diameter is smaller than the diameter of the annular scanning trajectory. In this embodiment, an iron-based metal repair powder compatible with the bridge steel plate substrate is used. The powder supply nozzle and the laser processing head maintain a set relative position and move synchronously along a predetermined repair path.

[0063] S3. Determine the forward action region and the backward action region. Using the movement direction of the laser processing head relative to the steel plate surface as a reference, for the same location to be processed on the steel plate surface, the portion of the closed-curve scanning trajectory that first passes through that location is defined as the forward action zone, and the portion that subsequently passes through that location is defined as the backward action zone. Along the movement direction of the laser processing head, the location to be processed is sequentially irradiated by the forward action zone, the powder supply zone within the trajectory, and the backward action zone. The powder supply nozzle delivers metal powder to the steel plate surface that has been treated by the forward action zone but has not yet been treated by the backward action zone, thus forming a sequential synergy of pre-laser treatment, powder supply within the trajectory, and post-laser fusion.

[0064] S4. Perform the first laser repair treatment. In the first pass, the laser output power was set to 3000 W, the rotating prism speed was maintained at 5000 rpm, and the laser processing head and powder supply nozzle moved synchronously along the predetermined repair path, gradually covering the 500 mm × 500 mm area to be processed with the circular scanning trajectory. During this pass, the laser output power remained constant, ensuring that the laser output power corresponding to the forward and backward action areas remained consistent.

[0065] The forward-acting zone first irradiates the attached rust layer on the steel plate surface, causing it to break down, ablate, and peel off, thereby removing the remaining rust layer. Simultaneously, the forward-acting zone heats the surface of the derusted steel plate substrate, creating surface temperature conditions in the powder supply area conducive to the initial adhesion of the metal powder. After the forward-acting zone passes the treatment area, the powder supply nozzle delivers metal powder to the derusted and preheated steel plate surface. Under the surface temperature conditions created by the forward-acting zone, some of the metal powder entering the powder supply area softens, sinters, or initially melts, adhering to the vertical steel plate surface. Subsequently, the backward-acting zone passes over the steel plate surface with the attached metal powder, continuing to heat both the metal powder and the steel plate substrate surface, further melting the metal powder and causing the corresponding steel plate substrate surface to melt. The molten metal powder and the steel plate substrate surface form a molten pool, which, after cooling and solidifying, forms a metal repair layer metallurgically bonded to the steel plate substrate. Although the forward and backward action zones use the same laser output power, the material and temperature states of the steel plate surface are different when they act. The forward action zone is mainly used to remove the remaining rust layer and establish the surface temperature conditions, while the backward action zone is mainly used to promote the melting and fusion of metal powder with the surface layer of the steel plate substrate. Thus, rust removal, preheating, powder supply and fusion are completed sequentially in one movement.

[0066] S5. Perform subsequent laser repair treatment. After the first pass, the remaining rust layer, powder coverage, and continuity of the repair layer are inspected in the repaired area. Based on the inspection results, the subsequent treatment path and areas requiring focused supplementary treatment are determined. Starting with the second pass, the laser output power is reduced to 1500 W, the rotating prism speed is maintained at 5000 rpm, and the distance between the powder supply nozzle outlet and the steel plate surface is maintained at 20 mm. During the same subsequent pass, the laser output power for the forward and backward action zones remains consistent. The subsequent treatment uses a 1500 W laser output power to control heat accumulation during multiple passes, reduce the degree of repeated melting of the formed metal repair layer and the risk of thermal damage, while maintaining the surface temperature conditions required for subsequent metal powder deposition and fusion.

[0067] Following the sequence of pre-laser treatment, internal powder supply, and post-laser fusion, continue with 3-5 passes of subsequent treatment. In principle, each pass should cover a 500 mm × 500 mm area to be treated along the predetermined repair path. Additional treatment can be performed on areas with residual rust, missed areas, or discontinuous repair layers based on the results of the previous pass. After each pass, check the remaining rust layer, metal powder coverage, and continuity of the repair layer. Adjust the treatment path for the next pass accordingly, supplementing areas with insufficient powder capture on the vertical steel plate surface or discontinuous repair layers to improve the integrity and continuity of the metal repair layer.

[0068] S6. Repair complete. Once the remaining rust layer in the area to be treated is removed and a continuous metal repair layer is formed on the steel plate surface, the laser output and metal powder delivery are stopped, completing the repair of the localized rust area of ​​the vertical steel plate of the bridge. This embodiment controls the relative positional relationship between the closed-curve scanning trajectory, the powder supply area within the trajectory, and the direction of laser processing head movement. This ensures that the forward action area, powder supply area, and backward action area sequentially act on the same area to be treated on the steel plate surface, achieving continuous processing of remaining rust layer removal, steel plate substrate preheating, initial metal powder adhesion, and fusion of metal powder with the steel plate substrate.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for repairing steel surfaces using a rotating laser and a feeding sequence within a trajectory, for laser surface treatment of rusted steel, characterized in that, include: S1. Determine the area to be treated on the steel surface. After the laser is deflected by the rotating optical deflection component, it forms a closed curve scanning trajectory on the steel surface. S2. Additive material is supplied to the feeding zone located within the closed curve scanning trajectory via the feeding assembly; S3. Control the processing head and the feeding assembly to move in the same direction along the processing direction. The area of ​​the closed curve scanning trajectory in front of the feeding area constitutes the forward action area, and the area of ​​the closed curve scanning trajectory behind the feeding area constitutes the backward action area. The area to be processed is irradiated by the forward action area to remove the adhering substances on the surface of the steel substrate and to perform surface pretreatment on the steel substrate surface. The area to which the additive material has been supplied is irradiated by the backward action area to make the additive material bond with the surface of the steel substrate to form a fusion interface. Specifically, based on at least two of the following parameters—the size of the closed curve scanning trajectory, the rotational phase difference between the forward and backward action zones, the rotational frequency of the forward and backward action zones, the forward speed of the processing head relative to the steel substrate to be treated, the feeding point position of the feeding assembly, and the feeding and transport time—the spatial interval or time interval between the forward action zone, the feeding zone, and the backward action zone is coordinated so that the completion time of irradiation of the forward action zone, the arrival time of the additive material in the feeding zone, and the start time of irradiation of the backward action zone in the same area to be treated sequentially satisfy the following: the completion time of irradiation of the forward action zone is earlier than the arrival time of the additive material in the feeding zone, and the arrival time of the additive material in the feeding zone is earlier than the start time of irradiation of the backward action zone.

2. The steel surface repair method according to claim 1, characterized in that, By using the size of the closed-curve scanning trajectory and the forward speed of the processing head relative to the steel substrate to be processed, the spatial interval or time interval between the forward action zone, the feeding zone and the backward action zone are coordinated. The time interval between the forward action zone and the backward action zone of a certain area of ​​the steel substrate to be treated is denoted as Δ. t macro The effective span of the closed curve scanning trajectory is denoted as . D eff The forward speed of the processing head relative to the steel substrate to be processed is denoted as . v head ; Satisfy Δ t macro = D eff / v head .

3. The steel surface repair method according to claim 1, characterized in that, By using the rotation phase difference and rotation frequency between the forward action zone and the backward action zone, the spatial interval or time interval between the forward action zone, the feeding zone and the backward action zone are coordinated. The time interval between the forward action zone and the backward action zone of a certain area of ​​the steel substrate to be treated is denoted as Δ. t phase The rotational phase difference between the forward action region and the backward action region is denoted as Δ. Φ The rotational frequencies of the forward and backward action regions are denoted as... n rot ; Satisfy Δ t phase = Δ Φ / (2π× n rot ).

4. The steel surface repair method according to claim 1, characterized in that, The feeding assembly feeds materials through at least one of the following methods: central axis powder feeding, central axis wire feeding, side powder feeding, side wire feeding, multi-path converging powder feeding, single-sided wire feeding, or double-sided wire feeding.

5. The steel surface repair method according to claim 1, characterized in that, The diameter of the closed curve scanning trajectory is denoted as D ring The distance from the outlet of the feed nozzle of the feeding assembly to the surface of the steel to be treated is denoted as . H nozzle The lateral dimension of the area formed by the additive material powder jet ejected from the feed nozzle outlet of the feeding assembly on the steel surface to be treated is denoted as . D feed ; satisfy , D ring It ranges from 10 to 50 mm. H nozzle It ranges from 5 to 50 mm. D feed ≤ D ring .

6. The steel surface repair method according to claim 1, characterized in that, The additive material is at least one of Fe-based materials, Ni-based materials, stainless steel materials, Al / Zn-based materials, ceramic-reinforced composite materials, metal powders, alloy powders, cored wires, solid wires, slurries, or pre-formed particles.

7. The steel surface repair method according to claim 1, characterized in that, The closed curve scanning trajectory is also provided with an avoidance sector, which is located in the upper and / or lower regions of the closed curve scanning trajectory. When the laser passes through the avoidance sector, the laser energy is reduced.

8. A steel surface repair system with coordinated rotary laser and in-track feeding timing, characterized in that, include: The motion execution unit is used to drive the processing head to move continuously along the processing direction of the steel surface to be processed; The laser action unit includes a continuous wave laser and a rotating optical deflection assembly. The laser is used to output continuous laser light, and the rotating optical deflection assembly is used to form a closed curve scanning trajectory on the steel surface to be treated after the continuous laser light is rotated and refracted. The feeding unit supplies additive material to the feeding zone located in the middle of the closed curve scanning trajectory. The area of ​​the closed curve scanning trajectory before the feeding zone constitutes the forward action zone, and the area of ​​the closed curve scanning trajectory after the feeding zone constitutes the backward action zone. The area to be treated is irradiated by the forward action zone to remove corrosive substances from the surface of the steel substrate and to preheat or activate the surface of the steel substrate. The area to which additive material has been supplied is irradiated by the backward action zone to cause the additive material to clad, melt, or remelt and form a fusion interface with the surface of the steel substrate. The timing coordination control unit is used to coordinate the spatial interval or time interval between the forward action zone, the feeding zone and the backward action zone based on at least two of the following parameters: the size of the closed curve scanning trajectory, the rotation phase difference between the forward action zone and the backward action zone, the rotation frequency of the forward action zone and the backward action zone, the forward speed of the processing head relative to the steel substrate to be treated, the feeding landing point position of the feeding assembly and the feeding and transport time. This ensures that the completion time of irradiation of the forward action zone, the arrival time of the additive material in the feeding zone and the start time of irradiation of the backward action zone in the same area to be treated satisfy the following in sequence: the completion time of irradiation of the forward action zone is earlier than the arrival time of the additive material in the feeding zone, and the arrival time of the additive material in the feeding zone is earlier than the start time of irradiation of the backward action zone.

9. The system according to claim 8, characterized in that, The system also includes a thermal state acquisition or prediction unit, which is connected to the timing coordination control unit. The thermal state acquisition or prediction unit is used to acquire or predict the background thermal state, surface temperature, steel substrate surface temperature, fusion depth, or heat-affected zone depth formed by the laser action unit in the forward action zone through temperature sensors or thermal conduction models, and send it to the timing coordination control unit to adjust the laser power, scanning speed, overlap rate, number of repeat passes, or processing head movement speed of the laser action unit in the backward action zone.

10. The system according to claim 9, characterized in that, The system further includes a feedback detection unit connected to the timing coordination control unit. This unit detects the surface morphology, layer thickness, fusion depth, heat-affected zone depth, porosity, cracks, residual corrosion, or rust recurrence of the repair protective layer, and sends the detection results to the timing coordination control unit to update one or more of the following parameters: The laser power, scanning speed, or overlap rate of the laser action unit in the forward action zone; The feeding amount of the feeding unit; The laser power, scanning speed, or overlap rate of the laser action unit in the backward action zone; The motion speed of the motion execution unit.

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