Negative-pressure powder suction system for large-length-diameter-ratio inner wall laser cladding and using method of negative-pressure powder suction system

Abstract

The invention discloses a negative-pressure powder suction system for large-length-diameter-ratio inner wall laser cladding and a using method thereof, and belongs to the technical field of laser cladding, the negative-pressure powder suction system comprises laser cladding equipment and a transmission arm assembly, a transmission channel assembly is arranged on the side, close to the transmission arm assembly, of the laser cladding equipment, a cladding head and a powder suction head are arranged in the transmission channel assembly, and the cladding head and the powder suction head are arranged in the transmission channel assembly. The transmission channel assembly comprises a laser transmission channel, a powder feeding channel and a protective gas channel, a powder recovery device, a pneumatic execution unit and a control unit are arranged on the side, away from the transmission arm assembly, of the laser cladding equipment, the pneumatic execution unit comprises a negative pressure guide pipe and a negative pressure source, and the negative pressure guide pipe communicates with the negative pressure source; the negative pressure conduit is connected with the negative pressure source and the laser cladding equipment, and the control unit comprises a time encoder. The problem that in the prior art, a molten pool is unstable generally in the length-diameter-ratio pipe fitting inner wall cladding process is solved, and high-quality, low-defect and high-consistency production of large-length-diameter-ratio inner wall laser cladding is achieved.

Description

Technical Field

[0001] This invention relates to the technical field of laser cladding, and more particularly to a negative pressure powder suction system for laser cladding of inner walls with a large aspect ratio and its usage method. Background Technology

[0002] Currently, pipes, deep-hole pipes, and thin-walled cylinders with large length-to-diameter ratios are widely used in petrochemical, nuclear power, aerospace, and equipment remanufacturing industries. Their inner walls often experience corrosion, wear, and fatigue damage during operation. Laser cladding, with its low dilution rate, wide range of selectable materials, and high repair efficiency, has become an important method for strengthening and repairing inner wall surfaces. For inner walls with large length-to-diameter ratios, long-distance transmission / small-diameter cladding heads and connecting arms have been developed both domestically and internationally, supporting processing scenarios with a minimum inner diameter of approximately 30 mm and cladding depths reaching meters, significantly expanding the application boundaries of inner wall cladding. However, within confined spaces, the combined effects of powder feed gas, protective gas, fumes / metal vapor, and the cavity wall easily create a low-speed backflow and powder accumulation zone at the leading edge of the molten pool. This disturbs the coupling between the laser, powder, and molten pool: fluctuations in molten pool morphology and flowability ultimately induce defects such as inclusions, porosity, and spatter re-fusion, leading to a decrease in coating density and bonding quality—one of the key bottlenecks limiting the stability of inner wall cladding. Recent reviews and experiments on the defect mechanism of laser cladding show that parameters such as powder flow morphology, cladding efficiency, powder beam diameter, and gas dynamic pressure are highly correlated with defect formation.

[0003] To improve powder utilization and cladding stability, researchers have conducted extensive research on nozzle structure and powder delivery paths. For example, coaxial, off-axis, and multi-channel nozzles, as well as annular powder beam forming and wide-bandgap powder beam nozzles, can effectively improve powder distribution, capture efficiency, and forming uniformity in outer wall cladding, thus improving cladding efficiency to some extent. However, most of these improvements focus on powder feeding and shaping, and flow field convergence, without fundamentally addressing the problem of excessive powder accumulation at the molten pool leading edge. Especially in long and narrow cavities, the confined space makes powder retention and molten pool disturbance more likely.

[0004] In recent years, researchers have proposed various nozzle optimization and flow field control methods, including line spot and broadband nozzles, which have shown good performance in terms of expanding power windows and deposition efficiency. However, in practice, even mature nozzle systems are inevitably affected by nozzle wear, geometric errors, and gas-solid two-phase flow coupling, leading to fluctuations in cladding efficiency and deposition stability. More importantly, these solutions generally focus on improving powder beam morphology and transport path, while paying insufficient attention to the active purification and dynamic control of the near-field powder environment of the molten pool. Therefore, they cannot effectively avoid powder accumulation and secondary disturbance at the molten pool leading edge. On the other hand, although laser cladding equipment for pipe walls has been commercialized and can achieve long stroke, meter-level depth, and small inner diameter adaptation (mostly using built-in rotating / extending cladding heads), existing publications mostly focus on long-distance transmission and motion control, lacking a systematic approach to real-time removal of powder accumulated at the molten pool leading edge. Therefore, typical defects such as porosity and inclusions are still prone to occur, restricting the improvement of coating density and stability consistency. Related patents and reviews also indicate that although there are nozzle-level suction ideas such as local vacuum / Venturi negative pressure, they are mainly used for powder beam gathering in open or semi-open scenarios, and no systematic solution for near-molten pool directional suction is constructed for large aspect ratio confined cavities.

[0005] It is evident that while existing technologies are mature in "powder feeding and shaping / long-distance transmission," there is a gap in the active control of the near-field powder environment of the molten pool within a confined cavity—this constitutes the entry point and inventiveness of this invention: by constructing a controllable local negative pressure field in front of the molten pool, "directional, real-time, and low-interference" removal of excess / unmelted powder is achieved; compared to the indirect improvement relying solely on nozzle shaping, this solution has a novel mechanism (near-field active purification), significant effects (reducing porosity / inclusions, stabilizing coupling), and is engineering-feasible (it can be modularly integrated with existing inner wall equipment, and its parameters are controllable), thus simultaneously satisfying novelty, inventiveness, and practicality.

[0006] Compared to existing laser cladding devices for the inner walls of large aspect ratio pipes, although it can meet the transmission and cladding requirements in meter-level depth and small inner diameter scenarios, and has made breakthroughs in motion control, it still has significant shortcomings:

[0007] 1. Unresolved powder buildup at the molten pool leading edge: In confined spaces, the interaction between the powder feed gas flow and the laser energy field causes powder to easily accumulate at the molten pool leading edge. Existing devices often focus on the stable operation of the transmission mechanism and the cladding head, but fail to consider the dynamic removal of powder buildup in the structural design, resulting in poor molten pool stability.

[0008] 2. Lack of real-time powder removal methods: Most current inner wall cladding equipment uses conventional powder feeding nozzles and does not integrate negative pressure powder suction or similar purification functions. It cannot dynamically control the powder when there is excessive powder or uneven distribution, resulting in uneven heat input to the molten pool.

[0009] 3. High defect rate of cladding layer: Due to powder accumulation and airflow turbulence, the molten pool is prone to defects such as inclusions, pores and spatter secondary fusion, which seriously affect the compactness and bonding quality of the cladding layer.

[0010] 4. Insufficient process consistency: The existing system lacks active control methods for the near-field powder environment of the molten pool, resulting in large fluctuations in the effect of the same process parameters on different workpieces, making it difficult to ensure the stability and consistency of the process.

[0011] Regarding the aforementioned technologies, the applicant has found that existing internal wall cladding equipment focuses more on long-distance transmission and light / powder / gas coupling, paying insufficient attention to the active "purification / rectification" of the near-field powder environment of the molten pool. Especially in confined spaces with large aspect ratios, accumulated powder that has not participated in melting is difficult to remove in a timely manner, becoming a direct cause of molten pool instability and defects. Based on this, the present invention proposes a "negative pressure powder suction device / system" for internal walls with large aspect ratios. This system constructs a controllable local negative pressure field in front of the molten pool to remove excess and unmelted powder in real time, stabilizing laser-powder-molten pool coupling, thereby reducing the incidence of defects such as inclusions and porosity, improving coating density and bonding quality, and achieving stability and high consistency in the internal wall cladding process. Summary of the Invention

[0012] This invention addresses the shortcomings of existing technologies by providing a negative pressure powder suction system and its application method for laser cladding of inner walls with large aspect ratios. It solves the problem of unstable molten pool that is common in the laser cladding process of inner walls of pipes with large aspect ratios, and achieves high-quality, low-defect and high-consistency production of laser cladding of inner walls with large aspect ratios.

[0013] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0014] A negative pressure powder suction system for laser cladding of inner walls with a large aspect ratio includes a laser cladding device and a transmission arm assembly. The transmission arm assembly is placed on one side of the laser cladding device. A transmission channel assembly is provided on the side of the laser cladding device near the transmission arm assembly. A cladding head and a powder suction head are provided in the transmission channel assembly. The cladding head and the powder suction head are both placed between the laser cladding device and the transmission arm assembly. The transmission channel assembly includes a laser transmission channel, a powder feeding channel and a protective gas channel. The laser transmission channel, the powder feeding channel and the protective gas channel all pass through the transmission arm assembly.

[0015] The side of the laser cladding equipment away from the transmission arm assembly is equipped with a powder recovery device, a pneumatic actuator, and a control unit. The pneumatic actuator includes a negative pressure conduit and a negative pressure source. The negative pressure conduit and the negative pressure source are interconnected. The negative pressure conduit connects the negative pressure source and the laser cladding equipment. The control unit includes a time encoder.

[0016] Furthermore, the transmission arm assembly adopts a modular structure, which can adapt to transmission channel assemblies of different sizes through a multi-section telescopic adjustment structure.

[0017] Furthermore, a synchronization structure is provided between the cladding head and the powder suction head, and the synchronization structure fixes the distance between the cladding head and the powder suction head.

[0018] Furthermore, the powder recovery device includes a separator and a filter element assembly, with the filter element assembly placed inside the separator, and the separator being connected to a negative pressure conduit.

[0019] Furthermore, the control unit includes a PLC module, which controls the opening and closing actions of the pneumatic actuator and the cylinder stroke through the PLC module and the time encoder.

[0020] Furthermore, the pneumatic actuator includes a pneumatic clamp, a pneumatic rotary chuck, and an adjustable stroke cylinder. The pneumatic rotary chuck is placed on the side of the laser cladding equipment away from the transmission arm assembly. The pneumatic clamp holds the negative pressure conduit, and the adjustable stroke cylinder is connected to the pneumatic clamp and the pneumatic rotary chuck, respectively.

[0021] A method for using a negative pressure powder suction system for laser cladding of inner walls with a large aspect ratio includes the following steps:

[0022] During the cladding process, the control unit uses the output signal of the time encoder as the control reference:

[0023] When the cladding head is fed to the preset position, the time encoder triggers a signal, causing the pneumatic clamp to release and the adjustable stroke cylinder to drive the powder suction head to move forward.

[0024] Subsequently, the pneumatic rotary chuck completes the angle adjustment within the time window of the time encoder;

[0025] Finally, the pneumatic clamp closes and secures itself again, maintaining a constant distance between the powder suction head and the cladding head, and completing synchronous suction.

[0026] In summary, compared with the prior art, the beneficial effects of the above technical solution are:

[0027] 1. This application constructs a controllable local negative pressure field in front of the molten pool, and removes excess and unmelted powder from the leading edge of the molten pool in real time through the powder suction head and negative pressure conduit, thereby achieving a stable coupling relationship between laser, powder and molten pool and avoiding powder accumulation that disturbs the molten pool.

[0028] 2. This application reduces the cladding defect rate, effectively reduces inclusions and porosity, and improves the metallurgical quality of the cladding layer.

[0029] 3. This application improves the density and bonding strength of the coating, thereby enhancing the overall mechanical properties and service resistance of the coating;

[0030] 4. This application guarantees process consistency, and can maintain the continuity and stability of the cladding process even under complex working conditions such as meter-level depth and small inner diameter. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the structure of the transmission arm assembly in an embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the powder recovery device side in an embodiment of the present invention.

[0034] Explanation of reference numerals in the attached figures:

[0035] 1. Laser cladding equipment; 2. Transmission arm assembly; 3. Transmission channel assembly; 31. Laser transmission channel; 32. Powder feeding channel; 33. Protective gas channel; 4. Cladding head; 5. Powder suction head; 6. Powder recovery device; 7. Pneumatic actuator; 71. Negative pressure conduit; 72. Negative pressure source; 73. Pneumatic clamp; 74. Pneumatic rotary chuck; 75. Adjustable stroke cylinder; 8. Control unit. Detailed Implementation

[0036] The principles and features of the present invention are described below with reference to all the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0037] This invention discloses a negative pressure powder suction system for laser cladding of inner walls with a large aspect ratio and its usage method.

[0038] The technical problem this invention aims to solve is that during laser cladding of the inner wall of a pipe with a large length-to-diameter ratio, powder accumulation easily occurs in the leading edge region of the molten pool due to space constraints and uneven powder flow field distribution. This phenomenon disrupts the heating and flow state of the molten pool, reduces its stability, and leads to the formation of metallurgical defects such as inclusions and pores in the solidified layer, severely affecting the density and service performance of the cladding layer.

[0039] To address this, the present invention employs a controllable negative pressure powder suction mechanism at the front of the molten pool to remove excess or unreacted powder in real time, thereby effectively maintaining uniform powder concentration and stable heat input in the molten pool region. This system not only significantly improves the stability of the molten pool and the controllability of the forming process, but also reduces the coating defect rate, ensures the density and bonding quality of the coating structure, and enables stable and efficient laser cladding of the inner wall of pipes with large aspect ratios.

[0040] Reference Figures 1 to 3 As shown, a negative pressure powder suction system for laser cladding of inner walls with a large aspect ratio includes a laser cladding device 1 and a transmission arm assembly 2. The transmission arm assembly 2 adopts a modular structure and adapts to transmission channel assemblies 3 of different sizes through a multi-section telescopic adjustable structure.

[0041] The transmission arm assembly 2 adopts a modular design with a total length of up to 2.4m, and supports telescopic adjustment to adapt to pipes of different depths. The internal laser transmission channel 31 has a diameter of 20mm, the powder feeding channel 32 has a diameter of 6mm, and the protective gas channel 33 has a diameter of 2mm. The three are arranged independently to avoid cross-interference.

[0042] The transmission arm assembly 2 is positioned on one side of the laser cladding equipment 1. The laser cladding equipment 1 has a transmission channel assembly 3 on the side closest to the transmission arm assembly 2. The transmission channel assembly 3 contains a cladding head 4 and a powder suction head 5. The cladding head 4 has an outer diameter of 22mm and is suitable for pipes with an inner diameter ≥30mm. During cladding, the laser power ranges from 200–1200W, and the spot diameter is 1.2–1.5mm. The powder feeding rate is 6–12g / min, and the protective gas flow rate is 10–15L / min to ensure uniform molten pool formation. The powder suction head 5 is positioned at the leading edge of the molten pool, with the suction port approximately 8–12mm from the center of the molten pool. The suction port width is 2mm, and the annular opening angle is approximately 120°.

[0043] The relative distance between the powder suction head 5 and the laser guide arm is fixed at 15mm, and the synchronization structure ensures that this distance remains consistent throughout the cladding process.

[0044] Both the cladding head 4 and the powder suction head 5 are placed between the laser cladding equipment 1 and the transmission arm assembly 2. A synchronization structure is provided between the cladding head 4 and the powder suction head 5 to fix the distance between the cladding head 4 and the powder suction head 5.

[0045] The transmission channel assembly 3 includes a laser transmission channel 31, a powder feeding channel 32, and a protective gas channel 33, all of which pass through the transmission arm assembly 2.

[0046] The laser cladding equipment 1 has a powder recovery device 6, a pneumatic actuator 7, and a control unit 8 located on the side away from the transmission arm assembly 2. The powder recovery device 6 includes a separator and a filter element assembly, with the filter element assembly placed inside the separator. The separator is connected to the negative pressure conduit 71. The powder recovery device 6 uses a cyclone separator + filter element combination, achieving a collection efficiency of ≥95%. The collection box has a volume of 10L, enabling continuous 24-hour powder recovery.

[0047] The control unit 8 includes a time encoder. The control unit 8 also includes a PLC module, which controls the opening and closing of the pneumatic actuator 7 and the cylinder stroke via the PLC module and the time encoder. The time encoder is installed in the PLC module's control system and is used to record and output time signals in real time. The time encoder can generate a trigger signal based on the set feed speed and process cycle of the cladding head 4.

[0048] The pneumatic actuator 7 includes a negative pressure conduit 71 and a negative pressure source 72. The negative pressure conduit 71 has an inner diameter of 8 mm and an outer diameter of 12 mm, and is made of wear-resistant stainless steel hose, which is laid along the transmission arm assembly 2. The negative pressure source 72 adopts a rotary vane vacuum pump or a Venturi pneumatic suction device, and the suction pressure is adjustable, ranging from -0.03 MPa to -0.08 MPa, with the optimal operating point being -0.05 MPa.

[0049] The negative pressure conduit 71 is interconnected with the negative pressure source 72, and the negative pressure conduit 71 connects the negative pressure source 72 to the laser cladding equipment 1. The pneumatic actuator 7 also includes a pneumatic clamp 73, a pneumatic rotary chuck 74, and an adjustable stroke cylinder 75. The pneumatic rotary chuck 74 is positioned on the side of the laser cladding equipment 1 away from the transmission arm assembly 2. The pneumatic clamp 73 clamps the negative pressure conduit 71, and the adjustable stroke cylinder 75 is connected to both the pneumatic clamp 73 and the pneumatic rotary chuck 74. The pneumatic clamp 73 and the pneumatic rotary chuck 74 are controlled by a timing mechanism. The PLC module precisely adjusts the opening and closing time of the pneumatic clamp 73 based on the signal from the time encoder, ensuring that the powder suction head 5 can be accurately released or locked when the cladding head 4 advances or adjusts.

[0050] The opening, closing, and rotation of the pneumatic rotary chuck 74 are also synchronously adjusted by the PLC module program in conjunction with time encoder feedback, so that the powder suction head 5 can complete angle switching and positioning at the appropriate time. The start and stop of the drive stroke of the adjustable stroke cylinder 75 are also controlled by the time encoder signal, thus achieving a high degree of coordination with the movements of the pneumatic clamp 73 and the pneumatic rotary chuck 74.

[0051] The pneumatic clamp 73 has a clamping force ≥100N and a response time ≤0.2s;

[0052] The pneumatic rotary chuck has a rotation angle of 0–180° and a positioning accuracy of ±0.5°.

[0053] The adjustable stroke cylinder has a stroke range of 0–100 mm and an adjustment accuracy of 0.1 mm.

[0054] The time encoder has a resolution of 1ms, enabling millisecond-level timing control.

[0055] During operation, the PLC module controls the opening and closing of the pneumatic clamp 73 and the pneumatic rotary chuck 74, as well as the stroke adjustment of the adjustable stroke cylinder 75, based on the timing signal output by the time encoder, so that the powder suction head 5 can always maintain synchronous movement and fixed spacing when the feeding speed of the cladding head 4 is 2–20 mm / s.

[0056] Reference Figures 1 to 3 As shown, a method for using a negative pressure powder suction system for laser cladding of inner walls with a large aspect ratio includes the following steps:

[0057] During the cladding process, control unit 8 uses the output signal of the time encoder as the control reference:

[0058] When the cladding head 4 is fed to the preset position, the time encoder triggers a signal, causing the pneumatic clamp 73 to release, and the adjustable stroke cylinder 75 drives the powder suction head 5 to move forward.

[0059] Subsequently, the pneumatic rotary chuck 74 completes the angle adjustment within the time window of the time encoder;

[0060] Finally, the pneumatic clamp 73 closes and fixes itself again, and the powder suction head 5 and the cladding head 4 maintain a constant distance and complete synchronous suction.

[0061] This control method enables the timing and automation of actions, ensuring that the powder suction head 5 is always in the optimal position to perform negative pressure suction on the leading edge of the molten pool, thereby significantly improving the stability of the molten pool and the coating forming quality.

[0062] This invention offers precise timing, with the time encoder correlating the feed speed with the action time to achieve millisecond-level synchronization. It also reduces errors, preventing misalignment of the powder suction head 5 due to manual operation or delays caused by single pneumatic control, ensuring stable suction points. The consistency of cladding is improved, as the movements of the pneumatic clamp 73, pneumatic rotary chuck 74, and adjustable stroke cylinder 75 are all controlled by a time reference, making the cladding process more uniform and controllable. Automation is enhanced; the combination of a PLC module and a time encoder forms a closed-loop control system, reducing manual intervention and making it suitable for long-duration, deep-penetration cladding operations on pipes.

[0063] A dedicated powder suction head 5 is arranged in the leading edge area of ​​the molten pool and connected to a negative pressure source 72 through a negative pressure conduit 71 to form a controllable local negative pressure field. This can remove excess or unmelted powder from the front of the molten pool in real time, preventing accumulation from the source and ensuring the stability of the molten pool.

[0064] The high aspect ratio inner wall adaptation structure of this application allows the system to adapt to the inner walls of pipes with meter-level depth and small diameter. The transmission arm assembly 2 is modular and compactly arranged, and the powder suction head 5 can extend into the deep inner cavity along with the cladding head 4. This ensures stable powder suction even in narrow spaces without affecting the laser, powder delivery, and protective gas channels 33.

[0065] The relative positions of the powder suction head 5 and the cladding head 4 between the laser guide arm are kept constant by a linkage mechanism with a synchronous structure, avoiding fluctuations in the suction effect caused by positional deviation. Combined with an adjustable stroke cylinder 75 and a precise fine-tuning mechanism, optimal distance control between the powder suction port and the molten pool is achieved.

[0066] The PLC module controls the timing adjustment of the time encoder. The control unit 8 uses a PLC program and combines it with a time encoder to achieve millisecond-level timing control. The coordinated action of the pneumatic clamp 73, the pneumatic rotary chuck 74 and the adjustable stroke cylinder 75 ensures the synchronous movement and angle adjustment of the powder suction head 5.

[0067] During the cladding process, the opening and closing timing of the pneumatic actuator is automatically controlled according to the feed rate and process cycle.

[0068] The powder recovery and anti-clogging design utilizes negative pressure to draw powder into a cyclone separator or filter cartridge recovery unit, enabling powder recycling and reducing waste and pollution. The duct is equipped with a backflush port or micro-vibrator to prevent powder clogging during prolonged use.

[0069] The specific implementation method is as follows: The transmission arm assembly 2 adopts a multi-section telescopic structure, and internally has a laser transmission channel 31, a powder feeding channel 32, and a protective gas channel 33, which are used to stably transmit the laser beam, powder, and protective gas to a small-diameter inner wall with a depth of meters. The cladding head 4 is located at the end of the transmission arm assembly 2, and the front is provided with a laser output port, a powder feeding port, and a protective gas outlet, which can form a molten pool on the inner wall to achieve effective fusion of the substrate and the fed powder.

[0070] A powder suction head 5 is arranged at the leading edge of the cladding head 4, with its suction port facing the front area of ​​the molten pool. The powder suction head 5 is connected to an external negative pressure source 72 through a negative pressure conduit 71. During the cladding process, when the powder feeding channel 32 introduces powder into the molten pool area, and some powder is stuck at the leading edge of the molten pool due to space constraints, the powder suction head 5 can form a local negative pressure field to remove excess powder in real time, thereby maintaining the stability of the molten pool.

[0071] The extracted powder is transported to the powder recovery device 6 via the negative pressure conduit 71. The powder recovery device 6 is equipped with a cyclone separator and filter element combination, which can separate the powder from the gas. The unmelted powder can be collected and reused, which improves the material utilization rate and reduces dust emissions.

[0072] The control unit 8 includes a PLC module program controller, a pneumatic clamp 73, a pneumatic rotary chuck 74, an adjustable stroke cylinder 75, and a time encoder. The PLC module program receives signals from the time encoder to precisely control the opening and closing actions of the pneumatic clamp 73 and the pneumatic rotary chuck 74, as well as the stroke of the adjustable stroke cylinder 75. Through this control method, the powder suction head 5 can move synchronously with the laser guide arm during the feeding process of the cladding head 4, and the relative distance is constant, ensuring that the suction port always acts on the optimal area at the leading edge of the molten pool.

[0073] To address the shortcomings of existing technologies, the present invention aims to propose a negative pressure powder suction system for the inner wall of pipe fittings with large length-to-diameter ratios. This system constructs a controllable local negative pressure field at the front of the molten pool, and removes excess and unmelted powder from the leading edge of the molten pool in real time through the powder suction head 5 and the negative pressure conduit 71, achieving the following effects:

[0074] To stabilize the coupling relationship between the laser, powder, and molten pool, and to prevent powder accumulation from disturbing the molten pool;

[0075] Reduce the cladding defect rate, effectively reduce inclusions and porosity, and improve the metallurgical quality of the cladding layer;

[0076] Improve coating density and bonding strength, and enhance overall mechanical properties and service life of the coating;

[0077] To ensure process consistency, the cladding process can maintain continuity and stability even under complex working conditions such as meter-level depth and small inner diameter.

[0078] Through the above improvements, the present invention solves the problem of unstable molten pool that is common in the cladding process of inner walls of pipes with large aspect ratio in the prior art, and realizes high-quality, low-defect and high-consistency production of laser cladding of inner walls with large aspect ratio.

[0079] The implementation principle of a negative pressure powder suction system for laser cladding of inner walls with a large aspect ratio and its application method according to an embodiment of the present invention is as follows:

[0080] This invention, by constructing a controllable local negative pressure field at the leading edge of the molten pool, can remove unmelted or excess powder in real time, significantly improving the thermal flow environment of the molten pool region. This ensures the stability of the molten pool throughout the cladding process, avoiding disturbances and instability caused by powder accumulation. The direct result is a significant reduction in metallurgical defects such as inclusions and porosity in the cladding layer, a denser cladding layer structure, significantly improved bonding strength, and overall service performance superior to existing technologies.

[0081] Meanwhile, this invention combines a negative pressure powder suction mechanism with a PLC control system, using a time encoder to precisely control the movements of the pneumatic clamp 73, the pneumatic rotary chuck 74, and the adjustable stroke cylinder 75, enabling the powder suction head 5 and the laser guide arm to move synchronously and maintain a constant distance during the cladding process. This design ensures that the powder suction position is always in the optimal area at the leading edge of the molten pool, greatly improving the consistency and reliability of the process, and making the cladding results of different workpieces and batches stable and controllable.

[0082] Furthermore, excess powder removed is fed into the powder recovery device 6 via a negative pressure conduit 71, where it is collected and reused after cyclone separation or filtration by a filter cartridge combination. This reduces powder waste and effectively minimizes dust pollution. The system has a compact overall structure, making it suitable for complex internal wall processing scenarios with meter-level depths and small inner diameters. It possesses excellent engineering feasibility and application value, providing a reliable solution for high-quality, low-defect, and consistently stable internal wall laser cladding.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A negative pressure powder suction system for laser cladding of inner walls with large length-diameter ratio, comprising a laser cladding device (1), characterized in that: The equipment includes a transmission arm assembly (2), which is placed on one side of the laser cladding equipment (1). The laser cladding equipment (1) is provided with a transmission channel assembly (3) on the side near the transmission arm assembly (2). The transmission channel assembly (3) is provided with a cladding head (4) and a powder suction head (5). The cladding head (4) and the powder suction head (5) are both placed between the laser cladding equipment (1) and the transmission arm assembly (2). The transmission channel assembly (3) includes a laser transmission channel (31), a powder feeding channel (32), and a protective gas channel (33). The laser transmission channel (31), the powder feeding channel (32), and the protective gas channel (33) all pass through the transmission arm assembly (2). The laser cladding equipment (1) is provided with a powder recovery device (6), a pneumatic actuator (7) and a control unit (8) on the side away from the transmission arm assembly (2). The pneumatic actuator (7) includes a negative pressure conduit (71) and a negative pressure source (72). The negative pressure conduit (71) and the negative pressure source (72) are interconnected. The negative pressure conduit (71) connects the negative pressure source (72) and the laser cladding equipment (1). The control unit (8) includes a time encoder.

2. The large aspect ratio inner wall laser cladding negative pressure powder suction system according to claim 1, characterized in that: The transmission arm assembly (2) adopts a modular structure and adapts to transmission channel assemblies (3) of different sizes through a multi-section telescopic adjustment structure.

3. The large aspect ratio inner wall laser cladding negative pressure powder suction system according to claim 1, characterized in that: A synchronization structure is provided between the cladding head (4) and the powder suction head (5), and the synchronization structure fixes the distance between the cladding head (4) and the powder suction head (5).

4. The large aspect ratio inner wall laser cladding negative pressure powder suction system according to claim 1, characterized in that: The powder recovery device (6) includes a separator and a filter assembly, the filter assembly being placed inside the separator, and the separator being connected to the negative pressure conduit (71).

5. The large aspect ratio inner wall laser cladding negative pressure powder suction system according to claim 1, characterized in that: The control unit (8) includes a PLC module, which controls the opening and closing actions of the pneumatic actuator (7) and the cylinder stroke through the PLC module and the time encoder.

6. The large aspect ratio inner wall laser cladding negative pressure powder suction system according to claim 1, characterized in that: The pneumatic actuator (7) includes a pneumatic clamp (73), a pneumatic rotary chuck (74), and an adjustable stroke cylinder (75). The pneumatic rotary chuck (74) is placed on the side of the laser cladding equipment (1) away from the transmission arm assembly (2). The pneumatic clamp (73) holds the negative pressure conduit (71). The adjustable stroke cylinder (75) is connected to the pneumatic clamp (73) and the pneumatic rotary chuck (74) respectively.

7. The use of a negative pressure powder suction system for laser cladding of an inner wall of a large aspect ratio according to any one of claims 1 to 6, characterized in that, The process includes the following: During the cladding process, the control unit (8) uses the output signal of the time encoder as the control reference: When the cladding head (4) is fed to the preset position, the time encoder triggers a signal to release the pneumatic clamp (73), and the adjustable stroke cylinder (75) drives the powder suction head (5) to move forward. Subsequently, the pneumatic rotary chuck (74) completes the angle adjustment within the time window of the time encoder; Finally, the pneumatic clamp (73) closes and fixes itself again, and the powder suction head (5) and the cladding head (4) maintain a constant distance and complete synchronous suction.

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