A method for controlling the wire feeding speed and hot wire current in laser-hot-wire hybrid welding

Abstract

The present application relates to the technical field of laser welding, and particularly relates to a control method for laser hot-wire composite welding wire feeding speed and hot-wire current; comprising the following steps: presetting laser power, hot-wire current rising rate, welding voltage limit value, welding speed and wire feeding speed as the reference parameters during welding; monitoring the hot-wire current signal value: in the welding process, the hot-wire current value is monitored in real time through a sensor; when the welding wire is separated from the molten pool, the hot-wire current value becomes 0, at this time, the control system increases the wire feeding speed by 5% through a servo motor until the welding wire is in contact with the molten pool; the hot-wire current value is continuously monitored until the wire feeding speed and the molten pool always maintain the contact state; the torque current component of the servo motor of the wire feeder is monitored, and the torque current component is the wire feeding resistance value.

Description

Technical Field

[0001] This invention relates to the field of laser welding technology, and specifically to a method for controlling the wire feeding speed and hot wire current in laser hot wire composite welding. Background Technology

[0002] Laser welding technology, a key process in modern advanced manufacturing, boasts advantages such as high energy density, low heat input, fast welding speed, and minimal deformation, making it widely used in aerospace, automotive manufacturing, and other fields. However, its stringent requirements for bevel assembly precision and the difficulty in controlling weld reinforcement in single-pass welding limit its application in complex structures. Laser filler wire welding technology introduces filler wire into the laser heat source, using the melting of the filler wire to compensate for the gap and control the weld formation, effectively reducing assembly precision requirements. However, the direct entry of cold filler wire into the molten pool increases the temperature gradient, easily leading to molten pool disturbance and spatter, and the improvement in deposition efficiency is limited, making it difficult to meet the demands of high-efficiency welding of thick plates.

[0003] To further improve weld formation quality and increase deposition efficiency, laser-hot wire composite filler welding technology has emerged. This technology combines a laser heat source with a resistance hot wire process, feeding a preheated welding wire into the laser molten pool via a bypass or coaxial method, achieving multiple technological synergies: First, the preheating of the welding wire reduces the temperature gradient of the liquid molten pool, significantly improving the wettability and fluidity of the molten pool, and effectively suppressing defects such as incomplete fusion and undercut; second, the continuous filling of the hot wire can compensate for the surface depression caused by laser deep penetration welding, achieving precise control of weld reinforcement; third, the resistance heating effect can increase the welding wire deposition efficiency by 30%-50%, reducing the amount of beveling required in thick plate narrow gap welding and lowering production costs.

[0004] Despite the obvious advantages of laser-hot wire hybrid welding technology, it still faces many challenges in engineering applications.

[0005] Regarding process stability, the contact state between the welding wire and the molten pool is easily affected by factors such as assembly gap and workpiece morphology, leading to drastic fluctuations in the hot wire current. When the welding wire separates from the molten pool, the hot wire current drops to zero instantaneously, the arc extinguishes, and defects such as weld discontinuity, lack of fusion, and undercut are likely to occur. When the welding wire re-contracts with the molten pool, it can trigger arc discharge or molten droplet spatter, which can, in severe cases, cause weld formation deterioration or even welding interruption.

[0006] In terms of parameter matching, there is a strong coupling relationship between laser power, hot wire current, wire feed speed and welding speed. Traditional fixed parameter control strategies are difficult to adapt to the dynamic changes in material state and heat dissipation conditions. When the wire feed speed is too fast and the welding wire is inserted into the molten pool too deeply, the wire feed resistance increases sharply, causing the welding wire to warp, the laser to defocus, or even the machine to stop.

[0007] These technological bottlenecks limit the large-scale application of laser-hot wire hybrid welding technology in high-end equipment manufacturing, and there is an urgent need to develop advanced control methods with real-time process monitoring and multi-parameter collaborative control capabilities. Summary of the Invention

[0008] In order to overcome the problems of (1) unstable welding process, poor contact between molten pool and welding wire, (2) abnormal wire feeding resistance leading to unstable wire feeding, (3) large amount of welding spatter, and (4) complex parameter adjustment and poor adaptability in the prior art, this invention provides a method for controlling the wire feeding speed and hot wire current of laser hot wire composite welding.

[0009] This invention is achieved through the following technical solution: A method for controlling the wire feeding speed and hot wire current in laser hot wire composite welding includes the following steps: S1. Preset laser power, hot wire current rise rate, welding voltage limit, welding speed and wire feed speed as reference parameters during welding; S2. Monitoring the hot wire current signal value: During the welding process, the hot wire current value is monitored in real time by a sensor; when the welding wire separates from the molten pool, the hot wire current value becomes 0. At this time, the control system increases the wire feeding speed by 5% through the servo motor until the welding wire contacts the molten pool. S3. Continuously monitor the hot wire current value until the wire feeding speed and the molten pool are always in contact. S4. Monitor the torque current component of the wire feeder servo motor, wherein the torque current component is the wire feeding resistance value; S5. If the wire feeding resistance value is greater than the normal value, the control system reduces the wire feeding speed by 5% through the servo motor and continues to monitor the wire feeding resistance value of the servo motor of the wire feeder in real time through the sensor; if the wire feeding resistance value is still greater than the normal value, the wire feeding speed is reduced by 3% again, and then remains unchanged until the wire feeding resistance value stabilizes. S6. During the welding process, control the rate of increase of hot wire current and the value of hot wire voltage when the welding wire comes into contact with the molten pool to reduce the amount of welding spatter.

[0010] Furthermore, the preset laser power, hot wire current rise rate, welding speed, and wire feed speed are matched with the properties and thickness of the material to be welded, and the preset values ​​serve as the initial parameters for the welding process.

[0011] Furthermore, after increasing the wire feeding speed, the value of the hot wire current is monitored in real time by the sensor; when the value of the hot wire current becomes 0 again, the wire feeding speed is increased again by the servo motor until the value of the hot wire current stabilizes, indicating that the wire feeding speed and the molten pool are always in contact, thereby ensuring the stability of the welding state.

[0012] Furthermore, it also includes a hot wire power supply based on this method as a constant current source device, used to provide preheating current to the welding wire, with its positive and negative terminals electrically connected to the welding torch nozzle and the workpiece, respectively.

[0013] The beneficial effects of this invention are: (1) Adaptive control: This invention employs a method that monitors the hot wire current signal value. When the welding wire separates from the molten pool, the control system increases the wire feeding speed via a servo motor until the welding wire contacts the molten pool. This adaptive control method can automatically adjust the wire feeding speed according to the actual situation during the welding process, thereby improving the stability of welding quality.

[0014] (2) Reduction of welding spatter: This invention reduces the amount of welding spatter by controlling the rate of increase of the hot wire current when the welding wire comes into contact with the molten pool. This not only improves the welding quality but also reduces the waste generated during the welding process, which is beneficial to environmental protection and cost control.

[0015] (3) Improved stability: This invention simultaneously monitors the resistance value of the wire feeder servo motor. When the resistance exceeds the normal value, the wire feeding speed is reduced. This dual monitoring and control makes the welding process more stable and reduces the problem of unstable welding quality caused by changes in the external environment or equipment failure.

[0016] (4) Simplified operation: The adaptive control method of the present invention does not require a lot of debugging and optimization, and is simple to operate and easy to implement. This is of great significance for the application of welding robot technology, and can greatly improve the working efficiency and application range of welding robots.

[0017] (5) Wide Applicability: The adaptive control method of this invention can automatically adjust welding parameters according to the welding requirements of different materials and thicknesses, thereby improving the adaptability and flexibility of welding technology. This is particularly relevant for the practical application of laser welding technology, automated control technology, and welding robot technology. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the mechanism based on the present invention; Figure 2 This is a flowchart of the control strategy of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0021] refer to Figure 1 , Figure 2 The present invention includes the following steps: S1. Preset laser power, hot wire current rise rate, welding voltage limit, welding speed and wire feed speed as reference parameters during welding; S2. Monitoring the hot wire current signal value: During the welding process, the hot wire current value is monitored in real time by a sensor; when the welding wire separates from the molten pool, the hot wire current value becomes 0. At this time, the control system increases the wire feeding speed by 5% through the servo motor until the welding wire contacts the molten pool. S3. Continuously monitor the hot wire current value until the wire feeding speed and the molten pool are always in contact. S4. Monitor the torque current component of the wire feeder servo motor, wherein the torque current component is the wire feeding resistance value; S5. If the wire feeding resistance value is greater than the normal value, the control system reduces the wire feeding speed by 5% through the servo motor and continues to monitor the wire feeding resistance value of the servo motor of the wire feeder in real time through the sensor; if the wire feeding resistance value is still greater than the normal value, the wire feeding speed is reduced by 3% again, and then remains unchanged until the wire feeding resistance value stabilizes. S6. During the welding process, control the rate of increase of hot wire current and the value of hot wire voltage when the welding wire comes into contact with the molten pool to reduce the amount of welding spatter.

[0022] Current ramp control: The controller inside the power supply (usually a DSP or MCU) controls the inverter's switching speed according to a preset ramp rate (e.g., 0.1 to 0.5 seconds from 0 to the set current value), ensuring a smooth current rise. This smooth transition prevents instantaneous overheating and breakage when the welding wire contacts the molten pool. The current ramp curve can be precisely divided into stages (e.g., pre-contact stage, ramp-up stage, and stabilization stage) using a control algorithm.

[0023] The formula for calculating the rate of current rise is (di / dt); The stability of the hot wire voltage directly determines the stability of the resistance heating, thus affecting the softening state of the welding wire and the smoothness of the droplet transfer. To reduce spatter, the power supply is often set to constant voltage (CV) mode to control the hot wire voltage.

[0024] The preset laser power, hot wire current rise rate, welding speed, and wire feed speed are matched with the properties and thickness of the material to be welded, and the preset values ​​serve as the initial parameters for the welding process.

[0025] This embodiment uses a 5mm thick 304 stainless steel plate as the welding material and employs a laser-hot wire hybrid welding method for butt welding. Based on the thermophysical properties of 304 stainless steel (such as melting point and thermal conductivity) and the plate thickness, matching welding parameters are preset: laser power 4.0kW, hot wire current 100A, welding speed 0.5m / min, and wire feed speed 1.5m / min. These preset values ​​are input into the control system as initial parameters for the welding process and are directly called upon at the start of the welding process to ensure stable arc initiation, good molten pool formation, and to provide a benchmark for subsequent dynamic adjustments.

[0026] After increasing the wire feeding speed, the value of the hot wire current is monitored in real time by the sensor. When the value of the hot wire current becomes 0 again, the wire feeding speed is increased again by the servo motor until the value of the hot wire current stabilizes. This indicates that the wire feeding speed and the molten pool are always in contact, thereby ensuring the stability of the welding state.

[0027] It also includes a hot wire power supply based on this method as a constant current source device, used to provide preheating current to the welding wire, with its positive and negative terminals electrically connected to the welding torch nozzle and the workpiece, respectively.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A method for controlling the wire feeding speed and hot wire current in laser hot wire composite welding, characterized in that: Includes the following steps: S1. Preset laser power, hot wire current rise rate, welding voltage limit, welding speed and wire feed speed as reference parameters during welding; S2. Monitoring the hot wire current signal value: During the welding process, the hot wire current value is monitored in real time by a sensor; when the welding wire separates from the molten pool, the hot wire current value becomes 0. At this time, the control system increases the wire feeding speed by 5% through the servo motor until the welding wire contacts the molten pool. S3. Continuously monitor the hot wire current value until the wire feeding speed and the molten pool are always in contact. S4. Monitor the torque current component of the wire feeder servo motor, wherein the torque current component is the wire feeding resistance value; S5. If the wire feeding resistance value is greater than the normal value, the control system reduces the wire feeding speed by 5% through the servo motor and continues to monitor the wire feeding resistance value of the servo motor of the wire feeder in real time through the sensor; if the wire feeding resistance value is still greater than the normal value, the wire feeding speed is reduced by 3% again, and then remains unchanged until the wire feeding resistance value stabilizes. S6. During the welding process, control the rate of increase of hot wire current and the value of hot wire voltage when the welding wire comes into contact with the molten pool to reduce the amount of welding spatter.

2. The method for controlling the wire feeding speed and hot wire current in laser hot wire composite welding according to claim 1, characterized in that: The preset laser power, hot wire current rise rate, welding speed, and wire feed speed are matched with the properties and thickness of the material to be welded, and the preset values ​​serve as the initial parameters for the welding process.

3. The method for controlling the wire feeding speed and hot wire current in laser hot wire composite welding according to claim 1, characterized in that: After increasing the wire feeding speed, the value of the hot wire current is monitored in real time by the sensor. When the value of the hot wire current becomes 0 again, the wire feeding speed is increased again by the servo motor until the value of the hot wire current stabilizes. This indicates that the wire feeding speed and the molten pool are always in contact, thereby ensuring the stability of the welding state.

4. The method for controlling the wire feeding speed and hot wire current in laser hot wire composite welding according to claim 3, characterized in that: It also includes a hot wire power supply based on this method as a constant current source device, used to provide preheating current to the welding wire, with its positive and negative terminals electrically connected to the welding torch nozzle and the workpiece, respectively.

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