High-voltage laser filler wire welding method based on laser power modulation

Abstract

A high-pressure laser filler wire welding method based on laser power modulation is disclosed. In this method, under a high-pressure environment of not less than 400 kPa, the welding wire is maintained at a predetermined distance from the surface of the object to be welded. A laser with instantaneous power varying in a rectangular wave is used to perform laser filler wire welding on the welding wire, allowing molten droplets to enter the object to be welded and generate a continuous weld. This method utilizes a large instantaneous peak power to rapidly heat the welding wire, forming large-sized molten droplets, increasing the driving force for droplet droplet fall and promoting droplet transfer. Simultaneously, a small instantaneous trough power provides sufficient time for plasma and metal vapor to dissipate, reducing the shielding effect of plasma and metal vapor on the laser beam and promoting the absorption of laser energy by the welding wire in the next cycle. Based on these two aspects, this method can significantly promote droplet transfer in high-pressure environment laser filler wire welding, effectively solving the problem of poor weld continuity in high-pressure environment laser filler wire welding.

Description

Technical Field

[0001] This invention belongs to the field of laser filler wire welding technology, and in particular, a high-pressure laser filler wire welding method based on laser power modulation. Background Technology

[0002] Offshore oil and gas facilities, nuclear power pressure vessels, pipelines, and other structures are prone to damage after long-term operation under heavy loads due to corrosion, impact, accidents, or natural disasters. Repairing these structures requires underwater welding technology. However, underwater welding is subject to the influence of water and pressure, resulting in an unstable molten pool, defects such as porosity and cracks in the weld, poor weld formation, and low joint performance.

[0003] Underwater localized dry welding eliminates the influence of water, resulting in high-quality weld joints, and is currently the main method used for underwater welding. Underwater laser welding utilizes optical fibers for long-distance energy transmission, offering high precision in welding and maintenance control, and highly concentrated heat source energy. Compared to other welding methods, laser welding has unique advantages in underwater welding. Compared to laser autofusion welding, laser wire-filled welding reduces the stringent requirements on assembly gaps, significantly improving welding efficiency. Furthermore, it can compensate for element loss during welding by adding welding wire. Currently, underwater localized dry laser wire-filled welding has been applied in the nuclear power industry.

[0004] The most critical factor affecting the quality of underwater dry welding is pressure. For every 10-meter increase in water depth, the underwater pressure increases by one atmosphere, or 100 kPa. The underwater welding experimental system for nuclear power plant maintenance built by the State Nuclear Power Technology Corporation can simulate an engineering environment at a water depth of 30 meters (400 kPa), meeting the needs of underwater welding mechanism research and equipment process experimentation for nuclear power plant maintenance. Underwater welding of offshore oil and gas facilities often takes place in even deeper waters, where environmental pressure has a more severe impact on weld quality.

[0005] Long Jian et al. studied the effect of environmental pressure on laser welding and found that after the environmental pressure increased, more nano-metal particles were sprayed upward along with metal vapor and plasma during the welding process, which significantly reduced the laser energy reaching the workpiece surface. Pang Shengyong et al.'s research showed that environmental pressure affects the boiling point of metal and thus affects the metal evaporation back pressure. Under high pressure, the laser welding penetration depth was significantly reduced. Jie Yansen et al.'s research found that increased environmental pressure would lead to a significant deterioration in the weld formation of laser filler wire welding. Their research showed that (1) the shielding effect of plasma and metal vapor on laser energy is enhanced under high pressure, which is an important reason for poor weld formation. At 700 kPa, the plasma reverse bremsstrahlung absorption coefficient is about 17 times that at 101 kPa. At 700 kPa, the absorption coefficient of nano-metal particles on laser is 5.7 times and 6.4 times that at 101 kPa and 20 kPa, respectively. This leads to a decrease in energy absorption rate, a reduction in laser energy reaching the welding wire and base material surface, a decrease in the evaporation back pressure on the droplet, and a decrease in the driving force for droplet transition. (2) After the environmental pressure increases, the boiling point of the material increases, and the metal evaporation back pressure further decreases. (3) The local surface of the droplet adheres to the end of the welding wire, while the rest of the surface is exposed to the high-pressure environment, making it more difficult for the droplet to detach from the end of the welding wire and significantly increasing the droplet drop resistance. The driving effect of the back pressure under high pressure is weakened, and the resistance that the droplet needs to overcome to detach from the welding wire increases. The droplet size needs to be large enough to allow the droplet to detach from the end of the welding wire under its own gravity. Therefore, the continuity of the droplet transition deteriorates and the continuity of the weld deteriorates.

[0006] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0007] This paper addresses the problem of discontinuous weld formation in laser-assisted wire-filled welding under high-pressure environments of 400 kPa-700 kPa. A high-pressure laser-assisted wire-filled welding method based on laser power modulation is proposed: laser power is applied to the welding wire using a rectangular wave with varying instantaneous power. On one hand, the large instantaneous peak power rapidly heats the welding wire, forming large-sized droplets, increasing the driving force for droplet droplet fall and promoting droplet transfer. On the other hand, the small instantaneous trough power provides sufficient time for plasma and metal vapor to dissipate, reducing their shielding effect on the laser beam. Results show that this method can significantly promote droplet transfer in high-pressure laser-assisted wire-filled welding, effectively solving the problem of poor weld formation continuity in high-pressure environments.

[0008] The objective of this invention is achieved through the following technical solution: a high-voltage laser filler wire welding method based on laser power modulation includes the following steps:

[0009] Under a high pressure environment of not less than 400 kPa, the welding wire should be kept at a predetermined distance from the surface of the object to be welded;

[0010] Laser filler wire welding is performed on the welding wire using a laser with instantaneous power varying in a rectangular wave, and molten droplets enter the object to be welded to produce a continuous weld.

[0011] In the method described, the predetermined distance is from zero to half the diameter of the welding wire.

[0012] In the method described, the object to be welded is a titanium alloy.

[0013] In the method described, the object to be welded is stainless steel.

[0014] In the method described, the welding wire material composition is the same as that of the object to be welded, and the welding wire diameter is 2mm.

[0015] In the method described, the relative positions of the welding wire and the object to be welded remain unchanged during laser wire filler welding.

[0016] In the method described, after a continuous weld is formed, argon gas is continued to be introduced until the object to be welded cools to room temperature.

[0017] In the method described, a high-pressure environment of not less than 400 kPa is formed by a pressure vessel, and both the welding wire and the object to be welded are subjected to laser filler wire welding in the pressure vessel.

[0018] In the method described, the laser filler wire welding is underwater laser welding.

[0019] In the method described, the modulation amplitude of the laser varies within the range of 40% to 50% of the average power.

[0020] In the method described, the modulation frequency of the laser varies in the range of 100Hz-325Hz.

[0021] In the method described, the high-pressure environment is 400kPa-700kPa.

[0022] Compared with existing technologies, this invention has the following advantages: Under normal pressure, the droplet transfer mode is a small-particle + liquid bridge transfer; under high pressure without modulation, it is a large-droplet particle transfer; and under high-pressure laser power modulation, it is a small-particle transfer, with the transfer period gradually increasing with the modulation frequency. Under high pressure, laser power waveform modulation is used, rapidly heating the welding wire with a large instantaneous peak power to form a large-size droplet, increasing the driving force for droplet droplet fall and promoting droplet transfer. Simultaneously, the small peak power at the trough helps plasma and metal vapor dissipate, promoting the material's absorption of the laser at the peak of the next cycle. This invention significantly improves the weld surface formation quality of laser filler wire welding in high-pressure environments. Attached Figure Description

[0023] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0024] In the attached diagram:

[0025] Figure 1(a) and Figure 1(b) are experimental schematic diagrams of the high-voltage laser filler wire welding method based on laser power modulation;

[0026] Figure 2 This is a schematic diagram of the weld surface morphology obtained without laser power waveform modulation.

[0027] Figure 3 This is a schematic diagram of the weld surface morphology obtained when the laser power modulation frequency is 50Hz.

[0028] Figure 4 This is a schematic diagram of the weld surface morphology obtained when the laser power modulation frequency is 150Hz.

[0029] Figure 5 This is a schematic diagram of the weld surface morphology obtained when the laser power modulation frequency is 500Hz.

[0030] Figure 6 This is a schematic diagram of high-speed photographic images showing the droplet transfer behavior during the welding process without laser power waveform modulation.

[0031] Figure 7 This is a high-speed photographic image illustrating the droplet transfer behavior during the welding process when the laser power modulation frequency is 50Hz.

[0032] Figure 8 This is a schematic diagram of a high-speed photograph of the droplet transfer behavior during the welding process when the laser power modulation frequency is 150Hz.

[0033] Figure 9 This is a schematic diagram of a high-speed photograph of the droplet transfer behavior during the welding process when the laser power modulation frequency is 500Hz.

[0034] Figure 10 This is a flowchart of the steps of a high-voltage laser filler wire welding method based on laser power modulation provided by the present invention.

[0035] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0036] Specific embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0037] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0038] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0039] For better understanding, in one embodiment, as shown in Figure 1(a) to Figure 10 As shown, the high-voltage laser filler wire welding method based on laser power modulation includes the following steps:

[0040] Under a high pressure environment of not less than 400 kPa, the welding wire is kept at a predetermined distance from the surface of the object to be welded;

[0041] Laser filler welding is performed on the welding wire using a rectangular wave laser with a modulation frequency of 100Hz-325Hz. The molten droplet enters the workpiece to produce a continuous weld. When the modulation frequency is below this range, the intense plasma generated during the laser power peak lasts for a longer period, reducing the laser energy reaching the material surface and causing unstable energy absorption by the material, resulting in a discontinuous weld. When the modulation frequency is above this range, the intense plasma annihilation process during the laser power trough cannot last long enough, which is detrimental to the material's energy absorption, thus preventing the formation of a smooth weld surface.

[0042] The boiling point of a material is an intrinsic property. Therefore, to control the droplet transfer behavior and weld formation in high-pressure laser wire-filler welding, one can only focus on two aspects: "reducing the shielding effect of plasma and nano-metal particles" and "increasing the metal evaporation recoil force by increasing the absolute energy reaching the material surface." Photoinduced plasma and metal nanoparticles are produced together. High-speed photography observed the transient processes of photoinduced plasma formation and annihilation under different environmental pressures, revealing that environmental pressure affects the rate of change of plasma height; the higher the pressure, the smaller this rate of change. This means that under relatively low environmental pressure, the plasma formation and annihilation process takes less time. Power modulation and periodic interruption (or reduction) of laser energy output can both cause periodic plasma annihilation and form continuous welds.

[0043] In a preferred embodiment of the method, the predetermined distance is from zero to half the diameter of the welding wire.

[0044] In a preferred embodiment of the method, the object to be welded is a titanium alloy.

[0045] In a preferred embodiment of the method, the object to be welded is stainless steel.

[0046] In a preferred embodiment of the method, the welding wire material is consistent with the material to be welded, and the welding wire diameter is 2mm.

[0047] In a preferred embodiment of the method, the relative positions of the welding wire and the object to be welded remain unchanged during laser wire filler welding.

[0048] In a preferred embodiment of the method, after a continuous weld is formed, argon gas is continued to be introduced until the object to be welded cools to room temperature.

[0049] In a preferred embodiment of the method, a high-pressure environment of not less than 400 kPa is formed by a pressure vessel, and both the welding wire and the object to be welded are subjected to laser filler wire welding in the pressure vessel.

[0050] In a preferred embodiment of the method, the laser filler wire welding is underwater laser welding.

[0051] In a preferred embodiment of the method, the laser power modulation amplitude varies within the range of 40% to 50% of the average power.

[0052] In a preferred embodiment of the method, the high-pressure environment is 400 kPa - 700 kPa. Within this pressure range, the continuity of the laser filler wire weld deteriorates significantly. Within this pressure range, the plasma formation and annihilation processes take less time, and power modulation and periodic interruption (or reduction) of laser energy output can both cause periodic plasma annihilation and form a continuous weld.

[0053] In one embodiment, a rectangular-wave laser is used for laser filler welding of the welding wire. The modulation frequency of the laser varies from 50Hz to 500Hz. The molten droplet enters the workpiece to produce a continuous weld, and a keyhole-like structure is formed on the droplet. Under high pressure, laser power waveform modulation is used to rapidly melt the welding wire at a high instantaneous peak power, forming a droplet and a keyhole-like structure on it. The recoil pressure of the evaporated metal inside the keyhole and the impact force of the laser beam on the droplet help promote droplet transfer. At the same time, the small peak power at the trough helps the plasma and metal vapor dissipate, promoting the absorption of laser by the material at the peak of the next cycle. This invention significantly improves the welding quality of laser filler welding in high-pressure environments.

[0054] In one embodiment, the main materials used are a Ti6Al4V titanium alloy substrate and welding wire. The substrate size is 40×20×3mm, and the welding wire diameter is 2mm. The experimental equipment includes a YSL-8000 fiber laser, a Presbyterian oscillating welding head, a YASKAWA HP20 welding robot, a Thousand-Eyed Wolf M220 high-speed camera, a self-made continuously variable pressure vessel, and related accessories. A high-speed camera is used to observe the plasma behavior and droplet transfer behavior during the welding process in real time. A self-made continuously variable pressure vessel is used to create a high-pressure environment by filling it with high-pressure gas (argon), and a vacuum pump is used to extract the gas inside the pressure vessel to create a negative pressure environment. Quartz glass transmission windows with a light transmittance of over 90% are installed at the top and front of the pressure vessel. Inlets and outlets are located on both sides of the vessel. The gas supply pipes are connected to the pressure reducing valve and inlet of a high-pressure argon cylinder, respectively, serving as the gas filling channel for creating a high-pressure environment. A back pressure valve is installed at the outlet, allowing for stepless pressure regulation of the internal pressure of the pressure vessel by controlling the knobs of the pressure reducing valve and back pressure valve. Welding bosses are installed inside the pressure vessel to hold and fix the welding substrate. Welding wire is placed parallel to the substrate at a certain height above it and fixed in position using a fixing device. A thin glass plate is placed at the upper projection window to collect metal vapor particles generated during welding. A laser welding head driven by a robot is installed on the upper exterior of the pressure vessel, with a spectral signal acquisition probe fixed at the bottom of the welding head to collect photo-induced plasma information. A Thousand-Eyed Wolf M220 high-speed camera is placed at the front of the pressure vessel, aligned with the front transmission window, to capture images of molten droplets, the molten pool, and plasma during the welding process.

[0055] Before the experiment, the inside of the pressure vessel was cleaned, and the oxide scale on the substrate and welding wire surfaces was removed by sanding. The substrate and welding wire were then fixed inside the pressure vessel. The high-speed camera focal length was adjusted to obtain clear images, and the robot position was adjusted to determine the welding path. After the preparation was completed, argon gas was introduced into the vessel by opening the back pressure valves at the inlet and outlet. The argon gas flow rate was 5 L / min, and the gas introduction time was 120 s. After the gas introduction was completed, the back pressure valve was closed, and the pressure of the inlet pressure reducing valve was adjusted to control the pressure inside the pressure vessel and achieve control of the welding pressure environment.

[0056] During the welding process, the relative positions of the welding wire and the substrate are kept constant. The relative movement speed between the welding wire, the substrate and the laser beam is applied by setting the robot's movement speed. After the welding is completed, inert gas (argon) is continuously introduced into the pressure vessel to create a protective environment until it cools to room temperature, and then the sample is taken out.

[0057] Example 1:

[0058] In one embodiment, the main materials used are a Ti6Al4V titanium alloy substrate and welding wire. The substrate size is 40×20×3mm, and the welding wire diameter is 2mm. The experimental equipment includes a YSL-8000 fiber laser, a Presbyterian oscillating welding head, a YASKAWA HP20 welding robot, a Thousand-Eyed Wolf M220 high-speed camera, a self-made continuously variable pressure vessel, and related accessories. A high-speed camera is used to observe the plasma behavior and droplet transfer behavior during the welding process in real time. A self-made continuously variable pressure vessel is used to create a high-pressure environment by filling it with high-pressure gas (argon), and a vacuum pump is used to extract the gas inside the pressure vessel to create a negative pressure environment. Quartz glass transmission windows are provided at the top and front of the pressure vessel, with a light transmittance of over 90%. An air inlet and an air outlet are provided on both sides of the vessel. The two ends of the gas supply pipe are connected to the pressure reducing valve and the air inlet on the high-pressure argon cylinder, respectively, which serve as the gas filling channel when creating a high-pressure environment. A back pressure valve is provided at the air outlet. The stepless pressure variation function of the internal pressure of the pressure vessel is realized by controlling the pressure reducing valve and the back pressure valve knob.

[0059] Before the experiment, the inside of the pressure vessel was cleaned, and the oxide scale on the substrate and welding wire surfaces was removed by sanding. The substrate and welding wire were then fixed inside the pressure vessel. The high-speed camera focal length was adjusted to obtain clear images, and the robot position was adjusted to determine the welding path. After the preparation was completed, argon gas was introduced into the vessel by opening the back pressure valves at the inlet and outlet. The argon gas flow rate was 5 L / min, and the gas introduction time was 120 s. After the gas introduction was completed, the back pressure valve was closed, and the pressure of the inlet pressure reducing valve was adjusted to control the pressure inside the pressure vessel and achieve control of the welding pressure environment.

[0060] During the welding process, the relative positions of the welding wire and the substrate are kept constant. The relative movement speed between the welding wire, the substrate and the laser beam is applied by setting the robot's movement speed. After the welding is completed, inert gas (argon) is continuously introduced into the pressure vessel to create a protective environment until it cools to room temperature, and then the sample is taken out.

[0061] The parameters used in the experiment are shown in Table 1.

[0062] Table 1 Welding Parameter Table

[0063]

[0064] Figure 4 The image shows the surface morphology of the weld obtained at a modulation frequency of 150 Hz. It can be seen that continuous and smooth weld formation can be obtained by using laser power modulation at 150 Hz in a 700 kPa high-pressure environment. Figure 8 This is a high-speed photograph of the plasma and droplet transfer behavior during the welding process when the laser power is modulated at a frequency of 150Hz. The high-speed image shows that after modulating the laser power with a 150Hz rectangular wave, the material rapidly melts and forms droplets during the peak of the laser power, while a strong plasma is generated above the welding wire. During the trough of the laser power, the plasma and metal vapor particles in the laser beam channel dissipate, which facilitates the absorption of laser energy by the material during the next laser power peak. The welding wire is then heated and melted, and smoothly transitions into the molten pool under the influence of recoil pressure and gravity. Therefore, rectangular wave modulation of the laser power can significantly improve weld formation.

[0065] Example 2:

[0066] In one embodiment, the main materials used are a Ti6Al4V titanium alloy substrate and welding wire. The substrate size is 40×20×3 mm, and the welding wire diameter is 2 mm. The experimental equipment includes a YSL-8000 fiber laser, a Presbyterian oscillating welding head, a YASKAWA HP20 welding robot, a Thousand-Eyed Wolf M220 high-speed camera, a self-made continuously variable pressure vessel, and related accessories. A high-speed camera is used to observe the plasma behavior and droplet transfer behavior during the welding process in real time. A self-made continuously variable pressure vessel is used to create a high-pressure environment by filling it with high-pressure gas (argon), and a vacuum pump is used to extract the gas inside the pressure vessel to create a negative pressure environment. Quartz glass transmission windows are provided at the top and front of the pressure vessel, with a light transmittance of over 90%. An air inlet and an air outlet are provided on both sides of the vessel. The two ends of the gas supply pipe are connected to the pressure reducing valve and the air inlet on the high-pressure argon cylinder, respectively, which serve as the gas filling channel when creating a high-pressure environment. A back pressure valve is provided at the air outlet. The stepless pressure variation function of the internal pressure of the pressure vessel is realized by controlling the pressure reducing valve and the back pressure valve knob.

[0067] Before the experiment, the inside of the pressure vessel was cleaned, and the oxide scale on the substrate and welding wire surfaces was removed by sanding. The substrate and welding wire were then fixed inside the pressure vessel. The high-speed camera focal length was adjusted to obtain clear images, and the robot position was adjusted to determine the welding path. After the preparation was completed, argon gas was introduced into the vessel by opening the back pressure valves at the inlet and outlet. The argon gas flow rate was 5 L / min, and the gas introduction time was 120 s. After the gas introduction was completed, the back pressure valve was closed, and the pressure of the inlet pressure reducing valve was adjusted to control the pressure inside the pressure vessel and achieve control of the welding pressure environment.

[0068] During the welding process, the relative positions of the welding wire and the substrate are kept constant. The relative movement speed between the welding wire, the substrate and the laser beam is applied by setting the robot's movement speed. After the welding is completed, inert gas (argon) is continuously introduced into the pressure vessel to create a protective environment until it cools to room temperature, and then the sample is taken out.

[0069] The parameters used in the experiment are shown in Table 2.

[0070] Table 2 Welding Parameter Table

[0071]

[0072] Figure 3 The image shows the surface morphology of the weld obtained at a modulation frequency of 50 Hz. It can be seen that welding using laser power modulation at 50 Hz in a 400 kPa high-pressure environment results in a discontinuous weld. Figure 7 These are high-speed photographs of the plasma and droplet transfer behavior during the welding process when the laser power modulation frequency is 50Hz. The high-speed images show that at 50Hz, the strong plasma generated during the laser power peak persists for a longer period due to the low modulation frequency, reducing the laser energy reaching the material surface. Therefore, the low modulation frequency leads to unstable energy absorption by the material, resulting in weld discontinuities.

[0073] Example 3:

[0074] In one embodiment, the main materials used are a Ti6Al4V titanium alloy substrate and welding wire. The substrate size is 40×20×3 mm, and the welding wire diameter is 2 mm. The experimental equipment includes a YSL-8000 fiber laser, a Presbyterian oscillating welding head, a YASKAWA HP20 welding robot, a Thousand-Eyed Wolf M220 high-speed camera, a self-made continuously variable pressure vessel, and related accessories. A high-speed camera is used to observe the plasma behavior and droplet transfer behavior during the welding process in real time. A self-made continuously variable pressure vessel is used to create a high-pressure environment by filling it with high-pressure gas (argon), and a vacuum pump is used to extract the gas inside the pressure vessel to create a negative pressure environment. Quartz glass transmission windows are provided at the top and front of the pressure vessel, with a light transmittance of over 90%. An air inlet and an air outlet are provided on both sides of the vessel. The two ends of the gas supply pipe are connected to the pressure reducing valve and the air inlet on the high-pressure argon cylinder, respectively, which serve as the gas filling channel when creating a high-pressure environment. A back pressure valve is provided at the air outlet. The stepless pressure variation function of the internal pressure of the pressure vessel is realized by controlling the pressure reducing valve and the back pressure valve knob.

[0075] Before the experiment, the inside of the pressure vessel was cleaned, and the oxide scale on the substrate and welding wire surfaces was removed by sanding. The substrate and welding wire were then fixed inside the pressure vessel. The high-speed camera focal length was adjusted to obtain clear images, and the robot position was adjusted to determine the welding path. After the preparation was completed, argon gas was introduced into the vessel by opening the back pressure valves at the inlet and outlet. The argon gas flow rate was 5 L / min, and the gas introduction time was 120 s. After the gas introduction was completed, the back pressure valve was closed, and the pressure of the inlet pressure reducing valve was adjusted to control the pressure inside the pressure vessel and achieve control of the welding pressure environment.

[0076] During the welding process, the relative positions of the welding wire and the substrate are kept constant. The relative movement speed between the welding wire, the substrate and the laser beam is applied by setting the robot's movement speed. After the welding is completed, inert gas (argon) is continuously introduced into the pressure vessel to create a protective environment until it cools to room temperature, and then the sample is taken out.

[0077] The parameters used in the experiment are shown in Table 3.

[0078] Table 3 Welding Parameter Table

[0079]

[0080] Figure 5 The image shows the surface morphology of the weld obtained at a modulation frequency of 500 Hz. It can be seen that although the weld obtained by using laser power modulation at 500 Hz in a 400 kPa high-pressure environment is continuous, the weld surface is not smooth and obvious ripples can be seen. Figure 9These are high-speed photographs of the plasma and droplet transfer behavior during the welding process when the laser power modulation frequency is 500 Hz. The high-speed images show that at a laser power modulation frequency of 500 Hz, the intense plasma annihilation process during the laser power trough cannot last long enough due to the high modulation frequency. This is detrimental to the material's energy absorption, thus preventing the formation of a smooth weld surface morphology.

[0081] Comparative example:

[0082] In the comparative example, the main materials used were a Ti6Al4V titanium alloy substrate and welding wire. The substrate size was 40×20×3 mm, and the welding wire diameter was 2 mm. The experimental equipment included a YSL-8000 fiber laser, a Presbyterian oscillating welding head, a YASKAWA HP20 welding robot, a Thousand-Eyed Wolf M220 high-speed camera, a self-made continuously variable pressure vessel, and related accessories. A high-speed camera was used to observe the plasma behavior and droplet transfer behavior during the welding process in real time. A self-made continuously variable pressure vessel was used to create a high-pressure environment by filling it with high-pressure gas (argon), and a vacuum pump was used to extract the gas inside the pressure vessel to create a negative pressure environment.

[0083] Before the experiment, the inside of the pressure vessel was cleaned, and the oxide scale on the substrate and welding wire surfaces was removed by sanding. The substrate and welding wire were then fixed inside the pressure vessel. The high-speed camera focal length was adjusted to obtain clear images, and the robot position was adjusted to determine the welding path. After the preparation was completed, argon gas was introduced into the vessel by opening the back pressure valves at the inlet and outlet. The argon gas flow rate was 5 L / min, and the gas introduction time was 120 s. After the gas introduction was completed, the back pressure valve was closed, and the pressure of the inlet pressure reducing valve was adjusted to control the pressure inside the pressure vessel and achieve control of the welding pressure environment.

[0084] During the welding process, the relative positions of the welding wire and the substrate are kept constant. The relative movement speed between the welding wire, the substrate and the laser beam is applied by setting the robot's movement speed. After the welding is completed, inert gas (argon) is continuously introduced into the pressure vessel to create a protective environment until it cools to room temperature, and then the sample is taken out.

[0085] The parameters used in the experiment are shown in Table 4.

[0086] Table 4 Welding Parameter Table

[0087]

[0088] Figure 2 The images show the surface and cross-sectional morphology of the weld seam without modulation. It can be seen that without laser power modulation in a 400 kPa high-pressure environment, the weld formation is very poor, and continuous weld seams are completely impossible to form. Figure 6This is a high-speed photographic image of the laser filler wire welding process under unmodulated conditions. The high-speed image shows that, under unmodulated laser power, plasma and metal vapor particles are continuously generated and persist in the laser beam channel during high-pressure laser filler wire welding. This creates a severe shielding effect on the laser energy, reducing the energy reaching the material surface and leading to difficulties in melting and transition, resulting in poor weld quality.

[0089] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A high-voltage laser filler wire welding method based on laser power modulation, characterized in that, It includes the following steps, Under a high pressure environment of not less than 400 kPa, the welding wire is kept at a predetermined distance from the surface of the object to be welded; Laser filler wire welding is performed on the welding wire using a laser with instantaneous power varying in a rectangular wave, and molten droplets enter the object to be welded to produce a continuous weld. The predetermined distance is from zero to half the diameter of the welding wire; The modulation amplitude of the laser is 40%-50% of the average power; The modulation frequency of the laser varies from 100Hz to 325Hz.

2. The method as described in claim 1, characterized in that, The material of the object to be welded and the welding wire is titanium alloy or stainless steel.

3. The method as described in claim 1, characterized in that, In laser filler wire welding, the relative positions of the welding wire and the object to be welded remain unchanged.

4. The method as described in claim 1, characterized in that, After a continuous weld is formed, argon gas is continued to be introduced until the object to be welded cools to room temperature.

5. The method as described in claim 1, characterized in that, A high-pressure environment of not less than 400 kPa is formed by a pressure vessel, and both the welding wire and the object to be welded are laser filler wire welded in the pressure vessel.

6. The method as described in claim 1, characterized in that, Laser filler wire welding is an underwater laser welding process.

7. The method as described in claim 1, characterized in that, The high-pressure environment is 400kPa - 700kPa.

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