Method and device for improving corrosion resistance of duplex stainless steel

Abstract

The invention discloses a method and a device for improving corrosion resistance of duplex stainless steel, the method adopts a galvanometer laser-induced arc hybrid welding method to weld the duplex stainless steel, the laser is a plurality of beams of pulse laser, a galvanometer controls the plurality of beams of pulse laser to be synchronous with a TIG (Tungsten Inert Gas) arc with different scanning parameters, and the corrosion resistance of the duplex stainless steel is improved by enhancing disturbance of a molten pool. And thus, defects are generated in the ferrite, and heterogeneous sites are provided for austenite nucleation. In the welding cooling process, austenite preferentially nucleates and grows at the defect position, so that generation of intragranular austenite is promoted, Widmannstan austenite structures are reduced, primary ferrite dendritic crystals can be broken through strong molten pool convection, a large number of dendritic crystal fragments are generated, and the ferrite grain size is effectively refined. According to the structure evolution, a corrosive medium can make contact with an austenite phase with the excellent corrosion resistance more easily, the potential corrosion expansion path is shortened, and therefore the corrosion resistance of the duplex stainless steel welded joint is improved.

Description

Technical Field

[0001] This invention relates to a method and apparatus for controlling corrosion resistance in the welding of metallic materials, specifically to a method and apparatus for improving the corrosion resistance of duplex stainless steel using galvanometer-guided multi-beam pulsed laser-induced arc composite welding. Background Technology

[0002] Duplex stainless steel is composed of a microstructure of two phases, austenite and ferrite, in equal proportions. Welding methods include continuous laser-arc hybrid welding. Continuous laser-arc hybrid welding can effectively suppress the precipitation of the second phase due to its fast cooling rate. However, the upper part is affected by both laser and arc, while the lower part is only affected by laser. This results in uneven microstructure between the upper and lower parts and a severe imbalance between the ferrite and austenite phases, which affects corrosion resistance. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a method and apparatus for improving the corrosion resistance of duplex stainless steel through multi-beam pulsed laser-induced arc composite welding.

[0004] Technical Solution: The present invention provides a method for improving the corrosion resistance of duplex stainless steel. The method employs a galvanometer-laser-induced arc hybrid welding method to weld duplex stainless steel. The laser is a pulsed laser with multiple beams. The galvanometer controls these multiple pulsed laser beams with different scanning parameters, synchronizing them with the TIG arc to enhance molten pool disturbance. This causes defects to form within the ferrite, promoting the formation of intragranular austenite and reducing Widmanstättenite. The scanning parameters include scanning frequency and scanning amplitude.

[0005] Furthermore, the pulsed laser process parameters are as follows: peak power of pulsed laser 1000~12000W, pulse width 2~10ms, duty cycle 10%~60%, pulse frequency 20~100Hz, and welding speed 7~30mm / s.

[0006] Furthermore, the galvanometer process parameters are as follows: a circular scanning path is adopted, the scanning frequency is 50~300Hz, the scanning amplitude is 0.5~2.5mm, and the distance between the pulsed laser and the TIG tip is 2~3mm.

[0007] Furthermore, the TIG arc welding process parameters are as follows: the TIG arc is placed at an angle of 45° to the vertical direction, using 190~220A DC power, voltage 10~20V, and the distance between the TIG tip and the workpiece is 2~3mm.

[0008] Furthermore, duplex stainless steel undergoes cleaning before welding.

[0009] This invention discloses a device for improving the corrosion resistance of duplex stainless steel, and a method for achieving the aforementioned improvement in the corrosion resistance of duplex stainless steel. The device includes a robotic arm, a galvanometer, a TIG welding torch, a mechanical control device, a laser, a programmer, and an arc welding machine. The galvanometer is mounted at the end of the robotic arm, which is controlled by the programmer to adjust the galvanometer's horizontal position relative to the worktable and the distance between the galvanometer and the workpiece. The galvanometer is connected to the laser to control the multiple pulsed laser beams generated by the laser to be perpendicular to the worktable and synchronized with the TIG arc in a specific scanning manner. The TIG welding torch is fixed to the mechanical control device, which is connected to the arc welding machine. The mechanical control device is used to adjust the placement angle of the TIG welding torch and set the TIG arc oscillation process parameters. The arc welding machine allows for adjustment of the current type and voltage magnitude.

[0010] Furthermore, the galvanometer and the laser are connected by optical fiber, which is fixed to the robotic arm.

[0011] Furthermore, the arc welding machine is connected to a gas cylinder, which is used to supply protective gas to the welding area during welding.

[0012] Furthermore, the protective gas is argon.

[0013] Furthermore, the device for improving the corrosion resistance of duplex stainless steel also includes a control system for setting parameters, including laser type, laser power, scanning path, scanning frequency, and scanning amplitude of the multi-beam galvanometer pulsed laser. The unified use of TIG arc and protective gas is also achieved by setting parameters in the control system.

[0014] The technical principle of this invention lies in the fact that traditional welding processes easily lead to problems such as coarse grains and an imbalance in the ratio of ferrite to austenite in the joint area. In particular, insufficient intragranular austenite content and excessive Widmanstätten austenite reduce the phase interface area, increasing the risk of microgalvanic corrosion and stress concentration, and also impairing the overall corrosion resistance of the joint. Therefore, this invention proposes a composite welding process using a galvanometer-controlled multi-beam pulsed laser-induced arc. The core of this process is to utilize the extremely high instantaneous power density of the pulsed laser to inject high energy into the molten pool in a very short time, generating strong local thermal shock and plasma / recoil pressure, thereby creating intense stirring of the molten pool. To further enhance the stirring effect, a galvanometer-controlled multi-beam pulsed laser is used for circular scanning, with different scanning parameters configured for each pulsed laser. Combined with the arc, this achieves synergistic enhancement of the range and intensity of molten pool disturbance. This enhanced stirring effect is regulated and optimized through multiple mechanisms. The intense molten pool stirring generates high-density thermal stress within the ferrite, inducing plastic deformation and forming numerous defects such as dislocations, vacancies, and small-angle grain boundaries. These defect regions have high atomic energy states, providing abundant heterogeneous nucleation sites for austenite nucleation, thus significantly promoting intragranular austenite formation while inhibiting Widmanstätten austenite growth from grain boundaries. Intense molten pool convection breaks up primary ferrite dendrites, generating numerous dendrite fragments and effectively refining the ferrite grain size. The combined effect of pulsed laser and electric arc enables rapid heating and cooling, shortening the residence time of the weld metal in the high-temperature zone and effectively inhibiting excessive growth and coarsening of the ferrite phase. Through the combined action of these mechanisms, the microstructure of the welded joint is significantly improved: intragranular austenite content increases and is dispersed in fine islands, Widmanstätten austenite decreases, the two phases become more balanced, the phase interface area increases, and the ferrite grains are refined. This microstructural evolution makes it easier for corrosive media to contact the highly corrosion-resistant austenite phase and shortens the potential corrosion propagation path, reducing not only the susceptibility to microgalvanic corrosion but also hindering the initiation and development of pitting and other localized corrosion. In summary, this invention achieves precise control over the microstructure of duplex stainless steel welded joints by generating strong molten pool stirring and rapid thermal cycling through a galvanometer multi-beam pulsed laser-induced arc composite welding process, thereby effectively improving its corrosion resistance and extending its service life in harsh environments.

[0015] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: This invention utilizes a galvanometer-guided multi-pulse laser to induce arc welding of duplex stainless steel. Compared to continuous lasers, the energy release of short pulses results in a more intense stirring effect on the molten pool during its formation. Simultaneously, a galvanometer is introduced to control the multi-pulse laser, and by setting different scanning parameters for each pulse and combining them with the arc, the stirring of the molten pool is further enhanced, causing localized areas of the molten pool to undergo extremely non-uniform thermal cycling. This thermal shock leads to drastic thermal expansion / contraction of the ferrite lattice, generating high-density thermal stress, inducing plastic deformation, and forming defects such as dislocations. This provides heterogeneous sites for austenite nucleation. During welding cooling, austenite preferentially nucleates and grows at these grain boundaries, thereby promoting intragranular austenite formation and reducing Widmanstätten structure. This structural evolution makes it easier for corrosive media to contact the highly corrosion-resistant austenite phase and shortens the potential corrosion propagation path. This not only reduces the susceptibility to microgalvanic corrosion but also hinders the initiation and development of localized corrosion such as pitting corrosion, thus improving the corrosion resistance of the duplex stainless steel welded joint. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a device structure for improving the corrosion resistance of duplex stainless steel according to an embodiment of the present invention. Detailed Implementation

[0017] The invention will now be further described with reference to the accompanying drawings.

[0018] Appendix Figure 1 The accompanying figure labels are as follows:

[0019] 1. Robotic arm; 2. Galvanometer; 3. TIG welding torch; 4. Mechanical control device; 5. Laser; 6. Programmer; 7. Arc welding machine; 8. Fiber optic cable; 9. Control system; 10. Gas cylinder.

[0020] Example 1: Example 1 provides a method for improving the corrosion resistance of duplex stainless steel. The method employs a galvanometer-laser-induced arc hybrid welding method to weld duplex stainless steel (e.g., 2205 duplex stainless steel). The duplex stainless steel undergoes cleaning before welding. The laser is a pulsed laser and consists of multiple beams (e.g.,...). Figure 1 As shown, there are four beams. The galvanometer controls multiple pulsed laser beams with different scanning parameters to synchronize with the TIG arc, which enhances the disturbance of the molten pool, causes defects to be generated inside the ferrite, promotes the formation of intragranular austenite and reduces Widmanstättenite; the scanning parameters include scanning frequency and scanning amplitude.

[0021] The pulsed laser process parameters are as follows: peak power of pulsed laser 1000~12000W, pulse width 2~10ms, duty cycle 10%~60%, pulse frequency 20~100Hz, and welding speed 7~30mm / s.

[0022] The galvanometer process parameters are as follows: a circular scanning path is used, the scanning frequency is 50~300Hz, the scanning amplitude is 0.5~2.5mm, and the distance between the pulsed laser and the TIG tip is 2~3mm.

[0023] The TIG arc welding process parameters are as follows: the TIG arc is placed at a 45° angle to the vertical direction, using 190~220A DC power, 10~20V voltage, and the distance between the TIG tip and the workpiece is 2~3mm.

[0024] Example 2: As Figure 1 As shown, Example 2 provides an apparatus for improving the corrosion resistance of duplex stainless steel, which is used to implement the method for improving the corrosion resistance of duplex stainless steel described in Example 1. The apparatus includes a robotic arm 1, a galvanometer 2, a TIG welding torch 3, a mechanical control device 4, a laser 5, a programmer 6, an arc welding machine 7, and a control system 9.

[0025] A galvanometer 2 is mounted at the end of a robotic arm 1, which is controlled by a programmer 6. The programmer 6 adjusts the galvanometer 2 to be horizontally aligned with the worktable and the distance between the galvanometer 2 and the workpiece. The galvanometer 2 is connected to the laser 5 via an optical fiber 8, which is fixed to the robotic arm 1. The galvanometer 2 is used to control the multiple pulsed laser beams generated by the laser 5 to be perpendicular to the worktable and synchronized with the TIG arc in a certain scanning pattern (e.g., a circular scanning pattern).

[0026] The TIG welding torch 3 is fixed on a mechanical control device 4, which is connected to both the arc welding machine 7 and the control system 9. The mechanical control device 4 is used to adjust the placement angle of the TIG welding torch 3 and set the TIG arc oscillation process parameters. The arc welding machine 7 can adjust the type and magnitude of the current. A gas cylinder 10 is connected to the arc welding machine 7, which is used to supply shielding gas (e.g., argon) to the welding area during welding. The control system 9 contains a computer program that allows for parameter settings, such as laser type, laser power, scanning path, scanning frequency, and scanning amplitude of the multi-beam galvanometer pulsed laser. The unified use of the TIG arc and shielding gas is also achieved by setting parameters in the control system 9.

[0027] The steps for implementing the method for improving the corrosion resistance of duplex stainless steel as described in Example 1 using this device are as follows:

[0028] S1. After cleaning the 2205 duplex stainless steel (e.g., with a thickness of 3mm) before welding, fix it on the workbench.

[0029] S2. Control the robot arm 1 through the programmer 6, adjust the angle and position of the robot arm 1 so that the galvanometer 2 mounted on the robot arm 1 is horizontal to the worktable and control the distance between the galvanometer 2 and the worktable, and keep the defocus amount at 0.

[0030] S3. Input the welding speed, welding start and end points (single weld) in programmer 6.

[0031] S4. Adjust the distance between the tungsten electrode and the pulsed laser, and at the same time adjust the angle of the tungsten electrode to 45° with the worktable.

[0032] S5. Input the current type and arc parameters on the arc welding machine 7; input the corresponding pulse laser parameters and galvanometer parameters on the control system 9.

[0033] S6. Open gas cylinder 10 for welding.

Claims

1. A method of improving corrosion resistance of duplex stainless steel, characterized by, The duplex stainless steel is welded by a galvanometer laser-induced electric arc hybrid welding method, wherein the laser is a pulsed laser and a multi-beam, the multi-beam pulsed laser is controlled by the galvanometer to be synchronized with the TIG arc at different scanning parameters, the molten pool disturbance is enhanced, the defects are generated in the ferrite, the intracrystalline austenite is promoted to be generated and the widmanstatten austenite is reduced; the scanning parameters include a scanning frequency and a scanning amplitude.

2. The method of improving corrosion resistance of duplex stainless steel according to claim 1, characterized in that, The pulsed laser process parameters are as follows: a pulsed laser peak power is 1000-12000 W, a pulse width is 2-10 ms, a duty cycle is 10%-60%, a pulse frequency is 20-100 Hz, and a welding speed is 7-30 mm / s.

3. The method of improving corrosion resistance of duplex stainless steel according to claim 1, characterized in that, The galvanometer process parameters are as follows: a ring-shaped scanning path is adopted, a scanning frequency is 50-300 Hz, a scanning amplitude is 0.5-2.5 mm, and the distance between the pulsed laser and the TIG tip is 2-3 mm.

4. The method of improving corrosion resistance of duplex stainless steel according to claim 1, characterized in that, The TIG arc welding process parameters are as follows: the TIG arc is placed at an angle of 45° with the vertical direction, a direct current of 190-220 A is adopted, a voltage is 10-20 V, and the distance between the TIG tip and the workpiece is 2-3 mm.

5. The method of improving corrosion resistance of duplex stainless steel according to claim 1, characterized in that, The duplex stainless steel is cleaned before welding.

6. An apparatus for improving corrosion resistance of duplex stainless steel for implementing the method for improving corrosion resistance of duplex stainless steel according to any one of claims 1 to 5, characterized by, The device for improving the corrosion resistance of the duplex stainless steel comprises a mechanical arm (1), a galvanometer (2), a TIG welding gun (3), a mechanical control device (4), a laser (5), a programmer (6) and an arc welding machine (7), the galvanometer (2) is installed at the end of the mechanical arm (1), the mechanical arm (1) is controlled by the programmer (6), the galvanometer (2) is adjusted to be horizontal to the workbench and the distance between the galvanometer (2) and the workpiece; the galvanometer (2) is connected with the laser (5) and is used for controlling the multi-beam pulsed laser generated by the laser (5) to be perpendicular to the workbench and to be synchronized with the TIG arc in a certain scanning mode; the TIG welding gun (3) is fixed on the mechanical control device (4), the mechanical control device (4) is connected with the arc welding machine (7), and the mechanical control device (4) is used for adjusting the placement angle of the TIG welding gun (3) and setting the TIG arc swing process parameters; the current type and the current voltage size can be adjusted through the arc welding machine (7).

7. The apparatus of claim 6, wherein the apparatus is configured to increase the corrosion resistance of duplex stainless steel by, The galvanometer (2) and the laser (5) are connected through an optical fiber (8), and the optical fiber (8) is fixed on the mechanical arm (1).

8. The apparatus of claim 6, wherein the apparatus is configured to increase corrosion resistance of duplex stainless steel by, The arc welding machine (7) is connected with a gas cylinder (10), and the gas cylinder (10) is used for conveying protective gas to the welding area during welding.

9. The apparatus of claim 8, wherein the apparatus is configured to increase the corrosion resistance of duplex stainless steel by, The protective gas is argon.

10. The apparatus of claim 8, wherein the apparatus is configured to increase corrosion resistance of duplex stainless steel by, A control system (9) is further included, which is used for setting parameters, including the laser type, the laser power, the scanning path of the multi-beam galvanometer pulsed laser, the scanning frequency, the scanning amplitude, the TIG arc and the unified calling of the protective gas, which are realized by setting parameters in the control system (9).

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