Vacuum laser welding method applicable to medium and thick titanium alloy plates

Abstract

This invention provides a vacuum laser welding method suitable for medium-thick titanium alloy plates. The method involves pre-treating the surface of the titanium alloy plate to be welded, removing the oxide film, and cleaning it thoroughly. An active agent powder is mixed uniformly with acetone to form an active solution. This active solution is then applied to the treated plate surface. After the acetone evaporates, the active agent powder adheres to the surface of the titanium alloy plate, forming a coating layer. The treated titanium alloy plates are then butt-fitted and fixed onto a processing platform, with the coated surface facing the laser. Welding is performed in a vacuum atmosphere according to a preset program and parameters. This vacuum laser welding method, by utilizing a vacuum atmosphere and the action of the active agent, enhances energy absorption efficiency, reduces the electron density of photo-induced plasma, lowers the molten pool density, and shrinks the plasma cloud, thereby suppressing the plasma generated during laser welding while reducing the vacuum pressure requirement.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy plate welding technology, and more specifically to a vacuum laser welding method suitable for medium-thick titanium alloy plates. Background Technology

[0002] Medium-thick titanium alloy plates generally refer to titanium alloy plates with a thickness of 4.5 to 25 mm. Currently, the commonly used welding methods for medium-thick TC4 titanium alloy plates are argon arc welding and gas metal arc welding.

[0003] Argon arc welding has a small weld width ratio and a large heat input, resulting in problems such as incomplete fusion, incomplete penetration, coarse grains, and post-weld deformation. Gas metal arc welding (GMAW) suffers from poor interlayer bonding, cracks, slag inclusions, and other defects. Multi-layer, multi-pass welding accumulates these defects, ultimately affecting weld quality. Furthermore, both of these welding methods require larger beveling when welding medium and thick plates, increasing the amount of work and reducing welding efficiency.

[0004] Electron beam welding, as a high-energy beam welding method, has strong penetration power compared to arc welding, achieving one-step forming without the need for beveling. However, electron beam welding has high requirements for product size and vacuum level, and its production cost is high. Therefore, how to control production costs while balancing welding efficiency and cost control has become an urgent problem to be solved.

[0005] For addressing the existing challenges in welding medium-thick titanium alloy plates, high-power laser welding, also a high-energy beam welding method, theoretically possesses similar penetration power to electron beam welding, but at a lower cost. However, as laser power increases, dense plasma and metal vapor are generated during laser welding. The intense plume phenomenon and metal vapor severely interfere with the stable and efficient transmission of laser energy, thus limiting the realization of high-power laser welding in the medium-thick plate field. Post-weld plates are highly susceptible to problems such as undercut, cracks, and surface oxidation.

[0006] Currently, several conventional solutions exist for addressing the interference of metal vapor and plume phenomena on laser energy transmission during medium-thick plate laser welding: side-blowing, side-suction, and vacuum methods. While side-blowing and side-suction methods are simple, easy to operate, and widely used, their suppression effects are limited and their stability is poor. The vacuum method, utilizing the suppression effect of vacuum on plume, can improve laser energy utilization, thereby increasing weld penetration, stabilizing the welding process, improving weld formation, suppressing welding defects such as porosity, and significantly enhancing weld protection.

[0007] Vacuum laser welding has lower requirements for vacuum levels compared to electron beam welding, and can be performed under negative pressure conditions. It also boasts higher welding efficiency than electron beam welding. However, compared to conventional laser welding, its size limitations and high cost remain significant drawbacks. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a vacuum laser welding method suitable for medium-thick titanium alloy plates. This method involves coating the surface of the medium-thick titanium alloy plate with an activator and combining it with a negative pressure atmosphere to suppress the plasma generated during laser welding while reducing the vacuum negative pressure standard.

[0009] This invention proposes a vacuum laser welding method suitable for medium-thick titanium alloy plates, comprising the following steps:

[0010] S1. Perform pretreatment on the surface of the titanium alloy medium-thick plate to be welded and the surface of the titanium alloy medium-thick plate to remove the oxide film and clean it.

[0011] S2. Apply an active agent solution to the surface of the titanium alloy medium-thick plate after S1 treatment. After the acetone evaporates, the active agent powder adheres to the surface of the titanium alloy medium-thick plate to form a coating layer for later use.

[0012] S3. The titanium alloy medium-thick plate after S2 treatment is butt-fixed on the processing platform, with the coated surface facing the laser. Welding is performed in a vacuum negative pressure atmosphere according to the preset program and parameters.

[0013] Therefore, in a vacuum negative pressure atmosphere, combined with the role of activators, the energy absorption efficiency is enhanced, the electron consumption of photo-induced plasma is reduced, the molten pool consumption is reduced, and the plasma cloud is reduced, thereby suppressing the plasma formed by laser welding under the premise of reducing the vacuum negative pressure standard.

[0014] In an optional embodiment, the activator powder is one or a mixture of two of SiO2 and TiO2.

[0015] In an optional embodiment, the coating amount of the surfactant powder is 0.6–1.2 g / cm³. 2 .

[0016] In an optional embodiment, the surfactant solution contains 30-50% by mass.

[0017] In an optional embodiment, the thickness of the coating layer is 0.3 to 0.5 mm.

[0018] In an optional implementation, a vacuum negative pressure atmosphere with a vacuum negative pressure value of 60 to 100 Pa is maintained.

[0019] In an optional embodiment, the titanium alloy medium-thick plate is a TC4 medium-thick plate.

[0020] In an optional implementation, the laser parameters include: the welding laser parameters are 2000-15000W, the defocusing amount is 0-10mm, the laser tilt angle is 13°, and the welding speed is 0.01-0.03m / s.

[0021] In an optional implementation, a fiber laser is used as the laser source.

[0022] In an optional implementation, the preprocessing procedure in step S1 is as follows:

[0023] Use a clean, dry, oil-free steel wire brush to polish the first surface of the medium-thick titanium alloy plate, as well as the oxide film and stains at the welding location. Then, wipe the residual oil stains in the polished area with acetone.

[0024] As can be seen from the above technical solution of the present invention, the vacuum laser welding method for medium-thick titanium alloy plates proposed in this invention uses vacuum laser welding to remove the plasma generated during the vacuum laser welding process. At the same time, an activator is coated on the first surface of the medium-thick titanium alloy plate. The activator increases the energy absorption efficiency, reduces the electron consumption of photo-induced plasma, reduces the amount of molten pool, and shrinks the plasma cloud. To a certain extent, it reduces the vacuum degree standard required to remove plasma. Thus, while retaining the advantages of increasing weld penetration, stabilizing the welding process, improving weld formation, and suppressing welding defects such as porosity, it reduces the vacuum degree requirement, significantly improves welding efficiency, and reduces welding costs. Attached Figure Description

[0025] Figure 1 This is a flowchart of the vacuum laser welding method for medium-thick titanium alloy plates according to the present invention.

[0026] Figure 2 This is a schematic diagram of the splicing of two titanium alloy medium-thick plates and the location of the active agent coating in this invention.

[0027] Figure 3 This is a cross-sectional view of the weld seam in Embodiment 1 of the present invention.

[0028] Figure 4 This is a cross-sectional view of the weld seam in Comparative Example 1 of the present invention.

[0029] Figure 5 This is a cross-sectional view of the weld seam in Comparative Example 2 of the present invention.

[0030] Figure 6 This is a cross-sectional view of the weld seam in Comparative Example 3 of the present invention. Detailed Implementation

[0031] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0032] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, in which numerous illustrative embodiments are shown. The embodiments of this disclosure are not necessarily intended to encompass all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described below in more detail, can be implemented in any of a number of ways.

[0033] Combination Figure 1 and Figure 2 As shown, this invention proposes a vacuum laser welding method suitable for medium-thick titanium alloy plates, comprising the following steps:

[0034] S1. Perform pretreatment on the surface of the titanium alloy medium-thick plate 1 to be welded and the surface of the titanium alloy medium-thick plate to remove the oxide film and clean it for later use.

[0035] S2. Apply an active agent solution to the surface of the titanium alloy medium-thick plate after the treatment in S1. The active agent solution is formed by uniformly mixing active agent powder with acetone. After the acetone evaporates, the active agent powder adheres to the surface of the titanium alloy medium-thick plate to form a coating layer for later use.

[0036] S3. The titanium alloy medium-thick plate after S2 treatment is butt-fixed on the processing platform, with the coated surface facing the laser. Welding is performed in a vacuum negative pressure atmosphere according to the preset program and parameters.

[0037] Therefore, the entire welding process is carried out in a vacuum negative pressure atmosphere. Combined with the role of the activator, the energy absorption efficiency is enhanced, the electron consumption of photo-induced plasma is reduced, the molten pool volume is reduced, and the plasma cloud is reduced. Thus, under the premise of reducing the vacuum negative pressure standard, the plasma formed by laser welding is suppressed.

[0038] In an optional embodiment, the activator powder is an oxide activator. For example, it may be one or a mixture of two of SiO2 and TiO2, or it may be one or a mixture of other common oxide activators, such as Cr2O3, Ti2O3, NiO, etc.

[0039] The preprocessing procedure in step S1 is as follows:

[0040] Use a clean, dry, oil-free steel wire brush to polish the 25-30mm area on both sides of the weld seam of the two medium-thick titanium alloy plates, or the entire surface area, as well as the oxide film and stains of the weld seam. Then wipe the residual oil stains in the polished area with acetone.

[0041] In an optional embodiment, the particle size of the activator powder ranges from 50 to 250 μm.

[0042] In an optional embodiment, the surfactant powder accounts for 30-50% of the surfactant solution by mass, and is uniformly coated on the surface of a medium-thick titanium alloy plate, forming a coating layer with a thickness of 0.3-0.5 mm, thereby achieving a surfactant powder coating amount of 0.6-1.2 g / cm³. 2 .

[0043] If the density of the activator coated on the surface of medium-thick titanium alloy plates is too low, the amount of activator will not meet the requirements and will not be able to cover the original color of the titanium alloy. This will prevent the effective increase of energy absorption efficiency, reduce the electron density of photo-induced plasma, reduce the density of the molten pool, and shrink the plasma cloud, thus affecting the welding effect. If the density of the activator coated on the surface of medium-thick titanium alloy plates is too high, too much activator will penetrate the weld, causing chemical corrosion and affecting the welding effect.

[0044] In optional embodiments, dispersants and / or suspending agents may also be added to the surfactant solution to make the surfactant powder more uniformly dispersed, and the solvent may also be a volatile organic solvent such as ethanol.

[0045] In optional embodiments, the surfactant solution can be brushed onto the surface of the medium-thick titanium alloy plate, or it can be applied by mechanical spraying or pressurized aerosol spraying. These are existing technologies, and those skilled in the art can choose according to the actual situation, which will not be elaborated here.

[0046] In an optional embodiment, the entire surface of the titanium alloy medium-thick plate is pretreated, and an activator solution is coated onto the treated entire surface.

[0047] In another alternative embodiment, a surface area of ​​the medium-thick titanium alloy plate extending 25-30 mm away from the edge to be welded is pretreated, and an activator solution is applied to the pretreated surface area. This reduces costs and improves efficiency.

[0048] In an optional embodiment, the mass of the surfactant powder can be determined according to the area of ​​the surface to be coated, and acetone can be used as a solvent to uniformly disperse the surfactant powder to obtain a mixed solution, and the entire mixed solution can be uniformly coated onto the first surface.

[0049] It should be understood that those skilled in the art can choose the scope of pretreatment according to the actual situation, as long as it is ensured that there is no oxide film and impurities near the weld to guarantee the quality of the weld.

[0050] In an optional embodiment, the processing platform is placed inside a vacuum chamber, and the vacuum chamber is maintained at the required vacuum negative pressure value. In embodiments of the present invention, a vacuum negative pressure atmosphere with a vacuum negative pressure value of 60–100 Pa is maintained.

[0051] Among them, the titanium alloy medium-thick plate is TC4 titanium alloy plate with a thickness of 2.5 to 25 mm.

[0052] In an optional embodiment, for medium-thick titanium alloy plates with a thickness of 10 to 20 mm, the laser welding parameters include: the welding laser parameters are 2000 to 15000 W, the defocusing amount is 0 to -10 mm, the laser tilt angle is 13°, and the welding speed is 0.01 to 0.03 m / s.

[0053] In an optional implementation, a fiber laser is used as the laser source.

[0054] To facilitate better understanding, the present invention will be further illustrated below with specific examples, but the processing technology is not limited thereto, and the content of the present invention is not limited thereto.

[0055] In the following examples and comparative examples, SiO2 powder was weighed and ground evenly to a particle size of about 200 μm.

[0056] The goal is to weld two TC4 titanium alloy plates together along their long side, with a weld length of 200mm, using a TC4 titanium alloy plate measuring 200mm*100mm*20mm (length*width*thickness).

[0057] The main chemical composition of TC4 titanium alloy sheet is shown in the table below:

[0058]

[0059] Example 1

[0060] (1) Use a clean, oil-free austenitic steel wire brush to grind away the oxide film on the welded area and the upper surface area of ​​200mm*25mm (length*width) near the welded area until the surface of the plate is shiny; then use a wiping cloth soaked in acetone to wipe the ground area until there is no oil on the surface; finally use a steel wire brush to remove the wiping cloth fibers remaining on the surface of the TC4 titanium alloy plate.

[0061] (2) Weigh 120g of SiO2 powder and add 120g of acetone, and stir until a uniform activator solution is formed.

[0062] Before welding, use a 2cm flat brush to evenly apply the activator solution layer by layer to the upper surface area of ​​the medium-thick TC4 plate after grinding. Keep the coating thickness uniform. During this process, wait for the acetone to evaporate and a uniform white film to appear. Use an ultrasonic thickness gauge to measure the thickness of the coating layer until the thickness of the coating layer is 0.3mm.

[0063] After completing the pre-welding treatment of the TC4 titanium alloy sheet, the sheet is immediately clamped onto the working platform of the vacuum negative pressure chamber with the coated side facing the laser.

[0064] (3) Adjust the laser head of the fiber laser so that the laser spot is located at the center of the weld between the two medium-thick TC4 titanium alloy plates.

[0065] (4) Set the laser parameters and the vacuum degree of the vacuum chamber to 100Pa, the spot size to 3mm, the laser power to 7000W, the defocusing amount to 0mm, the laser tilt angle to 13°, and the welding speed to 0.02m / s.

[0066] Then, the vacuum negative pressure chamber is activated to place the weld seam under a vacuum negative pressure protective atmosphere.

[0067] (5) Start the fiber laser to perform laser welding and complete the welding to obtain a welded joint.

[0068] Comparative Example 1

[0069] Under vacuum conditions and without surfactants

[0070] (1) Use a clean, oil-free austenitic steel wire brush to grind away the oxide film on the welded area and the upper surface area of ​​200mm*25mm (length*width) near the welded area until the surface of the plate is shiny; then use a wiping cloth soaked in acetone to wipe the ground area until there is no oil on the surface; finally use a steel wire brush to remove the wiping cloth fibers remaining on the surface of the TC4 titanium alloy plate.

[0071] After completing the pre-welding treatment of the TC4 titanium alloy sheet, the sheet is immediately clamped onto the working platform of the vacuum negative pressure chamber with the coated side facing the laser.

[0072] (2) Adjust the laser head of the fiber laser so that the laser spot is located at the center of the weld between the two medium-thick TC4 titanium alloy plates.

[0073] (3) Set the laser parameters and the vacuum degree of the vacuum chamber to 100Pa, the spot size to 3mm, the laser power to 7000W, the defocusing amount to 0mm, the laser tilt angle to 13°, and the welding speed to 0.02m / s.

[0074] Then, the vacuum negative pressure chamber is activated to place the weld seam under a vacuum negative pressure protective atmosphere.

[0075] (4) Start the fiber laser to perform laser welding and complete the welding to obtain a welded joint.

[0076] Comparative Example 2

[0077] In atmospheric environment and with surfactants

[0078] (1) Use a clean, oil-free austenitic steel wire brush to grind away the oxide film on the welded area and the upper surface area of ​​200mm*25mm (length*width) near the welded area until the surface of the plate is shiny; then use a wiping cloth soaked in acetone to wipe the ground area until there is no oil on the surface; finally use a steel wire brush to remove the wiping cloth fibers remaining on the surface of the TC4 titanium alloy plate.

[0079] (2) Weigh 120g of SiO2 powder and add 120g of acetone, and stir until a uniform activator solution is formed.

[0080] Before welding, use a 2cm flat brush to evenly apply the activator solution layer by layer to the upper surface area of ​​the medium-thick TC4 plate after grinding. Keep the coating thickness uniform. During this process, wait for the acetone to evaporate and a uniform white film to appear. Use an ultrasonic thickness gauge to measure the thickness of the coating layer until the thickness of the coating layer is 0.3mm.

[0081] After completing the pre-welding treatment of the TC4 titanium alloy sheet, the sheet is immediately clamped onto the working platform of the vacuum negative pressure chamber with the coated side facing the laser.

[0082] (3) Adjust the laser head of the fiber laser so that the laser spot is located at the center of the weld between the two medium-thick TC4 titanium alloy plates.

[0083] (4) Set the laser parameters: spot size 3mm, laser power 7000W, defocusing amount 0mm, laser tilt angle 13°, and welding speed 0.02m / s.

[0084] (5) Start the fiber laser and perform laser welding in an atmospheric environment to complete the welding and obtain a welded joint.

[0085] Comparative Example 3

[0086] In atmospheric environment and without surfactants

[0087] (1) Use a clean, oil-free austenitic steel wire brush to grind away the oxide film on the welded area and the upper surface area of ​​200mm*25mm (length*width) near the welded area until the surface of the plate is shiny; then use a wiping cloth soaked in acetone to wipe the ground area until there is no oil on the surface; finally use a steel wire brush to remove the wiping cloth fibers remaining on the surface of the TC4 titanium alloy plate.

[0088] After completing the pre-welding treatment of the TC4 titanium alloy sheet, the sheet is immediately clamped onto the working platform of the vacuum negative pressure chamber with the coated side facing the laser.

[0089] (2) Adjust the laser head of the fiber laser so that the laser spot is located at the center of the weld between the two medium-thick TC4 titanium alloy plates.

[0090] (3) Set the laser parameters: spot size 3mm, laser power 7000W, defocusing amount 0mm, laser tilt angle 13°, and welding speed 0.02m / s.

[0091] (4) Start the fiber laser and perform laser welding in the atmosphere to complete the welding and obtain a welded joint.

[0092] The welding images of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown below. Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown.

[0093] As can be seen from the figure, compared with Comparative Examples 1-3, the welding quality of TC4 medium-thick plates welded using the method of the present invention is significantly improved. The weld formation and welding quality of Comparative Examples 1-3 are relatively low. This indicates that the present invention achieves excellent weld quality while reducing the vacuum requirement through a vacuum-based combination of activators, thereby significantly improving welding efficiency and reducing welding costs.

[0094] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A vacuum laser welding method suitable for medium-thick titanium alloy plates, characterized in that, Includes the following steps: S1. Perform pretreatment on the surface of the titanium alloy medium-thick plate to be welded and the surface of the titanium alloy medium-thick plate to remove the oxide film and clean it for later use. S2. An activator solution is coated onto the surface of the medium-thick titanium alloy plate after the S1 treatment. The activator solution is formed by uniformly mixing activator powder with acetone. After the acetone evaporates, the activator powder adheres to the surface of the medium-thick titanium alloy plate to form a coating layer, which is then set aside. The activator powder is one or a mixture of SiO2 and TiO2, and the coating amount of activator powder is 0.6~1.2 g / cm³. 2 ; S3. The titanium alloy medium-thick plate after S2 treatment is butt-fixed on the processing platform, with the coated surface facing the laser. Welding is completed in a vacuum negative pressure atmosphere according to the preset program and parameters. The vacuum negative pressure atmosphere is configured as a vacuum negative pressure atmosphere with a vacuum negative pressure value of 60~100 Pa. By coating the surface of a medium-thick titanium alloy plate with an activator and combining it with a negative pressure atmosphere, plasma generated by laser welding can be suppressed while reducing the vacuum negative pressure standard.

2. The vacuum laser welding method for medium-thick titanium alloy plates according to claim 1, characterized in that, In the surfactant solution, the mass fraction of surfactant powder is 30-50%.

3. The vacuum laser welding method for medium-thick titanium alloy plates according to claim 1, characterized in that, The thickness of the coating layer is 0.3~0.5 mm.

4. The vacuum laser welding method for medium-thick titanium alloy plates according to any one of claims 1-3, characterized in that, The laser parameters include: the welding laser parameters are 2000~15000 W, the defocusing amount is 0~-10 mm, the laser tilt angle is 13°, and the welding speed is 0.01~0.03 m / s.

5. The vacuum laser welding method for medium-thick titanium alloy plates according to claim 1, characterized in that, The preprocessing procedure in step S1 is as follows: Use a clean, dry, oil-free steel wire brush to polish the surface of the medium-thick titanium alloy plate, as well as the oxide film and stains at the welding locations. Then, wipe the remaining oil stains in the polished area with acetone.

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