Ta-10W alloy composite welding method with optical fiber laser focus rotating along with welding laser shock

Abstract

The invention discloses a Ta-10W alloy hybrid welding method for optical fiber laser focus rotation along with welding laser shock, and belongs to the technical field of welding. In the Ta-10W laser welding process, the laser focus rotation and laser shock composite technology is adopted, and the comprehensive beneficial effects of pore inhibition and penetration depth increase are achieved through the synergistic effect of the laser focus rotation and laser shock composite technology. According to the specific design, a focus rotating fiber laser and nanosecond high-energy pulse laser paraxial composite method is adopted, the distance between an impact laser spot and a welding spot is adjusted, the vibration regulation and control effect of impact waves generated by pulse laser on a keyhole and a molten pool is utilized, collapse of the rear wall of the keyhole is restrained, bubble escape is promoted, the pore size is reduced, and the porosity is reduced; and the influence effect of laser focus spin welding on welding seam depth reduction is reduced.

Description

Technical Field

[0001] The present invention relates to the field of welding technology, and particularly to a composite welding method for Ta-10W alloy with laser shock during welding by rotating the fiber laser focus. Background Art

[0002] Ta-10W alloy has a melting point as high as 3035°C, a small linear expansion coefficient, and good high-temperature properties, and has important application value in key components serving at the hot end in the aerospace field. Laser welding technology has significant advantages such as high energy density, fast welding speed, strong penetration ability, flexible process, and can be implemented in an atmospheric environment. However, during high-power laser deep penetration welding, the molten pool and keyhole fluctuate violently, which easily causes the keyhole to become unstable and close during welding, resulting in the generation of bubbles. As the molten pool solidifies, pores are formed in the weld. Rotating the laser focus during welding expands the scanning range of the laser beam inside the keyhole and acts on the front and rear walls of the keyhole periodically. Compared with traditional laser linear welding, rotating the laser focus during welding can change the dynamic behavior of the keyhole and the melting and solidification behavior of the molten pool, and effectively control the weld formation and pores. However, the weld penetration depth of laser focus rotation welding is negatively correlated with the focus rotation radius. However, Ta-10W alloy has a high melting point, a small molten pool volume, and a fast solidification speed during welding; at the same time, the Ta-10W melt has a high viscosity and poor fluidity, resulting in difficulty in the escape of pores. Therefore, during the laser focus rotation welding of Ta-10W alloy, effective suppression of pore defects can be achieved under parameters of a large rotation radius and a high rotation frequency. However, a large rotation radius and a high rotation frequency will also disperse the laser energy, resulting in insufficient weld penetration depth. Therefore, it is difficult for laser focus rotation welding to balance joint quality and manufacturing efficiency. This phenomenon not only exists in the laser focus rotation welding of Ta-10W, but also exists in the laser focus rotation welding of metals such as aluminum alloy, titanium alloy, and superalloy.

[0003] Laser shock peening utilizes high-energy, short-pulse laser irradiation on the surface of materials to form a high-pressure plasma. The plasma expands and explodes, generating a laser shock wave. The shock wave forms pressure on the material surface, causing the material to deform and strengthen. Laser shock peening features high impact energy, high impact pressure, and non-contact processing. Compared with mechanical shock methods, during laser shock peening, the high-pressure plasma acts on the entire spot area, enabling full contact on the material surface. Moreover, leveraging the high degree of freedom of laser transmission, laser shock peening can achieve shock treatment of non-planar structures such as the molten pool and weld surface during the welding process. During laser welding, if laser shock peening is applied to the high-temperature weld area behind the molten pool, the pressure generated by the shock wave can deform the weld surface, introduce residual stress, and refine the surface grains. At the same time, the high-energy shock laser acts on the high-temperature area of the weld, and the generated shock wave will conduct to the keyhole and molten pool. Through the vibration effect on the keyhole and molten pool, it regulates the dynamic behavior of the keyhole and the flow behavior of the molten pool, achieving the beneficial effects of suppressing keyhole collapse and promoting the escape of bubbles in the molten pool, reducing the porosity of the joint, and improving the weld quality.

[0004] Therefore, aiming at the serious porosity problem in the laser welding of Ta-10W refractory alloy and the difficulty in suppressing the porosity phenomenon of Ta-10W alloy with the existing laser focus rotation welding process at a small rotation radius, while the penetration depth decreases, and the manufacturing capacity and efficiency decline at a large rotation radius, this patent develops a composite welding method for Ta-10W alloy with fiber laser focus rotation and in-situ laser shock peening to achieve high-quality and high-efficiency laser welding manufacturing of Ta-10W refractory alloy hot-end components in the aerospace field. Summary of the Invention

[0005] The object of the present invention is to propose a composite welding method for Ta-10W alloy with fiber laser focus rotation and in-situ laser shock peening to overcome the above defects, aiming at the serious porosity problem in the laser welding of Ta-10W refractory alloy and the difficulty in suppressing the porosity phenomenon of Ta-10W alloy with the existing laser focus rotation welding process at a small rotation radius, while the penetration depth decreases, and the manufacturing capacity and efficiency decline at a large rotation radius.

[0006] A composite welding method for Ta-10W alloy with laser shock during fiber laser focus rotation welding, which uses a composite welding system composed of a laser welding system and a laser shock system; the laser welding system is a fiber laser focus rotation welding system, and the laser focus moves in a high-frequency small-radius rotation within the keyhole to control the keyhole morphology and the molten pool flow; the laser shock system is a Q-switched laser with high energy and short pulses. During the focus rotation deep penetration welding, the shock laser acts on the surface of the high-temperature weld seam 3-8 mm behind the keyhole; the high-energy shock laser acts on the high-temperature weld seam area, and the generated shock wave will conduct to the keyhole and the molten pool. Through the vibration effect on the keyhole and the molten pool, the dynamic behavior of the keyhole and the flow behavior of the molten pool are controlled, the collapse of the keyhole is inhibited, and the bubbles in the molten pool are promoted to overflow, reducing the porosity of the joint; under the beneficial effect of laser shock, the weld depth during the high-frequency small-radius rotation welding of the laser focus is ensured. In addition, the shock wave pressure generated by the shock laser can deform the weld surface, introduce residual compressive stress, and refine the grains on the surface layer of the weld. This method combines the small-radius focus rotation welding method and the laser shock during welding method, and has the comprehensive beneficial effects of reducing porosity defects and increasing the joint penetration depth.

[0007] In the described composite welding method for Ta-10W alloy with laser shock during fiber laser focus rotation welding, the composite mode of the shock laser and the welding laser is paraxial. During welding, the welding laser beam is vertically incident on the welding surface. Along the welding direction, the shock laser beam is located behind the welding laser beam, coplanar with the welding laser beam, and the included angle with the welding laser beam is 0-40° and not 0. The spot of the shock laser is located 3-8 mm behind the keyhole, and the diameter range of the spot of the shock laser is generally 50%-100% of the width of the molten pool during welding.

[0008] In the described composite welding method for Ta-10W alloy with laser shock during fiber laser focus rotation welding, it is characterized in that: the laser used in the laser focus rotation welding system is a continuous fiber laser, the laser wavelength λ = 1064 nm, the focal length of the laser focusing lens is 300 mm, the laser power during welding is 2000-6000 W, and the welding speed is 1-5 m / min; the laser focus rotation is realized by a high-power galvanometer or a rotating welding head, the rotation radius range is 0.1-1 mm, and the rotation frequency is 50-500 Hz; the shock laser used in the laser shock system has a pulse width in the nanosecond range (τ ≤ 50 ns), a single-pulse energy in the joule range (Q = 0.5-3 J), a repetition frequency f = 10-200 Hz, and a focal length of 300-500 mm.

[0009] Compared with the prior art, the present invention has the following beneficial effects: The present invention proposes a composite welding method for Ta-10W alloy by laser shock with a rotating laser focus during welding. In the high-frequency and small-radius laser focus rotation welding of Ta-10W alloy, the laser shock method during welding is used to suppress the welding porosity defects during the high-frequency and small-radius focus rotation welding of Ta-10W alloy while ensuring that the welding penetration remains basically unchanged. On the one hand, compared with the existing laser welding process, the present invention utilizes the characteristics of easy melt flow and low yield strength of metals at high temperatures, and uses high-energy pulsed lasers to shock the high-temperature weld seam behind the molten pool, which can achieve the regulation of molten pool behavior without a constraint layer and an absorption layer, facilitating the suppression of welding porosity. At the same time, using this composite welding method can improve the ability to obtain welding penetration in laser focus rotation welding and increase the joint penetration. In addition, when shocking the high-temperature weld seam behind the molten pool, in addition to suppressing the porosity defects, the shock also changes the surface microstructure and stress state of the weld seam. The surface grains of the weld seam are significantly refined, and the residual tensile stress after welding becomes residual compressive stress, improving the weld quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic structural diagram of the present invention;

[0011] Figure 2 is a schematic diagram of the influence of laser shock on the porosity behavior in the molten pool and keyhole;

[0012] It includes a laser 1, a galvanometer 2, a laser shock system 3, a welding laser beam 4, a Ta-10W plate 5, a molten pool 6, a keyhole with deep penetration 7, a weld seam 8, a high-energy laser pulse 9, a high-temperature weld seam 10, a laser shock wave 11, a bubble 12, and a pore 13.

[0013] Figure 3 is the cross-sectional morphology of a high-frequency large-radius (150 Hz - 0.5 mm) focus rotation weld seam without shock;

[0014] Figure 4 is the longitudinal-section pores of a high-frequency large-radius (150 Hz - 0.5 mm) focus rotation weld seam without shock;

[0015] Figure 5 is the cross-sectional morphology of a high-frequency small-radius (150 Hz - 0.3 mm) focus rotation weld seam without shock;

[0016] Figure 6 is the longitudinal-section pores of a high-frequency small-radius (150 Hz - 0.3 mm) focus rotation weld seam without shock;

[0017] Figure 7 is the cross-sectional morphology of a high-frequency small-radius (150 Hz - 0.3 mm) focus rotation weld seam when shocking the high-temperature weld seam;

[0018] Figure 8 For the longitudinal section pores of the weld with the focus rotating at a high frequency and a small radius (150 Hz - 0.3 mm) when impacting the high-temperature weld;

[0019] Figure 9 For the surface layer structure of the weld with the focus rotating at a high frequency and a small radius (150 Hz - 0.3 mm) when impacting the high-temperature weld;

[0020] Figure 10 For the statistics of pores and residual stresses in different welds. Specific embodiments

[0021] The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments.

[0022] Embodiment 1

[0023] See Figure 1 As shown, the present invention uses an IPG YLS 6000 fiber laser 1, an HP30 - 6000 high-power galvanometer 2, and a Hercules lamp-pumped high-energy electro-optic Q-switched laser 3 to form a composite welding processing system for the composite welding of Ta-10W alloy plates with laser focus rotation and laser shock during welding. Before welding, adjust the distance L between the welding laser beam 4 and the high-energy pulsed laser 9 as needed so that the action position of the high-energy pulsed laser 9 is within 5 mm of the weld behind the molten pool.

[0024] When welding starts, under the action of the welding laser beam 4, a molten pool 6 and a deep penetration keyhole 7 are formed on the surface of the Ta-10W plate 5 and solidify to form a weld 8. At the same time, the high-energy pulsed laser 9 acts on the high-temperature weld 10 behind the welding molten pool 6 to generate a shock wave 11. When the shock wave 11 acts on the high-temperature weld 10 behind the molten pool 6, the pressure generated by the shock wave 11 causes the newly solidified high-temperature weld 10 to undergo slight deformation, the surface layer grains of the weld are refined, and the residual tensile stress caused by solidification is changed to compressive stress. At the same time, when the shock wave 11 acts on the weld, it can also vibrate the molten pool 6, promoting the escape of bubbles 12 in the molten pool 6 and realizing the suppression of pores 13.

[0025] For the welds obtained under different welding conditions, observing their cross-sections and central longitudinal sections, it is found that when the laser wavelength λ = 1064 nm, the welding laser power is 4000 W, the focal length of the laser focusing lens is 300 mm, and the welding speed is 2 m / min, without the action of the laser shock during welding, see Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 and Figure 10The cross-sectional morphology of the weld seam, the longitudinal-section pore distribution, and the pore statistics results shown: When the rotation frequency is 150 Hz and the focal rotation radius is 0.5 mm, there are no large-size pores 4 4 μm 2 with an area greater than 3.0×10 4 μm 2 in the weld seam, and only 17 small-size pores 4 3 μm 2 exist. The maximum area of the pores 4 4 is about 2.3×10 2 μm 5 and the average area is about 7.5×10 2 μm 4 μm 2 . However, the weld penetration is relatively shallow, being 2.185 mm. At the same frequency, when the focal rotation radius is reduced to 0.3 mm, the weld penetration deepens to 2.442 mm at this time, but there are a large number of large-size pores 4

[0026] with an area greater than 3.0×10 Figure 7 、 Figure 8 and Figure 10 in the weld seam. The maximum area is about 3.6×10 4 μm 2 and the average area is about 3.8×10 4 μm 2 μm 3 μm 2 μm 4 μm 2 μm

[0027] Moreover, according to Figure 9 and Figure 10, when the impact position is at the high-temperature weld 10 about 5 mm behind the molten pool 6, the surface grains of the weld are refined. According to GB / T 7704-2017 Non-destructive testing - X-ray stress determination method, stress testing is carried out on the weld surface. After applying the in-process pulsed laser shock, the residual stress of the weld changes from tensile stress to compressive stress.

[0028] Adopt the method of paraxial combination of a focused-rotating fiber laser and a nanosecond high-energy pulsed laser. By adjusting the distance between the impact laser spot and the welding spot, and using the shock wave generated by the pulsed laser to control the vibration of the keyhole and the molten pool, the collapse of the back wall of the keyhole is inhibited, the escape of bubbles is promoted, the pore size is reduced, the porosity is decreased, and the influence of focused-rotating laser welding on the reduction of the weld depth is reduced. Using this process, in Ta-10W joints with comparable pore numbers and sizes in the longitudinal section of the same-length weld, compared with the weld depth of single focused-rotating laser welding, the weld depth of the focused-rotating in-process impact composite welding method is increased by 27.8%; under the condition of applying in-process impact, at the same rotation parameters, the weld depth is increased by 14.4%. Therefore, compared with the current Ta-10W large-radius and high-frequency focused-rotating welding process, this composite method can simultaneously achieve the dual beneficial effects of pore suppression and ensuring the weld penetration, and solve the process bottlenecks of energy dispersion and insufficient weld penetration caused by focused-rotating laser. This method does not require a constraint layer and an absorption layer, the process implementation is flexible, the impact parameters (impact frequency, impact energy, and spot distance) can be accurately adjusted, and it is suitable for the high-efficiency and high-quality welding of Ta-10W hot-end service critical components in the aerospace field, and can be extended and applied to the focused-rotating laser welding processes of metals such as aluminum alloys, titanium alloys, and superalloys.

[0029] As described above, for Ta-10W materials, the fiber laser focused-rotating in-process impact composite welding process can achieve the dual beneficial effects of increasing the weld penetration and suppressing welding pores. At the same time, the impact also changes the surface microstructure and stress state of the weld. The surface grains of the weld are significantly refined, the residual tensile stress after welding becomes residual compressive stress, and the weld quality is improved.

[0030] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A composite welding method for Ta-10W alloy with laser shock during welding with a rotating fiber laser focus, characterized in that, A composite welding system is adopted, which is composed of a laser welding system and a laser shock system. The laser welding system is a fiber laser focus rotation welding system, and the laser focus moves in a high-frequency small-radius rotation within the keyhole to control the keyhole morphology and the molten pool flow. The laser shock system is a Q-switched laser with high energy and short pulses. During the focus rotation deep penetration welding, the shock laser acts on the surface of the high-temperature weld seam 3-8 mm behind the keyhole. The high-energy shock laser acts on the high-temperature weld seam area, and the generated shock wave will conduct to the keyhole and the molten pool. By the vibration effect on the keyhole and the molten pool, the dynamic behavior of the keyhole and the flow behavior of the molten pool are controlled, the collapse of the keyhole is inhibited, the bubbles in the molten pool are promoted to overflow, and the porosity of the joint is reduced. Under the beneficial effect of the laser shock, the weld depth during the high-frequency small-radius rotation welding of the laser focus is ensured. In addition, the shock wave pressure generated by the shock laser deforms the weld surface, introducing residual compressive stress and refining the grains on the weld surface layer.

2. The method according to claim 1, characterized in that The composite mode of the shock laser and the welding laser is paraxial. During welding, the welding laser beam is vertically incident on the welding surface. Along the welding direction, the shock laser beam is located behind the welding laser beam, coplanar with the welding laser beam, and the included angle with the welding laser beam is 0-40° and not 0. The spot of the shock laser is located 3-8 mm behind the keyhole, and the diameter range of the spot of the shock laser is generally 50%-100% of the width of the molten pool during welding.

3. The method according to claim 1, wherein The laser used in the laser focus rotation welding system is a continuous fiber laser, with a laser wavelength λ = 1064 nm, a laser focusing lens focal length of 300 mm, a laser power of 2000-6000 W during welding, and a welding speed of 1-5 m / min. The laser focus rotation is realized by a high-power galvanometer or a rotating welding head, with a rotation radius range of 0.1-1 mm and a rotation frequency of 50-500 Hz.

4. The method according to claim 1, characterized in that, The shock laser used in the laser shock system has a pulse width in the nanosecond range (τ ≤ 50 ns), a single-pulse energy in the joule range (Q = 0.5-3 J), a repetition frequency f = 10-200 Hz, and a focal length of 300-500 mm.

5. The method according to claim 1, characterized in that, The composite welding method is particularly suitable for welding non-penetrating welds such as lap welds, lock-bottom welds, and fillet welds.

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