T-joint laser welding method

Abstract

The application provides a T-shaped structure laser welding method, comprising the following steps: preparing alloy powder; establishing the relevance of cold spraying process parameters and alloy powder deposition layer thickness and density; designing a surface deposition layer on the contact surface of a skin and a stringer, and designing a weld leg deposition layer on the to-be-welded area of the skin and the stringer; performing surface cleaning on the skin and the stringer; cold spraying the alloy powder by using first cold spraying process parameters to form a surface deposition layer; placing the stringer on the surface deposition layer along the center line of the surface deposition layer; cold spraying the alloy powder by using second cold spraying process parameters to obtain a weld leg deposition layer with a second designed size; performing laser welding on the to-be-welded area by using preset laser welding process parameters to form a T-shaped structure. The application can improve the positioning accuracy of stringer assembly and the laser energy utilization rate of the material, fill the large assembly gap, realize flexible regulation and control of the filling welding material composition, and improve the welding process stability and welding quality.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and more specifically, to a laser welding method for T-shaped structures. Background Technology

[0002] To meet the demands of lightweight aircraft, large, complex curved fuselage panels have become one of the most critical components of the fuselage. The T-shaped structure of the fuselage panels is primarily composed of skin and stringers, and traditional manufacturing methods for this type of structure often employ mechanical connections. However, this method is not only inefficient but also fails to achieve weight reduction. Laser welding offers advantages such as high welding speed, low heat input, and minimal welding deformation. Therefore, using laser welding to replace mechanical connections for T-shaped structure connections can achieve weight reduction and lower aircraft energy consumption. Furthermore, the welding process is simple, highly efficient, and allows for increased material utilization and lower manufacturing costs through the combination of smaller components. In the 1990s, Airbus developed dual-beam laser welding technology. By using double-sided filler wires, it fills in the loss and evaporation of alloying elements during welding, suppressing welding defects such as undercut, voids, and cracks, ensuring weld quality, and improving weld mechanical properties. This technology has been successfully applied to the connection of T-shaped fuselage panel structures in various aircraft models, significantly reducing fuselage weight, improving fuel economy, and substantially lowering fuselage manufacturing costs. T-shaped structures exhibit high structural constraint during laser welding, leading to more pronounced stress concentration and a greater tendency to crack. Using filler wire can adjust the weld's chemical composition, preventing crystallization cracks and improving joint strength. However, existing commercially available filler wires are insufficient to meet the requirements for weld metal control and crack suppression. Developing entirely new filler wires based on actual needs would significantly increase research and development and production costs. Furthermore, in laser welding of T-shaped structures using filler wire, the wire feeding conditions (direction, angle, speed, and position) have a significant impact on welding stability. This places stringent requirements on the stability of the wire feeding mechanism. The wire is also susceptible to fluctuations in laser parameters (power, incident angle, focal point), welding speed, plasma, and spatter during its insertion into the molten pool. These fluctuations can disrupt the continuous and stable feeding of the wire into the molten pool, affecting the stability of the dual-beam laser welding process for T-shaped structures and the quality of the weld formation.

[0003] In addition, the T-shaped structure requires precise positioning of the stringer before welding, with a positioning tolerance of no more than 1mm. Existing technologies generally use other tooling fixtures or measuring tools to achieve this positioning. The high assembly precision requirements of the workpiece before welding reduce the reliability and production efficiency of dual-beam laser welding of the T-shaped structure.

[0004] Furthermore, due to the unique molten pool flow field of the T-shaped structure, the composition of the base material and welding wire is unevenly mixed in the molten pool, resulting in weak uniformity of the weld structure at the interface between the skin and the stringer. Moreover, due to the influence of raw material processing precision, excessively large gaps exist in some areas during the assembly of the skin and stringer, affecting the welding quality of the T-shaped structure. Additionally, because the alloy has a high reflectivity to lasers, the energy utilization rate is low during laser welding, limiting the expanded application of laser welding technology. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] The technical problems to be solved by the present invention are: the existing T-shaped structure has problems such as unstable welding process, low assembly accuracy and poor weld formation quality; and the existing aluminum alloy T-shaped structure has problems such as low stringer assembly positioning accuracy, low welding laser energy utilization rate, unstable welding process and poor weld formation quality.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A laser welding method for T-shaped structures is provided for welding skin and stringers to form a T-shaped structure, comprising the following steps:

[0010] S1. Prepare alloy powder, wherein the alloy powder is a base material powder, or a base material powder containing a reinforcing element, or a mixed powder composed of a base material powder and a single reinforcing element powder, or a mixed powder composed of a base material powder and a powder containing a reinforcing element, wherein the composition of the base material powder is consistent with the material composition of the T-shaped structure.

[0011] S2. Conduct a cold spraying process test on the alloy powder to form an alloy powder deposition layer, and establish the correlation between the cold spraying process parameters and the thickness and density of the alloy powder deposition layer.

[0012] S3. Design a surface deposition layer on the contact surface between the skin and the stringer, design a weld foot deposition layer in the area to be welded between the skin and the stringer, determine the first design size of the surface deposition layer according to the stringer size, and determine the second design size of the weld foot deposition layer according to the laser welding parameters.

[0013] S4. Perform surface cleaning on the skin and stringers;

[0014] S5. Determine the design thickness of the surface deposited layer, determine the first cold spraying process parameters of the alloy powder according to the design thickness, place a surface deposited layer mold corresponding to the first design size on the skin, and cold spray the alloy powder in the surface deposited layer mold using the first cold spraying process parameters to form the surface deposited layer having the first design size and design thickness.

[0015] S6. Place the stringer on the surface deposition layer along the centerline of the surface deposition layer;

[0016] S7. Based on the second design dimensions, determine the second cold spraying process parameters for the alloy powder, place a weld foot deposition layer mold corresponding to the second design dimensions in the welding areas on both sides of the stringer, and cold spray the alloy powder in the weld foot deposition layer mold using the second cold spraying process parameters to obtain a weld foot deposition layer with the second design dimensions.

[0017] S8. Laser welding is performed on the area to be welded using preset laser welding process parameters to form a T-shaped structure, wherein the weld pool size during the welding process is not less than the second design size.

[0018] Preferably, the method further includes the following steps:

[0019] S9. Perform non-destructive testing on the T-shaped welded joints. Non-destructive testing methods include X-ray inspection and penetrant testing.

[0020] Preferably, in step S1, when the alloy powder is a base powder containing reinforcing elements and the base powder is aluminum alloy powder, the base powder containing reinforcing elements includes Sc element with a mass fraction ranging from 0.15% to 0.30% and / or Zr element with a mass fraction ranging from 0.10% to 0.20%, and the particle size of the alloy powder is 15μm to 53μm.

[0021] Preferably, in step S1, when the alloy powder is a base material powder or a base material powder containing reinforcing elements, the preparation method of the alloy powder includes at least one of inert gas atomization method, plasma rotating electrode method, and radio frequency plasma method.

[0022] When the alloy powder is a mixture of base material powder and a single reinforcing element powder, or a mixture of base material powder and reinforcing element powder, the preparation method of the alloy powder is a mechanical mixing method.

[0023] Preferably, in step S3, the first design dimension includes the length and width of the surface deposition layer, wherein the length of the surface deposition layer is L, the width of the surface deposition layer is 1δ to 1.2δ, L is the length of the stringer, and δ is the width of the stringer.

[0024] Preferably, in step S3, the formula for calculating the second design dimension is as follows:

[0025]

[0026] Where x2 is the second designed weld leg size, x1 is the first designed weld leg size, x1 is the length of the right-angled side of the largest isosceles right triangle drawn in the cross-section of the fillet weld, r is the radius of the welding wire used in conventional dual-beam laser fillet welding, which is generally 0.4mm to 0.6mm, and v w v is the wire feed speed, v is the welding speed, and ρ is the coating density under specific cold spraying process parameters. The value of coating density ρ can be determined based on the database of cold spraying process parameters and coating density, and it is generally 75% to 95%.

[0027] Preferably, in step S4, the skin and the stringer are surface-cleaned using mechanical cleaning, chemical cleaning, or laser cleaning. When laser cleaning is used to clean the skin and the stringer, the process parameters of the laser cleaning method include pulsed laser power P, scanning speed v, and pulse frequency f. The pulsed laser power P is 160W-250W, the scanning speed is 1500mm / s-3000mm / s, and the pulse frequency is 2kHz-4kHz.

[0028] Preferably, in step S5, the first cold spraying process parameters include gas pressure p, working gas temperature T, spraying angle α, and spraying distance d, wherein the gas pressure p is 2MPa~5MPa, the working gas temperature T is 300℃~600℃, the spraying angle α is 40°-60°, and the spraying distance d is 10mm~50mm.

[0029] Preferably, in step S7, the second cold spraying process parameters include gas pressure p, working gas temperature T, spraying angle α, and spraying distance d, wherein the gas pressure p is 2MPa~5MPa, the working gas temperature T is 300℃~600℃, the spraying angle α is 40°-60°, and the spraying distance d is 10mm~50mm.

[0030] Preferably, in step S8, the preset laser welding process parameters include welding plane angle θ, laser processing head deflection angle η, laser offset y, laser power P, and welding speed v, wherein the welding plane angle θ is 20°-70°, the laser processing head deflection angle η is 0°-15°, the laser offset y is -1mm-3mm, the laser power P is 2000W-4000W, and the welding speed is 2m / min-4m / min.

[0031] (III) Beneficial Effects

[0032] The above-described technical solution of the present invention has at least the following advantages:

[0033] 1. In this invention, a surface deposition layer with a first design size and design thickness is cold-sprayed onto a specific area of ​​the skin. This surface deposition layer can assist in the precise positioning of the stringer on the skin. Compared with the existing technology that uses manual measurement and positioning, this invention improves the positioning accuracy of the stringer assembly.

[0034] 2. In this invention, in particular, when the base material is aluminum alloy, a weld foot deposition layer is designed in the area to be welded between the skin and the stringer. The weld foot deposition layer is formed by cold spraying alloy powder with a specific composition, which reduces the surface roughness of the area to be welded between the skin and the stringer, reduces its reflection of the laser, and improves the absorption rate of the material in the area to be welded and the utilization rate of laser energy.

[0035] 3. In this invention, during the welding process, the weld bead deposit layer absorbs the welding heat to form a molten pool. Under the action of gravity, the molten pool flows to the gap between the skin and the stringer assembly, effectively filling the excessive gap between the skin and the stringer assembly, thereby improving the forming quality of the T-shaped welded joint.

[0036] 4. In this invention, a surface deposition layer is formed by alloy powder with a specific composition. This surface deposition layer participates in the formation of the weld during the welding process. It can regulate the welding structure at the interface between the skin and the stringer, thereby optimizing the welding structure and further improving the mechanical properties of the T-shaped structure welded joint. By adjusting the type of strengthening element in the alloy powder, the alloy elements of the weld can be flexibly controlled.

[0037] 5. In this invention, alloy powder with specific composition is sprayed onto specific parts of the T-shaped structure using cold spraying technology, thereby forming a surface deposition layer with a first design size and a weld leg deposition layer with a second design size at the specific parts. This replaces conventional laser filler wire welding, which not only solves the problem of difficult-to-control the stability of filler wire feeding, but also facilitates flexible control of the composition of filler welding material, reduces the probability of welding defects, and improves the stability and welding quality of the T-shaped structure welding process. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a three-dimensional structural diagram of the T-shaped structure provided in an embodiment of the present invention.

[0040] Figure 2 yes Figure 1 A magnified view of a portion of point A in the middle.

[0041] Figure 3 This is a schematic diagram showing the position of the surface deposition layer model provided in an embodiment of the present invention.

[0042] Figure 4 This is a schematic diagram of the cross-sectional morphology of the T-shaped structure before and after laser welding, provided in an embodiment of the present invention.

[0043] Figure 5 This is a schematic diagram of the laser welding method for T-shaped structures provided in an embodiment of the present invention.

[0044] The labels for the attached figures are as follows:

[0045] 1. Surface deposit layer; 2. Weld foot deposit layer; 3. Skin; 4. Stringer; 5. Surface deposit layer mold; 6. Weld; 7. Laser beam. Detailed Implementation

[0046] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0047] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be located directly on or indirectly on the other component. When a component is referred to as "connected to" another component, it can be directly or indirectly connected to the other component.

[0048] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate that the device or element must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating relative importance or the number of technical features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. The specific implementation of this invention will be described in more detail below with reference to specific embodiments:

[0050] like Figure 1As shown, this embodiment of the invention provides a laser welding method for a T-shaped structure, used to weld the skin 3 to the stringer 4 to form a T-shaped structure, including the following steps:

[0051] S1. Prepare alloy powder, wherein the alloy powder is a base material powder, or a base material powder containing reinforcing elements, or a mixed powder composed of base material powder and a single reinforcing element powder, or a mixed powder composed of base material powder and a powder containing reinforcing elements; wherein the composition of the base material powder is consistent with the material composition of the T-structure; specifically, the base material powder refers to the powder of metallic alloying elements, for example, when the base material is an aluminum alloy, the base material powder is aluminum alloy powder of the corresponding composition; when the base material is a titanium alloy, the base material powder is titanium alloy powder of the corresponding composition; the single reinforcing element powder refers to the powder of pure metallic elements, for example, when the base material is an aluminum alloy, the single reinforcing element powder can be zirconium powder or scandium powder; the powder containing reinforcing elements refers to alloy powder containing reinforcing elements, and the powder containing reinforcing elements contains other metallic elements in addition to reinforcing elements, for example, the powder containing reinforcing elements can be powder made from an alloyed ingot formed by Zr and Al, or powder made from an alloyed ingot formed by Sc and Al. More specifically, when the base powder contains strengthening elements, and the base powder is aluminum alloy powder, the base powder containing strengthening elements preferably includes Sc (scandium) element with a mass fraction range of 0.15%-0.30% and Zr (zirconium) element with a mass fraction range of 0.10%-0.20%, and the particle size of the alloy powder is preferably 15μm to 53μm. Single strengthening element powders include, but are not limited to, Sc and Zr; strengthening elements in powders containing strengthening elements include, but are not limited to, Sc and Zr. Sc and Zr elements are effective nucleating agents in aluminum alloys, which can effectively refine the weld microstructure, inhibit the generation of welding cracks, and improve the mechanical properties of the weld. The shape of the alloy powder can be irregular or regular spherical. In some embodiments, the composition, shape, and particle size of the alloy powder can be designed based on the microstructure and metallurgical characteristics of the T-shaped joint. The microstructure of the T-shaped joint has five distinct characteristic regions from the weld center to the base material region: equiaxed crystal region, columnar crystal region, partially melted region, overheated region, and base material region. The T-shaped structure has the following metallurgical characteristics: during laser welding, metallurgical defects such as porosity and cracks are prone to occur due to the influence of the materials of the skin 3 and stringer 4, its own structural characteristics, and process parameters. Further, when the alloy powder is a base material powder or a base material powder containing reinforcing elements, the preparation method of the alloy powder includes at least one of the following: inert gas atomization method, plasma rotating electrode method, and radio frequency plasma method; when the alloy powder is a mixed powder composed of base material powder and a single reinforcing element powder, or a mixed powder composed of base material powder and a powder containing reinforcing elements, the preparation method of the alloy powder is a mechanical mixing method.

[0052] S2. Conduct cold spraying process experiments on alloy powder to form alloy powder deposits and establish the correlation between cold spraying process parameters and the thickness and density of the alloy powder deposits. Specifically, the specific operation procedure for the cold spraying process experiment is as follows: Select multiple sets of cold spraying process parameters with a single variable. In the same environment, cold spray the alloy powder onto the same material surface using multiple sets of different cold spraying process parameters to form multiple alloy powder deposits on the surface. Measure the thickness and density of the multiple alloy powder deposits. Through multiple sets of data, find the correlation (positive or negative correlation) between the cold spraying process parameters and the thickness and density of the alloy powder deposits.

[0053] S3, such as Figure 1 and Figure 2 As shown, a surface deposition layer 1 is designed on the contact surface between the skin 3 and the stringer 4, and a weld foot deposition layer is designed in the welding area between the skin 3 and the stringer 4. The first design dimension of the surface deposition layer 1 is determined based on the dimensions of the stringer 4, and the second design dimension of the weld foot deposition layer 2 is determined based on the laser welding parameters. Specifically, the first design dimension includes the length and width of the surface deposition layer 1, where the length of the surface deposition layer 1 is L, and the width of the surface deposition layer 1 is 1δ~1.2δ, where L is the length of the stringer 4, and δ is the width of the stringer 4. The calculation formula for the second design dimension is as follows:

[0054]

[0055] Where x2 is the second designed weld leg size, x1 is the first designed weld leg size, x1 is the length of the right-angled side of the largest isosceles right triangle drawn in the cross-section of the fillet weld, r is the radius of the welding wire used in conventional dual-beam laser fillet welding, which is generally 0.4mm to 0.6mm, and v w v is the wire feed speed, v is the welding speed, and ρ is the coating density under specific cold spraying process parameters. The value of coating density ρ can be determined based on the database of cold spraying process parameters and coating density, and it is generally 75% to 95%.

[0056] S4. Perform surface cleaning on the skin 3 and stringer 4 to remove oxide film, oil, and other impurities from their surfaces. The cleaning area should be 5mm-10mm larger than the welding area. Specifically, mechanical cleaning, chemical cleaning, or laser cleaning methods can be used to clean the surface of the skin 3 and stringer 4. When using laser cleaning, the process parameters include pulsed laser power P, scanning speed v, and pulse frequency f. The pulsed laser power P is 160W-250W, the scanning speed is 1500mm / s-3000mm / s, and the pulse frequency is 2kHz-4kHz.

[0057] S5, such as Figure 3As shown, the design thickness of the surface deposition layer 1 is determined, and the first cold spraying process parameters of the alloy powder are determined according to the design thickness. A surface deposition layer mold 5 corresponding to the first design size is placed on the skin 3, and the alloy powder is cold sprayed into the surface deposition layer mold 5 using the first cold spraying process parameters to form a surface deposition layer 1 with the first design size and design thickness. Specifically, the design thickness of the surface deposition layer 1 is controlled within the range of 0.1 mm to 0.5 mm.

[0058] S6. Place the stringer 4 on the surface deposition layer 1 along the center line of the surface deposition layer 1;

[0059] S7. Based on the second design dimensions, determine the second cold spraying process parameters for the alloy powder. Place weld foot deposition layer molds corresponding to the second design dimensions in the welding areas on both sides of the girder 4. Apply the second cold spraying process parameters to cold spray the alloy powder within the weld foot deposition layer molds to obtain a weld foot deposition layer 2 with the second design dimensions. The first cold spraying process parameters include gas pressure p, working gas temperature T, spraying angle α, and spraying distance d, wherein the gas pressure p is 2MPa~5MPa, the working gas temperature T is 300℃~600℃, the spraying angle α is 40°-60°, and the spraying distance d is 10mm~50mm. The second cold spraying process parameters include gas pressure p, working gas temperature T, spraying angle α, and spraying distance d, wherein the gas pressure p is 2MPa~5MPa, the working gas temperature T is 300℃~600℃, the spraying angle α is 40°-60°, and the spraying distance d is 10mm~50mm.

[0060] S8. Laser welding is performed on the area to be welded using preset laser welding process parameters to form weld 6 in the area to be welded, so that the skin 3 and the stringer 4 are welded together to form a T-shaped structure. The weld pool size during the welding process is not less than the second design dimension. Specifically, laser welding can be performed using two laser beams to achieve simultaneous welding on both sides or asynchronous welding on both sides, or a single laser beam to achieve single-sided double-sided welding. During the welding process, a shielding gas atmosphere can be formed by introducing shielding gas, including argon and helium, with a flow rate generally selected from 5L / min to 25L / min. The shielding gas can be applied coaxially with the laser beam or off-axis. More specifically, the preset laser welding process parameters include the welding plane angle θ, the laser processing head deflection angle η, the laser offset y, the laser power P, and the welding speed v. Among them, the welding plane angle θ is 20°-70°, the laser processing head deflection angle η is 0°~15°, the laser offset y is -1mm~3mm, the laser power P is 2000W~4000W, and the welding speed is 2m / min~4m / min.

[0061] S9. Perform non-destructive testing on the T-shaped welded joints. Non-destructive testing methods include X-ray inspection and penetrant testing.

[0062] The following is a specific embodiment provided in this application:

[0063] Example 1

[0064] The technical solution of this embodiment enables laser welding of a 7075 high-strength aluminum alloy T-shaped structure. This T-shaped structure consists of a horizontally placed skin 3 and a vertically placed stringer 4. Both the skin 3 and stringer 4 are made of 7075 high-strength aluminum alloy. The skin 3 has a length of 1000mm, a width of 600mm, and a thickness of 2mm. The stringer 4 has a length L of 400mm, a height w of 30mm, and a thickness δ of 2mm. The specific welding method is achieved through the following steps:

[0065] Step 1: To refine the microstructure of the 7075 high-strength aluminum alloy T-type structural joint, suppress the generation of welding cracks, and improve the weld formation quality and mechanical properties, a 7075 high-strength aluminum alloy powder with a particle size of 15-53 μm containing strengthening elements Sc and Zr was designed, wherein the content of Sc element is 0.20% and the content of Zr element is 0.15%.

[0066] Step 2: Alloy powder containing strengthening elements Sc and Zr is prepared using inert gas atomization technology. Through cold spraying process experiments, the correlation between the cold spraying process parameters of 7075-ScZr aluminum alloy powder and the deposited layer thickness t and density ρ is established. This is quantified using formulas, including gas pressure p, working gas temperature T, spraying angle α, and spraying distance d.

[0067] Step 3: Based on the dimensions of stringer 4, determine the first design dimensions. The length, width, and thickness of the surface deposition layer 1 are designed to be 400mm, 2mm, and 0.1mm, respectively. The welding wire radius used in conventional high-strength aluminum alloy dual-beam laser welding is 0.6mm, and the wire feed speed is v. w With a welding speed of 3 m / min and a welding speed v of 6 m / min, the first designed weld leg size x1 of the T-shaped structure is determined to be 1.06 mm. Based on the first designed weld leg size, the cold spraying process parameters are selected as follows: gas pressure p = 3 MPa, working gas temperature T = 300℃, spraying angle α = 45°, and spraying distance d = 10 mm. Under these cold spraying process parameters, the coating density ρ = 90%, therefore, the second designed weld leg size x2 of the weld leg deposition layer 4 is determined to be 1.12 mm.

[0068] Step 4: Use laser cleaning to clean the surface of the skin 3 and stringer 4 within a 10mm range of the area to be welded, removing oxide film, oil, and other impurities from the surfaces of the skin 3 and stringer 4. Laser cleaning parameters: pulsed laser power P = 200W, scanning speed = 1500mm / s, pulse frequency = 2kHz.

[0069] Step 5: Based on the designed thickness of the surface deposition layer 1, select the following cold spraying process parameters: gas pressure p = 3 MPa, working gas temperature T = 300℃, spraying angle α = 45°, and spraying distance d = 10 mm. Place the surface deposition layer model 5 on the surface of the skin 3, and use the cold spraying system to obtain the surface deposition layer 1 in the connection area between the skin 3 and the stringer 4, to assist in the precise positioning of the stringer 4 on the skin 3.

[0070] Step 6: Place the stringer 4 on the surface deposition layer 1 along the center line of the surface deposition layer 1. With the help of the deposition layer, the positioning accuracy of the stringer assembly is improved from ±1mm to ±0.5mm, so as to achieve precise assembly of the 7075 high-strength aluminum alloy T-shaped structure.

[0071] Step 7: Based on the second design dimensions of the weld foot deposition layer 4, select the following cold spraying process parameters: gas pressure p = 3 MPa, working gas temperature T = 300℃, spraying angle α = 45°, and spraying distance d = 10 mm. Place weld foot deposition layer molds in the areas to be welded on both sides of the stringer 4, and use the cold spraying system to obtain weld foot deposition layer 2 in the areas to be welded on both sides of the stringer 4. During the cold spraying of the weld foot deposition layer, the powder particles will fill the excessively large assembly gaps between the skin and the stringer, improving the welding quality of the T-shaped structure joint.

[0072] Step 8, as Figure 4 and Figure 5 As shown, during the dual-beam laser welding process of the T-shaped structure, two laser beams 7 are symmetrically placed on both sides of the stringer 4. A coaxial argon gas supply method is used to provide real-time protection for the dual-beam laser welding process, with a shielding gas flow rate of 15 L / min. A dual-beam, dual-sided synchronous welding system is used to laser weld the skin 3 and the stringer 4, ensuring that the weld pool size is greater than or equal to the weld bead deposition layer size, resulting in a symmetrical weld 6 on both sides. The process parameters for dual-beam laser welding are: welding plane angle θ = 45°, laser processing head deflection angle η = 10°, laser offset y = 1 mm, and welding speed = 6 m / min. Because the weld bead deposition layer reduces the surface roughness of the T-shaped structure to be welded, it improves the absorption rate of the aluminum alloy to the laser and the utilization rate of laser energy, allowing the laser power P to be reduced from 2500 W to 2000 W.

[0073] Step 9: Quality Inspection. Perform X-ray non-destructive testing on the T-shaped welded joint.

[0074] The 7075 high-strength aluminum alloy T-shaped joints obtained by dual-beam laser welding exhibit good surface formation, with no obvious surface depressions or undercuts. The fillet weld convexity is moderate, and welding defects such as cracks and porosity are effectively controlled. The tensile strength of the T-shaped joint can reach 60% to 70% of the tensile strength of the base material. In summary, this technical solution is reasonable and feasible, and is particularly suitable for the laser welding process of 7075, 7050, 2024, and other 7xxx and 2xxx series high-strength aluminum alloy T-shaped structures.

[0075] Example 2

[0076] The technical solution of this embodiment enables laser welding of a TC4 titanium alloy T-shaped structure. This T-shaped structure consists of a horizontally placed skin 3 and a vertically placed stringer 4. Both the skin 3 and stringer 4 are made of TC4 titanium alloy. The skin 3 has a length of 1200mm, a width of 800mm, and a thickness of 2mm. The stringer 4 has a length L of 600mm, a height w of 30mm, and a thickness δ of 1.5mm. The specific welding method is achieved through the following steps:

[0077] Step 1: To improve the mechanical properties of the weld of the TC4 titanium alloy T-type joint, TC4 titanium alloy powder with a particle size of 15-53 μm and containing the strengthening element Ce was designed. The alloy powder is spherical in shape, and the Ce content is 0.30%.

[0078] Step 2: Alloy powder containing the strengthening element Ce is prepared using inert gas atomization technology. Through cold spraying process experiments, the correlation between the cold spraying process parameters of TC4-Ce titanium alloy powder and the deposition layer thickness t and density ρ is established. This is quantified using formulas, including gas pressure p, working gas temperature T, spraying angle α, and spraying distance d.

[0079] Step 3: Based on the dimensions of stringer 4, determine the first design dimensions. The length, width, and thickness of the surface deposition layer 1 are designed to be 600mm, 1.5mm, and 0.1mm, respectively. The welding wire radius used for conventional TC4 titanium alloy dual-beam laser welding is 0.5mm, and the wire feed speed is v. w With a welding speed of 6 m / min and a welding speed v of 8 m / min, the first designed weld leg size x1 of the T-shaped structure is determined to be 1.09 mm. Based on the first designed weld leg size, the cold spraying process parameters are selected as follows: gas pressure p = 4 MPa, working gas temperature T = 600℃, spraying angle α = 45°, and spraying distance d = 10 mm. Under these cold spraying process parameters, the coating density ρ is 80%, therefore, the second designed weld leg size x2 of the weld leg deposition layer 4 is determined to be 1.22 mm.

[0080] Step 4: Use laser cleaning to clean the surface of the skin 3 and stringer 4 within a 10mm range of the area to be welded, removing oxide film, oil, and other impurities from the surfaces of the skin 3 and stringer 4. Laser cleaning parameters: pulsed laser power P = 250W, scanning speed = 1500mm / s, pulse frequency = 2kHz.

[0081] Step 5: Based on the designed thickness of the surface deposition layer 1, select the following cold spraying process parameters: gas pressure p = 4 MPa, working gas temperature T = 600℃, spraying angle α = 45°, and spraying distance d = 10 mm. Place the surface deposition layer model 5 on the surface of the skin 3, and use the cold spraying system to obtain the surface deposition layer 1 in the connection area between the skin 3 and the stringer 4, to assist in the precise positioning of the stringer 4 on the skin 3.

[0082] Step 6: Place the stringer 4 on the surface deposition layer 1 along the center line of the surface deposition layer 1. With the help of the deposition layer, the positioning accuracy of the stringer assembly is improved from ±1mm to ±0.5mm, thus realizing the precise assembly of the TC4 titanium alloy T-shaped structure.

[0083] Step 7: Based on the second design dimensions of the weld foot deposition layer 4, select the following cold spraying process parameters: gas pressure p = 4 MPa, working gas temperature T = 600℃, spraying angle α = 45°, and spraying distance d = 10 mm. Place weld foot deposition layer molds in the areas to be welded on both sides of the stringer 4, and use the cold spraying system to obtain weld foot deposition layer 2 in the areas to be welded on both sides of the stringer 4. During the cold spraying of the weld foot deposition layer, the powder particles will fill the excessively large assembly gaps between the skin and the stringer, improving the welding quality of the T-shaped structure joint.

[0084] Step 8, as Figure 4 and Figure 5 As shown, during the dual-beam laser welding process of the T-shaped structure, two laser beams 7 are symmetrically placed on both sides of the stringer 4. A coaxial argon gas supply method is used to provide real-time protection for the dual-beam laser welding process, with a shielding gas flow rate of 25 L / min. A dual-beam, dual-sided synchronous welding system is used to laser weld the skin 3 and the stringer 4, ensuring that the weld pool size is greater than or equal to the weld bead deposition layer size, resulting in a symmetrical weld 6 on both sides. The process parameters for dual-beam laser welding are: welding plane angle θ = 30°, laser processing head deflection angle η = 0°, laser offset y = 1 mm, laser power P = 3000 W, and welding speed = 8 m / min.

[0085] Step 9: Quality Inspection. Perform X-ray non-destructive testing on the T-shaped welded joint.

[0086] The TC4 titanium alloy T-shaped joint obtained by dual-beam laser welding has a good surface formation with no obvious surface depressions or undercuts. The convexity of the fillet weld is moderate, and welding defects such as cracks and porosity are effectively controlled. The tensile strength of the T-shaped joint is basically equivalent to that of the base material.

[0087] In summary, the technical solution of the present invention is reasonable and feasible, and can be applied to the laser welding process of T-shaped structures such as aluminum alloy, titanium alloy, and stainless steel.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of laser welding a T-structure for welding a skin to a stringer to form a T-structure, characterized by, The method comprises the following steps: S1, preparing an alloy powder, the alloy powder being a base material powder, or a base material powder containing a strengthening element, or a mixed powder composed of a base material powder and a single strengthening element powder, or a mixed powder composed of a base material powder and a powder containing a strengthening element, wherein the composition of the base material powder is consistent with the composition of the material of the T-shaped structure; S2, performing a cold spraying process test on the alloy powder to form an alloy powder deposition layer and establish the correlation between the cold spraying process parameters and the thickness and density of the alloy powder deposition layer; S3, designing a surface deposition layer on the contact surface of the skin and the stringer and designing a weld leg deposition layer on the welding area of the skin and the stringer, determining the first design size of the surface deposition layer according to the size of the stringer, and determining the second design size of the weld leg deposition layer according to the laser welding parameters; S4, performing surface cleaning on the skin and the stringer; S5, determining the design thickness of the surface deposition layer, determining the first cold spraying process parameters of the alloy powder according to the design thickness, placing a surface deposition layer mold corresponding to the first design size on the skin, and cold spraying the alloy powder in the surface deposition layer mold by using the first cold spraying process parameters to form the surface deposition layer with the first design size and the design thickness; S6, placing the stringer on the surface deposition layer along the center line of the surface deposition layer; S7, determining the second cold spraying process parameters of the alloy powder according to the second design size, placing a weld leg deposition layer mold corresponding to the second design size on both sides of the stringer in the welding area, and cold spraying the alloy powder in the weld leg deposition layer mold by using the second cold spraying process parameters to obtain the weld leg deposition layer with the second design size; S8, laser welding the welding area by using preset laser welding process parameters to form a T-shaped structure, wherein the size of the weld pool during the welding process is not less than the second design size.

2. The T-structure laser welding method according to claim 1, wherein The method further comprises the following steps: S9, performing non-destructive testing on the welded joint of the T-shaped structure, and the non-destructive testing methods include X-ray detection and penetration detection.

3. The T-structure laser welding method according to claim 1, wherein In step S1, when the alloy powder is a base material powder containing a strengthening element and the base material powder is an aluminum alloy powder, the base material powder containing a strengthening element comprises Sc elements with a mass fraction ranging from 0.15% to 0.30%, and / or Zr elements with a mass fraction ranging from 0.10% to 0.20%, and the particle size of the alloy powder ranges from 15 μm to 53 μm.

4. The T-structure laser welding method according to claim 1, wherein In step S1, when the alloy powder is a base material powder or a base material powder containing a strengthening element, the preparation method of the alloy powder comprises at least one of inert gas atomization, plasma rotating electrode method, and radio frequency plasma method. When the alloy powder is a mixed powder composed of a base material powder and a single strengthening element powder, or a mixed powder composed of a base material powder and a powder containing a strengthening element, the preparation method of the alloy powder is mechanical mixing.

5. The T-structure laser welding method according to claim 1, wherein In step S3, the first design size includes a length of the surface deposition layer and a width of the surface deposition layer, wherein the length of the surface deposition layer is L, the width of the surface deposition layer is 1δ-1.2δ, L is the length of the stringer, and δ is the width of the stringer.

6. The T-structure laser welding method according to claim 1, wherein In step S3, the calculation formula of the second design size is as follows: wherein x2 is the second designed fillet size, x1 is the first designed fillet size, x1 is the length of the right angle side in the largest isosceles right triangle drawn in the cross section of the fillet, r is the radius of the welding wire used in the conventional double-beam laser welding, generally 0.4mm-0.6mm, v w is the wire feeding speed, v is the welding speed, and p is the coating density under specific cold spraying process parameters, the value of the coating density p can be determined according to a database of cold spraying process parameters and coating densities, and is generally 75%-95%.

7. The T-structure laser welding method according to claim 1, wherein In step S4, the skin and the stringer are surface cleaned by a mechanical cleaning method, a chemical cleaning method or a laser cleaning method; when the skin and the stringer are surface cleaned by the laser cleaning method, the process parameters of the laser cleaning method include pulse laser power P, scanning speed v and pulse frequency f, the pulse laser power P is 160W-250W, the scanning speed is 1500mm / s-3000mm / s, and the pulse frequency is 2kHz-4kHz.

8. The T-structure laser welding method according to claim 1, wherein In step S5, the first cold spraying process parameters include gas pressure p, working gas temperature T, spraying angle α and spraying distance d, wherein the gas pressure p is 2MPa-5MPa, the working gas temperature T is 300℃-600℃, the spraying angle α is 40°-60°, and the spraying distance d is 10mm-50mm.

9. The T-structure laser welding method according to claim 1, wherein In step S7, the second cold spraying process parameters include gas pressure p, working gas temperature T, spraying angle α and spraying distance d, wherein the gas pressure p is 2MPa-5MPa, the working gas temperature T is 300℃-600℃, the spraying angle α is 40°-60°, and the spraying distance d is 10mm-50mm.

10. The T-structure laser welding method according to claim 1, wherein In step S8, the preset laser welding process parameters include a welding plane angle θ, a laser processing head deflection angle η, a laser offset y, a laser power P and a welding speed v, wherein the welding plane angle θ is 20°-70°, the laser processing head deflection angle η is 0°-15°, the laser offset y is -1mm-3mm, the laser power P is 2000W-4000W, and the welding speed is 2m / min-4m / min.

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