Aerospace aluminum alloy case frame welding blank forming method

Abstract

The invention relates to the technical field of aerospace equipment structural part manufacturing. The invention discloses an aerospace aluminum alloy case frame welding blank forming method. The method comprises the following steps that S1, a base material is pretreated; s2, butt joint without a tool is carried out; s3, layered welding is conducted; s4, shaping after welding; and S5, defect detection and cleaning. According to the method, the tool cost can be effectively saved, the efficiency is improved, a special pressing tool does not need to be designed, manufactured, assembled and disassembled, the tool input cost is reduced, the positioning time consumption is shortened, and the production period is shortened by 25% or above compared with a traditional tool welding process; the method is particularly suitable for preparing aluminum alloy case frame blanks which are high in strength, light in weight, low in deformation, high in size precision and capable of meeting the requirements of aerospace extreme working conditions, butt joint precision can be guaranteed without supporting of more other tools, and a high-quality base material is provided for subsequent precision machining.

Description

Technical Field

[0001] This invention relates to the field of aerospace equipment structural component manufacturing technology. Background Technology

[0002] In the aerospace field, the chassis frame is a key structural component that supports core electronic components. It must meet the dual requirements of "lightweight" and "high strength" at the same time. Furthermore, it has extremely high requirements for the precision of the blank assembly, the consistency of welding, and the internal defect rate (defects such as pores, cracks, and lack of fusion are not allowed).

[0003] Currently, there are two major pain points in the forming of this type of blank: First, the material utilization rate is less than 30% after integral forging and milling, resulting in high cost, long cycle, and difficulty in meeting batch demand; Second, the traditional segmented welding forming requires the use of clamping tooling for positioning, which not only increases the additional cost of tooling design and manufacturing, but also consumes time in tooling assembly and disassembly. If the tooling is worn, it will also lead to accuracy deviation. At the same time, manual docking is prone to uneven gaps, requiring a large number of subsequent correction processes, which not only affects efficiency, but may also reduce the mechanical performance of the frame and fail to meet the requirements of extreme working conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a method for forming welding blanks of aerospace aluminum alloy chassis frames. This forming process ensures welding accuracy without the need for tooling clamping or butt jointing, and ensures that the blanks meet the requirements of aerospace extreme working conditions for strength, lightweighting, and dimensional stability.

[0005] To solve the above technical problems, the present invention provides a method for forming a welding blank for an aerospace aluminum alloy chassis frame, comprising the following steps: S1. Substrate pretreatment: Select aluminum alloy sheet or profile that meets aerospace standards as the substrate. Cut a "stepped butt joint structure" at the butt joint position on the substrate, and cut an X-shaped or Y-shaped weld slope interface with an angle of 30°~45° at the welding position on the substrate. Then grind and clean the weld slope interface to remove oxide scale and burrs. S2, Toolingless docking: Connect the horizontal beams and vertical beams in the base material to form the top frame and bottom frame, then connect the columns between the top frame and bottom frame to obtain the main frame, and then connect the reinforcing ribs inside the main frame. S3. Layered welding: Pulsed gas metal arc welding is used to perform the following steps at each welding position: root pass welding, air cooling, fill pass welding, air cooling, and cover pass welding. The root pass welding current is 120-140A, the fill pass welding current is 160-180A, and the cover pass welding current is 130-150A. S4. Post-weld shaping: Low-temperature aging stress relief treatment is used to reduce the residual stress in the weld and heat-affected zone to below 80MPa, and CNC equipment is used to inspect key dimensions; S5. Defect detection and cleaning: Ultrasonic testing is used to inspect the weld and heat-affected zone. For those that pass the inspection, sandblasting is used to remove the surface oxide scale and welding slag.

[0006] In step S1, the cutting is performed using laser cutting or water jet cutting, with a cutting accuracy of ≤ ±0.02 mm.

[0007] In step S1, the "stepped docking structure" means that the step height is consistent with the corresponding single-unit wall thickness, and the step mating gap is ≤0.05mm.

[0008] In step S2, the mating gap of the main frame is ≤0.08mm and the flatness error is ≤0.03mm / min.

[0009] In step S3, the welding gas used is 99.99% pure argon, and the welding gas flow rate is 18-22 L / min.

[0010] In step S3, the welding voltage for the bottom layer is 18-20V and the welding speed is 80-100mm / min; the welding voltage for the filler layer is 20-22V and the welding speed is 100-120mm / min; and the welding voltage for the top layer is 19-21V and the welding speed is 90-110mm / min.

[0011] In step S3, the air velocity for air cooling is 0.5-1 m / s, and the temperature is reduced to below 150°C.

[0012] In step S4, the low-temperature aging stress relief treatment is carried out at a temperature of 120-150°C for 4-6 hours, followed by furnace cooling.

[0013] In step S4, the pass standard for the CNC equipment to inspect the key dimensions is that the key dimension error is ≤0.1mm; the key dimensions include perpendicularity and flatness.

[0014] In step S4, the sensitivity of ultrasonic testing is ≥ Φ2mm; the particle size of sandblasting is 80-120 mesh.

[0015] Compared to existing technologies, this invention effectively eliminates tooling costs and improves efficiency. It eliminates the need for designing, manufacturing, and disassembling specialized clamping tooling, reducing tooling investment costs and shortening positioning time. The production cycle is reduced by more than 25% compared to traditional tooling welding processes. The butt joint accuracy is stable and controllable. Through a single-unit "stepped positioning structure" and layered pulse welding temperature control, the butt joint gap can be controlled to ≤0.08mm without tooling, and the final blank's key dimensional error is ≤0.1mm, solving the problems of "poor accuracy and easy misalignment" in traditional tooling-free butt joints. It also balances material utilization and mechanical properties, employing "segmented processing + tooling-free butt welding," increasing material utilization to over 75%. The material is made of aerospace-grade aluminum alloy substrate and layered welding. The blank has a tensile strength of ≥350MPa and a yield tensile strength of ≥280MPa, which can meet the requirements of extreme working conditions in aerospace. At the same time, it has strong adaptability. The length of the single unit, the spacing of the reinforcing ribs and the step parameters of the "step-type positioning structure" can be adjusted according to the size requirements of different chassis frames without changing tooling. It is suitable for the production of various specifications of frames. It is especially suitable for preparing aluminum alloy chassis frame blanks with high strength, lightweight, low deformation and high dimensional accuracy, which can meet the requirements of extreme working conditions in aerospace (such as high altitude and low temperature, vibration and shock). It can ensure docking accuracy without additional tooling support, and provide a high-quality substrate for subsequent precision machining.

[0016] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0017] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0018] Figure 1 This is a flowchart illustrating at least one embodiment of the present invention; Figure 2 This is a schematic diagram of the target product structure according to at least one embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the embodiments of this invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are presented in the embodiments of this invention to facilitate a better understanding of this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments. The division of the following embodiments is for ease of description and should not constitute any limitation on the specific implementation of this invention. The embodiments can be combined with and referenced by each other without contradiction.

[0020] Example 1 like Figure 1 The method for forming a welding blank for an aerospace aluminum alloy chassis frame, as shown, includes the following steps: S1. Substrate pretreatment: Select aluminum alloy sheet or profile that meets aerospace standards as the substrate. Cut a "stepped butt joint structure" at the butt joint position on the substrate, and cut an X-shaped or Y-shaped weld slope interface with an angle of 30°~45° at the welding position on the substrate. Then grind and clean the weld slope interface to remove oxide scale and burrs. S2, Toolingless docking: Connect the horizontal beams and vertical beams in the base material to form the top frame and bottom frame, then connect the columns between the top frame and bottom frame to obtain the main frame, and then connect the reinforcing ribs inside the main frame. S3. Layered welding: Pulsed gas metal arc welding is used to perform the following steps at each welding position: root pass welding, air cooling, fill pass welding, air cooling, and cover pass welding. The root pass welding current is 120-140A, the fill pass welding current is 160-180A, and the cover pass welding current is 130-150A. S4. Post-weld shaping: Low-temperature aging stress relief treatment is used to reduce the residual stress in the weld and heat-affected zone to below 80MPa, and CNC equipment is used to inspect key dimensions; S5. Defect detection and cleaning: Ultrasonic testing is used to inspect the weld and heat-affected zone. For those that pass the inspection, sandblasting is used to remove the surface oxide scale and welding slag.

[0021] Example 2 Based on Example 1, the cutting in step S1 is performed using laser cutting or water jet cutting, with a cutting accuracy of ≤ ±0.02mm.

[0022] Furthermore, in step S1, the "stepped docking structure" means that the step height is consistent with the corresponding single-unit wall thickness, and the step mating gap is ≤0.05mm.

[0023] Furthermore, in step S2, the mating gap of the main frame is ≤0.08mm and the flatness error is ≤0.03mm / min.

[0024] Furthermore, in step S3, 99.99% pure argon is used as the welding gas, and the welding gas flow rate is 18-22 L / min.

[0025] Furthermore, in step S3, the welding voltage for the bottom layer is 18-20V and the welding speed is 80-100mm / min; the welding voltage for the filler layer is 20-22V and the welding speed is 100-120mm / min; and the welding voltage for the top layer is 19-21V and the welding speed is 90-110mm / min.

[0026] Furthermore, in step S3, the air velocity for air cooling is 0.5-1 m / s, and the temperature is reduced to below 150°C.

[0027] Furthermore, in step S4, the low-temperature aging stress relief treatment is carried out at a temperature of 120-150°C for 4-6 hours, followed by furnace cooling.

[0028] Furthermore, in step S4, the pass standard for the CNC equipment to inspect the key dimensions is that the key dimension error is ≤0.1mm; the key dimensions include perpendicularity and flatness.

[0029] Furthermore, in step S4, the sensitivity of ultrasonic testing is ≥ Φ2mm; the particle size of sandblasting is 80-120 mesh.

[0030] Example 3 Based on the above embodiments, the specific steps are as follows: S1. Precision pretreatment of substrate: Using 6-series or 7-series aerospace-grade aluminum alloy (such as 6061-T6, 7075-T7451, taking into account both high strength and weldability) profiles as the substrate, high-precision CNC cutting equipment (laser cutting or water jet cutting, cutting accuracy guaranteed ≤±0.02mm) is used to process the individual components required for the frame. The key is that the mating ends of each individual component are pre-set with a "stepped mating structure" (the step height is consistent with the corresponding individual component wall thickness, and the step mating gap is ≤0.05mm). At the same time, X-shaped or Y-shaped welding bevels (angle 30°-45°) are processed. After cutting, the bevels are ground to remove oxide scale and burrs, and alkaline degreasing and oxide removal are performed. Positioning is achieved through the structure of the individual component itself, replacing tooling.

[0031] S2. Precise Assembly Without Tooling: The pre-processed component units—the horizontal beam units and the vertical beam units—are first assembled to form the upper and lower rectangular surfaces of the frame. The "stepped positioning structure" at the assembly ends of the units is used to ensure that the assembly gap is ≤0.08mm and the flatness error is ≤0.03mm / m. Then, the column units are assembled vertically to the corresponding vertices of the upper and lower rectangular surfaces through the "stepped positioning structure" to complete the main frame unit assembly. Finally, the reinforcing rib units are assembled to the inside of the main frame unit at preset intervals through the "stepped positioning structure". The entire process requires no tooling clamping and relies solely on the structural clamping to achieve stable positioning. S3. Layered Pulsed MIG Welding: Layered pulsed gas metal arc welding (MIG welding) is adopted. The welding gas is 99.99% pure argon (flow rate 18-22L / min). The parameters are set according to the three layers of “root pass - fill pass - cap pass”: root pass current 120-140A, voltage 18-20V, welding speed 80-100mm / min; fill pass current 160-180A, voltage 20-22V, welding speed 100-120mm / min; cap pass current 130-150A, voltage 19-21V, welding speed 90-110mm / min. After each layer of welding is completed, air cooling (wind speed 0.5-1m / s) is used to cool the weld area to below 150°C to avoid heat accumulation and misalignment of the butt joint structure, and further ensure accuracy. S4. Post-weld stress relief and shaping: After welding, low-temperature aging stress relief treatment is adopted (temperature 120-150°C, holding for 4-6 hours, furnace cooling) to control the residual stress in the weld and heat-affected zone to ≤80MPa, so as to avoid dimensional deformation caused by stress; after stress relief, only the key dimensions (such as perpendicularity and flatness) are inspected by CNC equipment, without extensive correction, to ensure that the key dimension error is ≤0.1mm; S5. Defect detection and cleaning: Ultrasonic testing (sensitivity ≥ Φ2mm flat bottom hole) is used to inspect the weld and heat-affected zone in the whole range to remove defective blanks; qualified blanks are treated by sandblasting (sand particle size 80-120 mesh) to remove surface oxide scale and welding slag to obtain the final weld blank.

[0032] This embodiment is particularly applicable to, for example, Figure 2 The "rectangular three-dimensional frame" shown achieves docking and positioning through the structure of each individual unit, specifically including: • Main frame unit: Composed of 4 horizontal beams, 4 vertical beams, and 4 columns welded together. The horizontal and vertical beams form upper and lower rectangular surfaces, and the columns connect vertically to the corresponding vertices of the upper and lower rectangular surfaces. Each unit has a U-shaped cross-section (opening towards the inside of the frame, wall thickness 3-5mm, balancing lightweight and strength), and the joint ends are equipped with a "stepped positioning structure" (step width 5-8mm, fitting gap ≤0.05mm), which can achieve precise locking and positioning without tooling.

[0033] • Reinforcing rib unit: Located inside the main frame unit, it includes "transverse reinforcing ribs" and "longitudinal reinforcing ribs". The two ends of the transverse reinforcing ribs are connected to the inner side of the opposite horizontal beam unit, and the two ends of the longitudinal reinforcing ribs are connected to the inner side of the opposite vertical beam unit. The two are distributed in a "cross" pattern (spacing 100-150mm, which can be adjusted according to the frame size). The cross section of the reinforcing rib is "L-shaped" (wall thickness 2-3mm), and the connecting end is also equipped with a "stepped positioning structure" to ensure the connection accuracy and the strength of the main frame.

[0034] • Weld structure: All welds at the joints of individual units are “multi-layer fillet welds” (weld height 4-6mm), and the weld surface is a smooth arc transition (arc radius 1-2mm), without sharp corners to avoid stress concentration; the width of the weld and heat-affected zone is controlled at 15-20mm to ensure mechanical properties without affecting the overall dimensional accuracy of the frame.

[0035] Example 4 Based on the above embodiments, a 7075-T7451 aluminum alloy chassis frame welding blank (dimensions: 500mm×400mm×300mm) is used. S1. Precision pretreatment of substrate: Select 5mm thick 7075-T7451 aluminum alloy sheet, laser cut (accuracy ±0.01mm) to process into 4 horizontal beams (500mm), 4 vertical beams (400mm), 4 columns (300mm, U-shaped section), 6 transverse reinforcing ribs (400mm), and 6 longitudinal reinforcing ribs (500mm, L-shaped section); process 40° Y-shaped bevel and 6mm wide stepped positioning structure (fitting clearance 0.04mm) at the joint ends of each unit; after grinding the bevel, alkali wash removes oil stains; S2. Precise docking without tooling: First, dock the upper and lower rectangular surfaces formed by the crossbeam and the longitudinal beam, and check the docking gap to be 0.06mm and the flatness to be 0.02mm / m; then dock the column, and finally dock the cross reinforcing ribs. The whole process is tooling-free and the positioning is stable. S3. Layered pulsed MIG welding: Pure argon flow rate 20L / min, root pass 130A / 19V / 90mm / min, filler layer 170A / 21V / 110 mm / min, capping layer 140A / 20V / 100mm / min, each layer is air cooled to 140°C before welding the next layer; S4. Post-weld treatment: Aging and holding at 130°C for 5 hours, critical dimensional error was found to be 0.08mm, no additional correction required; S5. Inspection and cleaning: Ultrasonic testing showed no defects, and sandblasting with 80-mesh sand particles yielded a qualified blank.

[0036] Example 5 Based on the above embodiments, a 6061-T6 aluminum alloy chassis frame welding blank (dimensions: 600mm×500mm×350mm) is used. S1. Substrate Pretreatment: Select 4mm thick 6061-T6 aluminum alloy profiles, waterjet cut (accuracy ±0.02mm), and process into 4 horizontal beams (600mm), 4 vertical beams (500mm), 4 columns (350mm, U-shaped section), and 8 transverse reinforcing ribs (500mm) and 8 longitudinal reinforcing ribs (600mm, L-shaped section); process the butt joint with a 35° X-shaped bevel and a 5mm wide stepped positioning structure (fitting clearance 0.05mm); after grinding the bevel, use alkaline washing to remove oil stains; S2. Precise docking without tooling: After docking, the gap is 0.07mm, the flatness is 0.03mm / m, and the positioning is stable; S3. Welding parameters: pure argon flow rate 19L / min, root pass 125A / 18.5V / 85mm / min, fill pass 165A / 20.5V / 105 mm / min, cap pass 135A / 19.5V / 95mm / min, each layer is air-cooled to 135°C before welding the next layer; S4. Post-weld treatment: Aging and holding at 140°C for 5 hours, critical dimensional error detected as 0.09mm; S5. Inspection and Cleaning: Ultrasonic testing passed, and 100-mesh sandblasting was performed to obtain a qualified blank.

[0037] The results of the blank inspection of Examples 4 and 5 are as follows: material utilization rate 78% and 76%; tensile strength 380MPa and 360MPa; yield strength 300MPa and 290MPa; residual stress 75MPa and 72MPa; critical dimensional error ≤0.1mm, and no tooling was required, which meets the requirements of aerospace technology.

[0038] Those skilled in the art will understand that the above embodiments can be modified in form and detail in practical applications without departing from the spirit and scope of the invention.

Claims

1. A method for forming a welding blank for an aerospace aluminum alloy chassis frame, characterized in that, Includes the following steps: S1. Substrate pretreatment: Select aluminum alloy sheet or profile that meets aerospace standards as the substrate. Cut a "stepped butt joint structure" at the butt joint position on the substrate, and cut an X-shaped or Y-shaped weld bevel interface with an angle of 30°~45° at the welding position on the substrate. Then grind and clean the weld bevel interface to remove oxide scale and burrs. S2, Toolingless docking: Connect the horizontal beams and vertical beams in the base material to form the top frame and bottom frame, then connect the columns between the top frame and bottom frame to obtain the main frame, and then connect the reinforcing ribs inside the main frame. S3. Layered welding: Pulsed gas metal arc welding is used to perform the following steps at each welding position: root pass welding, air cooling, fill pass welding, air cooling, and cover pass welding. The root pass welding current is 120-140A, the fill pass welding current is 160-180A, and the cover pass welding current is 130-150A. S4. Post-weld shaping: Low-temperature aging stress relief treatment is used to reduce the residual stress in the weld and heat-affected zone to below 80MPa, and CNC equipment is used to inspect key dimensions. S5. Defect detection and cleaning: Ultrasonic testing is used to inspect the weld and heat-affected zone. For those that pass the inspection, sandblasting is used to remove the surface oxide scale and welding slag.

2. The method for forming welding blanks for aerospace aluminum alloy chassis frames as described in claim 1, characterized in that, In step S1, the cutting is performed using laser cutting or water jet cutting, with a cutting accuracy of ≤ ±0.02mm.

3. The method for forming welding blanks for aerospace aluminum alloy chassis frames as described in claim 1, characterized in that, In step S1, the "stepped docking structure" means that the step height is consistent with the corresponding single-unit wall thickness, and the step mating gap is ≤0.05mm.

4. The method for forming welding blanks for aerospace aluminum alloy chassis frames as described in claim 1, characterized in that, In step S2, the mating gap of the main frame is ≤0.08mm and the flatness error is ≤0.03mm / min.

5. The method for forming welding blanks for aerospace aluminum alloy chassis frames as described in claim 1, characterized in that, In step S3, the welding gas used is 99.99% pure argon, and the welding gas flow rate is 18-22 L / min.

6. The method for forming welding blanks for aerospace aluminum alloy chassis frames as described in claim 1, characterized in that, In step S3, the welding voltage for the bottom layer is 18-20V and the welding speed is 80-100mm / min; the welding voltage for the filler layer is 20-22V and the welding speed is 100-120mm / min; and the welding voltage for the top layer is 19-21V and the welding speed is 90-110mm / min.

7. The method for forming welding blanks for aerospace aluminum alloy chassis frames as described in claim 1, characterized in that, In step S3, the air velocity for air cooling is 0.5-1 m / s, and the temperature is reduced to below 150°C.

8. The method for forming welding blanks for aerospace aluminum alloy chassis frames as described in claim 1, characterized in that, In step S4, the low-temperature aging stress relief treatment is carried out at a temperature of 120-150°C for 4-6 hours, followed by furnace cooling.

9. The method for forming welding blanks for aerospace aluminum alloy chassis frames as described in claim 1, characterized in that, In step S4, the pass standard for the CNC equipment to inspect the key dimensions is that the key dimension error is ≤0.1mm; the key dimensions include perpendicularity and flatness.

10. The method for forming welding blanks for aerospace aluminum alloy chassis frames as described in claim 1, characterized in that, In step S4, the sensitivity of ultrasonic testing is ≥ Φ2mm; the particle size of sandblasting is 80-120 mesh.

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