Method for eliminating slip line of 2xxx aluminum alloy skin for aviation aircraft

Abstract

The invention discloses a method for eliminating a slip line of a 2xxx aluminum alloy skin for an aviation aircraft, which comprises the following steps: (1) pre-stretching the aluminum alloy skin by using a stretch-forming machine, and controlling the stretch rate to be less than or equal to 2% in the pre-stretching process; (2) the aluminum alloy skin pre-stretched in the step (1) is subjected to solid solution quenching treatment; (3) standing the aluminum alloy skin subjected to solid solution quenching in the step (2) at room temperature, and carrying out natural aging; (4) the aluminum alloy skin obtained after natural aging in the step (3) is stretched through a stretching machine, and skin stretching forming is completed; the natural aging time in the step (3) is calculated according to the stretch rate required by skin stretch forming in the step (4). The critical strain value is increased by controlling the stretching rate and the natural aging time in the aluminum alloy skin machining process, and therefore it is guaranteed that defects such as slip lines do not appear on the skin surface in the stretching process by controlling the stretching rate to be smaller than the critical strain value.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy skin parts processing, and in particular to a method for eliminating a slip line of a 2xxx aluminum alloy skin used in an aviation aircraft. Background Art

[0002] The function of aircraft skin is to maintain the shape of the aircraft and give it good aerodynamic characteristics. After the skin is subjected to aerodynamic force, it transmits the force to the connected fuselage and wing frames. The force is complex, and the skin is in direct contact with the outside world. Therefore, the skin material is required to have not only high strength and good plasticity, but also a smooth surface. The 2024-O state belongs to the fully annealed state, with excellent forming and processing properties, so it is widely used in the processing of aircraft skin parts. At present, aluminum alloy skin forming mostly adopts the stretching process, using a stretching machine to stretch the thin-walled aluminum plate, and the stretching rate reaches 8%. The relatively large stretching amount can easily lead to slip line defects on the surface during the stretching process. The light ones need to be manually polished, and the serious ones are directly scrapped, which seriously affects the product quality and production efficiency. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a method for eliminating slip lines of 2xxx aluminum alloy skins for aircraft, by controlling the stretching rate and natural aging time during the processing of the aluminum alloy skin to increase the critical strain value, and then by controlling the stretching rate to be less than the critical strain value to ensure that no defects such as slip lines appear on the skin surface during the stretching process.

[0004] The technical solution adopted by the present invention is:

[0005] The present invention provides a method for eliminating the slip line of a 2xxx aluminum alloy skin for an aircraft, comprising the steps of:

[0006] (1) Pre-stretching the aluminum alloy skin using a drawing machine, and controlling the stretching rate during the pre-stretching process to be ≤2%;

[0007] (2) subjecting the aluminum alloy skin pre-stretched in step (1) to a solution quenching treatment;

[0008] (3) leaving the aluminum alloy skin after solution quenching in step (2) to stand at room temperature for natural aging;

[0009] (4) using a stretching machine to stretch the aluminum alloy skin after natural aging in step (3) to complete the skin stretching forming;

[0010] The natural aging time in step (3) is calculated based on the stretching rate required for the skin stretching molding in step (4), and the calculation formula is:

[0011] f(x)=2.83ln(x)+4.99

[0012] Among them, f(x) is the critical strain value, f(x)≥the elongation rate required for skin stretch forming, and x is the natural aging time.

[0013] In the above technical scheme, the present invention controls the natural aging time by controlling the elongation rate required in step (4), thereby reducing the solubility of solute atoms in the aluminum alloy material, thereby increasing the critical strain of the material, and then by controlling the elongation rate not to exceed the critical strain value, it can be ensured that no slip line is generated during the stretching process. If the elongation rate required in step (4) is 8%, the natural aging time is at least 2.5 hours.

[0014] Furthermore, the stretching rate during the pre-stretching in step (1) is 0.05 to 0.1 mm / s.

[0015] In the above technical solution, the present invention delays the appearance of the slip line by reducing the stretching rate and increasing the critical strain, that is, the strain amount corresponding to the appearance of the slip line.

[0016] Furthermore, in the step (2), the solution treatment temperature is 470-480° C. and the time is 30-60 min.

[0017] Furthermore, after the solution treatment in step (2) is completed, water quenching needs to be performed within 5 seconds, and the water temperature before quenching is ≤40°C.

[0018] Furthermore, the stretching rate during stretching in step (4) is 0.05 to 0.1 mm / s.

[0019] In the above technical solution, the present invention delays the appearance of the slip line by reducing the stretching rate and increasing the critical strain.

[0020] Furthermore, in the step (4), the stretching rate of the skin during stretching molding is ≤8%.

[0021] Furthermore, the 2xxx aluminum alloy is a fully annealed aluminum alloy.

[0022] The beneficial effects of the present invention are:

[0023] The present invention provides a method for eliminating slip lines of 2xxx aluminum alloy skins for aircraft. The critical strain value is increased by controlling the stretching rate and natural aging time during the processing of the aluminum alloy skin, and then the stretching rate is controlled to be less than the critical strain value to ensure that no slip lines or other defects such as the skin surface appear during the stretching process, thereby improving the forming quality of the aircraft skin. At the same time, the subsequent grinding process is cancelled, a large amount of manpower is saved, and the production efficiency is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0025] Figure 1 This is a surface morphology photo of the aluminum alloy skin of Example 1;

[0026] Figure 2 is a three-dimensional morphology image of the aluminum alloy skin of Example 1;

[0027] Figure 3 This is a surface morphology photo of the aluminum alloy skin of Comparative Example 1;

[0028] Figure 4 is a three-dimensional morphology image of the aluminum alloy skin of Comparative Example 1; DETAILED DESCRIPTION

[0029] The present invention provides a method for eliminating the slip line of a 2xxx aluminum alloy skin for an aircraft. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] Example 1

[0031] This embodiment provides a method for eliminating the slip line of a 2xxx aluminum alloy skin for an aircraft, taking a 2000mm*2000mm*1.8mm 2024-O sheet as an example, comprising the steps of:

[0032] (1) Pre-stretching

[0033] The two ends of the sheet are clamped by the clamps of the drawing machine, and the drawing tire lifted by the workbench contacts the sheet, generating uneven plane tensile strain to make the sheet fit the drawing tire. During this process, the drawing machine pre-stretches the aluminum alloy skin at a stretching rate of 0.1mm / s, and the stretching rate during the pre-stretching process is 2%;

[0034] (2) Solution quenching

[0035] The aluminum alloy skin pre-stretched in step (1) is subjected to solution quenching treatment; the solution treatment temperature is 476°C, the time is 45 minutes, and water quenching is performed within 5 seconds after the solution treatment is completed, and the water temperature before quenching is not greater than 40°C;

[0036] (3) Natural aging

[0037] The aluminum alloy skin after solution quenching in step (2) is left to stand at room temperature for 4 hours for natural aging;

[0038] The natural aging time in this step is calculated based on the stretching rate required for the skin stretching in step (4), and the calculation formula is:

[0039] f(x)=2.83ln(x)+4.99

[0040] Where f(x) is the critical strain value, f(x)≥ the elongation required for skin stretch forming, and x is the natural aging time;

[0041] When the stretching rate of the stretch forming is 8%, the natural aging time is at least 2.5h, and in this embodiment it is 4h, which can meet the requirements;

[0042] (4) Stretch forming

[0043] The aluminum alloy skin after natural aging in step (3) is stretched by a stretching machine at a stretching rate of 0.1 mm / s, with a stretching rate of 8%, to complete the skin stretching forming.

[0044] Example 2

[0045] The difference between Example 2 and Example 1 is that in this example, the stretching rate during the pre-stretching in step (1) and the stretching forming in step (4) is 0.05 mm / s, and the natural aging time is 3 h.

[0046] Comparative Example 1

[0047] This comparative example provides a method for eliminating the slip line of a 2xxx aluminum alloy skin for an aircraft, comprising the steps of:

[0048] (1) Pre-stretching

[0049] The two ends of the sheet are clamped by the clamps of the drawing machine, and the drawing tire lifted by the workbench contacts the sheet, generating uneven plane tensile strain to make the sheet fit the drawing tire. During this process, the drawing machine pre-stretches the aluminum alloy skin at a stretching rate of 0.5mm / s, and the stretching rate during the pre-stretching process is 2%;

[0050] (2) Solution quenching

[0051] The aluminum alloy skin pre-stretched in step (1) is subjected to solution quenching treatment; the solution treatment temperature is 476°C, the time is 45 minutes, and water quenching is performed within 5 seconds after the solution treatment is completed, and the water temperature before quenching is not greater than 40°C;

[0052] (3) Natural aging

[0053] The aluminum alloy skin after solution quenching in step (2) is left to stand at room temperature for 1.5 hours for natural aging;

[0054] (4) Stretch forming

[0055] The aluminum alloy skin after natural aging in step (3) is stretched by a stretching machine at a stretching rate of 0.5 mm / s, with a stretching rate of 8%, thereby completing the skin stretching forming.

[0056] The aluminum alloy skins obtained in Examples 1 and 2 did not show any slip lines, while the aluminum alloy skins obtained in Comparative Example 1 showed slip lines. Figure 1 Its three-dimensional morphology is shown in Figure 2 As shown; the actual surface morphology of the aluminum alloy skin of Comparative Example 1 is as follows Figure 3 Its three-dimensional morphology is shown in Figure 4 As shown. Figure 1-4 It can be seen that the surface of the aluminum alloy skin of Example 1 is smooth without any slip lines, while obvious slip lines appear in Comparative Example 1, which requires grinding.

[0057] It should be noted that some parts not described in the present invention can be implemented by adopting or drawing on existing technologies.

[0058] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for eliminating slip lines of 2xxx aluminum alloy skins for aircraft, characterized in that: Includes steps: (1) Pre-stretching the aluminum alloy skin using a drawing machine, and controlling the stretching rate during the pre-stretching process to be ≤2%; (2) subjecting the aluminum alloy skin pre-stretched in step (1) to a solution quenching treatment; (3) leaving the aluminum alloy skin after solution quenching in step (2) to stand at room temperature for natural aging; (4) using a stretching machine to stretch the aluminum alloy skin after natural aging in step (3) to complete the skin stretching forming; The natural aging time in step (3) is calculated based on the stretching rate required for the skin stretching molding in step (4), and the calculation formula is: f(x)=2.83ln(x)+4.99 Among them, f(x) is the critical strain value, f(x)≥the elongation rate required for skin stretch forming, and x is the natural aging time.

2. A method for eliminating slip lines of 2xxx aluminum alloy skin for aircraft according to claim 1, characterized in that: The stretching rate during the pre-stretching in the step (1) is 0.05 to 0.1 mm / s.

3. A method for eliminating slip lines of 2xxx aluminum alloy skin for aircraft according to claim 1, characterized in that: In the step (2), the solution treatment temperature is 470-480° C. and the time is 30-60 min.

4. A method for eliminating slip lines of 2xxx aluminum alloy skin for aircraft according to claim 1, characterized in that: After the solution treatment in step (2) is completed, water quenching needs to be performed within 5 seconds, and the water temperature before quenching is ≤40°C.

5. A method for eliminating slip lines of 2xxx aluminum alloy skin for aircraft according to claim 1, characterized in that: The stretching rate during stretching in the step (4) is 0.05 to 0.1 mm / s.

6. A method for eliminating slip lines of 2xxx aluminum alloy skin for aircraft according to claim 1, characterized in that: The stretching rate of the skin during stretching molding in the step (4) is ≤8%.

7. A method for eliminating slip lines of 2xxx aluminum alloy skin for aircraft according to claim 1, characterized in that: 2xxx aluminum alloy is a fully annealed aluminum alloy.

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