Stress and Dimension Co-control Machining Method for Large Aluminum-Lithium Alloy Spherical Bottom Components

Abstract

This invention relates to a method for stress and dimension coordinated control machining of large aluminum-lithium alloy spherical bottom components, belonging to the field of precision machining technology. The process includes: solution treatment of the spherical bottom component blank; inspection of the inner surface of the spherical bottom component blank; shape correction of the spherical bottom component blank; rough machining of the inner surface of the spherical bottom component blank; artificial aging heat treatment; rough milling of the outer surface of the spherical bottom component blank; measurement of residual stress at the center points of each grid around the middle curvature position of the spherical bottom component blank, and sorting of peak values; overall machining of the outer surface grid of the spherical bottom component blank; finish machining of the inner surface of the spherical bottom component blank with a 0mm allowance; measurement of residual stress at the center points of each grid around the middle curvature position of the spherical bottom component blank again, and sorting of residual tensile stress peak values ​​for each grid; finish milling of the outer surface grid of the spherical bottom component blank; completion of machining. This invention solves the problems of sudden stress release and deformation deviation during the machining of large spherical bottom components made of 2195 aluminum-lithium alloy.

Description

Technical Field

[0001] This invention belongs to the field of precision machining technology and relates to a method for stress and dimension coordinated control of machining large aluminum-lithium alloy spherical bottom components. Background Technology

[0002] With the development of manned spaceflight, deep space exploration, and other fields, the requirements for high reliability, long lifespan, and lightweight design in next-generation spacecraft have increased significantly, making integrated monolithic structures a development trend. Aluminum-lithium alloys, due to their low density, high strength, high specific stiffness, good heat resistance, and good corrosion resistance, and the ability to be strengthened through heat treatment, are gradually being used in the aerospace field.

[0003] In the current aerospace field, 2195 aluminum-lithium alloy is mainly used to manufacture load-bearing components such as the spherical bottom and propellant tanks of large launch vehicles. The traditional multi-process manufacturing method involving both hot and cold heating presents the following problems for large spherical bottom components of spacecraft:

[0004] (1) 2195 aluminum-lithium alloy has high yield strength. During the manufacturing process of multiple processes such as hot and cold, the internal stress distribution becomes more uneven and the peak stress is high.

[0005] (2) The processing of large spherical bottom components involves a large amount of material removal, large deformation during processing, and uncontrollable dimensions.

[0006] (3) Traditional stress relief methods lead to a decline in material properties. Summary of the Invention

[0007] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a stress and dimension coordinated control processing method for large aluminum-lithium alloy spherical bottom components, which solves the problems of sudden stress release and deformation deviation in the processing of large spherical bottom components of 2195 aluminum-lithium alloy.

[0008] The solution of the present invention is:

[0009] A method for coordinating stress and dimensional control in the fabrication of large aluminum-lithium alloy spherical bottom components includes:

[0010] Solution treatment is performed on the blank of the spherical bottom component;

[0011] Inspect the inner surface of the blank of the spherical bottom component;

[0012] The blank of the spherical bottom component is shaped and corrected.

[0013] Rough machining of the inner surface of the spherical base component blank;

[0014] Artificial aging heat treatment;

[0015] Rough mill the outer surface of the spherical bottom component blank and machine the annular mesh;

[0016] The residual stress at the center point of each grid along the middle curvature of the spherical bottom component blank was measured, and the peak residual tensile stress of each grid was sorted.

[0017] The outer surface mesh of the spherical bottom component blank is machined as a whole;

[0018] The inner surface of the ball base component blank is precision machined, with a allowance of 0mm;

[0019] The residual stress at the center point of each grid along the middle curvature of the spherical bottom component blank was measured again, and the peak values ​​of residual tensile stress in each grid were sorted.

[0020] The outer surface grid of the ball-shaped component blank is precision milled; machining is completed.

[0021] In the aforementioned method for coordinating stress and dimensional control of large aluminum-lithium alloy spherical bottom components, the spherical bottom component blank is made of 2195 aluminum-lithium alloy material and has an inverted spherical shell structure; the solution treatment process for the spherical bottom component blank is as follows:

[0022] The blank of the ball bottom component is loaded into the furnace at room temperature; after 3.5 hours, it is heated to 495℃ and held for 3 hours; after 0.5 hours, it is heated to 505℃ and held for 0.5 hours; then it is cooled by spraying; the spray flow rate is 3000t / h and the spraying time is 4min.

[0023] In the aforementioned method for stress and dimensional control of large aluminum-lithium alloy spherical bottom components, an optical scanner is used to inspect the inner surface of the blank; using the bottom circle of the inner surface as a reference, a point cloud of the inner surface is formed and compared with the theoretical surface.

[0024] In the aforementioned method for coordinating stress and dimensional control of large aluminum-lithium alloy spherical bottom components, the method for shape correction is as follows:

[0025] When the error between the inner surface point and the theoretical surface point exceeds 5mm, it is determined that a correction process is required; otherwise, no action is taken. Let the height of the spherical bottom component blank be H. The local area discrete fitting processing method is used to perform local correction on the spherical bottom component blank. First, the correction is performed at the position where the curvature of the spherical bottom component blank changes abruptly in the middle, that is, at the position where the height of the spherical bottom component blank is 0.5H.

[0026] In the aforementioned method for stress and dimension coordinated control of large aluminum-lithium alloy spherical bottom components, a nine-grid nut plate is used as a shaping tool. Nine bolts are arranged in an array on the nine-grid nut plate. By adjusting the extension length of each bolt, a discrete curved surface is fitted, and the deformable surface is shaped.

[0027] In the above-mentioned stress and dimension coordinated control machining method for large aluminum-lithium alloy spherical bottom components, the machining allowance is 2mm when rough turning the inner surface; the aging temperature is 155℃ and the holding time is 32-36h.

[0028] In the above-mentioned stress and dimension coordinated control processing method for large aluminum-lithium alloy spherical bottom components, when rough milling the outer surface grid of the spherical bottom component blank, a 5mm allowance is left on the side wall and bottom surface; the processing is carried out circle by circle from the inner circle of the top of the sphere to the outer circle of the end frame, and for each circle of grid, the grid is processed in a clockwise direction.

[0029] In the above-mentioned stress and dimension coordinated control processing method for large aluminum-lithium alloy spherical bottom components, when machining the overall outer surface grid, a 3mm allowance is left for the side walls and bottom surface;

[0030] Machining proceeds from the inner ring at the top of the sphere towards the outer ring of the end frame, ring by ring. For each ring of mesh, machining is performed in the order of tensile stress peak values. Machining begins with the mesh with the highest residual tensile stress peak value, followed by the mesh with the second highest residual tensile stress peak value, and so on, until all meshes within a ring are machined. The order of tensile stress peak values ​​in each ring of mesh is consistent with the mesh corresponding to the middle curvature position along the radial direction.

[0031] In the above-mentioned stress and dimension coordinated control machining method for large aluminum-lithium alloy spherical bottom components, when precision milling the outer surface grid of the spherical bottom component blank, a 0mm allowance is left on the side wall and bottom surface.

[0032] Machining proceeds from the inner ring at the top of the sphere towards the outer ring of the end frame, ring by ring. For each ring of mesh, machining is performed in the order of tensile stress peak values, starting with the mesh with the highest residual tensile stress peak value, then machining the mesh with the second highest residual tensile stress peak value, and so on, until all mesh positions within a ring are machined. The order of tensile stress peak values ​​of each ring of mesh is consistent with the mesh corresponding to the middle curvature position along the radial direction.

[0033] The stress and dimension co-control machining method for the large aluminum-lithium alloy spherical bottom component mentioned above adopts a precision milling process of wall thickness measurement-compensation-machining the bottom surface inlet groove-machining the bottom surface to the dimension-machining the side wall to the dimension.

[0034] The advantages of this invention compared to the prior art are:

[0035] (1) This invention successfully solved the problem of precision machining of large spherical bottom components of 2195 aluminum-lithium alloy. It adopts tooling technology based on the product structure's own rigid support and hard top support to ensure the accuracy requirements of the thin-walled mesh of the large spherical bottom component.

[0036] (2) The present invention forms a comprehensive control method based on the results of size and stress measurement, which effectively reduces processing deformation, reduces the risk of deviation, and reduces the development cost;

[0037] (3) The present invention effectively achieves uniform distribution and peak control of overall stress in large spherical bottom components through solution treatment, shaping, artificial aging treatment and stress relief treatment, and ensures material strength. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the blank of the spherical bottom component of the present invention;

[0039] Figure 2 This is a schematic diagram of the calibration position of the present invention;

[0040] Figure 3 This is a schematic diagram of the calibration tool of the present invention;

[0041] Figure 4 This is a schematic diagram of the overall machining of the outer surface mesh of the present invention;

[0042] Figure 5 This is a schematic diagram showing the location for measuring residual stress according to the present invention;

[0043] Figure 6 This is a schematic diagram illustrating the final inspection of the product of this invention. Detailed Implementation

[0044] The present invention will be further described below with reference to the embodiments.

[0045] This invention provides a method for coordinating stress and dimensional accuracy control of large spherical bottom components made of 2195 aluminum-lithium alloy, which solves problems such as sudden stress release and deformation deviation during the processing of large spherical bottom components made of 2195 aluminum-lithium alloy.

[0046] A method for coordinating stress and dimensional control in the fabrication of large aluminum-lithium alloy spherical bottom components includes the following steps:

[0047] The structure of the blank of the spherical bottom component is as follows Figure 1 As shown, the spherical bottom component blank undergoes solution treatment. The spherical bottom component blank is made of 2195 aluminum-lithium alloy and has an inverted spherical shell structure. The specific solution treatment process for the spherical bottom component blank is as follows:

[0048] The blank of the ball bottom component is loaded into the furnace at room temperature; after 3.5 hours, it is heated to 495℃ and held for 3 hours; after 0.5 hours, it is heated to 505℃ and held for 0.5 hours; then it is cooled by spraying; the spray flow rate is 3000t / h and the spraying time is 4min.

[0049] The inner surface of the blank of the spherical bottom component is inspected.

[0050] The blank of the spherical bottom component is shaped and corrected.

[0051] An optical scanner is used to inspect the inner surface of the blank; using the bottom circle of the inner surface as a reference, a point cloud of the inner surface is generated and compared with the theoretical surface. The correction method is as follows:

[0052] When the error between the internal surface point and the theoretical surface point exceeds 5mm, it is determined that a correction process is needed; otherwise, no action is taken. Let the height of the spherical base component blank be H. A local discrete fitting method is used to locally correct the spherical base component blank. First, correction is performed at the location of the abrupt curvature change in the middle of the spherical base component blank, i.e., at the position where the height of the spherical base component blank is 0.5H. Figure 2 As shown.

[0053] Simultaneously, a nine-grid nut plate is used as a shaping tool; the nine-grid nut plate has nine bolts arranged in an array, and by adjusting the extension length of each bolt, a discrete curved surface is fitted to achieve the shaping of the deformed surface, such as... Figure 3 As shown.

[0054] Rough turn the inner surface of the ball-shaped component blank; the turning allowance is 2mm when rough turning the inner surface.

[0055] Artificial aging heat treatment; aging temperature is 155℃, and holding time is 32-36h.

[0056] Rough mill the outer surface of the spherical bottom component blank, and machine the annular grid. When rough milling the grid on the outer surface of the spherical bottom component blank, leave a 5mm allowance on the side walls and bottom surface. Machining proceeds from the inner ring of the top of the spherical bottom component towards the outer ring of the end frame, machining each ring of grid sequentially in a clockwise direction. Figure 4 As shown.

[0057] The residual stress at the center points of each grid along the middle curvature of the spherical base component blank was measured, and the peak values ​​of residual tensile stress in each grid were sorted, such as... Figure 5 As shown.

[0058] The outer surface mesh of the spherical bottom component blank is machined as a whole; when machining the outer surface mesh as a whole, leave a 3mm allowance on the side walls and bottom surface.

[0059] Machining proceeds from the inner ring at the top of the sphere towards the outer ring of the end frame, ring by ring. For each ring of mesh, machining is performed in the order of tensile stress peak values. Machining begins with the mesh with the highest residual tensile stress peak value, followed by the mesh with the second highest residual tensile stress peak value, and so on, until all meshes within a ring are machined. The order of tensile stress peak values ​​in each ring of mesh is consistent with the mesh corresponding to the middle curvature position along the radial direction.

[0060] The inner surface of the ball base component blank is precision machined, with a allowance of 0mm.

[0061] The residual stress at the center point of each grid along the middle curvature of the spherical bottom component blank was measured again, and the peak residual tensile stress of each grid was sorted.

[0062] When precision milling the outer surface grid of the ball bottom component blank, leave a 0mm allowance on the side walls and bottom surface.

[0063] Machining proceeds from the inner ring at the top of the sphere towards the outer ring of the end frame, ring by ring. For each ring of mesh, machining is performed in the order of tensile stress peak values, starting with the mesh with the highest residual tensile stress peak value, then machining the mesh with the second highest residual tensile stress peak value, and so on, until all mesh positions within a ring are machined. The order of tensile stress peak values ​​of each ring of mesh is consistent with the mesh corresponding to the middle curvature position along the radial direction.

[0064] The precision milling process employs a method of wall thickness measurement, compensation, machining the bottom infeed groove, machining the bottom to the required dimensions, and machining the sidewalls to the required dimensions.

[0065] Processing completed.

[0066] Inspect the roundness and flatness of the upper and lower ends, and the mesh wall thickness. Once all inspections are passed, the product is delivered. Figure 6 As shown.

[0067] This invention successfully solves the problem of precision machining of large spherical bottom components made of 2195 aluminum-lithium alloy. It adopts a tooling technology based on the product structure's own rigid support and hard top support to ensure the accuracy requirements of the thin-walled mesh of the large spherical bottom component.

[0068] This invention presents a comprehensive control method based on dimensional and stress measurement results, which effectively reduces processing deformation, minimizes the risk of deviations, and lowers development costs.

[0069] This invention effectively achieves uniform distribution and peak control of overall stress in large spherical bottom components through solution treatment, shaping, artificial aging treatment, and stress relief treatment, while ensuring material strength.

[0070] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for coordinating stress and dimensional control in the fabrication of large aluminum-lithium alloy spherical bottom components, characterized by: include: Solution treatment is performed on the blank of the spherical bottom component; Inspect the inner surface of the blank of the spherical bottom component; The blank of the spherical bottom component is shaped and corrected. Rough machining of the inner surface of the spherical base component blank; Artificial aging heat treatment; Rough mill the outer surface of the spherical bottom component blank and machine the annular mesh; The residual stress at the center point of each grid along the middle curvature of the spherical bottom component blank was measured, and the peak residual tensile stress of each grid was sorted. The outer surface mesh of the spherical bottom component blank is machined as a whole; When machining the overall outer mesh, leave a 3mm allowance on the side walls and bottom surface; Machining proceeds from the inner ring at the top of the sphere towards the outer ring of the end frame, ring by ring. For each ring of mesh, machining is performed in the order of tensile stress peak values. Machining begins with the mesh with the highest residual tensile stress peak value, followed by the mesh with the second highest residual tensile stress peak value, and so on, until all meshes within a ring are machined. The order of tensile stress peak values ​​in each ring of mesh is consistent with the mesh corresponding to the middle curvature position along the radial direction. The inner surface of the ball base component blank is precision machined, with a allowance of 0mm; The residual stress at the center point of each grid along the middle curvature of the spherical bottom component blank was measured again, and the peak values ​​of residual tensile stress in each grid were sorted. The outer surface grid of the ball-shaped component blank is precision milled; machining is completed.

2. The method for stress and dimension coordinated control of the machining of large aluminum-lithium alloy spherical bottom components according to claim 1, characterized in that: The spherical bottom component blank is made of 2195 aluminum-lithium alloy material, and the spherical bottom component blank has an inverted spherical shell structure; the solution treatment process of the spherical bottom component blank is as follows: The blank of the ball bottom component is loaded into the furnace at room temperature; after 3.5 hours, it is heated to 495℃ and held for 3 hours; after 0.5 hours, it is heated to 505℃ and held for 0.5 hours; then it is cooled by spraying; the spray flow rate is 3000t / h and the spraying time is 4min.

3. The method for stress and dimension coordinated control of the processing of large aluminum-lithium alloy spherical bottom components according to claim 1, characterized in that: An optical scanner is used to inspect the inner surface of the blank; using the bottom circle of the inner surface as a reference, a point cloud of the inner surface is formed and compared with the theoretical surface.

4. The method for stress and dimension coordinated control of the processing of large aluminum-lithium alloy spherical bottom components according to claim 3, characterized in that: The method for the correction process is as follows: When the error between the inner surface point and the theoretical surface point exceeds 5mm, it is determined that a correction process is required; otherwise, no action is taken. Let the height of the spherical bottom component blank be H. The local area discrete fitting processing method is used to perform local correction on the spherical bottom component blank. First, the correction is performed at the position where the curvature of the spherical bottom component blank changes abruptly in the middle, that is, at the position where the height of the spherical bottom component blank is 0.5H.

5. The method for stress and dimension coordinated control of the machining of large aluminum-lithium alloy spherical bottom components according to claim 4, characterized in that: A nine-grid nut plate is used as a calibration tool; the nine-grid nut plate has nine bolts arranged in an array. By adjusting the extension length of each bolt, a discrete curved surface is fitted, and the deformed surface is calibrated.

6. The method for stress and dimension coordinated control of the machining of large aluminum-lithium alloy spherical bottom components according to claim 1, characterized in that: When roughing the inner surface, the machining allowance is 2mm; the aging temperature is 155℃, and the holding time is 32-36h.

7. The method for stress and dimension coordinated control of the machining of large aluminum-lithium alloy spherical bottom components according to claim 1, characterized in that: When rough milling the outer surface grid of the spherical bottom component blank, leave a 5mm allowance on the side walls and bottom surface; process one ring at a time from the inner ring of the top of the sphere to the outer ring of the end frame, and process the grid in a clockwise direction for each ring.

8. The method for stress and dimension coordinated control of the machining of large aluminum-lithium alloy spherical bottom components according to claim 1, characterized in that: When precision milling the outer surface grid of the ball bottom component blank, leave a 0mm allowance on the side walls and bottom surface; Machining proceeds from the inner ring at the top of the sphere towards the outer ring of the end frame, ring by ring. For each ring of mesh, machining is performed in the order of tensile stress peak values, starting with the mesh with the highest residual tensile stress peak value, then machining the mesh with the second highest residual tensile stress peak value, and so on, until all mesh positions within a ring are machined. The order of tensile stress peak values ​​of each ring of mesh is consistent with the mesh corresponding to the middle curvature position along the radial direction.

9. The method for stress and dimension coordinated control of the machining of large aluminum-lithium alloy spherical bottom components according to claim 8, characterized in that: The precision milling process employs a method of wall thickness measurement, compensation, machining the bottom infeed groove, machining the bottom to the required dimensions, and machining the sidewalls to the required dimensions.

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