Stress and size cooperative control machining method for large aluminum-lithium alloy ball bottom component

Abstract

The invention relates to a stress and size cooperative control machining method for a large aluminum-lithium alloy ball bottom component, and belongs to the technical field of precision machining. The ball bottom component blank is subjected to solution treatment; the inner molded surface of the ball bottom component blank is detected; carrying out shape correction treatment on the ball bottom component blank; roughly turning the inner molded surface of the ball bottom component blank; performing artificial actual heat treatment; roughly milling the outer molded surface of the ball bottom component blank; measuring the residual stress of each grid center point of a circle at the middle curvature position of the ball bottom component blank, and carrying out peak value sorting; overall machining is conducted on an outer profile grid of the ball bottom component blank; the inner molded surface of the ball bottom component blank is subjected to finish turning, and the allowance is 0 mm; measuring the residual stress of the center point of each grid of one circle of the middle curvature position of the ball bottom member blank again, and sequencing the residual tensile stress peak values of each grid; performing finish milling on an outer molded surface grid of the ball bottom component blank; machining is completed; according to the method, the problems that stress release suddenly changes, deformation is out of tolerance and the like in the machining process of the large ball bottom component of the 2195 aluminum-lithium alloy are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of precision machining, and relates to a method for collaborative control of stress and size in the machining of large aluminum-lithium alloy spherical bottom components. Background Art

[0002] With the development of fields such as manned spaceflight and deep space exploration, the requirements for high reliability, long life, and lightweight of new-generation spacecraft have been greatly improved, and the integrated monolithic structure has become the development trend. Due to its low density, high strength, high specific stiffness, good heat resistance, and good corrosion resistance, and being able to be strengthened by heat treatment, aluminum-lithium alloy has gradually been applied in the aerospace field.

[0003] In the current aerospace field, 2195 aluminum-lithium alloy is mainly used to prepare load-bearing components such as spherical bottoms and storage tanks of large carriers. In the traditional multi-process manufacturing process of large spherical bottom components of spacecraft, the following problems will exist:

[0004] (1) The yield strength of 2195 aluminum-lithium alloy is high. During the multi-process manufacturing process of hot and cold, the non-uniformity of internal stress distribution becomes larger, and the peak stress is high;

[0005] (2) During the machining process of large spherical bottom components, the material removal amount is large, the deformation during the machining process is large, and the size is uncontrollable;

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

[0007] The technical problem solved by the present invention is: overcoming the deficiencies of the prior art, proposing a method for collaborative control of stress and size in the machining of large aluminum-lithium alloy spherical bottom components, and solving problems such as sudden stress release and deformation out-of-tolerance during the machining process of large spherical bottom components of 2195 aluminum-lithium alloy.

[0008] The technical solution adopted by the present invention to solve the problem is:

[0009] A method for collaborative control of stress and size in the machining of large aluminum-lithium alloy spherical bottom components, comprising:

[0010] Performing solution treatment on the blank of the spherical bottom component;

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

[0012] Performing shape correction treatment on the blank of the spherical bottom component;

[0013] Rough turning the inner surface of the blank of the spherical bottom component;

[0014] Performing artificial aging heat treatment;

[0015] Rough milling the outer surface of the blank of the spherical bottom component and machining a circular grid;

[0016] Measure the residual stress at the center points of each grid in a circle at the middle curvature position of the blank of the spherical bottom component, and sort the peak values of the residual tensile stress for each grid;

[0017] Overall machine the outer surface grid of the blank of the spherical bottom component;

[0018] Precision turn the inner surface of the blank of the spherical bottom component with a machining allowance of 0 mm;

[0019] Measure the residual stress at the center points of each grid in a circle at the middle curvature position of the blank of the spherical bottom component again, and sort the peak values of the residual tensile stress for each grid;

[0020] Precision mill the outer surface grid of the blank of the spherical bottom component; machining is completed.

[0021] In the above stress and size coordinated control machining method for the large aluminum-lithium alloy spherical bottom component, the blank of the spherical bottom component is made of 2195 aluminum-lithium alloy material, and the blank of the spherical bottom component is an inverted spherical shell structure; the solution treatment process of the blank of the spherical bottom component is specifically as follows:

[0022] Load the blank of the spherical bottom component into the furnace at room temperature; heat it to 495 °C in 3.5 h and hold for 3 h; heat it to 505 °C in 0.5 h and hold for 0.5 h; perform spray cooling treatment; wherein, the spray water volume is 3000 t / h and the spray time is 4 min.

[0023] In the above stress and size coordinated control machining method for the large aluminum-lithium alloy spherical bottom component, use an optical scanner to detect the inner surface of the blank; with the bottom circle of the inner surface as the reference, form the inner surface point cloud and compare it with the theoretical surface.

[0024] In the above stress and size coordinated control machining method for the large aluminum-lithium alloy spherical bottom component, the method of shape correction is as follows:

[0025] When the error between the inner surface point positions and the theoretical surface point positions exceeds 5 mm, it is judged that shape correction is required; otherwise, no action is taken; assume the height of the blank of the spherical bottom component is H, and use the local area discrete fitting processing method to perform local shape correction on the blank of the spherical bottom component. First, perform shape correction at the position where the middle curvature of the blank of the spherical bottom component changes suddenly, that is, the position where the height of the blank of the spherical bottom component is 0.5H.

[0026] In the above stress and size coordinated control machining method for the large aluminum-lithium alloy spherical bottom component, use a nine-square grid nut plate as the shape correction tool; there are 9 bolts distributed in an array on the nine-square grid nut plate, and the fitting discrete surface is realized by adjusting the protruding lengths of each bolt to perform shape correction on the deformed surface.

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

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

[0029] In the above-mentioned stress and size coordinated control processing method for the large aluminum-lithium alloy spherical bottom component, when machining the outer surface grid as a whole, a 3-mm allowance is left on the side wall and the bottom surface;

[0030] Machining is carried out circle by circle from the inner circle at the top of the sphere to the outer circle of the end frame; for each circle of grids, machining is carried out in the order of the peak tensile stress values; machining starts from the grid with the highest peak residual tensile stress, and then the grid with the second-highest peak residual tensile stress is machined, and so on in a cycle until all the grids within one circle are machined; the order of the peak tensile stress values of each circle of grids is consistent with the corresponding grids at the middle curvature position along the radial direction.

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

[0032] Machining is carried out circle by circle from the inner circle at the top of the sphere to the outer circle of the end frame; for each circle of grids, machining is carried out in the order of the peak tensile stress values, starting from the grid with the highest peak residual tensile stress, and then the grid with the second-highest peak residual tensile stress is machined, and so on in a cycle until all the grid positions within one circle are machined; the order of the peak tensile stress values of each circle of grids is consistent with the corresponding grids at the middle curvature position along the radial direction.

[0033] In the above-mentioned stress and size coordinated control processing method for the large aluminum-lithium alloy spherical bottom component, finish milling is carried out in the way of wall thickness measurement - compensation - machining the bottom feed groove - machining the bottom surface to the size - machining the side wall to the size.

[0034] The beneficial effects of the present invention compared with the prior art are as follows:

[0035] (1) The present invention successfully solves the problem of precision machining of large spherical bottom components of 2195 aluminum-lithium alloy. By adopting the self-rigid support of the product structure and the hard top support fixture technology, the precision requirements of the thin-walled grids of the large spherical bottom components are ensured.

[0036] (2) The present invention forms a comprehensive regulation method based on the measurement results of size and stress, effectively reducing the machining deformation, reducing the risk of out-of-tolerance, and reducing the research and development cost.

[0037] (3) Through solution treatment + shape correction + artificial aging treatment + stress relief treatment, the present invention effectively realizes the uniform distribution and peak control of the overall stress of the large spherical bottom components and ensures the material strength. Description of the Drawings

[0038] Figure 1 Schematic diagram of the blank of the spherical bottom component of the present invention;

[0039] Figure 2 Schematic diagram of the calibration position of the present invention;

[0040] Figure 3 Schematic diagram of the calibration tool of the present invention;

[0041] Figure 4 Schematic diagram of the overall machining of the outer surface grid of the present invention;

[0042] Figure 5 Schematic diagram of the residual stress measurement position of the present invention;

[0043] Figure 6 Schematic diagram of the final inspection of the product of the present invention. Specific embodiments

[0044] The present invention will be further described below in conjunction with embodiments.

[0045] The present invention provides a method for coordinated control of stress and dimensional accuracy in the machining of large spherical bottom components made of 2195 aluminum-lithium alloy, which solves problems such as sudden stress release and deformation out-of-tolerance during the machining of large spherical bottom components made of 2195 aluminum-lithium alloy.

[0046] The method for coordinated control of stress and dimensions in the machining of large aluminum-lithium alloy spherical bottom components specifically includes the following steps:

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

[0048] Load the blank of the spherical bottom component into the furnace at room temperature; heat it to 495 °C in 3.5 h and hold for 3 h; heat it to 505 °C in 0.5 h and hold for 0.5 h; perform spray cooling treatment; wherein, the spray water volume is 3000 t / h and the spray time is 4 min.

[0049] Inspect the inner surface of the blank of the spherical bottom component.

[0050] Perform calibration treatment on the blank of the spherical bottom component.

[0051] Use an optical scanner to inspect the inner surface of the blank; take the bottom circle of the inner surface as the reference to form the inner surface point cloud and compare it with the theoretical surface. The calibration treatment method is:

[0052] When the error between the inner surface point position and the theoretical surface point position exceeds 5 mm, it is judged that shape correction is required; otherwise, no action is taken. Let the height of the spherical bottom component blank be H, and local area discrete fitting processing is used to perform local shape correction on the spherical bottom component blank. First, shape correction is performed at the position where the curvature changes suddenly in the middle of the spherical bottom component blank, that is, the position where the height of the spherical bottom component blank is 0.5H, as Figure 2 shown.

[0053] At the same time, a nine-grid nut plate is used as a shape correction tool; there are 9 bolts distributed in an array on the nine-grid nut plate, and the fitting discrete surface is realized by adjusting the protruding length of each bolt to perform shape correction on the deformed surface, as Figure 3 shown.

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

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

[0056] Rough-mill the outer surface of the spherical bottom component blank and process the annular grid; when rough-milling the outer surface grid of the spherical bottom component blank, a 5 mm allowance is left on the side wall and the bottom surface; process circle by circle from the inner circle at the top of the ball to the outer circle of the end frame. For each circle of grid, process the grid in clockwise order, as Figure 4 shown.

[0057] Measure the residual stress of the center points of each grid in one circle at the middle curvature position of the spherical bottom component blank, and sort the peak values of the residual tensile stress of each grid, as Figure 5 shown.

[0058] Overall process the outer surface grid of the spherical bottom component blank; when overall processing the outer surface grid, a 3 mm allowance is left on the side wall and the bottom surface.

[0059] Process circle by circle from the inner circle at the top of the ball to the outer circle of the end frame; for each circle of grid, process in the order of the peak value of the tensile stress; start machining from the grid with the highest peak value of the residual tensile stress, and then machine the grid with the second highest peak value of the residual tensile stress, and so on until all the grids in one circle are processed; the order of the peak values of the tensile stress of each circle of grid is consistent with the corresponding grid at the middle curvature position along the radial direction.

[0060] Finish-turn the inner surface of the spherical bottom component blank with a 0 mm allowance.

[0061] Measure the residual stress of the center points of each grid in one circle at the middle curvature position of the spherical bottom component blank again, and sort the peak values of the residual tensile stress of each grid.

[0062] Finish-mill the outer surface grid of the spherical bottom component blank; when finish-milling the outer surface grid of the spherical bottom component blank, a 0 mm allowance is left on the side wall and the bottom surface.

[0063] Machining is carried out ring by ring from the inner ring at the top of the sphere towards the outer ring of the end frame; for each ring of grids, machining is carried out in the order of the peak tensile stress values. Machining starts from the grid with the highest peak residual tensile stress, and then the grid with the second highest peak residual tensile stress is machined, and so on in a cycle until all grid positions in one ring are machined; the order of the peak tensile stress values of the grids in each ring is consistent with the corresponding grids at the middle curvature position along the radial direction.

[0064] Finish milling is carried out by means of wall thickness measurement - compensation - machining the bottom feed groove - machining the bottom to the dimension - machining the side wall to the dimension.

[0065] The machining is completed.

[0066] Inspect the roundness and flatness at the upper and lower ports, and the wall thickness of the grids. After all inspections are qualified, deliver the product, as Figure 6 shown.

[0067] The present invention has successfully solved the problem of precision machining of large spherical bottom components made of 2195 aluminum - lithium alloy. By adopting the technology of self - rigid support of the product structure and hard - top support tooling, the precision requirements of the thin - wall grids of large spherical bottom components are ensured.

[0068] The present invention has formed a comprehensive control method based on the measurement results of dimensions and stresses, effectively reducing machining deformation, reducing the risk of out - of - tolerance, and reducing the research and development cost.

[0069] Through solution treatment + shape correction + artificial aging treatment + stress relief treatment, the present invention effectively realizes the uniform distribution and peak control of the overall stress of large spherical bottom components and ensures the material strength.

[0070] Although the present invention has been disclosed above with preferred embodiments, it is not used to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the disclosed methods and technical contents without departing from the spirit and scope of the present invention. Therefore, any simple modification, equivalent change, and modification made to the above embodiments according to the technical essence of the present invention without departing from the technical solution of the present invention all fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for coordinated control of stress and size of a large aluminum-lithium alloy ball bottom component, characterized in that: include: Performing solution treatment on the ball bottom component blank; Inspect the inner surface of the ball bottom component blank; Perform shape correction on the ball bottom component blank; Rough turning of the inner surface of the ball bottom component blank; Artificial effective heat treatment; Rough milling of the outer surface of the ball bottom component blank and processing of the annular grid; Measure the residual stress of each grid center point in a circle of the middle curvature position of the ball bottom component blank, and sort the residual tensile stress peak values ​​of each grid; Integral processing of the outer surface mesh of the ball bottom component blank; Finish turning the inner surface of the ball bottom component blank, with a margin of 0mm; The residual stress of each grid center point in a circle of the middle curvature position of the ball bottom component blank is measured again, and the peak value of the residual tensile stress of each grid is sorted; Finish milling the outer surface mesh of the ball bottom component blank; complete the processing.

2. The stress and size coordinated control processing method of a large aluminum-lithium alloy ball bottom component according to claim 1 is characterized in that: The ball bottom component blank is made of 2195 aluminum-lithium alloy material, and the ball bottom component blank is an inverted spherical shell structure; the solid solution process of the ball bottom component blank is specifically as follows: The spherical bottom component blank is loaded into the furnace at room temperature; the temperature is raised to 495℃ for 3.5h and kept for 3h; the temperature is raised to 505℃ for 0.5h and kept for 0.5h; and spray cooling treatment is performed; the spray water volume is 3000t / h and the spray time is 4min.

3. The stress and size coordinated control processing method of a large aluminum-lithium alloy ball bottom component according to claim 1 is characterized in that: An optical scanner is used to detect the inner surface of the blank; taking 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 stress and size coordinated control processing method of a large aluminum-lithium alloy ball bottom component according to claim 3 is characterized in that: The method of the shape correction processing is: When the error between the inner surface point and the theoretical surface point exceeds 5mm, it is determined that correction processing is required; otherwise, no action is taken; assuming that the height of the spherical bottom component blank is 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 on the position where the curvature mutation occurs in the middle of the spherical bottom component blank, that is, the position where the height of the spherical bottom component blank is 0.5H.

5. The stress and size coordinated control processing method of a large aluminum-lithium alloy ball bottom component according to claim 4 is characterized in that: The nine-grid nut plate is used as a shape correction tool; 9 bolts are distributed in an array on the nine-grid nut plate, and the discrete surface is fitted by adjusting the extension length of each bolt to correct the deformation surface.

6. The stress and size coordinated control processing method of a large aluminum-lithium alloy ball bottom component according to claim 1 is characterized in that: When rough turning the inner surface, the turning allowance is 2mm; the aging temperature is 155℃, and the holding time is 32-36h.

7. The stress and size coordinated control processing method of a large aluminum-lithium alloy ball bottom component according to claim 1 is characterized in that: When rough milling the mesh of the outer surface of the ball bottom component blank, leave a 5mm margin on the side wall and the bottom surface; process circle by circle from the inner circle of the ball top to the outer circle of the end frame, and for each circle of mesh, process the mesh in a clockwise direction.

8. The stress and size coordinated control processing method of a large aluminum-lithium alloy ball bottom component according to claim 1 is characterized in that: When machining the mesh of the outer surface as a whole, leave a 3mm margin on the side wall and bottom surface; Machining is performed circle by circle from the inner circle of the ball top to the outer circle of the end frame; for each circle of meshes, machining is performed in the order of tensile stress peak values; machining starts from the mesh with the highest residual tensile stress peak value, and then the mesh with the second highest residual tensile stress peak value is machined, and this cycle is repeated until all meshes in one circle are processed; the order of tensile stress peak values ​​of each circle of meshes is consistent with the corresponding mesh at the middle curvature position along the radial direction.

9. The stress and size coordinated control processing method of a large aluminum-lithium alloy ball bottom component according to claim 1 is characterized in that: When fine milling the outer surface mesh of the ball bottom component blank, leave 0mm margin on the side wall and bottom surface; The meshes are machined circle by circle from the inner circle of the ball top to the outer circle of the end frame. For each circle of meshes, they are machined in the order of tensile stress peak values, starting with the mesh with the highest residual tensile stress peak value, and then the mesh with the second highest residual tensile stress peak value, and this cycle continues until all mesh positions within a circle are machined. The order of tensile stress peak values ​​of each circle of meshes is consistent with the mesh corresponding to the middle curvature position along the radial direction.

10. The stress and size coordinated control processing method of a large aluminum-lithium alloy ball bottom component according to claim 9, characterized in that: The finishing milling is carried out by measuring the wall thickness - compensating - machining the bottom surface feed groove - machining the bottom surface to size - machining the side wall to size.

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