A processing method of an aluminum-lithium alloy oil tank cap

Abstract

The application provides a processing method of an aluminum-lithium alloy oil tank cover, which comprises the following steps: firstly, rough processing is performed on the profile features of the oil tank cover; then, after natural aging, the profile features are finely processed, and the threaded holes and countersunk holes are processed; then, the flatness of the product is detected; if the deformation is large, manual correction is performed by using a special correction tool; finally, the positioning hole with the highest precision requirement is processed again. The processing method has the advantages of simple processing process, convenient operation, high efficiency, stable product quality, realization of independent batch production of the aluminum-lithium alloy oil tank cover, and great saving of import cost.

Description

Technical Field

[0001] This invention belongs to the technical field of special material processing methods, and specifically relates to a processing method for an aluminum-lithium alloy fuel tank cap. Background Technology

[0002] With the continuous advancement of aerospace technology both domestically and internationally, many high-performance materials have emerged in the field of aerospace materials. Adding lithium to aluminum alloys forms aluminum-lithium alloys (ALLI). ALI has a lower density than aluminum alloys, and for every 1% lithium added, the density decreases by 3%, while the elastic modulus increases by 6%. ALI possesses high specific modulus and high specific strength, and can replace conventional high-strength aluminum alloys, reducing structural weight by 10%-20% and increasing stiffness by 15%-20%. It also exhibits excellent corrosion resistance and good thermal and electrical conductivity. ALI possesses high specific stiffness and excellent low-temperature resistance, allowing for weight reduction while maintaining the strength of aerospace products. It is considered a superior component material compared to traditional aluminum alloys in aerospace manufacturing. Currently, China has limited experience in the independent machining of ALI materials. Due to the unstable internal structure of forged ALI, the deformation amounts of different batches of raw materials are inconsistent, making it difficult to control the deformation patterns. During machining, the deformation is large and irregular between batches, leading to a large reliance on imports and high costs. Furthermore, testing the deformation amount for each batch through trial machining results in low production efficiency. Summary of the Invention

[0003] The technical problem solved by this invention is to provide a processing method for aluminum-lithium alloy fuel tank caps, which solves the problems of large deformation during the cutting and processing of aluminum-lithium alloy products and irregular deformation of each batch of products, resulting in high production costs and low production efficiency.

[0004] The technical solution adopted in this invention is: a machining method for an aluminum-lithium alloy fuel tank cap, using a Mikron MILL 700U high-speed milling machining center with a spindle speed of up to 20,000 r / min, which reduces the cutting force and deformation during milling of the fuel tank cap, and employing a vacuum chuck to clamp the fuel tank cap to be machined, including the following steps:

[0005] Step 1: Rough machining of surface features;

[0006] Step 1.1: Select a φ10R0 end mill to mill the flat surface of the oil tank cover, with a speed of 16000 r / min, a feed rate of 3000-4000 mm / min, and a depth of cut of 0.2 mm;

[0007] Step 1.2: Use a φ10R1 bullnose cutter to mill the beveled surface of the oil tank cover, with a rotation speed of 16000 r / min, a feed rate of 3000-4000 mm / min, and a depth of cut of 0.2 mm;

[0008] Step 1.3: Use a φ4 ball end mill to machine the sealing groove of the oil tank cover, with a rotation speed of 18000 r / min, a feed rate of 2000-3000 mm / min, a depth of cut of 0.1 mm, and a surface roughness of Ra0.8.

[0009] Step 2: After rough machining, perform natural aging for 8 hours to fully release cutting stress;

[0010] Step 3: Finish the surface features to the dimensions required by the design;

[0011] Step 3.1: Select a φ10R0 end mill to mill the flat surface of the oil tank cover, with a speed of 16000 r / min, a feed rate of 3000-4000 mm / min, and a depth of cut of 0.2 mm;

[0012] Step 3.2: Use a φ10R1 bullnose cutter to mill the inclined surface of the oil tank cover, with a rotation speed of 16000 r / min, a feed rate of 3000-4000 mm / min, and a depth of cut of 0.2 mm;

[0013] Step 3.3: Use a φ4 ball end mill to machine the sealing groove of the oil tank cover, with a rotation speed of 18000 r / min, a feed rate of 2000-3000 mm / min, and a cutting depth of 0.1 mm;

[0014] Step 4, Machining of threaded holes and countersunk holes: Use a φ6R0 end mill to machine the bottom hole at a speed of 4000 r / min, a feed rate of 100-200 mm / min, and a depth of cut of 0.5 mm. Then use a thread milling cutter to mill the thread at a speed of 1000 r / min and a feed rate of 300 mm / min.

[0015] Step 5: Fuel tank cap flatness deformation detection: If the flatness deformation of the fuel tank cap is greater than 0.3mm, manual aging is performed using a special straightening fixture;

[0016] Step 6: Machining 3 positioning holes: Use a φ5R0 end mill to mill 3 positioning holes at a speed of 6000r / min, a feed rate of 200-300mm / min, and a cutting depth of 1mm.

[0017] Preferably, the allowance on one side of the rough machining in step 1 is 1.5mm. After repeated experiments, the deformation of the aluminum-lithium alloy fuel tank cap after rough machining is 0.8-1.2mm. Therefore, the allowance on one side of the rough machining is 1.5mm to reduce the scrap rate of the product.

[0018] Preferably, the straightening fixture in step 5 includes a base, a pressure block, and screws for connecting the base and the pressure block. The base is a flat plate structure, and the flatness of the annular area on the upper surface of the base that contacts the fuel tank cap is 0.02, which can straighten the fuel tank cap to a flatness within 0.1. Threaded holes are machined on the base at positions corresponding to the threaded holes of the fuel tank cap. The pressure block consists of four pieces, including two arc-shaped strips and two straight strips. The four pressure blocks are connected end to end to form an annulus. The shape of the lower surface of the pressure block matches the shape of the upper surface of the fuel tank cap at the corresponding position. The upper surface of the pressure block is flat, and threaded holes are machined on the pressure block at positions corresponding to the threaded holes of the fuel tank cap. The screws pass through the threaded holes of the pressure block and the fuel tank cap sequentially from top to bottom and are threaded to the base to clamp the fuel tank cap between the pressure block and the base.

[0019] Preferably, the artificial aging in step 5 involves placing the product in a heat treatment furnace after installing it in the alignment fixture, maintaining the temperature at 110±5℃ for 3-4 hours.

[0020] Preferably, the minimum tolerance of the positioning hole processed in step 6 is 0.012 mm.

[0021] Preferably, the base and the pressure block are each machined with two inner and two outer threaded holes at corresponding positions on the top and bottom. The inner threaded hole is coaxial with the threaded hole of the fuel tank cap, and the diameter of the inner threaded hole is smaller than the diameter of the threaded hole of the fuel tank cap to prevent damage to the threaded hole of the fuel tank cap. The outer threaded hole is located on the outside of the fuel tank cap.

[0022] The beneficial effects of this invention are: the processing process is simple and easy to operate; by selecting processing equipment and cutting heads, the surface quality of the fuel tank cap is satisfied while improving efficiency; the vacuum suction cup clamping saves the time of the pressure plate; the cutting head connection caused by the pressure plate in the sealing groove is avoided; the processing efficiency is high and the product quality is stable; more than 100 qualified products have been processed with a 100% pass rate; the independent mass production of aluminum-lithium alloy fuel tank caps has been realized, which greatly saves import costs. Attached Figure Description

[0023] Figure 1 This is a top view of the aluminum-lithium alloy fuel tank cap.

[0024] Figure 2 This is a bottom view of the aluminum-lithium alloy fuel tank cap.

[0025] Figure 3 This is a structural diagram of the calibration fixture in use.

[0026] Figure 4 This is a schematic diagram of the base and pressure block structure of the alignment fixture.

[0027] Figure 5 This is a structural diagram of the base.

[0028] Reference numerals: 1-base, 2-pressure block, 3-screw, 4-oil tank cap, 101-annular area. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] like Figure 1 and Figure 2 The image shows an aluminum-lithium alloy fuel tank cap 4, made of 01420T1 aluminum-lithium alloy. The cap 4 has multiple ribs (3mm thin), two sealing grooves with a roughness of Ra0.8 along the entire circumference, a bottom surface thickness of only 2mm, 40 threaded holes and countersunk holes, and three φ102 positioning holes. + +0 0.. 1 1 2 5 5 7 φ94 ++0 0.. 1 1 2 5 5 7 φ6 + +0 0.. 0 0 3 4 2 4 The minimum tolerance is 0.012mm, and the thinnest part of the bottom surface is only 2mm. When removing the allowance during milling, deformation and deviation are likely to occur. The surface roughness of the sealing groove is 0.8, which requires high-speed machine tool processing, otherwise the surface roughness requirement cannot be met. When processing the three positioning holes with small tolerances, real-time measurement is required to perform final finishing based on the allowance to be processed to ensure the tolerance requirements. The oil tank cover 4 is processed by vacuum suction cup, which can save clamping time. Therefore, the threaded hole and countersunk head need to be finished before processing. However, the oil tank cover may deform after processing the threaded hole and countersunk head, so final calibration is also required.

[0031] The 01420T1 aluminum-lithium alloy fuel tank cap is an independently developed product. Through exploration and testing, it was found that the machining deformation of the aluminum-lithium alloy fuel tank cap 4 is more severe than that of other aluminum alloy products. For ordinary aluminum alloy parts with the same size and structure as the fuel tank cap 4, the deformation is half that of aluminum-lithium alloy. Therefore, when machining aluminum-lithium alloy, it is necessary to reduce the cutting force, use high speed and small depth of cut. Suitable cutting parameters were explored to balance deformation and efficiency based on the characteristics of the aluminum-lithium alloy fuel tank cap 4.

[0032] Therefore, this invention proposes a machining method for an aluminum-lithium alloy fuel tank cap. Considering the characteristics of the aluminum-lithium alloy fuel tank cap 4, a high-speed milling machining center, a suitable clamping method, and appropriate cutting tools and parameters are rationally selected to achieve the machining of the aluminum-lithium alloy fuel tank cap. Specifically, a Mikron MILL 700U high-speed milling machining center is selected, with a spindle speed of 20000 r / min. The low cutting force during milling of the fuel tank cap reduces deformation. A vacuum chuck is used to clamp the fuel tank cap to be machined. The specific steps include:

[0033] Step 1: Rough machining of surface features. The allowance for rough machining on one side is 1.5mm. After repeated experiments, it was found that the deformation of the aluminum-lithium alloy fuel tank cover 4 after rough machining is 0.8-1.2mm. Therefore, the allowance of 1.5mm on one side during rough machining reduces the scrap rate of the product.

[0034] Step 1.1: Select a φ10R0 end mill to mill the flat surface of the oil tank cover, with a speed of 16000 r / min, a feed rate of 3000-4000 mm / min, and a depth of cut of 0.2 mm;

[0035] Step 1.2: Use a φ10R1 bullnose cutter to mill the beveled surface of the oil tank cover, with a rotation speed of 16000 r / min, a feed rate of 3000-4000 mm / min, and a depth of cut of 0.2 mm;

[0036] Step 1.3: Use a φ4 ball end mill to machine the sealing groove of the oil tank cover, with a rotation speed of 18000 r / min, a feed rate of 2000-3000 mm / min, a depth of cut of 0.1 mm, and a surface roughness of Ra0.8.

[0037] Step 2: After rough machining, perform natural aging for 8 hours to fully release cutting stress;

[0038] Step 3: Finish the surface features to the dimensions required by the design;

[0039] Step 3.1: Select a φ10R0 end mill to mill the flat surface of the oil tank cover, with a speed of 16000 r / min, a feed rate of 3000-4000 mm / min, and a depth of cut of 0.2 mm;

[0040] Step 3.2: Use a φ10R1 bullnose cutter to mill the inclined surface of the oil tank cover, with a rotation speed of 16000 r / min, a feed rate of 3000-4000 mm / min, and a depth of cut of 0.2 mm;

[0041] Step 3.3: Use a φ4 ball end mill to machine the sealing groove of the oil tank cover, with a rotation speed of 18000 r / min, a feed rate of 2000-3000 mm / min, and a cutting depth of 0.1 mm;

[0042] Step 4, Machining of threaded holes and countersunk holes: Use a φ6R0 end mill to machine the bottom hole at a speed of 4000 r / min, a feed rate of 100-200 mm / min, and a depth of cut of 0.5 mm. Then use a thread milling cutter to mill the thread at a speed of 1000 r / min and a feed rate of 300 mm / min.

[0043] Step 5, Fuel tank cap 4 Flatness deformation detection: If the flatness deformation of the fuel tank cap is greater than 0.3mm, use a special straightening fixture for manual aging. The manual aging process is to put the product into the heat treatment furnace after installing it in the straightening fixture and keep it at a temperature of 110±5℃ for 3-4 hours.

[0044] Step 6: Machining 3 positioning holes with a minimum tolerance of 0.012mm: Use a φ5R0 end mill to mill the 3 positioning holes at a speed of 6000r / min, a feed rate of 200-300mm / min, and a depth of cut of 1mm.

[0045] like Figures 3 to 5 As shown, the straightening fixture used in step 5 includes a base 1, a pressure block 2, and screws 3 for connecting the base 1 and the pressure block 2. The base 1 is a flat plate structure. The annular area 101 of the upper surface of the base 1 that contacts the fuel tank cap 4 has a flatness of 0.02, which can straighten the fuel tank cap 4 to a flatness of less than 0.1. Threaded holes are machined on the base 1 at positions corresponding to the threaded holes of the fuel tank cap 4. There are four pressure blocks 2, including two arc-shaped strips and two straight strips. The four pressure blocks 2 are connected end to end to form an annular shape. The shape of the lower surface of the pressure block 2 matches the shape of the upper surface of the fuel tank cap 4 at the corresponding position. The upper surface of the pressure block 2 is flat. Threaded holes are machined on the pressure block 2 at positions corresponding to the threaded holes of the fuel tank cap 4. The screws 3 pass through the threaded holes of the pressure block 2 and the fuel tank cap 4 from top to bottom and are threaded to the base 1 to clamp the fuel tank cap 4 between the pressure block 2 and the base 1. The base 1 and the pressure block 2 are each machined with two rings of threaded holes, one inner and one outer, at corresponding positions on the top and bottom. The inner ring of threaded holes is coaxial with the threaded hole of the fuel tank cover 4, and the diameter of the inner ring of threaded holes is smaller than the diameter of the threaded hole of the fuel tank cover 4 to prevent damage to the threaded hole of the fuel tank cover 4. The outer ring of threaded holes is located on the outside of the fuel tank cover 4.

[0046] The above describes specific embodiments of the present invention and the technical principles employed. Any modifications or equivalent transformations based on the technical solutions of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for processing an aluminum-lithium alloy fuel tank cap, characterized in that, The high-speed milling machining center uses a Mikron MILL700U spindle with a spindle speed of 20,000 r / min. A vacuum chuck is used to clamp the oil tank cover to be machined. The process includes the following steps: Step 1: Rough machining of surface features; Step 1.1: Select a φ10R0 end mill to mill the flat surface of the oil tank cover, with a speed of 16000 r / min, a feed rate of 3000-4000 mm / min, and a depth of cut of 0.2 mm; Step 1.2: Use a φ10R1 bullnose cutter to mill the beveled surface of the oil tank cover, with a rotation speed of 16000 r / min, a feed rate of 3000-4000 mm / min, and a depth of cut of 0.2 mm; Step 1.3: Use a φ4 ball end mill to machine the sealing groove of the oil tank cover, with a rotation speed of 18000 r / min, a feed rate of 2000-3000 mm / min, a depth of cut of 0.1 mm, and a surface roughness of Ra0.

8. Step 2: After rough machining, perform natural aging for 8 hours to fully release cutting stress; Step 3: Finish the surface features to the dimensions required by the design; Step 3.1: Select a φ10R0 end mill to mill the flat surface of the oil tank cover, with a speed of 16000 r / min, a feed rate of 3000-4000 mm / min, and a depth of cut of 0.2 mm; Step 3.2: Use a φ10R1 bullnose cutter to mill the inclined surface of the oil tank cover, with a rotation speed of 16000 r / min, a feed rate of 3000-4000 mm / min, and a depth of cut of 0.2 mm; Step 3.3: Use a φ4 ball end mill to machine the sealing groove of the oil tank cover, with a rotation speed of 18000 r / min, a feed rate of 2000-3000 mm / min, and a cutting depth of 0.1 mm; Step 4, Machining of threaded holes and countersunk holes: Use a φ6R0 end mill to machine the bottom hole at a speed of 4000 r / min, a feed rate of 100-200 mm / min, and a depth of cut of 0.5 mm. Then use a thread milling cutter to mill the thread at a speed of 1000 r / min and a feed rate of 300 mm / min. Step 5: Fuel tank cap flatness deformation detection: If the flatness deformation of the fuel tank cap is greater than 0.3mm, manual aging is performed using a special straightening fixture; Step 6: Machining 3 positioning holes: Use a φ5R0 end mill to mill 3 positioning holes at a speed of 6000r / min, a feed rate of 200-300mm / min, and a cutting depth of 1mm.

2. The processing method of an aluminum-lithium alloy fuel tank cap according to claim 1, characterized in that: The roughing allowance in step 1 is 1.5mm on one side.

3. The processing method of an aluminum-lithium alloy fuel tank cap according to claim 1, characterized in that: The alignment fixture in step 5 includes a base, pressure blocks, and screws for connecting the base and pressure blocks. The base is a flat plate structure, and the flatness of the annular area on the upper surface of the base that contacts the fuel tank cap is 0.

02. Threaded holes are machined on the base at positions corresponding to the threaded holes on the fuel tank cap. There are four pressure blocks, including two arc-shaped strips and two straight strips. The four pressure blocks are connected end to end to form an annulus. The shape of the lower surface of the pressure block matches the shape of the upper surface of the fuel tank cap at the corresponding position. The upper surface of the pressure block is flat, and threaded holes are machined on the pressure block at positions corresponding to the threaded holes on the fuel tank cap. The screws pass through the threaded holes of the pressure blocks and the fuel tank cap from top to bottom and are threaded to the base to clamp the fuel tank cap between the pressure blocks and the base.

4. The processing method of an aluminum-lithium alloy fuel tank cap according to claim 1, characterized in that: The artificial aging process in step 5 involves placing the product in a heat treatment furnace after it has been installed in a calibration fixture, maintaining a temperature of 110±5℃ for 3-4 hours.

5. The processing method of an aluminum-lithium alloy fuel tank cap according to claim 1, characterized in that: The minimum tolerance for the positioning hole processed in step 6 is 0.012 mm.

6. The processing method of an aluminum-lithium alloy fuel tank cap according to claim 3, characterized in that: The base and the pressure block are each machined with two inner and two outer threaded holes at corresponding positions on the top and bottom. The inner threaded hole is coaxial with the threaded hole of the fuel tank cap, and the diameter of the inner threaded hole is smaller than the diameter of the threaded hole of the fuel tank cap. The outer threaded hole is located on the outside of the fuel tank cap.

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