A large-diameter aluminum alloy thin-walled pipe end ultra-low temperature plastic sealing device and a use method thereof

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By combining liquid nitrogen cryogenic treatment with a flaring device, a seamless connection between large-diameter aluminum alloy thin-walled tubes and flanges was achieved, solving the problems of complex and inefficient existing sealing processes and realizing a high-efficiency, green, and seamless plastic connection.

CN116532569BActive Publication Date: 2026-07-14HARBIN INST OF TECH

Patent Information

Authority / Receiving Office: CN · China
Patent Type: Patents(China)
Current Assignee / Owner: HARBIN INST OF TECH
Filing Date: 2023-05-25
Publication Date: 2026-07-14

AI Technical Summary

Technical Problem

The existing sealing process for large-diameter aluminum alloy thin-walled tubes is complex, has low production efficiency, cannot achieve large-area and efficient sealing, and is prone to burn-through during fusion welding, resulting in poor weld quality, numerous structural defects, and easy cracking.

Method used

The device employs an ultra-low temperature plastic sealing device, which utilizes liquid nitrogen cryogenic treatment combined with a flaring device and a flattening device. It achieves a seamless connection between the aluminum alloy thin-walled tube and the flange through a segmented die and a prestressed ring. The device uses a flaring arm and rolling elements for local folding and expansion, and finally flattens it with a horizontal pressure plate.

Benefits of technology

It achieves efficient, green, and seamless plastic connection between large-diameter aluminum alloy thin-walled pipes and flanges, reducing thermal defects and cracking tendency, and has the advantages of simple process, good sealing performance, and high efficiency and speed.

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Abstract

The utility model relates to a kind of large-diameter aluminum alloy thin-walled pipe end ultra-low temperature plastic sealing device and its using method, it belongs to light alloy plate pipe connecting technical field.Solve existing large-diameter aluminum alloy thin-walled pipe sealing process complex, production efficiency is low, cannot large area, high-efficiency plugging, and large-diameter aluminum thin-walled pipe fusion welding is easy to burn through, and weld quality is poor, and many organization defects, easy to crack problem.Device, it includes sealing folding device and sealing flattening device;Method: one, aluminum alloy thin-walled pipe is placed in flange, and sealing layer is set between aluminum alloy thin-walled pipe and flange, obtains to be sealed piece, to be sealed piece is placed in the inner recess center of split concave mould, and is clamped and positioned;Two, local cryogenic treatment;Three, to be sealed piece end is reamed and extruded in groove inner cavity;Four, using horizontal pressing plate, the folding position of to be sealed piece of end folding is flattened.

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Description

Technical Field

[0001] This invention belongs to the field of light alloy plate and tube connection technology. Background Technology

[0002] Large-diameter aluminum alloy thin-walled tubes are widely used in petrochemical, coal gas, natural gas, and aerospace cryogenic transportation fields. Aluminum alloy thin-walled tubes are typically sealed using traditional fusion-welded flanges followed by blind flange sealing. However, this sealing process is complex, has low production efficiency, cannot achieve large-area, efficient sealing, and the fusion welding of large-diameter aluminum thin-walled tubes is prone to burn-through, resulting in poor weld quality, numerous structural defects, easy cracking, and poor safety.

[0003] Therefore, how to achieve plastic sealing and high-quality seamless connection of large-diameter aluminum alloy thin-walled tube ends, while reducing the thermal defects and cracking tendency of the plastic sealing joint, has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0004] This invention aims to solve the problems of complex sealing processes, low production efficiency, inability to seal large areas efficiently, and easy burning-through of large-diameter aluminum thin-walled tubes during fusion welding, resulting in poor weld quality, numerous structural defects, and easy cracking. Therefore, it provides an ultra-low temperature plastic sealing device for the end of large-diameter aluminum thin-walled tubes and its usage method.

[0005] A cryogenic plastic sealing device for the end of a large-diameter aluminum alloy thin-walled tube, comprising a sealing folding device and a sealing flattening device;

[0006] The sealing and folding device comprises a prestressed ring, a segmented die, and a flaring device. The segmented die is fitted inside the prestressed ring, and the prestressed ring and the segmented die are press-fitted. An inner groove is provided on the upper surface of the segmented die, and the inner groove consists of a groove opening and an inner cavity, with the cross-sectional area of the inner cavity being larger than the cross-sectional area of the groove opening. The flaring device comprises a push-pull plate, a connecting block, flaring arms, rolling elements, and a flaring rod. The upper end of the push-pull plate is connected to a press punch, and the lower end of the push-pull plate is positioned and connected to the connecting block bushing. The lower end of the connecting block is hinged to the upper ends of multiple flaring arms, and a flaring rod is fixedly installed at the lower end of each of the multiple flaring arms. A rolling element is fitted onto the flaring rod.

[0007] The sealing and flattening device consists of a liquid nitrogen tank and a horizontal pressure plate; the upper end of the horizontal pressure plate is connected to the pressure ring.

[0008] A method for using a cryogenic plastic sealing device for large-diameter aluminum alloy thin-walled tube ends is as follows:

[0009] 1. Place the aluminum alloy thin-walled tube in the flange, and set a sealing layer between the aluminum alloy thin-walled tube and the flange to obtain the part to be sealed. Place the part to be sealed in the center of the inner groove of the segmented die, and use the prestressed ring to clamp and position it in the segmented die.

[0010] 2. Fill the interior of the part to be sealed with liquid nitrogen, and transport the liquid nitrogen from the cooling channel to the inner groove of the split die through the small hole in the split die for local deep cryogenic treatment for 20 min to 30 min, so that the local temperature of the part to be sealed reaches below -150℃.

[0011] 3. Under local liquid nitrogen cooling conditions, at a speed of 3 mm / min to 5 mm / min and a pressure of 6 MPa to 10 MPa, the push-pull plate is pressed down to push the end of the flaring arm to move. Then the flaring rod and rolling body expand the end of the part to be sealed and squeeze it into the cavity of the groove to obtain the part to be sealed with folded end.

[0012] 4. Place the folded end of the part to be sealed in a liquid nitrogen tank, fill the inside of the folded end of the part to be sealed and the liquid nitrogen tank with liquid nitrogen respectively, and perform local deep cryogenic treatment for 5 min to 10 min. Under liquid nitrogen conditions, use a horizontal pressure plate to flatten the folded position of the folded end of the part to be sealed, and obtain an aluminum alloy thin-walled tube end cryogenic plastic sealing component.

[0013] The beneficial effects of this invention are:

[0014] A method and apparatus for cryogenic plastic sealing of large-diameter aluminum alloy thin-walled tubes is disclosed. Utilizing the significantly enhanced plasticity of aluminum alloy thin-walled tubes at liquid nitrogen temperatures, the method involves placing the aluminum alloy thin-walled tube, sealing layer, and flange assembly in the center of a segmented die cavity and clamping them in place. Then, liquid nitrogen is filled into the interior of the aluminum alloy thin-walled tube and the segmented die to perform localized deep cryogenic treatment on the end portion of the assembly. A flaring arm is used to fold the cryogenically cooled tube-tube assembly through the segmented die for localized deep cryogenic expansion. Finally, a horizontal pressure plate flattens the folded portion of the tube-tube assembly, achieving an efficient, green, and weld-free plastic connection between the large-diameter aluminum alloy thin-walled tube and the flange. This method solves the problems of complex sealing processes, low production efficiency, inability to achieve large-area, efficient sealing, and the tendency for large-diameter aluminum alloy thin-walled tubes to burn through during welding, resulting in poor weld quality, numerous structural defects, and easy cracking. This method achieves efficient, green, and seamless plastic connection between large-diameter aluminum alloy thin-walled tubes and flanges, reducing thermal defects and cracking tendency at the plastic sealing end. It has advantages such as simple process, good sealing performance, high efficiency and speed, and suitability for mass production. Attached Figure Description

[0015] Figure 1 This is a positioning diagram for step one of the usage method of the device of the present invention;

[0016] Figure 2 This is a folding diagram of step three in the method of using the device of the present invention;

[0017] Figure 3 This is a schematic diagram of the flattening step four in the method of using the device of the present invention;

[0018] Figure 4 This is a schematic diagram of the aluminum alloy thin-walled tube end cryogenic plastic sealing component obtained in step four of the method of using the device of the present invention.

[0019] Figure 5 This is a side sectional view of the flaring device in Embodiment 1;

[0020] Figure 6 This is a top view of the flaring device in Embodiment 1;

[0021] Figure 7 This is a side sectional view of the flaring device in Embodiment 2;

[0022] Figure 8 This is a top view of the flaring device in Embodiment 2. Detailed Implementation

[0023] Specific implementation method one: Combining Figures 1-4 This embodiment describes a cryogenic plastic sealing device for the end of a large-diameter aluminum alloy thin-walled pipe. The sealing and folding device consists of a prestressed ring 1, a segmented die 2, and a flaring device. The segmented die 2 is fitted inside the prestressed ring 1, and the prestressed ring 1 and the segmented die 2 are press-fitted. The upper surface of the segmented die 2 is provided with an inner groove, which is composed of a groove opening and an inner cavity. The cross-sectional area of the inner cavity is larger than the cross-sectional area of the groove opening. The flaring device consists of a push-pull plate 4, a connecting block 5, flaring arms 6, rolling elements 8, and flaring rods 14. The upper end of the push-pull plate 4 is connected to the press punch, and the lower end of the push-pull plate 4 is positioned and connected to the bushing of the connecting block 5. The lower end of the connecting block 5 is hinged to the upper ends of multiple flaring arms 6. Each of the multiple flaring arms 6 is fixedly provided with a flaring rod 14, and a rolling element 8 is fitted on the flaring rod 14.

[0024] The sealing and flattening device consists of a liquid nitrogen tank 11 and a horizontal pressure plate 12; the upper end of the horizontal pressure plate 12 is connected to the pressure ring.

[0025] The prestressed ring 1 is fitted with a segmented die 2, which provides clamping force and positioning for the segmented die 2. The fit is a compression interference fit.

[0026] This specific embodiment utilizes the characteristic that the plasticity of aluminum alloy thin-walled tubes is significantly enhanced at liquid nitrogen temperature, and uses a flaring device and a segmented die to cause local plastic deformation at the tube end at liquid nitrogen temperature;

[0027] This specific embodiment is designed with a rigid flaring device, which can convert linear motion along the pipe axis into distributed motion along the pipe radial direction.

[0028] This specific embodiment is designed with a rolling element, which reduces the friction of the local flaring through radial rolling, and avoids cracking induced by friction due to local plastic deformation at the pipe end;

[0029] This specific embodiment designs a segmented die structure with a cavity. The aluminum alloy thin-walled tube, sealing layer and flange assembly are extruded into the cavity of the segmented die through the flaring device, and the partially folded blank generated by the assembly is stored.

[0030] This specific embodiment features a horizontal pressure plate shaping structure. The horizontal pressure plate further compacts and flattens the folded parts of the aluminum alloy thin-walled tube, sealing layer, and flange assembly in liquid nitrogen to form a folded seal.

[0031] The method and apparatus of this specific embodiment can seal not only the same type of thin-walled pipe with excellent low-temperature performance, but also different types of thin-walled pipe at liquid nitrogen temperature.

[0032] The method and apparatus of this specific embodiment are used to seal thin-walled aluminum alloy tubes with circular or square cross-sections at liquid nitrogen temperature.

[0033] The beneficial effects of this specific implementation method are:

[0034] A method and apparatus for cryogenic plastic sealing of large-diameter aluminum alloy thin-walled tubes is disclosed. Utilizing the significantly enhanced plasticity of aluminum alloy thin-walled tubes at liquid nitrogen temperatures, the method involves placing the aluminum alloy thin-walled tube, sealing layer, and flange assembly in the center of a segmented die cavity and clamping them in place. Then, liquid nitrogen is filled into the interior of the aluminum alloy thin-walled tube and the segmented die to perform localized deep cryogenic treatment on the end portion of the assembly. A flaring arm is used to fold the cryogenically cooled tube-tube assembly through the segmented die for localized deep cryogenic expansion. Finally, a horizontal pressure plate flattens the folded portion of the tube-tube assembly, achieving an efficient, green, and weld-free plastic connection between the large-diameter aluminum alloy thin-walled tube and the flange. This method solves the problems of complex sealing processes, low production efficiency, inability to achieve large-area, efficient sealing, and the tendency for large-diameter aluminum alloy thin-walled tubes to burn through during welding, resulting in poor weld quality, numerous structural defects, and easy cracking. This method achieves efficient, green, and seamless plastic connection between large-diameter aluminum alloy thin-walled tubes and flanges, reducing thermal defects and cracking tendency at the plastic sealing end. It has advantages such as simple process, good sealing performance, high efficiency and speed, and suitability for mass production.

[0035] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the prestressed ring 1 is made of 40Cr; the segmented die 2 is made of austenitic stainless steel; and the flared arm 6 and flared rod 14 are made of 40Cr. Everything else is the same as in Specific Implementation Method One.

[0036] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: both the liquid nitrogen tank 11 and the bottom of the segmented mold 2 are provided with cooling channels 10, and the cooling channels 10 at the bottom of the segmented mold 2 are connected to the inner groove through small holes. Everything else is the same as in Specific Implementation Method One or Two.

[0037] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the length of the flared rod 14 is 1 / 2 of the inner diameter of the aluminum alloy thin-walled tube; the outer diameter of the rolling element 8 is 1.1 to 1.2 times the diameter of the flared rod 14. Everything else is the same as in Specific Implementation Methods One to Three.

[0038] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that multiple flared rods 14 are arranged in a segmented circular or segmented square shape. Otherwise, it is the same as Specific Implementation Methods One to Four.

[0039] Specific Implementation Method Six: Combination Figures 1-4 This embodiment describes a method for using a cryogenic plastic sealing device for the ends of large-diameter thin-walled aluminum alloy tubes, which is carried out according to the following steps:

[0040] 1. Place the aluminum alloy thin-walled tube 3 in the flange 9, and set a sealing layer 7 between the aluminum alloy thin-walled tube and the flange to obtain the part to be sealed. Place the part to be sealed in the center of the inner groove of the split die 2, and use the prestressed ring 1 to clamp and position it in the split die 2.

[0041] 2. Fill the interior of the part to be sealed with liquid nitrogen, and transport the liquid nitrogen from the cooling channel 10 to the inner groove of the split die 2 through the small hole in the split die 2 for local deep cryogenic treatment for 20 min to 30 min, so that the local temperature of the part to be sealed reaches below -150℃.

[0042] 3. Under local liquid nitrogen cooling conditions, at a speed of 3 mm / min to 5 mm / min and a pressure of 6 MPa to 10 MPa, the push-pull plate 4 is pressed down to push the end of the flaring arm 6 to move. Then the flaring rod 14 and the rolling element 8 expand the end of the part to be sealed and squeeze it into the cavity of the groove to obtain the part to be sealed with folded end.

[0043] 4. Place the folded end of the part to be sealed into the liquid nitrogen tank 11, fill the inside of the folded end of the part to be sealed and the liquid nitrogen tank 11 with liquid nitrogen, and perform local deep cryogenic treatment for 5 min to 10 min. Under liquid nitrogen conditions, use the horizontal pressure plate 12 to flatten the folded position of the folded end of the part to be sealed, and obtain the aluminum alloy thin-walled tube end ultra-low temperature plastic sealing component.

[0044] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Six in that: the outer diameter of the aluminum alloy thin-walled tube 3 mentioned in step one is 50mm to 120mm; the thickness of the aluminum alloy thin-walled tube 3 and flange 9 mentioned in step one is 0.5mm to 2.5mm; the height of the flange 9 mentioned in step one is 1 / 6 to 1 / 4 of the outer diameter of the aluminum alloy thin-walled tube 3; the material of the sealing layer 7 mentioned in step one is polytetrafluoroethylene, polyurethane, or special low-temperature resistant rubber; the thickness of the sealing layer 7 mentioned in step one is 0.12mm to 0.45mm. Everything else is the same as in Specific Implementation Method Six.

[0045] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Six or Seven in that: before the push-pull plate 4 is pressed down in step three, the maximum included angle between the flared arm 6 and the bottom surface of the segmented die 2 does not exceed 75°. Everything else is the same as in Specific Implementation Method Six or Seven.

[0046] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods Six to Eight in that: in step two, the liquid nitrogen height inside the part to be sealed is greater than the flange height; in step four, the liquid nitrogen height inside the part to be sealed after end folding is greater than the end folding height. Everything else is the same as Specific Implementation Methods Six to Eight.

[0047] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods Six to Nine in that, in step four, under liquid nitrogen conditions, at a speed of 2 mm / min to 4 mm / min and a load of 5 tons to 8 tons, the folded position of the end-folded part to be sealed is flattened using a horizontal pressure plate 12. Everything else is the same as in Specific Implementation Methods Six to Nine.

[0048] The beneficial effects of the present invention are verified using the following embodiments:

[0049] Example 1, combined with Figures 1-6 Detailed explanation:

[0050] A cryogenic plastic sealing device for the end of a large-diameter aluminum alloy thin-walled tube, comprising a sealing folding device and a sealing flattening device;

[0051] The sealing and folding device consists of a prestressed ring 1, a segmented die 2, and a flaring device. The segmented die 2 is fitted inside the prestressed ring 1, and the prestressed ring 1 and the segmented die 2 are press-fitted. The upper surface of the segmented die 2 is provided with an inner groove, which is composed of a groove opening and an inner cavity. The cross-sectional area of the inner cavity is larger than the cross-sectional area of the groove opening. The flaring device consists of a push-pull plate 4, a connecting block 5, flaring arms 6, rolling elements 8, and flaring rods 14. The upper end of the push-pull plate 4 is connected to the press punch, and the lower end of the push-pull plate 4 is positioned and connected to the connecting block 5. The lower end of the connecting block 5 is hinged to the upper ends of multiple flaring arms 6. Each of the multiple flaring arms 6 is fixedly provided with a flaring rod 14, and a rolling element 8 is fitted on the flaring rod 14.

[0052] The sealing and flattening device consists of a liquid nitrogen tank 11 and a horizontal pressure plate 12; the upper end of the horizontal pressure plate 12 is connected to the pressure ring.

[0053] The prestressed ring 1 is made of 40Cr; the split die 2 is made of 304 austenitic stainless steel; and the flared arm 6 and flared rod 14 are made of 40Cr.

[0054] The liquid nitrogen tank 11 and the bottom of the segmented mold 2 are both provided with cooling channels 10, and the cooling channels 10 at the bottom of the segmented mold 2 are connected to the inner groove through small holes.

[0055] The length of the flared rod 14 is 1 / 2 of the inner diameter of the aluminum alloy thin-walled tube; the outer diameter of the rolling element 8 is 1.15 times the diameter of the flared rod 14.

[0056] Multiple flared rods 14 form a segmented circle.

[0057] A method for using a cryogenic plastic sealing device for large-diameter aluminum alloy thin-walled tube ends is as follows:

[0058] 1. Place the aluminum alloy thin-walled tube 3 in the flange 9, and set a sealing layer 7 between the aluminum alloy thin-walled tube and the flange to obtain the part to be sealed. Place the part to be sealed in the center of the inner groove of the split die 2, and use the prestressed ring 1 to clamp and position it in the split die 2.

[0059] 2. Fill the interior of the part to be sealed with liquid nitrogen, and transport the liquid nitrogen from the cooling channel 10 to the inner groove of the split die 2 through the small hole in the split die 2 for local deep cryogenic treatment for 20 minutes, so that the local temperature of the part to be sealed reaches below -150℃.

[0060] 3. Under local liquid nitrogen cooling conditions, at a speed of 4 mm / min and a pressure of 8 MPa, the push-pull plate 4 is pressed down to push the end of the flaring arm 6 to move. Then the flaring rod 14 and the rolling element 8 expand the end of the part to be sealed and squeeze it into the cavity of the groove to obtain the part to be sealed with folded end.

[0061] 4. Place the folded end of the part to be sealed into the liquid nitrogen tank 11, fill the inside of the folded end of the part to be sealed and the liquid nitrogen tank 11 with liquid nitrogen, and perform local deep cryogenic treatment for 10 minutes. Under liquid nitrogen conditions, at a speed of 3 mm / min and a load of 6.5 tons, use the horizontal pressure plate 12 to flatten the folded position of the folded end of the part to be sealed, and obtain the aluminum alloy thin-walled tube end ultra-low temperature plastic sealing component.

[0062] The aluminum alloy thin-walled tube 3 mentioned in step one is a circular tube of 6061 aluminum alloy with an outer diameter of 99.0 mm and a thickness of 2.0 mm; the flange 9 mentioned in step one is a circular cylinder of 6061 aluminum alloy with an inner diameter of 100 mm and a thickness of 2 mm; the height of the flange 9 mentioned in step one is 1 / 5 of the outer diameter of the aluminum alloy thin-walled tube 3.

[0063] The sealing layer 7 mentioned in step one has a thickness of 0.45 mm and is made of polytetrafluoroethylene.

[0064] Before the push-pull plate 4 is pressed down in step three, the maximum angle between the flared arm 6 and the bottom surface of the split die 2 is 60°.

[0065] In step two, the liquid nitrogen height inside the part to be sealed is greater than the flange height; in step four, the liquid nitrogen height inside the part to be sealed with the end folded is greater than the end fold height.

[0066] Example 2, combined with Figures 1-4 7-8 Specific Explanation:

[0067] A cryogenic plastic sealing device for the end of a large-diameter aluminum alloy thin-walled tube, comprising a sealing folding device and a sealing flattening device;

[0068] The sealing and folding device consists of a prestressed ring 1, a segmented die 2, and a flaring device. The segmented die 2 is fitted inside the prestressed ring 1, and the prestressed ring 1 and the segmented die 2 are press-fitted. The upper surface of the segmented die 2 is provided with an inner groove, which is composed of a groove opening and an inner cavity. The cross-sectional area of the inner cavity is larger than the cross-sectional area of the groove opening. The flaring device consists of a push-pull plate 4, a connecting block 5, flaring arms 6, rolling elements 8, and flaring rods 14. The upper end of the push-pull plate 4 is connected to the press punch, and the lower end of the push-pull plate 4 is positioned and connected to the connecting block 5. The lower end of the connecting block 5 is hinged to the upper ends of multiple flaring arms 6. Each of the multiple flaring arms 6 is fixedly provided with a flaring rod 14, and a rolling element 8 is fitted on the flaring rod 14.

[0069] The sealing and flattening device consists of a liquid nitrogen tank 11 and a horizontal pressure plate 12; the upper end of the horizontal pressure plate 12 is connected to the pressure ring.

[0070] The prestressed ring 1 is made of 40Cr; the split die 2 is made of 304 austenitic stainless steel; and the flared arm 6 and flared rod 14 are made of 40Cr.

[0071] The liquid nitrogen tank 11 and the bottom of the segmented mold 2 are both provided with cooling channels 10, and the cooling channels 10 at the bottom of the segmented mold 2 are connected to the inner groove through small holes.

[0072] The length of the flared rod 14 is 1 / 2 of the inner diameter of the aluminum alloy thin-walled tube; the outer diameter of the rolling element 8 is 1.15 times the diameter of the flared rod 14.

[0073] Multiple flared rods 14 form a segmented square shape.

[0074] A method for using a cryogenic plastic sealing device for large-diameter aluminum alloy thin-walled tube ends is as follows:

[0075] 1. Place the aluminum alloy thin-walled tube 3 in the flange 9, and set a sealing layer 7 between the aluminum alloy thin-walled tube and the flange to obtain the part to be sealed. Place the part to be sealed in the center of the inner groove of the split die 2, and use the prestressed ring 1 to clamp and position it in the split die 2.

[0076] 2. Fill the interior of the part to be sealed with liquid nitrogen, and transport the liquid nitrogen from the cooling channel 10 to the inner groove of the split die 2 through the small hole in the split die 2 for local deep cryogenic treatment for 20 minutes, so that the local temperature of the part to be sealed reaches below -150℃.

[0077] 3. Under local liquid nitrogen cooling conditions, at a speed of 3.5 mm / min and a pressure of 9 MPa, the push-pull plate 4 is pressed down to push the end of the flaring arm 6 to move. Then the flaring rod 14 and the rolling element 8 expand the end of the part to be sealed and squeeze it into the cavity of the groove to obtain the part to be sealed with folded end.

[0078] 4. Place the folded end part to be sealed in the liquid nitrogen tank 11, fill the inside of the folded end part to be sealed and the liquid nitrogen tank 11 with liquid nitrogen, and perform local deep cryogenic treatment for 10 minutes. Under liquid nitrogen conditions, at a speed of 3 mm / min and a load of 7.5 tons, use the horizontal pressure plate 12 to flatten the folded position of the folded end part to be sealed, and obtain the aluminum alloy thin-walled tube end ultra-low temperature plastic sealing component.

[0079] The aluminum alloy thin-walled tube 3 mentioned in step one is a square tube of 6061 aluminum alloy with an outer side length of 62.4 mm and a thickness of 1 mm; the flange 9 mentioned in step one is a square cylinder of 6061 aluminum alloy with an outer side length of 64.5 mm and a thickness of 1 mm.

[0080] The sealing layer 7 mentioned in step one has a thickness of 0.45 mm and is made of polytetrafluoroethylene.

[0081] Before the push-pull plate 4 is pressed down in step three, the maximum angle between the flared arm 6 and the bottom surface of the split die 2 is 60°.

[0082] In step two, the liquid nitrogen height inside the part to be sealed is greater than the flange height; in step four, the liquid nitrogen height inside the part to be sealed with the end folded is greater than the end fold height.

[0083] After the cryogenic plastic sealing in Examples 1 and 2, the water retention performance was tested, and the water loss rate was less than 0.001 mL / month, which meets the actual engineering requirements.

Claims

1. A cryogenic plastic sealing device for the ends of large-diameter aluminum alloy thin-walled pipes, characterized in that... It includes a sealing and folding device and a sealing and flattening device; The sealing and folding device consists of a prestressed ring (1), a segmented die (2), and a flaring device; the prestressed ring (1) is fitted with the segmented die (2), and the prestressed ring (1) and the segmented die (2) are in a pressing interference fit; the upper surface of the segmented die (2) is provided with an inner groove, which is composed of a groove opening and an inner cavity, and the cross-sectional area of the inner cavity is larger than the cross-sectional area of the groove opening; the flaring device consists of a push-pull plate (4) and a connecting block (5). The assembly consists of a flared arm (6), a rolling element (8), and a flared rod (14); the upper end of the push-pull plate (4) is connected to the press punch, the lower end of the push-pull plate (4) is positioned and connected to the bushing of the connecting block (5), the lower end of the connecting block (5) is hinged to the upper ends of multiple flared arms (6), and a flared rod (14) is fixedly installed at the lower end of each of the multiple flared arms (6), with a rolling element (8) sleeved on the flared rod (14); the multiple flared rods (14) form a segmented circle; The sealing and flattening device consists of a liquid nitrogen tank (11) and a horizontal pressure plate (12); the upper end of the horizontal pressure plate (12) is connected to the pressure ring. The length of the flaring rod (14) is 1 / 2 of the inner diameter of the aluminum alloy thin-walled tube; the outer diameter of the rolling element (8) is 1.15 times the diameter of the flaring rod (14); the material of the prestressed ring (1) is 40Cr; the material of the split die (2) is 304 austenitic stainless steel; the material of the flaring arm (6) and the flaring rod (14) is 40Cr. The above-mentioned method of using the ultra-low temperature plastic sealing device for large-diameter aluminum alloy thin-walled tube ends is carried out according to the following steps:

1. Place the aluminum alloy thin-walled tube (3) in the flange (9) and set a sealing layer (7) between the aluminum alloy thin-walled tube and the flange to obtain the part to be sealed. Place the part to be sealed in the center of the inner groove of the split die (2) and use the prestressed ring (1) to clamp and position it in the split die (2). The aluminum alloy thin-walled tube (3) is a circular tube of 6061 aluminum alloy with an outer diameter of 99.0 mm and a thickness of 2.0 mm; the flange (9) is a circular cylinder of 6061 aluminum alloy with an inner diameter of 100 mm and a thickness of 2 mm; the height of the flange (9) is 1 / 5 of the outer diameter of the aluminum alloy thin-walled tube (3); the material of the sealing layer (7) is polytetrafluoroethylene or polyurethane; the thickness of the sealing layer (7) is 0.12 mm to 0.45 mm.

2. Fill the interior of the part to be sealed with liquid nitrogen, and transport the liquid nitrogen from the cooling channel (10) to the inner groove of the split die (2) through the small hole in the split die (2) for local deep cryogenic treatment for 20min~30min, so that the local temperature of the part to be sealed reaches below -150℃.

3. Under local liquid nitrogen cooling conditions, at a speed of 4 mm / min and a pressure of 8 MPa, the push-pull plate (4) is pressed down to push the end of the flaring arm (6) to move. Then the flaring rod (14) and the rolling element (8) expand the end of the part to be sealed and squeeze it into the cavity of the groove to obtain the part to be sealed with folded end. Before the push-pull plate (4) is pressed down, the maximum angle between the flared arm (6) and the bottom surface of the split die (2) is 60°.

4. Place the end-folded part to be sealed in a liquid nitrogen tank (11), fill the inside of the end-folded part to be sealed and the liquid nitrogen tank (11) with liquid nitrogen respectively, and perform local deep cryogenic treatment for 5 min to 10 min. Under liquid nitrogen conditions, at a speed of 3 mm / min and a load of 6.5 tons, use a horizontal pressure plate (12) to flatten the folded position of the end-folded part to be sealed, and obtain an aluminum alloy thin-walled tube end cryogenic plastic sealing component.

2. The cryogenic plastic sealing device for large-diameter aluminum alloy thin-walled tube ends according to claim 1, characterized in that... Cooling channels (10) are provided at the bottom of the liquid nitrogen tank (11) and the split mold (2), and the cooling channels (10) at the bottom of the split mold (2) are connected to the inner groove through small holes.

3. The cryogenic plastic sealing device for large-diameter aluminum alloy thin-walled tube ends according to claim 1, characterized in that... In step two, the liquid nitrogen height inside the part to be sealed is greater than the flange height; in step four, the liquid nitrogen height inside the part to be sealed with the end folded is greater than the end fold height.