Large size thin wall metal tube sealing device and method

Abstract

A large-size thin-wall metal pipe sealing device and method relate to the technical field of plastic forming of metal pipes. The device comprises a bearing table, an induction heating coil guide rail, an induction heating unit, a rotary spinning tool body rotary guide rail, a rotary spinning tool body, a vertical fixed plate, a rear chuck, a front chuck, a transmission plate, an axial positioning column, a pushing ring, a penetrating push rod and a hollow rotary cylinder. The integrated design of inner and outer sleeve composite spinning, uniform conduction heating, rigid support anti-instability and automatic non-destructive separation realizes the defect-free, high-precision and high-efficiency sealing forming of large-size thin-wall metal pipes, and meets the high reliability requirements of thin-wall pipe sealing parts in the high-end equipment field.

Description

Technical Field

[0001] This invention relates to the field of metal tube plastic forming technology, and particularly to a sealing device and method for large-size thin-walled metal tubes. It is especially suitable for high-precision, defect-free integrated sealing forming of thin-walled metal tubes made of high-strength aluminum alloy, titanium alloy, and high-temperature alloy used in aerospace, new energy, and deep-sea exploration fields with a diameter ≥150mm and a diameter-to-thickness ratio ≥50. Background Technology

[0002] Against the backdrop of the nation's vigorous promotion of high-end equipment manufacturing, the upgrading of the new energy industry, and the self-reliance in the aerospace field, the demand for lightweight, high-strength structural components is becoming increasingly urgent. Large-size thin-walled metal tubes, due to their advantages of low density, high specific strength, corrosion resistance, and fatigue resistance, are widely used in key areas such as aerospace engine piping, high-pressure hydrogen storage cylinders for new energy vehicles, pressure-resistant hulls for deep-sea exploration, and pipeline systems for marine vessels. The sealing process of these tubes, as a core step in component forming, directly determines the sealing performance, load-bearing safety, reliability, and service life of the entire system.

[0003] Currently, the sealing processes for large-size thin-walled metal tubes are mainly divided into three categories: mechanical cold pressing sealing, fusion welding sealing, and hot spinning sealing. Each of these processes has a core bottleneck that makes them unsuitable for forming large-size thin-walled tubes. Mechanical cold pressing sealing: This method relies on axial extrusion using a die to close the pipe end, and is only suitable for small-sized, thick-walled pipes. For thin-walled pipes with a large diameter-to-thickness ratio, the pipe end is prone to instability, wrinkling, and axial cracking during the cold pressing process. Furthermore, the flow lines of the metal structure at the sealing point are cut off, resulting in a significant decrease in fatigue performance, which cannot meet the usage requirements of high-end equipment under alternating load conditions.

[0004] Fusion welding sealing: Although the sealing plugs are welded using processes such as argon arc welding and laser welding, the pipe opening can be sealed. However, the heat-affected zone of the weld is prone to defects such as porosity, microcracks, and welding deformation. For thin-walled pipes with a wall thickness of ≤5mm, the weld penetration problem is very likely to occur. At the same time, the difference in microstructure and properties between the weld and the base material is large, and failure is likely to occur under high pressure and corrosive conditions, which cannot meet the requirements for high reliability.

[0005] Hot spinning sealing technology utilizes induction heating coils to high-frequency heat the end of a metal tube to be sealed, raising the temperature of that section of metal to the plastic deformation range (adjusted to the corresponding temperature range depending on the material). Then, by high-speed rotation of the metal tube and the use of a spinning mechanism's blade to feed radially along the tube and rotate around its axis, the hot tube opening gradually undergoes plastic shrinkage, bonding, and shaping under the combined action of rotational centrifugal force and the radial pressure of the blade. This gradually squeezes the metal from the outside of the tube to the center, ultimately forming a closed tube structure. As a seamless, integrated forming process, it is currently the preferred solution for sealing thin-walled tubes. However, existing conventional hot spinning technology faces three major unsolvable technical challenges for large-size thin-walled metal tubes: (1) Poor heating uniformity: High-frequency induction heating has a significant skin effect. Large-sized thin-walled tubes have thin walls and large surface areas. During induction heating, the axial and circumferential temperature gradients can reach more than ±100℃. Some areas do not reach the plastic deformation range. During spinning, uneven wall thickness, folds, and non-welding defects are very likely to occur. (2) High risk of forming instability: The pipe with large diameter-to-thickness ratio has poor rigidity. When the spinning tool applies radial pressure, the pipe opening is not effectively supported, and circumferential instability and wrinkling are prone to occur. The yield of the existing process is extremely low. (3) Difficulty in controlling dimensional accuracy: Under the dual influence of uneven heating and insufficient rigidity of the pipe, the deformation of the pipe end during the spinning process is uncontrollable, the sealing profile and wall thickness uniformity cannot be stably met, and the dimensional fluctuations in mass production are extremely large.

[0006] In response to the inherent bottlenecks of conventional hot spinning sealing, the industry has undertaken a series of technical improvement attempts, but none of them have solved the problem at its root; instead, they have introduced new technical shortcomings. (1) In order to solve the problem of uneven heating, the industry has proposed a multi-segment induction heating coil segmented heating scheme. The temperature difference is reduced by dividing the temperature by multiple sets of coils. However, this scheme is only applicable to small pipes with a diameter of ≤100mm. It still cannot eliminate circumferential temperature unevenness for large-sized pipes. Moreover, the equipment structure is complex, the parameter debugging is extremely difficult, and the production cost is greatly increased. (2) In order to solve the problem of forming instability, the industry generally adopts the built-in core mold support scheme. By adding a rigid core mold inside the pipe, the radial force of spinning is offset. However, for large-sized long pipes, the disassembly and assembly of the core mold is extremely difficult and the production cycle of a single piece is greatly extended, which directly leads to complex processes and extremely low production efficiency. At the same time, the fit gap between the core mold and the inner wall of the pipe is extremely sensitive to the fluctuation of pipe size, and the consistency of batch production cannot be guaranteed at all. Moreover, it cannot meet the sealing requirements of variable diameter and irregular shaped pipes.

[0007] In summary, how to fundamentally solve the industry problems of uneven heating, unstable forming, and insufficient precision in hot spinning sealing of large-size thin-walled metal tubes without increasing complex processes or reducing production efficiency, and achieve high-quality, high-efficiency, and high-consistency sealing forming, has become an urgent problem to be solved in the field of tube sealing. To this end, this invention proposes a sealing device and method for large-size thin-walled metal tubes. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies in sealing large-size thin-walled metal tubes, such as uneven heating, easy instability and wrinkling during forming, uneven wall thickness, low yield, complex processes, and poor performance of formed parts, this invention provides a sealing device and method for large-size thin-walled metal tubes. Through an integrated design of inner and outer sleeve composite spinning, uniform conductive heating, rigid support to prevent instability, and automated non-destructive separation, it achieves defect-free, high-precision, and high-efficiency sealing of large-size thin-walled metal tubes, meeting the high reliability requirements of thin-walled tube sealing parts in the high-end equipment field.

[0009] The technical solution of this invention: A sealing device for large-size thin-walled metal tubes includes a support platform 1, an induction heating coil guide rail 2, an induction heating unit 3, a spinning cutter body rotary guide rail 4, a spinning cutter body 5, a vertical fixing plate 6, a rear chuck 7, a front chuck 8, a transmission plate 9, an axial positioning column 10, a push ring 11, an insert push rod 12, and a hollow rotary cylinder 13.

[0010] The induction heating coil guide rail 2 is horizontally fixed on the support platform 1. The induction heating unit 3 includes an insulating sliding bracket and an induction coil body mounted on the insulating sliding bracket. The insulating sliding bracket is mounted on the induction heating coil guide rail 2 and is driven by a servo motor and a ball screw mechanism to make precise linear feed motion along the axial direction of the induction heating coil guide rail 2. The spinning cutter body rotary guide rail 4 is rotatably mounted on the center position of the support platform 1 via a rotary spindle and can be driven by a rotary drive motor to make rotary motion around the central axis of the support platform 1 (coaxial with the pipe). The spinning cutter body 5 is mounted on the spinning cutter body rotary guide rail 4 and can be driven by a hydraulic propulsion cylinder or a servo electric cylinder to make linear feed motion along the radial direction of the spinning cutter body rotary guide rail 4. The vertical fixing plate 6 is vertically fixed on the support platform 1 and remains perpendicular to the support platform 1. The vertical end face of the vertical fixing plate 6 is rotatably mounted on the main bearing seat, and the rotary spindle can be driven to rotate by the spindle rotary motor. The rear chuck 7 includes a rear chuck body 701 and a rear chuck jaw 702. The rear chuck body 701 is coaxially fixed on the output end of the rotary spindle, and the rear chuck jaw 702 is installed in the slide groove of the rear chuck body 701, which can clamp the inner metal tube 14 to achieve positioning and fixation. The hollow rotary cylinder 13 is fixed to the center of the rear chuck body 701. The piston of the hollow rotary cylinder 13 travels from the inside to the outside along the axis of the rear chuck body 701. The hollow rotary cylinder 13 is connected to an external air source through a pneumatic rotary joint. One end of the through push rod 12 is fixedly connected to the piston of the hollow rotary cylinder 13. The through push rod 12 is arranged circumferentially on the piston, and the through push rod 12 is misaligned with the rear chuck jaw 702 in the circumferential direction to ensure that the axial extension and retraction of the through push rod 12 is in harmony with the radial extension and retraction of the rear chuck jaw 702. The opening and closing mechanisms do not interfere with each other in space, and during high-speed spinning, the hollow rotary cylinder 13, the insert push rod 12, and the push ring 11 maintain a relatively stationary synchronous rotation with the rear chuck body 701; the other end of the insert push rod 12 is fixedly connected to the push ring 11; the inner diameter of the hollow rotary cylinder 13 and the inner diameter of the annular surface formed by all the insert push rods 12 are both larger than the outer diameter of the inner metal tube 14; the push ring 11 is circular, its inner diameter is larger than the outer diameter of the inner metal tube 14, and its outer diameter is smaller than or equal to the outer diameter of the outer auxiliary sleeve 15.

[0011] The front chuck 8 includes a front chuck body 801 and a front chuck jaw 802. The front chuck body 801 is coaxially fixed on the front end face of the rear chuck body 701. The front chuck jaw 802 can clamp the outer auxiliary sleeve 15 to achieve positioning and fixation. The transmission plate 9 is horizontally fixed on the vertical end face of the vertical fixing plate 6. It is equipped with a lifting cylinder, which can drive the axial positioning column 10 to achieve vertical lifting and lowering movement. The axial positioning column 10 is installed in the positioning hole on the lower surface of the transmission plate 9. The axial positioning column 10 can achieve precise axial positioning and retraction avoidance of the pipe through lifting and lowering.

[0012] A method for sealing large-size thin-walled metal tubes includes the following steps: Step 1: Pipe pretreatment and pipe cutting: Select a metal pipe with an inner diameter larger than the outer diameter of the inner metal pipe 14 to be sealed as the outer auxiliary sleeve 15. Cut the outer auxiliary sleeve 15 to a set length, which is equal to the set horizontal distance between the front end face of the rear chuck body 701 and the positioning end face of the axial positioning post 10. After cutting, deburr and polish the end faces and mating surfaces of the inner and outer pipes, and apply a high-temperature anti-sticking agent to the mating surfaces.

[0013] Step 2: Sleeve assembly: Coaxially fit the outer auxiliary sleeve 15 onto the end of the inner metal tube 14 to be sealed, adjust the axial position to ensure that the end faces of the two tubes at the end to be sealed are completely flush, and ensure that the inner metal tube 14 has no axial translation or circumferential rotation freedom relative to the outer auxiliary sleeve 15 after assembly.

[0014] Step 3: Clamping and Positioning: Insert the assembled composite pipe axially into the center holes of the rear chuck body 701 and the front chuck body 801 until the non-sealed end face of the outer auxiliary sleeve 15 is completely in contact with the front end face of the rear chuck body 701. Activate the lifting cylinder to drive the transmission plate 9 to lower the axial positioning column 10, completing the axial positioning of the pipe. After confirming that the pipe position is correct, clamp it sequentially through the rear chuck jaws 702 and the front chuck jaws 802 to fix the inner metal pipe 14 and the outer auxiliary sleeve 15 respectively.

[0015] Step 4: Induction Heating: Retract the axial positioning column 10 to a safe position, start the spindle rotary motor to drive the rear chuck body 701 and the front chuck body 801 to rotate synchronously at high speed, thereby driving the inner metal tube to rotate at high speed around its own axis. The rotational motion of the inner metal tube achieves dynamic and uniform heating in the circumferential direction, eliminating the circumferential temperature gradient. In this rotating state, start the servo motor to drive the induction heating unit 3 to feed axially along the induction heating coil guide rail 2, so that its induction coil body is coaxially sleeved on the end of the composite tube to be spun and sealed, heating the tube until the entire section of the inner metal tube 14 to be heated reaches the plastic deformation phase transformation temperature.

[0016] Step 5: Spinning and Sealing: After induction heating is completed, the servo motor is reversed to drive the induction heating unit 3 to quickly return to a safe position along the induction heating coil guide rail 2. The inner metal tube is kept in a high-speed rotating state, utilizing its own rotational motion to provide tangential forming power and continuous material flow. Subsequently, the hydraulic propulsion cylinder or servo electric cylinder is activated to radially feed the spinning cutter body 5 along the spinning cutter body rotary guide rail 4, applying stable radial pressure to the sealing end of the rotating tube. Simultaneously, the rotary drive motor is activated to make the spinning cutter body rotary guide rail 4 rotate around the tube axis, driving the spinning cutter body 5 to complete a one-time spinning and sealing process until the tube opening is completely sealed. During the operation, the contour shape and final closure degree of the seal can be controlled by adjusting the radial feed speed and feed depth of the spinning cutter body 5 at different stages.

[0017] Step Six: Separation of Inner and Outer Pipes: After the spinning and sealing is completed, the spinning cutter body 5 retracts to the initial safe position along the spinning cutter body rotary guide rail 4, stops the rotation of the front and rear chuck bodies and the pipe, releases the front chuck jaws 802, releases the clamping constraint on the outer auxiliary sleeve 15, maintains the clamping state of the rear chuck jaws 702 on the inner metal pipe 14, starts the hollow rotary cylinder 13 to pressurize, drives the insertion push rod 12 to drive the push ring 11 to extend forward, applies axial thrust to the outer auxiliary sleeve 15, and smoothly pushes it out from the inner metal pipe 14, realizing the automated and non-destructive separation of the inner and outer pipes.

[0018] Step 7: Cooling and post-processing: Remove the sealed inner metal tube 14 from the rear chuck jaws 702 and allow it to cool naturally to room temperature. Deburr, polish and inspect the sealed area to obtain qualified sealed tube fittings.

[0019] Furthermore, the inner diameter of the outer auxiliary sleeve (15) is 0.2-0.5 mm larger than the outer diameter of the inner metal tube (14) to be sealed.

[0020] The beneficial effects of this invention are: (1) The present invention heats the pipe by using an outer auxiliary sleeve and coordinating with the high-speed axial rotation of the pipe. The outer auxiliary sleeve eliminates the temperature difference in the axial and wall thickness directions through interlayer heat conduction, while the high-speed rotation of the pipe utilizes the dynamic temperature uniformity effect to completely eliminate the circumferential temperature gradient caused by the non-absolute circumferential symmetry of the magnetic field of the induction coil. The two work together to ensure that the inner metal pipe section to be sealed reaches the plastic phase transition temperature uniformly, avoiding the material plasticity difference caused by local temperature imbalance, and laying a uniform thermal foundation for high-quality sealing.

[0021] (2) The “composite structure” formed by the inner and outer sleeves effectively increases the overall wall thickness during the sealing operation, significantly reduces the equivalent diameter-to-thickness ratio of the pipe, and fundamentally solves the core defects of large-size thin-walled metal pipes caused by excessive diameter-to-thickness ratio, such as spinning instability, wrinkling, and uneven wall thickness.

[0022] (3) The outer auxiliary sleeve can form a rigid support for the inner metal tube in the whole circumference. During the spinning operation, it can effectively disperse the radial pressure applied by the blade, avoid local deformation of thin-walled tube caused by pressure concentration, further suppress the generation of wrinkles and uneven wall thickness defects, and improve the sealing forming accuracy.

[0023] (4) The front and rear double chuck structures are coaxially set, which can independently and stably clamp and fix the inner and outer pipes respectively, solving the problem of difficult coaxial positioning of pipe fittings and easy slippage during the sealing of the sleeve composite structure, and ensuring the coaxiality and stability of the pipe rotation during the spinning process.

[0024] (5) The axially retractable pushing mechanism built into the rear chuck can directly apply axial thrust to the outer sleeve after sealing, realizing automated and non-destructive separation of inner and outer tubes, eliminating the manual separation process, reducing labor costs, and avoiding mechanical damage to the sealed tubes and the risk of high-temperature operation caused by manual operation. Furthermore, the axially retractable pushing mechanism adopts a structural design with a rigid pushing ring at the front end. Since the end face of large-size thin-walled tubes has a very small force-bearing surface, if multi-point insertion push rods are used for separation, it is easy for stress concentration to cause local buckling, deformation or tearing of the thin-walled tube end, and it is also easy for uneven force to cause skew jamming. This invention transforms the thrust from point contact to uniform surface contact in the entire circumference through the rigid pushing ring, which not only eliminates stress concentration when the thin-walled tube is demolded, but also forcibly ensures the absolute axial parallelism of the withdrawal direction, effectively avoiding tube scratches and deformation jamming during the separation process, and truly realizing automated and non-destructive separation of large-size thin-walled metal tubes.

[0025] (6) The clamping range of the front and rear chucks, the size of the built-in telescopic push mechanism of the rear chuck, the specifications of the induction heating unit, the spinning cutter head, etc. of the device can be quickly replaced and adapted to meet the sealing and forming requirements of metal pipes with different diameters, materials and wall thicknesses. It has a wide range of applications and strong versatility. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a large-size thin-walled metal tube sealing device according to the present invention; Figure 2 This is a cross-sectional view of the axially retractable pushing mechanism built into the rear chuck in the retracted state of a large-size thin-walled metal tube sealing device of the present invention, showing the state of the pushing ring retracting and avoiding collision; wherein (a) is the main view and (b) is the AA cross-sectional view in (a). Figure 3 This is a cross-sectional view of the axially retractable push mechanism of the rear chuck in the extended state of a large-size thin-walled metal tube sealing device of the present invention, showing the state in which the push ring extends forward to perform push unloading; wherein (a) is the main view and (b) is the AA cross-sectional view in (a). Figure 4 This is a schematic diagram showing the connection between a large-size thin-walled metal pipe sealing device and a pipe fitting according to the present invention; Figure 5 This is a schematic diagram of the state of the pipe fitting before sealing in step three of the present invention, which is a method for sealing large-size thin-walled metal pipes. Figure 6 This is a schematic diagram of the state of the pipe fitting after sealing in step five of the sealing method for a large-size thin-walled metal pipe according to the present invention; Figure 7 This is a schematic diagram of the separation process of the inner and outer layers of the pipe fittings in step six of the sealing method for a large-size thin-walled metal pipe according to the present invention.

[0027] In the diagram: 1-Bearing platform, 2-Induction heating coil guide rail, 3-Induction heating unit, 4-Spinning cutter body rotary guide rail, 5-Spinning cutter body, 6-Vertical fixing plate, 7-Rear chuck, 701-Rear chuck body, 702-Rear chuck jaws, 8-Front chuck, 801-Front chuck body, 802-Front chuck jaws, 9-Transmission plate, 10-Axial positioning column, 11-Push ring, 12-Through push rod, 13-Hollow rotary cylinder, 14-Inner metal tube, 15-Outer auxiliary sleeve. Detailed Implementation

[0028] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0029] The purpose of this invention is to provide a sealing device and method for large-size thin-walled metal tubes to solve the problems existing in the prior art. The specific embodiments of this invention are further described below with reference to the accompanying drawings.

[0030] Example 1: A sealing device for large-size thin-walled metal tubes includes a support platform 1, an induction heating coil guide rail 2, an induction heating unit 3, a spinning cutter body rotary guide rail 4, a spinning cutter body 5, a vertical fixing plate 6, a rear chuck 7, a front chuck 8, a transmission plate 9, an axial positioning column 10, a push ring 11, an insert push rod 12, and a hollow rotary cylinder 13.

[0031] The induction heating coil guide rail 2 is horizontally fixed on the support platform 1. The induction heating unit 3 includes an insulating sliding bracket and an induction coil body mounted on the insulating sliding bracket. The insulating sliding bracket is mounted on the induction heating coil guide rail 2 and is driven by a servo motor and a ball screw mechanism to make precise linear feed motion along the axial direction of the induction heating coil guide rail 2. The spinning cutter body rotary guide rail 4 is rotatably mounted on the center position of the support platform 1 via a rotary spindle and can be driven by a rotary drive motor to make rotary motion around the central axis of the support platform 1 (coaxial with the pipe). The spinning cutter body 5 is mounted on the spinning cutter body rotary guide rail 4 and can be driven by a hydraulic propulsion cylinder or a servo electric cylinder to make linear feed motion along the radial direction of the spinning cutter body rotary guide rail 4. The vertical fixing plate 6 is vertically fixed on the support platform 1 and remains perpendicular to the support platform 1. The vertical end face of the vertical fixing plate 6 is rotatably mounted on the main bearing seat, and the rotary spindle can be driven to rotate by the spindle rotary motor. The rear chuck 7 includes a rear chuck body 701 and three rear chuck jaws 702. The rear chuck body 701 is coaxially fixed on the output end of the rotary spindle, and the rear chuck jaws 702 are installed in the slide groove of the rear chuck body 701, which can clamp the inner metal tube 14 to achieve positioning and fixation. The hollow rotary cylinder 13 is fixed to the center of the rear chuck body 701. The piston of the hollow rotary cylinder 13 travels from the inside to the outside along the axis of the rear chuck body 701. The hollow rotary cylinder 13 is connected to an external air source through a pneumatic rotary joint. One end of the through push rod 12 is fixedly connected to the piston of the hollow rotary cylinder 13. The through push rod 12 is arranged circumferentially on the piston, and the through push rod 12 is misaligned with the rear chuck jaw 702 in the circumferential direction to ensure that the axial extension and retraction of the through push rod 12 is in harmony with the radial extension and retraction of the rear chuck jaw 702. The opening and closing mechanisms do not interfere with each other in space, and during high-speed spinning, the hollow rotary cylinder 13, the insert push rod 12, and the push ring 11 maintain a relatively stationary synchronous rotation with the rear chuck body 701; the other end of the insert push rod 12 is fixedly connected to the push ring 11; the inner diameter of the hollow rotary cylinder 13 and the inner diameter of the annular surface formed by all the insert push rods 12 are both larger than the outer diameter of the inner metal tube 14; the push ring 11 is circular, its inner diameter is larger than the outer diameter of the inner metal tube 14, and its outer diameter is smaller than or equal to the outer diameter of the outer auxiliary sleeve 15. Before the spinning operation, the hollow rotary cylinder 13 retracts, and the insert push rod 12 pulls the push ring 11 back to its stroke limit (usually near the front end face of the rear chuck 7), without interfering with the assembly and positioning of the outer auxiliary sleeve 15; during the separation operation, the hollow rotary cylinder 13 pressurizes and drives the insert push rod 12 to extend the push ring 11 forward so that its front end face flat abuts against the non-sealed end face of the outer auxiliary sleeve 15, thereby achieving the non-destructive flat-pushing peeling of the outer auxiliary sleeve 15 without loosening the inner metal tube 14; The front chuck 8 includes a front chuck body 801 and a front chuck jaw 802. The front chuck body 801 is coaxially fixed on the front end face of the rear chuck body 701. The front chuck jaw 802 can clamp the outer auxiliary sleeve 15 to achieve positioning and fixation. The transmission plate 9 is horizontally fixed on the vertical end face of the vertical fixing plate 6. It is equipped with a lifting cylinder, which can drive the axial positioning column 10 to achieve vertical lifting and lowering movement. The axial positioning column 10 is installed in the positioning hole on the lower surface of the transmission plate 9. The axial positioning column 10 can achieve precise axial positioning and retraction avoidance of the pipe through lifting and lowering.

[0032] A method for sealing large-size thin-walled metal tubes includes the following steps: Step 1: Pipe pretreatment and cutting: Select a metal pipe with an inner diameter 0.2-0.5mm larger than the outer diameter of the inner metal pipe 14 to be sealed as the outer auxiliary sleeve 15. Cut the outer auxiliary sleeve 15 to a set length, which is equal to the set horizontal distance between the front end face of the rear chuck body 701 and the positioning end face of the axial positioning post 10. After cutting, deburr and polish the end faces and mating surfaces of the inner and outer pipes, and apply a high-temperature anti-sticking agent to the mating surfaces.

[0033] Step 2: Sleeve assembly: Coaxially fit the outer auxiliary sleeve 15 onto the end of the inner metal tube 14 to be sealed, adjust the axial position to ensure that the end faces of the two tubes at the end to be sealed are completely flush, and ensure that the inner metal tube 14 has no axial translation or circumferential rotation freedom relative to the outer auxiliary sleeve 15 after assembly.

[0034] Step 3: Clamping and Positioning: Insert the assembled composite pipe axially into the center holes of the rear chuck body 701 and the front chuck body 801 until the non-sealed end face of the outer auxiliary sleeve 15 is completely in contact with the front end face of the rear chuck body 701. Activate the lifting cylinder to drive the transmission plate 9 to lower the axial positioning column 10, completing the axial positioning of the pipe. After confirming that the pipe position is correct, clamp it sequentially through the rear chuck jaws 702 and the front chuck jaws 802 to fix the inner metal pipe 14 and the outer auxiliary sleeve 15 respectively.

[0035] Step 4: Induction Heating: Retract the axial positioning column 10 to a safe position, start the spindle rotary motor to drive the rear chuck body 701 and the front chuck body 801 to rotate synchronously at high speed, thereby driving the inner metal tube to rotate at high speed around its own axis. The rotational motion of the inner metal tube achieves dynamic and uniform heating in the circumferential direction, eliminating the circumferential temperature gradient. In this rotating state, start the servo motor to drive the induction heating unit 3 to feed axially along the induction heating coil guide rail 2, so that its induction coil body is coaxially sleeved on the end of the composite tube to be spun and sealed, heating the tube until the entire section of the inner metal tube 14 to be heated reaches the plastic deformation phase transformation temperature.

[0036] Step 5: Spinning and Sealing: After induction heating is completed, the servo motor is reversed to drive the induction heating unit 3 to quickly return to a safe position along the induction heating coil guide rail 2. The inner metal tube is kept in a high-speed rotating state, utilizing its own rotational motion to provide tangential forming power and continuous material flow. Subsequently, the hydraulic propulsion cylinder or servo electric cylinder is activated to radially feed the spinning cutter body 5 along the spinning cutter body rotary guide rail 4, applying stable radial pressure to the sealing end of the rotating tube. Simultaneously, the rotary drive motor is activated to make the spinning cutter body rotary guide rail 4 rotate around the tube axis, driving the spinning cutter body 5 to complete a one-time spinning and sealing process until the tube opening is completely sealed. During the operation, the contour shape and final closure degree of the seal can be controlled by adjusting the radial feed speed and feed depth of the spinning cutter body 5 at different stages.

[0037] Step Six: Separation of Inner and Outer Pipes: After the spinning and sealing is completed, the spinning cutter body 5 retracts to the initial safe position along the spinning cutter body rotary guide rail 4, stops the rotation of the front and rear chuck bodies and the pipe, releases the front chuck jaws 802, releases the clamping constraint on the outer auxiliary sleeve 15, maintains the clamping state of the rear chuck jaws 702 on the inner metal pipe 14, starts the hollow rotary cylinder 13 to pressurize, drives the insertion push rod 12 to drive the push ring 11 to extend forward, applies axial thrust to the outer auxiliary sleeve 15, and smoothly pushes it out from the inner metal pipe 14, realizing the automated and non-destructive separation of the inner and outer pipes.

[0038] Step 7: Cooling and post-processing: Remove the sealed inner metal tube 14 from the rear chuck jaws 702 and allow it to cool naturally to room temperature. Deburr, polish and inspect the sealed area to obtain qualified sealed tube fittings.

[0039] Example 2: In the large-size thin-walled metal tube sealing device and method provided in this embodiment, when the inner metal tube 14 to be sealed is made of non-magnetic or weakly magnetic materials such as aluminum alloy or titanium alloy, a metal tube made of carbon steel or low alloy steel is used as the outer auxiliary sleeve 15. During the induction heating process in step four, the outer carbon steel auxiliary sleeve 15 is rapidly induced to heat in the high-frequency induction magnetic field and acts as a covering heat source. Through interlayer heat conduction, the heat is uniformly and rapidly transferred to the inner aluminum alloy or titanium alloy metal tube 14. Thus, without changing the original high-frequency heating equipment, efficient, dynamic uniform temperature heating and hot spinning sealing of non-magnetic thin-walled metal tubes are achieved. The other device structures and operating steps are exactly the same as in Embodiment 1.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A sealing device for large-size thin-walled metal tubes, characterized in that, Includes a support platform (1), an induction heating coil guide rail (2), an induction heating unit (3), a spinning cutter body rotary guide rail (4), a spinning cutter body (5), a vertical fixing plate (6), a rear chuck (7), a front chuck (8), a transmission plate (9), an axial positioning column (10), a push ring (11), an insert push rod (12), and a hollow rotary cylinder (13); The induction heating coil guide rail (2) is horizontally fixed on the support platform (1). The induction heating unit (3) includes an insulating sliding bracket and an induction coil body mounted on the insulating sliding bracket. The insulating sliding bracket is mounted on the induction heating coil guide rail (2) and is driven by a servo motor and a ball screw mechanism. It can make precise linear feed motion along the axial direction of the induction heating coil guide rail (2). The spinning cutter body rotary guide rail (4) is rotatably mounted on the center position of the support platform (1) through a rotary spindle. It can be driven by a rotary drive motor to make rotary motion around the central axis of the support platform (1). The spinning cutter body (5) is mounted on the spinning cutter body rotary guide rail (4) and can be driven by a hydraulic push cylinder or a servo electric cylinder to make linear feed motion along the radial direction of the spinning cutter body rotary guide rail (4). The vertical fixing plate (6) is vertically fixed on the bearing platform (1) and remains perpendicular to the bearing platform (1). A rotary spindle is rotatably mounted on the vertical end face of the vertical fixing plate (6) via a main bearing seat, and can be driven to rotate by a spindle rotary motor. The rear chuck (7) includes a rear chuck body (701) and rear chuck jaws (702). The rear chuck body (701) is coaxially fixedly mounted on the output end of the rotary spindle. The chuck jaws (702) are installed in the slide groove of the rear chuck body (701) and can clamp the inner metal tube (14) to achieve positioning and fixation; the hollow rotary cylinder (13) is fixed at the center of the rear chuck body (701), and the piston of the hollow rotary cylinder (13) travels from the inside to the outside along the axis of the rear chuck body (701); the hollow rotary cylinder (13) is connected to an external air source through a pneumatic rotary joint; the hollow rotary cylinder (13) The piston of the piston is fixedly connected to one end of the insert push rod (12). The insert push rod (12) is arranged circumferentially on the piston and is staggered with the rear chuck jaws (702) in the circumferential direction. This ensures that the axial extension and retraction of the insert push rod (12) and the radial opening and closing of the rear chuck jaws (702) do not interfere with each other in space. During high-speed spinning, the hollow rotary cylinder (13), the insert push rod (12) and the push ring (11) move together with the rear chuck. The disc body (701) maintains a relatively stationary synchronous rotation; the other end of the insert push rod (12) is fixedly connected to the push ring (11); the inner diameter of the hollow rotary cylinder (13) and the inner diameter of the annular surface formed by all the insert push rods (12) are greater than the outer diameter of the inner metal tube (14); the push ring (11) is circular, its inner diameter is greater than the outer diameter of the inner metal tube (14), and its outer diameter is less than or equal to the outer diameter of the outer auxiliary sleeve (15); The front chuck (8) includes a front chuck body (801) and a front chuck jaw (802). The front chuck body (801) is coaxially fixed on the front end face of the rear chuck body (701). The front chuck jaw (802) can clamp the outer auxiliary sleeve (15) to achieve positioning and fixation. The transmission plate (9) is horizontally fixed on the vertical end face of the vertical fixing plate (6). It is equipped with a lifting cylinder, which can drive the axial positioning column (10) to achieve vertical lifting and lowering movement. The axial positioning column (10) is installed in the positioning hole on the lower surface of the transmission plate (9). The axial positioning column (10) can achieve precise axial positioning and retraction avoidance of the pipe through lifting and lowering.

2. A method for sealing large-size thin-walled metal tubes using the sealing device for large-size thin-walled metal tubes as described in claim 1, characterized in that: Includes the following steps: Step 1: Pipe pretreatment and pipe cutting: Select a metal pipe with an inner diameter larger than the outer diameter of the inner metal pipe (14) to be sealed as the outer auxiliary sleeve (15). Cut the outer auxiliary sleeve (15) to a set length, which is equal to the set horizontal distance between the front end face of the rear chuck body (701) and the positioning end face of the axial positioning column (10). After cutting, deburr and polish the end faces and mating surfaces of the inner and outer pipes, and apply a high-temperature anti-sticking agent to the mating surfaces. Step 2: Sleeve assembly: Coaxially fit the outer auxiliary sleeve (15) onto the end of the inner metal tube (14) to be sealed, adjust the axial position to ensure that the end faces of the two tubes at the end to be sealed are completely flush, and ensure that the inner metal tube (14) has no axial translation or circumferential rotation freedom relative to the outer auxiliary sleeve (15) after assembly. Step 3: Clamping and positioning: Insert the assembled composite pipe axially into the center holes of the rear chuck body (701) and the front chuck body (801) until the non-sealed end face of the outer auxiliary sleeve (15) is completely in contact with the front end face of the rear chuck body (701); start the lifting cylinder to drive the transmission plate (9) to lower the axial positioning column (10) to complete the axial positioning of the pipe; after confirming that the position of the pipe is correct, clamp it in sequence through the rear chuck jaws (702) and the front chuck jaws (802) to fix the inner metal pipe (14) and the outer auxiliary sleeve (15) respectively. Step 4: Induction heating: Retract the axial positioning column (10) to a safe position, start the spindle rotation motor to drive the rear chuck body (701) and the front chuck body (801) to rotate synchronously at high speed, thereby driving the inner metal tube to rotate at high speed around its own axis. The rotational motion of the inner metal tube is used to achieve circumferential dynamic uniform heating and eliminate the circumferential temperature gradient. In this rotating state, start the servo motor to drive the induction heating unit (3) to feed axially along the induction heating coil guide rail (2), so that its induction coil body is coaxially sleeved on the end of the composite tube to be spun and sealed, and heat the tube until the entire section of the inner metal tube (14) to be heated reaches the plastic deformation phase change temperature. Step 5: Spinning and sealing: After induction heating is completed, control the servo motor to reverse and drive the induction heating unit (3) to quickly return to a safe position along the induction heating coil guide rail (2); maintain the high-speed rotation of the inner metal tube, and use the rotational motion of the inner metal tube itself to provide tangential forming power and continuous material flow conditions; then, start the hydraulic propulsion cylinder or servo electric cylinder to make the spinning cutter body (5) radially feed along the spinning cutter body rotary guide rail (4), apply stable radial pressure to the sealing end of the rotating pipe, and at the same time start the rotary drive motor to make the spinning cutter body rotary guide rail (4) rotate around the pipe axis, drive the spinning cutter body (5) to complete the one-time spinning and sealing until the pipe opening is completely closed and formed; during the operation, the contour shape and final closure degree of the sealing can be controlled by adjusting the radial feed speed and feed depth of the spinning cutter body (5) at different stages; Step 6: Separation of inner and outer pipes: After the spinning and sealing is completed, the spinning cutter body (5) returns to the initial safe position along the spinning cutter body rotary guide rail (4), stops the rotation of the front and rear chuck bodies and the pipes, releases the front chuck jaws (802), releases the clamping constraint on the outer auxiliary sleeve (15), maintains the clamping state of the rear chuck jaws (702) on the inner metal pipe (14), starts the hollow rotary cylinder (13) to pressurize, drives the insertion push rod (12) to drive the push ring (11) to extend forward, applies axial thrust to the outer auxiliary sleeve (15), and pushes it smoothly out of the inner metal pipe (14), realizing the automatic and non-destructive separation of inner and outer pipes; Step 7: Cooling and post-processing: Remove the sealed inner metal tube (14) from the rear chuck jaws (702), let it cool naturally to room temperature, deburr, polish and inspect the sealing area, and finally obtain qualified sealed tube fittings.

3. The sealing method for a large-size thin-walled metal tube according to claim 2, characterized in that, The inner diameter of the outer auxiliary sleeve (15) is 0.2-0.5 mm larger than the outer diameter of the inner metal tube (14) to be sealed.

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