A device for eliminating residual stress in seamless steel pipes

Abstract

This invention relates to the field of steel pipe processing equipment technology, and discloses a device for eliminating residual stress in seamless steel pipes. The device includes a base, a top seat fixedly connected to the top of the base, and a controller for controlling the overall operating status of the device located at the center of the front side of the top of the base; an initial release mechanism is also located at the center of the top of the base. By adding and setting an internal and external synchronous mechanism, when eliminating residual stress in seamless steel pipes, this mechanism can adaptively switch between hydraulic and pneumatic processing modes according to the steel pipe wall thickness, adapting to the processing requirements of different specifications of high-altitude and high-pressure seamless steel pipes. It balances the radial stress difference of the pipe wall through internal constant pressure, and, in conjunction with the external wall roller rotation structure, achieves synchronous stress homogenization and trimming of the pipe's internal and external surfaces. This mechanism takes over the pipe's condition after pre-treatment, removes residual and disordered stress in the middle layer, and standardizes the pipe's structural dimensions, providing a stable base for subsequent deep alternating shaping treatment.

Description

Technical Field

[0001] This invention relates to the field of steel pipe processing equipment technology, specifically to a device for eliminating residual stress in seamless steel pipes. Background Technology

[0002] High-pressure fluid transport pipelines in frigid regions typically use seamless steel pipes as the core transport medium. These pipelines face dual challenges during actual service: on one hand, they must withstand long-term high-pressure reciprocating alternating loads to ensure the stability and safety of fluid transport; on the other hand, they must adapt to extreme low-temperature and frigid environments to prevent pipe failure due to excessively low temperatures. Therefore, stringent performance requirements are placed on these seamless steel pipes. Not only must residual stress generated during processing be completely eliminated to prevent deformation and cracking during later use, but the original high strength of the pipe must also be fully preserved, while significantly improving its low-temperature resistance to brittle fracture to meet the dual service requirements.

[0003] During the processing and forming of seamless steel pipes, a series of technological operations generate a large amount of residual stress. Specifically, plastic processing processes such as high-temperature piercing rolling and cold drawing and cold rolling can cause distortion of the internal crystal lattice of the metal, forming plastic deformation stress. Subsequent mechanical straightening processes apply additional external force to correct the bending deformation of the pipe, further accumulating internal stress. These residual stresses remain inside the pipe for a long time, becoming a hidden danger affecting its service performance. Currently, the industry usually uses high-temperature annealing to remove these residual stresses. However, for thick-walled high-strength alloy seamless steel pipes used for high-pressure fluid transportation in cold regions, this treatment method has many fatal drawbacks.

[0004] High-temperature annealing treatment causes the grains of thick-walled high-strength alloy seamless steel pipes to become coarse, resulting in a significant decrease in the pipe's strength and hardness, directly destroying its original excellent mechanical properties and failing to meet the strength requirements of high-pressure transportation. Simultaneously, due to the large pipe wall thickness, uneven heating of the inner and outer layers during high-temperature annealing leads to the inability to completely eliminate deep residual stress, easily causing thermal bending deformation of the pipe and affecting its dimensional accuracy. Furthermore, this treatment method cannot achieve full-dimensional elimination of residual stress, nor can it improve the pipe's high-pressure bearing capacity and low-temperature brittle fracture resistance. Ultimately, the treated seamless steel pipe is unsuitable for the dual harsh service conditions of high-pressure fluid transportation in cold regions, posing safety hazards during use. Therefore, those skilled in the art have proposed a device for eliminating residual stress in seamless steel pipes to solve the aforementioned technical problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a device for eliminating residual stress in seamless steel pipes, solving the problem that pipes treated by traditional high-temperature annealing methods cannot be adapted to the service conditions in cold and high-altitude regions.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a device for eliminating residual stress in seamless steel pipes, comprising, The base has a top seat fixedly connected to its top, and a controller for controlling the overall operating status of the device is set in the middle of the front side of the top of the base. The initial release mechanism, located at the top center of the base, is used for the initial release of the seamless steel pipe before subsequent processing. The pretreatment mechanism, which is set on the base, is used to perform stress relief pretreatment on the seamless steel pipe after the initial release mechanism. The internal and external synchronization mechanism is located at the bottom of the top seat and is used to perform internal and external stress relief treatment on the seamless steel pipe after the pretreatment mechanism. The alternating circulation mechanism, which is set on the base, is used to perform alternating temperature circulation treatment on the seamless steel pipe after it has been processed by the internal and external synchronous mechanism.

[0007] Preferably, the initial release mechanism includes an insulating support frame, with insulating support frames fixedly connected to both sides of the middle of the top of the base, and V-shaped seats fixedly connected to the middle of the top of each insulating support frame. A hydraulic cylinder is provided at the middle of the top of the base, and a low-frequency vibrator for generating low-frequency vibration is provided at the top of the rod of the hydraulic cylinder. A transmission seat for uniformly transmitting low-frequency vibration to various parts of the steel pipe is provided at the top of the low-frequency vibrator, and an arc-shaped contact part for contacting the surface of the steel pipe is provided at the top of the transmission seat.

[0008] Preferably, the pre-processing mechanism includes a high-frequency pulse power supply, a high-frequency pulse power supply is provided at the front middle part of the top of the base, a conductive electrode seat is provided at the middle of the bottom inner side of the V-shaped seat, an electrode post is provided at the middle of the top of the conductive electrode seat, and a conductive contact seat is provided at the top of the electrode post.

[0009] Preferably, the internal and external synchronization mechanism includes a linear moving seat one, which is provided on one side of the top center of the base, and a linear moving seat two is provided on the other side of the top center of the base. Both the linear moving seat one and the linear moving seat two are fixedly connected to a sealing seat at their tops, and a sealing cavity matching the size of the seamless steel pipe is opened in the middle of the adjacent side of the sealing seat.

[0010] Preferably, the internal and external synchronization mechanism further includes a high-pressure infusion pump. A high-pressure infusion pump is installed in the lower middle part of one side of the linear motion seat. The outlet end of the high-pressure infusion pump is connected to the internal flow channel of the linear motion seat and the interior of the sealing cavity through a connecting pipe. A high-pressure vortex air pump is installed in the lower middle part of the other side of the linear motion seat. The outlet end of the high-pressure vortex air pump is connected to the internal flow channel of the linear motion seat and the interior of the sealing cavity through a connecting pipe. During use, the high-pressure vortex air pump cooperates with the variable frequency motor to realize the dynamic adjustment of airflow frequency and pressure, so that the airflow discharged into the seamless steel pipe through the sealing cavity forms a pulsating characteristic for output.

[0011] Preferably, the internal and external synchronization mechanism further includes a mounting base one, which is provided on the inner top of the top seat. Hydraulic cylinders two are provided on both sides of the middle part of the top seat. The bottom ends of the rods of the hydraulic cylinders two are connected to the top middle parts of the mounting base one. A semi-circular concave cavity is opened in the middle of the bottom end of the mounting base one. Multiple outer wall pressure rollers are arranged in a circular array on the inner wall of the concave cavity. Synchronous drivers for synchronously driving the multiple outer wall pressure rollers are provided on both sides of the top end of the mounting base one. The mounting base two is provided on the outer middle of the sealing seat on the linear moving seat two. A gradient pressure relief seat is provided in the middle of the mounting base two.

[0012] Preferably, the alternating circulation mechanism includes a mounting cover. Two mounting covers that can be spliced ​​and closed are provided on the top two sides of the base. Self-moving connecting frames are provided on both sides of the bottom end of the top base. The middle and lower parts of the connecting frames are respectively connected to the corresponding positions of the outer wall of the mounting cover on the same side. A dispersing seat is provided at the top of each mounting cover. An inclined spray seat is provided at the top of the inner wall of each mounting cover. The interior of the inclined spray seat is connected to the interior of the dispersing seat.

[0013] Preferably, the alternating circulation mechanism further includes side seats, and side seats are provided on both sides of the upper middle part of the insulating support frame. A friction drive wheel is provided on the side of the side seat near the V-shaped seat. A friction drive driver is provided on the side seat to drive the friction drive wheel. Plate heaters are provided on both sides of the inner wall of the mounting cover.

[0014] Working Principle: When performing stress relief operations on seamless steel pipes used as high-pressure transmission pipelines in cold regions, the equipment first activates the initial release mechanism. Workers move the seamless steel pipe to be processed to the equipment's processing station. The V-shaped seat mounted on the top of the insulating support frame provides overall stable support for the seamless steel pipe. Utilizing the fitting and limiting characteristics of the V-shaped structure, the offset and swaying of the steel pipe during operation are effectively limited, ensuring the stability and coaxiality of the seamless steel pipe throughout the entire processing. Subsequently, the hydraulic cylinder mounted on the base is activated. The telescopic rod of the hydraulic cylinder pushes upward at a uniform speed, simultaneously driving the low-frequency vibrator mounted at the end and the transmission seat to move vertically upward as a whole. During the upward movement of the transmission seat, the pre-set arc-shaped fitting part at its top precisely aligns with the bottom of the seamless steel pipe. The outer wall of the tube is tightly fitted to achieve gapless force transmission. After the fitting and positioning are completed, the low-frequency vibrator starts and outputs stable low-frequency vibration energy. The generated low-frequency vibration is completely and uniformly transmitted to the entire seamless steel pipe through the transmission seat, causing the entire seamless steel pipe to generate a synchronous resonance effect. With the help of uniform resonance, the surface macroscopic residual stress generated during the cold drawing and rolling process of the seamless steel pipe can be effectively released. At the same time, it can guide and dissipate the ultra-high initial residual stress accumulated inside the pipe, weaken the stress concentration phenomenon inside the pipe in advance, and effectively avoid the microstructural damage and structural defects of the steel pipe caused by local stress change during the subsequent pulse current high-temperature instantaneous treatment. The initial stress release pretreatment process before the stress elimination operation of the seamless steel pipe is successfully completed. After the initial pretreatment is completed... The equipment automatically starts the pre-processing mechanism. The operator sends a start command via the controller mounted on the base, activating the high-frequency pulse power supply. The controllable pulse current output by the high-frequency pulse power supply is transmitted evenly and stably to both ends of the seamless steel pipe via the conductive electrode base, electrode post, and conductive contact base mounted at the ends. This ensures the current completely flows through the entire seamless steel pipe. During current conduction, controllable instantaneous Joule heating is generated inside the steel pipe. Simultaneously, relying on the electroplastic effect of metals, the internal rheological stress of the steel is effectively reduced, significantly decreasing the resistance to lattice dislocation movement. This promotes the rapid slippage and relaxation of distorted dislocations inside the pipe, efficiently dissolving the macroscopic deformation residual stress remaining from the cold drawing and rolling processes. Throughout the operation, the accompanying infrared temperature probe continuously monitors the steel pipe in real time. If the surface temperature exceeds the preset safety threshold, the operator can manually adjust the pulse frequency, current, and other core parameters of the high-frequency pulse power supply in real time via the controller. This precisely avoids problems such as localized overheating and abnormal grain changes in the steel pipe, ensuring that the original mechanical properties of the pipe are not damaged. After the pulse treatment is completed, the high-frequency pulse power supply automatically stops working, and the seamless steel pipe is naturally air-cooled to room temperature, thoroughly completing the pre-treatment process for stress relief of the seamless steel pipe. After the pre-treatment process is completed, the equipment activates the internal and external synchronization mechanism. The operator issues a linkage command through the controller to control the linear moving seats one and two above the base to move synchronously and uniformly towards the center of the equipment. During the movement of the linear moving seats one and two...The equipment synchronously moves the top-mounted sealing seat, ultimately sealing both ends of the seamless steel pipe through the sealing cavity inside the sealing seat. This creates a completely closed pressure-bearing cavity inside the steel pipe, providing a sealed working environment for subsequent pressurization and stress relief operations. The equipment automatically matches the corresponding processing mode based on the actual wall thickness of the seamless steel pipe. Using a preset wall thickness value as the criterion, thick-walled steel pipes exceeding the set value are processed using hydraulic pressurization, while thin-walled steel pipes below the set value are processed using pneumatic pressurization. During hydraulic processing, the high-pressure pump mounted on the linear moving seat starts operating, continuously delivering hydraulic medium to the sealing cavity through a dedicated connecting pipeline, ultimately and smoothly injecting it into the sealed cavity of the seamless steel pipe. Internally, during operation, pressure detection equipment collects real-time pressure data inside the steel pipe. When the internal pressure reaches the preset stable pressure value, the high-pressure infusion pump automatically stops, and the equipment enters the constant pressure holding stage. Relying on the uniform and constant hydraulic pressure inside the steel pipe, a small amount of controllable elastic deformation is induced in the pipe wall, effectively balancing the compressive stress inside the pipe wall and the tensile stress outside, and eliminating the radial stress difference of the thick-walled pipe. After the holding process is completed, the staff controls the gradient pressure relief seat mounted on the second mounting base to operate in an orderly manner through the controller, strictly following the three-level gradient sequence of high pressure, medium pressure, and normal pressure to slowly release pressure, preventing the new additional residual stress caused by instantaneous pressure relief rebound, and ensuring the stress balance effect. When performing pneumatic treatment operations, the high-pressure vortex air pump rotates at high speed through the internal impeller, in the surrounding... The air inside the cavity undergoes multiple cycles of compression and circulation. Simultaneously, the frequency conversion motor regulates the airflow, creating a stable, pulsating airflow within the steel pipe. This pulsating airflow impacts all areas of the pipe's inner wall, achieving uniform stress distribution. As inflation continues, the internal pressure gradually rises to the preset pressure value. At this point, the equipment stops inflation and enters a constant pressure holding state, further balancing the residual stress distribution within the thin-walled steel pipe. After the holding process is complete, the operator uses the controller to control the gradient pressure relief seat on mounting base two, slowly releasing pressure in a gradient manner (high pressure, medium pressure, normal pressure) to avoid secondary stress damage caused by instantaneous pressure release. While the pressurization operation inside the seamless steel pipe is proceeding simultaneously, the pressure relief seat mounted at the bottom of the top base... Hydraulic cylinder two starts operating, and its telescopic rod extends downwards at a constant speed, simultaneously driving mounting base one, connected to the bottom of the rod, to move vertically downwards. During this downward movement, the seamless steel pipe gradually retracts into the concave cavity at the bottom of mounting base one until the outer wall pressure roller mounted inside the concave cavity is in close contact with the outer wall of the seamless steel pipe. After contact is established, the synchronous driver mounted on mounting base one starts operating, stably driving multiple sets of outer wall pressure rollers inside the concave cavity to rotate synchronously in the same direction. During the rotation of the outer wall pressure rollers, friction drives the seamless steel pipe to rotate at a constant speed, applying uniform and flexible circumferential pressure to the outer wall of the steel pipe. Through the constant pressure support inside the steel pipe and the balanced external roller pressure, the chaotic residual stress remaining on the surface and middle layers of the steel pipe is comprehensively eliminated.The system efficiently completes the internal and external stress relief treatment of seamless steel pipes. After the internal and external synchronous treatment is completed, the equipment starts the alternating circulation mechanism. First, the mounting base on the top seat moves synchronously towards the center of the equipment. During the displacement of the mounting base, the mounting cover fixed at the bottom moves accordingly. After the two sets of mounting covers move to the center position of the equipment, they are precisely spliced ​​and closed to form a complete closed cavity, which completely wraps and seals the processed seamless steel pipe. Then, the liquid nitrogen delivery pump starts, stably delivering low-temperature liquid nitrogen to the dispersion seat at the top of the mounting cover. After entering the dispersion seat, the liquid nitrogen is evenly distributed and introduced into each set of inclined spray seats. Finally, it is evenly sprayed on the outer surface of the seamless steel pipe in the form of atomized low-temperature fluid. At the same time, the friction drive on the side seat starts to operate. The friction drive drives the friction drive wheel on the side seat to rotate continuously. Through friction transmission, the seamless steel pipe placed inside the V-shaped seat rotates at a low speed and uniform speed, completely avoiding local spray blind spots and ensuring the steel pipe... The uniformity of the overall low-temperature spraying is ensured by the seamless steel pipe undergoing continuous liquid nitrogen spraying inside the installation hood, causing the overall temperature to drop uniformly to the ultra-low temperature range. Once the preset low temperature value is reached, the equipment enters a constant temperature insulation stage to stabilize the low-temperature lattice state of the pipe. After the low-temperature insulation process is completed, the plate heater installed inside the installation hood starts working. With the friction drive wheel continuously driving the steel pipe's rotation, the entire steel pipe achieves a gradient and uniform temperature recovery. After reaching the preset process temperature, it undergoes another constant temperature insulation cycle, completing a single cold and hot alternating cycle operation. The equipment can automatically repeat the cold and hot alternating cycle process multiple times according to the pipe's working conditions. Relying on the alternating aging mechanism of low-temperature freezing and gradient temperature recovery, and completely abandoning the traditional high-temperature annealing process, it thoroughly releases the deep-seated latent intergranular residual stress in the pipe, while refining the metal's micro-grain structure. This effectively improves the seamless steel pipe's low-temperature resistance to brittle fracture and structural stability under extremely cold conditions, ultimately completing the cold and hot alternating cycle shaping process for the seamless steel pipe.

[0015] This invention provides a device for eliminating residual stress in seamless steel pipes. It has the following beneficial effects: 1. By adding and setting an initial release mechanism, this invention relieves the concentrated residual stress on the surface of the seamless steel pipe through low-frequency resonance during residual stress elimination. This mechanism disperses the local stress accumulation points formed during pipe forming. Secondly, it can weaken the ultra-high initial stress inside the pipe in advance, avoiding the stress impact risk of subsequent processes. Furthermore, as the first pre-treatment structure of the entire equipment, this mechanism can optimize the initial stress state of the pipe, avoid microstructural damage during subsequent pulse current treatment, stabilize the basic state of pipe processing, and ensure the orderly and stable connection of subsequent multi-level coordinated stress treatment processes.

[0016] 2. By adding and setting a pre-treatment mechanism, this invention not only utilizes the electroplastic effect of pulsed current to effectively dissolve the macroscopic deformation stress remaining from cold drawing and rolling of the steel pipe and regulate the overall axial stress distribution of the pipe, but also relies on the temperature control function to avoid local overheating of the pipe and fully preserve the original high-strength mechanical properties of the pipe. It also inherits the pre-treatment effect of the initial release mechanism, further homogenizes the residual stress in the main body of the pipe, reduces the difficulty of subsequent internal and external synchronous stress repair, and improves the effect of shallow stress elimination in the pipe.

[0017] 3. By adding and setting an internal and external synchronous mechanism, this invention can adaptively switch between hydraulic and pneumatic processing modes according to the wall thickness of the seamless steel pipe when eliminating residual stress. This adapts to the processing requirements of different specifications of high-temperature and high-pressure seamless steel pipes. It balances the radial stress difference of the pipe wall through internal constant pressure. On the other hand, it cooperates with the external wall roller pressing and rotating structure to achieve synchronous stress homogenization and trimming inside and outside the pipe. This mechanism takes over the state of the pipe after the pre-treatment, removes the residual and disordered stress in the middle layer, and standardizes the structural dimensions of the pipe, providing a stable base for subsequent deep alternating shaping treatment.

[0018] 4. By adding and setting an alternating circulation mechanism, this invention not only eliminates the deep intergranular residual stress in the pipe that the previous mechanism could not completely remove through alternating hot and cold cycles, thus achieving full-dimensional stress closed-loop removal, but also refines the micro-grain structure of the pipe and improves the low-temperature mechanical properties of the pipe. As the final shaping process of the whole set of equipment, it inherits all the results of the previous stress treatment, permanently stabilizes the internal lattice structure and dimensional accuracy of the pipe, and effectively improves the service capability of the steel pipe to adapt to harsh working conditions of high temperature and high pressure. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the front structure of the present invention; Figure 2 This is a schematic diagram of the rear structure of the present invention; Figure 3 This is a partial structural diagram of the low-frequency vibrator of the present invention; Figure 4 This is a partial structural diagram of the insulating support frame of the present invention; Figure 5 This is a schematic diagram of the linear moving seat II structure of the present invention; Figure 6 This is a schematic diagram of the linear moving seat of the present invention; Figure 7 This is a schematic diagram of the bottom structure of the mounting base of the present invention; Figure 8 This is a schematic diagram of the internal structure of the mounting cover of the present invention.

[0020] The components are as follows: 1. Base; 2. Hydraulic cylinder one; 3. High-frequency pulse power supply; 4. Controller; 5. Mounting cover; 6. Connecting frame; 7. Mounting seat one; 8. Hydraulic cylinder two; 9. Top seat; 10. Synchronous driver; 11. Sealing seat; 12. Insulating support frame; 13. High-pressure infusion pump; 14. Linear movement seat one; 15. V-shaped seat; 16. Low-frequency vibrator; 17. Conducting seat; 18. Arc-shaped fitting part; 19. Conductive electrode seat; 20. Friction driver; 21. Side seat; 22. Conductive contact seat; 23. Friction drive wheel; 24. Electrode column; 25. Mounting seat two; 26. Gradient pressure relief seat; 27. Linear movement seat two; 28. High-pressure vortex air pump; 29. ​​Sealing chamber; 30. Concave cavity; 31. Outer wall pressure roller; 32. Inclined spray seat; 33. Dispersion seat; 34. Plate heater. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see the appendix Figure 1 -Appendix Figure 2 This invention provides a device for eliminating residual stress in seamless steel pipes, including a base 1, a top seat 9 fixedly connected to the top of the base 1, and a controller 4 for controlling the overall operating status of the device located at the center of the front side of the top of the base 1. Please see the appendix Figure 2 -Appendix Figure 4 An initial release mechanism, located at the top center of base 1, is used for the initial release of the seamless steel pipe before subsequent processing. The initial release mechanism includes an insulating support frame 12. The insulating support frame 12 is fixedly connected to both sides of the middle part of the top of the base 1. The V-shaped seat 15 is fixedly connected to the middle of the top of the insulating support frame 12. A hydraulic cylinder 2 is provided at the middle of the top of the base 1. A low-frequency vibrator 16 that generates low-frequency vibration is provided at the top of the rod of the hydraulic cylinder 2. A transmission seat 17 that evenly transmits low-frequency vibration to various parts of the steel pipe is provided at the top of the low-frequency vibrator 16. An arc-shaped contact part 18 that fits against the surface of the steel pipe is provided at the top of the transmission seat 17.

[0023] When the initial release mechanism is activated, the worker moves the seamless steel pipe to be processed to the equipment processing station. The seamless steel pipe is supported and stabilized by the V-shaped seat 15 mounted on the top of the insulating support frame 12. The fitting and limiting characteristics of the V-shaped structure effectively limit the deviation and shaking of the steel pipe during operation, ensuring the stability and coaxiality of the seamless steel pipe throughout the entire processing. Then, the hydraulic cylinder 2 mounted on the base 1 is activated. The telescopic rod of the hydraulic cylinder 2 pushes upward at a uniform speed, which simultaneously drives the low-frequency vibrator 16 and the transmission seat 17 mounted at the end to move vertically upward as a whole. During the upward movement of the transmission seat 17, the arc-shaped fitting part 18 at its top end is precisely and tightly fitted to the bottom outer wall of the seamless steel pipe, realizing gapless force transmission.

[0024] After the fitting and positioning are completed, the low-frequency vibrator 16 starts and outputs stable low-frequency vibration energy. The generated low-frequency vibration is completely and uniformly transmitted to the entire seamless steel pipe through the conduction seat 17, causing the entire seamless steel pipe to generate a synchronous resonance effect. With the help of uniform resonance, the surface macroscopic residual stress generated during the cold drawing and rolling process of the seamless steel pipe can be effectively released. At the same time, the ultra-high initial residual stress accumulated inside the pipe can be relieved and the stress concentration phenomenon inside the pipe can be weakened in advance. This effectively avoids the microstructural damage and structural defects of the steel pipe caused by local stress change during the subsequent pulse current high-temperature instantaneous treatment, and successfully completes the initial stress release pretreatment process before the stress elimination operation of the seamless steel pipe.

[0025] Please see the appendix Figure 2 -Appendix Figure 4 The pre-treatment mechanism, which is set on the base 1, is used to perform stress relief pre-treatment on the seamless steel pipe after the initial release mechanism. The pre-processing mechanism includes a high-frequency pulse power supply 3. The high-frequency pulse power supply 3 is provided at the front middle part of the top of the base 1. A conductive electrode seat 19 is provided at the middle of the bottom inner side of the V-shaped seat 15. An electrode post 24 is provided at the middle of the top of the conductive electrode seat 19. A conductive contact seat 22 is provided at the top of the electrode post 24.

[0026] When the pretreatment mechanism is started, the staff sends a start command through the controller 4 mounted on the base 1 to turn on the high-frequency pulse power supply 3. The controllable pulse current output by the high-frequency pulse power supply 3 is uniformly and stably conducted to both ends of the seamless steel pipe through the conductive electrode seat 19, the electrode post 24 and the conductive contact seat 22 mounted at the end, so that the current completely runs through the entire seamless steel pipe. During the current conduction process, controllable instantaneous Joule heat is generated inside the steel pipe. At the same time, relying on the metal electroplastic effect, the internal rheological stress of the steel is effectively reduced, the resistance to the movement of lattice dislocations is greatly reduced, and the distortion dislocations inside the pipe are rapidly slipped and relaxed, effectively dissolving the macroscopic deformation residual stress left by the cold drawing and rolling processes of the steel pipe.

[0027] During the operation, the matching infrared temperature probe collects and monitors the surface temperature data of the steel pipe in real time. Once the monitored temperature exceeds the preset safety threshold, the staff can manually adjust the core parameters such as the pulse frequency and current of the high-frequency pulse power supply 3 in real time through the controller 4 to accurately avoid problems such as local overheating of the steel pipe and abnormal changes in grains, ensuring that the original mechanical properties of the pipe are not damaged. After the pulse treatment is completed, the high-frequency pulse power supply 3 automatically stops working, and the seamless steel pipe is naturally air-cooled to room temperature in a normal environment, thus completely completing the pre-processing of stress relief for the seamless steel pipe.

[0028] Please see the appendix Figure 5 -Appendix Figure 7 The internal and external synchronization mechanism is located at the bottom of the top seat 9 and is used to perform internal and external stress relief treatment on the seamless steel pipe after the pretreatment mechanism. The internal and external synchronization mechanism includes a linear moving seat 14. The linear moving seat 14 is provided on one side of the top center of the base 1, and the linear moving seat 27 is provided on the other side of the top center of the base 1. The top of both the linear moving seat 14 and the linear moving seat 27 are fixedly connected to a sealing seat 11. The middle of the adjacent side of the sealing seat 11 is provided with a sealing cavity 29 that matches the size of the seamless steel pipe.

[0029] When the internal and external synchronization mechanism is started, the staff sends a linkage command through the controller 4 to control the linear moving seat 14 and linear moving seat 27 above the base 1 to move synchronously towards the middle of the equipment at a uniform speed. During the movement of the linear moving seat 14 and linear moving seat 27, the sealing seat 11 assembled at the top is moved synchronously. Finally, the sealing cavity 29 opened inside the sealing seat 11 seals the two ends of the seamless steel pipe, so that the inside of the steel pipe forms a completely closed pressure-bearing cavity, creating a closed working environment for subsequent pressurization and stress relief operations.

[0030] The internal and external synchronization mechanism also includes a high-pressure infusion pump 13. The high-pressure infusion pump 13 is installed in the lower middle part of one side of the linear motion seat 14. The outlet end of the high-pressure infusion pump 13 is connected to the internal flow channel of the linear motion seat 14 and the interior of the sealing cavity 29 through a connecting pipe. The high-pressure vortex air pump 28 is installed in the lower middle part of the other side of the linear motion seat 14. The outlet end of the high-pressure vortex air pump 28 is connected to the internal flow channel of the linear motion seat 14 and the interior of the sealing cavity 29 through a connecting pipe. During use, the high-pressure vortex air pump 28 works in conjunction with a variable frequency motor to achieve dynamic adjustment of airflow frequency and pressure, so that the airflow discharged into the seamless steel pipe through the sealing cavity 29 forms a pulsating characteristic for output.

[0031] The equipment can automatically match the corresponding processing mode according to the actual wall thickness of the seamless steel pipe. Using a preset wall thickness value as the judgment standard, thick-walled steel pipes exceeding the set value are processed using hydraulic pressurization, while thin-walled steel pipes below the set value are processed using pneumatic pressurization. During hydraulic processing, the high-pressure pump 13 mounted on the linear motion seat 14 starts operating. The high-pressure pump 13 continuously delivers hydraulic medium to the sealing cavity 29 through a dedicated connecting pipeline, ultimately injecting it smoothly into the sealed cavity of the seamless steel pipe. During the operation, the pressure detection equipment collects real-time pressure data inside the steel pipe. Once the pressure inside the pipe reaches the preset pressure stabilization value, the high-pressure infusion pump 13 automatically stops, and the equipment enters the constant pressure holding stage. Relying on the uniform and constant hydraulic pressure inside the steel pipe, a small amount of controllable elastic deformation is generated in the pipe wall, effectively balancing the compressive stress inside the pipe wall and the tensile stress outside, and eliminating the radial stress difference of the thick-walled pipe. After the holding process is completed, the staff controls the gradient pressure relief seat 26 mounted on the mounting base 25 to operate in an orderly manner through the controller 4, and slowly releases pressure in strict accordance with the three-level gradient sequence of high pressure, medium pressure and normal pressure, to prevent the new additional residual stress generated by instantaneous pressure relief rebound, and to ensure the stress balance effect.

[0032] The internal and external synchronization mechanism also includes mounting base 1 7. Mounting base 1 7 is provided on the inner top of top seat 9. Hydraulic cylinder 2 8 is provided on both sides of the middle part of top seat 9. The bottom end of the rod of hydraulic cylinder 2 8 is connected to the top middle of mounting base 1 7. A semi-circular concave cavity 30 is opened in the middle of the bottom end of mounting base 1 7. Multiple outer wall pressure rollers 31 are arranged in a circular array on the inner wall of concave cavity 30. Synchronous driver 10 is provided on both sides of the top of mounting base 1 7 to synchronously drive multiple outer wall pressure rollers 31. Mounting base 2 25 is provided on the outer middle of the sealing seat 11 on linear moving seat 2 27. Gradient pressure relief seat 26 is provided in the middle of mounting base 2 25.

[0033] During the pneumatic treatment operation, the high-pressure vortex air pump 28 rotates at high speed through its internal impeller, completing multiple cycles of air compression within the annular cavity. Simultaneously, in conjunction with the frequency regulation function of the variable frequency motor, the compressed air injected into the steel pipe forms a stable pulsating airflow. This pulsating airflow can impact all areas of the inner wall of the steel pipe from all directions, achieving uniform stress distribution within the pipe. As the air pressure is continuously increased, the internal pressure of the steel pipe gradually rises to the preset pressure value. At this point, the equipment stops increasing the air pressure and enters a constant pressure holding state, further balancing the residual stress distribution inside the thin-walled steel pipe. After the holding process is completed, the operator also controls the gradient pressure relief seat 26 on the mounting base 25 through the controller 4, slowly releasing pressure according to the gradient grading mode of high pressure, medium pressure, and normal pressure, avoiding secondary stress damage caused by instantaneous pressure release.

[0034] While the pressurization and pressure-boosting operation is carried out simultaneously inside the seamless steel pipe, the hydraulic cylinder 28 mounted at the bottom of the top seat 9 is started and operated. The telescopic rod of the hydraulic cylinder 28 is pushed downward at a uniform speed, which simultaneously drives the mounting seat 17 connected to the bottom of the rod to move vertically downward. During the downward movement, the seamless steel pipe is gradually housed into the concave cavity 30 opened at the bottom of the mounting seat 17 until the outer wall pressure roller 31 mounted on the inner side of the concave cavity 30 is in close contact with the outer wall of the seamless steel pipe. After the contact is completed, the synchronous driver 10 mounted on the mounting seat 17 starts to work. The synchronous driver 10 stably drives the multiple sets of outer wall pressure rollers 31 inside the concave cavity 30 to rotate synchronously in the same direction. During the rotation of the outer wall pressure rollers 31, the friction force drives the seamless steel pipe to rotate at a uniform speed, and applies uniform and flexible pressure to the outer wall of the steel pipe in a circumferential direction. Through the constant pressure support inside the steel pipe and the balanced external roller pressure, the internal and external synchronous pressure mode is used to completely eliminate the messy residual stress remaining on the surface and middle layer of the steel pipe, and efficiently complete the internal and external synchronous stress elimination process of the seamless steel pipe.

[0035] Please see the appendix Figure 8 An alternating circulation mechanism, which is mounted on the base 1, is used to perform alternating temperature circulation treatment on the seamless steel pipe after it has been processed by the internal and external synchronous mechanisms.

[0036] The alternating circulation mechanism includes a mounting cover 5. Two mounting covers 5 that can be spliced ​​and closed are provided on the top two sides of the base 1. The bottom two sides of the top seat 9 are provided with self-moving connecting frames 6. The middle and lower parts of the connecting frames 6 are respectively connected to the corresponding positions of the outer wall of the mounting cover 5 on the same side. The top of the mounting cover 5 is provided with a dispersing seat 33. The top of the inner wall of the mounting cover 5 is provided with an inclined spray seat 32, and the interior of the inclined spray seat 32 is connected to the interior of the dispersing seat 33.

[0037] When the alternating circulation mechanism is started, the mounting base 7 mounted on the top seat 9 moves synchronously towards the center of the equipment. During the displacement of the mounting base 7, the mounting cover 5 fixed at the bottom moves synchronously. After the two sets of mounting covers 5 move to the center position of the equipment, they are precisely spliced ​​and closed to form a complete closed cavity, which completely wraps and seals the finished seamless steel pipe. Then the liquid nitrogen delivery pump is started to stably deliver low-temperature liquid nitrogen to the inside of the dispersion seat 33 on the top of the mounting cover 5. After the liquid nitrogen enters the dispersion seat 33, it is evenly distributed and introduced into the inside of each set of inclined spray seats 32. Finally, it is evenly sprayed on the outer surface of the seamless steel pipe in the form of atomized low-temperature fluid.

[0038] The alternating circulation mechanism also includes side seats 21. Side seats 21 are provided on both sides of the upper middle part of the insulating support frame 12. Friction drive wheels 23 are provided on the side of the side seats 21 near the V-shaped seat 15. Friction drive drivers 20 that drive the friction drive wheels 23 are provided on the side seats 21. Plate heaters 34 are provided on both sides of the inner wall of the mounting cover 5.

[0039] At the same time, the friction drive 20 mounted on the side seat 21 starts to run. The friction drive 20 drives the friction drive wheel 23 on the side seat 21 to rotate continuously. Through friction transmission, the seamless steel pipe placed inside the V-shaped seat 15 rotates at a low speed and uniform speed, completely avoiding local spray blind spots and ensuring the uniformity of low temperature spraying of the steel pipe. The seamless steel pipe is continuously sprayed with liquid nitrogen inside the installation cover 5, and the overall temperature drops uniformly to the ultra-low temperature range. After reaching the preset low temperature value, the equipment enters the constant temperature insulation stage to stabilize the low temperature lattice state of the pipe.

[0040] After the low-temperature insulation process is completed, the plate heater 34 installed inside the installation cover 5 starts working. With the friction drive wheel 23 continuously driving the steel pipe to rotate, the steel pipe achieves a gradient uniform temperature recovery. After the temperature rises to the preset process temperature, it is kept at a constant temperature again to complete a single cold and hot alternating cycle operation. The equipment can automatically repeat the cold and hot alternating cycle process multiple times according to the working conditions of the pipe. Relying on the alternating aging mechanism of low-temperature freezing and gradient temperature recovery, the equipment completely releases the deep latent intergranular residual stress of the pipe while refining the micro-grain structure of the metal, effectively improving the low-temperature anti-brittle fracture performance and structural stability of the seamless steel pipe under high-altitude and cold working conditions, and finally completing the cold and hot alternating cycle shaping process of the seamless steel pipe.

[0041] 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 alterations 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 device for eliminating residual stress in seamless steel pipes, characterized in that, include, The base (1) is fixedly connected to the top of the base (1) and a controller (4) for controlling the overall device operation status is provided in the middle of the front side of the top of the base (1). An initial release mechanism is located at the top center of the base (1) and is used for the initial release of the seamless steel pipe before subsequent processing. The pretreatment mechanism is set on the base (1) and is used to perform stress relief pretreatment on the seamless steel pipe after the initial release mechanism. The internal and external synchronization mechanism is located at the bottom of the top seat (9) and is used to perform internal and external synchronous stress relief treatment on the seamless steel pipe after the pretreatment mechanism. An alternating circulation mechanism is set on the base (1) and is used to perform alternating circulation temperature treatment on the seamless steel pipe after the internal and external synchronous mechanism has been processed.

2. The device for eliminating residual stress in seamless steel pipes according to claim 1, characterized in that, The initial release mechanism includes an insulating support frame (12). The insulating support frame (12) is fixedly connected to both sides of the middle part of the top of the base (1). The V-shaped seat (15) is fixedly connected to the middle part of the top of the insulating support frame (12). A hydraulic cylinder (2) is provided at the middle part of the top of the base (1). A low-frequency vibrator (16) that generates low-frequency vibration is provided on the top of the rod of the hydraulic cylinder (2). A transmission seat (17) that transmits low-frequency vibration evenly to various parts of the steel pipe is provided on the top of the low-frequency vibrator (16). An arc-shaped fitting part (18) that fits against the surface of the steel pipe is provided on the top of the transmission seat (17).

3. The device for eliminating residual stress in seamless steel pipes according to claim 2, characterized in that, The pre-processing mechanism includes a high-frequency pulse power supply (3). The high-frequency pulse power supply (3) is provided at the front middle part of the top of the base (1). A conductive electrode seat (19) is provided at the middle of the bottom inner side of the V-shaped seat (15). An electrode post (24) is provided at the middle of the top of the conductive electrode seat (19). A conductive contact seat (22) is provided at the top of the electrode post (24).

4. The device for eliminating residual stress in seamless steel pipes according to claim 1, characterized in that, The internal and external synchronization mechanism includes a linear moving seat one (14), a linear moving seat one (14) is provided on one side of the top center of the base (1), and a linear moving seat two (27) is provided on the other side of the top center of the base (1). A sealing seat (11) is fixedly connected to the top of both the linear moving seat one (14) and the linear moving seat two (27). A sealing cavity (29) matching the size of the seamless steel pipe is opened in the middle of the adjacent side of the sealing seat (11).

5. The device for eliminating residual stress in seamless steel pipes according to claim 4, characterized in that, The internal and external synchronization mechanism also includes a high-pressure infusion pump (13). A high-pressure infusion pump (13) is provided on the lower middle part of one side of the linear moving seat (14). The outlet end of the high-pressure infusion pump (13) is connected to the internal flow channel of the linear moving seat (14) and the interior of the sealing cavity (29) through a connecting pipe. A high-pressure vortex air pump (28) is provided on the lower middle part of the other side of the linear moving seat (14). The outlet end of the high-pressure vortex air pump (28) is connected to the internal flow channel of the linear moving seat (14) and the interior of the sealing cavity (29) through a connecting pipe. During use, the high-pressure vortex air pump (28) works in conjunction with a variable frequency motor to achieve dynamic adjustment of airflow frequency and pressure, so that the airflow discharged into the seamless steel pipe through the sealing cavity (29) forms a pulsating characteristic for output.

6. The device for eliminating residual stress in seamless steel pipes according to claim 5, characterized in that, The internal and external synchronization mechanism also includes mounting base one (7), mounting base one (7) is provided on the inner top of the top seat (9), hydraulic cylinder two (8) is provided on both sides of the middle part of the top seat (9), the bottom end of the rod of the hydraulic cylinder two (8) is connected to the middle sides of the top of the mounting base one (7), a semi-circular concave cavity (30) is opened in the middle of the bottom end of the mounting base one (7), a plurality of outer wall pressure rollers (31) are arranged in a circular array on the inner wall of the concave cavity (30), and a synchronous driver (10) for synchronously driving the plurality of outer wall pressure rollers (31) is provided on both sides of the top of the mounting base one (7), mounting base two (25) is provided on the middle of the outer side of the sealing seat (11) on the linear moving seat two (27), and a gradient pressure relief seat (26) is provided in the middle of the mounting base two (25).

7. The device for eliminating residual stress in seamless steel pipes according to claim 1, characterized in that, The alternating circulation mechanism includes a mounting cover (5). Two mounting covers (5) that can be spliced ​​and closed are provided on the top two sides of the base (1). A self-moving connecting frame (6) is provided on both sides of the bottom end of the top seat (9). The middle and lower parts of the connecting frame (6) are respectively connected to the corresponding positions of the outer wall of the mounting cover (5) on the same side. A dispersing seat (33) is provided at the top of each mounting cover (5). An inclined spray seat (32) is provided at the top of the inner wall of each mounting cover (5). The interior of the inclined spray seat (32) is connected to the interior of the dispersing seat (33).

8. The apparatus for eliminating residual stress in a seamless steel pipe according to any one of claims 2 or 7, characterized in that, The alternating cycle mechanism also includes side seats (21). Side seats (21) are provided on both sides of the upper middle part of the insulating support frame (12). Friction drive wheels (23) are provided on the side of the side seats (21) near the V-shaped seat (15). Friction drive drivers (20) for driving the friction drive wheels (23) are provided on the side seats (21). Plate heaters (34) are provided on both sides of the inner wall of the mounting cover (5).

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