An impact-expansion composite electromagnetic forming tooling and process

Abstract

This invention discloses an impact-expansion composite electromagnetic forming fixture and process. The impact-expansion composite electromagnetic forming fixture includes a fixed support base and a positioning housing located directly above the support base and connected to the positioning end of a positioning actuator. An electromagnetic drive coil connected to the electromagnetic forming system circuit is fixedly installed on the upper inner side of the positioning housing. A copper drive block located below the electromagnetic drive coil is movably installed on the lower inner side of the positioning housing. A core rod expansion device corresponding to the heat transfer tube of the workpiece is installed at the bottom of the copper drive block. This invention uses a strong pulse power supply to connect the electromagnetic drive coil for instantaneous discharge, inducing a strong magnetic field, causing eddy currents on the copper drive block, generating Lorentz force, driving the copper drive block to impact downward at high speed, producing a mechanical impact strengthening effect on the welding area. The core rod expansion device realizes high-speed mechanical expansion of the tube wall, thereby achieving integrated high-performance manufacturing of the heat transfer tube bundle welding structure.

Description

Technical Field

[0001] This invention belongs to the field of weld performance enhancement technology, specifically an impact-expansion composite electromagnetic forming tooling and process. Background Technology

[0002] The steam generator (workpiece 100) is a core piece of equipment meeting nuclear safety level 1, seismic resistance level 1, and RCCM standard level 1 requirements. Figure 1 As shown, the U-shaped heat transfer tube bundle made of 690 nickel-based alloy constitutes the pressure boundary of the reactor coolant system, which has a key impact on the economy and safety of nuclear power plants. In the manufacturing process, the heat transfer tube bundle needs to be assembled onto a large tube sheet. The process usually includes: (1) using electroslag welding and other methods to weld a nickel-based alloy corrosion-resistant layer on the surface of tube sheet 101; (2) inserting the end of the heat transfer tube 102, which has a diameter slightly smaller than the diameter of the tube sheet 101 hole, into the tube sheet hole, exposing the end; (3) using hot wire tungsten inert gas welding (TIG welding), laser welding and other fusion welding technologies to weld the end of the heat transfer tube to the weld layer in the form of circumferential welding to fix the position of the pipe; (4) in order to ensure the airtightness between the pipe and the tube sheet, an internal high-pressure expansion joint device is used to tightly connect / press the position where the heat transfer tube is inserted into the tube sheet hole but not tightly attached to the tube sheet hole by local expansion.

[0003] The aforementioned structure contains numerous welded sections between the heat transfer tubes and the tube sheet (weld 103, formed by three materials: Inconel 690 alloy tube, ENiCrFe-7 strip electrode weld overlay, and ERNiCrFe-7TIG welding wire). These welded joints suffer from severe post-weld quality degradation, such as decreased strength and toughness, reduced thermal conductivity, and high susceptibility to solidification cracking and high-temperature deplasticity cracking. Furthermore, fouling accumulation on the heat transfer tubes during long-term service and the welding process generate multi-source residual stress, making the welded structure of the steam generator heat transfer tube bundle one of the weakest links in the main nuclear island equipment. In addition, while nickel-based alloy overlay welding on the tube sheet effectively improves corrosion resistance, the cyclic heat input during welding leads to the accumulation of residual stress, affecting the structural reliability. Therefore, current technology employs heat treatment to eliminate residual stress after welding, requiring treatment in a large heat treatment furnace at approximately 650°C for 30 minutes to several hours. However, the residual stress in the welds during the heat transfer tube-tube sheet assembly welding process cannot be eliminated using conventional heat treatment, further limiting reliability improvements. In addition, traditional processes require welding and expansion of each pipe-to-tube sheet hole one by one, which is extremely inefficient. Summary of the Invention

[0004] In existing technologies, expansion joints and post-weld treatments are mostly carried out in separate steps, resulting in complex processes, long production cycles, and low efficiency. At the same time, this single-point treatment method makes it difficult to solve the problems of stress control and joint performance improvement in a single operation.

[0005] To address the aforementioned technical problems, this invention proposes an integrated device and process for electromagnetically driven multi-tube synchronous expansion and welding / overlay layer electromagnetic-mechanical composite impact strengthening. A strong pulse power supply is used to instantaneously discharge the electromagnetic drive coil, inducing a strong magnetic field that generates eddy currents on the copper drive block, producing a Lorentz force that drives the copper drive block to impact downwards at high speed. On one hand, the high-speed impact of the copper drive block provides mechanical impact strengthening to the welded area, similar to shot peening. On the other hand, after the core rod expansion device enters the tube wall, the internal high-stiffness spring contracts, and the high-pressure resistant rubber expands, achieving high-speed mechanical expansion of the tube wall. This enables integrated high-performance manufacturing of the heat transfer tube bundle welding structure.

[0006] This process utilizes the strong Lorentz force generated by the electromagnetic forming system to drive a copper block at high speed to apply a severe impact (strain rate can reach) to the welding area. The impact velocity can reach 100-200 m / s. On the one hand, mechanical impact is used to strengthen the weld, improve the residual stress distribution, and enhance fatigue performance. On the other hand, the "high-speed superplastic effect" and strain rate hardening effect under high strain rate are fully utilized to effectively improve the forming limit and surface integrity of the material when the pressure-resistant elastomer is expanded to heat transfer tubes, avoiding expansion cracking. At the same time, a copper driving block is used as an integrated carrier, on which multiple core rod expansion devices are arranged in an array. The position of each core rod expansion device corresponds one-to-one with the heat transfer tube hole in the target area, so that the expansion of all heat transfer tubes in the target area can be completed in one positioning. The high strain rate generated by electromagnetic drive ( High-speed impact (100-200m / s) applies a violent impact to the welded area while achieving mechanical expansion, simultaneously optimizing residual stress and fatigue performance, avoiding performance degradation caused by multiple processing steps, and simplifying the multiple processes of expansion and welding area strengthening into a single operation, ultimately achieving high-performance manufacturing with streamlined process, improved efficiency and highly consistent joint quality.

[0007] One technical solution adopted in this invention is: An impact-expansion composite electromagnetic forming fixture includes a fixed support base and a positioning housing located directly above the support base and connected to the positioning end of a positioning actuator. The workpiece to be processed is placed on the top of the support base. An electromagnetic drive coil connected to the electromagnetic forming system circuit is fixedly installed on the upper inner side of the positioning housing. A copper drive block located below the electromagnetic drive coil is movably installed on the lower inner side of the positioning housing. Several core rod expansion devices corresponding to the heat transfer tubes of the workpiece are installed at the bottom of the copper drive block. The core rod expansion device includes a high-strength alloy core rod fixedly connected to the bottom of the positioning housing, a high-rigidity spring sleeved on the outside of the bottom of the high-strength alloy core rod, a high-pressure resistant rubber sleeved on the outside of the high-rigidity spring and embedded in the bottom end of the high-strength alloy core rod, and a high-strength alloy extrusion block fixedly connected to the copper drive block and movably sleeved on the outside of the high-strength alloy core rod. The positioning actuator drives the positioning housing downward, causing the high-stiffness spring and high-pressure resistant rubber to follow the high-strength alloy core rod into the heat transfer tube. The electromagnetic forming system circuit releases the stored high-voltage electrical energy instantaneously through the electromagnetic drive coil, exciting and forming a strong pulsed magnetic field B1 that changes rapidly with time. The copper drive block induces and generates an induced magnetic field B2 in the opposite direction to B1. Under the action of a huge Lorentz force, the copper drive block impacts the weld area at the top of the heat transfer tube at high speed. The high-strength alloy extrusion block squeezes the high-stiffness spring to contract, thereby causing the high-pressure resistant rubber to expand radially, realizing the mechanical expansion joint between the heat transfer tube and the tube sheet.

[0008] Furthermore, the top surface of the support base is provided with a groove, the workpiece is embedded in the groove, a positioning pin is provided in the groove that can be movably inserted into the tube plate of the workpiece, and a positioning hydraulic cylinder for driving the positioning pin to rise and fall is fixedly provided in the bottom of the support base.

[0009] Furthermore, a connecting groove is fixedly connected inside the positioning housing, the electromagnetic drive coil is placed inside the connecting groove, and the top end of the high-strength alloy core rod is fixedly connected to the bottom surface of the connecting groove.

[0010] Furthermore, an inner isolation sleeve located inside the electromagnetic drive coil and an outer isolation sleeve located outside the electromagnetic drive coil are respectively fixedly installed in the connecting groove.

[0011] Furthermore, a reset hydraulic cylinder located inside the electromagnetic drive coil is fixedly connected to the top surface of the bottom of the connecting groove. The output rod end of the reset hydraulic cylinder moves through the bottom of the copper drive block and is fixedly connected to a reset connecting block.

[0012] Furthermore, the top of the copper drive block is fixedly connected to an upper connecting plate and the bottom is fixedly connected to a lower connecting plate. A through hole is opened at the center of the copper drive block and the lower connecting plate. A hollow boss located in the through hole is integrally provided on the bottom surface of the upper connecting plate. The reset connecting block is movably inserted into the hollow boss, and the bottom end of the reset connecting block can overlap with the bottom surface of the hollow boss.

[0013] Furthermore, a limiting plate located below the lower connecting plate is movably disposed inside the bottom side wall of the positioning housing, and a limiting hydraulic cylinder for driving the limiting plate to move horizontally is fixedly connected to the outside side wall of the positioning housing.

[0014] A process for an impact-expansion composite electromagnetic forming tool is also provided, including the following steps: S1. Workpiece cleaning: Clean the surface of the tube sheet, the weld area, and the inner wall of the heat transfer tube; S2. Workpiece loading and positioning: Place the workpiece on the support base and adjust it to the forming working position; S3, tooling vertical positioning: the positioning actuator drives the positioning housing downward, so that the distance between the bottom surface of the copper drive block and the surface of the tube sheet is to the preset value to meet the impact strengthening process requirements. The high-rigidity spring and high-pressure resistant rubber of the core rod expansion device are inserted into the heat transfer tube to the preset expansion position. S4. Electromagnetic drive impact strengthening: When the electromagnetic forming system circuit is energized, the instantaneous pulse current in the electromagnetic drive coil is excited to form a magnetic field. The magnetic field interacts with the eddy current induced in the copper drive block to generate a huge transient Lorentz force. The copper drive block is driven by the Lorentz force to fall vertically at high speed, which strengthens the weld area through impact. S5. Expansion joint: The high-strength alloy extrusion block follows the copper drive block to impact downwards at high speed, causing the high-rigidity spring to be compressed instantaneously. The high-pressure resistant rubber expands rapidly in the radial direction and applies uniform and controllable radial pressure to the inner wall of the heat transfer tube, forcing the tube wall to undergo plastic deformation until its outer wall and the inner wall of the tube sheet hole are tightly fitted, thus completing the mechanical expansion joint. S6. Tooling Reset: After the impact-expansion operation is completed, the electromagnetic forming system circuit is de-energized, the positioning actuator drives the positioning housing to move upward, which in turn drives the electromagnetic drive coil and copper drive block to move upward and reset. The high-rigidity spring resets, which causes the high-pressure resistant rubber to retract radially and separate from the inner wall of the heat transfer tube. S7. Workpiece unloading: Remove the workpiece that has completed the impact-expansion joint from the support base.

[0015] Furthermore, the capacitance of the capacitor in the electromagnetic forming system circuit is continuously adjustable in the range of 0µF to 360µF, and the preset target discharge voltage is 12kV-18kV.

[0016] Furthermore, in step S4, the impact velocity of the copper driving block is 100-200 m / s, and the strain rate of the weld is 10. 3 -10 4 s -1 .

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The device of this invention is based on electromagnetic forming technology. It generates a strong Lorentz force through the instantaneous discharge of an electromagnetic coil, driving a copper drive block at extremely high speeds (100-200 m / s, strain rate 10³-10⁻¹⁰ m / s). 4s⁻¹) Impact welding zone utilizes the "superplastic" effect under high strain rate to close micro-defects, which can effectively improve weld density; introduce residual compressive stress field to effectively offset the harmful residual tensile stress generated by welding, significantly improving the stress corrosion cracking resistance and fatigue life of welded structure in corrosive environment; 2. This invention integrates the copper drive block with the core rod expansion device and uses timing control to achieve the integration of post-weld strengthening and expansion processes, which greatly shortens the manufacturing cycle and reduces equipment and energy costs. 3. The core rod expansion joint device of the present invention is arranged in an array and is highly matched with the tube sheet structure; through a single operation, multiple tube holes can be expanded simultaneously, effectively breaking through the efficiency bottleneck of the traditional single-point sequential processing method, significantly improving the overall manufacturing efficiency of the tube bundle, and is particularly suitable for large components with dense tube bundle structures, meeting the engineering requirements of integrated and efficient manufacturing. 4. This invention utilizes the radial expansion of high-pressure resistant rubber to apply uniform and controllable radial pressure to the inner wall of the heat transfer tube, thereby achieving a tight fit between the heat transfer tube and the tube sheet holes. This expansion method effectively avoids the risk of tube wall scratches that may be caused by mechanical rolling expansion, while also avoiding the complex sealing structure design in hydraulic expansion. It has high precision in expansion force control and strong joint connection reliability. After expansion is completed, the core rod expansion device automatically resets without the need for an additional power source or manual intervention, significantly improving the continuous operation capability of the equipment. 5. This invention enhances the fatigue and crack resistance of the weld area through impact strengthening, while ensuring a tight fit between the heat transfer tube and the tube sheet through precision expansion joints, thereby achieving a simultaneous improvement in welding strength and mechanical connection reliability. The synergistic effect of these two aspects provides key performance assurance for the long-term service of nuclear power heat exchange equipment. Attached Figure Description

[0018] Figure 1 A schematic diagram of the structure of the workpiece to be formed by impact-expansion bonding; Figure 2 This is one of the three-dimensional structural schematic diagrams of the impact-expansion composite electromagnetic forming tooling of the present invention; Figure 3 The second three-dimensional structural schematic diagram of the impact-expansion composite electromagnetic forming tooling of the invention; Figure 4 This is a cross-sectional structural schematic diagram of the impact-expansion composite electromagnetic forming tooling of the present invention. Figure 5 This is a schematic diagram of the structure of the support base; Figure 6 for Figure 4 A magnified structural diagram of part A in the middle; Figure 7 This is one of the three-dimensional structural schematic diagrams of the impact-expansion joint functional part of the present invention; Figure 8 This is a second three-dimensional structural schematic diagram of the impact-expansion joint functional part of the present invention; Figure 9 This is a schematic diagram of the core rod expansion joint device; Figure 10 This is a schematic diagram of the structure of the connecting groove; Figure 11 for Figure 4 A magnified structural diagram of part B in the middle section; Figure 12 This is a schematic diagram of the working state of the impact-expansion composite electromagnetic forming tooling of the present invention.

[0019] In the diagram: 1. Support base; 2. Positioning shell; 201. Connecting plate; 202. Connector; 203. Connecting groove; 2031. Connecting groove; 204. Inner isolation sleeve; 205. Outer isolation sleeve; 3. Positioning hydraulic cylinder; 4. Positioning pin; 5. Electromagnetic forming system circuit; 6. Electromagnetic drive coil; 7. Copper drive block; 701. Upper connecting plate; 702. Lower connecting plate; 8. Core rod expansion device; 801. High-strength alloy core rod; 802. High-stiffness spring; 803. High-pressure resistant rubber; 804. High-strength alloy extrusion block; 805. Connecting block; 9. Reset hydraulic cylinder; 10. Reset connecting block; 11. Limiting plate; 12. Limiting hydraulic cylinder; 100. Workpiece; 101. Tube sheet; 102. Heat transfer tube; 103. Weld. Detailed Implementation

[0020] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0021] It should be noted that when a component is said to be "installed on" another component, it can be directly on the other component or it may be in a component that is centered on it. When a component is said to be "set on" another component, it can be directly set on the other component or it may also be in a component that is centered on it. When a component is said to be "fixed to" another component, it can be directly fixed to the other component or it may also be in a component that is centered on it.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] See appendix Figures 2 to 4An impact-expansion composite electromagnetic forming fixture includes a fixed support base 1 and a positioning housing 2 located directly above the support base 1 and connected to the positioning end of a positioning actuator. The workpiece 100 to be processed is placed on top of the support base 1. To meet the requirements... Figure 1 The placement and positioning of the workpiece 100 shown requires, for example... Figure 5 As shown, the support base 1 is a hollow cylindrical frustum structure with a groove on its top surface. The horizontal cross-sectional shape of the groove wall matches the horizontal cross-sectional shape of the outer side of the tube sheet 101 of the workpiece 100, allowing the workpiece 100 to be embedded in the groove for axial positioning. The heat transfer tube 102 of the workpiece 100 is located inside the hollow cavity of the support base 1, and the weld 103 protrudes above the top surface of the support base 1. Several circumferentially distributed positioning pins 4 are provided at the edge of the groove bottom surface. The diameter of the positioning pins 4 matches the inner diameter of the connecting hole on the tube sheet 101. The circumferential positioning of the workpiece 100 is achieved by the engagement of the positioning pins 4 with the shaft hole of the connecting hole. By axially and circumferentially positioning the workpiece, the workpiece 100 can be accurately positioned in the forming working position.

[0024] Preferably, such as Figure 6 As shown, to facilitate the unloading of the formed workpiece 100 from the support base 1, the bottom of the support base 1 has several circumferentially distributed notches and slots, in which a positioning hydraulic cylinder 3 is fixedly installed. A through hole corresponding to the notch and slot is formed on the bottom surface of the notch and slot. The bottom end of the positioning pin 4 is movably inserted into the through hole and fixedly connected to the output rod end of the positioning hydraulic cylinder 3. A support plate is integrally provided at the axial center of the positioning pin 4, and the diameter of the support plate is larger than the inner diameter of the connecting hole on the plate 101. Thus, the positioning pin 4 can be driven to move up and down by the positioning hydraulic cylinder 3. After the positioning pin 4 rises, the support plate can lift the workpiece 100 above the top surface of the support base 1 for subsequent unloading operations. After the positioning pin 4 descends, the support plate moves down and resets synchronously. Furthermore, a recess is provided at the top of the through opening. After the support plate moves down and resets, it is located in the recess. Therefore, during the impact strengthening forming stage, the force transmitted by the workpiece 100 is entirely borne by the support base 1, and the positioning pin 4 does not bear the impact force.

[0025] like Figure 7 and Figure 8 As shown, an electromagnetic drive coil 6 connected to the electromagnetic forming system circuit 5 is fixedly installed on the upper inner side of the positioning housing 2, and a copper drive block 7 located below the electromagnetic drive coil 6 is movably installed on the lower inner side of the positioning housing 2. Several core rod expansion joint devices 8 corresponding to the heat transfer tube 102 of the workpiece 100 are installed at the bottom of the copper drive block 7.

[0026] Specifically, the positioning housing 2 is a hollow cylindrical shell structure, with a connecting plate 201 fixedly connected to its top by bolts. A connector 202 is integrally formed at the center of the top surface of the connecting plate 201, connecting to the positioning end of an external positioning actuator. The positioning actuator enables the vertical lifting and positioning of the positioning housing 2, thereby adjusting and positioning the vertical positions of the electromagnetic drive coil 6 and the copper drive block 7 to meet the requirements of the impact strengthening process. Clearly, the positioning actuator can be a hydraulic cylinder drive device, a servo motor driven linear module, an industrial robot arm, or other mechanical devices with linear positioning output functions.

[0027] To meet the assembly requirements of the electromagnetic drive coil 6, a stepped hole is provided at the top of the hollow cavity of the positioning housing 2. A connecting groove 203 is embedded in the stepped hole, and the side wall of the connecting groove 203 is fixedly connected to the side wall of the positioning housing 2 by bolts. The electromagnetic drive coil 6 is concentrically placed in the connecting groove 203, and the two ends of the electromagnetic drive coil 6 are respectively connected to the two output terminals of the electromagnetic forming system circuit 5. In this embodiment, the electromagnetic coil is preset to have 3 layers, a total of 30 turns, and is wound with rectangular copper wire with a cross-sectional area of ​​2mm×4mm. The electromagnetic forming system circuit 5 adopts an existing circuit structure, which consists of multiple capacitors forming a capacitor bank with continuously adjustable capacitance, which can store enough high-voltage energy to provide a preset Lorentz force for the copper drive block 7, thereby meeting the process requirements of impact strengthening forming.

[0028] Preferably, an inner isolation sleeve 204 located inside the electromagnetic drive coil 6 and an outer isolation sleeve 205 located outside the electromagnetic drive coil 6 are fixedly disposed within the connecting groove 203. By providing isolation sleeves on the inner and outer sides of the electromagnetic coil 6, electromagnetic radiation can be reduced to a certain extent even when it is assembled and positioned with the electromagnetic drive coil 6 within the connecting groove 203.

[0029] The copper drive block 7 is made of copper and utilizes its high magnetic permeability to generate a strong Lorentz force in a strong magnetic field, providing power for impact strengthening. The top of the copper drive block 7 is bolted to an upper connecting plate 701, and the bottom is bolted to a lower connecting plate 702. The lower connecting plate 702 is made of high-strength alloy steel. When the copper drive block 7 is subjected to a strong Lorentz force and impacts downwards, the lower connecting plate 702 follows the copper drive block 7 and moves downwards synchronously, impacting the area where the weld 103 is located. This avoids the copper drive block 7 directly participating in the impact, effectively extending its service life.

[0030] To achieve the upward reset of the copper drive block 7 after impact strengthening forming, a reset hydraulic cylinder 9 located inside the electromagnetic drive coil 6 is fixedly connected to the top surface of the bottom of the connecting groove 203. The output rod end of the reset hydraulic cylinder 9 movably passes through the bottom of the copper drive block 7 and is fixedly connected to a reset connecting block 10. Specifically, a through hole is opened at the center of the copper drive block 7 and the lower connecting plate 702. A hollow boss located in the through hole is integrally provided on the bottom surface of the upper connecting plate 701. The reset connecting block 10 is movably inserted into the hollow boss, and a lifting plate is integrally provided at the bottom end of the reset connecting block 10. The diameter of the lifting plate is not less than the inner diameter of the hollow boss. Thus, when the reset hydraulic cylinder 9 drives the reset connecting block 10 upward, the top surface of the lifting plate can overlap with the bottom surface of the hollow boss, thereby lifting the upper connecting plate 701 and the copper drive block 7 fixedly connected below it upward to achieve reset. During the electromagnetic drive impact strengthening stage, the output rod of the reset hydraulic cylinder 9 is in an extended state, releasing its restriction on the falling of the upper connecting plate 701 and the copper drive block 7. At the same time, in order to ensure that the bottom surface of the lower connecting plate 702 can effectively impact the weld 103, it is necessary to ensure that when the lifting plate is in the lowest position, the bottom surface of the hollow boss is at most in a critical contact state with the top surface of the lifting plate (preferably a non-contact state) when the lower connecting plate 702 impacts the weld 103. Therefore, the vertical distance between the bottom surface of the hollow boss and the bottom surface of the lower connecting plate 702 is greater than the vertical thickness of the lifting plate.

[0031] To ensure that the output rod of the reset hydraulic cylinder 9 is in the extended state, the copper drive block 7 is locked in a preset position below the electromagnetic drive coil 6, placing it in a preset strong pulse magnetic field and inducing a Lorentz force of preset intensity. A limiting plate 11 is movably installed inside the bottom side wall of the positioning housing 2, located below the lower connecting plate 702. A limiting hydraulic cylinder 12, which drives the limiting plate 11 to move horizontally, is fixedly connected to the outer side wall of the positioning housing 2. Figure 11 As shown. When the switch of the electromagnetic forming system circuit 5 is closed, the limiting hydraulic cylinder 12 drives the limiting plate 11 to retract quickly, so that the copper driving block 7 can be released smoothly and fall vertically; after the copper driving block 7 returns to its original position, the limiting hydraulic cylinder 12 drives the limiting plate 11 to extend below the bottom surface of the lower connecting plate 702, supporting and positioning the lower connecting plate 702, so that the copper driving block 7 is suspended below the electromagnetic driving coil 6. At this time, the reset hydraulic cylinder 9 can stop working. Preferably, a 2mm gap is preset between the top surface of the upper connecting plate 701 and the bottom surface of the connecting groove 203, firstly to meet the need for the copper driving block 7 to generate a reverse magnetic field in a strong pulsed magnetic field, and secondly to facilitate the smooth extension of the limiting plate 11 to the bottom surface of the lower connecting plate 702.

[0032] like Figure 9As shown, the core rod expansion device 8 includes a high-strength alloy core rod 801 fixedly connected to the bottom of the positioning housing 2, a high-stiffness spring 802 sleeved on the outside of the bottom of the high-strength alloy core rod 801, a high-pressure resistant rubber 803 sleeved on the outside of the high-stiffness spring 802 and embedded in the bottom end of the high-strength alloy core rod 801, and a high-strength alloy extrusion block 804 fixedly connected to the copper drive block 7 and movably sleeved on the outside of the high-strength alloy core rod 801.

[0033] Specifically, a connecting block 805 is threaded to the top of the high-strength alloy core rod 801, and the connecting block 805 is fixedly connected to the bottom surface of the connecting groove 203 by bolts. Preferably, the connecting block 805 is a square plate, and a connecting groove 2031 is formed on the bottom surface of the connecting groove 203 (e.g., Figure 10 As shown, the connecting block 805 is embedded in the connecting groove 2031, and the adjacent surfaces of the two connecting blocks 805 at the top of the two adjacent high-strength alloy core rods 801 are in contact with each other. The outer side of the outermost connecting block 805 is in contact with the groove side of the connecting groove 2031, so that each high-strength alloy core rod 801 can be accurately positioned in the connecting groove 2031 according to the preset arrangement (corresponding to the arrangement of the heat transfer tubes 102 of the workpiece 100).

[0034] The copper drive block 7 and the lower connecting plate 702 have stepped holes corresponding to the high-strength alloy core rod 801. The high-strength alloy extrusion block 804 has a "T" shaped axial section. Its top overlaps the stepped surface of the stepped hole, and its bottom passes through the stepped hole to the bottom surface of the lower connecting plate 702. Its top surface is in contact with the bottom surface of the upper connecting plate 701. That is, the high-strength alloy extrusion block 804 is pressed and fixed in the copper drive block 7 by the upper connecting plate 701. Before the electromagnetic shock strengthening begins, the positioning actuator drives the copper drive block 7 to move down to the preset working position. At this time, the bottom end of the high-strength alloy core rod 801 is inserted into each heat transfer tube 102 of the workpiece 100. The high-strength spring 802 and the high-pressure resistant rubber 803 are located on the inner side of the contact area between the heat transfer tube 102 and the side wall of the tube sheet 101. When the copper drive block 7 moves downward under the action of the Lorentz force, the high-strength alloy extrusion block 804 moves downward simultaneously. The lower connecting plate 702 acts on the area of ​​the weld 703 to achieve impact reinforcement, while the high-strength alloy extrusion block 804 acts on the high-stiffness spring 802 to cause it to contract, thereby causing the high-pressure resistant rubber 803 to expand radially, realizing the mechanical expansion joint between the heat transfer tube 102 and the side wall of the tube sheet 101. A linear bearing is fixedly sleeved inside the high-strength alloy extrusion block 804. The linear bearing is slidably sleeved on the outside of the high-strength alloy core rod 801, which allows the high-strength alloy extrusion block 804 to move smoothly downward, while guiding the vertical movement of the copper drive block 7 to ensure the smooth movement of the copper drive block 7.

[0035] The specific working principle of this device is as follows: The positioning actuator drives the positioning housing 2 downwards, causing the electromagnetic drive coil 6 and the copper drive block 7 to move to a preset working position above the top surface of the tube sheet 101. The high-stiffness spring 802 and the high-pressure resistant rubber 803 follow the high-strength alloy core rod 801 and are inserted into the preset working position inside the heat transfer tube 102. The electromagnetic forming system circuit 3 releases the stored high-voltage electrical energy instantaneously through the electromagnetic drive coil 6, generating a strong pulsed magnetic field B1 that changes rapidly with time around the electromagnetic drive coil 6. Under the action of this magnetic field, the copper drive block 7 generates a strong induced eddy current according to Faraday's law of electromagnetic induction and Lenz's law, thereby generating an induced magnetic field B2 in the opposite direction to B1. The interaction of the two opposing magnetic fields generates a huge Lorentz force. Under the action of the huge Lorentz force, the copper drive block 7 moves at a speed of 100~200 m / s within microseconds. The high-speed impact on the weld 103 area effectively improves the residual stress distribution in the weld area and can also improve surface integrity by utilizing the "high-speed superplasticity" of the material under high strain rate, thus avoiding cracking. At the same time, the high-strength alloy extrusion block 804 compresses the high-stiffness spring 802 to make it shrink, thereby causing the high-pressure resistant rubber 803 to expand radially, realizing the mechanical expansion joint between the heat transfer tube 102 and the side wall of the tube sheet 101.

[0036] This invention also provides a process for an impact-expansion composite electromagnetic forming tool, comprising the following steps: S1. Workpiece Cleaning: Clean the surface of tube sheet 101, the weld seam area 103, and the inner wall of heat transfer tube 102. This mainly involves removing welding spatter, oxide layer, and oil stains from the weld seam area 103, as well as debris adhering to the inner wall of heat transfer tube 102, ensuring the inner wall is clean and free of blockages to allow for smooth entry of the high-strength alloy core rod 801, high-pressure rubber 803, etc. Prior to this, the operating status of the equipment also needs to be checked to ensure that all functional components are working properly and to reduce the defect rate.

[0037] S2. Workpiece Loading and Positioning: Place the workpiece 100 on the support base 1 and adjust it to the forming working position. After the position is adjusted, the positioning hydraulic cylinder 3 operates, driving the positioning pin 4 upward and inserting it into the connecting hole of the tube sheet 101, completing the positioning of the workpiece 100 in the support base 1. At this time, the positions of each heat transfer tube 102 are respectively located directly below each high-strength alloy core rod 801, such as... Figure 12 As shown.

[0038] S3. Vertical positioning of the tooling: The positioning actuator drives the positioning housing 2 downward, so that the distance between the bottom surface of the copper drive block 7 / lower connecting plate 702 and the surface of the tube sheet 101 reaches the preset value to meet the impact strengthening process requirements. The high-rigidity spring 802 and high-pressure resistant rubber 803 of the core rod expansion device 8 are inserted into the heat transfer tube 102 to the preset expansion position. The reset hydraulic cylinder 9 works, driving the reset connecting block 10 downward to the lowest position.

[0039] S4. Electromagnetic Drive Impact Strengthening: When the electromagnetic forming system circuit 5 is energized, the instantaneous pulse current flowing into the electromagnetic drive coil 6 excites and forms a magnetic field. The magnetic field interacts with the eddy currents induced in the copper drive block 7, generating a huge transient Lorentz force. At the same time, the limiting hydraulic cylinder 12 operates, driving the limiting plate 11 to move horizontally and retract into the side wall of the positioning housing 2. Driven by the Lorentz force, the copper drive block 7 falls vertically at a high speed of 100~200m / s within microseconds, impacting the area where the weld 103 is located through the lower connecting plate 702 at its bottom for impact strengthening. The strain rate of the weld can reach 10. 3 -10 4 s -1 The capacitance of the capacitor in the electromagnetic forming system circuit 5 is continuously adjustable from 0µF to 360µF, and the preset target discharge voltage is 12kV-18kV to ensure that sufficient Lorentz force is generated on the drive block.

[0040] S5. Expansion joint: The high-strength alloy extrusion block 804 follows the copper drive block 7 to impact downwards at high speed, causing the high-rigidity spring 802 to be compressed instantaneously. The high-pressure resistant rubber 803 expands rapidly in the radial direction, applying uniform and controllable radial pressure to the inner wall of the heat transfer tube 102, forcing the tube wall to undergo plastic deformation until its outer wall is tightly fitted with the inner wall of the hole in the tube sheet 101, thereby completing the mechanical expansion joint.

[0041] S6. Tooling Reset: After the impact-expansion operation is completed, the electromagnetic forming system circuit 5 is de-energized, the positioning actuator drives the positioning housing 2 to move upward, and at the same time the reset hydraulic cylinder 9 works, driving the reset connecting block 10 to rise, which in turn drives the electromagnetic drive coil 6 and the copper drive block 7 to move upward and reset. The high-strength alloy core rod 801 moves upward and resets synchronously with the positioning housing 2, the high-strength alloy extrusion block 804 moves upward and resets synchronously with the copper drive block 7, the high-rigidity spring 802 resets, and drives the high-pressure resistant rubber 803 to retract radially and separate from the inner wall of the heat transfer tube 102, and moves upward and resets synchronously with the high-strength alloy core rod 801.

[0042] S7. Workpiece unloading: The workpiece 100, which has undergone impact-expansion bonding, is removed from the support base 1. The positioning hydraulic cylinder 3 drives the positioning pin 4 to rise vertically, raising the workpiece 100 above the top surface of the support base 1. After the workpiece 100 is removed, the positioning hydraulic cylinder 3 drives the positioning pin 4 to move down and reset.

[0043] For workpieces 100 that have already undergone impact-expansion bonding, samples can be taken for testing. The residual stress distribution in the weld zone and heat-affected zone can be measured using X-ray diffraction, and the hardness change along the wall thickness direction can be tested using a microhardness tester to comprehensively evaluate the impact-strengthening-expansion bonding effect.

[0044] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0045] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An impact-expansion composite electromagnetic forming fixture, comprising a fixedly mounted support base and a positioning housing disposed directly above the support base and connected to the positioning end of a positioning actuator, wherein the workpiece to be processed is placed on top of the support base, characterized in that: An electromagnetic drive coil connected to the electromagnetic forming system circuit is fixedly installed on the upper inner side of the positioning housing, and a copper drive block located below the electromagnetic drive coil is movably installed on the lower inner side of the positioning housing. Several core rod expansion joint devices corresponding to the heat transfer tubes of the workpiece are installed at the bottom of the copper drive block. The core rod expansion device includes a high-strength alloy core rod fixedly connected to the bottom of the positioning housing, a high-rigidity spring sleeved on the outside of the bottom of the high-strength alloy core rod, a high-pressure resistant rubber sleeved on the outside of the high-rigidity spring and embedded in the bottom end of the high-strength alloy core rod, and a high-strength alloy extrusion block fixedly connected to the copper drive block and movably sleeved on the outside of the high-strength alloy core rod. The positioning actuator drives the positioning housing downward, causing the high-stiffness spring and high-pressure resistant rubber to follow the high-strength alloy core rod into the heat transfer tube. The electromagnetic forming system circuit releases the stored high-voltage electrical energy instantaneously through the electromagnetic drive coil, exciting and forming a strong pulsed magnetic field B1 that changes rapidly with time. The copper drive block induces and generates an induced magnetic field B2 in the opposite direction to B1. Under the action of a huge Lorentz force, the copper drive block impacts the weld area at the top of the heat transfer tube at high speed. The high-strength alloy extrusion block squeezes the high-stiffness spring to contract, thereby causing the high-pressure resistant rubber to expand radially, realizing the mechanical expansion joint between the heat transfer tube and the tube sheet.

2. The impact-expansion composite electromagnetic forming tooling according to claim 1, characterized in that: The top surface of the support base is provided with a groove, the workpiece is embedded in the groove, and a positioning pin that can be movably inserted into the tube plate of the workpiece is provided in the groove. A positioning hydraulic cylinder that drives the positioning pin to rise and fall is fixedly installed in the bottom of the support base.

3. The impact-expansion composite electromagnetic forming tooling according to claim 1, characterized in that: A connecting groove is fixedly connected inside the positioning housing. The electromagnetic drive coil is placed inside the connecting groove, and the top end of the high-strength alloy core rod is fixedly connected to the bottom surface of the connecting groove.

4. The impact-expansion composite electromagnetic forming tooling according to claim 3, characterized in that: The connecting groove is respectively fixedly provided with an inner isolation sleeve located inside the electromagnetic drive coil and an outer isolation sleeve located outside the electromagnetic drive coil.

5. The impact-expansion composite electromagnetic forming fixture according to claim 3 or 4, characterized in that: A reset hydraulic cylinder located inside the electromagnetic drive coil is fixedly connected to the top surface of the bottom of the connecting groove. The output rod end of the reset hydraulic cylinder moves through the bottom of the copper drive block and is fixedly connected to a reset connecting block.

6. The impact-expansion composite electromagnetic forming tooling according to claim 5, characterized in that: The copper drive block is fixedly connected to an upper connecting plate at its top and a lower connecting plate at its bottom. A through hole is provided at the center of the copper drive block and the lower connecting plate. A hollow boss located in the through hole is integrally provided on the bottom surface of the upper connecting plate. The reset connecting block is movably inserted into the hollow boss, and the bottom end of the reset connecting block can overlap with the bottom surface of the hollow boss.

7. The impact-expansion composite electromagnetic forming tooling according to claim 6, characterized in that: A limiting plate located below the lower connecting plate is movably disposed inside the bottom side wall of the positioning housing, and a limiting hydraulic cylinder for driving the limiting plate to move horizontally is fixedly connected to the outside side wall of the positioning housing.

8. A process for an impact-expansion composite electromagnetic forming tool, characterized in that, Includes the following steps: S1. Workpiece cleaning: Clean the surface of the tube sheet, the weld area, and the inner wall of the heat transfer tube; S2. Workpiece loading and positioning: Place the workpiece on the support base and adjust it to the forming working position; S3, tooling vertical positioning: the positioning actuator drives the positioning housing downward, so that the distance between the bottom surface of the copper drive block and the surface of the tube sheet is to the preset value to meet the impact strengthening process requirements. The high-rigidity spring and high-pressure resistant rubber of the core rod expansion device are inserted into the heat transfer tube to the preset expansion position. S4. Electromagnetic drive impact strengthening: When the electromagnetic forming system circuit is energized, the instantaneous pulse current in the electromagnetic drive coil is excited to form a magnetic field. The magnetic field interacts with the eddy current induced in the copper drive block to generate a huge transient Lorentz force. The copper drive block is driven by the Lorentz force to fall vertically at high speed, which strengthens the weld area through impact. S5. Expansion joint: The high-strength alloy extrusion block follows the copper drive block to impact downwards at high speed, causing the high-rigidity spring to be compressed instantaneously. The high-pressure resistant rubber expands rapidly in the radial direction and applies uniform and controllable radial pressure to the inner wall of the heat transfer tube, forcing the tube wall to undergo plastic deformation until its outer wall and the inner wall of the tube sheet hole are tightly fitted, thus completing the mechanical expansion joint. S6. Tooling Reset: After the impact-expansion operation is completed, the electromagnetic forming system circuit is de-energized, the positioning actuator drives the positioning housing to move upward, which in turn drives the electromagnetic drive coil and copper drive block to move upward and reset. The high-rigidity spring resets, which causes the high-pressure resistant rubber to retract radially and separate from the inner wall of the heat transfer tube. S7. Workpiece unloading: Remove the workpiece that has completed the impact-expansion joint from the support base.

9. The impact-expansion composite electromagnetic forming process according to claim 8, characterized in that: The capacitance of the capacitor in the electromagnetic forming system circuit is continuously adjustable from 0µF to 360µF, and the preset target discharge voltage is 12kV-18kV.

10. The impact-expansion composite electromagnetic forming process according to claim 8 or 9, characterized in that: In step S4, the impact velocity of the copper driving block is 100-200 m / s, and the strain rate of the weld is 10. 3 -10 4 s -1 .

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