Durable ferritic stainless steel high-strength bolted connection

Abstract

This invention relates to the field of ferritic stainless steel technology, and more particularly to a durable high-strength ferritic stainless steel bolt connector. The durable high-strength ferritic stainless steel bolt connector includes a bolt head, a bolt shank, a nut, a mounting sleeve, a connecting assembly, and a first washer. A mounting plate is mounted on one side of the bolt head, and the bolt shank is mounted on one side of the mounting plate. A nut is threaded onto the outer wall of the bolt shank, and a mounting sleeve is mounted on one side of the nut. A connecting assembly is installed between the mounting sleeve and the bolt head. The durable high-strength ferritic stainless steel bolt connector provided by this invention forms an active tightening mechanism through the built-in connecting assembly. This mechanism can continuously compensate for preload loss throughout the bolt's service life, effectively offsetting the preload attenuation caused by stainless steel strain relaxation, wind-induced alternating loads, and cyclical deformation due to day and night and seasonal temperature changes. This prevents joint slippage and deformation, ensuring the stress accuracy and overall stability of the tower structure.

Description

Technical Field

[0001] This invention relates to the field of ferritic stainless steel technology, and in particular to a durable ferritic stainless steel high-strength bolt connector. Background Technology

[0002] As my country's power transmission line construction moves towards green, low-carbon, and long-life designs, the drawbacks of traditional hot-dip galvanized angle steel transmission towers are becoming increasingly apparent. Hot-dip galvanizing suffers from high pollution and complex processes, and the coating is prone to wear and peeling during service, leading to corrosion of tower components. This necessitates regular high-altitude corrosion inspections and maintenance, significantly increasing the total life-cycle cost of transmission lines. Against this backdrop, new high-strength ferritic stainless steel, as a green and high-performance structural material, is gradually being applied to transmission tower structures due to its excellent atmospheric corrosion resistance and matching mechanical strength. It allows for bare-metal operation, eliminating the need for galvanizing and subsequent corrosion maintenance, significantly reducing total life-cycle costs, and has become an important direction for the upgrading of transmission tower materials.

[0003] High-strength bolt connections are a core node type in the assembly of transmission tower components, and their service reliability directly determines the overall structural safety of the tower. Currently, transmission towers generally use galvanized carbon steel high-strength bolt connections, equipped with ordinary flat washers and spring washers for tightening and anti-loosening. However, directly applying existing bolt connection solutions to ferritic stainless steel towers presents many technical drawbacks. Stainless steel itself exhibits significant strain relaxation characteristics, and coupled with the long-term exposure of transmission towers to wind vibration loads and temperature cycling, the bolt preload continuously decreases over service life. Existing ordinary spring washers can only provide initial anti-loosening protection and cannot continuously and quantitatively compensate for preload loss. As the preload decreases, the anti-slip capability of the friction surface also decreases, making the joint prone to slippage and deformation, affecting the stress accuracy and overall stability of the tower structure. Regular high-altitude re-tightening operations are required during operation and maintenance, which is costly and carries significant safety risks.

[0004] Therefore, it is necessary to provide a new type of durable ferritic stainless steel high-strength bolt connector to solve the above-mentioned technical problems. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides a durable ferritic stainless steel high-strength bolt connector.

[0006] The durable ferritic stainless steel high-strength bolt connector provided by the present invention includes: a bolt head, a bolt shank, a nut, a mounting sleeve, a connecting assembly, and a first washer. A mounting plate is installed on one side of the bolt head, and a bolt shank is installed on one side of the mounting plate. A nut is threaded onto the outer wall of the bolt shank, and a mounting sleeve is installed on one side of the nut. A connecting assembly is installed between the mounting sleeve and the bolt head. The connecting assembly applies a pulling force between the bolt head and the nut to fasten the bolt head and the nut. A first washer is fitted onto the end of the bolt shank near the bolt head.

[0007] Preferably, the connecting assembly includes: a rotating plate, a tension / compression spring, and a threaded block. The rotating plate is rotatably connected to the inner wall of the end of the mounting cylinder, the tension / compression spring is fixedly connected to the side wall of the rotating plate, and the threaded block is fixedly connected to the other end of the tension / compression spring.

[0008] Preferably, the end of the bolt shank furthest from the bolt head has an installation groove, the inner wall of the installation groove has symmetrically formed limit grooves, the outer wall of the threaded block is symmetrically fixedly connected to limit protrusions, and the limit protrusions are all slidably embedded in the corresponding limit grooves.

[0009] Preferably, the bolt head has a placement groove inside, and a threaded rod is rotatably connected inside the placement groove. One end of the threaded rod extends into the mounting groove inside the bolt rod and is threadedly connected to the threaded block. The other end of the threaded rod is fixedly connected to a driving block, and an internal hexagonal groove is provided on the side of the driving block away from the threaded rod.

[0010] Preferably, a first connector and a second connector are provided between the bolt head and the nut, and both the first connector and the second connector have through holes inside, into which the bolt rod is inserted.

[0011] Preferably, the sidewall of the first washer is fixedly connected with insert rods at equal intervals around its circumference, and the inside of the mounting plate is provided with slots at equal intervals around its circumference, with the insert rods inserted into the corresponding slots. The side of the first washer away from the insert rods is in contact with the sidewall of the connector.

[0012] Preferably, a second washer is fitted on the outer wall of the end of the bolt rod near the nut. One side of the second washer is in contact with the side wall of the nut, and the other side is in contact with the side wall of the second connector.

[0013] Preferably, both the first washer and the second washer are made of cold-worked high-strength ferritic stainless steel.

[0014] Preferably, the bolt head, bolt shank, and nut are all made of 2205 duplex stainless steel.

[0015] Preferably, the inner diameter of the mounting sleeve is larger than the outer diameter of the bolt rod.

[0016] Compared with related technologies, the durable ferritic stainless steel high-strength bolt connector provided by the present invention has the following advantages: An active tensioning mechanism, formed by built-in connecting components, continuously compensates for preload loss throughout the bolt's service life, effectively offsetting preload attenuation caused by strain relaxation of stainless steel materials, alternating wind loads, and cyclical deformation due to day and night and seasonal temperature changes. Through the elastic rebound of the tension and compression springs, the opposing tension force between the bolt head and nut is actively maintained, ensuring long-term stable pressure on the friction surface, preventing slippage and deformation at the joints, and guaranteeing the stress accuracy and overall stability of the tower structure. Simultaneously, there is no need for periodic high-altitude re-tightening operations, significantly reducing maintenance costs and the safety risks associated with high-altitude work.

[0017] The bolt head, bolt shank, and nut are made of 2205 duplex stainless steel, while the first and second washers are made of cold-work hardened high-strength ferritic stainless steel. This material is highly compatible with the corrosion potential of the connected ferritic stainless steel tower components, eliminating the risk of galvanic corrosion caused by dissimilar metal contact at its source. This avoids the short lifespan issue of traditional carbon steel galvanized bolts being accelerated to rust as the anode. The entire set of connectors requires no hot-dip galvanizing or other anti-corrosion coatings and can be used without them, eliminating the risk of coating peeling and rust contamination of the stainless steel surface. Simultaneously, the mounting sleeve on the nut side, located around the bolt shank end, forms a semi-enclosed protective space, preventing rainwater, salt spray, industrial dust, and other corrosive media from directly intruding into the threaded joint and the bolt's internal mounting groove. This effectively reduces crevice corrosion and thread seizing, ensuring convenient disassembly and maintenance in the future.

[0018] The rotating connection structure between the rotating plate and the inner wall of the mounting cylinder can isolate the torsional torque during the tightening process of the nut from being transmitted to the tension and compression springs and the threaded block. This allows the elastic component and the transmission component to only perform axial translation and not rotate synchronously with the nut, thus avoiding fatigue fracture of the tension and compression springs due to repeated torsion and effectively extending the service life of the elastic mechanism. Attached Figure Description

[0019] Figure 1 A schematic diagram of the structure of the durable ferritic stainless steel high-strength bolt connector provided by the present invention; Figure 2 for Figure 1 The diagram shows the structure of the bolt head; Figure 3 for Figure 2 The diagram shows a cross-sectional view of the bolt head shank. Figure 4 for Figure 3 The diagram shows a cross-sectional view of the nut. Figure 5 for Figure 2 A schematic diagram of a partial cross-section of the bolt rod shown; Figure 6 for Figure 3 The diagram shows the structure of a tension / compression spring.

[0020] The following are the labels in the diagram: 1. Bolt head; 2. Mounting plate; 3. Bolt shank; 4. Nut; 5. Mounting sleeve; 6. First washer; 7. Rotating plate; 8. Tension / compression spring; 9. Threaded block; 10. Mounting groove; 11. Limiting groove; 12. Limiting protrusion; 13. Threaded rod; 14. Drive block; 15. Socket hexagonal groove; 16. Insert rod; 17. Slot; 18. Connector 1; 19. Connector 2; 20. Through hole; 21. Second washer. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] The specific implementation of the present invention will be described in detail below with reference to specific embodiments. Example

[0023] Please see Figures 1 to 6 A durable ferritic stainless steel high-strength bolt connector includes: a bolt head 1, a bolt shank 3, a nut 4, a mounting sleeve 5, a connecting assembly, and a first washer 6. A mounting plate 2 is mounted on one side of the bolt head 1, and a bolt shank 3 is mounted on one side of the mounting plate 2. A nut 4 is threaded onto the outer wall of the bolt shank 3, and a mounting sleeve 5 is mounted on one side of the nut 4. A connecting assembly is installed between the mounting sleeve 5 and the bolt head 1. The connecting assembly applies a pulling force between the bolt head 1 and the nut 4 to fasten them. A first washer 6 is fitted onto the end of the bolt shank 3 closest to the bolt head 1. The mounting sleeve 5 and the nut 4 are integrally machined from the same material. An annular groove is machined on the inner wall of the sleeve for embedding a rotating plate 7, enabling circumferential rotation and axial positioning of the rotating plate 7.

[0024] The connecting components include: a rotating plate 7, a tension / compression spring 8, and a threaded block 9. The rotating plate 7 is rotatably connected to the inner wall of the end of the mounting cylinder 5, and the tension / compression spring 8 is fixedly connected to the side wall of the rotating plate 7. The other end of the tension / compression spring 8 is fixedly connected to the threaded block 9. The tension / compression spring 8 is made of 17-7PH precipitation-hardening stainless steel wire, and the target elastic properties are obtained through solution treatment and aging treatment. Its corrosion potential is close to that of the surrounding duplex stainless steel and ferritic stainless steel components, and there is no significant risk of galvanic corrosion.

[0025] The bolt rod 3 has an installation groove 10 inside at the end away from the bolt head 1. The inner wall of the installation groove 10 has symmetrical limit grooves 11. The outer wall of the threaded block 9 is symmetrically fixedly connected to limit protrusions 12, and the limit protrusions 12 are all slidably embedded in the corresponding limit grooves 11. The end of the limit groove 11 near the bolt head 1 is a closed end, which serves as the stroke stop point of the threaded block 9. When the limit protrusion 12 abuts against the end of the limit groove 11, the tension of the tension spring 8 is still within the elastic deformation range, thus preventing the spring from undergoing permanent deformation and failure.

[0026] The bolt head 1 has a placement groove inside, and a threaded rod 13 is rotatably connected inside the placement groove. One end of the threaded rod 13 extends into the mounting groove 10 inside the bolt rod 3 and is threadedly connected to the threaded block 9. The other end of the threaded rod 13 is fixedly connected to a drive block 14. The drive block 14 has an internal hexagonal groove 15 on the side away from the threaded rod 13. The rotating plate 7, the threaded block 9, and the threaded rod 13 are all made of 2205 duplex stainless steel, which is the same material as the bolt rod 3 and the nut 4, to avoid corrosion by dissimilar metal galvanic coupling. Example

[0027] Please see Figure 1 , Figure 2 , Figure 4 and Figure 5 A connecting piece 18 and a connecting piece 29 are provided between the bolt head 1 and the nut 4, and both the connecting piece 18 and the connecting piece 29 have through holes 20 inside, and the bolt rod 3 is inserted into the through hole 20.

[0028] The first washer 6 has a circumferentially fixedly connected insert rod 16 on its side wall. The mounting plate 2 has slots 17 circumferentially opened inside, and the insert rod 16 is inserted into the corresponding slot 17. The side of the first washer 6 away from the insert rod 16 is in contact with the side wall of the connector 18.

[0029] A second washer 21 is fitted on the outer wall of one end of the bolt rod 3 near the nut 4. One side of the second washer 21 is in contact with the side wall of the nut 4, and the other side is in contact with the side wall of the connector 19.

[0030] Both the first washer 6 and the second washer 21 are made of cold-worked high-strength ferritic stainless steel.

[0031] Bolt head 1, bolt shank 3 and nut 4 are all made of 2205 duplex stainless steel.

[0032] The inner diameter of the mounting cylinder 5 is larger than the outer diameter of the bolt rod 3.

[0033] The working principle of the durable ferritic stainless steel high-strength bolt connector provided by this invention is as follows: During installation, the first washer 6 is fitted axially along the bolt shank 3 to the end closest to the bolt head 1. The first washer 6 is then pushed against the mounting plate 2 on the bolt head 1 side, so that the inserts 16 distributed circumferentially on the sidewall of the first washer 6 are correspondingly embedded into the slots 17 inside the mounting plate 2. Through the insertion and engagement of the inserts 16 and the slots 17, the first washer 6 is subjected to circumferential rotation constraint and radial positioning, preventing the washer from deflecting synchronously with the friction force during the subsequent tightening of the nut 4, thus ensuring the stability of the anti-slip coefficient of the friction surface.

[0034] The bolt shank 3, with the first washer 6 installed, is inserted into the through hole 20 of connector 18, and then sequentially through the through holes 20 of connector 18 and connector 29, so that the first washer 6 on the bolt head 1 side is tightly fitted against the outer wall of connector 18. Then, the second washer 21 is fitted along the protruding end of the bolt shank 3, so that one side of the second washer 21 is fitted against the outer wall of connector 29. The first and second washers 21 are respectively arranged on both sides of the connected parts to disperse the local compressive stress of the bolt head 1 and nut 4, preventing the surface of the connected parts from being crushed. At the same time, the washers are made of cold-worked high-strength ferritic stainless steel, which matches the corrosion potential of the connected ferritic stainless steel components, fundamentally preventing galvanic corrosion caused by dissimilar metal contact and ensuring synchronized corrosion resistance life of the joint.

[0035] Next, hold the nut 4 and align it with the end of the bolt rod 3, so that the side of the nut 4 away from the mounting sleeve 5 faces the bolt rod 3. Align the threaded block 9 inside the mounting sleeve 5 with the mounting groove 10 at the end of the bolt rod 3. At the same time, adjust the limiting protrusion 12 on the outer wall of the threaded block 9 to align with the limiting groove 11 on the inner wall of the mounting groove 10. Push the nut 4 axially so that the threaded block 9 slides into the mounting groove 10 along the limiting groove 11 until the end face of the nut 4 contacts the end of the bolt rod 3.

[0036] Then, rotate nut 4 to engage with the threads on the outer wall of bolt rod 3 and screw it in. During the screwing process, mounting cylinder 5 advances axially synchronously with nut 4, driving rotating plate 7, tension / compression spring 8, and threaded block 9 to move synchronously deeper into mounting groove 10. Since rotating plate 7 is rotatably connected to the inner wall of mounting cylinder 5, tension / compression spring 8 and threaded block 9 only perform axial translation when nut 4 rotates and do not rotate synchronously with nut 4, thus avoiding torsional damage to the springs.

[0037] When the end of the threaded block 9 contacts the end face of the threaded rod 13 inside the mounting groove 10, the threaded block 9 cannot continue to advance axially; during the process of continuing to tighten the nut 4, the tension spring 8 will be compressed by the bidirectional squeezing of the threaded block 9 and the rotating plate 7, storing elastic potential energy until the nut 4 reaches the initial tightening state and the pre-tightening is completed.

[0038] After the nut 4 is initially tightened, insert the hex wrench into the hex socket 15 of the drive block 14 on the end face of the bolt head 1, and rotate the wrench to drive the drive block 14 and the threaded rod 13 to rotate synchronously. When the threaded rod 13 rotates, it forms a threaded transmission engagement with the threaded block 9. Under the circumferential constraint of the limiting protrusion 12 and the limiting groove 11, the threaded block 9 cannot rotate with the threaded rod 13, and can only move axially towards the bolt head 1 along the mounting groove 10.

[0039] During the translation of the threaded block 9, the elastic potential energy of the previously compressed tension spring 8 is first released. As the threaded block 9 continues to move deeper into the mounting groove 10, the tension spring 8 gradually changes from a compressed state to a stretched state, generating a continuous axial tensile force. This force pulls the nut 4 closer to the bolt head 1 via the rotating plate 7 and the mounting cylinder 5, while simultaneously pulling the bolt head 1 closer to the nut 4 via the threaded rod 13 and the drive block 14. This creates a stable opposing tension force between the bolt head 1 and the nut 4, supplementing and strengthening the bolt preload. Finally, after adjusting to the designed preload, the rotation of the threaded rod 13 is stopped, completing the installation and fastening of the entire set of connectors.

[0040] During service, when the axial preload of the bolt decreases due to the strain relaxation of the stainless steel material, alternating wind loads, and diurnal temperature cycle deformation, the stretched tension spring 8 will automatically rebound and release its elastic potential energy, continuously maintaining the opposing tension between the bolt head 1 and the nut 4. This automatically compensates for the preload loss, preventing slippage or loosening of the joint due to insufficient preload, eliminating the need for periodic high-altitude re-tightening operations, and significantly reducing maintenance costs and safety risks. Because the tension spring 8 can withstand both compression and tension loads, it can adapt to the compression energy storage during installation and the tension compensation during service, remaining within its elastic working range throughout, ensuring the reliability of long-term cyclic compensation.

[0041] Bolt head 1, bolt shank 3, and nut 4 are made of 2205 duplex stainless steel, possessing excellent resistance to atmospheric corrosion and crevice corrosion, allowing for bare installation without galvanizing for corrosion protection. The washer is made of the same high-strength ferritic stainless steel, matching the corrosion potential of the connected ferritic stainless steel components, eliminating the risk of galvanic corrosion. Simultaneously, the mounting sleeve 5 is placed around the end of bolt shank 3, forming a semi-enclosed protective space. This prevents rainwater, salt spray, dust, and other corrosive media from directly penetrating the threaded joint and mounting groove 10, reducing the risk of crevice corrosion and thread seizing, and ensuring convenient disassembly and maintenance in the future.

[0042] The cooperation between the limiting protrusion 12 and the limiting groove 11 provides precise guidance for the axial movement of the threaded block 9, preventing it from deflecting and jamming. It also restricts the circumferential rotation of the threaded block 9, ensuring stable and effective thread transmission between the threaded rod 13 and the threaded block 9. The rotating plate 7's rotating connection design isolates the torsional torque of the nut 4 from being transmitted to the tension / compression spring 8, preventing fatigue fracture of the spring due to repeated torsion and extending the service life of the elastic mechanism.

[0043] All standard parts used in this invention can be purchased from the market, and irregular parts can be customized according to the description and drawings. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts and equipment adopt conventional models in the prior art. In addition, the circuit connection adopts conventional connection methods in the prior art, which will not be described in detail here.

[0044] 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 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. A durable ferritic stainless steel high-strength bolt connector, characterized in that, include: Bolt head (1), and mounting plate (2) is installed on one side of bolt head (1); Bolt rod (3), a bolt rod (3) is installed on one side of the mounting plate (2); Nut (4), the outer wall of the bolt rod (3) is threaded with nut (4); Mounting sleeve (5), mounting sleeve (5) is installed on one side of nut (4); A connecting assembly is installed between the mounting sleeve (5) and the bolt head (1). The connecting assembly applies a pulling force between the bolt head (1) and the nut (4) to fasten the bolt head (1) and the nut (4). The first washer (6) is fitted on one end of the bolt rod (3) near the bolt head (1).

2. The durable ferritic stainless steel high-strength bolt connector according to claim 1, characterized in that, The connecting components include: a rotating plate (7), a tension / compression spring (8), and a threaded block (9). The rotating plate (7) is rotatably connected to the inner wall of the end of the mounting cylinder (5). The tension / compression spring (8) is fixedly connected to the side wall of the rotating plate (7). The threaded block (9) is fixedly connected to the other end of the tension / compression spring (8).

3. The durable ferritic stainless steel high-strength bolt connector according to claim 2, characterized in that, The bolt rod (3) has an installation groove (10) inside the end away from the bolt head (1). The inner wall of the installation groove (10) is symmetrically provided with a limiting groove (11). The outer wall of the threaded block (9) is symmetrically fixedly connected with a limiting protrusion (12), and the limiting protrusion (12) is slidably embedded in the corresponding limiting groove (11).

4. The durable ferritic stainless steel high-strength bolt connector according to claim 3, characterized in that, The bolt head (1) has a placement groove inside, and a threaded rod (13) is rotatably connected inside the placement groove. One end of the threaded rod (13) extends into the mounting groove (10) inside the bolt rod (3) and is threadedly connected to the threaded block (9). The other end of the threaded rod (13) is fixedly connected to a drive block (14). The drive block (14) has an internal hexagonal groove (15) on the side away from the threaded rod (13).

5. The durable ferritic stainless steel high-strength bolt connector according to claim 1, characterized in that, A first connector (18) and a second connector (19) are provided between the bolt head (1) and the nut (4), and both the first connector (18) and the second connector (19) have through holes (20) inside, and the bolt rod (3) is inserted into the through hole (20).

6. The durable ferritic stainless steel high-strength bolt connector according to claim 5, characterized in that, The first washer (6) has a circumferentially fixed rod (16) fixedly connected to the side wall. The mounting plate (2) has slots (17) circumferentially fixed inside, and the rods (16) are all inserted into the corresponding slots (17). The side of the first washer (6) away from the rod (16) is in contact with the side wall of the connector (18).

7. The durable ferritic stainless steel high-strength bolt connector according to claim 6, characterized in that, A second washer (21) is fitted on the outer wall of one end of the bolt rod (3) near the nut (4). One side of the second washer (21) is in contact with the side wall of the nut (4), and the other side is in contact with the side wall of the connector (19).

8. The durable ferritic stainless steel high-strength bolt connector according to claim 7, characterized in that, Both the first washer (6) and the second washer (21) are made of cold-worked high-strength ferritic stainless steel.

9. The durable ferritic stainless steel high-strength bolt connector according to claim 1, characterized in that, The bolt head (1), bolt shank (3) and nut (4) are all made of 2205 duplex stainless steel.

10. The durable ferritic stainless steel high-strength bolt connector according to claim 1, characterized in that, The inner diameter of the mounting cylinder (5) is greater than the outer diameter of the bolt rod (3).

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