Novel connecting structure of stainless steel composite steel pipes and using method of novel connecting structure
The mechanical interlocking structure of the female and male sleeves solves the problem of insufficient torsional resistance in stainless steel composite pipe connections, achieving a connection effect with high safety and convenient installation.
Patent Information
- Application Number
- CN202512049202.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-03-06
AI Technical Summary
Existing stainless steel composite pipe connection methods have problems such as insufficient torsional resistance, easy decrease in friction coefficient, laborious installation, and damage to the surface of the steel pipe.
The system employs a mechanical interlocking structure between the female and male sleeves, and through the design of inserts and slots, combined with the two-stage operation of clamps and locking components, it achieves rapid alignment and stable connection of steel pipes.
It improves the safety and reliability of the connection, ensures long-term stability and load-bearing capacity under complex loads, and is easy to install without damaging the surface of the steel pipe.
Smart Images
Figure CN121611228A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of stainless steel pipe fittings technology, specifically to a novel connection structure for stainless steel composite pipes. Background Technology
[0002] With the development of modern architecture, bridges, pipeline engineering, and large temporary structures (such as scaffolding), stainless steel composite pipes have been widely used due to their excellent corrosion resistance and high structural strength. In practical engineering, it is often necessary to extend multiple steel pipes or form frames using reliable connection structures, which places strict requirements on the strength, stiffness, torsional resistance, and ease of installation of the connection nodes. Currently, the commonly used steel pipe connection methods in the industry mainly include welding, flange connections, and mechanical clamp connections. Although welded connections are strong, they have the disadvantage of requiring high on-site construction conditions. Flange connections are easy to assemble and disassemble, but they are usually structurally heavy, costly, and the bolt preload is difficult to control evenly.
[0003] In fields such as construction scaffolding, which require frequent disassembly and flexible assembly, various mechanical clamps or fasteners are widely used for connection. These connection structures typically rely on the radial friction generated by the clamps against the outer wall of the steel pipe to transfer loads and resist torsion. This friction-dependent connection method has inherent drawbacks: firstly, its torsional resistance depends entirely on the coefficient of friction and normal force. Under long-term dynamic loads, vibration, or when the surface is damp or contaminated with oil, the coefficient of friction can easily decrease, leading to loosening and safety hazards. Secondly, to achieve sufficient friction, a large locking force is often required, making installation and disassembly laborious and potentially damaging the anti-corrosion layer of the steel pipe surface due to overload (especially for stainless steel composite pipes). More importantly, simple radial clamping cannot provide direct, rigid mechanical restraint on the circumferential relative rotation of the two steel pipes, resulting in insufficient torsional reliability. Summary of the Invention
[0004] In view of the above problems, the present application provides a novel connection structure for stainless steel composite pipes, which can avoid the problem of insufficient torsional resistance caused by friction clamps in the prior art, and is easy to install with less impact on the surface of the steel pipe.
[0005] According to one aspect of the embodiments of this application, a novel connection structure for stainless steel composite pipes is provided. The novel connection structure for connecting a first steel pipe and a second steel pipe includes a sub-sleeve and a female sleeve, wherein the sub-sleeve and the female sleeve are respectively used to fixably connect to the ends of the first steel pipe and the second steel pipe. Both the sub-sleeve and the mother sleeve include a cylindrical main body. One end of the main body is a connecting end for connecting to a corresponding steel pipe, and the other end is a mating end. The mating end has multiple axially extending inserts evenly spaced along its circumference, and a slot is formed between adjacent inserts that matches the shape of the inserts. A reinforcing rod is axially inserted and fixed in the inner cavity of the main body of the sub-sleeve. One end of the reinforcing rod is fixed to the sub-sleeve, and the other end extends beyond the mating end of the sub-sleeve. The sub-sleeve has a clearance window in its circumference, which corresponds to the position of one of the missing inserts. A locking assembly includes a radial protrusion at the extended end of the reinforcing rod and two semi-circular clamps. The radial protrusion passes through the clearance window and is located outside the main body of the sub-sleeve. One end of each clamp is hinged to the radial protrusion. The two clamps surround and fit against the outer circumference of the mating end of the sub-sleeve and the mother sleeve, and the free ends of the two clamps are connected to each other by a locking member.
[0006] In some embodiments, the radial wall thickness of the insert of the sub-sleeve is less than that of the insert of the female sleeve, such that when the clamp surrounds and fits around the outer periphery of the mating end of the sub-sleeve and the female sleeve and is pressed by the locking member, the inner wall of the clamp abuts against the outer surface of the insert of the female sleeve.
[0007] In some embodiments, the locking element is a bolt pair.
[0008] In some embodiments, the bolt pair includes a U-shaped fixing seat fixedly connected to the free end of one of the clamps, the U-shaped fixing seat having a through hole, and a fastening bolt movably connected to the free end of the other clamp.
[0009] In some embodiments, a threaded ring is fixedly provided at the connecting end of both the sub-sleeve and the mother sleeve. The outer circumference of the threaded ring is provided with an external thread for engaging with the internal thread of the inner wall of the end of the first or second steel pipe.
[0010] In some embodiments, the outer diameter of the threaded ring is smaller than the outer diameter of the body component to which it is located, such that the body component forms an annular end face support at the root of the threaded ring.
[0011] In some embodiments, the plug-in has an axial protrusion on its free end face away from the main body, and an axial groove is provided on the inner wall of the main body at a position corresponding to the bottom of the slot; when the sub-sleeve and the female sleeve are fully inserted, the axial protrusion of the sub-sleeve plug-in engages with the axial groove on the female sleeve, and / or, the axial protrusion of the female sleeve plug-in engages with the axial groove on the sub-sleeve.
[0012] The beneficial effects of this application are:
[0013] 1. In this application, the structure of the plug-in and slot, the female sleeve and the male sleeve directly forms a mechanical interlock on the side of the plug-in. When subjected to torsional torque, the force is directly transmitted and borne through the side of the plug-in, which completely changes the traditional connection mode that relies entirely on the friction between the sleeve and the steel pipe. In principle, it eliminates relative sliding and loosening at the connection point, greatly improving the safety and reliability of the connection node, and is especially suitable for scenarios that bear large torsional forces and have extremely high stability requirements.
[0014] 2. In this application, a two-stage operation is adopted through the cooperation of components such as plug-in and clamp, involving first plugging and alignment, followed by clamp locking. During the plugging stage, the plug-in naturally guides the two steel pipes to quickly align and achieve initial circumferential and axial positioning, making installation convenient and easy for on-site construction. During the locking stage, the clamp is tightened using a simple locking device to complete the final fixation. The clamp's direct pressure on the outer surface of the female sleeve plug-in rigidly connects the two sleeves into a single unit. This allows the invention to ensure the long-term stability and load-bearing capacity of the entire connection structure under complex loads.
[0015] In another aspect of this application, a method for connecting stainless steel composite pipes is also provided, which utilizes the novel connection structure of stainless steel composite pipes as described in the above embodiments, and has the same beneficial effects as above. The method includes the following steps:
[0016] S1: The sub-sleeve is fixedly installed to the end of the first steel pipe through its connecting end, and the mother sleeve is fixedly installed to the end of the second steel pipe through its connecting end;
[0017] S2: Position the first steel pipe and the second steel pipe so that the mating ends of the sub-sleeve and the mother sleeve are directly opposite each other, and axially align the insert of the sub-sleeve with the slot of the mother sleeve, and the insert of the mother sleeve with the slot of the sub-sleeve.
[0018] S3: Push the first steel pipe and the second steel pipe closer together along the axial direction, so that the insert of the sub-sleeve is inserted into the slot of the mother sleeve, and at the same time the insert of the mother sleeve is inserted into the slot of the sub-sleeve, until the sub-sleeve and the mother sleeve are completely nested.
[0019] S4: Wrap the two clamps around and fit them to the outer periphery of the mating ends of the nested sub-sleeve and mother sleeve, and use the locking member to connect and lock the free ends of the two clamps until the inner wall of the clamps is pressed against the outer surface of the mother sleeve insert, thus completing the connection between the first steel pipe and the second steel pipe.
[0020] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description
[0021] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:
[0022] Figure 1 This is a schematic diagram of the overall installation structure provided in the embodiments of this application;
[0023] Figure 2 This is a schematic diagram of the overall exploded structure provided in the embodiments of this application;
[0024] Figure 3 A partial structural diagram of the connection between the third steel pipe and the female sleeve provided in an embodiment of this application;
[0025] Figure 4 This is a schematic diagram of the overall vertical cross-sectional structure provided in an embodiment of this application;
[0026] Figure 5 This is a schematic diagram of the overall cross-sectional structure provided for an embodiment of this application.
[0027] The reference numerals in the detailed embodiments are as follows:
[0028] The new connection structure of stainless steel composite steel pipe 100 includes a sub-sleeve 110, a main body 111, an insert 112, an axial protrusion 112a, a slot 113, an axial groove 113a, a reinforcing rod 114, a clearance window 115, a threaded ring 116, an end face support 117, a female sleeve 120, a locking assembly 130, a radial protrusion 131, a clamp 132, a locking element 133, a U-shaped fixing seat 133a, a fastening bolt 133b, a first steel pipe 200, and a second steel pipe 300. Detailed Implementation
[0029] The embodiments of the technical solution of this application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of this application, and are therefore merely examples and should not be used to limit the scope of protection of this application. 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 application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and the foregoing description of the accompanying drawings are intended to cover non-exclusive inclusion.
[0030] For details, please refer to Figures 1 to 5 Figure 1 This is a schematic diagram of the overall installation structure provided in an embodiment of this application. Figure 2 This is a schematic diagram of the overall exploded structure provided in an embodiment of this application. Figure 3 This is a partial structural diagram of the connection between the third steel pipe and the mother sleeve provided in an embodiment of this application. Figure 4 This is a schematic diagram of the overall vertical cross-sectional structure provided in an embodiment of this application. Figure 5This is a schematic diagram of the overall cross-sectional structure provided for an embodiment of this application. A novel connection structure 100 for stainless steel composite pipes, used to connect a first steel pipe 200 and a second steel pipe 300, includes a sub-sleeve 110 and a female sleeve 120. The sub-sleeve 110 and female sleeve 120 are respectively used to fixally connect to the ends of the first steel pipe 200 and the second steel pipe 300. The sub-sleeve 110 and female sleeve 120 can be connected to the first steel pipe 200 and the second steel pipe 300 by welding, or threaded holes can be opened at corresponding positions on the outer walls of the main body 111 of the sub-sleeve 110 and the female sleeve 120, and external threads can be machined at the corresponding ends of the first steel pipe 200 and the second steel pipe 300, then screwed in and welded. It should be noted that, although the first steel pipe 200 and the second lever can be welded to the sub-sleeve 110 and the female sleeve 120 in this application, this welding process occurs before on-site installation and can be completed on the ground or in the factory. Therefore, compared with welding performed during construction or installation in the prior art, it is easier to operate and has better precision and operability. Both the sub-sleeve 110 and the female sleeve 120 include a cylindrical main body 111. One end of the main body 111 is a connecting end for connecting to the corresponding steel pipe. The outer diameter of the cylindrical main body 111 can be the same as or similar to the outer diameter of the first steel pipe 200 and the second steel pipe 300 to be connected, so as to maintain the smooth appearance of the connection part. However, in some special cases, if the diameters of the first steel pipe 200 and the second steel pipe 300 to be connected are different, the connecting end of the main body 111 can also be set to different diameters to adapt to the first steel pipe 200 or the second steel pipe 300. The other end is the mating end, which has multiple axially extending inserts 112 evenly spaced along its circumference. A slot 113, matching the shape of the insert 112, is formed between adjacent inserts 112. Preferably, there are six inserts 112 and slots 113, evenly distributed circumferentially to ensure sufficient contact area while facilitating processing and alignment. The cross-sectional shape of the insert 112 can be rectangular, trapezoidal, or dovetail-shaped. Preferably, a trapezoidal cross-section is used, as the beveled sides help guide insertion and provide pre-tightening for initial circumferential rotation. A small clearance fit is used between the insert 112 of the sub-sleeve 110 and the slot 113 of the female sleeve 120, and between the insert 112 of the female sleeve 120 and the slot 113 of the sub-sleeve 110. For example, the clearance on one side can be controlled between 0.1-0.5 mm. This design ensures smooth insertion while minimizing post-connection shaking, ensuring the immediate effectiveness of the mechanical interlock.
[0031] A reinforcing rod 114 is axially inserted and fixed within the inner cavity of the main body 111 of the sub-sleeve 110. One end of the reinforcing rod 114 is fixed to the sub-sleeve 110, and the other end extends beyond the mating end of the sub-sleeve 110. A clearance window 115 is provided circumferentially on the sub-sleeve 110, corresponding to the position of one of the missing inserts 112. The reinforcing rod 114, the main body 111 of the sub-sleeve 110, and the inserts 112 can be an integral structure to enhance their strength. The length of the reinforcing rod 114 is such that after assembly, both ends can be inserted into the inner cavities of the first steel pipe 200 and the second steel pipe 300, respectively, further enhancing the stability of the connection. The size of the clearance window 115 is slightly larger than the size of the radial protrusion 131 to ensure the necessary movement space for the clamp 132 when it is rotated. The edges of the window can be chamfered or polished to avoid interference or stress concentration with the radial protrusion 131. The radial protrusion 131 can be integrally formed with the reinforcing rod 114 to ensure strength, or it can be a separate pin.
[0032] A locking assembly 130 includes a radial protrusion 131 located at the extension end of the reinforcing rod 114, and two semi-circular clamps 132. The radial protrusion 131 passes through the clearance window 115 and is located outside the main body 111 of the sub-sleeve 110. One end of each clamp 132 is hinged to the radial protrusion 131. When not connected, the two clamps 132 can be flipped outward around the radial protrusion 131 and opened in a drooping or open state, completely detached from the outer periphery of the sub-sleeve 110, which facilitates the insertion and connection of the sleeve and other operations without causing interference.
[0033] Two clamps 132 surround and fit around the outer periphery of the mating ends of the sub-sleeve 110 and the female sleeve 120, and the free ends of the two clamps 132 are connected to each other by a locking member 133. After the sub-sleeve 110 and the female sleeve 120 are fully nested, the operator flips the two clamps 132 upwards, closing them around the outer periphery of the mating ends of the two sleeves. At this time, the inner arc surface of the clamp 132 naturally fits against the outer surface of the female sleeve 120 insert 112 for pressing.
[0034] In some embodiments, the radial wall thickness of the insert 112 of the sub-sleeve 110 is less than that of the insert 112 of the female sleeve 120. This is so that when the clamp 132 surrounds and fits around the outer periphery of the mating ends of the sub-sleeve 110 and the female sleeve 120 and is pressed by the locking member 133, the inner wall of the clamp 132 abuts against the outer surface of the insert 112 of the female sleeve 120. In this embodiment, since the clamp 132 is directly connected to the sub-sleeve 110, the radial wall thickness of the insert 112 of the sub-sleeve 110 is made less than that of the insert 112 of the female sleeve 120, thereby concentrating the clamping force of the clamp 132 onto the insert 112 of the female sleeve 120. This further improves the stability of the connection between the sub-sleeve 110 and the female sleeve 120, achieving dual protection.
[0035] In some embodiments, the locking element 133 is a bolt pair, which includes a U-shaped fixing seat 133a fixedly connected to the free end of one of the clamps 132, the U-shaped fixing seat 133a having a through hole, and a fastening bolt 133b movably connected to the free end of the other clamp 132. In this embodiment, by setting the bolt pair as the locking element 133, it has the advantages and characteristics of simple structure, easy processing, and convenient operation and inspection.
[0036] In some embodiments, a threaded ring 116 is fixedly provided at the connecting end of both the sub-sleeve 110 and the female sleeve 120. The outer circumference of the threaded ring 116 is provided with external threads for engaging with the internal threads on the inner wall of the end of the first steel pipe 200 or the second steel pipe 300. This arrangement enables a quick connection between the sub-sleeve 110 and the female sleeve 120 and the first steel pipe 200 and the second steel pipe 300, respectively.
[0037] In some embodiments, the outer diameter of the threaded ring 116 is smaller than the outer diameter of the main body 111, such that the main body 111 forms an annular end face support 117 at the root of the threaded ring 116. In this embodiment, because the outer diameter of the threaded ring 116 is small, the annular end face support 117 naturally formed at the root of the main body 111 (formed by the main body 111, the first steel pipe 200 or the second steel pipe, and the outer wall of the threaded ring 116) constitutes a welding bevel and positioning surface. During welding, the weld is concentrated on the support, which not only facilitates operation and improves the quality of the weld, but also blocks the welding heat by the support, effectively isolating thermal damage to the internal structure.
[0038] In some embodiments, the plug-in 112 has an axial protrusion 112a on its free end face away from the main body 111, and an axial groove 113a is provided on the inner wall of the main body 111 at a position corresponding to the bottom of the slot 113; when the sub-sleeve 110 and the female sleeve 120 are fully inserted, the axial protrusion 112a of the plug-in 112 of the sub-sleeve 110 engages with the axial groove 113a on the female sleeve 120, and / or, the axial protrusion 112a of the plug-in 112 of the female sleeve 120 engages with the axial groove 113a on the sub-sleeve 110, further improving the connection strength.
[0039] In another aspect of this application, a method for connecting stainless steel composite pipes is also provided, using the novel connection structure 100 of the stainless steel composite pipes in the above embodiments. The method includes the following steps: S1: fixing the sub-sleeve 110 to the end of the first steel pipe 200 through its connecting end, and fixing the female sleeve 120 to the end of the second steel pipe 300 through its connecting end; S2: positioning the first steel pipe 200 and the second steel pipe 300 opposite each other, so that the mating ends of the sub-sleeve 110 and the female sleeve 120 are aligned. This is aligned, and the insert 112 of the sub-sleeve 110 is axially aligned with the slot 113 of the female sleeve 120, and the insert 112 of the female sleeve 120 is axially aligned with the slot 113 of the sub-sleeve 110; S3: The first steel pipe 200 and the second steel pipe 300 are pushed closer to each other along the axial direction, so that the insert 112 of the sub-sleeve 110 is inserted into the slot 113 of the female sleeve 120, and at the same time the insert 112 of the female sleeve 120 is inserted into the slot 113 of the sub-sleeve 110, until the sub-sleeve 110 and the female sleeve 120 are completely nested;
[0040] S4: Wrap the two clamps 132 around and fit them against the outer periphery of the mating ends of the nested sub-sleeve 110 and the mother sleeve 120, and use the locking member 133 to connect and lock the free ends of the two clamps 132 until the inner wall of the clamp 132 is pressed against the outer surface of the insert 112 of the mother sleeve 120, thus completing the connection between the first steel pipe 200 and the second steel pipe 300.
[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although the foregoing embodiments have provided a detailed description of this application, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.
Claims
1. A novel connection structure of a stainless steel composite pipe for connecting a first steel pipe and a second steel pipe, characterized by, The utility model relates to a new type of connecting structure of stainless steel composite pipe, which comprises a female sleeve and a male sleeve, the male sleeve and the female sleeve are respectively fixedly connected to the end of the first steel pipe and the second steel pipe, the male sleeve and the female sleeve each comprise a cylindrical main body, one end of the main body is a connecting end for connecting with the corresponding steel pipe, the other end is a butt joint end, a plurality of axially extending inserts are arranged on the butt joint end of the main body at equal intervals in the circumferential direction, and a slot with a shape matched with the insert is formed between adjacent two inserts, a reinforcing rod is axially arranged in the inner cavity of the main body of the male sleeve and is fixed in the inner cavity, one end of the reinforcing rod is fixed on the male sleeve, the other end of the reinforcing rod extends beyond the butt joint end of the male sleeve, a window is arranged on the male sleeve in the circumferential direction, and the window corresponds to the position of one missing insert, a locking assembly comprises a radial protrusion arranged on the extending end of the reinforcing rod and two half circular hoop clamps, the radial protrusion passes through the window and is located outside the main body of the male sleeve, one end of each of the two hoop clamps is hingedly connected to the radial protrusion, the hoop clamps are arranged around and attached to the outer periphery of the butt joint end of the male sleeve and the female sleeve, and the free ends of the two hoop clamps are connected to each other through a locking member. The radial wall thickness of the insert of the male sleeve is smaller than the radial wall thickness of the insert of the female sleeve, so that when the hoop clamps are arranged around and attached to the outer periphery of the butt joint end of the male sleeve and the female sleeve and are compressed by the locking member, the inner wall of the hoop clamps is in abutment with the outer surface of the insert of the female sleeve. The locking member is a bolt pair. The bolt pair comprises a U-shaped fixing seat fixedly connected to the free end of one of the hoop clamps, a through hole is formed in the U-shaped fixing seat, and a fastening bolt is movably connected to the free end of the other hoop clamp. The connecting end of the male sleeve and the connecting end of the female sleeve are each fixedly provided with a threaded ring, the outer periphery of the threaded ring is provided with external threads, and the external threads are matched with the internal threads in the inner wall of the end of the first steel pipe or the second steel pipe. The outer diameter of the threaded ring is smaller than the outer diameter of the main body in which the threaded ring is arranged, so that an annular end face support is formed at the root of the threaded ring.
2. The novel connection structure of stainless steel composite pipe according to claim 1, characterized by The insert is provided with an axial protrusion on the end face of the free end away from the main body in which the insert is arranged, and an axial groove is formed in the inner wall of the main body at a position corresponding to the bottom of the slot, when the male sleeve and the female sleeve are completely inserted, the axial protrusion of the insert of the male sleeve is engaged with the axial groove of the female sleeve, and / or the axial protrusion of the insert of the female sleeve is engaged with the axial groove of the male sleeve. The application of the new type of connecting structure of the stainless steel composite pipe as claimed in any one of claims 1 to 7 comprises the following steps:
3. The novel connection structure of stainless steel composite pipe according to claim 1, characterized by S1: the male sleeve is fixedly installed on the end of the first steel pipe through the connecting end of the male sleeve, and the female sleeve is fixedly installed on the end of the second steel pipe through the connecting end of the female sleeve; 4. The novel connection structure of stainless steel composite pipe according to claim 3, characterized by S2: the first steel pipe and the second steel pipe are arranged opposite to each other, the butt joint ends of the male sleeve and the female sleeve are arranged opposite to each other, and the insert of the male sleeve and the slot of the female sleeve, and the insert of the female sleeve and the slot of the male sleeve are respectively axially aligned.
5. The novel connection structure of stainless steel composite pipe according to claim 1, characterized by 6. The novel connection structure of stainless steel composite pipe according to claim 5, characterized by 7. The novel connection structure of stainless steel composite pipe according to claim 1, characterized by 8. A method of connecting a stainless steel composite pipe, characterized by S3: along the axial direction, push the first steel pipe and the second steel pipe close to each other, so that the insert of the female sleeve is inserted into the slot of the female sleeve, and at the same time, the insert of the female sleeve is inserted into the slot of the female sleeve, until the female sleeve and the female sleeve are completely nested; S4: the two hoops are wrapped around and attached to the outer periphery of the abutting end of the nested female sleeve and female sleeve, and the free ends of the two hoops are connected and locked by using the locking member, until the inner wall of the hoop is pressed against the outer surface of the female sleeve insert, completing the connection of the first steel pipe and the second steel pipe.