Trenchless drill rod and method of forming a drill rod

Abstract

The application belongs to the technical field of drilling tools, and discloses a non-excavation drill rod and a drill rod forming method. The non-excavation drill rod comprises a split designed pipe body, a male joint and a female joint. The male joint and the female joint are respectively provided with a connecting part for inserting the corresponding end part of the pipe body. The connecting part is interference inserted with the pipe body. The pipe body is provided with a clamping part which is pressed towards the connecting part. The clamping part is used for improving the connecting strength between the connecting part and the pipe body. The application adopts a double connecting structure of split design, interference insertion and mechanical clamping to ensure the integrity of the combined drill rod, eliminate the welding weak point, significantly improve the tensile strength and torsional resistance of the connecting part, meet the technical requirements of the drill rod, and greatly reduce the manufacturing difficulty and production process of the drill rod. The expensive friction welding equipment is not needed. The machining can be completed through the conventional heat treatment equipment and hydraulic extrusion equipment. The production cycle and equipment cost are effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of drilling tools, and in particular to a trenchless drill pipe and a method for forming the drill pipe. Background Technology

[0002] Trenchless construction refers to a new construction technology that uses various rock and soil drilling equipment and techniques to lay, replace, and repair various underground pipelines with minimal excavation on the ground surface through methods such as directional drilling. It does not obstruct traffic, damage green spaces and vegetation, or affect people's normal life and work order. Trenchless drill rods are key tools used in trenchless construction technology.

[0003] Currently, trenchless drill pipes are mainly divided into integral drill pipes and welded drill pipes, each with its own advantages and disadvantages. Integral drill pipes are forged from a single piece of steel pipe without weld seams, possessing high strength and reliability, and are suitable for high torque and high tensile force conditions. However, they are heavy, inconvenient to transport and operate, and local damage may lead to the scrapping of the entire pipe. Welded drill pipes are typically manufactured separately as the pipe body and male / female connectors, and then the male / female connectors are connected to the pipe body through friction welding. They allow for flexible design, full utilization of materials, and especially the optimization of combinations of different materials, with great potential for lightweighting. However, the welding process is complex, the equipment investment is large, the friction welding parameters need to be precisely controlled, and the weld quality is highly dependent on the stability of the process.

[0004] Patent CN116357238A proposes a trenchless drill pipe forming structure and process, which involves thermally inserting and assembling the pipe body and male / female connectors into a single unit, followed by welding at the joint. While this structure and process overcome the shortcomings of integral machining, the process is relatively complex and still has weak points in the welds, particularly in terms of tensile and torsional resistance, resulting in a shorter service life under complex working conditions. Therefore, further optimization is needed. Summary of the Invention

[0005] Based on the above problems, the purpose of this invention is to provide a trenchless drill rod and a drill rod forming method, which overcomes the shortcomings of integral drill rods and existing welded drill rods, reduces the difficulty of drill rod forming and manufacturing costs, ensures drill rod performance, and extends service life.

[0006] To achieve this objective, the present invention employs the following technical solution: A trenchless drill pipe includes a split-design pipe body, a male connector, and a female connector. The male connector and the female connector are respectively provided with connecting parts for inserting into the corresponding ends of the pipe body. The connecting parts are interference-fitted with the pipe body, and the pipe body is provided with a biting part that presses against the connecting parts. The biting part is used to improve the connection strength between the connecting parts and the pipe body.

[0007] As an alternative, the outer surface of the connector is pre-formed with a recess that mates with the interlocking part, and the cross-sectional shape of the interlocking part is adapted to the cross-sectional shape of the recess.

[0008] As an alternative, the recessed portion can be a number of pits or an annular groove provided circumferentially along the connection portion.

[0009] As an alternative, the interlocking part is a protrusion formed by radial compression deformation of the sidewall of the tube.

[0010] As an alternative, when the tube body is combined with a male or female connector, the corresponding end of the tube body is heated to red-hot.

[0011] As an alternative, the root of the connector is provided with a limiting step for abutting against the end face of the pipe body. After the pipe body is combined with the male connector and the female connector respectively, the outer surface of the pipe body is smoothly connected with the surface of the male connector and the surface of the female connector respectively.

[0012] On the other hand, the present invention adopts the following technical solution: A method for forming a drill pipe, based on the above-mentioned trenchless drill pipe, includes: Step 1: Separately process and shape the pipe body, male connector, and female connector, and perform heat treatment; Step 2: Heat both ends of the tube until they are red-hot, insert the male connector into one end of the tube, and insert the female connector into the other end of the tube to achieve pre-assembly; Step 3: While the tube is still red-hot, radially press the side wall of the tube using an extrusion die to form an interlocking part on the inner surface of the tube that applies pressure to the corresponding connection part, thus achieving a firm combination of the tube with the male and female connectors. Step 4: After the assembled drill pipe is heat-treated, straightened, and tempered as a whole, the internal stress caused by hot jointing and extrusion deformation is eliminated. Step 5: Perform fine machining on the surface of the drill pipe to ensure a smooth transition at the connection points between the pipe body and the male and female connectors, and then perform surface anti-corrosion treatment.

[0013] As an alternative, in step one, the male connector and the female connector are pre-formed with recesses; in step three, the extrusion die includes a pressure plate arranged around the tube body and designed in segments, the inner side of the pressure plate acts on the outer surface of the tube body, and the inner side of the pressure plate is provided with protrusions that match the position and shape of the recesses.

[0014] As an alternative, a hydraulic press is used to drive the extrusion die, with the extrusion pressure controlled between 800MPa and 1200MPa and the holding time between 3s and 8s, so that the interlocking part fully fills the recessed part.

[0015] As an optional solution, in step two, medium-frequency induction heating is used to heat both ends of the tube to 850℃~1050℃, and the heating length is 1.5 times the length of the connection.

[0016] The beneficial effects of this invention are: This trenchless drill pipe adopts a split design with a dual connection structure of interference fit and mechanical engagement, which ensures the integrity of the drill pipe after assembly. Compared with traditional welding process, it eliminates weak points in the welding and significantly improves the tensile strength and torsional resistance of the connection, thus meeting the technical requirements of the drill pipe.

[0017] This drill pipe forming method significantly reduces the manufacturing difficulty and production process of drill pipes. It eliminates the need to purchase expensive friction welding equipment and can complete the processing using only conventional heat treatment equipment and hydraulic extrusion equipment, thereby effectively reducing the production cycle and equipment costs. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the trenchless drill rod provided in an embodiment of the present invention.

[0019] In the attached image: 1. Pipe body; 2. Male connector; 3. Female connector; 4. Connecting part; 5. Engaging part; 6. Recessed part; 7. Limiting step. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] In the description of this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "on the upper side," and "over" the second feature include the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature include the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0024] To address the shortcomings of existing integral and welded drill pipes, this invention provides a trenchless drill pipe and a drill pipe forming method, which reduces the difficulty and cost of drill pipe forming and ensures drill pipe performance from the perspectives of structural optimization and manufacturing process optimization.

[0025] like Figure 1 As shown, the trenchless drill rod includes a split-design pipe body 1, a male connector 2, and a female connector 3. The male connector 2 and the female connector 3 are respectively provided with connecting parts 4 for inserting into the corresponding ends of the pipe body 1. The connecting parts 4 are interference-fitted with the pipe body 1, and the pipe body 1 is provided with a biting part 5 that presses against the connecting part 4. The biting part 5 is used to improve the connection strength between the connecting part 4 and the pipe body 1.

[0026] Therefore, the use of a split design combined with a dual connection structure of interference fit and mechanical engagement ensures the integrity of the drill pipe after assembly. Compared with traditional welding processes, it eliminates weak points in the weld, significantly improves the tensile strength and torsional resistance of the connection, and meets the technical requirements of the drill pipe.

[0027] Optionally, a recessed portion 6 that mates with the engaging portion 5 is pre-formed on the outer surface of the connecting portion 4, and the cross-sectional shape of the engaging portion 5 is adapted to the cross-sectional shape of the recessed portion 6.

[0028] The presence of the recess 6 facilitates the accurate forming of the interlocking part 5 and increases the interlocking force of the interlocking part 5 on the connecting part 4, forming a reliable mechanical locking structure and effectively preventing relative slippage or separation between the pipe body 1 and the male connector 2 or female connector 3 during use. The depth of the recess 6 is controlled at about 30% of the wall thickness of the connecting part 4, which ensures sufficient interlocking depth without excessively weakening the structural strength of the connecting part 4.

[0029] Furthermore, the recessed portion 6 is a plurality of pits or an annular groove provided along the circumference of the connecting portion 4.

[0030] When a recessed design is used, the recesses are regularly distributed and, when combined with the interlocking part 5, can achieve a multi-point locking effect; when an annular groove design is used, a continuous annular locking structure can be formed. Both designs effectively increase the contact area and locking strength between the connecting part 4 and the pipe body 1. Figure 1 An example is provided in which three annular grooves are provided on each connecting part 4 at intervals along the axial direction of the connecting part 4, which fully ensures the reliability of the connection.

[0031] Among them, the interlocking part 5 is a protrusion formed by radial extrusion deformation of the side wall of the tube body 1.

[0032] By applying pressure to the outer side of the tube body 1 at the position corresponding to the recess 6, a convex part matching the shape of the recess 6 can be easily formed. This extrusion deformation process is similar to a hot riveting process. It should be noted that after being pressed, the outer surface of the tube body 1 will form a recessed surface, but this will not affect the performance and use of the drill pipe, because the dimensions of the connection points between the tube body 1 and the male connector 2 and the female connector 3 are smaller than the outer diameter dimensions of the male connector 2 and the female connector 3, which are non-stressed areas.

[0033] To facilitate the accurate insertion of the tube body 1 and the connecting part 4 and the forming of the interlocking part 5, when the tube body 1 is combined with the male connector 2 or the female connector 3, the corresponding end of the tube body 1 is in a red-hot state.

[0034] In its red-hot state, tube 1 exhibits excellent plasticity and thermal expansion characteristics. In this state, the heated tube 1 is heat-jointed with male connector 2 or female connector 3, achieving an interference fit using the principle of thermal expansion and contraction. Subsequently, radial pressure is applied to the sidewalls of tube 1 using a specialized press or extrusion die, causing plastic deformation of the sidewalls and forming the interlocking part 5. After tube 1 cools, the pre-stress generated by material shrinkage further enhances the tightness and reliability of the connection.

[0035] To ensure that the pipe body 1 is accurately combined with the male connector 2 and the female connector 3 and that the combination is highly integrated, a limiting step 7 is provided at the root of the connecting part 4 to abut against the end face of the pipe body 1. After the pipe body 1 is combined with the male connector 2 and the female connector 3, the outer surface of the pipe body 1 is smoothly connected with the surface of the male connector 2 and the surface of the female connector 3, forming a continuous outer contour, avoiding unevenness at the connection, and improving the overall streamline and performance of the drill pipe.

[0036] The structural feature of this trenchless drill pipe is that the basic connection between the connecting part 4 and the pipe body 1 is achieved through an interference fit, and additional connection strength is provided by the mechanical locking of the interlocking part 5 and the recessed part 6. During drilling, when the drill pipe is subjected to torsional torque and axial tension, the interference fit provides frictional resistance, while the interlocking part 5 and the recessed part 6 provide mechanical locking force. The two work together to ensure the reliability of the connection. Compared with traditional integral drill pipes and welded drill pipes, this split design has the advantages of lower equipment cost and easier processing. At the same time, the unique interlocking structure design ensures connection strength, eliminates the need for welding, and eliminates concerns about weld quality, meeting the stringent requirements of trenchless operations.

[0037] Furthermore, since the pipe body 1, male connector 2, and female connector 3 are manufactured separately, different materials can be flexibly selected for combination and optimization according to the working conditions. For example, 42CrMo material can be used to make male connector 2 and female connector 3. This material has high strength and hardness, which can meet the requirements of heavy load and high fatigue, and can ensure that the threads have good wear resistance. On the other hand, 26CrMo material can be used to make pipe body 1, which has better plasticity and is easier to deform, thereby achieving a reasonable configuration of material properties.

[0038] Based on the aforementioned trenchless drill pipe structure, this drill pipe forming method achieves a firm connection between the pipe body 1 and the male connector 2, and between the pipe body 1 and the female connector 3, through a combination of hot-plugging and radial extrusion processes. Specifically, it includes the following steps: Step 1: Separately process and shape the tube body 1, male connector 2, and female connector 3, and perform heat treatment.

[0039] In this step, the connecting part 4 of the male connector 2 and the connecting part 4 of the female connector 3 are pre-formed with recesses 6. The recesses 6 can be designed as several pits or an annular groove arranged around the connecting part 4, providing a mating basis for subsequent extrusion molding. After the pipe body 1, the male connector 2 and the female connector 3 are respectively machined, they are subjected to corresponding heat treatment to obtain appropriate hardness and strength.

[0040] Step 2: Heat both ends of tube 1 until they are red-hot, insert the connecting part 4 of male connector 2 into one end of tube 1, and insert the connecting part 4 of female connector 3 into the other end of tube 1 to achieve pre-assembly.

[0041] Specifically, medium-frequency induction heating can be used to heat both ends of the tube body 1 to 850℃ to 1050℃, with the heating length being 1.5 times the length of the connecting part 4. This heating method can precisely control the heating area and temperature, ensuring that the insertion area at the end of the tube body 1 has good plasticity. When the tube body 1 is in a red-hot state, the prefabricated connecting parts 4 of the male connector 2 and female connector 3 are quickly inserted into both ends of the tube body 1, respectively, to achieve an interference fit using the principle of thermal expansion and contraction.

[0042] Step 3: While the tube body 1 is still red-hot, the side wall of the tube body 1 is radially extruded by the extrusion die, so that the inner surface of the tube body 1 forms an interlocking part 5 that applies pressure to the corresponding connecting part 4, thereby achieving a firm combination of the tube body 1 with the male connector 2 and the tube body 1 with the female connector 3.

[0043] The extrusion die includes a segmented pressure plate arranged around the tube body 1. The inner side of the pressure plate acts on the outer surface of the tube body 1, and the inner side of the pressure plate has protrusions that match the position and shape of the recessed portion 6. Specifically, a hydraulic press can be used to drive the extrusion die, with the extrusion pressure controlled between 800MPa and 1200MPa and the holding time between 3s and 8s, so that the interlocking portion 5 fully fills the recessed portion 6. Under high pressure, the sidewall of the tube body 1 undergoes plastic deformation, forming an inwardly protruding interlocking portion 5, which mechanically locks with the recessed portion 6 on the surface of the connecting portion 4.

[0044] Step 4: After the assembled drill pipe is heat-treated, straightened, and tempered as a whole, internal stress caused by hot jointing and extrusion deformation is eliminated.

[0045] The quenching and tempering process includes two stages: quenching and tempering. Quenching increases the material's hardness, while tempering balances hardness and toughness. The straightening process ensures the drill pipe's straightness meets usage requirements, and tempering eliminates residual stress generated during processing, improving the drill pipe's dimensional stability and service life.

[0046] Step 5: Perform fine machining on the surface of the drill pipe to ensure a smooth transition at the connection points between the two ends of the pipe body 1 and the male connector 2 and the female connector 3, and perform surface anti-corrosion treatment.

[0047] Finishing processes include turning and grinding to ensure a continuous surface at the connection between pipe body 1, male connector 2, and female connector 3, eliminating steps or unevenness. Surface anti-corrosion treatment can be achieved through galvanizing, spraying with anti-rust paint, etc., to improve the corrosion resistance of the drill pipe under harsh working conditions.

[0048] The core of this drill pipe forming method lies in the combination of hot-jointing and radial extrusion. Hot-jointing utilizes the thermal expansion and contraction properties of materials to achieve an interference fit, while radial extrusion forms a mechanically locked structure through plastic deformation. Compared to traditional welding processes, this method avoids the adverse effects of the heat-affected zone on material properties. Simultaneously, the precisely controlled extrusion process ensures the consistency and reliability of the connection strength, significantly reducing the manufacturing difficulty and production process of drill pipes. It eliminates the need for expensive friction welding equipment; processing can be completed using only conventional heat treatment equipment and hydraulic extrusion equipment, effectively reducing production cycle and equipment costs. Furthermore, optimal matching of drill pipe performance can be achieved through material sorting strategies. Therefore, this drill pipe forming method provides an economical, efficient, and quality-controllable technical route for drill pipe manufacturing, possessing broad application value.

[0049] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A trenchless drill pipe, comprising a split-design pipe body (1), a male connector (2), and a female connector (3), characterized in that, The male connector (2) and the female connector (3) are respectively provided with connecting parts (4) for inserting into the corresponding ends of the tube body (1). The connecting parts (4) are interference-fitted with the tube body (1), and the tube body (1) is provided with a biting part (5) pressing against the connecting parts (4). The biting part (5) is used to improve the connection strength between the connecting parts (4) and the tube body (1).

2. The trenchless drill rod according to claim 1, characterized in that, The outer surface of the connecting part (4) is pre-formed with a recess (6) that mates with the interlocking part (5), and the cross-sectional shape of the interlocking part (5) is adapted to the cross-sectional shape of the recess (6).

3. The trenchless drill rod according to claim 2, characterized in that, The recessed portion (6) is a plurality of pits or an annular groove arranged circumferentially along the connecting portion (4).

4. The trenchless drill rod according to claim 1, characterized in that, The interlocking part (5) is a protrusion formed by radial extrusion deformation of the side wall of the tube body (1).

5. The trenchless drill pipe according to claim 4, characterized in that when the pipe body (1) is combined with the male connector (2) or the female connector (3), the corresponding end of the pipe body (1) is in a red-hot state.

6. The trenchless drill pipe according to claim 1, characterized in that, The root of the connecting part (4) is provided with a limiting step (7) for abutting against the end face of the tube body (1). After the tube body (1) is combined with the male connector (2) and the female connector (3), the outer surface of the tube body (1) is smoothly connected to the surface of the male connector (2) and the surface of the female connector (3).

7. A drill pipe forming method, based on the trenchless drill pipe according to any one of claims 1-6, characterized in that, The drill pipe forming method includes: Step 1: Separately process and form the tube body (1), male connector (2) and female connector (3), and perform heat treatment; Step 2: Heat both ends of the tube (1) until they are red-hot, insert the connecting part (4) of the male connector (2) into one end of the tube (1), and insert the connecting part (4) of the female connector (3) into the other end of the tube (1) to achieve pre-assembly; Step 3: While the tube body (1) is still red-hot, the side wall of the tube body (1) is radially extruded by an extrusion die, so that the inner surface of the tube body (1) forms an interlocking part (5) that applies pressure to the corresponding connecting part (4), thereby achieving a firm combination of the tube body (1) with the male connector (2) and the female connector (3). Step 4: After the assembled drill pipe is heat-treated, straightened, and tempered as a whole, the internal stress caused by hot jointing and extrusion deformation is eliminated. Step 5: Perform fine machining on the surface of the drill rod to achieve a smooth transition at the connection between the tube body (1) and the male connector (2) and the female connector (3), and perform surface anti-corrosion treatment.

8. The drill pipe forming method according to claim 7, characterized in that, In step one, a recess (6) is pre-formed on the connecting part (4) of the male connector (2) and the connecting part (4) of the female connector (3); in step three, the extrusion mold includes a pressure template arranged around the tube body (1) and designed in segments, the inner side of the pressure template acts on the outer surface of the tube body (1), and the inner side of the pressure template is provided with a protrusion that matches the position and shape of the recess (6).

9. The drill pipe forming method according to claim 8, characterized in that, The extrusion die is driven by a hydraulic press, and the extrusion pressure is controlled at 800MPa to 1200MPa. The holding time is 3s to 8s, so that the interlocking part (5) fully fills the recessed part (6).

10. The drill pipe forming method according to claim 7, characterized in that, In step two, the two ends of the tube body (1) are heated to 850℃~1050℃ using medium frequency induction heating, and the heating length is 1.5 times the length of the connecting part (4).

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